Patent GB-528438-A (GB)
Title: Synthetic resins
IPC: C08F20/62
Filed: 1939-05-08
Abstract: 528,438. Esters of hydroxydiphenyls and their polymerization products. NORTON GRINDING WHEEL CO., Ltd. May 8, 1939, No. 13668. Convention date, Aug. 1, 1938. [A Specification was laid open to inspection under Sect. 91 of the Acts, Nov. 8, 1939.] [Class 2 (iii)] Esters of mono- or poly-hydroxy substituted diphenyls are prepared by reacting a mono- or poly-hydroxy diphenyl with an anhydride of acrylic acid or methacrylic acid. The esters so produced may be polymerized to produce synthetic resins which have a high softening point and which may be used as a bond for granular materials and may be ground and polished to produce a smooth optical surface which has a high refractive index. The monomeric diphenyl esters may also be co-polymerized with other polymerizable compounds which are called unsaturated methylene compounds and which contain the group CH  2  = CR- where R is hydrogen or a methyl or aryl group. The hardness and the optical properties may be regulated by a suitable choice of material to be co-polymerized. Such materials which are mentioned include allyl methacrylate, glycol dimethacrylate, acrylic acid, methacrylic acid, acryllic anhydride methacrylic anhydride, vinyl methacrylate, vinyl acrylate, vinyl acetate and styrene. The diphenyl ester monomer may be polymerized in a mould and yields a polymerization product very suitable for optical work. It may also be polymerized in the presence of abrasive grains such as silicon carbide, crystalline alumina, boron carbide or diamond granules. The refractive indices of the polymers are very high, but products with lower refractive indices may be obtained by co-polymerization with other bodies. The polymers may be increased in hardness by the addition of further unsaturated methylene compounds as defined above. Preferred compounds for this purpose are acrylic acid and methacrylic acid, or an unsaturated methylene compound which contains at least two polymerizable unsaturated groups per molecule such as the anhydride of acrylic acid or,methacrylic acid or esters thereof with allyl alcohol or alpha substituted allyl alcohol, or polyhydric alcohols such as mono-, di-, tri- or tetra-ethylene glycol, glycerol, pentaglycerol, pentacrythritol, trimethylolpropane and trimethyleneglycol. The effect of the modifying agents is to raise the softening point. In an example of the preparation of the monomer of a diphenyl ester, there are reacted together, ortho-hydroxy diphenyl, methycrylic anhydride, pyridine and an inhibitor of polymerization such as copper methacrylate. The yellow oily product is purified by distillation. This compound may be polymerized by heating it to 50‹-100‹C. with or without a catalyst such as benzoyl peroxide. As an example of the preparation of a resin of copolymerized substances there may be used 40 per cent. by volume of methyl methacrylate. 40 per cent. of the methacrylic acid ester of ortho-hydroxy diphenyl and 20 per cent. of methacrylic acid. A further example involves using 50 per cent. methyl methacrylate, 40 per cent. of the methacrylic acid ester of orthohydroxy diphenyl and 10 per cent. of ethylene glycol dimethacrylate. The resins so formed are light in weight, have high elasticity, high enough softening points to resist abrasion under ordinary conditions, and transparency and ability to be shaped by grinding.