Adhesive composition and structure comprising at least one layer of said composition
An adhesive composition including predominantly one or two polyamide(s) having units chosen from: at least one unit denoted A with a mean number of carbon atoms per nitrogen atom, denoted CA, ranging from 4 to 8.5, advantageously from 4 to 7; at least one unit denoted B with a mean number of carbon atoms per nitrogen atom, denoted CB, ranging from 7 to 10, advantageously from 7.5 to 9.5; at least one unit denoted C with a mean number of carbon atoms per nitrogen atom, denoted CC, ranging from 9 to 18, advantageously from 10 to 18, and to the use thereof.
1. An adhesive composition predominantly comprising a polyamide composition consisting of two polyamides, wherein at least one polyamide is a copolyamide, the polyamide composition consisting of units chosen from:
at least one amide unit denoted A (amide unit A) with a mean number of carbon atoms per nitrogen atom, denoted CA, ranging from 4 to 8.5;
at least one amide unit denoted B (amide unit B) with a mean number of carbon atoms per nitrogen atom, denoted CB, ranging from 7 to 10;
at least one amide unit denoted C (amide unit C) with a mean number of carbon atoms per nitrogen atom, denoted CC, ranging from 9 to 18; and
optionally at least one unit Z other than an amide unit;
the three units A, B and C being present together in said two polyamides;
one of the units A, B or C being in a very predominant proportion in the copolyamide and representing from 80% to 97% by weight relative to the total weight of the copolyamide;
the mean number of carbon atoms per nitrogen atom of the units A, B and C also corresponding to the following strict inequality: CA<CB<CC;
the mass-weighted mean of the heats of fusion of the polyamide composition being greater than 25 J/g (DSC);
the melting point of each of the polyamides being greater than 150° C. (DSC).
2. The composition as claimed in claim 1 , wherein the difference between mean numbers of carbon atoms per nitrogen atom (CB-CA) and/or (CC-CB) ranges from 1 to 4.
3. The composition as claimed in claim 1 , wherein the two polyamides denote a homopolyamide combined with a copolyamide.
4. The composition as claimed in claim 3 , wherein the polyamide composition is a mixture of a copolyamide consisting of two units chosen from units A, B and C and of a homopolyamide consisting of the third unit A, B or C, which is absent from the structure of the copolyamide.
5. The composition as claimed in claim 4 , wherein the homopolyamide is of unit A and the melting point of the homopolyamide is greater than or equal to 210° C.; or wherein the homopolyamide is of unit C and the melting point of the homopolyamide is less than 200° C.
6. The composition as claimed in claim 1 , wherein the two polyamides denote two copolyamides.
7. The composition as claimed in claim 6 , wherein the polyamide composition is a mixture of two different copolyamides each consisting of two units chosen from units A, B and C.
8. The composition as claimed in claim 1 , wherein
the amide unit A is chosen from units derived from the following monomers: 6, 4.6, 6.6, 6.T, 9.T and 9′.T, 9′ denoting 2 methyl-1,8-octanediamine;
the amide unit B is chosen from units derived from the following monomers: 6.10, 6.12, 9.T and 9′.T, and
the amide unit C is chosen from units derived from the following monomers: 10.10, 11, 12, 10.12, 6.18, 10.T, 12.T, 12/10.T, 12.12 and 10.10/10.T.
9. The composition as claimed in claim 1 , wherein
the amide unit A is chosen from units derived from the following monomers: 6, 4.6 and 6.6;
the amide unit B is chosen from units derived from the following monomers: 6.10, 6.12, and
the amide unit C is chosen from units derived from the following monomers: 10.10, 11, 12, 10.12, 12.12 and 6.18.
10. A structure comprising at least a first layer and a second layer, wherein the first layer is an adhesive layer (I) formed from the adhesive composition as defined in claim 1 .
11. The structure as claimed in claim 10 , wherein the structure is in the form of a pipe, a container, a film or a plate.
12. The structure as claimed in claim 10 , wherein the second layer is a barrier layer (II) formed from a composition comprising at least one polymer that is a barrier to biofuels, chosen from EVOH, a weakly-carbonic polyamide, and a mixture thereof.
13. The structure as claimed in claim 12 , wherein the structure comprises at least a third layer, the third layer is a long-lasting layer (III) formed from a composition comprising a high-carbon polyamide, the adhesive layer (I) being arranged between said long-lasting layer (III) and the barrier layer (II) and adhering to the respective zone of contact thereof.
14. The structure as claimed in claim 10 , wherein the second layer is a barrier layer (II), wherein the structure comprises at least a third layer, the third layer is a long-lasting layer (III) formed from a composition comprising a high-carbon polyamide, the adhesive layer (I) being arranged between said long-lasting layer (III) and the barrier layer (II) and adhering to the respective zone of contact thereof.
15. A method for transporting or storing a fluid, the method comprising transporting or storing a fluid in the structure as defined in claim 10 , in the form of a pipe.
16. The method as claimed in claim 15 , wherein the fluid is chosen from an oil, a brake liquid, a urea solution, a glycol-based cooling liquid, fuels, and compressed air.