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EP-4741135-A1 - TUBES AND METHODS OF MAKING SAME

EP4741135A1EP 4741135 A1EP4741135 A1EP 4741135A1EP-4741135-A1

Abstract

The disclosure relates to a tube having differentiated compositions and properties along its length, and to a method for making such a tube. The tube comprises a polymer resin, an elastomer, and optional components, and is formed by continuous extrusion using multiple feeders. The tube includes a first region containing a first composition of 70-100 wt.% polymer resin, 0-30 wt.% elastomer, and 0-10 wt.% optional components, and a second region, at a length from the first region of at least 30 times the OD, containing a second composition of 0-50 wt.% polymer resin, 50-100 wt.% elastomer, and 0-10 wt.% optional components. The polymer resin and elastomer concentrations vary continuously between the regions to produce a compositionally graded structure having a hardness, tensile strength, elasticity, or color differentiation of at least 10% between the first and second region.

Inventors

  • BALZANO, Luigi

Assignees

  • Kraton Polymers Nederland B.V.

Dates

Publication Date
20260513
Application Date
20251110

Claims (15)

  1. 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 elastomer; 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 elastomer, same or different from the first elastomer; 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 elastomer 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%, 20%, or 30% 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 elastomer is selected from styrenic thermoplastic elastomers, styrenic 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%, 25%, or 30 %.
  2. The tube of claim 1, wherein the tube is obtained by continuous extrusion, optionally using at least two feeders positioned along an extruder barrel to vary the relative proportions of the polymer resin and elastomer along the length of the tube.
  3. The tube of any of claims 1-2, wherein the elastomer is a styrenic-based thermoplastic elastomer selected from unhydrogenated styrenic block copolymers and hydrogenated styrenic block copolymers.
  4. The tube of any of claims 1-3, wherein the styrenic-based thermoplastic elastomer is a hydrogenated styrenic block copolymer having a general configuration selected from S-E/B-S, (S-E/B) n X, (S-E/B-S) n X, S-EP-S, (S-EP)nX, (S-EP-S)nX, S-E/B/S-S, (S-E/B/S-S) n X, (S-E/B/S) n X, S-EP/S-S, (S-EP/S-S) n X, (S-EP/S) n X, 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.
  5. The tube of any of claims 1-4, wherein the polymer resin is a polyolefin.
  6. The tube of any of claims 1-5, wherein the tube is obtained by continuous extrusion in an extruder, wherein the polymer resin and elastomer concentrations vary continuously along the extrusion direction to form a longitudinal composition gradient without co-extrusion of separate streams.
  7. The tube of any of claims 1-6, wherein the tube exhibits a hardness variation of at least 10 %, 20 %, or 30 % between the first region and the second region, and wherein said hardness varies continuously along the longitudinal direction of the tube corresponding to the extrusion direction over at least 30 %, 40 %, or 50 % of the total tube length.
  8. The tube of any of claims 1-7, wherein the tube exhibits a longitudinal hardness gradient ranging from a Shore D hardness of 60-90 at the first region to a Shore A hardness of 15-50 at the second region.
  9. The tube of any of claims 1-8, wherein the tube has a total length of 4 inches to 8.2 ft (0.1 m to 2.5 m), corresponding to a length-to-diameter (L/OD) ratio of 5-700.
  10. The tube of any of claims 1-9, wherein the tube is obtained by progressively varying the feed rate of the elastomer relative to the polymer resin over time during continuous extrusion through separate primary and secondary feeders positioned at different barrel sections of an extruder, thereby forming a longitudinal property gradient along the extrusion direction without joining separate tube sections.
  11. The tube of any of claims 1-10, wherein the tube length from the first region to the second region exhibits at least one of the following longitudinal property gradients: (a) hardness decreasing from 60-90 of Shore D at the first region to 15-50 of Shore A at the second region; (b) tensile strength decreasing from 25-120 MPa at the first region to 2-30 MPa at the second region; (c) flexural modulus decreasing from 1,000-5,000 MPa at the first region to 1-100 MPa at the second region; and (d) elongation at break increasing from 50-200 % at the first region to 150-1,000 % at the second region.
  12. 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%, 20%, or 30% 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 %, 25 %, or 30 %.
  13. The method of claim 12, wherein the polymer resin is a polyolefin and the elastomer is a styrenic-based thermoplastic elastomer selected from unhydrogenated or hydrogenated styrenic block copolymers.
  14. The method of any of claims 12-13, wherein the compositional gradient is established by progressively varying the feed rate of the elastomer relative to the polymer resin over time in a single extruder, thereby forming a longitudinal and continuous composition gradient along the extrusion direction without co-extrusion of separate material streams into the die.
  15. The method of any of claims 12-14, wherein the tube obtained exhibits a hardness variation of at least 10 %, 20 %, or 30 % between the first region and the second region, and wherein said hardness varies continuously along the longitudinal extrusion direction.

