The invention is a divisional application, and the application date of the original application is: 2021, 08, 30, application number: 202111001226.X, name: a polyolefin microporous membrane with high elongation rate, a preparation method thereof and a battery.
Disclosure of Invention
In view of the above, the present invention is expected to provide a polyolefin microporous membrane with high elongation to solve the technical problem.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
the invention aims to provide a polyolefin microporous membrane with high elongation rate, which is characterized in that: the high-elongation polyolefin microporous membrane has a tensile strength of 2900-7500 kgf/cm2 The high-elongation polyolefin microporous membrane has an MD elongation of more than 180% and a TD elongation of more than 180%.
Further, the high-elongation polyolefin microporous membrane has a needling strength of 800 to 2000gf.
Further, the high-elongation polyolefin microporous membrane has an MD-direction elongation of more than 200% and a TD-direction elongation of more than 200%.
Further, the MD directional elongation rate of the high-elongation polyolefin microporous membrane is more than or equal to 260%, and the TD directional elongation rate is more than or equal to 210%.
Further, the high-elongation polyolefin microporous membrane has a needling strength of 1400 to 1800gf and a tensile strength of 3000 to 6000kgf/cm2 。
Further, the value of (MD elongation+MD tensile strength+needling strength+TD elongation+TD tensile strength+needling strength)/2 is 5000 or more; wherein the unit of elongation is kgf/cm and the unit of tensile strength is kgf/cm2 The unit of the needling strength is gf.
Further, the value of (MD elongation+MD tensile strength+needling strength+TD elongation+TD tensile strength+needling strength)/2 is 5000 to 7000; wherein the unit of elongation is kgf/cm and the unit of tensile strength is kgf/cm2 The unit of the needling strength is gf.
Further, (MD elongation+MD tensile strength+needling strength +)The value of the elongation in the TD direction, the tensile strength in the TD direction and the needling strength)/2 is 5100 to 7000; wherein the unit of elongation is kgf/cm and the unit of tensile strength is kgf/cm2 The unit of the needling strength is gf.
Further, the polyolefin is a single component polyethylene.
Further, the polyolefin has a weight average molecular weight of 4.0X106 ～8.0×106 。
Further, the high-elongation polyolefin microporous membrane is a wet separator.
Further, the high-elongation polyolefin microporous membrane has a single-layer structure.
Further, the high elongation polyolefin microporous membrane does not include a nucleating agent.
The present invention also aims to provide a battery using a microporous membrane comprising the above-mentioned polyolefin with high elongation as a component separating the positive and negative poles.
Compared with the prior art, the high-elongation polyolefin microporous membrane has high elongation and high tensile strength, and is different from the prior polyolefin microporous membrane which has high elongation and can not realize high tensile strength or has high tensile strength and can not realize high elongation. Thus, the microporous membrane and the battery using the microporous membrane have wide application prospect and market.
The invention aims to provide a preparation method of the high-elongation polyolefin microporous membrane, which comprises the following steps:
(1) Mixing and heating polyolefin and pore-forming agent to be molten, extruding through a die head, contacting a chilled roller, and cooling to form a sheet; wherein, the distance between the die head and the chilled roller is adjustable and is 0.2-2 m;
(2) Longitudinally stretching the sheet, controlling the temperature between 110 ℃ and 130 ℃, and slowly retracting the sheet by 60% -80%, wherein the longitudinal stretching multiplying power is more than or equal to 10;
(3) Performing first transverse stretching, controlling the temperature between 110 and 130 ℃, enabling the first transverse stretching multiplying power to be more than or equal to 10, and then slowly retracting by 60 to 80 percent;
(4) And (3) performing second transverse stretching, controlling the temperature to be less than or equal to 130 ℃, and slowly retracting the second transverse stretching rate to be more than or equal to 5 percent.
Further, in the step (2), the longitudinal stretching multiplying power is more than or equal to 10 at the temperature of 110-130 ℃, then the slow retraction is carried out for 60-80%, and the heat setting is not carried out after that; in the step (3), the first transverse stretching multiplying power is more than or equal to 10 at 110-130 ℃, then the slow retraction is carried out for 60-80%, and the heat setting is not carried out after that; in the step (4), the second transverse stretching multiplying power is more than or equal to 5 at 120-130 ℃, and then the slow retraction is carried out for 20-30%, and the heat setting is not carried out after that.
