JPS5832606B2 - Agglomeration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes acrylamide, which has high stringability in an aqueous solution, and two
- A method of adding an acrylamide-2-methylpropanesulfonate copolymer as a flocculant to an aqueous medium to flocculate suspended solids.

Water-soluble acrylamide polymers are produced on an industrial scale and are widely used as flocculants for purifying various types of water, paper strength enhancers, fiber dispersants, soil stabilizers, etc., and their production has increased significantly in recent years. I'm coming.

Polymers used for each of these applications include, in addition to acrylamide alone, polymerizable monomers having a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, an amino group or a quaternary ammonium base, etc. Binary, tertiary or more copolymers with other copolymerizable polymerizable monomers, and polymer reaction products of these acrylamide polymers are used.

Among these, acrylamide-based polymers having sulfonic acid groups or their salts can be obtained by sulfomethylation to polyacrylamide, or from vinyl sulfonic acid (salt), N (sulfonated alkyl) acrylamide, etc., and acrylamide. Copolymers are known.

2-Acrylamido-2-methylpropanesulfonic acid is a type of N (sulfonated alkyl) acrylamide compound, and is a copolymer obtained from its homopolymer or/and other monomers that can be copolymerized with it. A method of using coalescence as a flocculant is proposed in JP-A-47-29287.

This prior art states that a homopolymer of 2-acrylamido-2-methylpropanesulfonic acid (salt) or a copolymer containing a predominant amount thereof is preferable as a flocculant, but it is an expensive monomer. A large amount of 2-acrylamido-2-methylpropanesulfonic acid (salt) is required, and when copolymerizing this monomer with acrylamide, if the composition ratio is large, it becomes difficult to increase the molecular weight of the copolymer. Therefore, the flocculation performance was not sufficiently improved and it was difficult to put it into practical use, so it was still unsatisfactory.

We conducted repeated studies to improve these shortcomings, and in the process, we discovered that the flocculation performance of aqueous suspensions and the stringiness behavior of flocculants are well matched, and we developed a new evaluation method for stringiness. If acrylamide and 2-acrylamide-2-methylpropanesulfonate copolymer with good performance obtained under a specific monomer composition ratio and specific conditions during polymerization are used as a flocculant, extremely excellent flocculation treatment is possible. This discovery led to the present invention.

That is, in the present invention, 65 to 98% by weight of acrylamide and 2 to 35% by weight of 2-acrylamide-2-methylpropanesulfonate are mixed at a monomer concentration of 65 to 98% by weight to agglomerate solids suspended in an aqueous medium. about 15% by weight or more, and the intrinsic viscosity in 1N saline at 30°C is 7.
To provide a flocculation method characterized in that acrylamide with high stringiness obtained by polymerization under the above conditions and a 2-acrylamide-2-methylpropanesulfonate copolymer are used as a flocculant. It is something.

In the present invention, a salt of 2-acrylamido-2-methylpropanesulfonic acid is used, and examples of the salt-forming cation include sodium, potassium, lithium, ammonium, and organic amines.

When copolymerizing such a monomer with acrylamide, any radical initiator can be used as long as it is soluble in water even in a trace amount.

For example, peroxides such as persulfate, hydrogen peroxide, peracetic acid (salt), chloric acid (salt), cumene hydroperoxide;
Or a redox polymerization initiator between these peroxides and sugars such as amine compounds, hydrazine and its derivatives, reducing sulfoxy compounds, Rongalit (formaldehyde sodium sulfoxylate), ascorbic acid (salt), and dextrose; azobisiso Butyronitrile, 2,2
Known initiators such as '-azobis(2-amidinopropane) hydrochloride and azobiscyanovalerate may be used alone or in combination with a low-temperature active initiator and a high-temperature active initiator; , or this and a sensitizer, or radiation, etc., to initiate polymerization.

If necessary, alcohol, mercaptan, amine,
Chain transfer agents such as urea and its derivatives, sodium sulfate, common salt, and other substances required in conventional methods may be present in the polymerization system.

Acrylamide polymers with a molecular weight of about 3 million or more, which are generally said to be effective as flocculants, account for about 15% by weight.
At higher concentrations, the aqueous polymer solution becomes rubbery and loses its fluidity.

Therefore, conventionally, for convenience of post-treatment, polymerization is carried out at a monomer concentration of about 4 to 7% by weight so that the aqueous polymer solution after polymerization becomes fluid, but when polymerization is carried out at such a low concentration, Acrylamide and 2-acrylamide-2 obtained
- The physical properties of the methylpropanesulfonate copolymer, especially the intrinsic viscosity, were not improved, and the stringiness behavior also reached its maximum value (30 to 50 weight), and no characteristic trend is observed.

