JPH0112766B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing bead-shaped water-soluble polymers. Specifically, the present invention relates to a method for producing bead-shaped water-soluble polymers having excellent solubility in water. A high molecular weight water-soluble polymer obtained by polymerizing acrylamide, methacrylamide, or a water-soluble vinyl monomer having a carboxylate, sulfonate, or ammonium base in the side chain,
It is a useful polymer used in many applications such as thickeners, thickeners, flocculants, paper strength enhancers in the paper industry, filler retention aids, and aqueous properties improvers. Among these uses, the higher the molecular weight of the polymer used as a flocculant, the better the performance. Furthermore, due to transportation problems, they are often provided in powdered form, and are generally dissolved in water at the site of use. Therefore, preferred coagulants are polymers that have a high molecular weight, are easy to handle during weighing and dissolving operations, do not generate dust, and have good solubility. Methods for directly producing water-soluble polymers in powder form include precipitation polymerization in a solvent that dissolves the monomer but does not dissolve the polymer, a method in which the monomer is melted under heating conditions and polymerized, and a method in which the monomer and polymer are polymerized in a solvent that does not dissolve the monomer. A method is known in which monomers are melted and polymerized. However, the precipitation polymerization method has the disadvantage that the obtained product has a low molecular weight and is in the form of a fine powder, while the method of polymerizing by melting the monomer has the disadvantage that it is difficult to control the heat generation of the polymerization reaction, and the molecular weight of the product is low. has. Furthermore, the method of polymerizing by melting the monomer in a dispersion medium has the disadvantage that the polymerization rate does not increase because the polymerization initiator is not uniformly mixed in the monomer phase, and the molecular weight of the product is also low. In order to obtain a high molecular weight water-soluble polymer, it is best to polymerize using an aqueous solution of water-soluble monomers, but since the polymer becomes a highly viscous or rubbery substance, it is necessary to dehydrate it and make it into a powder. requires complex operations. On the other hand, if an aqueous solution of a water-soluble monomer is polymerized by emulsifying or suspending it in a dispersion medium that does not dissolve the monomer, water, and the polymer, a high molecular weight polymer with uniform particles can be obtained, and it can be easily converted into a powder by dehydration. A polymer is obtained. Such a method includes
A method of polymerizing an aqueous monomer solution into water-in-oil and oil-in-water emulsions using a nonionic emulsifier in a hydrocarbon solvent as described in Japanese Patent Publication No. 47-40304 and Japanese Patent Publication No. 15033. 42−
There is a method, such as the method described in Publication No. 9656, in which an aqueous monomer solution is dispersed in a water-in-oil type and polymerized using water-soluble cellulose or oil-soluble cellulose, which are polymers, as a dispersion stabilizer without using an emulsifier. In the method using an emulsifier, the molecular weight of the product is high and the performance is excellent, but since polymerization proceeds in the emulsified state and the product becomes fine particles, it may generate dust when dissolved or contain air bubbles when added to water. There are problems such as the speed becoming extremely slow. On the other hand, when water-soluble or oil-soluble cellulose is used, polymerization proceeds while maintaining a constant particle size during the polymerization reaction, resulting in a high molecular weight polymer that does not contain fine particles. However, when water-soluble cellulose is used, a product with a large particle size is often obtained, requiring grinding, resulting in a finely divided polymer. When oil-soluble cellulose is used, a polymer with a uniform particle size can be obtained, but since the dispersing effect of the dispersant is insufficient, the particles tend to form lumps due to stickiness during polymerization. For this purpose, it is necessary to mix a hydrocarbon into a solvent mainly composed of halogenated olefins and adjust the specific gravity of the dispersion medium so that it is equal to or slightly greater than the specific gravity of the monomer aqueous solution. Therefore, it is necessary to change the dispersion medium every time the monomer composition or concentration changes, it is difficult to recycle the dispersion medium because a mixed solvent is used, and highly harmful halogenated olefins are required to adjust the specific gravity. There were drawbacks such as: Furthermore, when azeotropic distillation was performed to remove water contained in the polymer obtained by this method, the polymer tended to form lumps during the azeotropic distillation. The present inventors have conducted intensive studies on a method of polymerizing aqueous solutions of acrylamide, methacrylamide, or water-soluble vinyl monomers having carboxylates, sulfonates, or ammonium bases in their side chains by suspending them in a dispersion medium. By utilizing the phenomenon described below, we have completed a method for obtaining a high molecular weight water-soluble polymer as a bead-like solid material with a uniform particle size and no fine particles. When an aqueous monomer solution is dispersed in an oil-soluble cellulose ester or cellulose ether dissolved in a good solvent for these compounds as a dispersion medium, the aqueous solution is dispersed in the form of water droplets with a particle size of approximately 0.1 to 1 m/m. If the specific gravities of the dispersion medium and the monomer aqueous solution do not match, the particles will easily come into contact with each other during the polymerization reaction, resulting in agglomeration due to stickiness. However, as the cellulose ester or ether, a cellulose ester or ether that is poorly soluble or insoluble in the dispersion medium at room temperature (in the present invention, room temperature refers to 15 to 25°C) and dissolves at a temperature higher than room temperature is selected, and the heating conditions are It was found that when this compound was dissolved in a dispersion medium and used, the dispersion stability of the monomer aqueous solution and polymerization system was significantly improved. As a result, droplets of the aqueous monomer solution do not form agglomerates no matter how many times they come into contact with each other during the polymerization reaction, so there is no need to match the specific gravity of the dispersion medium and the aqueous monomer solution. Further, even if a new aqueous monomer solution is added during the polymerization, the dispersion stability will not be impaired. Therefore, there is no need to match the specific gravity of the dispersion medium and monomer aqueous solution, so there is no need to use harmful halogenated olefins, and even if the monomer composition changes, the same dispersion medium can be used for polymerization. This is extremely advantageous in practice. Furthermore, it is also possible to use a sole solvent that dissolves the dispersion stabilizer under heating conditions. In this case, recycling of the dispersion medium becomes extremely easy, which is very convenient for industrial production. Furthermore, since the dispersion stability of the polymer-containing suspension obtained under these conditions is extremely high, after the polymerization reaction is completed, the dispersion medium is
The product can be dehydrated by aqueous azeotropic distillation. It is advantageous to use a single solvent as a dispersion medium because the composition of the dispersion medium does not change during azeotropic distillation. That is, the gist of the present invention is to provide a method for producing a bead-shaped water-soluble polymer by dispersing an aqueous solution of a water-soluble vinyl monomer in a dispersion medium in the presence of a dispersion stabilizer in the form of water droplets and polymerizing the water-soluble vinyl monomer. General formula () to () below _CH2 =CH−Z− _SO3M ……() (In the formula, R ¹ represents a hydrogen atom or a methyl group,
Y is a -CONH group or a -COO M' group (in the formula
M' represents a monovalent cation), and Z
is -C _l H _2l - group (in the formula, l represents a number from 0 to 3),
-COO-(CmH ₂ m)- group (in the formula, m represents a number from 1 to 6), -CONH-(CnH ₂ n)- group (in the formula, n represents a number from 1 to 6)
) or a phenylene group, M
represents a monovalent cation, R ² , R ³ and R ⁶ represent an alkyl group having 1 to 4 carbon atoms, R ⁴ , R ⁵ and R ⁷ represent a hydrogen atom, and a hydroxy-substituted alkyl group having 1 to 4 carbon atoms. (represents an alkyl group or a benzyl group, and X, X' and Aromatic hydrocarbons are used, oil-soluble cellulose esters or cellulose ethers that are insoluble or poorly soluble at room temperature and soluble at the polymerization temperature are used as the dispersion medium used as a dispersion stabilizer, and the temperature is 40°C or higher. The present invention will be described in detail below. In the method of the present invention, compounds represented by the above general formulas () to () are polymerized into bead-shaped polymers. In the above general formulas () to (), M and M′
Monovalent cations represented by include alkali metal ions, ammonium ions, etc.
