JP2007134277A - Insulated wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulated wire containing a polylactic acid and having desired flexibility. <P>SOLUTION: The insulated wire 10 comprises a conductor 11, and a cover 12 covering the conductor 11. The cover 22 is formed by stacking a first layer 12b formed of a polylactic acid and having a thickness t1, and a second layer 12a located inside the first layer 12b, formed of an ethylene-based polymer, and having a thickness t2, and satisfies expression (I). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an insulated wire.

In recent years, it has been studied to use an insulating material made of an insulating composition containing polylactic acid as a covering material for insulated wires (see Patent Document 1). Polylactic acid is a thermoplastic resin obtained by chemically polymerizing lactic acid produced by fermenting starch or sugars obtained from plants such as corn or sugar beet, and is environmentally friendly and has excellent insulating properties.
JP 2002-358829 A

  However, conventional coating materials using polylactic acid are relatively brittle and lack flexibility. For this reason, an insulated wire used for such a covering material is cracked in the covering material when bent with a relatively large curvature (that is, a small radius) as seen in, for example, low-voltage wiring, and the insulation of the wire There is a possibility of lowering the withstand voltage.

  The present invention has been made to address such conventional problems. Therefore, an object of the present invention is to provide an insulated wire containing polylactic acid and having desired flexibility.

In order to solve the above problems, an insulated wire according to the present invention includes a conductor portion and a covering portion that covers the conductor portion, and the covering portion includes a first layer having a thickness t1 made of polylactic acid, It is located inside the first layer and is formed by laminating a second layer having a thickness t2 made of an ethylene-based polymer, and satisfies the following formula (I).

  ADVANTAGE OF THE INVENTION According to this invention, it has flexibility and the insulated wire excellent in the bending characteristic is provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  First, the insulated wire 10 which concerns on embodiment of this invention with reference to FIGS. 1-3 is demonstrated. FIG. 1 is a cross-sectional view of an insulated wire 10 obtained by extrusion-molding an ethylene polymer 1 and polylactic acid (PLA) 4 as coating materials 12a and 12b. FIG. 2 is a diagram of the ethylene polymer 1 and PLA 4 coated with coating materials 22a, 22b and 22c. It is sectional drawing of the cable 20 extruded as. FIG. 3 is a manufacturing process diagram.

  The insulated wire 10 includes a conductor portion 11 made of a stranded wire obtained by twisting a plurality of copper strands 11a, and a covering portion 12 for insulatingly covering the conductor portion 11. The covering portion 12 is formed of a laminate including an outer layer 12b having a thickness t1 made of PLA4 and an inner layer 12a having a thickness t2 made of an ethylene polymer 1 and located inside the outer layer 12b. The covering portion 12 is commercialized into a state 14 in which an insulating material containing an additive for electric wires is extruded onto the conductor portion 11 and is seamlessly formed so that the seam 13 indicated by the phantom line is eliminated.

The insulated wire 10 satisfies the following formula (I).

  The insulated wire 20 includes a conductor portion 11 made of a stranded wire obtained by twisting a plurality of copper strands 11a and a covering portion 22 for insulatingly covering the conductor portion 11. The covering portion 22 is located on the inner side of the outer layer 22b made of PLA4 and having the thickness t1, and is located on the inner side of the inner layer 22a made of the ethylene-based polymer 1 and on the outer side of the outer layer 22b. 1 and an outermost layer 22c having a thickness t3. The covering portion 22 is commercialized into a state 24 in which an insulating material containing an additive for electric wires is extruded onto the conductor portion 11 and is seamlessly formed so that the seam 23 indicated by an imaginary line is eliminated.

The insulated wire 20 satisfies the following formula (II).

  Next, a method for manufacturing the insulated wires 10 and 20 will be described.

  The manufacturing method of the insulated wire 10 includes a preparation step 30 for preparing the first and second insulating materials 3 and 6 for the wire, and the prepared first and second insulating materials 3 and 6 as a covering material. And a molding step 40 for extrusion molding.

