JP5371897B2 - Process for producing polyacetal copolymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a polyacetal copolymer which suppresses the degree of swelling due to chemicals and organic solvent gas permeability to the minimum even when being used in an environment where the chemicals exist while maintaining superior heat stability of the copolymer and also can be used suitably for precision molding components requiring the low secondary shrinkage rate. <P>SOLUTION: In the method of producing polyacetal copolymer, the acetal copolymer can be provided by copolymerizing cyclic ether and/or cyclic formal which contains 1,4-dioxane of 200 ppm or less, in the range of 0.1 to 2.0 wt.% with respect to trioxane. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a polyacetal resin composition that provides a molded article having excellent chemical resistance and thermal cycle resistance in the presence of chemicals and having a low secondary shrinkage, and the molded article thereof. It is useful as a part used in the presence of chemicals such as household chemicals, industrial oils, industrial greases, automobile fuels, automobile oils, etc., particularly as automobile fuel parts.

  Polyacetal resin has well-balanced mechanical properties, fatigue resistance, friction / wear resistance, chemical resistance, and moldability, and is widely used for automotive parts, electrical / electronic equipment parts, and other various machine parts. ing. However, in the presence of chemicals such as organic chemicals, inorganic chemicals, household chemicals, industrial oils, industrial greases, automotive fuels, automotive oils, etc., the harsh usage conditions in which the temperature during use varies However, the polyacetal resin has a relatively excellent chemical resistance, but further improvement is required.

  In general, since chemical erosion of a polyacetal resin proceeds from an amorphous part, it is considered that a polyacetal homopolymer having a high degree of crystallinity has better chemical resistance than a polyacetal copolymer. However, polyacetal homopolymers are hydrolyzed, for example, under basic chemicals, and are more susceptible to thermal degradation than polyacetal copolymers when used at high temperatures, resulting in reduced mechanical properties or due to degradation. Since there is a problem that formaldehyde and its formic acid, which is its oxide, are released into the chemicals, usable chemicals and operating temperatures are limited. Further, since the secondary shrinkage rate of the molded product is larger than that of the polyacetal copolymer, use as a precision part may be limited.

  In response to this technical problem, Patent Document 1 proposes a polyacetal copolymer having excellent chemical permeation resistance. However, except that the peak temperature of solid-phase crystallization is set lower than that of a general copolymer, In comparison, no improvement has been made in the process, and in particular under severe use conditions where the temperature during use varies, the main polyacetal copolymer deteriorates, so there is room for improvement in practical chemical resistance. It was left.

JP-A-11-130935

  The present invention is intended to solve the above-described problems, and while maintaining the excellent thermal stability of the copolymer, it has excellent chemical resistance, specifically, the degree of swelling of the molded product by chemicals and It has a characteristic of low organic solvent gas permeability, excellent heat and cold cycle resistance in the presence of chemicals, and low secondary shrinkage, so it can be used in an environment where a wider range of chemicals is present than ever. Another object of the present invention is to provide a polyacetal resin composition that can be suitably used for precision molded parts and a molded product thereof.

As a result of various studies to solve the above problems, the present inventors have determined that the molded article has a specific dynamic viscoelasticity and a specific range of crystallinity adjusted polyacetal. Copolymers have overturned the conventional common sense and have even better chemical resistance than polyacetal homopolymers with a high degree of crystallinity, in particular, the properties of the molded body with low chemical solvent swelling and organic solvent gas permeability. As a result, the present inventors have found that the above-described problems can be solved with excellent low temperature cycle resistance in the presence of chemicals and low secondary shrinkage rate.

That is, the present invention
[1] A process for producing a polyacetal copolymer obtained by copolymerizing 1,3-dioxolane containing 200 ppm or less of 1,4-dioxane in a range of 0.1 to 2.0% by weight based on trioxane,
[2] The method for producing a polyacetal copolymer according to [1], wherein the polymerization catalyst is in the range of 0.00001 to 0.0001 mol per mol of the polymerization raw material,
[3] The polyacetal copolymer according to [1] or [2], wherein the neutralization deactivator of the polymerization catalyst uses a quaternary ammonium compound represented by the following general formula (2). Production method,
[R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ⁻ⁿ (2)
Wherein R ¹ , R ² , R ³ and R ⁴ are each independently an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; An aralkyl group having 30 unsubstituted alkyl groups or substituted alkyl groups substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms having at least one carbon atom having 1 to 30 carbon atoms Represents an unsubstituted alkyl group or an alkylaryl group substituted with a substituted alkyl group, wherein the unsubstituted alkyl group or substituted alkyl group is linear, branched, or cyclic. An aldehyde group, a carboxyl group, an amino group, or an amide group, and the above-mentioned unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group are substituted with a halogen atom. N represents an integer of 1 to 3. X represents a hydroxyl group, a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than a hydrogen halide, an oxo acid, an inorganic thioacid, or a C 1 to 20 carbon atom. Represents an acid residue of an organic thioic acid of
[4] The method for producing a polyacetal copolymer according to any one of [1] to [3] above, wherein the number average molecular weight is in the range of 10,000 to 1,000,000. To do.

  The polyacetal resin composition of the present invention and the molded product thereof have excellent chemical resistance and cold cycle resistance in the presence of chemicals, and at the same time have low secondary shrinkage. Therefore, it is particularly useful for precision parts used in the presence of chemicals and automobile fuel parts.

It is a figure of the analysis chart of storage rigidity (G ') from -130 ° C to 160 ° C. It is a figure which gives impact repeatedly to a test piece.

The present invention will be described in detail below.
The storage elastic modulus defined in the present invention is an injection molding machine, cylinder temperature 200 ° C., injection pressure 60 kgf / cm ² , injection time 15 seconds, cooling time 25 seconds, mold temperature 70 ° C., dimensions 130 mm × 13 mm A molded product formed into a 3 mm strip is left for 48 hours in an environment of 23 ° C. and 50% humidity after completion of molding, and then attached to a dynamic viscoelasticity evaluation apparatus (RDA2 manufactured by Rheometrics Co., Ltd.). While raising the temperature range from 0 ° C. to 150 ° C. at a rate of 3 ° C./min, a periodic torsional vibration of 6.28 rad / s was applied, and the resulting vibration strain was measured. A more detailed measurement method will be described in Examples.

