Polyacetal resin composition and molded article

Abstract

To provide a polyacetal resin composition which can achieve further improvement of physical properties such as mechanical strength, creep resistance and low warpage, while using a heteromorphic cross-sectional glass fiber.SOLUTION: A polyacetal resin composition contains, with respect to 100 pts.mass of (A) a polyacetal resin, 1 to 100 pts.mass of (B) a heteromorphic cross-sectional glass fiber, and 0.001 to 2 pts.mass of (C) one or more binding agents selected from a quaternary onium salt compound and a boric acid compound. As (B) the heteromorphic cross-sectional glass fiber, a glass fiber having a flat cross-sectional shape with a ratio (heteromorphic ratio) of a major axis of the cross section to a minor axis of the cross section of 1.2 or more is preferable.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Polyacetal resin is widely used as an engineering plastic mainly for electrical and electronic parts, automotive parts and other various machine parts because it has an excellent balance of mechanical properties, chemical resistance, sliding properties, etc., and is easy to process. In order to further improve the mechanical properties, various fillers are generally added to polyacetal resin. Examples of such fillers include glass fibers. Glass fibers are widely used not only for polyacetal resin but also for various engineering plastics to improve their mechanical strength. Glass fibers having a circular cross-sectional shape are generally used. However, when using general glass fibers having a circular cross-sectional shape, the mechanical properties and shrinkage rate can be improved with an increase in the filling amount, but the warping of the obtained resin molded product tends to increase due to increased anisotropy. Therefore, in recent years, it has been proposed to use irregular cross-section glass fibers having a non-circular cross-section (see Patent Document 1). By using such irregular cross-section glass fibers, the warping of the resin molded product can be reduced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-316079 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, by adding irregular cross-section glass fibers to a resin composition, it is possible to reduce warpage of a resin molded product obtained by molding the resin composition. In addition, in Patent Document 1, a polyfunctional cyanate ester compound is used as a binder to impart adhesion at the interface between the irregular cross-section glass fiber and the polyacetal resin. However, even if such a binder is used, the interface adhesion between the irregular cross-section glass fiber and the polyacetal resin is not sufficient, and the mechanical strength and creep resistance are insufficient, leaving room for improvement.

[0005] The present invention has been made in consideration of the above-mentioned problems in the conventional art, and an object of the present invention is to provide a polyacetal resin composition and a molded article which can realize further improvements in physical properties such as mechanical strength, creep resistance, and low warpage while using modified cross-section glass fibers. [Means for solving the problem]

[0006] One aspect of the present invention that solves the above problems is as follows. (1) (A) per 100 parts by mass of polyacetal resin, (B) 1 to 100 parts by mass of irregular cross section glass fiber, (C) a polyacetal resin composition containing 0.001 to 2 parts by mass of one or more binders selected from the group consisting of quaternary onium salt compounds and boric acid compounds.

[0007] (2) The polyacetal resin composition according to (1) above, wherein the (B) irregular cross-section glass fiber is a glass fiber having a flat cross-sectional shape in which the ratio of the major axis of the cross-section to the minor axis of the cross-section (irregularity ratio) is 1.2 or more.

[0008] (3) The polyacetal resin composition according to (1) or (2) above, wherein the (C) binder is at least one compound selected from the group consisting of quaternary onium halide salts and quaternary onium carboxylate salts.

[0009] (4) The polyacetal resin composition according to any one of (1) to (3), wherein the (C) binder is at least one compound selected from the group consisting of a quaternary phosphonium halide, a quaternary ammonium halide, a quaternary phosphonium carboxylate, a quaternary ammonium carboxylate, and boric acid.

[0010] (5) The polyacetal resin composition according to any one of (1) to (4), wherein the (C) binder is at least one compound selected from the group consisting of ethyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, choline acetate, choline chloride, and orthoboric acid.

[0011] (6) The polyacetal resin composition according to any one of (1) to (5) above, further comprising (D) 0.002 to 10 parts by mass of a triazine derivative having a nitrogen-containing functional group.

[0012] (7) The polyacetal resin composition according to (6) above, wherein the (D) triazine derivative having a nitrogen-containing functional group is at least one compound selected from the group consisting of melamine, a melamine formaldehyde adduct, and benzoguanamine.

