JPH04239049A - Acetal homopolymer composition - Google Patents

Abstract

PURPOSE:To obtain the title compsn. which is excellent in thermal stability and resistance to thermal aging and releases a low HCHO odor during molding by compounding an acetal homopolymer with specific compds. CONSTITUTION:The title compsn. comprises an acetal homopolymer (e.g. one obtd. by polymerizing HCHO and acetylating the molecular terminals of the polymer), a hindered phenolic antioxidant having a mol.wt. of 400 or higher (e.g. Irganox 245, a product of Ciba Geigy), a hindered amine antioxidant having a mol.wt. of 300 or higher (Sanol LS765, a product of Sankyo), and an HCHO acceptor (e.g. a four-component polyamide 6/66/610/12 copolymer).

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention provides an acetal homopolymer composition that has excellent heat aging resistance, has very little formaldehyde odor during molding, and has excellent thermal stability. It is about things. [0002] Polyacetal resin is known as an engineering plastic with a good balance of mechanical strength and impact resistance, and is used in a wide range of fields as electronic equipment supplies and automobile parts. However, polyacetal resin has poor thermal stability due to its structure, and formaldehyde gas is generated during molding, which worsens the working environment, and the formation of oligomers, which are generally called mold deposits, formed on the mold. There are several points that should be improved, such as detracting from the appearance of the product. Polyacetal resins include acetal homopolymers, generally referred to as acetal homopolymers, and acetal copolymers, generally referred to as acetal copolymers. The acetal copolymer has achieved sufficient thermal stability to withstand injection molding and extrusion molding by introducing a comonomer having an oxyalkylene unit with two or more adjacent carbon atoms into the main chain. On the other hand, acetal homopolymers only have unstable ends blocked with ester or ether groups, and if the end groups or the middle of the main chain are thermally decomposed, a large amount of formaldehyde gas will be generated. However, since the entire molecule decomposes, it is not able to withstand high temperatures and long-term molding. [0005] In order to improve the above-mentioned drawbacks of acetal homopolymers, a wide variety of stabilizer formulations have been devised. Addition of an antioxidant is an essential condition in the stabilizer formulation for such an acetal homopolymer. However, the hindered phenol compound, which is generally used as an antioxidant for polyacetal resin, alone cannot be used alone.
In the case of acetal resin homopolymers it is not possible to obtain sufficient thermal stability. Additionally, although polyamide compounds have traditionally been added as heat stabilizers, it has not been possible to obtain sufficient thermal stability with these compounds alone or in combination with hindered phenolic antioxidants. . For example, Japanese Patent Publication No. 62-4422 describes a resin composition prepared by adding and blending a polyamide and a fatty acid metal salt having 12 to 35 carbon atoms together with a hindered phenolic antioxidant to a polyoxymethylene resin. There is. [0006] Furthermore, a method using a hydroxy group-containing polymer or oligomer such as poly(ethylene vinyl alcohol) as a heat stabilizer is described in JP-A-62-288648 and JP-A-62-288649. . [0007] Problem to be Solved by the Invention However, the stabilizers for resin compositions proposed in the above-mentioned Japanese Patent Publication No. 4422/1982, Japanese Patent Application Laid-Open No. 288648/1982, and Japanese Patent Application Laid-Open No. 288649/1982 It is difficult to obtain an acetal homopolymer with sufficient thermal stability through formulation. [0008] Therefore, the object of the present invention is to obtain an acetal homopolymer composition having excellent thermal stability and heat aging resistance sufficient to withstand high temperatures and long-term melt retention. [Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have developed a hindered phenolic antioxidant having a specific molecular weight for an acetal homopolymer, and We have discovered that by blending and adding a hindered amine compound having a specific molecular weight and a formaldehyde scavenger, an acetal homopolymer composition with extremely high thermal stability and good workability can be obtained, and we have arrived at the present invention. . That is, the present invention is an acetal homopolymer composition containing the following compounds (A) to (C) in an acetal homopolymer. (A) Hindered phenol antioxidant with a molecular weight of 400 or more (B) Hindered amine compound with a molecular weight of 300 or more (
C) Formaldehyde scavenger The acetal homopolymer used in the present invention refers to an oxymethylene homopolymer stabilized by substituting an unstable terminal hydroxyl group with an ester group or an ether group. For example, substantially anhydrous formaldehyde is polymerized by introducing it into an organic solvent containing an organic amine, an organic or inorganic tin compound, or a basic polymerization catalyst such as a metal hydroxide, and the polymer is filtered out. , in acetic anhydride;
It is produced by heating in the presence of sodium acetate to acetylate the terminal. The hindered phenolic antioxidant (A) used in the present invention has a molecular weight of 400 or more, and specifically, triethylene glycol-bis[3-(3-
t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3
-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N '-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamamide), 2-t-butyl-6-(3'-t-butyl-5'-methyl-2'-hydroxy benzyl)-4-
