JPS6315925B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing water-soluble partially hydrolyzed polyacrylamide. More specifically, an aqueous solution of acrylamide is dispersed in a water-in-oil type using an oil-soluble polymer substance as a dispersion stabilizer, and the resulting water-soluble polyacrylamide is modified in a dispersed state to partially hydrolyze a high-molecular-weight water-soluble polyacrylamide. The present invention relates to a method for producing polyacrylamide. Water-soluble partially hydrolyzed polyacrylamides are polymers used as thickeners, thickeners, papermaking agents, flocculants, and crude oil recovery. In particular, when used as a flocculant or crude oil recovery agent, it is supplied in powder form due to transportation problems, and requires extremely high molecular weight and good water solubility. Partially hydrolyzed polyacrylamide is generally produced by polymerizing a 20 to 30% by weight aqueous solution of acrylamide by adding a water-soluble radical polymerization initiator, pulverizing the obtained rubbery hydrous polyacrylamide, and then mixing it with an aqueous alkaline solution. It is produced by hydrolyzing, dehydrating and drying. In this method, it is difficult to grind the hydrous polyacrylamide, and it is extremely difficult to uniformly mix the alkaline aqueous solution, so there are many problems in obtaining a uniformly hydrolyzed high-quality polymer. On the other hand, the hydrated polyacrylamide obtained by suspension polymerizing an aqueous acrylamide solution in a dispersion medium using an emulsifier or dispersion stabilizer is in the form of particles, which is considered convenient for uniformly adding an aqueous alkaline solution. It will be done. However, polyacrylamide hydrate dispersions obtained by suspension polymerization using emulsifiers that emulsify an acrylamide aqueous solution and a dispersion medium into a water-in-oil type tend to break the emulsion and form lumps when the amount of alkali aqueous solution added is large. There is. In addition, a polyacrylamide dispersion obtained by suspension polymerization using an emulsifier that emulsifies an acrylamide aqueous solution and a dispersion medium into an oil-in-water type is smoothly hydrolyzed by an alkaline aqueous solution, but a highly concentrated acrylamide aqueous solution is emulsified in the polymerization process. In addition, there were problems such as a large amount of polymer adhering to the reactor, and the final polymer contained a large amount of fine powder, producing dust, reducing the dissolution rate, and causing problems in workability. On the other hand, an oil-soluble polymer substance such as oil-soluble cellulose is dissolved in a colloidal form in a dispersion medium,
The suspension polymerization method, in which an aqueous acrylamide solution is dispersed in the form of water droplets by utilizing this dispersion effect, allows a highly concentrated aqueous acrylamide solution to be dispersed and polymerized, and moreover, there is less adhesion of the polymer to the container. Furthermore, it is possible to polymerize efficiently by continuously adding the monomer aqueous solution to the dispersion medium and polymerizing while removing the heat of polymerization. Moreover, the polymer after drying is a fine powder in the form of beads with a particle size of 0.1 to 1 mm. It has the characteristic of being very easy to handle and work because it does not contain any substances.
However, even if an alkaline aqueous solution is added to the dispersion of hydrous spherical polyacrylamide obtained by this polymerization method for the purpose of producing partially hydrolyzed polyacrylamide, the dispersion effect of the oil-soluble polymer substance causes the dispersion of the hydrous polyacrylamide particles and the alkaline aqueous solution. Since the droplets did not come into contact with each other, hydrolysis did not proceed smoothly, making it impossible to obtain bead-shaped partially hydrolyzed polyacrylamide. The present inventors used an oil-soluble polymer substance as a dispersion stabilizer and added an alkaline aqueous solution to a dispersion of spherical hydrated polyacrylamide obtained by suspension polymerization of an acrylamide aqueous solution in a dispersion medium. As a result of intensive studies on the method of producing decomposed polyacrylamide, the hydrolysis reaction progresses quickly and uniformly by adding an alkaline aqueous solution in the presence of alcohols, and if necessary, by dehydrating this, bead-shaped partial hydrolysis can be achieved. The present invention was achieved by discovering that decomposed polyacrylamide can be produced. That is, the present invention provides a method for producing partially hydrolyzed polyacrylamide by dispersing water-in-oil type