Low-absorptivity multi-layer medical tube

Abstract

The medical tubing may have a continuous inner layer with a continuous outer layer thereon, where the inner layer comprises a polyolefin, such as polyethylene or polypropylene or a functionalized polyolefin. The outer layer may include a thermoplastic polymer, for example, including one or more or a mixture of a thermoplastic polyurethane (TPU), a thermoplastic olefin (TPO), a thermoplastic elastomer (TPE), a styrene-containing thermoplastic elastomer (S-TPE), a polyolefin elastomer (POE), a styrene block copolymer (SBC). Advantageously, the outer layer and / or the inner layer do not comprise polyvinyl chloride. Such tubing may be readily solvent bonded to a medical connector and used with an infusion kit.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to tubing, and in particular to flexible medical tubing having low absorption of medical fluids and components in such fluids, while being readily adhesive to other medical components by solvent bonding. Such tubing can be used in medical devices, for example tubing for administering medical fluids by infusion. BACKGROUND

[0002] Plastic tubing is widely used in the medical field, particularly for patient analysis and treatment procedures. However, medical tubing requires different, sometimes incompatible, requirements. For example, medical tubing should be strong yet flexible or bendable, kink resistant, avoid reaction with fluids, and avoid injecting harmful chemicals into fluids transported therethrough. But many plastic materials having such properties tend to be inflexible. The inertness of many plastic materials having such properties also makes it difficult to bond such tubing by solvent bonding. However, in many applications, medical tubing is clamped or pinched, or used with infusion pumps that cause fluid to flow through the tubing by compressing the tubing. Such uses require that the tubing be flexible, easily pinched, and quickly resilient. Flexible tubing, such as polyvinyl chloride with plasticizers, has been used in infusion sets for many years. Unfortunately, plasticized polymeric materials, such as plasticized polyvinyl chloride, can be tacky and can cause clogging and tearing of the tubing.

[0003] Accordingly, there is a continuing need for medical tubing that can meet the different requirements of medical applications. SUMMARY

[0004] Aspects of the subject technology relate to medical tubing comprising or consisting of a continuous inner layer having a continuous outer layer thereon. The inner layer can comprise or consist of a polyolefin, and the outer layer can comprise or consist of a thermoplastic polymer selected from the group consisting of thermoplastic polyurethane (TPU), thermoplastic olefin (TPO), thermoplastic elastomer (TPE), styrene-containing thermoplastic elastomer (S-TPE), polyolefin elastomer (POE), styrene block copolymer (SBC). Advantageously, the adhesive strength of the medical tubing is at least 25% higher relative to medical tubing comprising a single layer of thermoplastic polymer. It is believed that such a structure is advantageous for solvent bonding of the medical tubing to other medical components when the inner layer is stronger (e.g., stiffer) than the outer layer.

[0005] The polyolefin inner layer can comprise or consist of polyethylene or polypropylene or a functionalized polyolefin or a combination thereof, where the functionalized polyolefin can be selected from maleic anhydride modified polyethylene, maleic anhydride modified polypropylene, maleic anhydride modified plastomer, amine functionalized polyolefin, or a combination thereof. The outer layer can comprise or consist of a thermoplastic polymer, such as including one or more of or a mixture of: thermoplastic polyurethane (TPU), thermoplastic olefin (TPO), thermoplastic elastomer (TPE), styrene-containing thermoplastic elastomer (S-TPE), polyolefin elastomer (POE), styrene block copolymer (SBC). Advantageously, the inner layer is more robust (e.g., stiffer) than the outer layer. Such a structure facilitates solvent bonding of the medical tubing to other medical components. Further, the outer layer and / or the inner layer advantageously does not include polyvinyl chloride.

[0006] The subject technology also relates to a method of manufacturing a medical tubing by co-extruding a continuous inner layer having a continuous outer layer directly thereon, where the inner layer comprises or consists of a polyolefin and the outer layer comprises or consists of a thermoplastic polymer. The method can further include extruding a connecting layer between the continuous inner layer and the continuous outer layer. The manufactured medical tubing can be formed to be transparent to visible light.

[0007] The subject technology also relates to a medical tubing as described above bonded to a medical connector by solvent bonding.

[0008] The subject technology also relates to an infusion set comprising a medical tubing connected to one or more medical connectors, and a method of preparing an infusion set comprising a medical tubing connected to one or more medical connectors by solvent bonding.

[0009] Embodiments of the foregoing medical tubing and methods include one or more of the following features, alone or in combination. In some embodiments, the medical tubing can further include a connecting layer between the continuous inner layer and the continuous outer layer. The connecting layer can include maleic anhydride modified polypropylene, maleic anhydride modified polyethylene, ethylene-vinyl acetate copolymer, or a combination thereof. Alternatively, the inner layer can directly contact the outer layer. Further, in other embodiments, the medical tubing can include an intermittent solvent bondable segment layer directly contacting the outer layer, such as a thermoplastic polyurethane intermittent solvent bondable segment layer.

[0010] In other embodiments, an infusion set can be prepared by applying a thin layer of solvent on one or both of a surface of the medical tubing and a surface of the medical connector and securing the surface of the medical tubing and the surface of the medical connector together until a seal is formed therebetween. In some embodiments, the medical connector comprises an acrylic-based polymer.

[0011] Other advantages of the subject technology will become apparent to the skilled artisan from the following detailed description, wherein is shown and described only certain aspects of the subject technology, by way of illustration. As will be realized, the subject technology is capable of other and different configurations, and its several details are capable of modification in various other respects, all without departing from the subject technology. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification, illustrate disclosed embodiments and serve to explain principles of disclosed embodiments. In the drawings:

[0013] Figure 1 An exemplary medical tube having a continuous inner layer and an outer layer is shown in accordance with aspects of the present disclosure.

[0014] Figure 2 Another exemplary medical tube including a continuous inner layer, a continuous outer layer thereon, and a connecting layer between the continuous inner layer and the continuous outer layer is shown in accordance with aspects of the present disclosure.

[0015] Figure 3 A multi-material, polyolefin inner-liner medical tube including a continuous polyolefin inner layer, a continuous outer layer, and an intermittent solvent-bondable segment layer in direct contact with the outer layer is shown.

