JPH0326223B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel acetal polymer composition, and particularly to an acetal polymer composition having unprecedented and excellent impact properties. Many attempts have been made to improve the impact properties of acetal polymers. For example, special public service in 1977-
In Japanese Patent Publication No. 18023, the addition of a so-called ionomer was added, and in Japanese Patent Publication No. 45-26231, the addition of an ethylene-acrylic acid copolymer was added.
-33095 proposes the addition of aliphatic polyether. Polyacetal, which is a crystalline polymer, and the amorphous polymer proposed in these publications do not easily mix or dissolve, and it is extremely difficult to create a uniform composition of the two. For this reason, the compositions proposed in these publications do not sufficiently improve impact properties, and the appearance of molded products is also poor. To improve non-uniform mixing and dissolution
Publication No. 19425 describes the reaction of a trioxane copolymer containing free amino groups with a polyether containing isocyanate groups. This method requires reducing the nitro groups in the trioxane copolymer to amino groups, and the polymer has the defect of violently decomposing during the reduction operation. Furthermore, JP-A-54-155248 proposes adding an elastomer and processing aids such as segmented polyester and polyurethane to polyoxymethylene. By adopting this method, although the impact value is improved, the appearance of the molded product is still poor. This is due to the fact that uniform mixing and dissolution of the elastomer and polyoxymethylene is insufficient even when segmented polyester and polyurethane are used as processing aids. Furthermore, the strength and rigidity of molded articles based on this composition are greatly reduced due to the addition of segmented polyester and polyurethane. The decrease in strength and rigidity will become clear in the comparative examples later. Acetal polymers are useful as engineering plastics due to their well-balanced physical properties. Attempts to improve impact properties even at the expense of strength and rigidity, such as the composition of the present invention, cannot necessarily be said to be an advantageous direction. As a result of extensive studies on methods for improving the impact properties of acetal polymers, the present inventors have discovered that an acetal polymer composition containing a specific ethylene copolymer and an acetal block copolymer has been developed. Discovered that it has outstanding impact properties,
The present invention has now been completed. Moreover, this composition maintains high strength and stiffness, and this composition can be appropriately called a highly balanced composition. That is, the present invention provides (A) polyacetal 99.8 to 60.0
parts by weight, (B) has a secondary transition temperature of −120 to +20°C,
0.1 to 30.0 parts by weight of an ethylene copolymer having a number average molecular weight of between 10,000 and 500,000, and an elastomer having a secondary transition temperature of -120 to +40°C inserted into the main chain of the linear polymer (C). Acetal with excellent impact properties, consisting of three components: 0.1 to 39.9 parts by weight of an acetal block copolymer consisting of an acetal polymer part and an elastomer part with a number average molecular weight of between 10,000 and 500,000. The present invention relates to polymer compositions. The acetal polymer composition of the present invention has an Izot impact value (notched) of 8 to 65 Kg·cm/cm, and has excellent impact properties not found in the past. Demand for acetal polymers as engineering plastics has been increasing in recent years, and improving the impact properties of acetal polymers has great industrial significance. Next, the acetal polymer composition of the present invention will be explained in detail. The polyacetal used as component (A) in the present invention includes polyacetal homopolymers and polyacetal copolymers. A polyacetal homopolymer is a polymer consisting of repeating oxymethylene units (-CH ₂ O)-, and is obtained by homopolymerizing formaldehyde and trioxane. Polyacetal copolymer has oxyalkylene units in the chain consisting of oxymethylene units. (Ro: selected from hydrogen, an alkyl group, and an aryl group, each of which may be the same or different.
