JP2000117292A - Calcium oxalate scale inhibitor in paper pulp manufacturing process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calcium oxalate scale inhibitor capable of continuously and efficiently suppressing calcium oxalate scale generated in a paper pulp manufacturing process and having good biodegradability. PROBLEM TO BE SOLVED: To provide a calcium oxalate scale inhibitor in a paper pulp manufacturing process using a polyepoxysuccinic acid derivative obtained by reacting hydroxycarboxylic acid and epoxysuccinic acid at a molar ratio of 1: 3 to 1:30 as an active ingredient. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calcium oxalate scale inhibitor capable of efficiently suppressing calcium oxalate scale generated in a paper pulp manufacturing process.

[0002]

2. Description of the Related Art Raw materials for paper pulp contain oxalic acid components and calcium components which are eluted into process water, and oxidize organic substances in the bleaching process to form oxalic acid components. In some cases, calcium oxalate accumulates in the process water and precipitates as scale, partly due to the presence of calcium components.

[0003] The calcium oxalate scale is remarkable in the hypo stage (hypochlorous acid treatment stage: hereinafter, abbreviated as "H stage") in the bleaching process and in piping and equipment around the hypo stage. Significantly generated in the chlorine stage and its surrounding piping and facilities. It is also produced in the paper machine in the neutral paper making process and in the peripheral equipment. For example,
In the bleaching process, it is generated in a filter wire, a shower nozzle, various pipes, a filtration tank, a bleaching tower, and the like, and in the paper making process, it is generated in a seed box, a stock inlet, and the like, which poses a problem. For example, if a scale is generated in such a place,
Not only deteriorates operability, but also due to filter clogging, reduced drainage, and reduced washability, resulting in inadequate pulp washing and destabilization of pulp quality, requiring large amounts of bleaching chemicals. In addition, the detachment of the adhered scale may cause paper cuts, spots and perforations in the final product, resulting in poor quality, and in some cases, an emergency shutdown.

[0004] Once formed, calcium oxalate scale is difficult to remove by acid washing such as calcium carbonate scale, and is currently mechanically removed.
In order to suppress the formation of scale, a method of controlling scale by using a water-soluble phosphate, a water-soluble phosphonate, a water-soluble phosphinate and an anionic water-soluble polymer electrolyte (Japanese Patent Application Laid-Open No. 61-153199), A method in which an acid salt is used in combination with a water-soluble acrylic acid polymer (JP-A-1-143700), and a method in which a copolymer of maleic acid and another ethylenically unsaturated compound is used [US Pat. No. 5,320,957 (1994)]. ,
A method using polyaminohexamethylene phosphonate [US Pat. No. 5,490,942 (1996)] and the like have been proposed.

[0005] On the other hand, as the preservation of the environment around the factory has come to be called out, phosphorus compounds contained in water discharged from the factory cause eutrophication and red tide when flowing into lakes and marshes, In addition, it has been pointed out that phosphorus compounds and synthetic carboxylic acid compounds are difficult to be decomposed by microorganisms that inhabit the natural world and are therefore likely to accumulate in living organisms. Therefore, a process chemical which does not contain phosphorus and has good biodegradability has come to be desired.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to suppress calcium oxalate scale generated in a paper pulp manufacturing process continuously and efficiently, and to suppress calcium oxalate scale having good biodegradability. To provide an agent.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop a compound effective for inhibiting calcium oxalate scale, and have found that hydroxycarboxylic acid and epoxysuccinic acid have a certain ratio. It has been found that the polyepoxysuccinic acid derivative obtained by the above reaction is suitable for this purpose, and the present invention has been completed.

That is, according to the present invention, the hydroxycarboxylic acid and the epoxy succinic acid are mixed in a ratio of 1: 3 to 1:30.
A calcium oxalate scale inhibitor produced in a paper pulp manufacturing process, characterized in that it contains, as an active ingredient, a polyepoxysuccinic acid derivative obtained by reacting at a molar ratio of: The calcium oxalate scale inhibitor according to claim 1, wherein the acid is at least one selected from tartaric acid, malic acid and citric acid.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The hydroxycarboxylic acid which is one of the raw materials for producing the polyepoxysuccinic acid derivative in the present invention includes tartaric acid, malic acid, citric acid, lactic acid, gluconic acid, glucoheptonic acid, glycolic acid and the like.
Tartaric acid, malic acid and citric acid. These compounds may be used alone or in combination of two or more.

