JPS5846122B2 - Chemical modification method of acrylamide polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for chemically modifying a water-soluble acrylamide polymer. By adding a chemical substance that is reactive to the polymer to a heterogeneous polymer slurry consisting of gel particles and a liquid phase and causing a reaction, it is possible to chemically modify the polymer with ease of operation. It relates to a method for carrying out.

Demand for acrylamide polymers has increased significantly in recent years as they are used as paper strength enhancers, sticky agents for papermaking, flocculants for water treatment, and the like.

When using acrylamide-based polymers for these applications, it is widely practiced to further modify the polymer obtained by polymerization by reacting with a chemical substance to impart advantageous properties for various applications.

Examples of such modification include partial hydrolysis of amide groups, introduction of anionic groups by sulfomethylation, etc.
Alternatively, there is cationization modification due to Mannich reaction, Hofmann decomposition, etc.

A common method for modifying acrylamide-based polymers by polymer reaction is to mix and react chemical substances with an aqueous solution of the polymer. The upper limit of the concentration is about 10% by weight, which has drawbacks such as low productivity and the need for a large amount of energy during drying due to the low concentration.

The present inventors discovered that the addition of polyethylene glycol was extremely effective in improving the adhesion of acrylamide-based polymer hydrogels, and filed an application (Japanese Patent Application No.
(No. 1599, No. 51-150847), further investigation will be continued regarding the interaction between polyethylene glycol aqueous solutions and acrylamide polymers, and it was found that acrylamide polymers only swell and do not dissolve in polyethylene glycol aqueous solutions of a certain concentration or higher. Moreover, it was found that the adhesion between hydrogels was also reduced, and as a result of research into this application, the present invention was arrived at.

That is, in the present invention, when reacting a water-soluble polymer containing acrylamide as a main component with a chemical substance having chemical reactivity with the polymer in an aqueous system, the polymer is added to the reaction system in an amount of 10 to 50%. Weight% and average molecular weight 2000-20
000 in the presence of 1 to 30% by weight of polyethylene glycol, the polymer is made into a hydrogel particle dispersion and is reacted in contact with the chemical substance. be.

Acrylamide polymer is a water-soluble polymer substance, and in a system consisting of two components of polyacrylamide and water, it is usually in a viscous and homogeneous aqueous solution state at a relatively low concentration of about 10% by weight or less. However, when the concentration reaches a relatively high concentration range of about 18 to 35% by weight, it becomes an elastic solid hydrogel.

When polyethylene glycol is added to such a hydrogel-like system, its state changes and it separates into two phases: a hydrogel phase and a low-viscosity liquid phase, and the hydrogel phase becomes an acrylamide-based polymer hydrogel, Further, the liquid phase was an aqueous polyethylene glycol solution, and no acrylamide polymer was detected from this liquid phase.

That is, in a system consisting of three components: an acrylamide polymer, polyethylene glycol, and water.

It is divided into a water-containing gel phase and a polyethylene oxide solution phase, but the composition of these three components establishes a phase equilibrium between the two phases, so as the proportion of polyethylene glycol increases, the amount of the liquid phase increases, and the water-containing phase increases. The water content of the gel phase will be low.

Taking advantage of the above-mentioned physical properties, when an acrylamide polymer is dispersed in the form of particles in an aqueous polyethylene glycol solution, adhesion does not occur between individual polymer particles, and the entire system becomes a fluid slurry or Since it becomes a paste, chemical modification can be carried out efficiently and easily by adding a chemical substance thereto and stirring or kneading it.

In carrying out the present invention, the following method can be employed to obtain a dispersion system of acrylamide polymer particles.

That is, for example, if a monomer containing acrylamide as a main component is dissolved in an aqueous polyethylene glycol solution and polymerized by adding a known polymerization initiator while stirring, the polymer hydrogel will form into particles as the polymerization progresses. The entire system forms a slurry state.

Another method is to polymerize a monomer mainly consisting of acrylamide in a relatively high concentration of 1 to 30% by weight in the presence of polyethylene glycol to obtain a solid hydrogel. By crushing, a fluid slurry in which the hydrogel particles are surrounded by an aqueous polyethylene glycol solution is obtained.

In addition, polyethylene glycol is added in the form of a solid or aqueous solution to a hydrogel-like polymer obtained by polymerizing a monomer whose main component is acrylamide at a relatively high concentration and crushed into small lumps. A slurry similar to that described above can also be obtained.

