JPH07324146A - Heat-conductive rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubbery elastomer having high thermal conductivity and excellent electrical insulation properties. CONSTITUTION:This composition comprises 100 pts.wt. base material comprising a rubber, 20-100 pts.wt. carbon black and 20-60 pts.wt. at least one inorganic filler selected from among crystalline silica, magnesium oxide, fused quartz, quartz glass, zinc oxide and aluminum oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having thermal conductivity, which can be suitably used as a road material for vehicles and pedestrians around railroad crossings and intersections in cold and snowfall areas. Rubber composition.

[0002]

2. Description of the Related Art Snow removal work is essential to prevent snow damage in cold regions. For example, when snow is removed from a road surface, a manual method, a method using a snow plow, a method of spraying water, a method of blowing hot air, etc. are generally performed.

However, it is difficult to secure appropriate human resources in the method using human power and the method using a snow plow, and the method of spraying water is that water, snow, soil and the like are mixed with each other and the land landscape is significantly impaired. In addition, the method using hot air requires a large amount of equipment and requires enormous cost.
These methods were not preferred.

Further, in some areas, there is a method in which a heat generating means such as a hot water pipe or a nichrome wire is buried in the road, and the heat generated from the heat generating means is used to melt the snow on the frozen road surface. Has been adopted. This method is attractive in terms of solving the shortage of human resources and maintaining the landscape of the land, and this method has been attracting attention in the past.

[0005]

By the way, in recent years, there has been an increasing demand for improvement of living environment such as reduction of vehicle noise and improvement of walking feeling on general roads. In order to satisfy the requirement, a road material made of a rubber elastic body is partially used. However, the conventional rubber elastic body used for such a road material has a low thermal conductivity, and even if a snow-melting road material is formed by embedding the heat-generating means as described above, the heat of the heat-generating means is not generated. However, there was a problem that the snow was not efficiently transmitted to the road surface and a satisfactory snow melting effect could not be obtained.

On the other hand, it is conceivable to add a heat conductive filler such as a metal powder to a conventional rubber elastic body to increase the heat conductivity and use it as a road material. Then, although the thermal conductivity is certainly improved, at the same time, the conductivity is increased and the electrical insulating property is deteriorated. For this reason, there is a possibility that the electric signal may malfunction due to the electric leakage and the overcurrent, and it cannot be applied to the periphery of electric equipment and as a heater material.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a heat conductive rubber composition capable of forming a rubber elastic body having high heat conductivity and excellent electric insulation. And

<Consideration on Thermally Conductive Filler> The present inventor has conducted various studies on the thermally conductive filler to be filled in order to improve the thermal conductivity. According to the research, a rubber elastic body filled with a heat conductive filler such as a metal powder has an excessively high conductivity as expected, and is unsuitable for use around an electric device. In addition, since the thermally conductive filler such as boron nitride has a high hardness, when it is attempted to mix these with a rubber compound to manufacture a rubber composition, the mixer or the like may be damaged during mixing, which is a problem in manufacturing. It was something that had. Furthermore, since the heat conductive filler such as graphite has too high conductivity, the same problems as those of the above metal powder occur, and since calcium fluoride and beryllium oxide are expensive, use as a filler is not preferable. There wasn't.

[0009]

Further, as a result of meticulous research, the present inventor has found that by incorporating a specific amount of a specific compound into a rubber as a main material, the thermal conductivity capable of achieving the above object can be achieved. We have found that a rubber composition can be obtained, and have completed the present invention.

That is, the heat conductive rubber composition of the present invention comprises 20 to 100 parts by weight of carbon black, crystalline silica, magnesium oxide, fused silica, quartz glass and zinc oxide based on 100 parts by weight of the main material made of rubber. , One or more inorganic fillers selected from aluminum oxide 2
The gist is that 0 to 60 parts by weight are blended.

In the present invention, the inorganic filler is
It is preferable to adopt a structure specified by one or two kinds selected from crystalline silica and magnesium oxide.

Further, in the present invention, the main material is
It is preferable to adopt a constitution composed of a mixture of styrene-butadiene rubber and natural rubber in a ratio of 99 to 40% by weight: 1 to 60% by weight.

