Silicone-modified alkyd resins

Silicon modified alkyd resins to promote rapid curing of coatings [109]. 

Modified alkyd resins In this group one finds styrenated alkyds, vinyl toluenated alkyds, oil-modified vinyl resins, acrylic alkyds, silicone alkyds and polyurethane alkyds. The modifying component usually has a number of effects. It always increases the molecular weight of the alkyd polymer, and may impart hardness, durability, or chemical resistance. It also affects the solubility of the polymer in solvents. 

High phenyl content resins are compatible with organic resins of the P-F, U-F, M-F, epoxy-ester and oil-modified alkyd types but are not compatible with non-modified alkyds. Silicone resins are highly water repellent. 

Another specialty area is coil coating, which involves coating metal coils by continuous operation. Modern roller systems afford speeds of up to 200 m/min. Most coils are made of cold-rolled and surface treated steel, aluminum, or alloys of the latter with manganese or magnesium. Coating systems are based on alkyd or acrylic resins, oil-free polyester, silicone-modified polyester or acrylic resin, poly(vinylidene fluoride), or poly(vinyl fluoride). Water-reducible systems, mainly based on acrylic resins, have been developed for aluminum as well as for steel coils [21-24], Drying is carried out by continuous operation in gas- or oil-heated multichamber ovens. 

Although blending with other coating resins provides a variety of ways to improve the performance of alkyds, or of the other resins, chemically combining the desired modifier into the alkyd structure eliminates compatibility problems and gives a more uniform product. Several such chemical modifications of the alkyd resins have gained commercial importance. They include vinylated alkyds, silicone alkyds, urethane alkyds, phenolic alkyds, and polyamide alkyds. 

DIN 53183 defines an alkyd resin as follows Alkyd resins are synthetic polyester resins produced by esterifying polyhydric alcohols with polybasic carboxylic acids. At least one of the alcohols must be trihydric or higher. Alkyd resins are always modified with natural fatty acids or oils and/or synthetic fatty acids. In order to obtain particular application technology properties, alkyd resins may be additionally modified with compounds such as resin acids, benzoic acid, styrene, vinyltoluene, isocyanates, acrylic, epoxy, or silicone compounds. ... 

Chem. Descrip. Silicone-modified defoamer Uses Defoamer for emulsion paints, alkyd resin emulsions paints, waterborne two-component epoxy paints, gloss and silky gloss emulsion paints. 

Another classification is unmodified or modified alkyds. Modified alkyds contain other monomers in addition to polyols, polybasic acids, and fatty acids. Examples are styrenated alkyds and silicone alkyds. Since they are closely related to alkyd resins, uralkyds and epoxy esters are also discussed. 

The modifications with urethane and silicone are discussed in Section 2.11.3.2 and 2.12.5 respectively. Alkyd resins are modified by reacting them with polyamide resins to achieve special rheological properties (Section 5.3.2.5) and are called thixotropic alkyds. Although epoxy esters are a class of epoxy resin, they are frequently considered alkyds rather than epoxies. They are also ester-based... 

Alkyd chemistry lends itself to further modification beyond choice of polyol, dibasic acid, and drying oil. Vinyl-modified alkyds, for example, are produced for more durable and quicker drying films, although with some sacrifice in crosslinking rate and consequent development of solvent resistance. Styrene, vinyl toluene, and methyl methacrylate are the most commonly used modifiers. In the presence of a free radical initiator, vinyl polymer will graft onto the alkyd. Tack-free time (i.e. a surface-dry film) may be reduced from 4 to 6 hoius for an unmodified alkyd to 1 hour in styrenated form. Acrylics, silicones, phenolic resins, and natural resins are likewise used to tailor film gloss, flexibility, durability, and drying time for certain applications. 

Silicone resins may be combined with other resinous materials to give modified resins which find use in surface coatings. Combination of the two materials may be achieved either by blending or copolymerization. Silicone resins with a high phenyl content are compatible to some extent with various resins such as alkyd, esterified epoxy and phenol-, urea- and melamine-formaldehyde resins and cold blending may be carried out. However, the limited compatibility of the components restricts the scope of the products which may be obtained. Copolymerization has been applied mainly to silicone-alkyd resins, which are prepared by heating a low molecular weight... 

Silicone alkyds These are alkyds modified with silicone resin. They have superior resistance to weathering (particularly gloss retention) than pure alkyds but are generally significantly more expensive. They are useful for exterior use where appearance is important. 

Saturated polyesters and saturated alkyds cannot undergo such modification with vinyl monomers but can be modified with other polymers such as silicone resins by alcoholysis. Here outdoor durability is considerably improved. 

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