EP3218429A1

EP3218429A1 - Method for producing finished parts

Info

Publication number: EP3218429A1
Application number: EP15797883.4A
Authority: EP
Inventors: Andreas Radtke; Dagmar BUERCKEL; Andreas NIXDORF; Oliver Kraemer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2014-11-14
Filing date: 2015-11-04
Publication date: 2017-09-20
Also published as: JP2017537005A; US10632692B2; WO2016075010A1; KR20170084276A; US20180290401A1; CN107107599A

Abstract

The invention relates to a method for producing finished parts from at least one multi-layer, fiber-reinforced, flat semi-finished product structure, comprising the following steps: a) heating the at least one multi-layer, fiber-reinforced, flat semi-finished product structure to a first temperature T_a at ambient pressure, wherein the at least one multi-layer, fiber-reinforced, flat semi-finished product structure comprises at least two polymer layers arranged one over the other and the individual polymer layers are each fiber-reinforced and are not integrally bonded to each other or are only partially integrally bonded to each other and, for the case that at least one of the polymer layers contains a semicrystalline polymer, the first temperature T_a is higher than a melting temperature T_s of the crystalline polymer as per DIN EN ISO 11357-3:2013-04, and, for the case that the at least two polymer layers do not contain a semicrystalline polymer, the first temperature T_a is higher than a glass transition temperature T_g as per DIN EN ISO 11357-2:2013-09 of a polymer that is contained in at least one of the at least two polymer layers, b) pressing the heated at least one multi-layer, fiber-reinforced, flat semi-finished product structure into a finished part at a second temperature T_b and a pressure p_b of at least 3 bar.

Description

The invention relates to a method for the production of prefabricated parts from at least one multilayer, fiber-reinforced, flat semifinished product structure in which the at least one semifinished product structure is heated and pressed.

For example, prefabricated parts made of fiber-reinforced polymers are used in areas in which materials with high strength and compared to metals with lower weight are to be used. In particular, prefabricated parts made of fiber-reinforced polymers are used in the automotive industry in order to reduce the mass of vehicles and thus also the fuel consumption. Frequently, precast parts of fiber-reinforced polymers whose polymer phase surrounding the fibers is also referred to as a matrix are produced from intermediates, for example so-called organic sheets, which are fully impregnated and fully consolidated continuous fiber reinforced thermoplastic polymers with fabric or scrim reinforcement. In the case of organic sheets, individual layers of a laminate completely impregnated with polymer are virtually free of pores, which is also referred to as fully consolidated. The organo sheets can be produced from so-called prepregs. In prepregs, a thermoplastic matrix is finely dispersed without completely wetting the reinforcing fibers. The prepregs are completely impregnated and consolidated in a subsequent process step. M. Ostgathe, in "For mass production of fabric-reinforced semi-finished products for forming", Progress Reports VDI 2 (440), 1977, pages 48-51, examines the properties of molded parts depending on the used semi-finished product structures as semi-finished structures were organo sheets, Hybridge weave In the hybrid fabric, reinforcing and matrix fibers are mixed but there is no connection between the fiber and the matrix For fabricating the calendered semi-finished structures, the hybrid fabric was calendered, melting the matrix and largely wetting the reinforcing fibers and calendered material belong to the thermoplastic prepregs, and components made of organic sheets showed much better mechanical properties than components made of calendered semi-finished or hybrid fabrics, for satisfactory mechanical properties A high-volume production is expected to be fully impregnated and fully multi-layer consolidated semi-finished structures.

In Ostgathe the production of unidirectionally reinforced tapes is described on page 15, which are impregnated and consolidated as single layers and can be layered and processed in a subsequent step into flat semi-finished products. The textile processing of the tapes is complex and it is described longer process times compared to the forming of fully impregnated semi-finished products, since the Ausgangsma- material is not yet consolidated. Forming unidirectional ribbon reinforced semi-finished products requires fully consolidated semi-finished slab assemblies, also referred to as tapelayups, which, after tape making, require the additional step of consolidating multi-layered semi-finished slabs.

