Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-04-06
2004-06-08
Ahmad, Nassar (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S475800, C428S476100, C428S476900, C428S483000, C428S522000, C428S523000, C525S074000, C525S078000, C525S077000, C525S193000
Reexamination Certificate
active
06746738
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is related to a concurrently filed application entitled, “Coextrusion Binder, Its Use For A Multilayer Structure And The Structure Thus Obtained” the inventors being, Jean-Claude Jammet, Christophe Le Roy, Xavier Marical and Jérôme Pascal, Attorney Docket Number ATOCM-172, based on priority French application 99/04261 filed Apr. 6, 1999, said application b orated by reference herein.
FIELD OF THE INVENTION
The present invention relates to a coextrusion binder, to its use for making a multilayer structure and to the structure thus obtained.
SUMMARY OF THE INVENTION
More specifically, the coextrusion binder of the present invention comprises:
5 to 30 parts of a polymer (A), itself comprising a blend of a polyethylene (A1) of relative density between 0.935 and 0.980 and of a polymer (A2) chosen from elastomers, very low-density polyethylenes and ethylene copolymers, the (A1)+(A2) blend being cografted with an unsaturated carboxylic acid;
95 to 70 parts of a polyethylene (B) of relative density between 0.930 and 0.950;
the blend of (A) and (B) being such that:
its relative density is between 0.930 and 0.950,
the content of grafted unsaturated carboxylic acid is between 30 and 10,000 ppm,
the MFI (melt flow index) measured according to ASTM D 1238 at 190° C./21.6 kg is between 5 and 100.
The present invention also relates to a multilayer structure comprising a layer which comprises the coextrusion binder defined above and, directly attached to the latter, a layer (E) of a nitrogen-containing or oxygen-containing polar resin, such as a layer of a polyamide resin, of an aliphatic polyketone, of a saponified ethylene-vinyl acetate copolymer (EVOH) or of a polyester resin, or else a metal layer.
The invention also relates to a structure comprising the above structure and, directly attached to the latter on the binder side, either a polyolefin layer (F) or a layer of a resin chosen from the resins of the layer (E), or else a metal layer.
The invention also relates to a structure comprising, respectively, a polyolefin layer (F), a layer of the binder defined above, a layer of a polyamide resin or of a saponified ethylene-vinyl acetate copolymer (EVOH), a layer of the binder defined above and a polyolefin layer (F).
These structures are useful for manufacturing flexible or rigid packages, such as sachets, bottles or containers. These packages may be manufactured by coextrusion, lamination or coextrusion-blow moulding.
The invention is useful in particular for coextruded hoses or pipes and for motor-vehicle petrol tanks.
Petrol tanks usually consist of five layers consisting respectively of:
high-density polyethylene (HDPE);
a binder;
a <polyamide (PA) or a copolymer having ethylene units and vinyl alcohol units (EVOH);
a binder;
HDPE.
Very often, a sixth layer is added between one of the binder layers and one of the HDPE layers. This sixth layer consists of manufacturing scrap resulting from the moulding of the tanks or, for a much smaller quantity, tanks which are off-specification. This scrap and these off-specification tanks are ground up in order to obtain granules. This regrind is then remelted and extruded directly on the plant for coextruding the tanks. This regrind could also be melted and regranulated by an extrusion machine, such as a twin-screw extruder, before it is reused.
According to a variant, the recycled product may be blended with the HDPE of the two outermost layers of the tank. It is also possible, for example, to blend the granules of recycled product with the virgin HDPE granules of these two layers. Any combination of these recycling operations may also be used.
The amount of recycled material may represent up to 50% of the total weight of the tank.
This sixth layer therefore includes all the materials of the multilayer structure, namely HDPE, binders, PA or EVOH.
BACKGROUND OF THE INVENTION
The prior art has already described multilayer petrol tanks. EP 834,415 describes structures comprising:
Polyethylene/Binder/EVOH/Binder/Polyethylene.
The binder is a maleic-anhydride-grafted polyethylene having an MFI of 0.1 to 3 and a relative density between 0.920 and 0.930 and it contains 2 to 40% by weight of material insoluble in n-decane at 90° C. It is explained that the grafted polyethylene is dissolved in n-decane at 140° C. and cooled to 90° C., at which temperature products precipitate; it is then filtered and the insoluble content is the percentage by weight which precipitates and is collected by filtration at 90° C.
If the content is between 2 and 40%, the binder has good petrol resistance.
No example shows such a polymer. The text specifies that the binder is in fact a blend of 2 to 30 parts of a grafted polyethylene having a relative density between 0.930 and 0.980 and of 70 to 98 parts of an ungrafted polyethylene having a relative density between 0.910 and 0.940, preferably 0.915 and 0.935.
An attempt has been made to prepare binders and the corresponding structures in accordance with this teaching. It has found that the binders were not reproducible, that is to say the choice of the product by its relative density is not a sufficient indication.
It has also been found that these criteria were not sufficient for the binder to withstand petrol,
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described in detail.
With regard to the polymer (A1), this is a polyethylene homopolymer or a copolymer of ethylene with a comonomer chosen, for example, from:
&agr;-olefins, advantageously those having from 3 to 30 carbon atoms. Examples of &agr;-olefins having 3 to 30 carbon atoms as possible comonomers comprise propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, 1-dococene, 1-tetracocene, 1-hexacocene, 1-octacocene and 1-triacontene. These &agr;-olefins may be used by themselves or as a blend of two or more of them;
the esters of unsaturated carboxylic acids, such as, for example, alkyl (meth)acrylates, the alkyl of which has from 1 to 24 carbon atoms. Examples of alkyl acrylates or methacrylates that can be used are, in particular, methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate and 2-ethylhexyl acrylate;
the vinyl esters of saturated carboxylic acids, such as, for example, vinyl acetate or vinyl propionate.
Advantageously, (A1) is a high-density polyethylene (HDPE) of relative density between 0.940 and 0.965.
The MFI of (A1) is between 0.1 and 3 at 2.16 kg.
The copolymer (A2) may, for example, be an ethylene/propylene elastomer (EPR) or an ethylene/propylene/diene elastomer (EPDM).
(A2) may also be a very low-density polyethylene (VLDPE) which is either an ethylene homopolymer or an ethylene/&agr;-olefin copolymer.
(A2) may also be a copolymer of ethylene with at least one product chosen from (i) unsaturated carboxylic acids, their salts and their esters, (ii) vinyl esters of saturated carboxylic acids and (iii) unsaturated dicarboxylic acids, their salts, their esters, their half-esters and their anhydrides.
(A2) may be a metallocene polyethylene.
The amounts of (A1) and (A2) are advantageously 60 to 95 parts of (A1) for 40 to 5 parts of (A2).
The blend of (A1) and (A2) is grafted with an unsaturated carboxylic acid, that is to say (A1) and (A2) are cografted. It would not be outside the scope of the invention to use a functional derivative of this acid.
Examples of unsaturated carboxylic acids are those having 2 to 20 carbon atoms, such as acrylic, methacrylic, maleic, fumaric and itaconic acids. The functional derivatives of these acids comprise, for example, anhydrides, ester derivatives, amide derivatives, imide derivatives and metal salts (such as alkali metal salts) of unsaturated carboxylic acids.
Unsaturated dicarboxylic acids having 4 to 10 carbon atoms and their functional derivatives, particularly their anhydrides, are particularly preferred grafting monomers.
These grafting monomers comprise, for example, maleic, fumar
Le Roy Christophe
Marical Xavier
Pascal Jerome
Ahmad Nassar
Atofina
Millen White Zelano & Branigan P.C.
Rhee Jane
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