Process for the preparation of aqueous solution or dispersion containing cationic polymer

A process for the preparation of an aqueous solution or dispersion containing a cationic polymer, which comprises the steps of: polymerizing a monomer including an N-vinylcarboxylic acid amide represented by the general formula CH.sub.2 .dbd.CHNHCOR, wherein R represents a hydrogen atom or methyl group, in an aqueous medium in the presence of either or both of a polyethylene glycol and polypropylene glycol; and then modifying the resulting polymer with an acid or base. Furthermore, an aqueous composition containing a cationic polymer, which comprises (A) a modified N-vinylcarboxylic acid amide polymer, (B) either or both of a polyethylene glycol and polypropylene glycol, and (C) water is disclosed.

FIELD OF THE INVENTION 
The present invention relates to a process for the preparation of an 
aqueous solution or dispersion containing a cationic polymer. More 
particularly, the present invention relates to an aqueous solution or 
dispersion containing a cationic polymer having a vinylamine unit obtained 
by the modification of an N-vinylcarboxylic acid amide polymer. 
BACKGROUND OF THE INVENTION 
Heretofore, cationic polymers used as flocculants or paper chemicals are 
generally high molecular and water-soluble. Aqueous solutions of these 
cationic polymers exhibit a high viscosity even when they have a 
concentration as low as several percent and thus cannot be always handled 
easily during preparation, transportation and use. Therefore, various 
proposals have heretofore been made for the preparation process of 
cationic polymers and the form of these products. Among these proposals 
for the preparation process, the aqueous solution polymerization process 
is most commonly used as polymerization process. In this polymerization 
process, when the monomer concentration is raised to a value as high as 
scores of percent by weight for enhancing the production efficiency in an 
industrial mass production, the polymerization reaction solution exhibits 
an extremely high viscosity that causes gelation and thus can be hardly 
handled. In other polymerization processes such as suspension 
polymerization and emulsion polymerization, the handling and 
transportation of the resulting polymer solution are relatively easy. 
However, since these polymerization processes are effected with using a 
large amount of an organic solvent, the installation of a solvent recovery 
facility and the measure against dangers such as ignition add to the cost. 
Accordingly, it is considered most ideal to effect polymerization in an 
aqueous system in such a manner that the polymer solution can be easily 
handled from the whole standpoints of view. 
Referring to the form of the product thus obtained, the product, if used as 
a flocculant for example, is often supplied in the form of a powder, which 
is dissolved in water before use. However, the powder form is 
disadvantageous in that it takes a lot of time to dissolve. In particular, 
it may involve the formation of coagulated portion, slightly soluble bulk 
material which makes fish-eye. This trouble may require a special 
dissolution facility. For example, it is required that the powder be added 
to water little by little through a feeder or the like. Besides the powder 
form, a W/O type emulsion has been recently put on the market. This type 
of a product normally has a low solution viscosity and thus can be easily 
handled. Further, this type of a product can be easily dissolved in water 
when used. However, an oil component such as high boiling hydrocarbon is 
generally used to disperse the emulsion and thus must be separated from 
water upon dissolution before use. 
On the other hand, the above described polyvinylamine exerts an excellent 
effect in the application of cationic polymer as flocculant for waste 
water disposal, paper strength increasing agent, freeness improver or 
filler yield improver, and thus is expected to have a bright future. As a 
process for the preparation of such a polyvinylamine there has been known 
a process which comprises polymerizing an N-vinylformamide to obtain a 
poly-N-vinylformamide, and then modifying the poly-N-vinylformamide thus 
obtained under acidic or basic conditions so that the formyl group in the 
polymer is at least partially hydrolyzed, as described in JP-B-63-9523 
(The term "JP-B" as used herein means an "examined Japanese patent 
publication"). Further, in order to further improve the various physical 
properties of the vinylamine, many copolymer polyvinylamines have been 
proposed, which are obtained by a process which comprises copolymerizing 
vinyl acetate, acrylonitrile, acrylic acid ester, etc. as a hydrophobic 
monomer with an N-vinylformamide or N-vinylacetamide as an 
N-vinylcarboxylic acid amide, and then modifying the copolymer thus 
obtained so that the formyl group or acetyl group is at least partially 
hydrolyzed, as described in JP-A-59-39399 (The term "JP-A" as used herein 
means an "unexamined published Japanese patent application") 
JP-A-62-74902, JP-A-63-304, JP-A-63-10609 and JP-A-3-118804. 
The above described polyvinylamines have been studied of their practical 
application in relatively recent years. These polyvinylamines exhibit a 
high dehydrating ability as compared with conventional cationic polymers 
having a quaternary ammonium group. Thus, these polyvinylamines are 
excellent in many respects as flocculant. However, there are no sufficient 
knowledge of its preparation process. Products other than those of powder 
type have almost never been reported. 
