Method for producing expanded granulates

Abstract

The invention relates to a method for producing expanded granulates on the basis of high-temperature thermoplastics.

Description

[0001] Method for the production of expanded granules

[0002] Description

[0003] The present invention relates to a method for producing expanded granules based on high-temperature thermoplastics according to the features of claim 1, as well as a method for producing products from expanded granules with the features of claim 12 and expanded granules with the features of claim 13.

[0004] background

[0005] Foams based on high-temperature resistant polymers are in demand in engineering for the production of molded parts for a wide variety of purposes, for example in vehicle and aircraft construction, as well as in electronics.

[0006] Expandable granules and foams produced therefrom based on polyarylethersulfones or polyetherimides, and processes for their production, are known per se. (Prior art)

[0007] For example, an expanded granulate and a method for its production are disclosed in GB-A-1 569 10 763 and EP-A-186 308. However, with these previously known methods, the reproducibility of the expanded granulates produced according to these methods and the economic viability of using these methods are not fully given and guaranteed.

[0008] From WO 2013 / 092689, another process for producing foam sheets by extrusion of a blowing agent-loaded polymer melt of polyphenylene ethersulfone is known. Preferably, a mixture of isopropanol is used as the blowing agent. The resulting foam sheet is then formed into a shaped foam part under vacuum and temperature.

[0009] From EP 0 411 437 A1, a process for the production of expandable granules based on polyarylethersulfones, containing 5 to 20% wt.% of the granules, of methyl ethyl ketone or acetone as a blowing agent is known. The blowing agent and the polymers are mixed in an extruder at a housing temperature of at least 50°C and at most 170°C and then extruded directly into a medium with a temperature of less than 40°C. This process is limited to low throughputs. The granules are pressed into 10 mm thick, blowing agent-containing sheets in a dipping die and then foamed into 20 cm thick foam sheets. The cell diameters range from 0.2 to 0.8 mm.

[0010] From EP 3 2020 837 A1, a process for producing particle foams by sintering foam particles made of a polymer with a glass transition temperature of at least 180 °C, in particular polyethersulfone (PESU), polyetherimide (PEI), polyphenylenesulfone (PPSU) or polysulfone (PSU), is known. The foam particles preferably have a density in the range of 40 to 900 kg / m³ and a mean cell size in the range of 180 to 1500 pm. The particle foams obtained therefrom exhibit a high open-cell structure in the range of 33 to 64%.

[0011] Finally, EP 3 662 002 Al discloses a process for the production of expandable, blowing agent-containing granules based on high-temperature thermoplastics, which comprises the following stages:

[0012] - Production of a polymer melt by melting at least one polymer with a glass transition temperature according to ISO 11357-2-1999 of at least 180°C and mixing with at least one nucleating agent in an extruder at temperatures in the range of 300° to 350°C,

[0013] - Addition of a blowing agent to the polymer melt,

[0014] Cooling the polymer melt to a temperature in the range of 180° to 250°C,

[0015] - if necessary, pumping the polymer melt via a gear pump

[0016] - Conveying the blowing agent-containing polymer melt at a temperature in the range of 180° to 250°C through a die plate and granulating the blowing agent-laden polymer melt in an underwater granulator operated at a water temperature in the range of 75 to 99°C and a pressure in the range of 10 to 20 bar. Several disadvantages arise with previously known processes for the production of expandable, blowing agent-containing granules based on high-temperature thermoplastics. For example, the use of water is limited to temperature ranges below 100°C. Furthermore, the use of water leads to rapid cooling of the die plate on the extruder and the melt entering the water, resulting in the high pressures and high extrusion temperatures required for the process to be carried out.Furthermore, the use of water leads to high energy consumption for the aforementioned reasons and to potential residues of the blowing agents used, such as acetone, in the water. This water cannot simply be reused and must be disposed of or treated accordingly. In addition, achieving a sufficiently low-viscosity melt usually requires large quantities of blowing agents, especially flammable ones. Autoclave processes are also necessary as upstream steps for particle production, resulting in a discontinuous process and requiring a separate upstream step, thus rendering the entire process uneconomical.The necessary pre-expansion of propellant-containing particle foams potentially leads to emissions and the formation of explosive mixtures, which also hinder an economical and continuous process.

[0017] Task

[0018] The object of the present inventions is therefore to provide a continuous process for the production of expanded granules from high-temperature thermoplastics, which largely eliminates the need for water in the melt granulation process. Furthermore, it is an object to present a process for the production of products from expanded granules and such expanded granules.

[0019] Solution

[0020] These problems are solved by the features specified in claim 1 and the features specified in claims 12 and 13.

