Polyacetal resin composition

Abstract

To provide a polyacetal resin composition which, when formed into a component, can reduce wear of a metal component even when the component slides and comes into contact with the metal component, and has good mechanical strength.SOLUTION: (B) 5 to 15 parts by weight of glass fillers and (C) 3.5 to 6.5 parts by weight of graft copolymers of polyolefin-based polymers and vinyl-based polymers, based on 100 parts by weight of (A) polyacetal resins, wherein the melt flow rate of the polyacetal resins is 1 to 50g / 10min.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] The introduction of free address systems and diversifying work styles has led to an increase in the number of people carrying laptops around, resulting in a growing demand for thinner and lighter laptops. This has led to a demand for thinner and smaller laptop components. To meet this demand, components used in the retention mechanisms of thin keytops (keycaps) were manufactured using polyacetal resin compositions, but it was difficult to obtain sufficient strength for long-term use. Therefore, as described in Reference 1, glass fiber and a boric acid compound were blended into the polyacetal resin composition, resulting in the thinned components with the desired strength. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-151298 Summary of the Invention [Problem to be solved by the invention]

[0004] Laptop keyboards are equipped with keycaps, resin components for holding the keycaps, and switches for detecting inputs mounted on a metal component (base plate). Recently, in order to further reduce weight, laptop base plates are being replaced with aluminum instead of stainless steel. Aluminum is less hard than stainless steel. Therefore, when using the keyboard, sliding components made of polyacetal resin compositions containing glass fibers and the like may come into contact with the base plate, potentially causing wear to the base plate.

[0005] The present invention has been made in consideration of the above points, and aims to provide a polyacetal resin composition that, when used as a part, can reduce wear of a metal part even when the part comes into contact with the metal part during sliding, and has good mechanical strength. [Means for solving the problem]

[0006] The present inventors have conducted extensive research and found that the above problems can be solved, leading to the completion of the present invention. Specifically, the present invention is configured as follows [1] to [5].

[0007] [1] A polyacetal resin composition comprising, per 100 parts by weight of (A) polyacetal resin, 5 to 15 parts by weight of (B) glass-based filler and 3.5 to 6.5 parts by weight of (C) a graft copolymer of a polyolefin polymer and a vinyl polymer, wherein the melt flow rate of the polyacetal resin is 1 to 50 g / 10 min.

[0008] [2] The polyacetal resin composition according to [1], wherein the graft copolymer is a copolymer of a polyolefin polymer and a styrene polymer.

[0009] [3] When a thrust friction and wear test was conducted using a metal part as the mating material, the specific wear of the metal part was 1.4 mm 3 The polyacetal resin composition according to [1] or [2], wherein the viscosity is 1 / Nm or less.

[0010] [4] The polyacetal resin composition according to any one of [1] to [3], which is used for a part that comes into contact with a metal part.

[0011] [5] A keyboard part comprising a molded article of the polyacetal resin composition according to any one of [1] to [3]. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a polyacetal resin composition that, when used as a part, can reduce wear of a metal part even when the part comes into contact with the metal part during sliding, and has good mechanical strength. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0014] [Polyacetal resin composition] A polyacetal resin composition according to one embodiment of the present invention is a resin composition containing a polyacetal resin, a glass-based filler, and a graft copolymer of a polyolefin-based polymer and a vinyl-based polymer.

[0015] <(A) Polyacetal resin> The polyacetal resin may be either a homopolymer or a copolymer.

[0016] (homopolymer) A homopolymer is a polymer composed of a single monomer. In addition, a homopolymer in the case of polyacetal polymers refers to a polymer that has only oxymethylene groups (-OCH2-) as repeating units in the main chain.

[0017] The homopolymer can be obtained by anionic polymerization of formaldehyde in the presence of a polymerization catalyst. The terminals of the crude polyoxymethylene obtained in the polymerization process must be stabilized using an etherifying agent, an esterifying agent, or the like. Commercially available homopolymers, such as Delrin (manufactured by DuPont (USA), "Delrin" is a registered trademark of DuPont) and Tenac (manufactured by Asahi Kasei Corporation, "Tenac" is a registered trademark of DuPont), may also be used.

[0018] (copolymer) A copolymer is a copolymer made up of two or more monomers. In addition, a copolymer in the case of polyacetal polymer refers to a copolymer that has an oxymethylene group (-OCH2-) in the main chain and also has other groups such as oxyalkylene groups with two or more carbon atoms in the molecule.

[0019] The copolymer can be obtained by copolymerizing trioxane with a comonomer copolymerizable with trioxane in the presence of a polymerization catalyst. Alternatively, a commercially available copolymer such as Duracon (manufactured by Polyplastics Co., Ltd., "Duracon" is a registered trademark of the company) may be used.

