POLYCARBONATE WITH CARBOXY END GROUPS AND METHOD FOR PRODUCING THE POLYCARBONATE

Description

[0001] The present invention relates to an aromatic polycarbonate having carboxy end groups, a process for producing an aromatic polycarbonate, the use of the aromatic polycarbonate for producing copolymers, a process for producing the copolymers and a molding composition and a molded article containing the copolymers.

[0002] Polycarbonate has been used for many years to produce transparent or translucent (translucent) molded articles. In recent years, applications involving innovative lighting concepts and functional integration have emerged in the automotive, construction, and electronics sectors, for which translucent molding compounds are used.

[0003] However, polycarbonate is insufficient for some applications with regard to important properties such as scratch resistance, stress cracking resistance under the influence of chemicals, mechanical properties, and processing behavior (melt flowability). The development of polymer blends of polycarbonate with other thermoplastics is a frequently pursued approach to meet specific technical requirements by combining the specific property advantages of polycarbonate with those of the polymer blend partners, ideally in a synergistic manner. Polymer blends of polycarbonate (PC) and polymethyl methacrylate (PMMA), for example, can demonstrate improvements over pure polycarbonate in terms of scratch resistance, stress cracking resistance under the influence of chemicals, and melt flowability. At the same time, the material ductility can be increased compared to polymethyl methacrylate.

[0004] However, the advantageous combinations of properties achievable with polymer blends often preclude transparency or translucency of molded articles produced from them. Polycarbonate and the other thermoplastic contained in the polymer blend are generally not completely miscible and therefore form two-phase morphologies with a matrix phase consisting of one polymer and domains of the other polymer distributed therein. Due to the usually different refractive indices of the blend partners, light scattering occurs at the numerous phase boundaries and light transmission is therefore significantly reduced overall compared to that of the pure blend components. Such blends consisting of polycarbonate and polymers that are immiscible with polycarbonate are generally opaque, i.e. they cannot be translucent or can only be translucent with insufficient light output.

[0005] Furthermore, the phase boundaries can represent mechanical weak points and lead to material failure, particularly under the influence of chemicals.

[0006] One possibility described in the literature for achieving improved compatibility between polycarbonate and a thermoplastic blend partner that is immiscible with PC, such as PMMA, is the in-situ formation of block copolymers from polycarbonate and the polymer blend partner, in this specific case PMMA, in a reactive extrusion process. The chemical reaction between the two polymers at the interface of the two-phase melt mixture can be accelerated by the use of a catalyst.

[0007] WO 2020 / 212229 A1 discloses a reactive compounding process for producing a thermoplastic molding compound using aromatic polycarbonate that contains no reactive functional groups and another polymer that contains at least one type of functional group selected from ester, epoxy, hydroxy, carboxy, and carboxylic anhydride groups, with a specific phosphonium salt being used as the catalyst. The application also discloses, in particular, the production of transparent thermoplastic PC / PMMA molding compounds using such a process.

[0008] WO 2016 / 138246 A1 discloses transparent PC / PMMA blends containing 9.9 to 40 wt.% polycarbonate and 59.9 to 90 wt.% PMMA, which are produced from non-reactively functionalized polymer components in a reactive melt extrusion using 0.0025 to 0.1 wt.% of a tin catalyst.

[0009] WO 2016 / 189494 A1 discloses transparent PC / PMMA blends containing 80 to 95 wt.% of a specifically specified branched polycarbonate with an end-cap content of 45% to 80% and 4.9 to 20 wt.% PMMA, which are produced in a melt extrusion by transesterification using 0.1 to 1.5 wt.% of a catalyst, preferably selected from Zn, Sn and Ag compounds.

[0010] Although molded parts made from blend compositions produced by these processes are improved in terms of light transmission compared to molded parts made from PC / PMMA compositions produced by purely physical mixing processes, they generally have insufficient light output when illuminated by transillumination for many applications and insufficient mechanical properties, in particular insufficient material ductility.

[0011] In addition to the described use of a catalyst, the in-situ formation of copolymers can also be promoted by suitable functionalization of the polycarbonate.

[0012] US 4,853,458 and US 4,959,411 describe the production of terminally carboxy-functionalized polycarbonates, wherein a carboxylic acid or carboxylic acid derivative-substituted phenol, preferably t-butyl p-hydroxybenzoate, is incorporated terminally into the PC as a chain terminator in a polycarbonate-forming reaction. Also disclosed is a process for producing a block copolymer by reacting, in organic solution or by melt compounding, an epoxy-functionalized olefin polymer with such a carboxy- or carboxylic acid derivative-functionalized polycarbonate, as well as the use of such a copolymer for compatibilizing polymer blends of polycarbonate and polyolefin with the aim of reducing their tendency to delaminate. These applications provide no information on the suitability of such functionalized polycarbonates for producing transparent PC / PMMA blends.

[0013] For the latter approach, a reaction between a suitably functionalized polycarbonate and the polymeric blend partner, the precise type of functionalization of the polycarbonate—that is, the selection and concentration of suitable reactive groups—is of great importance, as is an efficient process for its production. Furthermore, the molding compound produced from the polycarbonate and the blend partner should be well-suited for thermoplastic processing into molded articles. There is still room for improvement in these aspects, given the current state of the art.

[0014] It was therefore desirable to provide an aromatic polycarbonate which is particularly suitable for the production of block copolymers containing at least one polycarbonate block, which are suitable, for example, as compatibilizers in polymer blends.

[0015] It was particularly desirable to provide an aromatic polycarbonate that is particularly suitable for the production of thermoplastic translucent molding compositions and moldings containing polycarbonate and a vinyl polymer, preferably polymethyl methacrylate.

[0016] It was also desirable to provide a process by which the functionalized polycarbonate could be produced simply and with a favorable ratio to undesirable by-products.

[0017] Surprisingly, it was found that an aromatic polycarbonate containing A) structural units derived from a hydroxybenzoic acid and present as end groups with free COOH functionality and B) structural units derived from a hydroxybenzoic acid, wherein component B) is selected from at least one representative of B1) structural units derived from a hydroxybenzoic acid and present as end groups with esterified COOH functionality, and B2) structural units derived from a hydroxybenzoic acid, which are incorporated into the polymer chain via an ester group (= B2-a) or acid anhydride group (= B2-b), wherein the molar ratio of the amount of component A to the amount of component B is in the range of 1.3 to 50, has the desired properties.

[0018] In a preferred embodiment, the polycarbonate further contains, as component C, structural units derived from monophenols (i.e., aromatics with only one phenolic OH functionality) which do not contain any carboxy or carboxy derivative functionalities, as end groups.

[0019] More preferably, component C is present in the polycarbonate according to the invention in a molar proportion, based on a total of 100 mol% of the molar proportions of components A, B1, B2 and C, of ​​20 to 90 mol%, particularly preferably 40 to 85 mol%, further preferably 45 to 80 mol%, particularly preferably 50 to 75 mol%.

[0020] In this application, the terms "carboxy" and "carboxyl" are used synonymously and stand for COOH groups.

[0021] The aromatic polycarbonate according to the invention is hereinafter referred to as aromatic polycarbonate containing (terminal) COOH end groups.

[0022] It has also been surprisingly found that such an aromatic polycarbonate can be produced by a process comprising the following steps: (i) Preparation of an aromatic polycarbonate containing end groups derived from a hydroxybenzoic acid ester by phosgenation in the interfacial process or in organic solution of aromatic diols in the presence of an ester of a hydroxybenzoic acid (preferably p-hydroxybenzoic acid) or a mixture of several esters of one or more structurally different hydroxybenzoic acids, more preferably esterified with an alcohol of the general structural formula (1) where R 1 and R 2 independently of one another represent hydrogen or an alkyl, aryl or alkylaryl radical having 1 to 10 C atoms, preferably hydrogen or an alkyl radical having 1 to 4 C atoms, particularly preferably hydrogen or a methyl radical, most preferably both represent a methyl radical, and R 3 and R 4 independently of one another represent hydrogen or an alkyl, aryl or alkylaryl radical having 1 to 10 C atoms, preferably hydrogen or an alkyl radical having 1 to 4 C atoms, particularly preferably hydrogen or a methyl radical, most preferably both represent hydrogen as chain terminators, wherein during the preparation according to process step (i) a temperature of 260°C is never exceeded, preferably a temperature of 240°C is never exceeded, more preferably a temperature of 230°C is never exceeded, most preferably a temperature of 200°C is never exceeded,and (ii) thermal end group pyrolysis of the end groups derived from hydroxybenzoic acid esters in the product from process step (i) with elimination of an alkene of the general structural formula R 3 R 4 C=CR 1 R 2 , where R 1 , R 2 , R 3 and R 4 have the meanings given above, where the product from process step (i) is pyrolyzed in process step (ii) with the addition of thermal or mechanical energy in the temperature range 230 to 265°C, preferably 230 to 260°C, particularly preferably 230 to 255°C and the resulting alkene is removed from the aggregate and where the residence time at the temperature in the range 230 to 265°C, preferably 230 to 260°C, particularly preferably 230 to 255°C is a minimum of 15 s and a maximum of 10 minutes, preferably a minimum of 20 s and a maximum of 5 minutes, particularly preferably a minimum of 30 seconds and a maximum of 2 minutes.

