JP2586526B2 - 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, workability, 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 a disadvantage that it hardens due to volatilization of the plasticizer when it is used for a long time in a heated atmosphere, which results in excellent heat resistance and versatility. At present, some curl codes have 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 the copolyester ether elastic body is directly coated on the conductor as in the inventions of the above-mentioned publications and Japanese Patent Publication No. Sho 58-1484, the elastic body may be heated when curled or used in a heated atmosphere. Since the polyether part in the inside was in contact with the metal conductor, it was found that oxidation deterioration was rapidly caused and durability was deteriorated.

Crystalline polyester has excellent electrical and thermal properties, but generally has high rigidity and a high melting point.If this is used for the insulating layer, the wire is heat-set in a helical shape, the so-called curling temperature does not increase significantly. And sufficient setability cannot be obtained. Even if the coating thickness of the insulating layer is reduced,
The curl cord using this is disadvantageous in that it is hard and has high stretching resistance.

In order to obtain a flexible curl cord, it is preferable to use a soft material for both the insulating layer and the sheath layer. In particular, the sheath material is preferably as soft as possible. In order to make a soft curl cord for telephones and the like, it is necessary to use an elastomer having a Shore hardness of 50 or less, preferably 40 or less, as a sheath. However, in general, the melting point of a polyester / ester copolymer is lower as the composition is more flexible, and thus the fact is that the polyester / ester copolymer cannot withstand heat setting at a high temperature.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a crystalline aromatic polyester segment and an aliphatic polyester among crystalline polyesters having good electrical insulation and no metal contact deterioration. A polyester ester block copolymer consisting of segments and having a Shore D hardness of 60 to 80 and a melting point of 200 to 240 ° C is used for the insulating layer (1). The sheath (2) is used to prevent the sheath from directly contacting the conductor to prevent oxidation deterioration,
The purpose of the present invention is to produce a flexible, durable and highly reliable heat resistant curl cord having excellent heat resistance for both sheath layers.

Insulation material with a Shore hardness of 60 to 80 and a melting point of 200 ° C
If a polyester / ester block copolymer with a shore hardness of 60 or less is used as the sheath material, a polyester / ester block copolymer with a shore hardness of 60 or less can be set sufficiently at a curling temperature of about 170 ° C or less, and can be softly curled. Code is made. 150 to 1
At a curling temperature of about 70 ° C., the polyester / ester block copolymer of the sheath layer does not melt, so that no special measures are required.

If only the curling temperature is to be lowered, it is possible to use a copolyester having a low melting point and containing a copolymer component such as isophthalic acid, orthophthalic acid or hexanediol. However, it has been found that the curl cord obtained by this method is limited in compliance, and is particularly impractical due to the large stretching resistance of the curl cord used for telephones.

Flexible curl cord without sacrificing electrical properties and heat resistance by using a specific polyester ester block copolymer that is somewhat soft and resilient for the insulating layer and a softer polyester ester block copolymer for the sheath layer. It became possible to make.

The polyester / ester block copolymer used for the sheath layer (2) of the insulating layer (1) of the present invention is a block copolymer composed of a crystalline aromatic polyester segment and an aliphatic polyester segment, for example, a crystalline aromatic polyester and a lactone. Obtained by the reaction with lactones and polylactones. 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. The polycarbodiimide compound used may be any compound having two or more carbodiimide groups in the molecule. The structure of the epoxy compound used is not particularly limited as long as it 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.

(Function) By using a polyester / ester block copolymer having a melting point and hardness in the characteristic range for the insulating layer, a conductor coating with high insulation resistance can be formed, and a polyester / ester block copolymer with a Shore D hardness of 60 or less is coated on it. Then, the curled product has a good curl setting property and excellent heat resistance, and is a flexible and curl cord excellent in stretchability and recoverability.

(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, recovery, and the degree of deterioration of the insulating layer and the sheath layer after the heat aging test 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 170 ° 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 in an oven at 140 ° C. 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 block copolyester having some flexibility and excellent properties as an insulating material is further flexible and has excellent heat resistance that can be used at a high temperature. By using block copolyester as the sheath, it is possible to produce a flexible, new heat-resistant curl cord that utilizes the heat resistance of each of the insulating material and the sheath material. For this new curl code, for example, the conventional vinyl chloride curl code could not be used.
It can also be used for applications such as car phone curl cords that require heat resistance.

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) comprises a crystalline aromatic polyester segment and an aliphatic polyester segment, and has a Shore D hardness. A polyester / ester mainly comprising a polyester / ester block copolymer having a melting point of 200 to 240 ° C. and a sheath (2) having a Shore D hardness of 60 or less and comprising a crystalline aromatic polyester segment and an aliphatic polyester segment. A curl cord mainly comprising a block copolymer. 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.