Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-07-31
2004-06-15
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S107000, C525S108000, C525S123000, C525S125000, C525S178000, C525S179000, C525S184000, C525S192000, C525S193000, C525S194000, C525S206000, C525S207000, C525S208000, C525S221000, C525S222000, C525S232000, C525S240000, C525S241000
Reexamination Certificate
active
06750288
ABSTRACT:
The present invention relates to an isotactic polypropylene obtained by metallocene catalysis, onto which is grafted a functionalised monomer, and also to a composition comprising such a polymer. The invention also relates to a multilayer structure, at least one of the layers of which comprises isotactic polypropylene obtained by metallocene catalysis in its composition.
The isotactic polypropylene obtained-by metallocene catalysis and grafted with a functionalised monomer may form part of the composition of a coextrusion binder. The coextrusion binder comprises isotactic polypropylene obtained by metallocene catalysis, grafted and then optionally diluted in at least one polyolefin (C1) and/or in at least one polymer of elastomeric nature (D).
These coextrusion binders are useful, for example, for manufacturing multilayer materials for wrapping. Mention may be made of materials comprising a polyamide (PA) film and a polypropylene (PP) film, the polypropylene film possibly being laminated over the polyamide film or coextruded with the polyamide. The coextrusion binder is arranged between the polypropylene film and the polyamide film for good adhesion of the two films. These multilayer materials may be, for example:
three-layer structures of the type such as, for example, PP/binder/EVOH in which EVOH denotes a copolymer of ethylene and of vinyl alcohol, or an ethylene/partially or totally saponified vinyl acetate copolymer, the binder layer being sandwiched between an EVOH layer and a PP layer, or
five-layer structures of the type such as, for example, PP/binder/EVOH/binder/PP, in which the EVOH layer is sandwiched between two layers of binders, each of them being sandwiched between the EVOH layer and a PP layer.
The grafted polymer according to the invention may also be useful as a compatibilizer, for example in blends of polyamide and polypropylene or in blends of polypropylene and glass fibres.
Polypropylene is described in Kirk-Othmer, Encyclopedia of Chemical Technology, 4th edition, Vol. 17, pages 784-819, John Wiley & Sons, 1996. Almost all of the polypropylene sold consists essentially of isotactic polypropylene obtained by Ziegler-Natta catalysis, possibly containing a small amount of atactic polypropylene.
Extensive prior art exists describing grafted polypropylene, but this is always isotactic polypropylene obtained by Ziegler-Natta catalysis, abbreviated as zniPP in the text hereinbelow.
Document U.S. Pat. No. 5,235,149 describes wrappings closed with caps consisting of an aluminium foil, a binder layer and a polypropylene layer. The binder layer of the cap consists of various polymers grafted with acrylic acid or maleic anhydride, and the polymers may be chosen from polyethylene, polypropylene, copolymers of ethylene and of vinyl acetate and copolymers of ethylene and of methyl acrylate.
Documents DE 19 535 915 A and EP 689 505 describe a grafted polypropylene block copolymer for adhesively binding polypropylene films to metal sheets.
Document EP 658 139 describes structures similar to those described above, but the binder is a grafted random polypropylene copolymer comprising from 1 to 10% comonomer, the Mw/Mn ratio being between 2 and 10 and the MFI (melt flow index) is between 1 and 20/10 min (at 230° C. under 2.16 kg).
The free-radical grafting of functionalised monomers onto the polyolefins is performed either in the melt or in solution using free-radical initiators, for instance peroxides, or in the solid state by irradiation. Under the action of the radicals, side reactions take place at the same time as the grafting reaction. They lead to an increase in the molecular mass in the case where the polymer to be grafted is polyethylene, or to a decrease in the molecular mass in the case where it is polypropylene. If the amount of free radicals required for the grafting reaction is large, the change in the molecular mass of the polyolefin leads to a large change in its melt viscosity. This grafting generally takes place in an extruder. The viscosity of the grafted polyethylene is then so high that it can no longer be extruded, whereas the viscosity of the grafted polypropylene is so low that it cannot be extruded either. These phenomena make it necessary to reduce the amount of reactive functions that may be incorporated into the polyolefin by free-radical grafting of functional monomers.
