JP2006111874A - Polyacetal resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal resin composition excellent in thermal stability and in which the amount of formaldehyde generated from pellets and molded products is remarkably suppressed.
SOLUTION: To 100 parts by weight of a polyacetal polymer (component A), hydrazide compound (component B) 0.01 to 0.5 parts by weight, and amine-substituted triazine compound (component C) 0.01 to 0.1 parts by weight. And a hindered phenol compound (component D) 0.01 to 5.0 parts by weight of a polyacetal resin composition, wherein the resin composition is a hydroxide of an alkali metal and an alkaline earth metal, A polyacetal resin composition, wherein the total content of metal compounds represented by the group consisting of an organic acid salt and an inorganic acid salt is 50 ppm by weight or less as a metal.
[Selection figure] None

Description

  The present invention relates to a polyacetal resin composition and a molded article comprising the same. More specifically, the present invention relates to a polyacetal resin composition that is excellent in thermal stability, suppresses the amount of formaldehyde generated from pellets and molded articles, and has little mold deposit (mold deposit) during molding, and a molded article comprising the same.

Polyacetal resin is widely used as an engineering plastic having balanced mechanical properties, good self-lubricating properties, and electrical properties in various mechanical parts and electrical parts. However, the polyacetal resin has an oxymethylene group (—CH ₂ O—) as a structural unit in the main chain. Therefore, a mold deposit is formed in a very small amount due to a slight thermal decomposition reaction with a thermal history during polymerization or molding. This generates and contaminates the molding die, causes molding defects, and causes appearance defects and dimensional anomalies. In addition, formaldehyde is generated from the final product, and its influence on sick house syndrome and the like has been pointed out. The Ministry of Health, Labor and Welfare stipulates that the indoor formaldehyde concentration guideline value is 0.08 ppm or less as a countermeasure against sick house syndrome, and the amount of formaldehyde generated from the product is required to be kept lower. For that purpose, polyacetal resin with low formaldehyde generation amount from the final product is required.

Conventionally, in order to suppress the amount of formaldehyde generated in pellets and molded products containing a polyacetal resin, it has been proposed to add various additives to the polyacetal resin. For example, a resin composition (see Patent Document 1) containing an amine-based antioxidant, carbon black and polyamide treated with a polymer compound in advance (see Patent Document 1), a resin composition containing a hydrazide compound (see Patent Document 2), hydrazide As a formaldehyde adsorbent, 1,2,3,4-butanetetracarboxylic acid hydrazide was formulated as a resin composition containing a borate of a nitrogen-containing compound such as Examples thereof include a resin composition (see Patent Document 4), a deodorant (see Patent Document 5) containing hydrazide and urea or a derivative thereof in a specific ratio. However, these have problems such as insufficient suppression of the amount of formaldehyde generated and reduced physical properties of molded articles, and a polyacetal resin composition having a lower amount of formaldehyde generated has been demanded.
JP-A-11-140272 Japanese Patent Laid-Open No. 04-345648 Japanese Patent Laid-Open No. 10-086630 Japanese Patent Laid-Open No. 06-080619 JP 2002-035098 A

  It has been known that amine-substituted triazine compounds contribute to improvement of thermal stability by capturing formaldehyde produced. However, when a hydrazide compound having a high formaldehyde scavenging effect is used, if an amine-substituted triazine compound is added in a necessary amount or more, the formaldehyde scavenging ability of the hydrazide compound is lowered, and more hydrazide compounds must be added. It has been found that this not only impairs thermal stability but also causes an increase in mold deposit.

  Furthermore, stabilizers such as metal hydroxides, organic acid salts and inorganic acid salts are used to improve the thermal stability due to the deactivation of formic acid produced by oxidation of formaldehyde gas generated in the remaining catalyst and stabilization process. Has been used. However, these stabilizers promote hydrolysis of formate ester end groups generated by side reactions during polymerization, even in trace amounts, so if they are placed under high temperature and high humidity conditions for a long time, they do not cause a decrease in thermal stability during molding. Causes a slight amount of formaldehyde generation. Therefore, it has been found that the amount of hydrazide compound, which is a formaldehyde scavenger, is inevitably increased, causing an increase in mold deposit as described above.