A. Wöginger in "Process Technologies for the Production of Continuously Fiber-Reinforced Thermoplastic Semi-Finished Products", Institute for Composites-GmbH-Kaiserslautern Series Volume 41, 2004, pages 4 to 6, calls for the three basic sub-processes impregnation, consolidation and transfer to the solid state for the production of semi-finished products The consolidation phase serves to establish a good bond between the individual reinforcing layers of a composite material.After the impregnation phase and the consolidation phase, ideally a pore-free composite is present Depending on the material throughputs, film stacking methods, prepreg methods and direct methods can also be used can be used, wherein in the direct process, the matrix component and the fiber component are brought together in the pressing process for the production of the semifinished product structure.

The methods known in the prior art have the disadvantages that a complex complete consolidation of the multi-layer semifinished product structure is carried out or that without complete multi-layer consolidation of the semifinished product structure, the mechanical properties of the prefabricated parts produced are insufficient.

The object of the present invention is to provide a process for the production of prefabricated parts from multilayer, fiber-reinforced, flat semifinished product structures, with which finished parts can be produced more effectively and with consistent or improved mechanical properties.

This object is achieved by a method for producing finished parts from at least one multilayer, fiber-reinforced, flat semifinished product, comprising the following steps: a) heating the at least one multilayer, fiber-reinforced, flat semi-finished construction at ambient pressure to a first temperature T _a , wherein the at least one multi-layered, fiber-reinforced, flat semi-finished construction comprises at least two superimposed polymer layers and the individual polymer layers are each fiber-reinforced and not materially connected to each other or only partially cohesively connected to each other and the first temperature T _a in the event that at least one of the polymer layers semi-crystalline polymer, is higher than a melting temperature Ts of the crystalline polymer according to DIN EN ISO 1 1357-3: 2013-04, and the first temperature T _a in the event that the at least two polymer layers no semicrystalline P is higher than a glass transition temperature T _g according to DIN EN ISO 1 1357-2: 2013-09 of a polymer which is contained in at least one of the at least two polymer layers, b) pressing the heated at least one multilayer, fiber-reinforced, flat semi-finished construction to a finished part at a second temperature Tb and a pressure pb of at least 3 bar. Due to the combination of materials and process management, fully consolidated multi-layer finished parts can be produced from non-fully consolidated multi-layer semi-finished structures in the component tool. Through the use of fiber-reinforced polymer layers, which are preferably single-layer fully consolidated semi-finished products in the form of tapes, for example, the cost in the production of finished parts can be reduced and at the same time a finished part can be produced which does not have the disadvantages described in the prior art and can be obtained in particular by good mechanical properties, in particular with respect to tensile strength and flexural strength, distinguished. Single-layer fully consolidated polymer layers, also referred to as semi-finished products or tapes, can be used for the production of finished parts. The polymer layers are arranged in the form of semi-finished structures that are not or not completely multilayered, such as stacked assemblies. By a complete consolidation is meant that the fibers are completely wetted. A multilayered complete consolidation of the individual polymer layers takes place according to the invention only in the further processing of the individual layers to the finished part, ie in steps a) and b). In the entire manufacturing process of the finished part, therefore, an intermediate step can be omitted, namely the one in which the semi-finished structure is pressed over several layers over a whole area or completely consolidated before the actual finished part is produced. By the method according to the invention, the productivity of the manufacturing process for finished parts can be increased since the time required for the separate production of multi-layer completely consolidated semifinished product structures, such as fully consolidated organic sheets, can be saved.

The finished part is produced from a layer structure comprising at least two polymer layers arranged one above the other, which are each fiber-reinforced in one layer. The at least two polymer layers can generally be any single-layer semifinished product known to the person skilled in the art. Preferably, the polymer layers are tapes or ribbons.

In the context of the invention, material-locking means that various layers or layers, in particular different layers or layers of a fiber-reinforcing structure, are continuously enclosed by a polymer mass and have only a low pore content. A high pore content would reduce the mechanical properties of the finished part. In contrast, non-cohesively interconnected layers merely overlap one another without a continuous interconnection of interlayer polymer mass between layers. In the case of a partial cohesive connection between the layers, the various layers adhere to one another in individual regions of their mutually facing surfaces, which may be due to the fact that layers lying above one another have already been heated as a layer. This heating, which precedes the process according to the invention, can be carried out under overpressure. Through this treatment, the polymer of the layers can be partially melted and polymers of adjacent layers can partially fuse together and the layers thus connect partially cohesively, without the separation of the layers would be completely eliminated by fused polymer.

