JP2014224200A - Highly thermally conductive mixture and highly thermally conductive molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly thermally conductive mixture which exhibits fire retardancy, high thermal conductivity, and an electrical insulation property, further, which can be molded into a thin-wall shape, and which is excellent in re-sticking workability even when an adhesive layer is provided thereon, and to provide a highly thermally conductive molded body using the highly thermally conductive mixture.SOLUTION: A highly thermally conductive mixture which contains: 100 pts.mass of α-olefin copolymer rubber including ethylene-propylene rubber and ethylene-α-olefin rubber (however, propylene is excluded from α-olefin), in which a mass ratio of the ethylene-propylene rubber to the ethylene-α-olefin rubber is 10:90 to 70:30; and 300-700 pts.mass of a thermally conductive filler, and a highly thermally conductive molded body formed by molding the highly thermally conductive mixture, are disclosed.

Description

  The present invention relates to a high thermal conductivity mixture and a high thermal conductivity molded body, and more particularly to a high thermal conductivity mixture and a high thermal conductivity molded body suitable for heat dissipation of a heat-generating electronic component.

In recent years, electrical and electronic devices are becoming lighter, thinner, and faster. Therefore, heat generation density tends to increase in heat generating electronic components such as arithmetic elements such as LEDs and CPUs and power transistors incorporated as internal components. Since these heats have an adverse effect on the product life and normal operation, it is becoming increasingly important to quickly diffuse, dissipate, cool, and eliminate the heat spots.
In addition, these members that diffuse heat, etc., are flame retardant for safety and have electrical insulation from the viewpoint of normal operation of electrical and electronic equipment. It has become.

  In general, in order to dissipate such heat, many methods of transferring heat by using heat pipes, heat sinks, heat dissipating parts such as aluminum and copper heat dissipating plates, etc. are used. As such heat radiating components, silicone rubber heat radiating pads, heat radiating sheets, heat radiating grease, and the like are frequently used for the purpose of reducing contact resistance with heat-generating electronic components (for example, Patent Documents 1 and 2). However, there is a concern that silicone rubber may adversely affect electronic components due to volatilization of low molecular weight siloxane.

  As an alternative to the heat dissipating component composed of a silicone rubber composition, there is one using acrylic rubber (for example, Patent Documents 3 and 4). However, there is a problem that acrylic rubber is inferior in electrical insulation.

  Incidentally, Patent Document 5 discloses a thermosoftening heat-dissipating sheet made of a polyolefin-based heat conductive composition that is softened by heat generated during operation of an electronic component and has a level at which the interfacial contact thermal resistance can be ignored. Specifically, the “thermosoftening heat-dissipating sheet” described in Patent Document 5 is an α-olefin polymer having 19 to 53 carbon atoms and ethylene · α having a polymerization degree p of 5 to 500 as a thermosoftening component. -Polyolefin heat having specific physical properties, comprising a polyolefin comprising three components of an olefin copolymer and an ethylene / α-olefin / terminal vinyl group-containing norbornene copolymer as essential components, and a thermally conductive filler. It consists of a conductive composition.

JP-A-6-163762 JP-A-7-157663 JP 2002-294192 A JP 2004-338124 A JP 2002-121332 A

  As the heat radiation component as described above, a heat radiation pad, a heat radiation sheet, or the like may be provided with an adhesive layer in order to improve workability of attaching to a substrate or the like. However, if an adhesive layer is provided on a heat dissipation component that has been thinned to reduce thermal resistance, it will be easy to tear when it is peeled off from the substrate, etc., and it will be reproducible when attached. There is a problem that the workability of re-sticking deteriorates.

  Therefore, the present invention exhibits flame retardancy, high thermal conductivity and electrical insulation, and also has a high thermal conductivity admixture that is excellent in workability for reattachment even if it is molded into a thin wall and is provided with an adhesive layer. It is an object of the present invention to provide a product and a high thermal conductive molded article using the high thermal conductive mixture.

  In view of the above-mentioned problems, the present inventors have made extensive studies, and an α-olefin copolymer rubber containing ethylene-propylene rubber and ethylene-butene rubber at a specific mass ratio is used as a matrix rubber. By molding a highly heat conductive blend containing a certain amount of heat conductive filler, it has both flame retardancy, heat conductivity and electrical insulation, and is a thin-walled one with an adhesive layer. It has also been found that a highly heat-conductive molded article excellent in workability can be obtained. In addition, it was also found that this highly heat-conductive mixture is not easily softened by heat generated from electronic components. The present invention has been completed based on these findings.