Anions represented by X, X′ and X″ include halogen ion, sulfate ion, nitrate ion,
Phosphate ion, carboxylate ion, carbon number 1-4
Examples include alkyl sulfate ions. Specific examples of compounds represented by the general formulas () to () include acrylamide, methacrylamide, sodium salts, potassium salts, lithium salts of acrylic acid and methacrylic acid,
Salts such as ammonium salt, trimethylammonium salt, tetramethylammonium salt, sodium vinylsulfonate, sodium allylsulfonate, sodium styrenesulfonate, sodium sulfoethyl acrylate, sodium sulfoethyl methacrylate, sodium sulfopropyl acrylate , sodium sulfohexyl acrylate, sodium 2-acrylamidoethanesulfonate, sodium 2-acrylamido-2-methylpropanesulfonate, P
-vinylbenzyltrimethylammonium chloride, P-vinylbenzyldimethylammonium chloride, P-vinylbenzyldimethylethylammonium ethyl sulfate, 2-vinylpyridinium chloride, 4-vinylpyridinium chloride, 4-vinyl-N-methylpyridinium methylsulfate, Examples include 4-vinyl-N-n-butylpyridinium bromide, methyldiallylammonium chloride, methyldiallylammonium chloride, dimethyldiallylammonium chloride, methylbenzyldiallylammonium chloride, dimethyldiallylammonium methylsulfate, and the like. In the method of the present invention, the general formula () ~
A homopolymer of the compound represented by () or a copolymer of at least two or more compounds selected from the group consisting of the compounds represented by the general formulas () to () in an arbitrary ratio is produced. When producing a copolymer, it is preferable to select a compound represented by the above general formula (), especially acrylamide, as a monomer component.
It is more preferable to use 60 mol% or more. Of course,
Copolymers of the compounds represented by the general formulas () to () above and other vinyl compounds that can be copolymerized therewith can also be produced, but in this case, the amount of other vinyl compounds used should be 5 mol% or less. It is preferable to In the method of the present invention, cellulose esters or ethers that are insoluble in water and soluble in organic solvents are used as dispersion stabilizers for suspension polymerization.
This material must have the property of being insoluble or sparingly soluble in the hydrocarbon or halogenated aromatic hydrocarbon serving as the dispersion medium at room temperature, and soluble at the polymerization temperature (40° C. or higher). Insoluble or poorly soluble means that when 3 g of cellulose ester or ether is added to 100 ml of dispersion medium and stirred at room temperature, it swells and becomes gelatinous.
When stirring is stopped and left for a while, fluidity is lost or phase separation occurs, and soluble means that it becomes a uniform solution when stirred and remains in this state even after stirring is stopped and left at the same temperature. refers to It is assumed that such a state exists in a colloidal state in which cellulose ester or ether is considerably associated, rather than a complete solution, and is distributed on the surface of the suspended particles, exhibiting strong dispersion stability. If a dispersion medium that dissolves cellulose ester or ether is used at room temperature, the aqueous monomer solution will be dispersed, but it will become agglomerated due to stickiness during the polymerization reaction. This is because the dispersion stabilizer exists in the form of a complete solution and therefore has little effect on protecting the surface of the suspended particles. Cellulose esters or ethers used in the method of the present invention include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, ethyl cellulose, benzyl cellulose, ethyl hydroxyethyl cellulose, etc. Can be mentioned. Particularly preferred are cellulose acetate butyrate, ethylcellulose, and ethylhydroxyethylcellulose. In the present invention, a hydrocarbon or a halogenated aromatic hydrocarbon is used as a dispersion medium. Preferred are aromatic hydrocarbons having 6 to 10 carbon atoms, alicyclic hydrocarbons, saturated aliphatic hydrocarbons, or chlorine-substituted benzene. Specifically, for example, benzene, toluene, xylene, ethylbenzene, isopropylbenzene, n-butylbenzene, cyclohexane,
