JP2018024650A - Quaternary ammonium compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quaternary ammonium compound for obtaining a polyacetal resin composition of high purity, where the quaternary ammonium compound prevents the occurrence of formaldehyde, acetaldehyde and acrolein even when subjected to a heating treatment such as heat melting.SOLUTION: The present invention provides a quaternary ammonium compound represented by formula (1): [(R1)(R2)N]X(R1's independently represent a C1-30 unsubstituted/substituted alkyl group, a C6-20 aryl group or the like; R2's independently represent a group represented by the following formula -(RO) k-H, the group having 2-60 carbon atoms and 2-30 oxygen atoms; R is a substituted/unsubstituted alkylene group; k is a natural number of 2 or more; m and n are each an integer of 1-3; X is a hydroxy group or an acid residue of a compound selected from C1-20 monocarboxylic acid, hydrogen acid, oxo acid, inorganic thio acid or C1-20 organic thio acid, representing a group free of N).SELECTED DRAWING: None

Description

  The present invention relates to a novel quaternary ammonium compound, and more particularly to a quaternary ammonium compound suitable for use as a volatile organic compound generation inhibitor from polyacetal.

Since polyacetal has balanced mechanical properties and excellent fatigue properties, it is widely used in parts such as automobiles, electronic devices, and electric devices. A polyacetal copolymer is produced by copolymerizing a cyclic acetal such as trioxane, which is formaldehyde or its cyclic trimer, and either or both of a cyclic ether and a cyclic formal. However, the polyacetal copolymer obtained by such copolymerization has-(OCH2) n-OH groups at some molecular ends, and since these end groups are thermally unstable, heating during molding processing, etc. Is easily decomposed and generates a large amount of formaldehyde, so it cannot be put into practical use as it is. That is, when a large amount of formaldehyde is generated, the resin foams at the time of molding, or a line from which gaseous formaldehyde is removed remains on the surface of the molded product, resulting in an inferior appearance. Further, the generated formaldehyde is oxidized by oxygen in the molding machine to become formic acid, and accelerates the main chain decomposition of the polyacetal copolymer.
In particular, from the viewpoint that formaldehyde is an undesirable substance for the human body in recent years, a material having an extremely low amount of formaldehyde generated from a molded product has been demanded, and polyacetals having a small amount of formaldehyde have been invented.

  In recent years, in extremely demanding areas such as applications that come into contact with living organisms, there has been a demand for materials that suppress the amount of formaldehyde generated to a level much lower than conventional levels. In addition, not only formaldehyde but also acetaldehyde and further reduction of acrolein, which is highly toxic to microorganisms, have been demanded. Accordingly, there is an urgent need for materials that have extremely low amounts of acetaldehyde and acrolein as well as formaldehyde.

  Since polyacetal is generally low in stability due to heat or the like, it is generally a resin composition to which a heat stabilizer or the like is added. A small amount of formaldehyde generated from the polyacetal itself as the base resin is indispensable for obtaining a material having an extremely low amount of formaldehyde generated.

Polyacetal generates formaldehyde by having unstable terminal parts after polymerization. Known methods for stabilizing a polyacetal copolymer (hereinafter sometimes referred to as crude polyacetal) include a method of acetylating, etherifying, or urethanizing a terminal, and a method of decomposing an unstable terminal. ing.
Among them, a method of decomposing and stabilizing the unstable terminal portion is advantageous. As a method for decomposing this unstable terminal portion, a method of heating and stabilizing a crude polyacetal copolymer in water or in an organic solvent in the presence of a basic substance capable of decomposing this unstable terminal portion, A method of stabilizing a polyacetal copolymer in a heated and melted state is known. Whereas the method of heating and stabilizing the crude polyacetal copolymer in water or an organic solvent requires operations such as separation (filtration), recovery, and washing, the method of stabilizing in the heated and melted state is Since a directly stabilized polyacetal copolymer is obtained, this is the most industrially advantageous method.
As a conventionally known heat treatment method, a crude polyacetal copolymer is unstable due to heat treatment while maintaining a heterogeneous system in a medium in which the polyacetal copolymer does not dissolve (for example, water, water / methanol mixture). A method for removing a terminal portion is known (for example, Patent Document 1 and Patent Document 2). However, in this method, it is necessary to operate at a temperature close to the melting point of the polyacetal copolymer in order to increase the decomposition rate of the unstable end portion, and it is necessary to perform a long treatment to reduce the unstable end portion. was there. Even if such a treatment is performed, the obtained polyacetal copolymer does not have sufficient decomposition and removal of unstable end portions, and there is a problem that the polyacetal copolymer is likely to be colored by a long-time treatment at a high temperature. .

Further, Patent Document 3 discloses that the crude polyacetal copolymer is unstable by exposing it to a pressure of atmospheric pressure or higher at a temperature of 100 ° C. or higher in a saturated vapor mixture composed of a volatile organic solvent, a volatile base and water. A method for removing the end portion is disclosed. However, even with this method, removal of the unstable end portion was not sufficient. Further, a method is known in which a crude polyacetal copolymer is heated and kept in a molten state to decompose and remove unstable terminal portions.
For example, Patent Document 4 discloses a method of kneading a molten copolymer on a roll mill for a certain time, and Patent Document 5 or Patent Document 6 uses an extruder or the like in the presence of water, alcohol, or an alkali component. Patent Document 7 discloses a method for performing heat-melting treatment. Patent Document 7 discloses a method in which a crude polyacetal copolymer is heated and melted, and then an unstable portion is decomposed and removed under reduced pressure using a special surface renewal mixer. Is a single screw extruder for melting a crude polyacetal copolymer, a reaction agent comprising a crude polyacetal copolymer and a compound that forms hydroxide in the presence of water and water by the principle of flow splitting and rearrangement The reaction device is composed of a static mixer having a reaction zone that decomposes unstable parts while mixing with a vent, and a vented screw extruder for devolatilization placed immediately after the static mixer. In addition, Patent Document 9 discloses that a powdery or powdery crude polyacetal copolymer is treated under reduced pressure at a temperature 5 to 35 ° C. lower than the melting temperature and then heated in an extruder. Each method of melting treatment has been proposed.
Even if these crude polyacetal copolymers are heated and kept in a molten state, only a thermally unstable terminal portion can be decomposed and removed, so that considerable stabilization is possible. Polyacetal copolymers subjected to such treatment are practical. However, a thermally unstable end portion remains, which may cause an undesirable phenomenon such as generation of mold deposit (mold deposit) in the molding process. Therefore, a more stable polymer is strongly desired.

In these known methods, in order to increase the decomposition rate, the above-mentioned basic physical properties, alkali components, compounds that generate hydroxide in the presence of water, etc. (for example, amines widely used for this kind of application) Must be added to the polyacetal copolymer to increase the amount added. However, if the addition amount of amines or the like is increased too much, the polymer is colored. Furthermore, in order to reduce unstable terminal portions, it was necessary to perform treatment for a long time or a plurality of times. For this reason, the stabilized polyacetal copolymer not only deteriorates in color, but also increases the size and complexity of the apparatus. Furthermore, there is also a problem that decomposition and removal of unstable end portions of the crude polyacetal copolymer are not always sufficient.
In Patent Document 10, in order to solve these problems, as a stabilization method for obtaining a polyacetal copolymer having very few unstable terminal portions by a simple method, heat treatment is performed in the presence of a quaternary ammonium compound having a specific structure. It is disclosed to do below. According to this method, drastic stabilization of the thermally unstable end portion of the polyacetal copolymer can be realized and various problems associated with the above-described stabilization method can be solved. The generation of acetaldehyde and acrolein generated after heating and melting, etc. has not been suppressed.

  Furthermore, Patent Document 11 discloses a stabilization method mainly using a quaternary ammonium compound of polyacrylic acid as a method for improving odor characteristics while removing unstable terminals. However, in this method, odor evaluation at a substantial processing temperature has not been achieved, and there remains a problem as odor evaluation at a processing temperature or higher. In addition, polyacrylic acid has a high boiling point and remains in the polymer, so it cannot be said that there is no concern about coloring properties in addition to decomposition behavior during heating, and suppresses the generation of acetaldehyde and acrolein generated after heating and melting such as molding. It does not lead to.

