JPH09302022A - Production of water-soluble polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for drying an acrylamide polymer or an acrylic acid polymer containing water which enables reducing the amount of a monomer remaining in the polymer without causing the decrease of the viscosity of the polymer. SOLUTION: A method used for drying a water-containing polymer of a water-soluble polymer produced mainly from an acrylamide monomer comprises drying the polymer in the presence of (1) an alkaline agent and (2) an amount of 2 to 15wt.%, based on the charged amount of a monomer, of at least one sulfite selected from the group consisting of a hydrogensulfite of an alkali metal, a sulfite of an alkali metal and a pyrosulfite of an alkali metal, wherein the weight of a sulfate is calculated in terms of a hydrogensulfite. In some cases, the water-soluble polymer is produced while being modified by hydrolysis.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a water-soluble polymer. More specifically, it relates to an improvement in a method for producing a water-soluble polymer in which an acrylamide-based and / or acrylic acid-based monomer is polymerized in an aqueous medium and then dried.

[0002]

2. Description of the Related Art Acrylamide-based or acrylic acid-based polymers or their copolymers (hereinafter sometimes simply referred to as "polymers") have excellent flocculating action, and therefore, sludge treatment agents, paper chemicals, and soil improvement agents. It is useful as an agent. Of the polymers used for these purposes, those having a higher molecular weight generally show better performance. On the other hand, there are residual monomers in the polymer, and it was necessary to reduce such residual monomers from the viewpoint of safety and the like. Therefore, in order to reduce the residual monomer, when the polymer in a water-containing state is dried and powdered, bisulfite, sulfite, and pyrosulfite are added, and these additives are added to the polymer. 0.1 to 3% by weight based on the total weight of the water-containing polymer, slurry, dispersion, etc.
It is used (JP-A-56-103207).

Furthermore, it is possible to use at least 1 mol of alkali metal sulphite per unreacted monomer to reduce the amount of unreacted monomer remaining in the polyacrylamide (USP 2,960,486), as well. 2/3 for residual monomer in polyacrylamide gel
Add less than mol% sodium sulfite, sodium bisulfite, etc. and dry (USP 3,755,2
80) is also known. However, when sodium bisulfite was added to the hydrous acrylamide polymer in an amount of 5 to 10%, unreacted monomers could be reduced, but the viscosity of the polymer was greatly reduced, and the performance as a polymer flocculant was deteriorated. . On the other hand, when the amount of sodium bisulfite used is about 0.1 to 1.0%, the decrease in viscosity is small, but the residual monomer content is 100 ppm to 500 ppm.
Since it can be reduced only to a certain degree, it was far from the target of 5 ppm or less in recent years.

[0004]

When industrially producing polyacrylamide, it is most advantageous in terms of environment and handling that unreacted acrylamide does not exist in the produced polyacrylamide, and residual acrylamide may be used depending on its use. The amount of monomer is regulated. For example, when used as a coagulant in waterworks, 500 ppm or less,
For general wastewater treatment, it is specified to be 2000 ppm or less. In addition, the higher the molecular weight of polyacrylamide,
Generally, since the aggregating performance is excellent, it is required to reduce the amount of unreacted acrylamide monomer without losing the function as a polymer aggregating agent.

[0005]

Means for Solving the Problems The present inventors have detailed the relationship between a polymerization product of an acrylamide polymer in an aqueous medium, a modified product thereof, and an additive for reducing residual monomer in a drying step and a decrease in molecular weight. As a result of study, the inventors have found that even under the specific conditions, even when the amount of the additive used is said to significantly decrease the viscosity of the polymer, the decrease in viscosity can be suppressed and the unreacted acrylamide monomer can be decreased, and the present invention has been achieved.

[0006] That is, the present invention is to provide a method for reducing the amount of residual monomers in a drying treatment of a water-containing acrylamide-based polymer and an acrylic acid-based polymer without lowering the viscosity thereof. And / or when the water-containing polymer of the acrylic acid-based water-soluble polymer is dried, (1) an alkali agent and (2) 2 to 15% by weight of sulfurous acid based on the charged monomers of the polymer. At least one selected from alkali metal hydrogen salts, alkali metal sulfites and alkali metal pyrosulfites (however, the weight% is calculated as alkali metal hydrogen sulfite) is allowed to exist and dried to obtain a water-soluble polymer. It depends on the manufacturing method.