Examples include cycloheptane, methylcyclohexane, cyclooctane, decalin, n-hexane, n-heptane, n-octane, n-decane, chlorobenzene, dichlorobenzene, bromobenzene, dibromobenzene, and particularly preferred are toluene and xylene. , cyclohexane, methylcyclohexane, n-hexane, n-heptane, chlorobenzene, and dichlorobenzene. The dispersion medium is a mixture of two or more solvents, depending on the type, degree of substitution, molecular weight, etc. of the cellulose ester or ether used, so that the cellulose ester or ether is sparingly soluble or insoluble at room temperature and soluble at the polymerization temperature. It can be used as a dispersion medium. Moreover, if the cellulose ester or ether used is selected, a sole solvent can be used as a dispersion medium. In this case, recycling of the solvent and dehydration operation by azeotropic distillation become easy, which is extremely advantageous for industrial production. Suitable cellulose esters or ethers when toluene, xylene, ethylbenzene, isopropylbenzene, monochlorobenzene, dichlorobenzene, etc. are used alone as a dispersion medium include ethylcellulose with an ethoxy group content of 43 to 47% by weight, and butyryl group-containing esters or ethers. Such as cellulose acetate butyrate with a content of 20 to 50% by weight. A suitable cellulose ester or ether when cyclohexane, cycloheptane, methylcyclohexane, cyclooctane, decalin, etc. are used alone as a dispersion medium is ethylcellulose having an ethoxy group content of 47 to 50% by weight. A suitable cellulose ester or ether when using n-hexane, n-heptane, n-octane, etc. alone as a dispersion medium is ethylhydroxyethylcellulose. The amount of dispersion stabilizer used is 0.05 to 10% of the dispersion medium.
% by weight, preferably in the range 0.5-5% by weight.
If the amount added is less than 0.05% by weight, the dispersion stability will be insufficient, and if it exceeds 10% by weight, the dispersion will become viscous and separation of the product will become difficult. The dispersion medium is 0.5 to 10 times the weight of the monomer aqueous solution containing the compounds represented by the general formulas () to ().
It is preferably used in a range of 1 to 5 times the weight. During polymerization, the order of adding the dispersion stabilizer, dispersion medium, aqueous monomer solution, and radical polymerization initiator is not particularly limited, but the following method is particularly preferred in order to obtain a product with a uniform particle size. First, a dispersion stabilizer is dispersed in a slurry in a dispersion medium, the temperature is raised while stirring to dissolve the dispersion stabilizer, and the dispersion medium is maintained at a predetermined temperature at which polymerization is to be performed. This is a method in which the mixture is then deoxidized by passing nitrogen gas through it, and an aqueous monomer solution containing a radical polymerization initiator that has been previously deoxygenated is added to the dispersion medium while stirring to carry out polymerization. The compounds represented by the general formulas () to () can be subjected to polymerization as an aqueous solution with an arbitrary concentration in the range of monomer concentration of 10 to 90% by weight,
Usually 10 to 70% by weight, preferably 30% due to the solubility limit of the monomer and the limit of obtaining a soluble polymer.
It is preferable to use a concentration in the range of ~60% by weight. As the polymerization initiator, general radical polymerization initiators such as peroxides and azo compounds are used, but polymerization can also be initiated by ultraviolet rays or ionizing radiation. Preferably, a water-soluble polymerization initiator is used, and in this case, it is preferable to dissolve the monomer aqueous solution in the monomer aqueous solution before adding the monomer aqueous solution to the dispersion medium. Water-soluble polymerization initiators include peroxides such as ammonium persulfate, potassium persulfate, peracetic acid, hydrogen peroxide, and 2,2'-azobis-2-amidinopropane hydrochloride, 4,4'-azobis-4- Examples include azo compounds such as cyanopentanoid acid and its salts. When a peroxide is used as an initiator, polymerization can be carried out by initiation of a redox system in the presence of a reducing substance if necessary. Although polymerization can be carried out at any temperature from 40°C to the boiling point of the dispersion medium, it is preferable to carry out the polymerization at a temperature of 50 to 70°C in order to obtain a high molecular weight polymer. After completion of polymerization, the final polymer and the dispersion medium are separated to obtain a bead-shaped polymer. However, when the dispersion medium is separated from a polymer-containing suspension obtained using an aqueous solution with a low monomer concentration, the polymers become agglomerated due to their stickiness. If a suspension containing a polymer after polymerization is poured into a large amount of acetone, a solid bead-like product can be obtained.
