JP4716793B2 - Composite material - Google Patents

Description

  The present invention relates to a composite material excellent in both conductivity and slidability.

Conventionally, as a composite material having conductivity, a material made by adding a conductive filler such as carbon black, carbon fiber, or metal powder to a matrix made of plastic such as polyethylene or polypropylene is known. . However, in order to impart high conductivity (particularly, volume resistivity of 1 × 10 ⁶ Ω · cm or less) to this type of composite material, it is necessary to add a considerable amount of conductive filler. There is a drawback that it is not possible to obtain a composite material that adversely affects the original physical properties of the plastic and reflects the original physical properties of the plastic. Therefore, there has been a demand for a composite material that exhibits sufficiently high conductivity even when the blending amount of the conductive filler is reduced.

In order to deal with such problems, the following Patent Document 1 proposes a technique for dispersing fibrous carbon having a diameter of 1 μm or less in a thermoplastic resin, which suggests that even a small amount of conductive filler can provide sufficient conductivity. (For example, see Patent Document 1 [Claim 1], paragraph [0015], etc.). Further, Patent Document 1 mentions vapor-grown carbon fiber as an example of fibrous carbon having a diameter of 1 μm or less (see, for example, paragraph [0009] in Patent Document 1).
JP 2003-342474 A

However, even with the conductive material described in Patent Document 1, it is not always easy to ensure sufficient conductivity.
More specifically, for example, paragraph [0013] of Patent Document 1 discloses that the conductivity can be improved by kneading at a high shear rate, but the kneading is performed at a high shear rate. In the absence of an environment, such a kneading process could not be employed.

  Also, when using vapor-grown carbon fibers as the conductive filler, vapor-grown carbon fibers are relatively expensive to manufacture because it takes time to produce, and when such vapor-grown carbon fibers are blended in large quantities, Since the production cost of the resulting composite material also increases, there is a drawback that the price of the final product produced using this composite material increases.

  In addition, this type of composite material may be used to form parts with contacts and other sliding surfaces, but some plastics that have a matrix have a relatively high coefficient of dynamic friction and are slidable. Many of them are inferior to the above, and improvement in slidability as well as improvement in conductivity has been demanded.

  The present invention has been made in order to solve the above-described problems, and the object thereof is to exhibit sufficiently high conductivity even when the compounding ratio of vapor-grown carbon fibers is suppressed, and the surface of the molded product is slid. The object is to provide a composite material capable of improving the mobility.

The characteristic configuration employed in the present invention to achieve the above object will be described below.
The composite material of the present invention is a composite material obtained by dispersing a vapor-grown carbon fiber and a fluororesin powder in the matrix using a plastic as a matrix, and the vapor-grown carbon fiber has a diameter of 0.1 to 0.1. 0.5 [mu] m, an aspect ratio of 100 to 3,000, a bulk density of 0.02~0.15g / cc, wherein are contained 5-30 wt% in the composite material, the fluorine resin powder, average particle size Is 0.5 to 500 μm, is contained in the composite material in an amount of 5 to 50% by weight, and the volume resistivity of the composite material is 1 × 10 ⁻¹ to 1 × 10 ⁶ Ω · cm, To do.

  In the present invention, the plastic used as a matrix is not particularly limited. To name a few, polyethylene, polypropylene, polyamide, polystyrene, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, polyacetal, polyphenylene oxide, polyethersulfide Phon, polyether imide, polyether ether ketone, polymethyl methacrylate, polyacrylonitrile and the like can be used.

  The vapor-grown carbon fiber has a diameter of 0.1 to 0.5 μm, an aspect ratio of 100 to 3000, and a bulk density of 0.02 to 0.15 g / cc, and the content in the composite material is 5 to 30% by weight. As for the diameter, even if the diameter is less than 0.1 μm or more than 0.5 μm, the vapor-grown carbon fiber tends to be fooled, which causes poor dispersion. On the other hand, when the diameter is less than 0.1 μm, the density is likely to occur when the amount of the vapor growth carbon fiber is small. When the aspect ratio is less than 100, it tends to be difficult to form a sufficient conductive path, while when it is less than 3000, a dispersion failure tends to occur due to the entanglement between fibers. The bulk density is preferably 0.02 to 0.15 g / cc, and the content is less than 5% by weight, it tends to be difficult to form a sufficient conductive path, If it exceeds 30% by weight, the original physical properties of the plastic as a matrix are impaired, and for example, adverse effects such as increased brittleness are likely to occur.

