JPS5838713A - Deactivation of polymerization catalyst - Google Patents

Abstract

PURPOSE:When a catalyst such as boron trifluoride is used to effect the copolymerization of trioxane and cyclic ether, the resultant copolymer is brought into contact with calcium hydroxide to deactivate the catalyst with no discoloration and reduction in heat stability of the copolymer. CONSTITUTION:The copolymerization of trioxane with a cyclic ether such as ethylene oxide or a cyclic formal such as diethylene glycol formal is carried out using a catalyst of boron trifuloride or a complex thereof with an organic compound bearing an oxygen atoms such as dibutyl ether or diethyl ether. The resultant copolymer is suspended in an aqueous solution of calcium hydroxide whose molar amount is preferably 10-100 times that of the catalyst, to bring into contact with calcium hydroxide and deactivate the catalyst. EFFECT:Even if the deactivated catalyst remains in the copolymer, the thermal stability of the copolymer is not affected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for deactivating a polymerization catalyst in order to stop a polymerization reaction when obtaining an oxymethylene copolymer with excellent thermal stability. For example, it was difficult to copolymerize trioxane and a cyclic ether or cyclic formal in the presence of a polymerization catalyst to obtain an oxymethylene copolymer with excellent thermal stability. It concerns the method of activating it.

In recent years, oxymethylene copolymers have been widely used as engineering plastics such as mechanical parts, automobile parts, and electronic/electrical equipment parts because of their excellent wear resistance and friction resistance.

It is well known that this oxymethylene copolymer can be obtained by copolymerizing trioxane and a cyclic ether or a cyclic formal in the presence of an acidic catalyst (for example, Japanese Patent Publication No. 3542/1983).

In the above production method, terminal stabilization is performed because the copolymer obtained is usually thermally unstable, but prior to this, it is necessary to neutralize and deactivate the acidic catalyst to stop the reaction. be. That is, unless the acidic catalyst present in the copolymer is neutralized and deactivated, the thermal stability of the copolymer will be impaired during subsequent steps such as terminal stabilization, pellet molding, and product molding. By the way, regarding the neutralization and deactivation of polymerization catalysts such as boron fluoride among acidic catalysts, for example, the polymerization catalyst is neutralized using an aliphatic amine or a heterocyclic amine, and then removed by washing to form a polymer. A stabilizing method (US Pat. No. 2,989,509) has been proposed. However, in this method, unless the catalyst is removed from the polymer after neutralizing the polymerization catalyst using an amine, silica polymerization occurs when the polymer is melted, which impairs thermal stability. Therefore, in this method, it is essential to neutralize and deactivate the polymerization catalyst with amine and then remove the catalyst from the polymer by thorough washing operations. As a method for improving this removal means, for example, a method has been proposed in which the polymerization catalyst is neutralized and deactivated using an excess trivalent organic phosphorus compound (Japanese Patent Publication No. 55-42085). In this method, even if the neutralized and deactivated catalyst remains in the polymer, it is said that it does not have an adverse effect on the thermal stability of the polymer. however,
Even in this method, if a catalyst that has been neutralized and deactivated with a trivalent organic phosphorus compound remains, this residual catalyst will decompose the polymer in the subsequent heat treatment step, so the effect on thermal stability is sufficient. I can't say that.

In view of these circumstances, the present inventors have conducted intensive studies regarding the deactivation of polymerization catalysts in the production of oxymethylene copolymers, particularly regarding the polymer decomposition activity of the catalyst after deactivation. When an aqueous calcium solution is brought into contact with a copolymer, the catalyst is deactivated, and surprisingly, even if the deactivated catalyst is present in the polymer, it can affect the thermal stability of the polymer. Furthermore, the undesirable coloring of the polymer due to residual deactivating agents, which has been pointed out as a drawback when deactivating polymerization catalysts with alkali metal or alkaline earth metal hydroxides, The present invention was completed based on this finding.

That is, in the present invention, when producing an oxymethylene copolymer by copolymerizing trioxane and a cyclic ether or a cyclic formal in the presence of a polymerization catalyst, an aqueous calcium hydroxide solution is brought into contact with the copolymer to form a polymerization catalyst. The present invention provides a method for inactivation.

Examples of the cyclic ether and cyclic formal in the present invention include ethylene oxide, 1,3-dioxolane,
Examples include 1,4-butanediol formal and diethylene glycol formal.

In addition, as the polymerization catalyst in the present invention, acidic catalysts such as boron trifluoride and its derivatives, phosphorus pentafluoride, and trifluoromethyl sulfuric acid are used, but boron trifluoride-based catalysts are particularly preferred, and boron trifluoride or A coordination complex compound of boron trifluoride and an organic compound having an oxygen atom is used. These catalysts may be used alone or in combination of two or more, and may be used in gaseous, liquid, or solution form in an appropriate organic solvent. Coordination complexes of boron trifluoride and organic compounds having an oxygen atom include, for example, phenol, ether, acid, acid anhydride, ester,
Examples include complex compounds of boron trifluoride with ketones, aldehydes, etc., and preferably complex compounds with dibutyl ether and diethyl ether.

The deactivator used in the method of the present invention is an aqueous calcium hydroxide solution, and the amount used is C! It is 2 to 200 times the mole of the catalyst in terms of a(OH)2, preferably 10 to 100 times the mole. Regarding the concentration of the calcium hydroxide aqueous solution, there is no particular restriction as long as the aqueous solution contains Ca(OH)2 in the above-mentioned range, and any value may be used.

