JP2009249451A - Method for producing polyacetal resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an effective method for producing a polyacetal resin. <P>SOLUTION: In this method for producing a polyacetal resin, when polymerization of trioxane is carried out in a melt condition, a cationic catalyst consisting of a superacid is inactivated by using a compound containing an alkali metal and/or an alkaline earth metal, which are/is soluble in trioxane and exhibit/exhibits basicity, and a stable polyacetal resin is obtained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to industrially obtaining an important polyacetal resin as an engineering resin. More particularly, the present invention relates to an improved production method for obtaining a stable polyacetal resin in a uniform reaction system in polymerization of trioxane or copolymerization of trioxane and cyclic formal.

Until now, attempts have been made to obtain polyacetal resins by polymerization of trioxane or copolymerization of trioxane with cyclic ether and cyclic formal. In particular, an attempt to obtain a stable polyacetal resin copolymer is interesting.
For example, in the conventional methods, a solid polyacetal resin copolymer is produced by polymerization of trioxane or copolymerization with cyclic formal, and then a method of pulverizing the polymer has been adopted. For example, Patent Document 1 made by the present applicant proposes a method of pulverizing a polyacetal resin copolymer and then deactivating the catalyst in an aqueous base solution. Similarly, in Patent Document 2 made by the present applicant, continuous polymerization, subsequent pulverization of the polymer, subsequent contact with a base, and drying of the polymer are all performed in succession. It is proposed to perform in an active gas atmosphere. In particular, the latter method of the present applicant has been noted as the most preferable method for obtaining a stable polyacetal resin copolymer. However, the problem is that the apparatus is complicated, such as fine pulverization of a solid polymer.

Furthermore, another method for producing a stable polyacetal resin has been proposed by the present applicant. For example, in Patent Document 3, trioxane is homopolymerized or copolymerized with 1,3-dioxolane by using a kneader at 80 ° C. to obtain trifluoromethanesulfonic acid (molar ratio of 5 × 10 ⁻⁸ to 2 × 10 ^{−7 in} the range) is used as a polymerization catalyst, an ion adsorbent is added to the obtained granular polyacetal resin (or polyacetal resin copolymer), and heated to the melting point or higher to adsorb the cationic polymerization catalyst. Has proposed. Similarly, Patent Document 4 proposes to add an ionic adsorbent to a polyacetal resin obtained using a cationically active polymerization catalyst to adsorb the cationic polymerization catalyst.
However, these methods clarify the adsorption method of the cationic polymerization catalyst obtained with the granular polyacetal resin, but do not clarify the adsorption method of the cationic polymerization catalyst obtained by melt polymerization.

On the other hand, as described in Patent Document 3, as a method for producing a polyacetal resin, a polymerization reaction is usually performed at a temperature below the ceiling temperature of the polyacetal resin (Ceiling Temperature: 119 ° C.), and a polymerization apparatus such as a kneader is used. Thus, a granular or powdery polyacetal resin is obtained.
In Patent Document 5, however, trioxane is mass-polymerized in a temperature range of 135 to 300 ° C., and a monomer and a polymer are present in a molten state during the polymerization to obtain a polyacetal resin having a molecular weight of 20,000 or more. Is proposing a simple manufacturing method.
Patent Document 6 proposes the use of a static mixer in a production method in which trioxane and polyacetal resin are in a molten state during polymerization. Patent Document 7 proposes a polymerization method by stirring using a protonic acid such as trifluoromethanesulfonic acid. In order to deactivate the cationic polymerization catalyst, it is proposed to use 0.05 to 1.0% (w / w) of a basic compound such as triethylamine with respect to the polymer.
It has been pointed out that these methods for obtaining a polyacetal resin in the molten state have side reactions during the polymerization reaction and difficulty in deactivating the polymerization catalyst. For example, Patent Document 7 shows that several% of unstable end portions exist even after inactivation.

