WO2012132892A1 - Scale preventing agent for reverse osmosis membrane and scale preventing method - Google Patents

Scale preventing agent for reverse osmosis membrane and scale preventing method Download PDF

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Publication number
WO2012132892A1
WO2012132892A1 PCT/JP2012/056500 JP2012056500W WO2012132892A1 WO 2012132892 A1 WO2012132892 A1 WO 2012132892A1 JP 2012056500 W JP2012056500 W JP 2012056500W WO 2012132892 A1 WO2012132892 A1 WO 2012132892A1
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scale
meth
acid
water
reverse osmosis
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PCT/JP2012/056500
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French (fr)
Japanese (ja)
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育子 西田
賢二 木幡
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栗田工業株式会社
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Priority to JP2012515836A priority Critical patent/JPWO2012132892A1/en
Priority to CN2012800154808A priority patent/CN103476714A/en
Publication of WO2012132892A1 publication Critical patent/WO2012132892A1/en

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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/08—Prevention of membrane fouling or of concentration polarisation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
    • C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
    • C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
    • C02F5/12—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances containing nitrogen
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F14/00—Inhibiting incrustation in apparatus for heating liquids for physical or chemical purposes
    • C23F14/02—Inhibiting incrustation in apparatus for heating liquids for physical or chemical purposes by chemical means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/16—Use of chemical agents
    • B01D2321/168—Use of other chemical agents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/22—Eliminating or preventing deposits, scale removal, scale prevention

Definitions

  • the present invention relates to a scale inhibitor for reverse osmosis membranes and a scale prevention method. More specifically, the present invention relates to a scale inhibitor and a scale prevention method for preventing adhesion of calcium phosphate scale generated in film treatment.
  • the scale generated in the heat exchange section causes heat transfer inhibition
  • the scale attached to the pipe causes a decrease in flow rate
  • the scale attached to the film causes a decrease in flux.
  • the generated scale is peeled off, it circulates in the system and causes the pump, the piping and the heat exchanging section to be blocked. Further, along with the blockage, the scaling in the pipe and the heat exchanging section is promoted.
  • a similar phenomenon can occur in the reduction well of a geothermal power plant.
  • Scale species generated in these aqueous systems include calcium phosphate, calcium carbonate, calcium sulfate, calcium sulfite, calcium silicate, magnesium silicate, magnesium hydroxide, zinc phosphate, zinc hydroxide, and basic zinc carbonate.
  • inorganic polyphosphoric acids such as sodium hexametaphosphate and sodium tripolyphosphate
  • phosphonic acids such as hydroxyethylidene diphosphonic acid and phosphonobutanetricarboxylic acid
  • maleic acid acrylic acid and itaconic acid
  • vinyl monomers having sulfonic acid groups such as vinyl sulfonic acid, allyl sulfonic acid and 3-allyloxy-2-hydroxypropane sulfonic acid, and nonionic vinyl monomers such as acrylamide are included
  • Copolymers combined according to water quality are used as scale inhibitors.
  • examples of the scale species generated in the reverse osmosis membrane (RO membrane) treatment include calcium phosphate, calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, and magnesium hydroxide.
  • the scale inhibitor generally has a relatively low molecular weight and a high scale prevention effect. Therefore, inorganic polyphosphates such as sodium hexametaphosphate and sodium tripolyphosphate, aminomethylphosphonic acid, hydroxyethylidene diphosphonic acid and phosphonobu Materials containing phosphorus such as phosphonic acids such as tantricarboxylic acid are used.
  • Patent Document 1 a terpolymer composed of monomers such as polyether polyaminomethylene phosphonate and acrylic acid is combined with hydroxyphosphonoacetic acid
  • Patent Document 3 A method using ⁇ -polyaspartic acid has also been proposed (see Patent Document 3).
  • a copolymer obtained by polymerizing monomers such as acrylic acid and sulfonic acid is used as a scale inhibitor (see Patent Documents 4 to 6).
  • the copolymer used in the scale inhibitors described in Patent Documents 4 to 6 is also free of phosphorus.
  • all these conventional scale inhibitors are premised on use in boilers and cooling water systems. It is difficult to say that it is suitable for RO membrane treatment.
  • scales generated in cooling water, evaporative concentration, boilers, etc. adhere to the surface of a heat exchanger or the like with a certain thickness, thereby causing heat transfer inhibition or affecting the stabilization of equipment.
  • the scale attached to the surface acts as an anticorrosion coating, and therefore some scale generation is allowed.
  • a scale inhibitor such as a cooling water system is required to have the ability to suppress the generated scale growth, and can be applied as long as it has a certain precipitation suppressing effect and gelation resistance.
  • the range of physical properties (molecular weight, composition, etc.) applicable as a scale inhibitor is wide.
  • RO membrane treatment has a small water flow path, and when fine precipitates such as scales and coexisting ions and scale inhibitor gels are formed, the membrane surface is clogged, affecting membrane treatment performance. .
  • the scale inhibitor for RO membrane treatment is required not to generate fine precipitates, and even if it is a material that can be applied in cooling water, evaporative concentration, etc., further limited physical property conditions are required. It is necessary to have.
  • the temperature at the location where scale should be prevented is lower, the residence time of water is shorter, and generally the concentration of the scale inhibitor added is lower than in the cooling water system.
  • the temperature at the place where scale should be prevented is about 10 to 40 ° C. in the RO membrane treatment, whereas it is 50 to 90 ° C. in the cooling water system or the like.
  • the residence time of water is about 15 minutes for the RO membrane treatment, whereas it is about 20 to 100 hours for the cooling water system.
  • the concentration of the scale inhibitor added is about 1 to 10 mg / L for the RO membrane treatment, whereas it is about 5 to 50 mg / L for the cooling water system.
  • the scale inhibitor for RO membrane treatment is different from the scale inhibitor used in other systems such as cooling water system, the processing conditions and required characteristics are different, the scale inhibitor such as cooling water system is treated with RO membrane treatment. Even if it is used, the same effect cannot be obtained.
  • the present invention is for a reverse osmosis membrane that can suppress the precipitation of calcium phosphate scale generated in the osmosis membrane treatment without increasing the phosphorus concentration in the waste water, and does not produce a fine precipitate such as a gelled product.
  • the main object is to provide a scale inhibitor and a scale prevention method.
  • the scale inhibitor for reverse osmosis membrane according to the present invention is a scale inhibitor that suppresses the precipitation of calcium phosphate scale in the reverse osmosis membrane treatment.
  • the main component is a unit derived from (meth) acrylic acid and 2- (meta) )
  • a structural unit derived from acrylamido-2-methylpropanesulfonic acid, the unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid is 10 to 40 mol%, and the mass average molecular weight is
  • the water-soluble copolymer is 1 ⁇ 10 4 to 5 ⁇ 10 4 .
  • the calcium phosphate scale is mainly composed of a water-soluble copolymer having a main constituent unit of a phosphorus-free monomer such as (meth) acrylic acid and 2- (meth) acrylamide-2-methylpropanesulfonic acid. It has a high prevention effect and does not increase the phosphorus concentration in the wastewater. Further, since the water-soluble copolymer has a mass average molecular weight of 1 ⁇ 10 4 to 5 ⁇ 10 4, it is difficult to produce precipitates such as gelled products. In this scale inhibitor, the water-soluble polymer can be a copolymer of non-phosphorus-containing monomers, that is, not containing phosphorus.
  • the reverse osmosis membrane scale prevention method comprises a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid.
  • a scale mainly composed of a water-soluble copolymer having a unit derived from (meth) acrylamide-2-methylpropanesulfonic acid of 10 to 40 mol% and a mass average molecular weight of 1 ⁇ 10 4 to 5 ⁇ 10 4
  • An inhibitor is added to the reverse osmosis membrane treated water system.
  • a water-soluble copolymer having a molecular weight within a specific range and containing as a main constituent unit a phosphorus-free monomer such as (meth) acrylic acid or 2- (meth) acrylamido-2-methylpropanesulfonic acid. Since the scale inhibitor mainly composed of is used, there is no increase in the phosphorus concentration in the waste water and no precipitation of gelled products, and the effect of suppressing the precipitation of calcium phosphate scale is high.
  • the “mass average molecular weight” in the present invention is a value measured by gel permeation chromatography using sodium polyacrylate as a standard substance.
  • the main component of the scale inhibitor is a water-soluble copolymer having a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid. Therefore, precipitation of calcium phosphate scale generated in the reverse osmosis membrane treatment can be suppressed without increasing the phosphorus concentration in the waste water, and fine precipitates such as gelled products are not generated.
  • the scale inhibitor of the present embodiment suppresses the precipitation of calcium phosphate scale that occurs in the reverse osmosis membrane treatment and prevents the scale from adhering to the RO membrane or the like, and its main component is (meth) acrylic acid. And a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid.
  • the water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment is a copolymer of (meth) acrylic acid and 2- (meth) acrylamido-2-methylpropanesulfonic acid or These are copolymers of these with other monomers.
  • (meth) acrylic acid means methacrylic acid, acrylic acid or a salt thereof, and these monomers may be used alone or in combination of two or more.
  • 2- (Meth) acrylamide-2-methylpropanesulfonic acid means 2-methacrylamide-2-methylpropanesulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid, one or both of which Can be used.
  • maleic acid and epoxy succinic acid can be used as the carboxylic acid.
  • the monoethylenically unsaturated hydrocarbon is not particularly limited, and may have a linear, branched or cyclic structure, but preferably has 3 to 8 carbon atoms.
  • isobutylene or styrene is used. can do.
  • the alkyl ester of monoethylenically unsaturated acid preferably has 1 to 8 carbon atoms.
  • methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl acrylate, N-butyl acrylate, 2-ethylhexyl acrylate is used. be able to.