These hydroxycarboxylic acids are structurally distinguished from dextrorotatory and levorotatory ones, but the type of these optical isomers is not limited in the present invention. It may be a racemic body.

Epoxysuccinic acid, which is another raw material for producing the polyepoxysuccinic acid derivative of the present invention, can be produced by a known method, and a specific example thereof is described in US Journal of Organic Chemistry (The Journal of Organic).
ic Chemistry), vol. 24, p. 54 (19
59). That is, cis-epoxysuccinic acid is obtained by reacting maleic anhydride or maleic acid with hydrogen peroxide using a tungstate or the like as a catalyst, and trans-epoxysuccinic acid is formed by reacting hydrogen peroxide with fumaric acid. can get.

In the present invention, the epoxy succinic acid may be either cis epoxy succinic acid or trans epoxy succinic acid, or a mixture of both.

The polymerization reaction between the hydroxycarboxylic acid and the epoxy succinic acid is carried out in an aqueous alkali solution using a hydroxide, oxide or various salts of an alkali metal or an alkaline earth metal, preferably a calcium ion donating compound as a catalyst.

The conditions of the polymerization reaction are not particularly limited, but in order to increase the reaction yield, the pH is preferably 9 or more, particularly preferably 10 to 14, and the reaction temperature is usually 50 to 15
0 ° C. is preferred.

In the present invention, the molar ratio between hydroxycarboxylic acid and epoxysuccinic acid is from 1: 3 to 1:30, preferably from 1: 9 to 1:19. If the molar ratio of epoxysuccinic acid is smaller than this range, the scale suppressing effect is significantly reduced, and if it is larger than this range, insoluble precipitates of calcium may be precipitated when a calcium compound is used as a catalyst.

The catalyst facilitates the reaction between the hydroxycarboxylic acid and the epoxy succinic acid. As described above, the alkali metal or alkaline earth metal hydroxide, oxide or various salts, preferably calcium Calcium compounds that donate calcium ions in an aqueous alkaline solution, such as hydroxides, oxides or various salts, are used. The amount of the catalyst used in the reaction varies depending on the type of the catalyst used, the reaction conditions and the like, and is not determined uniformly, but is usually 0.01 to 1 mol, preferably 0 to 1 mol, per mol of the epoxysuccinic acid. 0.05 to 0.7 mol. However, in the present invention, the type and amount of the catalyst are not limited.

Incidentally, in the case of the epoxy succinic acid homopolymerization reaction, similarly to the polymerization reaction of the hydroxycarboxylic acid and the epoxy succinic acid in the present invention, the epoxy succinic acid may be dissolved in an alkaline aqueous solution.
The reaction is carried out using a hydroxide, oxide or various salts of calcium as a catalyst. However, in this case, a large amount of insoluble matter of calcium is generated, so it is necessary to remove these insoluble matter, and the stability of the generated polyepoxysuccinic acid is poor, and a precipitate is formed during storage. There was such a problem. In contrast, in the present invention, the hydroxycarboxylic acid involved in the polymerization reaction forms a soluble complex having appropriate stability with calcium ions, and has the effect of suppressing the formation of calcium-insoluble substances while maintaining the catalytic ability. I have. Compounds that form chelate compounds that are extremely stable with calcium ions, such as ethylenediaminetetraacetic acid (EDTA), also have the effect of suppressing the formation of calcium insolubles, but calcium ions are completely masked by EDTA, and the catalyst And the polymerization reaction is not carried out smoothly, which is disadvantageous for obtaining a product having a high degree of polymerization.

The weight average molecular weight of the polyepoxysuccinic acid derivative of the present invention is preferably from 500 to 2,000, more preferably from 1,000 to 1,500. Outside this preferred molecular weight range, the scale inhibiting effect may be reduced.

