JP2009242665A - Rubber/plastic composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber/plastics composition having excellent wear resistance and low friction properties without impairing the characteristics of rubber or plastics. <P>SOLUTION: The rubber/plastic composition comprises a compound having a carbon backbone with a fluorine atom or oxygen atom bonded to two or three kinds of atoms, which have a fluorine resin grafting a compound having a group with a high affinity with rubber or plastics. The fluorine resin is contained in the composition in an amount of 5-50 part by mass based on the amount of rubber or plastics. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber / plastic composition used for sliding members of automobiles, OA, industrial machines and the like, and more particularly, to a rubber / plastic composition excellent in durability and low wear.

  In automobiles, OA, industrial machines, etc., a large number of sliding parts are used to transmit energy of force, movement and work. Metals, ceramics, rubber, and plastics are used for these sliding parts. However, recent trends include downsizing of parts, weight reduction of components to reduce transmission energy and loss, lower friction, It is desired to improve durability. Against this background, polymer materials such as rubber and plastic have been applied to applications where metal has been used frequently.

  The prior art document information related to the invention of this application includes the following.

JP-A-9-118802 JP 7-173230 A JP-A-7-173446 JP-A-7-173447 JP-A-7-53823 JP-A-9-263676

  Rubbers and plastics are characterized by being lighter and easier to shape than metals, but mechanical toughness, durability and low wear are not always sufficient for applications.

  In order to compensate for these problems, filling with a reinforcing material such as a filler or carbon fiber, or compounding with a metal is performed. However, the method of mixing the filler and the reinforcing material causes problems such as a decrease in mechanical strength, an increase in the friction coefficient, and a significant cost increase due to an increase in processing steps, and the application is limited.

  Accordingly, an object of the present invention is to provide a rubber / plastic composition which is excellent in wear resistance and low friction without impairing the features of rubber / plastic.

  The present invention was devised to achieve the above object, and the invention of claim 1 is composed of two or three atoms in which a fluorine atom or an oxygen atom is bonded to a main chain composed of carbon atoms, This is a rubber / plastic composition in which 5 to 50 parts by mass of a fluororesin grafted with a compound having a functional group having a high affinity with rubber or plastic is mixed with rubber or plastic.

  The invention according to claim 2 is the rubber / plastic composition according to claim 1, wherein the functional group is an epoxy group, an amine group, a mercapto group, or a methacryl group.

  The invention according to claim 3 is the rubber / plastic composition according to claim 1 or 2, wherein the rubber or plastic has a functional group in the molecular structure.

  According to the invention of claim 4, ionizing radiation is irradiated in a dose range of 100 kGy to 1 MGy in a state where a fluororesin whose constituent elements are only carbon and fluorine is heated to near the melting point under an oxygen concentration of 1333 Pa or less. The rubber / plastic composition according to claims 1 to 3, wherein a modified fluororesin is used, and the compound having the functional group is grafted onto the modified fluororesin.

  According to the invention of claim 5, the modified fluororesin is irradiated with ionizing radiation in an oxygen-free atmosphere and then brought into contact with the compound having a functional group while being heated to a temperature of about 100 ° C. The rubber / plastic composition according to claim 4, wherein the compound having the functional group is grafted onto the rubber / plastic composition.

  The invention according to claim 6 is the rubber / plastic composition according to claim 4 or 5, wherein the fluororesin is polytetrafluoroethylene.

  According to the present invention, the sliding characteristics are excellent, and a significant decrease in mechanical strength typified by bending elastic modulus can be suppressed, which greatly contributes to expanding the application range of polymer materials.

  Hereinafter, preferred embodiments of the present invention will be described.

  The rubber / plastic composition according to the present embodiment is obtained by mixing 5 to 50 parts by mass of a fluororesin grafted with a compound having a functional group having high affinity with rubber or plastic with respect to the rubber or plastic.

