JP5085962B2 - Silica-based antifouling agent and silica-based antifouling method - Google Patents

Description

  The present invention relates to a silica-based antifouling agent and a silica-based antifouling method. More specifically, the present invention relates to a technology for preventing silica-based dirt generated in a cooling water system, a boiler water system, a membrane processing apparatus, and the like.

  In a cooling water system, a boiler water system, a membrane processing apparatus, etc., a scale failure occurs on a heat transfer surface, piping, membrane surface, etc. that come into contact with water. The scale is deposited when calcium ions, magnesium ions, and the like contained in water are concentrated, and adheres to the inner surfaces of pipes and equipment. Such scale obstacles are particularly conducive to resource conservation and energy conservation, while reducing the amount of cooling water discharged outside the system and highly concentrating cooling water (operation with a high recovery rate in the case of a separation membrane). It is likely to occur in the case of a circulating water system.

  If this scale adheres to the heat exchange section, it causes heat transfer inhibition. Adhesion to piping causes a decrease in flow rate. Adhesion to the film causes a decrease in flux. Further, when the attached scale is peeled off, it circulates in the system, which may cause clogging / wearing of pumps, piping, heat exchangers, and the like.

  Examples of the scale species include calcium carbonate, calcium sulfate, calcium sulfite, calcium phosphate, magnesium hydroxide, zinc phosphate, zinc hydroxide, basic zinc carbonate, calcium silicate, and magnesium silicate.

  Among these, in particular, the silica-based scale (or silica-based soil) is difficult to cope with in that it takes a number of low-solubility chemical forms depending on the quality of water used (for example, pH). For example, when monomer silica is polymerized, it exists as oligomer silica, colloidal silica or the like, or exists as silicate ions. This generation of silica-based scale is difficult to cope with in that metal hydroxides such as magnesium, aluminum, and zinc are involved.

  Further, when silica-based scale (or silica-based soil) is stuck to a wall surface or the like, it becomes hard and has a property that it is difficult to scrape even if scratched with a screwdriver or the like. Such silica-based scales are not only for heat transfer inhibition due to adhesion to heat exchangers, etc., but also to flow reduction due to adhesion to non-heated surfaces such as piping, etc. It also causes problems due to circulation. For example, in the case of cooling water, a failure in which a predetermined cooling capacity cannot be obtained due to a decrease in the flow rate of cooling water, a failure in which cooling efficiency decreases due to a scale attached to a cooling tower, etc., or a scale attached to the cooling tower etc. It may cause troubles such as clogging heat exchangers.

  As an inhibitor for calcium scale and magnesium scale, carboxyl group-containing compounds such as maleic acid, acrylic acid and itaconic acid are effective, and vinyl sulfonic acid, allyl sulfonic acid, 2-acrylamide-2- As a scale inhibitor, a vinyl monomer having a sulfonic acid group such as methyl-1-propanesulfonic acid (AMPS) or a nonionic vinyl monomer such as acrylamide combined in accordance with the target water quality is used. In addition, inorganic polyphosphoric acids such as sodium hexametaphosphate and sodium tripolyphosphate, and phosphonic acids such as hydroxyethylidene diphosphonic acid and phosphonobutanetricarboxylic acid are also used.

  On the other hand, as an inhibitor for silica-based scale (or silica-based soil), polyethylene glycol (Patent Document 1), polyvinylformamide (PNVF) (Patent Document 2), polyacrylamide (Patent Document 3), acrylic acid and acrylamidomethylpropane A terpolymer (Patent Document 4) composed of sulfonic acid and substituted acrylamide has been proposed. Further, it is disclosed that a polymer having a high sulfonic acid ratio is effective (Patent Document 5).

  However, polyethylene glycol has an effect of preventing the adhesion of scale when the silicic acid concentration is low, but the effect is not stable because it is easily affected by other coexisting ions. Since polyvinylformamide is cationic, those having a high composition ratio are easily adsorbed by a metal constituting an aqueous system such as a pipe. The acrylamide polymer is effective when the concentration of silicic acid in water is low, but when the concentration of silicic acid is high, for example, when silica is 100 mg / L or more, the effect of preventing adhesion of scale is poor. Although terpolymers of acrylic acid, acrylamide methylpropane sulfonic acid and substituted acrylamide have good anti-scale adhesion effects, they are effective for high-temperature parts, for example, silica-based scales produced in aqueous systems at 40 ° C or higher. However, there is a problem that the effect may not be sufficient for a silica-based scale generated in a low temperature part, for example, an aqueous system of 30 ° C. or less.