The above described problems in the conventional process for the 
preparation of cationic water-soluble polymer and the product thus 
obtained arise also with respect to polyvinylamine. Thus, an efficient 
process for the preparation of polyvinylamine and a product which can be 
more easily handled as a flocculant or the like have been desired. Among 
N-vinylcarboxylic acid amide polymers are many polymers which are 
precipitated when obtained by polymerization in an aqueous medium and 
recovered as precipitates depending on the kinds and molecular weights of 
copolymerizing monomers. Such a water-insoluble polymer can hardly be kept 
in a stably dispersed state in the aqueous medium. Further, the polymer 
thus precipitated tends to be agglomerated. If this agglomeration is 
remarkable, the polymer solution can be insufficiently stirred, to thereby 
adversely affect the polymerization reaction. Further, the hydrolyzation 
reaction at the subsequent modification step cannot smoothly proceed. 
Moreover, polyvinylamines having satisfactory properties cannot be 
obtained. 
SUMMARY OF THE INVENTION 
Objects and effects of the present invention will be apparent from the 
description of the present specification. 
The inventors made extensive studies on method for inhibiting the 
agglomeration of a polymer produced in a process which comprises 
polymerizing monomers including an N-vinylcarboxylic acid in an aqueous 
medium, and then modifying the resulting polymer to obtain a cationic 
polymer and, for improving the handleability of the polymer thus modified. 
As a result, it was found that the polymerization and modification in the 
presence of a specific compound makes it possible to inhibit remarkable 
agglomeration of polymer. It was also found that this process makes it 
possible to obtain an aqueous solution or dispersion containing 
polyvinylamine which can be instantly used in various applications such as 
flocculant. Thus, the present invention has been achieved. 
The present invention relates to a process for the preparation of an 
aqueous solution or dispersion containing a cationic polymer, which 
comprises the steps of: 
polymerizing a monomer including an N-vinylcarboxylic acid amide 
represented by the general formula CH.sub.2 .dbd.CHNHCOR, wherein R 
represents a hydrogen atom or methyl group, in an aqueous medium in the 
presence of either or both of a polyethylene glycol and polypropylene 
glycol; and then 
modifying the resulting polymer with an acid or base. 
Furthermore, the present invention also relates to an aqueous solution or 
dispersion containing a cationic polymer, which comprises (A) a modified 
N-vinylcarboxylic acid amide polymer, (B) either or both of a polyethylene 
glycol and polypropylene glycol, and (C) water. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention is described in detail below. Examples of the 
N-vinylcarboxylic acid amide represented by the general formula CH.sub.2 
.dbd.CHNHCOR (in which R represents a hydrogen atom or methyl group) 
include N-vinylformamide and N-vinylacetamide. In order to obtain a 
modification product of N-vinylcarboxylic acid amide polymer, 
N-vinylformamide is preferred because the resulting polymer has a good 
hydrolyzability. 
The polymerizable monomer for use in process of the present invention may 
be the above described N-vinylcarboxylic acid amide alone. Alternatively, 
a vinyl compound other than N-vinylcarboxylic acid amide may be used in 
combination as a copolymerizable monomer taking into account the ease of 
improvement in the properties of the final product or the preference to 
precipitation of polymer in the polymer solution to provide for better 
handleability. 
Examples of the vinyl compound include acrylamide, methacrylamide, 
acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, 
styrene, ethylene, propylene, N-vinylpyrrolidone, alkylvinyl ethers having 
a C.sub.1-4 alkyl group (such as methylvinyl ether, ethylvinyl ether, 
isopropylvinyl ether, n-propylvinyl ether, t-butylvinyl ether), 
N-substituted alkyl(meth)acrylamides substituted by a C.sub.1-4 alkyl 
group (such as N-methylacrylamide, N-isopropylamide and 
N,N-dimethylacrylamide), and (meth)acrylic acid esters having a C.sub.1-20 
ester group (such as methyl acrylate, ethyl methacrylate, propyl acrylate, 
butyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, 
hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, 
hydroxybutyl methacrylate, 2-methylbutyl acrylate, 3-methylbutyl acrylate, 
3-pentyl acrylate, neopentyl acrylate, 2-methylpentyl acrylate, hexyl 
acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, 
heptyl acrylate, benzyl acrylate, tollyl acrylate, octyl acrylate, 2-octyl 
acrylate, nonyl acrylate and octyl methacrylate). 
If the N-vinylcarboxylic acid amide (A) is copolymerized with the above 
described vinyl compound (B), the copolymerization molar ratio of (A) to 
(B) is not particularly limited. The optimum range of this 
copolymerization molar ratio may vary with the kind of the vinyl compound 
(B). If the copolymer thus produced is water-insoluble so that 
precipitation polymerization occurs, this copolymerization molar ratio is 
generally from 95:5 to 10:90, preferably from 60:40 to 40:60. 
