Manufacturing processes for increasing the heat capacity of components and components

Abstract

The invention relates to a manufacturing method for increasing the heat capacity of components (5), wherein a base material (1) of a thermoplastic material in the solid phase is first melted, then introduced into a casting mold in the molten state, and subsequently solidified in the casting mold, wherein a phase change material (2) is added to the base material (1) before it solidifies, which phase change material (2) is present in the gaseous phase in the molten base material (1) at least immediately before it solidifies and thereby forms a plurality of cavities (3) enclosed by the base material in the base material (1), in which cavities the phase change material (2) is present in the solid phase after the base material (1) has solidified. The invention also relates to a component (5) produced using such a manufacturing method.

Description

[0001] The invention relates to a manufacturing method for increasing the heat capacity of components, wherein a thermoplastic material in the solid phase is first melted, then introduced into a mold in the molten state, and subsequently solidified in the mold. Before the plastic material solidifies, a phase change material is added to the plastic. This phase change material is present in the gaseous phase in the molten base material at least immediately before the base material solidifies, thereby forming a plurality of cavities enclosed by the base material in the base material, in which cavities the phase change material is present in the solid phase after the base material solidifies. The invention also relates to a component produced by such a manufacturing method.

[0002] EP 2 260 997 B1 shows a polymer foam injection molding and a method for introducing a blowing agent into a polymeric material in a polymer foaming process.

[0003] DE 10 2022 113 518 A1 shows a busbar with an outer casing that encloses at least one cavity in which a phase change material is located.

[0004] DE 10 2020 134 308 A1 shows a hybrid material for thermal insulation with a cement material as the base material, which encloses a large number of gas-filled bubbles and a large number of microcapsules containing phase change material are embedded in the cement material.

[0005] DE 103 29 583 A1 describes a material that is intended to enable the production of molded parts with thermal energy storage properties and comparatively low densities and masses while maintaining dimensional stability. To this end, porous particles of a filler are mixed into the plastic intended as the base material, with the voids in the particles being filled with a phase-change material.

[0006] CN 116970374 A shows a thermoplastic resin with a salt as a phase change material for energy storage, which has molding properties.

[0007] CN 110039864 A shows a polymer foam material with thermal shock absorption performance at 40-100 degrees Celsius.

[0008] KR 1020220114128 A shows a thermoplastic resin composition by means of which a molded article with a particularly high cell density and a particularly beautiful appearance without optical defects on the surface, such as swirl marks or silver streaks, can be produced without using a rapid heat cycle molding or a counter-pressure casting process.

[0009] It is therefore known, particularly for lightweight construction requirements, to use plastic components that are foamed with a propellant or gas, so that a large number of cavities filled with the gas are formed within a component. The gas-filled cavities or pores make such a component particularly thermally insulating, i.e., it has reduced thermal conductivity compared to the solid version, but it also has a reduced heat capacity, i.e., the ability to absorb heat energy. In general, the heat capacity of a component is the product of the specific heat capacity of the material from which the component is made and the mass of the component. In lightweight components, the mass should be kept particularly low, which means that the (absolute) heat capacity of the entire component (in contrast to the specific, i.e., mass-related heat capacity of the component) can also be particularly low due to the particularly low mass.

[0010] The object of the invention is to provide a manufacturing method for components, in particular lightweight components, with a particularly high heat capacity, as well as such components.

[0011] The object is achieved by the subject matter of the independent patent claims. Advantageous developments or embodiments of the invention are described by the dependent patent claims, the following description, and the figures.

[0012] A first aspect of the invention relates to the manufacturing method described above for increasing the heat capacity of components. This manufacturing method offers the advantage that components produced thereby have a particularly low mass due to the large number of cavities, i.e. are designed as lightweight components, wherein the heat capacity or thermal energy absorption capacity of the components is particularly large or high due to the phase change material embedded in these cavities. In particular, by increasing the heat capacity, damage to or destruction of the component can be prevented if it can absorb the introduced heat and does not begin to melt due to a particularly high thermal insulation effect, for example on the side on which the heat is introduced, because the introduced heat cannot be absorbed or transferred.

