JPS588681B2 - Method for producing partially hydrolyzed acrylamide polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a partially hydrolyzed acrylamide polymer.

Acrylamide polymers are widely used as flocculants, and for example, anionic polymers in which a part of the acrylamide polymer is hydrolyzed with caustic alkali or alkali carbonate are used depending on the purpose.

This partially hydrolyzed acrylamide polymer is usually produced by granulating a hydrous gel-like polymer obtained by polymerizing an aqueous acrylamide solution to a desired particle size, and adding the alkali aqueous solution to this.
Next, after drying, the product particle size is 0.1 to 1 m/
It is produced by grinding to a particle size of m.

In this method, ammonia gas is generated during hydrolysis, and although most of the generated ammonia gas is removed during the drying process, a portion of it is trapped inside the granular polymer.

Therefore, ammonia gas contained inside the polymer is generated again during the pulverization process to turn the polymer into a product.
When this polymer is subsequently packaged as a product, ammonia accumulates in the gas phase of the package, giving rise to an ammonia odor when the package is opened, which has the disadvantage of deteriorating the working environment.

In view of the above circumstances, the inventors of the present invention have investigated various methods for removing ammonia generated during the production of partially hydrolyzed acrylamide polymers. They discovered that ammonia was significantly reduced and completed the present invention.

That is, the gist of the present invention is that a gel-like polymer with a water content of 65 to 90% by weight obtained by polymerizing an acrylamide-containing aqueous solution is made into particles with an average particle size of 2 to 5%, and then a caustic alkali or alkali carbonate aqueous solution is formed. In the method of producing a partially hydrolyzed acrylamide polymer by adding the alkaline aqueous solution to the polymer, the polymer is partially hydrolyzed, and then dried, the polymer having a water content of 1
Dry with hot air at a temperature of 40 to 130°C until the water content is 5% by weight or less, and (b) Particle size of the polymer with a water content of 15% by weight or less is 0.1 to 1 m.
C. The method for producing a partially hydrolyzed acrylamide polymer is characterized in that: (c) the pulverized polymer is subjected to ventilation treatment at a temperature of 80 to 130° C. for 30 minutes or more.

The present invention will be explained in detail below.

The acrylamide-based polymer targeted by the present invention usually includes a homopolymer of acrylamide or a copolymer of acrylamide with, for example, acrylic acid, sodium acrylate, acrylic ester, methacrylic acid, sodium methacrylate, or the like.

In the present invention, such a polymer is further partially hydrolyzed with an alkali to produce a partially hydrolyzed acrylamide polymer.

The method for producing an acrylamide polymer is usually performed by adding a peroxide such as potassium persulfate or ammonium persulfate or azobis(2-amidinopropane) hydrochloride to a 10-35% by weight, preferably 20-30% by weight aqueous acrylamide solution. Add a known polymerization initiator such as an azo compound such as -
It is carried out by carrying out the polymerization at a temperature of 10 to 100°C.

The polymer obtained here is a gel-like polymer with a water content of 65 to 90% by weight, and prior to the hydrolysis treatment, this polymer is processed by, for example, a meat grinder-type extrusion granulator with an average particle size of 2 to 5%. %
granular material.

Next, the granulated acrylamide polymer is treated with a caustic alkali such as caustic soda, caustic potash, or soda carbonate.
A part of the acrylamide polymer is hydrolyzed by contact treatment with an aqueous solution of an alkali carbonate such as potassium carbonate.

This treatment is usually carried out by uniformly spraying the aqueous alkaline solution onto the polymer while stirring it.

The amount of the alkali compound added varies depending on the anionization rate of the product to be produced, but is preferably in an amount equivalent to or slightly in excess of the amide group to be hydrolyzed.

After adding the alkaline aqueous solution, the polymer is dried to have a water content of 15% by weight or less, preferably 10% by weight or less.

If this water content is too high, workability in the subsequent pulverization step for product production will be lowered, which is not preferable.