[0021] The inventive process for producing expanded granules from at least one high-temperature thermoplastic material in bulk form, with a bulk density according to ISO 11357-2-1999 in the range of 15 to 300 kg / m3 and a glass transition temperature according to ISO 11357-2-1999 of at least 180 °C, comprises the following process steps: lit 1) filling or1) Introduce at least one high-temperature thermoplastic material present in bulk into an extruder; 2) Produce a polymer melt from the at least one high-temperature thermoplastic material present in bulk in the extruder; 3) Add at least one blowing agent; 4) Homogenize the polymer melt in the extruder; 5) Temper the polymer melt in the extruder; 6) Extrude the polymer melt using the extruder; 7) Granulate and foam the extruded polymer melt using sub-air granulation, producing expanded particles of the extruded polymer melt.

[0022] It is particularly advantageous that granulation and foaming of the extruded polymer melt is carried out by means of sub-air granulation, which results in the formation of expanded particles of the extruded polymer melt.

[0023] The polymer melt is extruded from the extruder under pressure. As the polymer melt is forced out of the extruder through a perforated plate at the exit, it expands as it emerges in the form of several parallel strands. Behind the perforated plate, a rotating cutter disc or knife cuts the emerging strands of polymer melt into small pieces. These small pieces then form the granulated particles, which expand due to the blowing agent dissolved in the polymer melt. Under-air granulation, created by an airflow passing over the perforated plate, carries the granulated particles along. The airflow cools the granulated particles, and once a predefined temperature is reached, further expansion ceases.Small amounts of water can be introduced into the airflow. This is done, for example, using a spray nozzle that atomizes the water. The sprayed water allows for further regulation of the cooling behavior of the expanding particles. It also reduces the static charge of the particles, thereby improving their flowability and lowering the risk of electrical discharges. The particles then reach the desired, pre-set size. As a result of the expansion and the physical property that such particles assume a stable shape, the granulated particles take on an almost spherical form, although other shapes are also conceivable. This is due to physical limitations, especially since a sphere is a very stable shape and has a small surface area relative to its volume.The granulated particles can then be collected or, which is very advantageous in this process, immediately fed into a further processing step in which molded parts are produced from the granulated particles.

[0024] In the process according to the invention, the use of water for cooling the granulated particles exiting the extruder is eliminated. The omission of water and the alternative use of air for cooling the polymer melt exiting the extruder in the form of granulated particles, i.e., after extrusion, results in the granulated particles, which consist of polymer melt, being cooled more slowly than if they were immersed in water. This improves the expansion behavior of the granulated particles.

[0025] Another advantage of the process is that it requires no water or very little water, thus reducing the risk of the polymer melt freezing in the aperture and clogging it.

[0026] Advantageous further developments of the invention can be found in the dependent claims.

[0027] In an advantageous embodiment of the invention according to claim 2, it is provided that further polymers and / or additives are added subsequently or simultaneously with process step lit. 1). This allows the desired property of the granulated particles to be influenced and modified.

[0028] In an advantageous embodiment of the invention according to claim 3, the polymer melt is extruded from the extruder by means of a gear pump or an extruder screw arranged in or on the extruder. The throughput through the extruder can be varied by means of a gear pump or an extruder screw, and the residence time of the polymer melt in the extruder can thereby be varied.

[0029] In an advantageous embodiment of the invention according to claim 4, the tempering according to process step 5 is carried out in the form of cooling. Cooling results in a more homogeneous and viscous polymer melt, which is better suited for extrusion through the die of the extruder. Additional units in the form of melt chillers, static mixers, and gear pumps can be used for tempering, homogenizing, and conveying the polymer melt.

[0030] In an advantageous embodiment of the invention according to claim 5, the extruder is pre-tempered to a selectable temperature above the glass transition temperature of 180 °C. This enables rapid melting of the introduced bulk material and rapid tempering of the subsequently added polymers and / or additives.

[0031] In an advantageous embodiment of the invention according to claim 6, it is provided that only non-flammable liquids and gases are used as propellants in process step 3). The process according to the invention makes it possible to dispense with flammable liquids and gases, e.g., acetone, as propellants. Acetone, in particular, is used as a propellant in known processes according to the prior art. However, acetone is highly flammable and therefore poses a significant occupational safety risk. A decisive advantage of the present invention lies in the elimination of flammable or highly flammable propellants, such as acetone. Acetone is flammable and therefore poses a significant occupational safety risk. This hazardous propellant is replaced in the invention by non-hazardous propellants such as CO2, H2O, or N2.

[0032] In an advantageous embodiment of the invention according to claim 7, it is provided that the blowing agent is added to the polymer melt produced in the extruder. Thus, the blowing agent is added directly to the polymer melt.

[0033] In an advantageous embodiment of the invention according to claim 8, it is provided that CO2, water, N2 or a mixture of CO2 and water or of water and N2 or of CO2 and N2 are used as propellants, so that non-flammable and not easily flammable propellants can be used.

[0034] The blowing agents can also be in granular form, as a so-called masterbatch, or as chemical blowing agents together with the polymer granules, i.e., the HT polymer and other additives, added directly into the extruder via the feed hopper at the very beginning. Due to the temperature in the extruder, these decompose, producing CO2, N2, H2O, etc.

