Polyolefin co-extruded film for liquid-liquid multi-chamber infusion bag as well as preparation method and application of polyolefin co-extruded film

Abstract

The invention provides a polyolefin co-extrusion film for a liquid-liquid multi-chamber infusion bag as well as a preparation method and application of the polyolefin co-extrusion film, and relates to the technical field of infusion packaging materials. The polyolefin co-extruded film for the liquid-liquid multi-chamber infusion bag comprises a heat sealing layer, an outer surface layer and a middle layer, wherein the heat sealing layer comprises polypropylene random copolymer, polypropylene ternary copolymer, ethylene-alpha olefin copolymer and styrene block copolymer; the outer surface layer comprises polypropylene and a styrene block copolymer; and the middle layer comprises polypropylene and styrene block copolymer. The polyolefin co-extrusion film realizes pseudo soldering through a two-step method, has stable heat sealing strength, prevents accidental opening of pseudo soldering strips of the infusion bag, and ensures that the pseudo soldering strips are opened through extrusion to be smoothly communicated with all the cavities in clinical use.

Description

Technical Field

[0001] The present invention relates to the technical field of infusion packaging materials, and in particular to a polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag and a preparation method thereof. Background Art

[0002] Multi-chamber bag infusion products include powder-liquid multi-chamber bags and liquid-liquid multi-chamber bags. The bag body is divided into multiple independent chambers by virtual welding, and different liquid or powder medicines are placed in different chambers. In clinical use, medical staff squeeze the chambers to penetrate, and the medicine can be mixed and injected intravenously into the patient. Multi-chamber bags have many advantages, such as closed system dispensing to avoid microbial contamination; ready-to-use, easy to operate and portable, shortening the dispensing time; pre-prepared drug dosage to avoid medical accidents caused by dispensing errors.

[0003] The key technology of multi-chamber bags is to use a virtual welding rod structure to divide the bag into independent chambers. Before the use of the medicine, the virtual welding rod is used to isolate different drugs. When in use, the virtual welding rod can be smoothly opened to connect the chambers to mix the drugs. Heat sealing strength is a key indicator for evaluating virtual welding rods. On the one hand, in order to prevent the virtual welding rod from accidentally opening, the heat sealing strength of the virtual welding rod cannot be too low; on the other hand, the heat sealing strength cannot be too large to ensure that it can be opened smoothly during clinical use. The general requirement is 5-15N / 15mm. The virtual welding rod heat sealing strength of 5-10N / 15mm is more suitable for powder-liquid double-chamber bags, while for large-sized liquid-liquid multi-chamber bags that need to withstand greater impact, the virtual welding rod heat sealing strength is preferably 10-15N / 15mm. The existing virtual welding rod technology is realized in one step by a thermal welding process: the diaphragm is pressed together by the heated upper and lower molds. After the heat of the upper and lower molds is transferred to the inner layer, the polymer molecules of the material in the inner layer are melted and entangled. For a single heat welding process, it is easy to form a virtual welding rod with a heat-sealing strength of 5-10N / 15mm. When the heat-sealing strength is 10-15N / 15mm, because the welding temperature window of the virtual welding rod of the film material used is narrow and the welding is unstable, a slight fluctuation in the welding conditions (temperature, pressure, time) will cause the heat-sealing strength of the virtual welding rod to exceed the range. In addition, heat welding is not a closed environment, and the heat energy transferred to the film material during welding is also easily affected by the environment and changes, which causes the heat-sealing strength of the virtual welding rod to exceed the range. Summary of the invention

[0004] The object of the present invention is to provide a polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag and a preparation method thereof, which can realize virtual welding and real welding, and has stable virtual welding rod heat sealing strength and good low-temperature impact resistance.

[0005] Another object of the present invention is to provide an application of a polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag.

[0006] Another object of the present invention is to provide a liquid-liquid multi-chamber infusion bag, which is prepared using the above-mentioned polyolefin co-extrusion film for liquid-liquid multi-chamber infusion bag.

