Alkyd modification

Alkyds can be used in combination with either acrylamide or hydroxy functional acrylics. Very often this results in an improvement in application solids. However, the alkyd must be carefully chosen, firstly in terms of compatibility with acrylics, and secondly from the point of view of what it will contribute to (or detract from) film performance. Clearly, the colour retentive alkyds are most likely to be selected so that the excellent colour and colour retention of the acrylic is not compromised. 

Cardura ElO based alkyds have been found to have excellent compatibility with both acrylamide functional and hydroxy functional acrylics . In general, a maximum level of 30% alkyd on solid binder is recommended, which can, depending upon the choice of alkyd, result in an increase in solids content and an improvement in exterior durability. 

Higher levels result in significant reductions in hardness and general resistance properties. 

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Uses Drying oil for prep, of quality coating vehicles by cold blending (clear exterior finishes, aluminum paints, anticorrosive primers, blister-resist. wood primers, alkyd modification)... 

These products are useful for modification of alkyd resins (qv), preparation of paint vehicles, and copolymeri2ation with other monomers. Substitution on the amino group occurs readily, giving bases stronger than the parent amines. 

Synthetic Applications. Oxazolines, which ate synthesized as indicated above, have been utilized in many different appHcations (25). When used in resin formulations, AMP, AEPD, and TRIS AMINO can incorporate the oxazoline stmeture into the polymer stmeture (26). Because they ate polyols, both AEPD and TRIS AMINO can be used in polyester resin modification. Oxazoline alkyd films ate characterized by improved performance, particularly salt-spray resistance and gloss (see Alkyd resins Coatings, special purpose, high performance). 

Modification of Alkyd Resins by Blending with Other Polymers... 

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 stmcture eliminates compatibiUty problems and gives a more uniform product. Several such chemical modifications of the alkyd resins have gained commercial importance. 

Soybean oil and tall oil fatty acids are not used in paints without modification. These products, Hsted as used in paints, first must be converted to alkyds or other synthetic drying oils. Presumably significant amounts of the linseed oil Hsted under paints are also converted to alkyds or other derivatives before use. In addition to the numbers given in Table 2, relatively large amounts of the oils are reported to have been consumed by conversion into fatty acids. Some indeterrninate fraction of the fatty acids, especially tall oil fatty acids, are presumably converted into derivatives that are used like drying oils. 

Stripping of top coats soaked by rain or sea-water has occurred with alkyd-resin-based paint systems, mainly on ships. The risk of such intercoat failure is reduced if the time interval between application of coats is reduced, but is best controlled by modification of the alkyd resin with a proportion of a different material. 

Modification of alkyd resins with high proportions of silicones considerably reduces rates of attack, but the most spectacular extension of life is shown by fluorinated polymers such as polyvinylidene fluoride where erosion rates can be reduced to 0 -1 /tm/year. If this level of durability can be achieved an initial coating, if firmly adherent and free from any breaks, may often be expected to maintain protection over a metal substrate for the likely life of the structure. The considerably increased first cost, as compared with more conventional coatings, has to be balanced against the probable saving in maintenance costs or consequences of failure. 

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. 

Smith condensed phthalic anhydride with glycerol in 1901 to prepare a glassy brittle material. Kienle in 1924 started investigating these resins and called them alkyds, He modified the polyesters with drying oils. By this modification they become soluble, on exposure to oxygen rapid cross-linking occurs and... 

Fig. 36 Dispersion of Pigment Violet 19, (l-modification, in an alkyd-melamine resin baking enamel with a paint shaker. Reduction 1 2 with Ti02. Tinctorial strength-time curve.

Fig. 48 Electron micrographs of ultramicrotome-cut thin sections of a nonirradiated and an irradiated layer (alkyd-melamine resin baking enamel) containing Pigment Violet 19, y-modification. Above irradiated, below nonirradiated.

Several applications of hyperbranched polymers as precursors for synthesis of crosslinked materials have been reported [91-97] but systematic studies of crosslinking kinetics, gelation, network formation and network properties are still missing. These studies include application of hyperbranched aliphatic polyesters as hydroxy group containing precursors in alkyd resins by which the hardness of alkyd films was improved [94], Several studies involved the modification of hyperbranched polyesters to introduce polymerizable unsaturated C=C double bonds (maleate or acrylic groups). A crosslinked network was formed by free-radical homopolymerization or copolymerization. 

There are important modifications of alkyds that help in specific applications. Phenolics can be added to improve film hardness and water resistance, but these confer increased yellowing tendencies on the final coating. Silicones impart heat resistance and exterior durability. Styrene increases the drying speed. Methyl methacrylate when added gives faster drying properties and improves the color and durability of the coating. 

Polyester A resin formed by the reaction between a dibasic acid and a dihydroxy alcohol, both organic. Modification with multi-functional acids and/or bases and some unsaturated reactants permit crosslinking to thermosetting resins. Polyesters modified with fatty acids are called alkyds. 

MODIFICATION OF ALKYD RESINS BY BLENDING WITH OTHER POLYMERS 343... 

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