Radiation-curable resin composition, cured product thereof, and optical fiber

Abstract

A radiation-curable resin composition for forming a primary coating layer on an optical fiber, comprising a urethane oligomer having an ethylenically unsaturated group, a radically polymerizable non-urethane monomer, and a polymerization initiator, wherein the urethane oligomer comprises 30 mass% or more, relative to 100 mass% of the total amount of the radiation-curable resin composition, of a reaction product of a polyether polyol having a weight-average molecular weight of 9000 or more, a polyisocyanate, and an isocyanate-reactive compound containing one active hydrogen group, and the isocyanate-reactive compound comprises an isocyanate-reactive compound containing an ethylenically unsaturated group.

Description

[Technical field]

[0001] The present invention relates to a radiation-curable resin composition and a cured product thereof, and an optical fiber. [Background technology]

[0002] An optical fiber is composed of a glass fiber obtained by hot-melt spinning of glass, and a coating layer or the like provided on the glass fiber for the purpose of protection and reinforcement. For example, an optical fiber is manufactured by first providing a flexible primary coating layer (hereinafter also referred to as a "primary coating layer") on the surface of the glass fiber, and then providing a rigid secondary coating layer (hereinafter also referred to as a "secondary coating layer") on the primary coating layer. Optical fiber ribbons and optical fiber cables, in which multiple optical fibers provided with coating layers are bound together with a bundling material, are also well known.

[0003] A widely used method for forming a coating layer on a glass fiber is, for example, to apply a liquid curable resin composition to the glass fiber and cure it with heat or light, particularly ultraviolet light. For example, Patent Document 1 discloses a radiation curable composition that combines a urethane oligomer produced by a specific production method and a compound having one ethylenically unsaturated group as a resin composition for forming a primary coating layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-111674 A Summary of the Invention [Problem to be solved by the invention]

[0005] When pressure is applied locally to the side of an optical fiber, the core of the glass fiber in the area where pressure is applied is bent with a small curvature, resulting in optical loss. From the viewpoint of suppressing such optical loss (also called microbending loss), it is desirable for the primary coating layer to be sufficiently flexible. In addition, in recent years, from the viewpoint of increasing the density, reducing weight, and improving the handleability of optical fiber cables, the primary coating layer is required to have high mechanical strength (breaking strength and breaking elongation).

[0006] However, when the primary coating layer is made flexible, sufficient mechanical strength (breaking strength and breaking elongation) may not be obtained. In particular, it is difficult to achieve both excellent mechanical strength and excellent flexibility at low temperatures (e.g., -40°C).

[0007] Therefore, an object of the present invention is to provide a radiation-curable resin composition for forming a primary coating layer, which is capable of forming a cured product having excellent flexibility and mechanical strength, a cured product thereof, and an optical fiber. [Means for solving the problem]

[0008] As a result of extensive investigations conducted to achieve the above object, the present inventors discovered that by using a urethane oligomer having a specific structure, it is possible to obtain a radiation-curable resin composition capable of forming a cured product that is excellent in flexibility and mechanical strength, and thus completed the present invention.

[0009] That is, one aspect of the present invention relates to a radiation-curable resin composition for forming a first coating layer of an optical fiber, comprising a urethane oligomer having an ethylenically unsaturated group, a free-radically polymerizable non-urethane monomer, and a polymerization initiator, in which the urethane oligomer comprises 30 mass% or more, relative to 100 mass% of the total amount of the radiation-curable resin composition, of a reaction product of a polyether polyol having a weight average molecular weight of 9,000 or more, a polyisocyanate, and an isocyanate-reactive compound containing one active hydrogen group (excluding polyether polyol), and the isocyanate-reactive compound comprises an isocyanate-reactive compound containing an ethylenically unsaturated group.

[0010] According to the radiation-curable resin composition of the above aspect, a cured product having excellent flexibility and mechanical strength can be formed, and an optical fiber can be obtained having a primary coating layer made of the cured product.

[0011] The polyether polyol may be a polyether diol or a polyether triol.

[0012] The polyether polyol is preferably an aliphatic polyether polyol.

[0013] The reactant contained in the urethane oligomer may be a reactant of a reaction product of a polyether polyol and a polyisocyanate, and an isocyanate-reactive compound, or a reactant of a reaction product of a polyisocyanate and an isocyanate-reactive compound, and a polyether polyol.

[0014] The isocyanate-reactive compound preferably further comprises an aliphatic alcohol.

[0015] Another aspect of the present invention relates to a cured product of the above-mentioned radiation-curable resin composition.

[0016] Another aspect of the present invention relates to an optical fiber comprising a primary coating layer made of the above-mentioned cured product. Effect of the Invention

[0017] According to the present invention, it is possible to provide a radiation-curable resin composition for forming a primary coating layer, which is capable of forming a cured product having excellent flexibility and mechanical strength, a cured product thereof, and an optical fiber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Preferred embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In this specification, a numerical range indicated using "~" indicates a range including the numerical values ​​before and after "~" as the minimum and maximum values, respectively. The upper and lower limit values ​​described in stages in this specification may be combined in any combination.

[0019] The radiation-curable resin composition of the embodiment is a radiation-curable resin composition for forming a primary coating layer of an optical fiber, which contains a urethane oligomer having an ethylenically unsaturated group (hereinafter, also simply referred to as "urethane oligomer"), a radical-polymerizable non-urethane monomer, and a polymerization initiator. The composition for forming a primary coating layer of an optical fiber can also be called a primary material.

[0020] Here, radiation refers to infrared rays, visible light, ultraviolet rays, X-rays, electron beams, α rays, β rays, γ rays, etc., with ultraviolet rays being particularly preferred.

