JP4980986B2 - Polyacetal resin composition and molded article thereof - Google Patents

Description

  The present invention has excellent processability and stability, the amount of formaldehyde generated from the molded product is remarkably suppressed, and the exudation of compounding components and the like and the deposits on the mold (mold deposit) are also remarkable. The present invention relates to a prevented polyacetal resin composition.

  Polyacetal resin has excellent properties, and its molded products are used in a wide range of fields. However, due to its chemical structure, it is easily decomposed in a heated oxidizing atmosphere or under acidic or alkaline conditions. Have Therefore, the improvement subject of polyacetal resin includes improving thermal stability and suppressing the generation of formaldehyde in the molding process and the generation of formaldehyde from the molded product. When the thermal stability is low, the polymer is decomposed by heating in a processing step such as extrusion or molding, and mold deposits are generated, or the moldability and mechanical properties are reduced. Formaldehyde generated by decomposition is chemically active and becomes formic acid by oxidation, which adversely affects the heat resistance of polyacetal resin, or when polyacetal resin with a large amount of formaldehyde is used in parts of electrical and electronic equipment. In some cases, the generated formaldehyde or formic acid which is an oxide thereof corrodes metal contact parts, or causes discoloration or contact failure due to adhesion of organic compounds. In addition, the amount of formaldehyde generated from polyacetal resin moldings under normal use conditions is extremely small, but the generated formaldehyde itself is one of the factors that contaminate the working environment in the parts assembly process and the environment in which the final product is used. .

Therefore, antioxidants and other stabilizers are blended in order to stabilize the polyacetal resin. Known antioxidants added to polyacetal resins include sterically hindered phenolic compounds (hindered phenols), sterically hindered amine compounds (hindered amines), and other stabilizers such as melamine, polyamide, Alkali metal hydroxides and alkaline earth metal hydroxides are used. Usually, the antioxidant is used in combination with other stabilizers. However, it is difficult to significantly reduce formaldehyde generated, particularly formaldehyde generated from a molded product, by simply blending such a general-purpose stabilizer with a polyacetal resin having normal formaldehyde quality.
Furthermore, in order to solve the above problems and reduce the amount of formaldehyde generated, a polyacetal resin composition containing various compounds is disclosed.

  For example, a polyacetal resin composition containing a polyacetal resin and a glyoxydiureide compound [JP-A-10-182928 (Patent Document 1)], a polyacetal resin, a cyclic nitrogen-containing compound (glycocyanidin such as creatinine or a derivative thereof) And a polyacetal resin composition [JP-A-11-335518 (Patent Document 2)], polyacetal resin, and polyalkylene glycol, fatty acid ester, fatty acid amide and fatty acid metal salt. A polyacetal resin composition [JP-A-12-26704 (Patent Document 3)], a polyacetal resin, and a hindered phenol-based resin, comprising an agent and at least one inhibitor selected from urea or a derivative thereof and an amidine derivative Compound and triazine ring A polyacetal resin composition [Japanese Patent Laid-Open No. 2003-113289 (Patent Document 4)] composed of a spiro compound having at least one selected from a processing stabilizer and a heat-resistant stabilizer, as a stabilizer A polyacetal resin composition containing a guanamine derivative such as benzoguanamine [Japanese Patent Laid-Open No. 62-190248 (Patent Document 5)] is disclosed.

Japanese Patent Application Laid-Open No. 2005-112995 (Patent Document 6) discloses a polyacetal resin composition composed of a polyacetal copolymer having a specific terminal group and a formaldehyde inhibitor. As the formaldehyde inhibitor, a guanamine compound and urea are disclosed. Compounds, carboxylic acid hydrazide compounds, and the like are disclosed.
Japanese Patent Laid-Open No. 10-182928 (Claim 1) JP-A-11-335518 (Claim 1) JP-A-12-26704 (Claim 1) JP 2003-113289 A (Claim 1) JP-A-62-190248 JP 2005-112995 A

  According to the techniques disclosed in these documents 1 to 6, it is possible to reduce the generation of formaldehyde from the polyacetal resin. However, in order to remarkably reduce the generation of formaldehyde, it is necessary to add a relatively large amount of the compounding component, and the compounding component oozes out from the resulting composition or its molded product, causing problems such as poor appearance. Inevitable. In particular, it is extremely difficult to obtain a resin material in which the exudation of the blended components under high temperature and high humidity is suppressed. In addition, the use of a polyacetal copolymer having a specific terminal group as in Reference 6 is effective in reducing the generation of formaldehyde, but tends to further promote the exudation of the blended components.

  An object of the present invention is to provide a polyacetal resin composition in which the generation of formaldehyde from a molded article can be suppressed to an extremely low level, and exudation of compounding components and mold deposit are remarkably suppressed.

  The present inventor has intensively studied to develop the polyacetal resin material that achieves the above-mentioned object, can suppress the generation of formaldehyde from the molded product to an extremely low level, and suppresses the exudation of compounding components and mold deposits. As a result of overlapping, a polyacetal copolymer having specific end group characteristics is used as a base resin, a stabilizer component to be blended is selected, an iso (thio) cyanate compound is used in combination, and the amount and proportion of the component to be blended As a result of the control, the occurrence of formaldehyde from the molded product is greatly reduced, and the surprising effect that the exudation of the blended components and the mold deposit are remarkably suppressed is found, and the present invention has been completed. Is.

That is, the present invention
(A)) 100 parts by weight of a polyacetal copolymer having a hemi-formal terminal group amount of 1.0 mmol / kg or less, a formyl terminal group amount of 0.5 mmol / kg or less, and an unstable terminal group amount of 0.5% by weight or less. In contrast,
(B) 0.01 to 3 parts by weight of a hindered phenol antioxidant,
(C) 0.2 to 0.5 parts by weight of a hydrazide compound,
(D) It contains 0.2 to 1.5 parts by weight of a compound selected from the group consisting of an isocyanate compound, an isothiocyanate compound and a modified product thereof, and a mixing ratio of the component (C) and the component (D) The present invention relates to a polyacetal resin composition characterized in that (weight ratio) is adjusted to a range of (D) / (C) = 2.5 to 4.0, and a molded product thereof.

  According to the present invention, there are provided a polyacetal resin composition and a molded article in which the amount of formaldehyde generated is remarkably reduced, and exudation of compounding components and mold deposits are suppressed.