Further, as shown in Patent Document 7, when a volatile base such as triethylamine is used as a quenching agent, when unreacted trioxane is recovered, triethylamine and the like are contained in the recovered trioxane and used for polymerization. Requires further purification. Note that Patent Document 5 or Patent Document 7 reveals that the unreacted trioxane is about 20 to 40% by mass with respect to the trioxane charged normally.
In Patent Document 8, perchloric acid is used as a cationic polymerization catalyst, trioxane is polymerized in a melt state, and then a master batch in which CH ₃ ONa (sodium methoxide) is dispersed in a polyacetal resin is used for polymerization. It has been proposed that CH ₃ ONa in an amount 10 times the amount of the catalyst is introduced into the polymerization reaction product, mixed and neutralized for 10 minutes to deactivate the polymerization catalyst. However, this method has problems such as that the neutralization reaction takes 10 minutes and that the product tends to be colored due to the contact between CH ₃ ONa and formaldehyde at a high temperature for 10 minutes. Further, there is a problem that even when CH ₃ ONa is dispersed in the polyacetal resin, the neutralization reaction is not completed in a short time of 1 minute or less.

Japanese Patent Publication No. 2-33572 Japanese Patent Publication No. 6-89090 Japanese Patent Publication No. 6-92476 Japanese Patent No. 3115913 Japanese Patent Publication No. 63-9527 Japanese Patent No. 3285278 Japanese Patent No. 3359748 WO2007-009925

In the conventional method, the solid polyacetal resin copolymer once obtained is pulverized and then contacted with a base to deactivate the polymerization catalyst. Therefore, complicated equipment such as a pulverizer is required. Therefore, it is desired to eliminate the pulverizer and the like to deactivate the polymerization catalyst in a simpler form and obtain a polymer with less unstable parts.
Further, when polymerizing trioxane in a molten state, industrial advantages such as a simple polymerization apparatus and no need for equipment such as a pulverizer are recognized. However, there is a problem that the unstable end after inactivation is not yet at a satisfactory level. Furthermore, in the melt polymerization method, there are 20 to 40% by mass of unreacted trioxane, and the recovery process is complicated.

In order to solve the above-mentioned problems, the present inventors diligently studied, and as a result, achieved the following continuous production method of polyacetal resin and polyacetal resin copolymer having simple and excellent stability.
That is, the present invention is as follows.
1. Polymerization of trioxane or copolymerization of trioxane and cyclic formal in the presence of a compound represented by the general formula R ₁ OCH ₂ OR ₂ (where R ₁ and R ₂ are alkyl groups having 8 or less carbon atoms), a heteropolyacid, or Using a cationic polymerization catalyst composed of the acidic salt, the polymerization temperature is set to 130 ° C. to 200 ° C., the polymerization reaction is continuously performed under pressure, and the resulting polymerization reaction mixture containing the molten polymer is obtained. ,
(1) one or more selected from compounds containing basic alkali metal and / or alkaline earth metal that is soluble in trioxane;
(2) The mixture (I) comprising a mixed medium soluble in trioxane is continuously added and mixed, and the catalytic activity is deactivated by adsorbing a cationic polymerization catalyst comprising a heteropolyacid or an acid salt thereof. A process for producing a polyacetal resin characterized by the above.
2. After deactivating the cationic polymerization catalyst, the volatile component containing trioxane is evaporated, the volatile component is cooled to a liquid state, and then the liquid component is sent to a polymerization system to be reused as a polymerization component. 2. The method for producing a polyacetal resin as described in 1 above.
3. The compound containing an alkali metal and / or alkaline earth metal which is soluble in trioxane is a sodium alcoholate of polyethylene glycol monoalkyl ether, K alcoholate of polyethylene glycol monoalkyl ether, K of methoxyphenol 3. The method for producing a polyacetal resin according to the above 1 or 2, which is (potassium) salt, Na salt of bisphenol A, K salt of bisphenol A, or n-butyllithium.
4). 4. The method for producing a polyacetal resin according to any one of the above 1 to 3, further comprising a step of removing an unstable terminal present at a polymer terminal of the polymer.
5. 5. The method for producing a polyacetal resin according to any one of 1 to 4 above, wherein the mixed medium soluble in trioxane (2) comprises trioxane and / or a polyacetal resin copolymer.

  The present invention provides a continuous process for producing a polyacetal resin having high thermal stability. This method is useful as a method for producing a polyacetal resin.

