Multilayer tubular structure having better resistance to extraction in biofuel and use thereof

A multilayer tubular structure (MLT) suitable for the transport of fuels, wherein the MLT comprises, from the outside inwards, at least one first barrier layer, at least one inner layer located below the first barrier layer, and optional layers located below the first barrier layer, wherein:

• the first barrier layer comprises EVOH or comprises PPA;
• and
• the inner layer comprises at least two aliphatic polyamides, wherein the aliphatic polyamides are selected from the group consisting of PA610, PA612, and PA1012,
• with the proviso that when the inner layer comprises at least three polyamides, at least one of said polyamides PA610, PA612 and PA1012 is excluded,
• wherein at least one first outer layer is present and wherein the first outer layer is located further outwards, above the first barrier layer, wherein the at least one first outer layer comprises at least one polyamide of aliphatic type or comprises more than 75% of aliphatic units,
• wherein the first outer layer comprises plasticizer in a proportion from 0% to 5% by weight relative to the total weight of the composition of the at least one first outer layer,
• wherein at least one second outer layer located above the barrier layer is present, and is located above the at least one first outer layer wherein the at least one second outer layer comprises plasticizer in a proportion from 0% to 5% by weight relative to the total weight of the composition of the at least one second outer layer,
• wherein the inner layer and the optional layers located below the first barrier layer do not comprise plasticizer,
• wherein at least one first binder layer is present, where the first binder layer contains at most 15% by weight of plasticizer relative to the total weight of the constituents of the first binder layer, where the first binder layer comprises at least one aliphatic polyamide of an aliphatic type or which comprises more than 75% of aliphatic units, wherein the aliphatic polyamide is selected from the group consisting of:
• a polyamide denoted A, having a mean number of carbon atoms per nitrogen atom, denoted CA, of from 4 to 8.5;
• a polyamide denoted B, having a mean number of carbon atoms per nitrogen atom, denoted CB, of from 7 to 10;
• and
• a polyamide denoted C, having a mean number of carbon atoms per nitrogen atom, denoted CC, of from 9 to 18,
• with the proviso that when the first binder layer comprises at least three polyamides, at least one of the polyamides A, B and C is excluded;
• wherein the first binder layer is located between the first barrier layer and the inner layer;
• wherein the thickness of the first binder layer comprises at most 15% of the total thickness of the MLT.