JP2002097241A - Production method of stable polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal polymer with few unstable parts which deactivates a polymerization catalyst in a simple form, without needing complicated facilities. SOLUTION: When a copolymer of a trioxane and a cyclic formal is polymerized by a cationic catalyst in the presence of the formal of a formula R1OCH2 OR, a polymerization reaction is progressed in a homogeneous system during meeting a specific relation of P>=94-1.43T+5.67×10-3T2 between a pressure P (atm) which puts on a reaction system and a polymerization temperature ( deg.C). Thereafter reactants are blended uniformly in the presence of a base, and the production method of a polyacetal whose terminated unstable parts of the polymer are below 1 wt.% is provided by deactivating a cationic catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for producing a polyacetal resin which is important as an engineering resin. More specifically, the present invention relates to an improved method for obtaining a stable polyacetal resin in a homogeneous reaction system in the copolymerization of trioxane and cyclic formal.

[0002]

2. Description of the Related Art Heretofore, attempts have been made to obtain a stable copolymer by copolymerizing trioxane with a cyclic ether and a cyclic formal. For example, in the conventional methods, a method in which a solid polyoxymethylene copolymer is formed by polymerization of trioxane, and then the polymer is pulverized has been adopted. For example, Japanese Patent Publication No. 2-35772 of the present applicant proposes a method of pulverizing a polyoxymethylene copolymer and then deactivating the catalyst in an aqueous solution of a base. Similarly, Japanese Patent Publication No. 6-89090 of the present applicant discloses that continuous polymerization and subsequent pulverization of the polymer, subsequent contact with a base, and drying of the polymer are all performed continuously, It is proposed that any of them be performed in an inert gas atmosphere. In particular, the latter method consisting of the present applicant is required to obtain a stable polyoxymethylene copolymer,
However, attention was paid as a preferable method. However, there is a problem in that the apparatus is complicated such as pulverization of a solid polymer.

[0003]

In the conventional method, the obtained solid oxymethylene copolymer is pulverized once and then contacted with a base to deactivate the polymerization catalyst. Therefore, complicated equipment such as a crusher was required. Therefore, it has been desired to eliminate the pulverizer and the like, deactivate the polymerization catalyst in a simpler form, and obtain a polymer having less unstable parts.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have achieved the following simple and convenient method for producing an oxethylene methylene copolymer having excellent stability. . That is, the present invention provides a copolymer of trioxane and cyclic formal represented by the following general formula (I): R ₁ OCH ₂ OR ₂ (I) wherein R ₁ and R ₂ are alkyl groups having 8 or less carbon atoms. The polymerization temperature is from 130 ° C. to 18 ° C. for the polymerization using a cationic catalyst in the presence of formal represented by
0 ° C., the polymerization reaction was promoted in a homogeneous system while satisfying the relationship of the following formula (2) between the pressure P (atm) applied to the reaction system and the polymerization temperature T (° C.), and the polymerization rate for trioxane was 30 to
90%, and thereafter, the reactants are uniformly mixed in the presence of a base, and the cationic catalyst is deactivated to obtain a polymer having an unstable portion at the polymer terminal of 1% by weight or less. To provide a method for producing a polyacetal polymer. P ≧ 94-1.43T + 5.67 × 10 ⁻³ T ² (2) Another characteristic is that the unstable portion at the polymer terminal is 0.5 wt% or less. Another characteristic is that the polymerization temperature is maintained at 130 to 150 ° C.

Hereinafter, the present invention will be described in detail. First, the formula
P in (2) is the pressure applied to the polymerization machine. That is, the polymerization is performed in a uniform pressure system. If the pressure P in the polymerization machine is smaller than the value of the equation (2), a liquid polymer cannot actually be obtained. That is, it is necessary that the oxymethylene copolymer and trioxane form a homogeneous system in the polymerization machine. Examples of a method of adjusting the pressure include a method of installing a pressure regulating valve or the like at an outlet of the polymerization machine, but are not particularly limited. The polymerization machine for copolymerizing trioxane and cyclic formal is not particularly limited as long as it has a heatable jacket and a pressure regulating valve, but a tube reactor is preferably used.

Further, in the present invention, a base is uniformly mixed in a molten state in a homogeneous system of an oxymethylene copolymer containing the polymerization catalyst and trioxane, and the mixture is brought into contact with the catalyst to deactivate the catalyst. For the first time, it is possible to obtain a polymer having an unstable portion at the polymer terminal of 1% by weight or less.
In the present invention, the trioxane used needs to be highly purified. The total content of impurities such as water, methanol, and formic acid that induce OH groups at the polymer terminals is 3
It is 0 ppm or less, preferably 10 ppm or less, more preferably 3 ppm or less. This preferred method of purifying trioxane is disclosed in WO 98/13362 of the present applicant.

As a molecular weight regulator (terminal blocking agent)
R of formula (I) used₁OCH_TwoOR_TwoFormal indicated by (
But here R₁, R_TwoIs an alkyl group having 8 or less carbon atoms.
You. ) Is usually preferably methylal and butyral. Special
In particular, methylal is preferred. The addition amount of the molecular weight modifier is
Usually, 0.1 × 10 ^-3Mo
~ 6x10^-3Used in the molar range.