[0021] The urethane oligomer contains a reaction product (hereinafter also referred to as "urethane oligomer A") between a polyether polyol having a weight average molecular weight of 9000 or more (hereinafter also referred to simply as "polyether polyol"), a polyisocyanate, and an isocyanate-reactive compound containing one active hydrogen group (hereinafter also referred to simply as "isocyanate-reactive compound"), in which the isocyanate-reactive compound contains an ethylenically unsaturated group-containing isocyanate-reactive compound. That is, the urethane oligomer contains components derived from a polyether polyol, a polyisocyanate, and an isocyanate-reactive compound. The urethane oligomer A contains a structural unit derived from a polyether polyol, a structural unit derived from a polyisocyanate, and a structural unit derived from an isocyanate-reactive compound, and contains a urethane bond derived from the reaction between the polyether polyol and the polyisocyanate, and a bond (e.g., a urethane bond) derived from the reaction between the polyisocyanate and the isocyanate-reactive compound.

[0022] The urethane oligomer A is, for example, a reaction product of a polyether-based urethane prepolymer and an isocyanate-reactive compound. The polyether-based urethane prepolymer is a reaction product of a polyether polyol and a polyisocyanate, and has an isocyanate group.

[0023] The urethane oligomer A is, for example, a reaction product of a polyether polyol and an isocyanate group-containing end-capping compound. The isocyanate group-containing end-capping compound is a reaction product of a polyisocyanate and an isocyanate-reactive compound, and has an isocyanate group.

[0024] The weight average molecular weight (Mw) of the polyether polyol is 9000 or more, preferably 9500 or more, more preferably 9800 or more, and even more preferably 10000 or more. The weight average molecular weight (Mw) of the polyether polyol may be 20000 or less, 15000 or less, or 12000 or less. When the weight average molecular weight (Mw) of the polyether polyol is 20000 or less, excellent compatibility with radical polymerizable non-urethane monomers tends to be obtained. The weight average molecular weight is a value measured by gel permeation chromatography and converted based on a standard polystyrene calibration curve.

[0025] The polyether polyol is preferably a polyether diol or a polyether triol. That is, the number of hydroxyl groups (—OH) contained in the polyether polyol is preferably 2 or 3.

[0026] The polyether polyol is preferably an aliphatic polyether polyol, more preferably an aliphatic polyether diol or an aliphatic polyether triol.

[0027] Preferred aliphatic polyether diols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, polyheptamethylene glycol, polydecamethylene glycol, and aliphatic polyether diols obtained by ring-opening copolymerization of two or more kinds of ionically polymerizable cyclic compounds.

[0028] Examples of the ionically polymerizable cyclic compound include cyclic ethers such as ethylene oxide, propylene oxide, butene-1-oxide, isobutene oxide, 3,3-bischloromethyloxetane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, dioxane, trioxane, tetraoxane, cyclohexene oxide, styrene oxide, epichlorohydrin, glycidyl methacrylate, allyl glycidyl ether, allyl glycidyl carbonate, butadiene monoxide, isoprene monoxide, vinyl oxetane, vinyltetrahydrofuran, vinylcyclohexene oxide, phenyl glycidyl ether, butyl glycidyl ether, and benzoic acid glycidyl ester.

[0029] Specific examples of polyether diols obtained by ring-opening copolymerization of two or more of the above-mentioned ionically polymerizable cyclic compounds include binary copolymers obtained from combinations of tetrahydrofuran and propylene oxide, tetrahydrofuran and 2-methyltetrahydrofuran, tetrahydrofuran and 3-methyltetrahydrofuran, tetrahydrofuran and ethylene oxide, propylene oxide and ethylene oxide, butene-1-oxide and ethylene oxide, etc.; and terpolymers obtained from a combination of tetrahydrofuran, butene-1-oxide and ethylene oxide.

[0030] It is also possible to use polyether diols obtained by ring-opening copolymerization of the above ionically polymerizable cyclic compounds with cyclic imines such as ethyleneimine; cyclic lactone acids such as β-propiolactone and glycolic acid lactide; or dimethylcyclopolysiloxanes.

[0031] Among these aliphatic polyether diols, it is preferable to use one or more ring-opening polymers of ionically polymerizable cyclic compounds having 2 to 4 carbon atoms, from the viewpoint of achieving both high-speed application of the resin liquid and flexibility of the coating material. Such a preferred aliphatic polyether diol includes ring-opening polymers of one or more oxides selected from ethylene oxide, propylene oxide, butene-1-oxide, and isobutene oxide. As the aliphatic polyether diol, polypropylene glycol diol (ring-opening polymer of propylene oxide) is particularly preferable.

[0032] The aliphatic polyether triol is preferably an aliphatic polyether triol obtained by addition polymerization of an ionically polymerizable cyclic compound to a triol such as glycerin or trimethylolpropane. The ionically polymerizable cyclic compound may be the above-mentioned ionically polymerizable cyclic compound. Among the aliphatic polyether triols, it is preferable to use an addition polymer of a triol and one or more ionically polymerizable cyclic compounds having 2 to 4 carbon atoms from the viewpoint of both high-speed application of the resin liquid and flexibility of the coating material. Such a preferable aliphatic polyether triol includes an addition polymer of a triol and one or more oxides selected from ethylene oxide, propylene oxide, butene-1-oxide, and isobutene oxide. The aliphatic polyether triol is particularly preferably polypropylene glycol triol (an addition polymer of glycerin and propylene oxide).

