阅读说明：本技术 功能化微孔膜及其制备方法 (Functionalized microporous membrane and preparation method thereof ) 是由 薛山 刘杲珺 徐萌 董秋春 刘志刚 史新明 甘珊珊 马源 张绪杰 于 2021-08-17 设计创作，主要内容包括：本发明公开了功能化微孔膜及其制备方法。该微孔膜含有一层以聚烯烃为主要成分的多孔膜；该微孔膜也可含有层叠在多孔膜的一面或两面上的,含有无机颗粒或仅有有机物的涂层；该微孔膜具备优异的耐氧化性,氧气氛围条件下,氧化诱导期不低于20分钟。本发明通过该方法有效提升耐氧化效果,可有效保护微孔膜在氧化环境中的使用寿命；通过功能化特性的组合,可满足多种使用环境。(The invention discloses a functionalized microporous membrane and a preparation method thereof. The microporous membrane comprises a porous membrane containing polyolefin as a main component; the microporous membrane may also have a coating layer containing inorganic particles or only organic substances, laminated on one or both sides of the porous membrane; the microporous membrane has excellent oxidation resistance, and the oxidation induction period is not less than 20 minutes under the oxygen atmosphere condition. The method effectively improves the oxidation resistance effect, and can effectively protect the service life of the microporous membrane in an oxidation environment; through the combination of the functional characteristics, various use environments can be met.)

1. A functionalized microporous membrane, characterized by: the microporous membrane comprises a porous membrane and a coating layer which is laminated on one surface or two surfaces of the porous membrane and is provided with inorganic particles or organic matters; the microporous membrane has excellent oxidation resistance, and the oxidation induction period is not less than 20 minutes at 190 ℃ under the oxygen atmosphere.

2. The functionalized microporous membrane of claim 1, wherein: the polyolefin mass content in the porous membrane is as follows: 95 to 100 percent.

3. The functionalized microporous membrane of claim 1, wherein: the processing method of the functionalized microporous membrane comprises the following steps:

(1) a mixing procedure: mixing 5-50 parts of polyolefin, 0.01-0.5 part of antioxidant, 0.0-15 parts of fluororesin and 50-95 parts of white oil material, and performing melt mixing above the melting point of the polyolefin material;

(2) sheet molding: extruding and cooling the mixed mixture to obtain a sheet;

(3) a stretching process: stretching the sheet into a film;

(4) an extraction process: removing the white oil in the membrane by using an extractant to obtain a primary microporous membrane;

(5) a functionalization process: immersing the primary microporous membrane obtained in the step (4) into a functional solution to enable the microporous membrane to adsorb the solution, and then drying to obtain a treated microporous membrane;

wherein: the functional solution comprises the following components in parts by weight: 0.005-10 parts, 85-99.995 parts and 0.0-5 parts; the mass ratio of the functionalized solution to the primary microporous membrane is more than or equal to 1, preferably more than 50;

(6) a heat treatment step of heat-treating the microporous film at 110 to 135 ℃ to obtain a shaped porous film;

(7) the coating step of selectively coating the surface of the porous membrane treated as described above with an inorganic or organic coating to obtain a coated membrane.

4. The functionalized microporous membrane of claim 3, wherein: in the step (1), the polyolefin, the antioxidant, the fluororesin and the white oil are sequentially 20-30 parts, 0.1-1 part, 1-5 parts and 70-80 parts by weight.

5. The functionalized microporous membrane of claim 3, wherein: the auxiliary agent in the step (5) is at least one of an antistatic agent, inorganic particles and paraffin particles.

6. The functionalized microporous membrane of claim 3, wherein: the solvent in the step (5) is as follows: chlorine-based hydrocarbons such as dichloromethane, trichloromethane and 1, 1, 1-trichloroethane, non-chlorine-based halogenated solvents such as hydrofluoroethers and hydrofluorocarbons, alkanes such as pentane, hexane and heptane, alcohols such as methanol, ethanol, isopropanol and tripropylene glycol, ketones such as acetone, methyl ethyl ketone and N-methylpyrrolidone, ethers such as diethyl ether and tetrahydrofuran 1, 4-dioxane, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic hydrocarbons such as toluene and xylene and derivatives thereof.