The present invention will be described in detail below.
(A) Polyacetal copolymer In the present invention, a polyacetal copolymer (A) having specific terminal properties is used as the base resin. The polyacetal copolymer is a resin having an oxymethylene group (—OCH ₂ —) as a main constituent unit and other comonomer units in addition to the oxymethylene unit, and generally a formaldehyde or a cyclic oligomer of formaldehyde as a main monomer. It is produced by copolymerizing a compound selected from cyclic ether and cyclic formal as a comonomer, and is usually stabilized against thermal decomposition by removing an unstable portion at the end by hydrolysis.

  In particular, it is common to use trioxane, which is a cyclic trimer of formaldehyde, as the main monomer. Trioxane is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, which is purified and used by a method such as distillation. As described below, trioxane used for polymerization is preferably one having as little content of impurities as water, methanol, formic acid and the like. Examples of the cyclic ether and cyclic formal as comonomer include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, oxetane, tetrahydrofuran, trioxepane, 1,3-dioxane, 1,3-dioxolane, propylene glycol formal, diethylene glycol formal, Examples include ethylene glycol formal, 1,4-butanediol formal, 1,6-hexanediol formal, and the like. Further, a compound capable of forming a branched structure or a crosslinked structure can be used as a comonomer (or termonomer). Examples of such a compound include methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, and 2-ethyl-hexyl. Examples include alkyl or aryl glycidyl ethers such as glycidyl ether and phenyl glycidyl ether, alkylene glycols such as ethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, and butanediol diglycidyl ether, and diglycidyl ethers of polyalkylene glycol. These comonomers can be used alone or in combination of two or more.

  The polyacetal copolymer as described above can be generally obtained by cationic polymerization using a cationic polymerization catalyst by adding an appropriate amount of molecular weight regulator. The molecular weight regulator used, cationic polymerization catalyst, polymerization method, polymerization apparatus, deactivation treatment of the catalyst after polymerization, terminal stabilization treatment method of the crude polyacetal copolymer obtained by polymerization are well known in many literatures. Basically, any of them can be used.

  The molecular weight of the polyacetal copolymer used in the present invention is not particularly limited, but those having a weight average molecular weight of about 10,000 to 400,000 are preferred. Further, it is preferable that the melt index (measured at 190 ° C. under a load of 2.16 kg according to ASTM-D1238) of 0.1 to 100 g / 10 minutes, which is an index of resin fluidity, is more preferably 0.5. ~ 80 g / 10 min.

The polyacetal copolymer (A) used in the present invention is required to have specific terminal properties as described above. Specifically, the hemi-formal terminal group amount is 1.0 mmol / kg or less, formyl It is essential that the amount of terminal groups is 0.5 mmol / kg or less and the amount of unstable terminal groups is 0.5% by weight or less. Here, the hemiformal terminal group is represented by —OCH ₂ OH, and is also referred to as a hydroxymethoxy group or a hemiacetal terminal group. The formyl end group is represented by -CHO. The amount of such hemi-formal end groups and formyl end groups can be determined by ¹ H-NMR measurement, and the specific measurement method can be referred to the method described in JP-A No. 2001-11143. The unstable terminal group amount is the amount of a portion which is present at the terminal portion of the polyacetal copolymer and is unstable and easily decomposed with respect to heat or a base. The amount of such unstable end groups is as follows: 1 g of polyacetal copolymer is placed in a pressure-resistant airtight container with 100 ml of 50% (volume%) aqueous methanol solution containing 0.5% (volume%) ammonium hydroxide, and at 180 ° C. for 45 minutes. The amount of formaldehyde decomposed and dissolved in the solution obtained by cooling and opening after heat treatment was quantified, and expressed in weight% with respect to the polyacetal copolymer.

  When the polyacetal copolymer (A) to be used does not have the above terminal properties and exceeds the upper limit value, it is not possible to obtain a polyacetal resin composition in which the amount of formaldehyde generated is sufficiently reduced, and further, thermal history It becomes difficult to maintain the amount of formaldehyde generated by repeating the above at a low level.

  From such a viewpoint, the polyacetal copolymer (A) used in the present invention preferably has a hemi-formal terminal group amount of 1.0 mmol / kg or less, more preferably 0.6 mmol / kg or less. Further, the formyl terminal group amount is preferably 0.5 mmol / kg or less, more preferably 0.1 mmol / kg or less. The amount of unstable terminal groups is preferably 0.5% by weight or less, more preferably 0.3% by weight or less. The lower limit of the amount of hemi-formal end groups, formyl end groups, and unstable end groups is not particularly limited.

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

  Although the specific example of the method of manufacturing the polyacetal polymer (A) which has the specific terminal characteristic which satisfy | fills the requirements of this invention for the following is given, it is not limited to this method at all.

First, it is important to reduce impurities such as water, alcohol (for example, methanol), and acid (for example, formic acid) contained in the monomer and comonomer, which are active impurities that form unstable terminals in the polymerization system. The total amount of these active impurities is preferably 1 × 10 ⁻² mol% or less, more preferably 5 × 10 ⁻³ mol% or less, based on all monomers in the reaction system. Naturally, if the content is excessive, it is not preferable for obtaining a polyacetal polymer having a small number of unstable terminal portions. It should be noted that chain transfer agents that do not form unstable ends, for example, low molecular weight linear acetals having both ends having an alkoxy group, such as methylal, are contained in an arbitrary amount to adjust the molecular weight of the polyacetal polymer. Can do.

The catalyst used in the polymerization reaction is lead tetrachloride, tin tetrachloride, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimony trichloride, phosphorus pentafluoride, antimony pentafluoride, boron trifluoride. Boron trifluoride coordination compounds such as boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride dioxanate, boron trifluoride acetate anhydrate, boron trifluoride triethylamine complex, Inorganic and organic acids such as perchloric acid, acetyl perchlorate, t-butyl perchlorate, hydroxyacetic acid, trichloroacetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, triethyloxonium tetrafluoroborate, triphenyl Methyl hexafluoroantimo Over DOO, allyl diazonium hexafluorophosphate, complex salt compounds such as allyl diazonium tetrafluoroborate, diethyl zinc, triethyl aluminum, alkali metal salts such as diethyl aluminum chloride, heteropoly acid and isopoly acid. Of these, boron trifluoride, boron trifluoride coordination compound, heteropolyacid, and trifluoromethanesulfonic acid are particularly preferable. These catalysts can also be diluted with an organic solvent in advance. When using a catalyst comprising boron trifluoride or its coordination compound, the amount of the catalyst is preferably in the range of 5 × 10 ⁻³ to 1 × 10 ⁻² mol%, particularly 1 ×. 10 ^{−3 to} 7 × 10 ⁻³ mol% is preferable. Setting the amount of catalyst in such a limited range is effective in preventing the formation of unstable end portions. If the amount of the catalyst is too large, it is difficult to properly control the polymerization temperature, the decomposition reaction during the polymerization becomes dominant, and it becomes difficult to obtain a polyacetal polymer having a small number of unstable end portions that satisfies the requirements of the present invention. On the other hand, if the amount of the catalyst is too small, it is not preferable because the polymerization reaction rate is lowered and the polymerization yield is lowered.

