Method for producing foamed plastic particles

Abstract

Providing a plastic material in the form of compressed plastic material particles; - filling the compressed plastic material particles with at least one blowing agent under the influence of pressure; expanding the plastic material particles filled with at least one blowing agent to produce foamed plastic particles under the influence of temperature; A method for producing expanded plastic particles comprising the steps of:

Description

Technical Field

[0001] The present invention relates to a method for producing foamed plastic particles.

Background Art

[0002] Methods for producing foamed plastic particles to be further processed, particularly methods for producing particle foam molded bodies, are basically known from the prior art.

[0003] Known methods for producing foamed plastic particles are based on a two-step process. In the first step, a thermoplastic material is melted in an extruder, and a blowing agent is filled into the thermoplastic material melt thus produced in the extruder. In the second step, the thermoplastic material that comes out of the extruder in a strand shape and expands due to the action of the blowing agent is granulated or pulverized.

[0004] In the first step of the corresponding process, the blowing agent dissolves in the thermoplastic material melt depending on the pressure and temperature conditions in the extruder. After the thermoplastic material filled with the blowing agent exits the extruder, the plastic material expands as a result of the pressure drop, and the blowing agent is converted into the gas phase.

[0005] In the second step of the corresponding process, when the plastic material comes out of the extruder in a strand shape, it is granulated or pulverized using, for example, a cutting device. As described above, it expands immediately after exiting the extruder by the blowing agent, and as a result, foamed plastic particles that can be further processed in another process to form a particle foam molded body are obtained.

[0006] Known methods are relatively complex in both terms of equipment and process technology. Furthermore, foamed plastic particles produced by known methods need improvement in terms of characteristics such as the size, shape, and distribution of the bubbles. From the perspective of equipment and process technology, the possibility of influencing the corresponding characteristics of foamed plastic particles is clearly limited in known methods.

Summary of the Invention

[0007] Based on this, the present invention is particularly based on the object of providing an improved method for producing foamed plastic particles having properties that can be specifically adjusted for subsequent processing into particle foam moldings and their use or usage characteristics.

[0008] This object is achieved by the method according to claim 1. The dependent claims relate to possible embodiments of the method.

[0009] A first aspect of the present invention relates to a method for producing foamed plastic particles. Thus, the method described herein is used for the production of foamed plastic particles. Thus, the plastic particles produced or producible according to the method are plastic particles having a cellular structure, at least partially, and in some cases completely. The plastic particles can have a specific (further) expansion capacity due to a specific content of a blowing agent, even if they are residues from the described method or blowing agents subsequently introduced in another process step. Thus, the foamed plastic particles that can be produced or are produced according to the method can be expandable and / or (mechanically) compressible or compressible due to their cellular structure. In all cases, the plastic particles that can be produced or generated according to the method can be called or considered "foamed particles" or "foamed beads".

[0010] The foamed plastic particles that can be produced according to the method and are hereinafter also abbreviated as "plastic particles" can be further processed in one or more independent downstream processes to form a particle foam molding. The further processing of the foamed plastic particles into a particle foam molding can be carried out using steam or superheated steam (steam-based) or without using steam or superheated steam (non-steam-based or dry).

[0011] The steps of the method for producing foamed plastic particles are described in detail below.

[0012] In the first step of the method, the plastic material is provided in the form of compressed plastic material particles. The compressed plastic material particles provided according to the method are sometimes also referred to as "compressed plastic particles". Thus, the plastic material considered as the starting material, which is typically a thermoplastic material, is provided in the form of compressed (thermoplastic) plastic material particles in the first step of the method. Thus, the compressed plastic material provided is in particulate form, i.e., exists in a bulk form or shape in particular. Thus, in the first step, generally at least one means for providing a compressed plastic material in granular form, i.e., in a bulk form or shape in particular, in the form of corresponding compressed plastic material particles is carried out. The density of the compressed plastic material particles provided in the first step of the method is usually in the range of 0.8 - 2.2 g / cm 3 , from which the compression characteristics of the provided compressed plastic material particles are obtained, and thus the matrix of the provided compressed plastic material particles does not have a (substantial) porous or cellular structure.

[0013] The matrix of the compressed plastic material particles can contain at least one additive or additional material such as an elongate, spherical, or platelet-shaped filler. In particular, in the case of compressed plastic material particles containing an additive or additional material, the density can (substantially) exceed 1 g / cm 3 . The corresponding additive or material can exist by itself or act in cellular form.

[0014] The first step of the method can be carried out optionally, at least partially automated, or partially automated, using a feeding device configured to continuously or discontinuously feed the corresponding plastic material in the form of compressed plastic material particles. The corresponding feeding device can be, for example, a conveyor device that can convey the compressed plastic material particles to be processed into the corresponding foamed plastic particles to a filling device that performs the second step of the method. The corresponding conveying device can take the form of, for example, a belt conveyor or a flow conveyor, or can include a belt conveyor or a flow conveyor. Thus, the conveyance of the compressed plastic material particles to the filling device that performs the second step of the method, or into the filling device, can include picking up the compressed plastic material particles in the flow of conveyance, and thus, the compressed plastic material particles can be conveyed by the flow of conveyance to the filling device that performs the second step of the method, or into the filling device.

[0015] In the second step of the method, the compressed plastic material particles are filled with a blowing agent, at least under the influence of pressure. Thus, in the second step, the compressed plastic material particles are filled with a blowing agent, at least under the influence of pressure, and if necessary, depending on the material, in addition to a specific pressure, a specific (elevated) temperature can also be applied. Thus, in the second step, generally, at least one means for filling the compressed plastic material particles with a blowing agent is carried out, at least under the influence of pressure, and thus, at least under pressure. Phenomenologically, the concentration of the blowing agent in each compressed plastic material particle is usually carried out in the second step of the method. The concentration of the blowing agent in each compressed plastic material particle can, in particular, depending on the chemical composition of the compressed plastic material particles, the blowing agent and the additives or materials that may be contained therein, as well as, as described above, typically depending on the pressure or temperature conditions selected depending on the material, for example, can result from the process of absorption and / or dissolution of the blowing agent in each compressed plastic material particle, or can occur through the process of absorption and / or dissolution of the blowing agent in each compressed plastic material particle.

[0016] Gases such as carbon dioxide, or mixtures containing carbon dioxide and / or nitrogen, such as air, can be used as blowing agents. Generally, any flammable or non-flammable organic gas, i.e., in particular, butane or pentane, or noble gases, i.e., in particular, inert gases such as helium, neon, argon, etc., or nitrogen, or mixtures thereof can be used. Thus, the term "blowing agent" can also include mixtures of chemically and / or physically different blowing agents. The blowing agent is typically selected taking into account its solubility in the compressed plastic material particles, and thus, is selected taking into account the chemical and / or physical constitution or composition of the compressed plastic material particles. If the compressed plastic material particles contain additives or additive materials, the properties such as the chemical and / or physical constitution of the additives or additive materials can also be taken into account when selecting the blowing agent.

[0017] The second step of the method can be carried out optionally at least partially automated or semi-automated using a filling device configured to carry out a corresponding filling process by filling the compressed plastic material particles with a blowing agent, at least under the influence of pressure. The corresponding filling device can be configured, for example, as an autoclave device, i.e., generally as a pressure vessel device with a temperature-controllable pressure chamber or process chamber, or can be provided with such a pressure vessel device. The corresponding filling device can further be provided with a temperature control device configured to control the temperature of the corresponding pressure chamber or process chamber. In all cases, the corresponding filling device can be provided with a control unit and / or an adjustment unit implemented from a hardware and / or software perspective, which is configured to control and / or adjust, i.e., generally set, specific dynamic pressure and / or static pressure and / or temperature parameters within the corresponding pressure chamber or process chamber.

