Multilayer film and preparation method thereof

Abstract

The present invention discloses a multilayer film and a preparation method thereof, comprising a three-layer structure consisting of an outer layer, a middle layer, and an inner layer, wherein the outer layer material is a mixture of homopolymerized polypropylene, high-melting-point low-density polyethylene, and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 60-90:5-10:5-20; the middle layer material is a mixture of binary copolymerized polypropylene, high-melting-point low-density polyethylene, a polyolefin elastomer, and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 10-40:10-40:15-25:20-40; and the inner layer material is a mixture of ternary copolymerized polypropylene, high-melting-point low-density polyethylene, a polyolefin elastomer, and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 60-90:5-10:5-10:5-20. Large-size infusion bags of more than 2000 mL prepared from the multilayer film of the present invention can withstand impact without damage or leakage even after storage at 0°C.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical packaging materials, and in particular relates to a multilayer film and a preparation method thereof. Background Art

[0002] Peritoneal dialysis fluid products are one of the treatments for end-stage renal failure (ESRD). They are clinically effective and are the preferred treatment for the integrated treatment of end-stage renal failure (ESRD).

[0003] Because PVC (polyvinyl chloride) has good flexibility, most peritoneal dialysis fluid products currently used in clinical practice are packaged in PVC plastic soft bags. However, PVC soft bags generally contain DEHP (phthalate) and other plasticizers. According to literature reports, this plasticizer can migrate into the liquid medicine, affecting the normal physiological functions of the human body and posing potential hazards to patient health.

[0004] Currently, the non-PVC three-layer co-extruded infusion membranes used clinically are polypropylene and polyethylene. Existing polyethylene membranes cannot withstand high-temperature sterilization, resulting in severe deformation of the infusion bag, poor toughness, and easy leakage. Using existing non-PVC materials to package large-volume preparations exceeding 2000mL, especially in cold winter temperatures, can lead to film brittleness and a significant risk of bag damage and leakage during production, transportation, and use. Summary of the Invention

[0005] The invention provides a multilayer film, comprising a three-layer structure consisting of an outer layer, a middle layer and an inner layer, wherein the outer layer material is a mixture of homopolymerized polypropylene, high-melting-point low-density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 60-90:5-10:5-20; the middle layer material is a mixture of binary copolymerized polypropylene, high-melting-point low-density polyethylene, a polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 10-40:10-40:15-25:20-40; and the inner layer material is a mixture of ternary copolymerized polypropylene, high-melting-point low-density polyethylene, a polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 60-90:5-10:5-10:5-20.

[0006] In some embodiments of the present invention, the homopolypropylene has a melting point of 160-165° C. and a melt flow index of 2.0-8.0 g / 10 min.

[0007] In some embodiments of the present invention, the high melting point low density polyethylene has a melting point of 128-131° C. and a melt flow index of 1.0-3.8 g / 10 min.

[0008] In some embodiments of the present invention, the binary copolymer polypropylene has a melting point of 150-155° C. and a melt flow index of 2.0-8.0 g / 10 min.

[0009] In some embodiments of the present invention, the polyolefin elastomer has a melt flow index of 0.9-1.1 g / 10 min.

[0010] In some embodiments of the present invention, the terpolymer polypropylene has a melting point of 130-135° C. and a melt flow index of 7.0-8.0 g / 10 min.

[0011] In some embodiments of the present invention, the styrene-ethylene-butylene-styrene block copolymer has a melt flow index of 2.0-5.0 g / 10 min.

[0012] In some embodiments of the present invention, the multilayer film has a thickness of 180-250 μm.

[0013] In some embodiments of the present invention, the thickness ratio of the outer layer, the middle layer, and the inner layer of the multilayer film is 10-15:60-70:15-25.

[0014] In some embodiments of the present invention, the multilayer membrane can be used in peritoneal dialysis bags.

