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EP1181251A1 - Utilization of maleic acid copolymers as inhibitors of calcium oxalate coatings - Google Patents

Utilization of maleic acid copolymers as inhibitors of calcium oxalate coatings

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Publication number
EP1181251A1
EP1181251A1 EP00941979A EP00941979A EP1181251A1 EP 1181251 A1 EP1181251 A1 EP 1181251A1 EP 00941979 A EP00941979 A EP 00941979A EP 00941979 A EP00941979 A EP 00941979A EP 1181251 A1 EP1181251 A1 EP 1181251A1
Authority
EP
European Patent Office
Prior art keywords
weight
acid
copolymers
calcium oxalate
monomers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00941979A
Other languages
German (de)
French (fr)
Inventor
Birgit Potthoff-Karl
Roland Deubig
Michael Seufert
Axel Kistenmacher
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
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Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP1181251A1 publication Critical patent/EP1181251A1/en
Withdrawn legal-status Critical Current

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Classifications

    • 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

Definitions

  • the invention relates to the use of copolymers of maleic acid as an inhibitor for calcium oxalate coatings.
  • Calciu oxalate deposits affect processes for the production of pulp and paper and occur in particular, but not exclusively, in the bleaching stages of kraft pulp and wood pulping plants. Calcium oxalate coatings are also known from the sulfite pulp process.
  • the problem of calcium oxalate is exacerbated, particularly in modern plants with a reduced amount of waste water in combination with oxygen-containing bleaches.
  • the calcium oxalate deposits occur, for example, on the inner walls of pipes, on filter fabrics, on pumps, on heat exchanger surfaces e.g. from evaporator systems or in the digester.
  • the deposits which often appear in combination with other inorganic deposits such as calcium carbonate or calcium sulfate, reduce the heat exchange and lead to constrictions or blockages. If parts of the covering become detached, there can be massive disruptions in the subsequent processes, e.g. of papermaking come.
  • oxalic acid occurs in wood in concentrations of approx. 0.1 - 0.5 kg / t. Furthermore, oxalic acid is produced during the bleaching process by oxidative degradation of lignin and of mono-, oligo- or polysaccharides, e.g. Xylan.
  • Calcium ions are brought into the system through the wood.
  • Typical calcium ion concentrations in wood are e.g. 0.2-1.0 kg / t.
  • Calcium oxalate deposits have formed, they are extremely difficult to remove due to their low solubility. In practice, this is usually accomplished by mechanical removal, acid washing or using complexing agents in high concentrations. Disadvantages of these processes are the loss of production, damage to the systems due to corrosion and mechanical stress, and high costs for the feed materials. Calcium oxalate deposits also appear in evaporator systems in sugar production.
  • JP-A-04/018184 describes the use of copolymers of maleic acidic with lower alkyl acrylates and vinyl acetate known as a coating inhibitor in papermaking.
  • US-A-4575425 describes a method for inhibiting calcium oxalate in an aqueous system, a mixture of (a) a phosphate or phosphonate and (b) an anionic water-soluble polyelectrolyte being used as the inhibitor.
  • the polyelectrolytes used preferably have molecular weights in the range from 1,000 to 5,000.
  • EP-A-0276464 discloses the use of copolymers of maleic acid as water treatment agents for reducing scale deposition and water hardness excretion in water-bearing systems, for example maleic acid copolymers with K values of 7 to 20 (determined in 5% strength aqueous solution) 25 ° C and pH 7) used in the desalination of sea and brackish water by distillation or membrane processes and in the evaporation of sugar juices.
  • EP-A-0350985 recommends the use of a copolymer of maleic anhydride and diallyldimethylammonium chloride for controlling scale deposits.
  • US Pat. No. 5,320,757 describes a method for inhibiting calcium oxalate at a pH of at least 7.0 using a hydrolyzed terpolymer of maleic acid / ethyl acrylate / vinyl acetate.
  • the US-A-5409571 relates to a scale inhibitor for use in the Kraft pulp production, which is a terpolymer of Ma ⁇ leinklare / comprising acrylic acid and units of the hypophosphorous acid.
  • WO-A-96 29291 From WO-A-96 29291 a blend of (a) is an anionic organic polymer, (b) a polyphosphate, and (c) an organic phosphonic acid ⁇ rule for the inhibition of inorganic coatings known.
  • a terpolymer of maleic acid / acrylic acid / acrylamidopropanesulfonic acid is used as a scale inhibitor in the pulp production.
  • JP-A-10/180293 discloses the use of polymers containing carboxyl groups, such as, for example, polyacrylic acid, as a scale inhibitor for calcium oxalate in the production of cellulose.
  • US-A-5755971 relates to a method for preventing calcium oxalate deposits using ignin sulfonate and phosphate.
  • the coating inhibitors known from the prior art are in need of improvement in terms of their effectiveness because, despite their use, the formation of calcium oxalate coatings cannot be prevented sufficiently.
  • the situation is particularly unsatisfactory in aqueous systems with pH values below 7. In this pH range, massive formation of calcium oxalate deposits is frequently observed without this being able to be controlled with the products known from the prior art.
  • the object of the invention is therefore to provide substances which are more effective than known inhibitors for inhibiting calcium oxalate deposits.
  • copolymers contain polymerized and have a weight average molecular weight of 25,000 to 250,000, as an inhibitor for calcium oxalate deposits.
  • copolymers are preferred which
  • copolymerized ⁇ are sate whose weight average molecular weight is from 25,000 to 150,000.
  • Methacrylic acid fumaric acid, itaconic acid, mesaconic acid, methylene malonic acid, citraconic acid, maleic acid monomethyl ester, acrylonitrile, methacrylonitrile, styrene, Acrylic acid methyl ester, acrylic acid ethyl ester, methacrylic acid methyl ester, methacrylic acid ethyl ester, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, alkyl polyethylene glycol (meth) acrylate,
  • Vinylsulfonic acid allylsulfonic acid, methallylsulfonic acid, styrene sulfonic acid, 2-acrylamidomethyl propane sulfonic acid,
  • N-vinylpyrrolidone N-vinylcaprolactam
  • N-vinylformamide vinylphosphonic acid
  • N-vinylimidazole N-vinyl-2-methylimidazoline
  • diallyldimethylammonium chloride N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, vinylphosphonic acid, N-vinylimidazole, N-vinyl-2-methylimidazoline, diallyldimethylammonium chloride,
  • the basic monomers can also be used in quaternized form.
  • Monomer units (c) can optionally by reacting copolymers of (a) maleic acid or maleic anhydride and
  • alkyl polyethylene glycol with an average degree of ethoxylation of 2 to 45 alkyl polyethylene glycol block polypropylene glycols, such as e.g. Methyl polyethylene glycol block polypropylene glycol with up to 40 ethylene oxide units and up to 5 propylene oxide units
  • copolymers of maleic acid and acrylic acid are modified with monomer units (c), these units are preferably derived from methacrylic acid, vinyl sulfonate, methylpolyethylene glycol methacrylates from methylpolyethylene glycols with molecular weights from 200 to 2500 or mixtures thereof.
  • monomeric groups (a), (b) and optionally containing acid groups are preferably derived from methacrylic acid, vinyl sulfonate, methylpolyethylene glycol methacrylates from methylpolyethylene glycols with molecular weights from 200 to 2500 or mixtures thereof.
  • the copolymers can be partially or completely neutralized with alkali metal bases or ammonia.
  • a partial Wise neutralization means that the degree of neutralization of the acid groups in the copolymerizations is, for example, 1 to 99, preferably 30 to 75%.
  • the polymers used according to the invention are prepared by radical polymerization reaction of the ethylenically unsaturated monomers (a), (b) and, if appropriate, (c).
  • the monomers to be polymerized can be placed in the reaction vessel or added to the reaction batch in portions or, preferably, continuously.
  • the main amount and in particular at least 90% by weight of the maleic acid or the maleic anhydride are preferably introduced into the reaction vessel and the main amounts of the monomers (b) and optionally (c) are added continuously to the reaction mixture.
  • the polymerization can be carried out as a substance - polymerization, solution polymerization or, if the monomers are not very soluble in the reaction medium, as an emulsion, dispersion or suspension polymerization.
  • the reaction is preferably carried out as solution polymerization in water.
  • the monomers containing acid groups can be present in their acid form, but also partially or completely neutralized as a salt.
  • sodium hydroxide solution, potassium hydroxide solution, ammonia, triethanolamine or diethanolamine can be used as the neutralizing agent; sodium hydroxide solution is preferred.
  • Such methods are known, cf. for example in EP-A-075820, EP-A-076992, EP-A-0103254, EP-A-0106111, EP-A-0106991 and WO-A-97 31036.
  • Water is preferably used as the reaction medium, but mixtures of water with up to 80% by weight, based on the mixture, of a solvent containing OH groups can also be used.
  • solvents are, for example, from the group C1-C4-alkanols, C2-C10-alkylene glycols, in which the alkylene chain can be interrupted by one or more, non-adjacent oxygen atoms, and ether of the C2-C10-alkylene glycols with C1-C4-alkanols.
  • suitable solvents containing OH groups are methanol, ethanol, isopropanol, n-butanol, ethylene glycol, diethylene glycol, methyl diglycol, dipropylene glycol, butyl glycol, butyl diglycol, triethylene glycol, the methyl ethers of the glycols mentioned and oligomers of ethylene oxide with 4 to 6 ethylene oxide units, oligomers Propylene oxide with 3 to 6 propylene oxide units as well as polyethylene glycol-polypropylene glycol - cooligomers.
  • the aqueous reaction medium can also other water-miscible solvents such as acetone, methyl contain ethyl ketone, tetrahydrofuran, dioxane, N-methylpyrrolidone, dimethylformamide etc.
  • reaction medium cyclic ethers such as tetrahydrofuran or dioxane, ketones and acetone, methyl ethyl ketone, cyclohexanone, esters of aliphatic carboxylic acids with C1-C4-alkanols, such as ethyl acetate or n-butyl acetate, aromatic hydrocarbons such as toluene, xylenes, Cumene, chlorobenzene, ethylbenzene, technical mixtures of alkyl aromatics, cyclohexane and technical aliphatic mixtures.
  • cyclic ethers such as tetrahydrofuran or dioxane, ketones and acetone, methyl ethyl ketone, cyclohexanone, esters of aliphatic carboxylic acids with C1-C4-alkanols, such as ethyl acetate or n-butyl acetate
  • the polymerization can also be carried out as an emulsion or suspension polymerization if the monomers are poorly soluble in the reaction medium.
  • Such polymerization processes are known to the person skilled in the art and can be carried out in the usual manner for the preparation of the polymers according to the invention.