  As a result of intensive studies to solve the above problems, the addition amount of the amine-substituted triazine compound is 0.01 to 0.1 parts by weight, and the addition amount of the hydrazide compound is suppressed to a minimum without inhibiting the reactivity. I found that I can do it. In addition, the total content of metal compounds represented by the group consisting of hydroxides, inorganic salts and organic acid salts of alkali metals and alkaline earth metals is set to 50 ppm by weight or less as a metal, so that high-temperature and high-humidity conditions can be maintained for a long time. It is possible to suppress an increase in the amount of formaldehyde generated when stored at a lower temperature, and to further suppress the amount of hydrazide compound added. At the same time, the present inventors have found that the thermal stability that has been conventionally maintained by the addition of a metal compound can also be maintained by the addition of a hydrazide compound, resulting in the present invention.

  That is, in the present invention, 0.01 to 0.5 parts by weight of a hydrazide compound (B component) and 0.01 to 0. 0 to 0.1 parts by weight of an amine-substituted triazine compound (C component) with respect to 100 parts by weight of a polyacetal polymer (A component). A polyacetal resin composition comprising 1 part by weight and a hindered phenol compound (component D) of 0.01 to 5.0 parts by weight, the resin composition comprising an alkali metal and an alkaline earth metal hydroxide The polyacetal resin composition is characterized in that the total content of the product, organic acid salt and inorganic acid salt is 50 ppm by weight or less as a metal.

  The polyacetal resin composition of the present invention is not only excellent in thermal stability, but also the amount of formaldehyde generated from pellets and molded products is remarkably suppressed. At the same time, the amount of hydrazide compound added can be kept low, resulting in less mold deposit. Therefore, there is no fear of deteriorating the working environment at the time of manufacturing a molded article, and it is extremely useful as a material for automobile interior parts, building material parts used in houses, schools, etc., and electrical parts, particularly as a countermeasure against so-called sick house syndrome.

  In the resin composition of the present invention, the polyacetal polymer of component A is preferably a polyacetal polymer having an oxymethylene unit as a basic unit and an oxyalkylene unit having 2 or more carbon atoms as a copolymer unit.

  The comonomer component constituting the oxyalkylene unit having 2 or more carbon atoms in the polyacetal polymer is not particularly limited as long as it is a cyclic ether, a glycidyl ether compound, or a cyclic formal, but preferably ethylene oxide, propylene oxide, butylene oxide, styrene oxide, methyl Glycidyl ether, ethyl glycidyl ether, phenyl glycidyl ether, 1,3-dioxolane, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexane Any one or more of diol formal is used, preferably ethylene oxide, 1,3-dioxolane, diethylene glycol Rumaru, 1,4-butanediol formal is used, particularly preferably dioxolane 1,3 is used. Such a polyacetal polymer is obtained by copolymerizing the comonomer component constituting the oxyalkylene unit having 2 or more carbon atoms and trioxane, which is a cyclic trimer of formaldehyde, in the presence of a cationic polymerization catalyst.

  The content of oxyalkylene units having 2 or more carbon atoms in the polyacetal polymer is 0.1 to 30 mol, preferably 0.3 to 20 mol, more preferably 0.5 to 10 mol, per 100 mol of oxymethylene units. It is.

  As the polymerization catalyst, a general cationic active catalyst is used. Such cationically active catalysts include Lewis acids, especially halides such as boron, tin, titanium, phosphorus, arsenic and antimony, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, pentafluoride. Compounds such as phosphorus phosphide, arsenic pentafluoride and antimony pentafluoride, and complexes or salts thereof, protic acids such as trifluoromethanesulfonic acid, perchloric acid, esters of protic acids, especially perchloric acid and lower aliphatic alcohols Esters, protonic anhydrides, especially mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids, or triethyloxonium hexafluorophosphate, triphenylmethylhexafluoroarsenate, acetylhexafluoroborate, heteropolyacid Or its acid salt, isopolyacid or its Such as gender salts. Particularly preferred are compounds containing boron trifluoride, or boron trifluoride hydrate and coordination complex compounds. Boron trifluoride diethyl etherate and boron trifluoride which are coordination complexes with ethers Dibutyl etherate is particularly preferred.