  The reason why 5 to 50 parts by mass of a fluororesin grafted with a compound having a functional group is added to 100 parts by mass of rubber and plastic is that the effect on the sliding property cannot be expected if the value is less than the limit value. This is because exceeding the range causes a significant decrease in mechanical strength and elongation.

  Examples of the rubber / plastic include nitrile rubber, fluororubber, epoxy resin, nylon, polyether ether ketone, polyphenylene sulfide, polyimide, polyamideimide, phenol resin, polybutylene terephthalate, and the like.

  A fluororesin that is miscible with rubber and plastic is composed of two or three atoms in which a fluorine atom or oxygen atom is bonded to the main chain consisting of carbon atoms, and a compound having a functional group with high affinity for rubber and plastic. Specific examples of the grafted fluororesin and the base fluororesin include tetrafluoroethylene copolymer (PTFE), tetrafluoroethylene-fluoroalkoxytrifluoroethylene copolymer (PFA), and tetrafluoroethylene. -A hexafluoropropylene polymer (FEP) and a polytetrafluoroethylene-perfluorodioxysol copolymer (THF / PDD) are mentioned, and among them, PTFE is most preferable.

  PTFE includes those containing 0.2 mol% or less of polymerized units based on a copolymerizable monomer such as perfluoro (alkyl vinyl ether), hexafluoropropylene, (perfluoroalkyl) ethylene or chlorotrifluoroethylene. . Moreover, in the case of the said fluororesin, a small amount of 3rd components can also be included in the molecular structure.

  Examples of the compound having a functional group include silane coupling agents, titanate coupling agents, and reactive monomers. Representative functional groups include amine groups, epoxy groups, methacryl groups, and mercapto groups.

  Specifically, (aminoethyl) aminopropyltrimethoxysilane, (aminoethyl) aminopropylmethyldimethoxysilane, methacryloxypropyltrimethoxysilane, 3 glycidoxypropylmethyldiethoxysilane, 3 glycidoxypropyltriethoxysilane Typical examples include 3 methacryloxypropylmethyldimethoxysilane, 3 acryloxypropyltrimethoxysilane, 3 mercaptopropylmethyldimethoxysilane, 3mercaptopropyltrimethoxysilane, and the like.

  Preferable base materials for mixing the amine group graft-modified fluororesin include nitrile rubber, urethane rubber, polyamide resin, urethane resin, acrylic resin, phenol resin, and the like.

  Examples of a preferable base material into which the epoxy group graft-modified fluororesin is mixed include urethane rubber, nitrile rubber, epoxy resin, and acrylic resin.

  Examples of a preferable base material into which the methacrylic group-grafted modified fluororesin is mixed include polyester resin, acrylic resin, ABS resin and the like.

  Examples of a preferable base material into which the mercapto group graft-modified fluororesin is mixed include urethane rubber and polysulfide.

  In this embodiment, after modifying these fluororesins by the following method, it is necessary to graft a compound having a functional group.

  The modified fluororesin of this embodiment is a fluororesin in which a fluororesin composed of only carbon and fluorine is heated in an inert gas atmosphere having an oxygen concentration of 1333 Pa (10 torr) or less and at a temperature equal to or higher than its melting point. Can be produced by irradiating ionizing radiation within an irradiation dose range of 100 kGy to 1 MGy.

  In this embodiment, γ rays, electron beams, X rays, neutron rays, high energy ions, or the like are used as ionizing radiation.

  When performing irradiation with ionizing radiation, it is necessary to heat the fluororesin molded body to a temperature higher than its crystalline melting point. For example, when PTFE is used as the fluororesin, it is necessary to irradiate at a temperature higher than the melting point of 327 ° C., and when PFA or FEP is used, the former is 310 ° C. and the latter is 275 Irradiation is performed by heating to a temperature higher than the melting point specified in ° C. Heating the fluororesin beyond its melting point activates the molecular motion of the main chain constituting the fluororesin, and as a result, the intermolecular cross-linking reaction can be efficiently promoted. However, excessive heating leads to the cleavage and decomposition of the molecular main chain, so the heating temperature should be kept within a range of 10 ° C. to 30 ° C. higher than the melting point of the fluororesin.

