Process for continuous and efficient dry preparation of high capacity pp composite battery separator

Abstract

The application discloses a process for continuously and efficiently preparing a large-capacity PP composite battery diaphragm by a dry method, and belongs to the technical field of battery diaphragm processing.The application is used for solving the technical problems that the distribution of pores generated in the stretching process of the prior art PP composite battery diaphragm is uneven, and the tensile strength and puncture strength of the composite battery diaphragm need to be further improved, and comprises the following operation steps: 20-30 parts of butyl acrylate, 20-30 parts of 3-(methacryloyloxy) propyl trimethoxysilane, 60-90 parts of toluene and 0.5-0.7 parts of an initiator are weighed according to weight parts, and are stirred in a three-necked flask.The application not only effectively simplifies the production process of the PP composite battery diaphragm, improves the production efficiency, but also can build a net support skeleton on the PP composite battery diaphragm, improves the tensile strength and puncture strength, and makes the distribution of pores on the PP composite battery diaphragm more uniform, and improves the ionic conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery separator processing, in particular to a process for continuously and efficiently preparing a large-capacity PP composite battery separator by a dry method. BACKGROUND

[0002] A battery separator refers to a layer of separator material between the positive and negative electrodes of a battery, which is a very critical part of the battery and has a direct impact on the safety and cost of the battery. Its main function is to isolate the positive and negative electrodes and prevent the free passage of electrons in the battery, while allowing the free passage of ions in the electrolyte between the positive and negative electrodes. Battery separators are usually made of polyethylene or polypropylene.

[0003] In the prior art, to avoid pinholes and gels on the battery separator, three sub-separators are usually combined together to improve the mechanical properties of the composite separator. However, the existing three-layer composite battery separator is usually obtained by extruding three layers of sub-separators by a three-layer co-extrusion film blowing machine, followed by hot pressing and stretching. The three sub-separators are bonded together by hot pressing, but the bonding surfaces of the three sub-separators are only bonded together by simple melting and crosslinking, lacking a supporting skeleton. When the composite separator is stretched, the stretching forces on different parts of the composite separator are different, resulting in uneven distribution of pores on the composite separator, which needs to be improved. The electrical conductivity of the composite separator, and the tensile strength and puncture strength of the composite separator also need to be further improved due to the lack of a skeleton support.

[0004] In view of the above technical defects, a solution is proposed. SUMMARY

[0005] The present application aims to provide a process for continuously and efficiently preparing a large-capacity PP composite battery separator, which solves the technical problems of the prior art, i.e., the sub-separators of the multi-layer composite PP composite battery separator are bonded together by hot melting, the pores generated during the stretching process of the composite separator are unevenly distributed on the composite battery separator, and the tensile strength and puncture strength of the composite battery separator need to be further improved.

[0006] The object of the present application can be achieved by the following technical solution:

[0007] The process for continuously and efficiently preparing a large-capacity PP composite battery separator comprises the following operation steps:

[0008] S1. Weigh 20-30 parts of butyl acrylate, 20-30 parts of 3-(methacryloyloxy) propyl trimethoxysilane, 60-90 parts of toluene and 0.5-0.7 parts of initiator, and add them to a three-necked flask for stirring. The temperature of the three-necked flask is raised to 85-95℃, and the stirring reaction is carried out for 2-5h. After reaction and treatment, a modified crosslinking agent is obtained.

[0009] The reaction principle of the modified crosslinking agent is as follows:

[0010]

[0011] S2, high-density polyethylene 20-40 parts, modified crosslinking agent 1-2 parts, white carbon black 2-4 parts, nucleating agent 0.1-0.2 parts, antioxidant 0.2-0.4 parts and dispersing agent 0.1-0.2 parts by weight are weighed and added to a beaker and stirred for 30-50 min, the temperature of the beaker is raised to 135-145℃, and stirring is carried out for 20-30 min, then it is added to a twin-screw extruder to extrude into a strip, cooled in a water tank, and then cut into particles by traction to obtain modified PE particles;

[0012] S3, high-density polypropylene 20-40 parts, modified crosslinking agent 1-2 parts, white carbon black 2-4 parts, nucleating agent 0.1-0.2 parts, antioxidant 0.2-0.4 parts and dispersing agent 0.1-0.2 parts by weight are weighed and added to a beaker and stirred for 30-50 min, the temperature of the beaker is raised to 135-145℃, and stirring is carried out for 20-30 min, then it is added to a twin-screw extruder to extrude into a strip, cooled in a water tank, and then cut into particles by traction to obtain modified PP particles;

