JPS61141405A - Plastic fiber - Google Patents

Abstract

PURPOSE:To improve a transparency and a heat resistance of the title fiber by using a copolymer composed of a specific styrene and/or its derivative and dialkyl fumaric acid ester as a core material, and by using a polymer having a lower refractive index than that of the core material as a sheath material. CONSTITUTION:In the title film having the core and the sheath materials, the core material is composed of the copolymer of the styrene and/or its derivatives and dialkyl fumaric acid ester shown by the formula. The sheath material is composed of a polymer having a lower refractive index than that of the core material. In the formula, X is H, 1-4C alkyl group, halogen atom, CF3 group, (n) is 1-5, R1 and R2 are each 1-10C alkyl group, (a):(b) is (3:97)-(97:3). By using the prescribed core and sheath materials, the title fiber having >=100 deg.C heat resistance, good plasticity, workability and excellent transmission characteristic is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic optical fiber with excellent heat resistance and light transmission properties.

[Conventional technology]

Plastic optical fibers have traditionally been known to have cores made of highly transparent polymers such as polymethyl methacrylate and polystyrene (for example,
-89788, Special Publication No. 53-21660, etc.)
.

However, such plastic optical fibers suffer from increased light transmission loss as the temperature at which they are used increases, and may lack reliability as an optical signal medium.

Furthermore, such plastic optical fibers lack heat resistance and may not be usable depending on the purpose or location. The upper limit temperature at which plastic optical fibers that use polymethyl methacrylate or polystyrene as their cores can be used is approximately 80°C; at temperatures higher than that, the fibers will undergo thermal contraction, deformation, or structural distortion, and will no longer function as optical fibers. There was a desire to develop a plastic optical fiber with excellent heat resistance, as it could only be used in a narrow temperature range where it would no longer fulfill its function.

(Problems to be Solved by the Invention) However, the plastic optical fibers produced by the method described above are inferior to glass optical fibers in optical transmission properties, especially in heat resistance (upper limit operating temperature is 80°C or less); It has advantages such as good flexibility, light weight, and ease of processing. Taking advantage of these advantages, applications are being considered for short-distance communication light guides, sensors, industrial applications, and automotive applications, and some have been put into practical use. has been done.

Many of these applications require heat resistance,
For example, optical fibers used for optical data links for automobiles are heated at temperatures of 100 to 120 degrees Celsius due to heat buildup from the engine room.
It is required to withstand high temperatures. Plastic optical fibers having a core of polymethyl methacrylate yabori styrene cannot withstand use at such temperatures and therefore could not be applied.

The present inventors focused on and investigated the glass transition temperature of a polymer as a physical property that indicates the usability of a conventional plastic optical fiber core at high temperatures. The glass transition temperature of polymethyl methacrylate used as the core material is about 105°C, and that of polystyrene is about 100''C.

Looking at the relationship between the thermal shrinkage rate and flexibility of fibers with polymethyl methacrylate as their core, only a slight shrinkage is observed at temperatures below the glass transition temperature of polymethyl methacrylate, 1.05°C. When heated to temperatures above 11°C, shrinkage occurs within a very short time, deforming the fiber itself and reducing its translucency and mechanical strength, making it unusable for practical use. The cause of the shrinkage is that the molecules oriented during or after the spinning process are relaxed by heat in order to impart flexibility to the plastic optical fiber. “This stretching process is normally carried out to impart flexibility to such amorphous polymers, and without stretching it is difficult to obtain fibers with mechanical properties that can withstand practical use. It is also possible to heat set the fibers in advance to relax the orientation and eliminate heat shrinkage.

However, such treatment reduces the flexibility of the fiber itself. Therefore, in order to obtain fibers that can be used at high temperatures of 100° C. or higher, one method is to use a polymer with a high glass transition temperature as the core.

Many monomers such as methacrylic acid esters and styrene derivatives that provide polymers with high glass transition temperatures are known, but optical fibers with cores made of polymers with high glass transition temperatures obtained using these seven polymers have not yet been developed. However, the flexibility was poor and it was not practical. In addition to this addition polymer, polycarbonate is well known as a condensation polymer that provides a high glass transition temperature.

