Polyacetal resin composition

Abstract

Provided is a polyacetal resin composition that can reduce wear of a metal component even if the metal component comes into contact with a component (molded article) made of said polyacetal resin composition when the component made of the polyacetal resin composition slides, and that has preferable mechanical strength.　A polyacetal resin composition according to the present invention contains (A) 70-95 mass% of a polyacetal resin, (B) not less than 4 mass% to less than 25 mass% of a glass-based filler, and (C) 1-10 mass% of a glycidyl group-containing copolymer including an olefin and a glycidyl (meth)acrylate as copolymerization components.

Description

Polyacetal resin composition

[0001] The present invention relates to a polyacetal resin composition.

[0002] With the introduction of free addresses and the diversification of work styles, the frequency of carrying laptops has increased. As a result, the demand for thinner and lighter laptops has been on the rise. Therefore, components used in laptops are also required to be thinner and smaller. In response to this requirement, when a component used in a holding mechanism for a thin key top (key cap) was made of a polyacetal resin composition, it was difficult to obtain sufficient strength for long-term use. Thus, as described in Document 1, when glass fiber and a boric acid compound were blended into the polyacetal resin composition, a thin component having the desired strength could be obtained.

[0003] Japanese Patent Laid-Open No. 9-151298

[0004] On the keyboard of a laptop, there are installed metal parts (base plates), resin parts for holding key tops and key tops, and switches for detecting inputs. Recently, in order to further reduce weight, the base plates of laptops are being changed from stainless steel to aluminum. Aluminum has a lower hardness than stainless steel. Therefore, when a component made of a polyacetal resin composition containing glass fiber or the like slides during the use of the keyboard and comes into contact with the base plate, the base plate may be worn out.

[0005] The present invention has been made in view of such points, and an object thereof is to provide a polyacetal resin composition that can reduce wear of a metal part even when a part (molded product) made of the polyacetal resin composition slides and comes into contact with the metal part, and that has good mechanical strength.

[0006] As a result of intensive studies, the present inventor has found that the above problems can be solved, and has completed the present invention. Specifically, the present invention is configured as follows in [1] to [6] below.

[0007] [1] A polyacetal resin composition comprising (A) 70% to 95% by mass of polyacetal resin, (B) 4% to less than 25% by mass of glass-based filler, and (C) 1% to 10% by mass of a glycidyl group-containing copolymer having olefin and glycidyl (meth)acrylate as copolymer components. [2] The polyacetal resin composition according to [1], wherein the glycidyl group-containing copolymer is a copolymer having olefin and glycidyl methacrylate as copolymer components. [3] The polyacetal resin composition according to [1] or [2], wherein the ratio of the total mass of the glass-based filler and the glycidyl group-containing copolymer to the total mass of the polyacetal resin composition is 0.05 to 0.4. [4] When a thrust-type friction wear test is performed with a metal part as the mating material, the specific wear amount of the metal part is 1.5 mm. ３ A polyacetal resin composition according to any one of [1] to [3], wherein the density is less than or equal to / Nm. [5] A polyacetal resin composition according to any one of [1] to [4] used in parts that come into contact with metal parts. [6] A keyboard part made of a molded article of the polyacetal resin composition according to any one of [1] to [5].

[0008] According to the present invention, it is possible to provide a polyacetal resin composition that can reduce wear on metal parts even when parts (molded articles) made of the polyacetal resin composition come into contact with metal parts during sliding, and that also has good mechanical strength.

[0009] The embodiments of the present invention will be described in detail below, but the present invention is not limited to the embodiments described below.

[0010] [Polyacetal Resin Composition] A polyacetal resin composition according to one embodiment of the present invention contains a polyacetal resin, a glass-based filler, and a glycidyl group-containing copolymer having olefin and (meth)acrylate glycidyl as copolymer components.

[0011] <(A) Polyacetal resin> Both homopolymer and copolymer forms of polyacetal resin can be used.

[0012] (Homopolymer) A homopolymer is a polymer composed of a single monomer. In the case of polyacetal polymers, a homopolymer is defined as a polymer composed of repeating units of oxymethylene groups (-OCH₂). ２ This refers to a polymer that has only -) in its main chain.

[0013] Homopolymers can be obtained by anionic polymerization of formaldehyde in the presence of a polymerization catalyst. It is necessary to stabilize the ends of the crude polyoxymethylene obtained in the polymerization process using an etherifying agent, esterifying agent, etc. Alternatively, commercially available homopolymers such as Delrin® from DuPont (USA) or Tenac® from Asahi Kasei Corporation may be used.

