JPS6129964B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for making partially hydrolyzed acrylamide-based polymers. Partially hydrolyzed acrylamide-based polymers are widely used, for example, as flocculants and secondary recovery agents during oil extraction, and their manufacturing method is a gel obtained by polymerizing a 15 to 45% acrylamide aqueous solution. After granulating the polymer, the granules are contacted with an aqueous caustic solution, and then
A method of obtaining it by hot air drying is known. In this method, the hydrolysis reaction of the polymer proceeds, for example, only about 20 to 30% of the target hydrolysis rate during contact treatment with caustic alkali, and the remaining hydrolysis reaction proceeds during hot air drying. In other words, since the reaction rate of hydrolysis is slow at low temperatures, substantially all of the added caustic alkali adheres to the polymer particles during contact treatment with caustic alkali, but the reaction itself does not occur much, and during the subsequent hot air drying Hydrolysis is completed by the action of the caustic alkali attached to the surface of the polymer particles. However, when the polymer obtained by the above method is dissolved in water, it tends to contain some components that are not completely dissolved in water. Polymers containing this water-insoluble component can have undesirable consequences when used as flocculants or oil recovery agents. Therefore, it is desirable to reduce the amount of water-insoluble components as much as possible. In view of the above circumstances, the present inventors have conducted various studies on methods for producing partially hydrolyzed acrylamide-based polymers that do not contain water-insoluble components, and have found that the polymer after polymerization is hydrolyzed using a certain specific method. The present invention was completed by discovering that the amount of water-insoluble components described above can be minimized by this method. That is, the gist of the present invention is that the monomer concentration is 15~
An aqueous solution containing 45% by weight of acrylamide is polymerized in the presence of a catalyst to obtain a gel-like polymer with a water content of 85-55% by weight, which is granulated and then brought into contact with an aqueous caustic solution, followed by a polymer with a water content of 15% by weight. A method for producing a partially hydrolyzed acrylamide polymer by hot air drying to a temperature of 50 to 150°C, in which the water content of the granular polymer is substantially reduced. A method for producing a partially hydrolyzed acrylamide-based polymer, characterized in that the process is carried out under conditions such that a target hydrolysis rate of acrylamide groups of 60% or more is achieved, and then the polymer is dried. Exists. 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 copolymerizable monomers such as sodium acrylate and 2-acrylamide propane sulfonate, and in the case of copolymerization, the proportion of acrylamide is usually preferably 50 mol% or more. 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 resulting gel polymer have high stickiness, but drying of the gel polymer will be troublesome.If this concentration is too high, the temperature in the polymerization system will become too high, causing the polymer to heat up. This is not desirable as it may cause deterioration. 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, which cuts the polymer extruded by a screw with a cutter in front of the extrusion surface and granulates it. 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 achieve uniform hydrolysis in subsequent treatments, which is not preferable. The granulated polymer is subjected to contact treatment with an aqueous caustic solution, and usually a method is adopted in which the aqueous caustic solution is sprayed while stirring the polymer particles. Caustic soda or caustic potash is used as the caustic alkali, and the concentration of its aqueous solution is usually 20 to 47% by weight. The amount of caustic used is determined by the target hydrolysis rate, and is usually
The amount is slightly in excess of the theoretical amount. Various hydrolysis rates of acrylamide groups in the target polymer are used depending on the intended use, but it is usually 5 to 40 mol%. In the present invention, by carrying out the hydrolysis reaction of the polymer under specific conditions, it is essential to hydrolyze at least 60%, preferably at least 70% of the target hydrolysis rate before drying the granular polymer. This is a requirement. If the hydrolysis reaction does not proceed sufficiently before drying the granular polymer and a large amount of hydrolysis occurs during subsequent hot air drying, this is not preferable because the water-insoluble components in the polymer will increase. The temperature for the hydrolysis reaction to proceed is 50~
The temperature is 150℃, preferably 65 to 100℃; if the temperature is too low, the hydrolysis reaction will not proceed well;