As the main material of the present invention, any rubber such as natural rubber, synthetic rubber and rubber obtained by mixing them can be used, and it is not particularly limited, but is inexpensive. It is preferable to use styrene-butadiene rubber (SBR) which has high versatility and good workability, and particularly, a mixture of SBR and natural rubber in a ratio of 99 to 40% by weight: 1 to 60% by weight is preferable. , More preferably used. In this case, if the amount of SBR mixed exceeds 99% by weight, cracks are likely to occur due to a change with time, and when used as a road material, for example, it may not be able to sufficiently withstand the passage of a vehicle, which is not preferable.
Further, if the amount of SBR mixed is less than 40% by weight, sufficient durability may not be obtained, which is not preferable. On the other hand, if the mixing amount of the natural rubber exceeds 60% by weight, it may not be able to withstand the use of road materials, which is not preferable. Further, if the amount of the natural rubber mixed is less than 1% by weight, cracks are likely to occur due to aging, and there is a risk that it will not be able to withstand the use of road materials, which is not preferable.

The use of silicone rubber, fluororubber or ethylene / propylene rubber as the main material of the present invention is not so preferable. This is because these rubbers are all expensive, and when they are commercialized, the rubber products are extremely hard and brittle, making it difficult to form large products such as road materials, and moreover, they are suitable for use as road materials. This is because it cannot be fully tolerated.

In the composition of the present invention, it is necessary to blend 20 to 100 parts by weight of carbon black, and it is preferable to set the blending amount to about 60 parts by weight.
Although carbon black has excellent thermal conductivity, it is also highly conductive, so if the blending amount exceeds 100 parts by weight, the insulation will be poor, and it will be used as a road material around electrical equipment such as traffic lights and level crossings. If it is used, it may cause malfunction of those devices due to electric leakage, and the wear resistance may be reduced, which is not preferable. Further, if the blending amount is less than 20 parts by weight, the thermal conductivity is lowered, the tensile strength and the modulus are lowered, and the strength is lowered.

The particle size of the carbon black is not particularly limited, but the average particle size is 0.01 to 0.10 μm.
Those having an average particle size of m can be preferably used, and those having an average particle size of about 0.03 μm can be used more preferably.

In the composition of the present invention, crystalline silica,
Fused silica, fused silica, magnesium oxide, zinc oxide,
It is necessary to incorporate at least one inorganic filler selected from aluminum oxide. Among these, it is recommended to use magnesium oxide having high thermal conductivity and appropriate hardness and relatively inexpensive, and crystalline silica having high thermal conductivity and appropriate hardness and inexpensive.

The amount of the inorganic filler compounded is 20 parts by weight to 60 parts by weight.
It is necessary to set to the weight part, and especially the compounding quantity is 40
It is preferable to set around the weight part. That is, if the compounding amount of the inorganic filler exceeds 60 parts by weight, it becomes too hard and a good elastic modulus cannot be obtained, which is not preferable. Further, if the amount is less than 20 parts by weight, sufficient thermal conductivity cannot be obtained, which is not preferable.

The particle size of the inorganic filler is not particularly limited, but those having an average particle size of 1 to 100 μm can be preferably used, and those having an average particle size of around 3.5 μm are particularly preferable. It can be used more preferably.

A rubber composition in which only one of carbon black and the above-mentioned inorganic filler is added to the main material is not preferable because the initial purpose cannot be achieved. This is because the one containing only carbon black cannot control the electric conductivity to be low, and the one containing only the above inorganic filler cannot obtain a sufficient thermal conductivity.

On the other hand, in the composition of the present invention, various additives such as a vulcanizing agent, a vulcanization accelerator, an antiaging agent, etc. may be added, if necessary, in addition to the above-mentioned main material, carbon black and inorganic filler. It can be blended appropriately. Preferable specific examples of the vulcanizing agent include powdered sulfur, and preferable specific examples of the vulcanization accelerator include zinc white (zinc oxide), stearic acid, dibenzothiazyl sulfide (DM), cyclohexyl. Benzothiazylsulfenamidite (C
Z) etc. are illustrated. Further, specific examples of suitable antioxidants include 1,2-dihydro-2,2,4-trimethylquinoline (RD) and N-isopropyl-N'-phenyl-P-phenylenediamine (3C). It

To produce a heat conductive rubber product from the rubber composition of the present invention, for example, the above rubber composition is mixed with a mixer at room temperature, and the mixture is heated from room temperature to 10 times.
In the range of 0 ° C., kneading is performed by a roll mill to form an unvulcanized rubber. Then, a method of cutting the unvulcanized rubber into a predetermined size and thermally cross-linking it with a hot press machine to obtain a vulcanized rubber (rubber product) can be exemplified.

