WO2024200585A1

WO2024200585A1 - Reduction of acetaldehyde content in vinylether-based copolymers

Info

Publication number: WO2024200585A1
Application number: PCT/EP2024/058380
Authority: WO
Inventors: Roland Reichenbach-Klinke; Silke Flakus-Taube; Manfred Bichler; Christian Scholz
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2023-03-29
Filing date: 2024-03-27
Publication date: 2024-10-03
Anticipated expiration: 2025-09-29

Abstract

A process for removing acetaldehyde from a vinylether-based copolymer composition, the process comprising at least one of the steps of a) oxidating the acetaldehyde in the vinylether-based copolymer composition; b) reducing the acetaldehyde in the vinylether- based copolymer composition; c) reducing and oxidating the acetaldehyde in the vinylether- based copolymer composition.

Description

Reduction of Acetaldehyde Content in Vinylether-Based Copolymers

Technical Field

The present invention relates to the process for reducing or removing acetaldehyde content from compositions comprising vinylether-based copolymers. Furthermore, the present invention relates to the use of such process reduction in or removal of acetaldehyde content in vinylether-based copolymer compositions. Finally, the present invention relates to a vinylether-based copolymer composition having reduced or no acetaldehyde content.

Background

Vinylether-based copolymers are often used as dispersants for inorganic pigment suspensions, plasticizers and superplasticizers for hydraulic cement systems, concrete, mortar, gypsum suspensions and anhydrous calcium sulfate binder formulations, for ceramic materials comprising clays, kaolins, feldspars and quartz minerals and for pigment preparations of inorganic white and colored pigments in the paint and coating industry, and leather industry, and as scale inhibitors, dispersants and sequestering agents in the detergent and cleaning agent industry and water treatment.

Solid suspensions usually contain dispersants or plasticizers for fluidizing and dispersing inorganic solids. Such solids may be cement, gypsum, calcium sulfate hemihydrate, fly ash, kaolin in the building industry, titanium dioxide, calcium carbonate, talc, barium sulfate, zinc sulfite, bismuth vanadate, iron oxide pigments, chromium dioxide, cobalt spinel pigments and other inorganic, colored pigments in the paint and coating industry. Dispersants together with sodium carbonate and/or waterglass are also added to ceramic materials comprising clays, kaolins, feldspars and quartz minerals, in order to permit processability and press the green compact into the plaster mold.

DE 10017667 A describes the use of copolymers with vinyl-functionalized polyethers for the preparation of aqueous pigment preparations. These copolymers are prepared by free radical polymerization of, inter alia, vinylpolyalkylene glycol ethers and maleic anhydride and further monomers and are suitable for dispersing organic and inorganic pigments and fillers and for the preparation of pigment concentrates, pastes and preparations.

The aim of the addition of superplasticizers in the building industry is either to increase the plasticity of the concrete or to reduce the amount of water required for the mixture comprising cement slurry, fly ash and aggregates under the same processing condition.

WO 99/010407 A1 discloses a process for the preparation of copolymers from alkoxylated (meth)acrylic acid and ethylenically unsaturated carboxylic acids.

EP-A-0 311 157 discloses copolymers of alkoxylated (meth)acrylic acid, (meth)acrylic acid and styrene derivatives, which can be used as dispersant.

It has been found that in particularly suitable superplasticizers are weakly anionic, polyalkylene glycol ether-containing copolymers. These copolymers are also designated as polycarboxylate ethers (PCE) in the building industry. The information brochure “Modern Superplasticisers in Concrete Technology, January 2007” of the Verein Deutsche Bauchemie e.V., Frankfurt am Main, describes the use and the advantages of these polycarboxylate ethers.

Polycarboxylate ethers disperse the inorganic pigment particles not only via electrostatic charge build-up owing to the anionic groups present on the main chain (carboxylate groups, sulfonate groups) but additionally stabilize the dispersed particles by steric effects owing to the polyalkylene glycol ether side chains which form a stabilizing protective layer around the pigment particle by absorption of water molecules.

As a result, either the required amount of water for establishing a certain consistency can be reduced compared with the classical superplasticizers or the plasticity of the moist building material mixture is reduced by the addition of the polycarboxylate ethers to such an extent that self-compacting concrete can be produced at low water/cement ratios. The use of the carboxylate ethers also permits the production of ready-mixed concrete which remains pumpable over relatively long periods or the production of high-strength concretes by establishing a low water/cement ratio.

Polyvinyl ethers are usually obtained by cationic polymerization. A radical polymerization process for vinyl ethers is described by Masatoshi Miyamoto et al. in Macromol. Chem. Phys.199, 119-125 for ethylene glycol methyl vinyl ether and oligomeric ethylene glycol methyl vinyl ethers. As initiators 2,2'-Azobis(isobutyronitril) and 2,2'-Azobis(2- amidinopropane) dihydrochloride are used. A radical polymerization process for copolymers of hydroxyalkyl vinyl ethers is disclosed in EP 0 379 166 A1 , where tertiary butyl per acetate is used as initiator. According to WO 93/06142 A1 copolymers of hydroxyalkyl vinyl ethers may be obtained by cation initiated or radical initiated polymerization. In case of radical polymerization any initiator may be suitable, including azo initiators. In the examples of WO 93/06142 A1 tertiary butyl per pivalate is used. WO 2014 079722 A1 describes a process for the production of a polyvinylether by radical polymerization using an azocompound as polymerization initiator.

However, vinyl ethers are sensitive to ether cleavage at acidic and neutral pH values. This produces vinyl alcohol, which immediately tautomerizes to acetaldehyde, and a second alcohol. Even if the reaction is carried out at optimum conditions, this ether cleavage cannot be completely avoided during the free-radical polymerization of vinyl ethers, since the polymerization is usually not carried out in the basic pH range, where the vinyl ether is stable. Hence, the reaction always involves a cleavage of the vinyl ether, thus producing acetaldehyde as a by-product. Acetaldehyde can cause cancer and therefore leads to a labeling as carcinogenic 1 B with H350 (may cause cancer) already at a content in the product of > 1000 ppm.

Summary of the Invention

To avoid this risk for health, efforts are being made to minimize the acetaldehyde content in vinylether-based copolymers and to keep it below the critical limit of 1000 ppm. Hence, it is one object of the present invention to provide a process for efficient reduction, preferably removal, of acetaldehyde content from vinylether-based copolymer compositions. Furthermore, it is an object of the present invention to provide such acetaldehyde-reduced, preferably acetaldehyde-depleted, vinylether-based copolymer composition.

It has been found that this object is surprisingly achieved by a process for removing acetaldehyde from a vinylether-based copolymer composition, the process comprising at least one of the steps of a) Oxidating the acetaldehyde in the vinylether-based copolymer composition; b) Reducing the acetaldehyde in the vinylether-based copolymer composition; c) Reducing and oxidating the acetaldehyde in the vinylether-based copolymer composition.

Furthermore, it has been surprisingly found out that above-mentioned object is achieved by the use of said process for removing acetaldehyde from a vinylether-based copolymer, preferably a polyethercarboxylate or a maleic acid vinyl acetate, most preferably a polyethercarboxylate.

Finally, it has been surprisingly found out that above-mentioned object is achieved by a composition comprising a vinylether-based copolymer, preferably a polyethercarboxylate or a maleic acid vinyl acetate, most preferably a polyethercarboxylate, the composition comprising less than 600 ppm acetaldehyde, preferably less than 400 ppm acetaldehyde, more preferably less than 200 ppm acetaldehyde, even more preferably less than 50 ppm acetaldehyde, preferably less than 25 ppm acetaldehyde.

Detailed Description of the Invention

Before describing in detail exemplary embodiments of the present invention, definitions important for understanding the present invention are given.

As used in this specification and in the appended claims, the singular forms of "a" and "an" also include the respective plurals unless the context clearly dictates otherwise. In the context of the present invention, the terms "about" and "approximately" denote an interval of accuracy that a person skilled in the art will understand to still ensure the technical effect of the feature in question. The term typically indicates a deviation from the indicated numerical value of ±20 %, preferably ±15 %, more preferably ±10 %, and even more preferably ±5 %. It is to be understood that the term "comprising" is not limiting. For the purposes of the present invention the term "consisting of is considered to be a preferred embodiment of the term "comprising of. If hereinafter a group is defined to comprise at least a certain number of embodiments, this is meant to also encompass a group which preferably consists of these embodiments only. Furthermore, the terms "first", "second", "third" or "(a)", "(b)", "(c)", "(d)" etc. and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. In case the terms "first", "second", "third" or "(a)", "(b)", "(c)", "(d)", "i", "ii" etc. relate to steps of a method or use or assay there is no time or time interval coherence between the steps, i.e. the steps may be carried out simultaneously or there may be time intervals of seconds, minutes, hours, days, weeks, months or even years between such steps, unless otherwise indicated in the application as set forth herein above or below. It is to be understood that this invention is not limited to the particular methodology, protocols, reagents etc. described herein as these may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention that will be limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

As used herein the term “does not comprise”, “does not contain”, or “free of’ means in the context that the composition of the present invention is free of a specific compound or group of compounds, which may be combined under a collective term, that the composition does not comprise said compound or group of compounds in an amount of more than 0.8 % by weight, based on the total weight of the composition. Furthermore, it is preferred that the composition according to the present invention does not comprise said compounds or group of compounds in an amount of more than 0.5 % by weight, preferably the composition does not comprise said compounds or group of compounds at all.

For the purposes of the present invention the term “vinylether-based copolymer” means a polymer obtained by polymerization of monomers comprising at least one monomer having a vinyl ether group. Examples of those monomers are 4-hydroxybutylvinylether and poly(oxy- 1 ,2-ethanediyl), ,alpha.-[4-(ethenyloxy)butyl]-. omega. -hydroxy with various degree of polymerization, which are available as Pluriol A 1190 V, Pluriol A 2090 V, Pluriol A 3090 V and Pluriol A 5890 V from BASF SE.

When referring to compositions and the weight percent of the therein comprised ingredients it is to be understood that according to the present invention the overall amount of ingredients does not exceed 100% (± 1% due to rounding).

The present invention relates to a process, a use, and a composition, which will be described in the following.

The process for removing acetaldehyde from a vinylether-based copolymer composition according to the present invention comprises at least one of the steps of a) Oxidating the acetaldehyde in the vinylether-based copolymer composition; b) Reducing the acetaldehyde in the vinylether-based copolymer composition; c) Reducing and oxidating the acetaldehyde in the vinylether-based copolymer composition.

In one aspect the vinylether-based copolymer consists of two monomer components (A) and (B) wherein

(A) an olefinic unsaturated mono-carboxylic acid co-monomer or an ester or salt thereof or an olefinic unsaturated sulfuric acid co-monomer or a salt thereof, and

(B) a comonomer according to the general formula (I) -(CH₂-CH)-O-R¹ (I)

Whereby R¹ is represented by

-(C_mH_2rnO)_x(C_nH_2nO)_y-(CH₂-CH-O)_z-R⁴

R³ whereby R³ is a non-substituted or substituted aryl group and preferably phenyl, and R⁴ is hydrogen or an aliphatic hydrocarbon group having from 1 to 20-atoms, a cycloaliphatic hydrocarbon group having from 5 to 8 C-atoms, a substituted aryl group having from 6 to 14 C-atoms or a compound selected from the group consisting of

0 , 0 0 o

-O-C-R⁵ , -O-C-R⁶-C-OH , -O-C-(NH)R⁷ wherein R⁵ and R⁷ may each be an alkyl, aryl, aralkyl or alkaryl group and R⁶ may be an alkyliden, aryliden, aralkyliden or alkaryliden group and m, n = 2 to 4, x is from 1 to 350, y is from 0 to 350, and z= 0 to 200.

In one embodiment z is 0, in a further preferred embodiment z is 1 to 200, preferably 10 to 100.

Most preferably m is 4, x is 1 , y is 0, and z is 0.

The terms "alkyl" and "alkyliden" as used herein, determine hydrocarbon groups with preferably 1 to 20 C-atoms, preferably with 1 to 6 C-atoms.

The terms "aryl", "aralkyl", "alkaryl", "aryliden", "aralkyliden" and "alkaryliden" represent hydrocarbon groups with preferably 5 to 20, more preferably 5 to 10 C-atoms.

The copolymer of this invention shows more advantageous properties when it comprises the co-monomer component (A) in amounts of from 30 to 99 mol-% and the ether component (B) from 70 to 1 mol-%.

As used herein, the mentioned comonomers and any possible structures thereof are to be interpreted as structural units of the claimed copolymer after its polymerization.

The invention comprises an alternative characterized in that on the one hand the mol-% of the comonomer component (A) and the comonomer (B) is from 40 to 90 and from 60 to 10, respectively, and whereby on the other hand the ether component (B) contains a vinyl group and a polyether as R¹.

Additionally, the comonomer component (A) is in this alternative an acrylic acid or a salt thereof.

In general, the comonomer component (A) is selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, maleic acid, maleic anhydride, itaconic acid, allyl sulfonic acid, vinyl sulfonic acid and their suitable salts or their alkyl or hydroxyalkyl esters. Alternatively, other comonomers, such as styrene or/and acrylamides may be additionally co-polymerized with the ether component (B) and the comonomer component (A). Alternatively, there also may be used components with hydrophobic properties. Compounds with ester structural units, polypropylene oxide or polypropylene oxide/polyethylene oxide (PO/PE)-units are preferred. The corresponding structural units should be represented in the copolymer of the invention in amounts up to 5 mol-%, amounts from 0.05 to 3 mol-% are preferred and 0.1 to 1.0 mol-% are especially preferred.

Preferably, the vinylether-based copolymer is a polyethercarboxylate or a maleic acid vinyl acetate, most preferably a polyethercarboxylate.

As outlined above, the production process for such vinylether-based copolymers, in particular the radical polymerization, which is carried out at lower pH values, results in formation of significant and health-harming amounts of acetaldehyde. It has now been found out that these amounts of acetaldehyde can be removed from the composition comprising the vinylether-based copolymer by at least one of the steps as described above, which will now be described in detail.

In one embodiment of the present invention, the process comprises the step a) of oxidating the acetaldehyde in the vinylether-based copolymer composition. In this step, the acetaldehyde is reacted to acetic acid.

Generally, step a) comprises, preferably consists of, treating the vinylether-based copolymer composition with an oxidating agent. Suitable oxidating agents are selected from the list consisting of hydrogen peroxide and derivatives, percarbonates, permanganate, dichromate, chromium oxide, ozone, cerium (IV) salts, bromate, hypochlorite. Preferably, step a) comprises, preferably consists of, treating the vinylether-based copolymer composition with a peroxide. Preferably, the peroxide is selected from hydrogen peroxide or R-O-O-H, wherein R is selected from branched or linear, saturated or unsaturated alkyl, aryl, alkaryl, and phenyl. More preferably the peroxide is selected from hydrogen peroxide or tertbutyl peroxide. Most preferably, the peroxide is hydrogen peroxide.

Also preferably, in the process of the present invention, step a) is carried out in the presence of a metal-based catalyst. This facilitates the oxidation process. Generally, such catalyst can be selected from transition metal salts. Preferably, the metal of the metal catalyst is selected from Fe, Mo, Mn, Cu, Ni, Co, and Ti, preferably is Fe. Most preferably, the metal catalyst is FeSO₄.

Preferably, step a) is carried out for 0.5 to 10 h, more preferably from 1 to 5 h and most preferably from 2 to 4 h. Likewise, preferably, step a) is carried out at a temperature in the range of from 25 to 80 °C, more preferably at a temperature in the range of from 35 to 60 °C.

Preferably, in step a), the weight ratio of the amount of peroxide to the amount of vinyletherbased copolymer in the composition is in the range of from 0.01 to 0.3, preferably from 0.05 to 0.2, and most preferably from 0.1 to 0.15. Likewise, preferably, in step a), the weight ratio of the amount of catalyst to the amount of vinylether-based copolymer in the composition is in the range of from 1 to 30, preferably from 5 to 20, and most preferably from 10 to 15. Also preferably, in step a), the weight ratio of the amount of peroxide to the amount of catalyst is in the range of from 0.01 to 0.3, preferably from 0.05 to 0.25, and most preferably from 0.1 to 0.2.

Preferably, step a) is carried out in a protic solvent, most preferably in water.

In another embodiment of the present invention, the process comprises the step a) of reducing the acetaldehyde in the vinylether-based copolymer composition. In this step, the acetaldehyde is reacted to ethanol. Preferably, step b) comprises, more preferably consists of, treating the vinylether-based copolymer composition with a reducing agent.

Generally, suitable reducing agents are selected from the list consisting of hydrides, preferably lithiumaluminiumhydride or sodium boron hydride, sulfides, thiosulfates, sulfites, hydrazine, zinc, alumina and magnesium. Preferably, in step b) the reducing agent is selected from the list consisting of phosphinic acid and salts thereof, phosphoric acid and salts thereof, 2-hydroxy-2-sulfinatoacetic acid and salts thereof, 2-hydroxy-2-sulfonatoacetic acid and salts thereof, sulfurous acid and salts thereof, hydroxymethanesulfinic acid and salts thereof, sodium dithionite and mixtures thereof. More preferably, in step b) the reducing agent is selected from the list consisting of 2-hydroxy-2-sulfinatoacetic acid and salts thereof, 2-hydroxy-2-sulfonatoacetic acid and salts thereof, sulfurous acid and salts thereof, hydroxymethanesulfinic acid and salts thereof, and mixtures thereof. Even more preferably, in step b) the reducing agent is a mixture of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the bisodium salt of 2-hydroxy-2-sulfonatoacetic acid, and the sodium salt of sulfurous acid, or is the sodium salt of sulfurous acid. Most preferably, in step b) the reducing agent is the sodium salt of sulfurous acid.

Preferably, in step b), the weight ratio of the amount of reducing agent to the amount of vinylether-based copolymer in the composition is more than 0.001 , preferably more than 0.008, even more preferably more than 0.02, even more preferably more than 0.03, and most preferably more than 0.04.

Preferably, in step b), the molar ratio of the amount of reducing agent to the amount of acetaldehyde initially present in the vinylether-based composition is larger than 1 .5, more preferably is equal to or larger than 2, even more preferably is equal to or equal to or larger than 3, still even more preferably is equal to or larger than 4, and most preferably is equal to or larger than 5.

In an alternatively preferred embodiment, in step b), the molar ratio of the amount of reducing agent to the amount of acetaldehyde initially present in the vinylether-based composition is larger than 1.7, more preferably is equal to or larger than 2,0, even more preferably is equal to or equal to or larger than 3,4, still even more preferably is equal to or larger than 4,2, and most preferably is equal to or larger than 5,0.

Preferably, step b) is carried out in a protic solvent, most preferably in water.

In another embodiment of the present invention, the process comprises the step c) of reducing and oxidating the acetaldehyde in the vinylether-based copolymer composition. Preferably, step c) comprises, more preferably consists of, treating the vinylether-based copolymer with a protonic base to reach a pH value of more than 10, preferably more than 11 , even more preferably more than 12, most preferably more than 13, to yield an intermediate basic solution, and subsequently treating the intermediate basic solution with a protonic acid to reach a pH value of 7 to 9, preferably 7.8 to 8.2. Whilst not being bound by theory, it is believed that by the is procedure the acetaldehyde is object to a Cannizzaro reaction, wherein two acetaldehyde molecules are reacted to one ethanol and one acetic acid molecule.

Preferably, in step c) the protonic base is an alkali or earth alkali hydroxide, preferably an aqueous alkali or earth alkali hydroxide solution, more preferably a 20 to 70%, preferably 30 to 60%, aqueous alkali or earth alkali hydroxide solution, most preferably an aqueous 50% sodium hydroxide solution. Likewise, preferably. In step c) the protonic acid is selected from formic acid or sulphuric acid.

