JPH0745624B2 - Carbon fiber reinforced aromatic polyamide resin compression molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a carbon fiber reinforced aromatic polyamide resin compression molded product. More specifically, it relates to a carbon fiber reinforced aromatic polyamide resin compression molded product in which carbon fiber powder is blended and dispersed in a metaphenylene isophthalamide resin which is a condensation polymer of metaphenylenediamine and isophthalic acid.

(Prior Art) Conventionally, as a method for producing a metaphenylene isophthalamide resin molded article, as disclosed in JP-B-56-2092, JP-A-55-131024, JP-A-57-164, etc., an inert atmosphere is used. The sintering method in (normally nitrogen gas) is adopted.

This is because this resin has a high melting point (430 ° C.), and this melting point is close to the thermal decomposition temperature, and melting and thermal decomposition occur almost at the same time, so as in extrusion, injection, compression molding, etc., This is because it is extremely difficult to obtain a molded product that can be put to practical use by the melt molding method that involves melting the resin during molding.

Further, since this resin has hygroscopicity (saturated water content is 5.2% at a temperature of 21 ° C and relative humidity of 65%), the above-mentioned molding method involving melt flow is accompanied by the generation of gas due to thermal decomposition. As a result, the gasification of the water content greatly affects the occurrence of blisters, cracks, or cavities, and the molded products produced by the melt molding method have not been put on the market as commercial products.

(Problems to be Solved by the Invention) Generally, a resin molded product obtained by a sintering method (which should be called a “sintered product, but here it is referred to as a molded product”) is compared with a molded product obtained by a melt molding method. It has been pointed out that the mechanical strength becomes low.

The mechanical strength of the molded product obtained by the sintering method is significantly affected by the magnitude of the pressure applied when obtaining the preformed product (compacted powder).

That is, if the applied pressure is small, the compression ratio is inevitably small, and the porosity of the preform increases, so that the mechanical strength of the product obtained by sintering the preform becomes small.

Therefore, in order to bring the one obtained by the sintering method close to the mechanical strength of the molded article obtained by the melt molding method, the pressing force must be remarkably increased during the preforming.

In the case of metaphenylene isophthalamide resin, this pressure is 2,000 kg / cm ² or more, preferably 3,000 to 7,000 kg / cm.
² also needs high pressure.

In addition to such a problem, there is a problem that not only a sintering furnace capable of adjusting an atmosphere such as nitrogen gas is required at the time of sintering, but also a sintering time of 10 or more hours is required.

The present inventors have established a compression molding method for a metaphenylene isophthalamide resin as a solution to such a problem (Japanese Patent Application No. 59-59779) and succeeded in obtaining a satisfactory molded product. However, when the molded product is intended to be used for high-strength and wear-resistant applications in which it can be replaced with, for example, a metal material, further improvement in mechanical strength is desired.

(Means for Solving Problems) The present inventors have found that the problems can be solved by dispersing carbon fiber powder having a predetermined aspect ratio in this metaphenylene isophthalamide resin.

The carbon fiber has an aspect ratio of 9 to 40 and a length of 3 mm or less, particularly a powder of 0.2 to 0.7 mm is preferable, and the compounding amount is 10 to
40% by weight, preferably 15 to 30% by weight.

Taking the bending strength of the obtained molded product as an example, the strength increases in a quadratic curve with the blending amount of carbon fiber powder.
The maximum is 20% by weight and the strength tends to decrease at higher levels. Taking impact strength as an example, the strength increases exponentially with the blending amount of carbon fiber powder, but if it exceeds 40% by weight, the formability is impaired and the strength tends to vary.

If the blending amount of carbon fiber powder is less than 10% by weight, the strength improving effect is not remarkable.

From the above experimental results, it was found that the amount of the above carbon fiber powder is preferable.

The carbon fiber powder shows a fairly good dispersibility in the metaphenylene isophthalamide resin powder, but when an external force such as vibration is applied to this mixed powder, the uniformity is often impaired, and the carbon fiber powder is separated. Was observed to cause

Further, as compared with the additive-free resin powder, the one in which the carbon fiber powder is mixed is apt to cause galling of the mold by the fiber powder.

According to the experiments conducted by the present inventors, such a disadvantage is caused by the tetrafluoroethylene resin powder as the third component, particularly preferably the tetrafluoroethylene resin powder which is easily fibrillated by rubbing the powder (for example, Mitsui). It was found that it can be improved by adding Teflon 7AJ [trade name] manufactured by Fluorochemicals. The amount of the tetrafluoroethylene resin powder added is 0.5 to 5% by weight, preferably 1 to 3% by weight.

If it is added in an amount of more than 5% by weight, the effect of improving the strength obtained by blending the carbon fiber powder is impaired, which is not preferable, and if it is added in an amount of less than 0.5% by weight, the effect is not sufficiently exhibited.

It was found that the tetrafluoroethylene resin powder, which is prone to fibrillation, is entangled with and dispersed in the carbon fiber powder due to the progress of fibrillation during stirring and mixing of the component powders. Therefore, even if an external force such as vibration is applied to the obtained mixed powder, the carbon fiber powder is not easily separated from the metaphenylene isophthalamide resin powder.

Further, since the tetrafluoroethylene resin has a low coefficient of friction and has a lubricating action, it not only prevents galling of the mold due to blending of carbon fiber powder, but also helps reduce friction of the molded product.

In order to obtain the molded product of the present invention, a molding method according to Japanese Patent Application No. 59-59779 already made by the present inventors is adopted.