In the present invention, monomers including the above described 
N-vinylcarboxylic acid amide are polymerized in an aqueous medium. In-this 
polymerization process, these monomers are polymerized in the form of 
aqueous solution. The resulting polymer is water-soluble or 
water-insoluble. For example, a mixture of monomers may be polymerized in 
an aqueous medium with vigorous stirring in the presence of a radical 
polymerization initiator. The polymerization is effected when the total 
monomer concentration in the polymerization solution is generally from 5 
to 50% by weight, preferably from 10 to 40% by weight. The polymerization 
is preferably carried out by continuously introducing these monomer 
components separately or in admixture into water in such a manner that a 
predetermined ratio of the monomers can be obtained to cause successive 
polymerization. 
Any ordinary radical polymerization initiators which are used for 
polymerization of water-soluble or hydrophilic monomers may be used as the 
radical polymerization initiator. However, an azo compound is preferably 
used to obtain a desired polymer in a high yield. In particular, a 
water-soluble azo compound is preferred. Examples of the water-soluble azo 
compound include hydrochloride salts, sulfates and acetates of 
2,2'-azobis-2-amidinopropane and azobis-N,N'-dimethyleneisobutylamidine, 
and alkaline metal salts and ammonium salts of 4,4'-azobis-4-cyanovaleric 
acid. These radical polymerization initiators are generally used in an 
amount of from 0.01 to 5% by weight based on the weight of the monomers to 
be used as starting materials. 
The polymerization reaction is generally effected in a stream of inert gas 
at a temperature of from 30.degree. C. to 100.degree. C., preferably from 
50.degree. C. to 80.degree. C. The polymerization time is generally from 
0.5 to 10 hours, preferably from 1 to 8 hours. The polymerization reaction 
involves the generation of polymerization heat. Accordingly, the 
polymerization system is generally cooled so that the polymerization 
temperature is adjusted to the above defined range. 
In the present invention, it is an essential requirement that a 
polyethylene glycol and/or polypropylene glycol (hereinafter occasionally 
referred to as "polyethylene glycol or the like") be present during the 
above described polymerization reaction. In other words, the action of 
polyethylene glycol or the like makes it possible to inhibit remarkable 
agglomeration of the polymer and hence improve the industrial 
handleability of the polymer at the polymerization step and hydrolysis 
step. The addition of polyethylene glycol or the like little impairs the 
polymerization. The addition of polyethylene glycol or the like causes the 
precipitation of the polymer and thus can render the polymer dispersed 
stably in the aqueous medium, to exert an effect of improving the 
industrial handleability of the polymer at the polymerization step and 
modification step. Preferably, the polyethylene glycol or the like 
desirably stays solid and water-soluble. The weight-average molecular 
weight of the polyethylene glycol or the like is generally from 1,000 to 
1,000,000, preferably from 6,000 to 100,000. The polyethylene glycol or 
the like may be in the form of copolymer. Copolymers of ethylene glycol 
with propylene glycol are suitably used in the present invention as the 
copolymer type of polyethylene glycol or the like. In the case of the 
copolymer, the polymerization molar ratio of ethylene oxide to propylene 
oxide is generally from 90:10 to 40:60. 
The amount of the above described polyethylene glycol or the like to be 
added is generally from 1 to 150% by weight, preferably from 5 to 100% by 
weight, based on the total weight of the monomers used. If the amount of 
the polyethylene glycol or the like to be used is too small, the 
agglomeration of the copolymer cannot be sufficiently inhibited. On the 
contrary, if the amount of the polyethylene glycol or the like to be used 
is too great, the resulting effect remains much the same. This is 
uneconomical. The addition of the polyethylene glycol or the like is 
generally carried out by adding it to the aqueous medium prior to the 
polymerization of the monomers in the form of aqueous solution. The 
resulting polymer may be either water-soluble or water-insoluble. Since 
the effect of the polyethylene glycol or the like causes the precipitation 
of a hydrous gel polymer, the polymerization reaction is preferably 
effected with stirring from the first. In this manner, even the resulting 
precipitated water-insoluble polymer can be kept stably dispersed in 
water, making it possible to improve the industrial handleability of the 
polymer at the polymerization step and modification step. 
In order to enhance the precipitability of the polymer, various inorganic 
salts may be used together with the above described components. Since a 
divalent or higher acid tends to ionically crosslink a polymer to render 
it insoluble, an inorganic salt made of a monovalent acid is preferably 
used in general case. Preferred examples thereof include sodium chloride, 
sodium nitrate, ammonium chloride, ammonium nitrate, potassium chloride, 
potassium nitrate, lithium chloride and lithium chloride. 
The N-vinylcarboxylic acid amide polymer obtained according to the above 
described process is modified with an acid or base as it is in the form of 
solution or dispersion or after diluted with water or an alcohol so that 
it is converted to a water-soluble polyvinylamine. In some detail, the 
N-vinylcarboxylic acid amide polymer is modified at the second amide 
moiety of the N-vinylcarboxylic acid amide unit. As a result of the 
modification reaction involving hydrolysis, a vinylamine unit is produced 
as a repeating unit. In the case where a copolymer is produced, the 
structure of the vinyl compound used may be partially modified. For 
example, a nitrile group is hydrolyzed to an amide group and carboxyl 
group. These groups may further react with a primary amino group of 
vinylamine unit produced by the hydrolyzation of the above described 
secondary amide to form an amidine ring or lactam ring. 