[0016] Figure 4 A bar graph showing the maximum load (Newton) required to break a medical tube connected to a medical connector is shown. The graph compares a medical tube containing a single layer ("single") of polymeric material (control) and a medical tube having a polyolefin inner-liner thermoplastic polymer, and further compares such a tube and a medical tube made by an alternative extrusion technique (AET).

[0017] Figure 5 How certain variables affect the extrusion of a medical tube is shown.

[0018] Figure 6 The effect on adhesion strength by adjusting certain variables during extrusion is shown. DETAILED DESCRIPTION

[0019] The detailed description set forth below describes various configurations of the present subject matter and is not intended to represent the only configurations in which the present subject matter can be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the present subject matter. Accordingly, the descriptions set forth regarding certain aspects are not intended to be construed as limiting. It will be apparent, however, to one skilled in the art that the present subject matter can be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the present subject matter.

[0020] It is to be understood that the present disclosure includes examples of the present subject matter and does not limit the scope of the appended claims. Various aspects of the present subject matter will now be disclosed according to specific but non-limiting examples. The various embodiments described in the present disclosure can be in different ways and variations, and according to the desired application or implementation.

[0021] Various aspects of the present subject matter relate to medical tubing that can accommodate different performance requirements. Medical tubing requires advanced material formulations and structures to overcome technical challenges arising from conflicting design requirements of such tubing. For example, medical tubing should be able to be bonded, e.g., by solvent bonding, to connectors and other components to connect the tubing due to the relative ease, convenience, and lower cost of solvent bonding. In addition, medical tubing should simultaneously avoid absorbing medical fluids and components therein without significantly altering the tubing itself or any active pharmaceutical ingredients (APIs). This requires an inert material that is pharmaceutically compatible and a solvent-responsive material that has solvent bonding capability, which are typically conflicting requirements for a single material. In addition, there is a trend towards more environmentally friendly materials and away from polyvinyl chloride (PVC). Although the tubing is expected to quickly and completely recover, it also needs to be strong enough to enable a manufacturable cutting process.

[0022] In some aspects, the present subject matter relates to medical tubing that includes a continuous inner layer having a continuous outer layer thereon. Advantageously, the inner layer includes or consists of a polyolefin having low absorption properties such that the polyolefin inner layer resists absorbing medical fluids and / or components therein, or affecting any active pharmaceutical ingredients (APIs) delivered through the tubing. In addition, the polyolefin inner layer resists changes to the tubing itself caused by medical fluid delivery through the tubing.

[0023] In some embodiments, the continuous inner layer can include or consist of a functionalized polyolefin, such as a maleic anhydride modified polyethylene (e.g., high density polyethylene HDPE or low density polyethylene LDPE), a maleic anhydride modified polypropylene, a maleic anhydride modified plastomer, or a combination thereof. Such functionalized polyolefins facilitate interlayer adhesion between the inner layer and the outer layer.

[0024] Advantageously, the inner layer is more robust (e.g., stiffer) than the outer layer. Such a construction facilitates solvent bonding of the medical tube to other medical components. For example, the inner layer can have a tensile modulus in the range of about 1800 to about 3000 MPa, such as about 1000 MPa to 2000 MPa. Yield tensile stress (MPa) can be determined by DIN 53 504, elongation at break (%) can be determined by DIN 53 504, and Shore D can be determined by DIN 53 505.

[0025] The outer layer can include or consist of a polymeric material that is different than the inner layer, such that the outer surface of the tube can have different properties than the inner layer material. For example, the outer layer can include a thermoplastic polymer or mixture thereof, such as including one or more or a mixture of: thermoplastic polyurethane (TPU), thermoplastic olefin (TPO), thermoplastic elastomer (TPE), styrene-containing thermoplastic elastomer (S-TPE), polyolefin elastomer (POE), styrene block copolymer (SBC). The thermoplastic polymer used as the outer layer can also be mixed with other polymeric components and / or additives. For example, the thermoplastic polymer used as the outer layer can also be mixed with adhesion promoters (such as acrylic-based TPEs, or polar functionalized polyolefins, such as up to 15 wt% or more of the mixture), tackifiers, and clarifiers (such as up to 10 wt% of the mixture). Many thermoplastic polymers, such as thermoplastic polyurethane (TPU) and styrene-containing thermoplastic elastomer (S-TPE), have advantageous properties for the outer layer of a medical tube, which can be used for solvent bonding of the outer layer. Alternatively or in combination, many thermoplastic polymers advantageously improve the flexibility of the tube.

[0026] In some aspects of the medical tube of the present disclosure, a connecting layer can be included between the continuous inner layer and the continuous outer layer.

[0027] Advantageously, the medical tube of the present disclosure does not include polyvinyl chloride. That is, the outer layer and / or the inner layer and / or the connecting layer (if present) does not include polyvinyl chloride.

[0028] In some aspects, the medical tube of the present disclosure can have a Shore A hardness greater than about 85 or less than about 85. A Shore A hardness greater than about 85 is generally considered to be hard for medical tube applications. Pumping tubes generally employ softer tubes with a Shore A hardness less than about 65 (e.g., 55 or less).

[0029] The medical tubing of the present disclosure can be used as medical tubing for administering medical fluids by infusion, such as delivery of intravenous fluids to a patient by an intravenous set assembly, gravity container, and / or infusion pump. The assembly of tubing, valves, fittings, and an injection needle that intravenously connects a fluid container to a patient can be referred to as an "IV set." An infusion pump is a medical device that can be used to administer intravenous (IV) fluids. Such assemblies, containers, and pumps employ tubing that is connected to one or more medical connectors, to which the medical tubing of the present disclosure is equally useful.

[0030] For example, the medical tubing according to the present disclosure can be easily connected and adhered to a medical connector or other medical assembly by applying a thin layer of solvent on one or both contact surfaces, then bringing the two surfaces together and holding them in place until a seal is formed between them. The contact surface of the medical tubing can be the outer surface of the outer layer, and the contact surface of the medical connector can be the pocket surface or inner surface of the connector. Medical connectors that can benefit from the medical tubing of the present disclosure include, but are not limited to, connectors made from acrylic-based polymeric materials such as acrylonitrile-butadiene-styrene (ABS), methyl methacrylate-acrylonitrile-butadiene-styrene (mABS), acrylic-polycarbonate-based materials, polyesters, polycarbonates, acrylics, polyvinyl chlorides, and the like.

