JP2001081130A - Production of polyvinyl alcohol-based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyvinyl alcohol-based polymer free from an alkali metal salt such as sodium acetate at a high reaction rate and in high efficiency by saponifying at least one portion of vinyl ester monomer units in a polyvinyl ester-based polymer in the presence of a specific organic base as a catalyst in a specified solvent. SOLUTION: This method for producing a polyvinyl alcohol-based polymer comprises saponifying at least one portion of vinyl ester monomer units in a polyvinyl ester-based polymer, such as polyvinyl acetate, in the presence of an organic base as a catalyst in an organic solvent containing an alcoholic solvent such as methanol in an amount of >=50 vol.%. The organic base has a pKa of >=14 measured in dimethylsulfoxide at 25 deg.C and does not contain an alkali metal salt. The organic base is preferably a compound of the formula (X to Z are each R2R3 or the like; R1 to R3 are each H or a 1 to 8C alkyl) [for example, tert-butylimino-tri(pyrrolidino)phospholane]. The polymer has a good quality, and is useful for films used in the field of electronics, and so forth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polyvinyl alcohol-based polymer (hereinafter abbreviated as "PVA") which does not contain an alkali metal salt such as sodium acetate.

[0002]

2. Description of the Related Art Generally, PVA is produced by adding an alkali such as sodium hydroxide to a methanol solution of polyvinyl acetate to saponify a side chain. However, an alkali metal salt such as sodium acetate is mixed in the PVA obtained by such a method, and if mixed with the PVA, it causes coloring or a peculiar smell,
When VA is used for a film or an adhesive for electronics, it acts as a metal ion and causes problems such as impairing semiconductor characteristics.

As a saponification method which does not contain an alkali metal salt such as sodium acetate in PVA, for example, JP-A-62-225
No. 504 discloses 1,8-diazabicyclo [5.4.0] undece
A method using cycloamidines such as -7-ene (DBU) (pKa in dimethyl sulfoxide at 25 ° C. of 12) as a saponification catalyst is disclosed, but the rate of saponification is determined with an alkali metal salt such as sodium hydroxide. It is several times slower and is not satisfactory as a practical saponification method.

Further, Japanese Patent Application Laid-Open Nos.
No. 27218 discloses a saponification method using a guanidine compound or a specific amidine compound. Among them, 7-methyl-1,5,7-triazabicyclo [4.4 The pKa of .4] -dec-5-ene (MTBD) in dimethyl sulfoxide at 25 ° C. was 13, and the saponification rate was lower than that of sodium hydroxide, which was not satisfactory in practical use.

On the other hand, Polymer Chemistry, Vol. 23, No. 260,
890-894 (1966) discloses a method using a tetraalkylammonium hydroxide as a saponification catalyst in an acetone / water mixture (volume ratio 7/3). This is a direct saponification method to be used, in which the amount of tetraalkylammonium hydroxide used must be at least equimolar to the vinyl acetate unit, which is not only disadvantageous in terms of cost but also reduces the amount remaining in PVA. It has many disadvantages.

Further, Japanese Patent Application Laid-Open No. 10-130328 discloses a method in which tetraalkylammonium hydroxide is used as a saponification catalyst in a dialkylsulfoxide solution. There is a drawback that the operation becomes complicated due to collection or the like.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and does not contain an alkali metal salt such as sodium acetate in PVA and has a high efficiency of saponification having a high reaction rate. It provides a method.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies and have found that an organic base having a specific pKa containing no alkali metal is used as a saponification catalyst in an organic solvent mainly composed of an alcohol solvent. The inventors have found that the above-mentioned problems can be solved by saponifying a polyvinyl ester-based polymer, and have reached the present invention.

That is, the gist of the present invention is as follows. (1) In the presence of an organic solvent containing at least 50 vol% of an alcoholic solvent with a pKa of 14 or more measured in dimethyl sulfoxide at 25 ° C and containing no alkali metal salt as a catalyst, A method for producing PVA, comprising saponifying at least a part of a vinyl ester monomer unit in a polymer. (2) The organic base has the following formula

Embedded image The method for producing PVA according to the above (1), which is a phosphazene compound represented by the following formula: (3) The organic base has the following formula

Embedded image (Wherein, R ^{6 to} R ⁹ are an alkyl group having 1 to 16 carbon atoms, a benzyl group or a phenyl group), which is a quaternary ammonium hydroxide represented by the above (1). PVA
Manufacturing method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The polyvinyl ester polymer used in the present invention includes a homopolymer of vinyl ester,
Copolymers of two or more vinyl esters and copolymers of a vinyl ester with another monomer having an ethylenically unsaturated double bond are exemplified. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl chloroacetate and the like. Examples of other monomers having an ethylenically unsaturated double bond include, for example, α-olefins such as ethylene, propylene, 1-butene and 1-octene, and unsaturated monomers such as (meth) acrylic acid and crotonic acid. Monocarboxylic acid or its alkyl ester, unsaturated carboxylic acid such as maleic acid, fumaric acid, itaconic acid or its monoalkyl ester, dialkyl ester, acid anhydride, etc., (meth) acrylamides, N-sulfoalkyl (meth) acrylamide , Ethylene sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, styrene, styrene derivatives, allyl alcohol, alkyl vinyl ethers, vinyl chloride and the like. The degree of polymerization of the polyvinyl ester polymer is not particularly limited, but is usually in the range of 50 to 25,000.

The organic base used in the present invention has a pKa of 14 or more, preferably 14 or more and 50 or less in dimethyl sulfoxide at 25 ° C. and does not contain an alkali metal salt. Examples include a phosphazene compound represented by the above formula, a quaternary ammonium hydroxide represented by the above formula, and the like. The pKa of the organic base is a value measured at 25 ° C. in dimethyl sulfoxide, and a value determined at 25 ° C. in another solvent requires correction. For example, pKa in acetonitrile can be approximated to pKa in dimethyl sulfoxide by subtracting 12 therefrom. Also, p in tetrahydrofuran
For Ka, adding 2 here can approximate pKa in dimethyl sulfoxide. [Reference: R. Schwesing
er et al., Angew. Chem. Int. Ed. Engl., 26, 1167 (1987) and Angew. Chem. Int. Ed. Engl., 32,
1361 (1993)]

Specific examples of the phosphazene compound represented by the above formula include 2-tert-butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorin (BEMP), tert-butylimino -Tris (dimethylamino) phosphorane (tBu-P1), tert-butylimino-tris (pyrrolidino) phosphorane (tBu-P1-
t), 1-ethyl-2,2,4,4,4-pentakis (dimethylamino) -2λ ⁵ , 4λ ⁵ -catenadi (phosphazene) (Et-P
2), 1-tert-butyl-4,4,4-tris (dimethylamino) -2,2-bis [tris (dimethylamino) phosphoranylideneamino Rani isopropylidene amino] - 2λ ^5, 4λ ⁵ - Katenaji (phosphazene) ( tBu-P4) and the like.

Embedded image

Specific examples of the quaternary ammonium hydroxide used in the present invention represented by the above formula include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Benzyltrimethylammonium hydroxide, diethyldimethylammonium hydroxide, methyltriethylammonium hydroxide, methyltributylammonium hydroxide, hexadecyltrimethylammonium hydroxide, phenyltrimethylammonium hydroxide and the like. The pKa of these quaternary ammonium hydroxide salts in dimethyl sulfoxide at 25 ° C. is in the range of 25-50.

The amount of the organic base to be used is preferably from 0.02 to 20 mol%, more preferably from 0.1 to 5 mol%, based on the vinyl ester unit in the polyvinyl ester polymer. If the amount used is less than 0.02 mol%, the saponification reaction becomes very slow, while if it exceeds 20 mol%, the amount remaining in the PVA increases.

The solvent used in the present invention includes:
An organic solvent containing at least 50% by volume of an alcohol-based solvent and capable of dissolving a polyvinyl ester-based polymer, specifically, methanol, ethanol, n-propanol, i-propanol, n-butanol, t-butanol, etc. At least 50 vol% of lower aliphatic alcohols
Organic solvents. Organic solvents mainly composed of lower aliphatic alcohols, such as acetone, methyl ethyl ketone, dioxane, tetrahydrofuran, acetonitrile, etc., which are stable under basic conditions and have a boiling point of 150 ° C or less at normal pressure are mixed. May be done. The amount of the organic solvent used is not particularly limited as long as it dissolves the polyvinyl ester-based polymer, but may be usually 1/5 to 100 times (weight ratio) the polyvinyl ester-based polymer, and is preferably used. Is 1/2 to 20 times the amount.

Further, the saponification reaction is usually carried out at 20 to 100 ° C.
Preferably at a temperature of 30 to 80 ° C., under normal pressure or under pressure, 0.5
It is performed appropriately within a range of up to 6 hours. Also, the saponification reaction
The reaction can be performed until part or all of the vinyl ester units are converted to vinyl alcohol units.

[0018]

In the method of the present invention, the reason why the saponification reaction of the polyvinyl ester polymer is accelerated is that, for example, when methanol is used as a solvent, the nucleophilic reaction to the ester group by the methoxy anion is caused by the organic base. It is presumed that if the pKa of the organic base is 14 or more at this time, the organic base abstracts hydrogen of methanol and easily generates a methoxy anion.

[0019]

Next, the present invention will be described more specifically with reference to examples. In addition, the measuring method of the physical property test in an Example and a comparative example is as follows. 1. Measurement method (a) Degree of saponification Using "GEMINI 2000 (300 MHz)" manufactured by Varian, the saponification of PVA was determined from the integrated intensity ratio of the acetyl group and the main chain methylene group in ¹ H-NMR in deuterated dimethyl sulfoxide. The degree of conversion was calculated. (b) Residual amount of Na Using “ICAP575-II” manufactured by Japan Jarrell Ash Co., Ltd.
The amount of residual Na in PVA was quantified by inductively coupled plasma (CP) emission spectrometry. (c) 350 ° C weight loss Using PerkinElmer “TGA-7”, heating rate 10 ° C
The thermal analysis of PVA was performed at 350 ° C./min to determine the weight loss of PVA at 350 ° C.

Example 1 500 ml of internal volume equipped with a stirrer, a reflux condenser and a thermometer
Was charged with 21.5 g (vinyl acetate unit: 0.25 mol) of polyvinyl acetate (manufactured by Aldrich, weight average molecular weight: 167,000) and 158 g (200 ml) of methanol, and dissolved by heating at 50 ° C. Here tert- as an organic base
Butylimino-tri (pyrrolidino) phosphorane (tBu-
P1) 0.78 g (corresponding to 1 mol% based on vinyl acetate units) was added, and the reaction was started. After 20 minutes, the system gelled, and after 1 hour, the reaction system was cooled and acetic acid was added to stop the reaction. Next, the obtained gel was crushed, washed with methanol, filtered and dried. Table 1 shows the results obtained by measuring the degree of saponification, the amount of residual Na, and the weight loss at 350 ° C. of the obtained PVA.

Example 2 0.69 g of 2-tert-butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorin (BEMP) as an organic base (1 mol% based on vinyl acetate units) The saponification of polyvinyl acetate was carried out in the same manner as in Example 1 except that) was used. PVA obtained
Table 1 shows the results obtained by measuring the degree of saponification, the amount of residual Na, and the weight loss at 350 ° C.

Example 3 1-ethyl-2,2,4,4,4-pentakis (dimethylamino) -2λ ⁵ , 4λ ⁵ -catenadi (phosphazene) as an organic base
Saponification of polyvinyl acetate was carried out in the same manner as in Example 1 except that 0.85 g of (Et-P2) (corresponding to 1 mol% based on vinyl acetate units) was used. Table 1 shows the results obtained by measuring the degree of saponification, the amount of residual Na, and the weight loss at 350 ° C. of the obtained PVA.