[0007] The present invention is achieved through the following technical solutions:

[0008] In the first aspect, the present invention provides a polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag, comprising a heat-sealing layer, an outer layer and an intermediate layer, wherein the heat-sealing layer comprises, by weight, 30-40 parts of random copolymer polypropylene, 20-30 parts of ternary copolymer polypropylene, 5-15 parts of ethylene-α-olefin copolymer and 15-25 parts of styrene block copolymer; the outer layer comprises, by weight, 80-95 parts of polypropylene and 5-20 parts of styrene block copolymer; the intermediate layer comprises, by weight, 40-60 parts of polypropylene and 40-60 parts of styrene block copolymer.

[0009] Furthermore, the melting point of the terpolymer polypropylene is 125-135°C, the melting point of the random copolymer polypropylene is 140-160°C, and the melting point of the ethylene-α-olefin copolymer is 60-110°C.

[0010] Furthermore, the terpolymer polypropylene is a propylene-ethylene-butene copolymer, the random copolymer polypropylene is a propylene-ethylene copolymer, the ethylene-α-olefin copolymer comonomer is butene, hexene or octene, and the styrene block copolymer is a styrene-ethylene-ethylene-styrene block copolymer or a styrene-ethylene-butylene-styrene block copolymer.

[0011] In the second aspect, the present invention provides a method for preparing a polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag, comprising the following steps: the heat sealing layer, the outer layer and the middle layer are melted and plasticized by an extruder respectively, and then enter a multi-layer blown film die, the blown film die blows downward to form a film bubble, which is then cooled with purified water. After the film bubble is shaped by a herringbone plate, it is pulled by a traction roller and finally enters a winding roller for winding to obtain a polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag.

[0012] In a third aspect, the present invention provides an application of a polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag in the preparation of a liquid-liquid multi-chamber infusion bag.

[0013] In a fourth aspect, the present invention provides a liquid-liquid multi-chamber infusion bag, which is prepared using the above-mentioned polyolefin co-extrusion film for liquid-liquid multi-chamber infusion bag.

[0014] Furthermore, the method for preparing the liquid-liquid multi-chamber infusion bag comprises the following steps:

[0015] S1. Initial welding of virtual welding: two pieces of liquid-liquid multi-chamber infusion bags are initially welded with polyolefin co-extruded film to form virtual welding rods, and the heat sealing strength of the virtual welding rods is 5-8N / 15mm;

[0016] S2, bag making: hot pressing and welding the co-extruded film with virtual welding rod obtained in S1 to form a real welding rod, and the heat sealing strength of the real welding rod is 30-45N / 15mm;

[0017] S3. The liquid-liquid multi-chamber infusion bag obtained in S2 is sterilized by wet heat to obtain a virtual welding rod with a heat sealing strength of 10-15N / 15mm.

[0018] After the bag is made, it also includes welding the mouth tube, pouring in the medicine solution, and inserting the infusion stopper.

[0019] In the present invention, in step S1, the welding pressure of the initial welding is 0.4-0.6 MPa, the welding time is 0.4-0.8 s, and the welding temperature is 100-122°C.

[0020] In the present invention, in step S2, the hot pressing welding pressure is 0.4-0.6MPa, the welding time is 0.5-1s, and the welding temperature is 140-150°C; in step S3, the moist heat sterilization temperature is 120-125°C, and the sterilization time is 10-15min.

[0021] In the present invention, the width of the virtual welding rod is 2-5 mm, and the width of the real welding rod is 1-4 mm.

[0022] Random copolymer polypropylene is made by the simultaneous polymerization of ethylene molecules and propylene molecules. Since the ethylene molecules randomly inserted into the polymer main chain hinder the crystalline arrangement of the polymer molecules, random copolymer polypropylene has a lower melting temperature and higher impact resistance. The chemical structure of ethylene-α-olefin copolymer contains random copolymer sequences. The existence of this random copolymer sequence makes the chain structure of the material looser and the molecular weight distribution more dispersed, making the ethylene-α-olefin copolymer have better flexibility, stretchability and heat resistance. Terpolymer polypropylene introduces ethylene and butene into the polypropylene molecular chain, destroying the regularity of the polypropylene molecular chain and lowering the crystallization temperature, so that the initial heat sealing temperature of terpolymer polypropylene is low, the heat sealing strength is high, and it has a wider heat sealing window.

[0023] Ethylene-α-olefin copolymer has the lowest melting point and can melt, move and entangle at a lower temperature, which can realize the initial welding of virtual welding rods at low temperature. At the same time, it has high melt strength and flexibility, which can ensure the low-temperature impact performance of virtual welding rods and real welding rods. The melting point of ternary copolymer polypropylene is close to the wet heat sterilization temperature. During the wet heat sterilization process, the molecular chain can melt, move and entangle, thereby further improving the heat sealing strength of the virtual welding rod. Random copolymer polypropylene with a high melting point melts, moves and entangles the molecular chain during real welding under high temperature conditions, thereby forming a real welding rod. The molecular chains of polymers are crossed and staggered at different temperatures, so that the polymer molecular chains present a certain spatial structure and increase the interaction force between molecules. On the one hand, it can increase the viscosity of the material and improve the mechanical strength of the material. On the other hand, it can convert chain breakage into the extraction and extension of variable-length chains to improve the toughness of the material. By utilizing the different degrees of entanglement of each component at different temperatures, the entanglement density can be reasonably controlled, avoiding the excessive entanglement density affecting the material molding and processing, and preventing the entanglement from aggravating and reducing the strength and toughness of the material. The present invention adds three polymer materials with different melting points into the heat sealing layer, so that the welding temperature range of the film material is wider, and the specific proportion of the components can simultaneously achieve the virtual welding rod with stable heat sealing strength of the film material and low-temperature impact performance.

[0024] Random copolymer polypropylene, ternary copolymer polypropylene, and ethylene-α-olefin copolymer have different melting points, and molecular chains can melt, move, and entangle under different temperature conditions, thereby forming virtual welding rods and real welding rods with different heat-sealing strengths. The first step in the formation of virtual welding rods is initial welding, and the welding temperature is low. At this time, the molecular chains of ethylene-α-olefin copolymer and part of ternary copolymer polypropylene melt, move, and entangle, forming a low and stable virtual welding rod heat-sealing strength (5-8N / 15mm). The virtual welding rod is cleverly enhanced by wet heat sterilization. During this process, the virtual welding rod undergoes a constant sterilization temperature and a long sterilization process. In this step, the molecular chains of ternary copolymer polypropylene melt, move, and entangle, thereby forming a virtual welding rod with a higher heat-sealing strength (10-15N / 15mm). Under higher real welding temperature conditions, random copolymer polypropylene, ternary copolymer polypropylene, and ethylene-α-olefin copolymer all participate in molecular chain melting, movement, and entanglement, thereby obtaining a real welding rod with high heat-sealing strength (30-45N / 15mm).

[0025] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0026] 1. Using random copolymer polypropylene, ternary copolymer polypropylene and ethylene-α-olefin copolymer with different melting points as heat sealing materials and performing virtual welding through a two-step method can allow each component to gradually melt, move and entangle during the welding process, thereby improving the melt strength, ensuring that the melt is not easy to break during welding, and enhancing the toughness of the infusion bag; at the same time, it can also widen the welding temperature window, improve the stability and uniformity of the heat sealing strength of the virtual welding rod, and improve the quality of the infusion bag.

[0027] 2. By realizing the initial welding of the virtual welding rod under low temperature conditions, it is possible to prevent the molecular chain in the polyolefin co-extruded film from breaking due to the high initial welding temperature, reduce the precipitation of insoluble particles, and ensure the safety of the liquid medicine in the infusion bag.

[0028] 3. The middle layer is made of polypropylene and polyethylene block copolymer as the main material, which can improve the strength, toughness and barrier properties of the polyolefin co-extruded film. The outer layer is made of polypropylene as the main material, which can improve the mechanical strength of the polyolefin co-extruded film and provide better printing performance.

