EP1732748A1

EP1732748A1 - Method for processing cyclic oligomers to thermoplastic pbt plastics

Info

Publication number: EP1732748A1
Application number: EP05707530A
Authority: EP
Inventors: Markus Henne; Kurt Behre; Dietmar Rakutt; Martin Hintermann
Original assignee: Alcan Technology and Management Ltd
Current assignee: 3A Composites International AG
Priority date: 2004-03-04
Filing date: 2005-02-19
Publication date: 2006-12-20
Also published as: US20070182047A1; JP2007526375A; EP1995042A1; EP1992472A1; WO2005084925A1; EP1570976A1; CN1925977A

Abstract

The invention relates to method for producing fiber-reinforced plate material on the basis of a fiber web that contains at least one planar fiber structure and is impregnated with a thermoplastic plastic matrix,. The invention is characterized in that the one or more fiber structures are impregnated or coated with a reactive starting material, containing cyclic or macrocylic oligomers of the polyester, and in that the fiber web which contains one or more combined, impregnated or coated fiber structures is coated on one or both sides with a surface layer that contains a polymerized polyester. The fiber web that is coated with said surface layer is pressed in a pressing device to give a plate material, thereby polymerizing the reactive starting material into a plastic matrix that surrounds the fiber structure and that is permanently joined to the surface layer.

Description

Processing of cyclic oligomers into thermoplastic PBT plastics

The invention relates to methods for producing fiber-reinforced plastic articles containing PBT or a PBT blend, according to the preamble of the independent claims. The invention further relates to fiber-reinforced plastic articles containing PBT or a PBT alloy, according to the preamble of the independent claims.

Until now, it has been difficult to process thermoplastic systems for the production of fiber-reinforced plastic articles in the manufacturing processes designed for the processing of thermoset systems, such as RTM processes or prepreg processing. The difficulty in processing thermoplastic systems is, among other things, the provision of a suitable reactive starting material which is not only chemically stable but can also be converted into a low-viscosity state for further processing.

For some time now, efforts have been made to develop thermoplastic systems that can be processed similarly to thermosetting systems. A known system of this type is based, for example. on a polyamide (PA) such as PA-12 with lactam as the starting material. Another promising system is based on a polyester such as polybutylene terephthalate (PBT). The reactive starting material for the production of the polyester or PBT is in the form of so-called cyclic or macrocyclic oligomers, which are mixed with a corresponding polymer catalyst. The special thing about this system is that the reactive starting material can be converted into a low-viscosity melt, which is then used for processing by means of an injection process, e.g. of an LCM process.

LCM means "Liquid Composite Molding". In this text, LCM process or LCM technology is understood to be a process in which the cavity of a multi-part molding tool, in particular a two-part molding tool, is loaded with a single or multi-part fiber blank or fiber structure and a duro in the cavity of the closed molding tool. or thermoplastic plastic matrix is fed or injected, which flows through and impregnates the fiber blank to form a fiber composite component and fills the cavity of the molding tool, and after completion of the mold filling, the fiber composite component is cured or polymerized and then removed from the mold. That said Of course, the LCM process also includes variants with enamel cores or permanent cores, such as foam cores, which are inserted into the opened mold together with the fiber structures.

If a thermosetting plastic matrix system is processed in an LCM process, it is a resin transfer molding (RTM) process. The LCM process is therefore understood as a superordinate term for the injection process described above, which includes not only thermosetting plastic matrix systems but also thermoplastic plastic matrix systems. The RTM process is described in detail in Kötte, "The Resin Transfer Molding Process - Analysis of a Resin Injection Process", published by TÜV Rheinland, 1991.

However, an RTM process is often spoken of when processing thermoplastic matrix systems using LCM technology.

However, the low-viscosity properties of the cyclic oligomers mentioned are also advantageous for processing in other processes, since the low-viscosity, reactive starting material optimally impregnates or impregnates the fibers, which is particularly the case with plastic articles with a high fiber content in the form of dense ones Fiber structures are of great importance.

No. 6,369,157 describes, for example, a suitable reactive starting material which can be processed into a PBT plastic or a PBT plastic alloy. As processing methods e.g. Prepreg processes, RTM processes, pultrusion processes, extrusion processes and compression molding processes.

The object of the present invention is to propose specific methods for processing PBT plastic systems or the associated reactive PBT starting material based on cyclic oligomers. The present invention also relates to the resulting products containing PBT plastics.