The amount of the polymerization catalyst used is generally 1.0 × 10 ^{−7 to} 2.0 × 10 ⁻³ mol, preferably 1.0 ×, with respect to 1 mol of the total monomer of trioxane and comonomer. It is used in the range of 10 ^{−7 to} 8.0 × 10 ⁻⁴ mol, more preferably 1.0 × 10 ^{−7 to} 1.0 × 10 ⁻⁴ mol. In the present invention, usually, when the polymerization yield reaches 90% or more, preferably 95% or more, more preferably 97% or more, the catalyst is deactivated and the polymerization is stopped. In order to disperse these catalysts uniformly in the reaction system, it is preferable to dilute them with an organic solvent that does not adversely affect the polymerization reaction.

  Examples of the organic solvent include ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and n-butyl ether, aromatic hydrocarbons such as benzene and toluene, aliphatic hydrocarbons such as n-hexane and cyclohexane, methylene dichloride and ethylene dichloride. And halogenated hydrocarbons.

  The polymerization method for obtaining the polyacetal polymer can be carried out by the same equipment and method as those of conventionally known trioxane copolymerization. That is, it can be either batch type or continuous type, and can also be applied to bulk polymerization and polymerization methods performed in the presence of an organic solvent such as cyclohexane. A batch type reactor can be used with a stirrer, and in continuous bulk polymerization, rapid solidification during polymerization, powerful stirring ability to cope with heat generation, precise temperature control, and prevention of scale adhesion Such devices as a kneader having a self-cleaning function, a twin-screw continuous extrusion kneader, and a twin-screw paddle type continuous mixer are preferably used.

  In the polymerization, a low molecular weight acetal compound is generally used to adjust the molecular weight. Examples of the acetal compound include, but are not limited to, methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, oxymethylene di-n-butyl ether, and the like. Usually, methylal is preferably used. In general, the amount of the acetal compound added is adjusted in the range of 0 to 0.1% by weight based on the total monomer according to the target molecular weight.

The polyacetal polymer obtained by the polymerization reaction uses a deactivator such as a trivalent organic phosphorus compound, amine compound, alkali metal or alkaline earth metal hydroxide alone or in the form of an aqueous solution or an organic solution. The catalyst and polymerization growth terminal are deactivated by a known method. Among these quenchers, trivalent organic phosphorus compounds, tertiary amines, and hindered amines are particularly preferable. The amount used is not particularly limited as long as it is an amount sufficient to deactivate the catalyst, the molar ratio to the catalyst is used in an amount of ^1.0 × 10 -1 ~1.0 × 10 ¹ .

  In the polymerization deactivation treatment, the polyacetal polymer is preferably a fine particle, and the polymerization reactor preferably has a function of sufficiently pulverizing the bulk polymer. When the polyacetal polymer after polymerization is not a fine particle, the catalyst contained in the polymer is not sufficiently deactivated, and depolymerization proceeds gradually with the remaining active catalyst, resulting in a decrease in molecular weight. Therefore, the deactivator may be added after the polymerized polyacetal polymer is separately pulverized using a pulverizer, or pulverization and stirring may be simultaneously performed in the presence of the deactivator.

  The polyacetal polymer that has been subjected to the deactivation treatment of the polymerization is mixed with a stabilizer, and then melted with a twin screw extruder, continuously introduced into a biaxial surface renewal horizontal kneader in a molten state, Stabilization can be performed by performing devolatilization at a reduced temperature, but if further purification is required, washing, separation and recovery of unreacted monomers, drying, and the like can be performed.