[0031] In one embodiment of the present application, the medical tubing according to the present disclosure can be easily adhered to a medical connector by solvent bonding. As described in the preceding paragraph, solvent bonding includes applying a thin layer of solvent on one or both of the medical tubing and the medical connector. For example, a thin layer of solvent can be applied on the outer surface of the medical tubing and the tubing inserted into the inner surface (e.g., pocket or other element) of the medical connector, or a thin layer of solvent can be applied on the inner surface of the medical connector and the tubing inserted into the inner surface, or both. The two surfaces (e.g., tubing surface and connector surface) one or both of which are solvent-applied are then brought together and held in place until a seal is formed between them.

[0032] Solvents that can be used for solvent bonding the medical tubing of the present disclosure include, but are not limited to, one or more of the following: alcohols (e.g., methanol, ethanol, isopropyl alcohol, propanol, butanol, pentanol, benzyl alcohol), glycols (e.g., diethylene glycol, propylene glycol), ethers (e.g., dioxolane, tetrahydrofuran, 1,3-dioxane), ketones (e.g., acetone, methyl ethyl ketone, cyclohexanone), esters (e.g., ethyl acetate, ethyl formate), amides (e.g., dimethylformamide, dimethylacetamide, and diethylacetamide), N-methylpyrrolidone, sulfoxides (e.g., dimethyl sulfoxide), hydrocarbons (e.g., hexane, toluene), chlorinated solvents (e.g., dichloromethane), and the like.

[0033] Table 1 below provides examples of medical tubing structures that can be used in accordance with the present disclosure. Such medical tubing structures and material formulations can meet many of the requirements of IV sets and other requirements of medical tubing.

[0034] Table 1. Solvent bonded low absorption polyolefin inner liner TPU medical tubing structures.

[0035]

[0036] (1) Tecoflex EG-85A is a TPU aliphatic polyether

[0037] (2) Pellethane is an aromatic based polyether polyurethane

[0038] (3) Ellastollan 1180A is an ether based thermoplastic polyurethane

[0039] (4) Tecothane TT1095A is a Shore A 95 TPU that can meet the different needs of small bore tubing.

[0040] (5) Toyo-Tac M-100 is a maleic anhydride PP

[0041] (6) Exxelor PE1040 is a maleic anhydride modified HDPE

[0042] (7) TecnoBond PE-LMP is a maleic anhydride PE

[0043] (8) Exxelor VA1840 is a maleic anhydride modified plastomer

[0044] As shown in Table 1, the continuous inner layer can comprise or consist of an amine functionalized polyolefin or a maleic anhydride modified polyolefin. Such amine functionalized polyolefins can be made by combining and reacting a maleic anhydride modified polyolefin (e.g., select 1, 2, 3, 4 from Table 1 above) with a polyether amine through reactive extrusion. This formulation or maleic anhydride functionalized polyolefin allows for increased compatibility of polyolefins (non-polar low surface energy material) with the more polar material group. The tubing structures in Table 1 require good interlayer adhesion between the polar and non-polar material groups, so this customization should increase the adhesion of the inner layer to the outer layer.

[0045] The dual layer polyolefin lined TPU medical tubing component structure as provided in Table 1 has several advantages, which include: no three layer process, increased line speed / line output compared to three layer, for example, the co-extrusion run should be faster and simpler than three layer. Standard costs are expected to be lower than three layer, due to the compatibility of the functionalization of the inner layer, good adhesion of the layers, in contrast to poor adhesion of unmodified polyolefin due to the functionalized polyolefin inner layer. Polyolefin also advantageously has low drug absorption properties.

[0046] Further, in some embodiments, the continuous inner layer can be relatively thinner than the continuous outer layer, which would contribute to the tubing component having overall properties similar to the continuous outer layer, for example, a TPU outer layer. Further, the ether-based TPU layer provides better solvent adhesion, and the selection of an aliphatic backbone provides better color stability in some cases.

[0047] Figure 1 An example of a dual layer polyolefin lined medical tubing component is shown. Such a structure can be used with the polymeric materials listed in Table 1 above to provide a solvent bondable, low absorption dual layer polyolefin lined TPU medical tubing component. As shown, the dual layer medical tubing component includes an inner layer (10) and an outer layer (12) directly on the inner layer.

[0048] For use in applications including IV sets and / or infusion pumps, the tubing components of the present disclosure can have an inner diameter for fluid flow therethrough ranging from about 1.5 mm to about 6 mm, for example, 2 mm to 4 mm. The overall side wall thickness can be from about 0.2 mm to about 1 mm, for example, 0.4 mm to 0.6 mm. In some aspects of the present disclosure, the outer layer can occupy 10 to 90% of the side wall thickness, and the inner layer can occupy 90 to 10% of the side wall thickness. In one embodiment, the outer layer can have a thickness of about 0.01 mm to about 0.5 mm, for example, about 0.05 mm to about 0.2 mm, and the inner layer can have a thickness of about 0.01 mm to about 0.8 mm, for example, about 0.02 mm to about 0.1 mm, for example, about 0.038 mm (about 0.0015 inches).

[0049] Table 2 below is another example of a medical tubing component structure that can be used in accordance with the present disclosure.

[0050] Table 2. Solvent bondable, low absorption PE lined TPU tubing component with tie layer

[0051]

[0052] (1) TecnoBond PP / TLA is a maleic anhydride modified random block PP copolymer

[0053] (2) random PP copolymer extrusion grade

[0054] (3) LDPE

[0055] (4) Low Density Polyethylene EC800 is a general purpose low density formulation for extrusion coating applications.

[0056] (5) EVA Copolymer

[0057] (6) Other alternatives include ReZilok Rx, which is a linear low density polyethylene grafted with maleic anhydride.

[0058] As provided in Table 2, a medical tube can include a continuous inner layer, a continuous outer layer thereon, and a connecting layer between the continuous inner layer and the continuous outer layer. As provided in Table 2, the inner layer can comprise a polyolefin, such as polypropylene or polyethylene (e.g., linear low density polyethylene, LDPE). The outer layer can comprise a thermoplastic polyurethane (TPU), which can be used to solvent bond the outer layer of the tube. The medical tube can also include a connecting layer between the continuous inner layer and the continuous outer layer. Such a connecting layer can comprise a functionalized polyolefin (e.g., maleic anhydride modified polypropylene, maleic anhydride modified polyethylene), or other connecting layer polymer (e.g., ethylene-vinyl acetate copolymer (EVA copolymer)), or combinations thereof.

