Paints, Coatings and Solvents Episode 2 pps

2.3. CM~ritiated Rubber Courings 19 used in this area. Levels as low as 1 - 5 wt YO provide good flowout and leveling of the coating which often tends to form craters and pull back at edges. Another very important application is the dispersion qfpignzents that are difficult to disperse (e.g., carbon black, transparent iron oxides, phthalocyanine blue and green, and perylene red). The use of CAB and two-roll milling is the most efficient method of dispersion. Application. Cellulose acetate butyrate lacquers are usually applied by spraying (air atomization, airless, spinning disk). Application by brush or dip is possible but less commonly used. 2.2.2.2. Cellulose Acetate Propionate Cellulose acetate propionates (CAP) have the same characteristics as CAB, including high solubility and compatibility with other resins. They also have a very low odor; this is important in printing applications and in reprographic processes. Com- mercially available products and their typical properties are listed in Table 2.2. Cellulose acetate propionate is used mainly in printing inks where a low odor is required (e.g., in food packaging). It is also used for coating leather clothing and for printing gift wrapping paper. 2.3. Chlorinated Rubber Coatings 2.3.1. Starting Products [2.8]-[2.10] To manufacture chlorinated rubber (CR) natural or synthetic rubber such as polyethylene, polypropylene or polyisoprene is degraded to low molecular mass compounds by mastication or addition of radical formers and dissolved in carbon tetrachloride (CTC). Chlorine contents are typically 64-68 wt %. Chlorine gas is introduced into this solution and reacts with the raw material to form CR. The solution is then introduced into boiling water. The CR is precipitated, and the solvent vaporizes. The CR is separated from water, rinsed, dried and ground to form a white powder which is the saleable product. After removal of the water, chlorine, hydrochloric acid and other impurities the solvent is reused. Commercial Products. Chlorinated rubber is only produced by a few manufacturers. Trade names include Aquaprene (Asahi Denka), Chlortex (Caffaro), Pergut (Bayer) [2.8], Superchlon (Nippon Papers). These products are available in various viscosity grades, whose ranges largely coincide for the aforementioned commercial products (table 2.3). 20 Table 2.3. Viscosity grades of Pergut. an example of commerical chlorinated rubber product -7. T\!pes oj' Paints and Coatings (Binders) Designation Viscosity*, mPa s Mean molecular mass** Pergut S5 Pergut S 10 Pergut S20 Pergut S40 Pergut S90 Pergut S 130 Pergut S 170 3.5-6.5 9.0-13.0 16.0-24.0 33.0-51.0 74.0- 110.0 120.0- 150.0 130.0-200.0 60.000 124.000 160.000 213.000 302.000 327.000 3 59.000 ~ * measured in a 18.5% solution in toluene at 23'C in a Hoppler viscometer (DIN 53015) ** measured by a combination of gel permeation chromatography and viscometry. As CTC attacks the ozone layer, CTC-emission from modern plants are almost zero. The CTC-contents in chlorinated rubber from these plants is as low as 10 ppm (Bayer). CR from old or low standard plants has a CTC content of up to 10%. This product and products produced with this must be labelled downstream according to the relevant regulations in the different countries. Recently, an aqueous process has been developed to produce CR. Unfortunately, the CTC generated in this process leads to a CTC-content in CR of 100-500 ppm. Properties. The high degree of chlorination substantially alters the properties of the starting polymers. A hard, granular, white powder with the following properties is obtained: high resistance to oxidizing agents (e.g. ozone or peroxide), water, inorganic salts, acids, alkalis and gases; good solubility in almost all conventional solvents except water, aliphatic hydrocarbons, and alcohols; good compatibility with a wide range of paint resins and plasticizers; low flammability; fungistatic and bacteriostatic behavior; pigmentability with almost all inorganic pigments and extenders, as well as many organic pigments. Disadvantages of the pure CR resulting from the high chlorine content include low temperature resistance (60°C wet, 90°C dry) on account of elimination of hydrochloric acid. Chlorinated rubber also tends to undergo yellowing where exposed to atmospheric influences. 