JPH01221807A - Curl cord - Google Patents

Abstract

PURPOSE:To make it possible to skip backturn and reprocessing of curl set once curl set is processed and to aim at improvement of elasticity and curl retention of curl cord, by forming sheath layer with two kinds of elastic resin materials which have different contraction coefficients at molding from each other, divided in two parts along the longitudinal direction and combined in one body. CONSTITUTION:The element of sheath layer 3 of a curl cord is supported to be divided longitudinally and integrally composed of two kinds of elastic resin materials 3a, 3b which have different contraction coefficient at molding from each other. Curl set is processed, while holding the resin material 3a (or 3b) with a contraction coefficients larger than the other one toward inner surface. A helix diameter at molding is determined by taking the difference in contraction coefficients of the two resin materials 3a, 3b into account. As a result, the curl cord processed with curl set is naturally given its potential to hold the helix from generated by the difference in contraction coefficients of the resin materials 3a and 3b both of which constitute the sheath layer 3. The curl will not get loose even after backturn of the curl cord once curl set is processed and therefore, no reprocessing of curl set is required at all.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention does not require the additional steps of unwinding and recurling after curl setting, and exhibits stable curling with the initial curl setting. The present invention also relates to a curl cord with excellent elasticity and curl retention.

[Prior Art] As is well known, a curl cord is a sheath layer made of elastic resin formed around the outer periphery of a conductive wire coated with an insulating material, and this is processed into a spiral body with an appropriate radius. ,
It is widely used as a line cord that connects a telephone body and a handset, a line cord that connects a computer body and a keyboard board, and an elastic cord that connects various electrical devices such as vacuum cleaners and hair dryers to outlets.

The elasticity of such a curled cord is mainly given by the elasticity of the sheath layer, and when curling the cord, an uncurled cord with a sheath layer formed thereon is wound to a predetermined helical radius. A method has been adopted in which the curl is set by means such as heating and vulcanization, and then the curl is unwound and the curl setting process is performed again to stabilize the curl.

[Problems to be Solved by the Invention] However, such a series of steps for curl setting is complicated, and the large number of steps in particular is a major factor in lowering productivity. In particular, it is unreasonable to have to perform unwinding and re-curling after the initial curl-setting process is completed, and if these processes could be omitted, the number of processes would be significantly reduced and productivity would be improved. The improvement is clear. However, such omission of the number of steps must not impair the elasticity, curl retention, etc., which are originally required properties of the curl cord.

The present invention was made in view of these circumstances, and its purpose is to increase productivity by making it possible to omit unwinding and re-curl setting after curl setting, and to improve elasticity and The aim is to provide a curl cord that can exhibit properties superior to conventional curl cords in terms of curl retention and the like.

[Means for Solving the Problems] A curl cord according to the present invention that achieves the above object has a structure in which a sheath layer is further formed on the outer periphery of a conductive wire covered with an insulating material. In this case, the sheath layer is made by distributing two types of elastic resin materials with different shrinkage rates during molding in the longitudinal direction of the curl cord and integrating them, with the resin material having a higher molding shrinkage rate being placed on the inner surface of the curl. The gist lies in the fact that it is arranged in

[Function] The basic external structure of the curl cord according to the present invention is not particularly different from that of the conventional one; for example, as shown in FIG.
), (B) [(A) is the shortened state, (B) is the stretched state], it is made expandable and contractible by winding it with an appropriate spiral radius, and its cross-sectional structure is, for example, As shown in FIG. 2 [a cross-sectional view taken along the line 11--11 in FIG. Although this illustrated example shows a structure using two conductive wires 1, the conductive wires 1 may be used as a single conductive wire or three or more wires may be bundled together as required. Of course, the overall cross-sectional shape including the layer 3 can be not only a perfect circle but also an ellipse, a rectangle, or the like.

By the way, in the conventional curl cord, the sheath layer 3 is composed of a single elastic resin material, and in the curl set, as described above, an uncurled raw cord is wound in a spiral shape with a predetermined radius, and then heated and vulcanized. However, with conventional curl cords that use a single elastic resin material as the sheath layer 3, the curls loosen during the unwinding process after curl setting, so the curl shape must be adjusted and recurled. Therefore, the number of steps increases, and even after re-curling, depending on the usage conditions, the curl-setting effect may gradually be lost and the curl may loosen, causing problems such as a decline in restorability, especially after stretching. This is as explained earlier.