The modifier for use in the acid modification may be any compound which 
acts as a strong acid. Examples thereof include hydrochloric acid, bromic 
acid, hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid, 
sulfamic acid, and alkaneslfonic acid. Particularly preferred among these 
acids is hydrochloric acid. Sulfuric acid or the like can cause 
hydrolyzation. However, sulfuric acid tends to insolubilize the polymer 
when used in a large amount. Therefore, the use of sulfuric acid alone is 
not so desirable. 
The modifier for use in the base modification may be any compound which 
acts as a strong base. Examples thereof include sodium hydroxide, 
potassium hydroxide and quaternary ammonium hydroxide. The modification of 
the polymer may be effected with either an acid or a base. When an 
N-vinylcarboxylic acid amide homopolymer is modified with a base, it may 
undergo gelation. In general, the polymer is preferably modified with an 
acid. 
The modified percentage of N-vinylcarboxylic acid amide polymer is defined 
as the hydrolyzation percentage of formyl group or acetyl group in the 
polymer. The modified percentage may be properly selected depending on the 
properties of the intended polymer. If the modified percentage is too low, 
the resulting polymer can be hardly rendered water-soluble. Further, since 
the resulting cation content is too low to exert a sufficient effect as a 
flocculant, the modified percentage is generally from 5 to 100 mol %, 
preferably from 20 to 95 mol %. In other words, a vinylamine unit is 
incorporated as a repeating unit of modified polymer generally in an 
amount of from 5 to 100 mol %, preferably from 20 to 95 mol %. The amount 
of the modifier to be used may be properly selected within a range of from 
0.1 to 3 mol per mol of formyl group or acetyl group in the polymer 
depending on the desired modified percentage. The temperature at which the 
modification reaction effects is generally from 40.degree. C. to 
130.degree. C., preferably from 60.degree. C. to 100.degree. C., when an 
N-vinylformamide polymer is produced. When an N-vinylacetamide polymer is 
produced, the temperature is generally from 50.degree. C. to 150.degree. 
C., preferably from 90.degree. C. to 130.degree. C. The modification 
reaction may be effected in a pressure reaction system as necessary. The 
modification reaction time depends on the modification temperature and the 
desired modified percentage, but is generally from 0.5 to 10 hours. 
If the viscosity of the polymer solution is high, that is, the 
concentration of the modified N-vinylcarboxylic acid amide polymer is such 
that the reduced viscosity thereof at 25.degree. C. in a solution prepared 
by dissolving it in a 1-N sodium chloride aqueous solution to the 
concentration of 0.1 g/dl is generally from 3 to 10 dl/g, the modification 
reaction can be effectively carried out by adding an alcohol to a 
polymerizing solution containing an N-vinylcarboxylic acid amide polymer. 
Of course, the modification reaction can be effected free from alcohol. 
However, if the modification reaction is effected free from alcohol, the 
dispersed particles of polymer tend to agglomerate, making it difficult to 
maintain the polymer in the form of slurry. The addition of an alcohol 
exerts an effect of keeping the polymer slurry during the modification 
reaction. This is probably because the alcohol thus added becomes a poor 
solvent for the polymer which helps the precipitation of the polymer and 
hence inhibit the agglomeration thereof. The alcohol which may be used 
herein is a C.sub.1-4 alcohol. Further, the alcohol is a water-soluble 
alcohol such as methanol, ethanol, isopropanol, ethylene glycol and 
1,4-butanediol. The optimum amount of the alcohol to be added greatly 
varies with the composition of the polymer, the concentration of the 
polymerization solution, etc., but is generally from 0.05 to 5 times, 
preferably from 0.1 to 3 times the weight of the polymer. 
If an alcohol is added during the modification reaction, the alcohol may be 
volatilized away from the system when the system is heated during the 
modification reaction. Further, formic acid or acetic acid produced by the 
modification reaction may undergo esterification with the alcohol so that 
the alcohol can be efficiently removed from the system. 
The reaction solution (aqueous solution or dispersion) which has undergone 
the above described modification reaction can be used as a product such as 
flocculant or paper chemical as it is in the form of aqueous solution 
containing a modified N-vinylcarboxylic acid amide polymer having desired 
properties, i.e., cationic polymer having a vinylamine unit. The reaction 
solution containing a cationic polymer comprises, as main components, 
three components: (A) a modified N-vinylcarboxylic acid amide polymer, (B) 
a polyethylene glycol or the like and (C) water. The sum of the weight of 
the three components generally accounts for not less than 60% by weight, 
preferably not less than 80% by weight, of the total weight of the 
reaction solution. The various additives used at the polymerization step 
and modification step may be left as contained in the reaction solution. 
The alcohol added during the modification reaction is generally evaporated 
away for reuse but may be left in the reaction solution, which does not 
cause any particular trouble. 