The devolatilization under reduced pressure in the biaxial surface renewal type horizontal kneader is performed while melt kneading under a pressure of 1.01 × 10 ^{2 to} 1.33 × 10 ⁻² kPa. When the pressure is higher than this range, a sufficient devolatilizing effect cannot be obtained, and when the pressure is lower than this range, the decompression equipment becomes large, which causes a cost increase when the apparatus is installed. The vacuum devolatilization time is preferably 15 to 60 minutes. When the vacuum devolatilization time is shorter than 15 minutes, the formaldehyde gas generated when the treated polyacetal polymer is melted cannot be sufficiently devolatilized. Further, even in a biaxial surface renewal type horizontal kneader where the shear stress is much weaker than that of an extruder, if the residence time exceeds 60 minutes, the polyacetal polymer is yellowed or the thermal stability is deteriorated due to main chain decomposition. Absent. It is also preferable to introduce an inert gas such as nitrogen gas at the time of vacuum devolatilization, or to introduce alcohol or water vaporized under devolatilization pressure reduction conditions into the vacuum processing facility to avoid mixing in air from the outside, or to control the degree of vacuum It is.

  The internal resin temperature of the biaxial surface renewal type horizontal kneader during the vacuum devolatilization treatment is preferably 190 to 240 ° C, and if the temperature is low, the molten polyacetal copolymer may crystallize (solidify), On the other hand, a high temperature is not preferable because it causes yellowing or a decrease in thermal stability due to main chain decomposition of the polymer due to heat.

  The biaxial surface renewal type horizontal kneader has a sufficiently wide clearance between the stirring blade and the inner diameter of the kneader, and the space volume in the kneader (the space portion excluding the volume occupied by the molten polyacetal copolymer) is 20% of the total volume. A kneader excellent in surface renewal of the type that can be taken as described above is suitable. For example, Hitachi, Ltd. spectacle blade, lattice wing reactor, Mitsubishi Heavy Industries, Ltd. SCR, NSCR reactor, Examples include KRC kneaders and SC processors manufactured by Kurimoto Steel.

  As the hydrazide compound (component B) added and blended as a formaldehyde scavenger in the resin composition of the present invention, any aliphatic or aromatic hydrazide compound can be used.

  Aliphatic hydrazide compounds include propionic acid hydrazide, thiocarbohydrazide, and dihydrazide compounds such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanediodic acid, dodecanediodic acid, dodecanediodic acid Examples thereof include 18-octadecanedicarbohydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, 7,11-octadecandiene-1,18-dicarbohydrazide and the like.

  Examples of the aromatic hydrazide compound include salicylic acid hydrazide, terephthalic acid dihydrazide, 3-hydroxy-2-naphthoic acid hydrazide, p-toluenesulfonyl hydrazide, aminobenzhydrazide, 4-pyridinecarboxylic acid hydrazide, 1,5-naphthalenedicarbohydrazide, Examples include 1,8-naphthalenedicarbohydrazide, 2,6-naphthalenedicarbohydrazide, 4,4′-oxybisbenzenesulfonyl hydrazide, 1,5-diphenylcarbonohydrazide, and the like. Polyhydrazides such as aminopolyacrylamide and 1,3,5-tris (2-hydrazinocarbonylethyl) isocyanurate can also be used.

  Of these hydrazide compounds, dihydrazide compounds are preferred. Examples of the dihydrazide compounds include adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, 1,18-octadecane dicarbohydrazide, terephthalic acid dihydrazide, 1,8-naphthalenedicarbohydrate, 2,6-naphthalenedicarbohydrazide, and the like. Particularly preferred.

  The hydrazide compound (component B) may be used alone or in combination of two or more. The compounding quantity of the hydrazide compound (B component) in this invention composition is 0.01-0.5 weight part with respect to 100 weight part of polyacetal polymers (A component), Preferably it is 0.02-0.4 weight. Parts, more preferably 0.03 to 0.3 parts by weight. When the amount is less than 0.01 part by weight, the formaldehyde scavenging effect is not sufficient. When the amount exceeds 0.5 part by weight, not only the formaldehyde scavenging effect is decreased, but also the mold deposit is greatly increased.

