Converting of Polymer Packaging (Composite Packaging)

3

Converting of Polymer Packaging (Composite Packaging)

„„3.1 Technology of Converting Converting means upgrading of a packaging material. A monolayer web (single layer) can be converted to a multilayer composite through a suitable procedure to get better performance. Better performance means better mechanical properties like sealing or puncture strength. It may also mean better barrier properties against light, oxygen, moisture, or aroma or better ESCR (environmental stress crack resistance). Converting may also fulfill marketing aspects like an attractive surface through special printing, lacquering, or a soft touch. Better performance can already be achieved by blending resins or mixing additives into a basic resin. Also, radioactive treatment of some packaging films offers better mechanical properties, like tensile strength or sealing strength. But generally we understand converting to be the creation of one or more functional layers on a monolayer web to get a high-performance composite. In this chapter we shall deal with the usual converting processes for packaging webs, like coating, lamination, vacuum deposition, or treatment of packaging webs with radioactive rays.

84 3 Converting of Polymer Packaging (Composite Packaging)

3.1.1 Modes of Converting Packaging Material 1. Blends/Additives

A mixture of different components that gives the optimum property. Additives are the simplest way of converting and can be done with an extruder, which is necessary to produce a monolayer (single) web. Trials are necessary to optimize the processing and application. A sound knowledge of the compatibility of different materials and the legislative regulations is necessary.

2. Coextrusion

The target is to produce a multilayer web with superior functionality. This involves modification of a basic web with functional layers, like a high barrier, a colored layer, or better mechanical properties. In most cases the polymers are not compatible with each other, so suitable tie layers are necessary to bond the multilayer structure. The tie material is also supplied as a resin. Each polymer and tie material needs an extruder. The bonding of functional layers takes place with tie layers already in the melt phase. Coextrusion has versatile possibilities of application. Critical layers like a recycled layer should not be placed inside, to avoid direct contact with a product like food (see Section 2.1.1).

3. Coating

A basic web called a substrate is coated with a functional layer. The substrate may be a polymer film like PET, PVC, or PE or a nonpolymer like paper, cardboard, or aluminum foil. The functional layer may be a sealing layer, a high barrier layer, or a layer with a releasing function. Sometimes two or more coating processes can take place simultaneously to reduce cost, but the machines are expensive. Extrusion coating Molten functional resin is coated on a substrate, mostly as a sealing layer. A primer is necessary for proper bonding of the polymer with the substrate. Lacquer coating The functional polymer is applied as a solution or as a dispersion (insoluble). The solvent or dispersion liquid has to be evaporated.

4. Lamination

Lamination is an important upgrading process. It means combining two or more webs with a suitable adhesive for better functionality. The webs are also called substrates. They can be polymer film, paper, cardboard, or metal foil. Extrusion lamination The webs are bonded with a layer of molten polymer. Dry lamination The webs are bonded with a water-free (organic solvent) adhesive. Wet lamination The webs are bonded with water-based adhesive.

5. Vacuum deposition

The functional material is evaporated under high vacuum for vacuum deposition on a suitable substrate. Materials are mostly aluminum or an inorganic material like SiOx or AlOx. These are also called target materials.

6. Radiation

Upgrading of polymer packaging webs or flat tubes can also take place through radiation. Properties like tensile strength or sealing strength can be increased through tailor-made radiation with beta-rays.

7. Foaming

Upgrading of packaging webs or injection-molded parts can take place through foaming. The weight of the pack can be reduced, stiffness can be increased, and in some cases a whitening effect is possible. There is cost reduction of waste through weight reduction.

3.1 Technology of Converting

3.1.2 Technology of Coating A substrate is coated with one or more suitable functional solutions or dispersions. The substrate may be a polymer film like PET, paper, cardboard, or aluminum foil. A few typical terms or nomenclature that are used during the coating or lamination process are defined below. Adhesion

Bonding between two different layers or webs

Air knife

Air from a longish nozzle used to scrape off surplus lacquer

Bond strength

Ultimate adhesion strength between coated layer and substrate or between two substrates after coating or lamination

Coating

Create a layer on a substrate

Coating amount

Amount of lacquer or adhesive in g/m2 on a substrate.

Cohesion

Bond strength in a layer of adhesive or web (tensile strength)

Corona treatment

Adjustment of surface tension through electrical discharge

Curing

Cross-linking reaction of prepolymers to an ultimate net-like structure like polyurethane adhesives or UV curing

Curing time

Time for curing. Depends upon adhesive type and curing temperature

Doctor knife

A blade with which surplus lacquer is scraped off from the substrate

Drying

Removing the solvent from adhesive or lacquer with hot air

Green tack

Bond strength between substrates just after lamination before curing

Hot melt

Mixture of molten wax and polymer of lower molecular weight for sealing or adhesive purposes

Laminate strength

Bond strength between two substrates after curing

Primer

Agent used for increasing adhesion between adhesive and substrate

Pot life

Time up to which the viscosity of a two-component lacquer or adhesive is low enough for processing. Processing is not possible after this time as the viscosity gets too high through cross-linking

Residual solvent

Traces of solvent in a composite packaging material after curing or drying. It should be as little as possible. There are legislative limits on it

Substrate

Film, sheet, paper, board, or foil to be coated or laminated

Generally a substrate is treated with a corona to modify the surface tension so that the wettability of an adhesive or coating liquid is increased. This means that the adhesion force of adhesive or coating liquid on a substrate increases. If the adhesion is still poor, then a suitable primer is used on the corona-treated side. The bond strength of adhesive on substrate increases. 3.1.2.1 Extrusion and Coextrusion Coating For extrusion coating, a polymer is melted in an extruder and squeezed from a coat hanger die on the substrate (Fig. 3.1). The layer thickness is generally 20 to 60 μm. With modern technology a layer thickness of 10 μm is possible. Such thin layers of polymers are an alternative to lacquer coating, which generally has a thickness

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around 5 μm. The substrate is treated with corona or coated with primer to offer better adhesion for the coating material. The primer must be dried to get free from the solvent. The substrate is pressed with the coated layer between nip rolls. One nip roll is rubber coated, and the other roll is a highly polished, chromium-plated steel roll, and is cooled. The hardness of the rubber layer must be exact to ensure a constant pressure at every position on the substrate. The composite is then rolled up. The extrusion-coated layer is usually the sealing layer of the composite. Extruder PE, PP, PA, PET, Copolymers

Coating – Sealing function – Seal-peel-function – Protection layer – No curing

Chill roll

Unwinding Substrate 1 Paper, Carton, Al, Laminate, Polymer film

Winding up

Figure 3.1 Extrusion coating

For coextrusion coating, the number of molten layers is more than one and the same for the number of extruders. Usually a tie layer is molten to ensure high adhesion of the main coating layer with the substrate. Generally no primer is necessary. 3.1.2.2 Coating with Lacquer Lacquer means a solution of polymer in a suitable organic solvent. The solvent adjusts the viscosity of the solution for coating. After coating, the solvent is dried out so that a layer of the polymer material develops on the basic substrate (Fig. 3.2). This type of coating is usual in the packaging field and is used for versatile purposes. Typical applications are listed in Table 3.1.