The rubber product obtained from this composition has a high thermal conductivity and an insulating property, and has appropriate hardness and sufficient strength. Specifically, the thermal conductivity is 0.15.
Insulation is 1.0 × 1 above [kcal / h ・ m ・ ° C]
The hardness is 0 ⁴ [Ω] or more, the hardness according to JIS K6301 is 60 to 75, and the tensile strength according to JIS K6301 is 110 [kg · f / cm ² ] or more. Therefore, for example, it can be suitably used as a rubber elastic body for a snow melting road material in a cold or snowy region, and especially for a snow melting road material around an electric device / electric component such as a traffic signal.

Specifically, the snow melting road material shown in FIGS. 1A, 1B and 1C can be formed. That is, FIG.
In the snow melting road material (A) shown in (a), a heating means (2a) such as a heating tape or a nichrome wire is embedded inside a block-shaped rubber elastic body (1) made of the composition of the present invention. The heat generating means (2a) and the power source (3a) are electrically connected.

The snow melting road material (B) shown in FIG. 1 (b) is
Block-shaped rubber elastic body (1) (1) comprising the composition
A heating means (2b) such as a sheet heating element or heating paint is provided so as to be sandwiched between them, and the heating means (2b) and the power source (3b) are electrically connected.

Further, the snow melting road material (C) shown in FIG. 1 (c).
A heat generating means such as a hot water pipe (2c) is embedded inside a block-shaped rubber elastic body (1) made of the present composition, and hot water can be supplied from the water heater (3c) into the pipe (2c). It is configured as follows.

A road is formed by laying such snow melting road materials (A), (B) and (C) on the road ground around railroad crossings and intersections. When it is desired to remove the snow accumulated on this road, the power sources (3a) (3b) or the water heater (3c) are driven to generate heat (2a) (2b).
It is sufficient to heat (2c). As a result, the heat of the heat generating means (2a) (2b) (2c) is transferred to the road material (A) (B).
The snow on the road surface is melted and removed through the inside of (C).

Since the road materials (A), (B) and (C) have high thermal conductivity, the heat generating means (2a) (2).
b) The heat of (2c) is efficiently transmitted to the road surface, and snow on the road surface can be efficiently melted. Further road material (A)
Since (B) and (C) also have high electrical insulation properties, it is possible to prevent electric leakage and reliably prevent malfunction of electric devices such as traffic signals.

Further, since the road materials (A), (B), and (C) have good elasticity, vibrations during traveling of the vehicle can be absorbed, noise can be effectively prevented, and elastic effects can be obtained. Thus, a good walking feeling can be obtained when walking. Further, when the vehicle travels on a road surface that is snowed and frozen, the road materials (A), (B), and (C) elastically expand and contract, and the frozen snow splits and separates from the road surface. You can expect the snow removal effect.

In the above description, the case where the rubber composition of the present invention is used as a snow melting road material is described as an example, but the use of the rubber composition of the present invention is particularly limited. Not something. For example, it can be used as a building material in a broad sense such as ordinary road materials other than snow melting road materials, building materials for pedestrian bridges, building wall materials and floor materials, and is particularly preferably used as a thermistor material for snow melting snow, heating panels, etc. can do.

[0031]

EXAMPLES Next, examples related to the present invention and comparative examples for deriving their effects will be described.

<Example 1> Japan Synthetic Rubber Co., Ltd. (JS
R) styrene-butadiene rubber (SBR # 150
0) and natural rubber were mixed in a weight ratio of 60:40 to obtain a raw material rubber (main material). To 100 parts by weight of the raw rubber, 60 parts by weight of carbon black (diamond black H) made by Mitsubishi Kasei Co., Ltd. having an average particle size of 0.03 μm, and made by Tatsumori Co., Ltd. having an average particle size of 3.5 μm as an inorganic filler. 40 parts by weight of crystalline silica (Crystallite) was added to each, 3 parts by weight of powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. as a vulcanizing agent, and dibenzothiazyl sulfide (DM) manufactured by Sumitomo Chemical Co., Ltd. as a vulcanization accelerator. 1 part by weight, similarly 3 parts by weight of zinc white manufactured by Sakai Chemical Co., Ltd. as a vulcanization accelerator, and N-isopropyl-N′-phenyl-P-phenylenediamine (3C) manufactured by Sumitomo Chemical Co., Ltd. as an antioxidant. 1 part by weight and 1,2-
Dihydro-2,2,4-trimethylquinoline (RD) 1
A rubber composition was obtained by blending the mixture of 1 part by weight and 5 parts by weight with a mixer at room temperature for 5 minutes.

