JP2007186621A - Resin porous body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-strength resin porous body having a high open-cell ratio and holding a large amount of a lubricating oil, etc. <P>SOLUTION: The porous body made of a resin is obtained by molding the resin comprising a pore-forming material and, as necessary, short fibers compounded therein, providing a molded product and then extracting the pore-forming material with a solvent dissolving the pore-forming material without dissolving the resin and has open cells. The total volume of the open cells is in ≥10% ratio to the whole volume and the flexural strength is ≥50 MPa. Furthermore, the size of the pores forming the open cells is 0.001-1,000 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin porous body, and more particularly to a resin porous body having both a high porosity and high strength.

The resin porous body is manufactured by various methods, and there are the following three methods as typical manufacturing methods. “Foaming method” in which pores are formed by foaming, “sintering method” in which a powder is formed under a controlled heating / pressurizing condition and a gap between the powders is intentionally formed into a porous body, with a solvent This is an “extraction method” in which an extractable pore-forming material powder is blended and molded into a resin and extracted after molding to form a porous body.
The “foaming method” is a method that can produce a porous resin body with a high porosity, but it is mainly suitable for flexible materials such as rubber, and it is difficult to produce with a rigid resin with high strength. is there. In addition, a communicating porosity means the ratio for which the total volume of the mutually continuous pore in a resin porous body accounts to the volume of a resin porous body. In recent years, a method for forming a porous resin body using a supercritical fluid has been developed, and it has become possible to make a porous structure even with a fiber reinforced high-strength thermoplastic resin. Since only the material can be produced and the pores are not continuous, they cannot be used by impregnating with oil or the like.
The “sintering method” is suitable for a fluorine resin or a polyimide resin having a high melt viscosity, but a high communication porosity cannot be obtained. In addition, the strength is low due to insufficient bonding of the resin.
In the “extraction method”, a porous body having a high communication porosity can be produced relatively easily. Conventionally, a porous body with a high porosity is produced by the “extraction method”, which is solid at room temperature, but melts and forms a liquid state at the molding temperature of the polymer material forming the skeleton of the porous body. A porous material is molded using a pore-forming material that can be formed (see Patent Document 1), and a molding material obtained by dispersing a granular pore-forming material in a polymer substance is used as a part of the granular pore-forming material. Molding is performed at a melting temperature, and the molded body does not dissolve the polymer substance, but the pore-forming material forms a communicating hole by washing with a dissolving solvent (see Patent Document 2), particularly having open cells. There exists what manufactures a polyolefin porous body (refer to patent documents 3).

However, the porous resin body produced by the “extraction method” is often thin in consideration of the extractability of the pore-forming material, and the ink holding material for stamps using a polyolefin resin (see Patent Document 3) or polyurethane It is applied to synthetic leather using polyester or the like (see Patent Document 4, Patent Document 5, etc.). Alternatively, there is an example in which a thermoplastic elastomer is made porous and used as a cushioning material (see Patent Document 1, Patent Document 2, etc.). In these resin porous bodies, high communication porosity and flexibility are secured, but the strength of the resin porous body is low because the strength of the resin itself is low.
Further, sodium chloride, ammonium chloride, sodium sulfate, sodium nitrate, potassium sulfate, magnesium sulfate, calcium chloride and the like disclosed as pore forming materials in each patent document using the above extraction method are relatively easy to dissolve in water. However, since it is inexpensive and easily available, it is effective as a pore-forming material for use in the production of a porous body having a large pore diameter. However, when forming fine pores, it is difficult to completely dissolve and extract the pore-forming material. is there.
JP 2001-2825 A JP 2002-194131 A JP 2002-60534 A Japanese Laid-Open Patent Publication No. 2003-342341 JP 2003-342410 A

  The present invention has been made to cope with such problems, and an object of the present invention is to provide a porous resin body that has a high communication porosity, can hold a large amount of lubricating oil, and has high strength.

  The resin porous body of the present invention is a resin porous body having surface communication holes, the total volume of the communication holes being a ratio of 10% or more of the total volume of the resin porous body, and the bending strength. It is characterized by 50 MPa or more. In addition, the ratio of the total volume of the communication hole which occupies for the whole volume of said resin porous body is a communication hole ratio.

