JP4982947B2 - Method for producing polyoxymethylene resin composition - Google Patents

Description

The present invention relates to a method for producing a polyoxymethylene resin composition, and more particularly, to a method for producing a polyoxymethylene resin composition having excellent thermal stability in which the amount of formaldehyde generated is significantly reduced.

  Polyoxymethylene resin has been used extensively for automobile parts, electrical / electronic equipment parts, general functional parts, etc. because of its excellent moldability, mechanical strength, creep characteristics, lubrication characteristics, and electrical characteristics. ing. However, recently, the required characteristics of such parts are becoming more sophisticated and diversified, not only due to improved functionality such as mechanical strength and friction and wear characteristics, but also due to problems specific to polyoxymethylene resin, such as thermal decomposition and ultraviolet decomposition. Suppressing the formaldehyde that is generated has become a major issue every day.

Patent Document 1 discloses that the amount of formaldehyde generated can be reduced by adding a hydrazide compound to a polyoxymethylene resin. However, by simply adding a hydrazide compound, the amount of generated formaldehyde can be reduced, but the thermal stability has not been sufficiently improved. Patent Documents 2 and 3 disclose the combined use of an alkali or alkaline earth metal compound and a hydrazide derivative or melamine. However, in the methods described in these patent documents, what is specifically used as an alkali or alkaline earth metal compound is a metal hydroxide such as sodium hydroxide or magnesium hydroxide, or a saturation such as calcium stearate or sodium stearate. Although it is a metal salt of a fatty acid, although improvement in thermal stability is recognized, the amount of formaldehyde generated from the polyoxymethylene resin composition is insufficiently reduced.
JP 04-345648 A (pages 2 to 5) JP 06-322230 A (pages 2 to 12) JP 07-33953 A (pages 2 to 10)

  An object of the present invention is to obtain a polyoxymethylene resin composition excellent in thermal stability in which the amount of formaldehyde generated is significantly reduced.

  The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above-mentioned problems of the prior art.

That is, the present invention
(1) The mixture of trioxane and cyclic ether is selected from the group consisting of boron trifluoride, boron trifluoride hydrate, and coordination compounds of boron trifluoride and organic compounds containing oxygen or sulfur atoms. Polymerization is carried out in the presence of at least one polymerization catalyst to obtain a polyoxymethylene crude polymer containing oxymethylene units and other oxyalkylene units, and 100 parts by weight of the polyoxymethylene crude polymer is subjected to (E ) 0.01-5 parts by weight of a hindered amine compound, (A) 0.01-5 parts by weight of a hindered phenol antioxidant, ( B-1) 0.01-5 parts by weight of tripotassium citrate , (C ) Preparation of polyoxymethylene resin composition characterized by blending 0.01 to 5 parts by weight of hydrazide compound and heating at a temperature of 100 to 260 ° C. Law,

( 2) After completion of the polymerization, (D) 0.01-5 parts by weight of an ultraviolet absorber is further blended, and the method for producing a polyoxymethylene resin composition according to (1),
(3) After the completion of polymerization, (F) 0.01 to 5 parts by weight of a higher fatty acid amide is further blended, and the method for producing a polyoxymethylene resin composition according to (1) or (2), 4) The (C) hydrazide compound is one or more selected from carbodihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and isophthalic acid dihydrazide (1) to It is a manufacturing method of the polyoxymethylene resin composition in any one of (3).

  According to the present invention, it is possible to obtain a polyoxymethylene resin composition that is excellent in thermal stability and has a significantly reduced amount of generated formaldehyde.

  Hereinafter, the present invention will be described in detail.

(1) Polyoxymethylene resin The polyoxymethylene resin in the present invention is a homopolymer or copolymer having an oxymethylene unit. In the present invention, the polyoxymethylene resin is mainly composed of oxymethylene units, and has 2 to 8 polymethylene units in the main chain. It is preferable to use an oxymethylene copolymer containing not more than 15% by weight of oxyalkylene units having adjacent carbon atoms.

