Method for isolating alkyl (METH)acrylates

Abstract

The present invention relates to a novel method for isolating alkyl (meth)acrylates, in particular methyl (meth)acrylates. In this method, a polymer composition containing poly(alkyl (meth)acrylate) is first thermally cleaved to obtain at least one alkyl (meth)acrylate, at least one additional alkyl ester, and at least one benzene derivative. This mixture is subsequently condensed and mixed with a stream from an alkyl (meth)acrylate production process. High-purity alkyl (meth)acrylates are isolated by distillation.

Description

[0001] 202000044 1

[0002] Method for isolating alkyl(meth)acrylates

[0003] Description

[0004] Field of invention

[0005] The present invention relates to a novel process for the isolation of alkyl(meth)acrylates, in particular methyl(meth)acrylates. In this process, a polymer composition containing poly(alkyl(meth)acrylate) is first thermally cleaved to obtain at least one alkyl(meth)acrylate, at least one further alkyl ester, and at least one benzene derivative. This mixture is then condensed and mixed with a stream from an alkyl(meth)acrylate production process. High-purity alkyl(meth)acrylates are isolated by distillation.

[0006] State of the art

[0007] Alkyl(meth)acrylates, especially methyl methacrylate (MMA), are currently produced using various methods that start from C2, C3 or C4 building blocks.

[0008] In one of these processes (C4 process), MMA is obtained by oxidizing isobutylene or tert-butanol with atmospheric oxygen in the gas phase over a heterogeneous catalyst to methacrolein (MAL), followed by an oxidative esterification reaction of methacrolein using methanol. This process, developed by ASAHI, is described, among other places, in US publications 5,969,178 and US 7,012,039.

[0009] Another globally widespread commercial process uses acetone as a starting material and is usually referred to as the Cs process or ACH-Su Ifo process. In this process, acetone reacts with hydrogen cyanide (HCN) to form the central intermediate acetone cyanohydrin (ACH). This intermediate is isolated and used in subsequent process steps for the production of methacrylic acid (MAS) and MMA. Such a process is described, for example, in US 4,529,816.

[0010] WO 2014 / 170223 describes a highly efficient process in which propionaldehyde is obtained from C2 fractions in a first stage and reacted with formaldehyde in a second stage to form methacrolein. This methacrolein can then be oxidatively esterified to MMA in the presence of specific metal or metal oxide catalysts and methanol. This process is also known as the C2 process.

[0011] MMA is used in particular for the production of polymethyl methacrylate (PMMA), which is characterized by excellent optical (acrylic glass) and other physical properties. Its applications include glazing and facades in architecture, lighting elements and vehicle taillights in the automotive sector, and aircraft windows.

[0012] Decorative, design or furniture elements, flat screens and displays, noise barriers and illuminated advertising.

[0013] The processing of PMMA generates production waste, known as post-industrial waste. Furthermore, post-consumer waste, such as electronic waste and scrap metal, also contains PMMA, often alongside other plastics and additives. The proportion of MMA building blocks in the PMMA polymers contained in this waste varies and can range from 75% to over 99%.

[0014] PMMA, whether post-industrial or post-consumer waste, can generally be depolymerized into its monomers and reused as so-called recycled MMA. Various depolymerization processes are described in the prior art, such as depolymerization in metal baths, rotary kilns, fluidized bed reactors, or extruders.

[0015] For example, the documents DE 642289 C, US 2,030,901 , DE 3146194 A1 , EP 3635 043 and US 2,470,361 describe the thermal depolymerization of PMMA, partly with subsequent purification of the obtained monomers, for example by distillation.

[0016] Thermal-catalytic depolymerizations of PMMA with subsequent purification of the obtained monomers are described, for example, in US 2,858,255, DE 2132716, WO 2019 / 003253, DE 19729065 and EP 2 895 576.

[0017] The depolymerization of PMMA, sometimes together with other polymers, in a fluidized bed is also well known. This is described, for example, in US 5,663,420, WO 2000 / 017149 and US 8,304,573.

[0018] US 3,494,958 describes a thermal depolymerization process for PMMA. The resulting monomer can then be purified by distillation. US 3,494,958 describes that the purification can be carried out, for example, analogously to purification in an ACH process.

[0019] In the processes described above, the monomer yield is sometimes insufficient. Furthermore, the processes described in the prior art produce recycled alkyl(meth)acrylates whose purity is insufficient for the production of poly(alkyl(meth)acrylates) of adequate quality. This is particularly the case when poly(methyl methacrylate) containing a large proportion of additives, such as impact modifiers or pigments and / or other polymers, is used in the depolymerization processes. In addition, the global warming potential (GWP) of the proposed processes is insufficient. 202000044 3

[0020] Task

[0021] There was therefore a need to provide an improved method for isolating alkyl(meth)acrylates, particularly methyl methacrylate, from a depolymerization process that does not exhibit the disadvantages of the prior art methods described, or only to a lesser extent. In particular, the method should have a lower global warming potential (GWP), i.e., a lower emission of climate-relevant waste products such as CO2.

[0022] Solution

[0023] This problem is solved by a process for isolating alkyl(meth)acrylates comprising the following steps a) to e): a) thermal cleavage of at least one polymer composition containing at least one poly(alkyl(meth)acrylate) to obtain a first gas stream containing at least one alkyl(meth)acrylate, at least one further alkyl ester, and at least one benzene derivative; b) condensation of the first gas stream obtained in step a) to obtain a liquid first stream containing the at least one alkyl(meth)acrylate, the at least one further alkyl ester, and at least one benzene derivative; c) mixing of the liquid first stream obtained in step b) with a further stream containing alkyl(meth)acrylate, wherein the further stream is part of an alkyl(meth)acrylate manufacturing process, to obtain a mixed stream comprising the liquid first stream and the further stream.d) Distillation of the mixed stream obtained in step c) to obtain a bottom stream containing alkyl(meth)acrylate and an overhead stream containing the at least one further alkyl ester; e) at least partial hydrolysis of the overhead stream obtained in step d), wherein the at least one further alkyl ester is at least partially hydrolyzed to obtain an alkyl acid.

[0024] It was surprisingly found that the process according to the invention yields alkyl(meth)acrylates, in particular methyl methacrylate, with a purity of >99.5%.

[0025] In particular, the process according to the invention surprisingly enables the particularly efficient removal of byproducts such as further alkyl esters and benzene derivatives, even if their normal boiling point differs only slightly, for example by only ±20 K (Kelvin), preferably by ±1 K, and particularly preferably by ±0.6 K, from the normal boiling point of the alkyl(meth)acrylate. This is due in particular to process step e). 202000044 4

[0026] Additives and chain regulators that may be present in the polymer composition, and the products obtained from them during the thermal cleavage of the polymer compositions, such as mercaptans, can also be easily and cost-effectively separated by the process according to the invention. For example, the alkyl(meth)acrylates obtained by the process according to the invention contain a maximum of 0.5% by-products. Due to the process according to the invention and the resulting efficient separation of the by-products, the alkyl(meth)acrylates produced according to the invention have no or only a very slight odor, despite the sulfur-containing compounds present in the polymer composition.

[0027] The process according to the invention also exhibits a lower global warming potential (GWP), in particular a low CG2 emission. This is achieved especially because the process according to the invention also allows the use of polymer compositions with a relatively high proportion of additives and other impurities. In addition, the byproducts obtained during depolymerization can be further utilized after their separation, thus further reducing the global warming potential (GWP).

[0028] It was further surprisingly found that in a preferred embodiment of the process according to the invention, the at least partial hydrolysis in step e) can take place within the alkyl(meth)acrylate manufacturing process, so that no additional equipment for hydrolysis needs to be provided.

[0029] By mixing the obtained liquid first stream with the further stream, which is part of an alkyl(meth)acrylate production process, and by performing hydrolysis within the alkyl(meth)acrylate production process in a preferred embodiment of the process according to the invention, existing alkyl(meth)acrylate plants can be used to purify the liquid first stream. This significantly reduces the equipment requirements of the process according to the invention.

[0030] The method according to the invention is therefore superior to those known to date, as it meets the requirement of being able to reuse itself in the circular economy.

[0031] Furthermore, the by-products obtained during depolymerization can be further recycled after separation, thus further reducing the carbon footprint and therefore the global warming potential (GWP).

[0032] The method according to the invention is described in more detail below.

[0033] In step a) of the process according to the invention, at least one polymer composition is thermally cleaved, yielding a first gas stream. The at least one 202000044 5

[0034] The polymer composition contains at least one poly(alkyl(meth)acrylate). The gas stream contains at least one alkyl(meth)acrylate, at least one other alkyl ester, and at least one benzene derivative.

[0035] Within the scope of the present invention, the term "at least one polymer composition" means both exactly one polymer composition and a mixture of two or more polymer compositions. A mixture of two or more polymer compositions is preferred according to the invention.

[0036] The at least one polymer composition contains at least one poly(alkyl(meth)acrylate).

[0037] In the context of the present invention, “at least one poly(alkyl(meth)acrylate)” means both exactly one poly(alkyl(meth)acrylate) and a mixture of two or more poly(alkyl(meth)acrylates. Within the context of the present invention, “poly(alkyl(meth)acrylates)” refers to polymers and copolymers of alkyl(meth)acrylates.

[0038] Examples of copolymers of alkyl(meth)acrylates are copolymers of alkyl(meth)acrylates with 1-alkenes, other alkyl(meth)acrylates, (meth)acrylic acid, styrene, polyesters and / or polyurethane(meth)acrylates.

[0039] 1-Alkenes that can copolymerize with alkyl(meth)acrylates are known as such and include, for example, hexene-1, heptene-1, vinylcyclohexane, 3,3-dimethyl-1-propene, 3-methyl-1-diisobutylene and 4-methylpentene-1.

[0040] Within the scope of the present invention, the term "styrene" is understood to mean not only styrene as such, but also substituted styrenes such as α-methylstyrene, α-ethylstyrene, vinyltoluene, p-methylstyrene, monochlorostyrenes, dichlorostyrenes and tribromostyrene.

[0041] Suitable polyesters are known as such and are preferably available via polycondensation or ring-opening polymerization.

[0042] Within the scope of the present invention, "polyurethane (meth)acrylates" are understood to be (meth)acrylates linked to one another via urethane groups. They are obtainable by reacting hydroxyalkyl (meth)acrylates with polyisocyanates and polyoxyalkylenes having at least two hydroxy functionalities. Instead of hydroxyalkyl (meth)acrylates, esters of (meth)acrylic acid with oxiranes, such as ethylene oxide or propylene oxide, or corresponding oligooxiranes or polyoxiranes can also be used. Suitable polyurethane (meth)acrylates are known as such. 202000044 6

[0043] At least one polymer composition can, for example, originate from production waste. In this case, the polymer composition is typically so-called post-industrial waste, such as sprues, start-up lumps from extrusion, dust, chips, partially polymerized polymer syrups, edge trimmings, offcuts from sheets, rejects from sheets, films, blocks, semi-finished products, defective molded parts, or waste from injection molding.

[0044] It is also possible that at least one polymer composition originates from so-called post-consumer waste. This typically includes waste from sources such as electrical and electronic waste, greenhouses, exhibition stands, shop fittings, or illuminated advertising.

[0045] The at least one polymer composition therefore typically contains at least one further component. This at least one further component is, for example, selected from the group consisting of polymers other than poly(alkyl(meth)acrylate), pigments, dyes, fillers, additives, regulators, initiators, impact enhancers, release agents, and UV additives.

[0046] A preferred method is therefore also one in which the polymer composition in step a) contains at least one further component selected from the group consisting of polymers other than poly(alkyl(meth)acrylate), pigments, dyes, fillers, additives, regulators, initiators, impact strengtheners, release agents and UV additives.

[0047] Polymers other than poly(alkyl(meth)acrylate) are particularly suitable if they are commonly used as blends with poly(alkyl(meth)acrylate). These include, for example, polyethylene, polyvinyl chloride, polystyrene, polyamides, and biopolymers such as α-polysaccharides (starch), β-polysaccharides (cellulose, chitin), lignin, and polylactide.

[0048] Examples of pigments include white, red, blue, green, and / or yellow inorganic pigments. White inorganic pigments such as titanium dioxide are particularly preferred.

[0049] Dyes, for example, are organic dyes known to experts.

[0050] Typical fillers are primarily mineral fillers. Mineral fillers are preferably selected from the group consisting of calcium carbonate, barium sulfate, quartz, quartz flour, precipitated silicas, pyrogenic silicas, corundum, glass beads, and cristobalite.

[0051] Typical excipients are known as such and are selected, for example, from the group consisting of plasticizers, paraffins, and / or inhibitors. 202000044 7

[0052] Esters, polyols, oils, low molecular weight polyethers or phthalates are preferably used as plasticizers.

[0053] Paraffins that may be present in the polymer composition are known as such. For example, several paraffins with different melting points may be present in varying concentrations.

[0054] From the group of inhibitors, preferably substituted phenols, hydroquinone derivatives, phosphines and / or phosphites are used.

[0055] Chain length regulators are primarily compounds known from radical polymerization that control chain length. Common chain regulators include mercaptans such as n-dodecyl mercaptan, but also multivalent mercapto compounds such as pentaerythrol tetrathioglycolate.

[0056] Initiators are also known as such and are selected, for example, from the group consisting of peroxides, azo compounds, persulfates and mixtures thereof.

[0057] Impact tougheners are known as such and are, for example, polymer particles containing an elastomer.

[0058] Suitable separating agents include, in particular, long-chain wax acids such as stearic acid, palmitic acid or lauric acid, as well as monohydric fatty or wax alcohols such as diethylene glycol monopropyl ether.

[0059] Suitable UV additives include, in particular, UV stabilizers. Preferably, the UV stabilizers are selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, thioxanthonate derivatives, piperidinol carboxylic acid ester derivatives, and cinnamon acid ester derivatives.

[0060] The thermal decomposition of the at least one polymer composition can be carried out according to methods known to those skilled in the art.

[0061] Thermal cracking can be carried out in reactors known to those skilled in the art. For example, thermal cracking can be carried out in a pyrolysis reactor, in an extruder, in a rotary kiln, in fluidized bed pyrolysis, in a metal bath and / or as dry distillation.

[0062] The polymer composition can be in solid or liquid form during thermal decomposition. If the polymer composition is in solid form, it can exist as a pure solid. It is also possible that the polymer composition is dispersed in a medium. This medium can be, for example, a solid such as quartz, metal shavings, or diatomaceous earth. It is also possible that the medium is a gas such as nitrogen or a liquid such as water or a hydrocarbon. It is possible that the medium is a liquid at room temperature but exists as a gas under the conditions of thermal decomposition in step a).

[0063] The polymer composition is present in liquid (molten) form, for example, when thermal cracking takes place in an extruder.

[0064] The polymer composition, particularly when in solid form, can be mechanically comminuted before thermal decomposition, for example to an average particle size distribution of less than 6 mm (Qr, d50), preferably less than 1.5 mm (Qr, d50), or to a particle size distribution in the range of 0.1 mm (Qr, d50) to 6 mm (Qr, d50). Preferably, the particle size distribution is determined by laser diffractometry.

[0065] The temperature (T) during the thermal cracking in step a) is, for example, in a range of 240 °C to 800 °C, preferably in a temperature in the range of 300 °C to 500 °C, and particularly preferably in a temperature in the range of 325 °C to 400 °C.

[0066] The pressure during thermal cracking in step a) is, for example, in the range of 200 mbar to 1000 bar, preferably in the range of 400 mbar to 500 bar.

[0067] A method is therefore also preferred according to the invention in which the temperature during thermal cracking in step a) is in the range of 240 °C to 800 °C and / or the pressure during thermal cracking is in the range of 400 mbar to 500 bar.

[0068] The thermal decomposition in step a) can be carried out in the presence of a catalyst. Catalysts suitable for thermal decomposition are known as such and can be selected, for example, from the group consisting of molten metal, peroxides, potassium salts such as potassium acetate, and alkali metal persulfates such as potassium monopersulfate. Lead and / or eutectic lead / tin mixtures are particularly suitable as molten metals.

[0069] If the thermal cracking in step a) takes place in the presence of a catalyst, the cracking in step a) is also referred to as thermally catalytic cracking.

[0070] A method in which the thermal cracking in step a) is a thermally catalytic cracking is therefore also preferred according to the invention. 202000044 9

[0071] In the thermal cleavage in step a), the poly(alkyl(meth)acrylate) is cleaved. This cleavage is also called depolymerization. Depolymerizations as such are known to those skilled in the art. In depolymerizations, a polymer is cleaved into its monomer and oligomer units.

[0072] In the thermal cleavage in step a), the poly(alkyl(meth)acrylate) is cleaved into its monomer and oligomer units. As explained above, the poly(alkyl(meth)acrylate) is a polymer or copolymer of at least one alkyl(meth)acrylate. Therefore, at least one alkyl(meth)acrylate is formed during the thermal cleavage.

[0073] During the thermal cleavage of the polymer composition, at least one further alkyl ester is formed. Within the scope of the present invention, "at least one further alkyl ester" means both exactly one further alkyl ester and a mixture of two or more further alkyl esters. A mixture of two or more further alkyl esters is preferred according to the invention.

[0074] Furthermore, at least one benzene derivative is typically formed during thermal cleavage. This at least one benzene derivative is formed, for example, during the thermal cleavage of the polymer composition consisting of polymers other than poly(alkyl(meth)acrylate), such as polystyrene. Within the scope of the present invention, "at least one benzene derivative" means both exactly one benzene derivative and a mixture of two or more benzene derivatives. A mixture of two or more benzene derivatives is preferred according to the invention.

[0075] The first gas stream therefore contains the at least one alkyl(meth)acrylate formed during thermal cracking, the at least one further alkyl ester and the at least one benzene derivative.

[0076] The at least one alkyl(meth)acrylate is, as explained above, derived from the poly(alkyl(meth)acrylate).

[0077] In the context of the present invention, “at least one alkyl(meth)acrylate” means exactly one alkyl(meth)acrylate as well as a mixture of two or more alkyl(meth)acrylates.

[0078] Within the scope of the present invention, "alkyl(meth)acrylates" are understood to be alkyl esters of (meth)acrylic acid having 1 to 18, preferably 1 to 12, and particularly preferably 1 to 4, carbon atoms in the alkyl group. The alkyl group can be linear, cyclic, and / or branched. Furthermore, it can have aromatic groups. The alkyl group can also have heteroatoms within the alkyl group and / or be substituted with heteroatoms, as is the case, for example, with hydroxypropyl(meth)acrylate and / or hydroxyethyl(meth)acrylate. For example, alkyl(meth)acrylates according to the invention are selected from the group consisting of methyl(meth)acrylate, ethyl(meth)acrylate, 1-methyl-ethyl(meth)acrylate, propyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, isopentyl(meth)acrylate, cyclohexyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, allyl(meth)acrylate,

[0079] Polyethylene glycol (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, vinyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate and lauryl (meth)acrylate.

[0080] In a further embodiment of the present invention, the term "alkyl(meth)acrylates" also includes polyethylene glycol(meth)acrylates with a weight-average molecular weight Mw in the range of 250 g / mol to 10,000 g / mol.

[0081] Within the scope of the present invention, the term "(meth)acrylic acid" encompasses both acrylic acid and methacrylic acid. Within the scope of the present invention, the term "(meth)acrylates" encompasses both acrylates and methacrylates.

[0082] Within the scope of the present invention, the term "alkyl(meth)acrylates" refers to both alkyl methacrylates and alkyl acrylates. Alkyl methacrylates are preferred according to the invention. The at least one alkyl(meth)acrylate is, for example, a Ci-Ci8 alkyl(meth)acrylate, preferably a Ci-Ci2 alkyl(meth)acrylate, and particularly preferably a Ci-C4 alkyl(meth)acrylate. According to the invention, the at least one alkyl(meth)acrylate particularly preferably comprises methyl(meth)acrylate.

[0083] A preferred method is therefore also one in which the at least one alkyl(meth)acrylate contained in the first gas stream in step a) is selected from the group consisting of Ci- to C4- alkyl(meth)acrylates.

[0084] The at least one alkyl(meth)acrylate, for example, has a boiling point at normal pressure in the range of 50 °C to 300 °C, preferably in the range of 80 °C to 250 °C.

[0085] It goes without saying that the at least one further alkyl ester is different from the at least one alkyl(meth)acrylate. The at least one further alkyl ester preferably does not comprise a (meth)acrylate unit.

[0086] For example, at least one further alkyl ester is selected from the group consisting of Ci-C4 alkyl isobutyrates, Ci-C4 alkyl propionates, Ci-C4 alkyl pivalates and dicarboxylic acid diesters.

[0087] Within the scope of the present invention, Ci-C4 alkyl isobutyrates are understood to be alkyl esters of isobutyric acid having 1 to 4 carbon atoms in the alkyl group. The alkyl group can be linear or branched. It can also contain heteroatoms within the alkyl group and / or be substituted with heteroatoms. Examples of Ci-C4 alkyl isobutyrates containing heteroatoms within the alkyl group are methyl 3-methoxyisobutyrate and methyl 3-methoxyisobutyrate. Ci-C4 alkyl isobutyrates according to the invention are selected, for example, from the group consisting of methyl isobutyrate, ethyl isobutyrate, methyl 2-methoxyisobutyrate, and methyl 3-methoxyisobutyrate.

[0088] Within the scope of the present invention, Ci-C4 alkylpropionates are understood to be alkyl esters of propionic acid having 1 to 4 carbon atoms in the alkyl group. The alkyl group can be linear or branched. It can also contain heteroatoms within the alkyl group and / or be substituted with heteroatoms. Ci-C4 alkylpropionates according to the invention are, for example, selected from the group consisting of methyl propionate and ethyl propionate.

[0089] Within the scope of the present invention, Ci-C4 alkyl pivalates are understood to be alkyl esters of pivalic acid having 1 to 4 carbon atoms in the alkyl group. The alkyl group can be linear or branched. It can also contain heteroatoms within the alkyl group and / or be substituted with heteroatoms. Ci-C4 alkyl pivalates according to the invention are, for example, selected from the group consisting of methyl pivalate and ethyl pivalate.

[0090] Within the scope of the present invention, dicarboxylic acid diesters are understood to be alkyl esters of dicarboxylic acids having 1 to 4 carbons in the alkyl group. Likewise, dicarboxylic acid diesters are understood to be carboxylic acid esters of diols in which both hydroxyl groups are esterified with a carboxylic acid. Dicarboxylic acid diesters according to the invention are, for example, selected from the group consisting of dimethyl propanedioate, dimethyl pentanedioate, dimethyl hexanedioate, and dimethyl heptanedioate.

[0091] Preferably, the at least one further alkyl ester is selected from the group consisting of methyl propionate, ethyl propionate, methyl isobutyrate, methyl pivalate, methyl 3-methoxyisobutyrate and dicarboxylic acid diesters.

[0092] A preferred method is therefore also one in which the at least one further alkyl ester is selected from the group consisting of methyl propionate, methyl isobutyrate, methyl pivalate, methyl 3-methoxyisobutyrate and dicarboxylic acid diesters.

[0093] The at least one further alkyl ester, for example, has a boiling point at normal pressure in the range of 50 °C to 200 °C, preferably in the range of 75 °C to 150 °C.

[0094] According to the invention, the boiling point at normal pressure of at least one further alkyl ester differs from the boiling point at normal pressure of at least one alkyl(meth)acrylate by a difference in the range of -20 °C to +20 °C, preferably by a difference in the range of -1 °C to +1 °C, and particularly preferably by a difference in the range of -0.6 °C to +0.6 °C.

[0095] Within the scope of the present invention, the term "benzene derivative" refers to compounds derived from benzene in which at least one hydrogen atom of the benzene ring has been substituted. The substitution can be effected by a carbon-containing residue and / or heteroatoms. Carbon-containing residues include, in particular, alkyl groups, allyl groups, and vinyl groups. Preferably, the at least one benzene derivative is selected from the group consisting of toluene, trimethylbenzene, and styrene.

[0096] In the context of the present invention, "trimethylbenzene" means all isomers of trimethylbenzene, i.e. 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene.

[0097] For styrene as at least one benzene derivative, the previously described statements and preferences for styrene as a comonomer apply accordingly.

[0098] As explained above, the first gas stream is obtained by thermal decomposition of the at least one polymer composition. The first gas stream therefore typically contains at least one further component. It is understood that this at least one further component differs from the at least one alkyl(meth)acrylate, the at least one further alkyl ester, and the at least one benzene derivative.

[0099] The at least one further component is formed, for example, by thermal cleavage of copolymers of alkyl(meth)acrylate and / or by thermal cleavage of the at least one further component optionally contained in the at least one polymer composition. Furthermore, oligomers of alkyl(meth)acrylate can also be formed during thermal cleavage; these also fall under the term "at least one further component" within the scope of the present invention.

[0100] For example, the at least one further component is selected from the group consisting of (meth)acrylic acid, sulfur-containing compounds, oligomers, dimers, Ci-C4 alkyl acids, di(meth)acrylate diesters, Ci-C4 alcohols, aldehydes and ketones; preferably, the further component is selected from the group consisting of (meth)acrylic acid, sulfur-containing compounds, oligomers and dimers.

[0101] A preferred method therefore includes at least one further component selected from the group consisting of (meth)acrylic acid, sulfur-containing compounds, oligomers, and dimers. 202000044 13

[0102] Sulfur-containing compounds are derived in particular from sulfur-containing regulators that may be present in the at least one polymer composition and are in particular mercaptans such as dodecyl mercaptan and multivalent mercapto compounds such as pentaeryth ltetrathoglycolate.

[0103] Within the scope of the present invention, the term "oligomers" refers in particular to oligomers of at least one alkyl(meth)acrylate, of (meth)acrylic acid, and of mixtures thereof. The term "oligomer" encompasses not only higher oligomers but also lower oligomers, such as trimers, tetramers, and pentamers. In particular, the term "oligomer" includes a molecule composed of three to ten units, wherein the units are obtainable from the at least one alkyl(meth)acrylate, (meth)acrylic acid, or mixtures thereof.

[0104] Within the scope of the present invention, dimers are understood to be, in particular, dimers of at least one alkyl(meth)acrylate, of (meth)acrylic acid and of mixtures thereof.

[0105] Ci-C4 alkyl acids are aliphatic carboxylic acids with 1 to 4 carbon atoms. Ci-C4 alkyl acids can exhibit branching. For example, the C1-C4 alkyl acid is selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, and isobutyric acid.

[0106] Di(meth)acrylate diesters are defined as esters of (meth)acrylic acid with a diol. For example, di(meth)acrylate diester is selected from the group consisting of ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate.

[0107] Ci-C4 alcohols are defined as alcohols that have 1 to 4 carbon atoms in the alkyl group. The alkyl group can be linear or branched. It is also possible that it is substituted with heteroatoms. Examples of Ci-C4 alcohols are methanol, ethanol, ethylene glycol, n-butanol, and isobutanol.

[0108] Aldehydes are well known to those skilled in the art. For example, aldehydes are selected from the group consisting of formaldehyde, acetaldehyde, methacrolein, and acrolein.

[0109] Within the scope of the present invention, the term ketones refers to both monoketones, such as acetone, and diketones, such as diacetyl. Ketones according to the invention are, for example, selected from the group consisting of diacetyl, acetone, acetylacetone, and methyl ethyl ketone. 202000044 14

[0110] For example, the first gas stream obtained during thermal cracking contains 60 to 99 wt. %, preferably 80 to 98 wt. %, of the at least one alkyl(meth)acrylate, in each case based on the total weight of the first gas stream.

[0111] For example, the first gas stream obtained during thermal cracking contains 0.01 to 5 wt. %, preferably 0.1 to 1 wt. %, of the at least one further alkyl ester, in each case based on the total weight of the first gas stream.

[0112] For example, the first gas stream obtained during thermal cracking contains 0.01 to 5 wt.%, preferably 0.05 to 0.5 wt.%, of the at least one benzene derivative, in each case based on the total weight of the first gas stream.

[0113] For example, the first gas stream obtained from thermal cracking contains 0.01 to 5 wt.-%, preferably 0.1 to 3 wt.-%, of at least one further component, in each case based on the total weight of the first gas stream.

[0114] In step b), the first gas stream obtained in step a) is condensed to obtain a liquid first stream. The liquid first stream contains at least one alkyl(meth)acrylate, at least one further alkyl ester, and at least one benzene derivative.

[0115] The first gas stream can be condensed using methods known to experts; for example, condensation can take place in a condenser.

[0116] For example, the first gas stream in step b) is condensed at a temperature in the range of -10 °C to 100 °C, preferably in the range of 0 °C to 90 °C, particularly preferably in the range of 20 °C to 80 °C.

[0117] The pressure during the condensation of the first gas stream in step b) is, for example, in the range of 0.1 bar to 1.1 bar, preferably in the range of 0.3 bar to 1 bar and particularly preferably in the range of 0.4 bar to 0.8 bar.

[0118] Preferably, the first gas stream is condensed by being drawn into a previously condensed and cooled first gas stream, where it then condenses. A portion of the condensed first gas stream can then be separated as a liquid first stream, and the first gas stream can be drawn back into the condensed and cooled first gas stream.

[0119] During condensation, the first gas stream transitions from the gas phase to the liquid phase, retaining the liquid initial stream. 202000044 15

[0120] Typically, the at least one alkyl(meth)acrylate contained in the liquid first stream is the same at least one alkyl(meth)acrylate that was contained in the first gas stream. Therefore, the explanations and preferences previously described for the at least one alkyl(meth)acrylate contained in the first gas stream apply accordingly to the at least one alkyl(meth)acrylate contained in the liquid first stream.

[0121] Typically, the at least one additional alkyl ester contained in the liquid first stream is the same at least one additional alkyl ester that was contained in the first gas stream. Therefore, the previously described explanations and preferences apply to the at least one additional alkyl ester contained in the liquid first stream as they do to the at least one additional alkyl ester contained in the first gas stream.

[0122] Typically, the at least one benzene derivative contained in the liquid first stream is the same at least one benzene derivative that was contained in the first gas stream. Therefore, the previously described explanations and preferences apply to the at least one benzene derivative contained in the liquid first stream as they do to the at least one benzene derivative contained in the first gas stream.

[0123] The liquid first stream may additionally contain at least one further component that may be present in the first gas stream. The previously described provisions and preferences apply accordingly to this at least one further component.

[0124] Preferably according to the invention, the first gas stream is distilled after step a) and before step b). This yields a first overhead stream containing the at least one alkyl(meth)acrylate and the at least one further alkyl ester, and a first bottom stream containing the at least one benzene derivative and at least one component different from the at least one alkyl(meth)acrylate and the at least one further alkyl ester. In this embodiment, the first overhead stream obtained by distillation is then condensed in step b). The first overhead stream may contain residues of the at least one benzene derivative. If the first overhead stream contains residues of the at least one benzene derivative, these can also be separated in step e) described below. In one embodiment of the invention, for example, the at least one further alkyl ester is hydrolyzed in the presence of sulfuric acid.Then, for example, at least one benzene derivative can be reacted in the presence of this sulfuric acid and thus separated.

[0125] A preferred method is therefore also one in which the first gas stream is distilled according to step a) and procedure b) to obtain a first overhead stream containing the at least one alkyl(meth)acrylate and the at least one further alkyl ester, and a first bottom stream containing at least one component different from the at least one alkyl(meth)acrylate and the at least one further alkyl ester, wherein the first overhead stream is condensed in step b). 202000044 16

[0126] The first gas stream can be condensed before it is distilled according to step a) and before step b). Methods for condensing the first gas stream are known as such and are described, for example, above. Therefore, within the scope of the present invention, "distillation of the first gas stream" refers not only to the distillation of the first gas stream in the gas phase, but also, and in particular, to the distillation of the first gas stream after it has been condensed.

[0127] The distillation of the first gas stream can be carried out using methods and reactors known to those skilled in the art. For example, the first gas stream can be transferred to a distillation column and / or a rectification column and distilled there. During the distillation of the first gas stream, components contained in the first gas stream that have a higher boiling point than the at least one alkyl(meth)acrylate are obtained in the first bottom stream, while components contained in the first gas stream that have the same or a lower boiling point than the at least one alkyl(meth)acrylate are obtained in the first top stream.

[0128] Distillation can take place, for example, at a temperature in the range of 40 °C to 140 °C. Preferably, the bottoms temperature during distillation is in the range of 95 °C to 130 °C, and particularly preferably in the range of 97 °C to 126 °C.

[0129] Distillation can take place, for example, at a pressure in the range of 10 mbar to 250 mbar, preferably in the range of 15 mbar to 150 mbar.

[0130] Distillation of the first gas stream yields a first overhead stream. This first overhead stream contains the at least one alkyl(meth)acrylate and the at least one other alkyl ester that were already present in the first gas stream.

[0131] The first overhead stream may also contain further components. In particular, the first overhead stream contains at least one further component present in the first gas stream, which has a lower or the same boiling point as the at least one alkyl(meth)acrylate and the at least one further alkyl ester. Therefore, the first overhead stream typically contains at least one further component selected from the group consisting of methyl propionate, ethyl propionate, methyl isobutyrate, methyl pivalate, methyl 3-methoxyisobutyrate, and

[0132] Dicarboxylic acid diesters.

[0133] Similarly, the first headstream may contain residues of at least one benzene derivative. 202000044 17

[0134] For example, the first overhead stream obtained by distillation contains 60 to 99 wt.%, preferably 80 to 98 wt.%, of the at least one alkyl(meth)acrylate, in each case based on the total weight of the first overhead stream.

[0135] For example, the first overhead stream obtained by distillation contains 0.01 to 5 wt.%, preferably 0.1 to 1 wt.%, of the at least one further alkyl ester, in each case based on the total weight of the first overhead stream.

[0136] For example, the first overhead stream obtained by distillation contains 0.01 to 5 wt.%, preferably 0.1 to 3 wt.%, of at least one further component, in each case based on the total weight of the first overhead stream.

[0137] Furthermore, a first bottom stream is obtained. Within the scope of the present invention, a "bottom stream" is understood to mean not only a bottom product that is continuously removed from the distillation, in particular from the reactor, but also a bottom product that, for example during batch operation, remains in the reactor as a distillation residue and is only removed from the reactor at a later time.

[0138] The first gas stream contains at least one component different from the at least one alkyl(meth)acrylate and the at least one other alkyl ester. This component is usually at least one of the at least one other component contained in the first gas stream. In particular, this component usually has a higher boiling point than the at least one alkyl(meth)acrylate and the at least one other alkyl ester contained in the first gas stream. For example, this component is selected from the group consisting of sulfur-containing compounds, oligomers, and dimers. The specifications and preferences previously described for the sulfur-containing compounds, oligomers, and dimers contained in the first gas stream apply accordingly to the sulfur-containing compounds, oligomers, and dimers.

[0139] The first swamp stream therefore preferentially contains sulfur-containing compounds, oligomers and / or dimers.

[0140] Furthermore, the first sump stream contains at least one benzene derivative.

[0141] In step c) of the process according to the invention, the liquid first stream obtained in step b) is mixed with a further stream containing alkyl(meth)acrylate to obtain a mixed stream. The further stream is part of an alkyl(meth)acrylate manufacturing process. The mixed stream comprises the liquid first stream and the further stream. 202000044 18

[0142] For example, up to 20 wt.%, preferably up to 10 wt.%, particularly preferably up to 5 wt.% of the liquid first stream is mixed with the further stream, based on the total weight of the mixed stream.

[0143] The subsequent stream, with which the liquid first stream is mixed, contains alkyl(meth)acrylate. This subsequent stream may contain exactly one alkyl(meth)acrylate or a mixture of two or more alkyl(meth)acrylates. Exactly one alkyl(meth)acrylate is preferred. The embodiments and preferences previously described for the at least one alkyl(meth)acrylate contained in the first gas stream and the liquid first stream apply accordingly to the alkyl(meth)acrylate contained in the subsequent stream. The alkyl(meth)acrylate is, for example, selected from the group consisting of Ci-C4 alkyl(meth)acrylates. Methyl(meth)acrylate is particularly preferred as the alkyl(meth)acrylate contained in the subsequent stream.

[0144] The at least one alkyl(meth)acrylate contained in the liquid first stream preferably comprises the same alkyl(meth)acrylate as the further stream contains.

[0145] According to the invention, it is preferred that, based on the total weight of the at least one alkyl(meth)acrylate contained in the liquid first stream, at least 80 wt.%, preferably at least 90 wt.% of the at least one alkyl(meth)acrylate contained in the liquid first stream is the same alkyl(meth)acrylate as the alkyl(meth)acrylate contained in the further stream.

[0146] The additional stream is part of an alkyl(meth)acrylate production process, in particular a methyl(meth)acrylate production process. The additional stream can, for example, be part of a C3 process. It is also possible that the additional stream is part of a C2 process. Furthermore, the additional stream can be part of a C4 process. Preferably, the additional stream is part of a Cs process.

[0147] A preferred method according to the invention is therefore also a method in which the alkyl(meth)acrylate manufacturing process, of which the further current in step e) is a part, is a methyl methacrylate manufacturing process selected from the group consisting of a C2, a C3 and a C4 process.

[0148] The further stream may contain additional components. For example, the further stream contains at least one additional component selected from the group consisting of methyl propionate and methyl isobutyrate.

[0149] If the further stream is part of a C2 process, then the further stream contains at least one additional component selected from the group consisting of methyl propionate, 202000044 19

[0150] Methyl isobutyrate, isobutyraldehyde dimethyl acetal, methacrolein dimethyl acetal, isobutanal, isobutenol, 2-methoxyacetone, 2-methoxyisopropanol and methyl (meth)acrylate dimers.

[0151] If the further stream is part of a Cs process (ACH process), then the further stream contains at least one additional component selected from the group consisting of methyl isopropionate, methyl isobutyrate, methyl 3-methoxyisobutyrate, diacetyl, methacrylonitrile, methyl hydroxyisobutyrate, methyl formate, formic acid and methacrylic acid.

[0152] If the subsequent stream is part of a C4 process, then the subsequent stream contains at least one additional component selected from the group consisting of methyl propionate, methyl isobutyrate, isobutyraldehyde dimethyl acetal, isobutanol, acetone,

[0153] Pyruvic acid methyl ester, diacetyl, ethyl methacrylate, isopropyl methacrylate, methyl tert-butyl ether, dimethylfuran and methacrylic acid.

[0154] The liquid first stream can be mixed with the further stream using methods known to those skilled in the art. For example, and preferably according to the invention, the liquid first stream is fed into a plant for the production of an alkyl(meth)acrylate, which contains the further stream. The resulting mixed stream is then preferably also included in the plant for the production of an alkyl(meth)acrylate. The mixed stream is then preferably also part of the alkyl(meth)acrylate production process.

[0155] A preferred method is therefore one in which the mixed stream obtained in step c) is part of the alkyl(meth)acrylate manufacturing process.

[0156] The mixed stream comprises the liquid first stream and the subsequent stream. Therefore, the mixed stream typically includes the same components that were present in both the liquid first stream and the subsequent stream. Thus, the mixed stream typically includes the at least one alkyl(meth)acrylate, the at least one further alkyl ester, the alkyl(meth)acrylate, and optionally the additional components, the at least one benzene derivative, and / or the at least one further component.

[0157] In step d), the mixed stream obtained in step c) is distilled to obtain a bottom stream and an overhead stream. The bottom stream contains the alkyl(meth)acrylate, and the overhead stream contains at least one other alkyl ester.

[0158] The distillation of the mixed stream in step d) can be carried out using methods and reactors known to those skilled in the art. For example, the mixed stream can be transferred to a first distillation column and / or a first rectification column. Preferably, the first distillation column and / or the first rectification column is part of the alkyl(meth)acrylate production process. 202000044 20

[0159] According to the invention, in the distillation step d) a bottom stream is obtained which contains the alkyl(meth)acrylate and a top stream which contains the at least one further alkyl ester.

[0160] In the distillation step d), components present in the mixed stream that have a lower boiling point than the at least one alkyl(meth)acrylate are typically collected in the overhead stream. Components present in the mixed stream that have the same or a higher boiling point than the at least one alkyl(meth)acrylate are collected in the bottom stream. Therefore, the distillation in step d) is also referred to as low-boiling distillation. It is usually carried out in a low-boiling column of the alkyl(meth)acrylate production process.

[0161] The headstream contains at least one additional alkyl ester. Furthermore, the headstream may contain residues of at least one alkyl(meth)acrylate.

[0162] In the context of the present invention, “residues of alkyl(meth)acrylate” are understood to mean, for example, in the range of 25 wt.% to 30 wt.% of the at least one alkyl(meth)acrylate, based on the total weight of the headstream.

[0163] The headstream can, for example, be recycled into the alkyl(meth)acrylate manufacturing process.

[0164] The bottom stream contains at least one alkyl(meth)acrylate. The bottom stream may also contain residues of at least one other alkyl ester.

[0165] The term "residues of at least one further alkyl ester" refers, for example, to amounts in the range of 0.1 ppm by weight to 1% by weight of the at least one further alkyl ester, based on the total weight of the at least one further alkyl ester contained in the mixed stream.

[0166] Within this context, "residues of at least one further alkyl ester" also means that the mixed stream contains a mixture of two or more further alkyl esters, wherein at least one of the further alkyl esters has a lower boiling point than the at least one alkyl(meth)acrylate and at least one of the further alkyl esters has a higher boiling point than the at least one alkyl(meth)acrylate, and the top stream then contains the further alkyl ester with the lower boiling point, while the bottom stream contains the further alkyl ester with the higher boiling point.

[0167] For example, the mixed stream may contain at least one further alkyl ester, methyl propionate and methyl 3-methoxyisobutyrate. Then the overhead stream obtained from the distillation in step d) may contain methyl propionate as at least one further alkyl ester, and the one in 202000044 21

[0168] Step d) obtained bottom stream, for example methyl 3-methoxyisobutyrate as residues of at least one further alkyl ester.

[0169] Preferably, the bottom stream additionally contains residues of at least one further alkyl ester and following step d) the following step d1) is carried out: d1) Distillation of the bottom stream obtained in step d) to obtain a second overhead stream containing alkyl(meth)acrylate and a second bottom stream containing the at least one further alkyl ester.

[0170] A preferred method according to the invention is therefore also one in which the bottom stream obtained in step d) additionally contains residues of the at least one further alkyl ester and in which the following step d1) is carried out after step d): d1) Distillation of the bottom stream obtained in step d) to obtain a second overhead stream containing alkyl(meth)acrylate and a second bottom stream containing the at least one further alkyl ester.

[0171] The distillation in step d1) can be carried out in reactors known to those skilled in the art using methods known to them. For example, the bottoms stream obtained in step d) can be transferred to a second distillation column and / or a second rectification column. Preferably, the second distillation column and / or the second rectification column is part of the alkyl(meth)acrylate production process.

[0172] During the distillation in step d1), components present in the bottom stream with a higher boiling point than the at least one alkyl(meth)acrylate in the bottom stream are typically obtained. Components with the same or a lower boiling point than the at least one alkyl(meth)acrylate are obtained in the overhead stream. Therefore, the distillation in step d1) is also referred to as high-boiling distillation. It usually takes place in a high-boiling column of the alkyl(meth)acrylate production process.

[0173] According to the invention, in the distillation step d1) a second overhead stream containing alkyl(meth)acrylate and a second bottom stream containing at least one further alkyl ester are obtained.

[0174] The second sump stream may also contain further components, such as the additional component possibly present in the mixed stream and / or at least one other component. In particular, the second sump stream may contain sulfur-containing compounds as an additional component.

[0175] The second sump stream can be further processed. For example, the second sump stream can be processed with an acidic stream. 202000044 22

[0176] For example, the second sump stream can be treated with a stream containing ammonium hydrogen sulfate. In this ammonium hydrogen sulfate stream, the sulfur-containing compounds can then be reacted by partial oxidation.

[0177] A preferred method is therefore one in which the second sump stream is reacted with an ammonium hydrogen sulfate-containing stream to obtain a sulfuric acid-containing mixture.

[0178] It is particularly preferred that the ammonium hydrogen sulfate-containing stream originates from a Cs process for the production of methyl(meth)acrylate or is part of a Cs process for the production of methyl(meth)acrylate.

[0179] The second sump stream can additionally or alternatively, preferably alternatively, be mixed with a stream containing (meth)acrylic acid.

[0180] A method in which the second sump stream is mixed with a stream containing (meth)acrylic acid is therefore also preferred.

[0181] According to the invention, it is preferred that the (meth)acrylic acid-containing stream originates from a C4 process for the production of methyl(meth)acrylate or is part of a C4 process for the production of methyl(meth)acrylate.

[0182] The second sump stream can additionally or alternatively, preferably alternatively, be mixed with a stream containing 3-methoxyisobutyric acid methyl ester and / or methyl propionate.

[0183] According to the invention, it is preferred that the methoxyisobutyric acid methyl ester and / or methyl propionate-containing stream originates from or is part of a C2 process for the production of methyl(meth)acrylate. The C2 process is known as such to those skilled in the art.

[0184] In step e) of the process according to the invention, the overhead stream obtained in step d) is at least partially hydrolyzed. In this process, the at least one further alkyl ester contained in the overhead stream is at least partially hydrolyzed to yield an alkyl acid.

[0185] The head current obtained in step d) can be hydrolyzed using methods known to those skilled in the art. For example, hydrolysis can be carried out using an acidic ion exchanger. It is also possible to carry out the hydrolysis with an acid, for example, sulfuric acid.

[0186] To at least partially hydrolyze the overhead stream obtained in step d), the overhead stream can be removed from the alkyl(meth)acrylate production process. It is also possible, and preferred according to the invention, that the at least partial hydrolysis in step e) takes place within the alkyl(meth)acrylate production process of which the further stream is a part.

[0187] A method is therefore also preferred according to the invention in which the at least partial hydrolysis in step e) takes place within the alkyl(meth)acrylate manufacturing process, of which the further stream is a part.

[0188] If the alkyl(meth)acrylate manufacturing process includes, for example, an esterification step, it is preferred according to the invention that the hydrolysis in step e) takes place in the presence of an acid in the alkyl(meth)acrylate manufacturing process.

[0189] A preferred method is therefore one in which at least partial hydrolysis takes place in step e) within the alkyl(meth)acrylate manufacturing process in the presence of an acid in the alkyl(meth)acrylate manufacturing process.

[0190] For example, the alkyl(meth)acrylate production process is a Cs process. In that case, the hydrolysis in step e) can, for example, take place in the region of the amidation of acetone cyanohydrin. The alkyl acid obtained during the hydrolysis of at least one further alkyl ester can then be separated from the alkyl(meth)acrylate production process using methods known to those skilled in the art.

[0191] Preferably, the overhead stream obtained in step d) is condensed and subjected to phase separation. In the phase separation, an organic phase and an aqueous phase are obtained. The at least one further alkyl ester preferably has a higher solubility in the aqueous phase than the alkyl(meth)acrylate. In the aqueous phase, the at least one further alkyl ester is hydrolyzed according to step e).

[0192] In step d) of the process according to the invention, the alkyl(meth)acrylate is obtained.

[0193] In particular, the alkyl(meth)acrylate is obtained in the second overhead stream in step d1). The alkyl(meth)acrylate obtained according to the invention essentially contains the alkyl(meth)acrylate that is obtained in the alkyl(meth)acrylate production process of which the further stream is a part.

[0194] According to the invention, the liquid first stream contains at least one alkyl(meth)acrylate, at least one further alkyl ester, and at least one benzene derivative, as well as optionally at least one further component. The process according to the invention enables the isolation of alkyl(meth)acrylate that is essentially free of these other components contained in the liquid first stream.

[0195] The alkyl(meth)acrylate obtained in the process according to the invention therefore consists essentially of exactly one alkyl(meth)acrylate. The properties described above apply to the alkyl(meth)acrylate.

[0196] Descriptions and preferences. Particularly preferred is the obtained alkyl(meth)acrylate methyl(meth)acrylate, which contains at most 0.1 wt.%, preferably at most 0.01 wt.%, of further components and / or of the at least one alkyl ester.

