JPH032367B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new polyacetal, and particularly to a method for producing a new polyacetal having unprecedentedly excellent impact properties and fatigue resistance. Acetal polymers are usually formaldehyde,
It can be obtained by homopolymerizing trioxane or copolymerizing formaldehyde, trioxane, and a cyclic ether. In Japanese Patent Publication No. 41-21638, compounds such as methylal, methanol, formic acid, acetic anhydride, etc.
It is stated that it functions as a chain transfer agent during the polymerization reaction of trioxane. The impact properties of the polymers produced using these compounds are poor. US Pat. No. 3,346,663 describes polymerizing trioxane in the coexistence of polyethylene oxide. Also, special public service in 1987-
Publication No. 38603 also describes polymerizing trioxane in the presence of a copolymer of ethylene oxide and tetrahydrofuran. Further, Japanese Patent Publication No. 17895/1989 discloses a method of polymerizing trioxane in the coexistence of a primary polymer such as polyvinyl acetate. The impact properties of the polymers obtained using these methods are all poor, as will be clear from the comparative examples described later, and there is a large room for improvement. The present inventors extensively studied molecular weight regulators to be used during polymerization and found that a certain elastomer functions well as a molecular weight regulator. As a result, we have discovered a new polyacetal that has both excellent impact properties and fatigue resistance, which have not been seen in conventional acetal polymers. That is, the present invention has a soft segment and a hard segment, has a secondary transition temperature (Tg, glass transition temperature) in the range of -120 to +40°C, and is selected from a hydroxyl group, a carboxyl group, a carboxylic anhydride group, and an amino group. This is a novel method for producing polyacetal in which trioxane is homopolymerized or trioxane and a cyclic ether are copolymerized in the presence of a thermoplastic elastomer having three or more functional groups. The present invention will be specifically explained below. In the present invention, an elastomer having three or more functional groups selected from the group consisting of hydroxyl group, carboxyl group, carboxylic anhydride group, and amino group in the polymer is used as a molecular weight regulator in trioxane polymerization. The elastomer that can be used in the present invention is a thermoplastic polymer, which consists of an amorphous segment with a low secondary transition temperature (soft segment) and a segment that creates a thermoreversible crosslinked/bonded structure (hard segment). It is a copolymer of −120°C to +
It is a polymer with a second-order transition temperature of 40°C. Here, the second-order transition temperature of the elastomer is −120℃
It is necessary that the temperature is between ~+40℃. An improvement in the impact resistance of the polyacetal produced when an elastomer with a second-order transition temperature between -120°C and +40°C is used is observed. The elastomer functions as a molecular weight regulator during the polymerization reaction of trioxane, and at the same time controls the molecular weight of the polymer, it is also inserted into the polymer as a blocking macromer. Therefore, the polymer obtained in the present invention is a graft copolymer having an elastomer as a backbone polymer and polyoxymethylene as a branch polymer. The first elastomer that can be used in the present invention
This group is polyolefin elastomers, and includes unsaturated compound-modified ethylene-propylene copolymers and unsaturated compound-modified ethylene-propylene-diene terpolymers. The dienes to be copolymerized with ethylene and propylene as termonomers include dicyclopentadiene, ethylidene norbornene, methylene norbornene,
Examples include 1,4-hexadiene. Ethylene-propylene copolymers (EPM), ethylene-propylene-diene terpolymers (EPDM) can be used to synthesize acrylamide, maleic anhydride, acrylic acid, methacrylic acid, acrylic acid 2- It is modified with an acrylic ester such as hydroxyethyl, a methacrylic ester such as 2-hydroxyethyl methacrylate, or an unsaturated compound such as allyl alcohol. In the present invention, ethylene-propylene copolymers and ethylene-propylene-diene terpolymers modified with unsaturated compounds are used. Specifically, maleic anhydride modified ethylene-propylene copolymer (5 carboxylic anhydride groups),
2-hydroxyethyl methacrylate modified ethylene-propylene copolymer (4 hydroxyl groups), allyl alcohol modified ethylene-propylene-ethylidene norbornene terpolymer (~20 hydroxyl groups),
Methacrylic acid-modified ethylene-propylene copolymer (6 carboxyl groups), acrylamide-modified ethylene-propylene copolymer (amino groups ~
10 pieces) etc. The second group of elastomers are polystyrene-based elastomers, which are polymers in which polystyrene is used as a hard segment and modified with unsaturated compounds. Soft segments to be combined with polystyrene include diene polymers such as polybutadiene and polyisoprene, and hydrogenated diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene. Further, the unsaturated compound used for modification is the same as the compound used for modifying the polyolefin elastomer. Specifically, acrylamide-modified polystyrene-polybutadiene block copolymer (5 amino groups), maleic anhydride-modified polystyrene-polybutadiene block copolymer (10 carboxylic anhydride groups), 2-hydroxyethyl methacrylate-modified polystyrene-polyisoprene block Copolymer (5 hydroxyl groups, 1 carboxyl group), allyl alcohol-modified hydrogenated polystyrene-polybutadiene block copolymer (~20 hydroxyl groups),
Acrylic acid-modified polystyrene-polyisoprene block copolymer (5 carboxyl groups, 1 hydroxyl group), methacrylic acid-modified polystyrene-polybutadiene block copolymer (carboxyl group)
10, 1 hydroxyl group), etc. Prior to polymerization, elastomers are washed, adsorbed,
It is preferable that it be purified by methods such as drying.
