Process for producing an aqueous dispersion of a water-soluble cationic polymer

A process for producing an aqueous dispersion of a water-soluble cationic polymer which process comprises modifying a polymer obtained by homopolymerization of an N-vinylcarboxylic acid amide or copolymerization of an N-vinylcarboxylic acid amide and a vinyl monomer copolymerizable with the N-vinyl carboxylic acid amide with an acid in an aqueous medium in the presence of a nitrate ion. The process can produce an aqueous dispersion of a water-soluble cationic polymer having a high molecular weight from the above water-insoluble polymer easily in a single step without causing adverse effects on the handling property while the fluidity is maintained.

FIELD OF THE INVENTION 
The present invention relates to a process for producing an aqueous 
dispersion of a water-soluble cationic polymer. More particularly, the 
present invention relates to a process for producing an aqueous dispersion 
of a water-soluble cationic polymer which shows excellent effects as a 
flocculant for waste water, a dewatering agent for sludge, and an additive 
for paper manufacturing, wherein the aqeous dispersion can keep a low 
viscosity even at a high concentration, shows excellent handling property 
which is advantageous for automation and labor saving, does not use an oil 
which is required in emulsion polymers of the water-in-oil type, does not 
scatter dusts which cause problems in powder polymers, and is excellent 
for improvement of the working environment. 
PRIOR ART OF THE INVENTION 
It has been known that a polymer having the unit of vinylamine which is 
obtained by hydrolysis of a polymer containing the unit of 
N-vinylformamide or N-vinylacetamide as the essential monomer component 
(Japanese Patent Publication No. Heisei 3(1991)-64200, Japanese Patent 
Publication No. Heisei 4(1992)-2320, Japanese Patent Application Laid-Open 
No. Showa 63(1988)-304, Japanese Patent Application Laid-Open No. Showa 
63(1988)-165412, Japanese Patent Application Laid-Open No. Heisei 
6(1994)-39208, Japanese Patent Application Laid-Open No. Heisei 
6(1994)-65329, and Japanese Patent Application Laid-Open No. Heisei 
6(1994)-65366) and a polymer having an amidine structure which is obtained 
by hydrolysis of a polymer containing the units of an N-vinylcarboxylic 
acid amide and acrylonitrile as the essential monomer components (Japanese 
Patent Application Laid-Open No. Heisei 5(1993)-192513) show an excellent 
property as a flocculating and dewatering agent for sludge and an additive 
for paper manufacturing. 
In macromolecular flocculants such as those described above, the 
flocculation takes place by bonding two or more particles in water with 
the macromolecular substance by adsorption. Because a larger thickness of 
the layer for the adsorption is more advantageous for flocculation by the 
bonding by adsorption, a flocculant having a large molecular weight is 
generally required. Therefore, when the material polymer containing the 
unit of an N-vinylcarboxylic acid amide as the essential monomer component 
is soluble in water, an aqueous solution obtained by using the polymer 
becomes highly viscous to cause difficulty in the handling. For example, 
the aqueous solution cannot occasionally be transferred by a pump even at 
the concentration of 5% by weight. Moreover, uniform mixing is not easy 
when chemical materials are added to an aqueous solution of the material 
polymer and mixed together, and using a special stirrer or mixing for a 
long time is required. Particularly, because it is necessary for obtaining 
a dispersion of a cationic polymer having a high concentration that an 
aqueous solution of the material polymer have a high concentration, still 
more difficulty is caused in the handling, and gelation sometimes takes 
place. 
It is known that a macromolecular flocculant made of a cationic polymer can 
be formed into an emulsion of the water-in-oil type to improve the 
handling property (Japanese Patent Application Laid-Open No. Heisei 
5(1993)-117313, Japanese Patent Application Laid-Open No. Heisei 
5(1993)-125109, and Japanese Patent Application Laid-Open No. Heisei 
5(1993)-309208). By forming the cationic polymer into an emulsion of the 
water-in-oil type, the handling property is improved, and the labor saving 
is enabled. However, problems arise about smell and safety in the working 
because a mineral oil is used as the dispersant. The use of a mineral oil 
is not preferable either in view of the protection of the global 
environment. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention has an object of providing a process 
which can produce an aqueous dispersion of a water-soluble cationic 
polymer having a high molecular weight from a water-insoluble polymer 
obtained by homopolymerization of an N-vinylcarboxylic acid amide or 
copolymerization of an N-vinylcarboxylic acid amide and a vinyl monomer 
copolymerizable with the N-vinyl carboxylic acid amide easily in a single 
step without causing adverse effects on the handling property while the 
fluidity is maintained. 
As the result of extensive studies conducted by the present inventors, it 
was discovered that an aqueous dispersion of a water-soluble cationic 
polymer can easily be obtained by modifying a water-insoluble polymer, 
such as a polymer obtained by homopolymerization of an N-vinylcarboxylic 
acid amide or copolymerization of an N-vinylcarboxylic acid amide and a 
vinyl monomer copolymerizable with the N-vinyl carboxylic acid amide, with 
an acid in an aqueous medium in the presence of a nitrate ion. The present 
invention has been completed on the basis of the discovery. 
