JPS61127707A - Method of drying acrylamide polymer - Google Patents

Abstract

PURPOSE:In drying acrylamide polymer particles by a conveyor band dryer, to raise drying efficiency and to dry the particles in a short time, by crushing a particulate layer when the surface of polymer particulate layer is dried to a certain degree, so that new surface is made. CONSTITUTION:In feeding continuously hydrous gel acrylamide polymer particles having preferably 90-50wt% water content to the conveyor band dryer 1 to make a particulate layer with 10-200mm thickness on the bands 2a and 2b of the dryer, and drying the particles with hot air, when the water content of the fed polymer is reduced by 5-40wt%, the polymer particulate layer formed on the band is crushed by the grinder 3, and successively dried on the band.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for drying an acrylamide polymer69, and specifically, an improvement in a method for drying hydrogel-like acrylamide polymer particles using a band dryer. It is related to.

[Conventional technology]

Acrylamide-based polymers are useful, for example, as flocculants and paper strength agents, and a typical method for producing them is usually a method in which a polymerization initiator is directly added to an aqueous monomer solution of 10-so% by weight and polymerized. Are known. Since the polymer obtained by this method is a gel-like material containing about 2θ to 50% by weight of water, it is usually necessary to dry it to a water content of 10% by weight or less. As a drying means for this purpose, a method is generally known in which a hydrogel polymer is pulverized and then dried with hot air using, for example, a band dryer, a rotary dryer, or a combination thereof.

[Problem that the invention seeks to solve]

When drying a hydrogel-like polymer using a band dryer, the finely divided polymer is continuously fed onto the band of the band dryer so that the polymer particles form a layer and is dried with hot air. Although the surface layer of the polymer particles that comes into direct contact with the hot air dries relatively quickly,
The drying speed of the inside of the polymer particles and the parts where the polymer particles adhere to each other is slow, and the drying time takes a long time. This tendency is particularly noticeable when the amount of water-containing gel-like polymer supplied to the band dryer is increased and the polymer layer on the band is made thicker. This is due to the fact that the target acrylamide polymer is sticky and has a high water content, which is a problem specific to acrylamide polymers.

As a method to solve this problem, for example, water content of 60 to 2
0! Dry the polymer particles of the same amount using a band dryer or the like until the water content becomes /j - 26% by weight. Reduction rate of water content =
There is a known method of crushing the obtained oat-like material and then drying it to a water content of less than io weight (#!jKoakiyo Hiro-Hiro No. 0.277). No significant improvement in drying efficiency was observed.

[Means for Solving the Problems] In view of the above circumstances, the present inventors have developed a method for efficiently drying polymer particles when drying hydrogel-like acrylamide polymer particles with hot air using a band dryer. As a result of various studies, we found that in the method of continuously supplying and drying with hot air, the water content of the supplied polymer was /
The present invention was completed based on the discovery that drying can be carried out efficiently by continuing drying on a drying machine.

The present invention will be explained in detail below.

The acrylamide-based polymer targeted by the present invention is an acrylamide homopolymer or a copolymer of acrylamide and a monomer copolymerizable therewith. Monomers copolymerizable with acrylamide typically include known monomers such as acrylic acid, sodium acrylate, sodium λ-acrylamidomethylpropanesulfonate, diethylaminoethyl methacrylate and its ≠ class salts, and diethylamine ethyl acrylate and its class salts. is mentioned, and the amount used is compared to acrylamide! θ morti or less,
Preferably it is 30 molti or less.

Such acrylamide-based polymers are produced by adding a polymerization initiator to a 10-10% by weight aqueous monomer solution and polymerizing at a temperature of -10-100°C according to a known method. As a polymerization initiator, azo compounds such as azobis(2-amidinopropane) hydrochloride, dahazobis(≠-cyanowallerianic acid), potassium persulfate,
Peroxides such as ammonium persulfate and hydrogen peroxide, or redox catalysts made by combining peroxides and reducing agents, are used.

The acrylamide polymer obtained in this way usually has a water content of L? 0-50% by weight water-containing gel υ
Usually, this is granulated into granules with a particle diameter of about 2 to 100 m by using a granulator such as a meat grinder type screier extruder, and then dried.