  • the polymers according to the invention are prepared by radical aqueous emulsion polymerization, it is advisable to add surfactants or protective colloids to the reaction medium.
  • surfactants or protective colloids can be found, for example, in M Houben Weyl, Methods of Organic Chemistry, Volume XIV / 1 Macromolecular Substances, Georg Thieme Verlag, Stuttgart 1961, p. 411 ff.
  • the polymerization initiators used for the radical polymerization are preferably soluble in the reaction medium. They are used in amounts of up to 30% by weight, preferably 0.05 to 15% by weight, particularly preferably 1.5 to 10% by weight, based on the monomers used in the polymerization. It follows ⁇ m polymerization a water-containing solvent-m or water, preferably water-soluble Polymerisati - onsinitiatoren such as sodium persulfate, Kaliumper ⁇ sulfate, Ammoniumpersulf t, hydrogen peroxide, tert.
  • a water-containing solvent-m or water preferably water-soluble Polymerisati - onsinitiatoren such as sodium persulfate, Kaliumper ⁇ sulfate, Ammoniumpersulf t, hydrogen peroxide, tert.
  • redox initiator systems can also be used as polymerization initiators.
  • Such redox imiator systems contain at least one compound containing peroxides in combination with a redox co-initiator, for example reducing sulfur compounds, for example bisulfites, sulfites, thiosulfates, dthionites or tetrathionates of alkali metals and ammonium compounds, sodium hydroxymethanesulfate dihydrate and / or thiourea.
  • reducing sulfur compounds for example bisulfites, sulfites, thiosulfates, dthionites or tetrathionates of alkali metals and ammonium compounds, sodium hydroxymethanesulfate dihydrate and / or thiourea.
  • This is how combinations of Peroxodi - Use sulfates with alkali metal or ammonium hydrogen sulfites, e.g. ammonium peroxydisulfate
  • transition metal catalysts can be used, e.g. Iron, nickel, cobalt, manganese, copper, vanadium, or chromium salts, such as iron (II) sulfate, cobalt (II) chloride, nickel (II) sulfate, copper (I) chloride, manganese (II) acetate , Vanadium-III-acetate, manganese-II-chloride.
  • these transition metal salts are usually used in amounts of 0.1 to 1000 ppm. So you can use combinations of hydrogen peroxide with iron (II) salts, such as 0.5 to 30% hydrogen peroxide and 0.1 to 500 ppm Mohr's salt.
  • initiators such as dibenzoyl peroxide, dicyclohexyl peroxidicarbonate, dilauryl peroxide, methyl ethyl ketone peroxide, acetylacetone peroxide are preferred.
  • reac ⁇ tion mixture polymerized at the lower limit of the next for the polymerization into consideration temperature range and subsequently completed at a higher temperature, it is expedient to use at least two different initiators which decompose at different temperatures, so that in each temperature interval a sufficient concentration of radicals is available.
  • the polymerization reaction takes place, for example, at temperatures in the range from 30 to 300 ° C., preferably in the range from 50 to 160 ° C. and very particularly preferably in the range from 100 to 150 ° C. It is preferably carried out in the absence of oxygen, preferably in a nitrogen stream. As a rule, the polymerization is carried out at normal pressure, but the use of lower pressures or higher pressures is also possible, in particular if polymerization temperatures are used be above the boiling point of the monomers and / or
  • a molecular weight regulator i.e. a conventional chain terminating substance to polymerize.
  • Suitable molecular weight regulators include, for example, formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, formic acid, ammonium formate, hydroxylamine and its sulfate, chloride or phosphate; SH groups - compounds containing such as thioglycolic acid, mercapto-propionic acid, mercapotethanol, mercaptopropanol, mercaptobutanol, mercatophexanol, thiomaleic acid, thiophenol, 4-tert.
  • polymerization regulators are allyl alcohol, butenol, isopropanol, n-butanol, isobutanol, glycol, glycerol, pentaerythritol, hypophosphorous acid and their salts, such as e.g. Sodium hypophosphite, phosphorous acid and its salts, e.g. Sodium phosphite.
  • the polymerization regulators are used in amounts of up to 20% by weight, based on the monomers. Polymerization is preferably carried out in the presence of 0.5 to 15% by weight of a polymerization regulator containing SH groups, based on the monomers.
  • Crosslinked poly ⁇ merisate are either obtainable by copolymerization of said monomers with di- or multi-ethylenically unsaturated compounds, or by subsequent crosslinking of carboxyl, anhydride or hydroxyl groups in the polymer with appropriate polyfunctional compounds. If the crosslinking is carried out by means of copolymerization with polyethylenically unsaturated compounds, these are usually present in proportions of 0.01 to 20% by weight and preferably in amounts of 0.1 to 5% by weight, based on those to be polymerized Monomers.
  • Suitable two or more ethylenically unsaturated compounds include: diacrylates or dimethacrylates of at least dihydric saturated alcohols, such as, for example, ethylene glycol - diacrylate, ethylene glycol dimethylacrylate, 1,2-propylene glycol - diacrylate, 1,2-propylene glycol dimethacrylate, butanediol-1, -diacrylate Butanediol-1, 4-dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 3-methylpentanediol dimethacrylate, 3-methyl-pentanediol dimethacrylate; Acrylic acid and methacrylic acid esters of alcohols with more than 2 OH groups, such as, for example, trimethylolpropane methacrylate, trimethylolpropane
  • Glycidyl ethers of polyhydroxy compounds or the glycidyl esters of di- or polycarboxylic acids are particularly suitable as polyfunctional, reactive crosslinking compounds which can be used for subsequent crosslinking.
  • suitable crosslinking compounds include: ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, pentaerytol tolpolyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol glycidyl ether, resorcidiglycidyl ether, o-phthalate or diglycidyl ester.
  • the concentration of the monomers is usually 10 to 70, preferably 20 to 60% by weight.
  • phosphonates such as e.g. 2-phosphono-l, 2, 4-t ⁇ carbonsaure, Ami notri- (methylenphosphonsaure), 1-hydroxyethylene (1, 1-d phosp- honsaure), ethylenediamm-tetramethylene-phosphonic acid, hexamethylenediamm-tetramethylene-phosphonic acid and diethylenetriamine -pentarethylene-phosphonic acid,
  • ammocarboxylates such as e.g. Nit ⁇ lot ⁇ essigsaure, ethylenediammetetraacetic acid, Diethylenetriam pentaessigsaure, Hydroxyethylethylenendiam t ⁇ essigsaure and Methylglycmdi acetic acid,
  • water soluble polymers e.g. Homo- and copolymers of acrylic acid with a weight average molecular weight in the range from 500 to 15,000; Homo- and copolymers of sulfo-containing monomers, such as e.g. 2-Acrylam do-2-methylpropanesulfonic acid, styrene sulfonic acid or V ylsulfonic acid with a weight average molecular weight of 500 to 15,000 as well as naphthalene sulfonic acid formaldehyde polycondensates.
  • water soluble polymers e.g. Homo- and copolymers of acrylic acid with a weight average molecular weight in the range from 500 to 15,000
  • sulfo-containing monomers such as e.g. 2-Acrylam do-2-methylpropanesulfonic acid, styrene sulfonic acid or V ylsulfonic acid with a weight average molecular weight of
  • components (a) to (d) can optionally be used with further formulation components such as surfactants, dispersants, defoamers, corrosion inhibitors, oxygen scavengers, biocides, alkalis and / or bleaches.
  • further formulation components such as surfactants, dispersants, defoamers, corrosion inhibitors, oxygen scavengers, biocides, alkalis and / or bleaches.
  • the copolymers described above are used to inhibit calcium oxalate deposits. They prevent or reduce the formation of calcium oxalate deposits or the boiler separation of water-bearing systems which contain calcium ions and oxalic acid or water-soluble salts of oxalic acid.
  • the copolymers are used, for example, in amounts of 1 to 2000, preferably 2 to 200 ppm, based on the aqueous system. If there are failures, there are easily washed-out excretions that are remotely distributed. This keeps the inner walls of heat exchangers, pipes or pump components free of deposits and at the same time reduces their tendency to corrode.
  • the water-carrying systems are e.g. around open or closed cooling circuits, for example of power plants or chemical plants such as reactors, distillation apparatus and heat exchangers.
  • the copolymers to be used according to the invention can prevent damage to the membranes by crystallizing calcium oxalate. They are also used as deposit inhibitors when evaporating sugar juices from sugar cane or from sugar beet.
  • the copolymers to be used according to the invention in pulp and paper production because - as has already been explained in relation to the prior art - a considerable amount of calcium ions and oxalic acid are introduced into the aqueous system with the paper stock.
  • copolymers may be used for example in the entire pH range, which is in practice of In ⁇ teresse, eg in the range 2 to 12 to the inhibitors so far used have inhibitors of the invention at pH values below of 8, preferably below 7, a sufficient effect.
  • aqueous solution containing 114.5 ppm calcium chloride dihydrate, 105 ppm sodium oxalate and 10 ppm of the polymer to be tested is adjusted to the desired pH with 2% hydrochloric acid or 2% sodium hydroxide solution.
  • the solution is heated in a round-bottom flask with a reflux condenser to 70 ° C. with stirring. After 3 hours the solution is cooled, 150 ml removed and filtered.
  • the calcium ion concentration in the filtrate c (Ca) [ppm] is determined using Determined atomic absorption spectroscopy.
  • the polymer-specific inhibition IP is calculated using the following formula:
  • IP [%] (c (Ca) x 100) / 31.2
  • VSNa sodium methyl sulfonate
  • MPEGMA methyl polyethylene glycol methacrylate with a molecular weight of 1000.

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Abstract

The invention relates to the utilization of copolymers as inhibitors of calcium oxalate coatings, containing the following polymerized components: a) 10 to 80 % by weight percent maleic acid and/or maleic acid anhydride; b) 20 to 90 % by weight acrylic acid and c) 0 to 20 % by weight of at least one additional monomer which can be copolymerized with monomers (a) and (b) and having an average molecular weight ranging between 25,000 and 250,000.

Description

Verwendung von Copolymeren der Maleinsäure als Inhibitor von Cal- ciumoxa1atbe1ägen Use of copolymers of maleic acid as an inhibitor of calcium oxalate
Beschreibungdescription
Die Erfindung betrifft die Verwendung von Copolymeren der Maleinsäure als Inhibitor für Calciumoxalatbeläge.The invention relates to the use of copolymers of maleic acid as an inhibitor for calcium oxalate coatings.
