CN113459597A

CN113459597A - Multilayer flexible polymer tube

Info

Publication number: CN113459597A
Application number: CN202010179039.XA
Authority: CN
Inventors: 耿煜; 张伟
Original assignee: Suzhou Yingnawei Technology Co ltd
Current assignee: Suzhou Yingnawei Technology Co ltd
Priority date: 2020-03-15
Filing date: 2020-03-15
Publication date: 2021-10-01

Abstract

A multilayer flexible polymeric tube includes a polymeric backing layer and a polymeric outer layer adjacent the polymeric backing layer. The polymeric backing layer comprises the following components: a polyolefin-based polymer, wherein the polyolefin has a melt index of between 0.5 g/10 min and 30 g/10 min measured at a temperature of 190 degrees celsius under a load of 2.16 kilograms, following ASTM D1238; and a polymeric outer layer having an inner surface directly bonded to the outer surface of the polymeric backing layer, wherein the polymeric outer layer comprises polyvinyl chloride, PVC, or ethylene vinyl acetate copolymer, EVA, or thermoplastic polyurethane, TPU. Wherein the polymer backing layer has a Shore A hardness of 95 or less and the Shore A hardness of the polymer outer layer is less than the Shore A hardness of the polymer backing layer. The invention also includes a method of forming the multilayer flexible polymer tube.

Description

Multilayer flexible polymer tube

Technical Field

The present invention relates to a flexible pipe, in particular to a multilayer flexible pipe and a method for manufacturing the same.

Background

Flexible tubing is widely used in a variety of industrial and household products. Such as drinking water (e.g., drinking water contact applications as specified by NSF 51), food and beverage (food contact applications as specified by the chinese food safety act, the U.S. FDA and european union), dairy contact applications, laboratory fluid transfer applications, fuel transfer flexible tubing for engines and motors for automobiles and portable tools, medical fluid transfer device applications, peristaltic pump applications, fluid transfer applications in biopharmaceutical or chemical pharmaceutical engineering, and the like.

The single-layer flexible pipeline developed in recent years at home and abroad is widely applied to the industry, and the flexible pipeline generally comprises flexible pipes of polyvinyl chloride PVC, ethylene vinyl acetate copolymer EVA or thermoplastic polyurethane TPU, and is widely applied to industries of industrial filling, food, beverage, medical treatment, pharmacy and the like. However, such single layer hoses are difficult to achieve in terms of good mechanical properties and chemical resistance during use. Particularly, the material has excellent mechanical properties such as rebound resilience, permanent compression set rate, tear resistance and the like, and has excellent chemical resistance, particularly acid and alkali resistance, soap and detergent resistance, fuel oil and lubricant resistance and the like, which are difficult to be simultaneously considered, and the wide application of the material in the industrial field is limited to a great extent.

Disclosure of Invention

The invention, under unexpected conditions, finds that a flexible hose product with excellent mechanical properties and chemical resistance can be obtained by adopting a flexible hose with a multi-layer polymer structure under the condition that a polyolefin polymer with special performance indexes and polyvinyl chloride PVC, or ethylene vinyl acetate copolymer EVA, or thermoplastic polyurethane TPU resin are respectively used on a lining layer and an outer layer.

The multilayer flexible pipe of the present invention, having an annular cross-section with an inner surface, an outer surface, an inner diameter and an outer diameter, the annular cross-section defining a wall thickness of the flexible pipe, wherein the flexible pipe comprises:

a) a polymeric backing layer comprising the following components: a polyolefin-based polymer, wherein the polyolefin has a melt index between 0.5 g/10 min and 30 g/10 min measured at a temperature of 190 degrees celsius under a load of 2.16 kilograms, in accordance with ASTM D1238, and

b) a polymeric outer layer having an inner surface directly bonded to an outer surface of the polymeric backing layer, wherein the polymeric outer layer comprises polyvinyl chloride, PVC, or ethylene vinyl acetate copolymer, EVA, or thermoplastic polyurethane, TPU.

Drawings

The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings.

FIG. 1 includes an annular cross-sectional illustration of an exemplary multi-layer flexible tubing.

The use of the same reference symbols in different drawings indicates similar or identical items.

