High-solids paints alkyd resins

By depolymerizing PET waste with a polyol and subsequently condensing the oligomeric product with a polycarboxylic acid or anhydride, polyester resins are produced which have wide industrial applications. Depending on the polyol and polycarboxylic acid or anhydride used, saturated resins, alkyd resins, or unsaturated resins are obtained. PET wastes have been used for the production of alkyd resins in water thinnable paints. The materials obtained from the reaction of PET with a mixture of fatty acids high in linoleic acid content and trimethylolethane have been used in the preparation of water-dispersible coatings. Products of the depolymerization of PET with trimethylolpropane and pentaerythritol are used in the manufacture of high-solids paints. In the first step, PET is depolymerized with trimethylopropane and pentaerythritol at temperatures of 230-240°C. The final paint compositions contain 30-50% of PET depolymerization products.12... 

Another commercially important crosslinking process that involves unsaturated polymer precursors is the so-called drying of alkyd resins in paints. This process is not drying at all, at least not in the sense of mere loss of solvent to leave behind a solid residue. Instead, the main process is the conversion of high relative molar mass molecules to a crosslinked structure via... 

Recently, the development of environmentally friendly binders produced from renewable agricultural resources, e. g. linseed and tall oil fatty acids, has been described [36]. These new poly(HAMCL) resins were applied in high solid alkyd-like coatings and paints. 

A highly concentrated dispersion of carbon black is first prepared with a portion of the binder and solvent. The viscosity of this concentrate is a function of the particle size, structure, and surface chemistry of the black, the type of binder and its interaction with the pigment black, and the proportions of black, binder, and solvent. The final paint is made from the concentrate by adding more binder and solvent, its carbon black concentration is 3-8% referred to the solids content. Wetting agents are sometimes added to improve dispersibility and prevent flocculation. A number of concentrates for paint manufacture e.g., carbon black-nitrocellulose chips or carbon black -alkyd resin pastes, can be obtained from paint producers. 

Solvents are selected such that some will escape relatively quickly from paint films to prevent excessive flow, while others will escape slowly to provide film leveling and adhesion. With typical alkyd coatings, the first 30% of solvent has been observed to evaporate as quickly as the neat solvents, essentially at a constant rate which is dependent on volatility. Later stage evaporation occurred several times more slowly and was rate-controlled by solvent diffusion to the surface of the paint film. The transition point between this behavior was defined as the resin solids content at which the evaporation rate due to volatility equaled that due to diffusion. Transition points have been observed to typically occur at a resin solids content of 40-50% v/v. Thus alkyd paints, normally formulated at 27-40% v/v resin solids, generally exhibit rapid initial solvent-release driven by volatility while high solids coatings (usually 65-75% v/v resin solids) dry solely by a diffusion-controlled process with negligible influence by solvent volatility (Ellis, 1983). 

Epoxy paints (see also Section 2.10) are usually applied as two-pack systems. Curing with amines is preferred in high-solids systems. Epoxy resins may also be used as coreactants or reactive diluents in low-solvent paints based on acrylic, polyester, or alkyd resins. 

The relatively low molecular weights of alkyd resins allow medium-high solids at brushing viscosity (about 5 poises). Films dry to touch in about 1-4 hours in warm weather, but take longer when it is cold. Once air is allowed into the paint can, drying occurs at the surface forming a skin it does not usually go deeper. Alkyd films harden slowly over many days. Those designed to last outdoors are soft and easily marked, but very flexible. 

Mr B.M. Letsky, Industrial Finish Consultant, for the nitrocellulose lacquer formula in Table 11.2. Rohm Haas Company, Philadelphia, USA, for the acrylic lacquer formula in Table 11.2. Worlee Chemie GmbH for the water-borne air-drying formula in Table 12.1. DSM Resins (UK) Ltd for the emulsified alkyd paint formula in Table 12.5, the metallic car finish formula in Table 13.2 and the acrylic isocyanate formulae in Table 15.3. BIP Ltd for the woodfinish formula in Table 13.1. Amoco Chemicals UK Ltd for the high solids and water-based formula in Tables 13.4 and 13.5. 

US 3,870,664 and US 3,870,664 to Research Corporation New York disclose oil modified sucrose resins obtainable by reaction of a partial esterified sucrose ester with a cyclic dicarboxylic anhydride and a diepoxide. Although this work mentions alkyd resins based on renewables, it is not specifically aimed at deriving high solid alkyd paints based on resins with a low intrinsic viscosity. 

Characteristics of high solid alkyd paint formulations containing sucrose based alkyd resins are shown in Table II. 

Research projects carried out at A F clearly indicate that effective plasticisers for PVC and other resins and binders and additives for alkyd based decorative paints can be based on those raw materials which are the least undisputed from an environmental point of view i.e. renewable resources. These products are not only renewable based but also durable. Provided a positive life cycle analysis, after further R D work plasticisers and high-solid or water borne alkyd paints based on renewables therefore can make an important contribution to a sustainable chemical industry. 

Uses Deaerating agent for med. and high polar coating systems, esp. PU paints, high solids alkyds, ES spray tems, and urethane-polyesters resinous/poly-... 

---