Regarding the method of contacting the quenching agent and the reaction product, a method may be used in which the product is suspended in an aqueous calcium hydroxide solution after the reaction is completed, and then the solution is removed. A method may also be used in which an aqueous calcium hydroxide solution is mechanically mixed and dispersed in the product, and then the next step is carried out without removing the solution. A small amount of trioxane, catalyst, and deactivator remaining in the product may be removed by washing with a solvent, if necessary, or may be left behind. Even if the deactivated catalyst or deactivator remains in the polymer, the polymer remains stable against any subsequent thermal history, and no undesirable coloring phenomenon occurs.

The method of the present invention has the advantage that even if the catalyst deactivated by the aqueous calcium hydroxide solution remains in the polymer, it does not have any adverse effect on the thermal stability of the polymer. As described above, the method of the present invention is significantly superior to conventional methods using aliphatic amines or petrocyclic amines, and also shows less deactivation than methods using trivalent organic phosphorus compounds. The method of the present invention is superior in terms of the influence that the residual catalyst has on the thermal stability of the polymer.

Furthermore, according to the method of the present invention, even an excess of the deactivator does not adversely affect the thermal stability of the polymer, and when the catalyst is deactivated with an alkali metal or alkaline earth metal hydroxide, The quenching agent causes an undesirable coloring phenomenon when the polymer is heated, but the method of the present invention does not cause such a phenomenon.

Therefore, if the polymerization catalyst is deactivated by the method of the present invention, the subsequent washing operation can be omitted and the polymer production process can be simplified.

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Trioxane, ethylene oxide having a molar ratio of 4 to trioxane, and trifluoride having a molar ratio of lXl0"-' to trioxane were placed in a polymerization machine having a diameter of 50+ nm and a length of 600 wn, which had a pseudo-triangular paddle with two axes. Boron dibutyl etherate and 1 x 10 mol of methylal dissolved in cyclohexane were continuously fed, and polymerization was carried out at 80°C.

The copolymer coming out of the polymerization-like outlet is suspended in an aqueous calcium hydroxide solution with a concentration of 0.1 weight ratio containing Oa(OH)2 in an amount 50 times the mole of the catalyst amount, and after inactivation at room temperature. After filtering the excess aqueous solution, 0.1% by weight of dicyandiamide and 2.2'-methylenebis(4-methylene 67t-
Butylphenol) was added in an amount of 4% by weight, and the unstable portions at the terminals were removed by heating and kneading in a single-screw extruder equipped with a vent. The obtained copolymer had an RA120' (weight retention rate in air at 230° C. for 120 minutes) of 98.6.

Comparative Example 1 The same procedure as in Example 1 was carried out except that an aqueous triethylamine solution having a concentration of 0.1 weight ratio and containing triethylamine in an amount 50 times the mole of the catalyst was used as a deactivator. The RA12 (/) of the obtained copolymer was 95.5.

Example 2 A calcium hydroxide aqueous solution with a concentration by weight of 0.1 containing Ca(OH)2 in an amount 10 times the mole of the catalyst was used as a deactivator, and this aqueous solution was subjected to the same polymerization procedure as in Example 1. After kneading the Tegur copolymer with a tabletop kneader, 0.1% by weight of dicyandiamide and 2.2'-methylenebis(4-
0.4 weight percentage of methyl-6-t-butylphenol was added, and the unstable parts at the ends were removed by heating and kneading in a single-screw extruder equipped with a vent. R51 of the obtained copolymer
20' was 98.3.

Comparative Example 2 The same operation as in Example 2 was performed, except that triphenylphosphine was added as a deactivator in an amount 10 times the mole of the catalyst. The obtained copolymer had an RA 120 of 96.0.

Comparative Example 3 The same operation as in Example 2 was carried out, except that an aqueous solution of carbonic acid with a concentration of 0.1% by weight containing Na2CO3 in an amount 10 times the mole of the catalyst was used as a deactivator. The obtained copolymer had an RA120' of 93.3 and was colored yellow.

Example 3 A calcium hydroxide aqueous solution with a concentration of 0.1 weight ratio containing Oa(OH)2 in an amount 25 times the mole of the catalyst was used as a deactivator, and calcium hydroxide was added to this aqueous solution in the same manner as in Example 1. After suspending the Guru copolymer and inactivating it at room temperature, the excess aqueous solution was filtered, then washed with water, and dried.
and 5 parts by weight of an aqueous triethylamine solution having a concentration of 5 parts by weight were added, and the mixture was heated and kneaded in a single-screw extruder equipped with a vent to remove unstable portions at the ends. R of the obtained copolymer
AI20' was 98.8.

Comparative Example 4 The same operation as in Example 3 was carried out, except that an aqueous triethylamine solution having a concentration of 0.5 weight ratio and containing 25 times the mole of triethylamine as the catalyst amount was used as a deactivator. The RAI20' of the obtained copolymer was 95.7.

Patent applicant: Asahi Kasei Industries, Ltd. Agent Akira Agata

Claims (1)

[Claims] 1. In the presence of a polymerization catalyst, trioxane and a cyclic ether or a cyclic formal are copolymerized to produce an oxymethylene copolymer. Characteristic method for deactivating polymerization catalysts. 2. The method according to claim 1, wherein the polymerization catalyst is boron trifluoride or a coordination complex of boron trifluoride and an organic compound having an oxygen atom. 3. The method according to claim 2, wherein the organic compound having an oxygen atom is dibutyl ether or diethyl ether.