JP2590984B2 - Heat resistant curl cord - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an elastic curl cord suitable for telephones, headphones, and the like.

(Prior Art) The configuration and characteristics of curl cords suitable for telephones and the like are introduced in, for example, JP-A-62-17909. A sheath (2) formed by extruding a synthetic resin, for example, is formed on the outer side where a plurality of core wires each formed by covering a conductor with an insulating coating (1) are arranged, and then processed into a spiral shape. Its important functions are that it has an appropriate stretching property, that it has sufficient recovery characteristics as a coil spring, and that it has a good appearance that does not cause twisting or reversal.

The additional properties required are that the insulation layer has good electrical insulation, and that the insulation coating and the sheath can be easily extruded twice.

Polyester elastomer having a specific composition as a composition for making a curl cord having a small permanent elongation,
That is, a coated electric wire made of a specific copolyether-ester elastic material is introduced in Japanese Patent Publication No. 58-1484.

(Problems to be solved by the invention) The sheath material of the curl cord generally used at present is
Most of soft vinyl chloride is used because of its flexibility, processability, and inexpensiveness. Various patents such as the above-mentioned patent publication have been proposed to improve its recoverability, spring constant, and flexibility at low temperatures. At present, it is not possible to provide features that can replace vinyl.

In particular, since soft vinyl chloride contains a large amount of plasticizer, it has the disadvantage that it hardens due to volatilization of the plasticizer when used in a heated atmosphere for a long period of time. Currently, the code has not been put to practical use yet.

When a flexural modulus G introduced in Japanese Patent Application Laid-Open No. Sho 62-17909 has a specific elastic polymer, for example, a polyester-based or polyamide-based elastomer insulator, the curl cord recoverability is improved. However, these materials generally have low insulation resistance. In particular, polyamide-based elastomers are hygroscopic and are not preferable as an insulating layer.

Further, when an elastic body made of copolyester is directly coated on the conductor as in the inventions of the above-mentioned publications and Japanese Patent Publication No. 58-1484, when the conductor is heated such as curling, or when used in a heated atmosphere, the elasticity is reduced. Since the polyether part in the body was in contact with the metal conductor, it was found that the oxidative deterioration rapidly occurred and the durability deteriorated.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention uses a crystalline polyester having good electrical insulation and no metal contact deterioration for the insulating layer (1), and is flexible and recoverable. A good polyester / ester block copolymer is used for the sheath (2) so that the sheath does not come into direct contact with the conductor to prevent oxidative degradation, and both the insulating layer and the sheath layer have excellent heat resistance.
It is intended to produce a flexible, durable and more reliable heat resistant curl cord.

Crystalline polyester has excellent electrical and thermal properties, but generally has a high melting point. When this is used for the insulating layer, the wire is heat-set into a spiral shape, a sufficient setting unless the so-called curling temperature is considerably increased. I can not get the nature. In order to solve this problem, it is necessary to use a sealing material which does not melt at the curling temperature and has a high melting point. Further, in order to use the resulting curled cord in a high temperature atmosphere for a long time, the sheath material exposed to hot air must be a soft material having extremely excellent heat aging resistance.

A polyester / ester copolymer is used as a sheath material corresponding to the crystalline polyester of the insulating layer. Since the melting point of a polyester / ester copolymer generally becomes lower as the composition becomes softer, in order to produce a more flexible curled cord, it is advantageous to have a slightly lower curling temperature. From this point, depending on the use, it may be more suitable to use a copolymerized polyester having a lower melting point than a homopolyester containing a copolymerized component such as isophthalic acid, orthophthalic acid or hexanediol. Even in this case, the polyester of the insulating layer is 200% because the heat resistance of the curl cord is not sacrificed, and the insulating layer must not melt when the sheath is extruded and covered.
It is necessary to have a melting point of at least ℃.

The crystalline polyester having a melting point of 200 ° C. or higher used for the insulating layer (1) of the present invention has terephthalic acid or naphthalenedicarboxylic acid as a main component as an acid component.
Aromatic dicarboxylic acids as copolymer components other than terephthalic acid and naphthalenedicarboxylic acid include isophthalic acid, orthophthalic acid, bis (p-carboxyphenyl) methane,
Anthracene dicarboxylic acids and their ester-forming derivatives, and the like. And the like.

Preferred copolymer components are isophthalic acid and orthophthalic acid.

As the alcohol component, ethylene glycol or
Although 1,4-butanediol is a main component, glycol as a copolymer component other than ethylene glycol and 1,4-butanediol is propylene glycol,
Neopentyl glycol, 1,5-pentanediol, 1,6
-Hexanediol, decamethylene glycol, cyclohexane dimethanol, and the like, with preferred ones being
1,6-hexanediol and cyclohexanedimethanol.

Polyester used for the sheath layer (2) of the present invention
The ester block copolymer is a block copolymer composed of a crystalline aromatic polyester segment and an aliphatic polyester segment, and is obtained, for example, by reacting a crystalline aromatic polyester with a lactone or polylactone. The crystalline aromatic polyester segment in the present invention is a polymer mainly composed of an ester bond or an ester bond and an ether bond, has at least one aromatic group in a main repeating unit, and has a hydroxyl group at a molecular terminal. is there. The crystalline aromatic polyester segment is preferably a polyester having a melting point of 150 ° C. or higher when a high polymer is formed. The molecular weight is preferably 3000 or more.

