JPH04509B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an adhesive for light transmitting fibers that cures rapidly at room temperature and has excellent environmental resistance properties. <Prior Art> Light transmitting fibers obtained by drawing transparent materials such as polymethyl methacrylate, polystyrene, and glass at high speed are widely used in the communication industry, decorative displays, and the like. Among the light transmitting fibers made of these materials, polymethyl methacrylate is used as the core.
Fibers with a core-sheath structure using a fluororesin with a lower refractive index as a sheath have been found to have good optical transmission properties, as well as being lightweight, inexpensive, and easy to process, and are widely used. has been done. Conventionally, epoxy resin adhesives containing polyepoxy compounds and amine-based curing agents such as triethylenetetramine and meta-xylylene diamine have been used for glass optical fibers to bind optical fibers together. However, when this adhesive is used for optically transmitting fibers with a fluororesin sheath and polymethyl methacrylate as a core component, it has been pointed out that the adhesive part turns brown due to the amine, resulting in a decrease in optical transmittance. has been done. (Unexamined Japanese Patent Publication No. 56-161485
(Japanese Patent Application Laid-Open No. 56-161485) As adhesives that do not cause coloration, (1) a radical polymerization curing adhesive mainly composed of epoxy (meth)acrylate (Japanese Patent Application Laid-open No. 56-161485); Epoxy thiol adhesive using polythiol alkyl ester as a curing agent (Japanese Patent Application Laid-open No. 78230/1983)
is proposed. However, the radical polymerization type adhesive (1) has the disadvantage that the adhesive remains sticky and easily contaminated due to the polymerization inhibiting effect of oxygen in the air. In addition, the epoxy/thiol adhesive mentioned in (2) has the problem of the curing agent, polythiol alkyl ester, which emits an extremely strong unpleasant odor, and the water resistance of the cured product is lower than that of the epoxy/amine adhesive. The problem is that it drops significantly. <Structure of the Invention> Therefore, the present inventors have conducted intensive studies to develop a room temperature curable adhesive that overcomes the drawbacks of the conventional adhesives for optically transmitting fibers, and have finally arrived at the present invention. That is, the present invention provides an adhesive for optically transmitting fibers, characterized in that it contains at least one selected from (A) a polyepoxy compound, (B) isophorone diamine, and an amine compound derived from isophorone diamine. It is something to do. In the present invention, the polyepoxy compound as component (A) is a compound having at least two or more epoxy groups in the molecule. Among these, those that are liquid at 20°C are preferred in terms of workability. Specifically, (a) glycidyl ethers of polyhydric phenols: for example, 2,2-bis-(4-hydroxyphenyl)propane, 1,1
- glycidyl ethers of diphenyloalkanes such as bis(4-hydroxyphenyl)ethane and bis(4-hydroxyphenyl)methane:
Glycidyl ether of 4,4'-dihydroxydiphenyl sulfone, hydroquinone, resorcinol, dihydroxydiphenyl or dihydroxynaphthalene; derived from polyhydric phenols such as glycidyl ether of phenol or condensates of cresol and formaltehyde, novolak, and lusol. (b) poly(epoxyalkyl) ethers of aliphatic polyhydroxy compounds; for example, epoxy compounds derived from ethylene glycol, glycerol, trimethylolpropane, etc.; (c) polyglycidyl esters of polycarboxylic acids; for example, phthal Acids, diglycidyl esters of isophthalic acid, adipic acid, tetrahydrophthalic acid, other epoxidized dienes, polyglycidyl isocyanurate, glycidyl ether esters of hydroxybenzoic acid, etc. are used alone or in combination depending on the purpose. Among these, particularly preferred for use alone are diglycidyl ether of 2,2-bis-(4-hydroxyphenyl)propane and diglycidyl ether/ester of p-hydroxybenzoic acid. Next, neither the isophorone diamine of component (B) nor the amine compound derived from the diamine has the above-mentioned adverse effect on the light transmitting fiber.
The adhesive used in combination with component (A) can provide a cured adhesive with excellent curability, water resistance, and environmental resistance. Examples of amine compounds derived from isophorone diamine include adducts between isophorone diamine and polyepoxy compounds, and adducts between isophorone diamine and alkylene oxides such as ethylene oxide and propylene oxide. In addition to these components (A) to (B), organic solvents, inorganic fillers, pigments, reactive diluents, plasticizers, and ultraviolet absorbers can be blended depending on the purpose. The present invention will be explained below with reference to Examples. Hereinafter, parts represent parts by weight. Examples 1 to 3, Comparative Examples 1 to 2 100 light transmitting fibers with a diameter of 0.25 mm coated with polymethyl methacrylate as a core component and fluororesin as a sheath component were bundled and placed at a 3 cm end portion as shown in Table 1. Various adhesives such as these were applied and left to harden at room temperature. The results obtained are shown in Table 1.

【table】

[Table] <Effects of the Invention> As stated above, the adhesive of the present invention cures rapidly in the air at room temperature, has excellent adhesive strength and light transmittance, and does not cause discoloration of the adhesive layer. Therefore, it exhibits excellent effects as a light transmitting adhesive.

Claims (1)

[Scope of Claims] 1. An adhesive for light transmitting fibers, comprising at least one selected from (A) a polyepoxy compound, (B) isophorone diamine, and an amine compound derived from isophorone diamine.