2.3.2. Chlorinated Rubber Paints Chlorinated rubber and related chlorinated polymers form coating films by physical drying. Plasticizers or resins have to be added since otherwise brittle films are formed. Composition. The binder consists of ca. 65 YO chlorinated rubber (usually low-viscosity grades) and ca. 35 YO plasticizer. Chlorinated paraffins are delivered by ICI (Cereclor) and Clariant, Muttens (CH). Special nonhydrolyzable plasticizers may be 2.3. Chlorinated Rithhu Coutin,p.c 21 added if necessary, e.g., bisphenoxyethylformal (Desavin, Bayer) or resin-modified phenyl alkylsulfonates (Leromoll, Bayer). This composition ensures the “nonhy- drolyzability” of the binder (resistance to water, acid, and alkali), which is not the case if hydrolyzable phthalate or adipate plasticizers are used. Nonhydrolyzable resins (e.g., coumarone- indene resins or other hydrocarbon resins) are often added as “extenders”. Red lead has proved outstandingly suitable as apigineizt for priming coats on steel, and is fully effective in chlorinated rubber coatings. For reasons of environmental protection and occupational health, the use of toxic lead compounds is diminishing. Zinc phosphate is used instead, although it does not have the same corrosion protection effect. Conventional metal pigments (e.g., lead dust, aluminum bronze, and zinc dust) produce diffusionproof coatings with good mechanical properties. In the case of aluminum bronze and zinc dust, stabilization of the paint is required to prevent gelatinization. Iron oxide, chromium oxide, and titanium dioxide pigments, commonly used in the paint industry, are suitable for finishing and topcoats. Zinc oxide, white lead, and lithopone are, however, unsuitable. All inert minerals are suitable as e.utcnders. Carbonate-containing extenders may only be used if no stringent requirements have to be satisfied as regards resistance to water and chemicals. The choice of solvent is practically unlimited. Xylene or other alkylbenzenes are generally recommended. Mixtures of esters and mineral spirit can be used to avoid compulsory warning labels. Hydrogenated and modified castor oil is used as an additive to adjust the viscosity and facilitate application with a brush or spray gun (compressed air or airless); layer thicknesses of 2 100 pm are thereby achieved [2.11]-[2.13]. Production. Chlorinated rubber paints are produced by conventional means. The plasticizer, resins, and in some cases a proportion of the chlorinated rubber are first dissolved in the solvent. The high-boiling solvent contained in the formulation is preferred for this step. The hydrogenated castor oil is then added and the resultant mixture is dispersed in a dissolver. In order to obtain optimum “digestion”, the instructions of the castor oil supplier should be strictly observed; the temperature should not be allowed to exceed ca. 60’-C. Dispersion is followed by the formation of a paste with the pigments and extenders, and grinding. Conventional apparatus including dissolvers is suitable as grinding equipment; grinding with steel balls should be avoided since the iron dust that is formed can cause the final paint to gelatinize after prolonged storage. The ground material is then combined with the separately prepared chlorinated rubber solution. Application. Chlorinated rubber paints can be applied with all conventional coating equipment. The suppliers’ (manufacturers’) instructions must, however, be observed since the coating material (chlorinated rubber paint) is specifically formulated for the recommended application equipment. Uses. On account of their high water resistance, chlorinated rubber paints are used for underwater coatings on steel and concrete (e.g., water storage vessels, swimming pools, sewage systems, harbor installations, and docks). The chemical resistance is exploited in vessels, tanks, and constructional parts used in mines, chemical plants, etc., in which aqueous solutions of inorganic chemicals are handled. Coatings for concrete require chlorinated rubber as a binder due to the alkalinity of the concrete surface. The main area of use of chlorinated rubber paints is for underwater coatings on ships (see also Section 11.4). Favorable properties for this application are high water resistance, rapid drying (which is independent of the external temperature in the shipyard), good mutual adhesion of the individual layers, and the fact that old coats of paint can easily be renewed. 