RESIN COMPOSITION FOR COATING OPTICAL GLASS FIBERS

Abstract: A resin composition for coating optical glass fibers com­ prises (A) a di-(meth)acrylic acid ester of a carbonate diol of an average molecular weight of 500 to 3000 or of an addition compound of said carbonate diol with ε-caprolactone, (B) a monoethylenically unsaturated momomer and, optionally, (C) a photopolymerization initiator.

Description: The present invention relates to a novel di-(meth)acrylic acid ester, a resin composition and a coating agent for optical glass fibers for transmitting light. Since optical fibers have a large capacity transmitting information and are relatively insusceptible to outside interference, their use has markedly increased, particularly in the communications field, in recent years. Optical fibers are generally made of glass, because they are used in the communication field. However, since the glass fibers are frangible and chemically damaged by water vapour, they are easily broken and handling is difficult. Accordingly, optical glass fibers have hitherto been coated with a resinous material. As such a resinous coating material, epoxy resin and urethane resin have hitherto been used; However, a long time is required to cure such a resin, and therefore productivity of the coated glass fibers is poor. Furthermore, since cured resin lacks pliability, the coated glass fibers have a disadvantage in that they loose transmitting property if side pressure is applied In recent years, in order to overcome this disadvantage, a composition curable by ultraviolet rays containing urethane acrylate has been studied. A composition curable by ultraviolet rays for coating optical glass fibers and a method for forming a coating film therefrom have been proposed, for instance, in JP-A-58-223638 (1983) and CA-A-1198083. Although the composition curable by ultraviolet rays which is used at present has the advantages of a short curing time and that some desired properties can be reproduced easily and accurately, because of the large hygroscopic property thereof, glass fibers coated with such a composition are apt to be spoiled by water and the coated glass fibers have the disadvantage that the physical properties change a lot when the temperature changes from -60 to 80°C,thereby causing an increase in transmission loss. As a result of the present inventors' studies to solve the above-mentioned problems, they have found that a novel resin composition comprising a di-(meth)acrylic acid ester has a high curing speed, gives a soft resin film of low hygroscopicity which has stable physical properties which do not change between low and high temperatures, and has a low glass-transition temperature. Thus the novel resin composition is suitable for coating optical glass fibers for transmitting light. The present invention provides a resin composition comprising (A) di-(meth)acrylic acid ester of an addition compound of a carbonate diol of an average molecular weight of from 500 to 3000 with ε-caprolactone, (B) a monoethylenically unsaturated monomer, and as an optional component, (C) an initiator of photopolymerization. The present invention also provides a resin composition comprising (A) di-(meth)acrylic acid ester of a carbonate diol of an average molecular weight of 500 to 3000, (D) a polyurethane (meth)acrylate, (B) a monoethylenically unsaturated monomer, and as an optional component, (C) an initiator of photopolymerization. The present invention additionally provides a method of coating optical glass fibers, which method comprises coating said fibres with a coating agent comprising (A) di-(meth)acrylic acid ester of a carbonate diol of an average molecular weight of 500 to 3000 or of an addition compound of said carbonate diol with ε-caprolactone, (B) a monoethylenically unsaturated monomer and (C) an initiator of photopolymerization; and irradiating the thus coated fibres with actinic radiation so as to cure said agent. The present invention further provides a di-(meth)acrylic acid ester of an addition compound of a carbonate diol of an average molecular weight of 500 to 3000 with ε-caprolactone. The present invention yet further provides a di-(meth)acrylic acid ester represented by the formula (I): wherein R¹ represents an alkylene group having 4 to 10 carbon atoms, preferably 5 to 8 carbon atoms; R² represents a hydrogen atom or a methyl group, the mean values of a and b are each from 0 to 5, preferably from 0 to 2; the sum of the mean values of a and b is from 0.5 to 5, preferably from 0.5 to 3 and the mean value of ℓ is from 1 to 10, preferably from 3 to 8. In the resin composition or coating agent for optical glass fibers according to the present invention, it is preferred to use the di-(meth)acrylic acid ester (A) in an amount of 5 to 80 % by weight, particularly 10 to 70 % by weight, and the monoethylenically unsaturated monomer (B) in an amount of 20 to 80 % by weight, particularly 30 to 60 % by weight, based on the weight of said resin composition or coating agent. In addition, it is preferred to use the photopolymerization initiator in an amount of 0 to 10 % by weight in the resin composition, and in the coating agent, it is preferred to use the photopolymerization initiator in an amount of 0.1 to 10 % by weight, particularly 1 to 5 % by weight, based on the weight of said resin composition or coating agent. The following resin compositions and coating agents according to the present invention are exemplified. (1a) A resin composition comprising (A) a di-(meth)acrylic acid ester of an addition compound of a carbonate diol having an average molecular weight of 500 to 3000 with ε-caprolactone, (B) a monoethylenically unsaturated monomer and, optionally, (C) photopolymerization initiator; (2a) A coating agent for optical glass fibers, comprising (A) a di-(meth)acrylic acid ester of an addition compound of a carbonate diol of an average molecular weight of 500 to 3000 with ε-caprolactone, (B) a monoethylenically unsaturated monomer and (C) a photopolymerization initiator; (1b) A resin composition comprising (A) a di-(meth)acrylic acid ester of a carbonate diol of an average molecular weight of from 500 to 3000, (D) a polyurethane (meth)acrylate, (B) a monoethylenically unsaturated monomer and, optionally, (C) photopolymerization initiator; and (2b) A coating agent for optical glass fibers comprising (A) a di-(meth)acrylic acid ester of a carbonate diol of an average molecular weight of 500 to 3000, (D) a polyurethane (meth)acrylate, (B) a monoethylenically unsaturated monomer and (C) a photopolymerization initiator. A di-(meth)acrylic acid ester of the addition compound of a carbonate diol of an average molecular weight of 500 to 3000 with ε-caprolactone according to the present invention is produced, for instance, by reacting an addition compound (a), which is obtained by reacting a carbonate diol of an average molecular weight of 500 to 3000 with ε-caprolactone, with (meth)acrylic acid (b). An example of the process for producing the above-mentioned di-(meth)acrylic acid ester is as follows. To 0.5 mol of the addition compound obtained by reacting the carbonate diol with ε-caprolactone, preferably 1.0 to 2.0 mol, more preferably 1.0 to 1.5 mol of (meth)acrylic acid, preferably 0.01 to 5 % by weight of an esterification catalyst, for instance p-toluenesulfonic acid, sulfuric acid or methanesulfonic acid, and a polymerisation prohibitor, for instance methoquinone, hyroquinone or phenothiazine, are added. The thus prepared mixture is heated, preferably to a temperature of 70 to 130°C, and after dehydrating the mixture, the thus dehydrated mixture is washed with an alkali and water, and low-boiling matter is removed by distillation to produce the di-(meth)acrylic acid ester. The carbonate diol which is the starting material