Polyolefin multilayer film and preparation method and application thereof

Abstract

The invention belongs to the technical field of medical packaging, and discloses a polyolefin multilayer film as well as a preparation method and application thereof. The polyolefin multilayer film is composed of a film outer surface layer, a film middle layer and a film inner surface layer, the film outer surface layer contains a blend of first polypropylene and a first polybutylene copolymer, and the film middle layer contains a blend of second polypropylene and a second polybutylene copolymer; the film inner surface layer contains a blend of third polypropylene and a third polybutylene copolymer, and the first polypropylene, the second polypropylene and the third polypropylene are respectively and independently selected from a polypropylene homopolymer and a copolymer of propylene and ethylene or butylene; the first polybutylene copolymer, the second polybutylene copolymer and the third polybutylene copolymer are independently selected from copolymers of butylene and ethylene or propylene respectively. The polyolefin multilayer film has the advantages of high light transmittance, low haze, high toughness and proper rigidity, and is suitable for the field of medical packaging.

Description

Technical Field

[0001] This invention belongs to the field of medical packaging technology, specifically relating to a polyolefin multilayer film and its preparation method, as well as the application of the polyolefin multilayer film in the field of medical packaging. Background Technology

[0002] Flexible packaging is widely used in the medical field, such as infusion bags. Choosing the right packaging material is crucial to ensuring product quality. Currently, PVC materials are being phased out, and developed countries in Europe and America have largely adopted fully enclosed non-PVC flexible packaging. Raw materials for non-PVC packaging bags include polypropylene, polystyrene-poly(ethylene-butene)-polystyrene block copolymer (SEBS) modified polypropylene, and polyolefin elastomer (POE) modified polypropylene, among others.

[0003] Patent document CN117255746A discloses a multilayer film for medical packaging. The multilayer film has a three-layer structure. The first polymer layer contains polypropylene homopolymer modified with an impact modifier. The second polymer layer includes a polypropylene terpolymer, a styrene block copolymer elastomer, and a propylene-ethylene copolymer. The central polymer layer includes a styrene block copolymer elastomer, a polyethylene elastomer, and a propylene-ethylene copolymer.

[0004] Patent document CN116674272A discloses a three-layer co-extruded infusion membrane, which includes an inner layer, an outer layer, and a middle layer. The outer layer material is a mixture of homopolymer polypropylene, a low-ethylene-content ethylene-propylene polymer, and SEBS or SEPS; the middle layer material is a mixture of a high-ethylene-content ethylene-propylene polymer, a low-ethylene-content polymer, and SEBS or SEPS; and the inner layer material is a mixture of an ethylene-propylene-butene polymer, a high-ethylene-content ethylene-propylene polymer, a low-ethylene-content polymer, and SEBS or SEPS.

[0005] Patent document CN104497415A discloses a thermoplastic elastomer for infusion bags and its preparation method. Its composition includes polypropylene, propylene elastomer, and ethylene-vinyl acetate (EVA).

[0006] Patent document CN102397160A discloses a polypropylene infusion soft bag, wherein the material of the infusion soft bag is a copolymer of ethylene and propylene, or a copolymer of ethylene, propylene, and butene, or a copolymer of ethylene, propylene, and styrene and a mixture of polypropylene.

[0007] There is still room for improvement in the aforementioned films. For example, polypropylene has poor toughness and is not resistant to low temperatures and impacts; its composition is relatively complex, including various copolymers, benzene rings, and oxygen-containing groups; elastomers such as SEBS and POE have limited compatibility with polypropylene, which leads to whitening, increased haze, and reduced packaging transparency after sterilization when polypropylene materials modified with these materials are used to make infusion bags, thus affecting their use. Summary of the Invention

[0008] To address the aforementioned problems in the existing technology, the purpose of this invention is to provide a polyolefin multilayer film, its preparation method, and its applications. The polyolefin multilayer film of this invention possesses high light transmittance, low haze, and also exhibits high toughness and appropriate rigidity, making it suitable for use in medical packaging applications such as infusion bags.

[0009] A first aspect of the present invention provides a polyolefin multilayer film, which comprises an outer surface layer, an intermediate layer, and an inner surface layer, wherein:

[0010] The outer surface layer of the film contains a blend of a first polypropylene and a first polybutene copolymer, wherein the weight percentage of the first polybutene copolymer in the blend is 20-40%.

[0011] The film interlayer contains a blend of a second polypropylene and a second polybutene copolymer, wherein the weight percentage of the second polybutene copolymer in the blend is 50-90%.

[0012] The inner surface layer of the film contains a blend of a third polypropylene and a third polybutene copolymer, wherein the weight percentage of the third polybutene copolymer in the blend is 20-40%.

[0013] The first polypropylene, the second polypropylene, and the third polypropylene are each independently selected from polypropylene homopolymers or polypropylene copolymers. The polypropylene copolymer is a copolymer of propylene and ethylene or butene, wherein the molar percentage of propylene comonomer is not less than 94%, and the melt flow index of the polypropylene homopolymer or polypropylene copolymer at 230°C and 2.16 kg load is 0.5-8 g / 10 min. The first polybutene copolymer, the second polybutene copolymer, and the third polybutene copolymer are each independently selected from copolymers of butene and ethylene or propylene, wherein the molar percentage of butene comonomer is 95-99%, and the melt flow index of the butene and ethylene or propylene copolymer at 230°C and 2.16 kg load is 1-10 g / 10 min.

