JPH09249710A - Production of modified polyvinyl alcohol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a modified polyvinyl alcohol which can enhance the conversion of a vinyl compd. and is less likely to cause coloration of the product and produce by-products by adding a specified catalyst to powdery polyvinyl alcohol to prepare alcoholated polyvinyl alcohol, adding a vinyl compd. to this product, and subjecting the mixture to the Michael addition under soldi-liq. reaction conditions. SOLUTION: This process comprises adding a liq. basic catalyst to a powdery polyvinyl alcohol to produce an alcoholated polyvinyl alcohol, adding a vinyl compd. to the alcoholated polyvinyl alcohol, and subjecting the mixture to the Michael addition under solid-liq. reaction conditions. In this process, pref., a solvent insoluble in polyvinyl alcohol is added to the reaction system. Still pref., the reaction is conducted in a nitrogen atmosphere.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a modified polyvinyl alcohol (hereinafter abbreviated as “PVA”), and more particularly to a method for producing a modified PVA by subjecting PVA to a Michael addition reaction with a vinyl compound.

[0002]

PRIOR ART AND PROBLEMS TO BE SOLVED BY THE INVENTION Modified PV
As a method for producing A, for example, “Industrial Chemistry Magazine”, No. 6
Volume 3, Issue 2 (1960) Pages 142-145 and USP
5, 104, 933 and the like are known. All of these are methods of causing a Michael addition reaction in an aqueous solution of PVA.

In order to obtain powdered modified PVA by such a conventional technique, it is necessary to remove water as a solvent by distillation or to purify with a large amount of methanol or isopropyl alcohol, which is industrially necessary. It is very costly and disadvantageous.

Further, since the reaction is carried out at a low concentration, the reaction rate (effective utilization rate of vinyl compound) is low. For example, the contents are described in "Industrial Chemistry Magazine" Vol. 63, No. 2 (1960), pp. 142-145. According to the results, the reaction rate is less than 20% even after reacting for 15 hours. The modification rate at this time is 18 mol%.

On the other hand, JP-A-7-70230 describes a method of reacting PVA with a Michael-addable monomer under solid phase conditions. In this method, in order to keep the amount of solvent used throughout the reaction process to a minimum, the solvent containing the monomer is first spray added in an amount such that the PVA does not form a slurry and does not dissolve. The PVA is allowed to swell and then the basic catalyst is added by spraying.

As described above, when the monomer and the solvent are added before the basic catalyst, the degree of swelling of PVA increases, but the method of adding the drug is limited to spray addition. That is, when the powder PVA is stirred by a ribbon blender or the like and the monomer and the solvent are added by ordinary dropping, powder PVA granules are produced, and as a result, the heterogeneity of the reaction is promoted. This is because the particle size distribution of the product is also adversely affected.

When the reaction is carried out in an atmosphere of nitrogen or the like in order to prevent product coloring due to oxygen, if a monomer is added first, a polymerization reaction occurs in part before the basic catalyst is added. Not only the reaction rate of the Michael addition is lowered, but also the physical properties of the final product may be adversely affected.

Further, in JP-A-7-70230, the saponification degree is 87 to 89 in order to increase the swelling degree of PVA.
Although the use of mol% PVA is recommended, on the other hand, when such PVA is used, a saponification reaction by a basic catalyst occurs, so that there is a problem that by-production of sodium acetate is unavoidable.

The present invention has been made in view of the above, and provides a method for producing a modified PVA, which can mass-produce modified PVA and a powdered product thereof at a low cost, and which solves the above-mentioned problems of coloring and by-products. is there.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, after adding a liquid basic catalyst to powdered PVA, vinyl-vinyl alcohol was added under solid-liquid reaction conditions. It was found that the reaction rate of the vinyl compound can be increased by the Michael addition reaction of the compound, and the problems of coloring the product and the formation of by-products can be solved.
The present invention has been completed.

That is, in the method for producing a modified PVA according to claim 1, (1) a liquid basic catalyst is added to powdered polyvinyl alcohol to produce an alcoholated polyvinyl alcohol, and (2) this alcoholated polyvinyl alcohol. A vinyl compound is added to the mixture and a Michael addition reaction is performed under solid-liquid reaction conditions.