  • the vinyl ester of monoethylenically unsaturated acid preferably has 1 to 8 carbon atoms, and for example, vinyl acetate and vinyl propionate can be used.
  • the substituted acrylamide is preferably one in which acrylamide is substituted with hydrogen and / or an alkyl group having 1 to 4 carbon atoms.
  • acrylamide, propylacrylamide, N-isopropylacrylamide, dimethylacrylamide, diethylacrylamide and the like can be used. it can. These monomers may be used alone or in combination.
  • the water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment includes a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid. It is sufficient if it has a low phosphorus content, but is obtained by copolymerizing only (meth) acrylic acid and 2- (meth) acrylamido-2-methylpropanesulfonic acid without using other monomers. Water-soluble copolymers are particularly preferred.
  • the water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment has 10 to 40 mol% of sulfonic acid units, that is, structural units derived from 2- (meth) acrylamide-2-methylpropanesulfonic acid. is there.
  • sulfonic acid units that is, structural units derived from 2- (meth) acrylamide-2-methylpropanesulfonic acid. is there.
  • the strong electrolyte (sulfonic acid group) decreases, so that gelation easily occurs and the scale-preventing effect of calcium phosphate also decreases.
  • the water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment has a molecular weight of 1 ⁇ 10 4 to 5 ⁇ 10 4 .
  • the molecular weight defined here is a mass average molecular weight measured by gel permeation chromatography using sodium polyacrylate as a standard substance, and the same applies to the following description.
  • the gelation resistance can be improved by reducing the molecular weight.
  • a water-soluble copolymer having a small molecular weight has a weak calcium phosphate adsorption ability and is inferior in calcium phosphate scale prevention effect.
  • a water-soluble polymer having a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid has a molecular weight of 1 When it is less than 10 4, the effect of suppressing the precipitation of calcium phosphate scale is not sufficiently obtained.
  • the molecular weight of the water-soluble polymer is preferably 1.1 ⁇ 10 4 or more.
  • the molecular weight of the water-soluble polymer exceeds 5 ⁇ 10 4 , gelation is likely to occur due to binding with cations, and gelation occurs and fine precipitates are generated even in an environment where the concentration of cations is low. Lowers the flux (permeation flow rate).
  • the production method of the water-soluble polymer described above is not particularly limited, and various polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization can be applied. From the viewpoint of ease of solution, solution polymerization is desirable.
  • Solution polymerization is performed in an organic solvent system or an aqueous system.
  • an organic solvent such as toluene or xylene
  • the polymerization initiator can be selected from known peroxides. Examples include dibenzoyl peroxide, tert-butyl peroxybenzoate, dicumyl peroxide, tert-butyl peroxide. Only one type of polymerization initiator may be used, or two or more types may be used.
  • the organic solvent-based polymerization can be carried out either batchwise or continuously.
  • the polymerization conditions are, for example, a heating temperature of 100 to 200 ° C. and a polymerization time of 2 to 6 hours. After the polymerization, the mixture is allowed to cool to obtain a water-soluble copolymer.
  • the organic solvent polymerization conditions are not particularly limited, and the type, polymerization time, temperature, and the like of the organic solvent to be used can be appropriately changed.
  • aqueous polymerization method in which the polymerization is carried out in an aqueous system, an aqueous solution or dispersion of the monomer is prepared and the monomer is polymerized.
  • the pH of the aqueous monomer solution or aqueous dispersion is adjusted as necessary, the reaction atmosphere is replaced with an inert gas, and then heated to 50 to 100 ° C. in the presence of a water-soluble polymerization initiator.
  • the water-soluble polymerization initiator is not particularly limited.
  • 2,2-azobis (2-amidinopropane) dihydrochloride azobis-N, N′-dimethyleneisobutylamidine dihydrochloride
  • 4,4′-azobis Azo compounds such as 4-cyanovaleric acid
  • persulfates such as ammonium persulfate, sodium persulfate and potassium persulfate
  • peroxides such as hydrogen peroxide and sodium periodate.
  • water-soluble polymerization initiators may be used alone or in combination of two or more.
  • the aqueous polymerization is completed, for example, in a polymerization time of 2 to 6 hours, and allowed to cool, whereby an aqueous solution or dispersion of the polymer can be obtained.
  • Aqueous polymerization can also be performed in the state which added additives, such as a dispersing agent and surfactant, to aqueous solution or an aqueous dispersion.
  • the scale inhibitor of the present embodiment includes a slime control agent, an enzyme, a bactericide, a colorant, a fragrance, a water-soluble organic solvent, and a range that does not impair the object of the present invention.
  • An antifoaming agent etc. may be mix
  • examples of the slime control agent include quaternary ammonium salts such as alkyldimethylbenzylammonium chloride, chloromethyltrithiazoline, chloromethylisothiazoline, methylisothiazoline, ethylaminoisopropylaminomethylthiatriazine, hypochlorous acid, hypochlorous acid, and hypochlorous acid. Bromic acid, a mixture of hypochlorous acid and sulfamic acid, and the like can be used.
  • the scale inhibitor of the present embodiment has a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid, Since the main component is a water-soluble copolymer having a unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid of 10 to 40 mol%, the effect of suppressing precipitation of calcium phosphate scale is excellent.
  • this water-soluble copolymer does not contain phosphorus or contains only a small amount of phosphorus, it hardly affects the phosphorus concentration in the waste water. Furthermore, since the water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment has a molecular weight of 1 ⁇ 10 4 to 5 ⁇ 10 4, it is difficult to generate fine precipitates such as gelled products. For this reason, the scale inhibitor of this embodiment is suitable for reverse osmosis membrane treatment. In addition, there is no restriction
  • the scale prevention method of the present embodiment is a method for suppressing the precipitation of calcium phosphate scale in the reverse osmosis membrane treatment using the scale inhibitor of the first embodiment described above. That is, the scale prevention method of the present embodiment has a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid.
  • Scale inhibitor comprising a water-soluble copolymer having a unit derived from acrylamido-2-methylpropanesulfonic acid of 10 to 40 mol% and a weight average molecular weight of 1 ⁇ 10 4 to 5 ⁇ 10 4 as a main component Is added to the reverse osmosis membrane treated water system.
  • the addition method of the scale inhibitor is not particularly limited, and may be added at a place where scale adhesion is to be prevented or just before the place. Further, the addition amount is not particularly limited and can be appropriately selected according to the water quality of the aqueous system. However, the concentration of the water-soluble copolymer described above is 0.01 to 100 mg / L. In particular, from the viewpoint of prevention of film surface clogging, it is more preferable to add to 0.1 to 10 mg / L.
  • the scale prevention method of this embodiment can also use together the scale inhibitor of 1st Embodiment mentioned above and another scale inhibitor.
  • the scale inhibitor to be used in combination include polymaleic acid, polyacrylic acid, a copolymer of maleic acid and acrylic acid, a copolymer of maleic acid and isobutylene, a copolymer of maleic acid and sulfonic acid, and other maleic acid.
  • examples thereof include a copolymer, a copolymer of acrylic acid and sulfonic acid, a copolymer of acrylic acid and nonionic group-containing monomer, and a copolymer (terpolymer) of acrylic acid, sulfonic acid and nonionic group-containing monomer.
  • sulfonic acid examples include sulfonic acid such as vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, isoprene sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, 2-acrylamide.
  • sulfonic acid such as vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, isoprene sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, 2-acrylamide.
  • These sulfonic acids may be used alone or in
  • Nonionic group-containing monomers include, for example, alkyl amides having 1 to 5 carbon atoms, hydroxyethyl methacrylate, (poly) ethylene / propylene oxide mono (meth) acrylates having 1 to 30 addition moles, and addition moles. Examples thereof include 1 to 30 monovinyl ether ethylene / propylene oxide. These nonionic group containing monomers may use only 1 type, and may use 2 or more types.
  • the maleic acid polymer (homopolymer and / or copolymer) is not particularly limited, but preferably contains 50 to 100 mol% of maleic acid units.
  • the other monomer to be copolymerized with maleic acid may be a nonionic monomer.
  • Nonionic monomers include, for example, monoethylenically unsaturated hydrocarbons, alkyl esters of monoethylenically unsaturated acids, vinyl esters of monoethylenically unsaturated acids, substituted acrylamides, etc.
  • 1 to The two can be copolymerized with maleic acid.
  • the monoethylenically unsaturated hydrocarbon is preferably a linear, branched or cyclic one having 3 to 8 carbon atoms, such as isobutylene or styrene.
  • the alkyl ester of monoethylenically unsaturated acid preferably has 1 to 8 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl acrylate, N-butyl acrylate, 2-ethylhexyl acrylate, etc. It is.
  • the vinyl ester of a monoethylenically unsaturated acid preferably has 1 to 8 carbon atoms, and examples thereof include vinyl acetate and vinyl propionate.
  • the substituted acrylamide is preferably one substituted with hydrogen and / or an alkyl group having 1 to 4 carbon atoms, and examples thereof include acrylamide, propylacrylamide, N-isopropylacrylamide, dimethylacrylamide and diethylacrylamide.
  • the molecular weight is in a specific range, the unit derived from (meth) acrylic acid, and the structural unit derived from a specific amount of 2- (meth) acrylamido-2-methylpropanesulfonic acid.
  • Suppressing the precipitation of calcium phosphate scale produced in reverse osmosis membrane treatment without affecting the phosphorus concentration in the wastewater because it uses a scale inhibitor mainly composed of a water-soluble copolymer containing In addition, fine precipitates such as gelled products are not generated.
  • the scale prevention method of this embodiment can suppress the precipitation of scale stably only by adding a small amount of a scale inhibitor to the aqueous system.
  • the water quality condition and operation condition of the water system to which the scale prevention method of this embodiment is applied are not particularly limited.
