Process for the preparation of a water-in-oil type high-molecular-weight polymer emulsion

A process for the preparation of a water-in-oil type polymer emulsion which comprises polymerizing an acrylamide-containing monomer in a water-in-oil type emulsion. The acrylamide is prepared by hydrating acrylonitrile in the presence of a catalytic amount of nitrilehydratase.

FIELD OF THE INVENTION 
This invention relates to a process for the preparation of a water-in-oil 
type high-molecular-weight acrylamide polymer emulsion. 
BACKGROUND OF THE INVENTION 
A water-in-oil type emulsion of an acrylamide polymer is easy to handle 
because of a good dissolving power as compared with that of a powdered 
polymer. Thus, it is increasingly used as a coagulant or thickener in 
various fields, for example, in waste water disposal, sludge treatment, 
paper manufacturing or engineering works. In particular, there is a need 
in the art for an emulsion of a high-molecular weight polymer for use as a 
coagulant and in the field of paper manufacturing. 
An emulsion polymer contains an oil phase. Thus, the polymer concentration 
in the whole emulsion is relatively low, and this is a fundamental defect 
of the emulsion polymer. Namely, if the monomer concentration in the water 
phase at the time of polymerization is increased to heighten the polymer 
concentration and concurrently raise the molecular weight of the polymer, 
the molecular weight of the polymer, on the contrary, is lowered when the 
concentration exceeds a certain value. 
In other words, the polymer concentration in the product is inevitably 
reduced in order to increase the molecular weight, while the molecular 
weight is inevitably sacrificed in order to increase the polymer 
concentration. 
Hithereto, this phenomenon has been considered to occur specifically in the 
preparation of a water-in-oil type emulsion. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a 
water-in-oil type emulsion of a high-concentration and high-molecular 
weight acrylamide polymer. 
As a result of an extensive investigation to overcome the above problems of 
the prior art, the present inventors have surprisingly discovered that a 
water-in-oil type emulsion of a high concentration and high molecular 
weight acrylamide polymer can be obtained by using an aqueous acrylamide 
solution prepared by an enzymatic method, to thereby achieve the present 
invention. 
The present invention provides a process for the preparation of a 
water-in-oil type polymer emulsion which comprises polymerizing an 
acrylamide-containing monomer in an water-in-oil type emulsion. In this 
process, the acrylamide is prepared by hydrating acrylonitrile in the 
presence of a catalytic amount of nitrilehydratase. 
The above-described advantages of the present invention have been achieved 
for the first time using acrylamide prepared by an enzymatic method. The 
effects of the invention cannot be obtained using the product of an 
aqueous acrylamide solution prepared by a conventional catalytic hydration 
method which employs copper or a copper compound as a catalyst. This 
conventional catalytic hydration method is hereinafter called a "copper 
catalytic method". 
The difference between these two methods is considered to result from the 
presence or absence of impurities formed in accordance with the respective 
acrylamide preparation processes. 
According to the present invention, a water-in-oil type emulsion of a 
high-concentration and high-molecular-weight acrylamide polymer can be 
obtained. Because the monomer concentration in the water phase is 30 wt. % 
or more upon preparation, the advantages of the present invention are 
apparent. Due to its ease of hardling, the water-in-oil type emulsion 
polymer of the present invention is therefore suitable as a coagulant for 
industrial waste water or sewage disposal, as a retention aid in paper 
manufacturing or as a filtering aid, which applications require a polymer 
having a high molecular weight.

DETAILED DESCRIPTION OF THE INVENTION 
Acrylamide for use in the present invention is prepared by hydrating 
acrylonitrile via the catalytic action of nitrilehydratase. 
Nitrilehydratase is an enzyme which converts a nitrile compound into its 
corresponding amide. Examples of the nitrilehydratase include those 
derived from microorganisms belonging to the genus Bacillus, genus 
Bacteridium, genus Micrococcus, genus Brevibacterium (JP-B-62-21519) (the 
term "JP-B" as used herein means an "examined Japanese patent 
publication"), genus Corynebacterium, genus Nocardia (JP-B-56-17918), 
genus Pseudomonas (JP-B-59-37951), genus Rhodococcus, genus Microbacterium 
(JP-B-4-4873), genus Rhodococcus (JP-B-4-40948), Rhodococcus rhodochrous 
sp. (JP-B-6-55148, SU 173184), genus Fusarium (JP-A-64-86889) (the term 
"JP-A" as used herein means an "unexamined published Japanese patent 
application") and genus Agrobacterium (JP-A-5-103681, and JP-A-6-14786). 
Nitrilehydratase can be used in various forms including, for example, a 
culture solution of the above microorganism, a resting cell or immobilized 
cell separated from a culture solution, or nitrilehydratase active enzyme 
which is extracted from a resting cell, or which is extracted from a 
resting cell and then immobilized on a carrier. 
No particular limitations are imposed on the reaction conditions for 
hydrating acrylonitrile into acrylamide so long as they allow the 
enzymatic reaction to proceed at normal temperature and normal pressure. 
An aqueous acrylamide solution after the hydrating reaction can be 
polymerized as is or after increasing the acrylamide concentration by a 
condensation operation. 
The water-in-oil type emulsion polymerization according to the present 
invention is conducted with a water phase composed of an aqueous solution 
of an acrylamide-containing monomer that is dispersed in an oil phase 
composed of a hydrophobic liquid and a water-in-oil type emulsifier. The 
water-in-oil type polymer emulsion can be obtained in a form wherein the 
polymer-containing water phase is dispersed as fine particles having a 
particle size of 100 .mu.m or smaller. 
The monomer in the water phase can be composed of acrylamide along or in 
combination with a vinyl monomer that is copolymerizable with acrylamide. 
The higher the proportion of acrylamide or the higher the monomer 
concentration in the water phase, the more prominent the effects of the 
present invention and the higher the molecular weight of the resultant 
water-in-oil type polymer emulsion. Specifically, the proportion of 
acrylamide is 50 mol % or more, and the monomer concentration in the water 
phase is generally 30 wt. % or more, preferably 40 wt. % or more. 
Examples of the vinyl monomer copolymerizable with acrylamide include water 
soluble monomers, for example, quaternary ammonium salts of a cationic 
monomer, e.g., methacrylamide, 2-acrylamide-2-methylpropane sulfonic acid 
(sulfonate), acrylic acid (acrylate), dimethylaminoethyl (meth)acrylate, 
diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, 
dimethylaminohydroxypropyl (meth)acrylate, dimethylaminoethyl acrylamide 
or methacryloyloxyethyl trimethylammonium chloride, and vinylpyrolidone. 
In addition, sparingly-soluble or hydrophobic monomers, for example, 
acrylonitrile, methyl methacrylate or styrene can also be added to the 
extent that the water solubility of the target polymer is not 
deteriorated. 
Examples of the hydrophobic liquid of the oil phase include liquid 
hydrocarbons and substituted liquid hydrocarbons. Preferred are 
halogenated hydrocarbons, for example, perchloroethylene, and aromatic and 
aliphatic hydrocarbons, for example, benzene, xylene, kerosine and liquid 
paraffin. Aliphatic hydrocarbons are particularly preferred. 
Preferred examples of the emulsifiable surfactant that is used as an 
emulsion formation agent include those having a hydrophile-lyophile 
balance (HLB) of from 1 to 10, preferably from 2 to 6. Specific examples 
thereof include sorbitan monooleate, sorbitan monostearate, 
polyoxyethyelene sorbitan monooleate, polyoxyethylene oleyl ether and 
polyoxyethylene nonyl phenyl ether and mixtures thereof. 
To obtain a stable emulsion, the emulsifying surfactant is generally added 
in an amount of 1.0 wt. % to 20.0 wt. %, preferably 2.0 wt. % to 15.0 wt. 
%, based on the total weight of the hydrophobic liquid. 
The proportion of the water phase in the emulsion according to the present 
invention is generally within a range of from 50 wt. % to 90 wt. %, 
preferably from 55 wt. % to 80 wt. % based on the emulsion. The monomer 
concentration of the emulsion is generally within a range of from 30 wt. % 
to 80 wt. %, preferably from 30 wt. % to 70 wt. %. 
The emulsion can be formed by mechanically stirring the above mixture 
system in a WARING blender or the like. 
There is no particular limitation imposed on the preparation process of the 
water-in-oil type polymer emulsion. Known techniques can be used, for 
example, such as the process disclosed by Banderhof in JP-B-34-10644 (the 
term "JP-B" as used herein means an "examined Japanese patent 
publication"). Specifically, a monomer-containing water phase and a 
hydrophobic liquid are mixed, emulsified and dispersed using an 
emulsifiable surfactant. Then, the resultant water-in-oil type emulsion is 
polymerized in the presence of a polymerization initiator which forms a 
free radical, to thereby obtain a water-in-oil type polymer emulsion of 
the present invention. 
Exemplary polymerization initiators include redox initiators each of which 
contains both a peroxidation agent, for example, persulfate or alkyl 
peroxide, and a reducing agent, for example, sulfite, ferrous salt or an 
amine compound; azo-type thermal decomposition initiators, for example, 
azobisisobutylonitrile, 2,2'-azobis-(2-amidinopropane) hydrochloride or 
4,4'-azobis-(4-cyanovaleric acid); and photosensitizers, for example, 
benzophenone or benzoin methyl ether. Concerning the photosensitizer, the 
emulsion is exposed to light in the presence of the photosensitizer to 
thereby effect polymerization. The polymerization initiator may be added 
in an amount of from 10 ppm to 5000 ppm, preferably from 30 ppm to 3000 
ppm, based on the amount of the monomer. Upon polymerization, it is 
possible to add, in addition to the above-described components, a chain 
transfer agent, a surfactant for inversion, a chelating agent, a buffer 
and/or a salt as needed. 
The water-in-oil type polymer emulsion thus obtained can be converted into 
its corresponding aqueous polymer solution by adding the emulsion to a 
water medium containing a surfactant for inversion; or by adding the 
surfactant for inversion to the emulsion, followed by addition of the 
resultant emulsion to a water medium. 
The present invention is now illustrated in greater detail with reference 
to the following Examples. However, it is not intended that the present 
invention be limited to the these Examples. All the percents are by weight 
unless otherwise indicated. 
(Preparation of acrylamide by enzymatic method) 
PREATION EXAMPLE 1 
(1) Preparation of a J-1 strain biocatalyst: 
The Rhodococcus rhodochrous J-1 strain (FERM-BP 1478) described in 
JP-B-6-55148 was inoculated on a medium described below, followed by 
culturing at 30.degree. C. for 72 hours. The cells thus obtained were 
separated and washed, and then immobilized with a polyacrylamide gel in a 
manner well known in the art, to thereby obtain a biocatalyst. 
______________________________________ 
Glucose 10 g/l 
K.sub.2 HPO.sub.4 0.5 g/l 
KH.sub.2 PO.sub.4 0.5 g/l 
MgSO.sub.4.7H.sub.2 O 0.5 g/l 
Yeast extract 1.0 g/l 
Peptone 7.5 g/l 
Urea 7.5 g/l 
CoCl.sub.2 10 mg/l 
______________________________________ 
(2) Preparation of an aqueous acrylamide solution: 
The J-1 strain biocatalyst thus obtained was suspended in ion exchange 
water. Then, acrylonitrile was successively added under stirring at pH 7 
and 5.degree. C., to thereby obtain an aqueous solution having an 
acrylamide concentration of about 30%. After the reaction was completed, 
the biocatalyst was removed and the mixture was then filtered through a 
0.45 .mu.m filter. The filtrate was concentrated under reduced pressure, 
to thereby obtain a 50% aqueous solution of acrylamide (sample 1). 
PREATION EXAMPLE 2 
(1) Preparation of a B-23 strain biocatalyst: 
The Pseudomonas chlororaphis B-23 strain (FERM-BP 187) described in 
JP-B-59-37951 was inoculated on the medium described below, followed by 
culturing at 25.degree. C. for 48 hours. The cells thus obtained were 
separated and washed, and then immobilized with a polyacrylamide gel in a 
manner well known in the art, to thereby obtain a biocatalyst. 
______________________________________ 
Sucrose 30 g/l 
K.sub.2 HPO.sub.4 1.0 g/l 
KH.sub.2 PO.sub.4 1.0 g/l 
MgSO.sub.4.7H.sub.2 O 1.0 g/l 
FeSO.sub.4.7H.sub.2 O 0.05 g/l 
Yeast extract 1.0 g/l 
Mieki (flavor liquid) 20 g/l 
______________________________________ 
(2) Preparation of an aqueous acrylamide solution: 
A 50% aqueous solution of acrylamide (Sample 2) was obtained in a manner 
similar to Preparation Example 1, except for use of the B-23 strain as a 
biocatalyst instead of the J-1 strain. 
(Preparation of a water-in-oil type polymer emulsion) 
EXAMPLES 1-8 AND COMATIVE EXAMPLES 1-8 
(1) Monomers used: 
Sample 1 (a 50% aqueous acrylamide solution prepared according to the 
enzymatic method) 
Sample 2 (a 50% aqueous acrylamide solution prepared according to the 
enzymatic method) 
Comparative Sample 1 (a 50% aqueous acrylamide solution prepared according 
to the copper catalytic method (product of Mitsubishi Chemical Co., Ltd.)) 
Comparative Sample 2 (a 50% aqueous acrylamide solution prepared according 
to the copper catalytic method (product of Mitsui Toatsu Chemicals Inc.) 
