CA1247015A - Water-separating agent - Google Patents

Abstract

Abstract of the Disclosure This invention pertains to a water-insolubi-lized resin of a polymer of at least one monomer selected from N-alkyl- or N-alkylene-substituted acrylamides or methacrylamides represented by the following general formula (I);

(I) wherein R1 and R2 mean individually a hydrogen atom or methyl group and R3 denotes a methyl, ethyl or propyl group, with the proviso that R3 is an ethyl or propyl group when R2 stands for a hydrogen atom, and that R3 is a methyl or ethyl group when R2 stands for a methyl group, or wherein R2 and R3 form or in combination; or a copolymer of at least one monomer selected from the acrylamides or methacrylamides and another copolymerizable monomer.
The resin has water-absorbing capacity which varies in degree depending on temperature and, when heated, undergoes shrinkage even in the presence of a large excess of water to release once-absorbed water.
Because of this property, it may be used as a water-separating agent to remove water from a water-containing system. Since the resin can exhibit a sort of molecular sieve action, it can selectively control the concentration of a macromolecular material without affecting the concentration of a low molecular weight compound such as a buffer agent. The resin is useful particularly in concentrating an aqueous solution or emulsion containing a material susceptible to thermal denaturation, such as an edible substance, amino acid, protein, polysaccharide or, enzyme which is difficult to concentrate by the evaporation technique, and also in controlling the concentration of an aqueous solution while adjusting the degree of water-absorbing capacity of the resin by varying its temperature.

Description

SPECIFICATION

Title of the Invention:
~ATER-SEPARATING AGENT

Background of the In~ention:
a) Field of the Invention:

-This invention relates to an agent forseparating water from a water-containing system, and more specifically to a water-separating agent having water-absorbing capacity, which varies in degree depending on temperature r is capable of absorbing and retaining water therein and, when heated, is capable of undergoins shrinkage even in the presence of a large excess of water so as to release the thus-retained water.

b) Description of the Prior Art:
Separation of water has been routinely practiced in such process steps as concentration of aqueous solutions, crystallization from aqueous solu-tions and production of pure water.
As specific techniques useful in the practice of such process steps, may be mentioned inter alia 1) separation of water through such membranes as reverse osmosis membranes and ultrafiltration membranes; and s, ~

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2) separation of water by making use of phase change of water such as the multi-stage flash distillation method or lyophilizing mathod. There techniques have already found commercial utility. However, none of these conventional techniques are fully satisfactory.
Thus, a variety of improvements has been attemptedO
Recently, resins capable of absorbing and retaining water in amounts several hundreds times their own weights have been developed. These resins are generally called highly water-abosrbing resins and they are now being applied in various fields.
These resins are however accompanied by the following problems:
Cl) After absorbing water, the above resins may be regenerated only when heated to drive off the thus-absorbed water. When their regeneration i5 contemplated for reuse! enormous costs are required.
~ 2) The amounts of water which the above resins can absorb vary depending on whether the water is pure water or salt water. The amounts will generally decrease in salt water, in some instances to as little as one twentieth of that in pure water.

(3) After absorbiny water, the above resins may not be fully satisfactory in dynamic character-istics, especially in shape-retaining capacity.
On the other hand, various physical properties ~2~

of divexse water-retaining gels have recently been measured. From results of such measurements, it has been found that the water content of water-retaining gels at equilibrium is dependent on the temperature [Journal of polymer Science: Polymer Symposium 66, 209-219 (1979); European Polymer Journal 17, 361-366 (1981); Polymer Bulletin 7, 107-113 tl982)]. It may thus be suggssted that there is a chance to develope a water-separating technique making use of such gels under various temperatures. From the practical standpoint, the extent of the swelling of such gels at low temperatures are however not as large as the data given in the above literature. Furthermore, differences in water-absorbing capacity at various temperatures are not satisfactorily large. It has not been investigated how fast such gels would swell or shrink when their temperatures are changed.
They are however very unlikely to undergo fast swelling or shrinkage even when their temperatures are changed.
The present inventors have carried out an extensive research with the foregoing in view. As a result, it has been discovered that a water-insolubi-lized polymer or copolymer of certain specific acryl or methacryl amide derivatives can absorb water and can thus swell to a large degree even at low ~;~4t7~5 temperatures, that water-absorbing capacity can vary to a great degree due to temperature changes and that this change in water-absorbing capacity takes place extremely rapidly. Therefore, this water-insolubilized polymer or copolymer has been found to be extremely useful as a water-separating agent from the practical viewpoint.
Summary of the Invention An object of an aspect of this invention is to provide a method of controlling the water concentration of an aqueous solution or emulsion containing a macromolecular compound.
An aspect of the invention is as follows:
A method of controlling the water concentration of an aqueous solution or emulsion containing a macromolecular compound comprising (i) contacting said aqueous solution or emulsion with an agent for absorbing and releasing water, said agent comprising a water-insolubilized resin of a polymer of at least one monomer selected from N-alkyl- or N-alkylene-substituted acrylamides or methacrylamides represented by the following general formula (I):
Rl R2 I / (I) CH2 = C - CON
\R3 wherein Rl and R2 mean individually a hydrogen atom or methyl group and R3 denotes a methyl, ethyl or propyl group, with the proviso that R3 is an ethyl or propyl group when R2 stands for a hydrogen atom, and that R3 is a methyl or ethyl group when R3 stands for a methyl group, or wherein R2 and R3 form -~CH2~ or (CH2 ~ 0 -~CH2~ in combinat;on; or a copolymer of at least one monomer selected from the said acrylamides or methacrylamides and another copolymerizable monomer, and (ii) raising or lowering the temperature of the aqueous system by heating or cooling to vary the amount of water absorbed and retained by the said agent.

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Detailed Description of the Invention In the present invention, the water-insolubilized polymer or copolymer has typically the property that, when its aqueous solution is heated, it is rendered hydrophobic to develop cloud in the aqueous solution. ~owever, the water-insolubilized polymer or copolymer should not necessarily be limited to a polymer or copolymer equipped with this property. Any polymers or copolymers may be used as long as their water-absorbing capacity levels vary depending on temperature. These polymers or copolymers have amphiphilic properties~ In other words, they have broad solubility in that they are equipped with such hydrophilic and hydrophobic properties that they can be dissolved not only in water but also in an organic solvent such as benzene.
As examples of the above-described polymer and copolymer, may be mentioned pol~mers and copoly-mers of at least one of the following N-alkyl- or N-alkylene-substituted acryl and methacryl amides:

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Amide N-n-Propylacrylamide N-n-Propylmethacrylamide N-Isopropylacrylamide N-Isopropylmethacrylamide N-Ethylacrylamide N-Ethylmethacrylamide N,N-Dimethylacrylamide N,N-Dimethylmethacrylamide N-Methyl-N-ethylacrylamide N-Methyl-N-ethylmethacrylamide N-Acryloylpyrrolidine N-Methacryloylpyrrolidine N-Acryloylmorpholine N-~athacryloylmorpholine ~s will become apparent from data which will be described herein, resins obtained by insolubilizing polymers or copolymers of the following monomers are not preferred in view of their swelling characteris-tics:
~ 1) N-monoalkyl-substituted acrylamides and methacrylamides in the general formula (I), wherein when R2 and R3 mQan a hydrogen atom and alkyl group, respectively, the alkyl group contains 4 or more carbon atoms as in N-butylacrylamide ar N-butylmethacrylamide;

