Method for recovering rubber modified vinyl (co)polymers

Abstract

The present invention relates to a method for recovering a rubber modified vinyl (co)polymer from a polycarbonate resin or optionally crushed molded parts made therefrom, the polycarbonate resin comprising A) a polycarbonate based on an aromatic or aliphatic diol or mixtures thereof, and B) a rubber modified vinyl (co)polymer, the method comprising the steps of: i) contacting the resin or optionally crushed molded parts made therefrom with at least one alcohol together with at least one transesterification catalyst to obtain a slurry (i), the solids of which comprise the polycarbonate resin or optionally crushed molded parts made therefrom, and the liquids of which comprise the alcohol; ii) heating the slurry (i) to 60°C-90°C, preferably 65°C-85°C, most preferably 75°C-85°C and maintaining said temperature to obtain a slurry (ii), the solids of the slurry (ii) comprising the rubber modified vinyl (co)polymer and the liquids of the slurry comprising an aliphatic and / or aromatic diol, iii) separating the solids from the liquids of the slurry (ii), and iv) optionally washing the solids, both of the slurries (i) and (ii) being free of ammonia and ammonium salts, as well as the use of the recovered rubber modified vinyl (co)polymer for the manufacture of molded parts and as a blending partner in polycarbonate formulations. A further optional embodiment is the recovery of the aromatic and / or aliphatic diol and the use of said diol for the manufacture of polycarbonates.

Description

[Technical field]

[0001] The present invention relates to a method for recovering rubber-modified vinyl (co)polymers from the resin of polycarbonate compounds or from optionally crushed molded parts made therefrom. The present invention also relates to the use of the recovered rubber-modified vinyl (co)polymers for the manufacture of molded parts and as blending partners in polycarbonate compounds.

[0002] A further optional aspect is the recovery of the aromatic and / or aliphatic diol and the use of said diol for the production of polycarbonates. [Background technology]

[0003] Polycarbonate compositions for producing thermoplastic molding compounds have been known for many years. Said compositions and the molding compounds produced therefrom are used to produce moldings for various applications, for example in the automotive, building and electronics sectors.

[0004] The properties of the molded articles produced from such thermoplastic molding compounds can be tailored to the requirements of each application by selecting the components of the composition and the range of amounts in which these components are used in the composition.

[0005] To improve the notch resistance, especially at low temperatures, compounding partners with elastomeric properties are added to polycarbonates as impact modifiers. Furthermore, the chemical composition of the elastic component of the impact modifier, as well as its morphology, may vary. An important class of impact modifiers are rubber-modified vinyl (co)polymers. They can be compounded with polycarbonate in the compounding process, producing a two-phase morphology. In most cases, the phase morphology of these polycarbonate compounds is such that the polycarbonate forms the matrix phase and the rubber-modified vinyl (co)polymer forms domains within the matrix phase.

[0006] Among rubber modified vinyl (co)polymers, styrene-acrylonitrile-copolymer (SAN), commonly known as acrylonitrile-butadiene-styrene (ABS), in combination with polybutadiene-based rubber particles, is the most promising component.

[0007] ABS is used extensively as a compounding partner to incorporate impact modifiers for polycarbonate compositions, where the rubber particles improve notched impact resistance and additional mechanical properties, while SAN promotes the melt flowability of the resulting compound with polycarbonate, facilitating processing to provide molded articles.

[0008] Although polycarbonate resins, including polycarbonate and rubber-modified vinyl (co)polymers and optionally further components, are used in many applications, these materials are not biodegradable, and therefore there is a strong desire to utilize polycarbonate resin waste as a raw material for new products.

[0009] US Patent No. 5,399,633 discloses a method for the continuous depolymerization of polycarbonate by transesterification in a distillation column, which is suitable for recycling polycarbonate waste.

[0010] US Pat. No. 5,399,433 discloses a method for chemically recycling bisphenol A-based polycarbonate by transesterification with hydroxy compounds followed by melt polymerization.

[0011] US Patent No. 5,399,633 describes a method for alcoholysis of a polycarbonate-containing composition, which contains polycarbonate, a flame retardant, acrylonitrile-butadiene-styrene, or a combination of a flame retardant and acrylonitrile-butadiene-styrene. The method includes contacting the composition with a solvent that forms a solution or filterable suspension of the components but not the polycarbonate, separating the solution or filterable suspension from the polycarbonate, and depolymerizing in a subsequent step.

[0012] Patent Document 4 discloses a method for recovering dihydroxy aromatic compounds and dialkyl carbonates from a polycarbonate-containing composition containing polycarbonate and acrylonitrile-butadiene-styrene. The method includes depolymerizing polycarbonate to produce dihydroxy aromatic compounds and dialkyl carbonates, removing the dihydroxy aromatic compounds and dialkyl carbonates from a reactor to leave the acrylonitrile-butadiene-styrene as a coating on the surface of the reactor, adding a solvent to the reactor, heating the solvent, and removing the acrylonitrile-butadiene-styrene from the surface of the reactor.

[0013] US Patent No. 5,399,633 discloses a method for recovering dihydroxy aromatic compounds and urea from a polycarbonate-containing composition comprising polycarbonate and a phosphorus-containing flame retardant, the method comprising contacting the composition with ammonia in the presence of a swelling solvent for a time sufficient to depolymerize the polycarbonate to produce the dihydroxy aromatic compounds and urea.

[0014] Patent Document 6 discloses a method for recovering dihydroxy aromatic compounds and dialkyl carbonates from a polycarbonate-containing composition containing polycarbonate and a phosphorus-containing flame retardant. The method includes heating the composition in the presence of an alcohol and a transesterification catalyst having a non-neutralizing group at a temperature of 70° C. to 200° C. and a pressure of 50 mbar to 40 bar for a time sufficient to depolymerize the polycarbonate to produce dihydroxy aromatic compounds and dialkyl carbonates.

[0015] The aforementioned documents disclose the depolymerization of polycarbonate to obtain a polycarbonate component suitable for the subsequent production of new polycarbonate. If ABS is present, this copolymer must be separated before the depolymerization of the polycarbonate or remain as a coating on the reactor and be removed in a final step.