(2) Preparation of an emulsion: 
In each example, a predetermined amount of the aqueous acrylamide solution 
(for example, 307.9 g of the 50% aqueous acrylamide solution when the 
monomer concentration in the water phase is 48.6%) was weighed to provide 
a monomer concentration in the water phase as shown in Table 1. After pH 
adjustment to pH 7, water was added to a total amount of 316.8 g. To the 
resultant water phase, 114.6 g of liquid hydrocarbon ("Isozole 400", trade 
name; product of Nippon Petrochemicals Co., Ltd.) and 8.8 g of an 
emulsifier ("Span 80", trade name) were added, followed by preliminarily 
emulsifying for about three minutes using a magnetic stirrer. 
Emulsification was conducted for 30 minutes in a WARING blender at a 
stirring rate of 14,700 rpm to prepare an emulsion. 
(3) Polymerization: 
An emulsion in an amount of 400 g prepared as described above was charged 
to a 500-ml separable flask equipped with a stirrer, a nitrogen gas 
blowing inlet, a thermocouple and a gas outlet. After a water bath was 
heated to the polymerization initiation temperature, nitrogen purging was 
started while stirring at a rate of 240 rpm. An initiator (100 
ppm/emulsion of a solution of 1% benzoinethyl ether (BBE) in methanol) was 
added and nitrogen purging was conducted for 30 minutes. The resultant 
mixture was then exposed to a UV (ultraviolet) lamp to thereby start 
polymerization. The polymerization temperature was regulated to not exceed 
40.degree. C. by turning the UV lamp on or off by means of a temperature 
controller. Polymerization was continued until the amount of the remaining 
monomer became 1% or lower. 
(4) Addition of an inversion reagent after polymerization and measurement 
of the viscosity of the polymer: 
After polymerization, the polymer emulsion was weighed in a 500-ml beaker 
to provide a polymer concentration of 1% at the time of viscosity 
measurement, followed by addition of water to a total amount of 500 g. To 
the resulting solution, a 12% aqueous solution of an inversion reagent 
("Emulgen 810": "Emulgen 913"=2:1) was added in a concentration of 21% 
based on the amount of the emulsion while stirring at 240 rpm. The 
stirring was conducted for 8 hours to thereby complete the inversion. To 
the inverted reaction mixture, 10 ml of 2N sulfuric acid were added and 
the viscosity (1% acidic viscosity) under acidic conditions was measured 
using a B-type viscometer (product of Tokyo Keiki Co., Ltd.). 
(5) Measurement of coagulation performance (sedimentation half-value 
period): 
In a 100-ml beaker, 3 g of kaolin and 80 g of ion exchange water were 
weighed, followed by stirring with a magnetic stirrer. The reaction 
mixture was adjusted to pH 6.2 to 6.5 with 0.1N NaOH, followed by stirring 
for about one minute. The reaction mixture was then poured into a settling 
tube, and ion exchange water was added thereto to a total amount of 100 
ml. An aqueous polymer solution which had been diluted to a polymer 
concentration of 0.1% was added to the settling tank so that the amount of 
the polymer became 1.5 ppm based on the total amount of the liquid. The 
settling tube was turned upside down twenty times by an end-over-end 
mixer, and then was allowed to stand. The time (seconds) required to 
settle the flock thus formed until the upper end thereof reached a scale 
of 50 ml was measured. 
The results are shown in Table 1 below and in FIGS. 1 and 2. 
TABLE 1 
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Sedimen- 
Monomer tation 
Concentration 
1% Acidic 
half-value 
Experiment (water phase) 
Viscosity 
period 
No. Monomer (%) (cps) (sec) 
______________________________________ 
Example 1 
Sample 1 48.6 4600 30 
Example 2 
Sample 1 38.9 4400 -- 
Example 3 
Sample 1 27.8 3300 -- 
Example 4 
Sample 1 16.7 2250 -- 
Example 5 
Sample 2 48.6 4600 30 
Example 6 
Sample 2 38.9 4500 -- 
Example 7 
Sample 2 27.8 3100 -- 
Example 8 
Sample 2 16.7 2100 -- 
Comp. Ex. 1 
Comp. Sample 1 
48.6 1600 53 
Comp. Ex. 2 
Comp. Sample 1 
38.9 2400 -- 
Comp. Ex. 3 
Comp. Sample 1 
27.8 3000 -- 
Comp. Ex. 4 
Comp. Sample 1 
16.7 1800 -- 
Comp. Ex. 5 
Comp. Sample 2 
48.6 3400 40 
Comp. Ex. 6 
Comp. Sample 2 
38.9 4100 -- 
Comp. Ex. 7 
Comp. Sample 2 
27.8 3400 -- 
Comp. Ex. 8 
Comp. Sample 2 
16.7 1600 -- 
______________________________________ 
As apparent from Table 1 and FIG. 1, in each case where the raw material of 
comparative samples 1 and 2 was used as the acrylamide, the 1% viscosity 
of the resultant polymer showed a decrease as the monomer concentration in 
the water phase exceeded about 30 wt. % or 40 wt. %. On the other hand, in 
each case where samples 1 and 2 of the invention were used, even when the 
monomer concentration in the water phase exceeded 40 wt. %, the 1% acid 
viscosity of the polymer did not show a decrease. In those cases, the 
viscosity was maintained at a high level, which is entirely different from 
the results of comparative samples 1 or 2. 
