Tube and method of making the same

Abstract

The present invention relates to a tube having different compositions and properties along its length, as well as a method of making such a tube. The tube contains a polymer resin, an elastomer, and optionally components, and is formed by continuous extrusion using a plurality of feeders. The tube comprises a first region comprising a first composition of 70-100 wt% of a polymer resin, 0-30 wt% of an elastomer, and 0-10 wt% of an optional component, and a second region having a length from the first region of at least 30 times of at least OD and comprising a second composition of 0-50 wt% of a polymer resin, 50-100 wt% of an elastomer, and 0-10 wt% of an optional component. The polymer resin and elastomer concentrations continuously vary between the regions to create a compositional hierarchy having a hardness, tensile strength, elasticity, or color difference of at least 10% between the first and second regions.

Description

Technical Field

[0001] This invention relates to a tube prepared by extrusion and a method thereof, wherein the tube has a property gradient (e.g., hardness, tensile strength, elasticity, or color intensity) along its length. Background Technology

[0002] Polymer and elastomer tubing is widely used in many industries, including medical, industrial, automotive, and consumer applications. These tubings typically exhibit varying mechanical or physical properties along their length, such as different levels of stiffness, elasticity, toughness, or color, to meet the specific functional requirements of each segment. For example, in medical catheters, some sections may require greater flexibility and resilience to provide patient comfort near the insertion site, while other sections require higher stiffness for control, stability, or torque transmission. Similarly, in industrial or automotive tubing, performance gradients can enhance vibration damping, provide flexibility near couplings, or increase abrasion or chemical resistance in high-stress areas.

[0003] Traditional techniques for producing pipes with varying properties along their length typically involve joining or welding sections made of different materials. While these processes effectively create discrete hardness zones, they increase fabrication complexity and can introduce weak joints or discontinuities. Other methods, such as localized heating or cooling, can alter crystallinity and hardness but are difficult to control and produce inconsistent gradients. Co-extrusion technology, which simultaneously extrudes multiple materials through concentric dies, has also been used to create radial or stratified gradients, but requires complex mechanics, precise synchronization of multiple material flows, and is limited to polymer pairs exhibiting interfacial compatibility.

[0004] There is still a need for a simpler and more versatile process that can produce longitudinally (axially) and continuously graded pipes without relying on traditional co-extrusion or welding techniques. Invention Overview

[0005] In one aspect, a tube with different compositions and physical properties along its length is disclosed, as well as a method for preparing such a tube. The tube comprises at least a polymer resin and an elastomer, the concentration of which varies continuously along the tube. The tube includes a first region and a second region, the first region comprising a first composition having a defined concentration of components, wherein the defined concentration of components comprises 70-100 wt% polymer resin, 0-30 wt% elastomer, and 0-10 wt% optional components; the second region comprises a second composition having a defined concentration of components, wherein the defined concentration of components comprises 0-50 wt% polymer resin, 50-100 wt% elastomer, and 0-10 wt% optional components. The concentrations of the polymer resin and elastomer components vary continuously along the longitudinal length of the tube between a first region and a second region to form a compositional hierarchy. 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 and second regions, wherein hardness is determined 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 length-to-diameter ratio (L / OD) of the tube is approximately 5-1500. The polymer resin is selected from fluoropolymers, polyolefins, polyurethanes, styrene-based polymers, polyesters, polyamides, vinyl polymers, polycarbonates, and mixtures thereof. The elastomer is selected from styrene-based thermoplastic elastomers, styrene-based thermoplastic olefins, polyolefin elastomers, ethylene propylene rubber, thermoplastic polyurethanes, and mixtures thereof. The polymer resin and elastomer differ by at least 20%, 25%, or 30% in at least one of Shore A hardness, Shore D hardness, and flexural modulus, wherein the hardness is determined according to ASTM D2240 and the flexural modulus is determined according to ASTM D790.

[0006] In one aspect, a method for preparing a tube having an outer diameter (OD) is disclosed. The method includes feeding a first composition having components of defined concentrations into a first feeder of an extruder, wherein the components include a polymer resin, an elastomer, and optional components; feeding a second composition having components of defined concentrations into a second feeder located downstream of the barrel of the extruder, wherein the components include a polymer resin, an elastomer, and optional components; optionally, feeding one or more optional components into a main feeder, a secondary feeder, or both; controlling the relative feed rates of the first and second compositions during continuous extrusion to continuously change the concentrations of the polymer resin and elastomer components longitudinally along the extrusion direction, thereby forming a compositionally graded melt; and extruding the compositionally graded melt through a die to produce a tube, wherein 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 a first region and a second region, wherein hardness is determined 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 first composition comprises 70-100 wt% of a first polymer resin, 0-30 wt% of a first elastomer, and 0-10 wt% of an optional component. The second composition comprises 0-50 wt% of a second polymer resin that is the same as or different from the first polymer resin, 50-100 wt% of a second elastomer that is the same as or different from the first elastomer, and 0-10 wt% of an optional component that is the same as or different from the optional component in the first composition. The polymer resin is selected from fluoropolymers, polyolefins, polyurethanes, styrene polymers, polyesters, polyamides, vinyl polymers, polycarbonates, and mixtures thereof. The elastomer is selected from styrene-based thermoplastic elastomers, styrene-based thermoplastic olefins, polyolefin elastomers, ethylene propylene rubber, thermoplastic polyurethanes, and mixtures thereof. The polymer resin and elastomer differ by at least 20%, 25%, or 30% in at least one of Shore A hardness, Shore D hardness, and flexural modulus, wherein the hardness is determined according to ASTM D2240 and the flexural modulus is determined according to ASTM D790.

[0007] In one aspect, the tube is a catheter. The catheter includes a compositional gradation structure in which stiffness, tensile strength, and elasticity vary longitudinally along the tube length. In some embodiments, the catheter has a length of 30-150 cm, an outer diameter of 1-10 mm, and an inner diameter of 0.5-5 mm. The stiffness gradient ranges from 60-90 Shore D in a first region (polymer-resin-rich) to 15-50 Shore A in a second region (elastomer-rich), thereby providing improved pushability, torque response, and patient comfort during insertion and navigation through vascular access.

[0008] Brief description of the attached figures

[0009] Appendix Figure 1 The image is a grayscale photograph of the extruded tubular section, showing a continuous transition along the extrusion direction from a light-colored region rich in polymer resin to a dark-colored region rich in elastomer (corresponding to the composition and hardness gradient described herein). Invention Details

[0010] The following terms have the following meanings.

[0011] "Composed of..." means that the composition includes only the specifically listed components and excludes other components that have a substantial impact on the technical solution or unique function of the present invention. However, it is not excluded that there may be trace amounts of other components that do not substantially affect the technical effect of the present invention, such as trace amounts of stabilizers, process residues, or solvents used in the preparation process.

[0012] "At least one of A, B and C" or "any one of [A, B and C]" means a single member, more than one member, or a combination of members. For example, at least one of A, B and C includes, for example, only A, only B, or only C, as well as any other combination of A and B, A and C, B and C, or A, B and C, or A, B and C.

[0013] A series of implementation schemes represented by “A, B or C” should be interpreted as including implementation schemes with only A, only B, only C, “A or B”, “A or C”, “B or C”, or “A, B or C”.

[0014] "Any one of A, B or C" means one of the options in A, B or C.

[0015] "Any of A, B, and C" means one or more options from A, B, and C. "Copolymer" refers to a polymer derived from a variety of monomers.

[0016] A "block copolymer" is a copolymer containing multiple monomers, where the monomers exist in the form of blocks. Each block consists of a set of monomer units that are different from the set of monomers that connect (surround) the blocks in the same block copolymer. Each block can be composed of homopolymers or random copolymers.

[0017] The "vinyl aromatic unit content" (VAC) of a block copolymer refers to the weight percentage of polymerized vinyl aromatic monomers (such as styrene, p-methylstyrene, etc.) in the block copolymer. VAC is calculated by dividing the total molecular weight of all vinyl aromatic units by the total molecular weight of the block copolymer. It can be measured using proton nuclear magnetic resonance spectroscopy (NMR). 1 H NMR) and / or 13The determination is performed using C NMR. VAC is sometimes used interchangeably with PSC (polystyrene content).

