JPH0328441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an acrylamide polymer. Acrylamide-based polymers, for example, are widely used as flocculants. Usually, an acrylamide-containing aqueous solution is polymerized in a polymerization tank to obtain a polymer consisting of a gel-like mass, and then this polymer is taken out from the polymerization tank and treated with a suitable material. It is manufactured by granulating it to a suitable particle size and then drying it. In this method, when taking out the polymer from the polymerization tank after polymerization,
Usually, a method is adopted in which the polymerization tank is turned upside down to allow the polymer lumps to fall under its own weight, but since the polymer is a sticky gel-like substance, the polymer lumps can be easily peeled off. It is difficult to completely recover the polymer. Conventionally, in order to improve such drawbacks, a method has been known in which polymerization is carried out using a polymerization tank made of a synthetic resin or lined with a synthetic resin that has good peelability from polymer lumps. However, even in this method, if the polymerization operation is repeated using the same polymerization tank, there is no problem at first, but
Gradually, when recovering the polymer lumps, some of the polymer adheres to the inner wall of the polymerization tank, making it impossible to completely recover the polymer. Therefore, if the polymer adheres to the inner wall of the polymerization tank, it is necessary to scrape off the polymer, but since the polymer is a highly sticky gel, this scraping operation is extremely difficult. In addition, in order to prevent the adhesion of this polymer, there is no problem if the polymerization tank is cleaned every time after polymerization, but this cleaning operation becomes troublesome if the frequency increases. In view of the above-mentioned circumstances, the present inventors have developed a method to prevent the adhesion of polymer from the polymerization tank when taking out polymer lumps after polymerization, without having to wash the polymerization tank every time, in the polymerization of an aqueous acrylamide-containing solution. As a result of various studies with the aim of obtaining a method that can completely recover polymer lumps, we found that by adding a certain amount of ammonium sulfate to the polymerization system, polymerization could be achieved even if the polymerization tank was not washed and was repeatedly used for polymerization. The present invention was completed based on the discovery that adhesion of polymer to the inner wall of the tank can be prevented. That is, the gist of the present invention is that when an acrylamide-containing aqueous solution is polymerized in a polymerization tank in the presence of a catalyst to produce a gel-like polymer mass, ammonium sulfate is added in an amount of 0.2 to 5% by weight based on the monomer to carry out the polymerization. The present invention relates to a method for producing an acrylamide polymer. The present invention will be explained in detail below. The acrylamide-containing monomer targeted by the present invention is usually acrylamide alone or copolymerizable with acrylamide, such as acrylic acid, sodium acrylate, 2-acrylamide propane sulfonate, or quaternary salt of diethylaminoethyl methacrylate. Examples include mixtures with known monomers, but in the case of copolymerization, those with an acrylamide content of 50 mol% or more are usually preferred. In addition, the concentration of the monomer aqueous solution is usually 10 to 35% by weight, preferably 20 to 35% by weight.
The concentration is 30% by weight, and if this concentration is too low, the resulting gel-like polymer will have high stickiness, whereas if it is too high, the temperature in the polymerization system will become too high, causing thermal deterioration of the polymer, which is not preferable. Examples of polymerization catalysts include azo compounds such as azobis(2-amidinopropane) hydrochloride; peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide; sodium sulfite, ferrous sulfate,
Reducing agents such as ferrous chloride may be mentioned;
More than one species 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. In the present invention, it is essential to add ammonium sulfate during polymerization, and the amount added is 0.2 to 5% by weight, preferably 0.3 to 2% by weight, and more preferably 0.5 to 1.5% by weight based on the monomer. It is. If the amount of ammonium sulfate added is less than the above range, it will not be possible to sufficiently prevent the polymer from adhering to the polymerization tank during repeated polymerizations, and if it is more than the above range,
Although the adhesion prevention effect of the polymer remains unchanged, the performance of the obtained polymer as a flocculant is significantly reduced, which is not preferable. Ammonium sulfate is usually added to the polymerization system by supplying it as an aqueous solution to the polymerization tank together with the monomer aqueous solution. Polymerization is usually carried out by degassing the monomer aqueous solution mentioned above with nitrogen gas, adding a predetermined amount of catalyst, and increasing the temperature between -10 and 100.
