JP5147271B2 - 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. For example, acrylic acid / 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) polymer and 2-hydroxy-3-allyloxypropanesulfonic acid (HAPS) / N-acryloylmorpholine polymer have been proposed. (See Example 43 of Patent Document 1). 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), polyacrylamide (Patent Document 2), polyethylene glycol (Patent Document 3), polyvinylformamide (PNVF) (Patent Document 4), acrylic acid and acrylamide methylpropane A terpolymer using sulfonic acid and substituted acrylamide (Patent Document 5) has been proposed. Further, it is disclosed that a polymer having a high sulfonic acid ratio is effective (Patent Document 6).

  However, although the acrylamide polymer is effective when the concentration of silicic acid in water is low, the effect of preventing adhesion of scale is poor when the concentration of silicic acid is high, for example, when silica is 100 mg / L or more. When polyethylene glycol has a low silicic acid concentration, the effect of preventing the adhesion of scale is recognized, but the effect is not stable because it is easily influenced 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. Although terpolymers of acrylic acid, acrylamidomethylpropane sulfonic acid, and substituted acrylamide have a good anti-scale adhesion effect, they are effective for high-temperature parts, for example, silica-based scales that are produced in water systems of 40 ° C. or higher as a guideline. There is a problem that the effect may not be sufficient for a low-temperature part, for example, a silica-based scale produced in an aqueous system of 30 ° C. or lower.

  Patent Document 6 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. Moreover, the adhesion preventing agent described in Patent Document 1 does not target silica-based scales.

Japanese Patent No. 3832882. JP-A 61-107998. JP-A-2-31894. Japanese Patent Laid-Open No. 11-57783. 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 effectively prevented the adhesion of silica-based soils by using a polymer having both a carboxyl group, a sulfonic acid group, and N-acryloylmorpholine. Based on this finding, the present invention has been completed.

  First, the present invention provides a silica-based antifouling agent containing at least a polymer obtained by copolymerizing a monomer having a carboxyl group, a monomer having a sulfonic acid group, and an N-acryloylmorpholine monomer.

  In particular, the silica-based antifouling agent in which the carboxyl group-containing monomer is 40 to 90 mol%, the sulfonic acid group-containing monomer is 5 to 30 mol%, and the N-acryloylmorpholine is 5 to 50 mol%. Then, silica-based dirt can be efficiently prevented.

  Subsequently, the present invention provides a silica-based antifouling agent containing at least a polymer obtained by copolymerizing a monomer having a carboxyl group, a monomer having a sulfonic acid group, hydroxylalkylacrylic acid, and N-acryloylmorpholine. Provide the agent. By using such a monomer, silica-based soil can be more efficiently prevented.

  The present invention provides a silica-based antifouling agent in which the monomer having a carboxyl group is acrylic acid and the monomer having a sulfonic acid group is isoprenesulfonic acid. By using such a monomer, silica-based soil can be more efficiently prevented.

  The present invention also provides a silica-based antifouling method in which a polymer obtained by copolymerizing a monomer having a carboxyl group, a monomer having a sulfonic acid group, and an N-acryloylmorpholine monomer is added to an aqueous system. . By adding such a polymer, silica-based soil in the system can be efficiently prevented.

  Furthermore, the present invention provides a silica-based soil in which a polymer obtained by copolymerizing a monomer having a carboxyl group, a monomer having a sulfonic acid group, hydroxylalkyl acrylic acid, and N-acryloylmorpholine is added to an aqueous system. Provide prevention methods. By adding such a polymer, silica-based soil in the system can be 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.

  The silica-based antifouling agent according to the present invention contains at least a polymer having a monomer having a carboxyl group, a monomer having a sulfonic acid group, and N-acryloylmorpholine. First, the monomers used will be described below.

  The monomer containing a carboxyl group of the present invention is not particularly limited. For example, maleic acid, acrylic acid, methacrylic acid (hereinafter referred to as “acrylic acid” together with acrylic acid and methacrylic acid), itaconic acid, and these Or a metal salt thereof can be used.