The method for producing a modified PVA according to claim 2 is
The method according to claim 1, wherein a PVA insoluble solvent is added to the reaction system.

A method for producing a modified PVA according to claim 3 is
The method according to claim 1 or 2, wherein the reaction is performed in a nitrogen atmosphere.

The method for producing the modified PVA according to claim 4 is:
The method according to any one of claims 1 to 3, wherein the PVA of the powder has a saponification degree of 95 mol% or more.

The method for producing a modified PVA according to claim 5 is
The method according to any one of claims 1 to 4, wherein the vinyl compound is acrylamide.

The method for producing a modified PVA according to claim 6 is:
The method according to claim 5, wherein a hydrolysis treatment is further performed after the Michael addition reaction.

The method for producing the modified PVA powder product according to claim 7 is to directly dry the modified PVA produced by the method according to any one of claims 1 to 6 or to purify it with a small amount of an organic solvent. The method is characterized by drying after that.

The term "solid-liquid reaction conditions" means that when a powdered PVA and a vinyl compound are subjected to a Michael addition reaction in the presence of a liquid basic catalyst, a modified PVA is produced.
The PVA of the powder is a condition under which the PVA is hardly dissolved in the vinyl compound through the reaction and is modified while maintaining a solid state. Therefore, the liquid is powder PVA
The solid-liquid reaction conditions of the present invention also include the conditions in which all of the liquid permeates into and the presence of liquid cannot be visually confirmed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The degree of saponification of PVA used in the present invention is not particularly limited, but when a strong alkali is used as a catalyst, it is preferably 80 mol% or more, more preferably 95 mol% or more. This is to prevent the alkali of the catalyst from being consumed by saponification and to suppress the amount of by-products (acetate) generated by saponification.

The degree of polymerization of PVA is preferably 50 to 8,000, more preferably 300 to 4,000 from the viewpoint of easy availability.

In addition to the above PVA, a modified PVA such as carboxy-modified, sulfone-group-modified, cation-modified or silyl-group-modified can also be used as a raw material. When such a modified PVA is used, the modification rate is usually 0.5 to
The thing of about 10 mol% is used.

A feature of the present invention is that powdered PV is used as a raw material.
Using A, the PVA is not dissolved thereafter, and the reaction is allowed to proceed while maintaining the solid state.
The powdered PVA used in the present invention preferably has an average particle diameter of 1,000 μm or less from the viewpoint of enhancing the permeability of the reactive agent.

As the vinyl compound used in the present invention, acrylonitrile, acrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, acrylic acid or its salt, acrylic ester, 2-acrylamido-2-methylpropanesulfonic acid or its In addition to salts, vinyl sulfonic acids or salts thereof, vinyl sulfoxide, vinyl sulfone, maleic acid, nonionics such as maleic acid diesters, anionic vinyl compounds, N, N-dimethylaminoethyl acrylate or quaternary salts thereof, N, N -Cationic vinyl compounds such as dimethylaminopropyl acrylamide or a quaternary salt thereof, N-vinylformamide and N-vinylacetamide. Moreover, these can also be used in combination of 2 or more types. Of these, acrylamide and acrylonitrile are preferable because of their high reactivity and low cost.

Of the above-mentioned vinyl compounds, those which are liquid at room temperature (such as acrylonitrile) are used as they are without being diluted, or in the state of a solution diluted with an appropriate solvent such as water. Further, it is desirable to use a vinyl compound (such as acrylamide) that is solid at room temperature as a solution in which it is dissolved in a suitable solvent such as water.

The amount of vinyl compound used in the reaction is PV
It is preferably 1 to 150 mol%, more preferably 5 to 100 mol%, relative to A.

On the other hand, as the type of the basic catalyst, caustic soda, caustic potash, sodium methoxide, triethylamine and the like are used, among which caustic soda and caustic potash are preferred. This basic catalyst is also dissolved in water or the like to be used in a liquid state.

The amount of the basic catalyst is preferably 0.5 to 100 mol%, more preferably 2 to 5 with respect to PVA.
0 mol%.

As a procedure for adding each of the above-mentioned components, first, a liquid basic catalyst is added to powdered PVA and sufficiently permeated to form an alcoholated PVA. Then, a vinyl compound is added and the Michael addition reaction is allowed to proceed under solid-liquid reaction conditions. Regarding alcoholation of PVA,
Zhur. Prikland Khim. , 26, 90
0-8 (1953).