Steps a) and b) may be preceded by method steps for the production of the at least one multilayer, fiber-reinforced, flat semifinished product structure. The production of the at least one multi-layer, fiber-reinforced, flat semi-finished construction may comprise a consolidation, which is carried out only incompletely. In one embodiment, the at least two polymer layers of the at least one fiber-reinforced, flat semi-finished construction prior to step a) may already be partially bonded together in a materially cohesive manner.

Preferably, each of the at least two polymer layers is in each case fully consolidated. In a preferred embodiment, the at least two polymer layers prior to step a) are each fully consolidated by pressing at a temperature T _v in the range of 240 ° C to 280 ° C and a pressure P _v of more than 5 bar.

By combining steps a) and b), a complete cohesive connection between the various polymer layers is then achieved in the context of the method according to the invention. In a preferred embodiment, before step a) less than 80% of an area of the first polymer layer which is directed in the direction of the second polymer layer, positively connected to the second polymer layer, preferably less than 70%, particularly preferably less than 50%. The required temperature, which is heated in step a), depends on the composition of the polymer of the at least two polymer layers. The first temperature T _a and the second temperature Tb are locally attributable to the core of the finished part to be produced or the center of the superimposed polymer layers. If the polymer of at least one of the polymer layers contains a partially crystalline polymer, then the first temperature T _{a is} higher than the melting temperature T _{s of} the crystalline polymer contained. A corresponding method for determining the melting temperature is described in DIN EN ISO 1 1357-3: 2013- 04. If no semicrystalline polymer is contained in the at least one multilayer, fiber-reinforced, flat semifinished product structure, that is to say exclusively amorphous polymers, the first temperature T _{a is} higher than the glass transition temperature T _{g of} at least one polymer contained in at least one polymer layer whose determination in DIN EN ISO 1 1357-2: 2013-09 is described.

The heating in step a) is carried out at ambient pressure, which is also referred to as atmospheric pressure and is usually about 1 bar. The pressing in step b) is carried out at a pressure pb of at least 3 bar absolute. Preferably, the pressure is increased only when the first temperature T _{a is} reached.

Preferably, the at least one multilayer, fiber-reinforced, flat semifinished product structure is first heated and the first temperature T _a is held for a certain time before the Pressure for pressing is increased, so that a consolidation of the fibers is initially continued at ambient pressure. In a preferred embodiment, the first temperature T _a in step a) is maintained at ambient pressure for a period of at least 5 seconds, preferably at least 30 seconds, more preferably at least 120 seconds. By heating to a temperature which is greater than the melting temperature T _s , multi-layer prefabricated parts can be fully consolidated in the mold, without the prior production of a multi-layer fully consolidated semifinished product structure with construction of a plate and pressing into a multilayer, fully consolidated semi-finished structure or a multilayer, fully consolidated plate.

In a preferred embodiment, the pressure pb is between 3 bar and 50 bar, preferably between 5 bar and 30 bar and particularly preferably between 10 bar and 25 bar.

In a preferred embodiment, the first temperature T _a and the second temperature Tb are between 50 ° C and 400 ° C, preferably between 100 ° C and 350 ° C and particularly preferably between 200 ° C and 320 ° C.

The heating in step a) can be carried out by any method known to the person skilled in the art. In a preferred embodiment, the heating takes place without contact. Particularly preferably, the heating takes place by means of infrared radiation or in a circulating air oven.

In a preferred embodiment, the second temperature Tb is equal to or higher than the first temperature T _a . The at least one semifinished product structure is preferably heated in step a) to a temperature which is required during the pressing to produce a completely cohesive connection between the layers of the semifinished product structure. By the pressing process, the temperature of the semi-finished construction can continue to rise.

The pressing in step b) represents the actual finished part manufacturing step, which includes a consolidation and / or calibration. In a preferred embodiment, in step b) a thickness of the finished part is adjusted by pressing to a range of 1 mm to 4 mm or step b) is followed by a further step, in which the thickness of the finished part in a range of 1 mm to 4 mm is adjusted by pressing.

The pressing can be done in presses, mold carriers, injection molds and injection molding machines.

In a preferred embodiment, the finished part is cooled after pressing.

In a further preferred embodiment, the finished part is additionally injected or back-injected in step b). An encapsulation of continuous fiber reinforced plastic sheet-like parts is described for example in Marko Wacker et al., "Welding and encapsulation of Orga- noblechen", KU plastics, Carl Hanser Verlag Munich, born in 1992 (2002), 6. By injection molding or encapsulation functional elements to the The injection molding or encapsulation can be carried out with a polymer. gene, which is already contained in at least one of the polymer layers, alternatively, another polymer can be used, which is not yet included in the semifinished product structure. The injection of the polymer takes place under the usual parameters for injection molding. In a further preferred embodiment, step b) is followed by a step c) in which the finished part is formed by deep-drawing or thermoforming, or the finished part is overmolded or back-injected or elements are injection-molded or sprayed onto the finished part. For example, ribs can be sprayed on to reinforce the finished part. Further elements which can be supplemented by an injection molding process are functional elements such as fixtures for fasteners, clips, force introduction, screw-on domes or threaded receptacles.

In order to obtain increased strength, it is preferred if the injected polymer forms a closed skin on the finished part between the functional elements. In particular, when a plurality of adjacent functional elements are formed, an additional stabilization of the functional elements is achieved by the closed skin between the functional elements. The closed skin is thereby formed by forming a thin flow channel between the functional elements and injecting the polymer material into the flow channel.

By overmolding, back molding or injection molding, the connection between the different polymer layers is further improved. Also, the finished part and thus the layer structure can be flooded with polymer, which already a pressure above the ambient pressure, built and a defined surface structure and / or a higher surface quality with respect to, for example, a reduced roughness or better appearance of the finished part is achieved. Furthermore, there is good adhesion between the flooded polymer which then forms a coating and the finished part.

For encapsulation, injection molding, injection molding or spraying polymers are suitable which are injection-moldable. The injection moldable polymers may be fiber reinforced with long fibers or short fibers. A use of different polymers in the polymer layers of the finished part on the one hand and for encapsulation, injection molding, injection molding or spraying on the other hand is particularly advantageous if certain properties, for example, in terms of surface quality or strength to be achieved.

Suitable polymers for use in the process according to the invention are in particular thermoplastic polymers. In a preferred embodiment, the at least two polymer layers each contain at least 50 wt .-%, preferably at least 70 wt .-% and particularly preferably at least 90 wt .-%, each based on the polymer, polyolefins, for example polyethylene or polypropylene, polyvinyl polymers such as polyvinyl chloride, polyvinyl acetals, polyvinyl ethers, polyvinyl lactams or polyvinyl amines, styrene polymers, for example polystyrene, styrene-acrylonitrile copolymers, acrylonitrile-butadiene styrenes, polymers of

(Meth) acrylic acid, for example polyacrylic acid, poly (meth) acrylates, polyacrylates, polymethyl methacrylate, polyacrylamide, polycarbonates, polyoxymethylene, polyphenylene ethers, poly tetrafluoroethylene, polyphenylene sulfide, polyether sulfones, polyether ketones, polyimides, polyquinoxalines, polyquinolines, polybenzimidazoles, polyamides, polyesters or polyurethanes such as polyisocyanates, polyols, polyether polyols or polyester polyols or mixtures thereof. Particularly preferred are polyamides and polyesters such as polybutylene terephthalate.