[0014] A second aspect of the present invention provides a method for preparing the above-described polyolefin multilayer film, the method comprising:

[0015] 1) The raw materials for each layer of the polyolefin multilayer film are premixed separately, then mixed separately and extruded and granulated to obtain the materials for each layer;

[0016] 2) The materials for each layer are extruded through the screw of the multi-layer co-extrusion casting machine, cooled by cold rollers, and then wound up to obtain a polyolefin multilayer film.

[0017] A third aspect of the present invention provides the application of the above-described polyolefin multilayer film in the field of medical packaging.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) The multilayer membrane material of the present invention is polyolefin, which has high compatibility between components, thus having unique advantages in terms of transparency and mechanical strength; moreover, polyolefin itself has high water resistance and reagent inertness, and the inner layer of the multilayer membrane is mainly PP (PP is often used in infusion bags) with low drug absorption rate.

[0020] 2) The multilayer film of the present invention can be sterilized by hot steam at 121°C. It does not contain adhesives and plasticizers and has the characteristics of high light transmittance, low haze, high barrier properties, reagent inertness, low drug absorption rate, good flexibility and high mechanical strength. The packaging bags made from it are not easy to break and leak, and are suitable for use in medical packaging fields such as infusion bags.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0022] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0023] According to a first aspect of the present invention, a polyolefin multilayer film is provided, the polyolefin multilayer film comprising an outer surface layer, an intermediate layer, and an inner surface layer, wherein:

[0024] The outer surface layer of the film contains a blend of a first polypropylene and a first polybutene copolymer, wherein the weight percentage of the first polybutene copolymer in the blend is 20-40%.

[0025] The film interlayer contains a blend of a second polypropylene and a second polybutene copolymer, wherein the weight percentage of the second polybutene copolymer in the blend is 50-90%.

[0026] The inner surface layer of the film contains a blend of a third polypropylene and a third polybutene copolymer, wherein the weight percentage of the third polybutene copolymer in the blend is 20-40%.

[0027] The first polypropylene, the second polypropylene, and the third polypropylene are each independently selected from polypropylene homopolymers or polypropylene copolymers. The polypropylene copolymer is a copolymer of propylene and ethylene or butene, wherein the molar percentage of propylene comonomer is not less than 94%, and the melt flow index of the polypropylene homopolymer or polypropylene copolymer at 230°C and 2.16 kg load is 0.5-8 g / 10 min. The first polybutene copolymer, the second polybutene copolymer, and the third polybutene copolymer are each independently selected from copolymers of butene and ethylene or propylene, wherein the molar percentage of butene comonomer is 95-99%, and the melt flow index of the butene and ethylene or propylene copolymer at 230°C and 2.16 kg load is 1-10 g / 10 min.

[0028] Preferably, when the first polypropylene is a polypropylene copolymer, the molar percentage of propylene comonomer therein is not less than 97%; when the second polypropylene is a polypropylene copolymer, the molar percentage of propylene comonomer therein is not less than 94%; and when the third polypropylene is a polypropylene copolymer, the molar percentage of propylene comonomer therein is not less than 97%.

[0029] Preferably, the butene comonomer molar content percentage in the first polybutene copolymer is 98-99%; the butene comonomer molar content percentage in the second polybutene copolymer is 95-98%; and the butene comonomer molar content percentage in the third polybutene copolymer is 98-99%.

[0030] In a preferred embodiment, the weight percentage of the first polybutene copolymer in the outer surface layer of the film is 25-35%; the weight percentage of the second polybutene copolymer in the middle layer of the film is 55-80%; and the weight percentage of the third polybutene copolymer in the inner surface layer of the film is 25-35%.

[0031] Preferably, the melt flow index of the first polypropylene at 230°C and 2.16 kg load is 3-8 g / 10 min; the melt flow index of the second polypropylene at 230°C and 2.16 kg load is 2-5 g / 10 min; and the melt flow index of the third polypropylene at 230°C and 2.16 kg load is 0.5-3 g / 10 min.

[0032] Preferably, the melt flow index of the first polybutene copolymer at 230°C and 2.16 kg load is 1-6 g / 10 min; the melt flow index of the second polybutene copolymer at 230°C and 2.16 kg load is 3-8 g / 10 min; and the melt flow index of the third polybutene copolymer at 230°C and 2.16 kg load is 5-10 g / 10 min.

[0033] In this invention, the polyolefin multilayer film contains additives, including antioxidants. The antioxidants can be conventionally selected according to existing technology, and their dosage is based on the weight of the raw materials of each layer of the blend. Preferably, the amount of antioxidant is 0.1-0.5 wt% of the blend of each layer of the film. In addition, other additives, such as UV stabilizers and slip agents, can be added to the polyolefin multilayer film as needed, with the specific substances and dosages following conventional practices in the art.

[0034] The total thickness of the polyolefin multilayer film of the present invention can be 150-600 μm, wherein the thickness of the outer surface layer of the film accounts for 15-30% of the total thickness, the thickness of the middle layer of the film accounts for 50-75% of the total thickness, and the thickness of the inner surface layer of the film accounts for 10-25% of the total thickness.

[0035] The polyolefins used in this invention can be purchased commercially or synthesized using existing methods, as long as the required parameters can be achieved.

[0036] According to a second aspect of the present invention, the present invention provides a method for preparing the above-described polyolefin multilayer film, the method comprising:

[0037] 1) The raw materials for each layer of the polyolefin multilayer film are premixed separately, then mixed separately and extruded and granulated to obtain the materials for each layer;

[0038] 2) The materials for each layer are extruded through the screw of the multi-layer co-extrusion casting machine, cooled by cold rollers, and then wound up to obtain a polyolefin multilayer film.

[0039] In step 1), the raw materials for each layer of the film are first premixed using a high-speed mixer, and then co-extruded and granulated using a twin-screw extruder to obtain the materials for each layer.

[0040] In step 2), when using a multi-layer co-extrusion casting unit, the material for each layer is placed into the corresponding extruder hopper, extruded by the screw, cooled by cold rollers, and then wound up. The thickness of each layer and the total thickness are controlled by adjusting the corresponding screw speed and temperature.

[0041] Preferably, the extruder temperature for the outer surface layer of the film is 190-230°C, the extruder temperature for the middle layer of the film is 180-210°C, and the extruder temperature for the inner surface layer of the film is 190-230°C.

[0042] Preferably, the temperature of the cold roller is set to 20-30℃ and the winding speed is 2-12m / min.

[0043] According to a third aspect of the present invention, the present invention provides the application of the above-described polyolefin multilayer film in the field of medical packaging.

[0044] The substances and process parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0045] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0046] In the following embodiments and comparative examples, the data were obtained using the following methods:

[0047] 1. Melt Flow Index (MFR): Determined according to ISO 1133 at 230°C and 2.16 kg load.

[0048] 2. Determination of copolymer composition: Nuclear magnetic resonance (NMR) was used with a Bruker AVANCE III 400MHz NMR spectrometer and a 10mm probe. The solvent was deuterated o-dichlorobenzene. Approximately 200 mg of sample per 2.5 mL of solvent was used. The sample tube was heated in an oil bath at 130-140°C until the sample dissolved to form a homogeneous solution. The testing conditions were: probe temperature 125°C, 90° pulse, sampling time AQ of 5 seconds, and delay time D1 of 10 seconds.

[0049] 3. The transmittance and haze of the film shall be determined in accordance with GB / T 2410.

[0050] Example 1

[0051] A polyolefin multilayer film, comprising an outer surface layer, an intermediate layer, and an inner surface layer, wherein:

[0052] The outer surface layer of the film is composed of a blend of a first polypropylene and a first polybutene copolymer, wherein the first polybutene copolymer accounts for 30% by weight; the first polypropylene is a polypropylene homopolymer with an MFR of 3.0 g / 10 min at 230 °C and 2.16 kg load; the first polybutene copolymer is a copolymer of butene and ethylene with an MFR of 6.0 g / 10 min at 230 °C and 2.16 kg load, and its butene unit molar content is determined to be 98% by NMR.

[0053] The film interlayer is composed of a blend of a second polypropylene and a second polybutene copolymer, wherein the second polybutene copolymer comprises 80% by weight; the second polypropylene is a polypropylene homopolymer with an MFR of 5.0 g / 10 min at 230°C and a load of 2.16 kg; the second polybutene copolymer is a copolymer of butene and ethylene with an MFR of 3.0 g / 10 min at 230°C and a load of 2.16 kg, and its butene unit molar content is determined to be 98% by NMR.

[0054] The inner surface layer of the film is composed of a blend of a third polypropylene and a third polybutene copolymer, wherein the third polybutene copolymer accounts for 30% by weight; the third polypropylene is a polypropylene homopolymer with an MFR of 3.0 g / 10 min at 230 °C and 2.16 kg load; the third polybutene copolymer is a copolymer of butene and ethylene with an MFR of 5.0 g / 10 min at 230 °C and 2.16 kg load, and its butene unit molar content is determined to be 99% by NMR.

[0055] The above-mentioned method for preparing polyolefin multilayer films includes:

[0056] 1) Add 0.2wt% of antioxidant 168+1010 compounded in a mass ratio of 1:1 to the blend of each layer of the polyolefin multilayer film. First, premix with a high-speed mixer, and then use a twin-screw extruder to blend, extrude and granulate to obtain the materials for each layer.

[0057] 2) The materials for each layer are placed into the corresponding extruder hopper of the multilayer co-extrusion casting unit, extruded by the screw, cooled by the cold roller, and then wound up to obtain a polyolefin multilayer film.

[0058] The extruder temperature for the outer surface layer of the film is 190-230℃, the extruder temperature for the middle layer of the film is 180-210℃, and the extruder temperature for the inner surface layer of the film is 190-230℃.

[0059] The temperature of the cold roller is set to 25℃, and the winding speed is 6m / min.

[0060] The total thickness of the polyolefin multilayer film is 300 μm, of which the thickness of the outer surface layer accounts for 25% of the total thickness, the thickness of the middle layer accounts for 50% of the total thickness, and the thickness of the inner surface layer accounts for 25% of the total thickness.

[0061] Example 2

[0062] A polyolefin multilayer film, comprising an outer surface layer, an intermediate layer, and an inner surface layer, wherein:

[0063] The outer surface layer of the film is composed of a blend of a first polypropylene and a first polybutene copolymer, wherein the first polybutene copolymer accounts for 35% by weight; the first polypropylene is a polypropylene homopolymer with an MFR of 5.0 g / 10 min at 230°C and 2.16 kg load; the first polybutene copolymer is a copolymer of butene and ethylene with an MFR of 3.0 g / 10 min at 230°C and 2.16 kg load, and its butene unit molar content is determined to be 99% by NMR.

[0064] The film interlayer is composed of a blend of a second polypropylene and a second polybutene copolymer, wherein the second polybutene copolymer comprises 60% by weight; the second polypropylene is a polypropylene homopolymer with an MFR of 2.0 g / 10 min at 230 °C and 2.16 kg load; the second polybutene copolymer is a copolymer of butene and ethylene with an MFR of 8.0 g / 10 min at 230 °C and 2.16 kg load, and its butene unit molar content is determined to be 96% by NMR.

[0065] The inner surface layer of the film is composed of a blend of a third polypropylene and a third polybutene copolymer, wherein the third polybutene copolymer accounts for 25% by weight; the third polypropylene is a polypropylene homopolymer with an MFR of 1.0 g / 10 min at 230 °C and 2.16 kg load; the third polybutene copolymer is a copolymer of butene and ethylene with an MFR of 8.0 g / 10 min at 230 °C and 2.16 kg load, and its butene unit molar content is determined to be 98% by NMR.

[0066] The above-mentioned method for preparing polyolefin multilayer films includes:

[0067] 1) Add 0.1wt% of antioxidant 168+1010 compounded in a mass ratio of 1:1 to the blend of each layer of the polyolefin multilayer film. First, premix with a high-speed mixer, and then use a twin-screw extruder to blend, extrude and granulate to obtain the materials for each layer.

[0068] 2) The materials for each layer are placed into the corresponding extruder hopper of the multilayer co-extrusion casting unit, extruded by the screw, cooled by the cold roller, and then wound up to obtain a polyolefin multilayer film.

[0069] The extruder temperature for the outer surface layer of the film is 190-230℃, the extruder temperature for the middle layer of the film is 180-210℃, and the extruder temperature for the inner surface layer of the film is 190-230℃.

[0070] The temperature of the cold roller is set to 25℃, and the winding speed is 8m / min.

[0071] The total thickness of the polyolefin multilayer film is 250 μm, of which the thickness of the outer surface layer accounts for 20% of the total thickness, the thickness of the middle layer accounts for 70% of the total thickness, and the thickness of the inner surface layer accounts for 10% of the total thickness.

[0072] Example 3

[0073] A polyolefin multilayer film, comprising an outer surface layer, an intermediate layer, and an inner surface layer, wherein:

[0074] The outer surface layer of the film is composed of a blend of a first polypropylene and a first polybutene copolymer, wherein the first polybutene copolymer accounts for 25% by weight; the first polypropylene is a polypropylene homopolymer with an MFR of 8.0 g / 10 min at 230 °C and 2.16 kg load; the first polybutene copolymer is a copolymer of butene and ethylene with an MFR of 1.0 g / 10 min at 230 °C and 2.16 kg load, and its butene unit molar content is determined to be 98% by NMR.

[0075] The film interlayer is composed of a blend of a second polypropylene and a second polybutene copolymer, wherein the second polybutene copolymer comprises 55% by weight; the second polypropylene is a polypropylene homopolymer with an MFR of 3.0 g / 10 min at 230 °C and a load of 2.16 kg; the second polybutene copolymer is a copolymer of butene and ethylene with an MFR of 6.0 g / 10 min at 230 °C and a load of 2.16 kg, and its butene unit molar content is determined to be 95% by NMR.

[0076] The inner surface layer of the film is composed of a blend of a third polypropylene and a third polybutene copolymer, wherein the third polybutene copolymer accounts for 35% by weight; the third polypropylene is a polypropylene homopolymer with an MFR of 0.5 g / 10 min at 230 °C and 2.16 kg load; the third polybutene copolymer is a copolymer of butene and ethylene with an MFR of 10.0 g / 10 min at 230 °C and 2.16 kg load, and its butene unit molar content is determined to be 99% by NMR.

[0077] The above-mentioned method for preparing polyolefin multilayer films includes:

[0078] 1) Add 0.5wt% of antioxidant 168+1010 compounded in a mass ratio of 1:1 to the blend of each layer of the polyolefin multilayer film. First, premix with a high-speed mixer, and then use a twin-screw extruder to blend, extrude and granulate to obtain the materials for each layer.

[0079] 2) The materials for each layer are placed into the corresponding extruder hopper of the multilayer co-extrusion casting unit, extruded by the screw, cooled by the cold roller, and then wound up to obtain a polyolefin multilayer film.

[0080] The extruder temperature for the outer surface layer of the film is 190-230℃, the extruder temperature for the middle layer of the film is 180-210℃, and the extruder temperature for the inner surface layer of the film is 190-230℃.

[0081] The temperature of the cold roller is set to 25℃, and the winding speed is 8m / min.

