CN107785525B - Preparation method of self-flame-retardant co-extruded unidirectional stretching microporous membrane and microporous membrane - Google Patents
Preparation method of self-flame-retardant co-extruded unidirectional stretching microporous membrane and microporous membrane Download PDFInfo
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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Abstract
The invention provides a preparation method of a self-flame-retardant co-extruded unidirectional stretching microporous membrane, which comprises the following steps: A) respectively melt-extruding polyphenylene sulfide and polypropylene or polypropylene mixed resin containing polypropylene copolymer by adopting 3 extrusion casting machines, and carrying out casting through a multilayer neck ring die to obtain a multilayer composite casting film; wherein, the polyphenylene sulfide is positioned at the outer layer, and the polypropylene or polypropylene mixed resin containing polypropylene copolymer is positioned at the middle layer; B) carrying out heat treatment on the multilayer composite casting film for 8-20 h at 100-150 ℃ to obtain a multilayer heat treatment film; C) carrying out first-stage stretching on the multilayer heat-treated film at 80 ℃, wherein the stretching ratio is 3-20%; D) performing second-stage stretching on the multilayer heat-treated film at 130-140 ℃, wherein the stretching magnification is 100% -120%; E) and (3) setting the microporous membrane obtained after the second-stage stretching at 140-145 ℃ for 3-4 min, and then carrying out thermal shock setting at 240 ℃ for 5-8 s to obtain the microporous membrane.
Description
Technical Field
The invention relates to the technical field of production of isolating membranes, in particular to a preparation method of a self-flame-retardant co-extruded unidirectional stretching microporous membrane and the microporous membrane.
Background
The diaphragm is a core component of the lithium ion battery, which accounts for about 18-30% of the cost of the whole lithium battery, the performance of the diaphragm plays a crucial role in the overall performance of the lithium battery, the rapid charging technology and the cycle performance requirement of the battery under high rate are increasingly improved along with the development of the power battery, the danger of battery explosion and the like caused by self-heating of the battery is increasingly prominent, and the high-temperature-resistant and high-safety lithium battery diaphragm becomes an urgent need in the industry.
At present, the lithium ion battery isolating membrane is mainly made of crystalline polyolefin materials such as Polyethylene (PE), polypropylene (PP) and the like, is limited by the material performance of the polyolefin material, the membrane breaking temperature of the membrane does not exceed 180 ℃, and the dimensional stability of the polyolefin microporous membrane can not be maintained at high temperature. The safety of the separator can be improved by adopting a multi-layer coextrusion or coating method.
For example, the PP/PE/PP three-layer composite separator developed by Celgard corporation can maintain the safety of the battery to some extent by providing a large difference between the cell closing temperature and the membrane rupture temperature, but the main materials are still polypropylene and polyethylene, the heat resistance of the separator is not improved, and the safety of the battery is still limited.
The coating method is to coat an inorganic layer on the surface of the polyolefin diaphragm, and the inorganic layer is utilized to improve the dimensional stability of the polyolefin diaphragm of the core layer at high temperature and improve the safety of the diaphragm, but the thickness of the inorganic layer is only 2-3 microns, and the safety of the polyolefin diaphragm at high temperature under instantaneous thermal shock is still difficult to ensure. Meanwhile, the inorganic powder is bonded on the surface of the diaphragm by using a polymer binder, and can cause the inorganic powder to fall off and dissociate after being soaked in the electrolyte for a long time, so that the influence on the safety of the battery is not clear.
At present, there is a technology for manufacturing a polyolefin porous film by a melt drawing method, but the material characteristics of polyolefin itself cannot satisfy the requirements of a lithium battery separator with high heat resistance. In addition, researches show that the problem of heat resistance can be fundamentally solved by using the semicrystalline high-temperature-resistant material to replace the existing polyolefin material for coextrusion preparation of the composite diaphragm, but due to poor extrusion processing performance of the material, single-layer extrusion is only realized at present, and due to the membrane layer separation and the control of the initial lamellar structure caused by the interlayer shearing of different melts, the preparation of the multilayer microporous diaphragm by using the semicrystalline high-temperature-resistant material is not reported at present.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a method for preparing a self-flame-retardant co-extruded unidirectional stretching microporous membrane and a microporous membrane, wherein the prepared microporous membrane has uniform pore size and good heat resistance.