Further, the crystallinity specified in the present invention is obtained by scraping 10 mg of resin from the central part of the molded article for storage elastic modulus evaluation, and using a differential calorimeter (manufactured by Perkin Elmer, DSC-7). The heat of fusion ΔH (J / g) was determined from the exothermic peak generated in the process of raising the temperature to 200 ° C. at a rate of 5 ° C./min, and this was the value of the crystallinity 100% described in the literature (ΔHf = 222 J / g) and calculated by the following formula.
Crystallinity (%) = ΔH / ΔHf × 100%
To improve the chemical permeability of polyacetal resin (a) Increase the amount of crystal parts that do not pass through chemicals (b) Increase the molecular chain density of the amorphous part through which the chemicals permeate and increase the diffusion of chemicals in this part It seems necessary to delay. Conventionally, only (A) has been focused on, but the present inventors have found that (B) is as important as (A).

The polyacetal resin composition of the present invention has a storage elastic modulus (G ′ ₍₋₁₀₀₎ ) at −100 ° C. when the dynamic viscoelasticity of a molded article prepared by injection molding according to the above method is evaluated at −50 ° C. It is necessary that the value divided by the storage elastic modulus (G ′ ₍₋₅₀₎₎ ) is 2.4 or more, preferably 2.43 or more, more preferably 2.45 or more. When this value is smaller than 2.4, there is little improvement effect of the chemical resistance and secondary shrinkage rate of the molded body.

The principle of the present invention is that the γ relaxation temperature of the polyacetal resin is about −70 ° C. (described in J. Macromol. Sci.-Phys., B13 (3), 323-348 (1977), etc.). The value of (G ' _(-50)) ) is the value when the amorphous part is in thermal oscillation, whereas the value of (G' _(-100) ) is frozen when the amorphous part is thermally vibrated. It is the value in the state that was done. From these values and the crystallinity of the molded body, information on the structure of the amorphous part of the molded body can be obtained. When the green body has a certain degree of crystallinity, if the value of (G ' _(-100) ) / (G' _(-50)) ) is small, the density of the amorphous part is sparse. On the other hand, if this value is large, it is considered that the density of the amorphous part is dense.

  The chemical erosion is considered to proceed from the amorphous part of the polyacetal resin, and it is estimated that the product of the present invention in which the density of the amorphous part is dense does not easily cause chemical erosion. In addition, since the amorphous part has a dense and stable structure, the product of the present invention has excellent cold-heat cycle resistance in the presence of chemicals and has a low secondary shrinkage rate, which exceeds the common sense of conventional polyacetals. It is presumed that it exhibits excellent performance.

In addition to the above-described requirements, the polyacetal resin composition of the present invention needs to have a crystallinity of 58% to 80% in a molded body prepared by injection molding. Preferably it is 60 to 75% of range, More preferably, it is 62 to 71% of range. When the crystallinity is less than 58%, the chemical resistance of the molded product is not improved. When the crystallinity exceeds 80%, it is difficult to satisfy that the value of (G ′ ₍₋₁₀₀₎ ) / (G ′ ₍₋₅₀₎₎ ) is 2.4 or more.

  To reiterate, only the degree of crystallinity has been focused on within the scope of knowledge regarding chemical permeation resistance of conventional polyacetal resins. Therefore, it has been thought that the chemical resistance of homopolymers is superior to that of copolymers, but homopolymers are rapidly crystallized during molding and the shape is fixed, and the crystallization continues after the shape is fixed. The molecular chain in the crystal part is taken into the crystal part, and as a result, the molecular chain density in the amorphous part is lowered. On the other hand, a commercially available copolymer has a high molecular chain density in the amorphous part but a low crystallinity. Even if the crystallinity was increased by a technique such as annealing as an improvement measure, the amorphous part changed sparsely as the crystallinity increased, so that the chemical resistance could not be improved. By finding a copolymer having a specific dynamic viscoelasticity without using a technique such as annealing, the present invention has obtained chemical permeation resistance superior to both a commercially available homopolymer and copolymer.

The product of the present invention can be obtained by the method described below.
The polyacetal copolymer used in the present invention contains an oxyalkylene unit represented by the following formula (1) in a polymer composed of repeating oxymethylene units (—CH ₂ O—).
(R ⁰ , R ′ ^{0 are the} same or different and are selected from hydrogen and an alkyl group. N is an integer of 1 or more, the ratio of n = 1 is 95 mol% or more of the whole oxyalkylene unit, and m = 2 to 6 And the polymer end group is composed of an alkoxy group, a hydroxyalkoxy group, and a formate group, and the number average molecular weight is in the range of 10,000 to 1,000,000. It is characterized by being.

  When the ratio of n representing 1 representing the sequence of oxyalkylene units in the polymer is less than 95 mol% of the total oxyalkylene units, the stability of the polyacetal copolymer, particularly thermal stability, chemical resistance, and the presence of chemicals This is not preferable because the effect of improving the cold-heat cycle resistance is reduced. Preferably it is 96 mol% or more, More preferably, it is 98 mol% or more.

  Moreover, it is preferable that the insertion amount of the oxyalkylene unit in a polymer is the range of 0.05 mol-0.80 mol per 100 mol of oxymethylene units. If it is less than 0.05 mol, the thermal stability of the resulting polyacetal copolymer is remarkably impaired, and the density of the amorphous part of the molded article becomes sparse, and the effect of improving chemical resistance is impaired. On the other hand, when the amount is more than 0.80 mol, the crystallinity of the molded product becomes lower than 60%, so that the chemical resistance is not improved. Preferably it is the range of 0.20-0.70 mol, More preferably, it is the range of 0.30-0.60 mol.

