JP5269299B2 - Method for producing stabilized polyacetal resin, stabilized polyacetal resin, composition and molded article - Google Patents

Abstract

Disclosed is a method for producing a stabilized polyacetal resin wherein unstable end groups are reduced. Also disclosed is a processing agent for decomposing unstable end groups, which is excellent in odor characteristics and effective even when added in a small amount. Specifically disclosed is a method for producing a stabilized polyacetal resin wherein a polyacetal resin having unstable end groups is thermally processed in the presence of a processing agent for decomposing unstable end groups which is composed of a quaternary phosphonium salt, thereby reducing the unstable end groups.

Description

  The present invention provides a process for producing a stabilized polyacetal resin in which unstable end groups are reduced by heat-treating a polyacetal resin having unstable end groups in the presence of an unstable terminal decomposition treatment agent comprising a quaternary phosphonium salt. The present invention relates to a stabilized polyacetal resin, a composition thereof, and a molded body.

Polyacetal resin has excellent balance of mechanical properties, chemical resistance, slidability, etc. and is easy to process, so it is a representative engineering plastic such as electric / electronic parts, automobile parts, and other various machine parts. Etc. are widely used mainly.
Polyacetal resins include homopolymers and copolymers, the former using formaldehyde or its cyclic multimer as the raw material, the latter using formaldehyde or its cyclic multimer as the main monomer and cyclic ether and / or cyclic formal as the comonomer, in the presence of a catalyst. It is manufactured by polymerization. However, the resulting polyacetal resin is thermally unstable because some of its molecular ends are hemiacetal groups or formyl groups, and decomposes during molding to generate formaldehyde, which causes environmental problems. Formaldehyde is oxidized during molding to form formic acid, causing degradation of the polyacetal resin, foaming of the molded product, and silver lines due to outgassing.

As a method for stabilizing such a polyacetal resin having a thermally unstable terminal group, a method of acetylating, etherifying, or urethanizing a terminal, or an unstable terminal group followed by an unstable terminal part may be used. A method of decomposing / removing is known, and for copolymers, a method of decomposing and stabilizing unstable end groups is used.
Various methods are known as methods for decomposing and stabilizing unstable terminal groups of polyacetal resins.
Japanese Patent Publication No. 40-10435 discloses a method in which a crude polyacetal resin having unstable terminal groups is directly heat-treated in an insoluble medium (see Patent Document 1).
This method is operated at a temperature close to the melting point of the polyacetal resin in order to increase the decomposition rate of unstable end groups, but the decomposition rate is not sufficient, the decomposition process takes a long time, and the decomposition efficiency is not good. It was enough.
In JP-A-60-63216, a stabilizer and / or an alkaline substance is added to a crude polyacetal resin and once melt-treated, and then heated at 80 ° C. or higher in an insoluble medium while maintaining a heterogeneous system. A method of processing is disclosed (see Patent Document 2).
However, in this method, removal of unstable terminal groups in the melt treatment stage is insufficient, and it takes a long time to sufficiently decompose and remove remaining unstable terminal groups by heat treatment in an insoluble medium. There is a problem. There is also a problem that a special device is required and the operation becomes complicated.

Conventionally, as a decomposition treatment agent for promoting the decomposition of unstable terminal groups, ammonia; aliphatic amines such as triethylamine, tri-n-butylamine, and triethanolamine; quaternary ammonium such as tetrabutylammonium hydroxide It is known to use an alkali metal or alkaline earth metal hydroxide, an inorganic weak acid salt, an organic acid salt, or the like, and decompose an unstable terminal portion in the presence thereof.
JP-A-57-55916 discloses a method of obtaining a crude polyacetal copolymer by copolymerizing a polyoxymethylene homopolymer and a cyclic formal using a Lewis acid as a polymerization catalyst. Among them, a method is described in which a basic substance such as an amine or a quaternary ammonium salt is added to terminate the reaction, and then the polymer is heated with water to obtain a stabilized polyacetal copolymer (patent) Reference 3).
However, this document does not exemplify a specific quaternary ammonium salt and does not show its effect. Moreover, substances other than quaternary ammonium salts are not exemplified.
Japanese Patent Application Laid-Open No. 59-159812 discloses a continuous polymerization method of trioxane to obtain a crude polyacetal copolymer by polymerizing trioxane and a cyclic ether using a Lewis acid as a polymerization catalyst. Among them, Lewis acid was neutralized and deactivated with basic substances such as amines and quaternary ammonium salts, and then the polymer was heated with water to remove the unstable terminal portion of the polymer. A method for obtaining a copolymer is described (see Patent Document 4).
However, this document does not exemplify a specific quaternary ammonium salt and does not show its effect. Moreover, substances other than quaternary ammonium salts are not exemplified.

In Japanese Patent No. 3087912, an oxymethylene copolymer having a thermally unstable terminal portion is represented by a specific formula represented by the general formula [R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ^-n. A method for stabilizing an oxymethylene copolymer that is heat-treated in the presence of a quaternary ammonium salt is disclosed (see Patent Document 5).
However, this document does not disclose substances other than the quaternary ammonium salt specified by the formula.

According to these conventionally known decomposition treatment agents, the unstable end groups of the polyacetal resin can be removed fairly efficiently.
However, these conventionally known decomposition treatment agents are a group of substances belonging to tertiary amines or quaternary ammonium salts, and themselves or their decomposition products have an amine odor (fish odor). In some cases, an amine odor is generated, or an unfavorable amine odor (fish odor) remains in the stabilized polyacetal resin.
Recently, there has been a strong demand to further reduce formaldehyde generated from the molded product of polyacetal resin. To this end, it is necessary to reduce the unstable end groups of the polyacetal resin as a substrate to the limit. However, it is difficult to meet such high demands with the conventionally known decomposition treatment agents and treatment methods, and the production of new unstable terminal decomposition treatment agents with excellent decomposition efficiency and the production of stabilized polyacetal resins therewith. Is required.

Japanese Patent Publication No. 40-10435 (Claims) JP-A-60-63216 (Claims 1 to 9) JP-A-57-55916 (6 pages, lower left 15 lines to lower right 3 lines) JP 59-159812 (page 5, bottom left, lines 5-12) Japanese Patent No. 3087912 (Claims 1 to 22, column 11, lines 32 to 50, Examples 1 to 148)

  An object of the present invention is to find an unstable terminal decomposition treatment agent that has excellent decomposition efficiency of unstable terminals of polyacetal resin and does not leave amine odor in the polyacetal resin, and production of stabilized polyacetal resin using the same The method is to provide a highly stabilized polyacetal resin, its composition and molded article with sufficiently reduced unstable end groups.

  As a result of diligent research to solve the above-mentioned problems, the present inventor has made a polyacetal resin having an unstable terminal group such as a hemiacetal group or a formyl group, an unstable terminal group decomposition treatment comprising a quaternary phosphonium salt. It has been found that the above problems can be solved by heat treatment in the presence of an agent, and the present invention has been completed.

That is, the present invention relates to a process for producing a stabilized polyacetal resin in which a polyacetal resin having an unstable terminal group is heat-treated in the presence of an unstable terminal decomposition treatment agent comprising a quaternary phosphonium salt to reduce the unstable terminal group. I will provide a.
Furthermore, this provides a stabilized polyacetal resin, a resin composition and a molded article with reduced unstable end groups.

  According to the present invention, the residual amount of unstable terminal groups of the polyacetal resin can be sufficiently reduced by the unstable terminal group decomposition treatment agent comprising a small amount of quaternary phosphonium salt. In addition, the unstable end group decomposition treatment agent of the present invention does not have an amine odor, and it is difficult to cause undesirable restrictions on the decomposition treatment method and equipment.

