JPS59214802A - Light transmitting fiber - Google Patents

Abstract

PURPOSE:To obtain superior heat resistance by using as a core component, a copolymer of methyl methacrylate and a specified amt. of methacrylate having a hydrocarbon group specified in C number and another polymer having a specified volatile amt., and as a sheath component, a transparent resin having a refractive index lower than that of the core component by a prescribed amt. CONSTITUTION:Methacrylate having an alkyl moiety of >=8C alicyclic hydrocarbon group to be used for a part of core component is obtained by esterifying methacrylic acid or its acid chloride with an alicyclic hydrocarbon monool of the formula ROH, such as 2,6-dimethyl cyclohexanol. A proportion of it in the total polymer constituting the core component is 3-40wt%. An amt. of volatile matter composed essentially of the residual unreacted monomer in the core component of a light transmitting fiber is <=0.5%, preferably, <=0.3%. As a sheath component, a transparent resin or transparent fluororubber having a refractive index at least 3% lower than that of the core component is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission fiber having a core-sheath structure and having excellent heat resistance and flexibility.

Optical transmission fibers are conventionally manufactured using glass-based materials as a base material, and are used as optical signal transmission media for measurement control between devices and within devices.
It is widely used for data transmission, medical purposes, decoration, and image transmission. However, optical transmission fibers based on glass-based materials have the disadvantage of poor flexibility unless the fibers are made with a thin inner diameter, are easily broken, have a high specific gravity, and are difficult to use, including connectors. Recently, various attempts have been made to make them from plastic because they are expensive.

The major characteristics of using plastic are that it is lightweight, and even fibers with a thick inner diameter are strong and flexible.Therefore, high apertures and large diameters are possible, and it is easy to combine with light receiving and emitting elements. It has excellent repeatability. The general method for manufacturing such optical transmission fibers using plastic is to use a plastic with a high refractive index and good light transmission as a core component, and to use a plastic with a lower refractive index and transparent material as a core component. A fiber having a core-sheath structure is formed using plastic as a sheath component. This method transmits light by reflecting it at the core-sheath interface, and the larger the difference in refractive index between the plastics that make up the core and sheath, the better the light transmission properties.

Amorphous materials are preferable as plastics with high optical transparency, and polymethyl methacrylate and polystyrene are attracting attention from an industrial perspective (for example,
-8978, Japanese Patent Publication No. 53-21660).

However, as the temperature of such plastic optical transmission fibers increases, the light guiding loss increases, and the fibers sometimes lack reliability as an optical signal medium.

In addition, it has a drawback in heat resistance, and is used for moving objects such as automobiles,
When applied to ships, aircraft, robots, etc., there are restrictions on the use and the place where it can be applied. The upper limit temperature at which polymethyl methacrylate and polystyrene can be used is approximately 80°C; at temperatures higher than that, thermal contraction increases, deformation occurs, and microstructural fluctuations occur, making it difficult to function as an optical transmission fiber. Moreover, once it is used at a temperature of 80°C or higher, the light guide loss becomes large even if the temperature is returned to room temperature, making it difficult to use it again. It has been desired to develop a plastic optical transmission fiber with excellent heat resistance, which has the disadvantage that it can only be used in a narrow temperature range.

In view of the current situation, the present inventors investigated the development of plastic optical transmission fibers with excellent heat resistance and optical transmission properties, and first determined that the ester moiety is an alicyclic hydrocarbon group having 8 or more carbon atoms. To obtain an optical transmission fiber having excellent heat resistance, characterized in that the core component is a polymer made of a methacrylic acid ester having We succeeded in this and have already applied for a patent (Patent Application No. 105069/1983).
.

Although the optical transmission fiber of the invention according to the application was satisfactory in terms of heat resistance for a relatively short period of time, there is still room for consideration regarding the heat resistance of V-Teramon and the oxidation stability during one processing. It had been.

Therefore, the present inventors continued to conduct intensive studies on the development of plastic optical transmission fibers that have heat resistance during sheathing time, oxidation stability during processing, and excellent optical transmission properties, and as a result, they arrived at the present invention. did.

That is, the present invention provides 3 to 40 methacrylic acid esters having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety.
A transparent resin whose main component is a methyl methacrylate copolymer containing 0.5% by weight or less, whose core component is a polymer with a volatile content of 0.5% by weight or less, and which has a refractive index that is at least 3% smaller than the core component; Another object of the present invention is to provide an optical transmission fiber having excellent heat resistance and oxidation stability during processing, which has fluororubber as a sheath component.

