DE202020106955U1 - Device for the production of molded parts - Google Patents

Abstract

Hot pressing device (100) for the production of molded parts (150), each of which has a pre-pressed profile body blank (151) which is provided with a surface protection film (152) on at least part of its surface, the blank (151) being cold-pressed by a mixture is made of fibers and thermosetting binders, and wherein the surface protection film (152) is made of a carrier layer impregnated with thermosetting resin, the hot pressing device (100) having an upper tool part (110) and a lower tool part (120) as well as a controlled drive to Closing the hot pressing device (100), lowering the upper tool part (110) onto the upper tool part (110), the profile body blank (151) being placed in the lower tool part (120) and the surface protection film (152) being placed on the profile body blank (151) in order to join both in a hot pressing process (14), the surface protection film (152) in front the hot pressing process has a final moisture content of 2-20% by weight, characterized in that the controllable drive does not immediately lower the upper tool part (110) onto the lower tool part (120) to close the hot pressing device (100), but rather the upper tool part (110) initially for a dwell time of 1-5 seconds in a partially lowered position at a distance (D1, D2) from a profile body blank (151) located in the upper tool part (110) and a surface protection film (152) located thereon, in order to avoid heat radiation from the upper tool part (110) preheat the protective surface film (152) prior to closing the hot press device (100).

Description

The invention relates to a device for the production of molded parts, in particular molded parts, which have a pre-pressed profile body blank which consists of a mixture of fibers and thermosetting binders and is provided with a surface protection film at least on parts of its surface.

Molded parts of the type mentioned are produced in a multi-stage process and devices designed for this purpose, the blank being produced by cold pressing a mixture of fibers and thermosetting binders, and the surface protection film being produced from a carrier layer impregnated with thermosetting resin. In a hot pressing process, the blank is then connected to the surface protection film and brought into the final shape corresponding to the desired molded part. For this purpose, the profile body blank is placed in a tool lower part of a hot pressing device and the surface protection film is placed on the profile body blank, which has a final moisture content of 2-20% by weight before the hot pressing process.

The known methods and devices are disclosed, for example, in the following documents: EP 0 763 387 B1 , DE 42 10 528 A1 and EP 0 156 926 A1 .

Through intensive use of these methods, the applicant has developed advantageous further developments with regard to the method and device, which also include the present invention.

The hot pressing device according to the invention essentially has the upper tool part and the lower tool part as well as a controlled drive in order to lower the upper tool part onto the upper tool part in order to close the hot pressing device and is characterized in that the controllable drive does not immediately lower the upper tool part onto the lower tool part to close the hot pressing device , but first of all holds the upper tool part for a dwell time of 1-5 seconds in a partially lowered position at a distance from a profile body blank located in the upper tool part and a surface protection film on it, in order to preheat the surface protection film by radiating heat from the upper tool part before closing the hot pressing device.

Advantages of the invention: The preheating of the surface protection film leads to an increase in the elasticity of the film, since the reactivity of the resin is stimulated without it condensing out beforehand. The surface protection film adapts itself optimally to the contour of the profile body blank. This prevents the film from tearing or breaking at the steep edges of the blank.

• So wird vorzugsweise in der teilabgesenkten Position das Werkzeugoberteil mit einem Mindestabstand von 2 mm zu der auf dem Profilkörper-Rohling befindlichen Oberflächenschutzfolie gehalten und wird mit einem Maximalabstand von 50 mm zu der auf dem Profilkörper-Rohling befindlichen Oberflächenschutzfolie gehalten. Das Werkzeugoberteil wird von dem steuerbaren Antrieb der Heißpressvorrichtung entsprechend bewegt und gehalten. Versuche der Anmelderin haben ergeben, dass die im wesentlich durch Wärmestrahlung erreichte Vorwärmung der Oberflächenschutzfolie besonders gut gelingt, wenn das Werkzeugoberteil sich dazu in einem Abstand von 2-50 mm befindet.

