JP6041529B2 - Polyoxymethylene resin composition, method for producing the same, and molded article - Google Patents

Description

  The present invention relates to a polyoxymethylene resin composition, a production method, and a molded body.

  The polyoxymethylene resin is a highly crystalline thermoplastic resin, and is a material having high rigidity and excellent creep resistance, solvent resistance, slidability and the like. The application covers a wide range including mechanical parts such as automobiles, electrical products, and machines. When used for these various mechanical parts, the dimensional accuracy of the polyoxymethylene resin is important. That is, the polyoxymethylene resin shrinks when stored or used for a long period of time in a high temperature environment, the size of the molded body changes greatly, and malfunctions such as malfunctions occur. Therefore, methods such as annealing shrinkage in advance or designing a mold that allows for the annealing shrinkage rate are adopted.

  However, polyoxymethylene resin moldings are used in various environments, and it is impossible to anticipate how much the polyoxymethylene resin moldings shrink. In addition, the shrinkage varies depending on the resin temperature during molding, the mold temperature, and the operating environment temperature, which plagues mold designers for polyoxymethylene resin moldings. Therefore, a material having the same shrinkage rate or no dimensional change under any use environment is eagerly demanded.

  A method of improving the secondary shrinkage of the polyoxymethylene resin is generally a method of blending an inorganic filler. However, a polyoxymethylene composition containing an inorganic filler is inferior in mechanical properties, particularly in elongation and impact resistance, and has a marked decrease in moldability. In addition, the strength of the weld portion is low, making it difficult to use as a material for precision parts. On the other hand, a method of adding and blending different kinds of polyoxymethylene resins to improve shrinkage (for example, see Patent Document 1), and a full ester compound of a polyhydric alcohol having 3 or more carbon atoms and a fatty acid, A method for improving stability (see, for example, Patent Document 2) has been proposed.

Japanese Patent Laid-Open No. 04-108848 JP 2002-020777 A

  However, even in the above method, a polyoxymethylene resin composition with little difference in shrinkage after annealing has not been obtained.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a polyoxymethylene resin composition, a method for producing the same, and a molded article that have improved the shrinkage problem, which is a drawback of the polyoxymethylene resin. To do.

As a result of intensive studies to provide a polyoxymethylene resin composition, a method for producing the same, and a molded article with a small difference in shrinkage (hereinafter also referred to as “dimensional change amount”) due to a difference in use environment, The inventors have found that a specific compound controls the crystallinity of the polyoxymethylene resin and can obtain a molded product with little dimensional change, and reached the present invention.
That is, the present invention relates to the following inventions.

[1]
  Containing a polyoxymethylene resin (A), a fatty acid ester compound (B), a fatty acid (C), an aliphatic monohydric alcohol (D), and a polyolefin resin (E);
  The total content of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) is 0.2 to 3 with respect to 100 parts by mass of the polyoxymethylene resin (A). Mass part,
  The mass ratio ((C) / (D)) of the fatty acid (C) and the aliphatic monohydric alcohol (D) is in the range of 0.1 to 10,
  Content of the said polyolefin resin (E) is the range of 0.05-5 mass parts with respect to 100 mass parts of said polyoxymethylene resins (A),
  The fatty acid ester compound (B) is at least one selected from the group consisting of cetyl myristate, stearyl stearate, and behenyl behenate.
  Polyoxymethylene resin composition.
[2]
  The polyoxymethylene resin composition according to [1], wherein the fatty acid (C) is at least one selected from the group consisting of myristic acid, stearic acid, and behenic acid.
[3]
  The polyoxymethylene resin composition according to [1] or [2], wherein the aliphatic monohydric alcohol (D) is at least one selected from the group consisting of cetyl alcohol, stearyl alcohol, and behenyl alcohol.
[4]
  The polyolefin resin (E) is at least one selected from the group consisting of high-pressure process low-density polyethylene, ultra-low-density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, and ethylene-octene copolymer. The polyoxymethylene resin composition according to any one of [1] to [3], wherein the melt flow rate (ISO 1133, condition D) is 3 to 150 g / 10 min.
[5]
  Including a melt-kneading step of melt-kneading the molten polyoxymethylene resin (A), fatty acid ester compound (B), fatty acid (C), aliphatic monohydric alcohol (D), and polyolefin resin (E),
  The total addition amount of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) is 0.2 to 3 with respect to 100 parts by mass of the polyoxymethylene resin (A). Mass part,
  The polyoxymethylene resin whose mass ratio ((C) / (D)) of the addition amount of the fatty acid (C) and the addition amount of the aliphatic monohydric alcohol (D) is in the range of 0.1-10. A method for producing the composition.
[6]
  In the melt kneading step, the fatty acid ester compound (B), the fatty acid (C), the aliphatic monohydric alcohol (D), and the polyolefin resin (E) are added in a molten state. A method for producing a polyoxymethylene resin composition.
[7]
  The molded object obtained by shape | molding the polyoxymethylene resin composition as described in any one of [1]-[4].
[8]
  The molded product according to [7], wherein a shrinkage difference ((T1)-(T2)) between the shrinkage (T1) below and the shrinkage (T2) below is in the range of ± 0.07%;
  T1 (%) = (dimension (S0) −dimension (S1)) / (dimension (S0)) × 100,
  T2 (%) = (dimension (S0) −dimension (S2)) / (dimension (S0)) × 100,
  Dimension (S0): Dimension of the molded body immediately after molding (mold dimension),
  Dimension (S1): Dimension of the molded article after standing for 24 hours at a temperature of 23 ° C. and a humidity of 50%,
  Dimension (S2): Dimension of the molded article after standing at a temperature of 23 ° C. and a humidity of 50% for 24 hours, heating at a temperature of 90 ° C. for 4 hours, and then standing at a temperature of 23 ° C. and a humidity of 50% for 168 hours.