[0018] "Butene unit content" refers to the weight percentage of butene units (B) relative to all dienyl units in a given polymer (e.g., a hydrogenated block copolymer). Butene units are formed by the 1,2-addition polymerization of 1,3-butadiene monomers followed by hydrogenation. 1,3-butadiene monomers can also be polymerized by 1,4-addition polymerization, followed by hydrogenation to produce ethylene units (E). Both butene and ethylene units can be present in hydrogenated block copolymers, which may also contain vinyl aromatic units arranged in any order and / or other units derived from conjugated diene monomers. The butene unit content can be determined by... 1 HNMR and / or 13 C NMR determination. Before hydrogenation, the butene unit (B) content is sometimes used interchangeably with "vinyl content".

[0019] "Molecular weight" or M W This refers to the equivalent molecular weight of polystyrene in polymer blocks or block copolymers, expressed in kg / mol. W The molecular weight of a polymer can be determined using gel permeation chromatography (GPC) with polystyrene calibration standards, for example, according to ASTM 5296-19. The GPC detector can be an ultraviolet or refractive index detector, or a combination thereof. The chromatograph is calibrated using commercially available polystyrene molecular weight standards. The molecular weight of the polymer determined using GPC calibrated in this way is the polystyrene equivalent molecular weight or apparent molecular weight. M is referred to herein as... W It is measured at the peak of the GPC trace and is usually called the polystyrene equivalent "peak molecular weight", denoted as Mp.

[0020] "Hydrogenated SBC" or "HSBC" refers to a styrene block copolymer (SBC) in which the diene unit is hydrogenated to a level of >90 mol%, or preferably >95 mol%, or more preferably >98 mol%, or <100 mol%, and the vinyl aromatic unit is hydrogenated to a level of <20 mol%, or preferably <10 mol%, or more preferably <5 mol%.

[0021] "Hydrogenation level" refers to the saturation level (expressed as a percentage) of double bonds (e.g., olefins, aromatics, etc.) in a block copolymer, which can be determined by... 1 H NMR determination.

[0022] "Residual unsaturation," or RU, refers to the level of unsaturation, specifically the number of carbon-carbon double bonds per gram of block copolymer. RU can be used... 1 Determined by HNMR or ozone decomposition titration.

[0023] A "unit" refers to a structural block derived from one or more polymerized monomers, representing a repeating entity that forms part of a polymer or copolymer chain. Unlike a "monomer," which is a single molecule before polymerization, a "unit" is a transformed version of the monomer after the polymerization process.

[0024] "Coupling efficiency," or CE, refers to the percentage (wt%) of coupled polymer molecules relative to the total weight of coupled and uncoupled polymer molecules in a block copolymer. CE is expressed as a percentage (%) and can be used to estimate the content of diblock structures in a block copolymer, or more generally, the proportion of "uncoupled arms." For example, an CE of 80% indicates that the block polymer contains 20 wt% diblock (uncoupled) material and 80 wt% triblock and multi-arm material.

[0025] The polydispersity index (PDI) is the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), and is sometimes referred to as molecular weight distribution. PDI is used to indicate the distribution of molecular weight of polymer chains in a given polymer.

[0026] "Continuous" refers to a gradual change in components or physical properties along a defined direction (e.g., the longitudinal direction of the tube or the extrusion direction). A continuous change occurs when the relative proportions of the polymer resin, elastomer, and / or optional components gradually change over time or distance during extrusion, resulting in the absence of discrete boundaries, welds, or fusion lines between regions of different compositions. The inherent minute local fluctuations in polymer melt mixing are also included in the meaning of "continuous," provided that the entire transition occurs smoothly and gradually along the defined direction.

[0027] The terms “difference,” “variation / change,” and “gradient” are used interchangeably to describe measurable differences or changes in the composition and / or physical properties of the tube. Unless otherwise stated, these terms include both quantifiable differences between different longitudinal regions of the same tube (e.g., between a first region and a second region) and continuous transitions (e.g., along the longitudinal or extrusion direction of the tube) of parameters such as polymer resin content, elastomer content, optional component concentration, hardness, tensile strength, elasticity, color intensity, or other physical or chemical properties.

[0028] The difference or change in the physical property values ​​(e.g., hardness or flexural modulus) between the polymer resin and the elastomer refers to a relative change calculated according to the following relationship:

[0029] ΔP = │ – │ / × 100%

[0030] in and The values ​​represent the measured performance values ​​of the polymer resin and elastomer, respectively. Unless otherwise stated, This corresponds to polymer resins that typically exhibit higher hardness or flexural modulus. Hardness values ​​are determined according to ASTM D2240 (Shore A or Shore D scale, as applicable), and flexural modulus values ​​are determined according to ASTM D790. A difference (ΔP) of at least 20%, 25%, or 30% indicates that the two components are mechanically different, enabling the establishment of a measurable hardness or stiffness gradient in the resulting tube.

[0031] This invention relates to tubes having compositional (component) and performance gradients along their length, and to a method for preparing such articles. The tubes are formed from compositions comprising one or more polymer resins, one or more elastomers, and optional components. The relative concentrations of these components vary longitudinally along the extrusion direction to provide regions with different physical properties (e.g., hardness, flexibility, color, or chemical resistance) without discrete joints or welds.

[0032] In some embodiments, a first region of the tube (polymer resin-rich or "hard" region) comprises a first composition containing 70-100 wt% of a first polymer resin, 0-30 wt% of a first elastomer, and 0-10 wt% of optional components, based on the total weight of the first composition. A second region of the tube (elastomer-rich or "soft" region) comprises a second composition containing 0-50 wt% of a second polymer resin, the same as or different from the first polymer resin, 50-100 wt% of a second elastomer, the same as or different from the first elastomer, and 0-10 wt% of optional components, based on the total weight of the second composition.

[0033] The tube is continuously extruded using an extruder equipped with multiple feeders (thus allowing the relative feed rates and / or component ratios of the polymer resin, elastomer, and optional components to vary gradually during extrusion to establish the desired compositional gradient). As used herein, the term "region" refers to a component area or portion along the length of the tube and does not necessarily correspond to discrete physical boundaries or ends.

[0034] Polymer resin: The pipe comprises at least one polymer resin that provides structural integrity, chemical resistance, barrier properties, and thermal stability to ensure durability and performance in pipe applications. The polymer resin may be a homopolymer or copolymer selected from the following: fluoropolymers, olefin polymers, polyurethanes, styrene polymers, polyesters, polyamides, vinyl polymers, polycarbonates, and mixtures thereof.

[0035] In some embodiments, the polymer resin is biocompatible and suitable for medical or healthcare tubing that comes into contact with bodily fluids, while in other embodiments, the resin is an industrial or engineering grade material selected based on mechanical strength, chemical or heat resistance, optical transparency, or other functional requirements. The polymer resin contributes to the tubing's ability to maintain dimensional stability, resist chemicals or sterilization processes, and provide a smooth inner surface for fluid or material transport.

[0036] Examples of fluoropolymers include polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), and perfluoroalkoxy fluoropolymers (PFA).

[0037] Olefin-based polymers include polyethylene, polypropylene, or mixtures thereof. In some embodiments, olefin-based polymers include ethylene homopolymers, ethylene / α-olefin copolymers, propylene homopolymers, propylene / α-olefin copolymers, high-impact polypropylene, butene homopolymers, butene / α-olefin copolymers, and other α-olefin copolymers or interpolymers. Representative polyolefins include, for example, but not limited to, substantially linear ethylene polymers, uniformly branched ethylene polymers, and non-uniformly branched ethylene polymers, including linear low-density polyethylene (LLDPE), ultra-low-density or very low-density polyethylene (ULDPE or VLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and low-density polyethylene (LDPE). Other olefin-based polymers include ethylene / acrylic acid (EEA) copolymers, ethylene / methacrylic acid (EMAA) ionomers, ethylene / vinyl acetate (EVA) copolymers, ethylene / vinyl alcohol (EVOH) copolymers, ethylene / cyclic olefin copolymers, polyvinyl chloride (PVC), and blends of PVC with other materials.

