JPS6212927B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing stable polyacetals. For more details, the number average molecular weight is 10000.
This relates to a method for producing a stable polyacetal that is excellent in both stability such as thermal stability and base stability and mechanical properties by reacting the above polyoxymethylene and alkylene oxide in the presence of a Lewis acid. It is. Polyacetal, which is industrially produced as an engineering plastic, includes acetal homopolymer, which is a homopolymer of formaldehyde, trioxane and ethylene oxide, 1,
Two types of acetal copolymers obtained by copolymerizing 4-butanediol with a cyclic ether such as formal are known. Acetal copolymers have a structure in which oxyalkylene groups are distributed in the main chain mainly consisting of oxymethylene groups, and the performance of acetal copolymers as engineering plastics is as follows when the content of oxyalkylene groups is constant. , determined by the distribution of oxyalkylene groups in the main chain. That is, a so-called random copolymer in which oxyalkylene groups are randomly distributed in the main chain has excellent stability such as thermal stability and base stability, and mechanical properties such as tensile strength and tensile elongation. On the other hand, so-called block copolymers in which oxyalkylene groups are distributed in a block state in the main chain, conversely,
Poor stability and mechanical properties. Therefore, how to randomly distribute the oxyalkylene groups in the main chain is one of the most important points in the production technology of acetal copolymers. Japanese Patent Publication No. 44-27667 discloses a method of reacting polyoxymethylene and ethylene oxide in an acidic reaction medium. In this invention, the concentration of ethylene oxide in the acidic reaction medium is high;
A large excess of ethylene oxide relative to polyoxymethylene is used. In the method of the present invention using a high concentration of ethylene oxide, the oxyethylene group is inserted in the main chain in a block state, resulting in a block copolymer, which is only inferior in stability and mechanical properties. Furthermore, in this invention, an overwhelmingly large amount of ethylene oxide is used compared to the ethylene oxide that should be inserted into the main chain, and the excess ethylene oxide undergoes cationic ring-opening polymerization with an acidic catalyst to form an ethylene oxide homopolymer. Form. Therefore, the selectivity of ethylene oxide in the reaction is poor, and this method is extremely disadvantageous in terms of industrial production. A first object of the present invention is to provide a method for producing a random copolymer in which oxyalkylene groups are randomly distributed in the main chain consisting of oxymethylene groups. A second object of the present invention is to provide a method for producing polyacetal, which has both good stability and mechanical properties due to the random distribution of oxyalkylene groups, and is highly valuable as an engineering plastic. be. A third object of the present invention is to provide industrial production with good selectivity of alkylene oxide in the reaction. As a result of extensive studies on the stabilization reaction of polyoxymethylene, the present inventors found that when polyoxymethylene and alkylene oxide are reacted in the presence of a Lewis acid, the concentration (M) of alkylene oxide in an organic medium is Mc=0.096P+0.003 (M: alkylene oxide concentration, Mc: critical concentration,
P: Polyoxymethylene concentration (unit: parts by weight/organic medium - 100 parts by weight) is maintained below the limit concentration (Mc), which provides excellent stability and mechanical properties. They discovered that stable polyacetals can be obtained in high yields, leading to the completion of the present invention. The present invention will be specifically explained below. The polyoxymethylene used as a starting material in the present invention is a polymer consisting of repeating oxymethylene groups (-OCH ₂ -), and is a polymer in which both ends of the polymer are hydroxyl groups, or one end or It is a polymer with both ends blocked by a known method. Esterification methods, etherification methods, urethanization methods, etc. are known as methods for blocking polymer terminals. The molecular weight (number average molecular weight) of polyoxymethylene must be at least 10,000 or more, but it is more preferably 30,000 or more in view of the practical performance of the polyacetal obtained as a result of