PROCESS FOR PRODUCING POLYACETAL RESIN COMPOSITION

Abstract

A polyacetal resin composition. An aliphatic polycarboxylic acid having four or more carbons and two or more carboxyl groups and a hindered-phenol antioxidant are incorporated into a polyacetal copolymer obtained by copolymerizing trioxane as a major monomer with a cyclic ether and/or cyclic formal each having at least one carbon-carbon bond as a comonomer using a specific heteropoly acid as a polymerization catalyst, adding, to the resultant reaction product, a compound which is any of the carbonates, hydrogen carbonates, and carboxylates of alkali metal elements or alkaline-earth metal elements, the hydrates of these, and the hydroxides of alkali metal elements or alkaline-earth metal elements, and melt-kneading the mixture to deactivate the polymerization catalyst.

Claims

1. A method for producing a polyacetal resin composition, comprising: adding a compound (d) which is a carbonate, hydrogen carbonate, or carboxylate of an alkali metal element or an alkaline earth metal element or a hydrate thereof or a hydroxide of an alkali metal element or an alkaline earth metal element to a reaction product prepared by copolymerization of trioxane as a main monomer (a) and a cyclic ether and/or cyclic formal having at least one carbon-carbon bond as a comonomer (b) using a heteropoly acid represented by Formula (1) as a polymerization catalyst (c); melt-kneading the mixture to deactivate the polymerization catalyst (c) and prepare a polyacetal copolymer; and adding 0.002 parts by weight or more and 0.1 parts by weight or less of an aliphatic polycarboxylic acid (e) having four or more carbons and two or more carboxyl groups and 0.01 parts by weight or more and 0.5 parts by weight or less of a hindered phenolic antioxidant (f) to 100 parts by weight of the polyacetal copolymer,
H.sub.m[M.sup.1.sub.x.M.sup.2.sub.yO.sub.z].nH.sub.2O (1) where M.sup.1 represents at least one central element selected from the group consisting of P and Si; M.sup.2 represents one or more coordination elements selected from the group consisting of W, Mo, and V; and x represents an integer of 1 or more and 10 or less, y represents an integer of 6 or more and 40 or less, z represents an integer of 10 or more and 100 or less, m represents an integer of 1 or more, and n represents an integer of 0 or more and 50 or less.

2. The method for producing a polyacetal resin composition according to claim 1, wherein the aliphatic polycarboxylic acid is one or more selected from the group consisting of adipic acid, decanedioic acid, and dodecanedioic acid.

3. The method for producing a polyacetal resin composition according to claim 1, whereinthe aliphatic polycarboxylic acid is an ethylene acrylic acid copolymer resin or an ethylene methacrylic acid copolymer resin.

Description

EXAMPLES

[0077] The present invention will now be described in detail by Examples but is not limited thereto.

Examples 1 to 34, Comparative Examples 1 to 84

Copolymerization of Trioxane as Main Monomer (a) and Cyclic Ether and/or Cyclic Formal as Comonomer (b)

[0078] A continuous twin-screw polymerization apparatus was used as the apparatus for polymerization. The polymerization apparatus is equipped on the outside with a jacket through which a heating or cooling medium passes and is equipped on the inside with two rotary shafts having numerous buddles for stirring and driving in the longitudinal direction. Hot water of 80 C. was allowed to pass through the jacket of the twin-screw polymerization apparatus; a mixed liquid containing 96.2 wt % of trioxane as a main monomer (a) and 3.8 wt % of 1,3-dioxolane as a comonomer (b) and containing 1000 ppm of methylal as a chain transfer agent was continuously supplied to one end of the polymerization apparatus, while rotating the two rotary shafts at a constant speed; and phosphotungstic acid as a polymerization catalyst (c) was continuously added to the mixed liquid in an amount of 3 ppm relative to the total amount of the monomers. Copolymerization was thus performed. In Table 1, the amount of the polymerization catalyst is the weight ratio (unit: ppm) to the total amount of all the monomers.

