Flocculation treatment agent with suppressed deterioration

Abstract

To provide a flocculation treatment agent which improves long-term storage stability of a flocculation treatment agent product and a solution thereof, and to provide a deterioration suppression method for the flocculation treatment agent.SOLUTION: Provided is a flocculation treatment agent which contains an acid substance and a buffer salt in a water-soluble polymer having a specific structural unit. The flocculation treatment agent is prepared and manufactured by adding the acid substance and the buffer salt in a monomer mixture before polymerization or in a product after polymerization. Preferably, the addition rates are 0.7-10 mass% of the acid substance, and 0.05-2 mass% of the buffer salt relative to a flocculation treatment agent product. Further, the acid substance is preferably a carboxylate, and the buffer salt is preferably a carboxylate.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a flocculating treatment agent with suppressed deterioration, and more particularly to a flocculating treatment agent that is stable for a long period of time and that suppresses deterioration of the product and its dissolving solution compared to conventional products, and a method for suppressing the deterioration of the flocculating treatment agent. [Background technology]

[0002] Depending on the application, flocculating agents are widely used as wastewater treatment agents for wastewater and sludge treatment, sludge dewatering agents, sludge settling agents, or papermaking chemicals such as retention and / or drainage improvers, coagulants, paper strength enhancers, wet strength improvers, size fixing agents, deinking aids, etc. Water-soluble polymers are used as these flocculating agents, and among them, polyacrylamide (PAM)-based water-soluble polymers are widely used.

[0003] PAM-based water-soluble polymer products, especially high-concentration dispersion-type products such as water-in-oil emulsions and dispersions in saltwater, have problems such as deterioration of the product and reduced performance due to structural changes in the polymer over time after production. In the solution, the polymer deteriorates over time due to hydrolysis, and the viscosity of the solution decreases, resulting in a decrease in the coagulation treatment performance. Furthermore, these tendencies become more pronounced as the monomer concentration increases, making it difficult to obtain high-quality high-concentration products and their solutions.

[0004] Therefore, various proposals have been made regarding the prevention of deterioration of PAM-based water-soluble polymers. For example, Patent Document 1 discloses that cationic deterioration can be prevented by adjusting the pH of an aqueous solution of a water-soluble polymer in which the constituent ratio of cationic monomers is 50 mol % or less to 5.5 or less with sulfamic acid, citric acid, or the like. Patent Document 2 describes that deterioration of a water-soluble polymer is prevented by adding an alkali metal salt or ammonium salt of ethylenediaminetetraacetic acid to a (co)polymerization reaction system or a (co)polymer. Patent Document 3 discloses that the polymer flocculant solution is stabilized by combining three components: a polymer flocculant, a reducing agent such as thiosulfate or sulfite, and an acidic substance such as sulfamic acid or citric acid in an amount that makes the pH of the solution 6 or less when the polymer flocculant is dissolved at 0.1 mass% or more. However, these techniques may not provide satisfactory results depending on the form, structure, and composition of the water-soluble polymer, and they do not necessarily suppress the deterioration of both the product itself and the dissolving solution.Therefore, there is a demand for a flocculating treatment agent that can suppress the deterioration of both the water-soluble polymer flocculating treatment agent product and the dissolving solution and can achieve long-term storage stability.

[0005] [Patent Document 1] Japanese Patent Application Publication No. 54-69582 [Patent Document 2] Japanese Patent Application Publication No. 58-40306 [Patent Document 3] JP 2008-18344 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] An object of the present invention is to improve the long-term storage stability of an aggregating treatment agent and a solution thereof. [Means for solving the problem]

[0007] As a result of extensive research to achieve the above object, the inventors discovered that the long-term storage stability of a product and its solution can be improved by causing a water-soluble polymer having a specific structural unit to coexist with an acidic substance and a buffer salt, thereby arriving at the present invention.

[0008] The acidic substance and buffer solution contained in the flocculating treatment agent may be added during polymerization, or may be added to the product after polymerization. Effect of the Invention

