JPS60242404A - Preparation of plastic optical fiber - Google Patents

Abstract

PURPOSE:To obtain plastic optical fiber having a core consisting of polymethacrylic ester having superior light transmitting characteristic by prepg. the core by block polymn. at a specified temp. CONSTITUTION:A monomer consisting essentially of methacrylic ester is mixed with additives in a mixing vessel 15 and the mixture 16 is charged to a polymn. vessel 1 and polymerized by circulating a heat medium introduced from an introducing hole 20. The polymn. temp. is elevated gradually from 90 deg.C to 200 deg.C, thus, a polymer having uniform quality and superior transparency is obtd. with conversion as high as >=90% by the block polymn. method. Obtd. core polymer is transferred to a spinning soln. tank 2 where volatile matters are removed out of a vent hole 10. Then, the spinning soln. tank 2 is upset and a piston 4 is pushed down to extrude the core polymer through a die 28. An opening 26 is provided to a die block 24 so as to permit simultaneous extrusion of a sheath polymer. The opening 26 is connected to a sheath polymer extruder 25.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a plastic optical fiber with excellent light transmission performance.

[Conventional technology and problems]

It is already known that plastic optical fibers have a concentric structure using polymethyl methacrylate (hereinafter referred to as PMMA) for the core material and a fluorine-containing polymer having a lower refractive index than the core material for the sheath material.

When PMMA is used as the core through which light propagates, CI-
Since absorption based on harmonics of one-coupling vibrational transition absorption exists even in the visible range, there is a natural limit to reducing the loss of optical fibers.

Deuterated PMMA (Special Publication No. 57-516
45) or deuterated polystyrene (Japanese Unexamined Patent Application Publication No. 1973)
An optical fiber having a core of 7-81204) has been invented. In particular, optical fibers having deuterated PMMA as their core have been shown to have excellent light transmittance not only in the visible wavelength range but also in the near-infrared wavelength range of 850 nm.

In order to produce an optical fiber with excellent optical transmission properties, it is necessary to reduce as much as possible non-specific losses other than Rayleigh scattering loss and absorption loss, which are inherent optical loss factors of the core material through which light propagates.

The non-specific loss factors considered to be particularly important are:
Possible causes include foreign matter such as dust that may cause scattering loss, inorganic or organic impurities that may cause absorption loss, modified polymers, and structural defects when used as an optical fiber. It is difficult to quantitatively relate all of these factors to the optical transmission performance, that is, the transmission loss value (dB/km), and the details of each individual factor are currently not understood.

In order to avoid the contamination of foreign substances, which is one of the factors mentioned above, a method has already been proposed in which the core-forming polymer is produced by a bulk polymerization method, and the process from polymerization to spinning is carried out continuously without taking out the polymer outside the apparatus. There is.

For example, the polymerization rate is 50-8 at a temperature of 130-160°C.
One example is a method (Japanese Patent Publication No. 53-42261) in which continuous bulk polymerization is carried out so that the polymer is 0%, fed to a single-screw extruder equipped with a vent, and volatile matters are continuously removed to produce a core-type polymer.

Alternatively, a monomer mixture from which impurities, dust, and oxygen in the core polymer have been removed as much as possible is subjected to stationary bulk polymerization at a temperature above the glass transition temperature of the polymer to a polymerization rate of nearly 100%, and then the temperature is lowered to below the glass transition temperature. A method of obtaining a clean polymer with few microvoids by melt-spinning (Japanese Patent Application Laid-open No. 57-81205, Japanese Patent Application Laid-open No. 57-8440)
3) can be mentioned.

Furthermore, to avoid contamination of the polymer due to thermal degradation of the polymer or metal leaching from the equipment, the purified and cleaned monomer mixture was pressurized in the polymerization vessel to avoid free liquid levels. A method of static bulk polymerization in the range of 70 to 140°C to a polymerization rate of nearly 100% to produce a rod-shaped polymer, which is then taken out of the polymerization container and then fed to a ram extruder for spinning (Japanese Patent Publication No. 58 -68003).