  The amount and type of the comonomer greatly affects the thermal stability of the polyacetal polymer. As the polyacetal polymer of the present invention, a compound selected from trioxane (a-1), cyclic ether and cyclic formal (a-2). ) At least in the ratio (weight ratio) of the former (a-1) / the latter (a-2) = 99.9 / 0.1-80.0 / 20.0 More preferably, the former / the latter are copolymerized at a ratio (weight ratio) of 99.5 / 0.5 to 90.0 / 10.0. As the compound (a-2) selected from cyclic ether and cyclic formal, ethylene oxide, 1,3-dioxolane, 1,4-butanediol formal, and diethylene glycol formal are particularly preferable.

  As the polymerization method, any conventionally known method can be used, but a continuous bulk polymerization method for obtaining a solid powdery bulk polymer with the progress of polymerization using a liquid monomer is industrially preferable, and the polymerization temperature is 60 to It is desirable to maintain at 105 ° C, particularly 65 to 100 ° C.

  When a catalyst comprising boron trifluoride or a coordination compound thereof is used, the method for deactivating the catalyst after polymerization may include a method such as adding a polymer after polymerization to an aqueous solution containing a basic compound. In order to obtain a polyacetal polymer that satisfies the requirements of the present invention, it is preferable to pulverize and subdivide the polymer obtained by the polymerization reaction and bring it into contact with a deactivator to quickly deactivate the catalyst. For example, a polymer used for catalyst deactivation is pulverized, and 80% by weight or more, preferably 90% by weight, has a particle size of 1.5 mm or less, and 15% by weight or more, preferably 20% by weight or more is 0.00%. It is desirable that the particle size is 3 mm or less. Basic compounds for neutralizing and deactivating the polymerization catalyst include ammonia, amines such as triethylamine, tributylamine, triethanolamine, and tributanolamine, or oxides of alkali metals and alkaline earth metals. , Hydroxides, salts, and other known catalyst deactivators can be used, and these basic compounds are added in an aqueous solution of 0.001 to 0.5% by weight, particularly 0.02 to 0.3% by weight. Is preferred. Moreover, the temperature of the preferable aqueous solution is 10-80 degreeC, Most preferably, it is 15-60 degreeC. Further, after the polymerization is completed, it is preferable that the catalyst is deactivated by promptly adding it to these aqueous solutions.

  Prior to the polymerization, 0.01 to 0.1% by weight of a hindered phenolic antioxidant is added to the monomer in advance in the monomer, and the polymerization is performed in the presence of this to make the polymerization reaction system uniform. By making it exist, depolymerization during polymerization can be suppressed, and post-treatment such as drying after polymerization and oxidative degradation in a stabilization step can also be suppressed.

  Polyacetal polymers with a small amount of unstable terminals can be produced by reducing impurities contained in the monomers and comonomers as described above, selecting the production process, and optimizing the production conditions. It is possible to further reduce the amount of unstable terminals by passing through the conversion step. As the stabilization step, the polyacetal polymer is heated to a temperature equal to or higher than its melting point and processed in a molten state to decompose and remove only unstable parts, or a non-uniform system is maintained in an insoluble liquid medium at 80 ° C. or higher. For example, the unstable end portion may be decomposed and removed by heat treatment at a temperature of 5 ° C.

  In the present invention, a polyacetal resin having a branched or crosslinked structure may be added to the polyacetal copolymer as described above. In the production of a polyacetal resin, a polyacetal resin having a branched or crosslinked structure is copolymerized by further adding a compound that can be copolymerized with formaldehyde or trioxane and can form a branched unit or a crosslinked unit by copolymerization. Is obtained. For example, in copolymerization of trioxane (i) and a compound (ii) selected from a monofunctional cyclic ether compound having no substituent and a cyclic formal compound, a monofunctional glycidyl compound having a substituent (for example, phenylglycidyl) Ether, butyl glycidyl ether, etc.) are further added and copolymerized to obtain a polyacetal resin having a branched structure, and polyfunctional glycidyl ether compounds are added to carry out copolymerization to obtain a polyacetal resin having a crosslinked structure. . As the polyacetal resin to be added, those having a crosslinked structure are particularly preferable, and among them, a compound selected from 100 parts by weight of trioxane (i), a monofunctional cyclic ether compound having no substituent and a monofunctional cyclic formal compound. What is obtained by copolymerizing (ii) 0.1-10 weight part and polyfunctional glycidyl ether compound (iii) 0.01-2 weight part is preferable, and especially trioxane (i) 100 weight part, compound (ii) ) What is obtained by copolymerizing 0.3 to 3 parts by weight and 0.02 to 1 part by weight of a polyfunctional glycidyl ether compound (iii) is preferable. Moreover, the crosslinked polyacetal resin whose melt index is 0.1-10 g / min is preferable.

  Examples of the compound (ii) include the same compounds as described above, and one or more selected from the group consisting of ethylene oxide, 1,3-dioxolane, 1,4-butanediol formal and diethylene glycol formal are particularly preferable.

  The polyfunctional glycidyl ether compound (iii) includes ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl ether, resorcinol diglycidyl ether, bisphenol A diester. Glycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polybutylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, Polyglycerol polyglycidyl ether And diglycerol polyglycidyl ether. These compounds can be used for copolymerization with trioxane (i) alone or in combination of two or more.

  When a polyacetal resin having a crosslinked structure is added to the polyacetal copolymer (A) as described above, the polyacetal resin is one molecule among the polyfunctional glycidyl ether compounds (iii) as described above from the viewpoint of mechanical properties. Particularly preferred are those in which a crosslinked structure is formed by copolymerization using a compound having 3 to 4 glycidyl ether groups.

  Specifically, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, and pentaerythritol tetraglycidyl ether are particularly preferable polyfunctional glycidyl ether compounds (iii).