  Specific examples of the amine-substituted triazine compound (component C) blended in the present invention include, for example, guanamine, melamine, N-butylmelamine, N-phenylmelamine, N, N-diphenylmelamine, N, N-diallylmelamine, N , N ′, N ″ -triphenylmelamine, N, N ′, N ″ -trimethylolmelamine, benzoguanamine, 2,4-diamino-6-methyl-sym-triazine, 2,4-diamino-6-butyl-sym -Triazine, 2,4-diamino-6-benzyloxy-sym-triazine, 2,4-diamino-6-butoxy-sym-triazine, 2,4-diamino-6-cyclohexyl-sym-triazine, 2,4- Diamino-6-chloro-sym-triazine, 2,4-diamino-6-mercapto-sym-triazine, a Phosphorus (N, N, N ', N'- tetra-cyanoethyl benzoguanamine), or the initial weight condensate thereof with formaldehyde.

  Of these amine-substituted triazine compounds, melamine, methylolmelamine, benzoguanamine, and water-soluble melamine-formaldehyde resin are particularly preferable.

  The amount of the amine-substituted triazine compound (component C) added and blended in the present invention is preferably 0.01 to 0.1 part by weight, and 0.015 to 0.075 part by weight with respect to 100 parts by weight of the polyacetal polymer. More preferred.

  In the resin composition of the present invention, a hindered phenol compound (component D) is blended as an antioxidant. The hindered phenol compound is not particularly limited, but preferably 1,6-hexanediol-bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3 -(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], triethylene glycol -Bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2'-thiodiethyl-bis- [3- (3,5-di-tert-butyl-4-hydroxy) Phenyl) propionate] and the like.

  The hindered phenol compound (component D) added and blended in the present invention may be used alone or in combination of two or more. The blending amount is preferably 0.01 to 5.0 parts by weight and more preferably 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the polyacetal polymer.

  The polyacetal resin composition of the present invention preferably contains as little as possible a metal-containing compound composed of alkali metal and alkaline earth metal hydroxides, organic acid salts and inorganic acid salts which are usually blended as stabilizers. Examples of the alkali metal hydroxide or alkaline earth metal hydroxide include sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide. Examples of organic acid salts include metal salts of higher fatty acids such as magnesium salts, calcium salts and barium salts of higher fatty acids such as lauric acid, palmitic acid, stearic acid, behenic acid, and 12-hydroxystearic acid.

  The total content of metal compounds composed of alkali metal and alkaline earth metal hydroxides, organic acid salts and inorganic acid salts contained in the polyacetal resin composition of the present invention is derived from each of the polyacetal resin compositions. The weight of the metal is preferably 50 ppm by weight or less, more preferably 40 ppm by weight or less, and most preferably 30 ppm by weight or less.

  The polyacetal resin composition of the present invention preferably contains a higher fatty acid amide having a long chain having 10 or more carbon atoms as a release agent. The higher fatty acid amide having a long chain having 10 or more carbon atoms is not particularly limited, but preferably stearic acid amide, ethylene bisstearamide, methylene bisstearamide, methylene bislauramide, palmitic acid amide, oleic acid amide, etc. 1 type or 2 or more types can be mentioned. Among these, one or more of ethylene bisstearoamide, methylene bisstearoamide, and methylene bislauramide are more preferable.

  The amount of the higher fatty acid amide added and blended in the present invention is preferably 0.01 to 5 parts by weight and more preferably 0.01 to 3 parts by weight with respect to 100 parts by weight of the polyacetal polymer (component A).

  You may add polyalkylene glycol, paraffin wax, the fatty acid ester of a polyhydric alcohol, etc. as another mold release agent with respect to the polyacetal resin composition of this invention. Polyalkylene glycol, paraffin wax, fatty acid ester of polyhydric alcohol is not particularly limited, but polyethylene glycol, polyalkylene glycol such as polypropylene glycol, glycerin, diglycerin, pentaerythritol, sorbitan, ethylene glycol, diethylene glycol, trimethylol methane, Polyhydric alcohols such as trimethylolethane and fatty acid esters such as behenic acid, serotic acid, montanic acid, and laccellic acid are preferred.

