JPH0413361B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing water-soluble or water-swellable spherical polymers. Further details include paper sizing agents, coating agents, fiber sizing agents, wastewater treatment agents,
The present invention relates to a method for producing water-soluble polymers used in water-soluble thickeners, filter aids, etc., or superabsorbent polymers used in sanitary products, agricultural water retention agents, etc., in the form of spheres without causing aggregation or gelation.

Aqueous solution polymerization is the most common method for synthesizing water-soluble polymers such as polyacrylamide and polyacrylic acid, but other methods such as precipitation polymerization, reverse-phase emulsion polymerization, and reverse-phase suspension polymerization are also used. . Among these methods, the reverse phase suspension polymerization method is superior in that it can efficiently obtain spherical polymers with high molecular weight. However, when polymerization is carried out using sorbitan, long-chain fatty acid esters of sugars, higher alcohol esters of phthalic acid, etc., which are generally known as dispersants for reversed-phase suspension polymerization, gelatinized products are sometimes produced, which hinders the progress of polymerization. In addition, even if the polymerization is successful, the obtained polymer particles are extremely fine and filtration becomes complicated.

As a method of preventing the formation of gelatinized products and obtaining a polymer with a large particle size, at least one macromolecule component that can be solvated in a liquid monomer phase and at least one other component that can be solvated in an organic medium can be used as a dispersant. A method of performing reverse-phase suspension polymerization using a macromolecular compound consisting of a macromolecular component has been proposed. (Patent Publication No. 1985-8521). However, even this method has drawbacks such as particle aggregation and gelation that often occur during polymerization depending on the combination of the type of dispersant and the type of polymerization monomer.

The present inventors conducted intensive research to find a method for producing spherical water-soluble or water-swellable polymers in a stable and simple manner without causing the above-mentioned disadvantages. The inventors have discovered that by using these agents in combination under specific conditions, polymerization can be carried out favorably without causing agglomeration or gelation of particles, leading to the completion of the method of the present invention.

That is, the present invention provides a method for producing a polymer by polymerizing a dissolved mixture of at least one water-soluble ethylene monomer and water in an organic medium that is substantially incompatible with the mixture by reverse-phase suspension polymerization. , polymerization was initiated using a graft copolymer obtained by grafting methacrylic acid and an oil-soluble ethylene monomer to an ethylene-propylene-diene monomer copolymer as a dispersant, and the polymerization rate was about 50% or more. %
The object of the present invention is to provide a method for producing a stable spherical water-soluble or water-swellable polymer by adding a surfactant soluble in an organic medium as a dispersion stabilizing agent and polymerizing the polymer at a time of less than 10 minutes.

The method of the present invention is effective in reverse-phase suspension polymerization of a dissolved mixture of at least one water-soluble ethylene monomer and water.

In carrying out the method of the present invention, a graft copolymer obtained by grafting methacrylic acid and an oil-soluble ethylene monomer to an ethylene-propylene-diene monomer copolymer is used, and a dispersion stabilizer for post-addition is used. A surfactant soluble in the organic medium used is used as an auxiliary agent.

In carrying out the method of the present invention, the dispersant is made to exist in the polymerization system before the start of polymerization, while the dispersion stabilizing agent has a polymerization rate of about 50% or more and less than 100% after the start of polymerization.
Preferably it is added at 70-99.9%. If this polymerization rate is expressed in time, it is generally about 15 minutes after the start of polymerization.
It may be added between 30 minutes and 3 hours, preferably between 30 minutes and 3 hours.

When carrying out reverse phase suspension polymerization of a dissolved mixture of at least one water-soluble ethylene monomer and water in an organic medium that is substantially incompatible with the mixture, methacrylic acid and When a graft copolymer obtained by graft polymerizing an oil-soluble ethylene monomer is used alone as a dispersant, the average particle size will vary depending on the stirring intensity, but the average particle size will be approximately 50~
A spherical polymer of 1000 μm is produced, but the spherical polymers often aggregate with each other within 2 to 6 hours from the start of polymerization, and in severe cases, the entire system turns into agglomerated blocks, making stirring difficult. It would be extremely inconvenient to implement this method. However, by adding a surfactant soluble in an organic medium as a dispersion stabilizing agent at a polymerization rate of about 50% or more and less than 100%, it becomes possible to carry out polymerization without causing the above-mentioned disadvantages. If the dispersion stabilizing agent is added earlier than the polymerization rate of about 50%, the dispersing ability of the dispersant will be impaired and polymerization will proceed in lumps without being dispersed.
It is extremely dangerous if carried out industrially.

