JP7195037B2 - Mixed insulating materials and moldings - Google Patents

Description

The present invention relates to a new mixed insulating material and its molded product, and because it is particularly excellent in stress crack resistance and flexibility, it is mainly used for FA equipment such as industrial robots and semiconductor manufacturing equipment. Regarding.

2. Description of the Related Art Conventionally, electric wires/cables having excellent bending resistance have been known as electric wires/cables used in FA equipment.

For example, Patent Document 1 describes a material containing 0.5 to 3.0 wt % of an organic high-molecular-weight silicone polymer relative to a polyester elastomer as an insulating material for electric wires constituting a multicore cable. In this way, in a multi-core cable in which a plurality of insulated core wires coated with an insulating material containing an organic high-molecular-weight silicone polymer are twisted together and sheathed, silicone has a low affinity with other substances, and the surfaces adhere to each other. In order to prevent it from twisting and to provide releasability, the surface lubricity between the insulated core wires is improved, and when the cable is subjected to stress such as bending and twisting, the insulated core wires that are twisted together will be smooth to each other. It is described that it makes it easier to move, which in turn contributes to improvement in bending, twisting, and the like.

However, while the multi-core cable of Patent Document 1 can alleviate the stress between the insulated core wires, the durability of the insulated core wires themselves needs to be improved.

Japanese Patent No. 5307981

SUMMARY OF THE INVENTION An object of the present invention is to provide a mixed insulating material and a molded product thereof, which are excellent in stress crack resistance and bendability, and are particularly excellent in durability against repeated U-shaped and left-right 90° bending.

(1) A mixed insulating material composed of a main material made of polyester elastomer and a cushioning body made of silicone rubber , wherein the content of the cushioning body is more than 3 wt% and less than 10.0 wt% of the total mixed insulating material The main material is composed of at least two types of polyester elastomers with different flexural moduli, and the difference between the main material with the maximum flexural modulus and the minimum main material is 300 to 500 MPa, It is characterized by having a flexural modulus of 500 to 1000 MPa .
(2) It is preferable that each main material constituting the main material made of polyester elastomer is contained in the same weight.

ADVANTAGE OF THE INVENTION According to this invention, the following remarkable effects are exhibited.
(1) The mixed insulating material of the present invention contains a cushioning body made of silicone rubber in a main material made of polyester elastomer , thereby creating gaps between molecules, and the gaps relieve stress (distortion) between molecules. This improves stress crack resistance (that is, no cracks or the like occur even if left for a long time under a constant stress).
(2) Flexibility is imparted to the main material made of polyester elastomer , which is inherently excellent in rigidity, by containing the cushioning material. Therefore, when covering a conductor as an insulating material, the bending flexibility of the electric wire is improved.
(3) The buffer contains more than 3 wt% and less than 10.0 wt% of the total mixed insulating material, so that stress crack resistance and flexibility are improved without sacrificing formability. The durability against repeated 90° left and right bending is improved.
(4) When the main material made of polyester elastomer is composed of at least two main materials, and when the at least two main materials have different flexural moduli, molecules having both rigidity and flexibility characteristics is mixed, and the stress between molecules is relieved by the buffer, so that the durability against bending is improved.
(5) When the main material made of polyester elastomer is composed of at least two main materials and the difference between the maximum and minimum flexural modulus of each main material is 300 to 500 MPa, stress crack resistance and bending resistance are improved. The improvement in performance becomes remarkable.
(6) When the content of each of the main materials constituting the main material is the same, the dispersibility is excellent, and as a result, it contributes to the improvement of stress crack resistance and flexibility.
(7) When the flexural modulus is 500 to 1000 MPa, the stress crack resistance and flexibility are further improved, and the durability against repeated U-shaped and left-right 90° bending is improved.
(8) When the cushioning material is made of silicone rubber, it has excellent dispersibility with the polyester elastomer , so that a molded product with a smooth surface can be obtained.

Fig. 2 shows an image (a) taken by a scanning electron microscope (SEM) and an elemental mapping image (b) of a buffer, showing the mixed state of the mixed insulating material in the present invention. (Example 2) Schematic diagram of U-bending test is shown. The schematic of a right-and-left 90-degree bending test is shown.

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

The mixed insulating material of the present invention is a mixed insulating material composed of a main material made of polyester elastomer and a buffer made of silicone rubber , wherein the buffer is more than 3.0 wt% of the total mixed insulating material. and a content of less than 10.0 wt%. When the buffer content is more than 3.0 wt %, gaps are generated between the molecules of the polyester elastomer , which is the main material, to improve the stress crack resistance, and flexibility is exhibited, thereby improving flexibility. Here, stress cracking refers to a phenomenon in which cracks and breakage occur when the material is left under a constant stress for a long time. Improving the stress crack resistance means that cracks or the like are less likely to occur when left in a state where a certain amount of stress is applied, or that the material can withstand strong stress. When the content is less than 10.0 wt%, the rigidity of the main material is maintained and the flexibility of the cushioning body is obtained, so that the flexibility is improved and the productivity of the molded product is also excellent. From the standpoint of excellent durability against repeated U-shaped and left-right 90° bending, the content is more preferably 3.5 wt % to 7.0 wt %, and most preferably 4.0 wt % to 6.0 wt %.

