JPH0330628B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel polyacetal composition, and particularly to a polyacetal composition having unprecedented and excellent impact properties. Many attempts have been made to improve the impact properties of polyacetal. For example, the special public interest public
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 an 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 reacting a trioxane copolymer containing free amino groups with a polyether containing isocyanate groups. This method requires reducing the nitro groups in the polymer to amino groups, and the polymer has the defect of violently decomposing during the reduction operation. Furthermore, Japanese Patent Application Laid-Open No. 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. In addition, molded products based on this composition are
The addition of segmented polyester and polyurethane significantly reduces strength and rigidity. Strength·
The decrease in rigidity will become clear in the comparative examples later. Polyacetal is widely used as an engineering plastic due to its 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 polyacetal, the present inventors have found that a polyacetal composition made by adding a certain elastomer and an acetal block copolymer has outstanding impact properties. This discovery led to the completion of the present invention. Moreover, this composition maintains high strength and stiffness, and this composition can be appropriately called a highly balanced composition. That is, the present invention uses an elastomer having a second-order transition temperature of -120°C to +40°C and a number average molecular weight of between 10,000 and 500,000, and a linear polymer with -120°C in the main chain.
It has a structure in which an elastomer with a secondary transition temperature of ℃~+40℃ is inserted, and the number average molecular weight is 10,000.
The present invention relates to a polyacetal composition having excellent impact properties, which is comprised of polyacetal and an acetal block copolymer composed of an acetal polymer component and an elastomer component, and has a molecular weight between 500,000 and 500,000. The polyacetal composition of the present invention has an Izot impact value (notched) of 8 to 90 Kg·cm/cm, and has excellent impact properties never before seen. The demand for polyacetal as an engineering plastic has been increasing in recent years, and improving the impact properties of polyacetal has great industrial significance. Next, the polyacetal composition of the present invention will be explained in detail. The polyacetal used as the base material 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 copolymers are oxyalkylene units in a chain consisting of oxymethylene units. (R ₀ : 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 polyacetal composition,
Oxyethylene units [-(CH ₂ ) ₂ O]- and oxytetramethylene units [-(CH ₂ ) ₄ O]- are particularly preferred. A polyacetal copolymer is obtained by copolymerizing or reacting formaldehyde, trioxane, polyoxymethylene with a cyclic ether or cyclic formal. After polymerization and reaction, the polyacetal homopolymer and polyacetal copolymer are added as a base material after the polymer terminals are converted into stable groups. In the present invention, an elastomer and an acetal block copolymer composed of an acetal component and an elastomer component are added to the polyacetal base material. Further, the elastomer to be added and the elastomer component in the acetal block copolymer may have the same structure or may have completely different structures. The elastomer or elastomer component that can be used in the present invention has a second-order transition temperature (glass transition temperature, Tg) of -120°C to +40°C. What is elastomer and elastomer component here?
It is a thermoplastic polymer and is a copolymer of an amorphous segment with a low secondary transition temperature (soft segment) and a segment that creates a thermoreversible crosslinked/bonded structure (hard segment). The number average molecular weight of the elastomer or elastomer component is set between 10,000 and 500,000.
If the number average molecular weight is too low, the impact properties will not be improved sufficiently, and if it is too high, it will be difficult to mix and dissolve uniformly with the base material polyacetal. A first example of the elastomer or elastomer component of the present invention is a polystyrene-based elastomer, in which polystyrene is used as a hard segment. Soft segments to be combined with polystyrene include diene systems such as polybutadiene and polyisoprene, hydrogenated polybutadiene,
There are hydrogenated diene systems such as hydrogenated polyisoprene. Among these polystyrene elastomers, polystyrene-polybutadiene block copolymers and polystyrene-hydrogenated polybutadiene block copolymers are particularly preferred. The second part of the elastomer or elastomer component
An example of this is a polyester elastomer, in which a hard segment is a polyester such as polyethylene terephthalate, polybutylene terephthalate, modified polyethylene terephthalate, or 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 part of the elastomer or elastomer component