[0023] Preferably, the alcohol with which the hydroxybenzoic acid is esterified is a tertiary alcohol, most preferably tert-butanol.

[0024] It was surprisingly found that if the above-mentioned temperature and residence time conditions are not observed, no polycarbonates with the structural features according to the invention, as required to solve the technical problem, are obtained.

[0025] In a preferred embodiment, process step (ii) is carried out in a compounding unit selected from the group comprising single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, continuous or discontinuous internal kneaders and film extruders, wherein the product from process step (i) is melted in process step (ii) in these compounding units with the addition of thermal or mechanical energy and pyrolyzed at a melt temperature in the temperature range 230 to 265°C, preferably 230 to 260°C, particularly preferably 230 to 255°C and the resulting alkene is removed from the unit and wherein the residence time at the temperature in the range 230 to 265°C, preferably 230 to 260°C, particularly preferably 230 to 255°C is at least 15 s and at most 10 minutes, preferably at least 20 s and at most 5 minutes, particularly preferably at least 30 s and a maximum of 2 minutes.In this preferred embodiment, the aromatic polycarbonate produced in process step (i) is preferably processed after the . (ia) polymerization by phosgenation in the interfacial process or in organic solution of aromatic diols in the presence of an ester of a hydroxybenzoic acid (ib) in a subsequent work-up step, i.e. the solvent or solvent mixture used in process step (ia) is at least largely separated.

[0026] In both the polymerization process step (ia) and the workup step (ib), a temperature of 260°C is never exceeded, preferably a temperature of 240°C is never exceeded, more preferably a temperature of 230°C is never exceeded, most preferably a temperature of 200°C is never exceeded.

[0027] The processing according to step (ib) is preferably carried out by spray drying or by precipitation of the polycarbonate in a suitable solvent, for example in isopropanol, methanol, or water, followed by separation of the solvent phase. This separation can be carried out, for example, by filtration, sedimentation followed by decantation, centrifugation, or a combination of these processes, each followed by drying. The drying is preferably carried out at temperatures in the range of 60 to 120°C, particularly preferably under reduced pressure.

[0028] In an alternative, likewise preferred process, process step (ii) can also be carried out as part of the isolation of the polycarbonate from process step (i), that is to say, for example, as part of the removal of (residual) solvent.In this case, the solvent or solvent mixture or, after partial removal of the solvent or solvent mixture in a process step (ib), residual solvent or solvent mixture is removed in process step (ii) by supplying thermal or mechanical energy in the temperature range 230 to 265°C, preferably 230 to 260°C, particularly preferably 230 to 255°C, optionally by applying a reduced pressure, and at the same time the end groups derived from a hydroxybenzoic acid ester are thermally pyrolyzed and the resulting alkene is also removed from the aggregate, the residence time at the temperature in the range 230 to 265°C, preferably 230 to 260°C, particularly preferably 230 to 255°C being a minimum of 15 s and a maximum of 10 minutes, preferably a minimum of 20 s and a maximum of 5 minutes, particularly preferably a minimum of 30 s and a maximum of 2 minutes.For such a process according to the invention, process units selected from the group consisting of vented extruders, strand evaporators, film evaporators and foam evaporators are preferably suitable. Aromatic polycarbonate

[0029] The aromatic polycarbonate according to the invention contains A) structural units derived from a hydroxybenzoic acid and present as end groups with free COOH functionality (also referred to as COOH or synonymously as carboxy or carboxyl end groups) and B) structural units derived from a hydroxybenzoic acid, wherein component B) is selected from at least one representative of B1) structural units derived from a hydroxybenzoic acid and present as end groups with esterified COOH functionality, and B2) structural units derived from a hydroxybenzoic acid, which are incorporated into the polymer chain via an ester group (= B2-a) or acid anhydride group (= B2-b), and is characterized in that the molar ratio of the amounts of components A and B is in the range 1.3 to 50, preferably in the range 1.5 to 25, particularly preferably in the range 1.8 to 10, most preferably in the range 2.0 to 5.0.

[0030] When calculating the molar ratio of the amounts of components A and B, the sum of the molar amounts of components B1, B2-a and B2-b is used as the molar amount of component B.

[0031] The polycarbonates according to the invention preferably have an acid number of at least 0.3 mg potassium hydroxide (KOH) / g, more preferably at least 0.5 mg potassium hydroxide (KOH) / g, more preferably at least 1.0 mg KOH / g, most preferably at least 1.5 KOH / g, in each case determined in dichloromethane (DCM) / ethanol as solvent according to DIN EN ISO 2114, Method A in version 2002-6 by means of potentiometric titration with ethanolic KOH solution at room temperature.

[0032] The polycarbonates according to the invention preferably have an acid number in the range from 0.5 to 10 mg potassium hydroxide (KOH) / g, more preferably 1 to 7 mg KOH / g, particularly preferably 1.3 to 5.0 mg KOH / g, most preferably 1.5 to 3.5 mg KOH / g, in each case determined in dichloromethane (DCM) / ethanol as solvent according to DIN EN ISO 2114, Method A in version 2002-6 by means of potentiometric titration with ethanolic KOH solution at room temperature.

[0033] To determine the acid number, the polymer to be tested is dissolved in 50 ml of dichloromethane at room temperature at a concentration of 10 g / L. Before potentiometric titration with 0.1 N ethanolic KOH, 5 ml of ethanol is added to the sample solution.

[0034] In a preferred embodiment, the polycarbonate is characterized in that the molar ratio of the amount of component B2 to the sum of the amounts of components A and B2 is <0.3, preferably <0.2. When calculating this molar ratio, the sum of the molar amounts of components B2-a and B2-b is used as the molar amount of component B2.

[0035] In a further preferred embodiment, the polycarbonate is characterized in that the molar ratio of the amount of component A to the sum of the amounts of components A and B1 is >0.75, preferably >0.9.

[0036] Suitable hydroxybenzoic acids include hydroxybenzoic acids with the carboxylic acid group in the para, meta, or ortho position to the phenolic OH group. Hydroxybenzoic acids with the carboxylic acid group in the para position to the phenolic OH group are preferred. These can be monosubstituted or polysubstituted at the free aromatic ring positions with C 1 -C 10 alkyl, aryl, or alkylaryl radicals, preferably with C 1 -C 4 alkyl radicals, particularly preferably with methyl, or alternatively with halogen or ether groups, for example and preferably with methoxy.

[0037] Particularly preferably, the structural units derived from a hydroxybenzoic acid are structural units derived from p-hydroxybenzoic acid which does not contain any further substituents.

[0038] The structural units derived from a hydroxybenzoic acid and present as end groups with esterified COOH functionality according to component B1 are preferably esters of a hydroxybenzoic acid (preferably p-hydroxybenzoic acid), more preferably esterified with an alcohol of the structural formula (1) given above.

[0039] The alcohol is preferably a tertiary alcohol, most preferably tert-butanol.

[0040] The structures for components A, B1 and B2 are shown as examples for the particularly preferred p-hydroxybenzoic acid as hydroxybenzoic acid in formulas (2), (3), (4a) and (4b), where formula (2) stands for component A, formula (3) for component B1 (using the particularly preferred tert-butyl ester as an example), and formulas (4a) and (4b) for component B2. Formula (4a) shows the structural unit derived from a hydroxybenzoic acid, which is incorporated into the polymer chain via an ester group (component B2-a). Formula (4b) shows the structural unit derived from a hydroxybenzoic acid, which is incorporated into the polymer chain via an acid anhydride group (component B2-b).