[0013] The thermoplastic material used as the base material can, in particular, be a meltable and subsequently recurable material or plastic, such as PVC (polyvinyl chloride), PP (polypropylene), PE (polyethylene), PET (polyethylene terephthalate), PA (polyamide), and / or PS (polystyrene), to name just a few examples. The thermoplastic material is, in particular, a material that can be melted or liquefied by heating, whose shape can be changed in the liquid state, for example by pouring it into a mold, and then hardens in this new shape, i.e., solidifies upon cooling, and retains the new shape, for example, as predetermined by the mold, after solidification and cooling.To produce such a component, the base material is melted and introduced in the molten or liquid state into a casting mold or a shaping tool, in which it then solidifies or hardens and from which it can be removed in the hardened state. According to the invention, the phase change material added to the base material is in gaseous form in the molten state of the base material in order to form the cavities required for lightweight construction. During hardening or solidification of the base material in the casting mold, the invention provides that the phase change material cools from the gaseous phase as a result of the cooling of the base material, as a result of which it transforms into the solid phase in the cavities, for example via a liquid phase, and is present in this phase in the cavities.As the phase-change material cools, particularly during the phase change(s) from the gaseous phase to the solid phase, the density of the phase-change material can increase, so that in the cured state of the component or the base material, the cavities are only partially filled with the solid phase phase-change material. The manufacturing method according to the invention therefore takes into account that the phase-change material has at least a lower boiling point or a lower boiling temperature than the base material. The phase-change material becomes gaseous at a temperature at which the base material is still liquid or molten, for example, when both are heated.

[0014] The term phase change material or phase change materials within the meaning of the invention refers to a group of materials which are used for heat storage or heat absorption. The phase change materials within the meaning of the invention are designed in such a way that a phase change or change in state of aggregation occurs in a respective temperature range which occurs when the predetermined temperature is reached or below the predetermined temperature. This temperature can be predetermined, for example, by an application or use of the component. During a transition of a phase change material, for example from a gaseous state of aggregation to a liquid state of aggregation, the so-called enthalpy of vaporization is released or absorbed during evaporation when the phase change material has been cooled to boiling temperature from the gaseous phase to the liquid phase.Upon further cooling toward the melting temperature, the enthalpy of fusion or heat of fusion is released upon solidification or freezing of the phase-change material, or absorbed during its melting. By releasing or absorbing the enthalpy of vaporization and / or the enthalpy of fusion, cooling or heating of the component below or above the boiling point (evaporation) of the phase-change material and / or below or above the melting point of the phase-change material can be delayed or prevented. Phase-change materials considered within the meaning of the invention include sodium acetate trihydrate (used in the so-called "heat pad"), water, paraffins, fats, salts such as alum (salts of sulfuric acid with aluminum, gallium, indium, titanium, vanadium, chromium, manganese, iron, cobalt, rhodium, and / or iridium), sodium sulfate, and / or sodium hydroxide, to name just a few examples.

[0015] The first aspect of the invention also includes embodiments or further developments which result in additional advantages.

[0016] A further development of the manufacturing process provides for the base material to be present in the solid phase as base material granules, and for the phase-change material to be added to this as phase-change material granules in the solid phase before the base material is melted. In other words, the base material and the phase-change material are each present as granules in the solid phase before the base material is melted, for example, mixed, and heated together. This results in the advantage that the manufacturing effort for a component produced in this way is particularly low. The component can be manufactured, for example, using an extrusion process involving a piston extruder and / or a screw extruder.As is usual with these known processes, the base material or the material to be melted and formed is introduced into the extruder, for example the extruder screw, in the form of granules, i.e., as particularly small, solid pieces, before being heated and melted. According to this development, the base material and the phase-change material can each be introduced into the extruder as granules and mixed with one another, where they are heated and melted, and then homogenized, i.e., evenly mixed, using a screw, for example. Additionally, phase-change material in solid phase can be admixed or added to the molten base material or the molten mixture of phase-change material and the molten base material.

