Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1999-03-19
2001-06-26
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S421000, C428S422000
Reexamination Certificate
active
06251506
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to compositions of matter classified in the art of chemistry as laminated structures (laminates) of fluoropolymers and high temperature formable polymers, more particularly laminated structures of polyvinylidene fluoride and high temperature formable polymers selected from the group consisting of polyetherimide, polyethersulfone, polyphenylene sulfide and polyetheretherketone polymers, processes for the preparation and use of such laminates, as well as to formed products produced from the laminates.
Sheets of thermoplastic polymers may be classified in two major categories, those that can be thermoformed at low to moderate temperatures, up to 475° F. (246° C.), and those thermoformable at significantly higher temperature, from about 500° F. (260° C.) up to about 600° F. (316° C.). The former category includes polycarbonate, acrylic, polyvinyl chloride, chlorinated polyvinyl chloride and polyetherketoneketone sheet. The latter category includes polyetherimide, polyether sulfone, polyphenylene sulfide and polyetheretherketone sheet. Those sheets in the lower temperature category can be finished in three ways. They can be internally pigmented to achieve a desired color; the surface can be laminated with either a pigmented or clear film; and they can be painted. In fact, all three methods are utilized. Laminating with films is especially desirable in a number of applications, such as surface transportation, aircraft interiors and clean room enclosures, because the films provide greatly enhanced decorative and performance properties to the finished part. These properties include greater color control, improved color stability, improved cleanability and greater abrasion resistance. Because no suitable materials had been identified for forming laminates, only internal pigmentation and painting have been available for sheets in the higher temperature category. Since the introduction of these higher temperature sheets over the last 10 or 15 years, technicians in the applicable industries have sought a decorative film which can stand up to the high thermoforming temperatures these sheets must reach in order that a part will attain satisfactory geometry.
There are at least four types of decorative films used by thermoplastic sheet manufacturers for thermoforming at lower temperatures. These are polyvinyl fluoride films, acrylic films, polyvinyl chloride films and polyvinylidene fluoride-based films. With the polyvinyl fluoride, polyvinyl chloride, and acrylic films, it is well known that their upper use temperature limit is about 400° F. (205° C.), beyond which the films begin to disintegrate. The maximum use temperatures for polyvinylidene fluoride-based films had not been determined although the melting points, depending on the copolymer used, are known to be somewhat below 340° F. (170° C.) and lower. Nevertheless, it has been found that polyvinylidene fluoride films can survive intact through the high forming temperatures used in molding parts from high temperature formable polymer sheets.
Thus, sheet manufacturers can now use a film laminate with improved decorative and performance characteristics while also avoiding the problems such as environmental damage involved in painting of formed parts.
The polyvinylidene fluoride film is produced either from melted polymer or on equipment where solvents are controlled either by solvent recovery or by incineration. Many thermoformers, on the other hand, are poorly equipped to handle the solvents evaporated from paints and many operate under governmentally imposed restrictions on emission of solvents greater than present limits.
LISTING OF PERTINENT ART
While no literature relating to lamination of decorative films to high temperature formable plastic sheets and subsequent forming thereof is known to applicants, there is art related to the art of lamination and thermoforming at lower temperatures.
U.S. Pat No. 5,203,941 to Avery Dennison discloses a method of adhering flexible decorative cover sheets among which may be polyvinylidene fluoride/acrylic sheets onto polyvinyl chloride sheet, a low temperature formable plastic. The laminates so formed are embOsed with a wood grain pattern and are intended for use as building siding.
U.S. Pat. No. 4,943,680 to Rexam Industries discloses a method of making layered coatings which inter alia may be formed from fluoropolymers such as polyvinylidene fluoride for use on formed substrates of wood, metal or plastics suitable for automobile body panels. For wood or metal, the film is adhered to the pre formed part. For plastics (all of which are molded at low temperature), the film is placed in the mold against the face which will form the surface and the panel polymer is either placed or injected behind it.
U.S. Pat. No. 4,810,540 to Rexham Corp also discloses formed structures from vinylpolymers, urethane polymers or polyacrylates surfaced with polyvinyl fluoride film used as surface coatings on shaped automobile parts. All molding is done at relatively low temperature.
PCT Application WO94/03337 to 3M discloses multilayer plastic films having a fluorinated polymer outer layer, preferably of polyvinylidene fluoride, providing surface protection for the underlying object and sufficiently flexible to conform to the contours of the underlying object at processing temperatures. The principal use is for surface coating of molded automotive parts. Use in surface protection of high temperature formable polymers or of objects formed from such polymers is not suggested.
U.S. Pat. No. 5,304,413 to DuPont discloses formed structures from polycarbonate or polyaryletherketoneketone sheets faced with polyvinyl fluoride film. Thermoforming below 200° C. is required.
In all the above art, polyvinylidene fluoride films are adhered to and/or thermoformed with contoured parts at temperatures of 475° F. or below.
SUMMARY OF THE INVENTION
The invention provides in a first composition of matter aspect, a laminar structure comprising:
a) a layer of polyvinylidene fluoride polymer-based film having a thickness of from about 10.0 to about 100 &mgr;m adhered to
b) a layer having a thickness of from about 100 to 6000 &mgr;m and consisting essentially of at least one high temperature formable polymer. Special mention is made of aspects of the first composition aspect of the invention wherein the high temperature formable polymer is selected from the group consisting of
(i) polyetherimide,
(ii) polyethersulfone,
(iii) polyphenylene sulfide, and
(iv) polyetheretherketone.
The tangible embodiments of the first composition of matter aspect of the invention possess the inherent applied use characteristics of being laminated sheets which are thermoformable into parts having complex shapes and which are protected from degradation by ultraviolet light on exposed surfaces, resistant to heat and fire and easily cleanable, particularly when compared to painted surfaces.
The invention provides in a first process aspect, a process for the manufacture of a laminar sheet formed from at least one substantially amorphous polymer selected from the group consisting of polyetherimide, polyethersulfone, polyphenylene sulfide, and polyetheretherketone, having a polyvinylidene fluoride polymer-based film adhered on at least one surface thereof, said process comprising:
Adhering a polyvinylidene fluoride polymer-based film to a sheet of said high temperature formable polymer to form a laminate.
The invention provides in a second process aspect, a process for forming a three dimensional shaped article from a tangible embodiment of the first composition aspect of the invention which comprises thermoforming a tangible embodiment of the first composition aspect of the invention in a mold to a desired shape under sufficient pressure and at a temperature suitable for thermoforming the high temperature formable polymer contained in said tangible embodiment of the first composition aspect of the invention.
The invention provides in a second composition aspect a shaped article formed from a tangible embodiment of
Davis Robert F.
Simkin Benjamin
Truog Keith L.
ATO FINA Chemicals, Inc.
Bright Royal E.
Hess Bruce H.
Marcus Stanley A.
Maxwell Walter G.
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