for producing the addition compound (a) may be produced, for instance, as follows. The carbonate diol is obtained by an ester exchange reaction of a carbonate derivative, for example a diaryl carbonate such as diphenyl carbonate; bischlorophenyl carbonate; dinaphthyl carbonate; phenyl tolyl carbonate; phenyl chlorophenyl carbonate and 2,4-ditolyl carbonate or a dialkyl carbonate such as diethyl carbonate and dimethyl carbonate with a diol, for instance, 1,6-hexanediol; neopentyl glycol; 1,4-butanediol; 1,8-octanediol; 1,4-bis-(hydroxymethyl)-cyclohexane; 2-methylpropanediol; dipropylene glycol or dibutylene glycol, or with a polyester diol which is the reaction product of the diol with a dicarboxylic acid such as oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid or hexahydrophthalic acid or ε-caprolactone. When ε-caprolactone is reacted with 1,6-hexanediol, the mean amount of addition of ε-caprolactone to said diol is generally from one to ten mols per mole of carbonate diol. In addition, the carbonate diol can be also produced by the reaction of phosgene with the above-mentioned diol. The thus obtained carbonate diol is a monocarbonate diol having one carbonate group per molecule or a polycarbonate diol having more than one carbonate group per molecule, and is readily available from the market, for example as follows. DESMOPHEN®2020E (made by SUMITOMO-Bayer Co., Ltd. , having an average molecular weight of 2000), DN-980 (made by Nippon Polyurethane Co., Ltd. , having an average molecular weight of 2000), DN-981 (made by Nippon Polyurethane Co., Ltd. , having an average molecular weight of 1000), DN-982 (made by Nippon Polyurethane Co., Ltd., having an average molecular weight of 2000), DN-983 (made by Nippon Polyurethane Co., Ltd. , having an average molecular weight of 1000). Of these commercialized carbonate diols, DN-982 and DN-983 are particularly preferred for producing the addition compound (a). DN-982, and DN-983, for example, are carbonate diols obtained by an ester exchange reaction between a carbonate derivative and a diol obtained by adding ε-caprolactone to 1,6-hexanediol. The production of the addition compound (a) of a carbonate diol and ε-caprolactone is carried out, for instance, as follows. It is preferred in the reaction of a carbonate diol with ε-caprolactone to use an effective amount of a catalyst, namely, from 0.001 to 1.0 % by weight, in particular from 0.01 to 0.2 % by weight, with respect to the weight of ε-caprolactone. As the catalyst, for instance an organic titanium compound such as tetraisopropyl titanate or tetrabutyl titanate and an organic tin compound such as tetraphenyl tin, tetraoctyl tin, dilauryltin oxide or di-n-butyltin dichloride may be mentioned. The reaction of the carbonate diol and ε-caprolactone is preferably carried out at a temperature of from 50 to 300°C, in particular from 110 to 200°C, for a sufficient time to complete the reaction. The amount of ε-caprolactone introduced into the reactor is preferably from one to ten mols per mol of carbonate diol introduced into the reactor. It is preferred to use one to five mols of ε-caprolactone per mol of carbonate diol. In order to minimize an oxidative side reaction, it is preferred to carry out the reaction under an atmosphere of an inert gas such as nitrogen. The reaction product comprising the addition compound (a) may be used as is in the next reaction. In the di-(meth)acrylic acid ester of the present invention, the mean addition amount of ε-caprolactone per mol of carbonate diol is preferably from 1 to 10 mols, more preferably from 1 to 5 mols. The di-(meth)acrylic acid ester of a carbonate diol having an average molecular weight of 500 to 3000 (hereinafter referred to as "carbonate diol di-(meth)acrylate") can be obtained by reacting the carbonate diol with (meth)acrylic acid. Production of the carbonate diol di-(meth)acrylate may be carried out, for instance, by the following process. After adding a preferred amount of from 1.0 to 2.0 mols (particularly preferred of from 1.0 to 1.5 mols) of (meth)acrylic acid, a preferred amount of from 0.01 to 5 % by weight [based on the amount of (meth)acrylic acid] of an esterifying catalyst, for instance, p-toluenesulfonic acid, sulfuric acid or methanesulfonic acid, and a preferred amount of from 0.01 to 5 % by weight [based on the amount of (meth)acrylic acid] of a polymerization-prohibiting agent such as methoquinone, phenothiazine or hydroquinone to 0.5 mol of a carbonate diol, the mixture is heated, preferably to 70 to 130°C. After dehydrating, the reaction mixture is washed with an alkali and water and then low-boiling substances are removed to obtain the carbonate diol di(meth)acrylate. The carbonate diols described before can be used as the starting material for producing the carbonate diol di (meth) acrylate. Among these carbonate diols DN-982 and DN-983 are particularly preferred. Preferred carbonate diol di(meth)acrylates are the novel di-(meth) acrylic acid esters represented by the formula (I), and they can be produced as follows. Di-(meth)acrylic acid ester represented by the formula (I) can be produced by reacting, at an elevated temperature, a carbonate diol (obtained by the ester exchange reaction between an addition compound of ε-caprolactone with the diol compound and diaryl carbonate or dialkyl carbonate) of formula (II): wherein R¹, a , b and ℓ are defined above, with acrylic acid or methacrylic acid. As examples of the diol compound which is the starting material for the compound of formula (II), 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; 1,8-octanediol and hexylene glycol may be mentioned. The reaction between the diol compound and ε-caprolactone can be carried out easily at a temperature of from 50 to 300°C using an effective amount of a catalyst, for instance, stannous chloride or tetra-isopropyl titanate. The preferred amount of catalyst is from 0.001 to 1.0 % by weight based on the weight of ε-caprolactone. As examples of the diaryl carbonate or dialkyl carbonate used as the raw material, diphenyl carbonate, bis-chlorophenyl carbonate, dinaphthyl carbonate, phenyl tolyl carbonate, phenyl chlorophenyl carbonate, 2,4-ditolyl carbonate, dimethyl carbonate and diethyl carbonate may be mentioned. The ester exchange reaction between the addition compound of the diol compound with ε-caprolactone and diaryl carbonate or dialkyl carbonate is carried out under reduced pressure at a temperature of from 50 to 200°C while distilling, phenol by-product out of the reaction system. It is preferred to use an ester exchanging catalyst, for instance, tetrabutyl titanate or sodium phenolate, in an amount of from 0.01 to 1 % by weight based on the weight of the diaryl carbonate or dialkyl carbonate. The thus obtained carbonate diol of formula (II) is a monocarbonate diol having one carbonate group per molecule, or a polycarbonate diol having more than one carbonate group. Both are readily available in the market. For example, DN-982, a compound which contains a diol unit which is obtained by the reaction of one mol of 1,6-hexanediol and 0.83 mol (on average) of ε-caprolactone, and DN-983 a compound which contains a diol unit which is obtained by the reaction of one mol of 1,6-hexanediol and 0. 