Radiation polymerization of cationic monomer in aqueous alcohol

A process for the production of water-soluble, substantially solid, cationic polymers comprises the step of irradiating an aqueous solution with ionizing radiation, the aqueous solution comprising at least 50% by weight of one, or two or more of specific type of amino ester or esters optionally being accompanied by acrylamide, and at least 0.1% by weight of a specific type of alcohol as an agent for inhibiting water-insolubility of the resulting polymer. The amino esters have the generic formula ##STR1## wherein R.sub.1 represents a hydrogen atom or a methyl group; R.sub.2 represents a hydrogen atom or an alkyl group having 1-4 carbon atoms; R.sub.3 and R.sub.4 each represents an alkyl group having 1-4 carbon atoms and x.sup.(-) represents an anion; or from the combination of at least one of said amino esters and acrylamide. The alcohols have the formula ##STR2## wherein X', Y' and Z' each represents a hydrogen atom or a hydroxyl group, providing at least one of said X', Y' and Z' is OH; and L, m and n each represents a natural number; and include isopropyl alcohol, isobutyl alcohol, sec. butyl alcohol, glycerine and propylene glycol.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for the production of water-soluble 
cationic polymers. More particularly the invention relates to a process 
for producing water-soluble, substantially solid, cationic polymers by 
irradiating a high concentration aqueous solution of a monomer or monomers 
selected from the group consisting of tertiary and quaternary salts of 
aminoalkyl acrylate and aminoalkyl methacrylate, said monomer solution 
optionally containing acrylamide, with ionizing radiation in the presence 
of a specifically selected alcohol. 
2. Description of Prior Art 
Cationic polymers of the tertiary or quaternary salts of aminoalkyl 
acrylate or methacrylate having the generic formula: 
##STR3## 
wherein, R.sub.1 represents a hydrogen atom or a methyl group; R.sub.2 
represents a hydrogen atom or an alkyl group having 1-4 carbon atoms; 
R.sub.3 and R.sub.4 each represents an alkyl group having 1-4 carbon 
atoms; Y represents an alkylene group having 1-4 carbon atoms and 
X.sup.(-) represents an anion; or cationic copolymers of said tertiary or 
quaternary salts with acrylamide, are known. Such cationic polymers have a 
variety of uses as a high polymeric flocculant material to be used in 
industrial water, in service water or in sewage, or in the field of 
mining, public works and the like for the purposes of promoting settling 
out or floating upwards of fine particles suspended in each liquid, or 
they can also be used as a dewatering aid for sludge from waste water 
purification process. 
These cationic polymers or copolymers have hitherto been prepared by 
solution-polymerization in water under irradiation or in the presence of 
an initiator of polymerization such as a peroxide or a redox catalyst. 
These methods of polymerization, however, have defects in that since the 
polymerization is carried out in the solution of relatively low monomer 
concentration, the polymer is obtained as a mass in the state of a gel 
accompanied by a large amount of water, and accordingly the molecular 
weight thereof decreases as time elapses and in addition, since the mass 
is in the state of a gel, it is expensive to transport it. 
For these reasons, it has been proposed and tried to separate solid polymer 
from the mass in the state of a gel containing water by means of, for 
example, the precipitation of the solid polymer in an organic solvent such 
as methanol and acetone, or alternatively by drying the gelatinous mass in 
hot air to remove water therefrom. In any of these methods, complicated 
additional steps are generally required to follow the step of the aqueous 
solution polymerization and improvement of these points has been desired. 
As a result of thorough investigation with respect to the production of 
cationic polymers by irradiation, we have found that it is possible to 
obtain a substantially solid polymer in yield of 100% by irradiating a 
highly concentrated aqueous solution of at least one member selected from 
the group consisting of tertiary and quaternary salts of aminoalkyl 
acrylate and methacrylate, or a mixture of said member and acrylamide. 
However, the polymer thus obtained is water-insoluble and therefore its 
use is limited to only a few industrial applications. 
Hereupon, we have further studied to find a method of preventing the 
product polymer from becoming water-insoluble and have finally found that 
it is possible to obtain a water-soluble polymer if we carry out the 
polymerization by irradiating an aqueous high concentration solution of a 
monomer or monomers with ionizing radiation in the presence of a specific 
alcohol under specific conditions. Based on this discovery, the present 
invention has been accomplished. 