Description

FIELD The disclosure relates to a tube having a gradient of properties along the length of the tube, e.g., hardness, tensile strength, elasticity, or color intensity, etc., made by extrusion and methods of manufacturing same. BACKGROUND Polymeric and elastomeric tubes are widely used across many industries, including medical, industrial, automotive, and consumer applications. These tubes often exhibit differentiated mechanical or physical properties along their length, such as varying hardness, elasticity, flexibility, or color, to meet functional requirements specific to each segment of the tube. For example, in medical catheters, certain portions of the tube may need to be softer and more flexible for patient comfort near insertion sites, while other portions require higher rigidity for control, stability, or torque transmission. Similarly, in industrial or automotive tubing, property gradients can enhance vibration damping, provide flexibility near couplings, or increase wear or chemical resistance in high-stress regions. Traditional techniques for producing tubing with different properties along its length typically involve joining or welding segments made from different materials. While effective for creating discrete hardness zones, these processes increase manufacturing complexity and may introduce weak joints or discontinuities. Other approaches, such as localized heating or cooling, can alter crystallinity and hardness but are difficult to control and yield inconsistent gradients. Co-extrusion techniques, which extrude multiple materials simultaneously through concentric dies, have also been applied to create radial or layered gradients but require complex machinery, precise synchronization of multiple material flows, and are limited to polymer pairs that exhibit interfacial compatibility. There remains a need for a simpler and more versatile process capable of forming longitudinally (axially) and continuously graded tubing without reliance on conventional co-extrusion or welding techniques. SUMMARY In an aspect, a tube having differentiated composition and physical properties along its length, and a method for manufacturing such a tube is disclosed. The tube comprises at least a polymer resin and an elastomer whose concentrations vary continuously along the tube. The tube comprises a first region containing a first composition having defined concentrations of components comprising, consisting essentially of, or consisting of 70 to 100 wt.% polymer resin, 0 to 30 wt.% elastomer, and 0 to 10 wt.% optional components, and a second region containing a second composition having defined concentrations of components comprising, consisting essentially of, or consisting of 0 to 50 wt.% polymer resin, 50 to 100 wt.% elastomer, and 0 to 10 wt.% optional components. The concentrations of the polymer resin and elastomer 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, or flexural modulus differs by at least 10%, 20%, or 30% 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. The tube has a length-to-diameter (L/OD) ratio of about from 5 to 1,500. The polymer resin is selected from fluorine-based polymers, polyolefins, polyurethanes, styrenic polymers, polyesters, polyamides, vinyl polymers, polycarbonates, and mixtures thereof. The elastomer is selected from styrenic thermoplastic elastomers, styrenic thermoplastic olefins, polyolefin elastomers, ethylene-propylene rubber, thermoplastic polyurethanes, and mixtures thereof. 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%, 25%, or 30 %, the hardness being measured according to ASTM D2240 and the flexural modulus according to ASTM D790. In an aspect, a method of making a tube having an outside diameter (OD) is disclosed. The method comprises feeding a first composition having defined concentrations of components comprising, consisting essentially of, or consisting 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, consisting essentially of, or consisting 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 primary feeder, secondary 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 lo