Calciu oxalatbeläge beeinträchtigen Prozesse zur Herstellung von Zellstoff und Papier und treten insbesondere, aber nicht ausschließlich, in Bleichstufen von Kraftzellstoff- und Holzschliff - anlagen auf. Weiterhin sind Calciumoxalatbeläge auch aus dem Sulfitzellstoffverfahren bekannt.Calciu oxalate deposits affect processes for the production of pulp and paper and occur in particular, but not exclusively, in the bleaching stages of kraft pulp and wood pulping plants. Calcium oxalate coatings are also known from the sulfite pulp process.
Die Calciumoxalat-Problematik verschärft sich insbesondere bei modernen Anlagen mit reduzierter Abwassermenge in Kombination mit Sauerstoff enthaltenden Bleichmitteln. Die Calciumoxalatbeläge treten beispielsweise an Innenwänden von Rohrleitungen, auf Filtergeweben, an Pumpen, an Wärmetauscherflächen z.B. von Verdampferanlagen oder im Digester auf. Die Beläge, die oft in Kombination mit anderen anorganischen Belägen wie Calciumcarbonat oder Calciumsulfat auftreten, verringern den Wärmeaustausch und führen zu Verengungen oder Verstopfungen. Wenn sich Teile des Belages lösen, kann es zu massiven Störungen in den nachfolgenden Prozessen, wie z.B. der Papierherstellung kommen.The problem of calcium oxalate is exacerbated, particularly in modern plants with a reduced amount of waste water in combination with oxygen-containing bleaches. The calcium oxalate deposits occur, for example, on the inner walls of pipes, on filter fabrics, on pumps, on heat exchanger surfaces e.g. from evaporator systems or in the digester. The deposits, which often appear in combination with other inorganic deposits such as calcium carbonate or calcium sulfate, reduce the heat exchange and lead to constrictions or blockages. If parts of the covering become detached, there can be massive disruptions in the subsequent processes, e.g. of papermaking come.
Oxalsäure tritt in Holz beispielsweise in Konzentrationen von ca. 0,1 - 0,5 kg/t auf. Weiterhin wird Oxalsäure während des Bleichprozesses durch oxidativen Abbau von Lignin und von Mono-, Oligo- oder Polysacchariden, wie z.B. Xylan, gebildet.For example, oxalic acid occurs in wood in concentrations of approx. 0.1 - 0.5 kg / t. Furthermore, oxalic acid is produced during the bleaching process by oxidative degradation of lignin and of mono-, oligo- or polysaccharides, e.g. Xylan.
Calciumionen werden durch das Holz in das System gebracht. Typische Calciumionenkonzentrationen im Holz sind z.B. 0,2 -1,0 kg/t.Calcium ions are brought into the system through the wood. Typical calcium ion concentrations in wood are e.g. 0.2-1.0 kg / t.
Haben sich Calciumoxalatbeläge erst einmal gebildet, so sind diese aufgrund ihrer geringen Löslichkeit nur außerordentlich schwer wieder zu entfernen. In der Praxis wird dies meist durch mechanische Entfernung, Säurewäsche oder unter Verwendung von Komplexbildnern in hoher Konzentration bewerkstelligt. Nachteilig bei diesen Prozessen sind der Produktionsausfall, Schädigung der Anlagen durch Korrosion und mechanische Belastung bzw. hohe Kosten für die Einsatzstoffe. Calciumoxalatbeläge treten außerdem in Verdampferanlagen bei der Zuckerherstellung in Erscheinung.Once calcium oxalate deposits have formed, they are extremely difficult to remove due to their low solubility. In practice, this is usually accomplished by mechanical removal, acid washing or using complexing agents in high concentrations. Disadvantages of these processes are the loss of production, damage to the systems due to corrosion and mechanical stress, and high costs for the feed materials. Calcium oxalate deposits also appear in evaporator systems in sugar production.
Um die Belagsbildung zu kontrollieren, hat man bereits verschiedene belagsinhibierende Stoffe verwendet. So ist beispielsweise aus der JP-A-04/018184 die Verwendung von Copolymeren der Malein- saure mit niederen Alkylacrylaten und Vinylacetat als Belagsinhibitor bei der Papierherstellung bekannt. In der US-A-4575425 wird eine Methode zum Inhibieren von Calciumoxalat in einem wässrigen System beschrieben, wobei als Inhibitor eine Mischung aus (a) einem Phosphat oder Phosphonat und (b) einem anionischen wasserlöslichen Polyelektrolyten eingesetzt wird. Die eingesetzten Polyelektrolyten haben vorzugsweise Molekulargewichte im Bereich von 1,000 bis 5,000. Aus der US-A-4804476 ist eine Methode zum Inhibieren von Calciu oxalatablagerungen bekannt, wobei als Inhibitor eine Mischung aus Natriumhexametaphosphat und einer Polyacrylsäure mit gewichtsmittlerem Molekulargewicht von 7,000 bis 9,000 empfohlen wird. Die US-A-4872995 beschreibt Copolymere aus (Meth) acrylsäure und Allyletherverbindungen zur Inhibierung von Calciumoxalat. Aus der EP-A-0276464 ist die Verwendung von Copolymerisaten der Maleinsäure als Wasserbehandlungsmittel zur Verminderung der Kesselsteinabscheidung und der Wasserhärteausscheidung in wasserführenden Systemen bekannt, z.B. werden Ma- leinsäurecopolymerisate mit K-Werten von 7 bis 20 (bestimmt in 5 %iger wäßriger Lösung bei 25°C und pH 7) bei der Entsalzung von Meer- und Brackwasser durch Destillation oder Membranverfahren und beim Eindampfen von Zuckersäften verwendet.In order to control the formation of deposits, various deposit-inhibiting substances have already been used. For example, JP-A-04/018184 describes the use of copolymers of maleic acidic with lower alkyl acrylates and vinyl acetate known as a coating inhibitor in papermaking. US-A-4575425 describes a method for inhibiting calcium oxalate in an aqueous system, a mixture of (a) a phosphate or phosphonate and (b) an anionic water-soluble polyelectrolyte being used as the inhibitor. The polyelectrolytes used preferably have molecular weights in the range from 1,000 to 5,000. From US-A-4804476 a method for inhibiting calcium oxalate deposits is known, a mixture of sodium hexametaphosphate and a polyacrylic acid having a weight average molecular weight of 7,000 to 9,000 being recommended as the inhibitor. US-A-4872995 describes copolymers of (meth) acrylic acid and allyl ether compounds for inhibiting calcium oxalate. EP-A-0276464 discloses the use of copolymers of maleic acid as water treatment agents for reducing scale deposition and water hardness excretion in water-bearing systems, for example maleic acid copolymers with K values of 7 to 20 (determined in 5% strength aqueous solution) 25 ° C and pH 7) used in the desalination of sea and brackish water by distillation or membrane processes and in the evaporation of sugar juices.
In der EP-A-0350985 wird die Verwendung eines Copolymeren aus Maleinsäureanhydrid und Diallyldimethylammoniumchlorid zur Kontrolle von Kesselsteinablagerungen empfohlen. In der US-A-5320757 wird eine Methode zur Inhibierung von Calciumoxalat bei einem pH von mindestens 7,0 unter Verwendung eines hydrolysierten Terpoly- meren aus Maleinsäure / Ethylacrylat / Vinylacetat beschrieben. Die US-A-5409571 betrifft einen Belagsinhibitor für die Anwendung in der Kraft-Zellstoffherstellung, welcher ein Terpolymer aus Ma¬ leinsäure / Acrylsäure und Einheiten der hypophosphorigen Säure umfaßt .EP-A-0350985 recommends the use of a copolymer of maleic anhydride and diallyldimethylammonium chloride for controlling scale deposits. US Pat. No. 5,320,757 describes a method for inhibiting calcium oxalate at a pH of at least 7.0 using a hydrolyzed terpolymer of maleic acid / ethyl acrylate / vinyl acetate. The US-A-5409571 relates to a scale inhibitor for use in the Kraft pulp production, which is a terpolymer of Ma ¬ leinsäure / comprising acrylic acid and units of the hypophosphorous acid.
Aus der WO-A-96 29291 ist eine Mischung aus (a) einem anionischen organischen Polymer, (b) einem Polyphosphat und (c) einer organi¬ schen Phosphonsäure zur Inhibierung von anorganischen Belägen bekannt. Gemäß der JP-A-10025684 wird ein Terpolymer aus Maleinsäure / Acrylsäure / Acrylamidopropansulfonsäure als Belagsinhibitor bei der Zellstoffherstellung verwendet. Aus der JP-A-10/180293 ist die Verwendung von Carboxylgruppen enthaltenden Polymeren wie z.B. Polyacrylsäure als Belagsinhibitor für Calciumoxalat bei der Zellstoffherstellung bekannt. Die US-A-5755971 betrifft eine Methode zur Verhinderung von Calciumo- xalatbelägen unter Verwendung von igninsulfonat und Phosphat. Die aus dem Stand der Technik bekannten Belagsinhibitoren sind im Hinblick auf ihre Wirksamkeit verbesserungsbedürftig, weil trotz deren Einsatz die Ausbildung von Calciumoxalatbelägen nicht ausreichend verhindert werden kann. Besonders unbefriedigend ist die Situation in wässrigen Systemen mit pH-Werten unterhalb von 7. In diesem pH-Bereich wird häufig eine massive Ausbildung von Calciumoxalatbelägen beobachtet, ohne daß dies mit den nach dem Stand der Technik bekannten Produkten unter Kontrolle gebracht werden kann.From WO-A-96 29291 a blend of (a) is an anionic organic polymer, (b) a polyphosphate, and (c) an organic phosphonic acid ¬ rule for the inhibition of inorganic coatings known. According to JP-A-10025684, a terpolymer of maleic acid / acrylic acid / acrylamidopropanesulfonic acid is used as a scale inhibitor in the pulp production. JP-A-10/180293 discloses the use of polymers containing carboxyl groups, such as, for example, polyacrylic acid, as a scale inhibitor for calcium oxalate in the production of cellulose. US-A-5755971 relates to a method for preventing calcium oxalate deposits using ignin sulfonate and phosphate. The coating inhibitors known from the prior art are in need of improvement in terms of their effectiveness because, despite their use, the formation of calcium oxalate coatings cannot be prevented sufficiently. The situation is particularly unsatisfactory in aqueous systems with pH values below 7. In this pH range, massive formation of calcium oxalate deposits is frequently observed without this being able to be controlled with the products known from the prior art.
Der Erfindung liegt daher die Aufgabe zugrunde, gegenüber den bekannten Inhibitoren wirksamere Stoffe zur Inhibierung von Calciumoxalatbelägen zur Verfügung zu stellen.The object of the invention is therefore to provide substances which are more effective than known inhibitors for inhibiting calcium oxalate deposits.
