EP2214838A1

EP2214838A1 - Apparatus and method for producing reinforced composite polyurethane materials

Info

Publication number: EP2214838A1
Application number: EP08842572A
Authority: EP
Inventors: Detlef Mies; Andreas Frahm; Hans-Guido Wirtz
Original assignee: Bayer MaterialScience AG
Current assignee: Bayer Intellectual Property GmbH
Priority date: 2007-10-24
Filing date: 2008-10-16
Publication date: 2010-08-11
Also published as: BRPI0818026A2; WO2009052990A1; DE102007051129A1

Abstract

The invention relates to an apparatus and a method for producing fibre- and/or particle-reinforced composite polyurethane materials comprising at least one PU-spray mixing head with a defined spraying direction and at least one applicator for the directed application of fibres and/or solid particles, characterized in that the direction of emergence of the fibres and/or solid particles is spatially variable in relation to the spraying direction of the PU-spray mixing head.

Description

Apparatus and method for producing reinforced polyurethane composite materials

The invention relates to an apparatus and a method for producing reinforced polyurethane composite materials.

Spray methods for producing fiber or solid particle reinforced polyurethane composite materials have long been known. The preparation of such materials usually takes place in such a way that the fibers or solid particles used for the reinforcement, preferably compressed air-assisted, are laterally directed into the spray jet of the PUR reactive mixture via a funnel-shaped applicator firmly connected to the PU spray mixing head.

In the case of fiber-reinforced materials are used as starting material usually called rovings, that is bundles of endless, untwisted, stretched fibers, which initially pass an optionally also attached to the PUR spray mixing head cutting before the cut fibers are then then fed to the chute.

In spray processes of this type, the most uniform possible distribution of the fiber / particle PUR reaction mixture, usually over several layers, on the mold surface or the substrate carrier is sought. In applications with a high reproducibility claim, the spray mixing heads and the chute are therefore guided by robots.

With the device and the method, the solid particles are wetted substantially on all sides with a polyurethane reactive mixture, which leads to a significant increase in viscosity and thixotropy of the polyurethane reaction mixture. This in turn causes the polyurethane Reactive mixture without bleeding on slopes or even on vertical surfaces can be applied.

Also important is the effect that the mixture due to the viscosity increase and thixotropic penetration through a nonwoven fabric slower, so that can be adjusted on the solids content, how much polyurethane reactive mixture remains on the surface and how much penetrates into the interior of the composite component. By this additional degree of freedom, the optimum compromise between sufficient bonding of the composite, low weight and good surface of the structural element can be achieved.

The filler also has a positive influence on the microstructure on the surface of the structural element. The flow behavior of the pure polyurethane reactive mixture on the substrate, which contains, for example, a fiber fleece, is comparable to the flow of a liquid through a bed. The gravity or the pressure difference, which is applied by the closing of the tool, leads to a flow of the liquid through the bed (the nonwoven fabric).

At the surface, the liquid does not form a planar surface to the atmosphere because of the fiber structure; instead, the polyurethane reactive mixture forms an inhomogeneous surface due to the interaction of boundary or surface tensions to the fiber material and the air and the flow behavior. This causes air bubbles between the fibers.

The wetted with the polyurethane reactive mixture, fine-grained filler can better fill these spaces on the surface and thereby significantly improve the microstructure on the surface. This is achieved on the one hand by the increased viscosity due to the higher viscosity and on the other hand due to the breaking of the interface between Reactive mixture, air and fibers through the solid particles. As a result, the tendency to form a curved surface between the fibers at the surface due to the interfacial forces is significantly lower.

A particular effect which occurs in the process is that in the reaction of the thixotropic PUR reactive mixture during the molding process in a press, the PUR reactive mixture penetrates into the at least one nonwoven fabric and wets all the fibers which then stick together which are bonded with polyurethane. Reactive mixture wetted solid particles, however, are filtered off by the at least one nonwoven fabric to some extent and hang on the surface of the at least one nonwoven fabric and thereby fill all the gaps between the individual fibers. In this way, high-strength, easy-to-construct construction elements with a perfect, homogeneous surface and perfect formation of the desired contours, without having to make additional rework or lamination.

WO 2007/073825 also describes a spray head for spraying solid particles laden polyurethane reactive mixture, comprising

a) at least one spray mixing head for the polyurethane reactive mixture containing a spray nozzle for the polyurethane reactive mixture, and

b) at least one first channel section for pneumatically conveying the solid particles, comprising an inlet opening for a gas stream and a substantially concentrically arranged in the first channel section suction nozzle for the solid particles, wherein the direction of flow extended center of gravity of the first channel section and the spray nozzle in the spray nozzle extended axis of the spray form an angle α in the range of 10 ° to 120 °, and - A -

c) at least one second channel section for pneumatically conveying the solid particles, into which the first channel section opens, wherein the direction of flow extended center of gravity of the first channel section and the direction of flow extended axis of gravity at the outlet opening of the second channel section an angle ß in the range of 60 ° to 170 And wherein the outlet opening of the second channel section is disposed substantially in the immediate vicinity of the spray nozzle for the polyurethane reactive mixture and is substantially aligned with the area of the spray jet emerging from the spray nozzle for the polyurethane reactive mixture.

This ensures that the emerging from the discharge opening of the second channel section stream of solid particles in the spray jet from the spray nozzle for the polyurethane reactive mixture opens. As spray mixing heads, it is possible to use customary PUR mixing heads which work according to the high or low pressure mixing method. Round or flat jet spray nozzles can be adapted to these mixing heads by means of pressure or air atomization.

A serious disadvantage of a fixed side mounting of the applicator on the PUR spray mixing head as in the prior art is the geometric dependence of the entry of the fibers / particles in the spray of the direction of movement of the robot, which in turn varying wetting of the fibers / particles depending on the way of the spray mixing head (Fig. 1). Depending on the mounting side of the applicator member or the direction of movement of the PUR spray mixing head, the fibers / particles are either detected by the PUR spray jet and sprayed by the subsequent reaction mixture, or conveyed into the advance moving spray.

Fibers / particles (Fig. 1, direction of movement to the right) oversprayed by the following reaction mixture show a significantly more intense Wetting on the (upper) side facing the PUR spray mixing head. On the other hand, the side of the rovings facing the mold or the substrate carrier can have a much lower wetting and therefore generally insufficient wetting, which very often results in later marks or voids being formed on decorative layers.

Part of the fibers / particles which are to be conveyed into the advancing spray jet (FIG. 1, direction of movement to the left) are detected and deflected by the air flow of the PUR spray jet. In such a case, a deposition of the fibers / particles takes place outside of the actual spray jet, whereby an insufficient fixation of the fiber / particle PUR reaction mixture takes place at the contact surface to the previously sprayed with the reaction mixture areas.

The degree of wetting of the fibers / particles is therefore directly related to the input conditions and has a significant influence on:

1. the mechanical properties

2. the surface quality

3. voids formation in the polyurethane layer

4. Marking of fibers on decorative boundary layers

5. the entry of the max. possible amount of glass.

Apart from the above-outlined dependency of the fiber / particle entry from the attachment of the applicator member or direction of movement of the PUR spray mixing head results in devices with a fixedly connected to a polyurethane spray mixing head applicator another problem, namely that of a difficult fiber / particle deposition in Radii (or cavities) and border areas of three-dimensional shapes. In order to be able to realize fiber / particle deposition down to the edge areas, the spray angle is adjusted to the cavity shape by turning the PUR spray mixing head over the robot. Nevertheless, often overspraying the cavity with inhomogeneous fiber distribution must be accepted. In some cases, complete wetting with fiber / reaction mixture is virtually impossible (Figures 2 and 3).

In the case of a fiber / particle deposit in the anticipated PUR reaction mixture (following the spray jet), the fibers are caught by the spray jet and pressed into the bottom of the cavities (FIG. 2) (partly this is also due to the fact that the fibers / Particles of gravity follow and "fall out of the spray" in this direction of movement).

With the same mounting situation of the application member, however, the entry behavior changes on the opposite half of the mold (FIG. 3). The pivoting of the PUR-spray mixing head and the now more favorable entry of Fa fibers / particles allows storage up high in the edge region of the cavity. The entering fibers / particles are fixed on the cavity over the entire beam range of the PUR reaction mixture without being pressed into the bottom regions of the mold.