71 mol (on average) of ε-caprolactone, may be mentioned. The di-(meth)acrylic acid ester of formula (I) is produced by reacting the carbonate diol of formula (II) with acrylic acid, methacrylic acid or a mixture thereof. The amount of acrylic acid or methacrylic acid used in the reaction is generally from one to five mols per 0.5 mol of the carbonate diol introduced. The reaction is preferably carried out in the presence of a polymerization inhibitor to minimize or retard the polymerization of the acrylic double bond. Use of a polymerization inhibitor is well known among skilled persons in the art. The polymerization inhibitor is preferably used in an amount of from 0.01 to 5 % by weight of the reaction mixture. As examples of the polymerisation inhibitor, hydroquinone, p-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, p-benzoquinone, phenothiazine, N-nitrosodiphenylamine, thiourea and copper salts may be mentioned. The above-mentioned reaction is generally carried out at a temperature of from 50 to 130°C, preferably from 65 to 90°C, for a sufficient time to complete the esterification. This time depends on the size of the batch, the reactants, the catalyst and the reaction conditions. In addition, an esterification catalyst is used preferably in an amount of from 0.1 to 15 mol %, more preferably from 1 to 6 mol %, based on the the amount of acrylic acid or methacrylic acid used in the esterification. Any known esterification catalyst may be used, and as examples p-toluenesulfonic acid, methanesulfonic acid, sulfuric acid and phosphoric acid may be mentioned. It is preferred that an inert solvent such as hexane, cyclohexane, benzene or toluene is present in the reaction system to remove water formed during the esterification. In the resin composition and the coating agent according to the present invention, diacrylic acid ester is preferred to dimethacrylic acid ester as component (A). As the monoethylenically unsaturated monomer (B), various monoacrylates and monomethacrylates can be used. It is preferred to use a monomeric ester which forms homopolymers having a low glass transition temperature. As examples, phenyloxy (or alkylphenyloxy) polyethoxy (meth) acrylate; phenyloxy (or alkylphenyloxy) polypropoxy (meth) acrylate; nonylphenyloxy polyethoxy (meth) acrylate; phenyloxy (or alkylphenyloxy) ethoxy(meth)acrylate; phenyloxy (or alkylphenyloxy) propoxy(meth)acrylate; polyethoxy(meth)acrylate of tetrahydrofurfuryl alcohol; (meth)acrylate of an addition compound of tetrahydrofurfuryl alcohol and ε-caprolactone for example made by Nippon KAYAKU Co., Ltd., KAYARAD TC-110S and TC-120; an addition product of ε-caprolactone and β-hydroxyethyl (meth)acrylate for example made by DAICEL Chem. Ind. Co., Ltd., PLACCEL FA-1 and FM-1; carbitol acrylate, and (meth)acrylate of an addition compound of ε-caprolactone with polyethoxy- or polypropoxy compound of a phenol derivative disclosed in EP-A-0171654 may be mentioned. Preferred monoethylenically unsaturated monomers are alkylphenyl polyethoxy(meth)acrylate; (meth)acrylate of an addition compound of ε-caprolactone and tetrahydrofurfuryl alcohol (for example made by Nippon KAYAKU Co., Ltd., KAYARAD TC-110S and TC-120) and (meth)acrylate of an addition compound of ε-caprolactone with the polyethoxy- or polypropoxy compound of the phenol derivative disclosed in EP-A-0171654 of formula: wherein R³ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R⁴ and R⁵ represent independently a hydrogen atom or a methyl group; the mean value of m is 1 to 10 and the mean value of n is 1 to 10. The above-mentioned compound can be obtained by reacting (meth)acrylic acid with a compound obtained by reacting ε-caprolactone with an addition compound of ethylene oxide or propylene oxide with a phenol derivative such as phenol or nonylphenol in the presence of an esterifying catalyst such as p-toluenesulfonic acid and a polymerization inhibitor such as hydroquinone at a temperature of from 70 to 130°C. As the photopolymerization initiator (C), although any known photopolymerization initiator may be used, it is preferred that the stability in storage of the product is good. As such an initiator, for instance, benzoin alkyl ethers such as benzoin ethyl ether, benzoin isobutyl ether and benzoin isopropyl ether, acetophenones such as 2,2-diethoxyacetophenone and 4'-phenoxy-2, 2-dichloroacetophenone, propiophenones such as 2-hydroxy-2-methylpropiophenone, 4'-isopropyl-2-hydroxy-2-methylpropiophenone and 4'-dodecyl-2-hydroxy-2-methylpropiophenone, benzyl dimethylketal, 1-hydroxycyclohexyl phenyl ketone, anthraquinones such as 2-ethylanthraquinone and 2-chloroanthraquinone and thioxanthones may be mentioned. As the particularly preferred initiator, 1-hydroxycyclohexyl phenyl ketone and benzyl dimethyl ketal are mentioned. The photopolymerization initiator may be used singly or in combination in any ratio. In the resin composition (1a) and the coating agent (2a), the di-(meth)acrylic acid ester (A) is preferably used in an amount of from 5 to 80 % by weight, more preferably from 20 to 70 % by weight, based on the weight of said composition or agent. The amount of the monoethylenically unsaturated monomer (B) used in the resin composition (1a) and the coating agent (2a) is preferably from 20 to 80 % by weight, particularly from 30 to 60 % by weight, based on the weight of said composition or agent. On the other hand, the amount of the photopolymerization initiator (C) used in the resin composition (1a) is generally from 0 to 10 % by weight, based on the weight of said composition, and the amount used in the coating agent (2a) is preferably from 0.1 to 10 % by weight, particularly from 1 to 5 % by weight, based on the weight of said agent. In the resin composition (1b) and the coating agent (2b), the amount of the di-(meth)acrylic acid ester (A) is preferably from 5 to 50 % by weight, particularly from 10 to 40 % by weight, based on the weight of said composition or agent. The amount of the monoethylenically unsaturated monomer (B) used in the resin composition (1b) and the coating agent (2b) is preferably from 20 to 70 % by weight, particularly from 30 to 60 % by weight, based on the weight of said composition or agent. The amount of the photopolymerization initiator (C) used in the resin composition (1b) is preferably from 0 to 10 % by weight based on the weight of said composition, and the amount used in the coating agent (2b) is preferably from 0.1 to 10 % by weight, particularly from 1 to 5 % by weight, based on the weight of said agent. The average molecular weight of the polyurethane (meth)acrylate (D) used in the resin composition (1b) and the coating agent (2b) is preferably higher than 1000, more preferably from 2000 to 10000. As such a polyurethane (meth)acrylate, the polyurethane (meth)acrylate of a polyether polyol having an ether group within the molecule, the polyurethane (meth)acrylate of a polyester polyol having an ester group within the molecule, the polyurethane (meth)acrylate having both an ether group and ester group and the polyurethane (meth)acrylate of a carbonate diol having a carbonate group within the molecule may be mentioned. As the polyether polyol, for instance, polypropylene glycol, polyethylene glycol, polytetramethylene glycol and a compound formed by adding ethylene oxide or propylene oxide to 1,3- and 1,4-butylene glycol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, 2, 2-bis (4-hydroxycyclohexyl)propane or bisphenol A may be used. The polyester polyol can be obtained by reacting an alcoholic component with an acidic component. For instance, while using a compound such as polypropylene glycol, polyethylene glycol, polytetramethylene glycol or a compound formed by adding ethylene oxide or propylene oxide to 1,3- and 1,4-butylene glycol, 1,6-hexanediol, neopentyl glycol, cyclohexane dimethanol, 2, 2-bis (4-hydroxycyclohexyl)propane or bisphenol A or an addition compound formed by adding ε-caprolactone to the above compounds as the alcoholic component, a dibasic acid such as adipic acid, sebacic acid, azelaic acid and dodecanedicarboxylic acid and its anhydride is used as the acidic component. On the other hand, the compound obtained by reacting the three components, i.e., the acidic component, the alcoholic component and ε-caprolactone, simultaneously is also usable as the polyester