JPS5910385B2 - Method for stabilizing polyacrylamide cationic polymer aqueous solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing an aqueous solution of aminomethylated polyacrylamide, and more specifically, the present invention relates to a method for stabilizing an aqueous solution of aminomethylated polyacrylamide. Dicyandiamide, guanidine and its inorganic acid salts, biguanide,
A method for stabilizing an aqueous polyacrylamide cationic polymer solution, which comprises adding one or more nitrogen-containing compounds selected from the group of guanylurea and its inorganic acid salts, biuret, ethylene urea, and ethylene thiourea. It is something.

Conventionally, di-substituted aminomethylated polyacrylamide, which is produced by the so-called Mannitz reaction of polyacrylamide, formaldehyde, and secondary amines, has been used as a cationic polymer for various purposes such as polymer flocculants, papermaking aids, and textile aids. However, its biggest drawback is poor thermal stability and storage stability. It is said that an aqueous solution of di-substituted aminomethylated polyacrylamide obtained by this type of reaction normally thickens and gels in 1 to 3 months. This is because the Mannitz reaction of an amide is an equilibrium reaction as shown in equation 0), / -C0NH2+CH20+HN \ / = -C0NHCH2N+ H2O(I)\ In a dilute aqueous solution with excess water, the equilibrium is on the left, and in a concentrated aqueous solution, the equilibrium is on the left. The equilibrium proceeds to the right, but in any case, there is some formaldehyde or methylolamide group reacted with amide in the system, which creates a methylene bisamide bond as shown in formula XI), and the molecule It is thought that crosslinking occurs between molecules or within molecules, leading to gelation.

↓１▲▲νv ＼川′ As a result of various investigations into improving the stability of these di-monosubstituted monoaminomethylated polyacrylamide aqueous solutions, the present inventors found that one or two of the above-mentioned nitrogen-containing compounds
The present invention was achieved by discovering that extremely significant effects can be obtained by adding more than one species as a stabilizer.

The starting polyacrylamide includes the following. (1) Acrylamide homopolymer (2)
Copolymer of acrylamide and other vinyl monomers (for example, acrylonitrile, (meth)acrylic acid or its lower alkyl ester, styrene, methacrylamide, etc.) that does not impair the water solubility of the polymer (3) Joki 1
) and 2) partial hydrolyzate of the polymer There is no particular restriction on the molecular weight of these polyacrylamides, and a molecular weight of 10,000 or more is generally used, but in particular a molecular weight of 100,000 to 100,000 is used.
00,000 is preferable.

Di-monosubstituted aminomethyl (Mannichization) is carried out on polyacrylamide as described above, and there are three methods as follows.

(1) Formaldehyde and a secondary amine are added to a polyacrylamide aqueous solution and reacted. A method using the so-called Mannitzch reaction. (2) A method in which dimonosubstituted aminomethanol produced by reacting formaldehyde and a secondary amine is reacted with an aqueous polyacrylamide solution.

(3) A method in which a polyacrylamide aqueous solution is reacted with formaldehyde to form methylol, and then reacted with a secondary amine.

The aminomethylated polyacrylamide that is the object of the present invention includes not only those produced as described above, but also (partially) neutralized products and (partially) quaternized products of the amino groups thereof.

There is no particular restriction on the concentration of the aqueous solution when stabilizing these aminomethylated polyacrylamide aqueous solutions since it is essentially unrelated to stabilization, but it is usually about 0.1
It can be arbitrarily selected from a wide range from % (weight) to about 60% (weight). However, as mentioned above, the aminomethylation reaction is considered to be an equilibrium reaction, and in the region of very low concentration, it proceeds toward the original system, suppressing the production of aminomethylated products, and in the region of too high concentration, Due to its viscosity, it not only becomes extremely difficult to work with, but also slows down the reaction rate.
It is preferable to treat the polymer solution at a concentration of (by weight). Secondary amines used in aminomethylation include ordinary lower amines such as dimethylamine, diethylamine, and dipropylamine, as well as alkanolamines such as diethanolamine, and lactic amines such as pyrrolidine, piperidine, and morpholine. As formaldehyde, formalin is usually used, but any compound that can release formaldehyde during the reaction can be used, such as trioxane, which is a cyclic trimer of formaldehyde, and paraformaldehyde, which is a chain oligomer.

However, considering ease of use and economical efficiency, formalin is preferable. Amide groups, formaldehyde, and secondary amide groups in the production of aminomethylated polyacrylamide
The usage ratio (in molar form) of the three components of class amine is amide group:
Formaldehyde: 1:0.1-1.0 Formaldehyde:Secondary amine=1: Select from a range of 1.0-1.5.

The reaction temperature is preferably from room temperature to around 80°C, and the reaction time varies depending on the conditions and is suitably about 0.5 to 24 hours.