Its glass transition temperature is approximately 145 DEG C., and an optical fiber having this core as a core has already been proposed as a heat-resistant optical fiber (Japanese Patent Application Laid-Open No. 57-46204). However, the optical transmission properties were considerably inferior to optical fibers obtained using polymethyl methacrylate or polystyrene as cores. Polymers such as polysulfone and polyarylester are known as other polymers that exhibit a high glass transition temperature, but their transparency is insufficient due to the high spinning temperature of optical fibers and the contamination of polymer fractions and impurities. I failed.

The inventors believe that 660nm, 780nm or 850nm
As a result of intensive research to develop a plastic optical fiber that exhibits excellent light transmission in the wavelength range of high-brightness general-purpose light emitting elements such as m, and also has excellent heat resistance, we have developed a plastic optical fiber as shown in the example below. The present invention was achieved by finding that a polymer with excellent transparency and heat resistance can be obtained.

[Means for solving problems]

That is, in order to achieve the above object, the present invention has the following configuration.

(1) A plastic optical fiber characterized in that it is a copolymer of plastic photo-luric acid ester having a core-sheath structure, and the sheath is a polymer having a lower refractive index than the core-type combination.

(In the formula, X is H, an alkyl group of 01 to 4, halogen, CF
3 substituents, n is an integer from 1 to 5, R1 and R2 are C1
-1o alkyl group, a:bLt3:97-97;3. )'' In the present invention, the core is a polymer having the composition shown by the above formula, and the sheath is a polymer having a refractive index lower than that of the core-type combination.

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

The features of the present invention are as follows. That is, the aromatic hydrogen atom of styrene shown in the general formula is CH3,te
One or more types of styrene and styrene derivatives, which are replaced with atoms or atomic groups such as rt-C4R9, F, Cl3, Br, and CF3, to reduce the absorption exposed to harmonics of the vibrational transition of C)-1, 3 to 97% by weight, and one or more dialkyl fumarate esters having one or more substituents selected from alkyl groups in which R1 and R2 are 01 to CIO in the general formula. A polymer consisting of
An optical fiber having excellent transparency, a glass transition temperature higher than that of polymethyl methacrylate or polystyrene, and excellent heat resistance can be obtained, and flexibility can be improved. The following monomers can be used as component a to form the j' core polymer. consisting of styrene and one substituent, n
Mention may be made of chlorostyrene with n of 1 to 3, bromustyrene with n of 1 or 2 and/or trifluoromethylstyrene with n of 2, and fluorostyrene with n of 1 to 5. Those consisting of two types of substituents include halogenated styrene containing a plurality of F atoms and a maximum of two CrL atoms, a halogenated styrene containing a plurality of F atoms and a maximum of two Br atoms, and a plurality of F atoms. Halogenated styrene containing atoms and up to 2 CF3 groups, CO, and up to 2 CF3 groups
Examples of halogenated styrenes containing groups and monobromo/monotrifluoromethylstyrenes include halogens containing multiple F atoms, one CD atom, and one CF3 group. Examples include styrene oxide, halogenated styrene containing a plurality of F atoms, one 3r atom, and one CF3 group.

Among the above-mentioned styrene and styrene derivatives, preferred monomers are styrene, 0-chlorostyrene, m-chlorostyrene, 01m-chlorostyrene, and pentafluorostyrene.

The b component represented by the general formula used in the present invention is a dialkyl fumaric acid ester having a fumaric acid skeleton, and is an essential component for obtaining a plastic optical fiber having good light transmittance and excellent heat resistance. Specifically, the following monomers can be mentioned as dialkyl fumaric acid ester monomers.

That is, R1 and R2 in the formula are methyl, ethyl, n-propyl, 1so-propyl, n-butyl, cyclopentyl, a-menthyl, n-bornyl, and is.

- indicates a bornyl group, etc., and one or two of these
There are dialkyl fumarate esters obtained by combining more than one type of alkyl group.

Among the above dialkyl fumarate monomers, preferred are 1so-propyl, tert-butyl, cyclohexyl, cyclopentyl, n-bornyl, 1SO
- A monomer using one or more types of bornyl groups.

The core type combination in the present invention contains 3 to 97% by weight, preferably 20 to 80% by weight of one or more of styrene and styrene derivatives represented by the general formula, and one or more of dialkyl fumarate esters. 97-3% by weight
, preferably 80 to 20% by weight.

If the component represented by the general formula is 80% by weight or more (component a represented by the general formula is 20% by weight or less), the melting temperature of the polymer becomes extremely high and thermal/oxidative decomposition occurs, so it cannot be used.