[0020] The polyacetal resin according to one embodiment of the present invention has melt moldability (for example, a melt flow rate (MFR) of 1 to 50 g / 10 min measured at 190°C under a load of 2160 g in accordance with ISO 1133). The MFR can be measured using, for example, a Melt Indexer L220 (manufactured by Tateyama Kagaku High-Technologies Corporation).

[0021] In one embodiment of the present invention, the MFR is preferably 5 to 50 g / 10 min, and more preferably 8 to 50 g / 10 min.

[0022] <(B) Glass-based filler> The glass-based filler can be appropriately selected from glass fiber, 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 fiber.

[0023] In this specification, "glass fiber" refers to a fibrous material whose cross section cut perpendicular to the longitudinal direction has a perfect circle or the like. Examples of glass fibers include A-glass, C-glass, E-glass, AR-glass, D-glass, M-glass, and S-glass.

[0024] The number average fiber diameter of the single fiber of the glass fiber is preferably 1 to 25 μm, and more preferably 1 to 17 μm.

[0025] The glass fiber may be in the form of a glass roving obtained by continuously winding a single fiber or a bundle of multiple single fibers, a chopped strand cut to a length of 1 to 10 mm (glass fiber having a number average fiber length of 1 to 10 mm), or a milled fiber pulverized to a length of about 10 to 500 μm (glass fiber having a number average fiber length of 10 to 500 μm), etc. These may be used alone or in combination of two or more.

[0026] In one embodiment of the present invention, the content of the glass-based filler is 5 to 15 parts by weight relative to 100 parts by weight of the polyacetal resin. When the polyacetal resin composition contains the glass-based filler within the above range, a molded article having the desired mechanical strength can be obtained.

[0027] The content of the glass filler is preferably 5 to 12 parts by weight, more preferably 6 to 12 parts by mass, based on 100 parts by weight of the polyacetal resin.

[0028] <(C) Graft copolymer> A graft copolymer is a polymer having blocks of one or more polymers attached as side chain polymer structures to a main chain polymer structure.

[0029] The graft copolymer according to one embodiment of the present invention is a graft copolymer of a polyolefin polymer and a vinyl polymer. In addition, the graft copolymer according to one embodiment of the present invention is preferably a graft copolymer having a polyolefin polymer main chain and a styrene polymer side chain.

[0030] Examples of polyolefin polymers include polyethylene and polypropylene, and examples of styrene polymers include polystyrene and styrene-acrylonitrile copolymers.

[0031] The graft copolymer can be synthesized by known methods such as a macromonomer method, a method using a hydrogen abstraction reaction from a polymer chain, etc. Commercially available graft copolymers such as Modiper A1100, Modiper A1401, and Modiper A3400 (all manufactured by NOF Corporation; Modiper is a registered trademark of the company) can be used.

[0032] In one embodiment of the present invention, the content of the graft copolymer is 3.5 to 6.5 parts by weight relative to 100 parts by weight of the polyacetal resin. When the polyacetal resin composition contains the graft copolymer in the above range, when the polyacetal resin composition is made into a part (molded article), wear of the metal part can be reduced even if the part comes into contact with the metal part during sliding.

[0033] The content of the graft copolymer is preferably 4 to 6 parts by weight.

[0034] <Polyacetal resin composition> The polyacetal resin composition can be produced by melt-kneading 5 to 20 parts by weight of (B) a glass-based filler and 3.5 to 6.5 parts by weight of (C) a graft copolymer of a polyolefin polymer and a vinyl polymer with 100 parts by weight of (A) a polyacetal resin using a twin-screw continuous extrusion mixer, a twin-screw paddle screw extruder, a vented twin-screw extruder, or the like.

[0035] The polyacetal resin composition may contain various known stabilizers and additives.

[0036] Examples of stabilizers include hindered phenol compounds, hindered amine compounds, nitrogen-containing basic compounds, alkali or alkaline earth metal oxides, hydroxides, inorganic salts, carboxylates, etc. Examples of additives include colorants such as dyes and pigments, fluorescent brighteners, lubricants, nucleating agents, release agents, antistatic agents, surfactants, etc.

[0037] The polyacetal resin composition according to one embodiment of the present invention was subjected to a thrust friction and wear test using a metal part as a mating material, and the specific wear amount of the metal part was 1.4 mm 3 / Nm or less. In addition, the specific wear rate of metal parts can be reduced to 0mm 3 / Nm over 1.4mm 3 / Nm or less. As a result, even if a part (molded article) made of the polyacetal resin composition comes into contact with a metal part during sliding, wear of the metal part is reduced, making it possible to use the polyacetal resin composition with a metal part having low hardness (for example, an aluminum part). Furthermore, the polyacetal resin composition according to one embodiment of the present invention also has good mechanical strength.

