DE102020204871A1 - Process for the production of a sandwich component - Google Patents

Abstract

The invention relates to a method for producing a sandwich component (1) from a particle foam molded body (5) and at least one cover layer (3), in which method the cover layer (3) as an insert part in a tool cavity (15) of a foaming tool ( 17) is inserted, in a filling step thermoplastic particles (25) are injected into the mold cavity (15), and in a foaming step the particles (25) are foamed under pressure and heat to form the particle foam molding (5), wherein the particle foam molded body (5) is materially bonded to the cover layer (3) during the foaming step. According to the invention, the material of the cover layer (3) and the material of the thermoplastic particles (25) are made of the same polymer type, in particular PET, for increased bonding strength between the particle foam molded body (5) and the cover layer (3).

Description

The invention relates to a method for producing a sandwich component according to the preamble of claim 1, a sandwich component according to claim 9 and a process arrangement for carrying out the method according to claim 10.

Particle foam components offer a wide potential for use in automobile construction, for example in mobile home construction, with regard to lightweight construction as well as heat and sound insulation. In order to achieve increased strength and surface quality, the particle foam components can be integrated in a sandwich construction.

In common practice, a molded particle foam body made of expanded polystyrene (EPS), for example, is industrially produced in essentially two process steps: In the first process step (pre-foaming), a microgranulate loaded with blowing agent is first pre-foamed into foam beads. In the second process step (foaming), the foam beads are then poured into the mold cavity of a foaming tool and then foamed under pressure and heat to form the molded particle foam body. The heat energy input required for pre-foaming and foaming takes place in common practice by means of steam. During prefoaming, the water vapor causes the thermoplastic matrix of the microgranulate to soften and the blowing agents dissolved in it to pass into the gas phase, so that a foam structure (i.e. the foam beads) is formed. In the foaming step, the water vapor is fed into the mold cavity between the foam beads, which foam up and sinter together.

Such a molded particle foam body can be part of a sandwich component in which the molded particle foam body is covered with at least one cover layer. In a generic method for producing such a sandwich component, the cover layer is first placed as an insert part in the tool cavity of the foaming tool. In the subsequent filling step, the mold cavity is filled with the thermoplastic particles. This is followed by a back-foaming step in which the particles back-foam the insert part under pressure and heat.

When using water vapor for the input of thermal energy in the back-foaming step, it is necessary that the cover layer is vapor-permeable. Such a vapor-permeable cover layer is, however, a disadvantage especially in the case of complex component geometries of the sandwich component. In addition, adhesion problems between the outer layers and the core material can occur in the sandwich component produced in the foaming process.

From the DE 100 36 185 A1 a method for producing a composite material from a particle foam made of thermoplastic material and at least one layer connected to it is known. From the WO 03/033259 A1 a single-origin composite material made of plastic is known that consists of a core made of thermoplastic foam and at least one reinforcement layer made of a fiber composite.

The object of the invention is to provide a method for producing a sandwich component which, compared to the prior art, provides an increased connection strength between the cover layer and the particle foam molded body.

The object is achieved by the features of claim 1, claim 9 or claim 10. Preferred developments of the invention are disclosed in the subclaims.

The invention is based on the fact that an increased connection strength in the prior art is usually achieved by an additional joining process (gluing) in which the at least one cover layer is glued to the core material (i.e. the particle foam molding). In current practice, in the prior art no pure material is used for both the cover layer and the core material, but rather the cover layers are reinforced by means of carbon or glass fibers in order to achieve better material properties.

Against this background, according to the characterizing part of claim 1, both the cover layer and the thermoplastic particles are produced from the same type of polymer, in particular from PET, for increased bonding strength between the particle foam molding and the cover layer. Thus, both the cover layer and that of the particle foam molded body are of identical material, as a result of which an increased adhesive strength is achieved between the cover layer and the particle foam molded body compared to conventional sandwich components.

The present invention is a PET sandwich structure with PET particle foam beads. This is produced in a steam-free tool. First, a self-reinforced PET fabric is inserted into the tool and pressed (consolidated) under pressure and temperature. After pressing, the mold cavity is filled with particles. The particles weld together through temperature and pressure and bond with the PET fabric.

An essential aspect of the invention relates to the steam-free production of pure PET sandwich structures, which consist of a preconsolidated PET fabric (cover layer) and PET particles (core material). The sandwich structures to be produced are produced in a single-variety and steam-free manner. They consist of a pre-consolidated PET fiber fabric (cover layers) and a PET core material. The PET fiber fabric is first pre-consolidated through a forming process (for example in a press machine). Here, the thermoplastic fiber fabric consists of two types of fibers from the same polymer type. One type of fiber acts as a reinforcement fiber (semi-crystalline HTPET fibers), the other type of fiber (LPET fibers) as a matrix. When the melting temperature of the matrix is reached, the pre-consolidation of the PET fiber fabric takes place. Then the PET foam particles (core material) are filled into the mold cavity and pressed together with the pre-consolidated PET fiber fabric to form a PET sandwich structure under temperature and pressure. The mold then cools down and the PET sandwich structure can be removed.