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(2) N,N-dialkyl-substituted acrylamides and methacrylamides, N-methyl-N-propylacrylamide or N-methyl-N-propylmethacrylamide of the general formula (I) in which R2 and R3 denote a methyl group and propyl group, respectively, and those represented by the general formula (I) in each of which the total number of carbon atoms of the alkyl group is 4 or more as in N,N-diethylacrylamide or N,N-diethylmethacryl-amide; and (31 N-alkylene-substituted acrylamides those represented by the general formula (I) in which R2 and R3 forms a group and, as in N-acryloylpiperidine or N-methacryloylpiperidine, n is 5 or greater.
In addition, one or more monomers selected from for example hydrophilic monomers, ionic monomers - and hydrophobic monomers may additionally be copolymer-ized in order to control the amount of water to be absorbed and to improve the shape-retaining capacity of the water-absorbed resin.
As exemplary hydrophilic monomers, may be mentioned acrylamide, methacrylamide, N-methylacryl-amide, N-methylmethacrylamide, diacetoneacrylamide, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, various methoxypolyethyleneglycol methacrylates, various methoxypolyethyleneglycol acrylates, N vinyl-2-pyrrolidone, N-acryloyl alanine and N-methacryloyl alanine. Further, vinyl acetate or glycidyl methacrylate for example may be introduced by copolymerization, followed by hydrolysis to impart hydrophilicity.
Illustrative of such ionic monomers are acids such as acrylic acid, methacrylic acid r vinylsulfonic acid, allylsulfonic acid, methallyl-sulfonic acid, styrenesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic a~id and 2-acrylamido-2-methyl-propanesulfonic acid and their salts; amines such as N,N-dimethylaminoethyl methacrylate, N,N-dlethyl~minoethyl meth2crylate, N,N-dimet.h.ylaminoethyl acrylate, N,N-dimethylaminopropyl methacrylamide and N,N-dimethylaminopropylacrylamide and their salts.
Further, it is also possi~le to impart ionic properties by introducing various acrylates, methacrylates, acryl-amides, methacrylamides or acrylonitriles by copolymer-ization and then hydrolyzing the thus-introduced moieties~
As hydrophobic monomers, may for example be .
mentioned N-alkylacrylamide derivatives and M-alkylmethacrylamide derivatives such N-n-butylacrylamide, N-n-butylmethacrylamide, N-tert-butylacrylamide, N-tert-butylmethacrylamide, N,N-diethylacrylamide, ~L2~

N,N-diethylmethacrylamide, N-acryloylpiperidine, N-methacryloylpiperidine, ~-n-hexyl-acrylamide, N-n-hexylmethacrylamide, N-n-octylacrylamide, N-n-octylmethacrylamide, N-tert-octylacrylamide, ~-n-dodecylacrylamide, N-n-dodecylmethacrylamide and the like; N-~-glycidoxyalkyl)acrylamide derivatives and N-(~-glycidoxyalkyl)methacrylamide derivatives such as N,N-diglycidylacrylamide, N,N-diglycidyl-methacrylamide, N-(4-glycidoxybutyl)acrylamide, N-(4-glycidoxybutyl)methacrylamide, N-(5-glycidoxy-pentyl)acrylamide, N-(6-glycidoxyhexyl)acrylamide and the like; acrylate derivatives and methacrylate derivatives such as ethyl acrylate, methyl methacrylate, butyl methacrylate, butyl acryiate, iauryl acrylate, 2-ethylhexyl methacrylate and glycidyl methacrylate;
acrylonitrile; methacrylonitrile; vinyl acetate; vinyl chloride; olefins such as ethylene, propylene and butene; styrene; a-methylstyrene; butadiene; and isoprene.
The acceptable proportion of such a hydrophilic, ionic or hydrophobic monomer to the acrylamide or methacrylamide derivative may vary depending on the combination of the acrylamide or methacrylamide derivative and the above-mentioned monomer. Although not sweepingly applicable to every combination, the hydrophilic, ionic and hydrophobic monomers may generally be used in amounts of 60 wt.%
or less, 30 wt.% or less and 60 wt.% or less, respectively.
As a method for making a polymer of the above-described monomer insoluble in water, the polymer may be insolubilized to water either upon polymerization or by subjecting it to treatment after polymerization. As specific insolubilizing methods, the following various methods may be emp-loyed:
(1) to copolymerize a crosslinkable monomer containing at least two dou~le ~onds per molecule with the above-described acrylamide or methacrylamide derivatives;
(21 to copolymerize the polymer with an N-alkoxymethyl(meth)acrylamide derivatives;
~ 31 to increase the proportion of the above-mentioned hydrophobic monomer and to copolymerize it with acrylamide or methacrylamide derivatives7

(4) to effect polymerization by the bulk polymerization method;

(5) to ~ubject the polymer to a heat treatment;

(6) to integrate the polymer wi-th a water-insoluble fibrous material such as cellulose;

(7) when the polymer contains for example hydroxyl, amino or carboxy groups, to cause such groups with a polyfunctional compound such as epichlorohydrin to insolubilize the polymer; and

(8) to copolymerize the monomer represented by the general formula (I) with a monomer containlng a substituent group such as a caxboxyl group, sulfo group or hydroxyl group having at least one active hydrogen atom, or to form the polymer of the monomer represented by the general formula (I) and a polymer of the above monomer into a polymer complex, thereby insolubilizing the polymer.
The a~ove insolubilizing methods will next be described more speci~ically.
In the first method, it is possible to use as exemplary crosslinkable monomers ~,N'-methylene-bisacrylamide, N,N-diallylacrylamide, triacrylic formal, N,N-diacryloylimide, N,N-dimethacryloylimide, ethyleneglycol acrylate, ethyleneglycol dimeth-acrylate, various polyethyleneglycol diacrylates, various polyethyleneglycol dimethacrylates, ~0 propyleneglycol dimethacrylate, propyleneglycol diacrylate, various polypropyleneglycol diacrylates, various polypropyleneglycol dimethacrylates, 1,3-butyleneglycol diacrylate, 1,3-butyleneglycol dimethacrylate, 1,4-butyleneglycol dimethacrylate, glycelol dimethacrylate, neopentylglycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane ~2~7~

trimethacrylate, trimethylolethane trimethacrylate, trimethylolethane triacrylatel tetramethylolmethane tetramethacrylate, tetramethylolmethane triacrylate, divinylbenzene and diallyl phthalate. The proportion of each of these crosslinkable monomers to the above-described acrylamide derivative may vary depending on the combination of the acrylamide derivative and crosslinkable monomer as well as the desired crosslinking degree. Although not applicable sweepingly to every situation, the crosslinkable monomers may each ~e used in an amount of 0.01 - 10 wt.~. -N-Alkox~methyl(meth)acrylamide derivatives useful in the practice of the second method may include N-hydroxymethyl(meth)acrylamides. For example, N-methylol~meth)acrylamides, N-me~hoxymethyl-(meth)acrylamides, N-ethoxymethyl~meth)acrylamides~
N-n-butoxymethyl(meth)acrylamides and N-tert-butoxymethyl(meth)acrylamides may be used. The proportion of each of such N-alkoxymethyl~meth)acryl-amide derivatives to the above-described acrylamide derivatives may vary depending on the combination of the acrylamide derivatives and the N-alkoxymethyl-(meth)acrylamide derivatives. Although not applicable sweepingly to every combination, the N-alkoxymethyl-(meth~acrylamide derivatives may each be used generally ~L2~

in an amount of 0.01 - 30 wt.%.
In the third me~hod, the proportion of the hydrophobic monomer to the ~meth)acrylamide derivative having amphiphilic property may vary depending on the combination of the (meth)acrylamide derivative and the hydrophobic monomer. Although not conclusively limitable, the proportion of the hydrophobic monomer may generally ~e 1 wt.% or more, or preferably 3 wt.
or more. In this case, the copolymeri~ation may be effected using one of the random copolymerization method, block copolymerization method or graft copoly-merization method.
In the fourth method, the polymerization is carrled out by the ~ul~ polymerization method. This may be practiced by polymerizing the monomer as is without diluting it with any solvent to obtain a polymer block or ~y suspending the monomer in a solvent and then effecting the polymerization of the monomer in the form of droplets so as to obtain a granular polymer.
In the fifth method~ the polymer is su~jected to a haat treatment~ The heating conditions may vary depending on the polymer and do not remain constant. However, a polymer obtained by for example bulk polymerization, suspension polymerization or solution polymerization is heat-treated generally at ~2~

60 - 250C~ or preferably at 80 - 200C. In this case, when the polymer i5 obtained by ~he solution polymerization method, its heat treatment may be carried out concurrently with its drying or with the evaporation of the solvent~
Turning to the sixth method in which the polymer is integrated with for example a fibrous material, the above-described (meth)acrylamide derivative may be impregnation- or graft-polymerized to a water-insoluble fibrous material such as natural or synthetic fibers such as cellulose fibersl nylon fibers, polyester fibers or acrylic fibers or non-woven fabric made of polypropylene or an ethylene-propylene copolymer, or to a water-insoluble porous material such as silical alumina or zeolite. Alter-natively, the fibrous or porous material may be impregnated with the polymer~
In the seventh method, the polyfunctional compound such as epichlorohydrin is reacted with the polymer so that the polymer is crosslinked and insolubilized. In this method, it is necessary to introduce hydroxyl, amino or car~oxy groups in advance in the polymer. Amino and carboxy groups can be introduced readily by copolymerization. In the case of hydroxyl groups, they may be introduced by copolymerization hydroxyethyl methacrylate, :~L2~7~

isopropenyl phenol bv irst introducing for example vinyl acetate or glycidyl methacrylate by the copolymerization method and then saponifying it with a basic material to form hydroxyl groups. Thereafter, the above-prepared polymer and a polyfunctional compound such as epichlorohydrin are reacted to each other so as to crosslink and insolubilize the polymer.
~hen the polymer is insolubilized in an aqueous solution as is, it is converted into an agar-like state. By simply crushing the thus-obtained polymer, it can be used immediately. If it is solubilized after dispersing the aqueous solution in an oil, granular gels are obtained.
According to the eighth me.hod, a polymer complex is formed by copolymerizing the polymer with the above-described monomer containing an active hydrogen or combining the polymer with a copolymer of such a monomer. In this case, it is also possible to form polymer complex ~y regeneration the active hydrogen atoms of the copolymer which are substituted with ammonium ions or the like on mixing with the other component of the polymer by the addition of an acid then adding an acid to activate the active hydrogen atoms.
The above-described eight methods may be used singly or in combination~ Generally speaking, ~4~

more effective results are obtained when two or more of these methods are used in com~ination~
As more specific polymerization methods which may be used upon production of water-separating agents of this invention in accordance with the above-mentioned methods, the following polymerization methods may be mentioned by way of example:
(1) to polymerize a monomer as is without diluting it in a solvent and to produce a polymer block;
(2) after polymerizing in a solvent, to dry the resultant polymer or to cause the polymer to precipitate in a poor solvent, thereby obtaining the polymer;
lS (3) to obtain the polymer as a granular polymer in accordance with the suspension polymeriza-tion method;
C4) to obtain the polymer as a polymer latex in accordance with the emulsion polymerization method; and (5) to integrate the polymer with a water-insoluble fibrous material or porous material by impregnation- or graft-polymerizing a solution of the polymer to the water-insoluble ~ibrous material or porous material.
In the above specific polymerization methods, ~7~5 the polymerization may be initiated only by heating the polymerization systems. However, use of a polymerization initiator can generally bring about better results. No limitation is imposed on the polymerization initiator. Any polymerization initiators may be used as long as they can initiate radical polymerization. For example, inorganic peroxides, organic peroxides, combinations of such peroxides and - reducing agents, and azo compounds may be mentioned.
More specifically, such polymerization initiators may include ammonium persulfate, potassium persulfate, hydrogen peroxide, tert-butyl peroxide, benzoyl peroxide, cumenehydroxy peroxide, tert-butylperoxy-2-ethylnexanoate, and butyl perbenzoate. As reducing agents which may be used in combination with such polymerization initia~ors, may be mentioned sulfites, hydrogensulfites, salts of lower valence metals such as iron, copper and cobalt, organic amines such as aniline and reducing sugars such as aldose and ketose. Usable azo compounds may include azobisiso-butylonitrile, 2,2'-azobis-2-amidinopropane hydro-chloride, 2,2'-azobis-2,4-dimethylvaleronitrile and 4,4'-azobis-4-cyanovaleic acid. Two or more of the above-described polymerization initiators may be used in combination. In this case, the amount of the polymerization initiator to be added may be within the commonly-employed amount range, for example, may be within the range of 0.01 - 5 wt.%, or preferably .05 - 2 wt.%, both based on the monomer~
Among the thus-obtained polymers, the block-like polymer or the polymer obtained after evaporation of the solvent may be crushed into a powdery water-separating agent or may be melted and then formed into a flake-, fiber- or film-like ~ater-separating agent. The granular polymer may be provided as a granular water-separating agent without need for any further processing. The latex-like polvmer may be provided to impregnate and coat a fibrous or porous material such as fabric or paper or may be formed into films to provide a water-separ2t~ng agent.
In ~he manner mentioned above, the water-insolubilized polymer or copolymer (hereinafter called "the resin" for the sake or brevity) can be obtained in varlous forms. The particular form of the resin may suitably be determined depending on how the resin is to be used. When used for example in a form suspended or dispersed in a liquid as in a fluidized bed, it may often be used in the form of powder or beads.
A powdery product may be obtained by various methods as described above, for example, by conducting gel polymerization in an aqueous solution and then drying and grinding the resultant resin. ~ granular product may generally be produced with ease in accordance with the suspension polymerization method.
Since the N-alkyl- or N-alkylene-substituted ~meth~-acrylamide derivative has generally high solubilityin water, suspension polymerization may be practiced as the reversed phase suspension technique in which a monomer or its aqueous solution is dispersed in an oil, as the salted-out suspension polymerization technique in which an electrolyte is dissolved in a large amount in an aqueous solution to reduce the solubility of a monomer, or as the precipitation and suspension polymerization technique in which polymer-ization is carried out at an elevated te.,.pe ature of the cloud point of the intended polymer or higher so as to cause the polym~r to precipitate. In addition, it is also possible to integrate the polymer with porous beads such as silica, alumina or zeolite, for example, by impregnating the porous beads with a solution of the polymer or effecting graft polymer-ization on such porous beads. It is also possible to incorporate a third component miscible with the monomer or monomers but immiscible with the resulting polymer when conducting polymerization in accordance with one of the above-mentioned polymerization techniques. Incorporation of such a third component ~2~

permits production of a porous resin.
The water-separating agent produced by one of the above-mentioned techniques is solid and has such extremely unique properties that it can rapidly absorb water when ~rought into contact with water in a liquid state and can then retain the thus-absorbed water therein, and undergoes prompt shrinkage even in the presence of a large excess of water and releases the absorbed water when heated. It is also convenient in that the above process of water absorption/
retention and water release can be repeated. The amount of water to be absorbed in the water-separating agent varies depending on such factors as the compo-sition o the resln making up the agent, its tempera-ture and the composition of each aqueous solution.It can absorb water as much as 8 to 100 times its own weight at room temperature ~25C). The amount of water absorbed increases as the temperature drops.
When a low molQcular weight (m.w.) material such as an inorganic salt, organic salt or water-soluble organic material is contained in a dlssolved state in an aqueous solution, the aqueous solution may be absorbed in the resin while still containing the low m.w. material. Where an inorganic salt is contained in a dissolved state, the water-absorbing capacity of conventional water-absorbing resins decreases significantly. In the case of an acrylamide-sodium acrylate copolymer ~content of sodium acrylate:
21 wt.%l crosslinked by methylenebisacrylamide for example, the water absorbed by the copolymer in a lN
aqueous solution of sodium chloride was as little as one seventeenth that absorbed by the same copolymer in distilled water. On the other hand, the percent reduction of the water-separating agent according to this invention is as small as 10% or so. Therefore, it may be concluded that the amount of water which water-separating agents of this invention can absorb are affected only slightly by salts dissolved in the water. Conversely, it has been found that water-separating zgents of this invention may absorb mo~e water depending on the type of salt dissolved in the waterO Calcium chloride may be mentioned by way of example as such a salt.
As has been mentioned above, the resin of this invention may act in two ways depending on the molecular weight of a solute, i.e., a solution may be absorbed in the gel either together with its solute or without its solute~ In other words, the resin has a molecular sieve function. The critical molecular weight varies depending on the composition and temperature of each resin. Where the degree of insolubilization is low and a relatively large amount :, ~2~

of water can ~hus be absorbed because, for example, the crosslinking degree is low or the resin is a copolymer of a hydrophilic or ionic monomer, the critical molecular weight is generally large. On the other hand, where a resin can absorb only a relatively small amount of water because, for example, its crosslinking degree is high or it is a copolymer of a hydrophobic monomer, the critical molecular weight is generally small. Needless to say, when controlling the concentration of an a~ueous solution by a resin of this invention, the solute of the aqueous solution must have a molecular weight higher than the critical molecular weight of the resin.
As for the critical welsht, it is difficult to give any specific definite value because it changes considera~ly depending on the composition and tempera-ture of each resin, the composition of each aqueous solution and the type of each material to be con-centrated. For example, the critical molecular weight of a resin obtained by crosslinking poly(N-acryloyl-pyrrolidine) with methylenebisacrylamide is on th~ order of 1,000 at room temperature when it is used for the concentration of polyethylene glycol. On the other hand, its critical molecular weight is on the order of 10,000 when it is used to concentrate for example a dextran or protein. In other words, the critical molecular weight is dependent on the state of molecules dissolved in an aqueous solution, i.e., the e~tent of spread of the molecules. Therefore, it ,s impossible to give a specific value as the critical molecular weight. The critical molecular weight has a certain degree of distri~ution.
Needless to say, particles or droplets insoluble in water and suspended in water, such as droplets dispersed in emulsions, microorganisms or scum in liquid wastes from fermentation plants cannot ~e taken into a water absorbing gel of the resin.
When the temperatuxe of the resin is raised after a~sorption of water, the resin undergoes shrinkage and hence releases the water. If the temperature of the resin is raised further, the shrinkage of the resin becomes extremely slow, i~e., a transition point is observed. This transition point is governed by the composition of each resin. It is generally possible to control the transition points o~ resins according to this invention within the range of 10 - 100C. The extent of shrinkage of each resin around its transition point varies depending on such actors as the composition of the resin and the composition of an aqueous solution to which the resin is applied. However, it may generally range from 1 to 20 times its own weight. As mentioned above, ~2~

water may ~e separated and retained by repeatedl~
heating and cooling the resin. In this case, the resin may generally ~e caused to absorb water at a temperature within the range of 0 100C. To heat the resin subsequent to its water absorption so that the resin undergoes shrinkage, the heating temperature may generally range from 10 to 200C although this temperature will certainly vary depending on what end use is to be made on the resin.
Description will next be made on a specific method for the separation of water. The resin is first brought into contact with an aqueous solution from which one wants to remove water. The resin which has absor~ed wa~er therein is separated from the aqueous water, followed by its exposure to an atmos-phere of a higher temperature so that the water is released. By repeating this series of operations, the resin can separate a great deal of water. If a low m.w. material is dissolved in the aqueous water, water can be separated as an aqueous solution contain-ing the low m~w. material.
Where the remaining liquid, which has been obtained after the separation of water by the resin in the above process, is to be retained, the above process is considered to be a concentration or dewatering operation. On the other hand, where the ~7~
- 2~ -thus-separated water is important per se, the above process is considered to be a pure water production process .
In other words, when it is desired to concentrate an aqueous solution, the concentration may be effected by bringing the resin into contact with the aqueous solution and repeating the above-mentioned operation. A great deal of an aqueous solution can ~e concentrated in this manner. Even if a low m.w. material is present together with a macromolecular material in the aqueous solution at this time, the macromolecular material only will be concentrated without the low m.w. material in the remaining liquid because the resin has a molecular sieve function as mentioned above.
When it is desirous to control the concen-tration of an aqueous solution with the resin of this invention, the resin is brought into contact with the aqueous solution either as is or a~ter causing the resin to swell with a suitable aqueous solution.
The concentration of the aqueous solution may then be adjusted to a desired level by controlling the tem-perature o the aqueous solution suitably. In this case, a higher temperature pexmits dilution whereas a lowex temperature induces concentration. Then, the resin is separated by for example sedimentation, filtrations, centrifugation or the supernatant is collected, thereby o~taining an aqueous solution of the desired concentration level. In the above manner, the concentration of the aqueous solution may be adjusted to various levels by simply changing the temperature of the aqueous solution in the above-described process. The adjustable concentration range varies depending on the resin to be used, the proportion of the resin to the aqueous solution and the level of a temperature to be used. Although not sweepingly applicable to every situation, it is generally possi~le to achieve an adjustment range of from about 0.01 to 100 times for each starting aqueous solution. Even if a low m.w. material is present along wi~h a macromolecular material in the aqueous solution, the concentration of the macro-molecular material alone will be changed without affecting the concentration of the low m.w. material.
The thus-used resin may be readily regenerated, ~0 for example, by rinsing it with water or by heating and shrinking it to release the thus absorbed water.
Thus, the resin can be used repeatedly. It is one of the convenient features of the resin of this invention that it can ~e regenerated with ease as mentioned above.
The resin of this invention may be applied - 28 - .

in various ways, depending on individual purposesO As a basic embodiment, the water-separating agent, which may be in the form of powder, flakes, beads, fibers or film, is first brough.t into contact with the water contained in an aqueous solution from which one wants to remove water. The water-separating agent is then allowed to absorb water, followed by separation of the water-separating agent from the aqueous solution. As a specific method for causing the agent to absorb water and then separating the water from the aqueous solution, various methods may be employed, including for example to add the water-separating agent directly to the aqueous solution and then to separate the water-absor~ed agent by for example sedimentation, filtration or centrifuga-tion; to pack beforehand the water-separating agent in a member which holds the agent separately from the aqueous solution for example in a bag, to bring the agent still in the bag into contact with the aqueous 20 solution to absorb eater therein and then to separate the agent from the.aqueous solution: or to process the water-separating agent in for example fibers or plain weaves, to immerse the resulting fabric-like water-separating agent in the aqueous solution so ~5 as to allow it to absorb water therein, and then to pull it out of the aqueous solution. The above ~7~

operations may ~e carried out many times. Upon effecting the a~ove operations, it is convenient to cause the water-separating agent to absorb water at temperatures as low as feasible, because use of such low temperatures will lead to a larger amount of water being absorbed.
After absorption of water, the water-separating agent is then exposed to at an elevated temperature so as to release the thus-absorbed water. This may be achieved for example by dipping the agent in hot water, ~lowing a hot gas such as steam against the agent, or allowing the agent to stand in hot air, for example, in a drier. When using the water-separating agent repeatedly, it is effective to remove water from the agent as much as practically feasible from the viewpoint of achieving a higher efficiency in su~sequent water separation.
As specific examples of applications of water-separating agents of this invention, may be mentioned concentration of various aqueous solutions, particularly concentration of aqueous solutions containing for example edible materials, amino acids, proteins, polysaccharides or enzymes, the concentra-tion of which is difficult since they are susceptible to denaturation under heat, and concentration of emulsions which cannot be readily concentrated since ~7a;~

they are also denatured by heat; crystallization a-t low temperatures, especially crystallization of materials which are susceptible to thermal denaturation;
control of the concentration of aqueous solutions by chan~ing the temperatures of the aqueous solutions to adjust the water-absorbing capacity of resins; and production of pure water from various aqueous solu-tions, typically, production of pure water from water which contains microorganisms such as bacteria.
It is extremely easy to allow each water-separating agent of this invention to retain water therein. In o~her words, the water-separating agent can absorb and retain ~ater therein when it is merely brought into contact with water in its liquid state.
There is no particular limitation imposed on the shape of the water-separating agent. It may be used in the form of powder, flakes, fibers or film or in a com-posite form with another fibrous material, depending on its application field or purpose. In this case, it is possible to cause the water-separating agent to release the thus-absorbed water or to absorb additional water by changing its surrounding temper-ature. The above operation may be repeated as many times as desired. Accordingly, use of the water-separating agent of this invention permits theabsorption or release of water without inducing water ~2~

evaporation, ~y simply changing its surrounding temper ature. Hence, the water-separating agent may ~e applied to retain water in an extremely wide variety of fields.
As specific applications, may for example ~e mentioned maintenance of soil under wet conditions;
modification of fibers such as acrylic fibers; removal of water from solutions; modification of adhesives;
~ase materials for soft contact lenses; base matexials for resins suita~le for use in the separa-tion of proteins or enzymes; modification of polymer flocculants; destruction of concrete; raw materials for macromolecular absorbents suitable for use in sanitary products such as sanitary napkins and diapers; raw materials for heavy metal ion adsorbents;
solidification of sludge and liquid waste materials;
base materials for water-base gels; prevention of dew formation on wall materials and ceiling materials;
raw ma-terials for water-cutting sealing agents; and ~0 raw materials for fire-retardant and/or noise-insulating construction materials.
Where a low m.w. material is dissolved in an aqueous solution to be retained in a water-separating agent according to this invention, the water-separating agent can also retain the low m.w.
material ln the form dissolved in the aqueous solution.

- 3~ -As a further characteristic featuxe of the water-separating agent of this invention, it is also mentioned that, even when the agent has already retained water therein, it still permits prompt diffusion of the low m.w. material thereinto from the solution in which the material is dissolved, thereby making the concentration of the material in the solution equal to that in th~ agent. As specific utilization of such properties, it is possihle to apply water-separating agents of this invention for the removal of low m.w. materials from an aqueous solution or emulsion containing macromolecular materials such as proteins along with the low m.w.
materials dissolved therein although this separation lS has heretofore been carried out using for example membranes. For example, water-separating materials of this invention may be applied to the field of purification of macromolecular materials although it has conventionally believed to be difficult to remove for example salts from solutions of such macromolecular materials. In addition, it is also expected that water-separating agents of this invention will find utility as retaining agents for sustained release preparations in view of their ability to permit diffusion of low m.w. materials.
As described above, the water-separating ~4~

agents of this invention can be readily regenerated by making use of their swelling and shrinkage characteristics which are exhibited when their temperatures are changed. Since the water-separatlng agents of this invention have excellent properties such that, even in the concurrent presence of an inorganic salt, their water-absorbing capacity are not reduced too much and, even after absorption of water, they still have good shape-re-.aining properties, they have brought about the following advantageous effects: As the first advantageous effect, the separation of water does not rely upon its phase change such a~ evaporationor, lyophilization. Corollary to this, they permit water separation at iow energy costs. Water separation making use of one or more of the water-separating agents of this invention does not necessaril~ require large facilities, thereby making it possible to install water-separating facilities at a desired site or location. Second, the water-separating agents of this invention can control the concentrations of aqueous solutions merely by chan~ing their temperatures without developing phase change. Hence, it is possible to minimize the 105s 0~ each solute due to its denatura tion caused by changes in temperature or phase.
Third, the water-separating agents of this invention can arosor~ and thus separate morP water as the temper-ature decreases. Therefore, they are extremely effective for the concentration or crys-tallization of aqueous solutions which contain materials susceptible to thermal denaturation. Fourth, the water-separating agents of this invention have molecular sieve functions. Therefore, they can selectively adjust the concentrations of macromolecular materials such as for example proteins and enzymes while leaving unchanged the concentrations of low m.w. compounds such as ~uffer agents. Fifth, the amounts of water which the water-separating agents of this invention can retain may ~e reversibly controlled by changing the water temperature suita~ly. Thereore, i~ is possible to control the water content of the surround-ing atmosphere by adjusting its temperature. Sixth, ~he a~sorbed water may be released due to the inhexent nature of the resins even in an aqueous solution, provided that the resins are heated. In addition, water may be allowed to diffuse rapidly through the resins because of their inherent nature. Thus, the resins have the advanta~es that they may ~e washed with ease and may ~e repeatedly regenerated for reuse.
This invention will hereinafter be described in further detail by the Examples below. It should however be borne in mind that this inventlon is not ~%~

limited to or by the Examples.

Example 1:
N-Acryloylpyrrolidine containing 1 wt.% of tert-butyl peroxy-2-ethylhexanoate was allowed to stand at 40C for 50 hours to effect solventless polymerization, thereby obtaining a block-like polymer.
The polymer was then crushed, and a powder portion of particle sizes in the range of 20 - 100 mesh was collected as a sample. After pouring 1.0 g of the sample into distilled water of a prescri~ed tempera-ture and then allowing it to stand there so as to swell, the sample was collected by filtering the distilled water through a wire mesh so as to r.easure the ~xtent of its swelling. Measurement results are given in Ta~le 1.

Table 1 . _ ... _ . _ Temperature (C) 9 25 33 40 Extent of swelling (g) 30.7 24.8 18.6 15.1 ~ _ _ Temperature (C) 49 58 70 77 Extent of swelling ~g) 11.4 5.5 3.6 2.7 Example 2:

Poured into a 50-ml graduated cylinder was - 36 ~

1.0 g of the sample powder obtained in Example 1. It was first allowed to swell at room temperature and the volume of its swelling was measured ~y reading the gradations. Thereafter, the sample was allowed to stand for 15 minutes successively at each of temperatures given in Table 2 in the same order as they appear in the Table. After exposure to each of the temperatures, the volume of swelling was measured.
Results are also given in Table 2.

Table 2 _ _ .
Measurement order 1 2 3 4 5 6 Temperature (C) 32 25 10 25 32 50 Volume of 26.731.6 36.4 31.8 26.7 lS.8 swelllng (ml) - _ Measurement order 7 8 9 10 11 Temperature 1C) 58 68 58 50 32 Volume of 8 9 6.0 8.9 15 4 26.7 swelling ~ml) .

Examples 3 - 38:

Sample powders were obtained respectively ~y copolymerizing their corresponding monomers given in Ta~le 3 and grinding the resultant copolymers`in the same manner as in Example 1. Following the s procedure o~ Example 2, the volumes of swelling of 1.0 g of each sample powder were measured at 25C and 50C. Results are summarized in Ta~le 3.

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Example 39:
Added into a Dewar flask was a 30% aqueous solution of N-acryloylpyrrolidine. After purging the solution with nitrogen gas, sodium hydrogensulfite and potassium persulfate were added at 30C each in an amount of 0.5 wt.~ based on the N-acryloylpyrroli-dine. The N-acrylo~lpyrrolidine was then polymerized adiabatically. The resulting gel was chopped and then dried at 120C. It was then ground into powder, from which a fraction of 20 - 100 mesh was collected as a sample. Following the procedure of Example 2, the volum~s of swelling of 1.0 g of the sample powder were measured at 25~C and 50C and found to be 22.0 ml and 7.5 ml, respectively.

Example 40:
A 20~ aqueous solution of N-iso-propylacryl-amide containing 10,000 ppm of N,N'-methylenebisacryl-amide was adiabatically polymerized in the same manner as in Example 39. By conducting subsequent treatments in the same manner as in Example 39, a sample powder was obtained. Following the procedure of Example 2, the volumes of swelling of 1.0 g of the sample powder were measured at 25C and 50C and found to be 19.0 ml and 11.0 ml, respectively.

Examples 41 - 44:
To each of the aqueous electrolyte solutions shown in Table 4, 1.0 g of the sample powder obtained in Example l was added. In the same manner as in Example 2, the volumes of their swelling were each measured at 30C. Results are given in Table 4.

Table 4 , _ __ _ 10 Example Electrol~te(g/100 g-water) (ml) _ 41 Sodium chloride 5.8 24.4 42 Calcium chloride l.l 30.6 43 Ammonium sulfate 1.3 21.9 44 Sea water 25.5 Example 45:
One gram of the sample obtained in Example l was added to 100 ml of a 3.5~ aqueous NaCl solution of 30C. The resultant mixture was then allowed ~o stand for l hour. After that, a measurement of the NaCl concentration in the aqueous solution gave a value of 3.5%. The volume of its swelling at that time was 25.3 ml. Then, it was cooled to 10C and allowed to stand for 15 minutes. A measurement of the NaCl concentration in the aqueous solution gave a value of 3.5%. ~t that time, the volume of its swelling was 33.4 ml. It was then heated to 53C and allowed to stand for 15 minutes. A measurement of the NaCl solution in the aqueous solution gave a value of 3.5%. The volume of swelling was 19.5 ml at that time.

Example 46:
After causing a portion of the sample powder obtained in Example 1 to swell in distilled water, 20 g of the resulting gel was collected. It was then poured into 30 ml of a 5.0% solution of sodium chloride in water, followed by stirring of the resultant mixture. Three minutes later, the concen-tration of sodium chloride in the aqueotls solution was measured in terms of refractive index. It was found to be 3~1%. After collecting the thus-swelled sample by filtration, it was heated to 60C to release water. A measurement of the concentration of sodium chloride contained in the released water gave a value of 3.1~.

Example 47:
At 15C, 0.5 g of the sample powder obtained in Example 1 was added to 30 g of commercial milk.
After stirring the resultant mixture, it was filtered.

The weight of the iltrate was 21 g. Thus, 9 g of its : L2~
~ 46 -water was removed.

Example 48:
After causing a portion of the sample powder obtained in Example 1 to swell in distilled water, the resultant mixture was filtered through a glass filter. No water was released even when a water-containing gel left on the filter was pressed by a glass plate. Retention of water was thus confirmed.

Example 49:
After adding 0.2 g of the sample powder obtained in Example 1 to 35 ml of ~enzene having a water content of 800 ppm and stirring the resultant lS mixture thoroughly, the water content of the benzene was measured. It was found to have been dropped to 400 ppm.

Example 50:
A pressurized dewatering test was conducted using digested sludge which had in advance been caused to flocculate with a cationic flocculant as follows:
In a cylinder having an inner diameter of 9 cm, a sheet of filter paper, a portion of the sample powder obtained in Example 1, another sheet of filter paper, a portion of ~the thus-flocculated digested sludge~ a further sheet of filter paper, a portion of the sample powder obtained in Example 1 and a still fur-ther sheet of filter paper were placed one over another in the above order. It was downwardly pressed at a pressure of 3 kg/cm for 5 minutes. After pressing for the prescribed time period, the filter paper sheets were peeled off to measure the water content o~ the sludge. It was found to be 55%.
Another pressurized dewatering test was carried ou~ in a manner similar to that mentioned immediately above, except that a similar portion of the same sludge was sandwiched by filter paper sheets only. The water content of the thus treated sludge was found to be 61%.

Example 51:
Added a-t room temperature to 50 g of an SBR
latex having a concentration of 43% t"Polylac 755", trademark; product of Mitsui-Toatsu Chemicals, Inc.) was 0.5 g of the sample powder obtained in Example 1.
The resultant mixture was stirred thoroughly. The mixture was then filtered. The concentration of the SBR latex in the filtrate was found to be ~9%.

Example 52:
Five grams of N-acryloylpyrrolidine were 12~

placed in a 5-ml sample tube, followed by the addi~
tion of 0.02 g of 5-butyl peroxy-2-ethylhexanoate.
A bulk polymerization was effected at 40C to obtain a bloc~-like polymer. The polymer was then ground, and a fraction of 20 - 100 mesh was collected as a sample. Then, 0.5 g of the sample powder was added at room temperature to 50 g of an SBR latex having a concentration of 43~ ("Polylac 755", trademar~;
product of Mitsui-Toatsu Chemicals, Inc.). After stirring the resultant mixture thoroughly, the concentration of the liquid latex was measured. It was found ~o be 49%. Then, the liquid latex was cooled to 10C, followed ~y thorough stirring. Its concentration was measured again and found to be 58~.
The liquid latex was thereafter heated to 40C, at which it was thoroughly stirred. A measurement of its concentration gave a value of 45%. The liquid latex was stirred thoroughly, again at room tempera-ture. Its concentration was measured to be 48%.
In addition, the sample powder was microscopically observed both before and after each measurement.
It was found that the sample powder had not been ground or otherwise physically damaged by the temper-ature change or stirring.

Example 53:
An aqueous solution of N-acryloylpyrrolidine ~2~

containing 0.5 wt% N,N'-methylenebisacrylamide was prepared by dissolving 507.5 g of N-acryloylpyrro-lidine and 2 6 g of N,N'-methylenebisacrylamide in 1,170 g of water. After cooling the aqueous solution to 10C, it was poured into a 2-Q Dewar flask made of stainless steel. Nitrogen gas was then caused to bu~ble at a flow rate of 1 Q/min. through a ball filter in the aqueous solution for 1 hour. Then, an aqueous solution of 2.55 g of ammonium persulfate dissolved in 10 g of water and another aqueous solu-tion of 1.16 g of sodium hydrogensulfite dissolved in 10 g of water were added simultaneously to the N2-bubbled aqueous solution, followed by adiabatlc polymerization of the reactants. The resultant gel was chopped, dried and ground. A fraction of 20 ~ 100 mesh was collected as a sample. Thereafter, 0.5 g of the sample powder was added to 20 ml of a 0.5%
aqueous solution of bovine serum albumin. The resulting mixture was stirred at a prescribed tempera-ture for 1 hour. Then, it was allowed to stand for5 minutes. The a~sor~ance of the resultant super-natant was measured at 254 nm to determine its concentration. The stirring of the sample powder and aqueous solution of bovine serum albumin was effected at 30C, 15C and 5C. The concentrations of the supernatants corresponding to t~ese temperatures ~LZ~7~

were found to be 0.71% (at 30C~, 0.78% (at 15C) and 0.83% (at 5C), respectively. In addition, the sample powder was microscopically observed both before and after each of the above measurements. It was found that the sample powder was not ground or otherwise physically damaged by the temperature change and stirring.

Example 54:
To lO g of a solution which had ~een obtained by dissolving bovine serum albumin in a 0.96 aqueous `solution of sodium c~loride in such a way that the concentration of the bovine serum albumin had become 1%, was added lO g OI a gel (wacer concent: 9.5 g) obtained by causing a portion of the sample powder of Example 53 to swell in distilled water. After stirring the resultant mixture at room temperature for 15 minutes, the absorbance of the resulting supernatant was measured at 254 Nm to determine the concentration of bovine serum al~umin in the aqueous solution. The concentration of bovine serum albumin was 0.75O. A
measurement of the electric conductivity of the solu-tion gave an NaCl concentration of 0.476. When the solution was heated to 30C, the concentration of bovine serum albumin dropped to 0.71%. When it was cooled to 15C, the concentxation increased to 0.786.

7~

A further cooling of the solution to 5C increased the concentration of ~ovine serum albumin further to 0.83%. Then, t~e solution was heated again to room temperature. The concentration of bovine serum albumin decreased to 0.75~. The concentration of sodium chloride was maintained at 0.47% during the above measure.nents.

Examples 55 - 62:
Added to 20 g of a 0.5% aqueous solu~ion of polyethylene glycols having each of the molecular weights given in Table 5 was 0.5 g of the sample powdex obtained in Exampl,e 53. After stirring the ~hus-prepared mixture at a prescribed temperaiure ror 30 minutes, the refractive index of the resulting super-natant was measured to determine the concentra~ion of the polyethylene glycol in the supernatant.
Results are given in Table 5.

Table 5 . _ . .
Molecular weight Concentration of supernatant (~-) Ex. of polyethylene glycol 25C 50C 10C 25C l0C

200 0.55 0.51 0.53 56 600 0.52 0.54 0.52 57 l,000 0.53 0.55 0.57 _ _ 58 2,000 0.59 0.57 0.610.590.60 59 4,000 0.62 0.56 0.64O.Çl 0.65 60 6,000 0.75 0.62 0.840.740.86 6111,000 0.76 0.62 0.870.770.86 6220,000 0.82 0.64- 0.870.820.89 .

Examples 63 - 67:
Using 0.5 g of the sample powder obtained in Example 53 and 20 ml of a 0.5~ aqueous solution of dextrans ~aving each of the molecular weights given in Table 6, the concentration of the corresponding supernatan~ was measured in the same manner as that employed in Example 55. Results are tabulated in Table 6.

T_ble 6 :
E Molecular weight Concentration of supernatant (~) x. of:dextran 50C. 25C 10C
_ .

63 180 0.570.56 0.56 (fructose) 64 9,000 ~.520.59 0.63 40,000 0.540.69 0.79 66 460,000 0.510.71 0.80 . 67 2,000,000 0.540.71 0.80 Examples 68 - 71.
Using 10 g of a gel (water content: 9.5 g) obtained ~y causing the sample powder of Example 53 to swell ~n distilled water and 10 g of a 1~ aqueous solution of dextrans having each of the molecular weights shown in Table 7, the concentrations of the dextran in the corresponding supernatant was measured in the same manner as that employed in Example 55.
Results are shown in Table 7.

