Basecoat binder

The solvent-borne basecoat, consisting of polyester or acrylic binder to be cross-lined with melamine or isocyanate, is applied at a dry film thickness of between 0.6 and 1.5 mils, depending upon the color. Poorer-hiding colors, such as red and white straight shades, require the higher film builds, whereas metal lies and darker colors are applied at the lower film builds. The solvent-borne basecoat is allowed to flash-ofif solvent for approximately 3-5 min at ambient conditions prior to application or the solvent-borne clear-coat. This process is referred to as a wet-on-wet application because the basecoat is not in its cured or cross-linked state. 

Clearcoat, acrylic-melamine basecoat, polyester-cellulose, acetobutyrate-melamine, silver metallic bake 130"C, 30 min exposure Florida, 5 South, black box unheated percentage of light stabilizer relative to binder solids benzotriazole I, 2-(2//-benzotriazole-2-yl)-4,6-bis(l-methyl-1-phenylethyOphenol [70321-86-7], Cracking after 2.25 years. Cracking after 5.5 years. 

Uses Abrasion resist, aid, toughener, flexibilizer, hardener, gloss aid in water-based coatings (automotive OEM, refinish, primers, basecoats, topcoats), adhesives for wood/plastic/metal substrates, inks binder in waterborne inks, bonding and laminating applies. 

Chem. Descrip. Tliermosetting acrylic copolymer (60%) in butyl glycol Uses Binder for waterborne automotive solid color basecoats Properties Water-dilutable dens. = 1.02 g/cm (20 C) dynamic vise. 11,000-18,000 mPa s (23 C) acid no. 30-50 flash pt. (PM) = 65 C 58-62% NV... 

The solvent-borne clearcoat is spray-applied over the basecoat at a dry film thickness of 1.8 to 2.0 mils. The clearcoat, responsible for UV protection, chemical resistance, chip resistance, and so on, is most often composed of a hydroxy functional acrylic binder together with a melamine or an isocyanate cross-linker. Ultraviolet light absorbers and hindered amine light stabilizers also are added to achieve better free-radical oxidative degrada-... 

Critical to formulating a successful metallic basecoat is the selection of aluminium paste. In general the larger the particle size of the flake, the better the lustre. A polyethylene wax dispersion is also incorporated into the formulation to aid metal control and lustre. The binder in solvent based systems is a durable saturated polyester cured with a melamine formaldehyde resin and modified with CAB, to assist in film setting and hardness. 

Compared with conventional paints, white basecoats are formulated with high loadings of pigment. Pigment/binder ratios as high as 1.2/1.0 w/w are not uncommon. This is necessary to achieve the required opacity at low film thicknesses of around 8 microns. 

Water-borne emulsion polymers are used in formulating automotive coatings for electrocoat, primers and basecoats. Clearcoat polymers are primarily still solvent-borne. A powder dispersed in water (powder slurry) has been developed as a binder for clearcoats [7]. 

Polymer dispersions are applied as coating binder mainly in three of the four layers electrocoat, primer and basecoat. These layers are now described in more detail. 

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