Further, fluororesin powder, average particle diameter flat used as a 0.5 to 500, the content of a composite material is 5 to 50 wt%. Fluororesin powder weekend, the plastic comprising at least a matrix selected is different, preferably, a plastic, moldable plastic at lower temperatures than the melting point or softening point of the fluororesin for forming the fluororesin powder Thus, the fluororesin powder is selected in relation to the plastic . The average particle size, below the 0.5 [mu] m, there is a tendency that the effect of improving the conductivity decreases, whereas, if it exceeds the 500 [mu] m, smoothness of the molded article surface tends to be easily impaired. When the content is less than 5% by weight, the effect of improving the conductivity tends to be reduced. On the other hand, when the content exceeds 50% by weight, the original physical properties of the plastic as a matrix are impaired, for example, the brittleness is increased. It tends to cause harmful effects.

Furthermore, the volume resistivity of the composite material is 1 × 10 ⁻¹ to 1 × 10 ⁶ Ω · cm. It is desirable that the volume resistivity is lower, but it is not easy to make the volume resistivity less than 1 × 10 ⁻¹ Ω · cm while ensuring the original performance of the plastic as the matrix. In addition, when the volume resistivity is larger than 1 × 10 ⁶ Ω · cm, the performance unique to the present invention may not be sufficiently exhibited due to poor dispersion or other factors. By reviewing the conditions and others, the volume resistivity can be reduced to 1 × 10 ⁶ Ω · cm or less.

According to the composite material configured in this way, the fluororesin powder improves the conductivity of the composite material as compared with the case where only the vapor-grown carbon fiber is blended in the matrix. Even if the amount is suppressed, excellent conductivity of volume resistivity of 1 × 10 ⁻¹ to 1 × 10 ⁶ Ω · cm can be ensured. As compared only to plastic as a matrix, who formulated the vapor-grown carbon fibers is reduced dynamic friction coefficient of the molding surface, moreover, it compared only to plastic as a matrix, better blended with fluororesin Powder molding Since the dynamic friction coefficient of the product surface decreases, the slidability of the molded product surface can be made extremely high by blending both of them.

  Therefore, according to this composite material, although a relatively expensive vapor-grown carbon fiber is used as the conductive filler, the amount of the vapor-grown carbon fiber can be reduced by the amount that can be reduced. Manufacturing costs can be reduced, and final products manufactured using composite materials can be provided at low cost. Moreover, if the compounding ratio of the vapor-grown carbon fiber can be reduced, the original physical properties of the plastic that becomes the matrix are less likely to be impaired, so that a molded product utilizing the original physical properties of the plastic can be obtained. Furthermore, since the slidability of the surface of the molded product can be made extremely high, it is suitable as a material for forming parts having contacts and other sliding surfaces.

Incidentally, as described above, the plastic, the fluororesin powder is preferably a moldable plastic melting point or lower temperature conditions than the softening point of the fluororesin to form a, more specifically, the plastic The fluororesin powder is preferably a plastic that can be molded under a temperature condition that is 20 ° C. or more lower than the melting point or softening point of the fluororesin powder. Among these, the plastic is a fluororesin that forms the fluororesin powder. It is even more desirable that the plastic be moldable under temperature conditions that are 50 ° C. or more lower than the melting point or softening point.

According to the composite material configured as described above, when the composite material is molded by a method such as melting or softening the plastic that becomes the matrix, or polymerizing or crosslinking the precursor of the plastic that becomes the matrix, since the fluororesin powder can be carried out molding at lower temperatures than the melting point or softening point of the fluororesin for forming the, without thereby melting the fluororesin powder by heat during molding, more reliably fluororesin powder Can function.

  In addition, although the composite material of this invention demonstrated above can be used for various uses, if some examples are given, for example, a household appliance, a car, an EMC countermeasure member in a building related product, an antistatic member, a thermal countermeasure It is suitable for manufacturing a member or the like, and is particularly effective when used in the case of forming a composite member having a plurality of functions.