The invention provides a preparation method of a self-flame-retardant co-extruded unidirectional stretching microporous membrane, which comprises the following steps:
A) respectively melt-extruding polyphenylene sulfide and polypropylene or polypropylene mixed resin containing polypropylene copolymer by adopting 3 extrusion casting machines, and carrying out casting through a multilayer neck ring die to obtain a multilayer composite casting film; wherein, the polyphenylene sulfide is positioned at the outer layer, and the polypropylene or polypropylene mixed resin containing polypropylene copolymer is positioned at the middle layer;
B) carrying out heat treatment on the multilayer composite casting film for 8-20 h at 100-150 ℃ to obtain a multilayer heat treatment film;
C) carrying out first-stage stretching on the multilayer heat-treated film at 80 ℃, wherein the stretching ratio is 3-20%;
D) performing second-stage stretching on the multilayer heat-treated film at 130-140 ℃, wherein the stretching magnification is 100% -120%;
E) and (3) setting the microporous membrane obtained after the second-stage stretching at 140-145 ℃ for 3-4 min, and then carrying out thermal shock setting at 240 ℃ for 5-8 s to obtain the microporous membrane.
Firstly, respectively melting and extruding polyphenylene sulfide and polypropylene or polypropylene mixed resin containing polypropylene copolymer by adopting 3 extrusion casting machines, and carrying out casting through a multilayer die to obtain a multilayer composite casting film, wherein the multilayer composite casting film is of a 3-layer structure, the upper layer and the lower layer are polyphenylene sulfide, and the middle layer is polypropylene or polypropylene mixed resin containing polypropylene copolymer.
The adopted polyphenylene sulfide is preferably homopolymerized polyphenylene sulfide resin, and the melt index is 3-12 g/10 min.
The adopted polypropylene is preferably homopolymerized polypropylene, and the melt index is 1-5 g/10 min.
In the adopted polypropylene mixed resin containing the polypropylene copolymer, the polypropylene is preferably homopolymerized polypropylene, the melt index is 1-5 g/10min, the polypropylene copolymer is preferably a random copolymer of propylene and any one or more of ethylene, butene, pentene, hexene, heptene, octene and nonene, the molecular weight of the copolymer is 9000-40000 Da, and the content of the polypropylene copolymer in the mixed resin is preferably 5-20 wt% of the polypropylene.
In 3 extrusion casting machines, the temperature of the tail end of an extruder for extruding polypropylene or polypropylene mixed resin containing polypropylene copolymer is preferably 230-260 ℃; the tail section temperature of an extruder for extruding the polyphenylene sulfide is preferably 280-290 ℃.
The setting of the extrusion temperature is beneficial to fully melting polymers of all layers, has approximate relaxation time during extrusion, and reduces the influence on subsequent stretching pore-forming performance caused by interlayer separation and damage of a crystal structure due to cooling temperature difference and molecular chain relaxation during the reattachment of the three-layer film.
The multilayer die casting is preferably embodied as follows:
and stretching the polyphenylene sulfide and polypropylene or polypropylene mixed resin melt containing polypropylene copolymer between a neck mold and a casting roll, wherein the stretching ratio is 1.5-20, and the temperature of the casting roll is 120 ℃.
The temperature of the multilayer die is preferably 290 ℃.
The polyphenylene sulfide melt and polypropylene or polypropylene mixed resin melt containing polypropylene copolymer are stretched between a die head and a casting roller to form a multilayer composite casting film with a parallel arranged lamellar crystal structure vertical to the extrusion direction.
And then carrying out heat treatment on the obtained multilayer composite casting film at 100-150 ℃ for 8-20 h to obtain the multilayer heat treatment film with a further improved structure.
According to the invention, the multilayer heat treatment film is specifically stretched, so that the lamella and the lamella of the film are separated to generate a porous structure, and finally the composite diaphragm with the porous structure is obtained.