In the present invention, when a polyacetal resin having a branched or crosslinked structure is added to the polyacetal copolymer (A) as described above, the blending amount is 0 with respect to 100 parts by weight of the polyacetal copolymer (A). 0.1 to 20 parts by weight, particularly preferably 0.3 to 5 parts by weight. When the blending amount of the polyacetal resin having a branched or cross-linked structure is excessive, molding processability and the like are inferior, and as a result, the mechanical properties are also insufficient.
(B) Hindered phenol antioxidant (H) used in the present invention is a monocyclic hindered phenol compound, a hydrocarbon group or a group connected with a group containing a sulfur atom. Examples thereof include cyclic hindered phenol compounds, hindered phenol compounds having an ester group or an amide group.

  Specific examples of these compounds include 2,6-di-t-butyl-p-cresol, 2,2′-methylenebis (4-methyl-6-t-butylphenol), 4,4′-methylenebis (2,6 -Di-t-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 4,4'-butylidenebis (3-methyl-6-t-butylphenol) 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 4,4′-thiobis (3-methyl-6-tert-butylphenol) ), N-octadecyl-3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propionate, n-octadecyl-2- (4′-hydroxy-3 ′, 5′-di-t) -Butyl fluoride Nyl) propionate, 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], ethylenebis (oxyethylene) bis [3- (5-tert-butyl -4-hydroxy-m-tolyl) propionate], pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 3,9-bis [2- {3- (3 -T-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 2-t-butyl- 6- (3′-t-butyl-5′-methyl-2′-hydroxybenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3, -Di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, di-n-octadecyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate, N, N'- Hexamethylene bis (3,5-di-t-butyl-4-hydroxy-dihydrocinnamamide, N, N'-ethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propion Amido], N, N′-tetramethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide], N, N′-hexamethylenebis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionamide], N, N′-ethylenebis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionamide N, N′-hexamethylenebis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionamide], N, N′-bis [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N′-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionyl] hydrazine, 1,3,5-tris (3 Examples thereof include 5-di-t-butyl-4-hydroxybenzyl) isocyanurate and 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate. .

  These hindered phenolic antioxidants (B) can be used alone or in combination of two or more. The addition amount of the hindered phenol antioxidant (B) is 0.01 to 3 parts by weight with respect to 100 parts by weight of the polyacetal copolymer (A). If the amount is less than this amount, the effect is insufficient. If the amount is more than this amount, problems such as coloring and bleeding may be caused.

(C) Hydrazide Compound As the hydrazide compound (C) used in the present invention, an aliphatic carboxylic acid hydrazide compound, an alicyclic carboxylic acid hydrazide compound, an aromatic carboxylic acid hydrazide compound, a heteroatom-containing carboxylic acid hydrazide system Examples thereof include a compound and a polymer type carboxylic acid hydrazide compound. These carboxylic acid hydrazides can be used alone or in combination of two or more.

  Examples of aliphatic carboxylic acid hydrazide compounds include monocarboxylic acid hydrazides (such as lauric acid hydrazide, stearic acid hydrazide, 12-hydroxystearic acid hydrazide, 1,2,3,4-butanetetracarboxylic acid hydrazide), and polycarboxylic acids. Hydrazides (succinic acid mono or dihydrazide, glutaric acid mono or dihydrazide, adipic acid mono or dihydrazide, pimelic acid mono or dihydrazide, suberic acid mono or dihydrazide, azelaic acid mono or dihydrazide, sebacic acid mono or dihydrazide, dodecanedioic acid mono or Dihydrazide, hexadecanedioic acid mono- or dihydrazide, eicosane diacid mono- or dihydrazide, 7,11-octadecadien-1,18-dicarbohydrazide and the like.

  Examples of the alicyclic carboxylic acid hydrazide compounds include monocarboxylic acid hydrazides (such as cyclohexanecarboxylic acid hydrazide, polycarboxylic acid hydrazides (dimer acid mono- or dihydrazide, trimer acid mono-trihydrazide, 1,2-, 1,3 -Or 1,4-cyclohexanedicarboxylic acid mono or dihydrazide, cyclohexanetricarboxylic acid mono to trihydrazide, etc.).

Aromatic carboxylic acid hydrazide compounds include monocarboxylic acid hydrazides (benzoic acid hydrazide and functional groups thereof (alkyl group, hydroxy group, acetoxy group, amino group, acetamino group, nitrile group, carboxy group, alkoxycarbonyl group). , Carbamoyl group, alkoxy group, phenyl group, benzyl group, cumyl group, hydroxyphenyl group and other functional groups substituted with 1 to 5 phenyl residues of benzoguanamine: for example, o-toluic acid hydrazide, m-toluic acid Hydrazide, p-toluic acid hydrazide, 2,4-, 3,4-, 3,5- or 2,5-dimethylbenzoic acid hydrazide, o-, m- or p-hydroxybenzoic acid hydrazide, o-, m- Or p-acetoxybenzoic acid hydrazide, 4-hydroxy-3-phenylbenzoic acid Hydrazide, 4-acetoxy-3-phenylbenzoic acid hydrazide, 4-phenylbenzoic acid hydrazide, 4- (4′-phenyl) benzoic acid hydrazide, 4-hydroxy-3,5-dimethylbenzoic acid hydrazide, 4-hydroxy-3 , 5-di-t-butylbenzoic acid hydrazide, 4-hydroxy-3,5-di-t-butylphenylacetic acid hydrazide, 4-hydroxy-3,5-di-t-butylphenylpropionic acid hydrazide, etc.), α -Or β-naphthoic acid hydrazide and functional groups thereof (for example, 1-naphthoic acid hydrazide, 2-naphthoic acid hydrazide, 3-hydroxy-2-naphthoic acid hydrazide, 6-hydroxy-2-naphthoic acid hydrazide, etc.) Polycarboxylic acid hydrazides (isophthalic acid mono- or dihydrazide, terephthalic acid mono- or Dihydrazide, 1,4- or 2,6-naphthalenedicarboxylic acid mono- or dihydrazide, 3,3'-, 3,4'- or 4,4 'diphenyldicarboxylic acid mono- or dihydrazide, diphenyl ether dicarboxylic acid mono- or dihydrazide, diphenylmethane dicarboxylic acid Acid mono or dihydrazide, diphenylethane dicarboxylic acid mono or dihydrazide, diphenoxyethane dicarboxylic acid mono or dihydrazide, diphenyl sulfone dicarboxylic acid mono or dihydrazide, diphenyl ketone dicarboxylic acid mono or dihydrazide, 4,4 ''-terphenyl dicarboxylic acid mono or Dihydrazide, 4,4 ′ ″-quarterphenyl dicarboxylic acid mono- or dihydrazide, 1,2,4-benzenetricarboxylic acid mono-trihydrazide, pyromellitic acid mono-tetrahydrazide , 1,4,5,8-like naphthoic acid mono- to tetrahydrazide), etc.).