Die Aufgabe wird erfindungsgemäß gelöst mit der Verwendung von Copolymeren, dieThe object is achieved with the use of copolymers
(a) 10 bis 80 Gew.-% Maleinsäure und/oder Maleinsäureanhydrid,(a) 10 to 80% by weight of maleic acid and / or maleic anhydride,
(b) 20 bis 90 Gew.-% Acrylsäure,(b) 20 to 90% by weight of acrylic acid,
(c) 0 bis 20 Gew.-% mindestens eines weiteren mit den Monomeren (a) und (b) copolymerisierbaren Monomeren(c) 0 to 20% by weight of at least one further monomer which can be copolymerized with the monomers (a) and (b)
einpolymerisiert enthalten und die ein gewichtsmittleres Molekulargewicht von 25 000 bis 250 000 haben, als Inhibitor für Calciumoxalatbeläge. Für diese Verwendung werden Copolymerisate bevorzugt, diecontain polymerized and have a weight average molecular weight of 25,000 to 250,000, as an inhibitor for calcium oxalate deposits. For this use, copolymers are preferred which
(a) 20 bis 60 Gew.-% Maleinsäure,(a) 20 to 60% by weight of maleic acid,
(b) 40 bis 80 Gew.-% Acrylsäure und(b) 40 to 80% by weight acrylic acid and
(c) 0 bis 20 Gew.-% mindestens eines weiteren, mit den Monomeren (a) und (b) copolymerisierbaren Monomeren(c) 0 to 20% by weight of at least one further monomer which can be copolymerized with the monomers (a) and (b)
einpolymerisiert enthalten. Besonders bevorzugt sind Copolymeri¬ sate, deren gewichtsmittleres Molekulargewicht 25 000 bis 150 000 beträgt.polymerized included. Particularly preferred copolymerized ¬ are sate whose weight average molecular weight is from 25,000 to 150,000.
Als Monomere (c) eignen sich beispielsweise folgende Verbindungen :The following compounds are suitable as monomers (c):
Methacrylsäure, Fumarsäure, Itaconsäure, Mesaconsäure, Methylen- malonsäure, Citraconsäure, Maleinsäuremonomethylester, Acryl - nitril, Methacrylnitril, Styrol, Acrylsäuremethylester, Acrylsäureethylester, Methacrylsäure- methylester, Methacrylsäureethylester, Hydroxyethyl (meth) acrylat, Hydroxypropyl (meth) acrylat, Alkylpolyethylenglykol (meth) acrylat,Methacrylic acid, fumaric acid, itaconic acid, mesaconic acid, methylene malonic acid, citraconic acid, maleic acid monomethyl ester, acrylonitrile, methacrylonitrile, styrene, Acrylic acid methyl ester, acrylic acid ethyl ester, methacrylic acid methyl ester, methacrylic acid ethyl ester, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, alkyl polyethylene glycol (meth) acrylate,
Allylalkohol, Polyethylenglykolmonoallylether von Polyethylen- glykolen mit Molmassen von 80 bis 1500,Allyl alcohol, polyethylene glycol monoallyl ether of polyethylene glycols with molecular weights from 80 to 1500,
Acrylamid, Methacrylamid, N-Dimethylacrylamid,Acrylamide, methacrylamide, N-dimethylacrylamide,
Vinylsulfonsäure, Allylsulfonsäure, Methallylsulfonsäure, Styrol- sulfonsäure, 2-Acrylamidornethylpropansulfonsäure,Vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrene sulfonic acid, 2-acrylamidomethyl propane sulfonic acid,
Vinylacetat, Vinylpropionat,Vinyl acetate, vinyl propionate,
Vinylphosphonat , Allylphosphonat ,Vinyl phosphonate, allyl phosphonate,
N-Vinylpyrrolidon, N-Vinylcaprolactam, N-Vinylformamid, Vinyl - phosphonsäure, N-Vinylimidazol , N-Vinyl-2-Methylimidazolin, Diallyldimethylammoniumchlorid,N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, vinylphosphonic acid, N-vinylimidazole, N-vinyl-2-methylimidazoline, diallyldimethylammonium chloride,
Dimethylaminoethylacrylat, Diethylaminoethylacrylat, Dimethyl - aminoethylmethacrylat, Diethylaminoethylmethacrylat sowie die Salze dieser basischen Monomeren mit anorganischen oder organischen Säuren wie Salzsäure, Schwefelsäure, Phosphorsäure, Ameisensäure, Essigsäure oder Propionsäure. Die basischen Monomere können auch in quaternisierter Form eingesetzt werden.Dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the salts of these basic monomers with inorganic or organic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid or propionic acid. The basic monomers can also be used in quaternized form.
Monomereinheiten (c) können gegebenenfalls durch Reaktion von Copolymerisaten aus (a) Maleinsäure oder Maleinsäureanhydrid undMonomer units (c) can optionally by reacting copolymers of (a) maleic acid or maleic anhydride and
(b) Acrylsäure mit Cl-10-Alkoholen oder Alkylpolyalkylenglykolen, wie z.B. Methylpolyethylenglykol mit einem mittleren Ethoxilie- rungsgrad von 2 bis 45, Alkylpolyethylenglykol-block-poly- propylenglykolen, wie z.B. Methylpolyethylenglykol-block-Poly- propylenglykol mit bis 40 Ethylenoxid-Einheiten und bis 5 Propy- lenoxid-Einheiten, Cl-10-Aminen oder Polyalkylenglykolaminen, wie z.B. Methylpolyethylenglykolamin mit einem mittleren Ethoxilie- rungsgrad von 5 bis 50, in die Copolymeren aus (a) und (b) eingeführt werden.(b) acrylic acid with Cl-10 alcohols or alkyl polyalkylene glycols, e.g. Methyl polyethylene glycol with an average degree of ethoxylation of 2 to 45, alkyl polyethylene glycol block polypropylene glycols, such as e.g. Methyl polyethylene glycol block polypropylene glycol with up to 40 ethylene oxide units and up to 5 propylene oxide units, Cl-10 amines or polyalkylene glycol amines, such as e.g. Methyl polyethylene glycolamine with an average degree of ethoxylation of 5 to 50, into which copolymers from (a) and (b) are introduced.
Falls die Copolymerisate aus Maleinsäure und Acrylsäure mit Monomereinheiten (c) modifiziert sind, so leiten sich diese Einheiten vorzugsweise von Methacrylsäure, Vinylsulfonat, Methylpo- lyethylenglykolmethacrylaten von Methylpolyethylenglykolen mit Molmassen von 200 bis 2500 oder deren Mischungen ab. Die Säuregruppen enthaltenden Monomereinheiten (a) , (b) und gegebenenfallsIf the copolymers of maleic acid and acrylic acid are modified with monomer units (c), these units are preferably derived from methacrylic acid, vinyl sulfonate, methylpolyethylene glycol methacrylates from methylpolyethylene glycols with molecular weights from 200 to 2500 or mixtures thereof. The monomeric groups (a), (b) and optionally containing acid groups
(c) der Copolymerisate können teilweise oder vollständig mit Alkalimetallbasen oder Ammoniak neutralisiert sein. Eine teil- weise Neutralisation bedeutet, daß der Neutralisationsgrad der Säuregruppen in den Copolymerisationen z.B. 1 bis 99, vorzugsweise 30 bis 75 % beträgt.(c) The copolymers can be partially or completely neutralized with alkali metal bases or ammonia. A partial Wise neutralization means that the degree of neutralization of the acid groups in the copolymerizations is, for example, 1 to 99, preferably 30 to 75%.
Die Herstellung der erfindungsgemäß zur Anwendung kommenden Polymerisate erfolgt durch radikalische Polymerisationsreaktion der ethylenisch ungesättigten Monomere (a) , (b) und ggf. (c) . Die zu polymerisierenden Monomere können im Reaktionsgefäß vorgelegt oder dem Reaktionsansatz portionsweise oder vorzugsweise kontinuierlich zugeführt werden. Vorzugsweise wird die Hauptmenge und insbesondere wenigstens 90 Gew.-% der Maleinsäure bzw. des Maleinsäureanhydrids im Reaktionsgefäß vorgelegt und die Haupt - mengen der Monomeren (b) und ggf. (c) kontinuierlich zum Reakti- onsansatz gegeben. Dabei kann die Polymerisation als Substanz - Polymerisation, Lösungspolymerisation oder bei geringer Löslich- keit der Monomeren im Reaktionsmedium als Emulsions-, Dispersions- oder Suspensionspolymerisation durchgeführt werden. Ebenfalls ist es möglich, bei hinreichend schlechter Löslichkeit des Polymerisats im Reaktionsmedium die Polymerisation als Fällungspolymerisation durchzuführen. Vorzugsweise wird die Reaktion als Lösungspolymerisation in Wasser durchgeführt. Hierbei können die Säuregruppen enthaltenden Monomere in ihrer Säureform, aber auch teilweise oder vollständig neutralisiert als Salz vorliegen. Als Neutralisationsmittel kann beispielsweise Natronlauge, Kalilauge, Ammoniak, Triethanolamin oder Diethanolamin eingesetzt werden, bevorzugt ist Natronlauge. Solche Verfahren sind bekannt, vgl. beispielsweise in EP-A-075820, EP-A-076992, EP-A-0103254 , EP-A-0106111, EP-A-0106991 und WO-A-97 31036.The polymers used according to the invention are prepared by radical polymerization reaction of the ethylenically unsaturated monomers (a), (b) and, if appropriate, (c). The monomers to be polymerized can be placed in the reaction vessel or added to the reaction batch in portions or, preferably, continuously. The main amount and in particular at least 90% by weight of the maleic acid or the maleic anhydride are preferably introduced into the reaction vessel and the main amounts of the monomers (b) and optionally (c) are added continuously to the reaction mixture. The polymerization can be carried out as a substance - polymerization, solution polymerization or, if the monomers are not very soluble in the reaction medium, as an emulsion, dispersion or suspension polymerization. It is also possible to carry out the polymerization as precipitation polymerization if the polymer is sufficiently poorly soluble in the reaction medium. The reaction is preferably carried out as solution polymerization in water. Here, the monomers containing acid groups can be present in their acid form, but also partially or completely neutralized as a salt. For example, sodium hydroxide solution, potassium hydroxide solution, ammonia, triethanolamine or diethanolamine can be used as the neutralizing agent; sodium hydroxide solution is preferred. Such methods are known, cf. for example in EP-A-075820, EP-A-076992, EP-A-0103254, EP-A-0106111, EP-A-0106991 and WO-A-97 31036.
