Manufacturing method for polycarbonate beads

Abstract

This invention describes a method for producing polycarbonate beads using a chain extender. Polycarbonate beads have a low bulk density and are suitable for producing molded parts with good surface properties and good mechanical properties.

Description

[Technical Field]

[0001] The present invention relates to a process for manufacturing polycarbonate beads, polycarbonate beads obtained by the process, and molded articles obtained from the polycarbonate beads. [Background technology]

[0002] Particulate foams, and in this specification in particular EPS, EPP, and E-TPU, are becoming increasingly important. Modern technology now makes it possible to manufacture particulate foams of reliable quality and to use these foams to produce parts with advantageous properties. Their lower bulk density compared to "simple" thermoplastics opens up new application areas for foam materials or allows conventional applications to be achieved with significant weight reduction. Therefore, foamed thermoplastics are attractive materials, especially for lightweight applications, provided that the application-specific properties are sufficiently good. Recent mold developments have made it possible to manufacture visible parts made of foamed thermoplastics that are significantly lighter while having a surface appearance that makes them a true substitute for corresponding injection-molded parts. Due to their low material consumption, foam materials are also attractive from a sustainability standpoint, and furthermore, as an additional effect when used as thermal insulation or soundproofing material for noise reduction, they can generally contribute to energy savings due to their good thermal insulation properties.

[0003] There are already existing literature descriptions of polycarbonate particulate foams. Particulate foams made from engineering thermoplastics are of interest in the automotive industry, for example, due to their properties such as high thermal stability and good fire resistance. EPC is a particulate foam for high-temperature applications where conventional polymer foams such as EPP do not function. Patent Document 1 describes a process for producing polycarbonate foam from polycarbonate, in which a transesterification catalyst is added to aromatic polycarbonate in combination with aromatic polycarbonate acid or water, optionally together with aliphatic hydroxycarboxylic acid and / or aliphatic alcohol. This results in controlled partial decomposition of polycarbonate accompanied by the release of CO2, which helps to foam the remaining polycarbonate. The polycarbonate foam described in Patent Document 1 has a density of approximately 0.4 g / cm³. 3 ~0.8g / cm 3 It has a density of .

[0004] Patent Document 2 describes a process for producing foamed particles from aromatic polycarbonate, which involves extruding aromatic polycarbonate, pelletizing it, impregnating it with carbon dioxide as a foaming agent, foaming the particles, and then molding the particles to obtain a foamed molded product.

[0005] Patent Document 3 describes polyester foams and also explicitly considers polycarbonate foams that have good processability in addition to low density. For the production of these particulate foams, a starting polymer material is selected in which the degree of crystallinity, as reflected by the enthalpy of fusion, glass transition temperature, and melting temperature, is within a certain range. The process for producing the particulate foam includes providing the corresponding starting polymer component in a molten state, mixing a foaming agent component and optionally one or more additives into the molten material, extrusion, and pelletizing the foaming agent-containing molten material in water under high pressure of 1 to 20 bar. Patent Document 3 also describes a theoretical option of stabilizing the extrusion operation by increasing the molecular weight, for example, by adding a chain extender, but does not specify the amount. Furthermore, no further requirements are imposed on the polymer used in Patent Document 3. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] German Patent Application Publication No. 4100200 [Patent Document 2] European Patent Application Publication No. 3858906 [Patent Document 3] European Patent Application Publication No. 2603549 [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, the object of the present invention was to provide polycarbonate beads that are improved from the prior art through a continuous process, low-density polycarbonate beads from which molded articles having better mechanical properties can be manufactured. [Means for solving the problem]

[0008] Surprisingly, it has been newly found that molded articles made from polycarbonate particle foams, so-called "polycarbonate beads" having sufficiently good mechanical properties, can only be obtained when a polycarbonate containing a specific amount of OH end groups is reacted with a specific amount of a chain extender. It is only by this method that process control by reactive particle foam extrusion, which is required for good mechanical properties, becomes possible. As a result, the foaming can occur at a high melting temperature T which exceeds the conventional temperature range for foam production by extrusion of thermoplastic plastics using a physical blowing agent for expansion into a low-density foam, where T1=(T g +110 °C) to T2=(T g +170 °C) (T g = glass transition temperature of the aromatic polycarbonate composition), and at the same time it can proceed at high pressure. Those skilled in the art will understand that "particle foam extrusion" according to the prior art is a complete or partial extrusion process involving the addition of a foaming gas and the subsequent formation of foamed particles by pelletization and cooling, and in the case of an amorphous thermoplastic, the melting temperature T g +10 °C to T g +70 °C (T g = glass transition temperature of the polymer material).

[0009] Therefore, the present invention relates to a process for producing polycarbonate beads, particularly a continuous process, preferably in the following order: a) A step of providing an aromatic polycarbonate composition, wherein the aromatic polycarbonate has a content of OH end groups of at least 350 ppm as measured by 1 1H NMR spectroscopy using dichloromethane as a solvent at room temperature, based on the total weight of the aromatic polycarbonate; b) A step of mixing the aromatic polycarbonate composition with a chain extender suitable for OH groups in a molar ratio such that 0.64 mol to 1.10 mol of reactive groups of the chain extender are used per mole of OH end groups of the polycarbonate; c) A step of providing the mixture in a plasticized state; d) A step of mixing a physical blowing agent into the melt; e) the plasticized mixture, T1=(T g +110℃)~T2=(T g A process of foaming and extruding particles at a temperature T of a plasticizing mixture (+170℃), T g The process involves the glass transition temperature of the aromatic polycarbonate composition, f) A process of pelletizing the foaming agent-containing molten material, It provides a process that includes this.

[0010] The final pelletizing process yields expanded polycarbonate beads.

[0011] The OH-terminal group content was determined by evaluating the ratio of the integral signals at 6.68 ppm (two aromatic protons in the ortho position relative to the phenol OH group) and 1.68 ppm (six methyl protons of the bisphenol A unit), using dichloromethane as the solvent at room temperature. 1 It is measured by 1H NMR spectroscopy.

[0012] The glass transition temperature is determined according to DIN EN ISO 11357-1:2017.

[0013] "Providing the mixture in a plasticized state" means that the mixture is in the form of a polymer molten material.

[0014] Unless explicitly stated otherwise, all amounts expressed in ppm in this invention should be considered as weight ratios.

[0015] Regarding the production of particulate foam, there is a minimum value for the amount of OH-terminal groups and the concentration of the chain extender, and T1 = (T g +110℃)~T2=(T g (+170℃), preferably T1=(T g (T)~T2=(T g (+160℃), more preferably T1=(T g +130℃)~T2=(T gThere is also a maximum concentration for foaming extrusion at a high melting temperature T in the range of +150℃, and in this way, polycarbonate particle foam with good mechanical properties can be obtained in a bulk density range of 150g / L to 250g / L determined according to DIN EN ISO 60:2000-01. Here, "according to" means that the density of the material was determined by filling a 1L beaker and weighing its contents, rather than using a standardized aluminum container of known volume.

[0016] The number of OH groups in aromatic polycarbonate significantly affects whether the resulting molded article can produce beads with good mechanical properties at low density. Too many OH groups in the polycarbonate leads to excessively high reactivity, ultimately resulting in rearrangement reactions of the polycarbonate chains, a decrease in molecular weight due to excessively rapid branching and a corresponding excessively rapid increase in viscosity (excessively high shear input), and yellowing. On the other hand, too few OH groups in the polycarbonate result in insufficient or no reaction with the chain extender. However, this also means that a good particulate foam with sufficient mechanical properties cannot be obtained. Instead, the particulate foam will have many broken and collapsed cells.

[0017] According to the present invention, the OH-terminal group content of the aromatic polycarbonate used in the process is at least 350 ppm, preferably 350 ppm to 600 ppm, more preferably 380 ppm to 580 ppm, more preferably 400 ppm to 550 ppm, and most preferably 450 ppm to 550 ppm, based on the total weight of the aromatic polycarbonate used. The reference values ​​here refer to pure aromatic polycarbonate and not aromatic polycarbonate-based compositions. To achieve such terminal group content, preferably more than 70% by weight of SPC is used based on the total weight of the aromatic polycarbonate used, more preferably at least 80% by weight of SPC is used based on the total weight of the aromatic polycarbonate used, and most preferably only SPC is used as the aromatic polycarbonate for the production of polycarbonate beads.

[0018] The concentration of the chain extender is also important. Too much chain extender leads to an unworkable material due to excessively high viscosity resulting from an excessive increase in the molecular weight of the polycarbonate. Too little chain extender does not result in a significant increase in molecular weight, and therefore, not a sufficient increase in pressure (the viscosity of PC with no / insufficient chain extender at 300°C is too low), ultimately resulting in inferior mechanical properties, given that the reaction between the chain extender and polycarbonate is a function of time and temperature. For example, in the case of bisphenol A homopolycarbonate, the foaming extrusion process is T 1ハウジング =T g +100℃~T 2ハウジング =T g Housing temperature T of +150℃ ハウジング , and about T after the foaming agent has been mixed and dissolved g It is preferable to carry out the process at a melting temperature T of +(110℃~170℃). Production of particulate foam without cooling results in dense, collapsed particles. Depending on the process control, cooling will cause stabilization and solidification of the foam structure, leading to a rapid cessation of foam expansion. Higher temperatures in the process allow for the utilization of the full foaming potential of the formulation under cooling by compensating for excessively rapid cooling / solidification. However, at these temperature profiles, the pressure on the die plate is 80-90 bar without chain extender (despite the melting pump). The use of a chain extender increases the pressure on the die plate to 140-180 bar, preferably 150-160 bar. Production of particulate foam is impossible under these process conditions (temperature) without proper chain extension and therefore without an additional increase in viscosity.