[0014] (Copolymer) A copolymer is a copolymer composed of two or more monomers. In the case of polyacetal polymers, a copolymer refers to a copolymer with an oxymethylene group (-OCH). ２ This refers to a copolymer that has a carbon-neutral group (-) as its main chain and also has other groups such as oxyalkylene groups with two or more carbon atoms in the molecule.

[0015] Copolymers can be obtained by copolymerizing trioxane with a comonomer copolymerizable with trioxane in the presence of a polymerization catalyst. Alternatively, commercially available copolymers such as Duracon® manufactured by Polyplastics Co., Ltd. may be used.

[0016] Furthermore, the polyacetal resin in one embodiment of the present invention is melt-mold (for example, the melt flow rate (MFR) measured at 190°C and under a 2160g load in accordance with ISO 1133 is 1 to 100 g / 10 min). The MFR can be measured, for example, using a melt indexer L220 (manufactured by Tateyama Science High Technologies Co., Ltd.).

[0017] The above MFR is preferably 1 to 50 g / 10 min, and more preferably 5 to 50 g / 10 min.

[0018] Furthermore, the polyacetal resin content is preferably 70% by mass or more and 95% by mass or less, 72% by mass or more and 95% by mass or less, and more preferably 72% by mass or more and 90% by mass or less, based on the total mass of the polyacetal resin composition.

[0019] <(B) Glass-based filler> The glass-based filler can be appropriately selected from glass fibers, glass beads, glass powder, and glass flakes, depending on the desired mechanical strength of the molded product. In one embodiment of the present invention, the glass-based filler is preferably glass fibers.

[0020] In this specification, "glass fiber" means a fibrous material cut perpendicular to the length direction. Examples of glass fibers include A glass, C glass, E glass, AR glass, D glass, M glass, and S glass.

[0021] The glass fibers described above preferably have a number-average fiber diameter of 1 to 25 μm, and more preferably 1 to 17 μm.

[0022] Furthermore, the form of the glass fiber may be any of the following: glass roving made by continuously winding single fibers or bundles of multiple single fibers; chopped strands (glass fibers with a number-average fiber length of 1 to 10 mm) cut to a length of 1 to 10 mm; or milled fibers (glass fibers with a number-average fiber length of 10 to 500 μm) crushed to a length of approximately 10 to 500 μm. These may be used individually or in combination of two or more types.

[0023] In one embodiment of the present invention, the content of the glass-based filler is 4% by mass or more and less than 25% by mass of the total mass of the polyacetal resin composition. By setting the content of the glass-based filler within the above range, it is possible to provide a part (molded article) made of a polyacetal resin composition having the desired mechanical strength.

[0024] Furthermore, the content of the glass-based filler is preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 20% by mass or less, of the total mass of the polyacetal resin composition. By setting the content of the glass-based filler within the above range, it is possible to provide a polyacetal resin composition that has high mechanical strength while more effectively reducing wear on metal parts.

[0025] <(C) Glycidyl group-containing copolymer> The glycidyl group-containing copolymer in one embodiment of the present invention is a glycidyl group-containing copolymer having an olefin such as ethylene or propylene and glycidyl (meth)acrylate as copolymer components. In the present invention, it is preferable that the glycidyl group-containing copolymer has an olefin and glycidyl methacrylate (GMA) as copolymer components.

[0026] The glycidyl group-containing copolymer may be one manufactured by a known method or a commercially available product. Examples of commercially available products include IGETABOND® BF-30C, IGETABOND BF-E, and IGETABOND BF-2C (all manufactured by Sumitomo Chemical Co., Ltd.).

[0027] The content of the glycidyl group-containing copolymer is 1% by mass or more and 10% by mass or less of the total mass of the polyacetal resin composition. By including the glycidyl group-containing copolymer within the above range, wear of metal parts can be reduced even when parts (molded articles) made of the polyacetal resin composition come into contact with metal parts during sliding.

[0028] Furthermore, the content of the glycidyl group-containing copolymer is preferably 1% by mass or more and 9% by mass or less, and more preferably 2% by mass or more and 8% by mass or less, based on the total mass of the polyacetal resin composition. By setting the content of the glycidyl group-containing copolymer within the above range, wear of metal parts can be reduced more effectively.