Particularly advantageous, preferred embodiments result from the subclaims:

• In the partially lowered position, the upper part of the tool is preferably held at a minimum distance of 2 mm from the surface protection film on the profile body blank and is held at a maximum distance of 50 mm from the surface protection film on the profile body blank. The upper part of the tool is moved and held accordingly by the controllable drive of the hot pressing device. Tests by the applicant have shown that the preheating of the surface protection film, which is essentially achieved by thermal radiation, works particularly well when the upper part of the tool is located at a distance of 2-50 mm.

The upper tool part is preferably lowered hydraulically by means of a presettable pressure build-up in order to ultimately build up a predeterminable pressure between 220-330 bar against the profile body blank located in the lower tool part and the surface protective film on it, the dwell time being set inversely proportional to the pressure build-up becomes. With a rapid pressure build-up (high gradient) the dwell time is set shorter and vice versa. The pressure build-up takes place in a hydraulic system of the controllable drive of the hot-pressing device and is controlled accordingly, whereby it has been shown that the pressure build-up should preferably be achieved within 2-10 seconds.

As for the operating temperature of the hot press device, the operating temperature of the tool top is preferably set to an upper temperature between 130-180 ° C; and the operating temperature of the lower tool part is preferably set to a lower temperature between 120-180 ° C. The tool is heated by a controllable heating device of the hot-pressing device, it being crucial that the operating temperature of the upper tool part is always higher than that of the upper tool part. A difference of at least 10 ° C is preferably maintained between the upper and lower temperature, in most applications in the range of 20-25 ° C.

In many applications, a layer of resin-impregnated paper is first placed at the bottom of the lower part of the tool, and the profile body blank is then placed on top. In addition, a crepe layer made of resin-soaked cellulose material is placed on the profile body blank and then the surface protection film is placed on top. In this way, a sandwich structure is achieved that is mechanically particularly stable, with the layer of resin-impregnated paper (located at the bottom) acting as a mechanically acting counterbalance to the (upper) crepe layer.

• 1 zeigt eine erfindungsgemäße Vorrichtung zum Heißpressen und Beschichten eines Profilkörper-Rohlings mit einer Oberflächenschutzfolie, wobei die Vorrichtung (Heißpresse) sich im geöffneten Zustand befindet;
• 2 zeigt die Vorrichtung (Heißpresse) in einem Zustand, bei das Werkzeugoberteil zum Schließen der Heißpresse auf das Werkzeugunterteil abgesenkt wird, wobei das Werkzeugoberteil für eine Verweildauer in einer teilabgesenkten Position verbleibt; und
• 3 zeigt im Querschnitt den Aufbau des fertigen Formteils.

The invention is illustrated by means of the accompanying schematic drawings, which show:

• 1 shows a device according to the invention for hot pressing and coating a profile body blank with a surface protection film, the device (hot press) being in the open state;
• 2 shows the device (hot press) in a state in which the upper tool part is lowered onto the lower tool part to close the hot press, the upper tool part remaining in a partially lowered position for a dwell time; and
• 3 shows in cross section the structure of the finished molded part.

The invention will now be described in detail on the basis of exemplary embodiments with reference to these drawings.