2.3.3. Chlorinated Rubber Combination Paints Composition. Chlorinated rubber combination paints contain a second resin as the property-determining binder. The chlorinated rubber is added to an alkyd resin, acrylic resin, or bituminous substances to improve properties such as drying rate, water resistance, or chemical resistance. This application only accounts for a small proportion of the total chlorinated rubber consumption. The proportion of chlorinated rubber in the binder varies from 10 to 50 wt% depending on the intended application; plasticizers and/or alkyd resins and/or acrylic resins account for the remainder. In combinations with bituminous substances the proportion of chlorinated rubber ranges from 1 :10 to 1O:l. The ratio depends on whether the goal is to improve the bitumen-based coating without any substantial increase in cost, or to reduce the cost of the chlorinated rubber coating. Adhesion is improved but with the disadvantage of darker shades caused by the black bitumen. Production corresponds to that of pure chlorinated rubber paints (see Section 2.3.2). Chlorinated Rubber- Alkyd Resin Combinations. In these combinations chlorinated rubber accounts for 25-50% of the binder. Chlorinated rubber is used to increase the drying rate and/or improve the chemical resistance against inorganic chemicals like acidic or basic compounds. These paints also exploit the benefits of the alkyd resin, e.g., good brushability and nonsolubilization. They are used for corrosion protection in industrial plants or marine environments to protect steel, galvanized steel, and aluminum; air-drying or forced-dried industrial paints (e.g., for agricultur- al machinery); and road marking paints. Chlorinated Rubber- Acrylic Resin Combinations. Physically drying acrylic resins are used for these combinations. These combinations have the same drying rates as normal chlorinated rubber paints (see Section 2.3.2). They have improved flow properties (particularly when applied by pouring techniques), improved weather resistance (chalking and yellowing), and favorable mechanical properties (adhesion and extensibility). Applications include topcoats for ship superstructures and priming coats on galvanized surfaces. 2.4. Vinyl Courings 23 Combinations with Bituminous Substances. Chlorinated rubber can be combined with bitumen and tars but compatibility has to be checked. Addition of chlorinated rubber reduces thermoplasticity, accelerates drying, and prevents cracking of the final coating in adverse weather conditions, without, however, adversely affecting the good adhesion, water resistance, and chemical resistance of the bituminous substance. Bituminous coatings reinforced with chlorinated rubber are used in silos, tanning pits, drinking water containers, and on ships’ hulls (on the underwater part). Bitumi- nous substances for coatings are supplied as special products that are free from carcinogenic constituents. 2.4. Vinyl Coatings This section deals with paints based on vinyl resins (including vinyl copolymers) which are synthesized by polymerization of monomers containing terminal CH, = CH groups. Polyolefins, poly(viny1 halides) and vinyl halide copolymers, poly(viny1 esters), poly(viny1 alcohol), poly(viny1 acetals), poly(viny1 ethers), and polystyrene are discussed. Polyacrylates (acrylic resins) are treated in Section 2.5. 2.4.1. General Properties Paints and coating materials based on vinyl resins are generally physically drying. Only in a few cases vinyl resins can be chemically cross-linked with other reactants via incorporated reactive groups. The properties of the paints are therefore primarily determined by the chemical and physical nature of the vinyl resin. Despite the large number of available vinyl resins this class of binders has some common features. All vinyl resins have a linear carbon chain with lateral substituents and exhibit a range of molecular masses. Increasing molecular mass is accompanied by improved mechanical properties, a decrease in solubility, and an increase in the viscosity of their