The present invention will be specifically described below.
In the present invention, polymerization of trioxane or copolymerization of trioxane and cyclic formal is performed in the presence of a compound represented by the general formula R ₁ OCH ₂ OR ₂ (where R ₁ and R ₂ are alkyl groups having 8 or less carbon atoms). Then, using a cationic polymerization catalyst, the polymerization temperature is set to 130 ° C. to 200 ° C., and the polymerization reaction is continuously carried out under a pressurized condition to obtain a polymerization reaction mixture containing trioxane and a polymer in a molten state. Here, the polymerization reaction mixture containing trioxane and a polymer in a molten state may contain a partially crystallized polyacetal resin or polyacetal resin copolymer. The molten state of the present invention means that the polymerization reaction mixture is in a fluid state.
The trioxane used in the present invention needs to be highly purified. The total content of impurities such as water, methanol, and formic acid that induce OH groups at the polymer ends is 30 ppm or less, preferably 10 ppm or less, and more preferably 3 ppm or less.

Further, the compound represented by R ₁ OCH ₂ OR ₂ used as a molecular weight regulator (wherein R ₁ and R ₂ are alkyl groups having 8 or less carbon atoms) is usually preferably methylal or butyral. . Of these, methylal is particularly preferable. The amount of methylal added is usually in the range of 0.1 × 10 ⁻³ mol to 6 × 10 ⁻³ mol with respect to 1 mol of trioxane. The polymerization temperature is 130 ° C to 200 ° C, but usually 130 ° C to 180 ° C is preferable. More preferably, the temperature range is from 130 ° C to 150 ° C. The pressure during the polymerization is appropriately selected within the range of 1.5 bar to 200 bar. Preferably, it is in the range of 2 bar to 100 bar.
Further, as the cyclic formal as a comonomer of the copolymer, 1,3-dioxolane, 1,4-butanediol formal and the like are preferable. Usually, these comonomers are used in the range of 1 × 10 ⁻³ mol to 1 × 10 ⁻¹ mol with respect to 1 mol of trioxane.

Examples of the heteropolyacid used in the present invention are described in detail in JP-B-7-37504, and the general formula is represented by the following formula (A).
Hx [Mm · M′nOp] yH ₂ O (A)
(However, M represents a central element composed of one or two elements selected from P and Si.
M ′ represents one or more coordination elements selected from W, Mo, and V.
M is 1 to 10, n is 6 to 40, p is 10 to 100, x is an integer of 1 or more, and y is 0 to 50. )

  Specific examples of the heteropolyacids of the present invention include phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdotungstovanadic acid, cytungstotenic acid, xymolybdotungstic acid, and cimorib Detungstic acid, silicoribed tungsten tovanadate, and the like. Among them, preferred heteropolyacids are silicomolybdic acid, silicotungstic acid, phosphomolybdic acid, phosphotungstic acid and the like. Usually, it is used in the range of 0.01 to 10 mass ppm with respect to the total amount of trioxane and cyclic formal.

  The heteropolyacid is preferably used in a state diluted with a solvent in order to greatly influence the molecular weight of the produced polymer. Solvents for diluting the heteropolyacid are ethers and cyclic ethers which are organic solvents that do not adversely affect the polymerization. For example, n-butyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, dioxane, oxetane, tetrahydrofuran, tetrahydropyran and the like. The heteropolyacid can be used by being dissolved in methylal, and it is preferable that the monomer and the polymerization catalyst are mixed uniformly as quickly as possible, and then the polymerization reaction occurs to increase the viscosity of the reaction system. The crystal water bonded to the heteropolyacid can be used after being escaped by heat treatment at a high temperature. However, it is more convenient to use it after it is dissolved in the ethers to be used. In order to control undesirable side reactions that occur simultaneously with the polymerization reaction, it is preferable that the distribution of reactant residence times in the polymerization reactor is uniform. For this purpose, the polymerization reaction is usually carried out in a pipe reactor. The residence time of the polymerization reaction is 0.1 to 10 minutes, preferably 0.3 to 5 minutes, and particularly preferably 0.5 to 2 minutes. Such melt polymerization is usually performed under a pressure of about 50 atm. Moreover, 40-70 mass% of trioxane is converted into a polymer. Sometimes, 80% by mass is converted.

