JPH0329088B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel acetal copolymer, and particularly to a method for producing a novel acetal copolymer having unprecedentedly excellent impact resistance and fatigue resistance. Polyacetal is usually obtained by homopolymerizing formaldehyde or trioxane, or by copolymerizing formaldehyde or trioxane with a cyclic ether. Japanese Patent Publication No. 35-9435 states that the molecular weight of a formaldehyde polymer is determined by the amounts of trace amounts of water, methanol, and formic acid present in the polymerization system. Further, US Pat. No. 3,017,389 describes that formaldehyde is polymerized in the coexistence of a chain transfer agent such as an alcohol, ester, acid anhydride, amide, or imide. Furthermore, Japanese Patent Publication No. 35-2194 discloses that formaldehyde is polymerized in the presence of polymers such as polytetramethylene glycol, vinyl acetate copolymer, and methyl methacrylate/vinyloxymethylmethylamine copolymer. ing. The polyoxymethylene block copolymer produced using this method has slightly improved toughness, but has a significant decrease in strength. In other words, this copolymer has too much flexibility, resulting in a significant decrease in strength and rigidity. This will also become clear in the comparative examples later on. Acetal polymers are useful as engineering plastics due to their well-balanced physical properties. Attempts to improve toughness such as elongation and impact value even at the expense of strength and rigidity, as in the case of the copolymer of the present invention, cannot necessarily be said to be an advantageous direction. 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, this is not found in conventional acetal polymers. We have discovered a new acetal copolymer that has both extremely excellent impact resistance and fatigue resistance. Moreover, this copolymer has improved toughness while maintaining high strength and rigidity. Therefore, the copolymers of the present invention can be appropriately called highly balanced polymers. That is, the present invention provides a thermoplastic elastomer having a soft segment and a hard segment, a second-order transition temperature (Tg, glass transition temperature) of -120 to +40°C, and at least one carboxylic anhydride group. This is a novel method for producing acetal copolymers, in which formaldehyde is homopolymerized or formaldehyde or polyoxymethylene is copolymerized with a cyclic ether. The present invention will be specifically explained below. In the present invention, a thermoplastic elastomer having at least one carboxylic anhydride group in the polymer is used as a molecular weight regulator in the homopolymerization of formaldehyde or the copolymerization of formaldehyde or polyoxymethylene with a cyclic ether. The elastomer that can be used in the present invention is a thermoplastic polymer, consisting 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 with -120 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 to
It is necessary that the temperature be between +40℃. An improvement in the impact resistance of the resulting acetal copolymers is observed only when using elastomers with secondary transition temperatures between -120 and +40°C. The elastomer functions as a molecular weight regulator during the polymerization reaction, and at the same time controls the molecular weight of the polymer.
It is incorporated into the polymer as a blocking macromer. The first elastomer that can be used in the present invention
This group includes polyolefin elastomers, such as unsaturated compound-modified ethylene-propylene copolymers and unsaturated compound-modified ethylene-propylene-diene terpolymers. The dienes copolymerized with ethylene and propylene as termonomers include dicyclopentadiene, ethylidene norbornene, methylene norbornene, 1,4
-Hexadiene, etc. Ethylene-propylene copolymers (EPM), ethylene-propylene-diene terpolymers (EPDM) can be prepared in the presence or absence of peroxides by maleic anhydride, methylmaleic anhydride, itaconic anhydride, citraconic anhydride, It is modified with unsaturated compounds such as glutaconic anhydride, muconic anhydride, acetylene dicarboxylic anhydride, and phthalic anhydride. 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 (2 carboxylic anhydride groups), maleic anhydride-modified ethylene-propylene-ethylidene norbornene terpolymer (~10 carboxylic anhydride groups), itaconic anhydride-modified ethylene-propylene. There are copolymers (one carboxylic anhydride group), citraconic anhydride-modified ethylene-propylene-dicyclopentadiene terpolymers (five carboxylic anhydride groups), and the like. The second group of elastomers are polystyrene-based elastomers, which are unsaturated compound-modified elastomers that have polystyrene as a hard segment. 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. The unsaturated compound used to modify the polystyrene elastomer is the same as the compound used to modify the polyolefin elastomer. Specifically, maleic anhydride-modified polystyrene-polyisoprene block copolymer (2 carboxylic anhydride groups), maleic anhydride-modified hydrogenated polystyrene-polybutadiene block copolymer (~10 carboxylic anhydride groups), itaconic anhydride-modified polystyrene. -Polyisoprene block copolymer (5 carboxylic anhydride groups), citraconic anhydride-modified polystyrene-polybutadiene block copolymer (1 carboxylic anhydride group), and the like. 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 of them can be mixed and subjected to polymerization. In the polymerization of the present invention, sufficiently purified formaldehyde, polyoxymethylene, and cyclic ether are used as starting materials for the acetal copolymer. Here, polyoxymethyllene is a homopolymer of formaldehyde or trioxane,