When this monomer mixture is polymerized in the presence of oxygen, it is observed that the polymerization is delayed and starts to be inhibited by oxygen, and furthermore, the absorption intensity of the ultraviolet region of the polymer increases significantly and its absorption reaches the visible range. It was found that this effect caused a significant decrease in the light transmission performance of the manufactured optical fiber.

For example, if the air in the monomer mixture is not sufficiently replaced, the resulting polymer is colored and cannot be preferably used as an optical fiber.

The styrene and dicyclohexyl fumarate monomers are each carefully distilled and purified in a nitrogen stream, and then the styrene monomer and dicyclohexyl fumarate monomer are mixed, and the air in the 7mer is thoroughly purged with nitrogen. Optical fibers manufactured with polymers obtained by substituting the polymer and polymerizing under reduced pressure without exposure to air had good light transmittance.

As a polymerization method, any method such as bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, or precipitation polymerization is possible.
The most preferred method is the bulk polymerization method, which allows monomers, polymerization initiators, and chain transfer agents to be polymerized without exposing them to air. This is because in other methods, impurities, dust, etc. are mixed into the core assembly, and light scattering or absorption occurs due to these, resulting in a significant decrease in the light transmission performance of the obtained fiber. In the case of bulk polymerization, the viscosity of the system increases as the polymerization progresses, which tends to cause a gel effect, making it difficult to control the polymerization.However, by adjusting the polymerization temperature, type and concentration of initiator, etc. It is possible to control polymerization close to the theoretically achieved polymerization rate. It should be noted that if the volatile component is contained in the core-type combination in an amount of 11% or more, the resulting fiber will have low mechanical strength and a decrease in heat resistance. Usually 1% by weight
The following are preferred.

A common radical initiator can be used as the polymerization initiator. Preferably, a high-temperature decomposition type initiator that can be purified by distillation is used, such as di-t-butyl peroxide, t-butyl hydroperoxide, methyl ethyl ketone peroxide, acetyl peroxide, t-
-butylcumyl peroxide, 2-5-dimethyl-2
-5-di(t-butylperoxy) Organic peroxides such as hegisane, acetyl peroxide, propionyl peroxide, (J, A, C, S, 84.2922 (1
Examples include the azo compounds described in 962)), azobisisopropyl and azobiscyclohexyl.

As the molecular weight regulator, aliphatic mercaptans such as butyl mercaptan and hexyl mercaptan, mercaptans containing an acyl group such as mercaptoethyl acetate, and mercaptans containing a benzene ring such as phenyl mercaptan can be used, but in particular Molecular weight can be controlled only by changing the polymerization temperature without using a molecular weight regulator.

Temperature conditions can be freely selected depending on the seven-mer 1 initiator used or the polymerization rate achieved in the polymerization step, but the polymerization temperature is 90°C to 190°C, and the temperature in the volatile matter removal step is 190°C.
~250°C can be used.

Any polymer having a lower refractive index than the core type polymer can be used as the sheath polymer. For example, among the core-type combinations of the present invention, bentalfluorostyrene or
The refractive index (nd20) of a polymer using a monomer containing a large number of F molecules as a copolymerization component, such as tetrafluoro-trifluoromethylstyrene, is 1.45 to 1.50.
As the sheath material, fluoroalkyl methacrylate, fluoroalkyl acrylate alone or a copolymer, and a polymer made of tetrafluoroethylene, vinylidene fluoride, or hexafluoropropylene can be used. Furthermore, in the case of a core-type composite with a high refractive index, a wide variety of highly transparent polymers can be used as the sheath polymer.

For example, polymethyl methacrylate polymers, polyacrylates, vinyl acetate/ethylene copolymers, highly transparent olefin polymers such as poly4-methylpentene, styrene and their derivatives, polyesters, polyurethanes, etc. can also be used.

Optical fibers can be produced by melting and co-extruding core and sheath polymers, extruding core and sheath polymers, melt-coating a model combination, or coating a sheath polymer solution. .

Although the flexibility of the optical fiber manufactured in this manner is slightly inferior to that of polymethyl methacrylate optical fiber, it is practically acceptable, but the present invention is not limited to the examples below.