7. The functionalized microporous membrane of claim 5, wherein: the antioxidant in the step (5) is as follows: 2, 6-di-tert-butyl-p-cresol, pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], n-octadecyl beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, (±) - (2RS,4 ' RS,8 ' RS) -2,5,7, 8-tetramethyl-2- (4 ', 8 ', 12 ' -trimethyltridecyl) -6-chromanol acetate, tris [2, 4-di-tert-butylphenyl ] phosphite, And one or more antioxidants such as didodecyl thiodipropionate.

8. The functionalized microporous membrane of claim 3, wherein: the antistatic agent is as follows: octadecyl dimethyl hydroxyethyl Quaternary ammonium nitrate.

9. The functionalized microporous membrane of claim 3, wherein: the inorganic particles are: the particle matter with the median particle diameter less than or equal to 100nm, and the nano particles are phase change capsules, alumina ceramic particles or titanium oxide particles.

Technical Field

The present invention relates to a functional microporous membrane and a method for preparing the same. The microporous membrane can be used in lithium batteries and can also be applied to the fields of separation membranes, clothes and the like.

Background

Along with high energy density, the application of high voltage technology in the lithium ion battery field, the anti oxidation performance of diaphragm need promote by a wide margin, but present ordinary diaphragm can't satisfy the demand of novel battery anti oxidation. In addition, different application fields require different functionalities of the separator, and expanding the use of the separator requires imparting new functions to the separator.

In the existing wet-process porous membrane production process, small molecular substances such as white oil and the like are extracted out of the porous membrane by using an extracting agent, so that during production, a very small amount of functional auxiliary agent mixed and added in raw materials is remained in the porous membrane due to extraction, and the beneficial functions of the porous membrane are partially lost; the invention effectively solves the problems of insufficient performance of the porous membrane caused by the lack of the functional auxiliary agent and finally the lack of the performance of the porous membrane. Especially oxidation resistance, and the oxidation induction period of the porous membrane without functionalization treatment is less than 5min under the condition of 190 ℃ and oxygen atmosphere.

Disclosure of Invention

The invention provides a functionalized microporous membrane and a preparation method thereof aiming at the technical problems.

The purpose of the invention can be realized by the following technical scheme:

a functionalized microporous membrane comprising a porous membrane and a coating layer provided with inorganic particles or organic substances and laminated on one or both surfaces of the porous membrane; the microporous membrane has excellent oxidation resistance, and the oxidation induction period is not less than 20 minutes at 190 ℃ under the oxygen atmosphere.

The technical scheme of the invention is as follows: the polyolefin mass content in the porous membrane is as follows: 95 to 100 percent.

The technical scheme of the invention is as follows: the processing method of the functionalized microporous membrane comprises the following steps:

(1) a mixing procedure: mixing 5-50 parts of polyolefin, 0.01-0.5 part of antioxidant, 0.0-15 parts of fluororesin and 50-95 parts of white oil material, and performing melt mixing above the melting point of the polyolefin material;

(2) sheet molding: extruding and cooling the mixed mixture to obtain a sheet;

(3) a stretching process: stretching the sheet into a film;

(4) an extraction process: removing the white oil in the membrane by using an extractant to obtain a primary microporous membrane;

(5) a functionalization process: immersing the primary microporous membrane obtained in the step (4) into a functional solution to enable the microporous membrane to adsorb the solution, and then drying to obtain a treated microporous membrane;

wherein: the functional solution comprises the following components in parts by weight: 0.005-10 parts, 85-99.995 parts and 0.0-5 parts; the mass ratio of the functionalized solution to the primary microporous membrane is more than or equal to 1, preferably more than 50;

(6) a heat treatment step of heat-treating the microporous film at 110 to 135 ℃ to obtain a shaped porous film;

(7) the coating step of selectively coating the surface of the porous membrane treated as described above with an inorganic or organic coating to obtain a coated membrane.

The method comprises the following steps: in the step (1), the polyolefin, the antioxidant, the fluororesin and the white oil are sequentially 20-30 parts, 0.1-1 part, 1-5 parts and 70-80 parts by weight.

Further: the polyolefin is high-density polyethylene, the antioxidants are hindered phenol main antioxidant 1010 and auxiliary antioxidant 168, and the fluororesin is vinylidene fluoride.

The technical scheme of the invention is as follows: the auxiliary agent in the step (5) is at least one of an antistatic agent, inorganic particles and paraffin particles. Further: the antistatic agent is as follows: octadecyl dimethyl hydroxyethyl Quaternary ammonium nitrate.

The technical scheme of the invention is as follows: the solvent in the step (5) is as follows: chlorine-based hydrocarbons such as dichloromethane, trichloromethane and 1, 1, 1-trichloroethane, non-chlorine-based halogenated solvents such as hydrofluoroethers and hydrofluorocarbons, alkanes such as pentane, hexane and heptane, alcohols such as methanol, ethanol, isopropanol and tripropylene glycol, ketones such as acetone, methyl ethyl ketone and N-methylpyrrolidone, ethers such as diethyl ether and tetrahydrofuran 1, 4-dioxane, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic hydrocarbons such as toluene and xylene and derivatives thereof.

The technical scheme of the invention is as follows: the antioxidant in the step (5) is as follows: 2, 6-di-tert-butyl-p-cresol, pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], n-octadecyl beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, (±) - (2RS,4 ' RS,8 ' RS) -2,5,7, 8-tetramethyl-2- (4 ', 8 ', 12 ' -trimethyltridecyl) -6-chromanol acetate, tris [2, 4-di-tert-butylphenyl ] phosphite, And one or more antioxidants such as didodecyl thiodipropionate.

In some preferred embodiments: the antioxidant in the step (5) is BASF Irganox 3114.

The technical scheme of the invention is as follows: the inorganic particles are: the particle matter with the median particle diameter less than or equal to 100nm, and the nano particles are phase change capsules, alumina ceramic particles or titanium oxide particles.

The technical scheme of the invention is as follows: stretching may be added before or after the primary microporous membrane, specifically under conditions of pulling the primary microporous membrane at room temperature and stretching it in the transverse direction of the separator in an appropriate amount to widen the transverse width thereof by a ratio of 15%.

The functionalization process of the invention comprises the following steps: when the auxiliary agent contains inorganic particles, the process is as follows:

suspending inorganic particles in a solvent, wherein the mass of the prepared solution is 70-85 times of that of the pretreated diaphragm, and carrying out primary immersion; the above primary porous film was then pulled up the porous film at room temperature, immersed in the suspension, subjected to a treatment for 30 seconds, then pulled out under a tension of 100N per meter, and washed with pure water at 25 ℃, and dried through the microporous film at 90 ℃. And then mixing the antioxidant and other additives except inorganic particles with a solvent to prepare a solution, wherein the mass of the prepared solution is 90-120 times of that of the pretreated diaphragm, the mass of the treated diaphragm is calculated according to the hourly production of the diaphragm, the solution is filtered by a 50nm filter screen, then 0.01% of ethanol is added, then the solution is introduced into a semi-closed space, and meanwhile, a pure water solution is filled above the solution to prevent the solution concentration fluctuation caused by volatilization. The solution dissolved with the antioxidant is continuously self-circulated, the concentration of the solution is detected by the detection device and fed back to the control system, and the stability of the concentration is ensured.

The invention has the beneficial effects that:

the present invention has been made in view of the above problems, and it provides a functionalized microporous membrane and a method for preparing the same, in which a microporous membrane product having a specific function is obtained by treating a porous membrane with an aid solution or a filler suspension having a specific concentration before the porous membrane is coated, particularly before the porous membrane is heat-set. The auxiliary agent can be effectively added into the diaphragm through the invention, and the auxiliary agent is uniformly distributed, so that the air permeability of the diaphragm is not influenced, the problems of precipitation and the like are avoided, and finally, the functionality of the diaphragm is effectively improved.

Drawings

FIG. 1: is a schematic view of an oxidation resistance test of a microporous film (the porous film obtained in example 1, having an oxidation induction period (O.I.T.) test result of 43min)

Detailed Description

The invention is further illustrated by the following examples, without limiting the scope of the invention:

the main methods of measurement and experiment in the examples are as follows:

(1) method for testing membrane breaking temperature of porous membrane

The rupture temperature was measured by Q800DMA of TA;

the samples were cut to 10cm length (MD) and 2cm width (TD); the load was 0.02N; the temperature rise is set to be 30 ℃ to 200 ℃, and the temperature rise rate is 5 ℃/min. When the deformation of the porous membrane changes from decreasing to increasing or from unchanged to increasing, the corresponding temperature is the rupture temperature.