[0059] The three layer polyolefin inner liner TPU medical tube structure as provided in Table 2 has a number of advantages, including: compatible backbone selection matching PP with PP based TPO or POP, PE with PE based TPO or POE, enabling compatibility without the need for more expensive functionalized polymers, enabling low drug absorption performance by including a PP or PE based inner layer.

[0060] Further, in some embodiments, the continuous inner layer can be relatively thinner than the continuous outer layer, which can contribute to the tube having overall properties similar to the TPU layer. Further, the ether based TPU layer provides better solvent bonding, and the selection of an aliphatic backbone provides better color stability.

[0061] Figure 2 An example of a three layer polyolefin inner liner medical tube is shown. This structure can be used with the polymeric materials listed in Table 2 above to provide a solvent bondable low absorption polyolefin inner liner TPU medical tube with a connecting layer. As shown, the three layer medical tube includes an inner layer (20), an outer layer (22), and a connecting layer (24) between and directly contacting the inner layer (20) and the outer layer (22).

[0062] For use in applications including IV sets and / or infusion pumps, the tubing of the present disclosure can have an inner diameter for fluid flow therethrough ranging from about 1.5 mm to about 6 mm, for example, 2 mm to 4 mm. The overall side wall thickness can be from about 0.2 mm to about 1 mm, for example, 0.4 mm to 0.6 mm. In some aspects of the present disclosure, the outer layer can occupy 10 to 90% of the side wall thickness and the inner layer can occupy 90 to 10% of the side wall thickness. In one embodiment, the outer layer can have a thickness of about 0.01 mm to about 0.8 mm, for example, about 0.5 mm to about 0.5 mm, and the inner layer can have a thickness of about 0.01 mm to about 0.5 mm, for example, about 0.05 mm to about 0.2 mm.

[0063] Figure 3 An example of a multi-layer polyolefin-lined medical tubing is shown. Such a structure can be used to provide a solvent-bonded low-absorbent polyolefin-lined medical tubing. As shown, the medical tubing includes a continuous polyolefin inner layer (30) and a continuous outer layer (34). For this example, the medical tubing also includes an intermittent solvent-bondable segment layer (32) that directly contacts the outer layer 34. The intermittent solvent-bondable segment layer can include a thermoplastic polyurethane, for example, a TPU having good adhesion properties.

[0064] Table 3 below is another example of a medical tubing structure that can be used in accordance with the present disclosure.

[0065] Table 3. Low-absorbent PE-lined TPO dual-layer tubing.

[0066] Outer layer Inner layer Engage 8003 (1) LDPE, HDPE, other ethylene-based polyolefins Engage 8452 (2) LDPE, HDPE, other ethylene-based polyolefins Versify 3300 (3) Random PP copolymer, sterilization grade Vistamaxx 3020 (4) Random PP copolymer sterilization grade

[0067] (1) Ethylene-octene polyolefin elastomer (POE)

[0068] (2) Ethylene-butene polyolefin elastomer (POE)

[0069] (3) POP

[0070] (4) Propylene elastomer with i-PP repeat units of random ethylene

[0071] As provided in Table 3 above, the medical tubing can include a continuous inner layer and a continuous outer layer directly located thereon. The continuous inner layer can comprise a non-functionalized polyolefin, for example, a polyethylene (e.g., LDPE, HDPE) or a polypropylene. The continuous outer layer can comprise a thermoplastic polymer, for example, a polyolefin elastomer (POE), for example, an ethylene-octene polyolefin elastomer, an ethylene-butene polyolefin elastomer, a polyolefin plastomer (POP), a propylene elastomer, and other thermoplastic polymers or mixtures thereof.

[0072] Many thermoplastic polymers (which include thermoplastic elastomers (TPEs) and thermoplastic olefins) that can be used for the outer layer of the medical tubing of the present disclosure can be mixed with polyolefins to optimize cost, increase crystallinity, increase mechanical strength, expand the working envelope (i.e., environmental stability and shelf life), and increase material compatibility (i.e., interlayer adhesion with the inner layer). Below are some different customizations that can overcome certain deficiencies of the thermoplastic polymers of s-TPEs and TPOs.

[0073] Custom styrenic block copolymer (SBC) compounds: SBC grades are useful for their flexibility and solvent responsiveness (i.e., adhesion). However, some of our experiments have shown that styrenic TPEs are less resistant to kinking than other types of polymers. In addition, certain SBC grades lack high temperature resistance as observed by low softening points. Similarly, POP grades and POE grades (e.g., Engage reactor manufactured TPOs) lack high temperature resistance as observed by low softening points. Tables 4-5 provide examples of thermoplastic polymer mixtures that can be used as continuous outer layers of medical tubing according to the present disclosure.

[0074] SBC mixed with random PP copolymer: Mixing SBC with random PP copolymer will result in a solvent-bondable kink-resistant material, either for the tubing itself or a solvent-bondable delamination. The mixing ratio can vary from 5 to 95% olefin component (based on ethylene or propylene) addition in order to further refine based on clarity requirements. These mixtures can also contain adhesion promoters (e.g., acrylic-based TPEs, or polar functionalized polyolefins, up to 15 wt% of the mixture). When adjustments to the melt flow rheology and clarity of the tubing are needed, the addition of up to 10 wt% of tackifiers and clarifiers and polymer processing aids are typical for these types of compounds. Multiple processing variables will affect the clarity of the tubing and its mechanical properties.

[0075] TPO mixed with random PP copolymer, polyolefin, or temperature resistant TPO (e.g., olefin block copolymer). The mixing ratio can vary from 5 to 95% olefin component (based on ethylene or propylene) in order to adjust based on clarity requirements. These mixtures can also contain adhesion promoters (e.g., acrylic-based TPEs, or polar functionalized polyolefins, up to 15 wt% of the mixture). When adjustments to the melt flow rheology and clarity of the tubing are needed, the addition of up to 10 wt% of tackifiers and clarifiers and polymer processing aids are typical for these types of compounds. Multiple processing variables will affect the clarity of the tubing and its mechanical properties.

