JP2005171158A - Polyacetal resin composition and molded article comprised of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyacetal resin composition excellent in thermal stability, suppressed in an amount of generated formaldehyde and giving a small amount of mold deposit. <P>SOLUTION: The polyacetal resin composition comprises (A) a polyacetal resin, (B) 0.01-0.9 pt. wt. of an alkylene urea, (C) 0.01-5 pts. wt. of an aliphatic hydrazide compound having a solubility of less than 1 g in 100 g H<SB>2</SB>O at 20°C, (D) 0.01-5 pts. wt. of a sterically hindered phenol, (E) 0.01-7 pts. wt. of an amino-substituted triazine compound and (F) 0.004-5 pts. wt. of at least one metal-containing compound selected from among hydroxides, inorganic acid salts and alkoxides of alkali metals and alkaline earth metals, the (B)/(C) weight ratio being 0.1-2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 products, and has a small mold deposit during molding, and a molded product comprising the same.

Polyacetal resin is widely used as an engineering plastic having balanced mechanical properties and good self-lubricating properties and electrical properties in various mechanical and electrical components.
However, since the main raw material of the monomer in the polyacetal resin composition is formaldehyde, formaldehyde is generated in a very small amount due to a slight thermal decomposition reaction in the thermal history during polymerization or molding, and the working environment is deteriorated. In addition to incurring, mold deposits called mold deposits are generated during injection molding, causing molding defects. In addition, it is difficult to completely eliminate formaldehyde generation from the final product, and there is concern about the impact on sick house syndrome and the like. The indoor formaldehyde concentration guideline value from the Ministry of Health, Labor and Welfare is defined as 0.08 ppm, and as a measure against sick house syndrome, it is required to further reduce the amount of formaldehyde generated from the current level. For this purpose, a polyacetal resin composition having a low formaldehyde generation amount is desirable.

  Conventionally, various substances have been proposed as a deodorant for capturing formaldehyde and other odorous substances generated from a resin or the like or a resin additive for suppressing the generation of formaldehyde from a polyacetal resin or a molded product. For example, a melamine-formaldehyde polymer (Patent Document 1), a hindered phenol antioxidant and a specific polyamine reaction product (Patent Document 2), a glyoxydiureide compound (Patent Document 3), a urea derivative and / or an amidine derivative (Patent Document 4), triazine ring-containing spiro compound (Patent Document 5), tetracarboxylic acid hydrazide (Patent Document 6), and the like. Further, a deodorant composition comprising a composition in which hydrazides are mixed 0.05 to 10 times by weight with respect to a urea derivative has been proposed (Patent Document 7). As a hydrazide, adipic acid dihydrazide is particularly preferable and specific. Describes a blend of ethylene urea and adipic acid dihydrazide. However, these methods have problems such as suppression of formaldehyde generation and adsorption / removal ability, and there are problems such as lowering the physical properties of the resin composition. Further, an improved method for reducing formaldehyde is desired. It was rare.

JP-A-5-271516 JP-A-7-207118 Japanese Patent Laid-Open No. 10-182928 JP 2003-34417 A JP2003-113289A Japanese Patent Laid-Open No. 6-80619 JP 2002-35098 A

  An object of the present invention is to provide a polyacetal resin composition that is excellent in thermal stability, suppresses mold deposit during molding, and can significantly reduce the amount of formaldehyde generated from a product.

In order to achieve the above object, the present inventors have made extensive studies on a polyacetal resin composition containing various additives. As a result, alkylene urea, sterically hindered phenols, amino-substituted triazine compounds, and specific metal-containing compounds Can significantly reduce the formaldehyde generated from the polyacetal resin, but this composition is not necessarily sufficiently reduced in mold contamination during molding, and in order to reduce mold contamination, Knowing that it is effective to blend a specific amount of hydrazide compound, the present invention has been achieved. That is, the gist of the present invention is (A) polyacetal resin, (B) 0.01 to 0.9 parts by weight of alkylene urea, and (C) an aliphatic hydrazide compound having a solubility in 100 gH ₂ O at 20 ° C. of less than 1 g. 0.01-5 parts by weight, (D) 0.01-5 parts by weight of sterically hindered phenol, (E) 0.01-7 parts by weight of amino-substituted triazine compound, and (F) hydroxylation of alkali metal or alkaline earth metal At least one metal-containing compound selected from a product, an inorganic acid salt, or an alkoxide, and the weight ratio of (B) / (C) is 0.1-2. It exists in a polyacetal resin composition and a molded article comprising the same.