  • the configuration and effects other than those described above in the scale prevention method of the present embodiment are the same as those of the first embodiment described above.
  • ⁇ Flat membrane test> First, in order to measure the initial performance of the membrane, a 500 mg / L NaCl aqueous solution was passed through a polyamide reverse osmosis membrane (ES20 manufactured by Nitto Denko Corporation) at an operating pressure of 0.75 MPa and a recovery rate of 50%. (Flux) was measured for a predetermined time.
  • ES20 polyamide reverse osmosis membrane manufactured by Nitto Denko Corporation
  • an aqueous solution containing calcium chloride 500 mg CaCO 3 / L, Examples 1 to 3 and Comparative Examples 1 to 8 scale inhibitors (polymers): 1 mg / L, disodium hydrogen phosphate: 30 mg CaCO 3 / L
  • the pH was adjusted to 7.0 with a small amount of aqueous sodium hydroxide and sulfuric acid to prepare a test solution.
  • Each test solution was passed through a polyamide reverse osmosis membrane (ES20 manufactured by Nitto Denko Corporation) at an operating pressure of 0.75 MPa and a recovery rate of 50%, and flux was measured for a predetermined time.
  • FIGS. 1 and 2 are graphs showing changes with time in the ratio (flux ratio) to the flux measured with the test solution, where the flux in a 500 mg / L NaCl aqueous solution is 1.
  • FIG. Moreover, the blank (Blank) shown in FIG.1 and FIG.2 is a flux ratio when a chemical
  • Example 1 when the flux reduction rates of Examples 1 to 3 are compared, it is found that Example 1 ⁇ Example 2 ⁇ Example 3 in order, and Example 1 can most effectively suppress the flux reduction.
  • the scale inhibitor of Example 1 using a water-soluble copolymer having a unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid in the range of 15 to 25 mol% has reduced flux. was significantly suppressed.
  • the scale inhibitors of Comparative Examples 1 and 2 had the same composition of the scale inhibitor and monomer (AA / AMPS) of Example 1, but the flux was reduced. This is because the scale inhibitor of Comparative Example 1 had a molecular weight of the water-soluble copolymer of less than 1 ⁇ 10 4 , so the effect of suppressing the precipitation of scale was low, and the scale inhibitor of Comparative Example 2 was water-soluble. Since the molecular weight of the copolymer exceeded 5 ⁇ 10 4 , it is considered that a gelled product was generated. In particular, in the scale inhibitor of Comparative Example 2, it is considered that the film was clogged by the generated fine precipitate, and the flux decrease was faster than that of Blank.
  • the scale inhibitors of Comparative Examples 3 and 4 have a molecular weight of 1 ⁇ 10 4 to 5 ⁇ 10 4 of the water-soluble copolymer, but are units derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid. Was less than 10 mol% or more than 40 mol%, the flux decreased.

Abstract

Provided are a scale preventing agent for reverse osmosis membranes and a scale preventing method that can prevent attachment of calcium phosphate scale arising in reverse osmosis membrane processing without increasing the phosphorus concentration in discharged water and which does not give rise to fine sludge such as gelated materials. To a reverse osmosis membrane processing system is added a scale preventing agent having a unit derived from a (meth)acrylate and a structural unit derived from 2-(meth)acrylamide-2-methylpropanesulfonic acid. The unit derived from 2-(meth)acrylamide-2-methylpropanesulfonic acid is 10 - 40 mol%, and the main component of the scale preventing agent is a water-soluble copolymer having a mass average molecular weight of 1 × 104 - 5 × 104.

Description

逆浸透膜用スケール防止剤及びスケール防止方法Reverse osmosis membrane scale inhibitor and scale prevention method
　本発明は、逆浸透膜用スケール防止剤及びスケール防止方法に関する。より詳しくは、膜処理において発生するリン酸カルシウムスケールの付着を防止するスケール防止剤及びスケール防止方法に関する。 The present invention relates to a scale inhibitor for reverse osmosis membranes and a scale prevention method. More specifically, the present invention relates to a scale inhibitor and a scale prevention method for preventing adhesion of calcium phosphate scale generated in film treatment.
　冷却水系、ボイラ水系、膜処理又は地熱発電所の還元井においては、水と接触する伝熱面、配管或いは膜面に、スケール障害が発生する。特に、省資源・省エネルギーの観点から高濃縮運転をしたとき、また、膜の場合は回収率を高くしたときは、水に溶解している塩類が濃縮されて、難溶性の塩となってスケール化する。 In the cooling water system, boiler water system, membrane treatment, or reduction well of a geothermal power plant, scale failure occurs on the heat transfer surface, piping, or membrane surface in contact with water. In particular, when highly concentrated operation is performed from the viewpoint of saving resources and energy, and when the recovery rate is increased in the case of membranes, the salt dissolved in water is concentrated to form a sparingly soluble salt. Turn into.
　そして、例えば、熱交換部に生成したスケールは伝熱阻害を、配管に付着したスケールは流量低下を、膜に付着したスケールはフラックス低下を、それぞれ引き起こす。また、生成したスケールが剥離すると、系内を循環し、ポンプ、配管及び熱交換部の閉塞を引き起こし、更に、これらの閉塞に伴い、配管及び熱交換部でのスケール化が促進される。同様の現象は、地熱発電所の還元井でも起こり得る。 For example, the scale generated in the heat exchange section causes heat transfer inhibition, the scale attached to the pipe causes a decrease in flow rate, and the scale attached to the film causes a decrease in flux. Further, if the generated scale is peeled off, it circulates in the system and causes the pump, the piping and the heat exchanging section to be blocked. Further, along with the blockage, the scaling in the pipe and the heat exchanging section is promoted. A similar phenomenon can occur in the reduction well of a geothermal power plant.
　これらの水系において生成するスケール種としては、リン酸カルシウム、炭酸カルシウム、硫酸カルシウム、亜硫酸カルシウム、ケイ酸カルシウム、ケイ酸マグネシウム、水酸化マグネシウム、リン酸亜鉛、水酸化亜鉛及び塩基性炭酸亜鉛などがある。 Scale species generated in these aqueous systems include calcium phosphate, calcium carbonate, calcium sulfate, calcium sulfite, calcium silicate, magnesium silicate, magnesium hydroxide, zinc phosphate, zinc hydroxide, and basic zinc carbonate.
　また、一般に、カルシウム系スケールに対しては、ヘキサメタリン酸ソーダやトリポリリン酸ソーダなどの無機ポリリン酸類、ヒドロキシエチリデンジホスホン酸やホスホノブタントリカルボン酸などのホスホン酸類、マレイン酸、アクリル酸及びイタコン酸などのカルボキシル基含有素材に、必要に応じてビニルスルホン酸、アリルスルホン酸及び３－アリロキシ－２－ヒドロキシプロパンスルホン酸などのスルホン酸基を有するビニルモノマーや、アクリルアミドなどのノニオン性ビニルモノマーを、対象水質に応じて組み合わせたコポリマーが、スケール防止剤として使用されている。 In general, for calcium-based scales, inorganic polyphosphoric acids such as sodium hexametaphosphate and sodium tripolyphosphate, phosphonic acids such as hydroxyethylidene diphosphonic acid and phosphonobutanetricarboxylic acid, maleic acid, acrylic acid and itaconic acid If necessary, vinyl monomers having sulfonic acid groups such as vinyl sulfonic acid, allyl sulfonic acid and 3-allyloxy-2-hydroxypropane sulfonic acid, and nonionic vinyl monomers such as acrylamide are included Copolymers combined according to water quality are used as scale inhibitors.
　一方、逆浸透膜（Reverse Osmosis Membrane：ＲＯ膜）処理において生成するスケール種としては、リン酸カルシウム、炭酸カルシウム、硫酸カルシウム、硫酸バリウム、硫酸ストロンチウム及び水酸化マグネシウムなどがある。また、そのスケール防止剤としては、一般に、分子量が比較的小さく、スケール防止効果が高いことから、ヘキサメタリン酸ソーダやトリポリリン酸ソーダなどの無機ポリリン酸類、アミノメチルホスホン酸、ヒドロキシエチリデンジホスホン酸やホスホノブタントリカルボン酸などのホスホン酸類といったリンを含む素材が使用されている。 On the other hand, examples of the scale species generated in the reverse osmosis membrane (RO membrane) treatment include calcium phosphate, calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, and magnesium hydroxide. In addition, the scale inhibitor generally has a relatively low molecular weight and a high scale prevention effect. Therefore, inorganic polyphosphates such as sodium hexametaphosphate and sodium tripolyphosphate, aminomethylphosphonic acid, hydroxyethylidene diphosphonic acid and phosphonobu Materials containing phosphorus such as phosphonic acids such as tantricarboxylic acid are used.
　しかしながら、近年、排水中のリン濃度が規制されたことに伴い、リンの含有量を極力減らしたスケール防止剤が望まれている。また、近年、水資源を有効活用するために、排水をＲＯ膜で回収し、使用する場合が増えているが、リン酸を含む水を回収した場合、ＲＯ膜にリン酸カルシウムスケールが生成される場合がある。具体的には、ＲＯ膜処理の濃縮水のリン酸が、５ｍｇ／ＬａｓＰＯ４以上となる場合、リン酸カルシウムスケールが発生しやすい。 However, in recent years, with the regulation of phosphorus concentration in wastewater, a scale inhibitor that reduces the phosphorus content as much as possible is desired. In recent years, in order to effectively use water resources, wastewater is collected and used in RO membranes, but when water containing phosphoric acid is collected, calcium phosphate scale is generated in the RO membrane. There is. Specifically, when the phosphate of concentrated water for RO membrane treatment is 5 mg / LasPO 4 or more, calcium phosphate scale is likely to occur.
