JPH04335002A - Preparation of vinyl ester polymer and of vinyl alcohol polymer - Google Patents

Abstract

PURPOSE:To facilitate industrial production of a vinyl ester polymer and a vinyl alcohol polymer which have a high degree of polymerization and a high purity. CONSTITUTION:A process for producing a vinyl ester polymer which comprises polymerizing a vinyl ester by emulsion polymerization using a vinyl alcohol polymer as a dispersion stabilizer at -60 to 40 deg.C; and a process for effectively producing a vinyl alcohol polymer from the vinyl ester polymer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing vinyl ester polymers and a method for producing vinyl alcohol polymers. More specifically, the present invention relates to a method for producing a vinyl ester polymer with a high degree of polymerization by emulsion polymerization, and a method for producing a vinyl alcohol polymer with a high degree of polymerization using the vinyl ester polymer obtained by this method.

0002

BACKGROUND OF THE INVENTION Vinyl ester polymers, particularly vinyl acetate polymers, are widely used as base polymers for adhesives and paints, and are also extremely important as raw material resins for vinyl alcohol polymers. In addition, vinyl alcohol polymers have excellent interfacial and strength properties as one of the few crystalline water-soluble polymers, so they are used in paper processing agents, fiber processing agents, emulsion stabilizers, etc. First of all, it is well known that it occupies an important position as a raw material for vinylon film and vinylon fiber.

[0003] The upper limit of the polymerization degree of conventional vinyl alcohol polymers is 2000 because of processing characteristics and ease of handling, and because it is difficult to obtain a high degree of polymerization from the raw material vinyl acetate polymer. There were only about 3,000 special items. However, rapid advances in processing technology in recent years have made it possible to process polymers in the ultra-high degree of polymerization range, and are now succeeding in bringing out previously unknown physical properties. In the case of vinyl alcohol polymers, increasing the degree of polymerization not only improves physical properties in conventional applications, but also offers new possibilities in new fields such as high-strength fibers and highly durable polarizing films.

[0004] Polymers with a high degree of polymerization are generally obtained by polymerizing at low temperatures and slow polymerization rates, and some examples have been reported for vinyl acetate as well. [For example, A.
R. Shultz; J. Am. Chem.
Soc. , 76, 3422 (1954), G. M.
Burnett, M. H. George, H. W
．． Melville; J. Polym. Sci
．． , 16, 31 (1955), M. Matsumo
to, Y. Ohyanagi;J. Polym.
Sci. , 46, 148 (1960)] However, these methods are all bulk polymerization methods, and the polymerization system has an extremely high viscosity, making it difficult to stir, making it impossible to obtain a homogeneous polymer, and making it difficult to remove heat. It has the following problems. Therefore, it is considered that production on an industrial scale by these bulk polymerization methods is almost impossible.

A suspension polymerization method has been proposed as a method for overcoming these drawbacks of the bulk polymerization method (Japanese Patent Application Laid-Open No. 148209/1983). However, in systems with large chain transfer such as vinyl esters, it is essential to lower the polymerization temperature in order to increase the degree of polymerization. The polymerization rate must be very low.

Furthermore, as a method to overcome the drawbacks of these polymerization methods, the polymerization mechanism is different from bulk polymerization and suspension polymerization, and even when polymerization is performed at a relatively high polymerization rate, there are almost no problems with stirring and heat removal. , a low-temperature emulsion polymerization method capable of producing vinyl ester polymers and vinyl alcohol polymers with a high degree of polymerization has been proposed (Japanese Unexamined Patent Application Publication No. 1983-1991).
-37106).

However, in this low-temperature emulsion polymerization method, an emulsifier is used to stabilize the polymerization, but a reaction occurs between the emulsifier and the vinyl ester polymer, and the emulsifier is covalently bonded to the vinyl ester polymer. In some cases, the emulsifier is incorporated into the vinyl ester polymer during coalescence, or the emulsifier is mixed non-covalently into the vinyl ester polymer. A problem arises in that it is extremely difficult to completely remove the emulsifier from within. A soap-free polymerization method is known as a polymerization method that does not use an emulsifier. However, since this polymerization method does not use an emulsifier, the dispersibility of the emulsion particles produced is unstable, and agglomerates are likely to occur during emulsion polymerization. Alcohol-based polymers cannot be obtained. There is a problem.