Polyacetal resin The polyacetal resin used in the present invention is not particularly limited in its basic molecular structure. For example, the main monomer is cyclic acetal such as formaldehyde or trioxane, which is a cyclic trimer thereof, ethylene oxide, propylene oxide. , Styrene oxide, oxetane, 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3,5-trioxepane, 1,3-dioxane, etc. A copolymer having 1 to 4 glycidyl groups in addition to the above main monomer and comonomer (ethyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, 1,4-butane All diglycidyl ether, hexamethylene glycol diglycidyl ether, bisphenol-A-diglycidyl ether, glycerin mono-triglycidyl ether, trimethylolpropane mono-triglycidyl ether, pentaerythritol mono-tetraglycidyl ether, dipentaerythritol mono-hexa Multi-component copolymer obtained by adding and copolymerizing multi-component monomers such as glycidyl ether, (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) tetramethylene glycol diglycidyl ether) All known polymers such as polymers, multi-component copolymers having branched / crosslinked structures (particularly terpolymers), and block copolymers introduced with block components composed of other polymers. While acetal resin is included, it is preferably a copolymer or terpolymer.
When a multi-component copolymer such as a copolymer or a terpolymer is prepared using trioxane as the main monomer, the proportion of the comonomer component is preferably 0.01 to 20 mol%, more preferably 0.1 to 18 mol%, based on trioxane.
Examples of the polymerization catalyst for producing a polyacetal resin from the above raw materials include Lewis active acids, protonic acids, and cationic active polymerization catalysts such as metal salts, esters or anhydrides thereof. Examples of the Lewis acid include boric acid, tin, titanium, phosphorus, arsenic and antimony halides. Specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, pentachloride. Examples thereof include phosphorus, antimony pentafluoride, and complex compounds or salts thereof. Specific examples of the protonic acid and its metal salt, ester or anhydride include perfluoroalkanesulfonic acid such as perchloric acid, (anhydrous) trifluoromethanesulfonic acid, and perfluorocarbon such as methyl trifluoromethanesulfonate. Alkanesulfonic acid esters, scandium salts of trifluoromethanesulfonic acid, rare earth metal salts of perfluoroalkanesulfonic acid such as yttrium salts and lanthanum salts, metal salts of β-diketones such as bis (acetylacetone) copper and tris (acetylacetone) cobalt, Heteropoly acids such as trimethyloxonium hexafluorophosphate, phosphomolybdic acid, phosphotungstic acid, silicomolybdic acid, silicotungstic acid, isopolymolybdic acid, isopolytungstic acid, isopolyva Etc. isopoly acids such as ethidium acid. Among them, boron trifluoride; boron trifluoride hydrate; coordination complex compound of organic compound containing oxygen atom or sulfur atom and boron trifluoride; trifluoromethanesulfonic acid; and heteropolyacid are preferable, specifically Preferable examples include boron trifluoride, boron trifluoride diethyl ether, boron trifluoride di-n-butyl ether, trifluoromethanesulfonic acid, phosphomolybdic acid, and phosphotungstic acid.
The amount of these polymerization catalysts used is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻¹ mol%, more preferably 5 × 10 ⁻⁶ to the total amount of all monomer components (for example, trioxane and cyclic ether). 1 × 10 ⁻² mol%.
There is no restriction | limiting in particular as a polymerization method, Any of a batch type and a continuous type may be sufficient. Further, bulk polymerization, melt polymerization, solution polymerization, suspension polymerization and the like are possible, but bulk polymerization is preferable.
Further, the molecular weight or melt viscosity is not limited as long as it can be melt-molded.
The polyacetal resin obtained by the polymerization as described above has an unstable terminal group at a part of its molecular terminal, and it is necessary to efficiently decompose and remove the unstable terminal group.
Here, the end group characteristics and the stabilization mechanism of the polyacetal resin will be briefly described.
The unstable end groups of the polyacetal resin are a hemiacetal end group (= hemiformal group (—O—CH ₂ OH)) and a formyl end group (= formyloxy group (—OCHO)).
The stable end group is an alkoxy group such as a methoxy group (—OCH ₃ ), a carbon number such as a hydroxyethyl group (—CH ₂ CH ₂ OH), a hydroxybutyl group (—CH ₂ CH ₂ CH ₂ CH ₂ OH), etc. Two or more hydroxyalkyl groups.
The methoxy group is formed by, for example, formal, typically methylal (= methylene dimethyl ether), which is a molecular weight modifier added in the polymerization stage.
The terminal hydroxyalkyl group having 2 or more carbon atoms is derived from cyclic ether or cyclic formal used as a comonomer, and is formed in the following process. That is, when a polyacetal resin in which an oxyalkylene group derived from a cyclic ether or a cyclic formal is inserted in a repeating oxymethylene unit is polymerized, the polymerization is first stopped by a trace amount of water in the raw material, and the hemiacetal End groups are generated. When a polyacetal resin having a hemiacetal end group is heat-treated in the presence of an aqueous alkaline substance solution such as an aqueous triethylamine solution, unstable end groups are decomposed. When this decomposition proceeds from the terminal toward the main chain and reaches the site of the oxyalkylene unit having 2 or more carbon atoms, the oxyalkylene unit at that site is changed to the stable terminal of the hydroxyalkyl group.
If a large number of hemiacetal end groups remain as unstable end groups in the polyacetal resin, the polyacetal resin is compounded with a stabilizer, and the hemiacetal end groups are decomposed by heating when molding the polyacetal resin, and from there, one after another The oxymethylene unit is removed from the product to formaldehyde.
The formyl end group is a somewhat more stable end group than the hemiacetal end group. However, when the heating conditions for compounding or molding the polyacetal resin are severe, a part of the end group decomposes to become a hemiacetal end group. Generate formaldehyde as described above.

The present invention reduces the unstable terminal groups by heat-treating the polyacetal resin having the unstable terminal groups as described above in the presence of an unstable terminal group decomposition treatment agent described in detail later. The resulting stabilized polyacetal resin has a hemiacetal end group content of 1.0 mmol / kg or less, preferably 0.9 mmol / kg or less, more preferably 0.8 mmol / kg or less, particularly preferably 0.7 mmol / kg. kg or less.
Further, the formyl terminal group amount is preferably 1.3 mmol / kg or less, more preferably 1.2 mmol / kg or less.
Moreover, the manufacturing method of the stabilized polyacetal resin of this invention is applicable also to a polyacetal homopolymer.
The polyacetal homopolymer is obtained, for example, by polymerizing formaldehyde using a quaternary ammonium salt as an anionic polymerization initiator, and is stabilized by acetylating the terminal. Therefore, it basically has a stable acetyl end group, but a hemiacetal end group and a formyl end group, which are unstable end groups, are also partially generated by a thermal decomposition reaction or the like. The quaternary phosphonium salt used in the present invention is also effective for decomposing such unstable end groups of the polyacetal homopolymer to obtain a stabilized polyacetal resin.

