Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-03-22
2003-09-09
Dye, Rena L. (Department: 3627)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036700, C428S036910, C428S476900, C428S516000, C428S518000, C138S137000, C138S141000, C220S562000, C280S830000, C206S000600
Reexamination Certificate
active
06616994
ABSTRACT:
The present invention relates to a multilayer fuel tank or to a tubing for filling this tank, made of a thermoplastic.
Plastic extrusion and moulding techniques allow highly diverse articles to be produced, especially hollow bodies which can be used in numerous applications. Many of these applications require the hollow body in question to exhibit good impermeability with respect to the fluid that it is designed to contain. It is therefore well-known to produce multilayer hollow bodies having at least one structural layer made of plastic exhibiting in particular good mechanical properties and at least one layer fulfilling the impermeabilizing function. This layer is generally made of a thermoplastic having the desired barrier properties.
Among thermoplastics which can be used in the structural layer or layers, polyolefins are among the most commonly used. However, it turns out that the usual polyolefins exhibit virtually no adhesion to the usual barrier resins, thereby resulting in articles that have a low delamination resistance. The conventional solution to this problem resides in the use of an adhesive resin layer interposed between the barrier resin layer and the polyolefin layer.
However, adding additional interlayers has certain economical and technical disadvantages, especially given the fact that each type of resin employed requires its own extruder.
BACKGROUND OF THE INVENTION
An attempt at a solution to this problem is given in Patent U.S. Pat. No. 5,618,599 which describes a multilayer comprising a barrier layer and a polyolefin layer, without a separate adhesive layer, and in which the adhesive is preferably mixed with the barrier resin, the adhesive consisting of a polyolefin having a high degree of polycaprolactone or polymethyl methacrylate or polyvinyl acrylate grafting.
However, the adhesion levels obtained in this way are quite low compared with the adhesion levels conventionally obtained by interposing an adhesive layer.
The subject of the present invention is consequently a multilayer fuel tank or a tubing for filling this tank, made of a thermoplastic, without adhesive layers, and having good barrier properties and a high delamination resistance.
SUMMARY OF THE INVENTION
Consequently, the present invention relates to a multilayer fuel tank or a tubing for filling this tank, made of a thermoplastic, comprising at least one layer comprising a barrier resin, adjacent to at least one layer consisting of a blend comprising at least one polyolefin and at least one functionalized polyolefin, which is characterized in that the said functionalized polyolefin comprises functional monomeric units chosen from carboxylic acids, dicarboxylic acids and the anhydrides corresponding to the said dicarboxylic acids.
The expression “multilayer fuel tank or tubing for filling this tank” should be understood to mean any tank or tubing whose wall possesses at least two adjacent layers essentially consisting of different thermoplastics.
The said tank or tubing may be obtained especially by moulding or by coextrusion. In the case of a tank or tubing of finished length, excellent results have been obtained by moulding.
Any type of moulding operation can be used for manufacturing the tank or tubing of finished length according to the invention, as long as it comprises the use of a mould which defines the shape of the tank or of the tubing. This moulding operation may be carried out, for example, starting form a preform or by directly introducing the gelled thermoplastic into the mould.
The moulding operation may also, in particular, be combined with a blowing operation. It may also be followed by a subsequent assembly step, especially by welding. If the moulding operation is carried out starting from a preform, the latter may, especially, be obtained by coextrusion or coinjection.
Very good results have been obtained using coextrusion-blow moulding and coinjection-weld moulding. Preferably, the multilayer tank or tubing is produced by coextrusion-blow moulding. In the latter case, it is possible equally well to use a continuous extrusion technique, an extrusion technique with accumulation or a sequential extrusion technique—techniques all well-known to those skilled in the art.
The term “thermoplastic” should be understood to mean any thermoplastic polymer, including thermoplastic elastomers, as well as their blends. The term “polymer” should be understood to mean both homopolymers and copolymers (especially binary or ternary copolymers), for example random copolymers, copolymers produced by sequential polymerization, block copolymers, graft copolymers, etc.
Any type of barrier resin known to those skilled in the art can be used in the context of the invention, as long as it is a polymer or copolymer compatible with the moulding technique in question. It may also be a blend of various barrier resins. Among the resins that can be used, let us mention especially polyamides or copolyamides, or random ethylene-vinyl alcohol copolymers. Very interesting results have been obtained if the barrier resin is a random ethylene-vinyl alcohol copolymer.
The layer comprising the barrier resin may also contain certain additives well-known to those skilled in the art, which additives may or may not be polymeric, such as stabilizers, lubricants, etc. Advantageously, the layer comprising the barrier resin does not comprise a functionalized polyolefin as defined below.
Preferably, the layer comprising the barrier resin essentially consists of the barrier resin.
In the context of the present invention, the layer comprising the barrier resin is adjacent to at least one layer consisting of a blend comprising at least one polyolefin and at least one functionalized polyolefin.
Apart from the polyolefin or polyolefins and the functionalized polyolefin or polyolefins, the blend may also comprise certain additives well-known to those skilled in the art, which additives may or may not be polymeric, such as stabilizers, lubricants, etc.
Preferably, the said blend essentially consists of at least one polyolefin and of at least one functionalized polyolefin.
The term “polyolefin” should be understood to mean any olefin homopolymer, any copolymer containing at least two different olefins and any copolymer comprising at least 50% by weight of units derived from olefins. Several polyolefins may also be used in the blend. More particularly, the blend may contain a certain proportion of recycled polyolefin as a complement to the virgin polyolefin, or else a certain proportion of a blend of recycled resins coming from the grinding of scrap obtained at various steps in the manufacture of the multilayer tank or tubing.
Preferably, the polyolefin is a polyethylene. Very good results have been obtained with a high-density polyethylene.
The expression “functionalized polyolefin” should be understood to mean any polyolefin comprising, in addition to the units derived from olefins, functional monomeric units. These functional monomeric units may be incorporated into the polyolefin, either in the main chain or in the side chains. They may also be incorporated directly into the backbone of the said main and side chains, for example by copolymerization of one or more functional monomers with the olefin monomer or monomers, or else they may result from grafting one or more functional monomers onto the said chains after the manufacture of the polyolefin. In this case, the polyolefin/functionalized polyolefin blend may be produced especially in a single step, by reactive processing during the gelling step included in the process for manufacturing the tank or tubing.
Several functionalized polyolefins may also be used in the blend.
In the context of the present invention, the functional monomeric units are chosen from carboxylic acids, dicarboxylic acids and the anhydrides corresponding to the said dicarboxylic acids. These units therefore generally come from the copolymerization or from the grafting of at least one unsaturated monomer possessing these same functional groups. As an example of monomers that can be used, let us espec
Dupont Serge
Van Schaftingen Jules-Joseph
Dye Rena L.
Schneller Marina V.
Solvay ( Societe Anonyme)
Venable LLP
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