[0017] It is particularly advantageous if the base material and the phase change material are selected such that, in conjunction with the manufacturing process, a temperature range is created in which both the base material and the phase change material are in the liquid phase, so that they can be mixed or homogenized particularly well in liquid form. Following heating to melt it, for example along a conveying direction of the extruder screw, the liquid mixture of base material and phase change material can be heated further, whereby the phase change material, now evenly distributed in the base material, can transform into the gaseous phase, i.e., evaporate. This can create gas bubbles of the evaporated phase change material that are evenly distributed in the base material or in the melt, forming the cavities.

[0018] A further development of the manufacturing process provides for the phase change material to be heated prior to addition and then added to the molten base material in the liquid or gaseous phase before the base material solidifies. In other words, the phase change material is to be heated separately from the base material and added to the molten base material in the liquid and / or gaseous phase. The phase change material can therefore be at least partially gaseous by heating it separately from the heating of the base material before it is mixed into the liquid base material. This has the advantage that the phase change material can be introduced into the base material using known plastic foaming processes, i.e., when the phase change material is at least partially gaseous, which can reduce manufacturing costs particularly significantly.

[0019] A further development of the manufacturing process provides for the phase-change material to have a melting temperature in a temperature range of minus 20 to plus 100 degrees Celsius. In other words, the phase-change material should melt or solidify in the temperature range of minus 20 to plus 100 degrees Celsius. The phenomenon of supercooled melting can be taken into account. This offers the advantage, particularly in the finished component, that the phase-change material can absorb heat due to a melting temperature in this temperature range, although this temperature range is below the melting temperature of most plastics that can be used as raw materials.

[0020] A further development of the manufacturing process provides for at least the base material to be melted in an extruder screw. As already described, the manufacturing process can comprise a screw extrusion process, wherein at least the base material can be conveyed, for example, in an axial direction, by means of an extruder screw. Along the conveying direction, the base material or the mixture of base material and phase-change material can be heated, for example, by a heating element surrounding the extruder screw, i.e., can be melted, for example, and simultaneously compressed by the screw. The pressure in the base material or the mixture or the melt can increase along the conveying path through the extruder screw.This offers the advantage that, for the production of components with particularly high heat capacity, the incorporation of phase-change material allows for the use of well-known and proven manufacturing processes, particularly extrusion processes such as the screw extrusion process. This can advantageously reduce manufacturing costs.

[0021] A second aspect of the invention relates to a component, in particular produced by a manufacturing method according to the first aspect of the invention. Advantages and advantageous developments of the first aspect of the invention are to be regarded as advantages and advantageous developments of the second aspect of the invention, and vice versa.

[0022] The component has cavities, in particular a large number of cavities, which are partially filled with a phase change material. The phase change material can be present in the cavities, in particular in a solid or liquid phase, depending on its temperature and melting point. In other words, the cavities may not be completely filled with the phase change material. The phase change material in the cavities in the component has the advantage that the component can be protected from thermal failure, i.e. damage caused by overheating. Heat or thermal energy introduced into the component does not only have to be absorbed by the base material, but is also absorbed by the phase change material in the cavities. The phase change material can liquefy from a solid phase, i.e. liquefy by absorbing heat, in particular the enthalpy of fusion or latent heat of fusion.The reaching of a failure temperature or melting temperature of the base material can thus be advantageously delayed or shifted towards a higher amount of heat being introduced into the component than without the phase change material in the cavities.

[0023] A further development of the component provides that the component has a lower density or number of cavities in at least one edge region than in an inner region of the component spaced from the at least one edge region. In other words, the component should have fewer cavities near an outer region, to which the at least one edge region can be connected, than in a region of the component spaced from the edge region or in the inner region of the component. In other words, the component can have a compact edge layer with particularly few or no cavities adjacent to an outer side. This results in the advantage that the component has a closed, i.e., smooth surface without pores, which can advantageously promote heat input into the component, i.e. the component does not melt on its outer side.Another advantage is that the component can be more easily reworked, such as ground, after removal from the mold. Such a compact surface layer can be achieved using state-of-the-art plastic foaming processes, known for temperature control of the tool or mold.

[0024] A further development of the component provides that the component is at least partially manufactured from at least one of the following thermoplastics as the base material: polycarbonate (PC), polyethylene (PE-HG), polymethyl methacrylate (PMMA), polyethylene terephthalate (PETG), polypropylene (PP-H), acrylonitrile butadiene styrene (ABS), polystyrene (PS), and polyvinyl chloride (PVC). This results in the advantage that these thermoplastics are meltable, and the phase-change material can be incorporated into them using one of the described embodiments of the manufacturing process, so that, in the finished state, a component with embedded phase-change material can be produced using one of the aforementioned plastics as the base material.

[0025] A further development of the component provides that the component is at least partially made of corn starch and / or lignin as the base material. Corn starch is a polysaccharide with the molecular formula (C6H10O5)n is meant, i.e., a polysaccharide composed of α-D-glucose units. Lignin refers to solid biopolymers that are stored in the plant cell wall. Lignins form a group of phenolic macromolecules (biopolymers) composed of various monomer building blocks. The use of renewable raw materials as the basic material, such as corn starch and / or lignin, has the advantage of significantly reducing manufacturing costs due to the particularly easy procurement of these materials as the basic material for the component. For the purposes of the invention, lignin and corn starch are understood to refer to a group of so-called bioplastics that comprise corn starch and / or lignin and can be liquefied or melted, for example, by adding plasticizers such as glycerin and / or sorbitol.These bioplastics can represent a thermoplastic material within the meaning of the invention, in particular within the meaning of the manufacturing process according to the invention, and can be used alternatively or in combination with the aforementioned thermoplastic materials or base materials.

[0026] A further development of the component provides for the component to be manufactured at least partially from clay and / or a ceramic material as the base material. An example of a ceramic material that must be meltable for such a component is glass. In addition, a variety of glass ceramics are known, which can be melted, for example, by adding boron oxide, barium oxide, and / or zirconium oxide. Clay, as used in the invention, refers to fusible clay materials, i.e., for example, ceramic materials based on clay slurries that can be melted by adding fluxes such as feldspar, nepheline, or dolomite, and network formers such as boron oxide, barium oxide, and / or zirconium oxide.The clays and / or the ceramic material or a ceramic material may represent a thermoplastic material within the meaning of the invention, in particular within the meaning of the manufacturing process according to the invention, and may be used alternatively or in combination with the aforementioned thermoplastic materials or base materials.

[0027] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0028] Exemplary embodiments of the invention are described below. Shown are: Fig. 1 States of a base material and / or a phase change material along an embodiment of a manufacturing process according to the invention; Fig. 2 states of the base material and / or the phase change material along a further embodiment of the manufacturing process according to the invention; and Fig. 3 component according to the invention with cavities with phase change material and an edge region.

[0029] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0030] In the figures, the same reference symbols designate elements with the same function.

[0031] Fig. 1 shows states of a base material 1 and / or a phase change material 2 along an embodiment of a manufacturing process for increasing a heat capacity of components 5. The manufacturing process can be carried out at least partially in an extruder, for example a screw extruder. At the top of Fig. 1, a first state a1 can be shown along a temporal progression 4 of the manufacturing process. In the first state a1, the base material 1, for example a thermoplastic such as PET, as well as the phase change material 2 can each be present in a solid phase, for example as granules, and at least partially mixed. Along a conveying direction of the extruder screw, for example, or temporally following the first state a1, a second state a2 can follow, in which the mixture of phase change material 2 and the base material 1 has been heated and melted. As in Fig. 1, in the second state a2, i.e. when phase change material 2 and the base material 1 are already melted, additional solid-phase or solid phase change material can be added to the melt. In other words, in the second state a2, the phase change material 2 added in this state can still be present in the melt, for example for a particularly short time after addition, in the solid phase, before it melts and then evaporates. For example, further along the conveying direction along the screw or extruder screw, the melt of base material 1 and phase change material 2 can be further heated and simultaneously compressed, so that the phase change material 2 is in the gaseous phase and, due to the high pressure, forms particularly small cavities 3, shown as the third state a3 in the middle of Fig. 1. In a fourth state a4, the melt comprising the molten base material 1 and the gaseous phase change material can be introduced into a casting mold, whereby the pressure in the melt can have decreased again compared to the third state a3. As in Fig. 1, in the fourth state a4, the still gaseous phase change material 2 can form larger cavities 3 due to the lower pressure than in the third state a3. In the fifth state a5, shown below in Fig. 1, the melt may have cooled and solidified, whereby the base material 1 and the phase change material 2 in the cavities 3 may have cooled and both may be in the solid phase. As in Fig. 1 in the fifth state a5, the phase change material 2 in the finished or cooled component 5 can only partially fill the cavities 3. In Fig. 1 and in the other figures, not all elements are provided with reference symbols for the sake of clarity.