[0029] 4. Styrene block copolymer has a low glass transition temperature, which can improve the low-temperature impact resistance of the material and maintain the low-temperature performance of the film. Styrene block copolymer has good processing properties, making polyolefin co-extruded films and infusion bags easier to form and process during the production process, while maintaining the stability and durability of the film and infusion bags. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The heat sealing strength and welding temperature variation curve of Example 1;

[0031] Figure 2 The heat seal strength and welding temperature variation curve of Example 2;

[0032] Figure 3 This is the heat seal strength and welding temperature variation curve of comparative example 1;

[0033] Figure 4 The heat seal strength and welding temperature variation curve of comparative example 2;

[0034] Figure 5 This is the heat sealing strength and welding temperature variation curve of comparative example 3. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0036] Example 1

[0037] Preparation of polyolefin co-extruded film for liquid-liquid multi-chamber infusion bags: the heat sealing layer, the outer layer and the middle layer are melted and plasticized by the extruder respectively, and then enter the multi-layer blown film die head, the blown film die head blows downward to form a film bubble, which is then cooled with purified water. After the film bubble is shaped by the herringbone plate, it is pulled by the traction roller and finally enters the winding roller for winding.

[0038] The heat seal layer includes random copolymer polypropylene (propylene-ethylene copolymer), terpolymer polypropylene (propylene-ethylene-butene copolymer), ethylene-α-olefin copolymer (comonomer is hexene) and styrene block copolymer; the outer layer includes polypropylene and styrene block copolymer; the middle layer includes polypropylene and styrene block copolymer. Among them, the styrene block copolymer is styrene-ethylene-butylene-styrene block copolymer.

[0039] The melting point of propylene-ethylene-butene copolymer is 130°C, the melting point of propylene-ethylene copolymer is 150°C, and the melting point of ethylene-α-olefin copolymer (comonomer is hexene) is 80°C.

[0040] A method for preparing a liquid-liquid multi-chamber infusion bag comprises the following steps:

[0041] S1. Initial welding of virtual welding: two liquid-liquid multi-chamber infusion bags are initially welded with polyolefin co-extruded film. The welding pressure of the initial welding is 0.5 MPa, the welding time is 0.6 s, and a virtual welding rod is formed. The width of the virtual welding rod is 4 mm.

[0042] S2, bag making: hot pressing welding is performed on the co-extruded film with virtual welding rods obtained in S1, the hot pressing welding pressure is 0.6 MPa, the welding time is 0.8 s, the welding temperature is 145°C, and a real welding rod is formed, and the width of the real welding rod is 2 mm;

[0043] S3. The liquid-liquid multi-chamber infusion bag obtained in S2 is sterilized by wet heat sterilization at a temperature of 120°C for 12 minutes, so that the heat sealing strength of the virtual welding rod is further improved.

[0044] Example 2

[0045] Preparation of polyolefin co-extruded film for liquid-liquid multi-chamber infusion bags: the heat sealing layer, the outer layer and the middle layer are melted and plasticized by the extruder respectively, and then enter the multi-layer blown film die head, the blown film die head blows downward to form a film bubble, which is then cooled with purified water. After the film bubble is shaped by the herringbone plate, it is pulled by the traction roller and finally enters the winding roller for winding.

[0046] The heat seal layer includes random copolymer polypropylene (propylene-ethylene copolymer), terpolymer polypropylene (propylene-ethylene-butene copolymer), ethylene-α-olefin copolymer (comonomer is butene) and styrene block copolymer; the outer layer includes polypropylene and styrene block copolymer; the middle layer includes polypropylene and styrene block copolymer. Among them, the styrene block copolymer is styrene-ethylene-ethylene-styrene block copolymer.

[0047] The melting point of propylene-ethylene-butene copolymer is 125°C, the melting point of propylene-ethylene copolymer is 140°C, and the melting point of ethylene-α-olefin copolymer (comonomer is butene) is 60°C.