[0018] In the third step of this method, the compressed plastic material particles filled with a blowing agent are foamed under the influence of temperature, i.e., especially under the influence of high temperature, to produce foamed plastic particles. Therefore, the compressed plastic material particles filled with a blowing agent are usually, in the third step of this method, exposed to high temperature, i.e., generally to thermal energy, as a result of which gas evolution and expansion of the blowing agent contained in the compressed plastic material particles occur. This usually occurs in a dry state, i.e., in the absence of external influence of fluids such as steam or water. In particular, due to the gas evolution of the blowing agent in the thermally softened or softened compressed plastic material particles, the plastic material particles expand, and after cooling or "freezing", plastic particles having a permanent cellular structure are formed, and thus, the produced foamed plastic particles are formed. Therefore, in the third step of this method, generally, at least one measure for gas evolution or expansion of the blowing agent contained in the compressed plastic material particles, which is at least softened or softened by the influence of temperature, i.e., at least thermally, is carried out to produce foamed plastic particles. Phenomenologically, in the third step of this method, in particular, due to the desorption of the blowing agent from the softened or softened compressed plastic material particles, the formation and growth of bubbles occur within the compressed plastic material particles, whereby foamed plastic particles are produced. The formation of bubbles is usually based on the desorption of the aforementioned blowing agent at the nucleation points of the plastic material particles softened or softened by the influence of temperature, while the growth of bubbles is usually based on the expansion due to the overpressure of the blowing agent within the already formed bubbles. Also, as described above, the cellular structure formed by this method, or the expanded state realized thereby, is permanently "frozen" or fixed by the temperature drop of the foamed plastic particles produced by this method, i.e., for example, by cooling in the environment.

[0019] Basically, after pressurization in the second step of the method, i.e., especially after the pressure drop to normal or standard conditions, the desorption process occurs within each compressed plastic material particle filled with the blowing agent and typically softens due to thermal conditions. The desorption process of the blowing agent represents an essential prerequisite for the bubble formation process and the bubble growth process within each plastic material particle required for the production of the foamed plastic particles. The foamed plastic particles produced according to the method are formed in the third step of the method from the compressed plastic material particles that exist after the second step of the method, are filled with the blowing agent, and are typically softened for thermal reasons, and are formed especially as a result of the corresponding desorption process.

[0020] As will be explained below, by controlling the bubble formation process and the bubble growth process related to the corresponding desorption, it is possible to realize a bubble structure with locally different bubble characteristics, and thus a stepped foamed plastic particle.

[0021] The inventors assume that, when using a suitable compressed starting material, nucleation combined with the targeted adjustment of the softening behavior is likely to have a decisive influence on the desorption of the blowing agent surprisingly. In particular, a large number of small bubbles are formed by a large number of individual nucleation points or nucleation sites, and as a result, a fine bubble structure is obtained within each foamed plastic particle. The corresponding fine bubble structure is characterized especially by the small bubbles within each foamed plastic particle and their nearly uniform distribution.

[0022] Generally, foamed plastic particles with a bubble size in the range of 0.5 - 250 μm can be produced. Thus, the actual bubble size, of course, generally refers to the average value here, but can be adjusted over a very wide range depending on the selected process conditions and can be adjusted according to the process. The same applies to the distribution of the bubble size within each foamed plastic particle.

[0023] In particular, the (average) bubble size is less than 100 μm, in particular less than 90 μm, more particularly less than 80 μm, more particularly less than 70 μm, more particularly less than 60 μm, more particularly less than 50 μm, more particularly less than 45 μm, more particularly less than 40 μm, more particularly less than 35 μm, more particularly less than 30 μm, more particularly less than 25 μm, more particularly less than 24 μm, more particularly less than 23 μm, more particularly less than 22 μm, more particularly less than 21 μm, more particularly less than 20 μm, more particularly less than 19 μm, more particularly less than 18 μm, more particularly less than 17 μm, more particularly less than 16 μm, more particularly less than 15 μm, more particularly less than 14 μm, more particularly less than 13 μm, more particularly less than 12 μm, more particularly less than 11 μm, more particularly less than 10 μm, or smaller. All intermediate values not explicitly listed here are also conceivable.

[0024] The third step of the method is configured, if necessary, to expand the blowing agent, at least under the influence of temperature, to produce foamed plastic particles, or to carry out the corresponding expansion process, using an expansion device that is configured to be at least partially automated or carried out semi-automatically. The corresponding expansion device can be configured, for example, as a heating device, i.e., generally as a temperature control device comprising a temperature control chamber or process chamber that is temperature controllable or temperature controlled, or can be provided with such a temperature control device. The corresponding tempering device can further be provided with a conveying device configured to convey plastic material particles that expand along a conveying path through a corresponding tempering chamber or process chamber. In all cases, the corresponding expansion device can be provided with a control unit and / or an adjustment unit implemented from a hardware and / or software perspective, which is configured to control and / or adjust specific dynamic and / or static conveying and / or temperature and / or radiation parameters within the corresponding temperature control chamber or process chamber, i.e., generally to set them.

[0025] In particular, the third step of the method can be carried out continuously as required, which is more advantageous than a batch process.

[0026] The density of the foamed plastic particles produced in the third step of the method is usually significantly lower than the initial density of the compressed plastic material particles provided in the first step. As a result, the bubble characteristics of the plastic material particles that can be produced or are produced by this method are obtained. Therefore, the plastic material particles that can be produced or are produced according to this method have a cellular structure. The bulk density of the cellular plastic particles produced in the third step of the method is usually several times lower than the bulk density of the compressed plastic material particles provided in the first step of the method.

[0027] The foamed plastic particles produced in the third step of the method are expandable, as further described above, which can be an essential characteristic for the further processing of the foamed plastic particles for producing particle foamed molded articles, especially the described vapor-based or non-vapor-based ones.

[0028] Therefore, compared with known methods, this method is characterized by special dynamic process control, which requires the softening necessary for expansion. However, in contrast to the extrusion process, it is not necessary to completely melt the compressed plastic material filled with the blowing agent. Therefore, it does not require a high load of pressure and temperature to melt the plastic material together with the blowing agent. The dynamic process control, i.e., the rapid (volume) heating made possible especially thereby, is also important for excellent energy efficiency and the very fine cell morphology further described below (since there is no time for cell coalescence). Therefore, this process can fill the compressed plastic material particles with the blowing agent and can convert the corresponding plastic material particles filled with the blowing agent into foamed plastic particles under the influence of at least temperature, especially under the influence of temperature and pressure, and thus involves a relatively (significantly) simplified apparatus and process engineering effort for its implementation.

[0029] Furthermore, the properties of the foamed plastic particles that can be manufactured or produced according to the present method are improved, especially with regard to the size, morphology, and distribution of the bubbles, which can be easily adjusted and very well controlled in the filling process carried out in the second step of the method and the expansion process carried out in the third step of the method, and are obtained from the process conditions that can be adjusted and controlled very well.

[0030] Therefore, the present method enables a significantly extended process window that can be accurately set or controlled for each plastic material, and in principle, it becomes possible to manufacture foamed plastic particles having desired properties from any (thermoplastic) compressed plastic material particles.

[0031] As shown, the filling of the blowing agent into the compressed plastic material particles can be carried out under the influence of pressure and temperature. Thus, for filling the blowing agent into the compressed plastic material particles and, in a further process, for specifically setting the particular properties of the foamed plastic particles to be manufactured or manufactured, in particular depending on the material, the parameters that can be changed are, therefore, firstly, the general pressure and temperature conditions in the second step of the method. Of course, the time in the second step of the method, i.e., especially the duration of the pressure and temperature conditions, is also a parameter that affects the filling of the blowing agent into the compressed plastic material particles, i.e., in particular, the dissolution of the blowing agent in the compressed plastic material particles.

[0032] The following shows as an example the specific parameters for carrying out the second step of the method.

[0033] The filling of the blowing agent or a blowing agent into the compressed plastic material particles may be, for example, in the range of 1 to 200 bar, in particular in the range of 1 to 190 bar, more particularly in the range of 1 to 180 bar, more particularly in the range of 1 to 170 bar, more particularly in the range of 1 to 160 bar, more particularly in the range of 1 to 150 bar, more particularly in the range of 1 to 140 bar, more particularly in the range of 1 to 130 bar, more particularly in the range of 1 to 120 bar, more particularly in the range of 1 to 110 bar, more particularly in the range of 1 to 100 bar, more particularly in the range of 1 to 90 bar, more particularly in the range of 1 to 80 bar, more particularly in the range of 1 to 70 bar, more particularly in the range of 1 to 60 bar, more particularly in the range of 1 to 50 bar, more particularly in the range of 1 to 40 bar, more particularly in the range of 1 to 30 bar, more particularly in the range of 1 to 20 bar, more particularly in the range of 1 to 10 bar, depending in particular on the compressed plastic material particles and / or the chemical composition of the blowing agent at a certain pressure. Instead of 1 bar, 2, 3, 4, 5, 6, 7, 8, 9, or 10 bar can also be used as the lower limit value. All intermediate values not explicitly listed here are likewise conceivable. The above-mentioned pressures given as examples refer in particular to the pressure in the pressure chamber of the corresponding filling device or in the process chamber during the execution of the second step of the method.

[0034] The filling of the blowing agent or a blowing agent into the compressed plastic material particles may be at a temperature in the range of 0 to 250 °C, particularly in the range of 0 to 240 °C, more particularly in the range of 0 to 230 °C, more particularly in the range of 0 to 220 °C, more particularly in the range of 0 to 210 °C, more particularly in the range of 0 to 200 °C, more particularly in the range of 0 to 190 °C, more particularly in the range of 0 to 180 °C, more particularly in the range of 0 to 170 °C, more particularly in the range of 0 to 160 °C, more particularly in the range of 0 to 150 °C, more particularly in the range of 0 to 140 °C, more particularly in the range of 0 to 130 °C, more particularly in the range of 0 to 120 °C, more particularly in the range of 0 to 110 °C, more particularly in the range of 0 to 100 °C, more particularly in the range of 0 to 90 °C, more particularly in the range of 0 to 80 °C, more particularly in the range of 0 to 70 °C, more particularly in the range of 0 to 60 °C, more particularly in the range of 0 to 50 °C, more particularly in the range of 0 to 40 °C, more particularly in the range of 0 to 30 °C, more particularly in the range of 0 to 20 °C, depending, for example, particularly on the chemical composition of the compressed plastic material particles and / or the blowing agent. All intermediate values not explicitly listed here are likewise considered. The above temperatures given as examples particularly refer to the temperature in the pressure chamber or the process chamber of the corresponding filling device during the execution of the second step of the method.

[0035] The filling of the blowing agent or a blowing agent into the compressed plastic material particles can be carried out, for example, in the range of 1 to 1000 hours, particularly in the range of 1 to 950 hours, more particularly in the range of 1 to 900 hours, more particularly in the range of 1 to 850 hours, more particularly in the range of 1 to 800 hours, more particularly in the range of 1 to 750 hours, more particularly in the range of 1 to 700 hours, more particularly in the range of 1 to 650 hours, more particularly in the range of 1 to 600 hours, more particularly in the range of 1 to 550 hours, more particularly in the range of 1 to 500 hours, more particularly in the range of 1 to 450 hours, more particularly in the range of 1 to 400 hours, more particularly in the range of 1 to 350 hours, more particularly in the range of 1 to 300 hours, more particularly in the range of 1 to 250 hours, more particularly in the range of 1 to 200 hours, more particularly in the range of 1 to 150 hours, more particularly in the range of 1 to 100 hours, particularly in the range of 1 to 90 hours, particularly in the range of 1 to 80 hours, particularly in the range of 1 to 70 hours, particularly in the range of 1 to 60 hours, particularly in the range of 1 to 50 hours, particularly in the range of 1 to 40 hours, particularly in the range of 1 to 30 hours, particularly in the range of 1 to 20 hours, particularly in the range of 1 to 10 hours, depending especially on the chemical composition of the compressed plastic material particles and / or the blowing agent. All intermediate values not explicitly listed here are likewise considered. As described above, the exemplary duration refers in particular to the pressure or temperature applied to the plastic material particles in the pressure chamber or process chamber of the corresponding filling device during the execution of the second step of the method.

[0036] Specific parameters for performing the third step of the method are shown below as an example.

[0037] Under the influence of temperature, in particular depending on the chemical composition of the plastic particle material filled with the blowing agent and / or the blowing agent, expanding the plastic material particles filled with the blowing agent to produce foamed plastic particles can be carried out, for example, at normal pressure, i.e., an ambient pressure of about 1 bar. Thus, special pressure levels such as positive or negative pressure levels are possible but not absolutely necessary to foam the compressed plastic material particles filled with the blowing agent to produce cellular plastic particles, and they simplify the foaming process fundamentally.

[0038] Expanding plastic material particles filled with a blowing agent under the influence of temperature to produce foamed plastic particles can be carried out, for example, depending on the plastic particle material filled with the blowing agent and / or the chemical composition of the blowing agent, in the range of 1 to 300 °C, particularly in the range of 1 to 290 °C, more particularly in the range of 0 to 280 °C, more particularly in the range of 0 to 270 °C, more particularly in the range of 0 to 260 °C, more particularly in the range of 0 to 250 °C, more particularly in the range of 0 to 240 °C, more particularly in the range of 0 to 230 °C, more particularly in the range of 0 to 220 °C, more particularly in the range of 0 to 210 °C, more particularly in the range of 0 to 200 °C, more particularly in the range of 0 to 190 °C, more particularly in the range of 0 to 180 °C, more particularly in the range of 0 to 170 °C, more particularly in the range of 0 to 160 °C, more particularly in the range of 0 to 150 °C, more particularly in the range of 0 to 140 °C, more particularly in the range of 0 to 130 °C, more particularly in the range of 0 to 120 °C, more particularly in the range of 0 to 110 °C, more particularly in the range of 0 to 100 °C, more particularly in the range of 0 to 90 °C, more particularly in the range of 0 to 80 °C, more particularly in the range of 0 to 70 °C, more particularly in the range of 0 to 60 °C, more particularly in the range of 0 to 50 °C, more particularly in the range of 0 to 40 °C, more particularly in the range of 0 to 30 °C, more particularly in the range of 0 to 20 °C. All intermediate values not explicitly listed here are similarly considered.

[0039] The above temperatures particularly refer to the inlet temperature when the compressed plastic material particles filled with the blowing agent enter the corresponding expansion device and / or the outlet temperature when the foamed plastic particles exit the corresponding expansion device. The corresponding inlet temperature and outlet temperature may be the same, similar, or different. When the corresponding expansion device is provided with a conveying device arranged to convey the plastic material particles filled with the blowing agent along the corresponding tempering device, the aforementioned temperature refers to the temperature (inlet temperature) when the compressed plastic particle material filled with the blowing agent enters the corresponding expansion device or tempering device, that is, the temperature when entering the initial region of the corresponding conveying device, and / or the temperature (outlet temperature) when the plastic particles exit the corresponding expansion device or temperature control device, that is, the temperature when exiting the end region of the corresponding conveying device. Usually, the inlet temperature is lower than the outlet temperature.

[0040] The expansion of foaming agent-filled compressed plastic material particles under the influence of temperature can be achieved by irradiating the foaming agent-filled compressed plastic material particles with high-energy thermal radiation, particularly infrared rays. In particular, infrared radiation having a wavelength in the range of 1 to 15 μm, particularly in the range of 1.4 to 8 μm, and even more particularly in the range of 1.4 to 3 μm is considered. The wavelength of the infrared rays is usually selected according to the material. The temperature control of the foaming agent-filled compressed plastic material particles, i.e., particularly heating, is achieved by particularly selecting and / or adjusting the wavelength according to the material. This means that the heating of the foaming agent-filled compressed plastic material particles can be carried out in a very targeted manner without risking the undesirable softening of the foaming agent-filled compressed plastic material particles, i.e., the undesirable melting or complete melting of the softened plastic material particles, which is not desirable for the foaming method of the foaming agent-filled plastic material particles, by selecting and / or adjusting the characteristics of the energy-rich radiation, particularly its wavelength, according to the material. As a result of the investigation, infrared rays, in combination with a conveying device, enable a very easily controllable volumetric heating, a controllable softening process, and thus a controllable expansion process that is essential for setting the properties of the produced foamed plastic particles, which is particularly suitable for this purpose for the targeted expansion of the foaming agent-filled compressed plastic material particles.

[0041] In particular, the expansion of plastic material particles filled with a blowing agent can be carried out under the influence of temperature by irradiating the compressed plastic material particles filled with the blowing agent with high-energy thermal radiation, in particular infrared radiation. The plastic material particles filled with the blowing agent are conveyed along at least one conveying path defined by a conveying device, in particular continuously, along at least one corresponding high-energy radiation, i.e., a radiation generating device that generates in particular infrared radiation. The corresponding radiation generating device can in particular be configured as, or can include, an infrared oven, in particular a continuous infrared oven. The corresponding infrared oven can comprise one or more infrared emitters arranged or formed along the corresponding conveying path. The corresponding infrared emitter can have a radiation power that is variable, for example, in the range of 1 to 500 kW, more particularly in the range of 1 to 450 kW, more particularly in the range of 1 to 400 kW, more particularly in the range of 1 to 350 kW, more particularly in the range of 1 to 300 kW, more particularly in the range of 1 to 250 kW, more particularly in the range of 1 to 200 kW, more particularly in the range of 1 to 150 kW, more particularly in the range of 1 to 100 kW, more particularly in the range of 1 to 50 kW. Instead of 1 kW, 2, 3, 4, 5, 6, 7, 8, 9 or 10 kW can also be used as the lower limit value. All intermediate values not explicitly listed here are also conceivable.

[0042] The above output refers in particular to the area output per square meter. According to investigations, good results are obtained in particular with an area output of 5 to 100 kW / m 2 ². A variable radiator or variable radiator (area) output can be used to generate different temperature zones, thereby also providing parameters that affect the expansion process.

[0043] According to this method, as described above, after expanding plastic material particles filled with a blowing agent to produce foamed plastic particles, the produced foamed plastic particles can be cooled under the influence of temperature (especially a temperature lower than the temperature of the previous expansion process). It is convenient for the cooling to be carried out rapidly, and the bubble structure of the foamed plastic particles can be "frozen" after the expansion process. In this way, furthermore, it is possible to particularly prevent the overall or local expansion of plastic particles that may be undesirable, for example, after the expansion process, which can retain the bubble structure of plastic particles that may be desirable, for example, after the expansion process. In particular, room temperature can be used as the reference temperature, and in particular, the cooling can be carried out from a process temperature above the reference temperature to a cooling temperature below the process temperature or the reference temperature, especially room temperature. Therefore, a separate tempering device for cooling the plastic particles is not absolutely necessary, and it is sufficient to cool the plastic particles to room temperature or let them age at room temperature after the foaming process.

[0044] According to this method, as also shown above, at least one, especially functional additive or additional material, for example, fibrous substances or materials and / or dyes or coloring materials and / or nucleating substances or materials and / or additives for adjusting the melt viscosity such as chain extenders, or substances or materials such as graphite and carbon black for increasing the absorption coefficient, etc., can be provided or used for a compressed plastic particle material, and can be provided or used to particularly affect or control the softening behavior of plastic material particles filled with a blowing agent containing the compressed plastic particle material. Therefore, the compounded compressed plastic material particles can also be filled with a blowing agent and foamed, and as a result, foamed plastic particles with special properties can be obtained. In particular, through a targeted selection and concentration of appropriate additives or materials, custom-made plastic particles can be manufactured for specific applications or fields of application. The additives or materials may be introduced into the compressed plastic material particles during production.

[0045] Basically, organic or inorganic fibrous substances or materials, such as aramid, glass, carbon or natural fibers, may be used, in particular, fibrous substances or materials can be used to achieve special material properties of the foamed plastic particles that can be manufactured or are manufactured according to this method, or of the molded particle foam parts manufactured from the foamed plastic particles that can be manufactured or are manufactured according to this method, with respect to further processing. The corresponding foamed plastic particles or the particle foam moldings produced therefrom can be characterized, on the one hand, by a special density due to their cell structure and, on the other hand, by special mechanical properties due to the mechanical bonding of the adjacent cells within each foamed plastic particle and / or between each adjacent foamed plastic particle, which is caused in particular by the treatment. During the subsequent processing into particle foam moldings, these special mechanical properties can be utilized locally or integrally or further modified. The same applies, basically regardless of their chemical composition, to non-fibrous or non-fibrous-shaped additives or additive materials, such as spherical or spherical-shaped or platelet-shaped or platelet-shaped organic and / or inorganic additives or additive materials.

[0046] In addition to particularly influencing the mechanical properties of the plastic particles, it is also possible to particularly influence the electrical and / or thermal properties of the plastic particles, for example, by means of suitable additives or materials. Thus, plastic particles having special electrical conductivity and / or thermal conductivity properties can be manufactured, for example, using conductive and / or thermally conductive additives or materials such as metal and / or carbon black particles.

[0047] The concentration of the corresponding additive or additive material can in principle be freely selected, but usually varies depending on the material. Thus, by way of example, it has merely been shown that particulate plastic materials containing one (or more) additives or additive materials can be provided or used at concentrations between 0.01% by weight, which applies in particular to chemically active additives, and 60% by weight, which applies in particular to fibrous additives. As shown, the concentration usually depends on the specific chemical and / or physical properties of the additive or additive material, or combinations thereof.

[0048] It has been stated that in principle any thermoplastic material can be provided or used as the starting material. By way of example, it is understood that particulate material of plastics from the group of acrylonitrile - butadiene - styrene, acrylonitrile - butadiene - styrene blends, polyamides, polyamide blends, polycarbonates, polycarbonate blends, polyethylene, polyethylene blends, polypropylene, polypropylene blends, polyphenylene ether, polyphenylene ether blends, thermoplastic elastomers, polyethylene terephthalate, polyethylene terephthalate blends, polybutylene terephthalate, polybutylene terephthalate blends, polystyrene, polystyrene blends, polyvinyl chloride, thermoplastic elastomer blends is used in accordance with the method. Blends or mixtures of different thermoplastic materials can also be used, and modified PPE (mPPE) is mentioned merely as an example in this context.

[0049] When blends are used which contain at least two components which differ with respect to at least one chemical and / or physical parameter and / or a parameter regarding the molecular structure, these can in principle be present in any desired proportional composition, the respective proportions adding up to 100% by weight. Thus, the first component can have any weight proportion from 1 to 99% by weight and the second component can have any weight proportion from 99 to 1% by weight, the respective proportions adding up to 100% by weight. Of course, proportions below 1% by weight and above 99% by weight are also conceivable.

[0050] As described above, one or more additives such as fibers can be added to all plastic materials used. All plastic materials used may be recycled products or may contain some recycled products.

[0051] It has been mentioned that the properties of the foamed plastic particles that can be produced according to this method may be affected particularly by the process conditions during the filling process and the expansion process.

[0052] According to this method, depending on the selected process conditions, foamed plastic particles having a uniformly or non-uniformly distributed cell structure can be produced. Thus, the properties within each foamed plastic particle, i.e., in particular the distribution of the cell structure, can be (also) affected by the pressure, temperature, time during filling or expansion, and the transport time or residence time or conditions between individual steps of the method, in addition to the material-specific parameters.

[0053] When foamed plastic particles having a non-uniformly distributed cell structure are produced according to this method, each foamed plastic particle may have a different number and / or morphology of cells in the peripheral region from the core region. Thus, due to the different distribution of the number of cells and / or the morphology of the cells, stepwise foamed plastic particles having a special range of properties can be produced. Thus, the stepwise foamed plastic particles can have different cell characteristics in the (outer) peripheral region from the (inner) core region, for example, like core-shell particles.

[0054] The correspondingly configured foamed plastic particles can be achieved in particular by filling the compression starting material with the blowing agent for a (very) short time, and the blowing agent accumulates only near the outer periphery and expansion occurs particularly at the outer periphery. Conversely, an (excessively) long aging period between the filling and the expansion of the blowing agent can mainly result in foamed plastic particles in which the "core" has foamed.

[0055] Generally, it is possible to produce foamed plastic particles with a bubble size in the range of 0.5 to 250 μm. Thus, the actual bubble size, which of course generally refers to the average value here, can be adjusted over a very wide range depending on the selected process conditions and can therefore be adjusted according to this process. The same applies to the distribution of the bubble sizes within each foamed plastic particle.

[0056] It is also a fact that generally, depending in particular on the degree of expansion and, if necessary, the filler content, foamed plastic particles with a bulk density in the range of 20 to 1500 g / l can be produced by this process. The actual bulk density, of course, usually refers to the average here too, but can be adjusted over a very wide range depending on the selected process conditions and can therefore be made to order.

[0057] The following is a purely exemplary list of compressible plastic material particles that can be particularly processed or have been processed as part of this process, and the relevant parameters for carrying out the second and third steps of this process.

[0058] In the first example, compression polycarbonate plastic granulates, i.e., plastic material particles of polycarbonate with a bulk density in the range of 650 to 720 g / l, were prepared in the first step of the method. In the second step of the method, the compressed plastic material particles were filled with carbon dioxide as a blowing agent at a pressure in the range of 37 to 55 bar for 18 hours in a pressure vessel without separate tempering. In the third step of the method, the compressed plastic material particles filled with the blowing agent were conveyed, either continuously or discontinuously, through an infrared continuous furnace equipped with a plurality of infrared emitters, i.e., by conveying the plastic material particles along a conveying section or tempering section of about 5 m in length formed by a plurality of tempering elements in the form of infrared emitters with a total emitter output of about 10 kW, to expand the plastic material particles filled with the blowing agent. The temperature of the conveyor belt at the inlet of the conveyor section was about 140 °C, the temperature of the conveyor belt at the outlet of the conveyor / tempering section was about 180 °C, and the conveying speed was about 700 mm / s. The bulk density of the foamed plastic particles produced by this method was about 100 g / l.

[0059] In the second example, compressed polycarbonate / polyethylene terephthalate plastic granulates, i.e., plastic material particles made from a polycarbonate / polyethylene terephthalate blend with a bulk density of about 680 μm, were provided in the first step of the method. In the second step of the method, the compressed plastic material particles were filled with carbon dioxide as a blowing agent at a pressure of about 50 bar for 20 hours in a pressure vessel without separate tempering. In the third step of the method, the compressed plastic material particles filled with the blowing agent were expanded by transporting them continuously or discontinuously, in particular, through an infrared continuous furnace equipped with a plurality of infrared emitters, i.e., along a transport section or tempering section of about 5 m in length formed by a plurality of tempering elements in the form of infrared emitters with a total emitter output of about 10 kW. The temperature of the conveyor belt at the inlet of the conveyor section was about 80 °C, the temperature of the conveyor belt at the outlet of the conveyor section or temperature control section was about 240 °C, and the transport speed was about 450 mm / s. The bulk density of the foamed plastic particles produced by this method was about 340 g / l.

[0060] In the third example, compressed polybutylene terephthalate plastic granulates, i.e., plastic material particles of polybutylene terephthalate having a bulk density of about 740 g / l, were prepared in the first step of the method. In the second step of the method, the compressed plastic material particles were filled with carbon dioxide as a blowing agent at a pressure of about 50 bar for 80 hours in a pressure vessel without separate tempering. In the third step of the method, the compressed plastic material particles filled with the blowing agent were expanded by being conveyed, in particular continuously or discontinuously, through an infrared continuous furnace equipped with a plurality of infrared emitters, i.e., along a conveying section or a tempering section of about 5 m in length formed by a plurality of tempering elements in the form of infrared emitters with a total emitter output of about 20 kW, thereby conveying the plastic material particles filled with the blowing agent. The temperature of the conveyor belt at the inlet of the conveyor section was about 100 °C, and the temperature of the conveyor belt at the outlet of the conveyor / tempering section was about 220 °C. The conveying speed was about 450 mm / s. The bulk density of the foamed plastic particles produced by this method was about 100 g / l.

[0061] In the fourth example, compressed polyphenylene ether / polystyrene plastic granules, i.e., plastic material particles of a polyphenylene ether / polystyrene blend having a bulk density of about 715 g / l, were prepared in the first step of the method. In the second step of the method, the compressed plastic material particles were filled with carbon dioxide as a blowing agent at a pressure of about 55 bar for 120 hours in a pressure vessel without separate tempering. In the third step of the method, the compressed plastic material particles filled with the blowing agent were transported, in particular continuously or discontinuously, through an infrared continuous furnace equipped with a plurality of infrared emitters, i.e., along a transport section or tempering section of about 5 m in length formed by a plurality of tempering elements in the form of infrared emitters with a total emitter output of about 18 kW, to expand the plastic material particles filled with the blowing agent. The temperature of the conveyor belt at the inlet of the conveyor section was about 80 °C, and the temperature of the conveyor belt at the outlet of the conveyor / tempering section was about 220 °C. The transport speed was about 400 mm / s. The bulk density of the foamed plastic particles produced by this method was about 180 g / l.

[0062] A second aspect of the present invention relates to a particulate foamed material formed of or containing foamed plastic particles produced according to the method of the first aspect.

[0063] A third aspect of the present invention relates to a method for producing a granular foamed molded body by processing the plastic granular material according to the second aspect.

[0064] A fourth aspect relates to an apparatus for producing foamed plastic particles, in particular according to the method of the first aspect, · a first apparatus configured to fill a compressed thermoplastic with a blowing agent under the influence of pressure, in particular an apparatus provided with a filling device in the form of a pressure vessel device, and ·A second device configured to produce foamed plastic particles by expanding a blowing agent under the influence of temperature, the device particularly comprising an expansion device in the form of a radiation generating device for generating high energy radiation, in particular infrared radiation, and comprises.

[0065] The second device can comprise a conveying device, in particular a device combining a conveying device and a temperature control device. The corresponding combined conveying and temperature control device can be configured, for example, as a continuous furnace, in particular as an infrared continuous furnace comprising one or more infrared emitters, or can comprise at least one such furnace.

[0066] The second device can also be assigned a stress relaxation device, such as a stress relaxation chamber, in which the produced foamed plastic particles are stored for a predetermined time under defined chemical and / or physical conditions, in particular under a defined temperature ratio. The corresponding stress relaxation device can, for example, also be configured as a decompression device or can comprise such a device.

[0067] It is also conceivable that this device further comprises a conveying device through which the produced foamed plastic particles are conveyed continuously or discontinuously through the corresponding relaxation space.

[0068] This device can further comprise a suitable handling device for handling the compressed plastic material particles in order to supply the compressed plastic material particles and / or to remove the produced foamed plastic particles. The corresponding handling device can be configured as a conveying device or can comprise a conveying device. In particular, conveying devices suitable for conveying bulk materials are considered, such as a pneumatic conveying device configured to form a conveying stream.

[0069] Basically, this device can comprise a conveying device capable of conveying the compressed plastic material particles and further the foamed plastic particles continuously or discontinuously through the individual devices of this device.

[0070] All embodiments related to the method according to the first aspect are equally applicable to the particulate foamed material according to the second aspect, the method according to the third aspect, and the apparatus according to the fourth aspect.

Brief Description of the Drawings

[0071] The present invention will be described again below as an example of an embodiment with reference to the drawings. The drawings are as follows.

[0072] FIG. 1 is a flowchart showing a method according to an embodiment.

[0073] FIG. 2 is a schematic diagram of an apparatus for carrying out the method according to an embodiment.

[0074] FIGS. 3 and 4 are schematic diagrams of foamed plastic particles produced according to the method according to an embodiment, respectively.

Embodiments for Carrying Out the Invention

[0075] FIG. 1 shows a flowchart showing a method according to an embodiment.

[0076] This method is a method for producing foamed plastic particles, and thus this method is used for the production of foamed plastic particles. Therefore, plastic particles that can be produced according to this method, or plastic particles produced according to this method, are plastic particles that have a bubble structure, at least partially, and in some cases completely. The plastic particles may also be residues from the described process or blowing agents that are subsequently introduced in another method step, and in particular may have a specific (further) expansion or compression capacity depending on the content of the blowing agent. Therefore, the cellular plastic particles that can be produced or manufactured according to this method may be expandable and / or (mechanically) compressible.

[0077] The foamed plastic particles that can be manufactured or produced according to the present method can be further processed in one or more independent downstream processes to form particle foam molded articles. Further processing the plastic particles into particle foam molded articles can be carried out using steam or superheated steam (steam-based), or without using steam or superheated steam (non-steam-based or dry).

[0078] The steps of the method for generating foamed plastic particles will be described in more detail below with reference to FIGS. 1 and 2.

[0079] In the first step S1 of the method, a plastic material is provided in the form of compressed plastic material particles. The provided compressed plastic material particles may sometimes be referred to as "compressed plastic particles". Thus, the compressed plastic material particles considered as starting materials, which are typically thermoplastic material particles, are provided in the first step of the method. Thus, the provided starting material is in particulate form, i.e., present in a bulk form or shape in particular. Thus, in the first step, generally at least one means for providing a (thermoplastic) plastic material in particulate form, i.e., in a bulk or shaped form in particular, in the form of corresponding compressed plastic material particles is carried out. The density of the plastic material particles provided in the first step of the method is usually in the range of 0.8 to 2.2 g / cm 3 so that the compression characteristics of the provided compressed plastic material particles are obtained, and thus the matrix of the provided compressed plastic material particles does not have a porous or cellular structure.

