Patent Application
20200324445
The invention relates to a method of making a thin component in a lightweight sandwich construction having a high-quality surface.
Methods of this kind have been developed and implemented on a large scale by applicant for decades.
Solely by way of example, reference is made to the following German patent applications by applicant:
DE 10 2018 117 337, DE 10 2017 109 953, DE 10 2016 112 290 A1, DE 10 2013 018 694 A1, DE 10 2013 008 592 A1, DE 10 2013 005 523 A1, DE 10 2013 008 364 A1, DE 10 2015 111 052 A1 and DE 10 2012 017 698 A1,
whose content is hereby incorporated in the content of the present patent application in order to avoid repetition.
For the sake of completeness, reference is made to the subsequently published German patent application DE 10 2018 123 703 A1 [US 2020/0094449] by applicant.
The methods predominantly used by applicant until now of making such a thin component in particular include connecting thermoplastic deep-drawn films to polyurethane foam masses.
Proceeding therefrom, the problem addressed by the invention is to provide a method that can make a thin component that meets the requirements of low weight and high rigidity, that can have a high-quality surface, and that can be cost-effectively manufactured.
The invention solves this problem by the features of claim 1.
The principle of the invention first consists in an expandable particle foam being used instead of the polyurethane two-component foams that have previously been used.
Particle foams made of EPS, EPE and EPP, for example, are possible as suitable expandable particle foams. In this case, these are particle foams that can have densities that are typically in the range of from 15 kg/m3 to 80 kg/m3 once fully or completely expanded and foamed.
According to the invention, the starting material is provided in the form of loose particles of an expandable particle foam, the particle foam, when expanded, having a softening temperature, in particular a VICAT softening temperature, of greater than 160° C. Advantageously, materials are selected of which the softening temperature when expanded is above 180° C., in particular advantageously of greater than 200° C., more advantageously of greater than 220° C., more advantageously of greater than 235° C.
The VICAT softening temperature is a physical variable for quantitatively characterizing the dimensional stability of a plastics material. This information is used to determine the heat deflection temperature. For this purpose, reference is made in particular to the DIN EN ISO 306(2) standard.
According to the invention, materials can for example be used that are available under the trade name Ultrason by BASF SE with the names PSU, PESU or PPSU. According to some data sheets (as can be viewed at www.Kern.de for polyphenylsulfone (PPSU)), VICAT softening temperatures are not explicitly stated. However, these data sheets provide information regarding the heat deflection temperatures at 207° C. and 214° C. as well as a melting point according to ISO 11357 of 215° C. Other data sheets (such as from ALBIS for PESU-GF20) state a VICAT softening temperature of 217° C.
Depending on the material, determining the VICAT softening temperature is associated with difficulties. In these cases, as an alternative to determining the softening temperature, recourse can be made to determining the glass transition temperature or determining the heat deflection temperature or determining the melting point of the expanded granulate particles. These above-mentioned temperatures generally deviate from the VICAT softening temperature by just a few percentage points.
If the VICAT softening temperature can be determined for a substance in accordance with the above-mentioned standard, the determination of the VICAT softening temperature should take precedence, however.
According to a variant of the invention, a film-like substrate is first provided. This may for example be a film that can be deep-drawn, e.g. made of ABS or PMMA. This may have a wall thickness of between 0.2 mm and 13 mm. The film may for example be deep-drawn in a first mold. The substrate used may, however, be provided by a thin skin, a thin film, or another thin material. The substrate does not have to be deep-drawn.
According to this variant of the invention, the substrate is arranged in a lower mold part. The lower mold part provides a receiving space.
It should be noted at this point that, according to a variant of the invention, the provision of such a film-like substrate can also be omitted. In this variant of the invention, the component to be manufactured can be manufactured without such a film or substrate.
The method according to the invention provides that granular starting material in the form of loose particles of an expandable particle foam is provided. Those materials that are known as expandable particle foams are possible. In particular, these are understood to be particle foams made of EPS, EPE or EPP, or also expandable PEEK. There is another definition further on.
The granular starting material may be provided in the used form of small spheres or beads, or in the form of granular particles having different regular or irregular shapes and geometries. The starting material is in particular pourable.
The particles are provided so as to be loose in the granular starting material, i.e. are in particular not joined together.
According to a variant of the invention, the step of partial expanding of the particles is carried out first. Partial expanding means that the particles are not yet completely expanded. For example, it may be provided according to the invention that, based on an expanding or expansion process from 0% to 100%, proceeding from the volume of the particles of the starting material up to the volume of the particle when completely expanded, partial expanding of between 30% and 95% takes place. The term “partial expanding” in particular includes embodiments of the invention in which at least the step of additionally expanding the particles can still be carried out, through to a completely expanded state of the particles.