[0032] Fig. 2 shows states b1 to b5 of the base material 1 and / or the phase change material 2 along a further embodiment of the manufacturing method for increasing a heat capacity of components 5. In contrast to the embodiment of the manufacturing method shown in Fig. 1, in the first state b1 shown here, the base material 1 can be in the form of granules, without any solid-phase, admixed phase change material 2. For example, parallel to the melting of the base material 1, for example along an extruder screw, the phase change material 2 can be preheated and can be partially molten and / or gaseous in an intermediate state b1.1. The preheated phase change material 2, which can be at least partially in the gaseous phase or at least in the liquid phase, can be added to the molten base material 1, for example via a known injection process. After the addition of the preheated phase change material 2, a second state b2 can exist. In the second state B2, the phase change material 2 can be in the gaseous phase and form cavities 3.In the third state b3, the melt with the gaseous phase change material can be further compacted, for example along the extruder screw, which can increase the pressure in the melt, resulting in, as shown in . Fig. 2, the gaseous phase change material can be compressed, whereby the cavities 3 can be smaller than in the second state b2. In a fourth state b4, the melt with the gaseous phase change material 2 can be introduced into the casting mold and still be in liquid form, at least with respect to the base material 1. At the same time, the pressure can have dropped compared to the third state b3, for example to atmospheric pressure or ambient pressure, whereby the gaseous phase change material 3 and thus also the cavities 3 created by it can expand compared to the third state b3, before the base material 1 and phase change material 2 solidify by cooling in the casting mold.In the fifth state b5, the component 5 can, for example, be cooled in the casting mold or be in the finished state, wherein the base material 1 and the phase change material 2 can be solidified, wherein the phase change material 2 can be arranged in the solid phase in the cavities 3 previously created by it and can at least partially fill them.

[0033] Fig. 3 shows a finished component 5 with a particularly high heat capacity, which has cavities 3, which can be at least partially filled with a phase change material 2. In addition, the component 5 can have an edge region 6 adjacent to an environment of the component 5, or several edge regions 6, in which a smaller number or density of cavities 3 or no cavities 3 are present, as in Fig.3. This can result in the advantage that component 5 has a particularly pleasant surface compared to a porous, rough surface. Additionally, it can result in the advantage that heat can be transferred particularly well into the component 5 via the surface if it is smooth, i.e., if it does not have the porous structure that can have a heat-insulating effect.

[0034] A particularly preferred embodiment is described below.