  Examples of the heteroatom-containing carboxylic acid hydrazide-based compound include dioxane ring-containing carboxylic acid hydrazides (5-methylol-5-ethyl-2- (1,1-dimethyl-2-carboxyethyl) -1,3-dioxane mono or A tetraoxospiro ring-containing carboxylic acid hydrazide (3,9-bis (2-carboxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane mono- or dihydrazide, Mono- or dihydrazide of 9-bis (2-methoxycarbonylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-bis (1,1-dimethyl-1-carboxymethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane mono- or dihydrazide, 3,9-bis (1,1- Methyl-1-methoxycarbonylmethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane mono- or dihydrazide), isocyanuric ring-containing carboxylic acid hydrazides (1,3,5-tris [2 -Carboxyethyl] isocyanurate mono-trihydrazide, 1,3,5-tris (3-carboxypropyl) isocyanurate mono-trihydrazide), hydantoin ring-containing carboxylic acid hydrazides (1,3-bis (2 -Hydrazinocarbonylethyl) -5-isopropylhydantoin) and the like.

  As the polymer type carboxylic acid hydrazide compound, poly (meth) acrylic acid hydrazide which may be a crosslinked product, or a copolymer (olefin copolymer, vinyl monomer copolymer, styrene copolymer divinylbenzene crosslinked product, Bis (meth) acrylic acid ester cross-linked products, etc.): polymers described in JP-A-55-145529, JP-A-56-105905, commercially available “aminopolyacrylamide APA”, Otsuka Chemical Co., Ltd., USA And the like described in Japanese Patent No. 3574786].

  In the present invention, the amount of the hydrazide compound (C) as described above is 0.2 to 0.5 parts by weight with respect to 100 parts by weight of the polyacetal copolymer (A). When the compounding amount of the compound (C) is too small, a polyacetal resin composition in which the amount of formaldehyde generated is sufficiently reduced cannot be obtained, and the amount of formaldehyde generated by repeated thermal history is maintained at a low level. On the contrary, when the amount of compound (C) is excessive, problems such as deterioration of mechanical properties and poor appearance due to bleeding occur.

(D) Iso (thio) cyanate compounds and their modified products The polyacetal resin composition of the present invention further comprises an isocyanate compound, an isothiocyanate compound and their modified products in addition to the components (A) to (C). The compound (D) selected from the above is added and blended, and the blending ratio (weight ratio) of the component (C) and the component (D) is adjusted to a very limited range described later. As a result, the amount of formaldehyde generated from the molded product is significantly reduced, and the exudation of compounding components and the occurrence of mold deposits are remarkably suppressed. Among these, the use of the polyacetal copolymer (A) having the above-mentioned specific end group characteristics as a base resin makes the polyacetal copolymer that is originally poor in activity even more inactive, Although it exudes exudation, the exudation of the compounding component (C) is noticeable by blending the compound (D) and adjusting the compounding ratio of the component (C) and the component (D). It was unexpected that it was suppressed.
As the compound (D) used for this purpose, an isocyanate compound represented by the general formula O = C = NRN = C = O (R; divalent group), S = C = NRN = C = S (R; The isothiocyanate compounds represented by divalent groups) and their modified products are preferred. For example, as the isocyanate compound, 4,4′-methylenebis (phenyl isocyanate), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 1, 5-Naphthalene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, diisothionate corresponding to the above isocyanate compounds as isothiothionate compounds, and these as modified products Dimer or trimer of an isocyanate compound or an isothiocyanate compound, or a compound in which an isocyanate group (-NCO) is protected in some form. However, in consideration of various properties such as discoloration such as melt processing or safety in handling, 4,4′-methylenebis (phenyl isocyanate), isophorone diisocyanate, 1,5-naphthalene diisocyanate, 1, Particularly preferred are 6-hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and modified products (or derivatives) such as dimers and trimers thereof.

  Although the effect of the compound (D) selected from the group consisting of such isocyanate compounds, isothiocyanate compounds and modified products thereof has not been clarified, the reaction between the compound (C) and the compound (D) Presumed is a mechanism that suppresses the exudation of component (C) or a mechanism that suppresses the exudation of component (C) by the reaction of compound (C), compound (D), and polyacetal (A). Is done.

  In this invention, the compounding quantity of this compound (D) chosen from the group which consists of an isocyanate compound, an isothiocyanate compound, and those modified bodies is 0.2-1.5 with respect to 100 weight part of polyacetal resin (A). Parts by weight. When the amount of the component (D) is too small, the effect of reducing formaldehyde is small, and the effect of suppressing the bleeding out of the component (C) is not exhibited. On the other hand, when the compound (D) is added excessively, the viscosity of the molten resin increases or the compound (D) itself oozes out, causing trouble.

  Moreover, in this invention, the compounding ratio (weight ratio) of the said (C) component and the said (D) component is adjusted to the range of (D) / (C) = 2.5-4.0. In this way, by adjusting the blending ratio of the component (C) and the component (D) to a very limited range, it is desirable to reduce the amount of formaldehyde generated, suppress the exudation of the blended components, and suppress the generation of mold deposits. Properties can be achieved. Even if the blending ratio of the component (C) and the component (D) is larger or smaller than the above range, it is not possible to obtain desirable balanced characteristics.

  In the present invention, the compound (D) selected from the group consisting of the above isocyanate compounds, isothiocyanate compounds and modified products thereof is composed of 98 to 80% by weight of polyacetal resin and 2 to 20% by weight of compound (D). It is also possible to mix in the form of a masterbatch, which is preferable for stably preparing the resin composition of the present invention. Although there is no restriction | limiting in particular as polyacetal resin used for a masterbatch, It is preferable to use what satisfies the characteristic of the polyacetal copolymer (A) mentioned above.