[0009] The water-soluble polymer having a specific structural unit according to the present invention has excellent long-term storage stability and is therefore useful in a wide range of applications as an aggregating agent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The water-soluble polymer in the present invention is produced by polymerizing a monomer mixture containing 0 to 99 mol % of a cationic monomer represented by the following general formula (1), 0 to 99 mol % of an anionic monomer represented by the following general formula (2), and 1 to 100 mol % of a nonionic monomer. JPEG0007599647000001.jpg3583 General formula (1) R1 is hydrogen or a methyl group, R2 and R3 are an alkyl group or an alkoxy group having 1 to 3 carbon atoms, and R4 is hydrogen, an alkyl group or an alkoxy group having 1 to 3 carbon atoms, or a benzyl group, and may be the same or different. A is oxygen or NH, B is an alkylene group or an alkoxylene group having 2 to 4 carbon atoms, and X1 is an anion. JPEG0007599647000002.jpg3771 General formula (2) R5 represents hydrogen, a methyl group or a carboxymethyl group, Q represents SO3, C6H4SO3, CONHC(CH3)2CH2SO3, C6H4COO or COO, R6 represents hydrogen or COOY2, and Y1 or Y2 represents hydrogen or a cation.

[0011] The cationic monomer represented by the general formula (1) used in the present invention includes the following. That is, it is a quaternary product of methyl chloride or benzyl chloride such as dimethylaminoethyl (meth)acrylate or dimethylaminopropyl (meth)acrylamide. Examples of the cationic monomer represented by the general formula (1) include (meth)acryloyloxyethyl trimethylammonium chloride, (meth)acryloyloxy-2-hydroxypropyl trimethylammonium chloride, (meth)acryloylaminopropyl trimethylammonium chloride, (meth)acryloyloxyethyl dimethylbenzylammonium chloride, (meth)acryloyloxy-2-hydroxypropyl dimethylbenzylammonium chloride, and (meth)acryloylaminopropyl dimethylbenzylammonium chloride. At least one selected from these is used.

[0012] The anionic monomer represented by the general formula (2) used in the present invention includes vinyl sulfonic acid, vinylbenzene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, acrylic acid, itaconic acid, maleic acid, phthalic acid, p-carboxystyrene acid, etc. One or more selected from these are used.

[0013] The nonionic monomer used in the present invention includes (meth)acrylamide, N,N'-dimethylacrylamide, acrylonitrile, 2-hydroxyethyl (meth)acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, acryloylmorpholine, etc. One or more selected from these are used.

[0014] The product form of the water-soluble polymer in the present invention is not particularly limited, and can be produced by a known method. For example, after polymerization by aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, dispersion polymerization in salt water, etc., the product can be made into any product form such as an aqueous solution, a dispersion in salt water, a water-in-oil emulsion, or a powder. Among these, water-in-oil emulsion polymerization is preferred because it is easy to produce a high molecular weight and high concentration product, and long-term product stability is required.

[0015] These various polymerizations are carried out by a conventional method. For example, a polymerization initiator, for example, a water-soluble azo-based polymerization initiator such as 2,2'-azobis(amidinopropane) dihydrochloride or 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, or a water-soluble redox-based polymerization initiator such as a combination of ammonium persulfate and sodium hydrogen sulfite, is added under a nitrogen atmosphere, and radical polymerization is carried out with or without stirring.

[0016] The water-in-oil emulsion can be appropriately produced according to the methods described in JP-A-55-137147, JP-A-59-130397, JP-A-10-140496, JP-A-2011-99076, etc. A monomer mixture containing a cationic monomer and / or anionic monomer and a nonionic monomer is mixed with water, an oily substance consisting of a water-immiscible hydrocarbon, and at least one surfactant having an effective amount and HLB for forming a water-in-oil emulsion, and the mixture is stirred vigorously to form a water-in-oil emulsion, followed by polymerization.

[0017] Examples of oily substances made of hydrocarbons used as a dispersion medium include paraffins, mineral oils such as kerosene, light oil, and medium-weight oil, synthetic hydrocarbon oils having substantially the same ranges of boiling point, viscosity, and other properties, and mixtures thereof. The content is in the range of 20% by mass to 50% by mass, and preferably 20% by mass to 35% by mass, based on the total amount of the water-in-oil emulsion.

[0018] An example of at least one surfactant having an effective amount and HLB for forming a water-in-oil emulsion is a nonionic surfactant with an HLB of 3 to 11, and specific examples thereof include sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate, polyoxyethylene nonylphenyl ether, etc. The addition rate of these surfactants is 0.5 to 10% by mass, preferably 1 to 5% by mass, based on the total amount of the water-in-oil emulsion.

[0019] The polymerization concentration of the monomer is in the range of 20 to 60% by mass, and the polymerization concentration and temperature are appropriately set depending on the monomer composition and the selection of the initiator. The polymerization temperature is 20 to 80°C, preferably 20 to 60°C. A radical polymerization initiator is used to start the polymerization. These initiators may be either oil-soluble or water-soluble, and polymerization can be carried out with any of azo, redox, and peroxide initiators. Examples of oil-soluble azo initiators include 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 1,1'-azobiscyclohexanecarbonitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis-2-methylpropionate, and 4,4'-azobis-(4-methoxy-2,4-dimethyl)valeronitrile.