Detailed Description

As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, article, or apparatus that comprises a list of features is not necessarily limited to only those features but may include other features not expressly listed or inherent to such method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or, and not to an exclusive or. For example, condition a or B is satisfied by either: a is true (or present) and B is false (or not present), a is false (or not present) and B is true (or present), and both a and B are true (or present).

Also, the use of "a" or "an" is used to describe elements and components described herein. This is done merely for convenience and to provide a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural and vice versa unless it is obvious that it is meant otherwise. For example, when a single item is described herein, more than one item may be used in place of a single item. Similarly, when more than one item is described herein, a single item may replace the more than one item.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent not described herein, many details regarding specific materials and processing acts are conventional and may be found in the written description and other sources within the field of construction and corresponding manufacturing.

A multilayer flexible tube having an annular cross-section with an inner surface, an outer surface, an inner diameter and an outer diameter, the annular cross-section defining a wall thickness of the flexible tube, wherein the flexible tube comprises a polymeric liner layer and a polymeric outer layer, the inner surface of the polymeric outer layer being bonded directly to the outer surface of the polymeric liner layer. In one embodiment, the polyolefin-based polymer is selected as the polymeric backing layer to achieve desired properties, such as chemical resistance, low flaking, leaching resistance, low protein adhesion, and the like, or any combination thereof. In one embodiment, the polyvinyl chloride PVC, or ethylene vinyl acetate copolymer EVA, or thermoplastic polyurethane TPU-based resin is selected as the polymeric outer layer to obtain excellent mechanical properties such as mechanical crush resistance, high resilience, abrasion resistance, tear resistance, or any combination thereof.

The polyolefin-based polymer included in the polymer liner layer of the multilayer flexible tube may include a homopolymer, copolymer, terpolymer, alloy, or any combination thereof, formed from a monomer, such as ethylene, propylene, butene, pentene, hexene, octene, or any combination thereof. In one embodiment, the polyolefin is polypropylene. Polypropylene is an impact resistant polypropylene random copolymer without added nucleating agents to achieve at least one desired property, such as Low water absorption, Low exfoliation (Low dispersion), resistance to leaching in a fluid environment, hydrophobicity to prevent protein adhesion, chemical resistance, or any combination thereof. In one embodiment, the polypropylene forms a continuous phase having a rubber phase dispersed therein, wherein the rubber phase may be a polyolefin rubber, such as Ethylene Propylene Diene Monomer (EPDM) or styrenic rubber (SEBS). The addition of the dispersed phase to the polypropylene improves the toughness of the polypropylene. In one embodiment, the polyolefinIs polypropylene, polyethylene or a combination thereof. In one embodiment, the polyolefin is a polyethylene, such as a Very Low Density Polyethylene (VLDPE), a polyolefin plastomer (POP), a polyolefin elastomer (POE), or a combination thereof. In one embodiment, the polyolefin plastomer (POP) or polyolefin elastomer (POE) is polyethylene based, polypropylene based, or a combination thereof. In one embodiment, the polyolefin plastomer (POP) or polyolefin elastomer (POE) may be a copolymer, such as a copolymer of ethylene with propylene or an alpha-olefin made by a metallocene or non-metallocene polymerization process, or a copolymer of polypropylene with ethylene or an alpha-olefin made by a metallocene or non-metallocene polymerization process. Examples of commercially available polyolefins include, but are not limited to, the Flexomers from ExxonMobil (ExxonMobil), Lande Basell (LondelBasell), and Mitsui^TM, Exact^TM, Vistamaxx^TM, Softel^TM, Tafmer^TMAnd the like.

The polymer liner layer of the multilayer flexible pipe comprises a polyolefin having a melt index of between 0.5 g/10 min and 30 g/10 min, such as between about 1 g/10 min and 10 g/10 min, such as between about 1.2 g/10 min and 5 g/10 min, measured at a temperature of 190 degrees celsius under a load of 2.16 kg, in accordance with ASTM D1238. If the resin melt index of the liner layer of the multilayer flexible pipe is too high, for example, more than 30 g/10 min, the viscosity during extrusion processing is too low, the liner layer extruded stably to a uniform thickness is not easy, and the shrinkage coefficient difference with the resin of the outer layer is too large to produce a tightly bonded multilayer flexible pipe. If the resin melt index of the lining layer of the multilayer flexible pipe is too low, for example, less than 0.5 g/10 min, the viscosity during extrusion processing is too high, the processing difficulty is too high, and the multilayer flexible pipe is easy to shrink to cause delamination, so that the qualified multilayer flexible pipe cannot be prepared.