Preferable specific examples include polyethylene terephthalate, polytetramethylene terephthalate, poly-1,4-
Cyclohexylene dimethylene terephthalate, homopolyesters such as polyethylene-2,6-naphthalate, polyethylene oxybenzoate, polyester ethers such as poly-p-phenylenebisoxyethoxy terephthalate, mainly tetramethylene terephthalate units or ethylene terephthalate units, and Having a copolymerization component such as tetramethylene or ethylene isophthalate unit, tetramethylene or ethylene adipate unit, tetramethylene or ethylene sebacate unit, 1,4-cyclohexylene dimethylene terephthalate unit, tetramethylene or ethylene-p-oxybenzoate unit Copolymer polyester or copolymer polyester ether. In the case of a copolymer, the content of tetramethylene terephthalate or ethylene terephthalate unit is desirably 60 mol% or more.

The aliphatic polyester segment particularly includes polylactones. As the lactone used for the polymerization, ε-caprolactone is most preferable, but enantholactone, caprylolactone and the like are also used. Further, two or more lactones can be used.

The copolymerization ratio of the crystalline aromatic polyester segment and the lactone can be appropriately selected from the aromatic polyester / lactone in a weight ratio of 97/3 to 5/95. 80/20 for applications requiring flexibility, flexibility, such as telephone lines, power lines, power lines, etc.
It is preferred to select a range of ~ 60/40.

The polyester / ester block copolymer,
It is also obtained by heating and melting and reacting a crystalline polyester and a lactone, or by heating and melting a crystalline polyester and a polylactone,
The former method is preferable from the viewpoint of the physical properties of the polymer. In this case, a catalyst may be used or a catalyst may be used.

Further, a polycarbodiimide compound or an epoxy compound may be blended in order to improve the heat resistance, water resistance and the like of the polyester / ester block copolymer. As the polycarbodiimide compound to be used, the structure of two or more carbodiimide compounds in a molecule is not particularly limited as long as the compound has one or more epoxy groups in the same molecule.

In particular, the polyester / ester block copolymer of the sheath (2) may contain a filler or a flame retardant to such an extent that its basic properties are not lost. In particular, those containing flame retardants have high utility value in terms of fire prevention and safety.

(Operation) By using crystalline polyester with a melting point of 200 ° C or higher for the insulation layer, a conductor coating with high insulation resistance can be formed, and a polyester / ester block copolymer is coated on top of it and then curled. Is set at a high temperature, so that a curl cord having good curl setting properties, excellent heat resistance, and excellent stretchability and recoverability can be obtained.

(Examples) In order to clarify the effect of the invention, the following curl codes were created, and the appearance as curl codes (setability),
The stretchability, recoverability, insulation properties after the heat aging test, and the degree of deterioration of the sheath layer were evaluated.

For comparison, the results of trial production and evaluation of curl codes of combinations of materials not included in the present invention under the same conditions are shown as comparative examples.

The insulating polymer shown in Table 1 was extruded and coated at 250 ° C. on a stranded copper wire having a conductor outer diameter of 0.8 mm to obtain an insulated wire core having an insulating layer thickness of 0.5 mm. Next, a sheath polymer was extruded and coated on the insulated wire core to a thickness of 1.0 mm.
The wire was heated at 190 ° C. for 60 minutes to be curled in a state where the wires were wound around a mandrel having a diameter five times the self-diameter so that the wires were in close contact with each other.

After the wire wound around the mandrel was cooled to room temperature, the mandrel was pulled out, and the appearance of the curl cord (whether the wire was set to the mandrel diameter or the wires were in tight contact with each other) was examined.

An object in which the inner diameter of the curl is not larger than the outer diameter of the mandrel by 2% or more and whose electric wires are closely adhered to each other with no gap was judged as having good setting properties, and the other objects were judged as having poor setting properties. Then, both ends of the curl cord were stretched, and those which could be stretched smoothly and uniformly without sticking between the wires were determined to have good stretchability, and those having an abnormal stretch were determined to have poor stretchability.

The curl cord was stretched at 50 ° C. to 5 times the natural length L ₀ and held for 10 minutes, and then the length L was measured 5 seconds after loosening to examine the recoverability of the curl cord.

Those having (L−L ₀ ) / L ₀ × 100 smaller than 2.0 (%) were judged as having good recoverability, and those having 2.0 or more were judged as having poor recoverability.

After the curl cord was heated at 140 ° C. in an open state for 10 days, the insulating layer and the sheath layer were taken out and the strength retention was examined. Insulation layer, sheath layer strength retention rate is 70
% Or less was determined as good heat resistance, and less than 70% was determined as poor heat resistance.

Further, those having an insulating layer having a volume resistivity of 10 ¹³ Ωcm or more were judged as having good insulating properties, and those having a volume resistivity of less than 10 ¹³ Ωcm were judged as having poor insulating properties.

(Effects of the Invention) According to the present invention, a conductor coated with a crystalline polyester having excellent properties as an insulating material has excellent elasticity,
Moreover, polyester with excellent heat resistance that can be used at high temperatures
By using the ester copolymer as the sheath, it becomes possible to produce a new heat-resistant curl cord that makes full use of the heat resistance of each of the insulating material and the sheath material. This new curl code can be used, for example, for applications such as industrial robots requiring heat-resistant survivors, in which conventional vinyl chloride curl codes cannot be used.

Claims (2)

(57) [Claims] 1. A curled cord in which a conductor covered by an insulating layer (1) is covered by a sheath (2), wherein the insulating layer (1) mainly contains crystalline polyester having a melting point of 200 ° C. or higher, and the sheath (2) A curl cord mainly comprising a polyester / ester block copolymer comprising an aliphatic polyester segment of a crystalline polyester segment. 2. The curl cord according to claim 1, wherein the polyester / ester block copolymer is a block copolyester comprising a crystalline aromatic polyester and polylactone.