  The molten polymerization reaction mixture containing the molten trioxane and the polyacetal resin copolymer thus obtained is selected from a compound containing an alkali metal and / or an alkaline earth metal which is basic and soluble in trioxane. A seed or two or more kinds are continuously added and mixed. In the present invention, it is important to add a compound containing an alkali metal and / or an alkaline earth metal which is basic and soluble in trioxane as a mixture (I) composed of a mixed medium soluble in trioxane.

  In the present invention, the compound containing alkali metal and / or alkaline earth metal that is soluble in trioxane is a compound containing butyl lithium, naphthalene Na complex, tetraalkylene glycol monomethyl ether Na alcoholate, tetraethylene glycol monomethyl ether K alcoholate, Na salt of methoxyphenol, K salt of methoxyphenol, Na salt of bisphenol A, K salt of bisphenol A, Grignard reagents, alkylmagnesium, alkylzinc, etc. Among them, monoalkyl of polyethylene glycol is preferable. Na alcoholate of ether, or K alcoholate of monoalkyl ether of polyethylene glycol, K (potassium) salt of methoxyphenol, Na salt of bisphenol A, bisphenol K salt, and the like n- butyllithium.

  The mixed medium that is soluble in trioxane means that trioxane itself, a compound that is soluble in trioxane at the temperature under the present polymerization reaction conditions, or a mixed medium composed of a mixture of both, Examples include trioxane itself, polyacetal resin, polyacetal resin copolymer, polyethylene glycol, polyethylene glycol dimethyl ether, and the like, and a mixed medium having no active hydrogen in the molecule is preferable. Or even if it has active hydrogen, the amount of the active hydrogen is preferably 1/100 or less, or 1/500 or less of the substance in mass. Particularly preferred mixing media are trioxane, polyacetal resin copolymers, or a mixture of trioxane and polyacetal resin copolymers.

  As one example, a basic alkali metal compound is added to a mixture of 50% by mass of trioxane and 50% by mass of a polyacetal resin copolymer, and the mixture (I) is uniformly melted or dispersed. The mixing method of the alkali metal or alkaline earth metal compound that is soluble in trioxane and the above mixing medium is not particularly limited, but preferably in a mixing tank having a stirring function such as a stirring blade. The mixed medium is continuously fed with a quantitative feeder or the like, and is brought into a liquid state under heating and pressurizing conditions at a temperature equal to or higher than the melting point of the mixed medium. A compound containing an alkali metal or alkaline earth metal that is soluble in trioxane is continuously fed to the mixed medium in a liquid state while stirring until a predetermined concentration is reached, and is soluble in trioxane in the mixed medium. A compound containing an alkali metal or alkaline earth metal showing a certain basicity is uniformly dispersed. In general, it may be uniformly dispersed using a miscible apparatus such as a static mixer. The obtained mixture (I) of the compound containing alkali metal and alkaline earth metal that is soluble in trioxane and is basic is used to deactivate the cationic polymerization catalyst. In addition, the addition amount of the compound containing an alkali metal or alkaline earth metal that is soluble in trioxane and used in the present invention is 0.001% by mass with respect to the produced polymer. % Or more and 1.0 mass% or less. Preferably, it is the range of 0.001 mass% or more and 0.5 mass% or less. More preferably, it is the range of 0.001 mass% or more and 0.1 mass% or less.

In this way, trioxane having a cationic polymerization catalyst adsorbed and deactivated with a compound containing basic alkali metal and / or alkaline earth metal that is soluble in trioxane, a polymer product, and polymerization containing formaldehyde The reaction product is passed on to the next step. In addition, the adsorption process of the cationic polymerization catalyst is a kneading operation in an extruder or a compound containing an alkaline metal and / or an alkaline earth metal that is basic and soluble in the trioxane, such as a static mixer. May be carried out in a more miscible state.
The next step of the present invention is a step of removing unreacted volatile components such as trioxane from the polymerization reaction mixture. Also included is a step of adding a basic substance to the unstable part of the polymer in the polymerization reaction mixture to thermally decompose, hydrolyze, or decompose alcohol and then remove volatile components.

