Method for inhibiting silica scale using acid-grafted EO-PO copolymer

Abstract

To provide a method of inhibiting silica scale formation by using a polymer with scale inhibition performance exceeding those known in the art as a scale inhibitor.SOLUTION: A method includes a step of treating an aqueous system containing silica with an effective amount of polymerizable acid graft polymer containing about 3.0 wt.% to about 35 wt.% of an unsaturated graft acid and an alkylene oxide polymer backbone.SELECTED DRAWING: None

Description

Technical Field

[0001] Cross-reference This international patent application claims the priority of Indian Provisional Application No. 201841 020598 filed on June 1, 2018.

[0002] The present invention relates to scale inhibition. Specifically, the present invention relates to the use of acid-grafted EO-PO copolymers for inhibiting the formation of silica scale.

Background Art

[0006] Scale inhibitors are known in the art. For example, U.S. 6,166,1 Product No. 49 contains a hydrophilic graft polymer and a polyether compound, and is optionally unsaturated. Hydrophilic polymers, which are suitable as scale inhibitors, further contain carboxylic acid-type polymers. A process for producing a futopolymer-containing composition is disclosed. Similarly, U.S. Patent No. 5 Numbers 378 and 368 are for controlling silica / silicate deposition in industrial water systems. The use of polyether polyaminomethylene phosphonate is disclosed. Minomethylene phosphonate can be used alone or in combination with polymer additives. It is possible.

[0007] U.S. Patent No. 4,618,448 relates to carboxylic acid / sulfone as a scale inhibitor. While disclosing the use of acid / polyalkylene oxide polymers, U.S. Patent No. 4,933, No. 090 is a selected phosphonate and neutron for controlling silica / silicate deposition. The use of deselective carboxylic acid / sulfonic acid / polyalkylene oxide polymers is disclosed. U.S. Patent No. 6,051,142 relates to silica in cooling and boiler water systems. Ethylene oxide-propylene oxide (EO-) for controlling the scale of bisilicate The use of PO) block copolymers is disclosed. Finally, U.S. Patent No. 7,316,787 This involves the use of hydrophobic modified ethylene oxide polymers as colloidal silica scale inhibitors. Disclose its purpose.

[0008] Despite the development of new scale inhibitors, silica scaling persists in aqueous systems. This remains a major challenge, and therefore, it is necessary to go beyond what is known in this field. This indicates the need for polymers with kale-inhibiting properties. [Overview of the project]

[0009] According to one aspect of the present invention, an aqueous system containing silica is made into an unsaturated graft acid (acrylic Acids, methacrylic acid, itaconic acid, maleic acid, 2-acrylamido-2-methylpropyl Sulfonic acid (AMPS), 2-methacrylamido-2-methylpropylsulfonic acid, st Lensulfonic acid, vinyl sulfonic acid, ethylene glycol methacrylate phosphate, (or vinylphosphonic acid, etc.) and a percentage acid graph of approximately 3% to 35% by weight. Effective amounts of polymerizable acid graft copolymer having an alkylene oxide polymer backbone. A method is provided to inhibit silica scale formation by treating with alkylene. The oxide polymer backbone has the following formula: [ka] In the formula, each R' is independently either a hydrogen atom, a hydrogen radical, or an acyl radical. And R'' is independently a hydrogen atom, a hydrogen radical, an amine-containing radical, or an acyl. Either a radical, each "n" independently has a value of 2 to 4, and each "Z" independently has a value of 4 to about 1800, and "a" has a value of 1 to 4. In a preferred embodiment , "n" = 2 or 3, "a" has a value of 1, and each R' or R" is independently a hydrogen atom, a hydrogen radical, or either an acyl radical, and each results in either ethylene oxide ("EO") or propylene oxide ("PO") polymer. The base polymer preferably has a molecular weight of about 200 Daltons to 80,000 Daltons.

[0010] The disclosed invention is directed to the novel use of an acrylic acid grafted ethylene oxide - propylene oxide (EO - PO) copolymer as a colloidal silica scale inhibitor for use in reverse osmosis (RO), cooling towers, boilers, geothermal, and SAGD applications. In a preferred embodiment, the copolymer for use in the disclosed invention has a molecular weight of about 5000 Daltons and has about 10 wt% of acrylic acid grafted to an alkylene oxide polymer backbone, and is a copolymer of EO and PO. One advantage of this copolymer is that it inhibits the formation of colloidal silica that minimizes the formation of precipitates (flocs) that can adversely affect the above applications.

