Resin composition for cast polymerization

Abstract: Disclosed herein is a polybutylene glycol dimethacrylate which provides various kinds of plastics having good flexibility and low water absorption. Disclosed also herein is a resin composition for cast polymerization which provides molded products which have high heat resistance, good flexibility, and low water absorption, without sacrificing impact resistance and surface hardness. They will find use as optical materials, lenses, etc.

Description: The present invention relates to a resin composition for cast polymerization containing polybutylene glycol dimethacrylate. More particularly, the present invention relates to a resin composition for cast polymerization containing polybutylene glycol dimethacrylate, which are useful for the production of plastics having high heat resistance, good flexibility, and low water absorption. At present, plastics find use in a variety of fields as molding materials, optical lenses, optical discs, electric and electronic parts, film, machine parts, and laminated glass. Plastics for these applications are required to have improved toughness, flexibility, and impact resistance. This requirement is met by incorporating polymer chains with polyether, polyurethane, polyester, or polycarbonate which has an elastic structure. The incorporation is carried out in the stage of monomer or oligomer prior to polymerization. There are application areas where plastics are required to be moisture-resistant. This requirement is met by incorporating polymer molecules with hydrocarbon chains, aromatic rings, halogen atoms. etc. In the case where a polymer is produced by cast polymerization, it is desirable to use a monomer of low viscosity for good workability. This requirement is met when the polymer molecular chain has the polyether structure which is highly elastic. This polyether structure is imparted by polyethylene glycol di(meth)acrylate or polypropylene glycol di(meth)acrylate. The flexibility of polymer increases in proportion to the number of such repeating units as ethylene oxide and propylene oxide contained therein. Although it is possible to lower the water absorption of a polymer by incorporating it with hydrocarbon chains, aromatic rings, or halogen atoms, the resulting polymer lacks flexibility. The requirement for flexibility is met by the above-mentioned polyethylene glycol di(meth)acrylate for cast polymerization which has the polyether structure. This polymer, however, has a water absorption as high as 10-20%. The present invention was completed to eliminate the above-mentioned disadvantages. Accordingly, it is an object of the present invention to provide a resin composition for cast polymerization which yields a molded product having both good flexibility and low water absorption, without loss of impact resistance, heat resistance and surface hardness. The polybutylene glycol dimethacrylate is represented by the general formula below. (where n is an integer of 5 to 16.) The resin composition for cast polymerization pertaining to the present invention is composed of: (a) 10-90 parts by weight of at least one compound selected from the group consisting of epoxy poly-(meth)acrylate having two or more (meth)acryloyloxy groups in one molecule and urethane poly(meth)-acrylate having two or more (meth)acryloyloxy groups in one molecule, said urethane poly(meth)-acrylate having been obtained by the reaction of a hydroxy group-containing (meth)acrylate with isophorone diisocyanate, trimer of hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, dicyclohexyl-methane diisocyanate, 1,3-bis (α,α-dimethylisocyanatethyl)-benzene, xyloplene diisocyanate, tetramethylene diisocyanate, dimer acid diisocyanate, cyclohexane diisocyanate, tolylene diisocyanate, diphenyl-methane diisocyanate, m-phenylene diisocyanate, naphthalene diisocyanate or biphenyl diisocyanate, and (b) 10-90 parts by weight of polybutylene glycol di(meth)acrylate represented by the general formula below, (where R represents hydrogen or methyl, n is an integer of 5 to 16) with the total amount of components (a) and (b) being 100 parts by weight. The above and other objects, features, and advantages of the present invention will become readily apparent from the following detailed description. The