The core idea of the invention is therefore that core and outer layer materials of the same material (for example PET) should be selected for production of one type and for material recycling. PET is well suited for material recycling. Material recycling can often be found, for example, in vehicle interiors, where foams with textile decors are often used. Since both the fiber fabric and the foam particles are preferably made of PET, this results in a process-technically simple recycling option.

In general, the particle foam used according to the invention can be used in a variety of ways. In particular, the steam-free processing and the use of pure materials enable new sandwich structures. Examples of this are, for example, interior door panels, footwell panels, covers in the trunk or the like.

The invention can be used wherever lightweight construction issues play an important role, for example in aerospace engineering or in rail and ship traffic. The PET sandwich structures made of fiber fabric and foam particles can be integrated wherever sufficient material properties and surface qualities are required.

Relevant aspects of the invention are emphasized again in detail below: For example, the cover layer can preferably be made from a fiber-reinforced plastic. The starting point for the production of the cover layer can be a flat semi-finished fiber product, which consists of reinforcing fibers and matrix material fibers. With regard to purity of type, it is preferred if both the reinforcing fibers and the matrix material fibers of the semifinished fiber product are made from the same type of polymer, that is to say in particular PET. As particularly preferred with regard to increased strength of the cover layer, the reinforcing fibers can be partially crystalline HTPET fibers, while the matrix material fibers can be LPET fibers. The HTPET fibers are high-strength PET fibers (high temperature resistant). In contrast, the LPET fibers are made of an amorphous thermoplastic polyester that, compared to the HTPET fibers, melts at low temperatures.

The semi-finished fiber product can be pressed and heated in a hot pressing step under pressure and heat. This results in a pre-consolidation in which the matrix material fibers are melted to form a matrix in which the reinforcing fibers are embedded. The pre-consolidated semifinished fiber product can be inserted into the mold cavity of the foaming tool as an insert part before the foaming step is carried out. The semifinished fiber product can preferably already be preformed to near net shape in the hot-pressing step.

In a preferred process management, both the hot pressing step and the foaming step can take place in the foaming tool. The foaming tool can, for example, have two tool halves which delimit the tool cavity and which can be heated by means of a temperature control system in order to ensure an input of heat energy into the tool cavity in the hot-pressing step and in the foaming step. In terms of process technology, it is simple if the tool halves of the foaming tool have fluid channels through which a heating medium can flow. The fluid channels can be part of the temperature control system in order to enable variothermal temperature control in the foaming step.

To carry out the hot pressing step, the as yet untreated semi-finished fiber product can be inserted into the mold cavity of the foaming tool. The semi-finished fiber product is then pre-consolidated between the two mold halves under pressure and heat.

In the method according to the invention, it must be ensured that the cover layer formed from polymer material is impermeable to vapor. With regard to an operationally reliable process management, it is therefore preferred if the thermal energy input into the particles required in the foaming step takes place in the absence of vapor or water vapor, but rather takes place via the heated mold halves.

An exemplary embodiment of the invention is described below with reference to the accompanying figures.

• 1 in einer vergrößerten Teilschnittansicht den Materialaufbau eines fertiggestellten Sandwichbauteils;
• 2 eine skizzenhafte Darstellung der Prozessschritte zur Herstellung des Sandwichbauteils;
• 3 und 4 jeweils grob schematisch eine Anlageskizze einer Prozessanordnung in unterschiedlichen Betriebszuständen.

Show it:

• 1 in an enlarged partial sectional view the material structure of a finished sandwich component;
• 2 a sketchy representation of the process steps for the production of the sandwich component;
• 3 and 4th each roughly schematically a system sketch of a process arrangement in different operating states.

In the 1 is the material structure of a finished sandwich component 1 shown in detail. Accordingly, the sandwich component 1 two top layers 3 and an intermediate particle foam molded body 5 on. Each of the two top layers 3 is made as a fiber composite plastic with reinforcing fibers 7th that are in a matrix 9 are embedded.

In the following, the 2 until 4th the process steps for manufacturing the in the 1 sandwich component shown 1 described.

In the 2 become the two top layers 3 (in the 2 and 3 only one of the cover layers is shown) initially independent of the particle foam molding 5 manufactured. The starting point for the production of the outer layers is a flat semi-finished fiber product 11 made from the reinforcing fibers 7th and from matrix material fibers 13th consists. The reinforcing fibers 7th are semi-crystalline HTPET fibers, while the matrix material fibers 13th LPET fibers are.

The flat semi-finished fiber product 11 is pressed and heated in a hot pressing step under pressure and heat. In this way there is a pre-consolidation in which the matrix material fibers 13th to the matrix 9 melt, in which the reinforcing fibers 7th are embedded.

