JPH11147913A - Production of polyvinyl alcohol of high syndiotacticity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyvinyl alcohol having high syndiotacticity and good quality, properties, etc., from a vinyl ester more simply by polymerizing a vinyl ester in a specified fluorine-containing branched alcohol and saponifying the obtained polymer. SOLUTION: A vinyl ester is polymerized in a fluorine-containing branched alcohol solvent represented by the formula (wherein R<1> and R<2> are each a fluorohydrocarbon group which may be partially substituted by chlorine atoms; and R<3> is a hydrocarbon group, a fluorine atom, a chlorine atom, or a hydrogen atom) and having a pKa of below 4 or above, and the obtained polymer is saponified to obtain a polyvinyl alcohol having a syndiotacticity (diad) of 58% or above. It is desirable that R<1> , R<2> , an R<3> in the formula are each a 1-3C fluorohydrocarbon group. The fl uorine-containing branched alcohol is desirably perfluoro-tert-butanol, for example. The vinyl ester used is desirably vinyl acetate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The invention of this application relates to polyvinyl alcohol (hereinafter referred to as PVA) having a high syndiotacticity.
). More specifically, the invention of this application relates to a high syndiotactic PV comprising polymerizing a vinyl ester, in particular vinyl acetate, in a fluorine-containing branched alcohol and then saponifying it.
A relates to a method for producing A.

[0002]

2. Description of the Related Art In general, PVA is produced by saponifying a polyvinyl ester obtained by polymerization of an aliphatic vinyl ester, particularly, polyvinyl acetate with an alkali catalyst. It is well known that the physical properties of PVA greatly change due to the stereoregularity of the side chain hydroxyl group. That is, the higher the degree of isotacticity or syndiotacticity, the higher the crystallinity of PVA, and the higher the heat resistance and strength of molded products such as fibers and films. In particular, the increase in syndiotacticity leads to an increase in intermolecular hydrogen bonds, so that the physical properties are dramatically improved.

Generally, the stereoregularity of PVA obtained from polyvinyl acetate is as low as about 53% for syndiotacticity (dual), and the tacticity does not change much even when the polymerization solvent or polymerization temperature is changed. Have been. As a method for obtaining PVA having a high syndiotacticity, a method of polymerizing vinyl trifluoroacetate or bulky pivalate having a polar group, followed by saponification is known. However, not only are all monomers more expensive than vinyl acetate, but also the former vinyl trifluoroacetate is liable to be decomposed even by a very small amount of water, and has a problem of lack of storage stability. In the latter case, the obtained polyvinyl pivalate is difficult to be saponified, and the reaction is usually carried out under severe alkaline conditions. Therefore, there is a problem that the PVA is colored by impurities such as trace amounts of oxygen in the reaction system. Therefore, more preferably, there is a strong demand for the establishment of a method for producing highly syndiotactic PVA from vinyl acetate or the like which is currently generally used.

Until now, various studies have been made on the stereoregularity of PVA obtained by solution polymerization of vinyl acetate (for example, J. Polym. Sci., Part A-1, Vol. 4, No. 64).
9, 1966, and Makromol. Chem., 14
4, p. 29, 1971,
36, 557, 1979). However,
Even if the polymerization temperature and the polymerization solvent are variously changed, the tacticity hardly changes. As an example of a slight increase in syndiotacticity, when vinyl acetate is polymerized in phenol, syndiotacticity (dual) 56% PV
A is reported to be obtained (J. Polym. Sci., Part
A, 24, 3225, 1986). But,
Not only is syndiotacticity insufficient, but also the polymerization rate is low in an aromatic solvent, and the degree of polymerization is considerably reduced due to frequent chain transfer.

[0005]

SUMMARY OF THE INVENTION The invention of this application has been made to solve the above-mentioned problems of the prior art, and has been made simpler and has been made easier by using generally used vinyl acetate and the like. It is an object of the present invention to provide a method for producing PVA having high syndiotacticity and good quality and physical properties from a vinyl ester of the above.

[0006]

In order to solve the above-mentioned problems, the present application first provides a first invention as follows.