SUMMARY OF THE INVENTION 
Namely, the process of the present invention is characterized in that it 
comprises the step of irradiating an aqueous solution with ionizing 
radiation, said solution containing at least 50% by weight of a single 
monomer or a mixture of monomers selected from the amino esters having the 
generic formula: 
##STR4## 
wherein R.sub.1 represents a hydrogen atom or a methyl group; R.sub.2 
represents a hydrogen atom or an alkyl group having 1-4 carbon atoms; 
R.sub.3 and R.sub.4 each represents an alkyl group having 1-4 carbon 
atoms; Y represents an alkylene group having 1-4 carbon atoms and 
X.sup.(-) represents an anion; or a mixture of said monomer or monomers 
and acrylamide, said irradiation being carried out in the presence of at 
least 0.1% by weight of an alcohol also contained therein having the 
generic formula: 
##STR5## 
wherein X', Y' and Z' each represents a hydrogen atom or a hydroxyl group, 
providing at least one of said X', Y' and Z' is OH; and L, m and n each 
represents a natural number; said irradation with ionizing radiation being 
carried out under the conditions including an initial temperature of 
60.degree. C. or lower, an irradiation dose rate of 500-200,000 rads/Hr, 
and a total dose of 1,000-300,000 rads. 
The cationic polymers of the present invention can be prepared from one, or 
two or more amino esters having the generic formula: 
##STR6## 
wherein R.sub.1 represents a hydrogen atom or a methyl group; R.sub.2 
represents a hydrogen atom or an alkyl group having 1-4 carbon atoms; 
R.sub.3 and R.sub.4 each represents an alkyl group having 1-4 carbon atoms 
and X.sup.(-) represents an anion; or from the combinations of at least 
one of said amino esters and acrylamide. Representative examples of the 
above mentioned compounds include the tertiary salts such as the 
hydrochlorides, sulfates and acetates of dimethylaminoethyl acrylate, 
dimethylaminoethyl methacrylate, diethylaminoethyl acrylate and 
diethylaminoethyl methacrylate; and the quaternary salts of said monomers 
mentioned above with respect to the tertiary salts which have been 
quaternarized by methyl chloride, dimethyl sulfate, diethyl sulfate or the 
like. 
When copolymers are to be prepared from the mixtures of monomeric amino 
ester or esters and acrylamide, the copolymers having any desired degree 
of cationic strength can be prepared by varying the mixing ratio of the 
component monomers. Namely, since acrylamide is essentially nonionic, a 
highly cationic copolymer can be produced by decreasing the proportion of 
acrylamide component in the original mixture of monomers. 
The concentration of monomer(s) of the solution at the initial period of 
polymerization has influence on the molecular weight and the state of the 
resulting polymer. The higher the concentration of monomer or monomers, 
the larger the molecular weight of the resulting polymer and the smaller 
the amount of water contained therein. Thus, the resulting polymer becomes 
more and more solid-like, correspondingly. 
In the practice of the present invention, the concentration of monomer is 
preferably at least 50% by weight based on the total weight of the aqueous 
solution. In order to make the handling more easy, the concentration of at 
least 70% by weight is desirable. If the concentration is too low, in the 
range below the lower limit, the molecular weight of the resulting 
copolymer decreases and a solid polymer cannot be obtained. The upper 
limit of the concentration of monomer should be below the saturation point 
of the solution containing the monomer specifically used. The operation is 
impossible if the concentration exceeds the upper limit. 
According to the present invention, the aqueous solution of the monomer 
having the concentration within the range mentioned above is irradiated 
with ionizing radiation in the presence of a specific water-soluble 
alcohol. By this, the production of solid, water-soluble, cationic 
polymers is ensured. 
The water-soluble alcohols useful in the practice of the invention can be 
represented by the generic formula: 
##STR7## 
wherein X', Y' and Z' each represents H or OH, providing that at least one 
of X', Y' and Z' represents OH; and L, m and n each represents a positive 
integer. Representative examples of these alcohols include isopropyl 
alcohol, isobutyl alcohol, secondary butyl alcohol, glycerine, propylene 
glycol and the like. A mixture of two or more alcohols selected from these 
can of course be used in the practice of the present invention. 
Though the amount of alcohol which can be employed in the practice of the 
present invention can be varied depending on the type of alcohol 
specifically used, the type of monomer specifically used, the conditions 
under which irradiation is carried out, the desired molecular weight of 
the resulting polymer and the like, the amount of alcohol generally 
employed is in the range of 0.1-20% by weight. If the amount of alcohol 
added is below said lower limit, the advantage of the invention cannot be 
expected. If the amount of alcohol exceeds the upper limit given above, 
the molecular weight of the resulting polymer remarkably decreases and the 
polymer is not useful for practical applications. 
The use of such special types of alcohol as mentioned above is essential. 
If an n-alcohol such as methanol, ethanol or n-propanol etc., is used, it 
is almost impossible to effectively prevent the resulting polymer from 
becoming water-insoluble. 
