JPH0363578B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a porous sintered body containing a polyamideimide resin. Sponges with a spongy structure have long been known as porous materials made of plastic. However, these have poor chemical resistance and low heat resistance. Additionally, they are generally soft and difficult to make with high mechanical strength. Plastic sintered bodies are known as something that compensates for these drawbacks, and they have already been used in polyethylene,
Porous materials made from polyamide resins and the like are being 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 for use as engineering plastics. Further, in recent years, porous bodies of polyimide resin have been proposed as porous bodies with high heat resistance, but their mechanical strength is still insufficient in many cases. Therefore, at present, a sintered body that has high heat resistance, high chemical resistance, and high mechanical strength has not yet been developed. In view of these current circumstances, the inventors of the present invention have conducted intensive studies, and as a result, the present inventors have discovered a porous material obtained by heating and sintering fine powder of polyamide-imide resin at a temperature above the softening temperature and below the decomposition temperature of the resin. The inventors have discovered that quality sintered bodies have various properties such as excellent chemical resistance, high heat resistance, and high mechanical strength, and have thus arrived at the present invention. In other words, the gist of the present invention is that 98% or more of the particles have a particle size of 4 to 100 μm as measured by a Coulter counter, and D ₁ (length average particle size) calculated based on the particle size distribution of this part by the Coulter counter Decompose fine powder of polyamide-imide resin whose particle size and particle size distribution satisfy the following conditions: D ₁ ≦20μ, D ₄ /D ₁ ≦3 (diameter) and D ₄ (weight average particle diameter) above the softening temperature of the resin. It consists in a porous sintered body obtained by heating and sintering at a temperature below that temperature. The present invention will be explained in more detail below. The polyamideimide resin used in the present invention is well known and commercially available. This resin contains both amide bonds and imide bonds in the repeating units of the main chain. Of course, in addition to the repeating unit having an amide bond and an imide bond, a small amount of other repeating units such as a repeating unit having only an amide bond or a repeating unit having only an imide bond may be included. But more than 90 (wt%) of resin, especially 95 (wt%)
The above units are preferably occupied by repeating units containing both amide bonds and imide bonds. Preferably, the following formula (In the formula, Ar is a trivalent aromatic group containing at least one benzene ring, and R is a divalent aromatic group or aliphatic group.) A polyamide-imide resin having a repeating unit as a main structural unit is used. be done. For example, the product obtained by the reaction of trimellitic acid and an aromatic diamine such as 4,4'-diaminodiphenyl ether is shown by the following chemical structural formula. (In the formula, Ar' represents a divalent aromatic group containing at least one benzene ring, and n represents a number from 5 to 200.) Because such polyamide-imide resin has a combination of an aromatic nucleus and an imide bond, It exhibits excellent thermal stability and also exhibits excellent toughness due to flexibility, probably due to the amide bond,
It also has excellent chemical resistance. In the present invention, when heating and sintering the polyamide-imide resin, 98% or more of the particles have a particle size of 4 to 100μ as measured by a Coulter counter, and this portion is calculated based on the particle size distribution by the Coulter counter. ₁ (length average grain size) and D ₄
Fine particles with a particle size and particle size distribution that satisfy the following conditions (weight average particle size): D ₁ ≦20 μ, D ₄ /D ₁ ≦3 are used. Note that the method for obtaining fine particles is arbitrary, such as mechanical pulverization or a combination of pulverization and classification. When these fine particles are heated and sintered, a porous sintered body with significantly higher mechanical strength is obtained than when resin containing coarse particles or resin with a wide particle size distribution is sintered, and the pore size is also uniform. becomes minute. The resin used in the present invention preferably has a particle size (D ₁ ) of 15μ calculated from the particle size distribution in the 4 to 100μ portion.
These are as follows. Also, the part of 4 to 100μ
D ₄ /D ₁ is preferably 2.5 or less, particularly 2 or less. Various additives can be appropriately blended into this polyamide-imide resin as necessary. For example, a porous sintered body made by combining polyamide-imide resin with a solid lubricant such as molybdenum disulfide, graphite, or fluororesin has a low coefficient of friction and extremely wear resistance. Excellent. Of course, substances other than antifriction agents, such as calcium carbonate, can also be used as additives. It is known that polyamide-imide resin undergoes a polymerization reaction at the sintering temperature to increase its molecular weight. Therefore, during heating and sintering, the powder particles do not simply fuse together like other thermoplastic resins, 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 when additives are added, sintered bodies with high mechanical strength can be produced. These additives preferably do not contain coarse particles and have an average particle size smaller than the polyamideimide resin constituting the matrix. The blending ratio of the additive is 0.005 to 50% by weight based on the entire mixture with the polyamide-imide resin. The preferred range is 5-35% by weight. If the blending ratio is extremely lower than this, there is no point in mixing the inorganic material, and on the other hand, if the blending ratio is too high, the strength of the molded product will decrease. With conventional polyamide-imide resin molding methods (e.g. injection molding and extrusion molding), it has been impossible to incorporate additives at high concentrations due to the high melt viscosity of the resin, but this has been achieved with the present invention. It is possible. A preferred additive is a fluororesin. As the fluororesin, commonly known ones may be used, such as polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, hexafluoropropylene-tetrafluoroethylene copolymer, etc. 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. By blending the fluororesin, a porous sintered body having a low coefficient of friction useful as a sliding part can be obtained. In the present invention, a porous sintered body is obtained by heating and sintering a fine powder of polyamide-imide resin or a mixture of the fine powder and the above-mentioned additives at a temperature above the softening temperature and below the decomposition temperature of the resin. The heating sintering method is not particularly limited, and for example, a commonly used method such as a method of compressing fine powder as a raw material and then heating it in air for a certain period of time at a temperature above the softening temperature and below the decomposition temperature of the resin. is taken. The heating sintering temperature of polyamide-imide resin is 270
~400℃, and the heating sintering time is
It takes about 30 minutes to 3 hours. The resin filling rate (volume %) in the porous sintered body obtained by the present invention is about 90-50 volume %. If the resin filling rate (volume %) is extremely higher than this, the original meaning as a porous body is lost,
On the other hand, if it is too small, the strength will decrease and this will be a practical disadvantage. Such a porous sintered body is extremely useful when used as a filter or a sliding part after being impregnated with oil. 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 and Comparative Examples 1 to 3 Fine powder of Torlon (trademark, manufactured by Amoco, USA), which is a type of polyamideimide resin synthesized from trimethic acid anhydride and aromatic diamine, was heated in the air at room temperature. Due to the pressure of 4000Kg/ ^cm2 , the diameter is 40
mm, and compression molded into a disk with a thickness of 3 mm. The pressurization time was 3 minutes. This molded product was heated in air at a temperature of 290° C. for 1 hour to obtain a sintered body. A rectangular test piece with a width of 5 mm, a thickness of 3 mm, and a length of 20 mm was cut from this sintered body. For this specimen, between spans
12mm, a cross head speed of 1mm/mm, and a two-point support bending test (machine used: Toyo Baldwin Co., Ltd. Tensilon UTH-L) was performed using the conventional method to determine bending strength (Kg/cm ² ) and bending strain (%). )of
Measured at 20°C. In addition, the density of the test piece was measured to calculate the resin filling rate (volume %) of the test piece. The results are shown in Table 1.

