Composite thermoplastic material for composite tubular structures
The invention relates to a composition comprising at least one fluoropolymer and at least one high-density filler. The invention also relates to a thermoplastic composite tubular structure which comprises at least one external layer consisting of said composition. The invention also relates to the process for the manufacture of said composition, and also to its applications as external layer for weighing down thermoplastic composite pipes transporting fluids in the context of oil and gas exploration and exploitation.
1 . A composite material consisting of a thermoplastic fluoropolymer matrix, said thermoplastic fluoropolymer matrix containing fluoropolymer, in which are incorporated particles of at least one inorganic filler compatible with said fluoropolymer, said particles having a density of at least 3 g/cm 3 , the content by weight of fillers being from 50% and ranging up to 70%, said particles having a size defined by a D50 of less than 20 μm and of greater than or equal to 1 μm and a D90 of less than 50 μm and greater than or equal to 5 μm.
2 . The composite material as claimed in claim 1 , in which said fluoropolymer is selected from the group consisting of homopolymers of vinylidene fluoride (PVDF), copolymers comprising vinylidene fluoride (VDF) units and one or more types of units of comonomers compatible with vinylidene fluoride, and their mixtures.
3 . The composite material as claimed in claim 1 , in which said fluoropolymer is selected from the group consisting of:
a PVDF homopolymer;
a mixture of two PVDF homopolymers exhibiting at least one of different viscosities, or different molar masses, or different architectures;
a copolymer comprising VDF units and one or more types of units of comonomers;
a mixture of a PVDF homopolymer and of a VDF copolymer;
a mixture of two VDF copolymers.
4 . The composite material as claimed in claim 2 , in which said comonomer compatible with VDF is selected from the group consisting of: hexafluoropropylene, perfluoro(methyl vinyl) ether, perfluoro(ethyl vinyl) ether, perfluoro(propyl vinyl) ether, tetrafluoroethylene, perfluorobutylethylene, chlorotrifluoroethylene, fluorinated ethylene propylene and trifluoroethylene.
5 . The composite material as claimed in claim 2 , in which said comonomer is hexafluoropropylene, the copolymer having a content by weight of HFP of greater than 10%.
6 . The composite material as claimed in claim 1 , in which said filler is selected from the group consisting of: iron (II) oxide, iron (III) oxide, iron (II, III) oxide, zinc oxide, copper (I) oxide, copper (II) oxide, lead (II) oxide, nickel (II) oxide, aluminum (III) oxide, the mixtures of these oxides and the associated mineral compounds which can contain these metal oxides.
7 . The composite material as claimed in claim 1 , wherein said composite material has a density of greater than or equal to 2.15 g/cm 3 .
8 . The composite material as claimed in claim 1 , the particles of the filler having a size defined by a D50 of less than 10 μm and a D90 of less than 15 μm.
9 . The composite material as claimed in claim 1 , in which said filler comprises magnetite.
10 . The composite material as claimed in claim 1 , wherein said material is nonporous.
11 . A process for the manufacture of the composite material as claimed in claim 1 , said process comprising a step of heating the fluoropolymer to a molten state and mixing the fluoropolymer and the inorganic filler.
12 . The process as claimed in claim 11 , further comprising a step of extruding said composite material into a form of a pipe or sheath.
13 . A thermoplastic composite tubular structure comprising:
an internal polymer layer,
a laminate made of polymer reinforced with continuous fibers,
an external protective coating,
and at least one external layer comprising the composite material as claimed in claim 1 .
14 . The thermoplastic composite tubular structure as claimed in claim 13 , in which said at least one external layer exhibits a thickness of at least 5 mm, and a density of greater than or equal to 2.15 g/cm 3 .
15 . The composite material as claimed in claim 1 , in which said filler comprises a metal oxide.
16 . The composite material as claimed in claim 1 , wherein said particles have a density of at least 4 g/cm 3 .
17 . The composite material as claimed in claim 1 , wherein said particles have a density of at least 5 g/cm 3 .
18 . The composite material as claimed in claim 1 , wherein said composite material has a density of greater than or equal to 2.3 g/cm 3 .
19 . The composite material as claimed in claim 1 , wherein said composite material has a density of greater than or equal to 2.5 g/cm 3 .