Representative examples of ionizing radiation which can be used in the 
practice of the invention include gamma-rays, accelerated electron beams, 
X-rays and the like. 
The irradiation dose rate has influence on the molecular weight of the 
resulting polymer. Generally, the production of the polymer of a higher 
molecular weight requires the use of a lower dose rate. Namely, the lower 
the dose rate, the higher the viscosity of the solution of cationic 
polymer, providing all the other conditions are the same. On the other 
hand, the higher the dose rate, the shorter the time required for the 
completion of converting from the monomer to the polymer. 
When the industrial production of cationic polymer useful as an agent for 
treating water is intended, the dose rate should be in the range of 
500-200,000 rads/Hr. If the dose rate below 500 rads/Hr is employed, the 
time required to complete the reaction will be too long to be industrially 
feasible. If the dose rate exceeds 200,000 rads/Hr, at least part of the 
polymer product will become water-insoluble or the molecular weight of the 
resulting polymer will be reduced in spite of the presence of a specific 
alcohol. The total dose should be in the range of 1,000-300,000 rads. If 
it is below 1,000 rads, yield of polymerization is small, and if it 
exceeds 300,000 rads, at least part of the resulting polymer will become 
water-insoluble or the molecular weight of the resulting polymer will be 
reduced in spite of the presence of the specific type of alcohol added 
according to the invention. 
The temperature of the solution before being subjected to ionizing 
radiation (namely, temperature at the initiation of polymerizing reaction) 
should be in the range of 0.degree.-60.degree. C. If the temperature is 
below 0.degree. C., it is difficult to dissolve the monomer in the 
solution. If the temperature is above 60.degree. C., the molecular weight 
of the resulting polymer decreases substantially and the product cannot be 
useful as an agent for treating water. 
DETAILED DESCRIPTION OF THE INVENTION 
The method of this invention is now described in greater detail by 
reference to the following examples which are given for illustrative 
purposes only and are by no means intended to limit the scope of the 
invention.

EXAMPLE 1 
20 ml of demineralized water was placed in a 200 ml-capacity beaker and 80 
g of methyl chloride salt of dimethylaminoethyl methacrylate and 4 g of 
isopropyl alcohol were added thereto to be dissolved therein. Then, the 
solution was placed in a vessel used for irradiation and nitrogen was 
blown into the solution for 20 minutes. The temperature of the solution 
was adjusted to 30.degree. C. and the solution was irradiated with 
gamma-rays from cobalt-60 at a dose rate of 5,000 rads/Hr for 3 hours. 
The conversion of the monomer into the intended polymer was 97.8%. The 
powdered product obtained by pluverizing the polymer was soluble in 
distilled water. When the polymer content determined in a 1 N-NaNO.sub.3 
solution at 30.degree. C. was 0.5 g/dl, the reduced viscosity was 8.5 
dl/g. 
EXAMPLE 2 
20 ml of demineralized water was placed in a 200 ml-capacity beaker and 40 
g of methyl chloride salt of dimethylaminoethyl methacrylate, 40 g of 
acrylamide and 4 g of isobutyl alcohol were added to be dissolved therein. 
Then the solution was placed in a vessel used for irradiation and nitrogen 
was blown into the solution for 20 minutes. The temperature of the 
solution was adjusted to 30.degree. C. and the solution was irradiated 
with gamma-rays from cobalt-60 at a dose rate of 5,000 rads/Hr for 3 
hours. 
The conversion of the monomer into the polymer was 95.3%. The powdered 
product of the polymer was soluble in distilled water. When the polymer 
content determined in a 1 N-NaNO.sub.3 solution at 30.degree. C. was 0.5 
g/dl, the reduced viscosity was 8.2 dl/g. 
EXAMPLE 3 
20 ml of demineralized water was placed in a 200 ml-capacity beaker and 60 
g of methyl chloride salt of dimethylaminoethyl methacrylate, 20 g of 
acrylamide and 2 g of isobutyl alcohol were added thereto. Then, the 
solution was placed in a vessel used for irradiation and nitrogen was 
blown into the solution for 20 minutes. The temperature of the solution 
was adjusted to 30.degree. C. and the solution was irradiated with 
gamma-rays from cesium-137 at a dose rate of 5,000 rads/Hr for 5 hours. 
The convension of the monomer to the polymer was 95.7%. The powdered 
product of the polymer was soluble in distilled water. When the polymer 
content determined in a 1 N-NaNO.sub.3 solution at 30.degree. C. was 0.5 
g/dl, the reduced viscosity was 10.6 dl/g. 
