JP2020105281A - Resin composition and its molding - Google Patents

Abstract

To provide a resin composition which suppresses a fluctuation range of a coefficient of friction.SOLUTION: A resin composition contains, with respect to (A) 100 pts.mass of a polyacetal resin, at least (B) 0.01-1 pts.mass of a fatty acid metal salt and (C) 0.1-3 pts.mass of a zinc oxide, and has a melt flow rate (according to ISO 1133, 190°C and load of 2.16 kg) of 26-35 g/10 minutes.SELECTED DRAWING: None

Description

The present invention relates to a polyacetal resin composition and a molded product containing the same.

Polyacetal resin is widely used as an engineering resin having well-balanced mechanical properties and excellent friction and wear properties for various mechanical parts, OA equipment and the like. In automotive applications, improvement in heat resistance and acid resistance is required. Regarding the improvement of acid resistance of polyacetal resin, some disclosures have been made in the past. For example, a method of adding zinc oxide and polyalkylene glycol to a polyacetal resin in order to improve toughness and fuel resistance is disclosed (see, for example, Patent Documents 1 and 2).

JP, 2001-011284, A International Publication No. 2016-104255

However, the polyacetal resin composition containing zinc oxide has a problem that the wear coefficient cannot be kept constant. Furthermore, in recent years, the reduction of grease and the reduction in thickness have been progressing. For example, mechanical parts such as gears of printers are required to have stable slidability without using grease. Further, in thinning, high rigidity is required from the viewpoint of reliability as a material.
Therefore, an object of the present invention is to provide a polyacetal resin composition that suppresses the fluctuation range of the friction coefficient and is excellent in rigidity.

The present inventors have conducted extensive studies to solve the above-mentioned problems of the prior art, and in a resin composition comprising a polyacetal resin, a fatty acid metal salt, and zinc oxide, a polyacetal resin is used in combination with a fatty acid metal salt and zinc oxide. The inventors have found that the above conventional problems can be solved by specifying the MFR of the resin composition, and have completed the present invention.

That is, this embodiment is as follows.
[1] The melt flow rate (containing at least 0.01 to 1 part by mass of (B) fatty acid metal salt and (C) 0.1 to 3 parts by mass of (A) polyacetal resin (A) per 100 parts by mass of melt flow rate ( A resin composition according to ISO 1133, 190°C, 2.16 kg load) of 26 to 35 g/10 minutes.
[2] The resin composition according to [1], wherein the mass ratio of the (B) fatty acid metal salt to the (C) zinc oxide is 0.053 to 1.000.
[3] The resin composition according to [2], wherein the mass ratio of the (B) fatty acid metal salt to the (C) zinc oxide is 0.250 to 0.667.
[4] The resin composition according to any one of [1] to [3], wherein the fatty acid metal salt (B) is at least one selected from the group consisting of calcium stearate and zinc stearate.
[5] The resin composition according to any one of [1] to [4], wherein the (C) zinc oxide has an average primary particle size of 0.3 to 0.8 μm.
[6] The total amount of the (B) fatty acid metal salt and the (C) zinc oxide is 0.6 to 1.4 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin, [1] ~ The resin composition according to any one of [5].
[7] A molded product containing the polyacetal resin composition according to any one of [1] to [6].

According to the resin composition of the present invention, it is possible to provide a polyacetal resin composition having stable slidability and excellent in molding stability.

Hereinafter, modes for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and the present invention is not limited to the following contents. The present invention can be implemented with various changes within the scope of the gist thereof.

[Resin composition]
The resin composition of the present embodiment is a resin composition containing at least (A) a polyacetal resin, (B) a fatty acid metal salt, and (C) zinc oxide, and having an MFR of 26 to 35 g/10 minutes.

<(A) Polyacetal resin>
Examples of the (A) polyacetal resin according to the present embodiment include polyacetal homopolymers and polyacetal copolymers, and known ones may be used.
The polyacetal homopolymer is obtained by homopolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) and a tetramer (tetraoxane) thereof. Thus, the polyacetal homopolymer consists essentially of oxymethylene units.
The polyacetal copolymer is a formaldehyde monomer or a cyclic oligomer of formaldehyde such as trimer (trioxane) and tetramer (tetraoxane) thereof, ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, 1,4- It is obtained by copolymerizing a cyclic ether or cyclic formal such as cyclic formal of glycol or diglycol such as butanediol formal. Further, as a polyacetal copolymer, a polyacetal copolymer having a branch obtained by copolymerizing a monomer of formaldehyde and/or a cyclic oligomer of formaldehyde, and a monofunctional glycidyl ether, and a polyfunctional glycidyl ether are copolymerized. The resulting polyacetal copolymer having a crosslinked structure can also be used.