[0035] Injection molding processes with a microcellular foam structure are known from the state of the art, such as the so-called MuCell® process. These processes are used particularly for lightweight components, as the cavities allow component mass to be saved with little or no loss of strength. The disadvantage here is that no additional heat can be absorbed and / or transferred by these components, as the cavities within the components can act as heat insulation. According to the new idea, the cavities 3 are to be filled with phase-change material 2 so that additional heat (in addition to the heat capacity of the base material 1) can be absorbed and temporarily stored in the component 5.In particular, after cooling a heated, finished component 5, the phase-change material 2, which is present in the cavities 3, for example, in the liquid or gaseous phase, can release previously absorbed heat by releasing its enthalpy of vaporization (from gaseous to liquid phase) and / or its enthalpy of fusion (during the phase transition from the liquid to the solid phase). A particularly advantageous aspect of the new idea is that it can be integrated into "standard injection molding processes," such as extrusion processes. If the phase-change material 2 is heated at the same time as or in parallel with the heating and melting of the base material, it can be injected into the liquid or molten base material as a foaming agent or expanding agent.The resulting pores or cavities 3 can thus be at least partially filled with the phase change material 2, for example, because they are formed by gaseous phase change material 2. This allows the introduction of phase change material 2 into a component or into cavities 3 of the component 5 to be carried out in a manner similar to the known MuCell® process. As already described, injection molding processes and / or extrusion processes can be used additionally or alternatively to produce the component 5. By heating the phase change material 2 before introducing it into the molten base material 1, which can also be referred to as a plastic compound, the melt or the molten base material 1 can be physically foamed.Additionally or alternatively, it is conceivable that the phase change material 2 can be mixed into the still solid base material 1 in the solid phase, for example both in the solid phase as granules, as a so-called masterbatch before melting. During the manufacturing process, it can thus be provided that the phase change material 2 undergoes two phase transitions, once from solid to liquid and then from liquid to gaseous, whereby the gaseous state can be necessary for the formation of pores or the formation of the cavities 3. During operation of the component 5, it can be provided that the phase change material 2 undergoes only one phase transition, for example from solid to liquid (and of course back again when the component cools down), whereby energy, in particular heat energy, can be absorbed by the phase change material 2 during the phase transition from solid to liquid and can be released again when it cools down.A boundary layer 6 or compact boundary layer in which a density of cavities 3 with phase change material 2 is lower than in an inner region of the component 5, or has no cavities 3 at all, can be realized by carrying out temperature control in the casting mold or in the tool.

[0036] Overall, the examples show how an injection molding lightweight construction process with embedded PCM particles (PCM: Phase Change Material) can be provided.

Claims

[1] Manufacturing method for increasing a heat capacity of components (5), wherein a base material (1) of a thermoplastic material in the solid phase is first melted, then introduced into a casting mold in the molten state and then solidifies in the casting mold, wherein a phase change material (2) is added to the base material (1) before it solidifies, which phase change material is present in the gaseous phase in the molten base material (1) at least immediately before it solidifies and thereby forms a plurality of cavities (3) enclosed by the base material (1) in the base material (1), in which cavities the phase change material (2) is present in the solid phase after the base material (1) has solidified, wherein the phase change material (2) has a lower boiling point or a lower boiling temperature than the base material (1). [2] Manufacturing method according to claim 1, wherein the base material (1) is present in the solid phase as base material granules and the phase change material (2) is added thereto as phase change material granules in the solid phase before melting the base material (1). [3] Manufacturing method according to claim 1, wherein the phase change material (2) is heated before being added and is added to the molten base material (1) before it solidifies in the liquid or gaseous phase. [4] Manufacturing method according to one of the preceding claims, wherein the phase change material (2) has a melting temperature in a temperature range of minus 20 to plus 100 degrees Celsius. [5] Manufacturing method according to one of the preceding claims, wherein at least the base material (1) is melted in an extruder screw. [6] Component (5) produced by a manufacturing method according to one of the preceding claims, comprising cavities (3) which are partially filled with a phase change material (2) present in the solid phase. [7] Component (5) according to claim 6, wherein the component (5) has a lower density of cavities (3) in at least one edge region (6) than in an inner region of the component (5) spaced from the at least one edge region (6). [8] Component (5) according to claim 6 or 7, wherein the component (5) is at least partially made of at least one of the following thermoplastics as base material (1): polycarbonate, polypropylene, polyethylene, polyethylene terephthalate, polymethyl methacrylate, acrylonitrile butadiene styrene, polystyrene, polyamide, polyvinyl chloride. [9] Component (5) according to one of claims 6 to 8, wherein the component (5) is made at least partially from corn starch and / or lignin as the base material (1). [10] Component according to one of claims 6 to 9, wherein the component (5) is at least partially made of clay and / or a ceramic material as the base material (1).

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