Deactivation of Polymerization Catalyst (c)

[0079] The reaction product (crude polyacetal copolymer) by copolymerization was discharged from a discharge port provided on the other end of the polymerization apparatus, and salts (d) shown in Tables 1 to 3 were added for deactivation of the catalyst. The salt (d) was added as follows. When the Addition method column in Tables 1 to 3 is written as Solid, the component (d) was uniformly dispersed in a polyacetal copolymer powder in a solid state, and the powder after the dispersing process was then added to the reaction product. When the Addition method column in Tables 1 to 3 is written as Aqueous solution, a 10 wt % aqueous solution containing the component (d) was prepared so as to have a predetermined number of moles, 10 mL of the aqueous solution was added to a powder of the polyacetal copolymer, and the resulting mixture was added to the reaction product.

Melt-Kneading of Component (e) and Component (f)

[0080] Subsequently, the polycarboxylic acid (e) shown in Tables 1 to 3 was added in an amount shown in Tables 1 to 3, and 0.3 wt % of triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate] as an antioxidant was added thereto. The mixture was melt-kneaded and extruded with a twin-screw extruder equipped with a vent at 220 C. and a vacuum of 5 mmHg of the vent part to prepare each pellet of the polyacetal copolymers according to examples and comparative examples.

TABLE-US-00001 TABLE 1 HCHO (d)Deactivating agent (e)Multivalent carboxylic acid generation Amount Amount amount Appearance Deactivating agent [ppm] Addition method Type [ppm] [g/g] 1~3 Example 1 Sodium hydroxide 0.5 10 wt % aqueous Adipic acid(Number of carbons: 6) e-1 200 12 1 solution Example 2 Sodium hydroxide 0.5 10 wt % aqueous Decanedioic acid(Number of e-2 200 13 1 solution carbons: 10) Example 3 Sodium hydroxide 0.5 10 wt % aqueous Dodecanedioic acid(Number of e-3 200 15 1 solution carbons: 12) Example 4 Sodium hydroxide 0.5 10 wt % aqueous Ethylene methacrylic acid copolymer e-4 500 18 1 solution Example 5 Sodium hydroxide 0.5 10 wt % aqueous Ethylene acrylic acid copolymer e-5 500 15 1 solution Example 6 Anhydrous sodium 10 Solid Adipic acid(Number of carbons: 6) e-1 200 18 1 carbonate Example 7 Anhydrous sodium 10 Solid Decanedioic acid(Number of e-2 200 15 1 carbonate carbons: 10) Example 8 Anhydrous sodium 