  The present invention provides a polyoxymethylene resin composition having improved shrinkability (hereinafter also referred to as “dimensional change due to difference in use environment”), a method for producing the same, and a molded article, which are disadvantages of the polyoxymethylene resin. To do.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

[Polyoxymethylene resin composition]
The polyoxymethylene resin composition of this embodiment contains a polyoxymethylene resin (A), a fatty acid ester compound (B), a fatty acid (C), an aliphatic monohydric alcohol (D), and a polyolefin resin (E). ,
The total content of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) is 0.2 to 3 with respect to 100 parts by mass of the polyoxymethylene resin (A). Mass part,
The mass ratio ((C) / (D)) of the fatty acid (C) and the aliphatic monohydric alcohol (D) is in the range of 0.1 to 10,
Content of the said polyolefin resin (E) is the range of 0.05-5 mass parts with respect to 100 mass parts of said polyoxymethylene resins (A).

[Polyoxymethylene resin (A)]
Although it does not specifically limit as polyoxymethylene resin (A) used by this embodiment, Specifically, a polyacetal homopolymer and a polyacetal copolymer are mentioned. Although it does not specifically limit as a polyacetal homopolymer, The polyacetal homopolymer obtained by homopolymerizing a formaldehyde monomer or the cyclic oligomer of formaldehyde is mentioned as a representative example. The polyacetal copolymer is not particularly limited, and a representative example is a polyacetal copolymer obtained by copolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde and a cyclic ether and / or cyclic formal. Examples of the cyclic oligomer of formaldehyde include formaldehyde trimer (trioxane) and tetramer (tetraoxane). Examples of the cyclic ether and the cyclic formal include ethylene oxide, propylene oxide, epichlorohydrin, glycols such as 1,3-dioxolane and 1,4-butanediol formal, and cyclic formals of diglycol.

  Furthermore, as a polyacetal copolymer, the polyacetal copolymer which has a branch obtained by copolymerizing a monofunctional glycidyl ether, and the polyacetal copolymer which has a crosslinked structure obtained by copolymerizing a polyfunctional glycidyl ether can also be used.

  Furthermore, the polyacetal homopolymer includes a block component obtained by polymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde 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. The polyacetal homopolymer which has can also be used. The polyacetal copolymer also includes a compound having a functional group such as a hydroxyl group at both ends or one end, for example, a hydrogenated polybutadiene glycol, a formaldehyde monomer or a cyclic oligomer of formaldehyde, a cyclic ether and / or a cyclic formal. A polyacetal copolymer having a block component obtained by copolymerization with can also be used.

  As described above, in the present embodiment, any of a polyoxymethylene homopolymer and a polyoxymethylene copolymer may be used and is not particularly limited. These polyoxymethylene resins (A) may be used alone or in combination of two or more.

[Fatty acid ester compound (B)]
The fatty acid ester compound (B) used in the present embodiment is not particularly limited, but specifically, it is preferably a fatty acid ester compound represented by the following formula (I).

(In formula (I), R1 and R2 each independently represent a saturated aliphatic group having 1 to 35 carbon atoms, and the relationship between the carbon numbers of R1 and R2 is R1 ≧ R2.)

  Specific examples of such fatty acid ester compounds (B) include methyl laurate, methyl palmitate, methyl stearate, methyl oleate, methyl erucate, butyl laurate, butyl stearate, isopropyl myristate, isopropyl palmitate Octyl palmitate, octyl stearate, octyl oleate, cetyl myristate, stearyl stearate, behenyl behenate, and the like, and fatty acid ester compounds in which R1 has a carbon number equal to or greater than that of R2. Among these, the fatty acid ester compound (B) is preferably at least one selected from the group consisting of cetyl myristate, stearyl stearate, and behenyl behenate. With such a component (B), the mold shrinkage is small and the compatibility is good. These fatty acid ester compounds (B) may be used alone or in combination of two or more.

[Fatty acid (C)]
Although the fatty acid (C) used by this embodiment is not specifically limited, Specifically, it is preferable that it is a fatty acid represented by following formula (II).

(In formula (II), R3 represents an aliphatic group having 1 to 35 carbon atoms.)

  Specific examples of such fatty acids (C) include caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecyl acid, lauric acid, tridecic acid, myristic acid, pentadecylic acid, palmitic acid, pentadecylic acid, stearin Acid, nanodecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptaconic acid, montanic acid, myricic acid, laccellic acid, undecylenic acid, oleic acid, elaidic acid, celetic acid, erucic acid, brassic acid, sorbic acid, Examples thereof include linoleic acid, linolenic acid, arachidonic acid, propiolic acid, stearic acid; naturally occurring fatty acids containing such components; or a mixture thereof. These fatty acids may be substituted with a hydroxy group. Among these, the fatty acid (C) is preferably at least one selected from the group consisting of myristic acid, stearic acid, and behenic acid. With such a component (C), the mold shrinkage is small and the compatibility is good. These fatty acids (C) may be used alone or in combination of two or more.

[Fatty monohydric alcohol (D)]
Although it does not specifically limit as aliphatic monohydric alcohol (D) used by this embodiment, Specifically, it is preferable that it is a monohydric aliphatic alcohol represented by following formula (III).

(In formula (III), R4 represents an aliphatic group having 1 to 35 carbon atoms.)

  Specific examples of such aliphatic monohydric alcohol (D) include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, and undecyl alcohol. , Lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, oleyl alcohol, nonadecyl alcohol, eicosyl alcohol, ceryl alcohol, behenyl alcohol, melyl alcohol, hexyl decyl alcohol, octyl Dodecyl alcohol, decyl myristyl alcohol, decyl stearyl alcohol, unilin alcohol Is a saturated or unsaturated alcohols. Among these, the aliphatic monohydric alcohol (D) is preferably at least one selected from the group consisting of cetyl alcohol, stearyl alcohol, and behenyl alcohol. With such a component (D), the mold shrinkage is small and the compatibility is good. These aliphatic monohydric alcohols (D) may be used alone or in combination of two or more.