[0035] In an advantageous embodiment of the invention according to claim 9, it is selected that the high-temperature thermoplastic material used is a material from the group consisting of polyarylethersulfones, polyetherimides, polyamides, mixtures of the aforementioned materials, or a mixture with other polymers, or that polyethersulfone is used. In an advantageous embodiment of the invention according to claim 10, it is selected that during the sub-air granulation process step (lit. 7), water is added to control the expansion, cooling, and crystallization behavior, for example, by atomizing and spraying it into the airstream using a nozzle.

[0036] In an advantageous embodiment of the invention according to claim 11, it is chosen that the expanded particles are stimulated to foam up after extrusion by means of pressure loading, steam or IR irradiation.

[0037] As an alternative to extrusion processes, discontinuous autoclave processes can be used. However, this requires upstream particle production, resulting in a multi-stage and discontinuous process. This upstream process must be planned as a separate step, making the overall process economically disadvantageous.

[0038] The necessary pre-expansion of propellant-containing particle foams potentially leads to emissions and the formation of explosive mixtures, which also hinder an economical and continuous process.

[0039] In the embodiment of the invention according to claim 12, it is provided that the expanded particles are fed into a further process step after process step lit. 7) by means of which planar components such as, for example, 2D plates for use as core material in sandwich components or three-dimensional molded parts for use in insulation applications, crash elements, and non-load-bearing elements with low weight requirements are produced as products. This enables a continuous production process of products consisting of the obtained expanded particles.

[0040] In the embodiment of the invention according to claim 13, it is provided that high-temperature thermoplastics from the group consisting of polyarylethersulfones, polyetherimides, polyamides, mixtures thereof or mixtures with other polymers are used and / or that polyethersulfone is used.

[0041] Further advantages, features and design possibilities result from the following description of figures, which are not to be understood as limiting examples.

[0042] Brief description of the drawings

[0043] The drawings show:

[0044] FIG 1 a schematic representation of the process;

[0045] Fig. 1a is an alternative schematic representation of the

[0046] procedure

[0047] FIG 2 shows another schematic representation of the process;

[0048] Fig. 2a shows another alternative schematic representation of the

[0049] Procedure;

[0050] FIG 3 a product produced from particles obtained by the process;

[0051] FIG. 4 shows a section through a recovered particle; FIG. 4a shows an alternative section through a recovered particle.

[0052] In the drawings, elements designated with the same reference symbols are essentially equivalent to one another, unless otherwise indicated. Furthermore, components that are not essential for understanding the technical teaching disclosed herein are not shown or described. Additionally, reference symbols are not repeated for all elements already introduced and illustrated, provided that the elements themselves and their function have already been described or are known to a person skilled in the art.

[0053] Detailed description of examples

[0054] Figure 1 shows a schematic representation of the process, and Figure 1a shows an alternative schematic representation of the process, each with the essential elements used in the process and in the process steps. The reference numerals in Figure 1 and Figure 1a are chosen to be the same for identical elements.

[0055] An extruder 1 is shown. At one end of the extruder 1 is a filling opening connected to a hopper 2. The operating materials relevant for the process and its implementation, namely a granulate of plastic 9 or HT polymer, additives 10, and blowing agent 11, can be added to the extruder 1 via the hopper 2.

[0056] In an alternative embodiment, only the HT polymer 9 is added via the funnel 2; the additives 10 and the blowing agents 11 are introduced into the extruder 1 via special devices, some under pressure, at designated locations not shown in FIG. 1. The feed opening for attaching the funnel 2 is located at the outlet 5 of the extruder 1, which is essentially opposite the funnel 2 at the other end of the extruder 1.

[0057] In an advantageous embodiment of the invention, it is provided that the additives 10 and / or the blowing agent(s) 11 are fed into the extruder 1 at designated points between the hopper 2 and the outlet 5, either under pressure and already pre-tempered, or simply at ambient temperature.

[0058] The HT polymer 9, the additives 10, and the blowing agent 11, which are introduced into the extruder 1 via the hopper 2, are heated and thereby melted in the extruder 1. For this purpose, a temperature is generated in the extruder 1 that is well above the glass transition temperature of the HT polymer. It has proven advantageous to raise the temperature in the extruder 1 to more than 300°C at this point, preferably immediately after the hopper 2. This causes the HT polymer 9 to melt into a polymer melt, while simultaneously mixing the polymer melt with the additives 10 and the blowing agents 11. The polymer melt, i.e. the molten HT polymer 9, is mixed with the additives 10 and the blowing agent 11, wherein an extruder screw 3 is arranged in the extruder 1, which transports the components introduced via the hopper 2 from the hopper 2 towards the outlet 5 of the extruder 1.The polymer melt is compacted and simultaneously mixed by the extruder screw 3, producing a homogeneous polymer melt consisting of the molten HT polymer 9, the additives 10, and the blowing agents 11. A pressure significantly higher than ambient pressure is generated in the extruder 1. To prevent the polymer melt from escaping through the hopper 2 and its opening, flaps are provided that close automatically when the pressure in the extruder 1 increases.

