JPS6367166B2 - - 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) 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 formula (In the formula, R represents an aliphatic, alicyclic, or aromatic hydrocarbon group having 1 to 20 carbon atoms) and a monomer unit whose main components are 2% by weight or more of the ring structural unit and methyl methacrylate 98 % by weight or less, 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 polymer of the core component. A light transmitting fiber characterized by comprising:

In the light transmitting fiber of the present invention, the core component polymer consists of 98% by weight of monomer units consisting essentially of 2% by weight or more of N-substituted methacrylimide ring structural units represented by the formula () and 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 has basic optical properties as a light transmitting fiber.
A necessary component to maintain weather resistance and mechanical properties.

The N-substituent R in the methacrylimide component of structural 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, phenyl, substituted phenyl, etc., with methyl being the most preferred.

The monomer component mainly composed of methyl methacrylate contains, in addition to the methyl methacrylate component, a small amount of
Preferably 20% by weight or less of other components such as methyl acrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, methacrylic acid, acrylic acid,
At least one component selected from styrene, α-methylstyrene, etc. 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.

In order to produce the core component polymer of the light transmitting fiber of the present invention, polymethyl methacrylate or the copolymer containing methyl methacrylate monomer as a main component, an imidizing agent such as a primary aliphatic amine or an aromatic The target N-substituted methacrylimide polymer can be obtained by subjecting the group amine to a thermal condensation reaction with a 1,3-disubstituted urea or the like that generates a primary amine through a thermal reaction.

The heat treatment temperature for producing the N-substituted methacrylimide component of the present invention is 100°C or higher, particularly 130 to 450°C,
The temperature range is preferably 150 to 300°C, and heat treatment in an autoclave under an inert gas atmosphere such as nitrogen or argon is preferred in order to prevent abnormal reactions from occurring.

Further, 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.

The antioxidants mentioned here include phosphite-based antioxidants, hindered phenol-based antioxidants, sulfur-based antioxidants, and amine-based antioxidants.

Examples of phosphite-based antioxidants include phosphite esters such as torcresyl phosphite, cresyl phenyl phosphite, tributyl phosphite,
Examples include phosphite esters such as tributoxyethyl phosphite.

Examples of hindered phenolic antioxidants include hydroquinone, cresol, and phenol derivatives.

Examples of sulfur-based antioxidants include alkyl mercaptans and dialkyl disulfide derivatives.

Examples of amine antioxidants include naphthylamine,
Examples include phenylenediamine and hydroquinoline derivatives.

To prepare polymethyl methacrylate or a polymer mainly composed of polymethyl methacrylate, which is a raw material for obtaining the N-substituted methacrylimide component described above, conventional radical polymerization methods, ionic polymerization methods, etc. can be used. However, radical polymerization is preferred from the viewpoint of productivity.

The polymerization catalyst used to obtain the above polymer is, for example, azobisisobutyronitrile, 2,
Azobis-based catalysts such as 2'-azobis-(2,4-dimethylvaleronitrile), lauroyl peroxide, benzoyl peroxide, bis(3,
The catalyst can be selected from diacyl peroxide catalysts such as 5,5-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 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, ethylene tetrafluoride, propylene hexafluoride copolymers, polysiloxanes, as described in It can be selected from poly-4-methylpentene-1, ethylene-vinyl acetate copolymer, and the like. The above 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 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.

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.

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 component is polymethyl methacrylate or polystyrene. .

Further, 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 1 100 parts by weight of methyl methacrylate Against tert-
After adding and dissolving 0.75 parts by weight of dodecyl mercaptan and 0.4 parts by weight of lauroyl peroxide, a thermocouple was set in a cell formed by two tempered glass plates facing each other at a spacing of 3 mm through a polyvinyl chloride gasket, and the thermocouple was set in the cell. The above monomer solution was poured into the container and immersed in warm water at 80°C to polymerize and harden.
Thirty minutes after the internal temperature reached a peak due to polymerization heat generation after being immersed in hot water, it was taken out from the hot water and then heat treated in an air heating oven at 120°C for 2 hours.

After cooling, the cell was removed, and the resulting resin plate with a thickness of about 6 mm was pulverized in a clean box. The obtained polymer had an MI value (230°C, load 3.8Kg) of 13.0, a refractive index _nD of 1.4920, a specific gravity of 1.190, and a heat distortion temperature of 105°C. 1,3- for 100 parts by weight of this polymer
22 parts by weight of dimethyl urea, 4.5 parts by weight of water, Antige BHT (manufactured by Kawaguchi Chemical Co., Ltd., 2,6-tert-
Butyl-p-cresol) 0.01 part by weight was placed in a 3-volume autoclave, and nitrogen purging was repeated.
A reaction was carried out by heating in an oil bath at 230°C for 4 hours to obtain a transparent resinous polyN-methylmethacrylimide. From the infrared absorption spectrum, 1720, 1663,
Absorption characteristic of N-methylmethacrylimide was observed at 750 cm ^-1 . The MI value of the obtained polymer (230℃,
The load (3.8 kg) was 3.5, the refractive index was 1.536, the specific gravity was 1.210, and the heat distortion temperature was 175°C.