[0029] The ratio of the total mass of the glass-based filler and the glycidyl group-containing copolymer to the total mass of the polyacetal resin composition [(glass-based filler + glycidyl group-containing copolymer) / total mass of the polyacetal resin composition] is preferably 0.05 to 0.4, and more preferably 0.06 to 0.34. By setting this ratio to 0.05 to 0.4, it is possible to provide a polyacetal resin composition that has high mechanical strength and can reduce wear on metal parts even when it comes into contact with metal parts during sliding.

[0030] Furthermore, the ratio of the mass of the glass-based filler to the total mass of the polyacetal resin composition (glass-based filler / total mass of polyacetal resin composition) is preferably 0.03 to 0.3, and more preferably 0.05 to 0.25. By setting this ratio to 0.03 to 0.3, a polyacetal resin composition with high mechanical strength can be provided.

[0031] Furthermore, the ratio of the mass of the glycidyl group-containing copolymer to the total mass of the polyacetal resin composition (glycidyl group-containing copolymer / total mass of the polyacetal resin composition) is preferably 0.01 to 0.13, and more preferably 0.01 to 0.10. By setting this ratio to 0.01 to 0.13, a polyacetal resin composition that can reduce wear on metal parts can be provided.

[0032] <Method for producing polyacetal resin composition> Polyacetal resin composition can be produced by melt-kneading (A) 70% to 95% by mass of polyacetal resin, (B) 4% to less than 25% by mass of glass-based filler, and (C) 1% to 10% by mass of glycidyl group-containing copolymer using a twin-screw continuous extruder mixer, twin-screw paddle screw extruder, vented twin-screw extruder, etc.

[0033] The polyacetal resin composition may contain various known stabilizers and additives.

[0034] Examples of stabilizers include hindered phenol compounds, hindered amine compounds, nitrogen-containing basic compounds, oxides, hydroxides, inorganic salts, and carboxylates of alkali or alkaline earth metals. Examples of additives include colorants such as dyes and pigments, fluorescent whitening agents, lubricants, nucleating agents, mold release agents, antistatic agents, and surfactants.

[0035] A polyacetal resin composition according to one embodiment of the present invention, when subjected to a thrust-type friction and wear test with a metal part as the mating material, exhibits a specific wear amount of 1.5 mm for the metal part. ３ It is possible to provide a part (molded article) with a hardness of 1 / Nm or less. As a result, even when a part (molded article) made of the polyacetal resin composition comes into contact with a metal part when sliding, the wear of the metal part is reduced, making it possible to use it with metal parts with low hardness (for example, aluminum parts). Furthermore, the polyacetal resin composition according to one embodiment of the present invention can provide a part (molded article) that also has good mechanical strength.

[0036] Furthermore, the polyacetal resin composition according to one embodiment of the present invention reduces the specific wear amount of metal parts to 0.1 mm. ３ / Nm or more 1.5mm ３ We can provide parts (molded products) that can have a specific wear rate of / Nm or less. By setting the specific wear rate of metal parts within the above range, wear of metal parts can be further reduced.

[0037] [Parts that come into contact with metal parts] In one embodiment of the present invention, parts that come into contact with metal parts refer to parts used in the keycap retention mechanism (scissors type, pantograph type, etc.) of a keyboard, resin bearings, resin sheaves, etc.

[0038] [Keyboard Component] The polyacetal resin composition according to an embodiment of the present invention can be used for keyboard components of a personal computer. Specifically, it is a component used in the holding mechanism (such as a scissor type, pantograph type, etc.) of the key tops (key caps) of the keyboard. As described above, a component (molded product) made of the polyacetal resin composition according to an embodiment of the present invention can reduce the wear of a metal component (such as a base plate) that comes into contact when the holding mechanism slides.

[0039] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

[0040] [Manufacturing Method of Polyacetal Resin Composition] In a container into which the polyacetal resin in the amounts shown in Tables 1 to 2 was charged, a glass-based filler and a glycidyl group-containing copolymer were blended in the amounts shown in Tables 1 to 2, and using a twin-screw extruder with a vent, under the conditions that the temperature of the cylinder was 200°C and the degree of vacuum of the vent part was 5 mmHg, melt kneading and extrusion were carried out to obtain the polyacetal resin compositions shown in Tables 1 to 2. At this time, the glass-based filler was added by side feeding. The units of the numerical values in Tables 1 to 2 are mass%.