[0011] Best Mode for Carrying Out the Invention The disclosed invention involves treating an aqueous system containing silica with an unsaturated grafting acid (acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2 - acrylamido - 2 - methylpropylsulfonic acid (AMPS), 2 - methacrylamido - 2 - methylpropylsulfonic acid, styrene sulfonic acid, vinylsulfonic acid, ethylene glycol methacrylate phosphate, vinyl It contains acids selected from the group consisting of phosphonic acids, etc., and is present in a quantity of approximately 3% to 35% by weight. It has a scent acid graft and an alkylene oxide polymer skeleton, and alkylene oxide Treatment with an effective amount of polymerizable acid graft copolymer having a polymer backbone with the following formula. This article focuses on methods for inhibiting silica scale formation through [a specific method]. [ka] In the formula, each R' is independently selected from a hydrogen atom, a hydrogen radical, or an acyl radical. R'' is derived from a hydrogen atom, a hydrogen radical, an amine-containing radical, or an acyl radical. Selected, each "n" independently has a value between 2 and 4, and each "Z" independently has a value between 4 and approximately 180. It has a value of 0, and "a" has a value of 1 to 4. In one embodiment, R' is an aliphatic unsaturated It is an acyl radical that does not contain hydrogen. In another embodiment, R' and R'' are both hydrogen It's not an atom.

[0012] All percentages stated herein are weight percentages unless otherwise specified. It is -cent (by weight %).

[0013] Temperature is expressed in degrees Celsius (°C), and "ambient temperature" refers to 20°C to 2°C unless otherwise specified. It means 5℃.

[0014] A "polymer" is formed by polymerizing monomers, whether of the same or different types. Refers to polymer compounds or "resins" prepared by the means described herein. In this context, the general term "polymer" refers to a polymer made from one or more types of monomers. Contains a rimer compound. The term "copolymer" as used herein refers to two or more different types. It is a polymer compound prepared from monomers. Similarly, "terpolymer" is a polymer compound prepared from three monomers. These are polymer compounds prepared from different types of monomers.

[0015] "Water-based" generally refers to cooling water, boiler water, desalination, gas, etc., although not limited to these. Scrubbers, blast furnaces, sewage sludge heat treatment equipment, filtration, reverse osmosis, sugar evaporators, paper processing, mining circuits, etc. This refers to any system containing water, such as the following.

[0016] The term "silica scale" generally refers to the deposits and accumulations on the inner surfaces of water treatment equipment. This refers to a solid material containing silica. "Silica scale" generally refers to a colloidal or Multiple materials including amorphous silica (SiO2) and silicates (such as magnesium silicate). It contains silica scale of the type. The accumulated silica scale is silica and silicates. It may be a combination of types of scales, and in some cases one of them may be a tie. The porosity scale is often dominant. Colloidal / amorphous silica scale is... Below, silica scale deposits, mainly colloidal / amorphous silicate type, are common. This is a term used to refer to calcium carbonate, calcium sulfate, depending on the type of metal. Um, calcium phosphate, calcium phosphonate, calcium oxalate, barium sulfate, Other types of silica include silica, alluvial deposits, metal oxides, and metal hydroxides. A scale of this type may exist, and other ions are present in aqueous systems.

[0017] The chemical reaction mechanism for forming colloidal / amorphous silica scales is generally This involves the condensation polymerization of silica to polysilicates catalyzed by hydroxide ions. The response mechanism generally proceeds as follows: Si(OH)4+OH - →(OH)3SiO - +H2O (I) Si(OH)3 - +Si(OH)4+OH - →(OH)3Si-O-Si(OH)3( dimer)+OH - (II) (OH)3Si-O-Si(OH)3 (dimer) → cyclic → colloidal → amorphous Rika (Scale) (III)

[0018] The reaction mechanism is catalyzed by hydroxide ions, so it proceeds slowly at low pH. However, when the pH exceeds approximately 7, it increases significantly. Therefore, a "medium" pH of 6.5 to 8.5 is recommended. Preventing silica scale formation in aqueous systems with a specific pH is a particular concern.

[0019] The method of the present invention has a pH of 6.5 to 10.0 at a temperature in the range of 20°C to 250°C. Suitable for controlling the deposition of colloidal / amorphous silica scale in aqueous systems. Yes. This method involves using an effective amount of acrylic acid grafted ethylene oxide-propylene oxide ( This includes adding an EO-PO copolymer to an aqueous system.

[0020] Graft polymers Graft polymers are (1) linear skeletal polymers and (2) random graft polymers of another polymer. It is a segmented copolymer containing branches distributed throughout.

[0021] Skeletal polymers Poly(alkylene oxide) compounds used to produce graft copolymers Generally, alkylene oxide or a mixture of alkylene oxides is used, in succession or It is produced by reacting it with alcohol in combination. It can be monovalent or polyvalent, and the formula R''(OH) a Corresponding to the formula, where R'' represents a hydrogen atom, hydrogen Selected from the group consisting of radicals, amine-containing radicals, and acyl radicals, "a" It has a value of 1 to 4. Such alcohols include methanol, ethanol, and propano. Glycerol, butanol, ethylene glycol, glycerol, glycerol monoethyl alcohol Tel, dimethyl ether of glycerol, sorbitol, 1,2,6-hexanetriole Contains trimethylolpropane, etc.

[0022] Generally, the poly(oxyalkylene) compounds used in this invention have a yield of approximately 200 daltons. ~Approximately 80,000 Daltons, preferably approximately 1,500 Daltons to approximately 20,000 Daltons It has a molecular weight (number average) within a range.

[0023] Grafting polymerizable acids onto poly(oxyalkylene) compounds is a form of free radical polymerization. This can be done by using approximately 3 to 35 (preferably approximately 5 to 25) grafting acids. Give the content.

[0024] Useful graft acids include, in particular, acrylic acid, methacrylic acid, itaconic acid, and maleic acid. Acid, 2-acrylamido-2-methylpropylsulfonic acid (AMPS), 2-methacrylate Amido-2-methylpropylsulfonic acid, styrenesulfonic acid, vinylsulfonic acid, ethyl It contains ylene glycol methacrylate phosphate and vinylphosphonic acid, and acrylic Acids, maleic acid, and vinylphosphonic acid are more preferred, and acrylic acid is most preferred.

[0025] A poly(oxyalkylene) compound useful in the present invention has the following formula: death, [ka] In the formula, each R' is independently either a hydrogen atom, a hydrogen radical, or an acyl radical. And R'' is independently a hydrogen atom, a hydrogen radical, an amine-containing radical, or an acyl. It is one of the radicals, each "n" independently has a value between 2 and 4, and each "Z" is independent In a preferred embodiment, the value ranges from 4 to approximately 1800, and "a" has a value of 1 to 4. Poly(oxyalkylene) compounds have a value of "n" = 2 or 3 and "a" = 1, each R' or R'' independently consists of a hydrogen atom, a hydrogen radical, or an acyl radical. Yes, ethylene oxide ("EO") or propylene oxide ("PO") polymers Poly(oxyethylene-oxypropylene) polymers that provide either of the following effects —.

[0026] Poly(oxyethylene-oxypropylene) polymers are available in a ratio of 0:100 to 100:0. It has a weight ratio of oxyethylene ("EO") to oxypropylene ("PO"). EO- PO copolymers can inhibit silica scale formation, thus the graph of the present invention It is particularly suitable as a backbone for polymers. EO-PO copolymers have ethoxy groups and p The organic compound containing a ropoxy group, and a suitable EO-PO copolymer is EO / PO Random copolymers of EO, homopolymers of PO, homopolymers of EO / PO, blocks of EO / PO This may include cucumber copolymers and reverse block copolymers of EO / PO. The ratio can be approximately 100:0 to 0:100, preferably approximately 90:10 to 10:90. It is more preferably about 75:25 to about 25:75, and most preferably about 5 The ratio is 0:50. The graft polymer of the present invention preferably contains 65% to 97% by weight. Contains a skeletal polymer.

[0027] How to use "Effective amount" refers to the colloidal / amorphous silica scale in the aqueous system being treated. This is the amount of graft copolymer needed to inhibit the deposition of chromosomes. "Inhibit" means that the deposition of chromosomes is inhibited. Delaying the deposition of id-like / amorphous silica scale extends the period of maximum efficiency of the instrument. This means that the effective amount of graft copolymer added to an aqueous system is the amount present in the aqueous system. Depending on the concentration of silica, salt, and polyvalent metal ions, as well as the temperature and pH of the aqueous system It can vary. For most applications, the effective amount of graft copolymer is approximately 0.5 ppm to approximately The concentration is 1,000 ppm, and more preferably in the range of about 1 ppm to 100 ppm. Aqueous systems treated with Ming's graft copolymer are typically 30 ppm, 50 ppm, Alternatively, it has a silica content exceeding 100 ppm.

[0028] To prepare graft polymers useful in the method of the present invention for controlling deposition The polymerization method used is not particularly limited and may be any known to those skilled in the art, either now or in the future. This may be, but is not limited to, the methods described in U.S. Patent No. 4,146,488, and No. 4, Disclosed in Patent Nos. 392,972, 5,952,432, and 6,143,243. This includes emulsions, solutions, additives, and free radical polymerization techniques, including the method described above. These are incorporated herein by reference.

[0029] The uses, applications, and advantages of the present invention are discussed below in the following exemplary embodiments of the present invention and This will be clarified through explanation. [Examples]

[0030] The following examples illustrate various non-limiting aspects of the present invention disclosed and claimed herein. This indicates the application method and its specific attributes.

[0031] Acid grafting onto copolymers Acid graft copolymer, acrylic acid, molecular weight 770, viscosity 170 sebol-seconds A butanol-initiated poly(oxyethylene-oxypropylene) copolymer containing The following preparation was made using a polymer at 37.8°C. A 5L unit comprising a water condenser, thermocouple, stirrer, and means for introducing acrylic acid and catalyst. 2,700g of base polymer was placed in a three-necked round-bottom flask. Heating mantle Using this method, the flask is heated to a temperature of 150°C, followed by 35g of tertiary butyl perbenzoate. And 312g of acrylic acid was added. The peroxide supply was opened 10 minutes before starting the acid supply. Initially, both components were supplied over a period of 90 minutes, after which the product was allowed to cool to room temperature.

[0032] Static bottle test Static bottle testing was used to evaluate the effectiveness of various polymers that inhibit silica polymerization. The free silica (reactive silica) remaining in the solution was measured in the HACH silicic acid molybdate ratio. The results were tracked using a colorimetric method. Polymers that were highly effective in inhibiting the formation of colloidal silica dissolved The level of free silica in the liquid was maintained for a long period of time. The supersaturated silica solution was 40 as SiO2. To obtain an initial silica concentration of 0 ppm, dissolve sodium silicate salt in deionized water. It was prepared by [method / method].

[0033] In the first set of static bottle tests, 5, 15, and 25 ppm (as active substance) The inhibitor of the present invention was administered into a supersaturated silica solution, and the pH was adjusted to 7.5. Then, the test The material was left to stand at 20°C for 24 hours. After 24 hours, the silica solution was thoroughly mixed and the turbidity was measured using a turbidimeter. The sample was then analyzed to check for the presence of insoluble flocs. Next, the silica sample was 0.45 The filtrate was filtered through a μm filter and analyzed using the HACH colorimetric method. Sample A was acrylic It is an acid (AA) grafted ethylene oxide-propylene oxide copolymer. Sample B is It is a copolymer of ungrafted ethylene oxide and propylene oxide.

[0034] The final soluble silica concentration was measured for solutions containing the inhibitor and solutions without the inhibitor. Afterward, the percentage-scale inhibition was calculated according to the following formula.

number

[0035] Sample A does not form insoluble precipitates or flocs, and exhibits high levels in solution. It was decided to maintain reactive silica. In comparison, sample B inhibited colloidal silica. However, this resulted in insoluble flocs and a significant increase in the turbidity of the silica brine.