In the production of optical fibers, the polymer forming the core must satisfy practical properties and be optically transparent, so special considerations are required in the production of core-shaped composites.

However, as a result of the inventors' studies to produce a low-loss plastic optical fiber, it was discovered that there were some problems with this method.

That is, in order to remove volatile components, mainly monomers, in the polymer mixture, a screw extruder with a vent hole,
Generally, methods using devices such as an agitated thin film evaporator or a rotating disk devolatilizing extruder (Japanese Patent Publication No. 58-50644) are known, but because the polymer melt has a high viscosity, the polymer has a high viscosity. The shear force is added and significant heat is generated. When such a method is used to manufacture a core-shaped composite, there is a problem in that ultraviolet light absorption tends to increase due to thermal deterioration or metal elution.

f! Even if polymerization conditions are selected that theoretically achieves a polymerization rate of 100%, a few percent of monomers or oligomers are present, and a volatile matter removal step is necessary to obtain a polymer that poses no practical problems. be. This is because if the polymer contains 2% or more of volatile components, the resulting fiber will not satisfy practically necessary properties such as heat resistance and mechanical strength.

Furthermore, synthetic raw materials such as deuterated PMMA are
When using a polymer that is more expensive than MMA and using a similar optical fiber manufacturing process, there are problems in terms of cost and practical application from an industrial standpoint.

In view of the above, we have conducted extensive research into methods for manufacturing optical fibers with excellent light transmission properties and low cost, and as a result, we have arrived at the special manufacturing method of the present invention.

An object of the present invention is to provide a method for manufacturing a plastic optical fiber having a core made of polymethacrylic acid ester and having excellent light transmission performance.

[Means for solving problems]

The present invention provides a method for producing a plastic optical fiber using a polymer mainly composed of polymethacrylic acid ester as a core component, in which the core is polymerized in bulk at a temperature of 90 to 200°C to a polymerization rate of at least 90%. Then, the polymer mixture was fed in a molten state into a spinning dope tank composed of a piston and a cylinder and kept under reduced pressure, and the mixture was kept stationary under reduced pressure to remove volatile components. The present invention relates to a method for producing a plastic optical fiber, characterized in that the core assembly is extruded into a base by driving a piston and used as a core component.

Next, the features of the present invention will be explained in detail.

The features of the present invention are as follows.

That is, when polymerizing a monomer whose main component is polymethacrylic acid ester, a high polymerization rate of 90% or more can be achieved by bulk polymerization by gradually raising the polymerization temperature in the temperature range of 90 to 200°C. A polymer with uniformity and excellent transparency can be obtained, and since there is little unpolymerized monomer, residual monomers can be easily removed, and the polymer can be extruded only by driving the piston. This eliminates the need to use equipment with rotating parts, such as gear pumps or screw extruders, and avoids thermal deterioration due to abnormal heat generation of the polymer, elution of metals, and contamination of foreign matter caused by wear of the rotating parts. It is.

Furthermore, the production method according to the present invention has the effect that it is easy to design equipment to improve the yield from monomer to polymer and from polymer to optical fiber, which leads to cost reduction. There is also a point.

Furthermore, each process will be explained.

In the polymerization process, a bulk polymerization method is used, but in other polymerization methods, such as suspension polymerization, emulsion polymerization, or solution polymerization, suspending agents, emulsifiers, or solvents enter the polymer as impurities, causing optical problems. This method cannot be used because it is impossible to obtain a physically pure polymer, and the contamination of foreign substances contained therein is unavoidable.

In the polymerization reaction, a method in which a polymerization initiator that generates radicals by thermal decomposition and a chain transfer agent are coexisting is most preferably used, but a method in which the polymerization is initiated using radiation or light can also be used.

