JP4155981B2 - Resin porous body and method for producing the same - Google Patents

Description

  The present invention relates to a resinous porous body and a method for producing the same.

A desalting method is known as a method for producing an inexpensive porous body that allows adjustment of the communication porosity. In the desalting method, a molding material obtained by adding a powdery pore forming material such as sodium chloride or sodium sulfate to a resin or rubber is molded as a solid molded body including the pore forming material, and the resulting solid molded body is washed with water. This is a method for producing a porous body, in which the pore-forming material is eluted by washing, etc., and pores are formed in the portion where the pore-forming material was present.
Conventionally, a porous body having a high communication porosity by a desalting method is solid at room temperature, but is melted and present in a liquid state at a molding temperature of a polymer material forming a 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 in which a granular pore-forming material is dispersed in a polymer substance is melted at a temperature at which a part of the particulate pore-forming material melts. Molding the molded body so as not to dissolve the polymer substance, but forming the pores by washing the pore-forming material with a solvent that dissolves (see Patent Document 2), especially producing a porous polyolefin body having open cells (See Patent Document 3).
Moreover, in order to facilitate the separation of the extract and the reuse of the extract, there is one that uses a pore-forming material made of a water-soluble powder and extracts it with warm water (see Patent Document 4).

Sodium chloride, ammonium chloride, sodium sulfate, sodium nitrate, potassium sulfate, magnesium sulfate, calcium chloride and the like disclosed as pore forming materials in each of the above patent documents are relatively easy to dissolve in water, and are inexpensive and easily available. It is effective as a pore-forming material used for producing 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. For this reason, when the pore forming material is impregnated with, for example, a lubricating oil, there may be a problem that the non-extracted pore molding material oozes out during use and rusts the metal portion.
JP 2001-2825 A (paragraph “0011”) JP 2002-194131 A (paragraph “0009”) JP 2002-60534 A (paragraph “0004”) JP 2002-322310 A (paragraphs “0007” and “0008”)

  The present invention has been made to cope with such problems, and is a resin porous body having a high communication porosity and capable of holding a large amount of lubricating oil, etc., and is used particularly in applications that come into contact with metal parts and the like. An object of the present invention is to provide a resinous porous body that does not rust the metal part even if the pore-forming material of the unextracted portion of the porous body oozes out during use, and a method for producing the same.

The resin porous body of the present invention is obtained by molding a resin containing a pore forming material composed of an alkaline compound into a molded body, and then using a solvent that dissolves the pore forming material and does not dissolve the resin. It is obtained by extracting the pore forming material from the molded body.
Further, the pore forming material has a melting point higher than the molding temperature of the resin. The pore-forming material is a water-soluble substance.

  The pore forming material is an alkaline compound. The alkaline compound is at least one metal salt selected from an organic alkali metal salt and an organic alkaline earth metal salt, and also sodium benzoate, sodium acetate, sodium sebacate, sodium triphosphate, pyrophosphate It is characterized by being sodium or potassium carbonate.

  The method for producing a resinous porous body of the present invention includes a step of blending a pore-forming material with a resin, a step of molding a resin containing the pore-forming material to form a molded body, dissolving the pore-forming material, and And a step of extracting the pore forming material from the molded body using a solvent that does not dissolve the resin.

  Since the resin porous body of the present invention has a high communication porosity, it can be suitably used for applications such as oil retaining bodies. In addition, as a pore-forming material used in the production of a resin porous body, not an acidic salt, but an alkaline salt, particularly an organic alkali metal salt that plays a role of a rust preventive agent, etc. In the case of using the resin porous body, even if the pore forming material remaining in the porous body oozes out, the steel can be prevented from being rusted, so that it can be used for a porous oil retaining body or the like.

The resin porous body of the present invention is obtained by molding a resin containing a pore-forming material, particularly an alkaline pore-forming material, into a molded body, and then dissolving the pore-forming material and a solvent that does not dissolve the resin. The pore-forming material is obtained by extracting the pore-forming material from the molded body using the organic alkali metal salt or the like, even if the pore-forming material is not completely dissolved and extracted. Since it acts as a rust preventive agent, it can be suitably used for bearings having steel around them.
Hereinafter, the resin, the pore forming material, the molding method, the extraction method, and the like constituting the resin porous body of the present invention will be described.

As the resin of the present invention, resin powder and 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, those of 1 to 500 μm are preferable.
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 resin, polyethersulfone resin, polyetherimide resin, polyamideimide resin, polyetheretherketone resin, thermoplastic polyimide resin, thermosetting Examples thereof include a functional polyimide resin, an epoxy resin, a phenol resin, an unsaturated polyester resin, and a 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 preferred resins that can be used in the present invention include polyetheretherketone resins, polyphenylene sulfide resins, polyamideimide resins, thermoplastic polyimide resins, thermosetting polyimide resins, polyamide 9T resins, epoxy resins, polytetrafluoroethylene. Examples include resins, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resins, unsaturated polyester resins, 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.

