Cross-linking phthalate resins

Simply heating diallyl o-phthalate with benzoyl peroxide at 115°-125 C produced a highly cross-linked thermoset resin [92]. The usual methods of producing prepolymers involve the interruption of the polymerization process before gelation sets in (at about 25% conversion). 

The principal unsaturated acids used are maleic and fumaric. Saturated acids, usually phthalic and adipic, may also be included. The function of these acids is to reduce the amount of unsaturation in the final resin, making it tougher and more flexible. The acid anhydrides are often used if available and applicable. The dihydroxy alcohols most generally used are ethylene, propylene, diethylene, and dipropylene glycols. Styrene and diallyl phthalate are the most common cross-linking agents. Polyesters are resistant to corrosion, chemicals, solvents, etc. 

Whereas monoallyl derivatives sdeld thermoplastic polymers, allyl esters containing two or more unsaturated groups yield thermosetting resins. Thus, monoallyl esters of unsaturated acids, e.g., allyl acrylate, allyl methacrylate, allyl crotonate, and allyl itaconate, and diallyl esters of dibasic acids, e.g., diallyl oxalate, diallyl phthalate, and diallyl itaconate, yield thermoset resins, which generally combine solvent resistance, toughness, hardness, transparency, and heat resistance. The cross-linking tendency of the allyl esters makes them useful in copolymerization wherein they impart these properties to normally linear polymers. 

Diallyl phthalate is used as a monomer as well as in prepolymer form in the preparation of reinforced plastics. Diallyl itaconate is also used as a cross-linking agent for unsaturated polyester resins as well as in cross-linking of vinyl copolymers. 

The study of unconjugated diolefin polymerizations is usually considered quite difficult because complex, three-dimensional networks are set up at very low conversion. Such cross-linked materials are generally intractable. The situation is quite different in the case of diallyl esters, especially in the case of diallyl phthalates. Both diallyl o-phthalate and diallyl m-phthalate may be converted to prepolymers, which are soluble in a variety of solvents. These two prepolymers are commercially availabe. When dissolved in their respective monomers and heated in the presence of typical initiators, such solutions are converted to cross-linked resins. Most of the shrinkage related to the conversion of monomers to pol)mers has taken place when the pre-polymer was formed originally. Therefore solutions containing relatively high levels of diallyl o-phthalate prepolymer shrink little on polymerization. 

The most extensive research and development activity has involved diallyl o-phthalate. The studies on the cyclopolymerization of this monomer have already been discussed at length in Section 3 of this chapter. Diallyl isophthalate polymerizes more rapidly than the the ortAo-isomer. It cyclizes less during the early stages of polymerization. Consequently the prepolymer of the isophthalate has more reactive double bonds available for further reaction than the o-phthalate and the final resin produced from it is more highly cross-linked [91]. 

The variability in the pyrolysis profiles of the different classes of coatings is self-evident. The interpretation of the composition revealed is as follows The acrylic lacquer (General Motors) is a methyl methacrylate/methacrylic acid copolymer plasticized with dibutyl-, butyl cyclohexyl-, and butyl benzyl phthalates. The acrylic enamel (Ford) is a styrene/ethylhexyl acrylale/methyl methacrylate terpolymer. The alkyd enamel (Honda) pyrolysis profile indicates that the paint resin is an orthoph-thaUc alkyd containing a butylated-amino resin cross-linking component. 

Polyester resins, cross-linked butyl ben l phthalate (containing not more than 1.0 wt% of dibenzyl phthalate), dibutyl ph alate, dimethyl phdialate, triphenyl phosphate... 

Diallyl phthalate resins n. Laminating resin prepared by free radical polymerization of diallyl phthalate. The polymer is highly cross-linked, with good thermal stability and retention of electrical properties under conditions of wet and dry heat. 

The allergens in UP resin are often the auxiliary chemicals in the resin, such as cobalt naphthenate (Key et al. 1961 Bourne and Milner 1963 Malten and Ziehlhuis 1964 Kadlec et al. 1974), dibutyl phthalate, dimethyl phthalate, dioctyl phthalate (Malten and Ziehlhuis 1964), tricresyl phosphate (Key et al. 1961) or a cross-linking monomer, such as styrene (Key et al. 1961 Bourne and Milner 1963 Meneghini et al. 1963 Sjoborg et al. 1982 Conde-Salazar et al. 1989) or a hardening catalyst such as benzoyl peroxide (Bourne and Milner 1963 Malten and Ziehlhuis 1964 Vincenzi et al. 1991), cyclohexanone hydroperoxide (Malten 1964) or methyl ethyl ketone hydroperoxide (Bourne and Milner 1963 Malten and Ziehlhuis 1964). The... 

Unsaturated polyesters are produced from a mixture of esters made from unsaturated fatty acids, cross-linked vinyl monomer, and various polyols. The mixture is polymerized to form a cross-linked resin, with styrene monomer being used as a common vinyl cross-linking agent. Methacrylate esters, diallyl phthalate, a-methyl styrene, and vinyl toluene have also been used for this purpose. Certain dibasic unsaturated acids (or derivatives), such as... 

Certain alkyd resins are used for the production of moulding powders. In this case the resin is formulated on an unsaturated acid and alcohol producing an unsaturated polyester (see polyester resins). This polyester is reacted with a non-volatile monomer, usually diallyl phthalate, to give a hard cross-linked structure. 

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