According to the invention the object is achieved by the characterizing part of the independent claims. Further developments are described by the dependent claims, which are hereby part of the description.

definitions

Reactive starting material: A reactive starting material according to the following definition includes, among other things, cyclic or macrocyclic oligomers of the polyester, in particular of the PBT (called CPBT), which are mixed with a polymerization catalyst. Furthermore, a reactive starting material also includes blends (alloys) containing the aforementioned substances, which, for example. result in a PBT blend (PBT plastic alloy) after completion of the polymerization. The reactive starting materials mentioned for the production of polyester or PBT plastics are described in more detail in US Pat. No. 6,369,157, the content of which is hereby part of the disclosure. Particularly suitable reactive PBT starting materials in the form of cyclic oligomers are manufactured by the company Cyclics under the name CBT ™ (Cyclic Butylene Terephthalate). The polymerization catalyst can e.g. a zinc catalyst or another suitable catalyst.

Polyester:

Polyesters according to the following definition include plastics such as PET (polyethylene terephthalate) and associated blends and in particular PBT (polybutylene terephthalate) or PBT blends (PBT plastic alloys).

Fiber structure:

Fibrous structures as defined below are sheet-like structures and include, among other things, textile fabrics, e.g. Nonwovens, "non-wovens", non-stitch-forming systems such as fabrics, unidirectional or bidirectional scrims, braids or mats etc. or e.g. stitch-forming systems, such as knitted fabrics or knitted fabrics, and embroidered structures.

fibers:

The fibers of the fiber structures are, for example, as defined below. Long fibers with fiber lengths of e.g. 3-150 mm or continuous fibers and are ex. processed into fiber structures in the form of rovings.

The fibers can be glass fibers, aramid fibers, carbon fibers, plastic fibers, natural fibers or mixtures thereof. Plastic fibers can in particular be polyester fibers, such as PET, PBT or PBT blend. With regard to inorganic fibers, glass fibers are preferably used, since, in contrast to aramid or carbon fibers, these are relatively difficult to recycle when the fiber-reinforced plastic articles are recycled Have little effort separated from the plastic matrix and glass fibers are also relatively inexpensive.

PBT fibers are characterized in that they have a crystalline orientation in the fiber direction due to the manufacturing process, while the matrix between the fibers largely has no crystalline orientation, i.e. is amorphous.

Plate:

Plate according to the following definition means a flat body with a certain bending stiffness and a thickness that is small compared to the length and width expansion. The plates mentioned have, for example. a thickness of 0.5 mm or greater, preferably of 1 mm or greater, and in particular of 2 mm or greater and of 10 mm or less, preferably 6 mm or less, and in particular of 4 mm or less.

Topcoat method

For the production of pre-impregnated fiber structures (prepreg), usually fiber mats, the fiber structures have so far been impregnated (impregnated) with a reactive plastic matrix or coated with reactive powder, the powder, in particular the heated powder, having self-adhesive properties and therefore on the fiber structure sticks.

It is also known to use the reactive starting material, i.e. the cyclic oligomers to be applied in film form to the fiber structures, the melting of these films resulting in an impregnation of the fiber structure thanks to the low-viscosity properties of the reactive starting material in the molten state.

Since prepregs are generally sticky, they are provided on one or both sides with a release layer, that is to say a release film. Such a release layer allows the continuously produced prepregs to be rolled up into rolls on so-called coils for intermediate storage prior to further processing into fiber-reinforced plate materials without them sticking to one another. On the other hand, the release layers are also important in the further processing, since they protect the systems, ie the presses or rollers, from being glued to the prepregs in the production of hardened or polymerized plate material. After curing or polymerization of the prepregs to a sheet material, also organic Called sheet, the release layer is removed. The release layer is therefore not part of the end product but only a production aid.

The idea of the present invention lies in the improvement of the process for the production and further processing of so-called prepreg semifinished products and in the broader sense for the production of sheet material made of polyester, such as PET and in particular PBT or PBT blend, using a reactive starting material.

For this purpose, fiber structures are impregnated or coated with the reactive starting material in a first step. For this purpose, the fiber structures can be impregnated with a liquid, reactive starting material, for example. by immersing the fiber structures in a solution bath, the solvent being removed again after the impregnation. Furthermore, the liquid starting material can also be applied to the fiber structures by means of spraying, brushing, pouring, rolling or knife coating.