　このようなリン酸カルシウムスケールの析出を抑制する方法としては、例えば、ポリエーテルポリアミノメチレンホスホネートやアクリル酸などのモノマーからなるターポリマーと、ヒドロキシホスホノ酢酸などを組合せて使用する方法がある（特許文献１，２参照）。また、β－ポリアスパラギン酸を使用する方法も提案されている（特許文献３参照）。更に、冷却水系においては、スケール防止剤として、アクリル酸やスルホン酸などのモノマーを重合させた共重合ポリマーが使用されている（特許文献４～６参照）。 As a method for suppressing the precipitation of such calcium phosphate scale, for example, there is a method in which a terpolymer composed of monomers such as polyether polyaminomethylene phosphonate and acrylic acid is combined with hydroxyphosphonoacetic acid (Patent Document 1). , 2). A method using β-polyaspartic acid has also been proposed (see Patent Document 3). Furthermore, in the cooling water system, a copolymer obtained by polymerizing monomers such as acrylic acid and sulfonic acid is used as a scale inhibitor (see Patent Documents 4 to 6).
特開平９－１７４０９２号公報JP-A-9-174092 特開平１０－１３７７９０号公報Japanese Patent Laid-Open No. 10-137790 特許第３３４７３２５号公報Japanese Patent No. 3347325 米国特許第３９２８１９６号明細書US Pat. No. 3,928,196 特開昭５９－３９１号公報JP 59-391 A 特開平１０－３１４７９４号公報Japanese Patent Laid-Open No. 10-314794
　しかしながら、前述した従来の技術には、以下に示す問題点がある。即ち、特許文献１、２に記載のスケール防止剤は、リンを含むターポリマーなどを使用するため、排水にリンが含有されることとなる。また、特許文献３に記載の方法で使用されるβ-ポリアスパラギン酸は、リンは非含有であるが、生分解性が高いため、バクテリアや藻類の栄養源となり、スライムの発生を引き起こす可能性がある。 However, the conventional techniques described above have the following problems. That is, since the scale inhibitors described in Patent Documents 1 and 2 use a terpolymer containing phosphorus or the like, the wastewater contains phosphorus. In addition, β-polyaspartic acid used in the method described in Patent Document 3 does not contain phosphorus, but is highly biodegradable, so it may become a nutrient source for bacteria and algae and cause slime generation. There is.
　更に、特許文献４～６に記載のスケール防止剤で使用される共重合ポリマーも、リン非含有であるが、これら従来のスケール防止剤はいずれもボイラや冷却水系などでの使用を前提としており、ＲＯ膜処理用として適しているとは言い難い。 Furthermore, the copolymer used in the scale inhibitors described in Patent Documents 4 to 6 is also free of phosphorus. However, all these conventional scale inhibitors are premised on use in boilers and cooling water systems. It is difficult to say that it is suitable for RO membrane treatment.
　例えば、冷却水、蒸発濃縮及びボイラなどにおいて生成するスケールは、熱交換機などの表面に一定の厚さとなって付着することにより、伝熱阻害を起こしたり、機器の安定化に影響したりする。その一方で、冷却水系などにおいては、表面に付着したスケールが防食被膜として作用するため、多少のスケール生成は許容される。このため、冷却水系などのスケール防止剤には、生成したスケール成長を抑制する能力が求められ、ある一定の析出抑制効果や耐ゲル化能を有する素材であれば、適用することが可能である。更に、冷却水系などでは、スケール防止剤として適用可能な物性（分子量や組成など）範囲も広い。 For example, scales generated in cooling water, evaporative concentration, boilers, etc., adhere to the surface of a heat exchanger or the like with a certain thickness, thereby causing heat transfer inhibition or affecting the stabilization of equipment. On the other hand, in a cooling water system or the like, the scale attached to the surface acts as an anticorrosion coating, and therefore some scale generation is allowed. For this reason, a scale inhibitor such as a cooling water system is required to have the ability to suppress the generated scale growth, and can be applied as long as it has a certain precipitation suppressing effect and gelation resistance. . Further, in a cooling water system or the like, the range of physical properties (molecular weight, composition, etc.) applicable as a scale inhibitor is wide.
　これに対して、ＲＯ膜処理は、通水流路が小さく、スケール及び共存するイオンとスケール防止剤のゲル化物などの微小な析出物が生成すると、膜面が閉塞し、膜処理性能に影響する。このため、ＲＯ膜処理用のスケール防止剤には、微小な析出物を生成させないことが求められ、冷却水や蒸発濃縮などにおいて適用可能な素材であっても、更に、限られた物性条件を有する必要がある。 On the other hand, RO membrane treatment has a small water flow path, and when fine precipitates such as scales and coexisting ions and scale inhibitor gels are formed, the membrane surface is clogged, affecting membrane treatment performance. . For this reason, the scale inhibitor for RO membrane treatment is required not to generate fine precipitates, and even if it is a material that can be applied in cooling water, evaporative concentration, etc., further limited physical property conditions are required. It is necessary to have.
　更に、ＲＯ膜処理は、冷却水系などに比べて、スケールを防止すべき箇所の温度が低く、水の滞留時間も短く、一般にスケール防止剤の添加濃度も低い。具体的には、スケールを防止すべき箇所の温度は、ＲＯ膜処理が１０～４０℃程度であるのに対し、冷却水系などでは５０～９０℃である。また、水の滞留時間は、ＲＯ膜処理が１５分程度であるのに対し、冷却水系などでは２０～１００時間程度である。更に、スケール防止剤の添加濃度は、ＲＯ膜処理が１～１０ｍｇ／Ｌ程度であるのに対して、冷却水系などでは５～５０ｍｇ／Ｌ程度である。 Furthermore, in the RO membrane treatment, the temperature at the location where scale should be prevented is lower, the residence time of water is shorter, and generally the concentration of the scale inhibitor added is lower than in the cooling water system. Specifically, the temperature at the place where scale should be prevented is about 10 to 40 ° C. in the RO membrane treatment, whereas it is 50 to 90 ° C. in the cooling water system or the like. The residence time of water is about 15 minutes for the RO membrane treatment, whereas it is about 20 to 100 hours for the cooling water system. Further, the concentration of the scale inhibitor added is about 1 to 10 mg / L for the RO membrane treatment, whereas it is about 5 to 50 mg / L for the cooling water system.
　このように、ＲＯ膜処理用スケール防止剤は、冷却水系などの他の系に用いられるスケール防止剤と、処理条件や求められる特性が異なるため、冷却水系などのスケール防止剤を、ＲＯ膜処理に用いても、同様の効果は得られない。 Thus, since the scale inhibitor for RO membrane treatment is different from the scale inhibitor used in other systems such as cooling water system, the processing conditions and required characteristics are different, the scale inhibitor such as cooling water system is treated with RO membrane treatment. Even if it is used, the same effect cannot be obtained.
　そこで、本発明は、排水中のリン濃度を増加させることなく、浸透膜処理において生成するリン酸カルシウムスケールの析出を抑制することができ、かつゲル化物などの微小な析出物が生じない逆浸透膜用スケール防止剤及びスケール防止方法を提供することを主目的とする。 Therefore, the present invention is for a reverse osmosis membrane that can suppress the precipitation of calcium phosphate scale generated in the osmosis membrane treatment without increasing the phosphorus concentration in the waste water, and does not produce a fine precipitate such as a gelled product. The main object is to provide a scale inhibitor and a scale prevention method.
　本発明に係る逆浸透膜用スケール防止剤は、逆浸透膜処理においてリン酸カルシウムスケールの析出を抑制するスケール防止剤であり、主成分が、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有し、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する単位が１０～４０ｍｏｌ％であり、かつ、質量平均分子量が１×１０４～５×１０４である水溶性共重合物のものである。
　本発明においては、（メタ）アクリル酸及び２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸といったリン非含有モノマーを主な構成単位とする水溶性共重合物を主成分としているため、リン酸カルシウムスケールの防止効果が高く、排水中のリン濃度を増加させることもない。また、水溶性共重合物の質量平均分子量が１×１０４～５×１０４であるため、ゲル化物などの析出物を生成しにくい。
　このスケール防止剤では、水溶性重合物を非リン含有モノマーの共重合物、すなわち、リンを含有しないものとすることができる。 The scale inhibitor for reverse osmosis membrane according to the present invention is a scale inhibitor that suppresses the precipitation of calcium phosphate scale in the reverse osmosis membrane treatment. The main component is a unit derived from (meth) acrylic acid and 2- (meta) ) A structural unit derived from acrylamido-2-methylpropanesulfonic acid, the unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid is 10 to 40 mol%, and the mass average molecular weight is The water-soluble copolymer is 1 × 10 4 to 5 × 10 4 .
In the present invention, the calcium phosphate scale is mainly composed of a water-soluble copolymer having a main constituent unit of a phosphorus-free monomer such as (meth) acrylic acid and 2- (meth) acrylamide-2-methylpropanesulfonic acid. It has a high prevention effect and does not increase the phosphorus concentration in the wastewater. Further, since the water-soluble copolymer has a mass average molecular weight of 1 × 10 4 to 5 × 10 4, it is difficult to produce precipitates such as gelled products.
In this scale inhibitor, the water-soluble polymer can be a copolymer of non-phosphorus-containing monomers, that is, not containing phosphorus.