• - Erste Schrittfolge: Zuerst wird ein Profilkörper-Rohling vorgepresst, der als Kern (s. 151 in den 1-3) dient und auch als Vorpressling bezeichnet wird. Das Vorpressen erfolgt z.B. durch Kaltpressen eines Gemisches von Faserstoffen und wärmehärtenden Bindemitteln und ist an sich bekannt. Dazu hat die Anmelderin ein seit Jahren bewährtes Verfahren entwickelt und fortlaufend verbessert. Der Vorpressling bzw. Rohling wird einstückig aus einer mit span- oder faserförmigen und mit Bindemittel versetzten Pressmasse hergestellt. Bei der Pressmasse kann es sich beispielsweise um zerkleinerte lignozellulosehaltige Teilchen, wie etwa zerkleinerte und getrocknete Holzspänne, Bagassefasern und ähnliches, handeln, denen ein wärmehärtbares Kunstharz, wie z.B. ein Melamin-Harnstoffformaldehyd- oder Phenolformaldehyd-Harz beigemischt ist. Als Fasern können auch Fasergemische von verschiedenen Werkstoffen verwendet werden, denen entsprechende, vorzugsweise organische, Bindemittel zugemischt sind. Zum Herstellen des Rohlings 151 wird das Gemisch in ein Vorpresswerkzeug (nicht dargestellt) mit einer Schichtdicke eingefüllt, die etwa das drei- bis siebenfache des fertigen Formkörpers betragen kann. Durch Einfahren eines Pressstempels wird die Masse vorgepresst und dabei nahezu auf ihr Endmaß hin verdichtet. Der derart hergestellte Vorpressling bzw. Rohling 151 wird dann später mittels Heißpressen (mit einer Oberflächenschutzschicht versehen und unter Druck und Temperatureinwirkung ausgehärtet. Die Oberflächenschutzschicht kann auch Dekorzwecken dienen und besteht aus einer Oberflächenschutzfolie (siehe 152 in 1-3), die aus einer mit duroplastischem Tränkharz getränkten Trägerschicht hergestellt wird. Die Trägerschicht besteht z.B. aus einem mit Harz getränktem Papier.
• - Zweite Schrittfolge: Dieser Teil der Herstellung ist ebenfalls an sich bekannt und wird von der Anmelderin seit Jahren angewendet. In einer (hier nicht dargestellten) Anlage wird die ggf. mit einer zum Lack reaktiven Komponente versehene Trägerfolie mit einem Lack versehen. Dazu wird die Trägerfolie in einer Durchlauf-Gießanlage gleichmäßig mit dem Lack beschichtet. Wie gesagt, kann bei der Trägerfolie es sich beispielsweise um eine mit Melaminharz getränkte Papierfolie handeln. Sie kann auch mit einem Haftvermittler zur Verbesserung der Haftung der Lackschicht, beispielsweise einem Acrylat, versehen sein. In der Anlage wird die mit dem Lack beschichtete Trägerfolie in einem Trockner getrocknet, wobei zu beachten ist: Wenn es sich bei dem Lack um einen durch Wärmezufuhr trocknenden Lack handelt, dann soll beim Trocknen nur so viel Wärme zugeführt werden, dass kein vollständiges Auskondensieren der Trägerfolie erfolgt. Beim Lack kann es sich in diesem Fall z.B. um einen Polyurethanlack handeln. Es können aber auch mittels UV-Licht aushärtende oder elektronenstrahlhärtende Lacke verwendet werden. Um eine besonders widerstandsfähige Oberflächenschutzfolie 152 mit hoher Witterungsbeständigkeit herzustellen, wird vorzugsweise als Tränkharz ein wässriges Kondensationsharz verwendet, welches bei der Beschichtung etwa 50 Gew.% an flüchtigen Bestandteilen enthält, wobei die getränkte Folie vor dem Lackiervorgang noch 8 - 20 Gew.% an flüchtigen Bestandteilen enthält. Als Lack wird vorzugsweise ein wässriges System aus einem OH-Gruppen enthaltenden Acrylpolymerisat, Polyurethanpolymerisat oder Polyestercopolymerisat verwendet, welchem eine Vernetzungskomponente zugesetzt wurde, die einerseits das Lackbindemittel vernetzt und andererseits eine chemische Verbindung mit dem Tränkharz der Trägerfolie vermittelt. Die Folie wird vor dem Aufbringen auf den Profilkörper, also vor dem Heißpressvorgang (vierte Schrittfolge), auf eine Endfeuchte von 2 - 20 Gew. %, vorzugsweise 4 - 10 Gew. %, getrocknet.
• - Die dritte und vierte Schrittfolgen betreffen den wesentlichen Teil der mit Hilfe der erfindungsgemäßen Vorrichtung durchgeführten Herstellungsprozesses und beziehen sich auf das Heißpressen des Formteils 150 mit der damit einhergehenden Beschichtung, die durch die erfindungsgemäße Vorrichtung 100 (s. 1-3) ausgeführt wird:

