FR2776227A1 - Method for binding together fluorinated polymer and elastomer - Google Patents

Abstract

Method for binding together fluorinated polymer and elastomer comprises incorporating fire-proofing agent which is an activator for an organophosphonium salt into the elastomer, thereby causing the polymer to become dehydrofluorinated, thus producing double bonds which can form chemical bonds with the elastomer when the latter is crosslinked.- DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a fuel transport pipe which comprises said materials bound together

Description

PROCESS FOR ADHESION OF A FLUORINATED POLYMER AND A

  ELASTOMER, AND FLUID TRANSFER PIPE OBTAINED BY EXECUTING THE SAME. The invention relates to a method of adhesion of a fluoropolymer and an elastomer, as well as the composite products obtained by carrying out this method and comprising at least one layer of a fluoropolymer and a layer of elastomer directly adhering The invention relates more particularly to products of this type constituting fluid transfer pipes, in particular fuel for motor vehicles. It has already been proposed, to adhere a fluoropolymer to an elastomer, to use an intermediate film of an adhesive based on amines or compounds

  acrylic, but this known technique has a certain number of drawbacks (these adhesives are very expensive and sometimes toxic, the application of a film of adhesive complicates the manufacture of the products, and the adhesion is not always satisfactory) .

  It has also been proposed to obtain direct adhesion between a fluoropolymer and an elastomer such as an epichlorohydrin rubber or a nitrile / PVC rubber by adding 1, 8-diazabicyclo salts to the elastomer [5,4, 0] undecene-7 (EP-A-0739 712) with possibly an organophosphonium salt (US-A-5 588 469) but the results obtained are not sufficiently satisfactory in terms of adhesion between

  the fluoropolymer and the elastomer.

  The object of the present invention is in particular to avoid these drawbacks and to greatly improve

  the adhesion between a fluoropolymer and an elastomer.

  To this end, it proposes a process for the adhesion of a fluoropolymer and an elastomer containing an organophosphonium salt, characterized in that it consists in adding to the elastomer a flame-retardant agent which is an activator organophosphonium salt for the initiation of a dehydrofluorination reaction of the fluoropolymer allowing the creation of a double bond in the monomer unit of the fluoropolymer and the chemical bond of this polymer with the elastomer during the crosslinking of this last. The invention therefore makes it possible to make the elastomer incombustible and to make it adhere very strongly to the fluoropolymer, by chemical bond between them, by addition to the elastomer of an organophosphonium salt and of a flame-retardant agent which reacts with the organophosphonium salt to trigger a dehydrofluorination reaction of the fluorinated polymer, resulting in the creation of a double bond in the monomer unit of this fluorinated polymer, this double bond making it possible to ensure a chemical bond with the elastomer during of the crosslinking of the latter. Tests have shown that the adhesion thus obtained between a fluoropolymer and a

  elastomer was 2 to 3 times higher than with known methods of the prior art.

  In a preferred embodiment of the invention, the flame retardant comprises antimony trioxide and the elastomer is an epichlorohydrin rubber, a nitrile rubber / PVC or a nitrile rubber comprising chlorinated paraffins. The fluoropolymer is preferably a terpolymer of tetrafluoroethylene, hexafluoropropylene

  and vinylidene fluoride, of the thermoplastic type or of the elastomer type.

  The invention also provides a fluid transfer pipe, in particular fuel for a motor vehicle, characterized in that it comprises at least one layer of a fluoropolymer and a layer of elastomer adhering to each other. by carrying out the process described above, these layers of fluoropolymer and elastomer being advantageously coextruded or sequentially extruded. In the preferred embodiment of the invention, these layers of fluoropolymer and of elastomer are covered with a textile reinforcement layer and with a protective layer of elastomer. Such a hose has excellent fuel impermeability for a low thickness of the fluoropolymer layer, very good mechanical characteristics, in particular in terms of flexibility and resistance to delamination, and good resistance to oils and to fuel, to ozone, cold, heat and flame. The invention will be better understood and other characteristics, details and advantages thereof

  will appear more clearly on reading the description which follows, given by way of example with reference to the appended drawings in which: FIG. 1 is a diagram illustrating the composition of an epichlorohydrin rubber according to

  the invention; - Figures 2, 3 and 4 schematically represent fuel transport pipes

according to the invention.

  The invention is essentially based on the surprising observation that a flame-retardant agent such as antimony trioxide for an elastomer of the epichlorohydrin rubber type, can also serve as activator of an organophosphonium salt for the initiation of '' a dehydrofluorination reaction of a polymer

  fluorinated, making it possible to create a double bond in the monomer unit of the fluorinated polymer, this double bond serving to achieve adhesion by chemical bonding of the fluorinated polymer with the elastomer during the crosslinking of the latter.

  The proposed chemical reaction mechanism is as follows:

  Antimony trioxide reacts on the organophosphonium salt (such as organophos chloride)

  phonium) to form an antimony-organophosphonium reactive complex and an antimony chloride as indicated below: 3 [RPC1] + Sb203 -X [RPO] 3 Sb + SbC13 This antimony-organophosphonium complex reacts on the monomer unit of the polymer fluorinated used (such as a terpolymer of tetrafluoroethylene, propylene hexafluoride and vinylidene fluoride) to initiate a dehydroflorination reaction and create a double bond in the monomer unit of the fluorinated polymer, as indicated below: CF3 I 3 (--- -CF2 - CF - CH2 - CF2 ---) + [RPO] 3 Sb CF3 I 3 (--- - CF2 - C = CH- CF2- ---) + 3 [RPF] + Sb (OH) 3 This double bond is destroyed during the crosslinking of the elastomer and allows a chemical bond of the fluoropolymer to the elastomer, resulting in very strong adhesion.30 The fluoropolymers to which the invention is applicable are all those likely to experience

  dehydrofluorination reaction and include in particular the terpolymers of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride which are marketed under the names THV (a thermoplastic) and FKM (an elastomer).

  They also include fluorinated polymers of the PVDF (poly (vinylidene fluoride)) type, 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, PVC-nitrile rubbers, nitrile rubbers with the incorporation of chlorinated paraffins, chlorinated polymers such as chlorosulfonated polyethylene (CSM), etc. The epichlorohydrin rubber used in the present invention can be an epichlorohydrin polymer, a copolymer of epichlorohydrin and ethylene oxide or, preferably, a terpolymer of epichlorohydrin, ethylene oxide and

  allylglycidylether which has better resistance to ozone and cold than the two previous compounds, and a possibility of association with unsaturated polymers.

  As shown schematically in Figure 1, this epichlorohydrin rubber comprises from 15 to 23 parts

  by weight approximately of antimony trioxide, from 50 to 60 parts by weight approximately of carbon black N550 and from 2,525 to 10 parts by weight of plasticizer for 100 parts by weight of elastomer.

  More generally, the amount of antimony trioxide can be between 10 and 25 parts in

  weight or more, part of the antimony trioxide being consumed by reaction with the organophosphonium salt.

  Tests have shown that such an epichlorohydrin rubber is noncombustible, i.e. it

  does not burn on contact with a flame or extinguishes as soon as it is no longer on contact with a flame.

  This elastomer is therefore particularly well suited to the manufacture of fuel circuit elements, such as in particular fuel supply pipes, fuel vapor return pipes or tank fillers, in combination with a fuel barrier material. , such as a polymer

  fluorinated of the THV or FKM type, preferably a polymer of the THV (thermoplastic) type for its ease of implementation (no vulcanization) and its best qualities of impermeability to fuel for motor vehicles.

  Advantageously, this elastomer does not include lead.

  A pipe of the type shown schematically in FIG. 2 can be produced by extrusion, comprising a thin internal layer 10 of THV, covered with a thicker layer 12 of an epichlorohydrin rubber according to the invention, in particular of the GECO type ( a terpolymer of epichlorohydrin, ethylene oxide and allylglycidylether) .20 Typically, a THV thickness of 0.25 mm is sufficient to obtain a permeability of

  1 g / m2.day for a motor vehicle fuel comprising 5% methanol and 2% ethanol.

  To the epichlorohydrin rubber having the composition represented in FIG. 1, to make it adhere perfectly to the fluoropolymer of the inner layer 10, adhesion agents such as those marketed under the names Vitron Curative 20 and Dynamar FX-5166 are added. DU PONT DE NEMOURS and 3M30 respectively, VITON CURATIVE 20 being essentially composed of an organophosphonium chloride, while DYNAMAR FX-5166 is a mixture of organophosphonium chloride, silicone dioxide, sulfolane and methanol. In a preferred embodiment of the invention, 5 parts by weight of VITON may be added to the above composition of epichlorohydrin rubber.

  CURATIVE 20 and 1.5 parts by weight of DYNAMAR FX-5166, for 100 parts by weight of elastomer.

  It is of course possible to use only one of these adhesion agents. Generally, about 1.5 to 5 parts by weight of organophosphonium salt per 100 parts by weight of elastomer are added to the elastomer. The pipe of Figure 2, consisting of a thin layer of THV and a thicker layer of epichlorohydrin rubber is intended in particular to form a tank filling pipe. The pipe shown in FIG. 2 comprises a thin internal layer 10 of THV, covered with a layer 12 of the aforementioned epichlorohydrin rubber (GECO), a layer 14 of textile reinforcement of a conventional type (by

  example a braiding of polyamide threads or the like), and an outer layer 16 for covering or protecting epichlorohydrin rubber having the above composition to be flame retardant.