Preferred polyamides are PA6, PA12, PA4.6, PA66, PA6.10, PA6.12, PA10.10, PA12.12, PA13.13, PA6.T, PA9.T, PA MXD.6, PA6 / 6.6, PA6 / 6.T, PA6.I / 6.T, PA6 / 6.6 / 6.10, also known as nylon-6, nylon-6.6, nylon-4.6, nylon-6T-copolyamides and nylon-6 / 6.6. To adjust the properties of the finished part, the at least two polymer layers may contain additives. These are, for example, stabilizers, lubricants, nucleating agents, dyes, hardeners, plasticizers, blends with other polymers or any other additives known to the person skilled in the art. In a preferred embodiment, the at least two polymer layers contain the same polymer as the matrix material. Alternatively, finished parts can also be produced from a plurality of fiber-reinforced polymer layers containing different polymers as matrix material. In a preferred embodiment, the polymer layers are reinforced with a fibrous structure, wherein the fibrous structure is preferably a woven, knitted, knitted, braided, scrim, nonwoven or unidirectional or bidirectional fiber structure of parallel fibers or disordered fibers, yarns, threads or yarns Includes ropes. The fiber structures of the various polymer layers can be arranged parallel to one another, non-oriented or rotated relative to one another. Particularly preferably, the fiber structures are in the form of woven or layered layers of fibers, yarns, threads or ropes.

If layers or layers of parallel aligned fibers, yarns, threads or ropes are used rotated relative to each other, the individual layers are particularly preferably rotated by the angle of 90 ° to each other (bidirectional structure). When using three layers or a multiple of three layers, it is also possible to arrange the individual layers rotated by an angle of 60 ° to each other and rotated at four layers or multiples of four layers by an angle of 45 ° to each other. Furthermore, it is also possible to provide more than one layer of fibers with the same orientation. In this case, layers may likewise be twisted relative to each other, wherein the number of layers with fibers of the same orientation may be different in each of the orientations of the fibers, for example four layers in a first direction and one layer in a direction rotated for example by 90 ° (bidirectional structure with preferred direction). Furthermore, a quasi-isotropic structure is known in which the fibers of a second layer are rotated by 90 ° to the fiber of a first layer and further fibers of a third layer rotated by 45 ° to the fibers of the second layer. Preferably, all fibers have the same direction. In a preferred embodiment, fibers of the fiber structure are carbon fibers, glass fibers, aramid fibers, metal fibers, polymer fibers, potassium titanate fibers, boron fibers or mineral fibers, for example basalt fibers. Particularly preferred are glass fibers and carbon fibers.

The proportion of fibers based on the total volume of the semifinished product structure is preferably up to 70% by volume.

Finished parts that can be produced in this way are, for example, parts of vehicle bodies, structural components for vehicles, such as floors or roofs, component components for vehicles, such as mounting brackets, seat structures, door linings or interior linings. The manufactured finished parts can be used for bulkheads, battery carriers, side impact beams, bumper systems, structural inserts or pillar reinforcements in motor vehicles or also for side walls, structural fenders or side members in vehicle bodies. Likewise, the finished parts are also suitable as components for wind turbines or rail vehicles.

Examples Comparative Example

Two fully multi-layer consolidated semi-finished structures were heated in an infrared radiation field to 260 ° C and processed in a component tool by pressing each to a finished part. Both semi-finished structures each comprised six polymer layers, each of which was fiber-reinforced. The polymer used was PA6. In the first semifinished structure, four polymer layers were aligned in parallel with respect to their fiber reinforcement, and the two outer polymer layers were parallel to each other and offset by 90 ° from their adjacent layers. In the second semifinished product structure, a total of four polymer layers were aligned in parallel. The two externally calculated second of the six layers were parallel to each other and offset from the adjacent layers by 90 °. It was overmoulded with PA6-GF35. The finished parts had a thickness of 1, 5 mm.

Prefabricated parts with optically good surface and good mechanical properties were produced.

example

Three multi-layer semi-finished structures, whose polymer layers were arranged loosely on top of each other, were heated in an infrared radiation field to 260 ° C and processed in a component tool by pressing to a finished part. The polymer used was PA6. Before pressing, the temperature of 260 ° C was maintained between 2.5 minutes and 3 minutes. The semi-finished structures each comprised six polymer layers, each of which was fiber-reinforced. In all semi-finished product structures, four polymer layers were aligned parallel with regard to their fiber reinforcement and the two outer polymer layers were mutually parallel and offset by 90 ° relative to the adjacent layer. It was overmoulded with PA6-GF35. The finished parts had a thickness of 1, 5 mm.

