JPH0578002B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to a light transmitting fiber,
More specifically, the present invention relates to a step-index type plastic optical fiber having excellent heat resistance. Technical Background Conventionally, inorganic glass optical fibers having excellent optical transmission properties over a wide range of wavelengths have been known as optical transmission fibers. However, glass fibers have poor processability, are susceptible to bending stress, and are also expensive, so light transmitting fibers based on synthetic resins have been developed. Light transmitting fibers made of synthetic resin have a core made of a polymer with a high refractive index and good light transmission, and a sheath made of a transparent polymer with a smaller refractive index than the core polymer. It is obtained by producing a fiber having a core-sheath dual structure as a component. The polymer useful as a core component with high light transparency is preferably an amorphous material, and polymethyl methacrylate or polystyrene is generally used. Among these, polymethyl methacrylate has excellent not only transparency but also mechanical properties and weather resistance, and is therefore used industrially as a core material for high-performance plastic optical fibers, as well as for short-distance optical communications and optical sensors. Application development is progressing in the following fields. However, polymethyl methacrylate has a low heat distortion temperature.
Because it has insufficient heat resistance at around 100℃,
There are quite a few fields in which its application is restricted, and therefore there is a strong demand for improved heat resistance. The following methods are known for improving the heat resistance of methacrylic resins. (1) A method of copolymerizing methyl methacrylate and α-methylstyrene. (2) Method of dissolving poly-α-methylstyrene in methyl methacrylate monomer and then polymerizing methyl methacrylate (Japanese Patent Publication No. 1616-1616, No. 49
−8718). (3) A method of copolymerizing methyl methacrylate and N-allyl maleic acid imide (Japanese Patent Publication No. 43-9753). (4) Methyl methacrylate/α-methylstyrene/
A method of copolymerizing maleimide. and (5) a method of polymerizing methyl methacrylate in the presence of a crosslinked polymer using a polyfunctional monomer (JP-A-48-95490, JP-A-48-95491). However, in these conventional methods, although the heat resistance of the obtained polymer is improved, the one-sided polymerization rate is extremely low, resulting in a significant decrease in productivity and the resulting polymer is impractical. If the mechanical properties of the material are insufficient, the optical properties are insufficient, the material is markedly colored when molded, or the moldability is low, it may not be suitable for practical use. It has not yet reached the level where it can be realized. Purpose of the Invention The purpose of the present invention is to provide not only excellent optical properties, mechanical properties, weather resistance, and moldability comparable to polymethacrylic acid ester resins, but also excellent heat resistance and productivity. An object of the present invention is to provide a transmitting fiber having excellent light transmitting properties, which is composed of a core component polymer having the following properties and a sheath component polymer having excellent heat resistance and transparency. Composition of the Invention As a result of extensive studies to achieve the above object, the present inventors have discovered that a polymer containing a ring structural unit composed of methacrylic anhydride has excellent properties that could not be achieved with conventional copolymer resins. It exhibits excellent heat resistance, moldability, light transmission, and mechanical properties, as well as excellent productivity. By using a core component polymer with these excellent properties, it is possible to balance various performances. It has been discovered that a fiber with excellent optical transmission properties can be obtained. That is, the present invention has the following formula;