3.1 Technology of Converting

Dryer Coating unit (80 °C – 300 °C Air) Cooling Unwinding

Winding up

Figure 3.2 In lacquer coating, the solvent has to be removed in a dryer

Table 3.1 Typical Lacquer Applications Type of lacquer

Examples of function

Print protection lacquer

Mechanical protection of printing ink

Primer lacquer

Lacquer for better adhesion

Inner lacquer

Lacquer in Al tubes or cans to avoid chemical reaction between the product and packaging material

Heat seal lacquer

For heat sealing between two partners. Generally on die-cut lid to seal on cups or trays

Special lacquer

Special effects for sales promotion

Depending on the application there are different types of lacquer, including solvent based, solvent free, water based, dispersion, UV curing, electron beam curing, high solid, and low solid. The system chosen depends upon the application of the packaging material. A lacquer is generally formulated with following ingredients: ƒƒPolymer resin, also called binder ƒƒSolvent, mostly organic liquid but sometimes also water to dissolve or disperse the resin ƒƒPigments, or coloring agents of inorganic basis ƒƒColoring agents of organic basis ƒƒOrganic fillers for special effects, e.g., to adjust the viscosity ƒƒDifferent additives for different properties like quick drying The binder of a lacquer may be of different types: a cellulose nitrate, acrylate, or a two-component polyurethane system is used in a primer or in a print protection lacquer. Heat-seal lacquers (HSL) are generally acrylate, PVC copolymer, and terpolymers.

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There are different roller arrangements on coating or lamination machines. Depending on the application, there may be a double roller or reverse roller, with or without an air knife. Depending on the desired thickness of the coated layer, the number of rollers is different. For solvent-free adhesives with very thin layer thicknesses of only 1 to 2 μm, generally four-roller systems are used to generate a homogeneous layer. 3.1.2.3 Coating with Polymer Dispersion Dispersion lacquers are insoluble mixtures of a solid polymer in a liquid, most often water. Fine polymer particles are dispersed with stabilizing agents in water. The stabilizing agents hinder gelation of polymer particles into big agglomerates. A common application of dispersion coating is to convert substrates like PET, polyethylene, or paper with PVdC into high barrier composites. In comparison to EVOH as a high barrier material, PVdC offers a high barrier both against oxygen and moisture. Because PVdC is not sensitive to moisture, it can be coated on the outside of any substrate and can be used in any climate. The dispersions are unstable systems and are homogenized with an emulsifier. At very low temperatures, gelation may take place, which destroys the dispersion. It is important to handle a PVdC dispersion at temperatures around 10°C or higher. Another important factor is the drying process of dispersions. Because a lot of water has to be evaporated and the boiling point of water (100°C) is higher than the boiling points of common organic solvents like ethyl alcohol (78°C) or ethyl acetate (77°C), more energy is necessary for evaporation. Generally an infrared radiator dries the substrate just after coating and before it is diverted into the dryer. The temperature of the hot air in the dryer should not be too high. The substrate may shrink critically. Moreover, the shrinkage may be so great that the calculated number of roll stocks cannot be cut out of the mother roll. Particularly for substrates like LDPE, EVA, or ionomers, it should not exceed 70°C. One should be cautious also for substrates like CPP or BOPP. An ideal PVdC dispersion coating arrangement can be seen in Fig. 3.3. PVdC latex has to be stirred continuously and pumped through a suitable filter to free the dispersion from bigger agglomerates. Afterwards the dispersion is circulated through the coating pan to avoid any gelation in the system. A suitable defoaming agent has to be applied to avoid foaming during coating, or otherwise the coated layer is not homogeneous. The concentration of defoaming agent should not be too high because it can disturb proper adhesion of the PVdC onto the primer layer.

3.1 Technology of Converting

Figure 3.3 PVdC dispersion coating, courtesy of Matthias Huter, Solvay

In all coating or lamination processes, the substrate has to be corona treated; in particular for polyolefin substrates it is very important. Polyolefin films must have already been corona treated during production on a blown or chill roll line. A second treatment of corona on the same side of the film at the coating line is necessary. Trouble in bond strength arises if these requirements are not fulfilled. It is less critical to coat a substrate with PVdC dispersion to make a high barrier web than an extrusion or coextrusion coating with molten PVdC. Although the thermal stability of modified PVdC resin with a suitable comonomer is better, or a suitable tie-layer can reduce the thermal dissociation of PVdC, coating with a dispersion can be considered to be a more secure process than extrusion.

3.1.3 Technology of Lamination In order to fulfill all requirements in packaging a product, different webs are combined into a composite. One possibility is a coating, which has been discussed. Another procedure is lamination in which two or more substrates like paper, film, sheet, or foil are combined with a suitable adhesive. The roll stocks of webs should be absolutely horizontal, without waves, the cut sides must be straight without telescoping, and the web tension should be tight and homogeneous. If a substrate is not polarized enough like PVC, it has to be corona treated. During corona treatment the same side of the web has to be treated that was already corona treated during manufacturing of the web, e.g., blown film.

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If corona treatment had not been done during manufacturing of a polymer film, a treatment before coating or lamination does not help much. A critical fault is to treat the false side of the web with corona. First, the grade of corona treatment is not high enough, so the bond strength is insufficient, and second, the other side, which was selected as the sealing side, would not seal properly. The choice of adhesive for a particular lamination depends mainly upon the pair of substrates to be laminated and the mode of use of the laminate. All of these criteria influence the laminate strength of a composite, their technical applicability, and also the question of migration of different components of the adhesive into the packaged food. Another critical case is lamination on the printed side. Particularly in triplexes (three-layer composites) like PET/Al/PE 12/8/60 μm, the back side of the PET film is printed first, which is called reverse printing. The PET film itself gives some mechanical protection to the printed matter. The adhesive is fixed on both the PET film and also on the printing ink. Therefore, the laminate strength is not only determined by the compatibility of the adhesive between PET and Al, but also for its compatibility between ink and aluminum. Laminates for flexible pet food pouches of the type PET/Al/PP are manufactured in this way. The pouches are even retorted after filling at 125°C for 30 min. All of these criteria must be fulfilled for the successful manufacturing of such composites. 3.1.3.1 Extrusion and Coextrusion Lamination In these cases the adhesive is a molten polymer layer from an extruder. In order to coat the substrates better with the molten polymer, the viscosity of the melt is kept as low as possible at higher temperatures than the usual extrusion temperature for film manufacturing. For example, the temperature of an LDPE melt during manufacturing of a blown film is about 170°C. The temperature of molten LDPE for extrusion lamination is some 300°C—at the limit of its chemical stability. Moreover, the distance between the coat hanger die and the gap between two substrates on the rolls is as high as possible so that the melt can react with the oxygen of air to create polarized groups like aldehyde (–CHO), ketone (–C=O), or acid (–COOH) for better bonding. A better solution can be achieved with acid copolymers like EVA or EAA because their polarity is much higher than that of LDPE. Still, in most cases a primer is necessary on one or both substrates for better adhesion. Substrates also need a corona treatment when necessary. Bond strength of extrusion or coextrusion laminated composites is indeed acceptable but lower than with a PU adhesive. For critical applications like retorting, the laminates are always with a PU adhesive. An important advantage of extrusion lamination is that no curing is necessary. The composite is finished as soon as the melt has cooled down to room temperature.