  In addition, when a polyhydric alcohol is used instead of the aliphatic monohydric alcohol (D), the polyoxymethylene resin composition and the molded article excellent in shrinkage (hereinafter also referred to as “dimensional stability”) of the present embodiment. Can't get. The cause is estimated as follows. That is, many polyhydric alcohols are present in the amorphous part of the polyoxymethylene resin and do not penetrate into the crystal part, so that the polyoxymethylene resin is hardly controlled and maintains high crystallinity. As a result, the resulting molded product is considered to have a large dimensional change.

[Polyolefin resin (E)]
The polyolefin resin used for the component (E) of the present embodiment is not particularly limited. Specifically, the high-pressure method low-density polyethylene, ultra-low-density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, And at least one selected from the group consisting of ethylene-octene copolymers. Among these, those having a melt flow rate (ISO 1133, D condition) in the range of 3 to 150 g / 10 min are preferable, more preferably in the range of 10 to 120 g / 10 min, and still more preferably 20 to 100 g / 10 min. Range. When the melt flow rate is 3 g / 10 min or more, the difference in shrinkage ratio is good, and when the melt flow rate is 150 g / 10 min or less, the peeling of the molded article is good.

  The melt flow rate can be measured according to ASTM D1238 (190 ° C.).

[Other additives]
A well-known additive can also be suitably added to the polyoxymethylene resin composition of this embodiment. Examples of the additive include a lubricant, a crystallization nucleating agent, a thermoplastic resin, an inorganic filler, a conductive material, a thermoplastic elastomer, and a pigment.

  As the lubricant, alcohol, fatty acid and fatty acid ester thereof, polyoxyalkylene glycol, olefin compound having an average polymerization degree of 10 to 500, and silicone are preferably used.

  The crystal nucleating agent includes organic / inorganic and is not particularly limited. Specifically, boron nitride can be used.

  As the inorganic filler, fibrous, powder particle, plate and hollow fillers are used. Fiber fillers include glass fiber, carbon fiber, silicone fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and stainless steel, aluminum, titanium, copper, brass. And inorganic fibers such as metal fibers. In addition, whiskers such as potassium titanate whisker and zinc oxide whisker having a short fiber length are included. A high melting point organic fibrous material such as an aromatic polyamide resin, a fluororesin, or an acrylic resin can also be used.

  Examples of powder particulate fillers include carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, wollastonite, iron oxide, titanium oxide, and alumina. Examples thereof include metal oxides such as these, 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.

  Examples of the plate filler include mica, glass flakes, and various metal foils. Examples of the hollow filler include glass balloons, silica balloons, shirasu balloons, and metal balloons. These fillers can be used alone or in combination of two or more. These fillers can be used either surface-treated or unsurface-treated, but in some cases it is preferable to use a surface-treated one in terms of smoothness of the molding surface and mechanical properties. is there. A conventionally well-known thing can be used as a surface treating agent. For example, various coupling treatment agents such as silane, titanate, aluminum, and zirconium can be used. Specifically, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyl trisstearoyl titanate, diisopropoxyammonium ethyl acetate, n-butyl zirconate, etc. Can be mentioned.

  Examples of the conductive agent include conductive carbon black, metal powder, or fiber.

  Examples of the thermoplastic resin include polyolefin resin, acrylic resin, styrene resin, polycarbonate resin, and uncured epoxy resin. These modified products are also included. Examples of the thermoplastic elastomer include polyurethane elastomers, polyester elastomers, polystyrene elastomers, and polyamide elastomers.

  Examples of the pigment include inorganic pigments and organic pigments. Inorganic pigments are those commonly used for coloring resins, such as zinc sulfide, zinc oxide, titanium oxide, barium sulfate, titanium yellow, iron oxide, ultramarine, cobalt blue, fuel pigments, carbonic acid Salt, phosphate, acetate, carbon black, acetylene black, lamp black, etc., organic pigments are condensed azo, isoindoline, disazo, monoazo, anthraquinone, heterocyclic, pennon, It is a pigment such as quinacridone, thioindico, berylene, dioxazine, or phthalocyanine.

[Content of each component]
In the polyoxymethylene resin composition of the present embodiment, the total content of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) with respect to 100 parts by mass of the polyoxymethylene resin (A). The amount is in the range of 0.2 to 3.0 parts by mass, preferably in the range of 0.3 to 2.0 parts by mass, and more preferably in the range of 0.5 to 1.0 parts by mass. When the total content of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) is in the above range, a polyoxymethylene resin composition and a molded article excellent in dimensional stability are obtained. Can do.

  In the polyoxymethylene resin composition of the present embodiment, the content of the polyolefin resin (E) is in the range of 0.05 to 5.0 parts by mass with respect to the polyoxymethylene resin (A), preferably 0. 0.1 to 5.0 parts by mass, and more preferably 0.5 to 5.0 parts by mass. If it is 0.05 parts by mass or more, the effect of improving the shrinkage after annealing is obtained, and if it is 5 parts by mass or less, peeling of the molded product becomes good.

  The content ratio of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) is when the total of the components (B), (C), and (D) is 100% by mass. The component (B) is 91 to 98% by mass, the component (C) is preferably 0.5 to 4.5% by mass, and the component (D) is preferably 0.5 to 4.5% by mass. More preferably, the component is 92 to 97 mass%, the (C) component is 0.8 to 3.0 mass%, the (D) component is 1.0 to 4.0 mass%, and the (B) component is 94. It is more preferable that it is -96 mass%, (C) component is 1.2-2.5 mass%, and (D) component is 1.5-3.5 mass%.

