WO2024135260A1

WO2024135260A1 - Polyacetal copolymer production method

Info

Publication number: WO2024135260A1
Application number: PCT/JP2023/042706
Authority: WO
Inventors: 悠平細井
Original assignee: ポリプラスチックス株式会社
Priority date: 2022-12-23
Filing date: 2023-11-29
Publication date: 2024-06-27

Abstract

This polyacetal copolymer production method comprises: a step in which a trioxane and a comonomer that can be copolymerized with the troxane in the presence of a polymerization catalyst are copolymerized by a polymerization device; and a step in which a crude polyacetal copolymer obtained in the abovementioned step is melted/kneaded by an extruder. The polymerization catalyst is a protonic acid. In the melting/kneading step, a basic compound solution is added after the initiation of melting/kneading and before the completion of melting/kneading.

Description

Method for producing polyacetal copolymer

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

A known method for producing polyacetal copolymers is to cationic polymerize a main monomer (trioxane) and a comonomer copolymerizable with the main monomer in the presence of a polymerization catalyst. Lewis acids such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, phosphorus pentachloride, and antimony pentafluoride, as well as their complex compounds or salts, are commonly used as the cationic polymerization catalyst.

When using these polymerization catalysts, it is necessary to add a relatively large amount of the polymerization catalyst (for example, 40 ppm or more relative to the total monomers) during polymerization, which poses the problem that it is difficult to fully deactivate the catalyst remaining in the polyacetal copolymer after polymerization in the manufacturing process. Even if the polymerization catalyst can be deactivated, there are cases where problems such as accelerated decomposition of the copolymer occur due to substances derived from the catalyst remaining in the copolymer.

In recent years, there has been a demand for high-quality polyacetal copolymers that have excellent thermal stability and emit very little formaldehyde. For this reason, there has been research into efficient catalyst deactivation and stabilization of the crude polyacetal copolymer by decomposition of the unstable terminals after catalyst deactivation.

JP 2014-105278 A

According to Patent Document 1, by using a heteropolyacid as a polymerization catalyst and melt-kneading it together with a deactivator, polymerization becomes possible with a small amount of catalyst, complicated processes can be eliminated, and a high-quality polyacetal copolymer can be obtained.

However, there is room for further study regarding the physical properties (impact resistance) of molded products using polyacetal copolymers.

The present invention was made in consideration of these points, and aims to provide a method for producing a polyacetal copolymer that can produce molded products with high impact resistance.

As a result of extensive research, the inventors have completed the inventions described below in (1) to (5).

(1) A method for producing a polyacetal copolymer, comprising the steps of: copolymerizing trioxane and a comonomer copolymerizable with the trioxane in a polymerization apparatus in the presence of a polymerization catalyst; and melt-kneading the crude polyacetal copolymer obtained in the above step in an extruder, wherein the polymerization catalyst is a protonic acid; and in the melt-kneading step, a solution of a basic compound is added between the start of melt-kneading and the end of melt-kneading.

(2) The method for producing a polyacetal copolymer according to (1), wherein the protonic acid is a heteropolyacid.

(3) The method for producing a polyacetal copolymer according to (1), wherein the solution of the basic compound is an aqueous solution of an alkali metal carbonate, hydrogen carbonate, or carboxylate, or a hydrate thereof, or an aqueous solution of a nitrogen-containing organic compound, the pH of which at 1 g/L is 10 or higher.

(4) The method for producing a polyacetal copolymer according to (3), wherein the alkali metal is sodium or potassium.

(5) The method for producing a polyacetal copolymer according to (3), wherein the nitrogen-containing organic compound is an amine.

The present invention provides a method for producing a polyacetal copolymer that can produce molded products with high impact resistance.

FIG. 1 is a flow chart showing an outline of a manufacturing method according to one embodiment of the present invention.

Specific embodiments of the present invention are described in detail below. Note that the present invention is not limited to the following embodiments, and can be modified as appropriate without departing from the spirit of the present invention.

[Method for producing polyacetal copolymer]
A method for producing a polyacetal copolymer according to one embodiment of the present invention includes a step of copolymerizing trioxane and a comonomer copolymerizable with trioxane in a polymerization apparatus in the presence of a polymerization catalyst (protonic acid), and a step of melt-kneading the crude polyacetal copolymer obtained in the step in an extruder. The melt-kneading step includes a step of adding a solution of a basic compound as a deactivator into the extruder after the start of the melt-kneading and before the end of the melt-kneading.

The components and steps are explained below.

(Trioxane)
Trioxane is a cyclic trimer of formaldehyde. Trioxane according to one embodiment of the present invention is used as a main monomer. Here, the main monomer refers to a monomer that is contained in the largest amount among all monomers. Trioxane is generally obtained by reacting an aqueous solution of formaldehyde in the presence of an acid catalyst, and is used after being purified by a method such as distillation.