The Michael addition reaction is carried out by using an alcoholated PV.
A and a vinyl compound are stirred for 30 minutes to 10 hours while maintaining the solid state of PVA with a horizontal blender or the like. Suitable temperatures for carrying out the Michael addition reaction are in the range 5 to 90 ° C, preferably in the range 20 to 70 ° C.

Although the reaction mechanism in the production method of the present invention has not been sufficiently clarified, first of all, a basic catalyst added first causes a part of hydroxyl groups of PVA to be alcoholated, and then a vinyl compound to be added preferentially. It is presumed that Michael is added to the alcoholized hydroxyl group.

Depending on the type of vinyl compound (eg, acrylonitrile, acrylamide, etc.), it is also possible to add an alkali or the like for hydrolysis. In this case, it may be partially or completely hydrolyzed depending on the application. The hydrolyzate also corresponds to the modified PVA according to the present invention.

For hydrolysis, NaOH, KOH, LiO
In addition to alkaline preparations such as H, Na ₂ CO ₃ and NH ₄ OH, alkylamines such as dimethylamine and alkanolamines such as monoethanolamine can be used.

Furthermore, by substituting the system with nitrogen during the reaction, it is possible to prevent coloring of the product and breakage of the molecular chain due to radicals.

The product finally obtained can be dried as it is, or can be easily purified by drying with a small amount of 1 to 10 parts by weight of methanol or isopropyl alcohol and the like, and then dried. A powder product can be obtained.

Thus, in order to easily obtain a powder product after the reaction, the water content of the reaction system is adjusted to 0 to 70 throughout the reaction.
It is necessary to maintain the weight percentage, preferably 0-5.
0% by weight or less. If the water content of the reaction system exceeds 70% by weight, not only powdering becomes difficult but also the reaction rate becomes difficult to increase. In addition, PVA becomes sticky, which makes it difficult to maintain the solid state of PVA throughout the reaction. In such a case, PV is used as long as it does not affect the reaction.
You may add the auxiliary agent which reduces the adhesiveness of A. Examples of such auxiliaries include ethylene glycol, propylene glycol, glycerin, polyethylene glycol, polypropylene glycol, polyoxyethylene polyoxypropylene block polymer and the like.

In order to carry out the reaction more uniformly (that is, to prevent the bias of the reaction in the reaction system), P
A VA insoluble solvent can also be added. The PVA-insoluble solvent refers to a solvent that can form a slurry (suspension) by dispersing PVA without dissolving it, and specific examples thereof include methanol, isopropyl alcohol, acetone, and methyl ethyl ketone. By adding the PVA-insoluble solvent, the effect of preventing PVA (including those already modified) from forming a dumpling (lump) during the reaction can also be obtained.

The amount of the PVA insoluble solvent added is
0.1-5 parts by weight is suitable for 1 part by weight of PVA,
If it is less than this, the contribution to homogenization is small, and if it is more than this, it is difficult to form a slurry.

The modification ratio of the PVA modified product thus obtained can be determined by NMR or IR. Examples of other means for determining the modification rate include colloid titration for modification of anion or cation group, and semi-micro Kjeldahl method for modification with a compound containing nitrogen. Modified PVA obtained by the present invention
The modification rate is usually 0.5 to 45 mol%.

The weight average molecular weight of the modified PVA obtained in the present invention was measured by GPC to be 8,000-
It was in the range of 390,000.

According to the above-mentioned production method of the present invention, unlike the conventional method, even if a normal dropping method is adopted instead of spraying, a granulated substance which influences the reaction is not produced. Further, it is not necessary to use PVA having a low saponification degree in order to increase the swelling degree of PVA, and those having a high saponification degree (including completely saponified products) can be used, so that by-product of sodium acetate can be suppressed. it can. Furthermore, since the Michael addition reaction is started immediately when the vinyl compound is added, vinyl compounds that affect the physical properties of the final product even if they are reacted in a nitrogen atmosphere to prevent the product from coloring. There is no formation of the polymer. Therefore, it becomes possible to inexpensively mass-produce a high-quality modified PVA without coloring.

The embodiments of the present invention are listed below, but the present invention is not limited thereto.

