JP7034454B2 - How to make liquid fertilizer - Google Patents

Description

The present invention relates to a method for producing a liquid fertilizer. More specifically, the present invention relates to a method for producing a liquid fertilizer in which a polymer flocculant is added, mixed, and insoluble matter is removed by a sedimentation treatment in the process for producing the liquid fertilizer.

As a method for producing liquid fertilizer, magnesium nitrate and / or calcium nitrate is produced by reacting nitric acid with one or more selected from mainly dolomite, limestone, magnesium hydroxide and magnesium hydroxide, and free nitric acid is neutralized with ammonia. There are various methods depending on the type of fertilizer, such as the method of adding nitric acid to water, dissolving necessary components such as ammonia, potassium hydroxide, and calcium carbonate, and adjusting the pH with ammonium hydroxide or potassium hydroxide. It has been adopted.
However, in any of the production methods, after that, generally, the insoluble matter in the liquid fertilizer is removed by natural sedimentation, and the supernatant is recovered as a product or is sent to the next step. The insoluble matter is observed as turbidity, and it may take about half a month to a month for this turbidity to settle, which is rate-determining in terms of productivity and improvement is desired. Therefore, in order to shorten the sedimentation separation time of the turbid component, various methods have been proposed in which a polymer flocculant is added to perform sedimentation separation.
For example, Patent Document 1 describes that a polyacrylamide type is used, and a nonionic polyacrylamide is particularly preferable.
In Patent Document 2, aluminum nitrate and polyacrylamide or polyacrylamide and a partial hydrolyzate thereof are used.
Patent Document 3 describes that the washing wastewater containing a fermented product of organic waste can be used as a high-quality liquid fertilizer, and various polymer flocculants such as polyacrylamide can be used in the dehydration step. It is suggested that it can also be applied to.
However, none of these describes the effective composition or physical properties of the polymer used. In addition, a satisfactory effect cannot be obtained as compared with the chemical cost, and the application of a more effective polymer is desired.

Japanese Unexamined Patent Publication No. 2006-225175 Special Publication No. 46-25683 Japanese Unexamined Patent Publication No. 2000-84527

An object of the present invention is to provide a method for producing a liquid fertilizer in which an insoluble matter is settled and separated by a coagulation treatment by adding and mixing a polymer flocculant in the process of producing the liquid fertilizer.

As a result of diligent studies to solve the above problems, the present inventor has reached the invention described below. That is, it is a method for producing a liquid fertilizer in which a water-soluble polymer having a specific structural unit, composition and physical characteristics is added to the liquid fertilizer as a polymer flocculant, mixed, and the insoluble matter is settled and separated by a coagulation treatment. be.

By applying the water-soluble polymer in the present invention to the manufacturing process of liquid fertilizer, the insoluble matter expressed as turbidity can be efficiently sedimented and separated.

The method for producing a liquid fertilizer in the present invention is characterized in that a water-soluble polymer having a specific structural unit, composition and physical characteristics is added to the liquid fertilizer, mixed, and then settled and separated. Since it has a specific structural unit, composition, and physical characteristics as compared with a generally used polymer, it has a high coagulation treatment effect and can efficiently precipitate and separate insoluble matter.

The liquid fertilizer in the present invention may be any as long as it is liquid at room temperature of 10 to 35 ° C., and is applied in the manufacturing process of a liquid fertilizer commercially available as a liquid fertilizer. Specific examples of the fertilizer raw material include ammonia, ammonium carbonate and the like as an ammonium ion donor as a nitrogen component, and ammonium nitrate, potassium nitrate, sodium nitrate, magnesium nitrate and the like as nitrate ion donors. Further, as a phosphate ion donor as a phosphorus component, phosphoric acid, acidic ammonium phosphate, ammonium phosphate, acidic potassium phosphate, acidic calcium phosphate, acidic magnesium phosphate, etc., and as a potassium ion donor as a potassium component, water As calcium ion donors such as potassium oxide, potassium carbonate, potassium nitrate, and acidic potassium phosphate, calcium hydroxide, calcium carbonate, calcium nitrate, etc., magnesium ion donors as magnesium components, magnesium hydroxide, carbonic acid, etc. Examples of sulfate ion donors that are sulfur components such as magnesium, magnesium sulfate, and magnesium nitrate include sulfuric acid, magnesium sulfate, ammonium sulfate, and the like, and are used as liquid fertilizers produced according to the purpose by combining several kinds of these fertilizer raw materials. Apply.

