CN116345062A - Preparation method of wet-process PA/PE/PA three-layer lithium battery diaphragm - Google Patents
Preparation method of wet-process PA/PE/PA three-layer lithium battery diaphragm Download PDFInfo
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 239000004952 Polyamide Substances 0.000 claims abstract description 64
- 229920002647 polyamide Polymers 0.000 claims abstract description 64
- 238000001816 cooling Methods 0.000 claims abstract description 57
- 239000004698 Polyethylene Substances 0.000 claims abstract description 50
- 229920000573 polyethylene Polymers 0.000 claims abstract description 48
- 238000001125 extrusion Methods 0.000 claims abstract description 36
- 239000002994 raw material Substances 0.000 claims abstract description 34
- 238000007493 shaping process Methods 0.000 claims abstract description 33
- 238000001035 drying Methods 0.000 claims abstract description 26
- 238000002156 mixing Methods 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 14
- 239000012745 toughening agent Substances 0.000 claims abstract description 13
- -1 polyethylene Polymers 0.000 claims abstract description 7
- 238000000605 extraction Methods 0.000 claims description 11
- 239000012982 microporous membrane Substances 0.000 claims description 7
- 238000005096 rolling process Methods 0.000 claims description 7
- 238000009998 heat setting Methods 0.000 claims description 6
- 239000012528 membrane Substances 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 3
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 2
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical group O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 abstract description 20
- 239000010410 layer Substances 0.000 description 62
- 239000000463 material Substances 0.000 description 14
- 238000012545 processing Methods 0.000 description 14
- 239000007788 liquid Substances 0.000 description 11
- 238000002844 melting Methods 0.000 description 6
- 230000008018 melting Effects 0.000 description 6
- 238000007664 blowing Methods 0.000 description 5
- 238000005266 casting Methods 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
- 238000002791 soaking Methods 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 239000002131 composite material Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 238000011282 treatment Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 238000004880 explosion Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000009472 formulation Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000002145 thermally induced phase separation Methods 0.000 description 1
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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
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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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
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
- H01M50/406—Moulding; Embossing; Cutting
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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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
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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
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a preparation method of a wet PA/PE/PA three-layer lithium battery diaphragm, which comprises the following steps: blending polyamide, a compatilizer and a toughening agent to obtain a raw material (1); carrying out melt extrusion on the raw material (1), polyethylene and white oil to obtain a three-layer co-extrusion film; the front surface of the three-layer co-extrusion film is cooled and shaped by a cooling roller, and the back surface of the three-layer co-extrusion film is cooled and shaped by an air cooling roller; preheating the three-layer co-extrusion film after cooling and shaping, and carrying out low-rate longitudinal stretching on the three-layer co-extrusion film by a control roller; the preheated diaphragm is heated by up-and-down blast and transversely stretched, so that the diaphragm is ensured not to be broken and has uniform thickness in the stretching process; heating the diaphragm by up-down blast, longitudinally stretching, and controlling the thickness of the diaphragm to be 3-50 um; extracting the diaphragm by using methylene dichloride to extract white oil, so as to obtain a microporous diaphragm with uniform texture; drying the microporous diaphragm at a low temperature; and drying the diaphragm at high temperature, and transversely stretching at a small multiplying power to improve the thermal deformation temperature of the diaphragm, thereby obtaining the PA/PE/PA three-layer lithium battery diaphragm.
Description
Technical Field
The invention belongs to the technical field of lithium battery diaphragms, and particularly relates to a preparation method of a wet PA/PE/PA three-layer lithium battery diaphragm.
Background
The structure of the current lithium battery mainly comprises five parts, namely a positive electrode, a diaphragm, a negative electrode, an electrolyte and a shell, wherein the diaphragm is an important component part in the lithium battery and occupies more than 30% of the total battery cost. In addition, the performance of the current lithium battery diaphragm can directly influence the characteristics of battery charging efficiency, battery cycle times, battery safety and the like, so that the lithium battery diaphragm plays an important role in improving the comprehensive performance of the battery. The diaphragm exists between the anode and the cathode, which can not only prevent the anode from being in short circuit caused by direct contact with the electrolyte, but also realize the circulation of electrons in the electrolyte through micropores of the diaphragm, thereby ensuring the safety and the high efficiency of the charge and the discharge of the lithium battery.