As an example of a typical method for producing an oxymethylene copolymer, a high purity trioxane and a copolymer component such as ethylene oxide or 1,3-dioxolane are introduced into an organic solvent such as cyclohexane, and boron trifluoride diethyl ether complex is prepared. A method of producing by cationic polymerization using a Lewis acid catalyst, such as deactivation of the catalyst and stabilization of the end groups (the polymer before stabilization is a polyoxymethylene crude polymer, the polymer after stabilization is This is called polyoxymethylene resin) , or after introducing bulk polymerization with trioxane, copolymerization component and catalyst into a self-cleaning stirrer without using any solvent, and further decomposing and removing unstable terminals. (The polymer before the unstable end is decomposed and removed, i.e. Reoxymethylene crude polymer and stabilized polymer are called polyoxymethylene resin) .

  The viscosity of these polymers is not particularly limited as long as it can be used as a molding material, but the melt flow rate (MFR) can be measured by the ASTM D1238 method, and the temperature is 190 ° C. and the measurement load is 2,160 g. Below, it is preferable that it is a thing of the range of MFR 0.1-100g / 10min, and it is especially preferable that it is a thing of 1.0-50g / 10min.

(2) (A) Hindered phenolic antioxidant The hindered phenolic antioxidant used in the present invention preferably has a molecular weight of 400 or more. 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], triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate], 2,2′-methylenebis- (4-methyl-tert-butyl) Tilphenol), 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) propionyl hexamethylenediamine, N, N'-tetramethylene-bis-3- (3'-methyl-5'-t-butyl-4'- Hydroxyphenol) propionyldiamine, N, N′-bis- [3- (3,5-di-t-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 There are oxyamides 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. One type of these antioxidants may be used, or two or more types may be used in combination. Moreover, 0.01-5 weight part can be mix | blended with respect to 100 weight part of polyoxymethylene crude polymers, Most preferably, it is 0.1-3.0 weight part. If it is less than 0.01 part by weight, the effect of thermal stability is not sufficient, and if it exceeds 5 parts by weight, the antioxidant is precipitated in the form of white powder on the surface of the colored polyoxymethylene resin composition, thereby reducing the commercial value. Is not preferable.

(3) In the present invention, tripotassium citrate is used as the component (B-1).

In this invention, the compounding quantity of (B-1) component is 0.01-5 weight part with respect to 100 weight part of (A) polyoxymethylene crude polymers, Preferably it is 0.02-2 weight part, Especially preferably, 0.03 to 1 part by weight. If the blending amount of the component (B-1) is less than 0.01 parts by weight, the improvement in thermal stability is insufficient, and if it exceeds 5 parts by weight, the polyoxymethylene resin is decomposed and foamed and the stability is impaired. become.

(4) (C) About the hydrazide compound Examples of the hydrazide compound used in the present invention include hydrazide compounds such as monocarboxylic acid hydrazide, dicarboxylic acid monohydrazide, dicarboxylic acid dihydrazide, and polycarboxylic acid polyhydrazide. Among them, monocarboxylic acid dihydrazide Dicarboxylic acid dihydrazide is preferred.

  Specific examples of the monocarboxylic acid dihydrazide include carbonyl dihydrazide. Specific examples of the dicarboxylic acid dihydrazide include adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and isophthalic acid dihydrazide.

  Of these, sebacic acid dihydrazide is particularly preferred. These compounds can be used alone or in combination of two or more.

In the present invention, the blending amount of the (C) hydrazide compound is 0.01 to 5 parts by weight, preferably 0.02 to 2 parts by weight, particularly preferably 0 to 100 parts by weight of the (A) polyoxymethylene crude polymer. 0.03 to 1 part by weight. If it is less than 0.01 part by weight, the action of capturing formaldehyde generated by heating is insufficient, and if it exceeds 5 parts by weight, the polyoxymethylene resin is colored.

(5) (D) Ultraviolet Absorber In the present invention, (D) an ultraviolet absorber can be blended, and specific examples thereof include benzotriazole-based materials, benzophenone-based materials, and oxalic acid anilide-based materials. 1 type or 2 types or more selected from the group which consists of these are preferable, and it is also possible to use a hindered amine stabilizer and an ultraviolet absorber together.

Examples of benzotriazole-based materials 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 benzophenone-based materials include octabenzone, examples of oxalic acid alinide-based materials include 2-ethoxy-2′-ethyloxalic acid bisanilide, 2-ethoxy-5-t-butyl-2′-ethyloxa. Rick acid bisanilide, 2-ethoxy-3'-dodecyl oxalic acid bisanilide, etc. are mentioned. Among them, 2- [2′-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] benzotriazole, 2- (2′-hydroxy-3,5-di-t-butyl-phenyl) benzotriazole Etc. are preferable. Each of these substances may be used alone or in combination of two or more. The addition amount in the case of adding these ultraviolet absorbers can be 0.01 to 5 parts by weight, particularly preferably 1 to 2 parts by weight, per 100 parts by weight of the polyoxymethylene crude polymer .