  The volatile component removing step is a step of removing volatile components such as trioxane and formaldehyde from the polymer product, and the temperature is maintained at 170 to 250 ° C. to remove trioxane and formaldehyde. In order to increase the removal efficiency of volatile components, an apparatus that increases the surface area of the melt phase (the interface between the melt phase and the gas phase) is desirable. Such as a pot. The volatile component evaporated here is cooled to a liquid state containing trioxane and formaldehyde. The recovered liquid containing this trioxane is recycled again in the polymerization system. In order to prevent precipitation on the surface of the cooler during cooling, it is desirable that the temperature of the surface of the cooler be 100 ° C. or higher. Further, when volatile components are liquefied, all of them may be liquefied, or some gaseous formaldehyde may be led to a formaldehyde absorption system without liquefying.

If necessary, the polymer in a molten state from which volatile components have been removed can be transferred to the next step to further remove a trace amount of remaining volatile components under reduced pressure conditions. Alternatively, it can be subjected to a step of removing an unstable portion present at the polymer terminal of the polymer.
The process of removing the unstable part present at the polymer end of the polymer is carried out by providing a pipe reactor of the same type in the polymer discharge part of the polymerization reactor of the pipe reactor, and heating the pipe reactor to 170-230 ° C. Then, a basic substance such as a triethylamine aqueous solution or a triethylamine / methanol solution is supplied, and the polymer is heated to decompose and remove unstable portions present at the ends of the polymer. Alternatively, a conventionally known melt mixing device such as a single-screw continuous extrusion kneader, a kneader, or a twin-screw continuous extrusion kneader can be provided in the polymer discharge portion of the polymerization reactor of the pipe reactor. .

Hereinafter, the gist of the present invention will be described with reference to examples, but the scope of the present invention is not limited thereto. [Example 1]
A trioxane melt in which 5 mol% of 1,3-dioxolane was dissolved was continuously fed at 5 kg / h to a pipe reactor having an outer jacket heated to 135 ° C. In the pipe reactor, the contents are uniformly mixed by a static mixer. The pipe type reactor is composed of three parts, a pre-mixing part, a main polymerization part, and a catalyst deactivation part. To this pipe reactor, 8.4 g of methylal containing 600 ppm of phosphotungstic acid was continuously supplied. The trioxane melt containing 5 mol% of 1,3-dioxolane and methylal containing 600 ppm of phosphotungstic acid are uniformly mixed in the previous mixing section of the pipe reactor and supplied to the next polymerization section as it is. The polymerization reaction was carried out in a pipe reactor. The catalyst mixing and polymerization reaction in the previous stage were set to 135 ° C. The average residence time of the reaction mixture in the polymerization portion in the pipe type reactor was 1 minute.

Next, a mixture (I) composed of trioxane at 135 ° C. containing Na alcoholate of 0.1% by mass of triethylene glycol monomethyl ether was continuously fed to the pipe reactor at 10 g per hour. (The Na alcoholate supplied here corresponds to 10 moles of the proton of the heteropolyacid.) The mixture (I) consisting of the polymerization reaction mixture and the trioxane at 135 ° C. containing the sodium alcoholate of triethylene glycol monomethyl ether was homogeneous. And the catalytic activity of the cationic polymerization catalyst was deactivated. The average residence time of the catalyst deactivation part is 30 seconds.
Next, this polymerization reaction mixture containing trioxane, formaldehyde and polymer is heated through a heat tube heated to a jacket temperature of 180 ° C. and introduced into a flash pot whose internal temperature is maintained at 180 ° C., and volatile containing formaldehyde and trioxane. The ingredients were evaporated. Further, the polymer in a molten state was introduced into a twin-screw extruder, and volatile components were further removed under a reduced pressure condition at a resin temperature of 220 ° C. to obtain 3.5 kg of a polyacetal resin copolymer per hour. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining after heating of the obtained polymer was 99.7% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Comparative Example 1]
In Example 1, the same operation as Example 1 was performed except having changed the compound containing the basic alkali metal and / or alkaline earth metal which is soluble in trioxane into CH ₃ ONa. The concentration of CH ₃ ONa in trioxane was 0.029% by mass, and the supply amount of the mixture (I) with trioxane was 10 g per hour. (The Na alcoholate supplied here corresponds to 10 moles of the proton of the heteropoly acid.) The polymer was heated under a vacuum of 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 97.2% by mass before heating, and the melt index value at 190 ° C. was 43 g / 10 min.
These results indicate that CH ₃ ONa has a poor solubility in trioxane, and thus the cationic polymerization catalyst cannot be deactivated successfully.

