Patent Application
20050065229
Fluoropolymers, for example those based on vinylidene fluoride CF2=CH2 (VDF) such as PVDF (polyvinylidene fluoride), are known to offer excellent mechanical stability properties, very great chemical inertness and good ageing resistance. These qualities are exploited for various fields of application. For example, mention may be made of the manufacture of extruded or injection-moulded parts for the chemical engineering industry or for microelectronics, the use in the form of impermeable ducts for transporting gases or hydrocarbons, the production of films or coatings for protection in the architectural field, and the production of protective elements for electrical engineering uses.
However, this chemical inertness of fluoropolymers means that it is difficult to bond them or combine them with other materials. The present invention discloses a process in which a fluoropolymer is oxidized. This fluoropolymer thus modified may be easily bonded to or combined with other materials. The process of the invention consists in irradiating the fluoropolymer in the presence of oxygen.
Patent EP 214880 discloses a process for manufacturing polyvinylidene fluoride copolymers by grafting a monomer onto the polyvinylidene fluoride by means of ionizing radiation, which process comprises the following steps:
Patent Application WO 00/17889 discloses power cable jackets comprising, in succession, a layer formed from an ethylene/alkyl acrylate/maleic anhydride terpolymer and a layer of a VDF/HFP fluorocopolymer. To improve the adhesion of these layers, the assembly is subjected to ionizing radiation.
U.S. Pat. No. 5,576,106 discloses a process for grafting an unsaturated functional monomer onto the surface of a powdered fluoropolymer. Powdered maleic anhydride is blended with the fluoropolymer and then they are put in a polyethylene bag and, after the air contained in the bag has been expelled, the bag containing the powder blend is subjected to irradiation of between 3 and 6 Mrad. According to a variant, the maleic anhydride is dissolved in acetone, the solution is mixed with the powdered fluoropolymer and then the acetone is evaporated. The material is then irradiated as above. The grafted fluoropolymer is then used in multilayer structures. In all the examples, only fluoroelastomers are used.
Patent Application JP 56-139517 A published on 31 Oct. 1981 discloses the grafting of maleic anhydride onto polypropylene or high-density polyethylene pre-irradiated in the presence of oxygen. The polyethylene powder is irradiated in the presence of oxygen, which thus creates peroxide functional groups, and is then blended with maleic anhydride in an extruder.
Patent Application EP 1054023 discloses a process for modifying a fluoropolymer in the form of a latex, in which the polymer undergoes partial dehydrofluorination using a base and is then oxidized by hydrogen peroxide. This modified fluoropolymer is useful as an adhesion tie between a fluoropolymer and a metal or another polymer incompatible with the fluoropolymer.
A much simpler process has now been found for modifying a fluoropolymer and for obtaining an oxidized fluoropolymer. All that is required is to irradiate it in the presence of oxygen.
The present invention relates to a process for oxidizing a fluoropolymer, in which:
The oxidized fluoropolymer thus obtained may be used as such or in a blend with at least one polymer chosen from the same, but unoxidized, fluoropolymer, another fluoropolymer and another, non-fluorinated polymer such as, for example, an acrylic polymer. As examples acrylic polymers, mention may be made of PMMA and impact modifiers of the core/shell type.
The invention also relates to structures comprising at least one layer of this oxidized fluoropolymer and at least one layer of another material.
The invention also relates to the use of these structures to obtain a barrier effect.
These structures are barriers to many fluids and in particular to petrol and to air-conditioning fluids.
These structures may be formed into bottles, tanks, containers, pipes, hoses and vessels of all sorts. They may also be converted into films with which packaging is made.
The combined use of a fluoropolymer impermeable to a polar fluids and of a polyolefin impermeable to polar fluids is particularly beneficial as it allows a barrier to be obtained that is very effective against petrols containing liquids such as M15 (42.5% isooctane, 42.5% toluene and 15% methanol by volume) or TF1 (45% toluene, 45% isooctane and 10% ethanol).
The invention also relates to structures in which the fluoropolymer is used to protect substrates.
In the above structures, the oxidized fluoropolymer may be used by itself or in a blend as mentioned above.
The invention also relates to the oxidized fluoropolymer. It relates to the oxidized fluoropolymer in a blend with at least one polymer chosen from the same, but unoxidized, fluoropolymer, another fluoropolymer and another, non-fluorinated polymer such as, for example, an acrylic polymer. As examples of acrylic polymers, mention may be made of PMMA and impact modifiers of the core/shell type.
The term fluoropolymer thus denotes any polymer that has in its chain at least one monomer chosen from compounds that contain a vinyl group capable of opening in order to be polymerized and that contain, directly attached to this vinyl group, at least one fluorine atom, at least one fluoroalkyl group or at least one fluoroalkoxy group.