For example, the number average molecular weight is preferably 10,000 to 500,000
30,000 to 150,000. The first group of cyclic ethers has the general 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 For example, ethylene glycol formal, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4
-butanediol formal, 1,5-pentanediol formal, and 1,6-hexanediol formal. Among these cyclic formals, ethylene glycol formal, diethylene glycol formal and 1,4-butanediol formal are particularly preferred. Cyclic ether, based on 100 parts by weight of starting materials,
0.03 to 100 parts by weight, more preferably 0.1 to 50 parts by weight are used. Generally, an anionic polymerization catalyst is used for the homopolymerization of formaldehyde in the present invention, and a cationic polymerization catalyst or an anionic polymerization catalyst and a cationic polymerization catalyst is used for the copolymerization of formaldehyde and a cyclic ether. Further, a cationic polymerization catalyst is usually used for copolymerization (reaction) of polyoxymethylene and cyclic ether. Anionic polymerization catalyst used in the polymerization of the present invention,
Cationic polymerization catalysts are the following compounds. Typical groups of anionic polymerization catalysts include alkali metals such as sodium and potassium, alkali metal complexes such as sodium-naphthalene and potassium-anthracene, alkali metal hydrides such as sodium hydride, and alkaline earths such as calcium hydride. metal hydrides, alkali metal alkoxides such as sodium methoxide and potassium t-butoxide, alkali metal carboxylates such as sodium caproate and potassium stearate, alkaline earth metal carboxylates such as magnesium caproate and calcium stearate, Amines such as n-butylamine, diethylamine, trioctylamine, pyridine, ammonium stearate,
Quaternary ammonium salts such as tetrabutylammonium methoxide and dimethyldistearylammonium acetate; phosphonium salts such as tetramethylphosphonium propionate and trimethylbenzylphosphonium ethoxide; quaternary ammonium salts such as tributyltin chloride, diethyltin dilaurate, and dibutyltin dimethoxide Examples include valent organic tin compounds, alkyl metals such as n-butyllithium, and ethylmagnesium chloride. 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 anionic polymerization catalysts and cationic polymerization catalysts are used in an amount of 0.0005 to 5 parts by weight based on 100 parts by weight of the starting material. 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 reaction system. The concentration of the molecular weight regulator in the system can be easily determined by experiment, depending on the molecular weight requirements of the desired acetal copolymer. The polymerization temperature is usually set between -20 and 230°C, but preferably between 20 and 210°C when using no solvent, and between -10 and 120°C when using an organic medium.
It is more preferable. There are no particular restrictions on polymerization time, but from 5 seconds to
Set between 300 minutes. After a predetermined period of time has elapsed, a terminator is added to the reaction system to complete the polymerization reaction. The obtained polymer is stabilized by removing unstable ends by hydrolysis or blocking unstable ends by a method such as esterification. The stabilized acetal copolymer is put into practical use with the addition of a stabilizer and the like. The features of the acetal copolymer of the present invention and its production method which have been described in detail above are listed below. (1) The acetal copolymer has extremely high impact resistance, fatigue resistance, toughness, strength, and rigidity. (2) By using a specific elastomer, it is possible to impart excellent performance to the acetal copolymer, 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 piece was cut from this flat plate and measured according to ASTM-D256. The larger the Izot impact value, the better the impact resistance. 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 Formaldehyde gas with a purity of 99.9% was mixed at a rate of 100 parts (hereinafter, parts are by weight) per hour,
61.5 gr/maleic anhydride modified ethylene-propylene copolymer (~10 carboxylic anhydride groups) as a molecular weight regulator, 3.5 x 10 ^-4 mol/ as a polymerization catalyst
The mixture was continuously fed into 500 parts of toluene containing dimethyl distearyl ammonium acetate for 3 hours. Toluene containing the elastomer and polymerization catalyst at the above concentrations was also continuously fed at a rate of 500 parts/hr for 3 hours, and the polymerization temperature was maintained at 62° C. during this period. The polymer was separated from toluene, washed and dried to obtain 389 parts of polymer. After acetylating this polymer, it was extracted in benzyl alcohol at 160° C. for 5 hours, but no unreacted elastomer was extracted. From this, it became clear that all the elastomer was inserted into the polymer. The physical properties of this polymer were as follows. MI 1.6 (g/10 minutes) Izot impact value 32.4 (Kg・cm/cm) Fatigue strength 283 (Kg/cm ² ) This polymer has the desired molecular weight and has excellent impact resistance and fatigue resistance. It has performance. Example 2 Formaldehyde was used as a molecular weight regulator at a ratio of 100 parts/hr and ethylene oxide at a ratio of 2.2 parts/hr.
