JPH0550454B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to optical fiber coated and cured with a coating composition which, when cured with radiation, provides a flexible and tough cured film. [Prior Art] Recently, optical fibers have become important for transmitting light used in communications. Glass fibers for optical fibers are coated to protect the surface, maintain strength, and prevent microbending during mechanical movement and to prevent microbending when the optical fiber is subjected to temperature changes. be done. Special coatings are required to meet these complex properties. That is, both flexibility and toughness are required. Moreover, this toughness must be achieved without stiffness. This is because hardness causes microbending when the coating material becomes cold. Conventionally, thermosetting silicone resins have been used as coating compositions for glass fibers for optical fibers, but the slow curing speed of silicone resins makes it difficult to increase the productivity of coating glass fibers. A single layer coating of chisel is flexible but not strong, so a protective layer such as nylon is required on the outside. For this reason, research has been carried out on radiation-curable coating compositions to overcome the drawbacks of these silicone resins, but it has not been possible to obtain a fully satisfactory coating composition. [Problems to be Solved by the Invention] Conventional radiation-curable coating compositions become hard when cured. Of course, if these coating compositions are combined with a large amount of a radiation-curable monomer whose polymer has a low glass transition temperature (Tg) and then cured by radiation, a relatively soft coating layer can be formed, but the strength is weak. It also lacks toughness. The present inventor has completed the present invention as a result of intensive research aimed at developing an optical fiber coated with a cured product of a coating composition that has both flexibility and toughness and has a high curing speed through radiation curing. Ivy. That is, an object of the present invention is to provide an optical fiber coated with a cured product of a radiation-curable coating composition. [Means for Solving the Problems] The radiation-curable coating composition used in the present invention contains one or more groups selected from amide, urea, and urethane in the polymer chain, and between these groups, The bond contains at least one type selected from polyalkylene polyether structures having 2 to 6 carbon atoms,
The oligomer has a monoethylenically unsaturated polymerizable group bonded to the polymer chain, and contains an oligomer in which the polyalkylene polyether structure accounts for 40 to 90% by weight, and a monoethylenically monomer. The combination of these components provides a composition that satisfies both the flexibility and toughness required as a coating material for optical fibers and has a fast curing speed by radiation. For this reason, these compositions can sufficiently protect a glass fiber for optical fibers even when only a single layer is coated on the glass fiber. Of course, two-layer coating is also possible if necessary. Therefore, the optical fiber of the present invention includes an optical fiber coated with one or two layers of a cured product of a coating composition comprising these components. In the oligomer as the first component of the present invention, (a) the ethylenically unsaturated group is appropriately arranged, so the average molecular weight of the oligomer is generally 2000 to 2000.
8000, preferably 2500-6000. If the molecular weight is less than 2000, the cured coating composition will be hard; if the molecular weight is greater than 8000, it will be too soft to be suitable. (b) On average, one or more groups selected from amide, urea, and urethane are included in the molecular chain of the oligomer.
It contains one per molecular weight of 200 to 1000, preferably 300 to 900, more preferably 400 to 600. Preferred groups are urethane groups, but amide and urea groups are also useful. These bases create toughness. (c) 40 to 90% by weight of the oligomer, preferably 50 to 90% by weight
75% by weight consists of a portion selected from polyalkylene polyethers in which alkylene has 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and these may be copolymerized, and the molecular weight of these is generally for
300-2000, preferably 600-1200. This structure gives the cured coating composition appropriate elongation and allows it to absorb the pressure imparted to the glass fiber by thermal changes or mechanical stimulation. (d) Each end of the oligomer is terminated with a monoethylenically unsaturated polymerizable group. Preferably, an acrylic group is desirable. The second coating composition used in the present invention
The component monoethylenically unsaturated monomer can be any compound having monoethylenically unsaturated groups, many of which are well known as reactive diluents. And usually it is used in an amount of 20 to 50%, preferably 25 to 40% of the total weight of the coating composition. As described below, in the case of UV curing, acrylic monomers are best for this purpose. However, using other radiations than ultraviolet radiation allows the use of all types of unsaturated compounds. In order to soften the cured product of the coating composition, it is desirable to use a monomer whose homopolymer has a glass transition temperature of 10°C or lower, preferably 0°C or lower.
