JPH0128762B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for making partially hydrolyzed acrylamide polymers. Partially hydrolyzed acrylamide-based polymers are widely used, for example, as flocculants and secondary recovery agents during oil extraction, and are produced by polymerizing a 15-45% by weight acrylamide aqueous solution. After granulating the gel polymer,
A method is known in which the granules are brought into contact with an aqueous solution of caustic alkali or aqueous alkali carbonate and then dried with hot air. In this method, the contact treatment between the polymer particles and the alkaline aqueous solution is usually carried out by spraying the alkaline aqueous solution while stirring the polymer in a mixer having stirring blades. However, since the gel-like particulate polymer has adhesive properties, when the particulate polymer is stirred with a stirring blade, the polymer particles are mixed together, and some of the polymer particles tend to stick together in the form of lumps. Therefore, even if the aqueous alkali solution is sprayed onto the polymer particles, the alkali will not adhere uniformly to the polymer particles, resulting in a non-uniform hydrolysis rate of the polymer. In view of the above circumstances, the present inventors have proposed various methods for obtaining a polymer with a constant hydrolysis rate by bringing the polymer particles into contact with a caustic alkali or alkali carbonate aqueous solution without kneading the polymer particles. As a result of the study, it was found that by contacting the aqueous alkaline solution in a specific mixer, the polymer particles were easily loosened and there was less adhesion between the polymer particles, resulting in uniform and stable hydrolysis of the polymer. They discovered this and completed the present invention. That is, an acrylamide-containing aqueous solution with a monomer concentration of 15 to 45% by weight is polymerized in the presence of a catalyst to obtain a gel-like polymer with a water content of 85 to 55% by weight, which is granulated and then treated with a caustic alkali or alkali carbonate aqueous solution. In the method for producing a partially hydrolyzed acrylamide polymer by contacting and then drying with hot air, the contact treatment with the alkaline aqueous solution is carried out using a rotating cylindrical type without stirring blades whose inner surface is made of synthetic resin or The present invention relates to a process for producing a partially hydrolyzed acrylamide polymer, which process is carried out in a rotating plate mixer. The present invention will be explained in detail below. The monomers targeted by the present invention are acrylamide alone or together with acrylamide, for example, acrylic acid,
Examples include mixtures with known monomers that can be copolymerized with sodium acrylate, 2-acrylamide propane sulfonate, etc. In the case of copolymerization, those with an acrylamide ratio of 50 mol % or more are usually preferred. In the present invention, the concentration of the monomer aqueous solution during polymerization is
15-45% by weight, preferably 20-35% by weight,
If this concentration is too low, not only will the stickiness of the resulting gel-like polymer become high, but drying of the gel-like polymer will be troublesome, and if it is too high, the temperature in the polymerization system will become high, which may cause thermal deterioration of the polymer. This is not desirable. Examples of polymerization catalysts include azo compounds such as azobis(2-amidinopropane) hydrochloride, peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide, or sodium sulfite, monosulfuric acid, etc.
Examples include reducing agents such as iron, ferrous chloride, and
Two or more of these may be used in combination. The amount of catalyst used is usually 100 to 10,000 ppm, preferably 200 to 5,000 ppm based on the monomer. Polymerization is usually carried out by degassing the monomer aqueous solution mentioned above with _N2 gas, adding a predetermined amount of catalyst, and increasing the temperature from −10 to
It is carried out at a temperature of 100°C. The polymer obtained by this polymerization is a gel-like polymer with a water content of 85 to 55% by weight. The gel-like polymer after polymerization is then granulated, for example, into granules having an average particle size of 2 to 20 m/m, preferably 2 to 10 m/m. Granulation can usually be carried out using a meat grinder type extrusion granulator in which the polymer extruded by a screw is cut with a cutter in front of the extrusion surface. If the particle size of the polymer particles is too small, the particle size of the final product will be too small, and if it is too large, it will be difficult to carry out uniform hydrolysis in subsequent treatments, which is not preferable. The granulated polymer is then contacted with an aqueous solution of caustic alkali or alkaline carbonate to hydrolyze some of the amide groups in the polymer. As the alkali, caustic soda, caustic potash, soda carbonate, or potassium carbonate is usually used, and the concentration of the aqueous solution thereof is 20 to 47% by weight. The amount of alkali used is determined by the target hydrolysis rate of the polymer, and usually the target hydrolysis rate of the polymer is 5.
It is about 40 mol%. The present invention requires that the above-mentioned contact treatment between the polymer and the alkaline aqueous solution be carried out in a rotating cylindrical or rotating plate type mixer having an inner surface made of synthetic resin and having no stirring blades. . In the present invention, by carrying out the contact treatment in such a mixer, the polymer particles are not formed into lumps, and the polymer can be uniformly mixed, compared to the conventional method in which the contact treatment is carried out in a mixer equipped with stirring blades. Can be hydrolyzed. Examples of the synthetic resin forming the inner surface of the mixer include epoxy resin, methacrylic acid resin, tetrafluoroethylene resin, polyvinyl chloride, polystyrene, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, and polybutylene terephthalate. The mixer used in the present invention may be constructed of the above-mentioned synthetic resin, but usually a metal mixer whose inner surface is coated with the above-mentioned synthetic resin is used. The rotating cylindrical or rotating plate type mixer that is the object of the present invention is usually, for example, a rotating cylindrical (rotating drum type) granulator or a rotating plate type (pan type) granulator, which is known as a granulator for fertilizers, etc. Or Rossier type)
Granulation equipment is used. Although these devices do not have stirring blades, they have a structure in which particles are rolled and mixed by the rotation of the device. Further, in order to improve the mixing of the particles, it is preferable that an appropriate buffle is provided in the apparatus so that the particles are scraped up and mixed by the rotation of the apparatus. In the present invention, by mixing the polymer particles using such an apparatus, the polymer particles are appropriately loosened, and the particles do not stick together like lumps. The granular polymer that has been subjected to contact treatment with an alkali is usually heated at 40 to 130°C, preferably 60 to 130°C, according to a conventional method.
The water content of the polymer is not more than 15% by weight at a temperature of 110℃,
It is preferably dried with hot air until it becomes 12% by weight or less. The drying process is usually carried out using a rotary dryer, a band dryer, or the like. The dried polymer is subjected to a classification treatment, and granules having a size of usually 0.2 to 5 m/m, preferably 0.5 to 3 m/m are recovered as a product. As described above, according to the present invention, the particulate polymer does not become lumpy during the contact treatment with an alkali, and therefore, the polymer is uniformly hydrolyzed, so that a polymer of constant quality can be obtained. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example 1 10kg of 25wt% acrylamide aqueous solution was charged into a polymerization reactor, degassed with _N2 gas, and then 1000ppm of 2,2-azobis(2-amidinopropane) hydrochloride and acidic sodium sulfite were added as a polymerization catalyst.
100 ppm was added and polymerization was carried out for 5 hours at a polymerization initiation temperature of 20°C. The gel-like polymer obtained by polymerization was granulated into granules of about 3 m/m using a meat grinder type extrusion granulator. Next, 1 kg of granular polymer was coated with epoxy resin on the inner surface, with a diameter of 200 m/m and a length of 300 mm.
m/m horizontal cylindrical mixer, and while rotating the mixer at 40 rpm, 90 g of a 47% caustic soda aqueous solution was sprayed over 1 minute. After contact treatment with caustic soda, the granular polymer is dried with hot air at a temperature of 100℃ to reduce the polymer moisture content.
It was set to 12wt% or less. Samples of 10 g each were arbitrarily sampled three times from the granular polymer obtained by this method, and samples A to
C, and the hydrolysis rate of each of these samples was measured. In addition, in the contact treatment with caustic soda, the ratio of particulate polymer that became lump-like was measured. These results were as shown in Table 1. Example 2 In the method of Example 1, contact treatment with caustic soda was applied to a diameter whose inner surface was coated with epoxy resin.
The results are shown when processing was carried out at a rotation speed of 42 rpm in a rotating plate type mixer with a depth of 300 m/m and an inclination of 15°. Comparative Example In the method of Example 1, the caustic soda contact treatment was carried out using a method in which the inner surface was coated with an epoxy resin.
It has a gate-shaped stirring blade (as shown in Figure 4 of Japanese Patent Publication No. 54-40276), diameter 200 m/m, length
Gate-shaped stirring blades are installed in a 300m/m U-shaped trough.
The results are shown when processing was performed while rotating at 35 rpm. 【table】

Claims (1)

[Claims] 1 Polymerize an acrylamide-containing aqueous solution with a monomer concentration of 15 to 45% by weight in the presence of a catalyst to a water content of 85 to 45%.
A method for producing a partially hydrolyzed acrylamide polymer by obtaining a 55% by weight gel-like polymer, granulating it, contacting it with a caustic alkali or aqueous alkali carbonate solution, and then drying with hot air. A method for producing a partially hydrolyzed acrylamide polymer, characterized in that the contact treatment with the alkaline aqueous solution is carried out in a rotating cylindrical or rotating plate mixer having an inner surface made of synthetic resin and having no stirring blades. .