JP4563004B2 - Sliding parts made of polyacetal resin - Google Patents

Description

  The present invention relates to a sliding component comprising a polyacetal resin composition. More specifically, the present invention relates to a sliding component that retains the excellent mechanical properties, moldability, and the like inherent in polyacetal resin, and has further excellent sliding characteristics.

  Polyacetal resins have various physical properties balanced and have excellent sliding properties as resins, and are therefore widely used as sliding parts for automobiles, electrical / electronic products, office equipment, building materials and the like. However, as the application expands, the demand for sliding characteristics is also increasing, and further improvement of sliding characteristics and long-term sustainability are required.

  In order to meet such demands and improve slidability, there have been attempts to blend various lubricating oils with polyacetal resins. For example, a method of adding a fatty acid ester to a polyacetal resin (see, for example, Patent Document 1), a method of adding silicone oil and silicone gum to a polyacetal resin (see, for example, Patent Document 2), and a silicone having a viscosity of 150,000 cSt or more in a polyacetal resin Examples include a method of adding oil (see, for example, Patent Document 3), a method of adding silicone oil and an ester-based lubricant to a polyacetal resin (see, for example, Patent Document 4), and the like.

  However, since lubricating oils such as silicone oils are generally very poor in compatibility and affinity with polyacetal resins, it is extremely difficult to formulate them. Even if such a composition can be prepared, when it is molded, the oil easily oozes out on the resin surface, and the lubrication action causes slippage between the resins or between the resin and the screw. For this reason, poor biting into the molding machine, poor plasticization, and the like are caused, and in the case of remarkable, the processing becomes impossible. In addition, since the oil easily stains and sticks to the surface of the molded product, there is a disadvantage that the commercial value is lowered. Therefore, when lubricating oil is added for the purpose of improving sliding, it is ideally desired to reduce the amount of addition.

  In view of the above, for the purpose of improving the above-mentioned drawbacks, various studies have been made on adding a third substance as a retaining material together with the lubricating oil. For example, activated carbon, graphite or the like as an inorganic holding material, and high molecular weight polyethylene or the like as an organic polymer. However, activated carbon, graphite and the like have a small ability to adsorb and hold lubricating oil, and high molecular weight polyethylene and the like have poor affinity with the lubricating oil, so the holding power is also small and a practically satisfactory effect has been obtained. Absent. In some cases, the third component may deteriorate slidability.

On the other hand, various attempts have been made to blend a specific core-shell polymer with a polyacetal resin. A method of adding a core-shell polymer having a rubber-like polymer core and a glass-like polymer shell and a polyhydric alcohol fatty acid ester to a polyacetal resin (see, for example, Patent Document 5), a weather resistance (light) stabilizer and a rubber-like form to a polyacetal resin A method of adding a core-shell polymer having a glassy polymer shell made of a vinyl-based copolymer having a polymer core and an oxygen-containing polar group and an oxyalkylene polymer having 2 to 8 adjacent carbon chains (see, for example, Patent Document 6 ), A method of adding a core-shell polymer having a rubbery polymer core and a glassy polymer shell and a lubricant to a polyacetal resin (see, for example, Patent Document 7), and further, a rubbery polymer core and a glassy material to a high molecular weight polyacetal resin. Core-shell polymer and silicone with polymer shell A method of adding yl (for example, see Patent Document 8) and the like.
Japanese Patent Publication No.53-31900 Japanese Patent Publication No.57-10144 Japanese Examined Patent Publication No. 63-277263 Japanese Patent Publication No. 3-69378 Japanese Patent Laid-Open No. 6-100780 JP-A-6-299047 JP-A-6-1000075 JP 2000-265036 A

  However, these patent documents are written for the purpose of improving impact resistance, improving fluidity, or improving weather resistance, and are not written for the purpose of improving slidability. As described above, conventionally known methods cannot obtain a sliding part made of a polyacetal resin composition having good workability and excellent sliding characteristics in both the short term and the long term. Was anxious.

  As a result of intensive studies to meet such demands, the present inventors have formed a sliding component from a resin composition in which a lubricating oil and a specific core-shell polymer are blended with polyacetal resin, thereby forming the sliding component. The surface of the product is in a matte state, the contact area during sliding is reduced, and excellent sliding characteristics are found and the present invention has been achieved.