[Comparative Example 2]
In Example 1, the same operation as Example 1 was performed except having changed the mixed medium of mixture (I) into the liquid paraffin which does not melt | dissolve in trioxane. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 92.2% by mass before heating, and the melt index value at 190 ° C. was 87 g / 10 min.
These results indicate that liquid paraffin has poor solubility in trioxane, so that the cationic polymerization catalyst cannot be deactivated successfully.

[Example 2]
In Example 1, after deactivating the cationic polymerization catalyst in the polymerization reaction mixture, the volatile component containing trioxane evaporated from the flash pot was liquefied under a pressurized condition at 120 ° C., and then the liquefied product was again recycled. Recycled at 135 ° C. Here, the cationic polymerization catalyst and the deactivator of the cationic polymerization catalyst were changed as follows.
Alkaline metal, alkali, which is basic and soluble in trioxane at 135 ° C., containing 11 ppm per hour of methylal containing 600 ppm phosphotungstic acid and containing 0.1 wt% of triethylene glycol monomethyl ether Na alcoholate A mixture (I) comprising a compound containing an earth metal and trioxane was continuously fed to a pipe reactor at 13 g / h. (The Na alcoholate supplied here corresponds to 10 moles of the proton of the heteropolyacid.) Other than that, the same apparatus as in Example 1 was used. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.7% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Comparative Example 3]
In Example 2, the same operation as in Example 2 was performed, except that Na alcoholate of triethylene glycol monomethyl ether in the mixture (I) was changed to CH ₃ ONa. _The concentration in the trioxane CH 3 ONa is a 0.029 wt%, the supply amount was per hour 13 g. (The Na alcoholate supplied here corresponds to 10 moles of the proton of the heteropoly acid.) The polymer was heated under a vacuum of 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 97.0% by mass before heating, and the melt index value at 190 ° C. was 46 g / 10 min.
These results indicate that CH ₃ ONa has a poor solubility in trioxane, and thus the cationic polymerization catalyst cannot be deactivated successfully.

[Example 3]
In Example 2, the same procedure as in Example 2 was followed, except that the solution of Na alcoholate of triethylene glycol monomethyl ether was changed from trioxane at 135 ° C. to a trioxane / polyacetal resin copolymer (50/50 mass ratio) at 145 ° C. Went. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.7% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Comparative Example 4]
In Example 3, Na of triethylene glycol monomethyl ether of mixture (I)
The same operation as in Example 3 was performed except that the alcoholate was changed to CH ₃ ONa. The concentration of CH ₃ ONa in the trioxane / polyacetal resin copolymer was 0.029% by mass, and the supply amount was 13 g / hour. (The Na alcoholate supplied here corresponds to 10 moles of the proton of the heteropoly acid.) The polymer was heated under a vacuum of 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 96.8% by mass before heating, and the melt index value at 190 ° C. was 47 g / 10 min.
These results indicate that CH ₃ ONa has a poor solubility in trioxane, and thus the cationic polymerization catalyst cannot be deactivated successfully.

[Comparative Example 5]
In Example 3, the same operation as in Example 3 was performed except that the mixing medium of the mixture (I) was changed to liquid paraffin / polyethylene (50/50 mass ratio). The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 91.6% by mass before heating, and the melt index value at 190 ° C. was 89 g / 10 min.
These results indicate that when the mixture medium of the mixture (I) is liquid paraffin / polyethylene, the cationic polymerization catalyst cannot be deactivated due to poor solubility in trioxane.