Another aspect of the present invention is to polymerize an acrylamide monomer or a mixed monomer of an acrylamide monomer and another vinyl-based monomer in an aqueous medium, and at least a part of the resulting polymer. In the method for producing a water-soluble polymer by modifying with an alkali and then drying it, the polymer produced is (1) an alkali agent having a desired hydrolysis equivalent or more of the amide group of the produced polymer and (2) At least one selected from 2 to 15% by weight with respect to the charged monomers of the produced polymer, an alkali metal hydrogen sulfite, an alkali metal sulfite, and an alkali metal pyrosulfate (however, the weight% is an alkali hydrogen sulfite). It exists in the manufacturing method of the modified water-soluble polymer which consists of drying in presence of (metal salt conversion).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The acrylamide-based water-soluble polymer used in the present invention is a homopolymer or a copolymer of acrylamide-based monomers such as acrylamide, methacrylamide and salts thereof. The copolymerization component to be copolymerized with these amide-based monomers is not particularly limited as long as it is a vinyl-based monomer, and examples thereof include acrylic acid, methacrylic acid, and acrylic acid-based monomers such as salts or esters thereof. Body, acrylonitrile, vinyl sulfonic acid and salts thereof and the like.
Acrylic acid-based water-soluble polymers are homopolymers and copolymers of acrylic acid-based monomers such as acrylic acid, methacrylic acid and salts thereof, and the copolymerization component thereof is appropriately selected from those described above. . Of these polymers, acrylamide polymers and acrylamide are the main components (60-9
It is particularly advantageous to apply the method of the present invention to a copolymer of 9 mol%) because a polymer having excellent aggregating performance can be obtained.

The water-soluble polymer of the present invention can be obtained by polymerizing the above-mentioned monomers, and in the polymerization, a commonly used polymerization catalyst can be used. Examples of these catalysts include so-called redox catalysts composed of an azo catalyst and an oxidizing agent and a reducing agent. Examples of the azo catalyst include 2,2-azobis2-amidinopropane hydrochloride, azobisisobutyronitrile,
2,2-azobis (4-methoxy-2,4-ditylvaleronitrile), 1,1-azobis (cyclohexanecarbonitrile), and the like, particularly 2,2-azobis-2
-Amidinopropane hydrochloride is preferred. The amount of the azo compound added is 100 to 4000 ppm, preferably 300 to 800 ppm, relative to the monomer.

Examples of the oxidizing agent include ammonium persulfate and potassium persulfate. Further, examples of the reducing agent include ferrous sulfate, ferrous chloride and the like. The amount of the additive is usually 0.01 to 100 ppm, preferably 0.
1 to 50 ppm. These can be used in different amounts, but they are usually used in approximately equimolar amounts.

The monomer is polymerized in an aqueous medium, and its concentration is usually 10 to 35%, preferably 20 to 30%. If the concentration is too low, the load of subsequent drying is large, and if it is too high, the temperature of the polymerization reaction system becomes high and the quality of the polymer is liable to deteriorate, and depending on the type of polymer, it becomes a high concentration gel and is difficult to handle. The polymerization temperature is usually -10 to 100 ° C, and the polymerization initiation temperature is, for example, 20 ° C.
The following is assumed. The polymerization time is arbitrary, but is usually 0.5 to 10
It's about time. The type of polymerization reaction is not particularly limited as long as it is a type adopted for the polymerization of vinyl monomers such as acrylamide and acrylic acid. For example, in the case of the above acrylamide monomers, the monomers are polymerized in an aqueous solution. A water polymerization method can be mentioned.

Polymerization products are usually gels or slurries,
It is obtained as a dispersion liquid or the like (hereinafter sometimes collectively referred to as a reaction product system), and is dried because it contains water. In the present invention, when drying these polymers,
(1) Alkaline agent and (2) 2-15 wt% of sodium bisulfite, sodium sulfite, and sodium pyrosulfate with respect to the weight of the charged monomers (however, the wt% is converted to sodium bisulfite). And at least one of them are dried.

Examples of the alkali agent include alkali metal hydroxides, inorganic acids, salts of organic acids, and the like. Specifically, one of sodium and potassium such as caustic soda, caustic potash, sodium carbonate, and potassium carbonate is used. Valuable salts are mentioned. The amount thereof is usually 0.1 with respect to the charged monomers.
% To 10% by weight, preferably 0.1 to 2% by weight, and more preferably 0.3 to 1% by weight. The alkaline agent is added as an aqueous solution in order to make uniform contact with the polymer, and the concentration thereof is usually 30 to 48% by weight, preferably about 47% by weight.