The calcium oxalate scale inhibitor of the present invention is obtained by dissolving the above-mentioned polyepoxysuccinic acid derivative in water or a suitable organic solvent, and adding it during the process.
The addition method may be added at a portion where calcium oxalate scale adheres or at an upstream portion thereof, and is not particularly limited. For example, in the pulp bleaching step, in the pulp slurry before entering the H stage, Alternatively, it is added to the wash water added to the H stage to wash the pulp.

In the paper making step, the pulp slurry is continuously added to the pulp slurry in the seed box, or continuously added to the circulating white water removed by the paper making wire and mixed again with the pulp slurry. In addition, the amount of the calcium oxalate scale inhibitor of the present invention varies depending on the target process conditions and the degree of demand, and cannot be uniformly specified. However, in the bleaching process or the papermaking process, the pulp slurry is not used. 0.1 to 500 pp as a polyepoxysuccinic acid derivative against the liquid inside, washing water or white water
m, preferably 1 to 100 ppm.

[0022]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

[Production of Epoxysuccinic Acid] A production example of disodium epoxysuccinate used in the present invention is shown below. 200 ml of deionized water was put into a 1 L separable flask, and 98.1 g (1 mol) of maleic anhydride was added thereto and dissolved by stirring. While cooling, 125 g of 48% NaOH (1.
5 mol) was slowly added dropwise. The temperature in the system rose to 70 ° C. After cooling to 65 ° C., 132 g of 30% hydrogen peroxide
(1.16 mol) and 5.8 g of sodium tungstate
Was added and dissolved by stirring. Then, 48% NaOH was added to 4%
1.7 g (0.5 mol) was added and maintained at 70 ° C. for 2 hours. Thus, the desired disodium epoxysuccinate aqueous solution (solid content: 34.8%) was obtained.

[Polyepoxysuccinic acid derivatives used in Examples] The polyepoxysuccinic acid derivatives used in Examples are shown below. Polymer-A; tartaric acid / epoxysuccinic acid (reaction molar ratio:
1/3) To a 200 mL separable flask equipped with a reflux tube, 37.29 g (0.075 mol) of an aqueous solution of disodium epoxysuccinate and 3.75 g (0.025 mol) of L-tartaric acid were added.
The pH was adjusted to 10.0 by adding 48% sodium hydroxide. Then, 0.555 g of calcium hydroxide (0.05
075 mol), and the mixture was stirred for 8
Heat at 0 ° C. for 4 hours. Thus, a reaction product solution of tartaric acid and epoxysuccinic acid having a desired reaction molar ratio was obtained. The reaction product was found to have a weight average molecular weight of 14,10 by gel permeation chromatography. Polymer-B: malic acid / epoxysuccinic acid (reaction molar ratio: 1/3) Except for using 3.35 g (0.025 mol) of DL-malic acid as a hydroxycarboxylic acid component in the production of polymer-A Performs the same reaction operation and has a weight average molecular weight of 1
320 reaction products were obtained. Polymer-C; gluconic acid / epoxysuccinic acid (reaction molar ratio: 1/3) In the production of polymer-A, 9.81 g (0.025 mol) of 50% gluconic acid as a hydroxycarboxylic acid component
A reaction product having a weight average molecular weight of 1370 was obtained by performing the same reaction operation except that was used. Polymer-D; malic acid / epoxysuccinic acid (reaction molar ratio: 1/9) In a 200 mL separable flask equipped with a reflux tube, 44.74 g (0.09 mol) of an aqueous solution of disodium epoxysuccinate was added.
3.75 g (0.01 mol) of DL-malic acid was added, and 48
% Sodium hydroxide was added to adjust the pH to 10.0. Then, 0.666 g of calcium hydroxide (0.009
Mol) was added thereto, and the mixture was heated at 80 ° C. for 4 hours with stirring while passing nitrogen gas. Thus, a reaction product solution of malic acid and epoxysuccinic acid having a desired reaction molar ratio was obtained. As a result of gel permeation chromatography measurement, the reaction product was found to have a weight average molecular weight of 14,20. Polymer-E: citric acid / epoxysuccinic acid (reaction molar ratio: 1/9) Except that 3.84 g (0.01 mol) of 50% citric acid was used as a hydroxycarboxylic acid component in the production of polymer-D. Performs the same reaction operation and has a weight average molecular weight of 13
50 reaction products were obtained. Polymer-F; tartaric acid / epoxysuccinic acid (reaction molar ratio:
1/19) To a 200 mL separable flask equipped with a reflux tube, 47.23 g (0.095 mol) of an aqueous solution of disodium epoxysuccinate and 0.75 g (0.005 mol) of L-tartaric acid were added.
The pH was adjusted to 10.0 by adding 48% sodium hydroxide. Then, 0.703 g of calcium hydroxide (0.0
(095 mol) was added thereto, and the mixture was heated at 80 ° C. for 4 hours under aeration with nitrogen gas while stirring. Thus, a reaction product solution of tartaric acid and epoxysuccinic acid having a desired reaction molar ratio was obtained. As a result of gel permeation chromatography measurement, the reaction product was found to have a weight average molecular weight of 1,430. Polymer-G: citric acid / epoxysuccinic acid (reaction molar ratio: 1/19) Except that 1.92 g (0.005 mol) of 50% citric acid was used as a hydroxycarboxylic acid component in production of polymer-F. Performs the same reaction operation and has a weight average molecular weight of 1
380 reaction products were obtained. Polymer-H: malic acid / epoxysuccinic acid (reaction molar ratio: 1/30) In a 200 mL separable flask equipped with a reflux tube, 48.11 g (0.097 mol) of an aqueous solution of disodium epoxysuccinate, 0.1 ml of DL-malic acid. 43 g (0.003 mol) were added and the pH was adjusted to 10.0 by adding 48% sodium hydroxide.
Was adjusted. Then, 0.718 g of calcium hydroxide
(0.0097 mol) was added thereto, and the mixture was heated at 80 ° C. for 4 hours under aeration with nitrogen gas while stirring. Thus, a reaction product solution of tartaric acid and epoxysuccinic acid having a desired reaction molar ratio was obtained. As a result of gel permeation chromatography measurement, the reaction product was found to have a weight average molecular weight of 1320.