10 Solid Dodecanedioic acid(Number of e-3 200 19 1 carbonate carbons: 12) Example 9 Anhydrous sodium 10 Solid Ethylene methacrylic acid copolymer e-4 500 17 1 carbonate Example 10 Anhydrous sodium 10 Solid Ethylene acrylic acid copolymer e-5 500 14 1 carbonate Example 11 Sodium formate 10 Solid Adipic acid(Number of carbons: 6) e-1 200 14 1 Example 12 Sodium formate 10 Solid Decanedioic acid(Number of e-2 200 13 1 carbons: 10) Example 13 Sodium formate 10 Solid Dodecanedioic acid(Number of e-3 200 15 1 carbons: 12) Example 14 Sodium formate 10 Solid Ethylene methacrylic acid copolymer e-4 500 13 1 Example 15 Sodium formate 10 Solid Ethylene acrylic acid copolymer e-5 500 15 1 Example 16 Sodium hydrogen 10 Solid Adipic acid(Number of carbons: 6) e-1 200 13 1 carbonate Example 17 Sodium hydrogen 10 Solid Decanedioic acid(Number of e-2 200 12 1 carbonate carbons: 10) Example 18 Sodium hydrogen 10 Solid Dodecanedioic acid(Number of e-3 200 11 1 carbonate carbons: 12) Example 19 Sodium hydrogen 10 Solid Ethylene methacrylic acid copolymer e-4 500 13 1 carbonate Example 20 Sodium hydrogen 10 Solid Ethylene acrylic acid copolymer e-5 500 15 1 carbonate Example 21 Sodium acetate 10 Solid Adipic acid(Number of carbons: 6) e-1 200 18 1 Example 22 Sodium acetate 10 Solid Decanedioic acid(Number of e-2 200 13 1 carbons: 10) Example 23 Sodium acetate 10 Solid Dodecanedioic acid(Number of e-3 200 15 1 carbons: 12) Example 24 Sodium acetate 10 Solid Ethylene methacrylic acid copolymer e-4 500 15 1 Example 25 Sodium acetate 10 Solid Ethylene acrylic acid copolymer e-5 500 17 1 Example 26 Sodium stearate 20 Solid Adipic acid(Number of carbons: 6) e-1 200 11 1 Example 27 Sodium stearate 20 Solid Decanedioic acid(Number of e-2 200 15 1 carbons: 10) Example 28 Sodium stearate 20 Solid Dodecanedioic acid(Number of e-3 200 13 1 carbons: 12) Example 29 Sodium stearate 20 Solid Ethylene methacrylic acid copolymer e-4 500 18 1 Example 30 Sodium stearate 20 Solid Ethylene acrylic acid copolymer e-5 500 15 1 Example 31 Calcium stearate 20 Solid Dodecanedioic acid(Number of e-3 200 16 1 carbons: 12) Example 32 Magnesium stearate 20 Solid Ethylene methacrylic acid copolymer e-4 500 18 1 Example 33 Calcium hydroxide 3 Solid Dodecanedioic acid(Number of e-3 200 17 1 carbons: 12) Example 34 Magnesium hydroxide 3 Solid Ethylene methacrylic acid copolymer e-4 500 15 1