Further, trace element components can be added as needed. Examples of the compound as a trace element component include EDTA iron, EDTA zinc, EDTA copper, zinc sulfate, zinc chloride, copper sulfate, manganese chloride, manganese sulfate, ammonium molybdate, borosand, boric acid and the like. The selection and amount of these are appropriately adjusted depending on the type of fertilizer to be produced.

The fertilizer raw material and trace element components are dissolved in water, acid components such as nitric acid and phosphoric acid are appropriately added, the pH is adjusted, and the reaction treatment is performed under arbitrary conditions. After the reaction, the water-soluble polymer of the present invention is added and mixed under a temperature condition of 10 to 80 ° C.

一般式（１）
Ｒ_１は水素又はメチル基、Ｒ_２、Ｒ_３は炭素数１～３のアルキル基あるいはヒドロキシアルキル基、Ｒ_４は炭素数１～３のアルキルあるいはアルコキシル基、７～２０のアルキル基あるいはアリール基、Ａは酸素またはＮＨ、Ｂは炭素数２～４のアルキレン基を表わす、Ｘ_１ ^－は陰イオンをそれぞれ表わす。

一般式（２）
Ｒ_５は水素、メチル基又はカルボキシメチル基、ＱはＳＯ_３ ^－、Ｃ_６Ｈ_４ＳＯ_３ ^－、ＣＯＮＨＣ（ＣＨ_３）_２ＣＨ_２ＳＯ_３ ^－、Ｃ_６Ｈ_４ＣＯＯ^－あるいはＣＯＯ^－、Ｒ_６は水素又はＣＯＯ^－Ｙ_２ ^＋、Ｙ_１あるいはＹ_２は水素又は陽イオンをそれぞれ表わす。 The water-soluble polymer in the present invention has 2 to 95 mol% of a cationic monomer represented by the following general formula (1) and 0 to 30 mol% of an anionic monomer represented by the following general formula (2). , And a monomer mixture containing 5 to 98 mol% of nonionic water-soluble monomer, which is produced by polymerizing.

General formula (1)
R ₁ is a hydrogen or methyl group, R ₂ and R ₃ are an alkyl or hydroxyalkyl group having 1 to 3 carbon atoms, R ₄ is an alkyl or alkoxyl group having 1 to 3 carbon atoms, and 7 to 20 alkyl or aryl groups. , A represents oxygen or NH, B represents an alkylene group having 2 to 4 carbon atoms, and X ₁ ⁻ represents an anion.

General formula (2)
R ₅ is hydrogen, methyl group or carboxymethyl group, Q is SO ₃ ⁻ , C ₆ H ₄ SO ₃ ⁻ , CONHC (CH ₃ ) ₂ CH ₂ SO ₃ ⁻ , C ₆ H ₄ COO ⁻ or COO ⁻ , R ₆ ^Represents hydrogen or COO ⁻ Y ₂₊ , Y ₁ or Y ₂ represents hydrogen or cations, respectively.

Among the ionic monomers used in producing the water-soluble polymer in the present invention, the cationic monomer, that is, the monomer represented by the general formula (1) is 2 to 95 mol%. This is because within this range, the neutralizing action of neutralizing the anionic charge of the turbidity component in the liquid fertilizer and the aggregation effect of cross-linking adsorption can be exhibited in a well-balanced manner.

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 and dimethylaminopropyl (meth) acrylamide. Examples are (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxy-2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium. Chloride, (meth) acryloyloxy-2-hydroxypropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride. One of these cationic vinyl-based monomers can be used alone, or two or more of them can be used in combination.

The anionic monomer used in producing the amphoteric water-soluble polymer of the water-soluble polymer in the present invention, that is, the monomer represented by the general formula (2) is in the range of 0 to 30 mol%. .. If it is more than 30 mol%, the charge neutralizing action is lowered and the effect is lowered.

The anionic monomer represented by the general formula (2) used in the present invention is vinyl sulfonic acid, vinylbenzene sulfonic acid or 2-acrylamide-2-methylpropanesulfonic acid, methacrylic acid, acrylic acid, itaconic acid. , Maleic acid, phthalic acid, p-carboxystyrene acid and the like.