polybutylene glycol dimethacrylate is polybutylene glycol having a degree of polymerization in the range of 5 to 16, with its both terminals blocked with methacrylic acid. The degree of polymerization denotes the number of repeating units represented by the formula (CH₂CH₂CH₂CH₂O), and it should be in the range of 5 to 16 according to the present invention. With a degree of polymerization smaller than 5, it yields a polymer which lacks sufficient flexibility. With a degree of polymerization greater than 16, it yields a polymer which has a high water absorption and viscosity and a low crosslinking density and hardness and is poor in heat resistance and workability. The degree of polymerization should preferably be in the range 7 to 12. Needless to say, the polybutylene glycol dimethacrylate is a mixture of species which differ in molecular-weight distribution. The polybutylene glycol methacrylate includes, for example, pentabutylene glycol dimethacrylate, hexabutylene glycol dimethacrylate, heptabutylene glycol dimethacrylate, octabutylene glycol dimethacrylate, nonabutylene glycol dimethacrylate, decabutylene glycol dimethacrylate, undecabutylene glycol dimethacrylate, dodecabutylene glycol dimethacrylate, tridecabutylene glycol dimethacrylate, tetradecabutylene glycol dimethacrylate, pentadecabutylene glycol dimethacrylate, and hexadecabutylene glycol dimethacrylate. The polybutylene glycol dimethacrylate can be easily produced by the condensation reaction between polybutylene glycol (which is obtained by the ring-opening polymerization of tetrahydrofuran) and methacrylic acid, or by the ester interchange reaction between polybutylene glycol and methyl methacrylate. Which to choose depends on the end use of the polymer. If the polymer is to be made into a transparent material, it is necessary to choose the ester interchange reaction which gives rise to a colorless transparent monomer. The present invention covers resin composition for casing. It is composed of component (a) and component (b). Component (a) is at least one compound selected from the group consisting of urethane poly(meth)-acrylate having two or more (meth)acryloyloxy groups in one molecule and epoxy poly(meth)acrylate having two or more (meth)acryloyloxy groups in one molecule. The urethane poly(meth)acrylate includes those products which are formed by reaction between a hydroxyl group-containing (meth)acrylate and an isocyanate compound having at least two isocyanate groups in the molecule. Component (a) enhances the heat resistance imparted by component (b) which is polybutylene glycol di(meth)acrylate. Examples of the isocyanate compound having at least two isocyanate groups in the molecule include aliphatic, aromatic, and alicyclic isocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 1,3-bis-(α,α-dimethylisocyanatemethyl)benzene, diphenylmethane diisocyanate, m-phenylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, and biphenyl diisocyanate. Additional examples of the isocyanate compound include those compounds having at least two isocyanate groups in the molecule, which are formed by the reaction of one of said isocyanates with a compound having at least two active hydrogen atoms in the form of amino group, hydroxyl group, carboxyl group, or water. The above-mentioned diisocyanate compounds may be used in the form of trimer, tetramer, or pentamer. The hydroxyl group-containing (meth)acrylate to be reacted with a polyisocyanate includes hydroxyl group-containing (meth)acrylate (such as 2-hydroxyethyl (meth)-acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate); products formed by addition reaction between a monoepoxy compound and (meth)acrylic acid (such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl methacrylate); mono(meth)acrylic ester with polyethylene glycol or polypropylene glycol; and mono-(meth)acrylic ester with polycaprolactone diol (n = 1-5). The addition reaction between polyisocyanate and hydroxyl group-containing (meth)acrylate may be accomplished by any known process which consists of adding dropwise a mixture of hydroxyl group-containing (meth)-acrylate and a catalyst (such as di-n-butyl tin dilaurate) to an isocyanate compound at 50-90°C. The urethane poly(meth)acrylates may be used individually or in combination with one another. Those