JP2008285658A - Rubber composition blended with carbon powder and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition blended with carbon powder having vibration-damping properties, thermal conductivity, and electrical conductivity and suitably used as a damper material of a motor. <P>SOLUTION: The rubber composition blended with carbon powder is prepared by blending carbon powder with a rubber material, wherein the carbon powder is prepared by dispersing a carbon nanotube in a silk solution, drying the dispersion to obtain a mixed material, firing the dried mixed material in a non-oxidizing atmosphere, and pulverizing the fired material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carbon powder-containing rubber composition excellent in vibration damping properties and thermal conductivity and a method for producing the same.

  Although motors are used in various fields, for example, when used in an apparatus using a semiconductor, a motor having vibration damping properties for absorbing vibration and heat conductivity for heat dissipation is preferable. However, few materials with these two properties are known.

JP-A-5-310993 describes the following rubber materials.
That is, at least one filling selected from the group consisting of a metal fine powder and a filler containing (a) a metal oxide, a metal nitride and any of these in a polymer mainly composed of rubber and / or plastic And (b) at least one filler selected from the group consisting of crystalline silica, silicon carbide, silicon oxide, and fillers containing any of these, and the blending ratio of (a) and (b) Is in the range of 7: 3 to 3: 7, and the filler is molded with a compound having a thermal conductivity of 0.5 Kcal / m.h. 2 × 10 2 ηKg / cm 2 or more and a thermal conductivity of 0.49 Kcal / m. h. A rubber and / or plastic molding having vibration damping and thermal conductivity, characterized by having a vibration damping property and thermal conductivity at or above C. is described.

JP 2000-302970 describes the following CNT composite heat conductive rubber.
That is, the heat conductive silicone rubber composition is composed of silicone rubber rubber blended with Ni—Zn soft magnetic ferrite as a heat conductive filler, and in addition to Ni—Zn soft magnetic ferrite, soft magnetic There is disclosed a molded body in which a filler having a higher thermal conductivity than ferrite and / or a carbon nanotube or a carbon microcoil is blended and formed, and the composition is molded and cured.
JP-A-5-310993 JP 2000-302970

However, in the thing of patent document 1, metal fine powder tends to raise | generate a time-dependent change, such as oxidation, Therefore, the composite material of metal fine powder and rubber | gum also deteriorates with time, and physical properties (for example, elasticity, a shape, etc.) There is a reliability problem that performance cannot be maintained. Further, when metal oxide fine powder is used, deterioration with time is unlikely to occur, but there is a problem that electrical conductivity is impaired and it cannot be used as a ground for suppressing noise generated in a motor.
Further, in the case of metal fine powder, when the amount added is increased to increase the thermal conductivity, there is a problem that the hardness becomes relatively high and the vibration damping property is deteriorated.
In the thing of patent document 2, although heat conductivity is examined, the vibration damping property is not examined.
The present invention has been made in order to solve the above-mentioned problems. The object of the present invention is to provide a carbon that is stable over time, has vibration damping properties, thermal conductivity, and conductivity, and is suitable for use as a motor damper material. It is in providing a powder-blended rubber composition and a method for producing the same.

  The carbon powder blended rubber composition according to the present invention is a carbon powder blended rubber composition in which carbon powder is blended with a rubber material. The carbon powder is dispersed in a silk solution in the carbon powder and dried, and the mixed material is non-oxidized. It is characterized by using a calcined carbon component that has been baked in a neutral atmosphere and pulverized.

The rubber material is silicone rubber.
The rubber material is NBR.
A motor damper material comprising the carbon powder-containing rubber composition.

  Further, the method for producing a carbon powder-containing rubber composition according to the present invention includes a step of dispersing carbon nanotubes in a silk solution and firing the dried mixed material in a non-oxidizing atmosphere, and grinding the fired mixed material. And a step of blending the obtained calcined carbon powder into a rubber material.

  ADVANTAGE OF THE INVENTION According to this invention, the carbon powder compounded rubber composition excellent in damping property, heat conductivity, and electroconductivity can be provided. This rubber composition can be suitably used as a heat dissipation damper material for motors.

  As described above, the carbon powder-blended rubber composition according to the present invention is a carbon powder-blended rubber composition in which carbon powder is blended with a rubber material, and carbon nanotubes are dispersed in a silk solution in the carbon powder and dried. The mixed material is baked in a non-oxidizing atmosphere and pulverized baked carbon content is used. Carbon nanotubes are used as a concept including carbon nanofibers and carbon nanohorns. The carbon powder-containing rubber composition includes an elastomer in addition to rubber. In addition to the composition before molding and curing, this composition includes that after molding and curing.

  The silk solution can be formed by adding a silk material to an aqueous calcium chloride solution, dissolving it by heating, and further hydrolyzing it by adding a proteolytic enzyme. The silk material is a general term for woven fabrics, knitted fabrics, powders, cotton, yarns, and the like made of rabbits or wild silkworms. These can be used alone or in combination.

