Water-Based Epoxy Systems

10.28

Water-Based Epoxy Systems

A Klippstein, M Cook, and S Monaghan, Air Products & Chemicals Inc., Utrecht, The Netherlands © 2012 Elsevier B.V. All rights reserved.

10.28.1 10.28.2 10.28.3 10.28.4 10.28.5 10.28.6 10.28.6.1 10.28.6.2 10.28.6.3 10.28.7 10.28.7.1 10.28.7.2 10.28.7.3 10.28.7.4 10.28.7.5 10.28.7.6 10.28.7.7 10.28.7.8 10.28.7.9 10.28.8 10.28.9 10.28.10 10.28.11 10.28.12 10.28.12.1 10.28.12.2 10.28.13 10.28.13.1 10.28.13.2 10.28.14 10.28.15 10.28.16 10.28.17 10.28.18 References

Introduction Definition Classification of Waterborne Epoxy Technologies Comparison of Waterborne and Solvent-Borne Epoxy Coatings Waterborne Amine Hardeners: General Structural Requirements Type I Waterborne Epoxy Technologies Polyamide Curing Agents Polyamine Epoxy Adducts Miscellaneous Curing Agents Type II Waterborne Epoxy Technologies Epoxy Resin Dispersions Polyamine Curing Agents Formulation Guidelines Resin Stoichiometry Effect of Cosolvents Recommended Pigments for Waterborne Coatings Pot Life Film Formation Curing Agents in Detail Deep Penetrating and Green Concrete Primer Water Vapor Permeable Floor Systems Concrete Coating Systems Waterborne Epoxy Curing Agent Systems Self-Leveling Floor Formulation Carbamation of Floor Systems Water Vapor Permeability Self-Leveler Temperature Resistance Chemical Resistance Low-Emission Industrial Floorings Path to Low-Emission Floorings Water-Based Low-Emission Formulation Time Is Money Conclusions

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10.28.1 Introduction

10.28.2 Definition

Since the first viable commercial introduction, at least 25 years ago,1 waterborne epoxy coatings and floorings2 have become an increasingly commercially important technology. A key highlight in recent years is the transformation of patents into real-world application. A defining example of this is the emulsion curing agent technology which circumvents any issues of osmotic blistering in high film build flooring applications. A further example is the latest amine dispersion technol­ ogy which offers unique formulation and application possibilities.

The basic definition for a ‘2K epoxy binder’ (also called ‘2-pack epoxy binder’) is that this is a thermoset polymeric system formed by the reaction of an epoxide functional resin with a polyamine molecule. An epoxide functional resin or epoxy resin is a monomeric or short-chain polymer terminated with epoxide functionality. The most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A, although the latter may be replaced by similar chemicals. Overviews of typically used epoxy resins and their curing agents, including the reaction chemistry, can be found in comprehensive literature like ‘Lackharze’ by Stoye and Freitag.3

Polymer Science: A Comprehensive Reference, Volume 10

doi:10.1016/B978-0-444-53349-4.00281-8

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Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

O

O

O

O

O n

OH

O

Ia, n = 0−0.1

Ib, n >2

O

O

O

In the context of epoxy systems, the polyamine molecules are generally referred to as curing agents or hardeners. The curing agents can be based on a variety of chemistries but for ambient cure systems these are fundamentally multifunctional amine molecules. The ‘curing’ process for an epoxy system involves the polymerization and cross-linking of the system to form a solid. The nature of epoxy systems tends to yield polymers with a high level of cross-linking giving high mechanical and barrier properties. The reaction of an amine and an epoxide is a nucleophilic substitution reaction which occurs at ambient temperature. This reaction is exothermic, and as molecular weight increases the viscosity of the material increases as that of a solid. Careful formulation is required to allow for full reaction and crosslinking. The majority of epoxy resins are based on bisphenol-A diglycidlyether (BADGE) and/or bisphenol-F diglycidylether (BFDGE), with or without a variety of reactive diluents to control viscosity and improve handling for low-temperature applications. For ambient temperature-cured systems the epoxy resin can be reacted with a number of different amine-based chemistries to offer performance characteristics which fit a variety of applications including protective coatings on metal, chemical-resistant linings, concrete coatings, adhe­ sives, and composites. The main chemistries that curing agents are based on are polyamides and aliphatic amines. There are three generic

R

types of curing agents, which have the chemical structure required to carry out these roles. The products concerned are (1) amidoamines 1 – condensation reaction products between monomeric, C18 fatty acids such as tall oil fatty acid (TOFA) and polyalkyleneamines, for example, triethyle­ netetramine (TETA); (2) polyamides 2 – manufactured by a condensation reaction between C36 dimer fatty acids and polyalkyleneamines; and (3) amine adducts 3 – reaction products between an amine and an epoxy resin. This chemistry offers a wide range of performance properties such as good flexibility, high corrosion resistance, and long pot life, which are primarily used in protective coatings on metal. They are the industrial standard for solvent-borne and high solid marine coatings as well as heavy-duty anticorrosive coatings. Aliphatic amines are low molecular weight, high function­ ality amines which are used to increase reaction speed and cross-link density; these systems offer fast cure and high che­ mical resistance and are used as accelerators for other systems as well as chemical-resistant coatings such as storage container linings. Cycloaliphatic systems are primarily used in civil engineering applications, that is, applications on concrete. These systems are based on diamine molecules such as isophorone diamine, 4,4′­ methylenebis(cyclohexylamine), meta-xylene diamine, or 1,6-hexanediamine. These molecules are formulated with

(CH2)7CONH(CH2CH2NH)nCH2CH2NH2

H

O

N

N

n

(CH2)7CONH(CH2CH2NH)nCH2CH2NH2

NH2

H

CH3(CH2)5

CH2CH=CH(CH2)4CH3 2 n = 1–4

1 R = C17H29–35

n = 1–4

H 2N

N H

O n

O

II

N

O

OH

OH 3 n = 2–4

H

NH2 n

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

different accelerators such as tertiary amines (i.e., 2,4,6-tri (dimethylamino methyl)phenol), alkyl phenols, or carboxylic acids. They are further modified with a plasticizer such as benzyl alcohol which is essential for standard ambient cured cycloali­ phatic systems in order to develop optimum cross-link density. These systems offer a good balance of properties with excellent cure and esthetics at low temperature, good chemical resistance, and abrasion resistance. Due to the balance of properties offered by these systems they are used in a wide range of applications. The applications vary from concrete coatings and self-leveling flooring to high-performance screeds and protective coatings. Waterborne systems will be discussed in more detail in the following sections. This chemistry demonstrates a number of advantages over other systems and is primarily used in concrete coatings or self-leveling flooring offering high performance and esthetics.

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10.28.4 Comparison of Waterborne and Solvent-Borne Epoxy Coatings Epoxy resins are intrinsically highly water insoluble. In order to be used in an aqueous medium, the epoxy resin must be dispersed with the aid of a surfactant into colloidal particles, ranging in size from about 100 to several thousand nan­ ometers. Unlike most other aqueous dispersions used in coatings, the reactants in an epoxy coating react at room temperature. In clear solvent-borne epoxy formulations, the resin and amine curing agent exist in a true, isotropic solu­ tion. In an aqueous medium, the amphiphilic amine hardeners will partition between the aqueous and epoxy phases and the epoxy/water interface. They may also exist in self-assembling aggregates of their own. This mechanism of cure differentiates the waterborne system from the solvent-borne equivalent.

10.28.3 Classification of Waterborne Epoxy Technologies

10.28.5 Waterborne Amine Hardeners: General Structural Requirements

In general two different types of waterborne epoxy coating categories exist. These categories are based on the physical state of the epoxy resin used. Type I systems are the first that achieved commercial suc­ cess. Most epoxy resins used in waterborne systems are based on liquid epoxy resin (LER) manufactured from the diglycidyl ether of bisphenol-A or bisphenol-F and blend of these with and without reactive diluents. In typical type I systems, the amine hardener is usually designed to act as an emulsifier for the LER. Alternatively, the LER can be pre-emulsified in water by the use of surfactants; this practice aids in mixing and is also used as a method to adjust package ratios for commercial formulations. Type II waterborne epoxy systems are based on much higher molecular weight epoxy resins, which tend to be solids at room temperature. These systems are generally clas­ sified as solid epoxy resin dispersions (SER dispersions). To produce a small and reproducible particle size, a dispersion of such viscous materials requires specialized processing equipment, the application of heat, and/or the use of sol­ vents. Typical dispersions are always predispersed either by the coating manufacturer or the raw material supplier. Interestingly, the amine hardeners for type II systems also tend to be amphiphilic in nature, though they no longer serve to emulsify the resin. Performance differences between the two systems are diffi­ cult to point out. In most type I coatings little or no cosolvent is used, whereas type II typically require a coalescing agent (see 10.28.7.5. also refer to Chapter 10.18). Type II coatings, like solvent-borne coatings based on SER, will reach a touch-dry state as soon as enough of the water and co-solvent evaporate thus increasing the viscosity to the required level. This so-called lacquer dry is due to the very high viscosity of the binder.4 Type I coatings require a significant amount of chemical reaction before the requisite viscosity is achieved and are generally slower drying. Typically, the usable pot life of type I systems is also shorter than for type II. The differences in resin mole­ cular weight also result in different mechanical properties.

In many type I systems, the curing agent serves a dual role: (1) as emulsifying agent for the LER; and (2) as cross-linking agent. As mentioned earlier, there are three generic types of curing agents, which have been in common use in traditional solvent-borne epoxy coatings and which have the basic amphi­ philic structure required, that is, amidoamines, polyamides, and amine adducts. It should be noted that these are highly idealized structures. The polyethyleneamines themselves are mixtures of linear, branched, and cyclic structures. The general incompatibility of epoxy resins and amines can also lead to difficulties. This incompatibility has always been a problem with traditional epoxy coatings, which have a ten­ dency to exude amine on their surface. This can result in the formation of carbonate salts known as ‘blush’5 or a greasy surface layer. In waterborne formulations incompatibility may lead to other surface appearance defects such as cratering and may also decrease the stability of the epoxy emulsion. Compatibility of a hardener is frequently enhanced by reaction with mono-functional epoxy diluents, particularly aromatic diluents, or by reaction with epoxy resin. As polymer compat­ ibility normally decreases with increasing molecular weight, these modifications are even more important in type II tech­ nologies due to the higher molecular weight of the epoxy dispersions. These adduction procedures have the desirable effect of also reducing reactivity.