The step of partial expanding takes place in particular, but not necessarily, in a position that is remote from the lower mold part in which the substrate is arranged. More advantageously, the partial expanding of the particles can be carried out in an oven, in particular in an infrared oven.
According to another step of the variant of the method according to the invention, it may be provided that the partially expanded particles are placed into the lower mold part. The partially expanded particles may, for example, be immediately transported after the step of partially expanding the particles has been carried out. However, said partially expanded particles may also be transported at a considerably later point in time after the step of partially expanding the particles has been carried out. The partially expanded particles can be placed and/or arranged or positioned in the lower mold part by a machine, in an automated manner, or manually.
According to the invention, the mold is then closed. To do this, an upper mold part can be moved towards the lower mold part and a receiving space or cavity for the partially expanded particles, as well as for the substrate positioned in the lower mold part.
According to the invention, the mold is then heated. The invention also covers the case in which the mold is consistently kept at a constant temperature or at a temperature within a predetermined temperature range.
According to the invention, the previously already partially expanded particles are then fully expanded to form a completely expanded particle foam. The particles then expand to their maximum extent or to their maximum volume, and bake or sinter to one another, as it were. In the process, the particle-foam mass simultaneously binds to the substrate. The remaining expanding process is activated by the mold temperature. The invention also covers the case in which, additionally or alternatively, other activation agents are used to activate and carry out the remaining expanding process of the particles, i.e. for the expanding process of the already partially expanded particles through to a fully expanded state of the particles.
According to the invention, the particle-foam mass is allowed to cure. Owing to this curing process, the particle-foam mass forms a permanent, firm bond with the substrate.
The invention also covers the case in which the substrate is provided with a corresponding chemical, e.g. in the manner of an adhesive primer, on its inner face facing the particle-foam mass before the partially expanded particles are placed into the lower mold part, in order to optimize the bond between the substrate and the particle-foam mass or the formation of the bond between the substrate and the particle-foam mass.
After allowing the particle-foam mass to cure, the mold can be opened, and the molded body thus formed can be removed. The molded body thus formed constitutes the component to be manufactured according to the invention, or can be developed into such a component by subsequent processing steps.
The following materials are considered to be expandable particle foams within the meaning of the present patent application, for example:
The abbreviation EPS means expandable polystyrene. This is, for example, known by the brand name Styropor, and can e.g. be sourced from Metz EPS-Hartschaumzuschnitte in 74376 Gemmrigheim.
Expandable polyethylenes (EPE) are also considered to be a particle foam within the meaning of the present patent application. Lastly, expandable polypropylenes (EPP) are also considered to be well suited to the purposes according to the invention.
In particular, thermoplastic particle foams are in particular covered by the term particle foam within the meaning of the present patent application. These may comprise, as a starting material, a granulate, in particular also a microgranulate, for example having diameters of the particles in the order of magnitude of between 0.1 mm and 5 mm, more preferably particles having a diameter of approx. 1 mm.
Blowing agents are preferably arranged in the granular starting-material particles of the particle foam. Said blowing agents may be activated thermally and/or by chemicals, for example also by the action of water vapor, in order to initiate the pre-expanding process.
The process of the remaining expanding, i.e. completely expanding pre-expanded particles to form completely expanded particles, is also referred to as sintering within the meaning of the present patent application.
Pentane, which is polymerized into the granular particles, is taken into consideration for polystyrene particle-foam particles, for example. Once the particles are exposed to temperatures of above 100° C., the blowing agent can evaporate and, in the process, inflates the thermoplastic base material to form polystyrene foam particles.
The second expanding step can be carried out in the lower mold part according to the invention, with the mold temperature being selected such that the blowing agent can completely evaporate, and the particles can completely foam.
Lastly, the variant of the invention has been described according to which granular starting material in the form of loose particles is first pre-expanded, and these pre-expanded particles, which are still in the form of granular particles, are placed into the lower mold part and baked therein. However, according to a variant, the invention equally includes a method and a component made according to this method, in which the granular starting material in the form of loose particles is completely expanded, and is then placed into the mold while still being in an aggregate state in the form of a loose granulate. In this last-described variant, no further increase in volume takes place while the expanded particles are baked in the mold.
Lastly, for the sake of completeness, it is noted that the invention also includes methods in which the mold can also be overloaded, for example, or in which a reduction in the volume of the expanded particles inserted into the mold takes place in another way over the course of the baking process.