TABLE-US-00002 TABLE 2 HCHO (d)Deactivating agent gener- Addi- (e)Multivalent carboxylic acid ation Appear- Amount tion Amount amount ance Deactivating agent [ppm] method Type [ppm] [g/g] 1~3 Comparative Example 1 Sodium hydroxide 0.5 10 wt % 35 1 aqueous solution Comparative Example 2 Anhydrous sodium 10 Solid 45 1 carbonate Comparative Example 3 Sodium formate 10 Solid 39 1 Comparative Example 4 Sodium hydrogen 10 Solid 41 1 carbonate Comparative Example 5 Sodium acetate 10 Solid 42 1 Comparative Example 6 Sodium stearate 20 Solid 45 1 Comparative Example 7 Melamine 700 Solid 55 1 Comparative Example 8 Melamine 700 Solid Adipic acid(Number of carbons: 6) e-1 200 52 1 Comparative Example 9 Melamine 700 Solid Decanedioic acid(Number of carbons: 10) e-2 200 48 1 Comparative Example 10 Melamine 700 Solid Dodecanedioic acid(Number of carbons: 12) e-3 200 60 1 Comparative Example 11 Melamine 700 Solid Ethylene methacrylic acid copolymer e-4 500 49 1 Comparative Example 12 Melamine 700 Solid Ethylene acrylic acid copolymer e-5 500 62 1 Comparative Example 13 Melamine resin 700 Solid 83 1 Comparative Example 14 Melamine resin 700 Solid Adipic acid(Number of carbons: 6) e-1 200 65 1 Comparative Example 15 Melamine resin 700 Solid Decanedioic acid(Number of carbons: 10) e-2 200 72 1 Comparative Example 16 Melamine resin 700 Solid Dodecanedioic acid(Number of carbons: 12) e-3 200 80 1 Comparative Example 17 Melamine resin 700 Solid Ethylene methacrylic acid copolymer e-4 500 66 1 Comparative Example 18 Melamine resin 700 Solid Ethylene acrylic acid copolymer e-5 500 70 1 Comparative Example 19 CTU guanamine 700 Solid 45 1 Comparative Example 20 CTU guanamine 700 Solid Adipic acid(Number of carbons: 6) e-1 200 44 1 Comparative Example 21 CTU guanamine 700 Solid Decanedioic acid(Number of carbons: 10) e-2 200 50 1 Comparative Example 22 CTU guanamine 700 Solid Dodecanedioic acid(Number of carbons: 12) e-3 200 52 1 Comparative Example 23 CTU guanamine 700 Solid Ethylene methacrylic acid copolymer e-4 500 55 1 Comparative Example 24 CTU guanamine 700 Solid Ethylene acrylic acid copolymer e-5 500 72 1 Comparative Example 25 CMTU guanamine 700 Solid 50 1 Comparative Example 26 CMTU guanamine 700 Solid Adipic acid(Number of carbons: 6) e-1 200 52 1 Comparative Example 27 CMTU guanamine 700 Solid Decanedioic acid(Number of carbons: 10) e-2 200 60 1 Comparative Example 28 CMTU guanamine 700 Solid Dodecanedioic acid(Number of carbons: 12) e-3 200 55 1 Comparative Example 29 CMTU guanamine 700 Solid Ethylene methacrylic acid copolymer e-4 500 55 1 Comparative Example 30 CMTU guanamine 700 Solid Ethylene acrylic acid copolymer e-5 500 52 1 Comparative Example 31 Benzoguanamine 700 Solid 60 1 Comparative Example 32 Benzoguanamine 700 Solid Adipic acid(Number of carbons: 6) e-1 200 64 1 Comparative Example 33 Benzoguanamine 700 Solid Decanedioic acid(Number of carbons: 10) e-2 200 66 1 Comparative Example 34 Benzoguanamine 700 Solid Dodecanedioic acid(Number of carbons: 12) e-3 200 70 1 Comparative Example 35 Benzoguanamine 700 Solid Ethylene methacrylic acid copolymer e-4 500 50 1 Comparative Example 36 Benzoguanamine 700 Solid Ethylene acrylic acid copolymer e-5 500 52 1 Comparative Example 37 Polyamide6 700 Solid 120 1 Comparative Example 38 Polyamide6 700 Solid Adipic acid(Number of carbons: 6) e-1 200 100 1 Comparative Example 39 Polyamide6 700 Solid Decanedioic acid(Number of carbons: 10) e-2 200 132 1 Comparative Example 40 Polyamide6 700 Solid Dodecanedioic acid(Number of carbons: 12) e-3 200 122 1 Comparative Example 41 Polyamide6 700 Solid Ethylene methacrylic acid copolymer e-4 500 98 1 Comparative Example 42 Polyamide6 700 Solid Ethylene acrylic acid copolymer e-5 500 108 1 Comparative Example 43 Polyamide12 700 Solid 132 1 Comparative Example 44 Polyamide12 700 Solid Adipic acid(Number of carbons: 6) e-1 200 112 1 Comparative Example 45 Polyamide12 700 Solid Decanedioic acid(Number of carbons: 10) e-2 200 110 1 Comparative Example 46 Polyamide12 700 Solid Dodecanedioic acid(Number of carbons: 12) e-3 200 128 1 Comparative Example 47 Polyamide12 700 Solid Ethylene methacrylic acid copolymer e-4 500 125 1 Comparative Example 48 Polyamide12 700 Solid Ethylene acrylic acid copolymer e-5 500 123 1

