JPH0243507A - Polymer for optical fiber sheath and production thereof - Google Patents

Abstract

PURPOSE:To decrease the degree of coloration by polymerizing monomer components in which the content of the polymn. inhibitor in the monomer consisting of specific ratios of fluoroalkyl methacrylate and other copolymerizable monomers is <=20ppm and the content of dissolved oxygen is <=20ppm. CONSTITUTION:The monomer components in which the content of the polymn. inhibitor in the monomer mixture composed of 40-99.9wt.% fluoroalkyl methacrylate and 0.1-60wt.% other copolymerizable monomer components is <=20ppm and the content of the dissolved oxygen is <=20ppm are polymerized. The monomer components which can copolymerize with the fluoroalkyl methacrylate are exemplified by, for example, a methacrylate deriv. such as methyl methacrylate. These monomers are prepd. by adopting a soln. polymn. method in the state of not receiving the influence of gaseous oxygen. The polymer which is extremely low in the degree of yellow coloration and has the excellent transparency is obtd. in this way.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a novel copolymer usefully used as a sheath for an original fiber, and in particular, it relates to an optical fiber with a low degree of coloring and excellent transparency. The present invention relates to polymers for use in sheaths.

[Conventional technology]

The properties required for an optical fiber sheath material are a refractive index lower than that of the core component, high transparency, high heat resistance, and Examples of such characteristics include high adhesiveness, high mechanical strength, and resistance to thermal decomposition during thermoforming.

In the past, the development of polymers for sheaths with these properties has been progressing.
),! ' publication, JP-A-62-, pl, fia
Homopolymers and copolymers of fluoroalkyl methacrylate are known, such as those shown in Publication No. 1.

[Problem that the invention seeks to solve]

However, the polymers for sheath materials obtained by these inventions are colored in themselves, and the transmission loss of the original fiber made of colored polymers as the entire sheath material can be minimized. Therefore, it is desired to develop a sheath polymer with even lower degree of coloring in order to obtain a base fiber with less optical transmission loss.

[Means for solving problems]

Therefore, the present inventors studied to achieve the above object and obtain a sheath polymer with a low degree of coloration and found that 40 to 99.9% by weight of fluoroalkyl methacrylate and other copolymerizable monomers 1 A heptad-alkyl methacrylate polymer obtained by polymerizing a monomer component having a polymerization inhibitor content of 20 ppm or less and a dissolved oxygen content of 20 ppm or less in the monomer consisting of ~60% by weight. We have discovered that a polymer for optical fiber sheathing material that can be combined can achieve this purpose, and have completed the present invention.

In the monomers used in making the polymer for sheath material in the present invention, radical polymerization inhibitors such as benzoquinone, chloranil, p-1-butylcatechol, hydroquinone, m-dinitrobenzene, hydroquinone monomethyl ether, etc. Both of them turn into coloring substances during the polymerization reaction of the monomers or during melt extrusion as a sheath material of the polymer and color the polymer. (9) If oxygen is dissolved in these monomers, the coloring will become more pronounced during the polymerization.

As a result of various studies conducted by the present inventors, it was found that the original fiber with a sheath material made of a polymer obtained by polymerizing monomers with a polymerization inhibitor content exceeding 20 ppm' has a low optical transmission loss. It becomes noticeable. In particular, when the polymerization inhibitor content in the monomer is 1
When the content of the polymer is 0 ppm or less, the coloration of the polymer is significantly small, and the polymer has excellent properties as a sheath material for the original fiber.

The fluoroalkyl methacrylate monomer used as a raw material for the sheath material polymer used in the present invention has a large amount of saturated dissolved oxygen compared to monomers that do not contain fluorine in the molecule, such as methyl methacrylate. 1) 60 ppm o for 9m% methyl methacrylate
When the amount of dissolved oxygen is saturated, the polymer obtained by polymerizing fluoroalkyl methacrylate with such a large amount of dissolved oxygen has a high degree of coloration. Therefore, it is particularly preferable to take measures to prevent the dissolution of oxygen during the polymerization reaction of the fluoroalkyl methacrylate monomer. The nonapolymer obtained by polymerizing nine-fluoroalkyl methacrylate with an amount of dissolved oxygen in the monomer exceeding 20 ppm 'ft has a high degree of coloration, and the optical transmission loss of an optical fiber using this polymer as a sheath increases significantly. It is more preferable that the oxygen content in the heptafluorinated alkyl methacrylate used in making the sheath material is 5 ppm or less.