3.1 Technology of Converting

Further advantages of extrusion lamination are the freedom from the solvent of the composite and high-speed production. The processing speed of carton laminates is around 800 m/min. A sketch of the principle of extrusion lamination can be seen in Fig. 3.4. Coextrusion lamination can take place in the same way. The only difference is the number of melts and accordingly of extruders.

Extruder PE, PP, copolymers

Unwinding Substrate 2 Paper, Carton, Al, Film

Chill roll

Unwinding Substrate 1 Paper, Carton, Al, Film

Winding up

Figure 3.4 Extrusion lamination

3.1.3.2 Dry Lamination, Solvent Based The word “dry” is used in many companies and means simply “free of water.” The solvents are organic compounds like ethanol or ethyl acetate. Depending on the number of substrates, the composites are called duplex (two substrates) or triplex (three substrates) and so on. Examples for duplex are Al/PE and paper/wax and for triplex PET/Al/PE and paper/Al/PE. The number of substrates may be higher depending on the application. In order to vacuum-pack sharp-edged products like a knee prosthesis, some seven layers of composite with one or more nylon layers are used. Nylon offers the highest puncture resistance among the packaging polymers. X-ray plates are packed in a seven- or eight-layer composite: one of the layers is

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with Al for absolute light resistance. Also, composites for packing photographic film have multiple layers and are absolutely light resistant. Adhesives for dry lamination are almost always polyurethane (PU)-based and may be one or two components. The component in a one-component adhesive is isocyanate. It reacts with the “OH“ group of moisture from air and from a substrate like paper that contains sufficient moisture. The most usual however is two components (Fig. 3.5). The first component is the isocyanate, and the second component is “polyol” (multiply terminated alcohol). The components and their reaction mechanisms are complicated, but they can be simplified as in the following two charts. The one-component adhesives actually have two components because moisture is necessary for the ultimate cross-linked polyurethane macromolecules (Fig. 3.6). Similarly, two-component adhesives have actually “three components” because besides polyol, the moisture (the –OH group) from the air reacts with isocyanates to undergo complex reactions. Thus, the three components are isocyanate, polyol, and moisture. In tropical countries the influence of moisture during the monsoon months is significant; the laminate strength during the monsoon months is significantly higher. I R OH +

NH C O R

NCO

O Urethane

Alcohol Isocyanate

II HO R OH + OCN Bifunctional Alcohol

NCO

Bifunctional Isocyanate

OCN

NH C O R O C NH

NCO

O O Urethane, NCO-Terminated

Figure 3.5 Typical reaction mechanism of isocyanate-based, two-component adhesives; Reactions I and II show only the reaction mechanism. The reaction products have much less mol. wt. The above reactions must propagate further to create “prepolymers” of reasonable mol. wt. to be processed on a machine to produce very high mol. wt. cross-polyurethanes

3.1 Technology of Converting

H O H+ Water

NH2 + CO2

NCO Isocyanate

NH2+ Amine

Amine

NCO Isocyanate

NH C NH O Urea Derivates

O NH C NH

+

NCO

O Urea Derivates

N C NH C O

Isocyanate

NH

Biuret

Figure 3.6 Cross-linking reaction of a one-component PU adhesive. The reaction with OH-group takes place also during 2C adhesives in competition with other OH-groups. The reactivity of Isocyanate with other groups is as follows: aliphatic amine > NH3 > aromatic amines > aliphatic urea > primary alcohol > secondary alcohol > water > aromatic urea

The adhesive components are called “adhesive” and “activator” and are supplied as “prepolymers” with a viscosity that is suitable to be coated by rolls. Prepolymers are partly polymerized components from monomers and have higher molecular weight. After lamination, less time is necessary for them to get to the final crosslinked structure. Converters mix the prepolymers according to the recipe that the supplier suggests. For example, Liofol LA 3640 (previously UK 3640) adhesive and LA 6800 (previously UK 6800) activator from the company Henkel are mixed in a ratio of 50:1. As soon as the components are mixed, the cross-linking reaction starts and the viscosity of the adhesive increases. If necessary, the viscosity of the mixture is adjusted with organic solvents for proper machinability. The supplied components (adhesive and activator) may be solvent-based (SB) or solvent-free. The molecular weight of prepolymers in solvent-based applications is higher, as is the viscosity, than in those that are solvent-free. The solvent dilutes the prepolymers to the optimum viscosity for machinability. However, the solvent has to be removed through drying, not only because it has no influence on bond strength, but also because traces of solvent may be unhealthy for humans when used to pack food. There are legislative limits on residual solvent that have to be maintained.

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Prepolymers of solvent-free adhesives have lower viscosity and can be worked on the machine without solvent. There is no need to remove any solvent, and the machines have no dryer. Due to the lower molecular weight and lower viscosity of the adhesive, the machines for solvent-free lamination are much more sophisticated than solvent-based machines. Moreover, solvent-free adhesives need a longer curing time because the prepolymers have a lower molecular weight than the solvent-based. In order to reduce the curing time of solvent-free adhesives, new generations are supplied using a higher molecular weight prepolymer. The suitable viscosity for machinability is adjusted by heating the adhesive. The application temperature may be as high as 90°C. Because isocyanates are harmful to health, an appropriate exhaust system must be installed to maintain a proper working environment. The ultimate adhesive after curing is cross-linked polyurethane with a high molecular weight, and it offers very high bond strength. The curing time is generally 7 to 14 days, depending on the humidity and temperature of the storage room. Cross-Linking Reaction of Two-Component PU Adhesive The solid content of a solvent-based adhesive is between 30 and 60% and determines how much solvent has to be evaporated. The layer thickness of the adhesive after drying is generally 3 to 5 μm. The lower value is for general-purpose packaging application. These are packages for which the application is not critical. The coating weight of the adhesive is higher if the application is critical, as in retorting or packing aggressive products with a long shelf life. The advantages of solvent-based lamination are many, like higher “green tack” (bond strength just after lamination) due to higher molecular weight prepolymers. The handling of roll stock is easier than in solvent-free lamination. The fluctuation of web tension during winding does not cause any technical disadvantage. The curing process is quicker than in solvent-free processes. The bond strength of the laminate is the highest and hence is suitable for all applications. Full and quicker curing takes place at elevated temperatures (30 to 40°C) because the speed of the cross-linking reaction is higher. Particularly for critical laminates like retortable pet food, this is very important. Disadvantages are, first, the higher amount of adhesive necessary for this process, and second, the removal of 100% of the solvent is pretty difficult. The removed solvent has to be handled properly according to legislative rules and regulations. In processing (Fig. 3.7), the substrate with a higher mechanical or thermal property is selected for coating with the adhesive. The second substrate is laminated on the first one after the adhesive has been dried. Proper corona treatment for each substrate has to be done before lamination. A primer is used if necessary. The web tension and web propagation mode of the substrates through the machine have to be adjusted. The substrate should not float sideways, and its tension should not

