Method for plasticizing a thermoplastic raw material and plastic processing machine or machine combination comprising a plastic processing machine

Abstract

The invention relates to a method for plasticizing a thermoplastic plastic starting material, a plastics processing machine and a machine combination comprising a plastics processing machine.

Description

SUBJECT OF THE INVENTION

[0001] The invention relates to a method for plasticizing a thermoplastic plastic starting material, a plastics processing machine and a machine combination comprising a plastics processing machine. BACKGROUND OF THE INVENTION

[0002] Thermoplastic polymers, or thermoplastics for short, represent a significant proportion of the organic polymers processed in industry. Due to their excellent formability and high chemical resistance, they are among the preferred engineering materials. Under the influence of heat, thermoplastics can be repeatedly deformed, melted, and cooled without affecting their fundamental chemical and related mechanical properties. This characteristic allows for the efficient production of large numbers of identical components in a short time, particularly through processes such as injection molding.

[0003] The processing of thermoplastic materials requires heating to a temperature equal to or above the specific softening temperature of the respective material.

[0004] Typical machines for processing thermoplastic materials include a plasticizing unit, which usually consists of a heated cylinder with a rotating screw or shaft inside. During the manufacturing process, a plastic raw material, usually in granular form, is fed into the plasticizing unit via a hopper.

[0005] The energy for melting the plastic starting material typically comes from cylinder heating and the dissipative energy input, which is generated by converting drive energy of the screw or by conveying the highly viscous melt.

[0006] The cylinder is typically heated by direct electric heating or, less frequently, by steam or heat transfer oil. Both direct electric heating and electric drive often require the purchase of expensive industrial electricity. In addition to the financial costs, electricity generation generally produces emissions and consequently environmental pollution.

[0007] Particularly in larger plasticizing units, the energy input through dissipation in the plastic feedstock exceeds the energy input transferred to the plastic material through the heated cylinder wall. This is especially true for large plastic processing extruders, such as twin-screw extruders, which are used, for example, in the production of polyolefins and typically have a throughput of 60 t / h or more.

[0008] In addition to the direct thermal waste heat generated by the plasticizing unit and the equipment used, significant amounts of thermal emissions also arise in upstream and downstream process steps. A major source of this heat can be, for example, a granulation process that precedes plastic forming processes such as injection molding, extrusion, blow molding, or others. This thermal energy often remains unused and also contributes to more difficult working conditions for machine operators. Depending on the season, the upstream and downstream processes, as well as the actual plastic forming, can result in temperatures in the production areas often exceeding 50°C. To ensure the safety of the machine operators, complex and costly cooling of the work environment is necessary in such cases.In practice, cooling is usually achieved through the use of air conditioning systems, which, however, not only cool the ambient air but also indirectly cool the heated granules and component surfaces. This results in an increase in the net energy consumption of the overall process, as additional energy must be expended to bring the materials back down to the temperatures required for processing.

[0009] Prior art discloses methods in which the raw material is preheated before further processing. JPH01171811A discloses a method for preheating raw material in an injection molding machine, which effectively increases the plasticizing efficiency. In this method, the raw material is fed to the injection molding machine via a hopper, and from the hopper, the raw material reaches the machine via a feed pipe in which it is heated by a preferably electric heating system.

[0010] CN 104608321 A relates to a device for recovering waste heat from an injection molding machine. The waste heat from the heating element of the machine's melting cylinder is to be used to dehumidify and dry plastic granules in an insulated drying hopper.

[0011] DE 32 12 796 C1 relates to an injection molding machine in which the waste heat from the hot hydraulic oil is to be used for space heating. The oil is passed through a low-temperature radiator, which transfers the heat energy to the ambient air, thus warming it. The heat output is regulated by thermostatic valves that control either the airflow or the amount of oil flowing through the radiator.

[0012] DE 10 2008 025 557 A1 relates to an injection molding machine in which hot hydraulic fluid is used via a heat exchanger to heat a heat transfer medium. This heat transfer medium is then used to drive an adsorption chiller. This chiller generates cooling, which in turn is used to cool the cooling medium for the temperature control circuit of the injection mold.

[0013] Against the backdrop of increasing demand for more environmentally friendly and energy-efficient solutions, particularly in the industrial context, there is a need for optimization and further development. TASK

[0014] Against this background, the object of the present invention is to provide a process for the plasticization of thermoplastic polymer starting material which is more energy-efficient and sustainable, i.e., which requires less overall energy consumption than processes known from the prior art and / or which enables increased process stability and / or a higher throughput than processes known from the prior art. DESCRIPTION OF THE INVENTION

[0015] This problem is solved by a method according to claim 1 and by a plastics processing machine or a machine combination according to claim 12.

[0016] Plasticization is a process in which a solid material, usually a plastic, is transformed into a flowable or deformable state through heating and / or mechanical shearing. This often occurs in extrusion or injection molding machines, where the starting material, frequently in granular form, is melted in a heated cylinder, conveyed, and then injected into molds or forced through nozzles. Plasticization is a crucial step in processing plastics to bring them into the desired shape.