  Patent Document 5 discloses that a polymer having a high sulfonic acid ratio is effective against silica-based soil (or silica-based scale), but there are cases where the effect of preventing soil adhesion is still insufficient.

JP-A-2-31894. Japanese Patent Laid-Open No. 11-57783. JP-A 61-107998. Japanese Patent No. 3055815. JP 2006-88036 A.

  Therefore, the main object of the present invention is to prevent silica-based dirt generated in a cooling water system, a boiler water system, a membrane processing apparatus, and the like. In the present application, “silica-based scale” and “silica-based soil” are collectively referred to as “silica-based soil”.

  As a result of intensive studies to solve the above problems, the inventors of the present application have made it possible to attach silica-based soils by using a polymer having both a carboxyl group, isoprenesulfonic acid, and an unsubstituted or substituted acrylamide or ether group. The following invention was completed based on this finding.

First, the present invention provides a silica-based antifouling agent containing at least a polymer obtained by copolymerizing a monomer having a carboxyl group, an isoprenesulfonic acid monomer, and a monomer having an unsubstituted or substituted acrylamide.
In particular, silica-based soil prevention, in which the carboxyl group-containing monomer is 40 to 90 mol%, the isoprenesulfonic acid monomer is 5 to 30 mol%, and the unsubstituted or substituted acrylamide monomer is 5 to 30 mol%. When used as an agent, silica-based soil can be efficiently prevented.

Subsequently, the present invention provides a silica-based antifouling agent containing at least a monomer having a carboxyl group, an isoprene sulfonic acid monomer, and a monomer having an ether group. By using such a monomer, silica-based soil can be more efficiently prevented.
In particular, the silica-based antifouling agent is 40 to 90 mol% of the monomer having a carboxyl group, 5 to 30 mol% of the isoprenesulfonic acid monomer, and 5 to 30 mol% of the monomer having an ether group. It is possible to prevent silica-based dirt more efficiently.

  The present invention also provides a silica-based antifouling agent using a quaternary or higher polymer obtained by copolymerizing a hydroxyalkyl acrylate monomer in addition to the monomer. By using such a monomer, silica-based soil can be more efficiently prevented. In the present invention, “acrylate” includes a methacrylate structure.

  The present invention also provides a method for preventing silica-based soiling, in which a polymer obtained by copolymerizing a monomer having a carboxyl group, an isoprenesulfonic acid monomer, and a monomer having an unsubstituted or substituted acrylamide is added to an aqueous system. To do. By adding such a polymer, silica-based soil in the system can be efficiently prevented.

  Furthermore, the present invention provides a method for preventing silica-based soiling, in which a polymer obtained by copolymerizing a monomer having a carboxyl group, an isoprene sulfonic acid monomer, and a monomer having an ether group is added to an aqueous system. By adding such a polymer, silica-based soil in the system can be efficiently prevented.

  The present invention also provides a method for preventing silica-based soiling, wherein a quaternary or higher polymer copolymerized with a hydroxyalkyl acrylate monomer in addition to the monomer is added to an aqueous system. By using such a polymer, silica-based soil can be more efficiently prevented.

  ADVANTAGE OF THE INVENTION According to this invention, the silica type stain | pollution | contamination which generate | occur | produces with a cooling water system, a boiler water system, a membrane processing apparatus etc. can be prevented efficiently.

  Hereinafter, preferred embodiments according to the present invention will be described with reference to the accompanying drawings. Each embodiment shown in the accompanying drawings shows an example of a typical embodiment according to the present invention, and the scope of the present invention is not interpreted narrowly.

  One of the silica-based antifouling agents according to the present invention contains a polymer obtained by copolymerizing a monomer having a carboxyl group, an isoprenesulfonic acid monomer, and a monomer having an unsubstituted or substituted acrylamide. In addition, one of the silica-based antifouling agents according to the present invention contains a polymer obtained by copolymerizing a monomer having a carboxyl group, an isoprenesulfonic acid monomer, and a monomer having an ether group. First, the monomers used will be described below.