Specifically, the first-stage stretching temperature is preferably 80 ℃, the stretching ratio is preferably 3-20%, and the stretching speed is preferably 5-50 mm/min.
The second stage of stretching preferably has the temperature of 130-140 ℃, the stretching ratio of 100-120% and the stretching speed of 50-150 mm/min.
And finally, carrying out heat setting to obtain the microporous diaphragm.
The heat setting is preferably:
firstly, shaping at 140-145 ℃ for 3-4 min, and then carrying out thermal shock shaping at 240 ℃ for 5-8 s to obtain the microporous diaphragm.
The thermal shock setting is preferably performed in a hot air oven.
The invention also provides the microporous membrane prepared by the preparation method, which is a 3-layer composite membrane of polyphenylene sulfide and polypropylene or polypropylene mixed resin containing polypropylene copolymer, wherein the polyphenylene sulfide is positioned at the outer layer, and the polypropylene or polypropylene mixed resin containing polypropylene copolymer is positioned at the middle layer.
The composite diaphragm is of a 3-layer structure, the polyphenylene sulfide is positioned on the upper layer and the lower layer, and the polypropylene or polypropylene mixed resin containing polypropylene copolymer is positioned in the middle layer.
The porosity of the prepared composite membrane is 40-50%, the pore size distribution is uniform, the average pore size is 800-1000 nm, the pore closing temperature and the membrane breaking temperature are greatly improved, and the composite membrane has good high-temperature resistance. And the diaphragm has flame retardance, and the safety of the battery is greatly improved.
Compared with the prior art, the invention provides a preparation method of a self-flame-retardant co-extruded unidirectional stretching microporous membrane, which comprises the following steps: A) respectively melt-extruding polyphenylene sulfide and polypropylene or polypropylene mixed resin containing polypropylene copolymer by adopting 3 extrusion casting machines, and carrying out casting through a multilayer neck ring die to obtain a multilayer composite casting film; wherein, the polyphenylene sulfide is positioned at the outer layer, and the polypropylene or polypropylene mixed resin containing polypropylene copolymer is positioned at the middle layer; B) carrying out heat treatment on the multilayer composite casting film for 8-20 h at 100-150 ℃ to obtain a multilayer heat treatment film; C) carrying out first-stage stretching on the multilayer heat-treated film at 80 ℃, wherein the stretching ratio is 3-20%; D) performing second-stage stretching on the multilayer heat-treated film at 130-140 ℃, wherein the stretching magnification is 100% -120%; E) and (3) setting the microporous membrane obtained after the second-stage stretching at 140-145 ℃ for 3-4 min, and then carrying out thermal shock setting at 240 ℃ for 5-8 s to obtain the microporous membrane. According to the invention, the pore size distribution can be effectively controlled by adjusting the stretching process parameters, the air permeability of the diaphragm is adjusted, and the microporous diaphragm with uniform structure, high temperature resistance and self-flame retardance is finally obtained. In addition, the extrusion casting-melt stretching method does not need to add any auxiliary agent, pore-forming agent and solvent in the production process, avoids the problem of recycling and environmental protection of wet film-making solvent and extractant, has simple process and good continuity, and is beneficial to the control of pore structure.
Drawings
FIG. 1 is a flow chart of a method for making a self-flame retardant co-extruded uniaxially stretched microporous membrane provided in the present invention.
Detailed Description
In order to further illustrate the present invention, the following examples are provided to describe in detail the preparation method of the self-flame-retardant co-extruded uniaxially stretched microporous membrane and the microporous membrane provided by the present invention.
Example 1
And respectively adding 3g/10min fused polyphenylene sulfide and 1g/10min fused polypropylene into different extruders, co-extruding by using a multilayer die head, wherein the temperatures of the polyphenylene sulfide layer and the polypropylene laminar flow calendar at the tail sections are respectively 280 ℃ and 230 ℃, the temperature of the die head is 290 ℃, the temperature of a casting roll is 120 ℃, and the melt stretching ratio is 1.5, and casting to obtain the three-layer polyphenylene sulfide/polypropylene/polyphenylene sulfide composite casting film. Heat treatment is carried out for 8h at 100 ℃. The first stage stretching was carried out at 80 ℃ at a stretching rate of 5mm/min and a stretching ratio of 3%, and the second stage stretching was carried out at 130 ℃ at a stretching rate of 50mm/min and a stretching ratio of 100%. The heat setting temperature is 140 ℃, the heat setting time is 3min, three layers of polyphenylene sulfide/polypropylene/polyphenylene sulfide microporous membranes are obtained by heat shock for 5 seconds in a hot air furnace at 240 ℃, the sample porosity is 42%, the average pore diameter is 850nm, and the shrinkage rate is 12% after standing for 1 minute at 280 ℃.