3.1 Technology of Converting

fluctuate. The adhesive is coated on one substrate with rolls from the adhesive pan. The adhesive viscosity has to be checked regularly and is adjusted through dilution with solvent when necessary. The dryer temperature for solvent removal is around 70°C. The second substrate is pressed with the second substrate between nip rolls on the dried adhesive, which has high tackiness. The laminate is wound up on roll stock after cooling. All films must be cooled down before winding up, otherwise deterioration of the roll stock takes place through severe heat tension.

Dryer Unwinding Substrate 2 (Al, Paper, Film)

Coating unit 2C-Adhesive (PU) 1C-Adhesive (PU) Unwinding Substrate 1 (Al, Film) Winding up

Figure 3.7 In a dry-lamination system, the solvent has to be removed in a dryer

Examples of SB-laminated composites, particularly for heat application, like pasteurizing, retorting, or microwave applications: Tuna: PET/Al/OPA/CPP Pet food: PET/Al/OPA/CPP

Rice: OA-PET/OPA/CPP (microwaveable) Soups: PET/OPA/CPP

3.1.3.3 Dry Lamination, Solvent-Free Adhesive Solvent-free adhesives are 100% solid prepolymers. There is no solvent in the adhesive. The prepolymers have a lower molecular weight than in a solvent-based system. The viscosity cannot be adjusted for machinability with any solvent. That is why the components of the adhesive are dosed directly between the first two coating rolls through a nozzle. There is no adhesive pan in this system. The curing time is generally longer than for solvent-based adhesive. Prepolymers with

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moderate molecular weight are processed at elevated temperature (70–90°C). Machinability is better. The layer thickness is only 1–2 μm. The machines are much more sophisticated than SB machines. The green tack is lower than solvent-based adhesive due to lower molecular weight prepolymers. The handling of the mother roll is difficult because of the lower green tack. Advantages are that less adhesive is necessary due to the lower thickness, they are environmentally friendly because of freedom from solvents, and there is no problem with residual solvent in the laminate. The disadvantages are high machine cost, low green tack, difficult handling of rolls, and the isocyanate vapor at 70–90°C must be removed quantitatively. The laminate is not suitable for critical applications like retorting because the bond strength is lower than in SB systems. In processing (Fig. 3.8), a substrate with a higher mechanical or thermal property is selected for adhesive coating. In a composite with Al like PET/Al/PE, the adhesive is always coated on Al foil. The PET or PE is guided as the second substrate onto the Al-foil. Corona treatment of substrates must be done and if necessary also primer coating. As already mentioned, the adhesive is dosed from a nozzle directly between the heated rolls, and lamination occurs at heated nip rolls with a second substrate. The laminate has to be cooled down at a cooling roll before winding up.

Unwinding Substrate 2 Cooling Coating unit 2C-Adhesive (PU) 1C-Adhesive (PU) Unwinding Substrate 1

Winding up

Figure 3.8 In solvent-free lamination, no dryer is needed because there is no solvent

3.1 Technology of Converting

A few examples of SF-laminated composites are Coffee, tea: PET/Al/PE

Snacks: OPP/M-OPP white or M-PET/PE

Candies: OPP/OPP-A white/cold-seal

Biscuits: acrylic lacquer/OPP-A white

Table 3.2 Comparison of Solvent-Based and Solvent-Free Lamination Criteria

Solvent-based lamination

Solvent-free lamination

Molecular weight of prepolymer

high

low

Viscosity of adhesive

high

low

Green tack

high

low

Tackiness

long

short

Solid content

30–60%

100%

Coating amount, wet

2

5–8 g/m

1–2 g/m2

Coating amount, dry

3–5 g/m2

1–2 g/m2

Cost of raw material

high

low

Elasticity of adhesive layer

high

low

Winding tension of roll

broad

narrow

Curing time

7–14 days (20°C)

7–14 days (20°C)

Coating system

Adhesive in pan + dip rolls

Adhesive between rolls

Temperature of adhesive

Ambient temperature

70–90°C

Application of laminates

All applications

General-purpose only

3.1.3.4 Glue or Water-Based Lamination Glue or water-based lamination is used for composites where a lower bond strength is required (Fig. 3.9). It is applied generally for laminates of paper with polymer film or Al foil. The glue can be starch-based or a polymer dispersion. The system works like solvent-free lamination. Lamination of both substrates takes place just after coating with glue before the dryer. The moisture in the glue has to evaporate through one of the substrates. For this reason, paper is always one partner in such lamination. Examples are paper/Al for wrapping butter, tea, or cigarettes.

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Moisture permeable

Dryer Unwinding Substrate 2 Cooling Coating unit Dispersion Starch glue Unwinding Substrate 1

Winding up

Figure 3.9 Glue or wet lamination

3.1.3.5 Wax or Hot-Melt Lamination Hot melts are a mixture of wax with low molecular weight polymers. The process is comparable to extrusion lamination, but the bond strength is much lower. Like glue lamination it is used for packaging purposes, where high bond strength is not necessary. Similar to extrusion lamination, the laminate is ready for use just after the process. Applications include wrapping butter (print/Al/wax/parchment paper) or candies. An advantage is the flexibility of such laminates. Examples of converted packaging materials 1. Lidding film: Print

Paper

Adh. (SF)

50 g

PET

Adh. (SF)

12 μm

Al

Ionomer

9 μm

20 μm

SF = solvent free

2. Film for composite cans Paper

PE melt

Al

Ionomer

50 g

12

9

20 μm

3.1 Technology of Converting

3. Lidding for Yogurt Print

Paper

Adh. (SF)

50 g

PET met*

HSL

12 μm

7 μm

HSL= hot sealing lacquer* Metallized polyester

4. Stick pack for liquid pharmaceuticals: PET

Print

Adh. (SF)