Table 7 Ex Molecular weight Concentration o~ supernatant (%) . of dextran 25C 50C 10C 25C 10C

568 s,oao 0.59 0.52 0.63 0.52 0.64 69 40,000 0.69 0.54 0.79 0.68 0.79 460,000 0.71 0.51 0.~0 0.71 0.80 . 71 2,000,000 0.71 0.54 0.80 0.70 0.82 lQ Examples 72 - 76:
Using 0.05 g of the sample powder obtained in Example 53 and 2 ml of a 0.5~ aqueous solution of proteins having each of the molecular weight~s given in Table 8, the concentration o~ the protein in the corresponding supernatant was measured in the same manner as that followed in Example 53. Results are shown in Table 8.

Ta~le 8 ~ ~ _ . .._ . I Protein Concentration of Ex. _ supernatant (%) Name m w. 30C 20C 10C
_ .
72 Lysozyme 14,300 0.51 0.69 0.83 73 ~-lactoglobulin 18,400 0.62 0.66 0.76 74 Trypsinogen 24,000 0.53 0.56 0.62 Pepsin 34 J 700 0.52 0.61 0.77 76 Egg white 45,000 0.67 0.70 0.76 albumin , ~L2~7~

Example 77:
Using a 30% aqueous solution of N-n-propyl-acrylamide which contained 0.5 wt.% of N,N-methylene-~isacrylamide, a sample powder was o~tained in the same manner as that employed in Example 53. Using 0.6 g of the sample powder and 20 ml of a 0.5% aqueous solution of bovine serum albumin, the concentration of bovlne serum albumin in the aqueous solution was measured at various temperatures in accordance with the method used in Example 53. The concentrations were found to be 0.63% (at 30C~, 0.70% (at 15C) and 0.84% ~at 5C), respectively.

Example 78:
Using 10 g of a gel (water content: 9.4 g) obtained by causing a portion of the sample powder of Example 77 to swell in distilled water, the concen-tration of bovine serum albumin was measured at various temperatures in the same manner as that used in Example 54. The concentration was 0.65~ at room temperature. When heated to 30C, it dropped to 0.63%. When cooled to 15C, it increased to 0.70%.
When the solution was cooled further to 5C, the concentration increased to 0.84%. It however dropped to 0.69% when heated again to room temperature.
During these measurements, the concentration of sodium L7~

chloride remained constant at 0.46%.

Examples 79 - 83:
Using 0.6 g of the sample powder obtained in Example 77 and 20 g of a 0.5~ aqueous solution of polyethylene glycols having each of the molecular weights given in Ta~le 9, the concentration of the polyethylene glycol in the corresponding supernatant was measured in the same manner as that used in Example 55. Results are shown in Table 9.

Table 9 _ .
Molecular weight Conce~tration of suPernatant (%) Ex. of polyethylene . _ _ ~
~lycol 25C 50C 10C 50C ~5C
15 _ _ _ ~
79 1,000 0.54 0.51 0O52 - -2,000 0.56 0.56 0.56 81 4,00Q 0.59 0.55 0.590.540.58 82 6,000 0065 0.59 0.7g0.590.64 83 11,000 0.64 0.54 0.710.520.65 ~xamples 84 - 88:
Using 0.6 g of the sample powder obtained in Example 77 and 20 ml of a 0.5~ aqueous solution of dextrans having each of the molecular weights given in Table 10, the concentration of the dextran in the ~7q;~

corresponding supernatant was measured in the same manner as that employed in Example 55. Results are given in Ta~le 10.

Table 10 Molecular weight Concentration of supernatant (~) Ex.of dextran 50C 25C 10C

84 180 0.51 0.54 0.52 ~fructose) 859,000 0.54 0.62 0.62 8640,000 0.5~ 0.63 0.63 87460,000 0.53 0.66 0.80 882,000,000 0.54 0.67 0.76 Examples 89 - 92:
Using 10 g of a gel (water content: 9.4 g) o~tained by causing a portion of the sample power of Example 77 in distilled water and 10 g of a 1~ aqueous solution of dextrans having each of the molecular weights given in Ta~le 11, the concentration of the dextran in the corresponding supernatant was measured in the same manner as that used in Example 55. Resul-ts are given in Table 11.

7~

Ta~le 11 ....
. .~ . . _ E Molecular weight Concentration of su~ernatant (~) x. of dextran _ 25C 50C 10C 25C 10C

89 9,000 0.62 0.54 0.62 0.61 0.64 40,000 0.63 0.52 0.63 0.60 0.63 gl ~60,000 0.66 0.53 0.80 0.65 0,80 92 ~,000,000 0.67 0.54 0.76 0.67 0.77 Examples 93 - 97:
Using 0.06 g of the sample powder obtained in Example 77 and 2 ml of a 0.5% aqueous solution of proteins having each of the molecular weights given in Table 12, the concentration of the protein in the corresponding supernatant was measured in the same manner as in Example 53. Results are given in Table 12.
Table 12 -_ Protein Concentration of 20 Ex. _ -- _ suPernatant (%) Name m w. 30C 20C 10C
.

93 Lysozyme 14,300 0.53 0.56 0.61 94 ~-lactoglo~ulin 18,400 0.52 0.67 0.85 Trypsinogen 24,000 0.53 0.52 0.80 96 Pepsin 34,700 0.55 0.64 0.80 97 Egg white al~umin 45,000 0.54 0.68 o.a2 ~l2~

Examples 98 - 102:
After subjecting an aqueous solution of N-acryloylpyrrolidine, ~hich contained 4.7 wt.% of sodium 2-acrylamido-2-phenylpropanesulfonate, to salting-out suspension polymerization by using mira~ilite, the resulting gel beads were dried to o~tain a sample. The sample beads were caused to swell in distilled water to form a gel. Using 10 g of the thus-prepared gel ~water content: 9.75 g) and 10 g of a 1% aqueous solution of polyethylene glycols having each of the molecular weights shown in Table - 13, the concentration o the polyethylene glycol in the corresponding supernatant was measured in the same manner as that followed in Example 55. Results are given in Table 13.

Table 13 . .__.
Molecular weight Concentration of supernatant (~) Exo of polyethylene _ glycol 25C 50C 10C 25C 10C
_ _ __ _ 98 2,000 0.62 0.61 0.64 0.62 0.65 99 4,000 0.65 0.65 0.69 0.66 0.70 100 6,000 0.74 0.70 0.84 0.74 0.83 101 11,000 0.79 0.68 0.87 0.79 0.87 102 20,000 0.84 0.67 0.95 0.84 0.96 25 _____ . _ _ .

L71~iL5 ~ 60 -Examples 103 - 106:
Using ~.25 g of the sample beads obtained in Example 98 and 20 g of a 0.5~ aqueous solution of dextrans having each of the molecular weights shown in Table 14, the concentration of the dextran in t~e corresponding supernatant was measured in the same manner as that used in Example 55. Results are shown in Table 14.

Ta~le 14 . . .
Molecular weight Concentration of supernatant ~%) Ex. of dextran 25C 50C 10C 50C 25C
. .. ._ _ 103 9,000 0.60 0.59 0.62 0.57 0.60 104 40,000 0.80 0.63 0.90 0.63 0.~0 105 460,000 0098 0.66 1.18 0.65 0.97 . 106 2,000,000 1.02 0.68 l.23 0.69 l.02 -Example 107:

Added at 15C to 30 g of commercial milk was 0.5 g of the sample ~eads o~tained in Example 98.

After stirring the resultant mixture, it was filtered.

The weight of the resultant filtrate was 18 g. Thus 12 g of water was removed.

Example 108:

To 50 g of an SBR latex having a concentration ::L2~

of 43% ~"Polylac 755", trademark; product of Mitsui-Toatsu Chemicals, Inc.~, 0.5 g of the sample beads obtained in Example 98 was added at room temperature.
The resultant mixture was stirred at the same temper-ature. After stirring it thoroughly, it was filtered.The concentration of the SBR latex in t~e filtrate was found to be 52~.

Examples 109 - 113:
10 Using 0.25 g of the sample ~eads obtained in Example 98 and 20 ml of a 0.5~ aqueous solution of polyethylene glycols having each of the molecular weights shown in Table 15, thé concentration of polyethylene glycol in the corresponding supernatant was measured in the same manner as in Example 55.
Results are given in Ta~le lS.

