JP2013155272A - Mixed insulating material and molded article thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new mixed insulating material which has both characteristics of flexibility and heat resistance or cold resistance that conventional insulating materials lack, and is excellent in cost-effectiveness, and a molded article thereof.SOLUTION: The mixed insulating material is obtained by melting and mixing a polyester-based copolymer and silicone rubber under a desired condition without using a compatibilizing agent. The molded article such as a cable, tube or packing is obtained by molding the mixed insulating material. The content ratio (wt.%) of the polyester-based copolymer to the silicone rubber is preferably 90:10 to 5:95.

Description

The present invention relates to a novel mixed insulating material and a molded product thereof, and is particularly characterized by having all of heat resistance, cold resistance, oil resistance, mechanical strength and flexibility, and excellent cost performance. is there.

As a general insulating material, polyethylene is often used as an inexpensive and general-purpose material. In an environment where flexibility, heat resistance and cold resistance are required, silicone rubber is used. However, it has been pointed out that polyethylene has low heat resistance and silicone rubber has poor oil resistance and mechanical strength.
Fluororubber is a flexible material having better heat resistance and oil resistance than silicone rubber, but has poor cold resistance and has problems of high cost and high specific gravity.
Other high-performance materials include polyimide, fluororesin, and the like, but they have poor flexibility and are expensive and have a problem in terms of cost.
Under these circumstances, in recent years, while high performance is demanded for insulating materials, inexpensive materials that meet cost competition are desired. For example, in the automobile industry, development of hybrid cars and electric cars is active, but in hybrid cars, some wiring in the engine room etc. is used in harsh environments with high temperatures and a lot of oil. Insulating materials with oil resistance in addition to cold resistance are required. In electric vehicles, various units are modularized and compact for the purpose of cost reduction and weight reduction, and the wiring space is extremely small in such a place, so it is flexible so that wiring is easy. A highly insulating material is highly desired. It has been a challenge to obtain a high-performance insulating material having these characteristics at a lower cost.
As one of the conventional techniques for obtaining a high-performance insulating material, a thermosetting rubber plastic material obtained by co-vulcanization using a polyorganosiloxane and a polyester or polyether, which are main components of silicone rubber, and a compatibilizing agent. It has been known. (Patent Document 1)
In addition, a thermoplastic silicone elastomer composition obtained by mixing filled silicone rubber, compatibilizer, polyimide, polyester resin or the like and dynamically vulcanizing the silicone rubber in the presence of an initiator is also known. (Patent Document 2)
However, all of these known techniques are characterized by the use of a compatibilizer in order to improve the strength and dispersibility at the interface between different types of polymers, while the flexibility and heat resistance of the composition are excellent, The cost is increased due to the material cost and the addition / vulcanization process.

Japanese Patent No. 2608350 US Pat. No. 6,465,552

The object of the present invention is to combine all of heat resistance, cold resistance, oil resistance, mechanical strength and flexibility that cannot be realized with a single material such as polyethylene and silicone rubber and a polymer blend material as in the prior art. And it is providing the mixed insulation material excellent in cost performance, and its molded article.

The mixed insulating material according to the present invention comprises a polyester copolymer and silicone rubber, and is obtained by melt mixing without using a compatibilizer.
As a result of repeated trial manufactures, the inventors set the content ratio (wt%) of the polyester copolymer and the silicone rubber to 90:10 to 5:95, and melt-mixed them under desired conditions. A new mixed insulating material having excellent dispersibility has been obtained without using any other material.
Considering higher performance such as heat resistance and productivity at the time of molding into an electric wire, tube, packing, etc., a more preferable range of the content ratio (wt%) of the polyester copolymer and silicone rubber is 85:15. ~ 55: 45.
Moreover, the heat resistance temperature (based on UL758) of the mixed insulating material is at least 150 ° C., the embrittlement temperature indicating cold resistance (based on JIS K7216) is −60 ° C. or less, and the hardness indicating flexibility (JIS K6253 compatible type A) is 35 to 35 ° C. 95.