[0008]

[Problems to be Solved by the Invention] The present invention relates to a method for producing a vinyl ester polymer by emulsion polymerization and a method for producing a vinyl alcohol polymer using the vinyl ester polymer. The object of the present invention is to provide a new production method that can easily obtain pure vinyl ester polymers and vinyl alcohol polymers with a high degree of polymerization and without emulsifiers on an industrial scale.

[0009]

[Means for Solving the Problems] As a result of extensive research into a manufacturing method that would allow vinyl ester polymers to be easily obtained on an industrial scale, the present inventors discovered that vinyl alcohol polymers can be used as dispersion stabilizers. It has been found that by emulsion polymerizing vinyl esters using the present invention, a pure vinyl ester polymer having a high degree of polymerization and containing no emulsifier can be obtained. Furthermore, it has been found that by saponifying the vinyl ester polymer obtained by the above method, a pure vinyl alcohol polymer having a high degree of polymerization and containing no emulsifier can be obtained. The present invention was completed based on this knowledge.

That is, the present invention provides a method for producing a vinyl ester polymer, which is characterized in that vinyl ester is emulsion polymerized at a temperature of -60 to 40°C using a vinyl alcohol polymer as a dispersion stabilizer. It is. The present invention also provides a method for producing a vinyl alcohol polymer, which comprises saponifying the vinyl ester polymer.

First, a method for producing a vinyl ester polymer by emulsion polymerization using a vinyl alcohol polymer as a dispersion stabilizer will be explained. When emulsion polymerizing vinyl esters, the polymerization temperature is preferably as low as possible in order to suppress chain transfer. However, since the growth rate constant also decreases as the temperature decreases, if the polymerization temperature is lowered too much, problems such as a decrease in the polymerization rate and increased susceptibility to the influence of oxygen occur. Therefore, the polymerization temperature needs to be -60 to 40°C, preferably -50 to 40°C, and -40 to 40°C.
0°C is more preferable, -30 to 40°C is even more preferable,
-30 to 30°C is most preferred.

[0012] When the polymerization temperature is lower than 0°C, it is necessary to prevent the aqueous phase as a dispersion medium from condensing, and the freezing point of water-soluble alcohols, glycols, glycerin, dimethyl sulfoxide, inorganic salts, etc. Addition of a depressant to the aqueous phase is essential. Specific examples of the freezing point depressant include methanol, ethanol, propanol, t-butanol, ethylene glycol, glycerin, dimethyl sulfoxide, lithium chloride, sodium chloride, calcium chloride, and the like. Considering the effects on the solubility of the vinyl alcohol polymer used as a dispersion stabilizer and the stability of the emulsion, as well as the post-treatment after polymerization and the saponification reaction of the vinyl ester polymer,
Methanol and dimethyl sulfoxide are most preferred. The amount of freezing point depressant added varies depending on the polymerization temperature, but the weight ratio of (water/freezing point depressant) is 100/0 to 50/
50 is preferable, more preferably 100/0 to 60/
It is 40.

The vinyl alcohol polymer used as a dispersion stabilizer has a temperature range of -60 to 40°C and (water/
It is preferable that the emulsion is dissolved in a ratio of 100/0 to 50/50 (freezing point depressant) and has the ability to stabilize the resulting emulsion and maintain the emulsion state. There are no particular restrictions on such vinyl alcohol polymers,
Polyvinyl alcohol consisting only of vinyl alcohol units, copolymers having vinyl alcohol units, block polymers containing polyvinyl alcohol as one component, etc. can be used. The degree of saponification of the vinyl ester of the vinyl alcohol polymer is usually 40 to 100 mol%, more preferably 60 to 100 mol%. There is no particular restriction on the average degree of polymerization of the vinyl alcohol polymer, but it is preferably 50 to 30,000, and 100 to 200.
00 is more preferable because it is easily available. The above vinyl alcohol polymers may be used alone or in combination. The amount of vinyl alcohol polymer added to the emulsion polymerization system varies depending on the amount of vinyl ester used, but is 0.5 to 30 parts by weight, preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the dispersion medium. parts, particularly preferably 1.0 to 1
It is 0 parts by weight. If the amount of vinyl alcohol polymer used is less than 0.5 parts by weight, it will be difficult to keep the vinyl ester polymer particles in the emulsion stable.
Agglomeration of particles of the polymer may occur. Also, if the amount of vinyl alcohol polymer used exceeds 30 parts by weight,
The viscosity of the emulsion polymerization system may become too high, and emulsion polymerization may not proceed uniformly, or the heat of polymerization may be insufficiently removed.

The amount of vinyl ester used is 50 to 300 parts by weight, preferably 7 to 300 parts by weight, per 100 parts by weight of the dispersion medium.
It is 5 to 280 parts by weight, particularly preferably 100 to 250 parts by weight. If the amount of vinyl ester used is less than 50 parts by weight, it is unfavorable from the viewpoint of productivity. If the amount of vinyl ester used exceeds 300 parts by weight, it will be difficult to keep the vinyl ester polymer particles in the emulsion stable, and agglomeration of the polymer particles may occur.

Regarding the initiator, since the method of the present invention involves polymerization at a low temperature as described above, a redox initiator that effectively generates radicals at a low temperature, especially a water-soluble redox initiator, is most effective. used. The redox initiator suitably used in the present invention includes (a) at least one oxidizing substance selected from hydroperoxides, peroxides, and peresters, and (b) one that undergoes one electron transfer. It consists of a metal ion capable of oxidation, and (c) a reducing substance, and is used as components (a) and (b), or in combination of components (a), (b), and (c). Specifically, the oxidizing substances that are component (a) include hydrogen peroxide, cumene hydroperoxide, t-butyl hydroperoxide, persulfate (
K, Na or ammonium salt), t-butyl peracetate,
Examples include t-butyl perbenzoate, and metal ions as component (b) include Fe2+, Cr2+, V2+, Ti3
+, Co2+, and Cu+, and examples of the reducing substance (c) include rongalite, l-ascorbic acid, and the like. Among them, hydrogen peroxide, persulfate (K, Na or ammonium salt), cumene hydroperoxide is the most preferred component (a), Fe2+ is the component (b), and Rongalit is the most preferred component (c). used.

[0016] When using these initiators, they should be used in such a way that component (b) or the sum of components (b) and (c) is always present in sufficient excess relative to component (a) during polymerization. is preferred from the viewpoint of controlling the polymerization rate and polymerization rate, but the amounts of components (a), (b) and (c) are not particularly limited.

The low-temperature emulsion polymerization of the present invention as described above has a lower radical concentration in the polymerization system than ordinary emulsion polymerization at high temperatures, so it is more susceptible to the effects of oxygen and impurities in the polymerization system. , particular care must be taken regarding their removal from the polymerization system before polymerization and their introduction into the polymerization system during polymerization. Therefore, the water, freezing point depressant, and vinyl ester used in the present invention must be sufficiently deoxidized before use, and the system must be purified to a purity of 99.9% or higher, preferably 99.99% or higher. It is preferable to substitute with nitrogen or argon gas. Furthermore, the vinyl ester is preferably purified by conventional methods before use.

Vinyl esters used in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and versatic acid. Vinyl etc. are mentioned, and when finally obtaining a vinyl alcohol polymer,
Particularly preferred is vinyl acetate.

It is also possible to copolymerize monomers that can be copolymerized with the above vinyl ester, and examples of these monomers include olefins such as ethylene, propylene, 1-butene, and isobutene, acrylic acid and its salts, Methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-acrylate
Acrylic acid esters such as butyl, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, methacrylic acid and its salts, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, methacrylic acid n-butyl, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate,
Methacrylic acid esters such as octadecyl methacrylate, acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid and its salts, acrylamide propyldimethylamine and its salts, or their salts. Quaternary salts, acrylamide derivatives such as N-methylolmethacrylamide and its derivatives, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts, or its quaternary salts, methacrylamide derivatives such as N-methylolmethacrylamide and its derivatives, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i
- Vinyl ethers such as propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether, nitriles such as acrylonitrile and methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl fluoride, and Vinyl halides such as vinylidene chloride, allyl compounds such as allyl acetate and allyl chloride, maleic acid and its salts or its esters, itaconic acid and its salts or its esters, vinyl silyl compounds such as vinyltrimethoxysilane, isopropenyl acetate, etc. can be mentioned.

The present invention provides a method for obtaining a vinyl ester polymer with a high degree of polymerization and a vinyl alcohol polymer with a high degree of polymerization. important, usually 10
~95%, preferably 20-90%, more preferably 30-85%. There is no particular restriction on the polymerization time, but 1 to 15 hours is preferred. The average polymerization rate is also important as it affects the degree of polymerization, and the average polymerization rate is 2
~30%/hour is preferred, and 3-20%/hour is more preferred.

Furthermore, the average particle size of the vinyl ester polymer particles is not particularly limited as it varies depending on the amount of vinyl alcohol polymer added to the system, but
The thickness is preferably .mu.m or less, particularly preferably 5 .mu.m or less. The number of particles of the vinyl ester polymer is also important as it affects the polymerization rate and degree of polymerization, and the number of particles per unit volume is preferably 1010 to 1015 particles/ml, more preferably 1011 to 5 x 1014 particles/ml. /ml. When the number of particles is less than 1010 particles/ml, the polymerization rate becomes extremely low in order to obtain vinyl ester polymers and vinyl alcohol polymers with a high degree of polymerization, which impairs the advantages of emulsion polymerization. It turns out.

According to the emulsion polymerization method of the present invention, a vinyl ester polymer that is pure and has a high degree of polymerization can be produced more easily than when an emulsifier is used as a dispersion stabilizer. The emulsion polymerization method of the present invention is particularly suitable for producing vinyl ester polymers having an average degree of polymerization of 4,000 or more, preferably 7,000 or more. Here, the average degree of polymerization of the vinyl ester polymer is as follows for polyvinyl acetate obtained by saponifying the vinyl ester polymer and then re-acetating it.
It is expressed as a viscosity average degree of polymerization (P) determined from the intrinsic viscosity [η] measured in acetone at 30° C. using the following formula. P=([η]×103/7.94)(1/0.62)

Next, a method for producing a vinyl alcohol polymer will be explained. It is of course possible to precipitate and recover the vinyl ester polymer emulsion produced by the emulsion polymerization of the present invention by ordinary coagulation or stripping, but when obtaining a vinyl alcohol polymer, the produced vinyl ester It is preferable to dissolve the emulsion of the vinyl ester polymer in a large amount of methanol or dimethyl sulfoxide containing an inhibitor, and remove unreacted vinyl ester by distillation to obtain a methanol or dimethyl sulfoxide solution of the vinyl ester polymer. . Although these solutions contain water, vinyl is produced through alcoholysis using sodium hydroxide, sodium methylate, or sodium ethylate as a catalyst, or acid decomposition using acids such as sulfuric acid, hydrochloric acid, or phosphoric acid as a catalyst. Alcohol-based polymers can be obtained. Further, the amount of the alkali catalyst or acid catalyst used in the saponification reaction and the temperature of the saponification reaction are not particularly limited, and the saponification reaction can be carried out in the same manner as conventional methods.

According to the above method, the average degree of polymerization is 400
A pure vinyl alcohol polymer containing no emulsifier of 0 or more, preferably 7000 or more can be easily produced. Here, the average degree of polymerization of the vinyl alcohol polymer is the viscosity average calculated from the intrinsic viscosity [η] measured at 30°C in acetone using the following formula for polyvinyl acetate obtained by reacetylating the vinyl alcohol polymer. Degree of polymerization (P
). P=([η]×103/7.94)(1/0.62)

[0025]

[Examples] The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited by these in any way. In addition, "%" and "parts" in the examples represent "% by weight" and "parts by weight", respectively, unless otherwise specified. The average particle size of the polymer emulsion was measured using a submicron particle system analyzer NICOMP Mo
It was measured using del 370 (manufactured by Hiac/Royco). The number of particles per unit volume was calculated from the measured average particle diameter and polymerization rate using the following formula. Number of particles (particles/ml) = 3Mx/4πr3 dHere, M is the amount of monomer (g), x is the polymerization rate from monomer to polymer, and r is the average particle diameter of the emulsion (cm).
) and d represent the specific gravity of the emulsion, respectively. Also,
The film properties were determined using Shimadzu Autograph DCS-100 model (
(manufactured by Shimadzu Corporation).

Example 1 Into a reactor equipped with a stirrer, a thermometer, a nitrogen inlet tube and a cooling tube, 1000 parts of ion-exchanged water, 1000 parts of vinyl acetate, and polyvinyl alcohol (degree of polymerization 500, degree of saponification 80) were added.
Mol% (PVA-405, manufactured by Kuraray Co., Ltd.) 100 parts,
Rongalit 1.05 parts and FeSO4 7H2
After adding 0.05 parts of O and boiling for 30 minutes, the mixture was cooled to 5°C while introducing nitrogen.
Polymerization was started while adding uniformly and continuously at 0 parts/hour. During polymerization, the system was sealed with nitrogen gas to prevent oxygen from entering. Polymerization rate 84.1% after 6.1 hours (maximum polymerization rate 1
7.0%/hour), the addition of the hydrogen peroxide solution was stopped and the polymerization was stopped. The average particle size of the obtained emulsion was measured and found to be 0.51 μm. The number of polyvinyl acetate particles per unit volume of the emulsion was 9.6 x 1012 particles/ml.

The emulsion obtained here was poured into a solution of 1 part of hydroxy nonmonomethyl ether in 35,000 parts of methanol at room temperature, and dissolved with stirring. After dissolution, unreacted vinyl acetate was removed while adding methanol under reduced pressure to obtain a methanol solution of polyvinyl acetate. Take a part of this methanol solution, prepare a methanol solution with a polyvinyl acetate concentration of 6%, and add [NaOH]
/ [VAc] (molar ratio) = 0.1 and saponification at a temperature of 40°C, resulting in a polyvinyl alcohol of 0.1
1 part in a mixture of 8 parts of acetic anhydride and 2 parts of pyridine at 105°C.
For polyvinyl acetate, which was reacetylated with occasional stirring for 20 hours, and repeatedly purified by reprecipitation in an acetone-ether and acetone-water system, the viscosity average degree of polymerization was determined from the intrinsic viscosity measured at 30°C in acetone. It was 16,000.

Next, using a methanol solution of polyvinyl acetate with a concentration of 6%, [NaOH]/[VAc] (molar ratio)
= 0.15 and a temperature of 40°C, and after deliquifying the obtained polyvinyl alcohol, the N used for saponification was
The same amount of NaOH as aOH was added, and the mixture was immersed in methanol and resaponified at 40° C. for 24 hours. Thereafter, it was washed with methanol, deliquified, and dried at 40°C to obtain polyvinyl alcohol. This polyvinyl alcohol has a saponification degree of 99.8
The average viscosity polymerization was determined from the intrinsic viscosity measured at 30°C in acetone for polyvinyl acetate, which was obtained by reacetylating this polyvinyl alcohol under the same conditions as above and repeating reprecipitation purification in the same manner as above. The degree was 16,000.

[0029] This polyvinyl alcohol was dissolved in distilled water under heating at 95°C to obtain a polyvinyl alcohol aqueous solution having a concentration of 4%. The aqueous solution was cast onto a polyethylene terephthalate film and air-dried at room temperature to form a film. Further, the film was uniaxially stretched 5 times at 180°C, and then stretched 3 times at 180°C under a constant length in a nitrogen gas atmosphere.
By heat setting for a minute, a polyvinyl alcohol film with a thickness of 20 μm was obtained. The film was heated to 65°C at 20°C.
After adjusting the humidity to %RH, the physical properties of the film were measured using an autograph at a tensile speed of 100 mm/min and a sample length of 50 mm. The tensile strength was 42 kg/mm2, and the elongation was 5.
0% and Young's modulus of 250 kg/mm2.

Comparative Example 1 Polymerization, saponification and purification were carried out in the same manner as in Example 1, except that the polymerization conditions were changed to those shown below. The degree of polymerization was measured. As a dispersion stabilizer charged into the reactor, the emulsifier polyoxyethylene [POE (40)] nonylphenyl ether (Nonipol 400, manufactured by Sanyo Chemical Co., Ltd.) was used instead of polyvinyl alcohol.
40 parts, Rongalit 1.25 parts and FeSO4 ・
The amount was changed to 0.12 parts of 7H2O. The following is Example 1
Polymerization was started in the same manner as above. Polymerization rate 6 after 3.5 hours
Polymerization was stopped when the polymerization rate reached 0.2% (maximum polymerization rate 17.2%/hr). The average particle diameter of the obtained emulsion was 0.28 μm, and the number of polyvinyl acetate particles per unit volume of the emulsion was 4.2×10 13 particles/ml.

Using the obtained emulsion, saponification and reacetylation were carried out under the same conditions as in Example 1 to obtain purified polyvinyl acetate. The viscosity average degree of polymerization of the polyvinyl acetate was determined from the intrinsic viscosity measured in acetone at 30° C. and was 14,000. Next, the methanol solution of polyvinyl acetate was saponified, re-saponified, washed, and dried under the same conditions as in Example 1 to obtain polyvinyl alcohol. This polyvinyl alcohol has a saponification degree of 99.
The viscosity average degree of polymerization was determined from the intrinsic viscosity measured at 30°C in acetone for polyvinyl acetate obtained by re-acetating this polyvinyl alcohol under the same conditions as above and repeating reprecipitation purification. It was 14,000.

Using this polyvinyl alcohol, a polyvinyl alcohol film having a thickness of 21 μm was obtained in the same manner as in Example 1. After conditioning the film to 65% RH at 20°C, the physical properties of the film were measured using an autograph in the same manner as in Example 1, and the tensile strength was 25.2 kg/
mm2, elongation 44% and Young's modulus 181kg/mm
It was 2.

Although emulsion polymerization was carried out under almost the same polymerization conditions as described above, the polyvinyl alcohol film obtained by emulsion polymerization using the emulsifier shown in Comparative Example 1 had a tensile strength of 25.2 kg/ mm2, elongation 4
4% and Young's modulus of 181 kg/mm2, whereas the polyvinyl alcohol film obtained by emulsion polymerization using polyvinyl alcohol as a dispersant shown in Example 1 had a tensile strength of 42 kg/mm2 and an elongation of 50%.
and Young's modulus of 250 kg/mm2, which indicates that the film performance is very excellent.

Example 2 Into the same reactor as in Example 1, 1000 parts of ion-exchanged water,
1500 parts of vinyl acetate, polyvinyl alcohol (degree of polymerization 1700, degree of saponification 98.5 mol% (PVA-117,
60 parts (manufactured by Kuraray Co., Ltd.), 0.75 parts of Rongalit, and 0.04 parts of FeSO4 7H2 O were boiled, cooled to 40°C, and prepared using separately degassed ion-exchanged water. % potassium persulfate aqueous solution was uniformly and continuously added at a rate of 5 parts/hr, polymerization was started. Polymerization rate 76.8% after 3.0 hours (maximum polymerization rate 2
8.0%/hr), the addition of the potassium persulfate aqueous solution was stopped, and the polymerization was stopped. The average particle diameter of the obtained emulsion was 0.92 μm, and the number of polyvinyl acetate particles per unit volume of the emulsion was 2.3×10 12 particles/ml.

The emulsion obtained here was poured into a solution of 0.6 part of hydroquinone monomethyl ether in 15,000 parts of dimethyl sulfoxide at room temperature, and dissolved with stirring. After dissolution, unreacted vinyl acetate was removed at 70° C. while adding dimethyl sulfoxide under reduced pressure to obtain a dimethyl sulfoxide solution of polyvinyl acetate. A portion of this solution was taken and poured into distilled water to precipitate polyvinyl acetate. After repeating reprecipitation purification several times with acetone-n-hexane, it was poured into distilled water and purified by boiling. Polyvinyl acetate was obtained. The polyvinyl acetate was dissolved in methanol to prepare a methanol solution of polyvinyl acetate with a concentration of 10%, and saponified under the conditions of [NaOH]/[VAc] (molar ratio) = 0.10 and a temperature of 40°C, and the polyvinyl acetate was dissolved in methanol. Got alcohol. The polyvinyl alcohol was re-acetylated and purified under the same conditions as in Example 1 to obtain polyvinyl acetate. The viscosity average degree of polymerization of the polyvinyl acetate is 4,
It was 200.