(Comonomer)
The comonomer according to one embodiment of the present invention is not particularly limited as long as it is copolymerizable with trioxane. The comonomer is preferably selected from the group consisting of cyclic ethers and cyclic formals having at least one carbon-carbon bond.

Examples of comonomers include 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, ethylene oxide, propylene oxide, epichlorohydrin, etc. Among these, 1,3-dioxolane and 1,4-butanediol formal are preferred from the viewpoint of polymerization stability.

Also, as comonomers, compounds having two polymerizable cyclic ether groups or cyclic formal groups, such as diglycidyl ether of alkylene glycols, such as butanediol diglycidyl ether, and diformal, and compounds having three or more polymerizable cyclic ether groups or cyclic formal groups, such as glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether, can be used. By using these comonomers, it is possible to obtain polyacetal copolymers having a branched structure or a crosslinked structure.

The content of the comonomer in one embodiment of the present invention is preferably 0.01 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and particularly preferably 1 to 8 parts by mass, per 100 parts by mass of trioxane. If the content of the comonomer is 0.01 to 20 parts by mass per 100 parts by mass of trioxane, polymerization can proceed stably and a decrease in the crystallization rate and degree of crystallization of the polymer chain can be suppressed.

(Polymerization catalyst)
The polymerization catalyst is a cationic polymerization catalyst. Examples of the cationic polymerization catalyst include Lewis acids and protonic acids.

<Lewis Acid>
Examples of the Lewis acid include boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof.

<Protonic Acid>
Examples of protonic acids include perfluoroalkanesulfonic acids, heteropolyacids, isopolyacids, and the like.

Examples of perfluoroalkanesulfonic acids include trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid, nonafluorobutanesulfonic acid, undecafluoropentanesulfonic acid, tridecafluorohexanesulfonic acid, pentadecafluoroheptanesulfonic acid, and heptadecafluorooctanesulfonic acid.

Examples of heteropolyacids include phosphotungstic acid, phosphomolybdic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdotungstovanadic acid, phosphotungstovanadic acid, silicotungstic acid, silicomolybdic acid, silicomolybdotungstic acid, and silicomolybdotungstenovanadic acid.

Examples of isopolyacids include paratungstic acid, metatungstic acid, paramolybdic acid, metamolybdic acid, metapolyvanadic acid, and isopolyvanadic acid.

The amount of polymerization catalyst added in one embodiment of the present invention is preferably 0.1 ppm or more relative to the total amount of all monomers. The upper limit of the amount of polymerization catalyst added is not particularly limited, but is preferably 50 ppm or less, more preferably 30 ppm or less, and particularly preferably 10 ppm or less (hereinafter, the unit ppm is all based on mass). The polymerization catalyst is preferably added as a solution in a solvent that does not adversely affect polymerization, such as methyl formate or cyclohexane.

In addition, the polymerization catalyst according to one embodiment of the present invention is preferably a protonic acid, and more preferably a heteropolyacid. By using a heteropolyacid, the polymerization reaction can be sufficiently promoted with a smaller amount of the catalyst than before, and undesirable reactions such as decomposition of the polymer main chain and depolymerization caused by the catalyst can be suppressed.

(Basic Compound)
The basic compound according to one embodiment of the present invention is preferably an alkali metal carbonate, hydrogen carbonate or carboxylate, or a hydrate thereof, or an aqueous solution of a nitrogen-containing organic compound having a pH of 10 or higher when 1 g/L of the aqueous solution.

<Alkali metal carbonate, hydrogen carbonate or carboxylate, or hydrate thereof>
The carbonate, hydrogencarbonate or carboxylate of an alkali metal or a hydrate thereof is preferably a carbonate, hydrogencarbonate or carboxylate containing sodium or potassium or a hydrate thereof.

Examples of these include sodium formate, sodium acetate, sodium carbonate, sodium bicarbonate, disodium succinate, sodium laurate, sodium palmitate, sodium stearate, potassium carbonate, and potassium acetate. Of these, sodium carbonate and potassium carbonate are preferred. These may be used alone or in combination of two or more.

In addition, the above-mentioned alkali metal carbonates, hydrogen carbonates, or carboxylates, or their hydrates, are preferably used as aqueous solutions.

<Nitrogen-containing organic compounds>
Preferably, the nitrogen-containing organic compound is an amine.

Examples of amines include dimethylamine, trimethylamine, triethylamine, tributylamine, triethanolamine, and tributanolamine. Among these, dimethylamine, trimethylamine, triethylamine, and triethanolamine, which can be used as an aqueous solution, are preferred, and triethylamine is more preferred.