12

Al

PE melt

PET

PE layer

10

20

12

50 μm

5. Lidding for cream UV Print**

Al

HSL

39

6 μm

** Curing of ink by UV rays

6. Wrapper for champagne bottle***: Al

PE melt

AI

9

20

12 μm

*** Feels during tearing like soft lead foil

3.1.4 Important Features for the Technologist Technologists in a company in the packaging sector are not only responsible for production, quality management, R&D, or other topics, but they are also responsible for the workers without whom a company cannot run. As soon as a technologist suggests some proposal for better quality or a better production process, he or she should go to the spot and learn about the employees’ working environment. A healthy working environment is very important for these persons because they may work there for tens of years. A good technologist should realize personally the effect of a good proposal that he or she suggests. Only after that can one realize whether a proposal is feasible. One should discuss the feasibility with the workers in charge at that spot. A few examples are the noise in the workplace, unhealthy vapors of some critical organic solvent, or working with some pungent-smelling chemicals. A lot of misunderstanding can be avoided and time and money can be saved by planning and working with a sure instinct. A good atmosphere and a win-win situation between technologists and workers can only be created by avoiding critical situations.

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„„3.2 Vacuum Deposition of Ultrathin Layers Aluminum foil has proved to offer a very high barrier in composites when laminated with other substrates like PET/Al/PE. Aluminum foils with a thickness below approximately 18 μm are however not completely pinhole free. Still, foils are applied in composites for high barrier packaging satisfactorily down to a low thickness of 6 μm. During handling of flexible packs with aluminum foil, pinholes are created at the folding lines or points. Depending on the numbers of pinholes and their size, the pack may no longer offer a high barrier. In order to solve this problem, the idea of an ultrathin layer of vacuum-deposited Al film was born. Such a film also offers satisfactory barrier results after squeezing during handling. A functional layer of Al with an unimaginably low thickness of 30–100 nm is deposited on a flexible substrate under extremely high vacuum to get a high barrier composite. This metallized PET with 12 μm thickness is laminated with a suitable sealing layer like LDPE to make a perfectly flexible composite that can be squeezed during handling without getting pinholes. Basically any material can be deposited under high vacuum on a suitable substrate. Besides aluminum, AlOx and SiOx have also proved to be suitable depositing materials, called the target material for flexible laminates. AlOx or SiOx are oxides of aluminum and silicon with a mixture of two different oxides. For aluminum they are AlO and Al2O3. For silicon they are SiO and SiO2. AlOx and SiOx offer high barrier flexible films for packaging purposes, where freedom from metal is a big issue. Examples of packaging applications are pouches for potato chips and coffee and in holographic effects. Substrates that are deposited with suitable target materials under ultrahigh vacuum are the usual polymer films for packaging, like PET, BOPP, BON, and PVC. Even paper can be vacuum deposited when necessary. Because the deposition process is not continuous but discontinous, the substrate should be as thin as possible so that a larger area can be deposited. Because of technical difficulties, the deposition process is not a continuous process. Besides a barrier effect, target materials also offer optical and susceptor effects in a microwave oven. Aluminum is by far the most-used target material. SiOx is used particularly for transparent packaging with a high barrier effect and also for applications where freedom from metal is necessary. Under both oxides, SiO2 and SiO, SiO is responsible for the high barrier. But films deposited with SiO show a yellowish color. SiO2 offers high transparency but no barrier. An interesting property of SiOx is its barrier effect against UV rays, although it allows a large portion of visible light through the film. This is a key feature for transparent packs for sensitive products like food or cosmetics. The technology of deposition can be of a physical nature, called physical vapor deposition (PVD), where the target material is deposited by heating with electrical

3.2 Vacuum Deposition of Ultrathin Layers

resistance. Alternatively it can be deposited by an electron beam gun or under a plasma. In physical processes the target material is evaporated or ejected out of a block through the electron beam and is deposited onto the substrate. Chemical depositions are also possible, so-called chemical vapor deposition (CVD), where the target material undergoes a chemical reaction before it is deposited onto the substrate.

3.2.1 Physical Vapor Deposition (PVD) Process Thermal Deposition with Electrical Resistance Heating This is the most common process for vacuum deposition of thin layers. The depositing machine is a cylindrical horizontal container with two chambers one upon the other (Fig. 3.10). The winding chamber is at the top and has a bit lower vacuum (higher pressure) than the deposition chamber at the bottom. Aluminum wire of high purity (99.9%) is transported to an electrically heated crucible of high thermal stability at around 1500°C. Due to very high thermal strain, the boron nitride (BN) crucibles have an average duration of only 12 hours. The aluminum melts at once and is evaporated from the crucible under high vacuum. The substrate is then transported at high speed along a chill roll just over the crucible, on which aluminum particles deposit like fish scale. If there are impurities in the aluminum, then it can splash out of the crucible and make a hole in the substrate. The layer thickness of the aluminum can be adjusted with different processing parameters. Substrates with a high water content, like paper, disturb the process through evaporated moisture, which can hinder proper deposition of aluminum onto the substrate. A cold trap in the winding chamber captures the water vapor just after unwinding through freezing. In order to get a higher barrier effect, deposition of the target material is also possible on both sides of the substrate.

1. Unwinding 2. Depositing roll 3. Source of depositing material

4. Second depositing roll 5. Second source of depositing material 6. Wind up

Figure 3.10 Vacuum deposition of ultrathin layers with Al, AlOx, or SiOx

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Example of Process Parameters Substrate:

12 μm PET, 2000 mm breadth, 20.000 m long

Layer thickness:

100 nm

Working speed:

500 m/min

Pressure in winding chamber:

10–2 mbar

Pressure in deposition chamber:

10–4 mbar

Temperature of chill roll:

–10°C

Temperature of cold trap:

–120°C

Specific heat on substrate:

40 kW/m2 (condensation), 2.5 kW/m2 (radiation)

Electron Beam Gun Deposition The machine looks similar to an electrical resistance heating machine. Here there is again a winding chamber and a deposition chamber. The vacuum is not high as in resistance heating. A block of the target material is placed in the deposition chamber. A curtain of high energy electron beam hits the block and ejects out tiny particles to get deposited onto the running substrate on the chill roll. Besides physical deposition, chemical deposition is also possible after a suitable chemical reaction. The substrate is transported near the emerging material. The system is very robust (no damage of the crucible like in thermal deposition takes place), but it is very expensive. Plasma Deposition The third physical process for vacuum deposition of a thin layer is plasma deposition. The energy necessary to evaporate aluminum is created by a plasma (ionized gas). Also here aluminum can be deposited on the substrate after it has been transferred in vapor form. Not only aluminum but also AlOx or SiOx can be deposited on a substrate in all of the physical processes (electrical resistance heating, electron beam gun, or plasma).