Unstable terminal group decomposition treatment agent In the present invention, an unstable terminal decomposition treatment agent used for reducing unstable terminal groups of the polyacetal resin (hereinafter, may be abbreviated as a decomposition treatment agent within a range not causing misunderstanding). Is a quaternary phosphonium salt, preferably selected from quaternary phosphonium salts represented by the following general formula (1).
[R ¹ R ² R ³ R ⁴ P ⁺ ] _n Y ^n- (1)
[In the above formula, R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrocarbon group having 1 to 20 carbon atoms, and the hydrocarbon group is a linear or branched alkyl group, a cycloalkyl group, An aryl group, an aralkyl group, or an alkylaryl group. The hydrocarbon group may have a substituent, and the types of substituents are hydroxyl group, acyl group, acyloxy group, alkoxy group, alkoxycarbonyl group, carboxyl group, amino group, amide group, vinyl group, allyl group. A hydroxyalkyloxy group, a poly (oxyalkylene) group and an alkoxyalkyloxy group. R ¹ , R ² , R ³ and R ⁴ may be connected to each other to form a heterocyclic ring. n represents an integer of 1 or more. Y ⁿ⁻ is a counter anion. n [R ¹ R ² R ³ R ⁴ P ⁺ ] may be different from each other. ]
Here, the counter anion of Y ⁿ⁻ is not limited, but particularly preferred counter anions include hydroxide ion (OH ⁻ ), carbonic acid, organic carbonic acid, organic carboxylic acid, organic sulfonic acid, organic phosphonic acid, organic phosphinic acid, Acid amide compounds, acidic enol compounds, phenolic compounds, alcohol compounds, acidic azole compounds, acid residues of hydrogen acid and oxo acid.
In addition, at least one of R ^{1 to} R ⁴ is an alkyl group having 1 to 10 carbon atoms (methyl group, ethyl group, propyl group, butyl group, etc.), a hydroxyl alkyl group having 1 to 4 carbon atoms (hydroxymethyl group). , 2-hydroxypropyl group, 3-hydroxypropyl group, 2-hydroxy-1-methylethyl group, etc., poly (oxyalkylene) group having 4 to 15 carbon atoms (hydroxyethyloxyethyl group, hydroxypropyloxypropyl group, etc.) And at least one organic group selected from the group consisting of an alkoxyalkyl group having 2 to 10 carbon atoms (methoxymethyl group, ethoxymethyl group, methoxyethyl group, ethoxyethyl group, etc.).
When viewed from the side of the counter anion constituting the quaternary phosphonium salt, preferred unstable terminal decomposition agents include quaternary phosphonium hydroxide, carbonate, bicarbonate, organic carbonate [methyl carbonate, ethyl Monoalkyl carbonates such as carbonate, isopropyl carbonate and n-butyl carbonate, monoaryl carbonates such as monocycloalkyl carbonate and phenyl carbonate, monoalkyl carbonates such as benzyl carbonate, etc.), monoaralkyl carbonate Salts, etc.], organic carboxylates [formate salts, acetates, propionates, benzoates, phthalates, oxalates, glycolates, citrates and tartrates such as C1-C20 organic carboxylates Nitrilotriacetate, ethylenediaminetetraacetate, diethylenetriaminepentaacetate, triethylenediaminehexaacetate, 1,3 Propanediaminetetraacetate, glycol etherdiaminetetraacetate, dicarboxymethylglutamate, ethylenediaminedisuccinate, hydroxyethylethylenediaminetriacetate, 1,3-diamino-2-hydroxypropanetetraacetate and hydroxyethyliminodi Carboxyl group-containing unsaturated monomers (acrylic acid, methacrylic acid, maleic acid, fumaric acid, such as aminocarboxylates such as acetate, poly (meth) acrylate and olefin-poly (meth) acrylic acid copolymer salt, Polymer polycarboxylates obtained by homo- or copolymerization of itaconic acid, etc.], organic sulfonates [methanesulfonate, trifluoromethanesulfonate, ethanesulfonate, p-toluenesulfonate, etc. ], Organic phosphonate [ Til phosphonate, ethyl phosphonate, phenyl phosphonate, etc.], organic sulfinate [dimethyl phosphinate, diethyl phosphinate, methyl ethyl phosphinate, diphenyl phosphinate, etc.], acidic amide compound salt [isocyanuric] Acid salt, phthalimide salt, pyromellitic acid diimide salt, hydantoin salt, 5,5-dimethylhydantoin salt, allantoin salt, barbiturate salt, alloxan salt, glycoluril salt, benzimidazolone salt, urate salt, uracil salt, thymine Salts, saccharin salts, acesulfame salts, bistrifluoromethanesulfonylimide salts, etc.], acidic enol compound salts [β-diketone compound salts such as acetylacetone salt, diacetylacetone salt, methyl acetoacetate, ethyl acetoacetate, dehydrovinegar Salt, [alpha] -acetyl- [gamma] -butyrolactone salt, 1,3-cyclohexanedione salt, dimedone salt, meldrumate, suarinate, 2,3-dihydroxy-2-cyclopenten-1-one, (iso) ascorbic acid, Kojic acid, etc.], phenol compound salt [phenol salt, biphenol salt, bisphenol-A salt, hindered phenol salt, etc.], alcohol compound salt [methanol salt (methoxide), ethanol salt (ethoxide), ethylene glycol salt, propylene glycol salt , Butylene glycol salt, glycerin salt, pentaerythritol salt, etc.], acidic azole compound salt [purine, theophylline, benzimidazole salt, xanthine salt, hypoxanthine salt, guanine salt, 1H-tetrazole salt, 5,5′-bi-1H -Tetrazole salt, 5- Phenyl-1H-tetrazole salt, etc.], hydronates [hydrofluoric acid salts, hydrochlorides, odorates, hydroiodides, tetrafluoroborate, hexafluorophosphate, tetraphenylboric acid, etc.] And oxo acid salts [sulfate, nitrate, phosphate, borate, etc.].
In addition, when viewed from the side of the quaternary phosphonium constituting the quaternary phosphonium salt, a preferable unstable terminal treating agent includes a tetraalkylphosphonium salt which may have a substituent on the alkyl group, and a substituent on the aryl group. A tetraarylphosphonium salt [tetraphenylphosphonium salt, etc.] which may have a triarylalkylphosphonium salt [triphenylmethylphosphonium salt, triphenyl] which may have a substituent in the aryl group and / or alkyl group Ethylphosphonium salt, triphenylpropylphosphonium salt, triphenylbutylphosphonium salt, triphenyl (2-hydroxyethyl) phosphonium salt, etc.], aryl group and / or diaryl dialkylphosphonium salt which may have a substituent on the alkyl group [Diphenyl dimethyl Ruphosphonium salt, diphenyldiethylphosphonium salt, diphenyldipropylphosphonium salt, diphenyldibutylphosphonium salt, diphenylbis (2-hydroxyethyl) phosphonium salt, etc.], aryl group and / or alkyl group may have a substituent Monoaryltrialkylphosphonium salts [phenyltrimethylphosphonium salt, phenyltriethylphosphonium salt, phenyltripropylphosphonium salt, phenyltributylphosphonium salt, phenyltris (2-hydroxyethyl) phosphonium salt, etc.], having a substituent on the aralkyl group Tetraaralkyl phosphonium salt [tetrabenzylphosphonium salt etc.], triaralkyl alkyl phosphine optionally having a substituent on the aralkyl group and / or alkyl group. Substituents for phonium salts [tribenzylmethylphosphonium salt, tribenzylethylphosphonium salt, tribenzylpropylphosphonium salt, tribenzylbutylphosphonium salt, tribenzyl (2-hydroxyethyl) phosphonium salt, etc.], aralkyl groups and / or alkyl groups Diaralkyl dialkylphosphonium salts [dibenzyldimethylphosphonium salt, dibenzyldiethylphosphonium salt, dibenzyldipropylphosphonium salt, dibenzyldibutylphosphonium salt, dibenzylbis (2-hydroxyethyl) phosphonium salt, etc.] that may have, aralkyl Monoaralkyltrialkylphosphonium salt [benzyltrimethylphosphonium salt, benzyltriethylphosphonium salt, which may have a substituent in the group and / or alkyl group] Salt, benzyltripropylphosphonium salt, benzyltributylphosphonium salt, benzyltris (2-hydroxyethyl) phosphonium salt, etc.].
Specific tetraalkylphosphonium salts include tetramethylphosphonium salt, tetraethylphosphonium salt, tetra n-propylphosphonium salt, tetraisopropylphosphonium salt, tetra n-butylphosphonium salt, tetraisobutylphosphonium salt, tetra-t-butylphosphonium salt, Examples include methylene bis (trimethylphosphonium) salt, ethylene bis (trimethylphosphonium) salt, 1,4-butylene bis (trimethylphosphonium) salt, 1,6-hexamethylene bis (trimethylphosphonium) salt, and the like.
The tetraalkylphosphonium salt having a substituent in the alkyl group is particularly preferably a (hydroxyalkyl) mono to trialkylphosphonium salt or tetrakis (hydroxyalkyl) phosphonium salt having at least a hydroxyalkyl group.
Specific (hydroxyalkyl) trialkylphosphonium salts include (hydroxymethyl) trimethylphosphonium salt, (hydroxymethyl) triethylphosphonium salt, (hydroxymethyl) tri-n-propylphosphonium salt, (hydroxymethyl) triisopropylphosphonium salt, (Hydroxymethyl) tri-n-butylphosphonium salt, (2-hydroxyethyl) trimethylphosphonium salt, (2-hydroxyethyl) triethylphosphonium salt, (2-hydroxyethyl) tri-n-propylphosphonium salt, (2-hydroxyethyl) Triisopropylphosphonium salt, (2-hydroxyethyl) tri n-butylphosphonium salt, (2-hydroxypropyl) trimethylphosphonium salt, (2-hydroxypropyl) triethyl Suhoniumu salts, (2-hydroxypropyl) tri n- propyl phosphonium salts, (2-hydroxypropyl) triisopropyl phosphonium salts, and the like (2-hydroxypropyl) tri n- butyl phosphonium salt.
Specific bis (hydroxyalkyl) dialkylphosphonium salts include bis (hydroxymethyl) dimethylphosphonium salt, bis (hydroxymethyl) diethylphosphonium salt, bis (hydroxymethyl) di n-propylphosphonium salt, bis (hydroxymethyl) Diisopropylphosphonium salt, bis (hydroxymethyl) di n-butylphosphonium salt, bis (2-hydroxyethyl) dimethylphosphonium salt, bis (2-hydroxyethyl) diethylphosphonium salt, bis (2-hydroxyethyl) di n-propylphosphonium Salt, bis (2-hydroxyethyl) diisopropylphosphonium salt, bis (2-hydroxyethyl) di n-butylphosphonium salt, bis (2-hydroxypropyl) dimethylphosphonium salt, bis (2- Rokishipuropiru) diethyl phosphonium salts, bis (2-hydroxypropyl) di- n- propyl phosphonium salts, bis (2-hydroxypropyl) diisopropyl phosphonium salts, bis (2-hydroxypropyl) such as di n- butyl phosphonium salts.
Specific tris (hydroxyalkyl) monoalkylphosphonium salts include tris (hydroxymethyl) methylphosphonium salt, tris (hydroxymethyl) ethylphosphonium salt, tris (hydroxymethyl) n-propylphosphonium salt, tris (hydroxymethyl) isopropyl. Phosphonium salt, tris (hydroxymethyl) n-butylphosphonium salt, tris (2-hydroxyethyl) methylphosphonium salt, tris (2-hydroxyethyl) ethylphosphonium salt, tris (2-hydroxyethyl) n-propylphosphonium salt, tris (2-hydroxyethyl) isopropylphosphonium salt, tris (2-hydroxyethyl) n-butylphosphonium salt, tris (2-hydroxypropyl) methylphosphonium salt, tris ( - hydroxypropyl) ethyl phosphonium salt, tris (2-hydroxypropyl) n- propyl phosphonium salt, tris (2-hydroxypropyl) isopropyl phosphonium salt, tris (2-hydroxypropyl) such as n- butyl phosphonium salts.
Specific tetrakis (hydroxyalkyl) phosphonium salts include tetrakis (hydroxymethyl) phosphonium salts, tetrakis (2-hydroxyethyl) phosphonium salts, tetrakis (2-hydroxypropyl) phosphonium salts, tris (2-hydroxyethyl) (2 -Hydroxyethyloxyethyl) phosphonium salt, bis (2-hydroxyethyl) bis (2-hydroxyethyloxyethyl) phosphonium salt, (2-hydroxyethyl) tris (2-hydroxyethyloxyethyl) phosphonium salt, tetrakis (2- Hydroxyethyloxyethyl) phosphonium salts, and the like.
In addition, an alkoxyalkyl group in which a part or all of the hydroxyalkyl residues in the above (hydroxyalkyl) trialkylphosphonium salt, bis (hydroxyalkyl) dialkyl salt and tetra (hydroxyalkyl) phosphonium salt are alkylated (for example, Methoxymethyl group, methoxyethyl group, methoxypropyl group, ethoxymethyl group, ethoxyethyl group, ethoxypropyl group, propoxymethyl group, propoxyethyl group, propoxypropyl group, butoxymethyl group, butoxyethyl group, butoxypropyl group, methoxyethyl Substance groups having an oxyethyl group, an ethoxyethyloxyethyl group, etc.) can also be mentioned as preferred quaternary phosphonium salts.
Further, preferred unstable terminal decomposition agents include tetraalkylphosphonium, (hydroxyalkyl) trialkylphosphonium, bis (hydroxyalkyl) dialkylphosphonium, tris (hydroxyalkyl) monoalkylphosphonium, and tetrakis (hydroxyalkyl) phosphonium. At least one quaternary phosphonium selected, hydroxide (OH ⁻ ), carbonate, bicarbonate, organic carbonate (especially methyl carbonate, ethyl carbonate), organic carboxylate (especially formate) , Acetate, propionate, polyacrylate), acid amide compound salt (especially isocyanurate, phthalimide salt), acid enol compound salt (especially acetylacetone salt, methyl acetoacetate, ethyl acetoacetate), Phenol compound salts (especially Bisphenol-A salt, hindered phenol salt), alcohol compound salt (especially methanol salt, ethanol salt), hydrogenate salt (especially hydrochloride salt), and oxo acid salt (especially borate salt).
In addition, these quaternary phosphonium salts can also be used as a double salt / complex salt in which two or more kinds are mixed.
Particularly preferable unstable end-treatment agents include hydroxides and / or protonic acid salts (organic carbonates, organic carboxylates, acidic amide compound salts, β-diketone compound salts, etc.) of these quaternary phosphoniums. It is done.

