JP2002145926A - Method for manufacturing polyvinyl amine solution having low salt content - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyvinylamine solution having a low content of salts of by-products. SOLUTION: The method for manufacturing a polyvinylamine solution is carried out as follows: a polymer having a vinylamine as a constitutional unit is obtained by modifying a polymer having an N-vinylcarboxylic acid amide as a constitutional unit in the presence of an alkali; the modification reaction is carried out in a solvent whose water content is <=20 wt.%; and subsequently the precipitated salt of byproduction is separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a polyvinylamine solution. More specifically, the present invention relates to a method for producing polyvinylamine, which comprises producing polyvinylamine as a free amine and in a solution having a low content of by-product salts.

[0002]

2. Description of the Related Art Polyvinylamine has a characteristic reactivity based on a structure in which a primary amino group is directly connected to a main chain. Utilizing this reactivity, for example, water treatment, paper industry,
It can be widely used in the dyeing industry, adhesives, etc. Several routes for synthesizing polyvinylamine have been proposed, but industrially, a method of obtaining a polymer having N-vinylcarboxylic acid amide as a constituent component and then hydrolyzing the amide group in the presence of an acid or alkali is employed. ing. Hydrolysis in the presence of an acid produces a salt of polyvinylamine, and hydrolysis in the presence of an alkali produces a free amine.

At present, there is a great demand for free amines. Salts are limited in use because they are mixed only with aqueous media, but free amines dissolve in alcoholic solvents,
This is because water-insoluble organic additives can be blended. In the fields of adhesion, paints, inks, coatings, and the like, since the coating device is generally made of metal, it is corroded by a hydrochloride, but free amine does not cause corrosion. In addition, in the adhesive field, it has been reported that free amines have higher functions (Japanese Patent Application Laid-Open No. 7-164603).

However, when hydrolyzed in the presence of an alkali, a by-product salt (e.g., sodium carboxylate) equivalent to polyvinylamine is produced. In the fields of adhesion, paints, inks, coatings, and the like, when applied to a substrate and dried, by-product salts mixed into polyvinylamine remain in the coating film, which may cause a problem. In addition, when mixed with other materials or solvents, by-product salts are precipitated as crystals, which may impair product quality.

[0005] Accordingly, there has been a need for a method for producing free polyvinylamine having a low content of by-product salts. As a method for producing free polyvinylamine having a low content of by-product salt, JP-A-8-217818 discloses a method in which a formyl group is decomposed into an amino group and carbon monoxide in a non-aqueous solvent in the presence of a catalyst. Have been. Also, JP-A-8-245
No. 718 describes a method for decomposing a formyl group into an amino group, carbon dioxide and hydrogen in an aqueous solution in the presence of a catalyst. However, any of these methods is not suitable for industrial use because it requires the use of a large amount of expensive catalyst and the removal of the catalyst after the reaction.

Further, it is relatively easy to obtain a free amine from a copolymer having a low polyvinylamine content. Japanese Patent Application Laid-Open No. Hei 2-11609 discloses that N is less than 12%.
-N-vinylformamide containing vinylformamide /
A method is disclosed in which a vinyl acetate copolymer is alkali-saponified in methanol to obtain a polyvinylamine / vinyl alcohol copolymer. In this method, a by-product salt soluble in methanol is removed by utilizing the fact that the polyvinylamine / vinyl alcohol copolymer is insoluble in methanol.

[0007] Japanese Patent Application Laid-Open No. 7-304833 discloses 10
An N-vinylformamide / higher vinyl ester copolymer containing N-vinylformamide in an amount of not more than 10% by weight was subjected to alcoholysis with ethanol / toluene using sulfuric acid, and ethyl formate was distilled off and neutralized with alkali. A method of synthesizing a polyvinylamine / higher vinyl ester copolymer in which sulfate is removed by filtration is shown. In this method, the insoluble sulfate in the solvent is removed by utilizing the fact that the polyvinylamine / higher vinyl ester copolymer is soluble in a solvent such as toluene. In these methods, it is necessary to contain a unit other than polyvinylamine which controls solubility in a high ratio, so that only a polymer having a low amino group content can be obtained.

In the examples of Japanese Patent Application Laid-Open No. 2000-239634, an aqueous solution of polyvinyl N-vinylformamide is alkali-modified to obtain an aqueous solution containing polyvinylamine and sodium formate. A method for producing a polyvinylamine composition having a low salt content that precipitates and separates as a solid is disclosed. However, this method requires at least 50 times more alcohol than polyvinylamine, requires a concentration step after purification, and is difficult to recycle because the recovered alcohol contains a considerable amount of water. This is disadvantageous economically.

