DE19980666B4 - A method of forming an adhesive bond between a fluorinated polymer and an elastomer and tubing obtained by this method for delivering a fluid - Google Patents

Abstract

A method of forming an adhesive bond between a fluorinated polymer and an elastomer containing an organophosphonium salt in an amount of 1.5 to 5 parts by weight per 100 parts by weight of elastomer, characterized in that the elastomer is antimony trioxide in an amount of 15 to 23 parts by weight per 100 parts by weight of elastomer, which is a flame retardant and an activator of the organophosphonium salt at the same time to initiate a reaction of the dehydrofluorination of the fluorinated polymer, which results in the formation of a double bond in the monomer unit of the fluorinated polymer and the chemical bonding of this polymer with the elastomer enables the latter to be crosslinked and the elastomer is selected from epichlorohydrin rubber, PVC nitrile rubber, nitrile rubber containing chlorinated paraffins, or a chlorosulfonated polyethylene.

Description

The invention relates to a method for forming an adhesive bond between a fluorinated polymer and an elastomer, and to a conduit produced by carrying out this method for conveying a fluid having at least one layer of a fluorinated polymer and an elastomeric layer which adhere directly to one another.

The invention particularly relates to piping for conveying fuel for motor vehicles.

In order to form an adhesive bond of a fluorinated polymer with an elastomer, it has already been proposed to use an intermediate film of an adhesive based on amines or acrylic compounds, but this approach has a certain number of disadvantages (such adhesives are very costly and sometimes toxic, the application of an adhesive film complicates the manufacture of the products, and the adhesion is not always satisfactory).

It has also been proposed to directly produce an adhesive bond between a fluorinated polymer and an elastomer such as an epichlorohydrin rubber or a nitrile / PVC rubber by adding salts of 1,8-diazabicyclo [5,4,0] undecene to the elastomer -7 ( EP 0 739 712 A2 ) with optionally an organophosphonium salt ( US 5 588 469 A ), but the results achieved are insufficiently satisfactory in terms of adhesion, between the fluorinated polymer and the elastomer.

The opposing pamphlets JP 08118549 A and US 5798158 A disclose a method for improving the bonding between a fluoropolymer and an epichlorohydrin rubber by incorporating an organophosphonium salt. These references do not mention the crucial effect of a flame retardant, such as antimony trioxide, on the bonding between these layers, which occurs in the claimed tonnage range and was unexpected. The same applies to the pamphlets GÄCHTER, R .; MÜLLER, H (ed.): Paperback of the plastic additives / stabilizers, auxiliaries, plasticizers, fillers, reinforcing agents, 2nd edition, Munich: Carl Hanser Verlag, 1983, pp. 568-570; JP 03 028 285 A ; US Pat. No. 3,990,479 ; EP 0 212 825 B1 ; JP 02 008 583 A ,

The present invention has the object in particular of eliminating these disadvantages and of greatly improving the adhesive bond between a fluorinated polymer and an elastomer.

It proposes for this purpose a method of forming an adhesive bond between a fluorinated polymer and an elastomer containing an organophosphonium salt in an amount of from 1.5 to 5 parts by weight per 100 parts by weight of elastomer, the method being characterized in that to the elastomer is added antimony trioxide in an amount of 15 to 23 parts by weight to 100 parts by weight of elastomer which is simultaneously a flame retardant and an activator of the organophosphonium salt for initiating a reaction of dehydrofluorination of the fluorinated polymer, which results in the formation of a double bond in the monomer unit of the fluorinated polymer and the chemical bonding of this polymer with the elastomer in the crosslinking of the latter allows and the elastomer is selected from epichlorohydrin rubber, PVC nitrile rubber, nitrile rubber containing chlorinated paraffins, or a chlorosulfonated polyethylene.

The invention thus makes it possible to render the elastomer non-combustible and impart to it a very strong adhesion to the fluorinated polymer by means of a chemical bond between them by adding to the elastomer an organophosphonium salt and a flame retardant which reacts with the organophosphonium salt so as to initiate a reaction of the dehydrofluorination of the fluorinated polymer, with consequent formation of a double bond in the monomer unit of this fluorinated polymer, which double bond allows to chemically bond with the elastomer in the crosslinking of the latter.