3.2.2 Chemical Vapor Deposition (CVD) Process The CVD process differs from the PVD process in that in this process the target material undergoes a chemical reaction before it is deposited onto the substrate. It has the advantage that the target material needs a much lower boiling point than in the physical processes, so less energy is necessary. Another advantage is the large number of chemical compositions of the target material after a chemical reaction. The deposition of SiOx or AlOx from SiO or aluminum after oxidation is actually a CVD process. It is however not very easy to get the exact target material after a

3.2 Vacuum Deposition of Ultrathin Layers

chemical reaction. The reactive components must have an exact composition, and disturbing reaction products must be removed. Deposition of a thin layer is not only possible for web-like substrates like film or paper, but also bottles or cups can be vacuum deposited, e.g., high barrier PET bottles for beer or other drinks. Quality Control of Deposited Films Control of layer thickness of the deposited layer is necessary to ensure a standard quality. It can be done both in-line and off-line. In-line methods measure the electrical resistance of the aluminum layer or the capacity of the aluminum layer or the optical density of the layer. To measure electrical resistance, the deposited film is passed over two conducting rollers, and the resistance of a square field is measured. The unit is ohm per square. Because the resistance is directly proportional to the length and reciprocal to the breadth, it does not matter how big or small is the square. It is always constant and depends only on the thickness of the aluminum layer. Similarly, the electrical capacity of the deposited aluminum layer is measured between two conducting rollers. To measure the optical density, the intensities of light at the source and at the photocell behind the deposited film are measured. The calculated extinction is proportional to the thickness of the aluminum layer. All of these three tests are also made off-line in laboratories. A Tesa test or Scotchbond test is also made to test the adhesion of aluminum on the substrate, as is usual for printing ink. Important for the quality of deposition are generally pinholes and adhesion of the target material on the substrate. Pinholes are of two kinds; sometimes there are gaps in the aluminum particles in the layer, which covers the substrate like fish scales. This is not so critical. For a very high barrier, double-sided deposition was introduced in the 1980s. If, however, the substrate is molten through ejection of hot drops of aluminum, then it is a bigger issue. Naturally the magnitude of quality deficiency depends upon the number of such pinholes. Adhesion of the target layer on the substrate can be increased by suitable coating of the substrate by prior deposition.

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„„3.3 Radiation Upgrading of Packaging Material The properties of polymers can be modified by ionizing radiation like beta-rays and gamma-rays. In packaging technology there are also some applications, particularly to enhance sealing strength and mechanical properties like tensile or puncture strength. When polymer materials are irradiated, chain scissoring takes place in a random manner because of the absorption of high energy. Radicals are grown. In some polymers like LDPE, the radicals undergo cross-linking and create a partially cross-linked rubber-like structure. There are, on the other hand, some polymers like PVC, where there is not much cross-linking; instead they degrade and the molecular weight is reduced. If LDPE is radiated up to the proper dose, then properties like sealing strength and tensile strength can be enhanced. Packaging solutions can be solved with thinner films than those not radiated.

3.3.1 Effect of Radiation on Plastics When plastics are exposed to radiation, then the bonds break statistically through absorption of high-energy rays. This breakage is called degradation. A number of them reunite thereafter through cross-linking. A net-like structure is created. Three different effects can be recognized. In the first case, the cross-linking predominates rather than degradation, which can be seen with LDPE and acid copolymers of PE and PS. Mechanical properties like tensile strength and some thermomechanical properties like sealing strength increase. Packaging films with lower thickness can be used successfully to pack goods for which nonradiated packaging material with higher thickness would be necessary. Because of the lower thickness, the stiffness of such radiated films is less, and hence they show a better flexible character. Too high of a dose level, however, can change PE through extreme high cross-linking into an elastomer (rubber), which is no longer sealable. PET or PVOH is almost indifferent to radiation. PP, PVC, or PVdC degrades rather than cross-links. Gamma radiation is not suitable for radiation of plastic films because only films on roll stocks can be radiated through gamma radiation. The dose of radiation is inhomogeneous in a roll stock. The outer parts of the roll stock receive higher radiation than the inner part. Beta radiation is successfully used for radiation. One typical application of beta radiation is on flattened shrink tubes from which shrink pouches are manufactured. The structure of the tube is PE/Tie/PVdC/Tie/ PE. Both of the PE layers are generally tailor-made blends, where the outer PE (left

3.4 Extended (Foamed) Packaging Materials

side) has a slightly higher melting point than the inner one. The application of radioactive curing particularly for shrink pouches has another great benefit. Shrink tubes are generally preserved on roll stocks for a few weeks or even months before they are cut into pouches upon order from a customer. Nonradiated tubes can shrink to some extent if stored at elevated temperature, particularly during the summer months. Beta radiation in combination with a high barrier layer of PVdC hinders such premature shrinking. In comparison to the above-mentioned five-layer shrink pouches, the EVOH-based and nonradiated high barrier shrink pouches have a sophisticated nine-layer structure: PET or PA/Tie/PA/Tie/PA or EVOH/Tie/PE/PE/PE with two or three different nylon layers. One important purpose is to avoid premature shrinking of tubes during storage at elevated temperature.

„„3.4 Extended (Foamed) Packaging Materials Foamed packaging materials are dispersion systems of a polymer matrix with air or some other gas in it. There may also be a hollow space without air in a film—simply a vacuum. Soft, flexible foams are manufactured with polyolefins (PO) or plasticized amorphous polymers like PVC-P. Hard foamed packaging materials result from nonplasticized amorphous polymers like EPS (extended polystyrene). Foams may have a closed structure, captured under a polymer skin, or an open structure, where the foamed segments can be seen from the outside. Several targets are achieved through foaming. First, the weight of a package can be reduced and hence its cost. Second, it reduces the cost of packaging waste because of the lower weight, and third, the shock absorbing effect is better than in nonfoamed material. Thermal isolation is better, and finally, foamed packaging film like BOPP has a certain whitening effect without the use of a coloring agent, so whitening agent or printing ink can be saved. The density of a foamed material can be as low as 0.4 g/cm3.

3.4.1 Physical Foaming with Gas Single screw, double screw, or tandem extruders are used to manufacture foamed material through direct gas inlet. Gas with a higher pressure than the melt pressure is dissipated in the extruder; high dissipation can be achieved by enlarging the channel diameter. Foamed melt emerges generally through a horizontal annu-

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lar die, and then it is cut to produce a flat sheet. The foams from direct foaming are coarse. Foamed sheets can be laminated with nonfoamed film through heat-seal lamination into the required laminates, for example, PP/PP-foam (one foamy side and other side is plain) or PP/PP-foam/PP (foamy layer is sandwiched between inner and outer plain layers). Instead of air, low boiling point liquids like halogenized hydrocarbons such as propane or butane can also be used to make foam. The cell size is lower than from direct propagation of gas.

