JP6037799B2 - Process for producing polyacetal copolymer - Google Patents

Description

  The present invention relates to a method for producing a polyacetal copolymer.

  Conventionally, as a method for producing a polyacetal copolymer, cationic copolymerization using trioxane as a main monomer and cyclic ether having at least one carbon-carbon bond and / or cyclic formal as a comonomer is known. Cationic active catalysts used in these copolymers include Lewis acids, especially boron, tin, titanium, phosphorus, arsenic and antimony halides such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, pentachloride. Compounds such as phosphorus fluoride, arsenic pentafluoride and antimony pentafluoride, and complex compounds or salts thereof; protic acids such as perchloric acid; esters of protic acids, especially esters of perchloric acid and lower aliphatic alcohols; For example perchloric acid-tertiary butyl ester; anhydrides of protonic acids, especially mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids, such as acetyl perchlorate, or also trimethyloxonium hexafluorophosphate, triphenyl- Methyl hexafluoroarsenate, acetyl tetrafluoroborate, acetyl Kisa fluor phosphate and acetyl hexafluoroacetylacetone ARUZE diisocyanate and the like have been proposed. Among them, boron trifluoride or a coordination compound of boron trifluoride and an organic compound such as ether is the most common as a polymerization catalyst having trioxane as a main monomer and is widely used industrially.

  However, generally used polymerization catalysts such as boron trifluoride compounds require a relatively large amount of catalyst (for example, 40 ppm or more based on the total monomers) for polymerization. For this reason, it is difficult to sufficiently perform the catalyst deactivation treatment after polymerization, and even if the catalyst is deactivated, the substance derived from the catalyst remains in the copolymer, and the decomposition of the copolymer is promoted. Problems may arise. The catalyst deactivation step is generally performed in a large amount of an aqueous solution containing a basic compound such as triethylamine. After deactivation of the catalyst, the copolymer is separated from the treatment liquid and dried. This requires a complicated process such as recovering the dissolved unreacted monomer, and has a problem economically.

  In order to eliminate the complication associated with the deactivation treatment of the catalyst, a method of adding a trivalent phosphorus compound to the resulting copolymer (see, for example, Patent Document 1) or a method of adding a hindered amine compound (Patent Document) 2) has also been proposed, but not as much as expected.

  On the other hand, a method for producing a polyacetal copolymer using a heteropolyacid as a catalyst has been proposed (see, for example, Patent Document 3). In addition, after preparing a crude polyacetal copolymer by copolymerization using a heteropolyacid as a catalyst, the reaction product is a solid that is at least one selected from a triazine ring-containing compound having an amino group or a substituted amino group and a polyamide A method for producing a polyacetal copolymer in which a basic compound is added and a catalyst is deactivated by melt kneading has been proposed (see, for example, Patent Document 4). According to this method, since the heteropolyacid is highly active, polymerization is possible with a very small amount of catalyst, and a high-quality polyacetal copolymer can be provided. In addition, since the catalyst is deactivated by melt kneading without substantially using a solution, the complicated steps as described above are not required and the economy is excellent.

Japanese Patent Publication No. 55-42085 JP-A-62-257922 JP-A-1-170610 JP 2003-026746 A

  In recent years, there has been a demand for a high-quality polyacetal copolymer having particularly excellent thermal stability and an extremely small amount of formaldehyde generated. However, the methods described in Patent Documents 1 to 4 are difficult to meet the requirements. The situation is starting. In order to meet this requirement, further improvements such as more efficient deactivation of the catalyst and stabilization by more complete decomposition treatment of the unstable terminal portion of the crude polyacetal copolymer after deactivation of the catalyst are required. It has been demanded.

  An object of the present invention is to provide a facility and operating technique that can easily and efficiently deactivate a catalyst by a selection of a catalyst, a catalyst deactivator, an unstable terminal treating agent, or a selective combination thereof, and does not require a washing step. Provides a method for producing a stabilized polyacetal copolymer with a simple process, high polymerization yield, very little unstable terminal portion, extremely thermally stable, and extremely low formaldehyde emission That is.

  As a result of intensive studies on the type of catalyst and the corresponding catalyst deactivation method and unstable terminal treatment method in order to achieve the above-mentioned problems, the present inventor uses a heteropolyacid represented by the following general formula (1) as a catalyst. In addition, the catalyst is deactivated and the unstable terminal treatment is carried out by melt-kneading using an alkali metal or alkaline earth metal hydroxide or alkoxide compound. The present invention is completed by finding that it is possible to reliably and quickly deactivate a catalyst and reduce / stabilize unstable ends with a small amount, and that the equipment and operation technique can be easily achieved to achieve the above object. It came to. More specifically, the present invention provides the following.