[0017] According to the invention, the method according to claim 1 can be carried out using extrusion or injection molding machines as plastic processing machines, however, a method for plasticizing in calender machines, blow molding machines, rotational molding machines, compression molding machines or any other plastic processing machines is also possible according to the invention.

[0018] Preferably, the plastics processing machine is an injection molding machine or an extrusion machine. According to the invention, a plastics processing machine is an industrial machine that heats the raw material, the plastic starting material, and transfers it into an intermediate or final shape. This is distinct from plastics machining machines, which modify the shape of plastic objects using subtractive processes such as milling, drilling, turning, or grinding. Products such as injection-molded parts, films, hollow bodies, or profiles can be produced using plastics processing machines.

[0019] Conditioning refers to the targeted thermal pretreatment of thermoplastic materials prior to plasticization, in order to modify their physical and / or mechanical properties. This thermal pretreatment takes place at a temperature below the softening point of the thermoplastic starting material. Conditioning allows the material's properties to be modified to optimize them for the subsequent plasticization step.

[0020] According to the invention, the process comprises a conditioning step for the thermoplastic starting material prior to plasticization. This conditioning step is thus a pretreatment achieved through the application of heat, specifically preheating. Such conditioning offers the advantages of energy savings in the subsequent process, increased productivity through process acceleration, and consequently, higher throughput. The heat supplied to the starting material during the conditioning step reduces the energy required for both electrical heating and drive power in the downstream plasticizing unit. The saved energy can be used to increase throughput, resulting in a significant economic advantage, particularly for high-throughput plastics processing machines.Furthermore, such conditioning also increases the uniformity of the melting behavior, which has a positive effect on processing efficiency as well as product quality. Due to the conditioning, the melting process is more homogeneous, earlier, and better, resulting in a more energy-efficient overall process.

[0021] Both during plastics processing and in upstream and / or downstream processes, such as granulate production, large amounts of waste heat are generated. This heat is often largely released into the ambient air and / or process fluids, i.e., fluids used in the respective technical process, such as coolants, lubricants, and hydraulic fluids. This has the disadvantage of resulting in significant energy waste, which drives up production costs. Furthermore, it can lead to extremely high temperatures in the rooms where the relevant industrial machinery is located, making working conditions exceptionally difficult and posing a challenge to occupational health and safety.

[0022] In the process according to the invention, at least one heat pump is used, the useful heat from which is used to condition the thermoplastic starting material. That is, the useful heat generated by the heat pump from anergy and exergy is used at least partially, preferably ≥ 50%, and particularly preferably completely, to heat the plastic starting material in step a).

[0023] Preferably, the usable heat from the heat pump is also used in step b) for the plasticization of the conditioned thermoplastic starting material.

[0024] Additional heat sources can be used to assist in heating the thermoplastic starting material in step a) and / or in plasticizing the conditioned thermoplastic starting material in step b).

[0025] Preferably, the at least one heat pump utilizes the waste heat from at least one industrial machine, more preferably the waste heat from the first and / or a second industrial machine. An industrial machine is a mechanical or electromechanical device used in industrial processes to efficiently and repeatably perform tasks such as the production, processing, machining, or assembly of materials and products.

[0026] In a preferred embodiment, the at least one heat pump extracts energy from the air surrounding the first industrial machine, i.e., the plastics processing machine. This is typically the ambient air of the machine hall in which the plastics processing machine is located.

[0027] In another preferred embodiment, the heat pump uses the air surrounding a second industrial machine as a heat source. This is typically the air in the machine hall where the second industrial machine is located. Preferably, the first and second industrial machines are located in the same machine hall, so that the surrounding air is the same for both.

[0028] Alternatively or additionally, energy can be extracted from a process fluid of an industrial machine by the heat pump, which in turn, with the input of technical work, is used to heat thermoplastic raw material during conditioning. This process fluid is preferably a component of the first industrial machine, i.e., the plastics processing plant. In another preferred embodiment, the process fluid is part of a second industrial machine, preferably a granulating machine.

[0029] In a preferred embodiment, the energy used for conditioning is generated at least partially by means of at least one heat pump, wherein the at least one heat pump extracts energy as a heat source from the air surrounding the first and / or a second industrial machine and / or from a process fluid of the second industrial machine.

[0030] In particular, utilizing the energy in the air surrounding the industrial machinery—that is, the ambient heat of the machine hall(s) housing the industrial machinery, such as plastics processing machines—by means of a heat pump offers several advantages. Firstly, this allows for the utilization of all heat sources within a space, including the waste heat from all production units or industrial machinery located there, instead of focusing on a single specific unit or machine, such as the waste heat from a finished molded part during cooling. This increases the efficiency of heat recovery and the resulting energy and cost savings. Furthermore, it significantly reduces the ambient air temperature, making the space considerably more comfortable and thus improving workplace safety. Additional cooling or air conditioning systems can be at least partially replaced, resulting in energy savings.Additional energy can be saved when cooling the produced plastic products, for example by reducing the amount of process water that needs to be cooled.

[0031] In a preferred embodiment, the heating in step a) is carried out using the usable heat from at least one air-to-water heat pump. The air-to-water heat pump uses the ambient air as a heat source and functions even at relatively cool temperatures, since the refrigerant used in the refrigeration cycle evaporates at low temperatures and can thus raise the temperature level. However, the air-to-water heat pump operates particularly efficiently in rooms with high temperatures, such as machine halls.