On the other hand, it is considered possible to remove only the by-product salt from the mixture of polyvinylamine and the by-product salt using an ultrafiltration membrane or a reverse osmosis membrane. However, in order to carry out such a method industrially, the liquid viscosity needs to be low, and a polymer solution can inevitably be processed only at a low concentration. Therefore, not only the operation efficiency is poor, but also a concentration step after the treatment is required, which is economically disadvantageous.

[0010]

Accordingly, there is a need for a method for producing polyvinylamine having a high free amine equivalent and having a low content of by-product salts at a lower cost on an industrial scale. I was

[0011]

The inventor of the present invention has proposed a method for preparing poly (N-vinylcarboxylic acid amide) in a solvent having a low water content, a soluble polyvinylamine, and a low solubility of by-product salts. From polyvinylamine to polyvinylamine,
The present invention has been found to obtain a polyvinylamine solution having a low salt content by obtaining a slurry in which a by-product salt is precipitated in a solution of polyvinylamine, and then separating the by-product salt precipitated by filtration or centrifugation. Reached.

That is, the gist of the present invention is to modify a polymer containing N-vinylcarboxylic acid amide in the presence of an alkali to obtain a polymer containing vinylamine as a constitutional unit. Is carried out in a solvent of not more than 20% by weight, and then the precipitated by-product salt is separated.

[0013] The second gist is that the solubility of the by-product salt in the solvent at the end of the denaturation reaction (% by weight of the salt with respect to the weight of the saturated solution) is 6% or less. Be in the way.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the polyvinylamine solution is manufactured through the following steps. (1; polymerization step) a step of producing a (co) polymerized polymer having N-vinylcarboxylic acid amide as a constituent element (hereinafter referred to as “poly (N-vinylcarboxylic acid amide)”); (2; modification step) N-vinylcarboxylic acid amide)
Is modified in the presence of an alkali to obtain a (co) polymerized polymer having polyvinylamine as a constituent element (hereinafter referred to as polyvinylamine) (3; purification step) from a polyvinylamine solution containing a by-product salt solid, A step of removing by-product salt;

Hereinafter, each step will be described. (1; Polymerization Step) In the polymerization step, a monomer containing N-vinylcarboxylic acid amide is (co) polymerized to produce poly (N-vinylcarboxylic acid amide). In the present invention, N
- The vinyl carboxylic acid amide of the general formula CH ₂ = CH-
NHCOR (wherein, R represents a hydrogen atom, an alkyl group, or an aryl group) refers to a single compound or a mixture of two or more compounds. No particular limitation is imposed on the R, ease of reaction inducing the polyvinylamine, N- vinylformamide (R = H) or N- vinylacetamide (R = CH ₃₎ are preferred. Particularly preferred is N-vinylformamide.

The N-vinylcarboxylic amide may be copolymerized with a suitable comonomer. Specifically, N-vinyl lactams such as N-vinyl pyrrolidone and N-vinyl caprolactam; N-methyl-N-vinyl formamide;
N-alkyl-N such as methyl-N-vinylacetamide
N- (di) alkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide and N-isopropyl (meth) acrylamide; vinyl ethers such as ethyl vinyl ether and butyl vinyl ether; vinyl acetate And vinyl esters such as vinyl propionate. These comonomers may be used alone or as a mixture of two or more. (Meth) acrylamide, (meth) acrylic acid and its esters; (meth) acrylonitrile, etc. can also be copolymerized, but these units react with vinylamine units in a later modification step to form intramolecular lactams As a result, the number of vinylamine units decreases, which is not preferable.

The amount of N-vinylcarboxylic acid amide in the monomer composition is not particularly limited and may be appropriately controlled according to desired physical properties.
It is preferably at least 50 mol%, more preferably at least 50 mol%, even more preferably at least 80 mol%. A known method is used for polymerizing N-vinylcarboxylic acid amide to obtain poly (N-vinylcarboxylic acid amide).
That is, there are bulk polymerization, solution polymerization, dispersion polymerization, emulsion polymerization, suspension polymerization, gas phase polymerization and the like. The type of polymerization is selected mainly according to the composition of the poly (N-vinylcarboxylic acid amide) and the solvent. For example, when poly (N-vinylformamide) is polymerized in alcohol, dispersion polymerization is preferred because the monomer is soluble in the solvent and the polymer is insoluble in the solvent. Poly (N-vinylacetamide)
When polymerizing poly (N-vinylformamide-co-N-vinylpyrrolidone) or the like in an alcohol, solution polymerization is preferable since both the monomer and the polymer are soluble in a solvent.