An example of this is a polyamide elastomer, in which the hard segment is made of polyamide such as nylon 6, nylon 6-6, or nylon 6-10.
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, nylon 6-polypropylene glycol block copolymer, nylon 6-polypropylene glycol block copolymer,
Polytetramethylene glycol block copolymers are preferred. The fourth elastomer or elastomer component
An example of this is a polyurethane elastomer in which urethane is used as a hard segment. Here, the urethane is 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. Next, the acetal block copolymer used in the present invention means that the main chain of the linear polymer contains -120°C to +
It is a polymer in which an elastomer with a second-order transition temperature of 40°C is inserted, and the acetal polymer component (A)
It is an ABA type triblock copolymer of elastomer component (B) and elastomer component (B). The acetal polymer component includes an acetal homopolymer component and an acetal copolymer component. The acetal homopolymer component is a polymer component consisting of repeating oxymethylene units (-CH ₂ O). An acetal copolymer component is an oxyalkylene unit in a chain consisting of oxymethylene units. (R′ ₀ : selected from hydrogen, an alkyl group, and an aryl group, each of which may be the same or different.
This is a polymer component having a structure in which m'=2 to 6) are randomly inserted. The insertion rate of oxyalkylene units in the acetal copolymer component 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. Elastomer components to be inserted into the backbone of the linear polymer include the polymers described above. Furthermore, the acetal block copolymer of the present invention is
Formaldehyde and trioxane are polymerized in the presence of a telechelic elastomer having two functional groups selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group at the end of the polymer, or
It can be obtained by copolymerizing formaldehyde or trioxane with a cyclic ether or cyclic formal, or by 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 number average molecular weight of the acetal block copolymer is set between 10,000 and 500,000. The content of the elastomer component in the acetal block copolymer is set between 0.5 and 50% by weight. In the present invention, the elastomer is polyacetal
It is added in an amount of 0.1 to 40 parts by weight per 100 parts by weight. If the amount of elastomer added is too low, the impact properties will not be improved sufficiently, and if it is too high, strength and rigidity will decrease. In addition, the amount of acetal block copolymer added is
It is determined by balancing the amount of elastomer added, but is usually in the range of 0.1 to 40 parts by weight. It is also possible to further add and use a conventionally known compound as a stabilizer for polyacetal to the composition of the present invention. The first of the known stabilizers are thermal stabilizers, such as amide compounds, polyamides, amidine compounds, melamine, polyvinylpyrrolidone, carboxylic acid metal salts, and the like. A second type of known stabilizer is an antioxidant, such as a hindered phenol compound. A third type of known stabilizer is a light stabilizer, which includes benzotriazole compounds, hydroxybenzophenone compounds, and the like. These stabilizers are usually used in an amount of 0.05 to 10 parts by weight, more preferably 0.05 to 10 parts by weight, per 100 parts by weight of polyacetal.
It is added in an amount of 0.08 to 3 parts by weight. To produce the polyacetal composition of the present invention, each component is mixed with each other in powder or granular form,
It is then necessary to homogenize using a melting device such as an extruder. The present invention will be specifically explained below using Examples.
Note that the terms used in the examples have the following meanings. MI: Melt index at 190℃, 2.16Kg standard load (ASTM D1238 57T) Addition amount (phr): Addition amount per 100 parts by weight of polyacetal 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): A composition consisting of polyacetal, elastomer, and acetal block copolymer was homogeneously mixed and dissolved using an extruder after adding a stabilizer. Next, a flat plate is formed, and a test piece is cut from this flat plate.
Measured according to ASTM D256, the higher 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) Polymer synthesis 1-1 Polyacetal 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 15.2 (g/10 min). 1-2 Elastomer Polyethylene/butylene terephthalate-polytetramethylene glycol block copolymer (hereafter
PET-PTG), the number average molecular weight of this elastomer is 2.8×10 ⁴ . 1-3 Acetal block copolymer PET-PTG synthesized from anhydrous formaldehyde as a telechelic elastomer in 1-2,
Polymerization was carried out at 75°C by blowing into toluene containing tetrabutylammonium acetate as a polymerization catalyst. The structure of the resulting polymer after acetylation is as follows, and the number average molecular weight is 6.2×10 ⁴ . (Here, X ₁ is PET-PTG, which is composed of the following soft segment and hard segment. Soft segment