in an aqueous solution of acrylamide using an oil-soluble polymeric substance as a dispersion stabilizer, performing a polymerization reaction, and modifying the resulting hydrous polyacrylamide. The present invention relates to a method for producing bead-shaped partially hydrolyzed polyacrylamide, which comprises adding a caustic alkali aqueous solution to a polyacrylamide dispersion in the presence of an alcohol to carry out a hydrolysis reaction. The present invention will be explained in more detail below. In the method of the present invention, partially hydrolyzed polyacrylamide is produced by dispersing an aqueous acrylamide solution in a water-in-oil type in a dispersion medium in the form of water droplets and carrying out a polymerization reaction. This is the resulting dispersion of hydrated spherical polyacrylamide. As the dispersion medium used to obtain a dispersion of hydrous spherical polyacrylamide, hydrocarbons, halogenated hydrocarbons, or halogenated aromatic hydrocarbons that do not dissolve the aqueous solution of acrylamide are used, and in particular hydrocarbons having 6 to 10 carbon atoms are used. Aromatic hydrocarbons, alicyclic hydrocarbons, aliphatic hydrocarbons, chlorinated benzene and the like are preferred. Particularly suitable dispersion media include benzene, toluene, xylene, isopropylbenzene, cyclohexane, methylcyclohexane, cyclooctane, decalin, n-hexane, n-heptane, n-heptane,
-octane, n-decane, chlorobenzene, dichlorobenzene, etc. Among them, toluene,
Particularly preferred are xylene, cyclohexane, n-heptane, and chlorobenzene. The dispersion medium is generally used in an amount of 0.5 to 10 times the weight of the acrylamide aqueous solution. It is also possible to use the acrylamide aqueous solution in a range of 0.5 to 4 times the weight by adding it continuously or in portions. As the dispersion stabilizer, a non-emulsifying oil-soluble polymer substance such as oil-soluble cellulose ester or ether is used. For example, water-insoluble but oil-soluble cellulose esters such as cellulose propionate, cellulose butyrate, and cellulose acetate butyrate, and oil-soluble cellulose ethers such as ethylcellulose, benzylcellulose, and ethylhydroxyethylcellulose are preferred. The dispersion stabilizer is used in an amount of 0.05 to 10% by weight, preferably 0.1 to 1% by weight, based on the dispersion medium. When using oil-soluble cellulose esters or ethers as dispersion stabilizers, mix solvents that dissolve these dispersion stabilizers well with solvents that do not, or use a single solvent that is poorly soluble in these dispersion stabilizers. It is best to select a solvent for use as a dispersion medium in which the dispersion stabilizer undergoes phase separation at room temperature (15-25℃), but becomes uniform at the polymerization temperature (generally 40℃ or higher). . If such conditions are selected, even a highly concentrated aqueous solution of 45 to 90% by weight of acrylamide can be dispersed extremely stably. The aqueous solution of acrylamide used is an aqueous solution of acrylamide alone, acrylamide and methacrylamide, (meth)acrylonitrile,
An aqueous solution of a mixture of (meth)acrylic acid, (meth)acrylic ester, N-substituted (meth)acrylamide derivative, etc. is used. The monomer concentration can be used at a concentration of 10 to 90% by weight, but in order to facilitate hydrolysis after polymerization, it is necessary to use a monomer concentration of 20 to 80% by weight.
Preferably it is in the range of 30 to 70% by weight. Productivity is extremely good when using an aqueous solution with a monomer concentration of 45 to 90% by weight, but in this case, a water-soluble polyhydric alcohol such as propylene glycol or diethanolamine, or sodium bisulfite, etc. is added to the monomer aqueous solution to prevent crosslinking reactions during polymerization. It is desirable to add a reducing inorganic sulfur compound. As the radical polymerization initiator, water-soluble peroxides and water-soluble azo compounds are preferred. For example, peroxides such as potassium persulfate, ammonium persulfate, peracetic acid, hydrogen peroxide, and 2,2'-azobis-2
-amidinopropane (azobisisobutyramidine) hydrochloride, sulfate, acetate, azobis-N,
Water-soluble azo compounds such as the hydrochloride sulfate and acetate of N'-dimethyleneisobutyramidine, and the sodium and potassium salts of 4,4'-azobis-4-cyanovaleric acid are used. Acrylamide 45-90
When polymerization is carried out in the coexistence of a water-soluble polyhydric alcohol or a reducing inorganic sulfur compound using a wt % aqueous solution, it is preferable to use a water-soluble azo compound as the radical polymerization initiator. The amount of polymerization initiator used is 50 to 5000 ppm, preferably 200 to 5000 ppm, based on the aqueous solution of acrylamide.