Furthermore, the (A) polyacetal resin is obtained by polymerizing a formaldehyde monomer or a formaldehyde cyclic oligomer in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, polyalkylene glycol. It may be a polyacetal homopolymer having a block component.

Similarly, the (A) polyacetal resin is a formaldehyde monomer or its trimer (trioxane) and tetramer in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, hydrogenated polybutadiene glycol. It may be a polyacetal copolymer having a block component obtained by copolymerizing a cyclic oligomer of formaldehyde such as a compound (tetraoxane) with a cyclic ether or cyclic formal.

As described above, both the polyacetal homopolymer and the polyacetal copolymer can be used as the (A) polyacetal resin according to the present embodiment. Moreover, these (A) polyacetal resins are used individually by 1 type or in combination of 2 or more types. In this case, the (A) polyacetal resin preferably contains 50% by mass or more of the polyacetal copolymer, more preferably 80% by mass or more, and substantially all (95% by mass or more) is the polyacetal copolymer. Most preferred. The percentage here is based on 100% by mass of the total amount of the (A) polyacetal resin.

The method for obtaining the polyacetal copolymer will be described in detail below.

When a polyacetal copolymer is obtained using trioxane, the comonomer such as 1,3-dioxolane is generally 0.1 to 60 mol%, preferably 0.1 to 20 mol%, more preferably 100 mol% of trioxane. Is used in an amount of 0.13 to 10 mol %. As the polymerization catalyst used for the polymerization of the polyacetal copolymer, cationic active catalysts such as Lewis acid, protic acid and its ester or anhydride are preferable. Examples of the Lewis acid include boric acid, tin, titanium, phosphorus, arsenic and antimony halides, and more specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, Examples thereof include phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof. Further, specific examples of the protonic acid, its ester or anhydride include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate and trimethyloxonium hexafluorophosphate. Among these, boron trifluoride; boron trifluoride hydrate; and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable, and specifically, trifluoride Boron diethyl ether and boron trifluoride di-n-butyl ether are mentioned as suitable examples.

Further, when obtaining the polyacetal copolymer, a polymerization chain agent (chain transfer agent) such as methylal may be appropriately used in addition to the polymerization catalyst. Further, when using methylal, the content of water content is 100 mass ppm or less and the content of methanol content is 1 mass% or less, more preferably the content of water content is 50 mass ppm or less and the content content of methanol is 0.7 mass% or less. Methylal is preferred.

The polyacetal copolymer is a conventionally known method, for example, U.S. Pat. No. 3,027,352, U.S. Pat. No. 3,803,094, German Patent Invention No. 11614121, No. 1495228, No. 1720358, Polymerization can be carried out by the methods described in JP-A-3018898, JP-A-58-98322 and JP-A-7-70267. The polyacetal copolymer obtained by the above-mentioned polymerization may have a thermally unstable terminal part (-(OCH2)n-OH group; hereinafter referred to as "unstable terminal part").

Therefore, it is preferable to carry out the decomposition removal treatment (end stabilization) of the unstable end portion by using an end stabilizer. The end stabilizer is not particularly limited, ammonia, triethylamine, aliphatic amine compounds such as tributylamine, sodium, potassium, magnesium, hydroxide of alkali metal or alkaline earth metal such as calcium or barium, carbonate, Inorganic weak acid salts of alkali or alkaline earth metals, such as phosphates, silicates and borates, formates, acetates, stearates, palmitates, propionates and oxalates. Such a basic substance such as an organic acid salt of an alkali metal or an alkaline earth metal can be mentioned, and of these, an aliphatic amine compound is preferable, and triethylamine is more preferable.

The method for decomposing and removing the unstable terminal portion is not particularly limited, and, for example, a state in which the polyacetal copolymer is melted at a temperature of not lower than the melting point of the polyacetal copolymer and not higher than 260° C. in the presence of a terminal stabilizer such as triethylamine The method of heat-treating can be mentioned. Examples of the heat treatment method include a single-screw or twin-screw extruder equipped with a vent pressure reducing device, and preferably a twin-screw extruder.