(6) (E) Hindered amine stabilizer In the present invention, (E) a hindered amine stabilizer is blended . The hindered amine stabilizer used preferably has a molecular weight of 400 or more. Specifically, bis (1,2,2,6,6-pentamethyl-4-piperdinyl) sebacate, dimethyl succinate · 1- (2- Hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, N, N′-bis (3-aminopropyl) ethylenediamine · 2,4-bis [N-butyl-N- ( 1,2,2,6,6-pentamethyl-4-piperidinyl) amino] -6-chloro-1,3,5-triazine condensate, poly [{6- (1,1,3,3-tetramethylbutyl) ) Amino-1,3,5-triazine-2,4-diyl} {2,2,6,6-tetramethyl-4-piperidinyl} imino], bis (2,2,6,6-tetramethyl-4) -Piperidinyl) Kate and the like. Among them, bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, dimethyl succinate 1- ( 2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, N, N′-bis (3-aminopropyl) ethylenediamine · 2,4-bis [N-butyl-N -(1,2,2,6,6-pentamethyl-4-piperidinyl) amino] -6-chloro-1,3,5-triazine condensate, poly [{6- (1,1,3,3-tetra Methylbutyl) amino-1,3,5-triazine-2,4-diyl} {2,2,6,6-tetramethyl-4-piperidyl) imino}] is particularly preferred. The addition amount in the case of adding these hindered amine stabilizers may be 0.01 to 5 parts by weight, particularly 0.02 to 2 parts by weight, based on 100 parts by weight of the polyoxymethylene crude polymer .

(7) (F) Higher fatty acid amide In the present invention, (F) a higher fatty acid amide, that is, a higher fatty acid having 12 or more carbon atoms (monovalent or divalent higher fatty acid) and an amine (monoamine, diamine, polyamine, etc.) ) And higher fatty acid amides (monoamide, bisamide, etc.) can be used. A specific example of monoamide is stearylamide. Specific examples of bisamide include methylene bisstearylamide and ethylene bisstearylamide. The addition amount in the case of adding these higher fatty acid amides can be 0.01 to 5 parts by weight, particularly preferably 0.02 to 1.5 parts by weight, per 100 parts by weight of the polyoxymethylene crude polymer. .

(8) (G) Amino-substituted triazine compound In the present invention, (G) an amino-substituted triazine compound can be further blended. By using this together with (C) a hydrazide compound, Combined with the blending, it is possible to further reduce the generation of formaldehyde. Specific examples include melamine, melamine derivatives, urea, etc. Among them, melamine is preferable. When the amino-substituted triazine compound is added, 0.01 to 5 parts by weight can be blended with 100 parts by weight of the polyoxymethylene crude polymer , and 0.03 to 1 part by weight is particularly preferable. When used in combination with (C) a hydrazide compound, (C) :( G) is preferably in the range of 1:10 to 10: 1.

  Furthermore, in the present invention, other inorganic fillers, conductive carbon black, metal powder, polyolefin resin, acrylic resin, styrene resin, polycarbonate resin are added to the polyoxymethylene resin composition of the present invention within a range not impairing the effects of the present invention. , Thermoplastic resins represented by uncured epoxy resins or modified products thereof, polyurethane elastomers, polyester elastomers, polystyrene elastomers, polyamide elastomers and the like can be blended. .

(9) As a method for producing the polyoxymethylene resin composition of the present invention, a generally known method can be adopted. As a preferred method, a mixture of trioxane and cyclic ether is obtained by boron trifluoride or boron trifluoride hydration. And oxymethylene units and other oxyalkylene units by polymerizing in the presence of at least one polymerization catalyst selected from the group consisting of coordination compounds of boron trifluoride and organic compounds containing oxygen or sulfur atoms (B) component and (C) hydrazide compound are added to 100 parts by weight of a polyoxymethylene crude polymer obtained by producing an oxymethylene copolymer and deactivating the polymerization catalyst after completion of the polymerization, and a temperature of 100 to 260 ° C. Heat in range. When adding the component (B) to the polyoxymethylene crude polymer, it is more preferable to use a mixer to mix at a temperature not higher than the melting point of the polymer and then to heat in a temperature range of 100 to 260 ° C. More preferably, the component (B) is added to the polyoxymethylene crude polymer, mixed using a mixer, and then heated and kneaded in a temperature range of 170 to 260 ° C. using a vented twin screw extruder. .