The terminal group of the polymer is composed of an alkoxy group, a hydroxyalkoxy group, and a formate group, and the alkoxy group is preferably at least one selected from the group consisting of a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, and a butyloxy group. The hydroxyalkoxy group is preferably a hydroxyethoxy group and / or a hydroxybutyloxy group. A terminal group other than an alkoxy group, a hydroxyalkoxy group or a formate group, for example, a hydroxyl group (—OH), an acetyl group (—OCOCH ₃ ) or the like is not preferable because of poor thermal stability.

The number average molecular weight of the polymer is 10,000 to 1,000,000, and if it is less than 10,000, the effect of improving the cold-heat cycle resistance in the presence of chemicals is impaired, which is not preferable. On the other hand, if it is larger than 1,000,000, the crystallinity of the molded product will be lower than 60%, so that the chemical resistance is not improved. Preferably it is the range of 20,000-500,000, More preferably, it is the range of 40,000-100,000.
As a method for producing the polyacetal copolymer used in the present invention, a well-known method can be used, but a cationic active catalyst is used as a polymerization catalyst, trioxane, a comonomer component such as cyclic ether and / or cyclic formal, and a molecular weight regulator. The most preferred method is to produce by a continuous bulk polymerization reaction using as a raw material.

  Examples of the comonomer component include ethylene oxide, propylene oxide, butylene oxide, oxetane, tetrahydrofuran, trioxepane, 1,3-dioxolane, ethylene glycol formal, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, Examples include 1,5-pentanediol formal, 1,6-hexanediol formal, and the like. Among these, ethylene oxide, 1,3-dioxolane, and 1,4-butanediol formal are preferable.

  Of the comonomer components listed above, 1,3-dioxolane is most preferred, and 1,3-dioxolane having a 1,4-dioxane content of 200 ppm or less is particularly preferred. When the content of 1,4-dioxane is larger than 200 ppm, the thermal stability of the resulting polyacetal copolymer is impaired, and even if the requirements for dynamic viscoelasticity and crystallinity are satisfied, the practical thermal stability is not satisfactory. May be sufficient. Although details are not clear, as a result, there are cases where the chemical resistance and the effect of improving the thermal cycle resistance in the presence of the chemical are not sufficiently exhibited. The content of 1,4-dioxane is preferably 100 ppm or less, and more preferably 50 ppm or less. 1,3-dioxolane is copolymerized in the range of 0.1 to 2.0% by weight based on trioxane. Preferably it is the range of 0.3-1.8 weight%, More preferably, it is the range of 0.5-1.5 weight%.

As the molecular weight regulator, a low molecular weight compound that acts as a chain transfer agent for cationic polymerization, for example, a dialkyl acetal selected from the group of lower aliphatic groups such as methyl, ethyl, propyl, isopropyl, butyl and the like, and oligomers thereof, and molecular weight Polyalkylene glycols such as polyethylene glycol and polypropylene glycol of 3000 or less, and lower aliphatic alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol are used. Of these, dialkyl acetals are preferable, and methylal is particularly preferable. Usually, the molecular weight regulator can obtain a polymer having a number average molecular weight of 10,000 to 1,000,000 by using about 1 × 10 ⁻⁴ mol to 1 × 10 ⁻² mol with respect to 1 mol of trioxane, preferably 3 × 10 ⁻⁴ mol to 5 × 10 ⁻³ mol, more preferably 6 × 10 ⁻⁴ mol to ⁴ × 10 ⁻³ mol.

  Cationic active catalysts include Lewis acids, especially boric acid, tin, titanium, phosphorus, arsenic and antimony halides such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride. Arsenic pentafluoride and antimony pentafluoride, and their complex compounds or salts, protonic acids such as trifluoromethanesulfonic acid, perchloric acid, esters of protonic acids, especially perchloric acid and lower aliphatic alcohols Esters, anhydrides of protonic acids, especially mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids, or isopolyacids, heteropolyacids, triethyloxonium hexafluorophosphate, triphenylmethylhexafluoroarsenate, acetylhexafluoro Borate and the like. Among them, it is preferable to use boron trifluoride diethyl ether or boron trifluoride di-n-butyl ether in a range of 0.00001 to 0.0001 mol with respect to 1 mol of the polymerization raw material. If the amount of the cation active catalyst is too small, the polymerization yield is lowered and it is not economical. On the other hand, if the amount is too large, the thermal stability of the resulting polyacetal copolymer is impaired, which is not preferable. When boron trifluoride diethyl ether or boron trifluoride di-n-butyl ether is used as the cation active catalyst, it is more preferably in the range of 0.00001 to 0.00008 mol, further preferably 0.00001 to 0.00005 mol. Range.

  As a polymerization apparatus used for carrying out a continuous bulk polymerization reaction, self-cleaning type extrusion mixers such as a kneader, a twin screw type continuous extrusion kneader, a twin screw paddle type continuous mixer, and the like have been proposed so far. A continuous polymerization apparatus such as trioxane can be used.

  The deactivation of the polymerization catalyst contained in the crude oxymethylene polymer obtained by the continuous bulk polymerization reaction using a cationically active catalyst is amines such as ammonia, triethylamine, tri-n-butylamine, boric acid compounds, or It is carried out by filtering and drying after putting into an aqueous solution and / or an organic solvent containing a catalyst neutralization deactivator such as an alkali metal or alkaline earth metal hydroxide, inorganic acid salt, or organic acid salt. In this case, a quaternary ammonium compound can be used alone as a catalyst neutralization deactivator, or it can be used in combination with the catalyst deactivator, which is a preferable method because neutralization of the catalyst is more effectively performed. . Also, a method of deactivating the catalyst by contacting a vapor such as ammonia or triethylamine with a crude oxymethylene polymer, or at least one of hindered amines, triphenylphosphine, calcium hydroxide, boric acid compounds, quaternary ammonium compounds, etc. A method of deactivating the catalyst by bringing the seed and the crude oxymethylene polymer into contact with each other in a mixer is also possible.