[0016] ABS or rubber modified vinyl (co)polymers are an important part of polycarbonate resins and are also valuable raw materials. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] European Patent Application Publication No. 0547479 [Patent Document 2] German Patent No. 4326906 [Patent Document 3] International Publication No. 2014 / 099548 [Patent Document 4] International Publication No. 2014 / 099594 [Patent Document 5] US Patent Application Publication No. 2015 / 105531 [Patent Document 6] European Patent Application Publication No. 2746249 Summary of the Invention

[0018] It would therefore be desirable to provide a method for recovering rubber modified vinyl (co)polymers from polycarbonate formulations.

[0019] It was also desired that the recovered rubber-modified vinyl (co)polymer would maintain its basic properties, such as the low glass transition temperature of the rubber phase, so that the rubber-modified vinyl (co)polymer would maintain its elastic properties and be useful in standard applications for this type of material.

[0020] It was also desired that the method be simple and could be carried out in only a few method steps.

[0021] Optionally, the process is also suitable for recovering the constituents of the polycarbonate, in particular the aromatic and / or aliphatic diols.

[0022] Surprisingly, the technical object is a method for recovering rubber modified vinyl (co)polymers from polycarbonate resin or from optionally crushed molded parts made therefrom, comprising the steps of: Polycarbonate resin is A) a polycarbonate based on aromatic or aliphatic diols or mixtures thereof; B) a rubber modified vinyl (co)polymer; wherein the method comprises: i) contacting polycarbonate resin or optionally crushed molded parts made therefrom with at least one alcohol together with at least one transesterification catalyst to obtain a slurry (i), wherein the solids content of the slurry (i) comprises the polycarbonate resin or optionally crushed molded parts made therefrom and the liquid content of the slurry (i) comprises the alcohol; ii) heating the slurry (i) to 60°C to 90°C, preferably 65°C to 85°C, most preferably 75°C to 85°C, and maintaining said temperature to obtain a slurry (ii), the solid content of the slurry (ii) comprising the rubber modified vinyl (co)polymer and the liquid content of the slurry comprising the aliphatic and / or aromatic diol; iii) separating the solids from the liquid of the slurry (ii); iv) optionally washing the solids; Including, It has been found that this is achieved by a process in which both slurry (i) and slurry (ii) are free of ammonia and ammonium salts.

[0023] In the slurry (ii), the solid phase contains the rubber modified vinyl (co)polymer, i.e., the rubber modified vinyl (co)polymer remains below its softening temperature and has not softened. It exists as hard particles. The hard particles can be separated from the liquid portion of the slurry by filtration.

[0024] The polycarbonate resin may optionally contain one or more polymeric additives, i.e. polymeric components, as component C. In a further optional step (v), the aromatic and / or aliphatic diols are separated from the liquid fraction.

[0025] In the process according to the invention, the polycarbonate is depolymerized by alcoholysis.

[0026] The method according to the invention can be used to recover valuable materials from post-industrial and post-consumer waste. Post-industrial waste includes, for example, polycarbonate resin that did not meet the specifications of the respective product. This could be for example due to deviations from the target color. Another source of post-industrial waste is molded parts with defects that occurred during production, for example by injection molding of polycarbonate resin. Post-consumer waste includes finished molded parts collected after the useful life of the final product. It is also possible to collect finished molded products that show defects such as poor surface quality that occur during the production of the parts, for example by injection molding.

[0027] The advantages of the claimed process are that it is possible to maintain the property profile of the rubber modified vinyl (co)polymer at relatively low temperatures and that it is a simple procedure that does not require laborious cleaning of equipment such as reactors and stirrers. Moreover, the rubber modified vinyl (co)polymer can be obtained without the use of additional solvents.

[0028] Preferably, the recovered rubber-modified vinyl (co)polymer has a glass transition temperature of the rubber phase of less than -80°C, more preferably less than -85°C, which is determined according to the DIN EN ISO 6721-7 standard at a frequency of 1 Hz, a heating rate of 3 K / min, and in the temperature range from -150°C to the softening of the material, which is the temperature associated with the peak maximum of the loss modulus (G'') curve, in a non-resonant torsional mode (shear modulus G''). * (T)) was measured using dynamic mechanical analysis (DMA).

[0029] Polycarbonate Resin Ingredient A Polycarbonates are used as component A. The polycarbonates may comprise structural units derived from aromatic and / or aliphatic diols. Diols may also be referred to as dihydroxy compounds within the context of the present invention.

[0030] It is also possible to use mixtures of two or more of the abovementioned polycarbonates. It is particularly preferred when one or more aromatic polycarbonates are used as component A.

[0031] The polycarbonates with component A suitable according to the invention are known from the literature or can be prepared by methods known from the literature (for the preparation of aromatic polycarbonates, see, for example, Schnell, "Chemistry and Physics of Polycarbonates", Interscience Publishers, 1964, and also DE-A-1 495 626, DE-A-2 232 877, DE-A-2 703 376, DE-A-2 714 544, DE-A-3 000 610, DE-A-3 832 396).

[0032] Aromatic polycarbonates are prepared, for example, by reacting diphenols with carbonyl halides, preferably phosgene and / or aromatic diacyl dihalides, preferably dihalides of benzenedicarboxylic acids, by the interfacial method, optionally using chain terminators, for example monophenols, and optionally using trifunctional or higher branching agents, for example triphenols or tetraphenols. Preparation via the melt polymerization method by reacting diphenols with, for example, diphenyl carbonate is also possible.

[0033] The diphenols for the preparation of the aromatic polycarbonates and / or aromatic polyester carbonates preferably have the formula (I): [ka] (In the formula, A is a single bond, C1-C5-alkylene, C2-C5-alkylidene, C5-C6-cycloalkylidene, -O-, -SO-, -CO-, -S-, -SO2-, C6-C6-alkylene optionally condensed with a further aromatic ring containing a heteroatom. 12 -arylene, or a group represented by formula (II) or formula (III): [ka] This is the part B is, in each case, C1~C 12 - alkyl, preferably methyl, halogen, preferably chlorine and / or bromine, x is, independently in each occurrence, 0, 1, or 2; p is 1 or 0, and R 5 and R 6 For each X 1 are individually selectable and are each independently hydrogen or C1-C6-alkyl, preferably hydrogen, methyl or ethyl; X 1 represents carbon, and m is an integer from 4 to 7, preferably 4 or 5, provided that at least one atom X 1 R on top 5 and R 6 is a diphenol of the formula (I is alkyl at the same time).

[0034] Preferred diphenols are hydroquinone, resorcinol, dihydroxydiphenols, bis(hydroxyphenyl)-C1-C5-alkanes, bis(hydroxyphenyl)-C5-C6-cycloalkanes, bis(hydroxyphenyl)ethers, bis(hydroxyphenyl)sulfoxides, bis(hydroxyphenyl)ketones, bis(hydroxyphenyl)sulfones, and α,α-bis(hydroxyphenyl)diisopropylbenzene, and their ring brominated and / or ring chlorinated derivatives.

[0035] Particularly preferred diphenols are 4,4'-dihydroxybiphenyl, bisphenol A, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 4,4'-dihydroxybiphenyl sulfide, 4,4'-dihydroxybiphenyl sulfone, and their dibrominated or dichlorinated and tetrabrominated or tetrachlorinated derivatives, such as 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane, or 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane. 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) is particularly preferred.

[0036] The diphenols can be used individually or in the form of any desired mixtures. The diphenols are either known from the literature or can be obtained by methods known from the literature.

[0037] The diphenols can be completely or partially replaced by aliphatic diols. Suitable aliphatic diols include diols having 2 to 12 carbon atoms or cycloaliphatic diols having 6 to 21 carbon atoms, such as ethylene diol, propane-1,2-diol, propane-1,3-diol, 2-ethylpropane-1,3-diol, neopentyl glycol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, octane-1,8-diol, cyclohexane-1,4-dimethanol, cyclohexane-1,3-dimethanol, cyclohexane-1,2-dimethanol, 3-methylpentane-2,4-diol, 2-methylpentane-2,4-diol, 2,2,4-trimethylpentane-1,3-diol and 2-ethylhexane-1,6-diol, 2,2-diethylpropane-1,3-diol, hexane-2,5-diol, 1,4-di(β-hydroxyethoxy) Benzene, 2,2-bis(4-hydroxycyclohexyl)propane, 2,4-dihydroxy-1,1,3,3-tetramethylcyclobutane, 2,2-bis(3-β-hydroxyethoxyphenyl)propane and 2,2-bis(4-hydroxypropoxyphenyl)propane, cyclohexane-1,2-diol, cyclohexane-1,3-diol, cyclohexane-1,4-diol, tetrahydro-2,5-furandiethanol, 2-butyl-2-ethyl-1,3-propanediol, 2-(2-hydroxyethoxy)ethanol, 2,2,4,4-tetramethyl-cyclobutane-1,3-diol, 2,2,4-trimethyl-pentane-1,3-diol, 2,2-dimethylpropane-1,3-diol, cyclobutane-1,1-diyldimethanol, 1,4:3,6 dianhydro-D-glucitol, and mixtures thereof.

[0038] Within the context of the present invention, the aliphatic and / or aromatic diols used as building blocks in the production of polycarbonates and recovered by the process according to the invention are also referred to simply as diols.

[0039] Examples of chain terminators suitable for the preparation of thermoplastic aromatic polycarbonates include phenol, p-chlorophenol, p-tert-butylphenol or 2,4,6-tribromophenol, as well as long-chain alkylphenols, such as 4-[2-(2,4,4-trimethylpentyl)]phenol, 4-(1,3-tetramethylbutyl)phenol according to DE-A-2842005, or mono- or dialkylphenols having a total of 8 to 20 carbon atoms in the alkyl substituent, such as 3,5-di-tert-butylphenol, p-isooctylphenol, p-tert-octylphenol, p-dodecylphenol, as well as 2-(3,5-dimethylheptyl)phenol and 4-(3,5-dimethylheptyl)phenol. The amount of chain terminators used is generally between 0.5 mol% and 10 mol% relative to the total moles of the diphenols used in each case.

[0040] The thermoplastic aromatic polycarbonates can be branched in a known manner, preferably by incorporating 0.05 mol % to 2.0 mol % of trifunctional or more than trifunctional compounds, for example compounds having three or more phenolic groups, relative to the total diphenols used.

[0041] Both homopolycarbonates and copolycarbonates are suitable. In the preparation of the copolycarbonates of the invention with component A, polydiorganosiloxanes having 1% to 25% by weight, preferably 2.5% to 25% by weight, of hydroxyaryloxy end groups, based on the total amount of diphenols used, can also be used. These are known (US Pat. No. 3,419,634) and can be prepared by methods known from the literature. The preparation of copolycarbonates containing polydiorganosiloxanes is described in DE-A-3,334,782.

[0042] In a preferred embodiment, the weight-average molar mass M of the aromatic polycarbonate suitable as component A w(measured by gel permeation chromatography (GPC) in methylene chloride with polycarbonate standards) is between 10 000 g / mol and 50 000 g / mol, preferably between 22 000 g / mol and 35 000 g / mol, in particular between 24 000 g / mol and 32 000 g / mol.

[0043] Component B Component B is at least one rubber-modified vinyl (co)polymer. The rubber-modified vinyl (co)polymer comprises a rubber-based graft polymer and, optionally, a rubber-free vinyl (co)polymer. The rubber-free vinyl (co)polymer is also called free vinyl (co)polymer in the context of the present invention.

[0044] The graft polymers used in component B according to the invention are preferably B.1 5% to 95% by weight, preferably 20% to 92% by weight, in particular 30% to 91% by weight, of at least one vinyl monomer, based on the graft polymer, B.2 95% to 5% by weight, preferably 80% to 8% by weight, in particular 70% to 9% by weight, based on the graft polymer, of one or more rubber-elastic graft substrates having a glass transition temperature of less than -10°C, more preferably less than -40°C, particularly preferably less than -70°C.

[0045] Unless expressly stated otherwise in the present invention, the glass transition temperatures are determined for all components by dynamic differential scanning calorimetry (DSC) according to DIN EN 61006 (2004 edition) at a heating rate of 10 K / min using determination of the Tg as the midpoint temperature (tangent method).

[0046] The graft base material B.2 generally has a median particle size (D50) of 0.05 μm to 10.00 μm, preferably 0.1 μm to 5.0 μm, particularly preferably 0.1 μm to 1.5 μm.

[0047] The median particle size D50 is the diameter above which 50% of the particles by weight lie and below which 50% by weight lie. Unless otherwise expressly stated in the present invention, this is determined for all components by ultracentrifugation measurements (W. Scholtan, H. Lange, Kolloid, Z. und Z. Polymere [Polymers] 250 (1972), 782-1796).

[0048] The monomers B.1 are preferably B.1.1 65% to 85% by weight, particularly preferably 70% to 80% by weight, more preferably 74% to 78% by weight, of vinyl aromatic compounds and / or ring-substituted vinyl aromatic compounds (for example styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene) and / or (C1-C8)-alkyl (meth)acrylates, for example methyl methacrylate, ethyl methacrylate, in each case based on the sum of B.1.1 and B.1.2, B.1.2 15% to 35% by weight, particularly preferably 20% to 30% by weight, more preferably 22% to 26% by weight, of vinyl cyanides (unsaturated nitriles such as acrylonitrile and methacrylonitrile) and / or (C1-C8)-alkyl (meth)acrylates, for example methyl methacrylate, n-butyl acrylate, t-butyl acrylate, and / or derivatives of unsaturated carboxylic acids (for example anhydrides and imides), for example maleic anhydride, in each case based on the sum of B.1.1 and B.1.2, It is a mixture of.

[0049] Preferred monomers B.1.1 are selected from at least one of the monomers styrene, α-methylstyrene and methyl methacrylate, and preferred monomers B.1.2 are selected from at least one of the monomers acrylonitrile, maleic anhydride and methyl methacrylate. Particularly preferred monomers are B.1.1 styrene and B.1.2 acrylonitrile. Alternatively preferred monomers are B.1.1 methyl methacrylate and B.1.2 methyl methacrylate.

[0050] Suitable graft substrates B.2 for the graft polymers include, for example, diene rubbers, EP(D)M rubbers, i.e. those based on ethylene / propylene, and optionally diene, acrylate, polyurethane, silicone, chloroprene, ethylene / vinyl acetate, and also acrylate-silicone hybrid rubbers.

[0051] Preferred graft substrates B.1.2 are diene rubbers, preferably containing butadiene, or copolymers of dienes, preferably containing butadiene, and further copolymerizable vinyl monomers (for example according to B.1.1 and B.1.2), or mixtures of one or more of the abovementioned components.

[0052] A particularly preferred graft substrate B.2 is a pure polybutadiene rubber. In a further preferred embodiment, B.2 is a styrene-butadiene rubber, particularly preferably a styrene-butadiene block copolymer rubber.

[0053] The gel fraction of the graft substrate B.2 is in each case at least 30% by weight, preferably at least 40% by weight and in particular at least 60% by weight, based on B.2, measured as the proportion insoluble in toluene.

[0054] The gel content of the graft polymers in the graft substrate B.2 / component B is determined in suitable solvents at 25° C. as the content that is insoluble in these solvents (M. Hoffmann, H. Kroemer, R. Kuhn, Polymeranalytik I und II, Georg Thieme-Verlag, Stuttgart 1977).

[0055] The most preferred component B is acrylonitrile-butadiene-styrene (ABS).

[0056] The graft copolymer in component B is prepared by free radical polymerization, for example, emulsion polymerization, suspension polymerization, solution polymerization or bulk polymerization. A mixture of graft polymers prepared by various processes may also be used as component B. The graft polymer in component B is preferably prepared by emulsion polymerization or bulk polymerization.

[0057] Suitable graft polymers prepared in an emulsion polymerization process are, for example, ABS polymers prepared in an emulsion polymerization process by redox initiation using an initiator system consisting of an organic hydroperoxide and ascorbic acid, according to US Pat. No. 4,937,285.

[0058] Further suitable graft polymers made by emulsion polymerization processes are MBS modifiers having a core-shell structure.

[0059] Suitable polymers according to component B which are prepared by bulk polymerization are described, for example, in DE-A-2 035 390 (=U.S. Pat. No. 3,644,574) or DE-A-2 248 242 (=GB-A-1 409 275), or in Ullmanns, Enzyklopaedie der Technischen Chemie, Vol. 19 (1980), p. 280 et seq.

[0060] Component B may comprise vinyl (co)polymers composed of monomers according to B.1 in free form, i.e. not chemically bound to the rubber substrate and not contained in the rubber particles. These are either formed in component B in the polymerization of the graft polymer due to the manufacturing process (grafting on the graft substrate is not necessarily complete) or else polymerized separately and mixed with component B. It is likewise possible that part of the free vinyl (co)polymer in component B originates from the graft polymer itself due to the manufacturing process, and another part is polymerized separately and mixed with component B. The proportion of free vinyl (co)polymer in component B (irrespective of origin), measured as the acetone-soluble proportion, is preferably at least 5% by weight relative to component B.

[0061] The free vinyl (co)polymer has a weight average molecular weight M of 30 kg / mol to 250 kg / mol, preferably 70 kg / mol to 200 kg / mol, in particular 90 kg / mol to 180 kg / mol in the rubber-modified vinyl copolymer of component B. w has.

[0062] In the context of the present invention, the weight average molecular weight M of the free vinyl (co)polymer in component B w is determined by gel permeation chromatography (GPC) in tetrahydrofuran against polystyrene standards.

[0063] Component C As component C, the polycarbonate resin may optionally comprise one or more polymer additives, i.e. polymer components, selected from the group consisting of flame retardants, anti-dripping agents, flame retardant auxiliaries, smoke suppressants, lubricants and release agents, nucleating agents, antistatic agents, conductive additives, stabilizers (e.g. hydrolysis stabilizers, heat aging stabilizers and UV stabilizers, and also transesterification inhibitors), flow promoters, compatibilizers, further polymer constituents other than components A and B (e.g. functional blending partners), fillers and reinforcing agents, and dyes and pigments.