Carbon nanotubes are added to the silk solution. Although the addition amount is not particularly limited, it can be added in the range of 1 to 30 wt% with respect to the silk solution.
In order to disperse the carbon nanotubes in the silk solution, it is preferable to apply ultrasonic waves to the silk solution.

A silk solution in which carbon nanotubes are dispersed is spread on a support film such as polypropylene and dried at room temperature or by heating. The dried mixed material is peeled off from the support film.
Alternatively, the silk solution may be spray-dried to form a granular mixed material.

The above mixed material is baked at a temperature of about 500 ° C. to 3000 ° C. in a non-oxidizing atmosphere, and then pulverized to form a baked carbon powder.
Firing and pulverization may be repeated a plurality of times to form a calcined carbon powder having a required particle size.
This calcined carbon powder has a structure in which carbon nanotubes are bound and uniformly mixed with a carbide of silk material as a binder, and is a calcined carbon powder excellent in thermal conductivity and conductivity.

The above baked carbon powder can be blended in a rubber material such as silicone rubber and NBR, molded and cured to obtain a rubber composition.
What is necessary is just to determine the compounding quantity to a rubber material in consideration of heat conductivity and electroconductivity. The greater the amount, the higher the thermal conductivity and conductivity. On the other hand, the greater the amount, the higher the hardness. The lower the hardness, the better the vibration damping properties. Therefore, the blending amount may be determined in consideration of the thermal conductivity, conductivity, and vibration damping properties.

Example 1:
1) Preparation of silk solution First, a silk solution was prepared.
In a 65 wt% aqueous solution of calcium chloride hydrate, 240 g of silk raw material was added, and heating and dissolution were performed for 6 hours while maintaining the solution temperature at 95 ° C. Proteolytic enzyme was added and hydrolyzed by treatment at 60 ° C. for 24 hours.
Next, the dissolved solution after the decomposition is filtered to remove undissolved materials, and the silk solution obtained by desalting the filtrate using the dialysis membrane of the molecular fraction 300 is further concentrated to 35 wt%. Of silk solution.

2) Mixing and drying silk solution and carbon nanotube (CNT) The silk solution prepared in 1) and VGCF-H (registered trademark, Showa Denko) were dispersed and dried by the following method.
Place 3085 g of silk solution in a stainless beaker. Thereafter, 100 g of VGCF-H is put into a resin lid, and is gradually added to the silk solution and dispersed with a glass rod. When 100 g is added, 100 g is weighed and dispersed again, and a total of 200 g is added. Thereafter, the mixture was dispersed with an ultrasonic cleaner for 5 minutes while stirring with a glass rod.
Next, about 20 g of the mixed solution was applied to the polypropylene sheet within a specified range (450 cm ² : 25 cm × 18 cm). Four polypropylene sheets were placed on one stainless steel shelf of the dryer, a total of 10 stainless steel shelves and a total of 40 polypropylene sheets were placed in the dryer and dried at 105 ° C. for about 1 hour.
The polypropylene sheet was taken out from the dryer, bent about 10 seconds later to peel off the film from the polypropylene sheet, and the film (mixed material) adhering to the polypropylene sheet due to static electricity was collected with a stainless spatula. Membranes were collected from a total of 40 polypropylene sheets.

3) Primary firing The mixed material prepared in 2) was fired by the following method.
Each stainless steel tray was loaded with 600g of membranes and carried by a cart that put about 4kg of membranes into the required number of trays, and the trays were lined up in a ratio of two on one graphite plate in the basket of the primary firing furnace.
It was fired by holding at 750 ° C. for 6 hours in a nitrogen atmosphere, and cooled to room temperature.

4) Grinding The mixed material fired in 3) was ground by the following method.
It grind | pulverized with the mortar until the mesh opening passed through the large sieve, and grind | pulverized for 1 day with the ball mill.
Subsequently, each 200 g was classified with a sieve having an opening of 45 μm and collected in a resin container.
The powder that did not pass was ground again with a ball mill for 24 hours, and the classification process was repeated with a sieve.

5) Secondary firing The mixed material powder pulverized in 4) was fired by the following method.
Firing was carried out while maintaining an argon atmosphere at 2400 ° C. for 3 hours, and cooled to room temperature.
6) Classification The mixed material powder fired in 5) was classified by the following method.
They were classified with sieves of 20 μm, 32 μm, 45 μm, and 63 μm, and collected in resin containers as 20 μm or less, 20 to 45 μm, 45 to 63 μm, and 32 μm or less, respectively.
This time, 20 μm or less product: 6.7 wt%, 20-45 μm product: 53.3 wt%, 45-63 μm product: 40 wt% were mixed.