[0032] In another preferred embodiment, the heating in step a) is carried out using the useful heat from at least one air-to-air heat pump, one water-to-air heat pump or a combination of the aforementioned.

[0033] In a preferred embodiment, the heat pump fan, which extracts heat from the air surrounding the industrial machine(s), and / or the heat pump itself, is located in its intended position, i.e., its operating position, above the industrial machine(s), since warm air rises and the heat pump can operate more efficiently there. Particularly preferably, the heat pump and / or the heat pump fan are located on the ceiling of a machine hall in which the industrial machine(s) are located, since heat tends to concentrate there.

[0034] In a preferred embodiment, the at least one heat pump generates a cooler airflow by extracting low-temperature energy, which can then be used for room air conditioning or cooling. In a preferred embodiment, the airflow specifically cools a spatially separated work area and / or living area.

[0035] Alternatively or additionally to utilizing the heat from the air surrounding the industrial machine(s) (e.g., the ambient air of the machine hall), the waste heat from a process fluid of an industrial machine can also be used. Preferably, the waste heat from a process fluid of a second industrial machine is utilized. The waste heat from a granulating machine, which produces plastic granules, for example, by comminuting plastic strands and / or underwater cutting of a plastic melt, is particularly suitable for this purpose. In other embodiments, the second industrial machine may be a welding machine, drying system, cooling unit, cutting system (e.g., for cutting extruded products), conveyor system, or mill. The process fluid is preferably a cooling fluid, hydraulic fluid, and / or heat transfer fluid such as thermal oils.

[0036] In a preferred embodiment, the heat used for conditioning is generated at least partially by means of a water-to-water or water-to-air heat pump. A water-to-water or water-to-air heat pump extracts heat from a process fluid of one or more industrial machines. The process fluid is preferably water, but can also be other fluids such as thermal oils or antifreeze mixtures (e.g., glycol-water mixtures). With regard to both the heat source and the heat transfer medium that transfers the heat to the plastic feedstock, the term "water" encompasses any fluid such as hydraulic fluids, lubricants, or coolants. Since fluids generally have a higher thermal conductivity than air, water-to-water heat pumps are characterized by very high efficiency and a compact design.

[0037] By combining several heat pumps and thus utilizing different energy sources, process stability can be further increased. Furthermore, this can significantly improve energy efficiency. Preferably, the heat used for conditioning is generated at least partially using two heat pumps. In a preferred embodiment, an air-to-water heat pump and a water-to-water heat pump are used.

[0038] In a preferred embodiment, the heat used for conditioning is partially generated by at least one heat pump. In another preferred embodiment, the energy used for conditioning is generated entirely by at least one heat pump. This reduces the costs that would have to be incurred for supplying external energy and thus also reduces CO2 emissions, since the energy generated is utilized and no or fewer fossil fuels are needed to heat the conditioning step.

[0039] Preferably, the at least one heat pump is a high-temperature heat pump. A high-temperature heat pump can achieve temperatures above 65°C, preferably above 100°C, or even temperatures above 160°C on the useful heat side, making it particularly suitable for the methods according to the invention.

[0040] In a preferred embodiment, the working fluid of the at least one heat pump belongs to the group of substances known as hydrofluoroolefins (HFOs) or hydrofluorocarbons (HFCs), particularly preferably HFOs. The working fluid (also called refrigerant) in a heat pump is the substance that is circulated in a closed loop through various thermodynamic phases (evaporation, compression, condensation, and expansion) to transport heat. It is the central medium that enables the heat pump to absorb thermal energy from the environment (air, water, ground), raise it to a higher temperature level, and make this heat usable for heating or hot water production. This group of substances exhibits good energy efficiency and is considered future-proof because it has a low environmental impact due to its low global warming potential and does not contribute to ozone depletion.

[0041] In a preferred embodiment, the working fluid of the at least one heat pump is a substance selected from the group consisting of R1234ze(E), R245fa, R32 (difluoromethane), R717 (ammonia), R744 (CO2), R290 (propane), and R600a (isobutane). R1234ze(E), R717 (ammonia), R290 (propane), and R744 (CO2) are particularly preferred because these substances are especially future-proof due to their environmental friendliness.

[0042] Plastic raw materials refer to the polymeric raw materials used to manufacture plastic products. These materials can be natural or synthetic polymers, which are processed into finished plastic products using various manufacturing processes.

[0043] Thermoplastic raw materials are materials used to manufacture plastic products that become meltable and malleable when heated and solidify upon cooling. They can be heated and processed multiple times.

[0044] In a preferred embodiment, the thermoplastic starting material to be processed is a polymer selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polyamide (PA), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), perfluoroalkoxy polymers (PFA), polyoxymethylene (POM), polypropylene copolymer (PPC), polyetheretherketone (PEEK), polylactide (PLA), polyvinylidene fluoride (PVDF) and polyetherimides (PEI).