The present invention provides: 
(1) A process for producing an aqueous dispersion of a water-soluble 
cationic polymer which process comprises modifying a polymer obtained by 
homopolymerization of an N-vinylcarboxylic acid amide or copolymerization 
of an N-vinylcarboxylic acid amide and a vinyl monomer copolymerizable 
with the N-vinylcarboxylic acid amide with an acid in an aqueous medium in 
the presence of a nitrate ion; 
(2) A process described in (1), wherein the homopolymerization or the 
copolymerization is conducted in the presence of an inorganic salt; 
(3) A process described in (1), wherein the homopolymerization or the 
copolymerization is conducted in the presence of a nonionic or cationic 
water-soluble polymer; 
(4) A process described in (1), wherein the vinyl monomer copolymerizable 
with the N-vinylcarboxylic acid amide is acrylonitrile or 
methacrylonitrile; 
(5) A process described in (3), wherein the nonionic or cationic 
water-soluble polymer is polyvinyl alcohol, polyethylene glycol, or 
polyethyleneimine; 
(6) A process described in (1), wherein an inorganic salt is additionally 
present in the aqueous medium; 
(7) A process described in (1), wherein a water-soluble polymer or a 
surfactant is additionally present in the aqueous medium; 
(8) A process described in (4), wherein the ratio by mol of a unit of the 
N-vinylcarboxylic acid amide to a unit of acrylonitrile or 
methacrylonitrile in the polymer is 3:7 to 7:3; 
(9) A process described in (1), wherein the N-vinylcarboxylic acid is 
N-vinylformamide; 
(10) A process described in (1), wherein the acid is hydrochloric acid or 
nitric acid; 
(11) A process described in (1), wherein an amount by mol of the acid is 
0.5 to 5 times as much as an amount by mol of a unit of the 
N-vinylcarboxylic acid amide in the polymer; 
(12) A process described in (1), wherein concentration of the nitrate ion 
in a reaction mixture for the modification is 3 to 40% by weight; 
(13) A process described in (1), wherein concentration of the polymer is 5 
to 50% by weight; 
(14) A process described in (1), wherein the modification is conducted at a 
temperature of 40 to 100.degree. C.; 
(15) A process described in (1), wherein the modification is conducted in 
the presence of hydroxylamine; 
(16) A process described in (1), wherein the modification is conducted in 
the presence of a lower alcohol; and 
(17) A process described in (7), wherein concentration of the water-soluble 
polymer or the surfactant in a reaction mixture for the modification is 
0.1 to 20% by weight. 
DETAILED DESCRIPTION OF THE INVENTION 
In the process of the present invention, a water-insoluble polymer obtained 
by homopolymerization of an N-vinylcarboxylic acid amide or 
copolymerization of an N-vinylcarboxylic acid amide and a vinyl monomer 
copolymerizable with the N-vinyl carboxylic acid amide is used. As the 
water-insoluble polymer, a water-insoluble polymer having the unit of an 
N-vinylcarboxylic acid amide and the unit of (meth)acrylonitrile is 
preferable. The ratio of the unit of an N-vinylcarboxylic acid amide to 
the unit of (meth)acrylonitrile is not particularly limited. It is 
preferred that the ratio by mol of the unit of an N-vinylcarboxylic acid 
amide to the unit of (meth)acrylonitrile is 3:7 to 7:3. In the process of 
the present invention, the unit of an N-vinylcarboxylic acid amide is 
converted to the unit of vinylamine by hydrolysis in the modification of 
the polymer with an acid. Moreover, when the unit of vinylamine is placed 
adjacent to the unit of (meth)acrylonitrile, an amidine structure is 
formed by the reaction of both units. When the ratio by mol of the unit of 
an N-vinylcarboxylic acid amide to the unit of (meth)acrylonitrile is less 
than 3:7, the amount of the unit of (meth)acrylonitrile which remains 
unreacted or is converted into the unit of (meth)acrylic acid by 
hydrolysis is increased. When the ratio by mol of the unit of an 
N-vinylcarboxylic acid amide to the unit of (meth)acrylonitrile is more 
than 7:3, an N-vinylcarboxylic acid amide having a large number of carbon 
atoms must be used for obtaining a water-insoluble polymer. This causes 
increase in the relative weight of the carboxylic acid which is removed by 
the hydrolysis and is not advantageous. 
In the process of the present invention, examples of the N-vinylcarboxylic 
acid amide include N-vinylformamide, N-vinylacetamide, 
N-vinylpropionamide, and N-vinylbenzamide. Among these compounds, 
N-vinylformamide is preferable. 
In the process of the present invention, examples of the water-insoluble 
polymer having the unit of an N-vinylcarboxylic acid amide include 
homopolymer of an N-vinylcarboxylic acid amide, copolymers of an 
N-vinylcarboxylic acid amide and another monomer like (meth)acrylonitrile, 
and copolymers of three or more types of monomer including an 
N-vinylcarboxylic acid amide, (meth)acrylonitrile, and other monomers 
which are copolymerizable with the N-vinylcarboxylic acid amide as well as 
with (meth)acrylonitrile. The other monomers which are copolymerizable 
with the N-vinylcarboxylic acid amide as well as with (meth)acrylonitrile 
is not particularly limited as long as the obtained copolymer is insoluble 
in water. Examples of such monomer include nonionic monomers, such as 
(meth)acrylamide, styrene, methyl (meth)acrylate, ethyl (meth)acrylate, 
vinyl acetate, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, 
and N-vinylpyrrolidone; anionic monomers, such as (meth)acrylic acid, 
vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 
styrenesulfonic acid, and alkali metal salts of these acids; and cationic 
monomers, such as tertiary salts and quaternary ammonium salts of 
dimethylaminoethyl (meth)acrylate and dimethylaminopropyl 
(meth)acrylamide. 