3.4.2 Chemical Nucleating Agents These are mixed homogeneously with the resins, which when molten, react chemically to produce tiny gas bubbles. For example, citric acid and hydrogen bicarbonate react to produce CO2. This type of foam has very small particle sizes. The amount of nucleating agent is generally between 0.1 to 1 percent. All thermoplastics like PE, PP, PVC, or PS can be foamed with this method.

3.4.3 Foam Extrusion Generally, all types of extruders can be used to produce foamed material if the following requirements are fulfilled: ƒƒsufficiently high melt temperature to fully dissipate the nucleating agents, and ƒƒsufficiently high pressure distribution in the extruder to keep the reaction gas in a homogeneous dispersion in the melt.

3.4.4 Foam Injection Molding Foamed products can also be manufactured through injection molding, but certain requirements must be fulfilled. The closing valve must be absolutely tight to prohibit any leak of foamed melt at the feeding channel. The injection pressure is generally lower than for normal injection molding. There is practically no after-pressure in this process. The cooling intensity of tools must be high enough to avoid any after-swelling of the injection-molded piece.

3.5 Special Topics

3.4.5 Foam Thermoforming Thermoforming of foamed sheet has regulations similar to foam injection molding. Any type of crushing of the cup wall must be avoided during the  application of plugs or pressure. Factors like forming temperature, timing, and speed of pressure application or evacuation are important.

„„3.5 Special Topics The packaging process is very complex and mistakes can take place at different stages. Some interesting topics are discussed here in detail.

3.5.1 Sealing through Liquid and Dust Food or cosmetics packs are not always without fault and sometimes result in complaints. The quality of packaging films and the pouches thereof are of good quality. There are seldom mistakes like in thickness distribution, tensile strength, or barrier properties. Injection-molded articles are generally of high quality. Wall thickness distributions of thermoformed trays or cups are sometimes too low, particularly when some manufacturer tries to reduce the cost of production by reducing the wall thicknesses. Generally, two kinds of complaints for packages, particularly for food and cosmetics, arise often: printing mistakes and sealing problems. Printing mistakes are mostly of an optical nature and are seldom critical for packaging security. Mistakes in the sealing process, however, can create leakage in the pack, particularly during transport and handling. This means in most cases deterioration of the product. Care has to be taken in this most important step in a packaging process. Pouches are manufactured by sealing on one or more sides with the open side left open for filling. This side is sealed after filling. Cups, trays, or bottle membranes are sealed after filling. Closing the seal of a pack after filling is critical, particularly when liquids are packed. In many cases a drop of liquid falls down unintentionally after the dosing is finished and the pack starts moving to the next station on a packaging machine. This drop often falls at the future sealing position where the pack is closed (see Fig. 3.11).

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Drop of liquid fat or sauce

Figure 3.11 Unwanted drop of liquid on future sealing position in a tube

When the sealing jaw with a temperature of some 180 to 200°C presses this drop through the top film or die-cut lid, temperature of the drop is raised to a temperature of some 120°C. If we consider the drop as a water droplet, then it means an equivalent vapor pressure of some 2.5 bar. The sealing pressure on the usual packaging machine is around 6 bar. At the moment, the drop cannot cause any harm. As soon as the jaw is removed for the next cycle, the drop expands. Depending on its size and the breadth of the sealing seam, it may tear the seal or at least weaken it at this position. During transport or handling, the probability is high that the pack will leak at this position. This type of staining or even washing of a future sealing seam by the liquid product is a general case in a vertical-form-fill-seal machine. The product filling tube ends after the longitudinal sealing jaw and just before the transverse sealing jaw. The liquid product is filled in the pouch after the transverse seal is finished. As the liquid is filled, it splashes inside the web tube and washes the tube completely on the inner side. It means that the transverse jaw always seals the wet tube, mostly contaminated with fat or fat-like food ingredients, which actually hinder proper sealing. Precautions have to be taken in the sealing process to still achieve an acceptable sealing quality. Similar trouble with sealing arises if stains of fat from sausage or cheese or the juice of fresh meat or fish is left on the future sealing area when putting the product in a tray (Fig. 3.12). Precautions have to be taken to avoid weak sealing at those

3.5 Special Topics

positions. It is best to avoid such stains, which is not easy on quick packing machine. The sealing layer should be of a high performance polymer like LLDPE or ionomer of sufficiently high layer thickness. The profile of the sealing jaw must also be correct. The jaw profile on a VFFS machine for liquid packaging should be slightly convex. During pressing on films, such a profile presses out liquid drops from the sealing seam, and a secure seal is possible. Deeply profiled jaws are also helpful; they pierce through the liquid layer to combine the sealing polymers of both sides.

Drop of liquid fat or sauce

Figure 3.12 Unwanted liquid drop on future sealing position on a tray

It is unavoidable during the filling of bulk products to seal dust free. Bulk products are filled through volumetric dosing from the top in a pouch, whether on a VFFS machine or in sachets on a HFFS machine. The packaging process runs on a modern machine at a speed up to 120 pouches per minute or even more. The complete packaging process has to be finished within one-half of a second. Particularly on the VFFS machine, one cannot wait until all of the bulk product from the cup or auger dosing falls into the pack. One could analyze the particle size distribution of a dosed amount during falling and find out the highest particle size at a particular time. The thickness of a sealing layer should be higher than the highest particle size to capture it securely in the sealing seam. Solid particles do not cause any trouble like liquid drops when captured in the seal.

3.5.2 Transverse Sealing of Side-Folded Pouches Side-folded pouches offer a greater volume for products for comparatively less pouch breadth. During transverse sealing, at the top and bottom, three different layer combinations have to be sealed at a time; see Figs. 3.3 and 3.4. Not only for liquid filling but also for powder filling the transition positions A-B and B-A (Fig. 3.13) are critical. With the same sealing parameters, namely temperature, pressure, and time, two layers at B and four layers at A have to be sealed securely. The

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layer thicknesses of the pouch OPA/Al/LLDPE in Fig. 3.14 are 15/9/75 μm. The thickness of the sealing layer for these pouches is selected a bit higher than in pillow pouches or four-sided sealed pouches without folding. This is necessary to distribute sufficient melt to cover the transition positions. A jaw with a horizontal profile with a number of hills and valleys also offers the necessary tightness during transport and handling. In order to avoid critical folding of the bottom seam, the filled pouches should not simply be dropped down after cutting but should be transported by a soft conveyor system to avoid any impact through its own weight and hence eventual leakage at the transition positions.

