JPS6367167B2 - - 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 plastic optical fiber having a core-sheath dual structure and excellent heat resistance.

(Technical Background) Inorganic glass optical fibers having excellent optical transmission properties over a wide range of wavelengths have been known as optical 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 component that is a polymer that has a high refractive index and good light transmittance, and a sheath component that is a transparent polymer that has a lower refractive index than the core component polymer. As,
It is obtained by producing fibers with a core-sheath dual structure. 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, and is used for short-distance optical communications, optical sensors, etc. Application development is progressing in the following fields. However, polymethyl methacrylate has a heat distortion temperature of 100
Since the heat resistance is not sufficient at around 100°C, there are many 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) A method in which poly-α-methylstyrene is dissolved in methyl methacrylate monomer and then methyl methacrylate is polymerized (Special Publication No. 43-1616,
49-8718).

(3) Method of copolymerizing methyl methacrylate and N-allyl maleic acid imide (Japanese Patent Publication No. 43-9753
issue).

(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. 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, making it impossible to put it into practical use. It's not up to the level you deserve.

(Objective of the Invention) The object of the present invention is to have not only excellent optical properties, mechanical properties, weather resistance, and moldability comparable to polymethacrylic acid ester resins, but also excellent heat resistance and moldability. The object of the present invention is to provide a light transmitting fiber having excellent light transmitting properties, which is composed of a core component polymer having high productivity and a sheath component polymer having excellent heat resistance and transparency.

(Structure of the Invention) As a result of intensive studies aimed at achieving the above object, the present inventors have discovered that a polymer containing a ring structural unit composed of N-substituted methacrylimide can be produced in a manner that cannot be achieved with conventional copolymer resins. It exhibits excellent heat resistance, moldability, light transmission properties, and mechanical properties, as well as excellent productivity. By using a core component polymer with these excellent properties, various types of It has now been discovered that an excellent light transmitting fiber with balanced performance can be obtained.

That is, the present invention has the following formula: (In the formula, R represents an aliphatic, alicyclic, or aromatic hydrocarbon group having 1 to 20 carbon atoms.) A monomer unit containing 2% by weight or more of the ring structural unit represented by the formula (R represents an aliphatic, alicyclic, or aromatic hydrocarbon group having 1 to 20 carbon atoms) and methyl methacrylate as the main components98 a core component substantially comprising a polymer consisting of % by weight or less, and a sheath component covering the core component and comprising a polymer having a refractive index that is 1% or more smaller than the refractive index of the core component polymer. A light transmitting fiber characterized by comprising:

In the light transmitting fiber of the present invention, the core component polymer is substantially 2% by weight or more of N-substituted methacrylimide ring structural units represented by the formula () and 98% by weight of monomer units whose main components are methyl methacrylate. % or less. Among the above components, the N-substituted methacrylimide 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.

If the content of N-substituted methacrylimide ring structural units is less than 2% by weight, the heat resistance of the resulting polymer will be insufficiently improved.

On the other hand, the monomer component containing methyl methacrylate as a main component is a component necessary for maintaining basic optical properties, weather resistance, and mechanical properties as a light transmitting fiber.

The N-substituent R in the methacrylimide component represented by formula () must be a saturated or unsaturated aliphatic, alicyclic or aromatic hydrocarbon group having 1 to 20 carbon atoms.

From the viewpoint of improving heat resistance, it is preferable that the chain length of the N-substituent R be relatively short. Specific examples of the N-substituent R include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl group, phenyl group, substituted phenyl group, etc.
Most preferred is the methyl group.

In addition to methyl methacrylate, the monomer component containing methyl methacrylate as a main component may contain a small amount of other components, preferably 20% by weight or less, such as methyl acrylate, ethyl methacrylate, butyl methacrylate, and methacrylic acid. , acrylic acid, styrene,
At least one component selected from α-methylstyrene and the like may be included.

In addition to these copolymer components, the following components may also be included.

Consisting of one or more types of polyfunctional reactive monomers such as divinylbenzene, triallyl cyanurate, triallyl isocyanurate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, etc. It may be.

To produce the core component copolymer of the light transmitting fiber of the present invention, 2% by weight of N-substituted dimethacrylamide is used.
It is obtained by copolymerizing a mixture consisting essentially of the above and methyl methacrylate or 98% by weight or less of a monomer component mainly composed of methyl methacrylate.