In an alternative variant, the fiber structures can be coated with the reactive starting material in powder form or in the form of foils, in both cases the reactive starting material being melted during the course of the production process with impregnation of the fiber structures. If the reactive starting material is applied in powder form to the fiber structure, this can be heated in order to improve the adhesive properties, and the powder can even soften or melt. Alternatively or in combination, the fiber structure can be preheated and coated with the powder. The powder coating can be carried out on a horizontally or vertically continuous fibrous web, the powder being fed vertically or horizontally to the fibrous web. The powder can be supplied by gravity and / or by gas or air flow. The gas or air stream is preferably heated, so that the powder develops adhesive properties when it hits the fiber web. Furthermore, the powder can also be supplied by means of an electrostatic process.

In said method, two or more layers of fiber structures can also be impregnated or coated as described above and combined to form a multi-layer or multi-layer fiber web.

In a subsequent step, the single or multi-layer fiber web impregnated or coated with the reactive starting material is coated on one or both sides with a cover layer in the form of a plastic film or film. The plastic film or film becomes an integral part of the fiber-reinforced plate material to be produced.

The plastic film or foil can be made of a thermoplastic or thermosetting plastic. The cover layer is preferably a polymerized thermoplastic film made from a polyester, such as PET, and in particular from a PBT or PBT blend.

The plastic film has e.g. a thickness of greater than 50 μm, in particular greater than 100 μm and less than 2000 μm, especially less than 1000 μm. Due to the sticky properties of the reactive starting material, the plastic film adheres to the impregnated or coated fiber structure. The plastic film can be applied as a solid film unwound from a roll or by means of extrusion as a molten, partially solid or solid film.

The cover layer applied to the fiber web can also be a fiber-reinforced, web-shaped plastic material with an outer, fiber-free (polymerized) plastic layer of the above-mentioned composition.

The fibers of the fiber web are preferably made of glass or polyester, such as PET and in particular PBT or PBT blend. Through the use of polyester fibers, such as PBT fibers, a single-grade sheet material is achieved.

The prepregs with applied top layers are polymerized for further processing under pressure and heat to a polyester, such as PET and in particular PBT or a PBT blend, the top layers forming an intimate bond with the polymerizing plastic matrix of the fiber structure and the top layers being an integral part of the plate-shaped Become fiber composite.

The melting or decomposition point of the outer layers is higher than the polymerization temperature of the reactive starting material. The cover layer is thus not adversely affected during the polymerization process of the plastic matrix.

Since the melting point of PBT (approx. 220 ° C) is higher than the polymerization temperature of the reactive starting materials used (approx. 180-190 ° C), the top layers of PBT films are not adversely affected by the heat when polymerizing the plastic matrix. Cover layers made of a polyester, in particular of PBT, also result in a plastic in the composite material that is sorted according to recycling criteria. The integral application of cover layers has the additional advantage that a high surface quality of the plate material is achieved since the cover layers contain no fibers.

In the polymerized state, the cover layers and the plastic matrix of the fiber web preferably consist of the same plastic or of plastics or plastic alloys that are close to one another.

In a further development of the invention, the cover layers can be colored and thus already give the plate material the outer, colored appearance. The coloring can be such that the fiber-reinforced layer arranged under the cover layers is no longer visible. This may save a subsequent color coating step.

The production of the plate material according to the invention is preferably carried out continuously and inline, i.e. from the supply of the fiber structures and the starting material to the exit of the finished plate material from the press. in a production line.

For this purpose, one or more fiber structures are continuously fed to the processing device and, if necessary, brought together. unrolled from a roll and impregnated or coated inline with the reactive starting material. The impregnation or coating can continuously, for example. by means of an immersion bath in a continuous system, a spraying device, a powder scattering device, a device for electrostatically transferring the powder to the fiber structure or a device for supplying a liquid, partially solid or solid film made of a reactive starting material, e.g. by extrusion or from a roll.

A (polymerized) plastic film or film is then applied inline on one or both sides to the fiber web impregnated or coated with the reactive starting material, the plastic film being either unwound from rolls (coils) or extruded directly inline and in liquid, partially solid or solid state is applied to the impregnated or coated fiber web.