It could be shown by experiments that the adhesive bond thus obtained between a fluorinated polymer and an elastomer was two to three times higher than with the methods known from the prior art.

The fluorinated polymer is preferably a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride of the thermoplastic or elastomer type.

The invention further relates to a conduit for conveying a fluid according to claim 6, in particular fuel for motor vehicles, which is characterized in that it comprises at least one layer of a fluorinated polymer and an elastomer layer, between which a result of carrying out the method described above Bonding exists, wherein the layer of fluorinated polymer and the elastomer layer are advantageously coextruded or extruded successively.

In the preferred embodiment of the invention, the fluorinated polymer layer and the elastomer layer are coated with a textile reinforcing layer and a protective layer of elastomer.

Such a tubing has excellent impermeability to fuel with a small thickness of the fluorinated polymer layer, very good mechanical properties, in particular, flexibility and resistance to delamination, and good resistance to oils and fuels, ozone, cold, heat, and non-flammability ,

A better understanding of the invention and other features, details and advantages of the invention will become more apparent from a reading of the following exemplary description with reference to the accompanying drawings.

Show it:

1 a diagram illustrating the composition of an epichlorohydrin rubber used in the invention;

2 . 3 and 4 schematic representations of the tube pipes according to the invention for conveying fuel.

The invention is essentially based on the surprising discovery that antimony trioxide may also serve as an activator of an organophosphonium salt in an epichlorohydrin rubber type elastomer for initiating a dehydrofluorination reaction of a fluorinated polymer, which results in the formation of a double bond in the monomer unit of the fluorinated polymer this double bond serves to effect the bonding by chemically bonding the fluorinated polymer to the elastomer in the crosslinking of the latter.

The proposed chemical reaction mechanism is as follows:
The antimony trioxide reacts with the organophosphonium salt (such as an organophosphonium chloride) to form a reactive antimony-organophosphonium complex and an antimony chloride, as shown below: 3 [RPCl] + Sb ₂ O ₃ → [RPO] ₃ Sb + SbCl ₃

This antimony-organophosphonium complex reacts on the monomer unit of the fluorinated polymer used (such as a terpolymer of tetrafluoroethylene, propylene hexafluoride and vinylidene fluoride) to initiate a dehydrofluorination reaction and form a double bond in the monomer unit of the fluorinated polymer, as shown below :

This double bond is destroyed in the cross-linking of the elastomer and allows a chemical bonding of the fluorinated polymer to the elastomer, which translates into a very strong adhesive bond.

The fluorinated polymers to which the invention is applicable are all those capable of undergoing a dehydrofluorination reaction and, in particular, include the terpolymers of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, marketed under the names THV (a thermoplastic) and FKM ( an elastomer).

They further include the PVDF (poly (vinylidene fluoride)) fluorinated polymers, ETFE (a copolymer of ethylene and ethylene tetrafluoride), FEP (a copolymer of ethylene tetrafluoride and propylene hexafluoride), etc.

The elastomers to which the invention is applicable include all epichlorohydrin rubbers, the PVC-nitrile rubbers, the nitrile rubbers with an addition of chlorinated paraffins, or chlorosulfonated polyethylene (CSM).

The epichlorohydrin rubber used in the present invention may be a homopolymer of epichlorohydrin, a copolymer of epichlorohydrin and ethylene oxide, or, preferably, a terpolymer of epichlorohydrin, ethylene oxide and allyl glycidyl ether which has better resistance to ozone and cold than the previous two Compounds and a way of associating unsaturated polymers possesses.

As in 1 is shown schematically, this epichlorohydrin rubber from 15 to 23 parts by weight of antimony trioxide, from about 50 to about 60 parts by weight of carbon black N550 and from 2.5 to 10 parts by weight of plasticizer per 100 parts by weight of elastomer.

