Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
1995-10-19
2003-06-10
Thomas, Alexander S. (Department: 1772)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S421000, C428S492000, C428S520000
Reexamination Certificate
active
06576342
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a multilayered article including a layer of elastomer overmoulded onto a thermoplastic and vulcanized so as to adhere directly to the latter.
It also relates to a process for the preparation of a composite article including a vulcanized elastomer associated directly with a thermoplastic.
In the case where the thermoplastic has barrier properties in respect of fuels or heating fluids, a double layer may be sufficient for the application of the invention in the form of pipes for petrol or conditioned air. In the case where the thermoplastic does not have barrier properties per se, one (or more) layer(s) will be needed inside, for the same purpose, in order to ensure the imperviousness.
2. Description of the Related Art
The processes for assembling articles (tubular ones or sheets) made of vulcanized elastomer (synthetic or natural) that is associated with thermoplastics which are commonly employed are based on the extrusion-sheathing of a thermoplastic previously coated with an adhesive. The outer layer of elastomer is then vulcanized in an autoclave with hot air, with steam pressure or with radiation, which are usual in the rubber industry.
Nevertheless, a considerable saving where the process is concerned could be achieved by doing away with the application of the adhesive.
DETAILED DESCRIPTION OF BEST MODE AND SPECIFIC/PREFERRED EMBODIMENTS OF THE INVENTION
One of the objectives of the present invention is to propose a process for the preparation of a composite article as defined above, avoiding the application of adhesive.
Another objective of the present invention is to propose an article as defined above exhibiting a high peel strength of the vulcanized elastomer sheath when subjected to the separating stress, preferably higher than 2 daN/cm.
The problems which the invention intends to solve are the following:
the interfacial adhesion in the case of multilayered articles (especially, in the case of tubular articles, between the outer elastomeric layer and the inner thermoplastic layer),
the protection of thermoplastic pipes from hot spots by a vulcanized elastomer, an example of application in the motor vehicle sector.
For the conditioned air application the pipes are traditionally made of textile-reinforced rubber. With the new legislation, a barrier layer against fluorohydrocarbons must be incorporated, and this is done with a barrier thermoplastic. This barrier thermoplastic layer must be fine so as not to impair the acoustic damping properties of the rubber.
For the petrol pipe application these pipes are today made of textile-reinforced rubber. The problems related to the rubber are: the permeability, the swelling, the limited resistance to peroxidized fuel and the extraction of various products, resulting in the advantage of introducing a thermoplastic inner barrier layer.
The advantage of the interfacial adhesion is linked, among others, with the better properties of the pipes (flexibility, decrease in the crunching of the pipes and impact strength) and easier use during the fixing of connections than on a pipe consisting of two separate parts (a rubber jacket and a thermoplastic liner).
Other advantages linked with the use of the present invention will appear in the course of the description which follows.
Japanese Patent Application JP 5-44874 describes pipes with an outer layer of epichlorohydrin rubber and an inner layer of nylon or of a fluoro resin, but with the use of adhesive.
In Patent Applications DE 4232946 and GB 2023626 use has also been made of an adhesion promoter or of an adhesive for pipes made of polyamide (or fluoropolymer, in the former), covered with rubber.
French Patent FR 2660404 describes pipes produced by direct coextrusion of a vulcanizable elastomer on a polyolefin; the vulcanizable elastomer is chosen from nitrile-PVC or EPDM rubbers and nothing is said concerning the vulcanization or the mechanism which makes the adhesiveness possible.
German Application DE 3914011 describes a pipe including an outer layer of polyolefinic elastomer (devoid of carboxylic or other functional groups) and on inner layer of thermoplastic, for example polyamide, but it is accepted that it would be preferable to employ adhesive between the two layers—which is furthermore described explicitly in a subsequent application DE 4026161.
The vulcanized synthetic or natural elastomers which are suitable for making use of the present invention are well known to a person skilled in the art, the term “elastomer” in the definition of the present invention meaning that it may consist of mixtures of several elastomers.
These elastomers or elastomer mixtures exhibit a residual compression set (RCS) at 100° C. which is lower than 50%, generally between 5 and 40% and preferably lower than 30%. These vulcanized elastomers originate from the corresponding vulcanizable elastomers.
Among the latter there may be mentioned natural rubber, polyisoprene which has a high double-bond content in a cis position, a polymerized emulsion based on styrene/butadiene copolymer, a polymerized solution based on styrene/butadiene copolymer, a polybutadiene which has a high double-bond content in a cis position, obtained by catalysis with nickel, cobalt, titanium or neodymium, a halogenated ethylene/propylene/diene terpolymer, a halogenated butyl rubber, a styrene/butadiene block copolymer, a styrene/isoprene block copolymer, the halogenated products of the above polymers, an acrylonitrile/butadiene copolymer, an acrylic elastomer, a fluoro elastomer, an epichlorohydrin elastomer and chloroprene.
Some elastomers mentioned above may be functionalized by means of carboxylic (or anhydride), epoxy or amino groups, by grafting, in a known manner, of these elastomers or, in the case of elastomer mixtures, for example with acrylic elastomers.
Among the abovementioned elastomers those included in the following group will be advantageously chosen: carboxylated nitrile elastomers, acrylic elastomers, carboxylated polybutadienes, grafted ethylene/propylene/diene terpolymers, epichlorohydrin elastomers or mixtures of these polymers with the same elastomers but ungrafted, such as nitrile rubbers, hydrogenated nitriles, polybutadienes and ethylene/propylene/diene terpolymers, by themselves or mixed.
The thermoplastic may be chosen from polyamides 6, 66, 11 and 12 and preferably polyamides 11 and 12 (plasticized or otherwise) or their copolymers or blends of these polyamides with polyolefins, from polyesters (for example polybutylene terephthalate), ethylene/tetrafluoroethylene (ETFE) copolymers, copolymers containing ethylene/vinyl alcohol units and polyvinylidene fluoride (PVDF) or mixtures containing it.
Included in the term “polyvinylidene fluoride” is the homopolymer or the copolymers containing at least 70% by weight of vinylidene fluoride. The polyvinylidene fluoride may also be mixed with another thermoplastic polymer on condition that at least 50% by weight of polyvinylidene fluoride is present in the mixture.
An important example of a mixture containing polyvinylidene fluoride is the composition described in European Application EP 450994: a polymethacrylate plus an additive consisting of PVDF and of an acrylic or methacrylic elastomer.
The subject of the invention therefore includes a layer of rubber adherent to a thermoplastic, but it may also include one or a number of other layers, optionally secured by a binder; there is therefore: vulcanized rubber/thermoplastic/other layers with or without bond, for example: PA12/binder/PA6/EVOH/PA6 or PA12/binder/PVDF/PA12/PBT/PA12.
The invention is particularly useful for sheathing pipes which have one of the abovementioned thermoplastics as outer layer: polyamides and their blends, polyesters, and the like.
Another subject of the invention is a process for the preparation of the composite articles described above, characterized in that a thermoplastic is overmoulded, at an appropriate temperature, with an elastomeric composition comprising a synthetic or natural e
Cerf Martine
Denizart Olivier
Dousson Christian
Elf Atochem S.A.
Thomas Alexander S.
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