In a subsequent continuous press, the composite is polymerized under pressure and / or heat to a fiber-reinforced plate material. The pressing process can be carried out using downstream press rolls and / or using press plates. The press device can e.g. Floating, hydraulically operated lower press plates that work against an upper rigid press construction. A Such a continuous press is ex. operated with belts such as PTFE belts or steel belts and allows medium to high throughputs depending on the length of the heating section.

The web-like, polymerized plate material can then be cut lengthwise and / or transversely to the direction of passage into individual plates or strips and stacked in batches. Thanks to the cover layers, the systems are protected during further processing of the prepregs into sheet material.

In a specific embodiment of the invention, the prepregs are not passed through a press after coating with the cover layers, but are wound up on rolls or cut and stacked in batches, the individual plates not adhering to one another thanks to the release function of the cover layers. The prepregs thus supplied to the intermediate storage can be further processed into sheet material at a later point in time as described above or processed in another way, for example. in molding presses.

The fiber-reinforced plate material according to the invention is used as flat plates or strip goods. Furthermore, the plate material can be thermally formed articles, e.g. by deep drawing. Furthermore, said plate material can be processed further in the form of flat plates to form multi-layer composites, in particular sandwich composites, the further layers e.g. Foams, metal foils or metal plates can include.

Such multilayer composites can also be produced continuously and inline, the further layers, such as foam layers, also being fed continuously. In a preferred embodiment, the multilayer composites are produced inline and immediately after the production of the fiber-reinforced sheet material. If the said plate material is processed into multilayer composites, it may be sufficient that the prepreg material is only coated with a cover layer with a permanent plastic film as the release layer, while the second surface is coated with a temporary release layer that is used for the production the multilayer composite is removed again. The cover layer containing the permanent plastic film forms a cover layer of the multilayer composite, while the second surface is the contact surface with further composite layers. Said plate material or the composite plates or thermoformed articles produced therefrom are used in transportation, such as road vehicle construction (automobiles, buses, trucks, light vehicles, etc.), rail vehicle construction (railroad, tram, express train, magnetic levitation train), aviation (aircraft construction, space travel), in marine, boat and ship building as well as in cable car cabins. Furthermore, the said plate material is used in building construction and civil engineering, interior construction and in particular in building technology and in the manufacture of sports equipment.

Pure plastic articles

The present invention also relates to single-grade, fiber-reinforced plastic articles, hereinafter referred to as pure plastic articles, which contain fibers made of polyester, such as PET and in particular PBT or a PBT blend, and a plastic matrix likewise made of polyester, such as PET and in particular PBT or PBT blend , The pure plastic articles can be, for example, fiber-reinforced plastic plates, which are made from prepregs impregnated or coated with a reactive starting material, which are polymerized under pressure and / or heat to form fiber-reinforced plastic plates. The fiber structures can, for example, be coated with the reactive, powdery starting material or else soaked with the reactive starting material in liquid form, optionally in solution. It is also conceivable for the fiber structures to be coated on one or both sides with a film made of a reactive starting material, the film being melted at low viscosity for the purpose of impregnating the fibers.

Under the influence of pressure and heat, the plastic matrix is polymerized in a press device to form a fiber-reinforced plastic plate.

The fiber structures loaded with the reactive starting material can also be processed in a molding tool under pressure and heat application and polymerization of the plastic matrix to form a single-variety plastic article.

Said plate material can be produced according to the previously described cover film process and can furthermore contain a one- or both-sided coating with a cover film made of polyester, such as PET and in particular of a PBT or PBT blend.

Furthermore, said pure, fiber-reinforced one-component plastic articles can also be produced using a previously described LCM process. be body. For this purpose, the reactive starting material is expediently fed or injected into a molding tool designed with a fiber structure. The fibers of the fiber structures consist of a polyester, such as PET and in particular PBT or PBT blend.

One-component plastic articles

Another processing method is characterized in that the fiber-reinforced plastic article consists entirely of a polyester, such as PET, and in particular of a PBT or PBT blend. To produce the plastic articles mentioned, the reactive starting material is processed into linear fibers, which in turn are polymerized into a polyester, such as PET and in particular PBT or a PBT blend. Alternatively, the fibers can also be produced directly from a polyester, such as PET and in particular PBT or PBT blend. The fibers are characterized in that they have a crystallinity oriented in the direction of the fibers and therefore have good mechanical properties, such as rigidity and tensile strength. In a subsequent processing step, the fibers mentioned are processed into fiber structures, as previously defined.