  Since the crude oxymethylene polymer after deactivation of the polymerization catalyst has a thermally unstable terminal portion, the unstable terminal portion is decomposed and removed. Examples of the method for decomposing and removing unstable terminal portions include at least two steps: (1) a step of melt-kneading a polymer in the presence of a basic substance, and (2) a step of opening and removing formaldehyde generated by decomposition. Can be mentioned. As the apparatus, a vented single-screw extruder, a vented twin-screw extruder, or the like that can continuously carry out the two-stage process is preferably used. Examples of basic substances include ammonia, amines such as triethylamine and tri-n-butylamine, alkali metal or alkaline earth metal hydroxides, inorganic acid salts and organic acid salts such as calcium hydroxide, and quaternary ammonium. Compounds and the like. In particular, the use of a quaternary ammonium compound represented by the following formula (2) is most advantageous because an oxymethylene copolymer having almost no unstable terminal portion remaining can be obtained in a very short time with a very small addition amount. preferable. The basic substance may be used with water or methanol, or two or more basic substances may be used in combination.

[R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ⁻ⁿ (2)
Wherein R ¹ , R ² , R ³ and R ⁴ are each independently an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; An aralkyl group having 30 unsubstituted alkyl groups or substituted alkyl groups substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms having at least one carbon atom having 1 to 30 carbon atoms Represents an unsubstituted alkyl group or an alkylaryl group substituted with a substituted alkyl group, wherein the unsubstituted alkyl group or substituted alkyl group is linear, branched, or cyclic. An aldehyde group, a carboxyl group, an amino group, or an amide group, and the above-mentioned unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group are substituted with a halogen atom. N represents an integer of 1 to 3. X represents a hydroxyl group, a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than a hydrogen halide, an oxo acid, an inorganic thioacid, or a C 1 to 20 carbon atom. Represents an acid residue of an organic thioic acid of

The quaternary ammonium compound is not particularly limited as long as it is represented by the above formula (2), but R ¹ , R ² , R ³ and R ⁴ in the above formula (2) are each independently An alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 4 carbon atoms is preferable, and among them, at least one of R ¹ , R ² , R ³ , and R ⁴ is a hydroxyethyl group. Some are particularly preferred. Specifically, tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetra-n-butylammonium, cetyltrimethylammonium, tetradecyltrimethylammonium, 1,6-hexamethylenebis (trimethylammonium), decamethylene-bis- (trimethyl) Ammonium), trimethyl-3-chloro-2-hydroxypropylammonium, trimethyl (2-hydroxyethyl) ammonium, triethyl (2-hydroxyethyl) ammonium, tripropyl (2-hydroxyethyl) ammonium, tri-n-butyl (2 -Hydroxyethyl) ammonium, trimethylbenzylammonium, triethylbenzylammonium, tripropylbenzylammonium, tri-n-butyl Benzylammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, okdadecyltri (2-hydroxyethyl) ammonium, tetrakis (hydroxyethyl) ammonium Hydroxides such as hydrochloric acid, odorous acid, hydrofluoric acid, etc .; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, chlorous acid, hypochlorous acid Oxo acid salts such as chloric acid, chlorosulfuric acid, amidosulfuric acid, disulfuric acid and tripolyphosphoric acid; thioic acid salts such as thiosulfuric acid; formic acid, acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, caproic acid, caprylic acid, Carboxylates such as capric acid, benzoic acid and oxalic acid And the like. Among them, hydroxide (OH ⁻ ), sulfuric acid (HSO ₄ ⁻ , SO ₄ ²⁻ ), carbonic acid (HCO ₃ ⁻ , CO ₃ ²⁻ ), boric acid (B (OH) ₄ ⁻ ), and carboxylic acid salts are included. preferable. Of the carboxylic acids, formic acid, acetic acid, and propionic acid are particularly preferred. These quaternary ammonium compounds may be used alone or in combination of two or more. Further, in addition to the quaternary ammonium compound, amines such as ammonia and triethylamine may be used in combination.

The addition amount of the quaternary ammonium compound is preferably 0.05 to 50 in terms of the amount of nitrogen derived from the quaternary ammonium compound represented by the following formula (3) with respect to the polyoxymethylene copolymer. Ppm by weight.
P × 14 / Q (3)
(In the formula, P represents the concentration (weight ppm) of the quaternary ammonium compound relative to the polyoxymethylene copolymer, 14 represents the atomic weight of nitrogen, and Q represents the molecular weight of the quaternary ammonium compound.)
If the addition amount of the quaternary ammonium compound is less than 0.05 ppm by weight, the rate of decomposition and removal of the unstable end decreases, and if it exceeds 50 ppm by weight, the polyoxymethylene copolymer after the decomposition and removal of the unstable end is reduced. The color tone of coalescence deteriorates. There are no particular restrictions on the method of adding the quaternary ammonium compound, and there are a method of adding as an aqueous solution in the step of deactivating the polymerization catalyst, a method of spraying the oxymethylene copolymer before melting, a method of adding after melting, and the like. Any addition method may be used as long as it exists in the step of melting the polymer.

  The polyacetal copolymer used in the present invention has been described above. With respect to 100 parts by weight of this polyacetal copolymer, an antioxidant, a polymer or compound containing formaldehyde-reactive nitrogen, a formic acid supplement, a weather resistance (light) stabilizer, a mold release ( The polyacetal resin composition of the present invention can be obtained by blending 0.01 to 5 parts by weight of at least one lubricant. These compounding agents are added to the polyacetal copolymer after the unstable terminal portion decomposition removal, but depending on the compounding agent, it may be added simultaneously with the unstable terminal decomposition removal treatment.