((1) The present invention uses a trioxane as a main monomer (a) and a cyclic ether having at least one carbon-carbon bond and / or a cyclic formal as a comonomer (b). The catalyst (c) is copolymerized using a heteropoly acid represented by the following general formula (1), an alkali metal or alkaline earth metal hydroxide or alkoxide compound (d) is added to the reaction product, This is a method for producing a polyacetal copolymer, which is melt-kneaded to deactivate the polymerization catalyst (c).

H _m [M ¹ _x · M ² _y O _Z ] · nH ₂ O (1)

[In Formula (1), M1 shows the central element which consists of ¹ type or 2 types of elements chosen from P and Si. M ² represents one or more coordination elements selected from W, Mo and V. x represents an integer of 1 to 10; y represents an integer of 6 to 40; z represents an integer of 10 to 100; m represents an integer of 1; and n represents an integer of 0 to 50 Indicates. ]

  (2) Further, in the present invention, the comonomer (b) is at least one selected from 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, or ethylene oxide. 1) A process for producing a polyacetal copolymer according to 1).

  (3) Further, in the present invention, the heteropolyacid may be phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdotungstovanadic acid, phosphotungstovanadic acid, silicotungstic acid, silica The method for producing a polyacetal copolymer according to (1) or (2), wherein the polyacetal copolymer is at least one selected from molybdic acid, silicoribed tungstic acid, or silicoribed tungstovanadic acid.

(4) Further, in the present invention, any one of (1) to (3), wherein the alkali metal or alkaline earth metal hydroxide or alkoxide compound (d) is represented by the following general formula (2): It is a manufacturing method of the polyacetal copolymer of description.

(XO) _n M ³ (2)

[In Formula (2), X shows hydrogen, a C1-C6 unsubstituted alkyl group, a substituted alkyl group, or a phenyl group. An unsubstituted alkyl group is linear, branched or cyclic. The substituent of the substituted alkyl group is a methyl group. M ³ represents an alkali metal element or an alkaline earth metal element. n is 1 or 2. ]

  (5) Further, in the present invention, the alkali metal or alkaline earth metal hydroxide or alkoxide compound (d) comprises: (a) lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, hydroxide At least one hydroxide selected from calcium or barium hydroxide, or (i) lithium methoxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, sodium phenoxide, potassium methoxide, potassium ethoxide, potassium tert -The method for producing a polyacetal copolymer according to any one of (1) to (4), which is at least one alkoxide compound selected from butoxide, magnesium methoxide, or calcium methoxide.

  (6) Further, the present invention provides at least one hydroxide in which the alkali metal or alkaline earth metal hydroxide or alkoxide compound (d) is selected from lithium hydroxide, sodium hydroxide, and potassium hydroxide. It is a manufacturing method of the polyacetal copolymer as described in (5) which is.

  (7) Further, in the present invention, the alkali metal or alkaline earth metal hydroxide or alkoxide compound (d) is at least one hydroxide selected from lithium hydroxide or sodium hydroxide. 6) A method for producing a polyacetal copolymer described in 6).

  (8) Further, in the present invention, the alkali metal or alkaline earth metal hydroxide or alkoxide compound (d) is added in an amount of 0.001 to 1 kg of the crude polyacetal copolymer obtained by the copolymerization reaction. It is a manufacturing method of the polyacetal copolymer in any one of (1) to (7) which is -0.25 milliequivalent.

  (9) Further, in the present invention, the addition of the alkali metal or alkaline earth metal hydroxide or alkoxide compound (d) to the reaction product may include (a) water of the alkali metal or alkaline earth metal. The oxide or alkoxide compound (d) is added as a solution directly to the crude polyacetal copolymer obtained by the copolymerization reaction, or (i) the alkali metal or alkaline earth metal hydroxide or alkoxide compound ( d) The solution of d) is added to the powder of the polyacetal copolymer and uniformly dispersed, and then the dispersed powder is added to the crude polyacetal copolymer, or (c) the alkali metal or alkaline earth metal The hydroxide or alkoxide compound (d) was uniformly dispersed in the polyacetal copolymer powder in the solid state, The b value of the polyacetal copolymer pellets after deactivation of the polymerization catalyst (c), measured by using a color difference meter, is determined by adding uder to the crude polyacetal copolymer, is 2.0 or less. (1) It is a manufacturing method of the polyacetal copolymer in any one of (8).

  According to the present invention, by using an alkali metal or alkaline earth metal hydroxide or alkoxide compound as a deactivator for the polymerization catalyst, not only can the polymerization catalyst be effectively deactivated, but also the unstable end can be stabilized. It is possible to economically produce a high-quality polyacetal copolymer that is excellent in thermal stability and has a very small amount of formaldehyde generated by a simple production process.