[0045] In a further preferred embodiment, the thermoplastic starting material is in the form of granules, powders, grits, liquids, or films, preferably in the form of granules, grits, or powders, and most preferably in the form of granules. Granules are defined as a solid substance in the form of small, solid particles such as grains or spheres. Granules have particularly good flow properties because they hardly tend to clump and are therefore especially well suited for continuous processes. Granules can be processed particularly easily in plastics processing machines and can be dosed simply and precisely.

[0046] According to the invention, the thermoplastic starting material is heated to a temperature below the softening temperature during conditioning prior to plasticization.

[0047] The softening temperature of a thermoplastic can be determined using the Vicat method according to DIN EN ISO 306. For this method, a needle-shaped indenter, subjected to a test force, is penetrated into a specimen exposed to a defined heating rate. Once a specific penetration depth is reached, the measured temperature corresponds to the Vicat softening temperature.

[0048] Preferably, the thermoplastic starting material is heated during conditioning to a temperature that is 10-120°C below the softening temperature, more preferably 10-80°C, even more preferably 20-40°C and most preferably 25-35°C below the softening temperature.

[0049] In a preferred embodiment, the plastic starting material is heated to a temperature of 50–150°C during conditioning, more preferably to 70–130°C, even more preferably to 80–110°C, and most preferably to 90–100°C. These temperatures can be readily achieved using a heat pump and lead to the desired inventive effect.

[0050] In a preferred embodiment, the energy used for conditioning is transferred to the plastic starting material in step a) by means of at least one heat exchanger. A heat exchanger is a device that enables heat transfer between two or more material streams without these materials coming into direct contact with each other. This is particularly preferred according to the invention in order to avoid contamination of the plastic starting material.

[0051] In a particularly preferred embodiment, a shell and tube heat exchanger is used to condition the thermoplastic starting material prior to plasticization. A shell and tube heat exchanger is a type of heat exchanger used to transfer heat between two media separated by a pipe system. It typically consists of a bundle of tubes arranged within a cylindrical casing. The first medium is located inside the tubes, while the second medium flows around them. Heat exchange occurs through the tube walls without the two media directly mixing. A shell and tube heat exchanger offers a particularly large heat exchange surface area.

[0052] Preferably, the plastic feedstock is guided along the pipes as a second medium or within a second medium, while a first medium flows through the pipes. Preferably, this first medium is the heat pump's own heat transfer medium. This has the advantage of enabling direct heat transfer and thus reducing heat losses. Furthermore, it simplifies process control, facilitating and optimizing the automation and monitoring of the system.

[0053] In another preferred embodiment, the medium is a further medium heated by the heat pump.

[0054] Preferably, the first medium is a liquid, preferably water or thermal oil. Liquids typically have a high heat capacity and high thermal conductivity, which leads to efficient and rapid heat transfer between the media in the heat exchanger.

[0055] In a preferred embodiment, the movement of the plastic feed material during its passage through the heat exchanger occurs as a result of gravity, so that the plastic feed material moves downwards in the operating position, preferably in the direction of an outlet.

[0056] A large heat exchange surface area is necessary for conditioning because heat transfer to the plastic feed material, which is typically introduced as a solid, is significantly less efficient than with liquids. In a preferred embodiment, the plastic feed material can flow around the horizontally oriented tubes perpendicular to them in the operating position of the tube bundle heat exchanger. This has the advantage that the force of gravity moves the plastic feed material along with it.

[0057] In another preferred embodiment, the plastic feedstock flows inside the tubes of a shell-and-tube heat exchanger, where it is heated by a second medium flowing around the tubes. In such a case, the tubes can be arranged closer together, since the heated second medium, which is preferably a liquid or vapor, flows around the tubes laterally. However, the plastic granules are less thoroughly mixed within the tube, so that with large tube diameters, the temperature distribution can become inhomogeneous.

[0058] In the case of granules, grits or powders, the preferred pipe diameter is at least 5 times larger than the diameter of the granule, grit or powder particles, and particularly preferably at least 10 times larger, to avoid flow-impeding bridging of the solid.

[0059] Tube bundle heat exchangers with an outer tube diameter of 1-50 cm are preferably used, more preferably 2-30 cm, more preferably 2-20 cm or even 2-10 cm, and most preferably 2-5 cm. This allows for the unobstructed flow of plastic feed material granules, grit, or powder. The tube bundle heat exchanger preferably comprises at least 100, more preferably at least 200, and particularly preferably at least 500 tube bundles, preferably made of a metal such as steel, wherein the outer diameter of the individual tube bundles is preferably at least 2 cm, and more preferably at least 3 cm.

[0060] At the lowest point of the shell-and-tube heat exchanger in its operating position, a hopper of a plastics processing plant is preferably connected; more preferably, the shell-and-tube heat exchanger terminates in a funnel-shaped outlet equipped with a discharge device such as a rotary valve or a screw conveyor. This is particularly advantageous when a plastics processing machine with a gravimetric dosing unit is used.

[0061] The residence time in the shell-and-tube heat exchanger determines the outlet temperature of the plastic feed material. Preferably, this temperature is a maximum of 10°C lower than the temperature of the heating medium, such as the transfer medium of the at least one heat exchanger; more preferably, a maximum of 8°C; even more preferably, a maximum of 5°C; and most preferably, a maximum of 2°C. The temperature of the plastic feed material at the outlet of the heat exchanger can be changed, for example, by the extraction rate or the size of the heat exchanger.