  The polyacetal resin composition obtained in the present invention is excellent in thermal stability, has low mold deposit and excellent moldability, and can suppress the amount of formaldehyde generated from pellets and molded products, so-called sick house syndrome As a countermeasure, it is extremely useful for automobile interior parts, building material parts used in houses and schools, and electrical parts.

Hereinafter, the present invention will be described in detail.
The (A) polyacetal resin used in the present invention is a copolymer containing one or more structural units other than the oxymethylene group in addition to an acetal homopolymer having an oxymethylene group (—CH ₂ O—) as a main structural unit ( Block polymers are also included), and terpolymers are also included. The polyacetal resin may have not only a linear structure but also a branched or crosslinked structure. As structural units other than the oxymethylene group, an oxyethylene group (—CH ₂ CH ₂ O—), an oxypropylene group (—CH ₂ CH ₂ CH ₂ O—), an oxybutylene group (—CH ₂ CH ₂ CH ₂ CH). ₂ O-) and the like, which may be branched, may be an oxyalkylene group having 2 to 4 carbon atoms, and among them, an oxyethylene group is preferable. The content of the oxyalkylene structural unit in the resin is preferably 0.1 to 20% by weight.

The polyacetal resin which has an oxymethylene group (—CH ₂ O—) and an oxyalkylene group having 2 to 4 carbon atoms as a constituent unit is an oxymethylene group such as formaldehyde trimer (trioxane) or tetramer (tetraoxane). It is produced by copolymerizing a cyclic oligomer and a cyclic oligomer containing an oxyalkylene group having 2 to 4 carbon atoms such as ethylene oxide, 1,3-dioxolane, 1,3,6-trioxocan, 1,3-dioxepane. Can do. Among them, a copolymer of cyclic oligomer such as trioxane or tetraoxane and ethylene oxide or 1,3-dioxolane is preferable. In particular, a copolymer of trioxane and 1,3-dioxolane is preferable.

  Specifically, (B) alkylene urea used in the present invention has a structure represented by the following general formula (2).

(In the formula (2), R ₄ represents a linear or branched alkylene group having 1 to 10 carbon atoms).
As the alkylene urea represented by the general formula (2), ethylene urea in which R ₄ is an ethylene group is particularly preferably used.

Examples of the aliphatic hydrazide compound include monohydrazides such as propionic acid hydrazide and thiocarbohydrazide, carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, adipic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide hydrazide hydrazide hydrazide Dihydrazides such as acid dihydrazide, 1,12-dodecanedicarbohydrazide, 1,18-octadecanedicarbohydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, aminopolyacrylamide, 1,3,5-tris (2 Polyhydrazides such as -hydrazinocarbonylethyl) isocyanurate are known, and among the aliphatic hydrazide compounds, 100 gH _{2 at} 20 ° C. is included in the present invention. Hydrazides with a solubility in O of less than 1 g are used. Examples of such aliphatic hydrazide compounds include oxalic acid dihydrazide (0.2 g or less), sebacic acid dihydrazide (0.01 g or less), dodecanedioic acid dihydrazide (0.01 g or less), 1,18-octadecanedicarbohydrazide ( 0.1 g or less) and the like, and sebacic acid dihydrazide and dodecanedioic acid dihydrazide are particularly preferably used. On the other hand, an aliphatic hydrazide having a water solubility of 1 g or more is not sufficient in reducing the amount of formaldehyde generated. The said aliphatic hydrazide compound may be used independently and may be used in mixture of 2 or more types.

  The (D) sterically hindered phenol used in the present invention basically means a compound having at least one structure represented by the following general formula (3) in the molecule.

(In Formula (3), R ₅ and R ₆ each independently represents a substituted or unsubstituted alkyl group. Furthermore, the meta position and the para position with respect to the hydroxy group are substituted with an arbitrary substituent. May be.)