[0019] In order for the resulting polycarbonate beads to have good properties, it has been found that the molar ratio of the chain extender's reactive groups to 1 mole of polycarbonate OH-terminated groups is 0.64 mol to 1.10 mol, preferably 0.71 mol to 1.0 mol, more preferably 0.96 mol, even more preferably 0.8 mol to 0.9 mol, and especially 0.82 mol to 0.90 mol (in continuous processes, metered addition based on processing volume) is essential for the present invention.

[0020] Preferably, the content of OH-terminated groups in the aromatic polycarbonate is such that when dichloromethane is used as the solvent at room temperature. 1 If the concentration is measured by 1H NMR spectroscopy between 400 ppm and 550 ppm, then 0.71 mol to 0.96 mol of reactive chain extender groups are used per mole of OH-terminal groups of polycarbonate.

[0021] The use of chain extenders increases the molar mass of polycarbonate to a range of 40,000 g / mol to 230,000 g / mol, preferably 100,000 g / mol, which is associated with an additional increase of approximately 60 to 100 bar of pressure on the die plate at the temperature in which the polycarbonate is in a plasticized state.

[0022] In a particularly preferred embodiment of the present invention, the process is carried out continuously, preferably in the following order: a) A step of providing an aromatic polycarbonate composition, wherein the aromatic polycarbonate is used with respect to the total weight of the aromatic polycarbonate, using dichloromethane as the solvent at room temperature. 1 The process involves measuring the content of OH-terminal groups by 1H NMR spectroscopy, which is at least 350 ppm, preferably 400 ppm to 550 ppm. b) A step of mixing an aromatic polycarbonate composition with a chain extender suitable for OH groups in an amount (based on the processing amount) such that 0.64 mol to 1.10 mol, preferably 0.71 mol to 1.0 mol, more preferably 0.96 mol, even more preferably 0.8 mol to 0.9 mol, and especially 0.82 mol to 0.90 mol of the reactive groups of the chain extender per 1 mol of OH-terminated groups of polycarbonate is used, wherein the chain extender used is an epoxy-functionalized chain extender, preferably a styrene-acrylic polymer having epoxy-reactive groups, and especially having an epoxy equivalent weight (EEW) of 285 g / mol to 485 g / mol as determined according to DIN EN 1877-1:2000, c) A step of providing the mixture in a plasticized state, d) A step of mixing a physical blowing agent into a polymer molten material at a concentration of 0.1% to 2.3% by weight, wherein the physical blowing agent is nitrogen, carbon dioxide, or a mixture thereof, preferably carbon dioxide. e) the plasticized mixture, T1=(T g +110℃)~T2=(T g (+170℃), preferably T1=(T g (T)~T2=(T g A process of foaming and extruding particles at a melting temperature T of +160℃, g The process involves the glass transition temperature of the aromatic polycarbonate composition, f) A step of pelletizing the foaming agent-containing molten material, preferably in the form of pelletization in unpressurized water, Includes.

[0023] Each step of the process of the present invention can be carried out using tools and machines available in plastics technology known to those skilled in the art. Optionally, the individual steps can also be combined.

[0024] The process for producing polycarbonate beads can be carried out continuously or in batches. The polymer molten material can be taken directly from the polymerization reactor as newly polymerized material, for example, or directly from there to a mixed extruder where chain extenders, blowing agents, and optionally additives are finally introduced at various points. The process of the present invention is preferably carried out as a continuous process because there is a risk of polycarbonate crystallization in batch process control.

[0025] It will be clear that the molar ratio of the OH-terminated groups of the polycarbonate to the reactive groups of the chain extender, as defined in the claims, needs to be adjusted according to process control. In continuous procedures, the adjustment based on the processing rate of the concentration (mol / h:mol / h ratio) is appropriately performed.

[0026] The process of the present invention may be a one-stage or even two-stage extrusion process, in which the molecular weight of the polymer is increased in the presence of a chain extender, and polycarbonate pellets are obtained as the first product; then, in the second extrusion stage, foaming is performed with a physical blowing agent, preferably carbon dioxide, and as a result of subsequent pelletization in water, the polycarbonate beads of the present invention are finally obtained. In this case, pelletization can be performed at the end of the first extrusion stage. For this purpose, the molten material is extruded through a molding tool at the outlet opening of the extruder and then cut to a certain length. Cutting to a certain length is achieved by a cutting device, which is typically located immediately downstream of the molding tool through which the material is extruded. The cutting device may be in contact with the molding tool or may be located at a certain distance from the molding tool. Furthermore, the subsequent injection of the blowing agent in the same extruder may be performed only after a certain residence time of the polycarbonate-chain extender mixture, or simultaneously with the supply of the chain extender.

[0027] The process of the present invention enables the production of polycarbonate beads, which are particulate foams. The use of particulate foamed polycarbonate combines the lightweight and impact-resistant properties of the material with a higher continuous operating temperature (e.g., stability in cationic electrodeposition coating processes) compared to PP, ABS, PE, or PA6, thereby significantly reducing the weight of some vehicle components and lowering fuel consumption and CO2 emissions, while maintaining mechanical properties even at higher temperatures. Furthermore, the availability of foamed polycarbonate is expected to open up a wider range of application fields, particularly those requiring thermal insulation at high temperatures. [Effects of the Invention]

[0028] Accordingly, the present invention also provides polycarbonate beads produced by the process of the present invention. According to the present invention, “beads” typically means foamed pellets (=particle foams) having a maximum density of 50% or less of the unfoamed starting material (aromatic polycarbonate composition). The polycarbonate beads obtained by the process of the present invention preferably have an average molecular mass (measured here as absolute molar mass) of aromatic polycarbonate of at least 140 kDa (highly branched), more preferably at least 150 kDa, as determined by GPC MALLS measurement (multi-angle laser light scattering) according to DIN EN ISO 16014-5:2019-09. At the same time, the molar mass and even molecular dimensions of the molecules are determined, from which conclusions regarding the degree of branching of the material can be drawn. This is because branching affects the GPC separation mechanism, which is evident from the rising molar mass curve. A linear starting material is compared as a reference for comparison with the foamed sample. The greater the branching of the sample (the smaller the hydrodynamic volume for the same molar mass), the greater the curve deviates from the ideal line for unbranched polycarbonate. Polycarbonate materials with the corresponding minimum branching can be efficiently foamed, thus leading to polycarbonate beads with good form, from which molded articles with good mechanical properties can be manufactured.

[0029] The foamed polycarbonate particles, or "polycarbonate beads," produced by the process of the present invention have the following properties: A bulk density of 150 g / L to 250 g / L, preferably 180 g / L to 200 g / L, determined by the process via bulk density based on DIN EN ISO 60:1999, depending on continuous process control. Here, "based on" means that the density of the material was determined by filling a 1 L beaker and weighing its contents, rather than using a standardized aluminum container of known volume; Nominal diameter in the range of 2mm to 7mm, preferably 2.5mm to 5mm, more preferably 3mm ± 0.2mm (depending on the process); the exact size distribution is preferably determined using a Camsizer; Thermal properties of polycarbonate (T at 145°C to 150°C) g ) and mechanical properties, for example, 200 kg / m 3 With a component density of at least 70 MPa flexural modulus and 2.5 MPa flexural strength (ISO 6603-2:2000); 59 MPa compressive modulus and 1.73 MPa compressive strength (at 10% compression) (ISO 844-11:2014); at least 1.97 MPa tensile strength and 8% to 14% elongation at break (ISO 1926:2009); The average equivalent circle diameter of the cells for circles of equal projected area, as determined by SEM (ASTM E1508-12a:2019), is 150 μm or less, preferably 100 μm or less, and more preferably 80 μm or less.

[0030] Bead size is process-dependent and can be influenced by factors including the selected nozzle size, processing rate, blade speed, and the composition of the foaming agent-containing molten material. An exemplary process control using a 1.2 mm nozzle size yields beads with nominal diameters ranging from 1.8 mm to 3 mm. The maximum frequency distribution is 2.5 mm, with a distribution width of 28% on average. A 2.2 mm nozzle yields a particle size distribution with an average diameter of 5 mm and a distribution width of 40% on average.

[0031] Polycarbonate beads can be welded over a wide range of water vapor pressures, preferably 7 to 11 bar, more preferably 8 to 10 bar. Polycarbonate beads have a high molecular weight M, ranging from 40,000 g / mol to 230,000 g / mol, as can be determined by GPC, as described in the examples. w It has.

[0032] Polycarbonate beads offer good mechanical properties, low thermal conductivity ranging from 45 mW / (m·K) to 47 mW / (m·K) at 10°C (DIN EN 12667:2001), and a load capacity of 200 ± 10 kg / m³. 3 This shows the component density.

[0033] The beads have intact ("closed-cell") or at least predominantly intact cells, and thus, molded foam articles having a very uniform and flat surface and homogeneous weld of the beads can be produced from polycarbonate beads. Here, "premium" preferably means more than 85%, more preferably more than 90%, of the cells in the beads are intact, i.e., each individual cell structure in these beads shares a wall with at least three other structural elements (cells), and there are no more than two broken cell walls per single cell.

[0034] The starting material for producing the beads of the present invention in the process of the present invention is an aromatic polycarbonate composition.

[0035] In the context of this invention, the term "polycarbonate" is considered to mean both aromatic homopolycarbonates and aromatic copolycarbonates. These polycarbonates may be linear or branched, as is known.

[0036] The polycarbonates present in the composition are produced by known methods from dihydroxyaryl compounds, carbonate derivatives, and optionally chain arresters and branching agents.

[0037] Details of the preparation of polycarbonate have been described in numerous patent specifications over the past 40 years. For example, Schnell, "Chemistry and Physics of Polycarbonates", Polymer Reviews, Volume 9, Interscience Publishers, New York, London, Sydney 1964, D. Freitag, U. Grigo, PR Mueller, H. Nouvertne, BAYER AG, "Polycarbonates" in Encyclopedia of Polymer Science and Engineering, Volume 11, Second Edition, 1988, pages 648-718, and finally U. Grigo, K. Kirchner and PR Mueller "Polycarbonate" [Polycarbonates] in Becker / Braun, Kunststoff-Handbuch [Plastics Handbook], volume 3 / 1, Polycarbonate, Polyacetale, Polyester, Celluloseester [Polycarbonates, Polyacetals, Polyesters, Cellulose Esters], Carl Hanser Verlag Munich, Vienna 1992, pages 117 to 299.

[0038] Aromatic polycarbonates are prepared, for example, by an interfacial process reaction between a dihydroxyaryl compound and a carbonyl halogen, preferably phosgene, and / or an aromatic dihalogenated dicarbonyl, preferably a dihalogenated benzenedicarbonyl, optionally using a chain arresting agent and optionally a trifunctional or higher branching agent. Similarly, they can also be prepared by reacting a dihydroxyaryl compound with, for example, diphenyl carbonate via melt polymerization. According to the present invention, it is preferable to use polycarbonates prepared by melt polymerization, the so-called "transesterification method." The polycarbonates used according to the present invention have 350 ppm to 600 ppm of OH-terminated groups, and this value refers to the polycarbonate as the polymer itself without additives. The amount of OH-terminated groups is based on the total amount of polycarbonate used. It is also possible to use a mixture of polycarbonates obtained by melt polymerization and polycarbonates obtained by the interfacial method, provided that the total concentration of OH-terminated groups in the polycarbonates used is within the specified range. However, it is particularly preferable to use only polycarbonates prepared by melt polymerization.

[0039] Dihydroxyaryl compounds suitable for the production of polycarbonates include, for example, hydroquinone, resorcinol, dihydroxydiphenyl, bis(hydroxyphenyl)alkane, bis(hydroxyphenyl)cycloalkane, bis(hydroxyphenyl)sulfide, bis(hydroxyphenyl)ether, bis(hydroxyphenyl)ketone, bis(hydroxyphenyl)sulfone, bis(hydroxyphenyl)sulfoxide, α,α'-bis(hydroxyphenyl)diisopropylbenzene, phthaliumidines derived from isatin or phenolphthalein derivatives, and their cyclic alkylated, cyclic arylated, and cyclic halogenated compounds.

[0040] Preferred dihydroxyaryl compounds include 4,4'-dihydroxydiphenyl, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 1,1-bis(4-hydroxyphenyl)-p-diisopropylbenzene, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, dimethylbisphenol A, bis(3,5-dimethyl-4-hydroxyphenyl)methane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, bis(3,5-dimethyl-4-hydroxyphenyl)sulfone, 2,4-bis(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene, and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, as well as bisphenol(I)~(III): [ka] (In the formula, R' represents C1-C4 alkyl, aralkyl, or aryl, preferably methyl or phenyl, most preferably methyl, in each case.)

[0041] Particularly preferred bisphenols are 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 4,4'-dihydroxydiphenyl, and dimethylbisphenol A, as well as bisphenols of formulas (I), (II), and (III).

[0042] These and other suitable dihydroxyaryl compounds are, for example, U.S. Patent Nos. 3028635, 2999825, 3148172, 2991273, 3271367, 4982014, and 2999846, German Patent Publication Nos. 1570703, 2063050, 2036052, 2211956, and 3832396, French Patent Publication No. 1561518, and the research paper "H. Schnell, Chemistry and Physics of Polycarbonates, Interscience Publishers, New York" It is described in 1964, and in Japanese Patent Publication Nos. Sho 61 (1986)-62039, Sho 61 (1986)-62040, and Sho 61 (1986)-105550.

[0043] In the case of homopolycarbonates, only one type of dihydroxyaryl compound is used, while in the case of copolicarbonates, two or more types of dihydroxyaryl compounds are used.

[0044] Examples of suitable carbonate derivatives include phosgene or diphenyl carbonate.

[0045] Suitable chain-stopping agents that can be used in the production of polycarbonates include monophenols. Examples of suitable monophenols include phenol itself, alkylphenols such as cresol, p-tert-butylphenol, isooctylphenol, cumylphenol, and mixtures thereof.

[0046] Preferred chain arrestors are linear or branched chains C1-C1 30 -A phenol monosubstituted or polysubstituted with an alkyl radical, preferably unsubstituted or tert-butyl substituted. Particularly preferred chain arresters are phenol, cumylphenol, and / or p-tert-butylphenol.

[0047] The amount of chain arrestor used is preferably 0.1 mol% to 5 mol%, based on the moles of the dihydroxyaryl compound used in each case. The chain arrestor can be added before, during, or after the reaction with the carbonic acid derivative.

[0048] Suitable branching agents are compounds with three or more functionalities known in polycarbonate chemistry, particularly those having three or more phenol OH groups.

[0049] Examples of suitable branching agents include 1,3,5-tri(4-hydroxyphenyl)benzene, 1,1,1-tri(4-hydroxyphenyl)ethane, tri(4-hydroxyphenyl)phenylmethane, 2,4-bis(4-hydroxyphenylisopropyl)phenol, 2,6-bis(2-hydroxy-5'-methylbenzyl)-4-methylphenol, 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)propane, tetra(4-hydroxyphenyl)methane, tetra(4-(4-hydroxyphenylisopropyl)phenoxy)methane, and 1,4-bis((4',4''-dihydroxytriphenyl)methyl)benzene, and 3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.

[0050] The amount of branching agent used is preferably 0.05 mol% to 2.00 mol%, based on the moles of the dihydroxyaryl compound used in each case.

[0051] The branching agent can be added either by forming an initial input in the aqueous alkaline phase with the dihydroxyaryl compound and the chain termination agent, or by dissolving it in an organic solvent before phosgenation. In the transesterification process, the branching agent is used together with the dihydroxyaryl compound.

[0052] Particularly preferred polycarbonates include homopolycarbonates based on bisphenol A, copolycarbonates based on 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and 4,4'-dihydroxydiphenyl, and copolycarbonates based on two monomers, bisphenol A and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, as well as formulas (I), (II), and (III): [ka] The polycarbonate is a homopolycarbonate or copolicarbonate derived from a dihydroxyaryl compound of a C1-C4 alkyl, aralkyl, or aryl group, preferably methyl or phenyl, and especially preferably methyl, and particularly from bisphenol A. Most preferably, the polycarbonate composition comprises a bisphenol A-based polycarbonate, and the polycarbonate in the polycarbonate composition is very preferably a bisphenol A-based homopolycarbonate.

[0053] General formula (1a): [ka] (In the formula, R 5 This is hydrogen or C1-C4 alkyl, C1-C3 alkoxy, preferably hydrogen; methoxy or methyl. R 6 , R 7 , R 8 , and R 9 These are, independently, C1-C4 alkyl or C6-C 12 -aryl, preferably methyl or phenyl, Y consists of single bonds, -SO2-, -S-, -CO-, -O-, C1~C6-alkylene, C2~C5-alkylidene, and C6~C 12-Arylene (which may optionally be condensed to a further aromatic ring containing a heteroatom) or a C5-C6-cycloalkylidene radical which may be monosubstituted or polysubstituted with a C1-C4-alkyl group, preferably a single bond, -O-, isopropylidene, or a C5-C6-cycloalkylidene radical which may be monosubstituted or polysubstituted with a C1-C4-alkyl group. V is oxygen, C2-C6-alkylene, or C3-C6-alkylidene, preferably oxygen or C3-alkylene. p, q, and r are each independently either 0 or 1. When q=0, W is a single bond; when q=1 and r=0, W is oxygen, C2-C6 alkylene, or C3-C6 alkylidene, preferably oxygen or C3 alkylene. When q=1 and r=1, W and V are independently C2-C6-alkylene or C3-C6-alkylidene, preferably C3-alkylene. Z is a C1-C6 alkylene, preferably a C2 alkylene. o is the average number of repeating units, preferably 10 to 100, between 10 and 500. Copolycarbonates produced using diphenols (where m is the average number of repeating units, preferably 1 to 6, and more preferably 1.5 to 5) are also preferred. It is equally possible to use diphenols in which two or more siloxane blocks of general formula (1a) are bonded to each other via terephthalic acid and / or isophthalic acid to form ester groups.

[0054] Equations (2) and (3): [ka] (In the formula, R1 is hydrogen, C1-C4 alkyl, preferably hydrogen or methyl, particularly preferably hydrogen.) R2 is independently an aryl or alkyl, preferably methyl. X is a single bond, -SO2-, -CO-, -O-, -S-, C1~C6 alkylene, C2~C5 alkylidene, or C6~C12 It is an arylene, which may optionally be condensed with a further aromatic ring containing a heteroatom. X is preferably a single bond, C1-C5 alkylene, C2-C5 alkylidene, C5-C 12 Cycloalkylidenes, -O-, -SO-, -CO-, -S-, -SO2-, more preferably X is a single bond, isopropylidene, C5~C 12 Cycloalkylidene or oxygen, very preferably isopropylidene, n is an average number between 10 and 400, preferably between 10 and 100, and particularly preferably between 15 and 50. (where m is an average number of 1 to 10, preferably 1 to 6, and most preferably 1.5 to 5) (poly)siloxanes are particularly preferred.

[0055] The siloxane block also preferably has the following structure: [ka] (Here, a in formulas (IV), (V), and (VI) may be derived from the average number of 10 to 400, preferably 10 to 100, and particularly preferably 15 to 50.)

[0056] It is equally preferable that at least two identical or different siloxane blocks of general formula (IV), general formula (V), or general formula (VI) are bonded to each other via terephthalic acid and / or isophthalic acid to form an ester group.

[0057] In equation (1a), p=0, V is C3-alkylene, r=1, Z is C2-alkylene, R 8 and R 9 is methyl, q=1, W is C3-alkylene, m=1, R 5 is hydrogen or C1-C4 alkyl, preferably hydrogen or methyl, R 6 and R 7 It is equally preferable when each of them is independently a C1-C4 alkyl group, preferably a methyl group, and o is 10-500.

[0058] Copolycarbonates having monomer units of formula (1a), and especially the manufacture thereof, are also described in International Publication No. 2015 / 052106.

[0059] Copolycarbonates having monomer units of formula (IV), and especially the manufacture thereof, are also described in International Publication No. 2015 / 052106.

[0060] The aromatic polycarbonate used in the process of the present invention may be polycarbonate, or a mixture of two or more aromatic polycarbonates, provided that the total content of OH-terminated groups in the polycarbonate used is within the scope of the present invention. It is also possible to use recycled polycarbonate that has been used by consumers or industrially. Suitable recycled materials can be supplied to the extruder in the form of pellets or pulverized material. It is also possible to use recycled materials only as part of the aromatic polycarbonate.

[0061] In principle, one or more additives can be directly added to aromatic polycarbonate, or in practice, to the polycarbonate used as the starting material in the process of the present invention. However, one or more additives can also be supplied to the aromatic polycarbonate in an extruder, preferably together with a chain extender, only during the execution of the process of the present invention. If only one extrusion stage is used, incorporation via a side extruder is not possible in the process of the present invention because the foaming agent is present in the molten material and therefore escapes through the side feed. However, if an airtight side feed is available, the introduction of additives in this manner would be possible. Additives can also be introduced by powder premix or as a masterbatch. Liquid additives can be injected at any point in the process, preferably in the area of ​​a static or dynamic mixing unit, as long as sufficient homogenization is still possible. Additives can also be added in the first stage, followed by the addition of the foaming agent in the second stage. In this case, it is also possible to add the additives via a side extruder.

[0062] A mixture of aromatic polycarbonate as a starting material, an optional blending partner, and an optional additive is referred to as an "aromatic polycarbonate composition." Therefore, the use of an "aromatic polycarbonate composition" in process step a should be understood to mean not only the use of pure polymer but also the use of aromatic polycarbonate with additives. When an additive-containing polycarbonate composition is used, the composition contains, based on the total weight of the polycarbonate composition, preferably at least 70% by weight, more preferably at least 80% by weight, even more preferably at least 90% by weight, more preferably at least 95% by weight, and most preferably up to 98% by weight of aromatic polycarbonate. It is highly preferable that, apart from conventional additives to polycarbonate, the "aromatic polycarbonate composition" does not contain blending partners for polycarbonate, and that only aromatic polycarbonate is used in the process of producing polycarbonate beads of the present invention.

[0063] Further additives conventionally added to polycarbonates include, in particular, heat stabilizers, flame retardants, antioxidants, mold release agents, drip inhibitors, e.g., polytetrafluoroethylene (Teflon®) or SAN-encapsulated PTFE (e.g., Blendex 449), UV absorbers, IR absorbers, impact resistance modifiers, antistatic agents, fluorescent whitening agents, fillers such as talc and quartz, light scattering agents, transesterification inhibitors, compatibilizers, nucleating agents, colorants, pigments, e.g., titanium dioxide, carbon black, chemical blowing agents, and / or laser marking additives, in amounts conventionally used for polycarbonate compositions. Such additives are described, for example, in European Patent Application Publication No. 0839623, International Publication No. 96 / 15102, European Patent Application Publication No. 0500496, or "Plastics Additives Handbook", Hans Zweifel, 5th Edition 2000, Hanser Verlag, Munich. These additives may be added individually or in mixtures. It will be understood that such additives may be added only in such amounts, provided that they do not have a significant adverse effect on the production of beads by the process of the present invention.

[0064] The additives are preferably selected from the group consisting of heat stabilizers, flame retardants, antioxidants, mold release agents, colorants, pigments, drip inhibitors, UV absorbers, IR absorbers, nucleating agents, impact resistance modifiers, antistatic agents, fluorescent whitening agents, light scattering agents, transesterification inhibitors, compatibilizers, and / or additives for laser marking.

[0065] The aromatic polycarbonate composition is preferably determined according to ISO 1133:2012-3 (test temperature 300°C, mass 1.2 kg), with a maximum length of 14 cm. 3 (10 minutes), more preferably up to 12 cm 3 (10 minutes), more preferably 5 cm 3 / (10 minutes)~9cm 3 (10 minutes), most preferably 5.5 cm 3 / (10 minutes)~6.5cm 3It has a melt volume flow rate MVR of / (10 min).

[0066] As part of the process of the present invention, a sufficient amount of chain extender is added to the aromatic polycarbonate to be used such that the molar ratio of the OH-terminated groups of the polycarbonate to the reactive groups of the chain extender is 1:0.64 to 1.1, preferably 1:0.71 to 1.0, more preferably 1:0.96, even more preferably 1:0.8 to 0.9, and particularly 1:0.82 to 0.90. Here, the molar amount is preferably adjusted based on the processing rate per hour. This increases the molecular weight of the polymer, and the molecular weight of the aromatic polycarbonate increases due to the formation of long-chain branching.

[0067] Suitable chain extenders are, in principle, functionalized polymers based on amines, carboxyl compounds, maleic anhydride-modified compounds, epoxy-functionalized compounds, oxazolines, carbodiimides, and / or, for example, acrylates and / or styrene, having the corresponding functional groups. Such compounds can be used alone or in mixtures. Such groups are, for example, amine functional groups in amines, carboxyl functional groups in carboxyl compounds, anhydride functional groups in maleic anhydride-modified compounds, epoxy functional groups in epoxy-functionalized compounds, or other functional groups that can react with the OH-terminal groups of polycarbonates to increase chain length. Preferred chain extenders are particularly epoxy-functionalized compounds, most preferably epoxy-functionalized styrene-acrylic polymers, which are supplied from BASF SE, for example, as Joncryl additives, e.g., Joncryl ADR 4368, ADR 4400, ADR 4468. The amount / weight of the chain extender must be adapted to the aromatic polycarbonate so that 0.64 mol to 1.10 mol, preferably 0.71 mol to 1.0 mol, more preferably 0.96 mol, even more preferably 0.8 mol to 0.9 mol, and especially 0.82 mol to 0.90 mol of reactive groups of the chain extender per 1 mol of OH-terminated groups of the polycarbonate can be used. For example, starting with an aromatic polycarbonate having 350 ppm to 600 ppm of OH-terminated groups, the amount of the chain extender can be obtained by reacting it with a chain extender having an epoxy equivalent of 310 g / mol, such as Joncryl ADR 4468, at a concentration of 0.4 wt% to 1.2 wt%, preferably 0.5 wt% to 1.0 wt%, more preferably 0.7 wt% to 0.9 wt%, and the resulting overall composition (an aromatic polycarbonate-based composition, i.e., one containing the chain extender in addition to any blending partners and any additives) is based on this range of reactive group ratios. By controlling and establishing a molar ratio of 1 mol:0.64 mol to 1.10 mol, a molecular weight range of 40,000 g / mol to 230,000 g / mol, preferably 50,000 g / mol to 150,000 g / mol, and more preferably 75,000 g / mol to 100,000 g / mol, as determined as described, can be achieved.The wide processing range enables the manufacture of parts from particles with molecular weights ranging from 40,000 g / mol to 230,000 g / mol, each possessing different properties.

[0068] The following configurations can be used, but are not limited to, for carrying out reactive particle foam extrusion: a) Polymerization reactor / (static) extruder / mixer / gas metering system / melting pump / pelletization b) Extruders (twin-screw / single-screw) / Gas metering systems / Pelletizers c) Extruders (twin-screw / single-screw) / Gas metering systems / Static mixers / Pelletizers d) Extruders (twin-screw / single-screw) / Gas metering systems / Heat exchangers / Pelletizers e) Extruders (twin-screw / single-screw) / Gas metering systems / Static mixers / Heat exchangers / Pelletizers f) Twin-screw extruders / Gas metering systems / Single-screw extruders / Pelletizers g) Twin-screw extruders / Gas metering systems / Heat exchangers / Pelletizers h) Twin-screw extruders / Gas metering systems / Single-screw extruders / Melt pumps / Pelletizers i) Twin-screw extruders / gas metering systems / heat exchangers / melting pumps / pelletizers.

[0069] The extrusion process can be carried out in one or two stages.

[0070] In detail, the process can be carried out in various configurations. Key steps in the process include melting the aromatic polycarbonate composition, optionally adding a nucleating agent (talc, especially nanoscale talc, graphite, carbon black, pigment, etc.), injecting a blowing agent via a liquid injection system (e.g., Lewa GmbH (Germany)) or a compression unit (high-pressure unit) (e.g., Maximator GmbH (Germany)), optionally increasing the pressure to the die plate via technical aids such as cooling, addition of reactive macromonomers, or a breaker plate or melting pump (pressure is preferably increased by the addition of reactive macromonomers or the use of technical aids), and finally, chopping pellets / beads via pelletizing in a liquid medium, hot chopping, or pelletizing in a gas (gas mixtures can also be used). Note that the liquid medium used here may be an aqueous medium, or alternative media such as glycerin or glycerol.

[0071] The process of the present invention is particularly preferably carried out using a tandem configuration consisting of a twin-screw and a single-screw. In this case, the twin-screw is more preferably used for plasticizing the aromatic polycarbonate composition and mixing the physical blowing agent and chain extender, and the single-screw is then used for controlling the melting temperature. The molecular weight is already increased in the twin-screw / first extruder, and this continues to the nozzle exit (end of the extrusion system).

[0072] The metering and addition of the physicoblasting agent to the molten material, which contains aromatic polycarbonate and chain extender reacting throughout the entire process, is more preferably carried out in the last third of the first extrusion unit (depending on the structure). Mixing is preferably carried out so that the polymer molten material ultimately contains the physicoblasting agent in a uniform distribution, where the proportion of the physicoblasting agent in the mixture is preferably 1.0% to 2.3% by weight, more preferably 1.2% to 1.7% by weight, more preferably 1.3% to 1.5% by weight, based on the total weight of the polymer molten material (= polycarbonate composition) and chain extender, and for N2, it is preferably 0.1% to 0.5% by weight, more preferably 0.1% to 0.3% by weight, more preferably 0.15% to 0.25% by weight, and most preferably 0.15% to 0.2% by weight. It should be noted that the process of the present invention does not require step d to follow step b. Similarly, the mixing of the physical foaming agent into the molten material can be started simultaneously with, or overlapping in time with, the metering and addition of the chain extender.

[0073] To initiate foam cell formation for a finer and more homogeneous cell morphology, nucleating agents such as talc, particularly nanoscale talc, graphite, carbon black, and pigments are added at a low concentration of 0.1% to 1.0% by weight, more preferably 0.15% to 0.5% by weight, and more preferably 0.2% to 0.3% by weight, based on the overall composition obtained with the polycarbonate-based composition and chain extender.

[0074] In principle, any blowing agent commonly used for foaming thermoplastics can be used as a physical blowing agent. Examples here include propane, butane, n-pentane, and isopentane, but also include similar aliphatic hydrocarbons, aromatic hydrocarbons, alicyclic hydrocarbons, aliphatic alcohols, carbon dioxide, nitrogen, air, inert gases such as argon or helium, and others. Combinations of two or more of these blowing agents can also be used as physical blowing agents. Carbon dioxide, one or more inert gases, nitrogen, air, or mixtures thereof are preferred as physical blowing agents because they pose no toxicological or environmental concerns and do not promote fire. Nitrogen, carbon dioxide, or mixtures thereof are particularly preferred, with carbon dioxide being the most preferred.

[0075] When nitrogen is used as a physical blowing agent, the amount of nitrogen used is preferably 0.1% to 0.5% by weight, more preferably 0.1% to 0.3% by weight, more preferably 0.15% to 0.25% by weight, and most preferably 0.15% to 0.2% by weight, based on the polymer molten material containing the chain extender and additives (i.e., the chain extender in addition to the polycarbonate composition).

[0076] When carbon dioxide is used as a physical blowing agent, preferably 1.0% to 2.3% by weight, more preferably 1.2% to 1.7% by weight, and more preferably 1.3% to 1.5% by weight of carbon dioxide is used based on the polymer molten material containing the chain extender and additives.

[0077] In the manufacturing process, using the example of tandem plant configuration h), various physical blowing agents can be introduced into the polymer molten material at various points in time, for example, by liquid metering or high-pressure metering. The physical blowing gas is preferably added to the first extruder, but for best homogenization, it is preferable to add it to the last third of the extruder. Particles can also be obtained by metering and adding at the end of the tandem plant, but the operation will be more unstable and the resulting particles will be non-uniform. Most preferably, the blowing agent used is carbon dioxide. This is because carbon dioxide has the advantage of being non-flammable compared to other blowing agents used in the production of foamed thermoplastics, and is also available at a lower cost compared to inert gases and nitrogen. Furthermore, carbon dioxide can be relatively easily converted to a supercritical state (T>31.0°C and p>73.8 bar), which promotes miscibility and dissolution in polycarbonate due to its low compressibility and rapid diffusion. Therefore, the polycarbonate beads of the present invention, when carbon dioxide is used as a foaming agent in the manufacturing process of the present invention, can be used without concern in applications involving certain fire risks or in (interior) parts where gas release is not permitted. For this reason, applications in the field of e-mobility, such as body parts for composite parts, can be considered in particular. Possible applications here include sound-absorbing elements incorporated into the floor of a vehicle or thermal insulation layers for the vehicle body.

[0078] The melting pressure must be selected to exceed the critical dissolution pressure of the physical blowing agent.

[0079] The molten material, after being mixed with a foaming agent and dissolved, passes through the nozzle plate at the outlet opening of the extruder, generally T1=(T g +110℃)~T2=(T g (+170℃), preferably T1=(T g (T)~T2=(T g (+160℃), more preferably T1=(T g +130℃)~T2=(T gThe extrusion is performed at a molten material temperature T in the range of +150°C. The nozzle plate temperature is preferably T to further prevent the nozzle from freezing due to the cooling of the polymer molten material, thus ensuring constant polymer pelletization and achieving appropriate foaming expansion at the maximum expansion potential. g The temperature is set to +(130℃~150℃).

[0080] For single-hole nozzles, the diameter of the nozzle opening is preferably in the range of 0.8 mm to 2.2 mm, and more preferably in the range of 1.0 mm to 1.5 mm. For multi-hole nozzles, the nozzle diameter is preferably 0.4 mm to 0.8 mm, and more preferably 0.6 mm.

[0081] The pelletization of the molten material at the end of the process of the present invention is preferably carried out by underwater pelletization, more preferably without additional pressurization, i.e., at atmospheric pressure. Pelletization at atmospheric pressure can achieve the desired low density of polycarbonate beads. As the molten material exits the nozzle, the polycarbonate material undergoes a pressure drop of 140 to 180 bar, preferably 150 to 160 bar, to approximately 1 bar atmospheric pressure, which causes the material to begin foaming. A physical foaming agent, such as carbon dioxide, expands the polycarbonate material as the gas diffuses from the polymer molten material. After a certain period of time, complete or near-complete gas exchange occurs, and as a result, only the normal air composition may be present in the foamed polycarbonate in pelletized form, i.e., polycarbonate beads.

[0082] The present invention also provides a process for producing a molded article from polycarbonate beads manufactured by the process of the present invention, and such a molded article.

[0083] Polycarbonate beads can be transformed into molded articles, even those with complex shapes, by filling the corresponding cavities, ultimately requiring only one corresponding process. Subsequent dimensional cutting (which is still frequently necessary and generates associated waste) known from extruded foams is unnecessary. Furthermore, polycarbonate beads are easier to transport than the often bulky sheets of available extruded foam.

[0084] The corresponding molded articles of the present invention can be used in the automotive industry, transportation, construction industry, aerospace industry, packaging industry, and generally in lightweight and / or composite structures. Molded articles that can be made from polycarbonate beads include not only sheets but also complex three-dimensional parts.

[0085] Molded articles made of or containing polycarbonate beads of the present invention are particularly visible parts in various application fields, which can also be upgraded with laser textures, and are used in, for example, dashboard or interior trim elements, soundproofing elements, such as filling elements for carpets in the footwells of automobiles, core materials or supporting foam parts for composite materials, such as body insulation for vehicles, especially electric vehicles, as insulation in the HVAC field (heating, ventilation, air conditioning), as high-temperature insulation in industrial, housing and building technology or transportation, barriers and insulation materials, packaging, lightweight structural elements, wind turbine blades, and facade parts.

[0086] Generally, molded articles made of polymer foam are subjected primarily to compressive stress. Another relevant type of stress for polymer foam is bending. Here, the part is subjected to complex loads, with the top surface subjected to compressive stress and the bottom surface subjected to tensile stress. Pressure tests can draw conclusions about the mechanical properties relevant to the application, and tensile and bending tests can draw conclusions about the weld quality. Parts made from polycarbonate beads obtained by the process of the present invention have thermomechanical properties (145°C to 150°C) of polycarbonate. g) It can have a profile, for example, 200 kg / m 3 With this component density, it exhibits a flexural modulus of 59.1±11.4 MPa and a flexural strength of 2.2±0.3 MPa (23℃, ISO 1209-1:2007, 120×25×10mm). 3 (with shape modification), it can have a compressive modulus of 54.7±5 MPa and a compressive strength of 1.61±0.12 MPa (at 10% compression) (23℃, DIN EN ISO 844-11:2014), a tensile strength of at least 1.97 MPa and an elongation at break of 8.4% (DIN EN ISO 1926:2009), and simultaneously a good thermal insulation effect of 45.2±2 mW / (m·K) (10℃, EN ISO 8301-8:1991). Commercially available particulate foam EPP has the same density of 200 kg / m³. 3 It has a flexural modulus of approximately 56.1 ± 10.8 MPa, a flexural strength of 1.85 ± 0.25 MPa, a compressive modulus of 48.4 ± 3.6 MPa, and a compressive strength of 1.51 ± 0.5 MPa (at 10% compression). Furthermore, EPP has a tensile strength of 2.49 MPa and a fracture elongation of 20.2%, and simultaneously a thermal insulation effect of 54 ± 0.2 mW / (m·K) (at 10℃). These values ​​were determined for EPC as described above, and this represents remarkably low performance.

[0087] Polycarbonate beads, in some cases, have very large average diameters equivalent to circles of equal projected area, i.e., nominal diameters of approximately 4mm to 6mm, which necessitates overfilling the mold cavity by 10% to 20% on a volume basis. The vapor-based welding process for particulate foam proceeds according to the same mechanism for all particles and is widely described in the literature, for example, Raps et al. 2015; DOI: 10.1016 / j.polymer.2014.10.078.

[0088] For the manufacture of molded articles / parts, foamed particles are welded together in a steam molding machine or by variothermal means (thermal means by heating). In a steam molding machine, the particle surface is partially melted or softened using high-pressure steam (i.e., high-temperature steam), which leads to interdiffusion of polymer chains between different beads and, consequently, aggregation of the beads. Good aggregation between particles and a low proportion of macropores / gaps, i.e., cavities between particles, in the part due to insufficient filling are necessary to ensure good mechanical properties. The processing from foamed beads to a finished part is carried out in five steps in the molding machine: 1) complete or partial closure of the mold, 2) filling of the mold, followed by complete closure if necessary, 3) welding of particles, 4) cooling and stabilization, and 5) removal of the molded article. Two methods are identified here: the crack gap method and the pressure filling method. In the pressurized filling method, the mold is first closed, then the particles are drawn out of the container by air pressure and injected into the mold by an injector at approximately 3 bar, where they are compressed. The particles expand within the mold, resulting in better cavity filling (equivalent to approximately 10% overfilling in the crack gap method). In the crack gap method, the mold is not completely closed, but a certain percentage of the cavity is left open. Next, the mold is filled with particles so that the mold is overfilled by a certain percentage (10% to 20% by volume in the case of EPC). Then, the mold is closed and the particles are compressed to the target thickness. If the target thickness of the part is, for example, 20 mm, the mold cavity is further opened, for example, by 4 mm (= 20% by volume), and filled with polycarbonate beads. Next, the mold is shrunk to the 20 mm part thickness. This step is important to achieve a uniform distribution of beads within the mold. In the third step, the beads fuse together as steam flows through the mold according to a predetermined procedure. During steam treatment, the beads form physical bonds through the interdiffusion of polymer chains between adjacent particles. To ensure high-quality welding between particles, the EPC should preferably use 7 to 11 bar, more preferably 8 to 10 bar. In the steam-based welding process, the air between the beads is first expelled and the mold is preheated.While the valve is open, steam flows parallel to the mold. In the second step, steam flows through the mold. This is called cross-steaming. During this step, the steam inlet and outlet valves, located on opposite sides of each other, are open. To ensure a very uniform temperature distribution and uniform welding quality throughout the part, it is preferable to steam the mold from both sides. Finally, with the outlet valve closed, steam is introduced into the steam chamber at a specific pressure to improve surface quality by forming a skin layer (autoclave steaming). In the fourth step, the molded article is cooled. This is extremely important for dimensional accuracy. If the part is removed without cooling, further expansion of particles may occur, resulting in deviation from the original dimensions. For cooling, water is sprayed onto the mold until the temperature reaches approximately 80°C. After molding and cooling, in the final step, the part is removed, preferably by compressed air and a mechanical ejector.

[0089] The present invention will be explained with reference to the following diagrams. [Brief explanation of the drawing]

[0090] [Figure 1] This is a flowchart of the process of the present invention for manufacturing polycarbonate beads. [Figure 2a] This is an SEM image of the foamed form of polycarbonate beads obtained by the process of the present invention (for PC-1 component with an OH-terminated group content of 470 ppm, the molar ratio of OH to epoxy reactive groups is 1 mol:0.82 mol (E1)). The OH-terminated group content, based on the total weight of the aromatic polycarbonate used, was 470 ppm. [Figure 2b] This is an SEM image of the foamed form of further polycarbonate beads obtained by the process of the present invention (for PC-1 component with an OH-terminated group content of 470 ppm, the molar ratio of OH to epoxy reactive groups is 1 mol:0.90 mol (based on the processing rate per hour) (E2)). The OH-terminated group content based on the total weight of the aromatic polycarbonate used was 429 ppm. [Figure 2c]This is an SEM image of the foamed form of polycarbonate beads not according to the present invention (for PC-1 component with an OH-terminated group content of 470 ppm, the molar ratio of OH to epoxy reactive groups is 1 mol:1.12 mol (based on the processing rate per hour) (V4)). The OH-terminated group content based on the total weight of the aromatic polycarbonate used was 346 ppm. [Figure 2d] This is an SEM image of a further foamed polycarbonate bead morphology not according to the present invention (for PC-1 component with an OH-terminated group content of 470 ppm, the molar ratio of OH to epoxy reactive groups was 1 mol:1.47 mol (based on the processing rate per hour) (V6)). The OH-terminated group content, based on the total weight of the aromatic polycarbonate used, was 264 ppm. [Modes for carrying out the invention]

[0091] The system for carrying out the process of the present invention, shown in Figure 1, is a tandem configuration. It consists first of a co-rotating twin-screw extruder (A). The screw is optimized for the foaming process (e.g., two right-handed rotating elements for airtightness in the intake direction). The twin-screw extruder has 10 heating zones with appropriate temperature monitoring and pressure detection in the exemplary figure, and in this example, gas metering is performed at position 1.6. After the molten material is homogenized, it is forcibly transported to a single-screw (C) via a bypass (B). The single-screw extruder here has 4 heatable zones with appropriate temperature monitoring and pressure sensors. The gas-molten material mixture is mainly transported to a melting pump, which is kept at the same temperature as this process. The subsequent melting pump (D) has the function of generating back pressure in the upstream system (for better gas solubility) and controlling the pressure upstream of the die plate. The homogenized molten material is extruded through the die plate, foamed, separated by a rotating blade, and transported from the water circuit (E) (dried and separated).

[0092] Figures 2a to 2d show SEM images of different polycarbonate bead morphologies produced by the process steps of the present invention, but with different molar ratios of OH-terminal groups of polycarbonate to epoxy groups of the chain extender ("OH to epoxy"). In the production of the beads in Figures 2a and 2b, aromatic polycarbonates were used in which the OH:epoxy molar ratio was within the range of the present invention, but this is not the case for the materials in Figures 2c and 2d. Here, the OH:epoxy molar ratio of the formulations used was 1:1.12 or 1.47. In the case of these comparative beads, partially fractured cell morphology and cell coalescence are clearly observed. As a result, materials that cannot be processed into molded articles with good mechanical properties are obtained. However, the polycarbonate beads of the present invention produced by the process of the present invention have extremely substantially intact foam cells, and the quality of the foam structure is significantly improved within a particularly preferred range of reactive group equivalents of the formulation. [Examples]

[0093] 1. Description of raw materials and test methods a) Raw materials polymer: PC1: Aromatic polycarbonate based on bisphenol A, with an MVR of 6 cm². 3 The process is (10 minutes) (300℃ / 1.2kg, ISO 1133-1:2011), and the softening temperature (VST / B 120; ISO 306:2013) is 149℃. g This is determined according to DIN EN ISO 11357-1:2017: 148℃. w The concentration was determined as described below, approximately 30900 g / mol at 28 kDa (MALLS). It contains 0.06% heat stabilizer and 0.1% UV stabilizer. The OH-terminated group content was determined using dichloromethane as the solvent at room temperature. 1 Determined by 1H NMR spectroscopy (as above): 470 ppm. Manufactured via melt condensation (SPC) method.

[0094] PC2: Aromatic polycarbonate based on bisphenol A, with an MVR of 6 cm².3 The process is (10 minutes) (300℃ / 1.2kg, ISO 1133-1:2011), and the softening temperature (VST / B 120; ISO 306:2013) is 150℃. g This is determined according to DIN EN ISO 11357-1:2017: 148℃. w The concentration was determined as described below, approximately 30,900 g / mol at 28 kDa (MALLS). The OH-terminated group content was determined using dichloromethane as the solvent at room temperature. 1 Determined by 1H NMR spectroscopy (as above): 60 ppm. Manufactured via interfacial condensation (LPC) method.

[0095] Chain extender 1: A commercially available polyfunctional chain extender manufactured by BASF SE (Joncryl ADR 4468), based on a styrene / acrylic polymer having a reactive epoxy group, with an average molecular weight (in orthodichlorobenzene, gel permeation chromatography at 150°C, polystyrene calibrated) M w = 7250 g / mol, epoxy equivalent 310 g / mol (determined according to DIN EN 1877-1:2000-12), glass transition temperature T g The temperature at which it rises is 59°C, and the decomposition temperature is 350°C (determined according to DIN EN ISO 11357-1:2017).

[0096] b) Process procedure of the example The process of the present invention can, in principle, be carried out by various mechanical configurations, as already described above. The tests described below were carried out using twin-screw extruder-gas metering system-single-screw extruder-melt pump-water pelletization configurations i), ii), and iii) shown in Figure 1. Example i) describes successful particle production as described in the claims, Example ii) describes failed particle production as a result of exceeding the maximum concentration of chain extender, Example iii) describes failed particle production as a result of the absence of reactive components, Example iv) describes a series of tests using the same configuration and process parameters as in i), but with the OH concentration (ppm) of the PC molten gradually decreased while keeping the reactive components constant, and Example v) describes successful particle production using an alternative configuration of twin-screw extruder-static mixer / heat exchanger-melt pump-water pelletization.

[0097] i) A twin-screw extruder (43D) manufactured by Reifenhaeuser (Troisdorf, Germany) was operated at a rate of 35 kg / h, profile temperatures of 100°C to 160°C (positions 1 to 3), 240°C (position 4) to 280°C (positions 5 to 10), and a speed of 100 rpm. In addition, chain extender 1 was added to the PC1 molten material at a low concentration of 0.7 wt%. This corresponds to an OH:epoxy molar ratio of 1:0.82 (mol / mol). The melting temperature was 10°C to 20°C higher than the housing temperature. The foaming agent was supplied by Maximator (Maximator GmbH (Germany)) and / or a weighing station (Lewa GmbH (Germany)) at a CO2 level of 1.2 wt% to 1.5 wt% at position 6. From position 5, the pressure profile in the twin-screw gradually increased from 45 bar to 310 bar at the tip of the extruder. The molten material was transported to a single-screw extruder (Reifenhaeuser) via a transfer pipe (290°C). This extruder was also operated at a continuous housing temperature of 280°C, a processing rate of 35 kg / h, and a speed of 26 rpm. The melting pressure gradually decreased through the screw to the melting pump (from 250 bar to 120 bar). The melting pump was operated at a back pressure of 110 bar and a temperature of 280°C under pressure control. The pressure downstream of the melting pump was in the range of 160 bar to 180 bar in this process (pressure at the die plate). The diverter and die plate were also set to a temperature of 280°C, and the melting temperature was (T g +140℃)~(T g The temperature was +150°C. The UWP (EUP 50) and die plate were to be manufactured by ECON (Econ GmbH, Austria). The die plate consisted of five single-hole inserts with a diameter of 2.2 mm and a die land of 3.49 mm. The residence time of the molten material between the inlet and outlet was approximately 7 to 10 minutes. Downstream of the outlet, the molten material was separated by a 6-blade knife rotating at 1500 rpm and transported by a water circuit at 70°C to 80°C (28 m³). 3 The resulting particles were rounded with a bulk density of 150 g / L to 180 g / L and could be efficiently welded in the range of 8 bar to 10 bar.

[0098] ii) A twin-screw extruder (43D) manufactured by Reifenhaeuser (Troisdorf, Germany) was operated at a rate of 17 kg / h, profile temperatures of 160°C to 240°C (positions 1 to 3), 260°C to 270°C (positions 4 and 5), and 280°C (positions 6 to 10), and a speed of 86 rpm. In addition, chain extender 1 was added at a high concentration of 1.5 wt%. This corresponds to an OH:epoxy reactive group ratio of 1 mol:1.78 mol. The melting temperature was 10°C to 20°C higher than the housing temperature. The foaming agent was supplied by Maximator (Maximator GmbH (Germany)) and / or a weighing station (Lewa GmbH (Germany)) at a CO2 level of 2 wt% to 2.3 wt% at position 6. From position 5, the pressure profile in the twin-screw gradually increased from 67 bar to 250 bar at the tip of the extruder. The molten material was transported to a single-screw extruder (Reifenhaeuser) via a transfer pipe (290°C). This extruder was also operated at a continuous housing temperature of 280°C, a processing rate of 17 kg / h, and a speed of 15 rpm. The melting pressure gradually decreased through the screw to the melting pump (from 250 bar to 115 bar). The melting pump was operated under pressure control with a back pressure of 110 bar and a temperature of 280°C. The pressure downstream of the melting pump was 230 bar in this process (pressure at the die plate). The diverter was also set to a temperature of 280°C, and the die plate was set to 320°C. The melting temperature was (T g +150℃)~(T g The temperature was +160°C. Due to the over-dosing of reactive components, it was necessary to significantly reduce the processing rate and increase the die plate temperature to prevent an emergency shutdown due to critical system pressure. The UWP (EUP 50) and die plate were to be manufactured by ECON (Econ GmbH, Austria). The die plate consisted of five single-hole inserts with a diameter of 2.2 mm and a die land of 15 mm. The residence time of the molten material between the inlet and outlet was approximately 7 to 10 minutes. Downstream of the outlet, the molten material was separated by a 6-blade knife rotating at 1500 rpm and transported by a water circuit at 70°C to 80°C (28 m³).3 ( / h). The manufacturing process was unstable, producing non-weldable, disintegrating and shrinking particles (bulk density exceeding 500 g / L).

[0099] iii) A twin-screw extruder (43D) manufactured by Reifenhaeuser (Troisdorf, Germany) was operated at a rate of 15 kg / h, profile temperatures of 160°C to 240°C (positions 1 to 3), 260°C to 270°C (positions 4 and 5) to 280°C (positions 6 to 10), and a speed of 85 rpm. This series of tests was performed without chain extender. The melting temperature was 10°C to 20°C higher than the housing temperature. Gas was supplied by Maximator (Maximator GmbH (Germany)) and / or a weighing station (Lewa GmbH (Germany)) at a CO2 level of 2% to 2.3% by weight at position 6. From position 5, the pressure profile in the twin-screw gradually increased from 73 bar to 94 bar at the tip of the extruder. The molten material was transported to a single-screw extruder (Reifenhaeuser) via a transfer pipe (290°C). This extruder was also operated at a continuous housing temperature of 280°C, a processing rate of 15 kg / h, and a speed of 15 rpm. The melting pressure gradually decreased through the screw to the melting pump (from 94 bar to 87 bar). The melting pump was operated under pressure control with a back pressure of 110 bar and a temperature of 280°C. The pressure downstream of the melting pump was 90 bar in this process (pressure at the die plate). The diverter and die plate were set to a temperature of 280°C, and the melting temperature was (T g +140℃)~(T g The temperature was +150°C). Process control was maintained as close as possible to ii) despite the absence of reactive components. The UWP (EUP 50) and die plate were to be manufactured by ECON (Econ GmbH, Austria). The die plate consisted of five single-hole inserts with a diameter of 2.2 mm and a die land of 15 mm. The residence time of the molten material between the intake and outlet was approximately 7 to 10 minutes. Downstream of the outlet, the molten material was separated by a 6-blade knife rotating at 1500 rpm and transported by a water circuit at 70°C to 80°C (28 m³). 3 / h). The manufacturing process was impossible under the given conditions, and almost non-expanded round particles with a very high density of 500 kg / m 3 ~600 kg / m 3 were generated. These had very poor or zero weldability for obtaining parts.

[0100] iv) A twin-screw extruder (43D) manufactured by Reifenhäuser (Troisdorf, Germany) was operated at a throughput of 35 kg / h, a profile temperature of 100 °C to 160 °C (positions 1 to 3), 240 °C (position 4) to 280 °C (positions 5 to 10), and a speed of 100 rpm. Furthermore, chain extender 1 was added at a fixed concentration of 0.7% by weight. In this series, by changing the ratio of the second polycarbonate, the molar ratio of reactive groups OH:epoxy was varied from 1:0.82 to 1:1.47 (OH:epoxy, in both cases mol) (Table 1). The melting temperature was 10 °C to 20 °C higher than the housing temperature. The blowing agent was supplied at a CO2 level of 1.3% by weight at position 6 by Maximator (Maximator GmbH, Germany) and / or the metering station (Lewa GmbH, Germany). From position 5, the pressure profile in the twin-screw increased gradually from 45 bar for 100% SPC and reached 270 bar at the tip of the extruder. As a result of adding PC-2, a PC component with few OH end groups, the pressure profile increased slightly to 275 bar at the first 10% level. When the PC component with few OH end groups was further added beyond 20% by weight, the pressure profile decreased. The melt was conveyed through a transfer pipe (290 °C) to a single-screw extruder (Reifenhäuser). This extruder was also operated at a continuous housing temperature of 280 °C, a throughput of 35 kg / h, and a speed of 26 rpm. The melt pump was operated at a back pressure of 110 bar and a temperature of 280 °C under pressure control. The pressure downstream of the melt pump was determined by the content of the reactive polycarbonate and decreased with the content of the exogenous matrix (details are shown in Table 1). The diverter and die plate were also set at a temperature of 280 °C, and the melting temperature was T g +140 °C to T gThe temperature was +150°C. The UWP (EUP 50) and die plate were manufactured by ECON (Econ GmbH, Austria). The die plate consisted of five single-hole inserts with a diameter of 2.2 mm and a die land of 3.49 mm. The residence time of the molten material between the intake and outlet was approximately 7 to 10 minutes. Downstream of the outlet, the molten material was separated by a 6-blade knife rotating at 1500 rpm and transported by a water circuit at 70°C to 80°C (28 m³). 3 ( / h). The roundness of the particles gradually decreased, and the foam density increased.

[0101] If the concentration of polycarbonate at the OH-terminated groups is too low, specifically below 350 ppm, the manufacturing process collapses with a reactive group molar ratio of 1:1.12 (OH:epoxy, each in moles) (outside the scope of the claims). The increase in molecular weight no longer occurs to a sufficient degree, and therefore the viscosity of the molten mixture, and thus the pressure at the die plate, is no longer sufficient for a homogeneous particle foam. The resulting particles become more elongated in shape and non-uniform in shape and appearance as the foam density increases (smaller pressure drop) (as a result of decreased viscosity and the accompanying changes in flow properties) (Table 2). Such particles can no longer be welded sufficiently well within the claimed pressure range of 7 to 11 bar. The parts lack a continuous surface and have many sink points / cavities, resulting in reduced thermal conductivity, increased stiffness, a clear decrease in maximum bending strain, and reduced puncture performance (Tables 2 and 3).

[0102] v) A Coperion ZSK 26 MC twin-screw extruder (44D) was operated at a processing rate of 20 kg / h, a housing temperature of 280°C (from the melting zone), a torque of 60%, and a speed of 230 rpm. Furthermore, chain extender 1 was added at a low concentration of 0.9 wt%. This corresponds to a molar ratio of reactive groups of OH:epoxy of 1:0.9 to 1.1 for the PC component in a composition with a particularly preferred OH-terminated group content of 450 ppm to 550 ppm, and is therefore within the scope of the present invention. In housing 7 of the 10 housings of the twin-screw extruder, the foaming agent CO2 was introduced at a concentration of 1.2 wt% to 1.5 wt% via a gas metering station (Promix Solutions GmbH (Germany)). The melting temperature of the gas-polymer mixture was 280°C (=T g The temperature was +130°C. The homogenized gas-polymer mixture was forcibly transported to a static mixer. The residence time in this mixer was 6 to 8 minutes. The mixer was also operated at a profile temperature of 280°C. At the end of the static mixer, a melting pump manufactured by Maag-Germany GmbH adjusted the back pressure at the inlet of the melting pump to 90 bar. The pressure upstream of the die plate was 198 bar. The molten material was pelletized in an underwater pelletizer (Gala). The gas-molten material mixture was extruded through a die plate with two holes into a cutting chamber filled with water. The hole diameter of the die plate was 2.4 mm. In the cutting chamber, the molten material was cut into pellets by a rotating blade. The blade speed was 3500 rpm. Due to the pressure drop after passing through the die plate, the pellets foamed. A pressure of 2 bar was applied to the 80°C to 90°C process water flowing through the cutting chamber. The pellets were finally dried and separated by a centrifuge. The resulting particles were round, had a smooth and homogeneous surface with a bulk density of 220 g / L to 250 g / L, and were highly efficient at welding.

[0103] c) Test method The manufactured particles are processed using a Teubert TVZ162 / 100PP molding machine (Teubert Maschinenbau GmbH (Germany)) to a density of 200 ± 10 kg / m³. 3、Processed into a part with dimensions of 300×200×15mm 3 The pressure required for EPC welding was in the range of 7 bar to 10 bar. Finally, the characteristics of the part were determined. For visualizing the morphology, measurements were carried out using a scanning electron microscope (SEM, model: JEOL JSM - 6510 (Borken, Germany)) on graphite sputtered samples. Dynamic mechanical analysis (DMA) was performed using a Gabo Eplexor 500N manufactured by NETZSCH GmbH (Selb, Germany) on samples with dimensions of 15×15×15mm 3 in the temperature range of -25°C to 250°C, at a heating rate of 1 K / min, in the pressure adjustment mode, with amplitudes of 5% (static) and 2% (dynamic) of the sample height, at a frequency of 1 Hz, and in the pressure mode. Mechanical property evaluation was carried out using pressure tests, tensile tests, and three - point bending tests (at room temperature, 80°C, and 110°C), as well as puncture tests (RT). The pressure test was carried out using a Zwick Z020 universal testing machine manufactured by Zwick & Roell (Ulm, Germany) in accordance with DIN EN ISO 844:2014 - 11, using a 10 kN load cell on samples with a shape of 15×15×15mm 3 up to 60% compression. The three - point bending was carried out using the same universal testing machine at a speed of 10 mm / min and using a 20 kN load cell based on ISO 1209 - 1:2007 - 05. The samples were prepared by removing the skin layer to eliminate the influence of the dense boundary layer and the shape was adjusted to 120×25×10mm 3 The tensile measurement of the part was carried out using a Zwick Z050 universal testing machine (Zwick & Roell (Ulm, Germany)) in accordance with ISO 1926:2009, using a sample shape of 140(30 + 80 + 30)×80×15mm 3 and a 20 kN load cell. The puncture property evaluation was carried out using a Fractovis Plus drop weight tester manufactured by Instron Ceast (Pianezza, Italy) with a maximum energy of 40 J, a puncture speed of 4.4 m / s (in accordance with DIN EN ISO 6603 - 2:2002 - 04), on samples with dimensions of 60×60×15mm 3The tests were performed using the specified sample shape. All mechanical property evaluations were conducted at room temperature, 80°C, and 110°C, with a 10-minute intermediate step for temperature adjustment before each measurement. All parts were approximately 200 kg / m 3 The analysis was performed at the same density. Thermal conductivity measurements were taken using a NETZSCH (Selb, Germany) HFM 446 Lambda instrument at -10°C, 10°C, 25°C, 50°C, and 70°C.

[0104] Average molecular weight M for PC-1 and PC-2 w The result was determined by gel permeation chromatography. Calibration was performed against a bisphenol A polycarbonate standard using dichloromethane as the eluent. Calibration was performed using a linear polycarbonate (formed from bisphenol A and phosgene) with a known molar mass distribution from PSS Polymer Standards Service GmbH (Germany), according to Currenta GmbH & Co. OHG (Leverkusen) method 2301-0257502-09D (2009 German version). The eluent was dichloromethane. The column combination was cross-linked styrene-divinylbenzene resin. Analytical column diameter: 7.5 mm, length: 300 mm. Column material particle size: 3 mm to 20 mm. Solution concentration: 0.2 wt%. Flow rate: 1.0 ml / min, solution temperature: 30°C. Injection volume: 100 ml. Detection by UV detector. For highly branched polycarbonates formed by increasing molecular mass through the addition of chain extenders, measurements were performed by GPC MALLS, as described above. It is impossible to dissolve all highly branched / partially crosslinked fractions (XYZ% insoluble), and such high molecular weight fractions in particular cannot be characterized with existing analytical options. This is a problem known to those skilled in the art, and therefore the accuracy of determining molar mass in highly branched polymers is limited. The aforementioned molar mass ranges relate accordingly to the dichloromethane-soluble components.

[0105] The OH value of polymers was determined using dichloromethane as a solvent at room temperature. 1This was confirmed by evaluating the ratio of the integral signals at 6.68 ppm (two aromatic protons in the ortho position relative to the phenol OH group) and 1.68 ppm (six methyl protons of the bisphenol A unit) using 1H NMR spectroscopy.

[0106] 2.Results Composition and Analysis

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

Claims

1. The process for manufacturing expanded polycarbonate beads includes the following steps: a) A step of providing an aromatic polycarbonate composition, wherein the aromatic polycarbonate is used with respect to the total weight of the aromatic polycarbonate, using dichloromethane as the solvent at room temperature. １ The process involves measuring the content of OH-terminal groups by 1H NMR spectroscopy, which is determined to be at least 350 ppm. b) A step of mixing the aromatic polycarbonate composition with a chain extender suitable for OH groups in a molar ratio such that 0.64 mol to 1.10 mol of the reactive groups of the chain extender are used per 1 mol of OH-terminated groups of the polycarbonate, c) A step of providing the mixture in a plasticized state, d) A step of mixing a physical blowing agent into the molten material, e) The plasticized mixture is １ = (T ｇ +110℃) ~ T ２ = (T ｇ A process of foaming and extruding particles at a temperature T of +170°C, ｇ The process is such that the glass transition temperature of the aromatic polycarbonate composition is... f) A step of pelletizing the foaming agent-containing molten material.

2. The process according to claim 1, wherein carbon dioxide is used as a foaming agent.

3. The process according to claim 1 or 2, performed as a continuous operation.

4. The aromatic polycarbonate composition provided by step a is determined according to ISO 1133:2012-3 (test temperature 300°C, mass 1.2 kg), up to a maximum of 12 cm ３ The process according to any one of claims 1 to 3, having a melt volume flow rate MVR of / (10 minutes).

5. The process according to any one of claims 1 to 4, wherein the pelletizing is pelletizing in a liquid medium, pelletizing by hot chopping, or pelletizing in air.

6. The process according to any one of claims 1 to 5, wherein the pelletizing is pelletizing in unpressurized water.

7. The process according to any one of claims 1 to 6, wherein the chain extender used is one or more epoxy-functionalized compounds.

8. The process according to any one of claims 1 to 7, wherein in step d, a physical blowing agent is added in a proportion of 0.1% to 2.3% by weight, and the proportion is based on the total weight of the aromatic polycarbonate composition and the chain extender.

9. The aromatic polycarbonate in the composition provided by step a is obtained by using dichloromethane as a solvent at room temperature, based on the total weight of the aromatic polycarbonate. １ The process according to any one of claims 1 to 8, wherein the content of OH-terminal groups is measured by 1H NMR spectroscopy to be 350 ppm to 600 ppm.

10. in the composition provided by Project A, the aromatic polycarbonate, based on the total weight of the aromatic polycarbonate, using dichloromethane as a solvent at room temperature １ The process according to any one of claims 1 to 9, having a content of OH end groups of at least 380 ppm as measured by １ H NMR spectroscopy.

11. The process according to any one of claims 1 to 10, wherein steps b and d overlap in time.

12. The process according to any one of claims 1 to 10, wherein steps a to f are performed in the order described.

13. The process according to any one of claims 1 to 12, wherein the chain extender used is an epoxy-functionalized chain extender having an epoxy equivalent of 285 g / mol to 485 g / mol.

14. Polycarbonate beads manufactured by the process described in any one of claims 1 to 13.

15. A process for producing a molded article from polycarbonate beads according to claim 14 by the crack gap method or the pressure filling method.

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