polyol. In addition, as the carbonate diol, the carbonate diol which has been used as the starting material for producing the component (A) may be used. In order to obtain the polyurethane (meth)acrylate (D) by using a polyether polyol, polyester polyol or carbonate diol, an organic diisocyanate and a polymerizable monomer having a hydroxyl group are reacted with a hydroxyl group of the polyol until substantially no isocyanate (NCO) groups are contained in the reaction mixture. As representative organic diisocyanates, aromatic diisocyanate such as tolylenediisocyanate and 4,4,-diphenylmethanediisocyanate, cycloaliphatic diisocyanate such as isophorone diisocyanate and 4,4'-dicyclohexylmethanediisocyanate, aliphatic diisocyanate such as hexamethylene diisocyanate and 2,2'-trimethylhexamethylene diisocyanate may be mentioned. As the polymerizable monomer having a hydroxy group, (meth)acrylates having a hydroxyl group, such as ß-hydroxyethyl (meth)acrylate, β-hydroxypropyl (meth)acrylate, β-hydroxylauryl (meth)acrylate and an addition compound of ε-caprolactone and β-hydroxyethyl (meth)acrylate may be mentioned. Such a reaction of the isocyanate group and the hydroxyl group proceeds without any catalyst; However, a customary catalyst, for instance, a tertiary amine such as triethylamine, an organic metal compound such as dibutyltin dilaurate or dibutyltin diacetate or tin chloride may be used. As a particularly preferred polyurethane (meth)acrylate (D), a polyurethane acrylate of a carbonate diol may be mentioned, and as a particularly preferred organic diisocyanate, isophorone diisocyanate and 4,4, -dicyclohexylmethane diisocyanate may be mentioned. The amount of the polyurethane (meth)acrylate (D) used according to the present invention is preferably from 20 to 70 % by weight, based on the weight of the resin composition (1b) or the coating agent (2b), and more preferably from 40 to 60 % by weight. The larger amount may make the viscosity of the composition higher. The resin composition and coating agent according to the present invention may be used, according to the intended use, after further adding thereinto epoxyacrylate, polyester acrylate or polyurethane acrylate, for instance, polyurethane acrylate of a polyol having an ether group, ester group or carbonate group in the molecule, or a polymerizable monomer, for instance, polyethylene glycol di-(meth)acrylate, polypropylene glycol di-(meth)acrylate or trimethylolpropane tri-(meth)acrylate. In addition, a denaturation resin and various additives may be added to the resin composition and coating agent of the present invention. As the denaturation resin, epoxy resin, polyurethane, polybutadiene, polyether, polyamide imide, silicone resin and phenol resin may be mentioned. As the additives, organic silicon compounds, surfactants and polymerization inhibitors may be mentioned. The resin composition according to the present invention is useful for coating optical glass fibers and may also be used as an adhesive agent to laminate glass plates and as an agent for treating fibers. In the case where optical glass fibers are coated, the di-coating method is suitably adopted. In such a case, coating can be carried out at a very high speed of from 3 to 7 m/sec. The thickness of the agent coated on the optical glass fibers is not particularly limited. However, it is preferably from 20 to 300 µm in ordinary cases. The coating agent according to the present invention is easily cured by irradiation of ultraviolet rays, for example the curing of the coating agent of the present invention can be carried out in an ordinary method by irradiating ultraviolet rays from, for instance, a low pressure or high pressure mercury lamp or xenon lamp. Although the di-(meth)acrylic acid ester represented by the formula (I) is useful as a component of the coating agent for optical glass fibers, it is also useful as the vehicle of various coating compositions and ink compositions. Compositions containing di-(meth)acrylic acid ester represented by the formula (I) can be cured by radiation or by thermal means. Radiation curing can be carried out by particle radiation of an electron beam or ionization, or a chemical beam such as ultraviolet rays. In the case where curing is carried out by a chemical beam, a photopolymerization initiator, for instance, benzophenone, ethyl N,N-dimethylbenzoate or the aforementioned compounds, is mixed with the starting material. Curing by radiation or heat is well known to the person skilled in the art. The curing can be carried out by such known techniques The di-(meth)acrylic acid ester represented by the formula (I) is used singly or mixed with another monomeric compound, for instance, trimethylolpropane triacrylate, pentaerythritol triacrylate or pentaerythritol tetraacrylate, or a resin containing unsaturated groups, for instance, unsaturated polyester, polyester acrylate, epoxy acrylate or urethane acrylate, as a vehicle. When using the di-(meth)acrylic acid ester with another monomer or a resin, any mixing ration may by used. The di-(meth)acrylic acid ester represented by the formula (I) can be polymerized also by the addition of an organic peroxide, for instance, benzoyl peroxide, methyl ethyl ketone peroxide or cumene hydroperoxide. The present invention is now exemplified in the following Examples, wherein the term "part" means "part by weight". EXAMPLE A 1 : Into a 2-litre reaction vessel provided with a stirrer, a temperature controller, a thermometer, a condenser and a separator, 700 parts of the compound of the following formula: wherein the mean sum of a plus b is 0.71 (made by Nippon Polyurethane Co., Ltd., DN-983, an OH value of 112.2 mgKOH/g, an average molecular weight of about 1000 and a melting point of 5°C), 121 parts of acrylic acid, 14 parts of p-toluenesulfonic acid, 1.0 part of hydroquinone, 560 parts of benzene and 140 parts of cyclohexane were introduced, and the thus introduced substances were heated to a reaction temperature of 80 to 86°C while distillating the water formed in the reaction together with the solvent, removing the water from the reaction system by the separator and returning only the solvent to the reaction vessel. The reaction was carried out until 25.2 parts of water were removed. The thus obtained reaction mixture was dissolved in a mixture of 960 parts of benzene and 240 parts of cyclohexane, and after neutralizing the solution with an aqueous 20 % solution of sodium hydroxide, the neutralized solution was washed three times with each 500 parts of an aqueous 20 % solution of sodium chloride. By distilling the solvent from the thus treated solution, 690 parts of pale yellow liquid having the following properties were obtained: The result of determination of the absorption frequencies of the thus obtained product by nuclear magnetic resonance (NMR) of a high resolving power is shown below. In the determination, tetramethylsilane was used as the standard substance, chloroform was used as a solvent, and the determination was conducted first by ¹H and ¹³C-H coupling and finally by ¹³C-D coupling to obtain identification results. The absorption peaks of Nos. 6, 7 and 8 are those by the solvent, and that of No. 18 shows the position of the peak of tetramethylsilane. EXAMPLE A 2 : Into the same reaction vessel as in Example 1, 700 parts of a compound represented by the following formula: wherein the mean sum of a plus b is 0.83 (made by Nippon Polyurethane Co., Ltd., DN-982, an OH value of 56 mgKOH/g, the average molecular weight of about 2000 and a melting point of 5°C), 61 parts of acrylic acid, 6 parts of p-toluenesulfonic acid, 0.4 part of hydroquinone, 560 parts of benzene and 140 parts of cyclohexane were introduced, and the reaction was carried out as in Example A 1 until the amount of the thus formed