which are preferable from the standpoint of clarity and heat resistance of cast products are adducts of 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate with isophorone diisocyanate, trimer of hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,3-bis(α,α-dimethyl-isocyanatemethyl)benzene, or xylylene diisocyanate. Another member of component (a), which is epoxy poly(meth)acrylate, is a product formed by the ring-opening reaction of glycidyl group which takes place between an epoxy compound having two or more glycidyl groups in the molecule and a compound (such as acrylic acid and methacrylic acid) having a (meth)acryloyl group and a carboxylic acid in the molecule. This component enhances the heat resistance imparted by component (b) which is polybutylene glycol di(meth)acrylate. The epoxy compound having at least two glycidyl groups in the molecule includes the following. Aliphatic and alicyclic epoxy compounds such as 1,6-hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, tetraethylene glycol diglycidyl ether, nonaethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, tetrapropylene glycol diglycidyl ether, nonapropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, diglycidyl ether of neopentyl glycol hydroxypivalate ester, trimethylolpropane diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol diglycidyl ether, diglycerol triglycidyl ether, pentaerythritol diglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol tetraglycidyl ether, diglycidyl ether of tris-(2-hydroxyethyl)isocyanurate, triglycidyl ether of tris-(2-hydroxyethyl)isocyanurate, and 2,2-bis(4-glycidyloxy-cyclohexyl)propane. Aromatic epoxy compounds such as resorcin diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether (which are obtained by condensation of epichlorohydrin with bisphenol A, bisphenol F, and bisphenol S, respectively), tetrabromobisphenol A diglycidyl ether, orthophthalic acid diglycidyl ether, phenolnovolak polyglycidyl ether, and cresolnovolak polyglycidyl ether. The compound (such as acrylic acid and methacrylic acid) having a (meth)acryloyl group and a carboxylic acid in the molecule, which is to be reacted with one of the above-mentioned epoxy groups, includes acrylic acid, methacrylic acid, carboxylic acid-containing (meth)acrylate (which is obtained by reaction between hydroxyethyl (meth)acrylate and an acid anhydride such as o-phthalic anhydride), and carboxylic acid-containing (meth)acrylate (which is obtained by reaction between glycidyl (meth)-acrylate and a compound (such as adipic acid) which has two or more carboxyl groups in the molecule. The reaction between the epoxy compound and the carboxylic acid-containing (meth)acrylate may be accomplished by heating at 60-110°C in the presence of a catalyst, e.g., a tertiary amino compound (such as dimethylaminoethyl methacrylate) and a quaternary amine salt (such as benzyltrimethylammonium chloride). The epoxy poly(meth)acrylates may be used alone or in combination with one another. Those which are preferable from the standpoint of clarity and heat resistance of cast products are reaction products of acrylic acid or methacrylic acid with 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane triglycidyl, glycerol diglycidyl ether, glycerol triglycidyl, triglycidyl of tris(2-hydroxyethyl)isocyanurate, 2,2-bis(4-glycidyloxy-hexyl)propane, bisphenol A diglycidyl ether, bisphenol S diglycidyl ether, and tetrabromobisphenol A diglycidyl ether. According to the present invention, the resin composition for cast polymerization contains component (b) which is polybutylene glycol di(meth)acrylate. This compound is polybutylene glycol having a degree of polymerization in the range of 5 to 16, with its both terminals blocked with acrylic acid or methacrylic acid. The degree of polymerization denotes the number (n) of the repeating units represented by the formula (CH₂CH₂CH₂CH₂O) n . With the value of n smaller than 5, the resin composition yields a cast product which lacks sufficient flexibility. With the value of n greater than 16, the resin composition has such a high viscosity as to deteriorate workability and yields a cast product which has a high water absorption and a low crosslink density and hardness and is poor in heat resistance. The preferred degree of polymerization ranges