Methylphenyl acrylate, 3,9-bis[2-{3
-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]
Examples include undecan. Among these, triethylene glycol-bis[3-(3-t-butyl-5-methyl-
4-hydroxyphenyl)propionate], 1,6-
hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], pentaerythrityl-tetrakis[3-(3,5-di-t-
butyl-4-hydroxyphenyl)propionate] is particularly preferred. If the molecular weight is less than 400, the bleeding phenomenon will be significant, the appearance of the acetal homopolymer composition will be impaired, and the thermal stability will be reduced, making it unusable. [0013] The amount added is 10% of the acetal homopolymer.
The amount is usually 0.001 to 5.0 parts by weight, preferably 0.01 to 3.0 parts by weight. If it is less than 0.001 parts by weight, the thermal stability of the acetal homopolymer composition will not be sufficient, and if it is more than 5.0 parts by weight, a bleeding phenomenon will be observed, which is not preferable. The hindered amine compound (B) used in the present invention has a molecular weight of 300 or more, and specifically, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, succinic acid Dimethyl 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}hexamethylene{(2
, 2,6,6-tetramethyl-4-piperidyl)imino)], bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, and the like. Among them, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, dimethyl succinate 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl Piperidine 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}hexamethylene {(2,2,
6,6-tetramethyl-4-piperidyl)imino)]
is particularly preferred. If the molecular weight is less than 300, the bleeding phenomenon will be significant, the appearance of the acetal homopolymer will be impaired, and the thermal stability will be reduced, making it unusable. [0015] Also, the amount added is 10% of the acetal homopolymer.
The amount is usually 0.001 to 5.0 parts by weight, preferably 0.01 to 3.0 parts by weight. If it is less than 0.001 parts by weight, the thermal stability of the acetal homopolymer composition will not be sufficient, and if it is more than 5.0 parts by weight, coloring will be severe due to heat, which is not preferable. The formaldehyde scavenger (C) used in the present invention includes polyamide compounds, urethane compounds,
Examples include pyridine derivatives, pyrrolidone derivatives, urea derivatives, triazine derivatives, hydrazine derivatives, and amidine compounds. Specifically, polyamide 6, polyamide 66,
Polyamide 6/66 binary copolymer, Polyamide 6/66
/610/12 quaternary copolymer, melamine, benzoguanamine, acetoguanamine, N-methylolmelamine, N
, N'-dimethylolmelamine, N,N',N''-trimethylolmelamine, dicyandiamide and the like are preferred. Among these, polyamide 6/66/610/12 quaternary copolymer and melamine are particularly preferred. The polyamide 6/66/610/12 quaternary copolymer used in the present invention is a copolymer obtained by copolymerizing a salt of a dicarboxylic acid and a diamine, an ω-aminocarboxylic acid, or a lactam. 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, and polyamide 12. The composition of this copolyamide can have various ratios, and any ratio may be used in the present invention, but from the viewpoint of compatibility and dispersibility with the polyoxymethylene resin, the melting point of this copolyamide is usually The composition is in the range of 50 to 200°C, particularly preferably 80 to 170°C. The amount of these formaldehyde scavengers added is usually 0.001 to 5 parts by weight per 100 parts by weight of the acetal homopolymer.
．． 0 parts by weight, preferably 0.01 to 3.0 parts by weight. If the amount is less than 0.001 part by weight, the addition effect will not appear.
Further, if the amount is more than 5.0 parts by weight, a bleed phenomenon may occur, which is not preferable. [0017] As a method for producing the acetal homopolymer composition of the present invention, generally known methods can be employed. For example, a method of adding the stabilizer used in the present invention in the polymerization or stabilization process of the acetal homopolymer, a method of adding the stabilizer used in the present invention to the acetal homopolymer and the stabilizer used in the present invention in the form of pellets, powder, etc.
Alternatively, it may be mixed in granular form and melt-processed as is, but
A method of melt-mixing using a Banbury mixer, roll, extruder, etc. can also be adopted. It is also possible to adopt a method in which the stabilizer used in the present invention is melt-kneaded with a commercially available acetal homopolymer called acetal homopolymer in the same manner as described above. In particular, a method of melt-mixing using a single-screw or twin-screw extruder at a temperature of 150 to 250°C is preferred. The composition of the present invention may also contain fillers such as calcium carbonate, barium sulfate, clay, titanium oxide, silicon oxide, mica powder, glass beads, carbon fiber, glass, etc., to the extent that the effects of the present invention are not impaired. reinforcing agents such as fibers, ceramic fibers, aramid fibers, potassium titanate fibers,
Colorants (pigments, dyes), nucleating agents, plasticizers, mold release agents such as ethylene bisstearamide, polyethylene wax,