[0041] In formulas (2), (3), (4a) and (4b), m and n each represent the number of monomer units shown in the brackets.

[0042] The molar proportion of components A, B1, and the two possible structures for component B2, as well as the corresponding molar ratios of these components relevant to the invention, are determined using 1< H NMR spectroscopy. For this purpose, the polycarbonate is dissolved in deuterated chloroform at room temperature. The various structural units derived from a hydroxybenzoic acid can be differentiated using the NMR signals of the aromatic protons ortho to the carboxy functionality or the derivatized carboxy functionality, and the molar amounts or ratios of the various structures can be quantified based on the integrated intensities of these signals. In the case of the particularly preferred p-hydroxybenzoic acid, these are doublets in all cases due to the spin-spin coupling of the ortho aromatic protons with the meta aromatic protons to the carboxy functionality or the derivatized carboxy functionality.For all components A, B1 and B2, the corresponding NMR signals are each due to two protons, so that the ratios of the intensities of the corresponding NMR signals can be used to directly determine the corresponding molar ratio of the proportions of the various components in the polycarbonate.

[0043] In the special case of the particularly preferred p-hydroxybenzoic acid, the protons in the structural units derived from p-hydroxybenzoic acid according to component A in the range around 8.14 ppm, the protons in the structural units derived from p-hydroxybenzoic acid according to component B1 in the case of the tert-butyl ester according to formula (2) in the range around 8.05 ppm, the protons in the structural units derived from p-hydroxybenzoic acid according to component B2-b (formula 4b), which are incorporated into the polymer chain via an acid anhydride group, in the range around 8.22 ppm and the protons in the structural units derived from p-hydroxybenzoic acid according to component B2-a (formula 4a), which are incorporated into the polymer chain via an ester group, in the range around 8.26 ppm, where all chemical shifts are given in parts per million (ppm) relative to trimethylsilane (TMS) as a reference.

[0044] In this respect, preferred polycarbonates are characterized in that the structural units derived from hydroxybenzoic acid according to components A, B1 and B2 are in all cases structural units derived from p-hydroxybenzoic acid and the structural units derived from a hydroxybenzoic acid and present as end groups with esterified COOH functionality according to component B1 are of tert.-Butyl-4-hydroxybenzoate derived structural units according to formula (2), characterized in that in their 1< H NMR spectrum, which was measured in a solution of the polycarbonate in deuterated chloroform at room temperature, the ratio of the integrated intensity of the doublet signal in the range around 8.14 ppm to the sum of the integrated intensities of the doublet signals in the ranges around 8.05 ppm, 8.22 ppm and 8.26 ppm is in the range 1.3 to 50, preferably in the range 1.5 to 25, particularly preferably in the range 1.8 to 10, most preferably in the range 2.0 to 5.0, wherein the chemical shifts are in each case referenced against tetramethylsilane (TMS).

[0045] In an alternative embodiment, this ratio is in the range 3 to 50, preferably in the range 3 to 25, most preferably in the range 3 to 10.

[0046] Furthermore, these preferred polycarbonates are particularly preferably additionally characterized in that in their 1< H NMR spectrum, which was measured in a solution of the polycarbonate in deuterated chloroform at room temperature, the ratio of the sum of the integrated intensities of the doublet signals in the areas around 8.22 ppm and 8.26 ppm to the sum of the integrated intensities of the doublet signals in the areas around 8.14 ppm, 8.22 ppm and 8.26 ppm is <0.3, preferably <0.2, wherein the chemical shifts are referenced against tetramethylsilane (TMS).

[0047] Furthermore, these preferred polycarbonates are particularly preferably additionally characterized in that in their 1< H NMR spectrum, which was measured in a solution of the polycarbonate in deuterated chloroform at room temperature, the ratio of the integrated intensity of the doublet signal in the range around 8.14 ppm to the sum of the integrated intensities of the doublet signals in the ranges around 8.14 ppm and 8.05 ppm is >0.75, preferably >0.9, wherein the chemical shifts are referenced against tetramethylsilane (TMS).

[0048] In a preferred embodiment, the polycarbonate further contains, as component C, structural units derived from monophenols (i.e., aromatics with only one phenolic OH functionality) that do not contain any carboxy or carboxy-derivative functionalities, as end groups. The monophenols from which component C is derived are preferably phenol or alkyl-, aryl-, alkylaryl-, and / or halogen-substituted phenols, particularly preferably phenol or C 1 - to C 12 -alkylphenols, further preferably phenol or p-tert-butylphenol, most preferably p-tert-butylphenol.

[0049] Other substances that can be used include, for example, p-chlorophenol, 2,4,6-tribromophenol, 4-(2,4,4-trimethylpentyl)phenol, 4-(1,1,3,3-tetramethylbutyl)phenol, 3,5-di-tert-butylphenol, p-iso-octylphenol, p-tert-octylphenol, p-dodecylphenol and 4-(3,6-dimethyl-3-heptyl)phenol.

[0050] In the production of the polycarbonate according to the invention, the monophenols mentioned here, which do not contain any carboxy or carboxy derivative functionalities, are used in a preferred embodiment as further chain terminators.

[0051] Mixtures of several monophenolic chain terminators that do not contain carboxy or carboxy derivative functionalities can also be used.

[0052] More preferably, component C is present in the polycarbonate according to the invention in a molar proportion, based on a total of 100 mol% of the molar proportions of components A, B1, B2, i.e., the sum of the molar proportions of B2-a and B2-b, and C, of ​​20 to 90 mol%, particularly preferably 40 to 85 mol%, further preferably 45 to 80 mol%, particularly preferably 50 to 75 mol%. With these proportions, on the one hand, sufficient copolymer formation of polycarbonate and the blend partner can be achieved, and on the other hand, undesirable crosslinking reactions are avoided, as explained again below.

[0053] The amount of component C in the polycarbonate and its molar fraction, based on a total of 100 mol% of the molar fractions of components A, B1, B2, and C, can also be quantified by 1< H NMR spectroscopy. In the particularly preferred case where component C is structural units derived from p-tert-butylphenol, the NMR signal of the three methyl groups in the tert-butyl residue in the structural units derived from p-tert-butylphenol is particularly suitable for this purpose. This is a singlet with a chemical shift in the range of 1.32 ppm, referenced against trimethylsilane, which is assigned to nine protons.

[0054] The polycarbonates according to the invention can

[0055] as component A also several structural units with free COOH functionality derived from structurally different hydroxybenzoic acids, present as end groups, as component B1 also several different structural units present as end groups with esterified COOH functionality, which can differ both in the structural nature of the hydroxybenzoic acid and in the structural nature of the tertiary alcohol used to form the ester, as component B2 also several structural units derived from structurally different hydroxybenzoic acids, which are incorporated into the polymer chain via an ester or acid anhydride group and / or as component C several structural units derived from structurally different hydroxybenzoic acids which do not contain any carboxy or carboxy derivative functionalities, as end groups.

[0056] In this case, for all ratio ranges of these structural units mentioned in this application, the sums of all molar amounts of the structurally different components A, B1, B2 and C are used as molar amounts of the components A, B1, B2 and C to calculate the corresponding ratios.

[0057] The polycarbonate preferably has a weight-average molecular weight M w , measured by GPC (gel permeation chromatography) at room temperature in methylene chloride with BPA polycarbonate standard), of 5,000 to 40,000 g / mol, more preferably of 7,000 to 35,000 g / mol, particularly preferably of 10,000 to 30,000 g / mol.

[0058] For the use of the polycarbonate according to the invention as a molding composition for producing molded parts or as a component of a molding composition for producing molded parts, the polycarbonate according to the invention preferably has a weight-average molecular weight M w , measured by GPC (gel permeation chromatography) at room temperature in methylene chloride with BPA polycarbonate standard), of 18,000 to 40,000 g / mol, more preferably of 20,000 to 35,000 g / mol, particularly preferably of 24,000 to 32,000 g / mol.

[0059] For the use of the polycarbonate according to the invention for producing block copolymers comprising blocks of aromatic polycarbonate and blocks of a polymer immiscible with such aromatic polycarbonates, it may be advantageous and preferred, with regard to the effectiveness of these block copolymers as compatibilizers in thermoplastic polymer compositions comprising aromatic polycarbonate and those polymers immiscible with aromatic polycarbonate, to use a polycarbonate according to the invention having a weight-average molecular weight M w , measured by GPC (gel permeation chromatography) at room temperature in methylene chloride with BPA polycarbonate standard), of 5,000 to 25,000 g / mol, further preferably of 7,000 to 20,000 g / mol, particularly preferably of 8,000 to 18,000 g / mol, most preferably of 10,000 to 15,000 g / mol.

[0060] If a mixture of several polycarbonates with different individual acid numbers, different ratios of A / B, different ratios of B2 / (A+B2), different ratios of A / (A+B1) and / or different individual weight-average molecular weights Mw is used, this mixture has an acid number, a ratio of A / B, a ratio of B2 / (A+B2), a ratio of A / (A+B1) or a weight-average molecular weight Mw in one of the above-mentioned ranges.

[0061] The preparation of aromatic polycarbonates in general is known from the literature (for the preparation of aromatic polycarbonates see, for example, Schnell, "Chemistry and Physics of Polycarbonates", Interscience Publishers, 1964).

[0062] The preparation of the aromatic polycarbonates according to the invention containing terminal COOH groups is carried out in a manner similar to that in US 4,853,458 B by reacting diphenols (aromatic diols) with phosgene, according to the interfacial process using an ester of a hydroxybenzoic acid as described above or a mixture of several esters of one or a mixture of several structurally different hydroxybenzoic acids, wherein when using such a mixture the esters used can differ both in the nature of the hydroxybenzoic acid and in the nature of the alcohol used to form the ester, as a monophenolic chain terminator and subsequent release of the terminal COOH groups (COOH functionality).

[0063] In a preferred embodiment, in addition to the ester of a hydroxybenzoic acid, the above-described further monophenols which do not contain carboxy or carboxy derivative functionalities are used as chain terminators.

[0064] If such further monophenolic chain terminators which do not contain any carboxy or carboxy derivative functionalities are used, the aromatic polycarbonate thus produced contains, in addition to components A, B1 and B2, structural units derived from the monophenolic chain terminators as component C, most preferably derived from p-tert-butylphenol.

[0065] In the production of the polycarbonates according to the invention, the monophenolic chain terminators, which do not contain any carboxy or carboxy derivative functionalities, are used in the chain terminator mixture consisting of these monophenolic chain terminators, which do not contain any carboxy or carboxy derivative functionalities, and the esters of a hydroxybenzoic acid used as chain terminators, preferably in a proportion of 20 to 90 mol%, particularly preferably 40 to 85 mol%, further preferably 45 to 80 mol%, most preferably 50 to 75 mol%. The resulting respective difference from 100 mol% then corresponds to the proportion of the esters of one or more hydroxybenzoic acids. This is therefore preferably 10 to 80 mol%, particularly preferably 15 to 60 mol%, further preferably 20 to 55 mol%, most preferably 25 to 50 mol%.

[0066] If the content of hydroxybenzoic acid esters used in the chain-terminating mixture exceeds the specified preferred ranges, undesirable crosslinking reactions may occur during reactive compounding with the blend partner, resulting in the reactive mixture no longer being thermoplastically processable. If the content of hydroxybenzoic acid esters used in the chain-terminating mixture is lower than the specified preferred ranges, the desired copolymer formation between the polycarbonate and the blend partner can no longer occur to a sufficient extent to achieve the desired technical effect.

[0067] The molecular weight of the polycarbonates produced in this way can be precisely adjusted within a wide range in a manner known to the person skilled in the art by varying the ratio of monophenolic chain terminators to diphenols.

[0068] The ratio of the hydroxybenzoic acid esters used in the chain terminator mixture to the optionally used monophenolic chain terminators, which do not contain any carboxy or carboxy derivative functionalities, as well as the conditions during the subsequent release of the COOH groups, allows the content of COOH groups in the aromatic polycarbonate to be adjusted in a targeted manner over a wide range.

[0069] The terminal COOH groups (i.e., hydroxybenzoic acid end groups) can be released from polycarbonates with hydroxybenzoic acid ester end groups, for example, by thermal end group pyrolysis or by acidic ester cleavage.

[0070] The preferred method for releasing the terminal COOH groups is thermal end-group pyrolysis. Temperatures of 230 to 265°C are preferred, particularly preferably 230 to 260°C, and most preferably 230 to 255°C are used. The residence times at these temperatures are a minimum of 15 s and a maximum of 10 minutes, preferably a minimum of 20 s and a maximum of 5 minutes, particularly preferably a minimum of 30 s and a maximum of 2 minutes. Under these thermal conditions, the polycarbonate backbone is not significantly degenerated, and undesirable side reactions are minimized. By varying the temperature in particular, but also the residence time at this temperature, the proportion of COOH end groups released from component B1 according to component A and also the ratio to undesirable by-products or subsequent products according to component B2 can be controlled. Component C generally remains unaffected by thermal end-group pyrolysis.

[0071] Diphenols for the preparation of aromatic polycarbonates and / or aromatic polyester carbonates are preferably those of the formula (5) where A is a single bond, C 1 to C 5 alkylene, C 2 to C 5 alkylidene, C 5 to C 6 cycloalkylidene, -O-, -SO-, -CO-, -S-, -SO 2 -, C 6 to C 12 arylene, to which further aromatic rings optionally containing heteroatoms may be condensed, or a radical of the formula (6) or (7) B is each C 1 to C 12 alkyl, preferably methyl, halogen, preferably chlorine and / or bromine, x is each independently 0, 1 or 2, p is 1 or 0, and R 5< and R 6< for each X 1< can be selected individually, independently of one another are hydrogen or C 1 to C 6 alkyl, preferably hydrogen, methyl or ethyl, X1 is carbon and m is an integer from 4 to 7, preferably 4 or 5, with the proviso that on at least one atom X 1<, R 5< and R 6< are simultaneously alkyl.

[0072] Preferred diphenols are hydroquinone, resorcinol, dihydroxydiphenols, bis-(hydroxyphenyl)-C 1 -C 5 -alkanes, bis-(hydroxyphenyl)-C 5 -C 6 -cycloalkanes, bis-(hydroxyphenyl) ethers, bis-(hydroxyphenyl) sulfoxides, bis-(hydroxyphenyl) ketones, bis-(hydroxyphenyl) sulfones and α,α-bis-(hydroxyphenyl)-diisopropylbenzenes and their nuclear-brominated and / or nuclear-chlorinated derivatives.

[0073] Particularly preferred diphenols are 4,4'-dihydroxydiphenyl, 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'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfone, and their di- and tetrabrominated or chlorinated 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.

[0074] The diphenols can be used individually or as any mixture. The diphenols are known from the literature or are available by known methods.

[0075] In a preferred embodiment, the proportion of bisphenol A, based on the sum of all diphenols used in the preparation, is at least 50 mol%, particularly preferably at least 75 mol%, and most preferably at least 95 mol%. Most preferably, bisphenol A is used exclusively as the diphenol in the preparation of component A.

[0076] The aromatic polycarbonates may be branched in a known manner, preferably by incorporating 0.01 to 2.0 mol%, based on the sum of the diphenols used, of trifunctional or more than trifunctional compounds, for example those with three or more phenolic groups.

[0077] The polycarbonate containing COOH end groups is preferably a linear aromatic polycarbonate, more preferably a linear aromatic polycarbonate based on bisphenol A, particularly preferably based exclusively on bisphenol A. Additional polymer for producing a copolymer

[0078] The aromatic polycarbonate containing COOH end groups can be used to produce a copolymer. This is preferably a block copolymer, more preferably a block copolymer with a vinyl (co)polymer or polyolefin.

[0079] Suitable polymers with which the aromatic polycarbonate can form a copolymer have at least one type of functional group selected from ester, hydroxy, carboxy, carboxylic anhydride, and epoxy groups. Polymers containing ester, hydroxy, or epoxy groups are preferred. Particularly preferred are polymers containing epoxy groups.

[0080] In the case of an ester group as such a functional group, this can be a component of the polymer chain (polymer backbone), as is the case in a polyester, or a functional group of a monomer that is not directly involved in the structure of the polymer chain, as is the case in an acrylate polymer.

[0081] Mixtures of different such polymers can also be used. The mixtures can comprise polymers with similar functional groups or polymers with different functional groups.