In addition, the amount of the basic compound added in one embodiment of the present invention is preferably 5 ppm or more relative to the resin, and more preferably 10 ppm or more. In addition, the upper limit of the amount of the basic compound added is not particularly limited, but is preferably 50 ppm or less, and more preferably 20 ppm or less. By having the concentration of the aqueous solution of the basic compound be 10 ppm or more and 20 ppm or less, a molded product with high impact resistance can be obtained.

(Method for producing polyacetal copolymer)
The method for producing the polyacetal copolymer according to one embodiment of the present invention can be carried out using a known method and polymerization apparatus, such as a batch method or a continuous method.

In batch polymerization equipment, a commonly used reaction vessel equipped with an agitator can be used. In continuous polymerization equipment, a co-kneader, a twin-screw continuous extrusion mixer, a twin-screw paddle screw extruder, a vented twin-screw extruder, etc. can be used. The industrially preferred production method is the continuous method.

Specifically, as shown in Figure 1, the production method according to one embodiment of the present invention includes a step of continuously supplying a mixed liquid containing trioxane, a comonomer, a polymerization catalyst (protonic acid), and any additives for polymerization reactions to a polymerization apparatus heated to a predetermined temperature and polymerizing for a predetermined time (hereinafter also referred to as the "polymerization step"), and a step of melt-kneading the crude polyacetal copolymer obtained in the polymerization step in an extruder (hereinafter also referred to as the "melt-kneading step"). The melt-kneading step includes a step of adding an aqueous solution of a basic compound as a deactivator to the extruder after the start of melt-kneading and before the end of melt-kneading (step shown by A in Figure 1).

In the melt-kneading process, by adding an aqueous solution of a basic compound between the start and end of melt-kneading, a polyacetal copolymer with high impact resistance can be obtained. The impact strength of the polyacetal copolymer can be measured using an impact tester in accordance with ISO 179/1eA.

In addition, during catalyst deactivation treatment, other components such as other polymers, other fillers, nitrogen compounds, stabilizers such as ultraviolet absorbers, acid inhibitors such as metal salts, antistatic agents, flame retardants, colorants such as dyes and pigments, lubricants, release agents, crystallization accelerators, and crystal nucleating agents may also be added as appropriate depending on the required performance. These may be used alone or in combination of two or more types.

The present invention will be explained in detail below with reference to examples, but the present invention is not limited to these.

1. Production of polyacetal copolymers 1 to 13 [Polyacetal copolymer 1]
(Polymerization Apparatus)
A continuous twin-shaft paddle screw extruder was used as the polymerization device. The extruder was equipped with a jacket on the outside of the body for passing a heating or cooling medium. The body was divided into an upper and lower part, and the upper part was openable. Inside the extruder, two rotating shafts with many paddles for stirring and propulsion were installed in the longitudinal direction.

(Production method)
A mixed liquid containing 100 parts by mass of trioxane (TOX), 4.0 parts by mass of 1,3-dioxolane (DO), and a predetermined amount of methylal was continuously supplied per unit time to a polymerization apparatus in which a medium at 80° C. was passed through the jacket, and 5.0 ppm of tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ) was added as a methyl formate solution to carry out a polymerization reaction.

Next, 0.3% by mass of IRGANOX 1010 (manufactured by BASF Japan, "IRGANOX" is a registered trademark of BASF) was added to the crude polyacetal copolymer obtained from the discharge port of the polymerization apparatus, and the mixture was fed into a vented twin-screw extruder in the range shown by B in Figure 1. Melt-kneading was then started under conditions of an extruder cylinder temperature of 220°C and a vent vacuum of 5 mmHg. After the molten resin was discharged from the extruder discharge port and melt-kneading was completed (the process shown by A in Figure 1), 15 ppm of sodium carbonate was added to the resin as a 2.0 wt% aqueous solution, and after melt-kneading was completed, the mixture was extruded from the extruder to obtain pellets of polyacetal copolymer 1.

The amount of methylal added was adjusted so that the melt flow rate (MFR) of the resulting copolymer was 9 g/10 min. The MFR was measured in accordance with ISO 1133 using a Melt Indexer L220 (manufactured by Tateyama Kagaku High-Technologies Co., Ltd.) under conditions of a load of 2.16 kg, a temperature of 190°C, and a resin discharge time of 7 minutes.

[Polyacetal copolymers 2 and 3]
As shown in Table 1, pellets of polyacetal copolymers 2 and 3 were obtained by the same production method as for polyacetal copolymer 1, except that the content of 1,3-dioxolane (DO) was changed.

[Polyacetal copolymer 4]
As shown in Table 1, pellets of polyacetal copolymer 4 were obtained by the same production method as for polyacetal copolymer 1, except that the type of comonomer was changed to 1,4-butanediol formal (BDF).

[Polyacetal copolymers 5 and 6]
As shown in Table 1, pellets of polyacetal copolymers 5 and 6 were obtained by the same production method as for polyacetal copolymer 1, except that the type of polymerization catalyst was changed.