In the case of bulk polymerization, it is often accompanied by a gel effect in which a rapid increase in the polymerization rate is observed as the viscosity of the system increases as the polymerization progresses, making it difficult to control the polymerization. However, as seen in the known examples (JP-A-57-81205, JP-A-57-84403), there is a method of polymerizing at a polymerization temperature higher than the glass transition temperature of the polymer, or a method as seen in the known example (JP-A-58-68003). A core-type composite is produced by bulk polymerization using a method of polymerizing by mechanically pressurizing the monomer mixture at a relatively low temperature so that a free liquid level does not occur.

The present inventor has also investigated and found that by selecting the type, concentration, and polymerization temperature of the initiator, polymerization can be achieved by bulk polymerization even if the polymerization is carried out at a temperature of 90°C or higher, and even if a free liquid surface exists. It was found that it is possible to produce methacrylic acid ester.

That is, the polymerization is substantially started at a temperature of 90° C. or higher, and as the polymerization progresses, it is allowed to proceed according to a predetermined temperature program. The apparent polymerization rate can be kept constant until the polymerization rate approaches 80% by changing the type and concentration of the initiator and the amount of the chain transfer agent. Polymerization temperature is 90-200℃
℃ range, preferably 90 to 180℃.

In particular, it is preferable to maintain the temperature at 90 to 150°C until the polymerization rate is 80% or less. If the temperature is raised in a state where a large amount of monomer is present, the production of oligomers will increase, and although the reason is unknown, colored substances are likely to be generated, which is not preferable.

Although it is possible to increase the polymerization rate to 98% or more, it is practically 1
It is impossible to achieve a polymerization rate of 0.00%.

In order to increase the polymerization rate to 98% or more, it is necessary to extremely extend the polymerization time, which is not preferable in terms of the process.

Furthermore, when 2% or more of volatile components were present in the polymer, the obtained fibers did not satisfy the practically necessary properties such as mechanical properties and heat resistance. Therefore, a step for removing volatile components mainly consisting of monomers and oligomers is absolutely necessary.

For removing volatile matter from polymers, a screw extruder with a vent hole, a stirring thin film evaporator, or a rotating disc devolatilizing extruder (Japanese Patent Publication No. 58-50644) is equipped with a rotating part, which applies high shear force to the polymer. Polymers with excellent transparency cannot be obtained when the process is carried out using a recycling device.The reasons for this are as follows.
This is thought to be due to the inclusion of abrasion debris such as metal, elution of metal, or thermal deterioration due to heat generation of the polymer due to the presence of a rotating part. Optical fibers manufactured using this method cannot be used because their absorption in the ultraviolet region increases and affects even the visible region.

Furthermore, for the same reason, equipment having such a rotating part cannot be used when transporting polymers.

Known examples for polymer extrusion (Japanese Patent Publication No. 58-F38003
A method using a ram extruder is already known, as shown in >, but the manufacturing method of the present invention is that all the core molds are handled in a molten state, and moreover, the core molds are not taken out of the device until extrusion. There was a big difference in the results, and there was no contamination of the polymer by dust.

At the same time, the core type combined mixture with a polymerization rate of 90% or more is fed into a spinning dope tank kept under reduced pressure and is composed of a piston and a cylinder, and at the same time, volatile components are removed to at least 2% by weight or less. If it is less than 90%, foaming of the polymer becomes significant, the polymer becomes bulky, the transfer efficiency into the spinning dope tank decreases, and at the same time, the volatile matter removal efficiency becomes extremely poor, so it cannot be used. Preferably the polymerization rate is 94%
That's all.

In other words, the production method according to the present invention includes a polymerization step, a volatile matter removal step, and an extrusion step, and an optical fiber with excellent translucency can be obtained only when the conditions of the present invention are used in each step. It is.

The core-type combined polymethacrylic ester used in the present invention includes methyl, ethyl, n-propyl, 1so
-propyl, n-butyl, 5ec-butyl, tart-
Alkyl methacrylate derivatives such as butylcyclohexyl, adamantanyl, isophoronyl, aryl methacrylate derivatives such as phenyl and benzyl, halogenated aryl methacrylate derivatives such as pentafluorophenyl and pentafluorobenzyl, and deuterated derivatives of these derivatives alone. Alternatively, it is a polymer formed mainly from a mixture of one or more types.

