JPS61281204A - Super heat resistant plastic optical fiber and its production - Google Patents

Abstract

PURPOSE:To obtain the titled fiber which has an excellent optical transmitting property and a heat resistance property of 140 deg.C, by using a polymer composed of a six membered cyclic acid anhydride, a methacrylic acid and a methacrylic acid tertiary butylate as a core component, and a transparent polymer having a lower refractive index than that of the core component as a sheath component respectively. CONSTITUTION:The polymer constituting the core component is composed of 95-100wt% six membered cyclic acid anhydride shown by the formula, and 0-5wt% methylmethacrylate and <=1.0wt% tertiary butyl methacrylate. The sheath component coating the core fiber is preferable to be the hard and transparent polymer having the lower refractive index than that of the core component. The sheath component is further preferable to be the transparent polymer which has a high softening point and has the difference of the refractive indexes between the core and the sheath components by >=3%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-resistant plastic optical fiber that can be used in automobiles, outdoor ducts exposed to direct sunlight, and high-temperature factories with poor thermal environments.

[Prior art] Conventionally proposed heat-resistant plastic optical fibers include polycarbonate, copolymers of methyl methacrylate, maleic anhydride, and styrene, copolymers of methyl methacrylate and α-methylstyrene, and copolymers of methyl methacrylate and isobornyl. Those having a core of methacrylate or bornyl methacrylate copolymer have been proposed.

[Problems to be Solved by the Invention] Although polycarbonate plastic optical fibers that have been proposed so far have excellent heat resistance, they have drawbacks in light guiding performance and can only be used over extremely short distances. On the other hand, plastic optical fibers based on methyl methacrylate, styrene, and maleic anhydride copolymers have problems in mechanical strength, making them unsuitable for use in moving objects.

In the end, there is still no plastic optical fiber that has excellent light guiding performance and excellent heat resistance.

[Means for Solving the Problems] The present inventors have already developed a plastic optical fiber consisting of six-membered cyclic acid anhydride units, methacrylic acid units, styrene units, and methyl methacrylate units as a plastic optical fiber with high heat resistance and transparency. We are developing plastic optical fibers based on coalescence, but this core-type coalescence is induced secondarily by dehydrating or removing methanol from a copolymer of methacrylic acid, styrene, and methyl methacrylate at high temperatures. It is something that Although the six-membered cyclic acid anhydride unit is a component that imparts heat resistance to the polymer, it has been impossible to increase the concentration of this unit component to a high concentration exceeding 95% by weight. The reason for this is that the six-membered cyclic acid anhydride units are derived from methacrylic acid units, and as the number of methacrylic acid units increases, intermolecular crosslinking reactions occur and the fluidity of the polymer deteriorates. Therefore, heat resistance had to be given up at the upper limit of the concentration of six-membered cyclic acid anhydride units.

However, in polytert-butyl methacrylate obtained by polymerizing tert-butyl methacrylate without using methyl methacrylate and methacrylic acid, butene is relatively easily eliminated and a polymer consisting of six-membered cyclic acid anhydride units is formed. It is known to do. (D.H.Grant
and N., Grassie.

Polymer Earth, (1960)) By the way, when this tert-butyl methacrylate is copolymerized with methyl methacrylate, first the tert-butyl methacrylate is
Since the butyl unit becomes a methacrylic acid unit and reacts with the adjacent methyl methacrylate unit, this method has fewer advantages than when methacrylic acid is used as a starting material.

Polytert-butyl methacrylate can be easily produced by suspension polymerization or batch polymerization, and a known method is to heat-treat the isolated polymer under reduced pressure to perform a cyclization treatment. However, this method requires several hours of cyclization time and is undesirable because it causes coloration.

Therefore, the present inventors discovered that the objective could be achieved by synthesizing polytert-butyl methacrylate by continuous solution polymerization or continuous bulk polymerization, and heating the resulting polymer solution for a short time under reduced pressure. I arrived at the eggplant.

The core type assembly of the present invention has a composition consisting of 95-100% by weight of six-membered cyclic acid anhydride units, 0-5% by weight of methyl methacrylate units, and 1.0% by weight of tert-butyl methacrylate units. % by weight or less.

Here, the methacrylic acid unit cannot be cyclized into the six-membered ring acid position after the tert-butyl methacrylate unit undergoes a debutenization reaction, but it is used to suppress OH absorption, which causes light guide loss in plastic optical fibers. In order to prevent similar fluctuations in light guide performance due to moisture absorption, it is better to have fewer methacrylic acid units. Preferably it is 2% by weight or less.

Furthermore, the tert-butyl methacrylate unit is thermally unstable and causes foaming during fiber molding, so it must be kept at 1% by weight or less.