In a subsequent process step, at least the surfaces of the individual fibers or rovings are melted or melted, the molten plastic joining or gluing the fibers and solidifying under recrystallization to form a preferably isotropic plastic matrix arranged between the fibers. This process step is characterized by the application of pressure and / or heat. Such a method can e.g. a hot press or hot compaction process.

The result is a compact, self-reinforced plastic article that contains plastic fibers of the same type embedded in a plastic matrix. Said plastic article has mechanical properties similar to plastic articles reinforced with inorganic fiber structures. Same or single variety here means that both components are made of one polyester.

The polymerized plastic article described is characterized by its good thermoformability and can be further shaped or finished in subsequent forming processes using heat and / or pressure. Said plastic articles, hereinafter referred to as one-component plastic articles, can be produced in the form of plates or shaped bodies, the plates preferably being produced continuously in a corresponding pressing device or rolling device, while the shaped bodies are preferably produced piece by piece in appropriately designed molding tools, such as compression molding become.

Multilayer

The present invention also relates to a multilayer composite comprising at least one layer made of an open and / or closed cell foam. The foam consists of a polyester, such as PET and in particular PBT or PBT blend. In a preferred embodiment, at least one further layer of the multilayer composite contains a plastic matrix made of a polyester, such as PET and in particular PBT or PBT blend. The further layer is preferably a fiber-reinforced plastic plate.

The above-mentioned multilayer composite with foam layer can, for example. Layers, in particular cover layers on one or both sides, made of a pure plastic article or a one-component plastic article in plate form, as described above. Furthermore, said layers can also consist of a plate material produced according to the cover film process described above.

The multilayer composite can, for example. a sandwich element with a foam core made of a polyester, such as PET and in particular PBT or PBT blend, and cover layers on both sides made of fiber-reinforced plastic plates with a plastic matrix made of polyester, such as PET and in particular PBT or a PBT blend.

According to a specific embodiment for producing said multilayer composites, a fiber structure impregnated or coated with a reactive starting material, a so-called prepreg, is applied to a (polymerized) foam layer in a continuous or discontinuous process (for example a batch process), the prepreg is polymerized using heat and / or pressure to form a reinforcing layer which forms a permanent bond with the foam layer, the foam layer being a core material.

Due to the sticky properties of the reactive starting material, the reinforcement layer can be applied excellently to the foam layer. The polymer sation of the matrix material leads to a permanent, strong connection between the reinforcing layer and the foam layer.

Multi-layer composites, in particular 3-layer sandwich composites can e.g. Total layer thicknesses of greater than 3 mm, preferably greater than 5 mm, in particular greater than 8 mm and less than 30 cm, preferably less than 20 cm, in particular less than 10 cm.

Foam Extrusion

Another object of the invention is the continuous production of multilayer composites, in particular sandwich composites. In a, preferably continuous, process, fiber-reinforced plastic plates with a plastic matrix made of a (polymerized) polyester, such as PET and in particular PBT or PBT blend, are produced. A foamable starting material provided with a blowing agent and made of a (polymerized) polyester, such as PET and in particular PBT or PBT blend, is extruded through one or more nozzles by means of an extruder. The starting material expands to a flat, foamed plastic when exiting the extruder opening under pressure relief.

In a preferred embodiment of the extrusion step, the starting material is extruded in the form of spaghetti-shaped strands through a perforated disk, the strands expanding as they emerge from the extruder opening and gluing or fusing together to form a flat, foamed plastic. The feedstock can also be extruded through a single slot die.

The foamable starting material can be extruded directly onto the fiber-reinforced sheet material, which is also fed continuously, so that the extruded starting material sticks to the sheet material and thus forms an intimate connection with it.

In a further embodiment of the invention, the foamable (polymerized) starting material is extruded onto the not yet or only partially polymerized plate material, the reactive starting material being intimately bonded to the extruded starting material due to its adhesive properties. In a subsequent process step, the plate material is completely polymerized under the action of heat and / or pressure. The plate material can be produced, for example, by the cover film process described above, the plate material expediently being coated on one side only, ie on its free, not further coated surface, with a cover layer of the type mentioned above. The cover layer is in particular a plastic film or film made of a polyester, such as PET and in particular PBT, PBT blend.