Japanese Patent Publication No. 40-10435, Japanese Patent Publication No.43-7553 Japanese Patent Publication No. 40-11627 Japanese Patent Publication No.39-8071 Japanese Patent Publication No. 43-1875 (corresponding to US Pat. No. 3,337,504) Japanese Patent Publication No. 44-11907 (corresponding to US Pat. No. 3,418,280) Japanese Patent Publication No. 58-11450 (corresponding to US Pat. No. 4,366,305) JP 58-152012 A (corresponding to European Patent No. 88,541) JP-A-62-129311 Japanese Patent No. 3087912 Patent No. 5031196

  Accordingly, the present invention provides a quaternary ammonium compound that can be used to provide a high-purity polyacetal resin composition that generates little formaldehyde, acetaldehyde, and acrolein even when subjected to heat treatment such as heat melting. With the goal.

  As a result of intensive investigations to solve the above problems, the present inventors have found that a novel quaternary ammonium compound having a specific structure has an effect in suppressing the generation of volatile organic substances from polyacetal, The present invention has been completed.

That is, the present invention is as follows.
[1] Quaternary ammonium compound represented by the following formula (1) [(R1) _m (R2) _4-m N ⁺ ] _n X ^n- (1)
(In the formula, each R 1 independently represents an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; an unsubstituted alkyl group or substituted alkyl having 1 to 30 carbon atoms; An aralkyl group substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms with at least one unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; Represents a substituted alkylaryl group, and the unsubstituted alkyl group and the substituted alkyl group are linear, branched or cyclic, and the substituent of the substituted alkyl group is halogen, hydroxyl group, aldehyde group, carboxyl group, amino group A non-substituted alkyl group, an aryl group, an aralkyl group, and an alkylaryl group may be substituted with a halogen atom.
R2 independently represents a group represented by the following formula having 2 to 60 carbon atoms and 2 to 30 oxygen atoms.
-(RO) k-H (wherein R represents a substituted or unsubstituted alkyl group, and k represents a natural number of 2 or more)
m and n represent an integer of 1 to 3.
X is a hydroxyl group or an acid residue of a compound selected from the group consisting of a monocarboxylic acid having 1 to 20 carbon atoms, a hydrogen acid, an oxo acid, an inorganic thioacid, and an organic thioacid having 1 to 20 carbon atoms. Represents a group containing no nitrogen atom. ).
[2] The quaternary ammonium compound according to [1], wherein X in the formula (1) is an acid residue of a monocarboxylic acid.
[3] The quaternary ammonium compound according to [1] or [2], wherein the carboxylic acid is formic acid, acetic acid, or propionic acid.
[4] The quaternary ammonium compound according to any one of [1] to [3], wherein R2 in Formula (1) has 2 to 6 carbon atoms.
[5] A volatile organic compound generation inhibitor from polyacetal containing the quaternary ammonium compound according to any one of [1] to [4].
[6] The volatile organic compound generation inhibitor from polyacetal according to [5], further comprising a quaternary ammonium compound (B) represented by the following formula (3).
[R3R4R5R6N +] _l Y ^l− (3)
Wherein R 3, R 4, R 5 and R 6 are each independently an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; an unsubstituted group having 1 to 30 carbon atoms An aralkyl group in which an alkyl group or a substituted alkyl group is substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms is an unsubstituted alkyl group having 1 to 30 carbon atoms Or an alkylaryl group substituted with a substituted alkyl group, wherein the unsubstituted alkyl group and the substituted alkyl group are linear, branched, or cyclic, and the substituent of the substituted alkyl group is a halogen, hydroxyl group, aldehyde group , A carboxyl group, an amino group, or an amide group, and an unsubstituted alkyl group, an aryl group, an aralkyl group, and an alkylaryl group have a hydrogen atom substituted with a halogen atom It can have.
l represents an integer of 1 to 3.
Y represents a hydroxyl group or an acid residue of a compound selected from the group consisting of a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid, an oxo acid, an inorganic thioacid, and an organic thioacid having 1 to 20 carbon atoms. )
[7] The volatile organic compound generation inhibitor from polyacetal according to [5] or [6], further comprising at least one metal atom selected from the group consisting of magnesium, sodium and calcium.

  If the quaternary ammonium compound of the present invention is used, it is possible to provide a polyacetal and a resin composition thereof with less generation of formaldehyde, acetaldehyde and acrolein.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

<Quaternary ammonium compound (A)>
The quaternary ammonium compound (A) of this embodiment is represented by the following formula (1).
[(R1) _m (R2) _4-m N ⁺ ] _n X ⁿ⁻ (1)
In the formula, each R 1 independently represents an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; An aralkyl group substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms substituted with at least one unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms. An unsubstituted alkyl group or a substituted alkyl group is linear, branched, or cyclic, and the substituent of the substituted alkyl group is a halogen, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, or It is an amide group, and in the unsubstituted alkyl group, aryl group, aralkyl group and alkylaryl group, a hydrogen atom may be substituted with a halogen.
R2 independently represents a group represented by the following formula having 2 to 60 carbon atoms and 2 to 30 oxygen atoms.
-(RO) k-H (wherein R represents a substituted or unsubstituted alkyl group, and k represents a natural number of 2 or more)
m and n represent an integer of 1 to 3. Since the possibility of side reactions increases as n increases, it is particularly preferable that n is 1 in order to obtain a high-purity product and from the viewpoint of availability.
X is a hydroxyl group or an acid residue of a compound selected from the group consisting of a monocarboxylic acid having 1 to 20 carbon atoms, a hydrogen acid, an oxo acid, an inorganic thioacid, and an organic thioacid having 1 to 20 carbon atoms. Represents a group containing no nitrogen atom.
When X contains a nitrogen atom, it does not work effectively to suppress the generation of acetaldehyde and acrolein during heating.

  In Formula (1), R1 is preferably an alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 4 carbon atoms from the viewpoint of availability and ease of production.

Moreover, in Formula (1), R2 represents the group represented by the following formula | equation whose carbon number is 2-60 and oxygen number is 2-30 each independently.
-(RO) k-H (wherein R represents a substituted or unsubstituted alkyl group, and k represents a natural number of 2 or more)
By selecting such a group as R2, generation of formaldehyde, acetaldehyde and acrolein from the polyacetal when high-temperature heating such as heating and melting is performed can be suppressed.
If the number of carbons exceeds 60 or the number of oxygens exceeds 30, it may take time to isolate and produce the quaternary ammonium compound.
From the viewpoint of the synthesis of the quaternary ammonium compound, R2 preferably has 2 to 10 carbon atoms and 2 to 5 oxygen atoms, and from the viewpoint of colorability after melting and heating, it has 2 to 6 carbon atoms and oxygen. More preferably, the number is 2-3.

  In the formula (1), X is preferably an acid residue of a monocarboxylic acid from the viewpoint of availability. Among these, at least one acid residue selected from the group consisting of formic acid, acetic acid, and propionic acid is preferable because of ease of handling.

<Polyacetal>
The polyacetal in which the quaternary ammonium compound (A) of this embodiment acts effectively is a polymer having an oxymethylene group in the main chain, and is a formaldehyde monomer or its trimer (trioxane) or tetramer ( A cyclic oligomer such as tetraoxane), a cyclic ether such as ethylene oxide, propylene oxide, epichlorohydrin, glycols such as 1,3-dioxolane and 1,4-butanediol formal, and cyclic formals such as cyclic formal of diglycol, and cyclic formal. A typical example is a polyacetal copolymer obtained by polymerization. Moreover, the polyacetal copolymer which has a branch obtained by copolymerizing monofunctional glycidyl ether, and the polyacetal copolymer which has a crosslinked structure obtained by copolymerizing polyfunctional glycidyl ether can also be used. Furthermore, a polyacetal homopolymer having a block component obtained by polymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, polyalkylene glycol, A compound having a functional group such as a hydroxyl group at both ends or one end, for example, a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) or tetramer (tetraoxane) in the presence of hydrogenated polybutadiene glycol; A polyacetal copolymer having a block component obtained by copolymerizing cyclic ether or cyclic formal can also be used.
As described above, the quaternary ammonium compound (A) of this embodiment can be used for both polyacetal homopolymers and copolymers.

Incidentally, the polyacetal is generally thermally unstable end - Includes (-CH ₂ OH group or a (OCH ₂₎ group containing n-OH hydroxymethyl group such as), therefore, subjected to a heat And formaldehyde, and in some cases acetaldehyde and acrolein. In this embodiment, the quaternary ammonium compound (A) represented by the formula (1) is used to decompose and remove the unstable terminal portion of the polyacetal during heating, thereby suppressing the generation of formaldehyde and the like.
In particular, since the polyacetal copolymer contains many unstable terminals, the quaternary ammonium compound (A) of this embodiment can be effectively used for the polyacetal copolymer.

Therefore, the polyacetal copolymer will be described in detail below.
The ratio of comonomer such as 1,3-dioxolane in the polyacetal copolymer is generally 0.01 to 60 mol%, preferably 0.03 to 20 mol%, more preferably 0.05 to 20 mol% with respect to 1 mol of trioxane. 15 mol%, most preferably 0.1 to 10 mol% is used.
The polymerization catalyst used when polymerizing the polyacetal copolymer is not particularly limited, but cationically active catalysts such as Lewis acids, proton acids and esters or anhydrides thereof are preferred.
Examples of the Lewis acid include boric acid, tin, titanium, phosphorus, arsenic and antimony halides. Specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, pentachloride. Examples thereof include phosphorus, antimony pentafluoride, and complex compounds or salts thereof. Specific examples of the protonic acid, its ester or anhydride include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate, isopolyacids, heteropolyacids, trimethyloxonium hexafluorophosphate, etc. Is mentioned. Among these, boron trifluoride; boron trifluoride hydrate; and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable. Specifically, boron trifluoride diethyl ether is used. Boron trifluoride di-n-butyl ether can be mentioned as a preferred example.
The polymerization method of the polyacetal copolymer is not particularly limited, and is generally carried out by bulk polymerization, and can be either batch type or continuous type.
As the polymerization apparatus, for example, a self-cleaning type extrusion kneader such as a kneader, a twin screw type continuous extrusion kneader, a twin screw paddle type continuous mixer can be used, and a monomer in a molten state is supplied to the polymerization machine, A solid agglomerated polyacetal copolymer is obtained as the polymerization proceeds.

When the polyacetal having an unstable terminal group as described above is used in the form of a composition coexisting with the quaternary ammonium compound (A) of the present embodiment, generation of formaldehyde and the like due to heat treatment can be reduced.
In this case, the concentration of the quaternary ammonium compound (A) in the polyacetal resin composition is converted into the concentration n of nitrogen derived from the quaternary ammonium compound (A) represented by the following formula on a mass basis. It is preferably 0.1 ppb or more and 30 ppm or less.
If it is within this range, it can effectively suppress acrolein and acetaldehyde generation, and if it is 0.1 ppb or more, it can effectively suppress acrolein. If it is 30 ppm or less, generation of acetaldehyde and polyacetal resin Can be effectively suppressed. A more preferable range is 0.01 ppm or more and 30 ppm or less, further preferably 1 ppm to 20 ppm, and particularly preferably 5 ppm to 15 ppm.

The nitrogen conversion content n of the quaternary ammonium compound (A) is represented by the following formula (2).
n = P × 14 / Q (2)
(In the formula, P represents the amount (mass ppb or ppm) of the quaternary ammonium compound (A) with respect to the total mass of the polyacetal and the quaternary ammonium compound (A), 14 is the atomic weight of nitrogen, and Q Represents the molecular weight of the quaternary ammonium compound.)
Here, the content of the quaternary ammonium compound (A) is defined in terms of nitrogen in terms of the number of moles of the quaternary compound contained in the resin composition depending on the molecular weight of the quaternary ammonium compound (A). This is in order to avoid the fact that the change greatly occurs.

The amount of nitrogen derived from the quaternary ammonium compound (A) in the polyacetal resin composition can be quantified by NMR analysis as follows, for example.
After 15 kg of polyacetal resin composition pellets are freeze-pulverized with a Linlex mill or the like, they are placed in a 100 L SUS autoclave with a stirrer, and 50 L of distilled water is added. Then, it is placed in an oven set at 120 ° C., allowed to stand for 24 hours and then brought to room temperature, and solid liquid separation is performed by suction filtration. The obtained liquid is concentrated with an evaporator, and about 2.5 ml of liquid concentrated to about 5 ml and heavy water mixed at 1: 1 (volume ratio) are subjected to NMR analysis, and near 3.5 ppm and 3.9 ppm. The amount of nitrogen derived from the quaternary ammonium compound (A) is quantified from the nearby peak area.
When it is clear that the nitrogen source is only the quaternary ammonium compound (A), the amount of nitrogen atoms is quantified with a nitrogen analyzer (for example, a nitrogen analyzer TN-2100H manufactured by Mitsubishi Analytech). It can also be quantified.

As described above, even if a polyacetal having an unstable terminal group is used in the form of a resin composition in which the quaternary ammonium compound (A) of the present embodiment coexists, generation of formaldehyde or the like due to heat treatment is prevented. Can be reduced.
Also, the polyacetal is not used in the form of such a resin composition, but is manufactured in a pre-stabilized form (as a stabilized polyacetal) using the quaternary ammonium compound (A) of this embodiment. You can also.

Hereinafter, the method for stabilizing polyacetal using the quaternary ammonium compound (A) of the present embodiment will be described with specific examples.
The polyacetal having a thermally unstable terminal portion can be stabilized by heat treatment in the presence of the quaternary ammonium compound (A) of the present embodiment. Here, although there is no limitation in the aspect of heat processing, the following two can be mentioned, for example.
One is to heat and melt the crude polyacetal in the presence of the quaternary ammonium compound (A), and the other is to dissolve the crude polyacetal in the presence of the quaternary ammonium compound (A). It heats in a slurry state.

First, the heat treatment in the case where the crude polyacetal is melted will be described.
The crude polyacetal can be melted by, for example, a single screw extruder with a vent, a twin screw extruder with a vent, or the like. The heat treatment is preferably performed at a temperature which is not lower than the melting point of polyacetal and not higher than 260 ° C. If it exceeds 260 ° C., there may be a problem of coloring and a problem of decomposition (reduction in molecular weight) of the polymer main chain. In this case, before melting the crude polyacetal, the quaternary ammonium compound (A) may be added to the crude polyacetal in advance, or after melting the crude polyacetal, the quaternary ammonium compound (A) is added, You may add to the melted crude polyacetal.

  Examples of the method of adding the quaternary ammonium compound (A) to the crude polyacetal before melting include, for example, water or an organic solvent capable of dissolving the quaternary ammonium compound (A), specifically, a lower aliphatic alcohol. Etc. (for example, methanol) can be added after adding a solution of the quaternary ammonium compound (A) in an amount of 0.1 to 5 mass% with respect to the crude polyacetal. In this case, the mixing may be performed using a general solid mixer such as a horizontal cylindrical type, a V type, a ribbon type, a paddle type, or a high-speed flow type. Further, the extruder main body is added until the solution containing the quaternary ammonium compound (A) is directly added to the chute portion for supplying the polyacetal to the extruder or until the polyacetal is melted from the supply port of the extruder. It may be added directly to.

Another method for adding the quaternary ammonium compound (A) in advance to the crude polyacetal before melting is, for example, water or the above organic solvent (for example, lower fat such as methanol) of the quaternary ammonium compound (A). A method in which a crude polyacetal is added to a solution of a group alcohol) to form a slurry, and the slurry is filtered and dried to leave the quaternary ammonium compound (A) in the polyacetal before melting. it can. In this case, the solvent used for the solution is preferably a solvent that does not dissolve the crude polyacetal. By using such a solvent, post-treatment such as filtration and drying can be easily performed.
The amount of the quaternary ammonium compound (A) used relative to the total mass of the crude polyacetal and the quaternary ammonium compound (A) depends on the concentration of the quaternary ammonium compound (A) in the solution and the content of the polyacetal after filtration. By controlling the liquid ratio, it can be controlled to a specific usage amount.
By the above method, the crude polyacetal to which a predetermined amount of the quaternary ammonium compound (A) has been added is either as it is or, if necessary, dried and then melted by an extruder or the like and subjected to heat treatment. At the time of melting, it may be stabilized by adding at least one of amines, which are conventionally known decomposition accelerators, water, methanol, etc., or subjected to heat treatment without adding anything else. May be. It is preferable to add 0.1-5 mass parts with respect to 100 mass parts of polyacetals about the addition amount of decomposition accelerators conventionally used, such as amines, water, methanol, etc. Moreover, you may further add a quaternary ammonium compound (A) as needed. These decomposition accelerators such as amines, water, methanol, and quaternary ammonium compound (A) can be added alone or in combination of two or more.

On the other hand, as a method of adding the quaternary ammonium compound (A) to the molten crude polyacetal after melting the crude polyacetal, water or an organic solvent capable of dissolving the quaternary ammonium compound (A), specifically For example, a solution in which the quaternary ammonium compound (A) is dissolved in a lower aliphatic alcohol or the like (for example, methanol) is added, or the quaternary ammonium compound (A) and water or a quaternary ammonium compound are added. An organic solvent capable of dissolving (A) can be added separately to the polyacetal melted by an extruder or the like.
The addition amount of an organic solvent such as water or methanol is preferably about 0.1 to 5 parts by mass with respect to 100 parts by mass of the crude polyacetal. In addition to the quaternary ammonium compound (A), conventionally known amines, a quaternary ammonium compound (B) described later, and the like may be added.

In the present embodiment, the amount of the quaternary ammonium compound (A) used in the heat treatment step is not limited, but the nitrogen concentration n derived from the quaternary ammonium compound (A) represented by the following formula (2 ′ ″) In terms of ''', it is preferably 0.1 mass ppb to 30 mass ppm, more preferably 0.01 mass ppm to 25 mass ppm, still more preferably 1 mass ppm to 20 mass ppm, especially Preferably, it is 5 ppm to 10 ppm.
n ′ ″ = P ′ ″ × 14 / Q ′ ″ (2 ′ ″)
(In the formula, P ′ ″ represents an amount (mass ppb or ppm) relative to the total mass of the crude polyacetal and quaternary ammonium compound (A) of the quaternary ammonium compound (A), and 14 is the atomic weight of nitrogen. Q ′ ″ represents the molecular weight of the quaternary ammonium compound (A).)
When the nitrogen concentration n ′ ″ derived from the quaternary ammonium compound (A) is 0.1 mass ppb or more, the unstable terminal portion can be decomposed in a short time, and when it is 30 mass ppm or less, Even after stabilization, the color tone of the polyacetal is not impaired.
Here, the reason why the concentration of the quaternary ammonium compound (A) is converted into a nitrogen concentration is to avoid depending on the molecular weight of the quaternary ammonium compound (A) as described above. .

Next, heat treatment in the case where the crude polyacetal is not melted and performed in a slurry state will be described.
As such heat treatment, for example, polyacetal is put into a solution in which the quaternary ammonium compound (A) is dissolved in a medium in which polyacetal is not dissolved, and heat treatment is performed in a slurry state where the polyacetal is not melted. List the processes.
In this case, a solvent that does not dissolve the crude polyacetal is used as the solvent used in the solution, as described above, by using such a solvent, post-treatment such as filtration and drying can be easily performed. Because it becomes. Examples of the medium that does not dissolve the polyacetal include water and an aqueous solution containing about 10 to 30% by mass of methanol.
Although there is no limitation in heating temperature, it is preferable to carry out at the temperature which is 80 degreeC or more and is less than melting | fusing point of polyacetal.
Moreover, 5-50 mass% is normally selected as the density | concentration (slurry density | concentration) of the polyacetal in a slurry. When the slurry concentration is less than 5% by mass, a large amount of a medium that does not dissolve polyacetal is required, and the apparatus becomes large. On the other hand, if the slurry concentration exceeds 50% by mass, the stirring and mixing becomes insufficient, and a problem arises that the polyacetal is settled and the slurry is separated into two phases.

At this time, the concentration of the quaternary ammonium compound (A) in the solution in which the quaternary ammonium compound (A) is dissolved in a medium in which the polyacetal is not dissolved is quaternary ammonium represented by the following formula (2 "). In terms of the nitrogen concentration n ″ derived from the compound (A), it is preferably 0.5 mass ppb to 500 mass ppm, more preferably 0.05 mass ppm to 500 mass ppm, still more preferably 1 mass ppm to 300 ppm by mass.
n "= P" × 14 / Q "(2")
(Wherein P ″ represents the concentration (mass ppb or ppm) of the quaternary ammonium compound (A) in the solution, 14 represents the atomic weight of nitrogen, and Q ″ represents the molecular weight of the quaternary ammonium compound. .)
When the nitrogen concentration n ″ derived from the quaternary ammonium compound (A) is 0.5 mass ppb or more, unstable terminal portions can be decomposed in a short time, and when it is 500 mass ppm or less, stabilization is achieved. Later, the color tone of the polyacetal is not impaired.
Here, the reason why the concentration of the quaternary ammonium compound (A) is converted into a nitrogen concentration is to avoid depending on the molecular weight of the quaternary ammonium compound (A) as described above. .
The solution in which the quaternary ammonium compound (A) is dissolved in a medium in which the polyacetal is not dissolved may be used in combination with conventionally used amines, a quaternary ammonium compound (B) described later, and the like. Good.

In the case where the crude polyacetal is stabilized in a slurry state without melting, the polyacetal after the heat treatment is subjected to filtration and washing as a post-treatment, after removing formaldehyde and unreacted monomers generated by decomposition from the terminal portion. Dried. In the case of stabilization in the molten state, the polyacetal after the heat treatment is pelletized after removing the above-mentioned formaldehyde, unreacted monomer, excess quaternary ammonium compound (A) and the like from the vent under reduced pressure. .
The obtained stable polyacetal is made of an antioxidant, a formaldehyde scavenger, a formic acid scavenger, an ultraviolet absorber, a light stabilizer, a release agent, a reinforcing material, an electric material, a thermoplastic resin, a thermoplastic elastomer, and a pigment as necessary. After being mixed with one or more compounding agents such as an extruder or the like, it is put into practical use. There are no particular restrictions on the compounding time of the compounding agent, and depending on the type, for example, it may be added in advance to the crude polyacetal before the unstable terminal part is decomposed and removed. You may add to the polyacetal decomposed and removed.

Next, end groups contained in the polyacetal that can be stabilized by the quaternary ammonium compound (A) of the present embodiment will be described.
As a terminal group that the plurality of polyacetal (co) polymer chains constituting the polyacetal has as a whole, in addition to a group containing a hydroxymethyl group such as the above-described —CH ₂ OH group or — (OCH ₂ ) _n —OH group, Examples include alkoxyl groups such as methoxyl group (—OCH ₃ ), hydroxyalkyl groups such as hydroxyethyl group (—CH ₂ CH ₂ OH), and formate groups.
The terminal alkoxyl group is generally formed by formal, which is a molecular weight modifier added in the polymerization stage. For example, when methylal ((CH ₃ O) ₂ CH ₂ ) is used as a molecular weight modifier, a methoxyl group is formed as a terminal group. The carbon number of the terminal alkoxyl group is generally 1 to 10 carbon atoms and preferably 1 to 3 carbon atoms from the viewpoint of synthesis and purification of formal which is a molecular weight modifier.

A terminal hydroxyalkyl group such as a hydroxyethyl group or a hydroxybutyl group is derived from the aforementioned cyclic ether or cyclic formal used as a raw material comonomer of polyacetal, and is formed in the following process.
That is, when polymerizing a polyacetal in which an oxyalkylene group derived from a cyclic ether or a cyclic formal is inserted during repetition of a polyacetal unit, first, a thermally unstable terminal hydroxy group is generated by a small amount of water in the raw material. A methyl group (—CH ₂ OH) is formed. This unstable portion at the end is decomposed by the stabilization treatment, and this decomposition proceeds inward in the main chain containing the polyacetal unit and the oxyalkylene unit, and reaches the site of the oxyalkylene unit. The alkylene unit is converted to a stable terminal hydroxyalkyl group such as a hydroxyethyl group or a hydroxybutyl group. The number of carbon atoms of the hydroxyalkyl group is at least 2, and preferably 2 to 10 from the viewpoint of synthesis and purification of cyclic ether and cyclic formal.
On the other hand, when a hydroxymethyl group is present as a terminal group in polyacetal, the hydroxymethyl group is eliminated from the terminal by heating during molding to form formaldehyde. Therefore, if many terminal hydroxymethyl groups are present, the formaldehyde produced is excessive.
It is the quaternary ammonium compound (A) of the present embodiment that plays a role in suppressing this generation, and this terminal hydroxymethyl group is decomposed and removed by the action of the quaternary ammonium compound (A), thereby forming formaldehyde. It is thought that the generation of is suppressed.
Furthermore, the quaternary ammonium compound (A) of the present embodiment includes a trace amount of formaldehyde generated from a trace amount of unstable terminal remaining in the polyacetal in addition to the above-described decomposition and removal of the terminal hydroxymethyl group, When acetaldehyde and acrolein are polymerized by anionic polymerization at the time of cooling after heating and melting such as molding, it is also involved in immobilization in the polyacetal resin composition, thereby reducing the generation of formaldehyde, acetaldehyde, acrolein, etc. However, the mechanism of the effect of this embodiment is not limited to these.

  The method for stabilizing polyacetal using the quaternary ammonium compound (A) of the present embodiment may be performed after deactivating the polymerization catalyst remaining in the crude polyacetal obtained by the above polymerization reaction. In addition, the polymerization may be performed without deactivating the polymerization catalyst. Furthermore, the stabilization method using the quaternary ammonium compound (A) of this embodiment can be applied to a polyacetal which has been subjected to a known stabilization treatment but still has an unstable terminal portion remaining.

The deactivation of the polymerization catalyst is carried out by converting the crude polyacetal obtained by the polymerization reaction into amines such as ammonia, triethylamine, tri-n-butylamine, or alkali metal or alkaline earth metal hydroxides, inorganic acid salts, organic acids. It can carry out by throwing in the aqueous solution or organic solvent solution containing at least 1 type of catalyst neutralization deactivators, such as a salt, and generally stirring for several minutes-several hours in a slurry state. In this case, the slurry after deactivation of the catalyst neutralization is dried after the unreacted monomer, the catalyst neutralization deactivator and the catalyst neutralization salt are removed by filtration and washing.
In addition, the polymerization catalyst is deactivated by contacting a vapor such as ammonia or triethylamine with a crude polyacetal, or at least one of hindered amines, triphenylphosphine, calcium hydroxide, etc. and the crude polyacetal are contacted with a mixer. It is also possible to use a method of deactivating the catalyst. In addition, the above-described stabilization method is performed using polyacetal in which the polymerization catalyst is reduced in volatility by heating in an inert gas atmosphere at a temperature equal to or lower than the melting point of the crude polyacetal without deactivation of the polymerization catalyst. May be.
The above-described deactivation operation of the polymerization catalyst and the volatilization reduction operation of the polymerization catalyst may be performed after pulverizing the crude polyacetal obtained by the polymerization reaction, if necessary.

  The quaternary ammonium compound (A) of the present embodiment is represented by the above formula (1), and any of those represented by the formula (1) can be used in the above-described stabilization method.

Specific examples of the quaternary ammonium compound (A) of this embodiment include, for example, 1-hydroxymethoxy-N-((hydroxymethoxy) methyl) -N, N-dimethylmethaneammonium, 2- (2-hydroxyethoxy). ) -N- (2- (2-hydroxyethoxy) ethyl) -N, N-dimethylethane-1-ammonium, N-ethyl-N, N-bis ((hydrowood methoxy) methyl) ethaneammonium, 2- (2-hydroxy Ethoxy) -N- (2- (2-hydroxyethoxy) ethyl) -N, N-dimethylethane-1-ammonium N, N, N-triethyl-2- (2- (2-hydroxy) ethoxy) ethane-1-ammonium, N -(2- (2- (hydroxymethoxy) ethoxy) ethyl) -N, N-dipropylpropane-1-ammonium N-(((hydroxymethoxy) methoxy) methyl) -N, N-dipropylpropane-1-ammonium, N- (2- (2- (2-hydroxyethoxy) ethoxy) ethyl) -N, N-dipropyl Hydroxides such as propane-1-ammonium; Hydrochloric acid salts such as hydrochloric acid, odorous acid, and hydrofluoric acid; sulfuric acid, phosphoric acid nitrate, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, chlorous acid Oxo acid salts such as hypochlorous acid, chlorosulfuric acid, amidosulfuric acid, disulfuric acid and tripolyphosphoric acid; thioic acid salts such as thiosulfuric acid; formic acid, acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, caproic acid, Examples thereof include monocarboxylic acid salts such as caprylic acid, capric acid and benzoic acid.
Of these, the hydroxide is a strong alkali and needs to be handled with care, and is therefore preferably used in the form of a salt, particularly preferably a monocarboxylate.

Moreover, when stabilizing a polyacetal using the quaternary ammonium compound (A) of this embodiment, you may use together the quaternary ammonium compound (B) represented by following formula (3).
[R3R4R5R6N +] _l Y ^l− (3)
Wherein R 3, R 4, R 5 and R 6 are each independently an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; an unsubstituted group having 1 to 30 carbon atoms An aralkyl group in which an alkyl group or a substituted alkyl group is substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms is an unsubstituted alkyl group having 1 to 30 carbon atoms Or an alkylaryl group substituted with a substituted alkyl group, wherein the unsubstituted alkyl group and the substituted alkyl group are linear, branched, or cyclic, and the substituent of the substituted alkyl group is a halogen, hydroxyl group, aldehyde group A carboxyl group, an amino group, or an amide group, and the unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group have a hydrogen atom substituted with a halogen atom. It may be.
l represents an integer of 1 to 3.
Y represents a hydroxyl group or an acid residue of a compound selected from the group consisting of a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid, an oxo acid, an inorganic thioacid, and an organic thioacid having 1 to 20 carbon atoms.

Examples of such quaternary ammonium compounds (B) include tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetra-n-butylammonium, cetyltrimethylammonium, tetradecyltrimethylammonium, 1,6-hexamethylenebis. (Trimethylammonium), decamethylene-bis- (trimethylammonium), trimethyl-3-chloro-2-hydroxypropylammonium, trimethyl (2-hydroxyethyl) ammonium, triethyl (2-hydroxyethyl) ammonium, tripropyl (2-hydroxy) Ethyl) ammonium, tri-n-butyl (2-hydroxyethyl) ammonium, trimethylbenzylammonium, triethylbenzylammonium, tri Lopylbenzylammonium, tri-n-butylbenzylammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, octadecyltri (2-hydroxyethyl) Hydroxides such as ammonium and tetrakis (hydroxyethyl) ammonium; Hydrochloric acid salts such as hydrochloric acid, odorous acid and hydrofluoric acid; sulfuric acid, nitric acid phosphoric acid, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, Oxo acid salts such as chlorous acid, hypochlorous acid, chlorosulfuric acid, amidosulfuric acid, disulfuric acid and tripolyphosphoric acid; thioic acid salts such as thiosulfuric acid; formic acid, acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, Caproic acid, caprylic acid, capri Acid, benzoic acid, a carboxylic acid salt such as oxalic acid. Of these, the hydroxide is a strong alkali and needs to be handled with care, so it is preferably used in the form of a salt, particularly preferably a carboxylate.
In the stabilization method described above, the quaternary ammonium compound (B) may be used alone or in combination of two or more together with the quaternary ammonium compound (A).

  The above-mentioned method for stabilizing polyacetal can be carried out by appropriately using conventionally known apparatuses and operation methods. Furthermore, conventionally known amines such as ammonia and triethylamine may be used in combination.

In the stabilization method described above, the amount of the quaternary ammonium compound (B) used is derived from the quaternary ammonium compound (B) represented by the following formula (2 ′) with respect to the total mass of the polyacetal and the quaternary ammonium compound. The amount is preferably 0.5 mass ppb to 500 ppm by mass, more preferably 0.05 to 50 ppm by mass in terms of the amount of nitrogen n ′.
n ′ = P ′ × 14 / Q ′ (2 ′)
(Wherein P ′ represents an amount (mass ppb or ppm) relative to the total mass of the polyacetal and quaternary ammonium compound (B) of the quaternary ammonium compound (B), 14 is the atomic weight of nitrogen, and Q ′ Represents the molecular weight of the quaternary ammonium compound (B).)
When the usage amount n ′ of the quaternary ammonium compound (B) is 0.5 mass ppb or more, the decomposition rate of the unstable terminal portion of the polyacetal by the combined use of the quaternary ammonium compound (B) is improved. Moreover, even if it is 500 mass ppm or less, the color tone of a polyacetal is not impaired after stabilization.
Here, the amount of quaternary ammonium compound (B) used is defined in terms of nitrogen because the number of moles of quaternary ammonium compound (B) relative to polyacetal varies depending on the molecular weight of quaternary ammonium compound (B). This is to avoid that.

The quaternary ammonium compound (A) of this embodiment is preferably used in the presence of a specific metal atom.
In this embodiment, when the quaternary ammonium compound (A) is allowed to coexist with a specific metal atom, the effect of reducing the amount of acrolein generated in the polyacetal after stabilizing the unstable terminal is improved. Examples of such metal atoms include magnesium, sodium, and calcium. Furthermore, when magnesium, sodium, and calcium coexist, it becomes possible to suppress coloring when the quaternary ammonium compound (A) is concentrated.
The metal atom is preferably present in an amount of 0.001 ppm or more with respect to the quaternary ammonium compound (A) (the total of both when the quaternary ammonium compound (B) is used in combination). However, since the metal atom generally has a high boiling point and is not easily removed, it is preferably 10 ppm or less. If the content exceeds 10 ppm, the thermal stability of the polyacetal may be lowered.
On the other hand, when the quaternary ammonium compound (A) is allowed to coexist with a potassium atom, coloring when the quaternary ammonium compound (A) is concentrated may be deteriorated.