[0015] The present invention also provides a method for preparing a multilayer film, comprising the following steps: placing the outer layer material, the middle layer material and the inner layer material into the corresponding extruder hoppers of a three-layer co-extrusion film blowing machine respectively; after each layer of material is extruded by the extruder screw, the film embryo is blown down through the die head to form a film bubble, which is then water-cooled, shaped, rolled up and slit.

[0016] In some embodiments of the present invention, the outer layer material extruder temperature is 190℃-220℃, the middle layer material extruder temperature is 180℃-210℃, the inner layer material extruder temperature is 170℃-200℃, and the die head temperature is 190℃-220℃.

[0017] In some embodiments of the present invention, the membrane embryo is blown through a die head at a blow-up ratio of 0.8-3.0 to form a membrane bubble, and then water-cooled in purified water at a temperature of 8-20°C.

[0018] In some embodiments of the present invention, after the water-cooled film bubble is integrated and shaped by a herringbone plate, the film material is pulled by a traction roller and enters a winding roller for winding, wherein the traction roller tension is 8-20 kg and the winding speed is 4-15 m / min.

[0019] Compared with the prior art, the present invention has the following effective effects:

[0020] The materials of each film layer of the present invention are all medical-grade materials, are non-PVC materials, do not contain DEHP, and have no potential harm to human health.

[0021] The present invention utilizes the poor compatibility system of polypropylene and polyethylene to toughen, such as Figure 2 The scanning electron micrograph of the film's middle layer shows polyethylene distributed as small spheres within a matrix of polypropylene and elastomer. When impacted, the polyethylene spheres act as stress concentration points, generating silver streaks and shear bands, thereby dissipating energy. Simultaneously, other polyethylene spheres prevent, redirect, and terminate the development of small cracks, providing toughness. Large-format infusion bags (capacity of 2000 mL or larger) made from this multilayer film can withstand impact without breaking or leaking, even after being stored at 0°C.

[0022] The outer layer material of the present invention contains homopolymerized polypropylene, which enhances durability and protects the inner layers.

[0023] The large-scale infusion bag prepared by the present invention can withstand high-temperature sterilization at 121° C. for 12 minutes without deformation or adhesion. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the multilayer film in an embodiment of the present invention.

[0025] Figure 2 This is a scanning electron microscope image of a cross-section of the middle layer structure of the multilayer film in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following is a further detailed description of the above content of the present invention through specific embodiments. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technical solutions implemented based on the above content of the present invention fall within the scope of the present invention.

[0027] The term "melt flow index," also known as melt flow index, melt index, or melt flow rate, is a numerical value that indicates the fluidity of a plastic material during processing. It is defined as the amount of thermoplastic material extruded within a given time under specified conditions. This refers to the mass of melt passing through a standard die capillary per 10 minutes. This value is expressed as MFR, with units of g / 10min.

[0028] The term "melting point" is the temperature at which a solid changes its physical state from solid (melts) to liquid.

[0029] Styrene-ethylene-butylene-styrene block copolymer, referred to as SEBS, is a linear triblock copolymer with polystyrene as the terminal segment and ethylene-butylene copolymer obtained by hydrogenating polybutadiene as the middle elastic block.

[0030] Homopolymer polypropylene is made by polymerizing a single propylene monomer and does not contain ethylene monomer in the molecular chain.

[0031] High melting point low density polyethylene, melting point above 125 ℃, can withstand moist heat sterilization low density polyethylene; low density polyethylene, also known as high pressure polyethylene (LDPE), density of 0.91-0.93g / cm 3 between.

[0032] Polyolefin elastomer, abbreviated as POE, is a thermoplastic elastomer made by the polymerization of ethylene and octene.

[0033] Binary copolymer polypropylene is a copolymer formed by the polymerization of two monomers, propylene and ethylene.

[0034] Terpolymer polypropylene is a copolymer formed by the polymerization of three monomers: propylene, ethylene and butene.