Example 2
Respectively adding polyphenylene sulfide with a melt index of 12g/10min, polypropylene with a melt index of 5g/10min and propylene and ethylene random copolymer which account for 5 mass percent of the polypropylene and have a molecular weight of 9000Da into different extruders, co-extruding through a multilayer die head, and casting to obtain a three-layer polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide composite cast film, wherein the final-stage temperatures of a polyphenylene sulfide layer and a polypropylene layer flow casting machine are 290 ℃ and 260 ℃, the die head temperature is 290 ℃, the casting roll temperature is 120 ℃, and the melt stretching ratio is 20. Heat treatment at 150 deg.C for 20 h. The first stage stretching was carried out at 80 ℃ at a stretching rate of 50mm/min and a stretching ratio of 20%, and the second stage stretching was carried out at 140 ℃ at a stretching rate of 150mm/min and a stretching ratio of 110%. The heat setting temperature is 145 ℃, the heat setting time is 4min, three layers of polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide microporous membranes are obtained by heat shock for 8 seconds in a hot air furnace at 240 ℃, the sample porosity is 48%, the average pore diameter is 800nm, and the shrinkage rate is 10% after standing for 1 minute at 280 ℃.
Example 3
Respectively adding polyphenylene sulfide with a melt index of 5g/10min, polypropylene with a melt index of 3g/10min and propylene and butylene random copolymer which account for 20 mass percent of the polypropylene and have a molecular weight of 40000Da into different extruders, co-extruding through a multilayer die head, wherein the temperatures of the polyphenylene sulfide layer and the tail section of a polypropylene laminar flow calendar are respectively 280 ℃ and 260 ℃, the temperature of the die head is 290 ℃, the temperature of a casting roll is 120 ℃, the melt stretching ratio is 4, and casting to obtain a three-layer polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide composite casting film. Heat treatment is carried out for 12h at 110 ℃. The first stage stretching was carried out at 80 ℃ at a stretching rate of 50mm/min at a stretching ratio of 10%, and the second stage stretching was carried out at 130 ℃ at a stretching rate of 50mm/min at a stretching ratio of 100%. The heat setting temperature is 140 ℃, the heat setting time is 3min, three layers of polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide microporous membranes are obtained by heat shock for 5 s in a hot air furnace at 240 ℃, the sample porosity is 48%, the average pore diameter is 800nm, and the shrinkage rate is 13% after standing for 1 min at 280 ℃.
Example 4
Respectively adding 8g/10min polyphenylene sulfide, 4g/10min polypropylene and 30000Da molecular weight propylene and pentene random copolymer which account for 10 mass percent of polypropylene into different extruders, co-extruding through a multilayer die head, wherein the temperatures of the polyphenylene sulfide layer and the polypropylene layer flow calendar at the end sections are respectively 280 ℃ and 230 ℃, the temperature of the die head is 290 ℃, the temperature of a casting roll is 120 ℃, the melt stretching ratio is 8, and casting to obtain a three-layer polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide composite casting film. Heat treatment is carried out for 8h at 110 ℃. The first stage stretching was carried out at 80 ℃ at a stretching rate of 20mm/min and a stretching ratio of 14%, and the second stage stretching was carried out at 130 ℃ at a stretching rate of 50mm/min and a stretching ratio of 100%. The heat setting temperature is 140 ℃, the heat setting time is 3min, three layers of polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide microporous membranes are obtained by heat shock for 5 s in a hot air furnace at 240 ℃, the sample porosity is 46%, the average pore diameter is 900nm, and the shrinkage rate is 12% after standing for 1 min at 280 ℃.