  As the antioxidant, a hindered phenol antioxidant is preferable. Specifically, for example, n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) -propionate, n-octadecyl-3- (3′-methyl-5′-t -Butyl-4'-hydroxyphenyl) -propionate, n-tetradecyl-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) -propionate, 1,6-hexanediol-bis- [ 3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate], 1,4-butanediol-bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) -Propionate], 2,2'-methylenebis- (4-methyl-t-butylphenol), triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxy Phenyl) -propionate], tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, 3,9-bis [2- {3- (3-t -Butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] 2,4,8,10-tetraoxaspiro (5,5) undecane, N, N′-bis-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionylhexamethylenediamine, N, N'-tetramethylene-bis-3- (3'-methyl-5'-t-butyl-4 '-Hydroxyphenol) propionyldiamine, N, N'-bis- [3- (3,5-di-tert-butyl-4-hydroxyphenol) propionyl] hydrazine, N-salicyloyl N'-salicylidenehydrazine, 3- (N-salicyloyl) amino-1,2,4-triazole, N, N'-bis [2- {3- (3,5-di-t-butyl-4- Hydroxyphenyl) propionyloxy} ethyl] oxyamide and the like. Preferably, triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] and tetrakis [methylene-3- (3 ′, 5′-di-t-butyl) -4'-hydroxyphenyl) propionate] methane. These antioxidants may be used alone or in combination of two or more. Moreover, it is preferable to mix | blend 0.01-1 weight part with respect to 100 weight part of polyacetal copolymers.

Examples of polymers or compounds containing formaldehyde reactive nitrogen include polyamide resins such as nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 12, and polymers thereof. Examples thereof include nylon 6 / 6-6 / 6-10 and nylon 6 / 6-12. Further, acrylamide and its derivatives, and copolymers of acrylamide and its derivatives and other vinyl monomers include poly-β obtained by polymerizing acrylamide and its derivatives and other vinyl monomers in the presence of metal alcoholate. -Alanine copolymers can be mentioned. These polymers containing formaldehyde-reactive nitrogen atoms may be used alone or in combination of two or more.

  Examples of compounds containing formaldehyde-reactive nitrogen atoms having amino substituents include 2,4-diamino-sym-triazine, 2,4,6-triamino-sym-triazine, N-butylmelamine, N-phenyl Melamine, N, N-diphenylmelamine, N, N-diallylmelamine, N, N ′, N ″ -triphenylmelamine, melem, melon, melam, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine ), Acetoguanamine (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-s m-triazine, 2,4-diamino-6-chloro-sym-triazine, 2,4-diamino-6-mercapto-sym-triazine, 2,4-dioxy-6-amino-sym-triazine, 2-oxy- 4,6-diamino-sym-triazine, N, N, N ′, N′-tetracyanoethyl benzobuamine, succinoguanamine, ethylene dimelamine, triguanamine, melamine cyanurate, ethylene dimelamine cyanurate, triguanamine Nurate, ammelin, acetoguanamine and the like. These triazine derivatives may be used alone or in combination of two or more. Of the above polymers or compounds containing formaldehyde-reactive nitrogen, polyamide resins are preferred, and preferably 0.01 to 1 part by weight per 100 parts by weight of polyacetal resin.

  Examples of the formic acid scavenger include the above-mentioned amino-substituted triazines and polycondensates of amino-substituted triazines with formaldehyde, such as melamine-formaldehyde polycondensates. Other formic acid scavengers include alkali metal or alkaline earth metal hydroxides, inorganic acid salts, carboxylate salts or alkoxides. For example, hydroxides such as sodium, potassium, magnesium, calcium or barium, carbonates, phosphates, silicates, borates and carboxylates of the above metals. The carboxylic acid is preferably a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms, and these carboxylic acids may be substituted with a hydroxyl group. Examples of aliphatic carboxylic acids include capric acid, undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, liglyceric acid, serotic acid, Heptacosanoic acid, montanic acid, melissic acid, laceric acid, undecylenic acid, oleic acid, elaidic acid, celetic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propiolic acid, stearol Acid, 12-hydroxydodecanoic acid, 3-hydroxydecanoic acid, 16-hydroxyhexadecanoic acid, 10-hydroxyhexadecanoic acid, 12-hydroxyoctadecanoic acid, 10-hydroxy-8-octadecanoic acid, dl-erythro-9 · 10-dihydroxy Octadecanoic acid And the like.

  Among them, difatty acid calcium composed of fatty acids having 12 to 22 carbon atoms is preferable, and specific examples include calcium dimyristate, calcium dipalmitate, calcium diheptadecylate, calcium distearate, (myristic acid-palmitic acid) calcium. , (Myristic acid-stearic acid) calcium, (palmitic acid-stearic acid) calcium, and the like. Particularly preferred are calcium dipalmitate, calcium diheptadecylate, and calcium distearate. In the present invention, it is particularly preferable to blend 0.01 to 0.2 parts by weight of two or more selected from the difatty acid calciums consisting of the above fatty acids having 12 to 22 carbon atoms with respect to 100 parts by weight of the polyacetal copolymer. It is valid.

The weather resistance (light) stabilizer referred to in the present invention is preferably one or more selected from benzotriazole-based, oxalic anilide-based UV absorbers, and hindered amine-based light stabilizers.
Examples of benzotriazole ultraviolet absorbers include 2- (2′-hydroxy-5′-methyl-phenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butyl-phenyl). ) Benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-) Amylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-isoamyl-phenyl) benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis- (α, α- Dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole, and the like. Examples of the oxalic acid alinide ultraviolet absorbers include 2-ethoxy-2′-ethyloxalic acid bisanilide, 2-ethoxy-5-tert-butyl-2′-ethyloxalic acid bisanilide, and 2-ethoxy. -3'-dodecyl oxalic acid bisanilide and the like. These ultraviolet absorbers may be used alone or in combination of two or more.

  Examples of hindered amine light stabilizers include 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-2, 2,6,6-tetramethylpiperidine, 4- (phenylacetoxy) -2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy- 2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-benzyloxy -2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4- (ethyl carbonate) Vamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (cyclohexylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (phenylcarbamoyloxy) -2,2,6,6 -Tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4-piperidyl) -carbonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -oxalate, bis (2,2 , 6,6-tetramethyl-4-piperidyl) -malonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate, bis (2,2,6,6-tetramethyl-4- Piperidyl) -adipate, bis (2,2,6,6-tetramethyl-4-piperidyl) -terephthalate, 1,2-bis (2,2,6,6-tetramethyl- -Piperidyloxy) -ethane, α, α'-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -p-xylene, bis (2,2,6,6-tetramethyl-4- Piperidyltolylene-2,4-dicarbamate, bis (2,2,6,6-tetramethyl-4-piperidyl) -hexamethylene-1,6-dicarbamate, tris (2,2,6,6-tetra Methyl-4-piperidyl) -benzene-1,3,5-tricarboxylate, tris (2,2,6,6-tetramethyl-4-piperidyl) -benzene-1,3,4-tricarboxylate, 1 -[2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} butyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) Propionyloxy 2,2,6,6-tetramethylpiperidine, 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β ′, β ′ , -Tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (5,5) undecane] diethanol and the like. Each of the hindered amine light stabilizers may be used alone or in combination of two or more.