The polymeric outer layer of the multilayer flexible tube comprises polyvinyl chloride PVC resins, exemplary suppliers of which include debarket (TekniPlex), pulitan (PolyOne), tai plastic, suzhou mei, and the like. In a particular embodiment, the polyvinyl chloride resin includes a plasticizer, such as dioctyl terephthalate (DOTP), trioctyl trimellitate (TOTM), dioctyl adipate (DOA), diisononyl cyclohexane-1, 2-Dicarboxylate (DINCH), and the like, but does not include di (2-ethylhexyl) phthalate (DEHP) plasticizer.

The polymeric outer layer of the multilayer flexible tube comprises a copolymer of ethylene and a polar vinyl monomer such as acetate (EVA), endoolefine acid (EAA), methyl endoolefine acid (EMA), methyl endoolefine acid methyl Ester (EMMA), Ethyl Endoolefine Acid (EEA), butyl endoolefine acid (EBA), or combinations thereof. Exemplary suppliers of these ethylene copolymer resins include DuPont (DuPont), BASF (BASF), Mitsui (Mitsui), and Arkema (Arkema). In a particular embodiment, the outer polymer layer is ethylene vinyl acetate. In a more particular embodiment, the polymer outer layer is ethylene vinyl acetate without additives. As used herein, "additive-free" refers to an ethylene vinyl acetate copolymer having at least about 99.99% or even about 100% of the ethylene and vinyl acetate monomer units without any additives added. In one example, the ethylene vinyl acetate is at least partially crystalline, i.e., has a crystalline melting point. The amount of vinyl acetate present in the ethylene vinyl acetate polymer determines the crystallinity of the polymer. In particular, the higher the percentage of vinyl acetate in the EVA copolymer, the more disturbed or disrupted the crystalline regularity of the ethylene chains. In the case of EVA copolymers containing greater than about 50% vinyl acetate, crystallization is progressively hindered and is substantially absent, resulting in an amorphous polymer. In one embodiment, the ethylene vinyl acetate has a vinyl acetate content of less than about 50 weight percent of the total weight of the ethylene vinyl acetate, thereby producing an at least partially crystalline copolymer. In a particular embodiment, the ethylene vinyl acetate has a vinyl content of about 3 weight percent to about 28 weight percent of the total weight of the ethylene vinyl acetate.

The polymeric outer layer of the multilayer flexible tube comprises a thermoplastic polyether or polyester urethane TPU, exemplary suppliers including luobur, basf, petunia, and the like.

The polymeric outer layer may also contain any additives as desired, such as lubricants, fillers, plasticizers, antioxidants, or any combination thereof. Exemplary lubricants include silicone oils, waxes, slip aids, anti-tacking agents, and the like. Exemplary lubricants also include silicone grafted polyolefins, polyethylene or polypropylene waxes, oleamide, erucamide, stearates, fatty acid esters, and the like. Exemplary antioxidants include phenolic, hindered amine antioxidants. Exemplary fillers include calcium carbonate, talc, silica, opaque fillers (such as barium sulfate), bismuth oxychloride, any combination thereof, and the like. Exemplary plasticizers include any known plasticizer, such as mineral oil, but do not include di (2-ethylhexyl) phthalate (DEHP) plasticizer. Typically, the additive may be present in an amount of no greater than about 50 weight percent of the total weight of the polymeric outer layer, such as no greater than about 40 weight percent of the total weight of the polymeric outer layer, or even no greater than about 30 weight percent of the total weight of the polymeric outer layer. Alternatively, the polymeric outer layer may be free of lubricants, fillers, plasticizers, and antioxidants.

In one example, the backing layer 140 can include one or more antimicrobial additives. For example, the antimicrobial additive may be a silver-based antimicrobial additive in an amount between 0.1 weight percent and 5 weight percent, more preferably between 0.5 weight percent and 2.5 weight percent, based on the total liner layer polymer amount.