[0007]

Embedded image

(Wherein, R ¹ and R ² each represent a fluorinated hydrocarbon group which may be partially substituted with a chlorine atom, and R ³ represents a hydrocarbon group or a fluorinated hydrocarbon group. ,
In which a vinyl ester is polymerized in a fluorine-containing branched alcohol solvent having a pKa of 4 or more and less than 10, and then saponified. Provided is a method for producing polyvinyl alcohol having a syndiotacticity (duplex) of 58% or more.

This application relates to the first invention.
Then, as a second invention, R¹, R ^TwoAnd R^ThreeBut each
Each method is a fluorinated hydrocarbon group having 1 to 3 carbon atoms,
As a third invention, a fluorine-containing branched alcohol is
A process which is luoro-tert-butanol;
As the invention of the above, the vinyl ester is a vinyl acetate
A method is also provided.

[0010]

Embodiments of the present invention will be described below in detail. First, the fluorine-containing branched alcohol represented by the above formula will be described. In the formula, R ¹ and R ² each have a hydrogen atom bonded to a carbon atom of a hydrocarbon group partially or wholly substituted with a fluorine atom. Or a chlorinated fluorinated hydrocarbon group in which part of the hydrogen atoms is replaced by chlorine atoms and at least one or more fluorine atoms are bonded to carbon atoms.

The number of carbon atoms at this time may be arbitrarily selected, but from the viewpoint of easy synthesis and availability, stability and selectivity of the polymerization reaction, generally 10 or less, and more preferably 6 or less. It is appropriate to use the following as a guide, and more preferably, the carbon number is 1 to 3. The case where R ³ is a hydrocarbon group or a fluorinated hydrocarbon group is also considered as the same as described above.

Illustrative fluorine-containing branched alcohols having R ¹ , R ² and R ³ are, for example, fluorine-containing branched alcohols such as perfluoro-tert-butanol, hexafluoro-2-methylisopropanol,
Hexafluoroisopropanol, hexafluoro-2
-Phenylisopropanol, chlorooctafluoro-
tert-butanol, hexafluoro-2-trichloromethylisopropanol, and the like.

Incidentally, the pKa of the fluorine-containing branched alcohol used in the present invention must be in the range of 4 to 10, and methanol (pKa = 16), t
In alcohols having a low degree of substitution of fluorine, such as ert-butanol (pKa = 19) and trifluoroethanol (pKa = 12.4), and having a pKa of 10 or more, the hydrogen bonding strength with the side chain carbonyl group is weak, so that tacticity is low. Does not change much. On the other hand, acetic acid having an appropriate pKa (pKa
= 4.8) or bulky pivalic acid (pKa = 5.0) as a solvent does not significantly change tacticity. This is because hydrogen bonds between the carboxylic acids are possible and the hydrogen bonds with the carbonyl group of the monomer side chain are reduced.In addition, these carboxylic acids have insufficient bulk including electrostatic repulsion. It is estimated to be. Conversely, if the pKa is too small,
As in the case of trifluoroacetic acid (pKa = 0.23), there is a possibility of reacting with the monomer, which is inappropriate.
Therefore, as the fluorine-containing branched alcohol in the present invention, perfluoro-tert-butanol (pKa)
PKa such as chlorooctafluoro-tert-butanol (pKa = 5.3), hexafluoro-2-methylisopropanol (pKa = 9.6), hexafluoroisopropanol (pKa = 9.3), and the like. Is 4
To 10 are suitable.

As the polymerization initiator used in the polymerization reaction of the present invention, a radical polymerization initiator such as an azo compound and a peroxide can be used. In order to accelerate the polymerization reaction, a sensitizer may be added or ultraviolet light may be irradiated. The polymerization temperature is preferably in the range of -100C to 60C. If the polymerization temperature is too high, the syndiotacticity decreases, which is not preferable. On the other hand, if the polymerization temperature is too low, the polymerization reactivity is extremely reduced and productivity is lacking, which is not preferable.

As the vinyl ester of the monomer, vinyl acetate is typically shown. However, in the present invention, other than vinyl acetate, various carboxylic acid vinyl ester compounds may be used without being limited thereto.
In the polymerization of a vinyl ester in a fluorine-containing branched alcohol, monomers copolymerizable with the vinyl ester, for example, α-olefins such as ethylene, propylene, and isobutene, acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid , A small amount of unsaturated acids such as maleic anhydride or salts thereof or mono- or dialkyl esters, acrylonitrile, methacrylonitriles, acrylamide, methacrylamides, vinyl ethers, vinyl chloride, vinylidene chloride, vinyl sulfonic acid or salts thereof It is also possible to make it.