As the pore-forming material that can be used in the present invention, a resin containing the pore-forming material is molded into a molded body, and then the pore-forming material is dissolved and a solvent that does not dissolve the pore-forming material-containing resin is used. Any substance that can be extracted from the resin molding can be used.
In particular, as the pore forming material, a weak alkali salt that can be used as a rust inhibitor can be preferably 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 an 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 a rolling surface or a sliding surface. In addition, you may use these metal salts 1 type or in mixture of 2 or more types. 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.

In order to prevent dissolution of the pore-forming material during molding, it is preferable to use a substance having a melting point higher than the molding temperature of the resin used for the pore-forming material.
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.) or 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 sodium molybdate, potassium molybdate, sodium tungstate, sodium triphosphate, sodium pyrophosphate, potassium carbonate, and the like.

The pore-forming material can be used as a mixture of a substance having a melting point higher than the molding temperature of the resin and a substance having a melting point lower than the molding temperature of the resin.
Examples of the substance having a melting point lower than the molding temperature of the resin include pentaerythritol and boric acid (171 ° C.).

The pore forming material is controlled to have an average particle size according to the use of the resin porous body. When a resin porous body is used as an oil retaining body, a pore forming material having an average particle diameter of 1 to 500 μm is preferable.
The ratio of the pore forming material is 30% by volume to 90% by volume, preferably 40% by volume to 90% by volume, with respect to the total amount including other materials such as the resin powder, the porous body forming material, and the filler. If the volume is 30% by volume or less, the pores of the porous body are difficult to become continuous pores, and if it is 90% by volume or more, desired mechanical strength cannot be obtained.
Moreover, you may mix | blend the filler insoluble in the solvent used for extraction of a pore formation material at the time of a mixing | blending. For example, when the solvent is water, glass fiber, carbon fiber, or the like may be blended for the purpose of improving the mechanical strength of the porous body.

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 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 resin porous body having pores formed in the dissolved portion is obtained.

Example 1
An ultra-high molecular weight polyethylene powder (Miplon XM220 manufactured by Mitsui Chemicals, Inc.) having a volume ratio of 1: 1 and sodium benzoate powder (reagent manufactured by Wako Pure Chemical Industries, Ltd.) were mixed for 5 minutes with a mixer to obtain a mixed powder. . Using this mixed powder, a disk having a diameter of φ30 × thickness of t5 mm was formed by a heat compression molding method (200 ° C. × 30 minutes). The molded body was washed with warm water at 80 ° C. for 10 hours with an ultrasonic cleaner to elute the sodium benzoate powder. Thereafter, it was dried at 100 ° C. for 8 hours to obtain a porous body having a communication porosity of 43%. 7% by volume of sodium benzoate was not eluted and remained in the porous body.

Example 2
A volume ratio of 1: 1 ultra high molecular weight polyethylene powder (Mipperon XM220 manufactured by Mitsui Chemicals, Inc.) and sodium acetate powder (reagent manufactured by Wako Pure Chemical Industries, Ltd.) were mixed for 5 minutes with a mixer to obtain a mixed powder. Using this mixed powder, a disk having a diameter of φ30 × thickness of t5 mm was formed by a heat compression molding method (200 ° C. × 30 minutes). The molded body was washed with warm water at 80 ° C. for 10 hours with an ultrasonic cleaner to elute the sodium acetate powder. Thereafter, it was dried at 100 ° C. for 8 hours to obtain a porous body having a communication porosity of 44%. 6% by volume of sodium acetate was not eluted and remained in the porous body.

Example 3
A volume ratio of 1: 1 tetrafluoroethylene resin powder (M15 manufactured by Daikin Industries, Ltd.) and sodium benzoate powder (reagent manufactured by Wako Pure Chemical Industries, Ltd.) were mixed for 5 minutes with a mixer to obtain a mixed powder. . Using this mixed powder, a disk having a diameter of φ30 × thickness of t5 mm was formed by a heat compression molding method (350 ° C. × 30 minutes). The molded body was washed with warm water at 80 ° C. for 10 hours with an ultrasonic cleaner to elute the sodium benzoate powder. Thereafter, it was dried at 100 ° C. for 8 hours to obtain a porous body having a communication porosity of 48%. 2% by volume of sodium benzoate was not eluted and remained in the porous body.