That is, a metaphenylene isophthalamide resin powder having a bulk density of 0.2 to 0.4 g / cm ³ was prepared, and 10 to 40% by weight of carbon fiber powder having an aspect ratio of 9 to 40 and a length of 3 mm or less was prepared.
0.5 to 5 in addition to the carbon fiber powder
A weight% of tetrafluoroethylene resin powder is also mixed and mixed with stirring to obtain a mixed powder.

Using a mold, hold the mixed powder at a temperature of 290 ° C or higher and not higher than 360 ° C for 1 to 5 minutes per 1 mm of wall thickness of the molded product with a molding pressure of at least 70 kg / cm ² and then change the mold temperature. After cooling to a temperature of 250 ° C or less, the molded product is taken out of the mold.

Compared to the additive-free metaphenylene isophthalamide resin molded product, the molded product of the present invention has improved thermal conductivity of the carbon fiber powder blended therein, so that the moldability is improved and the molding retention time is also the above-mentioned predetermined value. It was found that the lower limit of the holding time was sufficient.

Incidentally, an attempt was made to obtain a molded product by a sintering method using a metaphenylene isophthalamide resin powder mixed with carbon fiber powder, but a satisfactory molded product was not obtained. It is considered that this is because, in the sintering method, the carbon fiber powder present at the resin powder interface hinders the progress of sintering, so that only a brittle molded product was obtained.

(Example) Hereinafter, an example will be described.

[Examples 1 to 5] As the metaphenylene isophthalamide resin powder, prepared is Teijin's Conex (trade name) powder having an average particle size of 150 mesh. The carbon fiber powder has an aspect ratio of 40 and a fiber length of 0.7 mm. Kureha Chemical Co., Ltd. Kureha Carbon Fiber M-107T (trade name), 10% by weight
(Example 1), 15% (Example 2), 20% (Example 3),
30% (Example 4) and 40% (Example 5) were added and mixed with stirring. This was heated and dried at an ambient temperature of 140 ° C. for 30 minutes to reduce the water content in the resin powder to 1% by weight or less.

Then, the mixed powder of these is molded at a molding temperature of 320
After holding for 10 to 15 minutes at 350 ° C. and a molding pressure of 350 kg / cm ² , the mold temperature was cooled to 250 ° C. or lower, and the mold was taken out.

[Examples 6 to 8] As a metaphenylene isophthalamide resin powder, prepared is a Conex (trade name) powder manufactured by Teijin Ltd. having an average particle size of 150 mesh, which has a carbon fiber powder having an aspect ratio of 40 and a fiber length of 0.7 mm. Kureha Chemical Co., Ltd. Kureha Carbon Fiber M-107T (trade name) 15% by weight and tetrafluoroethylene resin powder as Mitsui Fluorochemical Co. Teflon 7AJ
(Product name) is 1% in weight ratio (Example 6), 2%
(Example 7) 3% (Example 8) was added and mixed with stirring.
This was heated and dried at an ambient temperature of 140 ° C. for 30 minutes to reduce the water content in the resin powder to 1% by weight or less.

Hereinafter, molding was carried out under the same conditions as in the above-mentioned example to obtain a molded product.

Among the molded products thus obtained, the physical property values of Example 2 and Example 7 are shown in the table. The comparative examples in the table show additive-free metaphenylene isophthalamide resin moldings containing neither carbon fiber powder nor ethylene tetrafluoride resin powder.

FIG. 1 is a graph showing the relationship between the blending amount of carbon fiber powder and bending strength, the solid line containing only carbon fiber powder,
The broken line shows the one in which 2% by weight of tetrafluoroethylene resin powder was blended in addition to the carbon fiber powder.

Similarly, FIG. 2 is a graph showing the relationship between the carbon fiber powder blending amount and the impact strength, where the solid line is the blending of carbon fiber powder only, and the broken line is the carbon fiber powder plus 2 parts by weight of tetrafluoroethylene resin powder. % Is shown.

(Effects of the Invention) As described above, the molded product containing the carbon fiber powder according to the present invention has improved mechanical strength, and the carbon fiber has good thermal conductivity. At this time, the temperature distribution of the object to be molded tends to be uniform, so that the moldability is improved.

Since carbon fibers also have good electric conductivity, as can be understood from the indicated volume resistivity value, the molded product has less static electricity and has an antistatic effect.

When the tetrafluoroethylene resin powder is added in addition to the carbon fiber powder, the homogeneity is improved by preventing the separation of the carbon fiber powder with almost no loss of the above-mentioned performance improvements.
Moreover, since the galling of the mold during molding is significantly reduced, a molded product having a beautiful molding surface can be obtained.

The tetrafluoroethylene resin also imparts a low wear coefficient to the molded product and contributes to the improvement of wear resistance particularly in sliding material applications.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the compounding amount of carbon fiber powder and bending strength in the molded article of the present invention, and FIG. 2 is a graph showing the relationship between the compounding amount of carbon fiber powder and impact strength.

Claims (2)

[Claims] 1. A metaphenylene isophthalamide resin 60 to
A carbon fiber reinforced aromatic polyamide resin compression molded product comprising 90% by weight, 10 to 40% by weight of carbon fiber powder having an aspect ratio of 9 to 40 and a length of 3 mm or less. 2. A carbon fiber powder having a metaphenylene isophthalamide resin and an aspect ratio of 9 to 40 and a length of 3 mm or less.
~ 40 wt%, tetrafluoride ethylene resin powder 0.5 ~ 5 wt%
A carbon fiber reinforced aromatic polyamide resin compression molded product obtained by uniformly mixing