water became 12.6 parts at a reaction temperature of 81 to 86°C. After dissolving the reaction mixture in a mixture of 1200 parts of benzene and 300 parts of cyclohexane, the solution was neutralized, washed and subjected to de-solvent as in Example A 1 to obtain 654 parts of a pale yellow liquid of the following properties. The result of determination of NMR is as follows. Of the above-mentioned peaks, those of Nos. 5, 6 and 7 are the positions of the absorption peaks of the solvent, and that of No. 14 is that of tetramethylsilane. EXAMPLE A 3 : Into the same reaction vessel as in Example A 1, 700 parts of a compound represented by the following formula: wherein the mean sum of a plus b is 0.71 (made by Nippon Polyurethane Co., Ltd., DN-983, an OH value of 112.2 mgKOH/g, the average molecular weight of about 1000 and the melting point of 5°C), 145 parts of methacrylic acid, 4.5 parts of sulfuric acid, 1.1 parts of hydroquinone and 700 parts of toluene were introduced, and the reaction was carried out as in Example A 1 at a temperature of 105 to 116°C until the amount of the thus formed water became 25.2 parts. After dissolving the reaction mixture in 1000 parts of toluene, the solution was neutralized, washed and subjected to de-solvent as in Example A 1 to obtain 723 parts of a pale yellow liquid of the following properties: The result of NMR determination is shown below: Of the above-mentioned absorption peaks, those of Nos. 6, 7 and 8 are those of the solvent, and that of No. 18 is that of tetramethylsilane. The following Production Example A series are the examples of the production of the addition compound (a) obtained by the reaction of a carbonate diol and ε-caprolactone. PRODUCTION EXAMPLE A 1 : Into a 3-litre reaction vessel provided with a stirrer, a temperature controller, a thermometer and a condenser, 2000 parts of a carbonate diol (made by Nippon Polyurethane Co., Ltd., DN-982, an OH value of 56 mgKOH/g, an average molecular weight of about 2000 and a melting point of 5°C), 342 parts of ε-caprolactone (made by DAICEL Chem. Ind. Co., Ltd., PLACCEL®M) and 0.17 part of stannous chloride were introduced, and the thus introduced mixture was heated to 130 to 150°C under nitrogen gas atmosphere until the amount of unreacted ε-caprolactone became less than 1 % by weight. The thus obtained addition compound (a - 1) was a pale yellow liquid of an OH group value of 47.9 and an acid value of 1.1 As a result of determination of the molecular weight of the product, the present addition compound (a-1) of the carbonate diol and ε-caprolactone had, in average, about three molecular units of ε-caprolactone in one molecule of the addition compound. PRODUCTION EXAMPLE A 2 : Into the same reaction vessel as in Production Example A 1, 2000 parts of the same carbonate diol as that used in Production Example A 1, 798 parts of the same ε-caprolactone as that used in Production Example A 1 and 0.4 part of stannous chloride were introduced, and the thus obtained mixture was reacted under gaseous nitrogen atmosphere at a temperature of 130 to 150°C until the amount of the unreacted ε-caprolactone became less than 1 % by weight. The thus obtained addition compound (a-2) was a pale yellow liquid of an OH value of 40.1 and an acid value of 1.5. As a result of determination of the molecular weight of the product, it was found that the addition compound (a-2) of the carbonate diol and ε-caprolactone had, in average, about seven molecular units of ε-caprolactone in the molecule of the addition compound. PRODUCTION EXAMPLE A 3 : In the same reaction vessel as in Production Example A 1, 1000 parts of the same carbonate diol (DN-983) as that used in Example A 3, 224 parts of ε-caprolactone and 0.12 part of tetra-isopropyl titanate were introduced, and the thus obtained mixture was reacted at a temperature of 150 to 160°C under nitrogen gas atmosphere until the amount of the unreacted ε-caprolactone became less than 1 % by weight. The thus obtained addition compound (a- 3) was a pale yellow liquid of an OH value of 91.3 and an acid value of 2.1. As a result of determination of the molecular weight of the product, it was found that the addition compound (a-3) had, in average, two molecular units of ε-caprolactone in one molecule of the addition compound. PRODUCTION EXAMPLE A 4 : In the same reaction vessel as that used in Production Example A 1, 1014.6 parts of a carbonate diol (made by Nippon Polyurethane Co., Ltd., DN-981, an OH value of 110 mgKOH/g and an average molecular weight of about 1000 and a melting point of 43°C), 456 parts of ε-caprolactone and 0.23 part of stannous chloride were introduced, and the thus obtained mixture was reacted at a temperature of 130 to 150°C under nitrogen gas atmosphere. The thus obtained addition compound (a-4) was a pale yellow liquid of an OH value of 76.3 and an acid value of 1.3. As a result of determination of the molecular weight of the addition compound thus obtained, it was found that the addition compound (a-4) had, in average, about 4 molecular units of ε-caprolactone in one molecule of the addition compound (a-4). The following examples B series are the examples of producing the di-(meth)acrylic acid ester. EXAMPLE B 1 : Into a 2-litre reaction vessel provided with a stirrer, a temperature controller, a thermometer and a condenser, 749.4 parts of the addition compound (a - 1) which had been obtained in Production Example A 1, 55.4 parts of acrylic acid, 6.4 parts of p-toluenesulfonic acid, 0.5 part of hydroquinone, 588.8 parts of benzene and 147.2 parts of cyclohexane were introduced, the reaction was carried out at a temperature of 81 to 87°C in the similar manner as in Example A 1 until 11.5 parts of water were removed. After dissolving the reaction mixture in a mixture of 960 parts of benzene and 240 parts of cyclohexane, the solution was neutralized by an aqueous 20 % solution of sodium hydroxide and washed three times with each 500 parts of an aqueous 20 % solution of sodium chloride. By distilling the solvents from the thus treated solution, 678 parts of a pale yellow liquid of the following properties were obtained. As a result of NMR determination of the thus obtained ester, the following data were obtained. The data were arranged in the same manner as in Example A 1, and the peaks of Nos. 5, 6 and 7 are those of the solvent and that of No. 15 is that of tetramethylsilane. EXAMPLE B 2 : In the same reaction vessel as in Example B 1, 727.4 parts of the addition compound (a - 2) which had been obtained in Production Example A 2, 45 parts of acrylic acid, 5.2 parts of p-toluenesulfonic acid, 0.34 part of hydroquinone, 582.4 parts of benzene and 145.6 parts of cyclohexane were introduced, and the thus obtained mixture was reacted in the same manner as in Example A 1 at a reaction temperature of 81 to 86°C until 9.3 parts of water were removed. After dissolving the reaction mixture in a mixture of 1200 parts of benzene and 300 parts of cyclohexane, the thus formed solution was neutralized, washed and subjected to de-solvent in a similar manner as in Example A 1 thereby obtaining 657 parts of a pale yellow liquid of the following properties. The result of NMR determination of the thus obtained ester is shown below. Of the above-mentioned peaks, those of Nos. 5, 6 and 7 are those of the absorption peaks of the solvent, and that of No. 16 is that of tetramethylsilane. EXAMPLE B 3 : In the same reaction vessel as in Example B 1, 708.4 parts of the addition compound (a - 4) obtained in Production Example A 4, 72.6 parts of acrylic acid, 9.6 parts of p-toluenesulfonic acid, 0.5 part of hydroquinone, 576 parts of benzene and 144 parts of cyclohexane were introduced, and the thus obtained mixture was reacted in the same manner as in Example B 1 until the amount of the removed