JP2003238760A - Nonhalogen, flame retardant and heat radiation sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonhalogen, flame retardant and, heat radiation sheet that has excellent flame retardance, does not emit a poisonous halogen has when burned, and has good sheet processability. <P>SOLUTION: This nonhalogen, flame retardant and, heat radiation sheet is obtained by blending 100-160 pts.wt. of a metal hydroxide flame retargder, 1-10 pts.wt. of red phosphorus, and 500-700 pts.wt. of a heat conductive powder with 100 pts. wt. of a binder resin consisting of 60-90 wt.% of an ethyl acrylate polymer and 10-40 wt.% of an ethylene-methyl acrylate copolymer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a halogen-free flame-retardant heat-dissipating sheet, and more specifically, it has excellent flame-retardant properties, does not generate harmful halogen-based gas when burned, and has good sheet processability. The present invention relates to a halogen-free flame-retardant heat-dissipating sheet suitable for heat-dissipating heat-generating bodies such as electric devices and electronic devices.

[0002]

2. Description of the Related Art Conventionally, as a heat dissipation sheet used for heat dissipation treatment of a heating element of electric equipment or electronic equipment, a silicone rubber sheet or a polyimide (amide) film containing a heat conductive powder such as aluminum oxide or boron nitride is used. It is known that a thin adhesive layer or a silicone rubber composition is provided on the surface.

The heat dissipation sheet is required to have high thermal conductivity in order to meet safety requirements by contacting with a heating element, and UL-94 is required as the flame retardancy level.
It is required to have V-0 level flame retardancy in a combustion test. However, the above-mentioned conventional heat dissipation sheet is inferior in flame retardancy, and even if a flame retardant is used, it is necessary to use it together with the heat conductive powder to balance the electrothermal property and the flame retardant property. There is a problem that it is difficult to achieve the V-0 level flame retardancy in the test.

Heretofore, in order to make the heat-dissipating sheet flame-retardant, a halogen-based flame retardant such as a bromine compound or a chlorine compound has been mainly blended. However, in this case, since a harmful halogen-based gas is generated when burned, a halogen-free flame-retardant heat dissipation sheet has recently been demanded due to environmental problems.

Known halogen-free flame retardants include metal hydroxide flame retardants such as magnesium hydroxide and aluminum hydroxide, and zinc flame retardants such as zinc borate, zinc carbonate and zinc oxide. However, these non-halogen flame retardants have a problem that a sufficient flame retardant effect cannot be exhibited unless they are blended in a large amount.

The heat conductive powder used for the heat dissipation sheet is
Generally, a considerable amount is blended, and when a large amount of the above-mentioned non-halogen flame retardant is blended, there is a problem that the moldability into a sheet is unavoidably deteriorated.

[0007]

Under the circumstances described above, the present invention has good thermal conductivity, is excellent in flame retardance, and does not generate harmful halogen-based gas when burned. Moreover, it is an object of the present invention to provide a halogen-free flame-retardant heat-dissipating sheet having good sheet processability.

[0008]

Means for Solving the Problems The present inventors have conducted various studies on non-halogen flame-retardant heat-dissipating sheets, and as a result,
A heat-dissipating sheet that contains a binder resin and a metal hydroxide flame retardant, red phosphorus, and heat-conducting powder in the specified proportions provides excellent flame-retardant properties and sheet processability while maintaining good thermal conductivity. The present invention has been completed and the present invention has been completed.

That is, the present invention is based on 100 parts by weight of a binder resin composed of 60 to 90% by weight of an ethyl acrylate polymer and 10 to 40% by weight of an ethylene-methyl acrylate copolymer, and a metal hydroxide flame retardant. 10
It is characterized in that 0 to 150 parts by weight, 1 to 10 parts by weight of red phosphorus and 500 to 700 parts by weight of heat conductive powder are blended.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The binder resin used in the heat dissipation sheet of the present invention is an ethyl acrylate polymer 60-.
90% by weight and 10 to 40% by weight of ethylene-methyl acrylate copolymer.

