JP5143163B2 - Polyacetal resin composition and method for producing the same - Google Patents

Description

  The present invention relates to a polyacetal resin composition, a method for producing the same, an injection-molded article, and a gear.

Polyacetal resin is excellent in the balance of mechanical strength, chemical resistance and slidability, and easy to process, so as a typical engineering plastics, mechanical parts such as electrical equipment, gears of electrical equipment, It is widely used mainly for mechanical parts including automobile parts and other precision machines. In particular, polyacetal resin is often used for precision mechanism parts such as electric devices, automobile parts, gears, and cams. In that case, the polyacetal resin is not only slidable but also has long-term durability such as a balance of mechanical properties such as rigidity, strength, and toughness, and that there is no tooth deflection and tooth spill when used in gears. Sex is also required.
Therefore, conventionally, as a general method, a method of blending an inorganic filler such as glass fiber, talc, wollastonite, carbon fiber or the like with polyacetal has been used, thereby improving various performances of the polyacetal resin. It has been. However, when glass fibers or inorganic fillers are added to the polyacetal resin, it is effective in improving mechanical properties such as rigidity and strength, but the inherent characteristics of the polyacetal resin are slidability, creep resistance, and fatigue resistance. Long-term characteristics such as property and toughness may be significantly impaired, and it is not always an effective method. Also, if a large amount of glass fiber or inorganic filler is blended into the polyacetal resin, the thermal stability of the polyacetal resin may be lowered, which may adversely affect the moldability or heat aging resistance, which may be a problem. is there.

  The mechanical parts as described above are generally manufactured by an injection molding method using an injection molding machine, and the obtained molded product is used for mechanical parts of OA equipment. At that time, hot runner molding may be performed in order to obtain a complicated shape or improve recyclability, and in the case of a composition with low thermal stability, thermal decomposition or discoloration occurs, which adversely affects the obtained molded product As a result, the yield deteriorates. Therefore, it is important to obtain a molded product that has high rigidity and strength even under severe conditions such as hot runner molding, and that does not undergo thermal decomposition or discoloration. This demand is increasing. The current situation is.

In order to meet these demands, a surface treatment is performed on a granular inorganic filler represented by calcium carbonate with a fatty acid and a metal salt thereof, and the inorganic filler after the surface treatment is melt-kneaded into a polyacetal resin. And a polyacetal resin composition containing calcium carbonate, an organic acid, and a fatty acid ester having a specific aspect ratio, and an amount ratio of Na to Ca and an amount of Sr in the composition The composition (patent document 3) whose ratio is a specific ratio is disclosed.
Further, it is disclosed that a composition excellent in rigidity and slidability can be obtained by adding an inorganic filler, a silicon compound and a lubricant to a polyacetal resin (Patent Document 4).

Japanese Patent No. 2140744 Japanese Patent No. 3140502 No. 2005-071011 Japanese Patent Laid-Open No. 2002-060585

However, according to the methods described in Patent Documents 1 to 3 above, a polyacetal resin composition having an excellent balance of mechanical properties such as rigidity, toughness, and creep resistance can be obtained, but staying discoloration in a molten state. The current situation is that it is not sufficient for practical use.
Moreover, according to the method described in the said patent document 4, sufficient effect is not acquired regarding toughness and the stay discoloration property in a molten state.

  In view of the above circumstances, an object of the present invention is to provide a polyacetal resin composition excellent in mechanical properties such as rigidity and toughness, and excellent in retention discoloration in a molten state, and a method for producing the same.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have a specific amount of light calcium carbonate (II) 5 having a specific average particle diameter and pH with respect to 100 parts by mass of the polyacetal resin (I). -50 parts by mass, two specific fatty acids (III-I) and (III-II), a calcium salt of fatty acid (IV), and a specific ester compound (V), the light calcium carbonate The total mass ratio of fatty acid (III-I) and fatty acid (III-II) to (II) is in a specific range, and fatty acid (III-I) and fatty acid (III-II) to calcium salt (IV) of the fatty acid ) And a polyacetal resin composition in which the mass ratio of the ester compound (V) to the light calcium carbonate (II) is in a specific range. It can be solved, which resulted in the completion of the present invention.

That is, the present invention is as follows.
[1]
100 parts by mass of polyacetal resin (I),
5-50 parts by weight of light calcium carbonate (II) having an average particle size of 50 nm or more and 500 nm or less, a pH of 9.2 or more and 10.0 or less by JIS K5101 test method, and no surface treatment;
Monovalent fatty acid (III-I) having 12 to 27 carbon atoms;
A monovalent fatty acid (III-II) having 28 or more carbon atoms;
A calcium salt of fatty acid (IV);
An ester of fatty alcohol and fatty acid (V);
Containing
The total mass ratio [(III-I) + (III-II)] / (II) of the fatty acid (III-I) and the fatty acid (III-II) to the light calcium carbonate (II) is 0.020 to 0.055, and the total mass ratio [(III-I) + (III-II)] / (IV) of the fatty acid (III) and the fatty acid (III-II) to the calcium salt (IV) of the fatty acid is A polyacetal resin composition having a mass ratio (V) / (II) of the aliphatic alcohol and the fatty acid ester (V) to the light calcium carbonate (II) of 0.03 to 0.15. .
[2]
The polyacetal resin composition according to the above [1], wherein a mass ratio (III-I) / (III-II) of the fatty acid (III-I) to the fatty acid (III-II) is 1 to 5.
[3]
The polyacetal resin composition according to the above [1] or [2], wherein the fatty acid constituting the calcium salt (IV) of the fatty acid is the same as the fatty acid (III-I).
[4]
The polyacetal resin composition according to any one of the above [1] to [3], wherein the most probable void radius of the light calcium carbonate (II) is 0.12 μm or more and 0.16 μm or less in the measurement of the void radius by mercury porosimetry. object.
[5]
Said polyacetal resin (I) is a polyacetal resin composition in any one of said [1]-[4] containing the polyacetal copolymer which has melting | fusing point of 164 to 173 degreeC.
[6]
Said polyacetal resin (I) is a polyacetal resin composition in any one of said [1]-[5] containing the polyacetal copolymer which has melting | fusing point of 167 degreeC or more and 173 degrees C or less.
[7]
The polyacetal resin composition according to any one of [1] to [6], further including 0.01 to 3 parts by mass of (VI) polyamide resin with respect to 100 parts by mass of the polyacetal resin composition.
[8]
A method for producing the polyacetal resin composition according to any one of the above [1] to [6],
Light calcium carbonate (II) having an average particle size of 50 nm or more and 500 nm or less, a pH of 9.2 or more and 10.0 or less according to the JIS K5101 test method, and having no surface treatment; Monovalent fatty acid (III-I), monovalent fatty acid (III-II) having 28 or more carbon atoms, calcium salt of fatty acid (IV), aliphatic alcohol and fatty acid ester (V) are fixed. Mixing in a phase with a blender to obtain a mixture;
A step of continuously supplying the mixture and the polyacetal resin (I) from different feeders into the barrel of the extruder and melt-kneading to obtain a melt-kneaded product;
Continuously extruding the melt-kneaded product from the die of the extruder;
The manufacturing method of the polyacetal resin composition which has this.
[9]
A method for producing the polyacetal resin composition according to [7] above,
Light calcium carbonate (II) having an average particle size of 50 nm or more and 500 nm or less, a pH of 9.2 or more and 10.0 or less according to the JIS K5101 test method, and having no surface treatment; Monovalent fatty acid (III-I), monovalent fatty acid (III-II) having 28 or more carbon atoms, calcium salt of fatty acid (IV), fatty alcohol and fatty acid ester (V), and polyamide resin (VI) is mixed with a blender in a solid phase to obtain a mixture;
A step of continuously supplying the mixture and the polyacetal resin (I) from different feeders into a barrel of an extruder and melt-kneading to obtain a melt-kneaded product;
Continuously extruding the melt-kneaded product from the die of the extruder;
The manufacturing method of the polyacetal resin composition which has this.
[10]
The method for producing a polyacetal resin composition according to the above [9], wherein the polyamide resin (VI) is blended as a molten master batch with the polyacetal resin (I).
[11]
An injection-molded article comprising the polyacetal resin composition according to any one of [1] to [7].
[12]
A gear comprising the polyacetal resin composition according to any one of [1] to [7].