According to the present invention, the following remarkable effects are exhibited.
(1) The mixed insulating material of the present invention is superior in heat resistance, cold resistance, oil resistance and flexibility as compared with polyethylene.
(2) The mixed insulating material of the present invention has much improved oil resistance compared to silicone rubber, and is equivalent in flexibility, heat resistance, cold resistance and cost. As an incidental effect of mixing the polyester copolymer, the mechanical strength is improved as compared with the silicone rubber alone.
(3) The mixed insulating material of the present invention is slightly inferior in heat resistance as compared with fluororubber, but is extremely excellent in cold resistance and low in cost.
(4) Although the mixed insulating material of the present invention is slightly inferior in heat resistance as compared with high-performance materials such as polyimide and fluororesin, it is almost equivalent in cold resistance and remarkably excellent in flexibility. In addition, the weight can be reduced due to the small specific gravity.
(5) Since mixing and molding by heating and melting are possible, a process such as mixing and vulcanizing materials in advance is unnecessary, and manufacturing costs can be greatly reduced.
(6) Since a third component material such as a compatibilizer other than the polyester-based copolymer and silicone rubber is not required, the material cost can be suppressed and the deterioration of characteristics due to the third component material can be prevented.

FIG. 1 is an image taken by a scanning electron microscope showing a mixed state of the mixed insulating material in the present invention. (Example 6) FIG. 2 is a sectional view of an insulated wire using the mixed insulating material according to the present invention. (Example 6 and Example 7)

The main aspects of obtaining the mixed insulating material of the present invention are as follows.

The mixed insulating material of the present invention comprises a polyester copolymer and silicone rubber, and can be obtained by melt mixing without using a compatibilizer. Specifically, the polyester-based copolymer is a material obtained by copolymerizing several kinds of polyesters, and serves as a compatibilizer in the prior art.
The content ratio (wt%) of the polyester copolymer and the silicone rubber is 90:10 to 5:95. In view of high performance such as heat resistance and productivity at the time of molding into an electric wire, tube, packing, etc., a more preferable range is 85:15 to 55:45.

Here, if there is much content of a polyester-type copolymer, while the softness | flexibility of silicone rubber will be impaired, oil resistance and mechanical strength will be improved.
When the content of the silicone rubber is large, flexibility is imparted, but molding by melt extrusion becomes difficult, and oil resistance is also impaired.

By mixing the polyester copolymer of this content ratio and silicone rubber under desired conditions, a mixed insulating material having excellent strength and dispersibility at the interface between different polymers can be obtained without using a compatibilizer. It is done. Specifically, in consideration of the amount of self-heating due to shearing of the polyester copolymer during melt mixing, each is mixed with silicone rubber at a temperature lower by about 15 ° C. to 20 ° C. than the melting point of the polyester copolymer. Since the materials have substantially the same viscosity and excellent dispersibility can be obtained, a third component material such as a compatibilizer is not necessary.
The method of melt mixing is not particularly limited, but it is preferable to use a general heat melt extruder, a heat kneader or mixer, a heat double roll or the like.
In extrusion molding, a content ratio (wt%) of 90:10 to 55:45 is suitable for heat-melt extrusion, and a content ratio (wt%) of 30:70 to 5:95 is electron beam crosslinking or ultraviolet radiation after heat-melt extrusion. A method of forming a rubber elastic body by irradiation crosslinking is suitable. In addition, when the above-described crosslinking method cannot be performed at a content ratio (wt%) of 30:70 to 5:95, cooling is performed after compounding by heating and melt-kneading in advance, and a crosslinking agent is added and heated after molding. The optimum molding method varies depending on the content ratio such as crosslinking.

"Example 1 to Example 5"
Here, the content ratio (wt%) of the polyester-based copolymer (a) and the silicone rubber (b) and the results of examining various properties such as heat resistance, cold resistance, oil resistance and flexibility are shown in Table 1. Show.