  The communication hole is formed by molding a resin containing at least a pore forming material into a molded body, and then dissolving the pore forming material and using the solvent that does not dissolve the resin from the molded body to the pore forming material. It is obtained by extracting.

The porous resin body is characterized by containing short fibers.
The pores forming the communicating holes are 0.001 μm to 1000 μm. In the present invention, the “pore size” means the pore diameter.
The pore-forming material is an alkaline compound.

Since the porous resin body of the present invention has a communication hole volume of 10% or more of the total volume and a bending strength of 50 MPa or more, it can be impregnated with a liquid such as a lubricating oil, and can slide on the sliding surface. On the other hand, the lubricating oil can be stably supplied and can be used as a machine part without requiring a reinforcing material such as a back metal.
Moreover, since the porous resin body of the present invention is blended with short fibers, it becomes a high strength resin member even with a high communication porosity.
In addition, since the porous resin body of the present invention has a pore size of 0.001 μm to 1000 μm to form the communication holes, the pore formation material is insufficiently extracted due to the pores being too small, or the oil impregnation when oil is impregnated. Insufficiency is unlikely to occur, and conversely, the ease of breakage due to too large pores can be avoided.
In addition, by using a resin material that can be injection-molded, injection molding becomes possible, and even precision parts can be manufactured at low cost.

  As a result of intensive studies on the provision of high-strength resin porous bodies with a high communication porosity and a large amount of lubricating oil, etc., as a result of using a water-soluble and alkaline pore forming material, A resin porous body can be made of resin by injection molding, etc., and it can be reinforced by blending short fibers as necessary, resulting in high strength. As a result, the communication porosity is 10% or more and It was found that a porous resin body having a bending strength of 50 MPa or more can be obtained. The present invention is based on such knowledge.

The resin used in the resin porous body of the present invention may be any resin that can make the bending strength of the resin porous body 50 MPa or more. Resin powder or pellets such as thermoplastic resin, thermosetting resin, elastomer or rubber Can be used. The particle size and shape of the resin powder and pellets are not particularly limited when melt molding because they are kneaded with the pore forming material at the time of melting. In the case of dry blending and compression molding as it is, it is preferably 1 μm to 500 μm.
Examples of the thermoplastic resin or thermosetting resin include polyethylene resins such as low density polyethylene, high density polyethylene, and ultrahigh molecular weight polyethylene, modified polyethylene resins, water-crosslinked polyolefin resins, polyamide resins, aromatic polyamide resins, polystyrene resins, Polypropylene resin, silicone resin, urethane resin, polytetrafluoroethylene resin, chlorotrifluoroethylene resin, tetrafluoroethylene / hexafluoropropylene copolymer resin, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin, vinylidene fluoride resin , Ethylene / tetrafluoroethylene copolymer resin, polyacetal resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene ether resin, Recarbonate resin, aliphatic polyketone resin, polyvinylpyrrolidone resin, polyoxazoline resin, polyphenylene sulfide (hereinafter referred to as PPS) resin, polyethersulfone resin, polyetherimide resin, polyamideimide resin, polyamide 9T resin, polyether Examples include ether ketone (hereinafter referred to as PEEK) resin, thermoplastic polyimide resin, thermosetting polyimide resin, epoxy resin, phenol resin, unsaturated polyester resin, and vinyl ester resin. Moreover, the mixture of 2 or more types of materials chosen from the said synthetic resin, ie, a polymer alloy, etc. can be illustrated.

Among the resins mentioned above, resins that can be used for industrial applications such as automobile parts, machine parts, electrical / electronic parts, etc. are preferable, and in particular, a tensile strength of 49 MPa or more, a flexural modulus of 1.9 GPa or more, and a heat resistance of 100 ° C. or more. Engineering resin with heat resistance (heat deformation temperature (18.6 kg / cm ² )), special engineering resin or super engineering resin that has higher heat resistance and can be used for a long time even at high temperatures of 150 ° C or higher, and mechanical properties such as sliding characteristics Resins that can be used in industrial applications are preferred because some of their properties or thermal properties are particularly excellent.
Specific examples of preferable resins that can be used in the present invention include PEEK resin, PPS resin, polyamideimide resin, thermoplastic polyimide resin, thermosetting polyimide resin, polyamide 9T resin, epoxy resin, polytetrafluoroethylene resin, tetrafluoroethylene. -Perfluoroalkyl vinyl ether copolymer resin, unsaturated polyester resin, and ultrahigh molecular weight polyethylene.