[0013] (8) A molded article obtained by molding the polyacetal resin composition according to any one of (1) to (7) above. Effect of the Invention

[0014] According to the present invention, it is possible to provide a polyacetal resin composition and a molded article which use modified cross section glass fibers and which are capable of achieving further improvements in physical properties such as mechanical strength, creep resistance, and low warpage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Polyacetal resin composition> The polyacetal resin composition of the present embodiment contains, per 100 parts by mass of (A) polyacetal resin, 1 to 100 parts by mass of (B) modified cross section glass fiber, and 0.001 to 2 parts by mass of (C) one or more binders selected from the group consisting of quaternary onium salt compounds and boric acid compounds.

[0016] The polyacetal resin composition of the present embodiment contains a specific binder, i.e., (C) one or more selected from the group consisting of quaternary onium salt compounds and boric acid compounds, in a predetermined amount together with the irregular cross section glass fiber (B). By containing such a specific binder, the interfacial adhesion between the polyacetal resin (A) and the irregular cross section glass fiber (B) is improved, and physical properties such as mechanical strength and creep resistance can be improved. Each component of the polyacetal resin composition of the present embodiment will be described in detail below.

[0017] [(A) Polyacetal resin] In this embodiment, the polyacetal resin (A) is a polymeric compound having an oxymethylene group (-CHO-) as a main constituent unit, and may be either a polyoxymethylene homopolymer in which the only constituent unit is an oxymethylene group, or a copolymer, terpolymer, or block polymer in which the main constituent unit is an oxymethylene group and a small amount of other constituent units, for example, constituent units derived from comonomers such as ethylene oxide, 1,3-dioxolane, and 1,4-butanediol formal.

[0018] In addition, the polyacetal resin may be not only linear in molecule but also one having a branched or crosslinked structure obtained by copolymerizing a comonomer having a glycidyl ether structure, or may be a known modified polyoxymethylene into which other organic groups have been introduced, or may be a mixture of a linear resin and a resin having a branched or crosslinked structure.

[0019] The polyacetal resin is not particularly limited with respect to its degree of polymerization, and may be any resin having melt moldability (for example, a melt flow value (MFR) of 1.0 g / 10 min or more and 100 g / 10 min or less at 190° C. and a load of 2160 g in accordance with ISO 1133).

[0020] [(B) Irregular cross-section glass fiber] The polyacetal resin composition of the present embodiment contains 1 to 100 parts by mass of (B) modified cross section glass fiber per 100 parts by mass of (A) polyacetal resin. By containing (B) modified cross section glass fiber, in combination with (C) binder, it is possible to realize improvements in physical properties such as mechanical strength, creep resistance, and low warpage.

[0021] In this embodiment, the irregular cross-section glass fiber means a glass fiber whose cross section perpendicular to the longitudinal direction of the glass fiber has a shape that is not a so-called substantially perfect circle, such as an elongated flat shape such as an oval, cocoon shape, or ellipse shape. In addition, as the irregular cross section glass fiber, irregular cross section glass fiber obtained by the manufacturing method described in JP-B-4-32775, Japanese Patent No. 33369674, Japanese Patent No. 5505597, Japanese Patent No. 7075017, and International Publication WO2020 / 04033 can be used. The composition of the modified cross section glass fiber used in the polyacetal resin composition of this embodiment may be any composition that can be turned into glass fiber from molten glass, and examples of such composition include an E glass composition, an A glass composition, a C glass composition, a D glass composition, an H glass composition, an R glass composition, an S glass composition, a T glass composition, an AR glass composition, an NE glass composition, and an ECR glass composition (boron-free and / or fluorine-free glass composition). The irregular cross section glass fiber used in the polyacetal resin composition of the present embodiment is preferably surface-treated with a silane coupling agent, and may be surface-treated with a sizing agent having a film-forming ability, such as an epoxy resin, a urethane resin, or an acid polymer (e.g., the copolymer compound described in Japanese Patent No. 6136579).

[0022] From the viewpoint of improving physical properties such as mechanical strength, creep resistance, and low warpage, the (B) modified cross-section glass fiber preferably has a flat cross-sectional shape with a ratio of the major axis of the cross-section to the minor axis of the cross-section (modification ratio) of 1.2 or more. The modification ratio is more preferably 1.5 to 10, and further preferably 1.8 to 8. As the modified cross-section glass fiber, any glass having a fibrous shape can be used without any problem. Specific examples include chopped strand glass fiber, milled glass fiber, and glass fiber roving. Among these, chopped strand glass fiber and milled glass fiber are particularly preferred from the viewpoint of productivity. Furthermore, chopped strand glass fiber is more preferred for improving the creep resistance of the resin molded product. These modified cross-section glass fibers may be used alone or in combination of two or more.