The semi-finished fiber products pre-consolidated in this way 11 are placed as insert parts in a mold cavity 15th ( 4th ) of a foaming tool 17th inserted, that of two tool halves 19th , 21 is limited. The frothing tool 17th is part of a process arrangement that is included in the 3 or 4th a particle reservoir 23 has, in the thermoplastic particles 25th be kept as foam beads. The foam beads are prefoamed in a prefoaming process step (not shown) from microgranules loaded with propellant. To the particle reservoir 23 is a suction line 27 connected that to an injector 29 leads. Its injector line 31 opens into the mold cavity 15th . The process arrangement also has a temperature control system 33 with fluid channels that connect the two mold halves 19th , 21 enforce and through which a heating medium can flow. In the hot press step described later and in the foaming step, the temperature control system 28 regulates the flow of heating medium through the fluid channels of the two mold halves 19th , 21 , which means that the foaming step in particular can be temperature-controlled variothermically.

An essential aspect of the invention is that both the two cover layers 3 as well as the thermoplastic particles 25th are made of the same type of polymer, namely PET. In this way, during the foaming step, there is an increased bond strength between the particle foam molded body and the two cover layers 3 .

As from the 3 is shown, the hot pressing step takes place directly in the mold cavity 15th of the foaming tool 17th . For this purpose, the two as yet untreated semi-finished fiber products are used 11 each individually in the mold cavity 15th of the frothing tool 17th inserted. Then the respective semi-finished fiber product 11 under pressure and heat in the foaming tool 17th pre-consolidated.

Based on 4th the foaming step is explained: According to this, the suction line is used 27 a particle-air flow from the particle reservoir 23 sucked in. The particle-air flow is generated by the injector in an injection step 29 into the mold cavity 15th injected. The along with the particles 25th into the mold cavity 15th Inflowing air can escape from the tool cavity via immersion edges (not shown) or ventilation holes 15th escape. Then the particles 25th in the mold cavity 15th melted under pressure and heat

List of reference symbols

1

Sandwich component

3

Top layers

5

Particle foam moldings

7th

Reinforcement fibers

9

matrix

11

Semi-finished fiber products

13th

Matrix material fibers

15th

Mold cavity

17th

Foaming tool

19, 21

Tool halves

23

Particle Reservoir

25th

thermoplastic particles

27

Suction line

29

Injector

31

Injector line

33

Temperature control system

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

• DE 10036185 A1 [0006]
• WO 03/033259 A1 [0006]

Claims (10)

Method for producing a sandwich component (1) from a particle foam molded body (5) and at least one cover layer (3), in which method the cover layer (3) is placed as an insert part in a tool cavity (15) of a foaming tool (17) , in a filling step thermoplastic particles (25) are injected into the tool cavity (15), and in a foaming step the particles (25) are foamed under pressure and heat to form the particle foam molded body (5), the particle foam Shaped body (5) is firmly bonded to the cover layer (3) during the foaming step, characterized in that the material of the cover layer (3) and the material for increased bonding strength between the particle foam shaped body (5) and the cover layer (3) of the thermoplastic particles (25) are made of the same polymer type, in particular PET. Procedure according to Claim 1 , characterized in that the cover layer (3) is produced from a flat semi-finished fiber product (11) which consists of reinforcing fibers (7) and matrix material fibers (13), and that in particular the reinforcing fibers (7) and the matrix material fibers ( 13) are made from the same type of polymer, especially PET. Procedure according to Claim 2 , characterized in that the reinforcing fibers (7) are partially crystalline HTPET fibers, and that the matrix material fibers (13) are LPET fibers. Procedure according to Claim 2 or 3 , characterized in that the semi-finished fiber product (11) is pressed and heated in a hot pressing step under pressure and heat, whereby a preconsolidation takes place in which the matrix material fibers (13) melt into a matrix (9) in which the reinforcing fibers (7) are embedded. Procedure according to Claim 4 , characterized in that the pre-consolidated semi-finished fiber product (11) is inserted as an insert part in the tool cavity (15) of the foaming tool (17) before the foaming step is carried out. Procedure according to Claim 4 or 5 , characterized in that the hot-pressing step and the foaming step take place in the foaming tool (17), and that in particular the foaming tool (17) has tool halves (19, 21) which delimit the tool cavity (15) and use a temperature control system (33) can be heated, and that in particular the tool halves (19, 21) have fluid channels through which heating medium can flow, and that the fluid channels are part of the temperature control system (33). Procedure according to Claim 6 , characterized in that to carry out the hot pressing step, the as yet untreated semi-finished fiber product (11) is inserted into the tool cavity (15) of the foaming tool (17), and the semi-finished fiber product (11) between the two tool halves (19, 21) below Pressure and heat is pre-consolidated. Method according to one of the preceding claims, characterized in that the thermal energy input required in the foaming step into the particles (25) takes place without steam or without steam. Sandwich component which is produced in a method according to one of the preceding claims. Process arrangement for carrying out a method according to one of the preceding claims.

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