The object of the present invention has been achieved by the following means.
(1) α- containing ethylene-propylene rubber and ethylene-α-olefin (excluding propylene) rubber in a mass ratio of 10:90 to 70:30 of the ethylene-propylene rubber and the ethylene-α-olefin. A high thermal conductive admixture containing 100 parts by mass of an olefin copolymer rubber and 300 to 700 parts by mass of a thermal conductive filler.
(2) The high thermal conductive admixture according to (1), wherein the ethylene-α-olefin rubber is ethylene-butene rubber.
(3) The high thermal conductive admixture according to (1) or (2), wherein the ethylene-α-olefin rubber has a melting point of 40 to 100 ° C.
(4) Any of (1) to (3), wherein the thermally conductive filler is at least one selected from the group consisting of aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, aluminum nitride, and boron nitride. The high thermal conductivity admixture according to claim 1.
(5) The high thermal conductivity according to any one of (1) to (3), wherein the thermally conductive filler includes at least 200 parts by mass of a metal hydroxide with respect to 100 parts by mass of the α-olefin copolymer rubber. Sex admixture.
(6) A high thermal conductivity molded body obtained by molding the high thermal conductivity mixture according to any one of (1) to (5).
(7) The high thermal conductive molded article according to (6), which is molded into a sheet having a thickness of 0.1 to 1.0 mm.

The “high thermal conductivity” of the high thermal conductivity mixture and the high thermal conductivity molded body of the present invention is a property of the high thermal conductivity mixture and the high thermal conductivity molding of the present invention, and has a thermal conductivity of 1 W / It means more than mk.
The “thermal conductivity” of the thermally conductive filler refers to a property of the filler, which can increase the thermal conductivity of the mixture when blended.

  The high thermal conductive molded body of the present invention can efficiently transfer heat and exhibits excellent flame retardancy and electrical insulation. In addition, even if it is molded into a thin shape and has an adhesive layer, it is easy to re-attach, and it can be used for applications such as elimination of heat spots, temperature equalization, and heat diffusion in the aforementioned electrical and electronic devices. It can be used suitably.

  Hereinafter, embodiments of the present invention will be described in more detail, but the present invention is not limited to the following embodiments.

  The high thermal conductivity admixture of the present invention comprises an ethylene-propylene rubber and an ethylene-α-olefin (excluding propylene) rubber as an α-olefin copolymer rubber, and an ethylene-propylene rubber and an ethylene-α-olefin. The mass ratio (ethylene-propylene rubber: ethylene-α-olefin) is 10:90 to 70:30, and the heat conductive filler is contained in an amount of 300 to 700 parts by mass with respect to 100 parts by mass of the α-olefin copolymer rubber. To do.

(Α-olefin copolymer rubber)
The α-olefin copolymer rubber used in the present invention is a rubber (base rubber) that is the base of the high thermal conductivity admixture of the present invention, and is an ethylene-propylene rubber and an ethylene-α-olefin (however, excluding propylene) rubber. (Simply referred to as “ethylene-α-olefin rubber”). Ethylene-α-olefin rubber is excellent in electrical insulation, enhances the strength of the molded body, and has excellent shape retention even in a non-crosslinked molded body as well as a crosslinked molded body. Ethylene-propylene rubber is also excellent in electrical insulation, flexible and has high heat conductive filler receptivity, and is suitable for blending a large amount of heat conductive filler. Thus, as the α-olefin copolymer rubber, when a specific combination of rubbers, that is, a rubber composed of a combination of ethylene-propylene rubber and ethylene-α-olefin rubber is used, it is crosslinkable as described later. Even if it is non-crosslinkable, it can have both flame retardancy, high thermal conductivity and electrical insulation.

Ethylene-propylene rubber is a binary copolymer of ethylene and propylene (EPM), non-conjugated dienes such as ethylene, propylene, dicyclopentadiene (DCPD), ethylidene norbornene (ENB), 1,4-hexadiene. And a ternary copolymer. The ethylene-propylene rubber may be an alternating copolymer in which each constituent component is alternately polymerized, or may be a block copolymer in which segments of each constituent component are repeatedly bonded. May be a random copolymer in which the length of any of the segments is random, or may be a graft copolymer obtained by graft polymerization of any of the constituent components. It may be a mixture.
As the ethylene-propylene rubber, a terpolymer is preferable among the above when the high thermal conductive molded body of the present invention described later is crosslinked (also referred to as crosslinking), and a binary copolymer is used when it is not crosslinked. Both coalesced and terpolymers are suitable.