From Table 1, when the content ratio (wt%) of the polyester copolymer (a) and the silicone rubber (b) of Examples 1 to 5 is 90:10 to 5:95, heat resistance, cold resistance, and oil resistance are obtained. It can be seen that it has both mechanical strength and flexibility and is excellent in cost performance. In the content ratio (wt%) 85:15 to 55:45 of Example 2 and Example 3, the above characteristics are stable and good, the MFR is high, and heat melt extrusion is possible, and the productivity is good. Therefore, it can be said to be a particularly preferable range.
In the flexibility, that is, the hardness (JIS K6253 compliant type A), the mixed insulating material of the present invention is increased in flexibility by mixing silicone rubber, and the polyester-based copolymer alone of Comparative Example 1 and Comparative Example 2 and Compared to a mixture having a content ratio (wt%) of 95: 5, a polyethylene simple substance of Conventional Example 1 and a fluororesin simple substance such as FEP of Conventional Example 3, the flexibility is excellent.
Silicone rubber properties also contribute to the embrittlement temperature (conforming to JIS K7216) showing cold resistance. In particular, the superiority is significant compared to the conventional fluororubber alone.
In heat resistance (based on UL758), since the polyester copolymer and silicone rubber, which are constituent elements of the material of the present invention, are both superior, the fluororubber alone of Conventional Example 2 and the FEP alone of Conventional Example 3 are inferior. The polyethylene alone of Conventional Example 1 has much higher heat resistance.
In the mechanical strength (according to ASTM D638), the strength weakness of the silicone rubber is compensated by the superiority of the polyester-based copolymer, and good strength characteristics can be obtained stably.
Also in oil resistance (ISO 6722 compliant), the superiority of the polyester-based copolymer compensates for the weak oil resistance of the silicone rubber, and stably obtains good characteristics. The polyethylene alone of Conventional Example 1 and Comparative Example 3 Has much higher oil resistance than silicone rubber alone.
In compression set (according to JIS K6262), the superiority of silicone rubber compensates for the compression set weakness of the polyester copolymer, so that stable and good characteristics can be obtained. Comparative Example 1 and Comparative Example 2 The polyester-based copolymer alone and a mixture with a content ratio of 95: 5, the polyethylene simplex of Conventional Example 1 and the FEP simplex of Conventional Example 3 have far superior compression set characteristics.
In comprehensive evaluation, flexible and inexpensive electric wires having heat resistance / cold resistance of −40 ° C. to 150 ° C. and oil resistance (gasoline resistance), which are listed as required characteristics of electric wires for hybrid vehicles and electric vehicles in recent years The applicability was determined based on the above. In Examples 1 to 5 of the present invention, compared with the comparative example and the conventional example, it has comprehensively stable and excellent characteristics, and in Examples 2 and 3, it is particularly excellent. It can be said that.
In addition to the characteristic items listed in Table 1, improvement in weather resistance and corona resistance has also been confirmed as an accompanying effect of the present invention.

As described above, when the mixed insulating material of the present invention is used, it has all of heat resistance, cold resistance, oil resistance, mechanical strength and flexibility, which cannot be sufficiently compensated by the conventional insulating material, and is excellent in cost performance. In addition, molded products such as insulated wires, tubes and packings are obtained.
Hereinafter, the example of the insulated wire shown in FIG. 2 is given as an example of manufacturing a molded article using the mixed insulating material of the present invention.
"Example 6 and Example 7"

Insulated wire 4 (φ1.7 mm) shown in FIG. 2 in which a mixed insulating material 1 of the present invention is coated with a thickness of 0.4 mm on a tin-plated annealed copper wire conductor 5 (φ0.9 mm, conductor configuration 19 pieces / 0.18 mm) Get. The evaluation results of this insulated wire 4 are shown in Table 2.

