JPH0827217A - Production of vinyl alcohol-based polymer - Google Patents

Abstract

PURPOSE:To obtain the subject polymer having a high polymerization degree, syndiotacticity and saponification degree by saponifying a homopolymer or a copolymer of a vinyl ester under specific conditions. CONSTITUTION:This method for producing a vinyl alcohol-based polymer is to saponify a homopolymer or a copolymer of a vinyl ester of the formula (R<1> is H or a hydrocarbon group; R<2> and R<3> are independently each a hydrocarbon group) in an alcohol, capable of dissolving or swelling the polyvinyl ester and promoting the saponification reaction in the presence of a basic substance and having 9.0-12.0 (cal/cm<3>)<1/2> value of the solubility parameter such as n- propanol in the substantial absence of oxygen or in the presence of an oxidizing agent at 70-200 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a vinyl alcohol polymer by a novel saponification method of a vinyl ester polymer. In particular, the present invention relates to a method for producing a vinyl alcohol polymer having a high degree of polymerization and a high syndiotacticity and a high degree of saponification.

[Prior art]

Vinyl alcohol-based polymers such as saponified products of polyvinyl acetate-based polymers have excellent interfacial properties and strength properties as a few crystalline water-soluble polymers, and are therefore suitable for paper processing, fiber processing and emulsion. In addition to being used as stabilizers, vinylon film,
As is well known, it occupies an important position as a raw material for vinylon fibers and the like. Furthermore, recently, attention has been paid to it as a gel material, and the development of new fields is being actively pursued.

By the way, conventionally commercially available vinyl alcohol polymers are stereoregularly so-called atactic (syndiotactic content of about 53 in terms of diads).
Mol%). It is known that a vinyl alcohol polymer having excellent stereoregularity exhibits physical properties that are significantly different from those of an atactic substance due to the effect of hydrogen bonding. In particular, syndiotacticity is 55 mol% or more in terms of diads. The vinyl alcohol-based polymer is expected to expand the possibilities of the conventional vinyl alcohol-based polymer, such as being easily crystallized. Vinyl alcohol-based polymers obtained by saponifying a polymer of vinyl pivalate are known to be rich in syndiotacticity, but generally, polyvinyl polypivalate has a bulky group in its side chain such as polyvinyl pivalate. In the case of an ester, it is difficult to be hydrolyzed due to its steric hindrance, and a vinyl alcohol polymer having a sufficiently high degree of saponification cannot be obtained by alkali saponification such as is usually carried out with polyvinyl acetate. On the contrary,
Several methods have been tried, but saponification with KOH, for example, has only yielded a vinyl alcohol polymer having a degree of saponification of about 52 mol% (Sakaguchi et al.,
Polymer Chemistry, 27, 758 (1970)). According to the saponification method reported by Nozakura et al., A vinyl alcohol-based polymer having a somewhat high degree of saponification can be obtained, but it is blackish brown,
Only the one with a low degree of polymerization can be obtained, and the intended one cannot be obtained. More recently proposed method (K. Imai et.
al. , J. et al. Polym. Sci. , PA: Pol
ym. Chem. , 26, 1961 (1988)), some of the drawbacks of the above-mentioned method are improved, but the problems of coloration and decrease in polymerization degree are not solved, and it is necessary to carry out the reaction in two steps. It is not a process that can be done and a high degree of polymerization has not been obtained.

[0004]

Under these circumstances, the object of the present invention is to produce a vinyl alcohol rich in syndiotacticity by saponifying a vinyl ester polymer having a bulky group in the side chain by a novel method. It is intended to provide a method for producing a polymer.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that the solubility parameter value is 9.0 to 12.0 (cal / cm ↑ 3) ↑ (1
/ 2) alcohol, in the substantial absence of oxygen or in the presence of an antioxidant, reaction temperature 70 ℃ ~ 200 ℃
Then, the inventors have found a method for producing a vinyl alcohol polymer characterized by saponifying a homopolymer or copolymer of a vinyl ester represented by the following general formula (1), and completed the present invention.

[0006]

Embedded image

(In the formula, R ↑ 1 represents a hydrogen atom or a hydrocarbon group, and R ↑ 2 and R ↑ 3 each represent a hydrocarbon group.)

The present invention will be described in more detail below. First, the vinyl ester polymer used in the present invention is a homopolymer or copolymer of the vinyl ester represented by the general formula (1).

The hydrocarbon group is preferably a lower alkyl group such as methyl, ethyl, propyl or butyl; an aryl group such as phenyl group; a hydrocarbon group having 1 to 18 carbon atoms such as cycloalkyl group such as cyclohexyl. Considering the versatility of vinyl ester and the like, it is preferable that R ↑ 1, R ↑ 2 and R ↑ 3 are each a methyl group. That is, vinyl pivalate is preferable as the vinyl ester, and vinyl versatate is preferable as the other vinyl ester.