Further, these elastomers can be used alone, or two or more kinds can be mixed and subjected to polymerization. In the polymerization of the present invention, sufficiently purified trioxane and cyclic ether are used as starting materials for polyacetal. The first group of cyclic ethers has the general formula

[Formula] (R ₀ : selected from hydrogen, alkyl group, and aryl group, each of which may be the same or different. m
There are alkylene oxides represented by =2 to 6). For example, ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin,
Examples include styrene oxide, oxetane, 3,3-bis(chloromethyl)oxetane, tetrahydrofuran, oxepane, and the like. Among these alkylene oxides, ethylene oxide is particularly preferred. The second group of cyclic ethers has the general formula

There is a cyclic formal represented by the formula. For example, ethylene glycol formal,
Propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal,
1,5-pentanediol formal, 1,6-
There is hexanediol formal. Among these cyclic formals, ethylene glycol formal, diethylene glycol formal and 1,4-butanediol formal are particularly preferred. The cyclic ether is 0.03 to 100 parts by weight, more preferably 0.1 to 100 parts by weight, based on 100 parts by weight of trioxane.
50 parts by weight are used. A cationic polymerization catalyst is used in the homopolymerization and copolymerization of trioxane of the present invention. Cationic polymerization catalysts include tin tetrachloride, tin tetrabromide, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimony pentafluoride, boron trifluoride, boron trifluoride diethyl etherate,
So-called Friedel-Crafts type compounds such as boron trifluoride coordination compounds such as boron trifluoride acetic anhydrate and boron trifluoride triethylamine complex compounds, perchloric acid, acetyl perchlorate, hydroxyacetic acid, trichloroacetic acid, Inorganic and organic acids such as p-toluenesulfonic acid, complex salt compounds such as triethyloxonium tetrafluoroborate, triphenylmethylhexafluoroantimonate, allyldiazonium hexafluorophosphate, allyldiazonium tetrafluoroborate, diethylzinc, triethyl aluminum,
Examples include alkyl metals such as diethylaluminum chloride. These cationic polymerization catalysts are trioxane
It is used in a range of 0.0005 to 5 parts by weight per 100 parts by weight. Polymerization is carried out without a solvent or in an organic medium. Organic media that can be used in the present invention include aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, and cyclopentane, benzene, toluene,
Examples include aromatic hydrocarbons such as xylene, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, ethylene chloride, and trichloroethylene, and halogenated aromatic hydrocarbons such as chlorobenzene and o-dichlorobenzene. These organic media may be used alone or in combination of two or more. The elastomer, which is a molecular weight regulator, is used after being uniformly dissolved or dispersed in the polymerization system. The concentration of the molecular weight regulator in the system can be easily determined by experiment, depending on the desired molecular weight of the polyacetal. The polymerization temperature is usually set between -20 and 150°C, more preferably 55 to 140°C in the case of no solvent, and more preferably 20 to 120°C in the case of using an organic medium. There are no particular restrictions on the polymerization time, but it is usually set between 5 seconds and 300 minutes. After a predetermined period of time has elapsed, a terminator is added to the reaction system to complete the polymerization. The obtained polymer is stabilized by removing unstable ends by hydrolysis or blocking unstable ends by a method such as esterification. The stabilized polyacetal is put into practical use with the addition of stabilizers and the like. The features of the method for producing polyacetal of the present invention, which have been described in detail above, are listed below. (1) Polyacetal has extremely excellent impact properties and fatigue resistance. (2) By using a specific elastomer, it is possible to impart excellent performance to polyacetal, and at the same time, the molecular weight of the polymer can be controlled arbitrarily. Measurement items in the following examples are as follows. MI: 2,2-methylene-bis(4-