[0082] In the context of the present invention, polymers containing carbonate groups, i.e. esters of carbonic acid, provided they do not contain aromatic structural units, are also regarded as further polymers which can form block copolymers with the aromatic polycarbonate.

[0083] Preferably, the further polymer is selected from the aforementioned vinyl (co)polymers containing functional groups, the aforementioned polyolefins containing functional groups and polyesters.

[0084] The vinyl (co)polymers according to the invention containing functional groups are preferably (co)polymers of at least one monomer from the group of (meth)acrylic acid (C 1 to C 8 ) alkyl esters (such as methyl methacrylate, n-butyl acrylate, tert-butyl acrylate), unsaturated carboxylic acids and carboxylic anhydrides, vinyl aromatics (such as styrene, α-methylstyrene), vinyl cyanides (unsaturated nitriles such as acrylonitrile and methacrylonitrile) and olefins (such as ethylene) and further vinyl monomers containing ester, hydroxyl, carboxy, carboxylic anhydride and epoxy groups.

[0085] Epoxy groups are, for example, and preferably, introduced by copolymerizing glycidyl methacrylate as an additional monomer together with the other monomer or monomers.

[0086] These (co)polymers are resinous and rubber-free. Such (co)polymers are known and can be produced by radical polymerization, particularly by emulsion, suspension, solution, or bulk polymerization.

[0087] Particularly suitable vinyl polymers contain structural units derived from glycidyl methacrylate.

[0088] A particularly suitable vinyl polymer is a copolymer of methyl methacrylate and glycidyl methacrylate.

[0089] Other particularly suitable vinyl polymers are styrene-acrylonitrile-glycidyl methacrylate terpolymers and styrene-methyl methacrylate-glycidyl methacrylate terpolymers.

[0090] Suitable polyesters can be aliphatic or aromatic polyesters.

[0091] In a preferred embodiment, the polyesters are aromatic; more preferably, they are polyalkylene terephthalates. In a particularly preferred embodiment, these are reaction products of aromatic dicarboxylic acids or their reactive derivatives, such as dimethyl esters or anhydrides, and aliphatic, cycloaliphatic, or araliphatic diols, as well as mixtures of these reaction products.

[0092] Particularly preferred aromatic polyalkylene terephthalates contain at least 80% by weight, preferably at least 90% by weight, based on the dicarboxylic acid component, of terephthalic acid residues and at least 80% by weight, preferably at least 90% by weight, based on the diol component, of ethylene glycol and / or 1,4-butanediol residues.

[0093] The preferred aromatic polyalkylene terephthalates can contain, in addition to terephthalic acid residues, up to 20 mol%, preferably up to 10 mol%, residues of other aromatic or cycloaliphatic dicarboxylic acids having 8 to 14 C atoms or aliphatic dicarboxylic acids having 4 to 12 C atoms, such as residues of phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, cyclohexanediacetic acid.

[0094] The preferred aromatic polyalkylene terephthalates can contain, in addition to ethylene glycol or 1,4-butanediol residues, up to 20 mol%, preferably up to 10 mol%, other aliphatic diols having 3 to 12 C atoms or cycloaliphatic diols having 6 to 21 C atoms, e.g. residues of 1,3-propanediol, 2-ethyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexane-dimethanol, 3-ethyl-2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,2-diethyl-1,3-propanediol, 2,5-hexanediol, 1,4-di-(β-hydroxyethoxy)-benzene, 2,2-bis-(4-hydroxycyclohexyl)-propane, 2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane, 2,2-bis-(4-β-hydroxyethoxy-phenyl)-propane and 2,2-bis-(4-hydroxypropoxyphenyl)-propane.

[0095] The aromatic polyalkylene terephthalates can be branched by incorporating relatively small amounts of tri- or tetrahydric alcohols or tri- or tetrabasic carboxylic acids, e.g., according to DE-A 1 900 270 and US Pat. No. 3,692,744. Examples of preferred branching agents are trimesic acid, trimellitic acid, trimethylolethane and propane, and pentaerythritol.

[0096] Particularly preferred are aromatic polyalkylene terephthalates which have been prepared solely from terephthalic acid and / or its reactive derivatives (e.g. its dialkyl esters) and ethylene glycol and / or 1,4-butanediol, and mixtures of these polyalkylene terephthalates.

[0097] The preferably used aromatic polyalkylene terephthalates have a viscosity number of 0.4 to 1.5 dl / g, preferably 0.5 to 1.2 dl / g, measured in phenol / o-dichlorobenzene (1: 1 parts by weight) in a concentration of 0.05 g / ml according to ISO 307 at 25°C in an Ubbelohde viscometer.

[0098] The aromatic polyalkylene terephthalates can be produced by known methods (see, for example, Kunststoff-Handbuch, Volume VIII, p. 695 ff., Carl-Hanser-Verlag, Munich 1973).

[0099] The further polymers are also preferably polyolefins containing functional groups, preferably polyolefins containing epoxy groups, particularly preferably polyolefins containing structural units derived from glycidyl methacrylate.

[0100] Polyolefins are produced by chain polymerization, for example, by radical or anionic polymerization. Alkenes are used as monomers. An alternative name for alkenes is olefins. The monomers can be polymerized individually or as a mixture of different monomers. Preferred monomers are ethylene, propylene, 1-butene, isobutene, 1-pentene, 1-heptene, 1-octene, and 4-methyl-1-pentene.

[0101] Polyolefins can be semi-crystalline or amorphous, as well as linear or branched. The production of polyolefins has long been known to those skilled in the art.

[0102] The polymerization can be carried out, for example, at pressures of 1 to 3000 bar and temperatures between 20°C and 300°C, optionally using a catalyst system. Suitable catalysts include mixtures of titanium and aluminum compounds, as well as metallocenes.

[0103] By changing the monomer composition, the type of isomers used as monomers, the polymerization conditions, and the catalyst system, the number of branches, the crystallinity, and the density of the polyolefins can be varied within a wide range. These measures are also familiar to those skilled in the art.

[0104] Functional groups are introduced into the polyolefins, for example, by copolymerizing vinyl monomers containing the functional group with the olefin, as described above, preferably by free-radical polymerization. Suitable vinyl monomers include glycidyl methacrylate and methyl methacrylate.

[0105] An alternative production option is the radical grafting of vinyl monomers containing functional groups starting from a polyolefin.

[0106] In both production processes, in addition to the vinyl monomers containing functional groups, additional vinyl monomers without functional groups, such as styrene, can also be used.

[0107] The further polymers have average molecular weights (weight average M w , measured by GPC (gel permeation chromatography) against polystyrene as standard) of preferably 3,000 to 300,000 g / mol, more preferably 5,000 to 200,000 g / mol, particularly preferably 10,000 to 100,000 g / mol.

[0108] The solvent for the GPC measurement is selected so that it readily dissolves the other polymer, preferably at room temperature. If the selected solvent is soluble at room temperature, the GPC is performed at room temperature.

[0109] A suitable solvent for vinyl (co)polymers such as copolymers of methyl methacrylate and glycidyl methacrylate, styrene-acrylonitrile-glycidyl methacrylate terpolymers, and styrene-methyl methacrylate-glycidyl methacrylate terpolymers is, for example, tetrahydrofuran. A suitable solvent for polyolefins containing structural units derived from glycidyl methacrylate is, for example, ortho-dichlorobenzene or 1,2-dichloroethane. Adequate solubility often requires an elevated temperature, for example, 40°C, 60°C, 80°C, 100°C, or 120°C. In this case, GPC is carried out at the temperature necessary to achieve sufficient solubility for GPC. If the polyolefin requires a temperature above 40°C to achieve sufficient solubility for GPC, ortho-dichlorobenzene is the preferred solvent. Production of copolymers from the polycarbonates according to the invention

[0110] Copolymers containing at least one polycarbonate block, preferably block copolymers with vinyl (co)polymers or polyolefins, most preferably block copolymers with PMMA, can be produced from the aromatic polycarbonates according to the invention containing COOH end groups and the previously described further polymers. Such copolymers are a further subject of the present invention.

[0111] The production of such block copolymers is preferably carried out by a process comprising the steps: a) melting a composition comprising I) an aromatic polycarbonate according to the invention containing COOH end groups and II) another polymer containing functional groups as described in the previous chapter by introducing thermal energy and / or mechanical shearing, b) mixing and dispersing the various components of the composition with or into each other, c) solidifying the melt by cooling, d) granulating the material resulting from steps a) to c), wherein step (b) is carried out in a compounding machine selected from the group consisting of single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, internal kneaders or co-kneaders and at a melt temperature of preferably 230 to 300°C. Further components for the production of a thermoplastic molding compound

[0112] Both the aromatic polycarbonates of the invention containing COOH end groups themselves and block copolymers prepared therefrom can be used as a component of a thermoplastic molding composition, preferably containing one or more further polymers. The block copolymers are particularly suitable for use in thermoplastic molding compositions containing polycarbonate, preferably aromatic polycarbonate. These block copolymers are further preferably suitable for use in thermoplastic polymer blend molding compositions containing aromatic polycarbonate and at least one further polymer with a similar polarity to the polymer block, which is linked to the aromatic polycarbonate block in the block copolymer.These block copolymers are most preferably suitable for use in thermoplastic polymer blends containing aromatic polycarbonate and, as an additional polymer, the same polymer which is linked to the aromatic polycarbonate as a polymer block in the block copolymer.

[0113] These molding compounds may contain further components such as polymer additives, processing aids and / or further polymeric components, preferably selected from the group consisting of flame retardants, anti-drip agents, flame retardant synergists, smoke inhibitors, lubricants and mold release agents, nucleating agents, polymeric and non-polymeric antistatic agents, conductivity additives, stabilizers (e.g. hydrolysis, heat aging and UV stabilizers as well as transesterification inhibitors), flow promoters, impact modifiers (both with and without core-shell structure), polymeric blend partners, fillers and reinforcing materials as well as dyes and pigments.

[0114] Preferred polymeric blend partners are aromatic polycarbonate containing no COOH end groups, polyesters (for example and preferably polyethylene terephthalate and polybutylene terephthalate), vinyl (co)polymers, and polyolefins. Unlike the polymers used to produce copolymers, these do not need to contain any functional groups. This means they can also be free of functional groups selected from ester, hydroxy, carboxy, carboxylic anhydride, and epoxy groups. Thus, for example, polystyrene, polyolefins, copolymers of ethylene and / or propylene and acrylates, styrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer, and polymethyl methacrylate are also suitable as preferred polymeric blend partners. These can be either rubber-free or rubber-containing.

[0115] The latter applies, for example, to acrylonitrile butadiene styrene (ABS) or acrylonitrile butylacrylate styrene (ASA) polymers.

[0116] The above-mentioned further components are used in a total proportion of 0 to 40 wt.%, preferably 0.1 to 30 wt.%, more preferably 0.1 to 10 wt.%, based on the thermoplastic composition.

[0117] In order to achieve transparent thermoplastic compositions, it is generally appropriate or technically necessary to dispense with certain additional components such as fillers and reinforcing materials, impact modifiers and rubber-containing blend partners or to limit their concentration as well as the concentration of the other components used to significantly lower levels than previously stated. Production of molding compositions containing the polycarbonates and / or copolymers according to the invention and production of molded articles produced from such molding compositions

[0118] The thermoplastic molding compositions according to the invention can be produced, for example, by mixing the respective constituents, i.e. the polycarbonate according to the invention and / or the copolymer according to the invention and further polymeric components, polymer additives and / or processing aids (i.e. the composition) with one another in the melt at temperatures of 220°C to 320°C, preferably 230 to 300°C, particularly preferably 240 to 280°C, most preferably 250 to 270°C.

[0119] Mixing can take place in conventional equipment, such as single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, internal kneaders, or continuous or discontinuous co-kneaders. In these, the compositions are melt compounded or melt extruded to form molding compounds. This process is generally referred to as compounding or melt compounding in this application. Therefore, the term "molding compound" refers to the product obtained when the components of the composition are melt compounded and melt extruded.

[0120] The mixing of the individual components of the compositions can be carried out in a known manner both successively and simultaneously, both at approximately 20°C (room temperature) and at higher temperatures. This means, for example, that some of the components can be metered entirely or partially via the main feed of an extruder, and the remaining components can be added entirely or partially via a side extruder later in the compounding process.

[0121] The molding compounds according to the invention can be used to produce molded articles of any type. These can be produced, for example, by injection molding, extrusion, and blow molding. Another processing method is the production of molded articles by deep drawing from previously produced sheets or films.

[0122] It is also possible to dose the components of the compositions directly into the conveyor extruder of an injection molding machine, to produce the molding compound according to the invention in the conveyor extruder and to process it directly into molded articles by appropriately discharging the molding compound into an injection mold (compounding or reactive compounding injection molding).

[0123] A further subject matter of the present invention relates to the use of a composition according to the invention or a molding composition according to the invention for producing molded articles, and furthermore also to a molded article which is obtainable from a composition according to the invention or from a molding composition according to the invention or which contains such a molding composition.

[0124] Examples of such molded bodies are films, profiles, housing parts of all kinds, e.g. for household appliances such as juicers, coffee machines, mixers; for office machines such as monitors, flat screens, notebooks, printers, copiers; panels, pipes, electrical installation ducts, windows, doors and other profiles for the construction sector (interior and exterior applications) as well as electrical and electronic parts such as switches, plugs and sockets and components for commercial vehicles, particularly for the automotive sector.The compositions and molding compounds according to the invention are also suitable for producing the following molded bodies or molded parts: interior fittings for rail vehicles, ships, aircraft, buses and other motor vehicles, body parts for motor vehicles, housings of electrical devices containing small transformers, housings for information processing and transmission devices, housings and cladding of medical devices, massage devices and housings therefor, toy vehicles for children, flat wall elements, housings for safety devices, heat-insulated transport containers, molded parts for sanitary and bathroom equipment, cover grilles for ventilation openings and housings for gardening tools. Examples Production of the polycarbonate precursor (PC-1)

[0125] In a continuously operated laboratory reactor, bisphenol A was subjected to a polycondensation reaction with phosgene in an interfacial process in a mixture of methylene chloride and chlorobenzene as solvent in the presence of a chain terminator mixture consisting of p-tert-butylphenol and tert-butyl 4-hydroxybenzoate.

[0126] In this synthesis, 72.2 g / h of gaseous phosgene were dissolved in 959 g / h of an organic solvent mixture of 50 wt% methylene chloride and 50 wt% chlorobenzene at -7°C. The phosgene solution prepared in this way was brought into contact with 907 g / h of a 15 wt% aqueous alkaline bisphenol A solution maintained at 30°C. The alkaline bisphenol A solution was pressed through a stainless steel filter with a pore size of 90 µm in the phosgene solution, thereby dispersing it. In the bisphenol A solution, 2 mol of NaOH were used per 1 mol of bisphenol A. The reaction mixture was reacted in a Fink HMR040 mixing pump maintained at 25°C until the phosgene was completely converted. Thereafter, 4.11 g / h of a mixture of 50 mol% p-tert-butylphenol and 50 mol% tert-butyl 4-hydroxybenzoate were added as a chain terminator in the form of a 3 wt% solution in the solvent mixture of 50 wt% methylene chloride and 50 wt% chlorobenzene.

[0127] The resulting reaction mixture was further reacted in a second Fink HMR040 mixing pump maintained at 25°C with 66.52 g / h of 32 wt. % aqueous sodium hydroxide solution. This was followed by two flooded stirred tanks equipped with baffles, each with a residence time of 600 s, each followed by a gear pump, which served both to convey the reaction mixture and to further disperse it. Downstream of the first pump, i.e. upstream of the second stirred tank, 0.679 g / h of a 10 wt. % solution of N-ethylpiperidine in chlorobenzene was metered in as catalyst. At the end of the reaction, the pH was approximately 11.5. In a phase separation vessel, the organic phase was separated from the aqueous phase of the two-phase reaction mixture, and the organic phase was washed with a 0.1 wt. % aqueous HCl solution to remove the catalyst.