The alkali agent may be present before the water-containing polymer is dried, and the addition means is not limited, but it is usually added to the polymer produced at the end of the polymerization reaction. When the polymer produced is in the form of gel, the gel may be appropriately chopped and crushed in order to achieve sufficient mixing with the alkali. Further, when the polymer is an acrylamide polymer, depending on its use, at the time of production of the polymer, at least a part of the amide group of the produced polymer or copolymer may be hydrolyzed and modified. For this purpose, an alkaline agent is usually added to modify the alkali. In the present invention, an alkali agent may be added during the hydrolysis modification after the polymerization reaction so that a free alkali is present even after the hydrolysis and modified, and then dried. The modification can also be carried out simultaneously with the drying. Further, the acrylamide polymer may be in the form of gel, but in such a case, the alkali agent and the polymer are not sufficiently contacted, and the hydrolysis rate (modification rate) is 100.
Since there is a case where the content of the alkali is less than 10% and there is still a free alkali, in such a case, it can be directly subjected to the drying treatment. The hydrolysis-modification reaction with an alkali varies depending on the intended hydrolysis rate, but an alkaline aqueous solution is added to the polymer by a conventional method to bring them into sufficient contact, and
It is carried out by leaving at 0 to 100 ° C. for 1 to 100 minutes.

In the present invention, at least one of an alkali metal hydrogen sulfite, an alkali metal sulfite, and an alkali metal pyrosulfite is present together with an alkaline agent.
Among these metal salts, alkali metal sulfites and alkali metal hydrogen sulfites are preferable, and alkali metal hydrogen sulfites are particularly preferable. As an alkali metal,
Sodium and potassium are preferable, and sodium is particularly preferable. Therefore, in a particularly preferred embodiment of the invention, the drying is carried out in the presence of sodium sulfite and / or sodium bisulfite, in particular sodium bisulfite.

The amount of these sulfites present is 2 to 15% by weight, preferably 3 to 12% by weight, more preferably 4 based on the weight of the charged monomers of the polymer, in terms of alkali metal hydrogen sulfite. ~ 8% weight. If this amount is too small, a large amount of unreacted monomers such as unreacted acrylamide remain and the purpose cannot be achieved. On the other hand, when the amount of abundance is large, the viscosity of the polymer is reduced and the aggregating performance is reduced. These are usually added as an aqueous solution, in which case the concentration is usually 5 to 20% by weight, preferably 15 to 20% by weight.
It is. The temperature at the time of addition is usually 30 to 90 ° C, preferably 50 to 70 ° C.

To carry out the present invention, the polymer in a water-containing state to which an alkali agent and an additive such as sodium sulfite are added is dried by a commonly used dryer such as a drum dryer or a fluidized bed dryer. ~ 150 ° C, 30 ~
It is carried out by drying for 200 minutes, but if the temperature is too high, gelation of the polymer will proceed and cause deterioration of the quality, which is not preferable. When the method of the present invention is carried out subsequent to the polymerization reaction of acrylamide or the like, for example, a closed type polymerization tank is charged with an aqueous monomer solution and cooled to 10 ° C., and then nitrogen gas is blown to remove dissolved oxygen from the aqueous solution. Then, the above-mentioned polymerization catalyst is added as an aqueous solution to carry out polymerization. After the polymerization is completed, the polymer is usually a gel, and is ground to an average particle size of 1 to 10 mm according to a conventional method.
If necessary, an alkaline agent is added to the granules so that the granules remain after modification so as to carry out a modification reaction, and sodium bisulfite is added to the granules, and then the granules are dried to a water content of 10% by weight or less. Process it into a product.

[0018]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Examples 1 to 4 and Comparative Examples 1 to 4 A 15-liter closed polymerization tank was charged with 6.0 kg of a 50 wt% acrylamide aqueous solution and 6.0 kg of water. After blowing 0.2 m ³ of nitrogen gas into the aqueous solution to completely degas,
First, 500 ppm of 2,2-azobis-2-amidinopropane hydrochloride was added at a liquid temperature of 10 ° C., and then 20 ppm of an oxidizing agent (ammonium persulfate) and a reducing agent (ferrous sulfate).
Was added in an equimolar amount with the oxidant, and the polymerization was terminated in 2 hours. The reaction temperature was 88 ° C. After polymerization, the gel polymer produced is extruded and granulated with an average particle size of 2.
Granulate to 5 mm, then add and mix 47% caustic soda aqueous solution to the granules to modify with alkali, then continue to 20%
An aqueous sodium hydrogen sulfite solution was added as shown in Table 1, and then dried with a hot air dryer at 120 ° C. for 1.5 hours.
The dried granular material was pulverized and then sieved to obtain a water-soluble polymer (transformation rate: 20 mol%) having a size of 1 mm or less. Table of the results
It is shown in FIG.