[0035] Example 1

[0036] A multilayer film comprises a three-layer structure consisting of an outer layer, a middle layer and an inner layer, wherein the outer layer material is a mixture of homopolymer polypropylene, high melting point low density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 70:10:20; the middle layer material is a mixture of binary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 20:20:20:40; and the inner layer material is a mixture of ternary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 70:10:10:10.

[0037] Homopolymer polypropylene has a melting point of 164°C and a melt flow index of 3.0 g / 10 min. High-melting-point low-density polyethylene has a melting point of 130°C and a melt flow index of 1.1 g / 10 min. Polyolefin elastomer has a melt flow index of 0.9 g / 10 min. Binary copolymer polypropylene has a melting point of 150°C and a melt flow index of 2.0 g / 10 min. Terpolymer polypropylene has a melting point of 130°C and a melt flow index of 7.0 g / 10 min. Styrene-ethylene-butylene-styrene block copolymer has a melt flow index of 2.2 g / 10 min.

[0038] The total thickness of the multilayer film is 200 μm, and the thickness ratio of the outer layer, the middle layer, and the inner layer is 14:70:16.

[0039] The preparation method of the multilayer film is as follows: the outer layer material, the middle layer material and the inner layer material are respectively placed into the corresponding extruder hoppers of the three-layer co-extrusion film blowing machine. After each layer of material is extruded by the extruder screw, it is blown down through the die head under the condition of a blow-up ratio of 1.6 to form a film bubble, and then water-cooled in purified water at a water temperature of 15°C. After the water-cooled film bubble is integrated and shaped by a herringbone plate, the film material is towed by a traction roller and enters the winding roller for winding, wherein the traction roller tension is 14kg and the winding speed is 9m / min.

[0040] The temperature of the outer layer extruder is 190℃-220℃, the temperature of the middle layer extruder is 180℃-210℃, the temperature of the inner layer extruder is 170℃-200℃, and the die head temperature is 190℃-220℃.

[0041] Example 2

[0042] A multilayer film comprises a three-layer structure consisting of an outer layer, a middle layer and an inner layer, wherein the outer layer material is a mixture of homopolymer polypropylene, high melting point low density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 90:5:5; the middle layer material is a mixture of binary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 40:15:15:30; and the inner layer material is a mixture of ternary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 70:5:5:20.

[0043] Homopolymer polypropylene has a melting point of 164°C and a melt flow index of 3.0 g / 10 min. High-melting-point low-density polyethylene has a melting point of 128°C and a melt flow index of 1.4 g / 10 min. Polyolefin elastomer has a melt flow index of 0.9 g / 10 min. Binary copolymer polypropylene has a melting point of 150°C and a melt flow index of 2.0 g / 10 min. Terpolymer polypropylene has a melting point of 130°C and a melt flow index of 7.0 g / 10 min. Styrene-ethylene-butylene-styrene block copolymer has a melt flow index of 4.5 g / 10 min.

[0044] The total thickness of the multilayer film is 230 μm, and the thickness ratio of the outer layer, middle layer, and inner layer is 14:70:16.

[0045] The preparation method of the multilayer film is as follows: the outer layer material, the middle layer material and the inner layer material are respectively placed in the corresponding extruder hoppers of the three-layer co-extrusion film blowing machine. After each layer of material is extruded by the extruder screw, it is blown down through the die head under the condition of a blow-up ratio of 1.6 to form a film bubble, and then water-cooled in purified water at a water temperature of 15°C. After the water-cooled film bubble is integrated and shaped by a herringbone plate, the film material is pulled by a traction roller and enters the winding roller for winding, wherein the traction roller tension is 13kg and the winding speed is 9m / min.

[0046] The temperature of the outer layer extruder is 190℃-220℃, the temperature of the middle layer extruder is 180℃-210℃, the temperature of the inner layer extruder is 170℃-200℃, and the die head temperature is 190℃-220℃.

[0047] Example 3

[0048] A multilayer film comprises a three-layer structure consisting of an outer layer, a middle layer and an inner layer, wherein the outer layer material is a mixture of homopolymer polypropylene, high melting point low density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 80:5:15; the middle layer material is a mixture of binary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 30:30:20:20; and the inner layer material is a mixture of ternary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 80:5:5:10.

