Thermoplastic multilayer tubes and process for manufacturing

1. A multi-layer tube comprising:

A) a first layer comprising a first layer composition comprising

a1) about 35 to 90 weight percent of a semi-aromatic polyamide whose repeat units consist essentially of about 60 to about 85 molar percent of repeat units of the formula

—C(O)(CH 2 ) m C(O)NH(CH 2 ) 6 NH—tm (I)

wherein m is 8 and/or 10, and about 15 to about 40 molar percent of repeat units of the formula

a2) 0 to 40 weight percent of polymeric toughener;

a3) 0 to 15 weight percent plasticizer;

a4) 5 to 35 weight percent aliphatic homopolyamide having a repeat unit derived from an aliphatic diamine and aliphatic dicarboxylic acid, amino acid or lactam, wherein said aliphatic diamine, amino acid or lactam, have 6 or less carbon atoms;

a5) 0 to 5 of additives selected from the group consisting of colorants, antioxidants, heat stabilizers, light stabilizers, lubricants, and nucleants;

wherein the ratio of a1 :a4 in the first layer composition is about 80:20 to about 50:50; and

B) a second layer comprising a second layer composition comprising

b1) 50 to 100 weight percent of poly(caprolactam);

b2) 0 to 40 weight percent of polymeric toughener;

b3) 0 to 15 weight percent plasticizer;

b4) 0 to 5 of additives selected from the group consisting of colorants, antioxidants, heat stabilizers, light stabilizers, lubricants, and nucleants;

with the proviso that the first layer and second layer are in direct contact; and the weight percents are based upon the total weight of the first layer composition and the second layer composition, respectively; and

wherein the first layer (A) of the multilayer tube is an outer layer and the second layer (B) of the mufti-layer tube is an inner layer.

2. The multi-layer tube of claim 1 wherein the semi-aromatic polyamide repeat units consist essentially of about 68 to about 82 molar percent of formula (I) and about 18 to 32 molar percent, of repeat units of the formula (II).

3. The multi-layer tube of claim 1 wherein m is 10.