(2) Testing of oxidative Induction periods for porous membranes

The oxidation induction period of the porous membrane was measured using DSC 214 manufactured by sanchi corporation;

the porous membrane was folded several layers and then cut into a 5mm circle. The wafer is put into an aluminum crucible and weighed to be 10mg to 15mg, and the wafer is flatly laid in the crucible and is tightly attached to the bottom plane. And (3) pricking two small holes in the crucible by using a steel needle, wherein the diameter of each hole is more than or equal to 0.5mm, and the distance between the two small holes is more than 1.5 mm. The crucible cover is pressed tightly. Under the nitrogen atmosphere, the temperature is raised from room temperature to 200 ℃ at the temperature raising speed of 20 ℃/min, the temperature is kept constant for 3min, and then high-purity oxygen is introduced for measurement, wherein the oxygen flow is 40 ml/min. The time difference between the time of the tangent intersection points on the two sides of the inflection point of the initial exothermic curve and the time of oxygen introduction is taken as the time length value of the oxidation induction period.

The test result is shown in figure 1, and the time length corresponding to the intersection point of the tangent lines is the oxidation induction period value. The porous film obtained in example 1 had an oxidation induction period (o.i.t.) test result of 43 min: at ambient temperature stabilized at 190 ℃, oxygen was passed under the test conditions and at 43min the porous film began to significantly exotherm as the curve began to curve downward.

(3) In the functionalization process, the concentration of the solution at the inlet of each tank, the middle part of the treatment tank and the solution outlet needs to be detected. The detection is based on HPLC detection. But the detection needs to be normalized as follows:

when the sample is a uniform solution, the sampled solution is first filtered, and the filter is required to remove impurities of 0.1 μm or more. Then directly injecting into HPLC for detecting solute concentration.

When the sample was a suspension, HPLC was not used for detection. The suspension is tested by adopting an evaporation drying method. The drying method comprises the steps of taking 100ml of suspension, drying the suspension at the boiling point of a solvent below 10 ℃ until the weight of the suspension is constant, weighing the mass of the solvent, and calculating the concentration of the solvent to be the mass of the solvent per 100 ml.

Comparative example 1

The preparation process flow of the diaphragm comprises the following steps:

ultra-high molecular weight polyethylene (GUR2122, Ticona Sealanib) 15 wt%, white oil (40#, Zhejiang Corp.) 85 wt%, and 100 parts by weight of the total of the high molecular weight polyethylene and the white oil, 0.2 parts by weight of an antioxidant (Irg1010(Ciba Specialty Chemicals Basff)) and 0.1 parts by weight of an antioxidant (P168(Ciba Specialty Chemicals Corp.)) were added and mixed in this order. Firstly, the ultra-high molecular weight polyethylene powder and the antioxidant are uniformly mixed by using a high-speed mixer, and the mixing uniformity is determined by detecting the content of the antioxidant by infrared rays. In the kneading step, the mixed ultrahigh molecular weight polyethylene material is fed into a twin-screw extruder together with white oil, and kneaded at 200 ℃ to finally prepare a gel-like composition melt.

And entering a forming process, using a T-shaped die head to extrude the composition melt, then rapidly cooling on a constant-temperature metal roller pair with the temperature of 10 ℃, and rolling into a sheet with the thickness of 1.5 mm.

The formed sheet is drawn and then subjected to a drawing process. The composition is rapidly biaxially stretched at about 1 ℃ below the melt melting point, wherein stretching at 8 magnifications is performed in both MD and TD directions. The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. Since the stretched separator becomes thin and is likely to wrinkle in a non-stretched state, the separator needs to be stretched under a force of 1% or less of the tensile strength of the separator and pulled into an extraction step.

In the extraction process, washing by dichloromethane, extracting the white oil and the residual antioxidant in the diaphragm, and then carrying out constant-temperature hot air at 40 ℃ to carry out the residual dichloromethane in the diaphragm, thereby finally obtaining the primary porous film. However, the porous film has many crystal defects, a low melting point, and poor strength.

