Aqueous copolymer emulsions containing recycled MMA, methods for obtaining said aqueous copolymer emulsions with low VOC content, and uses of said aqueous copolymer emulsions.

Abstract

This invention relates to an aqueous copolymer emulsion (1) suitable for gas-liquid mass transfer to reduce VOCs, wherein the copolymer emulsion (1) is a copolymer based on: a) 1 wt.% to 99.5 wt.% methyl methacrylate (MMA), b) 0 wt.% to 20 wt.% of one or more hydrophilic monomers with a water solubility greater than 0.3 g / 100 cm3, and c) 0 wt.% to 99 wt.% of one or more hydrophobic monomers with a water solubility of 0.3 g / 100 cm3 or less, wherein the copolymer emulsion (1) comprises d) 0.2 wt.% to 20 wt.% of one or more stabilizers, wherein the content of 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 recycled methyl methacrylate (2r, rMMA), and the remainder is standard methyl methacrylate (2s, MMA). A method for emulsion copolymerization of recycled methyl methacrylate (2r, rMMA) to obtain a low-VOC water-based copolymer emulsion (1a), the water-based copolymer emulsion (1a) obtainable according to said method, and the use of the obtained low-VOC water-based copolymer emulsion (1a) are also claimed.

Description

[0001] This invention relates to a water-based copolymer emulsion comprising recycled methyl methacrylate (MMA), a method for emulsion copolymerization of recycled methyl methacrylate to obtain a low-VOC water-based copolymer emulsion with a VOC content of 500 ppm or less, the water-based copolymer emulsion obtainable according to the method, and the use of the water-based copolymer emulsion.

[0002] Sustainability and recycling of waste materials are more important than ever. Organic polymers (such as plastic materials) are often melted down and reused during recycling, for example, by molding new articles. However, this method does not change the base polymer. Therefore, new polymer combinations cannot be created.

[0003] In order to fundamentally alter polymers and allow for the preparation of new compositions, existing polymers will need to be depolymerized into their monomers, which can then be used in new polymerization reactions. However, this so-called depolymerization is challenging, particularly because the yield of the desired monomers should be as high as possible, and the residues should have no or only a minor effect on subsequent polymerization.

[0004] Acrylic glass, or poly(methyl methacrylate), or PMMA, is a widely used polymer that is also suitable for depolymerization. A preferred method is, for example, pyrolysis of waste PMMA at a temperature between 350°C and 600°C, preferably at 450°C. The resulting product is called “recycled methyl methacrylate,” or rMMA. Commercial grades comprise, for example, 93 wt.% to 98 wt.% monomeric methyl methacrylate, with the remainder being a wide mixture of various low molecular weight components, including other saturated, monomeric, and dimer compounds. In one study, Dimitris S. Achilias (European Polymer Journal 43 (2007) 2564-2575) identified a total of 10 different components in addition to MMA, including 2,4-dimethyl-1,3-pentadiene, methylene-dimethyl succinate, and 1-methyl-2-pentylcyclohexane. His own experiments have shown that other commercially available rMMA grades can contain even greater numbers of different byproducts.

[0005] Methyl methacrylate (MMA) is widely used as a monomer in free radical emulsion polymerization. Therefore, using recycled MMA (rMMA) instead of standard MMA (sMMA), i.e., industrial-grade MMA with a purity of, for example, 99 wt.% or higher, would be a key factor in reducing the carbon footprint of emulsion polymers and increasing their sustainability.

[0006] K. Gkaliou et al. (Waste Management 164 (2023) 191-199) prepared recycled MMA from the laboratory-scale pyrolysis of collected industrial waste PMMA. The pyrolysis oil consisted primarily of methyl methacrylate (MMA, >85%) and was used directly to prepare PMMA via suspension and emulsion polymerization. The results showed that pyrolysis crude oil could be efficiently polymerized via emulsion polymerization. However, the authors could not use crude monomers for suspension polymerization due to byproducts in the crude monomer mixture. These byproducts are believed to affect droplet stability and prevent the establishment of a sufficiently stable suspension. Although emulsion polymerization appeared to be tolerant of impurities, it was carried out at low solids % and a large amount of surfactant, close to 13 wt.%. However, this is several times the surfactant levels commonly used in industry. Furthermore, no comonomers were used, thus yielding MMA homopolymers. In addition, no attempts were made to remove residual VOCs. However, this was an additional stress on the resulting emulsion due to the harsh conditions imposed.