  In addition, according to the present invention, by using a dry method as compared with a conventional wet type deactivation method, the deactivation step is simplified and the cleaning step is omitted, and the polymerization process is extremely streamlined. Following the rapid and complete deactivation of the catalyst, the unstable ends can also be stabilized. As a result, it is possible to economically produce an excellent quality polyacetal copolymer that is free from decomposition and alteration caused by the catalyst, is thermally stable, and has a very low unstable terminal portion and formaldehyde release amount. it can.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. can do.

<Method for producing polyacetal copolymer>
In the present invention, a polyacetal copolymer is produced using trioxane which is a cyclic trimer of formaldehyde as a main monomer (a) and a cyclic ether having at least one carbon-carbon bond and / or a cyclic formal as a comonomer (b). In doing so, the polymerization catalyst (c) is copolymerized using a predetermined heteropoly acid, the predetermined salt (d) is added to the reaction product, and melt kneading is performed to deactivate the polymerization catalyst (c). Let

[Comonomer (b)]
As the comonomer, a compound (b) selected from cyclic ethers having at least one carbon-carbon bond and cyclic formal is used. Representative examples of the compound (b) used as a comonomer include 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, ethylene oxide, propylene oxide, epichlorohydrin, and the like. Can be mentioned. Among these, in view of polymerization stability, 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, ethylene oxide and the like are preferable. Further, cyclic esters such as β-propiolactone and vinyl compounds such as styrene can be used. As the comonomer, it is also possible to use a monofunctional cyclic ether or cyclic formal having a substituent unit, such as butyl glycidyl ether or 2-ethylhexyl glycidyl ether. Further, as a comonomer, a compound having two polymerizable cyclic ether groups or cyclic formal groups such as diglycidyl ether or diformal of alkylene glycol, for example, butanediol dimethylidene glyceryl ether, butanediol diglycidyl ether, A compound having three or more polymerizable cyclic ether groups or cyclic formal groups such as glycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether can also be used. A polyacetal copolymer in which a branched structure or a crosslinked structure is thereby formed is also an object of the present invention.

  In the present invention, the amount of the compound (b) selected from cyclic ether and cyclic formal used as a comonomer is 0.1 to 20 mol% as a ratio in the total monomer (total amount of main monomer and comonomer), preferably 0.2 to 10 mol%. If it is less than 0.1 mol%, the unstable terminal part of the crude polyacetal copolymer produced by the polymerization will increase and the stability will deteriorate, and if the amount of comonomer is excessive, the produced copolymer will become soft and the melting point will decrease. It is not desirable to occur.

[Polymerization catalyst (c)]
One feature of the present invention is that a heteropolyacid is used as the polymerization catalyst (c) in the production of the polyacetal copolymer as described above.

In the present invention, the heteropolyacid used as the polymerization catalyst (c) is a generic name for polyacids formed by dehydration condensation of different types of oxygen acids, and a specific different element exists at the center and shares an oxygen atom. And having a mononuclear or binuclear complex ion formed by condensation of condensed acid groups. Such heteronuclear condensed acid can be represented by the following general formula (1).

H _m [M ¹ _x · M ² _y O _Z ] · nH ₂ O (1)

In Formula (1), M ¹ represents a central element composed of one or two elements selected from P and Si. M ² represents one or more coordination elements selected from W, Mo and V. x represents an integer of 1 to 10; y represents an integer of 6 to 40; z represents an integer of 10 to 100; m represents an integer of 1; and n represents an integer of 0 to 50 Indicates.

  Specific examples of the heteropolyacids include phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdotungstovanadic acid, phosphotungstovanadic acid, silicotungstic acid, silicomolybdic acid, Examples thereof include molybdotungstic acid and silicomolybdotungstovanadate. Among these, in view of the stability of polymerization and the stability of the heteropolyacid itself, the heteropolyacid is preferably one or more of silicomolybdic acid, silicotungstic acid, phosphomolybdic acid or phosphotungstic acid.

In the present invention, the amount of the heteropolyacid used varies depending on the type and can be appropriately changed to adjust the polymerization reaction. It is in the range of 100 ppm (hereinafter referred to as weight / weight ppm), preferably 0.1 to 50 ppm. In addition, a usage amount of 0.1 to 10 ppm is sufficient for heteropolyacids such as phosphomolybdic acid and phosphotungstic acid that act very strongly. The fact that copolymerization is possible even with such a small amount of catalyst keeps undesired reactions such as main chain decomposition and depolymerization of the polymer by the catalyst slight, and unstable formate end groups (—O—CH═O). It is effective in suppressing the formation of hemiacetal end groups (—O—CH ₂ —OH) and the like, and is also economically advantageous.