Next, using a 10% dimethyl sulfoxide solution of polyvinyl acetate, [NaOH]/[VAc
] (Molar ratio) = 0.15, the resulting polyvinyl alcohol was saponified under the conditions of a temperature of 40°C and a nitrogen atmosphere, and the resulting polyvinyl alcohol was deliquified, and then re-saponified, washed with methanol, and dried in the same manner as in Example 1 to obtain polyvinyl alcohol. Got alcohol. The polyvinyl alcohol has a saponification degree of 99.8 mol%, and the viscosity average degree of polymerization was measured for polyvinyl acetate that had been repeatedly subjected to reacetylation and reprecipitation purification in the same manner as above.
It was 200.

Using this polyvinyl alcohol, 95
It was dissolved in distilled water under heating at 0.degree. C. to obtain an aqueous polyvinyl alcohol solution with a concentration of 7%. Using this aqueous solution, a polyvinyl alcohol film with a thickness of 20 μm was obtained in the same manner as in Example 1. After conditioning the film to 65% RH at 20°C, the physical properties of the film were measured using an autograph in the same manner as in Example 1, and the tensile strength was 37.6 kg/mm2.
, elongation was 48%, and Young's modulus was 230 kg/mm2.

Comparative Example 2 Polymerization, saponification and purification were carried out in the same manner as in Example 2, except that the polymerization conditions were changed as shown below, and the saponification degree and viscosity average of the obtained polyvinyl acetate and polyvinyl alcohol The degree of polymerization was measured. As a dispersion stabilizer charged in the reactor, the emulsifier polyoxyethylene [POE (35)] nonylphenyl ether sodium sulfate (Eleminol ES-70) was used instead of polyvinyl alcohol.
, 50 parts of an 80% aqueous solution (manufactured by Sanyo Chemical Co., Ltd.) and 0.90 parts of Rongalit, FeSO4 7H2 O 0
．． Polymerization was started in the same manner as in Example 2, except that 0.022% potassium persulfate aqueous solution was added uniformly and continuously at 5 parts/hr. After 4.0 hours, the polymerization was stopped when the polymerization rate reached 77.8% (maximum polymerization rate 21.0%/hr). The average particle diameter of the resulting emulsion was measured to be 0.382 μm, and the number of polyvinyl acetate particles per unit volume of the emulsion was 3.2×
It was 1013 pieces/ml.

Using the obtained emulsion, Example 2
Saponification and reacetylation were performed under the same conditions as above to obtain purified polyvinyl acetate. Regarding the polyvinyl acetate,
The viscosity average degree of polymerization determined from the intrinsic viscosity measured at 30° C. in acetone was 3,700. Next, a dimethyl sulfoxide solution of polyvinyl acetate was saponified, re-saponified, washed with methanol and dried under the same conditions as in Example 2 to obtain polyvinyl alcohol. The degree of saponification of this polyvinyl alcohol was 99.8 mol%, and polyvinyl acetate was obtained by re-acetylating the polyvinyl alcohol under the same conditions as above and repeating reprecipitation purification.
The viscosity average degree of polymerization determined from the intrinsic viscosity measured at 0°C is 3
,700.

Using this polyvinyl alcohol, a polyvinyl alcohol film having a thickness of 21 μm was obtained in the same manner as in Example 2. After conditioning the film to 65% RH at 20°C, the physical properties of the film were measured using an autograph in the same manner as in Example 2, and the tensile strength was 21.1 kg/
mm2, elongation 38% and Young's modulus 132kg/mm
It was 2.