In the polymer which is used in the present invention, the content of the 
unit of an N-vinylcarboxylic acid amide or the total content of the unit 
of an N-vinylcarboxylic acid amide and the unit of (meth)acrylonitrile in 
the whole structural units of the polymer is preferably 35% by mol or more 
in view of the obtained property when the aqueous dispersion produced by 
the process of the present invention is used as a macromolecular 
flocculant. However, the process of the present invention can be conducted 
without being restricted by the content of the unit of an 
N-vinylcarboxylic acid amide or the total content of the unit of an 
N-vinylcarboxylic acid amide and the unit of (meth)acrylonitrile in the 
whole structural units of the polymer, and a stable aqueous dispersion of 
a water-soluble cationic polymer can be obtained. 
In the process of the present invention, the process of the polymerization 
for obtaining the water-insoluble polymer having the unit of an 
N-vinylcarboxylic acid amide is not particularly limited, and the emulsion 
polymerization or the suspension polymerization can suitably be selected 
in accordance with the solubility of the used monomers. In the process of 
the present invention, the emulsion polymerization or the suspension 
polymerization using water as the medium is advantageously conducted 
because the modification of the polymer having the unit of an 
N-vinylcarboxylic acid amide with an acid is conducted in an aqueous 
medium. When the N-vinylcarboxylic acid amide is soluble in water, the 
polymerization is conducted by using a water-soluble polymerization 
initiator, and optionally an emulsifier and a dispersant. The 
polymerization is thus allowed to proceed while the polymer precipitated 
by the polymerization is kept in an emulsified or suspended condition, and 
an aqueous dispersion containing the polymer in an emulsified or suspended 
condition can be obtained. As the water-soluble polymerization initiator, 
a conventional initiator, such as ammonium persulfate, potassium 
persulfate, and 2,2'-azobis(2-amidinopropane) dihydrochloride, can be 
used. Among the conventional initiators, azo compounds are particularly 
preferable. When the N-vinylcarboxylic acid amide is insoluble in water, 
an aqueous dispersion of the polymer can be obtained by the conventional 
emulsion polymerization in which a water-soluble polymerization initiator 
and an emulsifier are used or by the conventional suspension 
polymerization in which an oil-soluble polymerization initiator soluble in 
the monomers and a dispersant are used. 
The polymerization is preferably conducted in the presence of an inorganic 
salt in order to lower the viscosity of the obtained polymer dispersion. 
As the inorganic salt, sodium chloride, potassium chloride, magnesium 
chloride, calcium chloride, ammonium chloride, sodium sulfate, potassium 
sulfate, magnesium sulfate, calcium sulfate, ammonium sulfate, sodium 
hydrogensulfate, potassium hydrogensulfate, ammonium hydrogensulfate, 
sodium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, 
and ammonium hydrogencarbonate can be used. 
In the process of the present invention, the above aqueous dispersion of 
the polymer having the unit of an N-vinylcarboxylic acid amide can be used 
for the modification with an acid directly without additional treatments, 
after concentration or dilution of the aqueous dispersion, or after 
separation of the polymer followed by preparation of an aqueous dispersion 
from the separated polymer. The unit of an N-vinylcarboxylic acid amide is 
converted into the unit of vinylamine by the modification with an acid. 
When the unit of vinylamine is placed adjacent to the unit of 
(meth)acrylonitrile, an amidine structure is formed by the reaction of 
both units. 
It is preferred that the polymer in the aqueous dispersion of the 
water-soluble cationic polymer produced by the process of the present 
invention has a high molecular weight when the polymer is used as a 
macromolecular flocculant. Therefore, it is also preferred that the 
polymer having the unit of an N-vinylcarboxylic acid amide which is used 
for the modification with an acid has a high molecular weight. However, 
the process of the present invention can be conducted without being 
restricted by the molecular weight of the polymer having the unit of an 
N-vinylcarboxylic acid amide, and a stable aqueous dispersion of a 
water-soluble cationic polymer can be obtained. 
In the process of the present invention, the water-insoluble polymer having 
the unit of an N-vinylcarboxylic acid amide is modified with an acid in an 
aqueous medium in the presence of nitrate ion. The used acid is not 
particularly limited, and for example, hydrochloric acid, nitric acid, or 
acetic acid can be used. The used amount by mol of the acid is preferably 
0.5 to 5 times, more preferably 1 to 3 times, as much as the amount by mol 
of the unit of the N-vinylcarboxylic acid amide in the polymer. When the 
amount by mol of the acid is less than 0.5 times as much as the amount by 
mol of the unit of the N-vinylcarboxylic acid amide in the polymer, the 
rate of the modification is slow, and there is the possibility that the 
modification does not proceed sufficiently. When the amount by mol of the 
acid is more than 5 times as much as the amount by mol of the unit of the 
N-vinylcarboxylic acid amide in the polymer, the used amount of the acid 
is much larger than the amount necessary for the modification and not 
economically preferable. The used amount of the acid can suitably be 
selected in accordance with the desired degree of the modification. 