Experiments have shown that such an epichlorohydrin rubber is non-combustible, i. H. it does not burn on contact with a flame or goes out as soon as there is no contact with a flame anymore.

This elastomer is thus particularly well suited for the manufacture of fuel system components, such as fuel delivery conduits, fuel vapor recirculation or refueling, in conjunction with a material which is a barrier to the fuel, such as a fluorinated polymer of the type THV or FKM, preferably a THV (thermoplastic) type polymer because of ease of use (no vulcanization) and its superior fuel impermeability properties for motor vehicles.

Advantageously, this elastomer contains no lead.

By means of extrusion, a tube of the in 2 schematically illustrated type, which has a thin inner layer 10 of THV coated with a thicker layer 12 an epichlorohydrin rubber according to the invention, in particular of the type GECO (a terpolymer of epichlorohydrin, ethylene oxide and allyl glycidyl ether).

Typically, a THV thickness of 0.25 mm is sufficient to have a permeability of 1 g / m ² . Day to get a fuel for motor vehicles, which has 5% methanol and 2% ethanol.

The epichlorohydrin rubber with the in 1 to form a perfect adhesive bond to the fluorinated polymer of the inner layer 10 adhesives such as those sold under the names VITON CURATIVE 20 and DYNAMAR FX-5166 by DU PONT DE NEMOURS and 3M, respectively, wherein the VITON CURATIVE 20 is composed essentially of an organophosphonium chloride while the DYNAMAR FX-5166 is a mixture of an organophosphonium chloride, silica, sulfolane and methanol.

It is of course possible to use only one of these adhesives.

According to the invention, 1.5 to 5 parts by weight of organophosphonium salt per 100 parts by weight of elastomer are added to the elastomer.

The pipes of the 2 , which consists of a thin layer of THV and a thicker layer of epichlorohydrin rubber, is particularly intended for forming a pipeline for refueling.

In the 3 shown tubing has a thin inner layer 10 from THV on that with a layer 12 the above epichlorohydrin rubber (GECO), a textile reinforcing layer 14 of a conventional type (for example, a mesh of filaments of polyamide or the like), and an outer covering or protective layer 16 of epichlorohydrin rubber coated with the above-mentioned composition for flameproofing.

Such a conduit is suitable for use as a conduit for fuel supply or for the return of fuel vapors.

The tubing of 4 has the same structure as that of 3 and further comprises a thin inner layer of elastomer which defines the inner surface of the layer 10 THV covered with this innermost layer 18 may be an epichlorohydrin rubber having the above-mentioned composition or else a layer of nitrile rubber (NBR).

Optionally, the inner elastomer layer could 18 made of FKM (an elastomeric terpolymer formed from the same monomers as the THV).

Typically, the thickness of the protective layer of epichlorohydrin rubber is on the order of 2 to 3.5 mm and may be substantially between about 1.5 and about 5 mm.

If this is necessary or desirable for reasons of tightness or connection to an extension, a thin layer of elastomer may also be provided on the inner surface of the layer 10 from THV the in 2 be formed tube shown.

• – wenn das Elastomer GECO weder flammhemmende Mittel noch Haftmittel beinhaltet, beträgt die erzielte Abziehfestigkeit ca. 2 N/cm,
• – wenn das Elastome GECO ein Haftmittel wie VITON CURATIVE 20 beinhaltet, beträgt die erzielte Abziehfestigkeit in der Größenordnung von 15 N/cm,
• – wenn das Elastomer GECO ein flammhemmendes Mittel wie Antimontrioxid und Haftmittel wie VITON CURATIVE 20 und DYNAMAR FC5166 beinhaltet, liegt die erzielte Abziehfestigkeit zwischen 40 und 45 N/cm.

Abrasion tests were carried out on samples of composite products with a layer THV 500 (sold by the company 3M) and a layer of epichlorohydrin rubber of the above-mentioned type GECO, with the following results:

• If the elastomer GECO contains neither flame retardants nor adhesives, the peel strength achieved is about 2 N / cm,
• If the elastomer GECO contains an adhesive such as VITON CURATIVE 20, the peel strength achieved is on the order of 15 N / cm,
• If the elastomer GECO contains a flame retardant such as antimony trioxide and adhesives such as VITON CURATIVE 20 and DYNAMAR FC5166, the peel strength achieved is between 40 and 45 N / cm.