  Examples of the elastomer or rubber include acrylonitrile butadiene rubber, isoprene rubber, styrene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, butyl rubber, acrylic rubber, silicone rubber, fluorine rubber, ethylene propylene rubber, chlorosulfonated polyethylene rubber, chlorinated Examples thereof include vulcanized rubbers such as polyethylene rubber and epichlorohydrin rubber; and thermoplastic elastomers such as polyurethane elastomer, polyester elastomer, polyamide elastomer, polybutadiene elastomer, and soft nylon elastomer.

The resin used in the present invention is used by blending short fibers such as carbon fibers and glass fibers. The short fibers are used to improve the mechanical strength of the resin, and the blending ratio of the short fibers may be blended so that the bending strength becomes 50 MPa or more at the stage of the resin porous body described later.
If the bending strength of the porous resin body is less than 50 MPa, breakage is likely to occur due to insufficient bending strength, and cages for rolling bearings used under high load and high speed conditions, and slide bearings used under high load and high speed conditions. It cannot be used in applications requiring mechanical strength, such as filters and heat insulating materials that need to function as structural members.

In the present invention, the pore-forming material uses a substance having a melting point higher than the molding temperature of the resin in order to prevent melting of the pore-forming material at the time of molding, but is not limited to this. It is also possible to use a material having a higher melting point and a material having a lower melting point than the molding temperature of the resin.
As the pore-forming material, any substance that can be extracted from a molded body by using a solvent that does not dissolve the resin after being blended with a resin to form a molded body can be used.
The pore-forming material is preferably an inorganic salt compound, an organic salt compound, or a mixture thereof, and particularly preferably a water-soluble substance that facilitates the washing and extraction process. Further, an alkaline substance, preferably a weak alkali salt that can be used as a rust preventive agent can be used. Examples of the weak alkali salt include organic alkali metal salts, organic alkaline earth metal salts, inorganic alkali metal salts, inorganic alkaline earth metal salts, and the like. Even when the unextracted part falls off, an organic alkali metal salt or an organic alkaline earth metal salt is preferably used because it is relatively soft and hardly damages the sealing surface. These metal salts may be used alone or in combination of two or more. In addition, it is preferable to use a water-soluble weak alkali salt because inexpensive water can be used as a cleaning solvent, and waste liquid treatment at the time of pore formation is facilitated.

Water-soluble organic alkali metal salts that can be suitably used in the present invention include sodium benzoate (melting point 430 ° C.), sodium acetate (melting point 320 ° C.), sodium sebacate (melting point 340 ° C.), sodium succinate, stearic acid Sodium etc. are mentioned. Sodium benzoate, sodium acetate, or sodium sebacate is particularly preferred because of its high melting point, compatibility with various resins, and high water solubility.
Examples of the inorganic alkali metal salt include potassium sulfate, potassium carbonate, sodium carbonate, sodium silicate, sodium triphosphate, sodium metaphosphate, sodium pyrophosphate, sodium molybdate, potassium molybdate, and sodium tungstate. Among these, potassium sulfate, potassium carbonate, sodium carbonate, sodium silicate, sodium triphosphate, sodium pyrophosphate, sodium metaphosphate are used because of their high melting point, compatibility with various resins, and high water solubility. Particularly preferred.

  The composition ratio of the pore-forming material is such that the communicating porosity is 10% or more and the bending strength is 50 MPa or more at the resin porous body stage. Specifically, it is 10 vol% to 60 vol%, preferably 20 vol% to 50 vol%, based on the total amount including other materials such as resin powder, pore forming material, and short fibers.