10.28.6 Type I Waterborne Epoxy Technologies 10.28.6.1

Polyamide Curing Agents

The first commercially available waterborne curing agents were essentially unmodified polyamides, partially neutralized with carboxylic acids.6–8 Although polyamides of this type readily emulsify a LER, the quality of the cured coatings was clearly inferior to their conventional solvent-borne polyamide coun­ terparts. They were slow to cure, extremely sensitive to the cure environment, and more often than not gave soft, low-gloss coatings with poor chemical and corrosion resistance. The lack of performance was probably due to poor system

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compatibility and film formation. In the mid-1970s, the per­ formance of the polyamides was significantly improved. This was accomplished via the partial adduction of the polyamide with either aromatic monoglycidyl ether,9 or diglycidyl ether of bisphenol-A, the latter approach being the preferred route. Although both LERs and SERs could be used, partial adduction with SERs with an average molecular weight ≥ 900 gave the greatest improvement in compatibility and emulsion quality. Partial neutralization with acetic acid was required to maintain water solubility. The above modifications resulted in products with improved water stability and resin compatibility. The resulting coatings offered improved dry speed, gloss, hardness, and chemical resistance. In the early 1970s, Richardson10 developed a curing agent for zero volatile organic component (VOC) systems based on a combination of modified polyamide and polyamine adducts. It was the first product to gain wide commercial acceptance and found widespread use in topcoats in hospitals, schools, indus­ trial warehouses, and as a sealer for concrete. Even today these are among the largest markets for waterborne epoxy coatings. Another application area where waterborne epoxy systems offered significant performance advantages over existing tech­ nology was coatings for nuclear power plants, since these coatings proved relatively easy to decontaminate.11 Despite the widespread introduction and application of modified polyamides, the relatively short pot life of waterborne systems was always considered a shortcoming. A conventional solvent-based system has a typical pot life of 6–8 h, compared to only 1 h for the modified waterborne polyamides. Richardson12 reacted the polyamide with carbon dioxide and achieved pot lives up to 6 h without adverse effect on the dry speed and coating performance. A patent published by Moes and Small13 describes a method of preparing a polyamide-based waterborne curing agent from a blend of a C18 dimer acid-tetraethylenepentamine polyamide and a monoepoxide-polyethyleneamine adduct. The addition of the monoepoxy adduct was shown to significantly reduce the dry time.

10.28.6.2

Polyamine Epoxy Adducts

Despite the success of the polyamide curing agents, the pro­ ducts suffered from several inherent weaknesses. These included (a) poor color, which made it difficult for formulators to develop high-gloss white enamels and pastel paints; (b) high initial viscosity resulting in low film build at application viscosity; and (c) poor water resistance and anticorrosive prop­ erties. The poor color appears to be an unavoidable result of the high temperatures required for polyamide production. Many developments have focused on resolving several of the above issues and have led to the introduction of new curing agents based on polyamine adduct technology. Use of cycloaliphatic amine epoxy adducts for waterborne epoxy systems was described by Neffgen and Allewelt.14 They were the first class of waterborne curing agents not to exhibit flash rusting on steel, thus opening up the potential for the use of these products as anticorrosive coatings. No chemical basis for the improvement was given. Excellent anticorrosive proper­ ties have been claimed.15 Cornforth and Darwen16 combined epoxides with differing levels of hydrophobicity to yield epoxy-amine adducts with an

appropriate balance of performance properties. A more hydro­ philic adduct was prepared by reacting a polyamine, preferably a high molecular weight polyethylene polyamine with a mix­ ture of mono- and polyepoxides. The latter are preferably a combination of aliphatic and aromatic polyepoxides. The pre­ ferred aliphatic diepoxides are those having an epoxy equivalent weight (EEW) in the region 120–140, for example, hexanediol diglycidyl ether. The aromatic polyepoxides include the polyglycidyl ethers of bisphenol-A or bisphenol-F. Preferably the levels of epoxides used ensure that about 20–40% of the available primary amine functionality in the polyethylene polyamine is allowed to react with the monoep­ oxide and about 5–65% of the available primary amine groups react with the polyepoxide. A more hydrophobic adduct was prepared by reacting a low molecular weight polyethylene polyamine with an aromatic monoglycidyl ether, preferably phenyl or cresylglycidyl ether. To facilitate dispersibility of the polyamine adduct blend, the mixture is finally treated with formaldehyde in order to further reduce the primary amine content of the preparation. An important property claimed for this technology is reduced viscosity in aqueous media when compared to com­ mercial waterborne polyamide hardeners. These result in higher formulated volume solids, in turn leading to higher film build per application. Commercial products have been formulated with both liquid resins (type I) and more recently with SER dispersions (type II). Coatings were shown to have rapid hardness development and excellent chemical and stain resistance in enamel topcoats.17 Another important property was long-term retention of gloss at ambient storage conditions, which has been shown to slowly deteriorate in some water­ borne epoxy systems.

10.28.6.3

Miscellaneous Curing Agents

As most type I curing agents utilize the amine as the hydro­ philic component of the emulsifier, Walker, Everett, and Kamat18 took the approach of covalently bonding a water-soluble polymer (WSP) to a large excess of a highly water-insoluble mixture of polycycloaliphatic polyamines (PCPA), as shown in Figure 1. The system was designed to yield a highly homogeneous film structure. By employing a highly compatible and hydro­ phobic amine and LER, driving forces for phase separation could be reduced. The amine structure was also chosen because of its lower reactivity with epoxy resin, which led to a pot life of about 4 h in a clear coat formulation. Recently, type I systems have been developed that exhibit some of the lacquer dry characteristics of type II technologies. This has been accomplished by the development of curing agents that contain higher molecular weight entities in the form of a colloidal dispersion. Klippstein19 described a process for preparing a curing agent dispersion by adding a solution of SER in glycol ether to an aqueous solution of a commercial curing agent. When equal weights of LER were substituted for the higher molecular weight resin, the system gelled. When compared to the original hardener from which the product was derived, phase 4 thin film set times (B-K recorder) for clear coats were reduced from 12 h down to 5 h and there was also a much more rapid

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

X

523

Z X

Z + WSP

Y ‘Coupling’ reagent

Y

Z X Excess PCPA

Y N

NH2

NH2

H Figure 1 Scheme for the preparation of a waterborne curing agent with covalently attached emulsifier.

buildup of hardness and solvent resistance. This was accom­ plished with no loss in pot life. This technology was primary to enable the development of flooring systems that circumvent the 40-year-old blister pro­ blem exhibited by other coating technologies when applied over humid concrete. The key factor for this application was the ability to establish a breathable, high layer thickness floor­ ing with resistance to osmotic blistering.

10.28.7 Type II Waterborne Epoxy Technologies 10.28.7.1

Epoxy Resin Dispersions

The impetus behind the development of type II technologies was specifically to improve dry speed and water resistance. This led researchers to change their strategy toward the development of high molecular weight SER dispersions. An article published by Kurnik and Roy20 discusses some of these early developments. The advantages of this approach are that coatings would reach the initial tack-free state much faster, since they would rely more on the lacquer dry effect of the solid resin during the early period following application, rather than any real degree of cross-linking. The higher molecular weight resins also help to improve flexibility and increase the level of hydrophobicity.

10.28.7.2

Polyamine Curing Agents

Shimp and coworkers21 were one of the first groups to success­ fully develop amine hardeners for use with the type II SER dispersion technology. Their approach was to prepare a poly­ amine adduct via a two-stage reaction process. Stage 1 involves reacting a bisphenol-A diglycidyl ether with a polyethylenea­ mine. Diglycidyl ethers having an EEW in the range of 180–900 are recommended, the actual resin used depends upon the desired physical and mechanical properties of the final coat­ ings. When the adduction reaction is complete, unreacted amine is removed by vacuum distillation. This is claimed to offer several performance advantages including reduced water sensitivity and improved system sta­ bility. Stage 2 involves reducing primary amine functionality by end-capping the polyamine adduct with a combination of aliphatic and aromatic monoglycidyl ethers. In a detailed study, the inventors have demonstrated that at least 25 mol.% of the end-capping agents employed must be aliphatic in nat­ ure, otherwise compatibility of the epoxy resin-curing agent

dispersion is compromised and the esthetics of the cured coat­ ing deteriorate. The preferred aliphatic end-capping agents are those obtained from a long-chain monohydric alcohol having 11–15 carbon atoms. Typical aromatic glycidyl ethers include phenyl or cresylglycidyl ether. Finally the curing agents are rendered water compatible via partial neutralization with acetic acid. The end-capped polyamine adducts have been shown to exhibit excellent compatibility with several of the epoxy resin dispersions previously described. In addition, they are also compatible with either standard or self-emulsifiable LERs. As a result, curing agents can be used to develop coatings with a variety of differing properties, including pot lives ran­ ging from 2 to 8 h. Compared to waterborne polyamide hardeners, color of the modified polyamine adduct is signifi­ cantly improved, allowing for the development of high-gloss white enamels and pastel shade decorative paints. Walker, Cook, and Dubowik22 report a new modified poly­ amine adduct which was specifically designed to give improved coating performance with the SER dispersions. An important property of this curing agent is that it exhibits uniform viscosity throughout the pot life. Formulated coatings have been shown not to experience the sharp viscosity decrease commonly observed with many products used in type II epoxy coating systems. The inherent viscosity stability on systems based on this technology allows for improved spray applications and handling. Anti-corrosion primer formulations applied to grit-blasted steel gave good performance, with little deterioration in over 2000 h accelerated corrosion and humidity resistance.

10.28.7.3

Formulation Guidelines

When formulating with waterborne epoxy resin systems, spe­ cial attention must be paid to the choice of pigments, wetting agents, defoamers, and cosolvents, and their likely effect upon the stability and performance properties of a formulated paint. In recent years, several papers have been published highlight­ ing formulation guidelines. Some of the important factors to be considered are discussed below.