In general, polyester elastomers are excellent in mechanical strength such as rigidity. In particular, polyester elastomers with high elasticity such as a flexural modulus of 450 MPa or more tend to be poor in flexibility and poor in durability against repeated bending. The present invention includes a certain amount of cushioning, particularly for the purpose of improving durability against repeated U-shaped and left-right 90° bending. By dispersing the buffer uniformly in the main material made of polyester elastomer , gaps between molecules are generated, and as a result, stress (distortion) between molecules is relieved and stress crack resistance is improved. In addition, flexibility is obtained in addition to the mechanical strength inherent in the polyester elastomer , thereby significantly improving flexibility. In particular, it is expected to improve the durability against repeated U-shaped and left-right 90° bending.

Also, the main material made of polyester elastomer is characterized by comprising at least two main materials.

Regarding the flexural modulus of the two main materials, it is preferable that the first main material is 500-600 MPa and the second main material is 900-1000 MPa.

Here, the bending elastic modulus is an index indicating how much bending stress can be withstood, and is a value calculated from the amount of change in bending load and the amount of change in deflection. (ASTM D790)

Further, the difference between the main material having the maximum flexural modulus and the main material having the minimum flexural modulus is 300 to 500 MPa.

Although the flexural modulus of the mixed insulating material of the present invention is not particularly limited, it is preferably 500 to 1000 MPa, more preferably 600 to 800 MPa. In particular, it is most preferably 650 to 750 MPa for the purpose of improving durability against repeated U-shaped and 90° right and left bending.

Although the content of each main material constituting the main material is not particularly limited, it is preferable that they all have the same weight [wt%].

Other mechanical properties of the mixed insulating material of the present invention are not particularly limited, and are shown below for reference.

The hardness is Shore D65-D80, preferably Shore D70-D75. (JIS Z2246)

For tensile properties, the tensile strength is between 30 MPa and 60 MPa, preferably between 35 MPa and 55 MPa. The elongation is 300-600%, preferably 400-500%. (JIS K7161)

Although the material of the buffer is not particularly limited, examples thereof include thermosetting elastomers such as silicone rubber, fluororubber, and urethane rubber, with silicone rubber being preferred.

The buffer is uniformly dispersed in the main material polyester elastomer . By uniformly dispersing, the effect of intermolecular stress relaxation by the buffer becomes remarkable, and flexibility is improved. Further, by uniformly dispersing the buffer in the state of the mixed material or during the extrusion molding process, it is possible to increase the content of the buffer while maintaining the extrudability.

The mixed insulating material of the present invention is excellent in durability against repeated U-shaped and left-right 90° bending. The test method is as follows.

The test samples are wires using the mixed insulation material of the present invention as insulation. A plurality of samples with a wire length of 300 mm are arranged in parallel and fixed on both sides with adhesive PET tape. A flat cable-shaped electric wire arranged in parallel is repeatedly bent in a U shape at a bending radius of 5 mm, and the number of times cracks occur in the insulating material is measured. (FIG. 2) The U-shaped bending characteristic is not particularly limited, but is preferably 20,000 times or more.

(Left and right 90° bending test method)
The samples are wires using the mixed insulation material of the present invention. The length of the electric wire is 500 mm. The wire is repeatedly bent at 90 degrees to the left and right with a bending radius of 5 mm and a load of 500 g, and the number of times the wire reaches complete disconnection is measured (Fig. 3). The 90° left/right bending characteristic is not particularly limited, but preferably 7000 times or more.

The molded article using the mixed insulating material of the present invention is not particularly limited, but is preferably an electric wire coated with a conductive material as an insulator, and a cable in which a plurality of electric wires are twisted together. When used in electric wires and cables, it is not limited to being used as an insulator coated on a conductive material, but may be applied as a protective material. Examples include insulated wires, protective materials for wires, and molded products such as tubes and packings.

Hereinafter, the mixed insulating material of the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to these.

(Examples 1 to 4)
Example 1 contains polyester elastomer A (flexural modulus of 555 MPa) and polyester elastomer B (flexural modulus of 930 MPa) of the same weight as main materials, and silicone rubber as a shock absorber in 3. out of all mixed insulating materials. It is a mixed insulating material containing 5 wt%. This mixed insulating material is coated on a conductor (60 tinned annealed copper wires/0.08 mm) to form an electric wire with an outer diameter of 1.1 mm (thickness of about 0.2 mm).