[0049] Homopolymer polypropylene has a melting point of 165°C and a melt flow index of 8.0 g / 10 min. High-melting-point low-density polyethylene has a melting point of 129°C and a melt flow index of 3.8 g / 10 min. Polyolefin elastomer has a melt flow index of 1.1 g / 10 min. Binary copolymer polypropylene has a melting point of 151°C and a melt flow index of 8.0 g / 10 min. Terpolymer polypropylene has a melting point of 130°C and a melt flow index of 8.0 g / 10 min. Styrene-ethylene-butylene-styrene block copolymer has a melt flow index of 4.5 g / 10 min.

[0050] The total thickness of the multilayer film is 230 μm, and the thickness ratio of the outer layer, middle layer, and inner layer is 14:70:16.

[0051] The preparation method of the multilayer film is as follows: the outer layer material, the middle layer material and the inner layer material are respectively placed in the corresponding extruder hoppers of the three-layer co-extrusion film blowing machine. After each layer of material is extruded by the extruder screw, it is blown down through the die head under the condition of a blow-up ratio of 1.6 to form a film bubble, and then water-cooled in purified water at a water temperature of 15°C. After the water-cooled film bubble is integrated and shaped by a herringbone plate, the film material is pulled by a traction roller and enters the winding roller for winding, wherein the traction roller tension is 13kg and the winding speed is 9m / min.

[0052] The temperature of the outer layer extruder is 190℃-220℃, the temperature of the middle layer extruder is 180℃-210℃, the temperature of the inner layer extruder is 170℃-200℃, and the die head temperature is 190℃-220℃.

[0053] Comparative Example 1

[0054] A multilayer film comprises a three-layer structure consisting of an outer layer, a middle layer and an inner layer, wherein the outer layer material is a mixture of homopolymer polypropylene, high-melting-point low-density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 70:10:20; the middle layer material is a mixture of binary copolymer polypropylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 50:10:40; and the inner layer material is a mixture of ternary copolymer polypropylene, high-melting-point low-density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 70:10:10:10.

[0055] Homopolymer polypropylene has a melting point of 164°C and a melt flow index of 3.0 g / 10 min. High-melting-point low-density polyethylene has a melting point of 130°C and a melt flow index of 1.1 g / 10 min. Polyolefin elastomer has a melt flow index of 0.9 g / 10 min. Binary copolymer polypropylene has a melting point of 150°C and a melt flow index of 2.0 g / 10 min. Terpolymer polypropylene has a melting point of 130°C and a melt flow index of 7.0 g / 10 min. Styrene-ethylene-butylene-styrene block copolymer has a melt flow index of 2.2 g / 10 min.

[0056] The total thickness of the multilayer film is 200 μm, and the thickness ratio of the outer layer, the middle layer, and the inner layer is 14:70:16.

[0057] The preparation method of the multilayer film is as follows: the outer layer material, the middle layer material and the inner layer material are respectively placed into the corresponding extruder hoppers of the three-layer co-extrusion film blowing machine. After each layer of material is extruded by the extruder screw, it is blown down through the die head under the condition of a blow-up ratio of 1.6 to form a film bubble, and then water-cooled in purified water at a water temperature of 15°C. After the water-cooled film bubble is integrated and shaped by a herringbone plate, the film material is towed by a traction roller and enters the winding roller for winding, wherein the traction roller tension is 14kg and the winding speed is 9m / min.

[0058] The temperature of the outer layer extruder is 190℃-220℃, the temperature of the middle layer extruder is 180℃-210℃, the temperature of the inner layer extruder is 170℃-200℃, and the die head temperature is 190℃-220℃.

[0059] Comparative Example 2

[0060] A multilayer film comprises a three-layer structure consisting of an outer layer, a middle layer and an inner layer, wherein the outer layer material is a mixture of homopolymer polypropylene, high melting point low density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 70:10:20; the middle layer material is a mixture of binary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 10:50:10:30; and the inner layer material is a mixture of ternary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 70:10:10:10.

