JPS6137215B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber with excellent transmission characteristics and high mechanical strength.

In order to make an optical fiber cable for normal transmission, it is being considered to cover the optical fiber core with plastic or the like to reinforce it.

However, with ordinary plastics, approx.
It is extremely difficult to uniformly coat an optical fiber core wire with a diameter of 200μφ or less with a plastic coating of 100 to 500μ. Even if the coating is done uniformly, distortion occurs during the solidification process of the plastic, increasing optical transmission loss, making it difficult to put into practical use. It cannot be offered to

Therefore, plastics having the following characteristics are useful as coating materials for transmission optical fiber cores.

1. In the coating process, a coat of 100 to 500μ can be coated with high efficiency on an optical fiber core wire with a mechanical strength of 200μφ or less.

2. Low molding distortion after molding and low optical transmission loss.

3. The quartz and optical glass materials used in optical fiber cores are subject to oxidative deterioration and chemical deterioration due to moisture, etc. To prevent this deterioration, a certain type of primer is applied to optical fiber cores. This primer can thermally decompose at temperatures above 200°C, leading to a decline in the performance of the optical fiber core, so it can be coated at a low molding temperature.

4. In the process of converging or laying optical fiber cables for transmission, the cables are flexible, easy to bend, have good sliding properties, connect cables easily, and further reduce the optical transmission loss. Small things.

5 Heat resistance stability of the coating material required in long-term practical tests of optical fiber cables (80 to 100
℃ thermal deterioration, cold/heat cycle deterioration), dimensional stability, moisture absorption stability, stability of mechanical properties, and stability against long-term changes in transmission loss of optical fiber cables for transmission.

Nylon-12 and copolymerized nylon are excellent coating materials with the above characteristics, but depending on the molding conditions, the crystallinity of nylon-12 differs between the inside and outside of the coating, and the internal strain caused by this differs. Therefore, optical transmission loss increases. On the other hand, since copolymerized nylon has low crystallinity, the above-mentioned molding distortion is small, but since the elastic modulus is low and the melting point is low, it is also inferior in the above-mentioned item 5. Furthermore, in both cases, secondary crystallization occurs after coating, which causes transmission loss. Therefore, the inventors of the present invention have conducted extensive research into a coating that satisfies all of the above-mentioned items 1 to 5, and as a result, have arrived at the present invention. That is, a) an ω-aminocarboxylic acid or lactam having 11 or 12 carbon atoms, b) an α,ω-dihydroxy-polytetrahydrofuran having a molecular weight between 160 and 3000, and c) a dicarboxylic acid having a) 100
The total amount of b) and c) is 15 to 150 parts by weight.
It has been found that a polyether amide obtained by polycondensing b) and c) in substantially equimolar proportions by weight is an excellent coating material.

More specifically, in addition to the toughness, moldability, etc. of polyamide resin, as a result of intensive studies to suppress crystallization after molding (secondary crystallization), which can cause molding distortion, the polyether of the present invention has been developed. The present invention was achieved by discovering that amides are very superior.

The polyether amide used in the present invention is produced, for example, by the method described in JP-A-53-119997. That is, components a), b) and c) are heated in the presence of water to obtain a low molecular weight polyether ester amide, and then heated in the presence or absence of a catalyst such as a phosphorus compound, a titanium compound or a tin compound. It can be obtained by proceeding condensation polymerization while removing sewage water under normal pressure or reduced pressure. In addition, the method described in JP-A No. 50-159586 is used, in which a low molecular weight polyamide having carboxyl groups at both ends is polymerized in advance from components a) and c), and this and component b) are combined in the presence of a catalyst. It is obtained by condensation polymerization under reduced pressure in the presence or absence of the compound. Alternatively, the terminal diol of component b) may be aminated and reacted.