Further, after the polymerization of the polyoxymethylene crude polymer is completed, (E) a hindered amine compound is added as a deactivator and / or heat stabilizer for the polymerization catalyst , and (A) a hindered phenol compound (B-1) Method of adding metal salt of carboxylic acid represented by formula (I), polyoxymethylene crude polymer and (B) component, (C) hydrazide compound, (E) hindered amine compound, (D) UV as optional component The absorbent and the ( F) higher fatty acid amide may be mixed in the form of pellets, powder, or granules and melt processed as they are, but a method of melting and mixing with a Banbury mixer, roll, extruder or the like can also be adopted.

  The polyoxymethylene resin composition of the present invention thus obtained can be molded by a generally known method such as injection molding, extrusion molding, press molding, heat and pressure molding, stamping molding or the like.

  Next, the present invention will be described with reference to examples and comparative examples. The present invention is not limited to these examples, and can be implemented with appropriate modifications within the scope of the gist of the present invention.

  Moreover, the generation | occurrence | production situation of formaldehyde odor at the time of the continuous molding shown in an Example and a comparative example, and the amount of formaldehyde generated at the time of a heating were measured or observed as follows.

  Molding: An ASTM No. 1 dumbbell specimen was injection molded using an injection molding machine with 5 ounce injection capability, setting the cylinder temperature to 190 ° C., the mold temperature to 65 ° C., and the molding cycle to 50 seconds.

Occurrence of formaldehyde odor during continuous molding:
10,000 shots of continuous molding were performed under the molding conditions described above, and the occurrence of formaldehyde odor at that time was evaluated as follows.
A: There is no formaldehyde odor.
○: Almost no formaldehyde odor.
Δ: Slightly formaldehyde odor
X: Formaldehyde gas is considerably generated, and eyes and throat become sore when in the place, or formaldehyde gas is generated so much that the person cannot stay there.

Formaldehyde amount during heating:
About 1 g of pellets dried for 3 hours in a hot air oven at 80 ° C. is precisely weighed and left in a container with excellent heat resistance in a nitrogen atmosphere at 240 ° C. for 15 minutes, and the generated formaldehyde is trapped in an aqueous methanol solution. . The amount of formaldehyde in the aqueous methanol solution was quantified by oxidation-reduction titration, and the amount of formaldehyde generated during heating was measured.

  The contents of each additive used in Examples and Comparative Examples are shown below.

Production of crude polyoxymethylene polymer A triaxial (22.5 kg / h), 1,3-dioxolane (100 mm diameter, cylinder length (L) / cylinder diameter (D) = 10.2) and trioxane (22.5 kg / h) 700 g / h), 100 ppm of boron trifluoride / diethyl etherate (2.5% benzene solution) as a catalyst with respect to trioxane, and 600 ppm of methylal as a molecular weight regulator were respectively supplied to carry out continuous polymerization. The polymerization was performed by controlling the outer jacket at 60 ° C. and rotating at 100 rpm. Methylal was dissolved in trioxane. Further, a premixing zone was provided so that 1,3-dioxolane and the catalyst solution were premixed immediately before being supplied to the polymerization machine. The polyoxymethylene crude polymer was obtained as a white fine powder at 22.4 kg / h.

(A) Hindered phenolic antioxidant
[Triethylene glycol-bis {3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate}] (A): “Irganox” 245 manufactured by Ciba Geigy Specialty Co., Ltd. was used.

(B-1) Alkali metal salt of carboxylic acid
Sodium lactate (B-1-2), potassium lactate (B-1-3), sodium malate (B-1-4), click ene trisodium (B-1-6), tripotassium citrate ( B-1-7), sodium tartrate (B-1-8): both used were manufactured by Kanto Chemical Co., Inc.

(B-2) Alkali metal salt or alkaline earth metal salt of saturated fatty acid
12-hydroxy calcium stearate (B-2): Dainichi Chemical "Die Wax OHC" was used.

(B-3) Metal hydroxide
Calcium hydroxide (B-3): manufactured by Kanto Chemical Co., Inc. was used.