In the present invention, in terms of loss reduction and manufacturing cost,
It is most effective when a polymer formed from a deuterated derivative is used as the core. For example, there is a polymer whose main component is D8-MMA, which is obtained by replacing all the hydrogens of methyl methacrylate (hereinafter referred to as MMA) with deuterium.
MA and D3-MMA in which the methyl groups of the ester residues are substituted with deuterium can be used as well, and are polymers formed from a mixture with 80% preferably 90% slack monomers. Moreover, a polymer formed by an azeotrope composition of these monomers and deuterated styrene can also be preferably used.

In the present invention, as a polymer other than polymethacrylic acid ester, deuterated polystyrene or a known example (
Copolymers described in JP-A-56-164597) can also be preferably used.

Other copolymerization components include methyl acrylate, ethyl, propyl, butyl, cyclohexyl, adamantanyl, isophoronyl, phenyl and benzyl esters of acrylic acid and methacrylic acid, and styrene, chlorostyrene, fluorostyrene, methylstyrene, t-butylstyrene, etc. Styrene derivatives, deuterated products thereof, etc. can be used, but are not particularly limited.

The manufacturing process of core assembly is the process that has the greatest impact on the performance of the manufactured optical fiber, and requires sufficient consideration. First, the monomer used for polymerization is 1. It is desirable that it contains virtually no impurities, but the water content is 400 PPM or less,
If the polymerization inhibitor has a content of 110 PP or less, there will be little problem. If the water content is high, foaming is likely to occur during polymerization, and not only will a uniform polymer not be obtained, but the polymer will become bulky due to foaming, resulting in unnecessary contamination of the polymerization tank. This is because if a large amount of polymerization inhibitor is contained, the produced optical fiber will have a strong absorption of ultraviolet light, which will have a negative effect on the light transmission performance.

Polymerization initiators that can be used include di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexene (3), diisopropylbenzene peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexene (3). Dimethylhexane-2,5-
Peroxides such as dihydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butylcumyl peroxide and J, A, C,'S,
, 84.2922 (1962), and
Examples include azobisisopropyl and azobiscyclohexyl, which can be used alone or in combination.

As the molecular weight regulator, aliphatic mercaptans such as butyl mercaptan and hexyl mercaptan, and mercaptans containing an amyl group such as ethyl mercaptoacetate can be used.

Dust or foreign matter in the monomer, polymerization initiator, and molecular weight modifier must be removed as much as possible because it causes scattering loss in the produced polymer. Dust can be removed by distilling it under reduced pressure. For this purpose, it is desirable to use comonomers, polymerization initiators, and molecular weight regulators that can be distilled under reduced pressure.

Even if foreign matter or dust is removed from the raw materials, if the equipment is not sufficiently cleaned, equipment that easily generates dust or foreign matter is used, or the airtightness of the equipment is poor. If the coalesced raw material or polymer comes into contact with the outside air, the light transmittance of the produced fiber will be extremely poor.

Removal of dust and foreign substances throughout the process is achieved by cutting off the inflow of outside air from outside the process and then cleaning the inside of the apparatus with clean steam.

As the vapor that can be used, water vapor or vapor of an organic solvent having a relatively low boiling point can be used.

For example, acetone, methanol, ethyl acetate, trichloroethane, benzene, monomers, etc. can be used. The steam is condensed on the inside walls of the device, cleans all walls, and is discharged outside the device. The degree of cleaning can be determined by applying a laser beam to the discharged liquid and checking the scattering intensity.

The most preferably used polymerization tank is one that is highly airtight under reduced pressure and under increased pressure, and has a height/diameter ratio in the range of 4 to 20.

The spinning dope tank composed of a cylinder and a piston has a highly airtight structure both under reduced pressure and under pressurized conditions, and is desirably connected to the polymerization tank through a detachable connection part.