There is a close mutual relationship between the sedimentation half-value 
period of kaolin and 1% acidic viscosity of each of the polymers obtained 
by polymerizing at a monomer concentration of 48.6 wt. % in the water 
phase (FIG. 2). The above results demonstrate that a higher molecular 
weight was attained when samples 1 and 2 of the invention prepared by an 
enzymatic method were used, as compared with comparative samples 1 and 2 
prepared by the copper catalytic method. 
EXAMPLES 9 AND COMATIVE EXAMPLES 9-10 
(1) Monomers used: 
Sample 1 (the same as above) 
Comparative Sample 1 (the same as above) 
Comparative Sample 2 (the same as above) 
Acrylic acid (product of Mitsubishi Petrochemical Company Limited) 
(2) Preparation of an emulsion: 
In 261.8 g of each of sample 1, comparative sample 1 or comparative sample 
2 were incorporated 23.1 g of acrylic acid. The resulting mixture was 
adjusted to pH 6.3 with a 40% aqueous NaOH solution, followed by addition 
of water to a total amount of 316.8 g to prepare the water phase. To the 
water phase, 114.6 g of liquid hydrocarbon ("Isozole 400", trade name; 
product of Nippon Petrochemicals Co., Ltd.) and 8.8 g of an emulsifier 
("Span 80:) were added, followed by preliminarily emulsifying for about 
three minutes using a magnetic stirrer. Emulsification was conducted for 
30 seconds in a WARING blender at a stirring rate of 14,700 rpm to prepare 
an emulsion. 
The emulsions thus obtained were subjected to step (3) to (5) of Example 1 
above in accordance with the procedures of Example 1. 
The results are shown in Table 2 below. 
TABLE 2 
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Monomer 
Concentration 
1% Acidic 
(water phase) 
Viscosity 
Experiment No. 
Monomer (%) (cps) 
______________________________________ 
Example 9 Sample 1 48.6 4000 
Comp. Ex. 9 
Comp. Sample 1 
48.6 2500 
Comp. Ex. 10 
Comp. Sample 2 
48.6 3100 
______________________________________ 
EXAMPLE 10 AND COMATIVE EXAMPLES 11 AND 12 
(1) Monomers used: 
Sample 1 (the same as above) 
Comparative Sample 1 (the same as above) 
Comparative Sample 2 (the same as above) 
Trimethylaminoethyl methacrylate hydrochloride (product of Kohjin Co., 
Ltd.) 
(2) Preparation of emulsion: 
In 246.3 g of each of sample 1, comparative sample 1 and comparative sample 
2 were incorporated 30.8 g of trimethylaminoethyl methacrylate 
hydrochloride. Water was added to the resulting mixture to a total amount 
of 316.8 g to prepare a water phase. To the water phase, 114.6 g of liquid 
hydrocarbon ("Isozole 400", trade name; product of Nippon Petrochemicals 
Co., Ltd.) and 8.8 g of an emulsifier ("Span 80") were added, followed by 
preliminarily emulsifying for about three minutes using a magnetic 
stirrer. Emulsification was conducted for 30 seconds in a WARING blender 
at a stirring rate of 14,700 rpm to prepare an emulsion. 
The emulsions thus obtained were subjected to steps (3) to (5) of Example 1 
above in accordance with the procedures of Example 1. 
Incidentally, the viscosity of the 1% aqueous polymer solution was measured 
in a manner similar to Example 1 except for using 20 g of NaCl instead of 
10 ml of 2N sulfuric acid. 
The results are shown in Table 3. 
TABLE 3 
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Monomer 
Concentration 
1% Salt 
(water phase) 
Viscosity 
Experiment No. 
Monomer (%) (cps) 
______________________________________ 
Example 10 Sample 1 48.6 3200 
Comp. Ex. 11 
Comp. Sample 1 
48.6 2200 
Comp. Ex. 12 
Comp. Sample 2 
48.6 3000 
______________________________________ 
While the invention has been described in detail and with reference to 
specific embodiments 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.