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 polyamide or polyamide copolymer.

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, the use of laptops has increased, and there is a growing demand for thinner and lighter laptops. Therefore, components used in laptops are also required to be thinner and smaller. In order to meet 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. Therefore, as 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.

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 laptop, there are metal parts (base plates), resin parts for holding 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 is less hard 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 wear.

[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 [5].

[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 polyamide or polyamide copolymer. [2] The polyacetal resin composition according to [1], wherein the ratio of the total mass of the glass-based filler and the polyamide or polyamide copolymer to the total mass of the polyacetal resin composition is 0.05 to 0.4. [3] 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 [1] or [2], wherein the m³ is less than or equal to / Nm. [4] A polyacetal resin composition according to any one of [1] to [3] 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 [5][1] to [4]. [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 comprises a polyacetal resin, a glass-based filler, and a polyamide or polyamide copolymer.

[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 is a copolymer composed of two or more monomers. In the context of polyacetal polymers, a copolymer is a copolymer that has an oxymethylene group (-OCH2-) as its main chain and also contains other groups such as oxyalkylene groups with two 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. Alternatively, a commercially available product such as Duracon (registered trademark) manufactured by Polyplastics Co., Ltd. may be used as the copolymer.

[0016] Moreover, 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 ISO 1133 is 1 to 100 g / 10 min). The MFR can be measured using, for example, a melt indexer L220 type manufactured by Tachibana 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, 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 in 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 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.

[0021] The above glass fiber preferably has a number average fiber diameter of 1 to 25 μm for single fibers, 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) Polyamide or polyamide copolymer> In one embodiment of the present invention, the polyamide or polyamide (nylon) copolymer may be one that has been produced by a known method or a commercially available product.

[0026] Examples of commercially available polyamides or polyamide copolymers include VESTAMID® Z9004, DAIAMID® L1600, DAIAMID L1800 (all manufactured by Polypla Evonik Co., Ltd.), ELVAMIDE® 8063 (manufactured by Toray Celanese Co., Ltd.), Amilan® CM4000, Amilan CM8000 (both manufactured by Toray Industries, Inc.), and others.

[0027] By using copolymers having polar parts such as polyamides and amide groups, wear on metal parts can be reduced even when a part (molded product) made of a polyacetal resin composition comes into contact with a metal part during sliding.

[0028] In one embodiment of the present invention, the content of polyamide or polyamide copolymer is 1% by mass or more and 10% by mass or less of the total mass of the polyacetal resin composition. By including polyamide or polyamide copolymer within the above range, wear of metal parts can be reduced even when a part (molded product) made of the polyacetal resin composition comes into contact with a metal part when sliding.

[0029] Furthermore, the content of polyamide or polyamide 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 polyamide or polyamide copolymer within the above range, wear of metal parts can be reduced more effectively.

[0030] The ratio of the total mass of the glass-based filler and the polyamide or polyamide copolymer to the total mass of the polyacetal resin composition [(glass-based filler + polyamide or polyamide) / 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.

[0031] 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.

[0032] Furthermore, the ratio of the mass of polyamide or polyamide copolymer to the total mass of the polyacetal resin composition (polyamide or polyamide copolymer / total mass of 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.

[0033] <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 polyamide or polyamide copolymer using a twin-screw continuous extruder mixer, twin-screw paddle screw extruder, vented twin-screw extruder, etc.

[0034] The polyacetal resin composition may contain various known stabilizers and additives.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] [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.

[0039] [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]

[0040] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0041] [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, polyamide, or polyamide copolymer was 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.

[0042] The constituent components of the polyacetal resin compositions shown in Tables 1 and 2 are as follows:

[0043] <(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)

[0044] MFR was measured in accordance with ISO 1133 at 190°C and under a 2160g load. MFR was measured using a Melt Indexer L220.

[0045] <(B) Glass-based filler> (b) Glass fiber: Chopped strands with a fiber diameter of 10.5 μm and a length of 3 mm

[0046] <(C) Polyamide or polyamide copolymer> ≪Polyamide≫ (c-1) VESTAMID Z9004 (c-2)DAIAMID L1600 (c-3)DAIAMID L1800 Copolymerized nylon (c-4) Amilan CM4000 (c-5) Amilan CM8000 (c-6) ELVAMIDE 8063

[0047] <(C') Resin, elastomer> (c'-1) Mipelon XM-220 (polyethylene resin) (c'-2)DAIAMID X4442W2 (Polyether Block Copolyamide) (c'-3)VESTAMID E47-S1 (Polyether Block Copolyamide)

[0048] (c'-1) is manufactured by Mitsui Chemicals, Inc., (c'-2) and (c'-3) are manufactured by Polypla Evonik Co., Ltd., and "Mipelon" is a registered trademark.

[0049] [evaluation] The abrasion properties and tensile strength of polyacetal resin compositions 1 to 27 were evaluated as follows. The results of each evaluation are shown in Tables 1 and 2.

[0050] <Wear characteristics evaluation> Using polyacetal resin compositions 1 to 27, 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)

[0051] <Tensile Test Evaluation> Polyacetal resin compositions 1 to 27 were each injected 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.

[0052] [Table 1]

[0053] [Table 2]

[0054] As shown in Tables 1 and 2, it was found that even in polyacetal resin compositions containing glass-based fillers, by incorporating polyamide or polyamide (nylon) 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]

[0055] 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) containing 1% by mass or 10% by mass of polyamide or polyamide copolymer, Polyacetal resin composition.

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

4.

3. 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.

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

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

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