Multi-layered tubing.

MULTI-PIPE PIPE

FIELD OF THE INVENTION

In general, the present invention relates to a polymeric pipe typically formed by a co-extrusion process, the pipe having multiple layers of different polymeric materials.

BACKGROUND OF THE INVENTION

The pipe comprised of a polymeric material is used in many industrial and commercial applications, including in the medical field. Several plastics that meet FDA are used, depending on the desired properties and the intended applications. When the pipe is used to transport fluids for the in vivo treatment of human patients or for the release of any fluid when the fluid itself, or a component contained in the fluid, needs to be isolated and contained inside and not spilled from the pipe walls , the selection of a polymeric material having a selective property may be a factor.

Polyvinyl Chloride (PVC) is one of the most widely used plastics. While structurally stable and easily molded into the desired shapes, PVC is typically manufactured using plasticizers that can migrate from the PVC matrix into body fluids and have other

Ref. 254328 properties not ideally suited for medical treatment applications. Also, due to the inherent nature of plasticized PVC pipe, the potential absorption of medicines and other components of aqueous fluids used in medical treatments on the side wall of the PVC pipe arises. U.S. Patent No. 4,627,844 by Schmitt (Schmitt), the description of which is incorporated herein by reference, as if fully established, describes a three-layer pipe that is modeled on a commercial product sold under the SUREPATH 151 trademark by Natvar Division of TekniPlex, Inc. As described in Schmitt, an outer layer of PVC and an inner layer of contact with the low density polyethylene fluid (LDPE) are co-extruded with an intermediate bond layer of acetate acetate copolymer. ethylene vinyl (EVA). Polyurethane is potentially a substitute for PVC, as described in co-pending US patents in common property Nos. Series 13 / 354,029 and 13 / 586,288. Other pipe configurations are described in U.S. Patent No. 7,647,949, U.S. Patent No. 4,211,741 and U.S. Patent Publication No. 2007/0119511, the descriptions of which are incorporated by reference as set forth herein. Examples of the prior art on which the pre-characterizing portions of the independent claims are based are given in US2009286028 and US2009087606.

BRIEF DESCRIPTION OF THE INVENTION

According to the invention, there is provided a pipe, tube or tubular device comprising at least three concentric layers of polymeric materials comprising inner and outer layers of a polymeric material comprised of thermoplastic polyurethane, and a middle layer comprised of a polymeric material comprised of a polymer containing acrylate that is placed between the two and that joins the inner and outer layers together by means of adhesion mechanisms, such as chemical adhesion, without the need for additional binders or adhesive layers. The polyurethane, of which each of the inner and outer layers are comprised, can be of an equal or different structure, molecular weight, crystallinity, purity, monomeric unit content, branching, chain length, additive content, inorganic content and properties physical, such as elongation, melting point, resistance to permanent deformation due to fatigue and hardness.

The layers of polymeric materials co-extrude each other to form the pipe, so that the inner and outer layers adhere to the middle layer and, in this way, the three layers adhere to each other. The pipe is formed with a central hollow channel, hole or passage that is radially surrounded and defined by the polymeric layers that act as the wall or walls of the pipe.

The tube or pipe is particularly suitable for the transport of aqueous fluids such as the fluids used in medical treatments and applications. Alternatively, the tube or pipe can be used for the direction, distribution and transportation of non-aqueous and aqueous liquid and gaseous fluids, which include organic materials, such as ethers, alcohols, hydrocarbons, amines, aldehydes, ketones, amides, carboxylic acids and esters and non-aqueous fluids, such as oxygen, carbon dioxide, carbon monoxide, helium, neon, argon, krypton, xenon, radon, hydrogen, nitrogen and the like, and mixtures of two or more of any of the above with each other, or one or more of the above with an aqueous fluid.

Preferably, the polymeric material of the inner and outer layer is comprised of a thermoplastic polyurethane elastomeric material (TPU), and the middle layer is comprised of an ethylenenetyl acrylate (EEA) copolymer, ethylene methyl acrylate (EMA) copolymer , an ethylenemethyl acrylate copolymer grafted with an anhydride (EEA), a copolymer of two or more such acrylates or a mixture of two or more of the foregoing.

