CN111805857A

CN111805857A - Method for sorting plastics, moulding method, plastifying assembly and moulding machine

Info

Publication number: CN111805857A
Application number: CN202010277343.8A
Authority: CN
Inventors: R·马尔库特-科尔; K·费尔纳; T·科普迈尔; G·克拉默
Original assignee: Engel Austria GmbH
Current assignee: Engel Austria GmbH
Priority date: 2019-04-10
Filing date: 2020-04-10
Publication date: 2020-10-23
Anticipated expiration: 2040-04-10
Also published as: DE102020109595A1; CN111805857B; AT522378A1; AT522378B1

Abstract

The invention relates to a method for sorting plastics, wherein the plastics are plasticized by supplying plasticizing energy in the form of mechanical and/or thermal energy with the temperature of the plastics increasing from a starting temperature value to an end temperature value, the volume and/or mass of the plastics and the supplied plasticizing energy being detected by a measuring technique as measuring variables, and at least one of the following being determined from the detected measuring variables, starting temperature value and end temperature value: the heat capacity of the plastic and/or the enthalpy change of the plastic and/or a parameter which can be derived from the heat capacity and/or the enthalpy change by calculation, and a plastic group containing plastic is identified on the basis of the determined heat capacity and/or the determined enthalpy change and/or the parameter which can be derived from the heat capacity and/or the enthalpy change by calculation. The invention also relates to a molding method, a plasticizing component and a molding machine.

Description

Method for sorting plastics, moulding method, plastifying assembly and moulding machine

Technical Field

The invention relates to a method for sorting plastics, a moulding method, a plastifying assembly and a moulding machine.

Background

The prior art is described below with the aid of a molding machine, wherein, inter alia, an example of an injection molding machine is discussed. But the types of molding machines include injection presses, and the like in addition to injection molding machines. The following description of the prior art applies analogously to the injection press, press and the like.

In the case of an injection molding process, basic settings are in practice usually made by the operator of the injection molding machine, as is conventional. This also applies to the setting of a plasticizing process by means of which plastic granules, for example in the case of a plasticizing screw, are converted into a moldable material.

The operator is limited in this case by his experience and by the "trial and error" practice, since the non-linear nature of the plasticizing and molding process largely prevents the automatic setting of the injection molding machine of the prior art, although efforts have been made to enable the automatic setting of the injection molding machine since a relatively long time. Due to the material dependence of the process and the mentioned non-linear nature of the process, the automated setting of the injection molding machine often fails because the plastic used is unknown or the operator's input relating to this cannot be checked automatically.

Disclosure of Invention

The object of the invention is to provide a method by means of which plastics can be sorted and which can be carried out at reasonable cost even on or at least next to a moulding machine.

In a first aspect of the invention, the object is achieved by a method for sorting plastics. This is achieved by:

a) plasticizing the plastic by supplying plasticizing energy in the form of mechanical and/or thermal energy with an increase in the temperature of the plastic from a starting temperature value to an end temperature value;

b) detecting the volume and/or mass of the plastic and the supplied plasticizing energy as measurement variables by means of a measurement technique;

c) determining, from the detected measurement quantity, the start temperature value and the end temperature value, at least one of: the heat capacity of the plastic and/or the enthalpy change of the plastic and/or a parameter derivable from the heat capacity and/or the enthalpy change by calculation; and

d) the group of plastics comprising the plastics is identified on the basis of the determined heat capacity and/or the determined enthalpy change and/or a parameter which can be derived from the heat capacity and/or the enthalpy change by calculation.

That is, plastics are classified by determining heat capacity and/or enthalpy change. By being able to ascertain the type of plastic and thus the properties of the plastic by the method according to the invention, preferably automatically, a large distance is approached from the automatic setting of the molding machine, since many of the settings are clearly strongly dependent on the material used in the molding machine.

In a second aspect of the invention, this is achieved by a method for sorting plastics, namely by:

e) detecting by measurement techniques the infrared radiation emitted by said plastic; and is

f) Identifying a plastic group comprising the plastic based on the detected infrared radiation.

In a third aspect of the invention, the object is achieved by a method for sorting plastics. This is achieved by:

a) plasticizing the plastic by supplying plasticizing energy in the form of mechanical and/or thermal energy with an increase in the temperature of the plastic from a starting temperature value to an end temperature value; and is

g) Identification information about the plastic is taken from at least two different sources, wherein at least one of the at least two different sources is a measuring device on a device used for plasticizing the plastic, and a plastic group containing the plastic is identified and preferably the plastic is identified on the basis of the identification information.

The features of the invention have in common that, on the basis of the detected information, a group of plastics containing the plastics or even the plastics themselves is identified, to be precise on the device for plasticizing the plastics, i.e. within the scope of the plasticizing process. An example for such a device is of course a plasticizing component (as used, for example, with an injection molding machine), or more generally a molding machine.

Statements relating to the identification of a plastic or of a plastic group (e.g. feature d), f) or g)) on the basis of one parameter or of another information do not mean, within the scope of the present invention, that the plastic or plastic group is identified solely in view of the given parameter or the other information. Rather, other parameters, measured values or additional information can always be taken into account for the identification. The identification of the plastic or plastic group can also relate to a mixture of two or more plastics or to a mixture of a plastic together with a filler material.

The present invention provides additional advantages. The present invention can realize, for example: estimating the load of the molding machine over time or providing another monitoring mechanism by means of which the operation and the operational safety can be monitored.

The plastic groups used as a classification for the plastics used include, for example, polyethylene, polypropylene, polystyrene, polyamide, polycarbonate, polymethyl methacrylate and the like.

In addition to the identification of the plastic group containing the plastic, it is also possible to ascertain the plastic itself, i.e. in particular which plastic is involved (for example PE 0.95, if appropriate even with production instructions (PE X of manufacturer Y)). In the sense of the present invention, the determination of the plastic itself is also understood as the identification of the plastic group containing the plastic. The determination of the plastic is also understood to mean, in addition to the classification of the plastic itself, the identification of the filler material (for example fibers) or the determination of the amount of the filler material in the plastic.

Another advantage of the invention is that the method according to the invention can be carried out automatically, so that the plasticizing assembly and/or the molding machine automatically determines the plastic used.

In addition to the method according to the invention, protection is also claimed:

a molding method, in which a plastic material plasticized and classified by means of the method according to the invention is used, in particular in the context of an injection molding method;

-a plasticizing assembly arranged for carrying out the method according to the invention; and

a molding machine, in particular arranged for carrying out the method according to the invention, comprising a plasticizing assembly according to the invention.

In a further advantageous embodiment, the plasticizing unit according to the invention and/or the molding machine according to the invention can be used as a heat measurer by means of the heat capacity and/or enthalpy change determination according to the invention.

The use of the expression "end temperature value" does not mean that further temperature changes (in particular temperature increases) of the plastic cannot be carried out or occur. This expression is merely illustrative: the temperature is substantially at the end of a time interval over which a corresponding determination of a change in heat capacity and/or enthalpy is performed. The subsequent thermodynamic processes can of course be carried out and in certain cases are even unavoidable. A similar situation applies to the start temperature value.

The measured variables (volume and/or mass, plasticizing energy) detected can be measured directly or indirectly. This obviously also applies to the start and end temperature values. The quantity derived by calculation from the heat capacity and/or the enthalpy change can either also be measured directly or indirectly (i.e. as a separate physical or chemical quantity), or the heat capacity and/or the enthalpy change can be measured and the quantity derived by calculation can be calculated from these measured values. In the following, explicit elucidation of the variables derived by calculation from the heat capacity and/or the enthalpy change is partially dispensed with. However, when it is said that the heat capacity and/or enthalpy change is (are) determined, the variables derived from the heat capacity and/or enthalpy change by calculation are always included in terms of meaning.

The detection of the infrared radiation emitted by the plastic by means of measurement techniques (method step e)) can preferably be carried out at the beginning of the plasticizing process after method step a) when the plastic is present, for example, also as particles. But it is also conceivable: infrared radiation is detected by measurement techniques during or after the plasticizing process.

Preference can be given to: an energy balance and/or a power balance for the plastic is established on the basis of the detected measurement variables, and the determined heat capacity, the determined enthalpy change and/or variables that can be derived from the heat capacity and/or the enthalpy change by calculation are determined as a function of the energy balance and/or the power balance. The establishment of an energy or power balance, which at least to some extent reflects reality, can significantly improve the accuracy of the determined heat capacity and/or enthalpy change (and thus of course also the quality of the plastic classification). However, alternatives consist in principle in different more or less precise approximations or estimations.

It has already been mentioned that further variables, i.e. for example the total load, the wear state and/or the operating state, can be ascertained on the basis of the energy balance and/or the power balance. The total load is a measure for the total load over a period of time, preferably over the entire service life of the device. Thus, the total load can be considered as a direct measure for the wear of the equipment. Of course, other wear measures, in particular more specific wear measures, for example for a plasticizing screw or a plasticizing cylinder, can also be determined from the data determined according to the invention. The operating state of the device can also be quantified by the ascertained data.

The supplied and/or extracted thermal energy and/or thermal power and/or the profile of the supplied thermal energy and/or the profile of the thermal power are ascertained (for example by means of a heating device) and the thermal energy and/or the thermal power and/or the profile of the thermal power are taken into account in an energy balance and/or a power balance. In this way, an energy or power balance can be established particularly simply.

In addition to the supply of thermal energy in the case of plastics in the plasticizing process, it is also necessary in some cases to cool the plastics, for example in order to prevent the temperature of the plastics from being so high that degradation of the plastics occurs (in the sense that undesirable chemical or physical changes occur when the temperature is too high).

The determination of the heat capacity can be designed particularly simply when the heat capacity is determined as the specific heat capacity at constant pressure and a plastic group containing plastic is identified on the basis of the specific heat capacity at constant pressure. Alternatively, the heat capacity with a constant volume or in a mixed form can be determined, but this is ready to accept challenges in the form of partly complex calculations in terms of data analysis and evaluation and difficult-to-manipulate operating states.

The starting temperature value and/or the end temperature value and/or the temperature profile of the plastic can be measured directly and/or indirectly by means of at least one temperature sensor, wherein the temperature regulation of the plastic is preferably carried out with the supplied mechanical energy and/or the supplied thermal energy as a regulating variable and with the measured value of the at least one temperature sensor as an actual value. The use of a temperature sensor enables a particularly simple and reliable temperature determination, wherein not only a direct measurement of the temperature of the plasticized or still unplasticized plastic can be provided, but also an indirect measurement via the determination of the temperature of a body in thermal contact with the plastic. When only the temperature profile is measured, it is clear that a start temperature value and/or an end temperature value can be derived from this profile.

The plastic can be plasticized with a substantially constant pressure, wherein the pressure is preferably set with the aid of a constant setpoint value using the measured values of the at least one pressure sensor. The advantages of performing the method with a constant pressure have already been mentioned. In many cases, the regulation of the (material) pressure according to a constant setpoint value is carried out in prior art plasticizing assemblies, so that the method according to the invention can be easily implemented.

The thermal energy can be supplied by means of a heating device, preferably an electric heating device, which is a particularly simple embodiment of the invention, wherein the heating energy and/or the heating power and/or the profile of the heating energy and/or the profile of the heating power of the heat generated by the heating device can be detected.

At least one drive sensor can be used, by means of which the mechanical energy supplied via the at least one drive and/or the mechanical power supplied by the at least one drive (directly or indirectly at the plastic) and/or the profile of the supplied mechanical energy and/or the profile of the supplied mechanical power are measured. This is also used to simply establish energy balance or power balance. Losses (e.g., due to friction and other drag) can be taken into account in energy or power balancing by correction factors (e.g., based on machine size and efficiency).

Both for the heating power or energy and for the supplied mechanical energy, measured or otherwise detected profiles can be used in order to derive or calculate from them (for example via integration) the originally desired variable.

In a particularly simple embodiment of the invention, a plasticizing screw and/or a plasticizing piston can be used for supplying the mechanical energy. The plasticizing screw in particular constitutes a widespread structural means for plasticizing components, so that the invention can be implemented in some cases without structural changes to the apparatus.

In this case, a plasticizing cylinder can be provided in which a plasticizing screw is arranged, wherein the plasticizing screw is rotated in the plasticizing cylinder and moved axially by means of the at least one drive for plasticizing the plastic. The plastic is sheared by rotating the plasticizing screw, wherein a (preferably constantly adjusted) pressure is maintained in the plastic at the same time by the axial drive. In this so-called metering, the screw is moved back in the axial direction with the mentioned pressure remaining.

However, the pressure sensor, which is for example in the form of a material pressure sensor in the plasticizing cylinder, can also directly detect the pressure in the plastic.

It can be provided that: in order to detect the supplied mechanical energy, the torque applied to the plasticizing screw and/or the rotational speed of the plasticizing screw are measured.

Both the rotational and axial movements may be achieved via one or more electric or hydraulic drives. The torque and axial movement and axial force application can be measured via corresponding sensors. The applied torque can be determined, for example, by the current and voltage applied to the motor driving the rotary motion. The axial force exerted by the hydraulic drive can be detected, for example, via the pressure of the hydraulic fluid.

A screw position sensor can be used, by means of which the volume of plastic plasticized in the plasticizing cylinder is detected. The volume in the plasticizing cylinder, for example before and after the plastification of the plastic, can be determined from the screw position by means of a known (cylindrical) geometry.

A funnel can be used for supplying the plastic to be plasticized into the plasticizing cylinder, wherein preferably a funnel temperature sensor in and/or on the funnel is used. The starting temperature value of the plastic can be easily ascertained via such a funnel temperature sensor without this having to entail significant technical or constructional expenditure.

In principle, it is also conceivable to mount a scale on the hopper, with the aid of which the mass of the plastic to be plasticized can be measured.

A plurality of drum temperature sensors can be used, which are associated with heating zones distributed axially on the plasticizing drum, wherein the heating zones are heated independently of one another, wherein the heating in the heating zones is set using the measured values of the drum temperature sensors associated with the heating zones. Such a regulated heating zone is already present in many existing plasticizing assemblies, which facilitates the implementation of the present invention. Similarly to the introduction of mechanical energy, losses can also occur here, which can be taken into account by correction factors (for example, depending on the size and efficiency of the machine construction). Finally, this generally applies to losses occurring during energy introduction (or energy extraction).

These adjusted heating zones can be used particularly advantageously to ascertain an end temperature value by temporarily switching off the adjustment of a specific heating zone, in particular the last heating zone in the direction of transport of the plastic, and using the measured values of the temperature sensors associated with the specific heating zone as the end temperature value. Here, it is possible to wait for some time, if possible, until it is expected that: the defined heating zone is in thermal equilibrium, so that the plasticizing cylinder has the temperature of the plasticized plastic in the region of the defined heating zone. Thereby, the end temperature value can be measured with high accuracy without using a material temperature sensor, which is relatively costly in the usual case. In this case, the accuracy can be increased even more when the plasticizing unit is operated in an extrusion operation, i.e. with the plastic continuously and thus contributing to the thermally stable exit from the plasticizing cylinder.

Nevertheless, there is of course an alternative to the special mass temperature sensor already mentioned, which directly measures the temperature of the plasticized plastic.

Furthermore, it can be provided that: in order to identify the plastic group containing the plastic,

correcting the enthalpy-temperature curves for plastics by means of the known relationship between temperature on the one hand and specific volume and/or density on the other hand for the plastics;

comparing the heat capacity of the plastic and/or the change in enthalpy of the plastic and/or a quantity which can be derived from the heat capacity and/or the change in enthalpy by calculation with the corrected enthalpy-temperature curves, in particular with the slopes of the corrected enthalpy-temperature curves; and is

-identifying a group of plastics comprising said plastics based on the comparison result.

The heat capacity can in particular assume the role of the slope of the curve in the (modified) enthalpy-temperature curve, so that a calculation or a graphical comparison of the respective curve with the determined values for the heat capacity and/or the enthalpy change can be carried out particularly easily.

In the case of a difficulty in providing the density or mass of the plastic to be plasticized, this embodiment of the method according to the invention allows a reliable determination of the plastic or of the plastic group containing the plastic.

The method according to the invention can be carried out several times, wherein the pressure and/or the supplied mechanical power are preferably varied. The mechanical power can be varied, for example, by varying the screw speed. This opens up a particularly simple possibility as follows: the test conditions were varied without having to make drastic changes in the regulation of the heating, in particular of the heating zones.

For the detection of infrared radiation, a near infrared sensor (NIR sensor) can be used. In principle, the use of (NIR) spectrometers is also conceivable.

Taking information about the plastic by at least one of the following sources and taking said information into account for identifying the group of plastics and preferably for identifying the plastic:

a method according to the first aspect of the invention for determining the heat capacity of a plastic and/or the change in enthalpy of a plastic and/or a parameter derivable from the heat capacity and/or the change in enthalpy by calculation;

-a method according to a second aspect of the invention in the case of detection of infrared radiation emitted by plastics by measurement techniques;

machine settings and/or measured values and/or machine configurations, in particular injection pressure (or parameters derived therefrom, such as viscosity or flow index), maximum and/or minimum processing temperature, material drum temperature at the tip of the plasticizing drum or over the entire extension of the plasticizing drum, particle temperature, coolant temperature, density of the melt, information about the mold used;

-a method for determining a characteristic parameter for the compression behaviour of a plastic, in particular the compression modulus or compressibility;

camera imaging of the plastic to be plasticized, in particular of plastic granules.

Characteristic parameters for the compression behavior of the plastic, such as the compression modulus or compressibility, can be determined, for example, according to the method disclosed in DE102016005780a 1. Determining the amount of filler material by determining compressibility is disclosed in DE102007030637a 1.

For machine settings and/or measurements and/or machine configuration: certain plastic groups have, for example, quite specific minimum or maximum processing temperatures. If such special processing temperatures occur, it is already possible to determine or at least to limit the plastic group or the plastic. Other component or external instrument data can likewise be used for identifying plastics or plastic groups. The relevant data can be generated, for example, in the dryer, the material conveyor and/or the storage. Each plastic group has defined characteristics with respect to all the above-mentioned parameters. Thus, together with the invention according to the first aspect (determination of the heat capacity of the plastic and/or the change in enthalpy of the plastic and/or the variables derivable therefrom by calculation) and/or the second aspect (detection of the infrared radiation emitted by the plastic by means of a measuring technique) and/or the characteristic parameters for the compression behavior of the plastic, it is possible to ascertain the current plastic set and in many cases to identify the plastic together with the charge (filling material) according to an exclusion method.

In order to generate a camera image of the plastic to be plasticized, in particular of the plastic granulate, a camera arranged in or on the funnel of the plasticizing unit can be provided, for example, in order to recognize the granulate shape of the plastic granulate.

The determination of the shape of the particles (or other shapes, e.g. powder) can be done by means of image recognition software, preferably automatically. Thus, it is possible, for example, to distinguish small rod-shaped particles (long glass fibers) from conventional particles (e.g. columnar cold shot (Kaltabschlag), round or lens-shaped particles as are typically produced in engineering plastics, or, for example, in underwater pelletizing, typically in polyolefins) or powders (e.g. PVC dry blends).

In order to carry out the method steps for detecting and/or calculating the parameters and for identifying the plastic or the plastic group containing the plastic, the plasticizing assembly and/or the molding machine may contain an evaluation device.

The evaluation device can be designed to carry out specific steps based on the identified plastic group, for example:

-outputting a prompt regarding an improved machine setting and/or an improved machine configuration, preferably after automatic recognition of the current machine setting and/or installed and/or used components in advance; and/or

-automatically changing machine settings; and/or

-outputting an alarm and/or a prompt regarding an occurring and/or expected impermissible operating state; and/or

In the event of an impermissible operating state, a switch-off signal for automatic switching-off is output.

The evaluation unit can be integrated into a central machine control of the molding machine. Alternatively, the evaluation unit can be arranged to leave the molding machine and/or the plasticizing component and to connect therewith, for example via a data teletransmission connection (keyword: cloud computing).

The method according to the invention can be performed not only within the scope of the reference cycle but also during manufacture. A specific automatic setting of the molding process can be ensured if the plastic set is already known at the beginning of the production. The method according to the invention can however also be used advantageously during operation, for example to check: the processing material (plastic) was unchanged.

The reference cycle can be carried out before the start of the production with a certain plastic to be identified. For this purpose, the machine may also be specially set up so that the measurement can be carried out under conditions defined in respect of certain aspects.

Drawings

Further advantages and details of the invention are obtained by means of the figures and the description of the figures relating thereto. In the drawings:

figure 1 shows enthalpy-temperature curves for different plastics,

fig. 2 shows a diagram of a plasticizing assembly, including an explanation of the power balance according to the invention,

figure 3 shows a comparison of the enthalpy-temperature curve with the determined heat capacity,

FIG. 4 shows two diagrams for illustrating plastification/dosing, an

Fig. 5 shows an example of a known temperature dependence for a specific volume of a certain plastic.

Detailed Description

In a given configuration of the plasticizing unit, on the one hand, the service life of the installed components should be optimized and, on the other hand, the processing parameters with regard to the requirements for the plastic to be processed should be adapted or recommended autonomously.

In order to use an optimization algorithm, knowledge of the plastic/plastic set being processed is necessarily required or at least significantly beneficial.

Another benefit of the invention according to the first aspect is the calculation of the total load: a characteristic value can be calculated which gives an explanation about the use according to the prescription. These values may also be used as a computational basis for leasing the business model.

The enthalpy (H) diagram known from the literature in fig. 1 and the power balance of the system, i.e. the plasticizing unit (fig. 2) serve as a basis for ascertaining.

The diagram from fig. 1 describes the internal energy/power brought about by the respective plastic in relation to the material temperature T (plastic temperature). Suitable plastics are those of one kilogram of H ═ f (t); the unit is J/g. In addition, with the unit cm³The specific volume v/g has a known physical relationship to the temperature T (in ℃ C.) of the material and the pressure p according to FIG. 5.

If the value of the function H is divided point by the value of the specific volume v under the same temperature, assuming a constant pressure, the function H (p) results from this relationship_x) (t), wherein the unit is J/cm³. This function is shown in fig. 3.

The functional relationship is prepared for the selected plastic group in a data-technical manner and is available for the control device of the machine.

When dosing is performed in the injection molding process, the plasticizing screw 4 is rotated at a rotational speed n. At this time, the torque M is supplied from the driving device 3. At the same time, the screw is withdrawn, so that the melt cushion is set in the screw prechamber. The withdrawal speed is set in such a way that the pressure p in the screw head chamber_xRemains constant (see fig. 4). The power introduced mechanically in the plasticizing process is proportional to the product of the torque M and the rotational speed n. The power can be ascertained on the injection molding machine side by evaluating electrical or hydraulic drive parameters by way of analysis.

It is also mentioned in connection with fig. 2 that, for example, the subsequent variables occurring during the plasticizing process can be adjusted from the outside: pressure p_x(stagnation pressure), temperature profile (intended for controlling or regulating the heating device), humidity on the hopper 6, additive material in the plastic (i.e. for example in the plastic granulate), temperature of the material, temperature in the hopper, rotational speed of the screw. The remaining variables (e.g. torque, stroke, mass flow) are then adjusted during the plasticizing process.

In fig. 4, the plasticizing assembly 1 is shown once (above) in the state during injection and the plasticizing assembly 1 is shown once (below) in the state during or after dosing. The granulate is supplied, for example, via a hopper 6 to a plasticizing cylinder 5 and plasticized by means of a plasticizing screw 4. A heating device 2 is arranged on the plasticizing cylinder 5, by means of which heating device the plasticizing cylinder 5 is locally heated. Furthermore, additional temperature sensors (not shown) can be provided for the local regulation of the heating power. Reference is made to fig. 2 for the arrangement of the drive 3 of the plasticizing screw 4. A funnel temperature sensor 7 and a near infrared sensor 8 are provided on the funnel 6.

Furthermore, a heating power Q is introduced into the power balance. The portion of the heating power is likewise ascertained and added to the mechanical power input. To be able to ascertain the enthalpy rise, the introduced power is subtracted by the pressure build-up power. This is determined from the ascertained volume flow V over the stroke and the pressure p maintained constant over the screw stroke_xThe product of (a) and (b). The power thus ascertained, which is introduced into the plastic, can now be compared with the curve set available in the control device. If the material temperature T is now known from the measurements carried out on the machine, the intersection point of the internal energy with the material temperature in fig. 2 can be calculated, which is likewise brought into agreement with the curve from the data record. The curve is associated with a plastic or a group of plastics. This results in preconditions for operating modes or monitoring in connection with the particular plastic.

Regarding the third aspect of the present invention, four embodiments are also given below. It is generally applicable within the scope of the invention to identify plastics or groups of plastics via logical combinations of chemical and physical properties known per se.

1. The plastics sought contain "carbon black" as black pigment in addition to 30% glass fibers. The determination of the chemical structure of plastics by means of NIR sensors is not unambiguous, since the filler material (in particular graphite) absorbs radiation in the near infrared range, and the plastics are therefore not visible to this characterization method. Some plastics can be inferred by other process parameters, such as processing or drying temperatures. Commonly used plastics, such as polyolefins (polyethylene, polypropylene), are not pre-dried and are processed below 260 ℃. Other plastics, such as polyamides, are predried at least 80 ℃ and processed above 260 ℃. By means of characterization methods, such as energy absorption (enthalpy) or compressibility (compression modulus), a defined filler content or a further limitation of the plastic set can be inferred from the calibration curve.

2. The plastics sought contain a specific molecular chain structure, for example in the case of PA6 or PA 66. In PA66, the carbonyl groups are always situated opposite one another in such a way that each functional group can form a hydrogen bond without the molecule deforming. In PA6, this is only possible with every two carbonamide groups. The higher melting point and the lower water absorption of PA66 are due to different molecular architecture. With conventional NIR sensors calibrated for some wavelengths, it is not univocal to distinguish between PA6 and PA66, and either an NIR spectrometer or another characterization method must be employed. Analytical evaluation of process data, such as processing temperature and energy absorption, based on the temperature based on the calibration curve can be used for the differentiation.

3. The plastics sought have a known chemical structure and a specific density, for example PE-HD (high density polyethylene) and PE-LD (low density polyethylene). The basic structure can be identified by means of an NIR sensor. Analytical evaluation of process data, such as processing temperature and energy absorption, based on the determination of the temperature and the characterization method, such as the compressive modulus, based on the calibration curve can be used in addition.

4. The plastics sought have a known chemical structure and a specific viscosity, for example one polypropylene with a melt mass flow rate MFR of 5g/10min and another polypropylene with a melt mass flow rate of 50g/10min (measured according to DIN EN ISO 1133). The basic structure can be identified by means of an NIR sensor. To determine the viscosity differences more accurately, the following characterization methods can be used, such as a flow index ascertained from the injection pressure profile. Furthermore, plastic masses in a specific viscosity range can be inferred from the ratio of the energy absorption by dissipation (power requirement of the metering drive) to the energy absorption by heat conduction (power requirement of the external heating/cooling device).

Claims

1. A method for sorting plastics, wherein,

2. The method according to claim 1, characterized in that an energy balance and/or a power balance for the plastic is established on the basis of the detected measurement variables, and the determined heat capacity, the determined enthalpy change and/or the variables derivable from the heat capacity and/or the enthalpy change by calculation are determined from the energy balance and/or the power balance.

3. The method according to claim 2, characterized by ascertaining, based on the energy balance and/or the power balance, at least one of: total load, wear state, running state.

4. Method according to claim 2 or 3, characterized in that the supplied and/or extracted thermal energy and/or thermal power and/or the profile of the supplied thermal energy and/or the profile of the thermal power are ascertained and the thermal energy and/or the thermal power and/or the profile of the thermal power are taken into account in the energy and/or power balance.

5. Method according to any one of the preceding claims, characterized in that the specific heat capacity at constant pressure is determined as heat capacity and the group of plastics containing the plastics is identified on the basis of the specific heat capacity at constant pressure.

6. Method according to one of the preceding claims, characterized in that a starting temperature value and/or an end temperature value and/or a temperature profile of the plastic is measured directly and/or indirectly by means of at least one temperature sensor, the temperature regulation of the plastic preferably being carried out with the supplied mechanical energy and/or the supplied thermal energy as a regulating variable and with the measured value of the at least one temperature sensor as an actual value.

7. Method according to any one of the preceding claims, characterized in that the plastic is plasticized with a substantially constant pressure, which pressure is preferably adjusted with the aid of a constant theoretical value using the measured values of at least one pressure sensor.

8. Method according to any of the preceding claims, characterized in that the thermal energy is supplied by means of a heating device (2), preferably an electric heating device.

9. Method according to any of the preceding claims, characterized in that at least one drive sensor is used, by means of which the mechanical energy supplied via at least one drive (3) and/or the mechanical power provided by the at least one drive and/or the course of the supplied mechanical energy and/or the course of the provided mechanical power are measured.

10. Method according to any one of the preceding claims, characterized in that for supplying the mechanical energy a plasticizing screw (4) and/or a plasticizing piston is used.

11. Method according to claims 9 and 10, characterized in that a plasticizing cylinder (5) is used, in which the plasticizing screw (4) is arranged and in which the plasticizing screw (4) is rotated and moved axially in the plasticizing cylinder (5) by means of the at least one drive for plasticizing the plastic.

12. Method according to claim 11, characterized in that the torque applied to the plasticizing screw (4) and/or the rotational speed of the plasticizing screw (4) is measured for detecting the supplied mechanical energy.

13. Method according to claim 6 and 11 or 12, characterized in that the pressure of the plastic is adjusted by means of the force exerted on the plastic by the plasticizing screw (4) as an adjustment variable.

14. Method according to any one of claims 10 to 13, characterized in that a screw position sensor is used, by means of which the volume of plastic plasticized in the plasticizing cylinder (5) is detected.

15. Method according to claim 5 and any one of claims 11 to 14, characterized in that a hopper (6) is used for supplying the plastic to be plasticized into the plasticizing cylinder (5), preferably a hopper temperature sensor (7) in the hopper (6) and/or on the hopper (6).

16. Method according to claims 6 and 8 and any of claims 11 to 15, characterized in that a plurality of drum temperature sensors are used, which are assigned to heating zones distributed axially on the plasticizing drum, wherein the heating zones are heated independently of one another, wherein the heating in the heating zones is regulated using the measured values of the drum temperature sensors assigned to the heating zones in each case.

17. Method according to claim 16, characterized in that, in order to ascertain the end temperature value, the regulation of a specific heating zone, in particular the last heating zone in the plastic conveying direction, is temporarily switched off and the measured value of the temperature sensor associated with the specific heating zone is used as the end temperature value.

18. Method according to any one of the preceding claims, characterized in that, for identifying the plastic group containing the plastic,

comparing a plurality of values of the heat capacity of the plastic and/or of the change in enthalpy of the plastic and/or of a variable which can be derived from the heat capacity and/or the change in enthalpy by calculation with the corrected enthalpy-temperature curves, in particular with the slopes of the corrected enthalpy-temperature curves; and is

19. Method according to any of the preceding claims, characterized in that the method is performed a plurality of times, preferably varying the pressure and/or the supplied mechanical power.

20. A method for sorting plastics, wherein,

21. Method according to claim 20, characterized in that for detecting the infrared radiation a near infrared sensor (8) is used.

22. A method for sorting plastics, wherein,

a) plasticizing the plastic by supplying plasticizing energy in the form of mechanical and/or thermal energy with the temperature of the plastic increasing from a starting temperature value to an end temperature value,

g) identification information about the plastic is taken from at least two different sources, wherein at least one of the at least two different sources is a measuring device on a device used for plasticizing the plastic, and a plastic group containing the plastic, and preferably the plastic, is identified on the basis of the identification information.

23. The method of claim 22, wherein the information about the plastic is taken from at least one of the following and taken into account for identifying the group of plastics and for identifying the preferred plastic:

-a method according to any one of claims 1 to 19;

-a method according to any one of claims 20 or 21;

-a method for determining a characteristic parameter for the compression behaviour of the plastic, in particular the compression modulus or compressibility;

24. A molding method, wherein a plastic plasticized and classified by means of the method according to one of the preceding claims is used, in particular within the scope of an injection molding method.

25. A plasticizing assembly configured to perform the method of any of claims 1 to 23.

26. A plasticizing assembly as defined in claim 25, which is configured for, based on the identified plastic or the identified group of plastics,

-automatically changing machine settings; and/or

27. Moulding machine, in particular provided for carrying out the method according to claim 24, comprising a plasticizing assembly according to claim 25 or 26.

28. The molding machine of claim 27, wherein the evaluation unit is integrated into a central machine control of the molding machine.

29. Moulding machine according to claim 27 or 28, provided for carrying out a moulding method according to claim 24, characterized in that it is configured for carrying out a method according to any one of claims 1 to 23 within the range of a reference cycle and/or during manufacturing.