Carboxyl-terminated polycarbonate and preparation method thereof

Abstract

The invention relates to polycarbonates containing structural units derived from bisphenol A and A) structural units derived from hydroxybenzoic acid and present as end groups having free COOH functional groups, and B) optionally structural units derived from hydroxybenzoic acid, wherein component B) is selected from the group consisting of at least one of the following representatives: B1) structural units derived from hydroxybenzoic acid and present as end groups having an esterified COOH function, and B2) structural units derived from hydroxybenzoic acid bound to the polymer chain via ester groups or anhydride groups, the content of free bisphenol A in the polycarbonate being at most 50 ppm, and wherein when component B is contained, the ratio of the molar amount of component B1 to the sum of the molar amounts of components A and B is at most 0.07, and to a method for producing such a polycarbonate, to the use of such a polycarbonate in a method for producing a copolymer or a thermoplastic material containing a copolymer, and to a method for producing such a polycarbonate. A copolymer containing a structural unit derived from a polycarbonate, a thermoplastic (molding compound) containing the polycarbonate and / or the copolymer, and a molded article.

Description

[0001] The present invention relates to polycarbonates containing structural units derived from bisphenol A and structural units derived from hydroxybenzoic acid and present as terminal groups and having free COOH functionalities, characterized by a low content of free bisphenol A that is thermally stable, as well as to processes for the preparation of such polycarbonates, the use of such polycarbonates in processes for the preparation of copolymers, copolymers containing structural units derived from the polycarbonates according to the invention, thermoplastic compositions (molding compositions) containing the polycarbonates according to the invention and / or the copolycarbonates according to the invention, and shaped articles containing the polycarbonates according to the invention, the copolycarbonates according to the invention and / or the thermoplastic compositions (molding compositions) according to the invention.

[0002] “Containing a structural unit derived from bisphenol A” means that bisphenol A is covalently bonded to the polymer chain via a hydroxyl group, wherein the chemical bonding occurs through a condensation reaction between the hydroxyl group of bisphenol A and a carbonic acid derivative to form a carbonate functional group. Similarly, “containing a structural unit derived from hydroxybenzoic acid and present as an end group” means that hydroxybenzoic acid is covalently bonded to the end of the polymer chain via a hydroxyl group, wherein the chemical bonding occurs through a condensation reaction between the hydroxyl group of hydroxybenzoic acid and a carbonic acid derivative to form a carbonate functional group.

[0003] Polycarbonates, especially those based on bisphenol A, have been used for many years to produce transparent or translucent (translucent) molded articles. In recent years, the automotive, construction, and electronics industries have found applications for new lighting concepts and functional integration using translucent molding compounds.

[0004] However, for some applications, polycarbonate lacks important properties such as scratch resistance, stress cracking resistance under the influence of chemicals, mechanical properties and processing characteristics (melt flow). Developing polymer blends of polycarbonate with other thermoplastics is a common approach to achieving specific technical requirements by combining the specific performance advantages of polycarbonate with those of the polymer blending partner, ideally in a synergistic manner. For example, polymer blends of polycarbonate (PC) and polymethyl methacrylate (PMMA) can show improvements in scratch resistance, stress cracking resistance under the influence of chemicals and melt flow compared to pure polycarbonate. The ductility of the material can also be increased compared to polymethyl methacrylate.

[0005] However, the advantageous combination of properties achievable by polymer blends often hinders the transparency or translucency of molded articles made therefrom. Polycarbonate and the other thermoplastics included in the polymer blend are typically not completely miscible, resulting in a two-phase morphology in which one polymer serves as the matrix phase and domains of the other polymer are distributed within it. Because the refractive indices of the blend partners typically differ, light scattering occurs at multiple phase interfaces, resulting in an overall significant reduction in light transmittance compared to the pure blend components. Consequently, blends of polycarbonate and polymers immiscible with polycarbonate are typically opaque, i.e., not translucent or translucent with only an insufficient light output.

[0006] Phase interfaces can also constitute mechanical weaknesses, particularly under the influence of chemicals, leading to material failure.

[0007] One possible way described in the literature to improve the compatibility of polycarbonate and a thermoplastic blending partner immiscible with PC (e.g. PMMA) is to form block copolymers of polycarbonate and the polymer blending partner (in this particular case PMMA) in situ during reactive extrusion. The chemical reaction of the two polymers at the phase interface of the two-phase melt mixture can be accelerated by using a catalyst.

[0008] WO 2020 / 212229 A1 discloses a reactive compounding method for preparing thermoplastic molding compounds using an aromatic polycarbonate without reactive functional groups and another polymer containing at least one functional group selected from ester, epoxy, hydroxyl, carboxyl, and carboxylic anhydride groups. The catalyst used is a special phosphonium salt. The application also discloses the preparation of transparent thermoplastic PC / PMMA molding compounds using this method.

[0009] 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 made from a non-reactive functionalized polymer component in reactive melt extrusion using 0.0025 to 0.1 wt% tin catalyst.

[0010] WO 2016 / 189494 A1 discloses transparent PC / PMMA blends containing 80 to 95% by weight of a specifically designated branched polycarbonate having an end group content of 45 to 80% and 4.9 to 20% by weight of PMMA, which are produced by transesterification in melt extrusion using 0.1 to 1.5% by weight of a catalyst, which is preferably selected from Zn, Sn and Ag compounds.

[0011] Although molded parts made from the blended compositions prepared by these methods have improved light transmittance relative to molded parts made from PC / PMMA compositions prepared by purely physical mixing processes, they generally have insufficient light output for many applications when transilluminated and also have insufficient mechanical properties.

[0012] In addition to the use of catalysts as described, appropriate functionalization of the polycarbonate can also facilitate the in situ formation of the copolymer.

[0013] US Pat. No. 4,853,458 and US Pat. No. 4,959,411 describe the preparation of terminal carboxyl-functionalized polycarbonates, in which a carboxylic acid or carboxylic acid derivative-substituted phenol, preferably tert-butyl paraben, is incorporated into the ends of the PC as a chain terminator during the polycarbonate-forming reaction. Also disclosed are methods for preparing block copolymers by reacting an epoxy-functionalized olefin polymer with such carboxyl- or carboxylic acid derivative-functionalized polycarbonates in organic solution or during melt compounding, as well as the use of such copolymers for compatibilizing polymer blends of polycarbonate and polyolefin to reduce their tendency to delaminate. These applications do not indicate whether polycarbonates functionalized in this manner are suitable for preparing transparent PC / PMMA blends.

[0014] For the latter method of preparing block copolymers by reacting a suitably functionalized polycarbonate with a suitably functionalized polymer blending partner, the precise type of polycarbonate functionalization, i.e., the selection and condensation of suitable reactive groups, is crucial for the successful preparation of block copolymers having the qualities required for the desired application. The use of carboxyl-functionalized polycarbonates, as described, for example, in US Pat. Nos. 4,853,458 and 4,959,411, has proven particularly advantageous in terms of reactivity and selectivity with epoxy-functionalized polymers when preparing block copolymers in melt compounding.

[0015] An essential quality characteristic for the desired applications is the lowest possible residual content of undesirable components that cannot or can only be removed incompletely during the downstream block copolymer preparation process. Against the backdrop of global regulation of free bisphenol A in polymers, compositions, and articles, a particular goal is to keep the free bisphenol A content in such functionalized polycarbonates containing structural units derived from bisphenol A as low as possible. This goal is driven by environmental policy objectives, namely to minimize the release of bisphenol A into the environment during the life cycle of such products when used. Against the backdrop of the current restrictions in the EU under the REACH Regulation, values ​​of <50 ppm by weight, preferably <20 ppm by weight, and particularly preferably <10 ppm by weight, are desired in polymers, compositions, and articles.

[0016] Bisphenol A itself has negligible volatility at the temperatures at which the polycarbonates according to the invention are processed and / or further processed, for example by melt degassing, when copolymers are prepared from such polycarbonates, for example by coupling reactions in the melt, and when thermoplastic molding compositions containing such polycarbonates or copolymers are prepared by compounding, or when they are further thermoformed. Consequently, in these downstream processing steps, the free bisphenol A contained in the polycarbonate as a result of its preparation can no longer be effectively removed from the product.

[0017] In downstream thermal processing steps for the preparation of carboxyl-terminated polycarbonates, even more free bisphenol A is typically formed from the polymer chain by retrocleavage, further increasing its content in the final marketed product.

[0018] It is therefore necessary to provide carboxyl-terminated polycarbonates and processes for the preparation of preferably carboxyl-terminated polycarbonates, wherein the (preferably carboxyl-terminated) polycarbonates have improved stability to the formation of free bisphenol A by retrolytic cleavage under thermal stress, for example when they are worked up in melt degassing, when they are used for the preparation of block copolymers in the melt reaction within the context of reactive extrusion (also referred to as melt compounding in the present invention), when they are used for the preparation of thermoplastic molding compositions containing such polycarbonates or such block copolymers in melt compounding and / or when they are thermoforming such polycarbonates, such block copolymers or thermoplastic compositions containing such polycarbonates or such block copolymers.

[0019] It is further desirable to improve the quality of carboxyl-terminated polycarbonates so that they are more suitable for the preparation of block copolymers or for the preparation of polymer molding compositions containing these block copolymers having improved technical properties, wherein the preparation of block copolymers or polymer molding compositions containing these block copolymers is carried out by means of epoxy-functional polymers other than polycarbonates in the melt mixture in reactive extrusion (also referred to herein as melt compounding).

[0020] The desired technical improvements in block copolymers prepared by melt compounding of carboxyl-terminated polycarbonates or in polymer molding compositions containing these block copolymers prepared by melt compounding of carboxyl-terminated polycarbonates can manifest themselves, for example, in better properties of the block copolymers or polymer molding compositions containing these block copolymers (e.g. improved mechanical properties, scratch resistance, chemical resistance, increased light transmittance (transparency), improved color neutrality with regard to color coordinates and / or their thermal stability and / or reduced free bisphenol A content or improved thermal stability of the free bisphenol A content in further thermal processing steps, for example, when compounding compositions containing the copolymers and / or molding copolymers or thermoplastic molding compositions containing such copolymers).

[0021] Alternative desired technical improvements to block copolymers prepared by melt compounding of carboxyl-terminated polycarbonates or polymer molding compounds containing these block copolymers prepared by melt compounding of carboxyl-terminated polycarbonates can be manifested in their higher efficacy as compatibilizers in polymer blends or as functional additives in polymer molding compounds, especially polycarbonate molding compounds.

[0022] The carboxyl-terminated polycarbonates prepared by the preparation processes according to US Pat. No. 4,853,458 and US Pat. No. 4,959,411 only inadequately meet the aforementioned objects.

[0023] In the methods disclosed in these documents, the terminal carboxyl functional groups in polycarbonates are released by thermal end-group pyrolysis of polycarbonates containing structural units as end groups derived from phenols substituted with carboxylic acid derivatives, preferably from phenols substituted with carboxylic acid esters, and particularly preferably from tert-butyl p-hydroxybenzoate. However, during this thermal end-group pyrolysis, the carboxyl end groups formed can undergo a considerable degree of transesterification with carbonate functional groups in the polymer chain, especially at high temperatures, whereas at lower temperatures, end-group pyrolysis generally does not proceed or proceeds only incompletely. Consequently, the possible methods for preparing carboxyl-terminated polycarbonates according to the prior art are limited to a very narrow process window that is technically difficult to achieve in a controlled manner.

[0024] It would therefore also be desirable—especially since it is desirable to achieve a process that is as energy-efficient as possible—to provide a process for preparing carboxyl-terminated polycarbonates in which the end group pyrolysis is carried out completely at low temperatures, thereby increasing the distance from the maximum permissible process temperature, above which undesirable transesterification can occur significantly, and thus increasing the width of the processing window permissible in this low-temperature regime.

[0025] Furthermore, it is desirable to provide a process for the preparation of carboxyl-terminated polycarbonates in which higher temperatures can be tolerated in the end group pyrolysis without the terminal carboxyl groups initially produced in the end group pyrolysis reacting again to a significant extent or even completely in the same process step in undesirable subsequent reactions (e.g., transesterification). It is also desirable that the polycarbonates prepared can be worked up according to methods customary in the art, such as melt degassing, which is usually carried out in polycarbonates at temperatures of >280° C., typically >300° C. or even >320° C., without the carboxyl groups reacting to a significant extent or even completely in undesirable subsequent reactions.

[0026] Transparent molded articles or translucent molded articles that need to be transilluminated in their applications often have very high requirements for their inherent color and consistency, that is, they are not affected by, for example, precise manufacturing conditions and / or the quality of the raw materials used to manufacture them. Such molded articles are often required to have high, wavelength-independent transmittance across the entire visible light wavelength range, thereby producing a color-neutral (i.e., essentially colorless) appearance. Therefore, it is also desirable to provide carboxyl-terminated polycarbonates that meet these requirements and have an improved original color tone and / or improved stability of this original color tone under thermal stress. In other words, preferably, they have high, wavelength-independent transmittance across the entire visible light wavelength range, regardless of their thermal history, thereby producing a color-neutral (i.e., essentially colorless) appearance that is as color-neutral as possible.

[0027] It is therefore desirable to provide polycarbonates which comprise structural units derived from bisphenol A and structural units with free COOH functions which are derived from hydroxybenzoic acid and present as terminal groups in the polymer chain (hereinafter also referred to as polymer backbone) and which have a low content of free bisphenol A after thermal stressing and preferably have an appearance that is as color-neutral as possible, more preferably a color-neutral appearance that is as thermally stable as possible, as well as processes for producing such polycarbonates, wherein the polycarbonates are preferably better suited for producing technically improved copolymers and / or technically improved molding compounds containing copolymers and / or thermoplastic molding compounds containing such polycarbonates or articles produced therefrom, each with a preferably likewise low content of free bisphenol A, wherein the copolymer comprises at least one polycarbonate block having structural units derived from bisphenol A.

[0028] In particular, it is desirable to provide polycarbonates which are particularly well suited for the production of thermoplastic molding compositions containing polycarbonate and vinyl (co)polymers, preferably polymethyl methacrylate, wherein these thermoplastic molding compositions are suitable for the production of transilluminable shaped articles, ie, have a high degree of transparency.

[0029] It would also be desirable to provide a process which allows the preparation of carboxyl-functionalized polycarbonates having a high content of COOH end groups in a process-technically simpler, more stable (i.e., with less off-spec waste and / or fewer process interruptions within a wider process parameter window), more cost-effective and / or more energy-efficient manner.

[0030] Surprisingly, it has now been found that polycarbonates comprising structural units derived from bisphenol A and

[0031] A) structural units which are derived from hydroxybenzoic acid and which have free COOH functions as terminal groups, and

[0032] B) optionally structural units derived from hydroxybenzoic acid,

[0033] Wherein component B) is selected from at least one representative of the following

[0034] B1) structural units which are derived from hydroxybenzoic acid and which have an esterified COOH function as a terminal group,

[0035] and

[0036] B2) structural units derived from hydroxybenzoic acid which are incorporated into the polymer chain via ester groups or anhydride groups,

[0037] wherein the content of free bisphenol A in the polycarbonate is a maximum of 50 ppm, preferably a maximum of 20 ppm, particularly preferably a maximum of 10 ppm, and

[0038] When component B is contained, the ratio of the molar amount of component B1 to the sum of the molar amounts of components A and B is at most 0.07, preferably at most 0.05, more preferably at most 0.02, and particularly preferably at most 0.01.

[0039] Preferred polycarbonates according to the invention are characterized by containing component B.

[0040] Further preferred polycarbonates according to the invention are characterized in that they contain component B2, and the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2 is from 0.001 to 0.25.

[0041] The polycarbonates according to the invention are preferably characterized in that the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2 is at most 0.12, preferably at most 0.10, particularly preferably at most 0.08 and most preferably at most 0.03.

[0042] Further preferred polycarbonates according to the invention are characterized in that the ratio of the molar amount of component A to the molar amount of component B is at least 8, more preferably at least 10, particularly preferably at least 12 and most preferably at least 25.

[0043] In a preferred embodiment, the polycarbonate according to the present invention may optionally further comprise

[0044] C) Structural units which are derived from at least one phenolic compound which has only one phenolic OH function and no carboxyl or carboxyl derivative functions and which are present as terminal groups.

[0045] In the context of the present invention, such phenolic compounds having only one phenolic OH function and no carboxyl or carboxyl derivative function are also referred to as monophenols having no carboxyl or carboxyl derivative function.

[0046] The polycarbonate according to the invention containing component C) preferably contains component C) in a molar proportion of 50 to 90 mol%, more preferably 60 to 80 mol%, particularly preferably 65 to 75 mol%, based on the total molar proportion of components A, B1, B2 and C being 100 mol%.

[0047] The preferred ranges of the above-mentioned molar ratio of A to B, the molar ratio of B2 to the sum of A and B2, the molar ratio of B1 to the sum of A and B, and the molar ratio of C to the sum of A, B1, B2 and C can be arbitrarily combined with each other.

[0048] Most preferred are polycarbonates having the above characteristics, wherein the ratio of the molar amount of component A to the molar amount of component B is at least 25, the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2 is at most 0.08, and the ratio of the molar amount of component B1 to the sum of the molar amounts of components A and B is at most 0.01.

[0049] The molar amount of component B is calculated as the sum of the molar amounts of components B1 and B2.

[0050] Preferred polycarbonates according to the invention are characterized by an acid number of 0.3 to 30 mg potassium hydroxide (KOH) / g, preferably 0.5 to 20 mg potassium hydroxide (KOH) / g, most preferably 1.0 to 10 mg potassium hydroxide (KOH) / g, determined in each case in dichloromethane (DCM) / ethanol as solvent by potentiometric titration with an ethanolic KOH solution at room temperature in accordance with DIN EN ISO 2114, Method A, 2002-6 edition.

[0051] The present invention further provides a process for preparing the polycarbonates according to the invention.

[0052] Surprisingly, it has been found that the preparation of polycarbonates (II) containing end groups with free COOH functions which are derived from at least one hydroxybenzoic acid can advantageously be carried out by a process in which

[0053] Polycarbonate (I) containing end groups derived from at least one hydroxybenzoate

[0054] In the presence of 0.01 to 0.30% by weight, preferably 0.02 to 0.15% by weight, particularly preferably 0.03 to 0.07% by weight, of phosphorous acid H3PO3, based in each case on the amount of polycarbonate (I)

[0055] When negative pressure is applied for 10 seconds to 15 minutes, preferably 20 seconds to 5 minutes

[0056] subjected to a temperature of 240°C to 360°C, preferably 250°C to 300°C,

[0057] Polycarbonate (II) is thus formed.

[0058] In a preferred embodiment, polycarbonate (I) and polycarbonate (II) contain structural units derived from bisphenol A.

[0059] In a preceding step, the preparation of polycarbonate (I) can be carried out by:

[0060] Phosgenation of bisphenol A or a mixture of a plurality of structurally different diols containing bisphenol A in the interfacial process or in organic solution in the presence of at least one hydroxybenzoic acid ester, preferably at least one p-hydroxybenzoic acid ester, or a mixture of at least one hydroxybenzoic acid ester and at least one monophenol without carboxyl or carboxyl derivative functions as chain terminator or a mixture of chain terminators,

[0061] The at least one hydroxybenzoate is an ester of hydroxybenzoic acid and an alcohol of the general formula (1).

[0062]

[0063] wherein R1 to R4 independently of one another represent hydrogen or an alkyl group, an aryl group or an alkylaryl group having 1 to 10 carbon atoms, preferably hydrogen or an alkyl group having 1 to 4 carbon atoms, particularly preferably hydrogen or methyl, most preferably both represent methyl, and

[0064] R3 and R4 independently represent hydrogen or an alkyl group, aryl group or alkylaryl group having 1 to 10 carbon atoms, preferably hydrogen or an alkyl group having 1 to 4 carbon atoms, particularly preferably hydrogen or methyl, most preferably both represent hydrogen.

[0065] After the preparation of polycarbonate (I), a post-treatment can be carried out as a separate step before the preparation of polycarbonate (II).

[0066] in

[0067] The solvent, preferably the solvent used in the polycarbonate (I) preparation process step, is preferably removed to a residual content of <0.1% by weight.

[0068] The post-treatment of the polycarbonate (I) is preferably carried out by spray drying or by precipitation in a suitable solvent, for example preferably in isopropanol, methanol or water, with subsequent separation of the solvent phase (mother liquor). This separation can be carried out, for example, by filtration or sedimentation with subsequent decantation, centrifugation or a combination of these methods. In each case, the separation of the precipitated polycarbonate solid is followed by drying, wherein the drying is preferably carried out at a temperature of 60° C. to 120° C., particularly preferably under applied negative pressure, and wherein the precipitated solid may optionally be subjected to one or more washing steps between precipitation and drying in order to remove process-induced impurities and / or monomers and / or oligomers from the product. During this post-treatment, the polycarbonate (I) is not subjected to temperatures > 200° C. at any time.

[0069] The phosphorous acid is preferably added to the process in the form of an aqueous solution. A physical premix of polycarbonate (I) and phosphorous acid or an aqueous solution of phosphorous acid is preferably prepared. The intermediate product thus prepared is also preferably dried at a temperature below 150° C. before being heated to a temperature of 240° C. to 360° C., preferably 250° C. to 300° C., i.e., before being heated to the temperature at which the end groups are pyrolyzed.

[0070] In another specific embodiment, the removal of the solvent for preparing polycarbonate (I) and the formation of polycarbonate (II) from polycarbonate (I) are not carried out sequentially, but simultaneously. In this embodiment of the process according to the invention for preparing the polycarbonates according to the invention, the phosgenation is carried out as described above in the interfacial process with bisphenol A or a mixture of a plurality of structurally different diols containing bisphenol A or in an organic solution in the presence of hydroxybenzoic acid esters, thereby forming polycarbonate (I). The reaction product in this preparation, which still contains solvent, is then subjected to a temperature of 240° C. to 360° C., preferably 250° C. to 300° C., for a period of 10 seconds to 15 minutes, preferably 20 seconds to 5 minutes, with the addition of 0.01 to 0.30% by weight, preferably 0.02 to 0.15% by weight, particularly preferably 0.03 to 0.07% by weight, of phosphorous acid (H 3 PO 3 ), based on the amount of polycarbonate (I), under applied reduced pressure, and in this case in a single process step

[0071] a) firstly removing the solvent until the residual content is preferably <0.1% by weight, and

[0072] b) On the other hand, structural units with free COOH functions, ie polycarbonate (II), are formed from the end groups derived from hydroxybenzoic acid and are present as end groups in the polycarbonate.

[0073] In the preparation of polycarbonate (II) from polycarbonate (I), olefins are preferably eliminated.

[0074] The olefin to be eliminated generally has the general structural formula R3R4C=CR1R2, wherein R1, R2, R3 and R4 are as defined above and correspond to the respective groups R1, R2, R3 and R4 in the alcohol, with which the hydroxybenzoate used as chain terminator in the preparation of polycarbonate (I) is esterified as a protecting group.

[0075] The preparation of polycarbonate (II) from polycarbonate (I) is preferably carried out in a process apparatus selected from single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, continuous or discontinuous internal kneaders, film extruders, strand evaporators and foam evaporators.

[0076] The resulting product of the preparation of polycarbonate (II) is a melt of carboxyl-terminated polycarbonate having a residual solvent content of preferably <0.1% by weight, which in a subsequent optional process step

[0077] a) cooling and thereby solidifying, and further

[0078] b) optionally granulating and / or

[0079] c) optionally ground into a powder.

[0080] The process product also contains at least some of the phosphorous acid used in the process and / or other phosphorus compounds formed therefrom under the conditions of the thermal treatment of the polycarbonate in the presence of phosphorous acid in the process according to the invention. These may, for example, preferably be phosphoric acid, phosphites, condensates of phosphates and phosphorous acid, and / or condensates of phosphoric acid.

[0081] The present invention therefore also relates to a thermoplastic composition containing a polycarbonate (II) according to the above-mentioned features and preferred ranges and at least one phosphorus compound selected from phosphorous acid, phosphoric acid, phosphites and phosphates and phosphorous acid condensates and phosphoric acid condensates, preferably selected from phosphorous acid and phosphites, in each case in a total amount of 0.01 to 0.30% by weight, preferably 0.02 to 0.15% by weight, particularly preferably 0.03 to 0.07% by weight.

[0082] In the context of this application, the terms "carboxyl" and "carboxyl" are used synonymously and represent a COOH group.

[0083] The polycarbonates according to the invention are also referred to hereinafter as aromatic polycarbonates or (aromatic) polycarbonates containing (terminal) COOH end groups.

[0084] Due to their features according to the invention, in particular the specific ratios of A to B, B2 to the sum of A and B2, and B1 to the sum of A and B, and due to their low content of free bisphenol A, which is achievable for the first time by the process according to the invention, the polycarbonates according to the invention are particularly suitable for the production of technically improved copolymers or molding materials containing such copolymers.

[0085] These copolymers or thermoplastic molding compounds containing such copolymers can be obtained by a process comprising the following steps:

[0086] a) melting a composition comprising:

[0087] The polycarbonate (II) of the present invention according to the above characteristics and preferred ranges contains component B, and

[0088] Containing at least one functional group selected from ester groups, hydroxyl groups and epoxy groups, preferably other polymers containing epoxy groups, more preferably polyolefins or vinyl (co)polymers, particularly preferably polymethyl methacrylate, which contains structural units derived from glycidyl methacrylate, said structural units being grafted onto the vinyl (co)polymer or polyolefin or incorporated into the polymer chain (i.e. the polymer backbone) of the vinyl (co)polymer or polyolefin,

[0089] b) mixing the different components of the composition with one another and dispersing them with one another,

[0090] c) solidifying the melt by cooling,

[0091] d) granulating the solidified product obtained in steps (a) to (c),

[0092] In the process, a chemical coupling reaction occurs in the melt between the structural units in the polycarbonate (II) which are derived from hydroxybenzoic acid and present as terminal groups and have free COOH functional groups and other polymers containing at least one functional group selected from ester groups, hydroxyl groups and epoxy groups, preferably containing epoxy groups.

[0093] Step (b) of the process is preferably carried out in a compounder selected from single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, internal kneaders or co-kneaders and is likewise preferably carried out at a melt temperature of 230° C. to 300° C.

[0094] In particular, it has surprisingly been found that copolymers of this type, prepared from the polycarbonate (II) according to the invention (where component B is present) using polymethacrylates randomly modified with glycidyl methacrylate comonomers as epoxy-containing polymers in the above-described process according to the invention, or molding materials containing such copolymers, have a higher light transmittance (transparency) than similar copolymers or molding materials containing copolymers prepared on the basis of similar polycarbonates prepared according to the process described in the prior art (i.e. without addition of H3PO3 in the end group pyrolysis step).

[0095] The polycarbonates and copolymers of the present invention or molding compounds containing such copolymers are thermoplastic and are particularly suitable for use as additives in thermoplastic polycarbonate compositions, preferably as compatibilizers in thermoplastic polycarbonate blends.

[0096] Such thermoplastic polycarbonate compositions and thermoplastic polycarbonate blends according to the invention containing the copolymers or polycarbonates (II) according to the invention are suitable for producing shaped articles for a wide variety of applications, for example by injection molding. Such thermoplastic polycarbonate compositions and thermoplastic polycarbonate blends containing the polycarbonates according to the invention and / or such copolymers according to the invention or molding materials containing such copolymers are particularly suitable for producing transilluminable shaped parts and articles.

[0097] polycarbonate

[0098] The polycarbonate of the present invention contains structural units derived from bisphenol A and

[0099] A) structural units which are derived from hydroxybenzoic acid and which have a free COOH function (also called COOH or synonymously carboxyl group or carboxyl end group) as terminal group, and

[0100] B) optionally structural units derived from hydroxybenzoic acid,

[0101] Wherein component B) is selected from at least one representative of the following

[0102] B1) structural units which are derived from hydroxybenzoic acid and which have an esterified COOH function as a terminal group,

[0103] and

[0104] B2) structural units derived from hydroxybenzoic acid which are bound to the polymer chain via ester groups (=B2-a) and / or anhydride groups (=B2-b),

[0105] wherein the content of free bisphenol A in the polycarbonate is a maximum of 50 ppm, preferably a maximum of 20 ppm, particularly preferably a maximum of 10 ppm, and

[0106] When component B is contained, the ratio of the molar amount of component B1 to the sum of the molar amounts of components A and B is at most 0.07, preferably at most 0.05, more preferably at most 0.02, and particularly preferably at most 0.01.

[0107] When calculating the ratio of the molar amounts of components A and B, the molar amount of component B is the sum of the molar amounts of components B1, B2-a, and B2-b. When calculating the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2, the molar amount of component B2 is the sum of the molar amounts of B2-a and B2-b.

[0108] The acid number of the polycarbonates of the invention is preferably at least 0.3 mg potassium hydroxide (KOH) / g, more preferably at least 0.5 mg potassium hydroxide (KOH) / g, most preferably at least 1.0 mg KOH / g, determined in each case in dichloromethane (DCM) / ethanol as solvent by potentiometric titration with an ethanolic KOH solution at room temperature in accordance with DIN EN ISO 2114, Method A, 2002-6 edition.

[0109] The acid number of the polycarbonates according to the invention is preferably from 0.3 to 30 mg potassium hydroxide (KOH) / g, particularly preferably from 0.5 to 20 mg potassium hydroxide (KOH) / g, most preferably from 1.0 to 10 mg potassium hydroxide (KOH) / g, determined in each case in dichloromethane (DCM) / ethanol as solvent by potentiometric titration with ethanolic KOH solution at room temperature in accordance with DIN EN ISO 2114, Method A, 2002-6 edition.

[0110] To determine the acid value, the polymer to be investigated was dissolved in 50 mL of dichloromethane at room temperature at a concentration of 10 g / L. Prior to potentiometric titration with 0.1 N ethanolic KOH solution, 5 mL of ethanol were added to the sample solution.

[0111] The hydroxybenzoic acids considered include those in which the carboxylic acid group is located in the para, meta or ortho position to the phenolic OH group. The hydroxybenzoic acid in which the carboxylic acid group is located in the para position to the phenolic OH group is preferred. These hydroxybenzoic acids can be replaced by C1-C 10 Alkyl, aryl or alkylaryl is preferably substituted by C1-C4-alkyl, particularly preferably by methyl, or by halogen or ether groups, for example preferably by methoxy, or mono- or polysubstituted.

[0112] The structural unit derived from hydroxybenzoic acid is particularly preferably a structural unit derived from p-hydroxybenzoic acid having no other substituent.

[0113] The structural units according to component B1 which are derived from hydroxybenzoic acid and present as terminal groups and have an esterified COOH function are preferably esters of hydroxybenzoic acid (preferably p-hydroxybenzoic acid), which are more preferably esterified with an alcohol of the abovementioned formula (1).

[0114] The alcohol is preferably a tertiary alcohol, most preferably tert-butyl alcohol.

[0115] The structures of components A, B1, and B2 are shown, for example, in formulas (2), (3), (4a), and (4b) for p-hydroxybenzoic acid, which is particularly preferred as a hydroxybenzoic acid, wherein formula (2) represents component A, formula (3) represents component B1 (e.g., a particularly preferred tert-butyl ester), and formulas (4a) and (4b) represent component B2. Formula (4a) represents a structural unit derived from hydroxybenzoic acid that is incorporated into the polymer chain via an ester group (component B2-a). Formula (4b) represents a structural unit derived from hydroxybenzoic acid that is incorporated into the polymer chain via an anhydride group (component B2-b). All structures contain structural units derived from bisphenol A.

[0116] In formulae (2), (3), (4a) and (4b), m and n each represent the number of monomer units shown in parentheses.

[0117]

[0118]

[0119] pass 1 H NMR spectroscopy determines the molar ratio of components A and B1 and two possible structures of component B2, as well as the corresponding molar ratio of these components relevant according to the present invention.For this reason, polycarbonate is dissolved in deuterated chloroform at room temperature.Can distinguish the different structural units derived from hydroxybenzoic acid by the NMR signal of the aromatic proton of the ortho position of carboxyl functional group or derivatized carboxyl functional group, and quantify the molar amount or ratio of different structures according to the integrated intensity of these signals.In the case of particularly preferred p-hydroxybenzoic acid, due to the spin-spin coupling of the aromatic proton of the ortho position of carboxyl functional group or derivatized carboxyl functional group and the aromatic proton of the meta position, all are bimodal in all cases.For all components A, B1 and B2, corresponding NMR signal is attributed to two protons separately, so the ratio of corresponding NMR signal intensity can directly deduce the corresponding ratio of the molar ratio of different components in polycarbonate.

[0120] In the special case of p-hydroxybenzoic acid, which is particularly preferred

[0121] - The protons in the structural unit of the derived p-hydroxybenzoic acid according to component A resonate at about 8.14 ppm,

[0122] - for the tert-butyl ester of formula (2), the proton in the structural unit derived from p-hydroxybenzoic acid according to component B1 resonates at about 8.05 ppm,

[0123] - the proton in the structural unit derived from hydroxybenzoic acid according to component B2-b (Formula 4b) bonded to the polymer chain via the anhydride group resonates at about 8.22 ppm, and

[0124] - the proton in the structural unit derived from hydroxybenzoic acid according to component B2-a (Formula 4a) bonded to the polymer chain via an ester group resonates at about 8.26 ppm,

[0125] All chemical shifts are expressed in parts per million (ppm) relative to the reference trimethylsilane (TMS).

[0126] Thus, preferred polycarbonates in which the structural units derived from hydroxybenzoic acid according to components A, B1 and B2 are in each case structural units derived from p-hydroxybenzoic acid and the structural units with esterified COOH functions according to component B1 which are derived from hydroxybenzoic acid and present as terminal groups are structural units derived from tert-butyl 4-hydroxybenzoate according to formula (2) are characterized in that: 1 In the H NMR spectrum, the ratio of the integrated intensity of the doublet signal at about 8.05 ppm to the sum of the integrated intensities of the doublet signals at about 8.14 ppm, about 8.05 ppm, about 8.22 ppm and about 8.26 ppm is at most 0.07, preferably at most 0.05, particularly preferably at most 0.02, most preferably at most 0.01, wherein the chemical shift in each case is referenced to tetramethylsilane (TMS).

[0127] The polycarbonate of the present invention is further characterized by: 1 The ratio of the integrated intensity of the H NMR doublet signal to the sum of the integrated intensities of the doublet signals at about 8.05 ppm, 8.22 ppm and 8.26 ppm is preferably at least 8, particularly preferably at least 10, more preferably at least 12 and most preferably at least 25, the chemical shifts being in each case referenced to tetramethylsilane (TMS).

[0128] The polycarbonates of the present invention are also preferably characterized in that the polycarbonate has a 1In the H NMR spectrum, the ratio of the sum of the integrated intensities of the doublet signal at about 8.22 ppm and 8.26 ppm to the sum of the integrated intensities of the doublet signal at about 8.14 ppm, 8.22 ppm and 8.26 ppm is preferably at most 0.12, more preferably at most 0.10, particularly preferably at most 0.08, most preferably at most 0.03, wherein the chemical shift is in each case referenced to tetramethylsilane (TMS).

[0129] In a preferred embodiment, the polycarbonate further comprises as component C a structural unit derived from a monophenol having no carboxyl or carboxyl derivative functional group and as an end group. The monophenol having no carboxyl or carboxyl derivative functional group derived from component C is preferably phenol or a phenol mono- or poly-substituted with an alkyl group, an aryl group, an alkylaryl group and / or a halogen, particularly preferably phenol or a C1- to C1- 12 -alkylphenol, more preferably phenol or p-tert-butylphenol, most preferably p-tert-butylphenol.

[0130] 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-isooctylphenol, p-tert-octylphenol, p-dodecylphenol and 4-(3,6-dimethyl-3-heptyl)phenol may also be used.

[0131] In a preferred embodiment, the monophenols mentioned here which do not contain carboxyl or carboxyl derivative functions are used as further chain terminators in the preparation of the polycarbonates according to the invention.

[0132] It is also possible to use mixtures of various monophenols which do not contain carboxyl or carboxyl derivative functional groups as chain terminators.

[0133] It is further preferred that component C is present in the polycarbonates of the present invention in a molar proportion of 50 to 90 mol%, particularly preferably 60 to 80 mol%, and most preferably 65 to 75 mol%, based on the total molar proportions of components A, B1, and B2 (i.e., the sum of the molar proportions of B2-a and B2-b) of 100 mol%. When using the polycarbonates of the present invention to prepare copolymers, these proportions allow, on the one hand, to achieve sufficiently high copolymer formation yields and, on the other hand, to avoid undesirable crosslinking reactions, as explained further below.

[0134] In addition, the amount of component C in the polycarbonate and its molar proportion (based on the sum of the molar proportions of components A, B1, B2 and C being 100 mol %) can be determined by 1Quantification is by H NMR spectroscopy. In the particularly preferred case where component C is a structural unit derived from p-tert-butylphenol, the NMR signal of the three methyl groups in the structural unit derived from p-tert-butylphenol and present as terminal groups is particularly suitable for this purpose. This is a single peak with a chemical shift of approximately 1.32 ppm, referenced to trimethylsilane, which is attributed to nine protons.

[0135] The polycarbonate according to the invention may contain

[0136] As component A, a plurality of structural units having free COOH functions which are derived from structurally different hydroxybenzoic acids and which are present as end groups,

[0137] As component B1, a plurality of different structural units with esterified COOH functions present as terminal groups, which differ both with regard to the structural nature of the hydroxybenzoic acid and with regard to the structural nature of the tertiary alcohol used for ester formation,

[0138] As component B2, various structural units derived from structurally different hydroxybenzoic acids, which are incorporated into the polymer chain via ester groups or anhydride groups,

[0139] and / or

[0140] As component C, various structural units derived from monophenols having no carboxyl group or carboxyl derivative functional group and serving as terminal groups.

[0141] In this case, for all the ranges of the amount ratios of these structural units described in the present invention, it applies that the molar amounts of components A, B1, B2 and C used to calculate the corresponding ratios are in each case the sum of all molar amounts of structurally different components A, B1, B2 and C.

[0142] The polycarbonate of the present invention preferably has a weight average molecular weight M wThe molecular weight is 5,000 to 40,000 g / mol, more preferably 7,000 to 35,000 g / mol, and particularly preferably 10,000 to 33,000 g / mol, as measured by GPC (gel permeation chromatography) using dichloromethane as the solvent, calibrated against bisphenol A polycarbonate standards. Calibration is performed using linear polycarbonates (formed from bisphenol A and phosgene) of known molar mass distribution from PSS Polymer Standards Service GmbH, Germany, using method 2301-0257502-09D (2009, German) from Currenta GmbH & Co. OHG, Leverkusen. The eluent is dichloromethane. The column assembly is a crosslinked styrene-divinylbenzene resin. Analytical column diameter: 7.5 mm; length: 300 mm. Column material particle size: 3 μm to 20 μm. Solution concentration: 0.2 wt%. Flow rate: 1.0 ml / min, solution temperature: 30°C. Use UV and / or RI detection.

[0143] For the use of the polycarbonate according to the invention for preparing copolymers, the polycarbonate according to the invention preferably has a weight-average molecular weight Mw of 5000 to 30000 g / mol, more preferably 7000 to 25000 g / mol, particularly preferably 10000 to 20000 g / mol. w Measured by GPC (gel permeation chromatography) in dichloromethane at room temperature using BPA polycarbonate standards.

[0144] For the use of the polycarbonate according to the invention as a molding compound for producing molded parts or as a component of a molding compound for producing molded parts, the polycarbonate according to the invention preferably has a weight-average molecular weight Mw of 18,000 to 40,000 g / mol, more preferably 20,000 to 35,000 g / mol, particularly preferably 24,000 to 33,000 g / mol. w Measured by GPC (gel permeation chromatography) in dichloromethane at room temperature using BPA polycarbonate standards.

[0145] When a mixture of a plurality of polycarbonates having different individual acid values, different A / B ratios, different B2 / (A+B2) ratios, different B1 / (A+B) ratios and / or different individual weight-average molecular weights Mw is used, it is suitable that the mixture has an acid value, A / B ratio, B2 / (A+B2) ratio, B1 / (A+B) ratio and weight-average molecular weight Mw within one of the above-mentioned (preferred) ranges.

[0146] The preparation of polycarbonates which contain incorporated structural units derived from bisphenol A (also referred to in the context of the present invention as bisphenol A-based polycarbonates or aromatic polycarbonates) is generally known in the literature (for the preparation of aromatic polycarbonates, see, for example, Schnell, "Chemistry and Physics of Polycarbonates", Interscience Publishers, 1964).

[0147] The preparation of the polycarbonates containing terminal COOH groups according to the invention is carried out in two steps. In the first step, a polycarbonate containing structural units derived from bisphenol A and terminal groups derived from hydroxybenzoates is provided. This polycarbonate is preferably prepared in a manner analogous to that described in US Pat. No. 4,853,458 B, by reacting bisphenol A or a mixture of diphenols (aromatic diols) containing bisphenol A with phosgene according to the interfacial process, with at least one hydroxybenzoate as described above or a mixture containing at least one hydroxybenzoate and at least one monophenol without carboxyl or carboxyl derivative functions being used as the monophenol chain terminator or chain terminator mixture. If a plurality of structurally different hydroxybenzoates are used in the chain terminator mixture, these esters can be distinguished both in the properties of the hydroxybenzoates and in the properties of the alcohols used to form the esters. In the second step, the terminal COOH groups (COOH functions) are released.

[0148] When monophenolic chain terminators which do not contain carboxyl or carboxyl derivative functional groups are used in the chain terminator mixture, the aromatic polycarbonates prepared contain not only components A, B1 and B2 but also structural units derived from monophenolic chain terminators, most preferably structural units derived from p-tert-butylphenol as component C.

[0149] When preparing the polycarbonates of the present invention, these monophenolic chain terminators, which do not contain carboxyl or carboxyl derivative functional groups, are preferably used in a molar proportion of 50 to 90 mol%, preferably 60 to 80 mol%, and particularly preferably 65 to 75 mol%, based on the total molar proportions of components A, B1, B2, and C being 100 mol%. The difference from 100 mol% in each case therefore corresponds to the proportion of the ester or esters of the hydroxybenzoic acid or esters or mixtures of different esters. Thus, the proportion is preferably 10 to 50 mol%, particularly preferably 20 to 40 mol%, and most preferably 25 to 35 mol%, based on the total molar proportions of components A, B1, B2, and C being 100 mol%.

[0150] If the content of hydroxybenzoates used in the chain terminator mixture is greater than the preferred range indicated, undesirable crosslinking reactions may occur during reactive compounding with the blending partners in the process according to the invention for preparing copolymers, so that thermoplastic processability of the reactive mixture is no longer guaranteed. If the content of hydroxybenzoates used in the chain terminator mixture is less than the preferred range indicated, the desired copolymers can no longer be formed between the polycarbonate and the blending partners in a yield sufficient to achieve the desired technical effects.

[0151] By varying the ratio of monophenolic chain terminators to diphenols, the molecular weight of the polycarbonates prepared therefrom can be adjusted in a targeted manner within a wide range in a manner known to those skilled in the art.

[0152] The COOH group content and therefore the acid number of the polycarbonates according to the invention can be adjusted in a targeted manner within wide ranges via the amount ratio of hydroxybenzoic acid esters to optionally used monophenolic chain terminators without carboxyl or carboxyl derivative functions in the chain terminator mixture.

[0153] Terminal COOH groups (ie, end groups derived from hydroxybenzoic acid) are liberated from polycarbonates having end groups derived from hydroxybenzoate by thermal end group pyrolysis.

[0154] The method according to the invention for releasing terminal COOH groups is thermal end group pyrolysis, wherein, based on the amount of polycarbonate precursor (I) containing end groups derived from hydroxybenzoate, 0.01 to 0.30% by weight, preferably 0.02 to 0.15% by weight, particularly preferably 0.03 to 0.07% by weight of phosphorous acid H3PO3 is added and under reduced pressure at a temperature of 240°C to 360°C, preferably 250°C to 300°C, for a period of 10 seconds to 15 minutes, preferably 20 seconds to 5 minutes.

[0155] Under these thermal conditions, the polycarbonate backbone (i.e., the polycarbonate polymer chain) does not significantly degrade and undesirable side reactions are minimized. Component C is generally unaffected by the thermal end group pyrolysis.

[0156] In combination with bisphenol A (hereinafter also referred to as "in addition to bisphenol A"), the other diphenol used for preparing the polycarbonate according to the present invention is preferably an aromatic diphenol of formula (5)

[0157]

[0158] in

[0159] A is a single bond, C1- to C5-alkylene, C2- to C5-alkylidene, C5- to C6-cycloalkylidene, -O-, -SO-, -CO-, -S-, -SO2-, C6- to C6-alkylene which may be fused to other aromatic rings optionally containing heteroatoms,12 -arylene group, or a group of formula (6) or (7)

[0160]

[0161] B represents C1 to C 12 - alkyl, preferably methyl, halogen, preferably chlorine and / or bromine,

[0162] x are each independently 0, 1 or 2,

[0163] p is 1 or 0, and

[0164] R 5 and R 6 For each X 1 Individually selected, independently of one another, are hydrogen or C1 to C6 alkyl, preferably hydrogen, methyl or ethyl,

[0165] X 1 is carbon, and

[0166] m is an integer from 4 to 7, preferably 4 or 5, provided that at least one atom X 1 R on 5 and R 6 At the same time it is an alkyl group.

[0167] In addition to bisphenol A, preferred diphenols are also 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.

[0168] Particularly preferred diphenols, besides bisphenol A, are 4,4′-dihydroxybiphenyl, 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 dibrominated and tetrabrominated or chlorinated derivatives, for example 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.

[0169] If a mixture of the above-mentioned diphenols containing bisphenol A is used in the preparation of the polycarbonates according to the invention, the mixture contains bisphenol A in an amount of at least 5 mol%, preferably at least 50 mol%, more preferably at least 75 mol%, and particularly preferably at least 90 mol%, based on the sum of all diphenols used. Most preferably, pure bisphenol A is used as the diphenol in the preparation of the polycarbonates.

[0170] The diphenols used, other than bisphenol A, can be used individually or in any desired mixtures. These diphenols are known from the literature or are obtainable by processes known from the literature.

[0171] The polycarbonates according to the invention can be branched in a known manner and preferably by adding 0.01 to 2.0 mol %, based on the total amount of diphenols used, of trifunctional or more than trifunctional compounds (for example compounds having three or more phenolic groups).

[0172] The polycarbonates containing COOH groups according to the invention are preferably linear polycarbonates.

[0173] Other polymers used to prepare copolymers

[0174] The polycarbonate containing COOH end groups of the present invention can be used to prepare copolymers or thermoplastic molding compounds containing copolymers. The copolymers are preferably block copolymers, more preferably block copolymers containing vinyl (co)polymers or polyolefins.

[0175] Suitable polymers that can form copolymers with the polycarbonate of the present invention contain at least one functional group selected from ester groups, hydroxyl groups and epoxy groups. The polymers particularly preferably contain epoxy groups.

[0176] When an ester group is used as such a functional group, the group can be an integral part of the polymer chain (polymer backbone) in the polymer, as in the case of polyesters, or a monomeric functional group that does not directly participate in polymer chain growth, as in the case of acrylate polymers.

[0177] It is also possible to use mixtures of these different polymers. The mixtures can in each case comprise polymers having identical functional groups or polymers having different functional groups.

[0178] Preferably, the other polymer is selected from the aforementioned (preferred) vinyl (co)polymers, polyolefins and polyesters containing functional groups, more preferably vinyl (co)polymers and polyolefins, and particularly preferably vinyl (co)polymers.

[0179] The functional group-containing vinyl (co)polymer according to the present invention is preferably a (co)polymer of at least one monomer selected from the group consisting of: (C1 to C8)-alkyl (meth)acrylates (e.g. methyl methacrylate, n-butyl acrylate, tert-butyl acrylate), unsaturated carboxylic acids and carboxylic anhydrides, vinyl aromatic compounds (e.g. styrene, α-methylstyrene), vinyl cyanides (unsaturated nitriles such as acrylonitrile and methacrylonitrile) and olefins (e.g. ethylene), as well as other vinyl monomers containing ester groups, hydroxyl groups, carboxyl groups, carboxylic anhydride groups or epoxy groups, preferably vinyl monomers containing epoxy groups, particularly preferably glycidyl methacrylate.

[0180] For example, the epoxy groups are preferably introduced by copolymerization of the other monomer glycidyl methacrylate with one further monomer or further monomers.

[0181] These (co)polymers are resinous and rubber-free. Such (co)polymers are known and can be prepared by free-radical polymerization, in particular by emulsion, suspension, solution or bulk polymerization.

[0182] Particularly suitable vinyl (co)polymers contain structural units derived from glycidyl methacrylate.

[0183] Particularly suitable vinyl (co)polymers are copolymers of methyl methacrylate and glycidyl methacrylate.

[0184] Particularly suitable vinyl (co)polymers also include styrene-acrylonitrile-glycidyl methacrylate terpolymers and styrene-methyl methacrylate-glycidyl methacrylate terpolymers.

[0185] Particularly suitable vinyl (co)polymers preferably have a glycidyl methacrylate content of 0.5 to 10% by weight, more preferably 0.7 to 7% by weight, particularly preferably 1 to 5% by weight.

[0186] Suitable polyesters may be linear or branched. The polyesters are preferably linear. They may be aliphatic or aromatic. In preferred embodiments, the polyesters are aromatic, more preferably polyalkylene terephthalates. In particularly preferred embodiments, they are reaction products of aromatic dicarboxylic acids or reactive derivatives thereof (e.g., dimethyl esters or anhydrides) with aliphatic, cycloaliphatic, or araliphatic diols, and mixtures of these reaction products.

[0187] Particularly preferred aromatic polyalkylene terephthalates contain at least 80% by weight, preferably at least 90% by weight, of terephthalic acid groups, based on the dicarboxylic acid component, and at least 80% by weight, preferably at least 90% by weight, of ethylene glycol groups and / or butane-1,4-diol groups, based on the diol component.

[0188] Aromatic polyalkylene terephthalates preferably employed have viscosity values ​​of 0.4 to 1.5 dl / g, preferably 0.5 to 1.2 dl / g, measured in an Ubbelohde viscometer in phenol / o-dichlorobenzene (1:1 parts by weight) at 25° C. at a concentration of 0.05 g / ml to ISO 307.

[0189] Aromatic polyalkylene terephthalates can be prepared by known methods (see, for example, Kunststoff-Handbuch, Vol. VIII, pp. 695 et seq., Carl-Hanser-Verlag, Munich, 1973). It is also preferred that the further polymer is a polyolefin containing functional groups, preferably a polyolefin containing epoxy groups, particularly preferably a polyolefin containing structural units derived from glycidyl methacrylate.

[0190] Polyolefins are produced by chain polymerization, for example by free radical or anionic polymerization. The monomers used are olefins. Another name for olefins is alkenes. The monomers can be polymerized individually or as mixtures of various monomers. Preferred monomers are ethylene, propylene, 1-butene, isobutylene, 1-pentene, 1-heptene, 1-octene, and 4-methyl-1-pentene.

[0191] Polyolefins can be semicrystalline or amorphous, and can also be linear or branched. The preparation of polyolefins is already known to those skilled in the art.

[0192] The polymerisation can be carried out, for example, at a pressure of 1 to 3000 bar and a temperature of 20° C. to 300° C., optionally using a catalyst system. Examples of suitable catalysts include mixtures of titanium and aluminium compounds and metallocenes.

[0193] The number of branches, crystallinity and density of polyolefins can be varied over a wide range by varying the monomer composition, the type of isomers used as monomers, polymerization conditions, catalyst system, etc. These measures are also well known to those skilled in the art.

[0194] Functional groups can be introduced into polyolefins, for example, by copolymerizing the above-mentioned vinyl monomers containing functional groups with the above-mentioned olefins, preferably by free radical polymerization. Suitable vinyl monomers are, for example, glycidyl methacrylate and methyl methacrylate.

[0195] Another preparation method is to free radical graft a vinyl monomer containing a functional group, such as glycidyl methacrylate, from a polyolefin.

[0196] The average molecular weight (weight average Mw, determined by GPC (gel permeation chromatography) using polystyrene standards) of the further polymers is preferably 3,000 to 300,000 g / mol, more preferably 10,000 to 200,000 g / mol, particularly preferably 20,000 to 100,000 g / mol.

[0197] The solvent used for the GPC measurement is selected so that it preferably dissolves the other polymer well at room temperature. If solubility in the selected solvent is observed at room temperature, GPC is performed at room temperature.

[0198] For example, tetrahydrofuran is a suitable solvent for preferred vinyl (co)polymers, such as copolymers of methyl methacrylate and glycidyl methacrylate, styrene-acrylonitrile-glycidyl methacrylate terpolymers, and styrene-methyl methacrylate-glycidyl methacrylate terpolymers. Suitable solvents for polyolefins containing structural units derived from glycidyl methacrylate are, for example, o-dichlorobenzene or 1,2-dichloroethane. Sufficient solubility generally requires elevated temperatures, for example 40° C., 60° C., 80° C., 100° C., or 120° C. In this case, GPC is carried out at the temperature required to achieve sufficient solubility for GPC. If the polyolefin requires temperatures above 40° C. to achieve sufficient solubility for GPC, o-dichlorobenzene is preferably used as the solvent.

[0199] Preparation of copolymers from the polycarbonates according to the invention and molding compounds containing the copolymers

[0200] From the polycarbonates according to the invention containing COOH end groups and the above-mentioned other polymers, copolymers containing at least one polycarbonate block can be prepared, preferably block copolymers with vinyl (co)polymers or polyolefins, most preferably block copolymers with PMMA. Another subject of the present invention is such copolymers.

[0201] The preparation of such block copolymers or molding compounds is preferably carried out according to a process comprising the following steps:

[0202] a) melting a composition comprising:

[0203] The polycarbonate (II) of the present invention contains component B and

[0204] Other polymers containing structural units derived from other polymers, the other polymers containing at least one functional group selected from ester groups, hydroxyl groups and epoxy groups, preferably containing epoxy groups, preferably vinyl (co)polymers or polyolefins containing structural units derived from glycidyl methacrylate, the structural units being grafted onto the vinyl (co)polymers or polyolefins or incorporated into the polymer chain of the vinyl (co)polymers or polyolefins,

[0205] b) mixing the different components of the composition with one another and dispersing them with one another,

[0206] c) solidifying the melt by cooling,

[0207] d) granulating the solidified product obtained in steps (a) to (c),

[0208] In this process, a chemical coupling reaction of the structural units in the polycarbonate (II) which are derived from hydroxybenzoic acid and present as terminal groups and have free COOH functions with the polymer containing epoxy groups takes place in the melt.

[0209] Step (b) of the process is preferably carried out in a compounder selected from single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, internal kneaders or co-kneaders and likewise preferably at a melt temperature of 230° C. to 300° C.

[0210] Other components for the preparation of thermoplastic molding compounds

[0211] The polycarbonates of the present invention containing COOH end groups, the thermoplastic compositions of the present invention containing such polycarbonates, the copolymers of the present invention prepared from such polycarbonates or molding compounds, and the molding compounds of the present invention containing such copolymers can be used as components of thermoplastic molding compounds, which preferably contain one or more other polymers. The copolymers of the present invention and the molding compounds of the present invention containing such copolymers are particularly suitable as components of thermoplastic molding compounds containing polycarbonates, preferably aromatic polycarbonates, as the other polymer. The copolymers of the present invention and the molding compounds of the present invention containing such copolymers are also suitable as components of thermoplastic polymer blend molding compounds, which contain aromatic polycarbonates and at least one other polymer having a polarity similar to that of the polymer block bonded to the polycarbonate block in the copolymer. These copolymers and the molding compounds of the present invention containing such copolymers are most preferably suitable as components of thermoplastic polymer blend molding compounds, which contain aromatic polycarbonates and, as the other polymer, a polymer that is the same as the polymer block bonded to the polycarbonate of the present invention in the block copolymer.

[0212] These molding compounds may contain further components, such as polymer additives, processing aids and / or other polymer components, which are preferably selected from flame retardants, anti-drip agents, flame retardant synergists, smoke suppressants, lubricants and release agents, nucleating agents, polymeric and non-polymeric antistatic agents, conductivity additives, stabilizers (such as hydrolysis, heat aging and UV stabilizers and transesterification inhibitors), flow promoters, impact modifiers (with or without core-shell structure), polymer blending partners, fillers and reinforcing agents and dyes and pigments.

[0213] Preferred polymer blending partners are aromatic polycarbonates, polyesters (e.g., preferably polyethylene terephthalate and polybutylene terephthalate), vinyl (co)polymers, and polyolefins that do not contain COOH end groups. Unlike the polymers used to prepare the copolymers, these polymers do not need to contain functional groups. Thus, suitable preferred polymer blending partners also include, for example, polystyrene, polyolefins, copolymers of ethylene and / or propylene with acrylates, styrene-acrylonitrile copolymers, styrene-methyl methacrylate copolymers, and polymethyl methacrylate. These polymers can be rubber-free or rubber-containing. The latter is suitable, for example, for acrylonitrile-butadiene-styrene (ABS) or acrylonitrile-butyl acrylate-styrene (ASA) polymers.

[0214] The aforementioned further components are used in an amount of 0 to 40% by weight, preferably 0.1 to 30% by weight, more preferably 0.2 to 20% by weight, based on the thermoplastic composition.

[0215] In order to obtain transparent thermoplastic molding compounds, it is often advantageous or technically necessary to avoid the use of certain other components in their composition, such as fillers and reinforcing agents, impact modifiers and rubber-containing blending partners, or to limit their concentration and the concentration of other components used in other ways to a content significantly lower than that mentioned above.

[0216] Preparation of molding compounds containing the polycarbonates and / or copolymers according to the invention and of products made from these molding compounds Molded products

[0217] For example, the thermoplastic molding material of the present invention can be prepared by melt-blending the individual components, i.e. the polycarbonate of the present invention or the thermoplastic material of the present invention containing such a polycarbonate of the present invention and / or the copolymer of the present invention or the thermoplastic molding material of the present invention containing such a copolymer and other polymer components, polymer additives and / or process aids (i.e. the composition) at a temperature of 220° C. to 320° C., preferably 230° C. to 300° C., particularly preferably 240° C. to 290° C., most preferably 250° C. to 280° C.

[0218] Mixing can be carried out 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. The composition is melt-compounded or melt-extruded therein to form the molding compound. In the context of this application, this process is generally referred to as compounding or melt compounding. Therefore, the term "molding compound" is understood to refer to the product obtained when the components of the composition are melt-compounded.

[0219] The mixing of the individual components of the composition can be carried out in a known manner, either continuously or simultaneously, and can be carried out at about 20° C. (room temperature) or at elevated temperature. This means, for example, that some components can be metered in completely or partially via the main feed of the extruder, while the remaining components can be introduced completely or partially subsequently during compounding via a side extruder.

[0220] The molding compound of the present invention can be used to prepare various types of shaped articles. These shaped articles can be prepared, for example, by injection molding, extrusion and blow molding. Another form of processing is to prepare shaped articles from previously prepared sheets or films by deep drawing.

[0221] It is also possible to meter the components of the composition directly into the conveying extruder of an injection molding machine, thereby preparing the molding compound of the invention in the conveying extruder and directly processing (compounding or reactive compounding injection molding) to form a molded article by discharging the molding compound accordingly into an injection molding mold.

[0222] A further subject matter of the present invention relates to the use of the composition according to the invention or the molding compound according to the invention for producing shaped articles, and furthermore to shaped articles obtainable from the composition according to the invention or the molding compound according to the invention or containing such a molding compound.

[0223] Examples of such shaped articles are films, profiles, various types of housing parts, for example, housing parts for household appliances such as juicers, coffee machines, blenders, etc.; housing parts for office machines such as displays, flat-panel displays, laptops, printers, copiers, etc.; panels, pipes, electrical installation channels, windows, doors and other profiles for the construction sector (interior decoration and exterior applications), as well as electrical and electronic components such as switches, plugs and sockets, and parts for commercial vehicles (especially in the automotive sector). The compositions and molding materials according to the invention are also suitable for producing the following shaped articles or shaped parts: interior decoration parts for rail vehicles, ships, aircraft, buses and other motor vehicles, body parts for motor vehicles, housings for electrical equipment including small transformers, housings for information processing and transmission equipment, housings and facings for medical equipment, massage equipment and their housings, children's toy cars, sheet wall elements, housings for safety equipment, insulated transport containers, shaped parts for sanitary and bathing equipment, protective grilles for ventilation openings, and housings for garden equipment.

[0224] Further embodiments of the present invention are listed below.

[0225] 1. Polycarbonate containing structural units derived from bisphenol A and

[0226] A) structural units which are derived from hydroxybenzoic acid and which have free COOH functions as terminal groups, and

[0227] B) optionally structural units derived from hydroxybenzoic acid,

[0228] Wherein component B) is selected from at least one representative of the following

[0229] B1) structural units which are derived from hydroxybenzoic acid and which have an esterified COOH function as a terminal group,

[0230] and

[0231] B2) structural units derived from hydroxybenzoic acid which are incorporated into the polymer chain via ester groups or anhydride groups,

[0232] The free bisphenol A content in the polycarbonate is a maximum of 50 ppm, and

[0233] When component B is contained, the ratio of the molar amount of component B1 to the sum of the molar amounts of components A and B is at most 0.07.

[0234] 2. The polycarbonate according to embodiment 1, which contains component B.

[0235] 3. The polycarbonate according to any one of the preceding embodiments, wherein component B2 is present and the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2 is from 0.001 to 0.25.

[0236] 4. The polycarbonate according to any of the preceding embodiments, wherein component B2 is present and the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2 is at most 0.12.

[0237] 5. The polycarbonate according to any of the preceding embodiments, wherein component B2 is present and the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2 is at most 0.08.

[0238] 6. The polycarbonate according to any of the preceding embodiments, wherein component B2 is present and the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2 is at most 0.03.

[0239] 7. The polycarbonate according to any one of the preceding embodiments 2 to 6, wherein the ratio of the molar amount of component A to the molar amount of component B is at least 8.

[0240] 8. The polycarbonate according to any one of the preceding embodiments 2 to 7, wherein the ratio of the molar amount of component A to the molar amount of component B is at least 12.

[0241] 9. The polycarbonate according to any one of the preceding embodiments 2 to 8, wherein the ratio of the molar amount of component A to the molar amount of component B is at least 25.

[0242] 10. The polycarbonate according to any one of the preceding embodiments, further comprising

[0243] C) a structural unit which is derived from at least one phenolic compound having only one phenolic OH function and no carboxyl or carboxyl derivative function and is present as a terminal group,

[0244] It is characterized in that component C is present in the polycarbonate in a molar proportion of 50 to 90 mol %, based on the molar proportions of components A, B1, B2 and C totaling 100 mol %.

[0245] 11. The polycarbonate according to embodiment 10, wherein component C is present in the polycarbonate in a molar proportion of 65 to 75 mol%, based on the molar proportions of components A, B1, B2 and C totaling 100 mol%.

[0246] 12. The polycarbonate according to any one of the preceding embodiments, wherein the polycarbonate is characterized by an acid number of 0.3 to 30 mg potassium hydroxide (KOH) / g, the acid number being determined in dichloromethane (DCM) / ethanol as solvent by potentiometric titration with an ethanolic KOH solution at room temperature according to DIN EN ISO 2114, Method A, 2002-6 edition.

[0247] 13. The polycarbonate according to embodiment 12, wherein the acid value is 1.0 to 10 mg potassium hydroxide (KOH) / g.

[0248] 14. The polycarbonate according to any of the preceding embodiments, wherein the ratio of the molar amount of component B1 to the sum of the molar amounts of components A and B is at most 0.05.

[0249] 15. The polycarbonate according to any of the preceding embodiments, wherein the ratio of the molar amount of component B1 to the sum of the molar amounts of components A and B is at most 0.01.

[0250] 16. The polycarbonate according to any of the preceding embodiments, wherein the content of free bisphenol A in the polycarbonate is maximum 20 ppm.

[0251] 17. The polycarbonate according to any of the preceding embodiments, wherein the content of free bisphenol A in the polycarbonate is maximum 10 ppm.

[0252] 18. Process for the preparation of polycarbonates (II) containing terminal groups derived from hydroxybenzoic acid and having free COOH functional groups, wherein

[0253] Polycarbonate (I) containing terminal groups derived from hydroxybenzoate

[0254] In the presence of 0.01 to 0.30% by weight of phosphorous acid H3PO3, based on the amount of polycarbonate (I)

[0255] When negative pressure is applied for 10 seconds to 15 minutes

[0256] Withstand temperatures from 240°C to 360°C,

[0257] Polycarbonate (II) is thus formed.

[0258] 19. The process according to embodiment 18, wherein polycarbonate (I) and polycarbonate (II) contain structural units derived from bisphenol A.

[0259] 20. The process according to any of embodiments 18 or 19, wherein in the preceding step, the polycarbonate (I) is prepared by phosgenation of bisphenol A or a mixture of a plurality of structurally different diols containing bisphenol A in the interfacial process or in organic solution in the presence of at least one hydroxybenzoic acid ester or a mixture containing at least one hydroxybenzoic acid ester and at least one phenolic compound having only one phenolic OH function and no carboxyl or carboxyl derivative functions as chain terminator or a mixture of chain terminators,

[0260] And wherein the at least one hydroxybenzoate is an ester of hydroxybenzoic acid and an alcohol of the general formula (1)

[0261]

[0262] wherein R1 to R4 independently represent hydrogen or an alkyl group, an aryl group or an alkylaryl group having 1 to 10 carbon atoms.

[0263] 21. The process according to embodiment 20, wherein directly after the preparation of polycarbonate (I), in a further process step upstream of the formation of polycarbonate (II), the solvent used for the preparation of polycarbonate (I) is removed to a residual content of <0.1% by weight.

[0264] 22. The process according to embodiment 21, wherein the solvent is removed by precipitation, optionally separating the precipitated solid from the mother liquor, optionally washing the precipitated solid and drying or alternatively by spray drying, and wherein the polycarbonate (I) is not subjected to temperatures > 200° C. at any time in this upstream workup process step.

[0265] 23. The process according to embodiment 20, wherein the solvent used for the preparation of polycarbonate (I) is removed to a residual content of <0.1% by weight in a single reaction step, and polycarbonate (II) is formed.

[0266] 24. The process according to any of embodiments 18 to 23, wherein olefins are eliminated during the preparation of polycarbonate (II) from polycarbonate (I).

[0267] 25. The process according to any one of embodiments 18 to 24, wherein phosphorous acid is used in the form of an aqueous solution.

[0268] 26. The process according to any of embodiments 18 to 25, wherein the preparation of polycarbonate (II) from polycarbonate (I) is carried out in a process apparatus selected from single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roller extruders, continuous or discontinuous internal kneaders, film extruders, strand evaporators and foam evaporators.

[0269] 27. The process according to any of embodiments 18 to 26, wherein the amount of phosphorous acid is 0.02 to 0.15% by weight, based on the amount of polycarbonate (I).

[0270] 28. The process according to any of embodiments 18 to 26, wherein the amount of phosphorous acid is 0.03 to 0.07% by weight, based on the amount of polycarbonate (I).

[0271] 29. A thermoplastic composition comprising a polycarbonate according to any of embodiments 1 to 17 and at least one phosphorus compound selected from phosphorous acid, phosphoric acid, phosphites and phosphates and phosphorous acid condensates and phosphoric acid condensates, the total amount of these phosphorus compounds being in each case 0.01 to 0.30% by weight.

[0272] 30. Thermoplastic material according to embodiment 29, wherein the phosphorus compound is selected from phosphorous acid and phosphites.

[0273] 31. Thermoplastic material according to embodiment 29 or 30, wherein the amount of phosphorus compound is from 0.02% to 0.15% by weight.

[0274] 32. Thermoplastic material according to embodiment 29 or 30, wherein the amount of phosphorus compound is from 0.03% to 0.07% by weight.

[0275] 33. A copolymer comprising structural units derived from the polycarbonate according to any one of embodiments 2 to 17 and structural units derived from another polymer containing at least one functional group selected from ester groups, hydroxyl groups and epoxy groups, preferably containing epoxy groups.

[0276] 34. A thermoplastic molding compound comprising a copolymer according to embodiment 33 and / or a polycarbonate according to any one of embodiments 2 to 17 and / or a thermoplastic composition according to any one of embodiments 29 to 32.

[0277] 35. Use of the polycarbonate according to any of embodiments 2 to 17 or the thermoplastic composition according to any of embodiments 29 to 32 for producing a copolymer containing at least one polycarbonate block containing structural units derived from bisphenol A and at least one block of a polymer different from this polycarbonate, or for producing a thermoplastic molding compound containing this copolymer, in a process comprising the following steps:

[0278] a) melting a composition comprising a polycarbonate according to any one of embodiments 2 to 17 or a thermoplastic according to any one of embodiments 29 to 32 by introducing thermal energy and / or mechanical shearing, and

[0279] Other polymers containing at least one functional group selected from ester groups, hydroxyl groups and epoxy groups, preferably containing epoxy groups,

[0280] b) mixing the different components of the composition with one another and dispersing them with one another,

[0281] c) solidifying the melt by cooling,

[0282] d) optionally granulating the solidified product obtained in steps (a) to (c),

[0283] In the process, a chemical coupling reaction occurs in the melt between the structural units in the polycarbonate (II) which are derived from hydroxybenzoic acid and present as terminal groups and have free COOH functional groups and other polymers containing at least one functional group selected from ester groups, hydroxyl groups and epoxy groups, preferably containing epoxy groups.

[0284] 36. The use according to embodiment 35, wherein the polymer containing epoxy groups is a vinyl (co)polymer or a polyolefin, which contains a structural unit derived from glycidyl methacrylate, which is grafted onto the vinyl (co)polymer or polyolefin or incorporated into the polymer chain of the vinyl (co)polymer or polyolefin.

[0285] 37. The use according to any of embodiments 35 or 36, wherein step b) is carried out in a compounder selected from a single-screw extruder, a co-rotating or counter-rotating twin-screw extruder, a planetary roller extruder, an internal kneader or a co-kneader and at a melt temperature of 230° C. to 300° C.

[0286] 38. Shaped articles comprising the polycarbonate according to any one of embodiments 2 to 17 and / or the copolymer according to embodiment 33. Example

[0287] Preparation of polycarbonate precursor PC(I)

[0288] In a continuously operated laboratory reactor, bisphenol A was polycondensed with phosgene in a phase-interfacial process using a mixture of dichloromethane and chlorobenzene as solvent in the presence of a chain terminator mixture consisting of p-tert-butylphenol and tert-butyl p-hydroxybenzoate.

[0289] In this synthesis, 71.9 g / h of gaseous phosgene was dissolved in 940.6 g / h of an organic solvent mixture consisting of 50 wt% dichloromethane and 50 wt% chlorobenzene at -7°C. The resulting phosgene solution was contacted with 895.8 g / h of a 15 wt% alkaline aqueous bisphenol A solution, temperature-controlled at 30°C. The alkaline bisphenol A solution was forced through a stainless steel filter with a pore size of 90 μm into the phosgene solution, thereby dispersing it. Two mol of NaOH were used per mol of bisphenol A in the bisphenol A solution. The reaction mixture was reacted in a Fink HMR040 mixing pump temperature-controlled at 25°C until the phosgene was completely reacted. Subsequently, 5.9 g / h of a mixture consisting of 50 mol% p-tert-butylphenol and 50 mol% tert-butyl 4-hydroxybenzoate was metered in as a chain terminator, in the form of a 10 wt% solution in a solvent mixture consisting of 50 wt% dichloromethane and 50 wt% chlorobenzene. The resulting reaction mixture was further reacted with 66.0 g / h of 32.2 wt% aqueous sodium hydroxide solution in a second Fink HMR040 mixing pump, temperature-controlled at 25°C. Downstream of this were two baffled stirred tanks operated in flooded mode, each with a residence time of 600 seconds. A gear pump was then connected to each of these, serving both as a conveyor and further dispersion mechanism. After the first pump, upstream of the second stirred tank, 0.666 g / h of a 10 wt% solution of N-ethylpiperidine in chlorobenzene was metered in as a catalyst. At the end of the reaction, the pH was approximately 11.5. In a phase separation vessel, the organic phase of the biphasic reaction mixture was separated from the aqueous phase and washed with a 0.1 wt% aqueous HCl solution to remove the catalyst. Subsequently, the organic phase was washed with deionized water to remove any salt residues. The polymer solution washed in this manner was precipitated in an organic solvent and dried overnight in a vacuum oven at 120°C.

[0290] The polycarbonate PC(I) prepared in this way is a powder with a weight average molecular weight M w The molecular weight was 18.8 kg / mol and the number average molecular weight Mn was 11.3 kg / mol, as measured by gel permeation chromatography (GPC) at room temperature using dichloromethane as solvent, calibrated against a polycarbonate standard based on bisphenol A, and using a wave number set at 1775 cm -1 Polycarbonate selective infrared (IR) detector.

[0291] The content of free bisphenol A in the polycarbonate PC(I) was measured to be 3 ppm by weight.

[0292] Preparation of the polycarbonate (II) of the present invention by pyrolysis of the end groups of the polycarbonate precursor PC (I)

[0293] The polycarbonate precursor PC(I), prepared according to the above method, was subjected to thermal end group pyrolysis to release COOH end groups by eliminating protective groups in the form of isobutylene gas in a continuous twin-screw extruder, Process 11 (Thermofischer Scientific, Karlsruhe, Germany). The extruder's screw configuration had three mixing zones and a length-to-diameter (L / D) ratio of 40. Various inventive and comparative examples were produced at varying melt temperatures ranging from 245°C to 320°C, as measured by a thermocouple installed in the last barrel element of the extruder, near the nozzle outlet. The melt temperature was generated by the introduction of mechanical energy via the kneading elements and thermal energy via heating of the extruder barrel. The extruder barrel was divided into eight independent, individually heatable zones, numbered 1 to 8 in ascending order when viewed from the extruder inlet toward the extruder outlet nozzle. The three kneading zones were located in the transition zone between heating zones 3 and 4, heating zone 5, and the transition zone between heating zones 6 and 7. The feedstock inlet was located in heating zone 1. Furthermore, the outlet nozzle was individually heated. To accommodate the varying melt temperatures detected by thermocouples installed in the last barrel element of the extruder near the nozzle outlet, the barrel and nozzle temperatures in the barrel zones were adjusted to different temperatures. The first barrel (feedstock inlet zone) was unheated in all cases, zone 2 was heated to a target temperature of 70°C, zone 3 was heated to a target temperature of 190°C, and zones 4 to 8 and the outlet nozzle were heated to the same target temperature (Ttarget) according to Table 1. In all cases, the same polycarbonate precursor (PC(I)) was used as the input feedstock. In all cases, the extruder was operated at a throughput of approximately 300 g / h and a rotational speed of 175 min-1. Under these process conditions, the isobutylene gas released in the extruder was continuously withdrawn from the extruder through the degassing port of the penultimate (seventh) heating zone by applying a negative pressure of at least -800 mbar. In all cases, these process conditions resulted in a polycarbonate residence time in the extruder of approximately 70 seconds.

[0294] Phosphorous acid was added as an aqueous solution by applying it to a powder of the polycarbonate precursor PC(I). Powder mixtures with varying H3PO3 contents were prepared using H3PO3 aqueous solutions of varying concentrations, by applying 2.5 parts by weight of each aqueous H3PO3 solution to a powder of the polycarbonate precursor PC-1. PC powder mixtures containing 0.002, 0.01, 0.05, and 0.25% phosphorous acid were prepared using aqueous H3PO3 solutions with concentrations of 0.08, 0.4, 2.0, or 10% H3PO3. These solutions were evenly applied to 99.998, 99.99, 99.95, or 99.75% by weight of the polycarbonate precursor PC(I) powder, and the mixture was then thoroughly homogenized. Because the phosphorous acid was applied as a dilute aqueous solution, this method introduced approximately equal amounts of water (2.25 to 2.5% by weight, depending on the composition) into the polycarbonate. The powder mixture thus prepared was either used for the end-group pyrolysis without further drying or was first dried in a vacuum drying cabinet at 100° C. for two hours in order to remove the water introduced by the aqueous H 3 PO 3 solution from the composition again before the thermal treatment.

[0295] Table 1 shows the process parameters set or measured for the polycarbonates according to the invention and comparative polycarbonates produced in different ways (target temperatures set in the extruder heating zone and at the melt outlet nozzle, melt temperature measured by a thermocouple installed in the last barrel element of the extruder close to the nozzle outlet, the amount of phosphorous acid added in the end group pyrolysis, and information on possible drying of the polycarbonate after addition of the H3PO3 aqueous solution and before end group pyrolysis).

[0296] Characterization of polycarbonate

[0297] The NMR spectrometer was used at room temperature using a Bruker Avance III HD 600 MHz NMR spectrometer with deuterated chloroform as solvent. 1 The structure of the polycarbonate was analyzed by H NMR spectroscopy based on the content of the structural units of components A, B1, B2-a, B2-b, and C.

[0298] The integrated signal intensity of each NMR signal divided by the number of protons responsible for that signal is proportional to the molar content of the respective structural unit. Therefore, the corresponding ratios of these normalized signal intensities are used to determine the molar ratios of the corresponding structural units characteristic of the polycarbonates according to the present invention. Table 1 also shows the measured intensities of the specific NMR signals of the various structural units of components A, B1, B2-a, B2-b, and C, and the molar ratios A / B, B2 / (A+B2), B1 / (A+B), and C / (A+B+C) determined therefrom, according to the characteristic structural features of the polycarbonate, as described above. B2 is the sum of B2-a and B2-b, and B is the sum of B1 and B2.

[0299] The content of phenolic OH groups is also 1 H NMR spectroscopy determination. For this purpose, the doublet signal at approximately 6.68 ppm, measured relative to trimethylsilane (TMS) reference, which is attributable to the two aromatic protons in the ortho position of the phenolic OH group, was evaluated and correlated with the singlet signal at approximately 1.68 ppm, measured relative to trimethylsilane (TMS) reference, which is attributable to the six methyl protons in the structural units of the polycarbonate backbone (polycarbonate polymer chain) derived from bisphenol A.

[0300] To determine the content of free bisphenol A, polycarbonates according to the invention, polycarbonates not according to the invention, and the starting polycarbonate PC(I) were dissolved in dichloromethane and precipitated with acetone. The filtrate was analyzed by high-pressure liquid chromatography (HPLC-UV) equipped with a UV detector. A C18 phase was used as the column material, and a gradient of water and methanol was used as the eluent.

[0301] The acid number of the polycarbonates was determined by potentiometric titration with ethanolic KOH solution at room temperature in dichloromethane (DCM) / ethanol according to DIN EN ISO 2114, Method A, Edition 2002-6. To this end, the polycarbonate to be investigated was dissolved in 50 mL of dichloromethane at a concentration of 10 g / L at room temperature. Prior to the potentiometric titration with 0.1 N ethanolic KOH solution, 5 mL of ethanol was added to the sample solution.

[0302] The intrinsic color of the polycarbonate pellets obtained as a product of the end-group pyrolysis extruder process was visually evaluated according to a relative scale based on color coordinates and color intensity as defined below, where a rating of 3 represents the best evaluation and a rating of 0 represents the worst evaluation:

[0303] 3 colorless

[0304] 2 slightly yellow

[0305] 1 light yellow

[0306] 0 yellow / brown or gray

[0307] Table 1 also shows the phenolic OH group content, free bisphenol A content, acid value and intrinsic color of the polycarbonate pellets of the polycarbonate.

[0308]

[0309] The examples in Table 1 demonstrate that polycarbonates (PC-3, PC-5, PC-7, and PC-9) prepared by the process of the present invention, i.e., by adding H3PO3 to the end group pyrolysis, possess the desired structural features of the present invention and, compared to similar polycarbonates (PC-2*, PC-4*, PC-6*, and PC-8*) prepared by prior art processes without the addition of H3PO3 to the end group pyrolysis, have a better (color-neutral) intrinsic color and a lower content of phenolic OH groups, especially free bisphenol A. The polycarbonates prepared by the process of the present invention have a significantly more defined end group structure, i.e., they have a higher content of free COOH end groups A and a lower content of precursor end group species B1 and transesterification species B2, which are undesirably formed by A in the subsequent reaction of the COOH end groups A downstream of the end group pyrolysis. Consequently, they exhibit higher A / B values ​​and lower B1 / (A+B) and B2 / (A+B2) values.

[0310] Furthermore, a comparison of the inventive example PC-3 with the comparative example PC-2*, similarly prepared without the addition of H₃PO₃, shows that the addition of H₃PO₃ during the end group pyrolysis step of the preparation process not only inhibits the transesterification of the released COOH end groups and the formation of free bisphenol A by thermal reversible cleavage, but surprisingly also catalyzes the end group pyrolysis of the tert-butyl 4-hydroxybenzoate end group species B1. Consequently, the end group pyrolysis can be performed not only at higher temperatures, as is technically difficult to avoid in many industrially established post-processing processes in the melt (e.g., degassing processes), but also, in principle, at very low melt temperatures below 240°C, i.e., in a process that reduces energy costs. Overall, the data demonstrate that for the first time, a very broad, flexibly configurable process window can be established for the end group pyrolysis process, thereby allowing for a wide variety of possible process modes and, overall, a more robust process. This results in fewer rejects and fewer operational disruptions, including undesirable plant downtime and cleaning times.

[0311] A comparison of the inventive example PC-9 with the similarly inventive examples PC-10 and PC-15 (all prepared in the process according to the invention by adding the same amount of 0.05 wt. % H₃PO₃) shows that the inventive polycarbonates are thermally stable to further / higher thermal stresses. Despite having melt temperatures in the end-group pyrolysis that are 18°C ​​and 36°C higher, respectively, than those of PC-9, PC-10 and PC-15 achieve very low residual contents of free BPA and phenolic OH groups, as well as an improved (more neutral) intrinsic product color compared to the prior art. This is particularly true compared to the comparative examples PC-4*, PC-6*, and PC-8*, which were prepared in the process according to the prior art at significantly lower melt temperatures in the end-group pyrolysis and without the addition of H₃PO₃. Despite the elevated temperatures in the end group pyrolysis, which can simulate further thermal stresses in downstream processing steps, for example, Examples PC-10 and PC-15 still exhibit the structural characteristics of the invention, namely, a high content of free COOH end groups A and a low content of transesterified species B2, which are undesirably formed from these end group species A in subsequent reactions downstream of the end group pyrolysis. In contrast to Example PC-15 of the invention, which was prepared at a melt temperature of 320° C. in the end group pyrolysis step and still contains an almost optimal (i.e., maximum possible) concentration of free COOH end groups A, Comparative Example PC-6*, which was prepared at a melt temperature of 265° C. in the end group pyrolysis step (i.e., at a temperature 55° C. lower than PC-15), no longer contains any free COOH end groups A, i.e., these end groups have already been completely and quantitatively transesterified in undesirable subsequent reactions.

[0312] Comparison of Examples PC-10, PC-11, PC-13*, and PC-14 demonstrates the effect of the amount of H3PO3 used in the end group pyrolysis, ranging from 0.002% by weight to 0.25% by weight (based on the amount of polycarbonate). Clearly, an amount of 0.002% by weight of H3PO3 (PC-13*) is insufficient, whereas an amount of 0.01% by weight of H3PO3 (PC-11) is sufficient in the end group pyrolysis step to achieve the desired technical effects, namely, a reduction in the content of free bisphenol A and phenol end groups, thermal stability of the free COOH end groups A against undesired transesterification, and a color-neutral intrinsic color of the polycarbonate. At an amount of 0.25 wt. % H₃PO₃ (PC-14), the technical effect of reducing the content of free bisphenol A and phenolic end groups and improving the thermal stability of free COOH end groups A against undesired transesterification is still achieved. However, the polycarbonate prepared by the process of the present invention using this amount of H₃PO₃ no longer has a favorable (color-neutral) intrinsic color. Therefore, this H₃PO₃ concentration, while still considered inventive, is no longer considered preferred.

[0313] Furthermore, a comparison of inventive Examples PC-11 and PC-12 with Comparative Example PC-13* demonstrates that the desired technical effects and structural characteristics of the polycarbonate produced can be achieved regardless of the moisture (i.e., water content) of the polycarbonate supplied during the end-group pyrolysis step of the production process, i.e., regardless of whether the polycarbonate after addition of H3PO3 in the form of a dilute aqueous solution is dried prior to end-group pyrolysis. However, a comparison of inventive Examples PC-11 and PC-12 also demonstrates that pre-drying is advantageous with respect to the content of free bisphenol A.

[0314] Preparation of thermoplastic molding compounds containing copolymers from polycarbonate and their structural characterization

[0315] Thermoplastic PC / PMMA molding compounds containing PC-PMMA copolymers were prepared from polycarbonates PC-2* and PC-3 by a reactive extrusion process. To this end, the polycarbonates were first ground into a powder and premixed with a similarly powdered methyl methacrylate-glycidyl methacrylate copolymer (PMMA-GMA) in a ratio of 80% of each polycarbonate and 20% of PMMA-GMA to provide a homogeneous powder mixture. PMMA-GMA is a random methyl methacrylate-glycidyl methacrylate copolymer prepared by free radical polymerization, with a content of structural units derived from glycidyl methacrylate of 1.0% and a weight-average molecular weight of M. w The epoxy equivalent weight of the PMMA-GMA copolymer, determined in accordance with DIN EN 1877-1 (December 2000 edition) in dichloromethane at room temperature, is 0.32% by weight.

[0316] Thermoplastic PC / PMMA molding compounds were prepared from the polycarbonate powder mixture and random PMMA-GMA copolymer in a continuous Process 11 twin-screw extruder (Thermofischer Scientific, Karlsruhe, Germany) at a melt temperature of 260° C., a throughput of approximately 300 g / h, and a rotation speed of 125 min -1 Compounding was performed under conditions of 100 mbar absolute pressure in an extruder with a screw configuration comprising two mixing zones. These conditions resulted in a residence time of approximately 90 seconds. After exiting through the nozzle plate, the melt strand cooled, solidified, and was subsequently pelletized. For compounding, the powder mixture of the PC and PMMA components was metered into the feed zone of the twin-screw extruder via a volumetric metering device.

[0317] The acid number of the thermoplastic molding compound thus produced was determined using the same analytical method as used for the corresponding characterization of the polycarbonate used as raw material in the reactive extrusion. The reduction in the acid number in the reactive extrudate compared to the acid number of the polycarbonate used, weighted by the mass proportion of polycarbonate in the reactive composition, indicates that the COOH groups of the polycarbonate reacted during the melt extrusion process. 1 There was no increase in the intensity of the H NMR signal, so this observation indicated that the COOH groups in the desired nucleophilic addition reaction reacted with the epoxy groups of the glycidyl methacrylate-derived structural units in the methyl methacrylate-glycidyl methacrylate copolymer to form the PC-PMMA copolymer.

[0318] The thermoplastic molding compound thus prepared was again recorded in deuterated chloroform at room temperature. 1 H NMR spectroscopy, where this analysis was used to verify the chemical reaction of the epoxy groups of the glycidyl methacrylate in the random methyl methacrylate-glycidyl methacrylate copolymer to form the PC-PMMA copolymer. The protons of the unopened epoxy rings at 2.64 ppm, 2.86 ppm, and 3.21 ppm were characterized relative to trimethylsilane (TMS) reference. 1 The H-NMR signals are used as the basis, where the intensity is evaluated relative to the singlet signal at 3.6 ppm attributed to the three methyl protons in methyl methacrylate (measured relative to the reference trimethylsilane (TMS)). When the molding compound of the present invention is prepared by reactive compounding, the relative intensities of these three signals decrease compared to the physical mixture of the starting components. 1 The H-NMR spectrum showed a very broad, relatively poorly resolved, multiple signal at 4.45-4.55 ppm, which was attributed to the bonding group formed by the nucleophilic addition of the carboxyl group of component A to the epoxy group of component B. Therefore, the appearance of this new signal indicated that a copolymer containing blocks of components A and B was formed through the chemical reaction of the epoxy group in component B.

[0319] Table 2 summarizes the analytical results measured on the three prepared thermoplastic molding compounds.

[0320] Preparation of molded articles from thermoplastic molding compounds containing copolymers and their technical evaluation

[0321] Using the thermoplastic PC / PMMA molding compound containing the PC-PMMA copolymer prepared as described above (which was prepared from the composition according to Table 2), circular plaques with a diameter of 25 mm and a thickness of 2 mm were produced in a laboratory injection molding machine of the Boy XS type (Dr. Boy GmbH & Co. KG, Neustadt-Fernthal, Germany) at a melt temperature of 280° C. and a mold temperature of 90° C.

[0322] The transparency and original color tone of the molded articles thus produced were first visually assessed. The corresponding wavelength-dependent total transmittance was further determined according to DIN 5033-7 (2014). From this, the transmittance value Ty(D65,10°) and the yellowness index YI(D65,10°) for light type D65 and an observer angle of 10° were calculated according to DIN EN ISO 11664-3 (2013). These values ​​are also shown in Table 2.

[0323] Table 2: Thermoplastic PC / PMMA molding compounds, their structural characteristics, and the properties of molded products made therefrom

[0324]

[0325] Polycarbonates marked with * are not examples of the present invention.

[0326] **Relative intensities are understood to be relative to the 3.22 ppm attributable to the unopened epoxy groups measured with reference to trimethylsilane (TMS). 1 The ratio of the intensity of the H NMR signal to the NMR signal intensity of the singlet signal at 3.6 ppm attributed to the three methyl protons in methyl methacrylate measured relative to trimethylsilane (TMS) reference. The decrease in this relative intensity in the PC / PMMA examples relative to the starting material PMMA indicates the conversion of epoxy groups during reactive extrusion.

[0327] The data in Table 2 demonstrate that the inventive polycarbonate PC-3 achieves a higher percentage conversion of epoxy groups in the PMMA-GMA copolymer in the target reaction to form the block copolymer than the comparative polycarbonate PC-2*. The data further demonstrate that the copolymer-containing PC / PMMA molding compound PC / PMMA-2, prepared from the inventive polycarbonate PC-3, exhibits higher transmittance than the comparative PC / PMMA molding compound PC / PMMA-1*, prepared similarly from the non-inventive polycarbonate PC-2*. The data in Table 2 further demonstrate that PC / PMMA-2 exhibits a lower yellowness index, i.e., improved color neutrality, than PC / PMMA-1*. PC-2* differs from the inventive PC-3 only in that phosphorous acid is not added during the pyrolysis of its end groups.

Claims

1. Polycarbonate containing structural units derived from bisphenol A and A) structural units which are derived from hydroxybenzoic acid and which are present as terminal groups and have free COOH functions, and B) optionally structural units derived from hydroxybenzoic acid, Wherein component B) is selected from at least one of the following representatives B1) structural units which are derived from hydroxybenzoic acid and which are present as terminal groups and have an esterified COOH function, and B2) structural units derived from hydroxybenzoic acid which are bound to the polymer chain via ester groups or anhydride groups, wherein the free bisphenol A content in the polycarbonate is a maximum of 50 ppm, and When component B is contained, the ratio of the molar amount of component B1 to the sum of the molar amounts of components A and B is at most 0.

07.

2. The polycarbonate according to claim 1, which contains component B.

3. The polycarbonate according to any one of the preceding claims, wherein component B2 is present and the ratio of the molar amount of component B2 to the sum of the molar amounts of components A and B2 is from 0.001 to 0.

25.

4. The polycarbonate according to any one of the preceding claims, wherein the ratio of the molar amount of component A to the molar amount of component B is at least 8.

5. The polycarbonate according to any one of the preceding claims, further comprising C) structural units which are derived from at least one phenolic compound which has only one phenolic OH function and contains no carboxyl or carboxyl derivative functions and which are present as terminal groups, Component C is present in the polycarbonate in a molar proportion of 50 to 90 mol %, based on the molar proportions of components A, B1, B2 and C totaling 100 mol %.

6. A process for preparing polycarbonates (II) containing end groups which are derived from at least one hydroxybenzoic acid and have free COOH functional groups, wherein Polycarbonate (I) containing terminal groups derived from at least one hydroxybenzoate In the presence of 0.01 to 0.30% by weight of phosphorous acid H3PO3, based on the amount of polycarbonate (I) When negative pressure is applied for 10 seconds to 15 minutes Withstand temperatures from 240°C to 360°C, Polycarbonate (II) is thus formed. 7 . The method according to claim 6 , wherein the polycarbonate (I) contains a structural unit derived from bisphenol A, and wherein the polycarbonate (II) contains a structural unit derived from bisphenol A.

8. The process according to claim 7, wherein in the preceding step, the polycarbonate (I) is prepared by phosgenation of bisphenol A or a mixture of a plurality of structurally different diols containing bisphenol A in a phase interface process or in an organic solution in the presence of at least one hydroxybenzoic acid ester or a mixture containing at least one hydroxybenzoic acid ester and at least one phenolic compound having only one phenolic OH function and no carboxyl or carboxyl derivative functions as chain terminator or a mixture of chain terminators, And wherein the at least one hydroxybenzoic acid ester is an ester of hydroxybenzoic acid and an alcohol of the general formula (1) wherein R1 to R4 independently of one another represent hydrogen or an alkyl group, an aryl group or an alkylaryl group each having 1 to 10 carbon atoms.

9. The process according to claim 8, wherein directly after the preparation of the polycarbonate (I), in a further process step upstream of the formation of the polycarbonate (II), the solvent used for the preparation of the polycarbonate (I) is removed to a residual content of <0.1% by weight. and wherein the removal of the solvent is carried out by precipitation, optionally separating the precipitated solid from the mother liquor, optionally washing the precipitated solid and drying or alternatively by spray drying, and wherein the polycarbonate (I) is not subjected to temperatures > 200° C. at any time in this upstream work-up process step.

10. The process according to claim 6 , wherein the preparation of polycarbonate (II) from polycarbonate (I) is carried out in a process apparatus selected from single-screw extruders, co-rotating or counter-rotating twin-screw extruders, planetary roll extruders, continuous or discontinuous internal kneaders, film extruders, strand evaporators and foam evaporators.

11. A thermoplastic material comprising a polycarbonate as claimed in any one of claims 1 to 5 and at least one phosphorus compound selected from the group consisting of phosphorous acid, phosphoric acid, phosphites and phosphates and phosphorous acid condensates and phosphoric acid condensates, wherein the phosphorus compounds are contained in the thermoplastic material in an amount of 0.01 to 0.30% by weight.

12. A copolymer comprising a structural unit derived from the polycarbonate according to any one of claims 2 to 5 and a structural unit derived from another polymer containing at least one functional group selected from an ester group, a hydroxyl group and an epoxy group.

13. A thermoplastic molding compound comprising a copolymer according to claim 12 and / or a polycarbonate according to any one of claims 2 to 5 and / or a thermoplastic composition according to claim 11.

14. Use of a polycarbonate according to any one of claims 1 to 5 or a thermoplastic composition according to claim 11 for preparing a copolymer containing at least one polycarbonate block containing structural units derived from bisphenol A and at least one block of a polymer different from this polycarbonate or for preparing a thermoplastic molding compound containing this copolymer in a process comprising the following steps: a) melting a composition comprising a polycarbonate or a thermoplastic material and another polymer having at least one functional group selected from ester groups, hydroxyl groups and epoxy groups by introducing heat and / or mechanical shear, b) mixing the different components of the composition with one another and dispersing them with one another, c) solidifying the melt by cooling, d) optionally granulating the solidified product obtained in steps (a) to (c), In the process, a chemical coupling reaction of the structural units in the polycarbonate (II) which are derived from hydroxybenzoic acid and present as terminal groups and have free COOH functional groups with a polymer having at least one functional group selected from ester groups, hydroxyl groups and epoxy groups occurs in the melt.

15. A shaped article comprising the polycarbonate according to any one of claims 2 to 5 and / or the copolymer according to claim 12.

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