In the temperature range from room temperature to around 80 degrees Celsius, the optical transmission fiber of the present invention has an increased light guide loss that occurs as the temperature increases, compared to conventionally proposed optical transmission fibers that use polymethyl methacrylate as the core component. The ratio is small, which significantly increases the reliability of the optical signal transmission medium. Furthermore, surprisingly, there is almost no increase in light guide loss even at temperatures at which the conventionally proposed optical transmission fibers cannot be used, and in terms of flexibility,
In practical terms, we can provide optical transmission fibers that pose no problems at all.

In the present invention, the methacrylic acid ester whose ester moiety has a cyclic hydrocarbon group having 8 or more carbon atoms is a methacrylic acid ester or an acid chloride thereof having the formula R
It is obtained by esterifying OH with an alicyclic hydrocarbon/monool.

Alicyclic hydrocarbons/monols represented by the formula ROH include 2,6-dimethylcyclohexanol, 1-adamantanol, 2-adamantanol, 3-methyl-1-
7 gmantanol, 3,5-dimethyl-1-adamantanol, 3-ethyladamantanol, 3-methyl-5
-Ethyl-1-adamantanol, 3,5.8-)liethyl-1-7damantanol and 3,5-dimethyl-
8-ethyl-1-7 damantanol, octahydro-4
, 7-mensonoinden-5-ol, octahydro-
4,7-mentunoinden-1-ylmethanol, 3-
Hydroxy-2,6,6-)limethyl-bicyclo[3,
1,11 hebutyl, 3,7゜7-drimethyl-4-
Hydroxy-bicyclo[4°1.0]heptamel, borneol, isoborneol, 2-methylcamph7ol, 7-ethyl alcohol, termenthol, p-menthan-2-ol, p-menthan-8-ol, 2,
Examples include alicyclic hydrocarbons and monools such as 2,5-trimethylcyclohexanol.

Among the methacrylic acid esters obtained from these, particularly preferred ones include 7-enthyl methacrylate, methacrylic acid-! -menthyl, bornyl methacrylate, isobornyl methacrylate, gmantyl-1-7 methacrylate,
Mention may be made of 1-7-damantyl-3°5-dimethyl methacrylate.

The reason why the ester moiety is limited to alicyclic hydrocarbon groups having 8 or more carbon atoms is that aromatic hydrocarbon groups cause large light guide loss in optical transmission fibers, which limits their use as optical signal transmission media. It is.

Among alicyclic hydrocarbon groups having 8 or more carbon atoms, alicyclic hydrocarbon groups having 10 or more carbon atoms are particularly preferably used, and in this case, they have a high contribution rate to improving heat resistance.

When a methacrylic acid ester having an alicyclic hydrocarbon group having 7 or less carbon atoms is used, heat resistance does not improve. Further, even when the number of carbon atoms is 8 or more, linear hydrocarbon groups such as methacrylic acid esters such as n-octyl methacrylate and 11-dodecyl methacrylate do not contribute to improving heat resistance.

On the other hand, the upper limit of the number of carbon atoms in the alicyclic hydrocarbon is desirably up to about 20, and if it exceeds that number, the mechanical strength of the polymer tends to deteriorate significantly.

In the present invention, the proportion of the methacrylic acid ester component having an alicyclic hydrocarbon group having 8 or more carbon atoms used in the core component is 3 to 40% by weight (
(hereinafter simply referred to as %).

If it is less than 3%, it has excellent flexibility, but if it is less than 1%
It is difficult to obtain a material with heat resistance of 30'C or more, on the other hand,
If it exceeds 40%, the heat resistance is excellent, but the flexibility is insufficient for practical use, which is not preferable.

Furthermore, the copolymer mainly composed of methyl methacrylate, which is the core component of the present invention, can contain an alkyl acrylate or alkyl methacrylate component having an alkyl group having 1 to 4 carbon atoms by copolymerization. Toru. In order to maintain heat resistance, these copolymer components should be contained in the minimum necessary amount, preferably at an amount not exceeding 5% based on the entire core component polymer.

The amount of volatile matter mainly composed of residual unreacted monomers in the core component of the optical transmission fiber, which is the most important requirement constituting the present invention, is 0.5% or less, preferably 0.3% or less. It is. If the amount of the volatile content exceeds 0.5%, yellow coloration or minute bubbles may occur during processing of the optical transmission fiber, resulting in increased light guide loss. Furthermore, when the optical transmission fiber is used at high temperatures for a long period of time, the core component gradually turns yellow or brown, and the light guide loss increases over time, making it unusable for practical use.