10.28.7.4

Resin Stoichiometry

One of the most important formulating tools that can be utilized with two-pack waterborne epoxy systems is varying the resin stoichiometry to achieve a whole range of perfor­ mance properties, as reviewed by Jackson23 and by Galgocci and Weinmann.24

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With solvent-borne two-pack epoxy coatings, it is conven­ tional formulating practice to combine the amine curing agent and epoxy resin at a stoichiometric ratio of about 1:1, where the loading of curing agent is calculated based on the EEW of the resin and the amine hydrogen equivalent weight (AHEW) of the curing agent. Typically, the curing agent usage is expressed as parts per hundred resin (PHR) in accordance with eqn 1: PHR ¼ 100 

½AHEW  ½EEW

½1

For waterborne type I technologies the 1:1 stoichiometry or a slight epoxy excess also tends to yield optimum performance. With type II technologies studies have shown that varying the stoichiometry from the theoretical loading can offer several performance advantages. Formulation with excess SER disper­ sion can dramatically improve water and corrosion resistance properties. Salt fog and humidity resistance of anticorrosive primers are significantly improved if resin levels as high as 60–90% above the theoretical level are used. Some of the effect is probably due to the fact that the amines are more hydrophilic than the epoxy resin, so that by reducing the amount of amine employed, the overall hydrophobicity of the composition is increased. In addition, at higher amine levels, the nonuniform film morphology may result in high concentrations of amine in localized domains, through which the transport of water is accelerated relative to other parts of the film.18,25 In certain applications, it can be more beneficial to employ conventional stoichiometry or even an excess of curing agent. This is of particular importance when solvent or stain resistance of the cured coating is required. Other advantages gained using high levels of curing agent include an improvement in the abrasion resistance, adhesion, and dry speed.

10.28.7.5

Effect of Cosolvents

Coating properties, particularly of type II systems, are fre­ quently improved if additional cosolvents are added during formulation. Cosolvents can affect several basic properties including film formation, pot life, gloss, and ultimate barrier protection. Sometimes a combination of water-soluble (e.g., glycol ethers) and water-insoluble solvents (e.g., benzyl alcohol) is required for optimum performance properties.22 Coating properties are enhanced due to the effect cosolvents have on both the minimum film formation temperature and film coalescence.

10.28.7.6

Recommended Pigments for Waterborne Coatings

In developing paint formulations, other considerations include the type of pigmentation packages that are acceptable for waterborne systems. For white gloss enamels, titanium dioxide is used as the main pigment and talc is often used as an extender. Usually a silica or alumina surface-treated grade of TiO2 is required for dispersion stability and optimum gloss development. Due to increasing environmental concerns the use of lead- and chromate-based corrosion-inhibiting pig­ ments is no longer considered acceptable. In an extensive study conducted by Jackson,23 anticorrosive pigments that

function well in waterborne epoxy primers are those that are relatively inert and do not release large amounts of water-soluble salts. Inert pigments are required to prevent adverse ionic interactions with the strong cationic character of the water-miscible amine functional curing agent. Pigments shown to offer the best salt fog, prohesion, and humidity resistance include calcium strontium phosphosilicate, modi­ fied zinc phosphates, and more recently calcium strontium zinc phosphosilicate. Typically, the loading of the anticorro­ sive pigment required to obtain maximum corrosion protection is in the range 0.5–1.0 lbs gal−1. In choosing the extender pigments, good results are often obtained if a combination of particle sizes and shapes are employed, which may improve barrier protection. It is usually important that extender pigments with low water-soluble con­ tent be employed. The use of pigments with low oil and water absorption minimizes adverse effects on vehicle-volatile demand and coating viscosity. Typical pigments used include calcium metasilicate, barium sulfate, silica–alumina ceramic spheres, and wet ground mica.

10.28.7.7

Pot Life

Working time, or pot life, is one of the key parameters in the application of waterborne epoxy systems. Pot life could act as differentiator between type 1 and type 2 technologies as well as between different curing agent chemistries. Typically in Type 1 systems the end of pot life for a waterborne epoxy system is signaled by a noticeable increase in viscosity. This is generally termed as a visible end of pot life and can be seen as an advantage of the Type 1 systems. For Type 2 systems the end of pot life more commonly is (only) indicated by a change in some important property of the resulting film. Pot life depends on the formulation and raw materials used. As Wegman26 has shown in Type 2 systems, the ongoing reaction increases the molecular weight and Tg of the disperse phase resins. This causes an increase in the minimum film-forming temperature (MFFT) of the composition. Pot life can be increased by raising the cure temperature or in some cases by addition of cosolvent or plasticizer to a formulation. In low-gloss coatings, the end of pot life may be indicated by some other property, such as a change in the humidity resis­ tance of the film.

10.28.7.8

Film Formation

Though a typical SER dispersion particle is only 500 nm in diameter, on a molecular level this is a large distance. Taking the density of epoxy resin to be 1.16 g ml−1, assuming a mole­ cular weight of 1000, and ignoring the effect of any swelling of the particle by water, it is easily calculated that there are about 4.6  107 molecules per 500 nm diameter particle. To achieve uniform film formation comparable to a solvent-borne epoxy formulation, it is necessary for the amine to diffuse uniformly throughout this viscous resin phase. For this rea­ son, film formation in some waterborne epoxy systems is incomplete, and complex, heterogeneous morphologies result. Meanwhile, the ongoing chemical reactions continu­ ally raise the viscosity even higher, increasing the barrier to diffusion. At a certain degree of reaction, Tg exceeds room temperature, at which point diffusion becomes very slow.27

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

Consequently, the morphology of films may also change as the pot life progresses.

10.28.7.9

Curing Agents in Detail

Waterborne epoxy curing agents have grown in market share since their development 30 years ago.28,29 The driving forces for conversion to waterborne systems have ranged from improved workers’ safety to the ease of cleaning tools with only water. Further demands of the coating industry have been met with the ability to formulate low-viscosity systems without the use of solvent. With each generation of waterborne curing agents, advancements have been made to expand their application potential. Original developments (see Table 1) were based around water-soluble polyamide technology30 that was predominantly used on old concrete substrates as concrete sealers. These sys­ tems have found limitations due to the inability to cure in high film build applications, with water entrapment being a major problem in coatings over 250 µm wet film thickness. The nat­ ure of this type of curing agent also tends to lead to high color and high viscosity (therefore, low solids), which have limited the variety of applications that water-soluble polyamides can service. Market demand for curing agent technology, which addresses the need for faster cure speed and higher film builds, was met by the development of a curing agent based on emul­ sion technology.31 This technology advanced the waterborne market by facilitating new applications such as self-leveling flooring. Systems greater than 3 mm dry film thickness are feasible without cracking and exhibit overall performance properties comparable to established solvent-free technology. In addition, the waterborne self-leveling coatings exhibit water vapor permeability thus allowing for application over sub­ strates known to be sensitive to osmotic pressure buildup where traditional solvent-free epoxy systems have shown dela­ mination failure.32 By now this technology has established itself as an industry standard for such problematic application areas with a great number of successful commercial flooring projects. Color and color stability, the ability to cure in thick transparent coatings, low viscosity, cement compatibility, and long working life are remaining challenges in

Table 1

water-based curing agent technology to expand in this field. Improved color and color stability would allow for the expansion into more decorative applications where the esthetics of the coating is important, such as pigmented topcoats or transparent sealers for stone carpets. With low viscosity comes the ability to produce coating systems with higher solids; this also provides the formulator with more flexibility when developing coating systems. Cement stable waterborne epoxy systems would allow primers to be used on freshly laid concrete, reducing the time required to put new build structures into service. Application such as wall coatings where time is needed to coat large areas or intricate structures requires a long working life after mixing; hence pot life is a critical performance parameter. To meet these emerging applications, continued innovation has led to two novel technological approaches to enhance the performance characteristics of waterborne epoxies. The first is the development of amine functional dispersion technology and the second a water-soluble curing agent based on a mod­ ified Mannich base. Dispersion curing agent technology,33,34 like Anquawhite® 100 curing agent, addresses the need for low viscosity, low color, good color stability, and long pot life. This technology is a stable amine functional dispersion based on a polymeric amine of hydrophobic nature that exhibits low solubility in water with an average particle size of 800 nm. The dispersion is nonionically stabilized and exhibits freeze–thaw stability as well as good storage stability. In this development, dispersion technology has been applied to yield an ultra-low-viscosity curing agent, unlike any other waterborne currently produced. As it is typical for an aqueous dispersion viscosity is inde­ pendent of molecular weight. The viscosity of 200 mPa s (55% solids) is more than an order of magnitude difference com­ pared to conventional water-soluble polyamine curing agents at 10 000–20 000 mPa s at similar solid levels. This offers obvious advantages in handling and formulation develop­ ment, providing handling characteristics comparable to well-established solvent-free technology based on cycloalipha­ tic curing agents. It can be utilized for primers and transparent waterborne epoxy coatings without further processing, thereby achieving cost savings for curing agent formulation and repackaging.

Key properties, features, and applications of waterborne systems

Technology

Key properties

Features

Applications

Water-soluble polyamides (circa 1970s)

Viscosity: 40 000 mPa s Solids: 50% Colour: 12–14 Viscosity: 7500 mPa s Solids: 55%

• Good adhesion

• Concrete sealers

• High film build • Water vapor permeability • Corrosion resistance • Low viscosity • Long pot life • Good colour • Cement stable • Excellent adhesion • Fast cure in damp conditions

• Self-levelers • Metal primers

Êpilink® 701 (circa 1990s) Anquawhite® 100 Dispersion-based curing agent Anquamine® 287 Water-soluble Mannich base

Viscosity: 200 mPa s Solids: 55% Particle size < 1μm Viscosity: 600 mPa s Solids: 50%

525

• Wall coatings • Top coats • Green concrete • Deep penetrating primers

526

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

In pigmented systems, Anquawhite® 100 curing agent shows very good pigment wetting, reducing the need for wetting additives and an easier application by brush or roller with no roller pick-up due to low viscosity and hydrophobic nature of the curing agent. This benefit translates into a faster paint application, allowing for the same surface area to be coated in less time. The low curing agent viscosity also translates into low mix viscosity for same solids or, in other words, the ability to use higher solids in a waterborne system at the same viscosity. Between 25% and 50% more solids can be applied compared to other waterborne technology at same application viscosity thereby reducing the number of coats and time to yield the desired film thickness. As less water is required to evaporate from the system, a higher film build can be achieved. Unfilled systems have cured up to a dry film thickness of 500 μm with high transparency and without any signs of water entrapment, thus providing application security and the possibility of application of transparent high film build water-based coatings. Coupled with this ability to cure in thick films and the low initial color and good yellowing resistance, very transparent and clear epoxy coatings are achievable. Yellowing upon UV exposure is a commonly known shortcoming of solvent-free and waterborne epoxy technologies and is inherent to the nature of the chemistry. Accelerated weathering benchmarking with QUV Accelerated Weathering Tester exposure shows that the newly developed dispersion technology exhibits better UV stability than estab­ lished waterborne and solvent-free systems. This opens new water-based epoxy applications, such as clear topcoats on stone carpets, where traditional waterborne technology could not have been utilized and traditionally solvent-borne 2K polyurethane systems have been applied. Cycloaliphatic curing agents have been used for a number of years in topcoat applications and have become an industry standard for highly durable topcoats. The following table shows the formulation for a standard white topcoat paint based on Anquawhite® 100 curing agent which can be brush, roller, or spray applied. This formulation shows very good color stability on exposure to UV light as shown in Figure 2 compared to similar formulations with a cycloaliphatic curing agent and a water-soluble polyamine. The paint has a pigment volume concentration (PVC) of 20.5% and shows stable gloss

80 70

Water-based polyamine Anquawhite® 100

Yellow index

60

Cycloaliphatic

50 40 30 20 10 0 0

50

100 Time (h)

150

Figure 2 Yellow index as a function of time of QUVA exposure.