  The ethylene-propylene rubber is not particularly limited, but preferably has a low molecular weight or a medium molecular weight. Specifically, “Mooney viscosity ML1 + 4 (100 ° C.)” defined in JIS K6300 is preferably 100 or less. Those having a Mooney viscosity ML1 + 4 (100 ° C.) higher than 100 are high in molecular weight and thus poor in flexibility and heat conductive filler receptivity. The Mooney viscosity ML1 + 4 (100 ° C.) is more preferably 80 or less, and preferably 80 to 20 in terms of excellent flexibility and heat-conducting filler acceptability.

  As the ethylene-propylene rubber, a commercially available product may be used. For example, as a commercially available product, EP11, 21, 22, 24, 25, 25, 51 (all trade names) made by Nippon Synthetic Rubber, Esprene 201 made by Sumitomo Chemical, 301, 305, 400, and 505A (all are trade names), EPT0045, 1045, 3045, and 3070 (all are trade names) manufactured by Mitsui Chemicals.

Ethylene-α-olefin rubber is a binary copolymer (EPM) of α-olefin excluding ethylene and propylene, α-olefin excluding ethylene and propylene, dicyclopentadiene (DCPD), ethylidene norbornene (ENB) And terpolymers with non-conjugated dienes such as 1,4-hexadiene. The ethylene-α-olefin rubber may be a block copolymer, an alternating polymer, a random copolymer, a graft copolymer, or a mixture thereof.
As the ethylene-α-olefin rubber, a terpolymer is preferable among the above when the highly heat-conductive molded article of the present invention to be described later is bridged, and the binary copolymer and ternary are used when the bridge is not bridged. Any of the original copolymers is suitable.

  Here, the α-olefin is an α-olefin excluding propylene, that is, an α-olefin having 4 or more carbon atoms. The α-olefin preferably has 12 or less carbon atoms, and more preferably 8 or less from the viewpoint of flexibility. Examples of such α-olefins include butene, hexene, octene, decene, dodecene and the like. Among these, the α-olefin is preferably butene because it is excellent in flame retardancy, thermal conductivity and electrical insulation, and can achieve both moderate flexibility and high strength.

  Although ethylene-alpha-olefin rubber is not specifically limited, It is preferable that melting | fusing point is 40-100 degreeC from the point of workability. When the melting point is less than 40 ° C., sagging (deformation) during molding becomes large, and when the melting point exceeds 100 ° C., it becomes hard and mixing workability may deteriorate. In this respect, the melting point is more preferably 50 to 90 ° C. The melting point of the ethylene-α-olefin rubber can be measured by differential scanning calorimetry (DSC) under a temperature rising rate of 10 ° C./min.

  As the ethylene-α-olefin rubber rubber, commercially available products may be used. For example, as commercial products, Mitsui Chemicals elastomer K9720 (trade name), Mitsui Chemicals elastomer X75 (trade name), Sumitomo Chemical Exelen FX301 and FX307 ( Both are trade names).

  The α-olefin copolymer rubber contains ethylene-propylene rubber and ethylene-α-olefin rubber in a mass ratio of 10:90 to 70:30. When the ethylene-propylene rubber and the ethylene-α-olefin rubber are contained in the above-described mass ratio, an effect of excellent workability can be obtained while maintaining flexibility and strength. In terms of excellent effects, the mass ratio of the ethylene-propylene rubber and the ethylene-α-olefin rubber is preferably 20:80 to 60:40.

(Thermal conductive filler)
The thermally conductive filler used in the present invention can be used without particular limitation as long as it is a heat conductive filler that is usually used for heat dissipation parts and has the above-described properties. For example, metal hydroxide, metal oxide And thermal conductive nitrides. Specifically, examples of the metal hydroxide include aluminum hydroxide and magnesium hydroxide, examples of the metal oxide include aluminum oxide, magnesium oxide, and zinc oxide. Examples of the thermally conductive nitride include aluminum nitride. And boron nitride.

Among these, the thermally conductive filler is at least one selected from the group consisting of aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, aluminum nitride, and boron nitride in terms of thermal conductivity. preferable.
In particular, metal hydroxides such as aluminum hydroxide and magnesium hydroxide are excellent in thermal conductivity and also in flame retardancy, and it is possible to impart more excellent flame retardancy at the same time as thermal conductivity. Therefore, it is suitable for the use of the present invention. In this case, the thermally conductive filler only needs to contain at least one metal hydroxide, and may contain only the metal hydroxide, or at least one metal hydroxide, the metal oxide, and the heat. It may contain at least one kind of conductive nitride. The “at least one of metal oxide and thermally conductive nitride” used in combination with at least one metal hydroxide is at least selected from the group consisting of aluminum oxide, magnesium oxide, aluminum nitride and boron nitride. One type is preferred.