[0082] The total thickness of the polyolefin multilayer film is 250 μm, of which the thickness of the outer surface layer accounts for 20% of the total thickness, the thickness of the middle layer accounts for 70% of the total thickness, and the thickness of the inner surface layer accounts for 10% of the total thickness.

[0083] Example 4

[0084] Same as Example 1, except that:

[0085] The outer surface layer of the film: the first polybutene copolymer has a weight percentage of 20%;

[0086] Intermediate layer of film: 90% by weight of the second polybutene copolymer;

[0087] Inner surface layer of the film: 20% by weight of the third polybutene copolymer; the molar content of butene units in the third polybutene copolymer is 99%.

[0088] The winding speed in the preparation of polyolefin multilayer films is 3 m / min.

[0089] The total thickness of the polyolefin multilayer film is 600 μm, of which the thickness of the outer surface layer accounts for 30% of the total thickness, the thickness of the middle layer accounts for 50% of the total thickness, and the thickness of the inner surface layer accounts for 20% of the total thickness.

[0090] Example 5

[0091] Same as Example 1, except that:

[0092] The outer surface layer of the film: the first polybutene copolymer accounts for 40% by weight;

[0093] Intermediate layer of film: 50% by weight of the second polybutene copolymer; the molar content of butene units in the second polybutene copolymer is 96%;

[0094] Inner surface layer of the film: 40% by weight of the third polybutene copolymer.

[0095] The winding speed in the preparation of polyolefin multilayer films is 10 m / min.

[0096] The total thickness of the polyolefin multilayer film is 150 μm, of which the thickness of the outer surface layer accounts for 15% of the total thickness, the thickness of the middle layer accounts for 75% of the total thickness, and the thickness of the inner surface layer accounts for 10% of the total thickness.

[0097] Example 6

[0098] A polyolefin multilayer film, comprising an outer surface layer, an intermediate layer, and an inner surface layer, wherein:

[0099] The outer surface layer of the film is composed of a blend of a first polypropylene and a first polybutene copolymer, wherein the first polybutene copolymer accounts for 25% by weight; the first polypropylene is a copolymer of propylene and ethylene, with an MFR of 3.0 g / 10 min at 230°C and a load of 2.16 kg, and its propylene molar content is 98% as determined by NMR; the first polybutene copolymer is a copolymer of butene and ethylene, with an MFR of 6.0 g / 10 min at 230°C and a load of 2.16 kg, and its butene molar content is 98% as determined by NMR.

[0100] The film interlayer is composed of a blend of a second polypropylene and a second polybutene copolymer, wherein the second polybutene copolymer comprises 60% by weight; the second polypropylene is a copolymer of propylene and ethylene, with an MFR of 5.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination showing a propylene molar content of 96%; the second polybutene copolymer is a copolymer of butene and ethylene, with an MFR of 3.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination showing a butene molar content of 95%.

[0101] The inner surface layer of the film is composed of a blend of a third polypropylene and a third polybutene copolymer, wherein the third polybutene copolymer accounts for 20% by weight; the third polypropylene is a copolymer of propylene and ethylene, with an MFR of 3.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination of propylene molar content of 97%; the third polybutene copolymer is a copolymer of butene and ethylene, with an MFR of 5.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination of butene molar content of 99%.

[0102] The above-mentioned method for preparing polyolefin multilayer films includes:

[0103] 1) Add 0.2wt% of antioxidant 168+1010 compounded in a mass ratio of 1:1 to the blend of each layer of the polyolefin multilayer film. First, premix with a high-speed mixer, and then use a twin-screw extruder to blend, extrude and granulate to obtain the materials for each layer.

[0104] 2) The materials for each layer are placed into the corresponding extruder hopper of the multilayer co-extrusion casting unit, extruded by the screw, cooled by the cold roller, and then wound up to obtain a polyolefin multilayer film.

[0105] The extruder temperature for the outer surface layer of the film is 190-230℃, the extruder temperature for the middle layer of the film is 180-210℃, and the extruder temperature for the inner surface layer of the film is 190-230℃.

[0106] The temperature of the cold roller is set to 25℃, and the winding speed is 6m / min.

[0107] The total thickness of the polyolefin multilayer film is 400 μm, of which the thickness of the outer surface layer accounts for 25% of the total thickness, the thickness of the middle layer accounts for 50% of the total thickness, and the thickness of the inner surface layer accounts for 25% of the total thickness.

[0108] Example 7

[0109] A polyolefin multilayer film, comprising an outer surface layer, an intermediate layer, and an inner surface layer, wherein:

[0110] The outer surface layer of the film is composed of a blend of a first polypropylene and a first polybutene copolymer, wherein the first polybutene copolymer accounts for 20% by weight; the first polypropylene is a copolymer of propylene and ethylene, with an MFR of 5.0 g / 10 min at 230°C and a load of 2.16 kg, and its propylene molar content is 99% as determined by NMR; the first polybutene copolymer is a copolymer of butene and ethylene, with an MFR of 3.0 g / 10 min at 230°C and a load of 2.16 kg, and its butene molar content is 99% as determined by NMR.