In obtaining the above polyetheramide a)
If the total amount of b) and c) is less than 15 parts by weight relative to 100 parts by weight, the resulting nylon-12 crystallinity will be almost the same, and therefore will not be effective in reducing internal strain. On the other hand, if the amount is 150 parts by weight or more, the mechanical strength will be poor and it will not be possible to form a good coating. Furthermore, if the ratio of b) and c) deviates significantly from the equimolar ratio, a polyether amide with a desired high degree of polymerization cannot be obtained, and therefore a good coating cannot be formed.

This is carried out by hydrolytic polycondensation under elevated pressure, the polyamide-forming starting components being, for example, ω-aminoundecanoic acid,
In particular, laurin lactam, as a diol component, has a molecular weight of 160 to 3000, especially 300 to 2200, especially 500 to 1200.
as dicarboxylic acids, in particular dicarboxylic acids having from 4 to about 30 carbon atoms, preferably dodecanedicarboxylic acid, hexahydroterephthalic acid, terephthalic acid and/or isophthalic acid are used respectively.

Hereinafter, it will be explained in detail using examples.

Example 1 100 parts by weight of laurin lactam, 26.3 parts by weight of α,ω-dihydroxy-(polytetrahydrofuran) with an average molecular weight of 860, 7.0 parts by weight of dodecanedicarboxylic acid and 4.5 parts by weight of water were charged into an autoclave and heated at 210°C for 8 hours. Heated. At this time, the autoclave internal pressure reached 19 atmospheres. The pressure was released over a period of 1 hour, and stirring was continued for 7 hours while flowing nitrogen to complete the condensation polymerization. The obtained polyether ester amide was applied to a multi-mode graded glass fiber core wire with an outer diameter of 150μ, which was coated with a primary coating of thermosetting polyurethane, using a 40m/mφ nylon extruder, and then secondary molded using a drop-down type die. Covering was performed.

0.84μ of the optical fiber created in this way
As a result of investigating the transmission loss due to a light source with a wavelength of
It is exactly the same as the transmission loss of the core wire, 2.3dB/Km,
There is no increase in loss due to coating. Further, no increase in loss was found due to the coating molding conditions, that is, the drawdown ratio and the ambient temperature of the optical fiber (-50 to 30°C).

Example 2 A polyether ester amide obtained in the same manner as in Example 1 from 100 parts by weight of laurin lactam, 27.9 parts by weight of α,ω-dihydroxy-(polytetrahydrofuran) with an average molecular weight of 860, and 5.4 parts by weight of terephthalic acid was used. A multimode graded glass fiber core was coated with thermosetting polyurethane as a secondary coating and silicone rubber as a buffer layer in the same manner as in Example 1. The transmission loss of the obtained optical fiber was measured in the same manner as in Example 1, and the result was 2.3 dB/Km. There was no increase in transmission loss due to the secondary coating, and there was no transmission loss due to coating conditions or environmental conditions. It was discovered that

Example 3 A polyether ester amide obtained in the same manner as in Example 1 from 100 parts by weight of laurin lactam, 78.9 parts by weight of α,ω-dihydroxy-(polytetrahydrofuran) having an average molecular weight of 860, and 21.1 parts by weight of dodecanedicarboxylic acid was used. A secondary coating was applied to a multimode graded glass fiber core coated with a primary coating of thermosetting polyurethane.

As a result of measuring the transmission loss of the obtained optical fiber, it was found that it was 2.3 dB/Km, and there was no increase in loss due to the secondary coating, nor was there any increase in transmission loss due to coating conditions or environmental conditions.

Claims (1)

[Claims] 1. As a secondary coating material for optical fiber cores for transmission, a) ω-aminocarboxylic acids or lactams having 11 or 12 carbon atoms, b) α,ω-dihydroxy-polytetrahydrofuran having a molecular weight between 160 and 3000. and c) polycondensing dicarboxylic acids in a ratio in which the total amount of b) and c) is 15 to 150 parts by weight relative to 100 parts by weight of a), and b) and c) are substantially equimolar. An optical fiber for transmission, characterized in that it uses polyether amide obtained by