The nonionic monomers used in the present invention are (meth) acrylamide, N, N'-dimethylacrylamide, acrylonitrile, (meth) acrylate-2-hydroxyethyl, diacetoneacrylamide, N-vinylpyrrolidone, N-. Examples thereof include vinylformamide, N-vinylacetamide, and acryloylmorpholine.

The water-soluble polymer in the present invention can be produced by copolymerizing a monomer mixture composed of an ionic monomer and a nonionic monomer. Polymerization can be carried out by a usual polymerization method after preparing an aqueous solution in which these monomers are mixed. As a polymerization method, after polymerization by aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, dispersion polymerization in salt water, or the like, any product form such as an aqueous solution, a dispersion, an emulsion, or a powder can be obtained. ..

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

Among the various polymerization methods described above, a preferable form is dispersion polymerization in salt water, which can produce a polymer having a low aqueous solution viscosity and high solubility. When the water-soluble polymer in the present invention is produced by the dispersion polymerization method in salt water, JP-A-61-123610, JP-A-62-20511, JP-A-2007-16086, JP-A-2016-003255. By a known method disclosed in the publications and the like. That is, a water-soluble polymer soluble in a salt aqueous solution is allowed to coexist as a dispersant, and a monomer mixture containing an ionic monomer and a nonionic monomer is dispersed and polymerized in the salt aqueous solution with stirring. To manufacture. In that case, by adding 0.5 to 5 mol% of the polymerization retarding substance to all the monomers, thickening can be suppressed and a water-soluble polymer having a high weight average molecular weight can be produced. Further, the polymerization retardant substance is one or more selected from itaconic acid, maleic acid, phthalic acid, allylamine and diallyldimethylammonium chloride.

The polymerization conditions at the time of dispersion polymerization in salt water are usually appropriately determined depending on the monomer used and the copolymer mol%, and the temperature is in the range of 0 to 100 ° C. A radical polymerization initiator is used to initiate polymerization. These initiators may be either oil-soluble or water-soluble, and can be polymerized by any of azo-based, peroxide-based, and redox-based initiators. Examples of oil-soluble azo-based initiators include 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2-methylbutyronitrile), Examples thereof include 2,2'-azobis (2-methylpropionate), 2,2'-azobis (4-methoxy-2,4-dimethyl) valeronitrile, etc., which are dissolved in a water-soluble solvent and added.

Examples of water-soluble azo initiators are 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride. 4, 4'-azobis (4-cyanovaleric acid) and the like can be mentioned. Further, as an example of the redox system, a combination of ammonium peroxodisulfite with sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine and the like can be mentioned. Further, examples of the peroxide include ammonium peroxodisulfate or potassium, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butyl peroxy2-ethylhexanoate and the like. be able to. The most preferable of these initiators is the water-soluble azo initiator 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl). ) Propane] Dihydrochloride. The addition rate of the azo-based initiator is 50 to 500 ppm, preferably 70 to 200 ppm, per monomer at the start of polymerization. However, since the polymerization rate is low with a single addition, it is preferable to add the mixture in several batches.

In addition, when copolymerizing with a redox-based initiator, it is difficult to control the polymerization if the polymerization is started under the condition of 40 ° C. or higher, and a rapid temperature rise or agglomeration of the polymerization solution occurs, so that the degree of polymerization is high and stable. Since a dispersion cannot be obtained, the temperature is preferably 15 to 35 ° C. The addition rate of this initiator is 5 to 100 ppm, preferably 10 to 50 ppm, per monomer at the start of polymerization. However, since the polymerization rate is low with one addition, it is preferable to add several times. The number of additions is 2 to 5 times, preferably 2 to 3 times. The addition ratio of the polymer dispersant composed of these ionic polymers is 1 to 30% by mass, preferably 2 to 20% by mass with respect to the monomer. If it is 1% by mass or less, it is not effective as a dispersant, and if it is 30% by mass or more, the viscosity of the dispersion liquid becomes high and it is disadvantageous in terms of cost.

A crosslinkable monomer may be used as a structural modifier during or after dispersion polymerization in salt water. When used, the crosslinkable monomer is present in the range of 0.00005 to 0.050% by mass with respect to the total amount of the monomers. Although it depends on the monomer composition and the polymerization conditions, if it exceeds 0.050% by mass, crosslinking proceeds too much and it becomes water-insoluble, which is not preferable for the use of the present invention. Examples of crosslinkable monomers include N, N'-methylenebis (meth) acrylamide, triarylamine, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and dimethacrylate. Methacrylate-1,3-butylene glycol, di (meth) acrylate polyethylene glycol, N-vinyl (meth) acrylamide, N-methylallylacrylamide, glycidyl acrylate, polyethylene glycol diglycidyl ether, achlorine, glioxal, vinyltrimethoxy Examples thereof include silane, and N, N'-methylenebis (meth) acrylamide is preferably applied.