  ADVANTAGE OF THE INVENTION According to this invention, the polyacetal resin composition excellent in the balance of mechanical characteristics, such as rigidity and toughness, and also excellent in the retention discoloration property in a molten state, and its manufacturing method can be provided.

The schematic diagram of the JIS1A No. dumbbell piece obtained in the Example is shown. The schematic diagram of the twin-screw extruder used in the Example is shown.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiment, and can be implemented with various modifications within the scope of the gist.

The polyacetal resin composition of the present embodiment is
100 parts by mass of polyacetal resin (I),
5-50 parts by weight of light calcium carbonate (II) having an average particle size of 50 nm or more and 500 nm or less, a pH of 9.2 or more and 10.0 or less by JIS K5101 test method, and no surface treatment;
Monovalent fatty acid (III-I) having 12 to 27 carbon atoms;
A monovalent fatty acid (III-II) having 28 or more carbon atoms;
A calcium salt of fatty acid (IV);
An ester of fatty alcohol and fatty acid (V);
Containing
The total mass ratio [(III-I) + (III-II)] / (II) of the fatty acid (III-I) and the fatty acid (III-II) to the light calcium carbonate (II) is 0.020 to 0.050, and the total mass ratio of the fatty acid (III-I) and the fatty acid (III-II) to the calcium salt (IV) of the fatty acid [(III-I) + (III-II)] / ( IV) is 3 to 15, and a mass ratio (V) / (II) of the aliphatic alcohol and the ester of fatty acid (V) to the light calcium carbonate (II) is 0.01 to 0.15.

[Polyacetal resin (I)]
As polyacetal resin (I) in this embodiment, if it is conventionally known, it will not specifically limit, A polyacetal homopolymer and a polyacetal copolymer are mentioned. The polyacetal homopolymer, for example, consists essentially of oxymethylene units obtained by homopolymerizing formaldehyde monomers or cyclic oligomers of formaldehyde such as trimers (trioxane) and tetramers (tetraoxane). A polyacetal homopolymer may be mentioned. Polyacetal copolymers include formaldehyde monomers or cyclic oligomers of formaldehyde such as trimers (trioxane) or tetramers (tetraoxane), ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, 1, Examples thereof include polyacetal copolymers obtained by copolymerization with cyclic ethers such as glycols such as 4-butanediol formal, or cyclic formals of diglycol, or cyclic formals. Furthermore, as a polyacetal copolymer, a polyacetal copolymer having a branch obtained by copolymerizing a formaldehyde monomer or a cyclic oligomer of the above formaldehyde with a monofunctional glycidyl ether; a formaldehyde monomer or a cyclic oligomer of the above formaldehyde, and a polyfunctional A polyacetal copolymer having a crosslinked structure obtained by copolymerization with glycidyl ether is also exemplified.

  The polyacetal resin (I) is a block obtained by polymerizing a compound having a functional group such as a hydroxyl group at both ends or one end, for example, a formaldehyde monomer or a cyclic oligomer of formaldehyde in the presence of polyalkylene glycol. It may be a polyacetal homopolymer having components. Similarly, it is obtained by copolymerizing a compound having a functional group such as a hydroxyl group at both ends or one end, for example, hydrogenated polybutadiene glycol with a formaldehyde monomer or a cyclic oligomer of the above formaldehyde, a cyclic ether, and a cyclic formal. It may be a polyacetal copolymer having a block component. As described above, in the present embodiment, either a polyacetal homopolymer or a polyacetal copolymer can be used, but a polyacetal copolymer is preferable. A polyacetal resin (A) is used individually by 1 type or in combination of 2 or more types.

  In the case of a polyacetal copolymer of trioxane and a comonomer such as 1,3-dioxolane, generally, the copolymerization ratio of the comonomer is preferably 0.001 to 0.6 mol, more preferably 0 to 1 mol of trioxane. The range is 0.001 to 0.2 mol, more preferably 0.0013 to 0.1 mol. A suitable melting point of the polyacetal copolymer is 164 ° C to 173 ° C, more preferably 167 ° C to 173 ° C, and further preferably 167 ° C to 171 ° C. A polyacetal copolymer having a melting point of 167 ° C. to 171 ° C. can be obtained by using about 0.0013 to 0.0035 mol% of a comonomer with respect to 1 mol of trioxane.

  The polymerization catalyst used when the polyacetal copolymer is obtained by copolymerization is not particularly limited, but cationically active catalysts such as Lewis acids, proton acids and esters or anhydrides thereof are preferred. Examples of Lewis acids include boric acid, tin, titanium, phosphorus, arsenic and antimony halides. More specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, Examples thereof include phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof. Specific examples of the protonic acid, its ester or anhydride include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate, trimethyloxonium hexafluorophosphate, and the like. Among these cationically active catalysts, boron trifluoride; boron trifluoride hydrate; and organic compounds containing oxygen atoms or sulfur atoms and three compounds from the viewpoint of excellent handleability and appropriate polymerization activity. A coordination complex compound with boron fluoride is preferred. Specifically, boron trifluoride diethyl ether and boron trifluoride di-n-butyl ether can be mentioned as preferred examples.

  As a polymerization method of the polyacetal copolymer, conventionally known methods, for example, US Pat. No. 3,027,352, US Pat. No. 3,803,094, German Patent No. 1,161,421, German Patent No. 1,495,228 are described. German Patent Invention No. 1720358, German Patent No. 3018898, JP-A-58-98322, JP-A-7-70267, and the like.

The polyacetal copolymer obtained by the above polymerization has a thermally unstable terminal portion [-(OCH ₂ ) _n —OH group]. Therefore, in order to improve its practicality, the following specific irregularities are required. It is preferable to subject the stable end portion to decomposition and removal.

Specific decomposing / removing treatment of unstable terminal portion (hereinafter, also simply referred to as “unstable end portion removing treatment”) refers to, for example, at least one quaternary ammonium compound represented by the following general formula (1): In the presence of the polyacetal copolymer, the polyacetal copolymer is subjected to a heat treatment in a molten state at a temperature not lower than the melting point of the polyacetal copolymer and not higher than 260 ° C.
[R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ^-n Formula (1)
Here, in formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; carbon An aralkyl group in which at least one hydrogen atom of the substituted or unsubstituted alkyl group having 1 to 30 is substituted with an aryl group having 6 to 20 carbon atoms; at least one hydrogen atom of the aryl group having 6 to 20 carbon atoms is The alkylaryl group substituted by the C1-C30 substituted or unsubstituted alkyl group is shown, and a substituted or unsubstituted alkyl group is linear, branched, or cyclic. The substituent of the substituted alkyl group is a halogen atom, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, or an amide group. Further, in the above unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group, the hydrogen atom may be substituted with a halogen atom. n shows the integer of 1-3. X represents a hydroxyl group or an acid residue of a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than a hydrogen halide, an oxo acid, an inorganic thioacid, or an organic thioacid having 1 to 20 carbon atoms. )

The quaternary ammonium compound is not particularly limited as long as it is represented by the general formula (1), but R ¹ , R ² , R ³ and R ⁴ in the general formula (1) are each independently is preferably a hydroxyalkyl group having 2 to 4 alkyl carbon atoms or 1 to 5 carbon atoms, further, R ^1, R ^2, at least one of R ³ and R ^4, those that are hydroxyethyl groups are particularly preferable. Specifically, tetramethylammonium, tetoethylammonium, tetrapropylammonium, tetra-n-butylammonium, cetyltrimethylammonium, tetradecyltrimethylammonium, 1,6-hexamethylenebis (trimethylammonium), decamethylene-bis- ( Trimethylammonium), trimethyl-3-chloro-2-hydroxypropylammonium, trimethyl (2-hydroxyethyl) ammonium, triethyl (2-hydroxyethyl) ammonium, tripropyl (2-hydroxyethyl) ammonium, tri-n-butyl ( 2-hydroxyethyl) ammonium, trimethylbenzylammonium, triethylbenzylammonium, tripropylbenzylammonium, tri-n-butylbenzene Zirammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, okdadecyltri (2-hydroxyethyl) ammonium, tetrakis (hydroxyethyl) ammonium, etc. hydroxide (X ^n- = OH ^-); hydrochloric acid, hydrobromic acid, hydrogen salts such as hydrofluoric acid, sulfuric acid _{^{(X n- = HSO 4 -,}} SO 4 2-), nitric acid, phosphoric acid, carbonic acid (X ^{n _{- = HCO 3 -, CO 3}} 2-), boric acid ^{(X n- = B (OH)} 4 -), chlorate, iodate, silicate, perchlorate, chlorite, hypochlorite, chloro acid Oxo acid salts such as amidosulfuric acid, disulfuric acid and tripolyphosphoric acid; thioic acid salts such as thiosulfuric acid; formic acid, acetic acid, propionic acid, butanoic acid, iso Acid, pentanoic acid, caproic acid, caprylic acid, capric acid, benzoic acid, carboxylic acid salts such as oxalic acid. Among the above, hydroxides, sulfates, carbonates, borates, and carboxylates are preferable. Among the carboxylates, formate, acetate, and propionate are particularly preferable. One of these quaternary ammonium compounds may be used alone, or two or more thereof may be used in combination. Further, in addition to the quaternary ammonium compound, amines such as ammonia and triethylamine which are known decomposition accelerators for unstable terminals may be used in combination.