Further, the polyolefin has a weight average molecular weight of 4.0X106 ～8.0×106 The mass ratio of the polyolefin to the pore-forming agent is 50:50-60:40.
Further, the polyolefin is composed of one or several polyolefin components.
Still further, the polyolefin is a single component polyethylene.
The invention also aims to provide a preparation method of the high-elongation polyolefin microporous membrane, which comprises the following steps:
(1) Mixing and heating polyolefin and pore-forming agent to be molten, extruding through a die head, contacting a chilled roller, and cooling to form a sheet; wherein, the distance between the die head and the chilled roller is adjustable and is 0.2 m-2 m;
(2) Synchronous biaxial stretching is carried out on the sheet, the temperature is controlled between 110 ℃ and 130 ℃, the stretching multiplying power is more than or equal to 10, and the sheet is slowly retracted by 60% -80%;
(3) And then transversely stretching, controlling the temperature to be less than or equal to 130 ℃, and slowly retracting by 20-30 percent, wherein the transverse stretching multiplying power is more than or equal to 5.
Further, in the step (2), synchronous biaxial stretching multiplying power is more than or equal to 10 at 110-130 ℃, slow retraction is carried out for 60-80%, and heat setting is not carried out after that; in the step (3), the transverse stretching multiplying power is more than or equal to 5 at 120-130 ℃, and then the slow retraction is carried out for 20-30%, and the heat setting is not carried out after that.
Further, the distance of the die head from the chilled roll may preferably be 1m to 2m.
Further, the polyolefin has a weight average molecular weight4.0X106 ～8.0×106 The mass ratio of the polyolefin to the pore-forming agent is 50:50-60:40, and the polyolefin is composed of one or more polyolefin components.
Still further, the polyolefin is a single component polyethylene.
Compared with the prior art, the invention can greatly improve the bidirectional extensibility, tensile strength and needling strength performance of the traditional single polyethylene component diaphragm under the condition that the performances of porosity, air permeability and the like are not affected by raising the distance between the die head and the chilled roller and adopting the technological means of stretching, slow retraction, non-heat setting and the like in the preparation process. With the development of high-end 3C consumer electronics, such as flexible screens, wearable devices and the like, the process can endow the diaphragm and a battery using the diaphragm with wide application prospect and market.
Detailed Description
The following detailed description of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
Referring to fig. 5 and 7, the embodiment of the invention provides a preparation method of a high-elongation polyolefin microporous membrane, which comprises the following steps:
(1) Mixing and heating polyolefin and pore-forming agent to be in a molten state, extruding S1 through a die head 1, contacting a chilled roller 2, and cooling to form a sheet S2; the distance 4 between the die head and the chill roll is adjustable (the height of the chill roll is adjusted up and down, particularly a chill roll bearing, is fixed on a running track, and a matching air cylinder rises and falls) to be 0.2-2 m, and further preferably 1-2 m, (the molten state of polyolefin and pore-forming agent thereof flows out from a lip until the chill roll is contacted for solid-liquid phase separation, which is called casting, in this state, molecules and molecular chains thereof can move freely at a high speed, because the stress is vertical downward gravity, a casting sheet moves downward, the molecules and molecular chains thereof are all stretched to be disentangled and orderly in a linear parallel arrangement along the moving direction, in the traditional process, the distance is generally 0.05-0.15 m, the diaphragm is too short in casting sheet time, and the movement of the molecules and the molecular chains is not thorough, when the casting time exceeds 2m, excessive convergence into columns are easy to generate due to overlong casting time, stacking occurs when passing through the chill roll, and further processing cannot be performed effectively;
(2) Longitudinally stretching the sheet S8, controlling the temperature between 110 and 130 ℃, controlling the stretching multiplying power of the longitudinal stretching S8 to be more than or equal to 10, adopting more than or equal to 3 levels of stretching (the levels represent the number of using rollers), slowly retracting 60-80%, and adopting more than or equal to 3 levels of retracting (the levels represent the number of using rollers); ( The melting point of the conventional selected polyolefin in the industry is about 130-150 ℃, and the optimal crystallization temperature is 0.85 times of the melting point, so the temperature selection is defined as 110-130 ℃; the molecular chain links are effectively opened and are unfolded along the stretching direction as much as possible, the stretching multiplying power is preferably more than or equal to 10, the molecular chain links are prevented from being opened/moved incompletely caused by excessively fast stretching, the molecular chain links are stretched at more than or equal to 3 stages, and the opening/moving time of the molecular chain is effectively prolonged; the retraction is defined as 60% -80%, and the adoption of the retraction of more than or equal to 3 grades ensures that the retraction time of chain links is sufficient, and the chain links retract gradually, so that disordered entanglement caused by too strong retraction process is avoided. )
(3) Performing first transverse stretching S9, controlling the temperature between 110 and 130 ℃, controlling the stretching multiplying power of the first transverse stretching S9 to be more than or equal to 10, and slowly retracting by 60 to 80 percent;
(4) And (3) performing second transverse stretching S10, controlling the temperature to be less than or equal to 130 ℃, controlling the stretching multiplying power of the second transverse stretching S10 to be more than or equal to 5, and slowly retracting by 20-30%.