This is a polymer having a structure in which m=2 to 6) are randomly inserted. The insertion rate of oxyalkylene units in the polyacetal copolymer is 0.05 to 50 mol, more preferably 0.1 to 20 mol, per 100 mol of oxymethylene units. Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxytrimethylene units, oxytetramethylene units, oxybutylene units, oxyphenylethylene units, and the like. Among these oxyalkylene units, from the viewpoint of improving the physical properties of the acetal polymer composition, oxyethylene units [-(CH ₂ ) ₂ O]- and oxytetramethylene units [-(CH ₂ ) ₄ O]- are used. Particularly preferred. A polyacetal copolymer is obtained by copolymerizing or reacting formaldehyde, trioxane, polyoxymethylene with a cyclic ether or a cyclic formal. After polymerization and reaction, the polyacetal homopolymer and polyacetal copolymer are added as component (A) after the polymer terminals are converted into stable groups. The amount of polyacetal added as component (A) is 99.8 parts by weight per 100 parts by weight of the acetal polymer composition.
~60.0 parts by weight. Next, the ethylene copolymer used as component (B) has a second-order transition temperature (Tg, glass transition temperature) of -120 to +20°C, and a number average molecular weight of 10,000 to 10,000.
It is a copolymer or terpolymer of ethylene, vinyl monomer, or diene with a molecular weight between 500,000 and 500,000. Here, if the number average molecular weight is 10,000 or less,
If the impact properties are not sufficiently improved, and conversely exceeds 500,000, it becomes difficult to mix and dissolve uniformly with the base material polyacetal. Next, the ethylene copolymer will be specifically explained. The first group of ethylene copolymers are ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, modified ethylene-propylene copolymers, modified ethylene-propylene-diene terpolymers. Examples of the diene to be copolymerized with ethylene or propylene as a termonomer include dicyclopentadiene, ethylidenenorbornene, methylenenorbornene, and 1,4-hexadiene. Ethylene-propylene copolymers (EPM), ethylene-propylene-diene terpolymers (EPDM) can be used to synthesize acrylics such as maleic anhydride, acrylic acid, methacrylic acid, and methyl acrylate in the presence or absence of peroxides. acid ester, methyl methacrylate, methacrylic acid 2
- Modified by unsaturated compounds such as methacrylic esters such as hydroxyethyl. In the present invention, these modified polymers are also preferably used. The second group of ester copolymers are ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, modified ethylene-acrylic acid copolymers, modified ethylene-methacrylic acid copolymers. Ethylene-acrylic acid copolymer, ethylene-
After polymerization, methacrylic acid copolymer contains Na, Zn,
Metals such as Mg and Ca are mixed and dispersed and modified. In the present invention, these modified polymers are also preferably used. The third group of ethylene copolymers are ethylene-acrylic ester copolymers and ethylene-methacrylic ester copolymers. Examples of acrylic esters include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and stearyl acrylate. In addition, methacrylic acid esters include methyl methacrylate, ethyl methacrylate, butyl methacrylate, and dimethacrylate.
-Hydroxyethyl, 2-hydroxypropyl methacrylate, 2-ethylhexyl methacrylate, etc. The fourth group of ethylene copolymers are ethylene-vinyl acetate copolymers. In addition to these four groups of ethylene copolymers, copolymers of ethylene and comonomers and termonomers such as vinyl monomers and dienes can also be used in the present invention. The amount of the ethylene copolymer (component (B)) added is 0.1 to 30.0 parts by weight per 100 parts by weight of the acetal polymer composition.
Parts by weight range. If the amount of the ethylene copolymer added is too small, the impact properties will not be improved sufficiently, whereas if it is too large, a decrease in strength and rigidity will be observed. The acetal block copolymer used as component (C) in the present invention is a linear polymer in which -
It is a polymer with a structure in which an elastomer having a second-order transition temperature (Tg, glass transition temperature) of 120 to +40°C is inserted, and it has an A-B-A type triblock combination of an acetal polymer part A and an elastomer part B. It is a polymer. In addition, the number average molecular weight of the acetal block copolymer is 10,000 to 500,000.