In the process of the present invention, the compound used as the source of 
nitrate ion present in the aqueous medium is not particularly limited. 
When nitric acid is used as the acid, nitric acid itself is the source of 
nitrate ion. A nitrate, such as sodium nitrate, potassium nitrate, calcium 
nitrate, and ammonium nitrate, can also be added as the source of nitrate 
ion. In the present invention, a nitrate is preferably used as the source 
of nitrate ion. A single type or two or more types of the source of 
nitrate ion can be used. The concentration of nitrate ion in the reaction 
mixture is preferably 3 to 40% by weight, more preferably 5 to 20% by 
weight. When the concentration of nitrate ion is less than 3% by weight, 
there is the possibility that the cationic polymer modified with the acid 
is dissolved into the aqueous medium, and the viscosity of the system is 
increased. When the concentration of nitrate ion in the reaction mixture 
is 40% by weight, the polymer modified with the acid is sufficiently 
dispersed in the aqueous medium, and a concentration of nitrate ion larger 
than 40% by weight is generally not necessary. The step in which the 
compound used as the source of nitrate ion is added is not particularly 
limited. For example, the compound may be added in the step of the 
polymerization of an N-vinylcarboxylic acid amide. However, the compound 
is preferably added in the step of the modification with an acid after the 
step of the polymerization. 
An inorganic salt can be additionally present in the aqueous medium. As the 
inorganic salt, sodium chloride, potassium chloride, magnesium chloride, 
calcium chloride, ammonium chloride, sodium sulfate, potassium sulfate, 
magnesium sulfate, calcium sulfate, ammonium sulfate, sodium 
hydrogensulfate, potassium hydrogensulfate, ammonium hydrogensulfate, 
sodium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, 
and ammonium hydrogencarbonate can be used. 
In the process of the present invention, the concentration of the 
water-insoluble polymer having the unit of an N-vinylcarboxylic acid amide 
in the reaction mixture is preferably 5 to 50% by weight, more preferably 
10 to 30% by weight. When the concentration of the water-insoluble polymer 
is less than 5% by weight, the concentration of the obtained aqueous 
dispersion of the water-soluble cationic polymer is decreased, and the 
concentration is not economically advantageous. When the concentration of 
the water-insoluble polymer is more than 50% by weight, there is the 
possibility that the uniform modification with an acid becomes difficult. 
In the process of the present invention, the temperature of the 
modification with an acid is preferably 40 to 100.degree. C., more 
preferably 50 to 90.degree. C. When the temperature is lower than 
40.degree. C., the rate of reaction is slow, and there is the possibility 
that the modification with an acid does not proceed sufficiently. When the 
temperature is higher than 100.degree. C., a pressure-resistant reactor is 
necessary to cause economic disadvantage, and there is the possibility 
that the control of the reaction becomes difficult. 
In the process of the present invention, it is preferred that hydroxylamine 
is added to the reaction mixture for the modification with an acid. The 
gelation can be prevented by adding hydroxylamine. 
In the process of the present invention, it is preferred that a lower 
alcohol, such as methanol, ethanol, and isopropanol, is added to the 
reaction mixture for the modification reaction with an acid. By adding a 
lower alcohol, carboxylic acids formed as the byproducts in the 
modification with an acid is converted to esters having a low boiling 
point and can easily be removed from the reaction system. The used amount 
by mol of the lower alcohol is preferably 1 to 3 times as much as the 
amount by mol of the unit of an N-vinylcarboxylic acid amide in the 
water-insoluble polymer. 
In the process of the present invention, a water-soluble polymer, such as 
polyvinyl alcohol, polyethylene glycol, and polyethyleneimine, or a 
surfactant, such as a polyoxyethylene alkylphenyl ether, a 
polyoxylethylene-polyoxypropylene block copolymer, a 
polyoxyethylene-alkylamine, and an alkylamine, may be added to the aqueous 
medium as the dispersant. A single type or two or more types of the 
water-soluble polymer or the surfactant can be added. By the presence of 
the water-soluble polymer or the surfactant in the aqueous medium, the 
stability and the fluidity of the aqueous dispersion of the water-soluble 
cationic polymer can be increased. The concentration of the water-soluble 
polymer or the surfactant in the reaction mixture is preferably 0.1 to 20% 
by weight, more preferably 0.5 to 10% by weight. When the concentration of 
the water-soluble polymer or the surfactant in the reaction mixture is 
less than 0.1% by weight, the effect of the water-soluble polymer or the 
surfactant to increase the stability and the fluidity of the aqueous 
dispersion of a water-soluble cationic polymer is not remarkably 
exhibited. When the concentration of the water-soluble polymer or the 
surfactant in the reaction mixture is more than 20% by weight, the 
stability and the fluidity of the aqueous dispersion of a water-soluble 
cationic polymer is not increased to the degree expected from the 
concentration of the water-soluble polymer or the surfactant, and the 
concentration is not economically advantageous. The step in which the 
water-soluble polymer or the surfactant is added is not particularly 
limited. The water-soluble polymer or the surfactant may be added in the 
step of the polymerization of an N-vinylcarboxylic acid amide, or in the 
step of the modification with an acid after the step of the 
polymerization. 