　本発明に係る逆浸透膜のスケール防止方法は、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有し、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する単位が１０～４０ｍｏｌ％であり、かつ、質量平均分子量が１×１０４～５×１０４である水溶性共重合物を主成分とするスケール防止剤を、逆浸透膜処理水系に添加する。
　本発明においては、分子量が特定の範囲内にあり、（メタ）アクリル酸や２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸といったリン非含有モノマーを主な構成単位とする水溶性共重合物を主成分とするスケール防止剤を使用しているため、排水中のリン濃度の増やゲル化物などの析出がなく、更に、リン酸カルシウムスケールの析出抑制効果が高い。 The reverse osmosis membrane scale prevention method according to the present invention comprises a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid. A scale mainly composed of a water-soluble copolymer having a unit derived from (meth) acrylamide-2-methylpropanesulfonic acid of 10 to 40 mol% and a mass average molecular weight of 1 × 10 4 to 5 × 10 4 An inhibitor is added to the reverse osmosis membrane treated water system.
In the present invention, a water-soluble copolymer having a molecular weight within a specific range and containing as a main constituent unit a phosphorus-free monomer such as (meth) acrylic acid or 2- (meth) acrylamido-2-methylpropanesulfonic acid. Since the scale inhibitor mainly composed of is used, there is no increase in the phosphorus concentration in the waste water and no precipitation of gelled products, and the effect of suppressing the precipitation of calcium phosphate scale is high.
　なお、本発明における「質量平均分子量」は、ポリアクリル酸ナトリウムを標準物質として用い、ゲル浸透クロマトグラフィにより測定した値である。 The “mass average molecular weight” in the present invention is a value measured by gel permeation chromatography using sodium polyacrylate as a standard substance.
　本発明によれば、スケール防止剤の主成分を、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有する水溶性共重合物にしているため、排水中のリン濃度を増加させることなく、逆浸透膜処理において生成するリン酸カルシウムスケールの析出を抑制することができ、更にゲル化物などの微小な析出物も生成しない。 According to the present invention, the main component of the scale inhibitor is a water-soluble copolymer having a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid. Therefore, precipitation of calcium phosphate scale generated in the reverse osmosis membrane treatment can be suppressed without increasing the phosphorus concentration in the waste water, and fine precipitates such as gelled products are not generated.
本発明の実施例のスケール防止剤の平膜試験の結果を示す図である。It is a figure which shows the result of the flat film test of the scale inhibitor of the Example of this invention. 本発明の比較例のスケール防止剤の平膜試験の結果を示す図である。It is a figure which shows the result of the flat film test of the scale inhibitor of the comparative example of this invention.
　以下、本発明を実施するための形態について、詳細に説明する。なお、本発明は、以下に説明する実施形態に限定されるものではない。 Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.
（第１の実施形態）
　先ず、本発明の第１の実施形態に係るスケール防止剤について説明する。本実施形態のスケール防止剤は、逆浸透膜処理で発生するリン酸カルシウムスケールの析出を抑制し、ＲＯ膜などにスケールが付着することを防止するものであり、その主成分は、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有する水溶性共重合物である。  (First embodiment)
First, the scale inhibitor according to the first embodiment of the present invention will be described. The scale inhibitor of the present embodiment suppresses the precipitation of calcium phosphate scale that occurs in the reverse osmosis membrane treatment and prevents the scale from adhering to the RO membrane or the like, and its main component is (meth) acrylic acid. And a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid.
　具体的には、本実施形態のスケール防止剤の主成分である水溶性共重合物は、（メタ）アクリル酸と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸との共重合体又は、これらと他のモノマーとの共重合体である。ここで、「（メタ）アクリル酸」は、メタクリル酸、アクリル酸又はこれらの塩を意味し、これらのモノマーは、単独で使用しても、２種以上を組み合わせて使用してもよい。また、「２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸」は、２－メタクリルアミド－２－メチルプロパンスルホン酸又は２－アクリルアミド－２－メチルプロパンスルホン酸を意味し、その一方又は両方を使用することができる。 Specifically, the water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment is a copolymer of (meth) acrylic acid and 2- (meth) acrylamido-2-methylpropanesulfonic acid or These are copolymers of these with other monomers. Here, “(meth) acrylic acid” means methacrylic acid, acrylic acid or a salt thereof, and these monomers may be used alone or in combination of two or more. “2- (Meth) acrylamide-2-methylpropanesulfonic acid” means 2-methacrylamide-2-methylpropanesulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid, one or both of which Can be used.
　更に、（メタ)アクリル酸及び２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸と共重合可能な他のモノマーは、特に限定されないが、リンを含有しないものが好ましい。これにより、リンを含有しない水溶性共重合物が得られるため、水溶性共重合物をスケール防止剤に使用した場合に、リンが排出されず、環境への影響を少なくすることができる。具体的には、リン非含有モノマーとしては、カルボン酸、モノエチレン性不飽和炭化水素、モノエチレン性不飽和酸のアルキルエステル、モノエチレン性不飽和酸のビニルエステル、置換アクリルアミドなどが挙げられる。 Further, other monomers copolymerizable with (meth) acrylic acid and 2- (meth) acrylamide-2-methylpropanesulfonic acid are not particularly limited, but those not containing phosphorus are preferable. Thereby, since the water-soluble copolymer which does not contain phosphorus is obtained, when water-soluble copolymer is used for a scale inhibitor, phosphorus is not discharged | emitted and the influence on an environment can be decreased. Specific examples of the phosphorus-free monomer include carboxylic acids, monoethylenically unsaturated hydrocarbons, monoethylenically unsaturated acid alkyl esters, monoethylenically unsaturated acid vinyl esters, and substituted acrylamides.
　そして、例えば、カルボン酸には、マレイン酸、エポキシコハク酸でなどを使用することができる。モノエチレン性不飽和炭化水素は、特に限定されず、直鎖、分岐、環状のいずれの構造のものを用いてもよいが、炭素数３～８のものが好ましく、例えば、イソブチレン、スチレンを使用することができる。モノエチレン性不飽和酸のアルキルエステルは、炭素数１～８のものが好ましく、例えば、メチル（メタ）アクリレート、エチル（メタ）アクリレート、イソプロピルアクリレート、Ｎ－ブチルアクリレート、２－エチルヘキシルアクリレートを使用することができる。  For example, maleic acid and epoxy succinic acid can be used as the carboxylic acid. The monoethylenically unsaturated hydrocarbon is not particularly limited, and may have a linear, branched or cyclic structure, but preferably has 3 to 8 carbon atoms. For example, isobutylene or styrene is used. can do. The alkyl ester of monoethylenically unsaturated acid preferably has 1 to 8 carbon atoms. For example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl acrylate, N-butyl acrylate, 2-ethylhexyl acrylate is used. be able to.
　モノエチレン性不飽和酸のビニルエステルは、炭素数１～８のものが好ましく、例えば、酢酸ビニル、プロピオン酸ビニルを使用することができる。置換アクリルアミドは、アクリルアミドが、水素及び／又は炭素数１～４のアルキル基で置換されたものが好ましく、例えば、アクリルアミド、プロピルアクリルアミド、Ｎ－イソプロピルアクリルアミド、ジメチルアクリルアミド、ジエチルアクリルアミドなどを使用することができる。なお、これらのモノマーは、単独で使用しても、複数組み合わせて使用してもよい。 The vinyl ester of monoethylenically unsaturated acid preferably has 1 to 8 carbon atoms, and for example, vinyl acetate and vinyl propionate can be used. The substituted acrylamide is preferably one in which acrylamide is substituted with hydrogen and / or an alkyl group having 1 to 4 carbon atoms. For example, acrylamide, propylacrylamide, N-isopropylacrylamide, dimethylacrylamide, diethylacrylamide and the like can be used. it can. These monomers may be used alone or in combination.
　本実施形態のスケール防止剤の主成分である水溶性共重合物は、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有し、リンの含有量が少ないものであればよいが、他のモノマーを用いず、（メタ）アクリル酸及び２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸のみを共重合して得た水溶性共重合物が、特に好適である。 The water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment includes a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid. It is sufficient if it has a low phosphorus content, but is obtained by copolymerizing only (meth) acrylic acid and 2- (meth) acrylamido-2-methylpropanesulfonic acid without using other monomers. Water-soluble copolymers are particularly preferred.
　本実施形態のスケール防止剤の主成分である水溶性共重合物は、スルホン酸の単位、即ち、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位が１０～４０ｍｏｌ％である。２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸の含有量が１０ｍｏｌ％未満であると、強電解質（スルホン酸基）が少なくなるため、ゲル化しやすくなる上、リン酸カルシウムのスケール防止効果も低下する。また、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸の含有量が４０ｍｏｌ％を超えると、水溶性共重合物の分子構造の変化により、リン酸カルシウムのスケール防止効果が低下する。なお、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位のより好適な範囲は、１５～２５ｍｏｌである。 The water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment has 10 to 40 mol% of sulfonic acid units, that is, structural units derived from 2- (meth) acrylamide-2-methylpropanesulfonic acid. is there. When the content of 2- (meth) acrylamido-2-methylpropanesulfonic acid is less than 10 mol%, the strong electrolyte (sulfonic acid group) decreases, so that gelation easily occurs and the scale-preventing effect of calcium phosphate also decreases. . On the other hand, when the content of 2- (meth) acrylamide-2-methylpropanesulfonic acid exceeds 40 mol%, the scale preventing effect of calcium phosphate decreases due to a change in the molecular structure of the water-soluble copolymer. A more preferable range of the structural unit derived from 2- (meth) acrylamide-2-methylpropanesulfonic acid is 15 to 25 mol.
　また、本実施形態のスケール防止剤の主成分である水溶性共重合物は、分子量が１×１０４～５×１０４である。なお、ここで規定する分子量は、ポリアクリル酸ナトリウムを標準物質として用い、ゲル浸透クロマトグラフィにより測定した質量平均分子量であり、以下の説明においても同様である。一般に、水溶性重合物は、分子量が大きいほどゲル化しやすくなるため、分子量を小さくすることにより、耐ゲル化能を向上させることができる。一方、分子量が小さい水溶性共重合物は、リン酸カルシウムの吸着能が弱く、リン酸カルシウムのスケール防止効果が劣る。 The water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment has a molecular weight of 1 × 10 4 to 5 × 10 4 . The molecular weight defined here is a mass average molecular weight measured by gel permeation chromatography using sodium polyacrylate as a standard substance, and the same applies to the following description. In general, since the water-soluble polymer is easily gelled as the molecular weight increases, the gelation resistance can be improved by reducing the molecular weight. On the other hand, a water-soluble copolymer having a small molecular weight has a weak calcium phosphate adsorption ability and is inferior in calcium phosphate scale prevention effect.