The amount of the above-mentioned fluorine-containing branched alcohol used in the polymerization of vinyl ester is about 10 to 90% by volume, preferably about 30 to 80% by volume. The PVA of the present invention is produced by saponifying a polyvinyl ester obtained by polymerization. The saponification method and its conditions are not particularly limited, and an alcohol solution of the polyvinyl ester is converted into an alkali solution such as sodium hydroxide and potassium hydroxide. Can be saponified by a known method as a catalyst.

Although it is not clear why PVA having high syndiotacticity can be obtained by polymerizing a vinyl ester, particularly vinyl acetate in a fluorine-containing branched alcohol solvent as in the present invention, it has an appropriate pKa. This enables relatively strong hydrogen bonding with the side chain carbonyl group, and further increases the apparent bulkiness of the side chain due to the synergistic effect of both the steric repulsion effect and the electrostatic repulsion effect of the branched fluorocarbon group, It is presumed that it had an advantageous effect on syndiotactic polymerization. Although the fluorine-containing branched alcohol solvent used is somewhat expensive, it can be recovered and reused, which is an advantage over the longer term than synthesizing PVA from a special vinyl ester other than vinyl acetate.

According to the method of the present invention, PVA having a syndiotacticity (duplet) of 58% or more even from vinyl acetate
It became possible to obtain. The resulting PVA is suitable for high-strength high-modulus materials, high-heat-resistant materials, and the like.

[0019]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The measuring methods used in the examples and comparative examples are as follows. <Syndiotacticity (two twins)> 400 MHz NM
Proton NMR of PVA by R instrument (Varian)
Is measured to determine the proportion (%) of triads (mm / mr / rr), and from the following formula, syndiotacticity (dual) (%)
Was calculated.

Syndiotacticity (duplex) = rr + (mr / 2) <degree of polymerization> column (TSKgelGMHH, manufactured by Tosoh Corporation)
Gel permeation chromatograph (manufactured by JASCO Corporation) equipped with RH and G3000HHR) and a differential refractometer (manufactured by JASCO Corporation, RI-930), number average molecular weight of polyvinyl ester in a tetrahydrofuran solvent at 40 ° C. Was calculated in terms of polystyrene, and the degree of polymerization was calculated by dividing each by the molecular weight of the monomer. Example 1 12 parts by weight of vinyl acetate (2.2 mol / L), 88 parts by weight of perfluoro-tert-butanol (80 vol.
%), 1.6 parts by weight (0.15 mol / L) of 2,2'-azobisisobutyronitrile as a polymerization initiator was added,
Polymerization was performed at 40 ° C. for 3 hours under a nitrogen atmosphere. The degree of polymerization of the polyvinyl acetate obtained by reprecipitation in ether was determined by gel permeation chromatography. Also, polyvinyl acetate is dissolved in methanol and alkali-saponified to obtain PVA.
The syndiotacticity (duplet) was determined from the proton NMR measurement of. The results are shown in Table 1. Example 2 The same composition as in Example 1 was used, and polymerization was carried out at 0 ° C. for 48 hours under ultraviolet irradiation by a high-pressure mercury lamp. The degree of polymerization and syndiotacticity (duplex) were determined in the same manner as in Example 1. The results are shown in Table 1. Example 3 12 parts by weight of vinyl acetate (2.2 mol / L), 88 parts by weight of perfluoro-tert-butanol (80 vol.
%), 1.8 parts by weight (0.15 mol / L) of tributyl boron as a polymerization initiator was added, air was introduced into the reaction system, and polymerization was carried out at -78 ° C for 72 hours. The degree of polymerization and syndiotacticity (duplex) were determined in the same manner as in Example 1. The results are shown in Table 1. Example 4 36 parts by weight of vinyl acetate (5.4 mol / L), 64 parts by weight of hexafluoro-tert-butanol (50 vol.
%), 1.9 parts by weight (0.15 mol / L) of 2,2'-azobisisobutyronitrile as a polymerization initiator was added,
Polymerization was carried out at 20 ° C. for 4 hours under irradiation with ultraviolet light from a high-pressure mercury lamp. The degree of polymerization and syndiotacticity (duplex) were determined in the same manner as in Example 1. The results are shown in Table 1. Example 5 To 13 parts by weight of vinyl acetate (2.2 mol / L) and 87 parts by weight of hexafluoroisopropanol (80 vol%), 1.7 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator (0 parts by weight) were added. .15 mol / L) and polymerized at 20 ° C. for 8 hours under irradiation of ultraviolet rays by a high-pressure mercury lamp. The degree of polymerization and syndiotacticity (duplex) were determined in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 1 23 parts by weight of vinyl acetate (2.2 mol / L) and 77 parts by weight of methanol (80 vol%)
3 'parts by weight of 2'-azobisisobutyronitrile (0.1
(5 mol / L) and polymerized at 20 ° C. for 24 hours under ultraviolet irradiation from a high-pressure mercury lamp. The degree of polymerization and syndiotacticity (duplex) were determined in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 2 2,2'-azobisisobutyronitrile was used as a polymerization initiator in 15 parts by weight (2.2 mol / L) of vinyl acetate and 85 parts by weight (80 vol%) of trifluoroethanol.
9 parts by weight (0.15 mol / L) was added, and polymerization was carried out at 20 ° C. for 24 hours under ultraviolet irradiation by a high-pressure mercury lamp. The degree of polymerization and syndiotacticity (duplex) were determined in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 3 18 parts by weight of vinyl acetate (2.2 mol / L) and 82 parts by weight of phenol (80 vol%) were mixed by heating at 60 ° C.
2.4 parts by weight (0.15 mol / L) of 2,2'-azobisisobutyronitrile was added thereto as a polymerization initiator,
Polymerization was performed at 60 ° C. for 24 hours. The degree of polymerization and syndiotacticity (duplex) were determined in the same manner as in Example 1. The results are shown in Table 1.