  That is, the present invention relates to (A) 100 parts by weight of polyacetal resin, (B) 0.05 to 20 parts by weight of lubricating oil having a liquid form at 200 ° C., and (C) a rubber-like polymer core and oxygen-containing polar group It is a sliding part which consists of a polyacetal resin composition which mix | blends 1-20 weight part of core-shell polymers which have the shell of the glassy polymer which consists of a vinyl-type copolymer which has.

Hereinafter, the present invention will be described in detail. First, the polyacetal resin (A) used in the present invention is a polymer compound having an oxymethylene group (—CH ₂ O—) as a main structural unit, and other structural units in addition to the polyacetal homopolymer and the oxymethylene group. It may be a polyacetal copolymer (including a block copolymer) or a terpolymer having a small amount, and the molecule may have a branched cross-linked structure as well as a linear shape. Further, two or more polyacetal resins having different characteristics can be blended and used.

  In the present invention, among the polyacetal resins, a polyacetal copolymer obtained by copolymerizing 1 to 30% by weight, particularly 1 to 5% by weight of a comonomer component is preferable, and thereby excellent thermal stability and moldability can be maintained. . Although it is known that various cyclic ether compounds or cyclic formal compounds can be used as the comonomer component used in the production of the polyacetal copolymer, it is not particularly limited, but preferred comonomer includes, for example, ethylene oxide, 1,3- Examples include dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, and propylene oxide.

  Next, the lubricating oil used as component (B) in the present invention has a liquid form at 200 ° C. That is, it can be in a liquid state or a state close to that at a temperature of about 190 to 220 ° C. used for forming a polyacetal.

  The lubricating oil used in the present invention is a lubricating oil based on one or more selected from the group consisting of silicone oil, polyalkylene glycol, α-olefin oligomer, paraffin oil, alkyl-substituted diphenyl ether, and fatty acid ester. An oil is preferable, and a silicone oil-based lubricant, a fatty acid ester-based lubricant, and an α-olefin oligomer-based lubricant are particularly preferable.

  Here, as the silicone-based oil, polydimethylsiloxane, polymethylphenylsiloxane and the like represented by the structure of the following formula (1) are preferably used as representatives.

(Where R is a methyl group, part of which may be an alkyl group, a phenyl group, a halogenated alkyl group, a halogenated phenyl group, etc.)
The viscosity of the silicone oil used in the present invention is not particularly limited, but when considering comprehensively the slidability and its sustainability, the dispersibility of the oil in the resin, the workability at the time of melt kneading and molding, The thing of 100-100,000 cSt (25 degreeC) is preferable. In the present invention, two or more types of silicone oils having different structures or different viscosities can be mixed and used, and viscosity can be adjusted by adding a thickener, solvent, etc. to the silicone oil. It is.

  The α-olefin oligomer is an aliphatic hydrocarbon mainly having a structure obtained by homopolymerizing a C6 to C20 α-olefin or copolymerizing ethylene and a C3 to C20 α-olefin. In the present invention, an ethylene / α-olefin oligomer having a number average molecular weight of 400 to 4000 is preferably used.

  The fatty acid ester is an ester of a monovalent or polyvalent aliphatic alcohol and a monovalent saturated or unsaturated fatty acid or dibasic acid, and practically preferred is a saturated aliphatic alcohol having 16 or more carbon atoms, An ester with a saturated fatty acid or polybasic acid having 16 or more carbon atoms. Examples of the saturated aliphatic alcohol having 16 or more carbon atoms include cetyl alcohol, stearyl alcohol, isostearyl alcohol, behenyl alcohol, erucyl alcohol, hexyldecyl alcohol, octyldodecyl alcohol and the like. Examples of the fatty acid having 16 or more carbon atoms include linear or branched fatty acids such as palmitic acid, stearic acid, isostearic acid, arachidic acid, behenic acid, and montanic acid. Any of these monovalent fatty acids and monovalent aliphatic alcohol esters can be preferably used. Examples of the dibasic acid that forms an ester by combining with an aliphatic alcohol having 16 or more carbon atoms include phthalic acid, adipic acid, sebacic acid, trimellitic acid, and the like. Such an ester composed of a dibasic acid and an aliphatic alcohol is preferably a full ester in order to maintain the thermal stability of the polyacetal. Of these aliphatic esters comprising carboxylic acid and alcohol, stearyl stearate, behenyl behenate, distearyl adipate, diester are particularly preferred from the viewpoints of cost, availability (synthesis, purification), and frictional wear characteristics. Stearyl phthalate and the like. In the present invention, one or more selected from these aliphatic esters are preferably used.