The lithium battery diaphragm in the current market is widely applied to new energy automobiles, energy storage power stations, digital electronic products, aviation, medical treatment and the like, faces the innovation situation of more complex use environments and faster charge and discharge speeds, and faces huge tests in the aspects of safety and charge and discharge efficiency. The battery temperature can rise fast in the process of fast charging and discharging of the lithium battery, the thermal shrinkage rate of the diaphragm is higher in the environment with higher temperature, the dimensional deviation of the diaphragm of the battery is larger, and the positive electrode and the negative electrode are in direct contact to cause the risk of short circuit. And the PE material is a nonpolar material and has relatively high resistance due to relatively poor wettability with electrolyte, so that the charge and discharge speed of the lithium battery is influenced. The existing wet lithium battery diaphragm mainly uses PE material as a base material, the melting point range of the PE material is basically 110-145 ℃, thermal runaway is possibly caused during overcharge or abuse, and in the process of rapidly increasing the temperature, the diaphragm generates thermal shrinkage phenomenon to cause large-area contact of positive poles and negative poles, so that short circuit and even explosion are caused. Compared with PA (melting point 200-330 ℃) material, the melting point of the PA material is lower, so the PA has obviously better temperature resistance than PE and higher safety.
And when the PA/PE composite membrane is prepared, dry preparation is adopted, and pore-forming agents are added to enable each layer of the composite membrane to form corresponding pore diameters, but the preparation cost is increased. The reason why the PA/PE composite film cannot be prepared by adopting the wet method in the prior art is that the problems of uneven pore diameter and unstable porosity caused by extraction can occur due to different materials of multiple layers during the multilayer extrusion of the wet method.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of a wet PA/PE/PA three-layer lithium battery diaphragm.
A preparation method of a wet PA/PE/PA three-layer lithium battery diaphragm comprises the following steps:
(1) Mixing: blending Polyamide (PA), a compatilizer and a toughening agent to obtain a raw material (1);
(2) Extrusion: carrying out melt extrusion on the raw material (1), polyethylene (PE) and white oil prepared in the step (1) to obtain a three-layer co-extrusion film by using extrusion equipment comprising two sets of double screws and a three-layer co-extrusion die head;
(3) Cooling and shaping: the front surface of the three-layer co-extrusion film obtained in the step (2) is cooled and shaped by a cooling roller, and the back surface is cooled and shaped by an air cooling and cooling roller;
(4) Low power machine direction stretching: the three-layer co-extruded film obtained in the step (3) after cooling and shaping passes through 10-15 groups of traction rollers, the temperature of the traction rollers is set to be 100-160 ℃ for preheating, and the control rollers are used for carrying out low-rate longitudinal stretching on the three-layer co-extruded film;
(5) And (3) transversely stretching: carrying out up-down blast heating on the membrane preheated in the step (4) to transversely stretch, so as to ensure that the membrane is not broken and has uniform thickness in the stretching process;
(6) Stretching in the longitudinal direction: heating the diaphragm prepared in the step (5) by up-and-down blast, and longitudinally stretching the diaphragm, wherein the thickness of the diaphragm is controlled to be 3-50 mu m;
(7) And (3) extracting and pore-forming: extracting the diaphragm by adopting an extracting agent to extract white oil, so as to obtain a microporous diaphragm with uniform texture;
(8) And (3) drying: drying the microporous membrane obtained in the step (7) at a low temperature;
(9) And (5) heat setting: and (3) drying the diaphragm obtained in the step (8) at high temperature, and performing small-magnification transverse stretching to improve the thermal deformation temperature of the diaphragm, thereby obtaining the PA/PE/PA three-layer lithium battery diaphragm.