  In order to carry out the reaction uniformly, the polymerization catalyst is preferably diluted with an inert solvent that does not adversely influence the polymerization and added to the main monomer and / or comonomer. Examples of the inert solvent include low molecular weight carboxylic acids having 1 to 10 carbon atoms such as formic acid, acetic acid, propionic acid, butyric acid, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2 Obtained by condensation of low molecular weight alcohols having 1 to 10 carbon atoms such as methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 3-methyl-1-butanol, and 1-hexanol. Esters: Preferred are low molecular weight ketones having 1 to 10 carbon atoms such as acetone, 2-butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, methyl isobutyl ketone, and methyl-t-butyl ketone. However, it is not limited to these. Considering industrial availability, methyl formate, ethyl formate, methyl acetate, ethyl acetate, butyl acetate, acetone, 2-butanone, methyl isobutyl ketone and the like are most suitable. The polymerization catalyst is preferably dissolved in the inert solvent at a concentration of 1 to 30% by weight / weight, but is not limited thereto. In addition, a predetermined amount of the polymerization catalyst is mixed in advance with a part or all of one or more of the main monomer, comonomer, molecular weight regulator, etc. described above, and this solution is added to the polymerization system for polymerization. The method of performing is also preferred.

[Preparation of copolymer]
In the present invention, the preparation of the crude polyacetal copolymer by polymerization can be carried out by the same equipment and method as those of conventionally known trioxane copolymerization. That is, any of a batch type, a continuous type, and a semi-continuous type is possible, and a method of using a liquid monomer and obtaining a solid lump-like polymer with the progress of polymerization is common. As a polymerization apparatus used in the present invention, a reaction vessel equipped with a stirrer that is generally used in a batch system can be used, and as a continuous system, a kneader, a twin-screw continuous extrusion mixer, and a biaxial paddle type continuous A mixer or other continuous polymerization apparatus such as trioxane proposed so far can be used, and two or more types of polymerization machines can be used in combination.

  The polymerization method is not particularly limited, but as previously proposed, trioxane, a comonomer, and a heteropolyacid as a polymerization catalyst are sufficiently mixed in advance while maintaining a liquid phase state, and a reaction raw material obtained is obtained. If the mixed solution is supplied to the polymerization apparatus to carry out the copolymerization reaction, the required amount of catalyst can be reduced, and as a result, it is advantageous to obtain a polyacetal copolymer with a smaller amount of formaldehyde emission, and a more suitable polymerization method It is. The polymerization temperature is performed in a temperature range of 60 to 120 ° C.

  In preparing the polyacetal copolymer by polymerizing the main monomer (a) and the comonomer (b) in the present invention, a low-molecular-weight line such as a known chain transfer agent such as methylal is used to adjust the degree of polymerization. Acetal or the like can also be added.

  The polymerization reaction is preferably carried out in a state in which impurities having active hydrogen, for example, water, methanol, formic acid and the like are substantially absent, for example, in a state where each of them is 10 ppm or less. It is desirable to use trioxane, cyclic ether and / or cyclic formal prepared so as not to contain as much as possible as the main monomer or comonomer.

[Alkali metal or alkaline earth metal hydroxide or alkoxide compound (d)]
In the present invention, a polyacetal copolymer (crude polyacetal copolymer) obtained by copolymerization as described above and containing a polymerization catalyst and having an unstable portion at its terminal is added to an alkali metal or an alkaline earth. Add a metal hydroxide or alkoxide compound (d), melt and knead to deactivate the polymerization catalyst and reduce the unstable end groups of the polyacetal copolymer (crude copolymer). It is characterized by becoming. Hereinafter, the “alkali metal or alkaline earth metal hydroxide or alkoxide compound” is also referred to as component (d). Such stabilization treatment is performed more simply and efficiently by adding the component (d) as it is without washing the crude polyacetal copolymer obtained by the copolymerization reaction. be able to.

The component (d) is preferably a compound represented by the following general formula (2).

(XO) _n M ³ (2)

In formula (2), X represents hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted alkyl group or a phenyl group. An unsubstituted alkyl group is linear, branched or cyclic. The substituent of the substituted alkyl group is a methyl group. M ³ represents an alkali metal element or an alkaline earth metal element. n is 1 or 2.

  (D) component is lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, lithium methoxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, sodium phenoxide, Potassium methoxide, potassium ethoxide, potassium tert-butoxide, magnesium methoxide, calcium methoxide and the like are most preferred, but not limited thereto.

  In particular, considering the hue of the polyacetal copolymer after the polymerization catalyst (c) is deactivated, the component (d) is preferably an alkali metal hydroxide, and is lithium hydroxide or sodium hydroxide. It is more preferable.

  In the present invention, the salt (d) represented by the general formula (2) may be one kind, a plurality may be used in combination, or a mixture thereof.