The production of molded parts comprises the following sequence of steps, the third and fourth sequence of steps being carried out with the aid of the hot pressing device:

• - First step sequence: First a profile body blank is pre-pressed, which is used as the core (see 151 in the 1-3 ) and is also referred to as a pre-press. The pre-pressing takes place, for example, by cold pressing a mixture of fiber materials and thermosetting binders and is known per se. To this end, the applicant has developed and continuously improved a method that has been tried and tested for years. The pre-pressed part or blank is produced in one piece from a molding compound mixed with chip-shaped or fibrous material and mixed with binding agent. The molding compound can be, for example, crushed lignocellulose-containing particles, such as crushed and dried wood chips, bagasse fibers and the like, to which a thermosetting synthetic resin, such as a melamine-urea-formaldehyde or phenol-formaldehyde resin, is mixed. Fiber mixtures of different materials can also be used as fibers, to which appropriate, preferably organic, binders are mixed. For making the blank 151 the mixture is poured into a pre-pressing tool (not shown) with a layer thickness that can be about three to seven times that of the finished molding. By moving in a ram, the mass is pre-pressed and compressed to almost its final size. The pre-pressed part or blank produced in this way 151 is then later provided with a surface protection layer by means of hot pressing (and cured under the action of pressure and temperature. The surface protection layer can also be used for decorative purposes and consists of a surface protection film (see 152 in 1-3 ), which is made from a carrier layer impregnated with thermosetting resin. The carrier layer consists, for example, of paper impregnated with resin.
• Second sequence of steps: This part of the production is also known per se and has been used by the applicant for years. In a system (not shown here), the carrier film, which may have been provided with a component reactive to the paint, is provided with a paint. To do this, the carrier film is evenly coated with the paint in a continuous casting system. As mentioned, the carrier film can be, for example, a paper film impregnated with melamine resin. It can also be provided with an adhesion promoter to improve the adhesion of the lacquer layer, for example an acrylate. In the system, the carrier film coated with the lacquer is dried in a dryer, whereby it should be noted: If the lacquer is a lacquer that dries through the supply of heat, then only enough heat should be supplied during drying that the Carrier film takes place. In this case, the lacquer can be, for example, a polyurethane lacquer. However, lacquers which harden by means of UV light or which harden by means of electron beams can also be used. To a particularly resistant surface protection film 152 With high weather resistance, an aqueous condensation resin is preferably used as the impregnating resin, which contains about 50% by weight of volatile constituents during the coating, with the impregnated film still containing 8-20% by weight of volatile constituents before the painting process. The lacquer used is preferably an aqueous system made from an acrylic polymer, polyurethane polymer or polyester copolymer containing OH groups, to which a crosslinking component has been added which, on the one hand, crosslinks the lacquer binder and, on the other hand, provides a chemical bond with the impregnating resin of the carrier film. Before it is applied to the profile body, i.e. before the hot pressing process (fourth step sequence), the film is brought to its final moisture content from 2 to 20% by weight, preferably 4 to 10% by weight, dried.
• The third and fourth sequences of steps relate to the essential part of the manufacturing process carried out with the aid of the device according to the invention and relate to the hot pressing of the molded part 150 with the associated coating produced by the device according to the invention 100 (see 1-3 ) is performed:

In the third step, the profile body blank 151 in or on the lower part of the tool 120 the device 100 placed; about the blank 151 then becomes the surface protection film 152 placed, in the subsequent hot pressing process with the press closed under pressure (220-330 bar) and heat (approx. 130-180 ° C) together with the blank 151 into the final shape to the desired coated molded part 150 to be shaped and cured.