[0038] Examples of polyurethanes include thermoplastic polyurethanes (TPUs), polycarbonate-based polyurethanes, aromatic polyurethanes, aliphatic polyurethanes, thermosetting polyurethanes, and mixtures thereof.

[0039] Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polycaprolactone, thermoplastic polyesters, and mixtures thereof.

[0040] Examples of polyamides include, but are not limited to, polyamide 6 (PA6), polyamide 66 (PA66), polyamide 46 (PA46), polyamide 410 (PA410), polyether block amide (PEBA), and mixtures thereof.

[0041] Examples of styrene polymers include acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), polystyrene (PS), and mixtures thereof.

[0042] Examples of vinyl polymers include polyvinyl chloride (PVC), polyvinyl acetate (PVA), and mixtures thereof.

[0043] Examples of polycarbonates include bisphenol A polycarbonates, aromatic-aliphatic copolycarbonates, poly(ester-carbonate) copolymers, aliphatic polycarbonates (e.g., poly(trimethylene carbonate) and poly(hexamethylene carbonate), and mixtures thereof.

[0044] In some embodiments, the tensile strength of the polymer resin is >5 MPa, or >10 MPa, or >15 MPa, or >25 MPa, or >30 MPa, or >40 MPa, or <120 MPa, or <100 MPa, or <90 MPa, or <80 MPa, or <70 MPa, or 5-120 MPa, or 10-100 MPa, or 25-90 MPa, or 25-75 MPa, or 30-70 MPa, as determined according to ASTM D638. Lower values ​​are typical for flexible or elastomeric modified resins (e.g., thermoplastic polyurethanes, vinyl polymers, or soft polyolefins), while higher values ​​are characteristic of rigid engineering resins (e.g., polyamides, polyesters, or highly crystalline polyolefins).

[0045] In some embodiments, the flexural modulus of the polymer resin is >50 MPa, or >100 MPa, or >250 MPa, or >750 MPa, or >1000 MPa, or <1200 MPa, or <6000 MPa, or <5000 MPa, or 50-6000 MPa, or 100-5000 MPa, or 750-4000 MPa, or 1000-4000 MPa, or 1000-3500 MPa, as determined according to ASTM D790.

[0046] In some embodiments, the polymer resin has a Young's modulus of >10 MPa, or >15 MPa, or >25 MPa, or >50 MPa, or <5000 MPa, or <4000 MPa, or <3500 MPa, or 10-5000 MPa, or 25-4000 MPa, or 50-3500 MPa, as determined according to ASTM D638. The lower end of this range corresponds to more flexible resins, such as thermoplastic polyurethanes, vinyl polymers, or elastomer-modified polyolefins, while the upper end corresponds to rigid resins, such as polyamides, polyesters, or highly crystalline polyolefins.

[0047] The tube is characterized in that the concentration of the polymer resin is gradient-distributed along its length. In some embodiments, a first region of the tube comprises a first composition having a defined concentration of a component comprising 70-100 wt%, 75-100 wt%, or 80-100 wt% of the first polymer resin based on the total weight of the first composition; a second region comprises a second composition having a defined concentration of a component comprising a smaller amount (e.g., 0-50 wt%, 10-40 wt%, or 15-35 wt%) of the second polymer resin based on the total weight of the second composition.

[0048] The gradient distribution can be achieved, depending on the tube length, by varying the amount of the polymer resin or by changing the type or blend of the polymer resin. In some embodiments, the gradient is formed by introducing different polymer resins or polymer resin blends using a secondary (side) feeder, thereby creating a continuous transition between regions of different compositions. For example, a first composition at one end of the tube may contain polyamide, a second composition downstream may contain a mixture of polyamide and polyester, and a third composition further downstream may contain a blend of polyamide, polyester, and a second polymer resin.

[0049] Elastomer: The tube includes at least one elastomer that provides flexibility, elasticity, and suppleness, enabling the tube to bend, stretch, and compress without permanent deformation, while maintaining dimensional stability and performance during handling or use. The elastomer enhances flexibility, impact resistance, and comfort in both medical and non-medical applications.

[0050] The elastomer is selected from styrene-based thermoplastic elastomers (TPE), styrene-based thermoplastic olefins (TPO), polyolefin elastomers (POE), ethylene propylene rubber (EPR), thermoplastic polyurethane, and mixtures thereof.

[0051] In some embodiments, the elastomer is functionalized or modified to enhance compatibility or performance for a particular application. Functionalization involves introducing reactive or polar groups (e.g., hydroxyl, carboxylic acids and salts, acid anhydrides, esters, imides, amides, epoxy groups, acyl chlorides, and other polar moieties) into the elastomer structure.

[0052] Examples of styrene-based thermoplastic olefins include styrene-ethylene-propylene-styrene (SEPS), styrene polyolefin blends, propylene-styrene blends, styrene TPO, and mixtures thereof.

[0053] Examples of styrene-based thermoplastic elastomers (TPEs) include styrene-based block copolymers (SBCs) in unhydrogenated and hydrogenated forms, such as styrene-ethylene / butene-styrene (SEBS), styrene-ethylene / propylene-styrene (SEPS), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-butene-styrene, styrene-polyolefin block copolymers, and mixtures thereof.

[0054] In some embodiments, the elastomer is a styrene-based block copolymer (SBC). The general structure of the styrene-based block copolymer is: AB, ABA, BAB, ABAB, ABABA, (AB). n (AB) n (A), (ABA) n (ABA) n X, (AB) n X, (BAB) n X, (ABAB) n X, (ABABA) n X, A-B', A-B'-A, B'-AB, BA-B', B'-A-B', A-B'-AB, ABA-B', A-B'-A-B', A-B'-ABA, ABA-B'-A, A-B'-A-B'-A, (A-B') n (A-B') n (A), (A-B'-A) n (A-B'-A) n X、(A-B') n X、(B'-AB) n X、(BA-B') n X、(B'-A-B') n X、(A-B'-AB) n X、(ABA-B') n X、(A-B'-A-B') n X、(A-B'-ABA) n X, (ABA-B'-A) n X、(A-B'-A-B'-A) n X, or a mixture thereof, where n is an integer from 2 to 30, and X is a residue of the coupling agent.

[0055] Each block A is a polymer block of a vinyl aromatic monomer. Each block B is a polymer block of a conjugated diene monomer or a mixture of two or more conjugated diene monomers, and each block B' is a polymer block composed of at least one vinyl aromatic monomer and a conjugated diene monomer. The mixture of vinyl aromatic monomers and conjugated diene monomers in each block B' can be any of cone-shaped, random, block-structured, or controlled-distribution copolymer blocks.

[0056] In some embodiments, the vinyl aromatic monomer is selected from styrene, p-methylstyrene, p-ethylstyrene, p-n-propylstyrene, p-isopropylstyrene, p-n-butylstyrene, p-sec-butylstyrene, p-isobutylstyrene, p-tert-butylstyrene, isomers of p-decylstyrene, isomers of p-dodecylstyrene, ortho-substituted styrene, meta-substituted styrene, α-methylstyrene, 1,1-diphenylethylene, and mixtures thereof.

[0057] In some embodiments, the conjugated diene monomer is selected from isoprene, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1-phenyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 3-butyl-1,3-octadiene, farnesene, myrcene, isoprene, cyclohexadiene, and mixtures thereof.

[0058] In some embodiments, the coupling agent comprises a bifunctional or polyfunctional compound, such as divinylbenzene, halides of aliphatic hydrocarbons (e.g., 1,2-dibromoethane, bis(chloromethyl)benzene, silicon tetrachloride, dialkyl or diaryl dichlorosilane, alkyl or aryl trichlorosilane, tin tetrachloride), alkylsilyl methanol salts, alkylsilyl ethanol salts, polyfunctional aldehydes (e.g., dialdehyde terephthalate), ketones, esters, acid anhydrides, or epoxides. In some embodiments, the coupling agent is selected from methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, dimethyl adipate, γ-epoxypropoxypropyltrimethoxysilane, and mixtures thereof.

[0059] In some embodiments, each block A and A' independently has a peak molecular weight of >1 kg / mol, or >5 kg / mol, or >7 kg / mol, or >10 kg / mol, or >15 kg / mol, or >30 kg / mol, or >40 kg / mol, or >50 kg / mol, or >75 kg / mol, or >100 kg / mol, or <200 kg / mol, or <150 kg / mol, or <100 kg / mol, or 1-200 kg / mol, or 1-150 kg / mol, or 1-100 kg / mol, or 1-75 kg / mol, or 1-50 kg / mol.