[0111] The intermediate layer of the film is composed of a blend of a second polypropylene and a second polybutene copolymer, wherein the second polybutene copolymer accounts for 55% by weight; the second polypropylene is a copolymer of propylene and ethylene, with an MFR of 2.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination showing a propylene molar content of 94%; the second polybutene copolymer is a copolymer of butene and ethylene, with an MFR of 8.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination showing a butene molar content of 98%.

[0112] The inner surface layer of the film is composed of a blend of a third polypropylene and a third polybutene copolymer, wherein the third polybutene copolymer accounts for 20% by weight; the third polypropylene is a copolymer of propylene and ethylene, with an MFR of 1.0 g / 10 min at 230 °C and a load of 2.16 kg, and an NMR determination of 97% propylene unit molar content; the third polybutene copolymer is a copolymer of butene and ethylene, with an MFR of 8.0 g / 10 min at 230 °C and a load of 2.16 kg, and an NMR determination of 99% butene unit molar content.

[0113] The above-mentioned method for preparing polyolefin multilayer films includes:

[0114] 1) Add 0.2wt% of antioxidant 168+1010 compounded in a mass ratio of 1:1 to the blend of each layer of the polyolefin multilayer film. First, premix with a high-speed mixer, and then use a twin-screw extruder to blend, extrude and granulate to obtain the materials for each layer.

[0115] 2) The materials for each layer are placed into the corresponding extruder hopper of the multilayer co-extrusion casting unit, extruded by the screw, cooled by the cold roller, and then wound up to obtain a polyolefin multilayer film.

[0116] The extruder temperature for the outer surface layer of the film is 190-230℃, the extruder temperature for the middle layer of the film is 180-210℃, and the extruder temperature for the inner surface layer of the film is 190-230℃.

[0117] The temperature of the cold roller is set to 25℃, and the winding speed is 6m / min.

[0118] The total thickness of the polyolefin multilayer film is 300 μm, of which the thickness of the outer surface layer accounts for 25% of the total thickness, the thickness of the middle layer accounts for 50% of the total thickness, and the thickness of the inner surface layer accounts for 25% of the total thickness.

[0119] Example 8

[0120] Same as Example 7, except that:

[0121] Outer surface layer of the film: The molar content of propylene units in the first polypropylene is 97%;

[0122] Intermediate layer of film: 50% by weight of the second polybutene copolymer;

[0123] Inner surface layer of film: The molar content of propylene units in the third polypropylene is 99%; the molar content of butene units in the third polybutene copolymer is 98%.

[0124] The total thickness of the polyolefin multilayer film is 250 μm.

[0125] Example 9

[0126] Same as Example 7, except that:

[0127] The outer surface layer of the film: the MFR of the first polypropylene at 230℃ and 2.16kg load is 8.0g / 10min; the MFR of the first polybutene copolymer at 230℃ and 2.16kg load is 1.0g / 10min.

[0128] Intermediate layer of film: The second polybutene copolymer has a weight percentage of 50%; the second polypropylene has a propylene unit molar content of 99% and an MFR of 3.0 g / 10 min at 230 °C and 2.16 kg load; the second polybutene copolymer has an MFR of 6.0 g / 10 min at 230 °C and 2.16 kg load.

[0129] Inner surface layer of film: The third polypropylene has a propylene unit molar content of 99% and an MFR of 0.5 g / 10 min at 230 °C and 2.16 kg load; the third polybutene copolymer has a butene unit molar content of 98% and an MFR of 10.0 g / 10 min at 230 °C and 2.16 kg load.

[0130] The outer surface layer of the film accounts for 25% of the total thickness, the middle layer accounts for 60% of the total thickness, and the inner surface layer accounts for 15% of the total thickness.

[0131] Example 10

[0132] A polyolefin multilayer film, comprising an outer surface layer, an intermediate layer, and an inner surface layer, wherein:

[0133] The outer surface layer of the film is composed of a blend of a first polypropylene and a first polybutene copolymer, wherein the first polybutene copolymer accounts for 30% by weight; the first polypropylene is a copolymer of propylene and butene, with an MFR of 3.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination showing a propylene molar content of 99%; the first polybutene copolymer is a copolymer of butene and propylene, with an MFR of 6.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination showing a butene molar content of 98%.

[0134] The film interlayer is composed of a blend of a second polypropylene and a second polybutene copolymer, wherein the second polybutene copolymer comprises 60% by weight; the second polypropylene is a copolymer of propylene and butene, with an MFR of 5.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination of 95% propylene molar content; the second polybutene copolymer is a copolymer of butene and propylene, with an MFR of 3.0 g / 10 min at 230°C and a load of 2.16 kg, and an NMR determination of 98% butene molar content.

[0135] The inner surface layer of the film is composed of a blend of a third polypropylene and a third polybutene copolymer, wherein the third polybutene copolymer accounts for 30% by weight; the third polypropylene is a copolymer of propylene and butene, with an MFR of 3.0 g / 10 min at 230 °C and a load of 2.16 kg, and an NMR determination of 98% propylene unit molar content; the third polybutene copolymer is a copolymer of butene and propylene, with an MFR of 5.0 g / 10 min at 230 °C and a load of 2.16 kg, and an NMR determination of 99% butene unit molar content.