TABLE-US-00003 TABLE 3 HCHO genera- Ap- (d)Deactivating agent (e)Multivalent carboxylic acid tion pear- Deactivating Amount Addition Amount amount ance agent [ppm] method Type [ppm] [g/g] 1~3 Comparative Example 49 Sodium hydroxide 0.5 10 wt % aqueous Caproic acid(Number of carbons: 6) e-6 200 28 3 solution Comparative Example 50 Sodium hydroxide 0.5 10 wt % aqueous Capric acid(Number of carbons: 10) e-7 200 25 3 solution Comparative Example 51 Sodium hydroxide 0.5 10 wt % aqueous Stearic acid(Number of carbons: 18) e-8 200 30 3 solution Comparative Example 52 Sodium hydroxide 0.5 10 wt % aqueous Oxalic acid(Number of carbons: 2) e-9 200 88 2 solution Comparative Example 53 Sodium hydroxide 0.5 10 wt % aqueous Malonic acid(Number of carbons: 3) e-10 500 95 2 solution Comparative Example 54 Sodium hydroxide 0.5 10 wt % aqueous Phthalic acid(Aromatic carboxylic e-11 500 88 2 solution acid) Comparative Example 55 Anhydrous sodium 10 Solid Caproic acid(Number of carbons: 6) e-6 200 20 3 carbonate Comparative Example 56 Anhydrous sodium 10 Solid Capric acid(Number of carbons: 10) e-7 200 23 3 carbonate Comparative Example 57 Anhydrous sodium 10 Solid Stearic acid(Number of carbons: 18) e-8 200 28 3 carbonate Comparative Example 58 Anhydrous sodium 10 Solid Oxalic acid(Number of carbons: 2) e-9 200 65 3 carbonate Comparative Example 59 Anhydrous sodium 10 Solid Malonic acid(Number of carbons: 3) e-10 500 82 3 carbonate Comparative Example 60 Anhydrous sodium 10 Solid Phthalic acid(Aromatic carboxylic e-11 500 92 3 carbonate acid) Comparative Example 61 Sodium formate 10 Solid Caproic acid(Number of carbons: 6) e-6 200 25 3 Comparative Example 62 Sodium formate 10 Solid Capric acid(Number of carbons: 10) e-7 200 20 3 Comparative Example 63 Sodium formate 10 Solid Stearic acid(Number of carbons: 18) e-8 200 18 3 Comparative Example 64 Sodium formate 10 Solid Oxalic acid(Number of carbons: 2) e-9 200 80 2 Comparative Example 65 Sodium formate 10 Solid Malonic acid(Number of carbons: 3) e-10 500 99 2 Comparative Example 66 Sodium formate 10 Solid Phthalic acid(Aromatic carboxylic e-11 500 73 2 acid) Comparative Example 67 Sodium hydrogen 10 Solid Caproic acid(Number of carbons: 6) e-6 200 20 3 carbonate Comparative Example 68 Sodium hydrogen 10 Solid Capric acid(Number of carbons: 10) e-7 200 22 3 carbonate Comparative Example 69 Sodium hydrogen 10 Solid Stearic acid(Number of carbons: 18) e-8 200 24 3 carbonate Comparative Example 70 Sodium hydrogen 10 Solid Oxalic acid(Number of carbons: 2) e-9 200 86 2 carbonate Comparative Example 71 Sodium hydrogen 10 Solid Malonic acid(Number of carbons: 3) e-10 500 56 2 carbonate Comparative Example 72 Sodium hydrogen 10 Solid Phthalic acid(Aromatic carboxylic e-11 500 67 2 carbonate acid) Comparative Example 73 Sodium acetate 10 Solid Caproic acid(Number of carbons: 6) e-6 200 25 3 Comparative Example 74 Sodium acetate 10 Solid Capric acid(Number of carbons: 10) e-7 200 31 3 Comparative Example 75 Sodium acetate 10 Solid Stearic acid(Number of carbons: 18) e-8 200 28 3 Comparative Example 76 Sodium acetate 10 Solid Oxalic acid(Number of carbons: 2) e-9 200 65 2 Comparative Example 77 Sodium acetate 10 Solid Malonic acid(Number of carbons: 3) e-10 500 68 2 Comparative Example 78 Sodium acetate 10 Solid Phthalic acid(Aromatic carboxylic e-11 500 88 3 acid) Comparative Example 79 Sodium stearate 20 Solid Caproic acid(Number of carbons: 6) e-6 200 27 3 Comparative Example 80 Sodium stearate 20 Solid Capric acid(Number of carbons: 10) e-7 200 25 3 Comparative Example 81 Sodium stearate 20 Solid Stearic acid(Number of carbons: 18) e-8 200 30 3 Comparative Example 82 Sodium stearate 20 Solid Oxalic acid(Number of carbons: 2) e-9 200 80 2 Comparative Example 83 Sodium stearate 20 Solid Malonic acid(Number of carbons: 3) e-10 500 98 3 Comparative Example 84 Sodium stearate 20 Solid Phthalic acid(Aromatic carboxylic e-11 500 67 2 acid)