Comparative Example 5 In the same closed polymerization tank as in Example 1, 748 g of 80% acrylic acid and 716 g of 47% NaOH aqueous solution were added to neutralize the mixture and, after neutralization, 4787 g of 50% by weight acrylamide aqueous solution.
And then 5739 g of water. Thereafter, the same operation as in Example 3 was carried out except that caustic soda was not added to obtain a dried product. The viscosity and unreacted acrylamide of the granular polymer thus obtained were measured. Table 1 shows the obtained results.

Example 5 Caustic soda was added at the same time as sodium bisulfite was added.
A dry product was obtained in the same manner as in Comparative Example 5 except that 5% by weight (the total weight of acrylic acid and acrylamide monomer) was added. The results are shown in Table 1.

Comparative Example 6 A dried product was obtained in the same manner as in Comparative Example 5 except that sodium hydroxide and sodium bisulfite were not added, and its viscosity and unreacted acrylamide were measured. Table 1 shows the results.
Shown in

[0023]

[Table 1]

Note (*) in Table 1 indicates the following. * 1: Alkaline agent The amount of alkali before drying, which is calculated from the amount of caustic soda charged and the modification ratio determined by colloid titration, is shown in% by weight based on the charged monomers. * 2: Viscosity: Add a polymer to 4% NaCl water to make a 0.5% polymer solution, then add 25% with a Brookfield viscometer.
C., rotor No. 2, 60 rpm. * 3: 2 g of unreacted acrylamide product was made into 4 with 20 ml of solvent (acetone: water = 8: 2).
After permeation extraction for hr, it was measured by high performance liquid chromatography.

[0025]

When the acrylamide polymer is dried by the method of the present invention, the unreacted acrylamide can be reduced to 5 ppm or less while suppressing the decrease in the viscosity of the polymer. It enables the production of polyacrylamide, and has great advantages in terms of environment and safety.

Claims (6)

[Claims] 1. When drying a water-containing polymer of an acrylamide-based and / or acrylic acid-based water-soluble polymer, to the polymer (1) an alkali agent and (2) a monomer charged to the polymer. 2 to 15% by weight of alkali metal hydrogen sulfite,
A method for producing a water-soluble polymer, which comprises: allowing at least one selected from an alkali metal sulfite and an alkali metal pyrosulfite (wherein weight% is calculated as an alkali metal hydrogen sulfite) and drying. 2. The water-soluble polymer is a homopolymer of acrylamide or methacrylamide, or a copolymer of these amides and another vinyl-based monomer. Method for producing water-soluble polymer. 3. The vinyl-based monomer is a salt or ester of acrylic acid, methacrylic acid or vinyl sulfonic acid,
Alternatively, it is selected from acrylonitrile and the method for producing a water-soluble polymer according to claim 2. 4. The water-soluble polymer according to claim 1, wherein the water-soluble polymer is an acrylamide polymer or a copolymer mainly composed of acrylamide and acrylic acid or an acrylic ester. Manufacturing method of coalescence. 5. The water-soluble polymer according to any one of claims 1 to 4, wherein the alkali agent is present in an amount of 0.1 to 10% by weight based on the charged monomers of the water-soluble polymer. Manufacturing method. 6. An acrylamide monomer or a mixed monomer of an acrylamide monomer and another vinyl-based monomer is polymerized in an aqueous medium, and at least a part of the resulting polymer is modified with alkali. In the method for producing a water-soluble polymer by drying, the produced polymer is (1) an alkaline agent having a desired hydrolysis equivalent or more of the amide group of the produced polymer and (2) a charged monomer of the produced polymer. At least one selected from alkali metal bisulfite salts, alkali metal sulfite salts, and alkali metal pyrosulfite salts in an amount of 2 to 15% by weight based on the amount of the monomer (provided that the weight% is equivalent to the alkali metal hydrogen sulfite salt). A method for producing a modified water-soluble polymer, which comprises heating and drying in the presence.