In this embodiment, the quaternary ammonium compound (A) is particularly preferably used in a state dissolved in water.
When an aqueous solution of the quaternary ammonium compound (A) is used for stabilization of the crude polyacetal, formaldehyde azeotropes with water, so that removal of formaldehyde generated from the polyacetal can be promoted.
Further, when the quaternary ammonium compound (A) is used as an aqueous solution, it is not necessary to provide a step of completely drying the water during the production thereof, and the heat energy for that purpose can be saved. Alteration and discoloration of the quaternary ammonium compound (A) can be prevented.

As described above, the quaternary ammonium compound (A) of this embodiment can be used as a volatile organic compound generation inhibitor from polyacetal.
The volatile organic compound generation inhibitor from the polyacetal of this embodiment is further at least one selected from the group consisting of the quaternary ammonium compound (B) represented by the above formula (3), magnesium, sodium and calcium. One metal atom, a solvent, and optional additives can be included.
Further, the dosage form of the volatile organic compound generation inhibitor from the polyacetal of the present embodiment is not limited, and may be, for example, a solid (powdered) or an arbitrary solvent (such as water) being quaternary ammonium. A solution in which the compound (A) is dissolved may be used.

  Hereinafter, the present invention will be described with reference to specific examples and comparative examples. However, the present invention is not limited to the following examples.

<Quantitative determination of formaldehyde, acetaldehyde and acrolein>
1. In the case of pellets (before heating and melting) 20.00 g of polyacetal resin composition pellets were placed in a 10 L Tedlar (registered trademark) bag having a valve and sealed, and nitrogen substitution was sufficiently performed. Thereafter, after exhausting all the nitrogen inside, 5.00 L of nitrogen was sealed in the Tedlar (registered trademark) bag. Two of these were prepared.
Thereafter, the Tedlar (registered trademark) bag is put in an oven having two sampling ports communicating with the outside at the upper part of the inside, and the Tedlar (registered trademark) bag is connected to the sampling port and then left at 90 ° C. for 2 hours. did.
Then, connect a DNPH (2,4-dinitrophenylhydrazine) cartridge to the outside of the sampling port connected to one Tedlar® bag, open the Tedlar® bag valve, and generate from the polyacetal composition 4.00 L of the gas was passed through a DNPH cartridge.
5 mL of acetonitrile was passed through the DNPH cartridge at a constant rate, and formaldehyde and acetaldehyde were collected in a 10 mL volumetric flask.
Then, it was made up to 10 mL with water and mixed well.
This mixed solution is dispensed into a vial, HPLC using Shimadzu Corporation, DNPH standard solution as standard solution, water / acetonitrile (52/48) as separation solution, flow rate of 1 mL / min, column temperature of 40 The amount of formaldehyde and acetaldehyde generated per mass of the polyacetal resin composition pellets was measured in ppm by quantification at ° C.
The upper limit of measurement is 15 ppm or less. D. (Not measurable), and below 0.01 ppm, N.I. D. It was.

Connect the CNET (O- (4-cyano-2-ethoxybenzyl) hydroxylamine) cartridge to the outside of the sampling port connected to the remaining one Tedlar® bag, and open the Tedlar® bag valve. Then, 4.00 L of gas generated from the polyacetal composition was passed through a CNET cartridge.
5 mL of acetonitrile was passed through the CNET cartridge at a constant rate, and acrolein was collected in a 10 mL volumetric flask.
Then, it was made up to 10 mL with water and mixed well.
This mixed solution is dispensed into vials, using Shimadzu HPLC, using CNET standard solution as the standard solution, water / acetonitrile (40/60) as the separation solution, flow rate of 1 mL / min, column temperature of 40. The amount of acrolein generated per mass of the polyacetal resin composition pellets was measured by ppb after quantification at ° C.
The upper limit of measurement is 30 ppb or less, but those exceeding 20 ppb are O.D. D. And below 1.0 ppb, N. D. It was.

2. In the case of a molded piece (after heating and melting) From a polyacetal resin composition pellet using a Toshiba IS-100GN injection molding machine, a cylinder temperature of 200 ° C., an injection pressure of 60 MPa, an injection time of 15 seconds, a cooling time of 20 seconds, The composition was heated and melted at a mold temperature of 80 ° C. to produce a flat molded piece having dimensions of 130 mm × 110 mm × 3 mm.
After being left for 24 hours in a temperature-controlled room maintained at 23 ° C. and 50% humidity, it was placed in an aluminum bag and packed. On the 14th day after molding, the molded piece was put in a 10 L Tedlar (registered trademark) bag having a valve and sealed, and nitrogen substitution was sufficiently performed. Thereafter, after exhausting all the nitrogen inside, 5.00 L of nitrogen was sealed in a Tedlar (registered trademark) bag. Two of these were prepared.
Thereafter, a Tedlar (registered trademark) bag was placed in an oven having a sampling port communicating with the outside at the upper part of the inside, and the Tedlar (registered trademark) bag was connected to the sampling port and left at 80 ° C. for 2 hours.
Thereafter, formaldehyde, acetaldehyde and acrolein were quantified in the same manner as in the case of pellets.

<Color characteristics of polyacetal>
Using a IS-100GN injection molding machine manufactured by Toshiba Corporation, from a polyacetal resin composition pellet, cylinder temperature 200 ° C., injection pressure 60 MPa, injection time 15 seconds, cooling time 20 seconds, mold temperature 80 ° C., dimensions A flat test piece of 130 mm × 110 mm × 3 mm was produced.
Two test pieces were stacked on this test piece using a Minolta handy color tester (CR-200), and the yellowness (b value) was measured with a D65 light source.
If the b value was −0.8 or less, the result was generally good, and if the b value was −1.6 or less, it was determined to be good.

<Evaluation of color tone of quaternary ammonium compound>
An aqueous solution of the quaternary ammonium compound (A) is measured for 10 cc in an aluminum container having a diameter of 10 cm and a height of 1 cm, and the aluminum container is placed on a hot plate set at 150 ° C. 10cc was measured and added. Thereafter, the color of the residue on the bottom of the aluminum container was visually checked at the same time as the water disappeared, and the color was evaluated.
The color close to brown was rated as x, the color near light yellow to colorless was marked as ◯, and the middle was marked as Δ.
This was implemented with respect to the aqueous solution of the quaternary ammonium compound (A) obtained by manufacture example 1, 7, 8, and 12-19.

<Method for producing crude polyacetal>
Two-axis paddle type continuous polymerization reactor with jacket through which heat medium can pass (made by Kurimoto Steel Works, diameter 2B (2 inches), L (distance from the raw material supply port to the discharge port of the polymerization reactor) / D ( The inner diameter of the polymerization reactor) = 14.8) was adjusted to 80.degree.
Next, 0.20 g / hr of boron trifluoride-di-n-butyl etherate as a polymerization catalyst, 1.53 g / hr of methylal as a low molecular weight acetal, 6.50 g / hr of cyclohexane, cyclic ether and / or cyclic formal As a result, 120.9 g / hr of 1,3-dioxolane and 3500 g / hr of trioxane were continuously supplied to the polymerization reactor through a pipe for polymerization to obtain a crude polyacetal copolymer (P-1).
This crude polyacetal copolymer (P-1) was put into a 0.1% by mass aqueous solution of triethylamine to deactivate the catalyst. Then, after filtration and washing, it was dried at 120 ° C. to obtain a crude polyacetal copolymer (P-2).

<Production of Quaternary Ammonium Compound (A) Represented by Formula (1)>
Deionized water was used for all the water used in the following Production Examples 1-11.
[Production Example 1]
14.1 g of 2- (2-hydroxyethoxy) ethyl acetate, 5.6 g of trimethylamine, 15.0 g of methanol, and 0.1 g of water are introduced into a pressure-resistant container having an inner volume of 60 ml that can be sealed, and stirred with a shaker. The mixture was heated to 120 ° C. Then, after reacting for 6 hours, the contents were obtained by cooling. As a result of analyzing the contents, 2- (2-hydroxyethoxy) ethyl-N, N, N-trimethylethane-1-ammonium acetate was obtained with a yield of 95%.
After adding 15 g of water to 30 g of this solution, the solution is concentrated to 30 g with an evaporator at 80 ° C., and water is added to make 60 g. Concentrate again to 30 g, then add water to 60 g. This operation was repeated 10 times and concentrated to 15 g, and then water was added to make 80 g. This liquid was designated as A-1.
The structural formulas (R1, R2 and X) of the quaternary ammonium compound (A) in the A-1 liquid confirmed by NMR are as shown in Table 1, and the concentration was about 20% by mass.

