JPH01319505A - Novel production of polyvinyl alcohol-based polymer - Google Patents

Abstract

PURPOSE:To obtain the subject polymer having high syndiotacticity and excellent in stereoregularity by reducing a (co)polymer of a specific vinyl ester. CONSTITUTION:A (co)polymer of a vinyl ester expressed by the formula (R1 to R3 are alkyl and the total number of carbon atoms thereof is 3-12) (preferably having 1000-30000 polymerization degree) is preferably reduced with lithium aluminum hydride as a reducing agent to afford the objective polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION A. INDUSTRIAL APPLICATION FIELD The present invention relates to a novel method for producing polyvinyl alcohol polymers. More specifically, the present invention relates to a novel method for producing a polyvinyl alcohol polymer using a vinyl ester homopolymer or copolymer represented by the following general formula (I) as a starting material.

CH2=CH・・・・・・・・・・・・・・・(I)
RI l 0=C-C-R2 In recent years, polyvinyl 7/l/cole polymers (hereinafter polyvinyl alcohol will be abbreviated as PvA) with excellent stereoregularity have been desired from various viewpoints.

General 2 CH2=CF, (However, R1, R2, R
3 is OR+ O=C-C-R2, each of which is an alkyl group, and the total number of carbon atoms thereof is 3 or more and 12 or less. ) is expected to provide a PVA-based polymer with high syndiotacticity and excellent stereoregularity due to its molecular structure. In saponification in the presence of an alkali catalyst (hereinafter referred to as alkali saponification), the saponification rate is extremely slow due to the bulky side chains in the molecule, and a PVA-based polymer with a sufficiently high degree of saponification has not been obtained.

For example, Polymer Chemistry Vol. 27, No. 306, pp. 758-
No. 762, (1970) [Sakaguchi et al.], in the polyvinyl pivalate (CI) formula, R1=R
2=R3=CH3) using a potassium hydroxide catalyst, and the results are shown in No. 760.
As is clear from Figure 5 (F: x mark) on page 5, even after 40 hours of saponification reaction, PV with a saponification degree of about 52 mol.
Only an A-based polymer can be obtained, and there is no disclosure of a PVA-based polymer with a high saponification degree of 55 molti or more.

Problems to be Solved by the C0 Invention Under these circumstances, the present invention aims to meet the strong demand for a PVA-based polymer with excellent stereoregularity.
The present invention aims to provide a new method for producing a PVA-based polymer using a vinyl ester homopolymer or copolymer represented by 1) as a starting material.

Especially in the above formula (1), Rz=R2=R3=
It is an object of the present invention to provide a new manufacturing method for obtaining a highly saponified PVA-based polymer having a saponification degree of 55 molti or more using polyvinyl hybarate as a starting material in the case of CH3.

00 Means for Solving the Problems As a result of intensive research aimed at solving the above-mentioned problems, the present inventor surprisingly discovered that a vinyl ester homopolymer represented by the general formula (1) or -4- By adopting a completely different reaction method from the conventional alkali saponification method of reducing the copolymer, it is possible to obtain a highly saponified PVA polymer, especially a highly saponified one with a saponification degree of 55 molar or higher. The present inventors have discovered that a PVA-based polymer can be obtained extremely easily, and have completed the present invention.

The present invention will be explained in more detail below.

First, the blue form used as a starting material in the present invention is CH2=CH (where R1, R2, and R3 are OR+ 0=C-C-R2, each of which is an alkyl group, and the total number of carbon atoms is 3. The vinyl ester polymer represented by [7,12 or less] may be a homopolymer of the vinyl ester [7,1, or a copolymer containing a small amount of other copolymer units]. There may be.

Examples of other copolymerized units include ethylene, propylene,
Inobutylene, α-octene, α-dodecene, Veo
va (long chain alkyl vinyl ester), olefins such as α-octadecene 7, acrylic acid, methacrylic acid,
Unsaturated acids such as crotonic acid, maleic anhydride, and itaconic acid, their salts, or mono- or sialgyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, ethylene sulfonic acid, and allyl sulfone. acids, olefin sulfonic acids such as methalylsulfonic acid or their salts, alkyl vinyl ethers, polyoxy/alkylene allyl ethers, alkyl allyl ethers, saturated carboxylic acid allyl esters, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride , an ethylenically unsaturated monomer containing an acetoacetyl group, an unsaturated monomer containing an oxyalkylene group, a primary, secondary or tertiary amine, an unsaturated vinyl monomer containing a quaternary ammonium salt, and the like.

In addition, there is no particular restriction on the degree of polymerization of 2, but it is 100 to 5.
The number is preferably 70,000, more preferably 70,000 to 30,000.

In the present invention, among the vinyl ester polymers represented by the above-mentioned formula (I), especially R+=R2=R3=
Polyvinyl pivalate, CN3, is preferably used.

Next, as a reducing agent used in the present invention, LiA
Including lH4, 1-Bu2AIH, NaAlF
(<, NaAlH4(OCH2CH20CH3) 2,
NaBH+ -AICI 3, NaBH4, -BF 3
, BH3, BH4-(CH3) 2 S or the like can be used as a system containing at least one component of a reducing agent. Particularly preferred is LiAlH4.

Next, the reaction conditions of the vinyl ester homopolymer or copolymer represented by the general formula (I) and the above-mentioned reducing agent in the present invention will be shown.

Care must be taken since many of the reducing agents used in the present invention are generally denatured by water. For example, general solvents such as THF and toluene can be used as the solvent, but they must be sufficiently dried before use. This also applies to the equipment used. Furthermore, for the same reason, the reaction is performed under an N2 atmosphere.