The concentration of the monomer in the polymerization system can be arbitrarily selected within a range in which the unit operation is possible.
% By weight, preferably 40% by weight or less, more preferably 30% by weight or less. Also, as the polymerization method,
A known method for polymerizing N-vinylcarboxylic acid amide is used. That is, azo catalysts, peroxide catalysts,
Radical polymerization using a redox catalyst and the like, or sulfuric acid, or a proton acid such as perchloric acid, such as by cationic polymerization using Lewis acids such as BF _3. Particularly, radical polymerization using an azo catalyst is preferable.

The azo radical polymerization catalyst is not particularly limited, but preferred is 2,2'-azobis (4
-Methoxy-2,4-dimethylvaleronitrile), 2,
2′-azobis (2,4-dimethylvaleronitrile),
2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,
2′-azobis (2-amidinopropane) dihydrochloride,
2,2′-azobis [2- (2-imidazolin-2-yl) propane] or a salt thereof, 2,2′-azobis [2
-Methyl-N- (2-hydroxyethyl) -propionamide], dimethyl 2,2'-azobisisobutyrate, 4,4'-azobis (4-cyanovaleric acid) or a salt thereof, alone or in combination. Mixtures of more than one type can be used. In particular, 2,2'-azobis (2,4-
Dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] or a salt thereof, dimethyl 2,2'-azobisiso Butyrate and the like are preferred. These polymerization catalysts can be used in any amount, but preferably 0.01 to 10% by weight, more preferably 0.03 to 5% by weight, based on the monomers.

As the polymerization solvent, any solvent can be used as long as the polymerization reaction is not inhibited. A strongly acidic or basic solvent is not preferable because it decomposes N-vinylcarboxylic acid amide. The later-described modification step is very important to select a solvent, from this point of view, also it is preferable to use an alcohol or a mixture thereof also C ₁ -C ₄ and denaturation step in the polymerization step. Specific examples include methanol, ethanol, propanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol, t-butyl alcohol, ethylene glycol, glycerin, propanediol, butanediol, diethylene glycol, methyl sesolorub, and ethyl cellosolve. . Particularly, methanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol and t-butyl alcohol are preferred. Water can also be used. Of course, even with solvents other than these, poly (N
-Vinylcarboxylic acid amide) may be separated from the solvent and the denaturation reaction may be performed again in a suitable solvent.

In obtaining poly (N-vinylcarboxylic acid amide), when the polymer is insoluble in the polymerization solvent, an appropriate dispersion stabilizer can be used to obtain a stable dispersion. As the dispersion stabilizer, any known substance can be used, but a polymer compound, a surfactant, and the like are generally used. In particular, it is preferable to use a polymer compound soluble in a solvent. Specifically, polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol; polyvinyl lactams such as polyvinyl pyrrolidone and polyvinyl caprolactam; cellulose derivatives such as ethyl cellulose and hydroxyethyl cellulose; polyvinyl acetate, polyvinyl alcohol and poly (Vinyl acetate-co-
Vinyl acetate (co) polymers such as vinylpyrrolidone) and vinyl alcohol (co) polymers derived therefrom; polyamines such as polyethyleneimine, polyvinylamine, polyallylamine, polydiallyldimethylammonium chloride and salts thereof, etc. May be exemplified. Particularly, polyalkylene glycols and polyvinyl lactams are preferable. (2; Modification step) Poly (N-vinylcarboxylic acid amide)
Is modified into polyvinylamine in the presence of an alkali.
In general, the poly (N-
This is performed by adding an alkali to a vinyl carboxylic acid amide) solution.

The modification reaction is performed in a solvent having a water content of 20% or less. If it exceeds 20%, the by-product salt will be dissolved in the solvent, and it will be difficult to remove the salt from the polyvinylamine solution. Water content is 1 to promote by-product salt precipitation.
0 or less, preferably 5% or less, more preferably 2%
The following is preferred. It is preferable that the water content is small from the viewpoint that the solvent can be easily recycled.