Such a core-type combination is tert-butyl methacrylate 10
This is polymerized as a solution consisting of 0% or tert-butyl methacrylate and 2-70% by weight of a solvent, and then the polymer solution is heated under reduced pressure at high temperature to
Obtained by holding for 5 minutes.

Although continuous bulk polymerization without using a solvent is possible, continuous solution polymerization using a solvent is more preferable in order to keep the polymerization reaction rate stable. In this case, examples of solvents that can be used include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and ethers such as tetrahydrofuran.

As the core-type polymerization method of the present invention, a complete mixing reactor, a complete mixing reactor connected to a plug flow reactor, etc. are preferred.

As the polymerization initiator, azoalkanes such as azobis-tert-octa and butane are preferred because they do not cause coloration, but it is also possible to use azonitrile compounds, peroxides, etc., which are known as radical polymerization initiators for methyl methacrylate. -Chain transfer agents used to adjust the fluidity of Banri coalescence include, for example, monovalent mercaptans such as butyl mercaptan, ethylene glycol dithioglycolate, trimethylolpropane tristhioglycolate, pentaerythritol tetrakisthioglycolate, Polyvalent mercaptans such as trimethylolpropane tris-3-mercaptopropionate and pentaerythritol tetrakis-3-mercaptopropionate can be used. However, even if no chain transfer agent is added, the fiber will have the maximum molecular weight at the upper limit that can be spun. The melt flow index of the preferred polymer is 2g/kg at 250°C and a load of IQkg.
10 minutes to 50 g/10 minutes. If the fluidity is low, smooth fibers cannot be obtained, and the fluidity is 50g710
This is because the mechanical strength of the fiber will be insufficient if it exceeds 100%. By the way, in order to produce a highly transparent core-shaped composite, it is important to purify the raw materials. The first important thing in refining raw materials is the removal of oxygen dissolved in all raw material systems.

It has been found that oxygen causes considerable coloration when subjected to thermal history during the devolatilization process and spinning. Dissolved oxygen is preferably 1/10 or less of the equilibrium oxygen concentration, more preferably about 1720 or less. To remove dissolved oxygen, countercurrent dissipation with an inert gas such as high-purity nitrogen or vacuum degassing is performed. It is possible in this way.

And then there's the garbage. Distillation is preferred for removing debris. At this time, in order to prevent polymerization, it is preferable to distill the mixture into the presence of oxygen and then deoxygenate it.

It is perfect if the chain transfer agent and polymerization initiator are filtered with or without a solvent through an ultrafiltration membrane resistant to these chemicals and capable of removing foreign matter of 100 angstroms or less, preferably 30 angstroms or less. Alternatively, if these chain transfer agents, polymerization initiators, and solvents can be distilled, they can also be added by distillation.

Preferred embodiments of the present invention are shown below.

The purified tert-butyl methacrylate, chain transfer agent, polymerization initiator, and solvent are continuously charged into a polymerization vessel, and after polymerization, this polymer solution is introduced into a high-temperature vacuum devolatilization device at a temperature of 230 to 300°C, While removing unreacted monomers and solvent for 0.1 to 5 minutes, a polymer is obtained by removing butene produced by cyclization and debutene reactions. This polymer is then introduced into a composite spinning die and coated with a sheath material to obtain a plastic optical fiber.As the sheath material to be coated on the core fiber of the present invention, a highly transparent polymer with a refractive index lower than that of the core fiber is used. are particularly preferred, especially polymers mainly composed of methyl methacrylate, polymers mainly composed of methyl methacrylate and fluoroalkyl methacrylate, polymers mainly composed of methyl methacrylate and styrene, maleic anhydride, and methyl methacrylate and methacrylic acid. , a polymer mainly composed of styrene, a polymer in which some or all of the methacrylic acid units of this polymer are converted into six-membered cyclic acid anhydride, and furthermore, some or all of the six-membered cyclic acid anhydride units of this polymer A polymer in which 6-membered cyclic imide units are modified, a polymer mainly composed of methyl methacrylate and methacrylic acid, and a polymer in which a part or all of the methacrylic acid units of this polymer are converted into a 6-membered cyclic acid anhydride, Furthermore, a polymer in which some or all of the six-membered cyclic acid anhydride units of this polymer are modified into six-membered cyclic imide units, a polymer consisting of fluoroalkyl methacrylate, methyl methacrylate, and methacrylic acid, and methacrylic acid of this polymer. Polymers in which some or all of the units are converted into six-membered cyclic acid anhydrides, polymers of methyl methacrylate, fluoroalkyl methacrylate and orthomethylphenylmaleimide, polymers mainly composed of fluoroalkyl methacrylate and isobornyl methacrylate or bornyl methacrylate. Examples include polymers. Particularly preferred is a transparent polymer with a high softening temperature and a refractive index difference of about 1% or more, more preferably 3% or more, with respect to the refractive index of the core-shaped composite.