  The preparation step 30 includes adding a first additive 2 (for example, a flame retardant) to the ethylene polymer 1 and kneading to obtain the first insulating material 3, and adding a second additive 5 (for example, the PLA 4). A flame retardant) and kneading to obtain the second insulating material 6.

  In the molding step 40, first, the first insulating material 3 is extruded as an inner layer 12a on the conductor portion 11, and is molded into a state in which the first insulating material 3 is seamlessly molded so as to eliminate the seam 13a indicated by a virtual line. Next, the second insulating material 6 is extruded as an outer layer 12b onto the conductor portion 11 covered with the inner layer 12a, and is molded into a state in which the second insulating material 6 is seamlessly molded so as to eliminate the seam 13b indicated by a virtual line (second molding 42). ), Manufacturing the insulated wire 10.

  In the case of manufacturing the insulated wire 20, in the molding step 40, first, the first insulating material 3 is extruded as the inner layer 22a on the conductor portion 11, and is seamlessly molded so that the seam 23a indicated by the phantom line is eliminated. To form. Next, the second insulating material 6 is extruded as the outer layer 22b onto the conductor portion 11 covered with the inner layer 22a, and is molded into a state of being seamlessly molded so that the joint line 23b indicated by the phantom line is eliminated (second molding 42). ). Next, the first insulating material 3 is extruded as the outermost layer 22c on the conductor portion 11 covered with the inner layer 22a and the outer layer 22b, and is molded into a state in which the seam 23c indicated by the phantom line is seamlessly formed ( 3rd shaping | molding 43) and the insulated wire 20 are manufactured.

  Insulated wires 10 and 20 have covering parts 12 and 22 made of a laminate of PLA 4 and ethylene polymer 1, PLA 4 has insulating properties, good biodegradability, and ethylene polymer 1 is flexible. Therefore, it functions as a flexible insulated wire.

  In the insulated wires 10 and 20, when the formulas (I) and (II) are not satisfied, the effect of the ethylene polymer 1 cannot be obtained, so that cracks occur in the covering portions 12 and 22 when bent.

  The ethylene polymer is preferably any one selected from ethylene-vinyl acetate copolymer resin (EVA), ethylene-acrylate copolymer resin, and ionomer resin. Since these ethylene polymers have flexibility, they are suitable for use as the first insulating material 3. Here, the ethylene-acrylate copolymer resin is selected from ethylene-methyl acrylate copolymer resin (EMA), ethylene-ethyl acrylate copolymer resin (EEA), and ethylene-butyl acrylate copolymer resin (EBA). Sure.

  The ethylene polymer preferably has a flexural modulus of 14 MPa or more. In this case, cracks do not occur in the covering portions 12 and 22 when the insulated wires 10 and 20 are bent. When the bending elastic modulus of the ethylene polymer is less than 14 MPa, cracks occur in the covering portions 12 and 22. For this reason, it is preferable that the ethylene-based polymer has a flexural modulus of 14 MPa or more.

  Examples 1 to 9 were performed as examples of the above embodiment, and Comparative Examples 1 to 3 were performed for comparison.

1. Sample Preparation Each sample was made to have a laminated structure in which an ethylene polymer layer and a PLA layer were layered to give flexibility to the electric wire. PLA is Mitsui Chemical Lacia H400, ethylene polymer is ethylene-ethyl acrylate copolymer resin (EEA) is Mitsui-DuPont Polychemical A-703, -704, ethylene-vinyl acetate copolymer resin (EVA) is Mitsui Poly Chemical companies EV260 and 220 were used.

Example 1
EEA A-703 (flexural modulus of 14 MPa) was used as the inner layer and PLA H400 (flexural modulus of 3280 MPa) was used as the middle layer. The inner layer has a thickness of 0.1 mm, and the middle layer has a thickness of 0.7 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.8 mm of the covering portion obtained by adding the thickness of the inner layer and the middle layer is 12.5%.

Example 2
EEA A-703 was used as the inner layer, and PLA H400 was used as the middle layer. The inner layer has a thickness of 0.2 mm, and the middle layer has a thickness of 0.6 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.8 mm of the covering portion obtained by adding the thickness of the inner layer and the middle layer is 25%.