[0061] Homopolymer polypropylene has a melting point of 164°C and a melt flow index of 3.0 g / 10 min. High-melting-point low-density polyethylene has a melting point of 130°C and a melt flow index of 1.1 g / 10 min. Polyolefin elastomer has a melt flow index of 0.9 g / 10 min. Binary copolymer polypropylene has a melting point of 150°C and a melt flow index of 2.0 g / 10 min. Terpolymer polypropylene has a melting point of 130°C and a melt flow index of 7.0 g / 10 min. Styrene-ethylene-butylene-styrene block copolymer has a melt flow index of 2.2 g / 10 min.

[0062] The total thickness of the multilayer film is 200 μm, and the thickness ratio of the outer layer, the middle layer, and the inner layer is 14:70:16.

[0063] The preparation method of the multilayer film is as follows: the outer layer material, the middle layer material and the inner layer material are respectively placed into the corresponding extruder hoppers of the three-layer co-extrusion film blowing machine. After each layer of material is extruded by the extruder screw, it is blown down through the die head under the condition of a blow-up ratio of 1.6 to form a film bubble, and then water-cooled in purified water at a water temperature of 15°C. After the water-cooled film bubble is integrated and shaped by a herringbone plate, the film material is towed by a traction roller and enters the winding roller for winding, wherein the traction roller tension is 14kg and the winding speed is 9m / min.

[0064] The temperature of the outer layer extruder is 190℃-220℃, the temperature of the middle layer extruder is 180℃-210℃, the temperature of the inner layer extruder is 170℃-200℃, and the die head temperature is 190℃-220℃.

[0065] Comparative Example 3

[0066] A multilayer film comprises a three-layer structure consisting of an outer layer, a middle layer and an inner layer, wherein the outer layer material is a mixture of homopolymer polypropylene, high melting point low density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 80:5:15; the middle layer material is a mixture of binary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 15:10:35:40; and the inner layer material is a mixture of ternary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 80:5:5:10.

[0067] Homopolymer polypropylene has a melting point of 165°C and a melt flow index of 8.0 g / 10 min. High-melting-point low-density polyethylene has a melting point of 129°C and a melt flow index of 3.8 g / 10 min. Polyolefin elastomer has a melt flow index of 1.1 g / 10 min. Binary copolymer polypropylene has a melting point of 151°C and a melt flow index of 8.0 g / 10 min. Terpolymer polypropylene has a melting point of 130°C and a melt flow index of 8.0 g / 10 min. Styrene-ethylene-butylene-styrene block copolymer has a melt flow index of 4.5 g / 10 min.

[0068] The total thickness of the multilayer film is 200 μm, and the thickness ratio of the outer layer, the middle layer, and the inner layer is 14:70:16.

[0069] The preparation method of the multilayer film is as follows: the outer layer material, the middle layer material and the inner layer material are respectively placed into the corresponding extruder hoppers of the three-layer co-extrusion film blowing machine. After each layer of material is extruded by the extruder screw, it is blown down through the die head under the condition of a blow-up ratio of 1.6 to form a film bubble, and then water-cooled in purified water at a water temperature of 15°C. After the water-cooled film bubble is integrated and shaped by a herringbone plate, the film material is towed by a traction roller and enters the winding roller for winding, wherein the traction roller tension is 14kg and the winding speed is 9m / min.

[0070] The temperature of the outer layer extruder is 190℃-220℃, the temperature of the middle layer extruder is 180℃-210℃, the temperature of the inner layer extruder is 170℃-200℃, and the die head temperature is 190℃-220℃.

[0071] Comparative Example 4

[0072] A multilayer film comprises a three-layer structure consisting of an outer layer, a middle layer and an inner layer, wherein the outer layer material is a mixture of homopolymer polypropylene, low-density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 80:5:15; the middle layer material is a mixture of binary copolymer polypropylene, low-density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 30:30:20:20; and the inner layer material is a mixture of ternary copolymer polypropylene, low-density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 80:5:5:10.