Further, the compatibilizer is selected from PE1040 maleic anhydride grafted compatibilizer particles;
the toughening agent is a PA and PE general acrylic acid ternary co-clustering toughening agent;
preferably, the polyamide of step (1) is selected from PA6 (solids content 4-30%); the toughening agent is selected from the group consisting of AX8900, brillouin M724, exxon VA1803 and DuPont N493.
Further, the molecular weight of the Polyethylene (PE) in the step (2) is 50-500 ten thousand (the solid content is 4-30%); the white oil is selected from industrial grade above white oil; preferably, the polyethylene of step (2) is selected from UHPE or GUR1020; the white oil is selected from the group consisting of # 10, # 15, # 26, # 32, # 46, # 68, # 90 and # 100 white oil.
Through the selection of the types of PA and PE, the outer layer PA of the PA/PE/PA three-layer lithium battery diaphragm has high solid content, and the inner layer PE has low solid content; under the same multiplying power stretching condition, the solid content of the two materials is controlled, so that the porosity of the outer layer PA is 30-40%, and the porosity of the inner layer PE is 45-55%. The pore structure is beneficial to improving the liquid absorption rate of the diaphragm, reducing the internal resistance of the diaphragm and ensuring that the diaphragm cannot be short-circuited.
Further, the wet PA/PE/PA three-layer lithium battery diaphragm comprises the following raw materials in percentage by weight:
further, the extrusion equipment comprising two sets of double screws in the step (2) comprises a screw (1) and a screw (2), the rotating speeds of the screw (1) and the screw (2) are 300r/min, the temperature of the screw (1) is changed within the range of 80-250 ℃, and the temperature of the screw (2) is changed within the range of 70-240 ℃.
Further, the front cooling and shaping temperature of the step (3) is 8-60 ℃, the back air cooling temperature is 15-50 ℃, and the back cooling and shaping temperature is 8-60 ℃.
Further, the temperature of the traction roller in the step (4) is set to be 70-140 ℃, and the low-magnification longitudinal stretching magnification is 1-3 times.
Further, the blast heating temperature in the step (5) is 90-170 ℃, and the transverse stretching multiplying power is 5-14 times.
Further, the blast heating temperature in the step (6) is 90-170 ℃, and the longitudinal stretching multiplying power is 5-14 times.
Further, the extraction time in the step (7) is 15-100 seconds.
Further, the extractant in the step (7) is dichloromethane.
Further, the low-temperature drying temperature in the step (8) is 30-70 ℃ and the drying time is 10-50 seconds.
Further, the high-temperature drying temperature in the step (9) is 110-170 ℃, the drying time is 10-50 seconds, and the multiplying power of small-multiplying power transverse stretching is preferably 1-1.6 times.
Further, the method further comprises the step (10): and (3) slitting and rolling the PA/PE/PA three-layer lithium battery diaphragm obtained in the step (9).
The second purpose of the invention is to provide a PA/PE/PA three-layer lithium battery diaphragm, which is prepared by the preparation method.
The invention has the beneficial effects that
The existing wet lithium battery diaphragm mainly uses PE material as a base material, the melting point range of the PE material is basically 110-145 ℃, thermal runaway is possibly caused during overcharge or abuse, and in the process of rapidly increasing the temperature, the diaphragm generates thermal shrinkage phenomenon to cause large-area contact of positive poles and negative poles, so that short circuit and even explosion are caused. According to the invention, a PA/PE/PA three-layer lithium battery diaphragm structure is introduced, when the lithium battery is heated sharply, the advantage of high temperature resistance of the outer layer PA (melting point 200-330 ℃) is exerted, the outer structure is kept from shrinkage deformation, when the battery temperature exceeds 145 ℃, the inner layer PE exerts the closed pore shutoff characteristic to stop ion exchange, the battery is prevented from continuing electrochemical reaction, the self-ignition and explosion of the battery are effectively prevented, and the safety characteristic of the diaphragm is improved. The polarity of the PA material introduced in the invention is obviously higher than that of the PE material and has better wettability with electrolyte, thus being beneficial to reducing the diaphragm resistance of the lithium battery and improving the charge and discharge efficiency of the lithium battery. The invention does not need surface coating and other post-treatments, and can solve the problems that the coating layer of the traditional PE lithium battery diaphragm post-treatment falls off in use and the service life is reduced.
The PA/PE/PA three-layer co-extrusion structure realizes the improvement of the effect of the PA/PE/PA three-layer lithium battery diaphragm by special process processing, (1) compatibility, control of the blending process of raw materials, guarantee of good compatibility between the PE layer and the PA layer and prevent layering; (2) the processing temperature, the melting point difference of PA and PE is very large, and the processing temperature of two screws and the processing temperature of a die head are reasonably controlled; (3) the cooling and shaping process controls the temperature of the chilled roller, and ensures that the PA layer and the PE layer have good thermally induced phase separation effect; (4) the extraction process improves the extraction efficiency and ensures the extraction to be complete.
Drawings
FIG. 1 is a schematic view of a chill roll apparatus according to the present invention.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments.
It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The raw materials comprise the following components in percentage by weight:
step one: mixing, namely mixing raw materials of PA, a toughening agent and a compatilizer in proportion to obtain a raw material (1);
step two: extrusion processing of the raw materials was accomplished using a processing apparatus having two screws and a three-layer coextrusion die, which was designated as screw (1) and screw (2), respectively. Raw material (1) is added into a bin of a screw (1) of a three-layer co-extrusion casting film double-screw extrusion device, white oil is added into the screw (1) by a liquid injector, UHPE is added into a bin of a screw (2), white oil is added into the screw (2) by the liquid injector, and an extruded diaphragm is of a PA-PE-PA three-layer structure.
Step three: cooling and shaping, namely cooling and shaping the front surface of the three-layer co-extruded film obtained in the second step by using a cooling roller 1# at 28 ℃, and cooling and shaping the back surface by using air cooling dried at 50 ℃ and a cooling roller 2# at 36 ℃;
step four: the three-layer co-extruded film obtained in the third step after cooling and shaping passes through 10 groups of traction rollers at 105 ℃, the temperature of the traction rollers is set to 105 ℃, the control rollers are used for carrying out 1.4-multiplying-power longitudinal stretching on the three-layer co-extruded film, the high-multiplying-power stretching of the diaphragm is preheated in advance, and the compatibility of the three-layer film is improved;
step five: transversely stretching, namely conveying the preheated diaphragm in the step four into a blast oven at 120 ℃ through a guide rail to heat the diaphragm in an up-down blast manner, and fixing two ends of the diaphragm by using a clamp to transversely stretch 7 times, so that the diaphragm is ensured not to be broken and has uniform thickness in the stretching process;
step six: longitudinally stretching, namely conveying the diaphragm prepared in the step five into a longitudinal stretching track through a guide rail, carrying out blowing heating at 125 ℃ on the diaphragm up and down, and controlling the speed ratio to longitudinally stretch the diaphragm by 7 times;
step seven: hole forming by extraction, transferring the diaphragm into a dichloromethane tank through a guide rail, soaking for 30 seconds, and extracting white oil to obtain a microporous diaphragm with uniform texture;
step eight: drying, namely conveying the microporous membrane obtained in the step seven into a blast oven at 50 ℃ through a guide rail to be dried for 40 seconds;
step nine: heat setting, namely conveying the diaphragm obtained in the step eight into a 126 ℃ blast oven through a guide rail for drying for 30 seconds, and transversely stretching at 1.3 multiplying power to improve the thermal deformation temperature of the diaphragm;
step ten: and D, slitting and rolling the diaphragm obtained in the step nine according to the size of the product.