[0036] In the second set of static bottle tests, 100 pp of calcium chloride dihydrate was added. m Network 2+, and 40 ppm Mg added as magnesium chloride hexahydrate. 2+ of In addition to 400 ppm SiO2 added as sodium silicate, the hardness of io The effects of the inhibitor were evaluated. The inhibitor was added at 5, 15, and 25 ppm (as the active substance). Next, the pH of the brine was adjusted to 7.5. Then, the sample was left to stand at 20°C for 24 hours. After 24 hours, the silica solution is thoroughly mixed and the turbidity is analyzed using a turbidimeter to determine the presence of insoluble flocs. The presence of was checked. Next, the silica sample was filtered through a 0.45 μm filter and HACH The filtrate was analyzed using a colorimetric method. Sample A was acrylic acid (AA) grafted ethylene oxide. It is a side-propylene oxide copolymer. Sample B is ungrafted ethylene It is an oxide-propylene oxide copolymer. The results of the turbidity and silica inhibition tests were... This is summarized in Table 2. [Table 2]

[0037] Sample A is a solution with minimal turbidity and a very small amount of insoluble precipitate or flocs. It was determined that a high level of reactive silica was maintained within it. In comparison, sample B was colloidal While it showed inhibition of silica, it resulted in a large amount of insoluble flocs and increased the turbidity of silica brine. The width increased.

[0038] Although the present invention has been described with reference to its preferred embodiments disclosed in the above specification and drawings, many more embodiments of the present invention are possible without departing from the present invention. Accordingly, the scope of the present invention should be limited only by the appended claims. The present invention may include the following embodiments. [1] A method for inhibiting silica scale formation, comprising the step of treating an aqueous system containing silica with an effective amount of polymerizable acid graft polymer containing about 3.0% to about 35% by weight of an unsaturated graft acid and an alkylene oxide polymer backbone, wherein the alkylene oxide polymer backbone has the following formula:

change

[10] The polymer has a number-average molecular weight of about 1,500 daltons to about 80,000 daltons, according to the method in [1].

[11] The method according to [1], wherein the graft acid is acrylic acid (10% by weight), and the alkylene oxide polymer backbone is poly(oxyethylene-oxypropylene) having a weight ratio of oxyethylene ("EO") to oxypropylene ("PO") of 50:50.

[12] The method according to [1]0, wherein the poly(oxyethylene-oxypropylene) has a molecular weight of about 5000 daltons.

[13] The method according to [1], wherein the effective amount of the graft polymer is about 0.5 ppm to about 1000 ppm.

[14] The aqueous system is the method according to [1], having a pH of about 6.0 to about 10.0.

[15] The aqueous system is the method according to [1], having a temperature of 20°C to 250°C.

[16] The aqueous system is selected from the group consisting of cooling water, desalination, filtration, reverse osmosis, sugar evaporator, paper processing, mining circuit, geothermal energy system, SAGD system, and silica brine, according to the method in [1].

[17] The aqueous system is the silica brine, and the graft polymer inhibits silica scale formation with minimal precipitate formation, according to the method of

[10] .

[18] The effective amount of the aqueous system is 5 ppm to 15 ppm. The aqueous system, after being treated with the graft polymer for 24 hours, exhibits a percentage inhibition of silica scale of more than 50%. The aqueous system, after being treated with the graft polymer for 24 hours, has a turbidity of less than 10 NTU, according to the method in [1].

Claims

1. A method for inhibiting silica scale formation, comprising the step of treating an aqueous system containing silica with an effective amount of polymerizable acid graft polymer consisting of an unsaturated graft acid and an alkylene oxide polymer skeleton, wherein the alkylene oxide polymer skeleton has the following formula: 【Chemistry 1】 In the formula, each R' is independently selected from the group consisting of hydrogen radicals and acyl radicals. R'' is independently selected from the group consisting of hydrogen radicals, amine-containing radicals, and acyl radicals. Each "n" independently has a value between 2 and 4. Each "Z" independently has a value between 4 and 1800. "a" has values ​​from 1 to 4. The graft acid is present in an amount of 10% by weight.

2. The method according to claim 1, wherein the graft acid is acrylic acid.

3. The method according to claim 1, wherein the alkylene oxide polymer backbone is poly(oxyethylene-oxypropylene) having a weight ratio of 50:50 oxyethylene ("EO") to oxypropylene ("PO").

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