Example 5
Respectively adding polyphenylene sulfide with a melt index of 6g/10min, polypropylene with a melt index of 2g/10min and propylene and hexene random copolymer which accounts for 6 mass percent of the polypropylene and has a molecular weight of 20000Da into different extruders, co-extruding through a multi-layer die head, wherein the temperatures of the polyphenylene sulfide layer and the tail section of a polypropylene laminar flow calendar are respectively 280 ℃ and 230 ℃, the temperature of the die head is 290 ℃, the temperature of a casting roll is 120 ℃, and the melt stretching ratio is 14, and casting to obtain a three-layer polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide composite casting film. Heat treatment is carried out for 8h at 110 ℃. The first stage stretching was carried out at 80 ℃ at a stretching rate of 15mm/min and a stretching ratio of 10%, and the second stage stretching was carried out at 130 ℃ at a stretching rate of 50mm/min and a stretching ratio of 100%. The heat setting temperature is 140 ℃, the heat setting time is 3min, three layers of polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide microporous membranes are obtained by heat shock for 5 s in a hot air furnace at 240 ℃, the sample porosity is 41%, the average pore diameter is 850nm, and the shrinkage rate is 10% after standing for 1 min at 280 ℃.
Example 6
Respectively adding polyphenylene sulfide with a melt index of 10g/10min, polypropylene with a melt index of 2g/10min and propylene and heptene random copolymer which account for 12 mass percent of the polypropylene and have a molecular weight of 8000Da into different extruders, co-extruding through a multilayer die head, wherein the temperatures of the polyphenylene sulfide layer and the tail section of a polypropylene laminar flow calendar are respectively 280 ℃ and 230 ℃, the temperature of the die head is 290 ℃, the temperature of a casting roll is 120 ℃, and the melt stretching ratio is 2, and casting to obtain a three-layer polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide composite casting film. Heat treatment is carried out for 8h at 110 ℃. The first stage stretching was carried out at 80 ℃ at a stretching rate of 15mm/min and a stretching ratio of 16%, and the second stage stretching was carried out at 130 ℃ at a stretching rate of 50mm/min and a stretching ratio of 100%. The heat setting temperature is 140 ℃, the heat setting time is 3min, three layers of polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide microporous membranes are obtained by heat shock for 5 s in a hot air furnace at 240 ℃, the sample porosity is 44%, the average pore diameter is 800nm, and the shrinkage rate is 13% after standing for 1 min at 280 ℃.
Example 7
Respectively adding 3g/10min polyphenylene sulfide, 2g/10min polypropylene and 14000Da molecular weight propylene and octene random copolymer into different extruders, co-extruding through a multilayer die head, wherein the temperatures of the polyphenylene sulfide layer and the polypropylene layer flow calendar at the end sections are respectively 280 ℃ and 230 ℃, the temperature of the die head is 290 ℃, the temperature of a casting roll is 120 ℃, and the melt stretching ratio is 2, and casting to obtain a three-layer polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide composite casting film. Heat treatment is carried out for 8h at 110 ℃. The first stage stretching was carried out at 80 ℃ at a stretching rate of 5mm/min and a stretching ratio of 6%, and the second stage stretching was carried out at 130 ℃ at a stretching rate of 50mm/min and a stretching ratio of 100%. The heat setting temperature is 140 ℃, the heat setting time is 3min, three layers of polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide microporous membranes are obtained by heat shock for 5 s in a hot air furnace at 240 ℃, the sample porosity is 48%, the average pore diameter is 1000nm, and the shrinkage rate is 12% after standing for 1 min at 280 ℃.
