Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
2003-07-16
2004-11-02
Zacharia, Ramsey (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S327000, C428S421000, C428S520000, C428S521000, C428S522000, C525S094000, C525S199000, C525S222000
Reexamination Certificate
active
06811859
ABSTRACT:
PVDF (polyvinylidene fluoride) because of its very good weatherablity, radiation resistance and chemical resistance is used to protect articles or materials. In addition, it is appreciated for its glossy appearance and its resistance to graffiti. This has therefore led all kinds of substrates to be coated with a PVDF film. However, PVDF adheres very poorly to most substrates and it is therefore necessary to place an adhesive composition between the PVDF and the substrate. The present invention relates to this composition.
Advantageously, this composition is coextruded with the PVDF in order to form a two-layer film, and then this film is attached to the substrate, for example by hot pressing. The two-layer film may also be placed in a mould, the PVDF layer being placed against the wall of the mould, and then the substrate may be injected in the melt state into the mould. It is also possible, depending on the nature of the substrate, to coextrude the PVDF, the adhesive composition and the substrate in order to obtain the PVDF-coated substrate directly, with the adhesive composition being between the PVDF and the substrate.
Patent GB 1 578 517 describes an ABS coated with a PVDF film, a polyurethane layer possibly being placed between the PVDF and the ABS.
Patent U.S. Pat. No. 4,226,904 describes a PMMA covered with a PVDF film. To improve the adhesion, a PMMA solution in dimethylformamide is deposited on the PVDF film and, after the solvent has evaporated, the PVDF film is pressed onto the PMMA.
Patent U.S. Pat. No. 4,415,519 describes an ABS or PVC substrate covered with a PVDF film, an adhesive being placed between the PVDF and the substrate. This adhesive may be either PMMA or a blend of 40% PMMA, 30% PVDF, and 30% ABS by weight, or else a blend consisting of 30% PMMA, 40% of a polyacrylic derivative and 30% ABS by weight.
Patent U.S. Pat. No. 4,364,886 describes an ABS or unsaturated polyester substrate covered with a PVDF film, an adhesive being placed between the PVDF and the substrate. This adhesive is a blend of 30% PMMA, 40% of an acrylic elastomer and 30% ABS by weight.
Patent U.S. Pat. No. 5,242,976 describes a composition coextrudable with PVDF in order to make it adhere to substrates. The composition is a blend of 27 to 50% PMMA, 17.5 to 36.5% PVDF and 25 to 47.45% of an acrylic elastomer by weight.
In all the above documents of the prior art, there is no mentioned of UV stabilisers in the adhesive composition.
Patent EP 733 475 B1 describes PVDF-coated substrates; the structure comprises, in succession, the substrate, an adhesive layer, a PVDF layer made opaque to UV and to visible radiation and a PVDF layer. The opaque PVDF layer is obtained by adding a product chosen from metal oxides, pigments and benzophenones to the PVDF. The examples illustrate only PVDF filled with 15% by weight of zinc oxide.
Patent U.S. Pat. No. 5,256,472 describes two-layer films comprising a first layer essentially consisting of PVDF and of a minor amount of PMMA and a second layer intended to ensure adhesion to a substrate. This adhesive layer consists by weight of 50 to 95 (preferably 70 to 90) parts of PMMA, 5 to 50 (preferably 10 to 30) parts of PVDF and 0.1 to 15 parts of a UV absorber. It is explained that the presence of the UV absorber is necessary because this adhesive layer is sensitive to radiation and that if no UV absorber is included then the adhesive is destroyed and the layer essentially consisting of PVDF debonds from the substrate. The term “PMMA” denotes methyl methacrylate homopolymers or methyl methacrylate copolymers with a copolymerisable monomer and also blends with an acrylate rubber, but without specifying the proportions of PMMA and of rubber. It is also specified that if the proportion of PMMA is less than 50 parts, the dispersion of the UV absorber tends to be inadequate and evaporation or dissipation of the UV absorber is likely to take place, such being undesireble (column 4, lines 25-29). In addition, it has been discovered that this exudation of absorber impairs the transparency of the films and above all causes debonding. In addition, these films have no mechanical strength, making them difficult to handle. It is therefore necessary for the adhesive layer to contain an elastomer; and, according to the teaching of U.S. Pat. No. 5,242,976 already mentioned, this proportion must be between 25 and 47.45% as calculated from the minimum and maximum values set forth in the abstract and column 2, lines 6-14.
