JPS59167234A - Plastic optical fiber - Google Patents

Abstract

PURPOSE:To greatly raise the efficiency of light transmission by using as a core component a methyl methacrylate polymer obtained by a block polymerization method in which a methyl methacrylate monomer purified to a high purity is circulated in a polymerizer of a completely enclosed system while being passed through a filter. CONSTITUTION:A pipe through which a monomer is circulated is provided in a polymerizer, a filter 4 is provided on the way of the pipe, and the monomer is circulated in the polymerizer while being passed through the filter 4. The inside of the polymerizer can thus be effectively cleaned with a small amount of monomer and the intermixture of dust into a polymer can be avoided. A high- purity monomer (methyl methacrylate) free of dust, transition metals, and coloring impurities, obtained by removing impurites in a distiller having a high refining effect, is used. The filter 4 used is preferably a membrane filter having a solvent resistance and a pore diameter of 0.2mum or less, more preferably a Teflon filter of a pore diameter of 0.1mum or less. In case where the removal of more fine dust is required, a filter of a pore diameter of 0.01mum or less may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plastic optical fiber having improved light curtain efficiency through the use of an improved core component methyl methacrylate polymer.

Compared to inorganic glass, especially quartz glass fiber, plastic optical fiber has excellent flexibility even when made to a large diameter, is lightweight, and can easily be obtained with a high numerical aperture, resulting in less connection loss with the light source, and is suitable for industrial use. It has the characteristic of being extremely inexpensive as it can be mass-produced, and has been applied to short-distance transmission systems. However, plastic optical fibers have the drawback of being inferior in light transmission efficiency compared to silica glass fibers, and various technical efforts have been made to improve this.

One factor that reduces optical transmission efficiency is that dust gets mixed into the core component methanol (methyl methacrylate) polymer, increasing scattering loss), conventional methyl methacrylate monomer, initiator, Various purification methods have been attempted to remove dust from chain transfer agents.

However, especially from an industrial perspective, the inventors of the present invention found that
Above all, we believe that thorough removal of dust inside the polymerization machine where the entire polymer is to be formed will contribute to improving the light transmission efficiency, and after conducting extensive tests, we have developed a core component as shown in the present invention. The present invention was achieved based on the discovery that light transmission efficiency is dramatically improved by using a methyl methacrylate polymerization group.

In other words, the gist of the present invention is to circulate highly purified methyl methacrylate monomer through a polymerization machine in a completely closed system while passing through a filter, and to reduce the amount of dust in the monomer after passing through the polymerization machine. This is a plastic optical fiber characterized by using as a core component a methyl tacrylic acid polymer obtained by reducing the amount and then polymerizing it into a bowl shape.

This will be explained in detail below.

According to the findings of the present inventors, no matter how high-purity methyl tutaacrylate monomer is used, when it is polymerized in the polymerization machine, dust adhering to walls, piping, valves, etc. was eluted and mixed into the final polymer, and an unexpectedly large amount of dust was mixed into the final polymer at the monomer stage, reducing the optical transmission efficiency of plastic optical fibers.

Inside the polymerization machine? As a cleaning method, there is a method of cleaning with an organic solvent, but in that case, an operation for removing the residual organic solvent is required, but this is not necessary in the present invention.

By the way, when methyl methacrylate monomer is used as a cleaning solvent, discarding or repurifying the monomer every time the cleaning is repeated is not a preferable method because it adds complicated operations from an industrial perspective9. .

Therefore, we installed piping to circulate the monomer with the interior of the polymerization machine shown in Figure 1, and inserted a filter in the middle to
By circulating the polymer while passing through it, it is possible to effectively clean the interior of the polymerization machine with a small amount of monomer, and it is possible to avoid dust from entering the polymer, which in turn contributes to improving the light transmission efficiency. It is something.

The methyl methacrylate monomer used in the present invention is purified by removing impurities in a distiller with a high sheath effect, or by performing an appropriate tjnj treatment, and then further distilling to make it free from dust, transition metals, and coloring impurities. A highly pure monomer is used.

The fininotar used in the present invention preferably has a pore size of 0.
．． It is preferable to use a solvent-resistant non-plan filter with a pore size of 2 μm or less, more preferably a Teflon filter with a pore size of 0.1 μm or less. Furthermore, if it is necessary to remove minute dust, it is also possible to use a fill goo with a pore diameter of 0.01 μ' or less.

Although any type of polymerization machine may be used in the present invention, it is preferable to have a structure without dead spaces so that dust and the like can be easily removed.

Any type of pump may be used to circulate the methyl methacrylate monomer, but a buffer tank must be installed in the middle of the circulation system to prevent polymerization of the monomer inside the pump. It is preferable to circulate by pressurizing with an inert gas such as nitrogen gas or argon gas.

Further, in order to prevent thermal polymerization of the methyl methacrylate monomer, the circulation system is preferably kept at 5° C. or lower with cold water.

Circulating cleaning within the polymerization system using the monomer shown in the present invention is as follows:
For example, observation using a laser beam inside a pressure-resistant glass tube installed midway through the circulation system reveals that the amount of dust in one tube is, for example, 1.
It is necessary to repeat this process until the number is one or less per rnm3. According to the findings of the present inventors, it usually takes 30 cycles or more to reach this level, and this result also suggests that a large amount of dust remains inside the polymerization machine, and that it is difficult to remove it. It is clear that this is most necessary in order to obtain highly pure polymers. Furthermore, in order to wash and remove this, it is clear that a large amount of waste is required if the waste used during washing is discarded, and it is recycled while passing through a filter like the one of the present invention. This method is extremely superior from an industrial perspective.