[0062] In another preferred embodiment, the heat exchanger is a plate heat exchanger, preferably with a sufficiently wide plate spacing to allow the unimpeded flow of the plastic solid. These heat exchangers are also particularly suitable for use in plastics processing, as they can withstand high temperatures.

[0063] In a preferred embodiment, the process for plasticizing a thermoplastic material takes place in an injection molding machine, i.e., as a sub-process of the injection molding process. Injection molding is a very fast and efficient method for producing large quantities of identical plastic parts in a short time. Furthermore, injection molding enables a high degree of precision and attention to detail. Complex geometries and fine surface details can be reproduced with high accuracy. Since the molten material is injected into a mold under high pressure during injection molding, a large amount of waste heat is generated, which is why this plastics processing method is particularly suitable for the process according to the invention.

[0064] In other preferred embodiments, the process for plasticizing a thermoplastic material takes place in an extrusion machine, a blow molding machine, an injection blow molding machine, a calender, a rotational molding machine, or a compression molding machine. An extrusion machine is particularly preferred because it can be operated continuously, thus generating a consistently high amount of waste heat that can be used effectively and efficiently by means of a heat pump. The process according to the invention is particularly economical for extrusion machines.

[0065] Preferably, for the heating in step a), at least part of the waste heat from a second industrial machine, in particular the waste heat from a process fluid of a second industrial machine, is used.

[0066] In a preferred embodiment, the second industrial machine is a granulating machine. The granulating machine is used to process materials such as plastics into small, uniform granules (small pellets, particles, or lentils). The process typically utilizes mechanical processes for this purpose. A granulating machine typically produces granules as feedstock for plastics processing machines, which are preferably selected from the group consisting of injection molding machines, blow molding machines, film extrusion machines, or profile extrusion machines. Granulating machines generate a large amount of energy, which is absorbed in process fluids, for example, during the cooling of the produced granules. Therefore, utilizing this energy in another process, such as operating a first industrial machine, is advantageous.

[0067] Preferably, the granulating machine is coupled with a melt pump for pressure build-up and conveying the melt into the cutting unit and / or an extruder for melting the starting material to be granulated; more preferably, the granulating machine is connected downstream of these.

[0068] In a preferred embodiment, the granulation machine is connected downstream of a first industrial plant, particularly preferably an extruder. This has the advantage that there is a spatial proximity between the machines, which makes the transport of energy in the form of heat over these relatively short distances particularly efficient.

[0069] In a preferred embodiment, the granulating machine utilizes a technique selected from the group consisting of strand granulation, hot-die granulation, underwater granulation, agglomeration granulation, disc or rotary granulation, and comminution granulation. Strand granulation or underwater granulation is particularly preferred. In strand granulation, molten plastic material is extruded into long strands through a die, which are then cooled and cut into small, uniform granules by means of a rotating blade. Strand granulation is characterized by a high production speed and allows for good control of the granule size. Furthermore, it is suitable for a wide range of plastics.In underwater granulation, the melt is cut in a water-filled chamber with a rotating cutter bar and immediately cools into individual granules, which are then rinsed out of the water-filled chamber.

[0070] In another preferred embodiment, the second industrial machine is a machine selected from the group consisting of welding machines, drying plants, cooling units, cutting plants, conveying systems or mills.

[0071] In a preferred embodiment, the method comprises the following additional steps: c) Filling a mold of the plastics processing machine, which defines the contour of the thermoplastic molded part to be formed, with the plasticized thermoplastic, preferably by injecting the plasticized thermoplastic into the mold, d) Cooling of the thermoplastic molded part in the mold, and e) Demolding of the thermoplastic plastic part, wherein preferably the waste heat of the cooling step d) and / or the waste heat of a second industrial machine, in particular the waste heat of a process fluid of the second industrial machine, is used as the heat source for the heat pump used in step a), wherein the second industrial machine is particularly preferably a granulating machine.

[0072] In a preferred embodiment, the at least one heat pump uses the air surrounding the first and / or a second industrial machine and / or a process fluid of the first and / or second industrial machine as a heat source. Preferably, the heat source for the heat pump can be switched between the surrounding air and a process fluid. More preferably, this switching is carried out by means of control and / or regulation electronics.

[0073] Control electronics encompasses all components and circuits responsible for the targeted control of machines or processes. A controller switches actuators on or off based on input signals from sensors or switches. In contrast, regulation electronics not only controls but also continuously regulates the output variables of a system to achieve or maintain specific setpoints. Regulation electronics reacts to feedback from the system, for example, from sensors, and dynamically adjusts the output signals to maintain a desired state.

[0074] In a preferred embodiment, switching is carried out semi-automatically, and more preferably fully automatically, by means of control and / or regulation electronics. However, switching can also be done manually. (Semi-)automated switching has the advantage of increasing process stability and enabling particularly energy-efficient operation, since (semi-)automatic switching is generally faster and allows for more stable control in the event of fluctuations.