[0020] Examples of water-soluble azo initiators include 2,2'-azobis(amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-imidazolin-2-yl)propane] dihydrochloride, 4,4'-azobis(4-cyanovaleric acid), etc. Examples of redox initiators include combinations of ammonium peroxodisulfate with sodium sulfite, sodium hydrogensulfite, trimethylamine, tetramethylethylenediamine, etc. Examples of peroxide initiators include ammonium or potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy-2-ethylhexanoate, etc. The addition rate of the azo-based or peroxide-based initiator is 50 to 5000 ppm, preferably 100 to 500 ppm, per monomer at the start of polymerization. However, since the polymerization rate is low when these initiators are added in one go, it is preferable to add them in several portions.

[0021] Also, a structural modifier, that is, a crosslinkable monomer that structurally modifies the polymer may be used during polymerization. The crosslinkable monomer is present in a range of 0.5 to 200 ppm by mass relative to the total amount of monomers. Examples of the crosslinkable monomer include N,N'-methylenebis(meth)acrylamide, triallylamine, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, polyethylene glycol di(meth)acrylate, N-vinyl(meth)acrylamide, N-methylallylacrylamide, glycidyl acrylate, polyethylene glycol diglycidyl ether, acrolein, glyoxal, vinyltrimethoxysilane, etc., but water-soluble polyvinyl compounds are more preferred, and N,N'-methylenebis(meth)acrylamide is the most preferred.

[0022] In addition, it is also effective to use a chain transfer agent such as sodium formate, isopropyl alcohol, sodium methallyl sulfonate, etc. in combination to adjust the degree of polymerization. The addition rate is 0.0005 to 5 mass %, preferably 0.01 to 0.5 mass %, based on the total amount of monomers.

[0023] After polymerization, a hydrophilic surfactant called a phase inversion agent is added to make the emulsion particles covered with an oil film more compatible with water and to make the water-soluble polymer inside more soluble, and then the emulsion is diluted with water for use. Examples of hydrophilic surfactants include cationic surfactants and nonionic surfactants with HLB of 9 to 15, such as polyoxyethylene polyoxypropylene alkyl ethers and polyoxyethylene alcohol ethers.

[0024] The flocculating agent in the present invention contains an acidic substance and a buffer salt. Examples of the acidic substance include hydrochloric acid, sulfuric acid, acetic acid, formic acid, sulfamic acid, citric acid, fumaric acid, phthalic acid, succinic acid, adipic acid, oxalic acid, malic acid, and salicylic acid. Among these, carboxylic acids such as acetic acid, formic acid, sulfamic acid, citric acid, fumaric acid, phthalic acid, succinic acid, adipic acid, oxalic acid, malic acid, and salicylic acid are preferred. Two or more of these may be combined. Examples of the buffer salt include sodium salts, potassium salts, and ammonium salts of the acidic substances. Among these, carboxylate salts are preferred. Two or more of these may be combined. The acidic substance and buffer salt contained in the flocculating treatment agent of the present invention may vary depending on the composition and physical properties, but the acidic substance is preferably contained in the range of 0.7 to 10 mass% of the flocculating treatment agent product. The buffer salt is preferably contained in the range of 0.05 to 2 mass% of the flocculating treatment agent product. If the acidic substance is not 0.7 mass% or more and the buffer salt is not 0.05 mass% or more, the significant effect of the present invention cannot be obtained, and even if the acidic substance and the buffer salt exceed 10 mass% and 2 mass%, respectively, no significant improvement effect is observed. More preferably, the acidic substance is 0.8 to 10 mass% and the buffer salt is 0.1 to 2 mass%.