Separately, 50 parts by weight of 2,2,2-trifluoroethyl methacrylate, 50 parts by weight of methyl methacrylate,
After mixing and dissolving 0.3 parts by weight of n-octyl mercaptan, 0.025 parts by weight of azobisbutyronitrile was added and dissolved as a polymerization catalyst, and two sheets were placed facing each other at an interval of 5 mm through a polyvinyl chloride gasket. In a cell formed from a tempered glass plate,
The above mixture was injected and immersed in hot water at 70°C to polymerize and harden. 30 minutes after reaching the peak temperature due to polymerization exotherm, the cell was removed from the hot water.
Then, it was heat treated in an air heating furnace at 130°C for 2 hours.
After cooling, remove the cell, crush the resulting resin plate in a clean box, and measure the MI value (230℃, load 3.8Kg)
is 5.0, refractive index _nD is 1.445, heat distortion temperature HDT is 98℃
A sheath component polymer was obtained.

The obtained core and sheath component polymers are combined into core and sheath components.
Supplied to a vented composite spinning machine with a double sheath structure 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 optical transmission fiber is 980dB/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, thereby obtaining 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 1500dB/
Km, but even after being exposed to a hot air heating furnace at 160°C for 1000 hours, the rate of decrease in light intensity was only 4%, indicating extremely 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) was obtained, and a precursor composition of polydimethylsiloxane (Shin-Etsu Silicone) was applied to the surface of this core component fiber.
After uniformly coating KE106LTV), 150
It was heated at .degree. C. for 10 minutes to form a polydimethylsiloxane film (refractive index: 1.42, thickness: 300 .mu.m).

This optical fiber had an excellent optical transmission loss of 890 dB/Km, and showed extremely excellent heat resistance and durability, with a decrease rate of light intensity of 2% after 1000 hours of exposure at 170°C.

Example 4 Methylamine aqueous solution (40%) based on 100 parts of polymethyl methacrylate obtained in Example 1
31 parts by weight was charged into a 3-volume autoclave, and the mixture was reacted for 3 hours in a 230°C oil bath with repeated nitrogen substitution.
A transparent resin N-methylmethacrylimide-methyl methacrylate copolymer was obtained.

The infrared absorption spectrum showed absorption characteristic of methacrylimide, and the imidization rate was 40%.

MI value of the obtained polymer (230℃, load 3.8Kg)
is 5.7, refractive index 1.530, specific gravity 1.20, heat distortion temperature 147℃
It was hot.

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).
m) was formed.

This optical fiber had an excellent optical transmission loss of 820 dB/Km, and exhibited extremely excellent heat resistance and durability, with a decrease rate of light intensity of 1% after 1000 hours of exposure at 130°C.

Example 5 90 parts of methyl methacrylate, 10 parts of methacrylic acid,
A methyl methacrylate/methacrylic acid copolymer was produced in the same manner as in Example 4 by adding and dissolving 0.75 parts of tert-dodecyl mercaptan and 0.4 parts of lauroyl peroxide.

An N-methylmethacrylimide/methyl methacrylate copolymer was obtained in exactly the same manner as the imidization method in Example 4.

MI value of the obtained polymer (230℃, load 3.8Kg)
is 7.5, refractive index 1.529, specific gravity 1.20, heat distortion temperature 145℃
It was hot.

In the same manner as in Example 4, fibers consisting only of the core component and sheath material were shaped.

This optical fiber has an excellent optical transmission loss of 950 dB/Km, and the decrease in light intensity after 1000 hours of exposure at 130°C was 1.5%, demonstrating extremely excellent heat resistance and durability.

Comparative Example 1 The polymethyl methacrylate obtained in Example 1 was used as it was, and the sheath material according to Example 1 was used to supply it to a vented composite spinning machine, and the spinning temperature was 240.
It was taken up at a spinning speed of 3 m/min at 140° C., and then continuously stretched 2.0 times at 140° C. and wound.

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) 98% by weight of a monomer whose main components are methyl methacrylate and 2% by weight or more of the ring structural unit % or less, and a sheath component consisting of a polymer having a refractive index 1% or more lower than that of the core component. .