solutions. Vinyl resins of high molecular mass can therefore only be used in the form of dispersions or powders for paint applications. Solvent-containing paints require vinyl resins of considerably lower molecular mass than plastics, since only then a sufficient binder content can be achieved in the viscosity range required for paint application. The properties of vinyl resins, paints, and coatings are chiefly determined by the nature and number of substituents. The substituents influence the crystallization behavior and thus the properties of interest in paint technology such as the softening range, mechanical properties (film flexibility, cold embrittlement tendency, film hardness), the film-forming temperature in dispersions, solubility, and compatibility 24 2. Tvpt~ qf Puints mnd Cocitings (Binders) with other binders. Chemical behavior also depends on the substituents: ester groups can be hydrolyzed, free carboxyl groups improve adhesion to metals, and hydroxyl groups permit cross-linking with reactants such as isocyanates. Pigment wetting, pigment loading, water swelling capacity, diffusion of water vapor and other gases, solvent retention, and many other phenomena are also largely determined by the substituents. Copolymerization and the associated introduction of further substituents allows individual properties to be modified. For example, internal plasticization can be achieved by copolymerizing “rigid” monomers with “soft” monomers. Vinyl paints are produced by conventional techniques (see Chap. 7) and can be applied by all conventional methods (e.g., spraying, brushing, roller coating, and dipping). They are dried at room temperature; heating can be used to shorten the drying process. 2.4.2. Coatings Based on Polyolefins and Polyolefin Derivatives Polyethylene can only dissolve in hydrocarbons above its melting point. On account of its low solubility it is used in coatings solely in the form of powders and dispersions. On account of their paraffinic nature, polyethylene coatings are highly resistant to chemicals. They are, however, attacked by strong oxidizing agents. Polyethylene coatings are elastically tough, flexible (even at low temperature), resistant to hot water, and nontoxic. Polyethylenes of lower molecular mass are added as slip and matting agents to paints and printing inks and can also produce dirt-repellent and abrasion-resistant effects. The wax dispersions are produced by hot dissolution and precipitation in aromatic hydrocarbons. This is not necessary with commercial microcrystalline grades. Aqueous dispersions of polyethylene are important as polishing agents. Polyisobutenes do not crystallize. Polyisobutenes of low molecular mass are flexible resins, and those of high molecular mass are elastomers. Their use in the paint sector is restricted on account of their aliphatic nature and limited compatibility with other binders. They are employed in combination with hydrocarbons such as paraffins, rubber, and bitumen. They are used as plasticizing components. Ethylene Copolymers. Ethjdene- vinjd acetate copol~~mers differ according to their vinyl acetate content and molecular mass. With increasing vinyl acetate content, compatibility with paraffin waxes decreases, but that with other binders increases. Low molecular mass types containing 25-40% vinyl acetate are readily or suffi- ciently soluble in solvents. With a 40% vinyl acetate content, they can be combined with polar resins and nitrocellulose. Terpolymers with free carboxyl groups exhibit improved adhesion. Ethylene-vinyl acetate copolymers are primarily added to waxes to improve their properties, but are also used to increase flexibility and adhesion in paints, printing inks and adhesives, and for hot melt coatings. Ethylene-vinyl acetate copolymers have low water vapor and gas permeabilities (barrier effect). 