It has been found out that the reaction is in particular significantly improved if a certain amount of a saccharide is added to the reaction mixture. It is in particular preferable to add the saccharide before the step of adding the protonic acid. Hence, preferably, step c) is catalyzed by saccharide, preferably a monosaccharide, and most preferably by glucose.

Preferably, step c) is carried out for 0.5 to 2 h, more preferably from 0.75 to 1 .5 h. Likewise, preferably, step a) is carried out at a temperature in the range of from 20 to 50 °C, more preferably at a temperature in the range of from 25 to 45 °C.

Preferably, in step a), the weight ratio of the amount of protonic base to the amount of vinylether-based copolymer in the composition is more than 0.002, preferably more than 0.0035, and most preferably more than 0.006.

Likewise, preferably, in step a), the weight ratio of the amount of saccharide to the amount of vinylether-based copolymer in the composition is in the range of from 0.0005 to 0.003, preferably from 0.001 to 0.0025, and most preferably from 0.0015 to 0.002.

Also preferably, in step a), the weight ratio of the amount of saccharide to the amount of protonic base is in the range of from 0.4 to 0.8, preferably from 0.5 to 0.75, and most preferably from 0.6 to 0.7.

Preferably, the process of the present invention comprises at least step c).

Preferably, in the process of the present invention, at least 70 % of the amount of acetaldehyde initially present in the vinylether-based composition is removed, more preferably at least 80 %, more preferably at least 90%, and most preferably at least 95%. Ins the most preferred embodiment of the present invention, in the process the amount of acetaldehyde is removed. Likewise, in the process of the present invention the amount of acetaldehyde in the vinylether-based composition is reduced to less than 600 ppm, preferably less than 400 ppm, more preferably less than 200 ppm, and even more preferably less than 100 ppm, and most preferably less than 50 ppm.

Furthermore, the present invention relates to the use of the process according to the invention to reduce the content of acetaldehyde in the vinylether-based composition to less than 600 ppm, preferably less than 400 ppm, more preferably less than 200 ppm, and even more preferably less than 100 ppm, and most preferably less than 50 ppm. Preferably, the present invention relates to the use of the process according to the invention to reduce the content of acetaldehyde in the vinylether-based composition by at least 70 % of the amount of acetaldehyde initially present in the vinylether-based composition is removed, more preferably at least 80 %, more preferably at least 90%, and most preferably at least 95%. Most preferably, the present invention relates to the use of the process according to the invention to remove the amount of aldehyde in the vinylether-based composition.

Finally, the present invention relates to a composition comprising a vinylether-based copolymer, preferably a polyethercarboxylate or a maleic acid vinyl acetate, most preferably a polyethercarboxylate, the composition comprising less than 600 ppm acetaldehyde, preferably less than 400 ppm acetaldehyde, more preferably less than 200 ppm acetaldehyde, even more preferably less than 50 ppm acetaldehyde, preferably less than 25 ppm acetaldehyde. Most preferably, the composition does not comprise aldehyde.

The invention is further illustrated by the appended drawings and the examples that follow.

Examples

Measurement methods: a) Amount acetaldehyde

Acetaldehyde is quantified by reaction with 2,4-dinitrophenylhydrazine and subsequent detection of the hydrazone by HPLC (high performance liquid chromatography. First, the analyte is dissolved in the eluent, which is a mixture of 55% acetonitrile and 45% 0.05M KH2PO4 buffer pH 2.5. Then 2,4-dinitrophenylhydrazine is added and the reaction mixture is stirred for 2 h. Next, the sample is injected into the HPLC apparatus, which is equipped with a Nucleosil C18 100-5 column. Detection is performed by UV with a wavelength of 360 nm. For quantification calibration is performed with five standards with known concentration of acetaldehyde.

Chemicals used in the following examples.

All Copolymers A to E are commercially available vinylether-based copolymers.

Copolymer A Copolymer A is a polycarboxylic ether dispersant based on maleic acid and Pluriol A 1190 V and is provided as a 49.5 wt.-% aqueous solution.

Copolymer B is a polycarboxylic ether dispersant based on acrylic acid, hydroxypropyl acrylate, Pluriol A 1190 V and Pluriol A 5890 V and is provided as 45 wt.-% aqueous solution.