[0033] The above-mentioned aliphatic polyether diols and aliphatic polyether triols can also be obtained as commercially available products such as PREMINOL S 3011, PREMINOL S 4011, PREMINOL S-X3015, PREMINOL 4016, and PREMINOL 7012 manufactured by AGC Corporation, and Acclaim Polyol 12200 N and Acclaim Polyol 18200 N manufactured by Sumika Covestro Urethane Co., Ltd.

[0034] Polyisocyanates are compounds having two or more isocyanate groups. Examples of polyisocyanates include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates.

[0035] The polyisocyanate is preferably a diisocyanate, such as an aromatic diisocyanate, an alicyclic diisocyanate, or an aliphatic diisocyanate. Examples of aromatic diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylphenylene diisocyanate, 4,4'-biphenylene diisocyanate, bis(2-isocyanateethyl)fumarate, 6-isopropyl-1,3-phenyl diisocyanate, 4-diphenylpropane diisocyanate, and tetramethylxylylene diisocyanate. Examples of alicyclic diisocyanates include isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, 2,5-bis(isocyanatemethyl)-bicyclo[2.2.1]heptane, 2,6-bis(isocyanatemethyl)-bicyclo[2.2.1]heptane, etc. Examples of aliphatic diisocyanates include 1,6-hexane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, etc.

[0036] From the viewpoint of economic efficiency and obtaining a composition of stable quality, the diisocyanate is preferably an aromatic diisocyanate, more preferably 2,4-tolylene diisocyanate or 2,6-tolylene diisocyanate. The diisocyanates may be used alone or in combination of two or more kinds.

[0037] The isocyanate-reactive compound is a compound containing one active hydrogen group. However, the above-mentioned polyether polyol is not included in the isocyanate-reactive compound. Examples of the active hydrogen group include a mercapto group (-SH), a hydroxyl group (-OH), and an amino group (-NH2).

[0038] The ethylenically unsaturated group-containing isocyanate-reactive compound is a compound having one active hydrogen group. Examples of the ethylenically unsaturated group include a (meth)acryloyl group, a vinyl group, a vinylene group, and a vinylidene group. In this specification, the term "(meth)acryloyl group" means an "acryloyl group" or the corresponding "methacryloyl group". The same applies to similar expressions such as "(meth)acrylate".

[0039] The ethylenically unsaturated group in the ethylenically unsaturated group-containing isocyanate-reactive compound is preferably a (meth)acryloyl group. The active hydrogen group in the ethylenically unsaturated group-containing isocyanate-reactive compound is preferably a hydroxyl group. That is, the ethylenically unsaturated group-containing isocyanate-reactive compound may be a compound having a (meth)acryloyl group and an active hydrogen group (active hydrogen group-containing (meth)acrylate), or may be a compound having a (meth)acryloyl group and a hydroxyl group (hydroxyl group-containing (meth)acrylate).

[0040] Examples of the hydroxyl group-containing (meth)acrylate include a hydroxyl group-containing (meth)acrylate in which a hydroxyl group is bonded to a primary carbon atom (also referred to as a first hydroxyl group-containing (meth)acrylate), a hydroxyl group-containing (meth)acrylate in which a hydroxyl group is bonded to a secondary carbon atom (also referred to as a second hydroxyl group-containing (meth)acrylate), and a hydroxyl group-containing (meth)acrylate in which a hydroxyl group is bonded to a tertiary carbon atom (also referred to as a third hydroxyl group-containing (meth)acrylate). From the viewpoint of reactivity with an isocyanate group, the hydroxyl group-containing (meth)acrylate may be a first hydroxyl group-containing (meth)acrylate or a second hydroxyl group-containing (meth)acrylate.

[0041] Examples of primary hydroxy group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,6-hexanediol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, neopentyl glycol mono(meth)acrylate, trimethylolpropane di(meth)acrylate, and trimethylolethane di(meth)acrylate.

[0042] Examples of secondary hydroxy group-containing (meth)acrylates include 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, and the like. Also included are compounds obtained by addition reaction of glycidyl group-containing compounds, such as alkyl glycidyl ether, allyl glycidyl ether, and glycidyl (meth)acrylate, with (meth)acrylic acid.

[0043] From the viewpoint of more significantly achieving the effects of the present invention, the content of the ethylenically unsaturated group-containing isocyanate-reactive compound in the isocyanate-reactive compound may be 40 mol% or more, 45 mol% or more, or 50 mol% or more, and may be 60 mol% or less, or 55 mol% or less.

[0044] The isocyanate-reactive compound preferably further contains an aliphatic alcohol. When the isocyanate-reactive compound further contains an aliphatic alcohol, the flexibility of the cured product can be further improved. The aliphatic alcohol has a hydroxyl group as an active hydrogen group. The carbon number of the aliphatic alcohol may be 1 to 15, 5 to 12, or 6 to 10. The carbon chain in the aliphatic alcohol may be linear or branched. Examples of the aliphatic alcohol include methanol, ethanol, propanol, butanol, and 2-ethyl-1-hexanol. From the viewpoint of more prominently exhibiting the effects of the present invention, the aliphatic alcohol may be methanol or 2-ethyl-1-hexanol.

[0045] From the viewpoint of more significantly achieving the effects of the present invention, the content of the aliphatic alcohol in the isocyanate-reactive compound may be 24 mol% or more, 30 mol% or more, 35 mol% or more, or 40 mol% or more, and may be 60 mol% or less, 55 mol% or less, 50 mol% or less, or 45 mol% or less.

