Recent Conference Topics Introduce New Technologies

FOCUS ON P O W D E R C O AT I N G S A MONTHLY REPORT FROM SID HARRIS

RECENT CONFERENCE TOPICS INTRODUCE NEW TECHNOLOGIES

JULY 2008 In this issue

TECHNICAL

2-4

Advances in powder rheology Photocatalytically active titanium dioxide Silicone-based powder coatings

INDUSTRY NEWS

4-6

PPG to build company’s first coatings plant in Russia Rohm and Haas honoured with prestigious award at Interlakokraska

LITERATURE

6-7

Uncle Sam Wants U...V

MARKETS

7

Coatings companies forge ahead despite negative environment Asia’s paints and coatings market surpasses Europe and the USA

CONFERENCES

7-8

PRA’s 6th International Wood Coatings Congress

EVENTS

AN INTERNATIONAL NEWSLETTER MONITORING TECHNICAL AND COMMERCIAL DEVELOPMENTS IN POWDER COATINGS ISSN 1364–5439

8

The recent American Coatings Conference and Show contained a number of papers relating to new coatings technologies that could be of interest to formulators of powder coatings. Increasing competition added to the background of higher raw material and processing costs have prompted powder coatings formulators to offer customers products with “value added” qualities, giving improved film performance and providing tangible cost savings at the application stage, with more uniform powder deposition, low film thicknesses and better transfer efficiency. Control of powder rheology can reduce manufacturing costs by speeding throughput at the extrusion stage, facilitating ease of packing, and lowering the risk of powder agglomeration during transportation and storage. Additionally, it will improve powder fluidity, charge acceptance, reduction of the faraday cage effect, more uniform powder deposition, greater transfer efficiency to reduce losses when overspray is not recovered, and enhanced aesthetics in the cured film. The beneficial effects of small additions of silicon or aluminium oxides during the manufacturing of powder coatings is described in the paper by Evonik Degussa and is a useful guide for powder formulators.

There is apparently a hitherto untapped potential in the use of titanium dioxide as semiconductors, which can be rendered capable of photocatalytic activity under the influence of visible light sources. The effect of UV light on films containing titanium dioxide is well known and film breakdown occurring with these materials during exterior exposure to sunlight has been largely countered by coating the pigment particles with various metallic oxides. The capability to enhance the semi-conductor qualities of titanium dioxide by doping the crystalline pigment particle with certain elements offers the possibility that coatings or other materials, such as concrete, could be modified for the main purpose of eliminating surface contaminants. A paper presented by Kronos affords some food for thought for all coatings formulators. Silicone based powder coatings have been examined on a number of occasions in the past as heat resistant powder products but they have previously been found to be too brittle when based on inorganic silicone resins alone, and blending with organic binder resins has not produced compatible powder coating systems. Wacker Chemie have now produced phenyl-substituted silicone resins that are claimed to be completely compatible with a

POWDER COATINGS POWDER COATINGS POWDER COATINGS POWDER COATINGS

F O C U S wide range of powder coating binders such as solid grade epoxies and polyesters. Combinations offer improved heat resistant qualities for some powder coated domestic appliances together with improved mechanical properties. Heat resistant qualities up to 650°C are also possible for powders based on the silicone resin only when pigmented with heat resistant pigments and fillers. A conference scheduled for October next will be of interest to many powder coatings formulators for it will provide an insight into the problems of coating wooden substrates. Powder coatings on wood or composite materials are a growing market especially for low temperature curing powder systems and UV curable powders. There are four papers relating to powder coatings in the thirty-five papers that are to be presented and those that are not directly related to powder coatings will provide a useful outline of the problems associated with this large coatings market. Emphasis on the frantic efforts of major coatings producers to saturate the global markets appears to have moved away from China. Russia and India are now the targets for commercial conquests. While South America and Africa seem to offer little attraction at the moment, no doubt they will also be invaded by the coatings “carpet baggers” when all others have been conquered. What will they do afterwards? Join the Space Race? Sid Harris

TECHNICAL Advances in powder rheology A paper presented at the recent American Coatings Conference and Show describes the latest progress in particle technology derived from high temperature flame hydrolysis and the beneficial effect of these materials 2

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on powder coating rheology. Although the paper also covers other coatings applications, the materials applied to powder coatings are predominantly those based on silicon dioxide and aluminium oxides. Particles resulting from flame hydrolysis are non-porous and exist as aggregates of sintered particles. Primary particle size for fumed silica ranges from 7 to 40 nm with surface areas from 38050 m2/g. Alumina particle sizes range from 10-20 nm and surface areas from 130-65 m2/g. Surface modification is necessary to convert hydrophilic particles to a hydrophobic character and these treatments are based on a range of organo-silicone chemicals. Structure modification of the particles is performed by several procedures. Granulation produces larger individual spherical particles in the range 20-30 microns, which are porous and their main function is to act as carriers of liquid based materials, such as flow additives. Other chemical and mechanical processes modify particle structure giving products with significantly higher bulk densities that are used to enhance scratch resistance. The main applications of modified silica’s and alumina’s in the powder coatings field are to improve fluidity, reduce moisture pick-up and give good package stability, with no caking. In application processes the powder attributes are: efficient fluidization, high transfer efficiency to reduce overspray waste, and reduced faraday cage effects to promote uniform film thickness and optimized appearance. All four classes of untreated hydrophilic; treated hydrophobic fumed silica and alumina are used to achieve improved flow, stability with reduced moisture pick-up, improved fluidization and transfer efficiency. Recent particle developments of a high surface area alumina (130 m2/g) and surface modification with trimethoxy-octylsilane (TMOS) to give

C OAT I N G S hydrophobicity, has brought about further improvements in conventional, fine and tribo applied powder coatings, in the areas of transfer efficiency and improved fluidization. These additives can be introduced in one of three stages in the powder manufacturing process: in the feed hopper prior to extrusion; added during the flaking of the extrudate; or post added after the fine grinding process. Some powder formulations are problematic at the premix stage and the addition of these additives at 0.1 to 0.3% by weight helps them to feed more consistently and homogeneously into the extruder. When powder flow additives are used to pre-treat the premix components, they are extruded into the powder matrix and do not influence the bulk flow properties after the powder is compounded and pulverized. If the additives are designed to influence the final powder coating properties, they must be added after extrusion so that they can be oriented on the surface of the powder coating particles. When they are added at the flaking stage care must taken since classification collection systems during the fine grinding stage can partially remove the additive and alter the final amount remaining in the powder coating. A typical dosage level at the flaking or post manufacture stages is 0.1 to 0.3% by weight. Assessment of the performance of these four classes of additives was carried out at a local university by testing each type in three powder coatings. Two of the three black polyester powder coatings were applied by a corona charged gun, while the third powder coating was applied with a tribo charged gun. The first powder coating was conventional with a coarse particle spread d50 of 31.5 microns, and the second powder coating had a fine particle size d50 of 21.5 microns. Dosage level of the additive was adjusted according to the particle size of the powder. A 0.3% dosage was JULY 2008