[0076] Table 4. Examples of custom TPE mixtures

[0077] Function Compound A Compound B Compound C Flexibility of elastomer, clarity Engage 8003 Engage 7256 Engage 8452 High temperature stability, drug compatibility (low absorption of most grades), cost optimization (most grades) Ethylene-based polyolefins, LDPE, HDPE, or similar Ethylene-based polyolefins, LDPE, HDPE, or similar Ethylene-based polyolefins, LDPE, HDPE, or similar Adhesion, rheology modification Acrylic-based TPE, polar functionalized polyolefins, tackifiers Acrylic-based TPE, polar functionalized polyolefins, tackifiers Acrylic-based TPE, polar functionalized polyolefins, tackifiers Clarity adjustment Clarifying or nucleating agents, polymer processing aids, if needed Clarifying or nucleating agents, polymer processing aids, if needed Clarifying or nucleating agents, polymer processing aids, if needed

[0078] Table 5 Other Examples of Custom TPE Blends

[0079] Function Compound D Compound E Compound F Flexibility of elastomer, clarity Engage 8003, POE Infuse 9010 olefin block copolymer (OBC) Ineos 4G80 SBC High temperature stability, drug compatibility (low absorption of most grades), cost optimization (most grades) Infuse 9010, OBC Random PP copolymer Random PP copolymer Adhesion, rheology modification Acrylic-based TPE, polar functionalized polyolefins, tackifiers Acrylic-based TPE, polar functionalized polyolefins, tackifiers Acrylic-based TPE, polar functionalized polyolefins, tackifiers Clarity adjustment Clarifying or nucleating agents, polymer processing aids, if needed Clarifying or nucleating agents, polymer processing aids, if needed Clarifying or nucleating agents, polymer processing aids, if needed

[0080] Infuse 9010 olefin block copolymer (OBC)

[0081] Engage 8003, Engage 7256, and Engage 8452 polyolefin elastomers

[0082] Ineos 4G80 styrene butadiene block copolymer

[0083] The dual layer polyolefin inner liner thermoplastic polymer medical tubing structure (such as provided in Table 3) has a number of advantages, which include: no three layer process, increased processing cycle time compared to three layer, e.g., coextrusion runs should be faster and simpler than three layer. Lower cost is expected than three layer, good layer adhesion due to compatibility with the inner layer, low drug absorption properties by including a non-functionalized polyolefin inner layer.

[0084] Advantageously, the bond strength of the medical tubing according to the present disclosure is at least 25% higher, such as at least 50%, 75%, and 100% higher, relative to a medical tubing comprising a single layer of thermoplastic polymer. To demonstrate the bond strength of the medical tubing of the present disclosure, a number of medical tubing structures were prepared and compared to medical tubing comprising only a thermoplastic polymer but having the same dimensions as the dual layer medical tubing (referred to as "single" tubing). It was not necessary to compare medical tubing of a single layer of polyolefin material since the polyolefin inner layer does not undergo significant, if any, solvent bonding.

[0085] The medical tubing provided in Tables 6A and 6B below were solvent bonded to a luer connector made from mABS Terlux® 2802HD. The maximum force required to break the tubing / connector assembly (bond strength) was recorded on an Instron at a pull rate of 20 inches / minute. Table 6C provides some physical properties of certain inner layers.

[0086] Table 6A: Tubing structures including dual or single layer tubing

[0087] Name Test number Outer layer Inner layer Single-PB 1 RB820 (polybutadiene) None Single-TPO1 3 Engage 8003 (TPO post reactor) None Single-TPO6 6 Vistamaxx 3020 (TPO post reactor) None Single-TPU1 2 Estane 58271 (TPU aromatic polyester) None Single-TPU2 9 Tecoflex EG-85A TPU aliphatic polyether None PE1 inner liner TPU2 15 Tecoflex EG-85A (TPU aliphatic polyether) Toyo-Tac M100 (modified polyolefin) PE2 inner liner TPU2 16 Tecoflex EG-85A (TPU aliphatic polyether) Exxelor PE1040 (modified HDPE) PE3 inner liner TPU3 22 PUR 9741 (TPU polyether) PE 140 / PE 770 (LDPE / EVA) Single-TPE 1 10 4G80 (SBC) No Single-TPE 2 8 PP 6649 (styrene-based TPE) No Single-TPE 3 23 Medalist MD50278 (styrene-based TPE) No Dual-TPE 3 14 Hexpol 880210 (SBC) Medalist MD50278 (sTPE) PE-liner-TPE 2 20 PP 6469 (styrene-based TPE) PE 140 / PE 770 (LDPE / EVA)

[0088] Table 6B: Tubing structures of one

[0089] Name Test No. End Section Middle Section AET-TPE 3 5 Hexpol 880210 (SBC) Medalist MD50278 (sTPE)

[0090] Table 6C

[0091] Exxelor PE1040 Toyo-tac Raumedic PE140 Density 0.96 0.9 0.9 Melt Index, g / 10 min 1.4 [190 / 2.16] 7 [190 / 2.16] NA Tm, C 132 150 NA Shore D, DIN 53 505 NA NA 45+ / -3

[0092] Note on melt index: [190 / 2.16] = 190 C and 2.16 kg

[0093] The data in Table 6B were determined using DIN 53 479 (density, g / cm 3 ) can be determined using Shore D (DIN 53505), yield tensile stress (MPa) using (DIN 53 504), and elongation at break (%) using (DIN 53 504). The inner layer wall thickness / total wall thickness was about 20%, and the outer layer wall thickness / total wall thickness was about 80%.

[0094] The results of the Instron testing are shown in Figure 4 As shown in Figure 4 , the medical tubing with a polyolefin-lined thermoplastic polymer exhibited significantly higher maximum load (Newton) (adhesion strength) required to break the medical tubing assembly adhesion to a medical connector (e.g., a luer connector) as compared to a medical tubing containing a single layer (“single”) of polymeric material (control). This was shown by comparing PE1-lined TPU2 and PE2-lined TPU2 (polyolefin-lined thermoplastic polyurethane) which had adhesion strengths of about 44 and 42 N, respectively, to single-TPU2 which had an adhesion strength of about 22 N.

[0095] The adhesion strength of the medical tubing with a polyolefin-lined thermoplastic polymer was about 100%-91% higher relative to a medical tubing containing a single layer of thermoplastic polymer. The same trend was demonstrated by comparing a polyolefin-lined styrene-based thermoplastic elastomer (PE-lined TPE2) to a single layer of styrene-based thermoplastic elastomer (single-TPE2). As shown in Figure 4 , the adhesion strength of the polyolefin-lined TPE was increased by about 67%. Medical tubing prepared by alternative extrusion technology (AET) also showed an increase in adhesion strength.

[0096] The outer layer of the tubing allows solvent bonding of the tubing to the pocket connector of a medical connector (e.g., a connector containing a rigid, acrylic-based material). It is believed that such a construction facilitates solvent bonding of the medical tubing to other medical components when the inner layer is more robust (e.g., stiffer) than the outer layer.

[0097] The medical tubing of the present disclosure can be manufactured by extrusion. For example, the medical tubing according to the present disclosure can be co-extruded as a continuous inner layer having a continuous outer layer thereon, wherein the inner layer comprises a polyolefin and the outer layer comprises a polymeric material different from the inner layer. It is preferred to manufacture the medical tubing to be transparent (e.g., transparent to visible light). Extruding transparent tubing presents a series of challenges; the following processing variables can create differences between transparent and hazy tubing. Clarity is affected by mold temperature, tool design, and parison venting.

[0098] Mold Temperature: (a) The mold temperature will affect the transparency of the tube through its interaction with the surface finish of the tube. Reducing the mold temperature near the end of the mold will cause the outermost layer (surface) of the tube to "stick" to the tool as it is being extruded. The sticking will cause a velocity differential of the polymer melt from the inside to the outside and will cause the surface to develop micro deformations ("cracks"). These cracks cause the tube to have an opaque or "frosted" appearance. (b) Conversely, increasing the mold temperature will help make the tube more transparent by reducing the velocity differential of the polymer melt from the inside to the outside, thus causing the surface to develop fewer micro deformations.

[0099] Tool Design: (a) The effect of the extrusion tool on the surface finish is similar to the effect of the mold temperature. By reducing the friction between the tool material and the polymer melt, the polymer melt velocity will be more uniform throughout the parison. This reduction in friction is achieved by applying a polishing or coating process to the tool.

[0100] Parison Venting: (a) The last process parameter that can have an effect on the transparency of the tube is the location of the parison vent. The purpose of the vent is to remove any fumes from the parison as it is being extruded, it is usually placed directly above the parison. A vent with a large opening can be placed further away from the parison to capture any fumes, but a small serpentine vent must be placed within a few inches of the parison. If the vent is placed too close to the parison, the parison will be affected by the air suction, which will change the surface finish of the tube, possibly producing an opaque / frosted finish. (b) This is similar to the frosted extrusion process, where cold air is blown directly onto the parison as it is being extruded.

[0101] Figure 5 It is shown how the article is affected during the extrusion process, Figure 6 It is shown how the adhesion strength is affected during the extrusion process by adjusting certain variables.

[0102] Other Considerations

[0103] In some embodiments, any of the clauses herein can be dependent on any of the independent clauses or any of the dependent clauses. In an aspect, any clause (e.g., dependent or independent) can be combined with any other one or more clauses (e.g., dependent or independent). In an aspect, a claim can include some or all of the words recited in a clause, sentence, phrase, or paragraph (e.g., steps, operations, devices, or components). In an aspect, a claim can include some or all of the words recited in one or more clauses, sentences, phrases, or paragraphs. In an aspect, some words can be removed from each clause, sentence, phrase, or paragraph. In an aspect, additional words or elements can be added to a clause, sentence, phrase, or paragraph. In an aspect, the subject technology can be implemented without utilizing some of the components, elements, functions, or operations described herein. In an aspect, the subject technology can be implemented with additional components, elements, functions, or operations.

[0104] For example, the subject technology is illustrated, by way of example, in accordance with various aspects described below. For ease of example, multiple instances of various aspects of the subject technology are described as numbered clauses (1, 2, 3, etc.). These clauses are provided as examples and are not intended to limit the subject technology. Note that any dependent clause can be combined in any combination and placed in respective independent clauses, e.g., Clause 1 or Clause 5. Other clauses can be presented in a similar manner.

[0105] Clause 1. A medical tubing comprising a continuous inner layer having a continuous outer layer on the continuous inner layer; wherein the inner layer comprises a polyolefin; wherein the outer layer comprises a thermoplastic polymer selected from the group consisting of thermoplastic polyurethane (TPU), thermoplastic olefin (TPO), thermoplastic elastomer (TPE), styrene-containing thermoplastic elastomer (S-TPE), polyolefin elastomer (POE), styrene block copolymer (SBC); and wherein the medical tubing has a bond strength that is at least 25% higher relative to a medical tubing comprising a single layer of the thermoplastic polymer.

[0106] Clause 2. The medical tubing of Clause 1, wherein the inner layer consists of a polyolefin and the outer layer consists of a thermoplastic polymer.

[0107] Clause 3. The medical tubing of Clause 2, wherein the polyolefin consists of polyethylene or polypropylene.

[0108] Clause 4. The medical tubing of Clause 2, wherein the polyolefin consists of maleic anhydride modified polyethylene, maleic anhydride modified polypropylene, or a combination thereof.

[0109] Clause 5. The medical tubing of Clause 2, wherein the thermoplastic polymer consists of thermoplastic polyurethane.

[0110] Clause 6. The medical tubing according to any one of clauses 1-5, wherein the thermoplastic polymer is one or more or a mixture comprising: a styrene-containing thermoplastic elastomer (S-TPE), a polyolefin elastomer (POE), a styrene block copolymer (SBC).

[0111] Clause 7. The medical tubing according to any one of clauses 1-6, wherein the outer layer and the inner layer do not comprise polyvinyl chloride.

[0112] Clause 8. The medical tubing according to any one of clauses 1-7, wherein the inner layer directly contacts the outer layer.

[0113] Clause 9. The medical tubing according to any one of clauses 1-8, wherein the Shore A hardness of the medical tubing is less than about 65.

[0114] Clause 10. An infusion set comprising the medical tubing according to any one of clauses 1-9, the medical tubing being bonded to a medical connector by solvent bonding.

[0115] Clause 11. The infusion set according to clause 10, wherein the medical connector comprises an acrylic-based polymer and the medical tubing is bonded to the acrylic-based polymer.

[0116] Clause 12. The infusion set according to clause 10, wherein the inner layer consists of a polyolefin and the outer layer consists of a thermoplastic polymer.