[0046] The urethane oligomer A may contain, for example, an oligomer (oligomers a1 to a5) having a structure represented by the following formula (a1), (a2), (a3), (a4) or (a5). A-(ICN-POD)n-ICN-A (a1) A-(ICN-POD)n-ICN-R 1 (a2) A-(ICN-POT)n-(ICN-A)(ICN-R 1 ) (a3) A-(ICN-POT)n-(ICN-R 1 )2(a4) A-(ICN-POT)n-(ICN-A)2(a5) In these formulas, n's each independently represent a number of 1.0 or more, ICN's each independently represent a structure derived from a diisocyanate, POD's each independently represent a structure derived from an aliphatic polyether diol having a weight average molecular weight of 9000 or more, POT's each independently represent a structure derived from an aliphatic polyether triol having a weight average molecular weight of 9000 or more, A's each independently represent a structure derived from an ethylenically unsaturated group-containing isocyanate-reactive compound, R 1 each independently represents a structure derived from an aliphatic alcohol.

[0047] n is 1.0 or more, and may be greater than 1.0, 1.1 or more, 1.3 or more, or 1.5 or more, or 3.0 or less, 2.5 or less, or 2.0 or less. n may be, for example, 1.1 to 3.0, 1.3 to 2.5, or 1.5 to 2.0.

[0048] The urethane oligomer A may contain a urethane (meth)acrylate oligomer having a (meth)acryloyl group as an ethylenically unsaturated group. The urethane oligomer A may contain at least two or more selected from the group consisting of a monofunctional urethane (meth)acrylate oligomer having one (meth)acryloyl group as an ethylenically unsaturated group (corresponding to oligomers a2 and a4), a bifunctional urethane (meth)acrylate oligomer having two (meth)acryloyl groups as an ethylenically unsaturated group (corresponding to oligomers a1 and a3), and a trifunctional urethane (meth)acrylate oligomer having three (meth)acryloyl groups as an ethylenically unsaturated group (corresponding to oligomer a5). The urethane oligomer A preferably contains a monofunctional urethane (meth)acrylate oligomer and a bifunctional urethane (meth)acrylate oligomer.

[0049] The ratio of the number of moles of monofunctional urethane (meth)acrylate oligomer to the number of moles of difunctional urethane (meth)acrylate oligomer may be from 3 / 1 to 100 / 1, from 5 / 1 to 75 / 1, from 7 / 1 to 50 / 1, or from 10 / 1 to 35 / 1.

[0050] The weight average molecular weight (Mw) of the urethane oligomer A may be 9000 or more, 16000 or more, 19500 or more, or 23000 or more, and may be 40000 or less, 37000 or less, or 33000 or less. The weight average molecular weight is a value measured by gel permeation chromatography and converted based on a standard polystyrene calibration curve.

[0051] The content of urethane oligomer A may be 30% by mass or more, 35% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, based on 100% by mass of the total amount of the radiation-curable resin composition, from the viewpoint of making it possible to further improve the flexibility and mechanical strength of the cured product; and may be 90% by mass or less, 85% by mass or less, or 83% by mass or less, from the viewpoint of making it easier to obtain a radiation-curable resin composition having an appropriate viscosity.

[0052] The urethane oligomer having an ethylenically unsaturated group may further contain a urethane oligomer other than the urethane oligomer A, or may consist only of the urethane oligomer A. For example, the urethane oligomer having an ethylenically unsaturated group may contain a reaction product of a polyether polyol having a weight average molecular weight of less than 9000, a polyisocyanate, and an isocyanate-reactive compound. The proportion of the urethane oligomer A in the total mass of the urethane oligomer having an ethylenically unsaturated group may be, for example, 90% by mass or more, 95% by mass or more, or 100% by mass.

[0053] The urethane oligomer A may be produced by reacting a polyether-based urethane prepolymer with an isocyanate-reactive compound. For example, the urethane oligomer can be produced by reacting a polyether-based urethane prepolymer with an ethylenically unsaturated group-containing isocyanate-reactive compound, and then adding and reacting an aliphatic alcohol.

[0054] In the production of the urethane oligomer A, a urethanization catalyst may be used as necessary. Examples of the urethanization catalyst include copper naphthenate, cobalt naphthenate, zinc naphthenate, dibutyltin dilaurate, dioctyltin dilaurate, triethylamine, 1,4-diazabicyclo[2.2.2]octane, and 2,6,7-trimethyl-1,4-diazabicyclo[2.2.2]octane. The amount of the urethanization catalyst used may be 0.01 to 1 mass% based on the total amount of the reactants. In addition, in the production of the urethane oligomer A, a radical polymerization inhibitor such as 2,6-di-t-butyl-p-cresol may be used as necessary. In addition, the reaction temperature is usually 5 to 90°C, and preferably 10 to 80°C.

[0055] The radiation-curable resin composition may further contain a urethane oligomer other than the urethane oligomer having an ethylenically unsaturated group, i.e., a urethane oligomer not having an ethylenically unsaturated group. For example, the urethane oligomer may further contain an oligomer having a structure represented by the following formula (a6) or (a7) (oligomers a6 to a7). R 1 -(ICN-POD)n-ICN-R 1 (a6) R 1 -(ICN-POT)n-(ICN-R 1 )2(a7) In the formula, ICN, POD, POT, n and R 1 is synonymous with the above.

[0056] The proportion of the urethane oligomer having no ethylenically unsaturated groups in the total mass of the radiation-curable resin composition may be, for example, 10 mass % or less, 5 mass % or less, or 1 mass % or less.

[0057] The radiation curable resin composition further contains a radically polymerizable non-urethane monomer. As the radically polymerizable non-urethane monomer, a monomer containing an ethylenically unsaturated group can be used. The ethylenically unsaturated group may be the group exemplified above. The radically polymerizable non-urethane monomer may be used alone or in combination of two or more kinds.