from 7 to 12. The value n denotes the center value because the polybutylene glycol dimethacrylate is a mixture of species which differ in molecular-weight distribution. The polybutylene glycol di(meth)acrylate used in the present invention can be easily produced by the condensation reaction between polybutylene glycol (which is obtained by the ring-opening polymerization of tetrahydrofuran) and acrylic acid or methacrylic acid, or by the ester interchange reaction between polybutylene glycol and methyl methacrylate or ethyl methacrylate. Which to choose depends on the end use of the polymer. If the polymer is to be made into a transparent material, it is necessary to choose the ester interchange reaction which gives rise to a colorless transparent monomer. According to the present invention, the resin composition for cast polymerization should be composed of 10-90 parts by weight of component (a) and 90-10 parts by weight of component (b), with the total amount of components (a) and (b) being 100 parts by weight. With component (a) less than 10 parts by weight, the resulting resin composition yields a polymer lacking sufficient heat resistance. With component (a) in excess of 90 parts by weight, the resin composition has such a high viscosity that it is poor in workability. The preferred amount of component (a) is 20-70 parts by weight. With component (b) less than 10 parts by weight, the resin composition yields a polymer lacking sufficient flexibility but having high water absorption. With component (b) in excess of 90 parts by weight, the resin composition yields a polymer lacking sufficient heat resistance and surface hardness. The preferred amount of component (b) is 20-60 parts by weight. According to the present invention, the resin composition for cast polymerization should preferably be incorporated further with a compound having at least one polymerizable double bond in the molecule. This compound imparts heat resistance and surface hardness and lowers viscosity. It is desirable that the resin composition have a low viscosity for the ease of casting operation, because it contains highly viscous urethane poly(meth)-acrylate and/or epoxy poly(meth)acrylate. The compound should preferably be a low-viscosity ester monomer. It includes mono(meth)acrylates such as methyl (meth)-acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, lauryl (meth)-acrylate, stearyl (meth)acrylate, butoxyethyl (meth)-acrylate, allyl (meth)acrylate, methallyl (meth)acrylate, glycidyl (meth) acrylate, N, N-dimethylaminoethyl (meth)-acrylate, N,N-diethylaminoethyl (meth)acrylate, 2-ciano-ethyl (meth) acrylate, dibromopropyl (meth) acrylate, N-vinyl-2-pyrrolidone (meth)acrylate, polyethylene glycol monoalkylether (meth)acrylate, polypropylene glycol monoalkylether (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)-acrylate, 4-hydroxybutyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)-acrylate, trimethylcyclohexyl (meth)acrylate, norbornyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phosphoethyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenyl-glycidyl (meth) acrylate, phenylcellosolve (meth) acrylate, nonylphenoxyethyl (meth)acrylate, biphenyl (meth) acrylate, naphthyl (meth) acrylate, bromophenyl (meth) acrylate, tribromophenyl (meth)acrylate, pentabromophenyl (meth)-acrylate, chlorobenzyl (meth)acrylate, bromobenzyl (meth)-acrylate, tribromobenzyl (meth)acrylate, and 2-phenylphenol (meth)acrylate; di(meth)acrylate of polyethylene glycol such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)-acrylate, triethylene glycol di(meth)acrylate, tetra-ethylene glycol di(meth)acrylate, pentaethylene glycol di(meth)acrylate, and nonaethylene glycol di(meth)-acrylate; di(meth)acrylate of polypropylene glycol such as polypropylene glycol di(meth)acrylate, dipolypropylene glycol di(meth)acrylate, tripolypropylene glycol di(meth)-acrylate, tetrapolypropylene glycol di(meth)acrylate, and nonapolypropylene glycol di(meth)acrylate; polyfunctional (meth)acryl compounds such as 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate 1,6-hexamethylene di(meth)acrylate, 1,14-tetradecamethylene di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, di-(meth)acrylate of caprolactone adduct of neopentyl glycol hydroxypivalate, neopentyl glycol