  Furthermore, in the polyoxymethylene resin composition of the present embodiment, the mass ratio ((C) / (D)) of the fatty acid (C) and the aliphatic monohydric alcohol (D) is in the range of 0.1 to 10. Yes, preferably in the range of 0.3 to 3.0, more preferably in the range of 0.5 to 1.0. When the mass ratio of the fatty acid (C) and the aliphatic monohydric alcohol (D) is in the above range, a polyoxymethylene resin composition and a molded article that are superior in dimensional stability can be obtained.

  The addition amount of the other additives is not particularly limited, but is preferably 0.001 to 10.0 parts by mass with respect to 100 parts by mass of the polyoxymethylene resin (A), and 0.005 to 5.0 It is more preferable that it is a mass part, and it is still more preferable that it is 0.01-3.0 mass parts.

[Method for producing polyoxymethylene resin composition]
The manufacturing method of the polyoxymethylene resin composition of the present embodiment includes a molten polyoxymethylene resin (A), a fatty acid ester compound (B), a fatty acid (C), an aliphatic monohydric alcohol (D), and a polyolefin resin. Including a melt-kneading step of melt-kneading (E),
The total addition amount of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) is 0.2 to 3 with respect to 100 parts by mass of the polyoxymethylene resin (A). Mass part,
The mass ratio ((C) / (D)) of the addition amount of the fatty acid (C) and the addition amount of the aliphatic monohydric alcohol (D) is in the range of 0.1 to 10.

  In the melt-kneading step, the fatty acid ester compound (B), the fatty acid (C), the aliphatic monohydric alcohol (D), and the polyolefin resin (E) are added in a powdered state even when added in a powder state. Any method may be used. Among them, a method in which the fatty acid ester compound (B), the fatty acid (C), the aliphatic monohydric alcohol (D), and the polyolefin resin (E) are added in a molten state to the molten polyoxymethylene resin (A). Is preferred. With such an addition method, it is possible to obtain a polyoxymethylene resin composition and a molded article having a small shrinkage difference (difference in dimensional change) and excellent in dimensional stability. In addition, the method in particular in a molten state is not restrict | limited, For example, each component can be made into a molten state with the same direction meshing type twin-screw extruder.

  The reason for this is to melt the polyoxymethylene resin, loosen the polymer intermolecular bond, and place a mixture of the fatty acid ester compound, fatty acid, and aliphatic monohydric alcohol in the molten state in the loose crystal part. Since the crystallinity of the polyoxymethylene resin can be controlled, it is considered that the difference in shrinkage rate (difference in dimensional change) can be kept low.

  Furthermore, in the method for producing the polyoxymethylene resin composition of the present embodiment, known additives can be appropriately added. Specifically, heat stabilizers, antioxidants, formaldehyde and formic acid inhibitors, weathering agents, lubricants, crystallization nucleating agents, thermoplastic resins, inorganic fillers, conductive materials, thermoplastic elastomers, pigments, etc. are added can do.

  Antioxidants, formaldehyde and formic acid scavengers, and combinations thereof are effective as the heat stabilizer. As the antioxidant, a hindered phenol-based antioxidant is preferable. For example, n-octadecyl-3- (3′5′-di-t-butyl-4′-hydroxyphenyl) -propionate, 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-tert-butyl-4-hydroxyphenyl) -propionate), 1,4-butanediol-bis- (3- (3,5-di -T-butyl-4-hydroxyphenyl) -propionate), triethyleneglycol-bis- (3- (3-t-butyl-5-methyl-4-hydroxyphenyl)- Lopionate), 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) priionyl hexamethylenediamine, N, N'-tetramethylenebis-3- (3'-methyl-5'-t-butyl-4-hydroxy) Phenol) propionyldiamine, N, N′-bis- (3- (3,5-di-tert-butyl-4-hydroxyphenol) propionyl) hydrazine, N-salicyloyl-N′-salicylide Hydrazine, 3- (N-salicyloyl) amino-1,2,4-triazole, N, N′-bis (2- (3- (3,5-di-butyl-4-hydroxyphenyl) propionyloxy) ethyl) Among these hindered phenolic antioxidants, triethylene glycol bis- (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate), tetrakis- (methylene- 3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate methane is preferred.

  Examples of formaldehyde and formic acid scavengers include (a) compounds and polymers containing formaldehyde-reactive nitrogen, (b) alkali metal or alkaline earth metal hydroxides, inorganic acid salts, carboxylate salts, or alkoxides. It is done.

  (I) Examples of the compound containing formaldehyde-reactive nitrogen include (1) dicyandiamide, (2) amino-substituted triazine, and (3) a co-condensate of amino-substituted triazine and formaldehyde. (2) Examples of amino-substituted triazines include guanamine (2,4-diamino-sym-triazine), melamine (2,4,6-triamino-sym-triazine), N-butylmelamine, N-phenylmelamine, N , N-diphenylmelamine, N, N-diallylmelamine, N, N ′, N ″ -triphenylmelamine, N-methylolmelamine, N, N′-dimethylolmelamine, N, N ′, N ″ -tri Methylolmelamine, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine), 2,4-diamino-6-methyl-sym-triazine, 2,4-diamino-6-butyl-sym-triazine, 2, 4-diamino-6-benzyloxy-sym-triazine, 2,4-diamino-6-butoxy-sym-triazine 2,4-diamino-6-cyclohexyl-sym-triazine, 2,4-diamino-6-chloro-sym-triazine, 2,4-diamino-6-mercapto-sym-triazine, 2,4-dioxy-6 Examples include amino-sym-triazine (Amelite), 2-oxy-4,6-diamino-sym-triazine (Ameline), N, N ′, N′-tetracyanoethylbenzoguanamine and the like. (3) Examples of the co-condensate of amino-substituted triazine and formaldehyde include melamine-formaldehyde polycondensate. Of these, dicyandiamide, melamine and melamine-formaldehyde polycondensate are preferred.