[0013] S4, the modified PP particles and the modified PE particles are added to a three-layer co-extrusion film blowing machine, and extruded through the three-layer co-extrusion film blowing machine to obtain a PP / PE / PP three-layer composite composite separator primary product;

[0014] S5, the composite separator primary product is cut according to the design requirements, and after heat treatment, a composite separator crude product is obtained;

[0015] S6, the composite separator crude product is stretched to obtain a composite separator finished product.

[0016] Further, the initiator in the S1 step is azobisisobutyronitrile, and the post-reaction treatment step is: after the reaction is completed, the temperature of the three-necked flask is raised to 90-100℃, the vacuum degree is-0.1MPa, and the three-necked flask is reduced to room temperature after distillation under reduced pressure until no liquid flows out, to obtain the modified crosslinking agent.

[0017] Further, in the S2 step: the nucleating agent is composed of one or more of monocyclic carboxylate, tricarboxylate, cyclohexamide, the antioxidant is one of antioxidant TNP and antioxidant TPP, and the dispersing agent is composed of one or more of zinc stearate, barium stearate and calcium stearate.

[0018] Further, in the S3 step: the nucleating agent is composed of one or more of monocyclic carboxylate, tricarboxylate, cyclohexamide, the antioxidant is one of antioxidant TNP and antioxidant TPP, and the dispersing agent is composed of one or more of zinc stearate, barium stearate and calcium stearate.

[0019] Further, the main machine rotation speed of the double screw extruder in the S2 and S3 steps is 300 r / min.

[0020] Further, the rotation speed of the granulator in the S2 and S3 steps is 400 r / min.

[0021] Further, the heat treatment operation in the S5 step is as follows: the cut composite diaphragm crude product is laid between two heating plates, the outside of the composite diaphragm crude product is covered with a metal film, the two heating plates are closed, the two heating plates are simultaneously powered and heated, the temperature is raised to 135-145 DEG C, and the temperature is kept for 10-20 min, the two heating plates are opened, the composite diaphragm crude product is taken out, and the temperature is lowered to room temperature, the metal film wrapped outside the composite diaphragm crude product is removed, and the composite diaphragm crude product is obtained.

[0022] Further, the specific operation steps of the stretching in the S6 step include: heating the composite diaphragm crude product to 120-130 DEG C, performing transverse stretching and longitudinal stretching on the composite diaphragm crude product, and stretching the composite diaphragm crude product to the designed size, to obtain the composite diaphragm finished product.

[0023] The present application has the following advantages:

[0024] 1、The PP composite battery diaphragm in the application is prepared by polyethylene, polypropylene, modified crosslinking agent and white carbon black, the modified crosslinking agent and the white carbon black are connected together through silicon-oxygen-silicon bond to construct a three-dimensional network framework, and the modified crosslinking agent is similar to polyethylene and polypropylene in compatibility, so that the three sub-diaphragms are organically connected together, and the PP composite battery diaphragm forms a stable whole, thereby effectively improving the tensile strength and puncture strength of the PP composite battery diaphragm.

[0025] 2、The three-dimensional network structure constructed by the modified crosslinking agent and the white carbon black in the PP composite battery diaphragm forms a stable whole, and when the composite diaphragm is stretched, each part of the composite diaphragm can bear force uniformly, avoids uneven pores generated in the stretching process of the composite diaphragm, and prevents the composite diaphragm from being broken during stretching, so that uniform pores are generated on the composite diaphragm during stretching, thereby effectively improving the ion conductivity and liquid absorption rate of the composite diaphragm, and effectively improving the capacity of the battery.