  The content of the component (d) is not particularly limited, but (a) the amount of the catalyst remaining in the polymer, (b) the type and amount of unstable terminal groups generated by various polymerization conditions, (c) ( d) It is preferable to change appropriately according to the degree of activity of the component, processing conditions (temperature, time, contact speed, etc.), etc. Specifically, the content of component (d) is preferably very small, preferably 0.001 to 0.25 milliequivalents per 1 kg of the crude polyacetal copolymer obtained by the copolymerization reaction. 0.002 to 0.10 milliequivalent, more preferably 0.002 to 0.025 milliequivalent. The lower limit of the content of the component (d) affects the melt index (MI) value, and the MI value is increased by setting the content of the component (d) to 0.001 milliequivalent or more with respect to 1 kg of the crude polyacetal copolymer. The MI value can be reduced to 10 or less by setting it to 0.002 milliequivalent or more. The upper limit of the content of the component (d) affects the hue (b value) in the pellet, and the content of the component (d) is set to 0.25 milliequivalent or less with respect to 1 kg of the crude polyacetal copolymer, thereby allowing a polymerization catalyst. (C) The b value of the polyacetal copolymer after deactivation can be made 2.0 or less. Further, by setting the content of the component (d) to 0.10 milliequivalent or less with respect to 1 kg of the crude polyacetal copolymer, the b value of the polyacetal copolymer after deactivation of the polymerization catalyst (c) is 1.0 or less. Can be. Further, by setting the content of the component (d) to 0.10 milliequivalent or less with respect to 1 kg of the crude polyacetal copolymer, the b value of the polyacetal copolymer after deactivation of the polymerization catalyst (c) is 0.0 or less. Can be.

  If the amount of the component (d) is excessive, the hue of the polyacetal copolymer after the polymerization catalyst (c) is deactivated may be inferior. If it is too small, the deactivation efficiency or unstable terminal This is not preferable in that there is a possibility that sufficient stabilization of the part cannot be achieved.

[Deactivation of catalyst]
In the present invention, in order to increase the hue of the polyacetal copolymer after the polymerization catalyst (c) is deactivated, the content of the component (d) is preferably a very small amount, but a very small amount of (d) It is extremely difficult to disperse the components uniformly throughout. Therefore, the addition of the component (d) is preferably performed by any one of the following (a) to (c).
(A) The component (d) is directly added to the crude polyacetal copolymer obtained by the copolymerization reaction as a solution.
(A) After the solution of the component (d) is contained in the polyacetal copolymer powder and uniformly dispersed, the dispersed powder is added to the crude polyacetal copolymer.
(C) After the component (d) is uniformly dispersed in the powder of the polyacetal copolymer in a solid state, the dispersed powder is added to the crude polyacetal copolymer.

  When included in the powder of the polyacetal copolymer, a general mixer such as a horizontal cylinder type, a V type, a ribbon type, a paddle type, or a high-speed fluid type can be used for mixing. The mixture may be melted as it is, or may be melted after the solvent is distilled off by heating, decompression or the like. Further, the deactivation / stabilizer solution may be supplied by injection or the like from the feed port of the extruder and / or midway. At this time, the deactivation / stabilizer solution may be divided and supplied in multiple stages.

  By adding the component (d) as described above, a very small amount of the component (d) can be uniformly dispersed throughout. As a result, the polymerization catalyst (c) polyacetal after deactivation was measured using a color difference meter. The b value of the polymer can be made 2.0 or less. In addition, b value in this specification uses color difference meter SE-2000 (made by Nippon Denshoku Industries Co., Ltd.), puts a predetermined amount of pellets in a cell for measuring pellets (round cell), puts it on a sample stage, and covers the cover. This is the value that is displayed when the cover is measured.

  In particular, the component (d) is preferably an alkali metal hydroxide, and if the addition amount is appropriate, the b value can be 0.0 or less. Further, the component (d) is more preferably lithium hydroxide or sodium hydroxide, and the b value can be set to −0.1 or less if the addition amount is appropriate.

  In the present invention, it is preferable that the amount of unreacted monomer is smaller when performing deactivation treatment of the catalyst after polymerization. Further, it is 5% by weight or less, particularly preferably 3% by weight or less. As a result, a particularly desirable aspect of the present invention can be achieved in which the crude polyacetal copolymer produced by polymerization is treated without washing. In order to reduce unreacted monomers, it is generally sufficient to increase the polymerization rate above a certain level. In the case of the present invention, this is achieved by appropriately adjusting the amount of catalyst used and the polymerization time (residence time in the continuous system). Since a heteropolyacid catalyst that is easily achieved and has high activity is used, even a small amount of catalyst can be achieved in a relatively short time. Further, after the copolymerization reaction, a part of the residual monomer may be removed by evaporation and vaporization so that a predetermined residual monomer amount is obtained. In addition, during or after the copolymerization, the unreacted trioxane and comonomer recovered as a gas can be liquefied and reused as a part of the raw material monomer as it is. is there.