  Content of a heat conductive filler is 300-700 mass parts with respect to 100 mass parts of alpha olefin copolymer rubber. When the thermally conductive filler is contained with this content, the flexibility as a sheet can be maintained while imparting thermal conductivity. It is preferable that content of a heat conductive filler is 400-600 mass parts at the point which can make heat conductivity and a softness compatible at a higher level.

  In particular, when the thermally conductive filler contains a metal hydroxide, the blending amount of the metal hydroxide is set so that the blending amount of the entire thermally conductive filler is within the above-mentioned range. Thus, it is preferably 200 parts by mass or more, more preferably 300 parts by mass or more, further preferably 350 parts by mass or more, more preferably 700 parts by mass with respect to 100 parts by mass of the α-olefin copolymer rubber. Part or less, preferably 600 parts by weight or less.

(Other ingredients)
The high heat conductive admixture of the present invention may contain components other than the α-olefin copolymer rubber and the heat conductive filler as necessary. Examples of such components include plasticizers, tackifiers, antioxidants, anti-aging agents, light stabilizers, copper damage inhibitors, and processing aids.
The plasticizer is preferably a paraffinic mineral oil having good compatibility with the α-olefin copolymer rubber, and may be used in an amount equal to or less than that of the α-olefin copolymer rubber. Moreover, although antioxidant, anti-aging agent, processing aid, etc. are 0.1-5 mass parts normally with respect to 100 mass parts of alpha olefin copolymer rubber, about 10 mass parts is needed as needed. May be blended.

The high thermal conductive admixture of the present invention containing the above-mentioned α-olefin copolymer rubber and the thermal conductive filler has high strength even if it does not have a bridge structure, that is, it is not cross-linked. (100 ° C.) An admixture with excellent shape retention that does not soften or flow even when left in an environment. Therefore, the highly heat-conductive blend of the present invention may be a non-crosslinkable blend as a material for forming a highly heat-conductive non-crosslinked molded article that has not been crosslinked even after molding, It may be a crosslinkable mixture as a material for forming a crosslinkable molded article.
The non-crosslinkable admixture may not be entirely non-crosslinkable, and if it is not intended, a part of the non-crosslinkable admixture may be bridged, that is, crosslinkable. In addition, the crosslinkable admixture may be crosslinkable to such an extent that the crosslinkability of a part thereof, for example, the degree of cross-linking of the highly heat-conductive crosslinkable molded product satisfies a range described later. Non-crosslinkable admixtures can greatly reduce costs, while crosslinkable admixtures exhibit even higher strength and heat resistance.

When the highly heat-conductive admixture of the present invention is a cross-linkable admixture, it may contain a cross-linking agent, a cross-linking aid, a radical polymerization initiator and the like as desired.
The crosslinking agent and crosslinking aid may or may not be used depending on the crosslinking method. Usable crosslinking agents and crosslinking aids are not particularly limited. For example, 1,1-bis (t-butylperoxy) cyclohexane, dicumyl peroxide, benzoyl peroxide, sulfur, ethylene glycol dimethacrylate, Examples include allyl isocyanurate, diallyl phthalate, divinyl benzene, metaphenylene bismaleimide, paraquinone dioxime, benzoyl quinone dioxime, dimethyl dithiocarbamic acid, 2-mercaptobenzothiazole and the like. As for the quantity of a crosslinking agent and a crosslinking adjuvant, 1-10 mass parts is preferable with respect to 100 mass parts of alpha olefin copolymer rubber.
The radical polymerization initiator is not particularly limited as long as it generates a radical that initiates a crosslinking reaction of an α-olefin copolymer rubber or a crosslinking agent. For example, an organic substance that generates a radical by a simple method such as a thermal decomposition method is used. Peroxides are preferred. Such an organic peroxide is not particularly limited, and examples thereof include hydroperoxides, dialkyl peroxides, and peroxyesters. The amount of the radical polymerization initiator is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the α-olefin copolymer rubber.

The highly heat-conductive admixture of the present invention can be obtained by kneading the above-described components. Therefore, the highly heat-conductive mixture of the present invention can also be referred to as a high heat-conductive composition.
Specifically, the high thermal conductive admixture of the present invention is a solid kneader such as an olefin copolymer rubber, a thermal conductive filler, and various additives as desired, such as a Banbury mixer and a kneader. The mixture is kneaded sufficiently with an extruder such as a single-screw extruder or twin-screw extruder or an open kneader such as an open roll until it becomes uniform. The kneader, extruder, etc. used at this time are not particularly limited as long as the heat conductive filler and the α-olefin copolymer rubber can be sufficiently mixed and stirred. The thermally conductive fillers may be mixed and kneaded all at once, or may be kneaded in several times. In addition, the kneading | mixing conditions at the time of kneading | mixing each above-mentioned component are not specifically limited.