[0075] In a preferred embodiment, the switching of the heat sources is carried out by means of control electronics, wherein the switching takes place in response to a control command specified by the control electronics.

[0076] In a further preferred embodiment, the plastics processing machine and / or the second industrial machine comprises one or more sensors, and one or more measurement parameters determined by the sensor(s) are transmitted to the control electronics, so that the switching of the heat source takes place in response to a control command specified by the control electronics, which takes the measurement parameter(s) into account.

[0077] Preferably, one or more sensors are selected from the group consisting of a temperature sensor, humidity sensor, compressed air sensor, airflow sensor, light sensor, electricity meter, and state-of-charge sensor of energy storage devices, such as renewable energy storage systems. Preferably, the plastics processing machine and / or the second industrial machine include at least one temperature sensor, more preferably one temperature sensor and one humidity sensor, and even more preferably one temperature sensor, one humidity sensor, one compressed air sensor, one airflow sensor, one light sensor, and one electricity meter.

[0078] In a preferred embodiment, the conditioning of the thermoplastic starting material takes place in a preheating device, which is preferably part of the plastics processing machine and preferably connected to the downstream plasticizing unit of the plastics processing machine. A preheating device is a machine that heats materials, such as plastic granules, to a specific temperature before the actual processing. Such a preheating device has the advantage of reducing the energy consumption in the downstream machine by accelerating the melting process, thus making material processing more efficient and increasing throughput.The preheating device can also be spatially separated from the plastics processing machine, whereby a supply of the conditioned thermoplastic plastic starting material to the plastics processing machine, in particular the plasticizing unit, is possible.

[0079] The preheating device is particularly advantageous when it simultaneously serves to convey the plastic raw material into the plastic processing machine. This has the advantage that no additional installation space is required for a separate heating system, such as a shell and tube heat exchanger.

[0080] In a preferred embodiment, the conditioning takes place within a heated vibratory conveyor.

[0081] In a particularly preferred embodiment, a heated spiral conveyor, preferably a spiral conveyor with heating channels, is used to condition the thermoplastic starting material prior to plasticization. In a preferred embodiment, these heating channels are supplied with the transfer medium supplied by the at least one heat pump. A spiral conveyor is a mechanical conveying system comprising a spirally arranged chute or conveyor belt. Objects or materials can be conveyed along the spiral conveying system, for example, by means of vibration. This ensures a uniform and controlled material flow without the material becoming jammed or blocked, and also allows material flow against gravity.

[0082] Heating channels are preferably located vertically below the conveying surface, i.e., below the chute or conveyor belt. This placement ensures that the conveying surface is heated evenly and that the materials being transported are heated consistently and remain warm without direct contact with the heating element.

[0083] In another preferred embodiment, the heating channels are located within the conveyor belt or chute. This enables precise heating of the conveyed material directly during transport.

[0084] In another preferred embodiment, the heating channels are integrated into the side wall of the spiral conveying system. This reduces heat loss through the outer surfaces and ensures that the heat reaches the material regardless of the material thickness being conveyed on the system.

[0085] The spiral balancing conveyor is particularly preferred when thermally insulated. This enables the most energy-efficient process possible.

[0086] In a further preferred embodiment, a heating funnel, particularly preferably a heated double-walled funnel, is used to condition the thermoplastic polymer material prior to plasticization. Most preferably, heating channels run within the double wall. In a preferred embodiment, these heating channels are supplied with the medium supplied by the at least one heat pump.

[0087] In a preferred embodiment, the preheating system is part of a storage tank. This storage tank is particularly preferably heated indirectly via a heated double jacket.

[0088] Preferably, the double jacket of the storage tank is heated with thermal energy originating from at least one heat pump.

[0089] In another preferred embodiment, a warm gas heated by the at least one heat pump flows through the plastic starting material, which is located inside the storage container.

[0090] In a preferred embodiment, the plastic starting material is heated in a preheating device using warm air, which is used by the heat pump as a heat transfer medium for the useful heat.

[0091] The invention further relates to a plastics processing machine or a machine combination comprising a plastics processing machine for carrying out one of the methods according to claims 1-11, which includes at least one heat pump.

[0092] Preferably, the plastics processing machine is an injection molding machine, an extrusion machine, a blow molding machine, an injection blow molding machine, a calendering machine, a rotational molding machine, or a compression molding machine. Particularly preferred is the plastics processing machine an injection molding machine or an extrusion machine. In particularly preferred embodiments, the plastics processing machine is a single-shaft extruder, a twin-shaft extruder, or a multi-shaft extruder. In particular, the plastics processing machine is a single-shaft extruder. Single-shaft extruders are particularly cost-efficient because they have a comparatively simple design and therefore relatively low acquisition and maintenance costs.Twin-shaft extruders are also particularly preferred, as they have a higher mixing capacity and therefore produce a greater amount of heat, which is released as waste heat into the ambient air, making them especially suitable for use in the processes according to the invention. The plastics processing machine can be further specified by the material features defined in claims 1-11 and the preceding description.

[0093] The heat pump is preferably an air-to-water heat pump. Due to the high thermal conductivity of water or other liquids, the heat energy extracted from the air can be used and transferred particularly efficiently, especially through coupling with a heat exchanger.

