Water-based copolymer emulsion with regenerated MMA, process to obtain the same having a low VOC-content, and their use

Abstract

The present invention relates to a water-based copolymer emulsion (1) suitable for undergoing a gas-liquid mass transfer for VOC-reduction, wherein the copolymer emulsion (1) is based on a copolymerizate of a) 1 to 99.5 wt.% of methyl methacrylate (MMA), b) 0 to 20 wt.% of one or more hydrophilic monomers having a water-solubility of more than 0.3 g / 100 cm3, and c) 0 to 99 wt.% of one or more hydrophobic monomers having a water-solubility of 0.3 g / 100 cm3 or less, wherein the copolymer emulsion (1) comprises d) 0.2 to 20 wt.% of one or more stabilizers, wherein the content of either the hydrophilic monomer b) or the hydrophobic monomer c) is at least 0.5 wt.%, and wherein at least 5 wt.% of the methyl methacrylate a) (MMA) is regenerated methyl methacrylate (2r, rMMA) and the remainder is standard methyl methacrylate (2s, MMA). Claimed is also a process of emulsion copolymerizing regenerated methyl methacrylate (2r, rMMA) to obtain a low-VOC water-based copolymer emulsion (1a), a water-based copolymer emulsion (1a) obtainable according to said process, as well as the use of the obtained low-VOC water-based copolymer emulsion (1a).

Description

[0001] Water-based copolymer emulsion with regenerated MMA, process to obtain the same having a low VOC-content, and their use.

[0002] The present invention relates to water-based copolymer emulsion comprising regenerated methyl methacrylate (MMA), a process of emulsion copolymerizing regenerated methyl methacrylate to obtain a low-VOC water-based copolymer emulsion with a VOC content of 500 ppm or lower, the waterbased copolymer emulsion obtainable according to said process, as well as the use of said water-based copolymer emulsion.

[0003] Sustainability and recycling of used materials is more important than ever. Organic polymers, such as plastic materials, are - upon recycling - typically melted and reused, e.g., by molding new articles. This method, however, does not change the base polymer. Therefore, no new polymer combinations can be made.

[0004] In order to be able to change the polymers fundamentally and to allow the making of new compositions, existing polymers would need to be broken into its monomers, which then can be employed in new polymerization reactions. However, such so-called depolymerizations are challenging - in particular since the yield of the wanted monomer should be as high as possible and the residue shall have no or only a marginal impact on the subsequent polymerization.

[0005] Acrylic glass, i.e., poly(methyl methacrylate), i.e., PMMA, is a widely used polymer, which is also suitable to be depolymerized. A preferred method is pyrolysis of waste PMMA, e.g., between 350°C to 600°C, at a preferred temperature at, e.g., 450°C. The product obtained is called “regenerated methyl methacrylate”, i.e., rMMA. Commercial grades comprise e.g., 93 to 98 wt.% of monomeric methyl methacrylate with the remainder being a wide mixture of different low molecular weight ingredients, including other saturated, monomeric, and dimeric compounds. In a study, Dimitris S. Achillas (European Polymer Journal 43 (2007) 2564-2575) has identified - besides MMA, a total of 10 different components, including 2,4-dimethyl 1 ,3- Pentadiene, methylene-dimethyl ester of butanedioic acid, and 1-methyl-2- pentyl cyclohexane. Own experiments have shown that other, commercially available rMMA-grades may comprise even a larger number of different side products.

[0006] Methyl methacrylate is widely used as monomer in radical emulsion polymerization. Therefore, using regenerated methyl methacrylate, rMMA, instead of standard MMA, i.e., sMMA, i.e., industrial grade MMA having a purity of e.g., 99 wt.% or higher, would be a key factor to reduce the carbon footprint of emulsion polymers and increase their sustainability.

[0007] K. Gkaliou, et al. (Waste Management 164 (2023) 191-199) prepared recycled MMA from lab-scale pyrolysis of collected industrial waste PMMA. The pyrolysis oils consisted mainly of methyl methacrylate (MMA, >85%) and was directly employed to prepare PMMA through, among others, suspension, and emulsion polymerization. It was found that the crude pyrolysis oils could be polymerized efficiently via emulsion polymerization. However, the authors were not able to conduct suspension polymerizations using the crude monomers, which was attributed to the side products in the crude monomer mixtures. It is believed that said side products affect drop stability and prevent the establishment of a sufficiently stable suspension. While emulsion polymerization seemed to tolerate the impurities, the emulsion polymerization was carried out at low % solids, and a large amount of surfactant of close to 13 wt.%. This is, however, a multiple of surfactant levels typically used in industry. Furthermore, no comonomers were employed, thus MMA- homopolymers were obtained. In addition, no attempts were made to remove residual VOC’s. This, however, is an additional stress for an obtained emulsion due to the applied harsh conditions.