[0081] In Tables 1 to 3, each component is as follows.

Deactivating agent (d)
CTU guanamine (3,9-bis[2-(3,5-diamino-2,4,6-triazaphenyl)ethyl]-2,4,8,10-tetraoxaspiro[5,5] undecane)
CMTU guanamine (3,9-bis[1-(3,5-diamino-2,4,6-triazaphenyl)methyl]-2,4,8,10-tetraoxaspiro[5,5] undecane)
Benzoguanamine (2,4-diamino-6-phenyl-1,3,5-triazine)
Polycarboxylic acid (e)
Ethylene methacrylic acid copolymer (product name: Nucrel Nucrel N1525, manufactured by Du Pont-Mitsui Polychemicals Co., Ltd. DU PONT-MITSUI POLYCHEMICALS CO.,LTD.)
Ethylene acrylic acid copolymer (product name: Primacor PRIMACOR 3460, manufactured by The Dow Chemical Company)

Evaluation

[0082] In order to evaluate the pellet-type polyacetal resin compositions according to Examples and Comparative Examples, the generation amount of formaldehyde and the molded product appearance were evaluated.

Amount of Formaldehyde Generated from Melt Product

[0083] Five grams of a pellet was precisely weighed and was retained in a metal container at 200 C. for 5 minutes, and the atmosphere in the container was absorbed in the distilled water. The amount of formaldehyde in the aqueous solution was quantified in accordance with JIS K0102, 29. (the paragraph of formaldehyde), and the amount (ppm) of formaldehyde gas generated from the pellet was calculated. The results are shown in Tables 1 to 3.

Molded Product Appearance

[0084] Evaluation of surface appearance: a plate having a 3-mm thickness and a 50-mm square with 1.5-mm diameter center one-point pin gate was injection molded with an injection molding machine J75SS2A (35) manufactured by The Japan Steel Works, Ltd. under the following conditions. The surface appearance of the resulting molded product was evaluated for two items: (1) the size (mm) of the flow mark near the gate and (2) visual evaluation of surface roughness. In the item (1), a smaller flow mark is better. Three-grade evaluation from 1 to 3 was performed. Grade 1 denotes good, grade 2 denotes moderate, and grade 3 denotes poor. The results are shown in Tables 1 to 3.

Molding Conditions

[0085] Cylinder temperature: 200 C.-200 C.-180 C.-150 C.
Mold temperature: 90 C.
Holding pressure: 750 kg/cm.sup.2

Injection conditions

[0086] Injection time: 5 seconds
Measuring (primary-secondary-holding pressure): 25-20-8 mm
Rate (primary-secondary): 25-2.5 mm/sec

Results

[0087] A polyacetal resin composition prepared using an appropriate material as the deactivating agent (d) for the polymerization catalyst (c) at an appropriate proportion and using an appropriate material as the polycarboxylic acid (e) to be mixed with a polyacetal copolymer at an appropriate proportion can achieve both the suppression of the generation amount of formaldehyde from the molded article to a low level and the provision of better appearance of the molded article (Examples 1 to 34). Accordingly, it can be said that the polyacetal resin compositions of Examples are extremely versatile.

[0088] In contrast, in the case of a polyacetal copolymer not containing the aliphatic polycarboxylic acid (e), the generation amount of formaldehyde cannot be sufficiently suppressed compared to Examples (Comparative Examples 1 to 6).

[0089] In addition, if the deactivating agent (d) is not a carbonate, hydrogen carbonate, or carboxylate of an alkali metal element or an alkaline earth metal element or a hydroxide of an alkali metal element or an alkaline earth metal element, the generation amount of formaldehyde cannot be sufficiently suppressed compared to Examples (Comparative Examples 7 to 48).

[0090] Regarding the component (e), even if a polyacetal resin composition contains a carboxylic acid, when the carboxylic acid is a monocarboxylic acid, not only that the generation amount of formaldehyde cannot be sufficiently suppressed compared to Examples but also that the appearance of the molded article is inferior to that in Examples (Comparative Examples 49 to 51, 55 to 57, 61 to 63, 67 to 69, 73 to 75, and 79 to 81).

[0091] Regarding the component (e), even if a polyacetal resin composition contains a polycarboxylic acid having two or more carboxyl groups, when the number of carbons of the carboxylic acid is less than four, the generation amount of formaldehyde cannot be suppressed, and the appearance of the molded product was also poor (Comparative Examples 52, 53, 58, 59, 64, 65, 70, 71, 76, 77, 82, and 83).

[0092] Even if a polyacetal resin composition contains a dicarboxylic acid, when the dicarboxylic acid is an aromatic compound, the generation amount of formaldehyde cannot be suppressed to a low level compared to Examples, and the appearance of the molded article is also poor (Comparative Examples 54, 60, 66, 72, 78, and 84).