The polymerization tank, spinning dope tank, and connecting parts must have smooth inner surfaces and be inert to the monomer mixture or core type coalescence, and must be chromium-plated or Kanigen-plated on the surface of inorganic glass or metal. can be preferably used.

A two-step polymerization method can be used in which stirring polymerization is followed by stationary bowl polymerization, but by making the polymerization tank a multi-vessel structure, it is possible to use the stationary polymerization method from the initial stage of polymerization to produce a uniform polymer. can be manufactured.

For the removal of volatiles, a method is preferably used in which the surface area of the polymer is increased by extruding the polymer in the form of a thread into a spinning dope tank maintained under reduced pressure. A method of increasing removal efficiency by flowing the polymer along the inner wall of the devolatilization tank can also be used, but if the polymer is brought into contact with a hot metal surface in a state that contains a large amount of residual monomer, the reason is unknown. There was a problem in that colored degraded products were likely to be generated.

Most preferably, the core is extruded only by driving a piston, and is combined with the sheath polymer at the base to produce the optical fiber by melt coextrusion.

As a sheath polymer, the refractive index is 1.45 (n D”)
Among the following, polymers made of vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, etc., or polymers made of esters of acrylic acid and methacrylic acid with fluoroalcohols, etc. can be used, but there are particularly stipulated conditions. It's not a thing.

Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples.

A schematic diagram of the apparatus used in the present invention is shown in FIG.

It consists of a polymerization tank (1) and a spinning dope tank (2), each equipped with a jacket capable of circulating heat medium, and connecting pipes (9) and 09 connect vacuum lines (b) and nitrogen lines θ1) and 09, respectively.
■Connected to. Polymerization tank (1) has an inner diameter of 40φ and an inner height of 5
It has a cylindrical shape and can be sealed with a valve. The spinning dope tank (2) consists of a cylinder (3) and a piston (4), and has an inner diameter of 35φ and an inner height of 400 rTW.
II. The cylinder (3) and piston (4) are kept airtight by a tightening type packing (6) and a variseal (5). The polymerization tank (1) and the spinning dope tank are connected via a connecting pipe (9), a removable connecting member <8), and a flange (7).

After mixing the predetermined monomers and additives in the mixing tank θ9, the mixture (l [D) is transferred to the polymerization tank (1) through the condenser (1).
The heating medium is circulated through the charging introduction hole (to) to carry out polymerization.

Using nitrogen pressure, the polymerized core type is transferred to the spinning dope tank through the valve and connecting pipe (9), and then transferred to the flange (7).
Then, volatile matter was removed from the exhaust hole 00) provided in the connecting member <8) using a vacuum line.

As shown in Figure 2, fiber production is carried out in a spinning dope tank (
2) was inverted and fixed to the base block (24), and the piston (4) was pushed down at a constant speed by the drive motor to extrude the core type assembly through the base (28>). Base block (
24) A polymer inlet (26) is provided so that it can be extruded simultaneously with the sheath polymer, and the sheath polymer extrusion IE!
(25) is connected. Extruded composite yarn (27)
was wound on a winder (29) at a constant speed to produce an optical fiber.

The light transmittance of the optical fiber was measured as follows.

The light emitted from the halogen lamp is split by a diffraction grating, focused by a lens, and then enters one end of an optical fiber. The light emitted from the other end is detected as optical power by a photodiode. Next, the optical fiber was measured using the so-called cut-back method in which the fiber was cut at a distance of about 2 m from the input end while the input end was fixed and the measurement was repeated in the same manner, and the loss value of the optical fiber was calculated according to the following formula.

P: Fiber length (m) P: Charging force value (63 m) S: Sample fiber r: Cutback reference fiber The monomer used in the example was purified as follows.

D8-MMA (deuteration rate 99.2%) was passed through a basic aluminum oxide column and charged into a distillation pot, and vacuum distilled under a nitrogen atmosphere at a pressure of 150 mmHD to cut off 10% of the distillate and 15% of the after-distillate. A middle distillate of 75% was used in the polymerization. MMA was purified in the same manner.

