Recycled MMA and its use in continuous polymerization processes

Abstract

The present invention relates to a novel method for producing poly(alkyl(meth)acrylate). In this method, first, a polymer composition containing at least one poly(alkyl(meth)acrylate) is thermally decomposed to obtain at least one alkyl(meth)acrylate and at least one further alkyl ester. Subsequently, this mixture is condensed and mixed with the flow of the poly(alkyl(meth)acrylate) production method. Then, polymerization is performed to obtain poly(alkyl(meth)acrylate).

Description

Technical Field

[0001] The present invention relates to a novel process for producing poly(alkyl (meth)acrylate). In this process, first, a polymer composition containing at least one poly(alkyl (meth)acrylate) is pyrolyzed to obtain at least one alkyl (meth)acrylate and at least one further alkyl ester. Subsequently, this mixture is condensed and mixed with the stream from the poly(alkyl (meth)acrylate) production process. Then, poly(alkyl (meth)acrylate) is obtained by polymerization.

[0002] Background Art Alkyl (meth)acrylates, especially methyl methacrylate (MMA), have a wide range of uses.

[0003] MMA is used especially in the production of polymethyl methacrylate (PMMA), which is excellent in terms of excellent optical properties, especially high transparency and weather resistance (acrylic glass), as well as other physical properties. Its fields of use include glazing and facades in architecture, lighting members and vehicle tail lights in the automotive field, aircraft windows, decorative members, design members or furniture members, flat screens and displays, soundproof walls and electric light advertisements.

[0004] During the processing of PMMA, manufacturing waste, so-called post-industrial waste, is generated. Post-industrial waste includes, in particular, the shavings and general waste generated during the manufacturing process as well as during subsequent processing and during the extrusion or casting of PMMA molding materials and after them.

[0005] Products manufactured from PMMA molding materials, such as greenhouse glazing, soundproofing barriers, aircraft glazing, spitproof glass and displays, and especially colored molding materials used in the automotive sector (e.g., light guides, taillights and body parts), are typically discarded after use by customers and disposed of in landfills along with other types of plastic waste, or heat-treated and incinerated at power plants. Such waste materials are usually referred to as post-consumer waste. Furthermore, post-consumer waste such as electrical scrap and discarded equipment scrap often contains PMMA as an impurity in the sorting process, in addition to other plastics and additives. The proportion of PMMA constituent units in the PMMA polymer contained in the waste varies, ranging from 75% to over 99%.

[0006] PMMA, whether post-industrial or post-consumer waste, can essentially be depolymerized into its monomers and reused as so-called recycled MMA. Conventional technologies describe various methods for depolymerization, such as metal baths, rotary tubular furnaces, fluidized bed reactors, or extruders.

[0007] For example, publications such as German Patent No. 642289, U.S. Patent No. 2,030,901, German Patent Application Publication No. 3146194, European Patent No. 3635043, and U.S. Patent No. 2,470,361 describe the thermal depolymerization of PMMA and, in some cases, the subsequent purification of the resulting monomers, for example, by distillation.

[0008] The thermally catalyzed depolymerization of PMMA and the subsequent purification of the obtained monomers are described, for example, in U.S. Patent No. 2,858,255, West German Patent Application Publication No. 2132716, International Publication No. 2019 / 003253, German Patent Application Publication No. 19729065, and European Patent No. 2895576.

[0009] Similarly, the depolymerization of PMMA is known to be carried out in a fluidized bed, sometimes together with other polymers. This is described, for example, in U.S. Patent No. 5,663,420, International Publication No. 2000 / 017149, and U.S. Patent No. 8,304,573.

[0010] U.S. Patent No. 3,494,958 describes a thermal depolymerization method for PMMA. The resulting monomer can then be purified by distillation. U.S. Patent No. 3,494,958 states that the purification can be carried out in a manner similar to that of the ACH process (C3 method), for example.

[0011] The methods described above often result in insufficient monomer yields. Furthermore, while the methods described in the prior art yield recycled alkyl(meth)acrylate, its purity is insufficient to produce poly(alkyl(meth)acrylate) of sufficient quality. This is particularly true when poly(methyl methacrylate) containing a large amount of additives, such as impact modifiers or pigments and / or other polymers, is used in the depolymerization process.

[0012] Consequently, the quality of recycled alkyl (meth)acrylate, particularly recycled MMA (recycled MMA), is clearly different from that of pure alkyl (meth)acrylate, especially pure MMA obtained directly from MMA manufacturing processes. The MMA content of recycled MMA typically does not meet the commercially available specification of 99.8% by weight purity for pure MMA. In many cases, it contains several hundred to several thousand ppm of interfering substances, which adversely affect the production of high-purity PMMA granules from recycled MMA.

[0013] Depending on the type of post-industrial and / or post-consumer waste used in the manufacture of recycled MMA, recycled MMA may also have unacceptable discoloration and / or odor. The latter may be due, for example, to sulfur-containing modifiers and other additives that are released during thermal depolymerization and can be converted into strongly odorous mercaptans.

[0014] Therefore, currently, recycled MMA from the depolymerization process can be directly used as a raw material for continuous PMMA polymerization.

[0015] Recycled alkyl (meth)acrylates have a limited range of applications due to their low purity. In particular, they can only be used to a limited extent in the manufacture of poly(alkyl (meth)acrylates).

[0016] Popescu et al. “The characterization of recycled PMMA”, Journal of Alloys and Compounds, vol. 483, pp. 432-436 describes the physical properties of PMMA produced from recycled MMA manufactured by the depolymerization of PMMA.

[0017] Kikuchi et al. “Design of recycling system for poly(methyl methacrylate) (PMMA). Part 1: recycling scenario analysis” Int. J. Life Cycle Assess (2014) 19:120-129 describes the depolymerization of PMMA and the purification of the resulting recycled MMA by distillation.

[0018] German Patent Application Publication No. 102007045156 describes a vented extruder for degassing polymer materials. The use of recycled MMA is not disclosed.

[0019] assignment Therefore, there was a need to provide an improved method for producing poly(alkyl(meth)acrylate) that had none or only minor drawbacks of the methods described in the prior art.

[0020] In addition, an object of the present invention was to use recycled alkyl(meth)acrylate, which has a lower purity than alkyl(meth)acrylate produced by an alkyl(meth)acrylate manufacturing method, in at least a portion of the production of poly(alkyl(meth)acrylate) according to specifications. It is desirable that any interfering substances contained can be effectively separated in the poly(alkyl(meth)acrylate) manufacturing method.

[0021] In particular, the method should ideally reduce the amount of waste products that have a climate impact, such as CO2.

[0022] solution The problem concerns a method for producing poly(alkyl(meth)acrylate), a) A step of thermally decomposing 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 and at least one further alkyl ester, b) A step of condensing the first gas stream obtained in step a) to obtain a liquid first stream containing at least one alkyl (meth)acrylate and at least one further alkyl ester, c) A step of mixing the liquid first stream obtained in step b) with a further stream which is part of a poly(alkyl(meth)acrylate) production method and contains at least one further alkyl(meth)acrylate, to obtain a mixed stream containing the liquid first stream and the further stream. e) A step of partially polymerizing the mixed flow obtained in step c) to obtain a syrup containing at least one partially polymerized alkyl (meth)acrylate, at least one further partially polymerized alkyl (meth)acrylate, and at least one further alkyl ester. f) Step of polymerizing the syrup obtained in step e) using a vented extruder to obtain a polymer mixture containing poly(alkyl (meth)acrylate). g) Step of degassing the syrup obtained in step e) and / or the polymer mixture obtained in step f) using a vented extruder to obtain a condensate stream containing at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, their oligomers and at least one further alkyl ester. h) Step of separating at least one further alkyl ester from the condensate stream obtained in step g) to obtain an alkyl (meth)acrylate stream containing at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate is solved by a method comprising.

[0023] Moreover, this problem is a method for producing poly(alkyl (meth)acrylate), a) Step of thermally decomposing 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 and at least one further alkyl ester, wherein at least one alkyl (meth)acrylate contained in the first gas stream is selected from the group consisting of C1-C4-alkyl (meth)acrylates. b) Step of condensing the first gas stream obtained in step a) to obtain a liquid first stream containing at least one alkyl (meth)acrylate and at least one further alkyl ester. c) Step of mixing the liquid first stream obtained in step b) with a further stream which is part of a method for producing poly(alkyl (meth)acrylate) and contains at least one further alkyl (meth)acrylate to obtain a mixed stream containing the liquid first stream and the further stream, wherein a maximum of 50% by weight of the liquid first stream is mixed with the further stream based on the total weight of the obtained mixed stream. e) Partially polymerizing the mixed stream obtained in step c) to obtain a syrup containing at least one partially polymerized alkyl (meth) acrylate, at least one further partially polymerized alkyl (meth) acrylate, and at least one further alkyl ester; f) Polymerizing the syrup obtained in step e) in a vented extruder to obtain a polymer mixture containing poly(alkyl (meth) acrylate); g) Degassing the syrup obtained in step e) and / or the polymer mixture obtained in step f) in a vented extruder to obtain a condensate stream containing at least one alkyl (meth) acrylate, at least one further alkyl (meth) acrylate, their oligomers, and at least one further alkyl ester; h) Separating at least one further alkyl ester from the condensate stream obtained in step g) to obtain an alkyl (meth) acrylate stream containing at least one alkyl (meth) acrylate and at least one further alkyl (meth) acrylate It is solved by a method including.

[0024] Surprisingly, it has been found that poly(alkyl (meth) acrylate) with a purity > 99% can be obtained by the method according to the invention.

[0025] The poly(alkyl (meth) acrylate) produced by the method according to the invention, especially polymethyl (meth) acrylate, has a purity sufficient for the production of colored poly(alkyl (meth) acrylate), especially colored polymethyl (meth) acrylate.

[0026] Partially, the poly(alkyl(meth)acrylate), particularly polymethyl(meth)acrylate, produced by the method according to the present invention has a purity high enough to be suitable for producing extremely colorless and clear poly(alkyl(meth)acrylate), especially colorless and clear polymethyl(meth)acrylate. In addition, the poly(alkyl(meth)acrylate) produced by the method according to the present invention has high transmittance and low yellowness at 450 nm, while also having a sufficiently high Vicat softening temperature.

[0027] In particular, the method according to the present invention remarkably efficiently removes by-products such as further alkyl esters, so that even if their standard boiling points differ from the standard boiling point of the alkyl (meth)acrylate by only a small amount, for example ±1 K (Kelvin), preferably ±0.6 K, they do not contaminate the produced poly(alkyl (meth)acrylate). This is due in particular to steps g) and h) of the method.

[0028] Furthermore, additives and chain transfer agents that may be contained in the polymer composition, as well as products such as mercaptans obtained from them during the thermal decomposition of the polymer composition, can be easily and inexpensively separated by the method according to the present invention. For example, the poly(alkyl(meth)acrylate) obtained by the method according to the present invention contains up to 0.5% of by-products. Based on the method according to the present invention and the efficient separation of by-products made possible thereby, the poly(alkyl(meth)acrylate) produced by the present invention has no odor or only a very small odor, despite the presence of mercaptans in the polymer composition.

[0029] In addition, the method according to the present invention and the poly(alkyl(meth)acrylate) produced by the method according to the present invention result in lower CO2 emissions and, consequently, a particularly low carbon footprint. This is achieved, in particular, by the fact that the method according to the present invention allows for the use of polymer compositions with relatively high proportions of additives and other impurities, and that the raw material source is recyclable.

[0030] Therefore, the method according to the present invention is superior to previously known methods because it satisfies the requirement of being reusable within a circulating chain (circular chain).

[0031] In addition, the by-products obtained during depolymerization can be reused after separation, thereby further reducing the carbon footprint and, consequently, the global warming potential (GWP).

[0032] The method according to the present invention will be described in more detail below.

[0033] In step a) of the method of the present invention, at least one polymer composition is thermally decomposed to obtain a first gas stream. The at least one polymer composition contains at least one poly(alkyl(meth)acrylate). The gas stream contains at least one alkyl(meth)acrylate and at least one further alkyl ester.

[0034] In the context of this invention, the term "at least one polymer composition" may mean a single polymer composition or a mixture of two or more polymer compositions. According to this invention, a mixture of two or more polymer compositions is preferred.

[0035] At least one polymer composition contains at least one poly(alkyl(meth)acrylate).

[0036] In the context of this invention, "at least one poly(alkyl(meth)acrylate)" may mean a single poly(alkyl(meth)acrylate) or a mixture of two or more poly(alkyl(meth)acrylates). In the context of this invention, "poly(alkyl(meth)acrylate)" is understood to mean polymers and copolymers of alkyl(meth)acrylates.

[0037] Alkyl (meth)acrylate copolymers are, for example, copolymers of alkyl (meth)acrylate with 1-alkenes, other alkyl (meth)acrylates, (meth)acrylic acid, styrene, polyester, vinyl ester, and / or polyurethane (meth)acrylate.

[0038] Several 1-alkenes that can copolymerize with alkyl (meth)acrylates are known, including, for example, 1-hexene, 1-heptene, vinylcyclohexane, 3,3-dimethyl-1-propene, 3-methyl-1-diisobutylene, and 4-methylpentene-1.

[0039] In the context of this invention, the term "styrene" is understood to mean not only styrene itself, but also substituted styrenes such as α-methylstyrene, α-ethylstyrene, vinyltoluene, p-methylstyrene, monochlorostyrene, dichlorostyrene, and tribromostyrene.

[0040] Suitable polyesters are known in themselves and can be advantageously obtained by polycondensation or ring-opening polymerization.

[0041] In the context of this invention, "polyurethane (meth)acrylate" is understood to mean (meth)acrylates bonded to each other via urethane groups. These can be obtained by reacting hydroxyalkyl (meth)acrylates with polyisocyanates and polyoxyalkylenes having at least two hydroxyl functional groups. Instead of hydroxyalkyl (meth)acrylates, esters of (meth)acrylic acid with oxiranes such as ethylene oxide or propylene oxide, or the corresponding oligo-oxiranes or polyoxiranes, can also be used. Suitable polyurethane (meth)acrylates are known in themselves.

[0042] At least one polymer composition may be derived from, for example, manufacturing waste. In this case, the polymer composition is typically so-called post-industrial waste, such as sprues, extrusion start-up clumps, dust, chips, partially polymerized polymer syrup, scraps, sheet shavings, sheets, films, blocks, defective semi-finished products, molded parts with shape defects, or waste from injection molding.

[0043] Similarly, at least one polymer composition may be derived from so-called post-consumer waste, which typically includes, for example, electrical scrap and discarded equipment scrap, greenhouses, exhibition structures, store fixtures, or illuminated advertising waste.

[0044] Therefore, at least one polymer composition typically contains at least one further component. The at least one further component is selected from the group consisting of polymers other than poly(alkyl(meth)acrylate), pigments, dyes, fillers, auxiliary agents, modifiers, initiators, impact modifiers, release agents, and UV additives.

[0045] Therefore, it is also preferable 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, auxiliary agents, modifiers, initiators, impact modifiers, release agents, and UV additives.

[0046] Polymers distinct from poly(alkyl(meth)acrylates) include, in particular, polymers that can typically be used in blends with poly(alkyl(meth)acrylates). These include, for example, polyethylene, polyvinyl chloride, polystyrene, polyamides, and biopolymers such as α-polysaccharides (starch), β-polysaccharides (cellulose, chitin), lignin, and polylactic acid.

[0047] The pigments are, for example, white, red, blue, green, and / or yellow inorganic pigments. Particularly preferred are white inorganic pigments such as titanium dioxide.

[0048] The dye is, for example, an organic dye known to those skilled in the art.

[0049] Typical fillers are, in particular, mineral-based fillers. Mineral-based fillers are advantageously selected from the group consisting of calcium carbonate, barium sulfate, quartz, quartz powder, precipitated silica, pyrolytic silicic acid, corundum, glass beads, and cristobalite.

[0050] Typical excipients are well known and are selected from the group consisting of, for example, plasticizers, paraffins, and / or inhibitors.

[0051] As plasticizers, esters, polyols, oils, low molecular weight polyethers, or phthalates are advantageously used.

[0052] The paraffins that may be included in the polymer composition are well known. For example, multiple paraffins with different melting points may be included at different concentrations.

[0053] The group of inhibitors advantageously includes substituted phenols, hydroquinone derivatives, phosphines, and / or phosphites.

[0054] As modifiers, compounds that adjust chain length, particularly those known from radical polymerization, are considered. Typically, chain transfer agents include mercaptans such as n-dodecyl mercaptan, but polyvalent mercaptan compounds such as pentaerythritol tetrathioglycolate are also included.

[0055] Initiators are also well known and are selected from the group consisting of, for example, peroxides, azo compounds, persulfates, and mixtures thereof.

[0056] Impact modifiers are well known, and are, for example, polymer particles containing elastomers.

[0057] As release agents, long-chain wax acids such as stearic acid, palmitic acid, or lauric acid, as well as monohydric fatty alcohols or wax alcohols such as diethylene glycol monopropyl ether, should be considered.

[0058] UV stabilizers are particularly noteworthy as UV additives. Advantageously, UV stabilizers are selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, thioxanthonate derivatives (thioxanthonatederivaten), piperidinol carboxylic acid ester derivatives, and cinnamic acid ester derivatives.

[0059] The thermal decomposition of at least one polymer composition can be carried out according to methods known to those skilled in the art.

[0060] Pyrolysis can be carried out in pyrolysis reactors known to those skilled in the art. For example, pyrolysis can be carried out in pyrolysis reactors, extruders, rotary tubular furnaces, fluidized bed pyrolysis, metal baths and / or dry distillation.

[0061] The polymer composition may exist in solid or liquid form during thermal decomposition. If the polymer composition exists in solid form, it may exist as a pure solid. Similarly, the polymer composition may exist dispersed in a medium in solid form. The medium in which the polymer composition may be dispersed may be a solid such as quartz, metal chips, or diatomaceous earth. Similarly, the medium may be a gas such as nitrogen, or a liquid such as water or hydrocarbons. The medium may be a liquid at room temperature but may exist as a gas under the thermal decomposition conditions of step a).

[0062] Polymer compositions exist in a liquid (molten) form, for example, when thermal decomposition is carried out in an extruder.

[0063] The polymer composition, especially if it exists in solid form, may be mechanically ground before thermal decomposition, for example, so that the average particle size distribution is less than 6 mm (Qr, d50), preferably less than 1.5 mm (Qr, d50), or so that the particle size distribution is in the range of 0.1 mm (Qr, d50) to 6 mm (Qr, d50). Advantageously, the particle size distribution is measured by laser diffraction.

[0064] The temperature (T) during thermal decomposition in step a) is, for example, in the range of 240°C to 800°C, preferably in the range of 300°C to 500°C, and particularly preferably in the range of 325°C to 400°C.

[0065] The pressure during thermal decomposition 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.

[0066] Therefore, according to the present invention, a method is preferred in which the temperature during thermal decomposition in step a) is in the range of 240°C to 800°C and / or the pressure during thermal decomposition in step a) is in the range of 400 mbar to 500 bar.

[0067] The thermal decomposition in step a) can be carried out in the presence of a catalyst. Suitable catalysts for thermal decomposition are known and are selected from the group consisting of, for example, molten metals, peroxides, potassium salts such as potassium acetate, and alkali metal persulfates such as potassium persulfate. Lead and / or lead / tin eutectic mixtures are particularly suitable as the molten metal.

[0068] When the thermal decomposition in step a) is carried out in the presence of a catalyst, the decomposition in step a) is also called catalytic thermal decomposition.

[0069] Therefore, according to the present invention, a method in which the thermal decomposition in step a) is catalytic thermal decomposition is also preferred.

[0070] During thermal decomposition in step a), the poly(alkyl(meth)acrylate) is decomposed. This decomposition is also called depolymerization. Depolymerization itself is known to those skilled in the art. During depolymerization, the polymer is broken down into its monomer and oligomer units.

[0071] In other words, during thermal decomposition in step a), the poly(alkyl(meth)acrylate) is broken down into monomer and oligomer units. As mentioned above, 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 thermal decomposition.

[0072] In addition, at least one further alkyl ester is formed during the thermal decomposition of the polymer composition. In the context of this invention, "at least one further alkyl ester" may mean just one further alkyl ester or a mixture of two or more further alkyl esters. According to this invention, a mixture of two or more further alkyl esters is preferred.

[0073] Therefore, the first gas stream contains at least one alkyl (meth)acrylate and at least one further alkyl ester formed during thermal decomposition.

[0074] At least one alkyl(meth)acrylate is derived from poly(alkyl(meth)acrylate), as described above.