(C) Hydrazide compound
Sebacic acid dihydrazide (C-1), adipic acid dihydrazide (C-2), carbodihydrazide (C-3), and isophthalic acid dihydrazide (C-4): all manufactured by Nippon Hydrazine Kogyo Co., Ltd. were used.

(D) UV absorber
[2- {2-Hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl} benzotriazole] (D): “Tinuvin” 234D manufactured by Ciba Geigy Specialty Company was used.

(E) Hindered amine stabilizer
Bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (E): Sankyo Pharmaceutical “Sanol” LS765 was used.

(F) Higher fatty acid amide
Ethylene bisstearylamide: Lion “Armowax” EBS was used.

(G) Amino-substituted triazine compound
Melamine: Kanto Chemical Co., Ltd. product was used.

Example 1-4, Comparative Example 1-35
9.0 g of “Sanol” LS765 [Sankyo Pharmaceutical, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) per 5 kg of the fine powder of the polyoxymethylene crude polymer obtained as described above ) Sebacate, tertiary amine type hindered amine compound] in 50 ml of benzene was added, and the mixture was stirred for 3 minutes in a Henschel mixer to deactivate the catalyst.

(A) “Irganox” 245 [Ciba Geigy, triethylene glycol-bis {3- (3-t-butyl-), based on 5 kg (100 parts by weight) of the polyoxymethylene crude polymer after deactivation of the catalyst. 5-methyl-4-hydroxyphenyl) propionate}, hindered phenol compound] 25 g, (B-1) alkali metal salt of carboxylic acid represented by general formula (I) (B-1-2-8) (C) Pre-mixed the hydrazide compounds (C-1 to 4) with the compositions shown in Tables 1 and 2, and the pressure was reduced at a cylinder temperature of 210 ° C. and 10 Torr using a vented twin-screw 30 mm diameter extruder manufactured by Nippon Steel Works. For 5 minutes.

  The resulting composition was extruded as a strand and pelletized with a cutter. The pellets were dried in a hot air circulating oven at 80 ° C. for 3 hours, and then molded and subjected to measurement of mechanical properties and color tone, and the generation state of formaldehyde odor during continuous molding was evaluated. Furthermore, the amount of formaldehyde generated during heating and the MI value were evaluated using the dried pellets. These results are summarized in Tables 1 and 2.

Comparative Examples 36 and 37
A polyoxymethylene resin composition was obtained in the same manner as in Example 1 except that (B-3) calcium hydroxide was blended in the composition shown in Table 2 instead of the component (B-1). Furthermore, in Comparative Example 10, melamine was blended in the composition shown in Table 2 instead of (C) the hydrazide compound. Evaluation was performed after injection molding, and the results are shown in Table 2.

Comparative Examples 38 and 39
Example 1 and Example except that sodium lactate (B-1-2) and 12-hydroxy-calcium stearate (B-2) were used in combination with the composition shown in Table 3 as the component (B-1). In the same manner as in Example 4, a polyoxymethylene resin composition was obtained. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Examples 40 and 41
(B-1) Sodium lactate (B-1-2) as a component, (C) Sebacic acid dihydrazide (C-1), and isophthalic acid dihydrazide (C-4) as hydrazide compounds are shown in Table 3 and melamine, respectively. A polyoxymethylene resin composition was obtained in the same manner as in Example 1 and Example 4 except that they were used in combination. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Examples 42 and 43
(B-1) Sodium lactate (B-1-2) as a component, (C) Sebacic acid dihydrazide (C-1), isophthalic acid dihydrazide (C-4) as a hydrazide compound are blended in the composition shown in Table 3. Further, a polyoxymethylene resin composition was obtained in the same manner as in Examples 1 and 4 except that (D) an ultraviolet absorber was blended in the composition shown in Table 3. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Example 44
A polyoxymethylene resin composition was obtained in the same manner as in Example 1 except that (E) a hindered amine compound was added to Comparative Example 43 in the composition shown in Table 3. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Example 45
A polyoxymethylene resin composition was obtained in the same manner as in Example 1 except that (F) a higher fatty acid amide was further added to Comparative Example 44 in the composition shown in Table 3. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Example 46
In Comparative Example 45 , the same procedure as in Example 1 was carried out except that sodium lactate (B-1-2) and 12-hydroxy-calcium stearate (B-2) were combined and blended in the composition shown in Table 3. An oxymethylene resin composition was obtained. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Example 47
In Comparative Example 45 , a polyoxymethylene resin composition was obtained in the same manner as in Example 1 except that isophthalic acid dihydrazide (C-4) and melamine were combined and blended in the composition shown in Table 3. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Example 48
In Comparative Example 45 , sodium lactate (B-1-2) and 12-hydroxy-calcium stearate (B-2), and isophthalic acid dihydrazide (C-4) and melamine were used together in the composition shown in Table 3. A polyoxymethylene resin composition was obtained in the same manner as in Example 1 except that it was blended. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Example 11
Example except that sodium lactate (B-1-2) and calcium hydroxide (B-3) were combined in the composition shown in Table 3 and sebacic acid dihydrazide (C-1) was not used. In the same manner as in Example 5, a polyoxymethylene resin composition was obtained. Evaluation was performed after injection molding, and the results are shown in Table 3.