Next, embodiments of the present invention will be described with more specific examples.
[First Embodiment]
In the first embodiment, a composite material sample as described below was prepared.

  First, polypropylene (made by Idemitsu Kosan Co., Ltd., trade name: IDEMITSU PP, product number: J-3021GR, melting point: 125 ° C .; hereinafter abbreviated as PP) was used as the plastic to be the matrix. The vapor growth carbon fiber has a diameter of 0.1 to 0.5 μm, an aspect ratio of 100 to 3000, a bulk density of 0.02 to 0.15 g / cc (manufactured by Showa Denko KK, trade name: VGCF ( Registered trademark)). Further, as the resin powder, polytetrafluoroethylene powder (manufactured by Asahi Glass Co., Ltd., trade name: Fluon (registered trademark) PTFE, product number: L169J, melting point 332 ° C., average particle diameter 17 μm; hereinafter abbreviated as PTFE powder). used.

  Then, these materials were kneaded in a lab plast mill (manufactured by Toyo Seiki Seisakusho Co., Ltd., 4C150 type). The temperature condition at the time of kneading is set to 145 ° C., which is higher than the melting point of PP and lower than the melting point of PTFE powder, and the time when the torque of the motor for rotating the rudder is in an equilibrium state at 15 rpm As the end time, kneading was performed while adding PP, PTFE, and vapor grown carbon fiber in this order. The kneaded composite material was processed into a coarse powder and molded with a press at 190 ° C. and a pressure of about 0.4 MPa.

  In 1st Embodiment, as shown to Fig.1 (a), the compounding ratio of vapor growth carbon fiber is fixed to 10% by weight ratio, and the compounding ratio of PTFE powder is 10% by weight ratio (Example 1). , 30% (Example 2), and 50% (Example 3), and three types of samples were prepared using the remainder as a matrix. For comparison, a sample (Comparative Example 1) in which the PTFE powder is not blended, the blending ratio of the vapor-grown carbon fibers is 10% by weight, and the rest is a matrix, and the resin powder and the vapor-grown carbon fibers are mixed. A sample (Comparative Example 2) in which neither was blended was also prepared.

Next, the characteristics of each sample were evaluated by the following method.
The surface resistance and volume resistance of each sample were measured using a commercially available resistivity meter (trade name: “Loresta-GP” and trade name: “Hiresta UP”, both manufactured by Dia Instruments Co., Ltd.).

Further, the thermal conductivity of each sample was measured using a commercially available thermal conductivity meter (trade name: “Rapid thermal conductivity meter QTM-500”, manufactured by Kyoto Electronics Industry Co., Ltd.).
Furthermore, the average dynamic friction coefficient of each sample was determined by the ball-on-disk test method (test speed: 0.1 m / s, test load: 0.987 kg, test time: 3 hours, test distance: 1080 m (actual work 1200 m), mating material: SUS304).

  The measurement results are collectively shown in FIG. FIG. 2 shows a graph in which the blending ratio of PTFE powder is taken on the horizontal axis and the volume resistance is taken on the vertical axis. FIG. 3 is a graph in which the blending ratio of PTFE powder is taken on the horizontal axis and the thermal conductivity is taken on the vertical axis.

  From FIG. 2, it can be seen that the volume resistance is decreased by blending PTFE powder having no electrical conductivity even though the blending ratio of the vapor growth carbon fiber is constant. Moreover, it turns out that heat conductivity improves by mix | blending PTFE powder from FIG. Furthermore, it can be seen from the average dynamic friction coefficient shown in FIG. 1B that the dynamic friction coefficient is remarkably reduced by blending both the vapor-grown carbon fiber and the PTFE powder. From Comparative Examples 1 and 2, it can be seen that even when only vapor-grown carbon fibers are added, the dynamic friction coefficient is lower than that of the blank. From Examples 1 to 3, it is understood that the dynamic friction coefficient is further reduced by the addition of PTFE powder. . Further, comparing Examples 1 to 3, it can be seen that PTFE powder is extremely effective even when added in a small amount.

