JPH0449868B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to an ultraviolet curable resin composition for a secondary coating material of an optical fiber core. [Prior art] Optical fiber is used in the form of an optical fiber core, which is made by forming two types of glasses or plastics with different refractive indexes into a core-sheath shape, and a coating layer is applied around the outer periphery of this core. There are two known structures: a structure in which a primary coating is applied to the core and then a secondary coating directly, and a structure in which a secondary coating is applied via a buffer layer. However, in either structure, the secondary coating is performed by extrusion molding of thermoplastic resin such as polyamide or polyethylene.
The drawing speed of optical fiber core wires was limited, which was a drawback in mass production of optical fibers. On the other hand, secondary coatings using ultraviolet curable resin compositions have been attempted, but a secondary coating material that is satisfactory in terms of elastic modulus, elongation, moist heat resistance, etc. has not yet been found. [Object of the Invention] The object of the present invention is to provide an ultraviolet curable resin composition that overcomes the above-mentioned conventional drawbacks, has excellent elastic modulus, elongation, and moisture and heat resistance, and is particularly suitable as a secondary coating material for optical fiber cores. It's about doing. [Structure of the Invention] The resin composition for optical fiber secondary coating material (hereinafter abbreviated as resin composition) of the present invention, which achieves the above object, is composed of acrylic oligomer, tris(2-
The acrylic oligomer is composed of triacrylate of hydroxyethyl isocyanurate (hereinafter abbreviated as THEIC-TA), a reactive diluent, and a photopolymerization initiator, and the acrylic oligomer is diphenylmethane diisocyanate, polytetramethylene glycol with a molecular weight of 650 to 1300, and A urethane acrylate obtained from acrylic acid monohydroxyalkyl ester, characterized in that the THEIC-TA is 25 to 100 parts by weight based on 100 parts by weight of the urethane acrylate, and the reactive diluent is an acrylic monomer. That is. In the present invention, urethane acrylate is used as the acrylic oligomer. This urethane acrylate is produced by acrylating a terminal NCO urethane prepolymer obtained from diphenylmethane diisocyanate and polytetramethylene glycol with a molecular weight of 650 to 1300 with a monoacrylate having one OH group, as shown in the formula below. Manufactured by. In the present invention, diphenylmethane diisocyanate is used as the diisocyanate as described above, and good results are given to the physical properties of the resulting resin composition. That is, the urethane acrylate using toluene diisocyanate has a lower elastic modulus than the urethane acrylate in the present invention. Further, in the present invention, the use of polytetramethylene glycol having a molecular weight of 650 to 1300 in the production of urethane acrylate also contributes to imparting physical properties suitable as a secondary coating material for optical fiber cores. For example, urethane acrylate using lactone polyol has poor UV curability;
Urethane acrylate using polypropylene glycol or polyester polyol has poor heat and humidity resistance and water resistance. Polytetramethylene glycol has a molecular weight of
The range of 650 to 1300 is elongated, the elastic modulus is large, and both are balanced. It is difficult to produce polytetramethylene glycol with a molecular weight of less than 650, and resin compositions using polytetramethylene glycol with a molecular weight of more than 1300 have too low an elastic modulus and low elongation. As the monoacrylate having one OH group, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc. are used. THEIC-TA used in the present invention is represented by the following formula. The amount of THEIC-TA used is 25 to 100 parts by weight, preferably 45 to 75 parts by weight, per 100 parts by weight of the urethane acrylate. If the amount of THEIC-TA used is less than 25 parts by weight, the elastic modulus of the resin composition after UV curing will be 25 kg/
mm ² or less, and if it exceeds 100 parts by weight, the elongation will be less than 15%, making it impossible to use it as a secondary coating material for optical fiber cores in particular. Furthermore, the acrylic monomer of the UV-curable reactive diluent used in the present invention includes isobutyl acrylate, t-butyl acrylate, and 2-butyl acrylate.
Ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-methoxyethyl acrylate,
2-methoxyethyl acrylate, 2-butoxyethyl acrylate, 2-phenoxyethyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, etc. are used, preferably 2-phenoxyethyl acrylate, dicyclopentenyl Acrylate is used. Such acrylic monomers can be used singly or in combination, and the amount used is 10 to 100 parts by weight per 100 parts by weight of the urethane acrylate. If the amount of the acrylic monomer used is less than 10 parts by weight, the workability of the resin composition of the present invention will deteriorate, and if it exceeds 100 parts by weight, the workability and elastic modulus will decrease. Furthermore, in the present invention, as a photopolymerization initiator, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, 4-methoxybenzophenone, 1-hydroxycyclohexyl phenyl ketone, benzyl dimethyl ketal, benzyl-β-