  In the present invention, a monomer having a carboxyl group is used as the monomer. For example, maleic acid, acrylic acid, methacrylic acid (hereinafter, acrylic acid and methacrylic acid are collectively referred to as “acrylic acid”), itaconic acid, and these metals A salt or the like can be used.

  In the present invention, isoprenesulfonic acid (= 2-methyl-1,3-butadiene-1-sulfonic acid) is used as a monomer (see formula (1)). In the present invention, a water-soluble metal salt of isoprene sulfonic acid may be used.

In the present invention, a monomer having unsubstituted or substituted acrylamide is used as the monomer (see formula (2)). The monomer structure is not particularly limited, and for example, acrylamide, N-dimethylacrylamide, N-diethylacrylamide, N-isopropylacrylamide, or the like or a metal salt thereof can be used as the compound represented by the formula (2) .

  Examples of the monomer having an ether group of the present invention include (poly) ethylene oxide monoacrylate having 2 to 30 addition moles (see formula (3)) and (poly) propylene oxide monoacrylate having 2 to 30 addition moles. Further, monovinyl ether of (poly) ethylene oxide having an addition mole number of 1 to 30 (see formula (4)), monovinyl ether of (poly) propylene oxide having an addition mole number of 1 to 30, and the like can be used. Here, “acrylate” includes methacrylate. And in this invention, said ethylene oxide and propylene oxide may be mixed in a polymer, and the sum total of the addition mole number in that case should just be 2-30 mol.

  In the present invention, a monomer having a carboxyl group / a monomer having an isoprene sulfonic acid / a monomer having an unsubstituted or substituted acrylamide or a monomer having a carboxyl group / a monomer having an isoprene sulfonic acid / an ether group. The effects of the present invention can be remarkably improved by using a quaternary copolymer obtained by copolymerizing a hydroxyalkyl acrylate monomer with respect to the terpolymer of the monomer. In particular, it is desirable to use a 2-hydroxyalkyl acrylate monomer, and among them, it is more preferable to use a 2-hydroxyethyl acrylate (HEMA; see formula (5)) monomer.

  In the present invention, if necessary, a cationic monomer may be further copolymerized. As the copolymerizable cationic monomer, for example, allylamine, dimethyl monoethyl acrylate, quaternary ammonium salt or tertiary ammonium salt of diethylaminoethyl acrylate, diallyldimethylammonium chloride and the like can be used.

  In the present invention, the mechanism of action to prevent silica-based scale is not clear, but hydroxides such as aluminum, magnesium and zinc are adsorbed on carboxyl groups in the polymer, and substituted acrylamide and ether groups are adsorbed on silica. Furthermore, it is considered that sulphonic acid groups in the polymer are dispersed, and thus the precipitates can be efficiently dispersed in water to prevent scaling.

  That is, the polymer contained in the antifouling agent according to the present invention not only prevents the hardness component compounds from gathering and crystallizing (scaling), but also not only silica that is a component of the silica-based scale. It is a polymer that can firmly adsorb aluminum, magnesium, zinc, etc., which affect this, and efficiently disperse them. In particular, this tendency is remarkably exhibited in low temperature conditions such as a low temperature part of an aqueous plant.

  In the silica-based antifouling agent according to the present invention, the composition ratio of the monomer having a carboxyl group, the isoprenesulfonic acid, and the monomer having an unsubstituted or substituted acrylamide is not particularly limited, but is preferably 40 to 90/5. It is desirable that it is ˜30 / 5 to 30 (mol%), more preferably 60 to 80/10 to 30/5 to 15 (mol%).

  Further, in the silica-based antifouling agent according to the present invention, the composition ratio of the monomer having a carboxyl group, the isoprenesulfonic acid, and the monomer having an ether group is not particularly limited, but is preferably 40 to 90/5. 30/5 to 30 (mol%), more preferably 60 to 80/10 to 30/5 to 15 (mol%).

  Furthermore, in this invention, it is good also as a quaternary copolymer which copolymerized the monomer which has a carboxyl group, the isoprenesulfonic acid, the monomer which has an unsubstituted or substituted acrylamide, and the monomer which has an ether group. And although it does not specifically limit about the said quaternary copolymer monomer composition ratio, Preferably it is 20-85 / 5-5-30 / 5-5 / 5-20 (mol%), More preferably, it is 40-80. It is desirable that it is / 10-30 / 5-5-15 / 5-15 (mol%).