It is also noted that, while baking the expanded particles, the mold is at a temperature that is above the VICAT softening temperature.
Furthermore, it is additionally noted at this point that, in the preceding passages, a variant of the invention has been described in which, before introducing the expanded particles into the mold, a film or substrate is arranged in the lower mold part and the step of baking the expanded particles to this substrate is carried out.
However, the invention also includes a variant in which the expanded particles are placed directly into the mold and are baked therein without a film or substrate having been inserted into the mold in advance.
In addition to EPS (extruded polystyrene), XPS is also taken into consideration for the invention.
For example, Schaumaplast GmbH & Co. KG in 68799 Reilingen comes into consideration as a reference source for expandable polypropylene EPP or XPS.
Particle foams for use with the invention can also be provided by expandable copolymers. Materials of this kind can be sourced under the trade name Grupor from the plastics manufacturing facility Katzbach GmbH & Co. KG in 93413 Cham, for example.
Expandable PEEK (polyether ether ketone) is also taken into consideration as a starting material for the particle foam that can be used in the context of the invention. This can be sourced under the trade names Gatone or Victrex, for example.
According to the invention, while the expanded particles are being baked to form a homogenous curable particle foam, the mold is heated to a temperature above the VICAT softening temperature of the particle foam such that the particles can bake to one another. The mold is then cooled to a temperature below the VICAT softening temperature such that the particle foam cures. After curing the foam, the molded body can be removed from the mold.
According to the invention, in another step a coating layer is applied to the surface of the molded body. In this case, a coating layer, or a plurality of coating layers in succession, can be applied to the entire surface of the molded body or to a portion of the molded body or to a plurality of portions of the molded body.
In a variant of the invention, the coating layer can be applied as part of a cathodic dip coating process. Here, the molded body is completely or partially immersed in an immersion bath and a cathodic dip coating method that is known per se is used. In this process, high temperatures can act on the molded body. Advantageously, the step of applying the coating layer takes place at a temperature below the VICAT softening temperature of the cured particle-foam mass.
In a variant of the invention, the coating layer is applied as part of a powder coating method. Here too, it is provided according to the invention that the step of applying the coating layer takes place at a temperature below the VICAT softening temperature.
According to the invention, it is further provided that a step of drying the coating layer takes place, in particular at a high temperature that is selected such that it is below the VICAT softening temperature of the particle foam.
According to the invention, lightweight components can be manufactured and coated, and conventional coating methods can be used that, until now, have only been used for coating metal components, for example. The components made using the method according to the invention can therefore be coated on existing coating lines of the coating apparatuses or devices using conventional coating methods.
The method according to the invention serves to produce a component having a high-quality surface. A high-quality surface may for example be particularly resilient, e.g. may be designed to be particularly impact-resistant, and furthermore may be particularly suitable for outdoor applications. In particular, a high-quality surface may have properties as required by so-called class A surfaces.
By applying a coating layer in a conventional high-quality coating process, a high-quality surface of this kind can be provided on the component.
If the component comprises a film or another suitable substrate, e.g. a thin metal film, which has been placed into the lower mold part before the expanded particles are inserted, the film or substrate can also be covered by the coating layer.
The invention relates to a method of making a thin component. The term “thin” means that the component has a considerably longer extension along a surface in the x and y directions than in a z direction perpendicular thereto. The surface may be flat or curved in space, or even curved multiple times, and may take any spatial form.
According to an advantageous embodiment of the invention, step ix) of applying a coating layer to a surface of the molded body and/or step x) of drying the coating layer are carried out at a high temperature, in particular a temperature above 150° C. The provides the option of utilizing known methods for applying a coating layer that, until now, have only been used for metal components or components manufactured from plastics injection-molded parts.
In another advantageous embodiment of the invention, the coating layer has a thickness of between 0.01 mm and 2 mm when cured.
According to an advantageous embodiment of the invention, the component comprises a substrate that is provided by a deep-drawn film. This makes it possible to utilize conventional constituents of a component that have already been comprehensively tested and that particularly make it possible to provide a high-quality surface for the component.
According to another advantageous embodiment of the invention, in addition, step xi) is carried out as follows: applying a cover layer to the face of the particle-foam mass directed away from the substrate.
Such a cover layer may for example be an interior decorative layer, for example wall paneling, in particular a plastics layer. If the manufactured component forms a wall or a wall portion of a caravan or a caravan trailer, for example, the decorative layer may e.g. be a typical interior fitting surface of such a caravan in a conventional manner.
According to another advantageous embodiment of the invention, the method according to the invention comprises the following step:
xii) processing the molded body to form a component.