Conductive agents such as carbon black, antioxidants such as thioether compounds and phosphite compounds, light stabilizers such as benzophenone compounds and benzotriazole compounds, adhesives, lubricants such as metal soaps, and water resistance. Additives such as decomposition improvers and adhesion aids can be optionally included. The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. EXAMPLES The present invention will be explained below with reference to Examples. Note that all percentages and parts in the examples are based on weight. [0021] In addition, the MI value, mechanical properties, thermal decomposition rate Kx, formaldehyde odor generation status during continuous molding, melt retention stability of the polymer, and heat aging resistance of the molded products shown in Examples and Comparative Examples was measured or observed as follows.・Molding: Using an injection molding machine with a 5 oz injection capacity, cylinder temperature 190°C
, the mold temperature was set to 65°C, the molding cycle was set to 50 seconds, and A
STM No. 1 dumbbell test pieces were injection molded. - MI value: Measured at a temperature of 190°C and a load of 2160 grams according to the ASTM D-1238 method using pellets dried in a hot air oven at 80°C for 3 hours. - Mechanical properties: AS obtained by the above injection molding
Using TM1 dumbbell test piece, ASTM D-63
Tensile strength was measured according to Method 8. - Thermal decomposition rate Kx: Kx means the decomposition rate when left at x°C for a certain period of time. Using a thermobalance device, approximately 15 milligrams of sample was weighed in an air atmosphere.
It was determined by the following formula after being left at x°C. [0025] Kx=(W0-Wy)×100/W0
(%) Here, W0 means the sample weight before heating, and Wy means the sample weight after heating for y hours. In addition, the thermobalance device is
Use Seiko Electronics' TG/DTA200, x=2
Measurement was performed at 20°C for y=60 minutes. - Generation of formaldehyde odor during continuous molding: Continuous molding was performed for 50,000 shots under the above-mentioned molding conditions, and the generation of formaldehyde odor at that time was evaluated as follows. There is almost no formaldehyde odor: ◎, There is a slight formaldehyde odor: ○, A lot of formaldehyde gas is generated and it hurts your eyes and throat if you stay in the area: △, Formaldehyde gas is generated intensely and remains in the area Cannot: ×. Polymer melt retention stability: The MI value was measured according to the ASTM D-1238 method at a temperature of 190°C.
After being allowed to stay for 2 hours, measurements were taken with a load of 2160 grams. - Heat aging resistance: The ASTM No. 1 dumbbell obtained by the above injection molding is placed in an oven set at 140°C, taken out after a predetermined period of time, and subjected to ASTM D-
Tensile strength was measured according to the 638 method. In the Examples and Comparative Examples, an acetal homopolymer (P-1) produced by the following method or a commercially available homopolymer (Dupont "Delrin" II500NC1) was used.
0) (P-2) was used.・Production of acetal homopolymer (P-1) In a polymerization reaction tank with a diameter of 30 cm and a depth of 3 meters equipped with a stirring blade and a formaldehyde supply nozzle at the bottom,
- Filled with hexane. In this solution, 0.5 parts by weight of di-n-butyltin dimerate was dissolved, and formaldehyde gas was introduced through a supply nozzle. Formaldehyde gas was purified after thermally decomposing paraformaldehyde at 140 to 180°C, and was introduced at a rate of 1.5 kg/hour. The temperature inside the polymerization tank was adjusted to 50° C. by flowing cold or hot water through the jacket. Although fine polymer particles were gradually produced in the polymerization tank, the polymer slurry was extracted and the catalyst solution (n-hexane) was supplied so as to maintain the polymer solid content at about 50% by weight. The extracted polymer was filtered, thoroughly washed with water, and then poured into acetic anhydride in an amount 10 times the amount of the polymer. Further, sodium acetate was added in an amount of 0.1% by weight based on acetic anhydride, and the mixture was heated and stirred at 140°C for 5 hours. After the reaction mixture cooled to room temperature, the polymer was filtered off, thoroughly washed with acetone and water, and then dried.
P-1 was obtained. The hindered phenol antioxidant, hindered amine compound, and formaldehyde scavenger used in the Examples and Comparative Examples are as follows.・O-1: Triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate] (Ciba Geigy “Irganox” 245) ・O-2: 1,6 -Hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (Ciba Geigy "Irganox" 259) ・O-3: Pentaerythrityl-tetrakis [3-(3, 5-di-t-butyl-4-hydroxyphenyl) propionate] (Ciba Geigy "Irganox" 1010) ・O-4:2,2'-methylenebis(4-methyl-6-t-butylphenol) (Sumitomo Chemical "Sumilizer""MDP-S)・O-5:2,6-
Di-t-butyl-4-methylphenol (Sumitomo Chemical “Sumilyzer” BHT)・A-1: Bis(1,2,2,6
, 6-pentamethyl-4-piperidinyl) sebacate (
Sankyo “Sanol” LS765)・A-2: Dimethyl succinate・1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (
Ciba Geigy "Tinuvin" 622LD)・A-3: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 (Ciba Geigy)
KimaSorb”119FL)・A-4: Poly[{6-(1
,1,3,3-tetramethylbutyl)amino-1,3,
5-triazine-2,4-diyl}{2,2,6,6-
Tetramethyl-4-piperidinyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino)}] (Ciba Geigy "Kimasorb" 944
FL)・T-1: Polyamide 6/66/610/12 quaternary copolymer (copolymer composition 6/66/610/12=22
/12/16/50 (wt%))・T-2: Polyamide 6/66/610/12 quaternary copolymer (copolymer composition 6/
66/610/12 = 33/17/33/17 (wt%
))・T-3: Melamine・T-4: Dicyandiamide. Examples 1 to 6 and Comparative Examples 1 to 5 Stabilizers were added to the acetal homopolymers P-1 to 2 in the proportions shown in Tables 1 and 2, and a vented 2-shaft 45 mmφ manufactured by Ikegai Iron Works was used. 220-230℃/10mm torr using an extruder
The mixture was melt-extruded and kneaded. [Table 1] [0035]