2.4. Vinyl Coatings 25 Powder coatings are also formed from ethylene- vinyl acetate copolymers (see Section 3.4). Copolymers of ethylerie with nialeic acid (anhydride) of low molecular mass are water-soluble, form salts, and undergo cross-linking reactions. Chlorinated Polyethylene and Polypropylene. Totally chlorinated polyethylene and polypropylene have a chlorine content of 64 - 68 %. Their properties largely corre- spond to those of chlorinated rubber (see Section 2.3). Chlorinated polypropylenes can be used for chemical-resistant and weather-resistant coatings. These binders are important in adhesion priming coats and heat-sealing lacquers for polypropylene foils. Commercial products include chlorinated polyolefins CP (Eastman) and Hardlen (Toyo Kasei KogY 0). Chlorosulfonated polyethylene is obtained from polyethylene by simultaneous treatment with chlorine and chlorosulfonic acid. The binder is cross-linked via its sulfonyl group with metal oxides, preferably lead oxide, in the presence of organic acids and sulfur-containing organic accelerators. The paints may be formulated as air- and oven-drying, one- and two-pack systems with a pot life of one to two weeks. Cross-linked films of chlorosulfonated polyethylene have an extremely high chemical resistance, particularly against oxidizing agents (it is used in internal coatings of chromic acid baths). 2.4.3. Poly(Viny1 Halides) and Vinyl Halide Copolymers 2.4.3.1. Poly(Viny1 Chloride) and Vinyl Chloride Copolymers Poly(viny1 chloride) [ 9002-86-21 (PVC) is sparingly soluble in the solvents used in the paint industry, and so is rarely used as a paint binder. It is used to a significant extent in the form of paste-forming PVC powders in plastisols and organosols. Plastisols are PVC dispersions in plasticizers that also contain stabilizers, extenders, pigments, and processing agents. Organosols additionally contain solvent-soluble binders. Since plastisols and organosols adhere poorly to metals, adhesion pro- moters are necessary; organosols can also be combined with adhesive resins when applied to metals. Film formation takes place at gelation temperatures from 160 to 200°C. The properties of the coating depend on the type and amount of PVC, plasticizer, and extender. A foaming effect can be achieved during gelation by adding blowing agents. Poly(viny1 chloride) is also used in powder coatings, which are applied by fluidized-bed coating and electrostatic spraying (corrosion protection for metal fur- niture, wire, aluminum front elements for buildings, and road-marking posts). PVC coatings have favorable mechanical properties, a high abrasion resistance, and high chemical resistance. Commercial products include Ekavyl, Lucovyl (Atochem); Geon (Goodrich); Solvic (Solvay); Vestolit (Hiils); and Vinnolit (Vinnolit). 26 2. T1pe.r of’ Paitits und Courings (Bindrr.7) Chlorinated Poly(Viny1 Chloride). Post-chlorinated PVC combines the advanta- geous properties of PVC, e.g., good chemical and weather resistance with good solubility in most conventional solvents. Its importance has, however, continually decreased in the paints sector. Vinyl Chloride Copolymers. Vinyl chloride copolymers can be used in a wide variety of paint technology applications. The solubility of vinyl chloride copolymers is considerably higher than that of the PVC homopolymer. Important examples are copolymers without additional functional groups formed with vinyl acetate, dibutyl maleate, or isobutyl vinyl ether; terpolymers with carboxyl groups formed with dibutyl maleate or vinyl acetate and a dicarboxylic acid; and copolymers and terpolymers with hydroxyl groups formed with hydroxyacrylates or with vinyl acetate and vinyl alcohol. Commercially available vinyl chloride copolymers differ in composition and molecular mass. They are physically drying binders that undergo film formation by solvent evaporation. (The types with hydroxyl groups can, however, also be used as combination binders in reactive systems. They can be cross-linked, for example, with melamine resins or polyisocyanate resins.) The films are tough, abrasion resistant, thermoplastic, of low flammability, colorless, odorless, tasteless, and physiologically harmless. Flexibility and abrasion resistance improve with increasing molecular mass. Vinyl chloride copolymers exhibit a good water resistance and outstanding resistance to alkalis, dilute mineral acids, salt solutions, oils, fats, greases, alcohols, and gasoline. Paints can readily be formulated with this group of binders and can be applied by conventional methods. Preferred solvents include ketones, esters, and chlorinated hydrocarbons. Aro- matic hydrocarbons have a swelling effect on most vinyl chloride copolymers, but are widely