JPH0689090B2 - Method for producing trioxane copolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a stabilized trioxane copolymer.

More specifically, the present invention relates to a method for producing a trioxane copolymer molding having a high stabilization rate after being polymerized.

(Prior Art) It has been well known that a polyacetal resin is obtained by copolymerizing trioxane with ethylene oxide or butanediol formal. For example, Japanese Patent Publication Sho 36-
No. 14640 discloses copolymerization of trioxane with a cyclic ether or cyclic formal such as ethylene oxide or dioxolane, 1,4-butanediol formal. In the case of this copolymerization, as a molecular weight regulator,
It is also well known to use methylal, butyral and the like.

However, the copolymer thus obtained has many unstable parts and cannot be used as it is, so that the unstable parts are removed. For example, Japanese Patent Publication 41
Japanese Patent Publication No. 29-29 proposes that the copolymer is heated in a solvent such as water in the presence of a base to hydrolyze the unstable portion at the terminal.

Hydrolysis of these labiles stabilizes the polymer, but many polymer losses are unavoidable. Usually there is a polymer loss of 5-10% by weight.

(Problems to be Solved by the Invention) Conventionally, due to hydrolysis of an unstable portion of a polymer,
In view of the fact that there is a polymer loss of 10% by weight, the present inventor has found that the polymer loss can be reduced by first examining the polymerization conditions (JP-A-57-141418).

Furthermore, the present inventor has found that the particle size is important for deactivating the polymerization catalyst (JP-A-58-34819).

However, even if these methods are adopted, in the above-mentioned publication, the unstable part of the polymer is in Example 1 (1.8%), Example 2 (1.5%; from FIG. 3), Example 3 ((1.5%; (From Fig. 4) and 1% or more.Therefore, there is a demand for a polyacetal resin excellent in thermal stability having an extremely small unstable portion of less than 1% and its production.

(Means for Solving the Problem) The present inventor has made earnest studies based on the above situation,
Compared with the case of the prior art (for example, JP-A-58-34819), the amount of the terminal blocking agent added to trioxane and cyclic ether or cyclic formal is 10 times or more, and the final drying step is continuously performed. We have succeeded in obtaining a trioxane copolymer which can be dried completely under exclusion of air and has very little instability below 1%.

That is, the present invention comprises: trioxane and a cyclic ether or cyclic formal;
A general formula: R ₁ OCH ₂ OR ₂ ... [I] (wherein R ₁ and R ₂ represent the same or different alkyl groups having 1 to 10 carbon atoms) as a terminal blocking agent with trioxane. 1 / 1000-1 / for 1 mol
Polymerization with a cationic catalyst in the presence of 100 amounts, then the resulting copolymer without contact with air, fine particle size
A copolymer having a terminal unstable portion of less than 1% of the polymer before the end stabilization treatment, which is obtained by treating with a base in a state of 1 mm or less and then continuously drying in an inert atmosphere, It is a method for producing a trioxane copolymer which is melted by an extruder and hydrolyzes an unstable portion at the terminal.

The present invention will be specifically described below.

Before being subjected to such an end stabilization step, the destabilizing part is
The presence of trioxane copolymers of less than% has not previously been known.

The existence of such a trioxane copolymer was first revealed by the present invention.

Next, a method for producing such a trioxane copolymer will be specifically described.

First, a highly purified trioxane is used as a copolymerization component of cyclic ether or cyclic formal, preferably in a hydrocarbon solvent, with the general formula: R ₁ OCH ₂ OR ₂ ... [I] (where, , R ₁ and R ₂ represent an alkyl group having 1 to 10 carbon atoms.) In the presence of an end capping agent, a polymerization catalyst, preferably a cationic catalyst, is polymerized to produce a trioxane copolymer, The particle size of the polymer is 1 mm or less, preferably 0.5
mm or less, more preferably 0.3 mm or less in contact with a base in the form of fine particles, but without contact with air, it is advantageously produced by drying in an atmosphere of 110 ° C. or more under an inert gas in a continuous operation To be done.

Further, embodiments of the present invention will be described in detail.

The trioxane used in the present invention is preferably highly purified. For example, impurities such as water and formic acid are 1 ppm each
The following is desirable.

As a method for purifying such trioxane, for example, the method described in Japanese Patent Publication No. 64-10513 by the present inventor can be adopted.

Next, examples of cyclic ether and cyclic formal used as a copolymerization component include ethylene oxide and 1,3-
Examples thereof include dioxolane, 1,4-butanediol formal, diethylene glycol formal, trioxepane and the like. Among them, ethylene oxide, 1,4-butanediol formal and diethylene glycol formal are preferable copolymerization components.

The proportion of the copolymerization component is not particularly limited, but is 0.5
-10 mol% is preferable, and 2-6 mol% is particularly preferable.
Is.