It is carried out for about 1 to 10 hours at a temperature of °C. The polymerization tank used in the present invention is usually made of synthetic resin or lined with synthetic resin, and examples of the synthetic resin include tetrafluoroethylene resin,
Examples include phenolic resin, vinyl chloride resin, polyethylene, and polypropylene. Also, if glass or metal is used as the material,
Since it has good affinity with the polymer lumps, the polymer tends to adhere to the inner wall of the polymerization tank when the polymer lumps are taken out, so it is not very preferable. After polymerization, the polymerization tank containing gel-like polymer lumps is usually turned upside down and water or air is injected into the space between the inner wall of the polymerization tank and the polymer lumps, depending on its own weight. An auxiliary operation such as lifting can be performed to allow the polymer lumps to fall and be collected. In the present invention, even if the polymerization operation is repeated without cleaning the polymerization tank, the polymer does not adhere to the inner wall of the polymerization tank, which is preferable. The polymer agglomerates recovered as described above are processed in a conventional manner, for example, from 0.2 to 5 m/m, preferably from 0.5 to 5 m/m.
After granulation into granules with a particle size of 3m/m,
This is then heated to e.g. 40-130°C, preferably
The product is produced by drying at a temperature of 60 to 110°C until the water content is 15% by weight or less, preferably 10% by weight or less. As described above, according to the present invention, by simply adding a very small amount of ammonium sulfate into the polymerization system, it is possible to prevent the polymer from adhering to the polymerization tank and to completely recover the polymer lumps. Therefore, there is no need to clean the interior of the polymerization tank each time after polymerization, and
This method is industrially extremely advantageous since there is no need to scrape off the polymer adhering to the polymerization tank.
It is known from Japanese Patent Publication No. 40-20195 that an inorganic salt such as ammonium sulfate is added in an amount of about 30 to 60% by weight based on the monomer to prevent hydrolysis of acrylamide in the polymerization system. It is surprising that the effects unique to the present invention can be obtained by adding a very small amount of ammonium sulfate. Next, the present invention will be explained in detail with reference to examples, but the present invention is not limited to the description of the following examples unless it exceeds the gist thereof. Examples 1 to 3 and Comparative Examples 1 to 2 900 kg of 25% by weight acrylamide aqueous solution was placed in a 1 m ³ polymerization tank lined with tetrafluoroethylene resin.
and ammonium sulfate in the amount shown in Table 1,
After sealing and degassing the system with nitrogen gas, 2,2-azobis(2-amidinopropane) hydrochloride 2000 ppm and acidic sodium sulfite were added as a polymerization catalyst.
200 ppm was added and polymerization was carried out for 5 hours at a polymerization initiation temperature of 20°C. After polymerization, the polymerization tank is turned upside down and the polymer mass (82 x 120
×90cm) was dropped and collected. After taking out the polymer lumps, the polymerization tank was used as it was without cleaning, and the same polymerization operation as described above was repeated, and the state of adhesion of the polymer to the inner wall of the polymerization tank was observed. The results are shown in Table 1. Got the results. In addition, in order to examine the performance of the polymers obtained by these polymerizations as flocculants, we used a meat grinder type extruder to reduce the particle size of polymer aggregates to 2 to 5 m/m.
After molding into granules, this was dried at 100°C for 1 hour to reduce the water content to 10% by weight or less, and the sedimentation rate of this polymer was measured.
The results shown in the table were obtained. 【table】

Claims (1)

[Claims] 1. An acrylamide-containing aqueous solution in the presence of a catalyst,
1. A method for producing an acrylamide polymer, which comprises adding 0.2 to 5% by weight of ammonium sulfate to the monomer to produce a gel-like polymer mass by polymerizing in a polymerization vessel. 2. The method according to claim 1, characterized in that 0.2 to 2% by weight of ammonium sulfate is added. 3 The monomer concentration of the acrylamide-containing aqueous solution is
A method according to claim 1, characterized in that the amount is 10 to 35% by weight. 4. The method according to claim 1, wherein the polymerization cell is made of synthetic resin or is lined with synthetic resin.