Als Reaktionsmedium wird bevorzugt Wasser eingesetzt, jedoch können auch Mischungen aus Wasser mit bis zu 80 Gew.-%, bezogen auf die Mischung, aus einem OH-Gruppen enthaltenden Lösemittel verwendet werden. Solche Lösemittel sind z.B. aus der Gruppe Cl-C4-Alkanole, C2-C10-Alkylenglykole, worin die Alkylenkette durch eine oder mehrere, nicht benachbarte Sauerstoffatome unterbrochen sein kann, und Haibether der C2-C10-Alkylenglykole mit Cl-C4-Alkanolen. Beispiele für geeignete OH-Gruppen enthaltende Lösungsmittel sind Methanol, Ethanol, Isopropanol, n-Butanol, Ethylenglykol, Diethylenglykol , Methyldiglykol , Dipropylenglykol , Butylglykol, Butyldiglykol, Triethylenglykol, die Methylether der genannten Glykole sowie Oligomere aus Ethylenoxid mit 4 bis 6 Ethylenoxideinheiten, Oligomere aus Propylenoxid mit 3 bis 6 Propylenoxideinheiten sowie Polyethylenglykol-polypropylenglykol - cooligomere. Darüberhinaus kann das wässrige Reaktionsmedium auch andere, mit Wasser mischbare Lösungsmittel wie Aceton, Methyl- ethylketon, Tetrahydrofuran, Dioxan, N-Methylpyrrolidon, Dimethylformamid etc. enthalten.Water is preferably used as the reaction medium, but mixtures of water with up to 80% by weight, based on the mixture, of a solvent containing OH groups can also be used. Such solvents are, for example, from the group C1-C4-alkanols, C2-C10-alkylene glycols, in which the alkylene chain can be interrupted by one or more, non-adjacent oxygen atoms, and ether of the C2-C10-alkylene glycols with C1-C4-alkanols. Examples of suitable solvents containing OH groups are methanol, ethanol, isopropanol, n-butanol, ethylene glycol, diethylene glycol, methyl diglycol, dipropylene glycol, butyl glycol, butyl diglycol, triethylene glycol, the methyl ethers of the glycols mentioned and oligomers of ethylene oxide with 4 to 6 ethylene oxide units, oligomers Propylene oxide with 3 to 6 propylene oxide units as well as polyethylene glycol-polypropylene glycol - cooligomers. In addition, the aqueous reaction medium can also other water-miscible solvents such as acetone, methyl contain ethyl ketone, tetrahydrofuran, dioxane, N-methylpyrrolidone, dimethylformamide etc.
Als Reaktionsmedium sind weiter geeignet: Cyclische Ether wie Tetrahydrofuran oder Dioxan, Ketone w e Aceton, Methylethylketon, Cyclohexanon, Ester aliphatischer Carbonsauren mit Cl-C4-Alkanolen, wie Essigsaureethylester oder Ess gsaure-n-buty- lester, aromatische Kohlenwasserstoffe wie Toluol, Xylole, Cumol, Chlorbenzol, Ethylbenzol, technische Mischungen von Alkyl - aromaten, Cyclohexan und technische Aliphatenmischungen.The following are also suitable as reaction medium: cyclic ethers such as tetrahydrofuran or dioxane, ketones and acetone, methyl ethyl ketone, cyclohexanone, esters of aliphatic carboxylic acids with C1-C4-alkanols, such as ethyl acetate or n-butyl acetate, aromatic hydrocarbons such as toluene, xylenes, Cumene, chlorobenzene, ethylbenzene, technical mixtures of alkyl aromatics, cyclohexane and technical aliphatic mixtures.
Die Polymerisation kann auch als Emulsions- oder Suspensionspolymerisation durchgeführt werden, wenn die Monomere im Reaktionsmedium schlecht löslich sind. Derartige Polymerisationsverfahren sind dem Fachmann bekannt und können für die Herstellung der erfmdungsgemaßen Polymerisate m der dafür üblichen Weise durchgeführt werden. Erfolgt die Herstellung der erfmdungsgemaßen Polymerisate durch rad kalische wäßrige Emuls onspolymeπsation, empfiehlt es sich, dem Reaktionsmedium Tenside oder Schutz - kolloide zuzusetzen. Eine Zusammenstellung geeigneter Emulgatoren und Schutzkolloide findet sich beispielsweise m Houben Weyl , Methoden der organischen Chemie, Band XIV/1 Makromolekulare Stoffe, Georg Thieme Verlag, Stuttgart 1961, S 411 ff.The polymerization can also be carried out as an emulsion or suspension polymerization if the monomers are poorly soluble in the reaction medium. Such polymerization processes are known to the person skilled in the art and can be carried out in the usual manner for the preparation of the polymers according to the invention. If the polymers according to the invention are prepared by radical aqueous emulsion polymerization, it is advisable to add surfactants or protective colloids to the reaction medium. A compilation of suitable emulsifiers and protective colloids can be found, for example, in M Houben Weyl, Methods of Organic Chemistry, Volume XIV / 1 Macromolecular Substances, Georg Thieme Verlag, Stuttgart 1961, p. 411 ff.
Die für die radikalische Polymerisation verwendeten Polymerisati - onsinitiatoren sind vorzugsweise im Reaktionsmedium löslich. Sie werden m Mengen von bis zu 30 Gew.-%, vorzugsweise 0,05 bis 15 Gew.-%, besonders bevorzugt 1,5 bis 10 Gew.-%, bezogen auf die bei der Polymerisation eingesetzten Monomere, verwendet. Er¬ folgt die Polymerisation m einem wasserhaltigen Losemittel oder m Wasser, so werden vorzugsweise wasserlösliche Polymerisati - onsinitiatoren wie beispielsweise Natriumpersulfat, Kaliumper¬ sulfat, Ammoniumpersulf t, Wasserstoffperoxid, tert . -Butylhydro peroxid, 2 , 2 ' -Azobis (2-amιdoιsopropan) dihydrochlorid, 2,2'-Azo- bis- (N, N' -dimethylemsobutyramidm) dihydrochlorid, und 2,2' -Azo¬ bis- (4-cyanopentansaure) verwendet. Die Initiatoren werden entwe¬ der allem oder m Mischung verwendet, z.B. Mischungen aus Wasserstoffperoxid und Natriumpersulfat.The polymerization initiators used for the radical polymerization are preferably soluble in the reaction medium. They are used in amounts of up to 30% by weight, preferably 0.05 to 15% by weight, particularly preferably 1.5 to 10% by weight, based on the monomers used in the polymerization. It follows ¬ m polymerization a water-containing solvent-m or water, preferably water-soluble Polymerisati - onsinitiatoren such as sodium persulfate, Kaliumper ¬ sulfate, Ammoniumpersulf t, hydrogen peroxide, tert. -Butylhydro peroxide, 2, 2-azobis (2-amιdoιsopropan) dihydrochloride, 2,2'-azo bis- (N, N '-dimethylemsobutyramidm) dihydrochloride, and 2,2'-azo ¬ bis- (4-cyanopentansaure ) used. The initiators are used entwe ¬ of all or m mixture, mixtures of hydrogen peroxide and sodium persulfate, for example.
Auch die bekannten Redox-Imtiatorsysteme können als Polymerisa- tionmitiatoren verwendet werden. Solche Redox-Imtiatorsysteme enthalten mindestens eine perox dhaltige Verbindung m Kombination mit einem Redox-Co itiator z.B. reduzierend wirkenden Schwefelverbmdungen, beispielsweise Bisulfite, Sulfite, Thio- sulfate, D thionite oder Tetrathionate von Alkalimetallen und Ammoniumverbindungen, Natπumhydroxymethansulfmat-Dihydrat und/ oder Thioharnstoff . So kann man Kombinationen von Peroxodi - sulfaten mit Alkalimetall- oder Ammoniumhydrogensulfiten einsetzen, z.B. Ammoniumperoxidisulfat und Ammoniumdisulfit. Das Gewichtsverhältnis von peroxidhaltigen Verbindungen zu den Redox- Coinitiatoren beträgt vorzugsweise 30:1 bis 0,05:1.The known redox initiator systems can also be used as polymerization initiators. Such redox imiator systems contain at least one compound containing peroxides in combination with a redox co-initiator, for example reducing sulfur compounds, for example bisulfites, sulfites, thiosulfates, dthionites or tetrathionates of alkali metals and ammonium compounds, sodium hydroxymethanesulfate dihydrate and / or thiourea. This is how combinations of Peroxodi - Use sulfates with alkali metal or ammonium hydrogen sulfites, e.g. ammonium peroxydisulfate and ammonium disulfite. The weight ratio of peroxide-containing compounds to the redox coinitiators is preferably 30: 1 to 0.05: 1.
In Kombination mit den Initiatoren bzw. den Redoxinitiator- systemen können zusätzlich Übergangsmetallkatalysatoren eingesetzt werden, wie z.B. Eisen-, Nickel-, Kobalt-, Mangan-, Kupfer-, Vanadium, oder Chromsalze, wie Eisen-II-sulfat, Kobalt- II-chlorid, Nickel-II-sulfat, Kupfer-I-chlorid, Mangan-II-acetat , Vanadium-III-acetat, Mangan-II-chlorid. Bezogen auf die Monomere werden diese Übergangsmetallsalze üblicherweise in Mengen von 0,1 bis 1000 ppm eingesetzt. So kann man Kombinationen von Wasserstoffperoxid mit Eisen-II-Salzen einsetzen, wie beispielsweise 0,5 bis 30 % Wasserstoffperoxid und 0,1 bis 500 ppm Mohrsches Salz.In combination with the initiators or the redox initiator systems, additional transition metal catalysts can be used, e.g. Iron, nickel, cobalt, manganese, copper, vanadium, or chromium salts, such as iron (II) sulfate, cobalt (II) chloride, nickel (II) sulfate, copper (I) chloride, manganese (II) acetate , Vanadium-III-acetate, manganese-II-chloride. Based on the monomers, these transition metal salts are usually used in amounts of 0.1 to 1000 ppm. So you can use combinations of hydrogen peroxide with iron (II) salts, such as 0.5 to 30% hydrogen peroxide and 0.1 to 500 ppm Mohr's salt.