  The compound having the functional group described above is grafted on the modified fluororesin. The reason for using the modified fluororesin as a base is that the abrasion resistance can be remarkably improved without significantly increasing the coefficient of friction by the modification. Furthermore, in the process of generating radicals in the fluororesin by irradiating ionizing radiation when grafting the functional groups, the polymer molecules are cut by the ionizing radiation and the mechanical strength is reduced. It is possible to suppress this decrease in mechanical strength.

  Grafting is performed by irradiating the modified fluororesin with ionizing radiation in an oxygen-free atmosphere and then contacting with a compound having a functional group while heating to a temperature of about 100 ° C. Among the above, the oxygen-free atmosphere is preferably an oxygen concentration of 133 Pa (1 torr) or less, and if it exceeds this, the grafting efficiency decreases. As a method for lowering the oxygen concentration to 133 Pa or less, it can be realized by making it in a vacuum state or in an inert gas atmosphere such as nitrogen, argon or helium.

  A compound having a functional group to be brought into contact with the modified fluororesin is not particularly defined, but the mixing amount is typically about 0.5 to 3 parts by mass with respect to 100 parts by mass of the modified fluororesin.

  Finally, 5 to 50 parts by mass of a modified fluororesin grafted with a compound having a functional group is mixed with 100 parts by mass of rubber / plastic.

  According to the rubber / plastic composition according to the present embodiment, by mixing a modified fluororesin having a functional group grafted on the rubber / plastic, it has excellent sliding characteristics without losing the characteristics of the rubber / plastic. A significant decrease in mechanical strength typified by bending elastic modulus can be suppressed, which can greatly contribute to expanding the application range of polymer materials.

  The same effect can be expected even when rubber or plastic has the above-mentioned functional group in the molecular structure. In addition to these, it is also possible to add organic fillers or inorganic fillers, processing aids, crosslinking agents, and the like.

  The present invention will be specifically described based on Examples and Comparative Examples.

  Table 1 shows examples of polyamide and comparative examples as typical examples.

(1) Compounding agent As a base polyamide, 66 nylon (Amilan CM3301L) manufactured by Toray DuPont Co., Ltd. was used. As the fluororesin, PTFE manufactured by Asahi Glass Co., Ltd., trade name P-192 was used. This PTFE was modified by irradiation with 100 kGy of an electron beam (acceleration voltage 1.5 MeV) under an oxygen concentration of 133 Pa (1 torr) and a temperature of 340 ° C. in a nitrogen atmosphere. This was finely pulverized to a mean particle size of 20 μm by a jet mill. The modified PTFE powder was further irradiated with an electron beam (acceleration voltage 1.5 MeV) at 10 kGy in nitrogen at room temperature.

  In graft-modified PTFE-A, 2 parts by mass of 3.10 parts by weight of this modified PTFE irradiated with 10 kGy in a nitrogen atmosphere. After spraying aminoprotrimethoxysilane, the modified PTFE was brought into contact with the powder surface, and then this modified PTFE was held in a heat treatment furnace in a nitrogen atmosphere maintained at 80 ° C. for 30 minutes, and then the graft was removed. Completed.

  Graft-modified PTFE-B was also prepared by the same method. 2 (Aminoethyl) 3 aminopropyltrimethoxysilane is used. Graft PTFE is obtained by using PTFE without using modified PTFE in the above-described method of graft modified PTFE-A. PTFE is unmodified with P-192.

(2) Preparation mixing, using a molding table 1 to 40 mm ² screw kneader holding material of 310 ° C. indicating (L / D = 30), were mixed at a rotation speed of 40 rpm, a cylindrical pellet of φ2mm while and then cooled did. Using a 45 mm screw injection molding machine with a nozzle temperature of 310 ° C., this was injected into a mold at an injection pressure of 100 MPa, and a disc-shaped sheet having a thickness of 1 mm and φ30 mm, a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. The plate-shaped sheet as Examples 1-6 and Comparative Examples 1-5 was produced.