[0060] In some embodiments, each block B and B' independently has a peak molecular weight of >5 kg / mol, or >10 kg / mol, or >15 kg / mol, or >25 kg / mol, or >50 kg / mol, or <100 kg / mol, or <250 kg / mol, or 5-350 kg / mol, or 5-300 kg / mol, or 7-250 kg / mol, or 10-200 kg / mol, or 5-150 kg / mol, or 10-100 kg / mol.

[0061] In some embodiments, the total peak molecular weight of the SBC is 5-1000 kg / mol, or 5-750 kg / mol, or 10-500 kg / mol, or 20-300 kg / mol, or 50-300 kg / mol, or 50-250 kg / mol, or <750 kg / mol, or <500 kg / mol, or >5 kg / mol, or >10 kg / mol.

[0062] In some embodiments, the SBC is a hydrogenated styrene-based block copolymer (HSBC). The HSBC has a general structure selected from: SE / BS, (SE / B). n X, (SE / BS) n X, S-EP-S, (S-EP)nX, (S-EP-S)nX, SE / B / SS, (SE / B / SS) n X, (SE / B / S) n X, S-EP / SS, (S-EP / SS) n X、(S-EP / S) n X, and mixtures thereof, wherein n is an integer from 2 to 30, and X is a residue of the coupling agent. The HSBC is formed by hydrogenating a styrene-based block copolymer (SBC) precursor, wherein the SBC precursor is any of a linear, branched, or radial block copolymer. The HSBC may be partially or fully hydrogenated.

[0063] 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 butene (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 / butene (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. Vinyl aromatic monomers may be introduced in any order and in any distribution or copolymerized with diene monomers to form any of the structures described.

[0064] In some embodiments, the HSBC is functionalized with at least one functional group, such as hydroxyl, amino, carboxyl, anhydride, epoxy, isocyanate, silanol, silyl, etc.

[0065] In some embodiments, the HSBC comprises a mixture of at least two block copolymers selected from diblock, triblock, tetrablock, and pentablock copolymers. In some embodiments, the diblock copolymer comprises 1-40, or 2-35, or 3-15, or 15-35, or >3, or <35 wt%; the triblock copolymer comprises up to 99 wt%, or 60-99, or 65-98, or 85-97, or 65-85, or >65, or <97 wt%; and the tetrablock copolymer comprises 0-70, or 2-20, or 4-15 wt% based on the total weight of the HSBC.

[0066] In some implementations, the coupling efficiency (CE) of the HSBC is 20-98%, or >20%, or <99%.

[0067] In some implementations, each block E / B independently has a residual unsaturation (RU) of 0-0.5, or 0.01-0.4, or 0.05-0.5, or <0.5, or <0.4, or <0.3, or <0.2, or <0.1 meq / g, through 1 H NMR determination.

[0068] In some embodiments, the butene unit (B) content of the HSBC is 30-90, 35-85, 40-80, >35, or <85 wt, based on the total weight of the block E / B.

[0069] In some implementations, the total VAC of the HSBC is 5-45, or 8-40, or 10-35, or >8, or >10, or <40wt, based on the total weight of the HSBC.

[0070] In some implementations, the molecular weight (Mp) of each block S is 2-20, or 3-18, or 4-15, or 3-12, or >2, or >4, or <15 kg / mol.

[0071] In some embodiments, the molecular weight (Mp) of the block E / B (if present) is 90-240, or 95-230, or 100-220, or 110-210 kg / mol.

[0072] In some embodiments, the molecular weight (Mp) of the HSBC is 50-250, 60-225, or 70-225 kg / mol.

[0073] In some embodiments, the melt flow rate (MFR) of the HSBC is 1-30, or 5-30, or 10-30, or 15-25 g / 10min, as determined according to ASTM D1238 at 230°C and a 5kg load.

[0074] In some embodiments, the HSBC has a general structure SE / BS, (SE / B)nX, (SE / BS)nX, wherein the butene unit (B) content is 30-60, 35-55, or 40-50 wt%, the VAC is 5-25, 5-20, 5-15, or 10-15 wt%, the Mp of the block S is 3-12 or 3-10 kg / mol, and the Mp of the block copolymer is 100-200, 125-175, or 130-160. kg / mol, coupling efficiency of 60-85, 60-80, or 65-75%, diblock content of 10-50, 20-40, or 25-35 wt%, MFR of 5-30, 10-25, or 15-25 g / 10min at 230℃ / 5kg, tensile strength of 5-40, 10-35, 15-30, or 20-25 MPa, elongation at break of 550-850, 600-800, or 700-800%, Shore A hardness of 30-60, 35-60, 35-55, or 40-55 (measured after 10 seconds).

[0075] The elastomer may include one or more unmodified elastomers and a mixture of one or more modified or functionalized elastomers. For example, the elastomer component may include a blend of styrene-based thermoplastic elastomers (TPE), polyolefin elastomers (POE), or thermoplastic polyurethanes (TPU) with maleic anhydride-modified or hydroxyl-modified SBCs to improve interfacial compatibility with the polymer resin phase.

[0076] In some embodiments, the elongation at break of the elastomer is >100%, or >150%, or >200%, or >250%, or >300%, or 150-1000%, or 200-800%, or 250-750%, or 300-700%, as determined according to ASTM D412.

[0077] In some embodiments, the Shore A hardness of the elastomer is 10-70, or 10-60, or 15-55, or 20-55, or 20-50, as determined according to ASTM D2240.

[0078] In some embodiments, the tensile strength of the elastomer is >2 MPa, or >5 MPa, or >10 MPa, or <40 MPa, or <35 MPa, or 2-40 MPa, or 5-30 MPa, or 10-25 MPa, as determined according to ASTM D412.

[0079] In some embodiments, the Young's modulus of the elastomer is >1 MPa, or >2 MPa, or >5 MPa, or >10 MPa, or <100 MPa, or <80 MPa, or <60 MPa, or <55 MPa, or 1-100 MPa, or 2-80 MPa, or 2-60 MPa, or 5-60 MPa, as determined according to ASTM D638.

[0080] In some embodiments, a first region (the end rich in polymer resin) contains a first composition having a defined concentration of a component comprising 0-30 wt%, 0-25 wt%, or 0-20 wt% of a first elastomer; and a second region (the end rich in elastomer) contains a second composition having a defined concentration of a component comprising 50-100 wt%, 60-90 wt%, or 65-85 wt% of a second elastomer, based on the total weight of the respective region. Variations in the elastomer composition may be due to differences in the concentration, type, or mixture of elastomer introduced through the secondary feeder.

[0081] The gradient distribution of the elastomer content or composition can be achieved by changing the feed rate or introducing different elastomer types or blends, depending on the extrusion distance or time. For example, the first region of the tube may primarily comprise a polymer resin, while the downstream second region may comprise a mixture of two or more elastomers (e.g., polyolefin elastomers, styrene-based thermoplastic elastomers, and thermoplastic polyurethanes).

[0082] Other components: The resin composition optionally includes one or more additional components selected to modify the processing behavior, mechanical properties, surface properties, appearance, or chemical resistance of the extruded tube. Suitable optional components include, for example, antioxidants, adhesion promoters, UV stabilizers, heat stabilizers, rheology modifiers, biocides, corrosion inhibitors, dehydrating agents, colorants (e.g., pigments and dyes), fillers, surfactants, flame retardants, and combinations thereof. Other suitable optional components include, for example, antistatic agents, lubricants or processing aids, slip additives or anti-caking additives, nucleating agents, reinforcing fibers, foaming agents or blowing agents, conductive or thermally conductive fillers (e.g., carbon black, graphite, metal flakes), and permeation barrier or oxygen scavenging additives.

[0083] In some embodiments, optional components are included in a first composition, a second composition, or both. Based on the total weight of the compositions, the total amount of optional components in any given composition is 0-10 wt%, or at least 1 wt%, or >2 wt%, or <10 wt%, or <8 wt%. The type and concentration of these components can also be varied along the length of the tube by adjusting the feed rate or components introduced via one or more side feeders, thereby providing a functional or visual gradient (e.g., stiffness, color, UV resistance, or electrical conductivity) along the tube.