  The amount of polyalkylene glycol, paraffin wax, and fatty acid ester of polyhydric alcohol added and blended in the present invention is preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the polyacetal polymer (component A). -3 parts by weight is more preferred.

  A nucleating agent may be added to the polyacetal resin composition of the present invention for the purpose of improving moldability and shortening the molding cycle. The nucleating agent is not particularly limited, but boron nitride, hydrous magnesium silicate, three-dimensional crosslinked polyacetal and the like are more preferable.

  The amount of the nucleating agent added and blended in the present invention is preferably 0.0001 to 10.0 parts by weight and more preferably 0.001 to 5.0 parts by weight with respect to 100 parts by weight of the polyacetal polymer (component A). .

  You may add a coumarin type | system | group fluorescent whitening agent and a benzoxazole type | system | group fluorescent whitening agent with respect to the polyacetal resin composition of this invention as a fluorescent whitening agent. Examples of the coumarin fluorescent brightener and benzoxazole fluorescent brightener include 3- (4′-acetylaminophenyl) -7-acetylaminocoumarin, 3- (4′-carboxyphenyl) -4-methyl-7- Diethylaminocoumarin, 2,5-bis (5′-t-butylbenzoxazol-2′-yl) thiophene, and 2,5-bis [5′-t-butylbenzoxazolyl (2)] thiophene are preferred. .

  The amount of the coumarin fluorescent brightener and benzoxazole fluorescent brightener added and blended in the present invention is preferably 0.001 to 500 ppm by weight, more preferably 0.01 to 100 ppm by weight based on the polyacetal polymer. .

  In addition to the above components, the polyacetal resin composition of the present invention is other than alkali metal and alkaline earth metal hydroxides, organic acid salts and inorganic acid salts, and within the range not impairing the object of the present invention, Known additives and / or fillers can be added. Examples of the additive include an antistatic agent, an ultraviolet absorber, and a light stabilizer.

  As an addition method of the additive of the present invention, an amine-substituted triazine compound (C component) and a hindered phenol compound (D component) are added to a polyacetal polymer (A component) subjected to a polymerization termination treatment containing a polymerization catalyst deactivator. Add and mix. Next, it was melt kneaded with a single screw or twin screw extruder, continuously introduced into a biaxial surface renewal type horizontal kneader in a molten state, and subjected to a stabilization treatment in which vacuum devolatilization was performed at a temperature above the melting point. A polyacetal resin composition containing no hydrazide compound (component B) (hereinafter referred to as a preliminary resin composition) is obtained. The pre-resin composition and the hydrazide compound (component B) are mixed by a tumbler type blender or the like, and heated and melt-kneaded by a single screw or twin screw extruder or the like, whereby the polyacetal resin composition of the present invention can be obtained.

  As a method for adding the hydrazide compound (component B), the hydrazide compound (component B) containing a hydrazide compound (component B) containing no hydrazide compound (component B) having a heat treatment weight loss rate of 0.6% or less after being stabilized is mixed. It is preferable to obtain by heating and kneading, more preferably a preliminary resin composition having a heating weight reduction rate of 0.5% or less, and even more preferably a preliminary resin composition having a heating weight reduction rate of 0.4% or less. Heat-knead with the product.

  As addition methods other than the above, various stabilizers such as polyacetal polymer (component A), amine-substituted triazine compound (component C) and hindered phenol compound (component D) subjected to the deactivation treatment of polymerization and hydrazide compound (B Ingredients) are mixed together with a Henschel mixer, melted with a twin screw extruder, continuously introduced into a biaxial surface renewal type horizontal kneader in a molten state, and devolatilized at a temperature above the melting point. This is achieved by performing the conversion process.

  According to the polyacetal resin composition of the present invention, a molded product can be obtained in accordance with a known polyacetal resin molding method. Examples of molded products obtained from the resin composition of the present invention include materials such as pellets, round bars, and thick plates, sheets, tubes, various containers, machinery, electricity, automobiles, building materials, and other various parts. It is not limited to.