200

at a value of 80 measured at 60° through the pot life, which is in excess of 6 h. A-Component

1.2.3.10/AQ100

1. Anquawhite® 100 2. Dispersant 3. Defoamer 4. Titanium dioxide 5. Barytes 6. Filler 7. Talc 8. Curing agent 9. Defoamer 10. Rheology modifier 11. Water

40.00 1.50 0.05 26.00 10.00 4.00 4.00 6.00 0.50 2.00 5.95 100.00

B-Component 1. Epoxy resin

25.00

Total

125.00

Another interesting feature, which is illustrated in the pre­ vious paint formulation, is the exceptional working time after mixing with epoxy resin. When cured with standard LER a pot life of up to 8 h is achievable; the system offers a very stable viscosity profile over a 6–8-h period with excellent film formation proper­ ties such as high and constant gloss and hardness. Traditional waterborne curing agent technology for LERs only provides a pot life of 1–2 h, whereas conventional cycloaliphatic systems exhibit pot lives of less than 1 h (Figure 3). This provides an economic route to long pot life water-based systems that currently can only be achieved utilizing predispersed resin systems. The long pot life offers an application window of a full working day, allowing for the mixing of one batch of material at the start of the day and then the continued application of the same material all day optimizing the efficiency of applicator work crews. Additionally, the longer pot life is beneficial for wall-coating application and usage in warmer climates, such as southern Europe and the Middle East. The high molecular weight of Anquawhite® 100 curing agent provides rapid drying and cross-linking with a lacquer dry on evaporation of water. The drying times exhibited are similar to emulsion-based curing agents and significantly quicker than soluble polyamide technology. Dry speeds are also comparable to solvent-free cycloalipha­ tic systems as depicted in Figure 4. The fast drying is also confirmed and supported by a fast cross-linking process that is indirectly measured as Persoz hard­ ness development (Figure 5). Again the hardness development is comparable to established waterborne curing agents and conventional solvent-free cycloaliphatic technology. For topcoat applications it is important for coatings to retain their high-quality esthetic finish. Benchmarking of top­ coats for chemical and stain resistance against conventional water-based technology has again highlighted improvements. Good solvent resistance is observed for all water-based systems; however, a marked improvement in acid resistance is

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

Mix viscosity @ 20 °C (mPa s)

10 000

8 000

6 000

Anquawhite® 100

4 000

Epilink® 701 Water-soluble polyamide

2 000

Cycloaliphatic 0 0

60

120

180

240 300 Time (min)

360

420

Figure 3 Pot life of water-based systems.

Hard dry

10

Set to touch

8

6

4

2

0

Anquawhite® 100

Epilink® 701

Water-soluble polyamide

Cycloaliphatic

Figure 4 Drying times of waterborne and solvent-free systems.

14 day

7 day

1 day

400

Persoz hardness

350

300 250 200 150 100 50

0

Anquawhite® 100

Epilink® 701

Water-soluble polyamide

Figure 5 Persoz hardness development of waterborne and solvent-free systems.

Cycloaliphatic

480

527

528

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

Table 2

Stain resistance of waterborne (WB) systems ®

Coffee Ketchup Mustard Red wine

Anquawhite 100

Water-soluble polyamine

No change No change No change Slight stain

Slight stain Yellow stain Yellow stain Yellow stain

noticeable with Anquawhite® 100 curing agent. Organic acid resistance has always been a severe limitation of water-based epoxy coatings. Results of the benchmarking show that coat­ ings based on the new dispersion remain intact upon exposure to dilute acetic acid (3%) contact whereas other water-based systems show severe failures, leading to blistering and delami­ nation from the substrate. The improved acid resistance translates to improved stain resistance against common foodstuffs, especially those contain­ ing low levels of acetic acid such as mustard, ketchup, and red wine. A summary of the results is outlined in Table 2. Coatings featuring the dispersion-based curing agent are virtually unaf­ fected after exposure whereas other waterborne systems show significant signs of attack. The increased chemical and acid resistance and the ability to cure in transparent low-color films suggests that films based on this technology can be uti­ lized in more decorative coatings where contact with foodstuffs may occur, such as emerging coating applications in institu­ tional areas or topcoats in food preparation areas. Next to good compatibility with standard LERs that are preferred for cost-effectiveness, Anquawhite® 100 curing agent also exhibits exceptionally good compatibility with predis­ persed SERs. Use of predispersed solid resins provides exceptionally fast dry speed and walk-on time with touch-dry times recorded at less than 1 h leading to faster return to service.

10.28.8 Deep Penetrating and Green Concrete Primer Finding a system which has applicability onto green concrete has been an industry requirement for a number of years. Green concrete is defined as freshly laid concrete which is not fully cured but is hard enough to walk on without leaving an imprint, typically about 8–12 h after application. Key require­ ments for a coating onto fresh concrete are low viscosity for good penetration and good adhesion to damp substrates.

Table 3

Typically, the application of waterborne epoxy systems is not ideal due to the instability of waterborne emulsions in strong alkaline environment leading to poor adhesion and other poor performance properties. A further requirement is quick cure under damp conditions to perform as an effective sealer. To demonstrate the benefits of a green concrete primer the process of manufacturing a new concrete floor will be briefly summarized. The conventional approach to coating a newly laid concrete floor is to allow the concrete to cure for 28 days before applying a coating to the surface; this approach has a number of drawbacks. After application of the concrete a curing compound is normally applied to the concrete to control water evaporation and allow the concrete to develop full mechanical properties without drying out too quickly, which would lead to a weak and brittle substrate. After curing for a further 28 days efflorescence will develop on the concrete surface which must be removed. This is typically done by shot-blasting to produce a clean concrete surface to ensure good adhesion of any applied coating. Thereafter, the surface is primed before being coated with the desired topcoat. Mannich base technology, although not innovative in itself, is a groundbreaking approach to developing waterborne curing agents and is a dramatic change to conventional thinking with remarkable results. The developed curing agent defined as Anquamine® 287 curing agent has shown the type of perfor­ mance properties that are essential for application over green concrete.35 Combining Anquamine® 287 curing agent with conventional LER results in a coating system, which offers rapid cure with a touch-dry time of 1 h and a hard dry of less than 5 h at 25 °C in thin film applications. Using this system the freshly laid concrete can be primed within 24 h of applica­ tion, the system will cure normally, and after 28 days the concrete can be immediately coated with a topcoat, saving on the need for surface preparation. Testing on concrete prepared in this way has shown that the applied green concrete primer exhibits improved bond strength over standard concrete with the primer giving excellent adhe­ sion on 24 h old concrete. Pull-off adhesion testing shows that there is approximately 95% concrete failure showing that the adhesion of the primer is in excess of the strength of the con­ crete itself. The bond strengths measured on concrete surfaces after various surface preparations are shown in Table 3. The surface preparations range from a simple hard trowel finish to shot-blasting. In addition, Anquamine® 287 curing agent has been tested in accordance with ASTM C 156-98, ‘Standard Test Method for Water Retention by Concrete Curing Material’, and shows an average water loss of 0.53 kg m−2 for coated surfaces compared

Waterborne self-leveling floor formulation Concrete finish Hard troweled

Broom finished

Shot blast finished

Time (days)

Primer

Un-primed control

Primer

Un-primed control

Primer

Un-primed control

1 7 30

2.6 3.2 3.9

-

2.4 2.8

1.1 0.8

2.0 2.7

1.0 1.9

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems to 3.84 kg m−2 for uncoated concrete leading to the assertion that Anquamine® 287 curing agent can also be used as a con­ crete curing compound. This performance allows to eliminate several steps after the concrete preparation. A primer can be applied directly onto the green concrete acting as concrete curing compound and at the same time providing the primer for the following coat to be applied at a point within a 28-day window without additional surface treatment. Further application testing has shown exceptional penetra­ tion into concrete and gypsum substrates. Primers ensure very good flow into the pores and deep penetration into the sub­ strate. Thereby providing mechanical strengthening of the substrate surface. Application examples include old and dete­ riorated concrete, other weaker substrates such as plaster, or high-density concrete where deep penetrating properties with­ out solvents are required. Anquawhite® 100

Anquamine® 287

• Extremely low viscosity • Transparent coatings, good color retention • Up to 8 h pot life

• Exceptional adhesion to green concrete • Fast cure in damp conditions • Deep penetration into porous substrates

10.28.9 Water Vapor Permeable Floor Systems A common mode of failure of conventional solvent-free, pro­ tective epoxy coatings applied over concrete is blister formation.36 This phenomenon is caused in part by a buildup of osmotic pressure, from within the concrete substrate. Osmotic blistering not only results in surface defects, but the blisters eventually lead to coating delamination and ultimately severe damage of the concrete base. For the first time, a novel water-based amine curing agent has been developed which helps to alleviate this problem. When used in combination with a LER this allows for the formulation of a high-build, self-leveling floor system, which when fully cured is permeable to water vapor but impermeable to liquids. Osmotic pressure or high hydrostatic pressure caused by underground water can therefore be safely released through the epoxy floor without causing damage to the coating and concrete base. In the cured state, the epoxy system forms a durable microporous structure based on a three-dimensional epoxy network. General performance properties, application examples, and a description of the polymeric structure of the floor coatings are discussed herein.