[0128] The polymer solution was then washed with deionized water to remove any salt residues. The washed polymer solution was precipitated in organic solvent and dried overnight in a vacuum oven at 120 °C. Production of polycarbonates according to the invention by end group pyrolysis of the polycarbonate precursor PC-1

[0129] The release of the COOH end groups by thermal end-group pyrolysis of the polycarbonate precursor PC-1, prepared according to the previously described process, with cleavage of the protecting group in the form of isobutylene gas, was carried out in a continuous twin-screw extruder of the Process 11 type (Thermofischer Scientific, Karlsruhe, Germany) with a screw configuration with three mixing zones and a length-to-diameter ratio (L / D) of 40. The various polycarbonate examples and comparative examples according to the invention were produced at different melt temperatures in the range of 227 to 288°C, measured using a thermocouple installed near the nozzle outlet in the last barrel element of the extruder. The melt temperature resulted from the input of mechanical energy by the kneading elements and the input of thermal energy by heating the extruder barrel.The extruder barrel is divided into eight separate and differently heated zones. The three kneading zones were located at the transition between heating zones 3 and 4, in heating zone 5, and at the transition between heating zones 6 and 7. The raw material feed was located in heating zone 1. In addition, the outlet nozzle is separately heated. To adjust the different melt temperatures, which were recorded by the thermocouple installed near the nozzle outlet in the last barrel element of the extruder, the barrel temperatures in the barrel zones and the nozzle temperature were set to different temperatures (see Table 1). The first barrel (raw material feed zone) was not heated in all cases, zone 2 was heated to a target temperature of 70°C in all cases, and zones 4 to 8 were heated to the same target temperature in all cases according to Table 1. In all cases, the same polycarbonate precursor (PC-1) was used as the raw material.In all cases, the extruder was operated at a throughput of approximately 300 g / h and a speed of 175 min -1<. By applying a negative pressure of approximately 100 mbar (absolute), the isobutylene gas released in the extruder under these process conditions was continuously withdrawn from the extruder via a vent dome in the penultimate (seventh) heating zone. Under these process conditions, the polycarbonate residence time in the extruder was approximately 70 s in all cases. The barrel temperatures used in the extruder heating zones for the differently produced polycarbonates according to the invention and comparison polycarbonates and the melt temperatures measured at the thermocouple installed near the die outlet in the last barrel element of the extruder can be found in Table 1. Table 1: Set temperatures in the various heating zones of the barrel and at the outlet nozzle of the twin-screw extruder as well as melt temperatures measured near the nozzle outlet during the production of the polycarbonates according to the invention and comparison polycarbonates Polycarbonate [°C] Heating zone 3 [°C] Heating zones 4-8 [°C] Nozzle temperature [°C] Melting temperature [°C] PC-1* Pre-stage Pre-stage Pre-stage Pre-stage PC-2* 160 220 235 227 PC-3 190 240 240 231 PC-4 160 260 260 252 PC-5* 160 280 280 270 PC-6* 190 290 290 274 PC-7* 160 300 300 288 Polycarbonates marked with * are examples not according to the invention. Structural characterization of polycarbonates

[0130] The molecular weight of the polycarbonates was determined by gel permeation chromatography (GPC) in methylene chloride at room temperature using BPA polycarbonate as the calibration standard. An FTIR detector was used at a wavelength of 1775 cm -1, which is selective for BPA polycarbonate.

[0131] The analysis of the polycarbonates with regard to the content of structural units according to components A, B1, B2-a, B2-b and C was carried out by 1H NMR spectroscopy in deuterated chloroform as solvent at room temperature (see Table 2).

[0132] The integrated signal intensity of the respective NMR signals divided by the number of protons causing the signal is proportional to the molar content of the respective structural unit. From the corresponding ratios of the thus normalized signal intensities, the molar ratios of the corresponding structural units were determined according to the various characteristics for the polycarbonates of the invention.

[0133] The acid number of the polycarbonates was determined in dichloromethane (DCM) / ethanol as solvent according to DIN EN ISO 2114, Method A, version 2002-6, using potentiometric titration with ethanolic KOH solution at room temperature. The polycarbonate to be tested was dissolved in 50 ml of dichloromethane at room temperature at a concentration of 10 g / L. Before the potentiometric titration with 0.1 N ethanolic KOH, 5 ml of ethanol was added to the sample solution.

[0134] Table 2 summarizes the structural characteristics of the polycarbonates produced in this way. Table 2: Results of the structural characterization of the produced polycarbonates feature PC-1* PC-2* PC-3 PC-4 PC-5* PC-6* PC-7* M w [kg / mol] 27,0 ng 23,6 24,8 ng ng ng M n [kg / mol] 15,8 ng 12,2 12,7 ng ng ng Acid number [mg KOH / g] <0,1 1,5 3,0 2,3 1,3 <0,1 <0,1 Signal intensity (8.14 ppm) = A 0 1,52 1,87 2,25 1,24 0 0 Signal intensity (8.05 ppm) = B1 2,84 1,28 0,54 0,04 0,06 0 0,09 Signal intensity (8.26 ppm) = B2-a 0 0,05 0,26 0,25 0,92 2,68 2,26 Signal intensity (8.22 ppm) = B2-b 0 0,03 0,14 0,20 0,39 0 0 Signal intensity (1.32 ppm) = C 14,89 15,77 15,08 15,63 15,50 14,42 14,75 AWAY 0 1,1 2,0 4,7 0,9 0 0 B2 / (A+B2) - 0,05 0,18 0,16 0,51 1 1 A / (A+B1) 0 0,54 0,78 0,98 0,95 - 0 C / (A+B+C) 0,54 0,55 0,54 0,56 0,57 0,54 0,58 Polycarbonates marked with * are not examples according to the invention. ng = not measured

[0135] The data in Table 2, in conjunction with the process parameters in Table 1, show that the structure of the produced polycarbonates surprisingly depends strongly on the thermal conditions (specifically, the melt temperature) in the end-group pyrolysis step (ii). Polycarbonates with a high A / B ratio result in a relatively narrow melt temperature range ((PC-3) and (PC-4)), whereas at lower melt temperatures of, for example, 227°C (PC-2*) as well as higher melt temperatures of 270°C (PC-5*), 274°C (PC-6*), and 288°C (PC-7*), as well as for the product obtained directly in process step (i), i.e., without the end-group pyrolysis step (ii) (PC-1*), significantly lower A / B ratios result. PC-4 shows a further improved A / B ratio compared to PC-3. Compared to PC-3, PC-4 also shows a further improved ratio A / (A+B1) - as a measure of the degree of the desired elimination of isobutylene from the tert.-Butyl ester protecting group with release of terminal COOH groups. The ratio B2 / (A+B2)—as a measure of the degree of conversion of intermediately formed COOH end groups in undesired subsequent transesterification reactions—is approximately the same for PC-3 and PC-4. Production of molding compounds from the polycarbonates according to the invention

[0136] PC / PMMA molding compounds were produced from the polycarbonates according to the invention and comparative polycarbonates using a reactive extrusion process. For this purpose, the polycarbonates were first ground to a powder and premixed with a methyl methacrylate-glycidyl methacrylate copolymer (PMMA-GMA), which had also been ground to a powder, in a ratio of 80 wt. % of the respective polycarbonate to 20 wt. % of the PMMA-GMA to form a homogeneous powder mixture. The PMMA-GMA was a random methyl methacrylate-glycidyl methacrylate copolymer with a content of 1.0 wt. % of structural units derived from glycidyl methacrylate, prepared by free-radical polymerization, which had a weight-average molecular weight M w of 60,000 g / mol, measured by gel permeation chromatography at room temperature in tetrahydrofuran as solvent against a polystyrene calibration standard.The epoxy equivalent of this PMMA-GMA copolymer was determined according to DIN EN 1877-1 (version 12-2000) in dichloromethane at room temperature to be 0.32 wt%.

[0137] In order to specifically adjust different A / B ratios, mixtures of a polycarbonate according to the invention (PC-8) and a polycarbonate not according to the invention (PC-6*) with different mixing ratios of these two polycarbonates were also used as polycarbonate components for the production of comparative PC / PMMA molding compounds PC / PMMA-4* to PC / PMMA-6*.

[0138] Polycarbonate PC-8 was also obtained from the precursor PC-1 by thermal end-group pyrolysis. PC-8 has an acid number of 2.4 mg KOH / g, determined in dichloromethane (DCM) / ethanol as solvent according to DIN EN ISO 2114, Method A, version 2002-6, using potentiometric titration with ethanolic KOH solution at room temperature. Using 1< H NMR spectroscopy, the A / B ratio was determined to be 1.8, the B2 / (A+B2) ratio to be 0.28, the B1 / (A+B1) ratio to be 0.85, and the C / (A+B+C) ratio to be 0.55.