In the case of ultraviolet curing, the number of carbon atoms in the alkyl group is from 2 to
Preferred are phenoxyalkyl acrylates of No. 4, such as phenoxyethyl acrylate, but other examples include 2-ethylhexyl acrylate, butyl acrylate, dodecyl acrylate, and 2-ethyl acrylate.
Esters of butoxyethanol or 2-ethoxyethanol are also useful. When using radiation other than ultraviolet radiation, the corresponding methacrylic esters, crotonic esters, maleic esters, etc. are also useful. The optical fiber of the present invention can be obtained by coating the optical fiber with a radiation-curable coating composition comprising the oligomer and ethylenically unsaturated monomer described above in a conventional manner and curing it by irradiating it with radiation. However, if a more tough and strong coating is desired, a crosslinking agent can be incorporated into the coating composition. As such a crosslinking agent, a monoethylenically unsaturated monomer capable of forming strong hydrogen bonds is preferred. Therefore, in the coating composition for coating the optical fiber of the present invention, it is desirable to use a monoethylenically unsaturated monomer as described above together with a monoethylenically unsaturated monomer capable of forming strong hydrogen bonds. The monoethylenically unsaturated monomer capable of forming strong hydrogen bonds accounts for 2 to 20% of the total weight of the composition;
It is desirable that the content is preferably 3 to 10%. This monoethylenically unsaturated monomer capable of forming strong hydrogen bonds serves to create a type of weak crosslink that provides limited strength without unduly reducing the elongation force. Conventional crosslinkers provide strength but significantly reduce elongation, and the coating material becomes excessively hard at low temperatures, bending the fibers sharply as they thermally shrink, causing microbending at low temperatures and causing optical loss. However, the use of monoethylenically unsaturated monomers capable of forming strong hydrogen bonds overcomes this drawback. The desired hydrogen bond is
This can be achieved by using monomers that act as electron acceptors or electron donors, with electron acceptors being preferred. As such a monomer, vinylpyrrolidone is preferred, but diacetone acrylamide, isobutoxymethyl acrylamide,
Acrylamide, N,N-dimethylacrylamide, acrylic acid, itaconic acid, dimethylaminoethyl acrylate are also useful monomers. In the coating composition for coating the optical fiber of the present invention, an initiator and/or sensitizer may be added as necessary. In particular, when curing with ultraviolet rays, it is preferable to use an initiator and/or a sensitizer. The initiator and/or sensitizer are those commonly used and are not particularly limited. An example of the method for producing the oligomer of the present invention will be described below. A polyurethane having isocyanate groups bonded to both ends is reacted with a hydroxyalkyl acrylate equivalent to the isocyanate. Another method is to react a polyurethane with isocyanate groups bonded to both ends with 1/2 equivalent of hydroxyalkyl acrylate, and then remove unreacted isocyanate groups from diols, diamines, amino alcohols, dithiols, etc. Coupling with dibasic acids and divalent chain extenders such as hydroxycarboxylic acids. Examples of such diols include:
ethylene glycol, 1,4-butanediol,
Examples of diamines include 1,6-hexane diol, polyalkylene diol, polyoxyalkylene diol, etc., and ethylene diamine, 1,4-
Examples of amino alcohols include ethanolamine, monomethylethanolamine, etc.; examples of dithiols include 1,6-hexanedithiol, Examples of dibasic acids include succinic acid, adipic acid, malonic acid, etc., and examples of hydroxycarboxylic acids include glycine and alanine. Of course, it is also possible to synthesize by a method other than the above. These coating compositions are sensitive to various types of radiation, such as beta radiation, electron beams and actinic radiation,
It is particularly hardened by ultraviolet light. The method of coating and curing glass fibers using these coating compositions can be carried out using conventional methods such as
This can be carried out by the method disclosed in DT2459320, Japanese Patent Application Laid-Open No. 139545/1983, and the like. When glass fibers are coated by these methods and cured by ultraviolet irradiation, the drawing speed of the glass fibers is very fast, 3 to 5 m/sec, which is usually 3 to 5 times better than when silicone resin is used. Also, coating the coating composition onto the glass fiber in one layer is sufficient. Of course, a two-layer coating may be used.