The method for removing volatile components mainly composed of unreacted monomers can be carried out by a known method. For example, the polymer obtained as a core component is continuously heated to 200 to 290°C under reduced pressure. A common method is to separate and remove it. Usually, the core component polymer is heated and extruded using vented extrusion (Ikuyo 1) to separate volatile components. The molten polymer from which volatile components have been separated is extruded from a die and directly introduced into the fiber manufacturing process, or taken out as pellets.

The polymer made of green methyl methacrylate of the present invention exhibits a higher refractive index than a homopolymer of methyl methacrylate, and therefore has favorable characteristics as an optical transmission fiber.

On the other hand, as the sheath component, which is another important element constituting the present invention, a transparent resin or fluororubber having a refractive index that is at least 3% lower than that of the core component is used. If the difference in refractive index is less than 3%, the rate of light deflection due to the sheath component will be small and the light guide loss will be large. Specifically, the refractive index is preferably 1.42 or less, and it is desirable that the polymer be a non-crystalline, nearly amorphous polymer and have good adhesion to the core component.

Preferred transparent resins include fluororesins and thermoplastic fluororubbers. Examples of the fluororesin include vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropene, trifluoromethyl trifluorovinyl ether, perfluoroprobyl trifluorovinyl ether, perfluoroisopropyl methacrylate, and methacrylic acid. Examples include fluorine-containing polymers such as per and fluoro-tert-butyl. Among these, particularly preferred fluororesins include vinylisofluoride dotetrafluoroethylene copolymer and trifluoroethylene-tetrafluoroethylene copolymer.
Vinylidene fluoride copolymers, vinylidene fluoride-tetrafluoroethylene-hexafluoropropene copolymers, perfluoroisopropyl methacrylate polymers, and perfluoro-tert-butyl methacrylate polymers can be produced.

In addition, thermoplastic fluororubber has a soft segment consisting of a fluororesin phase and a hard segment consisting of a fluororesin phase in its molecules, and has rubber elasticity due to physical crosslinking in the fluororesin phase at room temperature, and has rubber elasticity that is higher than its melting point. At high temperatures, it behaves similar to thermoplastics.

The fluororubber phase forming the soft segment includes vinylidene fluoride/hexafluoropropylene or pentafluoropropylene/tetrafluoroethylene (molar ratio 45-90:5-50:0-35) polymer and perfluoro(alkylvinyl L-thyl). )/tetrafluoroethylene/vinylidene fluoride (molar ratio 15~
75:0-85:O-85) Fluororubber 10 with a molecular weight of 30°000-1,200,000 selected from polymers
~95 parts and the fluororesin phase forming the hard segment includes vinylidene fluoride/tetrafluoroethylene (molar ratio O~100:0~100) polymer and ethylene/tetrafluoroethylene (mole ratio 40~60:60~
40) Molecular weight 10,000~ selected from polymers
Thermoplastic fluororubber combined with 5 to 90 parts of 400,000 fluororesin may be mentioned. A typical example of thermoplastic fluororubber is Guyer thermoplastic (
(manufactured by Daikin Industries, Ltd.).

Preferred fluororubbers include vinylidene fluoride-hexafluoropropene copolymer, vinylidene fluoride-pentafluoropropene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, and the like. Particularly preferred is vinylidene fluoride-hexafluoropropene copolymer.

In addition, by using a system in which a vulcanizing agent is added to these fluororubbers in advance, the fluororubber is crosslinked by heat treatment or light irradiation after being coated on the core material, significantly improving the heat resistance of the optical transmission fiber. . As a vulcanizing agent,
Examples include amines, polyols, and polyhydric peroxides. The vulcanizing agent is preferably added in an amount of about 0.001 to about 1% based on the fluororubber.

The core component polymer of the present invention can be produced by conventionally known methods such as suspension polymerization and bulk polymerization. However, in the suspension polymerization method, since a large amount of water is used, foreign substances contained therein are likely to get mixed into the polymer, and there is also a possibility that foreign substances can get mixed in during the dehydration process.
If necessary, use a filtration method or a distillation method to remove foreign substances such as 11) dust, and then polymerize. A more desirable method is
First, the core component polymer is produced in two steps: a continuous bulk polymerization step at high temperature, followed by a continuous separation step of volatile components mainly composed of residual unreacted monomers. There is a method in which the manufacturing stage and the optical transmission fiber manufacturing stage are performed in a continuous process.

It is also desirable to carry out bulk polymerization of the core component, and then form the core component and sheath component from the resulting polymer by double extrusion.

The radical polymerization initiators used in each of the above polymerizations include, for example, 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2°4 -dimethylvaleronitrile), azobisisobutanol diacetate, azo-tert-butane, and di-tert-butane.
rt-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, ter1.
-butyl per7tate, tert-butyl peracetate, di-tert-amyl peroxide, etc. (examples include di-tert-amyl peroxide).The addition ratio of these polymerization initiators is 0.001 to 1% relative to the monomer. Preferably it is mole %.