  The monomer containing a sulfonic acid group of the present invention is not particularly limited. For example, vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, isoprene sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, 2-acrylamide- 2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, methacrylic acid-4-sulfobutyl, allyloxybenzenesulfonic acid, methallyloxybenzenesulfonic acid, and their water-soluble metal salts may be used. Although it is possible, it is preferable to use isoprenesulfonic acid.

  In the present invention, N-acryloylmorpholine is used as a monomer (see formula (1)).

  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 the carboxyl group in the polymer, N-acryloylmorpholine is adsorbed on silica, It is considered that sulphonic acid groups in the polymer are dispersed, and thus the precipitates are 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 the present invention, the composition ratio of the monomer containing a carboxyl group, the monomer containing a sulfonic acid group, and N-acryloylmorpholine is not particularly limited, but is preferably 40 to 90/5 to 30/5 to 50. (Mol%), more preferably 40 to 80/10 to 30/5 to 30 (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).

  In the present invention, a nonionic monomer may be further copolymerized. Examples of the copolymerizable nonionic monomer include 2-hydroxylethyl acrylate (see formula (2)), methyl acrylate, ethyl acrylate, monoacrylate of (poly) ethylene oxide having an addition mole number of 1 to 30 (formula (See (3)), (poly) ethylene oxide monovinyl ether (see formula (4)) having 1 to 30 moles of addition, and the like can be used. Here, “acrylate” includes methacrylate. In the present invention, the effect of the present invention can be improved by copolymerizing hydroxyalkyl acrylate. Among these, when 2-hydroxyethyl methacrylate is copolymerized, the effect of the present invention is remarkably improved.

  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.

  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, although it can manufacture by solution polymerization, block polymerization, etc., since N-acryloyl morpholine is hydrophilic, aqueous polymerization can be used conveniently.

  The conditions for the aqueous polymerization are not particularly limited and can be appropriately determined in consideration of the physical properties of the monomer used.For example, an aqueous monomer solution or an aqueous dispersion is prepared, and the pH is adjusted as necessary. After substituting the atmosphere with an inert gas, it can be polymerized by heating to 50 to 100 ° C. 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 10 to 100 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 addition, the simulation cooling water system shown in FIG. 1 was used for the verification of the examples and comparative examples.

First, the simulated cooling water system used will be described. A symbol A in FIG. 1 indicates a simulated cooling water system. Circulating water is sent out from the circulating water pit 1 by the circulation pump 2, transferred by the heat exchanger 3, and guided to the cooling tower 4 (see arrow R). This simulated cooling water system A is a simulated cooling water system with a retained water amount of 100 L having the heat exchanger 3 with a heat transfer area of 0.25 m ² . As the heat exchanger 3, a tube made of SUS304 stainless steel and having an outer diameter of 19 mm was used. A heat exchanger tube (not shown) in the heat exchanger 3 and a non-heat transfer evaluation tube 5 (made of SUS304 stainless steel, outer diameter 19 mm) were provided in the system. The antifouling effect was evaluated by measuring the amount of scale adhered to the exchanger tube and the non-heat transfer evaluation tube 5.

Make-up water is appropriately supplied from the make-up water tank 6 to the circulating water pit 1 by the make-up water pump 7. 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.
The operation was carried out for 30 days while controlling the amount of blow water (circulated water out of the system) from the blow pipe 10 to maintain the concentration factor at 5 times and 7 times, respectively. The concentration ratio was controlled by measuring the concentration ratio of the circulating water using the water level sensor 8 and the conductivity meter 9 and appropriately adjusting the concentration impurities by the blow pipe 10.
During this time, the inlet temperature of the circulating water heat exchanger 3 was maintained at 30 ° C. and the outlet temperature at 40 ° C. Moreover, the passage flow rate of the heat exchanger tube of the circulating water and the non-heat transfer tube 5 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 the evaluation polymer tank 11 and supplied to the circulating water pit 1 by a chemical injection pump 12. 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 13 and the sodium hypochlorite solution was supplied to the circulating water pit 1 by the chemical injection pump 14. 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 adhered to the heat exchanger tube and the non-heat transfer tube 5 was measured to evaluate the antifouling effect. The results are shown in Tables 1 and 2.