Example
Acetal alone Hindered amide Formaldehy Polymer
Nol-based antioxidant compounds
Capture agent (parts by weight) Stop agent (parts by weight) (parts by weight) (parts by weight)
1 P-1
O-1 A-1
T-1 (100)
(0.5) (0.1) (0
．． 1) 2 P-1
O-2 A-2
T-1 (100)
(0.3) (0.1) (
0.1) 3 P-1
O-3 A-3
T-2 (100)
(0.5) (0.3)
(0.1) 4 P-2
O-1 A-4
T-1 (100)
(0.1) (0.1)
(0.1) 5 P-2
O-1 A-1
T-3 (100)
(1.0) (0.5)
(0.1) 6 P-2
O-1 A-2
T-4 (100)
(0.1) (1.0)
(0.5) 0036 [Table 2] 0037

Comparative example
Acetal alone Hindered amide Formaldehy Polymer
Nol-based antioxidant compounds
Capture agent (parts by weight) Stop agent (parts by weight) (parts by weight) (parts by weight)
1 P-1
O-1 A-1
- (100)
(0.5) (0.1) (
- ) 2 P-2
O-1-
T-1 (100)
(1.0) (-)
(0.2) 3 P-1
-A
-1 T-2
(100) (-) (
0.5) (0.1) 4
P-2 O-4
A-2 T-4
(100) (0.5)
(0.1) (0.1) 5
P-1 O-5
A-1 T-1
(100) (0.5)
(0.1) (0.1). The resulting composition was extruded as a strand and pelletized with a cutter. The pellets were dried at 80° C. for 3 hours in a hot air circulation oven, then molded, and subjected to measurement of mechanical properties and heat aging resistance test. In addition, the occurrence of formaldehyde odor during continuous molding was evaluated. Furthermore, the melt retention stability was evaluated using the dried pellets. These results are summarized in Tables 3-6. [Table 3]