(3) Evaluation Using these sheets, the sliding test was based on the ring-on method of JIS K7218, and the bending test was measured based on JIS K7171, and the specific wear amount, friction coefficient, and flexural modulus were obtained. . The measurement temperature is 24 ° C. in air. In the sliding test, a test piece (outer diameter 25.6 mm, inner diameter 20.6 mm, thickness 1 mm) is bonded to a cylindrical ring (outer diameter 25.6 mm, inner diameter 20.6 mm) made of SUS304, and a SUS304 plate is used as the mating material. (Length 30 mm, width 30 mm, thickness 5 mm, surface roughness Ra 0.2 μm) was used under the conditions of pressure 0.2 MPa, speed 60 m / min, and sliding time 50 hours. In the bending test, strain was applied at a speed of 10 mm / min to obtain a flexural modulus.

  As shown in Table 1, Examples 1 to 6 in which a polyamide and a fluororesin grafted with a compound having a functional group having high affinity are mixed are compared with Comparative Example 1 in which the polyamide is used alone. The amount of wear is reduced, wear resistance is improved, and the coefficient of friction is lowered. The flexural modulus also decreases slightly with the amount of graft-modified PTFE in comparison with the polyamide alone, but does not significantly decrease.

  On the other hand, Comparative Example 1 in which the graft-modified PTFE is not mixed has a large specific wear amount and a high friction coefficient. In Comparative Example 2 in which graft PTFE is blended instead of the modified PTFE, the specific wear amount is larger than that of the polyamide alone, and the flexural modulus is greatly reduced. This is presumably because the mechanical strength of the graft PTFE itself is significantly reduced.

  In Comparative Example 3 in which the modified PTFE was mixed, the specific wear amount and the friction coefficient were low and the mixing effect was recognized, but the decrease in the flexural modulus was large. Further, it can be seen that Comparative Example 4 in which PTFE is mixed does not show a large difference in specific wear amount from that of polyamide alone, and the decrease in flexural modulus is large.

  The graft ETFE of Comparative Example 5, which is a known example, is 2 parts by mass of ETFE (Asahi Glass Z8820) in an amount of 2 parts by mass with respect to ETFE under a nitrogen atmosphere irradiated with 10 kGy of electron beam in nitrogen. Aminoprotrimethoxysilane is brought into contact with the powder surface by spraying, brought into such a state, and then grafted by being held in a heat treatment furnace in a nitrogen atmosphere maintained at 80 ° C. for 30 minutes. However, since it does not contain graft PTFE, the specific wear amount is large and the wear resistance is poor.

Claims (6)

  A fluororesin composed of two or three atoms in which a fluorine atom or an oxygen atom is bonded to a main chain composed of carbon atoms and grafted with a compound having a functional group having high affinity with rubber or plastic is used as rubber or plastic. A rubber / plastic composition characterized by mixing 5 to 50 parts by mass.   The rubber / plastic composition according to claim 1, wherein the functional group is an epoxy group, an amine group, a mercapto group, or a methacryl group.   The rubber / plastic composition according to claim 1 or 2, wherein the rubber or plastic has the functional group in a molecular structure.   In a state in which a fluorine resin composed only of carbon and fluorine is heated to near the melting point under an oxygen concentration of 1333 Pa or less, ionizing radiation is irradiated in a dose range of 100 kGy to 1 MGy to obtain a modified fluorine resin. The rubber / plastic composition according to claim 1, wherein the compound having the functional group is grafted to a modified fluororesin.   A compound having the functional group in the modified fluororesin by irradiating the modified fluororesin with ionizing radiation in an oxygen-free atmosphere and then contacting with the compound having a functional group while heating to a temperature of about 100 ° C. The rubber / plastic composition according to claim 4, which has been grafted.   The rubber / plastic composition according to claim 4 or 5, wherein the fluororesin is polytetrafluoroethylene.