Further, the melt flow rate (ISO 1133 compliant, 190° C., 2.16 kg load) of the (A) polyacetal resin used in the present embodiment is preferably 25 to 35 g/10 minutes, more preferably from the viewpoint of stable slidability. It is in the range of 26 to 33 g/10 minutes. As a method for obtaining the (A) polyacetal resin having an MFR within the above range, specifically, in the production of the polyacetal resin, adjustment of the addition amount of a chain transfer agent typified by methylal and the like can be mentioned. ..

In the present embodiment, the content of the (A) polyacetal resin in the resin composition (100% by mass) is
It may be 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more.

<(B) Fatty acid metal salt>
Examples of the (B) aliphatic metal salt according to the present embodiment include saturated or unsaturated fatty acids having 10 to 35 carbon atoms or fatty acids substituted with a hydroxyl group, and hydroxides and oxides of alkali metals or alkaline earth metals. It is a fatty acid metal salt obtained from a salt or a chloride.

The amount of the fatty acid metal salt added is 0.01 to 1 part by mass, preferably 0.25 to 0.7 part by mass, and more preferably 0.3 to 0.5, with respect to 100 parts by mass of the polyacetal resin. Parts by weight, most preferably 0.3 to 0.4 parts by weight.

Raw material fatty acids of fatty acid metal salts are capric acid, undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecylic acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, reglyceric acid, cerotic acid. , Heptacosanoic acid, montanic acid, melissic acid, laxeric acid, undecylenic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propioic acid, stearo- Acid, 12-hydroxydodecanoic acid, 3-hydroxydecanoic acid, 16-hydroxyhexadecanoic acid, 10-hydroxyhexadecanoic acid, 12-hydroxyoctadecanoic acid, 10-hydroxy-8-octadecanoic acid, dl-erythro-9.10- Examples of the starting metal compound include dihydroxyoctadecanoic acid, and alkali metal such as sodium, lithium, potassium and calcium, magnesium, barium, zinc, aluminum and strontium, and hydroxide or chloride of alkaline earth metal.

Of these, preferably, the starting fatty acids of the fatty acid metal salt are myristic acid, palmitic acid, and stearic acid, and the starting metal compound is calcium hydroxide, oxide, and chloride.
Examples of specific fatty acid metal salts are calcium myristate, calcium palmitate, calcium stearate, (myristic acid-palmitic acid) calcium, (myristic acid-stearic acid) calcium, and (palmitic acid-stearic acid) calcium. .. Of these, calcium palmitate and calcium stearate are preferable.

Further, preferably, the starting fatty acid of the fatty acid metal salt is myristic acid, palmitic acid, and stearic acid, and the starting metal compound is zinc hydroxide, oxide, and chloride.
Examples of specific fatty acid metal salts are zinc myristate, zinc palmitate, zinc stearate (myristic acid-palmitic acid) zinc, (myristic acid-stearic acid) zinc, and (palmitic acid-stearic acid) zinc. .. Of these, zinc palmitate and zinc stearate are preferable.

In the present embodiment, two or more kinds of fatty acid metal salts, for example, calcium stearate and calcium palmitate may be added at the same time, and a metal salt composed of fatty acids having different carbon numbers, for example, (palmitic acid-stearic acid). Calcium may be mixed, and a metal salt composed of different metals, for example, calcium stearate and zinc stearate may be mixed.

The above fatty acid metal salts may be used alone or in combination of two or more.

<(C) Zinc oxide>
The zinc oxide (C) in the present embodiment is not limited to a production method, but is industrially a white powder produced by a dry method or a wet method.

The amount of zinc oxide (C) added is 0.1 to 3 parts by mass, preferably 0.2 to 0.9 parts by mass, and more preferably 0.5 to 0, with respect to 100 parts by mass of the polyacetal resin. 0.8 parts by mass. When the content of (C) zinc oxide is 0.1 to 3 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin, excellent toughness is obtained in the polyacetal resin composition of the present embodiment.

As the zinc oxide (C), zinc oxide having an average primary particle size of 0.07 to 1.0 μm, preferably 0.3 to 0.8 μm, and more preferably 0.4 to 0.7 μm is used. To use. By using (C) zinc oxide having an average primary particle size within the above range, stable slidability can be obtained in the polyacetal resin composition of the present embodiment. The reason why excellent balance between toughness and rigidity can be obtained by setting the average primary particle diameter of (C) zinc oxide within the above-mentioned specific numerical range is that dispersibility in the polyacetal resin composition is improved. It is thought to be because (but the effect is not limited to this).
The average primary particle size of (C) zinc oxide can be measured by a laser diffraction particle size distribution measuring device (for example, model number: SALD-2300 manufactured by Shimadzu Corporation).