Here, through the above processing characteristics, with the molecule as far as possible along MD & TD ordered arrangement, and then produce and possess the less spring-type structure of molecular chain entanglement, when carrying out tensile test, spring-type molecular structure receives the ordered extension of pulling force, more structure of traditional molecular chain entanglement, before the test fracture, polyolefin diaphragm whole will embody longer effective displacement, embody higher elongation.
As shown in fig. 6, the distance between the traditional die head 1 and the chilled roller 2 is generally about 0.05-0.15 m, the distance 4 between the die head 1 and the chilled roller 2 is raised, so that the stretching of fluid is facilitated, the molecule is opened to be linked, molecular motion is generated, long straight chains are formed, the crystallinity is effectively reduced, and the shaping is facilitated.
Further, in the step (2), S8 is longitudinally stretched for 10 times or more at 110-130 ℃, then slowly retracted for 60-80%, and then heat setting is not performed; in the step (3), S9 is stretched for 10 times or more in the first transverse direction at 110-130 ℃, then is retracted slowly by 60-80%, and is not subjected to heat setting; in the step (4), S10 is stretched for 5 times or more in the second transverse direction at 120-130 ℃, then slowly retracted by 20-30%, and then heat setting is not carried out.
Here, stretching and retracting are performed firstly to obtain better elongation, and stretching with high multiplying power can enable the membrane to provide longer breaking travel of molecular chain length in the process of material stress deformation; the slow retraction is beneficial to forming a special spring structure, so that the extension rate is better; the absence of heat setting can reduce the occurrence of crystallization and further improve the elongation of the separator.
Here, the MD stretch and slow retraction S8 and TD1 stretch and slow retraction S9 may each be preferably 15 times or more, preferably 10 to 15 times, and the TD2 stretch and slow retraction S10 may be preferably 7 times or more, preferably 5 to 7 times.
Further, as shown in fig. 7, the present invention further includes a pore-forming agent removing unit S5, and the pore-forming agent removing unit S5 may be disposed after the MD stretching and slow retracting S8 or the TD1 stretching and slow retracting S9, or before the MD stretching and slow retracting S8.
Further, the present invention may also include all the relevant processes related to the preparation of the separator, as long as the technical effects of the present invention are not affected, such as winding, slitting, etc.
Further, the polyolefin has a weight average molecular weight of 4.0X106 ～8.0×106 The mass ratio of the polyolefin to the pore-forming agent is 50:50-60:40.
Here, it is preferable that the high molecular weight can provide extremely long molecular chains under a high-rate stretching process, and that the longer the molecular chains can provide a longer breaking travel during the deformation of the material under stress, further contributing to the improvement of the elongation.
Further, the polyolefin is composed of one or several polyolefin components.
Still further, the polyolefin is a single component polyethylene.
Preferably, the single component polyethylene does not include additives such as nucleating agents that affect the crystallinity of the polymer, and more preferably is a pure polyethylene that does not contain other components.