The solvent at the time of the denaturation reaction, except for water, has 1 carbon atom.
~ 4 alcohols or mixtures thereof are preferred.
Specific examples include methanol, ethanol, propanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol, t-butyl alcohol, ethylene glycol, glycerin, propanediol, butanediol, diethylene glycol, methyl sesolorub, and ethyl cellosolve. . Particularly preferred are methanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol and t-butyl alcohol. In addition, other common solvents may coexist as long as the denaturation reaction and purification are not inhibited. C ₁ -C ₄
Is preferably 50% by weight or more, more preferably 70% by weight or more, further preferably 90% by weight or more based on the whole solvent.

In the above-mentioned alcohol-based solvent, polyvinylamine is soluble and the saturation solubility of the by-product salt is low, so that the by-product salt can be easily separated and removed. Further, since the solubility of the alkali used for denaturation is high and side reactions such as consumption of alkali do not occur, the denaturation reaction proceeds at a practical rate, which is desirable. Furthermore, since the boiling point is not too high and the odor is not too strong, it is suitable for use in products.

The solvent at the end of the denaturation reaction preferably has a solubility of the by-product salt (% by weight of the salt with respect to the weight of the saturated solution) of 6% or less, since a large amount of by-product salt precipitates. Preferably 2
%, More preferably 1% or less. The concentration of polyvinylamine in the solution at the end of the denaturation reaction is generally at least 3%, preferably at least 7%. If it is less than 3%, precipitation of by-product salts decreases, which is not preferable. In addition, generally 50%
Or less, preferably 40% or less, more preferably 3% or less.
0% or less.

At the end of the modification reaction, the amount of the solvent with respect to polyvinylamine is generally 1 to 32 times by weight, preferably 1.5 to 19 times, and more preferably 2 to 14 times.
During the modification reaction, water may be removed, an alcohol having 1 to 4 carbon atoms may be added, and the composition may be finally adjusted to the above-mentioned appropriate composition at the end of the modification reaction. After completion of the denaturation reaction, water may be removed, an alcohol having 1 to 4 carbon atoms may be added, and the composition may be adjusted to the above-mentioned appropriate composition before the purification step.

For the removal of water, a known method can be used, but it is convenient to carry out distillation. In the distillation, it is advantageous to have an azeotropic agent. Examples of the azeotropic agent include alcohols such as ethanol, propanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol and t-butyl alcohol; ketones such as methyl ethyl ketone; and hydrocarbons such as cyclohexane and hexane. The use of alcohols as the solvent for the modification reaction is advantageous because it also acts as an azeotropic agent.

As the alkali, one or more kinds of known compounds capable of a denaturation reaction are used. Specifically, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide; alkali metal alkoxides such as sodium methoxide and potassium t-butoxide; alkaline earth metal hydroxides such as calcium hydroxide Etc. are exemplified. Particularly preferred are sodium hydroxide, potassium hydroxide and sodium methoxide. The alkali may be added as a solid, but is preferably added as a solution in operation. The alkali solvent is not limited, but water and alcohols may be used.

The denaturing conditions can be arbitrarily determined according to the required reaction time. The amount of the alkali added may be determined according to the desired modification rate, but is usually 1 to 10 with respect to the desired vinylamine amount.
Two molar equivalents, preferably 1 to 1.5 molar equivalents, are used. The denaturation temperature is preferably from room temperature to 200 ° C., more preferably from 50 ° C. to 150 ° C., and even more preferably from 60 to 200 ° C.
120 ° C.

If unreacted N-vinylcarboxylic acid amide remains before the denaturation reaction, it may be decomposed by contact with an alkali, and the product may be colored.
This is mainly derived from a condensate of an aldehyde which is a decomposition product. In order to avoid such coloring, it is preferable to remove the aldehyde prior to modification, or to use a compound that captures or decomposes the aldehyde. Specific examples of such compounds include peroxides such as hydrogen peroxide and t-butyl hydroperoxide; hydroxylamines such as hydroxylamine hydrochloride; ammonium compounds such as ammonia and butylamine; and salts thereof. .

If the operation is difficult due to the sticking of the contents during the modification reaction, the sticking can be prevented by adding a suitable dispersant. As the dispersant, any known substance can be used, but a polymer compound, a surfactant and the like are generally used. In particular, it is preferable to use a polymer compound soluble in a solvent. Specifically, polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol; polyvinyl lactams such as polyvinyl pyrrolidone and polyvinyl caprolactam; cellulose derivatives such as ethyl cellulose and hydroxyethyl cellulose;
Vinyl acetate (co) polymers such as polyvinyl acetate, polyvinyl alcohol, poly (vinyl acetate-co-vinylpyrrolidone) and vinyl alcohol (co) polymers derived therefrom; polyethyleneimine, polyvinylamine, polyallylamine , Polydiallyldimethylammonium chloride and the like, and salts thereof. Particularly polyalkylene glycols,
Polyvinyl lactams are preferred.