[0064] Manufacturing of molding compounds and molded products For example, polycarbonate resins can be produced by mixing the respective components of the composition (A, B and optionally C) and melt compounding and melt extruding them as known in the art in conventional equipment such as internal mixers, extruders and twin screw systems at temperatures preferably between 200° C. and 320° C., more preferably between 240° C. and 310° C., and most preferably between 260° C. and 300° C. In the context of this application, this process is generally referred to as compounding.

[0065] The term molding compound is therefore understood to mean the product obtained when the constituents of the composition are melt compounded and melt extruded.

[0066] The individual components of the composition can be mixed in a known manner, either sequentially or simultaneously, at a temperature of about 20° C. (room temperature) or higher, i.e., for example, some components can be added through the main intake of an extruder, while the remaining components can be applied later in the compounding process through an auxiliary extruder.

[0067] Polycarbonate resins can be used to produce all kinds of moldings.They can be produced, for example, by injection molding, extrusion and blow molding processes.Another form of processing is the production of moldings by thermoforming from previously produced sheets or films.The molding compounds according to the present invention are particularly suitable for processing by extrusion, blow molding and thermoforming methods.

[0068] Alternatively, the components of the composition may be metered directly into an injection molding machine or extrusion unit and processed into molded articles.

[0069] Process Details alcohol In step (i) of the process according to the invention, an alcohol is used. The alcohol may have one or more OH groups. The alcohol may be a primary, secondary or tertiary alcohol, and the alcohol may be aliphatic or aromatic. Examples of suitable alcohols include methanol, ethanol, 1-propanol, isopropyl alcohol and tert-butanol. Mixtures of different alcohols may be used. The alcohol is preferably selected from methanol, ethanol and mixtures thereof. The depolymerization of the polycarbonate is achieved by alcoholysis in step (ii). Alcoholysis with methanol is called methanolysis, while alcoholysis with ethanol is called ethanolysis. Most preferred is methanol. Methanol has the advantage of being highly reactive with polycarbonate resins.

[0070] The weight ratio of alcohol to polycarbonate resin in step (i) is preferably from 0.8:1 to 12:1, more preferably from 0.9:1 to 8:1, and most preferably from 1:1 to 5:1. Since the alcohol is used as both a solvent and a reagent in the alcoholysis of the polycarbonate, it is preferred that it is in excess.

[0071] In an alternative embodiment, a mixture of alcohol and water is used. In this embodiment, it is preferable to select an alcohol that is fully miscible with water. Preferably, the weight ratio of alcohol to water is 10:90 to 90:10, preferably 25:75 to 75:25, more preferably 40:60 to 60:40.

[0072] When a mixture of alcohol and water is used, the weight ratio of the alcohol / water mixture to the polycarbonate resin is selected to satisfy the above-mentioned weight ratio of alcohol to polycarbonate resin.

[0073] The presence of water during the depolymerization of polycarbonate has the advantage that the final bisphenol A crystals will have a lighter natural color. A lighter natural color means that the crystals will have a less yellow color.

[0074] Alcoholysis of polycarbonate with aliphatic alcohols in the absence of water produces dialkyl carbonates and diols. Alcoholysis in the presence of water produces CO2 and diols, but does not ultimately produce significant amounts of dialkyl carbonate.

[0075] Transesterification Catalyst The alcoholysis of the polycarbonate is carried out in the presence of a transesterification catalyst. It is also possible to use mixtures of different transesterification catalysts.

[0076] The weight ratio of the transesterification catalyst to the polycarbonate resin in step (i) is preferably 0.001:1 to 3:1, more preferably 0.01:1 to 2:1, and most preferably 0.1:1 to 1:1.

[0077] The selected catalysts make it possible to carry out the depolymerization of polycarbonates at the moderate temperatures claimed. Lower temperatures are preferred, since the properties of the rubber-modified vinyl (co)polymers are better maintained. If the temperature is too high, especially the elastomeric graft substrates may be damaged and the glass transition temperature may shift to higher values.

[0078] Preferably, the catalyst is selected from the group consisting of titanium compounds, tin compounds, boron compounds, ammonium compounds, phosphonium compounds, silicon compounds, germanium compounds, tin compounds, titanium compounds, antimony compounds, zinc compounds, manganese compounds, zirconium compounds, alkali metal compounds, alkaline earth metal compounds, and mixtures thereof.

[0079] More preferably, the catalyst is selected from the group consisting of ammonium compounds, alkali metal compounds and alkaline earth metal compounds, and mixtures thereof.

[0080] The alkaline earth metal compounds and alkali metal compounds are selected from the group consisting of hydroxides, hydrides, alkoxides, aryloxides, and salts of organic acids, including acetic acid, propionic acid, butyric acid, benzoic acid, stearic acid, and mixtures of these compounds.

[0081] The ammonium and phosphonium compounds are selected from the group consisting of tetramethylammonium borohydride, tetrabutylammonium hydroxide, methyltributylammonium hydroxide, tetrabutylammonium acetate, tetrabutylphosphonium hydroxide, tetrabutylphosphonium acetate, and tetrabutylphosphonium phenolate, and mixtures thereof.

[0082] More preferred transesterification catalysts are alkali metal compounds, especially alkali metal hydroxides and methanolates, and even more preferred are sodium hydroxide and sodium methanolate.

[0083] The most preferred transesterification catalyst is sodium hydroxide, which provides a sufficiently high depolymerization rate at low to moderate temperatures.

[0084] Process conditions This process can be used for polycarbonate resin and its molded parts. Polycarbonate resin, such as from post-industrial waste, is usually available in the form of pellets. Molded parts collected as post-industrial or post-consumer waste may have many different shapes and sizes. It may be advantageous to reduce the particle size by processes known to those skilled in the art, such as crushing or chopping, before contacting the molded parts with alcohol and transesterification catalyst according to method step (i).

[0085] Reducing the part size increases the surface area and may increase the rate of depolymerization. Within the context of this invention, any means for reducing the size of collected molded parts is referred to as crushing, and the resulting molded parts are referred to as crushed molded parts.

[0086] The process can be carried out on a laboratory scale and on a larger scale in conventional equipment such as stirred flasks and stirred reactors. A condenser may be connected to the gas phase of the flask or reactor using a cooling water loop as the cooling medium to condense the vapors generated by heating. The reaction can also be carried out in a closed flask or reactor. The temperature in the flask or reactor can be regulated by circulating hot oil or hot water or by electrical heating. All these means are known to the person skilled in the art.

[0087] In step (i), a slurry (i) is obtained. Within the context of the present invention, a slurry is a mixture comprising a liquid component and a solid component. In the slurry (i), the polycarbonate resin or optionally a molded part made therefrom is the solid component, while the alcohol is the liquid component. The transesterification catalyst may be solid or dissolved in the liquid fraction.

[0088] In step (ii), the polycarbonate is depolymerized by alcoholysis to obtain slurry (ii). The depolymerization of the polycarbonate results in recovery of aromatic and / or aliphatic diols and (in the absence of water) dialkyl carbonates, both of which form part of the liquid phase, so that slurry (ii) has a lower solids content compared to slurry (i). In the event of 100% polycarbonate conversion, i.e. complete depolymerization, the solid phase of slurry (ii) contains the rubber-modified vinyl (co)polymer and optional component C.

[0089] The depolymerization of polycarbonate is carried out at a temperature range of 60° C. to 90° C., preferably 65° C. to 85° C. That is, in step (i), the polycarbonate resin or an optionally crushed molded part thereof is contacted with an alcohol and a transesterification catalyst, and then in step (ii), the resulting slurry (i) is heated to the above-mentioned temperature range and maintained at this temperature to obtain a slurry (ii).

[0090] If the temperature is lower than 60°C, the depolymerization rate is too slow for an economical process, and if the temperature is higher than 90°C, the graft substrate of the rubber modified vinyl (co)polymer may be damaged and the glass transition temperature may increase, which is undesirable.

[0091] The process can be carried out at ambient pressure, reduced pressure and elevated pressure up to 50 bar. It is preferred that the process is carried out at ambient pressure.

[0092] In a preferred embodiment, process step (i) and / or process step (ii) are carried out while stirring the slurry (i) and / or slurry (ii). Stirring can increase the rate of depolymerization of the polycarbonate and shorten the overall process time. Suitable stirrers are known to those skilled in the art.

[0093] Preferably, process step (ii) is carried out for a period of from 0.5 hours to 20 hours, more preferably from 1 hour to 8 hours, and most preferably from 3 hours to 5 hours. It is further preferred that the depolymerization of the polycarbonate is at least 98%, even more preferably at least 99%, and most preferably at least 99.5% complete. More complete depolymerization of the polycarbonate reduces the amount of residual oligocarbonate that may remain in the solid phase as an impurity in the recovered rubber modified vinyl (co)polymer.

[0094] The recovered rubber modified vinyl (co)polymers may prove useful as polymer blending partners for the production of new polycarbonate resins. A high proportion of oligomeric materials such as oligocarbonates may impair the properties of these polycarbonate resins, such as reduced heat distortion temperature. For this reason, a high polycarbonate conversion is preferred in the process according to the invention.

[0095] In process step (iii) the solid and liquid fractions of the slurry (ii) are separated. Step (iii) is preferably carried out without the addition of a solvent to dissolve or swell the solids or part of the solids. This has the advantage that the process is simplified. By avoiding the use of additional solvents less waste is generated and the process becomes more economical. Separation is preferably carried out by filtration. The rubber modified vinyl (co)polymer remains as a solid on the filter paper.

[0096] This solid may then be washed in an optional process step (iv). The washing liquid may be the alcohol and / or water used for the depolymerization of the polycarbonate. It is also possible to wash the solid with a separate washing liquid and / or a diluted acid, provided that this can be easily removed from the solid in a simple drying process.

[0097] Separation of the aromatic and / or aliphatic diols and dialkyl carbonates from the liquid fraction in optional step (v) can be carried out by first removing the components with lower boiling points, i.e. methanol and / or ethanol and dialkyl carbonate and / or water, preferably by evaporation under reduced pressure. Before evaporation, the liquid phase may be neutralized or acidified to salt out the catalyst used in the reaction. The remaining solid phase contains the aromatic and / or aliphatic diols and may also contain salts from the (optionally neutralized) catalyst. The aromatic and / or aliphatic diols may be dissolved in a suitable solvent mixture, e.g. water / toluene, to separate the diols from the residual salts. Finally, the diols can be obtained by crystallization.

[0098] A preferred embodiment of the present invention is as follows.

[0099] 1. A method for recovering rubber modified vinyl (co)polymers from polycarbonate resin or optionally crushed molded parts made therefrom, comprising: Polycarbonate resin is A) a polycarbonate based on aromatic or aliphatic diols or mixtures thereof; B) a rubber modified vinyl (co)polymer; wherein the method comprises: i) contacting polycarbonate resin or optionally crushed molded parts made therefrom with at least one alcohol together with at least one transesterification catalyst to obtain a slurry (i), wherein the solids content of the slurry (i) comprises the polycarbonate resin or optionally crushed molded parts made therefrom and the liquid content of the slurry (i) comprises the alcohol; ii) heating the slurry (i) to 60°C to 90°C, preferably 65°C to 85°C, and maintaining the temperature to obtain a slurry (ii), the solid content of the slurry (ii) comprising the rubber modified vinyl (co)polymer and the liquid content of the slurry comprising the aliphatic and / or aromatic diol; iii) separating the solids from the liquid of the slurry (ii); iv) optionally washing the solids; Including, The process, wherein both the slurry (i) and the slurry (ii) are free of ammonia and ammonium salts.

[0100] 2. The method of embodiment 1, wherein the polycarbonate is depolymerized by alcoholysis.

[0101] 3. The method of embodiment 1 or 2, wherein the weight ratio of alcohol to polycarbonate resin in step (i) is from 0.8:1 to 12:1.

[0102] 4. The method of any one of the preceding claims, wherein the weight ratio of alcohol to polycarbonate resin in step (i) is from 0.9:1 to 8:1.

[0103] 5. The method of any one of the preceding claims, wherein the weight ratio of alcohol to polycarbonate resin in step (i) is from 1:1 to 5:1.

[0104] 6. The method of any of the further embodiments, wherein the slurry (i) further comprises water in a weight ratio of alcohol to water of 10:90 to 90:10.

[0105] 7. The method according to embodiment 6, wherein the weight ratio of alcohol to water is 25:75 to 75:25.