Example 4 1-tert-butyl-4,4,4-tris (dimethylamino) -2,2-bis [tris (dimethylamino) phosphoranylideneamino] -2λ ⁵ , 4λ ⁵ as an organic base -Saponification of polyvinyl acetate in the same manner as in Example 1 except that 2.5 ml of a 1M hexane solution of -catenadi (phosphazene) (tBu-P4) (corresponding to 1 mol% based on vinyl acetate units) was used. Was done. Table 1 shows the results obtained by measuring the degree of saponification, the amount of residual Na, and the weight loss at 350 ° C. of the obtained PVA.

Example 5 Tetramethylammonium hydroxide (Me
4NOH), except that 0.91 g of a 25% by weight methanol solution (corresponding to 1 mol% based on vinyl acetate units) was used.
Saponification of polyvinyl acetate was performed in the same manner as in Example 1. About the obtained PVA, its saponification degree, residual Na
Table 1 shows the results of measurement of the amount and the weight loss at 350 ° C.

Example 6 1.05 g of a 40% by weight methanol solution of benzyltrimethylammonium hydroxide (BnMe3NOH) as an organic base
(Corresponding to 1 mol% based on the vinyl acetate unit.) Saponification of polyvinyl acetate was carried out in the same manner as in Example 1 except that it was used. About the obtained PVA, the saponification degree,
Table 1 shows the results of measuring the residual Na amount and the weight loss at 350 ° C.

Comparative Example 1 0.10 g of sodium hydroxide (NaOH) as an organic base
(Corresponding to 1 mol% based on the vinyl acetate unit.) Saponification of polyvinyl acetate was carried out in the same manner as in Example 1 except that it was used. About the obtained PVA, the saponification degree,
Table 1 shows the results of measuring the residual Na amount and the weight loss at 350 ° C.

Comparative Example 2 500 ml of internal volume equipped with a stirrer, a reflux condenser and a thermometer
Was charged with 21.5 g (vinyl acetate unit: 0.25 mol) of polyvinyl acetate (manufactured by Aldrich, weight average molecular weight: 167,000) and 158 g (200 ml) of methanol, and dissolved by heating at 50 ° C. Here, 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) 0.38 as an organic base
g (equivalent to 1 mol% based on vinyl acetate units) was added, and the reaction was started. After 55 minutes, the system gelled, and after 3 hours, the reaction system was cooled and the reaction was stopped by adding acetic acid. Next, the obtained gel was crushed, washed with methanol, filtered and dried. About the obtained PVA,
Table 1 shows the results obtained by measuring the degree of saponification, the amount of residual Na, and the weight loss at 350 ° C.

[0028]

[Table 1]

[0029]

According to the present invention, high-quality PVA containing no alkali metal salt such as sodium acetate can be obtained with high efficiency. These PVAs can be suitably used for films and adhesives for electronics.

Continued on the front page F term (reference) 4J100 AA02Q AA03Q AA04Q AA19Q AB02Q AB07Q AC03Q AD03Q AE02Q AG02P AG03P AG04P AG05P AG06P AG08P AJ01Q AJ02Q AJ09Q AK31Q AK32Q AL02Q AL34Q AL36Q BC01CA01 AP01

Claims (3)

[Claims] 1. An alcohol-based solvent having a pKa of 14 or more measured in dimethyl sulfoxide at 25 ° C. and containing no alkali metal salt as a catalyst.
A method for producing a polyvinyl alcohol-based polymer, comprising saponifying at least a part of a vinyl ester monomer unit in a polyvinyl ester-based polymer in the presence of an organic solvent containing 50 vol%. 2. The organic base has the following formula: The method for producing a polyvinyl alcohol-based polymer according to claim 1, which is a phosphazene compound represented by the following formula: 3. An organic base represented by the following formula: 2. A quaternary ammonium hydroxide represented by the formula: wherein R ^{6 to} R ⁹ are an alkyl group having 1 to 16 carbon atoms, a benzyl group or a phenyl group. A method for producing a polyvinyl alcohol-based polymer.