  (D) Specific examples of the sterically hindered phenol include 2,2′-methylene-bis (4-methyl-6-tert-butylphenol), 4,4′-methylene-bis (2,6-di-t-). Butylphenol), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 3,5-di-tert-butyl-4-hydroxybenzyl Dimethylamine, stearyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate, diethyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate, 2,6,7-trioxa-1-phospha -Bicyclo [2,2,2] -oct-4-yl-methyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate, 3,5-di-tert-butyl-4-hydroxyphen 3,5-distearyl-thiotriazylamine, 2- (4-hydroxy-3,5-di-t-butylphenyl) -5-chlorobenzotriazole, 2,6-di-t-butyl-4 -Hydroxymethylphenol, 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, N, N'-hexamethylene Bis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), octadecyl-3- (3,5-di-butyl-4-hydroxyphenyl) propionate, 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxypheny ) Propionate], triethylene glycol-bis [3- (3,5-dimethyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) ) Propionate] triethylene glycol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2′-thiodiethyl-bis [3- (3,5-di-t-) Butyl-4-hydroxyphenyl) propionate] and the like. Among these, a compound having at least one structure represented by the following general formula (4) is particularly preferable.

(In formula (4), R ₅ and R ₆ have the same meaning as in general formula (3)).
Preferred examples of the compound having the structure of the formula (4) include N, N-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), octadecyl -3- (3,5-di-butyl-4-hydroxyphenyl) propionate, 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], penta Erythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3,5-dimethyl-4-hydroxyphenyl) propionate], tri Ethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], triethyleneglycol -Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2'-thiodiethyl-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate].

  Further, among these, 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- ( 3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3,5-dimethyl-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-hydroxyphenyl) propionate].

  The (E) amino-substituted triazine compound used in the present invention is a substituted triazine having a structure represented by the following general formula (1), or an initial polycondensate of the substituted triazine and formaldehyde.

(In the general formula (1), R ₁ , R ₂ and R ₃ are each independently a hydrogen atom, halogen atom, hydroxyl group, mercapto group, alkyl group, aralkyl group, aryl group, cycloalkyl group, amino group or A substituted amino group, at least one of which represents an amino group or a substituted amino group.

  Specific examples of the amino-substituted triazine compound 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, ameline (N, N, N ′, N′— Tiger cyanoethyl benzoguanamine), and the like. Moreover, as an initial stage polycondensation product of an amino substituted triazine compound and formaldehyde, the initial stage polycondensation product of said amino substituted triazine compound and formaldehyde, etc. are mentioned. As the (E) amino-substituted triazine compound used in the present invention, melamine, methylol melamine, benzoguanamine, and a water-soluble melamine-formaldehyde resin are particularly preferable.

  The metal-containing compound (F) used in the present invention is selected from alkali metals such as sodium and potassium, or alkaline earth metal hydroxides such as calcium and magnesium, inorganic acid salts, and alkoxides. Examples of the inorganic acid salt include carbonates, phosphates, silicates, borates and the like of these metals, and examples of the alkoxide include methoxide and ethoxide. The metal-containing compound (E) is preferably an alkaline earth metal hydroxide, inorganic acid salt or alkoxide, and more preferably calcium hydroxide, magnesium hydroxide, calcium carbonate, and magnesium carbonate.

One part of the above components (B) to (F) is known as a resin stabilizer, and some of them are already blended in the polyacetal resin. However, the resin composition of the present invention has the components (B) to (B) to By including all of the component (F) at a specific quantitative ratio, both thermal stability and reduced formaldehyde generation can be achieved.
The amount of (B) alkylene urea in the resin composition of the present invention is 0.01 to 0.9 parts by weight, preferably 0.02 to 0.8 parts by weight, based on 100 parts by weight of (A) polyacetal resin. Preferably it is 0.03-0.8 weight part. (C) The amount of the aliphatic hydrazide compound is 0.01 to 5 parts by weight, preferably 0.02 to 3 parts by weight, more preferably 0.03 to 1 part by weight, based on 100 parts by weight of the (A) polyacetal resin. is there. The amount of (D) sterically hindered phenol is 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of (A) polyacetal resin. (E) The amount of the amino-substituted triazine compound is 0.01 to 7 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the polyacetal resin. (F) The amount of the metal-containing compound is 0.004 to 5 parts by weight, preferably 0.005 to 5 parts by weight, based on 100 parts by weight of the polyacetal resin.
The weight ratio of (B) alkylene urea to (C) aliphatic aldehyde compound is 0.1-2. If the blending ratio is greater than 2, mold deposits during molding increase, and if the blending ratio is less than 0.1, the amount of generated formaldehyde increases, which is not preferable. The blending ratio is preferably 0.2 to 1.5, and more preferably 0.3 to 1.2.