The polyacetal resin composition of the present embodiment is composed of the above-mentioned components (A) to (C) as basic components.

In the present embodiment, from the viewpoint of the variation of the sliding coefficient, the melt flow rate (ISO 1133 compliant, 190° C., 2.16 kg load) of the polyacetal resin composition is 26 to 35 g/10 minutes, more preferably 27 to 34 g/. It is 10 minutes, particularly preferably 27 to 33 g/10 minutes.

In the present embodiment, regarding the polyacetal resin composition, when the mating material is SUS sphere (for example, SUS304, diameter 5 mm), the variation ratio of friction coefficient (friction coefficient variation value) from the start of sliding to the end of sliding. Is preferably 1 to 3, more preferably 1 to 2.
The friction coefficient variation value may be calculated by the following formula.
Friction coefficient fluctuation value=maximum friction coefficient/minimum friction coefficient Further, the friction coefficient fluctuation value can be specifically measured by the method described in Examples.

In this embodiment, the polyacetal resin composition has a standard deviation of plasticization time stability when 50 shot molding is performed on a test piece having a thickness of 4 mm (for example, under conditions of injection and pressure holding time of 30 seconds and cooling time of 15 seconds). Is preferably 0.1 to 0.4, and more preferably 0.2 to 0.3. When the standard deviation of the depopulation time stability is within the above range, a molded product with little variation in physical properties can be obtained.
The plasticization time stability can be specifically measured by the method described in Examples.

In this embodiment, the mass ratio of the (B) fatty acid metal salt to the (C) zinc oxide is 0.053 to 1.000, preferably 0.250 to 1 from the viewpoint of toughness/rigidity balance and slidability. .000, more preferably 0.429 to 0.818, and most preferably 0.429 to 0.667.

In addition, from the viewpoint of rigidity and/or molding stability of the obtained resin composition, the total amount of the (B) fatty acid metal salt and (C) zinc oxide is 0. The amount is preferably 6 to 1.4 parts by mass, more preferably 0.6 to 1.3 parts by mass, and most preferably 0.8 to 1.1 parts by mass.

<Stabilizer>
The polyacetal resin composition of the present embodiment may contain various stabilizers conventionally used in polyacetal resin compositions as long as the object of the present invention is not impaired. Specific examples of the stabilizer include the following antioxidants and formaldehyde or formic acid scavengers. These may be used alone or in combination of two or more.

As the antioxidant, a hindered phenol-based antioxidant is preferable from the viewpoint of improving the thermal stability of the polyacetal resin composition.

Specific examples of the hindered phenol antioxidant include n-octadecyl-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)-propionate and n-octadecyl-3-(3. '-Methyl-5'-t-butyl-4'-hydroxyphenyl)-propionate, n-tetradecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate, 1, 6-hexanediol-bis-(3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate), 1,4-butanediol-bis-(3-(3,5-di-t) -Butyl-4-hydroxyphenyl)-propionate), triethylene glycol-bis-(3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate) and the like.

In addition, as the hindered phenol-based antioxidant other than the above, tetrakis-(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate methane, 3,9- Bis(2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro(5,5 ) Undecane, N,N'-bis-3-(3',5'-di-t-butyl-4-hydroxyphenol) prepionylhexamethylenediamine, N,N'-tetramethylenebis-3-(3 '-Methyl-5'-t-butyl-4-hydroxyphenol)propionyldiamine, N,N'-bis-(3-(3,5-di-t-butyl-4-hydroxyphenol)propionyl)hydrazine, N -Salicyloyl-N'-salicylidenehydrazine, 3-(N-salicyloyl)amino-1,2,4-triazole, N,N'-bis(2-(3-(3,5-di-butyl-4 -Hydroxyphenyl)propionyloxy)ethyl)oxyamide and the like can also be mentioned.

Among the hindered phenolic antioxidants described above, from the viewpoint of improving the thermal stability of the polyacetal resin composition, triethylene glycol-bis-(3-(3-t-butyl-5-methyl-4-hydroxyphenyl)). -Propionate), tetrakis-(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate)methane are preferred.

Specific examples of formaldehyde or formic acid scavengers include compounds containing formaldehyde-reactive nitrogen and polymers thereof, alkali metal or alkaline earth metal hydroxides, inorganic acid salts, and carboxylate salts.