[0075] In the context of this invention, "at least one alkyl (meth)acrylate" may mean a single alkyl (meth)acrylate or a mixture of two or more alkyl (meth)acrylates. A mixture of two or more alkyl (meth)acrylates is preferred.

[0076] In the context of this invention, "alkyl (meth)acrylate" is understood to mean an alkyl ester of (meth)acrylic acid having 1 to 18, preferably 1 to 12, and particularly preferably 1 to 4 carbon atoms in the alkyl residue. The alkyl residue may be linear, cyclic, and / or branched. Furthermore, it may also have aromatic residues. In addition, the alkyl residue may have a heteroatom within the alkyl residue and / or be substituted with a heteroatom, for example, hydroxypropyl (meth)acrylate and / or hydroxyethyl (meth)acrylate.

[0077] For example, the alkyl (meth)acrylate according to the present invention is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, 1-methylethyl (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, polyethylene glycol (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, vinyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, and lauryl (meth)acrylate.

[0078] In further embodiments of the present invention, "alkyl (meth)acrylate" is understood to mean polyethylene glycol (meth)acrylate having a weight-average molecular weight Mw in the range of 250 g / mol to 10,000 g / mol.

[0079] In the context of this invention, the term "(meth)acrylic acid" includes both acrylic acid and methacrylic acid. In the context of this invention, the term "(meth)acrylate" includes both acrylate and methacrylate.

[0080] Therefore, in the context of this invention, "alkyl (meth)acrylate" is understood to mean both alkyl methacrylate and alkyl acrylate. According to this invention, alkyl methacrylate is preferred. At least one alkyl (meth)acrylate is, for example, C1-C 18 -Alkyl (meth)acrylate, preferably C1-C 12 -Alkyl (meth)acrylates, particularly preferably C1-C4 alkyl (meth)acrylates. Most preferably according to the present invention, at least one alkyl (meth)acrylate comprises a methyl (meth)acrylate.

[0081] Therefore, a method is also preferred in which at least one alkyl (meth)acrylate contained in the first gas stream in step a) is selected from the group consisting of C1-C4 alkyl (meth)acrylates.

[0082] At least one alkyl (meth)acrylate has a boiling point in the range of 50°C to 300°C, preferably 80°C to 250°C, under normal pressure.

[0083] Needless to say, at least one further alkyl ester is distinct from the at least one alkyl (meth)acrylate. The at least one further alkyl ester is advantageously free from (meth)acrylate units.

[0084] For example, at least one further alkyl ester is selected from the group consisting of C1-C4 alkyl isobutyrates, C1-C4 alkyl propionates, C1-C4 alkyl pivalates, and dicarboxylic acid diesters.

[0085] In the context of this invention, C1-C4 alkyl isobutyrate is understood to mean an alkyl ester of isobutyric acid having 1 to 4 carbon atoms in the alkyl residue. The alkyl residue may be linear or branched. In addition, it may have a heteroatom within the alkyl residue and / or be substituted with a heteroatom. Examples of C1-C4 alkyl isobutyrates having a heteroatom within the alkyl residue are methyl 2-methoxyisobutyrate and methyl 3-methoxyisobutyrate. The C1-C4 alkyl isobutyrate according to the present invention is selected from the group consisting of, for example, methyl isobutyrate, ethyl isobutyrate, methyl 2-methoxyisobutyrate and methyl 3-methoxyisobutyrate.

[0086] In the context of this invention, C1-C4 alkylpropionates are understood to mean alkyl esters of propionic acid having 1 to 4 carbon atoms in the alkyl residue. The alkyl group may be linear or branched. In addition, it may have a heteroatom within the alkyl group and / or be substituted with a heteroatom. The C1-C4 alkylpropionates according to this invention are selected from the group consisting of, for example, methyl propionate and ethyl propionate.

[0087] In the context of this invention, C1-C4 alkyl pivalate is understood to mean an alkyl ester of pivalic acid having 1 to 4 carbon atoms in the alkyl residue. The alkyl group may be linear or branched. In addition, it may have a heteroatom within the alkyl group and / or be substituted with a heteroatom. The C1-C4 alkyl pivalate according to this invention is selected from the group consisting of, for example, methyl pivalate and ethyl pivalate.

[0088] In the context of this invention, a dicarboxylic acid diester is understood to mean an alkyl ester of a dicarboxylic acid having 1 to 4 carbon atoms in the alkyl residue. Similarly, a dicarboxylic acid diester is understood to mean a carboxylic acid ester of a diol in which both hydroxyl groups are esterified with a carboxylic acid. Dicarboxylic acid diesters according to the present invention are selected from the group consisting of, for example, dimethyl propanediate, dimethyl pentanediate, dimethyl hexanediate, and dimethyl heptanediate.

[0089] Advantageously, 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.

[0090] Therefore, it is also preferable that 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.

[0091] At least one further alkyl ester has, for example, a boiling point in the range of 50°C to 200°C, preferably 75°C to 150°C, under normal pressure.

[0092] According to the present invention, more preferably, the boiling point of at least one further alkyl ester at atmospheric pressure differs from the boiling point of at least one alkyl (meth)acrylate at atmospheric pressure by a range of -20°C to +20°C, preferably by a range of -1°C to +1°C, and particularly preferably by a range of -0.6°C to +0.6°C.

[0093] As mentioned above, the first gas stream is obtained by the thermal decomposition of at least one polymer composition. Therefore, the first gas stream typically contains at least one further component. Needless to say, the at least one further component is different from at least one alkyl (meth)acrylate and at least one further alkyl ester.

[0094] At least one further component is formed, for example, by the thermal decomposition of an alkyl (meth)acrylate copolymer and / or the thermal decomposition of at least one further component optionally contained in at least one polymer composition. Furthermore, alkyl (meth)acrylate oligomers may also be formed during thermal decomposition, and these are also included in the term "at least one further component" in the context of the present invention.

[0095] For example, at least one further component is selected from the group consisting of styrene, (meth)acrylic acid, sulfur-containing compounds, oligomers, dimers, C1-C4 alkyl acids, di(meth)acrylate diesters, C1-C4 alcohols, high-boiling aromatic compounds, aldehydes, and ketones, and preferably at least one further component is selected from the group consisting of styrene, (meth)acrylic acid, sulfur-containing compounds, oligomers, and dimers.

[0096] Therefore, a method in which the first gas stream contains at least one further component selected from the group consisting of styrene, (meth)acrylic acid, sulfur-containing compounds, oligomers, and dimers is also preferred.

[0097] In the context of this invention, high-boiling point aromatic compounds are understood to mean, for example, phenol, aniline, benzophenone, naphthalene, and / or pyridine, which may be substituted or unsubstituted.

[0098] For styrene as at least one further component, the description of styrene and preferred embodiments described above may be applied as appropriate.

[0099] The sulfur-containing compounds are, in particular, derived from sulfur-containing modifiers that may be contained in at least one polymer composition, and are especially mercaptans such as dodecyl mercaptan and polyvalent mercapto compounds such as pentaerythritol tetrathioglycolate.

[0100] In the context of this invention, "oligomer" is understood to mean, in particular, an oligomer of at least one alkyl (meth)acrylate, methacrylic acid, or mixtures thereof. The term "oligomer" includes not only higher-order oligomers but also lower-order oligomers such as trimers, tetramers, and pentamers. In particular, the term "oligomer" includes molecules composed of 3 to 10 units, which can be obtained from at least one alkyl (meth)acrylate, methacrylic acid, or mixtures thereof.

[0101] In the context of this invention, "dimer" is understood to mean, in particular, a dimer of at least one alkyl (meth)acrylate, methacrylic acid, or a mixture thereof.

[0102] C1-C4 alkyl acids are understood to mean aliphatic carboxylic acids having 1 to 4 carbon atoms. C1-C4 alkyl acids may have a branched structure. For example, C1-C4 alkyl acids are selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, and isobutyric acid.

[0103] The term "di(meth)acrylate diester" is understood to mean not only esters of (meth)acrylic acid and diols, but also esters of (meth)acrylic acid and polyols such as triols. For example, di(meth)acrylate diesters are selected from the group consisting of ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,3-butanediol di(meth)acrylate.

[0104] C1-C4 alcohols are understood to mean alcohols having 1 to 4 carbon atoms in an alkyl group. The alkyl group may be linear or branched. Similarly, it may be substituted with a heteroatom. Examples of C1-C4 alcohols are methanol, ethanol, ethylene glycol, n-butanol, and isobutanol.

[0105] Aldehydes are known to those skilled in the art. For example, aldehydes are selected from the group consisting of formaldehyde, acetaldehyde, methacrolein, and acrolein.

[0106] In the context of this invention, ketone is understood to mean both monoketones, such as acetone, and diketones, such as diacetyl. The ketones according to this invention are selected from the group consisting of, for example, diacetyl, acetone, acetylacetone, and methyl ethyl ketone.

[0107] For example, the first gas stream obtained during thermal decomposition contains at least one alkyl (meth)acrylate in an amount of 60 to 99% by weight, preferably 80 to 98% by weight, based on the total weight of the first gas stream.

[0108] For example, the first gas stream obtained during thermal decomposition contains at least one further alkyl ester in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the total weight of the first gas stream.

[0109] For example, the first gas stream obtained during thermal decomposition contains at least one additional component in an amount of 0.1 to 30% by weight, preferably 0.5 to 18% by weight, based on the total weight of the first gas stream.

[0110] In step b), the first gaseous stream obtained in step a) is condensed to obtain a liquid first stream. The liquid first stream contains at least one alkyl (meth)acrylate and at least one further alkyl ester.

[0111] The liquid first stream is also called recycled poly(alkyl(meth)acrylate). If poly(alkyl(meth)acrylate) contains poly(methyl(meth)acrylate), the liquid first stream is also called recycled poly(methyl(meth)acrylate) or recycled PMMA.

[0112] The first gas flow can be condensed according to methods known to those skilled in the art, for example, condensation can be carried out in a condenser.

[0113] For example, the first gas flow 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, and particularly preferably in the range of 20°C to 80°C.

[0114] The pressure during condensation of the first gas flow 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.

[0115] Preferably, the condensation of the first gas stream is carried out by drawing it into a first gas stream that has already been condensed and cooled, at which point the drawn-in first gas stream condenses. Subsequently, a portion of the condensed first gas stream is separated as a liquid first stream, and the first gas stream is drawn again into the condensed and cooled first gas stream.

[0116] During condensation, the first gas flow transitions from the gas phase to the liquid phase, resulting in a liquid first flow.

[0117] Typically, the at least one alkyl (meth)acrylate contained in the liquid first stream is the same as the at least one alkyl (meth)acrylate contained in the first gas stream. Therefore, the above description and preferred embodiments for the at least one alkyl (meth)acrylate contained in the first gas stream are appropriately applied to the at least one alkyl (meth)acrylate contained in the liquid first stream.

[0118] Typically, the at least one further alkyl ester contained in the liquid first stream is the same as the at least one further alkyl ester contained in the first gas stream. Therefore, the above description and preferred embodiments relating to the at least one further alkyl ester contained in the liquid first stream are appropriately applied to the at least one further alkyl ester contained in the first gas stream.

[0119] Additionally, the first liquid flow may contain at least one further component which may be optionally contained in the first gaseous flow. The above description and preferred embodiments apply as appropriate to the at least one further component.

[0120] According to the present invention, it is preferable that the first gas stream is distilled after step a) and before step b). At this time, a first top stream containing at least one alkyl (meth)acrylate and 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 at least one further alkyl ester are obtained. In this embodiment, the first top stream obtained during distillation is then condensed in step b).

[0121] Therefore, it is also preferable to distill the first gas stream after step a) and before step b) to obtain a first top stream containing at least one alkyl (meth)acrylate and 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 at least one further alkyl ester, and then condense this first top stream in step b).

[0122] The first gas stream may be condensed after step a) and before step b) before distillation. Methods for condensing the first gas stream are publicly known and are described above, for example. In other words, in the context of this invention, "distillation of the first gas stream" refers not only to the distillation of the first gas stream in the gas phase, but especially to the distillation of the first gas stream after it has been condensed.

[0123] The distillation of the first gas stream can be carried out in a reactor known to those skilled in the art, according to a method known to those skilled in the art. For example, the first gas stream can be transferred to a distillation column and / or rectification column, where it can be distilled. During the distillation of the first gas stream, components contained in the first gas stream and having a boiling point higher than at least one alkyl (meth)acrylate are obtained in the first bottom stream, while components contained in the first gas stream and having a boiling point equal to or lower than at least one alkyl (meth)acrylate are obtained in the first top stream.

[0124] Distillation can be carried out at temperatures in the range of, for example, 40 to 140°C. Preferably, the column bottom temperature during distillation is in the range of 95 to 130°C, and particularly preferably in the range of 97 to 126°C.

[0125] Distillation can be carried out, for example, at a pressure in the range of 10 to 250 mbar, preferably in the range of 15 to 150 mbar.

[0126] During the distillation of the first gas stream, a first top stream is obtained. The first top stream contains at least one alkyl (meth)acrylate and at least one further alkyl ester that were already present in the first gas stream.

[0127] Furthermore, the first top stream may contain additional components. In particular, the first top stream contains at least one additional component having a boiling point lower than or equivalent to that of at least one alkyl (meth)acrylate and at least one additional alkyl ester contained in the first gas stream. Thus, the first top stream typically contains at least one additional component selected from the group consisting of methyl propionate, ethyl propionate, methyl isobutyrate, methyl pivalate, methyl 3-methoxyisobutyrate, and dicarboxylic acid diesters.

[0128] For example, the first top flow obtained during distillation contains at least one alkyl (meth)acrylate in an amount of 60 to <99.8% by weight, preferably 85 to 98% by weight, based on the total weight of the first top flow.

[0129] For example, the first top flow obtained during distillation contains at least one further alkyl ester in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the total weight of the first top flow.

[0130] For example, the first top flow obtained during distillation contains at least one additional component in an amount of 0.1 to 30% by weight, preferably 0.5 to 14.5% by weight, based on the total weight of the first top flow.

[0131] In addition, a first bottom flow is obtained. In the context of this invention, "bottom flow" is understood to mean not only the bottom products that are continuously removed from the reactor by distillation, particularly from the reactor, but also bottom products that remain in the reactor as distillation residue during batch operation, for example, and are removed from the reactor for the first time at a later point.

[0132] The first bottom stream contains at least one component distinct from at least one alkyl (meth)acrylate and at least one further alkyl ester. This component is typically at least one of the at least one further component contained in the first gas stream. In particular, this at least one further component typically has a higher boiling point than the at least one alkyl (meth)acrylate and at least one further alkyl ester contained in the first gas stream. For example, this at least one further component is selected from the group consisting of sulfur-containing compounds, high-boiling aromatic compounds, oligomers, and dimers. For sulfur-containing compounds, high-boiling aromatic compounds, oligomers, and dimers, the above description and preferred embodiments for sulfur-containing compounds, high-boiling aromatic compounds, oligomers, and dimers contained in the first gas stream apply as appropriate.

[0133] Therefore, the first bottom flow preferably contains sulfur-containing compounds, high-boiling-point aromatic compounds, oligomers and / or dimers.

[0134] In step c), the liquid first stream obtained in step b) is mixed with a further stream to obtain a mixed stream. The further stream contains at least one further alkyl(meth)acrylate and is part of a poly(alkyl(meth)acrylate) production method. The resulting mixed stream includes the liquid first stream and the further stream.

[0135] If the further stream contains methyl (meth)acrylate as a further alkyl (meth)acrylate and is part of a poly(methyl (meth)acrylate) manufacturing method, the further stream is also called pure methyl (meth)acrylate or pure MMA.

[0136] Needless to say, the liquid first flow is different from the further flows. For example, the liquid first flow contains at least one alkyl (meth)acrylate in the range of 90 to <99.8% by weight, based on the total weight of the liquid first flow. The further flows, for example, contain at least 99.8% by weight of at least one further alkyl (meth)acrylate, based on the total weight of the further flow. Advantageously, the further flows contain at least 99.8% by weight of methyl (meth)acrylate, based on the total weight of the further flow, and the further flows can be obtained by methyl (meth)acrylate production methods using C1, C2, C3 and / or C4 starting materials (methanol, ethylene, acetone, hydrogen cyanide, isobutene and / or methyl-tert-butyl ether). These production methods are known to those skilled in the art.

[0137] For example, based on the total weight of the resulting mixed flow, up to 50% by weight, preferably up to 40% by weight, of the liquid first flow is mixed with the further flow. For example, based on the total weight of the resulting mixed flow, at least 1.5% by weight, preferably at least 5% by weight, of the liquid first flow is mixed with the further flow.

[0138] Therefore, in step c), it is also preferable to mix up to 50% by weight of the liquid first flow with the further flow, based on the total weight of the obtained mixed flow.

[0139] For example, each liquid first flow contains alkyl (meth)acrylate in the range of 90 to <99.8% by weight, preferably in the range of 94 to 98% by weight, based on the total weight of the liquid first flow, and 1.5 to 25% by weight, preferably 9 to 15% by weight, of the liquid first flow is mixed with the further flow based on the total weight of the resulting mixed flow. This embodiment is preferred when the optional step d) is not performed.

[0140] In a preferred embodiment of the present invention, if optional step d) is performed, the liquid first flow contains, for example, 90 to <99.8% by weight of alkyl (meth)acrylate based on the total weight of the liquid first flow, and 1.5 to 50% by weight, preferably 5 to 20% by weight of the liquid first flow is mixed with a further flow based on the total weight of the resulting mixed flow.

[0141] Therefore, a method is also preferred in which the liquid first flow contains alkyl (meth)acrylate in the range of 90 to <99.8% by weight based on the total weight of the liquid first flow, and 1.5 to 50% by weight of the liquid first flow is mixed with a further flow based on the total weight of the resulting mixed flow.

[0142] The further stream into which the liquid first stream is mixed contains at least one further alkyl (meth)acrylate. In the context of this invention, "at least one further alkyl (meth)acrylate" may mean just one further alkyl (meth)acrylate or a mixture of two or more further alkyl (meth)acrylates. Just one further alkyl (meth)acrylate is preferred.

[0143] For at least one further alkyl(meth)acrylate contained in the further stream, the above description and preferred embodiments for at least one alkyl(meth)acrylate contained in the first gas stream are applied as appropriate. Thus, the at least one further alkyl(meth)acrylate is selected from the group consisting of, for example, C1-C4 alkyl(meth)acrylates. Particularly preferably, the alkyl(meth)acrylate contained in the further stream is a methyl(meth)acrylate.

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

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

[0146] Further flow is part of a method for producing poly(alkyl(meth)acrylate). In the context of the present invention, “method for producing poly(alkyl(meth)acrylate)” is understood to mean a method for producing poly(alkyl(meth)acrylate) by polymerizing at least one alkyl(meth)acrylate, optionally in the presence of a monomer different from the alkyl(meth)acrylate. Polymerization may be, for example, radical polymerization or anionic polymerization, with radical polymerization being preferred. More preferably, polymerization is radical polymerization in an emulsion, solution or bulk, preferably in bulk. Particularly preferred, polymerization is radical polymerization in bulk, first partially polymerizing at least one alkyl(meth)acrylate, optionally in the presence of a monomer different from the alkyl(meth)acrylate, to obtain a syrup, and then polymerizing the syrup in a vented extruder to obtain a polymer mixture containing poly(alkyl(meth)acrylate).

[0147] The poly(alkyl(meth)acrylate) in the method for producing poly(alkyl(meth)acrylate) may be the same as or different from the poly(alkyl(meth)acrylate) contained in at least one polymer composition. The above description and preferred embodiments for the poly(alkyl(meth)acrylate) contained in at least one polymer composition may be applied as appropriate to the poly(alkyl(meth)acrylate) in the method for producing poly(alkyl(meth)acrylate).

[0148] Therefore, preferably, poly(alkyl(meth)acrylate) is poly(methyl(meth)acrylate).

[0149] Therefore, a method in which the poly(alkyl(meth)acrylate) contained in the polymer mixture is poly(methyl(meth)acrylate) is also preferred.

[0150] Further flows are part of the poly(alkyl(meth)acrylate) production method. Further flows may be, for example, reaction flows directly derived from the production of at least one further alkyl(meth)acrylate contained in the further flows. According to the present invention, it is preferably also possible that further flows can be obtained in the poly(alkyl(meth)acrylate) production method. For example, further flows may be condensate flows obtained in the second top flow and / or step g) described below.

[0151] The liquid first flow can be mixed with further flows according to methods known to those skilled in the art. For example, according to the present invention, the liquid first flow is advantageously supplied to a poly(alkyl(meth)acrylate) production facility containing further flows. In this case, the resulting mixed flow is advantageously also contained in the poly(alkyl(meth)acrylate) production facility. In this case, the mixed flow is advantageously also part of the poly(alkyl(meth)acrylate) production method.

[0152] Therefore, a method in which the mixed stream obtained in step c) is part of the poly(alkyl(meth)acrylate) production method is also preferred.

[0153] The mixed stream comprises a liquid first stream and a further stream. Therefore, the mixed stream typically contains the same components that were present in the liquid first stream and the further stream. Thus, the mixed stream typically contains at least one alkyl (meth)acrylate, at least one further alkyl ester, at least one further alkyl (meth)acrylate, and possibly at least one further component.

[0154] The liquid first stream can be mixed with further streams at any point in the poly(alkyl(meth)acrylate) production method. Preferably, the liquid first stream is mixed with further streams immediately before or in the purification portion of the poly(alkyl(meth)acrylate) production method described below. This is preferable because, in this case, in the optional step d), at least partial separation of at least one further alkyl ester can be performed in the purification portion of the poly(alkyl(meth)acrylate) production method.

[0155] In an optional step d), at least one further alkyl ester is at least partially separated from the mixed stream obtained in step c) to obtain a purified mixed stream. The purified mixed stream contains residues of at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, and at least one further alkyl ester. Then, in step e), the purified mixed stream obtained in step d) is partially polymerized. Step d) is preferred.

[0156] therefore, d) A step of separating at least one further alkyl ester from the mixed stream obtained in step c) to obtain a purified mixed stream containing a residue of at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, and at least one further alkyl ester. It also includes, Next, in step e), the purified mixed stream obtained in step d) is partially polymerized. The method is also preferable.

[0157] At least one further alkyl ester can be separated, at least partially, by any method. For example, at least one further alkyl ester can be separated, at least partially, from the mixed stream obtained in step c) by distillation.

[0158] Preferably, at least partial separation of at least one further alkyl ester is performed in the purification portion of the poly(alkyl(meth)acrylate) production method described later.

[0159] The purified mixed stream contains a residue of at least one further alkyl ester. In the context of the present invention, the term "at least one further alkyl ester residue" is understood to mean at least one further alkyl ester in an amount ranging from 0 to 8% by weight, preferably 0.1 to 3% by weight, and particularly preferably 0.1 to 2% by weight, based on the total weight of the purified mixed stream.

[0160] In step e) of the method according to the present invention, the mixed stream obtained in step c) is partially polymerized. At this time, a syrup is obtained that contains at least one partially polymerized alkyl (meth)acrylate, at least one further partially polymerized alkyl (meth)acrylate, and at least one further alkyl ester.

[0161] If optional step d) is performed, step e) of the method according to the present invention is performed by partially polymerizing the purified mixed stream obtained in step d) to obtain a syrup containing a residue of at least one partially polymerized alkyl (meth)acrylate, at least one further partially polymerized alkyl (meth)acrylate, and at least one further alkyl ester.

[0162] In the context of this invention, "partial polymerization" is understood to mean that the overall conversion rate of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate is in the range of 20-60%, preferably 35-50%, based on the amount of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate contained in the mixed stream, preferably in the purified mixed stream. The overall conversion rate of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate is defined as the ratio of the total amount of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate in the syrup obtained in step e) to the total amount of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate in the mixed stream obtained in step c). The total amount of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate is usually determined by GC analysis.

[0163] Therefore, in the partial polymerization in step e), a method is also preferred in which the overall conversion rate of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate is in the range of 20 to 60% based on the amount of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate contained in the purified mixed stream.

[0164] The partial polymerization in step e) can be carried out according to methods known to those skilled in the art. Preferably, the partial polymerization is carried out in the presence of at least one additive.

[0165] At least one auxiliary agent is also called at least one additive.

[0166] Therefore, a method in which the partial polymerization in step e) is carried out in the presence of at least one auxiliary agent is also preferred.

[0167] At least one additive can be supplied to the mixed flow at any point, for example, to the partial polymerization reactor described later.

[0168] Preferably, at least one additive is supplied to the mixed flow before transferring the mixed flow to the reactor.

[0169] Suitable additives include, for example, additives known to those skilled in the art that can initiate and / or influence partial polymerization.

[0170] For example, at least one auxiliary agent is selected from the group consisting of initiators, modifiers, and release agents.

[0171] Therefore, it is also preferable that at least one auxiliary agent is selected from the group consisting of initiators, modifiers, and release agents.

[0172] The initiator, modifier, and release agent can be appropriately applied as described above and in preferred embodiments.

[0173] The partial polymerization in step e) can be carried out, for example, by radical or anionic methods. Preferably, it can be carried out by radical methods. Furthermore, the partial polymerization can be carried out in emulsion, solution or bulk. Preferably, it can be carried out in bulk. Suitable reactors are those for partial polymerization known to those skilled in the art. For example, the partial polymerization can be carried out in a stirred tank reactor, preferably a continuous stirred tank reactor.

[0174] The temperature during the partial polymerization in step e) is, for example, in the range of 120 to 170°C, preferably in the range of 130 to 160°C.

[0175] For example, partial polymerization is carried out at a pressure in the range of 1 to 5 bara, preferably in the range of 1.5 to 3 bara.

[0176] A syrup is obtained during the partial polymerization. This syrup contains at least one partially polymerized alkyl (meth)acrylate, at least one further partially polymerized alkyl (meth)acrylate, at least one further alkyl ester, and, if optional step d) is carried out, at least one further alkyl ester residue. Furthermore, the resulting syrup also typically contains at least one auxiliary agent and / or its reaction product used during the partial polymerization.

[0177] In the context of this invention, the term “partially polymerized at least one alkyl(meth)acrylate” is understood to mean that a portion of at least one alkyl(meth)acrylate polymerizes by itself and / or with at least one further alkyl(meth)acrylate, and that a portion of at least one alkyl(meth)acrylate exists as a monomer. In the context of this invention, the term “partially polymerized at least one further alkyl(meth)acrylate” is understood to mean that a portion of at least one further alkyl(meth)acrylate polymerizes by itself and / or with at least one further alkyl(meth)acrylate, and that a portion of at least one further alkyl(meth)acrylate exists as a monomer.

[0178] When at least one alkyl(meth)acrylate polymerizes by itself and / or with at least one further alkyl(meth)acrylate, and when at least one further alkyl(meth)acrylate polymerizes by itself and / or with at least one alkyl(meth)acrylate, polymers of at least one alkyl(meth)acrylate by itself and / or with at least one further alkyl(meth)acrylate are formed, as well as polymers of at least one further alkyl(meth)acrylate by itself and / or with at least one alkyl(meth)acrylate. Furthermore, oligomers of at least one alkyl(meth)acrylate, at least one further alkyl(meth)acrylate, and mixtures thereof are also formed.

[0179] In this context, "oligomer" is understood to mean an oligomer of at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, and mixtures thereof. The term "oligomer" includes not only higher-order oligomers but also lower-order oligomers such as dimers, trimers, tetramers, and pentamers. In particular, the term "oligomer" in this context includes molecules composed of 2 to 10 units, which can be obtained from at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, and mixtures thereof.

[0180] In this context, "polymer" is understood to mean a polymer derived from at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, and mixtures thereof. For example, a polymer in this context may contain 1,000 to 100,000 units, and these units can be obtained from at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, and mixtures thereof.

[0181] In step f), the syrup obtained in step e) is polymerized using a vented extruder. At this time, a polymer mixture containing poly(alkyl(meth)acrylate) is obtained.

[0182] The temperature of the vented extruder in step f) is, for example, in the range of 150 to 290°C, preferably in the range of 170 to 270°C.

[0183] The pressure in the degassing region of the vented extruder in step f) is, for example, in the range of 0.1 bara to 2 bara, preferably in the range of 0.15 bara to 0.3 bara.

[0184] Suitable vented extruders are those known to those skilled in the art. Suitable vented extruders are described, for example, in European Patent Application Publication No. 2212091 and International Publication No. 2009 / 040190.

[0185] Typically, the syrup obtained in step e) is fed into a vented extruder via a material feed port, where it is advanced and polymerized to obtain a polymer mixture. In other words, the syrup and polymer mixture are transported along the vented extruder. At the extruder discharge port, the resulting polymer mixture is discharged from the extruder. The extruder discharge port is usually located at the end of the extruder opposite the material feed port.

[0186] During polymerization in step f), a polymer mixture is obtained. The polymer mixture contains poly(alkyl(meth)acrylate). In addition, the polymer mixture may contain components of the syrup.

[0187] The poly(alkyl(meth)acrylate) contained in the polymer mixture can be appropriately applied as described above and in preferred embodiments.

[0188] In step g) of the method according to the present invention, the syrup obtained in step e) and / or the polymer mixture obtained in step f) are degassed in a vented extruder to obtain a condensate stream. The condensate stream contains at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, their oligomers, and at least one further alkyl ester.

[0189] Degassing in a vented extruder can be carried out according to methods known to those skilled in the art. Preferably, polymerization in step f) is carried out simultaneously with degassing in step g).

[0190] Therefore, a method in which steps f) and g) are carried out simultaneously is also preferable.

[0191] In the context of this invention, "degassing" is understood to mean the removal of easily volatile components of the syrup and / or polymer mixture, i.e., at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, their oligomers, and at least one further alkyl ester, from the syrup and / or polymer mixture. These easily volatile components are obtained as a condensed liquid stream.

[0192] The condensate stream contains, for example, a total of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate in the range of 75% to 85% by weight, based on the total weight of the condensate stream, at least one further alkyl ester in the range of 0.1% to 5% by weight, and other components in the range of 10% to 20% by weight. The other components include, for example, oligomers of at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate.

[0193] The degassing in step g) can be carried out in a vented extruder known to those skilled in the art. Preferably, the degassing is carried out in a vented extruder such as that described in, for example, European Patent Application Publication No. 2212091 and International Publication No. 2009 / 040190.

[0194] The removal of the condensate flow is preferably carried out substantially opposite to the direction of conveyance of the syrup and / or polymer mixture. That is, the polymer mixture is discharged from the vented extruder in the opposite direction to the degassing.

[0195] Therefore, a method in which the degassing in step g) is performed in the countercurrent direction with respect to the transport direction of the polymer mixture obtained in step f) is also preferred.

[0196] This type of vented extruder is described, for example, in European Patent Application Publication No. 2212091 and International Publication No. 2009 / 040190.

[0197] Furthermore, degassing is preferably carried out in at least two steps; for example, the first degassing is performed in the front third of the vented extruder, and the second degassing is performed in the rear third of the vented extruder. Preferably, the first degassing is performed at ambient pressure, while the second degassing is performed under reduced pressure.

[0198] The condensed liquid stream is usually obtained in gaseous form. According to the present invention, it is preferably possible to condense the condensed liquid stream following step g) and before step h).

[0199] Therefore, typically, a degassed flow is obtained first, which is then condensed into a condensate flow. If degassing is performed in at least two steps in a vented extruder, for example, a first degassed flow is obtained during the first degassing, and a second degassed flow is obtained during the second degassing.

[0200] In step h), at least one further alkyl ester is removed from the condensate stream obtained in step g) to obtain an alkyl (meth)acrylate stream. The alkyl (meth)acrylate stream contains at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate.

[0201] In a preferred embodiment of the present invention, if an optional step d) is performed, in step h), at least one further alkyl ester residue is removed from the condensate stream obtained in step g). Therefore, the description of the at least one further alkyl ester and the preferred embodiments described below are also applicable as appropriate to the at least one further alkyl ester residue.

[0202] At least one additional alkyl ester is typically removed during the purification portion of the poly(alkyl(meth)acrylate) production process.

[0203] In the context of this invention, the term "purification portion" is understood to mean the portion of a poly(alkyl(meth)acrylate) production method in which the condensate stream is purified to obtain the alkyl(meth)acrylate stream. In particular, the purification portion separates at least one further alkyl ester at least partially, and optionally oligomers contained in the condensate stream. The purification portion typically includes apparatus for separating components, such as a distillation column, a rectification column and / or a thin-film evaporator.

[0204] Methods for purifying condensate streams and, in particular, separating at least one further alkyl ester from condensate streams are known.

[0205] For example, at least one additional alkyl ester can be removed by distillation. Preferably, the separation of at least one additional alkyl ester is carried out in at least two steps.

[0206] For example, process h) is h1) A step of separating the condensate stream into a second top stream containing at least one further alkyl (meth)acrylate and at least one further alkyl ester, and a second bottom stream containing at least one alkyl (meth)acrylate oligomer and at least one further alkyl (meth)acrylate oligomer. Includes.

[0207] The separation of the condensate flow into a second top flow and a second bottom flow can be carried out according to methods known to those skilled in the art. For example, this can be done by distillation and / or rectification and / or thin-layer evaporation.

[0208] Preferably, following step h1), h2) A step in which the second top stream obtained in step h1) is distilled to obtain a third top stream containing at least one further alkyl ester and a third bottom stream containing at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate. This will be implemented.

[0209] Therefore, the separation in step h) h1) A step of separating the condensate stream into a second top stream containing at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate and at least one further alkyl ester, and a second bottom stream containing at least one alkyl (meth)acrylate oligomer and at least one further alkyl (meth)acrylate oligomer, h2) A step in which the second top stream obtained in step h1) is distilled to obtain a third top stream containing at least one further alkyl ester and a third bottom stream containing at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate. Methods that include this are also preferable.

[0210] Typically, the second top flow obtained in step h1) is continuously transferred to the distillation in step h2).

[0211] The third bottom-of-column flow obtained in step h2) contains an alkyl (meth)acrylate flow.

[0212] The alkyl (meth)acrylate stream obtained in step h) and / or the third bottom stream obtained in step h2) can be returned at least partially to at least one of steps c), e) and / or f).

[0213] Therefore, it is also preferable to return at least partially the alkyl (meth)acrylate stream obtained in step h) to at least one of steps c), e) and / or f).

[0214] According to the present invention, in step c), it is preferable to mix the first liquid flow obtained in step b) with the condensed liquid flow before or during step h). In this case, the further flow corresponds to the condensed liquid flow. This embodiment is particularly advantageous because step h) can include an optional step d).

[0215] Therefore, a method in which step h) includes step d) is also preferred.

[0216] If step h) includes step d), at least one alkyl ester can be separated from the mixed stream together with the residue of at least one alkyl ester from the condensate stream.

[0217] A further subject of the present invention is a method for producing poly(alkyl(meth)acrylate), c1) A step of mixing a liquid first stream, which can be obtained by thermal decomposition of at least one polymer composition containing at least one alkyl (meth)acrylate and at least one further alkyl ester, with a further stream, which is part of a poly(alkyl (meth)acrylate) production method and contains at least one further alkyl (meth)acrylate, to obtain a mixed stream containing the liquid first stream and the further stream. e) A step of partially polymerizing the mixed stream obtained in step c1) to obtain a syrup containing at least one partially polymerized alkyl (meth)acrylate, at least one further partially polymerized alkyl (meth)acrylate, and at least one further alkyl ester. f) A step of polymerizing the syrup obtained in step e) using a vented extruder to obtain a polymer mixture containing poly(alkyl(meth)acrylate), g) degassing the syrup obtained in step e) and / or the polymer mixture obtained in step f) in a vented extruder to obtain a condensate stream containing at least one alkyl (meth)acrylate, at least one further alkyl (meth)acrylate, their oligomers and at least one further alkyl ester, h) Separating at least one further alkyl ester residue from the condensate stream obtained in step g) to obtain an alkyl (meth)acrylate stream containing at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate. This method includes [something].

[0218] In step c1), the liquid first flow is mixed with a further flow. The liquid first flow can be obtained by thermally decomposing at least one polymer composition. The polymer compositions are as described above and in preferred embodiments.

[0219] Therefore, preferably, the first liquid flow is a) A step of thermally decomposing 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 and at least one further alkyl ester, b) A step of condensing the first gas stream obtained in step a) to obtain a liquid first stream containing at least one alkyl (meth)acrylate and at least one further alkyl ester. It can be obtained by [method].

[0220] For steps a) and b), the above description and preferred embodiments are applied as appropriate.

[0221] Similarly, the above description and preferred embodiments apply appropriately to the liquid first flow. For step c1), the above description and preferred embodiments apply appropriately to step c).

[0222] For steps e) to h), the above explanation applies as appropriate.

[0223] In a preferred embodiment, step d) described above is additionally performed after step c1) and before step e). [Brief explanation of the drawing]

[0224] [Figure 1] This figure shows a conventional method for producing poly(alkyl(meth)acrylate). [Figure 2] This figure shows a first embodiment of a method for producing poly(alkyl(meth)acrylate) according to the present invention. [Figure 3] This figure shows a second embodiment of a method for producing poly(alkyl(meth)acrylate) according to the present invention.

[0225] The present invention will be described in more detail below with reference to the figures, however, the present invention is not limited to these figures.

[0226] Figure 1 shows a conventional method for producing poly(alkyl(meth)acrylate). A further stream (A) containing at least one further alkyl(meth)acrylate is mixed with a third bottom-of-column stream (B) similarly containing at least one further alkyl(meth)acrylate to obtain a mixed stream (C1). The third bottom-of-column stream (B) can be obtained in the purification section 5 of this method, as described later.

[0227] The mixed stream (C1) is mixed with the additive stream (D) and the atmospheric pressure condensate (E) to obtain a second mixed stream (F1). This second mixed stream (F1) is transferred to polymerization reactor 1. In this reactor, the second mixed stream (F1) is partially polymerized to obtain a syrup (G) containing at least one partially polymerized alkyl (meth)acrylate. Furthermore, the syrup (G) also contains at least one further alkyl (meth)acrylate that has not yet been polymerized. Subsequently, the syrup (G) is transferred to a vented extruder 2. In this extruder, the syrup (G) is further polymerized to obtain a degassed polymer mixture (J) containing poly(alkyl (meth)acrylate).

[0228] In the vented extruder 2, the syrup (G) and / or polymer mixture (J) are degassed to obtain a condensed liquid flow. In the embodiment shown in Figure 1, the syrup (G) and / or polymer mixture (J) are first degassed in a first region of the vented extruder 2 under ambient pressure to obtain a first degassed flow (H). A further degassing step is performed in a second region of the vented extruder 2 under reduced pressure to obtain a second degassed flow (H').

[0229] The first degassed flow (H) is condensed in condenser 4 to obtain atmospheric pressure condensate (E), which is at least partially mixed with the mixed flow (C1). Furthermore, it is also possible to mix a portion of the atmospheric pressure condensate (E) with syrup (G) (not shown in Figure 1).

[0230] The second degassed flow (H') is similarly condensed in the condenser 4. At this time, a vacuum degassed condensate (I) is obtained. This is transferred, at least partially, to the purification section 5. It is also possible to mix a portion of the vacuum degassed condensate (I) with the atmospheric pressure condensate (E) (not shown in Figure 1). The vacuum degassed condensate (I) is purified in the purification section 5. The purification section 5 may include, for example, a thin-film evaporator and a rectification column. In the thin-film evaporator, the vacuum degassed condensate (I) is partially evaporated to obtain a second top flow (not shown) and a second bottom flow (L). The second top flow is then transferred to the purification column and to a third top flow (K) and a third bottom flow (B).

[0231] The polymer mixture (J) is processed into polymer granules (M) in the polymer processing apparatus 3 according to a known method.

[0232] Figure 2 shows a first embodiment of the method for producing poly(alkyl(meth)acrylate) according to the present invention. The same reference numerals shown in Figure 1 have the same meaning.

[0233] A further stream (A) containing at least one further alkyl (meth)acrylate is mixed with a third bottom stream (B) containing at least one alkyl (meth)acrylate and at least one further alkyl (meth)acrylate, and a liquid first stream (N) containing at least one alkyl (meth)acrylate and at least one further alkyl ester to obtain a mixed stream (C).

[0234] The third tower bottom flow (B) can be obtained in the refinement section 5 of this method, as described later.

[0235] The mixed stream (C) is mixed with the additive stream (D) and the atmospheric pressure condensate (E) to obtain a second mixed stream (F). This second mixed stream (F) is transferred to polymerization reactor 1. In this reactor, the second mixed stream (F) is partially polymerized to obtain a syrup (G) containing at least one partially polymerized alkyl (meth)acrylate, at least one further partially polymerized alkyl (meth)acrylate, and at least one further alkyl ester. Furthermore, the syrup (G) contains at least one unpolymerized alkyl (meth)acrylate and at least one further unpolymerized alkyl (meth)acrylate. Subsequently, the syrup (G) is transferred to a vented extruder 2. In this vented extruder 2, the syrup (G) is further polymerized to obtain a degassed polymer mixture (J) containing poly(alkyl (meth)acrylate).

[0236] In the vented extruder 2, as described above with respect to Figure 1, the syrup (G) and / or polymer mixture (J) are degassed, and the resulting first degassed stream (H) and second degassed stream (H') are condensed in the condenser 4. The vacuum degassed condensate (I) thus obtained is purified as described in Figure 1, and the resulting third bottom stream (B) is recycled.

[0237] The polymer mixture (J) is processed into polymer granules (M) in the polymer processing apparatus 3 according to a known method.

[0238] Figure 3 shows a further embodiment of the method according to the present invention. The same reference numerals in Figure 3 as in Figure 2 have the same meaning. Below, only the differences from Figure 2 will be described in more detail.

[0239] A liquid first stream (N) containing at least one alkyl (meth)acrylate and at least one further alkyl ester is supplied directly to the processing unit 5 and purified together with the vacuum degassed condensate (I) via, for example, a thin-film condenser and a rectification column to obtain a third bottom stream (B), which is then mixed with a further stream (A). In other words, in this embodiment, the liquid first stream (N) is mixed with the vacuum degassed condensate (I), which is part of the method for producing poly(alkyl (meth)acrylate), and thus in this embodiment, the vacuum degassed condensate (I) is the further stream according to step c) of the method according to the present invention.

[0240] Next, the third tower bottom flow (B) is mixed with the further flow (A), as explained in Figure 2, to obtain a mixed flow. The further process steps in Figure 3 are the same as those explained in Figure 1.

[0241] Explanation of the symbols (A) Further flow (B) Third tower bottom flow (C) Mixed flow (C1) Mixed flow (D) Additive flow (E) Atmospheric pressure condensate (F) Second mixed flow (F1) Second mixed flow (G) Syrup (H) First degassing flow (H') Second degassing flow (I) Vacuum degassed condensate (J) Degassed polymer mixture (K) Third Tower Top Flow (L) Second tower bottom flow (M) Polymer Granules (N) Liquid first flow 1 Polymerization reactor 2. Vented extruder 3 Polymer Processing Equipment 4. Condenser 5 Purification part

[0242] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Examples]

[0243] [Production of polymethyl methacrylate (PMMA) in a two-step polymerization process starting from various monomer compositions] Further flows were prepared using the C3 manufacturing method for MMA. Table 1 shows the composition of the obtained further flows.

[0244] [Table 1]

[0245] Two types of liquid first flows were obtained by the depolymerization of poly(methyl methacrylate). The compositions of the obtained liquid first flows are shown in Tables 2 and 3.

[0246] [Table 2]

[0247] [Table 3]

[0248] Measurement method: The compositions shown in Tables 1, 2, and 3 were measured by gas chromatography (Agilent 88990, standard addition: isopropanol).

[0249] The quality and material properties of polymethyl methacrylate (PMMA) products manufactured according to the example were measured according to the following methods: The degree of yellowing (D65 / 10°) was measured by photometry (Varian Cary 5000) in accordance with DIN 6167 (1980;01). The melt volume flow rate (MVR) was measured at 230°C and using a 3.8 kg sample in accordance with DIN EN ISO 1133 (2012;03). The Vicat softening temperature (VST) was measured based on DIN EN ISO 306 (2014;03).

[0250] [Comparative Example V1: PMMA Manufacturing Starting from Further Flows] PMMA was manufactured using the equipment shown in Figure 1.

[0251] A further flow (A) of 5000 kg / h, as described in Table 1, was continuously mixed with a third bottom flow (B) of 384 kg / h at 8°C using a static mixer. The third bottom flow (B) had an MMA concentration of 98.8% based on the total volume of the third bottom flow (B). The third bottom flow (B) was recycled from the purification section 5 described below, at a temperature of 10°C. The purification section 5 includes a thin-film evaporator connected to the rectification column.

[0252] By mixing a further flow (A) with the third bottom flow (B), a mixed flow (C1) containing both the further flow (A) and the third bottom flow (B) was obtained. The mixed flow (C1) was mixed with an additive flow (D) at a rate of 100 kg / h. The additive flow (D) contained palmitin as a release agent, a high-boiling point substance as an additive, and polymerization regulators such as dodecyl mercaptan dissolved in MMA. The MMA concentration was >90% by weight. Additionally, an atmospheric pressure condensate (E) containing approximately 90% MMA and at a temperature of 5°C was added. The atmospheric pressure condensate (E) was obtained in condenser 4, described later.

[0253] The second mixed flow (F1) obtained during mixing was 18,200 kg / h, and was subsequently heated to 150°C in a shell-and-tube heat exchanger, and 10 m 3Partial polymerization was carried out by supplying the mixture to polymerization reactor 1 with a certain volume. By adding 5 kg / h of initiator solution (not shown in Figure 1), a second mixed flow (F1) was continuously polymerized at 150°C and slightly increased pressure, establishing a conversion rate of approximately 45%. The residence time was approximately 10 minutes.

[0254] Subsequently, the obtained syrup (G) was preheated to approximately 210°C on the tube side in a shell-and-tube heat exchanger and sent to a vented extruder 2 at a flow rate of approximately 12,800 kg / h. This was operated with a temperature profile of 170°C to 270°C, and degassing was performed at two locations. The first degassing was performed at ambient pressure in the front third of the vented extruder 2 to obtain the first degassed flow (H), and the second degassing was performed in a vacuum of approximately 150 mbar to obtain the second degassed flow (H').

[0255] The first degassed flow (H) obtained at atmospheric pressure condensed at 5°C and used as atmospheric pressure condensate (E). Approximately 5% of the atmospheric pressure condensate (E) was mixed with the vacuum degassed condensate (I) before supplying it to the purification section 5 (not shown in Figure 1).

[0256] 509 kg / h of vacuum degassed condensate (I) was supplied to the purification section 5. This included a thin-film evaporator DN500 connected to the rectification column DN400. The thin-film evaporator operated at 190 mbar and 75°C and had a special wiper structure (DVB type manufactured by SMS Buss). It used spring-loaded PTFE wiper blades, which resulted in low friction and thus no localized heating. The apparatus was 4 m 2The jacket side, which provides a heat transfer area, was heated with 1 barg of saturated steam. A stabilizer mixture containing 2,4-dimethyl-6-tert-butylphenol (Topanol A) and 1,6-di-tert-butyl-4-methylphenol (Topanol O) dissolved in MMA was added to the vacuum degassed condensate (I) before feeding it to the heat treatment. The concentration was approximately 200 ppm. The stabilized, low-temperature vacuum degassed condensate (I) was partially evaporated, thereby obtaining a second top flow and a second bottom flow (L). The second bottom flow (L), 98 kg / h, which contained approximately 25% MMA, was discharged from this process. A thin-layer evaporator was filled with 0.5 Nm³ to enhance the effect of the stabilizer mixture. 3 Air at / h was continuously blown in.

[0257] Subsequently, the obtained second top flow was supplied to a rectification column equipped with 6 m of ordered packing (MP452Y type) in the center. The rectification column was operated at 180 mbara, 55°C at the bottom and 29°C at the top. Vacuum was generated by a liquid-sealed vacuum pump (not shown in Figure 1) operated with a further flow (A) from the PMMA process as the working fluid. Energy was supplied to the rectification column via a short-residence natural circulation evaporator heated with 1 barg of saturated vapor. The evaporator was also supplied with 0.5 Nm to enhance the effect of the stabilizer. 3 Air was continuously blown in at a rate of / h. Condensation at the top of the column was carried out in two shell-and-tube heat exchangers operated with cooling water (20°C) and brine (2°C), and a third top flow (K) was continuously removed from the process at the top of the column with a reflux ratio of 0.95. The third bottom flow (B) was mixed with the further flow (A) as described above.

[0258] The degassed polymer mixture (J) obtained in the vented extruder 2 contained substantially PMMA. This was taken out as a sheet material—a continuous strand—and solidified in a water bath to be processed into polymer granules (M) consisting substantially of PMMA. The mass flow rate of the polymer granules (M) was approximately 4975 kg / h.

[0259] The polymer granules (M) obtained in this manner were subjected to quality and material properties measurements as described above. The results can be found in Table 4.

[0260] [Example B1 according to the present invention: Production of PMMA starting from a liquid first flow and further flows] PMMA was manufactured using the equipment shown in Figure 2.

[0261] The manufacturing process was carried out in substantially the same manner as described in Comparative Example V1. Therefore, the same reference numerals in the figures have the same meaning. Accordingly, the following will mainly describe the changes in this method compared to the method described in Comparative Example V1.

[0262] The additional flow (A) 5000 kg / h described in Table 1 was continuously mixed with the liquid first flow (N) 640 kg / h and the third bottom flow (B) 385 kg / h described in Table 2 in a static mixer at 8°C to obtain the mixed flow (C). The third bottom flow (B) had an MMA concentration of 97.3% based on the total volume of the third bottom flow (B). The third bottom flow (B) was obtained by recycling as described in Comparative Example V1. The mixing ratio of the liquid first flow (N) and the additional flow (A) is shown in Table 4.

[0263] The additive stream (D) and atmospheric pressure condensate (E) at a rate of 14390 kg / h were supplied to the mixed stream (C) to obtain a second mixed stream (F) of approximately 20400 kg / h. The by-products contained in the second mixed stream (F) are listed in Table 4. Subsequently, the second mixed stream was supplied to polymerization reactor 1 and further processed in the same manner as in Comparative Example V1.

[0264] The quality and material properties of the obtained polymer granules (M) were measured as described above. The results can be found in Table 4.

[0265] [Example B2 according to the present invention: Production of PMMA starting from a liquid first flow and further flows] PMMA was manufactured using the equipment shown in Figure 2.

[0266] The production was carried out substantially in the same manner as the production described in Example B1 according to the present invention. Therefore, hereinafter, the differences from the method described in Example B1 according to the present invention will be mainly described.

[0267] 5000 kg / h of the further stream (A) described in Table 1 was continuously mixed at 8 °C in a static mixer with 160 kg / h of the liquid first stream (N) and 391 kg / h of the third bottom stream (B) described in Table 2 to obtain a mixed stream (C). The third bottom stream (B) had an MMA concentration of 97.2% based on the total amount of the third bottom stream (B). The third bottom stream (B) was obtained by recycling as described in Comparative Example V1. The mixing ratio of the liquid first stream (N) and the further stream (A) is shown in Table 4.

[0268] An additive stream (D) and 13180 kg / h of atmospheric pressure condensate (E) were supplied to the mixed stream (C) to obtain a second mixed stream (F) of about 18840 kg / h. The by-products contained in the second mixed stream (F) are listed in Table 4. Subsequently, the second mixed stream was supplied to the polymerization reactor 1 and further processed in the same manner as in Comparative Example V1.

[0269] For the obtained polymer granules (M), the quality and material properties were measured as described above. The results can be found in Table 4.

[0270] [Example B3 according to the present invention: Production of PMMA starting from a liquid first purified stream and a further stream] PMMA was produced in the equipment described in FIG. 3.

[0271] The production was carried out substantially in the same manner as the production described in Comparative Example V1. Therefore, the same reference signs in the figures have the same meaning. Therefore, hereinafter, the differences in this method when compared with the method described in Comparative Example V1 will be mainly described.

[0272] Further flow (A) 5000 kg / h, as described in Table 1, was continuously mixed with the third bottom flow (B) 1575 kg / h in a static mixer at 8°C to obtain mixed flow (C). The third bottom flow (B) had an MMA concentration of 98.6%. The third bottom flow (B) was obtained by recycling. In the purification section 5, the first liquid flow (N) described in Table 2 was mixed with the vacuum degassed condensate (I), and both flows were purified together as described later to obtain the third bottom flow (B).

[0273] Next, the additive stream (D) and 15570 kg / h of atmospheric pressure condensate (E) were mixed with the mixed stream (C), as described in Comparative Example V1, to obtain a second mixed stream (F) of approximately 22240 kg / h. The by-products contained in the second mixed stream (F) are listed in Table 4. Subsequently, the second mixed stream (F) was supplied to polymerization reactor 1 and further processed in the same manner as in Comparative Example V1.

[0274] 532 kg / h of vacuum degassed condensate (I) was mixed with the liquid first flow (N) described in Table 2 in the purification section 5, as explained in Comparative Example V1, and purified. The reflux ratio of the rectification column was 1.5. The resulting third bottom flow (B) was mixed with the further flow (A) as described above.

[0275] The quality and material properties of the obtained polymer granules (M) were measured as described above. The results can be found in Table 4.

[0276] [Example B4 according to the present invention: Production of PMMA starting from a liquid first purification stream and a further stream] PMMA was manufactured using the equipment shown in Figure 3.

[0277] The manufacturing process was carried out in substantially the same manner as described in Example B3 of the present invention. Therefore, the following will mainly describe the differences from the method described in Example B3 of the present invention.

[0278] A further flow (A) of 5000 kg / h, as described in Table 1, was continuously mixed with a third bottom flow (B) of 723 kg / h in a static mixer at 8°C to obtain a mixed flow (C). The third bottom flow (B) had an MMA concentration of 97.3%. The third bottom flow (B) was obtained by recycling. In the purification section 5, the first liquid flow (N) described in Table 3 was mixed with the vacuum degassed condensate (I), and both flows were purified together as described later to obtain the third bottom flow (B).

[0279] Next, the additive stream (D) and 13,580 kg / h of atmospheric pressure condensate (E) were mixed with the mixed stream (C), as described in Comparative Example V1, to obtain a second mixed stream (F) of approximately 19,400 kg / h. The by-products contained in the second mixed stream (F) are listed in Table 4. Subsequently, the second mixed stream (F) was supplied to polymerization reactor 1 and further processed in the same manner as in Comparative Example V1.

[0280] 530 kg / h of vacuum degassed condensate (I) was mixed with the liquid first flow (N) described in Table 3 in the purification section 5, as described in Example B3 of the present invention, and purified.

[0281] The quality and material properties of the obtained polymer granules (M) were measured as described above. The results can be found in Table 4.

[0282] [Example B5 according to the present invention: Production of PMMA starting from a liquid first purification stream and a further stream] PMMA was manufactured using the equipment shown in Figure 3.

[0283] The manufacturing process was carried out in substantially the same manner as described in Example B3 of the present invention. Therefore, the following will mainly describe the differences from the method described in Example B3 of the present invention.

[0284] An additional stream (A) of 5000 kg / h as described in Table 1 was continuously mixed with the third bottoms stream (B) of 2360 kg / h at 8 °C in a static mixer to obtain a mixed stream (C). The third bottoms stream (B) had a MMA concentration of 96.4%. The third bottoms stream (B) was obtained by recycling. In the purification section 5, the liquid first stream (N) as described in Table 3 was mixed with the vacuum degassed condensate (I), and both streams were purified together as described below to obtain the third bottoms stream (B).

[0285] Subsequently, to the mixed stream (C), as described in Comparative Example V1, an additive stream (D) and 17400 kg / h of atmospheric pressure condensate (E) were mixed to obtain a second mixed stream (F) of about 24860 kg / h. The by-products contained in the second mixed stream (F) are listed in Table 4. Subsequently, the second mixed stream (F) was fed to the polymerization reactor 1 and further processed as in Comparative Example V1.

[0286] 535 kg / h of the vacuum degassed condensate (I) was mixed and purified in the purification section 5 with the liquid first stream (N) as described in Table 3 as described in Example B3 according to the present invention.

[0287] For the obtained polymer granules (M), the quality and substance characteristics were measured as described above. The results can be found in Table 4.

[0288]

Table 4-1

Table 4-2

[0289] The results shown in Table 4 clearly demonstrate that PMMA can be produced by combining pure MMA with recycled MMA. The PMMA produced by this invention has sufficient transmittance for its intended use and a yellowness low enough to produce at least colored products. The melt volume flow rate is sufficient, while the Vicat softening temperature is high. Therefore, the method according to this invention allows for resource conservation and MMA recycling while maintaining good product quality.

[0290] When the recycled MMA used already has a high purity (Examples B1 and B3) and / or is purified together with the vacuum degassed condensate before being mixed with pure MMA (Examples B3, B4, and B5), a colorless, clear PMMA can be obtained. In the latter case, a larger quantity of recycled MMA can be used, even if its purity is lower.

Claims

1. A method for producing poly(alkyl (meth)acrylate), a) A step of thermally decomposing 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 and at least one further alkyl ester, wherein the at least one alkyl(meth)acrylate contained in the first gas stream is C １ ~C ４ - A process selected from the group consisting of alkyl (meth)acrylates, b) A step of condensing the first gas stream obtained in step a) to obtain a liquid first stream containing the at least one alkyl (meth)acrylate and the at least one further alkyl ester, c) A step of mixing the liquid first flow obtained in step b) with a further flow which is part of a poly(alkyl(meth)acrylate) production method and contains at least one further alkyl(meth)acrylate to obtain a mixed flow containing the liquid first flow and the further flow, wherein up to 50% by weight of the liquid first flow is mixed with the further flow based on the total weight of the obtained mixed flow. e) A step of partially polymerizing the mixed flow obtained in step c) to obtain a syrup containing at least one partially polymerized alkyl (meth)acrylate, at least one further partially polymerized alkyl (meth)acrylate, and at least one further alkyl ester. f) A step of polymerizing the syrup obtained in step e) using a vented extruder to obtain a polymer mixture containing the poly(alkyl(meth)acrylate), g) degassing the syrup obtained in step e) and / or the polymer mixture obtained in step f) using the vented extruder to obtain a condensate stream containing the at least one alkyl (meth)acrylate, the at least one further alkyl (meth)acrylate, their oligomers and the at least one further alkyl ester. h) Separating the at least one further alkyl ester from the condensate stream obtained in step g) to obtain an alkyl (meth)acrylate stream containing the at least one alkyl (meth)acrylate and the at least one further alkyl (meth)acrylate. Methods that include...

2. d) Separating at least one further alkyl ester from the mixed stream obtained in step c) to obtain a purified mixed stream containing the residue of the at least one alkyl (meth)acrylate, the at least one further alkyl (meth)acrylate, and the at least one further alkyl ester. It also includes, Next, in step e), the purified mixed stream obtained in step d) is partially polymerized. The method according to claim 1, characterized in that

3. The method according to claim 1 or 2, 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.

4. The method according to any one of claims 1 to 3, characterized in that the first gas stream contains at least one further component selected from the group consisting of styrene, (meth)acrylic acid, sulfur-containing compounds, oligomers, and dimers.

5. The method according to any one of claims 1 to 4, characterized in that the first gas stream is distilled after step a) and before step b) to obtain a first top 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, and the first top stream is condensed in step b).

6. The method according to any one of claims 1 to 5, characterized in that the liquid first flow contains the alkyl (meth)acrylate in an amount of 90 to <99.8% by weight, based on the total weight of the liquid first flow, and 1.5 to 50% by weight of the liquid first flow is mixed with the further flow, based on the total weight of the resulting mixed flow.

7. The method according to claim 6, characterized in that at least one auxiliary agent is selected from the group consisting of initiators, modifiers, and release agents.

8. The method according to any one of claims 1 to 7, characterized in that, during the partial polymerization in step e), the overall conversion rate of the at least one alkyl (meth)acrylate and the at least one further alkyl (meth)acrylate is in the range of 20 to 60% based on the amount of the at least one alkyl (meth)acrylate and the at least one further alkyl (meth)acrylate contained in the purified mixed stream.

9. The method according to any one of claims 1 to 8, characterized in that steps f) and g) are carried out simultaneously.

10. The method according to any one of claims 1 to 9, characterized in that the degassing in step g) is carried out in a countercurrent with respect to the transport direction of the polymer mixture obtained in step f).

11. The method according to any one of claims 1 to 10, characterized in that the poly(alkyl(meth)acrylate) contained in the polymer mixture is poly(methyl(meth)acrylate).

12. The separation in step h) h1) A step of separating the condensate stream into a second top stream containing the at least one alkyl (meth)acrylate, the at least one further alkyl (meth)acrylate and the at least one further alkyl ester, and a second bottom stream containing the oligomer of the at least one alkyl (meth)acrylate and the oligomer of the at least one further alkyl (meth)acrylate. h2) Distilling the second top stream obtained in step h1) to obtain a third top stream containing the at least one further alkyl ester and a third bottom stream containing the at least one alkyl (meth)acrylate and the at least one further alkyl (meth)acrylate. The method according to any one of claims 1 to 11, characterized by including the following.

13. The method according to any one of claims 1 to 12, characterized in that the alkyl (meth)acrylate stream obtained in step h) is returned at least partially to at least one of steps c), e) and / or f).

14. The method according to any one of claims 2 to 13, characterized in that step h) includes step d).

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