• Im Teilschritt a) wird das Werkzeugoberteil 110 nicht ganz abgesenkt, so dass es mit dem Werkzeugunterteil 120 zusammen kommt und die Presse schließt. Vielmehr wird das Absenken des Werkzeugsoberteils 110 durch den steuerbaren Antrieb (nicht dargestellt) zeitweise gestoppt, so dass das Werkzeugsoberteil 110 in einer teilabgesenkten Position für eine vorgebbare Zeitdauer von ca. 1-5 Sekunden, vorzugsweise etwa 3 Sekunden, verweilt. Diese Situation kann man als Haltezustand bezeichnen und wird in der 2 dargestellt:
  • Das Werkzeugoberteil 110 verweilt in einer zur Oberflächenschutzfolie 152 beabstandeten Position, so dass ein Mindestabstand D1 von 2 mm eingehalten wird. Mit D2 wird hier ein Maximalabstand bezeichnet, der sich aufgrund des Profils des Rohlings bzw. des Werkzeugoberteils 110 ergibt; er sollte kleiner als 50 mm sein. Wichtig ist, dass sich Werkzeugoberteil 110 und aufgelegte Folie 152 sich im Haltezustand nicht berühren, dass aber die Abstände D1 und D2 auch nicht zu groß sind, damit durch Wärmeabstrahlung des Werkzeugoberteil 110 die Oberflächenschutzfolie 152 vor dem Schließen der Heißpressvorrichtung 100 vorgewärmt werden kann.

In the fourth step sequence, the hot pressing takes place essentially in two sub-steps a) and b):

• In sub-step a) the upper part of the tool is 110 not completely lowered so that it is with the tool base 120 comes together and the press closes. Rather, it is the lowering of the upper part of the tool 110 temporarily stopped by the controllable drive (not shown), so that the upper part of the tool 110 remains in a partially lowered position for a predefinable period of time of approx. 1-5 seconds, preferably approx. 3 seconds. This situation can be called a hold state and is used in the 2 shown:
  • The upper part of the tool 110 lingers in a surface protection film 152 spaced position so that a minimum distance D1 of 2 mm is observed. With D2 a maximum distance is referred to here, which is due to the profile of the blank or the upper part of the tool 110 results; it should be smaller than 50 mm. It is important that the upper part of the tool 110 and applied foil 152 do not touch each other when stopped, but the distances D1 and D2 are also not too big, so that they are caused by heat radiation from the upper part of the tool 110 the surface protection film 152 before closing the hot press device 100 can be preheated.

In sub-step b), the upper part of the tool is only activated after the predetermined period of 1-5 seconds has elapsed 110 completely lowered so that the hot press closes. Only now is the actual hot pressing into the desired molded part. This is where the blank or pre-pressed part 151 Under the influence of pressure and heat (here for example 150-170 ° C) brought into its final shape, cured and at the same time with the surface protection film 152 connected to be enveloped. Both sides of the blank can also be provided with a film, for example the top with a decorative film and the bottom with a neutral protective film; each film can, for example, have a thickness of approximately 0.1 to 2 mm. The blank can be pre-pressed for a wide variety of molded parts, such as window sills, balcony cladding or table tops, which for example have a plate thickness of about 16 mm (6-25 mm) in the middle and a thickness of about 30 mm (10-40 mm) on the edge can have. The molded parts produced in this way (see Example 150 in 3 ) are particularly well suited to be set up or built in outdoors, ie on balconies, terraces, squares and in gardens, as they have proven to be very weather-resistant. Because in the process presented here and carried out by the device, the blank is hot-pressed at temperatures of around 150-170 ° C, whereby the similar resins in the core and surface material harden, so that a material composite is created that is particularly resistant to heat and moisture and mechanical stress. The film used does not harden completely until the hot pressing process, but is optimally preheated by preheating in sub-step a) shortly before the actual hot pressing and can better fit the profile of the blank, so that material stresses in the surface protective layer are even better avoided.