Transverse seal bottom and top

Longitudinal seal

A – four fold B – two fold C – three fold

Figure 3.13 Transverse sealing with three different layer combinations on VFFS machine

3.5 Special Topics

Figure 3.14 Transverse sealing of side-folded pouches of OPA/Al/LLDPE15/9/75 μm on a VFFS machine. Photographed by the author

3.5.3 Weak Points of a Collapsible Polymer Tube Polymer tubes almost always have a circular cross section. When such a filled tube is closed through sealing, the circle is flattened. Depending on the stiffness of the tube wall, which depends upon the specification of the tube material, the diameter of the tube, and the wall thickness (generally 500 μm), there is a certain retention force on the seam. The tubes are heated in a first step with hot air (see Section 2.1.1) and then sealed with water-cooled jaws in the next step. Considering a speed of filling of 60 per minute, there is only some 250 milliseconds of time for sealing. As soon as the jaws move away after sealing, the sealing strength must be sufficiently high to counteract the retention force. Just at this seam and at both sides near this seal there is a sharp fold, which stays continuously under tension. Depending upon the specification of the product, there may be a pretty high environmental stress crack probability. This is unavoidable for tube filling. The specifications of the tube material and the tube geometry have to be selected to get a high ESCR so that no cracking takes place at this fold during shelf life and handling.

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In order to dispense the product, a tube always has to be squeezed. The shoulder seam must also be sufficiently good to function after multiple pressings at this position (Fig. 3.15).

Sharp fold

Sharp fold

Edge pressing during every dosing

Figure 3.15 Weak points on a collapsible tube

3.5.4 Pinholes in Packs Pinholes in a pack hinder proper function of a barrier effect. Pinholes can arise first in the web, whether monolayer or composite, and second in the sealing seam. A third possibility is during severe handling through squeezing. In particular, Al foil in a composite can create pinholes at folding corners. As much as possible pinholes must be avoided, particularly during sealing. By choosing the proper sealing layer, sealing parameter, jaw profile, and breadth of seam, pinholes can be avoided. Pinholes on packaging webs are not always possible to avoid completely, particularly in composites after lamination. Thin Al foils under 10 μm have a number of unavoidable pinholes. In a composite like PET/Al/PE, the pinholes on Al foil can be identified after lamination of Al with PET. Adhesive emerges through the pinholes because of the pressure from nip rolls. These spots can be viewed with a loupe. They look like tiny craters. Bigger craters mean bigger pinholes and smaller mean small pinholes. In order to judge the loss of barrier effect through pinholes, they have to be investigated. Theoretically a pinhole may exist only in a single web, which could be Al, PET, or PE. The other two webs would offer a certain barrier effect, so it is not too

3.5 Special Topics

critical. A pinhole through two webs is not always critical. Even a pinhole through all three webs might not be critical. It depends upon the size of the pinhole. A reasonable method is to regularly measure the permeation value of a composite and store the sample. If trouble arises through abnormally high permeation, then the pinholes of that particular sample have to be compared with the standard sample. Pinholes and the  loss of barrier effect are also influenced by the packaging machine, particularly by a VFFS machine. The condition of the shoulder, its roughness, and its surface have to be optimized. In Table 3.3, the significance of the size of pinholes can be seen. For comparison sake, a human hair is 50 μm. Table 3.3 Pinholes in Packages (Tightness Class VDMA 2006 / No. 13) Pinhole size(μm)

Significance

<200

Bulk tight

<100

Insect tight

<30

Dust tight

<25

Liquid tight

<20

Moisture tight

<1

Gas tight

3.5.5 Complaint Management for New Technologists Although quality control concepts try to avoid faults in a production process, mistakes happen in every production process. In spite of all efforts, it is unavoidable that the customer gets faulty products and complains about it. Generally, a complaint is directed to the sales department of the supplier from which the customer has bought the material. An experienced sales manager decides which complaint could be handled by the sales department itself and which ones have to be investigated thoroughly, and they are passed to the responsible department. Good companies take care that the customer should not wait long with a complaint. Renowned companies assure their customers worldwide that within 24 hours after the supplier is informed about the complaint, a professional service person will arrive. Generally, an experienced person is sent to the customer to investigate and solve problems. Sometimes a new technologist is sent to the customer, as more experienced persons are currently not available. This is a challenge and simultaneously an opportunity for less experienced people to prove that they are able to deal alone with critical cases.

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He or she must take time for preparation and should learn as many details as possible about the case before visiting the customer. He or she should analyze the case with some experienced person and take note of the possible scenarios of how to investigate and hopefully solve it: at least recognize what has caused the trouble and what is necessary to repair or replace it. It is a mistake to arrive at a customer’s business without exact knowledge of the complaint. In many cases the customer is frustrated, has had losses in production, and is not in an amused state. The attitude toward the service person may be harsh. One should not feel disappointed or even insulted but instead try to understand the situation of the customer as he is suffering from some mistake for which he is not to blame. During analysis of the case, one will notice how good the preparation was for the problem. The more confidence one has can be important for troubleshooting. The customer must realize that the supplier’s technologist has reviewed the case and is doing his best. Good complaint management keeps the business with the customer in good condition, which is very important for the supplier. Well-known companies know that their products are sold mostly by reputation and not only by the sales department. Satisfied customers are the best references for new customers. Professional and successful technologists are often rewarded by management, as well.

„„References Koblischek Alfred, Amcor, Lehrgang Kunststoffverpackungen, Stuttgart, (2012) Meckel-Jonas Claudia,  Henkel,  Henkel Technologies,  12th Stuttgarter Verpackungstage (Stuttgart Packaging Symposium), (2005) Obermann Uwe, Amcor, Folienverbunde für kritische Füllgüter - Stabilität und Materialeigenschaften, 13th Stuttgarter Verpackungstage (Stuttgart Packaging Symposium), (2006) Schrägle Matthias, Huhtamaki, Innovative Entwicklungen bei flexiblen Verpackungen, 18th Stuttgarter Verpackungstage (Stuttgart Packaging Symposium), (2011) Spaeter Helmut, Cavonic, 3D Coating, Barriere-Technologie, 18th Stuttgarter Verpackungstage (Stuttgart Packaging Symposium), (2011) Koblischek Alfred, Alcan, Überblick Al-Verbunde für Flüssigkeitsver-packung, 16th Stuttgarter Verpackungstage (Stuttgart Packaging Symposium), (2009) Junge Stefan, Sika Chemie, Praxisbeispiele & Trends für starre & flexible Kunststoffverpackungen für Haushalts- und Bauchemikalien, 16th Stuttgarter Verpackungstage (Stuttgart Packaging Symposium), (2009) Vetter Oliver, Alcan, Transparent inorganic barrier films for packaging Applications, 15th Stuttgarter Verpackungstage (Stuttgart Packaging Symposium), (2008) Aymar Felix, Henkel, Herausforderungen und Erfahrungen bei der Entwicklung eines Verpackungssystems für eine sehr reaktiven Polyurethan-Klebstoff, 14th Stuttgarter Verpackungstage (Stuttgart Packaging Symposium), (2007)