[Example 4]
In Example 2, Na alcoholate of triethylene glycol monomethyl ether of mixture (I) was K (potassium) salt of methoxyphenol, and the mixing medium was polyacetal resin copolymer (mp: 165 ° C., melt at 135 ° C. to 180 ° C.) The same operation as in Example 2 was performed except that the index was changed to 80 g / 10 min. In addition, the density | concentration contained in the polyacetal resin copolymer of a methoxyphenol K salt is 0.09 mass%, and 13 g / h was supplied continuously. (The K salt supplied here corresponds to 10 moles of the proton of the heteropolyacid.) The polymer was heated under a vacuum of 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.5% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Comparative Example 6]
The same operation as in Example 4 was performed except that the K (potassium) salt of methoxyphenol in the mixture (I) was changed to CH ₃ ONa in Example 4. The concentration of CH ₃ ONa in the polyacetal resin copolymer was 0.029% by mass, and the supply amount of the mixture (I) was 13 g per hour. (The Na alcoholate supplied here corresponds to 10 moles of the proton of the heteropoly acid.) The polymer was heated under a vacuum of 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 96.5% by mass before heating, and the melt index value at 190 ° C. was 49 g / 10 min.
From these results, it is shown that CH ₃ ONa has a poor solubility in the polymerization reaction system, so that the deactivation of the cationic polymerization catalyst is not successful.

[Example 5]
In Example 2, the same operation as in Example 2 was performed except that the polymerization catalyst used was changed to phosphomolybdic acid instead of phosphotungstic acid. The concentration of phosphomolybdic acid in methylal was 290 ppm. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.7% by mass before heating, and the melt index value at 190 ° C. was 27 g / 10 min.

[Example 6]
In Example 2, instead of the mixture (I) consisting of Na alcoholate of triethylene glycol monomethyl ether and trioxane used in Example 2, the mixture (I) consisting of n-butyllithium and trioxane was changed to Example 2 and The same operation was performed. Here, n-butyllithium was a 0.034 mass% trioxane mixture. (The n-butyllithium supplied here corresponds to 10 moles of the proton of the heteropolyacid.) This polymer was heated at 230 ° C. for 60 minutes under vacuum.
The polymer remaining amount after heating of the obtained polymer was 99.7% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Example 7]
In Example 2, the same operation as in Example 2 was performed, except that the mixture (I) composed of Na alcoholate of triethylene glycol monomethyl ether and trioxane used was changed to a supply amount of 5 g per hour. (The Na alcoholate supplied here corresponds to 5 moles of the proton of the heteropoly acid.) The polymer was heated under a vacuum of 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.7% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Example 8]
Subsequent to the polymerization catalyst deactivation part of the pipe type reactor of Example 1, the process until the terminal unstable part removing part and the addition of the mixture (I) were carried out in the same manner as in Example 1, and cationic polymerization was performed. The catalyst was deactivated. The average residence time of the polymerization catalyst deactivated part was 30 seconds.
Next, this molten polymerization reaction mixture was introduced into a terminal unstable portion removing step portion comprising a pipe reactor heated to 180 ° C. At the entrance of this step, 5 g of triethylamine / water (1/4 mass ratio) was supplied per hour. The residence time of the terminal unstable portion removal step was 10 minutes. The molten polymerization reaction mixture thus obtained was introduced into a twin-screw extruder, and volatile components including formaldehyde and trioxane were removed under reduced pressure conditions to obtain a polyacetal resin copolymer. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.9% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Example 9]
Subsequent to the removal / recovery part of unreacted trioxane of Example 2, a terminal unstable part removing part was attached. This molten polymerization reaction mixture was introduced into a terminal unstable portion removing step portion comprising a pipe reactor heated to 180 ° C. At the entrance of this process, 6 g of triethylamine was supplied every hour. The residence time in the removal process part of the terminal unstable part was 7 minutes. The molten polymerization reaction mixture obtained here was introduced into a twin-screw extruder, and volatile components including formaldehyde and trioxane were removed under reduced pressure conditions to obtain a polyacetal resin copolymer. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.9% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Example 10]
The same operation as in Example 9 was performed except that triethylamine / water (1/4 mass ratio) was used instead of triethylamine in Example 9. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.9% by mass before heating, and the melt index value at 190 ° C. was 20 g / 10 min.