[0084] Preparation method: The polymer resin and elastomer are fed into the extruder using at least two feeders positioned along the barrel of the extruder. The first feeder (main feeder or primary feeder) is located upstream of the second feeder (secondary feeder or side feeder). In some embodiments, one or more additional side feeders are positioned along the length of the barrel for adding different components or modifiers. In some embodiments, the extruder is a twin-screw extruder configured to provide sufficient mixing and shearing without degrading the components. In other embodiments, the extruder is a co-extrusion device configured with multiple feed ports but only one flow channel and a common die, wherein the component streams converge within the barrel to form a uniform melt. The relative flow rates of the component streams or the composition varies over time to establish a longitudinal composition gradient along the extrusion direction. The barrel may include multiple temperature control zones, each maintained at a temperature of approximately 150-250°C or 170-230°C, gradually increasing towards the die.

[0085] In some embodiments, the polymer resin is introduced via a main feeder, and the elastomer is metered at a controlled rate via a secondary feeder to produce the desired concentration distribution along the length of the tube. The feed rate of the elastomer can be gradually increased or decreased relative to the polymer resin to achieve a smooth compositional transition along the length of the tube. In some embodiments, the secondary feeder is located downstream of the main hopper in a section of the tube between approximately 60-90% or 60-80% of the tube length. In some embodiments, the extrusion process begins with either a polymer resin-rich composition or an elastomer-rich composition, causing the tube to be produced from a harder or softer region, with the compositional gradient developing longitudinally in a continuous manner in the extrusion direction. In other embodiments, the feed configuration is reversed, such that the elastomer is introduced via the main feeder and the polymer resin is introduced via the secondary feeder, thereby creating a similar compositional hierarchy in opposite directions.

[0086] In some implementations, a compositional gradient is created by gradually varying the feed rates of the polymer resin and elastomer during continuous extrusion. The relative proportions of the components are gradually adjusted over time, causing the melt composition to evolve continuously along the extrusion direction, thereby generating a longitudinal gradient in composition and corresponding changes in hardness, tensile strength, or elasticity. This time-varying feed rate control differs from typical co-extrusion, which delivers multiple polymer melts simultaneously through separate channels to form gradients or multilayer structures, requiring precise flow synchronization and interfacial compatibility. In contrast, this process uses a single extrusion flow to generate a smooth, controllable gradient.

[0087] In other embodiments, the polymer resin and elastomer are fed together via a main feeder, while the elastomer (same or different), polymer resin, or masterbatch is introduced via a secondary feeder to further adjust the composition or concentration gradient. The secondary feeder may employ a volumetric, gravimetric, or vibratory feeder mechanism operating at, for example, 100-1000 rpm, 200-600 rpm, or 300-600 rpm, and the total feed rate of the extruder is 2-10 kg / h, 2-8 kg / h, or 4-6 kg / h.

[0088] In some implementations, the main feeder delivers a masterbatch comprising a polymer resin and an elastomer, while the secondary feeder introduces the elastomer (same or different) or its masterbatch into the extruder at a controlled rate to establish a gradient. During extrusion, the feed ratio from the secondary feeder to the main feeder can vary from 0.1:1 to 1:1, or cause the concentration of the elastomer in the extrudate to increase or decrease by at least 10-50 wt% between the first and second regions.

[0089] In some implementations, both the main feeder and the secondary feeder introduce masterbatch, each masterbatch containing a polymer resin and an elastomer, the type, proportion, or colorant concentration of which may be different to obtain a gradient of desired concentration, hardness, or color along the extrusion tube.

[0090] Optional components may be added via one or more additional side feeders (typically located downstream of the secondary feeders) or premixed into the main and / or secondary feed streams. A third feeder may be introduced into any of the polymer resin, elastomer, or optional components to fine-tune the gradient or add functional or colorant additives.

[0091] In some embodiments, the tube is continuously extruded while the polymer resin, elastomer, and optional components are fed into the extruder, resulting in a first region containing a first proportion of polymer resin and a second region containing a higher proportion of elastomer. The first region contains a first composition having a defined concentration of components comprising 70-100 wt%, or 75-100 wt%, or 80-100 wt% of a first polymer resin, 0-30 wt%, or 0-25 wt%, or 0-20 wt% of a first elastomer, and 0-10 wt% of optional components; the second region contains a second composition having a defined concentration of components comprising 0-50 wt%, or 10-40 wt%, or 15-35 wt% of a second polymer resin that is the same as or different from the first polymer resin, 50-100 wt%, or 60-90 wt%, or 65-85 wt% of a second elastomer that is the same as or different from the first elastomer, and 0-10 wt% of optional components that are the same as or different from optional components in the first composition.

[0092] In some implementations, the die temperature is maintained between 200-240°C, and the screw speed is 100-600 rpm, depending on the resin viscosity and the required mixing strength. Cooling of the extrudate can be carried out in an air or water bath at 20-40°C.

[0093] The method can also be operated in continuous or semi-continuous mode, wherein the extruder produces an uninterrupted extrudate, which is then cut into individual tube segments, each with a defined gradient length corresponding to the desired product size. Each tube is a complete, weld-free segment continuously extruded. In embodiments for the continuous production of medical or industrial tubes with alternating “hard” and “soft” ends, the extrusion system operates under program control such that the ratio of polymer resin to elastomer varies periodically according to the extrusion time. In some embodiments, the primary and secondary feeders operate under weight or weight loss control connected to a programmable logic controller or monitoring system that synchronizes the feed rate profile with the extrusion linear velocity. The polymer resin to elastomer ratio continuously increases or decreases within a defined time period corresponding to the target tube length (e.g., 4 inches to 12 feet (0.1–3.6 m), or 4 inches to 8.2 feet (0.1–2.5 m)), such that each length of extrudate includes a first region rich in polymer resin (hard end) and a second region rich in elastomer (soft end). The programmed feed rate waveform is repeated at fixed intervals to generate continuous hard-to-soft gradient segments, thereby enabling the continuous fabrication and automatic cutting of discrete tubes of the required length.

[0094] To ensure the transition occurs at the intended location along the tube, the control system can introduce a residence time offset to compensate for melt hysteresis between the feeder and the die. Linear velocity feedback from the encoder or traction unit can be used to lock ratio changes and cutting operations so that each tube is cut off at the same composition stage. This approach allows for large-scale continuous extrusion of tubes with one hard end and one soft end without manual conversion or welding, while maintaining compositional constraints consistent with the first and second region ranges defined herein.

[0095] In some embodiments, the extrusion control curve is programmed such that the melt comprising the stages extends over a defined portion of the total tube length, for example, over at least 30%, 40%, or 50% of the tube length, thereby resulting in a measurable variation in at least one property (e.g., hardness, tensile strength, elasticity) between regions separated by the distance.

[0096] Applications: The tubes described herein can be used in a wide range of applications where it is necessary to vary physical properties (e.g., hardness, flexibility, color, or chemical resistance) continuously or gradually along the length of the tube. In some embodiments, the tubes may be single-lumen, multi-lumen, or multi-layered.

[0097] In medical applications, these tubes can be used in catheters and other devices (such as infusion sets, infusion tubes, peritoneal dialysis tubes, intravascular and balloon catheters, suction or drainage tubes, protective sheaths or covers), or as components of said catheters and other devices.

[0098] In industrial applications, these tubes can be used to transport or protect fluids, gases, or wires, such as pneumatic or hydraulic systems, fuel or coolant delivery lines, and sensor housings. Tubes with a stiffness or flexibility gradient can be advantageously used for vibration damping conduits, flexible-rigid transition joints, and hose segments (where one end requires higher stiffness for connection, while the other end requires greater flexibility for motion or damping).

[0099] In automotive and transportation applications, these tubes can be used in braking or fuel systems, wiring harness protection, cable management, exhaust or ventilation systems (where controlled mechanical properties or temperature tolerance gradients are beneficial).

[0100] In consumer and household products, these tubes can be used in appliances, sports equipment, and flexible packaging, such as gradient hose connectors, color gradient straws, or protective tubes for electronic products.