Set between. If the number average molecular weight is less than 10,000, the impact properties will not be improved sufficiently, and if the number average molecular weight is more than 500,000, it will be difficult to mix uniformly with polyacetal. Further, the content of the elastomer portion in the acetal block copolymer is set between 0.5 and 60% by weight. The acetal polymer portion, which is the block component of the triblock copolymer, includes an acetal homopolymer portion and an acetal copolymer portion. The acetal homopolymer portion is a polymer consisting of repeating oxymethylene units (-CH ₂ O)-. The acetal copolymer part is an oxyalkylene unit in a chain consisting of oxymethylene units. (R′o: selected from hydrogen, an alkyl group, and an aryl group, each of which may be the same or different.
This is a polymer having a structure in which m'=2 to 6) are randomly inserted. The insertion rate of oxyalkylene units in the acetal copolymer portion is 0.05 to 70 mol, more preferably 0.1 to 70 mol, per 100 mol of oxymethylene units.
It is 30 moles. Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxytrimethylene units, oxytetramethylene units, oxybutylene units, oxyphenylethylene units, and the like. Next, the elastomer part is a thermoplastic polymer that is amorphous and has a low secondary transition temperature segment (soft segment) and thermoreversible crosslinking.
It is a copolymer of segments (hard segments) that create a bonded structure. The first group of elastomer moieties to be incorporated into the acetal block copolymers of the present invention are polystyrene-based elastomers, with polystyrene as the hard segment. Soft segments to be combined with polystyrene include diene systems such as polybutadiene and polyisoprene, and hydrogenated diene systems such as hydrogenated polybutadiene and hydrogenated polyisoprene. Among these polystyrene elastomers, polystyrene-polybutadiene block copolymers and polystyrene-hydrogenated polybutadiene block copolymers are particularly preferred. The second group of elastomer portions are polyester elastomers, which have hard segments of polyester such as polyethylene terephrate, polybutylene terephthalate, modified polyethylene terephthalate, and polyethylene-butylene terephthalate. Soft segments to be combined with polyesters include polyethers such as polypropylene glycol, polytetramethylene glycol, and the like. Among these polyester elastomers, polybutylene terephthalate-polytetramethylene glycol block copolymer and polyethylene-butylene terephthalate-polytetramethylene glycol block copolymer are particularly preferred. The third group of elastomer parts are polyamide elastomers, which have hard segments of polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12. Soft segments to be combined with polyamides include polyethers such as polypropylene glycol, polytetramethylene glycol, and polyesters such as polyethylene adipate and polybutylene succinate. Among these polyamide elastomers, especially nylon 6
-Polypropylene glycol block copolymer and nylon 6-polytetramethylene glycol block copolymer are preferred. The fourth group of elastomer portions are polyurethane elastomers, with urethane as the hard segment. The urethane can be obtained by reacting a diisocyanate such as 4,4'-diphenylmethane diisocyanate or 4,4'-dicyclohexylmethane diisocyanate with a glycol such as ethylene glycol or tetramethylene glycol. Soft segments to be combined with urethane include polyester diols such as polyethylene adipate and polybutylene adipate, and polyether diols such as polypropylene glycol and polytetramethylene glycol. Among these polyurethane elastomers, polyurethanes synthesized from 4,4'-diphenylmethane diisocyanate, tetramethylene glycol and polytetramethylene glycol are particularly preferred. Further, the acetal block copolymer of the present invention can be used in the presence of a telescopic elastomer having two functional groups selected from the group consisting of a hydroxyl group, an amino group, and a carboxy group at the end of the polymer.