Additionally, in order to control the molecular weight, tert-butyl, n-butyl, n-octyl, n-dodecyl mercaptan, etc. are used as chain transfer agents in the polymerization system in an amount of about 1% per monomer.
It is added in an amount of mol% or less.

On the other hand, the sheath component polymer can be produced by conventionally known methods. In the case of the sheath component polymer, in the case of the core component polymer, the manufacturing method has no effect on optical transmission properties, so make sure that foreign substances such as dust do not get mixed in, and if necessary, use filtration methods etc. Due to garbage etc.
It is preferable to remove foreign substances before producing the sheath component polymer.

The ratio of the core component to the sheath component is approximately 70:3 (by weight).
98:2, preferably about 80:20 to 95:5. Further, the outer diameter of the optical transmission fiber having a core-sheath structure is about 0.15 to 1.5 vn, preferably about 0.15 to 1.5 vn.
20-1.0mm.

As mentioned above, the present invention uses a specific polymerized water for the core component and the sheath component in an optical transmission fiber having a core-sheath structure, and also controls the volatile content of the core component (this,
l) It is possible to expand the applicable temperature range of conventional plastic optical transmission fibers to large IJ, and provide a highly reliable optical transmission fiber with excellent heat resistance and practical flexibility, and low light guide loss. The industrial equipment is extremely expensive. The optical transmission fiber of the present invention has a normal temperature of 110
Since the temperature can be lowered to 0.degree. C. or higher, it can be applied to, for example, automobiles, ships, aviation (airplanes or robots), and the like. In addition, the range of application can be expanded by relaxing temperature-limiting conditions for in-plant and in-building communications.

Next, the present invention will be explained in more detail with reference to examples, but the present invention should not be limited by these in any way.

In addition, a diffraction grating spectrometer using a halogen tungsten lamp as a light source was used to measure the light guide loss in the examples.
The output intensities of the optical transmission fiber to be measured and the reference optical transmission fiber at a wavelength of nm were read using a silicon photodiode.

The light intensities at the entrance and exit of optical transmission fibers with different fiber lengths L(k+n) are respectively I. , ■, and the following formula is 11)
The light guide loss a was determined.

In this equation, the smaller the a value, the better the optical transmission performance.

The heat resistance test was conducted by heating the obtained optical transmission fiber for a predetermined period of time, and then measuring and comparing the light guide loss at the initial stage and after heating.

In addition, the determination of the volatile content, which is mainly composed of residual unreacted monomers, is
1 g of the core component polymer was accurately weighed, dissolved in 10 ml of chloroform, and cyclohexanol was added as an internal standard, followed by gastalomadography.

In addition, in each example, % means weight %.

Example 1 30% bornyl methacrylate purified by vacuum distillation
, 69% of methyl methacrylate, 1% of methyl acrylate, and further chopped into these monomers, 0.025% of 1]-dodecylmercaptan, 2.2'-asobis(2,,i
A monomer mixture to which 0.10% of (dimethylvaleroni) + full) was added was prepared under a nitrogen stream filtered through a porous membrane and free of suspended solids, and sent to a reaction tank maintained at 150°C where it remained. Prepolymerization was carried out with a distillation time of 8 hours. Next, the polymerization was completed by sending it into a screw conveyor maintained at 220°C for a residence time of 2 hours, and [η1 chloroform, 25°C: 0,
90, and a methyl methacrylate copolymer having a refractive index of 1.49 was obtained. Using 1 g of this polymer as a sample, cyclohexanol 5
When the volatile content was measured by the method described above using 0+++g as an internal standard substance, it was found that the volatile content was 1.6% consisting of 93% of residual unreacted monomer. Next, this copolymer was fed to a vented extruder heated to 255°C, and the copolymer was heated to 30°C.
After removing volatile components mainly composed of monomers at a pressure of ~60' Torr, the mixture was discharged as a core component in the form of a strand with a diameter of 1++ un from the center of a double extrusion nozzle maintained at 235°C.

At the same time, vinylidene fluoride-tetrafluoroethylene copolymer (vinylidene fluoride 60%, refractive index 1.40, melt flow index 141) (23
0°C)) was discharged as a sheath component and melted and coated on the core component to obtain a strand with a core-sheath structure. The thickness of the pod was approximately 10μ.

The strand was dissolved in chloroform and the volatile content was measured in the same manner as above and found to be 0.3%. When the light guide loss of the obtained optical transmission fiber was measured at 25° C. and 70° C., it was 320 dB/kIllc at a wavelength of 650 nm.