[0041] Each constituent component of the polyacetal resin composition shown in Tables 1 to 2 is as follows.

[0042] <(A) Polyacetal Resin>(a) Polyacetal resin (a polyacetal copolymer obtained by copolymerizing 96.7 mass% of trioxane and 3.3 mass% of 1,3-dioxolane (MFR: 30 g / 10 min)

[0043] The measurement of MFR was carried out in accordance with ISO1133 at 190°C under a load of 2160 g. MFR was measured using a melt indexer L220 type.

[0044] <(B) Glass-Based Filler>(b) Glass fiber: Chopped strand with a fiber diameter of 10.5 μm and a length of 3 mm

[0045] <(C) Glycidyl Group-containing Copolymer>(c-1) IGETABOND BF-30C (GMA content: 19%) (c-2) IGETABOND BF-E (GMA content: 12%) (c-3) IGETABOND BF-2C (GMA content: 6%)

[0046] <(C') Resin, Copolymer>(c'-1) Mipelon XM-220 (Polyethylene resin) (c'-2) Nuclel NI525 (Ethylene methacrylic acid copolymer) (c'-3) Himilan 1702 (Metal salt of ethylene methacrylic acid copolymer)

[0047] (c'-1) is manufactured by Mitsui Chemicals, Inc., and (c'-2) and (c'-3) are manufactured by Mitsui Dow Polychemical Co., Ltd. "Mipelon", "Nuclel" and "Himilan" are registered trademarks.

[0048] [Evaluation] For polyacetal resin compositions 1 to 22, the evaluation of wear characteristics and tensile test was carried out as shown below. The evaluation results are shown in Tables 1 to 2.

[0049] <Wear Characteristics Evaluation>Using polyacetal resin compositions 1 to 22, test pieces of the following shape of Type A were prepared in accordance with ISO3167. Using these test pieces, evaluation was carried out under the following conditions. Test piece: Hollow cylindrical shape (inner diameter: 20 mm, outer diameter: 25.6 mm, height: 15 mm) Testing machine: Thrust type friction and wear testing machine "EFM-III-E" (manufactured by Orientec Co., Ltd.) Environment: 23°C, 50% RH Speed: 1500 mm / sec Load: 0.01 N Counter material: Aluminum test piece (shape: hollow cylindrical shape, inner diameter: 20 mm, outer diameter: 25.6 mm, height: 15 mm)

[0050] <Tensile Test Evaluation>Each of the polyacetal resin compositions 1 to 22 was put into an injection molding machine, and test pieces of Type 1-A were prepared in accordance with ISO3167. Using these test pieces, the tensile strength was measured in accordance with ISO527-1, 2.

[0051]

[0052]

[0053] As shown in Tables 1 and 2, it was found that even in polyacetal resin compositions containing glass-based fillers, by incorporating a glycidyl group-containing copolymer in a predetermined amount, wear on metal parts can be reduced when parts (molded products) made of polyacetal resin compositions come into contact with metal parts during sliding.

[0054] The polyacetal resin composition of the present invention is effective for parts that come into contact with metal parts, as it can reduce wear on metal parts even when parts (molded articles) made of the polyacetal resin composition come into contact with metal parts during sliding, and also possesses good mechanical strength.

Claims

1. A polyacetal resin composition comprising: (A) 70% to 95% by mass of polyacetal resin; (B) 4% to less than 25% by mass of glass-based filler; and (C) 1% to 10% by mass of a glycidyl group-containing copolymer having olefin and glycidyl (meth)acrylate as copolymer components.

2. The polyacetal resin composition according to claim 1, wherein the glycidyl group-containing copolymer is a copolymer comprising an olefin and glycidyl methacrylate as copolymer components.

3. The polyacetal resin composition according to claim 1 or 2, wherein the ratio of the total mass of the glass-based filler and the glycidyl group-containing copolymer to the total mass of the polyacetal resin composition is 0.05 to 0.

4.

4. When a thrust-type friction and wear test was performed on a metal part as the mating material, the specific wear amount of the metal part was 1.5 mm. ３ A polyacetal resin composition according to claim 1 or 2, wherein the m³ is less than or equal to / Nm.

5. The polyacetal resin composition according to claim 1 or 2, used in a part that comes into contact with a metal part.

6. A keyboard component comprising a molded article of the polyacetal resin composition according to claim 1 or 2.

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