The amount of the quaternary ammonium compound used in the heat treatment method is converted to the amount of nitrogen derived from the quaternary ammonium compound represented by the following formula (2) with respect to the total mass of the polyacetal copolymer and the quaternary ammonium compound. The amount is preferably 0.05 to 50 ppm by mass, more preferably 1 to 30 ppm by mass.
P × 14 / Q Formula (2)
Here, in Formula (2), P shows the density | concentration (mass ppm) with respect to the polyacetal copolymer of a quaternary ammonium compound, 14 is the atomic weight of nitrogen, Q shows the molecular weight of a quaternary ammonium compound.

  When the amount of the quaternary ammonium compound used is less than 0.05 ppm by mass in terms of the amount of nitrogen derived from the quaternary ammonium compound, the decomposition and removal rate of the unstable terminal portion tends to decrease, 50 If it exceeds mass ppm, the color tone of the polyacetal copolymer after the decomposition and removal treatment of the unstable end tends to deteriorate.

  The unstable end portion removal treatment of the polyacetal copolymer is achieved by heat-treating the polyacetal copolymer in a melted state at a temperature not lower than the melting point of the polyacetal copolymer and not higher than 260 ° C. The apparatus used for the heat treatment at this time is not particularly limited, but it is preferable to perform the heat treatment using an extruder, a kneader or the like. Further, formaldehyde generated by decomposition is usually removed under reduced pressure. The addition method of the quaternary ammonium compound is not particularly limited, and examples thereof include a method of adding it as an aqueous solution in the step of deactivating the polymerization catalyst, and a method of spraying the polyacetal copolymer powder produced by the polymerization. Whichever addition method is used, it is sufficient that a quaternary ammonium compound is added to the polyacetal copolymer in the heat treatment step. For example, a quaternary ammonium compound may be injected into an extruder in which a polyacetal copolymer is melt kneaded and extruded. Alternatively, when a filler or pigment is blended with the polyacetal copolymer using an extruder or the like, a quaternary ammonium compound is first attached to the resin pellet of the polyacetal copolymer, and the unstable end portion of the filler or pigment is blended thereafter. A decomposition and removal process may be performed.

  The unstable terminal portion may be decomposed and removed after the polymerization catalyst in the polyacetal copolymer obtained by polymerization is deactivated or may be performed without deactivating the polymerization catalyst. Although it does not restrict | limit especially as a deactivation process of a polymerization catalyst, The method of neutralizing and deactivating a polymerization catalyst in basic aqueous solution, such as amines, is mentioned. Also, without deactivating the polymerization, the copolymer is heated in an inert gas atmosphere at a temperature below the melting point of the polyacetal copolymer, the polymerization catalyst is reduced by volatilization, and then the unstable terminal portion is decomposed and removed. It is also an effective way to do it.

  By performing the decomposition and removal treatment of the unstable terminal portion as described above, it is possible to obtain a polyacetal copolymer with very few unstable terminal portions and excellent in thermal stability.

[Light calcium carbonate (II)]
The light calcium carbonate (II) used in the present embodiment has an average particle size of 50 nm to 500 nm, a pH of 9.2 to 10.0 according to the JIS K5101 test method, and is not subjected to surface treatment. It is calcium carbonate.

  The shape of the light calcium carbonate (II) particles is not particularly limited, and specific examples include a spherical shape, a cubic shape, a spun shape, a flake shape, and an indeterminate shape. Among these, from the viewpoint of reducing the anisotropy of the injection-molded product and improving the mechanical strength, a cubic shape is preferable, and the aspect ratio (L) is the ratio of the average major axis (L) to the average minor axis (D) of the particles. More preferably, / D) is 3 or less.

  The crystal form of light calcium carbonate (II) may be any of the generally known calcite type, aragonite type, and patelite type, and among these, the interfacial adhesion with the polyacetal resin, the resin composition From the viewpoint of the balance of mechanical properties of materials, the calcite type is preferable. The light calcium carbonate (II) is preferably artificially synthesized light calcium carbonate (sometimes called colloidal calcium carbonate, precipitated calcium carbonate, or activated calcium carbonate). Among these, from the viewpoint that the shape and diameter of the calcium carbonate particles can be precisely controlled, those produced by reacting carbon dioxide with slurry calcium hydroxide are particularly preferable. Light calcium carbonate (II) may be used individually by 1 type, and may use 2 or more types together.

  The average particle size of light calcium carbonate (II) is from 50 nm to 500 nm, preferably from 80 nm to 300 nm, more preferably from 80 nm to 200 nm. If the average particle size of light calcium carbonate (II) is less than 50 nm, the thermal stability of the resin composition will be insufficient, and if it exceeds 500 μm, the slidability at high temperatures of the resin composition will be insufficient.

  Here, the average particle diameter, the average major axis, and the average minor axis of the light calcium carbonate (II) are sampled from the calcium carbonate particles to be measured by a scanning electron microscope (SEM). Each diameter was measured from at least 100 particles of calcium carbonate randomly selected in the obtained image taken at 50,000 times, and obtained as an arithmetic average thereof.

  Moreover, pH based on the JISK5101 test method of light calcium carbonate (II) is 9.2 or more and 10.0 or less, Preferably it is 9.4 or more and 9.7 or less. It is one requirement for achieving the object of the present invention that the pH of light calcium carbonate (II) is 9.2 or more and 10.0 or less.

  Furthermore, it is preferable that the most probable void radius by a mercury intrusion method using a mercury porosimeter of light calcium carbonate (II) is 0.12 μm or more and 0.16 μm or less. When the most probable void radius is 0.12 μm or more, calcium carbonate aggregates are not easily formed in the resin composition, and a good dispersion tends to be obtained. By being 0.16 μm or less, the resin composition There is a tendency that sufficient slidability at a high temperature is obtained.

  The light calcium carbonate (II) in the present embodiment is not subjected to surface treatment. “Surface treatment” as used herein refers to the addition of at least one of known surface treatment agents, adhesives or complexing agents, and anti-aggregation agents for the purpose of preventing particle aggregation in the calcium carbonate production process. As a result, the surface of calcium carbonate is covered with the substance. Here, the surface treatment technology agent, the adhesive or complexing agent, and the anti-agglomeration agent are, for example, 232 of “Analysis and application technology of dispersion / aggregation, 1992” (supervised by Fumio Kitahara, published by Techno System Co., Ltd.). Anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant as described on page 247. Further, silane coupling agents such as aminosilane and epoxysilane, titanate coupling agents, fatty acids (saturated fatty acids and unsaturated fatty acids), aliphatic carboxylic acids, resin acids and metal soaps are exemplified. The fact that the light calcium carbonate (II) is not subjected to the surface treatment is one requirement that the polyacetal resin composition of the present embodiment achieves the object of the present invention.

  The compounding quantity of the light calcium carbonate (II) in the polyacetal resin composition in this embodiment is 5-50 mass parts with respect to 100 mass parts of polyacetal resin, Preferably it is 10-50 mass parts. The blending amount of 5 to 50 parts by mass is one requirement that the polyacetal resin composition of the present embodiment achieves the object of the present invention.

[Fatty acids (III-I) and (III-II)]
The monovalent fatty acid (III-I) having 12 to 27 carbon atoms and the monovalent fatty acid (III-II) having 28 or more carbon atoms have a structure in which a carboxyl group is bonded to a linear or branched aliphatic hydrocarbon group. The total number of carbon atoms in the molecule is 12 to 27 for fatty acid (III-I) and 28 or more for fatty acid (III-II). These fatty acids are used alone or in combination of two or more. Specific examples of the fatty acid (III-I) include undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecylic acid, palmitic acid, pentadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, Examples include serotic acid, heptaconic acid, laccellic acid, undecylenic acid, oleic acid, elaidic acid, cetreic acid, erucic acid, brassic acid, linoleic acid, linolenic acid, arachidonic acid, stearolic acid and the like. Specific examples of fatty acids (III-II) include montanic acid, melissic acid, dotriacontanoic acid, and tetratriacontanoic acid.

  The fatty acid (III-I) and the fatty acid (III-II) may be natural or synthesized, and when natural are used, the polyacetal resin composition of the present embodiment is used. May contain a mixture of the fatty acid (III-I) and fatty acid (III-II) with other natural ingredients. These fatty acids may be substituted with a functional group such as a hydroxy group. Further, these fatty acids may be synthetic fatty acids obtained by carboxyl-modifying the end of uniline alcohol which is a synthetic aliphatic alcohol. Among the monovalent fatty acids (III-I) described above, stearic acid and palmitic acid and a mixture of any proportion thereof are particularly preferable from the viewpoint of suppressing aggregation of calcium carbonate in the resin composition. Among -II), montanic acid is particularly preferred.

  In the polyacetal resin composition of the present embodiment, the mass ratio of the monovalent fatty acid (III-I) having 12 to 27 carbon atoms to the monovalent fatty acid (III-II) having 28 or more carbon atoms (III-I) / ( III-II) is preferably 1-5. Further, the total mass ratio of the monovalent fatty acid (III-I) having 12 to 27 carbon atoms and the monovalent fatty acid (III-II) having 28 or more carbon atoms to the light calcium carbonate (II) described above [(III- I) + (III-II)] / (II) is 0.020 to 0.050, preferably 0.025 to 0.050. The value of the mass ratio [(III-I) + (III-II)] / (II) is 0.020 to 0.050, which means that the polyacetal resin composition of the present embodiment achieves the object of the present invention. It is one requirement for doing this.

  The fatty acid constituting the calcium salt (IV) of the fatty acid is a monovalent fatty acid, and is preferably the same fatty acid as (III-I) from the viewpoint of imparting good slidability to the resin composition. In particular, the fatty acid (III-I) is palmitic acid, the fatty acid calcium salt (IV) is calcium palmitate, the fatty acid (III-I) is stearic acid, and the fatty acid calcium salt (IV) is stearic. A combination of calcium phosphate, fatty acid (III-I) is behenic acid, fatty acid calcium salt (IV) is preferably calcium behenate, fatty acid (III-i) is stearic acid, fatty acid calcium salt A combination in which (IV) is calcium stearate is particularly preferred.

  Furthermore, in the polyacetal resin composition of the present embodiment, the total mass ratio of the fatty acid (III-I) and the fatty acid (III-II) to the calcium salt (IV) of the fatty acid [(III-I) + (III-II) ] / (IV) is from 3 to 15, preferably from 5 to 13, from the viewpoint of exhibiting the target performance of the present invention.

  The aliphatic alcohol and fatty acid ester of the component (V) in this embodiment refers to a monoester of an aliphatic alcohol and a fatty acid, and an ester of an aliphatic alcohol and an aliphatic dicarboxylic acid. Examples of the aliphatic alcohol include monohydric alcohols and polyhydric alcohols.

  Examples of monohydric alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, and 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, octyldodecyl alcohol, decyl myristyl alcohol, decyl stearyl Examples include saturated or unsaturated alcohols such as alcohol.

  Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, glycerin, diglycerin, triglycerin, pentaerythritol, arabitol, ribitol, xylitol, Examples include sorbite, sorbitan, sorbitol, mannitol and the like.

  Examples of fatty acids include caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, pentadecylic acid, stearic acid, nanodecanoic acid, arachidic acid, behenic acid Acid, lignoceric acid, serotic acid, heptaconic acid, montanic acid, melissic acid, lacteric acid, undecylenic acid, oleic acid, elaidic acid, cetreic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, Examples include propiolic acid and stearic acid. Moreover, the naturally-occurring fatty acid containing these components or a mixture thereof can be mentioned. These fatty acids may be partially substituted with hydroxy groups.

  Among these esters of fatty alcohol and fatty acid, monoesters of aliphatic alcohol and fatty acid are preferred, monoesters of aliphatic alcohol and fatty acid having 12 or more carbon atoms are more preferred, and aliphatic alcohols and carbons having 10 or more carbon atoms. Monoesters with fatty acids of several tens or more are more preferred, and monoesters of aliphatic alcohols with 10 to 30 carbon atoms and fatty acids with 12 to 30 carbon atoms are even more preferred. Among them, cetyl myristate and stearyl stearate are particularly preferable from the viewpoint of maintaining the thermal stability of the composition.

  In the polyacetal resin composition of the present embodiment, the mass ratio (V) / (II) of the aliphatic alcohol and fatty acid ester (V) to the light calcium carbonate (II) exhibits the target performance of the present invention. 0.03 to 0.15, preferably 0.05 to 0.13.

  In the polyacetal resin composition of this embodiment, in order to capture formaldehyde that can be generated from the polyacetal resin (I), the polyamide resin (VI) is added in an amount of 0.01 to 3 parts by mass with respect to 100 parts by mass of the polyacetal resin (I). It is preferable to further contain a part. Examples of the polyamide resin (VI) include nylon 4,6, nylon 6, nylon 6,6, nylon 6,10, nylon 6,12, nylon 12, and polymers thereof such as nylon 6 / 6,6. / 6,10, nylon 6 / 6,12. The form of blending the polyamide resin (VI) is not particularly limited, but from the viewpoint of dispersibility in the polyamide resin composition, the form of blending the polyamide resin (VI) as a master batch with the polyacetal resin (I) is particularly preferable. .

  If necessary, the polyacetal resin composition in the present embodiment further includes an antioxidant, a polymer or compound containing nitrogen reactive with formaldehyde, a formic acid scavenger, a weathering (light) stabilizer, a lubricant, and a release agent. May be added within a range of 0.01 to 1.0 part by mass with respect to 100 parts by mass of the polyacetal resin (I).

  As the antioxidant, a hindered phenol antioxidant is preferable. Specific examples of the hindered phenol antioxidant include 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-t-butyl-4-hydroxyphenyl) -propionate], 1,4-butanediol-bis- [3- (3,5-di-t- Butyl-4-hydroxyphenyl) -propionate], triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate] Pentaerythritol tetrakis [methylene-3- (3 ', 5'-di -t- butyl-4'-hydroxyphenyl) propionate] methane, and the like. Among the above, preferably, triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] and pentaerythritol tetrakis [methylene-3- (3 ′, 5 ′ -Di-t-butyl-4'-hydroxyphenyl) propionate] methane. These antioxidants are used alone or in combination of two or more.

  Examples of polymers or compounds containing nitrogen reactive with formaldehyde include acrylamide and derivatives thereof, and copolymers of acrylamide and derivatives thereof with other vinyl monomers. More specifically, for example, a poly-β-alanine copolymer obtained by polymerizing acrylamide and its derivatives and other vinyl monomers in the presence of a metal alcoholate can be mentioned. In addition to the above polymers or compounds, amide compounds, amino-substituted triazine compounds, adducts of amino-substituted triazine compounds and formaldehyde, condensates of amino-substituted triazine compounds and formaldehyde, urea, urea derivatives, hydrazine derivatives, imidazole compounds And imide compounds.

  Specific examples of the amide compound include polycarboxylic acid amides such as isophthalic acid diamide and anthranilamides. Specific examples of the amino-substituted triazine compound include 2,4-diamino-sym-triazine, 2,4,6-triamino-sym-triazine, N-butylmelamine, N-phenylmelamine, N, N-diphenylmelamine, N , N-diallylmelamine, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine), acetoguanamine (2,4-diamino-6-methyl-sym-triazine), 2,4-diamino-6-butyl -Sym-triazine and the like. Specific examples of the adduct of an amino-substituted triazine compound and formaldehyde include N-methylol melamine, N, N′-dimethylol melamine, and N, N ′, N ″ -trimethylol melamine. Specific examples of the condensate of the compound and formaldehyde include melamine / formaldehyde condensate, and examples of urea derivatives include N-substituted urea, urea condensate, ethylene urea, hydantoin compound, and ureido compound. Specific examples of the N-substituted urea include methylurea, alkylenebisurea, and aryl-substituted urea substituted with a substituent such as an alkyl group, etc. Specific examples of the urea condensate include a condensate of urea and formaldehyde. Specific examples of hydantoin compounds include hydantoin, 5, -Dimethylhydantoin and 5,5-diphenylhydantoin Specific examples of ureido compounds include allantoin Specific examples of hydrazine derivatives include hydrazide compounds Specific examples of hydrazide compounds include dicarboxylic acids More specifically, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, speric acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide Dihydrazide, phthalic acid dihydrazide, 2,6-naphthalenedicarbodihydrazide, etc. Specific examples of imide compounds include succinimide, glutarimide, phthalimid. And the like.

  Examples of the formic acid scavenger include condensates of the above amino-substituted triazine compounds and amino-substituted triazine compounds with formaldehyde, such as melamine / formaldehyde condensates. Examples of other formic acid scavengers include alkali metal or alkaline earth metal hydroxides, inorganic acid salts, and alkoxides. More specifically, for example, hydroxides of sodium, potassium, magnesium, calcium or barium, carbonates, phosphates, silicates and borates of the above metals can be mentioned. These formic acid scavengers are used singly or in combination of two or more.

  The weathering (light) stabilizer is preferably at least one selected from benzotriazole-based and oxalic acid anilide-based UV absorbers and hindered amine-based light stabilizers.

  Specific examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methyl-phenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butyl- Phenyl) benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3 ′, 5′- Bis- (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole, and the like. Specific examples of the oxalic acid alinide ultraviolet absorber include 2-ethoxy-2′-ethyloxalic acid bisanilide, 2-ethoxy-5-tert-butyl-2′-ethyloxalic acid bisanilide, 2- And ethoxy-3′-dodecyloxalic acid bisanilide. The benzotriazole-based ultraviolet absorber is preferably 2- [2′-hydroxy-3 ′, 5′-bis- (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy- 3 ', 5'-di-tert-butyl-phenyl) benzotriazole. These benzotriazole-based ultraviolet absorbers are used alone or in combination of two or more.

  Specific examples of the hindered amine light stabilizer include N, N ′, N ″, N ′ ″-tetrakis- (4,6-bis (butyl- (N-methyl-2,2,6,6-tetra). Methylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10-diamine, dibutylamine 1,3,5-triazine N, N′-bis (2,2 , 6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidi L) imino}], condensate of dimethyl succinate with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, bis (2,2,6,6-tetramethyl-decanoate) 1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and octane, the reaction product bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3 5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate, bis (2,2,6, 6-tetramethyl-4-piperidyl) -sebacate, 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β ′, And a condensate with ', -tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (5,5) undecane] diethanol.The hindered amine light stabilizer is preferably bis (2 , 2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 1,2,3,4-butanetetracarboxylic Acid, 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β ′, β′-tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (5 5) Undecane] Condensates with diethanol These hindered amine light stabilizers can be used alone or in combination of two or more.

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

  Moreover, you may mix | blend various additives for improving the lubricity with respect to a polyacetal as a lubricant. As such a lubricant, specifically, a polyolefin resin grafted with a silicon compound (hereinafter sometimes abbreviated as “silicon grafted polyolefin resin”), a silicon compound, and a polyolefin resin are blended. can do.

  Silicon grafted polyolefin resin is preferably low density polyethylene, linear low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene ethyl acrylate copolymer , Polyolefin resins such as polymethylpentene, polypropylene, and tetrafluoroethylene-ethylene copolymer (which may contain a small amount of vinyl monomer such as vinyl acetate if necessary); A silicon compound such as polydimethylsiloxane represented by the formula (3) is grafted.

（３）

(3)

Methyl group in the formula ₍₃₎ (CH 3) is hydrogen, alkyl group, phenyl group, an ether group, a hydroxyl group is an ester group or a reactive substituent group, an amino group, an epoxy group, a carboxyl group, carbinol group, It may be substituted with a substituent having a methacryl group, a mercapto group, a phenol group, a vinyl group, an allyl group, a polyether group, a fluorine-containing alkyl group, etc., and a substituent having a vinyl group or an allyl group for grafting It preferably has a group. The average polymerization degree n of the silicon compound is preferably in the range of 1000 to 10,000.

  The silicon compound may be the same as or different from the silicon compound used for grafting to the polyolefin resin, but the silicon compound does not have a cross-linked structure represented by the formula (3) ( Silicon gum) is preferable. In the present embodiment, two or more types of silicon compounds can be used. In the silicon grafted polyolefin resin, it is necessary that the polymer chains are not cross-linked with each other and exist as independent polymer chains. Therefore, the silicone-grafted polyolefin of this embodiment is a crosslinked structure type (three-dimensional structure type) resin having rubber elasticity that is crosslinked with each other via a silicon compound in which the main chains of the silicon grafted polyolefin resin are grafted together. Not included in resin.

  The polyolefin resin is a homopolymer or copolymer of an olefinically unsaturated compound represented by the general formula (4), or a modified product thereof.

（４）

(4)

[In the formula (4), R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a carboxyl group, an alkylcarboxy group containing 2 to 5 carbon atoms, 2 An acyloxy group having 5 carbon atoms or a vinyl group is shown. ]

  Specific examples of the polyolefin resin include polyethylene (high density polyethylene, medium density polyethylene, high pressure method low density polyethylene, linear low density polyethylene, ultra low density polyethylene), polypropylene, ethylene-propylene copolymer, ethylene- Butene copolymer, polypropylene-butene copolymer, polybutene, polybutadiene hydrogenated product, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-acetic acid A vinyl copolymer etc. are mentioned. Examples of these modified products include graft copolymers obtained by grafting one or more other vinyl compounds.

  The polyacetal resin composition of the present embodiment may further contain a known additive as required, as long as the object of the present invention is not impaired. Specific examples of such additives include inorganic fillers, crystal nucleating agents, conductive materials, thermoplastic resins, and thermoplastic elastomers and pigments.

  As the inorganic filler, for example, those in the form of fibers, powder particles, plates and hollows are used. Examples of the fibrous filler include 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, copper, Examples thereof include inorganic fibers such as metal fibers such as brass. Moreover, you may use whiskers, such as a potassium titanate whisker with short fiber length, and a zinc oxide whisker, as an inorganic filler. In addition, the polyacetal resin composition of this embodiment may contain high melting point organic fibrous materials, such as an aromatic polyamide resin, a fluororesin, and an acrylic resin.

  Examples of the particulate filler include carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, silicates such as wollastonite, iron oxide, and titanium oxide. 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. 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 are used alone or in combination of two or more. These fillers may be either surface-treated or non-surface-treated, but surface-treated ones may be preferable in terms of the smoothness of the molding surface and mechanical properties. A conventionally well-known thing can be used as a surface treating agent. As the surface treatment 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, and n-butyl zirconate Can be mentioned.

  Examples of the crystal nucleating agent include boron nitride.

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

  Examples of the thermoplastic resin include polyolefin resin, acrylic resin, styrene resin, polycarbonate resin, and uncured epoxy resin. Moreover, you may use the modified material of these resin as a thermoplastic resin. Examples of the thermoplastic elastomer include polyurethane elastomers, polyester elastomers, polystyrene elastomers, and polyamide elastomers.

  Examples of the pigment include inorganic pigments, organic pigments, metallic pigments, and fluorescent pigments. Here, examples of the inorganic pigment include those generally used for coloring resins, such as zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, combustion pigments, carbonates, Examples thereof include phosphate, acetate, carbon black, acetylene black, and lamp black. In addition, as organic pigments, condensed azo, inone, furothocyanin, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennon, quinacridone, thioindico, berylene, dioxazine, Examples thereof include phthalocyanine pigments. The addition ratio of the pigment to the polyacetal resin composition of the present embodiment is difficult to define clearly because it varies greatly depending on the required color tone, but in general, with respect to 100 parts by mass of the polyacetal resin (I) , 0.05 to 5 parts by mass.

  Next, the suitable manufacturing method of the polyacetal resin composition of this embodiment is demonstrated. Here, for the sake of simplification of explanation, polyacetal resin (I), light calcium carbonate (II), fatty acid (III), calcium salt of fatty acid (IV), and fatty alcohol and fatty acid ester (V) are used. , May be simply referred to as component (I), component (II), component (III), component (IV), and component (V), respectively.

  As a device used in the method for producing the polyacetal resin composition of the present embodiment, a kneader that is generally used can be applied. Examples of the apparatus include a single-screw or multi-screw kneading extruder, a roll, and a Banbury mixer. Among these, a twin screw extruder equipped with a decompression device and a side feeder is particularly preferable. The polyacetal resin composition of the present embodiment can be obtained by melting and kneading the above components using such an apparatus. Melt-kneading methods include a method of melt-kneading all components simultaneously, a method of melt-kneading a premixed mixture, and further supplying each component by using a side feeder sequentially from the middle of the barrel of the extruder. And a melt kneading method.

Specifically, the manufacturing method is as follows:
[A] Polyacetal resin (I), light calcium carbonate (II), fatty acid (III-I), fatty acid (III-II), calcium salt of fatty acid (IV), fatty alcohol and fatty acid ester (V) is a method comprising a step of obtaining a mixture, and a step of melt-kneading the mixture,
[B] Light calcium carbonate (II), fatty acid (III-I), fatty acid (III-II), fatty acid calcium salt (IV), aliphatic alcohol and fatty acid ester (V) A method comprising a step of mixing to obtain a premix, a step of melt kneading the premix and the polyacetal resin (I), and [C] two or three of the above components (I) to (V) Examples thereof include a method comprising a step of previously mixing or melt-kneading seed components to obtain a premix, and a step of melt-kneading the premix and the remaining components not mixed.
However, the mixing order and melt-kneading order of component (I) to component (V) are not particularly limited. Among these, from the viewpoint of more effectively and reliably achieving the object of the present invention, the component (II), the component (III-I), and the component (III-I) are added to the heated melt or solid state component (I). A method in which a mixture of II), component (IV) and component (V) is added and melt-kneaded is preferred.

  More specifically, from the viewpoint of obtaining a polyacetal resin composition that can achieve the object of the present invention more effectively and reliably, a preferred production method includes component (II), component (III-I), and component (III-II). ), Component (IV), and component (V) are mixed in a solid phase by a blender to obtain a mixture, and the mixture and component (I) are respectively fed from different feeders into the barrel of the extruder. A step of continuously supplying and melt-kneading to obtain a melt-kneaded product, and a step of continuously extruding the melt-kneaded product from a die of an extruder. This production method is a production method that does not go through a step of applying a surface treatment or coating to calcium carbonate (II) by heating Henschel coating or the like using fatty acid (III-I) and fatty acid (III-II). It is.

  When the polyacetal resin composition contains polyamide (VI), as a more preferable production method, component (II), component (III-I), component (III-II), component (IV), A step of mixing a fatty alcohol and a fatty acid ester (V) and a polyamide resin (VI) with a blender in a solid phase to obtain a mixture, and the mixture and component (I) from different feeders It is a production method comprising a step of continuously supplying into a barrel of an extruder and melt-kneading to obtain a melt-kneaded product, and a step of continuously extruding the melt-kneaded product from a die of the extruder. In this case, the polyamide resin (VI) is particularly preferably blended as a melt masterbatch with the polyacetal resin (I).

  Although the pressure reduction degree of an extruder is not specifically limited, 0-0.07 Mpa is preferable. The melt kneading temperature is preferably 1 to 100 ° C. higher than the melting point obtained by differential scanning calorimetry (DSC) measurement of the polyacetal resin (I) used according to JIS K7121. More specifically, it is preferably 160 to 240 ° C. The shear rate in the kneader is preferably 100 rpm or more, and the average residence time during kneading is preferably 30 seconds to 1 minute.

  The method for obtaining a molded product by molding the polyacetal resin composition of the present embodiment is not particularly limited, and conventionally known molding methods such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding. , Decorative molding, molding of other materials, gas assist injection molding, firing injection molding, low pressure molding, ultra thin injection molding (ultra high speed injection molding), and in-mold composite molding (insert molding, outsert molding).

  A molded product obtained from the polyacetal resin composition of the present embodiment by the above-described molding method is excellent in mechanical property balance such as rigidity and toughness, and further excellent in sliding property against metal at high temperature. Therefore, the molded product is useful when used as a part having a complicated shape, and can be used as a molded product for various applications. Examples of such molded products include gears, cams, sliders, levers, arms, clutches, felt clutches, idler gears, pulleys, rollers, rollers, key stems, key tops, shutters, reels, shafts, joints, shafts. , Mechanical parts such as bearings and guides, outsert molded resin parts, insert molded resin parts, chassis, trays, side plates, office automation equipment parts such as printers and copiers, VTR (Video Tape) Recorder), video movie, digital video camera, camera and 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 (Including Rewritable)], 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), DVD-Audio Blu-ray Disc, HD-DVD, other optical disk drives, MFD, MO, navigation systems and music, video or information equipment represented by mobile personal computers, communication equipment represented by mobile phones and facsimiles Examples include parts, electrical equipment parts, and electronic equipment parts.

  The molded product can also be used as parts for automobiles, for example, fuel-related parts such as gasoline tanks, fuel pump modules, valves, gasoline tank flanges, door locks, door handles. , Door regulators such as window regulators and speaker grills, seat belt slip rings, seat belt peripherals such as press buttons, combination switch parts, switches and clips, and mechanical pencils Mechanical parts for putting in and out the nib and mechanical pencil core, wash basin, drain outlet and drain valve opening / closing mechanism parts, opening / closing part locking mechanism of vending machine, product discharge mechanism parts, clothing cord stopper, adjuster and button , Sprinkler nozzle and sprinkler hose connection joy As industrial parts represented by building supplies, disposable cameras, toys, fasteners, chains, conveyors, buckles, sports equipment, vending machines, furniture, musical instruments, and housing equipment, which are support tools for floors, stair railings and flooring materials Are also preferably used.

  Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples, but the present embodiment is not limited to these.

(Measurement and evaluation methods of physical properties and characteristics)
<Measuring method of melting point>
The melting point of the polyacetal resin was measured using a differential calorimeter (trade name “DSC-2C” manufactured by Perkin Elmer Co., Ltd.). At that time, the temperature is first raised from room temperature to 200 ° C., the melted sample is cooled to 100 ° C., and the temperature is raised again at a rate of 2.5 ° C./min. The melting point.

<Measurement method of tensile properties>
Using an injection molding machine manufactured by Toshiba Machine Co., Ltd. (trade name “EC75NII injection molding machine”), the cylinder temperature is set to 205 ° C., the mold temperature is set to 90 ° C., the injection pressure is 73 MPa, the injection time is 35 seconds, and the cooling is 15 seconds. A polyacetal resin composition was injection molded under injection conditions, and an ISO dumbbell for evaluation was obtained as a test piece. About the obtained ISO dumbbell, the tensile elastic modulus and the tensile elongation were measured according to ISO527.

<Evaluation method of retention thermal discoloration>
The composition in a molten state was retained in a cylinder set at a temperature of 205 ° C. using an injection molding machine (trade name “EC75NII injection molding machine”) manufactured by Toshiba Machine Co., Ltd. After a certain period of time, the mold temperature was set to 90 ° C., and the mold was set to 90 ° C. under the injection conditions of an injection pressure of 73 MPa, an injection time of 35 seconds, and a cooling time of 15 seconds (the mold that obtained the ISO dumbbell for evaluation). The same piece was injected to obtain a molded piece (JIS 1A dumbbell piece). The color tone of the part indicated by a black circle in FIG. 1 of the obtained molded piece was measured in a Lab color system using a color difference meter (manufactured by Konica Minolta, trade name “CR-200”). At this time, the measured values of the color difference meter of the blank (molded piece obtained by normal molding in the molding machine) are L, a, and b, and the measured values of the molded piece after residence are L ^* , a ^* , b ^*. As a result, the color difference ΔE was calculated by the following formula (5), and the residence time in the cylinder in which this value exceeded 3.5 was determined.

(Production of polyacetal resin composition)
A polyacetal resin composition was produced using a twin screw extruder (manufactured by Toshiba Machine Co., Ltd., trade name “TEM-26SS extruder”, L / D = 48, with vent). A schematic diagram of this extruder is shown in FIG. In FIG. 2, 1 to 12 are barrel zones (independently) of the extruder, 13 is a die head, 14 is an extruder motor, 15 is a quantitative feeder (top 1), 16 is a quantitative feeder (top 2), Reference numeral 17 denotes a quantitative feeder (side), and 18 denotes a deaeration vent.

<Production method A>
Barrel zone 1 of the extruder was cooled with cooling water, barrel zones 2 and 3 were set at 210 ° C, barrel zones 4-11 were set at 215 ° C, and die head 15 was set at 210 ° C. Under this temperature condition, the polyacetal resin (I) is extracted from the quantitative feeder 15 with light calcium carbonate (II), monovalent fatty acid (III-I), monovalent fatty acid (III-II), and calcium salt of fatty acid (IV). The mixture is fed from the quantitative feeder 16 with a mixture of the fatty acid ester, fatty alcohol, fatty acid ester (V) and polyamide resin (VI) from the metering feeder 16, and is deaerated from the deaeration vent 18 using a vacuum pump. The mixture was melt-kneaded under the conditions of several 150 rpm and the extrusion rate of 14 kg / h, and the melt-kneaded product was extruded from the die with the die head 13 to obtain a polyacetal resin composition.

<Production method B>
Light calcium carbonate (II), monovalent fatty acid (III-I), monovalent fatty acid (III-II), fatty acid calcium salt (IV), fatty alcohol, fatty acid ester (V), and polyamide resin (VI A polyacetal resin composition was obtained in the same manner as in Production Method A, except that the mixture in a solid phase state was fed from the side quantitative feeder 17.

<Manufacturing method C>
Polyacetal resin (I), light calcium carbonate (II), monovalent fatty acid (III-I), monovalent fatty acid (III-II), calcium salt of fatty acid (IV), fatty alcohol and ester of fatty acid (V ) And the polyamide resin (VI) in the solid phase state, a polyacetal resin composition was obtained in the same manner as in Production Method A, except that the mixture was supplied from the quantitative feeder 15.

The following components were used in Examples and Comparative Examples.
(Polyacetal tree (I))
<Polyacetal resin I-i>
A twin-screw self-cleaning type polymerization machine (L / D = 8) with a jacket capable of passing a heat medium is adjusted to 80 ° C., 4 kg / hr of trioxane is added thereto, and 1,3-dioxolane is used as a comonomer. Melt based on JIS K7210 of polyacetal resin after polymerization with an addition amount of 8 g / h (0.013 mol with respect to 1 mol of trioxane) and methylal as a chain transfer agent (water content 1.3%, methanol content 0.99%) The flow rate was adjusted to 13 g / 10 minutes. Furthermore, boron trifluoride di-n-butyl etherate was continuously added as a polymerization catalyst in an amount of 1.5 × 10 ⁻⁵ mol with respect to 1 mol of trioxane, and polymerization was performed. The polyacetal copolymer discharged from the polymerization machine was put into a 0.1% aqueous solution of triethylamine to deactivate the polymerization catalyst. After filtering the deactivated polyacetal copolymer of the polymerization catalyst, 100 parts by mass of the polyacetal copolymer contains choline formate (triethyl-2-hydroxyethylammonium formate) as a quaternary ammonium compound. 1 part by weight of the aqueous solution was added and mixed uniformly, followed by drying at 120 ° C. The added amount of choline formate is adjusted by adjusting the concentration of choline formate in the aqueous solution containing the added choline formate, and converted to the amount of nitrogen represented by the above formula (2). To 20 ppm by mass. The dried polyacetal copolymer is supplied to a vented twin screw extruder, and 0.5 parts by mass of water is added to 100 parts by mass of the melted polyacetal copolymer in the extruder, and the extruder set temperature is 200 ° C. The unstable end portion was decomposed and removed under the condition of a residence time of 7 minutes in the extruder. The polyacetal copolymer with the unstable terminal portion decomposed was devolatilized under a condition of a vent vacuum of 20 Torr, extruded as a strand from the die portion of the extruder, and pelletized. Addition of 0.35 parts by mass of triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant to 100 parts by mass of the pelletized polyacetal resin Then, polyacetal resin pellets were obtained by melt-kneading with a vented twin-screw extruder. The melting point of the polyacetal resin (Ii) thus obtained was 169.5 ° C.

<Polyacetal resin I-ii>
The amount of 1,3-dioxolane added was changed to 128.3 g / h (0.039 mol relative to 1 mol of trioxane), and the amount of methylal added was changed to a melt flow rate based on JIS K7210 of the polyacetal resin after polymerization of 10 g / h. The polyacetal resin was pelletized in the same manner as the polymerization of the polyacetal resin (Ii) except that the amount was changed to 10 minutes. For 100 parts by mass of the pelletized polyacetal resin, 0.35 parts by mass of triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] is used as an antioxidant. The polyacetal resin pellet was obtained by adding and melt-kneading with a twin screw extruder with a vent. The polyacetal resin thus obtained had a melting point of (I-ii) of 164.5 ° C.

(Polyacetal resin (I-iii))
100 parts by mass of dehydrated formaldehyde gas and 0.1 part by mass of dimethyl distearyl ammonium acetate as a catalyst were charged into a tank capable of supplying monomers and the like continuously with a stirring blade. Next, acetic anhydride was polymerized at 58 ° C. while continuously supplying the acetic anhydride as a molecular weight regulator in such an amount that the melt flow rate of the polyacetal resin after polymerization was 10 g / 10 min. The obtained crude polyacetal polymer was put into a 1: 1 solvent mixture of hexane and acetic anhydride, and the end groups were chemically treated at 140 ° C. for 2 hours. The obtained polymer was vacuum dried at 120 ° C. for 3 hours under the conditions of 1 mmHg. Next, 0.35 mass of triethyleneglycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] as an antioxidant with respect to 100 mass parts of the dried polyacetal polymer. Polyacetal resin pellets were obtained by adding a part thereof and melt-kneading with a vented twin-screw extruder. The polyacetal resin (I-iii) thus obtained had a melting point of 175.0 ° C.

<Calcium carbonate (II)>
(II-i): Shiraishi Kogyo Co., Ltd., trade name “Brilliant-1500” (average particle size 150 nm, untreated surface, pH = 9.4, most probable void radius 0.13 μm)
(II-ii): manufactured by Shiraishi Kogyo Co., Ltd., trade name “Brilliant-1500” (average particle size 150 nm, untreated surface, pH = 9.7, most probable void radius 0.14 μm)
(II-iii): manufactured by Shiraishi Kogyo Co., Ltd., trade name “Brilliant-1500” (average particle size 150 nm, untreated surface, pH = 9.2, most probable void radius 0.12 μm)
(II-iv): manufactured by Shiraishi Kogyo Co., Ltd., trade name “Brilliant-1500” (average particle size 150 nm, untreated surface, pH = 10.0, most probable void radius 0.13 μm)
(II-v): Shiraishi Kogyo Co., Ltd., trade name “Brilliant-1500” (average particle size 150 nm, untreated surface, pH = 9.4, most probable void radius 0.10 μm)
(II-vi): manufactured by Shiraishi Kogyo Co., Ltd., trade name “Brilliant-1500” (average particle size 150 nm, untreated surface, pH = 9.4, most probable void radius 0.17 μm)
(II-vii): Shiraishi Kogyo Co., Ltd., trade name “Brilliant-1500” (average particle size 150 nm, untreated surface, pH = 9.1, most probable void radius 0.12 μm)
(II-viii): manufactured by Shiraishi Kogyo Co., Ltd., trade name “Brilliant-1500” (average particle size 150 nm, untreated surface, pH = 10.2, most probable void radius 0.14 μm)
(II-ix): manufactured by Shiraishi Kogyo Co., Ltd., trade name “Vigot-15” (average particle size 150 nm, surface fatty acid treatment, pH = 9.0, most probable void radius 0.12 μm)
(II-x): manufactured by Shiroishi Kogyo Co., Ltd., trade name “Shiraka Hana O” (average particle size 30 nm, surface rosin acid treatment, pH = 8.5, most probable void radius 0.02 μm)
(II-xi): manufactured by Shiraishi Kogyo Co., Ltd., trade name “PC-700” (average particle size 1.2 μm, untreated surface, pH = 9.9)
The calcium carbonates (II-i) to (II-viii) described above are produced by a lime milk / carbon dioxide reaction method that has undergone the following three steps (A), (B), and (C). It is a thing.
(A) Dense limestone was fired in a firing furnace and decomposed into carbon dioxide and quicklime.
(B) Water was added to the obtained quicklime and the mixture was hydrated and refined to obtain slurry-like slaked lime.
(C) Carbon dioxide obtained in (A) was blown into and reacted with the slurry-like slaked lime obtained in (B) to produce calcium carbonate.