Although, in contrast to the comparative example, a complete consolidation of the multilayer preform structure upstream of the finished part production was dispensed with, finished parts were produced which had optical and mechanical properties which were as good as the properties of the finished parts of the comparative example.

Claims

claims

A method for producing prefabricated parts from at least one multilayer, fiber-reinforced, flat semi-finished construction, comprising the following steps: a) heating the at least one multilayer, fiber-reinforced, flat semi-finished construction at ambient pressure to a first temperature T _a , wherein the at least one multilayer, fiber-reinforced, flat semi-finished construction comprises at least two superimposed polymer layers and the individual polymer layers are each fiber-reinforced and are not materially interconnected or only partially cohesively interconnected and the first temperature T _a in the event that at least one of the polymer layers contains a semi-crystalline polymer is higher than one Melting temperature Ts of the crystalline polymer according to DIN EN ISO 1 1357-3: 2013-04, and the first temperature T _a in the event that the at least two polymer layers do not contain a semi-crystalline polymer, is higher than a G lübergangstemperatur T _g according to DIN EN ISO 1 1357-2: 2013-09 of a polymer which is contained in at least one of the at least two polymer layers, b) pressing the heated at least one multilayer, fiber-reinforced, flat semi-finished construction to a finished part at a second temperature Tb and a pressure pb of at least 3 bar.

A method according to claim 1, characterized in that before step a) less than 80% of an area of the first polymer layer, wherein the surface is directed in the direction of the second polymer layer, are positively connected to the second polymer layer.

A method according to claim 1 or 2, characterized in that each of the at least two polymer layers is fully consolidated in each case.

A method according to claim 3, characterized in that the at least two polymer layers before step a) are each fully consolidated by pressing at a temperature T _v in the range of 240 ° C to 280 ° C and a pressure P _v of more than 5 bar.

Method according to one of claims 1 to 4, characterized in that the first temperature T _a in step a) is maintained at ambient pressure for a duration of at least 5 seconds.

Method according to one of claims 1 to 5, characterized in that the second temperature Tb is equal to or higher than the first temperature T _a .

7. The method according to any one of claims 1 to 6, characterized in that step b) directly to step a) follows.

8. The method according to any one of claims 1 to 7, characterized in that the finished part is additionally encapsulated or back-injected in step b).

9. The method according to any one of claims 1 to 7, characterized in that step b) is followed by a step c), in which the finished part is molded or injected behind or elements are molded onto the finished part.

10. The method according to any one of claims 1 to 9, characterized in that the heating takes place without contact.

1 1. Method according to one of claims 1 to 10, characterized in that the heating takes place by means of infrared radiation or in a convection oven.

12. The method according to any one of claims 1 to 1 1, characterized in that in step b) a thickness of the finished part is adjusted by pressing to a range of 1 mm to 4 mm or is followed by step b), a further step, in which the thickness of the finished part is adjusted to a range of 1 mm to 4 mm by pressing.

13. The method according to any one of claims 1 to 12, characterized in that the at least two polymer layers in each case at least 50 wt .-%, based on the polymer, polyolefins, polyvinyl polymers, styrene polymers, acrylonitrile-styrene copolymers, Acrylonitrile butadiene styrenes, polymers of (meth) acrylic acid, polymethyl methacrylates, polyacrylates, polyacrylamides, polycarbonates, polyphenylene ethers, polyphenylene sulfides, polyether sulfones, polyether ketones, polyimides, polyquinoxalines, polyquinolines, polybenzimididazoles, polyamides, polyesters, polyurethanes or mixtures thereof.

14. The method according to any one of claims 1 to 13, characterized in that the at least two polymer layers contain the same polymer as the matrix material.

15. The method according to any one of claims 1 to 14, characterized in that the at least two polymer layers are each reinforced with a fiber structure, wherein the

Fiber structure preferably comprises a woven fabric, a knitted fabric, a scrim, a non-woven or an unidirectional or bidirectional fiber structure of continuous fibers or disordered fiber. A method according to claim 15, characterized in that fibers of the fiber structure are carbon fibers, glass fibers, aramid fibers, metal fibers, polymer fibers, potassium titanate fibers, boron fibers or mineral fibers.