  The high thermal conductive molded body of the present invention is formed by molding the above-described high thermal conductive blend of the present invention. This high heat conductive molded body should just have the shape and dimension according to a use, an application location, etc., and a shape and a dimension are not specifically limited. For example, as a shape in which a highly heat-conductive molded object is shape | molded, strip | belt shape, sheet | seat shape (plate shape), pad shape, prismatic body shape (block shape) etc. are mentioned. Although the thickness of a sheet-like molded object is not specifically limited, For example, the thickness of 0.1-1.0 mm is mentioned. If the thickness is less than 0.1 mm, the strength of the high thermal conductive molded body may be reduced and easily broken. The thickness of the pad-shaped molded body is thicker than that of the sheet-shaped molded body, and examples thereof include a thickness exceeding 1.0 mm and 10 mm or less.

The high thermal conductive molded article of the present invention is produced by molding the high thermal conductive blend of the present invention. The molding method of the highly heat-conductive admixture of the present invention is not particularly limited, and examples thereof include rolling molding, press molding, and extrusion molding.
The high thermal conductive molded body of the present invention is obtained by molding the high thermal conductive molded body of the present invention into a strip shape or a sheet shape by passing through an open roll, an extruder, or a calendar roll, for example. If desired, this strip-shaped molded body may be molded again and adjusted to the required thickness, or may be molded by an extruder or a hot press.

  Here, when the radical polymerization initiator is not contained in the high thermal conductivity admixture of the present invention, or when the molding temperature is lower than the decomposition temperature of the radical polymerization initiator even if it is contained, the resulting high thermal conductivity is obtained. In the conductive molded body, ethylene-propylene rubber and ethylene-α-olefin rubber are not crosslinked, and become a highly thermally conductive non-crosslinked molded body. In addition, although the α-olefin rubber is basically not crosslinked in the high thermal conductivity non-crosslinked molded article of the present invention, it may contain unintended crosslinking in part.

On the other hand, a highly heat-conductive crosslinked molded article in which ethylene-propylene rubber and ethylene-α-olefin rubber are crosslinked can be produced as follows. That is, a highly heat-conductive crosslinked molded product can be produced by irradiating the highly heat-conductive mixture of the present invention with an electron beam. In addition, after adding at least one of the above-mentioned crosslinking agent, crosslinking aid and radical polymerization initiator to the high thermal conductive admixture of the present invention, a crosslinking means such as heating is applied to obtain a high thermal conductive crosslinked molded article. It can be manufactured by chemically bridging. Furthermore, a silane coupling agent or the like is added to the high thermal conductive admixture of the present invention, and the silane coupling agent is grafted to ethylene-propylene rubber and / or ethylene-α-olefin rubber, and then contacted with water to cause silanol condensation. Thus, it can be produced by chemically bridging the high thermal conductive crosslinked molded article.
The highly heat-conductive crosslinked molded article of the present invention is obtained by crosslinking α-olefin rubber by the above-described method and the like, and is not particularly limited. For example, the degree of crosslinking is preferably 10 to 50%. The method for measuring the degree of crosslinking (degree of crosslinking) is based on JIS C 3005. However, in the mass measurement of the sample, the calculation is performed by subtracting the blending amount of the filler.

As described above, the high thermal conductive molded article of the present invention has poor heat softening properties, and even a thin film has high tensile strength and tear strength, and is difficult to break. Excellent handling up to the transportation stage.
When an adhesive layer is formed by thinly applying a pressure-sensitive adhesive to one main surface of the high thermal conductivity molded body of the present invention, the workability of attaching the high thermal conductive molded body to a substrate or the like can be further improved.