The ethyl acrylate polymer which is one component of the binder resin is not particularly limited, but a polymer containing 90 mol% or more of ethyl acrylate units is preferable, and for example, butyl acrylate and other copolymers as other components. It is preferable that the content of the monomer is 10 mol% or less. Examples of commercial products of this ethyl acrylate polymer include Cyanacryl R (manufactured by American Cyanamid), Toacron AR-601, Toacron AR-740 (both manufactured by Toa Paint Co., Ltd.), Knoxtite PA-301, Knoxtite. PA-31
2, Knoxtite PA-401, Knoxtite PA
-512E (both manufactured by NOK Co., Ltd.) and the like.

The ethylene-methyl acrylate copolymer, which is the other component, is not particularly limited, but it is in the range of 61 to 77% and 23 to 39% in terms of the equivalent monomers of ethylene units and methyl acrylate units, respectively. A molar ratio is preferable, and a random copolymer is preferable from the viewpoint of the arrangement of the monomers. Further, it may contain 4 mol% or less of other copolymerizable monomer components. Examples of commercially available products of these copolymers include Baymac G and Baymac HG (both manufactured by Mitsui-DuPont Polychemical Co., Ltd.).

Although the filling property of the inorganic filler such as the above ethyl acrylate polymer heat conductive powder is good,
The non-vulcanized shape retention is poor, while the ethylene-methyl acrylate copolymer is excellent in shape retention but poor in the inorganic filler filling property. Therefore, considering the filling property and the shape retention property of the inorganic filler, the content ratios of the ethyl acrylate polymer and the ethylene-methyl acrylate copolymer are in the ranges of 60 to 90% by weight and 10 to 40% by weight, respectively. Preferably there is.

As the non-halogen flame retardant used in the heat dissipation sheet of the present invention, a combination of a metal hydroxide flame retardant and red phosphorus is used. Examples of the metal hydroxide flame retardant include magnesium hydroxide, aluminum hydroxide, zirconium hydroxide and the like, but magnesium hydroxide and aluminum hydroxide are particularly preferable. This metal hydroxide flame retardant has an average particle diameter of 0.1 to 0.1.
It is preferably in the range of 10 μm.

Thus, by using a combination of a metal hydroxide flame retardant such as magnesium hydroxide or aluminum hydroxide with red phosphorus, the endothermic reaction of the metal hydroxide flame retardant and the surface of red phosphorus. Due to the synergistic effect with char formation, V-0 level flame retardancy in the UL-94 combustion test can be achieved, and no harmful gas is generated when combusted.

The metal hydroxide flame retardant in the present invention is
They may be used alone or in combination of two or more. Further, the blending amount is 100% of the binder resin.
100 to 150 parts by weight, preferably 12 parts by weight
It is selected in the range of 0 to 140 parts by weight. This blend amount is 10
If the amount is less than 0 parts by weight, sufficient flame retardancy-providing effect is not exhibited, and if the amount exceeds 150 parts by weight, moldability of the composition is deteriorated.

On the other hand, red phosphorus has an average particle size of 0.1.
To 100 μm is preferable, and the compounding amount is 1 to 1 with respect to 100 parts by weight of the binder resin.
It is selected in the range of 0 parts by weight. If the blending amount deviates from the above range, a sufficient flame retardancy-providing effect cannot be exhibited.

Examples of the heat conductive powder used in the heat dissipation sheet of the present invention include aluminum oxide, magnesium oxide, aluminum nitride and boron nitride. Of these, aluminum oxide and magnesium oxide are particularly preferable. The average particle size of this heat conductive powder is preferably in the range of 0.1 to 100 μm.

The heat conductive powder in the present invention may be used alone or in combination of two or more kinds.
The blending amount is selected within the range of 500 to 700 parts by weight with respect to 100 parts by weight of the binder resin. If the amount is less than 500 parts by weight, sufficient thermal conductivity cannot be obtained, and if it exceeds 700 parts by weight, the moldability of the composition is deteriorated.