　具体的には、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有する水溶性重合物であっても、その分子量が１×１０４未満の場合、リン酸カルシウムスケールの析出抑制効果が十分に得られない。なお、スケール防止効果向上の観点から、水溶性重合物の分子量は１．１×１０４以上であることが好ましい。一方、水溶性重合物の分子量が５×１０４を超えると、カチオンとの結合によりゲル化が生じやすくなり、カチオンの濃度が低い環境下でも、ゲル化して微小な析出物が生じ、ＲＯ膜のフラックス（透過流速）低下を招く。 Specifically, even a water-soluble polymer having a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid has a molecular weight of 1 When it is less than 10 4, the effect of suppressing the precipitation of calcium phosphate scale is not sufficiently obtained. In addition, from the viewpoint of improving the scale prevention effect, the molecular weight of the water-soluble polymer is preferably 1.1 × 10 4 or more. On the other hand, when the molecular weight of the water-soluble polymer exceeds 5 × 10 4 , gelation is likely to occur due to binding with cations, and gelation occurs and fine precipitates are generated even in an environment where the concentration of cations is low. Lowers the flux (permeation flow rate).
　また、前述した水溶性重合物の製造方法は、特に限定されるものではなく、溶液重合、懸濁重合、乳化重合、塊状重合などの各種重合法を適用することができるが、重合反応の制御しやすさの点で、溶液重合が望ましい。 Further, the production method of the water-soluble polymer described above is not particularly limited, and various polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization can be applied. From the viewpoint of ease of solution, solution polymerization is desirable.
　溶液重合は、有機溶剤系又は水系で行われる。例えば、モノマー材料にマレイン酸を含有させる場合は、トルエンやキシレンなどの有機溶剤中で、モノマー材料を重合させる方法がある（英国特許公報１４１１０６３号明細書）。この場合、重合開始剤は、公知の過酸化物から選択して使用することができる。例えば、ジベンゾイルペルオキシド、第三ブチルペルオキシベンゾエート、ジクミルペルオキシド、第三ブチルペルオキドなどがある。重合開始剤は１種類だけを用いてもよいし、２種類以上を用いてもよい。 Solution polymerization is performed in an organic solvent system or an aqueous system. For example, when maleic acid is contained in the monomer material, there is a method of polymerizing the monomer material in an organic solvent such as toluene or xylene (UK Patent Publication No. 1411063). In this case, the polymerization initiator can be selected from known peroxides. Examples include dibenzoyl peroxide, tert-butyl peroxybenzoate, dicumyl peroxide, tert-butyl peroxide. Only one type of polymerization initiator may be used, or two or more types may be used.
　有機溶剤系の重合は、回分式、連続式のいずれでも行うことができ、重合条件は、例えば、加熱温度１００～２００℃、重合時間２～６時間である。重合後、放冷し、水溶性共重合物を得ることができる。有機溶剤系の重合条件は特に限定されず、使用する有機溶剤の種類、重合時間、温度などを適宜変更できる。 The organic solvent-based polymerization can be carried out either batchwise or continuously. The polymerization conditions are, for example, a heating temperature of 100 to 200 ° C. and a polymerization time of 2 to 6 hours. After the polymerization, the mixture is allowed to cool to obtain a water-soluble copolymer. The organic solvent polymerization conditions are not particularly limited, and the type, polymerization time, temperature, and the like of the organic solvent to be used can be appropriately changed.
　重合を水系で行う水性重合法は、モノマーの水溶液又は水分散液を作成し、モノマーを重合させる。重合は、例えば、モノマーの水溶液又は水分散液のｐＨを必要に応じて調整し、不活性ガスにより反応雰囲気を置換したのち、５０～１００℃に加熱し、水溶性重合開始剤の存在下で行う。 In the aqueous polymerization method in which the polymerization is carried out in an aqueous system, an aqueous solution or dispersion of the monomer is prepared and the monomer is polymerized. In the polymerization, for example, the pH of the aqueous monomer solution or aqueous dispersion is adjusted as necessary, the reaction atmosphere is replaced with an inert gas, and then heated to 50 to 100 ° C. in the presence of a water-soluble polymerization initiator. Do.
　水溶性重合開始剤は特に限定されないが、例えば、２，２－アゾビス（２－アミジノプロパン）二塩酸塩、アゾビス-Ｎ，Ｎ’－ジメチレンイソブチルアミジン二塩酸塩、４，４’－アゾビス（４－シアノ吉草酸）－２－ナトリウムなどのアゾ化合物、過硫酸アンモニウム、過硫酸ナトリウム、過硫酸カリウムなどの過硫酸塩、過酸化水素水、過ヨウ素酸ナトリウムなどの過酸化物である。これらの水溶性重合開始剤は、１種類だけを用いてもよいし、２種類以上を用いてもよい。 The water-soluble polymerization initiator is not particularly limited. For example, 2,2-azobis (2-amidinopropane) dihydrochloride, azobis-N, N′-dimethyleneisobutylamidine dihydrochloride, 4,4′-azobis ( Azo compounds such as 4-cyanovaleric acid) -2-sodium, persulfates such as ammonium persulfate, sodium persulfate and potassium persulfate, peroxides such as hydrogen peroxide and sodium periodate. These water-soluble polymerization initiators may be used alone or in combination of two or more.
　水系の重合は、例えば、重合時間２～６時間で終了し、放冷することにより、重合体の水溶液又は水分散液を得ることができる。水系の重合は、水溶液又は水分散液に、分散剤、界面活性剤などの添加剤を添加した状態で、行うこともできる。 The aqueous polymerization is completed, for example, in a polymerization time of 2 to 6 hours, and allowed to cool, whereby an aqueous solution or dispersion of the polymer can be obtained. Aqueous polymerization can also be performed in the state which added additives, such as a dispersing agent and surfactant, to aqueous solution or an aqueous dispersion.
　本実施形態のスケール防止剤には、前述した水溶性共重合物に加えて、本発明の目的を阻害しない範囲で、スライムコントロール剤、酵素、殺菌剤、着色剤、香料、水溶性有機溶媒及び消泡剤などが配合されていてもよい。その場合、スライムコントロール剤としては、例えば、アルキルジメチルベンジルアンモニウムクロライドなどの四級アンモニウム塩、クロルメチルトリチアゾリン、クロルメチルイソチアゾリン、メチルイソチアゾリン、エチルアミノイソプロピルアミノメチルチアトリアジン、次亜塩素酸、次亜臭素酸、及び次亜塩素酸とスルファミン酸の混合物などを使用することができる。 In addition to the water-soluble copolymer described above, the scale inhibitor of the present embodiment includes a slime control agent, an enzyme, a bactericide, a colorant, a fragrance, a water-soluble organic solvent, and a range that does not impair the object of the present invention. An antifoaming agent etc. may be mix | blended. In that case, examples of the slime control agent include quaternary ammonium salts such as alkyldimethylbenzylammonium chloride, chloromethyltrithiazoline, chloromethylisothiazoline, methylisothiazoline, ethylaminoisopropylaminomethylthiatriazine, hypochlorous acid, hypochlorous acid, and hypochlorous acid. Bromic acid, a mixture of hypochlorous acid and sulfamic acid, and the like can be used.
　以上詳述したように、本実施形態のスケール防止剤は、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有し、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する単位が１０～４０ｍｏｌ％の水溶性共重合物を主成分としているため、リン酸カルシウムスケールの析出抑制効果が優れている。 As described above in detail, the scale inhibitor of the present embodiment has a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid, Since the main component is a water-soluble copolymer having a unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid of 10 to 40 mol%, the effect of suppressing precipitation of calcium phosphate scale is excellent.
　また、この水溶性共重合物は、リン非含有か、リンを含有していてもわずかであるため、排水中のリン濃度にはほとんど影響がない。更に、本実施形態のスケール防止剤の主成分である水溶性共重合物は、分子量が１×１０４～５×１０４であるため、ゲル化物などの微小な析出物を生成しにくい。このため、本実施形態のスケール防止剤は、逆浸透膜処理に好適である。なお、本実施形態のスケール防止剤を適用する場合の水質条件及び水系の運転条件には、特に制限はない。 Moreover, since this water-soluble copolymer does not contain phosphorus or contains only a small amount of phosphorus, it hardly affects the phosphorus concentration in the waste water. Furthermore, since the water-soluble copolymer that is the main component of the scale inhibitor of the present embodiment has a molecular weight of 1 × 10 4 to 5 × 10 4, it is difficult to generate fine precipitates such as gelled products. For this reason, the scale inhibitor of this embodiment is suitable for reverse osmosis membrane treatment. In addition, there is no restriction | limiting in particular in the water quality condition in the case of applying the scale inhibitor of this embodiment, and the operating condition of water system.