A core component substantially comprising a polymer consisting of 2% by weight or more of ring structural units represented by [Chemical formula] and methyl methacrylate, and 98% by weight or less of monomer units excluding aromatic vinyl units. and a sheath component that covers the core component and is made of a polymer having a refractive index that is 1% or more smaller than the refractive index of the core component polymer. In the light transmitting fiber of the present invention, the core component consists essentially of 2% by weight or less of methacrylic anhydride ring structural units represented by formula () and 98% by weight or less of monomer units whose main component is methyl methacrylate. It is a polymer. Among the above components, the methacrylic anhydride ring structural unit is a component necessary for maintaining heat resistance and optical properties as a light transmitting fiber, and its content must be 2% by weight or more. In order to obtain especially excellent heat resistance, it is preferable to use 10% by weight or more. This is because if the methacrylic anhydride ring structural unit content is less than 2% by weight, the effect of improving the heat resistance of the obtained polymer will be insufficient. On the other hand, the monomer component containing methyl methacrylate as the main component and excluding aromatic vinyl units is a necessary component for maintaining basic optical properties, weather resistance, and mechanical properties as a light transmitting fiber. The main component is methyl methacrylate, and the monomer components excluding aromatic vinyl units include methyl methacrylate, as well as small amounts of other components, preferably 20% by weight or less, such as methyl acrylate, ethyl methacrylate, and methacrylic acid. At least one component selected from butyl, cyclohexyl methacrylate, benzyl methacrylate, methacrylic acid, acrylic acid, etc. may be included. In addition to these copolymerized components, the following components may also be included in small amounts, preferably 20% by weight or less. For example, it is composed of one or more polyfunctional reactive monomers such as triallyl cyanurate, triallyl isocyanate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, etc. It's okay. In order to produce the core component polymer of the light transmitting fiber of the present invention, methacrylic acid, methacrylic acid tert-
The desired methacrylic anhydride polymer can be obtained by subjecting a polymer consisting of butyl and a copolymer with methyl methacrylate containing a reaction precursor thereof or a copolymer containing the other components mentioned above to a thermal condensation reaction. It will be done. The heat treatment temperature when producing the methacrylic anhydride of the present invention is 100°C or higher, especially 130 to 450°C.
C, preferably in the range of 150 to 300 C. In order to prevent the formation of abnormal reactants, the heat treatment is preferably carried out in an autoclave under an atmosphere of an inert gas such as nitrogen or argon. Furthermore, in order to prevent thermal deterioration of the polymer during this heating reaction, it is also possible to add a thermal deterioration inhibitor such as an antioxidant. Examples of the antioxidant here include phosphite antioxidants, hindered phenol antioxidants, sulfur antioxidants, and amine antioxidants. Specific examples of phosphite-based antioxidants include phosphite-based antioxidants, such as tricresyl phosphite, cresyl phenyl phosphite, tributyl phosphite, and tributoxyethyl phosphite. Specific examples of hindered phenolic antioxidants include hydroquinone, cresol, and phenol derivatives. Examples of sulfur-based antioxidants include alkyl mercaptans and dialkyl sulfide derivatives. Examples of amine antioxidants include naphthylamine, phenylenediamine, and hydroquinoline derivatives. Methacrylic acid or methacrylic acid tert- which is a raw material for obtaining the above-mentioned methacrylic anhydride component
To prepare a polymer or copolymer containing butyl, common radical polymerization methods, ionic polymerization methods, etc. may be used, but radical polymerization methods are preferred from the viewpoint of productivity. The polymerization catalyst used to obtain the above polymer is one used in general radical polymerization, such as azobisisobutyronitrile, 2,2'-azobis-(2,4-dimethylvaleronitrile), etc. Azobis catalyst, lauroyl peroxide, benzoyl peroxide, bis(3,5,
The catalyst can be selected from diacyl peroxide catalysts such as 5-trimethylhexanoyl) peroxide, percarbonate catalysts, and the like. In the light transmitting fiber of the present invention, the core component is covered with a sheath component. The sheath component is formed by a polymer having a refractive index that is at least 1% less than the refractive index of the core component copolymer. This polymer preferably has a glass transition point of 80° C. or higher and is substantially transparent. As the sheath component polymer, for example, Japanese Patent Publication No. 43-8978