Specific examples of the compound containing formaldehyde-reactive nitrogen and a polymer thereof include dicyandiamide, melamine, a cocondensate of melamine and formaldehyde, nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon. Polyamide resins such as 6-12, nylon 12, nylon 6/6-6, nylon 6/6-6/6-10 and nylon 6/6-12, poly-β-alanine, polyacrylamide and the like can be mentioned. Among these, a cocondensate of melamine and formaldehyde, a polyamide resin, poly-β-alanine and polyacrylamide are preferable, and from the viewpoint of improving the thermal stability of the polyacetal resin composition, the polyamide resin and poly-β-alanine are More preferable.

Specific examples of the alkali metal or alkaline earth metal hydroxides, inorganic acid salts, and carboxylates include hydroxides of sodium, potassium, magnesium, calcium, barium, and the like, carbonates of the above metals, and phosphoric acid. Examples thereof include salts, silicates, borates, and carboxylates. From the viewpoint of improving the thermal stability of the polyacetal resin composition, calcium salt is preferable. Specific examples of calcium salts include calcium hydroxide, calcium carbonate, calcium phosphate, calcium silicate, calcium borate, and fatty acid calcium salts (calcium stearate, calcium myristate, etc.), and these fatty acids are substituted with hydroxyl groups. It may have been done. Among these, fatty acid calcium salts (calcium stearate, calcium myristate, etc.) are more preferable from the viewpoint of improving the thermal stability of the polyacetal resin composition.

A preferred combination of the above-mentioned various stabilizers is triethylene glycol-bis-(3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate from the viewpoint of improving the thermal stability of the polyacetal resin composition. ) Or tetrakis-(methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate)methane, a hindered phenolic antioxidant, a polyamide resin and poly-β. A combination of a polymer containing formaldehyde reactive nitrogen represented by alanine and a fatty acid salt of an alkaline earth metal represented by fatty acid calcium salt.

The content of each of the above-mentioned stabilizers is, for example, 0.1 part by mass or more and 2 parts by mass or less of a hindered phenol-based antioxidant, formaldehyde or the like as an antioxidant, relative to 100 parts by mass of the (A) polyacetal resin. As formic acid scavengers, for example, the polymer containing formaldehyde-reactive nitrogen is in the range of 0.1 parts by mass or more and 3 parts by mass or less, and the fatty acid salt of alkaline earth metal is in the range of 0.1 parts by mass or more and 1 part by mass or less. And preferred.

<Additive>
The polyacetal resin composition of the present embodiment may contain various additives conventionally used in the polyacetal resin composition within a range not impairing the object of the present invention and depending on desired properties. Specific examples of the additives include the following inorganic fillers, crystal nucleating agents, thermoplastic resins, thermoplastic elastomers and pigments. These may be used alone or in combination of two or more.

As the inorganic filler, specifically, a fibrous, powdery particle, plate, hollow or the like filler is used.
As the fibrous filler, specifically, glass fiber, carbon fiber, silicone fiber, silica/alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber; stainless steel, aluminum, titanium, Examples include inorganic fibers such as metal fibers such as copper and brass. In addition, whiskers such as potassium titanate whiskers and zinc oxide whiskers having a short fiber length; high-melting organic fibrous substances such as aromatic polyamide resins, fluororesins, acrylic resins and the like can also be mentioned.
As the powdery particulate filler, specifically, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, silicates such as wollastonite, iron oxide, titanium oxide, Examples thereof include metal oxides such as alumina, metal sulfates such as calcium sulfate and barium sulfate, carbonates such as magnesium carbonate and dolomite, silicon carbide, silicon nitride, boron nitride, and various metal powders.
Specific examples of the plate-like filler include mica, flake-shaped glass, various metal foils and the like.
Specific examples of the hollow filler include glass balloons, silica balloons, shirasu balloons, metal balloons and the like.
These inorganic fillers may be used alone or in combination of two or more.
These inorganic fillers may be surface-treated, non-surface-treated, and any of them may be used, but from the viewpoint of surface smoothness and mechanical properties of a molded article containing a polyacetal resin composition, surface treatment In some cases, the applied one is preferable.
As the surface treating agent, conventionally known ones can be used, and specific examples thereof include various coupling treating agents such as silane type, titanate type, aluminum type and zirconium type. As the coupling agent, specifically, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltrisstearoyl titanate, diisopropoxyammonium ethyl acetate, Examples thereof include n-butyl zirconate.
The inorganic filler is preferably 0.1 parts by mass or more and 200 parts by mass or less, more preferably 0.5 parts by mass or more and 100 parts by mass or less, and more preferably 1 part by mass with respect to 100 parts by mass of the polyacetal resin (A). It is more preferable that the amount is not less than 50 parts by mass.