1. A method for producing a modified PVA, which comprises adding a liquid basic catalyst to powdered PVA to form an alcoholated PVA, then adding a vinyl compound, and subjecting the mixture to a Michael addition reaction under solid-liquid reaction conditions.

2. The method according to item 1, wherein the water content of the reaction system is 70% by weight or less.

3. The method according to 1, wherein the water content of the reaction system is 50% by weight or less.

4. 4. The method according to any one of 1 to 3, wherein the degree of saponification of PVA is 80% or more.

5. The method according to any one of 1 to 3, wherein the degree of saponification of PVA is 95% or more.

6 The method according to any one of 1 to 5, wherein the degree of polymerization of PVA is 50 to 8,000.

7. Polymerization degree of PVA is 300 to 4,000
The method according to any one of 1 to 5, which is

8. 8. The method according to any one of 1 to 7, wherein the vinyl compound is acrylonitrile.

9. 8. The method according to any one of 1 to 7, wherein the vinyl compound is acrylamide.

10. Using two or more vinyl compounds 1 to
The method according to any one of claims 7 to 10.

11. The reaction temperature is in the range of 5 to 90 ° C. 1
10. The method according to any one of 10 to 10.

12. The method according to any one of 1 to 10, wherein the reaction temperature is in the range of 20 to 70 ° C.

13. Reaction under a nitrogen (N ₂ ) atmosphere 1
13. The method according to any one of to 12.

14. 14. The method according to any one of 1 to 13, wherein a PVA insoluble solvent is added to the reaction system to make PVA into a slurry.

15. 15. The method according to 14, wherein the addition amount of the PVA insoluble solvent is 10 to 500 parts with respect to 100 parts of PVA.

16. The method according to 8 or 9, wherein hydrolysis is further carried out after the Michael addition reaction.

17. Item 17. The method according to Item 16, wherein the hydrolysis is performed using an alkali.

18. Item 17. The method according to Item 16, wherein the hydrolysis is performed using an alkanolamine.

A method for producing a modified PVA powder product, which comprises directly drying the modified PVA produced by the method according to any one of 19.1 to 18.

A method for producing a modified PVA powder product, characterized in that the modified PVA produced by the method according to any one of 20.1 to 18 is purified with a small amount of an organic solvent and then dried.

21. The amount of organic solvent used for purification is the product 1
21. The method according to 20, wherein the amount is 1 to 10 parts per part.

22. In producing a modified PVA by subjecting PVA and a vinyl compound to a Michael addition reaction, powder P
A method for improving reactivity in the production of a modified PVA, comprising the step of alcoholating VA with a liquid basic catalyst and then adding a vinyl compound to cause a Michael addition reaction.

[0064]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In addition, "%" in the text means "% by weight" unless otherwise specified.

Example 1 Powdered PVA (1,750 after polymerization, saponification degree 98.8 mol%, was added to a horizontal blender having a volume of 5 liters under a nitrogen atmosphere.
Add 440 g of average particle size 540 μm and stir for 30%
-Add 130 g of caustic soda solution dropwise and add 1 at 40 ° C.
Time alcoholation was performed. Next, 426 g of a 50% aqueous solution of acrylamide and 5 g of polyethylene glycol (molecular weight: 300) were added dropwise, and a Michael addition reaction was performed at 40 ° C. for 6 hours. The water content of the reaction system at this time is 30%
Met. The obtained product was purified with 1000 g of methanol and then dried to obtain 598 g of white powder.

When the final product was analyzed by NMR, the carbamoylethylation degree (modification rate) was 23 mol% and the reaction rate was 77%. The weight average molecular weight measured by GPC is 90,000, and the viscosity of a 4% aqueous solution is 31.0.
It was mPa · S (B-type viscometer-60 rpm).

For the molecular weight measurement by GPC, 0.1N NaCl aqueous solution was used as an eluent, and Tosoh Corporation
4 columns (TSKgel G2500PW, G300
0PW, G4000PW, G5000PW) were connected in series (the same applies to the following Examples and Comparative Examples).