It can be obtained by polymerizing formaldehyde or trioxane, copolymerizing formaldehyde or trioxane with a cyclic ether or cyclic formal, or reacting polyoxymethylene with a cyclic ether or cyclic formal. Here, the telekirik elastomer functions as a molecular weight regulator during polymerization and reaction, and at the same time controls the molecular weight of the polymer, it is inserted into the polymer as a blocking macromer. Like the base material polyacetal, the acetal block copolymer is also subjected to addition after polymerization and reaction, converting the polymer terminal into a stable group. The amount of the acetal block copolymer added as component (C) is as follows:
It is selected from the range of 0.1 to 39.9 parts by weight. If the amount added is less than 0.1 part by weight, the impact resistance will not be improved sufficiently, and if it is more than 39.9 parts by weight, the strength and rigidity will decrease. It is also possible to further add a conventionally known compound to the composition of the present invention as a stabilizer for the acetal polymer. It is the first thermal stabilizer of known stabilizers, and includes amide compounds, polyamides, amidine compounds, melamine, polyvinylpyrrolidone, carboxylic acid metal salts, and the like. It is a second antioxidant of known stabilizers, and includes hindered phenol compounds and the like. Further, the third known stabilizer is a light stabilizer,
Examples include benzotriazole compounds and hydroxybenzophenone compounds. These stabilizers are usually acetal polymer compositions
It is added in an amount of 0.05 to 10 parts by weight, more preferably 0.08 to 3 parts by weight, per 100 parts by weight. To produce the acetal polymer composition of the present invention, each component is mixed with each other in powder or granular form,
Next, it is necessary to homogenize using a melting device such as an extruder. Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, the meanings of the terms in the examples are as follows. MI: Melt index at 190°C and 2.16Kg standard load (ASTM D1238 57T) Addition amount (Phr): Addition amount per 100 parts by weight of acetal polymer composition. Antioxidant AO-A: 2,2-methylenebis(4
-Methyl-6-t-butylphenol) Antioxidant AO-B: Pentaerythritol-tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenol)propionate] Izot impact value (notched): After adding a stabilizer, a composition consisting of polyacetal, ethylene copolymer, and acetal block copolymer was uniformly mixed and dissolved using an extruder. Next, a flat plate was formed, and a test piece was cut from this flat plate and measured according to ASTM D256. The larger the Izot impact value, the better the impact properties. Tensile strength: Cut a test piece from a flat plate, ASTM
Measured according to D638. The higher the tensile strength, the better the strength and rigidity. Example 1 (1) Synthesis of polymer (1-1) Polyacetal as component (A) Anhydrous formaldehyde was introduced into cyclohexane containing dibutyltin dilaurate as a polymerization catalyst, and polymerized at 56°C. After separating the polymer from cyclohexane, the terminals of the polymer were acetylated with acetic anhydride to stabilize the polymer. The MI of this polymer is 12.0 (g/10
minute). (1-2) Component (B) ethylene copolymer VOCl ₃ − (C ₂ H ₅ ) ₃ Mixing ethylene-propylene copolymer (EPM) synthesized from ethylene and propylene using an Al catalyst and maleic anhydride. Thereafter, dicumyl peroxide was added as a radical generator, and the mixture was denatured at 215°C in a 30 mmφ extruder. The number average molecular weight of the modified ethylene-propylene copolymer is 15×10 ⁴ . (1-3) Acetal block copolymer of component (C) Polyethylene-butylene terephthalate-polytetramethylene glycol copolymer (PET-PTG) is produced using terephthalic acid, ethylene glycol, tetramethylene glycol, and polytetramethylene glycol as starting materials. Synthesized. The number average molecular weight of this polymer is 2.8×10 ⁴ . Add anhydrous formaldehyde to the
The above PET-PTG was blown into toluene containing tetrabutylammonium acetate as a polymerization catalyst and polymerization was carried out at 75°C. The structure of the resulting polymer after acetylation was as follows, and the number average molecular weight was 6.2×10 ⁴ . (Here, X ₁ is PET-PTG, which is composed of the following soft segment and hard segment. Soft segment hard segment Moreover, a represents 1 to 1129. ) (2) Composition Components (A), (B), and (C) prepared in (1) and the stabilizer were mixed in the following proportions, and then melted and made uniform using a 50 mmφ extruder. Component (A) Polyacetal 82.7 parts by weight Component (B) Ethylene copolymer 5.0 parts by weight Component (C) Acetal block copolymer
12.3 parts by weight Nylon 6-6 0.5Phr AO-A 0.3Phr The physical properties of this composition were as follows. MI 12.1 (g/10 minutes) Izot impact value 22.6 (Kg·cm/cm) Tensile strength 615 (Kg/cm ² ) This composition has excellent impact properties as well as strength and rigidity. Moreover, the appearance of the molded product based on this composition was extremely beautiful, and no flow marks or the like were observed at all. This fact indicates that the polyacetal, ethylene copolymer and acetal block copolymer are mixed and dissolved extremely homogeneously. Example 2 (3) Synthesis of polymer (3-1) Polyacetal of component (A) After mixing 98% of anhydrous trioxane and 2% of ethylene oxide in a kneader with two Σ blades, trifluorocarbon was added as a polymerization catalyst. Boron dibutyl etherate was added to initiate polymerization. After polymerization at 78°C for 15 minutes, tributylamine was added to stop the polymerization. A mixture of triethylamine and water was added to this polymer, and the polymer was fed to a 30 mmφ extruder equipped with a vent to remove unstable portions at the ends.