<Discussion>
From the results of Tables 1 and 2, the homopolymer of the carboxyl group alone (Comparative Examples 1 and 2) has the lowest antifouling effect, and then a copolymer having a carboxyl group and a sulfonic acid group (Comparative Examples 3 and 4). The antifouling effect increased in the order of the copolymer having a carboxyl group and N-acryloylmorpholine (Comparative Example 5), but the terpolymer having a carboxyl group, a sulfonic acid group and N-acryloylmorpholine (Examples 1 to 3). It was shown that 5) exhibited an excellent adhesion preventing effect. And it was shown that the polymer of Example 7 which further copolymerized 2-hydroxyethyl methacrylic acid (HEMA) to this terpolymer has a more excellent antifouling effect.

  And about the copolymer (Comparative Examples 3 and 4) which has a carboxyl group and a sulfonic acid group, in the case of a concentration factor of 5 times, it has acquired the same dirt adhesion prevention effect as Examples 1-5, but the concentration factor is A difference appeared when the factor was 7 times.

  In addition, from the results of Examples 1 and 4 to 6, although sulfonic acid is any sulfonic acid, it has a certain antifouling effect, among which isoprenesulfonic acid (IPS) is excellent. It has been shown.

Next, changes with time in the permeation flow rate were examined.
First, water quality solutions shown in Table 3 were prepared. Then, as a slime control agent, an isothiazolone-based chlorine compound (“Cliverter (registered trademark) EC503”, manufactured by Kurita Kogyo Co., Ltd.) and an evaluation agent were added at predetermined concentrations. This was supplied to an ultra-low pressure flat membrane “ES-20” manufactured by Nitto Denko Corporation at an operating pressure of 0.75 MPa, and water was passed under conditions of a recovery rate of 80%. Table 4 shows changes with time in the flow velocity.

<Discussion>
As shown in Table 4, when Example 8 was compared with Comparative Examples 6 and 7, it was shown that the polymer according to the present invention was able to maintain a high permeation flow rate.

  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 which concern on this invention.

Explanation of symbols

A Simulated cooling water system 1 Circulating water pit 2 Circulating pump 3 Heat exchanger 4 Cooling tower 5 Non-heat transfer tube 6 Makeup water tank 7 Makeup water pump 8 Water level sensor 9 Conductivity meter
10 Blow piping 11 Evaluation polymer tank 11
12 Chemical Injection Pump 13 Sodium Hypochlorite Tank 14 Chemical Injection Pump

Claims (5)

  A silica-based antifouling agent containing at least a polymer obtained by copolymerizing a monomer having a carboxyl group, a monomer having a sulfonic acid group, and an N-acryloylmorpholine monomer.   A silica-based antifouling agent containing at least a polymer obtained by copolymerizing a monomer having a carboxyl group, a monomer having a sulfonic acid group, a hydroxylalkylacrylic acid, and an N-acryloylmorpholine monomer. The monomer having a carboxyl group is acrylic acid;
The silica-based antifouling agent according to claim 1 or 2, wherein the monomer having a sulfonic acid group is isoprenesulfonic acid.   A silica-based antifouling method in which a polymer obtained by copolymerizing a monomer having a carboxyl group, a monomer having a sulfonic acid group, and an N-acryloylmorpholine monomer is added to an aqueous system.   A silica-based antifouling method in which a polymer obtained by copolymerizing a monomer having a carboxyl group, a monomer having a sulfonic acid group, hydroxylalkyl acrylic acid, and an N-acryloylmorpholine monomer is added to an aqueous system.