（第２の実施形態）
　次に、本発明の第２の実施形態に係るスケール防止方法について説明する。本実施形態のスケール防止方法は、前述した第１の実施形態のスケール防止剤を使用して、逆浸透膜処理においてリン酸カルシウムスケールの析出を抑制する方法である。即ち、本実施形態のスケール防止方法は、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有し、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する単位が１０～４０ｍｏｌ％であり、かつ、質量平均分子量が１×１０４～５×１０４である水溶性共重合物を主成分とするスケール防止剤を、逆浸透膜処理水系に添加する。 (Second Embodiment)
Next, a scale prevention method according to the second embodiment of the present invention will be described. The scale prevention method of the present embodiment is a method for suppressing the precipitation of calcium phosphate scale in the reverse osmosis membrane treatment using the scale inhibitor of the first embodiment described above. That is, the scale prevention method of the present embodiment has a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid. Scale inhibitor comprising a water-soluble copolymer having a unit derived from acrylamido-2-methylpropanesulfonic acid of 10 to 40 mol% and a weight average molecular weight of 1 × 10 4 to 5 × 10 4 as a main component Is added to the reverse osmosis membrane treated water system.
　本実施形態のスケール防止方法においては、スケール防止剤の添加方法は、特に限定されるものではなく、スケールの付着を防止したい場所やその直前などで添加すればよい。また、その添加量も、特に限定されるものではなく、水系の水質に応じて適宜選択することができるが、上述した水溶性共重合物の濃度が、０．０１～１００ｍｇ／Ｌとなるように添加することが好ましく、特に、膜面の閉塞防止の観点から、０．１～１０ｍｇ／Ｌとなるように添加することがより好ましい。 In the scale prevention method of the present embodiment, the addition method of the scale inhibitor is not particularly limited, and may be added at a place where scale adhesion is to be prevented or just before the place. Further, the addition amount is not particularly limited and can be appropriately selected according to the water quality of the aqueous system. However, the concentration of the water-soluble copolymer described above is 0.01 to 100 mg / L. In particular, from the viewpoint of prevention of film surface clogging, it is more preferable to add to 0.1 to 10 mg / L.
　また、本実施形態のスケール防止方法は、前述した第１の実施形態のスケール防止剤と、他のスケール防止剤とを併用することもできる。併用するスケール防止剤としては、例えば、ポリマレイン酸、ポリアクリル酸、マレイン酸とアクリル酸の共重合体、マレイン酸とイソブチレンの共重合体、マレイン酸とスルホン酸の共重合体、その他のマレイン酸共重合体、アクリル酸とスルホン酸の共重合体、アクリル酸とノニオン基含有モノマーの共重合体、アクリル酸とスルホン酸とノニオン基含有モノマーの共重合体（ターポリマー）などがある。 Moreover, the scale prevention method of this embodiment can also use together the scale inhibitor of 1st Embodiment mentioned above and another scale inhibitor. Examples of the scale inhibitor to be used in combination include polymaleic acid, polyacrylic acid, a copolymer of maleic acid and acrylic acid, a copolymer of maleic acid and isobutylene, a copolymer of maleic acid and sulfonic acid, and other maleic acid. Examples thereof include a copolymer, a copolymer of acrylic acid and sulfonic acid, a copolymer of acrylic acid and nonionic group-containing monomer, and a copolymer (terpolymer) of acrylic acid, sulfonic acid and nonionic group-containing monomer.
　前述した共重合体などを構成するスルホン酸としては、例えば、スルホン酸は、ビニルスルホン酸、アリルスルホン酸、スチレンスルホン酸、イソプレンスルホン酸、３－アリロキシ－２－ヒドロキシプロパンスルホン酸、２－アクリルアミド－２－メチルプロパンスルホン酸、２－メタクリルアミド－２－メチルプロパンスルホン酸、メタクリル酸－４－スルホブチル、アリルオキシベンゼンスルホン酸、メタリルオキシベンゼンスルホン酸及びそれらの金属塩などが挙げられる。これらのスルホン酸は、１種のみを用いてもよいし、２種以上を用いてもよい。 Examples of the sulfonic acid constituting the above-described copolymer include sulfonic acid such as vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, isoprene sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, 2-acrylamide. Examples include -2-methylpropane sulfonic acid, 2-methacrylamide-2-methylpropane sulfonic acid, -4-sulfobutyl methacrylate, allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, and metal salts thereof. These sulfonic acids may be used alone or in combination of two or more.
　また、ノニオン基含有モノマーとしては、例えば、炭素数１～５のアルキルアミド、ヒドロキシエチルメタクリレート、付加モル数が１～３０の（ポリ）エチレン／プロピレンオキサイドのモノ（メタ）アクリレート及び付加モル数が１～３０のモノビニルエーテルエチレン／プロピレンオキサイドなどが挙げられる。これらのノニオン基含有モノマーは、１種のみを用いてもよいし、２種以上を用いてもよい。 Nonionic group-containing monomers include, for example, alkyl amides having 1 to 5 carbon atoms, hydroxyethyl methacrylate, (poly) ethylene / propylene oxide mono (meth) acrylates having 1 to 30 addition moles, and addition moles. Examples thereof include 1 to 30 monovinyl ether ethylene / propylene oxide. These nonionic group containing monomers may use only 1 type, and may use 2 or more types.
　前述した共重合体のうち、マレイン酸の重合体（ホモポリマー及び／又はコポリマー）は特に限定されないが、マレイン酸の単位を、５０～１００ｍｏｌ％含むものが好ましい。マレイン酸の共重合体の場合、マレイン酸と共重合させる他のモノマーは、ノニオン性のモノマーであればよい。ノニオン性モノマーとしては、例えば、モノエチレン性不飽和炭化水素、モノエチレン性不飽和酸のアルキルエステル、モノエチレン性不飽和酸のビニルエステル、置換アクリルアミドなどがあり、これらのモノマーのうち、１～２種を、マレイン酸と共重合させることができる。 Among the above-mentioned copolymers, the maleic acid polymer (homopolymer and / or copolymer) is not particularly limited, but preferably contains 50 to 100 mol% of maleic acid units. In the case of a maleic acid copolymer, the other monomer to be copolymerized with maleic acid may be a nonionic monomer. Nonionic monomers include, for example, monoethylenically unsaturated hydrocarbons, alkyl esters of monoethylenically unsaturated acids, vinyl esters of monoethylenically unsaturated acids, substituted acrylamides, etc. Among these monomers, 1 to The two can be copolymerized with maleic acid.
　モノエチレン性不飽和炭化水素は、炭素数３～８の直鎖、分岐、又は環状のものが好ましく、例えばイソブチレン、スチレンなどである。モノエチレン性不飽和酸のアルキルエステルは、炭素数１～８のものが好ましく、例えば、メチル（メタ）アクリレート、エチル（メタ）アクリレート、イソプロピルアクリレート、Ｎ－ブチルアクリレート、２－エチルへキシルアクリレートなどである。モノエチレン性不飽和酸のビニルエステルは、炭素数１～８のものが好ましく、例えば、酢酸ビニル、プロピオン酸ビニルである。置換アクリルアミドは、水素及び／又は炭素数１～４のアルキル基で置換されたものが好ましく、例えば、アクリルアミド、プロピルアクリルアミド、Ｎ－イソプロピルアクリルアミド、ジメチルアクリルアミド及びジエチルアクリルアミドである。 The monoethylenically unsaturated hydrocarbon is preferably a linear, branched or cyclic one having 3 to 8 carbon atoms, such as isobutylene or styrene. The alkyl ester of monoethylenically unsaturated acid preferably has 1 to 8 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl acrylate, N-butyl acrylate, 2-ethylhexyl acrylate, etc. It is. The vinyl ester of a monoethylenically unsaturated acid preferably has 1 to 8 carbon atoms, and examples thereof include vinyl acetate and vinyl propionate. The substituted acrylamide is preferably one substituted with hydrogen and / or an alkyl group having 1 to 4 carbon atoms, and examples thereof include acrylamide, propylacrylamide, N-isopropylacrylamide, dimethylacrylamide and diethylacrylamide.
　本実施形態のスケール防止方法では、分子量が特定の範囲内にあり、（メタ）アクリル酸に由来する単位と、特定量の２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有する水溶性共重合物を主成分とするスケール防止剤を使用しているため、排水中のリン濃度に影響を与えずに、逆浸透膜処理において生成するリン酸カルシウムスケールの析出を抑制することができ、更にゲル化物などの微小な析出物も生成しない。また、本実施形態のスケール防止方法は、水系にスケール防止剤を少量添加するだけで、安定してスケールの析出を抑制することが可能である。 In the scale prevention method of the present embodiment, the molecular weight is in a specific range, the unit derived from (meth) acrylic acid, and the structural unit derived from a specific amount of 2- (meth) acrylamido-2-methylpropanesulfonic acid. Suppressing the precipitation of calcium phosphate scale produced in reverse osmosis membrane treatment without affecting the phosphorus concentration in the wastewater, because it uses a scale inhibitor mainly composed of a water-soluble copolymer containing In addition, fine precipitates such as gelled products are not generated. Moreover, the scale prevention method of this embodiment can suppress the precipitation of scale stably only by adding a small amount of a scale inhibitor to the aqueous system.
　なお、本実施形態のスケール防止方法は、適用する水系の水質条件及び運転条件は、特に限定されない。また、本実施形態のスケール防止方法における上記以外の構成及び効果は、前述した第１の実施形態と同様である。 In addition, the water quality condition and operation condition of the water system to which the scale prevention method of this embodiment is applied are not particularly limited. In addition, the configuration and effects other than those described above in the scale prevention method of the present embodiment are the same as those of the first embodiment described above.