In Example 2, Example 1 is a mixed insulating material containing 5.0 wt % of silicone rubber as a buffer in the entire mixed insulating material.

In Example 3, Example 1 is a mixed insulating material containing 7.0 wt % of silicone rubber as a buffer in the entire mixed insulating material.

In Example 4, Example 1 is a mixed insulating material containing 10.0% by weight of silicone rubber as a buffer in the entire mixed insulating material.

(Comparative Examples 1 to 6)
Comparative Example 1 is a mixed insulating material containing 1.0 wt % of silicone rubber as a buffer in the entire mixed insulating material.

Comparative Example 2 is an insulating material composed only of polyester elastomer A (flexural modulus of elasticity: 555 MPa). The configuration of the electric wire is the same as that of the first embodiment.

Comparative Example 3 is a mixed insulating material composed of polyester elastomer A (flexural modulus of elasticity of 555 MPa) and polyester elastomer B (flexural modulus of elasticity of 930 MPa) of Comparative Example 2 at a ratio of 60:40.

Comparative Example 4 is a mixed insulating material composed of polyester elastomer A (flexural modulus of 555 MPa) and polyester elastomer B (flexural modulus of 930 MPa) of Comparative Example 2 with the same weight.

Comparative Example 5 is a mixed insulating material composed of Polyester Elastomer A (flexural modulus of 555 MPa) and Polyester Elastomer B (flexural modulus of 930 MPa) of Comparative Example 2 at a ratio of 40:60.

Comparative Example 6 is an insulating material composed only of polyester elastomer B (flexural modulus of elasticity: 930 MPa) in Comparative Example 2.

Each Example and Comparative Example were evaluated for tensile properties (tensile strength and elongation), flexural modulus, and durability against repeated U-shaped and left-right 90° bending, and the results are shown in Table 1.

(Method for measuring tensile properties)
As a measurement sample, a mixed insulating material (150 mm) in the form of a tube obtained by removing the conductor from the electric wire is used. Tensile strength [MPa] and elongation [%] are measured at a tensile speed of 50 [mm/min] using a general tensile tester.

All of Examples 1 to 4 are excellent in terms of durability against repeated U-shaped bending and left-right 90° bending. In particular, the mixed insulation material containing 5.0 wt% of the buffer of Example 2 is superior in both tests.

The U-shaped bending test is a test in which a load is applied to the entire electric wire, and particularly contributes to the improvement of stress crack resistance.
On the other hand, the left-right 90° bending test is a test in which a load is applied locally, and the improvement in flexibility due to the rigidity and flexibility that is obtained contributes.

As compared with Comparative Example 1, when the content of the cushioning material increases, the flexural modulus decreases, and as a result, the 90° bending test, that is, the flexibility tends to deteriorate.
On the other hand, the U-bending test tends to improve due to the improvement of the stress crack resistance as the content of the cushioning material increases.

From the comparison with Comparative Examples 2 to 6, it can be confirmed that the inclusion of the cushioning material improves the U-shaped bending, and improves the stress crack resistance.

From the above, it can be said that Examples 1 to 4 are excellent in both stress crack resistance and flexibility, and in particular, Example 2 has the best result due to the synergistic effect of both characteristics.

FIG. 1 is a scanning electron microscope image showing the outer surface of a wire (Example 2) using the mixed insulation material of the present invention.

From FIGS. 1(a) and 1(b), it can be seen that silicone rubber as a buffer is uniformly dispersed in two types of polyester elastomer as the main material.
In the elemental mapping diagram of FIG. 1(b), buffers are displayed in white.

In particular, the present invention is used in FA equipment such as industrial robots and semiconductor manufacturing equipment, in addition to various insulated wires and cable covering materials, as well as molded products such as tubes and packings, etc., which are required to have durability against repeated bending. It can be widely used in various fields.

Claims (3)

A mixed insulating material composed of a main material made of polyester elastomer and a cushion made of silicone rubber ,
The buffer comprises more than 3 wt% and less than 10.0 wt% of the total mixed insulating material,
The main material is composed of at least two types of polyester elastomers having different flexural moduli,
The difference between the main material having the maximum flexural modulus and the main material having the minimum flexural modulus is 300 to 500 MPa,
A mixed insulating material , wherein the bending elastic modulus is 500 to 1000 MPa . The various main materials constituting the main material made of the polyester elastomer are all contained by the same weight,
The mixed insulating material of claim 1 . 3. An electric wire in which a conductor is coated with the mixed insulating material according to claim 1 or 2 as an insulator, and/or a multi-core cable in which a plurality of said electric wires are twisted together.

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