[0026] 3、In the preparation of the PP composite battery diaphragm, the polyethylene and polypropylene are modified by the synthesized modified crosslinking agent, and then extruded by an extruder to obtain the composite diaphragm, which effectively simplifies the production process of the composite diaphragm and improves the production efficiency of the PP composite battery diaphragm. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be clearly and completely described below in combination with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0028] Embodiment 1

[0029] The process for continuously and efficiently preparing a large-capacity PP composite battery separator by a dry method in this embodiment includes the following operation steps:

[0030] S1, 20 g of butyl acrylate, 20 g of 3-(methacryloyloxy)propyl trimethoxysilane, 60 g of toluene and 0.5 g of azobisisobutyronitrile are weighed by weight parts and added to a three-necked flask for stirring. The temperature of the three-necked flask is raised to 85℃, and stirring is carried out for 2 h. After the reaction is completed, the temperature of the three-necked flask is raised to 90℃, and the vacuum degree is -0.1 MPa. The three-necked flask is reduced to room temperature after being distilled under reduced pressure until no liquid flows out. A modified crosslinking agent is obtained.

[0031] S2, 200 parts of high-density polyethylene, 10 g of modified crosslinking agent, 20 g of white carbon black, 1 g of monocyclic carboxylate, 2 g of antioxidant TPP and 1 g of zinc stearate are weighed by weight parts and added to a beaker for stirring for 30 min. The temperature of the beaker is raised to 135℃, and stirring is carried out for 20 min. The modified PE particles are obtained after being extruded into strips by a twin-screw extruder and then cut into particles by a water cooling tank and a traction cutter, wherein the rotating speed of the main machine of the twin-screw extruder is 300 r / min, and the rotating speed of the cutter is 400 r / min.

[0032] S3, 200 g of high-density polypropylene, 10 g of modified crosslinking agent, 20 g of white carbon black, 1 g of tricarboxylic acid salt, 2 g of antioxidant TNP and 1 g of zinc stearate are weighed by weight parts and added to a beaker for stirring for 30 min. The temperature of the beaker is raised to 135℃, and stirring is carried out for 20 min. The modified PP particles are obtained after being extruded into strips by a twin-screw extruder and then cut into particles by a water cooling tank and a traction cutter, wherein the rotating speed of the main machine of the twin-screw extruder is 300 r / min, and the rotating speed of the cutter is 400 r / min.

[0033] S4, the modified PP particles and the modified PE particles are added to a three-layer co-extrusion film blowing machine, and a PP / PE / PP three-layer composite separator primary product is obtained after being extruded by the three-layer co-extrusion film blowing machine.

[0034] S5, according to the design requirements, the composite diaphragm is cut, and the cut composite diaphragm is placed between two heating plates, the outside of the composite diaphragm is covered with a metal film, the two heating plates are closed, the two heating plates are powered on and heated, the temperature is raised to 135 DEG C, and the temperature is kept for 10 min, the two heating plates are opened, the composite diaphragm is taken out, and the temperature is lowered to room temperature, the metal film wrapped outside the composite diaphragm is removed, and the composite diaphragm is obtained;

[0035] S6, the composite diaphragm is heated to 120 DEG C, the composite diaphragm is stretched in the transverse direction and the longitudinal direction, and the composite diaphragm is stretched to the designed size, and the composite diaphragm is obtained.

[0036] Example 2

[0037] The process of the continuous and efficient dry method for preparing a large-capacity PP composite battery diaphragm of the embodiment comprises the following operation steps:

[0038] S1, 25g of butyl acrylate, 25g of 3-(methacryloyloxy) propyl trimethoxysilane, 75g of toluene and 0.6g of azobisisobutyronitrile are weighed according to the weight parts, added to a three-necked flask and stirred, the temperature of the three-necked flask is raised to 90 DEG C, and the stirring reaction is carried out for 2.5h, after the reaction is completed, the temperature of the three-necked flask is raised to 95 DEG C, the vacuum degree is-0.1MPa, and the pressure reduction distillation is carried out until no liquid flows out, the three-necked flask is lowered to room temperature, and the modified crosslinking agent is obtained;

[0039] S2, 300g of high-density polyethylene, 15g of modified crosslinking agent, 30g of white carbon black, 1.5g of ternary carboxylate, 3g of antioxidant TPP, 1g of zinc stearate and 0.5g of barium stearate are weighed according to the weight parts, added to a beaker and stirred for 40min, the temperature of the beaker is raised to 140 DEG C, and stirring is carried out for 25min, then it is added to a double-screw extruder and extruded into a strip, cooled in a water cooling tank and then cut into particles by traction, and the modified PE particles are obtained, wherein the main machine speed of the double-screw extruder is 300r / min, and the speed of the pelletizer is 400r / min;