  Further, (i) a polymer having a formaldehyde-reactive nitrogen group is obtained by polymerizing (1) a polyamide resin, (2) acrylamide and a derivative thereof or acrylamide and a derivative thereof with another vinyl monomer in the presence of a metal alcoholate. (3) Polymer obtained by polymerizing acrylamide and its derivative or acrylamide and its derivative and other vinyl monomer in the presence of radical polymerization, (4) Nitrogen such as amine, amide, urea and urethane Polymers containing groups may also be used. As the polyamide resin of (1), nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 12, etc. and copolymers thereof, such as nylon 6 / 6-6, Nylon 6 / 6-6 / 6-10, nylon 6 / 6-12, etc. are mentioned. (2) Polymers obtained by polymerizing acrylamide and derivatives thereof or acrylamide and derivatives thereof with other vinyl monomers in the presence of metal alcoholates include poly-β-alanine copolymers. These polymers can be produced by the methods described in JP-B-6-12259, JP-B-5-87096, JP-B-5-47568 and JP-A-3-234729. (3) Polymers obtained by polymerizing acrylamide and derivatives thereof or acrylamide and derivatives thereof with other vinyl monomers in the presence of radical polymerization can be produced by the method described in JP-A-3-28260. .

  (B) Alkali metal or alkaline earth metal hydroxide, inorganic acid salt, carboxylate or alkoxide, for example, hydroxide such as sodium, potassium, magnesium, calcium or barium, carbonate of the above metal, Examples include phosphates, silicates, borates, and carboxylates. The carboxylic acid of the carboxylate is a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms, and these carboxylic acids may be substituted with a hydroxyl group. Examples of saturated aliphatic carboxylic acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, montanic acid, melicic acid, and celloplastic acid. Examples of the unsaturated aliphatic carboxylic acid include undecylenic acid, oleic acid, elaidic acid, celetic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propiolic acid, stearic acid and the like. Examples of the alkoxide include methoxide and ethoxide of the above metals.

  As the weathering (light) stabilizer, (i) a benzotriazole-based material, (b) an oxalic acid anilide-based material, and (c) a hindered amine-based material are preferable.

  (I) Examples of the benzotriazole-based substance include 2- (2′-hydroxy-5′-methyl-phenyl) benzotriazole, 2- [2′-hydroxy-3,5-di-t-butyl-phenyl) benzo Triazole, 2- [2′-hydroxy-3,5-di-isoamyl-phenyl) benzotriazole, 2- [2′-hydroxy-3,5-bis- (α, α-dimethylbenzyl) phenyl] -2H— Examples include benzotriazole, 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole, and preferably 2- [2′-hydroxy-3,5-bis- (α, α-dimethylbenzyl) phenyl. ] -2H-benzotriazole, 2- [2'-hydroxy-3,5-di-t-butyl-phenyl) benzotriazole.

  (B) Examples of oxalic acid anilide-based substances include 2-ethoxy-2′-ethyloxalic acid bisanilide, 2-ethoxy-5-tert-butyl-2′-ethyloxalic acid bisanilide, 2 -Ethoxy-3'-dodecyl oxalic acid bisanilide and the like. These substances may be used alone or in combination of two or more.

  (C) As hindered amine substances, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2,2 , 6,6-tetramethylpiperidine, 4- (phenylacetoxy) -2,2,6,6-tetramethylpiperidine 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy-2, 2,6,6-tetramethylpiperidine, 4-stearyloxy-2,26,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-benzyloxy-2,2 , 6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4- (ethylcarbamo Ruoxy) -2,2,6,6-tetramethylpiperidine, 4- (cyclohexylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (phenylcarbamoyloxy) -2,2,6,6 -Tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4-piperidine) -carbonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -oxalate, bis (2,2 , 6,6-tetramethyl-4-piperidyl) -malonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate, bis (2,2,6,6-tetramethyl-4- Piperidyl) -adipate, bis (2,2,6,6-tetramethyl-4-piperidyl) -terephthalate, 1,2-bis (2,2,6,6-tetramethyl-4-pi Lysyloxy) -ethane, α, α′-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -p-xylene, bis (2,2,6,6-tetramethyl-4-piperidyl) Tolylene-2,4-dicarbamate, bis (2,2,6,6-tetramethyl-4-piperidyl) -hexamethylene-1,6-dicarbamate, tris (2,2,6,6-tetramethyl- 4-piperidyl) -benzene-1,3,5-tricarboxylate, tris (2,2,6,6-tetramethyl-4-piperidyl) -benzene-1,3,4-tricarboxylate , Preferably bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate. The above hindered amine materials may be used alone or in combination of two or more. The combination of the above benzotriazole-based material, oxalic acid anilide-based material and hindered amine-based material is most preferable.

  The crystal nucleating agent includes organic / inorganic and is not particularly limited. Specifically, boron nitride can be used.

  As the lubricant, alcohol, fatty acid and fatty acid ester thereof, polyoxyalkylene glycol, olefin compound having an average polymerization degree of 10 to 500, and silicone are preferably used.

  As the inorganic filler, fibrous, powder particle, plate and hollow fillers are used. Fiber fillers include glass fiber, carbon fiber, silicone fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and stainless steel, aluminum, titanium, copper, brass. And inorganic fibers such as metal fibers. In addition, whiskers such as potassium titanate whisker and zinc oxide whisker having a short fiber length are included. A high melting point organic fibrous material such as an aromatic polyamide resin, a fluororesin, or an acrylic resin can also be used.

  Examples of powder particulate fillers include carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, wollastonite, iron oxide, titanium oxide, and alumina. Examples thereof include metal oxides such as these, 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.

  Examples of the plate-like filler include mica, glass flakes, and various metal foils. Examples of the hollow filler include glass balloons, silica balloons, shirasu balloons, and metal balloons. These fillers can be used alone or in combination of two or more. These fillers can be used either surface-treated or unsurface-treated, but in some cases it is preferable to use a surface-treated one in terms of smoothness of the molding surface and mechanical properties. is there. A conventionally well-known thing can be used as a surface treating agent. For example, various coupling treatment agents such as silane, titanate, aluminum, and zirconium can be used. Specifically, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyl trisstearoyl titanate, diisopropoxyammonium ethyl acetate, n-butyl zirconate, etc. Can be mentioned.