Example 2
The raw materials comprise the following components in percentage by weight:
step one: mixing, namely mixing raw materials of PA, a toughening agent and a compatilizer in proportion to obtain a raw material (1);
step two: extrusion processing of the raw materials was accomplished using a processing apparatus having two screws and a three-layer coextrusion die, which was designated as screw (1) and screw (2), respectively. Raw material (1) is added into a bin of a screw (1) of a three-layer co-extrusion casting film double-screw extrusion device, white oil is added into the screw (1) by a liquid injector, UHPE is added into a bin of a screw (2), white oil is added into the screw (2) by the liquid injector, and an extruded diaphragm is of a PA-PE-PA three-layer structure.
Step three: cooling and shaping, namely cooling and shaping the front surface of the three-layer co-extruded film obtained in the second step by using a cooling roller 1# at 23 ℃, and cooling and shaping the back surface by using air cooling dried at 20 ℃ and a cooling roller 2# at 32 ℃;
step four: the three-layer co-extruded film obtained in the third step after cooling and shaping passes through 10 groups of traction rollers at 105 ℃, the temperature of the traction rollers is set to 105 ℃, the control rollers are used for carrying out 1.4-multiplying-power longitudinal stretching on the three-layer co-extruded film, the high-multiplying-power stretching of the diaphragm is preheated in advance, and the compatibility of the three-layer film is improved;
step five: transversely stretching, namely conveying the preheated diaphragm in the step four into a blast oven at 120 ℃ through a guide rail to heat the diaphragm in an up-down blast manner, and fixing two ends of the diaphragm by using a clamp to transversely stretch 7 times, so that the diaphragm is ensured not to be broken and has uniform thickness in the stretching process;
step six: longitudinally stretching, namely conveying the diaphragm prepared in the step five into a longitudinal stretching track through a guide rail, carrying out blowing heating at 125 ℃ on the diaphragm up and down, and controlling the speed ratio to longitudinally stretch the diaphragm by 7 times;
step seven: hole forming by extraction, transferring the diaphragm into a dichloromethane tank through a guide rail, soaking for 30 seconds, and extracting white oil to obtain a microporous diaphragm with uniform texture;
step eight: drying, namely conveying the microporous membrane obtained in the step seven into a blast oven at 50 ℃ through a guide rail to be dried for 30 seconds;
step nine: heat setting, namely conveying the diaphragm obtained in the step eight into a 126 ℃ blast oven through a guide rail for drying for 20 seconds, and transversely stretching at a multiplying power of 1.3 to improve the thermal deformation temperature of the diaphragm;
step ten: cutting and rolling the diaphragm obtained in the step nine according to the size of the product;
example 3
The raw materials comprise the following components in percentage by weight:
step one: mixing, namely mixing raw materials of PA, a toughening agent and a compatilizer in proportion to obtain a raw material (1);
step two: extrusion processing of the raw materials was accomplished using a processing apparatus having two screws and a three-layer coextrusion die, which was designated as screw (1) and screw (2), respectively. Raw material (1) is added into a bin of a screw (1) of a three-layer co-extrusion casting film double-screw extrusion device, white oil is added into the screw (1) by a liquid injector, UHPE is added into a bin of a screw (2), white oil is added into the screw (2) by the liquid injector, and an extruded diaphragm is of a PA-PE-PA three-layer structure.