In one embodiment, the polymeric backing layer has a shore a hardness of less than 95, such as 60 to 90, or even about 70 to 80 shore a hardness. In one embodiment, the polymeric outer layer is a thermoplastic resin or elastomer having a shore a hardness less than the polymeric backing layer. In one embodiment, the polymeric outer layer has a shore a hardness of less than about 65, such as from about 30 to about 65, or even from about 40 to about 50. In one embodiment, the lower shore a hardness of the polymeric outer layer provides flexibility to the stiffer, less flexible polymeric backing layer.

In one example, the polymer liner layer 140 thickness forms 5% to about 25% of the overall wall thickness of the multilayer flexible pipe 100, and the polymer outer layer 120 forms about 75% to about 95% of the thickness of the flexible pipe 100. In one example, the polymeric backing layer 140 has a thickness of no more than 0.50 mm, more preferably no more than 0.40 mm, and most preferably no more than 0.30 mm. In one example, the overall wall thickness of the flexible tube 100 is no greater than about 6.35 millimeters, such as no greater than about 5.00 millimeters, or even no greater than about 3.80 millimeters. Further, the overall wall thickness of the flexible tube 100 may be at least about 0.50 millimeters, such as at least about 1.30 millimeters, or even at least about 2.50 millimeters. The polymeric backing layer 140 can have a thickness of about 0.03 millimeters to about 0.50 millimeters, such as about 0.08 millimeters to about 0.40 millimeters, or even about 0.13 millimeters to about 0.25 millimeters. The thickness of the polymeric outer layer 120 can be about 0.5 mm to about 6.30 mm, such as about 1.27 mm to about 5.10 mm, such as about 2.54 mm to about 5.10 mm, or even about 2.54 mm to about 3.81 mm.

Figure 1 includes an illustration of a cross-section of an exemplary multi-layer flexible pipe 100. In one embodiment, the flexible tube 100 includes a polymeric liner layer 140 and a polymeric outer layer 120. The polymeric backing layer 140 is an inner layer or lining that forms an inner surface 150, the inner surface 150 defining a lumen 160 through which fluid flows. In one example, the polymer outer layer 120 forms the outer surface 110 of the flexible tube 100. In a particular embodiment, the polymeric backing layer 140 and the polymeric outer layer 120 are in direct contact with each other and are directly joined to each other at the surface 130 without the presence of any intermediate layers. In one embodiment, the polymeric backing layer 140 and the polymeric outer layer 120 are bonded to each other without a primer or adhesive. The surface 130 may be free of adhesive or other treatment to increase the adhesive properties of the polymeric backing layer 140 to the polymeric outer layer 120, such as free of surface treatment. In an alternative embodiment, the flexible tube 100 may include any reasonable intermediate layer between the polymer backing layer 140 and the polymer outer layer 120, such as a tie layer, an adhesive layer, a reinforcement layer, and the like (not shown). For example, the reinforcing layer may be disposed between the polymeric backing layer 120 and the polymeric outer layer 140, or substantially embedded within the polymeric outer layer 140. As used herein, "substantially embedded" refers to a reinforcing layer wherein at least 25%, such as at least about 50%, or even 75% of the total surface area of the reinforcing layer is in direct contact with the polymeric outer layer. In one embodiment, the polymeric backing layer 140 directly contacts the reinforcement layer (not shown). In one example, the reinforcement layer can be a polymer, such as a polyolefin, a polyester, a polyamide, a polyaramid, or a combination thereof. In one exemplary embodiment, the reinforcement layer is a polyolefin, such as polypropylene. In a more specific embodiment, the reinforcement layer is braided such that the polymer is in the form of interwoven yarns. The use of a reinforcing layer may provide additional advantageous properties to the flexible pipe. For example, by selection of the reinforcing layer polymer material, a compatible material with the desired adhesion can be provided, thereby improving the peel strength of the flexible pipe polymer liner layer and the polymer outer layer. In a particular embodiment, "desired adhesion" can be defined as cohesive failure, wherein the polymeric backing layer, the polymeric outer layer, or the reinforcing layer breaks before the bonds between the polymeric backing layer, the reinforcing layer, and the polymeric outer layer fail. The required adhesion will provide the following benefits compared to flexible pipes without a reinforcement layer or with a reinforcement layer as an incompatible material: for example, improved burst pressure and increased mechanical performance properties (especially at fluid pressures up to 5 to 6 bar). In case the reinforcement layer has the desired adhesion to the polymer backing layer and the polymer outer layer, the risk of leaching out small molecule volatiles from the yarns of the polymer reinforcement layer into the transported fluid is avoided, since the reinforcement layer is sandwiched between the polymer backing layer and the polymer outer layer.