The molecular weight of the polymer used as the silica-based antifouling agent according to the present invention is not particularly limited, but preferably the weight average molecular weight (M _w ) is 500 to 500,000, more preferably 5000 to 100,000. desirable. When the weight average molecular weight is less than 500, a sufficient antifouling effect cannot be exhibited. When the weight average molecular weight is greater than 100,000, the viscosity of the polymer becomes high and handling is difficult. This weight average molecular weight is measured by gel permeation chromatography (GPC, solvent: phosphate buffer, standard: acrylic acid).

  The method for producing the polymer used as the silica-based antifouling agent according to the present invention is not particularly limited, and conventionally known polymerization methods can be appropriately employed. For example, it can be produced by solution polymerization or bulk polymerization. The polymerization conditions and the like are not particularly limited and can be appropriately determined in consideration of the physical properties of the monomers used.For example, in the case of aqueous polymerization, an aqueous monomer solution or aqueous dispersion is prepared, and the pH is adjusted as necessary. After adjusting and substituting atmosphere with an inert gas, it can superpose | polymerize by heating to 50-100 degreeC and adding a water-soluble polymerization initiator.

  Examples of the water-soluble polymerization initiator include 2,2′-azobis- (2-aminodipropane) dihydrochloride, azobis-N, N′-dimethyleneisobutylamidine dihydrochloride, 4,4′-azobis- ( Water-soluble azo compounds such as 4-cyanovaleric acid) -2-sodium, persulfates such as ammonium persulfate, sodium persulfate and potassium persulfate, and water-soluble peroxides such as hydrogen peroxide and sodium periodate Etc. can be used.

  The aqueous polymerization polymerization reaction can be completed, for example, in 3 to 6 hours and allowed to cool to obtain an aqueous polymer solution or aqueous dispersion. The polymerization can be performed not only in an aqueous medium but also by solution polymerization, suspension polymerization, emulsion polymerization or the like in a general organic solvent.

  The method of using the silica-based antifouling agent of the present invention is not particularly limited, and it can be added to a place where it is desired to prevent the formation and adhesion of scale fouling, or a place immediately before that. The antifouling agent of the present invention can be used regardless of operating conditions and water quality conditions such as a cooling water system and a boiler water system. For example, the antifouling agent of the present invention can be added to various water-based circulating water and makeup water.

  The antifouling agent of the present invention can be used for both low-temperature water and high-temperature water, and particularly for silica-based soils having a high concentration such as calcium or magnesium having a high concentration factor (6 times or more). It can be used effectively.

  Moreover, since an aluminum compound such as polyaluminum chloride (PAC) is usually used as a flocculant used for turbidization of industrial water due to deterioration of water quality, this water tends to have a high aluminum concentration derived from the flocculant. is there. The inventors of the present application have found that silica-based soil containing aluminum adheres in an aqueous system using such water having a high aluminum concentration. Further, it has also been found that in a membrane treatment apparatus for irrigation water, silica-based dirt containing aluminum adheres to the membrane when the turbidity is removed with the flocculant as a pretreatment for preventing clogging of the membrane. The antifouling agent of the present invention can also be used effectively against silica-based dirt that occurs in such situations.

  The addition amount of the antifouling agent of the present invention is not particularly limited and can be appropriately selected according to the quality of the water to be added, but the polymer concentration in the applied water is preferably 1 to 200 mg / L. It is desirable to add such that the polymer concentration is 1 to 30 mg / L.

  The scale-based antifouling agent of the present invention can be used in combination with other scale inhibitors as required. Examples of scale inhibitors that can be used in combination include nitrilotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, phosphonobutanetricarboxylic acid, tripolyphosphoric acid, hexametaphosphoric acid, acrylic acid, maleic acid, and acrylic acid sulfonic acid copolymer. , And water-soluble metal salts thereof can be used.