On the other hand, in the curl cord of the present invention, the material of the sheath F13 is divided in the longitudinal direction of the cord, as shown in FIG.
The resin material 3a (or 3b) having a higher shrinkage rate during molding is set to the inner surface, and the resin material 3a (or 3b) is curled. In curl setting, the helical radius at the time of molding is set in consideration of the difference in molding shrinkage rate between the resin materials 3a and 3b. As a result, the curl cord after the curl setting process has resin materials 3a and 3 that constitute the sheath layer 3.
A force to maintain the helical shape is naturally applied due to the difference in molding shrinkage rate b. Therefore, even if the curl is unwound after curl setting, the curl will not be loosened, and there is no need for the conventional re-curl setting process. Moreover, the curl is naturally imparted due to the difference in molding shrinkage rate between the resin materials 3a and 3b constituting the sheath layer, and is not forcibly imparted. Since the expansion and contraction forces of the resin materials 3g and 3b are stably maintained in a balanced state within the cross section of the cord, the restoring force and durability after stretching are also superior to those of conventional curl cords. The difference in molding shrinkage rate between the resin materials 3a and 3b may be adjusted appropriately depending on the target helical radius of the curl cord, but if the difference is set to 0.3% or more, the curl characteristics after curl setting will be the same as before. It can be significantly improved compared to the previous one.

In this way, in the present invention, the sheath layer has two different molding shrinkage rates.
It is characterized by the fact that it is made of a variety of elastic resin materials, and is curled with the side with a higher molding shrinkage on the inner surface to form a spiral. Although there are no restrictions on the type, preferred examples are as follows.

First, the material of the insulation coating 2 may be any material as long as it has insulation properties, and natural rubber, synthetic rubber, or various synthetic resins are used, but the curl set provided by the sheath layer Polyester-based elastic resins are particularly preferred as materials that aid in elasticity and curling properties, and among these, polyester-based elastic resins whose soft segments are aliphatic polyesters tend to deteriorate upon contact with conductive wires made of metal. It is preferable because it has excellent durability and no oxidation.

Next is the elastic resin material 3a that constitutes the sheath layer 3.

3b does not matter what type it is as long as it has insulation and elasticity, but the elasticity, flexibility, curl retention, restorability, and resistance when stretched are required for normal curl cords. Taking all of the above into consideration, the most preferred is a polyester elastic resin and a polyvinyl chloride resin in a weight ratio of 100.
10-5/95, more preferably 70/30-10/9
This is a resin composition that is uniformly mixed at a ratio of 0. In other words, polyvinyl chloride resin has traditionally been the most commonly used material for forming the sheath layer of curl cords, and curl cords made of this resin have good curl retention under high-temperature usage conditions and curl recovery at low temperatures. However, using a resin composition in which 5 parts by weight or more of a polyester elastic resin is mixed with 95 parts by weight of a polyvinyl chloride resin solves the above problem and improves curl retention and curl recovery. A curl cord with excellent properties can be obtained. However, if the blending ratio of polyester elastic resin exceeds 70%, the elasticity of the curl cord will become too strong and the resistance during curl extension will become strong, so it is recommended to keep the blending ratio of polyester elastic resin below 70%. desirable.

Particularly preferred as the above-mentioned elastic polyester resin suitable as a material for forming the sheath layer is one in which aromatic polyester is used as a hard segment, and either or both of aliphatic polyether and aliphatic polyester are used as soft segments. The acid component that forms the aromatic polyester of the hard segment, which is a block copolymer, includes terephthalic acid, isophthalic acid, and orthophthalic acid.

Examples include aromatic dicarboxylic acids such as naphthalene dicarboxylic acid, and examples of glycol components include ethylene glycol and 1,3-propanediol.