The polymerization catalyst that can be used is preferably a cationic catalyst. Specific examples of the cationic polymerization catalyst include tin tetrachloride, titanium tetrachloride; boron trifluoride and boron trifluoride coordination compounds such as boron trifluoride diethyl ether and boron trifluoride dibutyl ether; pentafluoride Inorganic acids such as phosphorus, trifluoromethylsulfuric acid, trichloroacetic acid and P-toluenesulfonic acid, organic acids; alkyl metals such as diethylzinc and triethylaluminum, etc., but cationic polymerization in which boron trifluoride dibutyl ether is particularly preferable. It is a catalyst.

You may use these polymerization catalysts individually or in mixture of 2 or more types.

Although the amount of the polymerization catalyst used is not particularly limited, it is preferably 5 × 10 ⁻⁵ mol / mol or less with respect to the monomer used.

The end-capping agent used in the present invention has a general formula: R ₁ OCH ₂ OR ₂ ... [I] (wherein R ₁ and R ₂ are the same or different alkyl groups having 1 to 10 carbon atoms). Is represented by), and methylal and butyral are preferable. Further, as the terminal blocking agent,
Other optional acetals, such as those obtained by heating formalin with various alcohols, can also be used.

The amount of the end-capping agent used is not particularly limited, but it is generally preferably 1/1000 to 1/50, and particularly preferably 1/700 to 1/100 with respect to 1 mol of the monomer.

In the present invention, the copolymerization of trioxane with a cyclic ether or cyclic formal is carried out without solvent or in an organic solvent, particularly a hydrocarbon solvent.

Hydrocarbon solvents that can be used in the present invention include n
Aliphatic hydrocarbons such as pentane, n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and cyclopentane; aromatic hydrocarbons such as benzene, toluene and xylene; and those such as carbon tetrachloride and chlorobenzene Examples thereof include hydrocarbon halides, which may be used alone or in combination of two or more.

A preferable polymerization solvent is cyclohexane or the like.

The copolymerization of the present invention is 20 to 160 ° C, preferably 50 to 120 ° C,
More preferably, it is carried out at a reaction temperature of 80 to 110 ° C.

A preferred method for carrying out the copolymerization is a method using a self-cleaning continuous kneader.

As an example of the kneaders used, a co-kneader produced by Bus Industry Co., Ltd. and a kneader produced by Kurimoto Tekkosha
Examples include KRC kneader and ZSK twin-screw extruder manufactured by Werner.

In the present invention, the catalyst in the polymer after copolymerization is brought into contact with a base to be deactivated. At that time, the polymer particles to be brought into contact with a base as described in JP-A-58-34819 by the present inventors have a particle size of 1 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less. This is very important.

The base used for the deactivation treatment of the polymerization catalyst in the present invention is not particularly limited, and inorganic bases, organic bases and the like can be used, but bases such as calcium hydroxide and organic amines such as triethylamine are preferably used.

The amount of base used is not particularly limited, but a catalytic amount of 2 to 200
The molar amount is double, preferably 10 to 100 times.

Here, the copolymer particles obtained by copolymerization in a self-cleaning type kneader, before being subjected to the deactivation treatment with a base, be finely pulverized to a fine particle size of 1 mm or less by a known pulverizer or the like. is necessary. The stabilized trioxane copolymer molded product intended in the present invention cannot be obtained unless it is made into fine particles by this pulverization treatment.

In addition, what is important in the present invention is that the polymer after polymerization is contacted with a base without contact with air, and then continuously dried at an ambient temperature of 110 ° C. or higher under an atmosphere of an inert gas. That is.

Here, the atmospheric temperature means the temperature of the gas in contact with the polymer.

In this way, a fine particle polymer molded product having 1% of the ring-shaped unstable portion is obtained.

This polymer molded body is subjected to the next end stabilization step.
The end stabilization step is usually performed in an extruder in the presence of a hydrolyzing agent such as water.

In the present invention, the polymer molded product having less than 1% of the terminal unstable portion before being subjected to the terminal stabilization step is a substance that has not existed in the world until now. The final product obtained after subjecting such polymer moldings to a stabilization step shows very good thermal stability.

That is, even when the molten resin obtained by the method of the present invention is retained in a molding machine, the terminal unstable portion of the resin is less than 1%, so the formaldehyde generated by decomposition of the resin is very small. As a result, the generation of deposits (so-called mold deposit) on the mold of the injection molding machine based on formaldehyde is very small, and the thermal stability is excellent.

The molecular weight of the copolymer of the present invention is not particularly limited, but preferably 10,000 to 100,000, particularly preferably 25,000 to 70,00.
It has a molecular weight of 0.

The shape of the copolymer molded article of the present invention may be any shape such as pellets, powders, and particles.

In the stabilized copolymer molded article of the present invention, if desired, various additives conventionally used in polyacetal resins, such as antioxidants, ultraviolet absorbers, lubricants, lubricants,
Pigments, fillers, reinforcing agents, flame retardants and the like can be added alone or in various combinations.

The copolymer molded product of the present invention can be made into various molded products by employing a conventional molding means such as injection or extrusion molding.

(Example) Hereinafter, the gist of the present invention will be described with reference to examples, but this does not limit the scope of the present invention.