[0117] Clause 13. The infusion set according to any one of clauses 10-12, wherein the polyolefin consists of polyethylene or polypropylene and the thermoplastic polymer consists of a thermoplastic polyurethane.

[0118] Clause 14. A method of making an infusion set, the infusion device comprising the medical tubing according to any one of clauses 1-9, the method comprising: applying a thin layer of solvent on one or both of a surface of the medical tubing and a surface of a medical connector, and after applying the thin layer of solvent, securing the surface of the medical tubing and the surface of the medical connector together until a seal is formed between them.

[0119] Clause 15. The method according to clause 14, wherein the solvent is applied to the outer layer of the tubing as the surface of the tubing.

[0120] Clause 16. The method according to any one of clauses 14-15, wherein the medical connector comprises an acrylic-based polymer.

[0121] Clause 17. The method of any of clauses 14-16, wherein the solvent comprises one or more of an alcohol, a diol, a ketone, an ester such as ethyl acetate, an amide, a sulfoxide, or a hydrocarbon.

[0122] Clause 18. The method of any of clauses 15-17, wherein the inner layer consists of a polyolefin and the outer layer consists of a thermoplastic polymer.

[0123] Clause 19. The method of clause 18, wherein the polyolefin consists of polyethylene or polypropylene.

[0124] It is to be understood that any particular order or hierarchy of steps in the processes disclosed is an example of illustrative approaches. Based upon design or implementation preferences, it is understood that a particular order or hierarchy of steps in the processes could be rearranged, or that all illustrated steps could be performed at the same time. In some implementations, any of the steps could be performed concurrently.

[0125] The present disclosure is provided to enable any person skilled in the art to practice the various aspects described herein. The disclosure provides various examples of the subject technology, and the subject technology is not limited to these examples. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other aspects.

[0126] Unless specifically stated otherwise, a reference to a component means "one or more" unless otherwise indicated. Whenever a composition, an element or a component is described as having "about" a particular value, it is understood that the element, component, or composition is deemed to also cover the particular value. Any numerical value, however, should be understood in the context of the other disclosure. Numeric ranges are inclusive of the numbers at the ends of the range. Unless otherwise indicated, the use of "or" in the

[0127] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. In one aspect, various alternative results and operations can be described herein as being "exemplary."

[0128] As used herein, the phrase "at least one of," followed by a listing of items, and the term "comprises at least one of," followed by a listing of items, means one or more items from the listing of items, and that the items in the list can be selected individually or in any combination. The phrase "at least one of," followed by a listing of items, and the term "comprises at least one of," followed by a listing of items, is not meant to imply that only a single item is selected from a listing of items, or that a combination of items can not be selected from a listing of items. The phrase "at least one of," followed by a listing of items, and the term "comprises at least one of," followed by a listing of items, is meant to indicate that at least one item from the listing of items is selected, and that a combination of items from the listing of items can or can not be selected, depending on the specific examples described.

[0129] Phrases such as “aspect” do not imply that a particular aspect is critical, essential, or mandatory to the subject technology. The disclosures as to one aspect, including that of a particular example, can be applied to other aspects, or used in combination with other aspects. Phrases such as “embodiment” do not imply that a particular embodiment is critical, essential, or mandatory to the subject technology. The disclosures as to one embodiment, including that of a particular example, can be applied to other embodiments, or used in combination with other embodiments. Phrases such as “structure” do not imply that a particular structure is critical, essential, or mandatory to the subject technology. The disclosures as to one structure, including that of a particular example, can be applied to other structures, or used in combination with other structures. Phrases such as “structure” do not imply that a particular structure is critical, essential, or mandatory to the subject technology. The disclosures as to one structure, including that of a particular example, can be applied to other structures, or used in combination with other structures.

[0130] In one aspect, unless otherwise indicated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. In one aspect, they are intended to have a reasonable range commensurate with the functions to which they relate and with general

[0131] It should be understood that a specific order or hierarchy of steps, operations or processes, whether implemented as code, firmware, or software, is merely illustrative. Based on the disclosure provided herein, one of ordinary skill in the art should appreciate that other steps, operations, or processes can be performed or can be omitted. Additionally, one of ordinary skill in the art should appreciate that a number of elements can be repositioned or otherwise modified. Some steps, operations, or processes can be performed simultaneously. Some or all steps, operations, or processes can be performed automatically, without user intervention. The order or hierarchy of steps, operations or processes presented in the methods claims, if any, should not be deemed limiting. The steps, operations or processes can be performed in any order, or in parallel, or in any suitable order or hierarchy not expressly disclosed.

[0132] All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims herein. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The claims are not to be interpreted to perform a differential treatment between elements of a process or composition to the extent such treatment is not required by the rules of 35 U.S.C. § 112(f). The terms "comprises," "comprising," "includes," "including," and the like are to be construed as being analogous in meaning and function to the term "containing" or "comprising," as set forth above. Additionally, the terms "a / m an," "an," "a" and "the" are defined to encompass one or more of the referenced element or, when the quantity of elements is unspecified, any quantity of the referenced element.

[0133] The title, summary, background, brief description of drawings, and abstract of the disclosure are hereby incorporated into this disclosure and provided as illustrative examples of the disclosure and are not intended to limit the scope or meaning of the claims. It is understood that they will not be used to limit the scope or meaning of the claims at the time of issuance. Moreover, in the DETAILED DESCRIPTION, it can be seen that the embodiments provide illustrative examples and, in some embodiments, multiple features are combined where appropriate. This method of disclosure is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are explicitly recited in each claim. Rather, inventive subject matter lies in less than all features of a single disclosed structure or operation. The claims below, therefore, are hereby expressly incorporated into this detailed description, with each claim acting as a separate limitation on the whole of the claimed compositions and methods.