Methoxyethyl acetal, methylbenzoyl,
Acetophenone, 2,2-diethoxyacetophenone, diethylthioxanthone, 4-isopropyl-2-hydroxy-2-methylpropiophenone, 2-hydroxy-2-methylpropiophenone, 2-methoxyanthraquinone, etc. are used,
1-hydroxycyclohexyl phenyl ketone,
Benzyl dimethyl ketal is preferably used. One or more types of such photopolymerization initiators may be used, and the amount used is 0.5 to 10 parts by weight per 100 parts by weight of the total amount of the urethane acrylate, THEIC-TA, and the reactive diluent. be. If the amount of the photopolymerization initiator used is less than 0.5 parts by weight, the curing speed of the resin composition of the present invention will decrease, while if it is added in excess of 10 parts by weight, it will not only cause a decrease in heat and humidity resistance but also cause the resin composition to deteriorate. increases the cost of the composition. In addition, in the present invention, a thermal polymerization inhibitor and a photosensitizer can also be added as necessary. As the thermal polymerization inhibitor, hydroquinone, methoquinone, P-benzoquinone, t-butylhydroquinone, etc. are used, and the amount used is 0.001 to 1.0% of the total amount of urethane acrylate, THEIC-TA, and reactive diluent. It is. Such a thermal polymerization inhibitor has the function of improving the thermal stability of the resin composition of the present invention during storage. In addition, photosensitizers function as catalysts that promote ultraviolet curing, and include triethylamine,
2-dimethylaminoethanol, N-methyldiethanolamine, triethanolamine, 3-dimethylamino-1-propanol, 2-dimethylamino-1-propanol, p-dimethylaminobenzoic acid, isocyanyl p-dimethylaminobenzoate, p- Methyl dimethylaminobenzoate and the like are used. [Effects of the Invention] As described above, according to the present invention, in the ultraviolet curable resin composition comprising an acrylic oligomer, THEIC-TA, a reactive diluent, and a photopolymerization initiator, the acrylic oligomer is diphenylmethane diisocyanate. is a urethane acrylate obtained from polytetramethylene glycol with a molecular weight of 650 to 1300 and a monoacrylate having one OH group, and the THEIC-TA is 25 to 100 parts by weight based on 100 parts by weight of the urethane acrylate.
parts by weight, and since the reactive diluent is an acrylic monomer, it can achieve the following effects and is particularly suitable as a secondary coating material for optical fiber core wires. A The resin composition after being cured by ultraviolet rays has excellent heat and humidity resistance and water resistance. A modulus of elasticity of B 25-75 Kg/mm ² is obtained. The C elongation is 15% or more, which, in balance with the above B elasticity modulus value, indicates that the resin composition of the present invention is suitable as a secondary coating material for optical fiber core wires. D: Ultraviolet curing speed is rapid and high workability can be maintained. [Examples] Example 1 Production of urethane acrylate. Put 2 moles of diphenylmethane diisocyanate into a 3-4 neck flask equipped with a stirrer, thermometer, and dropping funnel, heat to 60°C, stir, and add 1 mole of polytetramethylene glycol with a molecular weight of 850 while flowing _N2 gas. was added dropwise and reacted for 4 hours,
A urethane prepolymer was produced. Completion of the reaction was confirmed by checking NCO%. Then, 2-hydroxyethyl acrylate 2
Mol was added dropwise and reacted for 6 hours to produce urethane acrylate. The reaction products were analyzed by infrared spectroscopy, but NCO
No peak was observed. Examples 2, 3, 4, 5, 6 and Comparative Examples 1 and 2 A resin composition consisting of the urethane acrylate produced in Example 1, THEIC-TA, a reactive diluent, and a photopolymerization initiator was cured by ultraviolet irradiation. , elastic modulus, elongation and moist heat resistance were measured. The relationship between changes in the composition of the resin composition and these physical properties is shown in the table below. As Comparative Example 1, when the amount of THEIC-TA used is less than 25 parts by weight per 100 parts by weight of urethane acrylate, as Comparative Example 2, THEIC-TA was used.
The results are also shown when the amount of TA used exceeds 100 parts by weight.

[Table] As is clear from the above table, the resin composition of the present invention has an elastic modulus of 25 to 75 Kg/mm ² after ultraviolet curing, an elongation of 15% or more, and has excellent heat and humidity resistance. It is suitable as a secondary coating material for fiber cores. On the other hand, Comparative Example 1 has a low elastic modulus, and Comparative Example 2 has too high elasticity and low elongation, making it unsuitable as a secondary coating material.

Claims (1)

[Claims] 1 Consisting of an acrylic oligomer, triacrylate of tris(2-hydroxyethyl) isocyanurate, a reactive diluent, and a photopolymerization initiator,
The acrylic oligomer is a urethane acrylate obtained from diphenylmethane diisocyanate, polytetramethylene glycol having a molecular weight of 650 to 1300, and acrylic acid monohydroxyalkyl ester, and the triacrylate of tris(2-hydroxyethyl) isocyanurate is 25 to 100 parts by weight of acrylate
100 parts by weight, and the reactive diluent is an acrylic monomer.