Example 1 Boron trifluoride dibutyl etherate was dissolved in trioxane at 3 × 10 ⁻⁵ mol% and dissolved in cyclohexane to serve as a catalyst, and ethylene oxide was used as 4 mol% with respect to trioxane.
A copolymer of trioxane and ethylene oxide is produced from a mixture with trioxane containing by a twin-screw self-cleaning type kneader.

However, methylal was previously added as a terminal blocking agent in a molar ratio of 1/300 to trioxane. The copolymer is contacted with a 0.5 wt% aqueous solution of triethylamine in a tank and stirred with a stirrer at 62 ° C for about 90 minutes. Copolymer 0.5
The ratio to the weight% triethylamine aqueous solution is about 20% by weight. Simultaneously with the stirring, a triethylamine aqueous solution of the copolymerized slurry was extracted from the bottom of the tank, and the copolymer was pulverized with a pulverizer. A slurry containing fine particles of a copolymer of about 0.4 mm or less is centrifuged, the copolymer is separated from an aqueous solution of triethylamine, washed with water, and then with an average residence time of about 3 hours at an ambient temperature of 125 ° C. under nitrogen flow. It was heated and dried continuously.

The ratio of the unstable part of the obtained dried copolymer was determined.

The unstable part is measured by drying the dried polymer under a vacuum.
Heat at 50 ° C for 50 minutes, measure the weight, and obtain the reduction rate relative to the weight before heating.

The unstable part of the polymer was 0.7%.

Further, 3% by weight of water and 0.1% by weight of triethylamine were added to the obtained polymer and the mixture was subjected to an extruder at 200 ° C. or lower to take out a volatile component from the vent.

A transparent strand was obtained from the extruder nozzle. This was a pellet that was cut and had good thermal stability.

Comparative Example 1 The same operation as in Example 1 was performed except that the crusher was not used in Example 1. The unstable part of the polymer after drying is 6.1
%Met.

3% by weight of water and 0.1% by weight of triethylamine were added to this polymer and the mixture was applied to an extruder at 200 ° C. to remove volatile components from the vent part. Foamed strands were obtained from the extruder nozzle.

This was a pellet that was cut and had poor thermal stability.

Example 2 The same operation as in Example 1 was carried out except that the copolymer fine particles of about 0.2 mm or less were used.

The unstable part of the polymer after drying was 0.4%.

Also, the strand from the extruder nozzle has good transparency,
Pellets with good thermal stability were obtained.

Reference Example The pellets obtained in Example 1 were held in an injection molding machine held at a resin temperature of 210 ° C. for 60 minutes, but no foaming based on decomposed formaldehyde was observed in the molten resin.

An injection-molded plate of 10,000 shots was prepared with a mold held at 50 ° C, but no deposit was observed on the mold surface.

Reference Comparative Example As described in JP-A-59-34819 in Example 1, the copolymer was pulverized with a pulverizer. The slurry containing copolymer particles of about 0.4 mm or less was centrifuged, and the copolymer was separated from the aqueous solution of triethyiamine and washed with water. Then, the powder cake was transferred to a drier and heated under a nitrogen stream at an ambient temperature of 125 ° C. for about 3 hours to be dried.

The proportion of unstable parts in the obtained dry copolymer was determined to be 1.4%.

Further, 3% by weight of water and 0.1% by weight of triethylamine were added to the obtained polymer, and the mixture was subjected to an extruder at 200 ° C. or lower, and volatile components were taken out from the vent part.

A transparent strand was obtained from the extruder nozzle. This was cut and pellets were obtained. When the pellets were held for 60 minutes in an injection molding machine maintained at a resin temperature of 210 ° C. as in Example 3, foaming based on decomposed formaldehyde was observed in the molten resin. Also, 50
When a 10,000-shot injection-molded plate was prepared with a mold kept at ℃, deposits were observed on the mold surface.

(Effect of the invention) In the present invention, since the trioxane copolymer molded product has a structure in which the unstable portion of the polymer end before the end stabilization treatment is less than 1%, the polymer loss due to the end stabilization treatment is small. Thus, a polyacetal resin molded product having good thermal stability can be obtained.

Further, in the present invention, since the catalyst deactivation treatment of the trioxane copolymer polymerized with the cationic polymerization catalyst in the presence of the acetal type end-capping agent was carried out in the form of fine particles with a base, conventionally, the unknown polymer end A trioxane copolymer having a stable portion of less than 1% is obtained.

Claims (1)

[Claims] 1. A trioxane and a cyclic ether or cyclic formal are represented by the general formula: R ₁ OCH ₂ OR ₂ ... [I] (wherein R ₁ and R ₂ have the same or different carbon numbers 1 to 1). 10 represents an alkyl group.) The end-capping agent is 1/1000 to 1/1 / mol of trioxane.
Polymerized with a cation catalyst in the presence of 100 amounts, then the resulting copolymer without contact with air, fine particle size 1m
Copolymers with less than 1% terminal unstable parts of the polymer obtained by treating with a base in a state of m or less and then continuously drying in an inert atmosphere before destabilizing the terminal A method for producing a trioxane copolymer, which comprises melting a coalesced product in an extruder and hydrolyzing an unstable part at a terminal.