Example 2 The Michael addition reaction was carried out at 40 ° C. for 6 hours in exactly the same manner as in Example 1, then the temperature was raised to 80 ° C., and hydrolysis was carried out for 1 hour only with the already added catalyst caustic soda. . The obtained product was purified with 1000 g of methanol and then dried to obtain 602 g of white powder.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 14 mol%, the degree of carboxyethylation was 10 mol% (total modification rate: 24 mol%), and the reaction rate was 80%. The weight average molecular weight was 90,000 as measured by GPC.

Example 3 Michael addition reaction was carried out at 40 ° C. for 6 hours in exactly the same manner as in Example 1, and then 48% -caustic soda 170 was further added.
g was added, the temperature was raised to 80 ° C., and hydrolysis was performed for 3 hours.
The water content of the reaction system at this time was 33%. The obtained product was neutralized with acetic acid and then directly dried to give a white powder 7.
10 g were obtained.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 0 mol%, the degree of carboxyethylation was 24 mol% (total modification rate: 24 mol%), and the reaction rate was 80%. The weight average molecular weight was 91,000 as measured by GPC.

Example 4 Michael addition reaction was carried out at 40 ° C. for 6 hours in the same manner as in Example 1, and then 48% -caustic soda 170 was further added.
230 g of a 50% aqueous solution of sodium 2-acrylamido-2-methylpropane sulfonate (230 g) was added, and the mixture was heated to 80 ° C. and reacted for 5 hours. The water content of the reaction system at this time was 39%. The obtained product was neutralized with acetic acid and then directly dried to obtain 829 g of a white powder.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 0 mol%, the degree of carboxyethylation was 24 mol%, and the modification ratio of the sulfone group was 2.7 mol% (total modification ratio of 26.7 mol%). ), And the reaction rate was 76%. The weight average molecular weight was 91,000 as measured by GPC.

Example 5 Polymerization degree 500, saponification degree 97.5 mol%, average particle size 44
592 g of a white powder was obtained in exactly the same manner as in Example 1 except that 0 μm powder PVA was used.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 22 mol% and the reaction rate was 73%. Further, the weight average molecular weight was measured by GPC and found to be 24,000.

Example 6 Polymerization degree 1650, saponification degree 98.5 mol%, average particle size 6
597 g of white powder was obtained in exactly the same manner as in Example 1 except that 50 μm of carboxy-modified PVA (saponified product of copolymer of vinyl acetate and itaconic acid, carboxy modification rate of 2 mol%) was used.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 22 mol% and the reaction rate was 73%. The weight average molecular weight measured by GPC was 81,000.

Example 7 507 g of a white powder was obtained in the same manner as in Example 1 except that 79 g of acrylonitrile was used instead of 426 g of a 50% acrylamide aqueous solution. The water content of the reaction system at this time was 14%.

When the final product was analyzed by NMR, the degree of cyanoethylation was 13 mol% and the reaction rate was 87%. Moreover, the weight average molecular weight was 88,000 as measured by GPC.

Example 8 A powder type PVA (3,500 after polymerization, saponification degree: 95.8 mol%, in a 5 liter horizontal blender under a nitrogen atmosphere was used.
440 g of average particle size 610 μm) was added and stirred, 30%
-60 g of an aqueous solution of caustic soda was added dropwise, and alcoholation was carried out at 20 ° C for 1 hour. Then, 50% of N, N-
621 g of an aqueous solution of methyl chloride quaternary salt of dimethylaminopropylacrylamide was added, and the mixture was stirred at 50 ° C. for 6 hours. At this time, the water content of the reaction system was 31%. The obtained product was purified with 500 g of isopropyl alcohol and then dried to obtain 640 g of white powder.

When the cationization degree of the obtained powder was analyzed by colloid titration, the modification rate was 10 mol% and the reaction rate was 6%.
7%. The weight average molecular weight measured by GPC was 172,000.

Example 9 In a horizontal blender having a volume of 5 liters, powder PVA (1,600 after polymerization, saponification degree 93.5 mol%, under a nitrogen atmosphere)
Add 440 g (average particle size 390 μm) and stir for 30%
-Add 130 g of caustic soda solution dropwise and add 1 at 20 ° C.
Time alcoholation was performed. Then, 284 g of 50% -acrylamide aqueous solution, isopropyl alcohol 20
0 g was added, and the mixture was stirred at 40 ° C. for 6 hours to carry out a Michael addition reaction. The water content of the reaction system at this time was 22%.
The product obtained is centrifuged and then dried to give a white powder 5
30 g were obtained.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 14 mol% and the reaction rate was 70%. Moreover, the weight average molecular weight was 88,000 as measured by GPC.