• – wenn das Elastomer GECO weder flammhemmende Mittel noch Haftmittel beinhaltet, beträgt die erzielte Abziehfestigkeit ca. 12 N/cm,
• – wenn das Elastomer GECO ein flammhemmendes Mittel wie Antimontrioxid und Haftmittel wie VITON CURATIVE 20 und DYNAMAR FC5166 in Mischung beinhaltet, beträgt die erzielte Abziehfestigkeit ca. 15 N/cm (was sich dadurch erklärt, daß der Kleberzwischenfilm eine Barriere bildet, welche die Reaktion der Dehydrofluorierung des THV500 verhindert, die normalerweise durch die im Elastomer enthaltene Mischung aus Antimontrioxid und Organophosphoniumchlorid angestoßen würde).

Comparative tests were carried out with a film of an adhesive between the elastomer GECO and the THV500, such as the DYNAMAR FC5166 marketed by the company 3M. The results were as follows:

• If the elastomer GECO contains neither flame retardants nor adhesives, the peel strength achieved is about 12 N / cm,
• When the elastomer GECO comprises a flame retardant such as antimony trioxide and adhesives such as VITON CURATIVE 20 and DYNAMAR FC5166 in admixture, the peel strength achieved is about 15 N / cm (which is explained by the fact that the intermediate adhesive film forms a barrier which inhibits the reaction of the Prevents dehydrofluorination of the THV500, which would normally be initiated by the mixture of antimony trioxide and organophosphonium chloride present in the elastomer).

This last test again demonstrates the importance of dehydrofluorination of the fluorinated polymer to obtain a strong bond with an elastomer of the above. Type.

Claims (8)

A method of forming an adhesive bond between a fluorinated polymer and an elastomer containing an organophosphonium salt in an amount of from 1.5 to 5 parts by weight per 100 parts by weight of elastomer, characterized by containing antimony trioxide in an amount of from 15 to 23 parts by weight of the elastomer to 100 parts by weight of elastomer which is simultaneously a flame retardant and an activator of the organophosphonium salt for initiating a reaction of dehydrofluorination of the fluorinated polymer, which contributes to the formation of a double bond in the monomer unit of the fluorinated polymer and the chemical bonding of this polymer to the elastomer permitting crosslinking of the latter and the elastomer is selected from epichlorohydrin rubber, PVC-nitrile rubber, nitrile rubber containing chlorinated paraffins, or a chlorosulfonated polyethylene. A method according to claim 1, characterized in that the epichlorohydrin rubber is selected from a homopolymer of epichlorohydrin, a copolymer of epichlorohydrin and ethylene oxide, or a terpolymer of epichlorohydrin, ethylene oxide and allyl glycidyl ether. Process according to claim 1 or 2, characterized in that said elastomer contains no lead. Process according to any one of the preceding claims, characterized in that the fluorinated polymer is a terpolymer of tetrafluoroethylene, propylene hexafluoride and vinylidene fluoride of the thermoplastic or elastomeric type. Process according to any one of claims 1 to 3, characterized in that the fluorinated polymer is a poly (vinylidene fluoride), a copolymer of ethylene and ethylene tetrafluoride, a copolymer of ethylene tetrafluoride and propylene hexafluoride. Tubing for conveying a fluid, characterized in that it comprises at least one layer ( 10 ) of fluorinated polymer and an elastomer layer ( 12 ), between which there is an adhesive bond as a result of the implementation of the method described in any one of the preceding claims 1 to 5. Tubing according to Claim 6, characterized in that the fluorinated polymer layer and the elastomeric layer are coextruded or extruded successively. Tubing according to Claim 6 or 7, characterized in that the fluorinated polymer layer and the elastomer layer are provided with a textile reinforcing layer ( 14 ) and a protective layer ( 16 ) are coated of elastomer.

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