10.28.10

applications including concrete primers, floor paints, self-leveling, screed, and mortar floors. Waterborne epoxy curing agents have long been utilized for concrete coating applications. However, their use has been limited to sealers, primers, and floor paints, where a wet film thickness in the region of 100–200 µm is usually applied. At significantly higher film build, such coating systems may encounter problems with entrapped water being present in the film after full cure. Entrapped water results in downgrading of the performance properties. Results are poor surface appear­ ance, loss of gloss, or soft films.

10.28.11

Waterborne Epoxy Curing Agent Systems

The first generation of epoxy waterborne curing agents was based on solvent-free polyamides and made water soluble by inclusion of a nonionic surfactant or through salting with an organic acid.29 The high viscosity and relatively flat water dilu­ tion profile of the polyamides allowed for low solid-coating formulations only. Formulated systems tended to have short pot lives and coatings were often high in color and slow to cure, particularly under the condition of low temperature (<10 °C) and high humidity (> 80%). Higher performance products were subsequently developed and introduced into the market­ place during the late 1980s and early 1990s. Their chemistry was based on aliphatic amine adducts, which exhibit better color stability and a higher solid content at the same viscosity compared to earlier polyamide products. The higher solid con­ tents coupled with the fast reactivity inherent in aliphatic amine curing agent has led to faster dry speed and thorough cure even under the adverse conditions mentioned above. A common disadvantage of waterborne epoxy systems is that higher film build coatings (e.g., > 500 μm [> 20 mils]) cannot be readily used. The principal problem caused by high film build is one of cracking of the coating during the evapora­ tion of water. The cracking observed with a typical waterborne self-leveling floor is illustrated in Figure 6. The novel waterborne Epilink® 701 curing agent technology has been developed31 to overcome the limitations of previous waterborne epoxy systems. The new technology is based on a curing agent emulsion of an ultra-high molecular weight ali­ phatic amine-epoxy adduct in water with high amine functionality and can be viewed as the third-generation water­ borne curing agent for LER.

Concrete Coating Systems

When a concrete substrate needs to be protected from environ­ mental attack, there are many different types of coating technologies that can be used. Examples of these include poly­ urethanes, methyl methacrylates, polyesters, and epoxies. Solvent-free epoxy systems are one of the most versatile tech­ nologies employed and are used in a wide variety of

529

Figure 6 Cracked waterborne self-leveling floor.

530

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

Table 4 finishes

Viscosity 25 °C (mPas)

100.000

Bond strengths (kN m−2) to green concrete with different

10.000 1.000 0.100 Aliphatic emulsion

0.010

Aliphatic solution Polyamide solution

0.001 10

30

50

70

% Solids Figure 7 Dilution profile of different curing agents.

A side:

Component

Supplier

Curing agent Curing agent Defoamer Pigment TiO2 Diluent Filler Filler Filler

Epilink® 701 Anquamine® 401 Byk-045 Kronos 2160 water Baryte powder F Quartz powder M6 Quartz sand 0.1–0.3 mm Deuteron VT 819 (3% in water)

Air Products Air Products Byk Chemie Kronos Titan Local Sachtleben Sibelco Local

Thixotropic agent

Weight (%) 11.00 2.50 0.70 3.80 9.10 36.00 18.00 18.50

Schöner GmbH

0.40 100.00

This new technology incorporates three key design features for optimum performance: (a) very high compatibility with LER ensuring good emulsification, (b) optimized hydrophile–lipophile balance for good emul­ sion stability, and (c) removal of unreacted raw materials and by-products, which could reduce performance. This new aliphatic amine emulsion technology results in coat­ ings that dry significantly faster at ambient temperature. This is clearly demonstrated by comparing the Beck Koller thin film set times (phases I–IV), for three types of waterborne curing agent-epoxy coating systems. The aliphatic amine emulsion achieves a hard dry time (phase IV), within 6 h compared to a hard dry time of 14 h for a similar coating based on a water­ borne polyamide curing agent. The new curing agent technology also exhibits a more effective dilution profile (Figure 7) allowing the application of higher solid coatings at the same viscosity.

10.28.12

Self-Leveling Floor Formulation

Ease of application combined with optimum mechanical and chemical protection as well as providing easy to clean surfaces has made solvent-free, self-leveling epoxy floors the first choice in concrete protection. Modified solvent-free systems using cycloaliphatic curing agents are predominantly used for this type of application and can be viewed as the industry standard. Typically, such protective flooring systems are formulated with low filler-to-binder ratios (1.5–2.6:1), which are deemed neces­ sary in order to ensure good flow and deaerating properties at the point of application. In order to overturn the old belief that with waterborne technology higher film build coatings cannot be formulated, recent application studies focused on the development of a waterborne self-leveling floor using the new-generation waterborne curing agent (Table 4). The significant difference compared to a solvent-free cycloa­ liphatic system is the fact that water can now be used as a diluent to achieve sufficient flow and deaeration. This allows reduction of the total binder content from approximately 30%

B side Epoxy resin

Table 5

Epires® ER8

Air Products

10.00

Formulation properties

Binder content (%) Filler:binder Volume solids (%) Water content (wt.%)

Waterborne self-leveler

Cycloaliphatic self-leveler

15 4.3:1 70.0 15.0

30 2.6:1 99.8 0.0

in a conventional cycloaliphatic epoxy floor formulation, down to 15% in the waterborne system (Table 5). This waterborne self-leveling floor contains approximately 15% by weight of water with theoretical volume solids of 70%. The composition would suggest a significant volume reduction to be observed upon evaporation of the water, eventually caus­ ing the floor to undergo severe shrinkage leading to cracking. However, upon visual inspection no defects are observed after the system has fully cured. To quantify this observation an experiment was conducted to determine the degree of shrinkage. A specimen of the floor was prepared and cast into a mold of 2.5 cm  2.5 cm  25 cm with two metal studs attached to each end. The distance between the studs was measured and used as a reference point. After 24 h the cured blocks were removed from the molds and measurements were taken between the two studs every 24 h to determine the degree of shrinkage. The level of shrinkage after 14 days cure is in the range of 1.3–1.5%, significantly lower than the maximum theoretical shrinkage of 30%. Most of the water is driven out during the very first day when the bulk part of the shrinkage occurs. Thereafter no significant change is observed as can be seen by the flat profile from day one onwards. Flow properties (Table 6) as measured by flow out diameter from a cylindrical container are the same for the two systems. The handling time of the waterborne system at 45 min is within the same range as the cycloaliphatic system, as well as offering a comparable final Shore D hardness. Hardness after day one of the waterborne system is in excess of a Shore D value of 65, sufficient for foot traffic.

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

Table 6 systems

and the strength of the water-based epoxy floor (40 MPa) exceeds this basic requirement.

Basic performance properties of epoxy self-leveler

Flow out (cm) Handling time (min) Hardness, 7days (Shore D) Bond strength (N mm−2) Abrasion resistance (mg per 1000 cycles) Surface appearance

Waterborne

Cycloaliphatic

15.9 45 80 5 156

16.5 30 85 3 138

Matte

Glossy

10.28.12.1

10.28.12.2

Compressive (mPa) Tensile (mPa) Flexural (mPa)

Cycloaliphatic

40 5 11

62 7 30

Water Vapor Permeability

Water vapor can readily pass through the capillaries of most concrete. However, concrete coated with a conventional solvent-free epoxy will act as a vapor seal and hinder water evaporation. Water transmission problems can occur from hydrostatic pressure and osmotic pressure, with the latter hav­ ing the greatest effect on concrete. The pressure generated by osmosis can greatly exceed other forces (e.g., adhesion) and ultimately cause delamination of a floor coating. Three conditions are required for osmosis to take place: water (liquid and/or vapor), soluble salts, and a semipermeable mem­ brane. All three conditions are typically found within concrete. The difference in soluble salt concentration coupled with concrete permeability for inorganic salts between the top and bottom sections has been identified as major contributor to the formation of an osmotic cell. This has been extensively studied and reported by other authors.41 Depending on the age of the concrete, moisture content can vary from about 4% when fully cured to 18% in freshly prepared ‘green’ concrete. Water con­ tent also depends on the water to cement ratio as well as the cure conditions. It has been suggested that higher

Mechanical properties of epoxy self-leveler Waterborne

Carbamation of Floor Systems

A significant problem in field-applied epoxy-coated thermoset floors based on cycloaliphatic curing agent technology is the formation of a white haze on the surface. In severe cases white patches known as water spotting are observed. This well-known problem can be attributed to the reaction of free amine with carbon dioxide in the presence of water at the air-coating inter­ face. The chemical side reactions that occur are reported in the literature37–39 and illustrated in Figure 8. A fundamental inves­ tigation of that problem has been published.40 Due to the presence of free amine in all cycloaliphatic curing agents, the formation of carbamate appears inevitable when conditions that favor carbamation reactions like lower temperature and high humidity are met. Free monomeric amines are absent in the novel waterborne curing agent, yielding a high compatibil­ ity with epoxy resin and ultimately no carbamate formation. This not only improves surface appearance but also prevents intercoat adhesion problems.

Bond strengths on shot-blasted concrete, coated with both the waterborne and solvent-free epoxy self-levelers, were deter­ mined by the dolly pull-off method according to DIN 1048 (test methods for concrete). Both systems exhibit bond strengths of > 2 N mm−2 (required minimum value), with a cohesive mode of failure occurring in the concrete substrate. Abrasion resistance was measured in accordance with ASTM D 5178-91 utilizing a Tabor abrasion tester fitted with wheel number C117. Similar weight losses within 1000 cycles are observed with both systems. The surface finish of the waterborne floor is matte in com­ parison to the glossy cycloaliphatic finish. While which surface appearance is more attractive is arguable, the matte surface appearance of the waterborne floor proves to yield better scratch resistant. Application on uneven substrates also proves to better hide the application/surface differences. It is anticipated that the lower binder content in the water­ borne floor formulation will affect the mechanical properties of the floor system. Experimental results confirm that the water­ borne system exhibits lower compressive as well as flexural strength compared to a cycloaliphatic floor (Table 7). Normal traffic areas typically require a compressive strength of 20 MPa

Table 7 systems

H R

NH2 + CO2

R

H OH

N

R

NH2 R

H

N

O

O

R

N

+

H

O Carbamate salt ion pair

O

R

CO2 + H2O HO

OH

NH2

H

O R HO

O

N H

Amine bicarbonate salt Figure 8 Chemical reactions leading to carbamate and water spotting.