When charging the monomer mixture to the polymerization tank, the purified monomer,
Weigh and mix the polymerization initiator and chain transfer agent,
After removing dissolved oxygen by freezing and degassing, the mixture was distilled under reduced pressure and charged into a polymerization tank.

Example 1 A monomer mixture of 100 parts by weight of D8-MMA, 8,5 x 10 parts of di-t-butyl peroxide, and 3 x 10 parts of n-butyl mercaptan was charged into a polymerization tank and heated at 105°C for 10 minutes. After maintaining the temperature of the polymerization tank for 10 hours
Raise the temperature to 160℃ at a heating rate of ℃/hour @Gakun f
Thousand ta to t-= mountain shiki no sen＾hiro (sen〇ζv↑
I was nervous. The temperature was further raised to 200° C., and the polymer was transferred into the spinning solution tank at a speed of 5 cc for 7 minutes using the pressure of ultra-high pure nitrogen (gauge pressure 0.6 k11/cJ). 200
The polymerization rate was 96% when the temperature was raised to 0.degree. C., and almost no increase in the polymerization rate was observed. The spinning solution tank was maintained at a pressure of 200 mmHg and a temperature of 210°C.

The optical fiber was produced by simultaneous melt extrusion at 193° C. using tetrafluoroethylene/nylidene fluoride copolymer as the sheath polymer. The monodominant residual rate of the obtained core-type composite was 0.5% and the oligomer was 0.1%, and the light transmittance was excellent as shown in Table 1 when a 30 m section was cut out from the fiber and measured. there were. Core diameter is 470μ
, the pod thickness was 13μ.

Example 2 D8-MMA 100 parts, azobis-1-butane 7
．． 2 x 10' parts by weight, n-butyl mercaptan 2.5 x
10-3 parts by weight of the monomer mixture was charged into a polymerization tank, and 1
After maintaining the temperature of the polymerization tank at 30℃ for 12 hours, the temperature was increased to 11℃/
Polymerization was carried out by raising the temperature to 180° C. at a temperature increase rate of 1 hour. The polymerization rate at this time was 96%. The temperature was further increased to 205° C. and the polymer was transferred to the spinning dope tank in the same manner as in Example 1. The spinning dope tank has a pressure of 150 mm l-I
Q. The temperature was kept at 215°C. The optical fiber was manufactured by co-melt extrusion at 200° C. using a polymer mainly composed of tetrafluorobutyl methacrylate as the sheath polymer. The monomer residual rate of the obtained core type union was 0.4
Weight%, oligomer is 0.15%, translucency is 55
As shown in Table 1, the results of measurements on the 0 m fiber were excellent. The core diameter was 453μ, and the diameter of the sheath was 21μ.

Comparative Example 1 A single rod mixture of 100 parts by weight of D8-MMA, 3.0 x 10' parts of di-t-butyl peroxide, and 3 x 10 parts of n-butyl merca' butane was charged into a polymerization tank. The temperature of the polymerization tank was maintained at ℃ for 16 hours.
Polymerization was carried out by raising the temperature to 160°C at a temperature increase rate of 0°C/B, y. The polymerization rate at this time was 84%. The temperature was further raised to 180° C. and the polymer was transferred in the same manner as in Example 1. The spinning dope tank has a pressure of 200m+nH.
17. The temperature was kept at 200°C, but due to significant foaming of the polymer during the process, the polymer invaded the degassing holes and degassing became impossible, so the pressure was changed to 400 mmH (+). Simultaneous melt extrusion was carried out at 190°C using a tetrafluoroethylene/vinylidene fluoride polymer.The monomer residual rate of the obtained core-shaped composite was 1.6% by weight, and the oligomer content was 0.6%. The obtained fiber lacked flexibility and had slightly poor light transmission performance as shown in Table 1.The core diameter of the optical fiber was 465μ;
The pod thickness was 19μ.