Furthermore, in some cases, a monomer containing acrylamide as a main component may be polymerized and dried by a known method, and a powdered polymer may be mixed with an aqueous polyethylene glycol solution.

In addition, the present invention can be implemented using a slurry or paste-like dispersion system obtained by mixing an aqueous polyethylene glycol solution and an acrylamide polymer by any method.

When chemically modifying the acrylamide polymer according to the present invention, stirring and mixing may be carried out in a reaction tank equipped with propeller-type or squid-type stirring blades, or in a kneader-type kneader. It may be mixed using.

In the former case, it is difficult to increase the stirring force, so a composition with a large liquid phase portion and relatively low stirring resistance is suitable, such as when the slurry concentration is low or when the polyethylene glycol concentration is high. ing.

In the latter method, it is better to have a certain degree of kneading resistance in order to improve the stirring effect, and a higher polymer slurry concentration is suitable than in the former method.

The main purpose of such stirring or kneading is to uniformly mix the chemical substance to be reacted into the polymer hydrogel dispersion system, and to prevent the accumulation of reaction heat or uneven temperature in the case of reaction heat generation. In particular, it is not essential if the reaction heat generation is not large and uniform mixing is achieved.

Therefore, stirring or kneading is not necessarily required in cases where stirring or kneading is performed only at the initial stage of the reaction and then only left to mature, or when the reaction is completed by post-treatment of a mixed gel slurry in which chemical substances have already been mixed.

The acrylamide polymer used in the present invention refers to a copolymer of polyacrylamide and other vinyl monomers that can be copolymerized with acrylamide and do not impair the water solubility of the polymer.

Specifically, monomers that can be copolymerized with acrylamide include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminohydroxypropyl acrylate, dimethylaminohydroxypropyl methacrylate, and dimethylamino Cationic vinyl monomers such as ethyl acrylamide and their water-soluble salts, quaternary ammonium salts of the monomers prepared by quaternizing agents such as alkyl halides and dialkyl sulfates, acrylonitrile, methacryladyl, and methacrylic Nonionic vinyl monomers such as amides and vinyl acetate, anionic vinyl monomers such as acrylic acid, methacrylic acid, or water-soluble salts thereof, and modified products of the above monomers within the equivalent range. There is.

The average molecular weight of the polyethylene glycol used in the present invention is suitably from 2,000 to 20,000.

Low molecular weight polyethylene glycol with an average molecular weight of 2000 or less is not preferred because the degree of swelling of the polymer subjected to the reaction or the modified polymer increases and the entire system becomes solidified.

On the other hand, when polyethylene glycol having a molecular weight of 20,000 or more is used, the molecular weight is too large, and when it is dissolved, the viscosity of the entire system increases too much, which is also disadvantageous.

When using such polyethylene glycol, it is preferably 1 to 30% by weight, preferably 2 to 20% by weight, based on the hydrogel dispersion.

If the proportion of polyethylene glycol used is too low than the above-mentioned range, the degree of swelling of the polymer will increase, and problems such as increased stirring resistance and caking of the dispersed hydrogel will occur.

On the other hand, from an economic point of view, adding more than necessary
Moreover, it becomes unfavorable from the viewpoint of polymer quality.

The concentration of polymer in the reaction system for chemical modification is:
The range is preferably 10 to 50% by weight, preferably 15 to 40% by weight.

If the concentration is outside this range, for example, if the concentration is too low, the required amount of polyethylene glycol will be relatively large and it will be economically disadvantageous, and if the concentration is too high, there will not be enough polyethylene glycol aqueous solution to cover the surface of the polymer hydrogel. Not born,
Therefore, the fluidity of the dispersion system becomes poor, making it unsuitable for carrying out the present invention.

As described above, the present invention is an extremely effective method for economically modifying water-soluble polymers containing acrylamide as a main component with good operability.

The present invention will be explained below with reference to Examples, but the present invention is not limited thereto.

Example 1 Polyethylene glycol 50? with an average molecular weight of 6250 was placed in an 11 four-bottle flask equipped with a stirrer and a reflux condenser. , 14.5f of sodium bisulfite was dissolved and the pH was adjusted to 12 with sodium hydroxide to form an aqueous solution of 425'? When 75 g of polyacrylamide powder with an average molecular weight of 8 million was dispersed in this, the polyacrylamide powder was dispersed while being swollen with water to some extent, and the system became a fluid slurry.