  Intramolecular phosphonium salts such as phosphobetaines and heterocyclic quaternary phosphonium salts are also included in the present invention as a preferred substance group.

Method for treating unstable end group The method for producing a stabilized polyacetal resin according to the present invention comprises the step of heat-treating the polyacetal resin polymerized as described above and having an unstable end group in the presence of at least one of the above decomposition treatment agents. The end group is reduced.
The amount of decomposition treatment agent added to 1 kg of polyacetal resin depends on the type and amount of unstable end groups contained, the type of decomposition treatment agent, the treatment state, and treatment conditions (temperature, time, contact speed, etc.). When processing in a state, it is converted into a phosphonium phosphorus atom (P ⁺ ) that gives a quaternary phosphonium salt, 0.005 to 3.5 mmol, preferably 0.01 to 3 mmol, particularly preferably 0.05 to 2 mmol. It is.
In addition, it can use together with a conventionally well-known decomposition processing agent as needed.

The heat treatment may be performed after deactivation of the polymerization catalyst remaining in the polyacetal resin after polymerization, or before deactivation, and the unstable end groups are still present even when a stabilization treatment other than the present invention is performed. It is also possible to apply to the remaining polyacetal resin.
When the polymerization catalyst is deactivated, the polyacetal resin after polymerization is converted to amines such as ammonia and alkylamine, onium salts [quaternary ammonium salts (such as choline hydroxide and cholinemate), and quaternary phosphonium salts of the present invention. Etc.] or an aqueous solution or an organic solvent containing at least one catalyst deactivator such as alkali metal or alkaline earth metal hydroxide, inorganic acid salt, or organic acid salt, and generally in a slurry state. It is carried out by standing or stirring for 1 minute to 6 hours. The slurry after deactivation of the catalyst is used as it is or after drying after removing unreacted monomers, catalyst deactivator and the like by filtration and washing.
Further, at least one selected from a method of deactivating a polymerization catalyst by bringing vapor such as amines into contact with a polyacetal resin, hindered amines, aminotriazines, triphenylphosphine, calcium hydroxide, magnesium hydroxide, etc. And the polyacetal resin may be mixed and stirred to deactivate the catalyst.
When the polymerization catalyst is not deactivated, a polyacetal resin in which the polymerization catalyst is reduced in volatilization can be used by heating in an inert gas atmosphere at a temperature lower than the melting point of the polyacetal resin after polymerization. . The deactivation of the polymerization catalyst or the volatilization reduction treatment of the polymerization catalyst may be performed after pulverizing the polyacetal resin after polymerization.

In the present invention, when treating the unstable end group of the polyacetal resin, various conventional treatment methods and apparatuses corresponding thereto can be selected except that the above-mentioned compound is used as the unstable end group decomposition treatment agent.
In the method of decomposing the unstable terminal group, after performing necessary treatment such as catalyst neutralization after polymerization, the thermal decomposition treatment with the decomposition treatment agent is performed in the melt state of the polyacetal resin or the solvent slurry state of the polyacetal resin. Is called.