  Since the polyacetal resin composition obtained in the present invention is excellent in thermal stability and suppresses formaldehyde generation from the product, as a countermeasure for so-called sick house syndrome, it is used for building material parts and electrical parts, and also for automobile interior parts. Very useful.

  EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples of the present invention, but the present invention is not limited to these. In addition, the term and measurement method in an Example and a comparative example are shown below.

<Method for producing polyacetal polymer (component A)>
In a biaxial continuous polymerization machine having a self-cleaning paddle with a jacket set at a temperature of 65 ° C., 100 parts by weight of trioxane and 4 parts by weight of 1,3-dioxolane and benzene boron trifluoride diethyl etherate as a catalyst Polymerization is continuously performed so that 0.05 mmol is added to 1 mol of all monomers as a solution and methylal is added as a molecular weight regulator to 500 ppm as a benzene solution with respect to all monomers, and the residence time is 20 minutes. It was.
Triphenylphosphine is added to the resulting polymer as a benzene solution in an amount of 2 mol with respect to 1 mol of boron trifluoride diethyl etherate used, the catalyst is deactivated, and pulverized to obtain a polyacetal polymer ( A component) was obtained. The polymer yield was 95% and the melt index (MI) was 10.5 g / 10 min.

Examples 1-21 and Comparative Examples 1-8
100 parts by weight of the obtained polyacetal polymer (component A), and an amine-substituted triazine compound (component C), a hindered phenol compound (component D), and Example 12 in the formulation shown in Tables 1 to 3 In Comparative Examples 4 and 5, magnesium hydroxide or calcium stearate is added to a polyacetal polymer (component A) so that the metal content shown in Tables 1 to 3 is obtained with respect to the finally obtained polyacetal resin composition of the present invention. ) 100 parts by weight was mixed with a Henschel blender. Next, the obtained mixture was introduced into a co-directional twin-screw extruder (manufactured by Nippon Steel Works, inner diameter 69 mm, L / D = 31.5) at 60 kg / hour, and the polyacetal polymer containing components C and D was vented. The mixture was melted at 220 ° C. under a reduced pressure of 20 kPa, and continuously introduced into a biaxial surface renewal type horizontal kneader (effective internal volume 60 L: volume excluding the volume occupied by the stirring blades from the total internal volume). Adjust the liquid level so that the residence time of the biaxial surface renewal type horizontal kneader is 25 minutes, and pelletize by continuously extracting with a gear pump while performing vacuum devolatilization at 220 ° C under a reduced pressure of 20 kPa. In Tables 1 to 3, preliminary resin compositions having a heating weight reduction rate were obtained.
The obtained preliminary resin composition and the hydrazide compound (component B) were mixed with a tumbler type blender, and the resulting mixture was mixed with a single-screw extruder (inner diameter 40 mm, manufactured by Tanabe Plastics, model: VS-40) with a cylinder. It was melt-kneaded and pelletized at a temperature of 200 ° C. and a discharge rate of 13 kg / h to obtain a desired polyacetal resin composition.

