JPS6154050B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a chlorinated polyethylene composition crosslinkable by an organic peroxide containing a thermally conductive inorganic filler and chlorinated polyethylene. In recent years, with the remarkable development of the electronic industry, the heat dissipation efficiency of electronic components has become a problem. In particular, this type of molded body generally has low thermal conductivity and poor heat dissipation effect, so it accumulates heat and damages circuit elements, shortening their lifespan. For this reason, a heat dissipation sheet is usually provided to prevent overheating of the components. However, at present, no material has been developed that can efficiently transfer the heat stored in electronic components to the heat dissipation sheet and has a satisfactory heat dissipation efficiency. For these reasons, research on improving the thermal conductivity of molded bodies of polymeric materials has been conducted for a relatively long time, and the main method used has been to fill polymeric materials with inorganic fillers with high thermal conductivity. ing. However, in commonly used rubber-like materials,
The filling amount of filler is limited. In other words, filling a large amount of filler to improve thermal conductivity not only reduces the moldability of the composition itself, but also
The reality is that the resulting molded product does not have mechanical properties that can withstand practical use. Based on the above, the present inventors conducted various searches in order to obtain a composition of a polymeric substance with excellent thermal conductivity, and as a result, an organic peroxide containing a thermally conductive inorganic filler and chlorinated polyethylene was developed. A chlorinated polyethylene composition that can be crosslinked by chlorinated polyethylene and has an inorganic filler content of 60 to 75% by volume is a composition with excellent thermal conductivity. They discovered this and arrived at the present invention. The composition obtained by the present invention not only has excellent thermal conductivity but also has the following characteristics (effects). (1) Excellent moldability despite the relatively high proportion of inorganic filler. (2) Excellent mechanical strength (e.g. tensile strength, tear strength). (3) Good electrical insulation. The chlorinated polyethylene used in the present invention can be obtained by chlorinating polyethylene powder or particles in an aqueous suspension, or by chlorinating polyethylene dissolved in an organic solvent (e.g., carbon tetrachloride) capable of dissolving the polyethylene. This is obtained by This chlorinated polyethylene is widely produced industrially and is commonly used. Generally, it is amorphous or crystalline chlorinated polyethylene whose chlorine content is 20 to 50% by weight,
In particular, those having a chlorine content of 25 to 45% by weight and being amorphous are preferred. Polyethylene, which is the starting material for this chlorinated polyethylene, generally has a density of 0.910 to 0.970.
g/cc, particularly preferably 0.930 to 0.960 g/cc. Further, the molecular weight is generally 50,000 to 500,000, and particularly preferably 100,000 to 400,000. Further, the conductive inorganic filler used in the present invention includes a wide range of known inorganic fillers, but in general, those having high thermal conductivity are preferred, and typical examples include copper, aluminum, and iron. Examples include powders of metals, powders of metal oxides such as alumina, magnesia and beryllia, and boron nitride, crystalline silica, talc and the like. In particular, materials with high thermal conductivity and excellent electrical insulation properties are desirable, and from these points of view, alumina and boron nitride are preferred. Furthermore, from the point of view of corrosion resistance and electrical insulation,
Inorganic fillers whose particle size distribution is 40μ or less are preferred, and those from 5 to 20μ are particularly preferred. On top of that,
In the present invention, in order to fill a large amount of inorganic material, a significant improvement in the quality of the filler can be seen by mixing materials with different particle size distributions. The content of the inorganic filler in the composition obtained in the present invention is 60 to 75% by volume, particularly 62 to 75% by volume.
73% by volume is preferred. If the amount of the inorganic filler in the composition is less than 60% by volume, the thermal conductivity of the composition is unsatisfactory. On the other hand, if it exceeds 75% by volume, the ratio of the inorganic filler to the polymer material such as chlorinated polyethylene becomes too large, and when the composition is molded, not only will the crosslinking effect of the organic peroxide be poor, but also the moldability will deteriorate. Moreover, problems such as a marked decrease in the high loading property, which is a characteristic of chlorinated polyethylene, occur. Although the composition of the present invention can be produced by blending these inorganic fillers with chlorinated polyethylene, it may also be produced by blending these inorganic fillers with rubbery and/or resinous substances that are highly compatible with chlorinated polyethylene. may be blended. Examples of the rubbery material include ethylene-propylene-diene ternary copolymer rubber (EPDM), natural rubber, chloroprene rubber, chlorosulfonated polyethylene rubber, styrene-butadiene copolymer rubber, and acrylonitrile-based rubber. Mention may be made of rubbery materials such as butadiene copolymer rubber and butadiene rubbery products, as well as silicone rubber. The Mooney viscosity (ML ₁₊₄ ) of these rubbery materials at 100° C. is generally 10 to 150. Furthermore, as resin-like materials, styrene homopolymer, acrylonitrile-styrene copolymer resin (AS resin), methyl methacrylate resin, acrylonitrile-butadiene-styrene ternary copolymer resin (ABS resin), methyl methacrylate-butadiene-styrene Thermoplastic resins such as ternary copolymer resins, vinyl chloride resins, polypropylene, high-density to low-density polyethylene, ethylene-vinyl acetate copolymers and ethylene-acrylic acid ester copolymers, as well as silicone resins, epoxy resins, and phenolic resins. Examples include thermosetting resins such as: In blending these rubber-like and/or resin-like materials, the characteristics of the composition of the present invention, such as maintaining thermal conductivity, high inorganic filler content, and excellent mechanical strength, are maintained. It goes without saying that the ingredients must be blended to the extent that they do not cause any essential damage. Therefore, the blending ratio of these is generally at most 30 parts by weight per 100 parts by weight of chlorinated polyethylene. The composition obtained according to the present invention can be crosslinked with an organic peroxide, and the organic peroxide or an organic peroxide and a crosslinking aid are used before producing the final composition or molded article. The agent is blended with the agent. The organic peroxide may be any organic peroxide as long as it can crosslink chlorinated polyethylene, but it is particularly desirable to have a decomposition temperature (temperature at which the half-life is 1 minute) of 110°C or higher, particularly 130°C or higher. suitable. Representative examples of desirable organic peroxides include:
1,1-bis-tertiary-butylperoxy-3.
Ketone peroxides such as 3,5-trimethylcyclohexane, 2,5-dimethylhexane-
Hydroperoxides such as 2,5-dihydroperoxide, diacyl peroxides such as 2,5-dimethyl-2,5-di-tertiary-butylperoxyhexane, and dialkyl peroxides such as dicumyl peroxide. can give. The crosslinking aid is not particularly limited as long as it promotes crosslinking of chlorinated polyethylene by organic peroxide, but typical examples include polyfunctional compounds such as triallyl cyanurate and triallyl isocyanurate. can be given. The proportion of organic peroxide to be used relative to 100 parts by weight of chlorinated polyethylene or the total of chlorinated polyethylene and other rubbery substances is usually 0.1 to 20 parts by weight, particularly preferably 1 to 10 parts by weight. Furthermore, when a crosslinking aid is added, it is at most 10 parts by weight per 100 parts by weight of chlorinated polyethylene. In producing the composition of the present invention, chlorinated polyethylene, inorganic fillers, other rubbery substances (if blended), resinous substances (if blended), organic peroxides, and crosslinking aids (if blended) may be used alone or in combination of two or more. Although the composition of the present invention can be obtained by homogeneously blending the above-mentioned substances, in addition, stabilizers, other fillers, lubricants, flame retardants and colorants commonly used in the rubber and resin industries can be obtained. Additives such as agents may be added depending on the intended use of the composition. Methods for producing the composition of the present invention include dry blending using mixers such as ribbon mixers and tumblers, and kneading using mixers such as open rolls, extruders, and Banbury mixers. . Among these mixing methods, the kneading method is preferable because it is relatively easy to obtain a homogeneous composition and its operation is relatively simple. In order to obtain this, two or more of these mixing methods may be applied (for example, a method of mixing with a ribbon mixer and then kneading the mixture using an open mixer). When producing the composition of the present invention, if there are three or more ingredients, they may be mixed at the same time, but some of them may be mixed in advance and then the other ingredients may be mixed into the resulting mixture. (For example, chlorinated polyethylene and an inorganic filler are mixed in advance, and an organic peroxide is mixed into the mixture.) The composition of the present invention can be produced by any of the above methods, but in either case, the mixing temperature must be such that the crosslinking reaction of the chlorinated polyethylene does not proceed with the organic peroxide. Of course. Usually, the kneading temperature is room temperature to 120°C. In order to produce a molded article from the composition obtained according to the present invention, a method of producing a molded article while crosslinking, which is commonly practiced in the rubber industry, may be employed. Although the crosslinking temperature varies depending on the type of organic peroxide used as a crosslinking agent, it is usually 130 to 200°C. Further, the crosslinking time is generally 5 to 40 minutes, and the optimum pressure is 30 to 200 Kg/cm ² . Furthermore, as a method for manufacturing the molded article, commonly used methods such as compression molding using a mold, injection molding (transfer), and press-fit molding may be applied. In order to manufacture molded products, there is a method of simultaneously proceeding crosslinking and molding as described above, but it is also possible to use molding machines other than those mentioned above, such as commonly used extrusion molding machines, compression molding machines, and calender molding machines. After molding into a desired shape using a press, crosslinking is performed using press pressure/heat crosslinking, salt bath crosslinking, ultra high frequency (UHF) crosslinking, lead crosslinking, and water immersion crosslinking using a vulcanizing can. This can also be achieved by crosslinking by a method. The composition obtained by the present invention not only has the excellent characteristics described above, but also the molded product obtained in the above manner has less brittleness than conventional inorganic-filled polymer molded products. The molded product has significantly improved hardness and elasticity. In particular, those containing alumina and boron nitride have a high thermal conductivity of 3 to 4 Kcal/m・hour・degree, which was impossible to obtain with conventional polymer moldings, and also have a high thermal conductivity of 10Ω ¹²・cm. Since it has become possible to produce an elastic molded body that also has electrical insulation properties, its practical value is extremely large. Hereinafter, the present invention will be explained in more detail with reference to Examples. In the Examples and Comparative Examples, the thermal conductivity was measured using a rapid thermal conductivity meter (manufactured by Showa Denko K.K., trade name: QTM-MD) for samples with a thickness of 2 mm. Insulation resistance (volume specific resistance value) was measured using an electrical insulation measuring device (manufactured by Kawaguchi Electric Co., Ltd., model P-601) on a sample having a thickness of 2 mm. Furthermore, the tensile strength and elongation rate are JIS K-6301.
Measured according to. In addition, the tensile strength is JIS K-
Measured based on 6301. Moreover, the bending test was performed by wrapping a sheet of 1 mm thickness, 10 mm width and 5 cm length around a cylinder (10 mm diameter) and visually observing the degree of cracking on the surface (shown below). 〇: No cracks △: Slight cracks ×: Large cracks and breaks Example 1 As an inorganic filler, boron nitride powder (particle size distribution 5 to 20
μ, density 2.27 g/cc, hereinafter referred to as "BN powder") Chlorinated polyethylene (chlorine content 30 wt. %, amorphous), respectively 100 parts by weight, 1.1 as organic peroxide
-bis-tertiary-butylperoxy-3, 3, 5
- 2 parts by weight each of trimethylcyclohexane, 2 parts each of dioctyl phthalate (as a plasticizer, hereinafter referred to as "DOP") as shown in Table 1, and 2 parts each of lead stearate as a stabilizer.
Parts by weight, Hoechstwax as lubricant, respectively.
After kneading 20 parts by weight and 3 parts by weight each of tribasic sulfate as a stabilizer with an 8-inch roll (surface temperature set at 70°C) until homogeneous for about 10 minutes, a sheet (about 2 mm thick) was mixed. I took it out. The obtained sheet was compression molded for 6 minutes while crosslinking under a pressure of 100 Kg/cm ² using a hot press machine with a mold temperature set at 150° C. to prepare a sample. The thermal conductivity, insulation resistance, tensile strength, elongation rate, and tear strength of each crosslinked molded product obtained were measured, and a bending test was also performed. The results are shown in Table 1. In addition, Experimental Example 1-7 and Experimental Example 1-8 are shown as comparative examples.