Step three: cooling and shaping, namely cooling and shaping the front surface of the three-layer co-extruded film obtained in the second step by using a 21 ℃ cooling roller 1#, and cooling and shaping the back surface by using 40 ℃ drying air cooling and a 30 ℃ cooling roller 2#;
step four: the three-layer co-extruded film obtained in the third step after cooling and shaping passes through 10 groups of traction rollers, the temperature of the traction rollers is set to 120 ℃, the control rollers perform 1.4-multiplying-power longitudinal stretching on the three-layer co-extruded film, the high-multiplying-power stretching of the diaphragm is preheated in advance, and the compatibility of the three-layer film is improved;
step five: transversely stretching, namely conveying the preheated diaphragm in the step four into a blast oven at 120 ℃ through a guide rail to heat the diaphragm in an up-down blast manner, and fixing two ends of the diaphragm by using a clamp to transversely stretch 7 times, so that the diaphragm is ensured not to be broken and has uniform thickness in the stretching process;
step six: longitudinally stretching, namely conveying the diaphragm prepared in the step five into a longitudinal stretching track through a guide rail, carrying out blowing heating at 125 ℃ on the diaphragm up and down, and controlling the speed ratio to longitudinally stretch the diaphragm by 7 times;
step seven: hole forming by extraction, transferring the diaphragm into a dichloromethane tank through a guide rail, soaking for 40 seconds, and extracting white oil to obtain a microporous diaphragm with uniform texture;
step eight: drying, namely conveying the microporous membrane obtained in the step seven into a blast oven at 50 ℃ through a guide rail to be dried for 35 seconds;
step nine: heat setting, namely conveying the diaphragm obtained in the step eight into a 126 ℃ blast oven through a guide rail for drying for 25 seconds, and transversely stretching at 1.3 multiplying power to improve the thermal deformation temperature of the diaphragm;
step ten: cutting and rolling the diaphragm obtained in the step nine according to the size of the product;
example 4
The raw materials comprise the following components in percentage by weight:
step one: mixing, namely mixing raw materials of PA, a toughening agent and a compatilizer in proportion to obtain a raw material (1);
step two: extrusion processing of the raw materials was accomplished using a processing apparatus having two screws and a three-layer coextrusion die, which was designated as screw (1) and screw (2), respectively. Raw material (1) is added into a bin of a screw (1) of a three-layer co-extrusion casting film double-screw extrusion device, white oil is added into the screw (1) by a liquid injector, UHPE is added into a bin of a screw (2), white oil is added into the screw (2) by the liquid injector, and an extruded diaphragm is of a PA-PE-PA three-layer structure.
Step three: cooling and shaping, namely cooling and shaping the front surface of the three-layer co-extruded film obtained in the second step by using a cooling roller 1# at the temperature of 28 ℃, and cooling and shaping the back surface by using air cooling dried at the temperature of 25 ℃ and a cooling roller 2# at the temperature of 36 ℃;
step four: the three-layer co-extruded film obtained in the third step after cooling and shaping passes through 10 groups of traction rollers, the temperature of the traction rollers is set to 120 ℃, the control rollers perform 1.4-multiplying-power longitudinal stretching on the three-layer co-extruded film, the high-multiplying-power stretching of the diaphragm is preheated in advance, and the compatibility of the three-layer film is improved;
step five: transversely stretching, namely conveying the preheated diaphragm in the step four into a blast oven at 120 ℃ through a guide rail to heat the diaphragm in an up-down blast manner, and fixing two ends of the diaphragm by using a clamp to transversely stretch 7 times, so that the diaphragm is ensured not to be broken and has uniform thickness in the stretching process;
step six: longitudinally stretching, namely conveying the diaphragm prepared in the step five into a longitudinal stretching track through a guide rail, carrying out blowing heating at 125 ℃ on the diaphragm up and down, and controlling the speed ratio to longitudinally stretch the diaphragm by 7 times;
step seven: hole forming by extraction, transferring the diaphragm into a dichloromethane tank through a guide rail, soaking for 30 seconds, and extracting white oil to obtain a microporous diaphragm with uniform texture;
step eight: drying, namely conveying the microporous membrane obtained in the step seven into a blast oven at 50 ℃ through a guide rail to be dried for 40 seconds;
step nine: heat setting, namely conveying the diaphragm obtained in the step eight into a 126 ℃ blast oven through a guide rail for drying for 30 seconds, and transversely stretching at 1.4 multiplying power to improve the thermal deformation temperature of the diaphragm;
step ten: cutting and rolling the diaphragm obtained in the step nine according to the size of the product;
comparative example 1
The raw materials comprise the following components in percentage by weight:
step one: mixing, namely mixing raw materials of PA, a toughening agent and a compatilizer in proportion to obtain a raw material (1);
step two: extrusion processing of the raw materials was accomplished using a processing apparatus having two screws and a three-layer coextrusion die, which was designated as screw (1) and screw (2), respectively. Raw material (1) is added into a bin of a screw (1) of a three-layer coextrusion casting film double-screw extrusion device, white oil is added into the screw (1) by using a liquid injector, UHPE is added into a bin of a screw (2), and white oil is added into the screw (2) by using the liquid injector.
