JPH0225939B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a porous sintered body. Specifically, the present invention relates to a porous sintered body that combines a polyamide-imide resin and a fluororesin to provide properties that cannot be achieved alone. Sponges with a spongy structure have long been known as porous materials made of plastic. However, these have weak chemical resistance and low heat resistance. Additionally, they are generally soft and difficult to make with high mechanical strength. Plastic sintered bodies are known to compensate for these drawbacks, and porous materials made from polyethylene, polyamide resins, etc., have already been mass-produced and used for various purposes. However, conventional sintered plastic bodies have a heat resistance of around 100° C. at most, and their mechanical strength is also insufficient. Furthermore, in recent years, porous sintered bodies of polyimide resin have been proposed as having high heat resistance, but these have been insufficient in terms of mechanical strength. Therefore, at present, a sintered body having high heat resistance, high chemical resistance, and mechanical strength has not yet been developed. In view of these current circumstances, the inventors of the present invention have conducted intensive studies and found that a mixed powder of polyamide-imide resin and fluororesin can be heated and sintered at a temperature above the softening temperature and below the decomposition temperature of the polyamide-imide resin. The present inventors have discovered that the porous sintered body obtained in this manner has high heat resistance, high chemical resistance, and high mechanical strength, and that these properties can be sufficiently imparted with fluorine resin. That is, the gist of the present invention resides in a porous sintered body obtained by heating and sintering a mixture of a polyamide-imide resin and a fluororesin at a temperature above the softening temperature and below the decomposition temperature of the polyamide-imide resin. The present invention will be explained in more detail below. The polyamide-imide resin used in the present invention is a synthetic resin having imide and amide bonds in the repeating unit of the main chain. Such synthetic resins are commercially available under various names, and any of them can be used in the present invention. Preferably, the general formula (wherein Ar is a trivalent aromatic group containing at least one benzene ring, R is a divalent organic group such as an aromatic and/or aliphatic residue) is used. . One type of such resin is one obtained by the reaction of trimellitic acid and aromatic diamine.
This product is shown by the following chemical structural formula. Such polyamide-imide resins exhibit excellent thermal stability due to the combination of aromatic nuclei and imide bonds, and also exhibit excellent toughness due to flexibility, which is probably due to the amide bonds.
It also has excellent chemical resistance. It is known that such a polyamide-imide resin undergoes a polymerization reaction at the sintering temperature to increase its molecular weight. Therefore, during heating and sintering, unlike other thermoplastic resins, they are not simply fused together, but bonding occurs between different powder particles through a chemical reaction. Therefore, it is an extremely excellent raw material for producing sintered bodies, and even in systems filled with fluorine resin, sintered bodies with high mechanical strength can be made. The fluororesin used in the present invention may be commonly known ones, such as polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, hexafluoropropylene-tetrafluoroethylene, and polyvinyl fluoride. Orethylene copolymer, chlorotrifluoroethylene-vinylidene fluoride copolymer, etc. are used. The blending ratio of the fluororesin mainly depends on the friction coefficient required of the sintered body, and the higher the blending ratio of the fluororesin, the lower the friction coefficient of the sintered body can be obtained.
Usually, the fluororesin is blended in an amount of 0.005 to 50% by weight, preferably 5 to 35% by weight, based on the entire mixture with the polyamideimide resin. If the blending ratio is extremely lower than this, there is no point in mixing the fluororesin, while if it is extremely high, the strength of the molded product will decrease and become impractical. In the present invention, a sintered body is manufactured using a powder mixture obtained by mechanically mixing the above-mentioned polyamide-imide resin powder and fluororesin powder as a raw material. The resin powder is
Although various particle sizes can be used, those having a particle size of 100 mesh or less, which have been conventionally used industrially, are usually used. Sintering is performed by compressing the powder mixture into a predetermined shape and then heating it to a temperature above the softening temperature and below the decomposition temperature of the polyamide-imide resin. The time required for sintering varies depending on the heating temperature set, but industrially it is several minutes to several hours. Although the sintering atmosphere is arbitrary, sintering is usually performed in air. The porous sintered body thus obtained is extremely useful when used as various sliding parts by taking advantage of its porous nature and low coefficient of friction, and is also extremely useful as a filter that utilizes its porous nature. In addition, conventional polyamide-imide resin molding methods,
For example, in injection molding or extrusion molding, it has been impossible to fill the fluororesin in a high concentration due to the high melt viscosity of the resin, but with the present invention, it is possible to mix the fluororesin in any ratio. is possible. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not restricted to the following Examples unless the gist thereof is exceeded. Examples 1 to 3 Torlon is a type of polyamideimide resin synthesized from trimellitic anhydride and aromatic diamine (Torlon is a registered trademark of Amoco, Inc., USA)
powder (average particle size 5μ, length average diameter as determined by electron microscopy) and polytetrafluoroethylene powder Leburon L-2 (Luburon is manufactured by Daikin Industries, Ltd.)
Co., Ltd. (registered trademark, average particle size: 0.3μ, length average diameter as determined by electron microscopy) was mechanically mixed. The proportion of polytetrafluoroethylene powder in the mixture is 10%, 25% and 50% by weight. The powder mixture was heated to 3180 (Kg/cm ² ) in the air at room temperature.
It was compression molded under the pressure of The pressurization time is 5 minutes. The shape of this molded product is 20φmm, ^3t mm.
It is a disc. Next, this molded product is placed in the air.
It was heated and sintered at a temperature of 300°C for 2 hours. The above molded product was cut into strips with a width of 5 mm, a thickness of 3 mm, and a length of 20 mm, and a three-point support bending test was conducted at a span distance of 12 mm and a crosshead speed of 1 mm/min.
Bending strength (Kg/cm ² ) and bending elongation (%) were measured. The measurement temperature is 20°C. Furthermore, the filling rate of the porous sintered body was calculated by measuring the density. The results are shown in Table-1.