To produce the core component copolymer, a radical polymerization catalyst is added to the mixture of the copolymerization components, and the resulting copolymerization mixture is first heated at 50 to 180°C, preferably 65°C.
After heating and polymerization to a temperature of ~130℃, further 100~
Heating at a temperature of 160°C for 30-180 minutes completes the polymerization.

The radical polymerization catalyst used to prepare the core component copolymer is one used in general radical polymerization, such as azobisisobutyronitrile, 2,2'-azobis-(2,4-dimethylvaleronitrile), etc. ), diacyl peroxide catalysts such as lauroyl peroxide, benzoyl peroxide, bis(3,5,5-trimethylhexanoyl) peroxide, and percarbonate catalysts.

In the light transmitting fiber of the present invention, the core component is covered with a sheath component. The sheath component is formed of 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 Interest Publication No. 53-42260
copolymers of vinylidene fluoride and tetrafluoroethylene, polymethyl methacrylate, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymers, polysiloxanes, as described in It can be selected from poly-4-methylpentene-1, ethylene-vinyl acetate copolymer, and the like. The methacrylic acid-fluorinated alcohol ester has the following general formula: 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, l represents an integer of 1 to 10, R ₁ and _R2
each represents an H atom or a CH ₃ , C ₂ H ₅ or CF ₃ group] There is a compound represented by the following. 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,
Maleic anhydride, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, glycidyl methacrylate, glycidyl acrylate, styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, p-chloro Examples include styrene, 2,4-dichlorostyrene, p-methoxystyrene, acrylonitrile, methacrylonitrile, vinyl acetate, methyl vinyl ketone, 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 perpenzoate, methyl isobutyl ketone peroxide, lauroyl peroxide, cyclohexane peroxide, 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane, tert-butyl peroxide Octanoate, 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.

Examples of 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 the amount is less than %, 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.

To form 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 then this is spun.
A core component fiber may also be formed. This method 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 component is 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) 650 μm I ₀ (total length of fiber) 5 ml (cutting length of fiber) 4 m D (diameter of bobbin) 190 mm Example 1 As monomer for core component Methyl methacrylate 5500
After mixing 4,500 g of N-methyldimethacrylamide and 10 g of tert-dodecyl mercaptan in a reaction vessel equipped with a cooling tube, a thermometer, and a stirring bar, the mixture was heated with stirring until the internal temperature reached 70 0.5 g of 2,2'-azobis-(2,4-dimethylvaleronitrile) was added at 0.0°C, and the internal temperature was maintained at 95-110°C for 10 minutes. Next, the reaction mixture was cooled to room temperature to obtain a partially polymerized product. This partially polymerized product was over-purified using a 0.1 μm filter made of polytetrafluoroethylene, and 0.3 parts by weight of tert-dodecyl mercaptan and 0.3 parts by weight of lauroyl peroxide were added to and dissolved in 100 parts by weight of the obtained purified product, and then the poly A thermocouple is set in a cell formed by two tempered glass plates facing each other at a spacing of 3 mm via a vinyl chloride gasket, and the above composition is injected into the cell.
It was immersed in warm water at 80°C to polymerize and harden.

The time from immersion in hot water until the internal temperature reaches its peak (hardening time) was measured, and 30 minutes after the peak temperature was reached, it was removed from the hot water and then placed in an air heating oven at 120℃ for 2 hours. Heat treated. After cooling, remove the cell and obtain a plate thickness of approximately 6 mm.
The resin plate was pulverized in a clean box to obtain a core component polymer.

MI value of the obtained core component polymer (230℃, load
3.8Kg) was 3.5, the refractive index was 1.530, the specific gravity was 1.210, and the heat distortion temperature was 152℃.

Separately, 50 parts by weight of 2,2,2-trifluoroethyl methacrylate, 50 parts by weight of methyl methacrylate and 0.3 parts by weight of n-octyl mercaptan were mixed and dissolved, and then 2,2'-azobisisobutylene was added as a polymerization catalyst. Add and dissolve 0.025 parts by weight of nitrile, inject the above mixture into a cell formed by two tempered glass plates facing each other at a 5 mm interval via a polyvinyl chloride gasket, and immerse it in hot water at 70°C. , polymerized and cured. Thirty minutes after the internal temperature reached 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 cell was removed, the resulting resin plate was crushed in a clean box, and the MI value (230
A sheath component polymer was obtained with a refractive index _nD of 1.445 and a heat distortion temperature of 98°C.