  The polyacetal resin composition of the present invention further comprises a compound (E) selected from organic carboxylic acid metal salts, metal oxides, and metal hydroxides in order to improve thermal stability, long-term thermal stability, and the like. It is possible and preferable to add. The addition amount is preferably 0.01 to 1 part by weight with respect to 100 parts by weight of the polyacetal copolymer (A).

  As the organic carboxylic acid forming the organic carboxylic acid metal salt, various aliphatic carboxylic acids having about 1 to 34 carbon atoms can be used, saturated aliphatic monocarboxylic acid, saturated aliphatic dicarboxylic acid, unsaturated fat. Group monocarboxylic acids, unsaturated aliphatic dicarboxylic acids, and oxyacids thereof. These aliphatic carboxylic acids may have a hydroxyl group. Further, it may be a copolymer of a polymerizable unsaturated carboxylic acid ((meth) acrylic acid, maleic acid, fumaric acid, maleic anhydride, monoethyl maleate, etc.) and an olefin. Specific examples of the organic carboxylic acid metal salt include alkali metal organic carboxylates such as lithium citrate, potassium citrate, sodium citrate, lithium stearate and lithium 12-hydroxystearate, magnesium acetate, calcium acetate, citric acid Examples thereof include alkaline earth metal organic carboxylates such as magnesium oxide, calcium citrate, calcium stearate, magnesium stearate, magnesium 12-hydroxystearate, and calcium 12-hydroxystearate, and ionomer resins. Of these organic carboxylic acid metal salts, alkaline earth metal salts such as calcium citrate, magnesium stearate, calcium stearate, magnesium 12-hydroxystearate, calcium 12-hydroxystearate and ionomer resins are preferred.

  As the metal oxide and metal hydroxide, calcium oxide, magnesium oxide, zinc oxide, calcium hydroxide, magnesium hydroxide and the like are preferable.

  To the polyacetal resin composition of the present invention, at least one compound (F) selected from a fatty acid ester, a fatty acid amide, a polyoxyalkylene glycol, and a silicone compound is further added in order to improve molding processability and the like. Is possible and preferred. The addition amount is preferably 0.01 to 1 part by weight with respect to 100 parts by weight of the polyacetal copolymer (A).

  Examples of fatty acid esters include ethylene glycol mono- or dipalmitate, ethylene glycol mono- or distearate, ethylene glycol mono- or dibehenate, ethylene glycol mono- or dimontanate, glycerin mono to tripalmitate, glycerin mono To tristearic acid ester, glycerin mono to tribehenic acid ester, glycerin mono to trimontanic acid ester, pentaerythritol mono to tetrapalmitic acid ester, pentaerythritol mono to tetrastearic acid ester, pentaerythritol mono to tetrabehenic acid ester, pentaerythritol mono to Tetramontannate, polyglycerol tristearate, trimethy Propane propane monopalmitate, pentaerythritol monoundecylate, sorbitan monostearate, mono or dilaurate of polyalkylene glycol (polyethylene glycol, polypropylene glycol, etc.), mono or dipalmitate, mono or distearate, mono or dibehenate, Mono or dimontanate, mono or diolate, mono or dilinoleate and the like.

  Examples of fatty acid amides include capric acid amides, lauric acid amides, myristic acid amides, palmitic acid amides, stearic acid amides, arachidic acid amides, behenic acid amides, primary fatty acid amides, olein Primary acid amides of unsaturated fatty acids such as acid amides, secondary acid amides of saturated and / or unsaturated fatty acids and monoamines such as stearyl stearic acid amide, stearyl oleic acid amide, ethylenediamine-dipalmitic acid amide, ethylenediamine -Distearic acid amide (ethylene bisstearyl amide), hexamethylenediamine-distearic acid amide, ethylenediamine-dibehenic acid amide, ethylenediamine-dimantanoic acid amide, ethylenediamine-dioleic acid amide, ethylenediamine- Examples thereof include dierucic acid amides, and examples thereof include bisamides having a structure in which different acyl groups are bonded to amine sites of alkylenediamine such as ethylenediamine- (stearic acid amide) oleic acid amide.

As polyoxyalkylene glycol, alkylene glycol (alkylene glycol such as ethylene glycol, propylene glycol, tetramethylene glycol and the like) alone or a copolymer, derivatives thereof and the like can be mentioned. Specific examples of the polyoxyalkylene glycol include polyoxyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol, polyoxyethylene-polyoxypropylene copolymers (random or block copolymers, etc.), polyoxyethylene Examples include copolymers such as polyoxypropylene glyceryl ether and polyoxyethylene polyoxypropylene monobutyl ether. Of these, polymers having oxyethylene units, such as polyethylene glycol, polyoxyethylene polyoxypropylene copolymers, and derivatives thereof are preferable. The average molecular weight of the polyoxyalkylene glycol is about 3 × 10 ² to 1 × 10 ⁶ , preferably about 1 × 10 ³ to 1 × 10 ⁵ .

  Examples of the silicone compound include (poly) organosiloxane. Examples of the (poly) organosiloxane include monoorganosiloxanes such as dialkylsiloxanes (such as dimethylsiloxane), alkylarylsiloxanes (such as phenylmethylsiloxane), diarylsiloxanes (such as diphenylsiloxane), and homopolymers thereof (polydimethylsiloxane, poly Examples thereof include phenylmethylsiloxane) and copolymers. The polyorganosiloxane may be an oligomer. In addition, (poly) organosiloxane has an epoxy group, a hydroxyl group, an alkoxy group, a carboxyl group, an amino group or a substituted amino group (such as a dialkylamino group), an ether group, a vinyl group, ) Modified (poly) organosiloxane having a substituent such as acryloyl group is also included.

  The polyacetal resin composition of the present invention further includes a wrinkle resistance (light) stabilizer, an impact resistance improver, a gloss control agent, a slidability improver, a filler, a colorant, a nucleating agent, an antistatic agent, an interface. Active agents, antibacterial agents, antifungal agents, fragrances, foaming agents, compatibilizers, physical property improvers (such as boric acid or derivatives thereof), fragrances, and the like can be blended, and the object of the present invention is impaired. Therefore, various properties according to each additive can be improved. In addition, antioxidants, heat stabilizers, processability improvers and the like other than those described above can be used in combination.