water became 17.2 parts. After dissolving the reaction mixture in a mixture of 1200 parts of benzene and 300 parts of cyclohexane, the thus formed solution was subjected to neutralization, washing and de-solvent in the same manner as in Example B 1 to obtain 654 parts of a pale yellow liquid of the following properties. The result of NMR determination of the thus obtained ester is shown below. Of the above-mentioned peaks, those of Nos. 6, 7 and 8 are those of the absorption peaks of the solvent, and that of No. 15 is that of the position of the peak of tetramethylsilane. EXAMPLE B 4 : In the same reaction vessel as in Example B 1, 700 parts of the addition compound (a - 3) obtained in Production Example A 3, 98.6 parts of acrylic acid, 7.6 parts of p-toluenesulfonic acid, 0.8 part of hydroquinone, 576 parts of benzene and 144 parts of cyclohexane were introduced, and the thus obtained mixture was reacted in the same manner as in Example B 1 until the amount of the removed water became 20.5 parts. After dissolving the reaction mixture in a mixture of 1200 parts of benzene and 300 parts of cyclohexane, the solution was subjected to neutralization, washing and de-solventing to obtain 537 parts of a pale yellow liquid of the following properties. The result of determination of NMR of the thus obtained ester is shown as follows. Of the above-mentioned peaks, those of Nos. 6, 7 and 8 are the absorption peaks of the solvent, and that of No. 16 shows the position of the absorption peak of tetramethylsilane. EXAMPLE B 5 : In the same reaction vessel as in Example B 1, 749.4 parts of the addition compound (a - 1) which had been obtained in Production Example A 1, 66.2 parts of methacrylic acid, 6.4 parts of p-toluenesulfonic acid, 0.5 part of hydroquinone, 588.8 parts of benzene and 147.2 parts of cyclohexane were introduced, and the thus obtained mixture was reacted in the same manner as in Example B 1 until the amount of the removed water became 11.6 parts. After dissolving the reaction mixture in a mixture of 960 parts of benzene and 240 parts of cyclohexane, the thus prepared solution was subjected to neutralization, washing and de-solventing to obtain 678 parts of a pale yellow liquid of the following properties. The result of determination of NMR is shown as follows. Of the above-mentioned peaks, those of Nos. 6, 7 and 8 are the absorption peak of the solvent, and that of No. 18 shows the position of the absorption peak of tetramethylsilane. The following Production Example B is an example of the production of monoacrylate of the addition compound obtained by the reaction of an addition compound obtained by reacting nonylphenol with ethyleneoxide (1 : 4 (mol)) and ε-caprolactone (1 : 2 (mol)). PRODUCTION EXAMPLE B 1 : In a 2-litre reaction vessel provided with a stirrer, a temperature controller, a thermometer and a condenser, 624 parts of a compound represented by the following formula: 108 parts of acrylic acid, 16.8 parts of p-toluenesulfonic acid, 1.0 part of hydroquinone, 560 parts of benzene and 140 parts of cyclohexane were introduced, and the thus obtained mixture was reacted in the same manner as in Example A 1 at a temperature of 80 to 87°C until the amount of the removed water became 18 parts. After dissolving the reaction mixture in a mixture of 1040 parts of benzene and 260 parts of cyclohexane, the thus formed solution was subjected to neutralization by an aqueous 20 % solution of sodium hydroxide and then washed three times with each 500 parts of an aqueous 20 % solution of sodium chloride, and the solvent of the thus washed solution was distilled off under a reduced pressure to obtain 596 parts of a pale yellow liquid of the following properties. The following Production Examples C are the examples for producing a polyurethane acrylate. PRODUCTION EXAMPLE C 1 : In the same reaction vessel as in Production Example B 1, 253.1 parts of polypropylene glycol of a molecular weight of about 2000 and an OH value of 56.1, 251.3 parts of polyester polyol which was the reaction product of neopentyl glycol, adipic acid and ε-caprolactone (made by DAICEL Chem. Ind. Co., Ltd., PLACCEL L-220AL, a molecular weight of about 2000 and an OH value of 57.5) and 84.7 parts of isophorone diisocyanate were introduced, and after heating the thus obtained mixture, the mixture was reacted for 10 hours at 75°C, and after cooling the reaction mixture to 60°C, 91.4 parts of an addition compound of ε-caprolactone and β-hydroxyethyl acrylate (made by DAICEL Chem. Ind. Co., Ltd., PLACCEL FA-2), 0.3 part of methoquinone and 0.12 part of di-n-butyltin dilaurate were additionally introduced into the reaction vessel, and the thus formed mixture was heated and reacted at a temperature of 75 to 80°C to obtain a product of a viscosity of 110 poise at 60°C and a refractive index of 1.4721 at 20°C. PRODUCTION EXAMPLE C 2 : In the same reaction vessel as in Production Example C 1, 500 parts of a carbonate diol (made by SUMITOMO-Bayer Co., Ltd., DESMOPHEN®2020E, a molecular weight of about 2000 and an OH value of 56) and 83.3 parts of isophorone diisocyanate were introduced, and after heating the content of the reaction vessel, the content was reacted at a temperature of 75°C for 10 hours, and after cooling the reaction mixture to 60°C, 90.3 parts of the same addition compound (PLACCEL FA-2) as in Production Example C 1, 0.3 part of methoquinone and 0.1 part of di-n-butyltin dilaurate were added to the reaction mixture. The mixture was reacted at a temperature of from 75 to 80°C. The thus obtained product showed a viscosity of 0.675 Pas (675 poise) at 80°C and a refractive index of 1.4730 at 20°C. PRODUCTION EXAMPLE C 3 : In the same reaction vessel as in Production Example C 1, 432 parts of a polyester diol (made by DAICEL Chem. Ind. Co., Ltd., PLACCEL P-2203, a molecular weight of about 2000 and an OH value of 57.9) which was the reaction product of polypropylene glycol and ε-caprolactone, and 84.9 parts of 4,4'-diphenylmethane diisocyanate were introduced, and the mixture was reacted at 75°C for 10 hours. Then, after cooling the reaction mixture to 60°C, 26.2 parts of 2-hydroxyethyl acrylate, 0.27 part of methoquinone and 0.11 part of di-n-butyltin dilaurate were added to the reaction mixture, and the mixture was brought into reaction at a temperature of 75 to 80°C. The thus obtained product showed a viscosity of 0.088 Pas (88 poise) at 80°C and a refractive index of 1.4920 at 20°C. The following series of Examples C are the examples of preparing the resin composition curable by ultraviolet rays. EXAMPLE C 1 : A resin composition C-A was prepared by mixing 70 parts of diacrylic acid ester obtained in Example B 1, 30 parts of monoacrylate of an addition compound of 2 mols of ε-caprolactone and one mol of an addition compound of one mol of nonylphenol and 4 mols of ethylene oxide, 5 parts of 1-hydroxycyclohexyl phenyl ketone (made by Ciba-Geigy Co., Ltd., IRGACURE®-184) and 0.01 part of methylhydroquinone. The properties of the resin composition C-A and that of the cured product of the resin composition C-A are shown in Table 1. EXAMPLE C 2 : A resin composition C-B was prepared by mixing 50 parts of diacrylic acid ester obtained in Example B 2, 50 parts of monoacrylate of an addition compound of one mol of nonylphenol and seven mols of ethylene oxide, 5 parts of 4'-dodecyl-2-hydroxy-2-methylpropiophenone (made by Merck Co., Ltd., DAROCURE®-953) and 0.01 part of methylhydroquinone. The property of the thus prepared resin composition and that of the cured product of the cured product of the resin composition are shown in Table 1. EXAMPLE C 3 : A resin composition C-C was prepared by mixing 20 parts of diacrylic acid ester obtained in Example B 3, 30 parts of polyurethan acrylate which had been obtained by reacting 0.5 mol of