In the heat dissipation sheet of the present invention, in addition to the above-mentioned components, other components can be appropriately blended within a range not impairing the object of the present invention. For example, a surface treatment agent, a surfactant, a lubricant, a stabilizer, a plasticizer, a softening agent, a coloring agent, an antiaging agent and the like can be added.

The stabilizer is one which makes the composition blended as described above have sufficient heat resistance at the extrusion processing temperature (for example, about 120 to 160 ° C.), and examples thereof include amine antioxidants. . As this amine-based antioxidant,
Aromatic compounds are preferable, for example, diphenyldiamine compounds such as N, N'-diphenyl-p-phenylenediamine and N, N'-di-β-naphthyl-p-phenylenediamine.

The heat dissipation sheet of the present invention contains the above composition and is formed into a long sheet by extrusion molding or calendar molding.

[0023]

The present invention will be described in detail below with reference to examples. The flame-retardant sheet was evaluated for the following items. (Workability) The compound was formed into a sheet by a test roll and visually observed, and the workability was evaluated according to the following criteria. ◯: There are no cracks on both ends of the sheet, and there is no adhesion to the roll surface. Δ: There are slight cracks at both ends of the sheet, or there is partial adhesion on the roll surface. X: Both ends of the sheet are cracked, or the sheet sticks to the roll surface and is difficult to peel off. (Flame retardancy) Obtained by a 20 mm vertical burning test according to UL-94 standard. (Thermal conductivity) It measured using the thermal conductivity meter ("QTM-500", Kyoto Electronics Manufacturing Co., Ltd.).

(Examples 1 to 4 and Comparative Examples 1 to 8) Compositions containing the components (parts by weight) shown in Table 1, 3 parts by weight of stabilizer, 2 parts by weight of lubricant, and 2 parts by weight of processing aid were prepared. After kneading with a kneader at a temperature of about 140 ° C and pulverizing, the product is fed to a calendering device set at a roll temperature of 80 ° C to give a thickness of
mm, a long sheet having a width of 350 mm was formed.

The components shown in the table are as follows. Ethyl acrylate polymer: ("Noxtite PA-312", manufactured by NOK), specific gravity 1.1 Ethylene-methyl acrylate copolymer: ("Mayi-DuPont Polychemical", "Baymac G", specific gravity 1.
0) Magnesium hydroxide: (Kyowa Chemical Industry Co., Ltd., “Kismer 5B”), average particle size 1 μm Red phosphorus: (Nippon Chemical Industry Co., Ltd., “Hishiguard TP”),
Average particle size 20 μm Aluminum oxide: (Showa Denko KK, “Alumina A-1
2 ”), average particle size 60 μm

The heat dissipation sheet thus obtained was evaluated for workability, flame retardancy and thermal conductivity. The results are shown in Table 1.

[0027]

[Table 1]

[0028]

EFFECTS OF THE INVENTION The heat dissipation sheet of the present invention has good thermal conductivity, is excellent in flame retardancy, does not generate harmful halogen-based gas when burned, and can be molded with good workability. it can.

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Claims (3)

[Claims] 1. An ethyl acrylate polymer 60 to 90% by weight and an ethylene-methyl acrylate copolymer 10
100 to 150 parts by weight of a binder resin composed of 100 to 150 parts by weight, 100 to 150 parts by weight of a metal hydroxide flame retardant, 1 to 10 parts by weight of red phosphorus, and 500 to 700 of thermally conductive powder.
A non-halogen flame-retardant heat-dissipating sheet characterized by being mixed in parts by weight. 2. The halogen-free flame-retardant heat radiation sheet according to claim 1, wherein the metal hydroxide flame retardant is at least one selected from magnesium hydroxide and aluminum hydroxide. 3. The halogen-free flame-retardant heat dissipation sheet according to claim 1, wherein the heat conductive powder is at least one selected from aluminum oxide and magnesium oxide.