[0040] S3, 300g of high-density polypropylene, 15g of modified crosslinking agent, 30g of white carbon black, 1.5g of ternary carboxylate, 3g of antioxidant TNP and 1.5g of dispersant are weighed according to the weight parts, added to a beaker and stirred for 40min, the temperature of the beaker is raised to 140 DEG C, and stirring is carried out for 25min, then it is added to a double-screw extruder and extruded into a strip, cooled in a water cooling tank and then cut into particles by traction, and the modified PP particles are obtained, wherein the main machine speed of the double-screw extruder is 300r / min, and the speed of the pelletizer is 400r / min;

[0041] S4, the modified PP particles and the modified PE particles are added to a three-layer co-extrusion film blowing machine, and the modified PP particles and the modified PE particles are extruded through the three-layer co-extrusion film blowing machine to obtain a PP / PE / PP three-layer composite composite diaphragm primary product;

[0042] S5, the composite diaphragm primary product is cut according to the design requirements, and the cut composite diaphragm primary product is laid between two heating plates, the outside of the composite diaphragm primary product is covered with a metal film on one side, the two heating plates are closed, the two heating plates are powered and heated at the same time, the temperature is raised to 140℃, and the temperature is kept for 15 minutes, then the two heating plates are opened, the composite diaphragm primary product is taken out, and the temperature is lowered to room temperature. The metal film wrapped outside the composite diaphragm primary product is removed to obtain a composite diaphragm primary product;

[0043] S6, the composite diaphragm primary product is heated to 125℃, and the composite diaphragm primary product is stretched in the transverse direction and the longitudinal direction, and the composite diaphragm primary product is stretched to the designed size to obtain a composite diaphragm product.

[0044] Example 3

[0045] The process of the continuous and efficient dry method for preparing a large-capacity PP composite battery diaphragm of the embodiment comprises the following operation steps:

[0046] S1, 30g of butyl acrylate, 30g of 3-(methacryloyloxy) propyl trimethoxysilane, 90g of toluene and 0.7g of azobisisobutyronitrile are weighed according to the weight parts, added to a three-necked flask and stirred, the temperature of the three-necked flask is raised to 95℃, and the stirring reaction is carried out for 5h. After the reaction is completed, the temperature of the three-necked flask is raised to 100℃, the vacuum degree is-0.1MPa, and the pressure is reduced to distill until no liquid flows out. The three-necked flask is lowered to room temperature to obtain a modified crosslinking agent;

[0047] S2, 400g of high-density polyethylene, 20g of modified crosslinking agent, 40g of white carbon black, 2g of cyclohexanamide, 4g of antioxidant TNP, 1g of zinc stearate and 1g of barium stearate are weighed according to the weight parts, added to a beaker and stirred for 50min, the temperature of the beaker is raised to 145℃, and the stirring is carried out for 30min. The mixture is extruded into a strip in a twin-screw extruder, cooled in a water cooling tank, and then cut into particles by traction. Modified PE particles are obtained, wherein the main machine speed of the twin-screw extruder is 300r / min, and the speed of the particle cutter is 400r / min;

[0048] S3, high-density polypropylene 400 g, modified crosslinking agent 20 g, white carbon black 40 g, monocyclic carboxylate 1 g, tricarboxylic acid salt 1 g, antioxidant TNP 4 g, zinc stearate 1 g and calcium stearate 1 g were weighed by weight parts, added to a beaker and stirred for 50 min, the temperature of the beaker was increased to 145 DEG C, and stirred for 30 min, then added to a double screw extruder to extrude into a strip, cooled in a water cooling tank, and then pulled and cut into particles to obtain modified PP particles, wherein the main machine speed of the double screw extruder was 300 r / min, and the speed of the cutting machine was 400 r / min;

[0049] S4, the modified PP particles and the modified PE particles were added to a three-layer co-extrusion film blowing machine, and the three-layer co-extrusion film blowing machine was extruded to obtain a PP / PE / PP three-layer composite composite diaphragm primary product;

[0050] S5, according to the design requirements, the composite diaphragm primary product was cut, and the cut composite diaphragm primary product was laid between two heating plates, the outside of the composite diaphragm primary product was covered with a metal film on one side, the two heating plates were closed, the two heating plates were powered and heated at the same time, the temperature was increased to 145 DEG C, and the temperature was kept for 20 min, then the two heating plates were opened, the composite diaphragm primary product was taken out, and the temperature was reduced to room temperature, the metal film wrapped outside the composite diaphragm primary product was removed, and the composite diaphragm primary product was obtained.

[0051] S6, the composite diaphragm primary product was heated to 130 DEG C, and the composite diaphragm primary product was stretched in the transverse direction and the longitudinal direction, and the composite diaphragm primary product was stretched to the designed size, and the composite diaphragm product was obtained.

[0052] Comparative Example 1

[0053] The difference between this comparative example and Example 3 is that no white carbon black is added.

[0054] Comparative Example 2

[0055] The difference between this comparative example and Example 3 is that the crosslinking agent is vinyl triethoxysilane.

[0056] Comparative Example 3

[0057] The difference between this comparative example and Example 3 is that no white carbon black and crosslinking agent are added.

[0058] Performance test:

[0059] The tensile strength, puncture strength, porosity and ion conductivity of the composite diaphragm prepared in Examples 1-3 and Comparative Examples 1-3 were detected according to the standard GB / T 36363-2018 "Polyolefin diaphragm for lithium ion battery", and the detection results are shown in the following table:

[0060]

[0061]

[0062] Analysis is made in combination with the data in the above table:

[0063] 1) Comparison is made in combination with the data of Comparative Examples 1-3 and Example 3, the tensile strength and puncture strength of Comparative Examples 1-3 are far lower than that of Example 3, which is because, the white carbon black contains a large amount of silicon hydroxyl group, the modified crosslinking agent contains siloxane group, the siloxane is decomposed by water to produce a group capable of reacting with the silicon hydroxyl group, and reacts with the silicon hydroxyl group to form a silicon-oxygen-silicon bond under the action of high temperature, the modified crosslinking agent is grafted together with the white carbon black, the modified crosslinking agent is similar compatible with polyethylene and polypropylene, so that the white carbon black is stably fixed on the modified PE particles and the modified PP particles, the modified PE particles and the modified PP particles are extruded into three-layer sub-separators by a three-layer co-extrusion film blowing machine, and the white carbon black and the modified crosslinking agent between adjacent sub-separators chemically react under the action of high temperature during heat treatment, the three sub-separators are combined together to form a stable network structure with the white carbon black as the node and the modified crosslinking agent as the chain, so that the tensile strength and the puncture strength of Example 3 are higher than those of Comparative Examples 1-3.

[0064] 2) Comparison is made in combination with the data of Comparative Example 2 and Example 3, the porosity of Comparative Example 2 is not much different from that of Comparative Example 3, but the ionic conductivity of Comparative Example 2 is far lower than that of Example 3, which is because, the network structure composed of white carbon black and modified crosslinking agent makes the stress of each part of the composite separator uniform during stretching, and prevents the composite separator from being broken during stretching, so that uniform pores are generated on the composite separator during stretching, thereby effectively improving the ionic conductivity of the composite separator, the vinyl triethoxysilane used in Comparative Example 2 also contains siloxane group, so that the white carbon black on the three sub-separators can be combined together through the silicon-oxygen-silicon bond, but the vinyl triethoxysilane cannot be similar compatible with polyethylene or polypropylene, and multiple white carbon blacks cannot be organically connected together, and then the pores generated during the stretching process of the composite separator are not uniform, which also leads to the low ionic conductivity of Comparative Example 2.

[0065] The above is only an example and description of the structure of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as the modifications or supplements do not deviate from the structure of the present application or exceed the scope defined by the present claims, and all of them shall belong to the protection scope of the present application.