  In the present invention, the (B) lubricating oil is blended at a ratio of 0.05 to 20 parts by weight with respect to 100 parts by weight of the (A) polyacetal resin, and exhibits an effect of improving the friction and wear characteristics. When the blending amount is less than 0.05 parts by weight, the effect of reducing the friction coefficient is not sufficiently exhibited. When the blending amount exceeds 20 parts by weight, the moldability and the frictional characteristics are extremely deteriorated, which is not preferable. Particularly preferred is 0.5 to 5 parts by weight.

  Next, the core-shell polymer (C) used in the present invention has a glassy polymer shell made of a vinyl copolymer having a rubbery polymer core and an oxygen-containing polar group. Such a core-shell polymer (C) is generally obtained by a continuous multi-stage emulsion polymerization method in which a polymer in a previous stage is sequentially coated with a polymer in a subsequent stage, among seed emulsion polymerization processes.

  When the core-shell polymer has an intermediate phase as will be described later, the intermediate phase may be formed by a multi-stage emulsion polymerization method in which the polymer in the subsequent stage enters the polymer in the previous stage. During particle generation polymerization, it is preferable to start the emulsion polymerization reaction by adding a monomer, a surfactant, and water to the reactor, and then adding a polymerization initiator. The first stage polymerization is a reaction that forms a rubbery polymer.

  Examples of the monomer constituting the rubbery polymer that is the core of the core-shell polymer (C) used in the present invention include conjugated dienes, alkyl acrylates having 2 to 8 carbon atoms in the alkyl group, and mixtures thereof. These monomers are polymerized to form a rubbery polymer. Examples of such conjugated dienes include butadiene, isoprene, chloroprene and the like. Examples of the alkyl acrylate having 2 to 8 carbon atoms in the alkyl group include ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, and 2-ethylhexyl acrylate. In particular, butyl acrylate is preferably used as the rubbery polymer. For the first stage polymerization, monomers that can be copolymerized such as conjugated dienes and alkyl acrylates, for example, aromatic vinyl such as styrene, vinyltoluene, α-methylstyrene, vinyl cyanide such as aromatic vinylidene, acrylonitrile, methacrylonitrile, etc. Further, alkyl methacrylates such as vinylidene cyanide, methyl methacrylate, and butyl methacrylate can be copolymerized.

The shell phase is formed of a glassy polymer made of a vinyl copolymer having an oxygen-containing polar group. Examples of the oxygen-containing polar group include a hydroxyl group, a group having an ether bond (for example, glycidyl group), an amide group (—CONH—), a nitro group (NO ₂ ), etc., and particularly a group having a hydroxyl group and an ether bond. Is preferred. The core-shell polymer having no oxygen-containing polar group in the shell phase hardly shows a matting effect, and does not produce the effect of improving the sliding property of the sliding part made of the polyacetal resin composition which is the object of the present invention.

  As the monomer constituting the vinyl copolymer having an oxygen-containing polar group, for example, (meth) acrylate of an alcohol having two or more oxygen-containing polar groups in the molecule is used. Here, the alcohol having two or more oxygen-containing polar groups in the molecule means an alcohol having at least one oxygen-containing polar group other than the hydroxyl group of the alcohol moiety. As the (meth) acrylate of alcohol having an oxygen-containing polar group, for example, (meth) acrylate of alcohol having a hydroxyl group and / or a glycidyl group is used. Examples of the (meth) acrylate of an alcohol having a hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and the like. Preferably, hydroxyethyl (meth) acrylate is used. Examples of the (meth) acrylate of alcohol having a glycidyl group include glycidyl (meth) acrylate, and preferably glycidyl methacrylate is used. In addition to the above (meth) acrylates, for example, vinyl monomers having an oxygen-containing polar group such as allyloxyethanol and allyl glycidyl ether can also be used as a component of the vinyl copolymer having an oxygen-containing polar group. Examples of the monomer constituting the glassy polymer other than the monomer having an oxygen-containing polar group include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate, styrene, and vinyl. Specific examples include aromatic vinyl such as toluene and α-methylstyrene, vinyl cyanide such as aromatic vinylidene, acrylonitrile, and methacrylonitrile, and vinyl polymerizable monomers such as vinylidene cyanide. Particularly preferred are methyl methacrylate and styrene. Acrylonitrile and the like are used. The shell phase is preferably in the range of 10 to 50% by weight of the total core-shell polymer.