The mixing method of the resin material and the pore forming material is not particularly limited, and a kneading method generally used for mixing the resin such as dry blending and melt kneading can be applied.
Alternatively, a method may be used in which the pore-forming material is dissolved in a liquid solvent to form a transparent solution, and then resin powder is dispersed and mixed in the solution, and then the solvent is removed. The pore-forming material is once dissolved in a liquid solvent and dispersed and mixed with the resin powder, so that the pores are uniformly distributed in the porous resin body after extraction of the pore-forming material, and the original pore-forming material A pore having a diameter smaller than the particle diameter can be formed.
The method of dispersing and mixing is not particularly limited as long as it can be mixed in a liquid, and examples thereof include a ball mill, an ultrasonic disperser, a homogenizer, a juicer mixer, and a Henschel mixer. It is also effective to add a small amount of a surfactant in order to suppress separation of the dispersion. At the time of mixing, the amount of solvent is secured so that the pore forming material is completely dissolved by mixing.
As a method for removing the solvent, methods such as heat evaporation, vacuum evaporation, bubbling with nitrogen gas, dialysis, and freeze-drying can be used. Since the method is easy and the equipment is inexpensive, it is preferable to remove the liquid solvent by heat evaporation.
For molding a mixture in which a pore molding material is blended with a resin, any molding method such as compression molding, injection molding, extrusion molding, blow molding, vacuum molding, transfer molding or the like can be employed. Moreover, in order to improve workability | operativity before shaping | molding, you may process into a pellet, a prepreg, etc.

Extraction of the pore-forming material from the obtained molded body is performed by washing the molded body with a solvent that dissolves the pore-forming material and does not dissolve the resin.
As the solvent, for example, water and alcohol solvents, ester solvents, ketone solvents, and the like can be used as solvents compatible with water. Among these, it is appropriately selected according to the above conditions depending on the type of resin and pore forming material. These solvents may be used alone or in combination of two or more. It is preferable to use water because of its advantages such as easy waste liquid treatment and low cost.
By performing the extraction treatment, a portion filled with the pore forming material is dissolved, and a porous resin body in which communication holes are formed in the dissolved portion is obtained.

  In the porous resin body of the present invention, it is preferable to control the size of the pores forming the communication holes to be 0.001 μm to 1000 μm. The size of the pores is basically adjusted by controlling the average particle diameter of the pore-forming material itself, and if minute communication holes are required, the pore size can be reduced by dispersion mixing as described above. Can do. If the pore size is less than 0.001 μm, the pore forming material will be insufficiently extracted, and oil impregnation will be likely to occur when oil is impregnated. If it exceeds 1000μm, the communication hole is likely to be damaged due to being too large.

The dumbbell test piece of each Example was obtained using the raw material of the Example shown below.
<Raw materials used in Examples>
PEEK resin powder: 150P made by Victrex
PPS resin powder: T4AG manufactured by Dainippon Ink
Sodium triphosphate powder: sodium tripolyphosphate manufactured by Taihei Chemical Industry Co., Ltd., average particle size 30μm
Potassium carbonate powder: Potassium carbonate manufactured by Nippon Soda Co., Ltd., average particle size 50μm
Carbon fiber: HTAC6S manufactured by Toho Tenax Co., Ltd.

Example 1
PEEK resin powder, carbon fiber, and sodium triphosphate powder are kneaded in a volume ratio of 50:10:40 with a twin screw extruder with a forced side feeder, pelletized with a pelletizer, and JIS K 7113 by injection molding. Molded into a No. 1 dumbbell test piece, immersed in hot water at 80 ° C. for 100 hours or more to extract the pore-forming material, and dried at 120 ° C. for 8 hours or more to obtain a resin porous dumbbell test piece. The bending strength was measured by the communication porosity and the bending test shown below. The results are shown in Table 1.
<Bending test>
Using a JIS K 7113 No. 1 dumbbell test piece, the bending strength was measured based on a JIS K 7171 bending test (three-point bending).