In one embodiment, the middle layer preferably has a substantially greater thickness of the combined thicknesses of the inner and outer layers. The thickness of the cross section, T2, of the middle layer, Figure 1, typically ranges from about 5% to about 98%, and more typically, between about 10% and about 85% of the total cross section wall thickness of the pipe 10 (that is, the thickness of the inner layer TI plus the thickness of the middle layer T2 plus the thickness of the outer layer T3). The thickness T2 of the middle layer can range from about 5% to about 3.0% of the thickness of the total cross-section of the pipe wall, or in another embodiment, from about 31% to about 60%, and in still another preferred embodiment of about 61% to about 98%. Increasing the thickness of the middle layer through the pipe wall, and thus, the proportional volume of the polymeric material of the middle layer of the pipe vs. The volume of the polymeric material of the inner and outer layers can be obtained at a much lower cost and / or other benefits. For example, when the polymeric material of the middle layer is soft ethylene ether acrylate (EEA) and / or soft ethylene methyl acrylate (EMA), these materials provide good adhesion to a thermoplastic polyurethane elastomer (TPU) and maintain delamination resistance of the pipe under conditions of high stress and temperature, but they are less expensive than thermoplastic polyurethane elastomers of which κ »cover the inner and outer layers. In general, the total wall thickness (TI plus T2), of the inner and outer layers of the thermoplastic polyurethane, should be at least about 2% of the total pipe wall thickness (TI plus T2 plus T3) for the pipes greater than or equal to

<td> 2.54</td><td>mm (0.100 inches)</td><td colspan="2">of thickness</td><td>from</td><td>wall</td><td>total for</td><td>the</td>

<td>less</td><td>about 3%</td><td>of the</td><td colspan="2">thickness</td><td colspan="3">total wall for</td>

<td colspan="2">pipes larger than 1,295</td><td>mm</td><td> (0.051</td><td colspan="2">inches)</td><td>of thickness</td><td>from</td>

<td>wall</td><td>total but less</td><td>from</td><td> 2.54</td><td>mm</td><td> (0.100</td><td>inches)</td><td>from</td>

total wall thickness and at least 5% of the total wall thickness for pipes greater than 0.025 inches (0.254 mm), but equal to or less than 0.027 inches (1.27 mm) total wall thickness to provide the necessary smoothness and elasticity together with the mechanical properties required in a typical pipe application.

In this way, it is visualized that, in one embodiment, most of the volume of the side wall of a pipe will be made of an EEA or ΞΜΑ material and the inner layer of TPU and the outer layer will be as thin as possible to operate even as the fluid contact layer (inner layer) and as the outer layer to which various accessories can be attached (luer adjustment, etc.).

With reference to Figures 1, 2, in one embodiment, a pipe 10 having a length L that extends along a longitudinal pipe axis A, has inner and outer polyurethane layers 3, 1, which are between approximately 0.00635 mm and approximately 0.635 mm (approximately 0.00025 and approximately 0.025 inches) thick, TI, T3, and a middle layer of acrylate 2 copolymer, between approximately 0.203 mm and approximately 3.048 mm (approximately 0.008 and approximately 0.120 inches) thick, T2. Layers 1, 2, 3 collectively form a tubular wall that surrounds and defines a central fluid flow passage 20.

The copolymers of ethylenenetyl acrylate (EEA), copolymers of ethylene methyl acrylate (EMA) and copolymers of ethylene methyl acrylate grafted with anhydride (EEA) are elastomeric in nature and have excellent visual clarity. In a typical co-extrusion process, TPU and EEA or EMA or EEA are melt extruded through a die head to form a tubular extrudate that is then cooled through conventional water baths or vacuum tanks of water, and that are subsequently rolled or cut to a particular length for use. The level of elasticity and softness of EEA, EMA, AEMA or copolymer thereof, is controlled by the amount of comonomer of ethyl acrylate or methyl acrylate used with ethylene in the copolymerization process. The resulting three-layer pipes manufactured by such a co-extrusion process act in a monolithic manner since they return to almost their original shape and dimensions after being deformed or stretched in a tension manner along the longitudinal axis A of the pipe at an effort of up to about 55 MPa and a deformation of up to about 900-950% and without visual delamination between any of the layers after they are submerged in water at about 60 ° C for approximately 36 hours.