Example 10 In the same manner as in Example 3 except that the reaction was performed in air, 707 g of a pale yellow powder was obtained.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 0 mol%, the degree of carboxyethylation was 23 mol% (total modification rate: 23 mol%), and the reaction rate was 77%. The weight average molecular weight measured by GPC was 85,000.

Comparative Example 1 (Example of Reaction in Aqueous Solution ) Powder PVA (polymerization degree: 1,750, saponification degree: 98.8 mol%, average particle size: 54 ) was placed in a 5 liter separable flask.
0 μm) 200 g and water 1500 g are added, and the temperature is 80 ° C.
The temperature was raised to 0 and the PVA was completely dissolved. Then 50%
-20 g of NaOH aqueous solution and 97 g of acrylamide were added, and the mixture was stirred at 50 ° C for 10 hours. By pouring the obtained reaction solution into a large amount of methanol and shearing it with a mixer, 167 g of a powder product could be finally obtained.

When the obtained powder was analyzed by NMR,
The degree of carbamoylethylation (modification rate) was 4 mol%, and the reaction rate was 13%, which were very low.

Comparative Example 2 690 g of a pale yellow powder was obtained in exactly the same manner as in Example 10 except that the order of addition of the caustic soda aqueous solution and the acrylamide aqueous solution was reversed. Many granules were found in the final product.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 0 mol%, the degree of carboxyethylation was 18 mol% (total modification rate: 18 mol%), and the reaction rate was 60%. Moreover, the weight average molecular weight was 84,000 as measured by GPC.

Comparative Example 3 White powder 5 was prepared in the same manner as in Example 1 except that the order of addition of the aqueous solution of caustic soda and the aqueous solution of acrylamide was reversed.
80 g were obtained. Many granules were found in the final product.

When the final product was analyzed by NMR, the degree of carbamoylethylation was 17 mol% and the reaction rate was 57%. Also, the viscosity of a 4% aqueous solution is 1240 mPa · S.
(B-type viscometer-60 rpm) showed strong spinnability due to the acrylamide polymer.

[0092]

EFFECTS OF THE INVENTION According to the method for producing a modified PVA of the present invention, it is possible to increase the effective utilization rate of a vinyl compound, that is, the reaction rate, with respect to PVA, suppress the production of by-products, and obtain high quality without coloring. It becomes possible to inexpensively mass-produce the modified PVA.

The modified P obtained by the above-mentioned production method
By directly drying VA or purifying it with a small amount of an organic solvent and then drying it, a powdered product of modified PVA, which has been very difficult in the past, can be easily obtained.

Modified PV obtained by the production method of the present invention
A has excellent dispersibility and is useful as a dispersant and a mud conditioner for excavation, as well as various additives such as paper additives, textile chemicals, civil engineering chemicals, water-soluble films, adhesives, etc. Available for

Further, the powder product has advantages in reducing distribution costs, storage, and maintaining quality.

Claims (7)

[Claims] 1. A liquid basic catalyst is added to powdered polyvinyl alcohol to produce an alcoholated polyvinyl alcohol, and (2) a vinyl compound is added to this alcoholated polyvinyl alcohol to obtain solid-liquid reaction conditions. A method for producing a modified polyvinyl alcohol, characterized in that a Michael addition reaction is carried out below. 2. The method for producing a modified polyvinyl alcohol according to claim 1, wherein a polyvinyl alcohol insoluble solvent is added to the reaction system. 3. The method for producing a modified polyvinyl alcohol according to claim 1, wherein the reaction is performed in a nitrogen atmosphere. 4. The polyvinyl alcohol of the powder has a degree of saponification of 95 mol% or more.
4. The production method according to any one of 3. 5. The production method according to claim 1, wherein the vinyl compound is acrylamide. 6. The production method according to claim 5, wherein a hydrolysis treatment is further performed after the Michael addition reaction. 7. A modified polyvinyl which is characterized in that the modified polyvinyl alcohol produced by the method according to any one of claims 1 to 6 is directly dried or purified with a small amount of an organic solvent and then dried. Method for producing alcohol powder product.