As shown in fig. 5 and 9, the present invention further provides a method for preparing a high-elongation polyolefin microporous membrane, comprising the following steps:
(1) Mixing and heating polyolefin and pore-forming agent to be molten, extruding through a die head 1, contacting a chilled roller 2, and cooling to form a sheet S2; wherein, the distance between the die head 1 and the chilled roller 2 is adjustable 4 and is 0.15-2 m;
(2) Synchronous biaxial stretching S11 is carried out on the sheet, the temperature is controlled between 110 ℃ and 130 ℃, the stretching multiplying power is controlled to be more than or equal to 10, and the sheet is slowly retracted by 60% -80%;
(3) Then transversely stretching S10, controlling the temperature to be less than or equal to 130 ℃, controlling the transverse stretching multiplying power to be more than or equal to 5, and slowly retracting by 20% -30%;
further, in the step (2), the synchronous biaxial stretching rate of S11 is more than or equal to 10 at 110-130 ℃, then the slow retraction is carried out for 60-80%, and the heat setting is not carried out after that; in the step (3), the S10 transverse stretching rate is more than or equal to 5 at 120-130 ℃, and then the slow retraction is carried out for 20-30%, and the heat setting is not carried out after that.
Here, stretching and retracting are performed firstly to obtain better elongation, and stretching with high multiplying power can enable the membrane to provide longer breaking travel of molecular chain length in the process of material stress deformation; the slow retraction is beneficial to forming a special spring structure, so that the extension rate is better; the absence of heat setting can reduce the occurrence of crystallization and further improve the elongation of the separator.
Here, the SBS stretching and slow retraction S11 may be preferably 15 times or more, preferably 10 to 15 times, and the TD2 stretching and slow retraction S10 may be preferably 7 times or more, preferably 5 to 7 times.
Further, as shown in fig. 9, the present invention further includes a pore-forming agent removing unit S5, and the pore-forming agent removing unit S5 may be disposed before or after the SBS stretching and slowly retracting S11.
Further, the present invention may also include all the relevant processes related to the preparation of the separator, as long as the technical effects of the present invention are not affected, such as winding, slitting, etc.
Further, the polyolefin has a weight average molecular weight of 4.0X106 ～8.0×106 The mass ratio of the polyolefin to the pore-forming agent is 50:50-60:40, and the polyolefin is composed of one or more polyolefin components.
Still further, the polyolefin is a single component polyethylene.
Preferably, the single component polyethylene does not include additives such as nucleating agents that affect the crystallinity of the polymer, and more preferably is a pure polyethylene that does not contain other components.
The invention also aims to provide a polyolefin microporous membrane with high elongation, which is characterized in that: the high-elongation polyolefin microporous membrane has a tensile strength of 2900-7500 kgf/cm2 The high-elongation polyolefin microporous membrane has an MD elongation of more than 180% and a TD elongation of more than 180%. It is understood that the high-elongation polyolefin microporous membrane may be prepared by any of the above-mentioned preparation methods, or may be prepared by other preparation methods not mentioned, and thus the high-elongation polyolefin microporous membrane should not be limited by any of the above-mentioned preparation methods.
Further, the high-elongation polyolefin microporous membrane has an MD/TD bidirectional elongation of greater than 200%. And preferably, the elongation in the MD direction is more than or equal to 260 percent, and the elongation in the TD direction is more than or equal to 210 percent.
Further, the MD directional elongation of the high elongation polyolefin microporous membrane is 260% -300%, 260% -290%, 260% -280%, 260% -270%, 270% -300%, 270% -290%, 270% -280%, 280% -300%, 280% -290%, or 290% -300%.
Further, the TD direction elongation of the high-elongation polyolefin microporous membrane is 210-240%, 210-230%, 210-220%, 220-240%, 220-230%, or 230-240%.
Further, the high-elongation polyolefin microporous membrane has an MD tensile strength of 4500-6000 kgf/cm2 、4500～5800kgf/cm2 、4500～5400kgf/cm2 、4500～4700kgf/cm2 、4700～6000kgf/cm2 、4700～5800kgf/cm2 、4700～5400kgf/cm2 、5400～6000kgf/cm2 、5400～5800kgf/cm2 Or 5800 to 6000kgf/cm2 。
Further, the TD direction tensile strength of the high-elongation polyolefin microporous membrane is 3000-4200 kgf/cm2 、3000～3500kgf/cm2 、3000～3200kgf/cm2 、3000～3100kgf/cm2 、3100～4200kgf/cm2 、3100～3500kgf/cm2 、3100～3200kgf/cm2 、3200～4200kgf/cm2 、3200～3500kgf/cm2 Or 3500-4200 kgf/cm2 。
Further, the polyolefin is a single component polyethylene.
