Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2002-04-10
2004-02-24
Seidieck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S114000, C256S013000
Reexamination Certificate
active
06696160
ABSTRACT:
The invention relates to composite components constructed of a layer i) having a paintable surface and comprising short fiber reinforced polyurethane and a layer ii) comprising long fiber reinforced polyurethane and to a process for producing them and to their use as exterior bodywork parts.
Composite components made of polyurethane (PU below) are diverse materials whose applications include use as exterior bodywork parts on account of the fact that, as compared with the conventional, metal components, they possess, for example, a lower weight. Stringent requirements are imposed on these components, however, with respect for example to their stiffness and visual surface qualities.
EP-A-995 667, WO 98/29233 and DE-A-197 32 425 describe the production of composite components constructed of a thermoplastic film which is foam backed with long glass fiber reinforced polyurethane. To produce colored components, a pigmented film is used. At present, however, it is not possible to produce these composite components with surface qualities which correspond to those of a high-quality paint finish (class A surface) or which make online painting possible, in particular. (Normal painting of the PFM film is unproblematic, but the aim when using PFM is to achieve an A class surface, including color matching to the rest of the vehicle, without painting.)
DE-A-198 08 026 describes components made of polyurethane (PU) for the exterior automotive sector: in a first workstep, a fiber reinforced, rigid PU foam core is produced and in a second workstep this core is overcast with a compact PU coating so as to give the basis for the class A surface which is produced by subsequent painting. These components are used, for example, as hardtops for cabriolets. A disadvantage with this process is the relatively high reject rate which arises owing to defects when applying the compact coating. Refinishing the defects is impossible owing to incompatibility of the repair sites (shrinkage of the refinish compound). A further disadvantage of the disclosed process is that the coating must be highly elastic and therefore soft in order to compensate the differences in expansion between core and coating when the temperature fluctuates. If it did not do so, a fine texture would become visible in the surface as soon as the parts cooled after demolding, and this texture would become more pronounced after painting, normally at 80-100° C. Online painting, normally 1 h at 180° C., is not possible owing to the low glass transition point of the elastic coating. A soft surface, however, harbors numerous disadvantages—for example, it is very sensitive to scratching.
It is an object of the present invention to provide composite components made of polyurethane for use as exterior bodywork parts from which the above-indicated disadvantages are absent. Accordingly, the invention intends to provide composite components which combine good mechanical properties such as high stiffness and heat distortion resistance, for example, with a surface which is not only paintable, preferably online, so that a class A surface may be obtained after painting, but which also has the required hardness in order to minimize greatly its sensitivity to scratching. A further object of the invention is to provide a process for producing said composite components that has technical and economic advantages.
We have found that these objects are achieved by a composite component comprising a layer of short fiber reinforced PU with a paintable surface, as the coating, and a layer of long fiber reinforced PU, as the support, and by a process for producing said composites by introducing first the coating and then the support into a mold.
The invention accordingly provides a composite component constructed of a layer i) having a paintable surface and comprising short fiber reinforced PU and a layer ii) comprising long fiber reinforced polyurethane.
The invention further provides a process for producing composite components constructed of a layer i) having a paintable surface and comprising short fiber reinforced PU and a layer ii) comprising long fiber reinforced PU, comprising the following steps:
A) introducing layer i) into a mold, with the paintable surface facing the mold wall, and then
B) applying layer ii) to layer i) by the LFI technique, and demolding the component.
The invention lastly provides for the use of the composite components of the invention to produce exterior bodywork parts.
The composite components of the invention comprise two layers. Layer i) of the composite component of the invention comprises short glass fiber reinforced polyurethane having a paintable surface, and serves as a coating, which covers at least one side of layer ii), comprising a long fiber reinforced polyurethane that functions as a strengthening support.
A paintable surface in the context of this invention is a surface whose qualities are such that it constitutes a high-grade optical surface after painting. There must accordingly be no visible defects, depressions and/or unevennesses, such as waviness. By paintable is meant preferably that, after painting, a class A surface can be obtained.
A class A surface is a surface which appears to be of high optical quality when viewed. In assessing the height of the quality, account may be taken of coarse and fine textures, defects and/or gloss.
A class A surface preferably has little coarse texturing, i.e., there are very few extruder marks, for example, and the surface has a very high distinctness of image (DOI). A class A surface should also have very little fine texturing, i.e., there should be very little perceptible fine texturing of the type known in the art as orange peel.
Additionally, a class A surface has very few defects. By defects are meant, for example, bubbles, inclusions, and scratches, and a distinction may be made between large and small defects. Small bubbles and inclusions have a diameter of from 0.2 to 0.5 mm, large bubbles and inclusions a diameter of from 0.5 to 1 mm. Small scratches have a depth of not more than 0.03 mm and a length of not more than 0.1 mm, large scratches a depth of not more than 0.03 mm and a length of not more than 6 mm. In one preferred embodiment of a class A surface, the minimum distance between two large defects is 150 mm and/or there are not more than 2 small defects in a radius of 150 mm around a large defect and/or there are not more than 4 small defects within a radius of 150 mm around a small defect.
A class A surface ought to have a very high gloss. In one preferred embodiment the surface has a gloss of 80 units (GU) at a viewing angle of 20°, measured in accordance with DIN 67530.
The quality of being paintable also means that the surface has qualities which allow online painting to be carried out. For this it is necessary for the composite component, and in particular the surface of the layer i), to have a dimensional stability under heating of at least 1 hour at up to 180° C., where appropriate at up to 200° C.
Online painting embraces the mounting of the exterior bodywork parts onto the so-called body in white (metal body), which then traverses the following process steps: cleaning—phosphating—electrocoating with baking (170°-210° C.)—underbody protection (110-150° C.)—surfacer coat, hard (130-160° C.)—basecoat/clearcoat, hard (130-140° C.)—quality control—final assembly. With inline painting, the separately primed component is mounted onto the body before the basecoat is applied. With offline painting the fully painted component is brought to the line for final assembly. The highest thermal load occurs during the baking of the electrocoat. The moldings must not undergo significant dimensional change nor significant changes in material properties.
Layer i), which has a paintable surface, ought also to be of a quality such that it is very largely insensitive to external mechanical influences such as impacts and scratches, for example. Accordingly, layer i) has a hardness of preferably 50 Shore D, more preferably 60 Shore D, with particular preference 65-70 Shore D.
The p
Bauer Michael
Fader Michael
Fritz Ralf
Partusch Georg
Pöltl Jörg
BASF - Aktiengesellschaft
Bissett Melanie
Borrego Fernando A.
Seidieck James J.
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