This is not necessarily a practical method. When the suspension containing the polymer after completion of polymerization is heated to perform azeotropic distillation of the dispersion medium-water system, water contained in the polymer can be efficiently dehydrated. If necessary, azeotropic distillation can also be carried out under reduced pressure conditions. The polymer obtained by dehydration in this manner is a solid bead-like polymer containing no fine powder and having a particle size of 0.1 to 1 m/m, and is easy to measure without producing dust during the dissolution operation. According to the present invention, a water-soluble polymer is produced in the form of beads containing no fine particles by suspension polymerizing an aqueous solution of a water-soluble monomer using a combination of a specific dispersion stabilizer and a dispersion medium. be able to. Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded. Examples 1 to 15 and Comparative Examples 1 to 6 Into a 50 c.c. four-necked flask equipped with a cooling tube, a nitrogen introduction tube, a dropping funnel, and a fluororesin stirring blade, the types and usage amounts shown in Table 1 ( A dispersion stabilizer (concentration relative to the dispersion medium) and 20 g of the dispersion medium shown in Table 1 were introduced and stirred. The dispersion stabilizer swelled but did not dissolve and separated when stirring was stopped at room temperature. When the temperature was raised while stirring, it began to melt in the temperature range shown in Table 1. Oxygen was removed by passing nitrogen gas while keeping the temperature at the polymerization temperature shown in Table 1. 30g of acrylamide
After dissolving in 69.75 g of demineralized water, a 10% aqueous solution of 2,2'-azobis-2-amidinopropane hydrochloride was added to this.
0.25g was added and dissolved. 5.0 g of a 30% by weight acrylamide aqueous solution containing 0.025% by weight of the polymerization initiator thus obtained was introduced into the dropping funnel. After removing oxygen by passing nitrogen gas under the dropping funnel, the aqueous solution of acrylamide was introduced into the flask with stirring, and polymerized for 3 hours under a nitrogen gas atmosphere while maintaining a predetermined temperature. Product 400c.c.
After dispersing the polymer in acetone to remove water in the polymer, the polymer was separated and dried. The shape of the product after completion of polymerization and the reduced viscosity of the dry polymer are shown in Table 1. The reduced viscosity (ηsp/c) was measured at 25°C using an Ostwald viscometer for a 0.1% by weight polymer solution in 1N saline. (to=30 seconds)

【table】

[Table] Examples 16 to 26 2.7 g of ethyl cellulose (manufactured by Hercules Co., Ltd., trademark ethyl cellulose) was placed in a 200 cc. T-100) and
When 90 g of cyclohexane was introduced and stirred, ethylcellulose was dispersed in a slurry form, but when the temperature was raised while stirring, it became a homogeneous solution. 2,2'-
The hydrochloride of azobis-2-amidinopropane was dissolved and introduced into the dropping funnel. After deoxygenating the flask and dropping funnel by passing nitrogen gas, the flask is maintained at the polymerization temperature shown in Table 1, and when the monomer aqueous solution in the dropping funnel is introduced while stirring, the monomer aqueous solution forms water droplets of 0.1 to 1 m/m. Dispersed. The mixture was maintained at a predetermined temperature and polymerized for 3 hours under a nitrogen gas atmosphere. After the polymerization was completed, the cooling tube was removed, and the azeotropic water was removed from the system by keeping the bath temperature at 80 to 90° C. while stirring in a flask equipped with an azeotropic water separator that recycled only cyclohexane. The shape of the product and the reduced viscosity measured on the dry polymer are shown in Table 2.