Using the sample obtained by the above method, measurement of the amount of formaldehyde generated in the molded product, thermal stability and mold contamination were evaluated by the following methods. The results are shown in Tables 1 to 3.
<Evaluation method>
(A) Generated formaldehyde amount: 100 mm × 40 mm × thickness 2 mm of the resin composition obtained in the example or comparative example was molded at a cylinder temperature of 215 ° C. using a PS-40E5ASE molding machine manufactured by Nissei Plastic Industry Co., Ltd. Using a flat plate as a test piece, measurement was performed on the day after molding in accordance with the method described in German Automobile Manufacturers Association Standard VDA275 (automobile interior parts-quantitative determination of formaldehyde emission by revised flask method).
(I) Put 50 ml of distilled water in a polyethylene container, close the lid with the test piece suspended, and keep it in a sealed state at 60 ° C. for 3 hours.
(Ii) Then, after leaving at room temperature for 60 minutes, a test piece is taken out.
(Iii) The formaldehyde concentration absorbed in distilled water in the polyethylene container is measured by an acetylacetone colorimetric method using a UV spectrometer.
(B) Formaldehyde amount after accelerated test: The resin composition obtained in the examples or comparative examples was humidified using a constant temperature and humidity machine (setting conditions: 60 ° C., 90% RH, 48 hr) manufactured by Espec. . Then, it measured according to the method described in (a).
(C) Thermal stability: The resin compositions obtained in the examples or comparative examples were molded in a cylinder temperature of 220 ° C. for 10 minutes using a PS-40E5ASE molding machine manufactured by Nissei Plastic Industry Co., Ltd. 10 mm × 40 mm × Using a flat plate with a thickness of 2 mm as a test piece, the molding stability at the time of retention (colorability, presence or absence of silver generation) was observed, and from the very good thermal stability to the defective one in six steps (1 2, 3, 4, 5, 6) Evaluation was made based on criteria.
(D) Mold deposit: The resin composition obtained in the examples or comparative examples was molded at a temperature of 230 ° C. using a mini-mold M8 / 7A molding machine manufactured by Sumitomo Heavy Industries, Ltd. and using a drop mold. Then, 500 shots are continuously molded at a mold temperature of 35 ° C., and after completion, the state of the deposit (mold deposit) of the mold is observed, and in order from the one with the least mold contamination to the one with the most mold contamination, Evaluation was made according to the criteria 1, 2, 3, 4, 5, 6).
(E) Weight reduction rate by heating: The weight (M ₁ ) of the pellets dried at 100 ° C. for 30 minutes at normal pressure, and after placing in a test tube, after heating at 222 ° C. under reduced pressure of 1333 Pa for 2 hours after nitrogen substitution The rate of decrease in the weight (M ₂ ) is represented by (M ₁ -M ₂ ) / M ₁ × 100, and the sample with higher thermal stability shows a lower value.

Claims (8)

Hydrazide compound (component B) 0.01 to 0.5 parts by weight, amine-substituted triazine compound (component C) 0.01 to 0.1 parts by weight and hindered with respect to 100 parts by weight of polyacetal polymer (component A) A polyacetal resin composition comprising 0.01 to 5.0 parts by weight of a phenol compound (component D), the resin composition comprising an alkali metal and alkaline earth metal hydroxide, an organic acid salt, and A polyacetal resin composition, wherein the total content of metal compounds represented by the group consisting of inorganic acid salts is 50 ppm by weight or less as a metal. The polyacetal resin composition according to claim 1, wherein the hydrazide compound (component B) is a dihydrazide compound. The hydrazide compound (component B) includes adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, 1,18-octadecanedicarbohydrazide, terephthalic acid dihydrazide, 1,8-naphthalenedicarbohydrazide and 2,6-naphthalene. The polyacetal resin composition according to claim 1, which is at least one dihydrazide compound selected from the group consisting of carbohydrazides. The polyacetal resin composition according to claim 1, wherein the amine-substituted triazine compound (component C) is at least one selected from the group consisting of melamine, methylolmelamine, benzoguanamine, and a water-soluble melamine-formaldehyde resin. A pre-resin composition containing a polyacetal polymer (component A), an amine-substituted triazine compound (component C) and a hindered phenol compound (component D) and not containing a hydrazide compound (component B) is added to the hydrazide compound (B 2. The polyacetal resin composition according to claim 1, obtained by blending a component). The polyacetal resin composition according to claim 5, wherein the preliminary resin composition has a weight loss rate of 0.6% by weight or less when heated at 222 ° C for 2 hours under a reduced pressure of 1333 Pa. A pre-resin composition containing a polyacetal polymer (component A), an amine-substituted triazine compound (component C) and a hindered phenol compound (component D) and not containing a hydrazide compound (component B) is added to the hydrazide compound (B 2. The method for producing a polyacetal resin composition according to claim 1, wherein a component) is blended. The method for producing a polyacetal resin composition according to claim 7, wherein the preliminary resin composition has a weight loss rate of 0.6 wt% or less when heated at 222 ° C for 2 hours under a reduced pressure of 1333 Pa.