[0197] The alkyl(meth)acrylate isolated according to the invention can, for example, be used in the process known to those skilled in the art for the production of alkyl(meth)acrylate oligomers and / or alkyl(meth)acrylate polymers by polymerization.

[0198] The present invention therefore also relates to a process for the production of alkyl(meth)acrylate oligomers and / or alkyl(meth)acrylate polymers by polymerization of an alkyl(meth)acrylate isolated in a process according to the invention.

[0199] The alkyl(meth)acrylate isolated according to the invention can be used, for example, to produce (meth)acrylic acid by hydrolysis of the alkyl(meth)acrylate.

[0200] The present invention therefore also relates to a process for the production of (meth)acrylic acid by hydrolysis of an alkyl(meth)acrylate isolated in a process according to the invention.

[0201] Methods for producing (meth)acrylic acid from alkyl(meth)acrylates are known to those skilled in the art.

[0202] Furthermore, the alkyl(meth)acrylate isolated according to the invention can be used to produce alkyl(meth)acrylate monomers by transesterification of the alkyl(meth)acrylate according to the invention.

[0203] Suitable transesterification processes are known to those skilled in the art.

[0204] The present invention therefore also relates to a process for the production of alkyl(meth)acrylate monomers by transesterification of an alkyl(meth)acrylate isolated in a process according to the invention.

[0205] A further object of the present invention is a method for isolating alkyl(meth)acrylates comprising the following steps c1) to e): c1) Mixing a liquid first stream containing at least one alkyl(meth)acrylate, at least one further alkyl ester and at least one benzene derivative, wherein the liquid first stream is obtainable by thermal cleavage of at least one polymer composition, with a further stream, wherein the further stream is part of an alkyl(meth)acrylate manufacturing process, to obtain a mixed stream comprising the liquid first stream and the further stream; d) Distilling the mixed stream obtained in step c) to obtain a bottom stream containing alkyl(meth)acrylate and an overhead stream containing the at least one further alkyl ester; e) At least partially hydrolyzing the overhead stream obtained in step d).wherein at least one further alkyl ester is at least partially hydrolyzed to obtain an alkyl acid.

[0206] In step c1), a liquid first stream is mixed with another stream, the liquid first stream being obtained by thermal cracking of at least one polymer composition. The previously described specifications and preferences apply to the polymer composition.

[0207] Preferably, the liquid first stream is therefore obtainable by the following steps a) and b): a) thermal cracking of at least one polymer composition containing at least one poly(alkyl(meth)acrylate) to obtain a first gas stream containing at least one alkyl(meth)acrylate, at least one further alkyl ester and at least one benzene derivative, b) condensation of the first gas stream obtained in step a) to obtain a liquid first stream containing the at least one alkyl(meth)acrylate, the at least one further alkyl ester and at least one benzene derivative.

[0208] The explanations and preferences described above apply accordingly to steps a) and b). The explanations and preferences described above for step c) also apply accordingly to step c1).

[0209] The above-described explanations apply accordingly to steps d) and e).

Claims

202000044 26 Claims 1. A process for isolating alkyl(meth)acrylates comprising the following steps a) to e): a) thermal cleavage of at least one polymer composition containing at least one poly(alkyl(meth)acrylate) to obtain a first gas stream containing at least one alkyl(meth)acrylate, at least one further alkyl ester, and at least one benzene derivative; b) condensation of the first gas stream obtained in step a) to obtain a liquid first stream containing the at least one alkyl(meth)acrylate, the at least one further alkyl ester, and at least one benzene derivative; c) mixing of the liquid first stream obtained in step b) with a further stream containing alkyl(meth)acrylate, the further stream being part of an alkyl(meth)acrylate manufacturing process, to obtain a mixed stream comprising the liquid first stream and the further stream; d) distillation of the mixed stream obtained in step c) to obtain a bottoms stream.containing the alkyl(meth)acrylate, and a headstream containing the at least one further alkyl ester, e) at least partial hydrolysis of the headstream obtained in step d), wherein the at least one further alkyl ester is at least partially hydrolyzed to obtain an alkyl acid.

2. Method according to claim 1, characterized in that the polymer composition in step a) contains at least one further component selected from the group consisting of polymers other than poly(alkyl(meth)acrylate), pigments, dyes, fillers, additives, regulators, initiators, impact strengtheners, release agents and UV additives.

3. Method according to claim 1 or 2, characterized in that the at least one alkyl(meth)acrylate contained in the first gas stream in step a) is selected from the group consisting of Ci- to C4-alkyl(meth)acrylates.

4. Method according to one of claims 1 to 3, characterized in that the at least one further alkyl ester is selected from the group consisting of methyl propionate, methyl isobutyrate, methyl pivalate, methyl 3-methoxyisobutyrate and dicarboxylic acid diesters.

5. Method according to one of claims 1 to 4, characterized in that the first gas stream contains at least one further component selected from the group consisting of (meth)acrylic acid, sulfur-containing compounds, oligomers and dimers. 202000044 27 6. A process according to any one of claims 1 to 5, characterized in that the first gas stream is distilled after step a) and before step b) to obtain a first overhead stream containing the at least one alkyl(meth)acrylate and the at least one further alkyl ester, and a first bottom stream containing at least one component different from the at least one alkyl(meth)acrylate and the at least one further alkyl ester, wherein the first overhead stream is condensed in step b).

7. A process according to any one of claims 1 to 6, characterized in that the bottom stream obtained in step d) additionally contains residues of at least one further alkyl ester and that following step d) the following step d1) is carried out: d1) Distillation of the bottom stream obtained in step d) to obtain a second a top stream containing alkyl(meth)acrylate and a second bottom stream containing at least one further alkyl ester.

8. Method according to claim 7, characterized in that the second sump stream is reacted with an ammonium hydrogen sulfate-containing stream to obtain a sulfuric acid-containing mixture.

9. Method according to claim 7, characterized in that the second sump stream is mixed with a stream containing (meth)acrylic acid.

10. A method according to any one of claims 1 to 9, characterized in that the alkyl(meth)acrylate manufacturing process, of which the further current in step c) is a part, is a methyl methacrylate manufacturing process selected from the group consisting of a C2, a C3 and a C4 process.

11. Method according to one of claims 1 to 10, characterized in that the at least partial hydrolysis in step e) takes place within the alkyl(meth)acrylate manufacturing process of which the further stream is a part.

12. Method according to claim 11, characterized in that the at least partial hydrolysis in step e) within the alkyl(meth)acrylate manufacturing process takes place in the presence of an acid in the alkyl(meth)acrylate manufacturing process.

13. Process for the production of alkyl(meth)acrylate oligomers and / or alkyl(meth)acrylate polymers by polymerization of an alkyl(meth)acrylate isolated in a process according to any one of claims 1 to 12.

14. Process for the production of (meth)acrylic acid by hydrolysis of an alkyl(meth)acrylate isolated in a process according to any one of claims 1 to 12. 202000044 28 15. Process for the production of alkyl(meth)acrylate monomers by transesterification of an alkyl(meth)acrylate isolated in a process according to any one of claims 1 to 12.