[0101] In industrial and special processing, the tube can be used as an extruded profile, coating, or lining for conveying corrosive materials, or as an optical or color indicator tube in a quality control system.

[0102] In all embodiments, the composition and method allow for the generation of gradients in a single continuous extrusion process without the need to connect separate tube segments, thereby simplifying preparation and improving reliability and visual uniformity.

[0103] Performance: In some embodiments, the tube lengths comprising the first and second regions exhibit gradient differences with respect to one or more optional components of the composition (e.g., polymeric resin, elastomer, or optional additives). Compositional variations result in measurable differences in at least one physical property (e.g., hardness, tensile strength, elasticity, density, or color intensity) along the length of the article.

[0104] In some implementations, the hardness difference between the first and second regions is at least 10% or at least 20%, based on the Shore hardness value determined according to ASTM D2240.

[0105] In some embodiments, the tube exhibits a longitudinal hardness gradient, as determined by ASTM D2240, ranging from a Shore A hardness of 20 to a Shore D hardness of 80, or from a Shore A hardness of 30 to a Shore D hardness of 70, or from a Shore A hardness of 40 to a Shore D hardness of 60.

[0106] In some embodiments, the tube exhibits a Shore D hardness of 60-90, 65-90, 70-90, 75-85, or >60 or >75 in a first region (the resin-rich end), and a Shore A hardness of 15-50, 15-40, 15-30, 15-25, or >15 or <50 in a second region (the elastomer-rich end).

[0107] In some embodiments, the tube length exhibits a gradient difference in tensile strength from a first region to a second region of the tube, which is >20%, >30%, >40%, >50%, or >60%. "Gradient difference" refers to an intentional and controlled variation in composition or properties at specific locations along the length of the tube to achieve tailored performance characteristics, such as increased stiffness in one region and increased flexibility, suppleness, or impact resistance in another.

[0108] In some embodiments, the tube also exhibits gradient differences in elastic modulus, elongation at break, flexural modulus, or impact strength, wherein at least one of these mechanical properties varies from one region of the tube to another by at least 10%, or >15%, or >25%, or 10-50%.

[0109] The tubes produced according to the above method can have any desired configuration, including single-cavity, multi-cavity, or multi-layer structures.

[0110] There are no particular limitations on the size, number of lumens, shape, or cross-sectional dimensions of the tube made from the composition. In some embodiments, the outer diameter of the tube is 1-60 mm, or 1-20 mm, or 1-10 mm; the inner diameter of the tube is 0.5-50 mm, or 0.5-25 mm, or 0.5-10 mm, or 0.5-5 mm; and the wall thickness of the tube is 0.1-20 mm, or 0.5-10 mm, or 1-5 mm.

[0111] Depending on the intended use, the total length can vary from less than 30 cm to several meters. In some embodiments, the tube length is 30-150 cm, or 30-140 cm, or 40-130 cm, or <150 cm, or <145 cm, or <140 cm, or <135 cm, or <130 cm, or >35 cm, or >40 cm, or >45 cm. In embodiments for veterinary or industrial use, the tube length is >150 cm, or 150-750 cm, or 150-500 cm, or <1000 cm, or <750 cm, or <600 cm.

[0112] In some implementations, L / OD (the ratio of the pipe's length L to its outer diameter OD) is 5-1,500, or 5-1,000, or 5-800, or 10-800, or 10-500, or 30-500, or 30-400, or 30-300, or at least 30, or > 35, or > 40, or < 1,500, or < 1,250, or < 1,000.

[0113] In some embodiments, the tube is a conduit. The length of the conduit is 30-150cm, or 30-140cm, or 40-130cm, or <150cm, or <145cm, or <140cm, or <135cm, or <130cm, or >35cm, or >40cm, or >45cm; the outer diameter is 1-60mm, or 1-20mm, or 1-10mm; and the inner diameter is 0.5-50mm, or 0.5-25mm, or 0.5-10mm, or 0.5-5mm.

[0114] In some implementations, the tube exhibits a gradient in visual or optical properties (e.g., color, gloss, or transparency) as the colorant concentration or pigment ratio varies between feed streams. The color change can be perceived as a continuous color transition or as a functional color indicator corresponding to a compositional or hardness gradient.

[0115] Analytical Methods: The analytical methods described below are used to determine the composition, structure, and physical properties of the tube, polymer resin, elastomer, and optional components. These methods can also be used to confirm the existence of a compositional hierarchy and to establish quantitative differences between regions of the tube for performance or validation purposes.

[0116] Component analysis and quantification: The concentration, identity, and distribution of each component (polymer resin, elastomer, and optional components) within a given region of the tube can be determined using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, differential scanning calorimetry (DSC), or nuclear magnetic resonance spectroscopy (NMR). The unique spectral or thermal characteristics of each component are identified, and relative wt% is quantified using calibration standards or spectral deconvolution.

[0117] Chemical differentiation and separation: When the polymer resin and elastomer are chemically distinct (e.g., polypropylene vs. styrene block copolymers), they can be easily distinguished by FTIR or Raman spectroscopy based on their functional group absorption or scattering bands. When the components are chemically similar (e.g., polyolefin-based systems), resin-rich and elastomer-rich fractions can be separated using selective dissolution, solvent extraction, or thermal fractionation. The recovered fractions can be analyzed by gravimetric analysis, gel permeation chromatography (GPC), or size exclusion chromatography (SEC) to determine the component ratios and molecular weight distribution.

[0118] Component separation and phase partitioning: Separated or enriched fractions are characterized by spectroscopic (FTIR, Raman, NMR) and thermal (DSC, TGA) analyses to assign each component to its corresponding polymer family, such as polyolefins, polyurethanes, or styrene block copolymers. In systems where direct separation is not possible, component identity is inferred based on characteristic spectral, thermal, or crystallinity features specific to each polymer class.

[0119] Longitudinal variation verification: These analytical methods can be applied to small segments taken along the length of the tube to verify longitudinal compositional variations. Changes in spectral intensity ratios, melt or glass transition temperatures, or decomposition curves along the extrusion direction indicate that continuous variations in polymer resin and elastomer concentrations are consistent with the compositional hierarchy.

[0120] Compositional Imaging and Gradient Verification: Spatial-resolution analyses such as FTIR imaging, Raman line scanning, micro-DSC, or energy-dispersive X-ray spectroscopy (EDX) imaging can be used to create the compositional distribution along the tube. Plotting the relative intensity versus location of characteristic peaks or elemental signals attributed to the polymer resin and elastomer confirms a continuous gradient. No abrupt discontinuities distinguish the tube of this disclosure from welded structures.

[0121] Additives and optical gradients: Gradients of colorants, fillers, or additives can be quantified using UV-Vis spectroscopy or X-ray fluorescence (XRF) for elemental pigments or metals. When plotted against location, these data confirm continuous variations in additive concentration or light intensity along the tube.

[0122] Molecular and structural characterization: The molecular weights of polymeric resins and elastomers (including block copolymers) were determined by GPC according to ASTM D5296 and calibrated using polystyrene standards. The vinyl aromatic content, butene content, and hydrogenation level of styrene-based block copolymers (SBCs or HSBCs) were determined by proton and carbon NMR (¹H and ¹³C NMR). Coupling efficiency was derived from the ratio of coupled to uncoupled material in the GPC trace. Residual unsaturation or hydrogenation level could be confirmed by ozone decomposition titration, UV-Vis spectroscopy, or NMR integration of olefin peaks.

[0123] Thermal and morphological analysis: The melting temperature (Tm), glass transition temperature (Tg), and crystallinity of the polymer resin or elastomer were determined by DSC according to ASTM D3418. Crystallinity can be used as an indicator of local composition. Phase morphology and elastomer dispersion in the polymer matrix were observed by scanning or transmission electron microscopy (SEM or TEM) after cryogenic fracturing and selective staining (e.g., osmium tetroxide staining of the polyolefin elastomer domain).

[0124] Density variation: The density gradient along the pipe can be determined by the specific gravity method (ASTM D792) or density-gradient column analysis, thus providing indirect evidence of compositional variation.