The method of contacting the poly (N-vinylcarboxylic acid amide) with an alkali is not particularly limited.
A method of adding an alkali to a solution or dispersion of poly (N-vinylcarboxylic acid amide), a method of adding a solution or dispersion of poly (N-vinylcarboxylic acid amide) to alkali, a method of adding poly (N-vinylcarboxylic acid amide) to an alkali. There is a method of contacting with an alkali after removal from the polymerization solvent.
The device for contacting is not particularly limited, but a general-purpose stirring tank, a stationary tank, a kneader such as a kneader, or a tube-type mixing device such as a static mixer may be used. (3; Purification Step) The by-product salt is separated from the polyvinylamine solution containing the by-product salt solid obtained in the denaturation step. As a separation method, a general method used for solid-liquid separation can be used. Specifically, there are pressure filtration, filtration under reduced pressure, centrifugal separation, inclination and the like.

Depending on the composition of the solvent, the by-product salt may still be dissolved at a certain concentration even after the solid-liquid separation. In this case, after adjusting the composition of the solvent to lower the saturation solubility of the by-product salt, the precipitated by-product salt may be separated again. The amount of by-product salt contained in the final product is preferably purified to 30 mol% or less based on the amount of amino groups of polyvinylamine. It is more preferably at most 10 mol%, further preferably at most 5 mol%.

After the purification, the concentration of polyvinylamine may be adjusted by dilution or concentration. The solvent may be replaced.

[0035]

EXAMPLES 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 departing from the gist of the invention. (Analysis method) The amount of amino groups in the solution was determined to be 1/40 in an aqueous solution of pH = 2.5 using toluidine blue as an indicator.
It was determined by titration with a 0N PVSK solution. The amount of sodium formate was measured using ion chromatography. The amount of residual NVF was measured using high performance liquid chromatography. Example 1 (1; polymerization step) 300 m equipped with a stirrer and a reflux condenser
To a 1-separable flask were added 43.5 g of isopropanol as a solvent and 2 g of polypropylene glycol (molecular weight 3000) as a dispersant, and the mixture was heated to 70 ° C. 2,
3 g of a 10% solution of 2-azobis (2,4-dimethylvaleronitrile) (V65 manufactured by Wako Pure Chemical Industries, Ltd.) in isopropanol was added. A solution consisting of 30 g of N-vinylformamide and 20 g of isopropanol was added dropwise over 2 hours. White polymer particles were precipitated as the polymerization proceeded. One hour after the addition, 1.5 g of a 10% solution of V65 in isopropanol was added. After completion of the dropwise addition, the temperature was maintained at 70 ° C. for 1 hour, and then the internal temperature was raised to 80 ° C. and maintained for 3 hours. A uniform slurry was obtained and the amount of residual NVF was 0.59% (conversion rate 98%). (2; Denaturation step) The internal temperature was lowered to 60 ° C., and 2.4 g of a 30% aqueous hydrogen peroxide solution was slowly added dropwise. 84.5 g of a 20% methanol solution of sodium hydroxide was added dropwise over 90 minutes. After completion of the dropwise addition, the internal temperature was raised to 70 ° C. and maintained for 6 hours. A slurry in which a white solid precipitated was obtained. The amount of amino groups in the solution was 1.82 meq / g,
-The conversion of vinylformamide to polyvinylamine was found to be 80%. Further, 33.8 g of a 20% methanol solution of sodium hydroxide was added, and the mixture was kept at 70 ° C. for 5 hours. The amount of amino groups in the liquid was 1.81 meq /
g, and the conversion of N-vinylformamide to polyvinylamine was found to be 95%. The internal temperature was further raised, and the solvent was distilled off at an internal temperature of 76 ° C. Internal temperature is 81 ° C
When it reached, the distillation was stopped and it was cooled. (3; Purification step) The content was filtered through a 200 mesh wire mesh to remove solids. The solid was further washed three times with 10 g of isopropanol and added to the mother liquor to obtain 135.6 g of the mother liquor. Further, when the mixture was allowed to stand still, some sedimentation of crystals was observed. When the supernatant was obtained and analyzed,
The amount of amino groups was 2.79 meq / g, corresponding to 16.3 g as polyvinylamine, and the theoretical yield was 16.9 g.
It was found that 96% was recovered for (= 30 g × (43/71) × 0.98 × 0.95). The amount of sodium formate in the solution was 0.087 meq / g, which was 3.1 mol% based on the amino groups. According to gas chromatography, the solvent composition in the product was isopropanol / methanol = 69/31% by weight. The saturated solubility of sodium formate in a solvent of this composition is about 0.2%. Example 2 (1; polymerization step) 300 m equipped with a stirrer and a reflux condenser
In a l separable flask, 43.5 g of isopropanol as a solvent and polyvinylpyrrolidone (K-
90) 2 g was added and the mixture was heated to 70 ° C. 2,2-azobis (2,4-dimethylvaleronitrile) (V6 manufactured by Wako Pure Chemical Industries, Ltd.)
3 g of the 10% isopropanol solution of 5) was added. Here, 30 g of N-vinylformamide and isopropanol 2
A solution consisting of 0 g was added dropwise over 2 hours. White polymer particles were precipitated as the polymerization proceeded. One hour after dropping, 1.5 g of a 10% solution of V65 in isopropanol
Was added. After the completion of the dropwise addition, the internal temperature was raised to 80 ° C. and maintained for 3 hours. A uniform slurry was obtained, and the amount of residual NVF was 0.95% (conversion rate: 95%). (2; Denaturation step) The internal temperature was lowered to room temperature, and 2.4 g of a 30% aqueous hydrogen peroxide solution was slowly added dropwise. 84.5 g of a 20% methanol solution of sodium hydroxide was added dropwise over 10 minutes. After completion of the dropwise addition, the internal temperature was raised to 70 ° C. and maintained for 6 hours. A slurry in which a white solid precipitated was obtained. The amount of amino groups in the liquid was 1.81 meq / g, and the charged N-
Conversion of vinylformamide to polyvinylamine is 8
It turned out to be 0%. Further, 8.5 g of a 20% methanol solution of sodium hydroxide was added, and the mixture was kept at 70 ° C. for 2 hours. The amount of amino groups in the solution was 1.89 meq / g, and the conversion of N-vinylformamide to polyvinylamine was found to be 88%. Cooled to room temperature. (3; Denaturation step) The crystals settled at room temperature, and the supernatant was decanted to obtain 159.7 g of a liquid. The amount of amino groups in the liquid was 2.01 meq / g, which was equivalent to 13.7 g as polyvinylamine, and the theoretical yield was 15.2 g.
It was found that 90% was recovered for (= 30 g × (43/71) × 0.95 × 0.88). The amount of sodium formate in the solution was 0.58 meq / g, which was found to be 29 mol% based on the amino groups. The solvent composition in the product depends on the charged amount,
Water = 47/52/1% by weight. The saturated solubility of sodium formate in a solvent of this composition is about 0.6%.
It is.