[0048] A method for preparing a liquid-liquid multi-chamber infusion bag comprises the following steps:

[0049] S1. Initial welding of virtual welding: two liquid-liquid multi-chamber infusion bags are initially welded with polyolefin co-extruded film, the welding pressure of the initial welding is 0.4MPa, the welding time is 0.8s, and a virtual welding rod is formed, and the width of the virtual welding rod is 2mm;

[0050] S2, bag making: hot pressing welding is performed on the co-extruded film with virtual welding rods obtained in S1, the hot pressing welding pressure is 0.6 MPa, the welding time is 0.5 s, the welding temperature is 150°C, and a real welding rod is formed, and the width of the real welding rod is 4 mm;

[0051] S3. The liquid-liquid multi-chamber infusion bag obtained in S2 is sterilized by moist heat sterilization at a temperature of 125° C. for 10 min.

[0052] Example 3

[0053] The difference between this embodiment and embodiment 1 is that the melting point of the propylene-ethylene-butene copolymer is 135°C, the melting point of the propylene-ethylene copolymer is 160°C, and the melting point of the ethylene-α-olefin copolymer (the comonomer is octene) is 110°C.

[0054] Example 4

[0055] The difference between this embodiment and embodiment 1 is that the middle layer of the polyolefin co-extruded film for the liquid-liquid multi-chamber infusion bag comprises 60% of polypropylene and 40% of styrene block copolymer by weight percentage.

[0056] Example 5

[0057] The difference between this embodiment and embodiment 1 is that the middle layer of the polyolefin co-extruded film for the liquid-liquid multi-chamber infusion bag comprises 50% of polypropylene and 50% of styrene block copolymer by weight percentage.

[0058] Example 6

[0059] The difference between this embodiment and embodiment 1 is that the outer surface layer of the polyolefin co-extruded film for the liquid-liquid multi-chamber infusion bag comprises 80% of polypropylene and 20% of styrene block copolymer by weight percentage.

[0060] Example 7

[0061] The difference between this embodiment and embodiment 1 is that the outer surface layer of the polyolefin co-extruded film for the liquid-liquid multi-chamber infusion bag comprises 95% of polypropylene and 5% of styrene block copolymer by weight percentage.

[0062] Comparative Example 1

[0063] In this comparative example, the heat seal layer includes random copolymer polypropylene (propylene-ethylene copolymer), terpolymer polypropylene (propylene-ethylene-butene copolymer) and styrene block copolymer. The rest is the same as in Example 1.

[0064] Comparative Example 2

[0065] In this comparative example, the heat seal layer includes random copolymerized polypropylene (propylene-ethylene copolymer), ethylene-α-olefin copolymer (the copolymerized monomer is hexene) and styrene block copolymer. The rest is the same as in Example 1.

[0066] Comparative Example 3

[0067] In this comparative example, the heat seal layer comprises random copolymerized polypropylene (propylene-ethylene copolymer) and styrene block copolymer. The rest is the same as in Example 1.

[0068] The polyolefin co-extrusion film formulations for liquid-liquid multi-chamber infusion bags of Comparative Examples 1-3 and Examples 1-2, each layer is calculated as 100%, and the composition ratios of the intermediate layer, the outer layer and the heat-sealing layer are as follows:

[0069] Table 1

[0070]

[0071] The polyolefin co-extruded film prepared in the above comparative example was welded at different welding temperatures using the same welding pressure and welding time as in Example 1. Ten welding strips of the same co-extruded film were welded under one welding temperature condition, and the welding strips were cut into a width of 15 mm. Five of them were tested for heat sealing strength to obtain the heat sealing strength before sterilization. After the five welding strips were sterilized by wet heat, the heat sealing strength was tested to obtain the heat sealing strength after sterilization. The average heat sealing strength of the welding strips before and after sterilization was recorded, as shown in the following table:

[0072] Table 2

[0073]

[0074] According to Table 2 and Figure 1-5It can be seen that the comparative example needs to control the initial welding temperature within a very narrow range (less than 3°C) to achieve a heat-sealing strength of 10-15N / 15mm after sterilization. The initial welding temperature of the embodiment is in the range of 100-122°C, which can form a virtual welding rod with a heat-sealing strength of 5-10N / 15mm. After wet heat sterilization, the heat-sealing strength of the virtual welding rod is increased to 10-15N / 15mm. The virtual welding rod of the polyolefin co-extruded film prepared by the present invention has a wide welding window, which is easier to control the production process.