[0058] The radical polymerizable non-urethane monomer may contain a vinyl group-containing compound (which may also be called a vinyl monomer, except for monomers that fall under the category of (meth)acrylate monomers described below), and may contain a (meth)acrylate monomer having a (meth)acryloyl group. The radical polymerizable non-urethane monomer may contain a vinyl group-containing compound and a (meth)acrylate monomer.

[0059] The vinyl group-containing compound may be at least one selected from the group consisting of vinyl ester compounds and vinyl amide compounds. That is, the radical polymerizable non-urethane monomer may contain at least one vinyl group-containing compound selected from the group consisting of vinyl ester compounds and vinyl amide compounds. The number of vinyl groups in the vinyl group-containing compound may be one or more.

[0060] Examples of the vinyl group-containing compound include vinyl amide compounds (vinyl group-containing lactams) such as N-vinylpyrrolidone and N-vinylcaprolactam, vinylimidazole, and vinylpyridine. From the viewpoint of further improving the curing speed, the vinyl group-containing compound may be a vinyl amide compound. From the same viewpoint, the vinyl amide compound may be N-vinylcaprolactam.

[0061] The content of the vinyl group-containing compound in the radiation curable resin composition may be 3 to 20 mass %, or 5 to 12 mass %, relative to 100 mass % of the total amount of the radiation curable resin composition.

[0062] The radically polymerizable non-urethane monomer may contain, as the (meth)acrylate monomer, a monofunctional (meth)acrylate monomer having one (meth)acryloyl group and a polyfunctional (meth)acrylate monomer having two or more (meth)acryloyl groups.

[0063] Examples of monofunctional (meth)acrylate monomers include alicyclic structure-containing (meth)acrylates such as 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 4-butylcyclohexyl (meth)acrylate, and acryloylmorpholine. Further, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, methoxyethylene glycol (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxylate nonylphenol (meth)acrylate, etc. Also, as the monofunctional (meth)acrylate monomer, the above-mentioned hydroxyl group-containing (meth)acrylate may be used.

[0064] The content of the monofunctional (meth)acrylate monomer in the radiation curable resin composition may be 3 to 30 mass %, or 8 to 15 mass %, relative to 100 mass % of the total amount of the radiation curable resin composition.

[0065] The radically polymerizable non-urethane monomer may contain a polyfunctional (meth)acrylate monomer, which increases the crosslink density in the cured product, thereby further improving the mechanical strength of the cured product.

[0066] Examples of polyfunctional (meth)acrylate monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane trioxyethyl (meth)acrylate, and tris(2-hydroxyethyl)isocyanate. di(meth)acrylate of a diol of an adduct of bisphenol A with ethylene oxide or propylene oxide, di(meth)acrylate of a diol of an adduct of hydrogenated bisphenol A with ethylene oxide or propylene oxide, epoxy (meth)acrylate in which (meth)acrylate is added to diglycidyl ether of bisphenol A, and triethylene glycol divinyl ether are included. Examples of commercially available products include Iupimer UV SA1002, SA2007 (both manufactured by Mitsubishi Chemical Corporation); Viscoat 700 (manufactured by Osaka Organic Chemical Industry Co., Ltd.); KAYARAD R-604, DPCA-20, -30, -60, -120, HX-620, D-310, D-330 (all manufactured by Nippon Kayaku Co., Ltd.); Aronix M-210, M-215, M-315, M-325 (all manufactured by Toagosei Co., Ltd.), and the like.

[0067] The content of the polyfunctional (meth)acrylate monomer in the radiation curable resin composition may be 2 mass% or less, 1.5 mass% or less, or 1.0 mass% or less, relative to 100 mass% of the total amount of the radiation curable resin composition, or may be more than 0 mass%.

[0068] The radiation curable resin composition contains a polymerization initiator. As the polymerization initiator, a typical polymerization initiator used as a photopolymerization initiator can be used. Examples of the polymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropanone, and the like. thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; IRGACURE184, 369, 651, 500, 907, CGI1700, CGI1750, CGI1850, CG24-61, DAROCUR1116, 1173 (all manufactured by Chiba Specialty Chemicals); LUCIRIN TPO (manufactured by BASF); and Ubecryl P36 (manufactured by UCB). Examples of photosensitizers include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate; Ubecryl P102, 103, 104, and 105 (all manufactured by UCB).

[0069] The content of the polymerization initiator in the radiation curable resin composition may be 0.1 to 10 mass %, or may be 0.3 to 7 mass %, relative to 100 mass % of the total amount of the radiation curable resin composition.

[0070] The radiation curable resin composition may further contain additives other than the above-mentioned components, such as Irganox 245.

[0071] In a radiation-curable resin composition in which the urethane oligomer and / or the radically polymerizable non-urethane monomer contains a (meth)acryloyl group-containing compound (for example, the above-mentioned urethane (meth)acrylate oligomer and (meth)acrylate monomer) and the radically polymerizable non-urethane monomer contains a vinyl group-containing compound (vinyl monomer), the ratio of the number of moles of the (meth)acryloyl group-containing compound to the number of moles of the vinyl group-containing compound may be 1 / 1 or more and 10 / 1 or less, 1 / 1 or more and 5 / 1 or less, 1 / 1 or more and 3 / 1 or less, 1 / 1 or more and 2 / 1 or less, or 1 / 1 or more and 1.5 / 1 or less.

[0072] In a radiation-curable resin composition in which the urethane oligomer and the radically polymerizable non-urethane monomer have an ethylenically unsaturated group, the ratio of the number of moles of the monofunctional compound having one ethylenically unsaturated group to the number of moles of the polyfunctional compound having two or more ethylenically unsaturated groups may be 2 / 1 or more and 100 / 1 or less, 5 / 1 or more and 75 / 1 or less, 10 / 1 or more and 50 / 1 or less, or 15 / 1 or more and 30 / 1 or less.