[Table] Example 2 Instead of the boron nitride powder used as the inorganic filler in Example 1, α-alumina powder (particle size distribution 6 to
30μ, density 3.95g/cc), and DOP whose compounding amount is shown in Table 2 was used.
A sheet was prepared by kneading under the same conditions as above. Example 1 except that each of the obtained sheets was used.
A crosslinked molded product was created in the same manner as in the above. The physical properties of each crosslinked molded product obtained were measured, and a bending test was also performed. The results are shown in Table 2. In addition,
Experimental Example 2-7 and Experimental Example 2-8 are shown as comparative examples.

[Table] Example 3 Instead of the boron nitride powder (BN powder) used as the inorganic filler in Example 1, the BN powder used in Example 1 and the BN powder used in Example 2, the blending amounts of which are shown in Table 3, were used. α used
- A sheet was prepared by kneading under the same conditions as in Example 1, except that alumina powder was used and DOP, the amount of which is shown in Table 3, was used. A molded article was created while crosslinking in the same manner as in Example 1, except that each of the obtained sheets was used. The physical properties of each crosslinked molded product obtained were measured, and a bending test was also performed. Those results in the third
Shown in the table. Note that Experimental Example 3-7, Experimental Example 3-8, and Experimental Example 3-9 are shown as comparative examples.

[Table] From the above Examples and Comparative Examples, when the composition obtained according to the present invention is crosslinked with an organic peroxide, the crosslinked product not only has excellent thermal conductivity, but also has excellent thermal conductivity. It is clear that the electrical insulation properties are good as well as the mechanical strengths such as tensile strength and tear strength are also excellent.

Claims (1)

[Claims] 1 A composition that can be crosslinked with an organic peroxide containing a thermally conductive inorganic filler and chlorinated polyethylene, and the amount of the inorganic filler in the composition is 60 to 75% by volume. A chlorinated polyethylene composition characterized by: