Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-06-21
2003-07-08
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S243000, C156S280000, C525S071000
Reexamination Certificate
active
06589378
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to laminated sheets or films, to processes for their production, to their use for producing moldings, to processes for producing the moldings and to moldings thereof.
2. Description of the Related Art
When plastics are used outdoors where they are subjected to weathering and, in particular, to UV radiation, high standards are required in terms of UV stability and weatherability. Especially when they are used in exterior bodywork parts in the automotive sector, high requirements are also set for other mechanical properties, such as the low-temperature impact strength, as well as for the visual quality. The processes and materials employed at present do not always meet these conditions.
Bodywork parts made from plastics are, for example, topcoated or mass-colored and clearcoated. Topcoating in this case requires high heat deformation resistance, which is a requirement met by only a few plastics. Mass coloring, especially using special-effect pigments, is very costly and in many cases lessens the mechanical properties of the substrate.
Instead of spray coating it is possible to use other coating processes, such as the backspraying technology. In this, coating films are produced by roller coating or intaglio printing processes and are backsprayed or backmolded with support materials.
J. H. Schut in Plastics World, July 1996, pages 48 to 52 describes the use of such coating films in the production of automotive components. Polyvinylidene fluoride films and polyvinyl fluoride films are described which are employed in conjunction with ABS as substrates. Polyvinylidene fluoride/acrylate films are also mentioned. Thermoplastic olefins can also be employed as substrates. Production techniques specified are thermoforming, thermoforming in conjunction with injection molding, and injection molding alone.
EP-B1-0 361 823 describes films of this kind which consist of fluoro polymers or mixtures thereof with acrylates. They are backmolded with curable, filler-reinforced polyester compositions. The layers can also comprise acrylonitrile-butadiene-styrene (ABS) copolymers.
To date, all known backspraying films have been used only for effect finishes and multicolored decoration, since the films are very costly.
U.S. Pat. No. 5,192,609 describes coating films for the roller coating of a thermoplastic support material. Films with up to six layers are applied to a substrate. Besides polyolefins, the substrates mentioned include ABS and polyvinyl chloride.
The topmost layer used is a clear coating which consists of a polymeric, crosslinkable two-component mixture, based for example on polyols.
EP-B-0 522 240 describes multilayer polymer film laminates which have a top layer based on polyvinylidene fluoride or polymethyl methacrylate and a substrate comprising a polyolefin. The coextrusion of the top layer with subsequent extrusion-coating with the support material or further layers is described.
Another known bodywork material comprises coextruded sheets of polymethyl methacrylate (PMMA) and ABS. For example H. Kappacher, in Kunststoffe 86 (1996), pp. 388 to 392, describes coextruded PMMA/ABS laminated sheets. The bodywork parts are produced by coextrusion through a slot die to form sheets, which are subsequently thermoformed. In some applications, however, the thermal aging resistance of the ABS is inadequate. In order to protect the ABS or ABS/PC against UV light it is necessary to employ relatively thick UV-absorbing PMMA top layers. The impact strength can also be inadequate, lessened as it is by the brittle PMMA top layer. Furthermore, the surface gloss decreases sharply at draw ratios of 1:2 and above.
The coextrusion process using a slot die is described, for example, in EP-A2-0 225 500.
It is an object of the present invention to provide laminated sheets or films and moldings thereof which are of superior UV stability and thermal aging resistance as compared with known sheets, films or moldings. Moreover, high draw ratios should be possible without detriment to the surface gloss. It should be possible to produce the moldings at favorable cost. The products, furthermore, should be of enhanced elongation at break, low-temperature impact strength and scratch resistance and of increased penetration resistance.
We have found that this object is achieved in accordance with the invention by means of laminated sheets or films comprising
(1) a substrate layer comprising—based on the sum of the amounts of components A and B and, if used, C and/or D, which totals 100% by weight—
a 1-99% by weight of a graft copolymer of
a1 1-99% by weight of a particulate graft base A1 comprising the following monomers:
a11 80-99.99% by weight of at least one C
1-8
-alkyl ester of acrylic acid as component A11,
a12 0.01-20% by weight of at least one polyfunctional crosslinking monomer as component A12;
a2 1-99% by weight of a graft A2 comprising the following monomers, based on A2:
a21 40-100% by weight of units of styrene, a substituted styrene or a (meth)acrylate, or mixtures thereof, as component A21 and
a22 up to 60% by weight of units of acrylonitrile or methacrylonitrile as component A22;
the graft A2 consisting of at least one graft shell and the graft copolymer having a mean particle size of 50-1000 nm,
as component A,
b 1-99% by weight of a copolymer of
b1 40-100% by weight of units of styrene, a substituted styrene or a (meth)acrylate, or mixtures thereof, as component B1,
b2 up to 60% by weight of acrylonitrile or methacrylonitrile as component B2,
as component B,
c 0-80% by weight of polycarbonates as component C, and
d 0-50% by weight of fibrous or particulate fillers or mixtures thereof as component D, and
(3) a transparent top layer of polymethyl methacrylate.
The object is also achieved by laminated films comprising, in this order,
(1′) a substrate layer comprising a molding compound of component (1) as described above, ABS, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyamide, polyetherimide, polyether ketone, polyphenylene sulfide, polyphenylene ether or blends thereof, having a layer thickness of from 90 to 990 &mgr;m,
(3′) a transparent top layer comprising polymethyl methacrylate (PMMA), high-impact polymethyl methacrylate (HI-PMMA), ABS, polycarbonate (PC), polyethylene terephthalate (PET), styrene-acrylonitrile copolymers (SAN), polyamide (PA), polyether sulfone (PES) or polysulfone (PSU), having a layer thickness of from 10 to 100 &mgr;m,
it being possible for the substrate layer to comprise colorants and comprising them if the substrate layer and the top layer are composed of the same molding compounds, and the overall thickness of the laminated film being from 100 to 1000 &mgr;m.
The novel laminated sheets or films and also the moldings produced therefrom are of better penetration resistance and/or low-temperature impact strength, scratch resistance and elongation at break than the known sheets, films and moldings and have better drawing properties with constant surface gloss. They are therefore particularly suitable for exterior use, where they are subject to UV radiation and the effects of weather. Use in the automotive sector is particularly appropriate.
The individual layers and components of the laminated sheets or films are described below.
Layer (1)
Layer (1) is composed of the following components A and B and, if used, C and/or D, which total to 100% by weight.
Component A is a graft copolymer of
a1 1-99% by weight, preferably 55-80% by weight, in particular 55-65% by weight, of a particulate graft base A1 having a glass transition temperature of below 0° C.,
a2 1-99% by weight, preferably 20-45% by weight, in particular 35-45% by weight, of a graft A2 comprising the following monomers, based on A2:
a21 40-100% by weight, preferably 65-85% by weight, of units of styrene, a substituted styrene or a (meth)acrylate or mixtures thereof, especially of styrene and/or &agr;-methylstyrene, as component A21, and
a22 up to 60% by weight, preferably 15-35% by weight, of units of ac
Grefenstein Achim
Lindenschmidt Gerhard
Netze Carsten
Zeltner Doris
Aftergut Jeff H.
BASF - Aktiengesellschaft
Keil & Weinkauf
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