[0007] However, most industrial emulsion polymers (also known as dispersions, latex, or latices) are copolymers, i.e., combinations of two or more monomers that have been copolymerized. This copolymerization reaction is, in most cases, a free radical emulsion polymerization in an aqueous medium. The various types of monomers used have different copolymerization parameters; that is, their reaction behavior differs between different monomer types. However, to obtain specific properties for a target application, it is important that the resulting copolymers are similar or only slightly different in terms of the distribution of polymeric monomers, the molecular weight and type of the resulting copolymer, the amount of branching, and the degree of crosslinking between polymer chains. Furthermore, the morphology of the resulting latex particles can be crucial to their target properties.

[0008] Due to the complexity of this free radical emulsion polymerization, those skilled in the art will recognize that the reaction is highly sensitive, especially when two or more monomers are used, i.e., in copolymerization. This is particularly true in the presence of impurities, such as byproducts from the depolymerization of PMMA. Indeed, it is well known that certain compounds—even in the smallest amounts—can terminate the polymerization, resulting in low molecular weight products, or may even inhibit the entire reaction.

[0009] Due to market sensitivity to emissions of organic compounds, particularly volatile organic compounds (VOCs), which have boiling points of 250°C or lower at standard pressures, commercial emulsion polymers must undergo process steps to reduce these VOCs. In fact, emulsion polymers typically require VOC levels of 500 ppm or lower, or even 100 ppm or lower. Widely used VOC reduction methods include stripping emulsion polymers obtained under harsh conditions, such as passing gas or vapor through the emulsion at high temperatures. Needless to say, this stripping is even more necessary when using monomers with low purity, such as rMMA, if possible. In any case, improving emulsion stability is required.

[0010] Therefore, the object of this invention is to find suitable parameters (if any) by which industrial-grade regenerated MMA (rMMA) can be reused in emulsion copolymerization with good conversion and, for example, 50 wt.% solids without pre-purification. The emulsion must be sufficiently stable to allow VOC reduction, for example, to 500 ppm or even lower, through a stripping process. Furthermore, it should be possible to replace at least some standard MMA (sMMA) with rMMA – preferably without altering or only slightly altering the polymerization formulation – while still possessing the same or at least substantially similar emulsion polymer properties, such as particle size and glass transition temperature T0. g This avoids altering the final application formulation.

[0011] Surprisingly, it was found that this objective can be achieved using an aqueous copolymer emulsion (1) suitable for gas-liquid mass transfer to reduce VOCs, wherein the copolymer emulsion (1) is a copolymerized product based on the following substances: a) 1 wt.% to 99.5 wt.% methyl methacrylate (MMA), b) 0 wt.% to 20 wt.% of one or more water-soluble substances with a solubility greater than 0.3 g / 100 cm³ 3 Hydrophilic monomers, and c) One or more water-soluble compounds ranging from 0 wt.% to 99 wt.% with a concentration of 0.3 g / 100 cm³ 3 Or smaller hydrophobic monomers, The copolymer emulsion (1) contains d) 0.2 wt.% to 20 wt.% of one or more stabilizers, The content of the hydrophilic monomer b) or the hydrophobic monomer c) is at least 0.5 wt.%, the water solubility is determined at 25°C and 1 atm, and the weight ratio of monomers a), b), and c) and stabilizer d) is based on the total amount of added monomers a), b), and c). At least 5 wt.% of the methyl methacrylate (MMA) is recycled methyl methacrylate (2r, rMMA), and the remainder is standard methyl methacrylate (2s, MMA).

[0012] A method for emulsion copolymerization of recycled methyl methacrylate (2r, rMMA) to obtain a low-VOC water-based copolymer emulsion (1a) is also claimed, wherein... i) Emulsion copolymerize monomers a) and b) and / or c) in an aqueous medium in the presence of stabilizer d) to obtain the aqueous copolymer emulsion (1) according to the invention, then ii) The obtained water-based copolymer emulsion (1) is subjected to a gas-liquid mass transfer operation to remove VOCs to a total VOC content of 500 ppm or lower, thereby obtaining the low-VOC copolymer emulsion (1a). The total VOC content is based on the total amount of the aqueous copolymer emulsion (1a), wherein the VOC is a volatile organic compound having a boiling point of 250°C or lower, measured at a pressure of 101.3 kPa and determined in accordance with Directive 2004 / 42 / EC of the European Parliament and the Council of 21 April 2004.

[0013] In addition, protection is also claimed for water-based copolymer emulsions (1a) obtainable according to any method of the present invention.

[0014] Furthermore, the use of the water-based copolymer emulsion (1a) obtained by the method of the present invention and the water-based copolymer emulsion (1a) according to the present invention as water-based copolymer emulsions in the fields of paints, coatings, textiles, building, adhesives, automobiles, paper, packaging, sealants, batteries and / or construction is also claimed.

[0015] Aqueous copolymer emulsions suitable for stripping processes for VOC reduction (1), methods for emulsion copolymerization of recycled methyl methacrylate (2r, rMMA) to obtain low-VOC aqueous copolymer emulsions (1a), aqueous copolymer emulsions (1a) obtainable according to said methods, and their uses exhibit many unexpected advantages. Thus, it has been found that rMMA from various sources, and even rMMA with purities as low as 93 wt.%, can be used to replace all standard MMA – even in formulations with MMA as the main monomer. Therefore, rMMA can be used for industrial emulsion copolymerization without the need for expensive preliminary refining processes, such as distillation. Furthermore, the experimental latexes obtained exhibit good conversion at, for example, a solids content of about 50 wt.%. Therefore, there is little or no inhibition. Moreover, in various formulations, no adverse effects were observed on copolymerization, particle size distribution, and glass transition temperature (T0). g Significant changes were observed in the latex, and therefore no significant changes were also observed in the latex morphology. Furthermore, the latex polymers obtained with VOC levels ten times or even higher than, for example, those with standard MMA (sMMA) were sufficiently stable to withstand stripping processes to VOC levels well below 100 ppm without significant coagulation.

[0016] Therefore, in existing emulsion polymerization formulations, it is possible to at least partially (if not entirely) replace standard methyl methacrylate with recycled methyl methacrylate (rMMA). This allows for a significant reduction in the carbon footprint of virtually all MMA-containing emulsion polymers.

[0017] Aqueous copolymer emulsion containing rMMA (1) The aqueous copolymer emulsion (1) according to the invention is suitable for gas-liquid mass transfer to reduce VOCs. Therefore, the volatile organic compound (VOC) content of the emulsion (1) is higher than the industry standard for currently commercial emulsions. This high VOC level may originate from residual volatile organic fractions in regenerated methyl methacrylate (2r, rMMA), which comprises a wide mixture of different low molecular weight components. Alternatively or additionally, the high VOC level may be attributed to residues from the polymerization reaction itself, such as unpolymerized MMA, and residual components from other comonomers or from the initiator.

[0018] Since emulsion (1) is suitable for gas-liquid mass transfer to reduce VOCs, such as steam stripping, emulsion (1) must be sufficiently stable to avoid condensation, for example, during the processes described.

[0019] A water-based copolymer emulsion (1), namely copolymer emulsion (1) or emulsion (1) alone, dispersion (1) or latex (1) is obtained by free radical emulsion polymerization. According to the present invention, the free radical emulsion polymerization further includes free radical microemulsion and free radical nanoemulsion polymerization.

[0020] The term copolymer refers to a polymer obtained by simultaneously polymerizing (i.e., copolymerizing) two or more monomers. If only two monomers are polymerized, the amount of the second monomer must be at least 0.5 wt.%, based on the total amount of monomers used.

[0021] The water-based copolymer emulsion (1) according to the present invention is a copolymer product based on the following substances: a) 1 wt.% to 99.5 wt.% methyl methacrylate (MMA), b) 0 wt.% to 20 wt.% of one or more water-soluble substances with a solubility greater than 0.3 g / 100 cm³ 3 Hydrophilic monomers, and c) One or more water-soluble compounds ranging from 0 wt.% to 99 wt.% with a concentration of 0.3 g / 100 cm³ 3 Or smaller hydrophobic monomers, The copolymer emulsion (1) contains d) 0.2 wt.% to 20 wt.% of one or more stabilizers, i.e., emulsifiers. The content of the hydrophilic monomer b) or the hydrophobic monomer c) is at least 0.5 wt.%, the water solubility is determined at 25°C and 1 atm, and the weight ratio of monomers a), b), and c) and stabilizer d) is based on the total amount of added monomers a), b), and c). At least 5 wt.%, preferably at least 10 wt.%, of the methyl methacrylate (MMA) is recycled methyl methacrylate (2r, rMMA), and the remainder is standard methyl methacrylate (2s, MMA).

[0022] Preferably, at least 40 wt.%, particularly at least 80 wt.%, and most preferably 100 wt.%, of methyl methacrylate (MMA) is recycled methyl methacrylate (2r,rMMA).

[0023] In another preferred embodiment, the standard (i.e., industrial grade) methyl methacrylate (2s, MMA) has a methyl methacrylate (MMA) content of 99.5 wt.% or higher, and the recycled methyl methacrylate (2r, rMMA) has a methyl methacrylate (MMA) content of 85 wt.% to 99.4 wt.%, preferably 90 wt.% to 99.4 wt.%, wherein the MMA content is preferably determined by gas chromatography (GC / FID) coupled to a flame ionization detector, a method well known to those skilled in the art.

[0024] Preferably, the copolymer emulsion (1) is based on a) 10 wt.% to 99.5 wt.%, preferably 20 wt.% to 89 wt.% of methyl methacrylate (MMA), b) 0.5 wt.% to 20 wt.%, preferably 1 wt.% to 15 wt.%, of one or more hydrophilic monomers. c) 0 wt.% to 89.5 wt.%, preferably 10 wt.% to 79 wt.%, of one or more hydrophobic monomers, and / or d) 0.2 wt.% to 20 wt.%, preferably 0.5 wt.% to 12.5 wt.% of one or more stabilizers.

[0025] It has a concentration greater than 0.3 g / 100 cm⁻¹ as measured at 25°C. 3 Water-soluble hydrophilic monomer (b) and having a concentration of 0.3 g / 100 cm⁻¹ as measured at 25°C. 3 A representative but non-limiting list of hydrophobic monomers (c) of smaller water solubility is disclosed by E. Penzel, Ullmann's Encyclopedia of Industrial Chemistry, 7th edition; Polyacrylates; Weinheim, Germany, 2005; Vol. A21. The water solubility of monomers not mentioned can be determined by those skilled in the art without undue burden.

[0026] Non-limiting examples of hydrophilic monomers (b) include carboxylic acid monomers such as (meth)acrylic acid, itaconic acid, fumaric acid and their salts; hydroxy (meth)acrylates such as hydroxyethyl (meth)acrylate; (meth)acrylamide; acrylonitrile; 2-acrylamido-2-methylpropanesulfonic acid.

[0027] Non-limiting examples of hydrophobic monomers (c) include monoenes and dienes, such as ethylene and butadiene; vinyl aromatics, such as styrene and its derivatives; alkyl esters of (meth)acrylates other than methyl methacrylate, particularly C4 to C40 alkyl esters of (meth)acrylates, such as butyl methacrylate; and vinyl esters, particularly C9 to C12 vinyl esters, such as C9-C12 vinyl tert-carbonates.

[0028] In a preferred embodiment, monomer c) is present in an amount of 5 wt.% or greater, particularly 10 wt.% or greater, based on the total amount of monomers a), b), and c), and wherein, except for optional monomer b), monomers a) and c) form a copolymer 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 represents one or more (meth)acrylic acids C1 to C1 other than methyl methacrylate. 40 Alkyl ester monomers.

[0029] The copolymer emulsion (1) contains one or more stabilizers (d) that stabilize the emulsion particles in the aqueous phase. - Surfactants, preferably nonionic and / or anionic surfactants, wherein the total amount of active ingredient in the surfactant is preferably present in an amount of 0.2 wt.% to 6 wt.%, particularly 0.3 wt.% to 5 wt.%, and most preferably 0.4 wt.% to 3 wt.%, based on the total amount of added monomers; and / or - Colloidal stabilizers, such as water-soluble and / or water-swellable polymers, wherein the colloidal stabilizer is preferably present in an amount of 3 wt.% to 20 wt.%, particularly 4 wt.% to 15 wt.%, and most preferably 4 wt.% to 10 wt.%, based on the total amount of monomers added.

[0030] One or more stabilizers may be added before, during, or in combination with the addition of any monomer.

[0031] Non-limiting examples of suitable nonionic surfactants (i.e., emulsifiers) include tert-octylphenoxyethyl poly(39)-ethoxyethanol, dodecyloxy poly(10)-ethoxyethanol, nonylphenoxyethyl-poly(40)-ethoxyethanol, polyethylene glycol 2000 monooleate, ethoxylated castor oil, fluorinated alkyl esters and alkoxylates, polyoxyethylene (20) dehydrated sorbitol monolaurate, sucrose monocolate, di(2-butyl)phenoxy poly(20)-ethyl Oxyethanol, hydroxyethyl cellulose polybutyl acrylate graft copolymer, dimethyl silicone polyoxyethylene graft copolymer, poly(ethylene oxide) poly(butyl acrylate) block copolymer, propylene oxide and ethylene oxide block copolymer, 2,4,7,9-tetramethyl-5-decyn-4,7-diol ethoxylated with 30 moles of ethylene oxide, N-polyoxyethylene (20) laurylamide, N-lauryl-N-polyoxyethylene (3)amine and poly(10) ethylene glycol dodecyl sulfide.

[0032] Non-limiting examples of suitable anionic surfactants include sodium lauryl sulfate, sodium dodecylbenzene sulfonate, potassium stearate, sodium dioctyl sulfosuccinate, sodium dodecyl diphenyl ether disulfonate, nonylphenoxyethyl poly(I)ethoxyethyl ammonium sulfate, sodium styrene sulfonate, sodium dodecyl allyl sulfosuccinate, linseed oil fatty acids, sodium or ammonium salts of ethoxylated nonylphenol phosphate, sodium octyl phenyl polyol-3-sulfonate, and cocoyl sarcosine. Sodium, sodium 1-alkoxy-2-hydroxypropyl sulfonate, sodium α-olefin (C14-16) sulfonate, sulfates of hydroxyalkanols, tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl sulfosuccinate, disodium N-octadecyl sulfosuccinate, disodium alkylamide polyethoxysulfosuccinate, disodium ethoxylated nonylphenol half ester of sulfosuccinic acid, and sodium salts of tert-octylphenoxyethoxy poly(39)ethoxyethyl sulfate.

[0033] Non-limiting examples of suitable colloidal stabilizers include polyvinyl alcohol (PVOH), i.e., partially hydrolyzed polyvinyl acetate with a degree of hydrolysis of, for example, 80 to 95 mol-%, polyvinylpyrrolidone (PVP), ethylene glycol, EO / PO block polymers, polyacrylic acid (PAA) with a MW up to, for example, 100,000 Da or even higher, polysaccharides and their derivatives, especially polysaccharide ethers, such as cellulose, starch, guar gum, xanthan gum, agar and dextrin, and their alkyl ethers, hydroxyalkyl ethers and carboxyl ethers, especially methyl ethers, ethyl ethers and propyl ethers, hydroxymethyl ethers, hydroxyethyl ethers and hydroxypropyl ethers, and one or more of carboxylmethyl ethers. Colloidal stabilizers can be anionic or nonionic.

[0034] Method for obtaining low-VOC copolymer emulsions containing rMMA (1a) The method according to the present invention for emulsion copolymerization of recycled methyl methacrylate (2r, rMMA) to obtain a low-VOC water-based copolymer emulsion (1a) includes: i) Emulsion copolymerize monomers a) and b) and / or c) in an aqueous medium in the presence of stabilizer d) (i.e., emulsifier d)) to obtain the aqueous copolymer emulsion (1) according to the invention, then ii) The obtained water-based copolymer emulsion (1) is subjected to a gas-liquid mass transfer operation (e.g., stripping) to remove VOCs to a total VOC content of 500 ppm or lower, thereby obtaining a low-VOC copolymer emulsion (1a). The total VOC content is based on the total amount of the aqueous copolymer emulsion (1a), wherein the VOC is a volatile organic compound having a boiling point of 250°C or lower, measured at a pressure of 101.3 kPa and determined in accordance with Directive 2004 / 42 / EC of the European Parliament and the Council of 21 April 2004. Preferably, the VOC is determined by a method including GC (such as GC / FID).

[0035] Despite the large quantity and wide range of various VOC components, the method is surprisingly simple, requiring little or no modification compared to existing production formulations. Furthermore, it eliminates the need for elaborate and expensive pre-cleaning of rMMA monomers, such as distillation. This allows for the extensive use of the method of the present invention and thus a significant reduction in carbon footprint.

[0036] Preferably, the gas-liquid mass transfer operation utilizes a gas to remove VOCs, wherein the gas is preferably steam (i.e., water vapor), CO2, supercritical CO2, nitrogen, and / or air, and wherein the gas-liquid mass transfer is preferably carried out at ambient pressure, below ambient pressure, or above ambient pressure.

[0037] In another preferred embodiment of the method, the VOCs of the copolymer emulsion (1) are removed to a total VOC content of 250 ppm or less, particularly 100 ppm or less. This can be achieved, for example, by longer stripping times and / or by stripping under more demanding conditions.

[0038] A water-based copolymer emulsion (1a) can be obtained according to the method described above. The water-based copolymer emulsion (1a) according to the invention can be obtained by the method according to the invention. Thus, the copolymer emulsion (1a) can be similar to commercially available emulsions today, but contains recycled MMA (rMMA) instead of standard MMA (sMMA).

[0039] To differentiate a water-based copolymer emulsion (1a) containing rMMA and having a low VOC level from a copolymer emulsion based on standard MMA, it is possible to add a tracer substance with a boiling point above 250°C and therefore not considered a VOC to the rMMA monomer composition. This addition is preferably made by the rMMA manufacturer. Suitable tracer substances can be silicones or alkanes having 15 or more carbon atoms, such as n-pentadecane (C164- ... 15 -alkanes), or n-eicosane (C1000-2000) with a boiling point of 343 °C at 101.3 kPa. 20 -Alkanes). Those skilled in the art are familiar with suitable tracers and can make the best choice.

[0040] Therefore, the water-based copolymer emulsion (1a) obtainable according to the method of the present invention can contain tracer substances with a boiling point above 250°C at 101.3 kPa.

[0041] Furthermore, the water-based copolymer emulsion (1a) obtainable according to the method of the invention preferably has a solids content of at least 20 wt.%, preferably at least 30 wt.%, and particularly at least 40 wt.%, as determined by gravimetric analysis at 130°C for 1 hour in an oven; and a volume average (MV) of particle size of 10 nm to 10 µm, preferably 50 nm to 2 µm, wherein the particle size distribution is determined by dynamic light scattering and may be unimodal or multimodal. Preferably, the solids content of the copolymer emulsion (1a) is not higher than 70 wt.%, particularly not higher than 65 wt.%, and most preferably not higher than 55 wt.%.

[0042] use The water-based copolymer emulsion (1a) obtained according to the method of the present invention and the water-based copolymer emulsion (1a) obtainable according to the method can be unexpectedly used to replace current MMA-containing emulsions.

[0043] In particular, it is used as an aqueous copolymer emulsion in the fields of paints, coatings, textiles, construction, adhesives, automobiles, paper, packaging, sealants, batteries and / or building (1a).

[0044] Example The monomers used: The standard, namely conventional MMA (2s), is provided 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).

[0045] Regenerated MMA (2r), or rMMA, is obtained through the pyrolysis of pMMA waste. Experiments were conducted using commercially available rMMA from the following sources: - Induacril, Chile (Example A- / B- / C-01; see Table 2). It has a measured MMA content of 93.3% (determined by GC / FID). - XISHUN Plastics Factory, Foshan, China (Example A- / B- / C-02; see Table 2). It has a measured MMA content of 98.1% (determined by GC / FID).

[0046] Acrylic acid was supplied by Sigma-Aldrich and had a purity of at least 99 wt.%.

[0047] Butyl acrylate, also known as n-butyl acrylate, was supplied by ECEM (European Chemical Marketing BV, Hogelhilweg 18, 1101 CD Amsterdam, the Netherlands) and had a purity of at least 99.5 wt.% (as determined by GC / FID).

[0048] Preparation of copolymer emulsion (1) Copolymer emulsions (1), i.e. latexes, i.e. latex or dispersions, were prepared by emulsion polymerization using the monomer compositions shown in Table 1. For each monomer composition (A, B, C, D), three different samples were prepared: a reference example with standard MMA (2s; A- / B- / C- / D-0) and two embodiments according to the invention with regenerated MMA (2r) from Induacril (A- / B- / C- / D-1) and XISHUN (A- / B- / C- / D-2).