Various processing methods come into consideration as processing steps. These include, for example, separating or cutting off parts or regions of the molded body, optionally also separating or cutting off portions of the substrate. These include, for example, a cleaning step and/or a surface-processing step, in particular on the outer face of the substrate, for example roughening or polishing or smoothing the substrate, optionally also applying an additional layer or film, for example an additional functional layer.
The invention also covers the case in which the face of the cured particle-foam mass directed away from the substrate is processed, for example is connected to an additional skin or an additional material or a film or has an additional skin or an additional material or a film applied thereto, e.g. sprayed thereon, bonded thereto, coated thereon, riveted thereto, screwed thereto, or bonded to another element.
According to another advantageous embodiment of the invention, the film has a wall thickness of between 0.2 mm and 13 mm. This embodiment of the invention likewise makes it possible to utilize conventional films that have been able to be tested with many composite materials and of which the deep-drawing properties and surface properties are sufficiently well known and have been adequately researched.
According to another advantageous embodiment of the invention, the cured particle-foam mass has a wall thickness of between 1 cm and 30 cm. Depending on the required strengths of the manufactured component, the wall thickness of the cured particle-foam mass is calculated and configured. Despite the comparatively large wall thicknesses, the final manufactured component can have only a very low weight.
According to another advantageous embodiment of the invention, the component is a vehicle part for a truck, or for a commercial vehicle, or for a trailer, and is, for example, an interior fitting, or a cargo-space cover, or a trim part, or a hood, or a roof element, or a roof segment, or a vehicle wall, or a vehicle wall element.
According to another advantageous embodiment of the invention, the granular starting material comprises expandable EPS, expandable EPP or expandable PEEK. These are all materials that can be expanded, i.e. are expandable, and that, according to the invention, are suitable for first being only partially expanded or expanded in order to subsequently undergo a step of final expanding or final expansion in a mold.
According to another advantageous embodiment of the invention, the method comprises step xiii) that is carried out before step vi):
xiii) positioning reinforcing elements, in particular in the manner of tie rods, for example in the manner of tapes, in the lower mold part, the partially expanded particles enveloping the reinforcing elements after the particles have been placed into the lower mold part.
According to this advantageous embodiment of the invention, the completely expanded, expanded particle-foam mass is reinforced or rigidified by reinforcing elements. These elements are in particular designed such that they can transmit or absorb tensile forces in a direction transverse to the thin extension of the component. This means that the rigidity of the component can be increased. The invention also covers the case in which the reinforcing elements extend in the extension direction of the thin component. In this case, thin fabrics such as mats, laid webs, knitted fabrics, etc. made of reinforcement fibers, for example of glass fibers, carbon fibers, aramid fibers, basalt fibers or other suitable reinforcement fibers can also be laid into the lower mold part before the cavity is filled with partially expanded particles.
According to another aspect, the invention relates to a thin component according to claim 17.
The problem addressed by the invention is to provide a component that has high strength and a high load-bearing capacity while only having a low weight and that can be manufactured cost-effectively.
The invention solves this problem by means of the features of claim 17.
In order to avoid repetition with regard to the explanation of the features of claim 17 and in order to explain the invention according to claim 11, reference is made to the preceding comments on claims 1 to 16 in an analogous manner.
Other advantages of the invention become apparent from the dependent claims that have not been cited, as well as with reference to the following description of the embodiments shown in the drawings, in which:
Embodiments of the invention are described by way of example in the following description of the figures, also with reference to the drawings. Here, for the sake of clarity, even if different embodiments are involved, identical or comparable parts or elements have been denoted by identical reference signs, sometimes with the addition of lower case letters.
Features that are only described, set out or disclosed in relation to one embodiment can also be provided in any other embodiment of the invention within the scope of the invention. Even if they are not shown in the drawings, such amended embodiments are covered by the invention.
All the features disclosed are essential to the invention per se. The content of the disclosure of the associated priority documents (copy of the previous application) and the cited documents and the prior art devices described are hereby incorporated into the disclosure of the application in their entirety, also for the purpose of incorporating individual features or a plurality of features of the subjects disclosed therein into one or more claims of the present application. Even if they are not shown in the drawings, such amended embodiments are also covered by the invention.