Comparative Example 1
A volume ratio of 1: 1 ultra high molecular weight polyethylene powder (Miperon XM220 manufactured by Mitsui Chemicals, Inc.) and sodium chloride powder (reagent manufactured by Wako Pure Chemical Industries, Ltd.) were mixed for 5 minutes with a mixer to obtain a mixed powder. Using this mixed powder, a disk having a diameter of φ30 × thickness of t5 mm was formed by a heat compression molding method (200 ° C. × 30 minutes). The molded body was washed with warm water at 80 ° C. for 10 hours with an ultrasonic cleaner to elute the sodium chloride powder. Thereafter, it was dried at 100 ° C. for 8 hours to obtain a porous body having a communication porosity of 44%. 6% by volume of sodium chloride was not eluted and remained in the porous body.

Comparative Example 2
Ultra-high molecular weight polyethylene powder (Miplon XM220 manufactured by Mitsui Chemicals, Inc.) having a volume ratio of 1: 1 and pentaerythritol (melting point 260 ° C., alcohols) were mixed for 5 minutes with a mixer to obtain a mixed powder. Using this mixed powder, a disk having a diameter of φ30 × thickness of t5 mm was formed by a heat compression molding method (200 ° C. × 30 minutes). This molded article was washed with warm water at 80 ° C. for 10 hours with an ultrasonic cleaner to elute pentaerythritol. Thereafter, it was dried at 100 ° C. for 8 hours to obtain a porous body having a communication porosity of 41%. 9% by volume of pentaerythritol was not eluted and remained in the porous body.

上記、数１において、各符号の意味を以下に示す。
Ｖ；加熱圧縮成形法にて成形された洗浄前成形体の体積
ρ；加熱圧縮成形法にて成形された洗浄前成形体の密度
Ｗ；加熱圧縮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；洗浄後の多孔体の体積
Ｗ₃；洗浄後の多孔体の重量
Ｖ'₂；洗浄後に多孔体に残存する気孔形成材の体積 In addition, in each Example, a communicating porosity means the ratio for which the total volume of the pores which are mutually continuous in a resin molding accounts to the volume of a resin molding.
Specifically, the communication porosity was calculated by the method shown in Equation (1) in Equation 1.

In the above Equation 1, the meaning of each symbol is shown below.
V: Volume ρ of the pre-cleaning molded body formed by the heat compression molding method; density W of the pre-cleaning molded body molded by the heat compression molding method; Weight V ₁ ; Volume ρ _{1 of} resin powder; Density W _{1 of} resin powder; Weight V _{2 of} resin powder; Volume ρ _{2 of} pore forming material; Density W _{2 of} pore forming material; Weight V _{3 of} pore forming material; Washing The volume W ₃ of the porous body after; the weight V ′ ₂ of the porous body after cleaning; the volume of the pore forming material remaining in the porous body after cleaning

Rust test Discs produced in Examples and Comparative Examples are sandwiched between SPCC steel plates (40 × 40 × t2) with thinly applied synthetic lubricating oil PAO (Shin Fluid 801, manufactured by Nippon Steel Chemical Co., Ltd.) The rust test was conducted by the wet test method (49 ± 1 ° C., relative temperature 95% or more). The rusting conditions of the mating surfaces after 96 hours (h), 192 hours (h), and 384 hours (h) were compared. The results are shown in Table 1.

  As shown in Table 1, in Example 1 according to the present invention, no rust was observed after 384 hours. In contrast, in Comparative Example 1, rust was observed after 96 hours. This is probably because rusting was accelerated by the elution of a small amount of sodium chloride. Moreover, the Example had higher rust prevention property than the comparative example 2 without the acceleration factor of rusting. This is considered that the sodium benzoate used as a pore forming material is acting as a rust preventive agent.

  Since the resin-made porous body of the present invention is excellent in rust prevention, it can be suitably used as a material for rolling bearings, cages for sliding bearings, and the like in applications where there is steel around.

Claims (7)

A resin porous body having communication holes, wherein the communication holes are formed by molding a resin containing a pore forming material composed of an alkaline compound to form a molded body, and then dissolving the pore forming material, and A resin porous body, which is a communication hole obtained by extracting the pore-forming material from the molded body using a solvent that does not dissolve the resin.   The resin porous body according to claim 1, wherein the pore forming material is a substance having a melting point higher than a molding temperature of the resin.   The resin porous body according to claim 1 or 2, wherein the pore forming material is a water-soluble substance.   The resin porous body according to claim 1, wherein the communication porosity is 30% or more. The alkaline compound is a resin porous body of claim 1, wherein said is at least one metal salt selected from organic alkali metal salts and organic alkaline earth metal salt. The alkaline compound, sodium benzoate, sodium acetate, sodium sebacate, sodium triphosphate, resin of claim 1, wherein the at least one compound selected from sodium or potassium carbonate pyrophosphate Porous body. A step of blending a resin with a pore-forming material composed of an alkaline compound, a step of molding a resin containing the pore-forming material to form a molded body, and a solvent that dissolves the pore-forming material and does not dissolve the resin. And a step of extracting the pore-forming material from the molded body. A method for producing a resinous porous body, comprising: