WO2015110297A1

WO2015110297A1 - New antiscalants

Info

Publication number: WO2015110297A1
Application number: PCT/EP2015/050295
Authority: WO
Inventors: Andreas Kempter; Torben GÄDT; Fabian Niedermair; Manfred Bichler
Original assignee: Basf Se
Priority date: 2014-01-24
Filing date: 2015-01-09
Publication date: 2015-07-30

Abstract

Use of a copolymer comprising acrylic acid, methacrylic acid and methallylsulfonic acid or salts thereof, wherein methallylsulfonic acid or salts thereof are comprised in said copolymer in an amount of 10 to 50 mol%, and wherein the molar ratio of acrylic acid to methacrylic acid or their salts is 0.5:1 to 5:1, as an antiscalant.

Description

New Antiscalants

Description The present invention relates to the use of a copolymer comprising acrylic acid, methacrylic acid and methallylsulfonic acid or salts thereof, wherein methallylsulfonic acid or salts thereof are comprised in said copolymer in an amount of 10 to 50 mol%, and wherein the molar ratio of acrylic acid to methacrylic acid is 0.5:1 to 5:1 , as an antiscalant.

The present invention further relates to novel copolymers comprising acrylic acid, methacrylic acid and methallylsulfonic acid. The present invention further relates to processes for making such copolymers. The formation and deposition of scales is an almost omnipresent problem in many applications in which devices are in constant or sporadic contact with water. The formation of scales is in many cases due to the formation and deposition of alkaline earth metal salts or silica. US 4,455,235 discloses the use of copolymers comprising acrylic acid, methacrylic acid as well as minor amounts of methallylsulfonate units as antiscalants. Copolymers according to US 4,455,235 comprise less than 20 % by weight of methallylsulfonate units.

WO 2008/017620 discloses cleaning formulations for dish washers, comprising copol- ymers that contain 1 to 50 % by weight of methallylsulfonic acid or its salts.

US 4,738,788 discloses copolymers comprising (meth)acrylic acid and 1 to 25 mol% of methallylsulfonic acid. The object of the present invention was to provide antiscalants with improved properties with respect to the prevention of the formation of scales.

This object has been achieved using copolymers comprising acrylic acid, methacrylic acid and methallylsulfonic acid or salts thereof, wherein methallylsulfonic acid or salts thereof are comprised in said copolymer in an amount of 10 to 50 mol%, and wherein the molar ratio of acrylic acid to methacrylic acid is 0.5:1 to 5:1 , as an antiscalant.

An antiscalant in the context of this application shall be understood to be a polymer that prevents, inhibits or reduces the formation and/or deposition of scales, typically inor- ganic scales. Scales include but are not limited to carbonates, hydrogen carbonates, hydroxides, sulfates of calcium, magnesium, strontium and barium as well as silica and silicates. In particular, antiscalants prevent, inhibit or reduce the formation and/or dep- osition of scales caused for example by calcium carbonate, calcium sulfate, barium sulfate, magnesium carbonate, magnesium hydroxide, strontium carbonate, strontium sulfate and/or silica or silicates of magnesium, aluminium and/or iron.

Molar contents of a monomer in a copolymer shall mean the molar content relative to the content of all monomers comprised in said copolymer.

In the context of this application, (meth)acrylic acid and methallylsulfonic acid shall be understood to mean these respective chemicals as the free acid bearing a -COOH or SO3H group or their salts, like sodium, potassium, calcium or magnesium salts of (meth)acrylic acid or methallylsulfonic acid.

Preferably, copolymers useful according to the invention comprise 10 to 25 mol% of methallylsulfonic acid, more preferably 1 1 to 23 mol%, even more preferably 12.5 to 22.5 and especially preferably 15 to 20 mol% of methallylsulfonic acid.

Preferably the molar ratio of acrylic acid to methacrylic acid is 1 :1 to 5:1 , more preferably 1 .2:1 to 4:1 and particularly preferably 1.5:1 to 3:1.

In one preferred embodiment, copolymers useful according to the invention comprise 10 to 25 mol% of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .2:1 to 4:1 .

In one preferred embodiment, copolymers useful according to the invention comprise 12.5 to 22.5 of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .2:1 to 4:1 .

In one preferred embodiment, copolymers useful according to the invention comprise 15 to 20 of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .2:1 to 4:1 .

In one preferred embodiment, copolymers useful according to the invention comprise 10 to 25 mol% of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .5:1 to 3:1 .

In one preferred embodiment, copolymers useful according to the invention comprise 12.5 to 22.5 of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .5:1 to 3:1 . In one preferred embodiment, copolymers useful according to the invention comprise 15 to 20 of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .5:1 to 3:1 . The average molecular mass Mw of copolymers useful according to the invention is normally 500 to 25,000, preferably 1500 to 20,000 and more preferably 2000 to 15,000 g/mol. In one preferred embodiment, copolymers useful according to the invention comprise less than 5 mol%, preferably less than 3 mol% and even more preferably less than 1 mol% of substituted or unsubstituted acrylamide or no substituted or unsubstituted acrylamide. In one preferred embodiment, copolymers useful according to the invention comprise less than 5 mol%, preferably less than 3 mol% and even more preferably less than 1 mol% of monomers that are hydrocarbons or no monomers that are hydrocarbons.

In one preferred embodiment, copolymers useful according to the invention comprise less than 5 mol%, preferably less than 3 mol% and even more preferably less than 1 mol% of dicarboxylic acids, their salts or anhydrides or no dicarboxylic acids, their salts or anhydrides.

In one preferred embodiment, copolymers useful according to the invention comprise less than 5 mol%, preferably less than 3 mol% and even more preferably less than 1 mol% of monomers different from acrylic acid, methacrylic acid and methallylsulfonic acid or salts thereof.

In one particularly preferred embodiment, copolymers useful according to the invention consist essentially of or consist of acrylic acid, methacrylic acid and methallylsulfonic acid or salts thereof.

Copolymers useful according to the invention can be used in combination with further antiscalants or further components like chelating agents, sequestering agents and/or dispersing agents. Suitable further antiscalants include but are not limited to polyacrylic acids, polyphosphonates, co- or multipolymers of acrylic acid and other monomers.

Preferably, copolymers useful according to the invention are used in combination with CaC03 antiscalants, CaSC antiscalants and / or polyacrylic acids, sulfonates, phos- phonates or copolymers of acrylic acid.

Copolymers useful according to the invention can be block copolymers or statistical polymers. Preferably copolymers useful according to the invention are statistical poly- mers. Copolymers useful according to the invention can in principle be used in all systems and devices that are constantly or sporadically in contact with water like seawater, fluvial water, brackish water, geothermal water, municipal or industrial wastewater, industrial process water like cooling water where scaling can occur.

Examples of such systems and devices include cooling towers, boilers, boiler feed systems, turbines, heat exchanging devices, heating systems, evaporators, hot water reservoirs, cooling circuits, desalination devices for sea water or brackish water, cleaning formulations, cleaning devices, waste water treatment plants, extraction devices, filtration devices, dialysis devices, reverse osmosis desalination plants and combinations thereof. Such water desalination units can for example be thermal desalination plants like multi-effect distillation desalination plant or / and Multi-stage-flash desalination plant and combinations of thermal and membrane desalination plants (hybrid systems) or rely on membrane technologies like reverse osmosis or electrodialysis.

For geothermal systems, it includes geothermal electric power generation and/or geo- thermal heating systems (e.g. district heating, space heating, spas, and industrial processes), where scaling can occur in wells, separators, pipes, heat exchangers and/or turbines.

Copolymers useful according to the invention are very effective and efficient antiscal- ants and are capable preventing, inhibiting or reducing the formation and/or deposition of scales, typically inorganic scales. Scales include but are not limited to carbonates, hydrogen carbonates, hydroxides, sulfates of calcium, magnesium, strontium and barium as well as silica and silicates. In particular, antiscalants prevent, inhibit or reduce the formation and/or deposition of scales caused for example by calcium carbonate, calcium sulfate, barium sulfate, magnesium carbonate, magnesium hydroxide, strontium carbonate, strontium sulfate and/or silica and silicates of e.g. magnesium, aluminium and/or iron. Copolymers useful according to the invention are especially effective for preventing, inhibiting or reducing the formation and/or deposition of scales caused by or silica and silicates of e.g. magnesium, aluminium and/or iron.

Use of the copolymers useful according to the invention prolongs the time between cleaning intervals of the devices, reduces the pressure increase in RO devices caused by deposition, reduces the use and costs of chemical cleaning agents and reduces pretreatment costs.

Another aspect of the present invention are copolymers comprising acrylic acid, meth- acrylic acid and, methallylsulfonic acid or salts thereof, wherein methallylsulfonic acid or salts thereof are comprised in said copolymer in an amount of 10 to 25 mol % and wherein the molar ratio of acrylic to methacrylic acid is 0.5:1 to 5:1 . Preferably, copolymers according to the invention comprise 1 1 to 23 mol%, more preferably 12.5 to 22.5 mol% of methallylsulfonic acid and even more preferably 15 to 21 mol% of methallylsulfonic acid. Preferably the molar ratio of acrylic acid to methacrylic acid is 1 :1 to 5:1 , more preferably 1 .2:1 to 4:1 and particularly preferably 1 .5:1 to 3:1.

In one preferred embodiment, copolymers according to the invention comprise 10 to 25 mol% of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .2:1 to 4:1 .

In one preferred embodiment, copolymers according to the invention comprise 12.5 to 22.5 of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .2:1 to 4:1 .

In one preferred embodiment, copolymers according to the invention comprise 15 to 20 of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .2:1 to 4:1 .

In one preferred embodiment, copolymers according to the invention comprise 10 to 25 mol% of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .5:1 to 3:1 . In one preferred embodiment, copolymers according to the invention comprise 12.5 to 22.5 of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .5:1 to 3:1 .

In one preferred embodiment, copolymers according to the invention comprise 15 to 20 of methallylsulfonic acid and the molar ratio of acrylic acid to methacrylic acid is 1 .5:1 to 3:1 .

The average molecular mass Mw of copolymers according to the invention is normally 500 to 25,000, preferably 1500 to 20,000 and more preferably 2000 to 15,000 g/mol.

In one preferred embodiment, copolymers according to the invention comprise less than 5 mol%, preferably less than 3 mol% and even more preferably less than 1 mol% of substituted or unsubstituted acrylamide or no substituted or unsubstituted acryla- mide. In one preferred embodiment, copolymers according to the invention comprise less than 5 mol%, preferably less than 3 mol% and even more preferably less than 1 mol% of monomers that are hydrocarbons or no monomers that are hydrocarbons.

In one preferred embodiment, copolymers according to the invention comprise less than 5 mol%, preferably less than 3 mol% and even more preferably less than 1 mol% of dicarboxylic acids, their salts or anhydrides or no dicarboxylic acids, their salts or anhydrides.

In one preferred embodiment, copolymers according to the invention comprise less than 5 mol%, preferably less than 3 mol% and even more preferably less than 1 mol% of monomers different from acrylic acid, methacrylic acid and methallylsulfonic acid or salts thereof.

In one particularly preferred embodiment, copolymers according to the invention consist essentially of or even consist of acrylic acid, methacrylic acid and methallylsulfonic acid or salts thereof. Copolymers according to the invention are normally made by radical polymerization of acrylic acid, methacrylic acid and methallylsulfonic acid.

In one embodiment of the invention, copolymers according to the invention are made using at least one azo initiator. In another embodiment, copolymers according to the invention are made using at least one redox initiator. In another embodiment, copoly- mers according to the invention are made using a combination of at least one redox initiator and at least one azo initiator. In one embodiment of the invention, copolymers according to the invention are made using at least one photo initiator.

Examples of suitable azo initiators include azobisisobutyronitrile AIBN, 1 ,1 '- Azobis(cyclohexanecarbonitrile) ABCN and 2,2'-Azobis[2-methylpropionamidin]- dihydrochloride.

Examples of suitable redox initiators include hydrogen peroxide, sodium peroxodisul- fate, di-tert-butyl peroxide and benzoyl peroxide.

Examples of suitable photo initiators include benzophenones, acetophenones, ben- zoinethers, benzildialkylketals or derivatives thereof.

Preferably, the polymerization is carried out without any polymerization regulators.

The polymerization is normally carried out at temperatures from 10 to 200 °C, preferably 30 to 150 and more preferably 50 to 130°C. Copolymers according to the invention can for example be prepared by bulk polymerization, solution polymerization or emulsion polymerization. Preferably copolymers according to the invention are prepared by solution polymerization.

In one preferred embodiment, copolymers according to the invention are produced by polymerization in aqueous medium.

The polymerization is normally carried out at a pH from 0.5 to 5.0, preferably at a pH from 0.9 to 3.9. After completion of the polymerization reaction, the pH of the aqueous solution of the copolymer obtained is normally adjusted to a value from 3.0 to 3.2. Copolymers according to the invention can be block copolymers or statistical polymers. Preferably copolymers according to the invention are statistical polymers.

Copolymers according to the invention are easy and economical to make and eco- friendly.

Copolymers according to the invention are useful as antiscalants, as drilling fluids, as dispersing agents and as surface modifying agents.

Examples

AA acrylic acid

MAS methacrylic acid

MASS methallylsulfonic acid

Wako V-502,2'-Azobis[2-methylpropionamidin]dihydrochloride

Preparation of copolymers

A 1000 ml. double-walled reactor equipped with a pH sensor, a thermometer and a redox-electrode was charged with 250 g water. Afterwards 75.8 g sodium- methylpropensulfonate and 2.0 g Wako V-50 were added. The mixture was purged with N2 and heated to 80°C. Once the mixture has reached 80°C three feed solutions were simultaneously added over a total of one hour:

1 ) methacrylic acid, 2) acrylic acid, 3) 2 g Wako V-50 in 14 g water.

Methacrylic acid and acrylic acid were added in an amount as given in table 1.

After completion of dosage the mixture was kept at 80°C for another hour. Afterwards the mixture was allowed to cool to room temperature and adjusted to pH 3 with 20% NaOH. The copolymer obtained had a Mw as given in table 1 (GPC, against Polyacrylic acid standards) Silica scale test method:

Batch tests were carried out to determine the inhibition performance of polymers in preventing silica polymerization under hard water conditions (1 mmol/l Mg²⁺, 4 mmol/l Ca²⁺, 28° German hardness) and high silicate concentration (750 ppm). All experiments were performed in plastic containers to prevent silica leeching from glassware.

A silicate stock solution was prepared by dissolving 3.717g Na2Si03 ^* 9H2O (98%) in 600 ml of distilled water. The pH of this solution was adjusted to pH 7 (± 0.1 ) with diluted hydrochloric acid and / or sodium hydroxide solution. Then, a stock solution of Ca²⁺ and Mg²⁺ was prepared by dissolving 600 mg CaCI₂ ^*2H₂0 and 207 mg MgCI₂ ^*6H₂0 in 100 ml of distilled water and then added to the aforementioned silicate solution. After adjustment of the pH again to pH 7 (± 0.1 ), the solution was diluted to reach a total of 1000 ml. 100 ml of this solution were used and 2 ml of a 2.55g/l stock solution of the inhibitor polymer was added to reach the desired inhibitor concentration of 50 ppm. The resulting solution with 750 ppm silicate, 4 mmol Ca²⁺, 1 mmol Mg²⁺ and 50 ppm inhibitor polymer (the antiscalant) was then kept at 40°C for 24 h. After filtration of the mixture through a 0.22 μηη filter, the filtrate was analyzed for dissolved silicate via a spectrophotometric method according to DIN 38405-D21 . The results are shown in table 1. A high number indicates that a high amount of silicate is present and that only a small amount of silicate has polymerized. Thus, a high number indicates that only little scale has been formed.

Table 1 : Composition of copolymers and inhibition of silica polymerization after 24h by these copolymers mol % ratio

No. acrylic methacrylic methallylsulfonic AA: MAS: MASS Mw residual acid acid (MAS) acid (MASS) silica

(AA) [ppm]

1 without polymer 180

2 64.4 27.6 8.0 2.33 1 0.29 41400 247

3 59.4 25.5 15.1 2.33 1 0.59 9000 337

4 58.2 25.5 16.6 2.33 1 0.66 6800 335

5 54.0 22.9 23.0 2.33 1 1 .0 2700 332

6 62.2 20.8 17.0 3.00 1 0.82 5800 308

7 59.3 23.7 17.0 2.50 1 0.72 4400 301

8 49.8 33.2 17.0 1 .50 1 0.51 2800 309

9 41.5 41.5 17.0 1 .00 1 0.41 1900 298

Claims

Patent Claims

Use of a copolymer comprising acrylic acid, methacrylic acid and methal- lylsulfonic acid or salts thereof, wherein methallylsulfonic acid or salts thereof are comprised in said copolymer in an amount of 10 to 50 mol%, and wherein the molar ratio of acrylic acid to methacrylic acid or their salts is 0.5:1 to 5:1 , as an antiscalant.

Use according to claim 1 , wherein the molar ratio of acrylic acid to methacrylic acid is 1.5:1 to 3:1

Use according to at least one of the previous claims, wherein the molecular mass Mw of said copolymer is 500 to 25000.

Use according to at least one of the previous claims, wherein said copolymer comprises less than 5 mol% of substituted or unsubstituted acrylamide.

Use according to at least one of the previous claims, wherein said copolymer comprises less than 5 mol% of dicarboxylic acids, their salts or anhydrides.

Use according to at least one of the previous claims, wherein said copolymer comprises less than 5 mol% of monomers different from acrylic acid, methacrylic acid and methallylsulfonic acid.

Use according to at least one of the previous claims, wherein said copolymer is used in a cooling tower, boiler, boiler feed system, turbines, heat exchanging devices, heating systems, evaporators, hot water reservoir, cooling circuit, desalination plant, cleaning formulation, cleaning device, waste water treatment plant , reverse osmosis device, dialysis device, extraction device, filtration device, thermal desalination plant like multi-effect distillation desalination plant or / and Multi-stage-flash desalination plant and combinations of thermal and membrane desalination plants.

Copolymer comprising acrylic acid, methacrylic acid and, methallylsulfonic acid or salts thereof, wherein methallylsulfonic acid or salts thereof are comprised in said copolymer in an amount of 12.5 to 23 mol % and wherein the molar ratio of acrylic to methacrylic acid is 0.5:1 to 5:1. 9. Copolymer according to claim 8, wherein said copolymer comprises less than 5 mol% of substituted or unsubstituted acrylamide.

10. Copolymer according to claims 8 to 9, wherein said copolymer comprises less than 5 mol% of dicarboxylic acids, their salts or anhydrides.

1 1 . Copolymer according to claim 8 to 10, wherein the molecular weight Mw of said copolymer is 500 to 25000.

12. Copolymer according to claim 8 to 1 1 , wherein said copolymer comprises less than 5 mol% of monomers other than acrylic acid, methacrylic acid and methal- lylsulfonic acid or salts thereof.

13. Process for making copolymers according to claims 8 to 12, wherein acrylic acid, methacrylic acid and methallylsulfonic acid are polymerized using an azo initiator.

14. Process for making copolymers according to claims 8 to 12, wherein acrylic acid, methacrylic acid and methallylsulfonic acid are polymerized using a redox initiator.

15. Process according to claims 13 or 14, wherein said polymerization is carried out in an aqueous medium.