  In addition to the above components, the polyacetal resin composition of the present invention can contain known additives and / or fillers as long as the object of the present invention is not impaired. Examples of the additive include a lubricant, an antistatic agent, an ultraviolet absorber, and a light stabilizer. Examples of the filler include glass fiber, glass flake, glass bead, talc, mica, calcium carbonate, potassium titanate whisker, and the like. Further, pigments and dyes can be added to achieve a desired color.

  The production method of the polyacetal resin composition of the present invention is not particularly limited, and is prepared by mixing and kneading the above components (A) to (F), and if necessary, other resin additives and / or fillers. can do. The mixing / kneading method is not particularly limited, and includes a method using a conventionally known mixing / kneading apparatus. The kneading is preferably performed at a temperature equal to or higher than the temperature at which the polyacetal resin melts, specifically, at a temperature higher than the flow start temperature of the polyacetal resin as a raw material (generally, 1700C or higher).

  Specifically, for example, for (A) polyacetal resin, (B) alkylene urea, (C) aliphatic hydrazide compound, (D) sterically hindered phenol, (E) amino-substituted triazine compound, (F) metal Add the compound in the specified amount at the same time, add other resin additives as necessary, mix by tumbler type blender, etc., and melt knead the resulting mixture with a single screw or twin screw extruder Then, a polyacetal resin composition having a desired composition can be obtained by extruding into a strand shape and pelletizing.

The resin composition of the present invention can produce a molded product by adopting any molding method known as a molding method of a thermoplastic resin. For example, molding methods such as injection molding, extrusion molding, and blow molding are applied, but the present invention is not limited to these methods.
The polyacetal resin composition obtained in the present invention is not only excellent in thermal stability, but also can suppress the generation of aldehydes in the product, particularly formaldehyde. It is extremely useful for parts, building material parts, and electrical parts.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the specific examples shown below as long as the gist thereof is not exceeded.
In addition, the material used by the Example and the comparative example and the physical-property measuring method are shown below.

<Material>
(1) Polyacetal resin: Acetal copolymer using 4.2% by weight (based on the total amount of resin) of 1,3-dioxolane as a comonomer, melt index (10.5 g / 10 min).
(2) Alkylene urea: ethylene urea.

(3) Aliphatic hydrazide compound-1: solubility of 0.01 g or less with respect to 100 g (20 ° C.) of dodecanedioic acid dihydrazide and water.
(4) Aliphatic hydrazide compound-2: Sebacic acid dihydrazide, solubility 0.01 g or less with respect to 100 g (20 ° C.) of water.
(5) Aliphatic hydrazide compound-3: Adipic acid dihydrazide, solubility 9.1 g in 100 g (20 ° C.) of water.

(6) Steric hindrance phenol: triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], trade name “Irganox 245”, Ciba Specialty Chemicals Made.

(7) Amino-substituted triazine compound: melamine.
(8) Metal-containing compound: magnesium hydroxide.

<Physical property measurement method>
(A) Generated formaldehyde amount: 100 mm × 40 mm × 2 mm flat plate obtained by injection molding the resin composition pellets obtained in Examples or Comparative Examples at a cylinder temperature of 215 ° C. using a PS-40E5ASE molding machine manufactured by Nissei Plastic Industry Co., Ltd. Was measured according to the following procedure in accordance with the method described in German Automobile Manufacturers Association Standard VDA275 (automobile interior parts-quantification of formaldehyde emission amount by revised flask method) on the next day of molding.
(i) 50 ml of distilled water was put in a polyethylene container, the test piece was hung, the lid was closed, and it was heated to 60 ° C. for 3 hours in a sealed state.
(ii) After leaving at room temperature for 3 hours, the test piece is taken out.
(iii) The formaldehyde concentration absorbed in distilled water in the polyethylene container is measured by an acetylacetone colorimetric method with a UV-spectrometer.