In one embodiment, the multilayer flexible tube 100 can be made by any reasonable means, such as extrusion molding using a single screw extruder. The polymeric backing layer and the polymeric outer layer may be extruded separately or coextruded. In one exemplary embodiment, an inner liner formed from a liner layer polymer may be extruded sequentially with an outer layer formed from an outer layer polymer. The lining layer polymer is first extruded into pipe in one extruder and cooled to draw the pipe product into flexible lining layer pipe product. And then the outer layer polymer is sent into an extruder, the lining layer flexible pipe is led to a special die and then directly extruded on the outer surface of the lining layer pipe, and the multilayer flexible pipe product is cut into a multilayer flexible pipe product through cooling and traction. In one exemplary embodiment, an inner liner formed from a liner layer polymer may be coextruded with an outer layer formed from an outer layer polymer. Multiple extruders were connected to a multilayer coextrusion die. The liner layer polymer is fed into one extruder and the outer layer polymer is fed into another extruder and extruded simultaneously through a multilayer coextrusion die into a multilayer flexible tube which is cooled, drawn and cut into articles. The polymeric backing layer can directly contact the polymeric outer layer and be directly bonded to the inner surface of the polymeric outer layer without an intermediate layer or adhesive. Further, the polymeric backing layer may be extruded in the absence of additives, plasticizers, or other processing aids.

The multilayer flexible pipe according to the invention can be used in applications such as: drinking water (e.g., drinking water contact applications as specified by NSF 51), food and beverage (food contact applications as specified by the chinese food safety act, the U.S. FDA and european union), dairy contact applications, laboratory fluid transport applications, fuel oil transport for engines and motors (e.g., meeting the fuel oil permeation requirements as specified by the U.S. EPA, CARB), medical fluid transport device applications, peristaltic pump applications, fluid transport applications in biopharmaceutical or chemical pharmaceutical engineering, and the like. In one exemplary embodiment, the multilayer flexible tube of the present invention may be used in applications such as: the flexible pipe is used as a fuel oil transmission pipeline of a motor in an engine and a portable device, a flexible water pipe in a sports and entertainment device, a fluid transmission flexible pipe in a food and beverage processing device, a fluid transmission flexible pipe of liquid medicines, body fluids and the like in the medical and health care fields, a peristaltic pump pipe used in laboratories, medical devices and biopharmaceuticals, and a disposable system fluid transmission pipeline used in the biopharmaceutical manufacturing process. For example as part of a molding assembly for pumping, bioreactor processing, sampling, filling, etc. In one embodiment, the multilayer flexible pipe of the present invention may be configured for high purity high pressure resistant braided flexible tubing products with an intermediate reinforcing layer. In another embodiment, the multilayer flexible tube of the present invention has been validated by regulatory approval of the chinese food and drug administration, the united states Food and Drug Administration (FDA), the United States Pharmacopeia (USP), the European Pharmacopeia (EP), the International Standard Organization (ISO), other regulatory approval, or combinations thereof. For example, the multilayer flexible tube has been validated using USP class VI standards, ISO 10993 standards, and the like.

The multilayer flexible tube of the present invention may be used in devices such as the following and may be used in conjunction with any reasonable device: wherein the device is a medical device, a pharmaceutical device, a biopharmaceutical device, a chemical delivery device, a laboratory device, a water treatment device, a food and beverage device, a document printing device, an industrial cleaning device, an automotive device, an aerospace device, an electronic device, or a fuel delivery device.

Examples of the invention

Various aspects of the multilayer flexible tube and method of forming of the present invention are further described with reference to the non-limiting examples described below.

Comparative example 1

Polyvinyl chloride PVC resin (ME-1065 EL-NP from Suzhou Mei Yi Polymer materials Co., Ltd.) was fed into a single screw extruder, and melt-extruded to obtain a standard No. 17 single-layer flexible tube having an inner diameter of 6.35 mm and an outer diameter of 9.53 mm, and the hardness of the tube was measured to be 65 Shore A.