The plate material can also be in the form of the pure plastic article described above or one-component plastic article. According to the latter version, there is a single-variety sandwich composite.

Hybrid fiber structure

In a further application of PBT plastics or its reactive PBT starting material, a hybrid fiber structure containing reinforcing fibers, such as inorganic fibers, e.g. Glass fibers, carbon fibers or aramid fibers, and matrix fibers in the form of plastic fibers made from either (a) a polyester, such as PET and in particular PBT or PBT blend, or (b) from a reactive starting material, such as CBT ™. The reinforcement and matrix fibers are preferably processed with one another in as uniform a distribution as possible.

The matrix fibers are melted by heat and / or pressure application in a subsequent work step and transformed into a plastic matrix surrounding the reinforcing fibers or penetrating the fiber structure of reinforcing fibers, while the reinforcing fibers remain undamaged. Matrix and reinforcing fibers can e.g. be interwoven or intertwined to form fiber structures.

The plastic articles made from hybrid fiber structures can be fiber-reinforced plastic plates, which are produced in a press, in particular a continuous press. Furthermore, said plastic articles can be molded articles which are molded in a molding tool, in particular a pressing tool, under the action of heat and / or pressure.

According to variant (a), the said polyester is merely melted into a plastic matrix and solidified again. According to variant (b), the reactive starting material is melted, polymerized and solidified into a plastic matrix. The low-viscosity properties of the reactive starting material in the molten state according to variant (b) result in good impregnation of the reinforcing fibers.

In a specific further development of the hybrid fiber structure, the reinforcing fibers can be made of a PBT or PBT blend and the matrix fibers of the hybrid fiber structure can be made of the reactive PBT starting material mentioned. Since the (polymerized) PBT or PBT blend has a higher melting point than the corresponding reactive PBT starting material, the reinforcing fibers are not melted when polymerizing the matrix fibers into a plastic matrix.

Manufacture of fiber-reinforced molded parts using a mold

Another method for processing PBT matrix systems relates to the production of fiber-reinforced moldings by means of molding tools, hereinafter referred to as compression molding processes. The molding tool contains at least two tool parts, which can be brought together to form a closed molding tool, forming a cavity that reproduces the outer contour of the molding.

In a first embodiment of the above-mentioned method, the cavity of the opened molding tool is loaded with fiber structures and with a reactive starting material in powder form that forms the plastic matrix, the amount of powder introduced being matched to the size of the molded part to be produced, so that in the subsequent molding process there is as little or no there is no excess of matrix material at all. The molding tool is closed, the powdery, reactive starting material being melted using heat and / or pressure and penetrating into the fiber structures and impregnating them. At the same time, the polymerization of the plastic matrix is started and the consolidation process is initiated. The molded part is almost completely polymerized and solidified. The result is a fiber-reinforced molded part made from a PBT, which can be demolded and, if necessary, tempered once it has reached its dimensional stability. Instead of PBT, other polyesters such as PET or a PBT blend or their starting materials can also be processed.

In a specific embodiment of the said method, the molding tool is closed in several stages, in particular in two stages, in order to initiate the shaping process. As a result, the closing pressure can be gradually reduced, so that molten powder material can penetrate continuously into the fiber structures without the fiber structures being displaced or deformed from their intended position when the mold is closed under maximum pressure. Furthermore, the multi-stage closing of the mold allows any excess matrix material to be removed from the cavity.

In a further embodiment of the said method, the reactive PBT starting material can also be added to the cavity of the opened mold in liquid form.

The present method has the advantage that the feeding or injecting of the matrix material in liquid form in a separate process step can be dispensed with by a separate device and can therefore be produced more cost-effectively with a technically simpler device.

Manufacture of plastic articles with a permanent foam core

Another aspect is the production of fiber-reinforced plastic articles with a foam core made of a polyester, such as PET, PBT or PBT blend, using a molding tool. For this purpose, one or more separate foam cores are covered with reinforcing fibers and placed in the mold.

In a first embodiment variant, a reactive starting material, in particular PBT starting material, is used in its various possible embodiment variants, e.g. fed in liquid or powder form into the opened mold.

In a second embodiment variant, a reactive starting material, in particular PBT starting material, is injected into the mold in liquid form in a known LCM process.

The polymerizing PBT plastic matrix forms an intimate connection both with the reinforcing fibers and with the foam core, which is expediently of the same type.