The MI of the polymer that has undergone melt hydrolysis in an extruder to remove unstable terminal parts is 9.0 (g/10 min)
It was hot. (3-2) Ethylene copolymer of component (B) Ethylene and vinyl acetate are copolymerized using benzoyl peroxide as a polymerization catalyst.
A vinyl acetate copolymer was synthesized. The ethylene content in this polymer was 45% by weight, and the number average molecular weight was 1.0×10 ⁵ . (3-3) Acetal block copolymer of component (C) Anhydrous formaldehyde is
A polystyrene-hydrogenated polybutadiene block copolymer (terminated with hydroxyl group) was used as an elastomer. It was blown into toluene containing tetrabutylammonium acetate as a polymerization catalyst and polymerized at 60°C. The structure of the polymer after acetylation was as follows, and the number average molecular weight was 4.2×10 ⁴ . (Here, X ₂ is a polystyrene-hydrogenated polybutadiene block copolymer, which is composed of the following soft segments and hard segments. Soft segment (-CH ₂ - CH ₂ - CH ₂ - CH ₂ )- hard segment Moreover, b represents 1 to 799. ) (4) Composition Components (A), (B), and (C) prepared in (3) and the stabilizer were mixed in the following proportions, and then melted and homogenized using a 50 mmφ extruder. Component (A) Polyacetal 91.0 parts by weight Component (B) Ethylene copolymer 3.5 parts by weight Component (C) Acetal block copolymer
5.5 parts by weight Nylon 0.5Phr AO-B 0.2Phr The physical properties of this composition are as follows, and it has excellent impact properties. MI 9.0 (g/10 min) Izot impact value 21.3 (Kg・cm/cm) Tensile strength 590 (Kg/cm ² ) Example 3 (5) Synthesis of polymer (5-1) Component (A) Polyacetal MI1 Boron trifluoride dibutyl etherate was added as a polymerization catalyst to cyclohexane containing .8 (g/10 minutes) of polyoxymethylene dihydroxide and ethylene oxide, and the mixture was reacted at 75°C for 20 minutes. After terminating the reaction by adding tributylamine, the polymer was separated. Next, a mixture of triethylamine and water was added to this polymer, and unstable terminal portions were removed in a vented 50 mmφ extruder. The MI of the polymer after terminal stabilization is
It was 4.3 (g/10 minutes). (5-2) Ethylene copolymer of component (B) Using benzoyl peroxide as a polymerization catalyst,
Ethylene and ethyl acrylate were copolymerized to synthesize an ethylene-ethyl acrylate copolymer. The ethylene content in this polymer is 60
% by weight, and the number average molecular weight was 3.0×10 ⁴ . (5-3) Acetal block copolymer of component (C) Formaldehyde, ethylene glycol formal, toluene containing nylon 6-polytetramethylene glycol block copolymer as a telechelic elastomer, dibutyltin dimethoxide as a polymerization catalyst, and trifluoride. Boron diethyl etherate was added separately to initiate copolymerization. After reacting for 15 minutes at 32°C, the polymer was separated from toluene and then the ends of the polymer were acetylated. The structure of this polymer was as follows, and the number average molecular weight was 8.0×10 ⁴ . (Here, X ₃ is a polyamide elastomer part. c is 1 to 1669, and d is 1 to 16. Also, here, {-(-CH ₂ O)- _c (-CH ₂ CH ₂ O)- _b }- is C
This shows that d oxyethylene units are randomly inserted into a chain consisting of d oxymethylene units. ) (6) Composition Components (A), (B), (C) prepared in (5) and the stabilizer were mixed in the following proportions, and then melted and homogenized using a 50 mmφ extruder. Component (A) Polyacetal 84.6 parts by weight Component (B) Ethylene copolymer 5.4 parts by weight Component (C) Acetal block copolymer