[0139] The thermoplastic PC / PMMA molding compounds with the compositions shown in Table 3 were compounded on a continuous twin-screw extruder of the Process 11 type (Thermofischer Scientific, Karlsruhe, Germany) with a screw configuration with two mixing zones at a melt temperature of 260°C, a throughput of approximately 300 g / h, a rotational speed of 125 min -1 <, and an absolute pressure of 100 mbar. Under these conditions, a residence time of approximately 90 s was achieved. After exiting through a die plate, the melt strand was cooled, thereby solidifying, and then granulated. For compounding, the powder mixtures of the PC and PMMA components were metered into the inlet zone of the twin-screw extruder via a volumetric metering device. Production of moldings from the molding compositions containing polycarbonates according to the invention and their technical evaluation

[0140] Round plates with a diameter of 25 mm and a thickness of 1 mm were produced from the thermoplastic PC / PMMA molding compounds, which were prepared from the compositions according to Table 3, using a laboratory thermopress of the type Polystat 200 from Servitec Maschinenservice GmbH (Wustermark, Germany) at a temperature of 260°C, a pressure of 100 bar and a pressing time of a total of 4 min.

[0141] The transparency of the resulting molded bodies and their homogeneity were first assessed visually. The corresponding wavelength-dependent total transmittances were then determined according to DIN 5033-7 (2014), and the transmittance value Y(D65, 10°) was calculated according to DIN EN ISO 11664-3 (2013) using illuminant D65 and a 10° observer.

[0142] The ductility of the molding compounds was also assessed in an impact test on these thermoformed round plates with a diameter of 25 mm and a thickness of 1 mm at room temperature. The measurements were performed using a home-made drop weight tester (drop weight 1.86 kg, support diameter 15 mm, mandrel diameter (hemispherical) 7 mm). The drop height of the drop weight was systematically varied, and the drop height at which the test specimen was not penetrated or showed no damage was assessed, as well as the drop height at which the test specimen exhibited a tough fracture pattern with stable crack propagation.

[0143] The data in Table 3 show that only with the inventive polycarbonate PC-3 could a PC / PMMA molding compound be produced which could be processed into a homogeneously transparent molding with high transmission. This molding compound also exhibits good ductility at room temperature. With the non-inventive comparative polycarbonate PC-6*, which was end-group pyrolyzed at a higher melt temperature, no transparent molding was produced. With the non-inventive comparative polycarbonate PC-1* from process step (i) a homogeneously transparent molding could also not be produced. The PC / PMMA molding compounds produced with this polycarbonate led to milky, streaky moldings. Even with the molding compounds PC / PMMA-4* to PC / PMMA-6*, which were produced with polycarbonate mixtures for the targeted variation of the A / B ratio in the range up to 0.9, no transparent moldings with high light transmission (i.e.fluorescence intensity). Table 3: PC / PMMA-Formmassen composition PC / PMMA-1* PC / PMMA-2 PC / PMMA-3* PC / PMMA-4* PC / PMMA-5* PC / PMMA-6* PC-1* 80 PC-3 80 PC-6* 80 20 40 60 PC-8 60 40 20 PMMA-GMA 20 20 20 20 20 20 Feature of the PC raw material mixture Acid number [mg KOH / g] 1,8 1,2 0,6 AWAY 0,9 0,5 0,2 B2 / (A+B2) 0,47 0,66 0,83 B1 / (A+B1) 0,85 0,85 0,85 C / (A+B+C) 0,55 0,55 0,55 Characteristics Visual assessment Inhomogeneous milky, streaky Homogeneous transparent Homogeneous opaque Homogeneous, cloudy Homogeneous, milky cloudy Homogeneous opaque Transmission Y(D65, 10°) [%] 83 Ductility: no damage up to a drop height of [cm] 20 Ductility: tough fracture pattern with stable crack propagation up to a drop height of [cm] 40 Polycarbonates marked with * are examples not according to the invention.

Claims

1. Aromatic polycarbonate containing A) structural units having a free COOH functionality derived from a hydroxybenzoic acid and present as end groups and B) structural units derived from a hydroxybenzoic acid, wherein component B) is selected from at least one representative of B1) structural units having an esterified COOH functionality derived from a hydroxybenzoic acid and present as end groups and B2) structural units derived from a hydroxybenzoic acid which are incorporated in the polymer chain via an ester group or acid anhydride group, wherein the molar ratio of the amount of component A to the amount of component B is in the range 1.3 to 50.

2. Aromatic polycarbonate according to Claim 1, wherein the polycarbonate is characterized by an acid number in the range from 0.5 to 10 mg potassium hydroxide (KOH) / g, determined in dichloromethane (DCM) / ethanol as solvent according to DIN EN ISO 2114, method A, 2002-6 version, by potentiometric titration with ethanolic KOH solution at room temperature.

3. Aromatic polycarbonate according to Claim 1 or 2, characterized in that the molar ratio of the amount of component B2 to the sum of the amounts of components A and B2 is <0.3.

4. Aromatic polycarbonate according to any of the preceding claims, characterized in that therein the molar ratio of the amount of components A to the sum of the amounts of components A and B1 is >0.75.

5. Aromatic polycarbonate according to any of the preceding claims, further containing as component C structural units derived from monophenols containing no carboxy or carboxy derivative functionalities, wherein component C is present in the polycarbonate in a molar proportion, based on a total of 100 mol% of the molar proportions of components A, B1, B2 and C, of 20 to 90 mol%.

6. Process for producing an aromatic polycarbonate comprising the steps of: (i) producing an aromatic polycarbonate containing end groups derived from a hydroxybenzoic ester by phosgenation in the phase interface process or in organic solution of aromatic diols in the presence of an ester of a hydroxybenzoic acid or a mixture of two or more esters of one or more structurally distinct hydroxybenzoic acids as chain terminator, wherein a temperature of 260°C is at no point exceeded in the producing according to process step (i), and (ii) thermal end group pyrolysis of the hydroxybenzoic ester-derived end groups in the product from process step (i) to eliminate an alkene wherein in process step (ii) the product from process step (i) is pyrolysed in the temperature range 230°C to 265°C by supplying thermal or mechanical energy and the resulting alkene is removed from the apparatus and wherein the residence time at the temperature in the range 230°C to 265°C is not less than 15 seconds and not more than 10 minutes.

7. Process according to Claim 6, wherein process step (i) employs an ester of a hydroxybenzoic acid and an alcohol of general structure (1) wherein R1, R2, R3 and R4 independently of one another represent hydrogen or an alkyl, aryl or alkylaryl radical having 1 to 10 carbon atoms.

8. Process according to either of Claims 6 or 7, wherein in process step (ii) the product from process step (i) is melted in a compounding apparatus selected from the group comprising single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, continuous or discontinuous internal kneaders and filmtruders by supplying thermal or mechanical energy and pyrolysed at a melt temperature in the range 230°C to 260°C and wherein the residence time of the melt in this temperature range is not less than 30 seconds and not more than 2 minutes.

9. Process according to any of Claims 6 to 8 for producing an aromatic polycarbonate according to any of Claims 1 to 5.

10. Copolymer containing structural units derived from an aromatic polycarbonate according to any of Claims 1 to 5.

11. Thermoplastic moulding compound containing a copolymer according to Claim 10 or a polycarbonate according to any of Claims 1 to 5.

12. Use of an aromatic polycarbonate according to any of Claims 1 to 5 or 10 for producing a copolymer containing at least one polycarbonate block and at least one vinyl polymer or polyolefin block.

13. Process for producing a copolymer containing at least one polycarbonate block comprising the steps of a) melting a composition containing I) an aromatic polycarbonate according to any of Claims 1 to 5 and II) a further polymer containing at least one type of functional group selected from ester, hydroxy, carboxy, carboxylic anhydride and epoxy groups through introduction of thermal energy and / or mechanical shear, b) mixing and dispersing the different components of the composition with / into one another, c) solidifying the melt by cooling, d) pelletizing the solidified polymer blend resulting from steps (a) to (c), wherein step (b) is carried out in a compounding machine selected from the group consisting of single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, internal kneaders or co-kneaders and at a temperature of the melt of 230°C to 300°C.

14. Process according to Claim 13, wherein component II) is a vinyl polymer or polyolefin containing structural units derived from glycidyl methacrylate.

15. Shaped article containing a copolymer obtainable in a process according to Claim 13 or 14 or containing a moulding compound according to Claim 11.