The proportion of the three main components of the reaction solution is 
generally as follows. The contents of the modified N-vinylcarboxylic acid 
amide polymer (A), the polyethylene glycol or the like (B) and water (C) 
are from 5 to 45% by weight, from 0.05 to 60% by weight, and from 5 to 
94.95% by weight, respectively, based on the total weight of the three 
components (A), (B) and (C). The modified N-vinylcarboxylic acid amide 
polymer (A) generally has a reduced viscosity of from 0.1 to 10 dl/g as 
determined at 25.degree. C. in a solution prepared by dissolving it in a 
1-N sodium chloride aqueous solution to the concentration of 0.1 g/dl. The 
modified polymer thus obtained stays as dissolved in the reaction 
solution, or is kept as stably dispersed in the reaction solution. The 
state of the modified polymer in the reaction solution, i.e., whether it 
is kept as dissolved or dispersed in the aqueous solution, greatly depends 
on the molecular weight of the modified polymer, the composition of the 
aqueous solution, etc. 
If the modified polymer is present as dissolved in the reaction solution, 
the contents of the modified N-vinylcarboxylic acid amide polymer (A), the 
polyethylene glycol or the like (B) and water (C) are preferably from 5 to 
45% by weight, from 0.05 to 18% by weight, and from 35 to 94.95% by 
weight, respectively, based on the sum of the weight of the components 
(A), (B) and (C). Particularly preferred contents of the components (A), 
(B) and (c) are from 10 to 40% by weight, from 1 to 15% by weight, and 
from 45 to 85% by weight, respectively, based on the sum of the weight of 
the components (A), (B) and (C). In addition, the reduced viscosity of the 
modified polymer is preferably from 0.1 to 2 dl/g as determined under the 
above defined condition. 
If the modified polymer is present as dispersed in the reaction solution, 
the contents of the modified N-vinylcarboxylic acid amide polymer (A), the 
polyethylene glycol or the like (B) and water (C) are preferably from 5 to 
45% by weight, from 0.05 to 60% by weight, and from 5 to 94.95% by weight, 
respectively, based on the sum of the weight of the components (A), (B) 
and (C). Particularly preferred contents of the components (A), (B) and 
(c) are from 10 to 40% by weight, from 2 to 40% by weight, and from 35 to 
85% by weight, respectively, based on the sum of the weight of the 
components (A), (B) and (C). In addition, the reduced viscosity of the 
modified polymer is preferably from 3 to 10 dl/g as determined under the 
above identified condition. In this embodiment, the modified polymer is 
finely dispersed in the reaction solution. However, when the aqueous 
dispersion is diluted with water, the concentration of auxiliaries such as 
polyethylene glycol which contribute to the precipitation and dispersion 
of the modified polymer is lowered so that the modified polymer is rapidly 
dissolved in water. Accordingly, the aqueous dispersion having the 
modified polymer dispersed therein can also be used as a product such as 
flocculant and paper chemical as it is.

The present invention will be described in more detail with reference to 
the following Examples, but the present invention should not be construed 
as being limited thereto. 
EXAMPLE 1 
In a 1 m.sup.3 reaction vessel equipped with an agitator and a temperature 
controller were charged 296.1 kg of distilled water and 27 kg of a 
polyethylene glycol (PEG, weight-average molecular weight: 20,000). A 
nitrogen gas was then passed through the reaction system. Subsequently, 
the reaction system was sealed, and then heated to a temperature of 
70.degree. C. To the reaction system was then added 
2,2'-azobis(2-amidinopropane) hydrochloride as a polymerization initiator 
in an amount of 1.5% by weight based on the weight of the monomers. With 
stirring at 200 r.p.m. at the same temperature, a 60 wt %-monomer aqueous 
solution comprising 54.7 kg of N-vinylformamide (purity: 93.7%) and 38.7 
kg of acrylonitrile (molar mixing ratio of these monomers: 50:50) 
dissolved therein was supplied into the reaction system over 3 hours. The 
reaction system further underwent polymerization for 2 hours (final 
monomer concentration: 18.9%) to obtain a suspension having a polymer 
precipitated in water. Thereafter, the temperature of the suspension was 
lowered to 50.degree. C. To the suspension was then added hydroxylamine 
sulfate as a gelation inhibitor in an amount of 5 mol % based on the 
amount of N-vinylformamide. The mixture was then stirred for 1 hour. To 
the reaction mixture was then added concentrated hydrochloric acid in an 
amount of 60 mol % based on the amount of N-vinylformamide unit in the 
polymer (i.e., formyl group in the polymer). The reaction mixture was 
stirred at a temperature of 70.degree. C. for 1 hour, and then at a 
temperature of 90.degree. C. for 3 hours. The resulting polymer was then 
modified with an acid to obtain an aqueous solution of the modified 
polymer. 
Thus obtained modified polymer was measured in terms of modified percentage 
and reduced viscosity, and the results thereof are set forth in Table 1. 
For the measurement of reduced viscosity, a predetermined amount of the 
aqueous solution of the modified polymer was sampled. The sample was 
diluted with a 1-N sodium chloride aqueous solution to obtain a solution 
in which the concentration of the modified polymer is 0.1 g/dl. Thus 
obtained solution was used for the measurement of reduced viscosity. The 
term "modified percentage" as used herein means the decomposed ratio of 
formyl groups in the polymer. 