[0073] In a radiation-curable resin composition in which the urethane oligomer or the radically polymerizable non-urethane monomer contains a monofunctional (meth)acrylate (a (meth)acryloyl group-containing compound having one (meth)acryloyl group) and a polyfunctional (meth)acrylate (a (meth)acryloyl group-containing compound having two or more (meth)acryloyl groups), the ratio of the number of moles of the monofunctional (meth)acrylate in the radiation-curable resin composition to the number of moles of the polyfunctional (meth)acrylate in the radiation-curable resin composition may be 1 / 1 or more and 75 / 1 or less, 2 / 1 or more and 50 / 1 or less, or 5 / 1 or more and 25 / 1 or less.

[0074] The radiation curable resin composition may be in a liquid state, i.e. the radiation curable resin composition granules may be a liquid radiation curable resin composition.

[0075] The radiation-curable resin composition may contain other oligomers, polymers, other additives, and the like, as required.

[0076] From the viewpoints of handleability and coatability, the viscosity of the radiation curable resin composition may be 0.1 to 10 Pa s or 1 to 8 Pa s at 25° C. The viscosity of the radiation curable resin composition is measured by the method described in the examples below.

[0077] The radiation-curable resin composition of the embodiment described above can form a cured product (e.g., a cured layer) that is excellent in flexibility and mechanical strength. Specifically, the radiation-curable resin composition of the embodiment can form a cured product that has a sufficiently low Young's modulus at 23°C and at -40°C, and is excellent in breaking strength and breaking elongation.

[0078] The cured product of the radiation curable composition is used for the primary coating layer of an optical fiber. In other words, one embodiment of the present invention relates to a cured product of the radiation curable resin composition used for the primary coating layer of an optical fiber. Another embodiment of the present invention relates to an optical fiber having a primary coating layer made of the cured product of the radiation curable resin composition. This optical fiber further has, for example, a secondary coating layer in contact with the outside of the primary coating layer. The Young's modulus of the secondary coating layer is, for example, 1,000 MPa or more, preferably 1,000 to 2,000 MPa. The optical fiber can be manufactured by a known method, but is generally manufactured by applying a primary material and a secondary material to a molten quartz base material while thermally melting and drawing the molten quartz base material, and then curing the material with radiation to form a primary coating layer and a secondary coating layer. In this case, the optical fiber of the embodiment is obtained by using the radiation curable resin composition of the above embodiment as the primary material. EXAMPLES

[0079] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0080] (Examples 1 to 5) [Synthesis of urethane oligomer] In a reaction vessel equipped with a stirrer, 68.87 g of polypropylene glycol triol (manufactured by AGC Corporation, product name PREMINOL S 3011) having a weight average molecular weight of 10,000, 3.60 g of 2,4-tolylene diisocyanate, and 0.018 g of 2,6-di-t-butyl-p-cresol were charged, and these were heated with stirring until the liquid temperature reached 40° C. Then, 0.020 g of dibutyltin dilaurate was added, and the liquid temperature was raised to 60° C. over 20 minutes with stirring. After that, the mixture was stirred for 60 minutes, and after the residual isocyanate group concentration became 1.20 mass% (ratio to the charged amount) or less, 1.33 g of 2-hydroxyethyl acrylate was added, and the mixture was reacted at a liquid temperature of 70° C. for 60 minutes. After the residual isocyanate group concentration reached 0.52% by mass or less (ratio to the charged amount), 1.20 g of 2-ethyl-1-hexanol was added and the mixture was allowed to react for 60 minutes at a liquid temperature of 70° C. The reaction was terminated when the residual isocyanate group concentration reached 0.05% by mass or less. The obtained urethane oligomer was a mixture mainly composed of a urethane oligomer (I) represented by the following formula (I) and a urethane oligomer (II) represented by the following formula (II). HEA-TDI-PPT10000-(TDI-HEA)(TDI-EH) (I) HEA-TDI-PPT10000-(TDI-EH)2(II) (In the formula, PPT10000 is a structural unit derived from polypropylene glycol triol having a weight average molecular weight of 10,000, TDI is a structural unit derived from 2,4-tolylene diisocyanate, HEA is a structural unit derived from 2-hydroxyethyl acrylate, and EH is a structural unit derived from 2-ethyl-1-hexanol. All bonds "-" are urethane bonds.)

[0081] The obtained urethane oligomer was used to produce curable liquid resin compositions of Examples 1 to 5 having the compositions shown in Table 1. The abbreviations shown in Table 1 represent the following compounds. In addition, (I) and (II) in Table 1 represent urethane oligomers (I) and (II), respectively. ACMO: Acryloyl morphorine ENPA:Ethoxylated nonylphenol acrylate IBOA: Isobornyl acrylate 2-EHA: 2-ethylhexylacrylate NVC: N-vinylcaprolactam HDDA:1,6-Hexanediol diacrylate TPO:2,4,6-Trimethylbenzoyl diphenylphosphineoxide