[0094] Preferably, a high-temperature heat pump is used, as high temperatures are particularly advantageous for heating in step a). This enables significant savings in heat and drive energy in the subsequent process steps, thus contributing to an increase in throughput.

[0095] In a preferred embodiment, the plastics processing plant comprises at least one heat exchanger. A shell and tube heat exchanger is particularly preferred, as it is especially suitable due to its large heat exchange surface area.

[0096] Furthermore, the invention relates to a recycling process in which the thermoplastic starting material is selected from used plastics and / or waste plastics. Used materials are materials or products that have already fulfilled their original purpose and are therefore considered waste or can no longer be directly reused.

[0097] Recycling is a process in which used or waste material is collected, processed, and transformed into a new form so that the material can be reused. Thermoplastic materials are particularly suitable for such recycling because they can be repeatedly heated to a fluid state without altering their chemical structure.

[0098] Furthermore, the invention relates to a recycling process for reshaping a thermoplastic material in a plastics processing machine, comprising the step of: ▪ Conditioning of the thermoplastic starting material prior to forming in the plastics processing machine by heating below the softening temperature, characterized in that the energy used for the conditioning is generated at least partially by means of a heat pump which extracts energy from the ambient air and / or a process fluid of an industrial machine as a heat source.

[0099] Preferably, the heat pump extracts energy as a heat source from the room air and / or a process fluid of a second industrial machine, which is not the plastics processing plant.

[0100] Forming is a manufacturing process in which a workpiece is brought into a new shape without removing or adding material. The workpiece is processed using mechanical and / or thermal processes. Decomposition into its chemical components by thermal decomposition is preferably not a form of forming.

[0101] The recycling process preferably involves regranulation. Regranulation utilizes plastic waste, which is typically first cleaned and shredded. The material is then melted in an extruder and formed into strands through a die. These strands are then cooled and cut into granules. According to the invention, the material to be recycled is conditioned by heating before forming; preferably, the conditioning takes place before melting in the extruder. The regranulate is particularly suitable as a raw material for various plastics processing machines.

[0102] In other preferred embodiments, the recycling process is a mechanical recycling process, injection molding with recycled material, blow molding with recycled material, film extrusion with recycled material, or compounding, i.e., refining of recycled material. Recycling processes are particularly sustainable because they reuse already produced materials, which conserves resources and saves energy. Overall, this leads to cost savings, waste reduction, promotion of the circular economy, and improved climate protection. EXAMPLES

[0103] The invention will now be explained in detail with the help of concrete examples. COMPARISON EXAMPLE 1:

[0104] In a comparative test, 1000 kg of 20°C warm polyamide 6 granules are first placed directly into the hopper of an injection molding machine located in a machine hall. The polyamide 6 granules are melted and processed into molded parts. The energy required for this is 250 kWh. Due to heat radiation from the injection molding machine and the heat generated during the cooling of the plastic components in the machine hall, a temperature of 32°C is reached in the working area of ​​the machine hall after 6 hours. On hot summer days, an additional cooling capacity of approximately 20 kWh is required, supplementing the hall's ventilation, so that a total of 270 kWh of energy is needed for processing the aforementioned plastic material. INVENTIONAL EXAMPLE 1:

[0105] When the inventive method is used, the 20°C warm plastic granules are additionally heated to approximately 90°C via a shell-and-tube heat exchanger under otherwise analogous conditions. This heat exchanger draws its thermal energy from a high-temperature heat pump, whose fan is mounted at the height of the machine hall ceiling. The shell-and-tube heat exchanger used for granule preheating has a cube-shaped design with an edge length of 1 m. It contains 16 x 16 parallel metal tubes, each with an outer diameter of 3 cm, which are offset by 3 cm from the row above and below each row. The approximately 3-4 mm polyamide 6 granules move towards a heated tube by gravity, flow around it, and then move directly towards the next heated tube section in the next row.

[0106] The specific enthalpy of polyamide 6 increases by approximately 100 kJ / kg due to the preheating of the granules, which corresponds to approximately 1 / 6 of the total enthalpy required to melt the polyamide 6 granules (see also Figure 8.16 of the Saechtlich Kunststoff Taschenbuch, Hanser Verlag München).

[0107] With the method according to the invention, the energy consumption of the injection molding machine is reduced by 35 kWh compared to the conventional method for the same production quantity of 1000 kg of processed polyamide 6 granules. Under these conditions, the electrical energy consumption of the heat pump is approximately 8 kWh, resulting in an electrical energy saving of 27 kWh.

[0108] By using the heat pump, which extracts heat from the air in the machine hall, the temperature on the working level is reduced to 21°C in this case, thus enabling the saving of the entire cooling capacity, which in the worst case can amount to 20 kWh of electrical energy consumption. COMPARISON EXAMPLE 2:

[0109] In a plastics processing extruder, 5000 kg / h of polyamide 6 is colored with 100 kg / h of color pigment mixture in a twin-shaft extruder and processed back into granules in the downstream underwater pelletizing machine.

[0110] Without the application of the inventive method, 1040 kWh of electrical drive energy is required for melting and mixing in the twin-screw extruder at the described throughput of 5.1 t / h. Depending on the type of cooling, further energy of approximately 30 to 100 kWh is required for the continuous cooling of the water in the granulating machine. When using evaporative cooling in a cooling tower, this electrical energy consumption is 30 kWh. INVENTIONAL EXAMPLE 2:

[0111] Using the inventive process under analogous conditions, the polyamide 6 plastic starting material in granular form, consisting of approximately 3-4 mm lentils, is preheated from 20°C to 100°C via a shell-and-tube heat exchanger. In this heat exchanger, the plastic granules slide past the 3 cm thick steel pipes, through which the 100°C hot medium flows, under the influence of gravity. For a throughput of 5 t / h, a larger shell-and-tube heat exchanger is required. This exchanger has a width and depth of 1.6 m and a height of 2 m. The 3 cm outer diameter tubes are installed at intervals of 3 cm and are staggered from row to row.

[0112] The heating medium flowing through the pipes is supplied by a high-temperature heat pump, which obtains its low-temperature heat from the 50°C hot water of the granulation machine, in which the polyamide 6 melt is cooled from approximately 280°C.

[0113] Preheating the plastic feedstock granules reduces the heating power and dissipative energy input required to melt the granules according to the enthalpy curves, resulting in a reduction of the electrical energy demand of the twin-shaft extruder by 190 kWh in the specific application case.

[0114] By making advantageous use of the high temperature level of the water in the granulation machine, the high-temperature heat pump achieves a comparatively high efficiency and requires only 45 kWh of electrical drive energy.

[0115] By using the heat from the circulating cooling water of the granulating machine via the heat pump, the otherwise necessary additional cooling capacity of approximately 30 kWh is reduced or eliminated.

[0116] By using the method according to the invention, an energy saving of 175 kWh can therefore be achieved with an extruder throughput of 5100 kg / h.

[0117] The inventive method also opens up the option of using the drive power freed up at the twin-shaft extruder to increase throughput, provided that the peripheral units such as dosing devices or granulators are also designed for this purpose.

[0118] Alternatively or additionally, a heat pump can be installed, which draws its low-energy heat from the air in the machine hall and thus also cools the machine hall, which is particularly necessary for extruders with high throughputs.

Claims

[1] Method for plasticizing a thermoplastic polymer feedstock in a first industrial machine, namely a plastics processing machine, comprising the following steps: a) Conditioning of the thermoplastic raw material prior to plasticization in the plastics processing machine by heating below the softening temperature, b) Plasticization of the conditioned thermoplastic starting material, in which the conditioned thermoplastic starting material is converted into a flowable state to obtain a plasticized thermoplastic, characterized by , that the heating in step a) is carried out using the useful heat of at least one heat pump. [2] Method according to claim 1, characterized bythat the useful heat used for conditioning is transferred to the plastic starting material by means of at least one heat exchanger, preferably a tube bundle heat exchanger. [3] Method according to any of the preceding claims, characterized by that the plastics processing machine is an injection molding machine. [4] Method according to any of the preceding claims, characterized by that the procedure includes the following additional steps: c) Filling a mold of the plastics processing machine, which defines the contour of the thermoplastic molded part to be formed, with the plasticized thermoplastic, preferably by injecting the plasticized thermoplastic into the mold, d) Cooling of the thermoplastic molded part in the mold, and e) Demolding of the thermoplastic plastic part, wherein preferably the waste heat from the cooling step d) and / or the waste heat from a second industrial machine, in particular the waste heat from a process fluid of the second industrial machine, is used as the heat source for the heat pump used in step a), wherein the second industrial machine is particularly preferably a granulating machine. [5] Method according to any of the preceding claims, characterized by that at least one heat pump uses the air surrounding the first and / or a second industrial machine and / or a process fluid of the first and / or second industrial machine as a heat source. [6] Method according to claim 5, characterized by, that the heat source for the at least one heat pump can be switched between the air surrounding the first and / or second industrial machine and the process fluid of the first and / or second industrial machine, preferably by means of control and / or regulation electronics. [7] Method according to claim 6, characterized by , that the switching of the heat source is carried out by means of control electronics, whereby the switching takes place in response to a control command specified by the control electronics. [8] Method according to claim 7, characterized by , that the first and / or second industrial machine includes one or more sensors, and one or more measurement parameters determined by the sensor(s) are transmitted to the control electronics, so that the switching of the heat source takes place in response to a control command specified by the control electronics, which takes the measurement parameter(s) into account. [9] Method according to any of the preceding claims, characterized by , that a heated spiral balancing conveyor is used to condition the thermoplastic plastic starting material before plasticization. [10] Method according to any of the preceding claims, characterized by , that a double-walled funnel is used to condition the thermoplastic starting material before plasticization. [11] Method according to any of the preceding claims, characterized by , that it is a recycling process in which the thermoplastic plastic starting material is selected from used plastics and / or waste plastics. [12] Plastics processing machine or machine combination comprising a plastics processing machine for carrying out the method according to claims 1-11, comprising a heat pump, preferably an air-to-water heat pump and / or a high-temperature heat pump.