[0136] The above-mentioned method for preparing polyolefin multilayer films includes:

[0137] 1) Add 0.2wt% of antioxidant 168+1010 compounded in a mass ratio of 1:1 to the blend of each layer of the polyolefin multilayer film. First, premix with a high-speed mixer, and then use a twin-screw extruder to blend, extrude and granulate to obtain the materials for each layer.

[0138] 2) The materials for each layer are placed into the corresponding extruder hopper of the multilayer co-extrusion casting unit, extruded by the screw, cooled by the cold roller, and then wound up to obtain a polyolefin multilayer film.

[0139] The extruder temperature for the outer surface layer of the film is 190-230℃, the extruder temperature for the middle layer of the film is 180-210℃, and the extruder temperature for the inner surface layer of the film is 190-230℃.

[0140] The temperature of the cold roller is set to 25℃, and the winding speed is 6m / min.

[0141] The total thickness of the polyolefin multilayer film is 300 μm, of which the thickness of the outer surface layer accounts for 25% of the total thickness, the thickness of the middle layer accounts for 50% of the total thickness, and the thickness of the inner surface layer accounts for 25% of the total thickness.

[0142] Comparative Example 1

[0143] Same as Example 1, except that:

[0144] Outer surface layer of film: Only polypropylene homopolymer is used, with an MFR of 3.0 g / 10 min at 230°C and 2.16 kg load;

[0145] Intermediate layer of film: Only polypropylene homopolymer is used, with an MFR of 5.0 g / 10 min at 230°C and 2.16 kg load;

[0146] Inner surface layer of film: Only polypropylene homopolymer is used, with an MFR of 3.0 g / 10 min at 230 °C and 2.16 kg load;

[0147] In the preparation of multilayer films, the extruder temperatures for the outer surface layer, the middle layer, and the inner surface layer are all 190-230℃.

[0148] The total thickness of the multilayer film is 300 μm, of which the thickness of the outer surface layer accounts for 25% of the total thickness, the thickness of the middle layer accounts for 50% of the total thickness, and the thickness of the inner surface layer accounts for 25% of the total thickness.

[0149] Comparative Example 2

[0150] Same as Example 6, except that:

[0151] The outer surface layer of the film is made of a copolymer of propylene and ethylene, with an MFR of 3.0 g / 10 min at 230 °C and 2.16 kg load, and an NMR determination of propylene molar content of 98%.

[0152] Intermediate layer of film: Only a copolymer of propylene and ethylene is used, with an MFR of 5.0 g / 10 min at 230 °C and 2.16 kg load, and NMR determination shows that its propylene unit molar content is 96%;

[0153] Inner surface layer of film: Only a copolymer of propylene and ethylene is used, with an MFR of 3.0 g / 10 min at 230 °C and 2.16 kg load, and NMR analysis shows that the molar content of propylene units is 97%.

[0154] In the preparation of multilayer films, the extruder temperatures for the outer surface layer, the middle layer, and the inner surface layer are all 190-230℃.

[0155] The total thickness of the multilayer film is 400 μm, of which the outer surface layer accounts for 25% of the total thickness, the middle layer accounts for 50% of the total thickness, and the inner surface layer accounts for 25% of the total thickness.

[0156] Comparative Example 3

[0157] Same as Example 5, except that:

[0158] The outer surface layer of the film: the MFR of the polypropylene homopolymer is 10.0 g / 10 min; the MFR of the first polybutene copolymer is 0.2 g / 10 min.

[0159] Intermediate layer of film: MFR of polypropylene homopolymer is 0.2 g / 10 min; MFR of second polybutene copolymer is 20.0 g / 10 min.

[0160] The inner surface layer of the film: the MFR of the polypropylene homopolymer is 10.0 g / 10 min; the MFR of the third polybutene copolymer is 15.0 g / 10 min.

[0161] Unable to form a film continuously.

[0162] Comparative Example 4

[0163] Same as Example 1, except that:

[0164] Outer surface layer of film: The first polybutene copolymer in the blend accounts for 50% by weight.

[0165] Intermediate layer of film: The second polybutene copolymer in the blend accounts for 95% by weight.

[0166] Inner surface layer of film: The third polybutene copolymer in the blend accounts for 50% by weight.

[0167] Comparative Example 5

[0168] Same as Example 1, except that:

[0169] Outer surface layer of film: The weight percentage of the first polybutene copolymer in the blend is 10%.

[0170] Intermediate layer of film: The second polybutene copolymer in the blend accounts for 40% by weight.

[0171] Inner surface layer of film: The weight percentage of the third polybutene copolymer in the blend is 10%.

[0172] Comparative Example 6

[0173] Same as Example 1, except that:

[0174] Outer surface layer of the film: The molar content of butene units in the first polybutene copolymer is 97%.

[0175] Intermediate layer of film: The molar content of butene units in the second polybutene copolymer is 94%.

[0176] Inner surface layer of the film: The molar content of butene units in the third polybutene copolymer is 97%.

[0177] Comparative Example 7

[0178] Same as Example 1, except that:

[0179] The outer surface layer of the film: The first polypropylene is a polypropylene copolymer (a copolymer of propylene and ethylene), wherein the molar content of propylene units in the polypropylene copolymer is 96%.