In the above described polymerization and modification reactions, no 
phenomena such as agglomeration and deposition of polymer was observed. 
Thus, the resulting polymer could be conveniently handled as a suspension 
or aqueous solution. The composition of the aqueous solution of the 
modified polymer is shown in Table 3. 
EXAMPLE 2 
The procedure of Example 1 was followed to prepare an aqueous solution of a 
modified polymer, except that the polymerization temperature was changed. 
As a result, the operating efficiency at the polymerization step and 
modification step was good as in Example 1. The quality of the resulting 
modified polymer is set forth in Table 1. The composition of the aqueous 
solution of the modified polymer is set forth in Table 3. 
EXAMPLE 3 
The procedure of Example 1 was followed to prepare an aqueous solution of a 
modified polymer, except that the concentration of the monomers during 
polymerization and the addition amounts of polyethylene glycol and 
hydrochloric acid were changed as shown in Table 1. As a result, the 
operating efficiency at the polymerization step and modification step was 
good as in Example 1. The quality of the resulting modified polymer is set 
forth in Table 1. The composition of the aqueous solution of the modified 
polymer is set forth in Table 3. 
EXAMPLE 4 
The procedure of Example 3 was followed to prepare an aqueous solution of a 
modified polymer, except that the addition amount of polyethylene glycol 
was changed as shown in Table 1. As a result, the operating efficiency at 
the polymerization step and modification step was good as in Example 1. 
The quality of the resulting modified polymer is set forth in Table 1. The 
composition of the aqueous solution of the modified polymer is set forth 
in Table 3. 
COMATIVE EXAMPLE 1 
Polymerization was effected in the same manner as in Example 1, except that 
the polyethylene glycol was not added. As a result, the resulting polymer 
caused remarkable deposition thereof on the polymerization tank, wall and 
agitating-blade, making it impossible to keep the polymer in the form of 
slurry. 
TABLE 1 
__________________________________________________________________________ 
Comparative 
Example 1 
Example 2 
Example 3 
Example 4 
Example 1 
__________________________________________________________________________ 
Monomer concentration 
18.9 18.9 30.0 30.0 18.9 
(wt %) 
Polymerization temperature 
70 60 70 70 70 
(.degree. C.) 
Addition amount of PEG 
30 30 10 7.5 -- 
(wt %) 
Addition amount of hydrochloric 
60 60 65 65 -- 
acid (mol %) 
Modified percentage 
62 65 74 75 -- 
(mol %) 
Reduced viscosity 
0.4 1.0 0.4 0.4 -- 
__________________________________________________________________________ 
Note 1) Addition amount of PEG (%): Weight percentage of addition amount 
of polyethylene glycol based on the total amount of monomers 
EXAMPLE 5 
In a 200 ml separable flask equipped with a reflux condenser, a paddle 
agitator, a nitrogen blowing pipe and a temperature controller were 
charged 24.3 g of an N-vinylformamide (purity: 91%), 2.97 g of methyl 
acrylate, 10 g of a polyethylene glycol (weight-average molecular weight: 
20,000), 10 g of sodium nitrate and 53 g of water. Further, a 0.1-N 
aqueous solution of NaOH was added to the mixture so that the pH value 
thereof was adjusted to 6.5. The air in the system was then replaced by 
nitrogen over 30 minutes. The reaction system was heated to a temperature 
of 55.degree. C. where 0.0375 g of 2,2'-amidinopropane hydrochloride was 
then added thereto as a polymerization initiator with stirring. The 
mixture was heated to a temperature of 60.degree. C. and stirred for 4 
hours, and further stirred for 1 hour at a temperature of 65.degree. C. 
The resulting polymer was precipitated in the form of hydrous gel, but 
stirring of the reaction system could be effected. Subsequently, to the 
reaction system was added 2.35 g of hydroxylamine hydrochloride. The 
reaction system was then stirred at a temperature of 50.degree. C. for 1 
hour. To the reaction system were then added 20.9 ml of a 35% hydrochloric 
acid and 32.5 g of methanol. The reaction mixture was then stirred at a 
temperature of 60.degree. C. for 4 hours. Subsequently, the supply of 
water through the reflux condenser was suspended. The reaction system was 
then stirred at a temperature of 90.degree. C. while being air-cooled for 
1 hour to volatilize methanol and methyl formate away. The reaction system 
was then allowed to cool to room temperature to terminate the reaction. 
Thus, a fine dispersion of the modified polymer was obtained. When the 
dispersion was allowed to stand as it was, the precipitation of finely 
divided particles was observed. However, the polymer was readily 
dispersed, when the polymer solution was stirred again. In the above 
described polymerization and modification reactions, no phenomena such as 
agglomeration and deposition of the polymer was observed. Thus, the 
resulting polymer could be conveniently handled as a suspension or aqueous 
solution. 