di(meth)acrylate, dicyclopentenyl di(meth)acrylate, dicyclopentanyl di(meth)-acrylate, 2-(2-hydroxy-1,1-dimethylethyl)-5-hydroxymethyl-5-ethyl-1,3-dioxane di(meth)acrylate,trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acryl-ate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, di(meth)acryloxyethylisocyanurate, tris (meth)acryloxyethyl isocyanurate, 2,2'-bis(4-(meth)acryloxyphenyl)-propane, 2,2'-bis(4-(meth)acryloxyethoxyphenyl)-propane, 2,2'-bis-(4-(meth)acryloxydiethoxyphenyl)-propane, 2,2' -bis-(4-(meth)acryloxypentaethoxyphenyl)-propane, 2,2'-bis-(4-(meth)acryloxyethoxy-3,5-dibromophenyl)-propane, 2,2'-bis(4-(meth)acryloxydiethoxy-3,5-dibromophenyl)-propane, 2,2'-bis(4-(meth)acryloxypentaethoxy-3,5-di-bromophenyl)-propane, 2,2'-bis(4-(meth)acryloxyethoxy-3,5-dimethylphenyl)-propane, 2,2'-bis(4-(meth)acryloxy-ethoxy-3-phenylphenyl)-propane, 2,2'-bis(4-(meth)acryl-oxyethoxyphenyl)-sulfone, 2,2'-bis(4-(meth)acryloxydi-ethoxyphenyl)-sulfone, 2,2'-bis(4-(meth)acryloxypenta-ethoxyphenyl)-sulfone, 2,2'-bis(4-(meth)acryloxyethoxy-3-phenylphenyl)-sulfone, 2,2'-bis(4-(meth)acryloxyethoxy-3,5-dimethylphenyl)-sulfone, di ((meth) acryloxyethoxy) phosphate, and tri((meth) acryloxyethoxy) phosphate; vinyl compounds such as styrene, vinyltoluene, chlorostyrene, bromostyrene, divinylbenzene, 1-vinylnaphthalene, 2-vinylnaphthalene, and N-vinylpyrrolidone; allyl compounds such as diethylene glycol bisallyl carbonate, trimethylolpropane diallyl, diallyl phthalate, dimethacryl phthalate, and allyl methacrylate; and metal salts of (meth)acrylic acid such as barium, lead, antimony, titanium, tin, and zinc (meth)acrylate. These compounds may be used alone or in combination with one another. According to the present invention, resin composition for cast polymerization may be incorporated with additives such as antioxidant, antiyellowing agent, UV light absorber, bluing agent, and pigment, in an amount not harmful to the effect of the present invention, if necessary. According to the present invention, the second resin composition for cast polymerization can be readily produced by mixing the above-mentioned components (a) and (b) and optional additives in the usual way. According to the present invention, the resin composition for cast polymerization may be used in various fields after curing in a proper way selected for the individual usage. Curing is accomplished by the aid of a polymerization initiator which includes organic peroxides (such as benzoyl peroxide, t-butyl peroxyisobutyrate, and t-butyl peroxy-2-ethylhexanoate), azo compounds (such as 2,2'-azobisisobutyronitrile, and 2,2'-azobis(2,4-dimethylvaleronitrile), and photopolymerization initiators (such as 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methylphenyl glyoxilate, and 2,4,6-tri-methylbenzoyldiphenylsulfonoxide. These polymerization initiators may be used alone or in combination with one another. They may be used in an amount of 0.005-5 parts by weight for 100 parts by weight of the total amount of components (a) and (b). Curing may be accomplished by casting the resin composition, which has been incorporated with a polymerization initiator, into a mold cavity through a gasket, and subsequently heating the mold or irradiating the mold (one side or both sides) with active energy rays. Heating and irradiation may be used together. The mold may be composed of two mold halves, each made of glass, plastics, or metal, if the resin composition is to be made into optical lenses, laminated glass, optical discs, or film. After polymerization and curing, the casting may be demolded or used without demolding (as in the case of laminated glass). The thus produced castings will find use as optical lenses, optical discs, electric and electronic parts, films, machine parts, and laminated glass. They are most suitable for optical lenses, optical discs, laminated glass, and films on account of their good flexibility and low water absorption. EXAMPLES The present invention will be described in more detail with reference to the following examples and comparative examples. Monomers used in the examples are abbreviated as follows: 9BGDM : nonabutylene glycol dimethacrylate 12BGDM : dodecabutylene glycol dimethacrylate 9BGDA : nonabutylene glycol diacrylate UA1 : urethane triacrylate formed by reaction