阅读说明：本技术 聚缩醛树脂组合物及其制造方法 (Polyacetal resin composition and method for producing same ) 是由 玉冈章宏 门间智宏 原科初彦 于 2020-04-02 设计创作，主要内容包括：本发明的目的在于,提供：耐候性优异、能将来自成型品的甲醛的产生抑制为极低水平、且成型时的模垢稳定地得到抑制的聚缩醛树脂组合物及其制造方法。本发明的目的通过聚缩醛树脂组合物而实现,所述聚缩醛树脂组合物至少含有：(A)聚缩醛聚合物100质量份、(B)受阻酚系抗氧化剂0.03～0.30质量份、(C)脂肪族羧酸酰肼0.01～0.50质量份、(D)具有2个肼基羰基烷基的乙内酰脲化合物0.001～0.50质量份、(E)脂肪族羧酸的碱土金属盐0.001～0.30质量份、(F)受阻胺化合物0.2～1.0质量份、(G)紫外线吸收剂0.2～1.0质量份,前述(C)与(D)的总计量相对于(A)聚缩醛聚合物100质量份为0.03～0.55质量份。(An object of the present invention is to provide: a polyacetal resin composition which is excellent in weather resistance, can suppress the generation of formaldehyde from a molded article to an extremely low level, and can stably suppress mold deposit during molding, and a process for producing the same. The object of the present invention is achieved by a polyacetal resin composition comprising at least: (A) 100 parts by mass of a polyacetal polymer, (B) 0.03 to 0.30 part by mass of a hindered phenol antioxidant, (C) 0.01 to 0.50 part by mass of an aliphatic carboxylic acid hydrazide, (D) 0.001 to 0.50 part by mass of a hydantoin compound having 2 hydrazinocarbonylalkyl groups, (E) 0.001 to 0.30 part by mass of an alkaline earth metal salt of an aliphatic carboxylic acid, (F) 0.2 to 1.0 part by mass of a hindered amine compound, and (G) 0.2 to 1.0 part by mass of an ultraviolet absorber, wherein the total amount of the (C) and (D) is 0.03 to 0.55 part by mass relative to 100 parts by mass of the polyacetal polymer (A).)

1. A polyacetal resin composition comprising at least:

(A) 100 parts by mass of a polyacetal polymer,

(B) 0.03 to 0.30 parts by mass of a hindered phenol antioxidant,

(C) 0.01 to 0.50 parts by mass of an aliphatic carboxylic acid hydrazide,

(D) 0.001 to 0.50 parts by mass of a hydantoin compound having 2 hydrazinocarbonylalkyl groups,

(E) 0.001 to 0.30 parts by mass of an alkaline earth metal salt of an aliphatic carboxylic acid,

(F) 0.2 to 1.0 part by mass of a hindered amine compound,

(G) 0.2 to 1.0 part by mass of an ultraviolet absorber,

the total amount of the (C) and (D) is 0.03 to 0.55 part by mass per 100 parts by mass of the polyacetal polymer (A).

2. The polyacetal resin composition according to claim 1, wherein the hindered amine compound (F) is a hindered amine compound having a sterically hindered piperidine derivative with a nitrogen of 3-order.

3. The polyacetal resin composition according to claim 1 or 2, wherein the (C) aliphatic carboxylic acid hydrazide is sebacic dihydrazide.

4. The polyacetal resin composition according to any one of claims 1 to 3, wherein the (E) alkaline earth metal salt of an aliphatic carboxylic acid is at least 1 selected from calcium stearate and calcium 12-hydroxystearate.

5. The polyacetal resin composition according to claim 1 to 4, wherein the hydantoin compound (D) having 2 hydrazinocarbonylalkyl groups is 1, 3-bis (hydrazinocarboethyl) -5-isopropylhydantoin.

6. The polyacetal resin composition according to any one of claims 1 to 5, wherein the hindered amine compound (F) is at least one member selected from the group consisting of tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) 1,2,3, 4-butanetetracarboxylic acid, a condensate of 1,2,2,6, 6-pentamethyl-4-piperidinol and β, β, β ', β' -tetramethyl-3, 9- (2,4,8, 10-tetraoxaspiro [5.5] undecane) diethanol, and a polymer of dimethyl succinate and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidineethanol.

7. The polyacetal resin composition according to any one of claims 1 to 6, wherein the ultraviolet absorber (G) is at least 1 selected from the group consisting of 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol and N- (2-ethylphenyl) -N' - (2-ethoxyphenyl) ethanediamide.

8. The polyacetal resin composition according to any one of claims 1 to 7, further comprising at least one or more selected from the group consisting of (H1) fatty acid ester and (H2) polyalkylene glycol.

9. The polyacetal resin composition according to claim 1 to 8, further comprising (I) 1 to 20 parts by mass of an aluminum powder.

10. A method for producing a polyacetal resin composition according to any one of claims 1 to 9, wherein the polyacetal polymer (a) is a polyacetal copolymer obtained by: trioxane is used as a main monomer (a), at least one selected from cyclic ethers and cyclic formals having at least one carbon-carbon bond is used as a comonomer (b), a heteropoly acid is used as a polymerization catalyst (c), and then a carbonate, a bicarbonate, a carboxylate or a hydrate thereof (d) of an alkali metal element or an alkaline earth metal element is added and melt-kneaded to deactivate the polymerization catalyst (c).

Technical Field

The present invention relates to: a polyacetal resin composition which is excellent in weather resistance of a molded article, remarkably suppresses the amount of formaldehyde generated from the molded article, and stably suppresses mold deposit during molding, and a method for producing the polyacetal resin composition.

Background

Polyacetal resins have excellent properties and molded articles thereof are used in a wide variety of fields, but due to their chemical structural characteristics, they are easily decomposed under a heat oxidizing atmosphere or under acidic or basic conditions. Therefore, the problems of the polyacetal resin include: improve the thermal stability and suppress the generation of formaldehyde from the molding process or the molded article. If the thermal stability is low, the polymer decomposes by heating in the processing steps such as extrusion and molding, and deposits (mold deposit) are generated on the mold, and moldability and mechanical properties are deteriorated.

Further, under ordinary use conditions, although the amount of formaldehyde generated from a polyacetal resin molded product is extremely small, the generated formaldehyde is chemically active and becomes formic acid by oxidation, which adversely affects the heat resistance of the polyacetal resin, or if used for parts of electric/electronic equipment, etc., the formaldehyde or formic acid as an oxide thereof corrodes metal contact parts, or discoloration or contact failure may occur due to adhesion of an organic compound.

Further, the polyacetal resin itself is not resistant to light energy and heat energy such as sunlight and ultraviolet rays, and if exposed to the atmosphere for a long time, cracks are generated on the surface of the molded article, resulting in a decrease in strength.

Therefore, an antioxidant and other stabilizers are blended to stabilize the polyacetal resin. As the antioxidant to be added to the polyacetal resin, a sterically hindered phenol compound (hindered phenol), a sterically hindered amine compound (hindered amine), and the like are known, and as the other stabilizer, melamine, polyamide, alkali metal hydroxide, alkaline earth metal hydroxide, and the like are used. In addition, antioxidants are generally used in combination with other stabilizers.

However, it is difficult to significantly reduce formaldehyde generated, particularly formaldehyde generated from a molded article, only by blending such a general-purpose stabilizer into a polyacetal resin having a quality of formaldehyde. Further, in order to solve the above-mentioned problems and reduce the amount of formaldehyde generated, polyacetal resin compositions containing various compounds have been disclosed.

For example, a technique of using a polyacetal resin having a specific terminal group, a hindered phenol antioxidant, a hydrazide compound, and an isocyanate compound in combination is disclosed (patent document 1).

Further, a technique of allowing a hindered phenol antioxidant, a hydrazide compound, and an alkaline earth metal salt of a specific carboxylic acid to coexist is disclosed (patent document 2).

On the other hand, in order to improve the weather resistance of polyacetal resins, for example, a technique of adding a hindered amine-based light stabilizer and a benzotriazole-based ultraviolet light absorber in the coexistence is disclosed (patent document 3).

Further, there is disclosed a technique of suppressing the generation of formaldehyde from a molded article and the bleeding of a compounding ingredient from the molded article while imparting weather resistance (patent document 4).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-286874

Patent document 2: japanese laid-open patent publication No. 2006-45489

Patent document 3: japanese laid-open patent publication No. 61-36339

Patent document 4: japanese laid-open patent publication No. 2008-7676

Disclosure of Invention

Problems to be solved by the invention

According to the techniques disclosed in these documents 1, mold deposit at the time of molding of polyacetal resin can be reduced at a considerable level. However, although effective for reducing mold deposit, it is not practical to sufficiently suppress the generation of formaldehyde.

Further, according to the technique disclosed in document 2, although the effect of suppressing formaldehyde generation is exhibited, the mold deposit suppressing effect is insufficient, and it is not a stable molding technique.

According to the technique disclosed in document 3, although a certain weather resistance is obtained, the generation of formaldehyde is not completely suppressed.

According to the technique disclosed in document 4, when a hydrazide compound is used, the effect of suppressing formaldehyde generation is exhibited to a large extent, and the weather resistance is maintained to a certain degree. However, the mold deposit-inhibiting effect is insufficient, and is not a stable molding technique.

An object of the present invention is to provide: a polyacetal resin composition which is excellent in weather resistance, can suppress the generation of formaldehyde from a molded article to an extremely low level, and can stably suppress mold deposit during molding, and a process for producing the same.

Means for solving the problems

The object of the present invention is achieved as follows.

1. A polyacetal resin composition comprising at least:

(A) 100 parts by mass of a polyacetal polymer,

(B) 0.03 to 0.30 parts by mass of a hindered phenol antioxidant,

(C) 0.01 to 0.50 parts by mass of an aliphatic carboxylic acid hydrazide,

(D) 0.001 to 0.50 parts by mass of a hydantoin compound having 2 hydrazinocarbonylalkyl groups,

(E) 0.001 to 0.30 parts by mass of an alkaline earth metal salt of an aliphatic carboxylic acid,

(F) 0.2 to 1.0 part by mass of a hindered amine compound,

(G) 0.2 to 1.0 part by mass of an ultraviolet absorber,

the total amount of the (C) and (D) is 0.03 to 0.55 part by mass per 100 parts by mass of the polyacetal polymer (A).

2. The polyacetal resin composition according to claim 1, wherein the hindered amine compound (F) is a hindered amine compound having a sterically hindered piperidine derivative with a nitrogen of 3-order.

3. The polyacetal resin composition according to 1 or 2, wherein the aliphatic carboxylic acid hydrazide (C) is sebacic dihydrazide.

4. The polyacetal resin composition according to any one of the preceding 1 to 3, wherein the (E) alkaline earth metal salt of an aliphatic carboxylic acid is at least 1 selected from calcium stearate and calcium 12-hydroxystearate.

5. The polyacetal resin composition according to any one of 1 to 4, wherein the hydantoin compound having 2 hydrazinocarbonylalkyl groups (D) is 1, 3-bis (hydrazinocarboethyl) -5-isopropylhydantoin.

6. The polyacetal resin composition according to any one of 1 to 5, wherein the hindered amine compound (F) is at least 1 selected from the group consisting of tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) 1,2,3, 4-butanetetracarboxylic acid, a condensate of 1,2,2,6, 6-pentamethyl-4-piperidinol and β, β, β ', β' -tetramethyl-3, 9- (2,4,8, 10-tetraoxaspiro [5.5] undecane) diethanol, and a polymer of dimethyl succinate and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidineethanol.

7. The polyacetal resin composition according to any one of 1 to 6, wherein the ultraviolet absorber (G) is at least 1 selected from the group consisting of 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol and N- (2-ethylphenyl) -N' - (2-ethoxyphenyl) oxalamide.

8. The polyacetal resin composition according to any one of the preceding 1 to 7, further comprising at least one or more selected from the group consisting of (H1) fatty acid ester and (H2) polyalkylene glycol.

9. The polyacetal resin composition according to any one of 1 to 8, further comprising 1 to 20 parts by mass of (I) an aluminum powder.

10. A method for producing a polyacetal resin composition according to any one of the above 1 to 9, wherein the polyacetal polymer (A) is a polyacetal copolymer obtained by: trioxane is used as a main monomer (a), at least one selected from cyclic ethers and cyclic formals having at least one carbon-carbon bond is used as a comonomer (b), a heteropoly acid is used as a polymerization catalyst (c), and then a carbonate, a bicarbonate, a carboxylate or a hydrate thereof (d) of an alkali metal element or an alkaline earth metal element is added and melt-kneaded to deactivate the polymerization catalyst (c).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there is provided: a polyacetal resin composition and a molded article having excellent weather resistance, capable of suppressing the generation of formaldehyde from the molded article to an extremely low level and stably suppressing mold deposit during molding.

Detailed Description

The present invention will be described in detail below.

< (A) polyacetal polymer

The polyacetal polymer (A) used in the present invention may be prepared by copolymerizing oxymethylene group (-OCH)₂-) the homopolymer having the structural unit may be a copolymer having a comonomer unit other than the oxymethylene unit, and is preferably a copolymer.

Generally, formaldehyde or a cyclic compound of formaldehyde is used as a main monomer, and a compound selected from cyclic ethers and cyclic formals is used as a comonomer, and the copolymer is copolymerized to produce the polymer, and usually stabilized by removing unstable parts at the ends by thermal decomposition, (alkali) hydrolysis, or the like.

In particular, trioxane, which is a cyclic trimer of formaldehyde, is generally used as a main monomer. Trioxane is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, and is used after being purified by a method such as distillation. The trioxane used in the polymerization is preferably contained in an amount as small as possible in the amount of impurities such as water, methanol and formic acid.

As the comonomer, two or more kinds may be used alone or in combination: glycidyl ether compounds which are generally cyclic ethers and cyclic formals and can form branched structures or crosslinked structures, and the like.

As described above, the polyacetal polymer can be usually obtained by cationic polymerization using a cationic polymerization catalyst by adding an appropriate amount of a molecular weight modifier. The molecular weight modifier, cationic polymerization catalyst, polymerization method, polymerization apparatus, deactivation treatment of the catalyst after polymerization, treatment method for stabilizing the terminal of the crude polyacetal polymer obtained by polymerization, and the like, which are used, are known from a large number of documents, and they can be basically used.

As a particularly preferable production method of the polyacetal polymer, the following production methods can be mentioned. That is, trioxane is used as a main monomer (a), one or more kinds selected from cyclic ethers and cyclic formals having at least one carbon-carbon bond are used as a comonomer (b), a heteropoly acid is used as a polymerization catalyst (c), and then a carbonate, a bicarbonate, a carboxylate or a hydrate thereof (d) of an alkali metal element or an alkaline earth metal element is added and melt-kneaded to deactivate the polymerization catalyst (c). By using the polyacetal polymer according to the present method, the amount of formaldehyde generated from a molded article and the generation of mold deposit during molding can be further reduced.

The heteropoly-acid used as the polymerization catalyst (c) is a generic name of polybasic acids produced by dehydration condensation of different kinds of oxo acids, and a mononuclear or polynuclear complex ion having a specific different element at the center and having an oxygen atom in common to condense a condensed acid group is present.

Specific examples of the heteropoly-acids include phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdotungstovanadic acid, phosphotungstovanadic acid, silicotungstic acid, silicomolybdic acid, silicomolybdotungstic acid, silicomolybdotungstovanadic acid, and the like. Among them, the heteropoly acid is preferably any one or more of silicomolybdic acid, silicotungstic acid, phosphomolybdic acid, and phosphotungstic acid in view of stability of polymerization and stability of the heteropoly acid itself.

The amount of the heteropoly-acid used varies depending on the kind thereof, and the polymerization reaction can be adjusted by appropriately changing the amount, and is usually in the range of 0.05 to 100ppm (hereinafter, mass/mass ppm), preferably 0.1 to 50ppm, based on the total amount of the monomers to be polymerized.

As the polymerization apparatus, a reaction tank with a stirrer which is generally used can be used in a batch system, and as a continuous system, a kneader, a twin-screw continuous extrusion mixer, a twin-screw paddle type continuous mixer, a continuous polymerization apparatus such as trioxane which has been proposed so far can be used, and 2 or more types of polymerization apparatuses can be used in combination.

The polymerization method is not particularly limited, and as previously proposed, it is sufficient to sufficiently mix trioxane, a comonomer and a heteropoly-acid as a polymerization catalyst while previously maintaining a liquid phase state, and to supply the obtained reaction raw material mixture liquid to a polymerization apparatus to perform a copolymerization reaction. The polymerization temperature is in the range of 60-120 ℃.

In the present invention, when the polyacetal copolymer is prepared by polymerizing the main monomer (a) and the comonomer (b), a known chain transfer agent, for example, linear acetal having a low molecular weight such as methylal, may be added to adjust the polymerization degree.

Further, it is desirable that the polymerization reaction is carried out in a state where impurities having active hydrogen, for example, water, methanol, formic acid, etc., are substantially absent, for example, in a state where each of them is 10ppm or less, and therefore, it is desirable to use trioxane, cyclic ether and/or cyclic formal prepared so as to contain as little of these impurity components as possible as a main monomer and a comonomer.

In the polyacetal polymer (crude polyacetal polymer) containing the polymerization catalyst obtained by the above-mentioned polymerization and having an unstable portion at the terminal thereof, the carbonate, the bicarbonate, the carboxylate or the hydrate thereof (d) of the alkali metal element or the alkaline earth metal element is melt-mixed to deactivate the polymerization catalyst and to reduce the unstable terminal group of the polyacetal polymer (crude polyacetal polymer) to stabilize the polyacetal polymer.

The molecular weight of the polyacetal polymer (A) used in the present invention is not particularly limited, but is preferably about 10000 to 400000 in terms of weight average molecular weight corresponding to PMMA (polymethyl methacrylate) determined by SEC (size exclusion chromatography). The melt index (measured at 190 ℃ under a load of 2.16kg in accordance with ASTM-D1238) which is an index of the fluidity of the resin is preferably 0.1 to 100g/10 min, more preferably 0.5 to 80g/10 min.

The polyacetal polymer (A) used in the present invention is particularly preferable to have specific terminal characteristics. Specifically, the amount of the hemiformaldehyde terminal group is 1.0mmol/kg or less, the amount of the formyl terminal group is 0.5mmol/kg or less, and the amount of the unstable terminal group is 0.5% by mass or less. Here the hemiformaldehyde end group is replaced by-OCH₂OH represents, also known as a hydroxymethoxy or hemiacetal terminal group. In addition, the formyl end group is represented by-OCHO. The amount of such hemiformaldehyde terminal groups and formyl terminal groups can be determined by¹The H-NMR value can be determined by measurement, and the specific measurement method can be referred to the method described in Japanese patent application laid-open No. 2001-11143.

The unstable terminal amount means an amount of a portion which is present at a terminal portion of the polyacetal polymer and is unstable to heat and alkali and easily decomposed. The amount of the unstable terminal is as follows: 1g of polyacetal polymer and 100ml of 50% (volume%) aqueous methanol solution containing 0.5% (volume%) of ammonium hydroxide were placed in a pressure-resistant closed vessel, heat-treated at 180 ℃ for 45 minutes, cooled, unsealed, and the amount of formaldehyde dissolved and eluted in the resulting solution was quantified as mass% relative to the polyacetal polymer.

The amount of the hemiformaldehyde terminal group in the polyacetal polymer (A) used in the present invention is preferably 1.0mmol/kg or less, and more preferably 0.6mmol/kg or less. The amount of the formyl terminal group is preferably 0.5mmol/kg or less, more preferably 0.1mmol/kg or less. The amount of unstable terminals is preferably 0.5% by mass or less, and more preferably 0.3% by mass or less. The lower limits of the amount of the hemiformaldehyde terminal group, the amount of the formyl terminal group and the amount of the unstable terminal group are not particularly limited.

As described above, the polyacetal polymer (a) having specific terminal characteristics can be produced by reducing impurities contained in the monomer and the comonomer, selecting a production process, optimizing production conditions, and the like.

Hereinafter, as a method for producing the polyacetal polymer (A) having the specific terminal characteristics satisfying the characteristics of the present invention, for example, the method described in Japanese patent laid-open No. 2009-286874 can be used. However, the method is not limited thereto.

In the present invention, the polyacetal polymer (A) may be used by adding a polyacetal polymer having a branched or crosslinked structure, and the amount of the polyacetal polymer (A) to be blended is 0.01 to 20 parts by mass, particularly preferably 0.03 to 5 parts by mass, based on 100 parts by mass of the polyacetal polymer (A).

[ B ] hindered phenol antioxidant

The hindered phenol antioxidant (B) that can be used in the present invention is not particularly limited, and examples thereof include: monocyclic hindered phenol compounds (e.g., 2, 6-di-t-butyl-p-cresol, etc.), polycyclic hindered phenol compounds linked by a hydrocarbon group or a sulfur atom-containing group (e.g., 2,2 '-methylenebis (4-methyl-6-t-butylphenol), 4' -methylenebis (2, 6-di-t-butylphenol), 1, 3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 4 '-butylidenebis (3-methyl-6-t-butylphenol), 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene, 4' -thiobis (3-methyl-6-t-butylphenol), etc.), hindered phenol compounds having an ester group or an amide group (for example, n-octadecyl-3- (4 '-hydroxy-3', 5 '-di-t-butylphenyl) propionate, n-octadecyl-2- (4' -hydroxy-3 ',5' -di-t-butylphenyl) propionate, 1, 6-hexanediol-bis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate ] (alternatively: ethylenebis (oxyethylene) bis [3- (3- (5-t-butyl-4-hydroxy-m-tolyl) propionate ]), pentaerythritol tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], 3, 9-bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] -1, 1-dimethylethyl } -2,4,8, 10-tetraoxaspiro [5.5] undecane, 2-tert-butyl-6- (3 ' -tert-butyl-5 ' -methyl-2 ' -hydroxybenzyl) -4-methylphenylacrylate, 2- [1- (2-hydroxy-3, 5-di-tert-pentylphenyl) ethyl ] -4, 6-di-tert-pentylphenylacrylate, di-n-octadecyl-3, 5-di-tert-butyl-4-hydroxybenzylphosphonate, di-tert-butyl-4-hydroxybenzylphosphonate, N, N ' -hexamethylenebis (3, 5-di-tert-butyl-4-hydroxy-dihydrocinnamamide, N ' -ethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], N ' -tetramethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], N ' -hexamethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], N ' -ethylenebis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide ], N ' -hexamethylenebis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide ], (ii) N, N ' -hexamethylenebis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide ], (iii), N, N '-bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl ] hydrazine, N' -bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionyl ] hydrazine, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3, 5-tris (4-tert-butyl-3-hydroxy-2, 6-dimethylbenzyl) isocyanurate, and the like.

In the present invention, at least one or two or more selected from these antioxidants may be used.

The content of the hindered phenol antioxidant (B) in the present invention is 0.03 to 0.30 parts by mass per 100 parts by mass of the polyacetal polymer (A). When the amount is less than the above amount, the effect is insufficient, and when the amount is more than the above amount, the weather resistance is poor due to the antagonistic action with the hindered amine compound.

< (C) aliphatic carboxylic acid hydrazide

Examples of the (C) aliphatic carboxylic acid hydrazide used in the present invention include adipic acid dihydrazide, sebacic acid dihydrazide, dodecane acid dihydrazide, stearic acid hydrazide, and the like. Preferably, sebacic dihydrazide is used in combination with a hydantoin compound having a hydrazide group to trap formaldehyde, thereby remarkably suppressing the mold deposit originally generated.

In the present invention, the amount of (C) to be added is 0.01 to 0.50 parts by mass, preferably 0.02 to 0.30 parts by mass, based on 100 parts by mass of the polyacetal polymer (A).

< (D) hydantoin compound having 2 hydrazinocarbonylalkyl groups

The hydantoin compound (D) having 2 hydrazinocarbonylalkyl groups (hereinafter, may be abbreviated as "hydantoin compound") of the present invention includes 1, 3-bis (hydrazinocarboxyethyl) hydantoin, 1, 3-bis (hydrazinocarboxyethyl) -5-methylhydantoin, 1, 3-bis (hydrazinocarboxyethyl) -5, 5-dimethylhydantoin, 1, 3-bis (hydrazinocarboxyethyl) -5-isopropylhydantoin and the like, and the hydantoin may have 1 or 2 substituents at the 5-position (e.g., a linear or branched alkyl group having 1 to 6 carbon atoms such as methyl, an aryl group having 6 to 10 carbon atoms such as phenyl and the like), and the hydantoin may have 2 substituents at the 5-position together with the carbon atom at the 5-position to form a ring. 1, 3-bis (hydrazinocarboethyl) -5-isopropylhydantoin is preferably used.

The hydantoin compound (D) of the present invention traps formaldehyde and is used in combination with the aliphatic carboxylic acid hydrazide (C) of the present invention, thereby inhibiting mold fouling. Particularly, when used in combination with sebacic dihydrazide, the effect is large.

The hydantoin compound (D) of the present invention is added in an amount of 0.001 to 0.50 parts by mass, preferably 0.01 to 0.30 parts by mass, based on 100 parts by mass of the polyacetal polymer (A).

In the present invention, if both (C) the aliphatic carboxylic acid hydrazide and (D) the hydantoin compound are contained, the effects of the present invention can be obtained, but the total amount is preferably 0.03 to 0.55 part by mass relative to 100 parts by mass of the polyacetal polymer (a). The content mass ratio of (C) to (D) is preferably (C): (D) 10: 90-99: 1.

< (E) alkaline earth metal salt of aliphatic carboxylic acid

The aliphatic carboxylic acid constituting the alkaline earth metal salt of the aliphatic carboxylic acid (E) of the present invention may be a saturated aliphatic carboxylic acid or an unsaturated aliphatic carboxylic acid. Examples of the aliphatic carboxylic acid include aliphatic carboxylic acids having 1 or 2 members of 10 or more carbon atoms, for example, saturated aliphatic carboxylic acids having 1 member of 10 or more carbon atoms [ e.g., saturated aliphatic carboxylic acids having 10 to 34 carbon atoms (preferably saturated aliphatic carboxylic acids having 10 to 30 carbon atoms) such as capric acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, montanic acid ], unsaturated aliphatic carboxylic acids having 1 member of 10 or more carbon atoms [ e.g., unsaturated aliphatic carboxylic acids having 10 to 34 carbon atoms (preferably unsaturated aliphatic carboxylic acids having 10 to 30 carbon atoms) such as oleic acid, linoleic acid, linolenic acid, arachidonic acid, erucic acid ], aliphatic carboxylic acids (dibasic aliphatic carboxylic acids) [ e.g., aliphatic carboxylic acids having 2 members of 10 to 30 carbon atoms (preferably saturated aliphatic carboxylic acids having 10 to 20 carbon atoms) such as sebacic acid, dodecanedioic acid, tetradecanedioic acid, and tetraprotic acid ], [ e.g., saturated aliphatic carboxylic acids having 2 members of 10 to 30 carbon atoms (preferably 10 to 20 carbon atoms), A 2-membered unsaturated aliphatic carboxylic acid having 10 or more carbon atoms [ e.g., a 2-membered unsaturated aliphatic carboxylic acid having 10 to 30 carbon atoms such as decenedioic acid or dodecenedioic acid (preferably a 2-membered unsaturated aliphatic carboxylic acid having 10 to 20 carbon atoms) ].

The aliphatic carboxylic acids also include aliphatic carboxylic acids having 1 or more hydroxyl groups in the molecule (for example, hydroxyl saturated aliphatic carboxylic acids having 10 to 26 carbon atoms such as 12-hydroxystearic acid) in which a part of the hydrogen atoms are substituted with a substituent such as a hydroxyl group, and also include aliphatic carboxylic acids having slightly different carbon numbers depending on the purification accuracy.

The alkaline earth metal in the present invention is preferably calcium or magnesium, and particularly preferably calcium. Particularly preferred alkaline earth metal salts of aliphatic carboxylic acids are calcium stearate and calcium 12-hydroxystearate.

The amount of the alkaline earth metal salt of an aliphatic carboxylic acid added to the polyacetal resin composition is 0.001 to 0.30 part by mass, preferably 0.01 to 0.25 part by mass, based on 100 parts by mass of the polyacetal polymer (A).

(F) hindered amine Compound

The hindered amine compound used in the present invention is not particularly limited, and a hindered amine compound having a nitrogen of a piperidine derivative having a steric hindrance group such as a methyl group on the adjacent carbon of 2 or 3 stages is preferably used. Particularly, a hindered amine compound having a sterically hindered group in which the nitrogen of the piperidine derivative is 3-order is preferably used.

Examples of the hindered amine stabilizer having a sterically hindered group-containing piperidine derivative of which nitrogen is the 2-th order used in the present invention include: bis (2,2,6, 6-tetramethyl-4-piperidyl) sebacate, a condensate of 1,2,3, 4-butanetetracarboxylic acid and 2,2,6, 6-tetramethyl-4-piperidinol and β, β, β ', β' -tetramethyl-3, 9- (2,4,8, 10-tetraoxaspiro [5.5] undecane) -diethylene glycol, tetrakis (2,2,6, 6-tetramethyl-4-piperidyl) 1,2,3, 4-butanetetracarboxylic acid, and a condensate of 1,2,3, 4-butanetetracarboxylic acid and 2,2,6, 6-tetramethyl-4-piperidinol and tridecanol, and the like.

As the hindered amine compound having a nitrogen of 3-order of the piperidine derivative having a sterically hindered group used in the present invention, there may be mentioned: bis (1,2,2,6, 6-pentamethyl-4-piperidyl) adipate, aliphatic di-or tricarboxylic acid-bis-or tripiperidyl esters (aliphatic dicarboxylic acid having 2 to 20 carbon atoms-bis-piperidyl ester, such as bis (1-octyloxy-2, 2,6, 6-tetramethyl-4-piperidyl sebacate), N ' -tetra- (4, 6-bis- (butyl- (N-methyl-2, 2,6, 6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4, 7-diazacyclodecane-1, 10-diamine, a polymer of dimethyl succinate and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidineethanol, a polymer of N, N ' -tetra- (4, 6-bis- (butyl- (N-methyl-2, 2,6, 6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl-4, 7-diazacyclodecane-1-diamine, a polymer of N ', a, Bis (2,2,6, 6-tetramethyl-1- (octyloxy) -4-piperidyl) decanedioate, bis (1,2,2,6, 6-pentamethyl-4-piperidyl) [3, 5-bis (1, 1-dimethylethyl) -4-hydroxyphenyl ] methyl ] butyl malonate, bis (1,2,2,6, 6-pentamethyl-4-piperidyl) sebacate, methyl-1, 2,2,6, 6-pentamethyl-4-piperidyl sebacate, tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) 1,2,3, 4-butanetetracarboxylic acid, condensate of 1,2,3, 4-butanetetracarboxylic acid with 1,2,2,6, 6-pentamethyl-4-piperidyl alcohol and tridecanol, The condensate of 1,2,3, 4-butanetetracarboxylic acid and 1,2,2,6, 6-pentamethyl-4-piperidinol with β, β, β ', β ' -tetramethyl-3, 9- (2,4,8, 10-tetraoxaspiro [5.5] undecane) -diethanol, the reaction product of 4-butylamino-2, 2,6, 6-tetramethylpiperidine and 2,4, 6-trichloro-1, 3, 5-triazine after oxidation treatment and cyclohexane with N, N ' -ethane-1, 2-diylbis (1, 3-propanediamine), 1- [2- {3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyloxy } ethyl ] -4- {3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyloxy } -2,2,6, 6-tetramethylpiperidine, and the like.

Particularly preferred examples include: 1,2,3, 4-butanetetracarboxylic acid tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) ester, a condensate of 1,2,3, 4-butanetetracarboxylic acid with 1,2,2,6, 6-pentamethyl-4-piperidinol with β, β, β ', β' -tetramethyl-3, 9- (2,4,8, 10-tetraoxaspiro [5.5] undecane) -diethanol, a polymer of dimethyl succinate with 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidineethanol.

In the present invention, the amount of the hindered amine compound (F) added is 0.2 to 1.0 part by mass, preferably 0.4 to 0.8 part by mass, based on 100 parts by mass of the polyacetal polymer (a).

(F) When the amount of the hindered amine compound is too small, a polyacetal resin composition having excellent weather resistance cannot be obtained, and on the contrary, when the amount is too large, problems such as reduction in mechanical properties and appearance failure due to bleeding occur.

(G) ultraviolet absorber

Examples of the ultraviolet absorber of the present invention include benzotriazole-based compounds and oxalic anilide-based compounds, and these light stabilizers can be used singly or in combination of two or more.

Examples of the benzotriazole-based compound include: 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol, 2- [ 5-chloro (2H) -benzotriazol-2-yl) -4-methyl-6- (tert-butyl) phenol, 2, 4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2- (2H-benzotriazol-2-yl) -4, 6-di-tert-amylphenol, 2- (2H-benzotriazol-2-yl) -4- (1, benzotriazoles having an aryl group substituted with a hydroxyl group and an alkyl group (an alkyl group having 1 to 6 carbon atoms) such as 3, 3-tetramethylbutyl) phenol and 2- (2 '-hydroxy-3', 5 '-di-isoamylphenyl) benzotriazole, benzotriazoles having an aryl group substituted with a hydroxyl group and an aralkyl (or aryl) group such as 2- [2' -hydroxy-3 ',5' -bis (. alpha.,. alpha. -dimethylbenzyl) phenyl ] benzotriazole, benzotriazoles having an aryl group substituted with a hydroxyl group and an alkoxy (alkoxy group having C1 to 12 carbon atoms) such as 2- (2 '-hydroxy-4' -octyloxyphenyl) benzotriazole, and the like.

These benzotriazole compounds may be used alone or in combination of two or more.

Among these benzotriazole compounds, 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol, 2- (2H-benzotriazol-2-yl) -4, 6-di-tert-amylphenol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3, 3-tetramethylbutyl) phenol, and the like are preferable.

Examples of the oxalanilide compound include oxalanilide compounds such as N- (2-ethylphenyl) -N '- (2-ethoxy-5-tert-butylphenyl) oxalamide, N- (2-ethylphenyl) -N' - (2-ethoxyphenyl) oxalamide, and oxalamide compounds having an optionally substituted aryl group on a nitrogen atom. The oxalanilide compound may be used alone or in combination of two or more.

In the present invention, the amount of the ultraviolet absorber (G) added is 0.2 to 1.0 part by mass per 100 parts by mass of the polyacetal polymer (A). Preferably 0.4 to 0.8 parts by mass. (G) When the amount of the ultraviolet absorber is too small, a polyacetal resin composition having excellent weather resistance cannot be obtained, and on the contrary, when the amount is too large, problems such as reduction in mechanical properties and appearance failure due to bleeding occur.

< (H1) fatty acid ester and (H2) polyalkylene glycol > (II)

The fatty acid constituting the (H1) fatty acid ester of the present invention is 1 or 2 or more kinds of saturated or unsaturated fatty acids, and examples of such fatty acids include: acetic acid, propionic acid, butyric acid, caproic acid, capric acid, undecanoic acid, pivalic acid, caprylic acid, lauric acid, tridecanoic acid, isotridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, 12-hydroxystearic acid, nonadecanoic acid, arachic acid, behenic acid, glyceric acid, cerotic acid, heptacosanoic acid, montanic acid, melissic acid, lacceric acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, arachidonic acid, cetoleic acid, erucic acid, etc., and fatty acids having 12 or more carbon atoms are preferred.

On the other hand, the alcohol constituting the (H1) fatty acid ester may be either a monohydric alcohol (e.g., stearyl alcohol) or a polyhydric alcohol, but is preferably a polyhydric alcohol. Examples of the polyhydric alcohol include C2-6 alkylene glycols such as ethylene glycol, propylene glycol and butylene glycol, diethylene glycol, glycerin and pentaerythritol.

Further, copolymers such as poly-C2-6 oxyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene-polyoxypropylene copolymers (random or block copolymers, etc.), polyoxyethylene polyoxypropylene glycerol ether, polyoxyethylene polyoxypropylene monobutyl ether, etc. may be mentioned as preferred polyols for constituting the (H1) fatty acid ester.

More preferred polyoxyalkylene glycols are polymers having oxyethylene units, such as polyethylene glycol, polyoxyethylene polyoxypropylene copolymers, and derivatives thereof.

Preferred (H1) fatty acid esters include esters of a fatty acid having 12 or more carbon atoms and a polyalkylene glycol having an average polymerization degree of about 20 to 300.

The polyalkylene glycol (H2) may be at least 1 selected from homopolymers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyglycerol, and copolymers such as polyoxyethylene-polyoxypropylene copolymer (random or block copolymer, etc.), and preferably polyalkylene glycol having an average degree of polymerization of about 20 to 300.

In the present invention, the compounding of the compound selected from the group consisting of the (H1) fatty acid ester and the (H2) polyalkylene glycol is not essential, but when these compounds are compounded, an effect advantageous for the improvement of weather resistance is produced. The amount of the compound (H1 and/or H2) to be blended is 0.01 to 5.0 parts by mass, preferably 0.05 to 2.0 parts by mass, based on 100 parts by mass of the polyacetal polymer (A). When (H1) and (H2) are used in combination, it is preferably 90: 10-5: 95 by mass.

Aluminium powder pigment

As the metallic color pigment used in the present invention, aluminum powder can be preferably used. Further, those obtained by dispersing them in a polyethylene resin, a polyethylene wax or the like may also be used.

(I) The amount of the aluminum powder is 1 to 20 parts by mass, preferably 3 to 10 parts by mass, based on 100 parts by mass of the polyacetal polymer (A). When the compounding amount is too small, a polyacetal resin composition having a good color tone cannot be obtained, and on the contrary, when the compounding amount is too large, problems such as a reduction in mechanical properties and a poor appearance may occur.

< other additives >

The polyacetal resin composition of the present invention may further contain one or more of an impact resistance improver, a gloss control agent, a sliding property improver, a filler, a coloring agent, a nucleating agent, an antistatic agent, a surfactant, an antibacterial agent, an antifungal agent, an aromatic agent, a foaming agent, a solubilizer, a physical property improver (boric acid or a derivative thereof, etc.), a perfume, and the like, as required, unless interfering with the present invention.

< method for producing polyacetal resin composition >

The method for producing the polyacetal resin composition of the present invention is not particularly limited, and the polyacetal resin composition can be produced by various methods known in the art as a method for producing a resin composition. For example, the following method can be employed: a method (1) in which all the components constituting the composition are mixed, supplied to an extruder, and melt-kneaded to obtain a pellet-shaped composition; a method (2) in which a part of the components constituting the composition is fed from a main feed port of an extruder, and the remaining components are fed from a side feed port and melt-kneaded to obtain a composition in the form of pellets; a method (3) in which pellets having different compositions are prepared temporarily by extrusion or the like, and the pellets are mixed and adjusted to a predetermined composition; and the like.

In the production of the composition using an extruder, it is preferable to use an extruder having one or more devolatilization vents, and it is more preferable to supply about 0.1 to 10 parts by mass of water or a low-boiling alcohol per 100 parts by mass of the polyacetal resin at any position from the main feed port to the devolatilization vent, thereby devolatilizing and removing formaldehyde and the like generated in the extrusion step together with the water or the low-boiling alcohol from the devolatilization vent. This can further reduce the amount of formaldehyde generated from the polyacetal resin composition and the molded article thereof.

The polyacetal resin composition of the present invention thus prepared can be molded by conventionally known various molding methods such as injection molding, extrusion molding, compression molding, vacuum molding, blow molding, and foam molding.

The present invention also includes the reuse of the polyacetal resin composition and a molded article formed from the colored polyacetal resin composition. Specifically, the present invention relates to a recycled resin composition obtained by melt-kneading a molded article or a pulverized product thereof formed from these resin compositions alone or together with a resin material or a molded article having the same or different composition and extruding the same, and a recycled molded article obtained by melt-kneading a molded article or a pulverized product thereof formed from these resin compositions alone or together with a resin material or a molded article having the same or different composition and molding the same.

Thus, the amount of formaldehyde generated from the recycled resin composition and the recycled molded article prepared by repeating the melting heat history is kept at an extremely low level, as in the case of the polyacetal resin composition as the base.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" all represent parts by mass. The characteristics and the evaluation methods of the examples and comparative examples are as follows. The units of the numerical values shown in tables 1 and 2 are parts by mass.

The respective components shown in tables 1 and 2 were added and mixed in the proportions shown, and melt-kneaded in a twin-screw extruder with an exhaust port to prepare a pelletized composition. The components shown in tables 1 and 2 used in the examples are as follows.

Polyacetal polymer (A)

A-1: 3.3 mass% of 1, 3-dioxolane and 1000ppm of trioxane in terms of methylal were continuously supplied to all monomers (trioxane and 1, 3-dioxolane) by a twin-screw paddle type continuous polymerizer, and boron trifluoride dibutyl ether complex (catalyst concentration: cyclohexane solution in terms of boron trifluoride) was supplied to the same site and polymerized.

The polymer discharged from the outlet of the polymerization machine was immediately discharged, and an aqueous solution containing 1000ppm of triethylamine was added thereto, mixed and pulverized, and stirred. Thereafter, the reaction mixture was centrifuged and dried to obtain a polymer in which the catalyst was deactivated. The polymer was fed to a twin-screw extruder having a vent, melt-kneaded at a resin temperature of about 220 ℃, and unstable terminals were removed while devolatilizing the polymer at the vent under reduced pressure to obtain a pelletized polymer. Thereafter, drying is carried out to obtain a desired polymer. (melt index (measured at 190 ℃ C. under a load of 2.16 kg): 9g/10 min)

A-2: 3.3 mass% of 1, 3-dioxolane was continuously supplied to all monomers (trioxane and 1, 3-dioxolane) by a twin-screw paddle type continuous polymerizer, and trioxane was added in an amount of 1000ppm of methylal, and phosphotungstic acid (catalyst concentration: methyl formate solution in an amount of 3ppm relative to all monomers) as a heteropoly acid catalyst was supplied to the same site and polymerized. 20ppm of sodium stearate was added to the polymer discharged from the discharge port of the polymerization machine, and the mixture was fed to a twin-screw extruder having a vent port, melt-kneaded at a resin temperature of about 220 ℃ and subjected to reduced pressure devolatilization at the vent port to deactivate the catalyst and remove unstable terminals, thereby obtaining a pelletized polymer. Thereafter, drying is carried out to obtain a desired polymer. (melt index (measured at 190 ℃ C. under a load of 2.16 kg): 9g/10 min)

Hindered phenol antioxidant of (B)

B-1: ethylene bis (oxyethylene) bis [3- (3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate ] (IRGANOX245 manufactured by BASF Corporation)

B-2: pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] (IRGANOX1010 manufactured by BASF Corporation)

(C) aliphatic carboxylic acid hydrazide

C-1: sebacic dihydrazide

C-2: adipic acid dihydrazide

C-3: dodecanedioic acid dihydrazide

Hydantoin compound (D)

D-1: 1, 3-bis (hydrazinocarbylethyl) -5-isopropylhydantoin ("Ajicure" VDH: Ajinomoto Fine Techno Co., manufactured by Ltd.)

Alkaline earth metal salts of (E) aliphatic carboxylic acids

E-1: calcium stearate

E-2V 12-calcium hydroxystearate

Hindered amine Compound (F)

F-1: condensate of 1,2,3, 4-butanetetracarboxylic acid and 1,2,2,6, 6-pentamethyl-4-piperidinol with β, β, β ', β' -tetramethyl-3, 9- (2,4,8, 10-tetraoxaspiro [5.5] undecane) diethanol (ADK STAB LA-63P, manufactured by ADEKA Co., Ltd.)

F-2: 1,2,3, 4-Butanetetracarboxylic acid tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) ester (ADK STAB LA-52, manufactured by ADEKA K.K.)

F-3: condensate of 1,2,3, 4-butanetetracarboxylic acid with 1,2,2,6, 6-pentamethyl-4-piperidinol and tridecanol (ADK STAB LA-62, manufactured by ADEKA Co., Ltd.)

Hindered amine compound having nitrogen of 3-order of piperidine derivative having a sterically hindered group

F-4: hindered amine compound having nitrogen of class 2 of piperidine derivative having sterically hindered group bis (2,2,6, 6-tetramethyl-4-piperidyl) sebacate (TINUVIN770 DF: manufactured by BASF Corporation)

(G) ultraviolet absorber

G-1: 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol (TINUVIN234 manufactured by BASF Corporation)

G-2: n- (2-ethylphenyl) -N' - (2-ethoxy-phenyl) ethanediamide (Sanduvor VSU, manufactured by Clariant AG)

(H1) fatty acid ester and (H2) polyalkylene glycol

H1-1: polyethylene glycol monostearate (average degree of polymerization of polyethylene glycol 90) (Nonion S-40: manufactured by Nichio oil Co., Ltd.)

H2-1: polyethylene glycol (average molecular weight about 8300) (PEG-6000S)

Aluminum powder pigment (I)

I-1: the aluminum powder was dispersed in polyethylene (aluminum 70% by mass/polyethylene 30% by mass)

< evaluation >

The characteristic evaluation items and evaluation methods in the examples are as follows. The results are shown in tables 3 and 4.

< evaluation of Formaldehyde Generation amount (VOC) from molded article >

Using the polyacetal resin compositions prepared in examples and comparative examples, flat test pieces (100 mm. times.40 mm. times.2 mmt) were molded under the following conditions. The flat plate-like test piece 2 was sealed in a 10L polyvinyl fluoride sampling bag and degassed, 4L of nitrogen gas was added, the bag was heated at 65 ℃ for 2 hours, and 3L of nitrogen gas in the sampling bag was extracted at 0.5 ml/min to adsorb the generated formaldehyde to a DNPH (2, 4-dinitrophenylhydrazine) trap (Sep-Pak DNPH-Silica: Waters).

Thereafter, the reaction product of DNPH and formaldehyde was solvent-extracted with acetonitrile from the DNPH trap, and the amount of formaldehyde generated was determined by a standard curve method using a standard substance of the reaction product of DNPH and formaldehyde using a high performance liquid chromatograph, and the amount of formaldehyde generated per unit mass of the test piece (μ g/g) was calculated.

A forming machine: FANUC ROBOSHOT alpha-S100 ia (FANUC Corporation)

Molding conditions: barrel temperature (. degree. C.) nozzle-C1-C2-C3

190℃-190℃-180℃-160℃

Injection pressure 60(MPa)

Injection speed 1.0 (m/min)

Mold temperature 80 (. degree. C.)

< evaluation of Mold Deposit (MD) >

Using the polyacetal resin compositions prepared in examples and comparative examples, mold deposit test pieces (33 mm. times.23 mm. times.1 mmt) were molded under the following conditions.

[ evaluation method ]

After 5000 shots of the molded article were continuously formed, the surface of the cavity in the mold was visually observed, and the amount of deposit was visually judged according to the following criteria.

Very good: no deposit was confirmed at all

O: hardly any adhered matter was observed

And (delta): some of the adhered matter was confirmed.

X: the attachment was confirmed as a whole

X: a large amount of adhered substances was confirmed as a whole

A forming machine: FANUC ROBOSHOT S-2000i 50B (FANUC corporation)

Molding conditions: barrel temperature (. degree. C.) nozzle-C1-C2-C3

205℃-215℃-20℃-185℃

Injection pressure 40(MPa)

Injection speed 1.5 (m/min)

Mold temperature 80 (. degree. C.)

< evaluation of weather resistance >

For a flat plate-shaped molded article (70mm × 40mm × 3mmt), a UV light resistance tester [ ultraviolet automatic light resistance tester FAL-AU-H · B · EM: suga Test Instruments Co., Ltd.), irradiated under fading conditions of 83 ℃ for 800 hours and then taken out, and the presence or absence of cracks on the Test piece surface and the change in color (Δ E) before and after irradiation were examined by the following methods.

Presence or absence of cracking

The surface of the test piece was visually observed to determine the presence or absence of the occurrence of cracks.

Change in hue (. DELTA.E)

The color tone (L, a, b) of the molded article was measured by a Z-300A color sensor manufactured by Nippon Denshoku industries Co., Ltd..

ΔE＝{(L*₁-L*₀)²+(a*₁-a*₀)²+(b*₁-b*₀)²}^1/2

Note that L is₀、a*₀、b*₀Denotes the initial hue, L₁、a*₁、b*₁The color tone after irradiation is shown.

Smaller values indicate less change in hue.

[ Table 1]

[ Table 2]

[ Table 3]

[ Table 4]

As is apparent from the above description, the composition of the present invention has excellent weather resistance, and the amount of formaldehyde and mold deposit generated are stably suppressed.