[0008] Most industrial emulsion polymers, also called dispersions, latex or latices, are, however, copolymers, i.e., a combination of two or more monomers which are copolymerized. This copolymerization reaction is in most cases a radical emulsion polymerization in an aqueous medium. The various type of monomers used have different copolymerization parameters, i.e., their reaction behavior differs between different monomer types. In order to receive specific properties in the targeted application, it is, however, important that the copolymer obtained does not - or only marginally - differ in terms of distribution of the polymerized monomers, the molecular weight and type and amount of branching of the obtained copolymers, as well as the degree of crosslinking between polymer chains. Furthermore, the morphology of the obtained latex particles may be essential for its targeted properties.

[0009] Due to the complexity of such radical emulsion polymerization, the skilled person is well aware that this reaction is highly delicate, in particular when two or more monomers are employed, i.e., copolymerized. This applies in particular for the case when impurities are present, such as side products from the depolymerization of PMMA. In fact, it is well known that certain compounds - even in smallest amounts - may terminate polymerization, thus leading to low molecular weight products, or may even inhibit the reaction as a whole.

[0010] Due to the sensitivity of the market with respect to the emission or organic compounds, in particular Volatile Organic Compound (VOC), which have a boiling point at standard pressure of 250°C or below, commercial emulsion polymers have to undergo a process step to reduce such VOCs. In fact, emulsion polymers often require VOC-levels of 500 ppm or lower, or even 100 ppm or lower. A widely used process for VOC-reduction includes stripping the obtained emulsion polymers under harsh conditions, e.g., passing a gas or steam at elevated temperature through the emulsion. It is needless to say that such stripping is more demanding, if ever possible, when monomers with a low purity, such as rMMA, are used. In any case, increased stability of the emulsions is required.

[0011] Therefore, it was the objective of the present invention to find suitable parameters - if at all - with which industrial grade regenerated MMA (rMMA) can be re-used without pre-purification in emulsion copolymerization with good conversion and at solids of, e.g., 50 wt.%. The emulsions must be stable enough to allow VOC-reduction, e.g., by a stripping process, down to 500 ppm or even lower. Furthermore, it should be possible to replace at least some of the standard MMA (sMMA) with rMMA - preferably without, or just marginally, changing the polymerization recipe - but still having the same, or at least fairly similar, emulsion polymer properties, such as particle size and glass transition temperature Tg, thus, to avoid changing the final application formulation.

[0012] Surprisingly, it was found that the objective can be solved with a water-based copolymer emulsion (1 ) suitable for undergoing a gas-liquid mass transfer for VOC-reduction, wherein the copolymer emulsion (1 ) is based on a copolymerizate of a) 1 to 99.5 wt.% of methyl methacrylate (MMA), b) 0 to 20 wt.% of one or more hydrophilic monomers having a watersolubility of more than 0.3 g / 100 cm3, and c) 0 to 99 wt.% of one or more hydrophobic monomers having a water-solubility of 0.3 g / 100 cm3or less, wherein the copolymer emulsion (1 ) comprises d) 0.2 to 20 wt.% of one or more stabilizers, wherein the content of either the hydrophilic monomer b) or the hydrophobic monomer c) is at least 0.5 wt.%, wherein the water-solubility is determined at 25°C and 1 atm, and wherein the weight ratio of the monomers a), b) and c) and of the stabilizer d) are based on the total amount of added monomers a), b), and c), wherein at least 5 wt.% of the methyl methacrylate a) (MMA) is regenerated methyl methacrylate (2r, rMMA) and the remainder is standard methyl methacrylate (2s, MMA).

[0013] Claimed also is a process of emulsion copolymerizing regenerated methyl methacrylate (2r, rMMA) to obtain a low-VOC water-based copolymer emulsion (1 a), wherein i) the monomers a) and b) and / or c) are emulsion copolymerized in an aqueous medium in the presence of stabilizer d) to obtain the water-based copolymer emulsion (1 ) according to the invention, followed by ii) a gas-liquid mass transfer operation is applied to the obtained water-based copolymer emulsion (1 ) to remove VOC to a total VOC-content of 500 ppm or lower to result in the low-VOC copolymer emulsion (1 a), wherein the total VOC-content is based on the total amount of aqueous copolymer emulsion (1 a), wherein the VOCs are volatile organic compounds having a boiling point of 250°C or below, measured at a pressure of 101.3 kPa, and determined according to the Directive 2004 / 42 / EC of the European Parliament and of the Council, of April 21 , 2004.

[0014] Furthermore, claimed also is the water-based copolymer emulsion (1 a) obtainable according to any one of the process according to the invention.

[0015] In addition, claimed is also the use of the water-based copolymer emulsion (1 a) obtained by the process of the invention, and of the water-based copolymer emulsion (1a) according to the invention as aqueous copolymer emulsion in the fields of paints, coatings, textiles, building, adhesives, automotives, paper, packaging, sealants, batteries, and / or construction.

[0016] The water-based copolymer emulsion (1 ) suitable for undergoing a stripping process for VOC-reduction, the process of emulsion copolymerizing regenerated methyl methacrylate (2r, rMMA) to obtain a low-VOC waterbased copolymer emulsion (1 a), the water-based copolymer emulsion (1a) obtainable according to the process, as well as their uses exhibit numerous of unexpected advantages. Thus, it was found that rMMA of various sources and even with a purity of as low as 93 wt.% could be used to replace all standard MMA - even in recipes with MMA being the major monomer. Hence, rMMA can be employed in industrial emulsion copolymerization without undergoing a preliminary costly refining process, e.g., by distillation. And even more, the obtained experimental latex had a good conversion at a solids content of e.g., about 50 wt.%. Hence there was no or only a marginal inhibition. Furthermore, with various formulations no significant change in copolymerization, particle size distribution, nor in glass transition temperature (Tg), and thus in latex morphology was observed. Even more, the obtained emulsion polymers having VOC-levels being e.g., tenfold, or even higher than the same latex with standard MMA (sMMA) are sufficiently stable to survive a stripping process to VOC-levels well below 100 ppm and without significant coagulum formation.

[0017] Thus, it is possible to replace in existing emulsion polymerization recipes at least partially - if not entirely - standard methyl methacrylate by regenerated methyl methacrylate (rMMA). This allows a distinct reduction of the carbon footprint in basically all emulsion polymers comprising MMA.

[0018] The water-based copolymer emulsion (1 ) comprising rMMA The water-based copolymer emulsion (1 ) according to the invention is suitable for undergoing a gas-liquid mass transfer for VOC-reduction. Hence, the content of Volatile Organic Compounds (VOC) of the emulsion (1 ) is higher than the today’s industry standard for commercial emulsions. This high VOC-level may come from the remaining volatile organic fraction from regenerated methyl methacrylate (2r, rMMA), which comprises a wide mixture of different low molecular weight ingredients. Alternatively, or in addition, the high VOC-level may be attributed to residues from the polymerization reaction itself, such as non-polymerized MMA, as well as remaining components from other comonomers or from the initiator.

[0019] Since the emulsion (1 ) is suitable for undergoing a gas-liquid mass transfer for VOC-reduction, such as steam stripping, the emulsion (1 ) must be sufficiently stable to avoid, e.g., coagulation during said process.

[0020] The water-based copolymer emulsion (1 ), i.e. , copolymer emulsion (1 ), or just emulsion (1 ), dispersion (1 ), or latex (1 ), is obtained by radical emulsion polymerization, which includes, according to the invention, also radical microemulsion and radical nanoemulsion polymerization.

[0021] The term copolymer stands for a polymer which is obtained by polymerizing, i.e., copolymerizing, at the same time two or more monomers. If only two monomers are polymerized, the second monomer amounts at least 0.5 wt.%, based on the total amount of monomers employed.

[0022] The water-based copolymer emulsion (1 ) according to the invenvention is based on a copolymerizate of a) 1 to 99.5 wt.% of methyl methacrylate (MMA), b) 0 to 20 wt.% of one or more hydrophilic monomers having a watersolubility of more than 0.3 g / 100 cm3, and c) 0 to 99 wt.% of one or more hydrophobic monomers having a watersolubility of 0.3 g / 100 cm3or less, wherein the copolymer emulsion (1 ) comprises d) 0.2 to 20 wt.% of one or more stabilizers, i.e. , emulsifier, wherein the content of either the hydrophilic monomer b) or the hydrophobic monomer c) is at least 0.5 wt.%, wherein the water-solubility is determined at 25°C and 1 atm, and wherein the weight ratio of the monomers a), b) and c) and of the stabilizer d) are based on the total amount of added monomers a), b), and c), wherein at least 5 wt.%, preferably at least 10 wt.%, of the methyl methacrylate a) (MMA) is regenerated methyl methacrylate (2r, rMMA) and the remainder is standard methyl methacrylate (2s, MMA).

[0023] Preferably, at least 40 wt.%, in particular at least 80 wt.%, and most preferably 100 wt.%, of the methyl methacrylate a) (MMA) is regenerated methyl methacrylate (2r, rMMA).

[0024] In another preferred embodiment, the standard, i.e., industrial grade, methyl methacrylate (2s, MMA) has a content of methyl methacrylate (MMA) of 99.5 wt.% or more, and the regenerated methyl methacrylate (2r, rMMA) has a content of methyl methacrylate (MMA) of between 85 wt.% and 99.4 wt.%, preferably between 90 and 99.4 wt.%, wherein the content of MMA is preferably determined by gas chromatography coupled with flame ionization detector (GC / FID), a well-known method to the skilled person in the art.

[0025] Preferably, the copolymer emulsion (1 ) is based on a) 10 to 99.5 wt.%, preferably 20 to 89 wt.%, of methyl methacrylate (MMA), b) 0.5 to 20 wt.%, preferably 1 to 15 wt.%, of one or more hydrophilic monomers, c) 0 to 89.5 wt.%, preferably 10 to 79 wt.%, of one or more hydrophobic monomers, and / or d) 0.2 to 20 wt.%, preferably 0.5 to 12.5 wt.%, of one or more stabilizers.

[0026] A representative, but non-limiting list of hydrophilic monomers b) having a water-solubility of more than 0.3 g / 100 cm3, determined 25°C, and of hydrophobic monomers c) having a water-solubility of 0.3 g / 100 cm3or less, determined 25°C, is disclosed by E. Penzel, Ullmann’s Encyclopedia of Industrial Chemistry, 7th ed.; Polyacrylates; Weinheim, Germany, 2005; Vol. A21. The water-solubility of non-cited monomers can be determined by the skilled person in the art without undue burden.

[0027] Non-limiting examples of hydrophilic monomers b) include carboxylic acid monomers, such as (meth)acrylic acid, itaconic acid, of fumaric acid, and their salts; hydroxy (meth)acrylates, such as hydroxyethyl (meth)acrylate; (meth)acrylamide; acrylonitrile; 2-acrylamido-2-methylpropansulfonic acid.

[0028] Non-limiting examples of hydrophobic monomers c) include mono- and dienes, such as ethylene, and butadiene; vinyl aromatics, such as styrene and their derivates; (meth)acrylate alkyl esters other than methyl methacrylate, in particular C4- to C40-alkyl (meth)acrylates, such as butyl (meth)acrylate; and vinyl esters, in particular C9- to C12- vinyl esters, such C9- C12 vinyl versatates.

[0029] In a preferred embodiment, the monomer c) is present in an amount of 5 wt.% or larger, in particular 10 wt.% or larger, based on the total amount of monomers a), b) and c), and wherein the monomers a) and c) form - besides the optional monomer b) a copolymerizate based on MMA / Ac, MMA / Ac / Styrene, MMA / Styrene / Butadiene, MMA / Butadiene, M MA / Ac / B utad iene, MMA / Ac / Styrene / Butadiene, MMA / AcA / inyl ester, MMA / Ac / Ethylene, MMA / Ac / EthyleneA / inyl ester, and / or MMA / Ethylene / Vinyl ester, wherein Ac stands for one or more Ci - to C4o-alkyl (meth)acrylate monomer other than methyl methacrylate.

[0030] The one or more stabilizers d), which stabilizes the emulsion particles in the aqueous phase, of the copolymer emulsion (1 ) is

[0031] - a surfactant, preferably a non-ionic and / or anionic surfactant, wherein the total amount of the active content of the surfactants is preferably present in an amount of 0.2 to 6 wt.%, in particular 0.3 to 5 wt.%, and most preferably 0.4 to 3 wt.%, based on the total amount of added monomers; and / or

[0032] - a colloidal stabilizer, such as a water-soluble and / or water-swellable polymer, wherein the colloidal stabilizer is preferably present in an amount of 3 to 20 wt.%, in particular 4 to 15 wt.%, and most preferably 4 to 10 wt.%, based on the total amount of added monomers.

[0033] The one or more stabilizers may be added prior to the addition of any monomer charge, during the addition of a monomer charge or a combination thereof.

[0034] Non-limiting examples of suitable nonionic surfactants, i.e., emulsifier, include tert-octylphenoxyethylpoly(39)-ethoxyethanol, dodecyl oxypoly (10) ethoxy ethanol, nonyl phenoxyethyl-poly(40)ethoxyethanol, polyethylene glycol 2000 monooleate, ethoxylated castor oil, fluorinated alkyl esters and alkoxylates, polyoxyethylene (20) sorbitan monolaurate, sucrose mono- cocoate, di(2-butyl)phenoxypoly(20)ethoxyethanol, hydroxyethyl cellulosepolybutyl acrylate graft copolymer, dimethyl silicone polyalkylene oxide graft copolymer, poly(ethylene oxide) poly(butyl acrylate) block copolymer, block copolymers of propylene oxide and ethylene oxide, 2,4,7,9-tetramethyl-5- decyne-4,7-diol ethoxylated with 30 moles of ethylene oxide, N-polyoxy ethylene(20)lauramide, N-lauryl-N-polyoxyethylene(3)amine and / or poly(10) ethylene glycol dodecyl thioether.

[0035] Non-limiting examples of suitable anionic surfactants include sodium lauryl sulfate, sodium dodecyl benzene sulfonate, potassium stearate, sodium dioctyl sulfo succinate, sodium dodecyldiphenyloxide disulfonate, nonyl- phenoxyethylpoly(l)ethoxyethyl sulfate ammonium salt, sodium styrene sulfonate, sodium dodecyl allyl sulfosuccinate, linseed oil fatty acid, sodium or ammonium salts of phosphate esters of ethoxylated nonylphenol, sodium octoxynol-3-sulfonate, sodium cocoyl sarcocinate, sodium 1 -alkoxy-2 - hydroxypropyl sulfonate, sodium alpha-olefin (C14-16)sulfonate, sulfates of hydroxyalkanols, tetrasodium N-(1 ,2-dicarboxy ethyl)-N-octadecylsulfo- succinamate, disodium N-octadecylsulfosuccinamate, disodium alkyl amido polyethoxy sulfosuccinate, disodium ethoxylated nonylphenol half ester of sulfo succinic acid and the sodium salt of tert-octylphenoxyethoxy- poly(39)ethoxyethyl sulfate.

[0036] Non-limiting examples of suitable colloidal stabilizers include one or more of polyvinyl alcohol (PVOH), i.e., partly hydrolyzed polyvinyl acetate with a degree of hydrolysis of e.g., 80 to 95 mole-%, polyvinyl pyrrolidone (PVP), ethylene glycol, EO / PO block polymers, polyacrylic acids (PAA) with a MW up to e.g., 100’000 Da or even higher, polysaccharides and their derivatives, in particular polysaccharide ethers, such as cellulose, starch, guar gum, xanthan gum, agar-agar, and dextrin, as well as their alkyl ether, hydroxy alkyl ether, and carboxy alkyl ether, in particular methyl, ethyl and propyl ether, hydroxy methyl, hydroxy ethyl, and hydroxy propyl ether, as well as carboxymethyl ether. The colloidal stabilizers may be of anionic or non-ionic nature.

[0037] The process to obtain a low-VOC copolymer emulsion (1 a) comprising rMMA The process according to the invention of emulsion copolymerizing regenerated methyl methacrylate (2r, rMMA) to obtain a low-VOC waterbased copolymer emulsion (1a) includes that i) the monomers a) and b) and / or c) are emulsion copolymerized in an aqueous medium in the presence of stabilizer d), i.e. , emulsifier d), to obtain the water-based copolymer emulsion (1 ) according to the invention, followed by ii) a gas-liquid mass transfer operation, e.g., stripping, is applied to the obtained water-based copolymer emulsion (1 ) to remove VOCs to a total VOC-content of 500 ppm or lower to result in the low-VOC copolymer emulsion (1a), wherein the total VOC-content is based on the total amount of aqueous copolymer emulsion (1a), wherein the VOCs are volatile organic compounds having a boiling point of 250°C or below, measured at a pressure of 101.3 kPa, and determined according to the Directive 2004 / 42 / EC of the European Parliament and of the Council, of April 21 , 2004. Preferably, the VOCs are determined by a method comprising GC, such as GC / FID.

[0038] This process is - despite of the large amount and wide range of the various VOC-components - surprisingly straightforward, wherein no or only marginal changes need to be made compared to existing production formulations. Furthermore, no elaborative and costly pre-cleaning, such as distillation, of the rMMA monomer is required. This allows a wide utilization of the process of the invention, and thus a wide reduction of the carbon footprint.

[0039] Preferably, the gas-liquid mass transfer operation makes use of gas to remove VOCs, wherein the gas is preferably steam, i.e., water vapor, CO2, supercritical CO2, nitrogen, and / or air, wherein the gas-liquid mass transfer is preferably carried out at, below or above ambient pressure. In another preferred embodiment of the process, the VOCs of the copolymer emulsion (1 ) are removed to a total VOC content of 250 ppm or lower, in particular of 100 ppm or lower. This can be performed e.g., by a longer stripping time, and / or by stripping under more sever conditions.

[0040] The water-based copolymer emulsion (1a) obtainable according to the

[0041] The water-based copolymer emulsion (1 a) according to the invention is obtainable according to the process of the invention. Hence, the copolymer emulsion (1a) may be similar to today’s commercial emulsions but comprising regenerated MMA (rMMA) instead of standard MMA (sMMA).

[0042] In order to distinguish water-based copolymer emulsions (1 a) comprising rMMA and having a low VOC level from copolymer emulsions based on standard MMA, it possible to add a tracer substance having a boiling point above 250°C, and thus not being considered a VOC, to the rMMA monomer composition. This addition is preferably done by the rMMA manufacturer. A suitable tracer substance may be silicones or alkanes having 15 or more carbon atoms, such as e.g., n-Pentadecane, a Cis-alkane, having a boiling point at 101 .3 kPa of 270°C, or n-Eicosan, a C2o-alkane, having a boiling point at 101.3 kPa of 343°C. the skilled person is well aware of suitable tracers, and he can make the optimal selection.

[0043] Hence, the water-based copolymer emulsion (1a) obtainable according to the process of the invention may comprise a tracer substance having a boiling point at 101 .3 kPa of above 250°C.

[0044] Furthermore, the water-based copolymer emulsion (1a) obtainable according to the process of the invention preferably has a solids content of at least 20 wt.%, preferably at least 30 wt.%, in particular at least 40 wt.%, determined gravimetrically in an oven at 130°C for 1 hr., and a volume mean of the particle size (MV) of from 10 nm to 10 pm, preferably 50 nm to 2 pm, wherein the particle size distribution is determined by dynamic light scattering and may be mono- or multimodal. Preferably, the solids content of the copolymer emulsion (1a) is not higher than 70 wt.%, in particular not higher than 65 wt.%, and most preferably not higher than 55 wt.%.

[0045] The uses

[0046] The water-based copolymer emulsion (1a) obtained according to the process of the invention and the water-based copolymer emulsion (1 a) obtainable according to said process can surprisingly be used to replace todays MMA- containing emulsions.

[0047] In particular, it is used as aqueous copolymer emulsion (1 a) in the fields of paints, coatings, textiles, building, adhesives, automotives, paper, packaging, sealants, batteries, and / or construction.

[0048] Examples

[0049] Monomers used:

[0050] Standard, i.e., regular, MMA (2s) was supplied by ECEM (European Chemical Marketing BV, Hogelhilweg 18, 1101 CD Amsterdam, the Netherlands). It has a measured MMA-content of 99.9 % (determined by GC / FID). Regenerated MMA (2r), i.e., rMMA, is obtained by pyrolysis of pM MA waste. The Experiments were performed with commercially available rMMA from the following sources:

[0051] - Induacril, Chile (Examples A- / B- / C-01 ; see Table 2). It has a measured MMA-content of 93.3 % (determined by GC / FID),

[0052] - XISHUN Plastics Factory, Foshan, China (Examples A- / B- / C-02; see Table 2). It has a measured MMA-content of 98.1 % (determined by GC / FID).

[0053] Acrylic acid was supplied by Sigma-Aldrich having a purity of at least 99 wt.%.

[0054] Butyl acrylate, i.e., n-Butyl acrylate was supplied by ECEM (European Chemical Marketing BV, Hogelhilweg 18, 1101 CD Amsterdam, the Netherlands) having a purity of at least 99.5 wt.% (determined by GC / FID).

[0055] Preparation of the copolymer emulsion (1)

[0056] The copolymer emulsions (1 ), i.e., latices, i.e., latexes or dispersions, were prepared by emulsion polymerization using the monomer compositions as shown in Table 1. For each monomer composition (A, B, C, D) were three different samples made: one reference example with standard MMA (2s; A- / B- / C- / D-0) and two examples according to the invention with regenerated MMA (2r) form Induacril (A- / B- / C- / D-1 ) and XISHUN (A- / B- / C- / D-2).

[0057] The polymerization was carried out in a 3.6- liter steel, jacketed and agitated reactor as a seeded radical emulsion polymerization at a temperature of 90° C. The seed was added in an amount of 0.411 parts per 100 parts of total monomer to an initial aqueous medium containing 78.92 parts deionized water and 0.010 parts of a 1 wt.% aqueous solution of chelating agent (trisodium salt of N-(hydroxyethyl) ethylenediaminetriacetic acid — Versenol® 120). The seed was a polystyrene latex having a solids content of 40 wt.% and a volume average particle size of 23 nm.

[0058] The monomer feed was started, and the reaction mixture was agitated during monomer addition at a rate of 300 rpm. The standard MMA (2s), and the rMMA (2r, respectively), was fed to the reactor over a period of 240 minutes. The other monomers (i.e., acrylic acid (AA), and n-Butyl acrylate (BA), see Table 1 ) started to be fed to the reactor 5 minutes after the MMA (2s) / rMMA (2r) starts and were fed over a period of 230 minutes.

[0059] An additional aqueous initiator stream was fed to the reactor over the course of the reaction. The stream contained DOWFAX™ 2A1 solution surfactant, sodium persulfate and sodium hydroxide, in an amount such that the total addition over the course of the reaction amounts to 1 .0 parts of DOWFAX™ 2A1 , 1.0 parts of sodium persulfate and 0.2 parts of sodium hydroxide dissolved in 20 parts by weight of water, (per 100 parts total monomers). The aqueous initiator feeding starts 5 minutes after MMA (2s) (or rMMA, 2r) feed started and was fed over a period of 265 minutes.

[0060] After completion of the monomer addition, the reaction mixture was heated to 97 °C and maintained at this temperature for 40 minutes. After this time, the reaction mixture was cooled to 30°C. The resulting copolymer emulsion was stabilized to pH 6.0 with a solution of 20 wt.% NaOH to result in the copolymer emulsions (1 ) according to the invention, which were analyzed and reported in Table 3.

[0061] Table 1 : Emulsion polymerization formulations for the sample series A to D. a) Added as Versenol 120 ® (1 % aqueous solution) Table 2: Type of methyl methacrylate employed in the emulsion polymerization formulations of Table 1 . Table 3: Characterization of the copolymer emulsion (1) samples made as described above, after emulsion polymerization and degassing, but before the stripping process. For the sample No’s see Tables 1 and 2.

[0062] Table 3 - Legend:

[0063] 1 ) The solids of the dispersion were determined gravimetrically in an oven at 130°C for 1 hr.

[0064] 2) The residue, i.e., grit or coagulum, is the sum of the filtration of the obtained copolymer emulsions first through a 100 US mesh followed by a 325 US mesh sieve.

[0065] 3) PS (MV) stands for the volume mean of the particle size, determined by dynamic light scattering using a Nanotrac 150 instrument.

[0066] 4) PS (MN) stands for the number mean of the particle size, determined by dynamic light scattering using a Nanotrac 150 instrument.

[0067] 5) The reported VOC data, determined by GC-measurement, are relative to the wet latex (in ppm).

[0068] The results reported in Table 3 demonstrate impressively that the obtained copolymer emulsions (1 ) according to the invention (A- / B- / C- / D-1 and -2) using regenerated MMA (2r) had a good conversion similar to the reference emulsions with standard MMA (2s; A- / B- / C- / D-0). It was particularly surprising that even the regenerated MMA (2r) from Induacril with an MMA- content of as low as 93.3 wt.% did neither inhibit the reaction nor formed a large amount of residue, i.e., coagulum - even at about 50 wt.% solids! It is noted that the lower solids content of the samples A- / B- / C-1 with rMMA from Induacril having an MMA content of about 93.3 wt.% is assumed to be reported at least partially to a lower content of copolymerizable monomer, i.e., in particular MMA. In addition, all samples resulted in stable latices, i.e., no sedimentation was observed visually after 28 days. Furthermore, all latexes revealed a white color, i.e., no visual differences could be found.

[0069] In addition, it was surprising to see that all obtained emulsions exhibit - besides the comparable monomer conversion - similar residue levels, particle size distribution, determined both as volume and number means. Furthermore, also the glass transition temperature (Tg) and the gel content (both measured after steam stripping, see Table 4) were about comparable, despite the fact that the lower MMA-content of 93.3 wt.% in the examples A- / B- / C- / D-1 was not compensated. In addition, some non-polymerizing, high boiling components having a boiling point above 250°C and therefore not being considered as VOC, might have become embedded in the latex, thus affecting the glass transition temperature (Tg). Among others, none of the emulsions revealed a phased latex having e.g., different glass transition temperature (Tg). Thus, the non-MMA components of the employed rMMA (2r) did not affect the copolymerization of MMA with acrylic acid (AA) and / or n-butyl acrylate (BA).

[0070] It is noted that the used polymerization recipe has not been optimized for the specific regenerated MMA’s (2r) and the skilled person in the art is well able to adjust the recipe to reduce significantly observed differences to the reference emulsions with standard MMA (2s).

[0071] Preparation of the low-VOC water-based copolymer emulsion (1a)

[0072] The obtained copolymer emulsions (1 ) as described above, e.g., in Tables 1 to 3, were subjected to a stripping process using steam to obtain the low- VOC copolymer emulsion (1a) according to the invention, having a total VOC- content of well below 500 ppm (see Table 4).

[0073] Table 4: Characterization of the same samples of Table 3, but after the stripping process described above. For the sample No’s see Tables 1 and 2.

[0074] Table 4 - Legend:

[0075] 1 ) and 5): See Table 3

[0076] 6) The difference of the solids content before and after stripping is - besides the removed VOC’s - attributed to low boiling VOC’s which could not be detected by the VOC-measurement, different amounts of steam removed or added during the stripping process, as well as grit formation.

[0077] 7) The glass transition temperature (Tg) was determined according to DIN 51007 using a heating rate of 10°C / min., wherein the midpoint of the segment of the mid-tangent between the extrapolated baselines is reported.

[0078] 8) The Gel Content was determined by the following procedure: A latex film was casted and weighed (dry latex film (A)) using a latex sample adjusted to pH 8 with a 20 wt.% NaOH solution. Said film was allowed to swell in toluene for 26 hrs at room temperature. The resulting toluene-insoluble portion, i.e. , wet gel, was separated from the liquid phase by filtration and weighed, dried in a vented oven at 130°C for 2 hrs, and weighed again to obtain the dry weight of the gel (C). The Gel Content (in %) was determined by the following formula:

[0079] Gel Content = (weight of dry gel (C) / weight of dry latex film (A))x100

[0080] 9) N / A stands for “no data available”.

[0081] For steam stripping, approximately 2.5 liter of copolymer emulsions (1 ; see Tables 1 -3) were charged to a 10-liter glass container and heated in a water bath to 100° C. The latices were sparged at ambient pressure with steam at a rate of approximately 2.0 l / h for 60 min., then with air over a period of 30 min. until approximately 200 mL of condensate was removed. The latex was then cooled to ambient temperature and filtered.

Claims

Claims1. Water-based copolymer emulsion (1 ) suitable for undergoing a gasliquid mass transfer for VOC-reduction, wherein the copolymer emulsion (1 ) is based on a copolymerizate of a) 1 to 99.5 wt.% of methyl methacrylate (MMA), b) 0 to 20 wt.% of one or more hydrophilic monomers having a water-solubility of more than 0.3 g / 100 cm3, and c) 0 to 99 wt.% of one or more hydrophobic monomers having a water-solubility of 0.3 g / 100 cm3or less, wherein the copolymer emulsion (1 ) comprises d) 0.2 to 20 wt.% of one or more stabilizers, wherein the content of either the hydrophilic monomer b) or the hydrophobic monomer c) is at least 0.5 wt.%, wherein the watersolubility is determined at 25°C and 1 atm, and wherein the weight ratio of the monomers a), b) and c) and of the stabilizer d) are based on the total amount of added monomers a), b), and c), characterized in that at least 5 wt.% of the methyl methacrylate a) (MMA) is regenerated methyl methacrylate (2r, rMMA) and the remainder is standard methyl methacrylate (2s, MMA).