fruit
MI value Tensile strength Thermal decomposition rate Forging during continuous molding (g/10 minutes)
(MPa) K220
Maldehyde odor example
(%)
Occurrence status 1 14.
5 70 1.
9 ◎2 14.7
70 2.4
○3 14.4
70 1.5
◎4 15.7
68 2.3
○5 16.0
69 1.5
◎6 16.0
69 1.8
◎ [0041] [Table 4] 0042]

ratio
MI value Tensile strength Thermal decomposition rate Hole comparison during continuous molding (g/10 minutes)
(MPa) K220
Maldehyde odor example
(%)
Occurrence status 1 14.
6 69 13.8
△2 14.7
68 25.2
△3 16.2
65 30.4
×4 16.5
68 19.6
△5 15.3
69 28.3
× 0043 [Table 5] 0044

Examples Melt retention stability Heat aging resistance
1 after residence at 190℃ for 2 hours
MI value after 20 days at 40℃ (
g/10 minutes) Tensile strength (MPa)
1 14.7
65 2
15.2
65 3 1
4.6
62 4 15.9
60 5
16.0
61 6
16.1
65 [0045] [Table 6] 0046]

Comparative example Melt retention stability Heat aging resistance
140 after residence at 190℃ for 2 hours
°C, MI value after 20 days (g/
10 minutes) Tensile strength (MPa) 1
−＊
-*2
32.5
24 3
−＊
-* 4 -*
10
5-*
9
*: Unable to measure due to severe decomposition. Effects of the Invention The acetal homopolymer composition of the present invention has very little formaldehyde odor during molding, has excellent thermal stability, and also has excellent heat aging resistance. Therefore, since it has excellent thermal stability and an extremely favorable working environment, long-term continuous production of molded products is possible. In addition, due to its good heat aging resistance, it
It can be widely used as mechanical parts in the electronic field, automobile field, etc.

Claims (5)

[Claims] 1. An acetal homopolymer composition comprising an acetal homopolymer containing the following compounds (A) to (C). (A) Hindered phenol antioxidant with a molecular weight of 400 or more (B) Hindered amine compound with a molecular weight of 300 or more (
C) Formaldehyde scavenger 2. The compound (A) is triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-
hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-
4-hydroxyphenyl)propionate] and pentaerythrityl-tetrakis [3-(3,5-di-t-
The acetal homopolymer composition according to claim 1, which is at least one compound selected from the group consisting of butyl-4-hydroxyphenyl) propionate. Claim 3: The compound (B) is 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 and poly[{6-(1,1,3,3-tetramethylbutyl) )amino-1,3,5-triazine-2,4-diyl}{2,2,6,6-tetramethyl-4-piperidinyl)imino}hexamethylene{(2,2,6,6-tetramethyl- The acetal homopolymer composition according to claim 1, wherein the acetal homopolymer composition is at least one compound selected from 4-piperidyl)imino). 4. The acetal homopolymer composition according to claim 1, wherein the compound (C) is at least one compound selected from polyamide, melamine, and cyanoguanidine. Claim 5: The compound (C) is polyamide 6/66
The acetal homopolymer composition according to claim 1, which is a /610/12 quaternary copolymer and/or melamine.