As examples of monomers, mention may be made of vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl)ether (PMVE), perfluoro(ethyl vinyl)ether (PEVE) and perfluoro(propyl vinyl)ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2═CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2═CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF═CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF═CF2 in which R1 is hydrogen or F(CF2)z and z is 1, 2, 3 or 4; the product of formula R3OCF═CH2 in which R3 is F(CF2)z— and z is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene.
The fluoropolymer may be a homopolymer or a copolymer; it may also contain non-fluorinated monomers such as ethylene.
For example, the fluoropolymer is chosen from:
Advantageously, the fluoropolymer is polyvinylidene fluoride (PVDF) homopolymer or copolymer. Preferably, the PVDF contains at least 50%, more preferably at least 75% and even better at least 85% VDF by weight. The comonomer is advantageously HFP.
Advantageously, the PVDF has a viscosity ranging from 100 Pa.s to 2000 Pa.s, the viscosity being measured at 230° C. with a shear rate of 100 s−1 using a capillary rheometer. These PVDFs are in fact well suited to extrusion and injection moulding. Preferably, the PVDF has a viscosity ranging from 300 Pa.s to 1200 Pa.s, the viscosity being measured at 230° C. with a shear rate of 100 s−1 using a capillary rheometer.
With regard to the irradiation, and firstly to step a), the products are advantageously packaged in polyethylene bags, and the bags are not inerted. Advantageously, the fluoropolymer is in powder form. The bags may also include an aluminium layer in addition to the polyethylene layer. It is unnecessary to irradiate in the presence of pure oxygen, all that is required is that oxygen be present. It is possible to irradiate in the presence of an inert gas containing oxygen. The “inert gas” denotes a gas that is not involved in the irradiation reaction or in the modification of the fluoropolymer by oxygen. Advantageously, the proportion of oxygen is between 1 and 20 vol % per 99 to 80 vol % of inert gas, respectively. Advantageously, irradiation is carried out in the presence of air. As regards the method of irradiation in step b), it is equally possible to use electron irradiation, more commonly known as beta irradiation, and photon irradiation, more commonly known as gamma irradiation. Advantageously, the dose is between 2 and 12 Mrad and preferably between 2 and 8 Mrad.
With regard to step c), the impurities may be removed by any means. A washing operation may be carried out with solvents that are inert vis-a-vis the oxidized fluoropolymer. It is also possible, more simply, to vacuum degas the product recovered in step b).
With regard to the blending, the oxidized fluoropolymer thus obtained may be used as it is or in a blend with at least one polymer chosen from the same, but unoxidized, fluoropolymer, another fluoropolymer and another, non-fluorinated, polymer such as, for example, an acrylic polymer. As examples of acrylic polymers, mention may be made of PMMA and impact modifiers of the core/shell type. The proportion of oxidized fluoropolymer may be between 1 and 99% by weight of the blend. Advantageously, the proportion of oxidized fluoropolymer is between 2 and 30% by weight of the blend. Preferably, the proportion of oxidized fluoropolymer is between 2 and 15% by weight of the blend.
The invention also relates to structures. As examples of structures according to the invention, mention may be made of that comprising, in succession:
In the above structures, it is possible to place, between the oxidized fluoropolymer layer and the polyolefin layer, a layer of functionalized polyolefin having functional groups capable of reacting with the oxidized fluoropolymer. For example, the functionalized polyolefin layer consists of a copolymer of ethylene, glycidyl methacrylate and optionally an alkyl acrylate, optionally in a blend with polytheylene. As another example, the functionalized polyolefin layer consists of a copolymer of ethylene, maleic anhydride and optionally an alkyl acrylate, the copolymer being optionally in a blend with polyethylene.
In the above structures, the inner layer in contact with the fluid to be transported or stored may contain carbon black, carbon nanotubes or any other additive capable of making it conductive in order to prevent static electricity from building up.
As an example of structures according to the invention, mention may be made of that comprising, in succession:
In the above structures, it is possible to place, between the oxidized fluoropolymer layer and one or both polyolefin layers, a layer of functionalized polyolefin having functional groups capable of reacting with the oxidized fluoropolymer. For example, the layer of functionalized polyolefin consists of a copolymer of ethylene, glycidyl methacrylate and optionally an alkyl acrylate, optionally in a blend with polyethylene. As another example, the functionalized polyolefin layer consists of a copolymer of ethylene, maleic anhydride and optionally an alkyl acrylate, the copolymer being optionally in a blend with polyethylene.
As another example of structures according to the invention, mention may be made of that comprising, in succession:
In the above structures, it is possible to place, between the oxidized fluoropolymer layer and the polyamide layer, a layer of functionalized polymer having functional groups capable of reacting with the fluoropolymer, this functionalized polymer being compatible with the polyamide.
In the above structures, the inner layer in contact with the fluid to be transported or stored may contain carbon black, carbon nanotubes or any other additive capable of making it conductive in order to prevent static electricity from building up.
As another example of structures according to the invention, mention may be made of that comprising, in succession:
In the above structures, it is possible to place, between the oxidized fluoropolymer layer and the substrate layer, a layer of functionalized polymer having functional groups capable of reacting with the oxidized fluoropolymer, this polymer being compatible with the substrate.
The oxidized fluoropolymer or PVDF used as layer for protecting a substrate may contain the usual UV stabilizers and/or radiation-absorbent fillers.
These structures may be manufactured by standard techniques, such as extrusion, coextrusion, coextrusion blow moulding, coating, extrusion coating.
The invention also relates to the oxidized fluoropolymer. It relates to the oxidized fluoropolymer in a blend with at least one polymer chosen from the same, but unoxidized, fluoropolymer, another fluoropolymer and another, non-fluorinated, polymer such, for example, an acrylic polymer. As examples of acrylic polymers, mention may be made of PMMA and impact modifiers of the core/shell type. The proportion of oxidized fluoropolymer may be between 1 and 99% by weight of the blend. Advantageously, the proportion of oxidized fluoropolymer is between 2 and 30% by weight of the blend. Preferably, the proportion of oxidized fluoropolymer is between 2 and 15% by weight of the blend.
The following polymers were used:
A KYNAR 711 powder was placed in a sealed bag comprising a layer of paper, a layer of aluminium and a layer of polyethylene. This bag was itself placed in an identical bag, both bags being hermetically sealed by heat sealing. This KYNAR powder was irradiated to 10 Mrad. After the bags were opened under a hood and after devolatilization for at least two hours, in order to remove all the volatiles produced during the irradiation step, the oxidized fluoropolymer was bonded to the LOTADER 8840 from Atofina in a symmetrical oxidized PVDF (500 μm)/LOTADER 8840 (200 μm)/oxidized PVDF (500 μm) structure. A peel test was carried out on this structure and a peel force of 35 N/cm was measured.
A KYNAR 711 powder was bonded to LOTADER 8840 from Atofina in a symmetrical PVDF (500 μm)/LOTADER 8840 (200 μm)/PVDF (500 μm) structure. A peel test was carried out on this structure and a peel force of 0.5 N/cm was measured.
KYNAR 710 granules were placed in a sealed bag comprising a layer of paper, a layer of aluminium and a layer of polyethylene. This bag was itself placed in an identical bag, both bags being hermetically sealed by heat sealing. The KYNAR was irradiated to 5 Mrad. After the bags were opened under a hood and after devolatilization for at least two hours, in order to remove all the volatiles produced during the irradiation step, the oxidized fluoropolymer was bonded to the LOTADER 8840 from Atofina in a symmetrical oxidized PVDF (500 μm)/LOTADER 8840 (200 μm)/oxidized PVDF (500 μm) structure. A peel test was carried out on this structure and a peel force of 30 N/cm was measured.
A KYNAR® 711 powder was placed in a sealed bag comprising a layer of paper, a layer of aluminium and a layer of polyethylene. This bag was itself placed in an identical bag, both bags being hermetically sealed by heat sealing. This KYNAR powder was irradiated to 10 Mrad. After the bags were opened under a hood and after devolatilization for at least two hours, in order to remove all the volatiles produced during the irradiation step, the oxidized fluoropolymer was bonded to an aluminium foil at 250° C. The structure obtained could not be peeled apart.
A KYNAR 711 powder was placed in a sealed bag comprising a layer of paper, a layer of aluminium and a layer of polyethylene. This bag was itself placed in an identical bag, both bags being hermetically sealed by heat sealing. This KYNAR powder was irradiated to 10 Mrad. After the bags were opened under a hood and after devolatilization for at least two hours, in order to remove all the volatiles produced during the irradiation step, the oxidized fluoropolymer was blended with an unmodified fluoropolymer in proportions of 50/50 by weight. This blend was bonded to the LOTADER 8840 from Atofina in a symmetrical oxidized PVDF (500 μm)/LOTADER 8840 (200 μm)/oxidized PVDF (500 μm) structure. A peel test was carried out on this structure and a peel force of 35 N/cm was measured.
| Number | Date | Country | Kind |
|---|---|---|---|
| 03.09223 | Jul 2003 | FR | national |
This application claims benefit, under U.S.C. § 119(a) of French National Applications Number 03.09223, filed Jul. 28, 2003; and also claims benefit, under U.S.C. § 119(e) of U.S. provisional application 60/509,619, filed Oct. 8, 2003.
| Number | Date | Country | |
|---|---|---|---|
| 60509619 | Oct 2003 | US |