The method of processing in the molten state of the polyacetal resin is, for example, melting the resin with a single-screw or twin-screw extruder or the like, the melting point of the polyacetal resin to 260 ° C., preferably the melting point of the polyacetal resin to 250 ° C., and the resin residence time 5 The treatment is performed for seconds to 30 minutes, preferably 20 seconds to 20 minutes. If the treatment conditions are less than the lower limit, the stabilization of the resin is insufficient, and if the treatment limits are exceeded, the resin may be decomposed or colored. The addition of the decomposition treatment agent may be performed at any stage before or after the polyacetal resin is melted, or may be performed at both stages. Moreover, the addition amount of the decomposition treatment agent to be added may be divided and supplied in multiple stages.
In addition, as a method of adding the decomposition treatment agent to the polyacetal resin before melting, an aqueous solution of the decomposition treatment agent, an organic solvent solution such as methanol or ethanol, or an alcohol aqueous solution is used with respect to the crude polyacetal resin having unstable terminal groups. Add the specified amount as uniformly as possible and mix. For mixing, a general mixer such as a horizontal cylindrical type, a V type, a ribbon type, a paddle type, or a high-speed flow type can be used. The mixture may be melted as it is without being dried, or may be melted after the solvent is distilled off by heating, decompression or the like. Further, the decomposition treatment agent solution may be supplied by injection or the like from the feed port of the extruder and / or midway. At this time, the decomposition treatment agent solution may be divided and supplied in multiple stages.
In addition, a treatment agent can be added by a method in which a resin is added to the solution to form a slurry, which is filtered and dried to attach the decomposition treatment agent to the resin.
In addition, as a method of adding the decomposition treatment agent to the molten polyacetal resin after melting the polyacetal resin, the decomposition treatment agent and the solvent can be fed and / or injected separately or as a solution.
When decomposed in the molten state, an antioxidant (hindered phenols, hindered amines, etc.), a decomposition accelerator [water; methanol; trimethylamine, triethylamine, tributylamine, mono-triethanolamine, diethyl as necessary. Amines such as ethanolamine; alkaline earth metal compounds such as magnesium hydroxide, calcium hydroxide, magnesium oxide; tetramethylammonium hydroxide, choline hydroxide, (2-hydroxyethyl) triethylammonium hydroxide, or protons thereof Acid salts (carbonates, bicarbonates, inorganic salts such as hydrochlorides; organic carboxylates such as formates, acetates, propionates, tartrates, citrates, polyacrylates; methyl carbonates, Organic carbonates such as ethyl carbonate; phenolic compound salts; phthalates Quaternary ammonium compounds of acid amide compound salts such as mid salt, isocyanurate and uric acid salt; β-diketone compound salts such as acetylacetone salt, methyl acetoacetate, ethyl acetoacetate, etc.] and hue stabilizer ( 1 type or 2 types or more selected from orthoboric acid, metaboric acid, tetraboric acid, boron oxide, boric acid metal salt, etc.) in an amount of 0.001 to 5 parts by weight, preferably 0 0.005 to 2 parts by weight may be added.
The polyacetal resin from which the unstable terminal portion has been decomposed and removed is subjected to removal of formaldehyde, unreacted monomer, oligomer, decomposition treatment agent, etc. generated by decomposition under reduced pressure from the vent portion of the extruder, and after cooling, strand cut or Pelletized by die face cutting.

When the polyacetal resin is used in a slurry state, the polyacetal resin is added to water, an alcohol solution, or an aqueous alcohol solution of the decomposition treatment agent, and the amount of the decomposition treatment agent relative to the resin is a phosphonium phosphorus atom that gives the quaternary phosphonium salt (P ^In terms of ⁺ ), the heat treatment is performed at normal pressure or under pressure so as to be 0.005 to 35 mmol, preferably 0.01 to 30 mmol, particularly preferably 0.1 to 25 mmol.
The slurry concentration is 3 to 70% by weight, preferably 5 to 60% by weight; the heating temperature is 60 ° C. or higher and lower than the melting point of the resin, preferably 80 to 140 ° C .; the heating time is 2 minutes to 30 hours, preferably 20 Min to 20 hours.
After the treatment, the polyacetal resin is freed of formaldehyde, unreacted monomers, oligomers, decomposition treatment agents, and the like produced by decomposition by filtration and washing, and becomes a product of a stabilized polyacetal resin after drying in the same manner as the treatment in the molten state.

The present invention also provides a stabilized polyacetal resin having a number average molecular weight of 5000 or more, a hemiacetal end group amount of 1.0 mmol / kg or less and / or a formyl end group amount of 1.2 mmol / kg or less. Is.
Thus, a polyacetal resin with few unstable terminal groups is a thing which has not existed conventionally, and can be used for the new use in which the drastic reduction of generation | occurrence | production of formaldehyde and reduction of a bad smell are calculated | required.

The resulting stabilized polyacetal resin, if necessary, with respect to 100 parts by weight thereof, the following additives:
(A) 0.001 to 5 parts by weight of at least one selected from the group consisting of an antioxidant, a formaldehyde scavenger, a formic acid scavenger, a weather resistance stabilizer, a light resistance stabilizer, a processing stabilizer and a crystal nucleating agent;
(B) 0 to 100 parts by weight of at least one selected from the group consisting of a filler, a reinforcing agent, a lubricant, a sliding agent, a conductive agent, an antistatic agent, a thermoplastic resin, a thermoplastic elastomer, and a core-shell polymer; And (c) 0-5 parts by weight of a colorant is added and mixed with an extruder or the like to form a polyacetal resin composition, which can be used for molding.
Additives such as scavengers, antioxidants, and stabilizers are generally added to the polyacetal resin after terminal stabilization treatment, and are preferably melt-kneaded to prepare a polyacetal resin composition. As long as the efficiency of catalyst deactivation, terminal stabilization, etc. is not impaired, it can be added to the raw material monomer or comonomer for polymerization or added at the polymerization stage. It is also possible to add to the polymer to be subjected to the treatment or at any stage of the terminal stabilization treatment step.

Specifically, the polyacetal resin composition of the present invention comprises a hindered phenolic antioxidant, a hindered amine antioxidant, a phosphorus secondary antioxidant, and a sulfur secondary antioxidant as the antioxidant. It is preferable to contain 0.01 to 1 part by weight of at least one selected from the group with respect to 100 parts by weight of the stabilized polyacetal resin.
The formaldehyde scavenger is selected from the group consisting of aminotriazine compounds, urea compounds, guanidine compounds, hydrazine compounds, amino acid compounds, amino alcohol compounds, imide compounds, azole compounds, amide compounds, polyamide resins, polyacrylamide resins and polyurethane resins. It is preferable to contain 0.01 to 2 parts by weight based on 100 parts by weight of the stabilized polyacetal resin.
Examples of the aminotriazine compound include melamine, benzoguanamine, CTU-guanamine, 2,4-diamino-6- (2′-methylimidazolyl-1 ′)-ethyl-s-triazine, 2,4-diamino-6- (2 '-Undecylimidazolyl-1')-ethyl-s-triazine, 2,4-diamino-6- (2'-ethyl-4'-methylimidazolyl-1 ')-ethyl-s-triazine, melamine resin, etc. Can be mentioned.
Examples of the urea compound include urea, ethylene urea, propylene urea, glycoluril, parbituric acid, uric acid, benzoimidazolone, form nitrogen, biuret, biurea, hydantoin, 5,5-dimethylhydantoin, allantoin, allantoin salt (allantoindihydroxyaluminum) And amino acid salts of allantoin).
Examples of the guanidine compound include cyanoguanidine, glycocyanidine, creatinine and the like.
Examples of the hydrazine compound include urazole, 4-aminourazole, lauric acid hydrazide, stearic acid hydrazide, 12-hydroxystearic acid hydrazide, adipic acid hydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, eicosanedioic acid dihydrazide, 8,12. -Eicosadiene diacid dihydrazide, 1,4-cyclohexanedicarboxylic acid dihydrazide, 1,3-bis (2-hydrazinocarbonylethyl) -5-isopropylhydantoin, benzoic hydrazide, α-naphthoic acid hydrazide, β-naphthoic acid hydrazide, Examples thereof include isophthalic acid dihydrazide, terephthalic acid dihydrazide, and 2,6-naphthalenedicarboxylic acid dihydrazide.
Examples of amino acid compounds include α-amino acids, β-amino acids, γ-amino acids, δ-amino acids, aromatic amino acids, and the like. α-amino acids include monoamino monocarboxylic acids (glycine, alanine, valine, norvaline, leucine, norleucine, isoleucine, phenylalanine, tyrosine, diiodotyrosine, sulinamine, threonine, serine, proline, hydroxyproline, tryptophan, methionine, cystine. , Cysteine, citrulline, α-aminobutyric acid, hexahydropicolinic acid, theanine, o-tyrosine, m-tyrosine, 3,4-dihydroxyphenylalanine, etc., monoaminodicarboxylic acids (aspartic acid, glutamic acid, asparagine, glutamine, hexahydro) Examples thereof include dipicolinic acid and hexahydroquinolinic acid) and diaminomonocarboxylic acids (lysine, hydroxylysine, arginine, histidine and the like). Examples of the β-amino acid, γ-amino acid, and δ-amino acid include β-alanine, β-aminobutyric acid, hexahydrocincomeronic acid, γ-aminobutyric acid, and δ-amino-n-valeric acid. Examples of the aromatic amino acid include o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid and the like. These amino acids may be any of D-form, L-form and DL-form, and carboxyl group is metal chloride (alkali metal salt, alkaline earth metal salt etc.), amidation, hydrazide Also included are amino acid derivatives that are esterified (methyl ester, ethyl ester, etc.).
Amino alcohol compounds include monoethanolamine, diethanolamine, 2-amino-1-butanol, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol, 2-amino -2-ethyl-1,3-propanediol, tris (hydroxymethyl) aminomethane and the like.
Examples of the imide compound include succinimide, phthalimide, trimellitic imide, pyromellitic diimide and the like.
Examples of the azole compound include 4-amino-1,2,4-triazole, benzimidazole, guanine, benzotriazole, and 5-phenyl-1H-tetrazole.
Examples of the amide compound include amide compounds such as malonamide, adipic acid amide, sebacic acid amide, dodecanedioic acid amide, benzoic acid amide, and anthranilamide.
Examples of the polyamide resin include polyamide resins such as nylon 3, nylon 6, nylon 66, nylon 6-66-610, nylon 6-66-610-12, and the like.