Still further, the single-component polyethylene does not include additives such as nucleating agents that affect the crystallinity of the polymer, and is more preferably a pure polyethylene that does not contain other components.
Further, the polyolefin has a weight average molecular weight of 4.0X106 ～8.0×106 。
Further, the high-elongation polyolefin microporous membrane has a single-layer structure.
Further, the value of (elongation in the length direction, i.e., elongation in the MD direction+tensile strength in the length direction+needling strength+elongation in the width direction, i.e., elongation in the TD direction+tensile strength in the width direction+needling strength)/2 is 5000 or more; wherein the unit of elongation is Kgf/cm and the unit of tensile strength is Kgf/cm2 The unit of the needling strength is gf.
Further, the value of (elongation in the MD direction+tensile strength in the longitudinal direction+needling strength+elongation in the TD direction+tensile strength in the width direction+needling strength)/2 is 5000 to 7000; further preferably, the value is 5100 to 7000; wherein the unit of elongation is Kgf/cm and the unit of tensile strength is Kgf/cm2 The unit of the needling strength is gf.
Further, the high elongation polyolefin is slightly polyThe needling strength of the porous film is 800-2000 gf, and the tensile strength is 2900-7500 kgf/cm2 。
Further, the high-elongation polyolefin microporous membrane has a needling strength of 1400 to 1800gf and a tensile strength of 3000 to 6000kgf/cm2 。
Further, the high-elongation polyolefin microporous membrane has a needling strength of 1400 to 1800gf, 1400 to 1700gf, 1400 to 1600gf, 1600 to 1800gf, 1600 to 1700gf, or 1700 to 1800gf.
Further, the high-elongation polyolefin microporous membrane has a thickness of 1-40 μm; the porosity is 35% -50%; the air permeability is 25-400 s/100ml; MD thermal shrinkage rate is 1.0-5.0% at 110 ℃/1h, and TD thermal shrinkage rate is 1.0-1.5%.
Further, the high-elongation polyolefin microporous membrane has a porosity of 50% -60%; the air permeability is 150-180 s/100ml; MD thermal shrinkage rate is 2.0-5.0% at 110 ℃/1h, and TD thermal shrinkage rate is 1.1-1.5%.
Still further, the high-elongation polyolefin microporous membrane has a thickness of 10 μm.
Still further, the high-elongation polyolefin microporous membrane has a permeability of 150 to 180s/100ml, 150 to 170s/100ml, 150 to 160s/100ml, 160 to 180s/100ml, 160 to 170s/100ml, or 170 to 180s/100ml.
Further, the high-elongation polyolefin microporous membrane has a porosity of 50% -56%, 50% -53%, 50% -52%, 50% -51%, 51% -56%, 51% -53%, 51% -52%, 52% -56%, 52% -53%, or 53% -56%.
Further, the high-elongation polyolefin microporous membrane has a maximum pore diameter of 40 to 49nm, 40 to 48nm, 40 to 44nm, 40 to 42nm, 42 to 49nm, 42 to 48nm, 42 to 44nm, 44 to 49nm, 44 to 48nm, or 49 to 50nm.
Further, the high-elongation polyolefin microporous membrane has an MD heat shrinkage of 2.0% -4.0%, 2.0% -3.0%, 3.0% -5.0%, 3.0% -4.0%, or 4.0% -5.0% at 110 ℃/1 h.
Further, the high-elongation polyolefin microporous membrane has a TD heat shrinkage rate of 1.1-1.3%, or 1.3-1.5%, at 110 ℃/1 h.
The present invention also aims to provide a battery using a microporous polyolefin membrane comprising any one of the above-mentioned high-elongation polyolefin membranes as an element separating positive and negative poles.
The present invention will be described in detail by examples.
In the following examples and comparative examples, the performance parameters were determined as follows:
1. thickness of (L)
The thickness of the plastic film and the sheet was measured by a German Mark film thickness measuring instrument 1216 according to the measurement method of GB/T6672-2001.
2. Air permeability
The measurement was carried out stably for 5 seconds by using a Wang Yan type air permeation instrument, and a stable value was obtained.
3. Heat shrinkage
100mm×100mm microporous membranes were placed at 110 ℃ for 1H using a high temperature test chamber Espec SEG-021H and measured by an image measuring instrument XTY-5040, TD and MD direction lengths were as follows: (before heat treatment to after heat treatment)/before heat treatment × 100% conversion
4. Needling strength
Measurements were made using an electronic universal material tester XJ830, 50mm/min travel speed.