For drying the granulated water-containing gel-like polymer particles, a conventional band dryer is used, in which the material is left still and moved over the throat while coming into contact with hot air. Therefore, by continuously supplying polymer particles onto the band, a layer of polymer particles is formed on the band, and hot air drying is performed. The thickness of the polymer particle layer at this time varies depending on the moving speed (drying time) of the band and the drying temperature, but is usually about 0 to 200 mtr. The drying temperature is usually selected from the range of tto-ioo<0>C.

In the present invention, the water content of the supplied polymer is r-g
It is an essential operation requirement to crush the polymer particle layer formed on the band at the time when the band has decreased by 30%, preferably io to 30%, and then continue drying on the nozzle. . In other words, the drying speed of the interior of the particles and the parts where the particles adhere to each other is slower than the surface of the polymer particle layer, so when the surface of the polymer particle layer has dried to a certain extent, the polymer particle layer is crushed and a new layer is formed. The aim is to shorten the drying time by creating a smooth surface.

The method for crushing the polymer particle layer is usually
As shown in Figure 1, the band of the band dryer (1) is
It is divided into two cores a) and (2b), and a crusher (3) is installed between them.
This is implemented by providing a As the crusher (3), for example, a paddle crusher, a roll crusher,
Known crushers such as a diesel incinerator, an impeller breaker, and a swing crusher can be used, but any mechanism that can destroy the polymer particle layer formed on the band (2a) may be used.

Drying of polymer particles in a band dryer is carried out as necessary.
For example, if a product granular polymer is obtained by drying only with a band dryer, drying is carried out until the moisture content is approximately 10% by weight or less, and drying is carried out until the moisture content is approximately 10% by weight or less. In the case of combining the above, it is carried out until the weight is reduced to about 20% by weight or less.

After drying the polymer particles as described above, the block-shaped polymers that adhere to each other are pulverized according to a conventional method, and then particles of a predetermined size are sorted by sieving and recovered as product granular polymers. .

〔Effect of the invention〕

According to the present invention, the drying efficiency when drying acrylamide polymer particles using a band dryer is increased, so the overall drying time can be shortened. Further, if the drying time is the same as the conventional method, the amount of drying processing can be increased.

〔Example〕

Example 1 7000 PPm of azobis(2-amidinopropane) based on the monomer was added to a 2j% by weight acrylamide aqueous solution.
Hydrochloride was added and adiabatic polymerization was carried out at a polymerization initiation temperature of 10°C. A hydrogel polymer with a water content of about 7J% by weight was granulated using a meat grinder type screw extruder to obtain polymer particles with a particle size of 2 to 1ml. was prepared.

The polymer particles were dried with hot air using a band dryer shown in FIG. The band dryer has a first endless band (2a) (length 10n) and a Jth endless band (λb) (length trm) in the main body (1), and a noddle type crusher in the middle. (3) is provided, and the polymer particles are fed through the supply chute (4) onto the endless band (2a), while the polymer particles that have reached the end of the endless band (2b) are discharged through the outlet. (5) Drying of the polymer particles, which have a structure that allows them to be easily recovered, is carried out by drying the polymer particles at a rate of K %/A O (7 k/hr) on a belt moving in hot air at 10°C at a speed of 9 km/hr. Supply (the thickness of the polymer particle layer is 71
0m). In this case, it took 71 minutes to reach the crusher (3), and the water content of the polymer particles at this time was 77% by weight (decreased by jJ% by weight compared to the time of supply).

In this drying method, the drying time until the water content of the polymer particles reached io weight % was determined, and the results shown in Table 1 were obtained.

Examples, 2 to 3 and Comparative Example/-2 In the method of Example 1, the length of the endless band (2a) was changed, and the time taken for the polymer particles to reach the crusher (3) (the water content at this time) was changed. ) and drying in the same manner are shown in Table 1.

Comparative Example 3 Table 1 shows the results obtained by using the method of Example 1, using one endless band, omitting the crusher (3), and drying under the same conditions.

Table 1

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the structure of the band dryer used in the embodiment of the present invention. 4) indicates the supply chute and i5) indicates the discharge port.

Claims (2)

[Claims] (1) In a method in which hydrous gel-like acrylamide polymer particles are continuously supplied onto a band of a band dryer so that the polymer particles are layered and dried with hot air, the water content of the supplied polymer is 5 to 40%. A method for drying an acrylamide-based polymer, which comprises crushing the polymer particle layer formed on the band when the amount of the polymer particles decreases, and then continuing drying on the band. (2) The method according to claim 1, wherein the water content of the hydrogel-like acrylamide polymer is 90 to 50% by weight.