Polymers of fluorinated alcohol esters of methacrylic acid as described in Japanese Patent Publication No. 56-8321, Japanese Patent Publication No. 56-8322, Japanese Patent Publication No. 56-8323, and Japanese Patent Publication No. 53-60243, etc. And, special public service 1973-
It can be selected from copolymers of vinylidene fluoride and latrafluoroethylene as described in No. 42260, polymethyl methacrylate, polysiloxanes, and ethylene-vinyl acetate copolymers. The methacrylic acid-fluorinated alcohol ester has the following general formula;

[ka] and

[However, in the above formula, X represents an H, F, or Cl atom, n represents an integer of 1 to 6, m represents an integer of 1 to 10, and l represents an integer of 1 to 10. , R ₁ and R ₂ each represent an H atom or a CH ₃ , C ₂ H ₅ or CF ₃ group]

There is a compound represented by Such methacrylic acid fluoroalkyl ester may be polymerized alone or may be copolymerized with other polymerizable vinyl monomers. Such vinyl monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, glycidyl methacrylate, methacrylic acid, acrylic acid,
Methyl maleic anhydride acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, glycidyl methacrylate,
Glycidyl acrylate, styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, p-chlorostyrene, 2,4-dichlorostyrene, p-methoxystyrene, acrylonitrile, methacrylonitrile, vinyl acetate, methyl vinyl ketone, Examples include hydroxypropyl acrylate, hydroxyethyl, acrylate, and the like. Two types of these monomers may be combined and copolymerized. Among them, methyl methacrylate is particularly preferred from the standpoint of providing a transparent copolymer. The sheath component polymer is produced by radical polymerization of polymerization components by a conventional method. As the polymerization catalyst at this time, an ordinary radical polymerization initiator can be used, and specific examples include, for example, di-tert
-butyl peroxide, dicumyl peroxide,
Methyl ethyl ketone peroxide, tert-butyl perphthalate, tert-butyl perbenzoate, methyl isobutyl ketone peroxide, lauroyl peroxide, cyclohexane peroxide, 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane, tert-butyl peroctano ate, tert-butyl perisobutyrate,
Organic peroxides such as tert-butylperoxyisopropyl carbonate, methyl 2,2'-azobisisobutyrate, 1,1'-azobiscyclohexanecarbonitrile, 2-phenylazo2,4-dimethyl-4-methoxyvaleronitrile , 2-carbamoyl-azobisisobutyronitrile, 2,2'-
azobis-2,4-dimethylpereronitrile,
Examples include azo compounds such as 2,2'-azobisisobutyronitrile. Polymerization methods include emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization, and bulk polymerization is preferred in order to obtain a highly pure polymer. In the light transmitting fiber of the present invention, it is necessary that the refractive index value of the sheath component is at least 1% smaller than that of the core component. The difference in refractive index between both components is 1%
When it is less than 1, the openings of the light transmitting fiber obtained will be too small, making it difficult to use practically. Also, if the refractive index of the sheath component is greater than that of the core component, the resulting fiber will not transmit light. Since light transmitting fibers may be exposed to high temperatures for long periods of time, it is preferred that they have good durability under such conditions. For this purpose, it is desirable that the sheath component polymer has a heat distortion temperature as high as possible, preferably 70°C or higher, more preferably 90°C or higher. For this reason, the sheath component polymer preferably has a glass transition point of 80°C or higher. The step index type light transmitting fiber of the present invention is manufactured by the method described below. (1) A composite spinning method in which a core component copolymer and a sheath component polymer are each melted and extruded into a core-sheath structure through a special nozzle. (2) Forming core component fibers from the core component copolymer,
A coating method in which this is coated with a solution of a sheath component polymer, and then the solvent is removed from this coating layer. In forming the core component, the core component polymer is continuously polymerized in bulk according to the method disclosed in Japanese Patent Publication No. 48-131391, and this is subsequently spun to form the core component fiber. Good too. This method is