  Examples of the conductive agent include conductive carbon black, metal powder, or fiber.

  Examples of the thermoplastic resin include polyolefin resin, acrylic resin, styrene resin, polycarbonate resin, and uncured epoxy resin. These modified products are also included. Examples of the thermoplastic elastomer include polyurethane elastomers, polyester elastomers, polystyrene elastomers, and polyamide elastomers.

  Examples of the pigment include inorganic pigments and organic pigments. Inorganic pigments are those commonly used for coloring resins, such as zinc sulfide, zinc oxide, titanium oxide, barium sulfate, titanium yellow, iron oxide, ultramarine, cobalt blue, fuel pigments, carbonic acid Salt, phosphate, acetate, carbon black, acetylene black, lamp black, etc., organic pigments are condensed azo, isoindoline, disazo, monoazo, anthraquinone, heterocyclic, pennon, It is a pigment such as quinacridone, thioindico, berylene, dioxazine, or phthalocyanine.

  As the melt kneader, a melt kneader generally used in practice can be applied. For example, a uniaxial, biaxial or multiaxial kneading extruder, a kneader, a roll, a Banbury mixer, etc. may be used. Among these, a twin-screw extruder equipped with a decompression device and side feeder equipment is more preferable, and in particular, a same-direction meshing twin-screw extruder is preferable.

  The melt kneading temperature is preferably 1 to 100 ° C. higher than the melting point determined by differential scanning calorimetry (DSC) measurement of the polyoxymethylene resin to be used according to JIS K7121. More specifically, the temperature is preferably 160 ° C to 240 ° C. The shear rate in the melt kneader is preferably 100 rpm or more, and the average residence time during melt kneading is preferably 30 seconds to 10 minutes.

[Molded body]
The molded body of the present embodiment is obtained by molding the above-described polyoxymethylene resin composition.

  The method for molding the polyoxymethylene resin composition is not particularly limited, and is a known molding method such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, molding of other materials. , Molding by any of molding methods such as gas-assisted injection molding, foam injection molding, low pressure molding, ultra-thin injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, outsert molding) it can.

  Since the molded body of this embodiment is obtained by molding the above-described polyoxymethylene resin composition, it has excellent dimensional stability.

In the molded product of the present embodiment, it is preferable that the shrinkage difference ((T1) − (T2)) between the shrinkage rate (T1) below and the shrinkage rate (T2) below is in a range of ± 0.07%. The range of ± 0.05% is more preferable, the range of ± 0.03% is more preferable, and the range of ± 0.02% is still more preferable. The shrinkage from the dimension S0 to the dimension S1 can also be called primary shrinkage, and the shrinkage from the dimension S1 to the dimension S2 (after annealing) can also be called secondary shrinkage. If the shrinkage ratio between the primary shrinkage and the secondary shrinkage is within the above range For example, it becomes a molded article of a polyoxymethylene resin composition that is more excellent in shrinkage.
T1 (%) = (dimension (S0) −dimension (S1)) / (dimension (S0)) × 100,
T2 (%) = (dimension (S0) −dimension (S2)) / (dimension (S0)) × 100,
Dimension (S0): Dimension of the molded body immediately after molding (mold dimension),
Dimension (S1): Dimension of the molded article after being left for 24 hours at a temperature of 23 ° C. and a humidity of 50%,
Dimension (S2): Dimension of the molded article after standing for 24 hours at a temperature of 23 ° C. and a humidity of 50%, followed by heating (annealing) at a temperature of 90 ° C. for 4 hours, and then standing for 168 hours at 23 ° C. and a humidity of 50%.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. First, contents of components used in Examples and Comparative Examples and evaluation methods are shown below.

<Ingredients>
1. Polyoxymethylene resin (A)
(A-1) Polyoxymethylene homopolymer A polyoxymethylene homopolymer having a melt flow rate of 30.0 g / 10 min (ISO 1133 D condition) blocked at both ends with an acetyl group (Tenac 7010 manufactured by Asahi Kasei Chemicals Corporation) )
2. Fatty acid ester compound (B)
(B-1) Cetyl myristate (B-2) Stearyl stearate (B-3) Behenyl behenate Fatty acid (C)
(C-1) Myristic acid (C-2) Stearic acid (C-3) Behenic acid Aliphatic monohydric alcohol (D)
(D-1) Cetyl alcohol (D-2) Stearyl alcohol (D-3) Behenyl alcohol Polyolefin resin (E)
(E-1) 1-butene-ethylene copolymer “Toughmer A70090” (MFR: 70) (manufactured by Mitsui Chemicals, Inc.)
(E-2) 1-butene / ethylene copolymer “Toughmer A4090” (MFR: 3.6) (manufactured by Mitsui Chemicals, Inc.)
(E-3) LDPE M1820 (MFR: 2) (manufactured by Asahi Kasei Chemicals Corporation)
(E-4) LDPE M6555 (MFR: 55) (Asahi Kasei Chemicals Corporation)
6). Other additives (F-1) Boron nitride, average particle size: ≈ 3 μm (trade name: Denkaboron nitride, manufactured by Denki Kagaku Kogyo)

[Method for evaluating shrinkage]
1. Injection Molding The pellets obtained in the following Examples and Comparative Examples were dried at 80 ° C. for 3 hours, and then the mold temperature was set using an IS-100GN molding machine manufactured by Toshiba Machine Co., Ltd. set at a cylinder temperature of 200 ° C. A flat plate having the following dimensions was molded under the conditions of 80 ° C. and cooling time of 30 seconds.
2. Flat plate dimensions: 100mm x 40mm x 4mm
3. Measurement of Shrinkage Ratio and Evaluation of Shrinkage The molded flat plate product is allowed to stand for 24 hrs in a thermostatic chamber at a temperature of 23 ° C. and a humidity of 50%, and the dimension in the flow direction after 24 hrs is measured. T1) was determined.
Next, the flat plate molded product was heated in an oven set at 90 ° C. for 4 hours, and again left in a constant temperature room at 23 ° C. for 168 hours. The dimensions after 168 hours were measured, and the shrinkage (T2) from the mold dimensions was determined. The difference in shrinkage between T1 and T2 was obtained from the obtained shrinkage (T1) and (T2), and the shrinkage was evaluated.