The glass transition temperature of the polymer is measured by the DSC method.
The Vicat softening temperature was measured according to JIS-7206, and the heat resistance of the optical fiber was measured according to the following method. Both ends of the optical fiber cut to a length of 5 to 15111 mm were optically polished, and the fibers were placed in a dryer equipped with a constant-rate heating device, and the light input and output ends were taken out of the dryer and the amount of output light was measured using a power meter at room temperature. . The temperature at which the received light level begins to decrease and the heat resistance are determined. The light transmittance of the optical fiber was measured using the cutback method, and the loss value of the optical fiber was determined according to the following formula.

L: Fiber length (m) P: Optical power value (dBm) S: Sample fiber r: Cutback reference fiber The polymer composition ratio was analyzed by IR, LJV, and NMR methods.

Example 11 Styrene 59% by weight, dicyclohexyl fumarate 41
% by weight, and 0.1 part by weight of di↑ert-butyl peroxide. After repeatedly freezing and degassing the mixture to remove oxygen, the temperature was raised to 100°C.
Continue to maintain the same temperature for 0 hours and increase the temperature by 10℃ until 160℃.
The temperature was raised at a rate of 1 hour, and the temperature was maintained at 180°C for 5 hours, after which the polymerization was completed. The polymerization rate at this point was 98%.

The temperature of the polymerization tank was roughly raised to 195°C, and the mixture was transferred to a spinning dope tank maintained at 215°C using nitrogen pressure at a gauge pressure of 0.5-/-. At the same time as the transfer, the inside of the spinning dope tank was brought to a pressure of 10 nwnl-10 via a vacuum line to remove volatile components. An optical fiber was produced by using a sheath component of vinylidene fluoride and tetrafluoroethylene in a molar ratio of 80:20, and extruding the core and sheath polymer simultaneously in concentric circles at 205°C. At that time, the temperature at which the core was combined was 200° C. as measured at the outlet of the mouthpiece, and the volatile component was 0.8% as measured by the GC method.

An optical fiber was prepared with a winding speed of 4 m7 minutes, a fiber outer diameter of 500 μm, and a core portion of 450 μm.

Analysis of the core-type composite used to create the optical fiber revealed that the polymer composition ratio was 59.5% by weight of P-styrene and 40.5% by weight of P-dicyclohexyl fumarate. Furthermore, the glass transition temperature of the polymer is 117°C, and the light transmittance of the obtained optical fiber is 300 dB/km (660 dB/km).
(stop). The heat resistance was 110°C, and it was confirmed that the heat resistance was improved compared to conventional plastic optical fibers.

Comparative Example 1 Styrene 100% by weight, n-butyl mercaptan 0.1
A monomer mixture consisting of parts by weight is repeatedly frozen and degassed,
After removing oxygen from the mixture, the temperature was raised to 130°C, kept at that temperature for 10 hours, and then raised to 160°C at a rate of 5°C/hour to complete the polymerization. Furthermore, the temperature of the polymerization tank was increased to 195
The temperature was raised to .degree. C., and the transfer was carried out in the same manner as in Example 1. The fibers were manufactured in the same manner as in Example 1. The glass transition temperature of the core-type assembly was measured and was 93°C. The heat resistance of the obtained optical fiber was measured and found to be 80°C.

Comparative Example 2 A monomer mixture consisting of 100% by weight of methyl methacrylate, 0.1 parts by weight of di-tert-butyl peroxide, and 0.15 parts by weight of n-butylcaptan was repeatedly frozen and degassed to remove oxygen, and the temperature The temperature was raised to 100°C, maintained at that temperature for 16 hours, and then raised to 160°C at a rate of 5°C/hour to complete the polymerization. Furthermore, the temperature of the polymerization tank was increased to 19
The temperature was raised to 6° C. and the transfer was carried out in the same manner as in Example 1. The sheath polymer shown in Example 1 was used, and an optical fiber was produced by combining cores and coextruding. The base part is 19
The temperature was 3° C., the winding speed was 4 m/min, and an optical fiber having an outer diameter of 500 μm and a core portion of 450 μm was manufactured.

When the glass transition temperature of the core-shaped composite was measured, it was found to be 105
It was at ℃. The heat resistance of the obtained optical fiber was measured and found to be 90°C.