531

+

H

H

532

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

Epilink ®701 epoxy floor

Impermeable synthetic floor Blister

Water vapor

Self-leveler Primer Partially sealed Concrete

Water-saturated concrete

Water Figure 9 Osmotic blistering.

concentrations of soluble salts are present in the top section of the concrete that cannot migrate into the interior of the slab due to a denser structure in the bottom section and are viewed as the determining factor for creating the semipermeable membrane. Figure 9 presents a comparison of how impermeable and permeable epoxy coatings affect blister formation. If pressures are allowed to accumulate without being dis­ sipated or vented, pressures can exceed the adhesive bond strength of the coating to the concrete, thus leading to disbond­ ment. However, permeable coatings are far less susceptible to the effects of these pressures than nonpermeable coatings. Two factors will influence the permeability of a coating. At PVCs higher than the critical PVC (CPVC), the presence of capillary channels in the film causes the water vapor perme­ ability to increase dramatically.42 It has also been suggested to determine CPVC by measuring water vapor permeability.43 The other contributing factor is permeability provided by the nature of the polymer matrix itself. The lack of any substantial shrink­ age in the external dimensions of the new waterborne floor as discussed earlier suggests that the cured polymer matrix forms a microporous structure. A study of water vapor permeability has therefore been conducted in accordance with DIN 52615 (determination of water vapor permeability of construction and insulating materials) to calculate moisture resistance factor and ASTM E96-95 Plastic Test Standard (Water Capor Transmission, WVT) to calculate permeance, comparing the conventional cycloaliphatic and the new waterborne floors.44 The moisture resistance factor (μ) indicates how many times the moisture resistance of the material is greater in comparison with the resistance of a motionless layer of air of the same thickness at the same temperature. The μ-factor is a dimension­ less quantity, hence is a material-specific constant that allows direct comparison of two systems excluding the effect of coat­ ing thickness. Results of the permeability study confirm the hypothesis of a water vapor permeable floor coating (Table 8). The

Table 8 floors

Water vapor permeability of epoxy self-leveling

Film thickness (μm) WVT (g m−2 per 24 h) Permeance (perms) Permeance (g s−1 m−2 Pa−1) μ-Factor

Waterborne

Cycloaliphatic

2,550 8.1 11.7 6.7  10−7 1000

1,870 0.4 0.09 0.05  10−7 30 000

measured permeability of the waterborne floor is 30 times greater than that of the solvent-free floor as expressed by the μ-factor. Coatings are classified as permeable when a U.S. permeabil­ ity rating of greater than 3 perms (= 1.7  10−7 g−1 s−1 m−2 Pa−1) is achieved.45 Standard concrete with a compressive strength of 21 MPa typically exhibits a permeance rating of 20–30 perms (= 1.1–1.5  10−6 g−1 s−1 m2 Pa−1). With the new waterborne sys­ tem46 a permeance of 11 perms is readily achieved, which is more than sufficient to comply with this definition of a perme­ able coating. Typically, cycloaliphatic floor systems do not exhibit the required permeability. This degree of permeability opens up the potential for the waterborne system to be used where osmotic pressure is a known problem. The increased permeability, as determined by the above test method, is confirmed in scanning electron microscopy (SEM) images on floor castings of the two systems under investigation. The SEM images in Figure 10 show a magni­ fication of 20 000 focused exclusively on the cured epoxy-amine binder system. A marked difference between the waterborne and the solvent-free system is evident. A continuous structure with very few voids is observed with the cycloaliphatic thermoset whereas the waterborne system shows a sponge-like appearance with voids and channels exhibiting a microporous structure that is permeable for water vapor. This analysis suggests that permeability is not only achieved due to a formulation beyond CPVC but that the underlying polymer structure created by the new waterborne curing agent is an integral part of this property.

10.28.13

Self-Leveler

Work has focused on the development of an amine curing agent that shows applicability in the area of permeable, water-based epoxy flooring. This approach can provide the formulator with an additional tool to solve the osmotic blister­ ing problem. Additionally, the control of the residual moisture in the concrete would not be viewed as critical, therefore redu­ cing the waiting times prior to application of the protective coating. The epoxy system is also an alternative to the applica­ tion of polymer-modified concrete, where the new approach will offer advantages in the area of improved mechanical and chemical properties as well as an improved decorative surface appearance.

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

(a)

533

(b)

Figure 10 Comparison of SEM: (a) waterborne (Epilink® 701) self-leveler and (b) solvent-free cycloaliphatic self-leveler.

10.28.13.1

Temperature Resistance

Another disadvantage of conventional solvent-free systems is their limited temperature resistance. When temperatures greater than 50 °C are employed for a long period of time a conventional cycloaliphatic amine-based floor will begin to soften. Benzyl alcohol plasticizer, which is present in all for­ mulated cycloaliphatic amine curing agents, is responsible for this effect. In contrast, the waterborne floor fully cures without benzyl alcohol and therefore allowing a significantly higher temperature resistance. The temperature-dependant hardness profiles are shown in Figure 11. Using the rule of thumb that a Shore D value of approxi­ mately 60 is required to accept traffic, the cycloaliphatic floor softens at about 50 °C, whereas the waterborne floor exhibits sufficient hardness up to 120 °C.

10.28.13.2

Chemical Resistance

The water-based epoxy self-leveling floor was evaluated for chemical resistance using a spot test method. Shore D hardness has been measured prior to chemical exposure and acts as a reference point for the analysis. After 7 days exposure to the test reagents Shore D hardness of each sample was re-measured. The percent hardness retention is calculated and gives an

100

indication of the severity of chemical attack. After an additional 24 h period a second measurement of Shore D hardness was obtained to determine the extent of recovery after evaporation of absorbed material. The results obtained are given in Figure 12. Results indicate that the self-leveling floor based on the new waterborne curing agent offers good resistance to water, etha­ nol, toluene, and 1,1,1-trichloroethane. The results are comparable to a standard cycloaliphatic epoxy floor system. The new-generation waterborne technology allows the formulation of waterborne high film build coatings with unique performance properties that are complementary to well-established solvent-free cycloaliphatic curing agent floors. The water vapor permeability of the waterborne self-leveling floor expands the range of applications for epoxy technology, allowing the formulator to apply floors in areas where osmotic blistering has been previously observed. For example, floors below grade or floors where a damp proof membrane is absent or has started to fail. Another new dimension in waterborne flooring technol­ ogy is the development of a matte surface and the absence of amine carbamation. The latter property allows floor coatings to be applied in colder and more humid conditions than currently possible with conventional solvent-free epoxy systems.

Shore D Waterborne

80

60 Cyclo-adduct

40 20

40

60

Figure 11 Temperature resistance of epoxy self-leveling floors.

80 100 Temperature (°C)

120

140

534

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

(a) 100

Shore D (% hardness retention)

90 80 70 60 50 40 30

7-day exposure

24-h recovery

7-day exposure

24-h recovery

20 10 0

1,1,1-TCE

71% H2SO4

11% AcOH

Toluene

Ethanol

30 20 10 0

Methanol

100 90 80 70 60 50 40

Water

Shore D (% hardness retention)

(b)

Figure 12 Chemical resistance test – 7 days contact time plus 24 h recovery time: (a) Epilink® 701 SL system, and (b) Anquamine® 1618 SL system.

10.28.14

Low-Emission Industrial Floorings

Current VOC legislation and material hazard classification are the tangible results of ongoing efforts to establishing a safe environment for professional applicators working with reactive systems. Increased environmental awareness in society and industry has turned the spotlight on ‘green’ technologies that meet the safety requirements both during the construction stage and during the lifetime of the building in service. Emerging EU regulations for the protection of inhabitants against hazardous emissions from building materials targets the enforcement of high indoor air quality. Waterborne epoxies have long been recognized as the technology of choice for high-performance flooring systems offering features including low odor, VOC compliance, easy handling, and clean up. In addition, this chapter will present recent advancements of waterborne epoxies that demonstrate the ability to formulate high-performance systems which are compliant to anticipated emission and out-gassing limits. Further, this chapter will pre­ sent the performance advantages of the latest waterborne epoxy curing agents offering high mechanical and chemical protec­ tion for concrete. For more than a decade, the coating industry has been working to reduce the VOC of formulated paints, varnishes,

and refinishing products in accordance with European guide­ lines. The solvent emissions directive, 1999/13/EC, introduced limits for volatile organic solvents from a so-called installation or stationary unit where a VOC was defined by its vapor pres­ sure at ambient temperature. Council Directive 2004/42/EC, also referred to as the ‘deco paint directive’, specifies VOC by its boiling point at ambient pressure and sets maximum limits of VOCs released into the environment for different types of coatings and varnishes. In both cases, the VOCs are released during the application of the paint or varnish until the point of dry film formation. In this respect, low VOC paints contribute positively to occupational health and safety. In the area of two-pack epoxy coatings and flooring products, the ongoing legislative and technical advances have made waterborne systems a fundamental solution to the market requirements. Many waterborne epoxies are formulated without volatile solvents and use merely water as a diluent lead­ ing to ultra-low, or even zero, VOC paints and varnishes.46 When a paint or flooring product is applied and has formed a dry film, the structure is taken back into service. Construction products, once applied, may be considered as inert materials with long service times, although there are exceptions. This was recognized in directive 1989/106/EEC essential requirement number 3, which targets protection of inhabitants from

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exposure of hazardous emissions coming from building mate­ rials.47 At the moment, many activities are ongoing at the European level to build our understanding in these areas in order to develop sound legislation for the future. With respect to the construction industry, the technical working group of the European committee for standardization (CEN TC 351) is charged with completion of EU mandate M/366.48 This is essential to develop new methods to assess hazardous emis­ sions from construction products. In support of this, the European Collaborative Action (ECA) has published several documents where Reports 18 and 24 have particular relevance to emission from flooring products.49,50 Coatings and flooring products based on two-pack thermo­ set epoxies have been widely used in the construction industry. Their excellent adhesion with high mechanical strength and chemical resistance offers solid protection of the concrete sub­ strate. Here, conventional technologies are frequently formulated with nonreactive components. These components often include plasticizers required for delivering high perfor­ mance, but these may also contribute to emissions during the lifetime of the building in service. The primary objective of the chapter is to address these shortfalls using a two-pack water­ borne epoxy system that delivers high end-performance, required for good protection.