[Examples 1 to 4]
The polyoxymethylene resin (A-1) was melted with the same direction meshing twin screw extruder. Cetyl myristate (B-1), myristic acid (C-1), and cetyl alcohol (D-1) melted at a temperature of 85 ° C. between the melting zone and the vent port of this twin-screw extruder. 0.5 parts by mass with respect to 100 parts by mass of the polyoxymethylene resin (A-1) was added using a liquid pump. Further, the polyolefin resin (E-1) was melted and added from the side using the same direction meshing twin screw extruder, and melt-kneaded with the polyoxymethylene resin (A-1). A polyoxymethylene resin composition was obtained. The mass ratio of melt-kneaded cetyl myristate (B-1), myristic acid (C-1), and cetyl alcohol (D-1) was 95% by mass of cetyl myristate (B-1), myristic acid (C -1) 1.8% by mass and cetyl alcohol (D-1) 3.2% by mass. Only the addition amount of polyolefin resin (E-1) was changed and the polyoxymethylene resin composition of Examples 2-4 was obtained. The obtained polyoxymethylene resin composition was dried and then molded into pellets to evaluate shrinkage. The results are shown in Table 1.

[Comparative Example 1]
A polyoxymethylene resin (A-1) was injection-molded and the shrinkage of the pellets was evaluated. The results are shown in Table 1.

[Comparative Examples 2-3]
A polyolefin resin (E-1) was added, and the same operation as in Example 1 was performed. The results are shown in Table 1. In Comparative Example 3, since the surface of the molded article was peeled off in the shrinkage evaluation, the shrinkage could not be evaluated.

[Comparative Example 4]
The same operation as in Example 1 was performed except that the polyolefin resin (E-1) was not added. The results are shown in Table 1.

[Examples 5 to 7]
The mass ratio of myristic acid (C-1) and cetyl alcohol (D-1) was fixed, and only the total addition amount of (B) to (D) was changed, and the same operation as in Example 1 was performed. The results are shown in Table 2.

[Comparative Examples 5-6]
Fixing the mass ratio of myristic acid (C-1) and cetyl alcohol (D-1), changing the total addition amount of (B) to (D), and melt-kneading without adding polyolefin resin (E) did. The same operation as in Example 1 was performed. The results are shown in Table 2.

[Comparative Example 7]
The mass ratio of myristic acid (C-1) and cetyl alcohol (D-1) is fixed, the total addition amount of (B) to (D) is changed to 5 parts by mass, and the addition amount of polyolefin resin (E) is changed. Melting and kneading was performed at 2.0% by mass. When the obtained resin composition was molded with an injection molding machine, it was not plasticized and a test piece could not be obtained. The results are shown in Table 2.

[Examples 8 to 10]
Example 1 except that the mass ratio of myristic acid (C-1) and cetyl alcohol (D-1) was as shown in Table 2 and the addition amount of the polyolefin resin (E) was 2.0% by mass. The same operation was performed. The results are shown in Table 2.

[Comparative Examples 8 to 10]
The mass ratio of myristic acid (C-1) and cetyl alcohol (D-1) was as shown in Table 2, except that melt kneading was carried out without adding the polyolefin resin (E). The operation was performed. The results are shown in Table 2.

[Examples 11 to 13]
As shown in Table 3, the same operation as in Example 1 was performed except that the polyolefin resin (E) type was changed and 2.0 mass% was added to the extruder. The results are shown in Table 3.

[Comparative Example 11]
As shown in Table 3, the same operation as in Example 1 was performed except that the melt kneading was performed without adding the polyolefin resin (E). The results are shown in Table 3.

[Comparative Examples 12-14]
As shown in Table 3, the same operation as in Example 1 was performed except that the type of polyolefin resin (E) was changed and the addition amount was 15% by mass. In Comparative Examples 13 to 15, since the surface of the molded article was peeled in the shrinkage evaluation, the shrinkage could not be evaluated. The results are shown in Table 3.

Example 14
Except that stearyl stearate (B-2), stearic acid (C-2) and stearyl alcohol (D-2) were added as shown in Table 4 and the addition amount of polyolefin resin (E-1) was changed, The same operation as in Example 1 was performed. The results are shown in Table 4.

[Comparative Example 15]
The same operation as Example 14 was performed except melt-kneading without adding polyolefin resin (E-1). The results are shown in Table 4.

Example 15
Example 1 except that behenic acid behenyl (B-3), behenic acid (C-3) and behenyl alcohol (D-3) were added as shown in Table 5 and the addition amount of the polyolefin resin (E) was changed. The same operation was performed. The results are shown in Table 5.

[Comparative Example 16]
The same operation as in Example 15 was performed except that melt-kneading was performed without adding the polyolefin resin (E-1). The results are shown in Table 5.

Example 16
Cetyl myristate (B-1), myristic acid (C-1) and cetyl alcohol (D-1) were added as shown in Table 6, boron nitride (F-1) was further added, and polyolefin resin (E ) The same operation as in Example 1 was performed except that the addition amount was changed. The results are shown in Table 6.

[Comparative Example 17]
The same operation as in Example 16 was performed except that melt-kneading was performed without adding the polyolefin resin (E-1). The results are shown in Table 6.