Step three: cooling and shaping, namely cooling and shaping the front surface of the three-layer co-extruded film obtained in the second step by using a cooling roller 1# at the temperature of 28 ℃, and cooling and shaping the back surface by using air cooling dried at the temperature of 25 ℃ and a cooling roller 2# at the temperature of 36 ℃;
step four: the three-layer co-extruded film obtained in the third step after cooling and shaping passes through 10 groups of traction rollers, the temperature of the traction rollers is set to 120 ℃, the control rollers perform 1.4-multiplying-power longitudinal stretching on the three-layer co-extruded film, the high-multiplying-power stretching of the diaphragm is preheated in advance, and the compatibility of the three-layer film is improved;
step five: transversely stretching, namely conveying the preheated diaphragm in the step four into a blast oven at 120 ℃ through a guide rail to heat the diaphragm in an up-down blast manner, and fixing two ends of the diaphragm by using a clamp to transversely stretch 7 times, so that the diaphragm is ensured not to be broken and has uniform thickness in the stretching process;
step six: longitudinally stretching, namely conveying the diaphragm prepared in the step five into a longitudinal stretching track through a guide rail, carrying out blowing heating at 125 ℃ on the diaphragm up and down, and controlling the speed ratio to longitudinally stretch the diaphragm by 7 times;
step seven: hole forming by extraction, transferring the diaphragm into a dichloromethane tank through a guide rail, soaking for 30 seconds, and extracting white oil to obtain a microporous diaphragm with uniform texture;
step eight: drying, namely conveying the microporous membrane obtained in the step seven into a blast oven at 50 ℃ through a guide rail to be dried for 40 seconds;
step nine: slitting and rolling the diaphragm obtained in the step eight according to the size of the product;
example Performance test
According to the following table 1, the wet PA/PE/PA composite lithium battery separator was prepared by pretreating and adding the 5 groups of formulations in the above examples according to the process, the performance test results are shown in table 2, wherein examples 1 to 4 all meet the performance requirements, and the proportion of comparative example 1 is the same as that of example 4 but the process step lacks the process treatment of transverse drawing shaping, and the output results do not meet the performance requirements.
Table 1 application example formulation and process
| Examples numbering | Example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 |
| GUR1020 powder | 8％ | 14％ | 13％ | 11％ | 11％ |
| PA6-P027 | 10％ | / | / | / | / |
| PA6-LX275 | / | 7％ | / | / | / |
| PA6-CM1017 | / | / | 8％ | / | / |
| PA6-CM1026 | / | / | / | 9％ | 9％ |
| PE1040 | 2％ | 1％ | 1％ | 1％ | 1 |
| AX8900 | |||||
| 3％ | / | / | / | / | |
| Dupont N493 | / | 1％ | / | / | / |
| Exxon VA1803 | / | / | 1％ | 2％ | 2％ |
| White oil 68 #) | 77％ | 77％ | 77％ | 77％ | 77％ |
| White oil 46 #) | / | / | / | / | / |
Table 2 test results of examples
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (14)
1. The preparation method of the wet-process PA/PE/PA three-layer lithium battery diaphragm is characterized by comprising the following steps:
(1) Mixing: blending Polyamide (PA), a compatilizer and a toughening agent to obtain a raw material (1);
(2) Extrusion: carrying out melt extrusion on the raw material (1), polyethylene (PE) and white oil prepared in the step (1) to obtain a three-layer co-extrusion film by using extrusion equipment comprising two sets of double screws and a three-layer co-extrusion die head;
(3) Cooling and shaping: cooling and shaping the front side cooling roller of the three-layer co-extruded film obtained in the step (2), and cooling and shaping the back side by using an air cooling and cooling roller;