However, the same acrylamide and 2-acrylamide-2
- Copolymerization with methylpropane sulfonate is carried out under conditions such that the total monomer concentration is about 15% by weight or more, preferably 20 to 40% by weight, to obtain a copolymer with a sufficiently high molecular weight. Although the Brookfield viscosity of an aqueous solution of the polymer reaches its maximum value when the amount of copolymerized 2-acrylamide-2-methylpropanesulfonate is 50 to 60% by weight, the stringability is only 6 to 8% by weight. They found that the maximum value occurs at a very low composition.

The figure shows these characteristics.

This stringiness behavior will fluctuate up or down if the molecular weight changes depending on the type and amount of the catalyst and chain transfer agent used in the polymerization reaction, but as long as the conditions for the method of the present invention are met, it can be seen from the examples below. As you can see, there is almost no shift left or right.

In this way, the maximum spinnability appears at a copolymerization amount of 6 to 8% by weight of 2-acrylamide-2-methylpropanesulfonate because the total monomer concentration is about 15% or more, that is, during the polymerization reaction. It can only be obtained under conditions that cause the liquid to become rubbery, that is, conditions that cause the so-called gel effect.

When a polymer has a sufficiently large molecular weight due to such a gel effect, its molecules spread in an aqueous solution due to electrical repulsion between sulfonic acid ion groups within the molecule, inducing entanglement between molecules, and resulting in poor spinnability. It is thought that.

However, even when polymerizing at such a high concentration, if the copolymerized amount of 2-acrylamide-2-methylpropanesulfonate in the mixed monomer exceeds 10% by weight, the chain transfer to this monomer may be large. Even with the gel effect, the molecular weight tends to decrease and the stringiness tends to decrease, and if the amount exceeds 35%, the advantages described in the present invention cannot be obtained.

In order to expect such a gel effect during polymerization, the higher the total monomer concentration is, the better; however, this upper limit is naturally limited by the solubility of the acrylamide and 2-acrylamide-2-methylpropanesulfonate monomer mixture in water. Ru.

The solubility of the mixture of both monomers is about 45% by weight at 0° C. and about 80% by weight at 40° C. in the present invention, although the latter is the main component.

If the total monomer concentration during polymerization is particularly high, care must be taken such as polymerizing in the form of a sheet or thin rod to sufficiently remove the polymerization reaction heat, or starting the polymerization at a sufficiently low temperature if heat is not removed. There is.

In order for the gel effect to appear, it is necessary that in addition to the above-mentioned monomer concentration, the molecular weight of the obtained copolymer is sufficiently high.

The molecular weight for rubber-like copolymer concentration at 15% is:
The intrinsic viscosity in 1N saline at 30°C is 7 or more,
The preferable intrinsic viscosity of the flocculant is 7 to 8 or more, and desirably 12 or more to obtain even better performance.

The polymerization conditions for obtaining such a copolymer having an intrinsic viscosity of 7 or more include using as little polymerization catalyst as possible in addition to the above-mentioned monomer concentration.

For example, at 40℃, add 0.1% potassium persulfate to the monomer.
In addition to using no chain transfer agent, or using only a small amount of chain transfer agent, for example, using mercaptoethanol or thioglycolic acid of 50 ppf11 or less based on the monomer, general polymerization methods such as carrying out the polymerization at as low a temperature as possible, etc. Follow the correct method.

When anionic polyacrylamide is used as a flocculant, as shown in the examples below, its practical performance, that is, the flocculation sedimentation rate, in most cases closely matches the stringiness of the anionic polyacrylamide aqueous solution, and B It was found to be independent of mold viscosity.

Comparing powdered acrylamide flocculants currently on the market with this stringability, the string length measured using the method described below is 20 to 5071 Lm, and those with high performance have a string length of approximately 4071 LrIL or more. It was confirmed.

In addition, in the present invention, acrylamide and 2-
Acrylamide-2-methylpropanesulfonate is used, but the copolymer may contain impurities in these monomers or a small amount of acrylic acid (salt) that is inevitably generated during the polymerization reaction. There is no problem.

As mentioned above, acrylamide and 2-
The aqueous solution of acrylamide-2-methylpropanesulfonate copolymer has very high stringiness and excellent flocculating performance, so it can be used in a small amount as a flocculant, and It is also economically preferable because the copolymerization ratio of acrylamide, which is cheaper than the N (sulfonated alkyl) acrylamide flocculant, can be increased to 98 to 65% by weight.

In addition, although the reason for the flocculant of the present invention is unknown, compared to partially hydrolyzed acrylamide flocculants, the flocculant of the present invention has a characteristic that the water content of the flocculates after flocculation treatment is lower, and for this reason, post-treatment of sludge is difficult. It also has the advantage of being easy to use.

EXAMPLES Hereinafter, embodiments of the present invention and their effects will be specifically explained with reference to Examples.

The characteristic values shown in the examples were measured by the following method.

