Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2000-05-18
2002-11-26
Nutter, Nathan M. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S412000, C428S423700, C428S424200, C428S424800, C428S425900, C428S403000, C428S404000, C428S405000, C428S406000, C428S407000, C525S467000, C525S452000
Reexamination Certificate
active
06485836
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to composite materials comprising at least two different layers of plastics material which are directly bonded to each other, wherein one layer comprises polyurethane and the layer which is directly bonded thereto comprises a thermoplastic plastics material which is different than the polyurethane layer.
It is known that composites comprising a thermoplastic material and a polyurethane, particularly a polyurethane foam, do not exhibit satisfactory bonding of the composite. In particular, this is because unreacted, low molecular weight reaction components segregate at the interfaces between the layers as residues from the production of the plastics materials. Accordingly, there have been numerous attempts aimed at improving the bonding of composites by the use of bonding agent layers. This is not desirable, however, for uses in the motor vehicle industry, where composite materials are increasingly being employed, since as few as possible different materials should be used in this area on account of the options for reprocessing and recycling which are required.
Therefore, one object of the present invention was to improve the composite bonding between a layer of polyurethane and a layer of a thermoplastic material which is directly bonded thereto.
This object is achieved according to the invention by the provision of a composite material which comprises at least two layers which are directly bonded to each other, comprising
A) one layer comprising polyurethane,
and
B) a second layer which is directly bonded to the polyurethane layer A) and comprises a thermoplastic plastics material which is different than the polyurethane layer A),
wherein layer A) contains homogeneously distributed particulate material having a particle size within the range of ≦50 nm, preferably within the range of from 1 to 10 nm, and the particles are at least coated with a thermoplastic plastics material which is different from A), preferably with the thermoplastic plastics material of layer B), and the total surface area of the particles corresponds at least to the extent of the total interface between layers A) and B).
The particles can comprise a core of what is preferably an inorganic material, most preferably comprising at least one oxide, hydrated oxide, nitride or carbide of silicon, aluminium, titanium, zirconium, cerium or bromine, particularly as Al
2
O
3
, SiO
2
, CeO
2
, ZrO
2
, TiO
2
or titanium nitride, wherein the core can optionally have a porous structure.
The core most preferably consists of SiO
2
or Aerosil, which optionally has a porous structure with a smooth surface.
The core is coated with a thermoplastic plastics material which is different from the material of layer A), i.e. the polyurethane layer, and is preferably coated with the thermoplastic plastics material which forms the basis of layer B). A polycarbonate of the type described below is most preferably used here as the thermoplastic plastics material.
The particles can also consist of a plastics material which is completely different from layer A), i.e., the polyurethane layer, and preferably consist of a plastics material which is identical, at least in part, to layer B). The particles most preferably consist essentially of polycarbonate, polyester carbonate or poly(meth)acrylates of the type described below.
The particles have a size ≦50 nm, preferably within the range of from 1 to 10 nm. The particle size is determined by known methods, such as, for example, transmission electron microscopy, sedimentation using ultracentrifuges, light scattering, or Fraunhofer diffraction.
The total surface area of the particles, as determined by nitrogen adsorption isotherms using the BET method, should correspond at least to the interfacial area between the bonded layers A) and B). The surface area of the particles is preferably greater than the extent of the interfacial area between layers A) and B), more preferably at least 10 times greater than the interfacial area, and most preferably 100 times greater than the interfacial area, provided that there is no discernible impairment of the mechanical properties of the composites.
The polyurethanes or polyurethane-ureas which are used as layer A) in accordance with the present invention are obtained by the reaction of one or more polyisocyanates with one or more polyfunctional compounds which contain active hydrogen, preferably polyols.
The preferred polyisocyanates are those which are known from polyurethane chemistry and which are customarily used therein. In particular, these comprise polyisocyanates with an aromatic basis, e.g. 2,4-diisoyanatotoluene and industrial mixtures thereof with 2,6-diisocyanatotoluene, 4,4′-diisocyanatodiphenylmethane and mixtures thereof with the corresponding 2,4′- and/or 2,2′-isomers, polyisocyanate mixtures of the diphenylmethane series, such as those which can be obtained in the known manner by the phosgenation of aniline/formalde-hyde condensates, modified products of these industrial polyisocyanates which contain biuret or isocyanate groups, and particularly NCO prepolymers of the aforementioned type which are based firstly on said industrial polyisocyanates and secondly on the simple polyols and/or polyether polyols and/or polyester polyols which are described below as component, as well as any mixtures of isocyanates of this type provided that they are sufficiently stable on storage.
Amongst the high molecular weight, modified polyisocyanates, the prepolymers which are known from polyurethane chemistry, which comprise terminal isocyanate groups and which have number average molecular weights ranging from 400 to 10,000 g/mol, preferably from 600 to 8000 g/mol, are of particular interest. These compounds are produced in the known manner by the reaction of excess amounts of simple polyisocyanates of the type cited above by way of example with organic compounds comprising at least two groups which are capable of reacting with isocyanate groups, particularly organic polyhydroxyl compounds. Suitable polyhydroxyl compounds of this type include both simple polyhydric alcohols having number average molecular weights in the range of 62 to 599, preferably 62 to 200, such as ethylene glycol, trimethylolpropane, 1,2-propanediol, 1,4-butanediol or 2,3-butanediol, and relatively high molecular weight polyether polyols and/or polyester polyols of the type known from polyurethane chemistry, having number average molecular weights of from 600 to 8000, preferably 800 to 4000, and which contain at least two, generally 2 to 8, preferably 2 to 4, primary and/or secondary hydroxyl groups. NCO prepolymers can also of course be used which are obtained, for example, from low molecular weight (number average) polyisocyanates of the type cited by way of example and from less preferred compounds which contain groups that are capable of reacting with isocyanate groups, such as polythioether polyols, polyacetals which contain hydroxyl groups, polyhydroxy polycarbonates, polyester amides which contain hydroxyl groups, or copolymers, which contain hydroxyl groups, of olefinically unsaturated compounds.
The compounds disclosed in U.S. Pat. No. 4,218,543, the disclosure of which is herein incorporated by reference, are examples of suitable compounds which contain groups which are capable of reacting with isocyanate groups and which are suitable for the production of NCO prepolymers. During the production of these NCO prepolymers, these compounds which contain groups capable of reacting with isocyanate groups are reacted with simple polyisocyanates of the type cited above by way of example, while maintaining an excess of NCO. The NCO prepolymers generally have an NCO content of 10 to 25% by weight, preferably 15 to 22% by weight. It follows from this that, in the context of the present invention, the expressions “NCO prepolymers” and “prepolymers comprising terminal isocyanate groups” are to be understood to comprise both the reaction products as such and mixtures thereof with excess amounts of unreacte
Kempkes Flore
Köhler Burkhard
Reihs Karsten
Warth Holger
Bayer Aktiengesellschaft
Bissett Melanie
Brown N. Denise
Gil Joseph C.
Nutter Nathan M.
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