[0080] However, the matrix of the compressed plastic material particles may contain at least one additive or additional material such as an elongated, spherical or platelet-shaped filler. In particular, in the case of compressed plastic material particles containing additives or additional materials, the density may (significantly) exceed 1 g / cm 3 The corresponding additives or materials can be present or act in the form of bubbles.

[0081] The first step S1 of this method can be carried out at least partially automatically or semi-automatically using a feeding device 2, shown purely schematically in FIG. 2, which is configured to feed the corresponding compressed plastic material particles continuously or discontinuously as required. The corresponding feeding device 2 can be, for example, a conveying device that can convey the compressed plastic material particles to be processed into the corresponding foamed plastic particles to a filling device 3 that executes the second step of this method. The corresponding conveying device can be configured, for example, as a belt conveyor or a flow conveyor, or can be provided with such a device. Therefore, the conveyance of the compressed plastic material particles to the filling device 3 that executes the second step of this method, or into the filling device 3, can include picking up the compressed plastic material particles in the conveying stream, and thus the compressed plastic material particles can be conveyed by the conveying stream to the filling device 3 that executes the second step of this method, or into the filling device 3.

[0082] In the second step S2 of the process, the compressed plastic material particles are filled with a blowing agent, at least under the influence of pressure. Thus, at least under the influence of pressure, in the second step, the compressed plastic material particles are filled with a blowing agent, and, if necessary, depending on the material, a specific (high) temperature can also be applied in addition to a specific pressure. Thus, in the second step, generally, at least one means for filling the compressed plastic material particles with a blowing agent is carried out at least under the influence of pressure and thus at least under pressure. Phenomenologically, the concentration of the blowing agent in each of the compressed plastic material particles is usually carried out in the second step of the method. The concentration of the blowing agent in each of the compressed plastic material particles depends, in particular, on the chemical composition of the compressed plastic material particles, the blowing agent and any additives or materials that may be contained therein, and also, as described above, typically on the pressure or temperature conditions selected depending on the material, for example, it may result from the process of absorption and / or dissolution of the blowing agent in each of the compressed plastic material particles, or it may occur through the process of absorption and / or dissolution of the blowing agent in each of the compressed plastic material particles.

[0083] Gases such as carbon dioxide, or mixtures containing carbon dioxide and / or nitrogen, such as air, can be used as blowing agents. Generally, any combustible or non-combustible organic gas, i.e., in particular, butane or pentane, or noble gases, i.e., in particular, inert gases such as helium, neon, argon, etc., or nitrogen, or mixtures thereof can be used. Thus, the term "blowing agent" can also include mixtures of chemically and / or physically different blowing agents. The blowing agent is typically selected taking into account its solubility in the compressed plastic material particles and thus taking into account the chemical composition of the compressed plastic material particles. If the compressed plastic material particles contain additives or additive materials, the properties such as the chemical and / or physical constitution of the additives or additive materials can also be taken into account when selecting the blowing agent.

[0084] The second step S2 of this method can be carried out at least partially automatically or semi-automatically using a filling device 3, which is schematically shown purely in FIG. 2 and which is configured to fill the plastic material particles with a blowing agent, if necessary, at least under the influence of pressure, or to carry out a corresponding filling process. The corresponding filling device 3 can be configured, for example, as an autoclave device, i.e., generally as a pressure vessel device 3.1 having a pressure chamber or a process chamber, or it can be provided with such a pressure vessel device. The corresponding filling device 3 can further be provided with a temperature control device 3.2 configured to control the temperature of the corresponding pressure chamber or process chamber. The corresponding filling device can, in all cases, be provided with a control and / or adjustment unit 3.3 implemented in hardware and / or software, which is configured to control and / or adjust, i.e., generally to set, specific dynamic pressure and / or static pressure and / or temperature parameters within the pressure chamber or the process chamber.

[0085] In the third step S3 of this process, the compressed plastic material particles filled with a blowing agent are foamed under the influence of temperature, i.e., especially under the influence of high temperature, to produce foamed plastic particles. Therefore, in the third step of this method, the compressed plastic material particles filled with a blowing agent are usually exposed to a high temperature, i.e., generally exposed to thermal energy, as a result of which gas evolution and expansion of the blowing agent contained in the compressed plastic material particles occur. In particular, due to the gas evolution of the blowing agent in the thermally softened or softened compressed plastic material particles, the plastic material particles expand, and after cooling or "freezing", plastic particles with a permanent bubble structure are formed, and thus the foamed plastic particles to be manufactured are formed. Therefore, in the third step S3 of this process, generally, at least one measure is taken to degas or foam the blowing agent contained in the compressed plastic material particles that soften, or at least are affected by temperature and thus at least thermally soften, for the production of foamed plastic particles. Phenomenologically, in the third step of this method, in particular, due to the desorption of the blowing agent from the softened or softened compressed plastic material particles, bubble formation and growth occur within the compressed plastic material particles, whereby foamed plastic particles are produced. Bubble formation is usually based on the desorption of the aforementioned blowing agent at the nucleation points of the plastic material particles that soften or are softened by the influence of temperature, while bubble growth is usually based on the expansion due to the overpressure of the blowing agent within the already formed bubbles. Also, as described above, the bubble structure formed by this method, or the expanded state realized thereby, is permanently "frozen" or fixed by the temperature drop of the foamed plastic particles produced by this method, i.e., for example, by cooling in the environment.

[0086] Basically, after pressurization in the second step S2 of this step, that is, especially after the pressure drop to normal or standard state, the desorption process occurs within each compressed plastic material particle filled with the blowing agent and typically softens under thermal conditions. The desorption process of the blowing agent represents an essential prerequisite for the bubble formation and growth processes within each plastic material particle required for the production of the foamed plastic particles. In the third step S3 of this process, the foamed plastic particles produced according to this method are formed from the compressed plastic material particles existing after the second step S2 of this process, filled with the blowing agent, and typically soften under thermal conditions, especially as a result of the corresponding desorption process. As will be further explained, by controlling the bubble formation and bubble growth processes related to the corresponding desorption, a bubble structure with locally different bubble characteristics, and thus stepwise foamed plastic particles, can be realized.

[0087] The target adjustment of nucleation and softening behavior has a decisive influence on the desorption of the blowing agent. In particular, a large number of small bubbles are formed by a large number of individual nucleation points, and a fine bubble structure is obtained within each foamed plastic particle. The corresponding fine bubble structure is characterized in particular by small bubbles and their nearly uniform distribution within each foamed plastic particle.

[0088] Generally, foamed plastic particles with a bubble size in the range of 0.5 - 250 μm can be produced. Therefore, the actual bubble size, of course, generally refers to the average value here, but can be adjusted over a very wide range according to the selected process conditions and can be adjusted according to this process. The same also applies to the distribution of the bubble size within each foamed plastic particle.

[0089] In particular, foamed plastic particles having an (average) bubble size of less than 100 μm, especially less than 75 μm, even more particularly less than 50 μm, and even more particularly less than 25 μm can be formed by this process.

[0090] The third step S3 of the method can, if necessary, be carried out at least partially automatically or be carried out using an expansion device 4 configured to at least partially automate or to carry out a corresponding expansion process for expanding a blowing agent for producing foamed plastic particles, in particular under the influence of temperature. The corresponding expansion device 4 can be configured, for example, as a heating device, i.e., generally as a temperature control device 4.1 comprising a temperature-controlled or temperature-regulated temperature control chamber or process chamber, or can be provided with such a temperature control device. The corresponding tempering device 4.1 can further be provided with a conveying device 4.3 configured to convey the expanding plastic material particles along a conveying path through the corresponding tempering chamber or process chamber. In all cases, the corresponding expansion device 4 can be provided with a control and / or adjustment unit 4.2 implemented from a hardware and / or software point of view, which is configured to control and / or adjust, i.e., generally to set, specific dynamic and / or static conveying and / or temperature and / or radiation parameters within the corresponding tempering chamber or process chamber.

[0091] The density of the foamed plastic particles produced in the third step S3 of the method is significantly lower than the density of the compressed plastic material particles provided in the first step S1, so that the bubble characteristics of the plastic material particles that can be produced or are produced by the method are obtained. The bulk density of the cellular plastic particles produced in the third step S3 of the method is usually many times lower than the bulk density of the compressed plastic material particles produced in the first step S1 of the process.