The polyacetal resin composition of the present invention is a fatty acid metal salt, poly (meth) acrylic acid (co) polymer metal salt, aminocarboxylic acid metal salt which may have a hydroxyl group as a formic acid scavenger (heat stabilizer). , (Iso) cyanuric acid metal salt, silicic acid metal salt (talc, zeolite, etc.), hydrotalcite, magnesium hydroxide and magnesium oxide, one or more selected from 100 parts by weight of stabilized polyacetal resin It is preferable to contain 0.001-1 weight part.
Examples of the fatty acid metal salt include calcium acetate, calcium propionate, calcium citrate, calcium stearate, calcium 12-hydroxystearate, magnesium stearate, zinc stearate, lithium stearate and the like.
The polyacetal resin composition of the present invention stabilizes at least one selected from the group consisting of a fatty acid ester having 12 to 36 carbon atoms, a fatty acid amide, a polyalkylene glycol, a polysiloxane, and a low molecular weight polyethylene as a processing stabilizer. It is preferable to contain 0.01-1 weight part with respect to 100 weight part of polyacetal resin.
Examples of the fatty acid ester include ethylene glycol mono-distearate, glycerin mono-tristearate, pentaerythritol mono-tetrastearate and the like. Examples of fatty acid amides include ethylene bisstearyl amide.

The stabilized polyacetal resin or polyacetal resin composition of the present invention can be formed into a molded body by injection molding, extrusion molding, blow molding, press molding, gas injection molding or foam molding.
The molded body of the present invention is (1) when stored in a sealed space at 80 ° C. for 24 hours, the amount of generated formaldehyde is ² μg or less, preferably 0.001 to 1.0 μg per 1 cm ² of the surface area of the molded body, and / or (2) When stored in a sealed space of 60 ° C. and saturated humidity for 3 hours, the amount of formaldehyde generated is 0.8 μg or less, preferably 0.001 to 0.6 μg or less per 1 cm ² of surface area of the molded body.
The molded article of the present invention is used for automobile parts, electrical / electronic parts, OA equipment parts, building materials / piping parts, daily / cosmetic parts, or medical parts.

(Example)
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to this.
The measurement method of [evaluation characteristics of the stabilized polyacetal resin] used as a quality index in the production examples and the measurement method of [evaluation characteristics of the stabilized polyacetal resin composition] used as a quality index in the examples are as follows.

[Method for measuring evaluation characteristics of stabilized polyacetal resin]
1. Hemiacetal end group amount and formyl end group amount Polyacetal copolymer was dissolved in hexafluoroisopropyl alcohol, reacted with N, O-bis (trimethylsilyl) trifluoroacetamide and pyridine, then air-dried, then The remaining solvent and unreacted substances were removed by drying at 40 ° C. under reduced pressure. The obtained reaction product was dissolved in deuterated hexafluoroisopropyl alcohol at a concentration of 5% by weight as a solvent, the solution was filled in an NMR sample tube, and an NMR spectrum was measured at room temperature (Japanese Patent Laid-Open No. 2001-11143). Issue gazette).
The amount of hemiacetal end groups (mmol / kg) and formyl end groups (mmol / kg) were calculated based on the corresponding NMR absorption peaks.
NMR apparatus: Bruker, AVANCE400 type FT-NMR
Measurement conditions: Pulse flip angle 30 °, integration repetition time 10 sec, integration count 128 times Unstable end amount (amount of unstable part at the end)
About 1 g of a polyacetal copolymer was precisely weighed, placed in a pressure-resistant sealed container together with 100 ml of a 60 volume% methanol aqueous solution containing 15 mg of calcium hydroxide and 0.5 volume% ammonium hydroxide, and heat-treated at 170 ° C. for 60 minutes. The inner solution was taken out after cooling and opening. The amount of formaldehyde generated by the decomposition of the unstable terminal portion and dissolved in the solution was quantified by JIS K0102, 29.1 acetylacetone absorptiometry, and the ratio to the polyacetal copolymer was calculated as wt%.
3. Odor of polyacetal copolymer (amine odor)
1 g of the pelletized stabilized polyacetal copolymer was put in a sealed container (capacity 20 ml), heated in a thermostatic bath at a temperature of 80 ° C. for 24 hours, and then the amine odor when opened was measured by human olfaction. Evaluated by criteria.
○: There is no amine odor.
Δ: Some amine odor.
X: Strong amine odor.

[Method for measuring evaluation characteristics of stabilized polyacetal resin composition]
1. Amount of formaldehyde generated by wet method 50ml of distilled water is placed in a polyethylene bottle with a volume of 1 liter, and two flat test pieces (100mm x 40mm x 2mm; total surface area 85.6cm ² ) are hung inside the lid. Seal the bottle by closing the lid. This is placed in a constant temperature bath at a temperature of 60 ° C., heated for 3 hours, taken out of the constant temperature bath, and left at 20 ° C. for 1 hour.
The amount of formaldehyde released from the test piece by heating and dissolved in water is determined by JIS K0102, 29.1 acetylacetone spectrophotometry, and the amount of formaldehyde generated per unit surface area (unit: μg / cm ² ) is calculated.
2. Formaldehyde generation amount in dry process Ten test pieces (total surface area of about 40 cm ² ) of test pieces (2 mm × 2 mm × 50 mm) are placed in a 20 ml container and sealed. This was heat-treated in a thermostat at 80 ° C. for 24 hours, then taken out from the thermostat and left at 20 ° C. for 1 hour, and then 5 ml of distilled water was injected into the container with a syringe, and the test piece was heat-treated. Absorbs formaldehyde released from water into water. The amount of formaldehyde dissolved in water is determined by JIS K0102, item 29.1 acetylacetone absorptiometry, and the amount of formaldehyde generated per unit surface area (unit: μg / cm ² ) is calculated.

[Preparation of crude polyacetal copolymer (A) for stabilization treatment]
It has a cross-sectional shape in which two circles partially overlap each other, and a barrel provided with a jacket through which a heat (cooling) medium passes outside, and two barrels each provided with a stirring paddle and a propulsion paddle in the longitudinal direction inside the barrel. The polymerization reaction was performed as follows using a continuous mixing reactor having a rotating shaft.
Warm water at 80 ° C. was passed through the jacket, the two rotating shafts were rotated at a speed of 100 rpm, and 0.05% by weight of triethylene glycol-bis [3- (3-tert-butyl-5-methyl) was used as an antioxidant. -4-hydroxyphenyl) propionate], trioxane containing 3.3% by weight of 1,3-dioxolane as comonomer and 700 ppm (by weight) of methylal as chain transfer agent are continuously fed to the reactor and in parallel Then, a solution of boron trifluoride / dibutyl etherate dissolved in cyclohexane (concentration of 1% by weight) is 10 ppm (weight) as boron trifluoride with respect to all monomers (total amount of trioxane and 1,3-dioxolane). Copolymerization was carried out with continuous addition at a standard) concentration. Subsequently, the crude polyacetal copolymer discharged from the discharge port of the reactor was added to an aqueous solution containing 0.1% by weight of triethylamine to deactivate the catalyst. The mixture was centrifuged and further dried to obtain a crude polyacetal copolymer (A).
The crude polyacetal copolymer (A) has a hemiacetal terminal group amount of 2.2 mmol / kg, a formyl terminal group amount of 1.5 mmol / kg, and an unstable terminal amount (amount of terminal unstable parts) of 0.87 weight. %Met.