The polymeric materials are preferably free of contaminants, which means that they contain no more than insignificant amounts of potentially unwanted materials (typically less than about 0.5% and, preferably, less than about 0.2%, by weight) and / or prevent leaching or spillage of unwanted materials, such as plasticizers, catalysts, monomers, metals, salts, ions or other substances that are potentially unwanted for a human being in an aqueous solution or other fluid medium with which one or the other of the three layers can come into contact during the normal course of using the pipe in the release of the aqueous fluid (or non-aqueous), such as insulin, chemotherapy drugs and other suspensions of potentially unstable aqueous drugs, to or from a human patient. The middle layer prevents delamination of the outer and inner layers of the middle layer under relatively low to moderate stress or deformation conditions. In addition, the middle layer acts as a barrier to leach or spill contaminants from the outer layer to, or through the inner layer in the hole or hollow central passage of the pipe.

According to one aspect of the invention, a pipe is provided comprising an inner layer, an outer layer and a middle layer, wherein the inner layer comprises a thermoplastic polyurethane, the outer layer comprises a thermoplastic polyurethane and the middle layer comprises a ethylenenetyl acrylate copolymer or an ethylene methyl acrylate copolymer or an anhydride grafted ethylene methyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of the foregoing.

Preferably, the inner and outer layers each comprise more than about 90% by weight of a polyurethane based on aromatic or aliphatic polyether. The middle layer may comprise more than about 90% by weight of an ethylenenetyl acrylate copolymer, an ethylene methyl acrylate copolymer, an anhydride grafted ethylene methyl acrylate copolymer, or more than about 90% by weight of a mixture or copolymer of two or more of the above.

One or both of the inner and outer layers may comprise a polyurethane based on polytetramethylene glycol.

The ethylene methyl acrylate copolymer typically comprises at least about 19.5 percent of methyl acrylate content by weight.

The ethylenenetyl acrylate copolymer typically comprises at least about 19.5 percent of ethyl acrylate content by weight.

In another aspect of the invention, a medical pipe is provided for the transport of an aqueous fluid comprising: an inner layer comprising more than about 90% by weight of a thermoplastic polyurethane, an outer layer comprising more than about 90% by weight of a thermoplastic polyurethane and a middle layer placed between the outer and inner layers comprising more than about 90 % by weight of an ethylenenetyl acrylate copolymer or an ethylene methyl acrylate copolymer or an anhydride grafted ethylene methyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of the foregoing.

In another aspect of the invention, a pipe for transporting a non-aqueous fluid is provided comprising: an inner layer comprising more than about 90% by weight of a thermoplastic polyurethane, an outer layer comprising more than about 90% by weight of a thermoplastic polyurethane and a middle layer placed between the outer and inner layers comprising more than about 90 % by weight of an ethylenenetyl acrylate copolymer or an ethylene methyl acrylate copolymer or an anhydride grafted ethylene methyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of the foregoing. In such an embodiment, the non-aqueous fluid may comprise a liquid or gaseous fluid that includes organic materials, such as ethers, alcohols, hydrocarbons, amines, aldehydes, ketones, amides, carboxylic acids and non-aqueous esters and fluids, such as oxygen, dioxide carbon, carbon monoxide, helium, neon, argon, krypton, xenon, radon, hydrogen, nitrogen and the like, and mixtures of two or more of any of the above, or one or more of the above with an aqueous fluid.

In another aspect of the invention, a medical pipe is provided for the transport of an aqueous fluid comprising: an inner layer comprising more than about 90% by weight of a thermoplastic polyurethane, an outer layer comprising more than about 90% by weight of a thermoplastic polyurethane and a middle layer placed between the outer and inner layers comprised of at least about 90% by weight of an ethylenenetyl acrylate copolymer, an ethylene methyl acrylate copolymer, an anhydride grafted ethylene methyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of the above, wherein the pipe does not visually delaminate after being immersed in water at 60 ° C for 36 hours.

In another aspect of the invention, a medical pipe is provided for the transport of an aqueous fluid comprising: an inner layer comprising more than about 90% by weight of a thermoplastic polyurethane, an outer layer comprising more than about 90% by weight of a thermoplastic polyurethane and a middle layer comprised of at least about 90% by weight of a copolymer of ethylenenetyl acrylate, a copolymer of ethylene methyl acrylate, a copolymer of ethylene methyl acrylate grafted with anhydride, a copolymer of such acrylates or a mixture of two or more of the foregoing, wherein the pipe does not visually delaminate at an effort of up to about 55 MPa and a deformation of up to about 900-950%, and, where the pipe does not visually delaminates after being submerged in water at 60 ° C for 36 hours.