The high thermal conductivity molded body of the present invention exhibits excellent flame retardancy and electrical insulation in addition to high thermal conductivity. Therefore, in addition to being a high thermal conductive molded body, the high thermal conductive molded body of the present invention can be referred to as a flame retardant molded body or an electrically insulating molded body.
The highly heat-conductive molded product of the present invention having such high heat conductivity, flame retardancy and electrical insulation, particularly those formed into a band shape, a sheet shape, and a pad shape, generate heat with the housing of electric / electronic devices. It is suitable as a heat dissipating component that is interposed between the heat dissipating electronic component and radiates heat from the heat generating electronic component.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

(Example 1)
70 parts by mass of ethylene-propylene rubber (EPM) and 100 parts by mass of α-olefin copolymer rubber containing 30 parts by mass of ethylene-butene rubber as the ethylene-α-olefin rubber, and 400 parts by mass of aluminum hydroxide as the thermally conductive filler Was kneaded with a pressure kneader at a temperature of 130 to 150 ° C. to prepare a highly heat-conductive mixture.
This highly heat conductive admixture was formed into a sheet having a thickness of 0.5 mm and 1.0 mm at 80 ° C. by using an extruder to produce a highly heat conductive non-crosslinked molded article.

(Example 2)
A high heat conductive admixture and a high heat conductive non-crosslinked molded article were produced in the same manner as in Example 1 except that the formulation shown in Table 1 was changed.

Example 3
100 parts by mass of an α-olefin copolymer rubber containing 40 parts by mass of ethylene-propylene rubber (EPM) and 60 parts by mass of ethylene-butene rubber as an ethylene-α-olefin rubber, 450 parts by mass of aluminum hydroxide as a thermally conductive filler, and 50 parts by mass of aluminum oxide and 15 parts by mass of a plasticizer were kneaded by a pressure kneader at a temperature of 130 to 150 ° C. to prepare a highly heat-conductive admixture.
This highly heat conductive admixture was formed into a sheet having a thickness of 0.5 mm and 1.0 mm at 80 ° C. using an extrusion apparatus to produce a highly heat conductive non-crosslinked molded body.

(Examples 4 to 7)
A high heat conductive admixture and a high heat conductive non-crosslinked molded article were produced in the same manner as in Example 3 except that the formulation shown in Table 1 was changed.

(Example 8)
A highly thermally conductive admixture was prepared in the same manner as in Example 3, except that 1.8 parts by mass of dicumyl peroxide was added as a radical polymerization initiator to the α-olefin copolymer rubber and the thermally conductive filler.
This highly heat-conductive mixture was formed into a sheet having a thickness of 0.6 mm and 1.1 mm at 80 ° C. using an extruder. This primary molded body is cross-linked with press molding under a press condition of a press pressure of 500 MPa, a press temperature of 170 ° C. and a press time of 15 minutes with a hot press machine, and has a high thermal conductive cross-linkage having a thickness of 0.5 mm and 1.0 mm. A molded body was produced. The degree of cross-linking (by the above-described measuring method) of this highly heat-conductive cross-linked molded product was 30%.

Example 9
A highly heat conductive admixture was prepared in the same manner as in Example 6 except that 1.8 parts by mass of dicumyl peroxide was added as a radical polymerization initiator to the α-olefin copolymer rubber and the heat conductive filler.
This highly heat-conductive mixture was formed into sheets having a thickness of 0.6 mm and 1.1 mm at 80 ° C. using an extruder. This primary molded body is cross-linked with press molding under a press condition of a press pressure of 500 MPa, a press temperature of 170 ° C. and a press time of 15 minutes with a hot press machine, and 0.5 and 1.0 mm thick high thermal conductive crosslinks. A molded body was produced. The degree of cross-linking (by the above-described measuring method) of this highly heat-conductive cross-linked molded product was 30%.

(Comparative Examples 1-4)
A blend and a molded article were produced in the same manner as in Example 1 except that the α-olefin copolymer rubber, the heat conductive filler, and the plasticizer 1 were changed to the blending amounts shown in Table 2.
In Comparative Example 2, the mixing processability was poor and the mixture was too hard to be molded. Further, in Comparative Example 4, the components were not mixed at all and could not be mixed, and an admixture could not be prepared.
(Comparative Example 5)
In place of the α-olefin copolymer rubber, 100 parts by mass of acrylic rubber, 350 parts by mass of aluminum hydroxide and 100 parts by mass of aluminum oxide as heat conductive fillers, and 10 parts by mass of plasticizer 210 are added by a pressure kneader device. The mixture was prepared by kneading at 150 ° C. This blend was molded into a sheet having a thickness of 0.5 mm and 1.0 mm at 80 ° C. using an extruder, and a molded body was produced.