The polymer dispersant used in the dispersion polymerization in salt water can be either ionic or nonionic, but is preferably ionic, more preferably cationic. In the case of a cationic polymer dispersant, a (co) polymer of a cationic monomer such as (meth) acryloyloxyethyltrimethylammonium chloride or dimethyldialylammonium chloride is used as the polymer dispersant, but it is cationic. Copolymers of monomers and nonionic monomers can also be used. Examples of nonionic monomers include acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N'-dimethylacrylamide, acrylonitrile, diacetoneacrylamide, 2-hydroxyethyl (meth) acrylate. However, a copolymer with acrylamide is preferable.

The nonionic polymer dispersant includes amide groups such as polyvinylpyrrolidone, acrylamide / polyvinylcaprolactam copolymer, acrylamide / styrene copolymer, and completely amidate of maleic anhydride / butene copolymer and some hydrophobicity. Water-soluble polymers having a group are also effective.

The molecular weight of these cationic polymer dispersants is 50 to 2 million, preferably 50,000 to 1 million. The molecular weight of the nonionic polymer dispersant is 1,000 to 100,000, preferably 1,000 to 50,000. The addition ratio of these nonionic or ionic polymer dispersants is 1 to 20% by mass, preferably 5 to 15% by mass with respect to the monomer.

As the salts to be used, salts in which cations such as alkali metal ions and ammonium ions such as sodium and potassium and anions such as halide ions, sulfate ions, nitrate ions and phosphate ions are combined can be used. However, salts with polyvalent anions are more preferred. The salt concentration of these salts can be used from 10% by mass to a saturated concentration.

The polymerization concentration is 10% by mass to 35% by mass, preferably 15% by mass to 30% by mass as the monomer concentration. This is because the higher the monomer concentration, the more economically advantageous it is due to the problem of transportation cost, but if the monomer concentration exceeds 35% by mass, the thickening increases during production and it becomes difficult to obtain a dispersion liquid. be. As a method for supplying the monomer, it may be charged all at once at the start of polymerization, or it may be charged in appropriate portions.

The water-soluble polymer in the present invention can be produced by a dispersion polymerization method in salt water in the coexistence of polyalkyleneimine and / or a modified polyalkyleneimine, and a known method such as JP-A-2004-26860 is applied. be able to.

The viscosity measured at 25 ° C. when completely dissolved in water so that the polymer concentration of the water-soluble polymer in the present invention is 0.2% by mass is preferably in the range of 100 mPa · s or less. 70 mPa · s or less is more preferable, and 50 mPa · s or less is even more preferable. When the water-soluble polymer has a viscous physical property in this range, it has good dispersibility and is efficiently mixed with the liquid fertilizer when added. The viscosity of the 0.2% by mass aqueous solution is a value measured with a No. 2 rotor and 30 rpm with a B-type viscometer. As the B-type viscometer, B8M manufactured by Tokyo Keiki Co., Ltd. is used.

The molecular weight of the water-soluble polymer in the present invention is in the range of 2 million to 8 million by weight average molecular weight by the ultimate viscosity method. Crosslink adsorption acts on the aggregation treatment of the insoluble matter by the water-soluble polymer, but if the weight average molecular weight is lower than 2 million, this action is insufficient, and if it exceeds 8 million, the filterability deteriorates, so 2 million to 800. 10,000 is an appropriate range, preferably 3 to 7 million. The viscosity of the aqueous salt solution measured with a rotational viscometer at 25 ° C. when completely dissolved in 4 mass% saline so that the polymer concentration becomes 0.5 mass% is 5 mPa · s or more and 70 mPa · s or less. The range is preferably 5 mPa · s or more and 60 mPa · s or less. If the viscosity is in this range, the coagulation treatment effect is optimal. However, in the case of the dispersed polymer in salt water, the measurement is carried out with a rotational viscometer at 25 ° C. when the polymer is completely dissolved in 2% by mass ammonium sulfate water so that the polymer concentration becomes 0.5% by mass. The viscosity of this 0.5 mass% salt aqueous solution is a value measured with a No. 1 rotor at 60 rpm with a B-type viscometer.