It is therefore an object of the present invention to provide an apparatus which avoids the above-described problems of the prior art due to a fixed attachment of the applicator for the fibers / solid particles to the PUR spray mixing head. In particular, it is an object of the present invention to design a device to produce fibrous / solid particle reinforced PUR moldings (optionally composed of multiple layers) with reproducible deposition and wetting of the fibers / solid particles independent of the direction of movement of the PUR spray mixing head also possible with three-dimensional shapes.

The object underlying the invention is achieved in a first embodiment by a device for producing fiber and / or solid particle-reinforced polyurethane composite materials, which comprises at least one PU spray mixing head with a defined spraying direction and at least one applicator for the directed application of fibers and / or solid particles, characterized in that the outlet direction of the fibers and / or solid particles relative to the spray direction of the PUR spray mixing head spatially changed is.

In the context of the present invention, an applicator element is to be understood as meaning, in particular, an outlet channel for guiding the fibers, that is to say the cut rovings, and / or solid particles serving hollow bodies. This may for example be a (funnel-shaped) bed, but also, for example, a pipe or hose with at least one defined outlet opening. This applicator organ serves - preferably with the aid of compressed air - to guide the fibers / solid particles to be introduced into the PUR reactive material and gives them a defined outlet direction, either by the orientation of the applicator element itself or by the fiber / solid particle beam deflecting internals present in the applicator element ,

The change in the exit direction of the fibers and / or solid particles relative to the spray direction of the PUR spray mixing head in space is to be understood firstly in relation to the angle enclosed by these directional vectors (corresponding to a change in direction of a directional vector within that of this and the other Vector spanned level), for example, caused by a change in the alignment of the applicator member to the spray direction of the PUR spray mixing head.

On the other hand, this also includes changes in which the position of the plane spanned by two vectors changes in space.

Not according to the invention are in this context such changes in direction, resulting from a change in the exit velocity of the fibers / solid particles, that is with In other words, that a corresponding change of the vectors to each other must be possible at a constant exit velocity.

In this case, such changes of the outlet direction of the fibers / solid particles to the spray direction of the PUR spray mixing head, in which a movement of the vector of the discharge direction of the fibers / solid particles around the vector of the spray direction of the PUR spray mixing head around is possible, wherein the applicator member relative to the spray direction of the PUR reactive mixture runs on a circular path of 360 °, but at least 180 °. This movement can take place in such a way that the tip of one vector describes an ellipse or preferably a circular orbit around the other vector.

Furthermore, it is possible for the exit direction of the fibers / solid particles to be variable independently of a change in the spray direction of the PU spray mixing head with respect thereto. This is to be understood that a change in the discharge direction of the fibers / solid particles should be possible (regardless of, for example, a possible rotation of the PU spray mixing head around itself) in a constant position of the PUR spray mixing head (the above-described vectorial design is based).

It is also possible that the exit direction of the fibers / solid particles is variable independently of a movement of the PUR-spray mixing head. This can be achieved if a change in the direction of emergence of the fibers / solid particles for spraying the PUR spray mixing head is to be possible with PUR spray mixing head stationary in space, that is to say no movement. (However, this does not preclude the PUR spray mixing head in principle being able to move that is, for example, can be rotatable about its axis). The application member, in particular the outlet channel of the cutting unit or the blowing device is preferably directly or indirectly connected to the particular robot-controlled PUR-Sprisch mixing head. A direct connection here is to be understood as meaning a physical connection between the application device and the PU spray mixing head. This can be achieved, for example, in that the applicator member is attached to the PUR spray mixing head or is connected to it indirectly via connecting struts, spacers or a cutting unit (cf. for example FIG. 1). In the case of an indirect connection, although there is no direct attachment to the PUR spray mixing head, it is still a component connected to the PUR spray mixing head in the sense of the invention (for example to a robot arm). Characteristic of both a direct and an indirect attachment is therefore the fact that the applicator on the one hand and the PUR spray mixing head on the other side can not be performed independently.

In order to achieve the most uniform possible distribution of the reaction mixture of PUR reactive mixture on the one hand and fiber / solid particles on the other hand and to ensure a high reproducibility, it is preferable to attach the above device to a robot / robot arm. The usual control is then carried out accordingly by a conventional computer system.