(B) Thermal stability: The resin composition pellets obtained in Examples or Comparative Examples were molded at a cylinder temperature of 215 ° C. for 10 minutes using a PS-40E5ASE molding machine manufactured by Nissei Plastic Industry Co., Ltd. 100 mm × 40 mm × A flat plate having a thickness of 2 mm was used as a test piece, and molding stability (colorability, presence / absence of silver generation, etc.) during residence was evaluated according to the following criteria.
◎: Thermal stability is very good ○: Thermal stability is good △: Thermal stability is normal ×: Thermal stability is poor

(C) Mold fouling property: The resin composition pellets obtained in the examples or comparative examples were molded at a molding temperature of 230 ° C. using a mini mat M8 / 7A molding machine manufactured by Sumitomo Heavy Industries, Ltd. and a drop mold. 500 shot continuous injection molding was performed at a mold temperature of 35 ° C., and after completion, the presence or absence of deposits on the mold was observed and evaluated according to the following criteria.
A: Very little deposit on the mold B: A little deposit on the mold B: A lot of deposit on the mold
X: There are very many deposits on the mold.

[Examples 1-5, Comparative Examples 1-9]
The raw materials were weighed according to the formulation shown in Tables 1 to 3 below, and mixed by a tumbler type blender. Next, the obtained mixture was melt-kneaded and pelletized with a 40 mmφ single screw extruder (manufactured by Tanabe Plastics Co., Ltd., model: VS-40) at a cylinder temperature of 200 ° C. and a discharge rate of 13 kg / hr. After obtaining the resin composition, a test piece was molded by the above-described method, and the amount of formaldehyde generated in the molded product, the thermal stability during molding, and the presence or absence of mold deposits were measured and evaluated. The results are shown in Tables 1 and 2.
The amount of formaldehyde generated was a relative value when the value in Comparative Example 1 was used as the standard (1.00).

  As is apparent from Tables 1 to 3, the polyacetal resin compositions of Examples 1 to 5 that satisfy the provisions of the present invention have significantly reduced formaldehyde generation, good thermal stability, and deposits on the mold. The composition of Comparative Examples 1 to 6 and Comparative Example 9 lacking at least one of the components (B) to (F), although the amount of (mold deposit) is small, is sufficiently improved in the amount of formaldehyde generated and the amount of deposits on the mold. It has not been. Further, the composition of Comparative Examples 7 and 8 containing the components (B) to (F) but the ratio of (B) / (C) is outside the scope of the present invention, the solubility in 100 g of water at 20 ° C. is 1 g. The compositions of Comparative Examples 5 and 6 using the above aliphatic hydrazide compound-3 also have drawbacks such as the amount of formaldehyde generated is not sufficiently reduced or the amount of deposits on the mold increases.

Claims (5)

(A) polyacetal resin, (B) 0.01 to 0.9 parts by weight of alkylene urea, (C) 0.01 to 5 parts by weight of an aliphatic hydrazide compound having a solubility in 100 g H ₂ O at 20 ° C. of less than 1 g, ( D) 0.01-5 parts by weight of sterically hindered phenol, (E) 0.01-7 parts by weight of amino-substituted triazine compound, and (F) alkali metal or alkaline earth metal hydroxide, inorganic acid salt or alkoxide. A polyacetal resin composition comprising 0.004 to 5 parts by weight of at least one metal-containing compound selected and a weight ratio of (B) / (C) of 0.1 to 2. 2. The polyacetal resin composition according to claim 1, wherein (B) the alkylene urea is ethylene urea. (E) The amino-substituted triazine compound is at least one selected from substituted triazines having a structure represented by the following general formula (1), or an initial polycondensate of the substituted triazines and formaldehyde. The polyacetal resin composition according to claim 1 or 2,
(In the general formula (1), R ₁ , R ₂ and R ₃ are each independently a hydrogen atom, halogen atom, hydroxyl group, mercapto group, alkyl group, aralkyl group, aryl group, cycloalkyl group, amino group or A substituted amino group, at least one of which represents an amino group or a substituted amino group.   The polyacetal resin composition according to any one of claims 1 to 3, wherein the metal-containing compound (F) is at least one selected from calcium hydroxide, magnesium hydroxide, calcium carbonate, and magnesium carbonate. . The molded article formed from the polyacetal resin composition in any one of Claims 1-4.