In another aspect of the invention, there is provided a method for forming a medical pipe comprising an outer layer, an inner layer and a middle layer placed between the outer layer and the inner layer, the method comprising: selecting the first and second polymeric materials , each comprising more than about 90% by weight of a thermoplastic polyurethane; select a third polymeric material that easily bonds and adheres to the first and second polymeric materials in the co-extrusion and cooling of the materials; co-extrude the first, second and third polymeric materials selected to form the medical tubing, in a configuration such that the inner and outer layers comprise the first polymeric material and the middle layer comprises at least about 90% by weight of the second material polymeric In such a method, the first polymeric material preferably comprises more than about 90% by weight of a polyurethane based on aromatic or aliphatic polyether.

Furthermore, according to the invention, there is provided a method for forming a fluid release pipe, comprising:

select a first material comprised of more than about 90% by weight of a thermoplastic polyurethane, select a second material comprised of more than about 90% by weight of a thermoplastic polyurethane, select a third material comprised of more than about 90% by weight of an ethylenenetyl acrylate copolymer or an ethylene methyl acrylate copolymer or an anhydride grafted ethylene methyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of the above, forming a pipe comprised of an inner layer of the first material, an outer layer of the second material and a middle layer of the third material, wherein the layer media adheres to the inner and outer layers with each other;

where the pipe has a central fluid flow passage surrounded by the inner, middle and outer layers.

In such a method, the formation step typically comprises co-extruding the first, second and third materials simultaneously to form the inner and outer layers having a cross-sectional thickness of between about 0.00635 mm and about 0.635 mm (about 0.00025 and about 0.025 inches) and forming the middle layer having a cross-sectional thickness of between approximately 0.203 mm and approximately 3.048 mm (approximately 0.008 inches and approximately 0.120 inches).

The forming step may comprise co-extruding the first, second and third materials, so that the middle layer is between about 5% and about 98% of the total cross-sectional thickness of the combined inner, outer and middle layers.

The forming step may comprise co-extruding the first, second and third materials, so that the middle layer is between about 10% and about 85% of the total cross-sectional thickness of the combined inner, outer and middle layers.

The forming step may comprise co-extruding the first, second and third materials, so that the middle layer is between about 61% and about 98% of the total cross-sectional thickness of the combined inner, outer and middle layers.

In another aspect of the invention, there is provided a method of releasing an aqueous fluid to a patient, comprising: selecting a pipe comprising an inner layer, an outer layer and a middle layer, wherein the inner and outer layers comprise more than about 90% by weight of one or more thermoplastic polyurethanes and the middle layer comprises an ethylenenetyl copolymer or a copolymer of ethylenemethyl acrylate or an anhydride grafted ethylenemethyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of the foregoing; wherein the pipe has a central fluid flow passage surrounded by the layers; directing an aqueous fluid through the passage of the central fluid flow of the pipe, and, releasing the aqueous fluid directed towards the passage of the central fluid flow in a patient's blood vessel. In such a method, the step of selecting preferably comprises co-extruding the outer, inner and middle layers to form the pipe, so that the intermediate layer comprises at least about

90% by weight of one or more of the acrylate copolymers.

In another embodiment of the invention, such a method allows directing and releasing liquid and gaseous non-aqueous fluids that include organic materials, such as ethers, alcohols, hydrocarbons, amines, aldehydes, ketones, amides, carboxylic acids, esters and the like and fluid materials , such as oxygen, carbon dioxide, carbon monoxide, helium, neon, argon, krypton, xenon, radon, hydrogen, nitrogen and the like, as well as mixtures of two or more of any of the foregoing with others or mixtures of one or more of the foregoing with an aqueous fluid.

More preferably, the inner, middle and outer layers of the aforementioned pipes or tubes do not visually delaminate each other at stresses of up to about 55 MPa and a strain of up to about 900-950%, when measured by tensile length of pipe approximately 50.8 mm (2 inches) in axial length along its axis, using a Lloyd LR5K plus mechanical tester at a tensile speed of approximately 5 mm / second (12 inches / minute) at ambient conditions of approximately 22.22 ° C (872 ° F) and approximately 50% relative humidity, the breaking point being of the pipeline of approximately 57-62 MPa and approximately 1,000-1,050%.