In the method of the present invention, surfactants soluble in organic media used as dispersion stabilizing agents include sorbitan monostearate, sorbitan monooleate, sorbitan monolaurate, sorbitan monopalmitate, cytearic acid monoglyceride, and oleic acid monoglyceride. , polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, and other surfactants having an HLB of 3 to 9. Especially sorbitan monostearate,
Sorbitan monooleate, sorbitan monolaurate and sorbitan monopalmitate are preferably used. If HLB is 9 or more, the compatibility with the organic medium will decrease, while if it is less than 3, it will not function as a dispersion stabilizer, which is not preferable.

In the method of the present invention, a graft copolymer obtained by graft-polymerizing methacrylic acid and an oil-soluble ethylene monomer to an ethylene-propylene-diene copolymer is used as the dispersant. Such graft copolymers are generally ethylene-propylene-diene monomer copolymers (hereinafter referred to as ethylene-propylene-diene monomer copolymers) dissolved in an organic solvent.
(abbreviated as EPDM), methacrylic acid, an oil-soluble ethylene monomer, and an oil-soluble radical initiator under stirring in a nitrogen atmosphere, preferably at a temperature of 40°C or higher and 100°C or lower. A milky wastewater emulsion or solution.

In carrying out the method of the present invention, it is essential that one component of the graft monomer is methacrylic acid,
This monomer makes it possible for the first time to produce polymers with large particle diameters with good dispersion. The above oil-soluble ethylene monomers include ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methyl methacrylate, styrene, ethyl acrylate, and acrylic. Butyl acid, etc. can be used. In particular, ethyl methacrylate, propyl methacrylate, butyl methacrylate, etc. are preferably used.

The charging ratio of EPDM, methacrylic acid, and oil-soluble ethylene monomer is 30 to 90 parts by weight of EPDM; 2 to 40 parts by weight of methacrylic acid, assuming that the total is 100 parts by weight.
Parts by weight: Desirably 2 to 40 parts by weight of the oil-soluble ethylene monomer. If it is out of the above range, the dispersibility will decrease, which is not preferable.
Examples of organic solvents that can dissolve EPDM include aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, and octane, and aromatic hydrocarbons such as benzene, toluene, and xylene. If the dispersant is less than 0.05% by weight of the monomer aqueous solution, the dispersing ability will be insufficient, while if it exceeds 4% by weight, the insoluble matter will increase in the product, so generally 0.05 to 4% by weight, Preferably
It is desirable to use 0.1 to 2% by weight.

In the method of the present invention, examples of water-soluble ethylene monomers include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, metal salts thereof such as sodium and potassium, or ammonium salts thereof, acrylamide, N-vinylpyrrolidone, etc. be able to. When producing a water-swellable polymer, it can be produced by self-crosslinking the water-soluble ethylene monomers described above, but it is also possible to produce water-swellable polymers by self-crosslinking the water-soluble ethylene monomers and ethylene dimeric bonds. monomers containing more than one, such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, polyethylene glycol,
Di- or tri-acrylic esters and di- or tri-methacrylic esters of polyols such as polypropylene glycol, unsaturated polyesters obtained by reacting the polyols with unsaturated acids such as maleic acid and fumaric acid,
Bisacrylamides such as N,N-methylenebisacrylamide, acrylic acid or methacrylic acid esters obtained by reacting polyepoxide with acrylic acid or methacrylic acid, polyisocyanates such as tolylene diisocyanate and hexamethylene diisocyanate, and hydroxyacrylic acid. Di(meth)acrylic acid carbamyl esters obtained by reacting with ethyl or hydroxyethyl methacrylate, allylated starch, allylated cellulose, diallyl phthalate,
It can also be produced by polymerizing a mixture with a crosslinking agent such as N,N',N''-triallylisocyanate.The amount of crosslinking agent used is generally 0.001% of the water-soluble ethylene monomer. The organic liquid used as a medium includes aliphatic hydrocarbons such as butane, pentane, hexane, heptane, octane, and cyclohexane, aromatic hydrocarbons such as benzene, toluene, and xylene, chloroform, and dichloromethane. , ethyl chloride, dichloroethane, and other chlorinated hydrocarbons.

The charging ratio of water-soluble ethylene monomer and organic liquid is 150 parts by weight of organic liquid to 100 parts by weight of monomer aqueous solution.
Preferably, it is 600 parts by weight. If it is less than 150 parts by weight, the dispersion stability will deteriorate, and if it exceeds 600 parts by weight, the volumetric efficiency will be markedly deteriorated, making it economically undesirable. As a radical initiator, a water-soluble radical initiator such as potassium persulfate,
Water-soluble initiators such as ammonium persulfate, hydrogen peroxide, or combinations of these with appropriate reducing agents such as sodium bisulfite, sodium thiosulfite, sodium pyrosulfite, and Rongarit; 2,2'-(azobis-2-amidei); Water-soluble azo initiators such as propane dihydrochloride and azobiscyanopentanoic acid are preferably used. The amount of initiator used is not particularly limited, but it is preferably 0.005% by weight or more and 1% by weight or less based on the monomer.

According to the method of the present invention as detailed above, the polymer does not aggregate or gel during polymerization, and operational difficulties such as inability to stir and damage to the equipment are avoided. A remarkable effect can be achieved. Furthermore, the water-soluble polymer or water-swellable polymer produced by the method of the present invention has a great advantage in that it is spherical and has a large particle size, so that it can be easily separated.

Hereinafter, the method of the present invention will be specifically explained with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

Example 1 (Synthesis of dispersant) 425 g of hexane was placed in a separable flask equipped with a stirrer, a Dimroth condenser, and a thermometer.
Charge 52.5 g of EPDM (trade name: Esprene 301A, manufactured by Sumitomo Chemical Co., Ltd.), dissolve the EPDM under reflux, and then add 11.3 g of methacrylic acid, 11.3 g of butyl methacrylate, and 0.22 g of azobisisobutyronitrile at room temperature. , the temperature was raised to 66°C under a nitrogen atmosphere, and the reaction was allowed to proceed for 12 hours. The obtained dispersant was a white emulsion with a solid content concentration of 14.4% by weight.

(Production of water-soluble polymer) Into a separable flask equipped with a stirrer, Dimroth condenser, thermometer, and dropping funnel, 72 g of acrylamide, 6.1 g of acrylic acid, and 62 g of water were added.
10% by weight sodium hydroxide 34g, potassium persulfate
0.03 g, 380 g of hexane, and 6.6 g of the dispersant synthesized above were charged. After purging with nitrogen, while stirring at 600 rpm and maintaining the temperature at 10°C, a 1.5% by weight aqueous solution of sodium bisulfite was added dropwise from the dropping funnel at a rate of 1.5 ml/hour over 2 hours. One hour after the start of the dropwise addition of the sodium bisulfite aqueous solution (polymerization rate of about 80%), 0.8 g of sorbitan monolaurate (HLB8.6) was added. After the addition of sorbitan monolaurate, the polymerization was further stirred for 6 hours, and the resulting polymer maintained a neat spherical shape during stirring. The resulting suspension was filtered through a glass filter, and the polymer was washed with 100 ml of hexane.
It was dried under reduced pressure at 60°C for 24 hours. The obtained polymer was spherical with an average particle diameter of 280μ, and [η] = 14
(30°C in 1N NaNO ₃ aqueous solution).

Comparative Example 1 The same experiment as in Example 1 was conducted except that sorbitan monolaurate was not added, but two hours after the start of dropping the sodium bisulfite solution, the polymer particles aggregated into aggregates with a diameter of about 1 cm. Therefore, the polymerization was stopped.

Comparative Example 2 In an experiment similar to Example 1, sorbitan monolaurate was charged at the same time as the dispersant, but when three drops of the sodium bisulfite aqueous solution were added, the monomer phase turned into a lumpy gel and the dispersion was not obtained. I couldn't help it.

Example 2 1 A flask was equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, and 72 g of acrylamide, 8 g of sodium acrylate, and 95 g of water were charged and dissolved, then 0.08 g of potassium persulfate was added, and the mixture was placed in a condenser. While circulating methanol cooled to 40°C, 190 g of pentane and 190 g of butane were charged into a flask, and the temperature of the system was controlled to the boiling point. Adding 6.6 g of the dispersant solution of Example 1 and stirring at 600 rpm, 1.5 wt.
The mixture was added dropwise at a rate of ml/hour for 2 hours. One hour after the start of the dropwise addition (polymerization rate of about 80%), 0.4 g of sorbitan monolaurate (HLB8.6) was added. then 6
Polymerized for hours. During the polymerization, the suspension was a homogeneous dispersion. The polymer was filtered through a 300 mesh wire gauze cooled to -10°C, washed with 100ml of hexane, and dried under reduced pressure at 60°C for 24 hours. The obtained polymer has an average particle size
220μ[η]=15 (1N-NaNO ₃ , 30°C).
For comparison, the same experiment as above was conducted except that sorbitan monolaurate was not added, and the particles became aggregated 3 hours after the start of polymerization.