2. Copolymer emulsion (1 ) according to claim 1 , wherein at least 40 wt.%, in particular at least 80 wt.%, and most preferably 100 wt.%, of the methyl methacrylate a) (MMA) is regenerated methyl methacrylate (2r, rMMA).

3. Copolymer emulsion (1 ) according to claim 1 or 2, wherein the standard methyl methacrylate (2s, MMA) has a content of methyl methacrylate (MMA) of 99.5 wt.% or more, and the regenerated methyl methacrylate (2r, rMMA) has a content of methyl methacrylate (MMA) of between 85 wt.% and 99.4 wt.%, preferably between 90 and 99.4 wt.%.

4. Copolymer emulsion (1 ) according to any one of claims 1 to 3, wherein the copolymer emulsion is based on a) 10 to 99.5 wt.%, preferably 20 to 89 wt.%, of methyl methacrylate (MMA), b) 0.5 to 20 wt.%, preferably 1 to 15 wt.%, of one or more hydrophilic monomers, c) 0 to 89.5 wt.%, preferably 10 to 79 wt.%, of one or more hydrophobic monomers, and / or d) 0.2 to 20 wt.%, preferably 0.5 to 12.5 wt.%, of one or more stabilizers.

5. Copolymer emulsion (1 ) according to any one of claims 1 to 4, wherein monomer c) is present in an amount of 5 wt.% or larger, in particular 10 wt.% or larger, based on the total amount of monomers a), b) and c), and wherein the monomers a) and c) form a copolymerizate based on MMA / Ac, MMA / Ac / Styrene, MMA / Styrene / Butadiene, MMA / Butadiene, MMA / Ac / Butadiene, MMA / Ac / Styrene / Butadiene, MMA / Ac / Vinyl ester, MMA / Ac / Ethylene, MMA / Ac / Ethylene / Vinyl ester, and / or MMA / Ethylene / Vinyl ester, wherein Ac stands for one or more C1- to C40-alkyl (meth)acrylate monomer other than methyl methacrylate.

6. Copolymer emulsion (1 ) according to any one of claims 1 to 5, wherein the one or more stabilizers d) is a surfactant, preferably a non-ionic and / or anionic surfactant, wherein the total amount of the active content of the surfactants is preferably present in an amount of 0.2 to 6 wt.%, in particular 0.3 to 5 wt.%, and most preferably 0.4 to 3 wt.%, based on the total amount of added monomers; and / or a colloidal stabilizer, such as a water-soluble and / or water- swellable polymer, wherein the colloidal stabilizer is preferablypresent in an amount of 3 to 20 wt.%, in particular 4 to 15 wt.%, and most preferably 4 to 10 wt.%, based on the total amount of added monomers.

7. Process of emulsion copolymerizing regenerated methyl methacrylate (2r, rMMA) to obtain a low-VOC water-based copolymer emulsion (1 a) characterized in that i) the monomers a) and b) and / or c) are emulsion copolymerized in an aqueous medium in the presence of stabilizer d) to obtain the water-based copolymer emulsion (1 ) of any one of claims 1 to 8, followed by ii) a gas-liquid mass transfer operation is applied to the obtained water-based copolymer emulsion (1 ) to remove VOC to a total VOC-content of 500 ppm or lower to result in the low-VOC copolymer emulsion (1 a), wherein the total VOC-content is based on the total amount of aqueous copolymer emulsion (1 a), wherein the VOCs are volatile organic compounds having a boiling point of 250°C or below, measured at a pressure of 101.3 kPa, and determined according to the Directive 2004 / 42 / EC of the European Parliament and of the Council, of April 21 , 2004.

8. Process of claim 7, wherein the gas-liquid mass transfer operation makes use of gas to remove VOCs, wherein the gas is preferably steam, CO2, supercritical CO2, nitrogen, and / or air, wherein the gas-liquid mass transfer is preferably carried out at, below or above ambient pressure.

9. Process of claim 7 or 8, wherein the VOCs of the copolymer emulsion (1 ) are removed to a total VOC content of 250 ppm or lower, in particular of 100 ppm or lower.

10. Water-based copolymer emulsion (1a) obtainable according to any one of the process according to claims 7 to 9.

11. Water-based copolymer emulsion (1a) of claim 10 having a solids content of at least 20 wt.%, preferably at least 30 wt.%, in particular at least 40 wt.%, and a volume mean of the particle size (MV) of from 10 nm to 10 pm, preferably 50 nm to 2 pm, determined by dynamic light scattering.

12. Use of the water-based copolymer emulsion (1 a) obtained by any one of claims 7 to 9, and of the water-based copolymer emulsion (1a) according to claim 10 or 11 as aqueous copolymer emulsion in the fields of paints, coatings, textiles, building, adhesives, automotives, paper, packaging, sealants, batteries, and / or construction.

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