Polyacetal resin composition

Abstract

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. [Solution] The polyacetal resin composition of the present invention contains (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.

Description

Technical Field

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

Background Art

[0002] Due to the introduction of free addresses and the diversification of work styles, etc., the carrying of notebook computers has increased, so the demand for thinner and lighter notebook computers is increasing. Therefore, parts used in notebook computers are also required to be thinned and miniaturized. In order to meet this requirement, when parts used in a holding mechanism for a thinned key top (key cap) were made of a polyacetal resin composition, it was difficult to obtain sufficient strength for long-term use. Therefore, as in Document 1, when glass fiber and a boric acid compound were blended into the polyacetal resin composition, it was possible to obtain the above-mentioned thinned parts having the desired strength.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the keyboard of a notebook computer, 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 the weight, the base plate of the notebook computer is being changed from stainless steel to aluminum. Aluminum is less hard than stainless steel. Therefore, when the notebook computer is in use, there is a risk that the base plate will wear due to contact with the base plate when parts made of a polyacetal resin composition containing glass fiber or the like slide.

[0005] The present invention has been made in view of the above, and aims 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 when sliding, and that has good mechanical strength. [Means for solving the problem]

[0006] The inventors, after diligent research, found that the above problems could be solved and completed the present invention. Specifically, the present invention is configured as follows: [1] to [6].

[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 comprising an 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 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 any one of [1] to [3], wherein the m³ is less than or equal to / Nm. [5] A polyacetal resin composition according to any one of [1] to [4] used in a part that comes into contact with a metal part. A keyboard component comprising a molded article of a polyacetal resin composition as described in any of [6][1] to [5]. [Effects of the Invention]

[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. [Modes for carrying out the invention]

[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 comprising an olefin and glycidyl (meth)acrylate as copolymer components.

[0011] <(A) Polyacetal resin> Polyacetal resin can be either homopolymer or copolymer.

[0012] (Homopolymer) A homopolymer is a polymer composed of a single monomer. In the context of polyacetal polymers, a homopolymer is a polymer whose main chain consists solely of oxymethylene groups (-OCH2-) as repeating units.

[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 refers to a copolymer composed of two or more monomers. In addition, a copolymer in a polyacetal polymer refers to a copolymer having an oxymethylene group (-OCH2-) in the main chain and also having other groups such as an oxyalkylene group having 2 or more carbon atoms in the molecule.

[0015] The copolymer can be obtained by copolymerizing trioxane and a comonomer copolymerizable with trioxane in the presence of a polymerization catalyst. Also, a commercially available product such as Duracon (registered trademark) manufactured by Polyplastics Co., Ltd. may be used as the copolymer.

[0016] In addition, the polyacetal resin in one embodiment of the present invention has melt molding processability (for example, the melt flow rate (MFR) measured at 190 °C under a load of 2160 g in accordance with ISO1133 is 1 to 100 g / 10 min). The MFR can be measured, for example, using a melt indexer L220 type manufactured by Tateyama Kagaku High-Technology Co., Ltd.

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

[0018] In addition, the content of the polyacetal resin is 70% by mass or more and 95% by mass or less in the total mass of the polyacetal resin composition, preferably 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.

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

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

[0021] The above glass fiber preferably has a number-average fiber diameter of 1 to 25 μm for single fibers, more preferably 1 to 17 μm.

[0022] Also, the form of the glass fiber may be any of a glass roving obtained by continuously winding a single fiber or a bundle of a plurality of single fibers, chopped strands cut to a length of 1 to 10 mm (glass fibers with a number-average fiber length of 1 to 10 mm), milled fibers crushed to a length of about 10 to 500 μm (glass fibers with a number-average fiber length of 10 to 500 μm), etc. These may be used alone only one kind, or two or more kinds may be used in combination.

[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 in 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 product) made of a polyacetal resin composition having a desired mechanical strength.

[0024] Also, the content of the glass-based filler is preferably 5% by mass or more and 20% by mass or less, more preferably 10% by mass or more and 20% by mass or less in 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 can more effectively reduce the wear of metal parts while having high mechanical strength.

[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, of the total mass of the polyacetal resin composition. By keeping 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 in contact with them 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 compositions 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 wear test with a metal part as the mating material, exhibits a specific wear amount of 1.5 mm for the metal part. 3It 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, the parts that come into contact with the metal parts refer to parts used in the keycap retention mechanism (scissors type, pantograph type, etc.) of the keyboard, resin bearings, resin sheaves, etc.

[0038] [Keyboard parts] A polyacetal resin composition according to one embodiment of the present invention can be used in keyboard components for personal computers. Specifically, it is used in components for the keycap retention mechanism (scissors type, pantograph type, etc.) of a keyboard. As described above, a component (molded product) made of the polyacetal resin composition according to one embodiment of the present invention can reduce wear on metal components (e.g., base plates) that come into contact with the retention mechanism when it slides. [Examples]

[0039] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0040] [Method for producing polyacetal resin composition] Polyacetal resin in the amounts shown in Tables 1 and 2 was placed in a container, and glass-based filler and glycidyl group-containing copolymer were added in the amounts shown in Tables 1 and 2. The mixture was then melt-kneaded and extruded using a twin-screw extruder with a vent, under conditions of a cylinder temperature of 200°C and a vacuum of 5 mmHg in the vent section, to obtain the polyacetal resin compositions shown in Tables 1 and 2. The glass-based filler was added via side feed. The units of the values ​​in Tables 1 and 2 are in mass percent.

[0041] The constituent components of the polyacetal resin compositions shown in Tables 1 and 2 are as follows:

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

[0043] MFR was measured in accordance with ISO 1133 at 190°C and under a 2160g load. MFR was measured using a Melt Indexer L220.

[0044] <(B) Glass-based filler> (b) Glass fiber: Chopped strands 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) Nucrel NI525 (ethylene methacrylic acid copolymer) (c'-3) Hymiran 1702 (metal salt of ethylene methacrylic acid copolymer)

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

[0048] [evaluation] The abrasion properties and tensile strength of polyacetal resin compositions 1 to 22 were evaluated as follows. The results of each evaluation are shown in Tables 1 and 2.

[0049] <Wear characteristics evaluation> Using polyacetal resin compositions 1 to 22, test specimens of Type A with the following shapes were prepared in accordance with ISO 3167. These test specimens were evaluated under the following conditions. Test specimen: Hollow cylindrical (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℃, 50%RH Speed: 1500mm / sec Load: 0.01N Test piece made of aluminum (shape: hollow cylinder, inner diameter: 20 mm, outer diameter: 25.6 mm, height: 15 mm)

[0050] <Tensile Test Evaluation> Polyacetal resin compositions 1 to 22 were each introduced into an injection molding machine, and Type 1-A test specimens were prepared in accordance with ISO 3167. Tensile strength was measured using these test specimens in accordance with ISO 527-1,2.

[0051] [Table 1]

[0052] [Table 2]

[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. [Industrial applicability]

[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 70% by mass or more and 95% by mass or less, (B) Glass-based filler 4% by mass or more and less than 25% by mass, (C) A copolymer containing 1% by mass or more and 10% by mass or less of a glycidyl group, wherein the copolymer is composed of an olefin and glycidyl (meth)acrylate. Polyacetal resin composition.

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. A 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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