The coating of the sheath material is carried out using a composite spinning die at a temperature of 230-280°C to produce a bare wire. It is also possible to code by multilayer extrusion coating of materials that require high-temperature coating, such as polyamide coatings such as nylon blends, high-density polyethylene coatings, polyvinylidene fluoride coatings, and polycarbonate coatings. Such a method is preferably carried out in accordance with the method already disclosed by the present applicant in Japanese Patent Laid-Open No. 5i80847.

Alternatively, molded plastic optical fibers can be exposed and coded with nylon, high-density polyethylene, or water-crosslinked polyethylene.

This will be explained in detail below using examples.

Example 1 Tert-butyl methacrylate was cleaned in the presence of partial pressure of oxygen to remove a small amount of polymerization inhibitor and color. Subsequently, deoxygenation was performed using high-purity nitrogen gas.

The concentration of dissolved oxygen was measured using an oxygen concentration measuring device for organic solvents.
It was set to 1/20 or less based on the deflection of a pointer for measuring oxygen concentration in an equilibrium state under atmospheric pressure at °C. 60 parts of purified tert-butyl methacrylate was continuously charged into a complete mixing reactor. On the other hand, 0.08 parts of 1,1-di-tertbutylperoxy-3,3,5-)limethylcyclohexane was dissolved in 40 parts of ethylbenzene treated at high temperature with alumina, and a solution of 0.08 parts of 1,1-di-tertbutylperoxy-3,3,5-)limethylcyclohexane was dissolved in 40 parts of ethylbenzene treated at high temperature with alumina. The product was filtered using an ultrafiltration membrane HC-1, and then subjected to a diffusion treatment with high-purity nitrogen gas to remove oxygen, and then charged into a polymerization vessel. The polymerization was carried out at 120°C to obtain a reaction solution with a polymer content of 43% by weight. This reaction solution was heated to a temperature of 270 at 15 torr.
It was fed into a devolatilizing extruder with a single vent at ℃.

The average residence time in the devolatilizing extruder was 0.5 minutes.

Subsequently, it was introduced into a composite spinning die. The resulting core-type aggregate contained 100% by weight of six-membered cyclic acid anhydride units, and no tert-butyl methacrylate units were detected from the absorption of ester carbonyl by an infrared spectrometer. In this way, cyclization was possible in a short period of time. Further, the melt flow index of this core type combination was 3 g/10 minutes at 250° C. and a load of 10 kg. As the sheath material, a copolymer consisting of 5% by weight of heptafluorinyl methacrylate, 64.6% by weight of methyl methacrylate, and 0.4% by weight of methacrylic acid, with a refractive index of 1.45 and a softening temperature of 99°C, was used. death,
A plastic optical fiber having a core diameter of 0.98 fins and a sheath outer diameter of 1.0 fins was obtained.

The light guide loss of this plastic optical fiber was 400 dB/Km at 660 Tsuru.

Furthermore, leave it in a dry heat oven at 140°C for 1 hour.
The performance was 0dB/Km, but the performance after 100 hours was 4.
This fiber, which was stable at 55 dB/Km, was
I measured the number of times it was bent and cut at 0 degrees, and it was more than 7 times.
It had sufficient strength.

Example 2 A core-type composite was obtained in the same manner as in Example 1 except that 0.05 part of octyl mercaptan was added as a chain transfer agent.

The melt flow index of this core type combination is 250'C
It was 15 g/10 minutes with a load of 10 kg.

The six-membered cyclic acid anhydride units in the polymer were 100%. Furthermore, a plastic optical fiber was obtained in the same manner as in Example 1. The light guide loss of this plastic optical fiber at 660 fi was 420 dB/K m after 100 hours. The number of times the fiber was cut in the folds was 5 or more, which was at the practical stage.

〔Effect of the invention〕

The purpose of the present invention is to provide a plastic optical fiber that can withstand temperatures of 140°C and has excellent light guiding performance.

Claims (1)

[Claims] 1) Structural formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ 95 to 100% by weight of six-membered cyclic acid anhydride units, 0 to 5% by weight of methacrylic acid units, and tert-butyl methacrylate units 1. 0% by weight or less, and a transparent polymer sheath with a lower refractive index than this polymer. 2) Continuous bulk polymerization of tert-butyl methacrylate from which oxygen and dust have been removed. Alternatively, polymerization is performed by continuous solution polymerization, and the resulting polymer monomer solution or monomer and solvent solution is heat-treated for 0.1 to 5 minutes under reduced pressure to heat-treat the weight body, and the polymer molecule is A six-membered cyclic acid anhydride unit represented by the structural formula ▲Mathematical formula, chemical formula, table, etc. Method for manufacturing plastic optical fiber with core-sheath structure by coating with polymer as sheath