The detail of each component of the mixture used in the Example and the comparative example is as showing below.
<Α-olefin copolymer rubber>
Ethylene-propylene rubber (EPM): ethylene component amount 52%, Mooney viscosity ML1 + 4 (100 ° C.) 40
Ethylene-butene rubber (EBM): melting point 68 ° C., ethylene component amount 70%, third component (dicyclopentadiene) amount and butene component amount 30% total component amount, weight average molecular weight (MW) 87,000 , Number average molecular weight (Mn) 21,000
<Thermal conductive filler>
Aluminum hydroxide: Gibbsite produced from bauxite by the Bayer method, fine particles with an average particle size of 8μm, dry product (water adhesion 0.1%)
Magnesium hydroxide: fine particles with an average particle size of 3.5 μm (trade name: Magseeds 10A, manufactured by Kamishima Chemical Industries)
Aluminum oxide: spherical product with an average particle size of 35 μm (trade name: AX35-125, manufactured by Nippon Steel & Sumikin Materials)
<Plasticizer>
Plasticizer 1: Paraffinic process oil (trade name: PW-380, manufactured by Idemitsu Petroleum)
Plasticizer 2: Polyether plasticizer (trade name: Adeka Sizer RS700, manufactured by Asahi Denka)
<Acrylic rubber>
Acrylic rubber with Mooney viscosity ML1 + 4 (100 ° C) 30 (trade name: Nipol AR54, manufactured by Nippon Zeon)
<Radical polymerization initiator>
Dicumyl peroxide (DCP, trade name: Park Mill D, manufactured by NOF Corporation)

Each blend and each molded body were evaluated by the following method. The results are shown in Tables 1 and 2.
(Mixed workability)
In preparing the admixture, in the kneading with a pressure kneader, “○” indicates that there was no problem in the kneading state, and “x” indicates that the kneading state was bad.
Note that “no problem in kneading state” refers to a material that is uniformly dispersed into a lump compound, and “poor kneading state” refers to a powder that is not settled.
(Formability)
When the mixture was passed through an extruder to form a molded article, “○” was assigned when there was no problem in moldability, and “X” was indicated when the moldability was poor.
“No problem in formability” means that the sheet is extruded into a uniform sheet with a certain thickness and width, and “poor formability” means that it is hard and has poor ejection properties, or has broken or cracked. This means that the sheet does not become a uniform sheet.

(Thermal conductivity: thermal conductivity (W / mk))
Each molded body was measured by a hot wire method specified in JIS R 2616. A measured value of 1.3 W / mk or more is regarded as “high thermal conductivity” and passed.
(Electrical insulation: Volume resistivity (Ω-cm))
The volume resistivity of each molded body molded into a 1 mm thick sheet was measured according to JIS K6911. A measured value of 1 × 10 ¹² or more is regarded as “high electrical insulation” and passed.

(Flame retardance: UL94 vertical flammability test)
Using each molded body formed into a sheet having a thickness of 0.5 mm (sometimes referred to as 0.5 mmt), a combustion test was performed in accordance with UL94 vertical flammability test standard. Specifically, the compact was supported vertically, a burner flame was applied to the lower end of the compact and held for 10 seconds (first flame contact), and then the burner flame was separated from the compact. Then, as soon as the flame disappeared, the burner flame was further applied for 10 seconds (second flame contact) to release the burner flame. The evaluation was based on whether it falls under V-0, V-1, or combustion. The case where the evaluation was “V-0” was “O”, the case where it was “V-1” was “△”, the case where it was “burning” was “X”, and the case where “Δ” or more was passed To do.
(I) The total of the flammable combustion time of the first and second flame contact of the molded body is within 10 seconds, and the total of the flammable combustion time and the flameless combustion time after the second flame contact is Those within 30 seconds were designated as “V-0”.
(Ii) The total of the flammable combustion time of the first and second flame contact of the molded body is within 30 seconds, and the sum of the flammable combustion time and the flameless combustion time after the second flame contact is The thing within 60 seconds was set to "V-1."
(Iii) A case where the molded body burned continuously to the upper end after releasing the burner flame or burned over the time of V-1 was defined as “burning”.

(Tensile strength)
In accordance with JIS K 6251 “Tensile test method for vulcanized rubber”, a dumbbell No. 1 test piece was prepared from a 1 mm thick sheet and measured at a tensile speed of 500 mm / min.
As a measure of handleability, the tensile strength is a good level of 0.7 N / mm ² or more.
(Tear strength)
In conformity with JIS K 6252 “How to determine the tear strength of vulcanized rubber and thermoplastic rubber”, a 1 mm thick sheet was used to produce an angle-type test piece without cutting and measured at a tensile speed of 500 mm / min.
As a measure of handleability, the tear strength is a good level of 3 N / mm or more.