In accordance with the process of the present invention, the 
water-insoluble polymer having the unit of an N-vinylcarboxylic acid amide 
is modified with an acid to form a water-soluble cationic polymer. Then, 
dissolution of the obtained water-soluble cationic polymer into the 
aqueous medium is suppressed by the nitrate ion in the aqueous medium, and 
the water-soluble cationic polymer formed by the modification with an acid 
is held in the form of dispersed particles. Therefore, an aqueous 
dispersion of the water-soluble cationic polymer can be obtained in a high 
concentration while the viscosity is held low. 
To summarize the advantages of the present invention, the viscosity is 
always held low to provide an excellent handling property in the process 
of production, the uniform mixing can be conducted easily to enable the 
modification with an acid in a short time, and a uniform low viscosity 
aqueous dispersion of a water-soluble cationic polymer can be obtained 
even at a high concentration. 
When the water-soluble cationic polymer dispersion prepared by the process 
of the present invention is diluted ten times or more, preferably around a 
hundred times, with water, the polymer dispersed in the aqueous medium can 
be easily dissolved to make into a uniform aqueous solution without 
gelation. Then, the solution is added waste water, sludge, or a raw 
material for manufacturing papers. The upper limit of the amount of water 
for diluting the dispersion is not limited but sufficient for dissolving 
the polymer into an aqueous medium.

EXAMPLES 
The present invention is described in more detail with reference to 
examples in the following. However, the present invention is not limited 
by the examples. 
Preparation Example 1 
A Copolymer of N-vinylformamide and Acrylonitrile 
Into a 2,000 ml flask equipped with a stirrer, a reflux condenser, a 
thermometer, and an inlet for nitrogen, 240 g (3.4 mol) of 
N-vinylformamide, 180 g (3.4 mol) of acrylonitrile, 960 g of water, and 20 
g of ammonium chloride were placed, and the flask was purged with 
nitrogen. The resultant mixture was heated to 60.degree. C. while being 
stirred, and 4.0 g of a 10% by weight aqueous solution of 
2,2'-azobis(2-amidinopropane) dihydrochloride was added. The obtained 
mixture was kept at 60.degree. C. to allow the polymerization to proceed 
for 6 hours, and an aqueous dispersion which contained particles of a 
copolymer having a diameter of several millimeters and had a viscosity of 
900 mPa.s was obtained. 
Preparation Example 2 
A Copolymer of N-vinylformamide and Acrylonitrile 
Polymerization was conducted in accordance with the same procedures as 
those conducted in Preparation Example 1 except that 940 g of water was 
used, and 20 g of a surfactant of the Pluronic type (NEWPOL PE108, a 
product of SANYO KASEI Co., Ltd.) was additionally used, and an aqueous 
dispersion which contained particles of a copolymer having a diameter of 5 
to 10 .mu.m and had a viscosity of 1,500 mPa.s was obtained. 
Preparation Example 3 
Poly-N-vinylformamide 
Into a 1,000 ml flask equipped with a stirrer, a reflux condenser, a 
thermometer, and an inlet for nitrogen, 200 g (2.8 mol) of 
N-vinylformamide and 800 g of water were placed, and the flask was purged 
with nitrogen. The resultant mixture was heated to 60.degree. C. while 
being stirred, and 3.0 g of a 10% by weight aqueous solution of 
2,2'-azobis(2-amidinopropane) dihydrochloride was added. The obtained 
mixture was kept at 60.degree. C. to allow the polymerization to proceed 
for 6 hours. The obtained viscous aqueous solution of a polymer was added 
to acetone, and the precipitated polymer was dried in a vacuum to obtain 
poly-N-vinyformamide as a white powder. 
Example 1 
Into a 500 ml separable flask equipped with a stirrer and a reflux 
condenser, 55 g of the aqueous dispersion obtained in Preparation Example 
1 in the form of a white slurry was placed with weighing, and 1.0 g of 
hydroxylamine hydrochloride was added to the aqueous dispersion. The 
resultant mixture was kept at 50.degree. C. for 1 hour while being 
stirred. Then, a mixture of 10 g of sodium nitrate, 20.7 g (1.5 times as 
much as the amount by mol of the unit of N-vinylformamide) of 35% by 
weight hydrochloric acid, 8.5 g (2.0 times as much as the amount by mol of 
the unit of N-vinylformamide) of methanol, and 4.8 g of water was added to 
the above mixture, and the obtained reaction mixture was kept being 
stirred at 70.degree. C. for 6 hours. After the condenser was removed, the 
reaction mixture was kept at 70.degree. C. for 1 hour, and formed methyl 
formate and methanol in the excess amount were removed by distillation to 
obtain a white uniform aqueous dispersion. During the above procedures, 
the polymer which was insoluble in water before the hydrolysis was 
dissolved in water as the hydrolysis proceeded and subsequently 
precipitated again as the hydrolysis further proceeded. Finally, a turbid 
uniform aqueous dispersion was obtained. The viscosity of the obtained 
aqueous dispersion was 7,300 mPa.s. 