The performance of the obtained optical fiber is comparable to or better than that coated with silicone resin, and has sufficient practical value. [Example] Synthesis Example 1 In a reaction vessel equipped with a stirrer, 4 mol (1064 g)
of 4,4'-methylenebis(cyclohexyl isocyanate), 2 g of dibutyltin dilaurate (0.1% relative to polyol) and 1 g of 2,6-
Di-tertiary butyl 4-methylphenol was charged. To this was added 2 moles (2000 g) of polyoxypropylene glycol having a molecular weight of 1000 over 4 hours. The temperature rises due to an exothermic reaction, approximately 65℃
Once it reached this temperature, it was maintained at this temperature. Stirring was continued for 1/2 hour after the polyol addition was complete, and then 2 moles (232 g) of 2-hydroxyethyl acrylate were added over 1/2 hour. As a result
Polyurethanes were synthesized that were 50% terminated with acrylate groups and 50% terminated with isocyanate groups. 1 mole (230g) of polyoxypropylene diamine
and 402.5 g of N-vinylpyrrolidone were premixed. This was then added to 1857.5 g of phenoxyethyl acrylate, and this mixture was quickly added to the previously synthesized polyurethane in a reactor maintained at about 65°C. This addition is carried out at such a rate that the temperature does not exceed 80°C, but it may be carried out with cooling to speed up the addition rate. The isocyanate reaction is selective and the acrylic functionality does not react with the already formed urethane hydrogen atoms. The reaction was terminated when the addition was complete. 3% diethoxyacetophenone (by weight of the composition) is added, which acts as a photoinitiator. The final product having the physical properties shown in Table 1 is passed through a 5 micron filter, then stored and ready for use. The composition had a specific gravity of 1.08 and a viscosity of 10,000 cps (at 25°C). In use, the liquid coating composition is applied to the glass fiber and cured by irradiation with ultraviolet light. An overcoating is usually further applied. Synthesis Example 2 In a reaction vessel equipped with a stirrer, 5 mol (1050 g)
of trimethylhexane diisocyanate, 1288g
of 2-ethylhexyl acrylate, 0.2 g of dibutyltin dilaurate, and 1 g of phenothiazine. To this was added 2 moles (232 g) of hydroxyethyl acrylate and maintained at 50° C. by heating or cooling as necessary for 30 minutes. Then 4 moles (1720 g) of polyoxypropylene diamine were added at such a rate that the temperature did not exceed 90°C. At this time, it may be cooled to increase the addition rate. After the diamine addition was completed, the whole was cooled. The composition thus synthesized contained a total of 70% by weight of polyurea oligomers terminated with acrylate groups. Next, add 260 g to 1000 g of the polyurea obtained above.
g of phenoxyethyl acrylate and 140 g
of diacetone acrylamide was added thereto, 1 to 5% (based on the weight of the composition) of a photoinitiator was added, and the mixture was passed through a 5 micron filter to obtain the desired composition having the physical properties shown in Table 1. Synthesis Example 3 1 mol (2000 g) of polyoxypropylene diamine, 2 mol (232 g) of hexamethylene diamine and 2 mol (376 g) of Added azelaic acid. The mixture was sparged with nitrogen at 180° C. until 4 moles (72 g) of water were removed. The reaction mixture was cooled to 60°C and 2 mol (256
The butyl acrylate of g) was added and reacted at 60°C for 2 hours to complete the Michael addition reaction between the butyl acrylate and the amino group.