Comparative example 2

Ethylene-vinyl acetate copolymer EVA resin (Baschiff V5110 resin, Germany) is fed into a single-screw extruder and is subjected to melt extrusion to prepare a standard No. 17 single-layer flexible pipe with the inner diameter of 6.35 mm and the outer diameter of 9.53 mm, and the hardness is tested to be 65 Shore A hardness.

Comparative example 3

Thermoplastic Polyurethane (TPU) resin (Tantajust Wanhua Wanthan resin) is fed into a single-screw extruder and is subjected to melt extrusion to prepare a standard No. 17 single-layer flexible pipe with the inner diameter of 6.35 mm and the outer diameter of 9.53 mm, and the hardness is 69 Shore A hardness through testing.

Comparative example 4

The preparation method of the multilayer flexible pipe comprises the following steps: using low density polyethylene (china shenhua chemical industry, melt index is 100 g/10 min measured according to ASTM D1238, 77 shore a hardness) resin as lining layer polymer, using the thermoplastic polyurethane TPU resin described in comparative example 3 as outer layer polymer, connecting one 25 type single screw extruder to another 65 type single screw extruder through a co-extrusion die head, feeding lining layer and outer layer polymer particles into the 25 type and 65 type single screw extruders respectively, co-extruding to prepare a standard No. 17 multilayer flexible pipe with an inner diameter of 6.35 mm and an outer diameter of 9.53 mm, wherein the lining layer thickness is designed to be 0.3 mm.

Comparative example 5

The preparation method of the multilayer flexible pipe comprises the following steps: a standard number 17 multilayer flexible tube having an inner diameter of 6.35 mm and an outer diameter of 9.53 mm was co-extruded as described in comparative example 4 using a low density polyethylene (china shenhua chemical, melt index of 0.4 g/10 min, 96 shore a hardness, measured following ASTM D1238) resin as the liner layer polymer and a thermoplastic polyurethane TPU resin as described in comparative example 3 as the outer layer polymer, wherein the liner layer thickness was designed to be 0.3 mm.

Experimental example 1

The preparation method of the multilayer flexible pipe comprises the following steps: a standard No. 17 multilayer flexible pipe having an inner diameter of 6.35 mm and an outer diameter of 9.53 mm was co-extruded using a low density polyethylene (china shenhua chemical, melt index of 5 g/10 min according to ASTM D1238, 84 shore a hardness) resin as the liner layer polymer and a PVC resin as described in comparative example 1 as the outer layer polymer by the procedure described in comparative example 4, wherein the thickness of the liner layer was 0.3 mm.

Experimental example 2

The preparation method of the multilayer flexible pipe comprises the following steps: a standard No. 17 multilayer flexible pipe having an inner diameter of 6.35 mm and an outer diameter of 9.53 mm was prepared by co-extrusion using the low density polyethylene resin of experimental example 1 as the liner layer polymer and the EVA resin of comparative example 2 as the outer layer polymer in the same manner as in comparative example 4, wherein the thickness of the liner layer was 0.3 mm.

Experimental example 3

The preparation method of the multilayer flexible pipe comprises the following steps: a standard No. 17 multilayer flexible pipe having an inner diameter of 6.35 mm and an outer diameter of 9.53 mm was prepared by co-extrusion using the low density polyethylene resin of experimental example 1 as the liner layer polymer and the TPU resin described in comparative example 3 as the outer layer polymer in the same manner as in comparative example 4, wherein the thickness of the liner layer was 0.3 mm.

The service life of the peristaltic pump of the flexible tube was tested by using the single-layer flexible tube of comparative examples 1 to 3, the multi-layer flexible tube of comparative examples 4 to 5 and the multi-layer flexible tube of experimental examples 1 to 3, which were manufactured as described above, as a standard pump head with YZ15 four rollers at 600rpm, in a condition that a strong alkali solution with a pH of 13.5 was used as a medium, an environment with a temperature of 35 ℃, an outlet pressure of 1.5 bar and a back pressure of 1 bar, or a condition that the flow rate of the flexible tube was reduced by 20% compared with the initial value of the experiment, and the test results were as follows,