Example 3 (Synthesis of dispersant) 22 g of EPDM (manufactured by Sumitomo Chemical Co., Ltd., trade name: Esplen 301A) and 270 g of hexane were placed in a 500 ml flask, heated and dissolved with stirring, and then
4 g of methacrylic acid, 4 g of ethyl methacrylate, and 0.3 g of azobisisobutyronitrile were added, and after purging with nitrogen, the mixture was reacted at 60° C. for 7 hours with stirring. The obtained dispersant had a solid content concentration of 14.2% by weight.

(Production of water-swellable polymer) 2.8 g of the above graft polymer dispersant hexane solution and 330 g of n-hexane in 1 separable flask.
g and stirred to mix.

Meanwhile, 24.9 g of sodium hydroxide was dissolved in 78 g of water, 56 g of acrylic acid was gradually added thereto and mixed, and N,N-methylenebisacrylamide was added.
11 mg and 38 mg of potassium persulfate were added to prepare an aqueous sodium acrylate solution. Next, the sodium acrylate aqueous solution was added to the above-mentioned separable flask, and after purging with nitrogen, the temperature was raised to 62° C. while stirring at 600 rpm to initiate polymerization. One hour after the start of polymerization (polymerization rate of about 95%), 0.28 g of sorbitan monolaurate (HLB4.7) was added, and the reaction was continued for an additional 6 hours. Polymerization could be carried out without producing agglomerates. After polymerization, the polymer obtained by over-drying was a spherical water-swellable polymer with an average particle size of 340 μm and a water absorption rate of 470 g/g.

For comparison, we conducted the same experiment as above without adding sorbitan monostearate, and found that the polymer particles agglomerated 2.5 hours after the start of polymerization, forming pomegranate-shaped aggregates with a diameter of 1 cm. Summer.

Example 4 1.5 hours after the start of polymerization (polymerization rate approximately 99%)
Polymerization was carried out in exactly the same manner as in Example 3 except that 0.56 g of sorbitan monooleate (HLB4.3) was added instead of sorbitan monostearate. During the polymerization, the suspension was a homogeneous dispersion. . As a result of post-treatment in the same manner as in Example 3, the average particle size was 370μ,
A spherical superabsorbent polymer with a water absorption rate of 520 g/g was obtained. Further, polymerization was carried out in the same manner except that 0.56 g of sorbitan palmylate (HLB6.7) was added in place of the sorbitan monooleate. As a result, a spherical superabsorbent polymer having an average particle diameter of 350 μm and a water absorption rate of 550 g/g was obtained.

Claims (1)

[Claims] 1. Producing a polymer by polymerizing a dissolved mixture of at least one water-soluble ethylene monomer and water in an organic medium that is substantially incompatible with the mixture by reverse-phase suspension polymerization. In this method, a graft copolymer obtained by grafting methacrylic acid and an oil-soluble ethylene monomer to an ethylene-propylene-diene monomer copolymer is used as a dispersant to initiate polymerization, and the polymerization rate is approximately 50%. A method for producing a water-soluble or water-swellable spherical polymer, characterized in that a surfactant soluble in an organic medium is added as a dispersion stabilizing agent at a time of less than 100% and polymerized. 2 Addition of dispersion stabilizing agent until the polymerization rate is approximately 70-99.9%.
2. A method for producing a water-soluble or water-swellable spherical polymer according to claim 1, which is carried out between the steps of: 3 As a dispersion stabilizing agent, soluble in organic medium
3. The method for producing a water-soluble or water-swellable spherical polymer according to claim 1 or 2, characterized in that a surfactant having an HLB of 8 to 9 is used. 4. The water-soluble or water-swellable compound according to claim 1 or 2, wherein sorbitan monostearate, sorbitan monooleate, sorbitan monolaurate, or sorbitan monopalmitate is used as the dispersion stabilizing agent. A method for producing a spherical polymer.