[0049] Polymerization was carried out as a seeded free radical emulsion polymerization at 90°C in a 3.6-liter steel-jacketed stirred reactor. The seed was added at a rate of 0.411 parts per 100 parts of total monomer to an initial aqueous medium containing 78.92 parts of deionized water and 0.010 parts of a chelating agent (trisodium salt of N-(hydroxyethyl)ethylenediaminetriacetic acid—Versenol® 120) in a 1 wt.% aqueous solution. The seed was a polystyrene latex with a solids content of 40 wt.% and a volume average particle size of 23 nm.

[0050] Monomer feeding was initiated, and the reaction mixture was stirred at 300 rpm during monomer addition. Standard MMA (2s) and rMMA (2r, respectively) were fed into the reactor over a 240-minute period. Other monomers (i.e., acrylic acid (AA) and n-butyl acrylate (BA, see Table 1) were fed into the reactor starting 5 minutes after the start of MMA (2s) / rMMA (2r) and over a 230-minute period.

[0051] During the reaction, an additional aqueous initiator stream is fed into the reactor. This stream contains a DOWFAX™ 2A1 solution surfactant, sodium persulfate, and sodium hydroxide in amounts such that the total addition during the reaction is 1.0 part DOWFAX™ 2A1, 1.0 part sodium persulfate, and 0.2 parts sodium hydroxide dissolved in 20 parts (by weight) of water (per 100 parts of total monomer). The aqueous initiator feed begins 5 minutes after the start of the MMA (2s) (or rMMA, 2r) feed and continues over a period of 265 minutes.

[0052] After the monomers were added, the reaction mixture was heated to 97°C and held at this temperature for 40 minutes. The reaction mixture was then cooled to 30°C. The resulting copolymer emulsion was stabilized to pH 6.0 with 20 wt.% NaOH solution to obtain the copolymer emulsion (1) according to the invention, which was analyzed and reported in Table 3.

[0053] Table 1: Emulsion polymerization formulations for sample series A to D.

[0054] a) Added as Versenol 120® (1% aqueous solution) Table 2: Table 1 lists the types of methyl methacrylate used in the emulsion polymerization formulations.

[0055] Table 3 - Legend: 1) The solids of the dispersion were measured by gravimetric analysis in an oven at 130°C for 1 hour.

[0056] 2) Residue (i.e., grit or coagulation) is the sum of the obtained copolymer emulsion first filtered through a 100 US screen and then through a 325 US screen.

[0057] 3) PS (MV) represents the volume average of the particle size, which is determined by dynamic light scattering using a Nanotrac 150 instrument.

[0058] 4) PS (MN) represents the number average of particle size, which is determined by dynamic light scattering using a Nanotrac 150 instrument.

[0059] 5) The VOC data in the report determined by GC measurement are relative to wet latex (in ppm).

[0060] The results reported in Table 3 impressively demonstrate that the copolymer emulsions (1) (A- / B- / C- / D-1 and -2) obtained according to the present invention using recycled MMA (2r) exhibit good conversion rates, similar to the reference emulsions (2s; A- / B- / C- / D-0) with standard MMA. Particularly surprising is that even recycled MMA (2r) from Induacril with an MMA content as low as 93.3 wt.% did not inhibit the reaction or form significant amounts of residue, i.e., coagulation – even at approximately 50 wt.% solids! It should be noted that the lower solids content of sample A- / B- / C-1, containing approximately 93.3 wt.% rMMA from Induacril, is considered to be at least partially reported as a copolymerizable monomer, i.e., a particularly low MMA content. Furthermore, all samples produced stable latexes, i.e., no sedimentation was visually observable after 28 days. Additionally, all latexes were white, i.e., no visual differences were detected.

[0061] Furthermore, it was unexpectedly observed that, in addition to comparable monomer conversion rates, all obtained emulsions exhibited similar residue levels and particle size distributions as measured by volume and number averages. Additionally, the glass transition temperature (Tg) was similar. g The gel content (both measured after steam stripping, see Table 4) was also roughly equivalent, although the lower MMA content of 93.3 wt.% in Examples A- / B- / C- / D-1 was not actually compensated for. Furthermore, some non-polymeric high-boiling-point components with boiling points above 250°C and therefore not considered VOCs may have been embedded in the latex, thus affecting the glass transition temperature (Tg). g None of the emulsions exhibited, for example, different glass transition temperatures (T0). g The phase latex of ) . Therefore, the non-MMA component of the rMMA (2r) used will not affect the copolymerization of MMA with acrylic acid (AA) and / or n-butyl acrylate (BA).