In the following, proceeding from
According to
According to
For this purpose, a heater 14, in particular an infrared heater 14, is provided, which introduces a predetermined radiant power into the oven 13 using infrared rays 15 (indicated), in order to reach a certain temperature or a certain temperature range. The granulate particles 30a, 30b, 30c are subjected to the effects of the temperature in the oven 13 for a predetermined time and partially foam. It can be seen that the individual particles 30a, 30b, 30c in
The partially expanded particles 31a, 31b, 31c are still loose, in particular not joined to one another. During the process of partially expanding according to
The production of the substrate 21 shall first be explained with reference to
According to
Owing to the mold being closed, the film 20 is deep-drawn from the flat state. The deep-drawing process can impart any spatial contour to the film. The deep-drawing process can be assisted by temperature in a conventional manner, and this is not shown in the drawings. For the deep-drawing process, as an alternative to the embossing/molding process used in the mold 17 in
After opening the mold 17 from the state in
The invention also covers the case in which the film 21 remains in the lower mold part 19 after the deep-drawing process, and only the upper mold part is changed. In the following, it is assumed that, proceeding from
According to
Here, a delivery or output device (not shown in the drawings) may be provided that evenly distributes the particles along the cavity 22 in the manner of a feed head.
The mold 17b is then closed. For this purpose, an upper mold part 24 is moved into a closed state, starting from a state according to
In particular, it is provided that the mold is temperature-controlled to a mold temperature that is above the VICAT softening temperature, in order to make it possible to carry out the baking step. After an intended period of action of the temperature, it is provided that the mold temperature is reduced to a temperature below the VICAT softening temperature in order to initiate the curing process.
Owing to the action of the temperature, the partially expanded particles 31a, 31b, 31c are completely expanded. A honeycomb structure can be seen in
Here, instead of the frame structure in
It should be noted that the expression “completely expanded particles 32a, 32b, 32c” is misleading:
In fact, the large number of completely expanded particles 32a, 32b, 32c overall forms a completely expanded particle-foam mass 33 or a completely expanded particle foam. According to
Owing to the process of complete expanding, with the mold closed, the particle foam becomes permanently and firmly joined to the inner face 35 of the deep-drawn film 21. As a result, a light, rigid and load-bearing composite component that can nevertheless be made cost-effectively is provided.
According to
The embodiment in
The invention also covers components in which, instead of a deep-drawn film 21 made of ABS or PMMA, a thin film made of polyethylene or polypropylene, or in particular also so-called slush skins, is used as the substrate 21, while ensuring that the deep-drawn film has a VICAT softening temperature in any case or, for a metal film, a melting point that is higher than the temperature applied in the step of applying the coating layer or the step of drying the coating layer that are to be carried out according to the invention.
The invention also in particular covers components that are designed as caravan wall elements. For example, wall portions of a caravan trailer or a caravan, or complete wall elements of a caravan, can be used in vehicle construction, with the use of the method according to the invention.
The invention also covers further embodiments that provide that reinforcing elements are deposited in the cavity 22 before the cavity 22 is filled with partially expanded particles 31a, 31b, 31c.
The reinforcing elements (not shown in the drawings) may e.g. comprise reinforcing fibers. Owing to the cavity 22 being filled with partially expanded particles 31a, 31b, 31c, the particles are evenly distributed and envelop the reinforcing elements on multiple sides, preferably on all sides. The completed component 10 comprises a cured particle-foam mass that securely surrounds the reinforcing elements.
By positioning the reinforcing elements, tensile forces in particular can thus be transmitted or absorbed.
After cutting off the excess regions 34a, 34b or, in alternative variants of the invention, also before cutting off the excess regions 34a, 34b, the component 10 in
According to
According to
It should be noted that, when introducing the component 10, the immersion coating can have a high temperature of between 150° C. and 220° C., for example. Owing to the fact that, according to the invention, a starting material of an expandable particle foam has been selected that has a VICAT softening temperature of greater than 160° C., and that advantageously has an even higher VICAT softening temperature, this step of immersion coating can be carried out in the first place for the purpose of applying a coating layer 39.
In order to dry the coating layer 39, the component 10 is then transported to a drying device 40. Said device may comprise one or more drying units 40a, 40b that ensure that a high temperature is applied to the component 10. The following applies here: the higher the temperature, the shorter the required dwell time of the component in the drying device 40 and the shorter the drying time.
It should be noted that, according to the invention, the component having the applied coating layer is exposed to a temperature that is in particular higher than 150° C. for the purpose of drying the coating layer. It is also noted that, according to a variant of the invention, the component 10 is exposed to a temperature that is below the VICAT softening temperature of the particle foam for the purpose of drying the coating layer 39.
The arrow 41 in
According to the embodiment in
If, proceeding from the view according to
Such a component can, as shown in
According to
The embodiments in
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019109820.3 | Apr 2019 | DE | national |