The operating temperature of the tool head 110 should be set to an upper temperature between 130-180 ° C and the operating temperature of the lower part of the tool 120 to a lower temperature between 120-180 ° C, with a difference of at least 10 ° C between the upper and lower temperature, preferably 20-25 ° C.

The molded part to be produced can also be constructed in a sandwich construction: for this in the lower part of the tool 120 first a layer of resin-soaked paper 154 (see 3 ) and then the profile body blank is inserted 151 inserted. There is also a layer of crepe 153 made of resin-soaked cellulose material on the profile body blank 151 then the surface protection film is placed on top 152 hung up. In the finished pressed state, the layer is made of resin-soaked paper 154 the underlay or the mechanically acting counter-tension to the crepe layer 153 , which represents the upper train. The dimensioning of the upper and lower beams / counter-members depends on the contour of the profile body and the required mechanical strength of the finished molded part and is primarily used to avoid material distortion.

List of reference symbols

100

Hot pressing device

110

Tool head

120

Tool base

150

Molding

151

Profile body blank

152

Surface protection film

153

Crepe layer made of resin-soaked cellulose material (cover)

154

Layer of resin-soaked paper (bottom or backing)

D1

Minimum distance between the upper part of the tool and the surface protection film

D2

Maximum distance between the upper part of the tool and the protective film

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 0763387 B1 [0003]
• DE 4210528 A1 [0003]
• EP 0156926 A1 [0003]

Claims (5)

Hot pressing device (100) for the production of molded parts (150), each of which has a pre-pressed profile body blank (151) which is provided with a surface protection film (152) on at least part of its surface, the blank (151) being cold-pressed by a mixture is made of fibers and thermosetting binders, and wherein the surface protection film (152) is made of a carrier layer impregnated with thermosetting resin, the hot pressing device (100) having an upper tool part (110) and a lower tool part (120) as well as a controlled drive to Closing the hot pressing device (100), lowering the upper tool part (110) onto the upper tool part (110), the profile body blank (151) being placed in the lower tool part (120) and the surface protection film (152) being placed on the profile body blank (151) in order to join the two in a hot pressing process (14), the surface protection film (152) in front the hot pressing process has a final moisture content of 2-20% by weight, characterized in that the controllable drive does not immediately lower the upper tool part (110) onto the lower tool part (120) to close the hot pressing device (100), but rather the upper tool part (110) initially for a dwell time of 1-5 seconds in a partially lowered position at a distance (D1, D2) from a profile body blank (151) located in the upper tool part (110) and a surface protection film (152) located thereon, in order to avoid heat radiation from the upper tool part (110) preheat the protective surface film (152) prior to closing the hot press device (100). Hot pressing device (100) Claim 1 , characterized in that the controllable drive holds the upper tool part (110) in the partially lowered position so that the upper tool part (110) is at a minimum distance (D1) of 2 mm from the surface protection film (152) and on the profile body blank (151) is at a maximum distance (D2) of 50 mm from the surface protection film (152) on the profile body blank (151). Hot pressing device (100) Claim 1 or 2 , characterized in that the controllable drive has a hydraulic system which lowers the upper tool part (110) by means of a presettable build-up of pressure in order to ultimately protect against the profile body blank (151) located in the lower tool part (120) and the surface protective film (152) located on it Build up a predeterminable pressure of 220-330 bar, with the controllable drive adjusting the dwell time in inverse proportion to the pressure build-up. Hot pressing device (100) Claim 3 , characterized in that the controllable drive controls the pressure build-up in the hydraulics so that the pressure build-up is achieved within 2-10 seconds. Hot pressing device (100) according to one of the preceding claims, characterized in that the hot pressing device (100) has at least one controllable heating device which sets the operating temperature of the upper tool part (110) to an upper temperature between 130-180 ° C and the operating temperature of the lower tool part ( 120) is set to a lower temperature between 120-180 ° C, with a difference of at least 10 ° C between the upper and lower temperature, preferably 20-25 ° C.

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