[0025] The acidic substance and buffer salt in the present invention may be added to the aqueous phase containing the monomer mixture during polymerization, or may be added after polymerization. They are also effective when added to the aqueous solution of the polymer product. In order to obtain a long-term storage stability effect for both the product and its solution, they must be contained in the aqueous phase containing the monomer mixture during polymerization, or in the product after polymerization. From the viewpoint of stable production and efficiency of the product, it is preferable to contain them in the monomer mixture during polymerization. By adding an acidic substance and a buffer salt, the pH of the solution having a polymer concentration of 0.2% by mass is preferably 5.5 or less, more preferably 4.5 or less. Coagulation treatment agent products may deteriorate and lose performance if a long time passes before use due to storage after production or transportation to the site of use, or if the storage location becomes hot. Furthermore, when used, they are generally diluted with water to a concentration of 0.01 to 1.0% by mass, but if it takes several days for the diluted solution to be used, the viscosity of the solution decreases due to hydrolysis, resulting in poor coagulation treatment performance. However, it has been found that the flocculation treatment agent of the present invention, by containing a water-soluble polymer, an acidic substance, and a buffer salt, can suppress deterioration of both the product and its dissolution liquid, improving long-term storage stability, and is particularly effective in improving the long-term storage stability of high-concentration water-in-oil emulsion products.

[0026] The flocculating agent of the present invention can be used as a wastewater treatment agent for wastewater or sludge treatment, a sludge dewatering agent, a sludge settling agent, or as a papermaking agent for improving retention and / or drainage, a coagulant, a paper strength enhancer, a wet paper strength enhancer, a size fixing agent, a deinking aid, etc. When used as a flocculating agent, the undiluted solution may be added to the target object as is, or it may be dissolved in water to an arbitrary concentration and added. The dissolved concentration is in the range of 0.01 to 1.0 mass%, and preferably 0.05 to 0.5 mass%. EXAMPLES

[0027] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0028] Water-soluble polymer samples 1 to 4, which are the basis of the present invention, were produced by the usual method for water-in-oil emulsions disclosed in JP-A-55-137147, JP-A-59-130397, JP-A-10-140496, JP-A-2011-99076, etc. The compositions and physical properties of these samples are shown in Table 1.

[0029] (Table 1) TIFF0007599647000003.tif2791DMQ;Acryloyloxyethyltrimethylammonium chloride AAM; Acrylamide

[0030] Example 1 When producing Sample 1 in Table 1, a flocculating treatment agent was produced and prepared in which 2.5% by mass of citric acid as an acidic substance and 0.3% by mass of sodium citrate (hereinafter, Na citrate) as a buffer salt were contained in the aqueous phase containing the monomer mixture, relative to the flocculating treatment agent product, and this was designated Example 1. This is shown in Table 2.

[0031] (Examples 2 to 10) In the same manner as in Example 1, flocculating treatment agents were produced and prepared by changing the types and addition rates of the water-soluble polymer sample, acidic substance, and buffer salt, to give Examples 2 to 10. These are shown in Table 2.

[0032] Comparative Examples 1 to 8 In the same manner as in Example 1, flocculating treatment agents outside the scope of the present invention were produced and prepared by changing the type and addition rate of the water-soluble polymer sample and acidic substance, and these were set forth as Comparative Examples 1 to 8. These are shown in Table 2.

[0033] (Table 2) TIFF0007599647000004.tif7190

[0034] (Example of Test 1) (Product Deterioration Rate Measurement Test) The viscosity of a 4% by mass saline solution (mPa·s, 0.5% by mass saline solution viscosity; SLV) measured by a rotational viscometer at 25°C when the polymer concentration was dissolved to 0.5% by mass is an index of molecular weight, and the measured value of SLV can be used to judge whether the flocculating treatment agent product has deteriorated. The flocculating treatment agent sample of Example 1 was stirred and dissolved at 800 rpm for 30 minutes to prepare a 0.5% by mass saline solution. The viscosity of the 0.5% by mass saline solution was measured (25°C) using a B-type viscometer with a rotation speed of 60 rpm and a No. 2 rotor, and the result was 117 mPa·s. In addition, the flocculating treatment agent sample of Example 1 was kept at 55°C, and the viscosity of the 0.5% by mass saline solution was measured (25°C) in the same manner after 7 days, and the result was 74.5 mPa·s. The product deterioration rate of 36.3% was calculated from the ratio of the viscosity of the saline solution on the first day to the viscosity of the saline solution after 7 days. In addition, the same test as in Example 1 was carried out on the flocculating treatment agent samples of Examples 2 to 10. The results are shown in Table 3.

[0035] (Comparative Test Example 1) For the flocculating treatment agent samples Comparative Examples 1 to 8 outside the scope of the present invention, the same product deterioration rate measurement test was carried out in the same manner as in Practical Test Example 1. The results are shown in Table 3.