There is no particular restriction on the reaction temperature, but the reaction temperature used = 7- It is desirable that the temperature is such that the solvent is appropriately refluxed.

In the production method of the present invention, there are no restrictions on the content of vinyl alcohol units in the PVA-based polymer obtained, but in particular, a PVA-based polymer having a vinyl alcohol unit content of 55 molar or more is used. In this process, the excellent features of the manufacturing method of the present invention are fully exhibited.

A more preferable content of vinyl alcohol units is 70 moles or more. More preferably, it is 80 molti or more.

89 Effects and Effects of the Invention According to the present invention, a vinyl ester homopolymer or copolymer represented by the general formula (I), particularly preferably polyvinyl pivalate, is used as a starting material, a PVA-based polymer, and a vinyl ester. A PVA-based polymer having a vinyl alcohol unit content of 55 moles or more can be obtained very easily.

Such results have not been achieved using conventional alkali saponification methods, as long as the vinyl ester homopolymer represented by the general formula (1) is used as a starting material. Ta.

The PVA-based polymer obtained by the production method of the present invention is
One of its characteristics is that it has high non-geo-toughness and excellent stereoregularity.

Another characteristic of the PVA-based polymer obtained by the production method of the present invention is that it has extremely little branched structure and extremely high linearity.

The PVA-based polymer of the present invention takes advantage of these characteristics to provide PVA-based polymers.
Suitable for use in applications such as vA fibers and PVA gels.

Next, the manufacturing method of the present invention will be explained in more detail with reference to Examples.

Hereinafter, "1 part" or 1%-1 is expressed on a weight basis unless otherwise specified.

Example 1.2 Vinyl polypivalate [hereinafter referred to as P (
It is abbreviated as VPiv). ] was completely dried using a vacuum dryer, and then the completely dried polymer was charged into a reactor equipped with a stirrer, thermometer, and condenser that had been previously dried, and dissolved in about 40 times the amount of THF. .

A 5% THF solution of lithium aluminum hydride was added to this so that the molar amount was about 3 times that of the ester of P(VPiv), and the mixture was refluxed for 24 hours (Example 1) and 168 hours (Example 2). .

Next, the reactor was transferred to an ice water bath, distilled water was gradually added while cooling, and the mixture was further neutralized with hydrochloric acid and filtered. The precipitate was thoroughly washed with hydrochloric acid-methanol to remove residual salts, and further purified by reprecipitation.

Table 1 shows the degree of saponification achieved for the polymer obtained in Example 1. (The degree of saponification was determined by measuring the infrared absorption spectrum of the obtained polymer and using the Lambert-Beer method based on the absorption of 1720tM-10carbo=,+1/.) Comparative Example 1 Acetone/Water-9515 P (VPiv) in the mixture of
was added in 2% portions, and KOH was added in an amount 1.2 times the mole of the ester, followed by stirring at room temperature for 72 hours. After the reaction, the polymer was neutralized with acetic acid, filtered, thoroughly washed with methanol, and purified by reprecipitation.

The infrared absorption spectrum of the obtained polymer was measured, and the degree of saponification was determined in the same manner as in Example 1.

The results are shown in Table 1.

Table 1 Figure 1 shows the infrared absorption spectrum chart of P(VPiv), and Figure 2 shows the infrared absorption spectrum chart of P(VPiv) obtained in Example 1.
FIG. 3 shows an infrared absorption spectrum chart of the reduced product by LiAlH4 of P(VPiv) obtained in Comparative Example 1.
Figure 4 shows an infrared absorption spectrum chart of an alkali saponified product of commercially available fully saponified PVA (
Saponification degree: 99.9 mol%) [■ Manufactured by Kuraray] Infrared absorption spectrum chart is shown. As is clear from Figure 2, the absorption of carbonyl at 1720 cm'' is due to LiAlH4.
In the reduced product, it disappeared almost completely, and the infrared absorption spectrum shown in FIG. 4 (control example) is similar to that of commercially available completely saponified PVA (degree of saponification 99.9 mol%) [manufactured by Kuraray].

On the other hand, as is clear from Figure 3, although the carbonyl absorption at 1720 cm' is weaker in the alkali saponified product, a considerable amount still remains, and P
(VPiv) is shown.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an infrared absorption spectrum chart of vinyl polypivalate [-P(VPiv)]. FIG. 2 was obtained in Example 1. L of P (VPiv)
It is an infrared absorption spectrum chart of a reduced product by iAlH4. FIG. 3 is an infrared absorption spectrum chart of the alkali saponified product of p(VPiv) obtained in Comparative Example 1. FIG. 4 is an infrared spectral chart of commercially available fully saponified PVA (saponification degree 99.9 mol%) [Kuraray Hibi Co., Ltd.] as a control example. Patent applicant RiRa Shi Co., Ltd.

Claims (4)

[Claims] (1) A novel method for producing a polyvinyl alcohol polymer, which comprises reducing a vinyl ester homopolymer or copolymer represented by general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・・・・
・・・・・・・・・・・・(I) (However, R_1, R
_2 and R_3 are each an alkyl group, and the total number of carbon atoms thereof is 3 or more and 12 or less. ) (2) The manufacturing method according to claim (1), wherein R_1=R_2=R_3=CH_3. (3) The production method according to claim (1), wherein the content of vinyl alcohol units in the polyvinyl alcohol polymer is 55 mol% or more. (4) The manufacturing method according to claim (1), wherein the reducing agent is lithium aluminum hydride.