  Hereinafter, (1) Examples and comparative production examples of the stabilized polyacetal resin, and (2) Examples and comparative examples of the composition using the stabilized polyacetal resin and the molded product thereof will be described.

(1) Examples of production and comparative production examples of stabilized polyacetal resins [Examples of Production Examples 1 to 8]
0.3 parts by weight of triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] and four parts per 100 parts by weight of the crude polyacetal copolymer (A). 2 parts by weight of an aqueous solution containing a secondary phosphonium salt was added and mixed uniformly.
In addition, the aqueous solution containing a quaternary phosphonium salt is converted into a phosphorus atom (P ⁺ ) of the quaternary phosphonium salt by adding 2 parts by weight of the quaternary phosphonium salt to 1 kg of the crude polyacetal copolymer. The concentration was adjusted to 1.4 mmol.
This mixture was then fed to a single twin screw extruder (diameter 30 mm) with a devolatilization port and volatile at a vent vacuum of 2.7 kPa (20 mmHg), a cylinder temperature of 200 ° C. and an average residence time of 300 seconds. The product was melt-kneaded while removing the product from the (vent) devolatilization port to obtain a pelletized stabilized polyacetal copolymer. The results are shown in Table 1.

[Example Production Examples 9 to 12]
0.05 parts by weight of triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] and a concentration with respect to 100 parts by weight of the crude polyacetal copolymer (A) 2 parts by weight of an aqueous solution containing the prepared quaternary phosphonium salt was added and mixed uniformly. In addition, the aqueous solution containing a quaternary phosphonium salt is converted into a phosphorus atom (P ⁺ ) of the quaternary phosphonium salt by adding 2 parts by weight of the quaternary phosphonium salt to 1 kg of the crude polyacetal copolymer. The concentration is adjusted to 0.7 mmol.
Subsequently, this mixture was supplied to one twin screw extruder (diameter 30 mm) with a devolatilization port. In the extruder, 0.5 part by weight of water is added per 100 parts by weight of the supplied crude polyacetal copolymer, and the vent vacuum is 2.7 kPa, the cylinder temperature is 200 ° C., and the average residence time is 300 seconds. The mixture was melt-kneaded while removing volatiles from the (vent) devolatilization port to obtain a pelletized stabilized polyacetal copolymer. The results are shown in Table 1.

[Example Production Example 13]
0.03 parts by weight of triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] with respect to 100 parts by weight of the crude polyacetal copolymer (A), 1 part by weight of an aqueous solution containing a quaternary phosphonium salt whose concentration was adjusted and 1 part by weight of an aqueous solution containing a (2-hydroxyethyl) triethylammonium formate whose concentration was adjusted were added and mixed uniformly. In addition, the aqueous solution containing a quaternary phosphonium salt is converted to the phosphorus atom (P ⁺ ) of the quaternary phosphonium salt by adding 1 part by weight of the quaternary phosphonium salt to 1 kg of the crude polyacetal copolymer. The aqueous solution containing a quaternary ammonium salt ((2-hydroxyethyl) triethylammonium formate) was added to 1 part by weight of the crude polyacetal copolymer. The concentration was adjusted so that the amount of quaternary ammonium salt added to 1 kg of coalescence was 0.5 mmol in terms of nitrogen atom (N ⁺ ) of quaternary ammonium.
This mixture was then fed to a single twin screw extruder (diameter 30 mm) with a devolatilization port and volatile at a vent vacuum of 2.7 kPa (20 mmHg), a cylinder temperature of 200 ° C. and an average residence time of 300 seconds. The product was melt-kneaded while removing the product from the (vent) devolatilization port to obtain a pelletized stabilized polyacetal copolymer. The results are shown in Table 1.

[Example Production Example 14]
1 part by weight of an aqueous solution containing a quaternary phosphonium salt whose concentration was adjusted was added to 100 parts by weight of the crude polyacetal copolymer (A), uniformly mixed and dried. In addition, the aqueous solution containing a quaternary phosphonium salt is converted to the phosphorus atom (P ⁺ ) of the quaternary phosphonium salt by adding 1 part by weight of the quaternary phosphonium salt to 1 kg of the crude polyacetal copolymer. The concentration was adjusted to 3.0 mmol.
Subsequently, this mixture was supplied to one twin screw extruder (diameter 30 mm) with a devolatilization port. In the extruder, 0.5 parts by weight of water is added per 100 parts by weight of the fed crude polyacetal copolymer, with a vent vacuum of 2.7 kPa, a cylinder temperature of 200 ° C., and an average residence time of 300 seconds. The mixture was melt-kneaded while removing volatiles from the (vent) devolatilization port to obtain a pelletized stabilized polyacetal copolymer. The results are shown in Table 1.

[Example Production Example 15]
1 part by weight of an aqueous solution containing a quaternary phosphonium salt whose concentration was adjusted was added to 100 parts by weight of the crude polyacetal copolymer (A), uniformly mixed and dried. In addition, the aqueous solution containing a quaternary phosphonium salt is converted to the phosphorus atom (P ⁺ ) of the quaternary phosphonium salt by adding 1 part by weight of the quaternary phosphonium salt to 1 kg of the crude polyacetal copolymer. The concentration was adjusted to 2.0 mmol.
Subsequently, 0.3 parts by weight of triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 0.1 parts by weight with respect to 100 parts by weight of the crude polyacetal copolymer. 05 parts by weight of nylon 6,6 (average particle size: 4 μm), 0.1 parts by weight of calcium stearate, and 0.2 parts by weight of ethylene bisstearylamide were further added and mixed to form one devolatilization port It supplied to the twin screw extruder (diameter 30mm). In the extruder, 0.5 parts by weight of water is added per 100 parts by weight of the fed crude polyacetal copolymer, with a vent vacuum of 2.7 kPa, a cylinder temperature of 200 ° C., and an average residence time of 300 seconds. The mixture was melt-kneaded while removing volatiles from the (vent) devolatilization port to obtain a pelletized stabilized polyacetal copolymer. The results are shown in Table 1.

[Comparative Production Example 1]
0.3 parts by weight of triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] and 2 parts per 100 parts by weight of the crude polyacetal copolymer (A) A part by weight of an aqueous triethylamine solution (0.72 wt% concentration: triethylamine (abbreviated as TEA) is 1.4 mmol in terms of tertiary amine nitrogen per kg of the crude polyacetal copolymer) was added and mixed uniformly.
Next, this mixture was supplied to the above-described twin screw extruder with a devolatilization port, and the volatiles were vented at a vent vacuum of 20 mmHg (2.7 kPa), a cylinder temperature of 200 ° C., and an average residence time of 300 seconds. While being removed from the devolatilization port, the mixture was melt-kneaded to obtain a pelletized stabilized polyacetal copolymer. The results are shown in Table 1.