Anti-fading (light) stabilizers include (a) benzotriazole compounds, (b) benzophenone compounds, (c) aromatic benzoate compounds, (d) cyanoacrylate compounds, and (e) oxalic acid anilide compounds. Compounds, (f) hydroxyphenyl-1,3,5-triazine compounds, (g) hindered amine compounds, and the like. Specific compounds (a) to (g) are known from literatures aimed at improving the weather resistance stability of polyacetal resins, and these compounds can also be used in the present invention.
A weathering (light) stabilizer may be used alone, or two or more of the same or different compounds may be used in combination. The weathering stabilizer is preferably a combination of a hindered amine compound (g) and at least one selected from other anti-light (light) stabilizers (a) to (f), and in particular, a benzotriazole compound (a ) And the hindered amine compound (f) are preferably used in combination. The content of the anti-light (light) stabilizer is, for example, 0 to 5 parts by weight (for example, 0.01 to 5 parts by weight), preferably 0.1 to 100 parts by weight of the polyacetal copolymer (A). It may be about 4 parts by weight, more preferably about 0.1 to 2 parts by weight.

  The impact resistance improver includes thermoplastic polyurethane resins, acrylic core shell polymers, thermoplastic polyester elastomers, styrene elastomers, olefin elastomers, polyamide elastomers, rubber components (natural rubber, etc.), and the like.

  Gloss control agents include acrylic core-shell polymers, thermoplastic polyurethanes, thermoplastic polyester elastomers, polyamide elastomers, alkyl (meth) acrylate homo- or copolymers (polymethyl methacrylate, etc.), polycarbonate resins, styrene resins ( Polystyrene, AS resin, AES resin, etc.), olefin resin (polypropylene, cyclic polyolefin, etc.) and the like.

  Examples of the slidability improver include olefin polymers (polyethylene, polypropylene, copolymers of ethylene and α-olefin, modified products thereof with acid anhydrides, etc.), waxes (polyethylene wax, etc.), silicone oils and silicones. Resin, fluorine resin (polytetrafluoroethylene, etc.), fatty acid ester and the like are included.

  As fillers, inorganic or organic fibrous fillers such as glass fiber, carbon fiber, boron fiber, potassium titanate fiber, metal fiber, aramid fiber, plate-like filler such as glass flake, mica, graphite, milled fiber, Examples thereof include powdery fillers such as glass beads, glass balloons, talc, kaolin, silica, diatomaceous earth, clay, wollastonite, alumina, graphite fluoride, silicon carbide, boron nitride, and metal powder.

  Various dyes and pigments can be used as the colorant. Examples of the dye include azo dyes, anthraquinone dyes, phthalocyanine dyes, and naphthoquinone dyes. As the pigment, both inorganic pigments and organic pigments can be used, and as inorganic pigments, titanium pigments, zinc pigments, carbon black, iron pigments, molybdenum pigments, cadmium pigments, lead pigments, cobalt pigments and Examples of the organic pigment include azo pigments, anthraquinone pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, dioxazine pigments, and selenium pigments. Etc. can be exemplified. Of these, the use of carbon black, titanium oxide, phthalocyanine pigments, and perylene pigments, which are colorants having a high light shielding effect, can also improve weather resistance (light). The amount of the colorant to be blended is not particularly limited, and a general amount for coloring purposes is used.

  The manufacturing method of the polyacetal resin composition of this invention is not specifically limited, It can prepare by the various methods conventionally known as a preparation method of a resin composition. For example, (1) a method in which all components constituting the composition are mixed, and this is supplied to an extruder and melt-kneaded to obtain a pellet-like composition; (2) a part of the components constituting the composition The remaining components are fed from the main feed port of the extruder through the side feed port and melt-kneaded to obtain a pellet-like composition. (3) Once the pellets having different compositions are prepared by extrusion or the like, the pellets are mixed Thus, a method of adjusting to a predetermined composition can be employed.

  In the preparation of the composition using an extruder, it is preferable to use an extruder having one or more devolatilization vent ports, and further, water or a low boiling point at any location from the main feed port to the devolatilization vent port. It is preferable to supply about 0.1 to 10 parts by weight of alcohol with respect to 100 parts by weight of the polyacetal resin, and devolatilize and remove formaldehyde and the like generated in the extrusion process from the devolatilization vent port together with water and low-boiling alcohols. Thereby, the amount of formaldehyde generated from the polyacetal resin composition and its molded product can be further reduced.

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

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples and comparative examples, all “parts” represent parts by weight. Moreover, the various characteristics evaluated in the Example and the comparative example, and the evaluation method are as follows.
(1) Formaldehyde generation amount from molded product Using the polyacetal resin compositions prepared in Examples and Comparative Examples, flat test pieces (100 mm x 40 mm x 2 mm) were molded under the following conditions. After leaving this flat test piece in an atmosphere of 23 ° C. and 50% RH, two flat test pieces were sealed in a 10 L vinyl fluoride sampling bag, degassed, charged with 4 L of nitrogen, and 80 After heating at 0 ° C. for 2 hours, 3 L of nitrogen in the sampling bag was extracted at 0.5 ml / min, and the generated formaldehyde was collected in a DNPH (2,4-dinitrophenylhydrazine) collection tube (Waters Sep-Pak DNPH-Silica). ). After that, the reaction product of DNPH and formaldehyde was extracted from the DNPH collection tube with acetonitrile, and the amount of formaldehyde generated was obtained by a calibration curve method using the standard substance of the reaction product of DNPH and formaldehyde by high performance liquid chromatography. The amount of formaldehyde generated per unit weight (μg / g) was calculated.

* Molding machine: Japan Steel Works J75E-P
* Molding conditions: Cylinder temperature (° C) Nozzle-C1-C2-C3
220 220 210 190
Injection pressure 60 (MPa)
Injection speed 1.0 (m / min)
Mold temperature 50 (℃)

(2) Amount of exudate from molded product The flat test piece molded in (1) is left for 96 hours in a constant temperature and humidity layer set at a temperature of 65 ° C. and a humidity of 90% RH, and then the exudate on the surface of the molded product. Was visually observed, and the amount of exudate was determined according to the following criteria.
0: No exudate is confirmed 1: Exudate is slightly confirmed in a part of the molded product.
2: Exudate is confirmed in a part of the molded product.
3: Exudate is confirmed on the entire surface of the molded product.

(3) Amount of deposit on mold A mold deposit test piece (disk type) was molded under the following conditions using the polyacetal resin compositions prepared in Examples and Comparative Examples. After 2000Shot molding, the surface of the cavity portion on the mold moving side was visually observed, and the amount of deposits was determined according to the following criteria.
0: No deposits are observed 1: Slight deposits are confirmed.
2: Deposits are confirmed.
3: A lot of deposits are confirmed.