Furthermore, after heat-treating this optical transmission fiber at 130° C. for 240 hours, the light guide loss was measured again and was 340 dB/+n, indicating excellent heat resistance.

Example 2 Monomer, suspension stabilizer (hydroxyethyl cellulose,
monomer (to Japan), 08%), fl peroxide (
lauroyl peroxide, 0°3% based on monomer),
The molecular weight modifier (11-dodecyl mercaptan, 0.16% relative to Moamer) and water were filtered through a porous membrane, and then they were formulated under a nitrogen atmosphere free of suspended solids and then polymerized using a suspension polymerization method. 7-ethyl methacrylate: methyl methacrylate: methyl acrylate = 14: 84
: 2 (wt%), 1η] Chloroform, 25°C: 0
, 90, a core component polymer with a refractive index of 1.49 was supplied to a vented extrusion rock heated to 270°C, and heated at 30 to 60 Torr.
A strand-like fiber having a diameter of 1 mm was obtained using an extruder maintained at 235° C. while removing unreacted monomers at a pressure of r. The volatile content (mainly composed of residual unreacted monomers) of this fiber was 4%.

Then, the #jk fibers were coated with vinylidene fluoride-hexafluoropropene copolymer, Guyer G901 (manufactured by Daikin Industries, Ltd., fluororubber) as a 30% hexafluoro-τ0-xyreso solution as a sheath component. A strand with a core-sheath structure was obtained.

The thickness of the pod was approximately 10 μm.

When the light guide loss in 2S'Ci was measured, it was 650.
It was 370 dB/km at wavelength n+n. Furthermore, after heat treatment at 115° C. for 40 days, the light guide loss was measured again, and as a result, it was 370 dB/+o, indicating excellent heat resistance.

Examples 3 to 5 Using the core component polymer and sheath component polymer shown in Table 1, an optical transmission fiber, 1i (0,
85-0,75II+mφ) was obtained. The light guide loss and heat resistance of the obtained optical transmission fiber were measured in the same manner as in Example 1, and the results are shown in Table 1. As shown in Table 1, all of the optical transmission #& fibers had excellent physical properties.

Comparative Example A core of a bornyl methacrylate-methyl methacrylate-methyl acrylate copolymer containing 1.6% volatile content mainly consisting of residual unreacted monomers was obtained by the same polymerization procedure as in Example 1. Using the same vinylidene fluoride dote) lafluoroethylene copolymer as in Example 1 as a sheath component, an optical transmission w1. I got m.

When we measured the light guide loss at a wavelength of 650 nm, it was approximately 400 dB/km up to 100 V length at the beginning of processing, but after 300 A+ length, the core material became somewhat pale yellow and the value exceeded 1000 dB/io++. , an increase in light guide loss over time was observed. Furthermore, the light guide loss is 400dB/
When the fiber exhibiting 1n was heat-treated at 130° C. for 240 hours, it exhibited a light guide loss of 520 dB/km and was inferior in long-term heat resistance.

Patent applicant: Sumitomo Chemical Industries, Ltd. Representative Patent Attorney Aoyama Aoyama and 2 others

Claims (5)

[Claims] (1) The main component is a methyl methacrylate copolymer containing 3 to 40% by weight of a methacrylic ester having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety, and the volatile content is 0.5% by weight or less. 1. A light transmitting fiber comprising a core component of a polymer "," and a sheath component of a transparent resin or fluororubber having a refractive index that is at least 3% lower than that of the core component. (2) A methacrylic acid ester having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety is 7-entyl methacrylate, -menthyl methacrylate, bornyl methacrylate, isobornyl methacrylate, agemantyl methacrylate, or dimethyl methacrylate. The optical transmission fiber according to item (1) above, which is adamantyl. (3) The transparent resin having a refractive index at least 3% lower than that of the core component is vinylidene fluoride-tetrafluoroethylene copolymer, trifluoroethylene-vinylidene fluoride copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoro The optical transmission fiber according to item (1) above, which is a propene copolymer, a perfluoroisopropyl methacrylate copolymer, a perfluoro-tert-butyl methacrylate polymer, or a thermoplastic fluororubber. (4) Item (1) above, wherein the fluororubber is a vinylidene fluoride-hexafluoropropene copolymer, a vinylidene fluoride-pentafluoropropene copolymer, or a vinylidene fluoride-chlorotrifluoroethylene copolymer. Optical transmission fiber. (5) The fluororubber forms a system containing a vulcanizing agent.
1) Optical transmission fiber.