[0036]

Industrial Applicability The polyvinylamine solution obtained in the present invention has a low content of by-produced salts, can sufficiently exhibit the performance of polyvinylamine, and is useful in the fields of adhesion, paints, inks, coatings and the like. is there. In addition, desalination can be performed at low cost without using a special device or catalyst, and an industrially useful method is provided. In addition, since the water content in the solvent is small, the solvent can be easily recycled.

Claims (6)

[Claims] When a polymer having vinylamine as a constitutional unit is modified in the presence of an alkali to obtain a polymer having vinylamine as a constitutional unit, a modification reaction is carried out so that the water content is 20% by weight or less. A method for producing a polyvinylamine solution, wherein the method is carried out in a solvent as described above, and then the precipitated by-product salt is separated. 2. The method for producing a polyvinylamine solution according to claim 1, wherein the component other than water of the solvent is an alcohol having 1 to 4 carbon atoms. 3. The polyvinylamine solution according to claim 1, wherein the solubility of the by-product salt in the solvent at the end of the denaturation reaction (weight% of the salt relative to the weight of the saturated solution) is 6% or less. Manufacturing method. 4. After the denaturation reaction, the reaction solution further contains 1 to 4 carbon atoms.
The method for producing a polyvinylamine solution according to any one of claims 1 to 3, wherein the alcohol of (1) is added, and then the precipitated by-product salt is separated. 5. The method according to claim 1, wherein the N-vinylcarboxylic acid amide is N-vinylformamide and / or N-vinylacetamide. 6. The method according to claim 1, wherein the concentration of polyvinylamine in the solution at the end of the denaturation reaction is 3% or more.
6. The method for producing polyvinylamine according to any one of items 1 to 5.