[0036] (Example of Test 2) (Dissolving liquid deterioration rate measurement test) The flocculating treatment agent sample of Example 1 was prepared with tap water (pH 7.0, electrical conductivity 110 mS / m) so that the polymer concentration was 0.2% by mass, and after stirring and dissolving for 30 minutes at 800 rpm, the viscosity of the solution was measured (25°C) using a B-type viscometer at a rotation speed of 30 rpm and a No. 2 rotor, and the result was 278 mPa·s. Next, this solution was kept at 25°C, and the viscosity of the solution was measured in the same manner after 24 hours, and the result was 270 mPa·s. The solution deterioration rate of 2.9% was calculated from the ratio of the viscosity of the solution at the time of dissolution to the viscosity of the solution after 24 hours. The results are shown in Table 3. The flocculating treatment agent samples of Examples 2 to 10 were also subjected to the same test as in Example 1. The results are shown in Table 3.

[0037] Comparative Test Example 2 For the flocculating treatment agent samples Comparative Examples 1 to 8 outside the scope of the present invention, the same test for measuring the degradation rate of the dissolving solution was carried out in the same manner as in Experimental Test Example 2. The results are shown in Table 3.

[0038] (Table 3) TIFF0007599647000005.tif7091 Viscosity of 0.5 mass% salt solution: Viscosity (mPa·s) measured at 25°C when the polymer is dissolved in 4 mass% salt solution to give a polymer concentration of 0.5 mass%. Viscosity of 0.2 mass% solution: Viscosity (mPa s) measured at 25°C when the polymer is dissolved in water to a polymer concentration of 0.2 mass%.

[0039] From the practical test examples 1 and 2, it was found that when the coagulation treatment agent sample of the present invention was applied, it was possible to suppress the decrease in both the viscosity of the 0.5% by mass salt aqueous solution and the viscosity of the 0.2% by mass solution of the product. On the other hand, in the comparative test examples 1 and 2, when only an acidic substance was contained, it was found that although it was possible to suppress the decrease in the viscosity of the solution by increasing the addition rate of the acidic substance, the effect of suppressing product deterioration was low.

[0040] As described above, the flocculation treatment agent of the present invention, which contains a water-soluble polymer having a specific structural unit, an acidic substance, and a buffer salt, can suppress deterioration of both the product and the dissolution liquid, and can be widely used as a flocculation treatment agent that is stable for a long period of time.

Claims

1. A flocculating treatment agent comprising a water-soluble polymer having as constituent units 20 to 80 mol % of (meth)acryloyloxyethyltrimethylammonium chloride as a cationic monomer represented by the following general formula (1) and 20 to 80 mol % of (meth)acrylamide as a nonionic monomer, 0.7 to 10 mass % of one or more acidic substances selected from acetic acid, formic acid, citric acid, fumaric acid, phthalic acid, succinic acid, adipic acid, oxalic acid, malic acid and salicylic acid relative to the flocculating treatment agent product, and 0.05 to 2 mass % of one or more buffer salts selected from sodium salts, potassium salts and ammonium salts of the acidic substances relative to the flocculating treatment agent product, wherein the water-soluble polymer is in the form of a water-in-oil emulsion. General formula (1) R １ is hydrogen or a methyl group, R ２ , R ３ is an alkyl group or alkoxy group having 1 to 3 carbon atoms; R ４ are hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkoxy group, or a benzyl group, and may be the same or different. A is oxygen or NH, B is an alkylene group or an alkoxylene group having 2 to 4 carbon atoms, X １ represents an anion.

2. A method for inhibiting deterioration of a flocculating treatment agent, comprising: a water-soluble polymer having as constituent units 20 to 80 mol % of (meth)acryloyloxyethyltrimethylammonium chloride as a cationic monomer represented by the following general formula (1); and 20 to 80 mol % of (meth)acrylamide as a nonionic monomer; and one or more acidic substances selected from acetic acid, formic acid, citric acid, fumaric acid, phthalic acid, succinic acid, adipic acid, oxalic acid, malic acid, and salicylic acid, in an amount of 0.7 to 10 mass % relative to the flocculating treatment agent product; and one or more buffer salts selected from sodium salts, potassium salts, and ammonium salts of the acidic substances, in an amount of 0.05 to 2 mass % relative to the flocculating treatment agent product, in an aqueous phase containing a monomer mixture during polymerization of the water-soluble polymer, or in the product after polymerization, wherein the water-soluble polymer is in the form of a water-in-oil emulsion. General formula (1) R １ is hydrogen or a methyl group, R ２ , R ３ is an alkyl group or alkoxy group having 1 to 3 carbon atoms; R ４ are hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkoxy group, or a benzyl group, and may be the same or different. A is oxygen or NH, B is an alkylene group or an alkoxylene group having 2 to 4 carbon atoms, X １ represents an anion.

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