The composite material of the first embodiment described above is suitable as a material for manufacturing a member that is required to have conductivity in addition to the characteristics peculiar to PP because the matrix is made of PP.
In addition, the presence of PTFE powder can ensure sufficiently high conductivity even if the blending ratio of vapor grown carbon fiber is reduced, so that the amount of expensive vapor grown carbon fiber used can be suppressed, and the manufacturing cost of the composite material Reduction can be achieved. Moreover, if the compounding ratio of the vapor-grown carbon fiber is reduced, the compounding ratio of PP is increased correspondingly, and a composite material utilizing the physical properties of PP is obtained.

  Furthermore, since the melting point or softening point of PTFE powder is higher than PP, when molding a composite material under a temperature condition higher than the melting point or softening point of PP, a temperature condition lower than the melting point or softening point of PTFE powder is set. Thus, the PTFE powder can be prevented from melting and excessively melting with PP, and the PTFE powder can function effectively.

[Second Embodiment]
In the second embodiment, a sample was prepared by the same procedure as in the first embodiment. However, as shown in FIG. 4A, the blending ratio of PTFE powder was 10% by weight, and the vapor-grown carbon fiber was blended. The ratio was set to 30% by weight (Example 4), and samples each having the remainder as a matrix were prepared. The characteristics of the samples were evaluated in the same manner as in the first embodiment.

The measurement results are shown in FIG. In FIG. 4B, Example 1 and Comparative Example 2 shown in the first embodiment are also shown.
From the average dynamic friction coefficient shown in FIG. 4 (b), it can be seen that the dynamic friction coefficient decreases by blending both the vapor-grown carbon fiber and the PTFE powder. In the second embodiment, the surface roughness of the sample was rougher than that in the first embodiment, so that the dynamic friction coefficient fluctuates up and down. However, the fluctuation range of both the vapor-grown carbon fiber and the PTFE powder. It is narrowed by compounding, and it turns out that the fluctuation | variation of a dynamic friction coefficient can be suppressed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said specific one Embodiment, In addition, it can implement with a various form.
For example, in the above embodiment, polypropylene is exemplified as the plastic forming the matrix. However, the desired composite material can be obtained by using other plastics as the matrix. Specific examples include polyethylene, polyamide, polystyrene, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, polyacetal, polyphenylene oxide, polyether sulfone, polyether imide, polyether ether ketone, polymethyl methacrylate, poly Acrylonitrile and the like can be used.

The table | surface which shows the mixture ratio of each sample in 1st Embodiment, and the result of characteristic evaluation. The graph which shows the volume resistance of each sample in 1st Embodiment. The graph which shows the heat conductivity of each sample in 1st Embodiment. The table | surface which shows the mixture ratio of each sample in 2nd Embodiment, and the result of characteristic evaluation.

Claims (6)

It is a composite material obtained by dispersing a vapor-grown carbon fiber and a fluororesin powder in the matrix using plastic as a matrix,
The vapor grown carbon fiber has a diameter of 0.1 to 0.5 μm, an aspect ratio of 100 to 3000, a bulk density of 0.02 to 0.15 g / cc, and 5 to 30% by weight in the composite material. Has been
The fluororesin powder, in average particle diameter 0.5 to 500, are contained 5-50 wt% in said composite material,
The composite material has a volume resistivity of 1 × 10 ⁻¹ to 1 × 10 ⁶ Ω · cm. The composite material of claim 1, wherein the plastic, wherein the fluororesin powder is moldable plastic at lower temperatures than the melting point or softening point of the fluororesin to form a. Composite material according to claim 2, wherein the plastic, wherein the fluororesin powder is moldable plastic at low temperatures 20 ° C. or higher than the melting point or softening point of the fluororesin to form a. The composite material of claim 3, wherein the plastic, wherein the fluororesin powder is moldable plastic at low temperatures 50 ° C. or higher than the melting point or softening point of the fluororesin to form a. The composite material according to claim 4, wherein the fluororesin powder is a powder of polytetrafluoroethylene. Composite material according to any one of claims 1 to 5 wherein the plastic is characterized in that it is a polypropylene.

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