the reaction. The upper limit of the molecular weight is mainly determined by the desired molecular weight of the polyacetal and, if a molecular weight regulator is used, the amount of the molecular weight regulator used, but it is more preferably 500,000 or less. In the present invention, the alkylene oxide to be reacted with polyoxymethylene has the general formula A compound having a structure represented by (R ₀ : selected from hydrogen, alkyl group, substituted alkyl group, aryl group, substituted aryl group, each of which may be the same or different, m = 2 to 6) This comes first. For example, ethylene oxide, propylene oxide, butylene oxide, trans-2,3-epoxybutane, cis-2,3-epoxybutane, isobutylene oxide, oxetane, 3,3-bis(chloromethyl)oxetane, tetrahydrofuran, 2-methyltetrahydrofuran, oxepane , styrene oxide, p-chlorostyrene oxide, etc. are included in this group. In addition to these compounds, cyclohexene oxide and the like can also be used. Among these alkylene oxides, ethylene oxide, propylene oxide, butylene oxide, styrene oxide and cyclohexene oxide are preferred, and ethylene oxide is particularly preferred, in view of the performance of the polyacetal produced as a result of the reaction. In the present invention, a Lewis acid is used as a catalyst for the reaction between polyoxymethylene and alkylene oxide. The first group of Lewis acids includes tin tetrachloride, tin tetrabromide, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, phosphorus pentafluoride, antimony trichloride, antimony pentafluoride, trichloride. Boron, boron tribromide, boron trifluoride, boron trifluoride methanolate, boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate,
Boron trifluoride acetate such as boron trifluoride triethylamine acetate, boron trifluoride dioxanate, boron trifluoride acetate anhydrate, boron trifluoride polyethylene glycol coordination compound, boron trifluoride ethylene oxide coordination compound Examples include Friedel-Crafts type compounds such as boron trifluoride coordination compounds such as , boron trifluoride tetrahydrofuran coordination compounds, and boron trifluoride epichlorohydrin coordination compounds. The second group of Lewis acids includes perchloric acid, acetyl perchlorate, t-butyl perchlorate, hydroxyacetic acid, trichloroacetic acid,
There are inorganic acids and organic acids such as trifluoromethanesulfonic acid and p-toluenesulfonic acid. The third group of Lewis acids includes complex salt compounds such as triphenylmethylhexafluoroantimonate, allyldiazonium hexachlorophosphate, and triethyloxonium tetrafluoroborate. A fourth group of Lewis acids includes organometallic compounds such as triethylaluminum, diethylaluminum chloride, aluminum isopropoxide, diethylzinc, and triethoxyboron. In addition to these four groups, molybdenum oxide acetylacetonate and the like can also be used as Lewis acids. Among these Lewis acids, Friederu-Crafts type compounds and complex salt compounds are more preferable in terms of activity, but inorganic acids, organic acids, and organometallic compounds can also be used by increasing the amount added. It can bring about the same effect as salt compounds. Among these Lewis acids, boron trifluoride, boron trifluoride acetate and boron trifluoride coordination compounds are preferred, and boron trifluoride dibutyl etherate is most preferably used. In the present invention, the molecular weight of the stabilized polyacetal polymer can also be arbitrarily adjusted using a molecular weight regulator. Molecular weight modifiers that can be used in the present invention include acetal compounds, orthoformates, alcohols, carboxylic acids, carboxylic acid anhydrides, and water. The first group of acetal compounds are:
There are formal compounds and hemiformal compounds represented by R ₂ OCH ₂ OR ₂ and HOCH ₂ OR ₂ . here
R ₂ is an alkyl group. Specific examples include methylal, diethoxymethane, di-iso-propoxymethane, di-n-butoxymethane, and butoxyhydroxymethane. The second group of acetal compounds are:
There is a polyacetal compound represented by R ₂ O(CH ₂ O) _o R ₂ . Here, n is an integer from 2 to 20. Specific examples include dioxymethylene dimethoxide, tetraoxymethylene dioctoxide, decaoxymethylene diisopropoxide, dioxymethylene diethoxide, and the like. These compounds are often difficult to isolate as single substances and are usually used as a mixture. The degree of polymerization (n) of these compounds can be determined using means such as nuclear magnetic resonance spectroscopy, gas chromatography, and liquid chromatography. The third group of acetal compounds is