  Such a pipe can be used as a fuel supply or fuel vapor return pipe. The pipe of Figure 4 has the same structure as that of Figure 3 and further comprises a thin inner layer of an elastomer covering the inner face

  layer 10 of THV, this innermost layer 18 can be an epichlorohydrin rubber having the above composition or a layer of nitrile rubber (NBR) or the like.

  Optionally, the inner layer 18 of elastomer could be FKM (a terpolymer

  elastomeric formed from the same monomers as THV).

  Typically, the thickness of the protective layer of epichlorohydrin rubber is of the order of 2 to 3.5 mm and more generally can be between 1.5 and 5 mm approximately. When this is necessary or useful, for example for reasons of tightness at connection to a nozzle, it is also possible to form a thin layer of elastomer on the internal face of the layer 10 of THV of the pipe shown in FIG. peel resistance tests were carried out on samples of composite products comprising a layer of THV 500 (sold by the company 3M) and a layer of epichlorohydrin rubber of the aforementioned GECO type, with the following results: - when the elastomer GECO does not include any flame retardant or adhesion agent, the peel resistance obtained is approximately 2 N / cm, - when the GECO elastomer comprises an adhesion agent such as VITON CURATIVE 20, the peel resistance obtained is of the order of 15 N / cm, - when the GECO elastomer comprises a flame-retardant agent such as antimony trioxide and adhesion agents such as VITON CURATIVE 20 and DYNAMAR FC5166, the resistance the coat obtained is between 40 and 45 N / cm. Comparative tests were carried out with an intermediate adhesive film such as DYNAMAR FC5155 sold by the company 3M, between the elastomer GECO and the THV500. The results were as follows: - when the GECO elastomer does not comprise any flame retardant or adhesion agent, the peel resistance obtained is approximately 12 N / cm, - when the GECO elastomer comprises a flame retardant such that antimony trioxide and adhesion agents such as VITON CURATIVE 20 and DYNAMAR FC5166 mixed, the peel resistance obtained is about 15 N / cm (which is explained by the fact that the intermediate film adhesive forms a barrier preventing the dehydrofluorination reaction of THV500 which would normally be caused by the mixture of antimony trioxide and organophosphonium chloride contained in the elastomer) .5 This last test proves, on the contrary, the interest dehydrofluorination of the fluoropolymer

  for obtaining a strong adhesion with an elastomer of the aforementioned type.

Claims (6)

RESELL I CAT I ONS   1) Method of adhesion of a fluoropolymer and an elastomer containing an organophosphonium salt, characterized in that it consists in adding to the elastomer5 a flame-retardant agent which is an activator of the organophosphonium salt for the initiation of a reaction   dehydrofluorination of the fluoropolymer, allowing the creation of a double bond in the monomer unit of the fluoropolymer and the chemical bond of this polymer10 with the elastomer during the crosslinking of the latter.   2) Method according to claim 1, characterized in that the flame retardant comprises antimony trioxide. 3) Method according to claim 1 or 2, characterized in that the elastomer is an epichlorohydrin rubber, a PVC-nitrile rubber, a nitrile rubber comprising chlorinated paraffins, or a chlorinated polymer such as chlorosulfonated polyethylene. 4) Method according to claim 3, characterized in that the elastomer is an epichlorohydrin homopolymer, a copolymer of epichlorohydrin and ethylene oxide or a terpolymer of epichlorohydrin, ethylene oxide and allylglycidylether. 5) Method according to claim 3 or 4,   characterized in that the aforementioned elastomer does not contain lead.   6) Method according to one of the preceding claims, characterized in that the fluoropolymer is   a terpolymer of tetrafluoroethylene, propylene hexafluoride and vinylidene fluoride, of the thermoplastic type or of the elastomer type.   7) Method according to one of claims 1 to   , characterized in that the fluoropolymer is a poly (vinylidene fluoride), a copolymer of ethylene and ethylene tetrafluoride, a copolymer of ethylene tetrafluoride and propylene hexafluoride,   or the like. 8) Method according to one of the preceding claims, characterized in that the elastomer comprises   from 10 to 25 parts by weight approximately, in particular from 15 to   23 parts by weight of flame retardant per 100 parts by weight of elastomer.   9) Method according to one of the preceding claims, characterized in that the elastomer comprises   about 1.5 to 5 parts by weight of organophosphonium salt per 100 parts by weight of elastomer.   ) Fluid transfer hose, in particular fuel for motor vehicles, characterized in that it comprises at least one layer (10) of fluoropolymer and one layer (12) of elastomer adhering to each other by carrying out the process described   in one of the preceding claims. 11) Pipe according to claim 10, characterized in that the layers of fluoropolymer and   of elastomer are coextruded or sequentially extruded.   12) Pipe according to claims 10 or 11, characterized in that the aforementioned layers of polymer   and elastomer are covered with a layer (14) of textile reinforcement and a protective layer (16) in elastomer.