[Table] Examples 27 to 28 Polymerization was carried out under the same conditions as in Example 16, except that the dispersion medium and dispersion stabilizer shown in Table 3 were used instead of ethylcellulose and cyclohexane. Water was removed from the system by azeotropic distillation of the water-dispersion medium under reduced pressure at a bath temperature of 50°C using an azeotropic water separator. The shape of the product and the reduced viscosity values determined for the dry polymer are shown in Table 3.

[Table] The contents of acetyl groups, butyryl groups, and ethoxy groups in the cellulose esters or ethers used in the examples are as follows. Eastman Kodak Company trademark CAB381-20 Acetyl group content 13% by weight Butyryl group content 37% by weight Trademark CAB500-5 Acetyl group content 6% by weight Butyryl group content 48% by weight Dow Chemical Company trademark Ethocel MED- 100
Ethoxy group content 45.0-46.5% by weight Trademark Ethocel STD-100
Ethoxy group content: 48.0-49.5% by weight Ethylcellulose K-50, trademark manufactured by Hercules Co., Ltd.
Ethoxy group content 45.5-46.8% by weight Trademark Ethylcellulose N-200
Ethoxy group content 47.5-49.0% by weight Trademark Ethylcellulose T-100
Ethoxy group content 49.0% by weight

Claims (1)

[Claims] 1. An aqueous solution of a water-soluble vinyl monomer is dispersed in the form of water droplets in a dispersion medium in the presence of a dispersion stabilizer and polymerized,
In the method for producing a bead-shaped water-soluble polymer, the water-soluble vinyl monomer has the general formula () ~
() _CH2 =CH−Z− _SO3M ……() (In the formula, R ¹ represents a hydrogen atom or a methyl group,
Y is -CONH ₂ group or -COO M' group (in the formula,
M' represents a monovalent cation), and Z
is -C _l H _2l - group (in the formula, l represents a number from 0 to 3),
-COO-(CmH ₂ m)- group (in the formula, m represents a number from 1 to 6), -CONH-(CnH ₂ n)- group (in the formula, n represents a number of 1 to 6)
(represents the number 6) or represents a phenylene group,
M represents a monovalent cation, R ² , R ³ and R ⁶
represents an alkyl group having 1 to 4 carbon atoms, R ⁴ , R ⁵
and R ⁷ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
hydroxy-substituted alkyl group or benzyl group, and X, X' and X'' represent anions. Alternatively, a halogenated aromatic hydrocarbon is used, and the dispersion medium used as a dispersion stabilizer is an oil-soluble cellulose ester or cellulose ether that is insoluble or poorly soluble at room temperature and soluble at the polymerization temperature, and the temperature is higher than 40°C. 2. A method for producing a bead-like water-soluble polymer, characterized in that the polymerization is carried out at a temperature of A manufacturing method characterized in that a compound selected from the group consisting of 10 aromatic hydrocarbons, alicyclic hydrocarbons, and aliphatic saturated hydrocarbons is used alone. 3 Claims 1 or 2 The method for producing a bead-like water-soluble polymer according to Claim 1, characterized in that water contained in the polymer obtained by polymerization is removed by azeotropic distillation of a dispersion medium-water system. In the method for producing a bead-like water-soluble polymer according to any one of items 1 to 3, a compound selected from the group consisting of toluene, xylene, chlorobenzene, and dichlorobenzene is used as a dispersion medium, and a butyryl group is used as a dispersion stabilizer. A manufacturing method characterized by using cellulose acetate butyrate containing 20 to 50% by weight of ethoxy groups or ethylcellulose containing 43 to 47% by weight of ethoxy groups. 5. Any one of claims 1 to 3. The method for producing a bead-like water-soluble polymer described in , characterized in that cyclohexane is used as a dispersion medium and ethyl cellulose containing 47 to 50% by weight of ethoxy groups is used as a dispersion stabilizer. The method for producing a bead-like water-soluble polymer according to any one of items 1 to 3, characterized in that n-hexane or n-heptane is used as a dispersion medium and ethylhydroxyethylcellulose is used as a dispersion stabilizer. manufacturing method.