Example 8
Respectively adding polyphenylene sulfide with a melt index of 12g/10min, polypropylene with a melt index of 5g/10min and propylene and nonene random copolymer which account for 18 mass percent of the polypropylene and have a molecular weight of 24000Da into different extruders, co-extruding through a multilayer die head, and casting to obtain a three-layer polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide composite cast film, wherein the final-stage temperatures of a polyphenylene sulfide layer and a polypropylene layer casting machine are 280 ℃ and 230 ℃, the die head temperature is 290 ℃, the casting roll temperature is 120 ℃, and the melt stretching ratio is 2. Heat treatment is carried out for 8h at 110 ℃. The first stage stretching was carried out at 80 ℃ at a stretching rate of 5mm/min and a stretching ratio of 6%, and the second stage stretching was carried out at 130 ℃ at a stretching rate of 50mm/min and a stretching ratio of 100%. The heat setting temperature is 140 ℃, the heat setting time is 3min, three layers of polyphenylene sulfide/polypropylene mixture/polyphenylene sulfide microporous membranes are obtained by heat shock for 5 s in a hot air furnace at 240 ℃, the sample porosity is 41%, the average pore diameter is 900nm, and the shrinkage rate is 8% after standing for 1 min at 280 ℃.
From the above examples, it is clear that the microporous separator prepared by the present invention has uniform pore size and good heat resistance.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (3)
1. A preparation method of a self-flame-retardant co-extruded unidirectional stretching microporous membrane is characterized by comprising the following steps:
A) respectively melt-extruding polyphenylene sulfide and polypropylene or polypropylene mixed resin containing polypropylene copolymer by adopting 3 extrusion casting machines, and carrying out casting through a multilayer neck ring die to obtain a multilayer composite casting film; wherein, the polyphenylene sulfide is positioned at the outer layer, and the polypropylene or polypropylene mixed resin containing polypropylene copolymer is positioned at the middle layer; the polyphenylene sulfide is homopolymerized polyphenylene sulfide resin, and the melt index is 3-12 g/10 min; the polypropylene is homopolymerized polypropylene, and the melt index is 1-5 g/10 min; in the polypropylene mixed resin containing the polypropylene copolymer, polypropylene is homopolymerized polypropylene, and the melt index is 1-5 g/10 min;
in the 3 extrusion casting machines, the temperature of the tail end of an extruder for extruding polypropylene or polypropylene mixed resin containing polypropylene copolymer is 230-260 ℃, and the temperature of the tail end of an extruder for extruding polyphenylene sulfide is 280-290 ℃;
the multilayer neck ring die casting specifically comprises the following steps:
stretching a polyphenylene sulfide and polypropylene or polypropylene mixed resin melt containing a polypropylene copolymer between a neck mold and a casting roll, wherein the stretching ratio is 1.5-20, and the temperature of the casting roll is 120 ℃;
the temperature of the multilayer neck mold is 290 ℃;
B) carrying out heat treatment on the multilayer composite casting film for 8-20 h at 100-150 ℃ to obtain a multilayer heat treatment film;
C) carrying out first-stage stretching on the multilayer heat-treated film at 80 ℃, wherein the stretching ratio is 3-20%; the stretching speed is 5-50 mm/min;
D) performing second-stage stretching on the multilayer heat-treated film at 130-140 ℃, wherein the stretching magnification is 100% -120%; the stretching speed is 50-150 mm/min;
E) and (3) setting the microporous membrane obtained after the second-stage stretching at 140-145 ℃ for 3-4 min, and then carrying out thermal shock setting at 240 ℃ for 5-8 s to obtain the microporous membrane.
2. The preparation method of claim 1, wherein the polypropylene copolymer is a random copolymer of propylene and one or more selected from ethylene, butene, pentene, hexene, heptene, octene and nonene, the molecular weight of the copolymer is 9000 to 40000Da, and the polypropylene copolymer is 5 to 20 wt% of polypropylene in the mixed resin.
3. The microporous membrane prepared by the preparation method of any one of claims 1 to 2 is a 3-layer composite membrane of polyphenylene sulfide and polypropylene or polypropylene mixed resin containing polypropylene copolymer, wherein the polyphenylene sulfide is positioned at the outer layer, and the polypropylene or polypropylene mixed resin containing polypropylene copolymer is positioned at the middle layer.
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| CN112310557B (en) * | 2020-11-03 | 2022-12-23 | 天津工业大学 | Preparation method of polyphenylene sulfide-based diaphragm based on viscous flow modification technology |
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