The obtained core and sheath component polymers were fed to a vented composite spinning machine with a core-sheath dual structure spinneret, taken out at a spinning temperature of 260°C and a spinning speed of 3 m/min, and then continuously heated at 200°C. I stretched it to 2.0 times and rolled it up.

The obtained fiber had a core component diameter of 980 μm, a sheath component thickness of 10 μm, and a weight ratio of the core component to the sheath component.
It was a light transmitting fiber with a concentric structure of 96:4.

The optical transmission loss of this optical transmission fiber is 930dB/Km.
It was capable of sufficiently transmitting optical signals over a length of 10 meters.

The obtained light transmitting fiber was coated with a crosshead type cable processing machine using aromatic polyamide fiber (Kevlar) as the first reinforcing fiber and 6-6 nylon with carbon black as the jacket polymer so that the outer diameter was 1.6 mm. Furthermore, a second jacket was coated with polyester elastomer containing carbon black to an outer diameter of 2.2 mm to obtain an optical cable with an optical transmission loss of 980 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 portion of the optical cable was exposed to a hot air heating furnace at 130°C. Changes in the amount of light transmitted were tracked to evaluate the heat resistance and durability of the optical cable.

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 was 1350dB/
Km, but even after being exposed to a hot air heating furnace at 150°C for 1000 hours, the rate of decrease in light intensity was only 3%, 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.
Fibers containing only the core component (750μ diameter)
m) is obtained, and 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 300μ).

This optical fiber had an excellent optical transmission loss of 870 dB/Km, and exhibited extremely excellent heat resistance and durability, with a decrease in light intensity of 3% after exposure to 150°C for 1000 hours.

Example 4 The core component was prepared in the same manner as in Example 1, except that 10 kg of N-methyl dimethacrylamide was used instead of 5,500 g of methyl methacrylate and 4,500 g of N-methyl dimethacrylamide as the core component monomers in Example 1. It was made into a polymer.

MI value of the obtained polymer (230℃, load 3.8Kg)
is 6.5, refractive index 1.532, specific gravity 1.325, heat distortion temperature 168
It was warm at ℃.

This core component polymer was taken up using a vented spinning machine at a spinning temperature of 240°C and a spinning speed of 6 m/min to obtain a fiber (750 μm in diameter) consisting only of the core component, and a precursor of polydimethylsiloxane was applied to the surface of the core component fiber. After uniformly coating the composition (KE106LTV from Shin-Etsu Silicon Co., Ltd.), it was heated at 150°C for 10 minutes to form a polydimethylsiloxane film (refractive index 1.42, thickness 300μ).
was formed.

This optical fiber had an excellent optical transmission loss of 900 dB/Km, and exhibited extremely excellent heat resistance and durability, with a decrease in light intensity of 1% after exposure at 150°C for 1000 hours.

Comparative Example 1 A core component polymer was obtained using the same recipe as in Example 1 except that 10 kg of methyl methacrylate was used as the core component monomer.

The sheath material according to Example 1 was used and fed to a vented composite spinning machine, and the spinning temperature was 240°C and the spinning speed was 3.
2.0 m/min and then continuously at 140°C.
I stretched it twice and rolled it up.

The obtained fiber has a core component diameter of 980 μm and a sheath component thickness of 10 μm.
It was m.

The optical transmission loss of this optical transmission 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 was impossible.

Claims (1)

[Claims] 1 Formula: (In the formula, R represents an aliphatic, alicyclic, or aromatic hydrocarbon group having 1 to 20 carbon atoms.) A monomer unit containing 2% by weight or more of the ring structural unit represented by the formula (R represents an aliphatic, alicyclic, or aromatic hydrocarbon group having 1 to 20 carbon atoms) and methyl methacrylate as the main components98 a core component substantially comprising a polymer consisting of % by weight or less, and a sheath component covering the core component and comprising a polymer having a refractive index that is 1% or more smaller than the refractive index of the core component polymer. A light transmitting fiber comprising: 2. The light transmitting fiber according to claim 1, wherein R in formula () is an aliphatic, alicyclic or aromatic hydrocarbon group having 1 to 8 carbon atoms. 3. The light transmitting fiber according to claim 1, wherein R in formula () is a methyl group.