Pre-coating of the mold

Another aspect of the invention relates to the pretreatment of the cavity of a mold in an LCM or compression molding process. The cavity is tive starting material coated, which polymerizes in the actual molding process, polymerizing to form the surface of the plastic article to a polyester, PET and in particular a PBT or PBT blend.

The coating can be applied in powder form to the, preferably preheated, cavity wall of the molding tool, the powder coating being melted into a thin film in a sintering process. The coating can also be applied in liquid form, e.g. be sprayed on or brushed on. Furthermore, the coating can also be applied as a solid film. The film can be applied to the contour of the cavity wall with softening or melting (e.g. by heating). Furthermore, the film can also be applied to the cavity wall by means of pressure or vacuum or generally by means of mechanical means.

Instead of the reactive starting material, it is also conceivable to apply a (polymerized) polyester such as PET and in particular a PBT or PBT blend to the wall of the tool cavity in accordance with one of the above-mentioned ways.

The coating in polymerized form preferably consists of the same or a similar plastic composition as the plastic matrix of the finished molded part. The coating can be, for example, greater than 10 μm, preferably greater than 100 μm, in particular greater than 500 μm, and less than 5 mm, preferably less than 3 mm, in particular less than 2 mm.

Before the aforementioned coating is applied, the mold can also be coated with a suitable release film, which facilitates the removal of the mold from the hardened plastic article.

The aim of the above-mentioned coating with a plastic is to produce a fiber-reinforced plastic article with a surface of high quality. One of the reasons for the high surface quality is that the coating does not contain any reinforcing fibers.

The invention is explained in more detail below by way of example and with reference to the accompanying drawings. Show it:

1 shows a device for carrying out a cover film process; 2 shows a device for producing a multilayer composite; 3 shows a perforated plate of a foam extrusion device; Fig. 4 shows a cross section of a sandwich element. Fig. 1 shows an apparatus for producing fiber-reinforced sheet material from a polyester. A continuously supplied web-shaped fiber structure 1 is coated with a reactive starting material in powder form 2 by means of a powder coating device 3. The powder applied to the fiber structure can be heated in order to improve the adhesive properties. Alternatively, the fiber structure can be preheated and coated with the powder. Subsequently, cover layers in the form of polyester films 4a, 4b are continuously fed in on both sides and applied to the free surfaces of the coated fiber structures. In a continuous press 5, the reactive starting material is polymerized with the formation of a plastic matrix and with intimate connection with the cover layers. After leaving the continuous press 5 on roller conveyors 8, the solidified plate material is fed to a cutting or sawing device 6 and cut into individual plates 7.

FIG. 2 shows the production of a sandwich composite, extruded polyester 21a, 21b being extruded through the openings 19 of a perforated plate 18 (FIG. 3) of an extrusion device 1. The extruded strands 21a, 21b expand after they emerge from the perforated plate 18 and stick to one another to form a plate-shaped foam body 22. The still soft foam body 22 is brought into the desired thickness and width in a straightening device 23. Subsequently, web-shaped fiber structures 24a, 24b impregnated or coated with a reactive starting material are fed in and applied to the free surfaces of the foam body 22. The layer composite is then pressed in a pressing or rolling device 25 with polymerization of the reactive starting material to form a plastic matrix and with an intimate connection thereof with the surface of the foam body 22 to form a sandwich composite. The sandwich composite is then cut to length to individual sandwich panels 10 on a cutting or sawing device (not shown). The aforementioned sandwich panel 10 (FIG. 4) consists of a polyester foam core 12 and two cover layers 11, 13 arranged on both sides and made of a fiber-reinforced PBT plastic.

Claims

Expectations

1. A method for producing a fiber-reinforced sheet material from a fiber web impregnated with a thermoplastic matrix, comprising at least one flat fiber structure, characterized in that the fiber structure or fibers are impregnated or coated with a reactive starting material, containing cyclic or macrocyclic oligomers of the polyester, and the fibrous web containing one or more merged, impregnated or coated fiber structures, coated on one or both sides with a cover layer containing a polymerized polyester, and the fibrous web coated with the cover layer is pressed in a press device to a plate material, the reactive starting material in a plastic matrix surrounding the fiber structures and permanently bonding to the cover layer is polymerized.