Among them, preferred weathering agents are 2- [2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di- t-butylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-amylphenyl) benzotriazole, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) Sebacate, bis- (N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 1,2,3 , 4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β ′, β ′,-tetramethyl-3,9- [2,4,8,10 -Tetraoxaspiro (5,5) Ndecane] is a condensate with diethanol.

  Examples of the release agent include alcohols, fatty acids and fatty acid esters thereof, polyoxyalkylene glycols, olefin compounds having an average polymerization degree of 10 to 500, and silicone. Among these, ethylene glycol difatty acid esters composed of fatty acids having 12 to 22 carbon atoms are preferable, and ethylene glycol distearate, ethylene glycol dipalmitate, and ethylene glycol diheptadecylate are particularly preferable. In this invention, 0.01-0.9 weight part is mix | blended with respect to 100 weight part of polyacetal copolymers 2 or more types chosen from ethylene glycol difatty acid ester which consists of these C12-C22 fatty acid. Is particularly effective.

  In the present invention, the polyacetal resin composition of the present invention includes a nucleating agent represented by boron nitride, talc, mica, alumina, boric acid compound, inorganic filler, glass fiber, glass, and the like within a range not impairing the effects of the present invention. Reinforcing agents represented by beads, carbon fibers, etc., conductive materials represented by conductive carbon black, metal powder, fibers, etc., polyolefin resin, acrylic resin, styrene resin, polycarbonate resin, uncured epoxy resin, or these Thermoplastic resins typified by modified products, thermoplastic elastomers typified by polyurethane elastomers, polyester elastomers, polystyrene elastomers, polyamide elastomers, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, etc. Inorganic pigments represented by System Mabet system, Furotashianin system, can be blended and organic pigments typified by monoazo like.

As described above, the present invention provides a polyacetal resin composition that is excellent in chemical resistance and resistance to cold and heat cycle in the presence of chemicals and has a low secondary shrinkage. Furthermore, a molded article obtained by injection molding the polyacetal resin composition to use these excellent properties is also provided. In addition, a molded product obtained by extrusion molding, blow molding, or pressure molding of this polyacetal resin composition is excellent in chemical resistance and resistance to cold and heat cycles in the presence of chemicals as well as an injection molded product. Secondary shrinkage is small and can be used effectively.
Such molded articles are particularly useful as parts used in the presence of chemicals such as organic chemicals, inorganic chemicals, household chemicals, industrial oils, industrial greases, automobile fuels, and automotive oils.

Representative examples of organic chemicals include heptane, octane, benzene, toluene, xylene, ethyl alcohol, ethylene glycol, propylene glycol, diethyl ether, oleic acid, gepal, linseed oil, castor oil and the like. Representative examples of inorganic chemicals include sodium chloride, sodium thiosulfate, sodium hypochlorite, sodium carbonate, sodium hydroxide, hydrogen peroxide water, and the like. Typical examples of household chemicals include kitchen detergents, cleansers, bath / toilet detergents, shampoos, rinses, hair tonics, hair liquids, shaving creams, shaving foams, shaving lotions, bath soap water, cresol soap solutions, cold perms. Liquid, thinner and the like. Representative examples of industrial oils include engine oil, gear oil, hydraulic oil, turbine oil, watch oil, silicone oil, insulating oil, synthetic oil, rust preventive oil, cutting oil, vacuum pump oil, spindle oil, etc. It is done. Representative examples of industrial greases include lithium, calcium, aluminum, fiber, molybdenum, and silicon. Typical examples of automotive chemicals include regular gasoline, high-octane gasoline, aromatic gasoline, methanol, gasohol / ethanol, gasohol / methanol, light oil, kerosene, LPG, engine oil, antifreeze, washer fluid, battery fluid, radiator Examples include cleaners, rust preventives, waxes, road freeze inhibitors.

  The polyacetal resin molded body of the present invention has excellent chemical resistance, particularly organic solvent gas permeability. Therefore, the polyacetal resin molded article is required to have low organic solvent gas permeability, such as regular gasoline and high-octane gasoline. Further, it can be used particularly suitably as a fuel component for automobile fuel such as a fuel pump module, a valve, a gasoline tank, a gasoline tank flange and the like that comes into contact with automobile fuel represented by methanol, methanol-containing gasoline and the like.