[Example 11]
The trioxane melt was continuously fed at 5 kg per hour to a pipe reactor whose outer jacket was heated to 135 ° C. The contents of the pipe reactor are mixed uniformly by a static mixer. The pipe type reactor is composed of three parts, a pre-mixing part, a main polymerization part, and a catalyst deactivation part. Further, 11 g of methylal containing 600 ppm of phosphotungstic acid was continuously supplied to this pipe type reactor. In addition, the trioxane melt and methylal containing 600 ppm of phosphotungstic acid were mixed in the previous mixing section of the pipe reactor, supplied to the next polymerization section, and polymerized in the pipe reactor. The mixing of the polymerization catalyst and the polymerization reaction in the previous stage were performed at 135 ° C.
Next, a mixture (I) of trioxane at 135 ° C. containing Na alcoholate of 0.1% by mass of triethylene glycol monomethyl ether, 13 g / h, was continuously fed to the pipe reactor. (The Na alcoholate supplied here corresponds to 10 moles of protons of phosphotungstic acid.) A mixture of a polymerization reaction mixture and 135 ° C. trioxane containing Na (sodium) alcoholate of triethylene glycol monomethyl ether ( I) was uniformly mixed to deactivate the catalytic activity of the cationic polymerization catalyst.

After deactivating the cationic polymerization catalyst in the polymerization reaction mixture, volatile components including trioxane evaporated from the flash pot are evaporated and liquefied under a 120 ° C. pressure condition, and this liquefied product is again cooled to 135 ° C. And then supplied to the polymerization system, mixed with trioxane and supplied to the polymerization system.
Subsequent to the removal / recovery section of unreacted trioxane, the polymerization reaction mixture was introduced into the removal section of the terminal unstable portion of the pipe reactor heated to 180 ° C. From the entrance of this step, 6 g of triethylamine / water (1/4 mass ratio) was supplied per hour. The residence time in the removal process part of the terminal unstable part was 7 minutes. The molten polymer mixture obtained here was introduced into a twin-screw extruder, and volatile components including formaldehyde and trioxane were removed under reduced pressure conditions to obtain a polyacetal resin homopolymer. The polymer was heated under vacuum at 230 ° C. for 60 minutes.
The polymer remaining amount after heating of the obtained polymer was 99.7% by mass before heating, and the melt index value was 20 g / 10 min.

  The production method of the present invention is useful as a production method of a polyacetal resin.

Claims (5)

Polymerization of trioxane or copolymerization of trioxane and cyclic formal in the presence of a compound represented by the general formula R ₁ OCH ₂ OR ₂ (R ₁ , R ₂ is an alkyl group having 8 or less carbon atoms), or a heteropolyacid, or Using a cationic polymerization catalyst composed of the acidic salt, the polymerization temperature is set to 130 ° C. to 200 ° C., the polymerization reaction is continuously performed under pressure, and the resulting polymerization reaction mixture containing the molten polymer is obtained. ,
(1) one or more selected from compounds containing basic alkali metal and / or alkaline earth metal that is soluble in trioxane;
(2) A mixture (I) composed of a mixed medium soluble in trioxane is continuously added and mixed, and the catalytic activity is deactivated by adsorbing a cationic polymerization catalyst composed of a heteropolyacid or an acid salt thereof. A process for producing a polyacetal resin characterized by the above.   After deactivating the cationic polymerization catalyst, the volatile component containing trioxane is evaporated, the volatile component is cooled to a liquid state, and then the liquid component is sent to a polymerization system to be reused as a polymerization component. The method for producing a polyacetal resin according to claim 1.   The compound containing an alkali metal and / or alkaline earth metal which is soluble in trioxane is a sodium alcoholate of polyethylene glycol monoalkyl ether, K alcoholate of polyethylene glycol monoalkyl ether, K of methoxyphenol The method for producing a polyacetal resin according to claim 1, wherein the salt is (potassium) salt, Na salt of bisphenol A, K salt of bisphenol A, or n-butyllithium.   The method for producing a polyacetal resin according to any one of claims 1 to 3, further comprising a step of removing unstable terminals present at the polymer terminals of the polymer.   The method for producing a polyacetal resin according to any one of claims 1 to 4, wherein the mixed medium (2) soluble in trioxane comprises trioxane and / or a polyacetal resin copolymer.