used as diluents. Normally alcohols and aliphatic hydrocarbons do not dissolve vinyl chloride copolymers. Both monomeric and polymeric plasticizers are suitable for plasticization. Practi- cally all monomeric plasticizers for PVC can be used. Suitable polymeric plasticizers include polyadipates, chlorinated paraffins, carbamide resins, and epoxides. Vinyl chloride copolymers are compatible with most conventional pigments and extenders. Despite their high intrinsic stability, paints based on vinyl chloride copolymers have to be stabilized against dehydrochlorination in the presence of heat and/or UV radiation for some applications. Epoxy compounds are often sufficient for thermal stabilization. The composition of vinyl chloride copolymers without functional groups influences their solubility behavior and compatibility with other paint binders. For example, copolymers with isobutyl vinyl ether or maleate esters dissolve in aromatic hydrocarbons, whereas copolymers with vinyl acetate merely swell in these solvents. Paint films formed from vinyl chloride copolymers without functional groups are heat sealable on account of their thermoplastic character. Since the films adhere poorly to nonabsorbing substrates such as metals, they are suitable as binders for strippable coatings. On account of their good chemical resistance, vinyl chloride copolymers are also extremely suitable as binders for exterior-use paints, traffic paints, and paper and foil lacquers; their lack of taste and odor means that they can be used as pasteurization-resistant coatings for can interiors. -7.4. Vinyl Couiings 27 Vinyl chloride terpolymers containing carboxyl groups adhere extremely well to metals. Due to their special properties (outstanding adhesion to aluminum, good chemical resistance, heat-sealable from ca. 140 'C-the sealing temperatures can be lowered by adding plasticizers) these copolymers are ideal binders for heat-sealable finishes of aluminum foils used in the packaging sector. Vinyl chloride copolymers containing hydroxyl groups can be used in combination with other binders in reactive systems. The non-cross-linked paint films are thermoplastic and therefore heat-sealable. Cross-linking (e.g., with melamine resins or polyisocyanate resins) lowers the thermoplasticity and improves adhesion and resistance. The hydroxyl groups are also responsible for very good adhesion to organic substrates; these copolymers are therefore used as intermediate layers in marine coatings. In two-component polyurethane lacquers, hydroxyl-containing vinyl chloride copolymers can be used alone or in combination with polyols. In the latter case, lacquer viscosity can be adjusted and initial physical drying can be accelerated. As a result of their outstanding pigment wetting and stabilization properties, their high pigment loading, and compatibility with polyester and polyurethane resins, hydroxyl-containing vinyl chloride copolymers are used as binders for magnetic storage media. Commercial products include Hostaflex (Vianova); Laroflex, Lutofan (BASF); S-Lec (Sekisui); Ucar. Vinylite (Union Carbide); Vilit (Hiils); and Vinnol (Wacker). 2.4.3.2. Vinylidene Chloride Copolymers On account of its low thermal stability, poly(viny1idene chloride) is seldom used in paints. Vinylidene chloride copolymers with vinyl chloride, acrylonitrile, or acry- lates are mainly employed. These heat-sealable copolymers are efficient gas barriers and have an outstanding resistance to chemicals. They are marketed as solid resins and dispersions. Vinylidene chloride copolymers are mainly used for coating food- packaging foils. They are also important in paint coatings where good chemical resistance is required. Commercial products include Diofan (BASF), Haloflex (ICI), Ixan (Solvay), and Saran (Dow Chemical). 