[0082] Example 6 In a reaction vessel equipped with a stirrer, 70.84 g of polypropylene glycol diol having a weight average molecular weight of 10,000 (manufactured by AGC Corporation, product name PREMINOL S 4011), 3.29 g of 2,4-tolylene diisocyanate, and 0.018 g of 2,6-di-t-butyl-p-cresol were charged, and these were heated with stirring until the liquid temperature reached 40° C. Then, 0.020 g of dibutyltin dilaurate was added, and the liquid temperature was raised to 60° C. over 20 minutes with stirring. After that, the mixture was stirred for 60 minutes, and after the residual isocyanate group concentration became 0.81% by mass (ratio to the charged amount) or less, 1.23 g of 2-hydroxyethyl acrylate was added, and the mixture was reacted at a liquid temperature of 70° C. for 60 minutes. After the residual isocyanate group concentration reached 0.20% by mass or less (ratio to the charged amount), 0.47 g of 2-ethyl-1-hexanol was added and the mixture was allowed to react for 60 minutes at a liquid temperature of 70° C. The reaction was terminated when the residual isocyanate group concentration reached 0.05% by mass or less. The obtained urethane oligomer was a mixture mainly composed of a urethane oligomer (III) represented by the following formula (III) and a urethane oligomer (IV) represented by the following formula (IV). HEA-TDI-PPG10000-TDI-HEA (III) HEA-TDI-PPG10000-TDI-EH (IV) (In the formula, PPG10000 is a structural unit derived from polypropylene glycol diol having a weight average molecular weight of 10,000, and TDI, HEA, EH and the bond "-" are defined as above.)

[0083] The obtained urethane oligomer was used to produce a curable liquid resin composition of Example 6 having the composition shown in Table 1. In addition, (III) and (IV) in Table 1 represent urethane oligomers (III) and (IV), respectively.

[0084] Example 7 A urethane oligomer was obtained in the same manner as in Example 6, except that the ratio of the amounts of various components charged was changed. The obtained urethane oligomer was a mixture mainly composed of a urethane oligomer (III) represented by formula (III) and a urethane oligomer (IV) represented by formula (IV). The obtained urethane oligomer was used to produce a liquid curable resin composition of Example 7 having the composition shown in Table 1.

[0085] Comparative Example 1 A urethane oligomer was obtained in the same manner as in Example 6, except that a polypropylene glycol diol having a weight average molecular weight of 3000 was used instead of the polypropylene glycol diol having a weight average molecular weight of 10000, and the ratio of the amounts of various components charged was changed. The obtained urethane oligomer was a mixture mainly composed of a urethane oligomer (V) represented by the following formula (V) and a urethane oligomer (VI) represented by the following formula (VI). HEA-(TDI-PPG3000) 2.0 -TDI-HEA(V) HEA-(TDI-PPG3000) 2.0 -TDI-EH (VI) (In the formula, PPG3000 is a structural unit derived from polypropylene glycol diol having a weight average molecular weight of 3000, and TDI, HEA, EH and the bond "-" are defined as above.)

[0086] The obtained urethane oligomer was used to produce a curable liquid resin composition of Comparative Example 1 having the composition shown in Table 1. In addition, (V) and (VI) in Table 1 represent urethane oligomers (V) and (VI), respectively.

[0087] (Examples 8 and 9) In a reaction vessel equipped with a stirrer, 70.86 g of polypropylene glycol diol having a weight average molecular weight of 10,000 (manufactured by AGC Corporation, trade name PREMINOL S 4011), 2.49 g of 2,4-tolylene diisocyanate, and 0.018 g of 2,6-di-t-butyl-p-cresol were charged, and these were heated while stirring until the liquid temperature reached 40°C. Then, 0.020 g of dibutyltin dilaurate was added, and the liquid temperature was raised to 60°C over 20 minutes while stirring. After that, the mixture was stirred for 60 minutes, and after the residual isocyanate group concentration became 0.82 mass% (ratio to the charged amount) or less, 1.66 g of 2-hydroxyethyl acrylate was added, and the mixture was reacted at a liquid temperature of 70°C for 60 minutes. The reaction was terminated when the residual isocyanate group concentration became 0.05 mass% or less. The obtained urethane oligomer was the urethane oligomer (III) represented by the above formula (III). Using the obtained urethane oligomer (III), the liquid curable resin compositions of Examples 8 and 9 having the formulations shown in Table 2 were produced.

[0088] Example 10 A urethane oligomer was obtained in the same manner as in Example 6, except that a polypropylene glycol triol having a weight average molecular weight of 10,000 was used instead of a polypropylene glycol diol having a weight average molecular weight of 10,000, and the ratio of the amounts of various components charged was changed. The obtained urethane oligomer was a urethane oligomer (I) represented by the above formula (I). The obtained urethane oligomer (I) was used to produce a liquid curable resin composition of Example 10 having the composition shown in Table 2.

[0089] Comparative Example 2 A urethane oligomer was obtained in the same manner as in Examples 8 and 9, except that a polypropylene glycol triol having a weight average molecular weight of 5000 was used instead of the polypropylene glycol diol having a weight average molecular weight of 10000, and the ratio of the amounts of various components charged was changed. The obtained urethane oligomer was a urethane oligomer (VII) represented by the following formula (VII). HEA-TDI-PPT5000-(TDI-HEA)2(VII) (In the formula, PPT5000 is a structural unit derived from polypropylene glycol triol having a weight average molecular weight of 5000, and TDI, HEA and the bond "-" are as defined above.) Using the obtained urethane oligomer (VII), a liquid curable resin composition of Comparative Example 2 having the composition shown in Table 2 was produced.

[0090] Comparative Example 3 A urethane oligomer was obtained in the same manner as in Examples 8 and 9, except that a polypropylene glycol diol having a weight average molecular weight of 3000 was used instead of the polypropylene glycol diol having a weight average molecular weight of 10000, and the ratio of the amounts of various components charged was changed. The obtained urethane oligomer was a urethane oligomer (VIII) represented by the following formula (VIII). HEA-(TDI-PPG3000) 3.0 -TDI-HEA (VIII) (In the formula, PPG3000, TDI, HEA and the bond "-" are defined as above.) Using the obtained urethane oligomer (VIII), a liquid curable resin composition of Comparative Example 3 having the composition shown in Table 2 was produced.

