Tubes and methods of making same

A method of making a tube having an outside diameter (OD), the method comprising:

• feeding a first composition having defined concentrations of components comprising a polymer resin, an elastomer, and optional components to a first feeder of an extruder;
• feeding a second composition having defined concentrations of components comprising a polymer resin, an elastomer, and optional components to a second feeder located downstream along a barrel of the extruder;
• optionally feeding one or more optional components to the first feeder, second feeder, or both;
• controlling the relative feed rates of the first composition and the second composition during continuous extrusion to vary the concentrations of the polymer resin and elastomer components longitudinally and continuously along the extrusion direction, thereby forming a compositionally graded melt;
• and
• extruding the compositionally graded melt through a die to produce a tube in which at least one physical property selected from hardness, tensile strength, elongation at break, or flexural modulus differs by at least 10% between the first region and the second region, wherein hardness is measured according to ASTM D2240, flexural modulus according to ASTM D790, tensile strength according to ASTM D638, and elongation at break according to ASTM D412;
• and
• wherein the first composition comprises 70-100 wt. % of a first polymer resin, 0-30 wt. % of a first elastomer, and 0-10 wt. % optional components;
• wherein the second composition comprises 0-50 wt. % of a second polymer resin, same or different from the first polymer resin, 50-100 wt. % of a second elastomer, same or different from the first elastomer, and 0-10 wt. % optional components, same or different from the optional components in the first composition, each based on the total weight of the respective composition;
• wherein the polymer resin is selected from the group of fluorine-based polymers, polyolefins, polyurethanes, styrenic polymers, polyesters, polyamides, vinyl polymers, polycarbonates and mixtures thereof;
• wherein the elastomer is selected from the group of styrenic-based thermoplastic elastomers, styrenic-based thermoplastic olefins, polyolefin elastomers, ethylene propylene rubber, thermoplastic polyurethanes, and mixtures thereof;
• and
• wherein the polymer resin and the elastomer differ in at least one of Shore A hardness, Shore D hardness, and flexural modulus by at least 20%.

A tube having an outside diameter (OD), the tube comprising along its length:

• a first region comprising a first composition having defined concentrations of components comprising:
• a) 70-100 wt. % of a first polymer resin;
• b) 0-30 wt. % of a first hydrogenated styrenic block copolymer;
• and
• c) 0-10 wt. % optional components;
• a second region comprising a second composition having defined concentrations of components comprising:
• a) 0-50 wt. % of a second polymer resin, same or different from the first polymer resin;
• b) 50-100 wt. % of a second hydrogenated styrenic block copolymer, same or different from the first hydrogenated styrenic block copolymer;
• and
• c) 0-10 wt. % optional components, same or different from the optional components in the first composition;
• wherein the concentrations of the polymer resin and hydrogenated styrenic block copolymer components vary longitudinally and continuously along the length of the tube between the first region and the second region to form a compositionally graded structure in which at least one physical property selected from hardness, tensile strength, elongation at break, and flexural modulus differs by at least 10% between the first region and the second region, wherein hardness is measured according to ASTM D2240, flexural modulus according to ASTM D790, tensile strength according to ASTM D638, and elongation at break according to ASTM D412;
• wherein the tube has a length-to-diameter (L/OD) ratio of from 5 to 1,500;
• wherein the polymer resin is selected from fluorine-based polymers, polyolefins, polyurethanes, styrenic polymers, polyesters, polyamides, vinyl polymers, polycarbonates, and mixtures thereof;
• and
• wherein the hydrogenated styrenic block copolymer has a general configuration selected from S-E/B-S, (S-E/B)nX, (S-E/B-S)nX, S-EP-S, (S-EP)nX, (S-EP-S)nX, S-E/B/S-S, (S-E/B/S-S)nX, (S-E/B/S)nX, S-EP/S-S, (S-EP/S-S)nX, (S-EP/S)nX, and mixtures thereof;
• wherein
• each block S is a polymer block composed of vinyl aromatic units;
• each block E/B is a polymer block composed of ethylene (“E”) units and butylene (“B”) units;
• each block EP is a polymer block composed of ethylene-propylene (“EP”) units;
• each block E/B/S is a polymer block composed of ethylene (“E”) units/butylene (“B”) units/and vinyl aromatic (“S”) units;
• each block EP/S is a polymer block composed of ethylene-propylene (“EP”) units and vinyl aromatic (“S”) units;
• n is an integer from 2 to 30;
• and
• X is a residue of a coupling agent;
• and
• wherein the polymer resin and the hydrogenated styrenic block copolymer differ in at least one of Shore A hardness, Shore D hardness, and flexural modulus by at least 20%.