[0073] Homopolymer polypropylene has a melting point of 165°C and a melt flow index of 8.0 g / 10 min. Low-density polyethylene has a melting point of 104°C and a melt flow index of 2.0 g / 10 min. Polyolefin elastomer has a melt flow index of 1.1 g / 10 min. Binary copolymer polypropylene has a melting point of 151°C and a melt flow index of 8.0 g / 10 min. Terpolymer polypropylene has a melting point of 130°C and a melt flow index of 8.0 g / 10 min. Styrene-ethylene-butylene-styrene block copolymer has a melt flow index of 4.5 g / 10 min.

[0074] The total thickness of the multilayer film is 200 μm, and the thickness ratio of the outer layer, the middle layer, and the inner layer is 14:70:16.

[0075] The preparation method of the multilayer film is as follows: the outer layer material, the middle layer material and the inner layer material are respectively placed into the corresponding extruder hoppers of the three-layer co-extrusion film blowing machine. After each layer of material is extruded by the extruder screw, it is blown down through the die head under the condition of a blow-up ratio of 1.6 to form a film bubble, and then water-cooled in purified water at a water temperature of 15°C. After the water-cooled film bubble is integrated and shaped by a herringbone plate, the film material is towed by a traction roller and enters the winding roller for winding, wherein the traction roller tension is 14kg and the winding speed is 9m / min.

[0076] The temperature of the outer layer extruder is 190℃-220℃, the temperature of the middle layer extruder is 180℃-210℃, the temperature of the inner layer extruder is 170℃-200℃, and the die head temperature is 190℃-220℃.

[0077] Test example

[0078] The test methods and standards for the appearance, light transmittance, water vapor transmission rate, oxygen transmission rate, nitrogen transmission rate and tensile strength of the film material are: YBB00102005-2015 Three-layer co-extruded infusion film (I), bag.

[0079] The test method for the drop impact resistance of the film material is as follows:

[0080] 1) The membrane material is welded at 135° C. to form a bag with a size of 320 mm×300 mm.

[0081] 2) Pour 2000mL or 3000mL of normal saline into the bag and place it at 0℃ or 23℃ for 24 hours.

[0082] 3) After the bags have been placed under the above conditions for 24 hours, they are immediately dropped freely from a height of 1 m onto a smooth surface at 23°C. The number of drops during which the bags break and leak is counted.

[0083] The test method for the membrane material's resistance to high-temperature sterilization is as follows: the membrane material is welded around its perimeter at 135°C to prepare a bag with a specification of 320mm×300mm. The bag is sterilized at 121°C for 12 minutes to observe whether it is deformed or adhered.

[0084] The performance tests of Examples 1-3 and Comparative Examples 1-3 are shown in the table below:

[0085]

[0086] Two commercially available non-PVC peritoneal dialysis infusion bag products were subjected to the above performance test, and the test results are as follows:

[0087]

[0088] The infusion bags available on the market have poor anti-drop performance and insufficient toughness of the film material, which makes the bag prone to damage and leakage during transportation and use.

[0089] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The embodiments described above only express several implementation methods of the present invention, which are convenient for understanding the technical solutions of the present invention in a specific and detailed manner, but they cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, several variations and improvements can be made, which all fall within the scope of protection of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided by the present invention are all within the scope of protection of the claims attached to the present invention. Therefore, the scope of protection of the patent of the present invention shall be based on the content of the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A multilayer film comprising a three-layer structure consisting of an outer layer, a middle layer and an inner layer, characterized in that: The outer layer material is a mixture of homopolymer polypropylene, high melting point low density polyethylene and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 60-90:5-10:5-20; the middle layer material is a mixture of binary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 10-40:10-40:15-25:20-40; the inner layer material is a mixture of ternary copolymer polypropylene, high melting point low density polyethylene, polyolefin elastomer and styrene-ethylene-butylene-styrene block copolymer in a mass ratio of 60-90:5-10:5-10:5-20; the high melting point low density polyethylene has a melting point of 128-131°C and a melt flow index of 1.0-3.8g / 10min; the thickness ratio of the outer layer, middle layer and inner layer of the multilayer film is 10-15:60-70:15-25.