65.2 gr/maleic anhydride modified hydrogenated polystyrene-polyisoprene block copolymer was continuously fed into 500 parts of toluene for 5 hours. Toluene containing elastomer at the above concentration was also continuously fed at a rate of 500 parts/hr for 5 hours.
Additionally, as polymerization catalysts, tetrabutylammonium acetate and boron trifluoride dibutyl etherate were continuously supplied through separate conduits at a rate of 0.03 parts/hr and 0.08 parts/hr, respectively, for 5 hours, and the polymerization temperature was maintained at 60°C during this time. did. The polymer was separated from toluene, then washed and dried to obtain 692 parts of polymer. After acetylating this polymer, it was extracted in benzyl alcohol at 160° C. for 5 hours, but no unreacted elastomer was extracted. From this, it became clear that all the elastomer was inserted into the polymer. The physical properties of this polymer are as follows. MI 2.8 (g/10 minutes) Izot impact value 268 (Kg・cm/cm) Fatigue strength 26.9 (Kg/cm ² ) This polymer also has a specified molecular weight and at the same time has excellent impact resistance. . Example 3 Polyoxymethylene thoroughly dried under reduced pressure
5.08Kg, ethylene glycol formal 418gr,
A reaction tank was charged with 3.35 kg of maleic anhydride-modified ethylene-propylene-ethylidene nobornene terpolymer (3 carboxylic anhydride groups) and 50 kg of cyclohexane as molecular weight regulators. After charging, the contents of the reaction tank were heated to 70°C. The reaction was started by adding 1.25g of boron trifluoride dibutyl etherate to the reaction tank. After maintaining the internal temperature of the reaction tank at 70℃ for 32 minutes,
The reaction was stopped by adding 550 gr of cyclohexane containing 130 gr of tributylamine. After filtering off the polymer,
After washing with a large amount of methanol 5 times, 8.41 kg of polymer was recovered. Even by hot benzyl alcohol extraction of this polymer, no elastomer could be detected. From this, it became clear that all the elastomer was inserted into the polymer. The physical properties of this polymer are as follows. MI 12.3 (g/10 minutes) Izot impact value 28.4 (Kg·cm/cm) Fatigue strength 267 (Kg/cm ² ) This polymer also has a desired molecular weight and excellent impact resistance. Examples 4 to 13 Using the starting materials and elastomers shown in Table 1, acetal copolymers having the physical properties shown in Table 1 were obtained. Both polymers have desired molecular weights and excellent impact resistance. Comparative Examples 1 to 4 Instead of the elastomer used in Example 1, the first
A block copolymer was obtained using a polymer having the active hydrogen shown in the table. The physical properties of these polymers are also shown in Table 1. A block copolymer of formaldehyde and a polymer having active hydrogen atoms shows almost no improvement in impact resistance.
At the same time, the fatigue strength also decreases significantly. The physical properties of the polyoxymethylene homopolymer are as follows. MI 12.2 (g/10 min) Izot impact value 6.8 (Kg・cm/cm) Fatigue strength 330 (Kg/cm ² ) Polyoxymethylene copolymer containing 1.5 mol% oxyethylene units obtained by copolymerization of trioxane and ethylene oxide The physical property values are as follows. MI 12.0 (g/10 minutes) Izot impact value 4.9 (Kg・cm/cm) Fatigue strength 260 (Kg/cm ² )

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Claims (1)

[Claims] 1. Formaldehyde alone in the presence of a thermoplastic elastomer that has soft segments and hard segments, has a secondary transition temperature of -120 to +40°C, and has at least one carboxylic anhydride group. A method for producing an acetal copolymer, which comprises polymerizing or copolymerizing formaldehyde or polyoxymethylene with a cyclic ether. 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 method according to claim 1 or 2, wherein the polystyrene elastomer is an unsaturated compound-modified polystyrene-polydiene block copolymer or an unsaturated compound-modified hydrogenated polystyrene-polydiene 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 method according to claim 1, wherein the compound is selected from 4-butanediol formal.