This is effective in reducing the loss of optical transmission performance of the core component. Effects of the Invention The light transmitting fiber of the present invention is significantly superior in heat resistance and durability compared to conventional plastic light transmitting fibers whose core components are polymethyl methacrylate or polystyrene. . Furthermore, the optically transmitting fiber of the present invention is relatively inexpensive, easy to handle, and has an extremely well-balanced variety of properties. Therefore, the optically transmitting fiber of the present invention can be used for wiring in the engine compartment of a car, and therefore has extremely high industrial significance and value as it can respond to the advancement of car electronics. be. The features and effects of the present invention as described above will be further explained with reference to Examples. Embodiments of the invention In the examples, the optical transmission performance of the fiber is
Measurement and evaluation were carried out using the apparatus shown in Figure 4 of Publication No. 58-7602. The measurement conditions are as follows: Interference filter (main wavelength) 650μm Io (total length of fiber) 5ml L (cutting length of fiber) 4m D (diameter of bobbin) 190mm The "part" described below is Parts by weight shall be expressed. Example 1 Tert-butyl methacrylate 100 parts
After adding and dissolving 0.75 parts of dodecyl mercaptan and 0.4 parts of azobisisobutyronitrile, a thermocouple was set in a cell formed by two tempered glass plates facing each other at a distance of 3 mm through a polyvinyl chloride gasket. The above monomer solution was injected into the cell and immersed in warm water at 80°C to polymerize and harden. After immersing in hot water, 30 minutes after the internal temperature reaches its peak due to polymerization exotherm, remove it from hot water, and then
Heat treatment was performed in an air heating furnace at 120°C for 2 hours. After cooling, the cells were removed and the resulting resin plate with a thickness of about 6 mm was crushed in a clean box. To 100 parts of this polymer, 0.01 part of Antige BHT (2,6-di-tert-butyl p-cresol manufactured by Kawaguchi Chemical Industry Co., Ltd.) was charged into a 3-volume autoclave, and after repeated nitrogen purges, it was placed in an oil bath at 250°C. After a heating reaction for a period of time, a transparent resin body and polymethacrylic anhydride were obtained. From the infrared absorption spectrum, 1802 cm ^-1 and
A characteristic absorption of methacrylic anhydride was observed at 1760 cm ^-1 . It was confirmed that the polymethacrylic anhydride obtained as described above contained 95% of the structural unit represented by the formula (). MI value of the obtained polymer (3.8Kg at 230℃
) is 4.0, the refractive index is 1.526, and the specific gravity is 4.0.
1.303, and the heat distortion temperature was 170℃. Separately, 50 parts of 2,2,2-trifluoroethyl methacrylate, 50 parts of methyl methacrylate, and 0.3 parts of n-octyl mercaptan were mixed and dissolved, and then 0.025 parts of azobisbutyronitrile was added and dissolved as a polymerization catalyst. The above mixture was then injected into a cell formed of two tempered glass plates facing each other at a 5 mm interval via a polyvinyl chloride gasket, and immersed in hot water at 70°C to polymerize and harden.
Thirty minutes after reaching the peak temperature due to polymerization exotherm, the cell was taken out of the hot water and then heat treated in an air heating oven at 130°C for 2 hours. After cooling, the cells were removed, and the resulting resin plate was crushed in a clean box to obtain a shell component with an MI value (230℃, load 3.8Kg) of 5.0, a refractive index no. of 1.445, and a heat distortion temperature HDT of 98℃. Obtained union. The obtained core and sheath component polymers were combined into core-
Supplied to a vented composite spinning machine with a two-layer sheath spinneret, spinning temperature 260℃, spinning speed 3m/min.
The film was then drawn up at 200°C, then continuously stretched 2.0 times at 200°C and rolled up. The obtained fiber had a core component diameter of 980 μm, a sheath component thickness of 10 μm, and a weight ratio of core component to sheath component of 96:4.
It was a light transmitting fiber with a concentric structure. The optical transmission loss of this optically transmitting fiber is ^890dB /Km
It was capable of sufficiently transmitting optical signals over a length of 10 meters. The obtained optically transmitting fiber was processed using a crosshead type cable processing machine using carbon black-filled nylon 6.6 as the first jacket polymer and aromatic polyamide fiber (Kevlar) as the reinforcing fiber.