Example 3
EEA A-703 was used as the inner layer, and PLA H400 was used as the middle layer. The inner layer has a thickness of 0.3 mm, and the middle layer has a thickness of 0.5 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.8 mm of the covering portion obtained by adding the thickness of the inner layer and the middle layer is 37.5%.

Example 4
EEA A-703 was used as the inner layer, PLA H400 as the middle layer, and EEA A-703 as the outer layer. Each of the inner layer and the outer layer has a thickness of 0.1 mm, and the middle layer has a thickness of 0.6 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.8 mm of the covering portion obtained by adding the thicknesses of the inner layer, the middle layer, and the outer layer is 12.5%, and the ratio of the thickness of the inner layer and the outer layer to the layer thickness is 25%.

Example 5
EEA A-703 was used as the inner layer, PLA H400 as the middle layer, and EEA A-703 as the outer layer. The inner layer has a thickness of 0.2 mm, the middle layer has a thickness of 0.5 mm, and the outer layer has a thickness of 0.1 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.8 mm of the covering portion obtained by adding the thicknesses of the inner layer, the middle layer, and the outer layer is 25%, and the ratio of the thickness of the inner layer and the outer layer to the layer thickness is 37.5%.

Example 6
EVA EV260 (flexural modulus 16 MPa) was used as the inner layer, PLA H400 was used as the middle layer, and EVA EV260 was used as the outer layer. The inner layer has a thickness of 0.1 mm, the middle layer has a thickness of 0.6 mm, and the outer layer has a thickness of 0.1 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.8 mm of the covering portion obtained by adding the thicknesses of the inner layer, the middle layer, and the outer layer is 12.5%, and the ratio of the thickness of the inner layer and the outer layer to the layer thickness is 25%.

Example 7
EEA A-703 was used as the inner layer, PLA H400 as the middle layer, and EEA A-703 as the outer layer. The inner layer has a thickness of 0.1 mm, the middle layer has a thickness of 0.4 mm, and the outer layer has a thickness of 0.1 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.6 mm of the covering portion plus the thickness of the inner layer, the middle layer, and the outer layer is 16.7%, and the ratio of the thickness of the inner layer and the outer layer to the layer thickness is 33.3%. .

Example 8
EEA A-704 (flexural modulus of 8 MPa) was used as the inner layer, PLA H400 was used as the middle layer, and EEA A-704 was used as the outer layer. The inner layer has a thickness of 0.1 mm, the middle layer has a thickness of 0.6 mm, and the outer layer has a thickness of 0.1 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.6 mm of the covering portion obtained by adding the thicknesses of the inner layer, the middle layer, and the outer layer is 12.5%, and the ratio of the thickness of the inner layer and the outer layer to the layer thickness is 25%.

Example 9
EVA EV220 (flexural modulus of 10 MPa) was used as the inner layer, PLA H400 was used as the middle layer, and EVA EV220 was used as the outer layer. The inner layer has a thickness of 0.1 mm, the middle layer has a thickness of 0.4 mm, and the outer layer has a thickness of 0.1 mm. The ratio of the thickness of the inner layer to the layer thickness of 0.6 mm of the covering portion obtained by adding the thicknesses of the inner layer, the middle layer, and the outer layer is 12.5%, and the ratio of the thickness of the inner layer and the outer layer to the layer thickness is 25%.

Comparative Example 1
A comparative example 1 was obtained by using only the PLA layer as a covering portion. The thickness of the covering portion is 0.8 mm.

Comparative Example 2
Comparative Example 2 was prepared by providing an EEA A-703 layer outside the PLA layer. The thickness of the PLA layer is 0.7 mm, and the thickness of the EEA layer is 0.1 mm.

Comparative Example 3
Comparative Example 3 was prepared by providing an EEA A-703 layer outside the PLA layer. The thickness of the PLA layer is 0.6 mm, and the thickness of the EEA layer is 0.2 mm.

  The samples obtained in each experimental example were evaluated by the cable bending test shown below.

2. Cable bending test In the cable bending test, an insulated wire made around a metal rod having a diameter of 12.8 mm, which is four times the diameter of the conductor, was wound twice, and the state of the covered portion of the insulated wire was observed.