[0062] It should be noted that the polymerization formulation used has not been optimized for a specific regenerated MMA' (2r), and those skilled in the art are fully capable of adjusting the formulation to reduce the significant observed differences from the reference emulsion containing standard MMA (2s).

[0063] Preparation of low-VOC water-based copolymer emulsion (1a) The copolymer emulsions (1) obtained as described above, for example in Tables 1 to 3, were subjected to a steam stripping process to obtain a low-VOC copolymer emulsion (1a) according to the invention, which has a total VOC content of much less than 500 ppm (see Table 4).

[0064] Table 4 – Legend: 1) and 5): See Table 3 6) In addition to the VOCs removed, the difference in solids content before and after stripping is attributed to low-boiling-point VOCs that cannot be detected by VOC measurement, the different amounts of steam removed or added during the stripping process, and the formation of grit.

[0065] 7) Glass transition temperature (T) g According to DIN 51007, the heating rate is 10 °C / min, and the midpoint of the line segment of the intermediate tangent between the extrapolated baselines is reported.

[0066] 8) The gel content was determined using the following procedure: a latex film was cast from a latex sample adjusted to pH 8 with 20 wt.% NaOH solution and weighed (dry latex film (A)). The film was then allowed to swell in toluene at room temperature for 26 hours. The resulting toluene-insoluble portion (i.e., wet gel) was separated from the liquid phase by filtration and weighed. The gel was then dried in a ventilated oven at 130°C for 2 hours and weighed again to obtain the dry weight (C) of the gel. The gel content (in %) was determined by the following formula: Gel content = (Dry gel weight (C) / Dry latex film weight (A)) × 100 9) N / A means "No data available".

[0067] For steam stripping, approximately 2.5 liters of copolymer emulsion (1; see Tables 1-3) were transferred to a 10-liter glass container and heated to 100°C in a water bath. The latex was then purged with steam at a rate of approximately 2.0 l / h at ambient pressure for 60 minutes, followed by purging with air for 30 minutes, until approximately 200 mL of condensate was removed. The latex was then cooled to ambient temperature and filtered.

Claims

1. A water-based copolymer emulsion (1) suitable for carrying out gas-liquid mass transfer to reduce VOCs, wherein the copolymer emulsion (1) is a copolymerization product based on a) 1 wt.% to 99.5 wt.% of methyl methacrylate (MMA), b) 0 wt.% to 20 wt.% of one or more hydrophilic monomers having a water solubility greater than 0.3 g / 100 cm 3 and c) 0 wt.% to 99 wt.% of one or more hydrophobic monomers having a water solubility of 0.3 g / 100 cm 3 or less, wherein the copolymer emulsion (1) comprises d) 0.2 wt.% to 20 wt.% of one or more stabilizers, wherein the content of 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 the stabilizer d) is based on the total amount of monomers a), b) and c) added, characterized in that at least 5 wt.% of the methyl methacrylate a) (MMA) is recycled methyl methacrylate (2r,rMMA) and the remainder is standard methyl methacrylate (2s,MMA).

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

3. The 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 recycled methyl methacrylate (2r,rMMA) has a content of methyl methacrylate (MMA) of 85 wt.% to 99.4 wt.%, preferably 90 wt.% to 99.4 wt.%.

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

5. The copolymer emulsion (1) according to any one of claims 1 to 4, wherein monomers c) are present in an amount of 5 wt.% or more, in particular 10 wt.% or more, based on the total amount of monomers a), b) and c), and wherein the monomers a) and c) form a copolymerization product 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 (meth)acrylic C1 to C40 alkyl ester monomers other than methyl methacrylate.

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

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

8. The process according to claim 7, wherein the gas-liquid mass transfer operation utilizes a gas, wherein the gas is preferably steam, CO2, supercritical CO2, nitrogen and / or air, wherein the gas-liquid mass transfer is preferably carried out at ambient pressure, below ambient pressure or above ambient pressure.

9. The method according to claim 7 or 8, wherein the VOC of the copolymer emulsion (1) is removed to a total VOC content of 250 ppm or less, in particular 100 ppm or less.

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

11. The water-based copolymer emulsion (1a) according to 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 average of the particle size (MV) determined by dynamic light scattering of 10 nm to 10 pm, preferably 50 nm to 2 pm.

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

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