[0075] The heat-sealing strength of the virtual welding rods of the polyolefin co-extruded films of Examples 3-7 before and after sterilization was tested. The results showed that the heat-sealing strength of the virtual welding rods of Examples 3-7 before and after sterilization was not much different from that of Example 1, indicating that under the conditions of Examples 3-7, the virtual welding rods had a wider welding window and a higher heat-sealing strength.

[0076] The quality of the heat seal of the virtual welding rod (including the size and uniformity of the heat seal strength) will affect the performance of the liquid-liquid multi-chamber soft bag: if the heat seal strength is too low, the virtual welding rod will accidentally open when the soft bag falls, and if the heat seal strength of the virtual welding rod is too high, it will be difficult to open the bag during clinical use. Therefore, it is necessary to test the quality of the virtual welding rod of the infusion bag. The test method is as follows:

[0077] According to the proportions in Table 1, a liquid-liquid multi-chamber infusion bag was prepared. The preparation processes of the virtual welding rods in Comparative Examples 1-3 and Examples 1-2 were different, but the preparation processes of the real welding rods were the same. Specifically, the virtual welding rods in Comparative Examples 1-3 were welded at a temperature when the heat seal strength after sterilization was 13N / 15mm, and no wet heat sterilization was performed; the welding temperature of the virtual welding rods in Example 1-2 was 110°C, and wet heat sterilization was performed to complete the preparation of the liquid-liquid multi-chamber infusion soft bag. The bags were packed in a standard packing method and placed for 7 days.

[0078] Heat seal strength test of virtual welding rod: randomly select 20 liquid-liquid multi-chamber infusion soft bags, cut a sample with a width of 15mm and a length of 100mm in the middle position of the virtual welding rod, and test it with a universal testing machine according to the heat seal strength determination method (YBB00122003-2015).

[0079] Whole box drop test: drop a whole box of liquid-liquid multi-chamber infusion soft bags from a height of 2.8 meters onto a hard ground, and open the box to check whether the virtual welding rods are opened.

[0080] Clinical simulation opening test: Use both hands to reel in the liquid-liquid multi-chamber infusion soft bag from the tail. As the bag is reeled in, the storage space for the liquid medicine is reduced and the pressure inside the bag increases until the virtual welding rod is connected and the bag opens.

[0081] Insoluble particles: After manually opening the virtual welding rod and mixing the liquid, measure it according to the method for measuring insoluble particles in packaging materials (YBB00272004-2015) and count the number of particles of 5μm and above in every 1ml.

[0082] Table 3

[0083]

[0084] It can be seen from Table 3 that the welding temperature of the comparative example virtual welding rod is relatively high, higher than 120° C. The welding temperature of the embodiment virtual welding rod is relatively low and the welding temperature window is relatively wide, which is not only beneficial to quality control but also has lower energy consumption.

[0085] The standard deviation of the heat-sealing strength of the comparative example is large, indicating that the heat-sealing strength fluctuates greatly, while the standard deviation of the embodiment is small, indicating that the heat-sealing strength is more stable.

[0086] In the comparative example, the weak welding rod opens after falling. This is because the minimum value of the heat sealing strength of the weak welding rod is small, the impact resistance of the weak welding rod is poor, and it is easy to open accidentally.

[0087] The heat sealing strength of the virtual welding rod in the embodiment is uniform and stable, so the manual opening is smoother and the clinical use experience is good.

[0088] The number of insoluble particles in the embodiment is lower, because the welding temperature of the virtual welding rod in the comparative example is higher, which may cause the molecules in the polyolefin co-extruded film to break easily and precipitate into the liquid medicine, so the number of insoluble particles is higher, indicating that the infusion bag prepared in the embodiment is safer for patients.