　以下、本発明の実施例及び比較例を挙げて、本発明の効果について具体的に説明する。本実施例においては、以下に示す方法で、本発明の範囲内の実施例１～３のスケール防止剤及び本発明の範囲から外れる比較例１～４のスケール防止剤について、その性能を評価した。実施例１～３のスケール防止剤の詳細を下記表１に、比較例１～４のスケール防止剤の詳細を下記表２にそれぞれ示す。なお、下記表１及び表２に示す各モノマーは、ＡＡ：アクリル酸、ＡＭＰＳ：２－アクリルアミド－２－メチルプロパンスルホン酸である。 Hereinafter, the effects of the present invention will be described in detail with reference to examples and comparative examples of the present invention. In this example, the performances of the scale inhibitors of Examples 1 to 3 within the scope of the present invention and the scale inhibitors of Comparative Examples 1 to 4 outside the scope of the present invention were evaluated by the following methods. . Details of the scale inhibitors of Examples 1 to 3 are shown in Table 1 below, and details of the scale inhibitors of Comparative Examples 1 to 4 are shown in Table 2 below. The monomers shown in Tables 1 and 2 below are AA: acrylic acid and AMPS: 2-acrylamido-2-methylpropanesulfonic acid.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
＜平膜試験＞
　先ず、膜の初期性能を測定するため、５００ｍｇ／ＬのＮａＣｌ水溶液を、ポリアミド逆浸透膜（日東電工社製　ＥＳ２０）に、操作圧を０．７５ＭＰａ、回収率を５０％として通水し、フラックス（Ｆｌｕｘ）を所定時間測定した。 <Flat membrane test>
First, in order to measure the initial performance of the membrane, a 500 mg / L NaCl aqueous solution was passed through a polyamide reverse osmosis membrane (ES20 manufactured by Nitto Denko Corporation) at an operating pressure of 0.75 MPa and a recovery rate of 50%. (Flux) was measured for a predetermined time.
　次に、塩化カルシウム：５００ｍｇＣａＣＯ３／Ｌ、実施例１～３及び比較例１～８のスケール防止剤（重合物）：１ｍｇ／Ｌ、リン酸水素２ナトリウム：３０ｍｇＣａＣＯ３／Ｌを含有する水溶液を調整し、更に、少量の水酸化ナトリウム水溶液と硫酸水溶液でｐＨを７．０に調製して試験溶液とした。そして、各試験溶液を、ポリアミド逆浸透膜（日東電工社製　ＥＳ２０）に、操作圧を０．７５ＭＰａ、回収率を５０％として通水し、フラックス（Ｆｌｕｘ）を所定時間測定した。 Next, an aqueous solution containing calcium chloride: 500 mg CaCO 3 / L, Examples 1 to 3 and Comparative Examples 1 to 8 scale inhibitors (polymers): 1 mg / L, disodium hydrogen phosphate: 30 mg CaCO 3 / L Further, the pH was adjusted to 7.0 with a small amount of aqueous sodium hydroxide and sulfuric acid to prepare a test solution. Each test solution was passed through a polyamide reverse osmosis membrane (ES20 manufactured by Nitto Denko Corporation) at an operating pressure of 0.75 MPa and a recovery rate of 50%, and flux was measured for a predetermined time.
　その結果を、図１及び図２に示す。なお、図１及び図２は、５００ｍｇ／ＬのＮａＣｌ水溶液におけるフラックスを１とし、試験溶液で測定したフラックスとの比（フラックス比）の経時変化を示す図である。また、図１及び図２に示すブランク（Ｂｌａｎｋ）は、薬品未添加のときのフラックス比である。 The results are shown in FIG. 1 and FIG. FIGS. 1 and 2 are graphs showing changes with time in the ratio (flux ratio) to the flux measured with the test solution, where the flux in a 500 mg / L NaCl aqueous solution is 1. FIG. Moreover, the blank (Blank) shown in FIG.1 and FIG.2 is a flux ratio when a chemical | medical agent is not added.
　図１に示すように、薬品未添加のＢｌａｎｋでは、フラックスの低下が見られたが、実施例１～３のスケール防止剤を添加したものでは、いずれもフラックスの低下が抑制されていた。これにより、実施例１～３のスケール防止剤を添加した系では、スケールの析出が抑制され、安定した膜処理が可能であることがわかった。 As shown in FIG. 1, in the blank to which no chemical was added, a decrease in flux was observed, but in the cases where the scale inhibitors of Examples 1 to 3 were added, the decrease in flux was suppressed. As a result, it was found that in the systems to which the scale inhibitors of Examples 1 to 3 were added, scale deposition was suppressed and stable film treatment was possible.
　また、実施例１～３のフラックスの低下速度を比較すると、実施例１＜実施例２＜実施例３の順であり、実施例１が最もフラックス低下を抑制できていることがわかる。特に、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する単位が１５～２５ｍｏｌ％の範囲内にある水溶性共重合物を使用している実施例１のスケール防止剤は、フラックス低下が大幅に抑制されていた。 Further, when the flux reduction rates of Examples 1 to 3 are compared, it is found that Example 1 <Example 2 <Example 3 in order, and Example 1 can most effectively suppress the flux reduction. In particular, the scale inhibitor of Example 1 using a water-soluble copolymer having a unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid in the range of 15 to 25 mol% has reduced flux. Was significantly suppressed.
　これに対して、図２に示すように、比較例１～４のスケール防止剤を使用した系では、フラックスの低下が見られた。その低下速度を比較すると、実施例１～３＜比較例１＜比較例３、４＜Ｂｌａｎｋ＜比較例２の順であった。 On the other hand, as shown in FIG. 2, in the system using the scale inhibitor of Comparative Examples 1 to 4, a decrease in flux was observed. The rate of decrease was compared in the order of Examples 1 to 3 <Comparative Example 1 <Comparative Example 3 and 4 <Blank <Comparative Example 2.
　比較例１、２のスケール防止剤は、実施例１のスケール防止剤とモノマー（ＡＡ／ＡＭＰＳ）の組成は同じであるが、フラックスが低下していた。これは、比較例１のスケール防止剤は、水溶性共重合物の分子量が１×１０４未満であったため、スケールの析出抑制効果が低く、また、比較例２のスケール防止剤は、水溶性共重合物の分子量が５×１０４を超えていたため、ゲル化物が生成したものと考えられる。特に、比較例２のスケール防止剤では、生成した微小な析出物により膜閉塞が生じ、Ｂｌａｎｋよりもフラックス低下が早くなったと考えられる。 The scale inhibitors of Comparative Examples 1 and 2 had the same composition of the scale inhibitor and monomer (AA / AMPS) of Example 1, but the flux was reduced. This is because the scale inhibitor of Comparative Example 1 had a molecular weight of the water-soluble copolymer of less than 1 × 10 4 , so the effect of suppressing the precipitation of scale was low, and the scale inhibitor of Comparative Example 2 was water-soluble. Since the molecular weight of the copolymer exceeded 5 × 10 4 , it is considered that a gelled product was generated. In particular, in the scale inhibitor of Comparative Example 2, it is considered that the film was clogged by the generated fine precipitate, and the flux decrease was faster than that of Blank.
　また、比較例３、４のスケール防止剤は、水溶性共重合物の分子量は１×１０４～５×１０４あるが、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する単位が１０ｍｏｌ％未満又は４０ｍｏｌ％を超えていたため、フラックスが低下した。 Further, the scale inhibitors of Comparative Examples 3 and 4 have a molecular weight of 1 × 10 4 to 5 × 10 4 of the water-soluble copolymer, but are units derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid. Was less than 10 mol% or more than 40 mol%, the flux decreased.
　以上の結果から、本発明によれば、排水中のリン濃度を増加させることなく、逆浸透膜処理において生成するリン酸カルシウムスケールの析出を抑制することができ、かつゲル化物などの微小な析出物が生成しない逆浸透膜用スケール防止剤を実現できることが確認された。  From the above results, according to the present invention, it is possible to suppress the precipitation of calcium phosphate scale generated in the reverse osmosis membrane treatment without increasing the phosphorus concentration in the waste water, and fine precipitates such as gelled substances are present. It was confirmed that a scale inhibitor for reverse osmosis membrane that does not form can be realized.

Claims (4)

  1. 　逆浸透膜処理においてリン酸カルシウムスケールの析出を抑制するスケール防止剤であって、
    　主成分が、（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有し、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する単位が１０～４０ｍｏｌ％であり、かつ、質量平均分子量が１×１０４～５×１０４である水溶性共重合物である逆浸透膜用スケール防止剤。     A scale inhibitor that suppresses the precipitation of calcium phosphate scale in reverse osmosis membrane treatment,
    The main component has a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid, and has 2- (meth) acrylamido-2-methylpropanesulfone. A scale inhibitor for reverse osmosis membranes, which is a water-soluble copolymer having an acid-derived unit of 10 to 40 mol% and a mass average molecular weight of 1 × 10 4 to 5 × 10 4 .
  2. 　前記水溶性共重合物は、リンを含有しない請求項１記載の逆浸透膜用スケール防止剤。 The scale inhibitor for reverse osmosis membrane according to claim 1, wherein the water-soluble copolymer does not contain phosphorus.
  3. 　前記水溶性重合物は、（メタ）アクリル酸と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸との共重合体である請求項１又は２に記載の逆浸透膜用スケール防止剤。 The scale inhibitor for reverse osmosis membrane according to claim 1 or 2, wherein the water-soluble polymer is a copolymer of (meth) acrylic acid and 2- (meth) acrylamido-2-methylpropanesulfonic acid.
  4. 　（メタ）アクリル酸に由来する単位と、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する構成単位とを有し、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸に由来する単位が１０～４０ｍｏｌ％であり、かつ、質量平均分子量が１×１０４～５×１０４である水溶性共重合物を主成分とするスケール防止剤を、逆浸透膜処理水系に添加するスケール防止方法。  It has a unit derived from (meth) acrylic acid and a structural unit derived from 2- (meth) acrylamido-2-methylpropanesulfonic acid, and is derived from 2- (meth) acrylamide-2-methylpropanesulfonic acid A scale in which a scale inhibitor mainly composed of a water-soluble copolymer having a unit of 10 to 40 mol% and a mass average molecular weight of 1 × 10 4 to 5 × 10 4 is added to a reverse osmosis membrane treated water system Prevention method.
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