Thus obtained modified polymer was measured in terms of reduced viscosity, 
cation equivalent and modified percentage, and the results obtained are 
set forth in Table 2. For the measurement of reduced viscosity, a 
predetermined amount of the aqueous solution of the modified polymer was 
sampled. The sample was diluted with a 1-N sodium chloride aqueous 
solution to obtain a solution in which the concentration of the modified 
polymer is 0.1 g/dl. The cation equivalent was determined by colloidal 
titration. The term "modified percentage" as used herein means the 
decomposition ratio of formyl groups in the polymer. The composition of 
the aqueous solution of the modified polymer is set forth in Table 3. 
EXAMPLE 6 
In the same 200 ml separable flask as used in Example 5 were charged 14 g 
of an N-vinylformamide (purity: 91%) as an only monomer, 26 g of water, 10 
g of a polyethylene glycol (weight-average molecular weight: 20,000) and 
0.01875 g of 2,2'-amidinopropane hydrochloride. The air in the system was 
then replaced by nitrogen over 30 minutes. The reaction system was heated 
to a temperature of 60.degree. C. and stirred for 4 hours, and then 
further stirred at a temperature of 65.degree. C. for 1 hour. As the 
polymerization reaction proceeded, a polymer was precipitated. 
Subsequently, to the reaction system were added 1.2 g of hydroxylamine 
hydrochloride and 12.8 g of ammonium chloride. The reaction mixture was 
then stirred at a temperature of 50.degree. C. for 1 hour. To the reaction 
system were then added 18.4 g of a 35% hydrochloric acid and 17 g of 
methanol. The reaction mixture was stirred at a temperature of 60.degree. 
C. for 2 hours, and then at a temperature of 65.degree. C. for 1 hour. 
Subsequently, the supply of water through the reflux condenser was 
suspended. The reaction system was then stirred at a temperature of 
75.degree. C. while being air-cooled for 2 hours to volatilize methanol 
and methyl formate away. The reaction system was then allowed to cool to 
room temperature to terminate the reaction. Thus, a dispersion of a 
modified polymer was obtained. The particles in the dispersion were 
greater and thus were more readily precipitated than those in Example 1 
when the solution was allowed to stand as it was, but were readily 
dispersed when the solution was stirred again. In the above described 
polymerization and modification reactions, no phenomena such as 
agglomeration and deposition of polymer was observed. Thus, the resulting 
polymer could be conveniently handled as a suspension or aqueous solution. 
The quality of the modified polymer thus obtained is set forth in Table 2. 
The composition of the aqueous solution of modified polymer is set forth 
in Table 3. 
EXAMPLE 7 
In a 200 ml separable flask equipped with a reflux condenser, a paddle 
agitator, a nitrogen blowing pipe, a temperature controller and a dropping 
funnel were charged 10 g of sodium nitrate, 10 g of a polyethylene glycol 
(weight-average molecular weight: 20,000), 38.3 g of water and 0.01875 g 
of 2,2'-amidinopropane hydrochloride. The air in the system was then 
replaced by nitrogen over 30 minutes. Separately, a mixture of 24.4 g of 
an N-vinylformamide (purity: 91%), 2.97 g of methyl acrylate, 0.0187 g of 
2,2'-amidinopropane hydrochloride and 14.33 g of water was prepared, and 
the air in the mixture was replaced by nitrogen over 30 minutes. This 
monomer mixture was then put in the dropping funnel. The monomer mixture 
was then added dropwise to the reaction system in the separable flask over 
2 hours while the separable flask was heated to a temperature of 
60.degree. C. The reaction system was stirred for 2 hours at a temperature 
of 60.degree. C., and further stirred for 1 hour at a temperature of 
65.degree. C. The resulting polymer was precipitated in the form of 
hydrous gel, but stirring of the reaction system could be effected. 
Subsequently, to the reaction system was added 2.15 g of hydroxylamine 
hydrochloride. The reaction mixture was then stirred at a temperature of 
50.degree. C. for 1 hour. To the reaction system were then added 19.4 g of 
a 35% hydrochloric acid and 29.8 g of methanol. The reaction mixture was 
then stirred at a temperature of 60.degree. C. for 4 hours. Subsequently, 
the supply of water through the reflux condenser was suspended. The 
reaction system was then stirred at a temperature of 90.degree. C. while 
being air-cooled for 1 hour to volatilize methanol and methyl formate 
away. The reaction system was then allowed to cool to room temperature to 
terminate the reaction. Thus, a dispersion of a modified polymer was 
obtained. When the dispersion was allowed to stand as it was, the 
precipitation of fine particles was observed. However, the particles were 
readily dispersed, when the solution was stirred again. In the above 
described polymerization and modification reactions, no phenomena such as 
agglomeration and deposition of polymer was observed. Thus, the resulting 
polymer could be conveniently handled as a suspension or aqueous solution. 
The quality of the thus obtained modified polymer is set forth in Table 2. 
The composition of the aqueous solution of the modified polymer is set 
forth in Table 3. 