* Molding machine: FANUC ROBOSHOT S-2000i 50B
* Molding conditions: Cylinder temperature (° C) Nozzle-C1-C2-C3
205 215 205 185
Injection pressure 40 (MPa)
Injection speed 1.5 (m / min)
Mold temperature 60 (℃)

Examples 1-4
A hindered phenolic antioxidant (B), a hydrazide compound (C), an isocyanate compound (D) and other compounds are blended with the polyacetal copolymer (A) in the composition shown in Table 1, and a 30 mm twin screw extruder is used. The mixture was melt-kneaded to prepare a pellet-shaped composition. Next, a test piece was molded from the pellet using the injection molding machine under the molding condition (1) described above, the amount of formaldehyde generated from the molded product was measured, and the exudate from the molded product was observed. Moreover, the deposit | attachment to the metal mold | die in which this pellet can be measured. The results are shown in Table 1.

Comparative Examples 1-11
As shown in Table 1, when one or more components of the hydrazide compound (C) and the isocyanate compound (D) are too little or too large, or not blended, the polyacetal copolymer (A) is further used as the polyacetal copolymer (A). About the case where the thing which does not satisfy end rule is used, the composition was prepared like the Example and the characteristic was evaluated. The results are shown in Table 1.

Each component used in the examples and comparative examples is as follows.
・ Polyacetal copolymer (A)
a-1: Polyacetal copolymer [hemiformal terminal group content = 0.38 mmol / kg, formyl terminal group content = 0.03 mmol / kg, unstable terminal group content = 0.15 wt%, melt index = 9 g / 10 min ]
a-2: Polyacetal copolymer [hemiformal end group amount = 1.20 mmol / kg, formyl end group amount = 0.60 mmol / kg, unstable end group amount = 0.6 wt%, melt index = 9 g / 10 min ]
Polyacetal copolymers a-1 and a-2 were prepared as follows.

  A biaxial paddle type continuous polymerization machine was continuously fed with a mixture of 96.7% by weight of trioxane and 3.3% by weight of 1,3-dioxolane, and 15 ppm of boron trifluoride was added as a catalyst for polymerization. . The mixture of trioxane and 1,3-dioxolane used for polymerization contains 0.03% by weight of pentaerythritol-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] based on the total amount of the mixture. Was included. Further, the mixture of trioxane and 1,3-dioxolane used for polymerization contained 6 ppm water, 3.5 ppm methanol, and 5 ppm formic acid as impurities.

  The polymer discharged from the discharge port of the polymerizer is immediately added with an aqueous solution containing 1000 ppm of triethylamine, pulverized and stirred to deactivate the catalyst, and then centrifuged and dried to remove crude polyoxymethylene copolymer. A polymer was obtained.

  Next, this crude polyoxymethylene copolymer is supplied to a twin-screw extruder having a vent port, and the unstable terminal portion is decomposed by melting and kneading at a resin temperature of about 220 ° C., and the volatilization containing a decomposition product is included. Minutes were evacuated from the vent. The polymer taken out from the die of the extruder was cooled and chopped to obtain pellet-shaped polyacetal copolymer a-2 from which unstable terminal portions were removed.

  Next, using a cylindrical pressure-resistant container capable of keeping heat, the above pellet-shaped polymer was continuously supplied from the upper part, and a 135 ° C. aqueous solution containing 500 ppm of triethylamine was supplied from the lower part for 8 hours. Then, the polyacetal copolymer a-1 in which hemi-formal terminal group, formyl terminal group, and unstable terminal part were further reduced was obtained by performing centrifugation and drying.

The hemi-formal terminal group amount and formyl group terminal group amount of the polyacetal copolymer were measured according to the method described in JP-A-2001-11143 using an AVANCE400 FT-NMR apparatus manufactured by Bruker Co., Ltd. Is the value (mmol / kg) obtained by Moreover, the said melt index is the value (g / 10min) calculated | required on conditions of 190 degreeC and 2160g according to ASTM-D1238.
・ Antioxidant (B)
b-1: Pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]
・ Hydrazide compounds (C)
c-1: Sebacic acid dihydrazide-isocyanate compound (D)
d-1: Isophorone diisocyanate (trimer) (VESTANAT T1890 / 100)
・ Metal compounds (E)
e-1: 12-hydroxycalcium stearate. Compound (F): In Table 1, it is described as a release agent.
f-1: Glycerol monostearate

Claims (7)

(A) For 100 parts by weight of a polyacetal copolymer having a hemi-formal terminal group amount of 1.0 mmol / kg or less, a formyl terminal group amount of 0.5 mmol / kg or less, and an unstable terminal group amount of 0.5% by weight or less. ,
(B) 0.01 to 3 parts by weight of a hindered phenol antioxidant,
(C) 0.2 to 0.5 parts by weight of a hydrazide compound,
(D) It contains 0.2 to 1.5 parts by weight of a compound selected from the group consisting of an isocyanate compound, an isothiocyanate compound and a modified product thereof, and a mixing ratio of the component (C) and the component (D) (Weight ratio) is adjusted in the range of (D) / (C) = 2.5 to 4.0, A polyacetal resin composition characterized by the above-mentioned.   The polyacetal resin composition according to claim 1, wherein the compound (D) is at least one selected from diisocyanate compounds, diisothiocyanate compounds, dimers and trimers thereof.   Compound (D) is 4,4′-methylenebis (phenyl isocyanate), isophorone diisocyanate, 1,5-naphthalene diisocyanate, 1,6-hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate The polyacetal resin composition according to claim 1 or 2, which is at least one selected from these dimers and trimers.   The compound (D) is blended in the form of a masterbatch comprising 98 to 80% by weight of polyacetal resin and 2 to 20% by weight of the compound (D). Polyacetal resin composition.   Furthermore, it contains 0.01 to 1 part by weight of at least one metal compound (E) selected from a metal oxide, a metal hydroxide and an organic carboxylic acid metal salt with respect to 100 parts by weight of the polyacetal copolymer (A). The polyacetal resin composition according to any one of claims 1 to 4.   Furthermore, it contains 0.01 to 1 part by weight of at least one compound (F) selected from fatty acid esters, fatty acid amides, polyoxyalkylene glycols, and silicone compounds with respect to 100 parts by weight of the polyacetal copolymer (A). The polyacetal resin composition according to any one of claims 1 to 5.   The polyacetal resin molded product formed by shape | molding the polyacetal resin composition of any one of Claims 1-6.