[0091] Comparative Example 4 A urethane oligomer was obtained in the same manner as in Example 6, except that a polypropylene glycol triol having a weight average molecular weight of 5000 was used instead of the polypropylene glycol diol having a weight average molecular weight of 10000, and the ratio of the amounts of various components charged was changed. The obtained urethane oligomer is urethane oligomer (IX) represented by the following formula (IX). HEA-TDI-PPT5000-(TDI-HEA)(TDI-EH) (IX) (In the formula, PPT5000, TDI, HEA, EH and the bond "-" are defined as above.) Using the obtained urethane oligomer (IX), a liquid curable resin composition of Comparative Example 4 having the composition shown in Table 2 was produced.

[0092] (evaluation) (1) Viscosity: The viscosity at 25° C. of the compositions obtained in the examples and comparative examples was measured using a viscometer TV-10H (manufactured by Toki Sangyo Co., Ltd.).

[0093] (2)Young's modulus: The Young's modulus of the cured products of the compositions obtained in the Examples and Comparative Examples was measured at 23° C. and −40° C. The liquid curable resin composition was applied onto a glass plate using an applicator bar with a thickness of 354 μm, and this was subjected to a tensile test at 1 J / cm in air. 2 The film was cured by irradiating ultraviolet rays with an energy of 1000 to obtain a test film. A rectangular sample was prepared from the cured film so that the stretched portion had a width of 6 mm and a length of 25 mm. A tensile test was performed in accordance with JIS K7127 using a tensile tester 5542C4600 (manufactured by Instron Japan) under conditions of a temperature of 23°C and a humidity of 50%. The Young's modulus at 23°C was obtained from the tensile strength at a strain of 2.5% at a tensile speed of 1 mm / min. In addition, a tensile test was performed in the same manner as above except that the tensile tester was changed to a 5567P5961 (manufactured by Instron Japan) and the temperature was changed to -40°C, and the Young's modulus at -40°C was obtained. It should be noted that when the Young's modulus at -40°C was 30 MPa or less, it was evaluated as having excellent flexibility at low temperatures.

[0094] (3) Breaking strength and breaking elongation: A liquid curable resin composition was applied onto a glass plate using an applicator bar with a thickness of 354 μm, and this was subjected to 1 J / cm in air. 2 The film was cured by irradiating ultraviolet light with an energy of 1000 MPa to obtain a test film. The breaking strength and breaking elongation of the test piece were measured under the following measurement conditions using a tensile tester (Shimadzu Corporation, AG-IS). The mechanical strength was evaluated as excellent when the breaking strength was 4.0 MPa or more and the breaking elongation was 220% or more. Pulling speed: 50mm / min Gauge distance (measurement distance): 25mm Measurement temperature: 23℃ Relative humidity: 50%

[0095] [Table 1]

[0096] [Table 2]

Claims

1. A radiation-curable resin composition for forming a primary coating layer of an optical fiber, comprising a urethane oligomer having an ethylenically unsaturated group, a radical-polymerizable non-urethane monomer, and a polymerization initiator, the urethane oligomer contains 30% by mass or more of a reaction product of a polyether triol having a weight average molecular weight of 9,000 or more, a polyisocyanate, and an isocyanate-reactive compound containing one active hydrogen group, relative to 100% by mass of the total amount of the radiation-curable resin composition; the urethane oligomer contains a monofunctional urethane (meth)acrylate oligomer having one (meth)acryloyl group as an ethylenically unsaturated group, and a bifunctional urethane (meth)acrylate oligomer having two (meth)acryloyl groups as ethylenically unsaturated groups, the radical polymerizable non-urethane monomer contains, as an ethylenically unsaturated group, a (meth)acrylate monomer and a vinyl monomer, and, as the (meth)acrylate monomer, contains a monofunctional (meth)acrylate monomer having one (meth)acryloyl group and a polyfunctional (meth)acrylate monomer having two or more (meth)acryloyl groups; the isocyanate-reactive compound includes an ethylenically unsaturated group-containing isocyanate-reactive compound and an aliphatic alcohol, the content of the ethylenically unsaturated group-containing isocyanate-reactive compound in the isocyanate-reactive compound is 40 mol % or more and 60 mol % or less, and the content of the aliphatic alcohol in the isocyanate-reactive compound is 24 mol % or more and 60 mol % or less, in the radiation curable resin composition, a ratio of a total number of moles of the monofunctional urethane (meth)acrylate oligomer, the monofunctional (meth)acrylate monomer, and a vinyl monomer, as monofunctional compounds having one ethylenically unsaturated group, to a total number of moles of the bifunctional urethane (meth)acrylate oligomer and the polyfunctional (meth)acrylate monomer, as polyfunctional compounds having two or more ethylenically unsaturated groups, is 15 / 1 or more and 30 / 1 or less; Radiation curable resin composition.

2. 2. The radiation curable resin composition according to claim 1, wherein the polyether triol is an aliphatic polyether polyol.

3. The reactants are a reaction product of the polyether triol and the polyisocyanate with the isocyanate-reactive compound; or 3. The radiation-curable resin composition according to claim 1, which is a reaction product of the polyisocyanate, the isocyanate-reactive compound, and the polyether triol.

4. A cured product of the radiation-curable resin composition according to any one of claims 1 to 3.

5. An optical fiber comprising a primary coating layer comprising the cured product according to claim 4.

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