[0125] Mechanical and physical property determinations: Tensile properties (including tensile strength, elongation at break, and Young's modulus) are determined according to ASTM D638 for rigid or semi-rigid materials, or according to ASTM D412 for elastomers. Flexural modulus is determined according to ASTM D790, and impact strength is determined according to ASTM D256 (cantilever beam) or ASTM D6110 (pendulum). Dynamic mechanical analysis (DMA) (ASTM D4065) can be used to characterize viscoelastic behavior and capture gradient effects.

[0126] Hardness and Gradient Quantification: Hardness is determined according to ASTM D2240 using the Shore A or Shore D scale (as applicable). Measurements are taken along the pipe at incremental distances to establish a quantitative hardness distribution. A difference of at least 10%, 20%, or 30% between the first and second zones confirms the desired performance gradient. A difference of 20–60% in tensile strength or modulus is confirmed according to ASTM D638 or D412.

[0127] Component Performance Comparison: The inherent Shore hardness or flexural modulus of the polymer resin and elastomer can be determined by direct measurement where feasible, or estimated based on recognized reference data (including supplier technical data sheets, published literature, or standard material performance databases), each measured according to ASTM D2240 and D790. If the polymer resin and elastomer cannot be physically separated from the tube without altering their composition or structure, corresponding performance values ​​can be obtained from recognized sources of these validated materials under comparable test conditions. When measured or reference values ​​show such a difference, the polymer resin and elastomer must differ by at least 20%, 25%, or 30% in one of these properties. This can be further supported by microindentation or localized mechanical testing of resin-rich and elastomer-rich areas within the tube.

[0128] Dimensional Analysis: The outer diameter (OD) and total length of the tube shall be measured using precision calipers, optical micrometers, or laser measuring instruments in accordance with ASTM D3567 or equivalent standards. The length-to-diameter ratio (L / OD) is calculated by dividing the total tube length by the outer diameter.

[0129] Optical and surface characterization: Surface gloss and transparency gradients are evaluated using a gloss meter (ASTM D523) and haze or transmittance tests (ASTM D1003). Visual indicators, such as color or opacity variations along the tube length, can also confirm compositional gradients.

[0130] Gradient continuity assessment: To confirm the existence of a continuous compositional or performance gradient, the measured values ​​of hardness, color intensity, tensile strength, or modulus are plotted relative to their positions along the pipe length. A statistically monotonic trend (no discontinuities) indicates a compositional hierarchy as defined in this paper. Example

[0131] The following examples are not limiting.

[0132] Example 1: Extrusion of a product with a hardness gradient

[0133] Samples were prepared using a 26mm twin-screw co-rotating extruder with 13 barrel sections (the first (feed) section being unheated). The temperature distribution along the remaining 12 heating zones of the barrel was as follows (°C): 170 / 180 / 190 / 200 / 210 / 210 / 220 / 220 / 220 / 220 / 220 / 220. The screw speed was maintained at 300 rpm, and the total feed rate was approximately 5 kg / h. A "circulating screw" configuration was employed to provide a moderate level of shear.

[0134] The extruder is equipped with two feed inlets:

[0135] Feeder 1: Main hopper (single screw feeder) located in the feeding section.

[0136] Feeder 2: A side feeder located in section 11 of the cylinder, which adopts vibration feeding technology.

[0137] Extrude strips (or tubes) using a slit die (24mm x 2mm). The materials used are as follows.

[0138] Table 1

[0139]

[0140] Extrusion Procedure: The process is initiated by feeding polypropylene (PP) at a rate of 5 kg / h via feeder 1. After achieving stable operation, the PP feed is stopped, followed by a brief delay of approximately 10 seconds, after which HSBC is introduced at 500 rpm via feeder 2. Under these conditions, the extrudate color gradually changes from light (PP-rich) to dark (HSBC-rich), thus creating a continuous gradient along the extrusion direction.

[0141] The lighter-colored regions of the extrudate correspond to compositions primarily containing PP (e.g., 70-100 wt% PP, 0-30 wt% HSBC). The darker-colored regions, compared to the lighter-colored regions, correspond to compositions containing a higher proportion of HSBC (e.g., 50-100 wt% HSBC and 0-50 wt% PP). The intermediate region between these two areas represents a continuous compositional transition between these boundaries. Representative images of the resulting gradient samples are shown below. Figure 1As shown (in grayscale), the continuous transition along the extrusion strip is illustrated from a light region rich in polymer to a dark region rich in elastomer.

[0142] Hardness assessment: Disks are cut from the extrusion belt at discrete locations along the color transition area. Shore A hardness is determined using a Type A hardness tester, held for 30 seconds at each location, according to ASTM D2240.

[0143] Table 2: Shore A hardness (30s) of the tube at different locations along the gradient region

[0144]

[0145] The data above show that the hardness gradually transitions from the high-hardness PP region to the low-hardness HSBC region. This confirms that controlling the variation in feed composition during extrusion can produce a continuous gradient of physical properties (such as hardness and color) along the length of the extruded tubular product.

[0146] Example 2: Extrusion of graded tubes

[0147] Example 2 was conducted using the same extrusion structure, temperature distribution, and operating conditions as described in Example 1, except that a tubular die with an outer diameter of 10 mm was used instead of a slit die. This process demonstrates that equivalent gradient formation can be achieved by using a premixed feed mixture instead of pure component feed.

[0148] Feeder 1 contains a premixed mixture of PP and HSBC in a ratio of 85 / 15 (w / w).

[0149] Feeder 2 contains a premixed mixture (PP / HSBC) in a ratio of 45 / 55 (w / w).

[0150] At startup, feeder 1 operates at a feed rate of 5.0 kg / h (feeder 2 = 0), providing an initial melt composition of approximately 85 wt% polymer resin and 15 wt% elastomer. Over 2-minute intervals, the relative feed rates change linearly, with feeder 1 decreasing from 5.0 kg / h to 0 and feeder 2 increasing from 0 to 5.0 kg / h. Therefore, the instantaneous melt composition continuously varies along the extrudate length from 85 / 15 to 45 / 55 (PP / HSBC).

[0151] The resulting tube exhibits a smooth color transition along its wall, from a lighter resin-rich region to a darker elastomer-rich region (corresponding to a gradual change in composition). The Shore A hardness decreases from approximately 84 for 85 / 15 (PP / HSBC) to approximately 66 for 45 / 55 (a decrease of approximately 20.6%). The flexural modulus decreases from approximately 1714 MPa to approximately 950 MPa (a decrease of approximately 44.6%). With increasing elastomer content, tensile strength decreases while elongation at break increases.

[0152] Example 3: Extrusion of gradient tubes (80 / 20→20 / 80 PP / HSBC)

[0153] Example 3 used the same extrusion setup, temperature distribution, and operating conditions as Example 1, except that a tubular die (OD=10mm) was used instead of a slit die. Premixed feed was used to broaden the composition range.

[0154] Feeder 1 (mixture A): PP / HSBC = 80 / 20 (w / w).

[0155] Feeder 2 (mixture B): PP / HSBC = 20 / 80 (w / w).

[0156] At startup, feeder 1 operates at a feed rate of 5.0 kg / h (feeder 2 = 0). Within a preset 2-minute interval, feeder 1 linearly decreases to 0, while feeder 2 linearly increases to 5.0 kg / h, thereby creating a continuous composition transition along the extrudate from 80 / 20 to 20 / 80 (PP / HSBC).

[0157] The resulting tube exhibits a smooth color transition from a lighter, resin-rich region to a darker, elastomer-rich region. The Shore A hardness decreases from approximately 81 for 80 / 20 (PP / HSBC) to approximately 56 for 20 / 80. The flexural modulus decreases from approximately 1618 MPa to approximately 472 MPa. With increasing elastomer content, the tube displays lower tensile strength and higher elongation at break, thus confirming a continuous gradient of hardness, stiffness, and elasticity along its length.

[0158] Example 4: Preparation of gradient tubes from masterbatch

[0159] Example 4 was performed using the same extrusion configuration and parameters as described in Example 1, except that a tubular die (OD=10mm) and two different PP / HSBC masterbatches were used to simplify material handling.

[0160] Feeder 1 (mixture A) contains premixed PP / HSBC=80 / 20 (w / w) masterbatch (light color).