[Production Example 2]
The same procedure as in Example 1 was carried out except that 18.2 g of 2- (2- (2-hydroxyethoxy) ethoxy) ethyl acetate was used instead of 14.1 g of 2- (2-hydroxyethoxy) ethyl acetate. This liquid was designated as A-2.
The structural formula (R1, R2 and X) of the quaternary ammonium compound (A) in the liquid A-2 confirmed by NMR is as shown in Table 1, and its concentration was about 22% by mass.
[Production Example 3]
The same procedure as in Production Example 1 was carried out except that 7.8 g of triethylamine was used instead of 5.6 g of trimethylamine and 11.4 g of 2- (2-hydroxyethoxy) ethyl acetate was used. This liquid was designated as A-3.
The structural formulas (R1, R2 and X) of the quaternary ammonium compound (A) in the A-3 liquid confirmed by NMR are as shown in Table 1, and the concentration was about 20% by mass.
[Production Example 4]
Instead of 5.6 g of trimethylamine, 7.8 g of triethylamine was used, and 14.8 g of 2- (2- (2-hydroxyethoxy) ethoxy) ethyl acetate was used instead of 2- (2-hydroxyethoxy) ethyl acetate. Otherwise, the same procedure as in Production Example 1 was performed. This liquid was designated as A-4.
The structural formulas (R1, R2 and X) of the quaternary ammonium compound (A) in the A-4 liquid confirmed by NMR are as shown in Table 1, and the concentration was about 21% by mass.
[Production Example 5]
Similar to Production Example 1 except that 9.4 g of 2- [2- (dimethylamino) ethoxy] ethanol was used instead of 5.6 g of trimethylamine, and 10.5 g of 2- (2-hydroxyethoxy) ethyl acetate was used. Implemented. This liquid was designated as A-5.
The structural formulas (R1, R2 and X) of the quaternary ammonium compound (A) in the A-5 solution confirmed by NMR are as shown in Table 1, and the concentration was about 20% by mass.

[Production Example 6]
A 10 ml microwave reaction tube was charged with 5.0 g of trimethylamine and 2.63 g of 2- (2-chloroethoxy) ethanol and stirred at 150 ° C. for 1 hour while irradiating with microwaves. After completion of the reaction, the reaction solution was dried under reduced pressure to obtain powder crystals. As a result of analyzing the reaction solution after completion of the reaction by HPLC, it was confirmed that the reaction rate was 100%. After dichloroethane was added to the obtained powder crystals and stirred, the crystals were filtered. This operation was repeated three times and dried under reduced pressure to obtain 2.58 g of powder crystals.
To this powder, 5.62 g of a 1 kg ethanol solution in which 100 g of sodium hydroxide at 40 ° C. was dissolved was added, sodium chloride was filtered off, and the filtrate was collected. After adding 6.46g of formic acid aqueous solution consisting of formic acid / water = 10/90 (mass ratio) to this filtrate, it was concentrated to 5g with an evaporator, and 10g of water was added.
Concentration and addition of 10 g of water were repeated three times, and the final weight of 15 g was designated as A-6.
The structural formula (R1, R2 and X) of the quaternary ammonium compound (A) in the A-6 liquid confirmed by NMR is as shown in Table 1, and the concentration was about 17% by mass.

[Production Example 7]
4.5 g of trimethylamine was carried out in the same manner as in Production Example 6 except that 3.21 g of 2- [2- (2-chloroethoxy) ethoxy] ethanol was used instead of 2- (2-chloroethoxy) ethanol. 3.10 g of powder crystals were obtained.
This powder was filtered with sodium chloride and concentrated in the same manner as in Production Example 6 using 5.44 g of the sodium hydroxide ethanol solution used in Production Example 6 and 6.26 g of formic acid aqueous solution. This was designated as A-7.
The structural formula (R1, R2 and X) of the quaternary ammonium compound (A) in the A-7 solution confirmed by NMR is as shown in Table 1, and the concentration was about 20% by mass.
[Production Example 8]
The same procedure as in Production Example 6 was carried out except that 5.8 g of triethylamine and 1.79 g of 2- (2-chloroethoxy) ethanol were used instead of trimethylamine to obtain 1.76 g of powder crystals.
This powder was subjected to filtration and concentration of sodium chloride in the same manner as in Production Example 6 using 3.11 g of the sodium hydroxide ethanol solution used in Production Example 6 and 3.58 g of formic acid aqueous solution. Was designated as A-8.
The structural formula (R1, R2, and X) of the quaternary ammonium compound (A) in the A-8 liquid confirmed by NMR is as shown in Table 1, and the concentration thereof was about 12% by mass.
[Production Example 9]
Similar to Production Example 6 except that 5.4 g of triethylamine was used instead of trimethylamine and 2.25 g of 2- [2- (2-chloroethoxy) ethoxy] ethanol was used instead of 2- (2-chloroethoxy) ethanol To obtain 2.18 g of powder crystals.
This powder was filtered with sodium chloride and concentrated in the same manner as in Production Example 6 using 3.24 g of the sodium hydroxide ethanol solution used in Production Example 6 and 3.72 g of formic acid aqueous solution. Was designated as A-9.
The structural formula (R1, R2 and X) of the quaternary ammonium compound (A) in the A-9 liquid confirmed by NMR is as shown in Table 1, and its concentration was about 14% by mass.
[Production Example 10]
Production Example 6 except that 4.0 g of trimethylamine and 3.60 g of 2- [2- [2- (2-chloroethoxy) ethoxy] ethoxy] ethanol were used instead of 2- (2-chloroethoxy) ethanol In the same manner, 3.41 g of powder crystals were obtained.
Sodium hydroxide was filtered and concentrated in the same manner as in Production Example 6 using 5.02 g of the sodium hydroxide ethanol solution used in Production Example 6 and 5.77 g of formic acid aqueous solution, and the final powder was 15 g. Was designated as A-10.
The structural formula (R1, R2 and X) of the quaternary ammonium compound (A) in the A-10 solution confirmed by NMR is as shown in Table 1, and the concentration was about 22% by mass.
[Production Example 11]
Except for using 5.0 g of triethylamine instead of trimethylamine and 2.63 g of 2- [2- [2- (2-chloroethoxy) ethoxy] ethoxy] ethanol instead of 2- (2-chloroethoxy) ethanol, In the same manner as in Production Example 6, 2.50 g of powder crystals were obtained.
This powder was filtered with sodium chloride and concentrated in the same manner as in Production Example 6 using 3.19 g of the sodium hydroxide ethanol solution used in Production Example 6 and 3.67 g of formic acid aqueous solution. Was designated as A-11.
The structural formula (R1, R2, and X) of the quaternary ammonium compound (A) in the A-11 liquid confirmed by NMR is as shown in Table 1, and its concentration was about 16% by mass.

[Production Example 12]
To the aqueous solution A-1 obtained in Production Example 1, 0.05 mass ppm of magnesium hydroxide was added with respect to the quaternary ammonium compound. This was designated as A-12.
[Production Example 13]
0.1 mass ppm of magnesium hydroxide was added to the aqueous solution A-1 obtained in Production Example 1 with respect to the quaternary ammonium compound. This was designated as A-13.
[Production Example 14]
To the aqueous solution A-1 obtained in Production Example 1, 0.7 mass ppm of magnesium hydroxide was added with respect to the quaternary ammonium compound. This was designated as A-14.
[Production Example 15]
To the aqueous solution A-1 obtained in Production Example 1, 0.4 mass ppm of sodium hydroxide was added with respect to the quaternary ammonium compound. This was designated as A-15.
[Production Example 16]
1.6 mass ppm magnesium hydroxide was added to the aqueous solution A-1 obtained in Production Example 1 with respect to the quaternary ammonium compound. This was designated as A-16.
[Production Example 17]
To the aqueous solution A-1 obtained in Production Example 1, 0.28 mass ppm of calcium hydroxide was added to the quaternary ammonium compound. This was designated as A-17.
[Production Example 18]
0.28 mass ppm magnesium hydroxide with respect to the quaternary ammonium compound was added to the aqueous solution A-7 obtained in Production Example 7. This was designated as A-18.
[Production Example 19]
To the aqueous solution A-8 obtained in Production Example 8, 10.0 mass ppm of sodium hydroxide was added to the quaternary ammonium compound. This was designated as A-19.
[Production Example 20]
To the aqueous solution A-1 obtained in Production Example 1, 8.0 mass ppm of potassium hydroxide was added to the quaternary ammonium compound. This was designated as A-20.