  There may also be an intermediate phase between the first stage and the final polymerization phase. For example, polymerization monomers having functional groups such as glycidyl methacrylate, methacrylic acid, hydroxyethyl methacrylate, polymerization monomers that form glassy polymers such as methyl methacrylate, polymerization monomers that form rubbery polymers such as butyl acrylate, etc. Is subjected to seed emulsion polymerization to form an intermediate phase. Such an intermediate phase can be variously selected depending on the properties of the desired core-shell polymer. The structure of the core-shell polymer having such an intermediate phase is, for example, a multi-layer structure in which another layer exists between the core and the shell, or the intermediate layer is finely granular in the core. The thing which has the structure of the distributed salami is mentioned.

  In the present invention, the (C) core-shell polymer is blended in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of the (A) polyacetal resin, making the surface of the molded article matt and effective in improving frictional wear characteristics. If it is less than 1 part by weight, the effect of reducing the friction coefficient is not sufficiently exhibited, and if it exceeds 20 parts by weight, the moldability and the frictional characteristics are extremely deteriorated, which is not preferable. Particularly preferred is 2 to 10 parts by weight.

  In the present invention, when forming a sliding part from the polyacetal resin composition having the above components, the polyacetal resin composition preferably has a glossiness of 50% or less, particularly Preferably, it has a glossiness of 30% or less, and this produces a particularly excellent sliding effect in the sliding component of the present invention. Such glossiness can be adjusted mainly by the use of the core-shell polymer selected as described above and in particular by its addition amount, and is adjusted in consideration of the blending of the lubricant (B) and optional components. In addition, the glossiness said here means what is measured by the measuring method mentioned later.

  The polyacetal resin used in the present invention may further contain various known additives. For example, various colorants, release agents, nucleating agents, antistatic agents, other surfactants, various polymers, and the like. In addition, if it is in a range that does not significantly reduce the performance of the molded article that is the object of the present invention, one kind of known fillers such as inorganic, organic, and metallic fibers, plates, powders, etc. Alternatively, two or more types can be combined and blended. Examples of such a filler include, but are not limited to, glass fiber, glass bead, talc, mica, wosterite, and carbon fiber.

  The method for preparing the composition of the present invention is not particularly limited, and it can be easily prepared by a known facility and method generally used as a conventional resin composition preparation method. For example, i) a method in which each component is mixed and then kneaded and extruded by an extruder to prepare pellets, and then molded, ii) pellets having different compositions are once prepared, and the pellets are mixed in a predetermined amount for molding. Any method can be used, such as a method of obtaining a molded product having a desired composition after molding, or a method of directly charging one or more of each component into a molding machine. Moreover, mixing a part of the resin component as a fine powder and adding it with other components is a preferable method for uniformly blending these components.

  The resin composition according to the present invention can be molded by any of extrusion molding, injection molding, compression molding, vacuum molding, blow molding, and foam molding.

  The sliding component of the present invention has a columnar or cylindrical shape like a roller, and has a configuration in which the central axis is supported in the horizontal direction and rotates, particularly the upper part of the circumferential surface thereof. A particularly noticeable effect occurs when the article moves as it slides. Therefore, it is particularly effective to use a plurality of such sliding parts and arrange them so that their central axes are parallel to each other as an article transfer device.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

In the examples and comparative examples, all “parts” indicate parts by weight. In the examples and comparative examples, the methods used for evaluating the surface gloss and the friction coefficient are as follows.
(1) Surface glossiness Digital variable angle glossmeter (UGV- Suga Test Instruments Co., Ltd.) based on JIS K7105 glossiness measurement using test pieces (70mm × 40mm × 3mm thickness) molded under the following conditions 40), the glossiness at 45 ° -45 ° reflection was measured.
Molding machine: Toshiba Corporation IS80
(Molding condition)
Nozzle C1 C2 C3
Cylinder temperature (℃); 200 200 180 160
Injection pressure: 65MPa
Injection speed: 1m / min
Mold temperature: 85 ℃
(2) Friction coefficient The test piece was used and evaluated according to ASTM D-1894. Further, Duracon M90-44 manufactured by Polyplastics Co., Ltd. was used as the counterpart material.
(3) Practical characteristics First of all, a roller molded product having the shape shown in FIG. Many pieces were molded.

  Next, prepare two polystyrene plates with many 0.20 cm diameter support holes on the side, and insert the support parts of the above-mentioned roller molded products into the support holes. A test article transfer device arranged in the state 2 was formed. In addition, the position of the support hole is adjusted so that the upper surface of the arranged roller molded product is above the upper surface of the polystyrene plate.