2.4.3.3. Fluoropolymer Coatings Organic fluoropolymers have been used in many fields because they have special properties that no other polymers can provide. Coating is one of the important uses of fluoropolymers, since it enables them to exhibit their characteristics on the surface of a substrate. Some of the conventional fluoropolymers such as polytetrafluoroethylene [ 9002-84-01 (PTFE), tetrafluoroethylene- hexafluoropropylene copolymer [25067-11-21 (FEP), and ethylene- tetrafluoroethylene copolymer [ 25038-71-51 (ETFE) have been used as antistick or anticorrosive coatings. Only poly(viny1idene fluoride) [ Y002-58-11 (PVDF) has so far been used in paints. The major difficulties in employing thermoplastic fluoropolymers in paints and coatings result from their poor solubility in organic solvents and 28 2. Tvprs qf Paints arid Coatings ( Bindtw) also from the necessity to bake them at a rather high temperature (> 200°C). In recent years, however, novel fluoropolymers with curable characteristics have been developed (one of them was successfully commercialized), mainly as highly weather- resistant paints [2.14], [2.15]. Coatings with Thermoplastic Fluoropolymers. Pol?,(vin~lidenefluoride), PVDF, is the only conventional thermoplastic fluoropolymer that is used as a commercial product for weather-resistant paints. This crystalline polymer is composed of -CH,CF,- repeating units; it is soluble in highly polar solvents such as dimethyl- formamide or dimethylacetamide. Poly(viny1idene fluoride) is usually blended with 30-30 wt% of an acrylic resin such as poly(methy1 methacrylate) to improve melt flow behavior at the baking temperature and substrate adhesion. The blended polymer is dispersed in a latent solvent (e.g., isophorone, propylene carbonate, dimethyl phthalate). The dispersion is applied to a substrate and baked at ca. 300°C for ca. 40-70 s. The weather resistance of the paints exceeds 20 years [2.16]-[2.18]. Commercial products include Kynar (Elf Atochem), Hylar (Ausimont), and Soles (Solvay). Copolymers of vinylidene fluoride with tetrafluoroethylene or hexafluoropropylene have recently been developed as an air-drying paint mainly for repair coating of the PVDF finish [2.19]-[2.21]. Poly(viny1idene fluoride) is now widely used for coil coating of galvanized iron and aluminum sheets, and as a maintenance-free coating for walls of skyscraper buildings and roofing of industrial constructions. Pol~tetrufluororth?~le~~e. An aqueous dispersion of PTFE is produced by emulsion polymerization of tetrafluoroethylene followed by thermal concentration of the latex up to ca. 60 wt%. Since the polymer has a very high melt viscosity and does not adhere to many substrates, the properties of the finish are greatly influenced by pretreatment of the substrate. On physically or chemically pretreated iron or aluminum, the PTFE coating is rather vulnerable to scratching (soft coat). If, however, the treated substrate is first coated with a ceramic-powder primer to form a coarse, hard surface, the subsequently applied PTFE finish becomes tough and scratch-resistant (hard coat). These coatings are used in hot cooking ware (e.g., frying pans) with the advantage of being nonstick and easily lubricated [2.22], [2.23]. Recently, mixtures of PTFE dispersions and heat-resistant hydrocarbon polymers (e.g., poly- imide, polyether sulfone, or polyphenylene sulfide) have been developed to improve the poor adhesion of fluoropolymer to a substrate and applied as a primer or one-coat enamel [2.24]. Tetrufluoroethylene Copolymers. Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and tetrafluoroethylene-perfluoroalkoxyethylene (PFA) are used as dispersion coatings in the same way as PTFE, taking advantage of their low melt viscosity and low viscosity at baking temperature. Powder coating is another popular technique in fluoropolymer coating. Tetraflu- oroethylene ethylene copolymer (ETFE) has a highly alternating sequence with a low melting point (280 "C) and low melt viscosity. Tetrafluoroethylene-ethylene copolymer powder has a better melt processability than PTFE; electrostatic coating gives thick finishes without pinholes that have excellent anticorrosive and antistick characteristics. Tetrafluoroethylene-perfluoroalkoxyethylene is also applied as a powder coating, exploiting its low melt viscosity in the same way as ETFE. [...]... Figure 2. 2 Structure of Lumiflon polymer -I j F-C-X Several fluorooletin-vinyl terpolymers have been developed based on the Lumiflon polymer [2. 32] - [2. 35]: +CF,CF - C H , C H W C F , C F -CH,CHt;; I X I OR' X bR2 +CF2CF - C H , C H W C F , C F -CH,CHt;; X OK' X OCR2 ll [2. 14] 12. 291 [2. 32] O fC'F,C'F -CHICHt;;tCF,CF X OR' X -CH,CHt &H,OR~ 12. 331 [2. 34] [7.35] 2. 