between hexamethylene diisocyanate trimer and 2-hydroxyethyl acrylate UA2 : urethane dimethacrylate formed by reaction between dicyclohexylmethane diisocyanate and 2-hydroxypropyl methacrylate EA1 : epoxy dimethacrylate formed by reaction between bisphenol A diglycidyl ether and methacrylic acid EA2 : epoxy dimethacrylate formed by reaction between tetrabromobisphenol A diglycidyl ether and acrylic acid EA3 : epoxy dimethacrylate formed by reaction between 2,2-(4-glycidyloxycyclohexyl)propane and methacrylic acid BP2EA : 2,2'-bis(4-acryloxydiethoxyphenyl)-propane HDDM : 1,6-hexamethylene dimethacrylate TMPM : trimethylolpropane trimethacrylate MMA : methyl methacrylate St : styrene 2GDM : diethylene glycol dimethacrylate n-BMA : n-butyl methacrylate 9EGDM : nonaethylene glycol dimethacrylate 9EGDA : nonaethylene glycol diacrylate 9PGDM : nonapropylene glycol dimethacrylate 14EGDM : tetradecaethylene glycol dimethacrylate 14EGDA : tetradecaethylene glycol diacrylate Example 1 (Synthesis of 9BGDM by ester interchange) In a 5-liter four-neck flask were placed 2.0 kg of nonabutylene glycol (having an average molecular weight of 680, PTG-650SN, a product of Hodogaya Kagaku Co., Ltd.), 2.0 kg of MMA, 0.5 g of hydroquinone monomethyl ether, and 50 g of titanium tetrabutyl-n-butoxide (as a catalyst). Reaction was carried out for 3 hours by stirring the reactants at 100-120°C, while slowly removing methanol (formed by the reaction) together with MMA by azeotropic distillation. After the reaction, excess MMA was distilled away under reduced pressure. To the residue was added 1 kg of toluene and the toluene solution was washed with alkaline water and finally freed of toluene by vacuum distillation. Thus there was obtained 9BGDM, which was colorless transparent and 100% pure according to the bromine addition purity test. Example 2 (Synthesis of 12BGDM by condensation reaction) In a 5-liter four-neck flask were placed 2.0 kg of dodecabutylene glycol (having an average molecular weight of 890, PTG-850SN, a product of Hodogaya Kagaku Co., Ltd.), 1.5 kg of toluene, 0.6 kg of methacrylic acid, 1 g of hydroquinone, and 50 g of sulfuric acid. Reaction was carried out for 4 hours by stirring the reactants at 120°C, while removing water (formed by the reaction) together with toluene by azeotropic distillation. After the reaction, 1 kg of toluene was added, and the toluene solution was washed with alkaline water and finally freed of toluene by vacuum distillation. Thus there was obtained 12BGDM, which was slightly yellowish transparent and 98% pure according to the bromine addition purity test. Synthesis Example 1 (Synthesis of urethane triacrylate) In a three-neck flask were placed 200 parts of hexamethylene diisocyanate trimer ("Sumidule N3200", a product of Sumitomo Bayer Urethane Co., Ltd.) and 0.2 part of hydroquinone monomethyl ether. To the flask was added dropwise a mixture of 140 parts of 2-hydroxyethyl acrylate and 0.2 part of n-butyl tin laurate over 3 hours with stirring and heating at 60°C. Reaction was continued for 3 hours at 70°C. Thus there was obtained urethane triacrylate. Synthesis Example 2 (Synthesis of urethane dimethacrylate) In a three-neck flask were placed 258 parts of dicyclohexylmethane diisocyanate and 0.3 part of hydroquinone monomethyl ether. To the flask was added dropwise a mixture of 302 parts of 2-hydroxypropyl methacrylate and 0.3 part of n-butyl tin laurate over 3 hours with stirring and heating at 60°C. Reaction was continued for 3 hours at 70°C. Thus there was obtained urethane dimethacrylate. Examples 3 to 10 The resin composition pertaining to the present invention was prepared from components (a), (b) and (c) shown in Table 2 and 0.02 g of 2,2'-azobis(2,4-dimethylvaleronitrile) by mixing at room temperature. The resin composition was cast into a mold made up of two tempered glass plates (each measuring 100 mm square and 5 mm thick) and a gasket of PVC tube (6 mm in outside diameter for 2 mm thick plate or 10 mm in outside diameter for 5 mm thick plate). The cast resin composition was cured by heating at 80°C for 3 hours and further heating at 120°C for 3 hours. After demolding, the cured product was annealed at 100°C for 1 hour to remove internal strains. The thus obtained plate was tested for physical properties in the following