In a second embodiment, the object underlying the invention is achieved by the use of the device as described above for the production of fiber or solid particle reinforced polyurethane composite materials.

In a third embodiment, the object underlying the invention is achieved by a process for the production of fibrous or solid particle-reinforced polyurethane composite materials, in which one uses the device described above and the applicator organ of Fibers / solid particles coupled to the direction of movement of the PUR spray mixing head. The adjustment of the exit direction of the fibers / solid particles to the direction of movement of the PUR spray mixing head is preferably carried out in such a way that the fibers / solid particles are introduced into the, trailing 'spray of the PUR spray mixing head (Fig. 1, direction of movement to the right). Because only this allows the reproducible production of fiber / particle-reinforced PUR moldings under uniform wetting of the fibers / particles even in demanding three-dimensional shapes. In particular, the method according to the invention is characterized in that the flow of the fibers / solid particles is controlled in a path-controlled manner relative to the spray jet of the PUR reactive mixture.

The amount of solid particles applied is preferably adjusted so that only as much solid particles are applied to the substrate as are required to balance uneven surfaces or broken edges or contracted stress points. The optimum amount of PUR reactive mixture and solid particles to be applied can be easily determined for the person skilled in the art by simple experiments in which different amounts of PUR reactive mixture and solid particles are applied to the substrate or composite element.

Particularly suitable solid particles are those having a granular or powdery structure with particle sizes in the range of preferably 5 .mu.m to 500 .mu.m. In this case, mixtures of different particle sizes are of particular importance, since in this way optimum packing densities are possible in order to compensate for irregular irregularities on the surface of the substrates. It has been shown that powders made of recycled, finely ground PUR foams, especially rigid foams, are suitable as particle mixtures. The comminution of the Ze 11 structures produces a particle mix size of preferably 10-30, eg about 20% by weight over 300 μm, 30-50, for example about 40% by weight over 100 μm and under 300 μm and 30-50 eg about 40% by weight below 100 μm (values determined by sieving). Fibers with number-average fiber lengths of preferably 5 μm to 500 μm and a diameter-length ratio of preferably 1.0 to 0.01 (rovings) are also suitable according to the invention. The microfibers preferably consist of the same material as the at least one substrate to be coated, in particular non-woven fabric. This results in homogeneous and at the same time fibrous surface structures. It is then especially important to ensure that broken edges compensate for composite elements with spacers (eg honeycomb core) or confiscated stress points, so as to achieve a perfect formation of the contours and wall thicknesses.

Also, platelet-shaped solid particles having number-average plate diameters (for example, as determined by microscopic analysis) of preferably 5 μm to 500 μm and thickness-to-diameter ratios of preferably 1.0 to 0.01 are suitable as solid particles in the process. In this way, special surface structures can be generated. For example, platelets made of glass or mineral are suitable for increasing the impression resistance of the surface.

As fibers, preferably glass, mineral, metal, plastic or natural products such. Hemp or jute can be used. In general, one will use especially those fibers / solid particles that are particularly light. Preference is therefore given to plastics. In order to achieve special surface effects, for example, metal powders are particularly suitable with which an optical Metallic effect is possible.

As solid particles and mixtures of different solid particles with respect to materials and / or structure and / or particle size distribution can be used. However, it is also possible to use mixtures of the same material and the same structure and of different volume-average particle size. Preferably, the fibers / solid particles are added to the stream of PUR reactive mixture before spraying and sprayed together with this on the substrate. In this way, the solid particles are optimally wetted on all sides. In addition, the desired thixotropy of the PUR reactive mixture acts directly, ie without any time delay.

However, it is also possible, especially for simple applications, to apply the fibers / solid particles only after spraying or wetting the substrate with the PUR reactive mixture onto the PUR reactive mixture or the nonwoven fabric. However, this subsequent application of the solid particles is then preferably carried out directly, i. without significant time delay after application of the PUR reactive mixture, so as to ensure the required thixotropation of the PUR reactive mixture in the time tolerance range.