Example 2 
The same procedures as those conducted in Example 1 were conducted except 
that a mixture of 20 g of calcium nitrate, 20.7 g of 35% by weight 
hydrochloric acid, 8.5 g of methanol, and 4.8 g of water was used in place 
of the mixture of 10 g of sodium nitrate, 20.7 g of 35% by weight 
hydrochloric acid, 8.5 g of methanol, and 4.8 g of water used in Example 
1. A uniform white aqueous dispersion was obtained, and the viscosity of 
the dispersion was 9,200 mPa.s. 
Example 3 
Into a 500 ml separable flask equipped with a stirrer and a reflux 
condenser, 55 g of the aqueous dispersion obtained in Preparation Example 
1 in the form of a white slurry was placed with weighing, and 1.0 g of 
hydroxylamine hydrochloride was added to the aqueous dispersion. The 
resultant mixture was kept at 50.degree. C. for 1 hour while being 
stirred. Then, a mixture of 20.9 g (1.5 times as much as the amount by mol 
of the unit of N-vinylformamide) of 60% by weight nitric acid, 8.5 g (2.0 
times as much as the amount by mol of the unit of N-vinylformamide) of 
methanol, and 14.6 g of water was added to the above mixture, and the 
obtained reaction mixture was kept being stirred at 70.degree. C. for 6 
hours. After the condenser was removed, the reaction mixture was kept at 
70.degree. C. for 1 hour, and formed methyl formate and methanol in the 
excess amount were removed by distillation to obtain a white uniform 
aqueous dispersion. The viscosity of the obtained aqueous dispersion was 
5,500 mPa.s. 
Example 4 
The same procedures as those conducted in Example 3 were conducted except 
that a mixture of 5 g of sodium nitrate, 14.0 g (1.0 times as much as the 
amount by mol of the unit of N-vinylformamide) of 60% by weight nitric 
acid, 8.5 g (2.0 times as much as the amount by mol of the unit of 
N-vinylformamide) of methanol, and 16.5 g of water was used in place of 
the mixture of 20.9 g of 60% by weight nitric acid, 8.5 g of methanol, and 
14.6 g of water used in Example 3. A uniform white aqueous dispersion was 
obtained, and the viscosity of the dispersion was 4,700 mPa.s. 
Example 5 
The same procedures as those conducted in Example 1 were conducted except 
that a mixture of 10 g of polyvinyl alcohol, 10 g of sodium nitrate, 20.7 
g of 35% by weight hydrochloric acid, 8.5 g of methanol, and 4.8 g of 
water was used in place of the mixture of 10 g of sodium nitrate, 20.7 g 
of 35% by weight hydrochloric acid, 8.5 g of methanol, and 4.8 g of water 
used in Example 1. 
A uniform white aqueous dispersion was obtained, and the viscosity of the 
dispersion was 1,300 mPa.s. This dispersion showed no change in the 
dispersed condition after the dispersion had been left standing at 
40.degree. C. for 3 months and thus had an excellent storage stability. 
Example 6 
The same procedures as those conducted in Example 1 were conducted except 
that a mixture of 10 g of polyethylene glycol, 10 g of sodium nitrate, 
20.7 g of 35% by weight hydrochloric acid, 8.5 g of methanol, and 4.8 g of 
water was used in place of the mixture of 10 g of sodium nitrate, 20.7 g 
of 35% by weight hydrochloric acid, 8.5 g of methanol, and 4.8 g of water 
used in Example 1. 
A uniform white aqueous dispersion was obtained, and the viscosity of the 
dispersion was 1,300 mPa.s. This dispersion showed no change in the 
dispersed condition after the dispersion had been left standing at 
40.degree. C. for 3 months and thus had an excellent storage stability. 
Example 7 
The same procedures as those conducted in Example 1 were conducted except 
that a mixture of 10 g of a surfactant of the Pluronic type (NEWPOL PE108, 
a product of SANYO KASEI Co., Ltd.), 10 g of sodium nitrate, 20.7 g of 35% 
by weight hydrochloric acid, 8.5 g of methanol, and 4.8 g of water was 
used in place of the mixture of 10 g of sodium nitrate, 20.7 g of 35% by 
weight hydrochloric acid, 8.5 g of methanol, and 4.8 g of water used in 
Example 1. 
A uniform white aqueous dispersion was obtained, and the viscosity of the 
dispersion was 900 mPa.s. This dispersion showed no change in the 
dispersed condition after the dispersion had been left standing at 
40.degree. C. for 3 months and thus had an excellent storage stability. 
Example 8 
The same procedures as those conducted in Example 1 were conducted except 
that the aqueous dispersion obtained in Preparation Example 2 in the form 
of a white slurry was used in place of the aqueous dispersion obtained in 
Preparation Example 1 in the form of a white slurry which was used in 
Example 1. 
A uniform white aqueous dispersion was obtained, and the viscosity of the 
dispersion was 2,300 mPa.s. This dispersion showed no change in the 
dispersed condition after the dispersion had been left standing at 
40.degree. C. for 3 months and thus had an excellent storage stability. 
Example 9 
The same procedures as those conducted in Example 5 were conducted except 
that the aqueous dispersion obtained in Preparation Example 2 in the form 
of a white slurry was used in place of the aqueous dispersion obtained in 
Preparation Example 1 in the form of a white slurry which was used in 
Example 5. 