In the present invention, the copolymerization of trioxane and cyclic formal can be carried out without a solvent since the copolymerization is carried out at high temperature and high pressure. Further, since the polymer is obtained in a liquid state, it is not necessary to pulverize the polymer as in the conventional method for obtaining a solid polymer. The polymerization temperature of the present invention is usually 130-1.
It is used at a high temperature of 80C, preferably 130-150C. Particularly preferred is 130-140 ° C.

The cyclic formal as a comonomer of the copolymer includes ethylene oxide, 1,3-dioxolan, 1,4-butanediol formal, diethylene glycol formal, trioxeban and the like. Among them, 1,3-dioxolan, 1,4-butanediol formal and the like are preferred comonomers. Usually, these comonomers are used in the range of ¹ × 10 ^-3 mol to 4 × 10 ^-1 mol per mol of trioxane.

As the cationic catalyst, a Lewis acid catalyst such as boron trifluoride dibutyl ether and a protic acid such as trifluoromethanesulfonic acid and heteropoly acid can be used. The base for deactivating the cationic catalyst is not particularly limited. For example, inorganic bases and organic bases are specifically tertiary amines such as triethylamine; phosphine compounds such as triphenylphosphine;
Alkali metal compounds such as quaternary ammonium salts, quaternary phosphonium salts, sodium carbonate, etc., and alkaline earth metal compounds can be used. Although the amount of the base used is not particularly limited, it is 2 to 200 times the amount of the catalyst, preferably 10 to 100 times.
It is twice.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The gist of the present invention will be described below with reference to examples, but this does not limit the scope of the present invention. Example 1 A trioxane melt in which 5 mol% of 1,3-dioxolane was dissolved was heated at 135 ° C.
Heated tube reactor (internal volume 500 mL)
Was continuously supplied at 5 kg / h. The contents inside the tube reactor are uniformly mixed by a static mixer. In this tube reactor, boron trifluoride dibutyl ether (2 × 10
^-5 mol). In addition, methylal was continuously supplied to a 2 × 10 ⁻³ mol reactor per 1 mol of trioxane. According to the calculation formula of the equation (2), the pressure P of the reactor is P
Since it was calculated as ≧ 4.3, a pressure regulating valve was attached so that the pressure of the reactor became 8 atm, and the reaction was performed while maintaining the internal pressure of the reactor. Next, the outlet of the reactor was connected to a tube having a diameter of 1 cm and a length of 10 cm (the outer side was jacket-heated to 135 ° C.).
In L), the reactants were fed continuously. The contents inside the tube reactor are uniformly mixed by a static mixer. From the inlet of this reactor, a 10 wt% aqueous solution of triethylamine cooled to 10 ° C. was continuously supplied at 50 g / h.

The outlet of the reactor has a diameter of 1 cm and a length of 10 cm.
cm tube (outside jacket heated to 135 ° C). From this outlet, the reaction mixture was taken out into a nitrogen atmosphere and cooled. The solid taken out was pulverized. The pulverized product was extracted with methanol to remove unreacted trioxane, and dried by heating in nitrogen. 3.5 kg of polymer per hour were obtained. 230 ° C. of this polymer
Heated under vacuum for 60 minutes. The remaining polymer amount after heating was 99.7% by weight before heating. 19 of the obtained polymer
The melt index value at 0 ° C. was 30 g / 10 minutes.

Example 2 The procedure of Example 1 was repeated except that the temperature of the jacket of the reactor of the first polymerization machine was 140 ° C., the reaction pressure was 12 atm, and the temperature of the jacket of the second reactor was 140 ° C. The same operation as in Example 1 was performed. 3.2 kg of polymer per hour were obtained. The residual amount of the polymer at 230 ° C. under vacuum for 60 minutes was 99.6 wt%. The melt index value was 35.

Example 3 The procedure of Example 1 was repeated except that the jacket temperature of the reactor of the first polymerization machine was 150 ° C., the reaction pressure was 20 atm, and the temperature of the jacket of the second reactor was 150 ° C. The same operation as in Example 1 was performed. 3.0 kg of polymer per hour were obtained. The residual amount of the polymer at 230 ° C. under vacuum for 60 minutes was 99.6 wt%. The melt index value was 40.

[0015]

The present invention provides a method for producing a new polyacetal resin having high heat stability. This method is useful as a method for producing a polyacetal resin.

Claims (3)

[Claims] A copolymer of trioxane and cyclic formal is represented by the following general formula (I): R ₁ OCH ₂ OR ₂ (I) (where R ₁ and R ₂ are alkyl groups having 8 or less carbon atoms). In the polymerization using a cationic catalyst in the presence of formal represented by
0 ° C., the polymerization reaction was promoted in a homogeneous system while satisfying the relationship of the following formula (2) between the pressure P (atm) applied to the reaction system and the polymerization temperature T (° C.), and the polymerization rate for trioxane was 30 to
90%, and thereafter, the reactants are uniformly mixed in the presence of a base, and the cationic catalyst is deactivated to obtain a polymer having an unstable portion at the polymer terminal of 1% by weight or less. Of producing a polyacetal polymer. P ≧ 94-1.43T + 5.67 × 10 ⁻³ T ² (2) 2. The polymer has an unstable portion at the terminal of the polymer of 0.5 wt%.
The method for producing a polyacetal polymer according to claim 1, wherein: 3. The method for producing a polyacetal polymer according to claim 1, wherein the polymerization temperature is maintained at 130 to 150 ° C.