  Furthermore, the polyacetal resin molded product of the present invention has excellent properties such as chemical resistance, thermal cycle resistance in the presence of chemicals, and low secondary shrinkage, as well as creep properties, repeated impact properties, hinge properties, In terms of abrasion, it has improved performance compared to conventional polyacetal resins. In addition to the above applications, it is used in office automation equipment such as printers and copiers, VTR (Video Tape Recorder) and Used in video equipment typified by video movies, cassette player, LD (Laser Disk), MD (Mini Disk), CD (Compact Disk) [CD-ROM (Read Only Memory), CD-R (Recordable), CD -Including RW (Rewritable)], DVD (Digital Video Disk) [DVD-ROM, DVD-R, DVD-R, DVD-RAM (Random Acess Memory), DVD-Audio Used in music, video or information equipment typified by navigation systems and mobile personal computers, used in communication equipment typified by mobile phones and facsimiles, used in automobile interior and exterior parts, and disposable cameras and toys Gears, cams, sliders, levers, arms, clutches, joints, shafts, bearings used for industrial parts such as fasteners, chains, conveyors, buckles, sports equipment, vending machines, furniture, and housing equipment , Key stems, key tops, and other mechanical parts, resin parts for outsert chassis, chassis, trays and side plates. In particular, a component that fits and slides on a lead screw that drives a pickup of an optical disk drive represented by a DVD (digital video disk) that is required to have excellent creep characteristics and repeated impact resistance, a gear that rotates the lead screw, It is suitably used as a part such as a rack gear for driving the pickup and a gear fitted to the rack gear to drive it.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention more concretely, this invention is not limited at all by these. In addition, the term and measurement method in an Example and a comparative example are as follows.
<Dynamic viscoelasticity (storage rigidity (G ' _(-100) ), (G' _(-50)) ))>
Using an IS-80A injection molding machine manufactured by Toshiba Corporation, cylinder size 200 ° C., injection pressure 60 kgf / cm ² , injection time 15 seconds, cooling time 25 seconds, mold temperature 70 ° C., dimensions 130 mm × 13 mm × 3 mm A strip-shaped molded body was molded. After the molding was completed, the molded body was allowed to stand for 48 hours in an environment of 23 ° C. and 50% humidity, and then measured using a dynamic viscoelasticity evaluation apparatus (RDA2 manufactured by Rheometrics) under the following conditions: −100 The storage rigidity (G ′ ₍₋₁₀₀₎ ) at 50 ° C. and the storage elastic modulus (G ′ _{(−50)) at} −50 ° C. were determined.
Geometry Type: Torsion Rectangular
(Sample length 20 mm, width 13 mm, thickness 3 mm)
Test Type: Dynamic Temperature Ramp
(Torsion period: 6.28 rad / s, measurement temperature range: -130 ° C to 150 ° C, heating rate: 3 ° C / min, strain amount: 0.05%)

<Crystallinity>
10 mg of resin is cut out from the center of the molded article for storage modulus evaluation described above, and the temperature is increased to 200 ° C. at a rate of 5 ° C./min using a differential calorimeter (DSC-7, manufactured by Perkin Elmer). The heat of fusion ΔH (J / g) was determined from the exothermic peak generated during the heating process, and this was obtained from the literature ('61
It calculated | required by calculating with the following formula | equation from the value ((DELTA) Hf = 222J / g) of the crystallinity degree 100% described in Journal of Research: Hoffman, Lauritzen.
Crystallinity (%) = ΔH / ΔHf × 100%

<Analysis of main chain composition of polyacetal copolymer>
When 5 g of polyacetal copolymer is heated in 30 ml of 1N aqueous hydrochloric acid solution at 120 ° C. for 2 hours, all oxymethylene units are formaldehyde and oxyalkylene units are alkylene glycol. By analyzing and quantifying the alkylene glycol using gas chromatography, n representing the sequence of oxyalkylene units in the polyacetal copolymer, the ratio of n = 1, and the amount of oxyalkylene units inserted were determined.
<Number average molecular weight>
Using a GPC (gel permeation chromatography) (solvent: hexafluoroisopropanol) apparatus (HLC-8120 manufactured by Tosoh Corporation), the number average molecular weight (Mn) is detected with a low angle laser light scattering detector, and polyoxymethylene single molecule It calculated | required using the analytical curve obtained from the standard sample of the polymer.

<Content of 1,4-dioxane in 1,3-dioxolane (ppm)>
It was measured by a flame ion detector by gas chromatography equipped with a plot column (Pola plot Q).
<Chemical resistance>
The above-mentioned molded product for storage elastic modulus evaluation is placed in a stainless steel sealed container containing an organic solvent (gasoline, methanol having a methanol concentration of 15 vol%, and methanol) and immersed in the organic solvent at 60 ° C. Then, the weight increase rate (%) of the test piece was evaluated. The smaller the value, the better the chemical resistance.

<Gas permeability (g · mm / day / m ² )>
A test piece having a thickness of 2 mm was prepared under the same injection molding machine and injection conditions as the above-described molded product for storage modulus evaluation. With this test piece, a stainless steel cylindrical container with a diameter of 38 mm containing an organic solvent (three kinds of gasoline, gasoline having a methanol concentration of 15 vol% and methanol) is covered. A packing was inserted between the test piece and the cylindrical container so that the organic solvent gas did not decrease except through the test piece. The sample prepared as described above was allowed to stand at 60 ° C. for 750 hours, and then the reduction amount (g) of the organic solvent was measured, and the amount of gas permeating through the test piece having an area of 1 m ² and a thickness of 1 mm per day was calculated. The gas permeability was determined (g · mm / day / m ² ). The smaller the value, the better the gas permeability.
<Cold and heat cycle resistance in the presence of chemicals>
The above-mentioned molded product for storage elastic modulus evaluation is placed in a stainless steel sealed container containing an organic solvent (gasoline, methanol having a methanol concentration of 15 vol% and methanol) and immersed in the organic solvent at 100 ° C. A series of operations of standing for 20 hours and then standing at 20 ° C. for 4 hours was repeated 30 times, and the presence or absence of cracks occurring on the surface of the molded body was observed. If there are no cracks, the heat and cycle resistance in the presence of chemicals is excellent.

<ESCR: Stress cracking resistance (seconds)>
The molded body for evaluation of storage elastic modulus was mounted on a jig having a length of 111 mm while being bent, and after being immersed in a 2N hydrochloric acid aqueous solution at 23 ° C., the time until a crack was generated and broken was measured. The longer the time until destruction, the better the chemical resistance.
<Secondary shrinkage (%)>
A test piece was prepared under exactly the same conditions as the above-described molded product for storage elastic modulus evaluation. After molding, the dimension in the flow direction after being left in an environment of 23 ° C. and 50% humidity for 48 hours was defined as D ₁ (mm), and after completion of molding, it was left in an environment of 23 ° C. and 50% humidity for 72 hours. Thereafter, the film was heated at 120 ° C. for 5 hours and then allowed to stand at 23 ° C. for 48 hours, and the dimension in the flow direction was taken as D ₂ (mm), and the secondary shrinkage (%) was determined according to the following formula.
Secondary shrinkage (%) = (D ₁ −D ₂ ) / die size × 100
The smaller the value, the better the secondary shrinkage.
<%, Ppm>
Unless otherwise noted, all are by weight.