Für die Polymerisation im nichtwäßrigen Milieu werden bevorzugt Initiatoren wie Dibenzoylperoxid, Dicyclohexylperoxidicarbonat, Dilaurylperoxid, Methylethylketonperoxid, Acetylacetonperoxid, tert . -Butylhydroperoxid, Cumolhydroperoxid, tert . -Butylperneode - canoat, tert . -Amylperpivalat, tert . -Butylperpivalat, tert.-Butyl- perneohexanoat , tert . -Butylper-2-ethylhexanoat, tert . -Butylper- benzoat , 2,2' -Azobis (N, N' -dimethylenisobutyramidin) -dihydro - Chlorid, 2 , 2 ' -Azo-bis- (isobutyronitril) , 4 , 4 ' -Azobis (4-cyano- valeriansäure) eingesetzt. In Kombination mit diesen Initiatoren können Reduktionsmittel wie Benzoin, Dimethylanilin, Ascorbin- säure sowie gegebenenfalls im Reaktionsmedium lösliche Komplexe und Salze von Übergangsmetallen verwendet werd . >. Falls die Reak¬ tionsmischung an der unteren Grenze des für die Polymerisation in Betracht kommenden Temperaturbereiches anpolymerisiert und anschließend bei einer höheren Temperatur auspolymerisiert wird, ist es zweckmäßig, mindestens zwei verschiedene Initiatoren zu verwenden, die bei unterschiedlichen Temperaturen zerfallen, so dass in jedem Temperaturintervall eine ausreichende Konzentration an Radikalen zur Verfügung steht.For the polymerization in a non-aqueous environment, initiators such as dibenzoyl peroxide, dicyclohexyl peroxidicarbonate, dilauryl peroxide, methyl ethyl ketone peroxide, acetylacetone peroxide are preferred. -Butyl hydroperoxide, cumene hydroperoxide, tert. -Butylperneode - canoat, tert. -Amyl perpivalate, tert. Butyl perpivalate, tert-butyl perneohexanoate, tert. -Butylper-2-ethylhexanoate, tert. -Butylper- benzoate, 2,2 '-azobis (N, N' -dimethyleneisobutyramidine) -dihydro - chloride, 2, 2 '-azo-bis- (isobutyronitrile), 4, 4' -azobis (4-cyano-valeric acid) used. In combination with these initiators, reducing agents such as benzoin, dimethylaniline, ascorbic acid and, if appropriate, complexes and salts of transition metals which are soluble in the reaction medium can be used. >. If the reac ¬ tion mixture polymerized at the lower limit of the next for the polymerization into consideration temperature range and subsequently completed at a higher temperature, it is expedient to use at least two different initiators which decompose at different temperatures, so that in each temperature interval a sufficient concentration of radicals is available.
Die Polymerisationsreaktion erfolgt beispielsweise bei Temperaturen im Bereich von 30 bis 300°C, vorzugsweise im Bereich von 50 bis 160°C und ganz besonders bevorzugt im Bereich von 100 bis 150°C. Dabei wird bevorzugt unter Ausschluß von Sauerstoff gearbeitet, vorzugsweise in einem Stickstoffström. In der Regel wird die Polymerisation bei Normaldruck durchgeführt, jedoch ist auch die Anwendung von niedrigeren Drucken oder höheren Drucken möglich, insbesondere wenn Polymerisationstemperaturen angewendet werden, die oberhalb des Siedepunktes der Monomere und/oder desThe polymerization reaction takes place, for example, at temperatures in the range from 30 to 300 ° C., preferably in the range from 50 to 160 ° C. and very particularly preferably in the range from 100 to 150 ° C. It is preferably carried out in the absence of oxygen, preferably in a nitrogen stream. As a rule, the polymerization is carried out at normal pressure, but the use of lower pressures or higher pressures is also possible, in particular if polymerization temperatures are used be above the boiling point of the monomers and / or
Lösungsmittels liegen.Solvent.
Zur Einstellung des gewünschten Molekulargewichts der Polymerisate kann es erforderlich sein, in Gegenwart eines Molekulargewichtsreglers, d.h. einer üblichen kettenabbrechenden Substanz, zu polymerisieren. Geeignete Molekulargewichtsregler umfassen beispielsweise Formaldehyd, Acetaldehyd, Propionaldehyd, n-Buty- raldehyd, Isobutyraldehyd, Ameisensäure, Ammoniumformiat, Hydroxylamin sowie dessen Sulfat, Chlorid oder Phosphat; SH-Grup - pen enthaltende Verbindungen wie Thioglykolsäure, Mercapto- propionsäure, Mercapotethanol, Mercaptopropanol, Mercaptobutanol, Mercatophexanol, Thiomaleinsäure, Thiophenol, 4-tert . -Butylthio- phenol, n-Dodecylmercaptan und/oder tert . -Dodecylmercaptan. Weitere Beispiele für Polymerisationsregler sind Allylalkohol, Butenol, Isopropanol, n-Butanol, Isobutanol, Glykol, Glycerin, Pentaerythrit, hypophosphorige Säure und deren Salze, wie z.B. Natriumhypophosph.it, phosphorige Säure und deren Salze, wie z.B. Natriumphosphit . Die Polymerisationsregler werden, sofern ihr Einsatz erforderlich ist, in Mengen bis zu 20 Gew.-%, bezogen auf die Monomeren, eingesetzt. Vorzugseise polymerisiert man in Gegenwart von 0,5 bis 15 Gew.-% eines SH-Gruppen enthaltenden Poylmerisationreglers, bezogen auf die Monomeren.To set the desired molecular weight of the polymers, it may be necessary in the presence of a molecular weight regulator, i.e. a conventional chain terminating substance to polymerize. Suitable molecular weight regulators include, for example, formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, formic acid, ammonium formate, hydroxylamine and its sulfate, chloride or phosphate; SH groups - compounds containing such as thioglycolic acid, mercapto-propionic acid, mercapotethanol, mercaptopropanol, mercaptobutanol, mercatophexanol, thiomaleic acid, thiophenol, 4-tert. -Butylthio-phenol, n-dodecyl mercaptan and / or tert. -Dodecyl mercaptan. Further examples of polymerization regulators are allyl alcohol, butenol, isopropanol, n-butanol, isobutanol, glycol, glycerol, pentaerythritol, hypophosphorous acid and their salts, such as e.g. Sodium hypophosphite, phosphorous acid and its salts, e.g. Sodium phosphite. If necessary, the polymerization regulators are used in amounts of up to 20% by weight, based on the monomers. Polymerization is preferably carried out in the presence of 0.5 to 15% by weight of a polymerization regulator containing SH groups, based on the monomers.
Weiterhin kann es für den Anwendungszweck sinnvoll sein, ver¬ zweigte bzw. vernetze Polymerisate zu verwenden. Vernetzte Poly¬ merisate sind entweder durch Copolymerisation der genannten Monomere mit zwei- oder mehrfach ethylenisch ungesättigten Verbindungen oder durch nachträgliche Vernetzung der Carboxyl-, Anhydrid- oder Hydroxylgruppen im Polymerisat mit geeigneten polyfunktionellen Verbindungen erhältlich. Erfolgt die Vernetzung auf dem Wege der Copolymerisation mit mehrfach ethylenisch ungesättigten Verbindungen, dann werden diese üblicherweise in Anteilen von 0,01 bis 20 Gew.-% und vorzugsweise in Mengen von 0,1 bis 5 Gew.-%, bezogen auf die zu polymerisierenden Monomere, eingesetzt. Bei nachträglicher Vernetzung der funktionellen Grup¬ pen im Polymerisat mit polyfunktionellen reaktiven Verbindungen werden diese üblicherweise in Mengen von 0,2 Gew.-% bis 20 Gew.-% und insbesondere 0,5 bis 10 Gew.-%, bezogen auf das Polymerisat, verwendet .It may also be useful for the purpose of using ver ¬ branched or crosslinked polymers. Crosslinked poly ¬ merisate are either obtainable by copolymerization of said monomers with di- or multi-ethylenically unsaturated compounds, or by subsequent crosslinking of carboxyl, anhydride or hydroxyl groups in the polymer with appropriate polyfunctional compounds. If the crosslinking is carried out by means of copolymerization with polyethylenically unsaturated compounds, these are usually present in proportions of 0.01 to 20% by weight and preferably in amounts of 0.1 to 5% by weight, based on those to be polymerized Monomers. In case of subsequent cross-linking of the functional groups in the polymer Grup ¬ with polyfunctional reactive compounds they are usually used in amounts of 0.2 wt .-% to 20 wt .-% and in particular 0.5 to 10 wt .-%, based on the polymer, used.