2. The method of claim 1, wherein the reactive starting material contains cyclic oligomers of PBT (CPBT) mixed with a polymerization catalyst.

3. The method according to any one of claims 1 to 2, wherein the cover layer contains or consists of a PET, PBT or a PBT plastic alloy.

4. The method according to any one of claims 1 to 3, wherein the cover layer is applied to the fiber web in the form of a pure plastic film.

5. The method according to any one of claims 1 to 3, wherein the cover layer is extruded in solid, semi-solid or liquid form on the fiber web.

6. The method according to any one of claims 1 to 3, wherein the cover layer as a fiber-reinforced sheet-shaped plastic material with an outer, exposed and fiber-free plastic layer made of a polyester, preferably a PET, PBT or a PBT blend, is applied to the fiber web.

7. The method according to any one of claims 1 to 6, wherein the plate material is produced continuously and inline with the supply of web-shaped fiber structures.

8. The method according to any one of claims 1 to 7, wherein the fiber structure or fibers of the fiber web are impregnated or coated inline with the reactive starting material or are supplied to the system already pre-impregnated or pre-coated.

9. The method according to any one of claims 1 to 8, wherein the or the impregnated or coated with the reactive starting material fiber structures continuously and in web form and brought together to form a fiber web, and the fiber web inline on one or both sides with a cover layer, preferably in the form of a film or an extruded film.

10. The method according to any one of claims 1 to 9, wherein the fiber web coated on one or both sides with a cover layer is pressed inline in a continuous press to form a plate material.

11. A process for producing a fiber-reinforced plastic article containing a fiber structure embedded in a plastic matrix made of a polyester, wherein the cavity of a molding tool is loaded with at least one fiber structure and a reactive starting material containing cyclic or macrocyclic oligomers of the polyester mixed with a polymerization catalyst and the molding tool is closed and, using pressure and / or heat, the reactive starting material is polymerized to form a thermoplastic plastic matrix, characterized in that the wall of the tool cavity is covered with a film of a reactive starting material containing cyclic or macrocyclic oligomers of the polyester or a polymerized polyester, such as PET , PBT or a PBT blend.

12. A method for producing a multilayer composite, comprising at least one layer made of a foam and a cover layer connected therewith made of a fiber-reinforced plate material, characterized in that Both the foam and the sheet material contain a plastic matrix made of a polyester and for the production of the multilayer composite one with a reactive starting material containing cyclic or macrocyclic oligomers of the polyester mixed with a polymerization catalyst, impregnated or coated single or multi-layer fiber web with a foam layer made of one polymerized polyester is connected to a laminate, and the reactive starting material is polymerized to form a polyester, forming the plastic matrix of the plate material and with intimate connection with the foam layer.

13. The method according to claim 12, wherein by means of an extruder, a starting material loaded with a blowing agent is extruded onto the impregnated or coated fiber web and expanded under pressure relief to form a foam layer which is brought together with the impregnated or coated fiber web and combines with it.

14. The method according to claim 13, wherein the starting material is extruded through a perforated plate in the form of individual strands, which expand as they emerge to form a foam and bond to one another to form a foam layer.

15. The method according to any one of claims 11 to 13, wherein the foam layer is coated on both sides with a plate material.

16. A process for the production of a multilayer composite comprising at least one layer made of a foam and a cover layer connected therewith made of a fiber-reinforced plate material, characterized in that both the foam and the plate material contain a plastic matrix made of a polyester and for producing the multilayer composite a a blowing agent-loaded starting material is extruded onto the plate material, which expands to a foam layer under pressure relief and is combined with the plate material to form a multilayer composite.

17. The method according to claim 16, wherein the starting material is extruded through a perforated plate in the form of individual strands, which expand as they emerge to form a foam and bond to one another to form a foam layer.

18. The method according to any one of claims 16 to 17, wherein the foam layer is coated on both sides with a plate material.

19. A method for producing a fiber-reinforced plastic article, characterized in that both the reinforcing fibers of the fiber structure and the plastic matrix consist of a polyester, the polyester fibers with directed crystallinity being processed to form a fiber structure and the fiber structure to form a plastic matrix, fiber-reinforced Plastic article is processed by melting the surfaces of the fibers and solidifying them to form an isotropic plastic matrix surrounding the non-melted part of the fibers.

20. The method according to claim 19, wherein the plastic article is produced in a hot pressing process.