  Further, if necessary, a conventionally known catalyst deactivator or unstable terminal decomposition treatment agent can be used in combination with the above component (d).

  In the present invention, the addition of the component (d) that functions as a deactivator / stabilizing agent may be performed at any stage before or after melting the crude polyacetal copolymer, or at both stages. May be. Further, the method of adding the component (d) may be divided and supplied in multiple stages.

  In addition, when the component (d) is added as a deactivation / stabilization treatment agent, it is preferable that the crude copolymer is a fine granular material. For this purpose, the reactor sufficiently pulverizes the bulk polymer. Although what has a function is preferable, you may grind | pulverize the reaction material after superposition | polymerization using a grinder separately. As for the particle size of the crude copolymer in the deactivation treatment, at least 90% by weight is 10 mm or less, preferably 4 mm or less, more preferably 2 mm or less.

  The melt-kneading apparatus is not particularly limited, but has a function of kneading the melted copolymer, and preferably has a vent function, for example, a uniaxial or multiaxial continuous having at least one vent hole. Examples include an extrusion kneader and a kneader. In the melt-kneading process of the present invention, the polymerization catalyst is completely deactivated and unstable terminals are reduced and stabilized. The temperature range from the melting point of the copolymer to 260 ° C. is preferable for the melt-kneading treatment. When the temperature is higher than 260 ° C., the polymer is degraded and deteriorated.

  In the present invention, the melt kneading treatment is preferably performed in the presence of an antioxidant. As the antioxidant, known substances such as various hindered phenol antioxidants are used as stabilizers for conventional polyacetal resins. For example, 2,6-di-tert-butyl-4-methylphenol, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexane Diol-bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane, N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxyhydrocinnamide), 2-t-butyl-6- (3′-t-butyl-5′-methyl-2 ′) -Hydroxybenzyl) -4-methylphenyl acrylate, 3,9-bis [2-{(3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1'-di Chiruechiru] -2,4,8,10-spiro [5,5] - undecane, and the like. These hindered phenolic antioxidants may be polymerized by adding a part or all of them in advance to the main monomer or comonomer before polymerization. Is not particularly excessive, there is no adverse effect on the activity of the polymerization catalyst, which is one of the preferred embodiments.

  Further, at this stage, if necessary, a known substance may be added as a stabilizer for various polyacetal resins. Further, for example, an inorganic filler such as glass fiber, a crystallization accelerator (nucleating agent), a release agent, an antioxidant and the like may be added.

  As described above, after adding the component (d) as a deactivation / stabilization treatment agent to the crude copolymer and subjecting it to melt-kneading treatment, it is usually decomposed to formaldehyde gas, unreacted monomer, oligomer, deactivation・ Stabilizers and the like are removed from the vent portion of the extruder under reduced pressure, and are formed into pellets and the like to become products for resin processing. The pellets are dried as necessary. In the case of drying, for example, it is dried at 135 ° C. for about 4 hours.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Examples 1 to 26>
[Copolymerization of trioxane as main monomer (a) with cyclic ether and / or cyclic formal as comonomer (b)]
A continuous biaxial polymerization machine was used as the polymerization reactor. This polymerization machine has a jacket for passing a heating or cooling medium on the outside, and two rotating shafts with a large number of paddles for stirring and propulsion are provided in the longitudinal direction in the inside. ing. As a main monomer (a) containing 80 ppm of warm water at 80 ° C. through the jacket of this biaxial polymerization machine and rotating the two rotating shafts at a constant speed and containing 1000 ppm of methylal as a chain transfer agent at one end thereof. A mixture containing 96.2% by weight of trioxane and 3.8% by weight of the comonomer (b) shown in Table 1 was continuously fed, and as a polymerization catalyst (c), Table 1 Copolymerization was carried out by continuously adding a methyl formate solution containing 0.3% by weight of the heteropolyacid shown in Table 1 in the amount shown in Table 1 with respect to all monomers. In Table 1, the addition amount of the polymerization catalyst is a weight ratio (unit: ppm) with respect to the total of all monomers, and a molar equivalent (unit: milliequivalent) with respect to 1 kg of the crude polyacetal copolymer obtained by the copolymerization reaction.