From Table 2, the insulated wires having the content ratio (wt%) of the polyester copolymer (a) of Example 6 and Example 7 and the silicone rubber (b) of 85:15 and 55:45 in any characteristics. It turns out that it has the intermediate characteristic of the polyester-type copolymer single-piece | unit of Comparative Example 4 and Comparative Example 5, and a silicone rubber single-piece | unit.
In terms of the tensile strength after heating and the remaining elongation rate (based on UL758), Example 6 and Example 7 have characteristics comparable to the fluororubber electric wire of Conventional Example 5 and the FEP electric wire of Conventional Example 6.
The tensile strength and the remaining elongation rate after immersion in gasoline are as follows. The insulated wire with the content ratio (wt%) 85:15 in Example 6 has characteristics comparable to the fluororubber wire in Conventional Example 5 and the FEP wire in Conventional Example 6. doing.
On the other hand, the insulated wire having a content ratio of 55:45 in Example 7 is slightly deteriorated due to the influence of silicone rubber, as is apparent from the result of the silicone rubber wire in Comparative Example 5, but is equivalent to the polyethylene wire in Conventional Example 4. Has characteristics.
The tensile strength and the residual elongation rate after immersion in ATF are far superior to the polyethylene wire of Conventional Example 4, and have the same level of characteristics as the fluororubber wire of Conventional Example 5 and the FEP wire of Conventional Example 6. ing.
The electrical characteristics of insulation resistance and dielectric breakdown voltage are inferior to those of the conventional wires 4 to 6, but for example, it is confirmed that they are at a level that can be used satisfactorily with low-voltage wires for vehicles. Has been. Furthermore, when the mixed insulating material of the present invention is used as a jacket material, a high-voltage electric wire can also be used.

The mixed state of the polyester-based copolymer 3 and the silicone rubber 2 when the mixed insulating material 1 of the present invention is formed into the covered electric wire 4 is shown in FIG.
FIG. 1 is an image obtained by observing the mixed state of the insulated wire 4 having a content ratio (wt%) of 85:15 in Example 6 with a scanning electron microscope. By extracting only the silicone rubber part 2 from the insulator cross section of the insulated wire 4 with a solvent, the silicone rubber part 2 having a small round gap and the other polyester-based copolymer part 3 can be confirmed. From FIG. 1, it can be confirmed that the silicone rubber portion 2 is uniformly dispersed at the nano-order level.

The present invention can be widely used for molded products such as various insulated wires, wire coating materials, tubes, and packings. In particular, flexibility, heat resistance, cold resistance, mechanical strength and oil resistance are required, such as motors for hybrid vehicles and electric vehicles, and can be effectively used in fields with severe cost performance.

1 Mixed insulating material of the present invention 2 Silicone rubber (extraction part by solvent)
3 Polyester copolymer 4 Insulated wire 5 using the mixed insulating material of the present invention 5 Conductor

Claims (7)

A mixed insulating material of a polyester copolymer and silicone rubber, which is obtained by melt mixing without using a compatibilizer. A molded product such as a covered electric wire, a tube, and packing obtained by molding the mixed insulating material according to claim 1. 3. The mixed insulating material according to claim 1, wherein the content ratio (wt%) of the polyester copolymer and the silicone rubber is 90:10 to 5:95. 4. 4. The mixed insulating material according to claim 1, wherein the content ratio (wt%) of the polyester copolymer and the silicone rubber is 85:15 to 55:45. 5. Goods. The mixed insulating material or molded product thereof according to any one of claims 1 to 4, wherein the heat resistant temperature (based on UL758) is at least 150 ° C. The mixed insulating material according to any one of claims 1 to 5, or a molded article thereof, wherein the embrittlement temperature at a cold resistant temperature (based on JIS K7216) is -60 ° C or lower. Hardness (JIS K6253 conformity type A) is 35-95, The mixed insulation material in any one of Claims 1-6, or its molded article.