JPS60192713A - Production of polyacrylamide - Google Patents

Abstract

PURPOSE:To produce polyacrylamide of excellent properties at a high rate of production, by polymerizing an aqueous acrylamide solution in the presence of an azoic polymerization catalyst, a sulfite, and a salt of Co, Mn or Fe. CONSTITUTION:The polymerization of an aqueous acrylamide solution of a 10- 35wt% concentration is carried out in he presence of (a) 100-2,000ppm of an azoic polymerization catalyst, (b) 3-200ppm of an acid sulfite or a sulfite, and (c) 0.1-20ppm (in terms of a metal) of at least one salt of Co, Mn, or Fe. The above amounts are based on the acrylate monomer. As the azoic polymerization catalyst, 2,2'-azobis(2-amidinopropane)hydrochloride is particularly desirable. As the metal salts, water-soluble salts of a higher oxidation number metal are commonly used, among which sulfates are particularly desirable. The polymerization temperature is, for example, 20 deg.C or below, preferably 10 deg.C or below.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyacrylamide.

Polyacrylamide is widely used as a flocculant, and one known method for producing it is, for example, a method in which an aqueous acrylamide solution is polymerized in the presence of an azo polymerization catalyst. A possible method for polymerizing acrylamide is that it is an exothermic reaction and increases the vorticity of the cohesion, but if the monomer concentration is low, it has the disadvantage that it takes time and effort to dry the polymer after one polymerization. Another possibility is to lower the temperature at the start of 1st polymerization, but when an azo polymerization catalyst is used, polymerization does not proceed smoothly in Amaruhakagata, and the polymerization rate is particularly slow at the beginning of 1st polymerization. The downside is that it takes a long time and productivity is low.
Furthermore, there is a drawback that the performance of the obtained polymer is also low.

In view of the above circumstances, the present inventors set the monomer concentration relatively high and lowered the temperature for starting one polymerization during the busy polymerization of an aqueous acrylamide solution.

A good polymerization reaction was carried out with a short polymerization time.

What's more, this was the result of extensive research aimed at finding a polymerization method that would yield excellent polymer performance.

The inventors have discovered that this object can be achieved by polymerizing in the presence of an azo polymerization catalyst and a certain specific compound, and have completed the present invention.

That is, the gist of the present invention is /θ~3! When polymerizing an aqueous solution of acrylamide with a weight of -, with respect to the acrylamide monomer,
The method of producing polyacrylamide is characterized by the presence of at least seven types of gold maple salts selected from cobalt, mankan, or iron.

The present invention will be explained in detail below.

The method for producing polyacrylamide, which is the object of the present invention, is a method of polymerizing an aqueous solution of acrylamide monomer.
Monomer concentration is 10-3j% by weight, preferably 20-3j%
It is 0 times heavy.

If the monomer concentration is too high, the quality of the obtained polymer will deteriorate due to the high temperature during polymerization, and if it is too low, the polymer will dry out, which is undesirable.

In the present invention, it is essential to use a known azo-based monocatalyst, an acidic sulfite, or a sulfite and a specific metal salt together as a catalyst. When an azo-based monopolymer catalyst is used alone, mono! - Even if the polymerization initiation temperature is lowered by increasing the temperature, the polymerization rate is slow and good polymerization cannot be carried out.

Examples of azo polymerization catalysts include co,2'-azobis(-2-amidip-p-pan) hydrochloride, azobisisobutylene with nitrile, co,-'-azobis(4t-methoxy-a
, 4t-dimethylvaleronitrile).

/,/′-Azobis(cycloμhexanecarbonitrile)
In particular, 2. ．． 2'-azobis(--
Amizip Tepan) hydrochloride is preferred.

The amount of this azo compound added is /θ0~.
2θooppm, preferably aOθ~/4t00ppm
However, if the amount added is too small, the polymerization will not be carried out well, and if the amount is too large, the molecular weight of the resulting polymer will decrease, which is not preferable.

On the other hand, as acidic sulfite W1 salt or '4tL salt.

Typically, sodium or potassium salts are mentioned.

The amount added is 3 to 30% of the monomer. 2θθppm.

Preferably! ~/00 pI)m. If the amount added is too small, polymerization will not be carried out well, and
If the amount is too large, the performance of the resulting polymer will deteriorate, so it is not preferable.

The gold striped salt used in the present invention is a base of at least one metal selected from cobalt, manganese, or iron, and usually a water-soluble ferric iA base is used. These gold J
@The type of ground is an example.

Sulfate, hydrochloride, bromate, acetate, oxalate.

Examples include nitrates, among which sulfates are preferred.
If the amount is small, use m.