(Re-paste workability)
An acrylic pressure-sensitive adhesive (trade name: SK Dyne 1717, manufactured by Soken Chemical) is uniformly applied to a thickness of 20 μm on one main surface of each molded body and dried to form a pressure-sensitive adhesive layer. 0.5 mm × 20 mm A test sheet cut out to a size of 50 mm was attached to an aluminum plate by a reciprocating pressure of 1 kg of a 2 kg rubber roller by an automatic pressure bonding apparatus defined in JIS C 2107. When the aluminum plate was peeled off from the test sheet after 5 minutes, the test sheet was not torn, and “○” indicates that the aluminum sheet was pasted again in the same manner as before peeling, and “×” indicates that the test sheet was torn. "
In this re-sticking workability test, the test sheet that can be peeled without tearing sufficiently satisfies the handleability.

(hardness)
The hardness of each molded body was measured in accordance with the method described in JIS K 7312 (type C (Asker C type)).

As shown in Table 1, each of Examples 1 to 9 has good mixing processability and moldability, passed both thermal conductivity and volume resistivity, and also has flame retardancy of UL94V-0. It was considerable. Furthermore, the tensile strength and tear strength are large, and in the re-working workability test, it can be peeled without tearing, and can be re-applied in the same state with good reproducibility, molded into a thin shape, and provided with an adhesive layer However, there was no problem in re-working workability. In Examples 4 and 7, the high thermal conductive admixture was slightly hard and the extrusion speed tended to be slow, but the degree was small and the moldability was not impaired.
Moreover, although the high heat conductive crosslinked molded object of Example 8 and 9 has high hardness compared with the high heat conductive non-crosslinked molded object of Examples 1-7, mixed workability, moldability, thermal conductivity, The volume resistivity, flame retardancy and handling were not impaired.

On the other hand, as shown in Table 2, Comparative Example 1 in which the content of the α-olefin copolymer rubber is out of the above-described range is that the thermal conductivity, the volume resistivity, and the flame retardance are all the standards of the present invention. In addition, it was excellent in mixing processability and moldability. On the other hand, the tensile strength was as small as 0.5 N / mm ² and the tear strength was as small as 2.7 N / mm. In the reworking workability test, tearing occurred and the strength was rejected.
In Comparative Example 3 in which the content of the heat conductive filler is outside the above range, the mixing workability and the moldability were good, but the heat conductivity was low, and the molded body burned in the UL94 vertical flammability test. However, the flame retardancy was unacceptable.
Comparative Example 5 containing no α-olefin copolymer rubber had good mixing processability, molding processability, and thermal conductivity, but had low volume resistivity, poor electrical insulation, and tensile strength and tearing. The strength was extremely small.

(Example 10)
The sheet-like high thermal conductive non-crosslinked molded body produced in Example 3 was further rolled to obtain a thin sheet molded body having a thickness of 0.1 mm. This thin sheet body was re-applied in accordance with the above-mentioned “re-attachment workability” and the workability was evaluated. As a result, the thin sheet body was not torn and could be re-applied to the aluminum plate in the same manner as before peeling, and no reduction in re-workability due to thinning could be confirmed.

(Example 11)
When a thin sheet body was produced in the same manner as in Example 10 except that the thickness was changed to 0.07 mm, this thin sheet body was sometimes re-applied and sometimes torn during peeling in the workability test. In order to ensure re-working workability, the thickness should exceed at least 0.07 mm, and in order to ensure sufficient re-working workability, the thickness should be 0.10 mm or more as in Example 10. I found it good.

Claims (7)

  Α-olefin copolymer containing ethylene-propylene rubber and ethylene-α-olefin (excluding propylene) rubber in a mass ratio of 10:90 to 70:30 of the ethylene-propylene rubber and the ethylene-α-olefin. A highly heat-conductive mixture containing 100 parts by weight of rubber and 300 to 700 parts by weight of heat-conductive filler.   The high thermal conductivity admixture according to claim 1, wherein the ethylene-α-olefin rubber is ethylene-butene rubber.   The high thermal conductive admixture according to claim 1 or 2, wherein the ethylene-α-olefin rubber has a melting point of 40 to 100 ° C.   The heat-conductive filler is at least one selected from the group consisting of aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, aluminum nitride, and boron nitride. High thermal conductivity blend.   The high thermal conductivity admixture according to any one of claims 1 to 3, wherein the thermal conductive filler contains at least 200 parts by mass of a metal hydroxide with respect to 100 parts by mass of the α-olefin copolymer rubber.   The high heat conductive molded object formed by shape | molding the high heat conductive mixture of any one of Claims 1-5. The highly heat-conductive molded article according to claim 6, which is molded into a sheet having a thickness of 0.1 to 1.0 mm.