Table 15 _ .._.
Molecular weight Concentration of supernatant (%) Ex. of polyethylene ~l~col 50C 25C 10C
_ .
. .... _ ... _ . _ ..

109 2,000 0.61 0.62 0.64 110 4,000 0.65 0.65 0.69 111 6,000 0.70 0.74 ~ 0.84 25 112 11,000 0.68 0.79 0.87 113 20,000 0.67 0.84 0.95 Examples 114 - 117:
Using 0.25 g of the sample beads obtained in Example 98 and 20 ml of a 0.5% aqueous solu~ion of dextrans having each of the molecular weights given in Table 16, the concentration of the dextran in the corresponding supernatant was measured in the same manner as in Example 55. Results are gi~en in Ta~le 16.

Ta~le 16 . .,., ., ~ . . . ~"~
Molecular weight _oncentration of supernatant (%) Ex.of dextran 50C 25C 10C
. _ .__ __ 1149,000 0.59 0.63 0.62 11540,000 0.63 0.80 0.90 116460,000 0.66 0.98 1.18 1172,000,000 0.68 1.02 1v23 Example 118:
To a benzene solution containing 5 wt.% of N-acryloylpyrrolidine, azobisisobutylonitrile was added in an amount of 1.0 wt.~ based on N-acryloyl-pyrrolidine. The reactants were allowed to undergo polymerization at 60C for 5 hours and under a nitrogen gas stream. After polymerization, 5 sheets of poly-propylene-made non-woven fabric ("Neunetz", trademark;

~2~t7~

product of Mitsui-Toatsu Chemicals, Inc.) were super-posed and then dipped in the ~enzene solution for impregnation with the benzene solution. Thereafter, the non-woven fabric was then withdrawn from the benzene solution and allowed to stand for 10 hours in a drier maintained at 150C. After drying, the non-woven fa~ric was readily ~roken into a pulp-like form when pressed by fingers. After causing 1.0 g of the pulp-like sample to be suspended in distilled water, the resulting suspension was filtered. The weight of the sample was found to be 3.1 g. Thus the sample had a~sorbed 2.1 g of water.

Example 119:
A 30% aqueous solution of N-acryloylmorpho-line, which contained 5,000 ppm of N,N'-methylene bisacrylamide, was charged in a Dewar flask and then purged with nitrogen gas. Thereafter, 2,2'-azobis-~2-amidinopropane) hydrochloride was added at 20C
in an amount of 1.3% ~ased on the N-acryloylmorpholine.
The reactants were su~jected to adiabatic polymeriza-tion. The resulting gel was chopped and then dried at 120C. It was thereafter ground, and a fraction of 20 - 100 mesh was collected as a sample. Following the procedure of Example 2, the volumes of swelling of 1.0 g of the sample powder were measured at 25C

and 50C and found to be 14.5 ml and 11.5 ml, respec-tively.

Example 120:
A sample powder was obtained by conducting polymerization and grinding in the same manner as in Example 119 except that N-ethylmethacrylamide was used in place of N-acryloylmorpholine and the polymerization initiator was added at 50C. In the same manner as that used in Example 2, the volumes of swelling of 1.0 g of the sample powder were measured at 25C and 5QC and found to ~e 18.5 ml and 13.5 ml, respectively.

Example 121:
A sample powder was obtained by conducting polymerization and grinding in the same manner as in Example 119 except that a 30% aqueous solution of N-n-pxopylmethacrylamide ~50%) and N,N~dimethylacryl-amide (50%), which contained 10,000 ppm of N,N'-methylene~isacrylamide was used as monomer solution and potassium persulfate and sodium bisulfite were used as the polymerization initiator in amounts of 1.5% and 0.69% based on the monomers respectively, then the polymerization initiators were added at 30C.
In the same manner as that used in Example 2, the volumes of ~welling of l.0 g of the sample powder were measured at 25C and 50C and found to be 28.0 ml and 21.0 ml, respectively.

Compaxative Example 1:
A 30~ solution of N-n-butylacrylamide, which contained 5,000 ppm of N,NI-methylene~isacrylamide, in N,N-dimethvlformamide, was charged in a Dewar flask.
After purging the solution with nitrogen gas, azobisisobutylonitrile was added at 30C in an amount of 1.5%. The reactants were subjected to adiabatic pol~erization. The thus-obtained gel was chopped and dried at 120C. It was then ground, and a fraction of 20 - 100 mesh was collected as a sam.ple.
Following the same procedure as in Example l, the weights of swelling of l.0 g of the sample powder were measured at 25C and 50C and found to be 2.2 g and 2.0 g, respectively.

Comparative Example 2:
A sample powder was ohtained by conducting polymerization and grinding in the same manner as in Comparative Example 1 except that N,N-die-thylacrylamide was used in place of N-n-~utylacrylamide. In the same manner as that used in Example 1, the weights of swelling of 1.0 g of the sample powder were measured 7~

~ 66 -at 25C and 50C and found to be 4.8 g and 2.5 g, respecti~ely.

Comparative Example 3:
A sample powder was o~tained by conducting polymerization and grinding in the same manner as in Comparative Example 1 except that N-acryloylpiperidine was used in place of N-n-butylacrylamideO In the same manner as that used in Example 1, the weights of swelling of 1.0 g of the sample powder were mea~ured at 25C and 50C and found to be 3.3 g and 2.3 g, respectively.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of controlling the water concentration of an aqueous solution or emulsion containing a macromolecular compound comprising (i) contacting said aqueous solution or emulsion with an agent for absorbing and releasing water, said agent comprising a water-insolubilized resin of a polymer of at least one monomer selected from N-alkyl- or N-alkylene-substituted acrylamides or methacrylamides represented by the following general formula (I):

(I) wherein R1 and R2 mean individually a hydrogen atom or methyl group and R3 denotes a methyl, ethyl or propyl group, with the proviso that R3 is an ethyl or propyl group when R2 stands for a hydrogen atom, and that R3 is a methyl or ethyl group when R3 stands for a methyl group, or wherein R2 and R3 form or in combination; or a copolymer of at least one monomer selected from the said acrylamides or methacrylamides and another copolymerizable monomer, and (ii) raising or lowering the temperature of the aqueous system by heating or cooling to vary the amount of water absorbed and retained by the said agent.

2. A method according to claim 1, wherein the aqueous solution or emulsion contains a protein, polysaccharide, enzyme, antibiotic or microorganism.

3. A method according to claim 1, wherein after water absorption by the said agent, the water-containing agent is removed from the aqueous solution or emulsion and is raised to a higher temperature so that the water is released therefrom, and the released water is separated from the said agent which is recycled.

4. A method according to any of claims 1, 2 or 3, wherein the aqueous system is heated or cooled to a temperature within the range of 0°C to 100°C to vary the amount of water absorbed therefrom.

5. A method according to any of claims 1, 2 or 3, wherein the aqueous system is heated or cooled to a temperature within the range of 0°C to 77°C to vary the amount of water absorbed therefrom.

6. A method according to any of claims 1, 2 or 3, wherein the said agent is the water-insolubilized resin of either a polymer of at least one monomer selected from N-alkylene-substituted acrylamides or methacrylamides represented by the general formula (I), wherein R1 is as defined in claim 1, and R2 and R3 are or in combination; or a copolymer of at least one monomer selected from the said acrylamides or methacrylamides and another copolymerizable monomer.

7. A method according to any of claims 1, 2 or 3, wherein the monomer is N-acryloylpyrrolidine.

8. A method according to any of claims 1, 2 or 3, wherein the resin employed is a copolymer of said at least one monomer with one or more copolymerizable monomers selected from hydrophilic, ionic and hydrophobic monomers.

9. A method according to any of claims 1, 2 or 3, wherein the resin employed is impregnation- or graft-polymerized on a water-insoluble fibrous or porous material.

10. A method according to any of claims 1, 2 or 3 wherein the solution or emulsion is contacted with the said agent, which already contains water therein, and the temperature of the system is so controlled as to cause the agent to shrink and expel its previously absorbed water, thereby causing dilution of the solution or emulsion.