JPS6337121B2 - - 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 adding a water-soluble radical polymerization initiator to a 20 to 30% by weight aqueous solution of acrylamide, polymerizing it, crushing the resulting rubber-like 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 the acrylamide aqueous solution and the dispersion medium into an oil-in-water type is smoothly hydrolyzed by an alkaline aqueous solution, but a highly concentrated acrylamide aqueous solution cannot be emulsified during 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, resulting in dust generation, a decrease in dissolution rate, and problems in workability. On the other hand, the suspension polymerization method, in which an oil-soluble polymer material such as oil-soluble cellulose is dissolved in a colloidal form in a dispersion medium, and this dispersion effect is used to disperse an aqueous solution of acrylamide in the form of water droplets, produces a high concentration of acrylamide. It is possible to disperse and polymerize an aqueous solution,
Moreover, there is less polymer adhesion 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 alkali aqueous solution is added to a dispersion of hydrated spherical polyacrylamide obtained by this polymerization method for the purpose of producing partially hydrolyzed polyacrylamide, the particles of hydrated polyacrylamide and the alkaline aqueous solution are separated by the dispersing action of the oil-soluble polymer substance. Since the droplets did not contact each other, hydrolysis did not proceed smoothly and it was not possible to obtain bead-shaped partially hydrolyzed polyacrylamide. The present inventors added an alkaline aqueous solution to a dispersion of spherical hydrous polyacrylamide obtained by suspension polymerizing an acrylamide aqueous solution in a dispersion medium using an oil-soluble polymer substance as a dispersion stabilizer, and partially hydrolyzed the bead-like shape. As a result of intensive studies on the method for producing polyacrylamide, the hydrolysis reaction progresses quickly and uniformly by adding an alkaline aqueous solution in the presence of an emulsifier in which water and a dispersion medium form an oil-in-water type dispersed phase. The present inventors have discovered that partially hydrolyzed polyacrylamide in the form of beads can be produced by dehydrating the polyacrylamide. That is, the present invention produces partially hydrolyzed polyacrylamide by dispersing an aqueous solution of acrylamide in a dispersion medium in a water-in-oil type using an oil-soluble polymer substance as a dispersion stabilizer, performing a polymerization reaction, and modifying the resulting hydrous polyacrylamide. Bead-shaped partial hydrolysis characterized in that a hydrolysis reaction is carried out by adding an emulsifier having a property that a dispersion medium and water form an oil-in-water type phase and a caustic alkaline aqueous solution to a dispersion of hydrous polyacrylamide. It consists in a method for producing polyacrylamide. 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. The dispersion medium used to obtain a dispersion of hydrated spherical polyacrylamide includes hydrocarbons, halogenated hydrocarbons, and halogenated aromatic hydrocarbons that do not dissolve the aqueous solution of acrylamide. 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-octane, n-decane, chlorobenzene, dichlorobenzene, and the like. . Among them, toluene, xylene, cyclohexane, n-
Particularly preferred are 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, cellulose esters such as water-insoluble and oil-soluble cellulose propionate, cellulose butyrate, and cellulose acetate butyrate, and oil-soluble cellulose ethers such as ethyl cellulose, benzyl cellulose, and ethyl hydroxyethyl cellulose 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 or a mixture of acrylamide and methacrylamide, (meth)acrylonitrile, (meth)acrylic acid, (meth)acrylic acid ester, N-substituted (meth)acrylamide derivatives, etc. be done. Monomer concentrations of 10 to 90% by weight can be used, but
In order to facilitate hydrolysis after polymerization, the amount is in the range of 20 to 80% by weight, preferably 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,
N′-dimethyleneisobutyramidine hydrochloride,
Water-soluble azo compounds such as sulfate, acetate, sodium salt, potassium salt 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 the polymerization initiator used is in the range of 50 to 5000 ppm, preferably 200 to 1000 ppm, based on the aqueous solution of acrylamide. When obtaining the hydrous spherical polyacrylamide dispersion used to obtain partially hydrolyzed polyacrylamide, there are restrictions on the order of addition of the 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 of the present invention for producing partially hydrolyzed polyacrylamide, a surfactant having a property of forming an oil-in-water phase between water and a dispersion medium as an emulsifier is added to a dispersion of hydrous spherical polyacrylamide. The surface of hydrous polyacrylamide particles is modified. By mixing the caustic alkali aqueous solution with stirring in the coexistence of such a surfactant, the caustic alkaline aqueous solution uniformly penetrates into the polyacrylamide while maintaining the particle shape of the polyacrylamide, and the hydrolysis reaction is carried out smoothly. proceed. The surfactants used include nonionic, anionic, cationic, and zwitterionic surfactants, which are substances in which the dispersion medium and water used for polymerization form an oil-in-water dispersed phase. Either can be used. Preferred nonionic surfactants are surfactants that are soluble in the dispersion medium and have an HLB of 8 to 20, more preferably surfactants that have an HLB of 10 to 16. For example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxy These include ethylene phenyl ether, polyoxyethylene laurate, polyoxyethylene oleate, polyoxyethylene stearate, polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan stearate, and polyoxyethylene sorbitan oleate. Preferred anionic, cationic and amphoteric surfactants are those having high lipophilic properties. Preferred examples include ammonium alkylbenzenesulfonate, sodium dialkyl sulfosuccinate, polyoxyethylene nonyl phenyl ether ammonium sulfate, alkyl phosphate, polyoxyethylene laurylamine, cetyltrimethylammonium chloride, stearylmethyltrimethylammonium chloride, distearyl These include dimethylammonium chloride and betaine type surfactants. Among these, compounds containing two or more long-chain alkyl groups in one molecule are particularly excellent. The amount of surfactant used is 0.05 to 10% of the dispersion medium.
It is preferably used in a range of 0.5 to 5% by weight. The surfactant is preferably added during the step of adding caustic alkali and performing hydrolysis after polymer particles are formed in suspension polymerization. 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 amount of caustic alkali used is 1 to 100 mol% based on the raw material acrylamide.
Although it can be used in a range of 5 to 60 mol%, it is effective. In this way, usually 1 to 60 mol % of the polyacrylamide is hydrolyzed. By adding a caustic alkali aqueous solution to a dispersion of aqueous polyacrylamide dispersed in a dispersion medium in the presence of the surfactant and heating it, the aqueous caustic alkali solution uniformly impregnates the aqueous polyacrylamide, and ammonia Gas is generated and hydrolysis proceeds rapidly. In addition, if necessary, perform azeotropic distillation of the dispersion medium-water system during the hydrolysis reaction, or
When heated to a temperature above .degree. C. and then dehydrated by contacting with acetone or methyl alcohol, partially hydrolyzed polyacrylamide in the form of beads of uniform particle size and easy to handle can be 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 exceeds the gist thereof. Examples 1 to 9, Comparative Examples 1 to 2 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 was charged with 0.4 g
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 azobis-N,N'-dimethyleneisobutyramidine sulfate
After the solution was added and dissolved, the solution was introduced into the stirring flask at a rate of 3 g per minute using a metering pump. Furthermore, at 50℃ while stirring under a nitrogen gas stream.
After heating for 90 minutes, a dispersion of hydrous spherical polyacrylamide and cyclohexane with a particle size of 0.1 to 1 mm was obtained. The compounds shown in Table 1 are added to this dispersion.
1.3 g (1% by weight of cyclohexane) was added and the temperature was raised to 70° C. with stirring. Add 7.5 g of a 47% by weight caustic soda aqueous solution (30% by mole based on the raw material acrylamide) and further raise the bath temperature to 85°C while stirring vigorously.
Water was continuously removed from the system by azeotropic distillation of the cyclohexane-water 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. The reduced viscosity (ηsp/C) at 25° C. of a 0.1% by weight aqueous solution of the product dissolved in 1N saline was measured using an Ostwald viscometer (t ₀ =30 seconds). 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
0.5 ml of NaOH aqueous solution and then 0.1% by weight poly-β-methacryloyloxyethyltrimethylammonium chloride (reduced viscosity ηsp/
Add 5 ml of C=1.6). 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. A blank test was conducted without adding an aqueous solution of the product, and the anionization rate was measured from the difference between the blank and the titration value. Acrylamide and Sodium Acrylate (70
The measured value for the copolymer (mol % vs. 30 mol %) was an anionization rate of 29.6 mol %.

[Table] Examples 10 to 12 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 1.3g of polyoxyethylene nonyl phenyl ether (HLB10.9) and stirring for 5 minutes, 47
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.

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Claims (1)

[Scope of Claims] 1. Polymerization reaction is carried out by dispersing an aqueous solution of acrylamide in a dispersion medium in a water-in-oil type using an oil-soluble polymer substance as a dispersion stabilizer, and the resulting hydrous polyacrylamide is modified and partially hydrolyzed. In the method for producing polyacrylamide, an emulsifier having a property that the dispersion medium and water form an oil-in-water type phase and an aqueous caustic alkaline solution are added to a dispersion of water-containing polyacrylamide to perform hydrolysis. A method for producing a characteristic bead-shaped partially hydrolyzed polyacrylamide.