polypropylene glycol of the molecular weight of about 2000, 0.5 mol of polyester polyol (made by DAICEL Chem. Ind. Co., Ltd., PLACCEL L-220AL, a molecular weight of about 2000) and 1.5 mol of isophorone diisocyanate at 75 to 80°C and further reacting the thus obtained reaction mixture with 1.1 mol of an addition compound of ε-caprolactone and β-hydroxyethyl acrylate (PLACCEL FA-2), 30 parts of monoacrylate of an addition compound of 1 mol of nonylphenol and 7 mols of ethylene oxide, 20 parts of monoacrylate of an addition compound of 2 mols of ε-caprolactone and one mol of another addition compound of one mol of nonylphenol and 4 mols of ethylene oxide, 5 parts of 1-hydroxycyclohexyl phenyl ketone and 0.01 part of methylhydroquinone. The property of the thus prepared resin composition and that of the cured product of the thus prepared resin composition are also shown in Table 1. EXAMPLE C 4 : A resin composition C-D was prepared by mixing 20 parts of diacrylic acid ester obtained in Example B 4, 10 parts of dimethacrylic acid ester obtained in Example B 5, 25 parts of polyurethane acrylate used in Example C 3, 15 parts of monoacrylate of a compound obtained by reacting one mol of ε-caprolactone with one mol of tetrahydrofurfuryl alcohol (made by NIPPON KAYAKU Co., Ltd., KAYARAD TC-110S), 30 parts of monoacrylate of an addition compound of one mol of nonylphenol and 7 mols of ethylene oxide, 5 parts of 1-hydroxycyclohexyl phenyl ketone and 0.01 part of methylhydroquinone. The property of the thus prepared resin composition C-D and that of the cured product of the resin composition C-D are also shown in Table 1. COMPARATIVE EXAMPLE A 1 : For comparison, as a conventional coating composition which was curable by ultraviolet rays for use in optical fibers, a commercialized product (by Desoto Chemical Co. under the registered trade name of DESOTO 950 x 065 was used as a resin composition A-E. The property of the resin composition A-E and that of the cured product thereof are also shown in Table 1 for comparison. Notes in Table 1 : Determination of Shore Hardness A (Shore A) : By exposing each of the resin compositions C-A, C-B, C-C, C-D and A-E to ultraviolet rays from a high-pressure mercury lamp (output of 2 kw) placed parallel to the resin composition and at a height of 8 cm from the resin composition, at a conveyer speed of 30 m/min, each of the sheets of cured material of 250 µm in thickness was produced and the hardness (Shore A) of the sheet was determined following the method of Japanese Industrial Standards (JIS)-Z2246. Determination of Glass Transition Temperature : Glass Transition Temperature of every specimens of the sheets prepared as in the Determination of Shore Hardness A was determined by using viscoelasticity spectrometer (made by Iwamoto Mfg. Co., Ltd.). Young's Modulus (kg/cm²) : Young's modulus of every specimens of the sheets prepared as in the Determination of Shore Hardness A was determined at one of several temperatures shown in Table 1. Determination of Rate of Water Absorption : The rate of water absorption of the cured resin composition was determined from the weights before and after immersion of the specimen prepared by the same method as in the Determination of Shore Hardness A in pure water at 20°C for 24 hours. Namely the increase of the weight of the specimen by absorbing water was determined. EXAMPLE C 5 : By heating the parent material for optical glass fibers to about 2000°C, the optical glass fibers of 125 µm in outer diameter were prepared at a spinning velocity of 5 m/sec. In the successive step, each of the resin compositions C-A to C-D was coated onto the thus spun optical glass fibers by die-coating method, and the thus coated optical glass fibers were exposed to ultraviolet rays from a high pressure mercury lamp of 2 kw to cure the resin compositions on the glass fibers. No transmission loss was observed on the thus coated optical glass fibers until -60°C. EXAMPLE D 1 : A resin composition D-A was prepared by mixing 10 parts of the carbonate diol diacrylate obtained in Example A 1, 40 parts of polyurethane acrylate obtained in Production Example C 1, 40 parts of a monoacrylate of an addition compound of 2 mols of ε-caprolactone and one mol of another addition compound of one mol of nonylphenol and 4 mols of ethylene oxide, 10 parts of monoacrylate of a compound obtained by reacting one mol of ε-caprolactone with one mol of tetrahydrofurfuryl alcohol (made by NIPPON KAYAKU Co., Ltd., KAYARAD TC-110S), 5 parts of 1-hydroxycyclohexyl phenyl ketone (refer to Example C 1), and 0.01 part of methylhydroquinone. The properties of the thus prepared resin composition D-A and the cured material thereof are shown in Table 2. EXAMPLE D 2 : A resin composition D-B was prepared by mixing 40 parts of the carbonate diol diacrylate obtained in Example A 2, 25 parts of polyurethane acrylate obtained in Production Example C 1, 25 parts of monoacrylate of an addition compound of 2 mols of ε-caprolactone and one mol of another addition compound of one mol of nonylphenol and 4 mols of ethylene oxide, 5 parts of 1-hydroxycyclohexyl phenyl ketone (refer to Example C 1) and 0.01 part of methylhydroquinone. The physical property of the resin composition D-B and the cured product thereof is shown also in Table 2. EXAMPLE D 3 : A resin composition D-C was prepared by mixing 20 parts of the carbonate diol diacrylate obtained in Example A 2, 20 parts of polyurethane acrylate obtained in Production Example C 2, 40 parts of monoacrylate of an addition compound of 2 mols of ε-caprolactone and one mol of another addition compound of one mol of nonylphenol and 4 mols of ethylene oxide, 20 parts of monoacrylate of an addition compound of one mol of nonylphenol and 7 mols of ethylene oxide, 5 parts of 4'-dodecyl-2-hydroxy-2-methyl-propiophenone (made by Merck Co., Ltd., DAROCURE®-953) and 0.01 part of methylhydroquinone. The physical property of the thus prepared resin composition D-C and the cured product thereof is also shown in Table 2. EXAMPLE D 4 : A resin composition D-D was prepared by mixing 10 parts of the carbonate diol dimethacrylate obtained in Example A 3, 10 parts of the carbonate diol diacrylate obtained in Example A 2, 30 parts of polyurethane acrylate obtained in Production Example C 3, 10 parts of phenoxyethyl acrylate, 40 parts of monoacrylate of an addition compound of one mol of nonyl phenol and 7 mols of ethylene oxide, 5 parts of IRGACURE®-184 (refer to Example C 1) and 0.01 part of methylhydroquinone. The physical property of the thus prepared resin composition D-D and the cured product thereof is also shown in Table 2. In Table 2, the determination of the physical property was carried out as shown after Table 1. EXAMPLE D 5 : In the same method as in Example C 5, each of the resin compositions D-A to D-D was coated on the same optical glass fibers, thereby preparing the coated optical glass fibers. No transmission loss of the coated optical glass fibers was observed until -60°C. The resin compositions and the coating agents according to the present invention have the advantage of a high curing rate. Cured films of the compositions and agents are soft and have a low glass transition temperature. The cured films have the advantage of low water absorption and the change of physical properties of the cured film is very small over a wide temperature range. Therefore, the resin composition of the present invention is suitable for coating optical glass fibers for light transmission. In the case where ε-caprolactone is added to the carbonate diol in the di-(meth)acrylic acid ester, the di-(meth)acrylic acid ester does not form a wax easily and the viscosity is lowered, whereby the handling becomes easier and the glass transition temperature of the cured composition or agent is lowered.