Copolymer C is a polycarboxylic ether dispersant based on acrylic acid, Pluriol A 1190 V and Pluriol A 3090 V and is provided as a 46 wt.-% aqueous solution.

Copolymer D is a polycarboxylic ether dispersant based on maleic acid, 4- hydroxylbutylvinylether and an ester made from maleic anhydride and MPEG 2000 and is provided as a 47 wt.-% aqueous solution. Copolymer E is a polycarboxylic ether dispersant based on acrylic acid and Pluriol A 3090

V and is provided as a 40 wt.-% aqueous solution.

Bruggoh'te FF6\s a mixture of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the bisodium salt of 2-hydroxy-2-sulfonatoacetic acid, and the sodium salt of sulfurous acid available by L. Bruggemann GmbH & Co. KG and usually applied in a 5 wt.-% aqueous solution.

Rongalit'xs the sodium salt of the hydroxymethanesulfinic acid.

Inventive Example 1 (IE 1)

24.8 g Copolymer A (49.5 wt.-% aqueous solution) having an initial acetaldehyde content of 740 ppm were mixed with 30% H2O2 in an amount as indicated in Table 1 . To the solution the amount of FeSO4 as indicated in Table 1 was added and the solution was heated to and kept at the temperature as also indicated in Table 1 . The solution was stirred for either 1 or 3 h as also indicated in Table 1 . Finally, the aldehyde content of the solutions was determined by above-described method.

Table 1 : Parameters and results of IE1

Percentage of removed acetaldehyde

Inventive Example 2 (IE 2)

24.8 g Copolymer A (49.5 wt.-% aqueous solution) having an initial acetaldehyde content of 740 ppm were mixed with the reducing agent in an amount as indicated in Table 2. The solution was heated to and kept at the temperature as also indicated in Table 2. The solution was stirred for either 1 or 3 h as also indicated in Table 2. Finally, the aldehyde content of the solutions was determined by above-described method. Table 2: Parameters and results of IE2

Percentage of removed acetaldehyde

Inventive Example 3 (IE3)

22.5 g Copolymer B having an initial acetaldehyde content of 720 ppm were mixed with Bruggolite FF6 (5%) in an amount as given in Table 3. The solution was heated to and kept at the 30 °C. The solution was stirred for 1 h. Finally, the aldehyde content of the solutions was determined by above described method.

Table 3: Parameters and results of IE3

Percentage of removed acetaldehyde

Inventive Example 4 (IE4)

50 g Copolymer A (49.5 wt.-% aqueous solution) having an initial acetaldehyde content of 1000 ppm were mixed with 10% active, aqueous sodium bisulfite solution in an amount as indicated in Table 4. The solution was heated to and kept at the temperature as also indicated in Table 4. The solution was stirred for either 1 or 3 h as also indicated in Table 4. Finally, the aldehyde content of the solutions was determined by above-described method. Table 4: Parameters and results of IE4

Percentage of removed acetaldehyde

Inventive Example 5 (IE5)

50 g Copolymer A (49.5 wt.-% aqueous solution) having an initial acetaldehyde content of 1000 ppm were mixed with 10% active, aqueous sodium bisulfite solution in an amount as indicated in Table 5. The solution was heated to and kept at the temperature as also indicated in Table 5. The solution was stirred for 7 d. Finally, the aldehyde content of the solutions was determined by above-described method.

Table 5: Parameters and results of IE5

Percentage of removed acetaldehyde

Inventive Example 6 (IE 6)

An amount as indicated in Table 6 of an aqueous solution as described in Table 6 was mixed with 50% NaOH as base in an amount according to Table 6 and stirred for a time and at a temperature given in Table 6 resulting in a pHi (cf. Table 6). The pH was then adjusted to pH2 (cf. Table 6) using a 20% aqueous solution of sulfuric acid (for exceptions, cf. Table 6). If indicated by Table 6, an amount of glucose was added to the solution during stirring. Table 6: Parameters and results of IE4

a 500 g of aqueous solution with the given percentage of polymer were used in each example if not mentioned otherwise b 50% aqueous NaOH solution was used in each example c 20% aqueous sulfuric acid solution was used in each example if not mentioned otherwise e 50% aqueous sulfuric acid solution was used g 99% aqueous formic acid solution was used h Percentage of removed acetaldehyde