If the temperature is too high, the polymer will undergo thermal deterioration, which is not preferable. Furthermore, it is necessary to prevent the water content in the polymer from substantially decreasing during the hydrolysis reaction. For example, it is preferable not to reduce the water content of the polymer by more than 10% (wet basis) compared to that before treatment. If the water content of the polymer decreases significantly during the initial progress of the hydrolysis reaction, the expected effects of the present invention cannot be obtained. The time for the above treatment varies depending on the treatment temperature, but usually
The time is 1 minute or more, preferably 3 minutes or more, and a sufficient hydrolysis reaction cannot be carried out in too short a time. To actually perform the above-mentioned treatment, for example, polymer particles to which caustic alkali has been added in advance are placed in a closed container, steam is blown into the polymer particles, the polymer is heated to a predetermined temperature, and the polymer is sufficiently hydrated. Examples include a method of holding the polymer for a predetermined period of time until it is decomposed, and a method of adding caustic alkali to the granular polymer while supplying steam to the granular polymer and performing contact treatment at a high temperature. The granular polymer, which has undergone sufficient hydrolysis reaction through the above treatment, is usually treated with a 40 to 130
The polymer is dried with hot air at a temperature of 60 to 110°C, preferably 60 to 110°C, until the water content of the polymer is 15% by weight or less, preferably 10% by weight or less. The drying process is typically carried out using a band dryer, rotary dryer, or the like. The dried polymer is classified, usually 0.2
-5 m/m, preferably 0.5-3 m/m granules are recovered as product. As described above, according to the present invention, when the obtained polymer is dissolved in water, the water-insoluble components are extremely small, so that a polymer suitable as a flocculant or a secondary petroleum recovery agent can be obtained. Furthermore, when a polymer is dissolved in calcium-containing water, the aqueous solution tends to become cloudy, but the polymer obtained by the present invention has little tendency to become cloudy, and is an extremely excellent polymer. 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. 90 g of a 47% aqueous sodium hydroxide solution (an amount to hydrolyze 30 mol% of acrylamide groups) was sprayed onto 1 kg of the granules (water content: about 75 wt%) while stirring. Then, this granular material (water content approximately 75wt%) was
After spraying steam at ℃ for the time shown in Table 1 and maintaining the temperature of the granules at 70℃ to allow the hydrolysis reaction to proceed, the resulting granules (water content approximately 74 wt%)
Dry with hot air at a temperature of 100℃ for 60 minutes to reduce the moisture content.
It was dried to less than 12wt%. Regarding the granular polymer thus obtained, the proportion of insoluble components when dissolved in water was measured, and the results shown in Table 1 were obtained.

[Table] Example 2 10kg of 25wt% acrylamide aqueous solution was charged into a polymerization reactor, and after degassing with _N2 gas, 2.
2-azobis(2-amidinopropane) hydrochloride
Add 1000ppm and acidic sodium sulfite 100ppm,
Polymerization was carried out for 5 hours at a polymerization initiation temperature of 20°C. The gel-like polymer obtained by polymerization was taken out from the polymerization reactor, and then granulated into particles of about 3 m/m using a meat grinder type extrusion granulator. For 1 kg of this granulated material (water content approximately 75 wt%, particle temperature 20°C), 47
% caustic soda aqueous solution (temperature 25° C.) (an amount to hydrolyze 30 mol % of the acrylamide groups) was sprayed on the mixture with stirring and mixed uniformly for 3 minutes. After spraying granules with a caustic soda aqueous solution (water content approximately 75 wt%, particle temperature 22°C), 135°C
of water vapor was sprayed for the time shown in Table 2, and the temperature of the granules was maintained at 80°C to allow the hydrolysis reaction to proceed. The water content of the obtained granules was 74.5 wt%, and it was observed that the water content hardly decreased during the hydrolysis reaction. Then 100℃
The sample was dried with hot air for 60 minutes at a temperature of 12% to a moisture content of 12wt% or less. Regarding the granular polymer thus obtained, the proportion of insoluble components when dissolved in water was measured, and the results shown in Table 2 were obtained.

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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 55% by weight gel-like polymer was obtained, which was granulated and then brought into contact with an aqueous caustic solution, and then
In a method for producing a partially hydrolyzed acrylamide polymer by drying with hot air to a water content of 15% by weight or less, the hydrolysis reaction of a particulate polymer is carried out at a temperature of 50 to 150°C, and the content of the particulate polymer is Under conditions where the amount of water does not substantially decrease, the target rate of hydrolysis of acrylamide groups can be achieved.
1. A method for producing a partially hydrolyzed acrylamide polymer, characterized in that the process is carried out until 60% or more is achieved, and then the polymer is dried.