[Table] Example 4 The fine powder of the polyamide-imide resin used in Example 1 was compression molded into a disk having a diameter of 20 mm and a thickness of 3 mm under a pressure of 3180 Kg/cm ² in the atmosphere at room temperature. The pressurization time is 5 minutes. This molded product was heated in air at a temperature of 300° C. for 2 hours to obtain a sintered body. A rectangular test piece with a width of 5 mm, a length of 2 mm, and a thickness of 3 mm was cut from this sintered body. The bending strength of this product is 2200Kg/cm ² , the bending strain is 19.0%, and the filling rate is
It was 89.3% by volume. Examples 5 to 11 Sintered bodies were manufactured under the same conditions as in Example 4 using the mixture of the fine polyamide-imide resin powder used in Example 1 and additives. The test results for this product are shown in Table 2.

[Table] Example 12 The mixture of the polyamideimide resin and fluororesin of Example 9 was compression molded into a disk having a diameter of 40 mm and a thickness of 3 mm at room temperature and in the atmosphere under a pressure of 4000 Kg/cm ² . The pressurization time was 3 minutes. This molded body was heated in air at 300° C. for 2 hours to obtain a sintered body. Friction made by Toyo Baldwin Co., Ltd.
The wear rate and dynamic friction coefficient of this sintered body were measured using an abrasion tester (EFM--B). The test was conducted without lubrication, and the mating material was SUS304. The results are shown in Table 3. Example 13 Using the polyamide-imide resin of Example 1, a sintered body was produced in exactly the same manner as in Example 12, and its wear rate and coefficient of dynamic friction were measured. The results are shown in Table 3.

【table】

Claims (1)

[Claims] 1. Particle size of 4 to 4 when measured with a Coulter counter.
100μ is 98% or more, and D ₁ (length average particle diameter) and D ₄ (weight average particle diameter) calculated based on the particle size distribution by Coulter counter of this part are D ₁ ≦20μ, D Porous sintered material obtained by heating and sintering fine powder of polyamideimide resin having a particle size and particle size distribution satisfying the following conditions: ₄ /D ₁ ≦3 at a temperature above the softening temperature and below the decomposition temperature of the resin. body.