Methods for removing the polymerization inhibitor from the monomers used in the present invention include (a) chemical treatment to remove the polymerization inhibitor, and (b) distillation to remove the polymerization inhibitor. Since it is solid at room temperature and has an extremely low vapor pressure, it is best to use a method of purifying the monomer by distillation. In addition, methods for removing dissolved oxygen in the monomer used include (1) converting it into a stable compound using a reducing agent, and (11) entraining and removing oxygen by contacting it with an inert gas. In view of the simplicity of the dissolved oxygen removal step, it is particularly preferable to use a method in which these monomers are brought into contact with an inert gas and removed along with the monomers.

The amount of fluoroalkyl methacrylate used in the monomers used in producing the sheath polymer of the present invention needs to be 40% by weight or more in order to keep the refractive index of the resulting polymer sufficiently low. In addition, fluoroalkyl methacrylate is CH which satisfies the properties of the polymer, such as mechanical strength and adhesion to the core material.

CH2=C'-COOCII2(CF2)bX
[1] (In the formula, s is an integer of 1 to 3, X is H, F or C
JF) Monomer 10-70 weight upper back 3 CH2= C-C00CH2C)I2(ClF3)(
It is particularly preferable to be composed of 20 to 90 monomers represented by lX (in the formula, d is an integer of 6 to 15, and X is the same as above).

Monomer components copolymerizable with these fluoroalkyl methacrylates include methacrylic acid ester conductors such as methyl methacrylate, acrylic ester derivatives, acid components such as methacrylic acid and acrylic acid, and α-fluoroacrylic acid and its esters. Examples include conductors, maleimide, and its derivatives of red vinyl ester.

The sheath polymer of the present invention can be produced by solution polymerization, bulk polymerization, or naked polymerization using a monomer that satisfies the above-mentioned nine conditions without being affected by oxygen gas.

The sheath polymer of the present invention has extremely low yellow coloration and excellent transparency, and the original fiber with this polymer as a sheath has an increased optical transmission loss due to light absorption and diffuse reflection by the sheath. In order to minimize the amount of
This results in a base fiber with good optical transmission characteristics.

Hereinafter, the present FIA will be explained in more detail using examples.

Example 1 Commercially available fluoroalkyl methacrylate CH3 0M2=c-coocH2ca2(ay2), ay,
(hereinafter referred to as 17F) was analyzed by gas chromatography, and hydroquinone (hereinafter referred to as H
Q) contained 100 ppm. 171P
When simple distillation was carried out at M'i distillation temperature of 94C and vacuum degree of 5 Hg, the HQ content was 5 ppm.

Commercially available fluoroalkyl methacrylate with the following structure CH.

When CH= c-coocH2ay, (hereinafter referred to as 3FM) was analyzed using gas chromatography, it was found that 100 ppm of Umugiidoquinone monomethyl ether (hereinafter referred to as Mll:HQ) was contained. 3PMt - Distillation temperature 30C1 When simple distillation was performed at a vacuum degree of 33 mHg, the MIIHQ content was 7 ppI21.

A monomer consisting of distilled 17FM5Q weight range, distilled 3FM30 weight range, purified methyl methacrylate (hereinafter referred to as MMA), 19 weight range, and methacrylic acid (hereinafter referred to as MAA), 1 weight range. n-octyl mercaptan s o o o ppm to the mixture,
2.2'-azobisinbutynitrile 100100o
pp, stirred and mixed uniformly, and this mixture was
When filtered with a membrane filter and bubbled with purified nitrogen gas (oxygen concentration 0.05 ppm or less, Co2 0.2 ppm or less) for 1 hour, the amount of dissolved oxygen was 61)p.
I21 and 9. This mixture was then heated in nitrogen gas for 30 minutes.
00 amount x 300 ts This polymer f170c was subjected to devolatilization treatment for 10 hours in a vacuum drying chamber, and there was no residual monomer.
．． 5 Weight coefficient, intrinsic viscosity [η) = 0.45 dt/i (M
II x, 25 C) We specialize in sheath material polymers.

Next, a plastic optical fiber with this polymer as the sheath material and polymethyl methacrylate as the core is made using a composite spinning method. The optical transmission performance of this original fiber is 650nm, 520n
188dB/ICm1921 respectively at m! B/ni!
It was good as In.

Comparative Example 1 Commercially available 177M (HQ content 100 p) used in Example 1
pm), 3 FM (MKHQ content 100 ppm)
A sheath material polymer was prepared using the same method as in Example 1 except that the monomer was used as a monomer (residual monomer 0.3 weight ratio, [η)
=0.47dt/ji).

A plastic optical fiber having this polymer as a sheath material and polymethyl methacrylate as a core material was obtained. The total polymerization inhibitor content in the monomers used, the amount of dissolved oxygen, and the optical transmission property of the obtained fiber V! are shown in Table 1 ^ Comparative Example 2 The same commercially available 171 as used in Example 1 was used as a monomer.
A sheath material polymer was obtained in the same manner as in Example 1 except that FM, 5FMt- was used and the nitrogen bubbling operation was not performed when preparing the monomer mixture (residual monomer 0.3% by weight, [η)]
=0.47dl111).