[0066] In the description of the specification, reference to "one embodiment", "an example", "a specific example" or the like means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. The appearances of the phrases "in one embodiment", "an example", "a specific example" or the like in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0067] The preferred embodiments of the application disclosed above are only to help explain the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments. Obviously, many modifications and variations can be made in light of the contents of the specification. The specification selects and specifically describes these embodiments in order to better explain the principles and practical application of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A process for continuous and efficient dry preparation of high capacity PP composite battery separator, characterized by, It comprises the following operation steps: S1, butyl acrylate 20-30 parts, 3-(methacryloyloxy) propyl trimethoxysilane 20-30 parts, toluene 60-90 parts and initiator 0.5-0.7 parts are weighed by weight parts, added to a three-necked flask and stirred, the temperature of the three-necked flask is raised to 85-95℃, stirred for 2-5h, and after reaction treatment, the modified crosslinking agent is obtained; S2, high density polyethylene 20-40 parts, modified crosslinking agent 1-2 parts, white carbon black 2-4 parts, nucleating agent 0.1-0.2 parts, antioxidant 0.2-0.4 parts and dispersing agent 0.1-0.2 parts are weighed by weight parts, added to a beaker and stirred for 30-50min, the temperature of the beaker is raised to 135-145℃, stirred for 20-30min, added to a twin-screw extruder and extruded into a strip, cooled in a water tank and then cut into particles by traction, to obtain modified PE particles; S3, high density polypropylene 20-40 parts, modified crosslinking agent 1-2 parts, white carbon black 2-4 parts, nucleating agent 0.1-0.2 parts, antioxidant 0.2-0.4 parts and dispersing agent 0.1-0.2 parts are weighed by weight parts, added to a beaker and stirred for 30-50min, the temperature of the beaker is raised to 135-145℃, stirred for 20-30min, added to a twin-screw extruder and extruded into a strip, cooled in a water tank and then cut into particles by traction, to obtain modified PP particles; S4, the modified PP particles and the modified PE particles are added to a three-layer co-extrusion film blowing machine, extruded through the three-layer co-extrusion film blowing machine, and a PP / PE / PP three-layer composite separator primary product is obtained; S5, the composite separator primary product is cut according to the design requirements, and after heat treatment, a composite separator crude product is obtained; S6, the composite separator crude product is stretched to obtain a composite separator finished product; The specific operation steps of stretching in the S6 step include: heating the composite separator crude product to 120-130℃, stretching the composite separator crude product in the transverse direction and the longitudinal direction, stretching the composite separator crude product to the designed size, and obtaining the composite separator finished product.

2. The process for continuous high efficient dry process preparation of high capacity PP composite battery separator as claimed in claim 1 wherein, The initiator in the S1 step is azobisisobutyronitrile, and the post-reaction treatment step is: after the reaction is completed, the temperature of the three-necked flask is raised to 90-100℃, the vacuum degree is-0.1MPa, the pressure is reduced and distilled until no liquid flows out, the three-necked flask is lowered to room temperature, and the modified crosslinking agent is obtained.

3. The process for continuous high efficient dry process preparation of high capacity PP composite battery separator as claimed in claim 1 wherein, In the S2 step: the nucleating agent is composed of one or more of monocyclic carboxylate, tricarboxylate and cyclohexamide, the antioxidant is one of antioxidant TNP and antioxidant TPP, and the dispersing agent is composed of one or more of zinc stearate, barium stearate and calcium stearate.

4. The process for continuous high efficient dry process preparation of high capacity PP composite battery separator as claimed in claim 1 wherein, In the S3 step: the nucleating agent is composed of one or more of monocyclic carboxylate, tricarboxylate and cyclohexamide, the antioxidant is one of antioxidant TNP and antioxidant TPP, and the dispersing agent is composed of one or more of zinc stearate, barium stearate and calcium stearate.

5. The process for continuous high efficient dry process preparation of high capacity PP composite battery separator as claimed in claim 1 wherein, The main machine rotation speed of the twin-screw extruder in the S2 and S3 steps is 300r / min.

6. The process for continuous high efficient dry process preparation of high capacity PP composite battery separator as claimed in claim 1 wherein, The rotation speed of the pelletizer in the S2 and S3 steps is 400r / min.

7. The process for continuous high efficient dry process preparation of high capacity PP composite battery separator as claimed in claim 1 wherein, The heat treatment operation in the S5 step is as follows: the cut composite diaphragm crude product is laid between two heating plates, the outside of the composite diaphragm crude product is covered with a metal film, the two heating plates are closed, the two heating plates are simultaneously powered and heated, the temperature is raised to 135-145 DEG C, and the temperature is kept for 10-20 min, the two heating plates are opened, the composite diaphragm crude product is taken out, and the temperature is lowered to room temperature, the metal film wrapped outside the composite diaphragm crude product is removed, and the composite diaphragm crude product is obtained.

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