Comparative Example 12
In Comparative Example 11, a polyoxymethylene resin composition was obtained in the same manner as in Example 5, except that melamine was used in combination with the composition shown in Table 3 instead of (C) the hydrazide compound. Evaluation was performed after injection molding, and the results are shown in Table 3.

  The following matters are clear from the results of Tables 1 and 2.

(1) A mixture of trioxane and a cyclic ether is selected from the group consisting of boron trifluoride, boron trifluoride hydrate, and a coordination compound of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom. A polyoxymethylene crude polymer polymerized in the presence of a kind of polymerization catalyst is obtained, and (E) a hindered amine-based compound and (A) a hindered phenol-based oxidation are obtained after completion of the polymerization with respect to 100 parts by weight of the polyoxymethylene crude polymer. 0.5 parts of inhibitor, 0.1 parts by weight of (B-1) tripotassium citrate , and (C) hydrazide compound are mixed and heated, so that there is very little formaldehyde odor and mold deposit at the time of molding. A polyoxymethylene resin composition having excellent properties can be obtained. (Examples 1 to 4)

(11) When the component (C) is less than 0.01 parts by weight, the formaldehyde odor and mold deposit at the time of molding deteriorate and the thermal stability becomes insufficient. (Comparative Examples 3 and 4)
(12) When the component (B-1) and the component (C) are less than 0.01 parts by weight or more than 5 parts by weight, the formaldehyde odor and mold deposit at the time of molding are deteriorated, resulting in poor thermal stability. It will be enough. (Comparative Examples 5 to 8)
(13) When a metal hydroxide such as calcium hydroxide is added instead of the component (B-1), the formaldehyde odor and mold deposit during molding deteriorate and the thermal stability becomes insufficient. . (Comparative Examples 9 and 10)
(14) When (B-1) and a metal hydroxide such as calcium hydroxide are added in combination, the formaldehyde odor and mold deposit at the time of molding deteriorate and the thermal stability becomes insufficient. (Comparative Examples 11 and 12)

  Since the present invention provides a polyoxymethylene resin composition having excellent thermal stability with significantly reduced formaldehyde generation, it can be used in practical applications such as automotive parts, electrical / electronic equipment parts, and general functional parts. Can do.

Claims (4)

A mixture of trioxane and a cyclic ether is at least one selected from the group consisting of boron trifluoride, boron trifluoride hydrate, and a coordination compound of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom. Polymerization is carried out in the presence of a polymerization catalyst to obtain a polyoxymethylene crude polymer containing an oxymethylene unit and another oxyalkylene unit. 0.01-5 parts by weight of compound, (A) 0.01-5 parts by weight of hindered phenol antioxidant, (B-1) 0.01-5 parts by weight of tripotassium citrate , (C) hydrazide compound 0 A method for producing a polyoxymethylene resin composition, comprising blending 0.01 to 5 parts by weight and heating at a temperature of 100 to 260 ° C. 2. The method for producing a polyoxymethylene resin composition according to claim 1, further comprising (D) 0.01 to 5 parts by weight of an ultraviolet absorber after completion of the polymerization. 3. The method for producing a polyoxymethylene resin composition according to claim 1, wherein 0.01 to 5 parts by weight of (F) a higher fatty acid amide is further blended after completion of the polymerization. (C) The hydrazide compound is one or more selected from carbodihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and isophthalic acid dihydrazide. The manufacturing method of the polyoxymethylene resin composition in any one.