There is an acetal compound represented by the formula: Specifically, dimethyl acetal, diethyl acetal, di-iso-propyl acetal,
Examples include di-t-butyl acetal, dihexyl acetal, dioctyl acetal, and the like. Orthoformate is a compound represented by HC(OR ₃ ) ₃ , where R ₃ is a group selected from an alkyl group and an aryl group. Specific examples include methyl orthoformate, ethyl orthoformate, diethylpropyl orthoformate, propyl orthoformate, and phenyl orthoformate. Alcohol is a compound represented by R ₃ OH, and specifically includes aliphatic alcohols such as methanol, ethanol, n-propanol, iso-butanol, lauryl alcohol, and stearyl alcohol, benzyl alcohol, and 2-phenyl ethanol. There are aromatic alcohols. Carboxylic acid is a compound represented by R ₄ COOH, where R ₄ is a group selected from hydrogen, an alkyl group, and an aryl group. Specifically, there are aliphatic carboxylic acids such as formic acid, acetic acid, propionic acid, lauric acid and stearic acid, and aromatic carboxylic acids such as benzoic acid and iso-phthalic acid. Carboxylic acid anhydride is

【formula】

【formula】

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It is a compound represented by the formula: Here, R ₅ is hydrogen or an alkyl group. Specifically, aliphatic carboxylic anhydrides such as acetic anhydride, propionic anhydride, stearic anhydride, succinic anhydride, dodecenylsuccinic anhydride, and maleic anhydride; aromatic carboxylic anhydrides such as phthalic anhydride and 4-methylphthalic anhydride; There are acid anhydrides. Among these molecular weight modifiers, formal compounds represented by R ₂ OCH ₂ OR ₂ , R ₂ O (CH 2 O) _o are used from the viewpoint of improving stability such as thermal stability and base _{stability of} the polymer. A polyacetal compound represented by R ₂ , and