[0023] Examples of modified cross section glass fibers having an oval cross section include chopped strand and oval FF manufactured by Nitto Boseki Co., Ltd., chopped strand and oval FGF manufactured by Nippon Electric Glass Co., Ltd., chopped strand and flat CS manufactured by Central Glass Fiber Co., Ltd. Examples of modified cross section glass fibers having a cocoon-shaped cross section include chopped strand and cocoon-shaped HIS manufactured by Nitto Boseki Co., Ltd.

[0024] The polyacetal resin composition of the present embodiment contains 1 to 100 parts by mass of (B) modified cross section glass fiber per 100 parts by mass of (A) polyacetal resin. If the amount of (B) modified cross section glass fiber is less than 1 part by mass, physical properties such as mechanical strength, creep resistance, and low warpage properties become insufficient, whereas if the amount exceeds 100 parts by mass, the melt fluidity is significantly reduced.

[0025] [(C) Binder] The polyacetal resin composition of the present embodiment contains 0.001 to 2 parts by mass of one or more compounds selected from the group consisting of quaternary onium salt compounds and boric acid compounds, based on 100 parts by mass of the polyacetal resin (A). As described above, the binder (C) is used to improve the interfacial adhesion between the polyacetal resin (A) and the modified cross section glass fiber (B).

[0026] As the quaternary onium salt compound (C) as a binder, it is preferable to use at least one compound selected from the group consisting of quaternary onium halide salts and quaternary onium carboxylates. Specifically, it is preferable to use at least one compound selected from the group consisting of quaternary phosphonium halide salts, quaternary ammonium halide salts, quaternary phosphonium carboxylate salts, quaternary ammonium carboxylate salts, and boric acid. More specifically, the quaternary phosphonium salts and quaternary ammonium salts are represented by the formula [R4X + ] n Y n- In the formula, R represents an alkyl group, an aryl group, a cycloalkyl group, or an aralkyl group, which may be the same or different, X represents a phosphorus atom or a nitrogen atom, and Y represents a halogen atom or a carboxylic acid group. In the above formula, examples of the alkyl group represented by R include linear or branched unsubstituted or hydroxyl-substituted alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, 2-hydroxyethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, octyl, and stearyl groups. Preferred alkyl groups include linear or branched unsubstituted or hydroxyl-substituted alkyl groups having 1 to 6 carbon atoms. Examples of the aryl group include aryl groups having 6 to 20 carbon atoms, such as phenyl and naphthyl groups. Examples of the cycloalkyl group include cycloalkyl groups having 4 to 10 carbon atoms, such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Examples of the aralkyl group include aralkyl groups having 7 to 14 carbon atoms, such as benzyl, phenethyl, and benzhydryl groups. n is an integer of 1 to 6. In the above formula, the halogen atom represented by Y includes chlorine, bromine and iodine atoms, and the carboxylic acid group includes carboxylic acids such as formic acid, acetic acid, propionic acid, oxalic acid and citric acid. For example, at least one compound selected from the group consisting of ethyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, choline acetate, choline chloride, and orthoboric acid is preferred. These binders may also be used in combination, and it is particularly preferable to use a quaternary onium salt in combination with boric acid.

[0027] In the polyacetal resin composition of the present embodiment, 0.001 to 2 parts by mass of (C) binder is contained per 100 parts by mass of (A) polyacetal resin, but if it is less than 0.001 part by mass, the improvement of the interface adhesion between (A) polyacetal resin and (B) modified cross section glass fiber becomes insufficient, and if it exceeds 2 parts by mass, foaming of strands occurs during melt kneading, formaldehyde odor occurs, and the color of the molded product deteriorates. The content of (C) binder is preferably 0.005 to 0.5 parts by mass, more preferably 0.003 to 0.3 parts by mass.

[0028] [(D) Triazine derivatives having nitrogen-containing functional groups] The polyacetal resin composition of the present embodiment preferably further contains 0.002 to 10 parts by mass of (D) a triazine derivative having a nitrogen-containing functional group, based on 100 parts by mass of (A) the polyacetal resin. By containing (D) a triazine derivative having a nitrogen-containing functional group, creep resistance can be significantly improved.