Specific examples of the crystal nucleating agent include boron nitride and the like. The crystal nucleating agent is preferably 0.001 part by mass or more and 10 parts by mass or less, more preferably 0.003 parts by mass or more and 7 parts by mass or less, and 0 with respect to 100 parts by mass of the polyacetal resin (A). It is more preferably 0.005 parts by mass or more and 5 parts by mass or less.

Specific examples of the thermoplastic resin include olefin resins other than those listed as the component (C), and more specifically, the olefin compound represented by the general formula (3) as a whole monomer. Examples thereof include a copolymer, a styrene resin, a polycarbonate resin, etc., which is contained in the range of less than 40 mol% with respect to the unit. Moreover, these modified products are also mentioned. The thermoplastic resin is preferably 0.1 parts by mass or more and 200 parts by mass or less, more preferably 0.3 parts by mass or more and 150 parts by mass or less, and more preferably 0 parts by mass to 100 parts by mass of the polyacetal resin (A). More preferably, it is not less than 0.5 parts by mass and not more than 100 parts by mass.

Specific examples of the thermoplastic elastomer include styrene elastomer, polybutadiene, polyisoprene, ethylene-propylene rubber, acrylic rubber, and chlorinated polyethylene. The thermoplastic elastomer is preferably 0.1 part by mass or more and 200 parts by mass or less, more preferably 0.3 parts by mass or more and 150 parts by mass or less, and 0, based on 100 parts by mass of the polyacetal resin (A). More preferably, it is not less than 0.5 parts by mass and not more than 100 parts by mass.

Specific examples of the pigment include inorganic pigments, organic pigments, metallic pigments, and fluorescent pigments. Inorganic pigments are those generally used for coloring resins, and specifically, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, ignited pigments, carbonates, phosphorus. Acid salts, acetate salts; carbon black, acetylene black, lamp black and the like. Specific examples of the organic pigments include condensed azo pigments, inone pigments, flotacyanine pigments, monoazo pigments, diazo pigments, polyazo pigments, anthraquinone pigments, heterocyclic pigments, pennon pigments, quinacridone pigments, thioindico pigments, berylylene pigments, and dioxazine pigments. Examples thereof include pigments such as pigments and phthalocyanine pigments. The amount of the pigment can be selected according to the desired color tone, but is preferably in the range of 0.05 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the (A) polyacetal resin.

[Method for producing polyacetal resin composition]
The polyacetal resin composition of the present embodiment can be produced by melt-kneading the above-mentioned (A) polyacetal resin, (B) fatty acid metal salt, (C) zinc oxide and, if necessary, other components.
As a device for producing the polyacetal resin composition of the present embodiment, a kneading machine which is generally used can be applied. Specific examples of the kneader include a single-screw or multi-screw kneading extruder, a roll, and a Banbury mixer. Among these, a single screw extruder and a twin screw extruder are preferable.
As the melt-kneading method, specifically, a method in which a blended product of all components is continuously fed from an extruder top feeder (hereinafter referred to as a top feeder) and melt-kneaded, and (C) zinc oxide other than A blend of the components is continuously fed from an extruder top feeder and melt-kneaded, and then (C) zinc oxide is continuously fed from a feeder (hereinafter referred to as a side feeder) provided on the side of the extruder. Then, a method of further melt-kneading can be mentioned, and any of them can be used without any problem.

[Molded body]
The molded product of the present embodiment contains the above-mentioned polyacetal resin composition. For that purpose, the molded product of the present embodiment can be obtained by molding the above-mentioned polyacetal resin composition. The method for molding the polyacetal resin composition is not particularly limited, and a known molding method can be applied. Specifically, extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, other material molding, gas assist injection molding, foam injection molding, low pressure molding, ultra-thin wall injection molding (ultra high-speed injection). Molding), in-mold composite molding (insert molding, outsert molding) and the like.