5. Porosity of the porous material
A 100mm x 100mm sample was taken, weighed using an electronic scale and according to the formula: (1-weight/swatch area)/weight×0.957×100% conversion.
6. Maximum pore diameter
Measured by bubble point method using a narrow pore size tester.
7. Kinematic viscosity
The kinematic viscosity is measured after the measurement temperature is set to 60 ℃ and the stability is carried out for 1 hour by using a kinematic viscosity measuring instrument DSY-004.
8. Residual oil ratio
Cutting into 10mm×10mm diaphragm sample, weighing with electronic balance, placing pure water in Ultrasonic Cleaner 1740T, placing 300ml pure dichloromethane in 500ml beaker, placing sample, setting ultrasonic time to 60s, drying in 105 deg.C oven for 5min, weighing with electronic balance, and converting residual oil rate.
Example 1
Mw was 8.0X106 Polyethylene and white oil as raw materials. The method comprises the steps of feeding 60% of polyethylene and 40% of white oil by mass into an extruder at a flow rate of 240Kg/h to extrude S1, extruding a die head at a temperature of 220 ℃ and a distance (2 m) between a chilled roller through a T-type die head under a condition of 100rpm, performing contact cooling by a cold roller at a temperature of 25 ℃ to form a sheet S2, then entering a pore-forming agent removing unit, heating a driving hot roller and a driven hot roller to 90 ℃ through heat conduction oil, stretching the cast sheet after removing the pore-forming agent by using a stretcher at 130 ℃ and S8 along a Mechanical Direction (MD), wherein the stretching ratio is 15, then performing slow retraction 80% without heat setting, then performing S9 at 130 ℃ along a width direction (TD), then performing slow retraction 80% without heat setting, then performing S10 secondary stretching at 120 ℃, performing slow retraction 30% without heat setting, and winding by using a winding roller to obtain the polyolefin microporous membrane with the MD and TD direction two-way elongation of more than 180%.
Example 2
Mw was 8.0X106 Polyethylene and white oil as raw materials. Putting 50% polyethylene and 50% white oil in mass percentage into an extruder at a flow rate of 500Kg/h to extrude S1, extruding at 220 ℃ under the condition of 100rpm, performing contact cooling by a cold roll with the temperature of 25 ℃ through a T-shaped die head (the distance between the die head and a chilled roll is adjusted to be 1.0 m) to form a sheet S2, then entering a pore-forming agent removing unit, heating a driving hot roll and a driven hot roll to 90 ℃ through heat conduction oil, stretching the cast sheet with the pore-forming agent removed S5 at 110 ℃ by using a stretcher at the Mechanical Direction (MD) at the S8 with the stretching multiplying power of 10, then performing slow retraction for 60%, not performing heat setting, then stretching at the 110 ℃ at the S9 in the width direction (TD) with the stretching multiplying power of 10, then performing slow retraction for 60%, not performing heat setting, then performing S10 secondary TD stretching at the 130 ℃, and then performing slow retraction20% shrinkage, no heat setting, and coiling with a coiling roller to obtain the polyolefin microporous membrane with the bidirectional extensibility of more than 180% in MD and TD directions.
Example 3
Mw was 4.0X106 Polyethylene and white oil as raw materials. The method comprises the steps of feeding 60% of polyethylene and 40% of white oil by mass into an extruder at a flow rate of 240Kg/h, extruding S1, extruding at 220 ℃ under a condition of 100rpm, passing through a T-shaped die head (the distance between the die head and a chilled roller is 0.2 m), performing contact cooling by a cold roller at 25 ℃ to form a sheet S2, then entering a pore-forming agent removing unit, heating a driving hot roller and a driven hot roller to 90 ℃ by heat conduction oil, stretching the cast sheet after removing the pore-forming agent S5 in a Mechanical Direction (MD) at 130 ℃ by using a stretcher at S8, wherein the stretching multiplying power is 10, then performing slow retraction for 60%, not performing heat setting, then stretching at 110 ℃ at S9 in a width direction (TD), then performing slow retraction for 60%, not performing heat setting, then performing S10 secondary TD stretching at 120 ℃, performing slow retraction for 20%, not performing heat setting, and performing coiling by using a coiling roller to obtain the polyolefin microporous membrane with the MD and the bidirectional stretching ratio of 180.