Claims: A resin composition comprising (A) di-(meth)acrylic acid ester of an addition compound of a carbonate diol of an average molecular weight of from 500 to 3000 with ε-caprolactone, (B) a monoethylenically unsaturated monomer, and as an optional component, (C) an initiator of photopolymerization. A resin composition according to claim 1, wherein the amount of said di-(meth)acrylic acid ester (A) is 5 to 80% by weight, the amount of said monoethylenically unsaturated monomer (B) is 20 to 80% by weight and the amount of said initiator of photopolymerization (C) is 0 to 10% by weight, based on the weight of said resin composition. A resin composition according to claim 1 or 2, wherein said di-(meth)acrylic acid ester (A) is a diacrylate of an addition compound of ε-caprolactone with a carbonate diol produced by an ester-exchange reaction of a carbonate derivative and a diol obtained by reacting ε-caprolactone with 1,6-hexanediol. A resin composition comprising (A) di-(meth)acrylic acid ester of a carbonate diol of an average molecular weight of 500 to 3000, (D) a polyurethane (meth)acrylate, (B) a monoethylenically unsaturated monomer, and as an optional component, (C) an initiator of photopolymerization. A resin composition according to claim 4, wherein the amount of said di-(meth)acrylic acid ester (A) is 5 to 50% by weight, the amount of said polyurethane (meth)acrylate (D) is 20 to 70% by weight, the amount of said monoethylenically unsaturated monomer (B) is 20 to 70% by weight and the amount of said initiator of photopolymerization (C) is 0 to 10% by weight, based on the weight of said resin composition. A resin composition according to claim 4 or 5, wherein said di-(meth)acrylic acid ester (A) is a di-acrylate of a carbonate diol produced by an ester-exchange reaction of a carbonate derivative and a diol obtained by reacting ε-caprolactone with 1,6-hexanediol. A resin composition according to any one of the preceding claims wherein said monoethylenically unsaturated monomer (B) is at least one compound selected from the group consisting of phenyloxy (or alkylphenyloxy) polyethoxy(meth)acrylate; phenyloxy (or alkylphenyloxy)polypropoxy(meth)acrylate; nonylphenyloxy polyethoxy(meth)acrylate; phenyloxy (or alkylphenyloxy)ethoxy(meth)acrylate; phenyloxy (or alkylphenyloxy)propoxy(meth)acrylate; polyethoxy(meth)acrylate of tetrahydrofurfuryl alcohol; (meth)acrylate of an addition compound of ε-caprolactone with tetrahydrofurfuryl alcohol; an addition compound of ε-caprolactone with β-hydroxyethyl (meth)acrylate; carbitol acrylate and the compounds represented by the formula: wherein R³ is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R⁴ and R⁵ represent independently a hydrogen atom or a methyl group; the mean value of m is 1 to 10 and the mean value of n is 1 to 10. A method of coating optical glass fibers, which method comprises coating said fibres with a coating agent comprising (A) di-(meth)acrylic acid ester of a carbonate diol of an average molecular weight of 500 to 3000 or of an addition compound of said carbonate diol with ε-caprolactone, (B) a monoethylenically unsaturated monomer and (C) an initiator of photopolymerization; and irradiating the thus coated fibres with actinic radiation so as to cure said agent. A method according to claim 8, wherein the amount of said di(meth)acrylic acid ester (A) is 5 to 80% by weight, the amount of said monoethylenically unsaturated monomer (B) is 20 to 80% by weight and the amount of said initiator of photopolymerization (C) is 0.1 to 10% by weight, based on the weight of said coating agent. A method according to claim 8 or 9 wherein the coating agent is in the form of a resin composition as defined in any one of claims 1 to 7. A method according to claim 10 wherein the amount of said initiator of photopolymerization (C) in said coating agent is 0.1 to 10% by weight, based on the weight of said coating agent. A di-(meth)acrylic acid ester of an addition compound of a carbonate diol of an average molecular weight of 500 to 3000 with ε-caprolactone. A diacrylic acid ester according to claim 12, wherein said carbonate diol is a carbonate diol produced by an ester-exchange reaction of a carbonate derivative and a diol obtained by reacting ε-caprolactone with 1,6-hexanediol, and the mean amount of addition of ε-caprolactone to said carbonate diol is one to ten mols per mol of carbonate diol. A di-(meth)acrylic acid ester represented by the formula: wherein R¹ represents an alkylene group having 4 to 10 carbon atoms; R² represents a hydrogen atom or a methyl group, the mean values of a and b are each from 0 to 5; the sum of the mean values of a and b is from 0.5 to 5 and the mean value of ℓ is from 1 to 10. A di-(meth)acrylic acid ester according to claim 14, wherein R¹ represents an alkylene group having 5 to 8 carbon atoms; R² represents a hydrogen atom; the sum of the mean values of a and b is from 0.5 to 3 and the mean value of ℓ is from 3 to 8. A process for the preparation of a di-(meth)acrylic acid ester as defined in claim 14, which process comprises reacting a carbonate diol of formula: wherein R¹, a , b and ℓ are defined in claim 14, with acrylic acid or methacrylic acid.

Inventors: KIYOMOTO, MASAYUKI, OHKUBO, TETSUO, YOKOSHIMA, MINORU
Applicants: NIPPON KAYAKU KABUSHIKI KAISHA
Application year: 1986
Main classification: C08F299
IPC codes: C08F299, C08F2, C07C69, C03C25