A uniform white aqueous dispersion was obtained, and the viscosity of the 
dispersion was 800 mPa.s. This dispersion showed no change in the 
dispersed condition after the dispersion had been left standing at 
40.degree. C. for 3 months and thus had an excellent storage stability. 
Example 10 
Into a 500 ml separable flask equipped with a stirrer and a reflux 
condenser, 16.5 g of poly-N-vinylformamide obtained in Preparation Example 
3 and 40 g of water were placed with weighing, and 1.0 g of hydroxylamine 
hydrochloride was added to the obtained mixture. The resultant mixture was 
kept at 50.degree. C. for 10 hours while being stirred to dissolve the 
polymer into a uniform solution. The obtained solution of the polymer had 
the viscosity of 9,500 mPa.s and could be handled in an ordinary manner. 
Then, a mixture of 10 g of sodium nitrate, 16.9 g (0.7 times as much as 
the amount by mol of the unit of N-vinylformamide) of 35% by weight 
hydrochloric acid, 14.8 g (2.0 times as much as the amount by mol of the 
unit of N-vinylformamide) of methanol, and 10 g of polyvinyl alcohol was 
added to the above mixture, and the obtained reaction mixture was kept 
being stirred at 70.degree. C. for 6 hours. After the condenser was 
removed, the reaction mixture was kept at 70.degree. C. for 1 hour, and 
formed methyl formate and methanol in the excess amount were removed by 
distillation to obtain a homogenous white aqueous dispersion. The obtained 
aqueous dispersion had the viscosity of 4,700 mPa.s. 
Comparative Example 1 
The hydrolysis was conducted under the condition that nitrate ion was 
absent. The same procedures as those conducted in Example 1 were conducted 
except that a mixture of 20.7 g of 35% by weight hydrochloric acid, 8.5 g 
of methanol, and 14.8 g of water was used in place of the mixture of 10 g 
of sodium nitrate, 20.7 g of 35% by weight hydrochloric acid, 8.5 g of 
methanol, and 4.8 g of water used in Example 1. 
As the reaction proceeded, the reaction system gradually became 
transparent, and the viscosity increased. A gelled material having a 
viscosity as high as 10,000 mPa.s or more was obtained as the final 
product. 
Comparative Example 2 
The hydrolysis was conducted under the condition that nitrate ion was 
absent. Into a 500 ml separable flask equipped with a stirrer and a reflux 
condenser, 55 g of the aqueous dispersion obtained in Preparation Example 
2 in the form of a white slurry was placed with weighing, and 1.0 g of 
hydroxylamine hydrochloride was added to the aqueous dispersion. The 
resultant mixture was kept at 50.degree. C. for 1 hour while being 
stirred. Then, a mixture of 20.7 g (1.5 times as much as the amount by mol 
of the unit of N-vinylformamide) of 35% by weight hydrochloric acid, 8.5 g 
(2.0 times as much as the amount by mol of the unit of N-vinylformamide) 
of methanol, and 14.8 g of water was added to the above mixture, and the 
obtained reaction mixture was kept being stirred at 70.degree. C. for 6 
hours. As the reaction proceeded, the reaction system gradually became 
transparent, and the viscosity increased. After the condenser was removed, 
the reaction mixture was kept at 70.degree. C. for 1 hour, and formed 
methyl formate and methanol in the excess amount were removed by 
distillation. A gelled material having a viscosity as high as 10,000 mPa.s 
or more was obtained as the final product. 
Comparative Example 3 
The hydrolysis was conducted under the condition that nitrate ion was 
absent. The same procedures as those conducted in Example 1 were conducted 
except that a mixture of 10 g of polyvinyl alcohol, 20.7 g of 35% by 
weight hydrochloric acid, 8.5 g of methanol, and 4.8 g of water was used 
in place of the mixture of 10 g of sodium nitrate, 20.7 g of 35% by weight 
hydrochloric acid, 8.5 g of methanol, and 4.8 g of water used in Example 
1. 
As the reaction proceeded, the reaction system gradually became 
transparent, and the viscosity increased. A gelled material having a 
viscosity as high as 10,000 mPa.s or more was obtained as the final 
product. 
Comparative Example 4 
The hydrolysis was conducted under the condition that nitrate ion was 
absent and chlorine ion was present. The same procedures as those 
conducted in Example 1 were conducted except that a mixture of 10 g of 
sodium chloride, 20.7 g of 35% by weight hydrochloric acid, 8.5 g of 
methanol, and 4.8 g of water was used in place of the mixture of 10 g of 
sodium nitrate, 20.7 g of 35% by weight hydrochloric acid, 8.5 g of 
methanol, and 4.8 g of water used in Example 1. 
As the reaction proceeded, the reaction system gradually became 
transparent, and the viscosity increased. A gelled material having a 
viscosity as high as 10,000 mPa.s or more was obtained as the final 
product. 
The results obtained in Examples 1 to 10 are shown in Table 1, and the 
results obtained in Comparative Examples 1 to 4 are shown in Table 2. 