[Deactivation of polymerization catalyst (c)]
The reaction product (crude polyacetal copolymer) by copolymerization was discharged from a discharge port provided at the other end of the polymerization machine, and the salt (d) shown in Table 1 was added to deactivate the catalyst. . The salt (d) was added as follows. When the “addition method” column in Table 1 is “solid”, the component (d) is uniformly dispersed in the powder of the polyacetal copolymer in the solid state, and the dispersed powder is used as the reaction product. Added to. When the “addition method” column in Table 1 is “aqueous solution”, it is prepared as a 10 wt% aqueous solution containing the component (d) so as to have a predetermined number of moles, and 10 mL of the aqueous solution is added to the polyacetal copolymer powder. And added to the reaction product. When the “addition method” column in Table 1 is “methanol solution”, a 10-30 wt% methanol solution containing the component (d) is prepared so as to have a predetermined number of moles, and the solution is prepared as a polyacetal copolymer solution. 10 mL was added to the powder and added to the reaction product.

  Next, 0.3% by weight of triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyfehl) propionate] was added as an antioxidant, and a vented twin screw extruder was used. Then, the mixture was melt-kneaded and extruded at a temperature of 220 ° C. and a degree of vacuum of 5 mmHg in the vent portion to prepare polyacetal copolymer pellets according to Examples 1-16.

<Comparative Examples 1-4>
As a quencher, the polyacetal copolymers according to Comparative Examples 1 and 2 were prepared in the same manner as in Examples except that the compounds shown in Table 1 (melamine or melamine resin) were added in the amounts shown in Table 1. A pellet was prepared. Moreover, the pellet of the polyacetal copolymer in connection with the comparative examples 3 and 4 was prepared by the same method as an Example except having used boron trifluoride as a polymerization catalyst and having used the quantity of Table 1.

<Evaluation>
After drying the pellet of the polyacetal copolymer which concerns on an Example and a comparative example on condition of 135 degreeC and 4 hours, melt index (MI), alkali decomposition rate, formaldehyde discharge | release amount, and the polymerization catalyst (c) were deactivated. The hue of the later polyacetal copolymer was measured.

[Evaluation of Melt Index (MI)]
Melt index measuring device: Melt Index L202 type (manufactured by Takara Thermistor) was used as a melt index (g / 10 min) when measured under conditions of a load of 2.16 kg, a temperature of 190 ° C. and 7 minutes. The results are shown in Table 2. In this example, the melt index (MI) is a characteristic value corresponding to the molecular weight. That is, the lower the MI, the higher the molecular weight, and the higher the MI, the lower the molecular weight.

[Evaluation of alkali decomposition rate (abundance of unstable part)]
The copolymer pellets in Examples and Comparative Examples were pulverized, and about 1 g thereof was precisely weighed and sealed in a sealable container together with 100 mL of 50% aqueous methanol solution containing 0.5% by weight of ammonium hydroxide. 180 After heating at ° C for 45 minutes, the amount of formaldehyde decomposed and eluted in the liquid was quantitatively analyzed. The results are shown in Table 2. The alkali decomposition rate is shown as a ratio (unit:%) to 100% by weight of the copolymer pellets.

[Evaluation of formaldehyde emission]
Samples in Examples and Comparative Examples were filled in a cylinder maintained at 200 ° C., melted in 5 minutes, and then the melt was extruded from the cylinder into a sealed container. Nitrogen gas was allowed to flow through this sealed container, and formaldehyde contained in the nitrogen gas that had come out was dissolved and collected in water, and the formaldehyde concentration in the water was measured to determine the weight of formaldehyde released from the melt. The formaldehyde weight was divided by the weight of the melt to obtain formaldehyde emission (unit: ppm). The results are shown in Table 2.

[Evaluation of hue in pellets]
Using a color difference meter SE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), a predetermined amount of pellets is placed in a pellet measurement cell (round cell), placed on a sample stage, covered with a cover, and displayed. Read the value. The results are shown in Table 2.

  In the present invention, the polymerization catalyst is a heteropolyacid represented by the above general formula (1), and the deactivator of the heteropolyacid is an alkali metal or alkaline earth metal hydroxide or alkoxide compound (d). A high polymerization yield can be obtained with an extremely small amount, and after polymerization, an extremely high-quality polyacetal copolymer can be provided as a product simply by adding the component (d) to the crude copolymer and melt-kneading. It was confirmed (Examples 1 to 26).

  By the way, the lower limit of the content of the component (d) affects the MI value. When the content of the component (d) is 0.002 milliequivalent or more with respect to 1 kg of the crude polyacetal copolymer, the MI value is 10 g / 10 min or less, the polymerization catalyst can be deactivated efficiently, and is unstable. It was confirmed that the terminal can be sufficiently stabilized (Examples 2 to 26).