More preferably, all the above-mentioned pipes or mechanical tubes do not visually delaminate after being immersed in water at 6 ° C for 36 hours, and subsequently mechanically flattened by manually squeezing the pipe from its normal rounding in the condition cross section to a flattened or oval cross section shape or condition.

Preferably, the aforementioned tubes or the medical tubing have a central axial fluid flow passage through which the aqueous fluid is directed, the inner layer having a radially internal wall surface that contacts the aqueous fluid, the layers exterior and interior that resist delamination of the middle layer at an effort of up to about 55 MPa and a deformation of up to about 900-950%.

More preferably, the middle layer serves as a barrier against, substantially prevents or decreases the migration of mobile radicals, such as monomers, short chain polymers, ions, water, small organic molecules, metals, plasticizers, catalysts and the like, between the outer and inner layers of the outer layer in the inner layer or the central flow passage or the central flow passage or the inner layer in the outer layer.

In another aspect of the invention, there is provided a method for releasing a non-aqueous fluid comprising:

selecting a pipe comprising an inner layer, an outer layer and a middle layer, wherein the inner and outer layers comprise more than about 90% by weight of a thermoplastic polyurethane and the middle layer comprises an ethylenenetyl acrylate copolymer or a copolymer of ethylenemethyl acrylate or an anhydride grafted ethylenemethyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of the foregoing;

wherein the pipe has a central fluid flow passage surrounded by the layers, direct the non-aqueous fluid through the central flow passage of the pipe, and, release the non-aqueous fluid directed through the central fluid flow passage to a reservoir for the reception of the fluid.

In such a method, preferably, the fluid comprises a liquid or gaseous non-aqueous fluid selected from the group of ethers, alcohols, hydrocarbons, amines, aldehydes, ketones, amides, carboxylic acids, esters, oxygen, carbon dioxide, carbon monoxide, helium, neon, argon, krypton, xenon, radon, hydrogen and nitrogen and mixtures of two or more of any of the above with each other, or one or more of the above with an aqueous fluid.

Preferably, the pipe does not visually delaminate at an effort of up to about 55 MPa and a deformation of up to about 900-950%.

In another aspect of the invention, there is provided a method for releasing a selected fluid for a selected reservoir comprising:

select a first material comprised of more than about 90% by weight of a thermoplastic polyurethane, select a second material comprised of more than about 90% by weight of a thermoplastic polyurethane, select a third material comprised of more than about 90% by weight of an ethylenenetyl acrylate copolymer or an ethylene methyl acrylate copolymer or an anhydride grafted ethylene methyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of the above, forming a pipe comprised of an inner layer of the first material, an outer layer of the second material and a middle layer of the third material, wherein the layer media adheres to the inner and outer layers with each other;

wherein the pipe has a central fluid flow passage surrounded by the inner, middle and outer layers;

directing the fluid through the central fluid flow passage of the pipe, and, releasing the directed fluid through the central fluid flow passage to the selected reservoir to receive the fluid.

In all the embodiments and aspects of the invention described herein, the polymer or polyurethane material of which the inner and outer layers are comprised separately, can be of the same or can be of different structure, molecular weight, crystallinity, purity, monomeric unit content, branching, chain length, inorganic content and physical properties, such as elongation, melting point, resistance to permanent deformation due to fatigue and hardness.

BRIEF DESCRIPTION OF THE FIGURES

The figures represent one or more embodiments of the invention shown by way of examples of the invention, wherein:

Figure 1 is a schematic perspective view of a three layer pipe showing the outer and middle layers cut in order to better illustrate the construction and arrangement of the pipe;

Figure 2 is a cross-sectional view taken along lines 2-2 of the pipe 10 shown in Figure 1.