The quaternary phosphonium salts used in the practical production examples as unstable terminal decomposition treatment agents are as follows.
(A-1): Tetraethylphosphonium hydroxide (A-2): Tetraethylphosphonium salt of formic acid (A-3): Tris (tetraethylphosphonium) salt of isocyanuric acid (A-4): Tetrabutylphosphonium hydroxide (A-) 5): Tetrabutylphosphonium salt of formic acid (A-6): Tetrabutylphosphonium salt of acetic acid (A-7): Hydroxylated (2-hydroxyethyl) trimethylphosphonium (A-8): (2-hydroxyethyl of formic acid ) Trimethylphosphonium salt (A-9): tetraethylphosphonium salt of ethyl acetoacetate (A-10): tetrabutylphosphonium tetraphenylphosphate (A-11): tetrabutylphosphonium salt of acetylacetone (A-12): (carboxymethyl) ) Trimethylphosphonium hydroxide

(2) Examples and comparative examples (stabilized polyacetal resin compositions and molded articles thereof)
[Examples 1 to 8]
The various stabilized polyacetal copolymers obtained in the above production examples are mixed with formaldehyde scavengers, antioxidants, processing stabilizers and heat stabilizers in the proportions shown in Table 2, and devolatilized in one place. It melt-mixed with the 30-mm diameter twin-screw extruder which has an opening | mouth, and the pellet-shaped polyacetal resin composition was prepared. Using this pellet, a predetermined test piece was molded by an injection molding machine, and the amount of formaldehyde generated was measured according to the evaluation method. The results are shown in Table 2.

[Comparative Example 1]
The stabilized polyacetal copolymer (a-8) prepared in Comparative Production Example 1 was mixed with a formaldehyde scavenger, an antioxidant, a processing stabilizer and a heat stabilizer in the proportions shown in Table 2, and In the same manner, a polyacetal resin composition in the form of pellets was prepared by melt mixing with a twin screw extruder. Using this pellet, a predetermined test piece was molded by an injection molding machine and evaluated in the same manner as in the above examples. The results are shown in Table 2.

The polyacetal copolymers, formaldehyde scavengers, hindered phenol compounds, hindered amine compounds, processing stabilizers and heat stabilizers used in the examples and comparative examples are as follows.
The melt index is a value measured under conditions of a temperature of 190 ° C. and a load of 2160 g according to ASTM-D1238, and the unit is g / 10 minutes.
[Stabilized polyacetal copolymer a]
(A-1): Stabilized polyacetal copolymer prepared in Example Production Example 1 [Hemiacetal end group amount = 0.5 mmol / kg, Formyl end group amount = 1.1 mmol / kg, Unstable end group amount = 0 .41 wt%, melt index = 9 g / 10 min]
(A-2): Stabilized polyacetal copolymer prepared in Example Production Example 2 [Hemiacetal end group amount = 0.5 mmol / kg, Formyl end group amount = 1.2 mmol / kg, Unstable end group amount = 0 .47 wt%, melt index = 9 g / 10 min]
(A-3): Stabilized polyacetal copolymer prepared in Example Production Example 5 [Hemiacetal end group amount = 0.5 mmol / kg, Formyl end group amount = 0.9 mmol / kg, Unstable end group amount = 0 .38 wt%, melt index = 9 g / 10 min]
(A-4): Stabilized polyacetal copolymer prepared in Example Production Example 8 [Hemiacetal end group amount = 0.4 mmol / kg, Formyl end group amount = 0.6 mmol / kg, Unstable end group amount = 0 .27 wt%, melt index = 9 g / 10 min]
(A-5): Stabilized polyacetal copolymer prepared in Example 9 [Hemiacetal terminal group amount = 0.5 mmol / kg, Formyl terminal group amount = 0.5 mmol / kg, Unstable terminal group amount = 0 .28 wt%, melt index = 9 g / 10 min]
(A-6): Stabilized polyacetal copolymer prepared in Example Production Example 13 [Hemiacetal end group amount = 0.3 mmol / kg, Formyl end group amount = 0.2 mmol / kg, Unstable end group amount = 0 .15 wt%, melt index = 9 g / 10 min]
(A-7): Stabilized polyacetal copolymer prepared in Example Production Example 14 [Hemiacetal end group amount = 0.3 mmol / kg, Formyl end group amount = 0.9 mmol / kg, Unstable end group amount = 0 .29% by weight, melt index = 9 g / 10 min]
(A-8): Stabilized polyacetal copolymer prepared in Comparative Production Example 1 [Hemiacetal end group amount = 1.7 mmol / kg, Formyl end group amount = 1.4 mmol / kg, Unstable end group amount = 0 .74 wt%, melt index = 9 g / 10 min]
[Formaldehyde scavenger b]
(B-1): Melamine (b-2): Benzoguanamine (b-3): CTU-guanamine [Ajinomoto Fine Techno Co., Ltd.]
(B-4): Allantoin (b-5): Biurea (b-6): Sebacic acid dihydrazide (b-7): Nylon 66 [average particle size = 3 μm]
(B-8): Sebacic acid dihydrazide [antioxidant c]
(C-1): Pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]
(C-2): Triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate]
[Processing stabilizer d]
(D-1): Ethylene bisstearylamide (d-2): Glycerol monostearate
(D-3): ethylene glycol distearate [heat stabilizer (organic carboxylic acid metal salt, alkaline earth metal salt) e]
(E-1): 12-hydroxy calcium stearate (e-2): magnesium oxide (e-3): calcium citrate (e-4): calcium stearate

Claims (10)

A method for producing a stabilized polyacetal resin in which a polyacetal resin having an unstable terminal group is heat-treated in the presence of an unstable terminal decomposition treatment agent comprising a quaternary phosphonium salt to reduce unstable terminal groups ,
The unstable terminal decomposition agent is at least one selected from tetraalkylphosphonium, (hydroxyalkyl) trialkylphosphonium, bis (hydroxyalkyl) dialkylphosphonium, tris (hydroxyalkyl) monoalkylphosphonium and tetra (hydroxyalkyl) phosphonium. Quaternary phosphonium, hydroxide, carbonate (hydrogen), organic carbonate, organic carboxylate, organic phosphonate, organic phosphinate, acidic amide compound salt, acidic enol compound salt, phenolic compound salt, alcohol A process for producing a stabilized polyacetal resin which is at least one quaternary phosphonium salt selected from the group consisting of compound salts, acidic azole compound salts, and double salts / complex salts thereof . The stabilized polyacetal resin according to claim 1 , wherein the polyacetal resin is a polyoxymethylene copolymer obtained by copolymerizing trioxane as a main monomer and cyclic ether and / or cyclic formal as a comonomer in the presence of a cationic polymerization catalyst. Manufacturing method. 3. The method according to claim 1, further comprising adding at least one compound selected from protonic acids and alkali (earth) metal compounds, and heat-treating in the presence of an unstable terminal decomposition treatment agent comprising a quaternary phosphonium salt. A method for producing a stabilized polyacetal resin. Protic acids are selected from the group consisting of organic carboxylic acids, acidic amide compounds, acidic enol compounds, phenolic compounds, hydrogen acids and oxo acids, and alkali (earth) metal compounds are alkaline earth metal hydroxides The stabilized polyacetal resin according to claim 3 , which is selected from an alkaline earth metal oxide, an alkaline earth metal carbonate, and an alkaline earth metal salt of a fatty acid which may have a hydroxyl group. Production method. Furthermore, at least 1 sort (s) chosen from the group which consists of antioxidant, water, alcohol, tertiary amine, and a quaternary ammonium salt is added, and it heat-processes in the coexistence, The heat treatment in any one of Claims 1-4. Of producing a stabilized polyacetal resin. An unstable terminal decomposition treatment agent and at least one selected from the above protonic acids and alkali (earth) metal compounds, and / or from the above-mentioned antioxidant, water, alcohols, tertiary amines and quaternary ammonium salts at least one and a pre-mixed, method for manufacturing the stabilized polyacetal resin according to any one of claims 3 to 5 heat treated in the presence of the mixture selected from the group consisting. Heat treated, method for manufacturing the stabilized polyacetal resin according to any one of claims 1 to 6, carried out in the molten state of the polyacetal resin having an unstable terminal group. The amount of use of an unstable terminal decomposition treatment agent is 0.005 to 3.5 mmol in terms of phosphorus atom (P ⁺ ) giving a quaternary phosphonium salt with respect to 1 kg of polyacetal resin having unstable terminal groups. method of manufacturing a stabilized polyacetal resin according to any one of 1-7. The heat treatment temperature is the melting point to 250 DEG ° C. of the polyacetal resin, method for manufacturing the stabilized polyacetal resin according to any one of claims 1-8 heat treatment time is 20 seconds to 20 minutes. Method of manufacturing a stabilized polyacetal resin according to hemiacetal terminal group amount of the stabilized polyacetal resin is less than 1.0 mmol / kg any one of claims 1-9.