Example 2 A monomer mixture consisting of 59.0% by weight of styrene, 41.0% by weight of cyclohexyl isopropyl fumarate, and 0.1 part by weight of di-tert-butyl peroxide was repeatedly frozen and degassed. After removing oxygen, the temperature was raised to 100°C, kept at that temperature for 20 hours, and then raised to 160°C at a rate of 10"C/hour to complete the polymerization. At this point, the polymerization rate was 97%. An optical fiber was prepared by carrying out transfer and composite spinning in the same manner as in Example 1. Analysis of the core-type amalgamation revealed that the polymer composition ratio was 60.0% by weight of P-styrene and P-cyclohexyl isopropyl fumarole. The rate was 40.0% by weight.The glass transition temperature was 115°C.The light transmittance of the obtained optical fiber was 320dB/km (660qm).The heat resistance was 10B, which was higher than that of conventional plastics. Improved heat resistance was confirmed compared to optical fiber.

Example 3 Styrene 55.0% by weight, diisopropyl fumarate 4
5.0% by weight, 0 di-tert-butyl peroxide
．． A monomer mixture consisting of 1 part by weight was repeatedly frozen and degassed to remove oxygen from the mixture, and then charged into a polymerization tank purged with nitrogen, and heated with ultra-high purity nitrogen at a gauge pressure of 5-/d. Polymerization was carried out at 100° C. for 2 hours under pressure to obtain a polymer mixture with a polymerization rate of 55%. From this point, transfer of the polymer mixture to the spinning dope tank started at a rate of 20 CC/hour, and at the same time, the monomer mixture was continuously supplied to the polymerization tank at a rate of 17 CC/hour using nitrogen pressure. did.

The spinning stock solution tank was maintained at a pressure of 1 mm H 1 liter and a temperature of 210°C. The monomer polymer was transferred to the spinning dope tank in 45 minutes. The sheath polymer used in Example 1 was used.

At that time, the temperature of the core combined is 210 as measured at the outlet of the cap.
℃, and the winding speed was 5 R1/min.

An optical fiber having an outer diameter of 500 μm and a core portion of 450 μm was prepared. Analysis of the core-type composite revealed that the polymer composition ratio was 56.0% by weight of P-styrene and 44.0% by weight of P-diisopropyl fumarate. Moreover, the glass transition temperature was 116°C. The light transmittance of the obtained optical fiber is 330dB/km (660qm)? ) Tsuta. The heat resistance was 109°C, and it was confirmed that the heat resistance was improved compared to conventional plastic optical fibers.

Example 4 A monomer mixture consisting of 60% by weight of p-tert-butylstyrene, 40% by weight of diisopropyl fumarate, and 0.1 part by weight of di-tert-butyl peroxide was repeatedly frozen and degassed to remove oxygen from the mixture. After removal, the temperature was raised to 100°C, kept at that temperature for 20 hours, and then raised to 160°C at a rate of 10°C/hour, and then raised to 180°C.
After holding for 5 hours, the polymerization was completed. The polymerization rate at this point was 98.5%. Roughly increase the temperature of the polymerized layer to 205
Example 1
Transfer and removal of volatile components were carried out under the same conditions as. An optical fiber was prepared using the sheath component shown in Example 1. At that time, the temperature at which the core was combined was 205° C. as measured at the outlet of the cap. The winding speed was 4 m/min, the fiber outer diameter was 500μ, and the core was 450μ. Analysis of the core type composite used to create the optical fiber revealed that the polymer composition ratio was 61% by weight of P-tert-butylstyrene and P-tert-butylstyrene.
Diisopropyl fumarate was 39% by weight. The light transmittance of 1q optical fiber is 330dB/km (66
Qnm). The glass transition temperature of the polymer is 126℃
I failed. The heat resistance was 120°C, and it was confirmed that the heat resistance was improved compared to conventional plastic optical fibers.

〔Effect of the invention〕

The plastic optical fiber of the present invention has the following features compared to conventional ones.

(1) As for heat resistance, a plastic optical fiber that can withstand use at temperatures of 100°C or higher can be obtained.

(2) Excellent flexibility and good workability.

(3) Excellent optical transmission properties.

Claims (2)

[Claims] (1) In plastic optical fibers with a core/sheath structure, the core is styrene and/or
Or a plastic optical fiber, which is a copolymer of a styrene derivative and a dialkyl fumaric acid ester, and the sheath is a polymer having a lower refractive index than the core polymer. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula,
R_2 is an alkyl group of C_1_ to_1_0, a:b is 3
:97 to 97:3. ) (2) The plastic optical fiber according to claim (1), wherein the polymer mainly composed of styrene and a styrene derivative-dialkyl fumaric acid ester copolymer has a heat resistance temperature of 100° C. or higher. (However, the heat resistance temperature refers to the value measured according to JIS-K-7206.)