Examples include aliphatic or alicyclic glycols having 2 to 12 carbon atoms, such as 1,4-butanediol and 1,6-hexanediol. The acid component preferably contains terephthalic acid and/or naphthalene dicarboxylic acid in an amount of 60 mol % or more. Furthermore, if necessary, a small amount of trivalent or higher polyhydric carboxylic acid or polyhydric alcohol may be used in combination.

The aliphatic polyether constituting the soft segment is preferably an alkylene oxide polymer having an average molecular weight of 400 to 6,000 and a carbon number of 2 to 10, such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. , polyhexamethylene glycol, ethylene glycol, propylene glycol, and other block or random copolymers, and these can be used alone or in combination.

The aliphatic polyester constituting the soft segment is polyethylene adipate.

In addition to polytetramethylene sebacate, polyesters of dimer acid and alkylene glycol, etc., aliphatic copolymerized polyesters made of mixed acids and mixed glycols may be mentioned, and these can also be used alone or in combination. Furthermore, polylactones such as polyε-caprolactone and polyvalerolactone may be used.

Preferred polyvinyl chloride resins to be mixed with the above-mentioned polyester elastic resins include vinyl chloride homopolymers, vinylidene chloride, vinyl acetate, ethylene, propylene, acrylic acid, acrylic esters, Examples include copolymers with chlorinated polyethylene and the like, and among them copolymers with vinyl acetate are most preferred, with an average degree of polymerization of 500 or more, more preferably 1000 or more. These resins contain stabilizers, lubricants, pigments,
Commonly used compounding agents such as plasticizers may be added, and modifiers such as polyurethane may also be used in combination.

[Example] A stranded copper body with an outer diameter of 0.31011 was coated with polyester elastic resin A (hard segment: polybutylene terephthalate, soft segment: polylactone) by extrusion molding to obtain a core wire with a diameter of 0.5+ am. . Four of the obtained core wires were twisted together, and blended resin compositions (1) and (II) of polyester elastic resin and polyvinyl chloride resin having the composition and molding shrinkage rate shown in Table 1 below were applied onto each cylinder. The resin compositions (I) and (II) were simultaneously extruded through two divided mold discharge ports to form a sheath layer in which the resin compositions (I) and (II) were combined into a bimetallic structure. The diameter of the obtained cord is 1. The thickness of the s'MW+s sheath layer was approximately 1.0 mm.

This cord has a diameter of 8 m with the resin composition (! Summer) inside.
The cord was wound around a cylindrical cylinder having a diameter of 1.5 mm and heat set at 140° C. for 30 minutes to obtain a curled cord with a curled outer diameter of 13 mm (no unwinding or resetting).

The resulting curled cord with a horizontal free length (Lo) of 200a++s (cord length before curling: 20000111)
Table 2 shows the performance of

Table 1 Umbrella Nihard segment is polybutylene terephthalate, soft segment is polytetramethylene glycol (
Content 80! ! amount%).

◆ Nihard segment is polybutylene terephthalate, soft segment is polytetramethylene glycol (content 40% by weight).

In the axis: injection molding plate (measured by molding shrinkage rate of 100X100X2M).

As is clear from Table 2, the curl cord of the present invention can stretch curls with a small load, and also has excellent curl recovery properties after weight removal.

[Effects of the Invention] The present invention is configured as described above, and by making the sheath layer a composite of elastic resin materials with different molding shrinkage rates,
It is now possible to omit the re-curl setting process and to provide a curled cord with excellent elasticity and curl retention (curl restorability).

[Brief explanation of the drawing]

FIGS. 1A and 1B are partial side views illustrating the curl cord, and FIG. 2 is a cross-sectional view illustrating the curl cord of the present invention. 1... Conductive wire 2... Insulating material 3.3a,
3b...Sheath layer Figure 1 Old Figure 2

Claims (1)

[Claims] A curl cord is made by forming a sheath layer on the outer periphery of a conductive wire covered with an insulating material.The sheath layer consists of two types of elastic resin materials with different shrinkage rates during molding, distributed in the longitudinal direction of the curl cord. A curl cord is characterized in that it is a composite integrated cord, and a resin material with a high molding shrinkage rate is arranged on the inner surface of the curl.