[0134] The claims are not intended to be limited to the aspects described herein, but are to be accorded the full scope consistent with the language claims, and to encompass all legal equivalents thereof. Regardless of the language in which the claims are expressed, however, none should be construed as including an unnecessary feature or excluding an essential feature unless otherwise indicated by the patentee. None of the claims are intended to be limited to the embodiments or examples described herein, but rather the scope is to be given the full breadth consistent with the language claims, and to encompass all structural equivalents. CLAIM (AMENDED PURSUANT TO ARTICLE 19 OF THE TREATY) 1. A medical tubing comprising a continuous inner layer having a continuous outer layer thereon; wherein the inner layer comprises a maleic anhydride modified polyolefin or an amine functionalized polyolefin; wherein the outer layer comprises a thermoplastic polymer selected from the group consisting of thermoplastic polyurethane (TPU), thermoplastic olefin (TPO), thermoplastic elastomer (TPE), styrene-containing thermoplastic elastomer (S-TPE), polyolefin elastomer (POE), styrene block copolymer (SBC); and wherein the medical tubing has a bond strength that is at least 25% higher relative to a medical tubing comprising a single layer of thermoplastic polymer. 2. The medical tubing of claim 1, wherein the inner layer consists of a polyolefin and the outer layer consists of a thermoplastic polymer. 3. The medical tubing of claim 2, wherein the polyolefin consists of polyethylene or polypropylene. 4. The medical tubing of claim 2, wherein the polyolefin consists of a maleic anhydride modified polyethylene, a maleic anhydride modified polypropylene, or a combination thereof. 5. The medical tubing of claim 2, wherein the thermoplastic polymer consists of a thermoplastic polyurethane. 6. The medical tubing of any one of claims 1-5, wherein the thermoplastic polymer is one or more or a mixture comprising: a styrene-containing thermoplastic elastomer (S-TPE), a polyolefin elastomer (POE), a styrene block copolymer (SBC). 7. The medical tubing of any one of claims 1-6, wherein the outer layer and the inner layer do not comprise polyvinyl chloride. 8. The medical tubing of any one of claims 1-7, wherein the inner layer directly contacts the outer layer. 9. The medical tubing of any one of claims 1-8, wherein the medical tubing has a Shore A hardness of less than about 65. 10. An infusion set comprising the medical tubing of any one of claims 1-9, the medical tubing being solvent bonded to a medical connector. 11. The infusion set of claim 10, wherein the medical connector comprises an acrylic-based polymer and the medical tubing is bonded to the acrylic-based polymer. 12. The infusion set of claim 10, wherein the inner layer consists of a polyolefin and the outer layer consists of a thermoplastic polymer. 13. The infusion set of any one of claims 10-12, wherein the polyolefin consists of polyethylene or polypropylene and the thermoplastic polymer consists of a thermoplastic polyurethane. 14. A method of making an infusion set comprising the medical tubing of any one of claims 1-9, the method comprising: applying a thin layer of solvent on one or both of a surface of the medical tubing and a surface of the medical connector, and after applying the thin layer of solvent, securing the surface of the medical tubing and the surface of the medical connector together until a seal is formed between them. 15. The method of claim 14, wherein solvent is applied to the outer layer of the tubing as a surface of the tubing. 16. The method of any one of claims 14-15, wherein the medical connector comprises an acrylic-based polymer. 17. The method of any one of claims 14-16, wherein the solvent comprises one or more of an alcohol, a glycol, a ketone, an ester such as ethyl acetate, an amide, a sulfoxide, or a hydrocarbon. 18. The method of any one of claims 14-17, wherein the inner layer consists of a polyolefin and the outer layer consists of a thermoplastic polymer. 19. The method of claim 18, wherein the polyolefin consists of polyethylene or polypropylene.

Claims

1. A medical tubing comprising a continuous inner layer and having a continuous outer layer thereon; The inner layer contains polyolefins; The outer layer comprises a thermoplastic polymer selected from the following: thermoplastic polyurethane (TPU), thermoplastic olefin (TPO), thermoplastic elastomer (TPE), styrene-containing thermoplastic elastomer (S-TPE), polyolefin elastomer (POE), and styrene block copolymer (SBC); and The adhesive strength of the medical fitting is at least 25% higher than that of a medical fitting comprising a single layer of thermoplastic polymer.

2. The medical tubing according to claim 1, wherein the inner layer is composed of polyolefin and the outer layer is composed of thermoplastic polymer.

3. The medical fitting according to claim 2, wherein the polyolefin is composed of polyethylene or polypropylene.

4. The medical fitting according to claim 2, wherein the polyolefin is composed of maleic anhydride modified polyethylene, maleic anhydride modified polypropylene, or a combination thereof.

5. The medical fitting according to claim 2, wherein the thermoplastic polymer is composed of thermoplastic polyurethane.

6. The medical fitting according to any one of claims 1-5, wherein the thermoplastic polymer comprises one or more or a mixture of the following: styrene-containing thermoplastic elastomer (S-TPE), polyolefin elastomer (POE), and styrene block copolymer (SBC).

7. The medical fitting according to any one of claims 1-6, wherein the outer layer and the inner layer do not include polyvinyl chloride.

8. The medical fitting according to any one of claims 1-7, wherein the inner layer directly contacts the outer layer.

9. The medical fitting according to any one of claims 1-8, wherein the Shore A hardness of the medical fitting is less than about 65.

10. An infusion kit comprising a medical fitting according to any one of claims 1-9, the medical fitting being bonded to a medical connector by solvent bonding.

11. The infusion kit of claim 10, wherein the medical connector comprises an acrylic-based polymer, and the medical fitting is bonded to the acrylic-based polymer.

12. The infusion kit of claim 10, wherein the inner layer is composed of a polyolefin and the outer layer is composed of a thermoplastic polymer.

13. The infusion kit according to any one of claims 10-12, wherein the polyolefin is composed of polyethylene or polypropylene, and the thermoplastic polymer is composed of thermoplastic polyurethane.

14. A method for preparing an infusion kit, the infusion kit comprising medical tubing according to any one of claims 1-9, the method comprising: Apply a thin layer of solvent to one or both of the surfaces of the medical tubing and the medical connector, and After applying a thin layer of solvent, the surfaces of the medical fittings and the medical connectors are held together until a seal is formed between them.

15. The method of claim 14, wherein the solvent is applied to the outer layer of the fitting as the surface of the fitting.

16. The method according to any one of claims 14-15, wherein the medical connector comprises an acrylic-based polymer.

17. The method according to any one of claims 14-16, wherein the solvent comprises one or more of alcohols, glycols, ketones, esters such as ethyl acetate, amides, sulfoxides, or hydrocarbons.

18. The method according to any one of claims 14-17, wherein the inner layer is composed of a polyolefin and the outer layer is composed of a thermoplastic polymer.

19. The method of claim 18, wherein the polyolefin is composed of polyethylene or polypropylene.

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