[0092] The foamed plastic particles produced in the third step S3 of the method are, as described, expandable, which can be an essential property for further processing of the foamed plastic particles for the production of particle foam moldings, in particular the described vapor-based or non-vapor-based ones.

[0093] As shown, the filling of the blowing agent into the compressed plastic material particles can be carried out under the influence of pressure and temperature. Thus, in order to fill the compressed plastic material particles with the blowing agent and then, in particular depending on the material, the parameters that can be changed to clearly set the specific properties of the produced or produced foamed plastic particles are, therefore, initially the general pressure and temperature conditions in the second step S2 of the method. Of course, the time in the second step of the process, i.e., in particular the duration of the pressure and temperature conditions, is also a parameter that affects the filling of the blowing agent into the compressed plastic material particles, i.e., in particular the dissolution of the blowing agent in the compressed plastic material particles.

[0094] The filling of the blowing agent or a blowing agent into the compressed plastic material particles can be carried out, for example, in particular depending on the chemical composition of the compressed plastic material particles and / or the blowing agent, at a pressure in the range of, for example, 1 to 200 bar. The pressure refers in particular to the pressure in the pressure chamber of the corresponding filling device 3 or in the process chamber during the execution of the second step S2 of the process.

[0095] The filling of the blowing agent or a blowing agent into the compressed plastic material particles can be carried out, for example, in particular depending on the chemical composition of the compressed plastic material particles and / or the blowing agent, at a temperature in the range of, for example, 0 to 200 °C. The temperature refers in particular to the temperature in the pressure chamber of the corresponding filling device or in the process chamber during the execution of the second step S2 of the process.

[0096] The filling of the blowing agent or a blowing agent into the compressed plastic material particles can be carried out, for example, in particular depending on the chemical composition of the compressed plastic material particles and / or the blowing agent, over a period in the range of, for example, 1 to 1000 hours. As described above, the exemplary duration refers in particular to the pressurization of the plastic material particles or the application of temperature in the pressure chamber of the corresponding filling device 2 or in the process chamber during the execution of the second step S2 of the process.

[0097] To produce foamed plastic particles, under the influence of temperature, in particular depending on the plastic particle material filled with a blowing agent and / or the chemical composition of the blowing agent, expanding the plastic material particles filled with the blowing agent can be carried out, for example, at normal pressure, i.e., an ambient pressure of about 1 bar. Thus, special pressure levels such as positive or negative pressure levels are possible but not absolutely necessary to foam the compressed plastic material particles filled with the blowing agent to produce cellular plastic particles, and it simplifies the foaming process fundamentally.

[0098] To expand the plastic material particles filled with a blowing agent to produce foamed plastic particles under the influence of temperature can be carried out, for example, in the range of 0 to 300 °C, in particular depending on the plastic particle material filled with the blowing agent and / or the chemical composition of the blowing agent. In particular, the above temperature may refer to the inlet temperature when the compressed plastic material particles filled with the blowing agent enter the corresponding expansion device 4, and / or the outlet temperature when the foamed plastic particles exit the corresponding expansion device 4. The corresponding inlet temperature and outlet temperature may be the same, similar, or different. When the corresponding expansion device 4 comprises a conveying device 4.3 arranged to convey the plastic material particles filled with the blowing agent along the corresponding tempering device 4.1, the aforementioned temperature is the temperature (inlet temperature) when the compressed plastic particle material filled with the blowing agent enters the corresponding expansion device or tempering device (temperature control device) 4.1, thus the temperature when entering the initial region of the corresponding conveying device 4.3, and / or the outlet temperature (outlet temperature) when the plastic particles exit the corresponding expansion device or temperature control device 4.1, thus, that is, the temperature when reaching the end region of the corresponding conveying device. Usually, the inlet temperature is lower than the outlet temperature.

[0099] The expansion of the compressed plastic material particles filled with the blowing agent under the influence of temperature can be achieved by irradiating the compressed plastic material particles filled with the blowing agent with high-energy thermal radiation, namely infrared rays in particular. The temperature control, namely heating in particular, of the compressed plastic material particles filled with the blowing agent can be achieved by selecting and / or adjusting the characteristics of the high-energy radiation, in particular according to the material. This means that the heating of the compressed plastic material particles filled with the blowing agent can be carried out in a targeted manner, in particular according to the material, by selecting and / or adjusting the characteristics of the energy-rich radiation, namely its wavelength in particular, without risking the undesired softening of the compressed plastic material particles filled with the blowing agent, namely the undesired melting or complete melting of the softened plastic material particles, which is not desirable for the method of expanding the plastic material particles filled with the blowing agent. As a result of the investigation, it has been shown that infrared radiation, in combination with the conveyor device 4.3, enables a very controllable volumetric heating, a controllable softening process and thus a controllable expansion process, which is essential for setting the properties of the produced foamed plastic particles, of the compressed plastic material particles filled with the blowing agent in a targeted manner.

[0100] In particular, the expansion of plastic material particles filled with a blowing agent can be carried out under the influence of temperature by irradiating the compressed plastic material particles filled with the blowing agent with high-energy thermal radiation, especially infrared rays. The plastic material particles filled with the blowing agent are transported along at least one transport path defined by the transport device 4.3, especially continuously, along at least one corresponding high-energy radiation, i.e., a radiation generating device 4.4 that generates especially infrared rays. The corresponding radiation generating device 4.4 can be configured as, or can include, especially an infrared oven, especially a continuous infrared oven. The corresponding infrared oven can include one or more infrared emitters arranged or formed along the corresponding transport path. The corresponding infrared emitter can have a radiation power that is variable, for example, in the range of 1 to 500 kW. The aforementioned output refers especially to the area output per square meter. In particular, an area output of 5 to 100 kW / m 2 is used. By using a variable radiator or variable radiator (area) output, different temperature zones can be generated, thereby also providing parameters that affect the expansion process.

[0101] According to this method, as described above, after expanding plastic material particles filled with a blowing agent to produce foamed plastic particles, the produced foamed plastic particles can be cooled under the influence of temperature (especially a temperature lower than the temperature of the previous expansion process). It is convenient for the cooling to be carried out rapidly, and the bubble structure of the foamed plastic particles can be "frozen" after the expansion process. In this way, furthermore, for example, in order to retain the desired bubble structure of the plastic particles after the expansion process, it is possible to particularly prevent the overall or local expansion of the plastic particles that may be undesirable after the expansion process. In particular, room temperature can be used as the reference temperature, and in particular, the cooling can be carried out from a process temperature above the reference temperature to a cooling temperature below the process temperature or the reference temperature, especially to room temperature. Therefore, a separate tempering device for cooling the plastic particles is not absolutely necessary, and it is sufficient to cool the plastic particles to room temperature or to age them at room temperature after the foaming process.

[0102] According to this method, as also shown above, it is possible to provide or use at least one, especially functional, additive or additional material, for example, fibrous substances or materials and / or dye substances or coloring materials and / or nucleating substances or materials and / or blowing agents, substances or materials for particularly influencing or controlling the softening behavior of plastic material particles containing a compressed plastic particle material filled therewith. Therefore, the compounded compressed plastic material particles can also be filled with a blowing agent and foamed, and as a result, foamed plastic particles with special properties are obtained. In particular, through a targeted selection and concentration of suitable additives or materials, it is possible to produce custom-made plastic particles for specific applications or fields of application. The additives or materials may be introduced into the compressed plastic material particles during production.

[0103] Basically, organic or inorganic fibrous substances or materials, such as aramid, glass, carbon or natural fibers, may be used, in particular fibrous substances or materials, to achieve special material properties for further processing of the foamed plastic particles that can be produced or are produced according to this method, or of the molded particle foam parts produced from the foamed plastic particles that can be produced or are produced according to this method. The corresponding foamed plastic particles or the particle foam moldings produced therefrom are characterized, on the one hand, by a special density due to their cell structure and, on the other hand, by special mechanical properties due to the mechanical bonding of the adjacent cells within each foamed plastic particle and / or between each adjacent foamed plastic particle, which is caused in particular by the treatment. During the subsequent processing into particle foam moldings, these special mechanical properties can be used locally or integrally or further modified. The same applies basically regardless of their chemical composition to non-fibrous or non-fibrous-shaped additives or additive materials, such as spherical or spheroidal or platelet-shaped or platelet-shaped organic and / or inorganic additives or additive materials.