A composition coextrudable with PVDF has now been found such that the UV stabilisers no longer exude, such that the PVDF/coextrudable composition two-layer film has good mechanical strength, which results in excellent adhesion of the PVDF layer to the substrate and which is resistant to radiation.
The present invention relates to a composition suitable as an adhesive layer coextrudable with PVDF and comprising:
20 to 40 parts of PVDF;
40 to 60 parts of PMMA;
5 to 18 parts of an acrylic elastomer;
1 to 4 parts of a UV absorber;
the total making 100 parts.
Thus, the composition of the invention on the one hand can tolerate less than 50 parts by weight of PMMA and on the other hand the relationship among the components is very different than the relationships in U.S. Pat. No. 5,242,976.
The invention also relates to coextruded films comprising:
a layer of the above coextrudable composition (also called adhesive layer) directly attached to the latter; and
a PVDF-based layer comprising, as main constituents, 50 to 100 parts of PVDF per 50 to 0 parts of PMMA respectively (this layer is also called for simplification “PVDF layer”).
According to a second form of the invention, the PVDF layer is in the form of two layers:
one placed against the coextrudable layer and comprising, as main constituents, 50 to 90 parts of PVDF per 50 to 10 parts of PMMA respectively; and
the other (also called the outer layer) comprising, as main constituents, 75 to 100 parts of PVDF per 25 to 0 parts of PMMA respectively.
These films possess mechanical properties sufficient to allow them to be handled to be processed and to be used as a coating transparent to visible light but opaque to UV radiation.
The invention also relates to the substrates coated with this film, the coextrudable (adhesive) composition being placed against the substrate.
With regard to PVDF, this term denotes PVDFs, vinylidene fluoride (VF2) homopolymers and vinylidene fluoride (VF2) copolymers preferably containing at least 50% by weight of VF2 and at least one other monomer copolymerisable with VF2. Advantageously, the comonomer is fluorinated and may be chosen, for example, from the vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl)vinyl ethers, such as perfluoro(methyl)vinyl ether (PMVE), perfluoro(ethyl) vinyl ether (PEVE) and perfluoro(propyl)vinyl ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD). Preferably, the possible comonomer is chosen from chlorotrifluoroethylene (CTFE), hexafluoroproylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE).
Advantageously, the PVDF has a viscosity ranging from 100 Pa.s to 2000 Pa.s, the viscosity being measured at 230° C. at a shear rate of 100 s
−1
using a capillary rheometer. This is because these PVDFs are well suited to extrusion and to injection moulding. Preferably, the PVDF has a viscosity ranging from 300 Pa.s to 1200 Pa.s, the viscosity being measured at 230° C. at a shear rate of 100 s
−1
using a capillary rheometer.
With regard to PMMA, this term denotes methyl methacrylate homopolymers and copolymers containing at least 50% methyl methacrylate by weight. As examples of comonomers, mention may be made, for example, of alkyl(meth)acrylates, acrylonitrile, butadiene, styrene and isoprene. Examples of alkyl(meth)acrylates are described in Kirk-Othmer Encyclopaedia of Chemical Technology, 4
th
Edition in Vol. 1, pages 292-293 and in Vol. 16, pages 475-478. Advantageously, the PMMA may contain
Beaume Francois
Bonnet Anthony
Loyen Karine
Silagy David
Triballier Karine
Atofina
Zacharia Ramsey
LandOfFree
Composition coextrudable with PVDF does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composition coextrudable with PVDF, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composition coextrudable with PVDF will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3340797