[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 keyboard key top (key cap) holding mechanism (scissor type, pantograph type, etc.), resin bearings, resin sheaves, etc.

[0039] [Keyboard parts] The polyacetal resin composition according to one embodiment of the present invention can be used in keyboard parts for personal computers. Specifically, it is a part used in a holding mechanism (scissor type, pantograph type, etc.) for keyboard key tops (key caps). As described above, a part (molded product) made from the polyacetal resin composition according to one embodiment of the present invention can reduce wear of metal parts (for example, a base plate) that come into contact with the holding mechanism when the holding mechanism slides. [Example]

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

[0041] [Method for producing polyacetal resin composition] A glass-based filler and a graft copolymer were blended in the amounts shown in Tables 1 and 2 into a vessel containing 100 parts by mass of polyacetal resin, and the blend was melt-kneaded and extruded using a vented twin-screw extruder under conditions of a cylinder temperature of 200°C and a vacuum degree of 5 mmHg at the vent, to obtain the polyacetal resin compositions shown in Tables 1 and 2. The glass-based filler was added by side feed. The values ​​in Tables 1 and 2 are in parts by mass.

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

[0043] <(A) Polyacetal resin> (a-1) Polyacetal resin (polyacetal copolymer obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane (MFR: 30 g / 10 min) (a-2) Polyacetal resin (polyacetal copolymer obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane (MFR: 10 g / 10 min)

[0044] The MFR was measured at 190° C. under a load of 2160 g in accordance with ISO 1133. The MFR was measured using a Melt Indexer L220 (manufactured by Tateyama Scientific High-Technologies Corporation).

[0045] <(B) Glass-based filler> (b) Glass fiber: Fiber diameter: 10.5 μm, length: 3 mm chopped strand

[0046] <(C) Graft copolymer> (c-1) Modiper A1401 (c-2) Modiper A1100 (c-3) Modiper A3400

[0047] <Other resins> (c') Mipelon XM-220 (manufactured by Mitsui Chemicals, Inc.; Mipelon is a registered trademark of Mitsui Chemicals, Inc.)

[0048] [evaluation] The polyacetal resin compositions 1 to 13 were evaluated for abrasion properties and tensile strength as follows. The results of the evaluations are shown in Tables 1 and 2.

[0049] <Wear characteristic evaluation> Polyacetal resin compositions 1 to 13 were used to prepare Type A test pieces having the following shapes in accordance with ISO 3167. These test pieces were used to perform evaluations under the following conditions. Test piece: Hollow cylinder (inner diameter: 20 mm, outer diameter: 25.6 mm, height: 15 mm) Testing machine: Thrust friction and wear testing machine "EFM-III-E" (manufactured by Orientec Co., Ltd.) Environment: 23℃, 50%RH Speed: 1500mm / sec Load: 0.01N Counterpart: Aluminum test piece (shape: hollow cylinder, inner diameter: 20 mm, outer diameter: 25.6 mm, height: 15 mm)

[0050] <Tensile test evaluation> Each of the polyacetal resin compositions 1 to 12 was placed in an injection molding machine, and a Type 1-A test piece was prepared in accordance with ISO 3167. Using these test pieces, tensile strength was measured in accordance with ISO 527-1,2.

[0051] [Table 1]

[0052] [Table 2]

[0053] As shown in Tables 1 and 2, even in the case of a polyacetal resin composition containing a glass-based filler, by blending a graft copolymer in a predetermined content, when the composition is made into a part (molded product), it is possible to reduce the wear of the metal part even when the part comes into contact with the metal part during sliding. [Industrial Applicability]

[0054] According to the present invention, when the polyacetal resin composition of the present invention is made into a part (molded article), it can reduce wear of the metal part even when the part comes into contact with the metal part during sliding, and has good mechanical strength, so it is effective for parts that come into contact with metal parts with low hardness.

Claims

1. (A) per 100 parts by weight of polyacetal resin, (B) 5 to 15 parts by weight of a glass-based filler; (C) 3.5 to 6.5 parts by weight of a graft copolymer of a polyolefin polymer and a vinyl polymer; Including, The melt flow rate of the polyacetal resin is 1 to 50 g / 10 min. Polyacetal resin composition.

2. 2. The polyacetal resin composition according to claim 1, wherein the graft copolymer is a copolymer of a polyolefin polymer and a styrene polymer.

3. When a thrust friction and wear test was conducted using a metal part as the mating material, the specific wear amount of the metal part was 1.4 mm ３ The polyacetal resin composition according to claim 1 or 2, wherein the viscosity is 1 / Nm or less.

4. The polyacetal resin composition according to claim 1 or 2, which is used for a part that comes into contact with a metal part.

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

Images