10.28.15

Path to Low-Emission Floorings

3 days

The evaluation of the exposure consequences from VOC emis­ sions of cured flooring products to inhabitants and employees can be viewed as a three-stage process. In the first stage a certain test method for evaluation of floor specimens is selected that defines preparation conditions and conditions during testing. Using this method, emission components are analyzed and characterized. The floor specimen is found suitable when the data generated meet the requirements set forth by an accepted interpretation scheme. International technical work to under­ stand critical test parameters and round robin testing between laboratories led to the introduction of EN-ISO 16000 for the

assessment of accumulated emissions from construction pro­ ducts. In this standard, cured floor specimens of 1 m2 applied on a substrate are evaluated for emissions up to 28 days at ambient conditions using a so-called emission chamber. The chamber method using a floor specimen applied onto a sub­ strate is generally accepted to offer best comparison with a real-life situation. Further, for the evaluation of emission components, ECA Report 18 defines the concept of ‘lowest concentration of inter­ est (LCI)’. LCI is defined as a critical level of emission of a single component reported in μg m−3, below which a healthy indoor air quality for inhabitants and users during long-term contin­ uous use is established. LCI values have been determined for many chemical substances.51 Based on these values, the German AgBB committee52 has proposed an interpretation scheme as outlined in Figure 13. This scheme validates the accumulated emission products at 3, 7, and 28 days after applying the flooring product.53 EN-ISO 16000 divides emis­ sions in subclasses with the following definitions: • VOC. Volatile organic component ranging between C6–C16 • TVOC. Total VOC, accumulated VOC of products ≥ 5 μg m−3 ranging between C6 and C16 • SVOC. Slow VOC > C16–C22 • ΣSVOC. Total SVOC, accumulated SVOC of products ≥ 5 μg m−3 with > C16–C22. The first measurement of the flooring sample is taken at 3 days after application and curing at 23 °C and 50% relative humidity (RH). The emission limits are met when TVOC3 ≤ 10 mg m−3 and categories 1 and 2 carcinogenic substances54 are less than 0.01 mg m−3. When the emissions are less than 50% of the criteria, a second measurement after 7 days may be considered. If this measurement demonstrates less than 50% of the 28-day emission requirements, the floor specimen passes the emission testing. The 28-day emission measurement, however, requires the flooring product to comply with additional requirements, which each have more stringent limits than the 3 days data point. In the following order the 28-day requirements are

TVOC3 ≤ 10 mg m–3

no

yes

Carcinogenics: Σ ≤ 0.01 mg m–3

no

28 days

yes

TVOC28 ≤ 1.0 mg m–3

no

yes

Σ SVOC28 ≤ 0.1 mg m–3

no

yes

Carcinogenics: Σ ≤ 0.001 mg m–3

no

yes

VOC with LCI: R = ΣCi/LCIi≤ 1

no

yes

VOC w/o LCI: Σ VOC28 ≤ 0.1 mg m–3 yes

Product suitable for indoor application Figure 13 AgBB evaluation scheme.

535

no

Product unsuitable

536

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TVOC28 ≤ 1.0 mg m−3; ΣSVOC28 ≤ 0.1 mg m−3; carcinogenic substances ≤ 0.001 mg m−3; substances with reported LCI value, R = Σ (Ci/LCIi) ≤ 1; while substances without any known LCI value need to demonstrate an accumulated VOC28 ≤ 0.1 mg m−3. In general, flooring products with low emissions find their application in the electronics industry where this feature is paramount in the manufacture of high-quality electronic components. More specifically, flooring products that meet the above AgBB requirements are suitable for use in the institutional and domestic flooring markets. Examples of these include schools, hospitals, and nursing homes where inhabitants and users experience either prolonged exposure to flooring emissions or simply require additional care.

10.28.16

Water-Based Low-Emission Formulation

High film build floor systems offer a high level of protection to the concrete substrate. Flooring systems based on Anquamine® 735 curing agent have low odor and can be formulated free of VOCs as defined by the deco paint directive. The application of coatings in confined spaces limits the use of solvents and other volatiles, due to odor and regulatory constraints. This is equally important for sensitive application areas such as schools, offices, or hospitals which can stay occupied during application. As discussed previously, increasingly stringent regulations will further limit emissions from flooring systems during the lifetime of the coating. Conventional epoxy flooring products are frequently formulated with nonreactive components, such as benzyl alcohol, which has resulted in substantial emission levels above the proposed limits.55 Self-leveling coatings based on Anquamine® 735 curing agent are fully reactive and contain no plasticizers or solvents and therefore offer a compliant system. The self-leveling 3-component (3K) flooring formula­ tion, as described in Figure 14, has been evaluated for emission levels according to the German AgBB Scheme (Figure 13) for the evaluation of emissions from building products on a 2.5 mm floor applied on concrete. The results are shown in Figure 15. After 3 days cure of the floor specimen at ambient tempera­ ture and 50% RH, a first specimen is analyzed for emission products. Figure 15 showed only 1% emission of VOC

A-component 1. Anquamine® 735 2. Defoamer 3. Pigment TiO2 4. Thixotropic agent 5. Water B-component 6. Epoxy resin C-component 7. Fine quartz powder 8. Quartz powder 9. Quartz sand (0.1–0.3 mm) Total

Self-leveling floor – 3K 10.00 0.70 3.70 0.07 10.53 25.00 9.00 12.00 28.00 35.00 75.00 109.00

Figure 14 Anquamine® 735 self-leveling floor formulation.

(C6–C16) components of the maximum norm and no detection of any carcinogenic substances. As a result of this extremely low emission, a second emission determination was taken after 7 days cure instead of the required 28 days. It should be noted that the maximum allowed emission limits after 28 days are much more stringent than those at 3 days because only 10% of the 3-day emissions are allowed. Despite this, emission levels at 7 days cure were found at only 10% of the 28-day limits (or 1% of the original limit set for 3 days). In addition, the R-value of components with a reported LCI was determined at less than 35% of the maximum allowable value at 28 days. Also the accumulated VOC (ΣVOC28) of compo­ nents without a reported LCI value was extremely low, that is, 5% of the 28-day maximum. These results clearly demonstrate that Anquamine® 735 curing agent self-leveling formulation exceeds the AgBB criteria and can be categorized as a low-emission flooring system. The data demonstrate that the system will meet the stringent future regulations in Europe and will have low emissions ideal for applications in the electronics industry or where low odor and tainting is of importance. Water-based flooring systems provide comprehensive tech­ nical advantages over competitive technologies. They prove the high esthetics and durable protection of concrete. Increased environmental awareness in society and industry has turned the spotlight on ‘green’ technologies that meet the safety requirements both during the construction stage and during the lifetime of the building in service. Modern water-based curing agents like Anquamine® 735 curing agent can be for­ mulated without any solvent to result in zero VOCs. In addition, Anquamine® 735 curing agent-based flooring systems have been demonstrated to comply with emerging EU emissions regulation as set forth by the German AgBB protocol. Test data reported here highlight that a flooring system has less than 5% of the required emission limits (TVOC and ΣSVOC). In particular, Anquamine® 735 curing agent has applicability in the institutional and domestic flooring markets where continuous exposure to flooring emissions is present. Another flooring application focused on low emissions is the electronics industry. Here, the requirement for low emissions is paramount enabling the manufacture of high-quality electronic components. Finally, technology discussed here has potential application in the indus­ trial flooring sector, which ultimately may also move toward low-emission requirements. Given this, waterborne epoxies will continue to be the technology of choice for high-performance flooring systems for future applications.

10.28.17

Time Is Money

Self-leveling water-based flooring system, as described earlier, offers rapid property development, allowing for a quick return to service. The fast property development is demonstrated at 23 °C and 10 °C indicating that even at low temperatures the system will produce a walk-on hardness after 24 h. The system will withstand light traffic after limited cure time, allowing the floor to be back in service after application of or overcoat with a further decorative surface finish much quicker than competitive technologies. This has the advantage of reducing the time a floor will be out of service which has economic and logistical advantages.

Sustainable Manufacturing, Processing and Applications for Polymers and Polymer Systems | Water-Based Epoxy Systems

3 days

7 days (28 day limits)

100 Emissions (% of max limit)

10

75

7.5

50

5.0

25

2.5

10 0

1%

537

0%

TVOC Σ Carcino­ (C6–C16) genics

1%

0%

0%

TVOC ΣSVOC Σ Carcino­ (C6–C16) (C6–C16) genics

0

Figure 15 Emission results of self-leveling floor based on Anquamine® 731.

Self-leveling coatings based on Anquamine® 735 curing agent provide a desirable satin/matt finish to lessen the visibi­ lity of floor defects and reduce scratch sensitivity. However, the surface is very adaptable and can be modified to produce highly decorative surface appearances. Due to the inherent good overcoat ability the self-leveling floor can be readily coated with a transparent sealer or topcoat to produce a high-gloss or decorative finish with improved chemical resis­ tance and cleanability.56,57 The surface can be easily modified by broadcasting sand or pigment effects and then sealing with a transparent topcoat such as industrial two-component polyur­ ethane coatings, waterborne polyurethane/acrylic hybrid dispersions, or a two-component waterborne epoxy system to offer highly decorative or nonslip flooring. The self-leveling system also offers a high level of protection to the substrate, protecting it from abrasion, impact, and che­ mical spill. Commonly applied concrete such as C25/30 offers a standard level of performance which is acceptable for general purpose use. Such concretes will require a protective coating in order to enable a wider variety of uses such as forklift traffic and chemical exposure.