(4) Low power machine direction stretching: the three-layer co-extruded film obtained in the step (3) after cooling and shaping passes through 10-15 groups of traction rollers, the temperature of the traction rollers is set to be 100-160 ℃ for preheating, and the control rollers are used for carrying out low-rate longitudinal stretching on the three-layer co-extruded film;
(5) And (3) transversely stretching: heating the preheated diaphragm in the step (4) by up and down blast, transversely stretching and transversely stretching to ensure that the diaphragm is not broken and has uniform thickness in the stretching process;
(6) Stretching in the longitudinal direction: performing blast heating on the membrane prepared in the step (5) up and down, performing longitudinal stretching, and controlling the thickness of the membrane to be 3-50 um;
(7) And (3) extracting and pore-forming: extracting the diaphragm by adopting an extracting agent to extract white oil, so as to obtain a microporous diaphragm with uniform texture;
(8) And (3) drying: drying the microporous membrane obtained in the step (7) at a low temperature;
(9) And (5) heat setting: and (3) drying the diaphragm obtained in the step (8) at high temperature again, and carrying out small-magnification transverse stretching to improve the thermal deformation temperature of the diaphragm, thereby obtaining the PA/PE/PA three-layer lithium battery diaphragm.
2. The method of claim 1, wherein the compatibilizer is a maleic anhydride grafted compatibilizer and the toughening agent is an acrylic ternary co-clustered toughening agent;
preferably, the polyamide of step (1) is selected from PA6.
3. The method according to claim 1, wherein the Polyethylene (PE) in step (2) has a molecular weight of 50 to 500 tens of thousands; preferably, the polyethylene of step (2) is selected from UHPE or GUR1020.
4. The preparation method of the wet-process PA/PE/PA three-layer lithium battery diaphragm according to claim 1, wherein the raw materials of the wet-process PA/PE/PA three-layer lithium battery diaphragm comprise the following components in percentage by weight:
5. the preparation method according to claim 1, wherein the extrusion equipment comprising two sets of double-screw and three-layer co-extrusion dies in the step (2) comprises a screw (1) and a screw (2), the rotation speeds of the screw (1) and the screw (2) are 300r/min, the temperature of the screw (1) is changed within the range of 80-250 ℃, and the temperature of the screw (2) is changed within the range of 70-240 ℃.
6. The method according to claim 1, wherein the front cooling and shaping temperature in step (3) is 8-60 ℃, the back air cooling temperature is 15-50 ℃, and the back cooling and shaping temperature is 8-60 ℃.
7. The method according to claim 1, wherein the temperature of the pulling roll in the step (4) is set to 70 to 140 ℃, and the low-magnification longitudinal stretching magnification is 1 to 3 times.
8. The method according to claim 1, wherein the blast heating temperature in the step (5) is 90 to 170 ℃, and the transverse stretching ratio is 5 to 14 times.
9. The method according to claim 1, wherein the air blast heating temperature in the step (6) is 90 to 170 ℃ and the longitudinal stretching ratio is 5 to 14 times.
10. The process according to claim 1, wherein the extraction time in step (7) is 15 to 100 seconds.
11. The method according to claim 1, wherein the low-temperature drying temperature in the step (8) is 30-70 ℃ and the drying time is 10-50 seconds.
12. The method according to claim 1, wherein the high temperature drying temperature in step (9) is 110 to 170 ℃, the drying time is 10 to 50 seconds, and the small-magnification lateral stretching magnification is preferably 1 to 1.6 times.
13. The method of manufacturing according to claim 1, characterized in that the method further comprises the step (10): and (3) slitting and rolling the PA/PE/PA three-layer lithium battery diaphragm obtained in the step (9).
14. A PA/PE/PA three-layer lithium battery separator, characterized in that it is prepared by the preparation method according to any one of claims 1 to 13.
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