Then, the porous film was subjected to a heat treatment step at 132 ℃ under a tension of 50N/m to obtain a shaped porous film.

Comparative example 2

The porous film obtained in comparative example 1 was slit and coated.

And (3) coating PVDF (polyvinylidene fluoride) coatings with the thickness of 1 micrometer on two sides of the porous membrane to obtain a porous membrane product with excellent electrical property.

Example 1

An ultra-high-molecular-weight polyethylene powder (145M, mitsui chemical) was used in an amount of 25 wt%, a white oil (X420, shell) was used in an amount of 75 wt%, and 3 parts of polyvinylidene fluoride (DS205, east of shandong yunshi boat) was added, 0.2 parts of an antioxidant (Irg1010(Ciba Specialty Chemicals basf)) and 0.1 parts of an antioxidant (P168(Ciba Specialty Chemicals corporation)) were added to 100 parts by weight of the total of the high-molecular-weight polyethylene and the white oil, and these were mixed in this order. The materials were first mixed uniformly using a high speed mixer, the uniformity of mixing being determined by infrared detection of the antioxidant content. In the kneading step, the mixed materials are put into a twin-screw extruder and kneaded at 200 ℃ to finally prepare a gel-like composition melt.

And entering a forming process, using a T-shaped die head to extrude the composition melt, then rapidly cooling on a constant-temperature metal roller pair with the temperature of 10 ℃, and rolling into a sheet with the thickness of 1.5 mm.

The formed sheet enters a stretching process through traction; the composition is rapidly biaxially stretched at about 1 ℃ below the melt melting point, wherein stretching at 8 magnifications is performed in both MD and TD directions. The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. Since the stretched separator becomes thin and is likely to wrinkle in a non-stretched state, the separator needs to be stretched under a force of 1% or less of the tensile strength of the separator and pulled into an extraction step.

In the extraction process, washing by dichloromethane is carried out, white oil and residual antioxidant in the diaphragm are extracted, and then the residual dichloromethane in the diaphragm is taken out by constant-temperature hot air at 40 ℃, so as to finally obtain the primary microporous membrane.

The porous film was pulled at room temperature and stretched appropriately in the transverse direction of the separator to widen the transverse width thereof at a width increase ratio of 15%. And then drawing the porous membrane to be immersed into the functional solution, so that the microporous membrane adsorbs the solution, and then drying to obtain the treated microporous membrane.

The functional solution comprises the following components: dissolving an antioxidant (BASF Irganox 3114) into dichloromethane at the mass concentration of 0.05% at room temperature to prepare a solution, wherein the mass of the prepared solution is 100 times of that of the pretreated diaphragm, the mass of the treated diaphragm is calculated by the hourly production of the diaphragm, the solution is filtered by a 50nm filter screen, then 0.01% of ethanol is added in mass fraction, and then the solution is introduced into a semi-closed space, and meanwhile, a pure water solution is injected above the solution to prevent the solution concentration from fluctuating due to volatilization. The solution dissolved with the antioxidant is continuously self-circulated, the concentration of the solution is detected by the detection device and fed back to the control system, and the stability of the concentration is ensured.

Drawing the porous membrane into a semi-closed space to be in contact with the solution for not less than 15s, wherein the drawing tension is 100N per meter, the longitudinal running speed is 50m/min, and the running distance of the porous membrane in the solution is 13 m;

then dried again at a drying temperature of 40 ℃.

Finally, the film with higher oxidation resistance is obtained by constant temperature hot air treatment and shaping at 133 ℃ for 6 s.

Example 2

With respect to 100 parts by weight of the total of the high molecular weight polyethylene (VH200U, KPIC)25 parts by weight and the white oil (X430, shell) 75 parts by weight, 3 parts by weight of polyvinylidene fluoride (DS205, yoto mountain kanos) 0.2 parts by weight of an antioxidant (Irg1010(Ciba Specialty Chemicals basf)) and 0.1 parts by weight of an antioxidant (P168(Ciba Specialty Chemicals co., ltd.)) were added, and these were mixed in this order. Firstly, the ultra-high molecular weight polyethylene powder, the fluororesin and the antioxidant are uniformly mixed by using a high-speed mixer, and the mixing uniformity is determined by detecting the content of the antioxidant by infrared rays. In the kneading step, the mixed ultrahigh molecular weight polyethylene material and white oil are put into a twin-screw extruder together for kneading, the mixing temperature is 200 ℃, and finally a gel-like resin composition melt is prepared.