[0104] In addition to particularly influencing the mechanical properties of the plastic particles, it is also possible to particularly influence the electrical and / or thermal properties of the plastic particles, for example, by means of suitable additives or materials. Thus, plastic particles having special electrical conductivity and / or thermal conductivity properties can be produced, for example, by means of conductive and / or thermally conductive additives or materials such as metal and / or carbon black particles.

[0105] The concentration of the corresponding additive or additive material can in principle be freely selected, but usually varies depending on the material. Thus, by way of example, it has only been shown that compressed plastic material particles containing one (or more) additives or additive materials can be provided or used at concentrations between 0.01% by weight, which applies especially to chemically active additives, and 60% by weight, which applies especially to fibrous additives. As shown, the concentration usually depends on the specific chemical and / or physical properties of the additive or additive material or combinations thereof.

[0106] According to the present method, basically any thermoplastic material can be provided or used as the starting material. By way of example, according to the present method, acrylonitrile-butadiene-styrene, acrylonitrile-butadiene-styrene blend, polyamide, polyamide blend, polycarbonate, polycarbonate blend, polyethylene, polyethylene blend, polypropylene, polypropylene blend, polyphenylene ether, polyphenylene ether blend, thermoplastic elastomer, polyethylene terephthalate, polyethylene terephthalate blend, polybutylene terephthalate, polybutylene terephthalate blend, polystyrene, polystyrene blend, polyvinyl chloride, thermoplastic elastomer blend. Compressed plastic material particles from the group are used.

[0107] According to the present method, depending on the selected process conditions, foamed plastic particles having a uniform or non-uniformly distributed bubble structure can be produced. Thus, the properties within each foamed plastic particle, i.e., especially the distribution of the bubble structure, can (also) be affected by the pressure, temperature, time during filling or expansion, and the transport time or conditions between the individual steps S1 to S3 of the present method, in addition to the material-specific parameters.

[0108] When foamed plastic particles having a non-uniformly distributed cell structure are produced according to the present method, each foamed plastic particle may have a different number and / or morphology of cells in the peripheral region from the core region. Therefore, due to the different distribution of the number and / or morphology of the cells, it is possible to produce stepwise foamed plastic particles having a special range of properties. Therefore, the stepwise foamed plastic particles can have different cell characteristics in the (outer) peripheral region from the (inner) core region, for example, like core-shell particles.

[0109] In general, it is also a fact that foamed plastic particles having a bulk density in the range of 20 to 1500 g / l can be produced by this process, particularly depending on the degree of expansion and, if necessary, the filler content. The actual bulk density, of course, usually refers to the average here, but can be adjusted over a very wide range depending on the selected process conditions and can thus be made to order.

[0110] An example of an embodiment of the apparatus 1 for carrying out the method shown in FIG. 2 comprises the aforementioned feeding device 2, a filling device 3 which can generally be designed as a first device and is configured to fill the foaming agent into the compressed plastic under the influence of pressure, and an expansion device 4 which can generally be designed as a second device and is configured to expand the foaming agent to produce foamed plastic particles under the influence of temperature.

[0111] The staging device 2 can be provided with a suitable handling device for handling and staging the compressed plastic material particles. In a similar manner, although not shown, the apparatus 1 can be provided with a handling device 5 downstream of the expansion device 4 for removing the produced foamed plastic particles. The corresponding handling device can be configured as a conveying device or can be provided with a conveying device as described above. In particular, a conveying device suitable for conveying bulk materials, such as a pneumatic conveying device configured to form a conveying stream, is considered.

[0112] As described above, the second device can include a conveying device, in particular a device combining a conveying device and a temperature control device. The corresponding combined conveying and temperature control device can be configured, for example, as a continuous furnace, in particular as an infrared continuous furnace including one or more infrared emitters, or can include at least one such furnace.

[0113] The second device can also be assigned a stress relaxation device (not shown), such as a stress relaxation chamber, in which the produced foamed plastic particles are stored (stress relaxed) for a predetermined time under defined chemical and / or physical conditions, in particular under a defined temperature ratio. The corresponding stress relaxation device can be configured, for example, as a decompression device or can include such a device.

[0114] In all example embodiments, it is conceivable that device 1 includes a conveying device through which the compressed plastic material particles or, further, the foamed plastic particles are conveyed continuously or discontinuously through the individual devices 2 to 4.

[0115] FIG. 3 shows in cross-section a schematic diagram of foamed plastic particles produced according to the method of an example embodiment. Specifically, this is a part of a microscopic image of foamed plastic particles having a bulk density of about 120 g / l, produced from compressed PBT having a bulk density of about 375 g / l according to this method.

[0116] FIG. 4 shows a schematic diagram of foamed plastic particles produced according to the method of an example embodiment. This schematic diagram shows cellular plastic particles having locally different bubble characteristics, i.e., stepwise foamed plastic particles. Specifically, the foamed plastic particles have a non-uniformly distributed bubble structure, unlike plastic particles having a different number of bubbles in the peripheral region R, i.e., a greater number of bubbles than in the core region K. The inner dashed line indicates that the transition between the peripheral region R and the core region K can be continuous. The peripheral region R can optionally have locally different strengths.

Claims

Step of providing a plastic material in the form of plastic material particles; Step of filling the plastic material particles with a blowing agent at a pressure in the range of 5 to 200 bar; Step of expanding the plastic material particles filled with the blowing agent to produce foamed plastic particles at a temperature in the range of 0 to 300 °C characterized by, a gas is used as the blowing agent, the expansion of the plastic material particles filled with the blowing agent occurs under the influence of temperature by irradiating the plastic material particles filled with the blowing agent with high-energy thermal radiation, and the plastic material particles filled with the blowing agent are transported along at least one transport path along at least one radiation generating device that generates the corresponding high-energy radiation, a method for producing foamed plastic particles. The method according to claim 1, characterized in that the filling of the blowing agent into the plastic material particles is carried out at a temperature in the range of 0 to 300 °C. The method according to claim 1, characterized in that the filling of the blowing agent into the plastic material particles is carried out in the range of 1 to 1000 hours.

4. The method according to claim 1, characterized in that the expansion of the plastic material particles filled with the blowing agent is carried out by irradiating the plastic material particles filled with the blowing agent with high-energy thermal radiation.

5. The method according to claim 1, characterized in that after expanding the plastic material particles filled with the blowing agent to produce foamed plastic particles, the foamed plastic particles are cooled.

6. The method according to claim 1, characterized in that a plastic particle material containing at least one additive or additive material is provided or used. The method according to claim 6, characterized in that plastic material particles containing an additive or additive material at a concentration of 0.01 to 60% by weight are provided or used.

8. The method according to claim 1, wherein a plastic particle material selected from the group consisting of acrylonitrile butadiene styrene, acrylonitrile butadiene styrene blend, polyamide, polyamide blend, polycarbonate, polycarbonate blend, polyethylene, polyethylene blend, polypropylene, polypropylene blend, polyphenylene ether, polyphenylene ether blend, thermoplastic elastomer, polyethylene terephthalate, polyethylene terephthalate blend, polybutylene terephthalate, polybutylene terephthalate blend, polystyrene, polystyrene blend, polyvinyl chloride, and thermoplastic elastomer blend is provided or used.

9. The method according to claim 1, characterized in that foamed plastic particles having a homogeneous or heterogeneous distributed bubble structure are produced.

10. The method according to claim 9, characterized in that foamed plastic particles having a bubble structure unevenly distributed within each foamed plastic particle are produced, and each foamed plastic particle has a number and / or morphology of bubbles in a peripheral region different from the core region.

11. The method according to claim 1, characterized in that carbon dioxide, nitrogen, or a mixture containing carbon dioxide and / or nitrogen is used as the blowing agent.

12. The method according to claim 1, characterized in that foamed plastic particles having a bubble size in the range of 1 to 250 μm are produced.

13. The method according to claim 1, characterized in that foamed plastic particles having a bulk density in the range of 20 to 1500 g / l are produced.

14. - A first device configured to fill plastic material particles with a blowing agent at a pressure in the range of 5 to 200 bar, the device including a pressure vessel device; - A second device configured to expand the blowing agent at a temperature in the range of 0 to 300 °C to produce foamed plastic particles, the device including a radiation generating device for generating high energy radiation An apparatus (1) for producing foamed plastic particles by the method according to any one of claims 1 to 13, including the above and using a gas as the blowing agent.

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