[0029] In the present embodiment, the (D) triazine derivative having a nitrogen-containing functional group is preferably at least one compound selected from the group consisting of melamine, a melamine formaldehyde adduct, and benzoguanamine.

[0030] In the polyacetal resin composition of the present embodiment, the content of the (D) triazine derivative having a nitrogen-containing functional group per 100 parts by mass of the (A) polyacetal resin is preferably 0.005 to 1 part by mass, and more preferably 0.01 to 0.5 part by mass.

[0031] [Other stabilizers and additives] The polyacetal resin composition of the present embodiment may further contain various known stabilizers to enhance its stability, and may further contain various known additives to improve its physical properties depending on the intended use.

[0032] Examples of additives include various stabilizers (antioxidants, anti-acid agents, etc.), ultraviolet absorbers, light stabilizers, formaldehyde scavengers, colorants (carbon black, etc.), release agents, nucleating agents, antistatic agents, sliding agents, other surfactants, heterogeneous polymers, etc. In addition, fibrous, powdery, or plate-like fillers such as circular cross-section glass fibers, inorganic, organic, or metallic fillers may be used alone or in combination, so long as they do not significantly impair the performance of the composition of the present embodiment.

[0033] [Preparation of polyacetal resin composition] The polyacetal resin composition according to the present embodiment can be easily prepared by a known method generally used for preparing conventional resin compositions. For example, (1) a method of mixing all the components constituting the composition, feeding the mixture to an extruder and melt-kneading the mixture to obtain a pellet-shaped composition, (2) a method of feeding a part of the components constituting the composition from the main feed port of an extruder and the remaining components from a side feed port, melt-kneading the mixture to obtain a pellet-shaped composition, or (3) a method of preparing pellets having different compositions by extrusion or the like, mixing the pellets to adjust the composition to a desired composition, etc. can be adopted.

[0034] <Molded products> The molded article of the present embodiment is obtained by molding the polyacetal resin composition. The method for producing the molded article using the polyacetal resin composition of the present embodiment is not particularly limited, and a known method can be adopted. For example, the polyacetal resin composition of the present embodiment can be produced by feeding the polyacetal resin composition of the present embodiment into an extruder, melt-kneading the composition to form pellets, feeding the pellets into an injection molding machine equipped with a predetermined mold, and injection molding the composition.

[0035] Examples of molded products of this embodiment include automobile parts such as door locks, door handles, window regulators (carrier plates), power window switch housing parts, and other door-related parts; seat belt peripheral parts such as seat belt slip rings and press buttons; pulleys, wiper device parts; sunroof device parts; convenience store switch parts: parts such as clips; fuel-related parts such as fuel pump modules, valves, and gasoline tank flanges; office automation parts such as printer and copier parts, personal computer parts such as keyboard parts (plunger parts), communication equipment parts such as mobile phone and facsimile parts, electrical equipment parts, and electronic equipment parts. EXAMPLES

[0036] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0037] [Examples 1 to 17, Comparative Examples 1 to 9] In each of the Examples and Comparative Examples, 100 parts by mass of (A) polyacetal resin was mixed with (B) glass fiber, (C) binder, and (D) triazine derivative having a nitrogen-containing functional group (excluding Examples 1 to 3) in the amounts (parts by mass) shown in Tables 1 to 3, and melt-kneaded in an extruder with a cylinder temperature of 200°C to prepare a pellet-shaped polyacetal resin composition.

[0038] The materials used in Tables 1 to 3 are as follows. The units for the compositions are parts by mass. (A) Polyacetal resin (A-1) Polyacetal resin (polyacetal copolymer (POM) obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane, melt flow value (measured in accordance with ISO133 at 190°C and a load of 2160 g): 45 g / 10 min) (A-2) Polyacetal resin (polyacetal copolymer (POM) obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane, melt flow value (measured in accordance with ISO113 at 190°C and a load of 2160 g): 9 g / 10 min)

[0039] (B) Irregular cross-section glass fiber (B-1) Irregular cross-section glass fiber (manufactured by Nitto Boseki Co., Ltd., chopped strand, oval FF, long diameter / short diameter ratio: 4, short diameter = 7 μm) (B-2) Irregular cross-section glass fiber (manufactured by Nitto Boseki Co., Ltd., chopped strand, oval FF, long diameter / short diameter ratio: 6, short diameter = 5.5 μm) (B-3) Irregular cross-section glass fiber (Nippon Electric Glass Co., Ltd., chopped strand, oval FGF, long diameter / short diameter ratio: 4, short diameter = 7 μm) (B-4) Irregular cross-section glass fiber (manufactured by Nitto Boseki Co., Ltd., chopped strand, cocoon-shaped HIS, long diameter / short diameter ratio: 2, short diameter = 10 μm) (B'-1) Circular glass fiber (Owens Corning, chopped strand, long diameter / short diameter ratio: 1, single fiber diameter = 13 μm)