In the case of mixtures of virtually equivalent amounts of polyethylene and of polypropylene to be grafted by free-radical grafting with large amounts of functionalised monomers, as is the case in document EP 802 207, the increase in the molecular mass of the grafted polyethylene is compensated for by the decrease in the molecular mass of the grafted polypropylene.
It has now been found that a functionalised monomer can be grafted in large amount onto isotactic polypropylene obtained by metallocene catalysis (miPP) and that the melt flow index of the grafted miPP obtained is lower than in the case of the grafted isotactic polypropylene obtained by Ziegler-Natta catalysis (zniPP), thus making the grafted miPP or compositions comprising it easier to extrude.
Furthermore, it has been found that grafted miPP is advantageous in terms of application compared with the polypropylenes obtained by Ziegler-Natta catalysis during its use in coextrusion binders.
One subject of the invention is a composition comprising:
10% to 100% by weight of isotactic polypropylene homopolymer or copolymer obtained by metallocene catalysis (miPP);
0% to 90% by weight of polyethylene (A) homopolymer or copolymer;
0% to 90% by weight of polymer (B) chosen from isotactic polypropylene homopolymer or copolymer obtained by Ziegler-Natta catalysis (B1), poly-(1-butene) homopolymer or copolymer (B2), polystyrene homopolymer or copolymer (B3), a blend of (B1) and (B2), a blend of (B1) and (B3), a blend of (B2) and (B3) and a blend of (B1), (B2) and (B3); the percentages being based on the total weight of the isotactic polymer (miPP) and any polymer (A) and polymer (B); and,
the said polymer or polymers being grafted with a functional monomer.
According to one embodiment of the composition, the functionalised monomer is unsaturated and non-aromatic. The term “functionalised monomer” means a monomer comprising at least one chemical function.
According to one embodiment of the composition, the functionalised monomer is taken from the group comprising alkoxysilanes, carboxylic acids and derivatives thereof, acid chlorides, isocyanates, oxazolines, epoxides, amines and hydroxides.
According to one embodiment of the composition, the functionalised monomer is maleic anhydride.
According to one embodiment of the composition, at least one comonomer of polyethylene (A) copolymer is chosen from &agr;-olefins containing from 3 to 30 carbon atoms, esters of unsaturated carboxylic acids, vinyl esters of saturated carboxylic acids, unsaturated epoxides, alicyclic glycidyl esters and ethers, unsaturated carboxylic acids, salts thereof, anhydrides thereof and dienes.
According to one embodiment of the composition, the polyethylene (A) is chosen from LDPE, HDPE, LLDPE, VLDPE, PE obtained by metallocene catalysis, EPR and EPDM elastomers and blends thereof, ethylene/alkyl (meth)acrylate copolymers, ethylene/alkyl (meth)acrylate/maleic anhydride copolymers and ethylene/vinyl acetate/maleic anhydride copolymers.
According to one embodiment of the composition, it is diluted in a polyolefin (C1) and/or a polymer of elastomeric nature (D).
According to one embodiment of the composition, the amount of polyolefin (C1) and/or of polymer of elastomeric nature (D) is advantageously from 20 to 1000 and preferably from 30 to 500 parts by weight per 10 parts of grafted isotactic polypropylene obtained by metallocene catalysis.
According to one embodiment of the composition, the proportions of polyolefin (C1) and of polymer of elastomeric nature (D) are such that the ratio (D)/(C1) is between 0 and 1 and more particularly between 0 and 0.5.
According to one embodiment of the composition, it is included in a coextrusion binder.
A subject of the in
Atofina
Millen White Zelano & Branigan P.C.
Nutter Nathan M.
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