An acetal compound represented by the formula is preferable, and methylal and diethyl acetal are particularly preferable from the viewpoint of ease of purification and availability. The reaction between polyoxymethylene and alkylene oxide is carried out 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. When using a molecular weight regulator, the molecular weight regulator is uniformly dissolved or dispersed in the reaction system. The concentration of the molecular weight regulator in the system is
Depending on the requirements of the desired molecular weight of the polyacetal, it can be easily determined by experiment. In the present invention, the concentration (M) of alkylene oxide in the organic medium is Mc=0.096P+0.003 (M: alkylene oxide concentration, Mc: critical concentration,
P: Polyoxymethylene concentration (unit: parts by weight/organic medium - 100 parts by weight) must be maintained below the critical concentration (Mc). When alkylene oxide is used at a concentration above the critical concentration, the oxyalkylene group inserted into the main chain becomes blocked. Further, in this case, a large amount of alkylene oxide homopolymer is produced, and the selectivity of alkylene oxide is greatly reduced. On the other hand, when alkylene oxide is used at a concentration below the critical concentration, the polymer produced as a result of the reaction becomes a random copolymer, which has poor stability such as thermal stability and base stability, and poor tensile strength and tensile elongation. It is possible to obtain polyacetal with excellent mechanical properties. Furthermore, almost no homopolymer of alkylene oxide is observed, and the selectivity of alkylene oxide is good. In the present invention, the Lewis acid is 1-10 ^-7 to 1×
Used at a concentration of 10 ^-1 mol/- organic medium. The reaction temperature is usually set between -20 and 230°C, but when the polyoxymethylene concentration (P) is 0 to 35 (parts by weight/organic medium -100 parts by weight), the temperature is set at 10 to 150°C.
℃, and when the polyoxymethylene concentration (P) is 35 or higher, it is often set between 80 and 230℃. There is no particular limit to the reaction time, but from 5 seconds
Set between 300 minutes. After a predetermined reaction time has elapsed, a basic substance such as sodium hydroxide, amine, or quaternary ammonium salt is added to the polymer, and the reaction is terminated. The polymer is usually heated with water and alcohol to remove unstable parts, and then stabilizers and the like are added before it is put into practical use. By using the production method of the present invention described in detail above, it has become possible to obtain a good polyacetal. The features of the present invention are listed below. (1) It is possible to produce a random copolymer in which oxyalkylene groups are randomly distributed in the main chain consisting of oxymethylene groups. (2) Polyacetals with excellent stability and mechanical properties can be obtained. (3) A polyacetal with a sufficiently high content of oxyalkylene groups in the main chain can be obtained. (4) The selectivity of alkylene oxide in the reaction is high and there is little loss of alkylene oxide. (5) By using a molecular weight regulator. , The molecular weight of polyacetal can be adjusted arbitrarily (6) By using a specific molecular weight regulator, it is possible to simultaneously adjust the molecular weight and improve stability. Measured values in the following examples are based on the following measurement method. Reduced viscosity: 0.5gr/in p-chlorophenol-tetrachlorethylene (1:1 weight ratio) solution
Polymer concentration of dl, measured at 60℃. It is a measure of molecular weight. Base stabilization yield: at 5% polymer concentration in benzyl alcohol containing 1% tributylamine
Polymer recovery rate when heat treated at 150℃ for 60 minutes.
It is a measure of stability. Rv222: The amount of polymer remaining after heating at 222°C under vacuum for 50 minutes. It is a measure of stability. Tensile yield point strength/Tensile yield point elongation: Polymer 20
80 parts water, 10 parts methanol, triethylamine
0.20 part was placed in an autograve and heated at 150°C for 1 hour to remove unstable parts in the polymer. 0.2 parts of cyanoguanidine and 0.5 parts of 2,2-methylene-bis(4-methyl-6-t-butylphenol) were added to 100 parts of this polymer, and the mixture was granulated and molded using a 50 mmφ extruder. The tensile yield point strength and tensile yield point elongation of molded products are measured based on ASTM D-638.
A measure of mechanical properties. NMR: Measured in a p-chlorophenol solution at 165°C with a polymer concentration of 5%, and analyzed the content and distribution of oxyalkylene groups. The present invention will be explained below with reference to some examples.
The present invention is not limited to these examples. Example 1 Polyoxymethylene dihydroxide having a reduced viscosity of 2.95 and thoroughly dried under reduced pressure 5.02
2.32 gr of methylal as a molecular weight regulator, 250 gr of ethylene oxide, and 50 kg of anhydrous toluene were charged into the reaction tank. After charging, the contents of the reaction tank were heated to 70°C. The reaction was started by adding 1.23g of boron trifluoride dibutyl etherate to the reaction tank. After maintaining the internal temperature of the reaction tank at 70℃ for 45 minutes,
The reaction was stopped by adding 550 gr of toluene containing 130 gr of tributylamine. After separating the polymer, it was washed five times with a large amount of methanol, and 5.03 kg of polymer was recovered. This polymer had a reduced viscosity of 1.76 and a desired molecular weight. The base stabilization yield of this polymer was 97%, and the Rv of the polymer after base stabilization was 97%.
was 99.2%, indicating good stability. The tensile strength at yield point and elongation at tensile yield point of this polymer were 638 Kg/cm ² and 25%, respectively, and it had good mechanical properties. Further, as a result of NMR measurement, this polymer contained 1.53 mol% of oxyethylene groups based on 100 mol of oxymethylene groups. Furthermore, the distribution of oxyethylene groups was random as shown in the table below.