[0059] Furthermore, the extruder screw 3 is designed to simultaneously create a relative seal within the extruder 1, ensuring that the polymer melt is forced through the screw 3 only towards the outlet 5 and cannot flow back. The outlet 5 of the extruder 1 is designed to taper, meaning its cross-section narrows. This increases the density of the polymer melt in this area, which in turn leads to a pressure increase.

[0060] The HT polymer 9, the additives 10, and the blowing agents 11 are mixed and blended in a molten state to form a polymer melt, thereby creating a homogeneous polymer melt. Within this homogeneous polymer melt, the molten HT polymer 9, the additives 10, and the blowing agents 11 are distributed relatively uniformly.

[0061] To achieve a homogeneous polymer melt, the polymer melt is cooled in a section of the extruder 1; alternatively, it can be heated to an even higher temperature.

[0062] To monitor the homogeneity of the polymer melt, sensors 8 are arranged in the extruder 1, by means of which the polymer melt, the temperature, the pressure and other environmental parameters within the extruder 1 are recorded.

[0063] There is at least one heating element 6 and cooling fins 7 on the

[0064] The extruder 1 is arranged. The temperature in the extruder 1, and thus the temperature of the homogeneous polymer melt, can be controlled by a control unit (not shown in FIG. 1) via the heating element 6 or the cooling fins 7, which advantageously have a Peltier element, an airflow, or water cooling system. This allows the temperature of the homogeneous polymer melt in the extruder 1, as it passes between hopper 2 and outlet 5, to be controlled as desired, i.e., the temperature can be increased or decreased.

[0065] In particular, a particularly homogeneous polymer melt is achieved by changing the temperature and simultaneously mixing and transporting the material through the extruder screw 3.

[0066] The polymer melt is forced through the extruder screw 3 in the extruder 1 to its outlet 5. The outlet 5 is designed to taper, i.e., the inner diameter of the extruder 1 decreases, wherein in an advantageous embodiment of the invention this tapering is continuous or linear, and an orifice plate 4 is arranged directly at, in, or behind the outlet 5.

[0067] Due to the narrowing and the arrangement of the aperture 4, the polymer melt in the extruder 1 is further compressed before the aperture 4, the pressure on the polymer melt in the extruder 1 increases and the polymer melt exits through the aperture 4 in thin strands under increased pressure compared to the external pressure, i.e. the atmospheric pressure present outside the extruder 1.

[0068] Behind the aperture 4, a rotary cutter (not shown in FIG. 1) is arranged that chops or cuts the emerging thin strands of the polymer melt into small pieces. These small pieces are particles 15 consisting of polymer melt and have an exit temperature and an internal pressure.

[0069] The extruder 1 is arranged with its outlet 5 at an air duct 13 in which an airflow 14 circulates, generated by a compressor (not shown in FIG. 1). The airflow 14 in the air duct 13 is matched to the mass of the particles 15 that enter the air duct 13 after the rotary encoder. The particles 15 are carried along by the airflow 14 in the air duct 13 and transported away from the outlet 5 of the extruder 1. Small amounts of water can be added to the airflow 14, or small amounts can be injected in the area of ​​the aperture 4, which can also be designed as a perforated plate.

[0070] Immediately after the particles 15 enter the air duct 13 with the airflow 14, the particles 15 expand due to the pressure difference in the extruder 1 and the pressure in the air duct 13, as well as the blowing agent 11.

[0071] The airflow 14 in the air duct 13 causes the particles 15 to granulate and at the same time to foam up, which are produced from the extruded polymer melt.

[0072] Furthermore, the expansion of the particles 15 occurs due to the blowing agent dissolved in the polymer melt, which is present in each particle 15 due to its homogeneous distribution in the polymer melt.

[0073] Under-air granulation is achieved by the airflow 13, which passes by the aperture 4 and carries the particles 15 along. After exiting the extruder 1 through the aperture 4, after passing the rotary cutter, the polymer melt, and thus the particles 15, have a temperature sufficient for the foaming of the particles 15. Additionally, the blowing agents 11 exert their effect due to the pressure drop after exiting the extruder 1.

[0074] Since the heat transfer between the polymer melt or the particles 15 made of polymer melt and the air is lower than that between the polymer melt or the particles 15 made of polymer melt and water, as in the prior art, the particles 15 cool down more slowly than in the prior art.

[0075] The airflow 14 has an air pressure range between 0.1 bar and 30 bar and a variable temperature range between 5°C and 400°C.

[0076] In the airflow 13 the particles 15 are cooled, but the cooling is slower than if the particles 15 are introduced directly into water, as is known in the prior art.

[0077] The particles 15 do not need to be in loaded form, as required by the prior art, which then needs to be further foamed in an additional step; rather, this step can be omitted, since the particles 15 can be processed directly.

[0078] When a predefined temperature is reached for the particles

[0079] No further expansion of the particles 15 occurs. They then reach the desired preset size. As a result of the expansion and the physical property that such particles assume a stable shape, the particles 15 almost take on the shape of a sphere. This is due to physical reasons, since a sphere represents a very stable shape, and a sphere has a small surface area relative to its volume.

[0080] After cooling, the particles 15 can be collected, gathered, or, which is very advantageous in this process, immediately and directly fed into a further processing step. In this subsequent processing step, molded parts are produced from the particles 15.

[0081] The particles 15 have a cellular microstructure consisting of an HT polymer matrix and a cell gas, the cell gas being essentially CO2, H2O, N2 or a mixture of CO2 and H2O or of H2O and N2 or of CO2 and N2.

[0082] Examples of HT polymers used include: high-temperature thermoplastic materials, such as polyarylethersulfones, polyetherimides, polyamides, mixtures of the aforementioned materials, or mixtures with other polymers. Polyethersulfone has proven to be the preferred choice.

[0083] The propellant 11 used is CO2, water, N2, or a mixture of CO2 and water, or of water and N2, or of CO2 and N2. It is essential, however, that substances that are not easily flammable or combustible are used, thus virtually preventing the formation of explosive and / or flammable gases or gas mixtures during the manufacturing process. After production, the particles 15 have a particle diameter between 0.5 mm and 10 mm and a particle bulk density between 15 g / L and 300 g / L.

[0084] The addition of specific substances to the polymer melt allows the physical properties of particles 15 to be influenced, which is particularly important for the molded parts produced from these particles. For example, the inherent flame retardancy can be improved by eliminating the use of problematic flame retardants such as boron, fluorine, or chlorine compounds. Furthermore, the high operating temperature can be positively influenced in this way, which is typical for HT thermoplastics and crucial for their use in aircraft, trains, and battery technology.

[0085] Fig. 1a differs from Fig. 1 in that the air duct 13 is rounded.

[0086] Figure 2 shows another schematic representation of the method, and Figure 2a shows another alternative schematic representation of the method. The reference symbols in Figure 2 and Figure 2a are chosen to be the same for identical elements.

[0087] The diagram again schematically shows an extruder 1 with a hopper 2, through which HT polymers 9, preferably in granular form, additives 10, and blowing agents 11 can be added.

[0088] The HT polymers 9, the additives 10, and the blowing agent 11 are heated and melted after being introduced into the extruder 1 via the hopper 2. The temperature in the extruder 1 is significantly higher than the glass transition temperature of the HT polymers 9. The HT polymers 9 melt in the extruder 1 and are heated together with the additives 10 and the blowing agent 11 (several different blowing agents or a mixture of blowing agents can also be used) to form a polymer melt. The polymer melt is then mixed with the additives 10 and the blowing agents 11 in the extruder 1. A screw conveyor 3 is arranged in the extruder 1, which transports the polymer melt from the hopper 2 towards the outlet 5 of the extruder 1. The polymer melt is compacted and simultaneously mixed in extruder 1 by means of the extruder die 3.thoroughly mixed to create a homogeneous polymer melt consisting of the melted HT polymer 9, the additives 10 and the blowing agents 11.

[0089] The polymer melt is forced through the extruder screw 3 in the extruder 1 to its outlet 5. The outlet 5 has a tapered design. A perforated aperture 4 is arranged at, in, or behind the outlet 5.

[0090] The polymer melt, which is under increased pressure, is forced out of the extruder 1 in strands through the aperture 4.

[0091] Behind the aperture 4, a rotary cutter (not shown in FIG. 2) is arranged that chops or cuts the emerging strands of the polymer melt into pieces. These pieces are the particles 15 produced from the polymer melt, and they have an exit temperature and an internal pressure.

[0092] The extruder 1 is arranged with its outlet 5 at an air duct 13 in which an airflow 14 exists. The airflow 14 in the air duct 13 is matched to the mass of the particles 15 being produced. The particles 15 are carried along by the airflow 14 in the air duct 13 and transported away from the outlet 5 of the extruder 1. Immediately after the particles 15 enter the air duct 13 with the airflow 14, they expand due to the pressure difference in the extruder 1 and the pressure in the air duct. This expansion is caused, among other things, by the presence of the particles.

[0093] 15 existing propellants produced 11.

[0094] The amount of propellant 11 is chosen such that the particles 15 expand but do not burst or rupture, and the surface tension holds the particles 15 together, forming an almost closed surface. The particles 15 assume an almost spherical shape.

[0095] The airflow 14 in the air duct 13 causes granulation or subgranulation of the particles 15 and at the same time foaming of the particles 15 which are produced from the extruded polymer melt.

[0096] The sub-air granulation is provided by the airflow 13, which is also guided past the aperture 4 and carries away the escaping particles 15.

[0097] In the airflow 13, the particles 15 are cooled until they reach the predefined temperature.

[0098] The particles 15 are then guided into a mold 16 or a mold 17 until the mold 16, 17 is filled with particles 15. Then the mold 16, 17 is closed and the particles in the mold are removed.

[0099] The 16 existing particles 15 are manufactured into a molded part using radio wave-based processing, while the particles 17 present in mold 15 are manufactured into a molded part using variothermal processing. Any component in various shapes can be produced using appropriate molds. For example, flat components, such as 2D plates for use as core material in sandwich components, can be produced.

[0100] It is also possible to manufacture three-dimensional molded parts for use in insulation applications, crash elements, and non-load-bearing elements with low weight requirements.

[0101] The illustration in Fig. 2a, unlike Fig. 2, has a rounded air duct 13.

[0102] FIG 3 schematically shows a molded part 18 which consists of particles 15 which are produced according to the inventive method.

[0103] The molded part 18 has an S-shaped curve. The molded part 18 consists of individual particles 15, which are produced using a mold 16, 17 shown in FIG. 2. Domes 20 are placed on the molded part 18 and connected to it by a form-fit and / or force-fit. Furthermore, inserts 22 are incorporated into the surface of the molded part 18 and connected to it by a form-fit and / or force-fit. Recesses are provided in the inserts 22 and the domes 20, into which fasteners, such as screws 21, can be inserted. A snap hook 19 is also directly connected to the molded part 18, preferably to its surface. The snap hook 19 is manufactured as a molded part using a 3D printing process. Likewise, the domes 20 and the inserts 22 are manufactured as molded parts using a 3D printing process.

[0104] Figure 4 shows a section through a recovered particle 15, and Figure 4a shows an alternative section through a recovered particle 15. The reference symbols in Figure 4 and Figure 4a are chosen to represent identical elements.

[0105] The spherical shape of particle 15 is shown. The outer wall 23 is closed and almost smooth. Inside, the polymer matrix 24, formed from the HT polymer and the blowing agent 11 enclosed in the polymer matrix 24, is shown.

[0106] In a further embodiment of the invention, two extruders are used that operate in parallel. However, it is also possible to arrange one extruder followed by a static mixer or heat exchanger.

[0107] It is also possible to arrange and use melt pumps and start-up valves before the orifice plate or graduation and after the extruder.

[0108] In Fig 4a, the already enlarged particle 15 is shown as a real image.

[0109] Examples

[0110] Raw materials used:

[0111] - Ultrason E2010 (trade name)

[0112] Polyethersulfone (PESU) from BASF SE, density 1370 kg / m³, viscosity 56 cm³ / g (in 0.01 g / ml phenol / 1,2-ortho-dichlorobezole, 1:1), glass transition temperature DSC (10°C / min) 225°C) o Base polymer: Polyethersulfone o Manufacturer: BASF SE o Pretreatment: Drying at 130°C for 16h

[0113] - Propellant CO2 0 1.5 wt. -%

[0114] The weight percentages refer to 100% solids.

[0115] (Polymer granules + additives) without propellant or injection pressure 67 bar

[0116] - Additives: o Nucleating agents: talc Fintalk ATI M15;

[0117] 0.5 wt. -%

[0118] The weight percentages refer to 100% solids.

[0119] (Polymer granules + additives) without propellant

[0120] Process parameters:

[0121] Extruder nozzle temperature: 322 °C

[0122] Nozzle pressure: 162 bar

[0123] Blade speed: 1250 rpm

[0124] Fan speed ULG: 90%

[0125] Welding parameters RE: 8.5 kV, 115 s, pressureless

[0126] Electrode temperature control 195°C Particle / molded part properties:

[0127] Average particle size: 4.8 mm

[0128] Bulk density: 128 g / l

[0129] Molded part density: 320 kg / m³ 3

[0130] The determination of the molded part density is carried out according to the buoyancy principle according to DIN EN ISO 845 (2009-10) .

[0131] The following section details the

[0132] Machine components and materials described with temperature profiles.

[0133] General information:

[0134] • Plant technology o Dosing units for talc and chain extender (Coperion K-CV-MT12) o Collin extrusion plant

[0135] ■ Tandem setup

[0136] ■ A-Extruder Twin Screw ZK 25 P

[0137] (Temperature zones were set between 290 - 340 °C, screw speed 150 rpm)

[0138] ■ B-Extruder single screw E 45 M (temperature zones set between 300 - 340 °C, screw speed 17 rpm) o ECON water and air pelletizing EWA 50

[0139] ■ Polymer start-up valve AV 15

[0140] ■ Discontinuous screen changer ESD 26

[0141] ■ Melt pump

[0142] ■ Nozzle size 1.2 mm (diameter) , 6 nozzles

[0143] ■ Granulating head with 6 knives o Density scale Mettler Toledo AG245 according to DIN EN ISO 845 (2009-10) materials o PESU

[0144] ■ Type Ultrason E2010 NAT

[0145] ■ Manufacturer: BASF SE

[0146] ■ Polymer type: Polyethersulfone

[0147] ■ Pretreatment: Drying at 130 °C for 16h or chain extender

[0148] ■ Joncryl ADR4468

[0149] ■ Manufacturer: BASF SE o Talk

[0150] ■ Finntalk ATI M15

[0151] ■ Manufacturer: Elementis

[0152] The process and its sequence are described below:

[0153] To produce the particles, the materials described in Examples Vl-3 were first pretreated. The PESU granules are dried for 16 hours at 130°C before use.

[0154] The granules are poured into the extruder's feed hopper. The rotary motion of the twin-screw extruder guides the material into eight different temperature zones, where it is melted and homogenized. Additives are added in powder form using a dosing system (type Coperiopon K-CV-MT12). The blowing agent is a variable-weight Maximator DSD500.

[0155] Adjacent to extruder A is extruder B with a single-screw configuration. This homogenizes the melt.

[0156]

[0157] Analyses:

[0158] The bulk density of the expanded granules was determined according to DIN ISO 697:1982.

[0159] Particle sizes were determined using dynamic image analysis according to ISO 13322-2. The Camsizer xt from the manufacturer RETSCH was used as the instrument.

[0160] The part density was determined using the buoyancy method according to DIN EN ISO 845 (2009-10).

[0161] Furthermore, the following extrusion line from COLLIN is used for further embodiments and comparisons. This line features a tandem setup consisting of a ZK 25P twin-screw extruder. Temperature zones between 290°C and 340°C were set within this extruder, which operated at a screw speed of 150 rpm. A COLLIN E45M single-screw extruder is connected to this, in which temperature zones between 300°C and 340°C were set, and which operated at a screw speed of 17 rpm. Additionally, an EWA 50 water and air pelletizer from ECON is used. This pelletizer includes an AV 15 polymer start-up valve, an ESD 26 discontinuous screen changer, and a gear melting pump.A single nozzle with a nozzle diameter, also referred to as nozzle size, of 2.2 mm is used, and the granulating head has six blades.

[0162] The polymer used was a polyaryl ether ion, specifically Ultrason E 2010 NAT from BASF. To better understand the material's temperature behavior, the glass transition temperature of the polymer was determined according to ISO 11357-2-1999, yielding a value of 225°C at a heating rate of 10°C / min, which corresponds to the glass transition temperature in the data sheet. Furthermore, the material, in this case the aforementioned granules, was dried in a granule dryer for 4 hours at 150°C before use, i.e., before being transferred to the extruder.

[0163] For the blowing agent used according to the invention, CO2 with a purity of 99.5%, corresponding to the designation TM5, was used. The blowing agent is an inert, non-flammable gas. The blowing agent was metered into the twin-screw injector via a gas injector, homogenized, and dissolved, with the injection point located downstream of the melting zone.

[0164] Furthermore, the particle density and shape were determined. DIN EN ISO 1183-1 was used to determine the particle density. The particle shape, on the other hand, was determined optically. The cell structure of the foamed particles was also determined using digital microscopy. For this purpose, sections were made through the center of the particles using a razor blade, and the resulting surfaces were sputtered with gold to increase the contrast in the optical microscopy. To assess the foam morphology, the view was magnified 40 times, and photographs were then taken.

[0165] The tables below present the results of individual tests. The propellant content and the blade speed were varied.

[0166]

[0167] For experiment VI, no blowing agent was initially added; therefore, no blowing agent was added. Furthermore, the starting granules were metered into the twin-screw extruder at a throughput of 15 kg / h using a gravimetric dosing unit and melted there. The melt was then conveyed directly into the single-screw extruder and subsequently conveyed further by the gear pump. The pressure build-up from the two units caused the melt to be discharged through the die plate, granulated by the rotating knife (operated at a blade speed of 2500 rpm), and cooled in an airflow. This airflow was generated by a fan, which operated at a speed of 1800 rpm during experiment VI. The temperature at the cylinder, the die plate, and the start-up valve was determined to be 330 °C during experiment VI. Atomized water was sprayed under pressure into the airflow to cool the melt.Air granulation is used. The resulting product is a compact, non-foamed granulate with a particle density of 1370 kg / m³. 3 Analogous to Experiment VI, in Experiment V2 the granules were first melted. However, after melting, CO2 was gravimetrically added as a blowing agent to the resulting melt in the twin-screw extruder at a blowing agent concentration of 1.0 wt%. The remaining process parameters, as well as the determined temperatures at the cylinder, the die plate, and the start-up valve, remained unchanged compared to Experiment VI. The described addition of CO2 resulted in foaming at the die, allowing the particles foamed via air granulation to be granulated. The measured particle density according to DIN EN ISO 1183-1 was 650 kg / m³. 3 .