  The molded product of the polyacetal resin composition of the present invention can be used for molded products for various purposes by improving the secondary shrinkage after molding, which is a drawback, and by improving the slidability by adding a sliding agent. Is possible. Examples include gears, cams, sliders, levers, arms, clutches, felt clutches, idler gears, pulleys, rollers, rollers, key stems, key tops, shutters, reels, shafts, joints, shafts, bearings, and guides. Mechanical parts; resin parts for outsert molding, resin parts for insert molding, chassis, trays, side plates, parts for office automation equipment represented by printers and copiers; VTR (Video Tape Recorder), video movies, digital video cameras, Cameras and parts for cameras represented by digital cameras or video equipment; cassette player, DAT, LD (Laser Disk), MD (Mini Disk), CD (Compact Disk) [CD-ROM (Read nly Memory), CD-R (Recordable), CD-RW (Rewriteable) included), DVD (Digital Video Disk) [DVD-ROM, DVD-R, DVD + R, DVD-RW, DVD + RW, DVD-R DL, DVD + R DL, DVD-RAM (including Random Access Memory), DVD-Audio), Blu-ray Disc, HD-DVD, other optical disk drives, MFD, MO, navigation systems, and music, video represented by mobile personal computers or Information equipment; parts for communication equipment typified by mobile phones and facsimiles; parts for electrical equipment; parts for electronic equipment; parts for automobiles such as gasoline tanks, fuel pump modules, valves Fuel-related parts typified by gasoline tank flanges, etc .; Door-related parts typified by door locks, door handles, window regulators, speaker grills, etc .; seat belt peripherals typified by seat belt slip rings, press buttons, etc. Parts: Combination switch parts, switch parts, clip parts parts; mechanical pencil pen tip and mechanical pencil core parts; wash basin, drain outlet, drain valve opening / closing mechanism parts; vending machine Opening / closing part locking mechanism and product discharge mechanism parts; cord stoppers, adjusters and buttons for clothing; nozzles for watering, and sprinkling hose connection joints, stair railings, and building materials that support floor materials; disposable Camera, toy, fastener, chain, conveyor, buckle, Sports equipment, vending machines, furniture, musical instruments, and can be suitably used as industrial parts typified by the housing equipment.

Claims (8)

Containing a polyoxymethylene resin (A), a fatty acid ester compound (B), a fatty acid (C), an aliphatic monohydric alcohol (D), and a polyolefin resin (E);
The total content of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) is 0.2 to 3 with respect to 100 parts by mass of the polyoxymethylene resin (A). Mass part,
The mass ratio ((C) / (D)) of the fatty acid (C) and the aliphatic monohydric alcohol (D) is in the range of 0.1 to 10,
The content of the polyolefin resin (E) is, with respect to the polyoxymethylene resin (A) 100 parts by mass of, Ri range der of 0.05 to 5 parts by weight,
Said fatty acid ester compound (B), cetyl myristate, Ru least 1 Tanedea selected from the group consisting of stearyl stearate, and behenyl behenate,
Polyoxymethylene resin composition. The polyoxymethylene resin composition according to claim 1 , wherein the fatty acid (C) is at least one selected from the group consisting of myristic acid, stearic acid, and behenic acid. The polyoxymethylene resin composition according to claim 1 or 2 , wherein the aliphatic monohydric alcohol (D) is at least one selected from the group consisting of cetyl alcohol, stearyl alcohol, and behenyl alcohol. The polyolefin resin (E) is at least one selected from the group consisting of high-pressure process low-density polyethylene, ultra-low-density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, and ethylene-octene copolymer. The polyoxymethylene resin composition according to any one of claims 1 to 3 , wherein the melt flow rate (ISO 1133, condition D) is 3 to 150 g / 10 min. Including a melt-kneading step of melt-kneading the molten polyoxymethylene resin (A), fatty acid ester compound (B), fatty acid (C), aliphatic monohydric alcohol (D), and polyolefin resin (E),
The total addition amount of the fatty acid ester compound (B), the fatty acid (C), and the aliphatic monohydric alcohol (D) is 0.2 to 3 with respect to 100 parts by mass of the polyoxymethylene resin (A). Mass part,
Mass ratio of the addition amount and the addition amount of the aliphatic monohydric alcohol (D) of said fatty acid (C) ((C) / (D)) is Ri range der of 0.1 to 10,
Content of the said polyolefin resin (E) is the range of 0.05-5 mass parts with respect to 100 mass parts of said polyoxymethylene resins (A),
It said fatty acid ester compound (B) is cetyl myristate, stearyl stearate, and Ru at least Tanedea selected from the group consisting of behenyl behenate, method for producing a polyoxymethylene resin composition. In the melt-kneading step, wherein the fatty acid ester compound (B), said fatty acid (C), the aliphatic monohydric alcohol (D), and the polyolefin resin (E) is according to claim 5 which is added in the molten state A method for producing a polyoxymethylene resin composition. The molded object obtained by shape | molding the polyoxymethylene resin composition as described in any one of Claims 1-4 . The molded article according to claim 7 , wherein a difference in shrinkage ((T1) − (T2)) between the following shrinkage (T1) and the following shrinkage (T2) is within a range of ± 0.07%;
T1 (%) = (dimension (S0) −dimension (S1)) / (dimension (S0)) × 100,
T2 (%) = (dimension (S0) −dimension (S2)) / (dimension (S0)) × 100,
Dimension (S0): Dimension of the molded body immediately after molding (mold dimension)
Dimension (S1): Dimension of the molded body after being left for 24 hours at a temperature of 23 ° C. and a humidity of 50%,
Dimension (S2): Dimension of the molded article after standing at a temperature of 23 ° C. and a humidity of 50% for 24 hours, heating at a temperature of 90 ° C. for 4 hours, and then standing at a temperature of 23 ° C. and a humidity of 50% for 168 hours.