Then, the rubber composition is kneaded with two rolls at 80 ° C. for 15 minutes to form an unvulcanized rubber sheet, and the unvulcanized rubber sheet is 400 mm × 400 mm ×
A vulcanized rubber (rubber product) was obtained by heating at 180 ° C. for 40 minutes in a frame of 50 mm size.

The thermal conductivity of this rubber product was measured according to the Shibayama-type acetone-benzene method, and JIS K69 was used.
Electrical insulation was measured according to 11. Further JIS
Hardness and tensile strength were measured according to K6301.
In addition, workability up to the production of rubber products, such as molding workability, is evaluated in three stages of "good", "normal", and "poor",
Based on the price spent on the compounded material, the cost was evaluated in three stages of "cheap", "normal" and "expensive". The results are shown in Table 1 below together with the blending amounts of the main blending materials. In addition, "part" in the table indicates "part by weight".

[0035]

[Table 1] <Example 2> As shown in the same table, a rubber product was obtained in the same manner as in Example 1 except that the amount of carbon black was set to 20 parts by weight and the amount of crystalline silica was set to 40 parts by weight. The measurement and the like were performed in the same manner as above.

<Example 3> As shown in the table, a rubber product was obtained in the same manner as above except that the amount of carbon black and the amount of crystalline silica were set to 100 parts by weight and 40 parts by weight, respectively. The measurement and the like were performed in the same manner as above.

<Example 4> As shown in the same table, a rubber product was obtained in the same manner as above except that the amount of carbon black and the amount of crystalline silica were set to 60 parts by weight and 20 parts by weight, respectively. The measurement and the like were performed in the same manner as above.

<Example 5> As shown in the same table, a rubber product was obtained in the same manner as above except that the amount of carbon black and the amount of crystalline silica were set to 60 parts by weight and 60 parts by weight, respectively. The measurement and the like were performed in the same manner as above.

<Comparative Example 1> As shown in Table 1 above, a rubber product was prepared in the same manner as in the above Example except that the amount of carbon black was set to 15 parts by weight and the amount of crystalline silica was set to 50 parts by weight. Was obtained, and the measurement and the like were performed in the same manner as above.

<Comparative Example 2> As shown in the same table, a rubber product was obtained in the same manner as above except that the amount of carbon black was set to 120 parts by weight and the amount of crystalline silica was set to 20 parts by weight. The measurement and the like were performed in the same manner as above.

<Comparative Example 3> As shown in the same table, a rubber product was obtained in the same manner as described above except that the amount of carbon black and the amount of crystalline silica were set to 60 parts by weight and 15 parts by weight, respectively. The measurement and the like were performed in the same manner as above.

<Comparative Example 4> As shown in the table, a rubber product was obtained in the same manner as above except that the amount of carbon black and the amount of crystalline silica were set to 60 parts by weight and 75 parts by weight, respectively. The measurement and the like were performed in the same manner as above.

<Example 6>

[Table 2] As shown in Table 2 above, a rubber product was obtained in the same manner as in Example 1 except that 40 parts by weight of magnesium oxide was mixed instead of crystalline silica, and the measurement and the like were performed in the same manner as above.

Example 7 As shown in the same table, a rubber product was prepared in the same manner as in Example 6 except that the amount of carbon black and the amount of magnesium oxide were set to 20 parts by weight and 40 parts by weight, respectively. Was obtained, and the measurement and the like were performed in the same manner as above.

<Example 8> As shown in the same table, a rubber product was prepared in the same manner as in Example 6 except that the amount of carbon black was set to 100 parts by weight and the amount of magnesium oxide was set to 40 parts by weight. Was obtained, and the measurement and the like were performed in the same manner as above.

<Example 9> As shown in the table, a rubber product was prepared in the same manner as in Example 6 except that the amount of carbon black and the amount of magnesium oxide were set to 60 parts by weight and 20 parts by weight, respectively. Was obtained, and the measurement and the like were performed in the same manner as above.

<Example 10> As shown in the same table, a rubber product was prepared in the same manner as in Example 6 except that the amount of carbon black and the amount of magnesium oxide were set to 60 parts by weight and 60 parts by weight, respectively. Was obtained, and the measurement and the like were performed in the same manner as above.

Comparative Example 5 As shown in Table 2 above, a rubber was prepared in the same manner as in Example 6 except that the blending amount of carbon black was set to 15 parts by weight and the blending amount of magnesium oxide was set to 50 parts by weight. The product was obtained, and the measurement and the like were performed in the same manner as above.