[0040] (C) Binder (C-1) Ethyltriphenylphosphonium bromide (C-2) Tetraphenylphosphonium bromide (C-3) Choline Acetate (C-4) Choline chloride (C-5) Orthoboric acid

[0041] (D) Triazine derivatives having nitrogen-containing functional groups (D-1) Melamine (D-2) Melamine formaldehyde adduct (Nikaredin S-260, manufactured by Nippon Carbide Industries Co., Ltd.) (D-3) Benzoguanamine

[0042] <Physical property evaluation> Using the pellet-shaped compositions prepared in each of the Examples and Comparative Examples, test pieces were molded in an injection molding machine in accordance with ISO3167. Then, measurements were carried out for tensile strength in accordance with ISO527-1,2, bending strength in accordance with ISO178, and Charpy impact strength (notched, 23°C) in accordance with ISO179·1eA. The measurement atmosphere was 23°C and 50% RH. The evaluation results are shown in Tables 1 to 3.

[0043] <Creep resistance evaluation> Using a tensile test piece conforming to ISO 1367, a load of 40 MPa was applied at 80° C. in air under high temperature and high load conditions in a creep tester, and the time until the test piece broke was measured. The evaluation results are shown in Tables 1 to 3.

[0044] <Flatness evaluation> A 120 mm square flat test piece (2 mm thick) was molded, placed on a flat surface plate, and the maximum deformation of the test piece (where the gap between the surface plate and the test piece was the largest) was measured as the amount of deformation. The evaluation results are shown in Tables 1 to 3.

[0045] <Mold shrinkage evaluation> After molding a 120 mm square flat plate-shaped test piece (thickness 2 mm), the mold shrinkage rate (%) was measured in the resin flow direction and in the direction perpendicular to the resin flow direction (referred to as the perpendicular direction in the table). The evaluation results are shown in Tables 1 to 3.

[0046] [Table 1]

[0047] [Table 2]

[0048] [Table 3]

[0049] It can be seen from Tables 1 to 3 that good results were obtained in all evaluations in Examples 1 to 17. In contrast, in Comparative Examples 1 to 5 and 9, which used glass fibers with a circular cross section, all evaluation results were inferior to Examples 1 to 17. In addition, Comparative Examples 6 to 8, which did not use the (C) binder, were inferior in physical properties and creep resistance.

Claims

1. (A) per 100 parts by mass of polyacetal resin, (B) 1 to 100 parts by mass of irregular cross section glass fiber; (C) 0.001 to 2 parts by mass of one or more binders selected from the group consisting of quaternary onium salt compounds and boric acid compounds.

2. 2. The polyacetal resin composition according to claim 1, wherein the irregular cross section glass fiber (B) is a glass fiber having a flat cross section in which the ratio of the major axis of the cross section to the minor axis of the cross section (irregularity ratio) is 1.2 or more.

3. 3. The polyacetal resin composition according to claim 1, wherein the binder (C) is at least one compound selected from the group consisting of quaternary onium halide salts and quaternary onium carboxylate salts.

4. 3. The polyacetal resin composition according to claim 1, wherein the binder (C) is at least one compound selected from the group consisting of a quaternary phosphonium halide, a quaternary ammonium halide, a quaternary phosphonium carboxylate, a quaternary ammonium carboxylate, and boric acid.

5. 3. The polyacetal resin composition according to claim 1, wherein the binder (C) is at least one compound selected from the group consisting of ethyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, choline acetate, choline chloride, and orthoboric acid.

6. 3. The polyacetal resin composition according to claim 1, further comprising: (D) 0.002 to 10 parts by mass of a triazine derivative having a nitrogen-containing functional group.

7. 7. The polyacetal resin composition according to claim 6, wherein the (D) triazine derivative having a nitrogen-containing functional group is at least one compound selected from the group consisting of melamine, a melamine formaldehyde adduct, and benzoguanamine.

8. A molded article obtained by molding the polyacetal resin composition according to claim 1 or 2.

Images