[Table] Furthermore, the selectivity of ethylene oxide (ethylene oxide inserted into the polymer/ethylene oxide reacted) was as good as 94%. Examples 2 to 8 The same reagents as in Example 1 were used, and the same procedures as in Example 1 were carried out, except that the ethylene oxide used in Example 1 was used in the amount shown in Table 1. Results first
Shown in the table. In all Examples, random copolymers having both good stability and mechanical properties were obtained. Moreover, the selectivity of ethylene oxide is also good. Comparative Examples 1 to 4 The same reagents as in Example 1 were used, and the same operations as in Example 1 were carried out, except that the ethylene oxide used in Example 1 was used in the amount shown in Table 1. The results are shown in Table 1. When ethylene oxide is used at a high concentration, both stability and mechanical properties are poor, and the oxyethylene groups in the main chain become blocked and the content decreases. Furthermore, the selectivity of ethylene oxide also decreased, indicating that homopolymerization of ethylene oxide was occurring at the same time. Examples 9 to 11 All operations were performed in the same manner as in Example 1, except that among the reagents used in Example 1, ethylene oxide was increased to 608 gr, and polyoxymethylene was used in the amount shown in Table 2. are shown in Table 2. Good polymers were obtained in all Examples. Comparative Examples 5 to 6 All operations were performed in the same manner as in Example 1, except that among the reagents used in Example 1, ethylene oxide was increased to 608 gr, and polyoxymethylene was used in the amount shown in Table 2. are also shown in Table 2.
In all comparative examples, the blocking properties of oxyethylene groups increased and the selectivity of ethylene oxide decreased. Example 12 A flask was charged with 200 gr of polyoxymethylene diacetate having a reduced viscosity of 3.25, 12 gr of propylene oxide, and 1000 gr of cyclohexane, and the contents of the flask were heated to 75°C. The reaction was then started by adding 15 mg of triethyloxonium tetrafluoroborate to the flask. After maintaining the contents of the flask at 75 °C for 35 minutes,
The reaction was stopped by adding 12g of triethylamine.
Separately, washing and drying were performed to obtain 201gr of polymer.
The reduced viscosity of this polymer is 2.75, and the base stabilization yield is
The Rv of the polymer after base stabilization was 98.5%. Furthermore, as a result of NMR measurement, oxypropylene groups were found in this polymer.

[Formula] was found to be contained in an amount of 2.20 mol % based on 100 mol of oxymethylene groups, and its distribution was found to be almost random. Moreover, the selectivity of propylene oxide was 89%, which was good. Examples 13-17 Polyoxymethylene with a reduced viscosity of 2.80 (all
53% hydroxyl group, 47% methoxy group) 5.00
25 kg of alkylene oxide shown in Table 3, a molecular weight modifier when a molecular weight modifier was used, and toluene were charged into the reaction tank. The reaction was started by adding the Lewis acids listed in Table 3 to the reaction vessel. After maintaining the contents of the flask at 60 °C for 65 minutes,
The reaction was stopped by adding 500g of triethylamine. Then, the results shown in Table 3 were obtained without using separation, washing, or drying. In all Examples, random copolymers having desired molecular weights and good stability and mechanical properties were obtained. Comparative Examples 7 and 8 Among the reagents used in Example 12, except for increasing propylene oxide as shown in Table 3,
All the same reagents as in Example 12 were used, and the same procedure as in Example 12 was carried out. The results are shown in Table 3. It is clear that the use of propylene oxide in high concentrations is undesirable. Example 18 3.5 liters of slurry having the following composition was placed in a pressure-resistant screw conveyor with an inner diameter of 2 inches and a length of 4 m having a jacket heated to 105°C by a heating medium.
It was supplied continuously at the rate of Kg/HR. Polyoxymethylene dimethoxide (reduced viscosity 2.25) 52.0wt% Ethylene oxide 4.1wt% Toluene 43.9wt% Boron trifluoride dioxanate 0.01wt% The polymer was sampled from the exit of the screw conveyor and analyzed, and the following results were obtained. Obtained. Reduced viscosity 1.92 Base stabilized yield 93.5% Tensile strength at yield 620 Kg/cm ² Ethylene oxide content 1.61 mol% NMR measurements revealed that the oxyethylene groups in this polymer were randomly distributed.

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Claims (1)

[Claims] 1. When polyoxymethylene having a number average molecular weight of 10,000 or more and an alkylene oxide are reacted in an organic medium using a Lewis acid, the general formula (R ₀ : hydrogen, alkyl group, substituted alkyl group, aryl group, substituted aryl group, each of which may be the same or different, m = 2 to 6) The concentration (M) in the medium is Mc=0.096 P+0.003 (M: alkylene oxide concentration, Mc: critical concentration,
P: A method for producing a stable polyacetal, characterized by maintaining the polyoxymethylene concentration below the limit concentration (Mc) defined in (all parts by weight/organic medium - 100 parts by weight).