Example 4
Mw was 4.0X106 Polyethylene and white oil as raw materials. The method comprises the steps of putting 60% of polyethylene and 40% of white oil in percentage by mass into an extruder at a flow rate of 240Kg/h, extruding S1, extruding at 220 ℃ under a condition of 100rpm, performing contact cooling by a cold roll with a temperature of 25 ℃ through a T-shaped die head (the distance between the die head and a chilled roll is 0.2 m), forming a sheet S2, then entering a pore-forming agent removing unit, heating a driving hot roll and a driven hot roll to 90 ℃ through heat conduction oil, performing SBS synchronous stretching S11 on the cast sheet with the pore-forming agent removed S5 at 130 ℃ by using a stretcher, performing slow retraction for 60%, performing no heat setting, performing S10 secondary TD stretching at 130 ℃ with the stretching ratio of 5, performing slow retraction for 20%, performing no heat setting, and coiling by using a coiling roll to obtain the polyolefin microporous membrane with the bi-directional elongation rate of 180.
Example 5
Mw was 8.0X106 Polyethylene and white oil as raw materials. The method comprises the steps of putting 50% of polyethylene and 50% of white oil in percentage by mass into an extruder at a flow rate of 500Kg/h to extrude S1, extruding the polyethylene and the white oil through a T-shaped die head (the distance between the die head and a chilled roller is 2 m) at 220 ℃ under the condition of 100rpm, cooling the polyethylene and the white oil by a cold roller at 25 ℃ to form a sheet S2, then entering a pore-forming agent removing unit, heating a driving hot roller and a driven hot roller to 90 ℃ through heat conduction oil, synchronously stretching the cast sheet after removing the pore-forming agent S5 at 110 ℃ by using a stretcher at S11, slowly retracting the sheet to 80% without heat setting, secondarily stretching the sheet at 120 ℃ by S10 at 7, slowly retracting the sheet to 30% without heat setting, and coiling the sheet by a coiling roller to obtain the polyolefin microporous film with the bi-directional elongation of 180.
Comparative example 1
Mw was 4.0X106 Polyethylene and white oil as raw materials. The raw materials with the mass percentage of 60 percent of polyethylene and 40 percent of white oil are put into an extruder for extrusion S1 according to the flow rate of 240Kg/h, extruded through a T-shaped die head (the distance between the die head and a chilled roller is 0.15 m) under the condition of 220 ℃ and 100rpm, and are contacted and cooled by a cold roller with the temperature of 25 ℃ to form a sheet S2. And (3) under the heating of a heat conduction oil roller at 90 ℃, the heat conduction oil roller is positioned in a dichloromethane groove body at 30 ℃, and the pore-forming agent is removed. And (3) stretching and shaping the material in MD (machine direction) at 130 ℃ to obtain the stretch ratio of 10. And (3) stretching the material into TD1, and stretching and shaping the material at 110 ℃ to obtain the stretch ratio of 10. And (3) stretching the material in TD2, stretching the material at 120 ℃ to obtain a stretching ratio of 5, performing heat setting, and coiling the material by a coiling roller, wherein the stretching ratio is S6.
Comparative example 2
Mw was 4.0X106 Polyethylene and white oil as raw materials. Putting 60% polyethylene and 40% white oil in mass percentage into an extruder at a flow rate of 240Kg/h to extrude S1, extruding at 220 ℃ under 100rpm through a T-shaped die head (the distance between the die head and a chilled roller is 2 m), contacting and cooling through a cold roller at 25 ℃ to form a sheet S2, then entering a pore-forming agent removing unit, and extruding through heat conducting oilDriving a hot roller and heating the driven hot roller to 90 ℃, synchronously stretching the cast sheet after removing the pore-forming agent S5 by using a stretcher at 130 ℃ for SBS (styrene-butadiene-styrene) synchronous stretching S12, stretching the cast sheet at 10 times, then stretching the cast sheet at 130 ℃ for S6 secondary TD (time division) stretching, stretching the cast sheet at 5 times, performing heat setting S7, and coiling the cast sheet by using a coiling roller.
Table 1 processing technique and physical properties of examples and comparative examples
The above description of the common general knowledge will not be described in detail, as will be appreciated by those skilled in the art.
The foregoing description of the embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.