[Formula] Hard segment

【formula】

[Formula] Also, a represents 1 to 1129) (2) Composition The following polymers and stabilizers were added to the polyacetal of 1-1, and then melt-mixed in a 50 mmφ extruder. Elastomer 1-2 (PET-PTG) 10.2 phr Acetal block copolymer 1-3 5.1 phr Nylon 6-6 0.5 phr AO-A 0.3 phr The MI of this composition is 14.6 (g/10 min). ,
It has the following physical properties. Izot impact value: 23.6 (Kg/cm/cm) Tensile strength: 610 (Kg/cm ² ) This composition has excellent impact properties as well as strength and rigidity. Furthermore, the appearance of molded products based on this composition was extremely beautiful, with no flow marks or the like being observed at all. This fact indicates that the polyacetal, elastomer and acetal block copolymer are mixed and dissolved extremely homogeneously. Example 2 (3) Synthesis of polymer 3-1 Polyacetal Anhydrous trioxane 98% and ethylene oxide 2
% in a kneader having two Σ blades, boron trifluoride dibutyl etherate as a polymerization catalyst was added to initiate polymerization. 15 at 78℃
After polymerization for one minute, tributylamine was added to stop the polymerization. A mixture of triethylamine and water was added to this polymer, and the mixture was supplied to a 30 mmφ extruder equipped with a vent. The MI of the polymer that has undergone melt hydrolysis in an extruder to remove unstable terminal parts is 9.0 (g/10
minute). 3-2 Elastomer Nylon 6-polypropylene glycol block copolymer obtained by polycondensing a prepolymer (n1550) made by reacting polypropylene glycol with adipic acid and ε-caprolactam polymer (nylon 6, n1170), this elastomer The number average molecular weight of is 1.8×10 ⁴ . 3-3 Acetal block copolymer Anhydrous formaldehyde was blown into toluene containing polystyrene-hydrogenated polybutadiene block copolymer (hydroxyl group terminal) as a telechelic elastomer and tetrabutylammonium acetate as a polymerization catalyst, and polymerization was carried out at 60°C. Summer. The structure of the polymer after acetylation is as follows, and the number average molecular weight is 4.2×10 ⁴ . (Here, X ₂ is a polystyrene-hydrogenated polybutadiene block copolymer and is composed of the following soft segments and hard segments. Soft segment (-CH ₂ -CH ₂ -CH ₂ -CH ₂ )- hard segment (b represents 1 to 799) (4) Composition The following polymers and stabilizers were added to the polyacetal of Composition 3-1, and then melt-mixed using a 50 mmφ extruder. Elastomer 3-2 3.6 phr Acetal block copolymer 3-3 2.0 phr Nylon 6-10 0.5 phr AO-B 0.2 phr The physical properties of this composition are as follows, and it has excellent impact properties. There is. MI 9.4 (g/10 minutes) Izot impact value 17.7 (Kg・cm/cm) Tensile strength 630 (Kg/cm ² ) Example 3 (5) Polymer synthesis 5-1 Polyacetal MI 1.8 g/10 minutes Poly Boron trifluoride dibutyl etherate was added as a polymerization catalyst to cyclohexane containing oxymethylene dihydroxide and ethylene oxide, and the mixture was reacted at 75°C for 20 minutes. After adding tributylamine to stop the reaction,
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 4.3 (g/10 min). 5-2 Elastomer 4,4'-diphenylmethane diisocyanate,
A polyurethane synthesized from tetramethylene glycol and polytetramethylene glycol, this elastomer has a number average molecular weight of 3.0×10 ⁴ . 5-3 Acetal block copolymer Formaldehyde, ethylene glycol formal, toluene containing nylon 6-polytetramethylene glycol block copolymer as a telechelic elastomer, and dibutyltin dimethoxide and boron trifluoride diethyl etherate as polymerization catalysts separately. and started copolymerization. 32℃
After reacting for 15 minutes, the polymer was separated from toluene, and then the terminals of the polymer were acetylated. The structure of this polymer is as follows, and the number average molecular weight is 8.0×10 ⁴ . (Here, X ₃ is a polyurethane elastomer component. c is 1 to 1669, and d is 1 to 16. Also, here [-(-CH ₂ O)- _c (-CH ₂ CH ₂ O)- _d ] - indicates that d oxyethylene units are randomly inserted into a chain consisting of c oxymethylene units) (6) Composition The following polymer is added to the polyacetal of 5-1, After adding the stabilizer, the mixture was melt-mixed using a 65 mmφ extruder. Elastomer 5-2 5.4 phr Acetal block copolymer 5-3 30.0 phr Melamine 0.5 phr AO-B 0.2 phr The physical properties of this composition are as follows, while maintaining good strength and rigidity. The characteristics have been greatly improved. MI 5.6 (g/10 minutes) Izot impact value 36.3 (Kg・cm/cm) Tensile strength 580 (Kg/cm ² ) Comparative example 1 (method of JP-A-54-155248) Example 2-3-1 ethylene-vinyl acetate copolymer as an elastomer, a segmented polyester synthesized from dimethyl terephthalate, dimethyl isophthalate, tetramethylene glycol, and polyethylene glycol (n1000) as processing aids, melamine and Add AO-A in the following amount,
The mixture was melt-mixed using a 50 mmφ extruder. EVA copolymer 4.0 phr Segmented polyester 4.0 phr Melamine 0.5 phr AO-B 0.2 phr The physical properties of this composition are as follows. MI 9.2 (g/10 minutes) Izot impact value 9.6 (Kg・cm/cm) Tensile strength 520 (Kg/cm ² ) Although the impact properties have been improved, the strength and rigidity have decreased, and this composition It has unbalanced physical properties. In addition, melamine is added to the polyacetal in 3-1.
The physical properties of the composition containing 0.5 phr and 0.2 phr 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) In 1-1 of Example 1 The elastomer obtained in Example 1-2 as an elastomer and the following stabilizer were added to the obtained polyacetal and melt-mixed using a 50 mmφ extruder. Elastomer 1-2 (PET-PTG) 10.2 phr Nylon 6-6 0.5 phr AO-A 0.3 phr The physical properties of this composition are as follows. MI 14.7 (g/10 min) Izot impact value 6.5 (Kg·cm/cm) Tensile strength 610 (Kg/cm ² ) The impact properties of this composition are poor. This is caused by the polyacetal and elastomer 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 of 1-1.
The physical properties of the composition to which 0.5 phr of AO-A and 0.3 phr of AO-A were added are as follows. MI 15.1 (g/10 min) Izot impact value 6.3 (Kg・cm/cm) Tensile strength 720 (Kg/cm ² ) Examples 4 to 9 Polyacetal homopolymer (MI 12.0 g/10
0.5 phr of elastomer, acetal block copolymer and nylon 6-10 as shown in Table 1)
0.3phr of AO-A was added and mixed and dissolved using a 65mmφ extruder. Further, the physical property values of these compositions are also shown in Table 1. In all Examples, compositions with excellent impact properties were obtained. Examples 10-13 Polyacetal copolymer (oxytetramethylene units per 100 moles of oxymethylene units)
Polymer containing 1.8 mole MI 9.0 g/10 minutes), elastomer as shown in Table 1, acetal block copolymer, and nylon 6 0.3 phr, AO-B
0.4phr was added and uniformly mixed and dissolved in a 30mmφ twin-screw extruder. The obtained physical property values are also included in the first
Shown in the table. In all Examples, compositions with excellent impact properties were obtained.