[Compounds used in Comparative Examples] The compounds used in Comparative Examples are shown below. Polymer-I; Epoxysuccinic acid homopolymer In a 200 mL separable flask equipped with a reflux tube, 49.72 g (0.1 mol) of an aqueous solution of disodium epoxysuccinate was added, and the pH was adjusted to 10.0 by adding 1N hydrochloric acid. did. Then, 0.74 g (0.01 mol) of calcium hydroxide was added, and the mixture was heated at 80 ° C. for 4 hours under nitrogen gas while stirring. The reaction product was found to have a weight average molecular weight of 1270 by gel permeation chromatography. Polymer-J: malic acid / epoxysuccinic acid (reaction molar ratio: 1/1) In a 200 mL separable flask equipped with a reflux tube, 24.86 g (0.05 mol) of an aqueous solution of disodium epoxysuccinate was added.
6.71 g (0.05 mol) of DL-malic acid was added, and 48
% Sodium hydroxide was added to adjust the pH to 10.0. Then, 0.37 g (0.005 mol) of calcium hydroxide was added, and the mixture was stirred at 80 ° C. under nitrogen gas stream while stirring.
Heated for hours. This reaction product was found to have a weight average molecular weight of 1360 by gel permeation chromatography. Polymer-K: aspartic acid / epoxysuccinic acid (reaction molar ratio: 1/3) In a 200 mL separable flask equipped with a reflux tube, 37.29 g (0.075 mol) of an aqueous disodium epoxysuccinate solution was added.
3.33 (0.025 mol) of L-aspartic acid was added and 4
The pH was adjusted to 10.0 by adding 8% sodium hydroxide. Then, 0.555 g of calcium hydroxide (0.00
75 mol), and the mixture is stirred under a stream of nitrogen gas.
Heated at 0 ° C for 4 hours. The reaction product was found to have a weight average molecular weight of 1480 by gel permeation chromatography. Polymer-L; ethylenediaminetetraacetic acid / epoxysuccinic acid (reaction molar ratio: 1/9) In a 200 mL separable flask equipped with a reflux tube, 44.74 g (0.09 mol) of an aqueous solution of disodium epoxysuccinate and disodium ethylenediaminetetraacetate were added. Dihydrate3.
72 g (0.01 mol) were added and the pH was adjusted to 10.0 by adding 48% sodium hydroxide. Then, 0.666 g (0.009 mol) of calcium hydroxide was added,
The mixture was heated at 80 ° C. for 4 hours under nitrogen gas while stirring.
The reaction product was found to have a weight average molecular weight of 780 by gel permeation chromatography. Polymer-M: Acrylic acid homopolymer (weight average molecular weight 5
000) "AQUALIC DL-40" (trade name) manufactured by Nippon Shokubai Co., Ltd. was used. Compound-N: sodium hexametaphosphate A special grade reagent manufactured by Kanto Chemical Co., Ltd. was used. Compound-O: Malic acid "malic acid 50B" (trade name) manufactured by Fuso Chemical Co., Ltd. was used.