The water-soluble polymer in the present invention may be added as it is as a product, but it is preferable to dissolve and dilute it in water at an arbitrary concentration. When dissolving, a dissolution concentration of 0.05 to 0.3% by mass is applied. The addition rate to the liquid fertilizer is preferably 2 to 30 ppm. In addition to the water-soluble polymer, it may be used in combination with an inorganic flocculant such as ferric chloride, ferric polysulfate, polyaluminum chloride, and sulfate band. Sulfuric acid for pH adjustment, caustic soda, or the like may be used, but it is preferable to treat the water-soluble polymer alone from the viewpoint of chemical cost and control. The water-soluble polymer in the present invention can be applied in a wide range of pH, preferably in the range of pH 1.5 to 10, and more preferably in the range of 1.8 to 10. It can be applied even under strong acidity of pH 1.5 to 3.0 and exerts its effect. For example, there is a concern that polyacrylamide tends to precipitate under strong acidity, but the water-soluble polymer in the present invention does not precipitate because it has the structural unit and composition of a specific cationic monomer.

The water-soluble polymer of the present invention is added to and mixed with the liquid fertilizer solution, and any method can be applied as the addition / mixing method. Then, it is allowed to stand to separate the insoluble matter by sedimentation. The insoluble matter can be removed by passing through a filter having an opening of 1 μm or less. The liquid fertilizer solution after removal is recovered as a product or is sent to the next process.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

First, the water-soluble polymer samples A and B used in the present invention were prepared and prepared by a conventional method. In addition, samples 1 and 2 outside the scope of the present invention were prepared and prepared. Table 1 shows these monomer compositions and physical properties.

ＤＭＱ：アクリロイルオキシエチルトリメチルアンモニウム塩化物
ＤＭＣ：メタクリロイルオキシエチルトリメチルアンモニウム塩化物
ＤＭＢＺ：アクリロイルオキシエチルジメチルベンジルアンモニウム塩化物
ＤＭＭ：ジメチルアミノエチルメタアクリレート
ＡＡＭ：アクリルアミド
ＡＡＣ：アクリル酸
形態；ＤＲ：塩水液中分散重合液、Ｐ：粉末
０．２質量％水溶液粘度；高分子濃度が０．２質量％になるように水で溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）
０．５質量％塩水溶液粘度（塩水中分散重合体）：２質量％硫酸アンモニウム水中に高分子濃度が０．５質量％になるように溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）。
０．５質量％塩水溶液粘度（粉末）；４質量％食塩水中に高分子濃度が０．５質量％になるように溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）。 (Table 1)

DMQ: Acryloyloxyethyltrimethylammonium chloride DMC: Methacryloyloxyethyltrimethylammonium chloride DMBZ: Acryloyloxyethyldimethylbenzylammonium chloride DMM: Dimethylaminoethylmethacrylate AAM: Acrylamide AAC: Acrylic acid form; DR: Dispersion in salt solution Polymer solution, P: Viscosity of 0.2% by mass aqueous solution of powder; Viscosity (mPa · s) measured at 25 ° C. when dissolved in water so that the polymer concentration becomes 0.2% by mass.
Viscosity of 0.5% by mass salt aqueous solution (dispersion polymer in salt water): Viscosity measured at 25 ° C. when dissolved in 2% by mass ammonium sulfate water so that the polymer concentration becomes 0.5% by mass (mPa · s). ..
0.5 mass% salt aqueous solution viscosity (powder); viscosity (mPa · s) measured at 25 ° C. when dissolved in 4 mass% saline solution so that the polymer concentration becomes 0.5 mass%.

Further, commercially available polymer flocculants samples 3 to 6 were prepared and prepared. Table 2 shows these compositions and physical properties.

形態；ＡＱ：水溶液重合体、Ｐ：粉末
０．２質量％水溶液粘度；高分子濃度が０．２質量％になるように水で溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）
０．５質量％塩水溶液粘度；４質量％食塩水中に高分子濃度が０．５質量％になるように溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）。 (Table 2)

Form; AQ: aqueous polymer, P: powder 0.2% by mass aqueous solution viscosity; viscosity measured at 25 ° C. when dissolved in water so that the polymer concentration becomes 0.2% by mass (mPa · s).
Viscosity of 0.5 mass% salt aqueous solution; viscosity (mPa · s) measured at 25 ° C. when dissolved in 4 mass% saline solution so that the polymer concentration becomes 0.5 mass%.