Examples 3 to 6 Polymerization, saponification, washing, etc. were carried out in the same manner as in Example 1, except that the emulsion polymerization conditions were changed to those shown in Table 1. Furthermore, using the obtained polyvinyl alcohol, the physical properties of the polyvinyl alcohol film were measured in the same manner as in Example 1. The conditions and results of emulsion polymerization are shown in Table 1, and the physical properties of the polyvinyl alcohol film are shown in Table 2.
Shown in the table.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

Comparative Example 13 Polymerization, saponification and purification were carried out in the same manner as in Example 1, except that the polymerization conditions were changed as shown below, and the saponification degree and viscosity average polymerization of the obtained polyvinyl acetate and polyvinyl alcohol The degree was measured. Instead of polyvinyl alcohol as a dispersion stabilizer charged in the reactor, the emulsifier polyoxyethylene [POE (30)] sodium lauryl ether sulfate (Trax K-300, NOF
40 parts of a 35% aqueous solution of Rongalit 1.40
% and 0.15 parts of FeSO4 7H2 O, further added 360 parts of methanol, cooled to -20°C, and uniformly and continuously added 0.020% hydrogen peroxide solution at 10 parts/hr. Polymerization was started in the same manner as in Example 1. After 6.0 hours, the polymerization was stopped when the polymerization rate reached 51.2% (maximum polymerization rate 9.1%/hr). The average particle size of the obtained emulsion was 0.317 μm
The number of polyvinyl acetate particles per unit volume of the emulsion was 1.7 x 1013 particles/ml. The emulsion obtained here was mixed with methanol 7000 ml at room temperature.
The mixture was poured into a solution of 1 part of hydroquinone monomethyl ether and dissolved with stirring. The viscosity average degree of polymerization of the polyvinyl acetate was 24,000. Furthermore, the degree of saponification of polyvinyl alcohol obtained by saponifying the polyvinyl acetate is 99.8 mol%, and the viscosity average degree of polymerization is 24.00.
It was 0.

Using this polyvinyl alcohol, 95
It was dissolved in distilled water under heating at 0.degree. C. to obtain an aqueous polyvinyl alcohol solution with a concentration of 3.5%. Using this aqueous solution, a polyvinyl alcohol film with a thickness of 20 μm was obtained in the same manner as in Example 1. After conditioning the film to 65% RH at 20°C, the physical properties of the film were measured using an autograph in the same manner as in Example 1, and the tensile strength was 26.3 kg/mm2.
, elongation was 45%, and Young's modulus was 190 kg/mm2. Compared to Examples 4 and 5, in Comparative Example 3, in which an emulsifier was used as a dispersion stabilizer, the obtained polyvinyl alcohol film had inferior film properties.

[0049]

Effects of the Invention As is clear from the above examples, a method for producing a vinyl ester polymer by emulsion polymerization using the vinyl alcohol polymer of the present invention as a dispersion stabilizer, and a method for producing a vinyl ester polymer obtained by the emulsion polymerization. Compared to conventional methods, the method for producing vinyl alcohol polymers using polymers produces vinyl ester polymers and vinyl alcohol polymers with a higher degree of polymerization, and is a pure vinyl ester polymer that does not contain an emulsifier. This is a new production method that allows polymers and vinyl alcohol polymers to be easily obtained on an industrial scale. Surprisingly, the vinyl alcohol polymer film obtained by the production method of the present invention has very excellent film physical properties. It is not clear why this vinyl alcohol-based polymer has such excellent film properties, but in low-temperature emulsion polymerization using an emulsifier,
During polymerization, a reaction occurs between the emulsifier and the vinyl ester polymer, and the emulsifier is incorporated into the vinyl ester polymer, or the emulsifier used is mixed into the vinyl ester polymer. It is presumed that this is because the emulsifier cannot be completely removed from the vinyl ester polymer and the vinyl alcohol polymer. The vinyl alcohol polymer obtained in the present invention can be used as a paper processing agent by taking advantage of the above characteristics.
Including textile processing agents and emulsion stabilizers,
It has extremely high industrial value, as it is used in new fields such as high-strength fibers and highly durable films.

Claims (4)

[Claims] 1. A method for producing a vinyl ester polymer, which comprises emulsion polymerizing a vinyl ester at a temperature of -60 to 40°C using a vinyl alcohol polymer as a dispersion stabilizer. 2. The method for producing a vinyl ester polymer according to claim 1, wherein the vinyl alcohol polymer has an average degree of polymerization of 4,000 or more. 3. A method for producing a vinyl alcohol polymer, which comprises saponifying the vinyl ester polymer obtained by the method according to claim 1. 4. The method for producing a vinyl alcohol polymer according to claim 3, wherein the vinyl alcohol polymer has an average degree of polymerization of 4,000 or more.