Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Optical fiber – waveguide – or preform
Reexamination Certificate
2000-06-23
2002-09-10
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Optical fiber, waveguide, or preform
C264S001600
Reexamination Certificate
active
06447700
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a resin composition for optical fiber loose tubes which has excellent hydrolysis resistance and extrusion moldability and enables an optical fiber loose tube to be extrusion molded at a high haul-off speed, an optical fiber loose tube obtained by extrusion molding the resin composition, and a production process thereof.
An optical fiber loose tube contains loosely an optical fiber in tube to be used as a structure having a gel-like intimate mixture filled In a space therein. A plurality of the optical fiber loose tubes are bundled into an optical fiber cable. Heretofore, polybutylene terephthalate and compositions thereof have been widely used in the optical fiber loose tube thanks to their excellent mechanical strength and chemical resistance.
JP-A 8-227030 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a resin composition which comprises 100 parts by weight of polybutylene terephthalate having an intrinsic viscosity of 1.0 or more and a terminal carboxyl group concentration of 45 eq/ton or less, 0.01 to 1.0 part by weight of a phosphorus-based compound and 0.01 to 2. 0 parts by weight of a hindered phenol compound or thioether compound.
Polybutylene terephthalate and compositions thereof for use in optical fiber loose tubes must overcome problems with heat resistance and hydrolysis.
Optical fiber loose tubes must be produced stably with uniform quality and there is seen a tendency toward an increase in haul-off speed for extrusion molding to improve productivity.
Although there is no problem when conventional resin compositions are extrusion molded at a haul-off speed of 150 m/min or less, when the haul-off speed is increased to 200 m/min or more to improve productivity, so-called scum which is a resin or the like adhering to a dice is separated from the dice and adheres to the inner side of the loose tube. As a result, the quality of the tube is impaired, yield is lowered, and productivity cannot be improved.
It is an object of the present invention to provide a resin composition for optical fiber loose tubes which has excellent hydrolysis resistance and extrusion moldability, is free from a defect caused by scum even at a high haul-off speed, particularly a haul-off speed of 200 m/min or more, and enables an optical fiber loose tube to be extrusion molded at a high yield.
It is another object of the present invention to provide an optical fiber loose tube which can be produced from the above resin composition of the present invention.
It is still another object of the present invention to provide a process for producing the optical fiber loose tube of the present invention from the resin composition of the present invention.
Other objects and advantages of the present invention will become apparent from the following description.
The inventors of the present invention have conducted intensive studies to solve the above problem and have found that a loose tube can be produced at a high yield at a high haul-off speed by adding polyethylene wax to a resin composition while a defect caused by the formation of scum is suppressed.
That is, according to the present invention, firstly, the above objects and advantages of the present invention are attained by a resin composition for optical fiber loose tubes which comprises (A) 100 parts by weight of polybutylene terephthalate having a terminal carboxyl group concentration of 10 eq/ton or less and an intrinsic viscosity of 1.0 to 1.2. and (B) 0.005 to 0.1 part by weight of polyethylene wax.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by an optical fiber loose tube which comprises (A′) 100 parts by weight of polybutylene terephthalate having a terminal carboxyl group concentration of 15 eq/ton or less and an intrinsic viscosity of 1.0 to 1.2 and (B) 0.005 to 0.1 part by weight of polyethylene wax.
Further, according to the present invention, thirdly, the above objects and advantages of the present invention are attained by a process for producing the above optical fiber loose tube of the present invention which process comprises the step of extrusion molding the above resin composition of the present invention at a haul-off speed of 200 m/min or more. According to the production process of the present invention, the optical fiber loose tube of the present invention can be produced at a high yield without a defect caused by the formation of scum.
The present invention will be described in detail hereinafter.
Polybutylene Terephthalate (A)
The polybutylene terephthalate (A) is a polyester comprising terephthalic acid as the main dicarboxylic acid component and 1,4-butanediol as the main glycol component.
The expression “main” as used herein means that the component is contained in an amount of 80 mol % or more, preferably 90 mol % or more based on the total of all the dicarboxylic acid components or all the glycol components.
The polybutylene terephthalate (A) encompasses not only a homopolymer but also a copolymer comprising a comonomer. When the comonomer is copolymerized, the proportion of the comonomer is 20 mol % or less, preferably 10 mol % or less based on the total of all the dicarboxylic acid components or all the glycol components.
The copolymerizable acid component is an aromatic dicarboxylic acid other than terephthalic acid, such as isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ketone dicarboxylic acid or diphenylsulfone dicarboxylic acid; aliphatic dicarboxylic acid such as succinic acid, adipic acid or sebacic acid: or alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid, tetralindicarboxylic acid or decalindicarboxylic acid.
The copolymerizable glycol component other than 1,4-butanediol is ethylene glycol, hexamethylene glycol, neopentyl glycol, cyclohexane dimethanol, tricyclodecane dimethylol, xylylene glycol, bisphenol A, bisphenol B, bishydroxyethoxy bisphenol A or the like.
A polyfunctional compound having a functionality of 3 or more, such as glycerin, trimethylol propane, pentaerythritol, trimellitic acid, trimesic acid or pyromellitic acid may be copolymerized in limits that the polyester does not lose its moldability substantially.
The terminal carboxyl group concentration of polybutylene terephthalate (A) constituting the resin composition of the present invention is 10 eq/ton or less.
When the terminal carboxyl group concentration is higher than 10 eq/ton, a loose tube which can retain tensile elongation under a high-temperature and high-humidity environment for a long time cannot be obtained and a loose tube which is easily cracked or broken by external force when it is used under the above conditions is provided, thereby impairing the function of protecting an optical fiber. The terminal carboxyl (COOH) group concentration is the number of equivalents (eq) per 10
6
g (ton) of a polymer measured by an A. Conix method (Makromol. Chem. 26,226 (1958)).
The intrinsic viscosity of polybutylene terephthalate (A) is 1.0 to 1.2. preferably 1.1 to 1.2. When the intrinsic viscosity is lower than 1.0, the resulting composition deteriorates in moldability for the extrusion molding of a tube and does not have satisfactory shapability. Further when external force is applied, the obtained loose tube is easily cracked or broken, thereby impairing the function of protecting an optical fiber. When the intrinsic viscosity is higher than 1.2. the extrusion moldability of an optical fiber loose tube deteriorates and the production cost of polybutylene terephthalate boosts. The intrinsic viscosity is a value calculated from solution viscosity measured at 25° C. in orthochlorophenol.
As means of obtaining the above polybutylene terephthalate (A) is preferably solid-phase polymerization. more preferably the solid-phase polymerization of polybutylene terephthalate containing an alkaline metal compound. This mak
Ohno Masamori
Oki Hiroyasu
Sasaki Shin-ichi
Sugie Kiyoshi
Sughrue & Mion, PLLC
Teijin Limited
Vargot Mathieu D.
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