Thermoplastic composition for monolayer tube, air-conditioning circuit and method for preparing the composition

A thermoplastic composition capable of forming a monolayer tube for transporting a fluid, the monolayer tube being in particular adapted for transporting a refrigerant gas in an air-conditioning circuit of a motor vehicle, wherein the thermoplastic composition comprises in weight fractions:

• more than 20% and up to 40% of a PA 6.10 and/or a PA 6.12 as at least one aliphatic polyamide,
• from 45% to less than 60% of at least one polyphthalamide having a glass transition temperature higher than 120° C. and selected from the group consisting of PA 6.I/6.T, PA 9.T, PA 10.T, PA 10.T/X and mixtures thereof, where X represents at least one polyamide unit other than PA 10.T derived from an aliphatic diamine having from 6 to 9 carbon atoms and from an aromatic dicarboxylic acid comprising terephthalic or isophthalic acid, and
• from 10% to 20% of a compatibilizing system comprising a product of a reaction between (a) a polymer of at least one first olefin comprising an unsaturated epoxide and (b) a polymer of at least one second olefin comprising an unsaturated carboxylic acid, with a weight ratio (a):(b) greater than 1, said at least one second olefin being identical to or different from said at least one first olefin.