Dissolved oxygen t in the monomer was 95 ppm.

A plastic original 7-IPA was obtained in which this polymer was used as a sheath material and polymethyl methacrylate was used as a core material.

Table 1 shows the total polymerization inhibitor content in the monomers used, the amount of dissolved oxygen, and the optical transmission performance of the obtained fiber.

Example 2 Commercially available 4% by weight fluoroalkyl methacrylate mixture (13FM) IH3 CI'12= (!-C'0OC1'(2CH2(CF
), C.F.

(17FM) 600% by weight 2tyM) (25FM) was analyzed by gas chromatography and found to contain 200 ppm of HQ as a polymerization inhibitor, and the monomer mixture was distilled at a temperature of 75 to 105C.

When simple distillation was performed at a vacuum level of 5 m Hg, the HQ content was 15 ppm.

Commercially available fluoroalkyl methacrylate with the following structure Cm.

CH2=c-coocu2c+r2aF3(5F M
) is analyzed by gas chromatography, MgH
Contains 10 fl ppm of Q. When this 5FM was subjected to simple distillation at a distillation temperature of 90 C and a vacuum degree of 20 Hg, the amount of MmTIQ contained was 5 ppm.

A monomer consisting of 65 parts by weight of distilled long-chain fluoroalkyl meccrylate monomer mixture, 15 parts by weight of distilled 51FM, 17% by weight of purified inhibitor-free methyl methacrylate, and 3% by weight of acrylic acid (MA). n-octyl mercaptan 5000 pPffl for the polymer mixture
, 2.2'-azobisisobutyronitrile 1000
The mixture was stirred and mixed uniformly, filtered through a 0.1 μm Teflon filter, and bubbled with purified nitrogen gas for 1 hour to obtain a dissolved oxygen concentration of 10 ppm. Subsequently, this monomer mixture'i300imX300u in nitrogen gas
It was placed in a glass cell cast plate using a X5mO silicone rubber frame and polymerized for 15 hours at 70G and 2 hours at 120CK, resulting in a polymer with a polymerization rate of 91qIl. This polymer was fed to a 2-vent type twin-screw devolatilizing extruder with a total diameter of 50 mm, and the vacuum level at the vent section was 5 mm Hg x the temperature at the vent section was 250 mm.
C.

The devolatilization process was carried out at a speed of Sky/hour at a temperature of 230C, and the residual monomer was 0°2 by weight, [η] = 0.4
A sheath material polymer of 5 di/I was obtained.

This polymer was fused and coated onto a core material prepared by drawing a quartz glass base material (Diasil SP manufactured by Mitsubishi Metals Co., Ltd.) at a melting temperature of 2200 t:' to obtain an original fiber.

Table 1 shows the total amount of polymerization inhibitor in the monomers used, the amount of dissolved oxygen, and the optical transmission performance of the obtained fiber.

Comparative Example 5 The commercially available long chain fluoroalkyl methacrylate mixture monomer containing 200 ppm H Q used in Example 2 and 5
A sheath material polymer was obtained in the same manner as in Example 2, except that PM (containing 100 ppm of MEHo) was used as a monomer and the nitrogen bubbling operation was not performed when preparing the monomer mixture for polymerization (residual monomer 0.2 weight coefficient, [η)=o
, 4 sdt/l), the total polymerization inhibitor content in the monomer, the amount of dissolved oxygen, and the optical transmission performance of the obtained fiber are shown below.
Shown in 1.

Table-1 Table-1 Norizuki Patent applicant: Mitsubishi Rayon Co., Ltd.

Claims (1)

[Scope of Claims] 1. Polymerization inhibitor content in a monomer mixture consisting of 40 to 99.9% by weight of fluoroalkyl methacrylate and 0.1 to 60% by weight of other copolymerizable monomer components. is 2
A polymer for optical fiber sheath material that is polymerized to have a dissolved oxygen content of 0 ppm or less and a dissolved oxygen content of 20 ppm or less. 2. Fluoroalkyl methacrylate has ▲mathematical formulas, chemical formulas, tables, etc.▼[I] (b is an integer from 1 to 3, X represents H, Cl, or F) monomer 10-70% by weight and ▲mathematical formula , chemical formulas, tables, etc. ▼ [II] (In the formula, d is an integer of 6 to 13, and X represents the same group as above) A patent characterized by being composed of 20-90% by weight of the monomer represented by A polymer for optical fiber sheath material according to claim 1.