Used in the weight range of 1000ppm. When obtaining a water-containing spherical polyacrylamide dispersion used to obtain partially hydrolyzed polyacrylamide, there are restrictions on the order of addition of dispersion medium, dispersion stabilizer, aqueous acrylamide solution, radical polymerization initiator, and additives for preventing crosslinking reactions. However, the following method is preferred. A dispersion stabilizer is dispersed or dissolved in a dispersion medium, maintained at a predetermined temperature for polymerization, and deoxidized by passing nitrogen gas. After a radical polymerization initiator and, if necessary, an additive for preventing a crosslinking reaction are mixed with the monomer aqueous solution, the monomer aqueous solution is added to the dispersion medium while stirring and passing nitrogen gas. Polymerization can be carried out at any temperature from 40°C to the boiling point of the dispersion medium. In order to obtain a high molecular weight polymer, it is preferable to polymerize at 40°C to 70°C. In this way, a dispersion of hydrous spherical polyacrylamide having a uniform particle size in the range of 0.1 to 1 mm is obtained. When a caustic alkali aqueous solution is added to this dispersion, it is uniformly dispersed, but the hydrolyzed polyacrylamide and the caustic alkali aqueous solution do not come into contact and the hydrolysis reaction is extremely slow. Moreover, if the mixture is stirred for a long period of time, the partially hydrolyzed polyacrylamide will turn into lumps. In the method for producing partially hydrolyzed polyacrylamide according to the present invention, alcohols are added to a dispersion of hydrous spherical polyacrylamide to modify the surface of the hydrous polyacrylamide particles. By mixing the caustic alkali aqueous solution with stirring in the coexistence of alcohols, the caustic alkali aqueous solution uniformly permeates into the polyacrylamide while maintaining the particle shape of the polyacrylamide, and the hydrolysis reaction proceeds smoothly. . The alcohols used have carbon numbers starting from 1.
15 Preferably, mono- or polyhydric alcohols having 1 to 8 carbon atoms are used. For example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-
Butanol, n-pentanol, n-octanol, 2-ethylhexanol, ethylene glycol, diethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,
3-butanediol, glycerin, trimethylolpropane, sorbitol and 7 to 15 carbon atoms
These include higher oxo alcohols derived from α-olefins. The amount of alcohol used is 5 to 100% by weight, preferably 10 to 50% by weight, based on the water-containing polyacrylamide. It is preferable that the alcohol be added during suspension polymerization, after the formation of polymer particles, during the step of adding caustic alkali and performing hydrolysis. The caustic alkali such as caustic soda or caustic potash used for hydrolysis may have any concentration from 10% by weight to a saturated aqueous solution. The caustic alkali can be used in an amount of 1 to 100 mol % based on the raw material acrylamide, but it is effective to use it in an amount of 5 to 60 mol %. In this way, polyacrylamide usually
60 mol% is hydrolyzed. A caustic alkali aqueous solution is added to a dispersion of water-containing polyacrylamide in a dispersion medium obtained by suspension polymerizing an acrylamide aqueous solution using an oil-soluble polymer substance as a dispersion stabilizer in the above method. By adding and heating the aqueous caustic alkali solution, the water-containing polyacrylamide is uniformly impregnated, ammonia gas is generated, and hydrolysis proceeds rapidly. In addition, if necessary, azeotropic distillation of the dispersion medium-water system during the hydrolysis reaction or dehydration by contacting with acetone or methyl alcohol after heating to 40°C or higher can result in uniform particle size beads for easier handling. Partially hydrolyzed polyacrylamide with good properties is obtained. The present invention will be explained in more detail with reference to examples below, but the present invention is not limited to the following examples unless it goes beyond the gist of the invention. Examples 1 to 6 and Comparative Example 1 0.4 g was placed in a 200 c.c. four-neck separable flask equipped with a cooling tube, a nitrogen introduction tube, a fluororesin stirring blade, and a monomer aqueous solution introduction tube connected to a metering pump.
Ethyl cellulose (trademark manufactured by Hercules)
EC-T-100) and 130 g of cyclohexane were introduced, and the temperature was raised to 60°C while stirring to dissolve the ethyl cellulose, and the oxygen in the flask was removed by passing nitrogen gas while keeping the temperature at 50°C. Add propylene glycol to 42 g of a 50% acrylamide aqueous solution.