Example 2:
The same as Example 1 except that VGCF-S was mixed instead of VGCF-H and the classification ratio was changed to 32 μm or less.

Example 3:
Example 1 is the same as Example 1 except that the primary firing temperature was changed to 450 ° C., VGCF-S was mixed instead of VGCF-H, and the classification ratio was changed to 32 μm or less.

Example 4:
Example 1 is the same as Example 1 except that the primary firing temperature was changed to 600 ° C., VGCF-S was mixed instead of VGCF-H, and the classification ratio was changed to 32 μm or less.

Comparative Example 1:
4) Same as Example 1 except that the pulverization process was changed after the secondary firing instead of the primary firing, VGCF-S was mixed instead of VGCF-H, and the classification ratio was changed to 32 μm or less. is there.

Example 5:
7) Mixing with silicone rubber The mixed material powder (calcined carbon powder: hereinafter referred to as CNT composite powder) classified in Example 1 was mixed with silicone rubber by the following method.
Thereafter, 50 wt% of CNT composite powder was dispersed with an open roll in a silicone rubber compound to which silica and a curing agent were added. The open roll is a simple two roll and the front and rear rotational speeds are different. Due to the difference in rotational speed, the rubber is sheared and the CNT composite powder is kneaded. The number of rotations was different depending on the roll, and the front roll was 12 rpm and the rear roll was 14 rpm. Further, the gap between the rolls varies depending on the amount of kneading, and is about 1 to 10 mm. Further, the kneading time is 20 to 40 minutes although this also varies depending on the kneading amount.

8) Molding and curing The material prepared in 7) was filled in a mold and heated and cured by a conventional method to prepare a rubber sample piece.

Example 6:
The same as Example 5 except that the classification ratio of the CNT composite powder was changed to only 32 μm or less.

Example 7:
The same as Example 5 except that the classification ratio of the CNT composite powder was changed to 32 μm or less and the addition amount of the CNT composite powder was changed to 45 wt%.

Example 8:
Example 5 is the same as Example 5 except that the classification ratio of the CNT composite powder was changed to 32 μm or less and VGCF-S was mixed instead of VGCF-H.

Example 9:
The same as Example 5 except that the classification ratio of the CNT composite powder was changed to 32 μm or less, VGCF-S was mixed instead of VGCF-H, and the addition amount of the CNT composite powder was changed to 45 wt%.

Example 10:
Example 5 is the same as Example 5 except that the classification ratio of the CNT composite powder is changed to 32 μm or less, VGCF-S is mixed instead of VGCF-H, and the addition amount of the CNT composite powder is changed to 40 wt%.

Comparative Example 2
It is an example of the silicone rubber compound when not mixing CNT composite powder.

Example 11:
Example 5 is the same as Example 5 except that the base material is changed from a silicone rubber compound to a raw silicone rubber containing no silica.

Example 12:
Example 5 is the same as Example 5 except that the base material is changed from a silicone rubber compound to a raw silicone rubber containing no silica and the amount of CNT composite powder is changed to 45 wt%.

Comparative Example 3:
It is an example of raw silicone rubber when not mixing CNT composite powder.

Example 13:
The base material is changed from silicone rubber compound to NBR, which is often used as a motor damper material, and the proportion of CNT composite powder classification is 20μm or less: 6.7wt%, 20-45μm: 46.7wt%, 46-63μm: 46.7wt%) Example 5 is the same as Example 5 except that the change is made.

Example 14:
The base material is changed from silicone rubber compound to NBR, which is often used as a motor damper material, and the classification ratio of CNT composite powder is 20μm or less: 6.7wt%, 20-45μm: 46.7wt%, 46-63μm: 46.7wt%) The same as Example 5 except that the amount of CNT composite powder added was changed to 40 wt%.

Comparative Example 4:
It is an example of NBR when not mixing CNT composite powder.

Measuring method:
1) Hardness Measured using JIS K 6253 type A durometer 2) Tensile strength Measured using JIS K 6251 No. 3 dumbbell 3) Elongation Measured using JIS K 6251 No. 3 dumbbell 4) Thermal conductivity Kyoto Electronics 5) Volume resistance value measured using the QTM-500 probe method manufactured by Kogyo Co., Ltd. Measured using Loletus GP (four-terminal four-probe method) and Hiresta IP (double ring method) manufactured by Mitsubishi Chemical Corporation 6) SEM + EDX S-3400NX manufactured by Hitachi High-Technologies Corporation

SEM photographs of Examples 2 to 4 and Comparative Example 1 are shown in FIGS. 1 to 4, and measurement results of Examples 5 to 14 and Comparative Examples 2 to 4 are shown in Table 1.
Table 1