10.28.18

Conclusions

The new generations of waterborne technology address the need for environmentally friendly systems on the one hand, and higher performance on the other. Waterborne curing agent solutions, emulsion, and dispersion technology employs high molecular weight amines with very low free amine content that proves to be beneficial from a health and safety perspective. This is evident by improved labeling and risk classification when compared to conventional solvent-free systems. Additionally, there is no need for reactive or nonreactive dilu­ ents in the final formulations, which provides improved safety during mixing, application, and in-service use. The perfor­ mance envelope has been expanded from traditionally water-based floor primers and paints to self-leveling floors, fillers, and adhesives, to epoxy-cement-concrete systems and fiber reinforced concrete to yield higher mechanical properties. The unique properties of waterborne self-leveling epoxy floors expand the range of applications in areas where traditional

solvent-free systems cannot be used. The improved esthetics and handling allow for a wide range of applications including wall and topcoat applications offering improved scratch resis­ tance and UV stability. The ability to formulate emission-compliant systems has applicability in the institutional and domestic flooring markets where continuous exposure to flooring emissions are present. Another flooring application focused on low emissions is the electronics industry. Here, the requirement for low emissions is paramount enabling the manufacture of high-quality electronic components. Given this, waterborne epoxies will continue to be the technology of choice for high-performance flooring systems for future applications.

References 1. Richardson, F. Pigment Resin Technol. 1973, 5, 41–43. 2. Klippstein, A. H., Wäßrige Epoxidharzsysteme, Farben und Lacke im Spannungsfeld Mensch/Umwelt, Vortragsveranstaltung VILF, 1997; Klippstein, A.; Lohe, M.; Cook, M., Water-Based Epoxy Flooring Systems under Environmental Aspects, European Coating Show/4th European Congress on Construction Chemicals, Nürnberg (2003). 3. Stoye, D.; Freitag, W. Lackharze; Carl Hanser Verl: München, Wien, 1996. 4. Wicks, Z. W.; Jones, F. N.; Papas, S. P. Organic Coatings: Science and Technology; John Wiley and Sons: New York, 1992; Vol. 1. 5. Wicks, Z. W.; Jones, F. N.; Pappas, S. P. Organic Coatings: Science and

Technology; John Wiley and Sons: New York, 1992; Vol. 1; pp 173–174.

6. Bolgar, L. GB Patent 1,108,558, 1965 (Thomas Swan). 7. Alford, J. A. U.S. Patent 4,013,601, 1977 (Westvaco). 8. Ashjian, H.E.; Gawel, H.A.; Blakely, A. K., DE Patent 2519390, 1975 (Mobil Oil). 9. Shackelford, W. E., GB Patent 1,242,783, 1969 (General Mills). 10. Richardson, F. B. Waterborne Coatings, Surface Coatings 3; Elsevier Scientific Publishing: New York, 1990; pp 229–254. 11. Richardson, F. B. Polym. Paint Colour J. 1982, 714–715. 12. Richardson, F. B. U.S. Patent 4,526,721, 1985 (Thomas Swan). 13. Moes, N.S.; Small, M. P. U.S. Patent 4,089,826, 1975 (Ciba Geigy). 14. Neffgen, B.; Allewelt, K. H. Pitture e Vernici 1985, 91 (5), 33–43. 15. Nelson, I. Polym. Paint Colour J. 1982, 251. 16. Darwen, S.P.; Cornforth, D. A. U.S. Patent 5,246,984, 1993 (Air Products). 17. Dubowik, D. A. Proceedings of the Epoxy Resin Formulators Conference 1995. 18. Walker, F.H.; Everett, K.E.; Kamat, S. Proceedings of XXII Waterborne, High-Solids and Powder Coatings Symposium. 1995, p 88. 19. Klippstein, A. WO Patent 93/21250, 1993 (Akzo). 20. Kurnik, W. J.; Roy, G. A. Am. Paint Coat. J. 1989, 36–44.; Shimp, D. A., U.S. Patent 4,246,148, 1981. 21. Toshiaki, N.; et al. European Patent 548,493 A1, 1993.

538

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22. Walker, F.H.; Cook, M.I.; Dubowik, D. A. Proceedings of XXII Waterborne, High-Solids and Powder Coatings Symposium 1996, p 289. 23. Jackson, M. A. J. Protective Coat. Linings 1990, 54–64.; Galgocci, E. C.; Weinmann, D. J. Proceedings of XXII Waterborne, High-Solids and Powder Coatings Symposium 1995, p 119. 24. Galgocci, E.C.; Weinmann, D. J. Proceedings of XXII Waterborne, High-Solids and Powder Coatings Symposium 1995, p 119. 25. El-Aasser, M. S.; Vanderhoff, J. W.; Mirsa, S. C.; Manson, J. A. J. Coat. Technol. 1977, 49 (645), 71. 26. Wegman, A. J. Coat. Technol. 1993, 65 (827), 27. 27. Gillham, J. K.; Wisanrakkit, G. J. Coat. Technol. 1990, 62 (783), 35. 28. Richardson, F. B. In Waterborne Coatings; Wilson A. D.; Nicholson, J. W.; Prosser, H. J., Eds.; Elsevier: Barking, New York, 1990. 29. Walker, F. H.; Cook, M. I. In Technology for Waterborne Coatings; Glass, J. E., Ed.; ACS Symposium Series 663, American Chemical Society: Washington, DC, 1997. 30. Richardson, F. B. Water-Borne Epoxy Coatings: Past, Present and Future, Modern Paint and Coatings, April 1988. 31. Klippstein, A. H. WO Patent 93/21250, 1993 (Akzo Nobel). 32. Lohe, M.; Cook, M. I.; Klippstein, A. H. Macromol. Symp. 2002, 187, 493–502. 33. Lohe, M.; Cook, M.I.; Walker, F. H., Waterborne Epoxy Technology: A New Route to Ambient Cured Thermosets, FSCT Midyear Symposium, 12–14 May 2004. 34. Lohe, M.; Cook, M.; Klippstein, A. EP 1544230, 2003 (Air Products). 35. Lucas, P. A.; Shah, D. N.; Raymond, W. J. Protective Coat. Linings July 2002. 36. 5th. International Colloquium Industrial Floors 2003 Stuttgart. 37. Critchfield, F. E.; Johnson, J. B. Anal. Chem. 1956, 28, 430. 38. Wright, H. B.; Moore, M. B. J. Am. Chem. Soc. 1948, 70, 3865–3866. 39. Katchalski, E.; Berliner-Klibanski, C.; Berger, A. J. Am. Chem. Soc. 1951, 73, 1829–1831. 40. Lucas, P.; Clark, P.; Haney, R.; Kittek, M.; American Concrete Institute Conference, Seattle, Washington, 1997. 41. Pfaff, F. A.; Gelfant, F. S. J. Protective Coat. Linings 1997, 52–64. 42. Arcozzi, A.; Arietti, R.; Bongiovanni, R.; et al. Surface Coat. Int. 1995, 4, 140–143. 43. Lyssy, G. H. Coating 1977, 8, 204–205.

44. TNO Netherlands, private communication. 45. Hall, C.; O’Connor, S. J. Protective Coat. Linings 1997, 2, 86–102. 46. See, for example, Anquamine® 721 curing agent, technical datasheet, Air Products and Chemicals, Inc. 47. Council Directive 89/106/EEC of 21 Dec 1988 on the approximation of laws, regulations and administrative provisions of the Member States relating to construction products, OJ L 40, 11 Feb 1989; often referred to as “Construction Products Directive (abbrev. CPD)”. 48. Mandate M/366 “Development of horizontal standardized assessment methods for harmonized approaches relating to dangerous substances under the Construction Products Directive (CPD)”, EU Commission, DG Enterprice, Brussels, 19 Mar 2005. 49. European Collaborative Action “Indoor Air Quality and Its Impact On Man”, Evaluation of VOC emissions from building products; solid flooring materials (Report no. 18), EUR17334EN, European Commission, Joint Research Centre, Environment Institute, 1997. 50. European Collaborative Action “Urban Air, Indoor Environment and Human Exposure”, Harmonisation of indoor material emissions labeling systems in the EU; inventory of existing schemes (Report no. 24), EUR21891EN, European Commission, Joint Research Centre, Institute for Health and Consumer Protection, 2005. 51. See, for example, for a recent list of substance LCI values: Ausschuss zur Gesundheitlichen Bewertung von Bauprodukten (AgBB), “Bewertungsschema für VOC aus Bauprodukten”, Part 3, 1 Mar 2008. 52. AgBB – Ausschuss zur Gesundheitlichen Bewertung von Bauprodukten. 53. AgBB – Ausschuss zur Gesundheitlichen Bewertung von Bauprodukten id. 11, Part 1 and 2. 54. Definitions per EU Dir 67/548/EEG. 55. Glöckner, Statement der Deutschen Bauchemie; presented at: “Zweite Fachgespräch zur Vorgehensweise bei der gesundheitlichen Bewertung der Emissionen von flüchtigen organischen Verbindungen (VOC) aus Bauprodukten”, DIBt, Berlin, 25 Nov 2004. 56. Lim, T. J.; Galgocci, E. C.; Walker,, F. H.; Yoxheimer, K. A. Eur. Coat. J. May 2005, 24–30. 57. Anquawhite® 100 curing agent, technical datasheet, Air Products and Chemicals, Inc.

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Biographical Sketches Achim Klippstein has worked in the paint industry for more than 30 years, following his degree in chemistry. After 10 years of research and development work for Akzo-Nobel on epoxy curing agent, he joined Air Products Netherlands as Technical Manager in the Performance Chemicals Division. In 1997, he was appointed as Business Development Manager Europe and this role was extended in 2005 to North America. In 2009, he was promoted to his current position as Global Business Development Manager for epoxy amine curing agents. Achim Klippstein is the inventor of several key patents for waterborne amine curatives.

Michael Cook obtained a BSc in chemistry (1981) and a PhD in organic chemistry (1985) from Birmingham University (UK). He then conducted postdoctoral research at Clemson University in organofluorine chemistry before joining Anchor Chemicals (UK), now Air Products & Chemicals Inc. in 1986. After working as a research chemist in the design and applications of amine-based systems for epoxy resins both in the United Kingdom and in the United States, in 1997 he was appointed as technology manager for the Epoxy Additives European applications group based in Utrecht (the Netherlands). In 2005 he was appointed as the global technology manager for the Epoxy Additives business, responsible for new product development in amine curing agents designed for use in a range of market segments, including civil engineering, coatings, and composites.

Stephen Monaghan obtained a BSc (Hons) in chemical physics from the University of Glasgow, UK, in 1996 and received a PhD from the University of Strathclyde, UK, in the field of physical chemistry in 2000. Since joining Air Products in 2003, he has specialized in the field of waterborne epoxy curing agents and is currently the Sales Manager for the Air Products Epoxy Additive group for Northern Europe.