manner. The results are shown in Table 1. Light transmission (%) : Measured according to ASTM D1003-61. Water absorption at saturation (wt%) : The weight gain of a discoid specimen (75 mm in diameter and 5 mm thick) was measured after standing in a saturated steam bath at 70°C for 3 days. Ball chop test : The 2-mm thick plate specimen was tested according to the FDA standards. The result is indicated in terms of the maximum weight of the steel ball which broke the specimen when dropped at a height of 127 cm. Comparative Examples 1 to 11 Molded products for comparison were prepared and evaluated in the same manner as in Example 3 to 10, except that the combination of components (a) and (b) was changed as shown in Table 1. The results are shown in Table 1. a component (g) b component (g) c component (g) light transmission (%) water absorption at saturation (%) ball drop test (g) Rockwell hardness (M) heat resistance (Tg, °C) example 3 UA170 9BGDM30 - 92 1.5 24 95 105 example 4 UA150 9BGDM50 - 92 1.2 32 85 100 example 5 UA130 9BGDM70 - 92 1.1 50 72 85 example 6 UA280 9BGDM15 MMA5 91 1.3 24 102 117 example 7 UA260 9BGDM30 BP2EA10 90 1.4 28 97 110 example 8 UA240 12BGDM40 HDDM20 91 1.2 32 89 105 example 9 UA220 9BGDM70 TMPM10 90 1.1 50 78 98 example 10 UA240 9BGDM40 HDDM20 90 1.3 35 85 101 comparative example 1 - - MMA100 92 2.2 10 90 80 comparative example 2 UA1100 - - 91 2.4 12 110 130 comparative example 3 UA280 - MMA20 92 2.2 12 105 108 comparative example 4 UA240 - HDDM60 90 1.5 8 100 115 comparative example 5 - 9BGDM70 HDDM30 91 1.1 32 40 58 comparative example 6 - 9BGDM30 MMA70 92 1.5 22 50 70 comparative example 7 - 9BGDA30 MMA70 90 1.7 22 45 50 comparative example 8 UA15 9BGDM95 - 91 1.1 100 48 60 comparative example 9 UA150 [9EGDM]50 - 89 3.7 24 70 101 comparative example 10 UA150 [9PGDM]50 - 87 3.4 16 75 105 comparative example 11 UA150 [14EGDA]50 - 88 4.5 28 55 82 Synthesis Example 3 (Synthesis of epoxy dimethacrylate) In a 5-liter three-neck flask were placed 3015 g of bisphenol A diglycidyl ether ("YD-8125", a product of Toto Kasei Co., Ltd.), 1485 g of methacrylic acid ("Methacrylic acid", a product of Mitsubishi Rayon Co., Ltd.), 45 g of benzyltrimethylammonium chloride (as a catalyst), and 1 g of hydroquinone monomethyl ether (as an inhibitor). Reaction was carried out at 70°C for 3 hours, at 80°C for 3 hours, and at 110°C for 8 hours. Reaction was suspended when the acid value of the reaction product reached 0.15. Thus there was obtained epoxy dimethacrylate (EAl). Examples 11 to 18 The resin composition pertaining to the present invention was prepared from components (a), (b) and (c) as shown in Table 2 and 0.02 g of 2,2'-azobis(2,4-dimethylvaleronitrile) by mixing at room temperature. The resin composition was cast into a mold made up of two tempered glass plates (each measuring 100 mm square and 5 mm thick) and a gasket of PVC tube (6 mm in outside diameter for 2 mm thick plate or 10 mm in outside diameter for 5 mm thick plate). The cast resin composition was cured by heating at 80°C for 3 hours and further heating at 120°C for 3 hours. After demolding, the cured product was annealed at 100°C for 1 hour to remove internal strains. The thus obtained plate was tested for physical properties in the same manner as in Examples 3 to 10. The results are shown in Table 2. Comparative Examples 12 to 21 Molded products for comparison were prepared and evaluated in the same manner as in Example 11 to 18, except that the combination of components (a), (b) and (c) was changed as shown in Table 2. The results are shown in Table 2. As mentioned above in detail, the polybutylene glycol dimethacrylate of the present invention provides various kinds of plastics having good flexibility and low water absorption. The resin composition for cast polymerization pertaining to the present invention provides molded products which have good flexibility and low absorption, without sacrificing heat resistance, impact resistance, and surface hardness. Therefore, they will find use as optical materials, lenses, optical discs, laminated glass, and film. Having described a specific preferred example of the present invention, it is to be understood that the invention is not limited to that precise example, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.