1 to 4, it can be seen that the protrusions considered to be CNT protrude innumerably from the surface of the carbon material derived from silk as compared with the comparative example. Thereby, even when it mixes with silicone etc., the network of CNTs is easy to build, and as a result, heat conductivity and electroconductivity are favorable.
From Table 1, both the thermal conductivity and the electrical conductivity of the example are very good as compared with the comparative example.
Hardness is a guide for vibration control. The smaller the value, the softer the rubber-like elastic body. The hardness of the example is 25 to 81, which is a range that can be suitably used as a damper material for a motor. In the case where a large damping performance is required, a small numerical value may be selected from the embodiments. In addition, although the thing of a comparative example also has low hardness, this is only the hardness low because the total amount of a filler is small to which CNT composite powder is added. In the case of the examples, it is worth noting that the hardness is not so great despite the large amount of CNT composite powder added. In addition, the volume resistivity is about 4 to 13 orders of magnitude smaller than that of all the comparative examples, indicating that the conductivity is excellent. Thereby, it can use suitably also as a ground which suppresses the noise etc. which generate | occur | produce with a motor.

An embodiment when molded into a motor damper material is shown.
Example 15:
A composite material of CNT composite powder and silicone rubber was formed into a damper material (motor mount) by the following method.
Two metal plates of the same shape that are screwed to the casing (aluminum plate) and the motor, which will be described later, were press punched. The 2mm-thick iron plate was used for press punching. The punched metal plate has a lemon-like shape and has a hole with a diameter of 40 mm in the center for the motor shaft. The two metal plates were tilted 90 degrees so that the holes in the center matched and overlapped, and an interval of 2 mm was provided. A composite material of the CNT composite powder and silicone rubber prepared in Example 2 was poured into the mold and processed into a damper.

Measurement Method 6) Test with Motor Mount As a comparative example, damper materials (Comparative Examples 5 to 9) which were processed in the same manner as described above except that the rubber material was different were prepared.
First, the stepping motor was attached to the housing by screw fastening via the damper material (NBR Hs65) of Comparative Example 8, and the current conditions such as the motor surface temperature of 80 ° C. were set and held. Thereafter, the damper material of Example 15 and another comparative example was replaced with the setting, and it was confirmed how much the surface temperature of the motor decreased with respect to 80 ° C. (heat radiation temperature). The measurement was performed under the following conditions.
Motor: Oriental Motor 2-phase 56 angle motor (model: PH266-01B)
Case specifications: Aluminum 6mm thick, approx. 400mm x approx. 450mm
Atmosphere temperature: Room temperature

Comparative Example 5:
This is an example of an Hs45 damper made of silicone rubber for heat conduction to which 73 wt% of metal oxide filler currently mass-produced is added.

Comparative Example 6:
This is an example of Hs60 damper made of silicone rubber for heat conduction to which 77 wt% of metal oxide filler currently mass-produced is added.

Comparative Example 7:
This is an example of an NBR Hs45 damper to which a metal oxide filler currently mass-produced is not added.

Comparative Example 8:
This is an example of an NBR Hs65 damper to which no metal oxide filler currently mass-produced is added.

Comparative Example 9:
This is an example in which a motor is brought into direct contact with a casing without using a damper, and an example showing a heat dissipation limit.

The measurement results are shown in Table 2.
Table 2

In Table 2, the measured values indicate the degree of temperature drop when the temperature drop from 80 ° C. in Comparative Example 8 is zero.
In the case of Example 15, 13.8 ° C. was dissipated on average more than that of Comparative Example 8, and it was found that the damper material was superior to the heat-conductive silicone rubber damper currently mass-produced.
Thus, since it is excellent in heat conductivity and conductivity, it can be used for fixing and transfer rollers of copying machines and the like.

2 is a SEM photograph of the calcined carbon powder obtained in Example 1. 3 is a SEM photograph of the calcined carbon powder obtained in Example 2. 4 is a SEM photograph of the calcined carbon powder obtained in Example 3. 3 is a SEM photograph of the baked carbon powder obtained in Comparative Example 1.

Claims (5)

In the carbon powder-containing rubber composition in which carbon powder is added to the rubber material,
A carbon powder-containing rubber composition, wherein a carbon mixture is obtained by dispersing carbon nanotubes in a silk solution and drying the mixed material, calcined in a non-oxidizing atmosphere, and pulverized carbon.   2. The carbon powder-containing rubber composition according to claim 1, wherein the rubber material is silicone rubber.   2. The carbon powder-containing rubber composition according to claim 1, wherein the rubber material is NBR.   A motor damper material comprising the carbon powder-containing rubber composition according to any one of claims 1 to 3. A step of dispersing carbon nanotubes in a silk solution and firing the dried mixed material in a non-oxidizing atmosphere;
Crushing the calcined mixed material into a calcined carbon powder;
The manufacturing method of the carbon powder compounded rubber composition characterized by including the process of mix | blending the obtained baked carbon powder with a rubber material.