A second jacket was coated with polyester elastomer containing carbon black so as to have an outer diameter of 2.2 mm, thereby obtaining an optical cable with an optical transmission loss of 920 ^dB /Km. Cut 10m of this optical cable and fix one end to a light source (using a 650μm interference filter).
The other end was connected and fixed to a photodiode, and the 5 m middle part of the optical cable was exposed to a hot air heating furnace at 130°C.
The heat resistance and durability of the optical cable was evaluated by tracking changes in the amount of light transmitted. As a result, this optical cable exhibited stable heat resistance and durability, with no decrease in light intensity observed even after 1000 hours had passed. Example 2 An optical cable was obtained in exactly the same manner as in Example 1, except that the sheath component polymer was polyvinylidene fluoride (refractive index: 1.43). The optical transmission loss of the obtained optical cable is ^1400dB /K
However, even after being exposed to a hot air heating furnace at 160°C for 1000 hours, the amount of light decreased by only 5%, demonstrating excellent heat resistance and durability. Example 3 The core component polymer obtained in Example 1 was spun using a vented spinning machine at a spinning temperature of 240°C and a spinning speed of 6 m/min.
Fiber containing only the core component (diameter 750 μm)
A precursor composition of polydimethylsiloxane (Shin-Etsu Silicone) is applied to the surface of this core component fiber.
After uniformly coating KE106LTV), 150
It was heated at ℃ for 10 minutes to form a polydimethylsiloxane film (refractive index: 1.42, thickness: 300 μm). The optical transmission loss of this optical fiber is ^830dB /Km
Furthermore, after exposure to 170°C for 1000 hours, the rate of decrease in light intensity was 3%, showing extremely excellent heat resistance and durability. Example 4 Methacrylic acid was used as the monomer component that was the raw material for the core material.
The same treatment as in Example 1 was carried out using 50 parts of tert-butyl and 50 parts of methyl methacrylate. MI value of the obtained polymer (230℃, load 3.8Kg)
was 5.5, the refractive index was 1.504, the specific gravity was 1.235, the content of the structural unit of formula () was 60%, and the heat distortion temperature was 141°C. This core component polymer was spun using a vent spinning machine at a spinning temperature of 240°C and a spinning speed of 6 m/min to obtain a fiber (diameter 750 μm) consisting only of the core component. After uniformly coating the composition (KE106LTV, Shin-Etsu Silicone Co., Ltd.), it was heated at 150°C for 10 minutes to form a polydimethylsiloxane coating (refractive index 1.42, thickness
300 μm). The optical transmission loss of this optical fiber is ^800dB /Km
It also showed extremely excellent heat resistance and durability, with a decrease in light intensity of 1% after exposure to 130°C for 1000 hours. Comparative Example 1 A polymer was obtained in the same manner as in Example 1 using 100 parts of methyl methacrylate monomer. The obtained polymethyl methacrylate was directly used as a core component polymer. The sheath material used in Example 1 was fed to a vented composite spinning machine together with the core component polymer, and taken off at a spinning temperature of 240°C and a spinning speed of 3 m/min.
Further, it was continuously stretched 2.0 times at 140°C and wound. The obtained fiber had a core component diameter of 980 μm and a sheath component thickness of 10 μm. The optical transmission loss of this optically transmitting fiber was 170 ^dB /Km. After jacket coating processing similar to Example 1
When an exposure test was conducted at 120°C for 1000 hours, the light intensity decreased significantly, by 100%, and optical transmission became impossible.

Claims (1)

[Claims] 1: A polymer consisting of 2% by weight or more of ring structural units represented by the formula: [Chemical formula] and 98% by weight or less of monomer units excluding aromatic vinyl units, the main component of which is methyl methacrylate. a core component substantially comprising; a core component coated with the core component;
A light transmitting fiber comprising a sheath component made of a polymer having a refractive index that is 1% or more lower than the refractive index of the core component polymer.