[Evaluation of Effect of Preventing Precipitation of Calcium Oxalate] <Test 1> The H-stage filtrate collected from the bleaching process of the pulp mill was subjected to No. 2 filtration. 6 Filtrate filtered through a quantitative filter paper (calcium ion concentration: 40 ppm, oxalate ion concentration: 17 ppm, p
H: 7.0), after adding a predetermined amount of various scale inhibitors, sodium oxalate [Kanto Chemical Co., Ltd. special grade reagent]
Was added as oxalate ions, and the pH was adjusted to 7.0 with dilute hydrochloric acid and dilute sodium hydroxide. After allowing this test solution to stand at 65 ° C. for 1 hour, the concentration of the suspended substance (hereinafter abbreviated as “SS”) in the test solution was measured by Nippon Seimitsu Kogaku Co., Ltd.
The scale inhibition rate was determined by the following equation using a Poic integrating sphere SS densitometer manufactured by the company. The precipitated suspended substance was confirmed to be calcium oxalate by an infrared spectrophotometer.

[0027]

(Equation 1)

The results are shown in Table 1.

[Table 1]

<Test 2> White water collected from a paper mill in a neutral papermaking process [total calcium concentration: 352 ppm (dissolved calcium ion concentration: 223 ppm), total oxalic acid concentration: 5 ppm (dissolved oxalate ion concentration: 5 pp)
m), pH 7.2], adding a predetermined amount of various scale inhibitors and stirring for 10 minutes. 6 Filtered with a quantitative filter paper. After adding 50 ppm of sodium oxalate [special grade reagent manufactured by Kanto Chemical Co., Ltd.] as oxalate ions to the filtrate, the pH was adjusted to 7.2 with dilute hydrochloric acid and dilute sodium hydroxide. After the test solution was allowed to stand at 40 ° C. for 1 hour, the concentration of a suspended substance (hereinafter abbreviated as “SS”) in the test solution was measured with a Poick integrating sphere SS densitometer manufactured by Nippon Seimitsu Kogaku KK The scale suppression rate was determined by the following equation. The precipitated suspended substance was confirmed to be calcium oxalate by an infrared spectrophotometer.

[0030]

(Equation 2)

The results are shown in Table 2.

[Table 2]

From the results shown in Tables 1 and 2, it can be seen that the compounds of the present invention have an extremely high effect of inhibiting calcium oxalate precipitation.

[0033]

By applying the scale inhibitor of the present invention,
With a small amount of use, calcium oxalate scale generated in the pulp and paper manufacturing process can be effectively suppressed, the operability is deteriorated due to the adhesion of the scale, the cost of bleaching chemicals is increased, the pulp quality is unstable, and the final product is inefficient. Many problems can be solved, such as the increase in non-defective products, which will benefit the pulp and paper industry. Further, since the scale inhibitor of the present invention has good biodegradability and does not contain phosphorus, it may cause a pollution problem in the surrounding environment even when it is discharged as wastewater from the paper pulp manufacturing process. There is a great advantage that it can be applied without worry.

Claims (2)

[Claims] 1. A paper pulp production process comprising, as an active ingredient, a polyepoxysuccinic acid derivative obtained by reacting a hydroxycarboxylic acid and an epoxy succinic acid in a molar ratio of 1: 3 to 1:30. Calcium Oxalate Scale Inhibitor in Japan. 2. The hydroxycarboxylic acid is at least one selected from tartaric acid, malic acid and citric acid.
The calcium oxalate scale inhibitor in the paper pulp manufacturing process according to the above.