¹ 200 g of aqueous solution with the given percentage of polymer were used

Inventive Example 7 (IE 7)

50 g Copolymer A (50 wt.-% aqueous solution) having an initial acetaldehyde content of 813 ppm were mixed with the amount of sodium dithionite (Hydrosulfit E as available by BASF SE) as indicated in Table 7 was added and the solution was heated to and kept at the temperature as also indicated in Table 7. The solution was stirred for either 1 or 3 h as also indicated in Table 7. Finally, the aldehyde content of the solutions was determined by abovedescribed method.

Table 7: Parameters and results of IE7

Percentage of removed acetaldehyde

Claims

1. A process for removing acetaldehyde from a vinylether-based copolymer composition, the process comprising at least one of the steps of a) Oxidating the acetaldehyde in the vinylether-based copolymer composition; b) Reducing the acetaldehyde in the vinylether-based copolymer composition; c) Reducing and oxidating the acetaldehyde in the vinylether-based copolymer composition.

2. The process according to claim 1 , wherein step a) comprises, preferably consists of, treating the vinylether-based copolymer composition with a peroxide.

3. The process according to claim 2, wherein step a) is carried out in the presence of a metal-based catalyst.

4. The process according to any of the preceding claims 2 or 3, wherein the peroxide is selected from hydrogen peroxide or R-O-O-H, wherein R is selected from branched or linear, saturated or unsaturated alkyl, aryl, alkaryl, and phenyl, most preferably R is tert-butyl.

5. The process according to any of the preceding claims 3 to 4, wherein the metal of the metal catalyst is selected from Fe, Mo, Mn, Cu, Ni, Co, and Ti, preferably is Fe.

6. The process according to claim 5, wherein the metal catalyst is FeSC .

7. The process according to any of the preceding claims, wherein step b) comprises, preferably consists of, treating the vinylether-based copolymer composition with a reducing agent.

8. The process according to claim 7, wherein the reducing agent is selected from the list consisting of phosphinic acid and salts thereof, phosphoric acid and salts thereof, 2- hydroxy-2-sulfinatoacetic acid and salts thereof, 2-hydroxy-2-sulfonatoacetic acid and salts thereof, sulfurous acid and salts thereof, hydroxymethanesulfinic acid and salts thereof, and mixtures thereof.

9. The process according to claim 8, wherein the reducing agent is a mixture of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the bisodium salt of 2-hydroxy-2- sulfonatoacetic acid, and the sodium salt of sulfurous acid, or is the sodium salt of sulfurous acid.

10. The process according to any of the preceding claims, wherein step c) comprises, preferably consists of, treating the vinylether-based copolymer with a protonic base to reach a pH value of more than 10, preferably more than 11 to yield an intermediate basic solution, and subsequently treating the intermediate basic solution with a protonic acid to reach a pH value of 7 to 9, preferably 7.8 to 8.2.

11 . The process according to claim 10, wherein the protonic acid is selected from formic acid or sulphuric acid.

12. The process according to any of the preceding claims 10 or 11 , wherein step c) is catalyzed by saccharide, preferably monosaccharide, preferably glucose.

13. The process according to any of the preceding claims, wherein the vinylether-based copolymer is a polyethercarboxylate or a maleic acid vinyl acetate, preferably a polyethercarboxylate.

14. Use of a process according to any of the preceding claims to reduce the content of acetaldehyde in a vinylether-based composition to less than 600 ppm, preferably less than 400 ppm, more preferably less than 200 ppm, and most preferably less than 200 ppm.

15. A composition comprising a vinylether-based copolymer, preferably a polyethercarboxylate or a maleic acid vinyl acetate, most preferably a polyethercarboxylate, the composition comprising less than 600 ppm acetaldehyde, preferably less than 400 ppm acetaldehyde, more preferably less than 200 ppm acetaldehyde, even more preferably less than 50 ppm acetaldehyde, preferably less than 25 ppm acetaldehyde.