[Uses of molded products]
The applications of the molded body of the present embodiment include cams, sliders, levers, arms, clutches, felt clutches, idler gears, pulleys, rollers, rollers, key stems, key tops, shutters, reels, shafts, joints, shafts, bearings, Mechanical parts typified by guides; outsert molding resin parts, insert molding resin parts, chassis, trays, side plates, printers, copiers, and other office automation equipment parts; VTR (Video Tape Recorder), video Movies, digital video cameras, cameras, parts for cameras or video equipment represented by digital cameras; cassette player, DAT, LD (Laser Disk), MD (Mini Disk), CD (Compact Disk) [CD-ROM (Read Only) Memory), CD-R (Recordable), CD-RW (Rewritable) are included], DVD (Digital Video Disk) [DVD-ROM, DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-R DL, DVD+R DL. , DVD-RAM (Random Access Memory) and DVD-Audio], Blu-ray (registered trademark) Disc, HD-DVD, and other optical disk drives; represented by MFD, MO, navigation system, and mobile personal computer. Examples include music, video or information equipment, parts for communication equipment typified by mobile phones and facsimiles, parts for electric equipment, parts for electronic equipment, and lamp materials for hard disk internal parts. Further, the molded body of the present embodiment is used as a part for automobiles such as gasoline tanks, fuel pump modules, valves, fuel tank flanges, and other fuel parts; door locks, door handles, window regulators, speaker grills, etc. Parts around doors; Slip rings for seat belts, Seat belt peripheral parts such as press buttons; Parts such as combination switch parts, switches, clips; Mechanical pencil tip, mechanical pencil lead Mechanism parts to be put in and taken out; washbasin, drainage port, drain plug opening and closing mechanism parts, lock mechanism for opening and closing parts of vending machines, product discharge mechanism parts; cord stoppers for clothes, adjusters, buttons; nozzles for sprinkling, sprinkling hose connection joints ; Stair railings, building materials that are the support for floor materials; Disposable cameras, toys, fasteners, chains, conveyors, buckles, sports equipment, vending machines, furniture, musical instruments, industrial parts such as housing equipment It is preferably used.

Hereinafter, the present embodiment will be specifically described with reference to Examples and Comparative Examples, but the present embodiment is not limited to the Examples and Comparative Examples described below as long as the gist thereof is not exceeded. Various measuring methods for the polyacetal resin compositions and molded articles of Examples and Comparative Examples, and raw material components of the polyacetal resin compositions and molded articles used in Examples and Comparative Examples are shown below.

(1) MFR
The MFR (g/10 minutes) of the polyacetal resin composition pellets was measured according to ISO1133 at 190° C. under a load of 2.16 kg.

(2) Evaluation method of slidability The polyacetal resin composition pellets were injection molded under the injection molding conditions of a cylinder temperature of 205°C and a mold temperature of 120°C using an EC-75NII molding machine manufactured by Toshiba Machine Co., Ltd. An ISO test piece having a thickness of 4 mm was obtained. Using a reciprocating friction and wear tester (Toyo Seimitsu Co., Ltd., trade name "AFT-15MS type"), a load of 500 g, a linear velocity of 30 mm/sec, a reciprocating distance of 20 mm, 23°C, and a humidity of 50%, 5000 times. The reciprocating test was conducted. A SUS ball (SUS304, diameter 5 mm) was used as the mating material. The fluctuation ratio of friction coefficient (friction coefficient fluctuation value) during the period from the start of sliding to the end of sliding was calculated by the following formula.
Friction coefficient fluctuation value = maximum friction coefficient / minimum friction coefficient

(3) Rigidity The polyacetal resin composition pellets were injection molded under the injection molding conditions of a cylinder temperature of 205° C. and a mold temperature of 120° C. to form a box-shaped molded product having a length of 90 mm×a width of 70 mm×a height of 35 mm. Holding both ends of the molded product, the rigidity feeling when bending deformation was applied was evaluated. The evaluation was performed according to the following criteria based on the displacement (mm) at both ends with the center of the molded product as a reference when bending deformation was applied.
++: Displacement amount 0 or more and less than 5 mm ++: Displacement amount 5 or more and less than 10 mm +: Displacement amount 10 mm or more

(4) Plasticization time stability Pellets of the polyacetal resin composition were injection molded under the injection molding conditions of a cylinder temperature of 205° C. and a mold temperature of 120° C. using an EC-75NII molding machine manufactured by Toshiba Machine Co., Ltd. 50 shots were molded into 4 mm thick ISO test pieces. At that time, the injection and pressure holding time was set to 30 seconds and the cooling time was set to 15 seconds, and the plasticization time stability was evaluated by the standard deviation. The plasticization time stability is specifically determined by the injection into the mold being completed, and while the ISO test piece is being cooled, the molten resin to be injected next is measured in the molding machine cylinder. The time until it was measured was measured, and the standard deviation was calculated from the plasticizing time for the 50 shots.