Geeignete zwei- oder mehrfach ethylenisch ungesättigte Verbindungen umfassen: Diacrylate oder Dimethacrylate von mindestens zweiwertigen gesättigten Alkoholen, wie z.B. Ethylenglykol - diacrylat, Ethylenglykoldimethylacrylat, 1, 2-Propylenglykol - diacrylat, 1, 2-Propylenglykoldimethacrylat, Butan- diol-1, -diacrylat, Butandiol-1, 4-dimethacrylat, Hexandiol- diacrylat, Hexandioldimethacrylat, Neopentylglykoldiacrylat, Neo- pentylglykoldimethacrylat, 3-Methylpentandιoldιacrylat, 3-Methyl - pentandioldimethacrylat; Acrylsäure- und Methacrylsaureester von Alkoholen mit mehr als 2 OH-Gruppen, wie z.B. Tπmethylolpropan- tπacrylat, Trimethylolpropantπmethacrylat, Glycerm- tπ (meth) acrylat; Diacrylate oder Dimethacrylate von Polyethylen- glykolen oder Polypropylenglykolen mit Molekulargewichten von jeweils 200 bis 9000, wie z.B. D ethylenglykoldiacrylat, Diethylen- glykoldimethacrylat , Tπethylenglykoldiacrylat , Triethylenglykol - dimethacrylat , Tetraethylenglykoldiacrylat , Tetraethylenglykoldi - methacrylat, Polyethylenglykol (meth) acrylat, Dipropylenglykoldia- crylat, Tπpropylenglykoldiacrylat, Polypropylenglykol (meth) acrylat; V ylester von ethylenisch ungesättigten C3-C6-Carbonsauren, z.B. Vmylacrylat, V ylmethacrylat, Vmylitaconat; Vmylester von mindestens 2 Carboxylgruppen enthaltenden gesattigten Carbonsauren sowie Di- und Polyv ylether von mindestens zweiwertigen Alkoholen, wie z.B. Adipmsaurediv ylester, Butandioldivmyl - ether, Trimethylolpropantrivmylether; Allylester ethylenisch ungesättigter Carbonsauren, wie z.B. Allylacrylat , Allylmeth- acrylat; Allylether von mehrwertigen Alkoholen wie z.B. Penta- erithπttπallylether, TπallylSaccharose, PentaallylSaccharose, Pentaallylsucrose; Methylenbis (meth) acrylamid, D vmylethylen- harnstoff, Divmylpropylenharnstoff , Divnylbenzol, Divmyldioxan, Triallylcyanurat, Tetraallylsilan und Tetrav ylsilan, Bis- oder Polyacrylsiloxane, Diallylphthalat , Allylvmylether und/oder Diallylfumarat . Als polyfunktionelle, reaktive vernetzende Verbindungen, die für die nachtragliche Vernetzung verwendet werden können, sind insbesondere Glycidylether von Polyhydroxy- verbmdungen oder die Glycidylester von Di- oder Polycarbonsauren geeignet. Beispiele für geeignete vernetzende Verbindungen umfassen: Ethylenglykoldiglycidylether, Polyethylenglykoldiglycidyle- ther, Pentaerythπtolpolyglycidylether, Propylenglykoldiglycidyl - ether, Polypropylenglykold glycidylether, Resorcmdiglycidyl ether, o-Phthalsaurediglycidylester oder Adipmsaurediglycidyl - ester .Suitable two or more ethylenically unsaturated compounds include: diacrylates or dimethacrylates of at least dihydric saturated alcohols, such as, for example, ethylene glycol - diacrylate, ethylene glycol dimethylacrylate, 1,2-propylene glycol - diacrylate, 1,2-propylene glycol dimethacrylate, butanediol-1, -diacrylate Butanediol-1, 4-dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 3-methylpentanediol dimethacrylate, 3-methyl-pentanediol dimethacrylate; Acrylic acid and methacrylic acid esters of alcohols with more than 2 OH groups, such as, for example, trimethylolpropane methacrylate, trimethylolpropane methacrylate, glycerm tπ (meth) acrylate; Diacrylates or dimethacrylates of polyethylene glycols or polypropylene glycols with molecular weights of 200 to 9000 each, such as, for example, ethylene glycol diacrylate, diethylene glycol dimethacrylate, polyethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, methylene glycol, methylene glycol, methylene glycol, methylene glycol, methylene glycol, methacrylate, tetraethylene glycol Polypropylene glycol (meth) acrylate; V ylester of ethylenically unsaturated C3-C6 carboxylic acids, for example Vmyl acrylate, V yl methacrylate, Vmylitaconat; Methyl esters of saturated carboxylic acids containing at least 2 carboxyl groups, and di- and polyvinyl ethers of at least dihydric alcohols, such as, for example, adipic acid divylester, butanediol divmyl ether, trimethylolpropane trimethyl ether; Allyl esters of ethylenically unsaturated carboxylic acids, such as allyl acrylate, allyl methacrylate; Allyl ethers of polyhydric alcohols, such as, for example, pentaerythritol allyl ether, tiallyl sucrose, pentaallyl sucrose, pentaallyl sucrose; Methylenebis (meth) acrylamide, D vmylethylene urea, divmyl propylene urea, divnyl benzene, divmyl dioxane, triallyl cyanurate, tetraallylsilane and tetrav ylsilane, bis- or polyacrylic siloxanes, diallyl phthalate, allylvmyl ether and / or diallyl fumarate. Glycidyl ethers of polyhydroxy compounds or the glycidyl esters of di- or polycarboxylic acids are particularly suitable as polyfunctional, reactive crosslinking compounds which can be used for subsequent crosslinking. Examples of suitable crosslinking compounds include: ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, pentaerytol tolpolyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol glycidyl ether, resorcidiglycidyl ether, o-phthalate or diglycidyl ester.
Wird die Polymerisation m wäßrigem Medium ausgeführt, betragt die Konzentration der Monomeren üblicherweise 10 bis 70, vorzugsweise 20 bis 60 Gew.-%.If the polymerization is carried out in an aqueous medium, the concentration of the monomers is usually 10 to 70, preferably 20 to 60% by weight.
Insbesondere m Fallen, m denen Calciumoxalat-Belage vergesellschaftet mit anderen anorganischen oder organischen Belagen, wie z.B. Calciumcarbonat, Calciumsulfat, Calciumsilikat , Calcium- phosphat, Magnesiumhydroxid, Bariumsulfat oder Calciumres at auftreten, kann es sinnvoll sein, die erf dungsgemaß zu verwendenden Copolymere als Formulierung m Mischung mit anderen Kompo- nenten einzusetzen. Solche Formulierungsbestandteile sind beispielsweise:In particular, in cases where calcium oxalate coatings are associated with other inorganic or organic coatings, such as calcium carbonate, calcium sulfate, calcium silicate, calcium phosphate, magnesium hydroxide, barium sulfate or calcium resate, it may be useful to use the copolymers according to the invention as a formulation m mix with other compo to use. Examples of such formulation components are:
(a) Kondensierte lineare und ringförmige Polyphosphate, wie z.B. Natriumtriphosphat und Natriumhexametaphosphat ,(a) Condensed linear and ring-shaped polyphosphates, e.g. Sodium triphosphate and sodium hexametaphosphate,
(b) Phosphonate, wie z.B. 2-Phosphono-l , 2 , 4-tπcarbonsaure, Ami notri- (methylenphosphonsaure) , 1-Hydroxyethylen (1 , 1-d phosp- honsaure) , Ethylendiamm-tetramethylen-phosphonsaure, Hexame- thylendiamm-tetramethylen-phosphonsaure und Diethylentπa- min-pentarnethylen-phosphonsaure,(b) phosphonates such as e.g. 2-phosphono-l, 2, 4-tπcarbonsaure, Ami notri- (methylenphosphonsaure), 1-hydroxyethylene (1, 1-d phosp- honsaure), ethylenediamm-tetramethylene-phosphonic acid, hexamethylenediamm-tetramethylene-phosphonic acid and diethylenetriamine -pentarethylene-phosphonic acid,
(c) Ammocarboxylate, wie z.B. Nitπlotπessigsaure, Ethylendi- ammtetraessigsaure, Diethylentriam pentaessigsaure, Hydroxyethylethylendiam tπessigsaure und Methylglycmdi essigsaure,(c) ammocarboxylates such as e.g. Nitπlotπessigsaure, ethylenediammetetraacetic acid, Diethylenetriam pentaessigsaure, Hydroxyethylethylenendiam tπessigsaure and Methylglycmdi acetic acid,
(d) wasserlösliche Polymere, w e z.B. Homo- und Copolymere der Acrylsäure mit gewichtsmittlerem Molekulargewicht im Bereich von 500 bis 15,000; Homo- und Copolymere von sulfogruppenhal - tigen Monomeren, wie z.B. 2-Acrylam do-2-methylpropansulfon saure, Styrolsulfonsäure oder V ylsulfonsäure mit gewichts- m ttlerem Molekulargewicht von 500 bis 15 000 sowie Naphthalinsulfonsaure-Formaldehyd-Polykondensate.(d) water soluble polymers, e.g. Homo- and copolymers of acrylic acid with a weight average molecular weight in the range from 500 to 15,000; Homo- and copolymers of sulfo-containing monomers, such as e.g. 2-Acrylam do-2-methylpropanesulfonic acid, styrene sulfonic acid or V ylsulfonic acid with a weight average molecular weight of 500 to 15,000 as well as naphthalene sulfonic acid formaldehyde polycondensates.
Die obengenannten Komponenten (a) bis (d) können gegebenenfalls mit weiteren Formulierungskomponenten wie Tensiden, Dispergier mittein, Entschäumern, Korrosionsinhibitoren, Sauerstoffangern, Bioziden, Alkalien und/oder Bleichmitteln eingesetzt werden.The above-mentioned components (a) to (d) can optionally be used with further formulation components such as surfactants, dispersants, defoamers, corrosion inhibitors, oxygen scavengers, biocides, alkalis and / or bleaches.
Die oben beschriebenen Copolymerisate werden zur Inhibierung von Calciumoxalatbelagen verwendet. Sie verhindern bzw. vermindern die Bildung von Calciumoxalatbelagen bzw. die Kesselstem- abscheidung wasserführenden Systemen, die Calciumionen und Oxalsäure bzw. wasserlösliche Salze der Oxalsäure enthalten. Die Copolymeren werden z.B. Mengen von 1 bis 2000, vorzugsweise 2 bis 200 ppm, bezogen auf das wäßrige System, eingesetzt. Sofern es dennoch zu Ausfallungen kommt, entstehen leicht ausschwemm bare, Wasser fern verteilte Ausscheidungen. Dadurch werden die Innenwände von Wärmetauschern, Rohren oder Pumpenbauteilen von Belagen frei gehalten und deren Korrosionsneigung gleichzeitig vermindert. Insbesondere wird die Gefahr der Lochfraßkorrosion, die üblicherweise unter Ablagerungen von Calciumoxalatbelagen oder Abscheidungen von Kesselstein auftritt, wirksam verringert. Auch das Aufwachsen von Mikroorganismen wird Gegenwart der erf mdungsgemaß einzusetzenden Copolymerisate erschwert. Der Einsatz der Copolymerisate m wasserführenden Systemen erhöht die Lebensdauer der Anlagen und reduziert Stillstandzeiten zur Reinigung von Anlagenteilen erheblich.The copolymers described above are used to inhibit calcium oxalate deposits. They prevent or reduce the formation of calcium oxalate deposits or the boiler separation of water-bearing systems which contain calcium ions and oxalic acid or water-soluble salts of oxalic acid. The copolymers are used, for example, in amounts of 1 to 2000, preferably 2 to 200 ppm, based on the aqueous system. If there are failures, there are easily washed-out excretions that are remotely distributed. This keeps the inner walls of heat exchangers, pipes or pump components free of deposits and at the same time reduces their tendency to corrode. In particular, the risk of pitting corrosion, which usually occurs with deposits of calcium oxalate deposits or deposits of scale, is effectively reduced. The growth of microorganisms is also made more difficult in the presence of the copolymers to be used according to the invention. The use of the copolymers in water-bearing systems increases the Lifetime of the systems and significantly reduces downtimes for cleaning system parts.
Bei den wasserführenden Systemen handelt es sich z.B. um offene oder geschlossene Kühlkreisläufe, beispielsweise von Kraftwerken oder chemischen Anlagen, wie Reaktoren, Destillationsapparaturen und Wärmetauscher. Auch bei Membranverfahren, die z.B. bei der Entsalzung von Meerwasser angewendet werden, können die erfindungsgemäß einzusetzenden Copolymerisate eine Schädigung der Membranen durch auskristallisierendes Calciumoxalat verhindern. Sie werden außerdem als Belagsverhinderer beim Eindampfen von Zuckersäften aus Zuckerrohr oder aus Zuckerrüben verwendet. Von besonderem Interesse ist der Einsatz der erfindungsgemäß einzusetzenden Copolymerisate bei der Zellstoff- und Papierherstellung, weil - wie bereits zum Stand der Technik dargelegt wurde - mit dem Papierstoff eine beträchtliche Menge an Calciumionen und an Oxalsäure in das wäßrige System eingetragen wird.The water-carrying systems are e.g. around open or closed cooling circuits, for example of power plants or chemical plants such as reactors, distillation apparatus and heat exchangers. Also in membrane processes, e.g. are used in the desalination of sea water, the copolymers to be used according to the invention can prevent damage to the membranes by crystallizing calcium oxalate. They are also used as deposit inhibitors when evaporating sugar juices from sugar cane or from sugar beet. Of particular interest is the use of the copolymers to be used according to the invention in pulp and paper production because - as has already been explained in relation to the prior art - a considerable amount of calcium ions and oxalic acid are introduced into the aqueous system with the paper stock.