DETAILED DESCRIPTION OF THE INVENTION

It is shown in Figure 1, an embodiment of a co-extruded three-layer pipe 10, according to the invention, comprising an outer layer 1 and an inner layer 3, each of which comprised separately of at least 90 % by weight of a polyurethane material, typically, a polyurethane based on polytetramethylene glycol, an example of which is Lubrizol TPU Pellethane 2363-90AE. The pipe or tube 10 includes a middle layer 2 comprising an ethylenenetyl acrylate copolymer, an ethylene methyl acrylate copolymer, an anhydride grafted ethylene methyl acrylate copolymer, a copolymer of two or more such acrylates or a mixture of two or more of these acrylate-based compounds or compositions. An example of an appropriate ethylenenetyl acrylate copolymer is Dow Amplify EA 103 (the ethylenenetyl acrylate content being approximately 19.5% by weight). Examples of suitable ethylene methyl acrylate copolymers are Westlake MA SP2268 (the ethylene methyl acrylate content being approximately 24% by weight), Westlake MA SP2220 (the ethylene methyl acrylate content being approximately 20% by weight). An example of an anhydride grafted ethylenemethyl acrylate copolymer is Westlake Tymax GA 7001 (Anhydride grafted ethylene methyl acrylate).

As shown in Figure 1, the outer polyurethane layer 1 has a radially internal face surface SI, which joins and adheres to a radically external face surface S2 of the medium acrylate copolymer layer 2. Similarly, the inner layer 3 has a radially external face surface S4, which joins and adheres to the radically internal face surface S3 of the middle acrylate copolymer layer 2. The middle layer 2 adheres to the outer and inner layers 1, so that the layers 1 and 3 remain adhered to the layer 2 and one another when the pipe 10 is subjected to an effort of up to about 55 MPa and a deformation up to about 900-950%, measured by pulling a length of pipe 10 of approximately 50.8 mm (2 inches) along an axial length L along axis A using a Lloyd LR5K Plus mechanical tester at a tensile speed of approximately 5 mm / second (12 inches / minute) ) at ambient conditions of approximately 22.22 ° C (72 ° F) and approximately 50% relative humidity, the pipe breaking point being approximately 57-62 MPa and a deformation of approximately 1,000-1,050%. Layers 1, 2, 3 of such pipe 10 do not visually delaminate after being immersed in water at 60 ° C for 36 hours and subsequently mechanically flattened by manually squeezing the pipe from its normal rounding in the section condition transverse to a flattened or oval cross section shape or condition.

As shown in Figures 1 and 2, layers 1, 2, 3 are formed in structurally stable walls that surround and enclose a passage of central hollow fluid 20 through which a fluid is directed and flows in an axial direction A which it contacts the radially internal face surface S5 of the inner layer 3. The middle layer 2 joins and holds the inner layers 3 and outer 1 together.

The inner layer 3 provides a radially internal fluid contact surface S5, typically varying the thickness of the inner layer 3 in the thickness of the cross-sectional area TI between about 0.000635 and about 0.635 mm (about 0.00025 inches and about 0.025 inches). The middle layer 2 has a cross-sectional thickness T2 of between about 0.203 mm and about 3,048 mm (about 0.008 inches and about 0.120 inches). The outer layer 1 typically ranges in cross-sectional thickness T3 between about 0.00635 mm and about 0.635 mm (about 0.00025 inches and about 0.025 inches).

The polyurethane elastomer (TPU) is typically the reaction product of a polyol and isocyanate and usually includes a combination of hard and soft segment domains. A TPU based on aromatic polyether or a TPU based on aliphatic polyether, such as a polyurethane based on polytetramethylene glycol, can be used. Preferred TPUs include the Pellethane 2363-80 AE series available from Lubrizol Corporation, Wilmington, MA, such as Lubrizol TPU Pellethane 2363-90AE.

The respective thickness of each layer of pipe 10, 20 can be controlled by the extrusion tool used, such as the Tri Die extrusion apparatus manufactured by the Genca Division of General Cable Company, Clearwater, Fia. The extrusion apparatus is selected to provide a uniform thickness of layers 1, 2, 3 along substantially the entire axial length L of the three layers 1, 2, 3.

The polymeric materials of which layers 1, 2, 3 are comprised are selected to be visually clear or transparent and manually flexible along and around the A axis of the pipe. Polymeric materials are also selected to maintain the integrity of the pipe 10 (i.e. no delamination occurs) and its transparency or clarity is then subjected to sterilization processes with ethylene oxide (EtO) and gamma radiation.

The foregoing description is intended to illustrate and not limit the scope of the invention, those skilled in the art will realize that equivalents thereof are contemplated by the foregoing description and that changes and modifications may be made thereto without departing from the spirit of the invention, all these equivalents, changes and modifications falling within the scope 5 of the present claims.

It is noted that in relation to this date, the best method known by the applicant to implement said invention is that which is clear from the present description of the invention.