[0089] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag, characterized in that: It comprises a heat-sealing layer, an outer layer and an intermediate layer, wherein the heat-sealing layer comprises 30-40 parts of random copolymer polypropylene, 20-30 parts of terpolymer polypropylene, 5-15 parts of ethylene-α-olefin copolymer and 15-25 parts of styrene block copolymer by weight; the outer layer comprises 80-95 parts of polypropylene and 5-20 parts of styrene block copolymer by weight; The middle layer comprises 40-60 parts of polypropylene and 40-60 parts of styrene block copolymer by weight.

2. The polyolefin co-extruded film for liquid-liquid multi-chamber infusion bag according to claim 1, characterized in that: The melting point of the terpolymer polypropylene is 125-135°C, the melting point of the random copolymer polypropylene is 140-160°C, and the melting point of the ethylene-α-olefin copolymer is 60-110°C.

3. The polyolefin co-extruded film for liquid-liquid multi-chamber infusion bag according to claim 2, characterized in that: The terpolymer polypropylene is a propylene-ethylene-butene copolymer, the random copolymer polypropylene is a propylene-ethylene copolymer, the ethylene-α-olefin copolymer comonomer is butene, hexene or octene, and the styrene block copolymer is a styrene-ethylene-ethylene-styrene block copolymer or a styrene-ethylene-butylene-styrene block copolymer.

4. The method for preparing a polyolefin co-extruded film for a liquid-liquid multi-chamber infusion bag according to any one of claims 1 to 3, characterized in that: The following steps are involved: The heat sealing layer, outer layer and middle layer are melted and plasticized by the extruder respectively, and then enter the multi-layer blown film die head, which blows downward to form film bubbles, which are then cooled with purified water. After the film bubbles are shaped by the herringbone plate, they are pulled by the traction roller and finally enter the winding roller for winding to obtain a polyolefin co-extruded film for liquid-liquid multi-chamber infusion bag.

5. Use of the polyolefin co-extruded film for liquid-liquid multi-chamber infusion bag as described in any one of claims 1 to 3 in the preparation of liquid-liquid multi-chamber infusion bag.

6. A liquid-liquid multi-chamber infusion bag, characterized in that: The liquid-liquid multi-chamber infusion bag is prepared using the polyolefin co-extrusion film for liquid-liquid multi-chamber infusion bag according to any one of claims 1-3.

7. The liquid-liquid multi-chamber infusion bag according to claim 6, characterized in that: The method for preparing the liquid-liquid multi-chamber infusion bag comprises the following steps: S1. Initial welding of virtual welding: two pieces of liquid-liquid multi-chamber infusion bags are initially welded with polyolefin co-extruded film to form virtual welding rods, and the heat sealing strength of the virtual welding rods is 5-8N / 15mm; S2, bag making: hot pressing and welding the co-extruded film with virtual welding rod obtained in S1 to form a real welding rod, and the heat sealing strength of the real welding rod is 30-45N / 15mm; S3. The liquid-liquid multi-chamber infusion bag obtained in S2 is sterilized by wet heat to obtain a virtual welding rod with a heat sealing strength of 10-15N / 15mm.

8. The liquid-liquid multi-chamber infusion bag according to claim 7, characterized in that: In step S1, the welding pressure of the initial welding is 0.4-0.6 MPa, the welding time is 0.4-0.8 s, and the welding temperature is 100-122°C.

9. The liquid-liquid multi-chamber infusion bag according to claim 8, characterized in that: In step S2, the hot pressing welding pressure is 0.4-0.6MPa, the welding time is 0.5-1s, and the welding temperature is 140-150°C; in step S3, the moist heat sterilization temperature is 120-125°C, and the sterilization time is 10-15min.

10. The liquid-liquid multi-chamber infusion bag according to claim 9, characterized in that: The virtual welding rod width is 2-5 mm, and the real welding rod width is 1-4 mm.

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