EP4330003A1

EP4330003A1 - Method for producing cellular plastic particles

Info

Publication number: EP4330003A1
Application number: EP22725420.8A
Authority: EP
Inventors: Jörg Vetter; Josua SCHNEIDER; Mirjam Lucht
Original assignee: Fox Velution GmbH
Current assignee: Fox Velution GmbH
Priority date: 2021-04-30
Filing date: 2022-04-25
Publication date: 2024-03-06
Also published as: WO2022229070A1; DE102021111247A1; CN117529397A; KR20240005810A; JP2024516426A

Abstract

The invention relates to a method for producing cellular plastic particles, comprising the steps of: - providing a plastic material in the form of pre-expanded plastic material particles, - loading the pre-expanded plastic material particles with a blowing agent under pressure, - expanding the pre-expanded plastic material particles loaded with blowing agent in order to produce cellular plastic particles, particularly cellular plastic particles having a lower density, under the effects of temperature, wherein the plastic material particles loaded with blowing agent are expanded under the effects of temperature by irradiating said plastic material particles loaded with blowing agent with high-energy thermal radiation, in particular infrared radiation.

Description

Process for the production of cellular plastic particles

The invention relates to a method for producing cellular plastic particles.

Methods for the production of cellular plastic particles, which are further processed, in particular for the production of molded particle foam parts, are known in principle from the prior art.

Known methods for the production of cellular plastic particles are based on a two-stage process which, in a first stage, involves melting a thermoplastic material in an extruder and charging the thermoplastic material melt produced in this way within the extruder with a blowing agent, and in a second stage granulating or Crushing of the strand-like emerging from the extruder and propellant telconditioned expanding or expanded thermoplastic material provides.

In the first stage of a corresponding process, the blowing agent is dissolved material melt in the thermoplastic synthetic material due to the pressure and temperature conditions prevailing in the extruder. After exiting the extruder of the thermoplastic material loaded with blowing agent, due to the drop in pressure, the plastic material expands as a result of the blowing agent being converted into the gas phase.

By in the second stage of a corresponding process, z. B. by means of a cutting device, subsequent granulation or comminution of the plastic material exiting the extruder in strand form and, as described, immediately expanding after exiting the extruder due to the blowing agent, cellular plastic particles are formed, which can be further processed into a particle foam molding in a separate processing step.

Known methods are first of all comparatively complex in terms of plant and process technology. In addition, the producible with known methods zel lular plastic particles in terms of properties such. B. size, morphology and Ver distribution of cells, room for improvement; the possibilities of influencing the corresponding properties of the cellular plastic particles in terms of plant or process technology are clearly limited in known methods.

Furthermore, it is not possible with known methods to produce cellular plastic particles starting from a pre-expanded plastic material. This applies in particular because the extrusion-based process described damages or destroys the structure of the pre-expanded plastic material particles, in particular due to the mechanical as well as the thermal energy input.

This applies in particular to autoclave processes, which are known in principle, in which pre-expanded plastic material particles are placed in an autoclave device (so-called post-/further foamer) is expanded batchwise and thus discontinuously to form foam beads using superheated steam. Some of the things that could be improved here include energy inefficiency, the infrastructural requirements for steam generation and supply, the risk of a deterioration in the morphology of the foam beads produced over their entire volume, a high degree of scattering due to different thermal conditions in the various areas of the autoclave facility) and necessary subsequent drying processes to remove the moisture from the superheated steam.

Proceeding from this, the present invention is based on the object of specifying an improved method for the production of cellular plastic particles, which, starting from pre-expanded plastic material particles, also enables the production of cellular plastic particles, in particular with specifically adjustable properties for the subsequent processing into particle foam moldings and their application or usage properties , allows.

The object is achieved by a method according to claim 1. The claims dependent on this relate to possible embodiments of the method.

A first aspect of the invention relates to a method for producing cellular plastic particles; the method described herein is therefore generally used for the production of cellular plastic particles. The plastic particles which can be produced or are produced according to the method are therefore plastic particles which have a cellular structure at least in sections, typically completely. In addition, the plastic particles can have a certain (further) expansion capacity, in particular due to a certain content of blowing agent—whether it is a residue from the described method or is introduced subsequently in a separate process step. The cellular plastic particles that can be produced or produced according to the method can therefore be expandable and/or (mechanically) compressible or compressible due to their cellular structure. The cellular plastic particles that can be produced or produced according to the method can in all cases be referred to or considered as “foam particles” or “foam beads”. As follows, the method can also be used as a method for radiation-based modification, i. H. be designated or considered in particular for post-expansion or further expansion of pre-expanded plastic particles. The radiation-based modification serves in particular for the targeted radiation-based influencing of the cellular properties and thus the cellular structure of corresponding pre-expanded plastic particles, which, as mentioned, means in particular post-expansion or further expansion.

The cellular plastic particles that can also be referred to or referred to below as “plastic particles” for short and that can be produced or produced according to the method can be further processed in one or more independent subsequent processes to form a molded particle foam part. The further processing of the cellular plastic particles into a molded particle foam part can be carried out using steam or superheated steam (steam-based) or without the use of steam or superheated steam (non-steam-based or dry).

The steps of the method for producing cellular plastic particles are explained in more detail below.

In a first step of the method, a plastic material is provided in the form of pre-expanded plastic material particles. The pre-expanded plastic material particles provided according to the method can optionally also be referred to as “pre-expanded plastic particles”. The plastic material to be regarded as the starting material, which is therefore a particle foam material and therefore already a cellular plastic material, is provided in the first step of the method in the form of pre-expanded plastic material particles. The provided pre-expanded plastic material is therefore in the form of particles, ie in particular in the form of bulk goods. In the first step, therefore, at least one measure is generally carried out to provide a particulate, ie in particular bulk material-like or shaped, pre-expanded plastic material in the form of corresponding pre-expanded plastic material particles. The density of the pre-expanded plastic material particles provided in the first step of the method is typically below 1 g/cm ³ , in particular in a range between 0.05 and 2.2 g/cm ³ , depending on the material composition or modification due to the cellular structure. resulting in the pre-expanded properties of the provided pre-expanded plastic material particles; the matrix of the provided pre-expanded plastic material particles therefore has a porous or cellular structure.

Despite its cellular structure, the matrix of the pre-expanded plastic material particles can optionally contain at least one additive or material, such as e.g. B. elongate, spherical or platelet-shaped fillers included. In particular for pre-expanded plastic material particles with additives or materials, the density may also be above 1 g/cm ³ depending on the concentration. Appropriate additives or materials can, if appropriate, themselves be present or have a cellular effect.

The first step of the method can be carried out, optionally at least partially or partially automated, by means of a supply device which is set up for the continuous or discontinuous supply of a corresponding plastic material in the form of pre-expan ded plastic material particles. A corresponding loading device can, for. B. be a conveyor, by means of which to be processed to corresponding cellular plastic particles pre-expanded plastic material particles to a or in a second step of the method executing (n) loading device can be promoted. A corresponding conveyor can, for. B. be designed as Bandför dereinrichtung or flow conveyor device or include such. The promotion of the pre-expanded plastic material particles to a or in a second step of the method executing (s) loading device can thus include the include pre-expanded plastic material particles in a delivery flow; the pre-expanded plastic material particles can then be conveyed by means of a conveying flow to or into a loading device executing the second step of the method.

In a second step of the method, the pre-expanded plastic material particles are loaded with a blowing agent, at least under the influence of pressure. In the second step, the pre-expanded plastic material particles are then loaded with a blowing agent, at least under the influence of pressure—if necessary, depending on the material, a certain pressure and a specific (elevated) temperature can also be used. In the second step, therefore, generally at least one measure for loading the pre-expanded plastic material particles with a blowing agent is carried out at least under the influence of pressure, thus at least under pressure. Phenomenologically, in the second step of the process, the blowing agent typically accumulates in the respective pre-expanded plastic material particles. The enrichment of the blowing agent in the respective pre-expanded plastic material particles can, in particular depending on the chemical configuration of the pre-expanded plastic material particles, the blowing agent and the additives or materials possibly contained therein, as well as depending on the pressure or Temperature conditions, for example resulting from or due to absorption and/or solution processes of the blowing agent in the respective pre-expanded plastic material particles. Because of the cellular structure of the pre-expanded plastic material particles, the blowing agent can also accumulate within the cell spaces defined by the cellular structure; consequently, the inner volume defined by the cell spaces of a respective pre-expanded plastic material can be used as a receiving space for receiving blowing agent in the second step of the method.

The pressure level in the second step of the method is typically selected, in particular depending on the material, in such a way that the cellular structure of the pre-expanded plastic material particles is not damaged; In particular, the pressure level in the second step of the method is chosen so that the cellular structure of the pre-expanded plastic material particles is not damaged in an undesired manner due to the pressure, i. H. e.g. B. plastically deforms and even collapses completely. In this context, the effective difference between the external loading pressure and the internal cellular pressure is of particular importance.

The same applies in particular to the rate of pressure rise, ie the rate at which the external pressure is increased from an initial level to a target level in the second step. Typically, the rate of pressure rise is in a range between 0.001 bar per minute and 1000 bar per minute. In particular between 0.01 bar per minute and 1000 bar per minute, further in particular between 0.1 bar and 1000 bar per minute, further in particular between 1 bar and 1000 bar per minute, further in particular between 2, 3, 4, 5, 6 , 7, 8, 9 or 10 bar and 1000 bar per minute, more particularly between 15, 20, 25, 30, 35, 40, 45, 50.55, 60, 65, 70, 75, 89, 85, 90, 95 or 100 bar per minute and 1000 bar per minute, more particularly between 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, 600,0625, 650, 675, 700, 735, 750, 775, 800, 825, 850, 875, 900.0 925, 950 or 975 bar per minute and 1000 bar per minute. All intermediate values not explicitly listed here are also conceivable.

Gases such as B. carbon dioxide or a mixture containing carbon dioxide and / or nitrogen, such as. As air, can be used. In general, any combustible or non-combustible organic gas, i. H. especially butane or pentane; or inert gases such as B. Noble gases, d. H. in particular helium, neon, argon; or nitrogen, or mixtures thereof. The term “blowing agent” can therefore also include a mixture of chemically and/or physically different blowing agents. The propellant is typically selected taking into account its absorption capacity in the pre-expanded plastic material particles, and therefore taking into account the chemical and/or physical configuration or composition of the pre-expanded plastic material particles. If the pre-expanded plastic material particles contain additives or materials, the properties such. B. the chemical and / or physical Konfig ration of the additives or materials are also taken into account when selecting the propellant.

The second step of the method can be carried out, if necessary at least partially automated or partially automated, by means of a loading device which is set up to load the pre-expanded plastic material particles with a blowing agent at least under the influence of pressure or to carry out a corresponding loading process. A corresponding loading device can e.g. B. as an autoclave device, d. H. in general, be designed as or comprise a pressure vessel device that includes a pressure or process space that can optionally be temperature-controlled. A corresponding loading device can also have a temperature control device, which is set up to control the temperature of a corresponding pressure or process space. A corresponding loading device can in all cases have a hardware and/or software implemented control and/or regulation unit which is used for control and/or regulation, i. H. is generally set up for setting certain dynamic and/or static pressure and/or temperature parameters within a corresponding pressure or process space.

In a third step of the method, the pre-expanded plastic material particles loaded with blowing agent are expanded under the influence of temperature, ie in particular elevated temperature, to produce cellular plastic particles. In the third step of the process, the pre-expanded plastic material particles loaded with blowing agent are then typically exposed to elevated temperature, ie generally thermal energy, which leads to outgassing and/or expansion of the blowing agent contained in the pre-expanded plastic material particles. This is typically done dry, i.e. without external influence of fluids, such as e.g. B. steam or water. In particular, the outgassing of the blowing agent in the cells and the matrix areas of the thermally softened or softened pre-expanded plastic material particles causes renewed or further expansion of the plastic material particles, which after cooling or "freezing" leads to the formation of plastic particles with a possibly compared to the starting material, for example with regard to cell number and/or shape and/or size, permanent cellular structure and thus leads to the formation of the cellular plastic particles to be produced. In the third step of the method, at least one measure for outgassing or expanding the blowing agent contained in the cells and the matrix regions of the pre-expanded plastic material particles softening or softened at least as a result of the influence of temperature and thus at least thermally is generally carried out for the production of cellular plastic particles. Phenomenologically, in the third step of the process, in particular due to the outgassing or desorption of the blowing agent from the cells and the matrix areas of the softening or softened pre-expanded plastic material particles, further cell growth and possibly renewed cell formation with subsequent cell growth within the pre-expanded plastic material particles, which leads to the cellular plastic particles to be produced, which, in comparison to the pre-expanded plastic particles, have a, possibly significantly, lower density. The cell formation, if such occurs, is typically based on the aforementioned desorption of the propellant at nucleation points in the plastic material particles that are softening or softened by the influence of temperature, while cell growth is typically based on an overpressure-related expansion of the propellant in already formed or existing cells. As also mentioned, the cellular structure formed in this way or the further expansion state thus realized is reduced by the or a temperature reduction of the cellular plastic particles thus produced, i.e. by their cooling, e.g. B. in the environment, permanently "frozen" or fixed.

In principle, therefore, it applies that after the completion of the pressurization that follows in the second step of the method, i. H. in the event of a pressure drop, in particular to normal or standard conditions, outgassing or desorption processes take place within respective preexpanded plastic material particles loaded with propellant and typically thermally softened. The outgassing or desorption processes of the blowing agent are an essential prerequisite for the cell growth processes required for the production of cellular plastic particles and, if necessary, cell formation processes within the respective plastic material particles pre-expanded plastic material particles, the cellular plastic particles to be produced according to the method are formed in the third step of the method, in particular due to corresponding outgassing or desorption processes.

As mentioned, the cellular plastic particles to be produced or produced according to the method have a lower density than the pre-expanded plastic particles, so that the method, as also mentioned, serves to produce cellular plastic particles of lower density and can therefore also be referred to or considered as a method for radiation-based modification, ie in particular for radiation-based post-expansion or further expansion of pre-expanded plastic particles.

As explained below, cellular structures with locally different cell properties and thus graded cellular plastic particles can be realized by controlling corresponding outgassing or desorption-related cell formation and cell growth processes.

In general, it is true that, according to the method, in particular cellular plastic particles with a cell size in a range between 0.5 and 250 μm can be produced. The actual cell size - of course, an average is typically mentioned here - can therefore be set over a very wide range and thus tailor-made according to the method, depending on the selected process conditions. The same applies to any distribution of the cell sizes within the respective cellular plastic particles.

In particular, with the method described herein, cellular plastic particles with an (average) cell size below 250 μm, in particular below 240 μm, further in particular below 230 μm, further in particular below 220 μm, further in particular below half 210 μm, further in particular below 200 μm, further in particular below 190 μm, further in particular below 180 μm, further in particular below 170 μm, further in particular below 160 μm, further in particular below 150 μm, further in particular below half 140 μm, further in particular below 130 μm, further in particular below 120 μm, in particular below 110 μm, in particular below 100 μm, in particular below 90 μm, in particular below 80 μm, in particular below 70 μm, in particular below 60 μm, in particular below 50 μm, in particular below 45 μm, further in particular below 40 μm, further in particular below half 35 pm, further in particular below 30 pm, further in particular below 25 pm, further in particular below 24 pm, further in particular below 23 pm, further in particular below 22 pm, further in particular below 21 pm, further in particular below 20 pm, further in particular below 19 μm, further in particular below 18 μm, further in particular below 17 μm, further in particular below 16 μm, further in particular below 15 μm, further in particular below 14 μm, further in particular below 13 μm, further in particular below 12 μm, further in particular below 11 pm, more particularly below 10 pm, or even lower. All intermediate values not explicitly listed here are also conceivable.

The third step of the method can optionally be at least partially automated or partially automated by means of an expansion device which is used for radiation-based expansion of the blowing agent to produce cellular plastic particles, at least under the influence of temperature to carry out a corresponding radiation-based expansion process is set up to run. A corresponding expansion device is typically embodied as a radiation-based heating device, ie generally as a temperature control device comprising a temperature control or process chamber that can be temperature-controlled or controlled at least on the basis of radiation, or comprise such a temperature control device. A corresponding temperature control device can also have a conveying device, which is set up for conveying the plastic material particles to be expanded along a conveying path through a corresponding tempering or process space. A corresponding expansion device can in all cases have a hardware and/or software implemented control and/or regulation unit which is used to control and/or regulate, ie generally to set, certain dynamic and/or static conveying and/or temperatures - Is set up and/or radiation parameters within a corresponding temperature control or process room.

In particular, the third step of the process can optionally be carried out continuously, which is advantageous compared to the batchwise autoclave-based processes mentioned at the outset.

The density of the cellular plastic particles produced in the third step of the method is typically well below the initial density of the pre-expanded plastic material particles provided in the first step, which results in the cellular properties of the plastic particles that can be produced or produced according to the method. The bulk density of the cellular plastic particles produced in the third step of the process is correspondingly well below the bulk density of the pre-expanded plastic material particles provided in the first step of the process.

As mentioned above, the cellular plastic particles produced in the third step of the process are typically further or post-expandable; this can represent an essential property for the described, in particular steam-based or non-steam-based, further processing of the cellular plastic particles for the production of particle foam moldings.

Compared to known methods, the method is characterized by a special dynamic process control, which requires a softening for expansion, but in contrast to an extrusion process, no complete melting of a pre-expanded plastic material loaded with blowing agent and thus no pressure- and temperature-intensive loading of a plastic material melt with requires a propellant. The dynamic process control, i.e. in particular the rapid (volume) heating that is possible with it - in contrast to convective and conductive energy transport in steam-based post-foaming - is also important for good energy efficiency and the significantly finer cell morphology mentioned below (due to lack of time for cell unions). The method is therefore associated with a (significantly) simplified installation and process engineering effort for its implementation in comparison to pre-expanded plastic material particles loaded with a blowing agent, and corresponding plastic material particles loaded with blowing agent can be converted into cellular plastic particles at least under the influence of temperature, in particular under the influence of temperature and pressure.

In addition, the properties of the cellular plastic particles that can be produced or produced according to the method are improved, in particular with regard to the number, size, shape and distribution of the cells, which is evident from the easily adjustable and very easily controllable process conditions in the context of the second step of the method taking place loading as well as in the course of the taking place in the third step of the process expanding results.

In contrast to the autoclave-based expansion processes described at the outset, the method enables a continuous expansion process of corresponding pre-expanded plastic particles loaded with blowing agents, which requires no subsequent drying due to the lack of use of superheated steam.

The method thus enables a significantly expanded process window that can be precisely adjusted or regulated for each plastic material, which in principle makes it possible to produce cellular plastic particles with desired properties from any (thermoplastic) pre-expanded plastic material particles.

As indicated, the loading of the pre-expanded plastic material particles with a blowing agent can be carried out under the influence of pressure and temperature. The parameters that can be varied, in particular depending on the material, for loading the pre-expanded plastic material particles with blowing agent and for the targeted adjustment of certain properties of the cellular plastic particles to be produced or produced are therefore initially the pressure and temperature conditions prevailing in the second step of the method. Of course, the time, i. H. in particular the course and the duration of the pressure and temperature conditions, in the second step of the method, a parameter which has an influence on the loading of the pre-expanded plastic material particles with blowing agent, d. H. in particular the inclusion of the blowing agent in the pre-expanded plastic material particles.

Specific parameters for carrying out the second step of the process are given below by way of example:

The loading of the pre-expanded plastic material particles with the or a propellant can, for. B., in particular depending on the chemical composition of the pre-expanded plastic material particles and/or the blowing agent, at a pressure in a range between 1 and 200 bar, in particular in a range between 1 and 190 bar, more particularly in a range between 1 and 180 bar, further in particular in a range between 1 and 170 bar, further in particular in a range between 1 and 160 bar, further in particular in a range between 1 and 150 bar, further in particular in a range between 1 and 140 bar, more particularly in a range between 1 and 130 bar, more particularly in a range between 1 and 120 bar, more particularly in a range between 1 and 110 bar, more particularly in a range between 1 and 100 bar, further in particular in a range between 1 and 90 bar, further in particular in a range between 1 and 80 bar, further in particular in a range between 1 and 70 bar, further in particular in a range between 1 and 60 bar, further in particular in a range between 1 and 50 bar, further in particular in a range between 1 and 40 bar, further in particular in a range between 1 and 30 bar, further in particular in a range between 1 and 20 bar, further in particular in a range between 1 and 10 bar, be performed. Instead of 1 bar, 2, 3, 4, 5, 6, 7, 8, 9 or 10 bar can also be used as the lower limit. The pressures mentioned above as examples relate in particular to pressures within a pressure or process chamber of a corresponding loading device during the execution of the second step of the method. All intermediate values not explicitly listed here are also conceivable.

As mentioned, the pressure level and in particular the rate of pressure rise in the second step of the method is, in particular dependent on the material, typically selected in such a way that the cellular structure of the pre-expanded plastic material particles is not damaged; In particular, the pressure level and in particular the rate of increase in pressure are selected in the second step of the method such that the cellular structure of the pre-expanded plastic material particles does not deform plastically due to the pressure (effective difference between the external loading pressure and the internal cellular pressure) and possibly even collapses.

The loading of the pre-expanded plastic material particles with the or a propellant can, for. B., in particular depending on the chemical composition of the pre-expanded plastic material particles and / or the propellant, at a temperature in a range between 0 and 250 ° C, more particularly in a range between 0 and 240 ° C, more particularly in a range between 0 and 230°C, further in particular in a range between 0 and 220°C, further in particular in a range between 0 and 210°C, further in particular in a range between 0 and 200°C, further in particular in a range between 0 and 190°C, further in particular in a range between 0 and 180°C, further in particular in a range between 0 and 170°C, further in particular in a range between 0 and 160°C, further in particular in a range between 0 and 150° C, further in particular in a range between 0 and 140°C, further in particular in a range between 0 and 130°C, further in particular in a range between 0 and 120°C, further in particular in a range ch between 0 and 110°C, further in particular in a range between 0 and 100°C, further in particular in a range between 0 and 90°C, further in particular in a range between 0 and 80°C, further in particular in a range between 0 and 70°C, further in particular in a range between 0 and 60°C, further in particular in a range between 0 and 50°C, further in particular in a range between 0 and 40°C, further in particular in a range between 0 and 30°C, especially especially in a range between 0 and 20°C. The temperatures mentioned above as examples relate in particular to temperatures within a pressure or process space of a corresponding loading device during the execution of the second step of the method. All intermediate values not explicitly listed here are also conceivable.

The loading of the pre-expanded plastic material particles with the or a propellant can, for. B., in particular depending on the chemical composition of the preexpandier th plastic material particles and / or the propellant, for a period of time in a range between 0.1 and 1000 h, in particular in a range between 0.1 and 950 h, further in particular in a Range between 0.1 and 900 h, further in particular in a range between 0.1 and 850 h, further in particular in a range between 0.1 and 800 h, further in particular in a range between 0.1 and 750 h, further in particular in a range between 0.1 and 700 h, further in particular in a range between 0.1 and 650 h, further in particular in a range between 0.1 and 600 h, further in particular in a range between 0.1 and 550 h in particular in a range between 0.1 and 500 h, further in particular in a range between 0.1 and 450 h, further in particular in a range between 0.1 and 400 h, further in particular in a range between 0.1 and 350 h , further in particular Others in a range between 0.1 and 300 h, more particularly in a range between 0.1 and 250 h, more particularly in a range between 0.1 and 200 h, more particularly in a range between 0.1 and 150 h , further in particular in a range between 0.1 and 100 h, in particular in a range between 0.1 and 90 h, in particular in a range between 0.1 and 80 h, in particular in a range between 0.1 and 70 h, in particular in a range between 0.1 and 60 h, in particular in a range between 0.1 and 50 h, in particular in a range between 0.1 and 40 h, in particular in a range between 0.1 and 30 h, in particular be carried out in a range between 0.1 and 20 h, in particular in a range between 0.1 and 10 h. The time durations mentioned above, as mentioned, relate in particular to the pressure or temperature loading of the plastic material particles within a pressure or process space of a corresponding loading device during the execution of the second step of the method. All intermediate values not explicitly listed here are also conceivable.

Specific parameters for carrying out the third step of the process are given below by way of example:

The expansion of the plastic material particles loaded with blowing agent to produce the cellular plastic particles under the influence of temperature, in particular depending on the chemical composition of the plastic particle material loaded with blowing agent and/or the blowing agent, can, for. B. at normal pressure, and therefore an ambient pressure of about 1 bar, can be carried out. A particular pressure level, e.g. B. a positive or negative pressure level, is to expand the loaded with blowing agent pre-expanded plastic material particles for the production of the cellular plastic particles are therefore possible, but not absolutely necessary, which fundamentally simplifies the expansion process.

The expansion of the loaded with blowing agent plastic material particles to produce the cellular plastic particles under the influence of temperature can, for. B., in particular depending on the chemical composition of the laden with propellant plastic particle material and / or the propellant, at a temperature in a range between 20 and 300 ° C, in particular in a range between 20 and 290 ° C, more particularly in a Range between 20 and 280°C, further in particular in a range between 20 and 270°, further in particular in a range between 20 and 260°C, further in particular in a range between 20 and 250°C, further in particular in a range between 20 and 240°C, further in particular in a range between 20 and 230°C, further in particular in a range between 20 and 220°C, further in particular in a range between 20 and 210°C, further in particular in a range between 20 and 200 °C, further in particular in a range between 20 and 190°C, further in particular in a range between 20 and 180°C, further in particular in a range between 20 and 170°C, further in particular ere in a range between 20 and 160°C, more particularly in a range between 20 and 150°C, more especially in a range between 20 and 140°C, more especially in a range between 20 and 130°C, more especially in a range between 20 and 120°C, further in particular in a range between 20 and 110°C, further in particular in a range between 20 and 100°C, further in particular in a range between 20 and 90°C, further in particular in a range between 20 and 80°C, further in particular in a range between 20 and 70°C, further in particular in a range between 20 and 60°C, further in particular in a range between 20 and 50°C, further in particular in a range between 20 and 40° C., more particularly in a range between 20 and 30° C. All intermediate values not explicitly listed here are also conceivable.

The temperatures mentioned above can relate in particular to an inlet temperature when the pre-expanded plastic material particles loaded with propellant enter a corresponding expansion device and/or to an outlet temperature when the cellular plastic particles exit a corresponding expansion device. Corresponding inlet and outlet temperatures can be the same, similar or different. If a corresponding expansion device has a conveyor device which is designed to convey the plastic material particles loaded with propellant along corresponding temperature control devices, the aforementioned temperatures can be reduced to a temperature when the pre-expanded plastic particle material loaded with propellant enters a corresponding expansion or temperature control device (Inlet temperature), consequently to an initial area of a corresponding conveying device, and/or to an exit temperature when the plastic particles exit from a corresponding expansion or tempering device (exit temperature), consequently to an end area of a corresponding conveying the facility. Typically, the inlet temperature is lower than the outlet temperature.

The expansion of the pre-expanded plastic material particles loaded with blowing agent under the influence of temperature takes place by irradiating the pre-expanded plastic particle material loaded with blowing agent with high-energy thermal radiation, d. H. especially infrared radiation. Infrared radiation with wavelengths in a range between 1 and 15 pm, in particular between 1.4 and 8 pm, more particularly between 1.4 and 3 pm, is particularly suitable. The wavelengths of the infrared radiation are typically selected depending on the material. The tempering, i. H. In particular, the heating of the pre-expanded plastic material particles loaded with blowing agent can be carried out, in particular depending on the material, by selecting and/or adjusting the properties of the high-energy radiation used, d. H. in particular their wavelength, can be carried out in a very targeted manner, without the softening associated with heating of the pre-expanded plastic material particles loaded with blowing agent leading to melting which is undesirable for the expansion process of the plastic material particles loaded with blowing agent, i.e. insufficient stability of the softened plastic material particles take risk. Infrared radiation has been shown in investigations to be particularly suitable, as it provides a targeted and, in conjunction with a conveyor, very well controllable volume heating of the pre-expanded plastic material particles loaded with propellant, a controllable softening process and thus - this is for setting the properties of the cellular plastic to be produced particles - enables a controllable expansion process.

In particular, the expansion of the plastic material particles loaded with blowing agent can take place under the influence of temperature by irradiating the pre-expan ded plastic material particles loaded with a blowing agent with high-energy thermal radiation, in particular infrared radiation, with the plastic material particles loaded with blowing agent on at least one conveying path defined by a conveying device, in particular are continuously conveyed along at least one corresponding high-energy radiation, ie in particular infrared radiation, generating radiation generating device. A corresponding radiation-generating device can be designed in particular as an infrared oven, in particular an infrared continuous oven, or can include one. A corresponding infrared oven can comprise one or more infrared emitters arranged or formed along a corresponding conveying path. Corresponding infrared emitters can, for example, have an optionally variable radiation power in a range between 1 and 500 kW, more particularly in a range between 1 and 450 kW, more particularly in a range between 1 and 400 kW, more particularly in a range between 1 and 350 kW, further in particular in a range between 1 and 250 kW, further in particular in a range between 1 and 200 kW, further in particular in a range between 1 and 150 kW, further in particular in a range between 1 and 100 kW in particular in a range between 1 and 50 kW. As a lower limit, instead of 1 kW 2, 3, 4, 5, 6, 7, 8, 9 or 10 kW can also be used. Any intermediate values not explicitly listed here are also conceivable.

The performances mentioned above can relate in particular to area performance per m ² . Studies have shown that, in particular, area outputs between 5 and 100 kW/m ² deliver good results. Different temperature zones can be generated by variable emitters or variable emitter (area) outputs, which also provides a parameter for influencing the expansion process.

According to the method, after the expansion of the plastic material particles loaded with blowing agent for the production of the cellular plastic particles under the influence of (in particular compared to the expansion process previously carried out) temperature, the produced cellular plastic particles can be cooled, as indicated above. The cellular structure of the cellular plastic particles that is present after the expansion process can be “frozen” by the cooling, which takes place expediently quickly. In this way, any further, integral or even local expansion of the plastic particles that may be undesirable after the expansion process can be specifically prevented, for example in order to maintain a cellular structure of the plastic particles that may be desired after the expansion process. The cooling can take place in particular from a process temperature lying above a reference temperature, in particular room temperature can be used as the reference temperature, to a cooling temperature lying below the process or reference temperature, in particular room temperature. Consequently, separate temperature control devices for cooling the plastic particles are not absolutely necessary, but it may be sufficient if the plastic particles are cooled to room temperature after the expansion process or stored at room temperature.

According to the method, as also indicated above, at least one, in particular functional, additive or material, for example a fibrous substance or material and/or a dye or material and/or a nucleating substance or material and/or or a substance or material such as B. Additives for adjusting a melt viscosity, such as chain lengtheners, or for increasing the absorption coefficient, such as graphite, carbon black, etc., for the targeted influencing or control of the softening behavior of the plastic material particles loaded with propellant, containing pre-expanded plastic parti kelmaterial, provided or . be used. Consequently, according to the method, compounded and pre-expanded plastic material particles can also be loaded with blowing agent and expanded, which leads to cellular plastic particles with special properties. In particular, customized plastic particles can be produced for specific applications or fields of application through a targeted selection and concentration of appropriate additives or materials. The additives or additives can have been introduced into the pre-expanded plastic material particles during their production. In particular, by fibers or materials - this can basically be organic or inorganic fibers or materials. B. aramid, glass, carbon or natural fibers - can be, with regard to the further processing, special material properties of the process according to produce or manufactured cellular plastic particles or a from the process according to manufacturable or manufactured cellular plastic particles produced particle foam molded part realized . Corresponding cellular plastic particles or molded foam parts made from them can, on the one hand, be characterized by a special density due to their cellular structure and, on the other hand, in particular due to processing-related mechanical connections between adjacent cells within respective cellular plastic particles and/or between respective adjacent cellular plastic particles due to special mechanical characterize properties. During the subsequent processing into molded particle foam parts, these special mechanical properties can be used locally or integrally or modified. The same applies - basically regardless of their chemical composition for non-fibrous or -shaped additives or materials, such. B. for spherical or -shaped or platelet-like or -shaped organic and / or inorganic cal additives or materials.

In addition to influencing the mechanical properties of the plastic particles in a targeted manner, appropriate additives or materials, e.g. B. also the electrical properties and / or the thermal properties of the plastic particles can be influenced sen targeted. Consequently, for example by electrically and/or thermally conductive additives or materials, such as e.g. B. metal and / or soot particles, etc., plastic particles with special electrically and / or thermally conductive properties can be produced.

The concentration of corresponding additives or materials can in principle be freely selected, although typically depending on the material. It is therefore only given as an example that pre-expanded plastic material particles with one (or more) additives) or material(s) in a (respective) concentration between 0.01% by weight, this applies in particular to chemically active additives, and 60 % by weight, this applies in particular to fibrous additives, can be provided or used. As indicated, the concentration is typically dependent on the specific chemical and/or physical properties of the additives or materials or their combination.

It was mentioned that basically any thermoplastic material can be provided or used as the starting material according to the method. Merely by way of example, it is to be understood that plastic material particles pre-expanded according to the method from the group: 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, polyvinyl chloride, polystyrene blend, thermoplastic Elastomer blend provided or used. Blends or copolymers or mixtures of different thermoplastic materials can also be used; Modified PPE (mPPE) is only mentioned as an example in this context.

If blends are used which contain at least two components that differ in at least one chemical and/or physical parameter and/or the parameter relating to the molecular configuration, these can basically be in any proportionate compositions, with the respective proportions being 100% add, present. Correspondingly, a first component can have any proportion by weight between 1 and 99% by weight and a second component can have any proportion by weight between 99 and 1% by weight, with the respective proportions adding up to 100% by weight. Of course, proportions below 1% by weight and above 99% by weight are also conceivable.

All plastic materials used can, as mentioned, with one or more additives such. As fibers, be provided. All plastic materials used can be recyclates or contain a proportion of recyclates.

It was mentioned that the properties of the cellular plastic particles of lower density that can be produced or produced according to the method can be influenced in particular by the process conditions during the loading process and the expansion process.

According to the method, depending on the selected process conditions, e.g. B. cellular plastic particles are made with a uniformly or unevenly distributed cellular structure forth. The properties, i. H. In particular, the distribution of the cellular structure within the respective cellular plastic particles can therefore be determined not only by material-specific parameters (also) by pressure, temperature and time during loading or expansion as well as by the conveying or dwell times or conditions between the individual process steps influence.

If cellular plastic particles with an unevenly distributed cellular structure are produced according to the method, each cellular plastic particle can have a different number, shape and/or size of cells in an edge area than in a core area. It is therefore possible to produce graded cellular plastic particles which, due to the different distribution of cell number, cell shape and/or cell size, have a special spectrum of properties. Graded cellular plastic particles can therefore have different cellular properties in an (outer) edge area than in an (inner) core area, for example in the manner of core-shell particles.

Correspondingly configured cellular plastic particles can be achieved in particular by (too) short loading of the compact starting material with propellant, which then only accumulates near the edge, so that further expansion occurs, especially at the edge. Conversely, an (excessively) long aging period between loading of propellant and expansion can lead to cellular plastic particles in which the “core” is predominantly foamed.

In general, it is true that, according to the method, in particular cellular plastic particles with a cell size in a range between 0.5 and 250 μm can be produced. The actual cell size - of course, an average is typically mentioned here - can therefore be set over a very wide range and thus tailor-made according to the method, depending on the selected process conditions. The same applies to any distribution of the cell size within the respective cellular plastic particles.

In general, it also applies that, in particular depending on the degree of expansion and optionally the proportion of filler, cellular plastic particles with a bulk density in a range between 5 and 1500 g/l can be produced according to the method. The actual bulk density - of course, an average is typically mentioned here as well - can therefore be set over a very wide range depending on the selected process conditions and can therefore be tailored.

In the following, purely as an example, pre-expanded plastic material particles that can be specifically processed or processed within the scope of the method as well as associated parameters for carrying out the second and third steps of the method are listed:

As part of a first example, a pre-expanded polycarbonate plastic material, ie plastic material particles made of polycarbonate, with a bulk density of approx. 140 g/l was (were) provided in the first step of the method. In the second step of the process, the pre-expanded plastic material particles were loaded with air as the blowing agent in a pressure vessel at a pressure of approx. 40 bar for a period of 10 hours without separate temperature control. The pressure rise rate was about 10 bar per hour. In the third step of the process, the plastic material particles loaded with propellant were expanded by, in particular continuously or discontinuously, conveying the pre-expanded plastic material particles loaded with propellant through an infrared continuous oven comprising a plurality of infrared emitters, thus by conveying the plastic material particles along one by one A conveyor or temperature control section with a length of approx. 5 m was formed by a number of temperature control elements in the form of infrared radiators with a total radiator output of approx. 10 kW. The temperature of the conveyor belt at the entrance to the conveyor section was approx. 80°C, the temperature of the conveyor belt at the exit of the conveyor or temperature control section was approx. 160°C. The conveying speed was approx. 700 mm/s. The cellular plastic particles produced in this way had a bulk density of approx. 115 g/l.

As part of a second example, a pre-expanded, expandable polyamide plastic material, ie plastic material particles made of an expandable polyamide, with a bulk density of approx. 420 g/l was/are provided in the first step of the method. the Expanded plastic material particles were loaded with air as blowing agent in a pressure vessel at a pressure of about 8 bar for a period of 40 h without separate temperature control in the second step of the process. The pressure rise rate was about 1 bar per hour. In the third step of the method, the plastic material particles loaded with blowing agent were expanded by, in particular continuously or discontinuously, conveying the pre-expanded plastic material particles loaded with blowing agent through an infrared continuous oven comprising a plurality of infrared emitters, thus by conveying the plastic material particles along one through a plurality 10 kW conveying or temperature control section with a length of approx. 5 m. The temperature of the conveyor belt at the entrance to the conveyor section was approx. 90°C, the temperature of the conveyor belt at the exit of the conveyor or temperature control section was approx. 220°C. The conveying speed was approx. 450 mm/s. The cellular plastic particles produced in this way had a bulk density of approx. 225 g/l.

As part of a third example, a pre-expanded, expandable polypropylene plastic material, ie plastic material particles made of polypropylene, with a bulk density of approx. 75 g/l was/are provided in the first step of the method. The pre-expanded synthetic material particles were charged with air as the propellant for a period of 100 h without separate temperature control in the second step of the procedural procedure in a pressure vessel at a pressure of about 8 bar. The pressure rise rate was about 0.2 bar per hour. In the third step of the process, the plastic material particles loaded with blowing agent were expanded by, in particular continuous or discontinuous, conveying of the pre-expanded plastic material particles loaded with blowing agent through an infrared continuous oven comprising several infrared emitters, thus by conveying the plastic material particles along a line through a line A plurality of tempering elements in the form of infrared radiators with a total radiator power of about 20 kW formed a conveying or tempering section with a length of about 5 m The temperature of the conveyor belt at the exit of the conveyor or temperature control section was around 160°C. The conveying speed was approx. 450 mm/s. The cellular plastic particles produced in this way had a bulk density of about 35 g/l.

A second aspect of the invention relates to a particle foam material which is formed by or contains or comprises cellular plastic particles which were produced using the method according to the first aspect.

A third aspect of the invention relates to a method for processing a plastic particle material according to the second aspect for the production of a particle foam molding.

A fourth aspect relates to a device for producing cellular plastic particles, in particular according to a method according to the first aspect, comprising: - A first device, which is set up for loading the pre-expanded thermoplastic with a blowing agent under the influence of pressure, the device in particular a loading device, z. B. in the form of a pressure vessel means comprises; and

- A second device, which is set up to expand the propellant for producing cellular plastic particles under the influence of temperature, the second device in particular comprising an expansion device in the form of a radiation generating device for generating high-energy radiation, in particular infrared radiation.

The second device can therefore be designed in particular as a radiation-based heating device or can include such a device.

The second device can include a conveying device, in particular a combined conveying and temperature control device. A corresponding combined funding and Temperierein direction z. B. as a continuous furnace, in particular as one or more infrared emitters comprehensive infrared continuous furnace, or at least one such comprehensive sen.

The second device can also be an expansion device, such as e.g. B. a relaxation room in which the cellular plastic particles produced rule under defined chemical and / or physical conditions, d. H. in particular a defined temperature ratio, be outsourced (relaxed) for a defined time, be assigned or who the. A corresponding relaxation device can, for. B. be designed as a decompression device or include such.

It is conceivable that the device also comprises the or a conveying device, by means of which the cellular plastic particles produced are conveyed continuously or discontinuously through a corresponding expansion space.

The device can also include suitable handling devices for handling the pre-expanded plastic material particles for their provision and/or for removing the cellular plastic particles produced. Corresponding handling devices can also be designed as conveyor devices or include such. In particular, suitable conveyors, such as e.g. B. pneumatic Fördereinrichtun gene, which are set up to form a conveying flow into consideration.

In principle, the device can comprise a conveying device, by means of which the pre-expanded plastic material particles or subsequently the cellular plastic particles can be conveyed continuously or discontinuously through the individual devices of the device. All statements in connection with the method according to the first aspect apply analogously to the particle foam material according to the second aspect, the method according to the third aspect and the device according to the fourth aspect.

The invention is explained again below by way of example using exemplary embodiments with reference to the figures. It shows:

FIG. 1 shows a flow chart to illustrate a method according to an embodiment; FIG.

2 shows a schematic representation of a device for carrying out a method according to an exemplary embodiment; and

3, 4 each show a basic representation of a cellular plastic particle produced according to the method according to an exemplary embodiment.

FIG. 1 shows a flow chart to illustrate a method according to an exemplary embodiment.

The process is a process for producing cellular plastic particles; the method is therefore used to produce cellular plastic particles. The plastic particles that can be produced or produced according to the method and have a lower density compared to the starting material are therefore plastic particles that have a cellular structure at least in sections, if necessary completely. In addition, the plastic particles can have a certain (further) expansion capacity, in particular due to a certain content of blowing agent—whether it is a residue from the described method or is introduced subsequently in a separate process step. The cellular plastic particles density that can be produced or produced according to the method can therefore be expandable and/or (mechanically) compressible or compressible.

The cellular plastic particles with low density that can be produced or produced according to the method can be further processed in one or more independent subsequent processes to form a particle foam molding. The further processing of the plastic particles into a particle foam molded part can take place using steam or superheated steam (steam-based) or without the use of steam or superheated steam (non-steam-based or dry).

The steps of the process for the production of cellular plastic particles density are explained in more detail below with reference to FIGS. 1 and 2. FIG.

In a first step S1 of the method, a plastic material is provided in the form of pre-expanded plastic material particles. The provided pre-expanded plastic material particles can also be referred to as "pre-expanded plastic particles". be designated. The pre-expanded plastic material particles to be considered as starting material, which are typically thermoplastic plastic material particles, are thus provided in the first step of the process. The starting material provided is therefore in the form of particles, ie in particular in the form of bulk material. In the first step, therefore, at least one measure is generally carried out to provide a particulate, ie in particular bulk material-like or shaped, (thermoplastic) plastic material in the form of corresponding pre-expanded plastic material particles. The density of the pre-expanded plastic material particles provided in the first step of the method is typically below 1 g/cm ³ , depending on the material composition or modification due to the cellular structure, in particular in a range between 0.05 and 2.2 g/cm ³ , from which the pre-expanded properties of the provided pre-expanded plastic material particles result; the matrix of the pre-expanded plastic material particles provided therefore has a porous or cellular structure.

The first step S1 of the method can be carried out, optionally at least partially or partially automated, by means of a supply device 2 shown purely schematically in FIG. 2, which is set up for the continuous or discontinuous supply of corresponding pre-expanded plastic material particles. A corresponding delivery device 2 can, for. B. be a conveyor, by means of which to be processed into corresponding cellular plastic particles pre-expanded plastic material particles to a or in a second step of the method executing (n) loading device 3 can be promoted. A corresponding conveyor can, for. B. be designed as a belt conveyor or flow conveyor or to summarize such. The conveying of the pre-expanded plastic material particles to or into a loading device 3 executing the second step of the method can therefore include receiving the pre-expanded plastic material particles in a conveying flow; the pre-expanded plastic material particles can then be conveyed by means of a conveying flow to or into a loading device 3 executing the second step of the method.

In a second step S2 of the method, the pre-expanded plastic material particles are loaded with a blowing agent at least under the influence of pressure. In the second step, the pre-expanded plastic material particles are then loaded with a propellant, at least under the influence of pressure—if necessary, depending on the material, in addition to a specific pressure, a specific (elevated) temperature can also be used. In In the second step, at least one measure for loading the pre-expanded plastic material particles with a blowing agent is carried out at least under the influence of pressure, and therefore at least under pressure. Phenomenologically, in the second step of the process, the blowing agent typically accumulates in the respective pre-expanded plastic material particles. The enrichment of the blowing agent in the respective pre-expanded plastic material particles can, in particular depending on the chemical configuration of the pre-expanded plastic material particles, the blowing agent and the additives or materials possibly contained therein, as well as depending on the pressure or Temperature conditions, for example resulting from or due to absorption and/or solution processes of the blowing agent in the respective pre-expanded plastic material particles. Because of the cellular structure of the pre-expanded plastic material particles, the blowing agent can also accumulate within the cell spaces defined by the cellular structure; consequently, the inner volume defined by the cell spaces of a respective pre-expanded plastic material can be used as a receiving space for receiving blowing agent in the second step of the method.

The pressure level and the rate of pressure rise in the second step of the method are typically selected, in particular depending on the material, in such a way that the cellular structure of the pre-expanded plastic material particles is not damaged; in particular, the pressure level and rate of pressure rise are selected in the second step of the method so that the cellular structure of the pre-expanded plastic material particles does not deform plastically and even collapses under pressure (effective difference between the external loading pressure and the internal cellular pressure).

Gases such as B. carbon dioxide or a mixture containing carbon dioxide and / or nitrogen, such as. As air, can be used. In general, any combustible or non-combustible organic gas, i. H. especially butane or pentane; or inert gases such as B. Noble gases d. H. in particular helium, neon, argon; or nitrogen, or mixtures thereof. The term “blowing agent” can therefore also include a mixture of chemically and/or physically different blowing agents. The propellant is typically selected taking into account its absorption capacity in the pre-expanded plastic material particles, and therefore taking into account the chemical and/or physical configuration or composition of the pre-expanded plastic material particles. If the pre-expanded plastic material particles contain additives or materials, the properties such. B. the chemical and / or physical Konfig ration of the additives or materials are also taken into account when selecting the propellant.

The second step S2 of the method can, if necessary, be at least partially automated or partially automated by means of a loading device 3 shown purely schematically in FIG Propellant is set up at least under the influence of pressure or to carry out a corresponding loading process. A corresponding loading device 3 can, for. B. as an autoclave device, ie generally as a pressure vessel device 3.1 comprising a pressure or process space, or include such a device. A corresponding loading device 3 can also have a temperature control device 3.2, which is set up to control the temperature of a corresponding pressure or process space. A corresponding loading device can in all cases have a control and/or regulation unit 3.3 implemented in terms of hardware and/or software, which is used for controlling and/or regulating, ie generally for setting, certain dynamic and/or static pressure and/or or temperature parameters is set up within the pressure or process space.

In a third step of the method, the pre-expanded plastic material particles loaded with blowing agent are expanded under the influence of temperature, ie in particular elevated temperature, to produce cellular plastic particles. In the third step of the method, the pre-expanded plastic material particles loaded with blowing agent are then typically exposed to <elevated> temperature, ie generally thermal energy, which leads to outgassing and/or expansion of the blowing agent contained in the pre-expanded plastic material particles. In particular, the outgassing of the blowing agent in the cells and the matrix areas of the thermally softened or softened pre-expanded plastic material particles causes renewed or further expansion of the plastic material particles, which, after cooling or "freezing", leads to the formation of plastic particles with a, possibly compared to the starting material , For example with regard to cell number, cell shape and/or cell size, permanent cellular structure and thus leads to the formation of the cellular plastic particles to be produced. In the third step of the method, at least one measure for outgassing or expanding the blowing agent contained in the preexpanded plastic material particles softening or softened at least under the influence of temperature and thus at least thermally is generally carried out for the production of cellular plastic particles. Phenomenologically, in the third step of the method, in particular due to the outgassing or desorption of the propellant from the cells and the matrix areas of the softening or softened pre-expanded plastic material particles, cell growth, possibly further cell growth and possibly renewed cell formation with subsequent cell growth within, occur of the pre-expanded plastic material particles, which leads to the cellular plastic particles to be produced. The cell formation, if such occurs, is typically based on the aforementioned desorption of the propellant at nucleation points in the plastic material particles that are softening or softened by the influence of temperature, while cell growth is typically based on an overpressure-related expansion of the propellant in already formed or existing cells. As also mentioned, the cellular structure formed in this way or the further expansion state thus realized is reduced by or by a temperature reduction of the cellular plastic particles thus produced, i.e. by cooling them down, e.g. B. in the environment, permanently "frozen" or fixed. In principle, therefore, it applies that after completion of the pressurization that follows in the second step of the method, ie when the pressure drops, in particular to normal or standard conditions, outgassing or desorption processes take place within respective preexpanded plastic material particles loaded with propellant and typically thermally softened . The outgassing or desorption processes of the blowing agent are an essential prerequisite for the cell growth processes required for the production of cellular plastic particles and, if necessary, cell formation processes within the respective plastic material particles pre-expanded plastic material particles, the cellular plastic particles to be produced according to the method are formed in the third step of the method, in particular due to corresponding outgassing or desorption processes. As will be explained below, cellular structures with locally different cell properties and thus graded cellular plastic particles can be realized by controlling corresponding outgassing or desorption-related cell formation and cell growth processes.

The nucleation in connection with a targeted adjustment of the softening behavior has a decisive influence on the desorption of the propellant. In particular, a large number of new small cells can be formed by a large number of individual nucleation points, which leads to a fine cell structure within the respective cellular plastic particles. A corresponding fine cell structure is characterized in particular by small cells and a largely homogeneous distribution of these within the respective cellular plastic particles.

In particular, the process can be used to form cellular plastic particles with an (average) cell size below 100 μm, in particular below 75 μm, more particularly below 50 μm, more particularly below 25 μm.

The third step S3 of the method can be carried out, optionally at least partially or partially automated, by means of an expansion device 4, which is set up for the radiation-based expansion of the blowing agent for the production of cellular plastic particles at least under the influence of temperature for carrying out a corresponding radiation-based expansion process. A corresponding expansion device 4 is therefore typically designed as a radiation-based heating device, ie in general as a temperature control or process room comprehensive temperature control device 4.1, be formed or include such. A corresponding temperature control device 4.1 can also have a conveyor device 4.3, which is set up for conveying the plastic material particles to be expanded along a conveyor path through a corresponding temperature control or process space. A corresponding expansion device 4 can in all cases have a control and/or regulation unit 4.2 implemented in terms of hardware and/or software, which is used for controlling and/or regulating, ie generally for setting, specific dynamic and/or static conveying and/or or temperature parameters are set up within a corresponding temperature control or process room.

The density of the cellular plastic particles produced in the third step S3 of the method is typically well below the initial density of the pre-expanded plastic material particles provided in the first step S1, which results in the cellular properties of the plastic particles that can be produced or produced according to the method. The bulk density of the cellular plastic particles produced in the third step S3 of the method is correspondingly well below the bulk density of the pre-expanded plastic material particles provided in the first step S1 of the method.

As mentioned above, the cellular plastic particles produced in the third step S3 of the method can be (further) expandable; this can represent an essential property for the described, in particular steam-based or non-steam-based, further processing of the cellular plastic particles for the production of particle foam moldings.

As indicated, the loading of the pre-expanded plastic material particles with a blowing agent can be carried out under the influence of pressure and temperature. The parameters that can be varied, in particular depending on the material, for loading the pre-expanded plastic material particles with blowing agent and for the targeted adjustment of certain properties of the cellular plastic particles to be produced or produced are therefore initially the pressure and temperature conditions prevailing in the second step S2 of the method. Of course, the time, i. H. in particular the course and the duration of the pressure and temperature conditions in the second step of the method, a parameter which has an influence on the loading of the pre-expanded plastic material particles with blowing agent, d. H. in particular the absorption or enrichment of the blowing agent in the pre-expanded plastic material particles.

The loading of the pre-expanded plastic material particles with the or a propellant can, for. B., in particular depending on the chemical composition of the preexpandier th plastic material particles and / or the propellant, z. B. at a pressure in a range between 1 and 200 bar. The pressure refers in particular to the pressure within a pressure or process space of a corresponding loading device 3 during the execution of the second step S2 of the method. The loading of the pre-expanded plastic material particles with the or a propellant can, for. B., in particular depending on the chemical composition of the preexpandier th plastic material particles and / or the propellant, z. B. be carried out at a temperature in a range between 0 and 250 ° C. The temperatures relate in particular to temperatures within a pressure or process space of a corresponding loading device during the execution of the second step S2 of the method.

The loading of the pre-expanded plastic material particles with the or a propellant can, for. B., in particular depending on the chemical composition of the preexpandier th plastic material particles and / or the propellant, for a period of time z. B. be carried out in a Be rich between 0.1 and 1000 h. The time durations mentioned above as examples relate in particular to the pressure or temperature loading of the plastic material particles within a pressure or process space of a corresponding loading device 2 during the execution of the second step S2 of the method.

The expansion of the plastic material particles loaded with blowing agent to produce the cellular plastic particles under the influence of temperature, in particular depending on the chemical composition of the plastic particle material loaded with blowing agent and/or the blowing agent, can, for. B. at normal pressure, and therefore an ambient pressure of about 1 bar, can be carried out. A particular pressure level, e.g. B. a positive or negative pressure level, is therefore possible to expand the loaded with propellant pre-expanded plastic material particles for the production of cellular plastic particles, but not mandatory, which basically simplifies the expansion process.

The expansion of the plastic material particles loaded with blowing agent for the production of the cellular plastic particles under the influence of temperature can, for. B., in particular in depen dence on the chemical composition of the laden with propellant Kunststoffinstrumentema material and / or the propellant, at a temperature z. B. in a range between 0 and 300 ° C can be carried out. The temperatures mentioned above can relate in particular to an inlet temperature when the pre-expanded plastic material particles loaded with blowing agent enter a corresponding expansion device 4 and/or to an outlet temperature when the cellular plastic particles exit from a corresponding expansion device 4 . Corresponding inlet and outlet temperatures can be the same, similar or different. If a corresponding expansion device 4 has a conveyor device 4.31, which is set up to convey the plastic material particles loaded with propellant along corresponding temperature control devices 4.1, the aforementioned temperatures can increase to a temperature when the pre-expanded plastic particle material loaded with propellant enters a corresponding expansion or Temperature control device 4.1 (inlet temperature), consequently to an initial area of a corresponding conveyor device 4.3, and/or to an outlet temperature when the plastic particles exit from a corresponding expansion or temperature control device 4 (outlet temperature temperature), and therefore to an end area of a corresponding conveyor. Typically, the inlet temperature is lower than the outlet temperature.

The expansion of the pre-expanded plastic material particles loaded with blowing agent under the influence of temperature can take place by irradiating the pre-expanded plastic particle material loaded with blowing agent with high-energy thermal radiation, in particular infrared radiation. The tempering, i. H. in particular the heating of the pre-expanded plastic material particles loaded with propellant can, in particular depending on the material, by selecting and/or adjusting the properties of high-energy radiation, d. H. in particular their wavelength, so take place in a targeted manner, without risking melting through which is undesirable for the expansion process of the plastic material particles loaded with blowing agent, i.e. insufficient stability of the softened plastic material particles, when the pre-expanded plastic material particles loaded with blowing agent soften . Infrared radiation has been shown to be particularly suitable in investigations, as this allows for a targeted and, in conjunction with a conveying device, very well controllable volume heating of the pre-expanded plastic material particles loaded with blowing agent, a controllable softening process and thus - this is for setting the properties of the cellular plastic particles to be produced essential - enables a controllable expansion process.

In particular, the expansion of the plastic material particles loaded with blowing agent can take place under the influence of temperature by irradiating the pre-expanced plastic material particles loaded with a blowing agent with high-energy thermal radiation, in particular infrared radiation, with the plastic material particles loaded with blowing agent on at least one conveying path defined by a conveying device 4.3. in particular continuously, along at least one corresponding high-energy radiation, ie in particular infrared radiation, generating radiation generating device 4.4. A corresponding radiation-generating device 4.4 can be designed in particular as an infrared oven, in particular an infrared continuous oven, or can include one. A corresponding infrared oven can comprise one or more infrared emitters arranged or formed along a corresponding conveying path. Corresponding infrared emitters can, for example, have an optionally variable radiation power in a range between 1 and 500 kW. The services mentioned above can relate in particular to area performance per m ² . In particular, area outputs between 5 and 100 kW/m ² can be used. Different temperature zones can be generated by variable emitters or variable emitter (area) outputs, which also provides a parameter for influencing the expansion process.

According to the method, after the expansion of the plastic material particles loaded with blowing agent for the production of the cellular plastic particles under the influence of (in particular compared to the expansion process previously carried out) temperature, cooling of the cellular plastic particles produced can be carried out, as indicated above. the. The cellular structure of the cellular plastic particles that is present after the expansion process can be “frozen” by the cooling, which takes place expediently quickly. In this way, any further, integral or even local expansion of the plastic particles that may be undesirable after the expansion process can be specifically prevented, for example in order to maintain a cellular structure of the plastic particles that may be desired after the expansion process. The cooling can take place in particular from a process temperature lying above a reference temperature, in particular room temperature can be used as the reference temperature, to a cooling temperature lying below the process or reference temperature, in particular room temperature. Consequently, separate temperature control devices for cooling the plastic particles are not absolutely necessary, but it may be sufficient if the plastic particles are cooled to room temperature after the expansion process or stored at room temperature.

According to the method, as also indicated above, at least one, in particular functional, additive or material, for example a fibrous substance or material and/or a dye or material and/or a nucleating substance or material and/or or a substance or a material for specifically influencing or controlling the softening behavior of the plastic material particles loaded with propellant, containing pre-expanded plastic particle material, is provided or used. Thus, according to the method, compounded pre-expanded plastic material particles can also be loaded with propellant and expanded, which leads to cellular plastic particles with special properties. In particular, it is possible to produce tailor-made plastic particles for certain applications or fields of application by means of a targeted selection and concentration of the corresponding additives or materials. The additives or additives can have been introduced into the pre-expanded plastic material particles during their production.

In particular, by fibers or materials - this can basically be organic or inorganic fibers or materials. B. aramid, glass, carbon or natural fibers - can be, with regard to the further processing, special material properties of the process according to produce or manufactured cellular plastic particles or a from the process according to manufacturable or manufactured cellular plastic particles produced particle foam molded part realized . Corresponding cellular plastic particles or molded foam parts made from them can, on the one hand, be characterized by a special density due to their cellular structure and, on the other hand, in particular due to processing-related mechanical connections between adjacent cells within respective cellular plastic particles and/or between respective adjacent cellular plastic particles due to special mechanical characterize properties. During the subsequent processing into molded particle foam parts, these special mechanical properties can be used locally or integrally or modified. The same applies - basically regardless of their chemical composition for non-fibrous or -shaped additives or materials, such. B. for spherical or -shaped or platelet-like or -shaped organic and/or inorganic additives or materials.

The concentration of corresponding additives or materials can in principle be freely selected, although typically depending on the material. It is therefore only given as an example that pre-expanded plastic material particles with one (or more) additives) or material(s) in a (respective) concentration between 0.01% by weight, this applies in particular to chemically active additives, and 60 % by weight, this applies in particular to fibrous additives, can be provided or used. As indicated, the concentration is typically dependent on the specific chemical and/or physical properties of the additives.

According to the method, basically any thermoplastic material can be provided or used as the starting material. For example, according to the method, pre-expanded plastic material particles from the group: 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, provided or used. Blends or copolymers or mixtures of different thermoplastic materials can also be used.

According to the process, depending on the selected process conditions, e.g. B. cellular plastic particles can be produced with a uniformly or unevenly distributed cellular structure. The properties, i. H. In particular, the distribution of the cellular structure within the respective cellular plastic particles can therefore be influenced not only by material-specific parameters (also) by pressure, temperature and time during loading or expansion as well as by the conveying times or conditions between the individual process steps S1 - S3.

If cellular plastic particles with an unevenly distributed cellular structure are produced according to the method, each cellular plastic particle can have a different number and/or shape and/or size of cells in an edge area than in a core area. Consequently, graded cellular plastic particles can be produced, which due to the different distribution of cell number, cell shape and/or cell size have a special spectrum of properties. Graded cellular plastic particles can therefore have different cellular properties in an (outer) edge area than in an (inner) core area, for example in the manner of core-shell particles.

The embodiment shown in Fig. 2 of a device 1 for carrying out the procedural procedure comprises the mentioned provision device 2, which is generally the first device, which is set up for loading the pre-expanded thermoplastic with a blowing agent under the influence of pressure, loading device 3 and the general as a second device, which is set up to expand the blowing agent for the production of cellular plastic material particles under the influence of temperature, expansion device 4.

The provision device 2 can comprise a suitable handling device for handling the pre-expanded plastic material particles for their provision. In an analogous manner, the device 1, although not shown, can include a handling device 5 downstream of the expansion device 4 for removing the cellular plastic particles produced. Corresponding handling devices can, as mentioned, be designed as conveying devices or include such devices. In particular, for the promotion of bulk suitable conveyors such. B. pneumatic conveyors, which are set up to form a conveying flow, into consideration.

As mentioned, the second device can comprise a conveying device, in particular a combined conveying and temperature control device. A corresponding combined conveyor and temperature control device can, for. B. as a continuous furnace, in particular as one or more infrared emitters comprehensive infrared continuous furnace, be formed or comprise at least one such.

The second device may also include an expansion device (not shown), such as e.g. B. a relaxation room, in which the produced cellular plastic particles are stored under defined chemical and / or physical conditions, ie in particular defined temperature ratio, for a defined time, be or will be assigned. A corresponding relaxation device can, for. B. be formed as a decompression device or include such. In all of the exemplary embodiments, it is conceivable for the device 1 to comprise a conveying device, by means of which the pre-expanded plastic material particles or subsequently the cellular plastic particles are conveyed continuously or discontinuously through the individual devices 2 - 4 .

3 shows a basic illustration of a cellular plastic particle produced according to the method according to an exemplary embodiment in a sectional view. Specifically, this is a detail of a microscopic image of a foam bead made of pre-expanded polypropylene (EPP) with an initial bulk density of about 75 g/l cellular plastic particle produced according to the process with a reduced bulk density of about 17 g/l.

FIG. 4 shows a basic representation of a cellular plastic particle produced according to the method according to an exemplary embodiment. The schematic diagram shows a cellular plastic particle with locally different cell properties and thus a graded cellular plastic particle. In concrete terms, the cellular plastic particle has an unevenly distributed cellular structure when the plastic particle has a different number of cells in an edge region R, namely a higher number than in a core region K. The dashed inner line indicates that the transitions between the edge area R and the core area K can be continuous. The edge region R can optionally be shaped to different degrees locally.

Claims

GODFATHER TAN SAYINGS

1. A method for producing cellular plastic particles, characterized by the steps:

- Providing a plastic material in the form of pre-expanded plastic material particles,

- Loading the pre-expanded plastic material particles with a blowing agent under the influence of pressure,

- Expanding the pre-expanded plastic material particles loaded with propellant to produce cellular plastic particles, in particular cellular plastic particles with lower density, under the influence of temperature, the expansion of the plastic material particles loaded with propellant under the influence of temperature by irradiating the plastic material particles loaded with propellant high-energy thermal radiation, in particular infrared radiation, takes place.

2. The method according to claim 1, characterized in that the loading of the pre-expan ded plastic material particles with a blowing agent is additionally carried out under the influence of temperature.

3. The method according to claim 1 or 2, characterized in that the loading of the pre-expanded plastic material particles with a blowing agent, in particular depending on the chemical composition of the plastic material particles, is carried out at a pressure in a range between 1 and 200 bar.

4. The method according to claim 2 or 3, characterized in that the loading of the pre-expanded plastic material particles with a propellant, in particular depending on the chemical composition of the plastic material particles, is carried out at a temperature in a range between 0 and 250°C.

5. The method according to any one of the preceding claims, characterized in that the loading of the pre-expanded plastic material particles with a blowing agent, in particular special depending on the chemical composition of the plastic material particles, is carried out for a period in a range between 0.1 and 1000 hours.

6. The method according to any one of the preceding claims, characterized in that the expansion of the plastic material particles loaded with blowing agent under the influence of temperature, in particular depending on the chemical composition of the plastic material particles loaded with blowing agent, at a temperature in a range between 20 and 300 ° C is performed.

7. The method according to any one of the preceding claims, characterized in that the expansion of the loaded with blowing agent plastic material particles under the influence of temperature by irradiating the loaded with blowing agent plastic material particles high-energy thermal radiation, in particular infrared radiation, takes place, the plastic material particles loaded with propellant being conveyed on at least one conveying path along at least one corresponding high-energy radiation-generating radiation generating device.

8. The method according to any one of the preceding claims, characterized in that after the expansion of the plastic material particles loaded with blowing agent for the production of the cellular plastic particles under the influence of temperature, the cellular plastic particles are cooled from a process temperature to a cooling temperature below the process temperature .

9. The method according to any one of the preceding claims, characterized in that pre-expanded plastic material particles are provided or used, which contain at least one, in particular functional, additive or material, in particular a fibrous material or material and/or a dye or material and/or nucleating agents and/or additives for the targeted influencing of the softening behavior.

10. The method according to claim 9, characterized in that plastic material particles are provided or used with at least one additive or material in a concentration of between 0.01% by weight and 60% by weight.

11. The method according to any one of the preceding claims, characterized in that pre-expanded plastic material particles from the group: 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 or is used.

12. The method according to any one of the preceding claims, characterized in that cellular plastic particles are produced with a uniformly or unevenly distributed cellular structure.

13. The method according to claim 12, characterized in that cellular plastic particles are produced with an unevenly distributed cellular structure within respective cellular plastic particles, wherein respective cellular plastic particles have a different number and/or size and/or shape in an edge area Have cells than in a core area.

14. The method according to any one of the preceding claims, characterized in that a combustible or non-combustible organic gas, d. H. especially butane or pentane; or an inert gas such as B. Noble gases, d. H. in particular helium, neon, argon; or nitrogen, carbon dioxide, or a mixture such as. B. air is used.

15. The method according to any one of the preceding claims, characterized in that cellular plastic particles are produced with a cell size in a range between 1 and 250 μm, in particular a cell size below 25 μm.

16. The method according to any one of the preceding claims, characterized in that cellular plastic particles are produced with a bulk density in a range between 5 and 1500 g/l.

17. Plastic particle material, which is formed by cellular plastic particles, which are produced according to a method according to any one of the preceding claims, or comprises such.

18. Method for processing a plastic particle material according to claim 17 for the production of a three-dimensional object.

19. Device (1) for the production of cellular plastic particles, in particular according to a method according to any one of claims 1 to 16, comprising:

- A first device which is set up for loading pre-expanded plastic material particles with a propellant under the influence of pressure, the device comprising in particular a pressure vessel device; and

- A second device, which is set up to expand the blowing agent for the production of cellular plastic particles under the influence of temperature, the second device comprising a radiation generating device for generating high-energy radiation, in particular infrared radiation.