<(A) Polyacetal resin>
(A-1) Polyacetal resin MFR (conditions: ISO 1133 compliant, 190°C, 2.16 kg load) containing 1.5 mol% of 1,3-dioxolane as a copolymerization component with respect to 100 mol% of trioxane is 30 g/10 min. Polyacetal copolymer (A-2) Polyacetal resin MFR (conditions: ISO 1133 compliant, 190°C, 2.16 kg load) is 20 g/10, containing 1,3-dioxolane 1.5 mol% as a copolymerization component with respect to 100 mol% of trioxane. Min polyacetal copolymer (A-3) polyacetal resin 100 mol% of trioxane, containing 1,3-dioxolane 1.5 mol% as a copolymerization component, MFR (condition: ISO1133 compliant 190 ℃, 2.16kg load) 25g /10 min polyacetal copolymer (A-4) polyacetal resin 100 mol% of trioxane, containing 1.5 mol% of 1,3-dioxolane as a copolymerization component, MFR (conditions: ISO 1133 compliant, 190° C., 2.16 kg load) Of polyacetal copolymer (A-5) polyacetal resin (40 g/10 min) to trioxane (100 mol %) contains 1,3-dioxolane (1.5 mol %) as a copolymerization component, MFR (conditions: ISO 1133 compliant, 190° C., 2.16 kg). Polyacetal copolymer (A-6) having a load of 27 g/10 min. Polyacetal resin To 100 mol% of trioxane, MFR containing 1.5 mol% of 1,3-dioxolane as a copolymerization component (conditions: ISO 1133 compliant, 190° C., 2 Polyacetal copolymer with a load of 16 kg) of 34 g/10 min

<(B) Fatty acid metal salt>
(B-1) calcium stearate

<(C) Zinc oxide>
(C-1) Zinc oxide (average primary particle size: 0.53 μm)
(C-2) Zinc oxide (average primary particle size: 0.17 μm)

[Production of polyacetal resin composition]
In this example, a twin-screw extruder (TEM-26SS manufactured by Toshiba Machine Co., Ltd.) was used to set the cylinder temperature to 200° C., and the components (A) to (C) were quantified from the extruder main throat. It was supplied from a feeder, the resin kneaded material was extruded in a strand shape under the conditions of an extrusion rate of 15 kg/hour and a screw rotation speed of 150 rpm, quenched in a strand bath, and cut by a strand cutter to obtain pellets. Each physical property of the obtained resin composition was evaluated. The evaluation results are shown in Table 1.

[Examples 1 to 10, Comparative Examples 1 to 9]
The respective components were blended in the proportions shown in Table 1 and melt-kneaded by the above-mentioned manufacturing method. The obtained pellets were used for evaluation by the method described above. The measurement and evaluation results are shown in Table 1.

According to the polyacetal resin composition of the present invention, in various fields where the polyacetal resin composition has been preferably used, since it can be used as a metal substitute for cost reduction and weight reduction, automobiles, precision of electrical and electronic equipment It has industrial applicability in fields such as parts and other industries.

Claims (7)

Melt flow rate (according to ISO 1133, containing at least 0.01 to 1 part by mass of fatty acid metal salt (B) and 0.1 to 3 parts by mass of zinc oxide (C) with respect to 100 parts by mass of (A) polyacetal resin. A resin composition having a temperature of 190° C. and a load of 2.16 kg of 26 to 35 g/10 minutes. The resin composition according to claim 1, wherein the mass ratio of the (B) fatty acid metal salt to the (C) zinc oxide is 0.053 to 1.000. The resin composition according to claim 2, wherein the mass ratio of the (B) fatty acid metal salt to the (C) zinc oxide is 0.250 to 0.667. The resin composition according to any one of claims 1 to 3, wherein the (B) fatty acid metal salt is at least one selected from the group consisting of calcium stearate and zinc stearate. The resin composition according to any one of claims 1 to 4, wherein the (C) zinc oxide has an average primary particle size of 0.3 to 0.8 µm. Any of claims 1 to 5, wherein the total amount of the (B) fatty acid metal salt and the (C) zinc oxide is 0.6 to 1.4 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. The resin composition according to 1 above. A molded article comprising the polyacetal resin composition according to claim 1.