JPH032366B2 - - 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 the polymerization of trioxane in the presence of polyethylene oxide. Also, special public service in 1984.
Publication No. 38603 also describes polymerizing trioxane in the presence of a copolymer of ethylene oxide and tetrahydrofuran. Furthermore, Japanese Patent Publication No. 57-17895 discloses a method of copolymerizing 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 one functional group. The present invention will be specifically explained below. In the present invention, an elastomer having one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a carboxylic anhydride group, and an amino group is used as a molecular weight regulator in the polymerization of trioxane. 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 to +40
It is a polymer with a second-order transition temperature of °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 resulting polyacetal is observed only when using an elastomer with a second-order transition temperature between -120°C and 40°C. The elastomer functions as a molecular weight regulator during the polymerization reaction of trioxane, and simultaneously controls the molecular weight of the polymer and is added to the polymer as a blocking macromer. Therefore, the polyacetal produced in the present invention is an AB type diblock copolymer. 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 prepared with maleic anhydride, acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate in the presence or absence of peroxide. It is modified with unsaturated compounds such as acrylic esters such as, methacrylic esters such as 2-hydroxyethyl methacrylate, and 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 (one carboxylic anhydride group),
2-hydroxyethyl methacrylate modified ethylene-propylene copolymer (1 hydroxyl group), allyl alcohol modified ethylene-propylene-ethylidene norbornene terpolymer (1 hydroxyl group),
Examples include methacrylic acid-modified ethylene-propylene copolymer (one carboxyl group). The second group of elastomers are polystyrene-based elastomers, which have polystyrene as the 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. Further, in the present invention, it is also possible to use a modified polymer such as unsaturated compound-modified polystyrene-polybutadiene. Specifically, polystyrene-polybutadiene block copolymer (one hydroxyl group), hydrogenated polystyrene-polybutadiene block copolymer (one carboxyl group), maleic anhydride-modified polystyrene-polybutadiene block copolymer (one carboxylic anhydride group), methacrylic Examples include acid-modified polystyrene-polyisoprene block copolymer (one carboxyl group). The third group of elastomers are polyester elastomers, which have aromatic polyester as a hard segment. Soft segments to be combined with aromatic polyesters include aliphatic polyethers, aliphatic polyesters, and the like. Specifically, polyethylene terephthalate-polypropylene glycol block copolymer (one hydroxyl group), polybutylene terephthalate-polytetramethylene glycol block copolymer (one hydroxyl group), polyethylene-butylene terephthalate-polytetramethylene glycol block copolymer (one carboxyl group) ), bis(β-
Examples include elastomers (one hydroxyl group) synthesized from hydroxyl ethyl) terephthalate, terephthalic acid, and polytetramethylene glycol. The fourth group of elastomers is polyamide-based elastomers, which have polyamide as the hard segment. Soft segments to be combined with polyamides include aliphatic polyesters.
There are polyesters, aliphatic polyesters, etc. Specifically, nylon 6-polypropylene glycol block copolymer (one amino group), nylon 6-polyethylene adipate block copolymer (one carboxyl group), nylon 6,6-
Polybutylene succinate block copolymer (1 amino group), nylon 6-polytetramethylene glycol block copolymer (1 hydroxyl group),
Examples include nylon 12-polypropylene glycol block copolymer (one carboxyl group). The fifth group of elastomers is polyurethane-based elastomers, which have polyurethane as a hard segment. Soft segments to be combined with polyurethane include aliphatic polyethers, aliphatic polyesters, and the like. Specifically, elastomers (one hydroxyl group) synthesized from 4,4'-diphenylmethane diisocyanate, tetramethylene glycol, and polytetramethylene glycol, elastomers (one hydroxyl group) synthesized from tolylene diisocyanate, propylene glycol, and polypropylene glycol, 1
elastomers (having one carboxyl group) synthesized from 4,4'-dicyclohexylmethane diisocyanate, ethylene glycol, and polyethylene propylene adipate. 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 [Formula]. 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. 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 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 1 500 parts of sufficiently purified trioxane (hereinafter, parts indicate parts by weight), 10 parts of ethylene oxide, and polybutylene terephthalate-polytetramethylene glycol block as a molecular weight regulator were placed in a kneader having two Σ-type stirring blades. 120 parts of a copolymer (one hydroxyl group, hereinafter abbreviated as PBT-PTG) was charged and heated to 70°C. Next, to this kneader,
0.35 part of boron trifluoride dibutyl etherate was added and 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 chloroform. This washing removes unreacted PBT-PTG. Next, 517 parts of polyacetal was obtained by vacuum drying. The physical properties of this polymer were as follows. MI 9.4 (g/10 minutes) Izot impact value 20.6 (Kg・cm/cm) Fatigue strength 268 (Kg/cm ² ) This polymer has the desired molecular weight and has excellent impact resistance and fatigue resistance. It has performance. Examples 2 to 14 The same reagents as in Example 1 were used, except that the starting materials and elastomers listed in Table 1 were used in place of the starting materials and elastomers used in Example 1, and the same procedure as in Example 1 was carried out. 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, it was difficult to control the molecular weight;
Also, 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 one thermoplastic elastomer. 2. The manufacturing method according to claim 1, wherein the thermoplastic elastomer is an elastomer selected from polyolefin elastomers, polystyrene elastomers, polyester elastomers, polyamide elastomers, and polyurethane elastomers. 3. The production 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. Claim 1 or 2, wherein the polystyrene elastomer is an elastomer selected from polystyrene-polybutadiene block copolymers, hydrogenated polystyrene-polybutadiene block copolymers, and unsaturated compound-modified polystyrene-polybutadiene block copolymers.
Manufacturing method described in section. 5 The polyester elastomer is polybutylene terephthalate-polytetramethylene glycol block copolymer or polyethylene. The method according to claim 1 or 2, which is a butylene terephthalate-polytetramethylene glycol block copolymer. 6 Polyamide elastomer is nylon 6-
Claim 1, which is a polypropylene glycol block copolymer or a nylon 6-polytetramethylene glycol block copolymer.
The manufacturing method described in Section 1 or Section 2. 7. The production method according to claim 1 or 2, wherein the polyurethane elastomer is a polyurethane synthesized from 4,4'-diphenylmethane diisocyanate, tetramethylene glycol, and polytetramethylene glycol. 8. The production method according to claim 1, wherein the cyclic ether is ethylene oxide. 9 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.