[Polyacetal Copolymers 7-9]
As shown in Table 1, pellets of polyacetal copolymers 7 to 9 were obtained by the same production method as for polyacetal copolymer 1, except that the type of the deactivator was changed.

[Polyacetal copolymer 10]
As shown in Table 1, pellets of polyacetal copolymer 10 were obtained by the same production method as for polyacetal copolymer 1, except that the amount of methylal added was changed so that the MFR of the resulting copolymer would be 27 g/10 min.

[Polyacetal copolymer 11]
A mixed liquid containing 100 parts by mass of trioxane (TOX), 4.0 parts by mass of 1,3-dioxolane (DO), and a predetermined amount of methylal was continuously supplied per unit time to a polymerization apparatus in which a medium at 80° C. was passed through the jacket, and 5.0 ppm of tungstophosphoric acid (H ₃ PW ₁₂ O ₄₀ ) was added as a methyl formate solution to carry out a polymerization reaction.

A 15 ppm aqueous sodium carbonate solution and 0.3 mass% IRGANOX 1010 were added to the crude polyacetal copolymer obtained from the discharge port of the polymerization apparatus in the range shown by B in Figure 1, and the mixture was melt-kneaded and extruded continuously using a vented twin-screw extruder at a cylinder temperature of 220°C and a vacuum level of 5 mmHg in the vent section, to obtain pellets of polyacetal copolymer 11.

[Polyacetal copolymer 12]
As shown in Table 1, pellets of polyacetal copolymer 12 were obtained by the same production method as for polyacetal copolymer 11, except that the amount of methylal added was changed so that the MFR of the resulting copolymer would be 27 g/10 min.

[Polyacetal copolymer 13]
As shown in Table 1, pellets of polyacetal copolymer 13 were obtained by the same production method as for polyacetal copolymer 11, except that the type of the deactivator was changed.

2. Evaluation The polyacetal copolymers 1 to 13 obtained by the above-mentioned production method were evaluated for Charpy impact strength.

(Preparation of test specimens)
In accordance with ISO179/IeA, pellets of polyacetal copolymers 1 to 13 were used to mold notched Charpy test specimens.

(Evaluation method)
The Charpy impact strength of the test pieces was measured at 23° C. in accordance with ISO 179/IeA.

[Measurement of MFR]
In the production of polyacetal copolymers 1 to 13, the MFR, which is an index of fluidity in melt state of the resulting crude polyacetal copolymers, was determined as follows.
(Measuring method)
Using a Melt Indexer L220 manufactured by Tateyama Kagaku High-Technologies Corporation, the measurement was performed under conditions conforming to ISO1133, such as a load of 2.16 kg, a temperature of 190° C., and a discharged resin acquisition time of 7 minutes.

The main components and evaluation results of polyacetal copolymers 1 to 13 are shown in Table 1. The abbreviations in Table 1 are as follows:

(Main Monomer)
TOX: Trioxane (comonomer)
DO: 1,3-dioxolane BDF: 1,4-butanediol formal

(Polymerization catalyst)
H ₃ PW ₁₂ O ₄₀ : Phosphotungstic acid H ₃ PMo ₁₂ O ₄₀ : Phosphomolybdic acid

As shown in Table 1, when comparing molded articles made of polyacetal copolymers produced at the same melt flow rate (MFR), it was confirmed that adding the deactivator at position "A" results in a molded article with higher impact resistance than adding the deactivator at position "B," when compared to adding the deactivator at position "A."

The method of the present invention makes it possible to produce polyacetal copolymers that can be used to obtain molded products with high impact resistance, and is expected to contribute to the advancement and dissemination of technology in this field.

Claims

copolymerizing trioxane and a comonomer copolymerizable with said trioxane in a polymerization apparatus in the presence of a polymerization catalyst;
A step of melt-kneading the crude polyacetal copolymer obtained in the above step in an extruder;
having
the polymerization catalyst is a protonic acid;
In the melt-kneading step, a solution of a basic compound is added during the period from the start of melt-kneading to the end of melt-kneading.
A method for producing a polyacetal copolymer.
The method for producing a polyacetal copolymer according to claim 1, wherein the protonic acid is a heteropolyacid.
The method for producing a polyacetal copolymer according to claim 1, wherein the solution of the basic compound is an aqueous solution of an alkali metal carbonate, hydrogen carbonate, or carboxylate, or a hydrate thereof, or an aqueous solution of a nitrogen-containing organic compound having a pH of 10 or more at 1 g/L.
The method for producing a polyacetal copolymer according to claim 3, wherein the alkali metal is sodium or potassium.
The method for producing a polyacetal copolymer according to claim 3, wherein the nitrogen-containing organic compound is an amine.