0.4 g and 0.105 g of a 10% by weight aqueous solution of sulfate of azobis N, N' dimethylene isobutyramidine were added and dissolved, and this solution was introduced into the flask under stirring at a rate of 3 g per minute using a metering pump. did. Further, while stirring under a nitrogen gas stream, the temperature was 90°C at 50°C.
When heated for a minute, a dispersion of water-containing spherical polyacrylamide and cyclohexane with a particle size of 0.1 to 1 mm was obtained. To this dispersion was added 10 g of the compound shown in Table 1 (24% by weight to water-containing polymer), and the temperature was raised to 70° C. with stirring. 7.5 g of a 47% by weight aqueous caustic soda solution (30% by mole based on the raw material acrylamide) was added, the bath temperature was further raised to 85°C while stirring vigorously, and the cyclohexane-water system was continuously distilled by azeotropic distillation. Water was removed from the system. It took 2 hours to dehydrate. When the obtained polymer was subjected to thermal separation, bead-shaped partially hydrolyzed polyacrylamide with uniform particle size was obtained. In some cases, several bead-like polymers coalesced during hydrolysis or dehydration, but they could be easily broken down. Ostwald viscometer (t ₀ = 30 seconds) for a 0.1% by weight aqueous solution of the product in 1N saline.
The reduced viscosity (ηsp/c) at 25°C was measured using the following. The anion modification rate (mol%) was measured by colloid titration using a 0.1% by weight aqueous solution of the product.
The results are shown in Table 1. (Colloid titration) 90 ml of demineralized water and 1/10 standard in a 200 c.c. beaker
0.5ml of NoOH aqueous solution was then added to 0.1% by weight poly-β-methacryloyloxyethyltrimethylammonium chloride (reduced viscosity ηsp/
c=1.6) Add 5 ml. While stirring with a magnetic stirrer, a 0.1% by weight aqueous solution of the product was added to
Add ml and stir for 5 minutes. Titrate with a 1/400N polyvinyl potassium sulfate aqueous solution using toluidine blue as an indicator, and the end point is the point at which the deep blue color changes to reddish-purple.
Perform a blank test without adding an aqueous solution of the product,
The anionization rate was measured from the difference between the blank and titration values. The actual value for the copolymer of acrylamide and sodium acrylate (70 mol % vs. 30 mol %) was an anionization rate of 29.6 mol %.

[Table] Examples 7 to 9 A second 200 c.c. four-necked separable flask equipped with a cooling tube, a nitrogen introduction tube, a fluororesin stirring blade, and a monomer aqueous solution introduction tube connected to a metering pump was used.
0.65g of dispersion stabilizer shown in the table and dispersion medium shown in Table 2
130 g of the flask was introduced and the temperature was raised to 70° C. while stirring to dissolve the dispersion stabilizer. While maintaining this temperature, nitrogen gas was passed through the flask to remove oxygen. After adding and dissolving 0.42 g of propylene glycol and 0.105 g of a 10 wt% 2,2'-azobisamidinopropane dihydrochloride aqueous solution to 42 g of a 50 wt% aqueous solution of acrylamide, the solution was poured into a flask with stirring using a metering pump. was used at a rate of 3 g/min. Further, the mixture was kept at 70° C. for 60 minutes while stirring under a nitrogen gas stream. After adding 10g of methanol and stirring for 5 minutes,
7.5 g of caustic soda aqueous solution (30 mol % based on raw material acrylamide) was added and stirred at high speed.
It was held at 70°C for 2 hours. 500ml of product after cooling
After stirring, the solvent was removed by decantation, followed by dehydration in 200 ml of methanol, and the polymer was dried separately. The reduced viscosity and anionization rate of the product are shown in Table 2.

【table】

Claims (1)

[Claims] 1. In a method for producing partially hydrolyzed polyacrylamide by dispersing an aqueous solution of acrylamide in a water-in-oil type using an oil-soluble polymer substance as a dispersion stabilizer and carrying out a polymerization reaction, the resulting hydrous polyacrylamide is modified to produce partially hydrolyzed polyacrylamide. 1. A method for producing bead-shaped partially hydrolyzed polyacrylamide, which comprises adding a caustic alkali aqueous solution to a dispersion of the polyacrylamide in the presence of an alcohol to perform hydrolysis.