2. The multilayer film according to claim 1, wherein The homopolypropylene has a melting point of 160-165° C. and a melt flow index of 2.0-8.0 g / 10 min.

3. The multilayer film according to any one of claims 1 to 2, characterized in that The binary copolymer polypropylene has a melting point of 150-155° C. and a melt flow index of 2.0-8.0 g / 10 min.

4. The multilayer film according to any one of claims 1 to 2, characterized in that The polyolefin elastomer has a melt flow index of 0.9-1.1 g / 10 min.

5. The multilayer film according to claim 3, wherein The polyolefin elastomer has a melt flow index of 0.9-1.1 g / 10 min.

6. The multilayer film according to any one of claims 1 to 2 or 5, characterized in that The terpolymer polypropylene has a melting point of 130-135°C and a melt flow index of 7.0-8.0 g / 10 min; The melt flow index of the styrene-ethylene-butylene-styrene block copolymer is 2.0-5.0 g / 10 min.

7. The multilayer film according to claim 3, wherein The terpolymer polypropylene has a melting point of 130-135°C and a melt flow index of 7.0-8.0 g / 10 min; The melt flow index of the styrene-ethylene-butylene-styrene block copolymer is 2.0-5.0 g / 10 min.

8. The multilayer film according to claim 4, wherein The terpolymer polypropylene has a melting point of 130-135°C and a melt flow index of 7.0-8.0 g / 10 min; The melt flow index of the styrene-ethylene-butylene-styrene block copolymer is 2.0-5.0 g / 10 min.

9. The multilayer film according to any one of claims 1 to 2, 5 or 7 to 8, characterized in that The thickness of the multilayer film is 180-250 μm.

10. The multilayer film according to claim 3, wherein The thickness of the multilayer film is 180-250 μm.

11. The multilayer film according to claim 4, wherein The thickness of the multilayer film is 180-250 μm.

12. The multilayer film according to claim 6, wherein The thickness of the multilayer film is 180-250 μm.

13. The multilayer film according to any one of claims 1 to 2, 5, 7 to 8 or 10 to 12, characterized in that The multilayer membrane is used for peritoneal dialysis bags.

14. The multilayer film according to claim 3, wherein The multilayer membrane is used for peritoneal dialysis bags.

15. The multilayer film according to claim 4, characterized in that The multilayer membrane is used for peritoneal dialysis bags.

16. The multilayer film according to claim 6, wherein The multilayer membrane is used for peritoneal dialysis bags.

17. The multilayer film according to claim 9, wherein The multilayer membrane is used for peritoneal dialysis bags.

18. The method for preparing a multilayer film according to any one of claims 1 to 17, characterized in that: The method comprises the following steps: placing the outer layer material, the middle layer material and the inner layer material into the corresponding extruder hoppers of the three-layer co-extrusion film blowing machine respectively; after each layer of material is extruded by the extruder screw, the film embryo is blown down through the die head to form a film bubble; and then the film is water-cooled, shaped, wound and slit.

19. The preparation method according to claim 18, characterized in that: The extruder temperature of the outer layer material is 190℃-220℃, the extruder temperature of the middle layer material is 180℃-210℃, the extruder temperature of the inner layer material is 170℃-200℃, and the die head temperature is 190℃-220℃; The membrane embryo is blown down through the die head at a blow-up ratio of 1.6-3.0 to form a membrane bubble, and then water-cooled in purified water at a temperature of 8-20°C; After water cooling, the film bubble is integrated and shaped by the herringbone plate, and then the film material is pulled by the traction roller and enters the winding roller for winding. The tension of the traction roller is 8-20kg and the winding speed is 4-15m / min.

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