The polymerization rate cannot be made fast enough;

Even if there is a lot of sweeteners, the effect remains the same, so it is not economical.

In the present invention, the order of addition of the above-mentioned additives into the polymerization system is usually such that the acidic sulfite or sulfite is added first.
It is added in the order of acidic sulfite or subchloride.

The polymerization temperature in the present invention is usually -70 to 700°C.
The polymerization initiation temperature is, for example, 1.2θ°C or lower, preferably 1
The temperature is preferably 0°C or lower. In the present invention, one polymerization proceeds satisfactorily even if the polymerization initiation temperature is lowered. Polymerization time is usually
0. It is approximately 70 hours.

To carry out the present invention, for example, an aqueous seven-mer solution is charged into a closed heavy metal tank, nitrogen gas is blown in to remove dissolved oxygen in the aqueous solution, and then the catalyst of the present invention is added as an aqueous solution to carry out polymerization. After the polymerization is completed, the polymer is a gel-like substance.Then, the average particle size is determined by a conventional method.
0%, preferably 1~! The granules are then dried to a water content of less than 1 inch.

According to the present invention, when polymerizing acrylamide, for example, even if the polymerization initiation temperature is lowered, the polymerization can be carried out smoothly in a short period of time, resulting in extremely high productivity.

Furthermore, the resulting polymer has excellent viscosity and aggregation performance, making it extremely advantageous industrially.

Next, the present invention will be described in detail, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example/~! and comparative example/~! Acrylamide 2 j wt water solution/it 7! The mixture was placed in a closed type polymerization tank. After blowing nitrogen gas (70,2,/) into the aqueous solution to completely degas it.

At a liquid temperature of 10°C, first add the metals and salts shown in Table 7.
Then 1.2. ．． 2'-Azobis(,2-Achinobu μpan) hydrochloride Jθθppm and acidic sulfite sodaco Opp
The mixture was successively added and mixed and left to stand for 1 hour to carry out 1 cup.

After polymerization, the gel-like polymer is processed using an extrusion granulator to reduce the average particle size and
The granules were granulated to a concentration of 2.1%, and the first and fifth granules were dried with hot air at 0° C. for 3 hours.

Regarding the granular polymer thus obtained, the viscosity and aggregation performance were measured, and the multiple polymerization rate was determined by measuring the temperature change within one polymerization system, and the results shown in Table 7 were obtained.

Example g~? Table m2 shows the results obtained when polymerization was carried out in the same manner as in Example 1 using sodium sulfite instead of acidic sodium sulfite in Example 1 and Comparative Example.

*1) Addition i Weight percentages are given relative to monomers.

*2) Polymerization rate The rise in temperature per unit time was calculated based on the time required from the start of polymerization until the temperature in the system (10°C at the start of polymerization) reached jθ°C.

*3) Polymer is added to viscosity Zchi Na0t water and the viscosity is 0. After making it into a polymer solution, it was heated to 21'C using a B-type rotational viscometer, rotor A, and 40r.

It was measured under the conditions of p and m.

*4) Coagulation performance For paper manufacturing wastewater with solids concentration o, i%.

Polymer/ppm was added as a 0.1% polymer aqueous solution at /3θr, p, m for 30 seconds.

70 r, 30 seconds at plm, 10 at 4tOr, p, m
After stirring for each second, the size of the flocs was examined and expressed (according to the criteria below).

Woptsuku size display Hiro~! % diameter ・・・・・・・・・−・・・・・・・・・・
・・◎2〜3 l ・・・・・・・・・・・・・・・・
・・・・・・○7〜. 2 l・・・・・・・・・・・・
・・・・・・・・・・・・ Δ/Ninth diameter or less・・・・・・
・・・・・・・・・・・・・・・・・・X Applicant Mitsubishi Chemical Industries, Ltd. Agent Patent Attorney Hase - (1 other person)

Claims (1)

[Scope of Claims] (1)/Q~36M'A-% acrylamide aqueous solution is polymerized, ■10θ~, 2000 ppm azo polymerization catalyst, ■3
~． 200 ppm acidic sulfites or sulfites and 0.0 ppm as metals. A method for producing polyacrylamide, characterized in that /~-0 ppm of a salt of at least a metal selected from cobalt, manganese or iron is present. (2) The method according to claim 1, characterized in that the gold kJ4 base is a water-bathable No. 2 Golden Pengzhen. (3) The method according to claim 7, characterized in that the acidic vulcanization base or sulfite base is also added to the polymerization system first. (4) Azo polymerization catalyst is 2.-′-azobis(-2-
2. The method according to claim 1, wherein the method is Amidiptetrapan) hydrochloride. (5) The method according to claim m7, characterized in that the polymerization initiation temperature is 20° C. or lower.