JP2590936B2 - 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 Application Laid-Open 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.

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. It was found that the polyether portion in contact with the metal conductor caused rapid deterioration of participation, resulting in poor durability.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention uses a crystalline polyester copolymer having good electrical insulation and no metal contact deterioration for the insulating layer (1), and is flexible and recoverable. A highly reliable curl cord is manufactured by using a polyetherester copolymer having good properties for the sheath (2) so as to prevent the sheath from directly contacting the conductor to prevent oxidative deterioration.

Crystalline homopolyesters have excellent electrical and thermal properties, but generally have a high melting point.If this is used for the insulating layer, the so-called curl processability of heat setting the wire in a spiral shape is not good. In order to solve the problem, a crystalline polyester copolymer having good heat setting properties is used. Further, by using a polyester copolymer having a Shore D hardness of 40 or more and 80 or less so as not to hinder the extensibility of the curl cord, a curl cord having excellent workability and excellent functionality can be produced.

Also, when the sheath is extruded and coated on the conductor coated with the polyester copolymer, the polyester copolymer in the insulating layer must not come into contact with the conductor. Therefore, the polyester copolymer must have a melting point of 200 ° C. or higher.

The crystalline polyester copolymer of the present invention having a melting point of 200 ° C. or higher has terephthalic acid or naphthalenedicarboxylic acid as a main component as an acid component.
Aromatic dicarboxylic acids other than naphthalenedicarboxylic acid include isophthalic acid, orthophthalic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid and ester-forming derivatives thereof, and the like. Examples thereof include 1,4-cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, 4,4'-biciglohexyldicarboxylic acid, and ester-forming derivatives thereof.

 Preferred are isophthalic acid and orthophthalic acid.

As the alcohol component, ethylene glycol or
Although 1,4-butanediol is a main constituent, glycols other than ethylene glycol and 1,4-butanediol include propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, Examples include decamethylene glycol and cyclohexane dimethanol, and preferred are 1,6-hexanediol and cyclohexane dimethanol.

Further, as a copolymer component in the polyester copolymer of the present invention, polylactones may be mentioned, δ-valerolactone, ε-caprolactone, β-propiolactone,
A polyester obtained by subjecting a lactone such as β-2,2-dimethylpropiolactone to ring-opening addition polymerization of a crystalline polyester component or a polyester copolymer obtained by copolymerizing a polylactone can be used.

The polyester copolymer used for the sheath (2) has at least one polyester selected from the group consisting of polybutylene terephthalate, polyethylene terephthalate, polybutylene naphthalate and polyethylene naphthalate as a hard segment, and polytetramethylene glycol, polypropylene glycol And an elastic body having at least one or more polyalkylene glycols selected from the group of the copolyethers of these glycols as soft segments.

The polyetherester copolymer of the sheath (2) may contain a filler or a flame retardant to the extent that its basic characteristics are not lost, and is particularly useful in terms of fire prevention and safety including the flame retardant.

(Operation) By using a polyester copolymer having a melting point of 200 ° C or more and a Shore D hardness of 40 or more and 80 or less for the insulating layer, a conductor coating with high insulation resistance can be formed, and then a polyetherester copolymer is coated thereon and then curled. The resulting curled cord has a good curl setting property, an excellent appearance, and a curl cord having excellent stretchability and recoverability.

(Examples) In order to clarify the effects of the present invention, the following electric wires were prepared, and the appearance as a curl cord (setability), stretchability, recoverability, deterioration of the insulating layer and sheath layer after the heat aging test. The degree was 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.

An 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 insulating core wire having an insulating layer thickness of 0.5 mm. Next, a sheath polymer was extruded and coated on the insulated core wire so as to have a thickness of 1.0 mm.
The electric wire was heated at 150 ° C. for 30 minutes in a state of being wound around a mandrel having a diameter five times its own diameter so that the electric wires were in close contact with each other, and subjected to curling.

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 it was determined that the wires had smooth and uniform stretchability without sticking between the wires and good 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 open at 100 ° C. for 10 days, the insulating layer and the sheath layer were taken out and their strength retention and elongation retention were examined. A material with both heat retention and elongation retention of 95% or more for insulation layer and sheath layer has good heat resistance.
Those with less than 95% were judged as having poor heat resistance.

An insulating layer having a volume resistivity of 10 ¹³ Ωcm or more was determined to have good insulating properties, and an insulating layer having a volume resistivity of less than 10 ¹³ Ωcm was determined to have poor insulating properties.

(Effects of the Invention) According to the present invention, a conductor coated with a crystalline polyester resin having excellent properties as an insulating material is used as a core wire,
It is possible to use a polyetherester copolymer (elastomer), which has excellent elasticity and can be used at a wide range of temperatures, as the sheath, and therefore manufactures a new curl cord that makes full use of the advantages of the insulating material and the sheath material. It becomes possible to do. This new configuration of curl cord eliminates the drawbacks of curl cords of conventional vinyl chloride telephones, for example, which are hardened in cold regions, have poor stretchability, and have poor recoverability. It can also be used for automobile phone cords and the like that require reliability, and can be developed for new applications.

Claims (4)

(57) [Claims] A curled cord obtained by curling a cord in which a conductor covered with an insulating layer (1) is covered with a sheath (2), wherein the insulating layer (1) has a Shore D hardness of 40 or more.
The sheath (2) is mainly composed of a crystalline polyester copolymer having a melting point of 200 ° C. or higher and a sheath (2) having a Shore D hardness of 50 or lower and a polyether ester copolymer comprising a crystalline polyester and an amorphous polyether. A curl cord mainly constituted. 2. A crystalline polyester copolymer comprising terephthalic acid or naphthalenedicarboxylic acid as an acid component, ethylene glycol or 1,4-butanediol as an alcohol component, and terephthalic acid as a copolymer component. 2. The curl cord according to claim 1, further comprising an aromatic dicarboxylic acid other than naphthalenedicarboxylic acid and / or a glycol other than ethylene glycol and 1,4-butanediol. 3. The curl cord according to claim 1, wherein the polyester copolymer is a polyester comprising a crystalline aromatic polyester and a polylactone. 4. A polyetherester copolymer comprising: polybutylene terephthalate, polyethylene terephthalate,
One or more polyester components selected from the group consisting of polybutylene naphthalate and polyethylene naphthalate are used as hard segments, and polytetramethylene glycol,
The curl cord according to claim 1, characterized in that the curl cord is an elastic body having as a soft segment at least one polyalkylene glycol selected from the group consisting of polypropylene glycol and copolyethers of these glycols.