<The quaternary ammonium compound (B) represented by Formula (3)>
B-1: Choline acetate (manufactured by Aldrich)
B-2: Choline hydroxide (manufactured by Tama Chemical Industries)
It was used.

Examples 1 to 29
The crude polyacetal copolymer (P-1) was put into a 0.5% aqueous solution of triethylamine to deactivate the polymerization catalyst. Thereafter, the solution of the quaternary ammonium compound (A) prepared in each production example is filtered and washed, and the nitrogen concentration n is as shown in Table 2 with respect to 100 parts by mass of the crude polyacetal copolymer (P-1). Was added, mixed uniformly, and dried at 130 ° C.
For 100 parts by mass of the resulting crude polyacetal copolymer composition containing the quaternary ammonium compound (A), 2,2′-methylenebis- (4-methyl-t-butylphenol) was added as an antioxidant. 2 parts by mass were added and fed to a twin screw extruder with a vent.
If necessary, water is added to the molten crude polyacetal copolymer composition in the extruder, and the unstable end of the crude polyacetal copolymer is obtained at a setting temperature of the extruder of 210 ° C. and a residence time of 5 minutes in the extruder. The parts were disassembled. The polyacetal copolymer in which the unstable terminal portion was decomposed was devolatilized under the condition of a vent vacuum of 20 Torr, extruded as a strand from the extruder die portion, and pelletized.
Type of quaternary ammonium compound (A) used, and amount (content) of quaternary ammonium compound (A) used relative to the total mass of polyacetal copolymer and quaternary ammonium compound (A) (fourth Nitrogen concentration derived from quaternary ammonium compound (A) n), water added to extruder, addition amount of triethylamine to 100 parts by mass of crude polyacetal copolymer composition, formaldehyde (FA), acetaldehyde (AA) and acrolein (AL) Table 2 summarizes the amount and color tone.

[Comparative Examples 1-3]
The same operation as in Example 16 was carried out except that the quaternary ammonium compound (A) was not used and the amount of (B) used was changed. The results are summarized in Table 3.
[Comparative Examples 4 and 5]
The same operation as in Example 17 was carried out except that the quaternary ammonium compound (A) was not used and the amount of (B) used was changed. The results are summarized in Table 3.
[Comparative Example 6]
The same procedure as in Example 1 was carried out except that the quaternary ammonium compound (A) was not used and the addition amount of water / triethylamine was changed. The results are summarized in Table 3.
[Comparative Example 7] Tetrakis [(2-hydroxyethyl) trimethylammonium] salt of ethylenediaminetetraacetic acid (D-1) was used in place of the quaternary ammonium compound (A), and the addition amount of water / triethylamine was changed. Was carried out in the same manner as in Example 1. The results are summarized in Table 3.

[Comparative Example 8]
Instead of tetrakis [(2-hydroxyethyl) trimethylammonium] salt (D-1) of ethylenediaminetetraacetic acid, (2-hydroxyethyl) trimethylammonium salt of polyacrylic acid (equimolar salt of acrylic acid unit, polyacrylic acid The number average molecular weight of 7000) was carried out in the same manner as Comparative Example 7 except that (D-2) was used. The results are summarized in Table 3.

As shown in Table 2, in Examples 1 to 28, polyacetal in which generation of formaldehyde, acetaldehyde and acrolein is suppressed can be obtained both before and after heat-melting processing (pellets and molded pieces), and excellent in color tone. was gotten.
In Examples 4, 14, 15 and 20, although the b value was slightly higher, polyacetal resin compositions in which the generation of formaldehyde, acetaldehyde and acrolein was suppressed were obtained. The reason why the b value slightly increased in Example 4 is presumed to be that the amount of the quaternary ammonium compound (A) used was large, and in Examples 14, 15 and 20, the b value slightly increased. The reason is that since R2 in the quaternary ammonium compound (A) used is long, the quaternary ammonium compound (B) tends to remain in the polyacetal resin composition even after the stabilization treatment, and this is colored when heated and melted. It is guessed. In Examples 21 to 28 in which magnesium, calcium or sodium was allowed to coexist with the quaternary ammonium compound (A), a polyacetal having better color tone was obtained. In contrast, in Example 29 in which potassium was coexisted with the quaternary ammonium compound (A), a slight decrease in color tone was observed after heat-melting processing.

As shown in Table 3, in Comparative Examples 1 to 5 using only the quaternary ammonium compound (B) without using the quaternary ammonium compound (A), generation of formaldehyde, acetaldehyde and acrolein was suppressed. Polyacetal pellets could be obtained, but generation of formaldehyde, acetaldehyde and acrolein during heating and melting could not be sufficiently suppressed.
In Comparative Example 6 in which no quaternary ammonium compound was used, it was also impossible to obtain a polyacetal in which generation of formaldehyde, acetaldehyde and acrolein was suppressed.
Moreover, the comparative example using the quaternary ammonium compounds (D-1) and (D-2) which contain a nitrogen atom in the group corresponding to X of Formula (1) instead of the quaternary ammonium compound (A). 7 and 8, the generation of formaldehyde, acetaldehyde and acrolein could not be sufficiently suppressed.

Claims (7)

A quaternary ammonium compound represented by the following formula (1) [(R1) _m (R2) _4-m N ⁺ ] _n X ^n- (1)
(In the formula, each R 1 independently represents an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; an unsubstituted alkyl group or substituted alkyl having 1 to 30 carbon atoms; An aralkyl group substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms with at least one unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; Represents a substituted alkylaryl group, and the unsubstituted alkyl group and the substituted alkyl group are linear, branched or cyclic, and the substituent of the substituted alkyl group is halogen, hydroxyl group, aldehyde group, carboxyl group, amino group A non-substituted alkyl group, an aryl group, an aralkyl group, and an alkylaryl group may be substituted with a halogen atom.
R2 independently represents a group represented by the following formula having 2 to 60 carbon atoms and 2 to 30 oxygen atoms.
-(RO) k-H (wherein R represents a substituted or unsubstituted alkyl group, and k represents a natural number of 2 or more)
m and n represent an integer of 1 to 3.
X is a hydroxyl group or an acid residue of a compound selected from the group consisting of a monocarboxylic acid having 1 to 20 carbon atoms, a hydrogen acid, an oxo acid, an inorganic thioacid, and an organic thioacid having 1 to 20 carbon atoms. Represents a group containing no nitrogen atom. ).   The quaternary ammonium compound according to claim 1, wherein X in the formula (1) is an acid residue of a monocarboxylic acid.   The quaternary ammonium compound according to claim 1 or 2, wherein the monocarboxylic acid is formic acid, acetic acid or propionic acid.   The quaternary ammonium compound as described in any one of Claims 1-3 whose carbon number of R2 in the said Formula (1) is 2-6.   The volatile organic compound generation | occurrence | production inhibitor from a polyacetal containing the quaternary ammonium compound as described in any one of Claims 1-4. Furthermore, the volatile organic compound generation | occurrence | production inhibitor from the polyacetal of Claim 5 containing the quaternary ammonium compound (B) represented by following formula (3).
[R3R4R5R6N +] _l Y ^l− (3)
Wherein R 3, R 4, R 5 and R 6 are each independently an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; an unsubstituted group having 1 to 30 carbon atoms An aralkyl group in which an alkyl group or a substituted alkyl group is substituted with at least one aryl group having 6 to 20 carbon atoms; or an aryl group having 6 to 20 carbon atoms is an unsubstituted alkyl group having 1 to 30 carbon atoms Or an alkylaryl group substituted with a substituted alkyl group, wherein the unsubstituted alkyl group and the substituted alkyl group are linear, branched, or cyclic, and the substituent of the substituted alkyl group is a halogen, hydroxyl group, aldehyde group , A carboxyl group, an amino group, or an amide group, and an unsubstituted alkyl group, an aryl group, an aralkyl group, and an alkylaryl group have a hydrogen atom substituted with a halogen atom It can have.
l represents an integer of 1 to 3.
Y represents a hydroxyl group or an acid residue of a compound selected from the group consisting of a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid, an oxo acid, an inorganic thioacid, and an organic thioacid having 1 to 20 carbon atoms. )   Furthermore, the volatile organic compound generation | occurrence | production inhibitor from the polyacetal of Claim 5 or 6 containing the at least 1 metal atom chosen from the group which consists of magnesium, sodium, and calcium.