The present invention will be illustrated and explained by way of example with reference to embodiments shown in FIGS. 4-7. Show it:

1 shows a device for the production of reinforced polyurethane composite materials of the prior art, comprising a rigidly connected via a cutting with the PUR spray mixing head applicator (in this case, a funnel-shaped bed).

Fig. 2, 3: problems arising during the spraying of cavities with a device of the prior art.

Fig. 4a, b show schematic illustrations of a device according to the invention in side view and plan view, comprising a PUR- spray mixing head and a pivotally mounted on this combination consisting of a cutting unit and a funnel-shaped chute. This construction ideally allows optional positioning of the header-bed combination over the pivoting range of the Device, wherein preferably the pivot drive is designed as the 7th axis of the robot and thus the fiber / solid particles entry into the PUR spray with the movements of the robot can be tuned.

FIGS. 5 and 6 show the principle of a device according to the invention.

For example, as shown in FIG. 5, when the PUR spray mixing head is moving to the left, the combination of cutter and bed is also on the left side (position A) to allow entry of the fibers / particles in the 'trailing' PUR spray, which, as discussed above (see discussion regarding FIG. 1) results in better wetting of the fibers / solid particles. If the direction of movement of the PUR spray mixing head now changes to the right (rotation through 180 °), the cutting unit-bed combination (computer-controlled) also swivels to the right in order to be able to maintain the entry direction of the fibers / particles in the PUR spray jet unchanged. Regardless of the change made by the robot change the direction of movement of the spray head can thus be done by a corresponding pivoting of the cutting unit-bed combination of the fiber / particle entry under constant conditions.

The advantages of this device according to the invention in the spraying of cavities, as shown in FIG. 6, are particularly evident. The combination of cutting unit and bed is always located above the PUR spray jet, so that a fiber / solid particle entry can take place up to the outer edge of the cavities. The wedge-shaped entry of the fibers / solid particles between the cavity and spray jet also allows a fiber deposit or fixation in even extremely steep form and radius areas. In total, therefore, the pivoting of the cutting unit-bedding combination enables an absolutely symmetrical fiber distribution of both mold halves.

Similar to Fig. 6, Fig. 7 shows a particular type of mixing head guide on flat surfaces where the inclination of the PUR spray mixing head produces a larger entrance surface (projected ellipse) for the incoming fibers, thereby overcoming conventional techniques (perpendicular to the surface ) also significantly larger quantities of fiber or solid particles can be processed.

Claims

claims

1. A device for the production of fiber and / or particle-reinforced polyurethane composite materials comprising at least one PUR- spray mixing head with a defined spray direction and at least one applicator member for the directed application of fibers and / or solid particles, characterized in that the exit direction of the fibers and / or solid particles is spatially variable relative to the spray direction of the PUR- spray mixing head.

2. Apparatus according to claim 1, characterized in that the outlet direction of the fibers and / or particles is spatially variable relative to the spray direction of the polyurethane spray mixing head at a constant exit velocity of the fibers / solid particles.

3. Device according to one of claims 1 or 2, characterized in that the change of the exit direction of the fibers / particles to the spray direction of the PUR-spray mixing head runs on a circular path.

4. Device according to claim 1, characterized in that the exit direction of the fibers / solid particles is variable independently of a change in the spray direction of the PU spray mixing head with respect thereto.

5. Device according to one of claims 1 to 4, characterized in that the outlet direction of the fibers / solid particles is independent of a movement of the PUR-spray mixing head changeable.

6. Device according to one of claims 1 to 5, characterized in that the application member is directly or indirectly connected to the polyurethane spray mixing head.

7. Device according to one of claims 1 to 6, characterized in that it is part of a robot or a robot arm.

8. Use of a device according to any one of claims 1 to 7 for the production of fiber or particle reinforced polyurethane composite materials.

9. A process for the production of fiber or particle-reinforced polyurethane composite materials, wherein a PUR reactive mixture on a spray head on the one hand and fibers / solid particles on the other hand from an exit member to a substrate sprayed, characterized in that the flow of fibers / solid particles relative to Spray jet of PUR reactive mixture changed path-controlled.

10. The method according to claim 9, characterized in that between the exit direction of the fibers / particles and the surface to be sprayed an angle w in a range of 0 ° <w <90 °, preferably 20 ° <w <70 °, adjusts.