In this way, a polyamide terminated with a secondary amine was produced. Two moles (310 g) of isocyanoethyl methacrylate were slowly added to the polyamide at such a rate that the temperature did not exceed 80°C. After the reaction is completed,
Add 1500g of ethoxyethyl acrylate and 550g of isobutoxymethylacrylamide,
g of phenothiazine was added, mixed, and passed through a 5 micron filter to obtain the desired composition having the physical properties shown in Table 1. Synthesis Example 4 In a reaction vessel equipped with a stirrer, 4 mol (1064 g)
of 4,4'-methylenebis(cyclohexyl isocyanate), 2 g of dibutyltin dilaurate and 1
g of 2,6-di-tert-butyl 4-methylphenol was added. 2 moles (2000
g) polyoxypropylene glycol (molecular weight
1000) was added. Although the temperature rose due to the exothermic reaction, it was maintained at 65°C. After the reaction was completed and held for an additional 1/2 hour, 2 moles (232 g) of 2-hydroxyethyl acrylate were added over a period of 1/2 hour. As a result, a polyurethane with 50% acrylate termination and 50% isocyanate group termination was synthesized. One mole (250 g) of tetrapropylene glycol was added to the previously synthesized urethane at a temperature of 65° C. or higher. 65 until the isocyanate reaction is completed.
The temperature was kept at ℃ or higher for about 1 hour. Completion of this reaction was confirmed by measuring the infrared absorption spectrum of the reactant. After the reaction is complete, 407g of N-vinylpyrrolidone and
1860g of phenoxyethyl acrylate was added. Finally, 3% by weight of diethoxyacetophenone was added to the total composition. The final product having the physical properties shown in Table 1 was passed through a 5 micron filter and stored for use. Synthesis Example 5 A desired composition having the physical properties shown in Table 1 was prepared in the same manner as Synthesis Example 4, except that N-vinylpyrrolidone was not used and the amount of phenoxyethyl acrylate was changed to 2267 g. I got it.

[Table]
Example 1 Data on optical loss of an optical fiber when coated on a glass fiber using the composition of Synthesis Example 1 is shown. Temperature Optical loss (dB/Km) +60°C 0 +20°C 0 -20°C 0 -60°C 0.1 Glass fiber: Gradet index fiber Core diameter 50 μM Outer diameter 125 μM The coating composition was coated to a thickness of 50 μM. Curing conditions were UV energy of 3.5 Joule/cm ² . Example 2 When a glass fiber was coated using the composition of Synthesis Example 2-5 in the same manner as in Example 1, the optical loss of the optical fiber was the same as in Example 1 and caused no practical problems. Moreover, the optical fibers using the compositions of Synthesis Examples 2 to 5 showed no increase in optical loss even when stored in the air or warm water at 60° C. for one month. [Effects of the Invention] Thus, according to the present invention, an optical fiber having both flexibility and toughness and excellent productivity can be obtained.

Claims (1)

[Scope of Claims] 1 The polymer chain contains one or more groups selected from amide, urea, and urethane, and the bonds between these groups are formed from a polyalkylene polyether structure having 2 to 6 carbon atoms. An oligomer containing at least one selected from the group, a monoethylenically unsaturated polymerizable group bonded to the polymer chain, and in which the polyalkylene polyether structure accounts for 40 to 90% by weight;
and an optical fiber coated with a cured product of a coating composition containing a monoethylenically unsaturated monomer. 2. The optical fiber according to claim 1, which uses, as the monoethylenically unsaturated monomer, a monomer that forms a homopolymer with a glass transition temperature of 10° C. or less and a monomer that can form strong hydrogen bonds. 3. The optical fiber according to claim 2, wherein the monomer forming a homopolymer having a glass transition temperature of 10° C. or less is an acrylic monomer.