(Example 1)
The sedimentation test of the water-soluble polymer in the present invention was carried out at room temperature. The untreated liquid fertilizer stock solution obtained from a certain fertilizer manufacturing plant was used as the target. The analysis values of liquid fertilizer were as follows. pH 2.0, SS concentration 82 ppm, turbidity 79 NTU, hue brown. The turbidity was measured by HACH DR-4000 (JISK-0102 method). No flocculant was added to the sedimentation treatment in the production process of the fertilizer, and the fertilizer was allowed to stand for one week until the insoluble matter settled. 200 mL of the fertilizer was collected in a jar tester, a 0.2 mass% aqueous solution of Sample A was added at 10 ppm to solution, and the mixture was stirred at 150 rpm for 2 minutes. Then, the fertilizer was transferred to a cylinder, and the turbidity of the supernatant after standing for 16 hours was measured. The results are shown in Table 3.

(Examples 2 and 3)
A similar test was carried out using the same fertilizer as in Example 1. A 0.2% by mass water-dissolved solution of Sample B was added at 10 ppm or 30 ppm with respect to the solution. The results are shown in Table 3.

(Comparative Examples 1 to 8)
As a comparative test, the same fertilizer as in Example 1 was used, and the same test was carried out. The results are shown in Table 3.

(Table 3)

When the water-soluble polymer sample was added in the present invention, the turbidity 16 hours after stirring was lower than that of the comparative example. It was confirmed that the sedimentation treatment effect of the insoluble matter of the water-soluble polymer in the present invention is excellent. On the other hand, in Comparative Examples 1 to 8 using a polymer outside the range of the water-soluble polymer in the present invention, the effect of reducing turbidity was lower than that of Examples. Further, each was left for 72 hours, but no significant decrease in turbidity was observed. Considering the scale at the time of actual production of liquid fertilizer, it is considered that this difference in effect can greatly shorten the sedimentation treatment time and greatly improve the productivity efficiency.

The water-soluble polymer in the present invention has an appropriate monomer composition and physical properties, and thus has an excellent sedimentation treatment effect. Further, pH adjustment is not required even under strong acidity, and the water-soluble polymer alone can be applied without adding an inorganic flocculant. The water-soluble polymer in the present invention can be applied to the manufacturing process of liquid fertilizer, and its industrial utility value is extremely large.

Claims (2)

In the manufacturing process of liquid fertilizer (excluding sludge and animal manure-derived ), as a cationic monomer represented by the following general formula (1) , (meth) acryloyloxyethyltrimethylammonium chloride 10 to 30 mol%, ( Meta) 25 to 50 mol% of acryloyloxyethyldimethylbenzylammonium chloride, 0 to 30 mol% of anionic monomer represented by the following general formula (2), and 20 to 65 mol% of nonionic monomer. A water-soluble polymer soluble in a salt aqueous solution coexists with the contained monomer mixture as a dispersant, and the mixture is dispersed and polymerized in the salt aqueous solution with stirring, and has a weight average molecular weight of 2 million to 8 million. A method for producing a liquid fertilizer, which comprises adding a water-soluble polymer in a range, mixing the mixture, and precipitating and separating the insoluble matter.

General formula (1)
R ₁ is a hydrogen or methyl group, R ₂ and R ₃ are an alkyl or hydroxyalkyl group having 1 to 3 carbon atoms, R ₄ is an alkyl or alkoxyl group having 1 to 3 carbon atoms, and 7 to 20 alkyl or aryl groups. , A represents oxygen or NH, B represents an alkylene group having 2 to 4 carbon atoms, and X ₁ ⁻ represents an anion.

General formula (2)
R ₅ is hydrogen, methyl group or carboxymethyl group, Q is SO ₃ ⁻ , C ₆ H ₄ SO ₃ ⁻ , CONHC (CH ₃ ) ₂ CH ₂ SO ₃ ⁻ , C ₆ H ₄ COO ⁻ or COO ⁻ , R ₆ ^Represents hydrogen or COO ⁻ Y ₂₊ , Y ₁ or Y ₂ represents hydrogen or cations, respectively. The method for producing a liquid fertilizer according to claim 1, wherein the viscosity of the 0.2% by mass aqueous solution of the water-soluble polymer at 25 ° C. is 100 mPa · s or less.