10.0 parts by weight Melamine 0.5Phr AO-B 0.2Phr The physical properties of this composition are as follows, and the impact properties were greatly improved while maintaining good strength and rigidity. MI 4.6 (g/10 minutes) Izot impact value 22.4 (Kg・cm/cm) Tensile strength 580 (Kg/cm ² ) Comparative example 1 (method disclosed in JP-A-54-155248) Example 2 (3- Polyacetal synthesized in 1), ethylene-vinyl acetate copolymer synthesized in (3-2), dimethyl terephthalate, dimethyl isophthalate, tetramethylene glycol, and polyethylene glycol (n1000) as processing aids.
The synthesized segmented polyester, melamine and AO-A as stabilizers were added in the amounts shown below, and the mixture was melted and homogenized using a 50 mmφ extruder. (3-1) polyacetal 91.0 parts by weight (3-2) ethylene-vinyl acetate copolymer
3.5 parts by weight Segmented polyester 5.5 parts by weight Melamine 0.5 Phr AO-B 0.2 Phr The physical properties of this composition are as follows. MI 9.1 (g/10 minutes) Izot impact value 8.5 (Kg・cm/cm) Tensile strength 510 (Kg/cm ² ) Although the impact properties have been slightly improved, the strength and
The stiffness is reduced and the composition has unbalanced physical properties. In addition, melamine is added to the polyacetal (3-1).
The physical properties of the composition containing 0.5Phr and 0.2Phr of AO-B are as follows. MI 9.1 (g/10 minutes) Izot impact value 5.8 (Kg・cm/cm) Tensile strength 640 (Kg/cm ² ) Comparative example 2 (when no acetal block copolymer is added) Example 1 (1-1) ) polyacetal obtained from
The modified ethylene-propylene copolymer (1-2) and a stabilizer were added and melt-mixed using a 50 mmφ extruder. Polyacetal (1-1) 95.0 parts by weight (1-2) Modified ethylene-propylene copolymer 5.0 parts by weight Nylon 6-6 0.5 Phr AO-A 0.3 Phr The physical properties of this composition were as follows. MI 12.3 (g/10 min) Izot impact value 6.4 (Kg.cm/cm) Tensile strength 580 (Kg/cm ² ) The impact properties of this composition are poor. This is caused by polyacetal and modified ethylene-propylene copolymer not being uniformly mixed and dissolved. The appearance of molded articles based on this composition is poor and many flow marks are observed. This fact also indicates non-uniform mixing and dissolution. In addition, nylon 6 is added to the polyacetal (1-1).
The physical properties of the composition containing -60.5Phr and AO-A0.3Phr were as follows. MI 12.1 (g/10 minutes) Izot impact value 6.3 (Kg cm/cm) Tensile strength 720 (Kg/cm ³ ) Examples 4 to 9 Polyacetal homopolymer as component (A) (MI 15.0 g/10 minutes) , the ethylene copolymer shown in Table 1 as component (B) and the acetal block copolymer shown in Table 1 as component (C) were mixed, and then 0.5Phr of nylon 6/6-6 copolymer, AO- A0.3Phr
was added to this and homogenized using a 65 mmφ extruder. The physical properties of these compositions are also shown in Table 1. In all examples, compositions with excellent impact properties are obtained. Examples 10 to 14 Polyacetal copolymer (oxytetramethylene units, 100 oxymethylene units) as component (A)
Polymer containing 1.8 moles of MI9.0g/10 min), ethylene copolymer shown in Table 1 as component (B), acetal block copolymer shown in Table 1 as component (C) and then nylon 6
Add 0.2Phr, AO-B 0.4Phr to this, 30mmφ
Homogenization was carried out using a twin screw extruder. The physical properties of these compositions are also shown in Table 1. In all Examples, compositions with excellent impact properties were obtained.