EXAMPLE 8 
The procedure of Example 7 was followed to effect polymerization, except 
that as the monomers used in Example 7 were replaced by 23.9 g of 
N-vinylformamide (purity: 91%) and 3.38 g of methyl methacrylate. As a 
result, a polymer mixture which exhibits a lower viscosity and thus can be 
more easily stirred than in Example 7 was obtained. Subsequently, to the 
polymer mixture was added 2.15 g of hydroxylamine hydrochloride. The 
reaction mixture was then stirred at a temperature of 50.degree. C. for 1 
hour. To the reaction system were then added 18.8 ml of a 35% hydrochloric 
acid and 29.8 g of methanol. The reaction mixture was then stirred at a 
temperature of 60.degree. C. for 4 hours. Subsequently, the supply of 
water through the reflux condenser was suspended. The reaction system was 
then stirred at a temperature of 90.degree. C. while being air-cooled for 
1 hour to volatilize methanol and methyl formate away. The reaction system 
was then allowed to cool to room temperature to terminate the reaction. 
Thus, a dispersion of modified polymer was obtained. When the dispersion 
was allowed to stand as it was, the precipitation of fine particles was 
observed. However, the particles were readily dispersed, when the solution 
was stirred again. In the above described polymerization and modification 
reactions, no phenomena such as agglomeration and deposition of polymer 
was observed. Thus, the resulting polymer could be conveniently handled as 
a suspension or aqueous solution. The quality of the modified polymer thus 
obtained is set forth in Table 2. The composition of the aqueous solution 
of the modified polymer is set forth in Table 3. 
EXAMPLE 9 
The procedure of Example 7 was followed to effect polymerization and 
modification, except that the used amount of 35% hydrochloric acid was 
changed to 16.6 ml. The resulting polymer, modified polymer and dispersion 
stability were similar to that in Example 7. The quality of the modified 
polymer thus obtained is set forth in Table 2. The composition of the 
dispersion of the modified polymer is set forth in Table 3. 
EXAMPLE 10 
The procedure of Example 8 was followed to effect polymerization and 
modification, except that the polyethylene glycol having a weight-average 
molecular weight of 20,000 was replaced by a polyethylene glycol having a 
weight-average molecular weight of 6,000. As a result, as compared with 
Example 8, the resulting polymer was more finely divided to exhibit a 
tendency for better slurry condition. The resulting polymer, modified 
polymer and dispersion stability were similar to that in Example 8. The 
quality of the modified polymer thus obtained is set forth in Table 2. The 
composition of the dispersion of the modified polymer is set forth in 
Table 3. 
TABLE 2 
______________________________________ 
Reduced Cation Modified 
viscosity equivalent 
percentage 
(dl/g) (meq.) (%) 
______________________________________ 
Example 5 
4.21 8.3 72.0 
Example 6 
3.90 9.0 69.3 
Example 7 
4.31 6.3 53.7 
Example 8 
4.62 7.6 66.8 
Example 9 
4.23 5.3 44.7 
______________________________________ 
COMATIVE EXAMPLE 2 
The same reaction system as used in Example 5 was subjected to 
polymerization, except that the polyethylene glycol was omitted. As a 
result, an insoluble gel was produced throughout the reaction solution, 
making it difficult to stir and transport the product. 
TABLE 3 
______________________________________ 
Formulation of various components in 
aqueous solution (wt %) 
(A) (B) (C) 
______________________________________ 
Examples 1, 2 
17.5 (18.4) 5.0 (5.3) 72.5 (76.3) 
Example 3 27.0 (29.3) 2.7 (2.9) 62.6 (67.8) 
Example 4 27.0 (29.3) 2.0 (2.2) 63.3 (68.6) 
Example 5 22.7 (25.9) 8.4 (9.6) 56.6 (64.5) 
Example 6 17.7 (22.1) 13.0 (16.2) 
49.5 (61.7) 
Examples 7, 8 
23.0 (26.3) 8.6 (9.8) 56.0 (63.9) 
Example 9 23.3 (26.6) 8.7 (9.9) 55.5 (63.5) 
______________________________________ 
Note 1) 
(A) Modified Nvinylcarboxylic acid amide polymer 
(B) Polyethylene glycol 
(C) Water 
Note 2) 
The figure in the parenthesis indicates the weight percent based on the 
sum of the weight of the components (A), (B) and (C). 
As mentioned above, the use of an N-vinylcarboxylic acid amide as a monomer 
material makes it possible to simply and efficiently prepare an aqueous 
solution containing a cationic water-soluble polymer. In particular, 
remarkable agglomeration of polymer during the polymerization in an 
aqueous medium is inhibited, making it possible to keep the polymer 
solution easily handleable at the polymerization step and the subsequent 
acid modification step. The aqueous solution containing a cationic 
water-soluble polymer according to the present invention can be easily 
handled and can be used as a product such as flocculant and paper chemical 
as it is. 
While the invention has been described in detail and with reference to 
specific examples thereof, it will be apparent to one skilled in the art 
that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.