4 Vinvl Coatings 31 Recently waterborne coatings. .. are its excellent weatherability and its ease of handling and processing [2. 23], [2. 29]- [2. 31] The hydroxyalkyl groups in the polymer react with polyisocyanates at room temperature and with melamine resin or blocked isocyanates at higher temperature Lumiflon can therefore be formulated for both on-site coatings that are cured at ambient temperature and for thermoset coatings in the factory Practical... alkyd resins replaced stand oils on account of their faster drying and curing rates as well as their better film hardness and gloss retention 42 2 Types of‘ Paints iind Cocliings (Binders) Alkyd paints are used for protection and decoration in virtually all sectors including coatings in the steel, sheet, and metal processing sector, house and decorative paints, do-it-yourself paints, wood varnishes,... after reaction with 10 -20 % polyamidoamines at elevated temperature (ca 20 0''C) [2. 67], [2. 68] Thixotropic resins are mainly used for decorative paints and primers, and in corrosion protection coatings Thixotropic alkyd resins prevent the formation of precipitates, improve brushability, and reduce the sagging of paints on vertical surfaces and from edges and corners Thixotropic coatings (including those... the term alkyd resins and contains a summary of international standards for testing alkyd resins ASTM D 47 12- 87 (Standard Guide for Testing Industrial Water-Reducible Coatings) may also be mentioned; it includes standards covering the testing of wet paints (properties, storage, application, film formation) and paint films ~ 2. 6 .2 Additional Raw Materials (See also Chapter 5 ) Solvents Alkyd resins... Environmental and Health Protection Measures The solvents in the as-supplied alkyd resin solutions and in the paint composition represent a potential hazard due to their (eco)toxicological effects and flammability Manufacturers and suppliers of resin solutions and paints must indicate the potential dangers involved in the handling, transportation, and storage of solvents by labeling drums and containers... coil and can coatings [2. 83] The reaction system consisting of “acid” (i.e., carboxy-functional) polyester resins and epoxy resins is important for powder coatings [2. 84] Acid polyester resins can be neutralized (e.g., with amines), diluted with water, and processed into aqueous stoving enamels [2. 85] Acrylate-modified polyester resins have proved suitable as binders for radiationcurable coatings [2. 86]... elasticity and resistance to chemicals The coatings are resistant to overstoving and have a good gloss retention and chalking resistance under weathering conditions Their very good adhesion (even on untreated metal) is an important advantage They are used in enamels and coatings for domestic appliances, washing machines, and refrigerators, as well as for OEM automotive finishes Waterborne Alkyd Resins t2. 721 ... molecular mass and molecular mass distribution [2. 45]- [2. 47], [2. 50]- [2. 53] Oligomers with a molecular mass of ca 1000-3000 are required for high-solids paints [2. 48], [2. 54] An acrylate binder with a molecular mass of 100000 can be processed to form a paint with 12. 5% solids content at the application viscosity; a molecular mass of ca 6000 results in a paint with 50% solids content [2. 46] A narrow... oil and water repellency, and antifouling properties [2. 38], [2. 39] 2. 4.4 Poly(Viny1 Esters) Poly(viny1esters) used in paints and adhesives are available as homopolymers and copolymers in the form of solid resins, solutions, and dispersions 2. 4.4.1 Solid Resins Poly(viny1 acetate) and vinyl acetate copolymers with crotonic acid, vinyl laurate, and dibutyl maleate are important solid resins; some are . bR2 +CF2CF -CH,CHWCF,CF -CH,CHt;; X OK' X OCR2 ll O fC'F,C'F -CHICHt;;tCF,CF -CH,CHt X OR' X &H,OR~ [2. 14] 12. 291 [2. 32] 12. 331 [2. 34] [7.35] 2. 4 material. The outstanding characteristics of this polymer as a coating material are its excellent weatherability and its ease of handling and processing [2. 23], [2. 29]- [2. 31]. The hydroxyalkyl. S20 Pergut S40 Pergut S90 Pergut S 130 Pergut S 170 3.5-6.5 9.0-13.0 16.0 -24 .0 33.0-51.0 74.0- 110.0 120 .0- 150.0 130.0 -20 0.0 60.000 124 .000 160.000 21 3.000 3 02. 000 327 .000

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