JPH08138439A - Conductive composite material composition and conductive composite material to mold its composition - Google Patents

Abstract

PURPOSE: To set switching speed equal as usual, and improve reproducibility by molding a composition containing a conductive material and a polymer of thermoplastic elastomer obtained by directly polymerizing homo PP and a random copolymer of ethylene and propylene. CONSTITUTION: A conductive composite material is obtained by molding a composition containing a conductive material and a polymer of thermoplastic elastomer obtained by polymerizing homo PP and a random copolymer of ethylene and propylene. This switching temperature Ts is almost equal to conventional polyethylene type resin, and hysteresis is reduced in the relationship between a temperature and resistance to electric continuity, and reproducibility is excellent. That is, since a homo PP part plays a role of a kind of fixing point, reproducibility of an interval change between conductive materials caused by thermal expansion of an ethylene-propylene copolymer part becomes excellent, and as a result, while the temperature Ts is almost equal to a case of a conventional polyethylene type resin matrix, it is thought to exhibit a characteristic more excellent in reproducibility.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a conductive composite material composition and a conductive composite material obtained by molding the composition.

[0002]

2. Description of the Related Art Conventionally, as a switching element as a conductive composite material composed of a polymer and a conductive material, a composite composed of polyethylene and carbon black has been used (US Pat. No. 2,978,665, Japanese Patent Laid-Open Publication No. Sho. 54-16697, JP-A-55-78406).

[0003]

A switching element composed of particles of a composite of polyethylene and carbon black has a switching temperature (Ts) of 80 to 140 ° C. (Japanese Patent Laid-Open No. 55-78406) and is suitable for practical use. However, the conduction resistance changes with time due to Joule heat (JP-A-55-78406), and the relationship between the conduction resistance and the temperature of the element shows hysteresis (JP-A-2-92960, Therefore, it is necessary to further improve the reproducibility. It is an object of the present invention to provide a conductive composite material which improves the above-mentioned drawbacks and is excellent in reproducibility, and a composition for obtaining the conductive composite material.

[0004]

The present invention provides a conductive composite material composition containing a polymer of a thermoplastic elastomer obtained by directly polymerizing a random copolymer of ethylene and propylene and a homopolypropylene, and a conductive material. And an electrically conductive composite material obtained by molding the composition. In the present invention, a thermoplastic elastomer obtained by directly polymerizing a random copolymer of ethylene and propylene and homopolypropylene (hereinafter referred to as homoPP) is homoPP
The proportion of the polymer is in the range of 1 to 60% by weight and the ethylene component is in the range of 10 to 40% by weight, but it is not particularly limited. The main characteristic of the polymer is MFR (Melt F
low rate), melting point and the like. Of these, MFR
(JIS K7210) is preferably 0.2 to 50 g / min, more preferably 1.0 to 20 g / min. On the other hand, the melting point (DSC) is generally in the range of 135 to 170 ° C, preferably 140 to 155 ° C.

In the present invention, the above thermoplastic elastomer may be mixed with another polymer. For example, polyethylene (LDPE, MDPE, HDPE, LLDP
E), a copolymer of α-olefin and a polar monomer (E
VA, EA, EEA) and the like. The mixing ratio of the thermoplastic elastomer and the other polymer is not particularly limited, but the thermoplastic elastomer has a mixing ratio of 10 to 80.
90 to 20 parts by weight of the other polymer is preferable.
By using the above-mentioned polymer, in the present invention, the temperature at which the conduction resistance greatly changes, that is, Ts, is recognized near the melting point of the polymer in the composition.

The conductive material in the present invention is carbon black such as furnace black or Ketjen black,
Examples thereof include graft products of these polar monomers, metal-plated carbon black, graphite, and the like, and further, metals such as nickel, cobalt, silver, copper, and alloys of metals represented by these can be used. The form of the above material is not particularly limited, but a granular material is generally used. For example, in the case of carbon black, 10
Granules with a diameter of -100 nm are used. The amount of the conductive material added to the polymer is generally 1 to 100 parts by weight with respect to 100 parts by weight of the polymer, but is not particularly limited.

In the present invention, in addition to the conductive material, other additives such as an inorganic filler, an antioxidant, an antistatic agent and a silane coupling agent can be added.
The composition of the polymer, the conductive material and the like can be mixed by using a kneading device such as a roll, a Banbury mixer, a Henschel mixer, a Brabender plastograph, an extruder (single screw, multi screw). Further, in the present invention, a plate, sheet, or film-shaped conductive composite material can be usually produced by using a molding method such as compression molding, extrusion molding, or injection molding.