  Furthermore, the antifouling agent of the present invention may contain an anticorrosive agent such as organic phosphonic acid or zinc chloride, hydrazine, S-chloro-2-methyl-4-isothiazolin-3-one (Cl-MIT), if necessary. These can be used in combination with a hypochlorous acid-sulfamic acid-based disinfectant or antibacterial agent, or these chemicals can be added separately.

  Hereinafter, the present invention will be described in more detail with reference to examples. The invention is not limited by the examples shown here. In this example, the high temperature part and the low temperature part were respectively verified, and the silica-based antifouling effect was verified.

<Evaluation at high temperature part>
First, the simulated cooling water system used will be described. FIG. 1 is a diagram for explaining the concept and configuration of a preferred embodiment of a silica-based antifouling method in a high temperature part according to the present invention. In the simulated cooling water system shown in FIG. 1, the circulating water is sent out from the circulating water pit 1 (retained water amount 100 L) by the circulating pump 2 and circulated to the circulating water pit 1 via the heating unit 3 (see arrow R). . At that time, the amount of circulating water was adjusted by the flow rate control valve 5. The heating unit 3 was provided with an evaluation tube 4 (made of SUS304 stainless steel, outer diameter 19 mm).

  For the operation of the circulating water system, synthetic water is prepared in advance, this synthetic water is stored in the make-up water tank 6 (retained water amount 300 L), and is injected by the make-up water pump 7 so that the residence time is 24 hours. did. During this period, the circulating water temperature was maintained at 30 ° C., and when it reached 30 ° C. or higher, the circulating water was cooled by operating the chiller 8. The surface temperature of the evaluation tube 4 was set to 90 ° C. with a constant electric energy, and the flow rate of circulating water in the evaluation tube 4 was maintained at 0.5 m / s.

The water quality conditions of the circulating water used were pH 9.0, silica concentration 150 mg / L as SiO ₂ , calcium concentration 300 mg / L as CaCO ₃ , and magnesium concentration 150 mg / L as MgCO ₃ . Further, the turbidity of the water quality was controlled as necessary, and batch treatment was performed once a day so that the turbidity was equivalent to 10 degrees.

An evaluation polymer (used as a silica-based antifouling agent) and a calcium-based antifouling agent were supplied to the circulating water pit 1. The evaluation polymer was set to have a solid content concentration of 15 mg / L as solid. As the calcium-based scale inhibitor, sodium hydroxydiethylidenephosphonate was added to 6 mg / L as PO ₄ .

  After the operation for 30 days, the amount of scale adhered to the evaluation tube 4 was measured, and the stain adhesion rate of the heating portion was calculated by the following calculation formula (1) to evaluate the stain prevention effect of the high temperature portion.

<Evaluation at non-heated part>
First, the simulated cooling water system used will be described. FIG. 2 is a diagram for explaining the concept and configuration of a preferred embodiment of the silica-based antifouling method in the low temperature part according to the present invention. In the simulated cooling water system shown in FIG. 2, the circulating water is sent out from the circulating water pit 21 by the circulation pump 22, transferred by the heat exchanger 23, and guided to the cooling tower 24 (see arrow R). This simulated cooling water system is a simulated cooling water system with a retained water amount of 100 L having a heat exchanger 23 with a heat transfer area of 0.25 m ² . As the heat exchanger 23, a tube made of SUS304 stainless steel and having an outer diameter of 19 mm was used.
A non-heat transfer evaluation tube 25 (SUS304 stainless steel, outer diameter 19 mm) was provided in the system. The antifouling effect was evaluated by measuring the amount of scale attached to the non-heat transfer evaluation tube 25.

Make-up water is appropriately supplied from the make-up water tank 26 to the circulating water pit 21 by the make-up water pump 27. The makeup water was operated using actual industrial water (Kawasaki City Industrial Water). This industrial water has a silica concentration of 25 mg / L as SiO ₂ and an aluminum concentration of 0.5 mg / L as Al.
The operation was performed for 30 days while controlling the amount of blow water (circulated water out of the system) from the blow pipe 30 to maintain the concentration factor at 7 times. The concentration ratio was controlled by measuring the concentration ratio of the circulating water using the water level sensor 28 and the conductivity meter 29 and appropriately adjusting the concentration impurities by the blow pipe 30.
During this time, the inlet temperature of the circulating water heat exchanger 23 was maintained at 30 ° C. and the outlet temperature at 40 ° C. Moreover, the passage flow rate of the non-heat transfer evaluation tube 25 of circulating water was maintained at 0.5 m / s.