The comonomer in the case of the copolymer is not particularly limited as long as it is a monomer which can be copolymerized with the vinyl ester represented by the above general formula (1). Specific examples include vinyl acetates such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl laurate, vinyl stearate, vinyl benzoate, ethylene, propylene, 1-butene, isobutene, etc. Olefins; acrylic acid and its salts; acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate; methacrylic acid and its salts; methyl methacrylate, ethyl methacrylate, methacryl Acid n-propyl methacrylic acid i
-Methacrylic acid esters such as propyl; acrylamide; acrylamide derivatives such as N-methyl acrylamide and N-ethyl acrylamide; methacrylamide; N
-Methacrylamide derivatives such as methylmethacrylamide and N-ethylmethacrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether and i-propyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride, chloride Vinyl halides such as vinylidene, vinyl fluoride, vinylidene fluoride; allyl acetate,
Allyl compounds such as allyl chloride; maleic acid, salts thereof or esters thereof; itaconic acid, salts thereof or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate. The copolymerization ratio of these comonomers is also not particularly limited. The degree of polymerization of the vinyl ester homopolymer or copolymer of the present invention is not particularly limited.

A feature of the present invention is that the solubility parameter value is 9.0 to 12.0 (cal / cm ↑ 3) ↑ (1/2).
Alcohol is used for saponification in a substantially oxygen-free state. Such an alcohol alone can dissolve or swell the polyvinyl ester and promote the saponification reaction in the presence of a basic substance, such as n-propanol, isopropanol, n-butanol, isobutanol and Dibutanol, tertiary butanol, n-amyl alcohol, isoamyl alcohol, secondary amyl alcohol, 3-pentanol, tertiary amyl alcohol, amyl alcohol, fusel oil, n-hexanol, methylamyl alcohol, 2-ethylbutanol, cyclo Hexanol, n-heptanol, n-octanol, 2-ethylhexanol, n-nonanol,
Examples thereof include n-decanol, triethylene glycol, dipropylene glycol, tripropylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether and triethylene glycol monomethyl ether.
Among these, n-propanol, isopropanol, n-
Butanol, tert-butanol, n-amyl alcohol,
Amyl alcohol, n-hexanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether and the like are preferably used.

The saponification reaction of the present invention is carried out in the presence of a basic substance. Examples of the basic substance include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, potassium-n.
Examples include alkali metal alkoxides such as -butoxide and potassium-t-butoxide.

The polymer concentration at the time of saponification is determined by the degree of polymerization of the homopolymer or copolymer of the vinyl ester represented by the above general formula (1) and the desired degree of saponification, but is usually 1 to 70 weight. Set between%.

The amount of the basic substance added is represented by the molar ratio of the basic substance to all vinyl ester units contained in the homopolymer of the vinyl ester represented by the general formula (1),
Usually basic substance / total vinyl ester unit (molar ratio)
= 0.005-10 is set. This value varies depending on the target degree of saponification and the type of solvent and basic substance used, but if it is less than 0.005, the degree of saponification does not rise sufficiently, and if it is greater than 10, the saponification reaction proceeds without problems.
The molecular weight is likely to decrease due to oxidation. This molar ratio is used when the copolymer of the vinyl ester of the general formula (1) contains a group such as a carboxyl group which obviously reacts with a basic substance or when the antioxidant reacts with a basic substance. , The amount consumed by these is compensated.

The saponification temperature of the present invention is usually set to 70 ° C. to 200 ° C., preferably 100 ° C. to 150 ° C. in order to prevent a decrease in molecular weight and coloration and increase the efficiency of the saponification reaction.

The time required for saponification varies depending on the desired degree of saponification, solvent for saponification, basic substance, molar ratio, temperature, etc., but heating in the presence of a basic substance after completion of saponification causes coloration and a decrease in molecular weight. Be careful because it may cause

As a method for making the saponification system substantially free of oxygen, a method of introducing an inert gas such as nitrogen gas or argon gas from which oxygen has been removed into the system and bubbling is employed. There is no particular limitation on the means and method, and any oxygen adsorbent or the like that does not affect the saponification reaction may be used.

As the antioxidant, usual ones can be used, and hindered phenol type, phenol type, hindered amine type and the like are used. Specifically, for example, IRGANOX
1010, IRGANOX 1098, SANOL LS
-770 (above, manufactured by Nippon Ciba Geigy) or the like is used alone or in combination. If an antioxidant is added, the object of the present invention can be achieved without carrying out an operation of removing oxygen in the saponification system, but the addition of the antioxidant after the operation of removing oxygen can reduce the object of addition. Can be achieved,
A vinyl alcohol polymer with few impurities can be obtained.

The vinyl alcohol polymer produced as described above is purified by various methods, for example, an operation of neutralizing a basic substance and then washing.

According to the present invention, a vinyl alcohol polymer having a high degree of polymerization and a high syndiotacticity can be obtained. The syndiotacticity here means that PVA is dissolved in deuterated dimethylsulfoxide and the peak of the hydroxyl group in the proton NMR measurement (T. Moritani e.
t al. , Macromolecules, 5, 57
7, (1972). It is syndiotacticity by the dyad display obtained from.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "part" in the following examples means "part by weight".