[0106] 8. The method according to embodiment 6, wherein the weight ratio of alcohol to water is 40:60 to 60:40.

[0107] 9. The method according to any of the previous embodiments, wherein the alcohol used in step (i) is selected from methanol, ethanol, and mixtures thereof.

[0108] 10. The method of any of the previous embodiments, wherein the alcohol is methanol.

[0109] 11. The method of any of the preceding embodiments, wherein the transesterification catalyst is selected from the group consisting of titanium compounds, tin compounds, boron compounds, ammonium compounds, phosphonium compounds, silicon compounds, germanium compounds, tin compounds, titanium compounds, antimony compounds, zinc compounds, manganese compounds, zirconium compounds, alkali metal compounds, alkaline earth metal compounds, and mixtures thereof.

[0110] 12. The method of any of the previous embodiments, wherein the transesterification catalyst is an alkali metal salt or an alkaline earth metal salt.

[0111] 13. The method of any of the previous embodiments, wherein the transesterification catalyst is an alkali metal hydroxide or methanolate.

[0112] 14. The method of any of the previous embodiments, wherein the transesterification catalyst is sodium hydroxide.

[0113] 15. The method according to any of the previous embodiments, wherein the weight ratio of transesterification catalyst to polycarbonate resin in step (i) is from 0.001:1 to 3:1.

[0114] 16. The method according to any of the previous embodiments, wherein the weight ratio of transesterification catalyst to polycarbonate resin in step (i) is from 0.01:1 to 2:1.

[0115] 17. The method according to any of the previous embodiments, wherein the weight ratio of transesterification catalyst to polycarbonate resin in step (i) is from 0.1:1 to 1:1.

[0116] 18. The method according to any of the previous embodiments, wherein the temperature in step (ii) is between 65°C and 85°C.

[0117] 19. The method according to any of the previous embodiments, wherein the temperature in step (ii) is 75°C to 85°C.

[0118] 20. The method according to any of the previous embodiments, wherein step (ii) is carried out for 0.5 hours to 20 hours.

[0119] 21. The method according to any of the previous embodiments, wherein step (ii) is carried out for 1 hour to 8 hours.

[0120] 22. The method according to any of the previous embodiments, wherein step (ii) is carried out for 3 hours to 5 hours.

[0121] 23. The method according to any of the previous embodiments, wherein in step (i) and / or step (ii), slurry (i) and / or slurry (ii) are stirred.

[0122] 24. The method according to any of the previous embodiments, wherein step (iii) is carried out without the addition of a solvent that dissolves or swells the solids or a portion of the solids.

[0123] 25. The method according to any of the previous embodiments, wherein step (iii) is carried out by filtration.

[0124] 26. The method according to any of the previous embodiments, wherein step (iv) is carried out with an alcohol selected from methanol, ethanol, a mixture thereof, and optionally water.

[0125] 27. The method of any of the previous embodiments, wherein in a further step (v), aromatic and / or aliphatic diols are separated from the liquid fraction.

[0126] 28. The method of embodiment 27, wherein in step (v), the diol is isolated by crystallization.

[0127] 29. The method according to any of the previous embodiments, wherein the polycarbonate is an aromatic polycarbonate comprising structural units derived from bisphenol A.

[0128] 30. A rubber-modified vinyl (co)polymer B, B.1 5% to 95% by weight of at least one vinyl monomer, based on component B; B.2 on one or more elastomeric graft substrates, in an amount of 95% by weight to 5% by weight relative to component B, having a glass transition temperature of less than -10°C, determined by dynamic differential scanning calorimetry (DSC) according to DIN EN 61006 (1994 edition) at a heating rate of 10 K / min and by determination of Tg as the midpoint temperature, 4. The method according to any of the preceding embodiments, comprising:

[0129] 31. The method of any of the previous embodiments, wherein the rubber modified vinyl (co)polymer is acrylonitrile-butadiene-styrene.

[0130] 32. The method according to any of the previous embodiments, wherein the recovered rubber-modified vinyl (co)polymer has a glass transition temperature of the rubber phase of less than -80°C, measured as disclosed in the experimental part.

[0131] 33. The method according to any of the previous embodiments, wherein the recovered rubber-modified vinyl (co)polymer has a glass transition temperature of the rubber phase of less than -85°C, measured as disclosed in the experimental part.

[0132] 34. The method according to any of the above embodiments, wherein the polycarbonate resin further comprises, as component C, one or more polymer additives, i.e. polymer components, preferably selected from the group consisting of flame retardants, anti-dripping agents, flame retardant auxiliaries, smoke suppressants, lubricants and release agents, nucleating agents, antistatic agents, conductive additives, flow promoters, compatibilizers, further polymer constituents other than components A and B, fillers and reinforcing agents, and dyes and pigments.

[0133] 35. Use of the aromatic and / or aliphatic diol recovered in the process according to embodiment 27 or 28 in the production of polycarbonates.

[0134] 36. Use of the rubber-modified vinyl (co)polymer recovered in the process according to any one of embodiments 1 to 34 as a compounding partner in a polycarbonate compound.

[0135] 37. Use of the rubber-modified vinyl (co)polymer recovered according to any of the methods of embodiments 1 to 34 in the manufacture of a molded part.

[0136] 38. A polycarbonate compound comprising the rubber-modified vinyl (co)polymer recovered by the method of any one of embodiments 1 to 34.

[0137] 39. A molded part comprising the rubber-modified vinyl (co)polymer recovered according to the method of any one of embodiments 1 to 34.

[0138] Experimental Part 180 g of a PC-ABS compound was prepared from the following ingredients in a twin-screw extruder ZSK-25 (Werner & Pfleiderer) at a mass temperature of 260° C. A) 70 parts by weight of a bisphenol A-based polycarbonate (Makrolon™ M.2600, Covestro) having a weight average molecular weight of 26,000 g / mol (determined by gel permeation chromatography at room temperature using methylene chloride as solvent and a bisphenol A polycarbonate standard). B) 30 parts by weight of ABS (Magnum™ 3404, Trinseo) with an acrylonitrile:butadiene:styrene ratio of 23:10:67. The weight average molecular weight of the free styrene-acrylonitrile copolymer is 160.000 g / mol (measured by gel permeation chromatography (GPC) in tetrahydrofuran against polystyrene standards). C) 0.3 parts by weight of a mold release agent (pentaerythritol tetrastearate, Cognis Oleochemicals) and 0.1 parts by weight of a heat stabilizer (Irganox™ 1076, BASF)

[0139] 180 g of PC-ABS was introduced into a 1000 ml flask equipped with a tap water cooled condenser together with 166.65 g of 50 wt.% aqueous NaOH solution (Acros Organics, analytical grade), 216.66 g of methanol (Sigma Aldrich, analytical grade) and 216.66 g of demineralized water to obtain slurry (i). Slurry (i) was stirred for 240 minutes at 77 °C, the boiling point of the mixture at ambient pressure, using a magnetic stirrer. After 240 minutes, slurry (ii) was obtained containing solid particles in solution, which was filtered through a pleated filter paper (Whatman 595 1 / 2 type) with pore sizes of 4 μm to 7 μm, leaving ABS solid particles on the filter paper. The ABS solid particles were washed with 1200 g of methanol and five times with 1600 g of demineralized water. The ABS particles were dried overnight in an oven at 70 °C and analyzed as described below.

[0140] The liquid fraction containing bisphenol A was acidified to pH 2-3 with 37% HCl (supplier: Sigma Aldrich, 37% ACS reagent) and the liquid containing water and methanol was evaporated at a temperature of 90 °C, starting from ambient pressure and then reduced to 20 mbar. The remaining solid containing NaCl and BPA was dissolved in a mixture of 900 g demineralized water and 1200 g toluene (supplier: Merck, analytical grade) at 90 °C. The aqueous and toluene phases were separated through a separatory funnel at 90 °C and the toluene fraction was cooled to a temperature of about 5 °C. Under these conditions, bisphenol A crystallizes from the solvent, so that it is possible to selectively separate the bisphenol A crystals by filtration. For this filtration, pleated filter paper (Whatman 595 1 / 2 type) with a pore size of 4 μm to 7 μm was also used.

[0141] The quality of the recovered ABS powder was evaluated in terms of glass transition temperature and phase morphology and compared with virgin ABS (Magnum™ 3404, Trinseo).

[0142] The glass transition temperatures Tg of the recovered and virgin ABS were determined in accordance with the DIN EN ISO 6721-7 standard in the non-resonant torsional mode (shear modulus G'') at a frequency of 1 Hz and a heating rate of 3 K / min in the temperature range from -150 °C to the softening of the material, which is the temperature associated with the peak maximum of the loss modulus (G'') curve. * The results were measured using dynamic mechanical analysis (DMA) at 37 °C (T). The results are summarized in Table 1.

[0143] [Table 1]

[0144] As can be seen from Table 1, the glass transition temperatures of both polybutadiene and SAN are very similar. Especially the Tg(polybutadiene) indicates that the rubber graft substrate in the recovered ABS maintains its elastomeric properties, and therefore it can be expected that this ABS can be used in standard applications for this type of material.

[0145] In addition to the mechanical data, the phase morphology was also investigated.

[0146] After imaging with OsO4, TEM images of ultrathin sections of both recovered and virgin ABS were made (made with a Hitachi HT7800). As the recovered ABS was obtained in a powder state, it had to be dried at 80 °C for at least 4 h and then pressed before ultrathin sectioning. Control experiments with raw ABS demonstrated that the pressing operation had no effect on the morphology.

[0147] Figure 1 is a TEM image of the recovered ABS, whereas Figure 2 is a TEM image of the virgin ABS raw material used to prepare the PC-ABS resin.

[0148] The images show the same morphology and the same domain size for both ABS materials, further supporting that the method according to the present invention preserves the properties of rubber modified vinyl (co)polymers.

Claims

1. 1. A method for recovering rubber-modified vinyl (co)polymers from polycarbonate resin or optionally crushed molded parts made therefrom, comprising: The polycarbonate resin is A) a polycarbonate based on an aromatic or aliphatic diol or a mixture thereof; B) a rubber-modified vinyl (co)polymer; wherein the method comprises: i) contacting the polycarbonate resin or optionally crushed molded parts made therefrom with at least one alcohol together with at least one transesterification catalyst to obtain a slurry (i), wherein the solids content of the slurry (i) comprises the polycarbonate resin or optionally crushed molded parts made therefrom, and the liquid content of the slurry (i) comprises the alcohol; ii) heating the slurry (i) to 60°C to 90°C and maintaining the temperature to obtain a slurry (ii), wherein the solid content of the slurry (ii) comprises the rubber-modified vinyl (co)polymer and the liquid content of the slurry comprises the aliphatic and / or aromatic diol; iii) separating the solids from the liquids of the slurry (ii); iv) optionally washing the solids; Including, The process wherein both the slurry (i) and the slurry (ii) are free of ammonia and ammonium salts.

2. 10. The method of claim 1, wherein the slurry (i) further comprises water in a weight ratio of alcohol to water of from 10:90 to 90:

10.

3. 3. The method of claim 1 or 2, wherein step (iii) is carried out without the addition of a solvent that dissolves or swells the solids or a portion of the solids.

4. 3. The method according to claim 1 or 2, wherein the temperature in step (ii) is from 75°C to 85°C.

5. 3. The process of claim 1 or 2, wherein the transesterification catalyst is an alkali metal hydroxide or methanolate.

6. 6. The method of claim 5, wherein the transesterification catalyst is sodium hydroxide.

7. 3. The process of claim 1 or 2, wherein the weight ratio of transesterification catalyst to polycarbonate resin in step (i) is from 0.1:1 to 1:

1.

8. 3. The method of claim 1 or 2, wherein the weight ratio of alcohol to polycarbonate resin in step (i) is from 0.8:1 to 12:

1.

9. 3. The method according to claim 1 or 2, wherein the recovered rubber-modified vinyl (co)polymer has a glass transition temperature of the rubber phase of less than -80°C, measured as disclosed in the experimental part.

10. 3. Use of the rubber-modified vinyl (co)polymer recovered in the process according to claim 1 or 2 as a compounding partner in polycarbonate compounds.