methyl-6-tert-butylphenol) 0.25 parts,
0.50 part of nylon 6,6 was added and pelletized using a 50 mmφ extruder. The MI of this pellet is
Measured according to ASTM-D1238-57T, MI is a measure of molecular weight. Izot impact value (notched): The above pellet was molded into a flat plate using an injection molding machine. A test plate was cut from this flat plate and measured according to ASTM-D256. The larger the Izot impact value, the better the impact properties. Vibration fatigue characteristics: Cut a test piece from a flat plate,
Measured at 20°C and repeated vibration cycles of 1800 times/min in accordance with ASTM-D671. 10 The maximum stress that does not cause the specimen to break when subjected to repeated vibrations ⁶ times = fatigue strength is used as an index of fatigue resistance. The higher the fatigue strength, the better the fatigue resistance. Example 1 In a kneader having two Σ-type stirring blades, 500 parts of sufficiently purified trioxane (hereinafter, parts indicate parts by weight), 10 parts of ethylene oxide, and 2-hydroxyethyl methacrylate modified ethylene as a molecular weight regulator were added. -Propylene copolymer (5 hydroxyl groups
116 parts (hereinafter abbreviated as MEPM) were charged and heated to 70°C. Then, 0.35 part of boron trifluoride dibutyl etherate was added to this kneader, and the mixture was stirred for 35 minutes. After 35 minutes, 15 parts of tributylamine was added to stop the polymerization. The contents were taken out from the kneader and thoroughly washed with hot xylene. This washing removes unreacted MEPM. Next, 562 parts of polyacetal was obtained by vacuum drying. The physical properties of this polymer were as follows. MI 8.5 (g/10 minutes) Izot impact value 20.6 (Kg・cm/cm) Fatigue strength 267 (Kg/cm ² ) This polymer has the desired molecular weight and has excellent impact resistance and fatigue resistance. It has performance. Examples 2 to 12 The same reagents as in Example 1 were used, except that the starting materials and elastomers listed in Table 1 were used instead of the starting materials and elastomers used in Example 1. operated. The obtained results are also shown in Table 1. In all Examples, polyacetals having the desired molecular weight and excellent impact resistance and fatigue resistance were obtained. Comparative Examples 1 to 3 Instead of the elastomer used in Example 1, the first
Example 1 except that the polymers listed in the table were used.
The same procedure as in Example 1 was carried out using the same reagents.
The obtained results are also shown in Table 1. In all comparative examples, the impact resistance of the polymer was poor.

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Claims (1)

[Claims] 1. It has a soft segment and a hard segment, has a secondary transition temperature of -120 to +40°C, and has a functional group selected from a hydroxyl group, a carboxyl group, a carboxylic anhydride group, and an amino group. A method for producing polyacetal, which comprises homopolymerizing trioxane or copolymerizing trioxane and a cyclic ether in the presence of a thermoplastic elastomer having three or more elastomers. 2. The manufacturing method according to claim 1, wherein the thermoplastic elastomer is a polyolefin elastomer or a polystyrene elastomer. 3. The manufacturing method according to claim 1 or 2, wherein the polyolefin elastomer is an unsaturated compound-modified ethylene-propylene copolymer or an unsaturated compound-modified ethylene-propylene-dien terpolymer. 4. The production method according to claim 1 or 2, wherein the polystyrene elastomer is an unsaturated compound-modified polystyrene-polybutadiene block copolymer or an unsaturated compound-modified hydrogenated polystyrene-polybutadiene block copolymer. 5. The production method according to claim 1, wherein the cyclic ether is ethylene oxide. 6 The cyclic ether is ethylene glycol formal, diethylene glycol formal and 1,
The manufacturing method according to claim 1, wherein the compound is selected from 4-butanediol formal.