The polymer in the conductive composite is generally crosslinked, but with t-butylcumyl peroxide, 2,
5 dimethyl-di (t-butylperoxy) hexane,
Chemical cross-linking method using an organic peroxide such as 2,5 dimethyl-di (t-butylperoxy) hexyne-3, or silane cross-linking in which polyolefin is grafted with vinylsilane and then cross-linked by siloxane condensation reaction in the presence of water. Any of the methods, and further, a radiation crosslinking method using an electron beam or the like can be used. The cross-linking may be performed at any stage such as raw material, molding, and after molding. In the present invention, the conductive composite material is connected to an electrode material such as nickel or copper by a method such as thermocompression bonding, and further, heat treatment is generally performed for the purpose of relaxing molding strain and stabilizing the internal structure. Is. The heat treatment may be performed before or during the connection between the conductive composite material and the electrode material.

[0009]

The conductive composite material of the present invention is obtained by molding a composition containing a polymer of a thermoplastic elastomer obtained by directly polymerizing a random copolymer of ethylene and propylene and homo PP and a conductive material. The obtained Ts is almost the same as that of the conventional polyethylene-based resin, has less hysteresis due to the relationship between temperature and conduction resistance, and has excellent reproducibility. The reason for this is that the homo PP part plays a role of a kind of fixed point, which improves the reproducibility of the spacing change between the conductive materials due to the thermal expansion of the ethylene / propylene copolymer part, and as a result, It is considered that the Ts is almost the same as that of the polyethylene-based resin matrix of 1), but exhibits more excellent reproducibility.

[0010]

EXAMPLES Examples of the present invention will be described below. The following materials were used. That is, as the thermoplastic elastomer, Tokuyama P.I. E. FIG. R. R410E (MFR; 1.8
g / min, melting point; 143 ° C., specific gravity; 0.88), and other polymers include polyethylene resin (Sumitomo Chemical, LDPE,
MFR: 10 g / min, melting point: 118 ° C., specific gravity: 0.9
35), furnace black (average particle size; 50 nm) as the conductive material, and Ciba-Geigy Irganox 1010 as the antioxidant. A single-screw extruder was used for molding, and the extrusion molding conditions were such that the screw was φ20.
Full flight type (L / D; 24), cylinder temperature is C1; 150 ° C, C2; 165 ° C, C3; 170 ° C, die temperature D is 175 ° C, screw rotation speed is 50 rpm.
Is.

Example 1 60 parts by weight of thermoplastic elastomer, 40 parts of polyethylene resin, 70 parts of furnace black and 0.5 parts by weight of antioxidant.
5 parts of the composition was mixed with an 8-inch roll to 16
The mixture was kneaded at 0 ° C. for 10 minutes, pelletized at room temperature, and subjected to an extruder to form a sheet having a thickness of about 0.5 mm. The conductive composite obtained above was cut into a size of 1 cm × 2 cm, cross-linked by performing electron beam radiation of 5 Mrad, and then metal electrodes (Ni foil, thickness 300 nm) were thermocompression bonded at 165 ° C. on both surfaces. The relationship between temperature and conduction resistance was measured. In addition, the conduction resistance at room temperature was measured again in order to confirm the recoverability after cooling. Table 1 shows the conduction resistance (R25) at room temperature, 110 ° C.
Conduction resistance (R110), ratio of both R25 / R110,
The conduction resistance (R25 *) and Ts after cooling are shown.

Example 2 Furnace Black 70 of Example 1 as a conductive composite
A conductive composite was obtained in the same manner as in Example 1 except that 20 parts by weight of nickel particles (about 80 nm) was used instead of the parts by weight.
Also, the relationship between temperature and conduction resistance was measured. The results are shown in Table 1.
Shown in Example 3 Particles (about 100 nm) obtained by plating polystyrene particles with gold instead of the nickel particles of Example 2 as a conductive composite.
A conductive composite was obtained in the same manner as in Example 2 except that was used, and the relationship between temperature and conduction resistance was measured. The results are shown in Table 1. Comparative Example A composition containing 100 parts by weight of the same polyethylene as in Example 1, 70 parts of furnace black and 0.5 part of an antioxidant was prepared in the same manner as in Example 1 to prepare a 1 cm × 2 cm conductive composite. The relationship between temperature and conduction resistance was measured. Table 1 shows the results.

[0013]

[Table 1]

From Table 1, it is shown that R110 and R25 / R110 of the example are much better than those of the comparative example, and that the recoverability is also good. Ts shows almost the same value as the comparative example.

[0015]

EFFECTS OF THE INVENTION According to the present invention, Ts is almost the same as the conventional conductive composite material using a polyethylene resin, has a characteristic of excellent self-restoration of conduction resistance, and has excellent reproducibility. A composite material is obtained.

Claims (3)

[Claims] 1. A conductive composite material composition comprising a polymer of a thermoplastic elastomer obtained by directly polymerizing a random copolymer of ethylene and propylene and homopolypropylene, and a conductive material. 2. A conductive composite material obtained by molding the composition of claim 1. 3. The conductive composite material according to claim 2, having at least one switching temperature.