[0021]

[Table 1]

[0022]

As described in detail above, according to the invention of this application, PVA having a high syndiotacticity is obtained from vinyl esters, especially vinyl acetate, under industrially advantageous conditions.
Can be manufactured. These are useful for high-strength high-modulus materials, heat-resistant materials, and the like.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Mitsuo Sawamoto, Inventor 920-23, 920-23, Haramachi, Shizuichi, Sakyo-ku, Kyoto-shi, Kyoto (72) Inventor Hiroshi Nakajima 23 Uji Kozakura, Uji-shi, Kyoto Unitika's Central Research Laboratory ( 72) Inventor Kazutoshi Terada 2045-1, Sakurazu, Kurashiki-shi, Okayama Pref.Kura Rekurashiki Research Laboratories Co., Ltd. (72) Inventor Daiji Ida Yoshida Honcho, Sakyo-ku, Kyoto-shi, Kyoto Prefecture Graduate School of Engineering, Kyoto University (72) Inventor Tetsuya Asahi 1-8, Kasumi, Yokkaichi-shi, Mie Prefecture Tosoh Corporation Yokkaichi Research Laboratory (72) Inventor Shoka Oki 1-8, Kasumi, Yokkaichi-shi, Mie Prefecture Yokkaichi Research Center (72) Inventor Yoshimichi Okano Aboshi Himeji, Hyogo Prefecture (12) Inventor Masamichi Nishimura 1239 Shinzai-ku, Himeji-shi, Hyogo Iseru Chemical Industry Co., Ltd. Research Institute in

Claims (4)

[Claims] 1. The following formula: (Wherein, R ¹ and R ² each represent a fluorinated hydrocarbon group, a part of which may be substituted with a chlorine atom;
³ is a hydrocarbon group, a fluorinated hydrocarbon group, a fluorine atom,
Represents a chlorine atom or a hydrogen atom), and
A method for producing a polyvinyl alcohol having a syndiotacticity (duplex) of 58% or more, comprising polymerizing a vinyl ester in a fluorine-containing branched alcohol solvent having a pKa of 4 or more and less than 10 and then saponifying the vinyl ester. . 2. The method according to claim ¹ , wherein R ¹ , R ² and R ³ are each a fluorinated hydrocarbon group having 1 to 3 carbon atoms. 3. The method according to claim 1, wherein the fluorine-containing branched alcohol is perfluoro-tert-butanol. 4. The method according to claim 1, wherein the vinyl ester is vinyl acetate.