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Claims (1)

[Scope of Claims] 1 (A) 99.8 to 60.0 parts by weight of polyacetal, (B) 0.1 ethylene copolymer having a second order transition temperature of -120 to +20°C and a number average molecular weight of between 10,000 and 500,000. ~30.0 parts by weight, (C) has a structure in which an elastomer having a secondary transition temperature of -120 to +40°C is inserted into the main chain of a linear polymer, and the number average molecular weight is between 10,000 and 500,000. An acetal polymer composition having excellent impact properties, comprising 0.1 to 39.9 parts by weight of an acetal block copolymer composed of an acetal polymer part and an elastomer part. 2 The polyacetal has oxymethylene units (-
The composition according to claim 1, which is a polyacetal homopolymer consisting of repeating _CH2O )-. 3 Polyacetal is a polymer consisting of repeating oxymethylene units, in which oxyalkylene units are (R ₀ : selected from hydrogen, an alkyl group, and an aryl group, each of which may be the same or different.
The composition according to claim 1, which is a polyacetal copolymer having a structure in which m=2 to 6) is inserted. 4. The composition according to claim 1 or 3, wherein the oxyalkylene unit is an oxyethylene unit [-(CH ₂ ) ₂ O]-. 5. The composition according to claim 1 or 3, wherein the oxyalkylene unit is an oxytetramethylene unit [-( _CH2 ) _4O ]-. 6. The composition according to claim 1, wherein the ethylene copolymer of component B is an ethylene-propylene copolymer, an ethylene-propylene-diene terpolymer, a modified ethylene-propylene copolymer, or a modified ethylene-propylene-diene terpolymer. . 7. The composition according to claim 1, wherein the ethylene copolymer of component B is an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, a modified ethylene-acrylic acid copolymer, or a modified ethylene-methacrylic acid copolymer. . 8 The ethylene copolymer of component B is an ethylene-acrylic acid ester copolymer or an ethylene-
The composition of claim 1 which is a methacrylate copolymer. 9. The composition according to claim 1, wherein the ethylene copolymer of component B is an ethylene-vinyl acetate copolymer. 10. The composition according to claim 1, wherein the elastomer portion in the acetal block copolymer of component C is a polystyrene elastomer. 11. The composition according to claim 1 or 10, wherein the polystyrene elastomer is a polystyrene-polybutadiene block copolymer or a polystyrene-hydrogenated polybutadiene block copolymer. 12. The composition according to claim 1, wherein the elastomer portion in the acetal block copolymer of component C is a polyester elastomer. 13 The polyester elastomer is a polybutylene terephthalate-polytetramethylene glycol block copolymer or a polyethylene glycol block copolymer.
13. The composition of claim 1 or 12, which is a butylene terephthalate-polytetramethylene glycol block copolymer. 14. The composition according to claim 1, wherein the elastomer portion in the acetal block copolymer of component C is a polyamide elastomer. 15 Polyamide elastomer is nylon-
15. The composition according to claim 1 or 14, which is a 6-polypropylene glycol block copolymer or a nylon-6-polytetramethylene glycol block copolymer. 16. The composition according to claim 1, wherein the elastomer portion in the acetal block copolymer of component C is a polyurethane elastomer. 17 Polyurethane elastomer is 4,4'-
17. The composition according to claim 1 or 16, which is a polyurethane synthesized from diphenylmethane diisocyanate, tetramethylene glycol, and polytetramethylene glycol.