EXAMPLE 4 
20 ml of demineralized water was placed in a 200 ml-capacity beaker and 40 
g of methyl chloride salt of dimethylaminoethyl methacrylate, 40 g of 
acrylamide and 10 g of glycerine were added thereto. Then, the solution 
was placed in a vessel used for irradiation and was irradiated with 
gamma-rays from cobalt-60 at a dose rate of 5,000 rads/Hr for 3 hours. The 
conversion of the monomer into the polymer was 94.3%. The powdered product 
of the polymer was soluble in distilled water. When the polymer content 
determined in a 1 N-NaNO.sub.3 solution at 30.degree. C. was 0.5 g/dl, the 
reduced viscosity was 14.5 dl/g. 
EXAMPLES 5-15 
The monomer and alcohol were added to demineralized water according to the 
conditions as set forth in Table 1. Nitrogen was blown into the resulting 
solution for 20 minutes before the vessel containing the solution was 
closed. Then, the solution was subjected to irradiation at a predetermined 
dose rate for a predetermined time each as set forth in the table 
mentioned above. When irradiation was finished, the irradiated sample was 
taken out of the vessel and reduced viscosity of the polymer and the 
conversion of the monomer to the polymer were measured. The reduced 
viscosity is the value at the time when the polymer content determined in 
a 1 N-NaNO.sub.3 solution at 30.degree. C. was 0.5 g/dl. These conditions 
and results are shown in Table 1 below. 
TABLE 1 
__________________________________________________________________________ 
Secondary 
DMAEN 
DMAEN 
DEAEM 
Acryl- 
Isopropyl 
Isobutyl 
butyl Monomer 
Example 
Water 
--MC --DMS 
--MC amide 
alcohol 
alcohol 
alcohol 
content 
No. (ml) 
(g) (g) (g) (g) (g) (g) (g) (%) 
__________________________________________________________________________ 
5 20 40 40 2 78.4 
6 20 40 40 1 79.2 
7 20 40 40 4 76.9 
8 20 40 40 4 76.9 
9 20 41 41 2 80.4 
10 20 80 4 76.9 
11 20 80 4 76.9 
12 15 85 1 84.2 
13 20 60 20 2 78.4 
14 20 20 60 4 76.9 
15 20 10 70 4 76.9 
__________________________________________________________________________ 
Irradiation 
Irradiation 
Polymerization Reduced 
Example 
dose rate 
time temperature 
Conversion 
Water viscosity 
No. (rad/Hr) 
(Hr) (.degree.C.) 
(%) solubility 
(dl/g) 
__________________________________________________________________________ 
5 5,000 3 30 98.0 soluble 
10.4 
6 5,000 3 30 99.1 " 14.8 
7 10,000 2 30 97.8 " 7.3 
8 500 10 50 95.1 " 10.2 
9 5,000 3 50 94.6 " 11.5 
10 5,000 3 30 96.2 " 5.1 
11 5,000 3 30 95.8 " 6.0 
12 5,000 3 30 98.6 " 9.8 
13 5,000 3 30 98.3 " 8.2 
14 5,000 3 50 96.7 " 9.8 
15 5,000 3 50 96.0 " 12.5 
__________________________________________________________________________ 
Notes: 
DMAEM--MC Dimethylaminoethyl methacrylate Methyl chloride salt 
DMAEM--DMS Dimethylaminoethyl methacrylate Dimethyl sulfate salt 
DEAEM--MC Diethylaminoethyl methacrylate Methyl chloride salt 
REFERENCE EXAMPLE 1 
The experiment was carried out in the same manner as in Example 1 except 
that 4 g of ethanol was used instead of isopropyl alcohol in Example 1. 
0.5 g of powder of the resulting polymer was mixed with 100 g of distilled 
water and agitated for 2 hours, while the temperature was kept at 
30.degree. C. It was observed that the polymer was slightly swollen with 
water but the polymer was substantially water-insoluble. 
REFERENCE EXAMPLE 2 
The experiment was carried out in the same manner as in Example 2 except 
that the temperature after the blowing-in of nitrogen (namely, the initial 
temperature) was adjusted to 70.degree. C. The reduced viscosity of the 
resulting polymer as determined in the same manner as in Example 2 was 2.3 
dl/g. 
REFERENCE EXAMPLE 3 
The experiment was carried out in the same manner as in Example 3 except 
that the irradiation time of gamma-rays was 7 hours instead of 5 hours. 
0.5 g of the resulting powdered polymer was mixed with 100 g of distilled 
water and was agitated for 2 hours, while the temperature was kept at 
30.degree. C. It was observed that the polymer was slightly swollen with 
water, but the polymer was substantially water-insoluble.