Example 1 A reaction vessel equipped with a stirrer was charged with 600 parts of vinyl pivalate monomer and 200 parts of methanol, and the system was replaced with nitrogen by bubbling nitrogen gas. Separately, a solution in which 0.0712 parts of 2,2′-azobisisobutyronitrile as an initiator was dissolved in 26 parts of methanol was prepared, and the atmosphere was replaced with nitrogen by bubbling nitrogen gas. The temperature of the reaction vessel was raised, and when the internal temperature reached 60 ° C., a methanol solution containing an initiator was injected to initiate polymerization. After 240 minutes the polymerization rate is 60
When it reached a weight%, the polymerization was stopped by cooling, and unreacted vinyl pivalate monomer was removed under reduced pressure while adding n-butanol from time to time.
A butanol solution. Then, n-butanol was removed under reduced pressure to obtain vinyl polypivalate. Next, in a reactor equipped with a stirrer and a reflux condenser, 10 parts of this polyvinyl pivalate was weighed out, and degassing under reduced pressure-nitrogen gas introduction was repeated to replace nitrogen, and then 90 parts of n-butanol separately replaced with nitrogen. In addition, the temperature was raised to 110 ° C. and the solution was dissolved by stirring. Then, 22 parts of a separately prepared 1.7% by weight nitrogen-substituted n-butanol solution of metallic sodium in nitrogen was added and sufficiently stirred and mixed. At this time, the dissolved oxygen concentration in the polymer solution and the metallic sodium solution was quantified by the Winker method, and as a result, both were 3 × 10 ↑ (−5) mol / l or less. Subsequently, after maintaining at 110 ° C. for 1 hour under a nitrogen gas seal, 1.0 part of acetic acid was added together with 10 parts of n-butanol to neutralize metallic sodium. Then, after crushing the gel, soxhlet washing with methanol was carried out to obtain a vinyl alcohol polymer. After adding 10 parts of acetic anhydride and 2 parts of pyridine to 0.5 part of the obtained vinyl alcohol polymer and sealing the tube, the mixture was heated at 120 ° C. for 8 hours for acetylation. The obtained polyvinyl acetate was precipitated in n-hexane and then purified twice by repeating reprecipitation with an acetone-n-hexane system. Vinyl alcohol polymer is d ↓ 6-
It was dissolved in DMSO and NMR was measured to determine the saponification degree, syndiotacticity, and 1,2-glycol bond amount. Next, polyvinyl acetate obtained by acetylation was dissolved in benzene, and the intrinsic viscosity [η] was measured at 30 ° C. The measurement results show that the saponification degree is 99.3 mol% and the syndiotacticity is 61.4.
%, 1,2-glycol bond amount 1.7 mol%, [η] =
It was 0.90 dl / g.

Example 2 1.7% by weight solution of metallic sodium in n-butanol 2
31.3 parts of a 7 wt% potassium hydroxide n-butanol solution was used instead of 2 parts, and the mixture was mixed in the same manner as in Example 1, and the mixture was kept at 110 ° C. for 2 hours under a nitrogen gas seal, 2.4 parts of acetic acid was added together with 10 parts of n-butanol to neutralize potassium hydroxide. Then, the same process as in Example 1 was performed. The obtained vinyl alcohol polymer has a saponification degree of 98.9 mol% and a syndiotacticity of 6
1.4%, 1,2-glycol bond amount 1.7 mol%,
[Η] = 0.92 dl / g.

Comparative Example 1 10 parts of vinyl polypivalate synthesized in Example 1 and 90 parts of diethylene glycol dimethyl ether were heated to 110 ° C. and dissolved with stirring, and subsequently 1.7% of metallic sodium n-butanol prepared separately. After adding 22 parts of the solution and thoroughly stirring and mixing the mixture, and holding the mixture at 110 ° C. for 1 hour, acetic acid 1.
Sodium metal was neutralized by adding 0 part with 10 parts of methanol. Then, the same process as in Example 1 was performed. The obtained vinyl alcohol polymer has a saponification degree of 9
Although it was 9.1 mol%, it was colored brown and [η] = 0.
The molecular weight was significantly reduced to 29 dl / g.

[0025]

The manufacturing method of the present invention is carried out according to the general formula (1).
A vinyl alcohol polymer having a high degree of polymerization and having a high syndiotacticity can be easily obtained from a homopolymer or copolymer of a vinyl ester having a bulky group in the side chain represented by The obtained vinyl alcohol-based polymer is used for high-strength fiber, high-modulus fiber, water-resistant fiber, heat-resistant fiber, water-resistant film, heat-resistant film, high-strength gel, high-durability gel, fiber treatment agent, Examples include paper processing agents, which have extremely high industrial value.

Claims (1)

[Claims] 1. A solubility parameter value of 9.0 to 1
In an alcohol of 2.0 (cal / cm ↑ 3) ↑ (1/2), in the substantial absence of oxygen or in the presence of an antioxidant, at a reaction temperature of 70 ° C. to 200 ° C. Formula (1)
A method for producing a vinyl alcohol polymer, which comprises saponifying a homopolymer or copolymer of a vinyl ester represented by: Embedded image (In the formula, R ↑ 1 represents a hydrogen atom or a hydrocarbon group,
↑ 2 and R ↑ 3 each represent a hydrocarbon group)