A predetermined amount of monomer is introduced into the polymerization machine that has been cleaned in this way.
A plastic optical fiber with improved light transmission efficiency can be obtained by using a methyl methacrylate polymer obtained by bulk polymerization with an initiator and a chain transfer agent as a core component.

The core component methyl methacrylate polymer used in the present invention may be a copolymer with other copolymerizable monomers such as methyl acrylate, ethyl acrylate, and butyl acrylate under a 10-weight plate.

The initiator used in the present invention may be selected according to the desired physical properties, polymerization temperature, and rate; examples include azobisisobutyronitrile, azobisisovaleronitrile, tertiary azobutane, benzoyl Peroxide, butyl peroxide, etc. The amount used may be within a range that allows appropriate polymerization control.

Any chain transfer agent used in the present invention may be selected as long as it does not have an adverse effect such as coloring on the final polymer. Tan, t-
Examples include Dodecyl Mercaf 0 Tan. The amount used is preferably such that the weight average molecular weight of the final polymer is in the range of 80,000 to 150,000.

As for the method of charging the initiator and chain transfer agent used in the present invention, since the amount used is small, it is possible to dissolve them in a small amount of polymer and charge them into the polymerization machine under environmental conditions where dust and the like are not mixed. Unexpected contamination of dust, etc.? To avoid distillable initiators such as monoazobutane, t-butyl peroxide, and distillable chain transfer agents such as n-butyl norcaptan, 1-butyl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan, use distillation. Alternatively, it is possible to dissolve an initiator and a chain transfer agent in a small amount of polymer, and then to pass the mixture through a filter and charge it into the polymerization machine.

The thus obtained methyl methacrylate polymer is used as a core component for spinning. As the sheath component resin, a fluororesin whose refractive index is adjusted to 1.38 to 1.41 is used. Further, as the spinning method, any method such as a coating method or a melt spinning method may be selected, and the melt spinning method is preferable from an industrial viewpoint.

The plastic optical fiber obtained as described above has dramatically improved optical transmission efficiency, and can expand the range of application to short-distance transmission systems.

The present invention will be explained below with reference to Examples.

Optical transmission efficiency was automatically measured between 400 and 7 OQ nm using an optical fiber loss spectrometer manufactured by Operex.
(dEAm).

Example: Internal volume 100 with valve metal in the north lower part as shown in Figure 1
Qcc round stainless steel polymerization machine IK A filter holder loaded with a non-plan filter with a pore size of 0.01 μm and a monomer filtration circulation system piping having two 104 buffer tanks are connected in a removable manner. Put the high-purity freeze-refined product and MA monomer into the buffer tank 2, pressurize it to 107 cq/d with high-purity nitrogen gas from the top, and filter the filter 4.
The liquid is passed through the polymerization tube from the lower part to the inside of the polymerization tube while being washed, and then put into the buffer tank 3. Next, after switching the valve, the same operation is performed on the buffer tank 3, and the unit amount m=2 is put into the buffer tank 2. By repeating this operation, the polymerization machine is cleaned.

In order to measure the degree of cleaning during cleaning, the amount of monomer dust passing through the pressure-resistant glass tube 5 provided in the middle of the piping was measured using a sensor beam.

When the above cleaning operation was carried out approximately 32 times while maintaining the circulation system at 5° C. or lower, the amount of dust particles per 1 mm” of monomer was reduced to one or less.

8 QQcc of high purity methyl methacrylate, 0.8 g of t-azobutane, and n-butyl mercaptan IFi were charged and adjusted by distillation into a 100 Qcc monomer adjustment tank 6. Pressurize from the top and charge it into the polymerization machine. After closing the upper pulp, remove the piping and turn the polymerization machine to 130°.
C for 76 hours, and further heated at 180°C for 16 hours to complete polymerization.

While heating the polymerization machine to 200°C, heat it from the top to 60°C.
Discharge the resin from the pressurized lower part of the CD using high-purity nitrogen gas.
Composite melt-spinning is performed using a fluororesin with a refractive index of 1.40 as the sheath resin, and the fiber is made of resin. The optical transmission efficiency of this material was s()dBAm at a wavelength of 5701 m.

[Brief explanation of the drawing]

FIG. 1 is an explanatory flow sheet of a polymerization machine equipped with a washing and filtration device for producing a methyl methacrylate polymer used as a core material in the plastic optical fiber of the present invention. DESCRIPTION OF SYMBOLS 1... Polymerization a, 2.3... Buffer tank, 4... Filter, 5... Pressure-resistant glass tube, 6... Monotonometry adjustment tank. Patent applicant: Kanedenfuchi "Higaku Kogyo Co., Ltd. agent, patent attorney Makoto Asano - ] Concave 1

Claims (4)

[Claims] (1) Highly purified methyl methacrylate monomer is passed through a filter and circulated inside the polymerization machine in a completely closed system to reduce the amount of dust in the monomer after passing through the polymerization machine, and then subjected to bulk polymerization. A plastic optical fiber characterized in that it uses a methyl methacrylate polymer obtained as a core component. (2) The plastic optical fiber according to claim 1, wherein a solvent-resistant membrane filter with a pore size of 02 μm or less is used as the filter. (3) The plastic optical fiber according to claim 1, wherein a Teflon filter with a pore diameter of 0.1 μm or less is used as the filter. (4) The plastic optical fiber according to claim 1, wherein a filter having a pore diameter of 0.01 μm or less is used as the filter.