[0161] Feeder 2 (mixture B) contains premixed PP / HSBC=40 / 60 (w / w) masterbatch (dark color).

[0162] At startup, the melt is 80 / 20 (PP / HSBC); during a preset 2-minute change, the feed rate is linearly adjusted to produce a continuous transition to 40 / 60 (PP / HSBC).

[0163] The tube exhibits a continuous hardness gradient consistent with the increase in elastomer fraction. The Shore A hardness decreases from approximately 81 at 80 / 20 (PP / HSBC) to approximately 64 at 40 / 60. The flexural modulus decreases from approximately 1618 MPa to approximately 854 MPa.

[0164] Example 5: Fabrication of gradient tubes from PA6 / HSBC

[0165] Example 5 follows the same extrusion setup and procedure as Example 1, but uses polyamide 6 (PA6) instead of polypropylene. PA6 is a polyamide resin with a Shore D hardness of about 75 and a flexural modulus of about 2000 MPa as tested according to ASTM D2240 and ASTM D790.

[0166] Feeder 1 feeds the premix PA6 / HSBC=80 / 20 (w / w) at a feed rate of 5.0→0.0 kg / h within 2 minutes.

[0167] Feeder 2 feeds premix PA6 / HSBC=40 / 60(w / w) at a feed rate of 0.0→5.0kg / h in the same interval (linear change).

[0168] The melt composition changed continuously along the extruder length from 80 / 20 to 40 / 60 (PA6 / HSBC). The Shore A hardness decreased from about 85 in 80 / 20 to about 66 in 40 / 60. The flexural modulus decreased from about 1.6 GPa to about 0.8 GPa.

Claims

1. A pipe having an outer diameter (OD), the pipe comprising along its length: A first region comprising a first composition having a defined concentration 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% of optional components; The second region comprises a second composition having a defined concentration of components including: a) 0-50 wt% of a second polymer resin that is the same as or different from the first polymer resin, b) 50-100 wt% of a second elastomer that is the same as or different from the first elastomer, and c) 0-10 wt% of optional components that are the same as or different from optional components in the first composition. The concentrations of the polymer resin and elastomer components vary continuously along the longitudinal length of the tube between the first and second regions to form a compositional hierarchical structure, wherein 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 and second regions, wherein hardness is determined according to ASTM D2240, tensile strength according to ASTM D638, elongation at break according to ASTM D412, and flexural modulus according to ASTM D790. The length-to-diameter ratio (L / OD) of the tube is approximately 5-1500. The polymer resin is selected from fluoropolymers, polyolefins, polyurethanes, styrene polymers, polyesters, polyamides, vinyl polymers, polycarbonates, and mixtures thereof; and The elastomer is selected from styrene-based thermoplastic elastomers, styrene-based thermoplastic olefins, polyolefin elastomers, ethylene propylene rubber, thermoplastic polyurethane, and mixtures thereof; and The polymer resin and the elastomer differ by at least 20%, 25%, or 30% in at least one of Shore A hardness, Shore D hardness, and flexural modulus.

2. The tube of claim 1, wherein the tube is obtained by continuous extrusion, wherein at least two feeders positioned along the extruder barrel are optionally used to vary the relative proportions of the polymer resin and elastomer along the length of the tube.

3. The tube according to claim 1, wherein the elastomer is a styrene-based thermoplastic elastomer selected from unhydrogenated styrene block copolymers and hydrogenated styrene block copolymers.

4. The pipe according to claim 1, wherein the polymer resin is a polyolefin.

5. The tube according to any one of claims 1-4, wherein the tube is obtained by continuous extrusion in an extruder, wherein the concentrations of the polymer resin and the elastomer are continuously varied along the extrusion direction to form a longitudinal composition gradient, without the need for co-extrusion of separate streams.

6. The tube according to any one of claims 1-4, wherein the tube exhibits a hardness variation of at least 10%, 20% or 30% between the first region and the second region, and wherein the hardness varies continuously along the longitudinal direction of the tube corresponding to the extrusion direction at least 30%, 40% or 50% of the total tube length.

7. The tube according to any one of claims 1-4, wherein the tube exhibits a longitudinal hardness gradient from a Shore D hardness of 60-90 in a first region to a Shore A hardness of 15-50 in a second region.

8. The tube according to any one of claims 1-4, wherein the total length of the tube is 4 inches to 8.2 feet (0.1-2.5 m), corresponding to a length-to-diameter ratio L / OD of 5-700.

9. The tube according to any one of claims 1-4, wherein the tube is obtained by: during continuous extrusion, by gradually changing the feed rate of the elastomer relative to the polymer resin over time through separate main feeders and secondary feeders positioned in different sections of the extruder, thereby forming a longitudinal performance gradient along the extrusion direction without connecting the individual tube sections.

10. The pipe according to claim 3, wherein the styrene-based thermoplastic elastomer is a hydrogenated styrene block copolymer having a general structure selected from the following: SE / BS, (SE / B)nX, (SE / BS)nX, S-EP-S, (S-EP)nX, (S-EP-S)nX, SE / B / SS, (SE / B / SS)nX, (SE / B / S)nX, S-EP / SS, (S-EP / SS)nX, (S-EP / S)nX, and mixtures thereof, wherein each block S is composed of... Polymer blocks composed of vinyl aromatic units, each block E / B is a polymer block composed of ethylene (E) units and butene (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 / butene (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 the coupling agent.

11. The pipe according to any one of claims 1-4, wherein the pipe length from the first region to the second region exhibits at least one of the following longitudinal performance gradients: (a) The hardness decreases from approximately 60-90 Shore D in the first region to approximately 15-50 Shore A in the second region. (b) The tensile strength decreases from about 25-120 MPa in the first region to about 2-30 MPa in the second region. (c) The flexural modulus decreases from approximately 1000-5000 MPa in the first region to approximately 1-100 MPa in the second region, and (d) The elongation at break increases from about 50-200% in the first region to about 150-1000% in the second region.

12. A method for preparing a tube having an outer diameter (OD), comprising: A first composition having a defined concentration of components is fed into a first feeder of an extruder, wherein the components include a polymer resin, an elastomer, and optional components; A second composition having a defined concentration of components is fed into a second feeder located downstream of the extruder barrel, the components including a polymer resin, an elastomer, and optional components; Optionally, one or more optional components are fed into a first feeder, a second feeder, or both; In a continuous extrusion process, the relative feed rates of the first and second compositions are controlled to continuously change the concentrations of the polymer resin and elastomer components longitudinally along the extrusion direction, thereby forming a compositionally graded melt; and The component-graded melt is extruded through a die to produce a tube, wherein 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 a first region and a second region, wherein hardness is determined according to ASTM D2240, tensile strength according to ASTM D638, elongation at break according to ASTM D412, and flexural modulus according to ASTM D790; and The first composition comprises 70-100 wt% of a first polymer resin, 0-30 wt% of a first elastomer, and 0-10 wt% of optional components; The second composition comprises 0-50 wt% of a second polymer resin that is the same as or different from the first polymer resin, 50-100 wt% of a second elastomer that is the same as or different from the first elastomer, and 0-10 wt% of an optional component that is the same as or different from an optional component in the first composition, each based on the total weight of the respective composition. The polymer resin is selected from fluoropolymers, polyolefins, polyurethanes, styrene polymers, polyesters, polyamides, vinyl polymers, polycarbonates, and mixtures thereof; The elastomer is selected from styrene-based thermoplastic elastomers, styrene-based thermoplastic olefins, polyolefin elastomers, ethylene propylene rubber, thermoplastic polyurethane, and mixtures thereof; and The polymer resin and the elastomer differ by at least 20%, 25%, or 30% in at least one of Shore A hardness, Shore D hardness, and flexural modulus.

13. The method of claim 12, wherein the polymer resin is a polyolefin and the elastomer is a styrene-based thermoplastic elastomer selected from unhydrogenated or hydrogenated styrene block copolymers.

14. The method according to any one of claims 12-13, wherein the composition gradient is established by gradually changing 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, rather than co-extruding separate material streams into the die.

15. The method according to any one of claims 12-13, wherein the obtained tube exhibits a hardness variation of at least 10%, 20%, or 30% between the first and second regions, and wherein the hardness varies continuously along the longitudinal extrusion direction.

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