An evaluation polymer (used as a silica-based antifouling agent) and a calcium-based antifouling agent were charged into an evaluation polymer tank 31 and supplied to the circulating water pit 21 by a chemical injection pump 32. The evaluation polymer was set to have a solid content concentration of 15 mg / L as solid. As the calcium-based scale inhibitor, sodium hydroxydiethylidenephosphonate was added to 6 mg / L as PO ₄ .

For slime control treatment, sodium hypochlorite was put into the sodium hypochlorite tank 33 and the sodium hypochlorite solution was supplied to the circulating water pit 1 by the chemical injection pump 34. The slime control agent was set to be sodium hypochlorite 0.5 to 1.0 mg / L as Cl ₂ .

  After operating for 30 days, the amount of scale attached to the non-heat transfer evaluation tube 5 is measured, and the dirt adhesion rate of the non-heated part is calculated based on the above formula (1), and the effect of preventing dirt at the low temperature part is obtained. evaluated.

  In these verifications, the polymers shown in Examples 1 to 6 and Comparative Examples 1 to 4 were used as evaluation polymers. Tables 1 and 2 show the results of each experiment.

<Discussion>
From the results of Tables 1 and 2, when Example 1 and Comparative Example 2 are compared, among the terpolymers containing acrylic acid / sulfonic acid / unsubstituted or substituted acrylamide, the sulfonic acid group is isoprenesulfonic acid. It has been shown that the polymer is a high antifouling effect. Further, Example 6 also showed that the polymer containing acrylic acid / isoprenesulfonic acid / ether group had a high antifouling effect.
When Examples 2, 3, and 4 were compared with Comparative Example 1, it was shown that the polymer having unsubstituted or substituted acrylamide had a high antifouling effect.
From Comparative Examples 2 and 3, when the sulfonic acid group is 2-acrylamido-2-methylpropanesulfonic acid (AMPS), the effect of the presence or absence of 2-hydroxyethyl methacrylate (HEMA) is not observed. According to the above, it was shown that the antifouling effect was further increased by copolymerizing 2-hydroxyethyl methacrylate.

  In Comparative Examples 1 to 4, the effect of preventing the adhesion of dirt at the heating part is recognized to some extent, but the effect of preventing the adhesion of dirt at the non-heating part is small. On the other hand, in Examples 1 to 6, it was shown that the effect of preventing the adhesion of dirt was high whether it was a heating part or a non-heating part.

  As mentioned above, according to the present Example, it was shown that the polymer which concerns on this invention has the antifouling effect outstanding as a silica type | system | group antifouling agent and a silica type antifouling method.

  INDUSTRIAL APPLICABILITY The present invention can be used in a wide range of industrial fields including geothermal power plants as a technique for preventing silica-based dirt, particularly as a technique for preventing silica-based dirt generated in cooling water systems, boiler water systems, membrane treatment devices, and the like.

It is a figure for demonstrating the concept and structure of suitable embodiment of the silica type dirt prevention method in the high temperature part which concerns on this invention. It is a figure for demonstrating the concept and structure of suitable embodiment of the silica type pollution prevention method in the low temperature part which concerns on this invention.

Explanation of symbols

1,21 Circulating water pits 2,22 Circulating pump 3 Heating part 4 Evaluation tube 25 Non-heat transfer evaluation tube

Claims (4)

A silica-based antifouling agent containing at least a polymer obtained by copolymerizing a monomer having a carboxyl group, an isoprenesulfonic acid monomer, and a monomer having an unsubstituted or substituted acrylamide represented by the following formula (2) .
The silica-based antifouling agent according to claim 1, wherein the polymer is a quaternary or higher polymer obtained by copolymerizing a hydroxyalkyl acrylate monomer. Silica-based soil prevention by adding a polymer obtained by copolymerizing a monomer having a carboxyl group, an isoprenesulfonic acid monomer, and a monomer having an unsubstituted or substituted acrylamide represented by the following formula (2) to an aqueous system Method.
4. The silica-based soil prevention method according to claim 3, wherein the polymer is a quaternary or higher polymer obtained by copolymerizing a hydroxyalkyl acrylate monomer.