Example 2
PEEK resin powder, carbon fiber, and sodium triphosphate powder were kneaded by a twin screw extruder with a forced side feeder at a volume ratio of 50:15:35, and then treated in the same manner as in Example 1. The communication hole ratio and bending strength of the dumbbell specimen were measured. The results are shown in Table 1.

Example 3
PEEK resin powder, carbon fiber, and sodium triphosphate powder were kneaded by a twin-screw extruder with a forced side feeder at a volume ratio of 60:10:30, and then treated in the same manner as in Example 1. The communication hole ratio and bending strength of the dumbbell specimen were measured. The results are shown in Table 1.

Example 4
Communication of dumbbell specimens obtained by kneading PEEK resin powder and sodium triphosphate powder at a volume ratio of 70:30 in a twin-screw extruder with a forced side feeder and processing in the same manner as in Example 1 below. Porosity and bending strength were measured. The results are shown in Table 1.

Example 5
PPS resin powder, carbon fiber, and sodium triphosphate powder were kneaded by a twin screw extruder with a forced side feeder at a volume ratio of 50:15:35, and then treated in the same manner as in Example 1. The communication hole ratio and bending strength of the dumbbell specimen were measured. The results are shown in Table 1.

Comparative Example 1
A polyamideimide resin sintered body (MELDIN 9000 manufactured by Saint-Gobain Co., Ltd.) was cut to prepare a JIS K 7113 No. 1 dumbbell test piece, and the communication hole ratio and bending strength of the obtained dumbbell test piece were measured. The results are shown in Table 1.

上記、数１において、各符号の意味を以下に示す。
Ｖ；射出成形法にて成形された洗浄前成形体の体積
ρ；射出成形法にて成形された洗浄前成形体の密度
Ｗ；射出成形法にて成形された洗浄前成形体の重量
Ｖ₁；樹脂粉末の体積
ρ₁；樹脂粉末の密度
Ｗ₁；樹脂粉末の重量
Ｖ₂；気孔形成材の体積
ρ₂；気孔形成材の密度
Ｗ₂；気孔形成材の重量
Ｖ₃；洗浄後の多孔質体の体積
Ｗ₃；洗浄後の多孔質体の重量
Ｖ'₂；洗浄後に多孔質体に残存する気孔形成材の体積 In each example, the communication porosity is the ratio of the total volume of pores that are continuous with each other in the resin molded body to the total volume of the resin molded body. It was calculated by the method shown in (1).

In the above Equation 1, the meaning of each symbol is shown below.
V: Volume ρ of the molded body before cleaning molded by the injection molding method; density W of the molded body before cleaning molded by the injection molding method; Weight V _{1 of the} molded body before cleaning molded by the injection molding method Resin powder volume ρ ₁ ; resin powder density W ₁ ; resin powder weight V ₂ ; pore former volume ρ ₂ ; pore former density W ₂ ; pore former weight V ₃ ; Volume W ₃ of porous body; Weight V ′ ₂ of porous body after washing; Volume of pore forming material remaining in porous body after washing

  As shown in Table 1, in the example using the porous resin body of the present invention, a high strength of 70 MPa or more was obtained, but in Comparative Example 1, the bending strength was 10%, although the communicating porosity was over 10%. The strength was as low as 14 MPa.

  The resin porous body of the present invention is excellent in bending strength and can supply lubricating oil to the sliding surface from the communication hole, so it has a sliding interface such as a rolling bearing and a sliding bearing and requires mechanical strength. It can be suitably used for machine parts.

Claims (5)

  A porous resin body having surface communication holes, characterized in that the total volume of the communication holes is 10% or more of the total volume of the resin porous body, and the bending strength is 50 MPa or more. Resin porous body.   The communication hole is formed by molding a resin containing at least a pore-forming material into a molded body, and then dissolving the pore-forming material and using the solvent that does not dissolve the resin from the molded body to the pore-forming material. The porous resin body according to claim 1, which is obtained by extracting   The resin porous body according to claim 1 or 2, wherein the resin porous body contains short fibers.   4. The resin porous body according to claim 1, wherein the pores forming the communication holes have a size of 0.001 to 1000 [mu] m. The resin porous body according to any one of claims 1 to 4, wherein the pore forming material is an alkaline compound.