TABLE 1-1 
__________________________________________________________________________ 
acid nitrate dispersant 
amount amount amount 
polymer type 
(eq/NVF) 
type (g) type 
(g) 
__________________________________________________________________________ 
Example 1 
Preparation 
HCl 1.5 NaNO.sub.3 
10 -- -- 
Example 1 
Example 2 
Preparation 
HCl 1.5 Ca(NO.sub.3).sub.2 
20 -- -- 
Example 1 
Example 3 
Preparation 
HNO.sub.3 
1.5 -- -- -- -- 
Example 1 
Example 4 
Preparation 
HNO.sub.3 
1.0 NaNO.sub.3 
5 -- -- 
Example 1 
Example 5 
Preparation 
HCl 1.5 NaNO.sub.3 
10 PVA 10 
Example 1 
Example 6 
Preparation 
HCl 1.5 NaNO.sub.3 
10 PEG 10 
Example 1 
Example 7 
Preparation 
HCl 1.5 NaNO.sub.3 
10 Pluronic 
10 
Exatnple 1 
Example 8 
Preparation 
HCl 1.5 NaNO.sub.3 
10 -- -- 
Example 2 
Example 9 
Preparation 
HCl 1.5 NaNO.sub.3 
10 PVA 10 
Example 2 
Example 10 
Preparation 
HCl 1.5 NaNO.sub.3 
10 PVA 10 
Example 3 
__________________________________________________________________________ 
TABLE 1 - 2 
______________________________________ 
product 
handling in viscosity 
production 
property (mPa .multidot. s) 
______________________________________ 
Example 1 
good turbid white 7300 
uniformly dispersed 
Example 2 
good turbid white 9200 
uniformly dispersed 
Example 3 
good turbid white 5500 
uniformly dispersed 
Example 4 
good turbid white 4700 
uniformly dispersed 
Example 5 
good turbid white 1300 
uniformity dispersed 
good storage stability 
Example 6 
good turbid white 1200 
uniformly dispersed 
good storage stability 
Example 7 
good turbid white 900 
uniformly dispersed 
good storage stability 
Example 8 
good turbid white 2300 
uniformly dispersed 
good storage stability 
Example 9 
good turbid white 800 
uniformly dispersed 
good storage stability 
Example 10 
ordinary turbid white 4700 
uniformly dispersed 
______________________________________ 
Notes: 
eq/NVF: ratio by mol relative to the unit of Nvinylformamide 
PVA: polyvinyl alcohol 
PEG: polyethylene glycol 
Pluronic: NEWPOL PE108, a product of SANYO KASEI Co., Ltd. 
Table 2 - 1 
______________________________________ 
acid 
amount nitrate dispersant 
(eq/ amount amount 
polymer type NVF) type (g) type (g) 
______________________________________ 
Compara- 
Prepara- HCl 1.5 -- -- -- -- 
tive tion 
Example 1 
Example 1 
Compara- 
Prepara- HCl 1.5 -- -- -- -- 
tive tion 
Example 2 
Example 2 
Compara- 
Prepara- HCl 1.5 -- -- PVA 10 
tive tion 
Example 3 
Example 1 
Compara- 
Prepara- HCl 1.5 NaCl 10 -- -- 
tive tion 
Example 4 
Example 1 
______________________________________ 
TABLE 2 - 2 
______________________________________ 
product 
handling in viscosity 
production 
property (mPa .multidot. s) 
______________________________________ 
Comparative 
poor high viscosity, gelled 
-- 
Example 1 
Comparative 
poor high viscosity, gelled 
-- 
Example 2 
Comparative 
poor high viscosity, gelled 
-- 
Example 3 
Comparative 
poor high viscosity, gelled 
-- 
Example 4 
______________________________________ 
Notes: 
eq/NVF: ratio by mol relative to the unit of Nvinylformamide 
PVA: polyvinyl alcohol 
It can be understood from the results shown in Table 1 that the aqueous 
dispersions of a water-soluble cationic polymer which were uniform and 
showed the excellent handling property in the production could be obtained 
in accordance with the process of the present invention. The aqueous 
dispersions of a water-soluble cationic polymer which were obtained in 
Examples 5, 6, 7, and 9 by the modification with an acid in the presence 
of a water-soluble polymer or a surfactant had low viscosities and showed 
the excellent storage stability. The aqueous dispersions of a 
water-soluble cationic polymer which were obtained in Examples 8 and 9 by 
using the copolymer of N-vinylformamide and acrylonitrile prepared by the 
emulsion polymerization had low viscosities and showed the excellent 
storage stability. It can be understood from these results that the 
presence of a water-soluble polymer or a surfactant is effective for 
decreasing the viscosity and increasing the storage stability of the 
aqueous dispersion of a water-soluble cationic polymer. When a homopolymer 
of N-vinylformamide was used in place of the polymer of N-vinylformamide 
and acrylonitrile as shown in Example 10, a uniform aqueous dispersion of 
a water-soluble cationic polymer could be obtained. 
In contrast, a desirable result could not be obtained when the modification 
with an acid was conducted in the absence of nitrate ion. Aqueous 
dispersions could not be obtained but gelled materials having a high 
viscosity were obtained as shown by the results obtained in Comparative 
Example 1 and 2. A gelled material was obtained although polyvinyl alcohol 
was added as shown by the result obtained in Comparative Example 3. A 
gelled material was obtained by the modification with an acid in the 
presence of chlorine ion in place of nitrate ion as shown by the results 
obtained in Comparative Example 4. Thus, it can be understood that 
conducting the modification with an acid in the presence of nitrate ion is 
essential in order to obtain a uniform aqueous dispersion.