Since the hydrolysis reaction is completed in the drying process, ammonia is also generated in the drying process, so it is better to always replace the gas phase in the drying process with fresh gas.

The drying method is usually carried out at 40 to 130°C, preferably at 60°C using a band dryer, hot air dryer, or a combination thereof.
It is carried out at a temperature of ~110°C.

The dried polymer is pulverized to a particle size for commercialization, and the particle size is 0.1 to 1 m/m.

The pulverization process is usually performed using a pulverizer such as a hammer mill, and then sieved using a classifier.

In the present invention, it is further essential that the polymer that has reached the particle size of the product be subjected to ventilation treatment.

Ventilation treatment at 80-130°C, preferably 80-110°C
It is carried out at a temperature of 30 minutes or more, preferably 60 minutes or more.

If the treatment temperature at this time is too low, ammonia gas cannot be removed efficiently, and if the treatment temperature is too high, there is a risk of thermal deterioration of the polymer, which is not preferable.

If the treatment time is less than 30 minutes, ammonia gas will not be removed sufficiently, which is not preferable.

When carrying out this process, it can be carried out using, for example, a rotating drum type hot air dryer, and it is preferable to carry out the process while replacing the gas in the gas phase as in the drying process.

After the product thus manufactured is cooled to room temperature, it is sealed and packaged in accordance with conventional methods.

In the present invention, most of the ammonia is removed from the polymer by first drying it to a specific particle size and a predetermined moisture content, and then, after pulverizing the polymer to a product-ready particle size, a specific ventilation treatment is applied to substantially remove the ammonia. All ammonia can be removed.

In particular, in the final ventilation treatment, not only the ammonia attached to the surface of the granules is removed, but also the ammonia trapped inside the granules can be removed.

Therefore, even if the bag in which the polymer of the present invention is sealed and packaged for a long time is opened, there is almost no ammonia odor, and the working environment at the time of opening is not deteriorated.

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 it exceeds the gist thereof.

Example 1,000 ml of a 25 wt% acrylamide aqueous solution was placed in a polymerization reactor.
After degassing by blowing in nitrogen gas, 3000 ppm of 2,2-azobis(2-amidinopropane) hydrochloride was added as a polymerization initiator, and the polymerization initiation temperature was 20.
Polymerization was carried out at ℃ for 5 hours.

The obtained gel-like polymer was made into particles with an average particle diameter of 2.5 m/m using a meat grinder type extrusion granulator, and then, while stirring the granules uniformly, 20 moles of the amide group of the acrylamide polymer was added. A theoretical amount of 20 wt% aqueous caustic soda solution to hydrolyze % was added by spraying.

Thereafter, the granules were dried at 100°C using a band dryer.
The sample was dried for 1 hour at 100° C. using a rotary dryer.

Next, the granules were crushed and classified using a hammer mill type pulverizer to a particle size of 0.1 to 1% of the product particle size, and then the granules having the product particle size were treated with hot air under the conditions shown in Table 1.

200 g of the hydrolyzed polymer with a water content of approximately 10 wt% obtained in this manner was stored in a closed glass container for 24 hours, and the ammonia concentration in the gas phase was then measured, and the results shown in Table 1 were obtained. Ta.

Claims (1)

[Claims] 1. Water content obtained by polymerizing an acrylamide-containing aqueous solution: 6
After 5 to 90% by weight of gel-like polymer is made into particles with an average particle size of 2 to 5%, caustic alkali or alkali carbonate aqueous solution is added to partially hydrolyze the polymer, which is then dried to form partially hydrolyzed acrylamide-based polymers. In the method for producing a polymer, (a) the polymer to which the alkali aqueous solution is added has a water content of 1
Dry the polymer with hot air at a temperature of 40 to 130°C until it becomes 5% by weight or less, and (b) the polymer with a water content of 15% by weight or less and a particle size of 0.1 to 1%.
(c) A method for producing a partially hydrolyzed acrylamide polymer, comprising: (c) subjecting the pulverized polymer to ventilation treatment at a temperature of 80 to 130° C. for 30 minutes or more.