<Comparative Example 6> As shown in the same table, a rubber product was prepared in the same manner as in Example 6 except that the blending amount of carbon black was set to 120 parts by weight and the blending amount of magnesium oxide was set to 20 parts by weight. Was obtained, and measurements and the like were performed in the same manner as above.

Comparative Example 7 As shown in the table, a rubber product was prepared in the same manner as in Example 6 except that the amount of carbon black and the amount of magnesium oxide were set to 60 parts by weight and 15 parts by weight, respectively. Was obtained, and the measurement and the like were performed in the same manner as above.

Comparative Example 8 As shown in the same table, a rubber product was prepared in the same manner as in Example 6 except that the amount of carbon black and the amount of magnesium oxide were set to 60 parts by weight and 75 parts by weight, respectively. Was obtained, and the measurement and the like were performed in the same manner as above.

<Comprehensive Evaluation> As can be understood from the above Tables 1 and 2, the products of Examples 1 to 10 related to the present invention are:
It was confirmed that good values were obtained in all of the thermal conductivity, insulating property, hardness and tensile strength, and there was no problem in workability, and it was possible to manufacture at low cost. Among them, Examples 1 and 6
Excellent measurement results were obtained and it was the most excellent product.

On the other hand, it was confirmed that the products of Comparative Examples 1 to 8, which deviate from the regulations of the present invention, do not satisfy all the measurement results. That is, the products of Comparative Examples 1 and 5 could not obtain good results in terms of thermal conductivity, hardness, and tensile strength, and the manufacturing cost was high. Further, the products of Comparative Examples 2 and 6 could not obtain good results with respect to insulation properties and hardness, and were inferior in workability. Further, the products of Comparative Examples 3 and 7 could not obtain good results in terms of thermal conductivity, and the manufacturing cost was high. Furthermore, the products of Comparative Examples 4 and 8 are too hard, and it is difficult to obtain a good walking feeling,
It was also inferior in workability.

[0054]

As described above, according to the heat conductive rubber composition of the present invention, 20 to 100 parts by weight of carbon black, crystalline silica, magnesium oxide, and melt are added to 100 parts by weight of the main material made of rubber. 20 to 60 parts by weight of one or more kinds of inorganic fillers selected from quartz, quartz glass, zinc oxide, and aluminum oxide are mixed, so that the thermal conductivity is high and the electrical insulating property is high. It is excellent in that it has the effect of being able to form a rubber elastic body having appropriate hardness and sufficient strength. Therefore, for example, when the composition of the present invention is used as a snow melting road material around the intersection in a cold snowfall area and around a railroad crossing, it does not cause a malfunction due to earth leakage in a traffic signal, a circuit breaker, etc. The heat from the means can be efficiently transmitted to the road surface, and a good snow melting effect can be obtained. In addition, the elastic force absorbs vibrations when the vehicle is running and noise can be effectively prevented, and a good walking feeling can be obtained when walking.

In the present invention, when an inorganic filler made of crystalline silica or magnesium oxide is used, a rubber elastic body having higher thermal conductivity and excellent electrical insulation can be obtained at a low cost. There is an advantage that you can.

Further, in the present invention, when the main material is a mixture of styrene-butadiene rubber and natural rubber in a ratio of 99 to 40% by weight: 1 to 60% by weight, heat conduction is further improved. There is an advantage that a rubber elastic body having a high rate and excellent electric insulation can be easily obtained.

[Brief description of drawings]

1 (a) and 1 (c) are perspective views showing a snow melting road material formed from a rubber composition of an example of the present invention, respectively.
(B) is a partially cutaway perspective view showing a snow melting road material formed from the rubber composition of the above example with a part thereof cut away.

Claims (3)

[Claims] 1. 100 to 100 parts by weight of a main material made of rubber, 20 to 100 parts by weight of carbon black, and 1 selected from crystalline silica, magnesium oxide, fused silica, quartz glass, zinc oxide and aluminum oxide.
20-60 weight part of inorganic fillers of 1 or more types are mix | blended, The heat conductive rubber composition characterized by the above-mentioned. 2. The heat conductive rubber composition according to claim 1, wherein the inorganic filler is specified to one or two selected from crystalline silica and magnesium oxide. 3. The heat conductive rubber according to claim 1, wherein the main material is a mixture of styrene-butadiene rubber and natural rubber in a ratio of 99 to 40% by weight: 1 to 60% by weight. Composition.