Stabilizers added to the aminomethylated polyacrylamide obtained under the conditions described above include dicyandiamide, guanidine and its carbonates, hydrochlorides, nitrates, phosphates, sulfamates, and sulfates. one or more nitrogen-containing compounds selected from inorganic acid salts such as biguanide, guanylurea and their phosphates, sulfates, and hydrochlorides, biuret, biurea, ethylene urea, and ethylene thiourea. However, there is no problem in using these substances in combination with other known stabilizers such as methyl ethyl ketone.

When using stabilizers from this group,
It is used in an amount of 0.1 to 50 mol%, preferably 1 to 20 mol%, based on the aminomethyl group. The method of use is to simply add the stabilizer to the aqueous polymer solution and stir and dissolve, but it may also be heated at 40 to 80°C for 10 minutes to 2 hours.

The aminomethylated polyacrylamide aqueous solution to which the stabilizer of the present invention has been added can be stored for 6 months to 1 year without gelation, and its performance (for example, flocculation performance when used as a polymer flocculant) This has the secondary effect that not only is there almost no change from the case where no stabilizer is added, but it may even be improved.

EXAMPLES Hereinafter, the effects of the present invention will be specifically explained in Examples.

Reference Example 1 Production of polyacrylamide 150 parts of acrylamide was dissolved in 1350 parts of deionized water, and nitrogen was introduced for about 30 minutes to remove dissolved oxygen and oxygen in the reactor.

Next, 0.15 parts of potassium persulfate, 0.15 parts of dimethylaminopropionitrile, and β as a molecular weight regulator were added.
-0.038 part of mercaptopropionic acid was added, and the mixture was reacted for about 8 hours at a polymerization temperature of 40°C. An aqueous polyacrylamide solution was obtained, and the average molecular weight was determined to be around 1.1 million from the results of viscosity measurement.

Reference Example 2 Aminomethylation of Polyacrylamide After mixing and dissolving 200 parts of the 10% aqueous solution of polyacrylamide with an average molecular weight of 1.1 million obtained in Reference Example 1 in 200 parts of ion-exchanged water, 23.0 parts of 37% formalin and 40% 32.0 parts of dimethylamine aqueous solution was added and heating was continued for 10 hours at a reaction temperature of 40°C. After heating, the mixture was aged at room temperature for 1 day.

The concentration of the product is 8% (weight) based on the solid content measurement in the aqueous solution.
The dimethylaminomethylation rate was 98.5% by coronoid titration. Example 1 0.8 rr of dicyandiamide (reagent) (10% (weight) based on the polymer) was added to 100 rr of the 8% aqueous solution of dimethylaminomethylated polyacrylamide synthesized in Reference Example 2, and after uniformly dissolving it, the mixture was heated at room temperature. The properties were observed at regular intervals.

As a result, it was confirmed that there was almost no change in appearance for two months after the product was left standing, and that it existed stably for more than six months with only a slight increase in viscosity. On the other hand, when no stabilizer is added, the viscosity begins to thicken clearly after one month,
After two months, it becomes gel-like and takes a very long time to dissolve.
Similar observations were made using other stabilizers and the results are summarized in the table below. Example 2 0.8% of the stabilizer of the present invention was added to 100fr of the 8% aqueous solution of dimethylaminomethylated polyacrylamide synthesized in Reference Example 2.
tr was added and dissolved, the mixture was left in a water bath at 80°C, and its viscosity was measured every 2 hours. The results are summarized in the following table.

However, the viscosity was measured at 80° C. using a B-type viscometer at a speed of 6 revolutions per minute.

(Unit: centipoise) As is clear from the table above, the system to which the stabilizer according to the present invention is added has significantly increased stability against heating. Example 3 Regarding the dimethylaminomethylated polyacrylamide aqueous solution that was added with the stabilizer of the present invention in Example 1 and left to stand at room temperature for three months, the flocculation performance was evaluated as follows.

Ultramarine Blue ◆ 1200 (manufactured by Daiichi Kasei Kogyo, main component SiO, A4O) in a sedimentation tube with a 100d scale
,,Na,O)2fr, add 50-70d of pure water, then add 2d of N/10 sulfuric acid...adjust, add pure water to the 98d scale, cover and boil in 1 minute. 1
It was well dispersed by falling over 0 times (back and forth).

Claims (1)

[Claims] 1. To an aqueous solution of aminomethylated polyacrylamide obtained by treating polyacrylamide with formaldehyde and a secondary amine or aminomethanol, which is a reaction product thereof, dicyandiamide, guanidine and its inorganic acid salt, biguanides, guanylureas and their inorganic acid salts,
A method for stabilizing a polyacrylamide-based cationic polymer aqueous solution, which comprises adding one or more nitrogen-containing compounds selected from the group of biuret, biurea, ethylene urea, and ethylene thiourea. 2 Nitrogen-containing compound to aminomethyl group, 0.1 to
A method for stabilizing an aqueous solution of polyacrylamide-based cationic polymer according to claim 1, wherein 50 mol%, preferably 1 to 20 mol% is used.