TABLE 1

	Service life of peristaltic pump (hours)	Test results
			Comparative example 1	31	The flow rate is reduced by 20 percent compared with the initial value of the experiment
Comparative example 2	17.5	The flow rate is reduced by 20 percent compared with the initial value of the experiment
			Comparative example 3	12	The flow rate is reduced by 20 percent compared with the initial value of the experiment
Comparative example 4	6.5	Flexible pipe layer breaking leakage
			Comparative example 5	2.5	Flexible pipeLeakage of layer rupture
Experimental example 1	56.5	The flow rate is reduced by 20 percent compared with the initial value of the experiment
			Experimental example 2	48	The flow rate is reduced by 20 percent compared with the initial value of the experiment
Experimental example 3	167	The flow rate is reduced by 20 percent compared with the initial value of the experiment

From the results of table 1, it can be seen that the service life of comparative examples 1 to 3, single-layer flexible pipes, is significantly increased due to the good chemical resistance of the lining layer and the multi-layer structure closely adhered to the outer layer, compared to the corresponding experimental examples 1 to 3. Comparative examples 4 to 5 resulted in leakage due to delamination cracking of the backing layer from the outer layer.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A multilayer flexible pipe having an annular cross-section with an inner surface, an outer surface, an inner diameter and an outer diameter, the annular cross-section defining a wall thickness of the flexible pipe, wherein the flexible pipe is characterized by:

a polymeric backing layer comprising the following components: a polyolefin-based polymer, wherein the polyolefin has a melt index between 0.5 g/10 min and 30 g/10 min measured at a temperature of 190 degrees celsius under a load of 2.16 kilograms, in accordance with ASTM D1238, and

a polymeric outer layer having an inner surface directly bonded to an outer surface of the polymeric backing layer, wherein the polymeric outer layer comprises polyvinyl chloride, PVC, or ethylene vinyl acetate copolymer, EVA, or thermoplastic polyurethane, TPU.

2. A multilayer flexible tube as recited in claim 1, wherein the polymer liner layer has a shore a hardness of 95 or less, and the polymer outer layer has a shore a hardness that is less than the shore a hardness of the polymer liner layer.

3. A multilayer flexible pipe according to any one of claims 1 to 2, wherein the polymer lining layer thickness forms 5% to 25% of the total thickness of the multilayer flexible pipe.

4. A multilayer flexible pipe according to any one of claims 1 to 2, wherein the multilayer flexible pipe is used in the following applications: food contact applications, dairy, beverage and drinking water contact applications, laboratory fluid transfer applications, medical applications, pharmaceutical applications, peristaltic pump applications, fuel oil transfer applications for engines and motors, or combinations thereof, as specified by the national food safety act, the FDA and european union of the united states.

5. A device comprising the multilayer flexible tube of any one of claims 1 to 2, wherein the device is a medical device, a pharmaceutical device, a biopharmaceutical device, a chemical delivery device, a laboratory device, a water treatment device, a food and beverage device, a document printing device, an industrial cleaning device, an automotive device, an aerospace device, an electronic device, or a fuel delivery device.

6. The multilayer flexible tube of any one of claims 1 to 2, further comprising a reinforcement layer disposed between the polymer liner layer and polymer outer layer.

7. A method of forming a multilayer flexible tube, the method comprising:

first extruding a polymeric backing layer comprising the following components: a polyolefin-based polymer, wherein the polyolefin has a melt index between 0.5 g/10 min and 10 g/10 min, as measured at a temperature of 190 degrees celsius under a load of 2.16 kilograms, and in accordance with ASTM D1238

Extruding a polymeric outer layer directly onto the polymeric backing layer, wherein the polymeric outer layer comprises polyvinyl chloride, PVC, or ethylene vinyl acetate copolymer, EVA, or thermoplastic polyurethane, TPU.

8. A method of forming a multilayer flexible tube, the method comprising:

coextruding a polymeric liner layer and a polymeric outer layer, wherein,

the polymeric backing layer comprises the following components: a polyolefin-based polymer, wherein the polyolefin has a melt index between 0.5 g/10 min and 10 g/10 min, as measured at a temperature of 190 degrees celsius under a load of 2.16 kilograms, and in accordance with ASTM D1238

The outer polymer layer comprises polyvinyl chloride (PVC), or Ethylene Vinyl Acetate (EVA), or Thermoplastic Polyurethane (TPU).