Comparative Example An optical fiber was manufactured under the same conditions as in Example 1 except that MMA was used as the monomer. Table 1 shows the light transmission performance of the obtained fiber. Core diameter is 455μ, -sheath thickness is 2
It was 1μ.

Comparative Example 3 A core type assembly was produced under the same conditions as in Example 1 except that MMA was used as the monomer. To manufacture optical fibers, a gear pump was inserted between the spinning dope tank and the spinneret block to extrude the core assembly. The spinning temperature was 195° C., and the optical fiber was manufactured by simultaneous melt extrusion using tetrafluoroethylene/vinylidene fluoride polymer as the sheath polymer. The light transmittance of the obtained fibers was variable, and the light transmittance loss value tended to decrease from the beginning to the end of the discharge of the core-type combination. The transmission loss factor is 590 dB/kill (570 μm) at 20 m of fiber in the early stage of spinning, and 232 dB/kill (570 μm) at the best point in the latter half.
km (570 μm). Table 1 shows the light transmission loss values at the best part in the second half.

The fiber core diameter is 465 μm, and the sheath thickness is 21 μm.
Met.

Table 1 [ 〔Effect of the invention〕 The present invention exhibits the following effects.

(2) Since bulk polymerization is carried out at a temperature of 90 to 200°C, polymerization can be carried out to a high polymerization rate, and residual monomers can be easily removed.

◎ Since the polymer is extruded only by driving the piston, there is no elution of metal due to abrasion of the rotating parts, and contamination of foreign substances can be avoided.

Since there is no contamination of O foreign matter and no shearing force is applied to the polymer, a plastic optical fiber with excellent translucency can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a core-type combination production apparatus, and FIG. 2 is an explanatory diagram of a spinning apparatus for producing fibers from the core-type combination. 1: Polymerization 1 2 + Spinning dope tank 3 Niji cylinder - 4 = Piston 5: Variseal 6: Packing 7: Flange 9: Connecting pipe 10: Connecting pipe 18: Condenser 20: Heat medium inlet 21: Heat TS inlet 22: Connecting pipe
23: Valve 24: Base block 27: Fiber 28 Niro gold 2
9: Winder Patent Applicant Toshi Co., Ltd. Figure 1 Figure 2 Manabu Shiga, Commissioner of the Japan Patent Office (Monday, Showa) 1. Indication of the case 1982 Patent Application No. 94545 2. Name of the invention Plastic optical fiber Manufacturing method 3, relationship with the case of the person making the amendment Patent applicant address 2-2 Nihonbashi Muromachi, Chuo-ku, Tokyo Name (3
15) Masatoshi Ito, Representative Director and President of Toshi Co., Ltd. 4. Date of amendment order Voluntary 5. Number of inventions increased by amendment: None 6. Column 7 of “Detailed description of the invention” of the specification to be amended, Amendment (1) "tert-butylcyclohexyl, adamantanyl, isophoronil" on page 12, lines 12-13 in the description of contents of "
tert-butyl, cyclohexyl, adamantanyl,
Isobornyl” is corrected. (2) On page 13, lines 8 to 10, "Can be used in the same way, and is an 80% polymer." instead of "Can be used in the same way." I will correct it. (3) “Isophoronil” on page 13, lines 19-20
is corrected to "isobornyl". (4) Correct “amyl group” on page 15, line 11 to “acyl group”. (5) Correct “Halogen lamp” on page 20, line 10 to “Tungsten lamp”. (6) Correct “fluctuation force” in line 7 of page 25 to “fluctuation.”

Claims (1)

[Claims] In a method for manufacturing a plastic optical fiber using a polymer mainly composed of polymethacrylic acid ester as a core component, the core is polymerized in bulk at a temperature of 90 to 200°C to a polymerization rate of at least 90%, and then The polymer mixture is fed in a molten state into a spinning dope tank that is kept under reduced pressure and is made up of a piston and a cylinder, and is kept stationary under reduced pressure to remove volatile components. 1. A method for manufacturing a plastic optical fiber, characterized in that the combined core type is extruded into a base by driving and used as a core component.