  As shown in FIG. 3, the transfer device was tilted at an angle of 3 °, and the time required for the PET bottle (245 ml: ITO EN Oi Ocha) to slide over a certain distance (30 cm) on the main body of the roller molded product was measured.

Abbreviations used in Examples and Comparative Examples are as follows.
Ethyl acrylate; EA
Methyl methacrylate; MMA
Butyl acrylate; BA
Butadiene; BD
2-ethylhexyl acrylate; EHA
2-hydroxyethyl methacrylate; HEMA
Examples 1-13, Comparative Examples 1-13
As shown in Table 1, (A) polyacetal resin (manufactured by Polyplastics Co., Ltd., Duracon M270), (B) various lubricants, (C) vinyl copolymer having a rubbery polymer core and oxygen-containing polar groups A core-shell polymer having a glassy polymer shell made of (Gantz Kasei Co., Ltd., PO-0935, core: BA / MMA copolymer, shell: HEMA / MMA) was mixed in the ratio shown in Table 1, and then twin-screw extrusion The mixture was melt kneaded with a machine to prepare a pellet-shaped composition. Next, test pieces were prepared by injection molding using the pellets and evaluated. The results are shown in Table 1.

  For comparison, as shown in Table 2, a composition not containing the component (C) core-shell polymer, and a glassy polymer made of a vinyl copolymer having no oxygen-containing polar group in the shell portion were used. Evaluations were similarly made on compositions containing a core-shell polymer (manufactured by Ganz Kasei Co., Ltd., PO-0198, core; BD / EHA / MMA terpolymer, shell; MMA / EA copolymer). The results are shown in Table 2.

B-1: Polydimethylsiloxane (60,000 cSt, manufactured by Toray Dow Corning Silicone, SH-200)
B-2: Polypropylene glycol (580cSt, Sanyo Chemical Industries, PP3000)
B-3: Poly (ethylene glycol / propylene glycol copolymer) (1700cSt, manufactured by Sanyo Chemical Industries, 50HB-5100)
B-4; α-olefin oligomer (900cSt, manufactured by Mitsui Petrochemical Co., Ltd., Lucant HC40)
B-5; α-olefin oligomer (28000cSt, manufactured by Mitsui Petrochemical Co., Ltd., Lucant HC600)
B-6: Paraffin oil (1000 cSt, manufactured by Idemitsu Co., Ltd., process oil)
B-7; alkyl-substituted diphenyl ether (200 cSt, manufactured by Matsumura Petrochemical Laboratory, Moresco High Loop)
B-8; Stearyl stearate
B-9; Distearyl adipate
C-1: Core shell polymer (manufactured by Ganz Kasei Co., Ltd., PO-0935, core: BA / MMA copolymer, shell: HEMA / MMA)
C-2: Core-shell polymer (manufactured by Ganz Kasei Co., Ltd., PO-0198, core: BD / EHA / MMA terpolymer, shell: MMA / EA copolymer)

It is a figure which shows the roller molded article used for the practical property test of the Example. It is a top view which shows the structure of the test article transfer apparatus which has arrange | positioned the roller molded article. It is a side schematic diagram which shows the condition of the practical property test using the test article transfer apparatus.

Claims (5)

(A) To 100 parts by weight of polyacetal resin, (B) 0.05 to 20 parts by weight of lubricating oil having a liquid form at 200 ° C., and (C) a rubbery polymer core and a hydroxyl group and / or glycidyl group It consists of a polyacetal resin composition having a glossiness of 30% or less formed by blending 1 to 20 parts by weight of a core-shell polymer having a glassy polymer shell made of a vinyl-based copolymer having an oxygen polar group. A sliding part that has a cylindrical shape and rotates with its central axis supported. The sliding component according to claim 1, wherein the lubricating oil (B) is one or more selected from the group consisting of a silicone oil-based lubricating oil, a fatty acid ester-based lubricating oil, and an α-olefin oligomer-based lubricating oil. . A vinyl copolymer having an oxygen-containing polar group constituting the shell of the core-shell polymer (C) is co-polymerized with (meth) acrylate of an alcohol having two or more oxygen-containing polar groups in the molecule as one of the monomer components. The sliding component according to claim 1 or 2, wherein the sliding component is formed by polymerization . The sliding component according to claim 3, wherein the (meth) acrylate of alcohol having two or more oxygen-containing polar groups in the molecule is hydroxyethyl methacrylate or glycidyl methacrylate . An article transfer device using a plurality of sliding parts according to any one of claims 1 to 4 and having a central axis parallel thereto.

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