Die erfindungsgemäß zu verwendenden Copolymerisate können beispielsweise im gesamten pH-Bereich, der in der Praxis von In¬ teresse ist, eingesetzt werden, z.B. in dem Bereich von 2 bis 12. Gegenüber den bisher verwendeten Inhibitoren weisen die erfindungsgemäßen Inhibitoren auch bei pH-Werten unterhalb von 8, vorzugsweise unterhalb von 7, eine ausreichende Wirkung auf.According to the invention to use copolymers may be used for example in the entire pH range, which is in practice of In ¬ teresse, eg in the range 2 to 12 to the inhibitors so far used have inhibitors of the invention at pH values below of 8, preferably below 7, a sufficient effect.
PrüfmethodenTest methods
Bestimmung des mittleren MolekulargewichtesDetermination of the average molecular weight
Die Bestimmung des gewichtsmittleren Molekular, ichtes erfolgte durch Gel-Per eations-Chromatographie (=GPC) bei Raumtemperatur mit wäßrigen Elutionsmitteln (0,08 m TRIS- Puffer (TRIS bedeutet: Tris (hydroxymethyl) aminomethan) mit pH 7,0 in dest. Wasser + 0,15 m NaCl + 0,01 m NaN3) . Die Proben besaßen eine Konzentration von c = 0,1 Massen-%, das Injektionsvolumen betrug Vinj = 200 μL. Die Kalibrierung erfolgte mit einer breit verteilten Natrium- Polyacrylat-Kalibriermischung. Die Chromatographiesäulen waren TSK PW-XL 3000 und TSK PW-XL 500 (Fa. TosoHaas) . Zur Detektion wurde ein Differentialrefraktometer eingesetzt.The weight-average molecular weight was determined by gel chromatography (GPC) at room temperature with aqueous eluents (0.08 m TRIS buffer (TRIS means: tris (hydroxymethyl) aminomethane) with pH 7.0 in dist. Water + 0.15 m NaCl + 0.01 m NaN 3 ). The samples had a concentration of c = 0.1 mass%, the injection volume was Vi n j = 200 μL. The calibration was carried out using a widely distributed sodium polyacrylate calibration mixture. The chromatography columns were TSK PW-XL 3000 and TSK PW-XL 500 (TosoHaas). A differential refractometer was used for detection.
Bestimmung der Calciumoxalat-InhibierungDetermination of calcium oxalate inhibition
Eine wässrige Lösung enthaltend 114,5 ppm Calciumchlorid-dihy- drat, 105 ppm Natriumoxalat und 10 ppm des zu prüfenden Polymers wird mit 2 %iger Salzsäure bzw. 2 %iger Natronlauge auf den gewünschten pH eingestellt. Die Lösung wird in einem Rundkolben mit Rückflusskühler unter Rühren auf 70°C erhitzt. Nach 3 Stunden wird die Lösung abgekühlt, 150 ml daraus entnommen und filtriert. Die Calciumionen-Konzentration im Filtrat c(Ca) [ppm] wird mittels Atomabsorptionsspektroskopie bestimmt. Die polymerspezifische Inhibierung IP berechnet sich nach folgender Formel:An aqueous solution containing 114.5 ppm calcium chloride dihydrate, 105 ppm sodium oxalate and 10 ppm of the polymer to be tested is adjusted to the desired pH with 2% hydrochloric acid or 2% sodium hydroxide solution. The solution is heated in a round-bottom flask with a reflux condenser to 70 ° C. with stirring. After 3 hours the solution is cooled, 150 ml removed and filtered. The calcium ion concentration in the filtrate c (Ca) [ppm] is determined using Determined atomic absorption spectroscopy. The polymer-specific inhibition IP is calculated using the following formula:
IP [%]= ( c(Ca) x 100 ) / 31,2IP [%] = (c (Ca) x 100) / 31.2
Nach der oben angegebenen Methode wurde die Calciumoxalatinhibie- rung für die in Tabelle 1 angegebenen Copolymerisate bei den ebenfalls angegebenen pH-Werten bestimmt. Die dabei erhaltenen Ergebnisse für die Inhibierung IP sind in Tabelle 1 aufgeführt.The calcium oxalate inhibition for the copolymers given in Table 1 was determined at the pH also given by the method given above. The results obtained for the IP inhibition are listed in Table 1.
Tabelle 1Table 1
Die Abkürzungen den Tabellen haben folgende Bedeutung: The abbreviations in the tables have the following meanings:
AS: AcrylsäureAS: acrylic acid
AM: AcrylamidAM: acrylamide
MS: MaleinsäureMS: maleic acid
MAS: MethacrylsaureMAS: methacrylic acid
VSNa: NatπumvmylsulfonatVSNa: sodium methyl sulfonate
MPEGMA: Methylpolyethylenglykolmethacrylat der Molmasse 1000.MPEGMA: methyl polyethylene glycol methacrylate with a molecular weight of 1000.
Zum Vergleich wurde die Inhibierung IP m Abwesenheit eines Polymers sowie m Gegenwart von bekannten Inhibitoren nach der oben beschriebenen Prufmethode bestimmt. Die Versuchsbedingungen und die Ergebnisse der Vergleichsversuche sind Tabelle 2 ange geben.For comparison, the inhibition IP in the absence of a polymer and in the presence of known inhibitors was determined by the test method described above. The test conditions and the results of the comparative tests are given in Table 2.
Tabelle 2Table 2

Claims

Patentansprüche claims
1. Verwendung von Copolymeren, die1. Use of copolymers
(a) 10 bis 80 Gew.-% Maleinsäure und/oder Maleinsäure - anhydrid,(a) 10 to 80% by weight of maleic acid and / or maleic anhydride,
(b) 20 bis 90 Gew.-% Acrylsäure,(b) 20 to 90% by weight of acrylic acid,
(c) 0 bis 20 Gew.-% mindestens eines weiteren mit den Monomeren (a) und (b) copolymerisierbaren Monomeren(c) 0 to 20% by weight of at least one further monomer which can be copolymerized with the monomers (a) and (b)
einpolymerisiert enthalten und die ein gewichtsmittleres Molekulargewicht von 25 000 bis 250 000 haben, als Inhibitor für Calciumoxalatbeläge .contain polymerized and have a weight average molecular weight of 25,000 to 250,000, as an inhibitor for calcium oxalate deposits.
2. Verwendung nach Anspruch 1, dadurch gekennzeichnet, daß die Copolymerisate2. Use according to claim 1, characterized in that the copolymers
(a) 20 bis 60 Gew.-% Maleinsäure,(a) 20 to 60% by weight of maleic acid,
(b) 40 bis 80 Gew.-% Acrylsäure und(b) 40 to 80% by weight acrylic acid and
(c) 0 bis 20 Gew.-% mindestens eines weiteren, mit den Monomeren (a) und (b) copolymerisierbaren Monomeren(c) 0 to 20% by weight of at least one further monomer which can be copolymerized with the monomers (a) and (b)
einpolymerisiert enthalten.polymerized included.
3. Verwendung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß das gewichtsmittlere Molekulargewicht der Copolymerisate 25 000 bis 150 000 beträgt.3. Use according to claim 1 or 2, characterized in that the weight average molecular weight of the copolymers is 25,000 to 150,000.
4. Verwendung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Copolymerisate als Monomere (c) Methacryl- säure, Vinylsulfonat , Methylpolyethylenglykolmethacrylate von Methylpolyethylenglykolen mit Molmassen von 200 bis 2500 oder deren Mischungen einpolymerisiert enthalten.4. Use according to one of claims 1 to 3, characterized in that the copolymers contain as monomers (c) methacrylic acid, vinyl sulfonate, methyl polyethylene glycol methacrylates of methyl polyethylene glycols with molecular weights from 200 to 2500 or mixtures thereof.
5. Verwendung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die Säuregruppen enthaltenden Monomereinheiten (a) , (b) und gegebenenfalls (c) der Copolymerisate teilweise oder vollständig mit Alkalimetallbasen oder Ammoniak neutralisiert sind. Verwendung von Copolymeren der Maleinsäure als Inhibitor von Calciumoxalatbelagen5. Use according to one of claims 1 to 4, characterized in that the monomer units (a), (b) and optionally (c) of the copolymers containing acid groups are partially or completely neutralized with alkali metal bases or ammonia. Use of copolymers of maleic acid as an inhibitor of calcium oxalate deposits
ZusammenfassungSummary
Verwendung von Copolymeren, dieUse of copolymers
a) 10 bis 80 Gew.-% Maleinsäure und/oder Maleinsäureanhydrid, b) 20 bis 90 Gew.-% Acrylsäure und c) 0 bis 20 Gew.-% mindestens eines weiteren mit den Monomeren (a) und (b) copolymerisierbaren Monomerena) 10 to 80% by weight of maleic acid and / or maleic anhydride, b) 20 to 90% by weight of acrylic acid and c) 0 to 20% by weight of at least one further monomer copolymerizable with the monomers (a) and (b)
einpolymerisiert enthalten und die ein gewichtsmittleres Moleku- largewicht von 25 000 bis 250 000 haben, als Inhibitor für Calciumoxalatbeläge . polymerized in and which have a weight average molecular weight of 25,000 to 250,000, as an inhibitor for calcium oxalate deposits.
EP00941979A 1999-05-28 2000-05-24 Utilization of maleic acid copolymers as inhibitors of calcium oxalate coatings Withdrawn EP1181251A1 (en)

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DE1999124706 DE19924706A1 (en) 1999-05-28 1999-05-28 Use of copolymers of maleic acid as an inhibitor of calcium oxalate deposits
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PCT/EP2000/004719 WO2000073218A1 (en) 1999-05-28 2000-05-24 Utilization of maleic acid copolymers as inhibitors of calcium oxalate coatings

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IT1230862B (en) * 1989-06-06 1991-11-08 Ausidet Spa WATER SOLUBLE COPOLYMERS OF MALEIC ANHYDRIDE.
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