(Monovalent fatty acid (III-I) having 12 to 27 carbon atoms)
(III-Ii): Stearic acid manufactured by Kawaken Fine Chemical Co., Ltd., trade name “F-3” (melting point: 64 ° C.)
(III-I-ii): Behenic acid (melting point: 82 ° C.)

(C28 or more fatty acid (III-II))
(III-II-i): Montanic acid manufactured by Clariant Japan Co., Ltd., trade name “Licow ax-S” (melting point: 84 ° C.)
(III-II-ii): Melicic acid (melting point 94 ° C.)

(Calcium salt of fatty acid (IV))
(IV-i): Calcium stearate manufactured by Nitto Kasei Co., Ltd. (IV-ii): Calcium behenate

(Ester of fatty alcohol and fatty acid (V))
(Vi): Cetyl myristate (Kitahiro Chemical Co., Ltd.)
(V-ii): Stearyl stearate (V-iii): Ethylene glycol distearate

(Polyamide resin (VI))
(VI-i): nylon 6,6 (10%)-copolymer acetal A polyacetal copolymer having a melt flow rate of 30 g / 10 min and polyamide 6,6 having a relative formic acid viscosity VR of 22 are mixed at a mass ratio of 9: 1. The mixture was melt kneaded with a twin screw extruder set at a cylinder temperature of 260 ° C. The extruded strand was pelletized with a strand cutter, and this was used as a polyamide resin (VI-i).

[Examples 1 to 64]
Each component was blended in the proportions shown in Tables 1 and 2, and melt kneaded by the production methods shown in Tables 1 and 2, respectively. The extruded polyacetal resin composition was pelletized with a strand cutter. About the obtained pellet, the tensile elasticity modulus and the tensile elongation were measured by the above-mentioned method, and the residence thermal discoloration test was done. The results are shown in Tables 1-4.

[Comparative Examples 1-39]
Each component was mix | blended in the ratio shown in Table 5, and it melt-kneaded with the manufacturing method shown in Table 5, respectively. The extruded polyacetal resin composition was pelletized with a strand cutter. About the obtained pellet, the tensile elasticity modulus and the tensile elongation were measured by the above-mentioned method, and the residence thermal discoloration test was done. The results are shown in Tables 5 and 6.
For Comparative Examples 2, 3, 24, and 25, 1.5 parts by mass of fatty acid (III-I) is blended with respect to 100 parts by mass of polyacetal resin (I), and Comparative Examples 4, 5, 26, and 27 are included. Contains 1.5 parts by mass of fatty acid (III-II) per 100 parts by mass of polyacetal resin (I), and for Comparative Examples 17, 18, 37 and 38, fatty acid calcium salt (IV) is added to polyacetal resin ( I) 0.15 mass part was mix | blended with respect to 100 mass parts.

  As is clear from the above test results, the polyacetal resin compositions of the present embodiment (Examples 1 to 64) are excellent in the balance of mechanical properties such as rigidity and toughness, and are further excellent in staying discoloration in a molten state. I understand that.

  Since the present invention is excellent in mechanical properties such as rigidity and toughness as described above, the present invention has industrial applicability in fields such as automobiles represented by gears, precision parts of electrical and electronic equipment, and other industries. Furthermore, since the polyacetal resin composition of the present invention is excellent in staying discoloration in a molten state, it can cope with a severe molding method represented by hot runner molding.

1-12: Barrel zone 13: Die head 14: Extruder motor 15-17: Metering feeder 18: Degassing vent

Claims (12)

100 parts by mass of polyacetal resin (I),
5-50 parts by weight of light calcium carbonate (II) having an average particle size of 50 nm or more and 500 nm or less, a pH of 9.2 or more and 10.0 or less by JIS K5101 test method, and no surface treatment;
Monovalent fatty acid (III-I) having 12 to 27 carbon atoms;
A monovalent fatty acid (III-II) having 28 or more carbon atoms;
A calcium salt of fatty acid (IV);
An ester of fatty alcohol and fatty acid (V);
Containing
The total mass ratio [(III-I) + (III-II)] / (II) of the fatty acid (III-I) and the fatty acid (III-II) to the light calcium carbonate (II) is 0.020 to 0.055, and the total mass ratio [(III-I) + (III-II)] / (IV) of the fatty acid (III) and the fatty acid (III-II) to the calcium salt (IV) of the fatty acid is A polyacetal resin composition having a mass ratio (V) / (II) of the aliphatic alcohol and the fatty acid ester (V) to the light calcium carbonate (II) of 0.03 to 0.15. .   The polyacetal resin composition of Claim 1 whose mass ratio (III-I) / (III-II) of the said fatty acid (III-I) with respect to the said fatty acid (III-II) is 1-5.   The polyacetal resin composition of Claim 1 or 2 whose fatty acid which comprises the calcium salt (IV) of the said fatty acid is the same kind as the said fatty acid (III-I).   The polyacetal resin composition according to any one of claims 1 to 3, wherein the most probable void radius of the light calcium carbonate (II) is 0.12 µm or more and 0.16 µm or less in measurement of the void radius by a mercury intrusion method. .   The polyacetal resin composition according to any one of claims 1 to 4, wherein the polyacetal resin (I) includes a polyacetal copolymer having a melting point of 164 ° C or higher and 173 ° C or lower.   The said polyacetal resin (I) is a polyacetal resin composition of any one of Claims 1-5 containing the polyacetal copolymer which has melting | fusing point of 167 degreeC or more and 173 degrees C or less.   The polyacetal resin composition of any one of Claims 1-6 which further contains 0.01-3 mass parts of (VI) polyamide resin with respect to 100 mass parts of said polyacetal resin compositions. A method for producing the polyacetal resin composition according to any one of claims 1 to 6,
Light calcium carbonate (II) having an average particle size of 50 nm or more and 500 nm or less, a pH of 9.2 or more and 10.0 or less according to the JIS K5101 test method, and having no surface treatment; Monovalent fatty acid (III-I), monovalent fatty acid (III-II) having 28 or more carbon atoms, calcium salt of fatty acid (IV), aliphatic alcohol and fatty acid ester (V) are fixed. Mixing in a phase with a blender to obtain a mixture;
A step of continuously supplying the mixture and the polyacetal resin (I) from different feeders into the barrel of the extruder and melt-kneading to obtain a melt-kneaded product;
Continuously extruding the melt-kneaded product from the die of the extruder;
The manufacturing method of the polyacetal resin composition which has this. A method for producing the polyacetal resin composition according to claim 7, comprising:
Light calcium carbonate (II) having an average particle size of 50 nm or more and 500 nm or less, a pH of 9.2 or more and 10.0 or less according to the JIS K5101 test method, and having no surface treatment; Monovalent fatty acid (III-I), monovalent fatty acid (III-II) having 28 or more carbon atoms, calcium salt of fatty acid (IV), fatty alcohol and fatty acid ester (V), and polyamide resin (VI) is mixed with a blender in a solid phase to obtain a mixture;
A step of continuously supplying the mixture and the polyacetal resin (I) from different feeders into a barrel of an extruder and melt-kneading to obtain a melt-kneaded product;
Continuously extruding the melt-kneaded product from the die of the extruder;
The manufacturing method of the polyacetal resin composition which has this.   The said polyamide resin (VI) is a manufacturing method of the polyacetal resin composition of Claim 9 mix | blended as a molten masterbatch with the said polyacetal resin (I).   An injection-molded article comprising the polyacetal resin composition according to any one of claims 1 to 7.   A gear comprising the polyacetal resin composition according to any one of claims 1 to 7.

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