【table】

[Table] Example 4 and Comparative Example 1 A mixture of Torlon powder, which is a type of polyamideimide resin used in Examples 1 to 3, and polytetrafluoroethylene powder/Luburon L-2 (in the mixture of Luburon L-2) (proportion of 10 wt%) was compression molded at room temperature in the atmosphere at a pressure of 4000 (Kg/cm). The pressurization time was 3 minutes. The shape of this molded product is a disc with a diameter of 40mm and a diameter of 3tmm. Subsequently, this molded article was sintered by heating at a temperature of 300° C. for 2 hours in air. In order to check the friction and wear characteristics of the above molded products, we used a friction and wear tester (EFM) manufactured by Toyo Baldwin Co., Ltd.
--B), the wear rate (μ/min) and the coefficient of dynamic friction were measured, and the results are shown in Table 2. The test was conducted without lubrication, and the mating material was
This was done with SUS304. On the other hand, a sintered body was obtained in exactly the same manner as in Example 4, except that polytetrafluoroethylene powder and Lublon L-2 were not blended and only Torlon was used. It was measured. The results are shown in Table 2 as Comparative Example 1.

【table】

Claims (1)

[Claims] 1. A porous sintered body obtained by heating and sintering a mixture of a polyamide-imide resin and a fluororesin at a temperature that is above the softening temperature and below the decomposition temperature of the polyamide-imide resin. 2 Polyamideimide resin has the general formula (In the formula, Ar is a trivalent aromatic group containing at least one benzene ring, and R is a divalent organic group.) body. 3. Claim 1, wherein the blending ratio of the fluorine resin is 0.005 to 50% by weight based on the entire mixture.
Porous sintered body according to item 1 or 2. 4. The porous sintered body according to any one of claims 1 to 3, wherein the fluororesin is polytetrafluoroethylene.