B-type viscosity A sample with a concentration of 0.1% by weight was measured at 25° C. at 5 rpm using a B-type viscometer (manufactured by Tokyo Keiki).

A glass rod with length and diameter of 6 mm was immersed in a sample solution with a concentration of 0.1% by weight for 10 times, and pulled up at 5001 m/min. It was measured with

Intrinsic viscosity [η] 0.01 to 0.197 d using 1N saline as a solvent
The viscosity was measured using an Ostwald viscometer at 30° C. in the BD range.

Sedimentation half-life: In a glass tube with an outer diameter of 25 mm, put 1 oz of 5% kaolin suspension water (ion-exchanged water is used) adjusted to pH 7, stir well, add 5 ppIn of polymer to the liquid, cover with a lid, and invert 20 times. After that, the time required for the kaolin to settle to 50 m was measured.

In the case of valve wastewater, take 500rfLl of wastewater with a solid content of 0.01% in a 500rnl beaker, add sulfuric acid band with a liquid resistance of 300 (kt2 (804)a, 18H20) (pH 5-7), and put it in a jar tester. So 120
Rotate at rpm, add flocculant of IPPM to liquid,
After stirring for a minute, the time required for sedimentation to reach 250 rILl was measured.

Example 1. and Comparative Example 1 Acrylamide (abbreviated as AA) and 2-acrylamide-
A total monomer concentration of 21 parts by weight of sodium 2-methylpropanesulfonate (AMPS) and 79 parts by weight of water were charged into a polymerization reactor, and after the atmosphere was sufficiently purged with nitrogen, 2,2'-azobis(2-amidinopropane) was added. When 0.005 parts by weight of hydrochloride was added and polymerization was started at 30°C, the maximum temperature (48 to 92°C) was reached after 4 to 5 hours.

Thereafter, the mixture was taken out for 4 hours, cooled, and the polymerization rate was measured, and all results were 98.5 to 99.8%.

The resulting polymer was dried at 60°C for 15 hours and pulverized, and then dissolved to a concentration of o and i weight% to determine the intrinsic viscosity [η], type B viscosity, string layer, kaolin sedimentation half-life, and valve wastewater (CGP).
The sedimentation half-life of Bulb: was measured.

The results are listed in /161-9 of the table.

In the table, /161 and A6.7-9 are comparative examples.

Based on this table, the relationship between the AMPS copolymerization amount, B-type viscosity, thread layer, and kaolin sedimentation half-life is shown in a diagram.

From the results in these tables and figures, it is recognized that the yarn layer corresponds more closely to the sedimentation rate (half-life) than type B viscosity, and in the case of this example, the best results were obtained when the amount of AMPS was 7.5%. It can be seen that this shows good performance.

Example 2 Aqueous solution of AA-AMPS mixed monomers with monomer concentrations of 30 and 40% by weight (mixing ratios are shown in the table), 0.01% by weight of 2,2'-azobisamidinopropane hydrochloride, dimethylaminopropio 0.02% by weight of nitrile was sealed in an ampoule and polymerized at 40°C.

The polymerization rates of the obtained copolymers were all 96.5 to 99.2.
%Met.

Intrinsic viscosity [η] of these copolymers, type B viscosity, string layer,
The half-life of kaolin sedimentation was measured and shown in //610-17, and the results show that the higher the total monomer concentration, the higher the quality yarn length behavior, and the larger the yarn layer, the higher the sedimentation rate. I understand.

Comparative Example 2 A flask was charged with a total monomer concentration of 6% or 10% by weight, potassium persulfate 0.003% by weight, dimethylaminopropionitrile 0.003% by weight, and an amount of water leakage.
Polymerize from ℃, and the characteristic value of the obtained co-electrical ※※ coalescence is A6
．． It was shown in the table as 18-25.

The yarn length is generally low, and as the amount of AMPS copolymerized increases, B
The mold viscosity, string length, and kaolin sedimentation rate (half-life) all increased in a similar manner, and did not show any characteristic tendency.

[Brief explanation of the drawing]

The figure shows powdered acrylamide and 2-acrylamide-2-methylpropanesulfonic acid sodium copolymer.
The relationship between the string length, Type B viscosity, and kaolin sedimentation half-life of a 1% by weight aqueous solution and the amount of sodium 2-acrylamide-2-methylpropanesulfonate charged in the polymerization reaction to obtain the copolymer is shown.

Claims (1)

[Claims] 1. In coagulating solid matter suspended in an aqueous medium, 65 to 98% by weight of acrylamide and 2 to 35% by weight of 2-acrylamide-2-methylpropanesulfonate are mixed at a monomer concentration of 15% by weight. Acrylamide with high stringiness and 2-acrylamide-2-methylpropanesulfonate obtained by polymerizing the above and under conditions such that the intrinsic viscosity in 1N saline at 30°C becomes 7 or more. A flocculation method characterized by using a copolymer as a flocculant.