  On the other hand, the upper limit of the content of the component (d) affects the b value. When the content of the component (d) is 0.10 milliequivalent or less with respect to 1 kg of the crude polyacetal copolymer, the b value is 1.0 or less, and the polyacetal copolymer after deactivating the polymerization catalyst (c) It was confirmed that it was excellent in the hue of the polymer (Examples 1 to 25). Moreover, when content of (d) component is 0.025 milliequivalent or less with respect to 1 kg of crude polyacetal copolymers, b value is 0.0 or less, and after deactivating a polymerization catalyst (c) It was confirmed that the polyacetal copolymer was more suitable in terms of hue (Examples 1 to 18).

  On the other hand, when the deactivator is melamine, melamine resin or CTU guanamine, the polymerization catalyst can be sufficiently deactivated, and in terms of economy, a large amount of deactivator is required compared to the examples. It was confirmed that problems remained (Comparative Examples 1 to 3). Moreover, it was confirmed that the alkali decomposition rate and the amount of formaldehyde released do not satisfy the quality level required in recent years (Comparative Examples 1 to 3).

Claims (8)

In producing a polyacetal copolymer using trioxane as a main monomer (a) and a cyclic ether and / or cyclic formal having at least one carbon-carbon bond as a comonomer (b), the polymerization catalyst (c) has the following general formula. effecting copolymerization using heteropoly acid represented by (1), the hydroxide or alkoxide compound of an alkali metals to the reaction product was added (d), and melt-kneaded, a polymerization catalyst and (c) Deactivated ,
The amount of the alkali metal hydroxide (d) added is 0.001 to 0.10 milliequivalent to 1 kg of the crude polyacetal copolymer obtained by the copolymerization reaction .
H _m [M ¹ _x · M ² _y O _Z ] · nH ₂ O (1)
[In Formula (1), M1 shows the central element which consists of ¹ type or 2 types of elements chosen from P and Si. M ² represents one or more coordination elements selected from W, Mo and V. x represents an integer of 1 to 10; y represents an integer of 6 to 40; z represents an integer of 10 to 100; m represents an integer of 1; and n represents an integer of 0 to 50 Indicates. ]   The polyacetal copolymer according to claim 1, wherein the comonomer (b) is at least one selected from 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, or ethylene oxide. Manufacturing method.   The heteropolyacids include phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdotungstovanadic acid, lintonguestovanadic acid, silicotungstic acid, silicomolybdic acid, and cimolybdotungstic acid. Or the manufacturing method of the polyacetal copolymer of Claim 1 or 2 which is at least 1 sort (s) selected from the moss-rib-tungstovanadic acid. The alkali metals hydroxide or alkoxide compound (d) are represented by the following general formula (2), the production method of the polyacetal copolymer according to any of claims 1 to 3.
(XO) _n M ³ (2)
[In Formula (2), X shows hydrogen, a C1-C6 unsubstituted alkyl group, a substituted alkyl group, or a phenyl group. An unsubstituted alkyl group is linear, branched or cyclic. The substituent of the substituted alkyl group is a methyl group. M ³ represents an alkali metal elemental. n is 1 or 2. ] The alkali metals hydroxide or alkoxide compound (d) is
(A) lithium hydroxide, at least one hydroxide selected either sodium hydroxide or hydroxide potassium et al, or (b) lithium methoxide, sodium methoxide, sodium ethoxide, sodium tert- butoxide, sodium phenoxide , potassium methoxide, at least one alkoxide compound or we selected potassium ethoxide or potassium tert- butoxy-de,
The manufacturing method of the polyacetal copolymer in any one of Claim 1 to 4. The alkali metals hydroxide or alkoxide compound (d) is lithium hydroxide, sodium hydroxide, is at least one hydroxide selected from potassium hydroxide, polyacetal copolymer according to claim 5 Manufacturing method. The alkali metals hydroxide or alkoxide compound (d) is at least one which is a hydroxide, a manufacturing method of the polyacetal copolymer according to claim 6 which is selected from lithium or sodium hydroxide. Addition of the alkali metal hydroxide or alkoxide compound (d) to the reaction product,
(A) The alkali metal hydroxide or alkoxide compound (d) is added directly to the crude polyacetal copolymer obtained by the copolymerization reaction as a solution,
(A) The solution of the alkali metal hydroxide or alkoxide compound (d) is included in the powder of the polyacetal copolymer and uniformly dispersed, and then the dispersed powder is added to the crude polyacetal copolymer. Or (c) after the alkali metal hydroxide or alkoxide compound (d) is uniformly dispersed in the powder of the polyacetal copolymer in the solid state, and then the dispersed powder is converted into the crude polyacetal copolymer. Done by adding to
The b value of the polyacetal copolymer pellet after deactivation of the polymerization catalyst (c) measured using a color difference meter is 1.0 or less, and the polyacetal copolymer according to any one of claims 1 to 7 Production method.