【table】

【table】

Claims (1)

[Claims] 1. An elastomer having a second-order transition temperature of -120°C to +40°C and a number average molecular weight of between 10,000 and 500,000, and a main chain of a linear polymer containing -120°C to +40°C. +40℃
An acetal block copolymer composed of an acetal polymer component and an elastomer component, which has a structure in which an elastomer having a second-order transition temperature of A polyacetal composition with excellent impact properties. 2. The composition according to claim 1, wherein the elastomer component in the elastomer or acetal block copolymer is a polystyrene elastomer. 3. The composition according to claim 1 or 2, wherein the polystyrene elastomer is a polystyrene-polybutadiene block copolymer or a polystyrene-hydrogenated polybutadiene block copolymer. 4. The composition according to claim 1, wherein the elastomer component in the elastomer or acetal block copolymer is a polyester elastomer. 5. The composition according to claim 1 or 4, wherein the polyester elastomer is a polybutylene terephthalate-polytetramethylene glycol block copolymer or a polyethylene-butylene terephthalate-polytetramethylene glycol block copolymer. 6. The composition according to claim 1, wherein the elastomer component in the elastomer or acetal block copolymer is a polyamide elastomer. 7 Polyamide elastomer is nylon 6-
Claim 1, which is a polypropylene glycol block copolymer or a nylon 6-polytetramethylene glycol block copolymer.
6. The composition according to item 6. 8. The composition according to claim 1, wherein the elastomer component in the elastomer or acetal block copolymer is a polyurethane elastomer. 9. The composition according to claim 1 or 8, wherein the polyurethane elastomer is a polyurethane synthesized from 4,4'-diphenylmethane diisocyanate, tetramethylene glycol, and polytetramethylene glycol. 10. The composition according to claim 1, wherein the amount of the elastomer added is in the range of 0.1 to 40 parts by weight based on 100 parts by weight of the polyacetal. 11. The composition according to claim 1, wherein the amount of the acetal block copolymer added is in the range of 0.1 to 40 parts by weight based on 100 parts by weight of the polyacetal. 12 Polyacetal has oxymethylene units (-
The composition according to claim 1, which is a polyacetal homopolymer consisting of repeating CH ₂ O). 13 In a polymer in which polyacetal is composed of repeating oxymethylene units, oxyalkylene units (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. 14. The composition according to claim 1 or 13, wherein the oxyalkylene unit is an oxyethylene unit [-(CH ₂ ) ₂ O]-. 15. The composition according to claim 1 or 13, wherein the oxyalkylene unit is an oxytetramethylene unit [-(CH ₂ ) ₄ O]-.