[0168] In test V3, the cylinder temperature and the temperature of the perforated plate were set to 330 °C. Furthermore, the temperature at the start-up valve was adjusted to 310 °C. Compared to test V2, the propellant content was reduced to 0.4 wt.%. The remaining test parameters remained unchanged compared to VI and V2. These changes made it possible to produce spherical and cylindrical particles with a lower propellant content. The measured particle density according to DIN EN ISO 1183-1 was 286 kg / m³. 3 measured and is therefore reduced by more than a factor of 2 compared to experiment V2.

[0169] Building on test V3, the knife speed was increased from 2500 rpm to 3000 rpm for test V4. No further adjustments to the test parameters were made. The measured particle density according to DIN EN ISO 1183-1 remained at 285 kg / m³. 3virtually unchanged. The slight difference can also be attributed to typical measurement deviations. Here too, spherical or cylindrical particles are produced. Although the invention has been illustrated and described in detail by the advantageous embodiments, the invention is not limited by the disclosed examples. Other variations can be derived from these by a person skilled in the art without departing from the scope of protection of the invention. In particular, the invention is not limited to the combinations of features specified below, but other combinations and partial combinations of the disclosed features can also be formed from them, which are obviously feasible for a person skilled in the art.

[0170] Reference numerals: Extruder, feed hopper, extruder screw, orifice plate, outlet, heating element, cooling fins, sensors, granules made of plastic / HT polymer, additive(s), blowing agent, air duct, airflow, particles, shape, molded part, snap hook, dome, screw, insert, surface, polymer matrix, outer wall

Claims

Method for the production of expanded granules Patent claims 1. A process for producing expanded granules from at least one high-temperature thermoplastic material (9) in bulk form, with a bulk density according to ISO 11357-2-1999 in the range of 15 to 300 kg / m³ and a glass transition temperature according to ISO 11357-2-1999 of at least 180 °C, comprising the process steps: 1) filling or introducing at least one high-temperature thermoplastic material into the bulk material (9) into an extruder (1); (2) generate a polymer melt from the bulk material containing at least one high-temperature thermoplastic polymer (9) in the extruder (1); (3) add at least one blowing agent (11); (4) homogenize the polymer melt in the extruder (1); (5) temper the polymer melt in the extruder (1); (6) extrude the polymer melt using the extruder (1); (7) granulate and foam the extruded Polymer melt by means of sub-air granulation, resulting in expanded particles (15) of the extruded polymer melt.

2. Method according to claim 1, characterized in that further polymers and / or additives (10) are added subsequently or simultaneously to process step lit 1).

3. Method according to claim 1, characterized in that the extrusion of the polymer melt from the extruder (1) is carried out by means of a gear pump or extruder screw (3) arranged in or on the extruder (1).

4. Method according to one of the preceding claims, characterized in that the tempering according to process step lit 5) is carried out in the form of cooling.

5. Method according to one of the preceding claims, characterized in that the extruder (1) is pre-tempered to a selectable temperature which is above the glass transition temperature of 180 °C.

6. Method according to one of the preceding patent claims, characterized in that only non-flammable liquids and / or gases are used as propellant (11) in process step lit 3).

7. Method according to one of the preceding claims, characterized in that the blowing agent (11) is added to the polymer melt produced in the extruder.

8. Method according to one of the preceding claims, characterized in that CO2, water, N2 or a mixture of CO2 and water or of water and N2 or of CO2 and N2 is used as a propellant (11).

9. Method according to one of the preceding claims, characterized in that the high-temperature thermoplastic plastic (9) is plastics from the group consisting of polyarylethersulfones, polyetherimides, polyamides, mixtures of the aforementioned plastics or a mixture with other polymers, or that polyethersulfone is used.

10. Method according to one of the preceding claims characterized in that during the process step of sub-air granulation lit 7) water is added to control the expansion, cooling and crystallization behavior, for example by means of a nozzle atomized and sprayed into the air stream ( 14 ).

11. Method according to one of the preceding claims, characterized in that the expanded particles ( 15 ) are stimulated to foam up after extrusion by means of pressure loading, by means of steam or by means of IR irradiation.

12. Method for producing products with expanded particles ( 15 ) manufactured according to any one of the preceding claims 1 to 11, wherein the expanded particles ( 15 ) are fed directly after the process step lit 7 ) to a further process step by which planar components such as 2D plates for use as core material in sandwich components or three-dimensional molded parts for use in insulation applications, crash elements, and non-load-bearing elements with low weight requirements are produced as products.

13. Expanded granules produced according to any one of claims 1 to 12, wherein high-temperature thermoplastics from the group consisting of polyarylethersulfones, polyetherimides, polyamides, mixtures thereof or mixtures with other polymers can be used and / or polyethersulfone can be used.

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