3. Test Results FIG. 4 shows the results of the cable bending test.

  In Comparative Example 1 in which the covering portion was formed of PLA alone, cracks occurred in the PLA layer. On the other hand, in Examples 1 to 3, no cracks occurred in the PLA layer, an inner layer of an ethylene polymer was provided inside the PLA layer, and the thickness of the inner layer relative to the thickness of the entire coating portion was 12.5%. In this case, it was found that cracks generated in the PLA layer can be suppressed. Further, from Comparative Example 2 and Comparative Example 3, when only the outer layer of the ethylene-based polymer is provided outside the PLA layer, even if the thickness of the outer layer is 12.5% or more with respect to the total thickness of the covering portion It has been found that the effect of suppressing crack generation cannot be obtained.

  From Example 4 to Example 7, the ratio of the thickness of the inner layer to the layer thickness of the covering portion obtained by adding the thickness of the inner layer, the PLA layer (middle layer), and the outer layer by providing an ethylene polymer layer inside and outside the PLA layer When the ratio of the thickness of the inner layer and the outer layer to the layer thickness is 25% or more, it was found that cracks generated in the PLA layer can be suppressed.

  In Example 8, the thickness of the inner layer was 12.5% with respect to the thickness of the entire coating portion, and the ratio of the thickness of the inner layer and the outer layer to the layer thickness was 25%, but the bending elastic modulus of the inner layer and the outer layer was Since it was 8 MPa, cracks occurred in the PLA layer. In Example 9, the thickness of the inner layer was 12.5% with respect to the total thickness of the covering portion, and the ratio of the thickness of the inner layer and the outer layer to the layer thickness was 25%. Since the elastic modulus was 10 MPa, cracks occurred in the PLA layer. Thus, from Example 8 and Example 9, even when the ethylene polymer layer is provided on the inside and outside of the PLA layer, if the bending modulus of the ethylene polymer is 14 MPa or less, the PLA layer A crack occurred.

  As described above, in the cable bending test, the dielectric breakdown can be prevented by providing the ethylene polymer layer inside the PLA layer or inside and outside the PLA layer. However, it has been found that when the flexural modulus of ethylene polymer is 14 MPa or less, dielectric breakdown occurs when bending with a large curvature.

  Although the embodiment of the present invention has been described above, it should not be understood that the description and the drawings, which constitute a part of the disclosure of the above embodiment, limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

It is sectional drawing of the insulated wire which concerns on embodiment of this invention. It is sectional drawing of the insulated wire which concerns on embodiment of this invention. FIG. It is a table | surface which shows the result of a cable bending test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 ... Insulated wire 11 ... Conductor part 11a ... Elementary wire 12, 22 ... Covering part 12a, 22a ... Inner layer 12b, 22b ... Outer layer 22c ... Outermost layer

Claims (7)

It consists of a conductor part and a covering part covering this conductor part, and the covering part is located inside the first layer made of polylactic acid and having a thickness t1, and made of an ethylene-based polymer. An insulated wire characterized by being laminated with a second layer having a thickness t2 and satisfying the following formula (I).

  The insulated wire according to claim 1, wherein the second layer is an innermost layer of the covering portion. Further, according to claim 1 or claim 2, further comprising a third layer having a thickness t3 made of an ethylene-based polymer, located outside the first layer, and satisfying the following formula (II): Insulated wire as described.

  The insulated wire according to claim 3, wherein the third layer is an outermost layer of the covering portion.   The said ethylene polymer is any one selected from ethylene-vinyl acetate copolymer resin, ethylene-acrylate copolymer resin, and ionomer resin, It is any one of Claim 1 thru | or 4 characterized by the above-mentioned. Insulated wires.   The ethylene-acrylate copolymer resin is any one selected from an ethylene-methyl acrylate copolymer resin, an ethylene-ethyl acrylate copolymer resin, and an ethylene-butyl acrylate copolymer resin. Insulated wires. The insulated wire according to any one of claims 1 to 6, wherein the ethylene polymer has a flexural modulus of 14 MPa or more.

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