Example 1
A biaxial paddle type continuous polymerization machine with a jacket through which a heat medium can pass is adjusted to 80 ° C., and 12 kg / Hr of trioxane and 1,3-dioxolane with 1,4-dioxane content adjusted to 10 ppm as a comonomer 150 g / Hr (0.015 mol with respect to 1 mol of trioxane) and methylal 7.0 g / Hr (0.7 × 10 ⁻³ mol with respect to 1 mol of trioxane) as a molecular weight regulator were continuously added. . Further, as a polymerization catalyst, a cyclohexane solution of 1% by weight of boron trifluoride di-n-butyl etherate so that boron trifluoride is 1.5 × 10 ⁻⁵ mol per mol of trioxane. Polymerization was carried out by continuously adding 6 g / Hr. The polyacetal copolymer discharged from the mixer was put into a 0.1% aqueous solution of triethylamine to deactivate the polymerization catalyst. The deactivated polyacetal copolymer was filtered with a centrifuge. 1 part by weight of an aqueous solution containing choline hydroxylate (trimethyl-2-hydroxyethylammonium formate) as a quaternary ammonium compound was added to 100 parts by weight of the polyacetal copolymer after filtration and mixed uniformly. After drying at 120 ° C. The amount of choline formate added was 20 ppm in terms of the amount of nitrogen. The amount of choline formate added was adjusted by adjusting the concentration of choline formate in the aqueous solution containing the choline formate to be added. The dried polyacetal copolymer was fed into a vented twin screw extruder. 0.5 parts by weight of water was added to 100 parts by weight of the melted polyacetal copolymer in the extruder, and the unstable end portion was decomposed at an extruder set temperature of 200 ° C. and a residence time of 5 minutes in the extruder. . The oxymethylene copolymer decomposed at the unstable end was devolatilized under a condition of a vent vacuum of 20 Torr, extruded as a strand from the extruder die, and pelletized. No. 2 in Table 2 was further added to this pellet. The compounding agent was added and mixed as shown in 1 and melt-kneaded with a single screw extruder with a vent to obtain final polyacetal resin pellets. The pellets were dried at 80 ° C. for 3 hours and then subjected to a predetermined evaluation.

Table 1 summarizes the properties of the polyacetal copolymer resin composition obtained and its evaluation results. Moreover, the analysis chart of the storage rigidity (G ') from -130 degreeC to 160 degreeC was shown in FIG.
(Examples 2-11 Comparative Examples 1-5)
In Examples 2 to 11 and Comparative Examples 1 to 5, the amount of 1,3-dioxolane used in the polymerization, the content of 1,4-dioxane in 1,3-dioxolane, and the amount of the molecular weight regulator were changed. The same experiment was conducted. The results are summarized in Table 1.
(Comparative Example 6)
A commercially available polyacetal homopolymer (Tenac 4010) having a number average molecular weight of 61,000 was evaluated. The results are summarized in Table 1. Moreover, the analysis chart of the storage rigidity (G ') from -130 degreeC to 160 degreeC was shown in FIG.
(Comparative Example 7)
A commercially available oxymethylene copolymer resin (Tenac 4520) having a number average molecular weight of 63,000 was evaluated. The results are summarized in Table 1. Moreover, the analysis chart of the storage rigidity (G ') from -130 degreeC to 160 degreeC was shown in FIG.

Table 3 shows the results of evaluating the repeated impact properties and creep properties of the polyacetal copolymer resin compositions obtained in Example 1 and Comparative Example 2. The measurement was performed by the following method.
<Repetitive impact>
Set a test piece exactly the same as the storage elastic modulus characteristic as shown in FIG. 2, and repeatedly apply a shock to the test piece by dropping a weight of 1.5 kg from a height of 8 cm until the test piece is broken. The number of impacts was measured. The greater the number of impacts until destruction, the better the impact. <Creep characteristics>
Using an IS-80A injection molding machine manufactured by Toshiba Corporation, cylinder temperature 200 ° C., injection pressure 60 kgf / cm ² , injection time 15 seconds, cooling time 25 seconds, mold temperature 70 ° C., dimensions 110 mm × 6 A strip-shaped test piece of 5 mm × 3 mm was molded. The test piece was subjected to a tensile stress of 18 MPa and left in air at 80 ° C., and the time until the test piece was broken was measured. The longer the time until destruction, the better the creep properties.
The polyacetal resin composition and molded product thereof according to the present invention are excellent in chemical resistance, thermal cycle resistance in the presence of chemicals, and low secondary shrinkage, and at the same time, excellent in repeated impact properties and creep properties. Recognize.

Claims (4)

A process for producing a polyacetal copolymer obtained by copolymerizing 1,3-dioxolane containing 200 ppm or less of 1,4-dioxane in a range of 0.1 to 2.0% by weight with respect to trioxane. Polymerization catalyst, per polymerization raw material 1 mol, the production method of the polyacetal copolymer according to claim 1, characterized in that in the range of 0.00001～0.0001Mol. The method for producing a polyacetal copolymer according to claim 1 or 2 , wherein the neutralization quencher of the polymerization catalyst uses a quaternary ammonium compound represented by the following general formula (2).
[R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ⁻ⁿ (2)
Wherein R ¹ , R ² , R ³ and R ⁴ are each independently an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; An aralkyl group having 30 unsubstituted alkyl groups or substituted alkyl groups substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms having at least one carbon atom having 1 to 30 carbon atoms Represents an unsubstituted alkyl group or an alkylaryl group substituted with a substituted alkyl group, wherein the unsubstituted alkyl group or substituted alkyl group is linear, branched, or cyclic. An aldehyde group, a carboxyl group, an amino group, or an amide group, and the above-mentioned unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group are substituted with a halogen atom. N represents an integer of 1 to 3. X represents a hydroxyl group, a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than a hydrogen halide, an oxo acid, an inorganic thioacid, or a C 1 to 20 carbon atom. Represents an acid residue of an organic thioic acid of The method for producing a polyacetal copolymer according to any one of claims 1 to 3 , wherein the number average molecular weight is in the range of 10,000 to 1,000,000.