[0180] Intermediate layer of film: The second polypropylene is a polypropylene copolymer (a copolymer of propylene and ethylene), wherein the propylene unit molar content in the polypropylene copolymer is 93%.

[0181] Inner surface layer of the film: The third polypropylene is a polypropylene copolymer (a copolymer of propylene and ethylene), wherein the molar content of propylene units in the polypropylene copolymer is 96%.

[0182] The parameters and properties of the multilayer films prepared in each embodiment and comparative example are shown in Table 1.

[0183] Table 1

[0184]

[0185]

[0186] As can be seen from the data of the above embodiments and comparative examples, the material selected in this invention has good film-forming properties, is stable under hot steam sterilization conditions, has high light transmittance and low haze, and also has high toughness and appropriate rigidity, making it suitable for medical packaging.

[0187] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A polyolefin multilayer film, characterized in that, This polyolefin multilayer film consists of an outer surface layer, a middle layer, and an inner surface layer, wherein: The outer surface layer of the film contains a blend of a first polypropylene and a first polybutene copolymer, wherein the weight percentage of the first polybutene copolymer in the blend is 20-40%. The film interlayer contains a blend of a second polypropylene and a second polybutene copolymer, wherein the weight percentage of the second polybutene copolymer in the blend is 50-90%. The inner surface layer of the film contains a blend of a third polypropylene and a third polybutene copolymer, wherein the weight percentage of the third polybutene copolymer in the blend is 20-40%. The first polypropylene, the second polypropylene, and the third polypropylene are each independently selected from polypropylene homopolymers or polypropylene copolymers. The polypropylene copolymer is a copolymer of propylene and ethylene or butene, wherein the molar percentage of propylene comonomer is not less than 94%, and the melt flow index of the polypropylene homopolymer or polypropylene copolymer at 230°C and 2.16 kg load is 0.5-8 g / 10 min. The first polybutene copolymer, the second polybutene copolymer, and the third polybutene copolymer are each independently selected from copolymers of butene and ethylene or propylene, wherein the molar percentage of butene comonomer is 95-99%, and the melt flow index of the butene and ethylene or propylene copolymer at 230°C and 2.16 kg load is 1-10 g / 10 min.

2. The polyolefin multilayer film according to claim 1, wherein, When the first polypropylene is a polypropylene copolymer, the molar percentage of propylene comonomer therein is not less than 97%; when the second polypropylene is a polypropylene copolymer, the molar percentage of propylene comonomer therein is not less than 94%; when the third polypropylene is a polypropylene copolymer, the molar percentage of propylene comonomer therein is not less than 97%.

3. The polyolefin multilayer film according to claim 1, wherein, The first polybutene copolymer has a butene comonomer molar content percentage of 98-99%; the second polybutene copolymer has a butene comonomer molar content percentage of 95-98%; and the third polybutene copolymer has a butene comonomer molar content percentage of 98-99%.

4. The polyolefin multilayer film according to claim 1, wherein, The weight percentage of the first polybutene copolymer in the outer surface layer of the film is 25-35%; the weight percentage of the second polybutene copolymer in the middle layer of the film is 55-80%; and the weight percentage of the third polybutene copolymer in the inner surface layer of the film is 25-35%.

5. The polyolefin multilayer film according to claim 1, wherein, The melt flow index of the first polypropylene at 230℃ and 2.16kg load is 3-8 g / 10min; the melt flow index of the second polypropylene at 230℃ and 2.16kg load is 2-5 g / 10min; and the melt flow index of the third polypropylene at 230℃ and 2.16kg load is 0.5-3 g / 10min.

6. The polyolefin multilayer film according to claim 1, wherein, The melt flow index of the first polybutene copolymer at 230℃ and 2.16kg load is 1-6 g / 10min; the melt flow index of the second polybutene copolymer at 230℃ and 2.16kg load is 3-8 g / 10min; and the melt flow index of the third polybutene copolymer at 230℃ and 2.16kg load is 5-10 g / 10min.

7. The polyolefin multilayer film according to claim 1, wherein, The polyolefin multilayer film contains additives, including antioxidants, and the amount of antioxidants used is 0.1-0.5 wt% of the blend of each layer of the film.

8. The polyolefin multilayer film according to claim 1, wherein, The total thickness of the polyolefin multilayer film is 150-600 μm, wherein the thickness of the outer surface layer accounts for 15-30% of the total thickness, the thickness of the middle layer accounts for 50-75% of the total thickness, and the thickness of the inner surface layer accounts for 10-25% of the total thickness.

9. A method for preparing a polyolefin multilayer film according to any one of claims 1-8, characterized in that, The preparation method includes: 1) The raw materials for each layer of the polyolefin multilayer film are premixed separately, then mixed separately and extruded and granulated to obtain the materials for each layer; 2) The materials for each layer are extruded through the screw of the multi-layer co-extrusion casting unit, cooled by cold rollers, and then wound up to obtain a polyolefin multilayer film; Preferably, the extruder temperature for the outer surface layer of the film is 190-230℃, the extruder temperature for the middle layer of the film is 180-210℃, and the extruder temperature for the inner surface layer of the film is 190-230℃; the cold roll temperature is set to 20-30℃, and the winding speed is 2-12m / min.

10. The application of the polyolefin multilayer film according to any one of claims 1-8 in the field of medical packaging.

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