Claims: A resin composition for cast polymerization which comprises (a) 10-90 parts by weight of at least one compound selected from the group consisting of epoxy poly(meth)acrylate having two or more (meth)acryloyloxy groups in one molecule and urethane poly(meth)-acrylate having two or more (meth)acryloyloxy groups in one molecule, said urethane poly(meth)-acrylate having been obtained by the reaction of a hydroxy group-containing (meth)acrylate with isophorone diisocyanate, trimer of hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1.3-bis (α,α-dimethylisocyanatethyl)-benzene, xylylene diisocyanate, tetramethylene diisocyanate, dimer acid diisocyanate, cyclohexane diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, naphthalene diisocyanate or biphenyl diisocyanate, and (b) 10-90 parts by weight of polybutylene glycol di(meth)acrylate represented by the general formula below: where R represents hydrogen or methyl and n is an integer of 5 to 16,with the total amount of components (a) and (b) being 100 parts by weight . A resin composition for cast polymerization as claimed in claim 1 , wherein the urethane poly(meth)acrylate having two or more (meth)acryloyloxy groups in one molecule is an adduct of 2 -hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate with isophorone diisocyanate, trimer of hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,3-bis(α,α-dimethylisocyanatemethyl)benzene, or xylylene diisocyanate. A resin composition for cast polymerization as claimed in claim 1 , wherein the epoxy poly(meth)acrylate having two or more (meth)acryloloxy groups in one molecule is a reaction product of acrylic acid or methacrylic acid with 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, triglycidyl of tris(2-hydroxyethyl)isocyanurate, 2,2-bis(4-glycidyloxycyclohexyl) propane, bisphenol S diglycidyl ether, or tetrabromobisphenol A diglycidyl ether. A resin composition for cast polymerization as claimed in claim 1 , wherein the polybutylene glycol di(meth)acrylate is one member selected from the group consisting of heptabutylene glycol di(meth)acrylate, octabutylene glycol di(meth)acrylate, nonabutylene glycol di(meth)acrylate, decabutylene glycol di(meth)acrylate, undecabutylene glycol di(meth)acrylate, and dodecabutylene glycol di(meth)acrylate. A resin composition for cast polymerization as claimed in claim 1 , which further comprises a compound having at least one polymerizable double bond in the molecule. A resin composition for cast polymerization as claimed in claim 5 , wherein the compound having at least one polymerizable double bond in the molecule is at least one member selected from the group consisting of methyl methacrylate, styrene, n-butyl methacrylate, diethylene glycol dimethacrylate, and 1,6-hexamethylene dimethacrylate.

Inventors: FUKUSHIMA HIROSHI, MOTONAGA AKIRA, SUDA ERIKO, SUGITANI SUSUMU, FUKUSHIMA, HIROSHI, MOTONAGA, AKIRA, SUDA, ERIKO, SUGITANI, SUSUMU, FUKUSHIMA, HIROSHI, C/O PRODUCTS DEVELOPMENT LAB., MOTONAGA, AKIRA, C/O PRODUCTS DEVELOPMENT LAB., SUDA, ERIKO, C/O PRODUCTS DEVELOPMENT LAB., SUGITANI, SUSUMU, C/O CENTRAL RESEARCH LAB.
Applicants: MITSUBISHI RAYON CO, MITSUBISHI RAYON CO., LTD.
Application year: 1990
Main classification: C08G65
IPC codes: C08F22, G02B1, C08F290