To this was added 8.5 liters of a 37% formaldehyde aqueous solution, and while stirring, the mixture was heated to 40° C. in a hot water bath and reacted for 3 hours.

Thereafter, stirring was stopped and the mixture was left at room temperature for 16 hours.

The obtained modified polymer was a partially sulfomethylated polyacrylamide, and 7 mol% of the amino groups were sulfomethylated.

The solubility behavior of this modified polymer in water was good.

The degree of sulfomethylation was determined by titrating unreacted sulfite ions using iodine and starch.

Comparative Example Modification was attempted using the same apparatus and method as in Example 1, except that polyethylene glycol having an average molecular weight of 1500 was used.

In this case, the degree of swelling of the polyacrylamide powder was large, and the stirring resistance was quite large even before the reaction, but when the formaldehyde aqueous solution was added and the reaction started, the stirring resistance further increased, and after the start of the reaction, the stirring resistance was about 30. Stirring became impossible within minutes.

At this time, the contents had solidified into a sticky consistency.

Example 2 120 tons of acrylamide was added to the reaction vessel used in Example 1.
, polyethylene glycol 30f with an average molecular weight of 4000
, 0.3 fI of dimethylaminopropionitrile, and 4001 l of ion-exchanged water were added and dissolved.

Next, the container was placed in a water bath at 40°C, nitrogen gas was introduced for 15 minutes while stirring, and then 0.3S' of potassium persulfate was added.
, dissolved in 50 ml of water, was added dropwise over 5 minutes.

This temperature was maintained with stirring for 55 minutes.

As the reaction progressed, the contents became cloudy and finally became a slurry.

Next, the temperature of this slurry was lowered to 25°C, 12 g of a 10% aqueous sodium hydroxide solution and 20 P of a 40% aqueous dimethylamine solution were added, and 13.65' of 37% formaldehyde was added dropwise over 10 minutes. 25
Stirring was continued for 1 hour at °C.

The obtained reaction product was a cationically modified product having the following properties.

1% aqueous solution viscosity 91 CPS Cation content 1.22 Equivalent/1 Polymer cation ratio 9% Solid content (excluding polyethylene glycol 19.8%) Example 3 A 25% aqueous solution of acrylamide was polymerized in an aqueous solution according to a conventional method. As a result, a polyacrylamide hydrogel having an average molecular weight of about 4 million was obtained.

This water-containing gel is crushed by an extrusion crusher, and the 50
0f? Polyethylene glycol powder with an average molecular weight of 20,000 25? The mixture was sprinkled with water and placed in a small kneader with an internal capacity of 11 to perform cross-mixing.

A slurry with good fluidity consisting of small agglomerates of hydrogel was obtained.

While kneading, add 90 fI of a 40% aqueous solution of sodium hydroxide and dimethylamine from No. 21, and when these are dispersed, add 55 g of a 37% formalin aqueous solution while cooling by passing 20°C water through the jacket. did.

After 3 hours, kneading was stopped and the mixture was aged for 24 hours.

The cation ratio of this polymer was 3.7 equivalents/g polymer, resulting in a Mannich polymer in which about 35% of the amide groups were cationized.

Example 4 A 25% aqueous solution of acrylamide was slowly polymerized using a conventional method to obtain a polyacrylamide hydrogel having an average molecular weight of about 10 million.

This was crushed in the same manner as in Example 3, and the crushed gel 50 (l
Polyethylene glycol powder 2 with an average molecular weight of 6000
5? The mixture was sprinkled with water, placed in a small kneader having an internal capacity of 11, and further added with 41 parts of sodium hydroxide for kneading.

When the hydrogel slurry was uniformly mixed, the slurry was taken out from the kneader, wrapped in a synthetic resin film, placed in a hot air dryer, and heated at 90° C. for 4 hours.

The modified polymer after heat treatment has a 1% aqueous solution viscosity of 12,500 CPS as measured by a Brookfield viscometer.

It was a polyacrylamide partial hydrolyzate with a hydrolysis rate of 18 mol%.

Claims (1)

[Claims] 1. When reacting a water-soluble polymer containing acrylamide as a main component with a chemical substance having chemical reactivity with the polymer in an aqueous system, the polymer is added to the reaction system in an amount of 10 to 50% by weight and an average molecular weight of 2000 to 20000. 1. A method for chemically modifying an acrylamide-based polymer, which comprises causing the polymer to react in the form of a hydrogel particle dispersion with the chemical substance in the presence of 1 to 30% by weight of polyethylene glycol having the following.