And entering a forming process, using a T-shaped die head to extrude the composition melt, then rapidly cooling on a constant-temperature metal roller pair with the temperature of 10 ℃, and rolling into a sheet with the thickness of 1.5 mm.

The formed sheet is drawn and then subjected to a drawing process. The composition is rapidly biaxially stretched at about 1 ℃ below the melt melting point, wherein stretching at 8 magnifications is performed in both MD and TD directions. The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. Since the stretched separator becomes thin and is likely to wrinkle in a non-stretched state, the separator needs to be stretched under a force of 1% or less of the tensile strength of the separator and pulled into an extraction step.

In the extraction process, washing by dichloromethane is carried out to extract the white oil and the residual antioxidant in the diaphragm, and then the residual dichloromethane in the diaphragm is taken out by constant-temperature hot air at 40 ℃ to finally obtain the primary porous film.

The porous film was pulled at room temperature and stretched appropriately in the transverse direction of the separator to widen the transverse width thereof at a width increase ratio of 15%. The porous membrane is then pulled to dip into a solution containing the adjuvant.

An antistatic agent (octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate, manufactured by Haitian auxiliary manufacturing Co., Ltd. in Shaoxing county) and an antioxidant (BASF Irganox 3114) were dissolved in acetone at mass concentrations of 1% and 0.05%, the mass of the prepared solution was 60 times that of the pretreated membrane, the mass of the treated membrane was calculated as the amount of the membrane produced per hour, and the membrane was filtered through a 50nm filter screen, and the solution was introduced into a semi-closed space, while an anti-overflow air curtain was provided above the solution. The solution is circulated continuously, the concentration of the solution is detected by the detection device at all times and fed back to the control system, and the stability and the rapid circulation of the concentration are ensured.

And (3) drawing the primary porous membrane into a semi-closed space to contact with the solution for 15s, and then drying again at the drying temperature of 60 ℃. Finally, the film with excellent oxidation resistance and antistatic property is obtained by constant temperature hot air treatment and shaping at 133 ℃ for 6 s.

Finally, the porous membrane can also be subjected to a coating process, and one side of the membrane is coated with a 0.2-micron aluminum oxide coating to prepare the coated membrane.

Example 3

With respect to 100 parts by weight of the total of the high molecular weight polyethylene (VH200U, KPIC)25 parts by weight and the white oil (X430, shell) 75 parts by weight, 3 parts by weight of polyvinylidene fluoride (DS205, yoto mountain kanos) 0.2 parts by weight of an antioxidant (Irg1010(Ciba Specialty Chemicals basf)) and 0.1 parts by weight of an antioxidant (P168(Ciba Specialty Chemicals co., ltd.)) were added, and these were mixed in this order. Firstly, the ultra-high molecular weight polyethylene powder, the fluororesin and the antioxidant are uniformly mixed by using a high-speed mixer, and the mixing uniformity is determined by detecting the content of the antioxidant by infrared rays. In the kneading step, the mixed ultrahigh molecular weight polyethylene material is fed into a twin-screw extruder together with white oil and kneaded to finally prepare a gel-like composition melt.

And entering a forming process, using a T-shaped die head to extrude the composition melt, then rapidly cooling on a constant-temperature metal roller pair with the temperature of 10 ℃, and rolling into a sheet with the thickness of 1.5 mm.

The formed sheet is drawn and then subjected to a drawing process. The composition is rapidly biaxially stretched at about 1 ℃ below the melt melting point, wherein stretching at 8 magnifications is performed in both MD and TD directions. The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. Since the stretched separator becomes thin and is likely to wrinkle in a non-stretched state, the separator needs to be stretched under a force of 1% or less of the tensile strength of the separator and pulled into an extraction step.

The porous film was pulled at room temperature and stretched appropriately in the transverse direction of the separator to widen the transverse width thereof at a width increase ratio of 15%. The porous membrane is then pulled to dip into a solution containing the adjuvant.

In the extraction process, washing by dichloromethane is carried out to extract the white oil and the residual antioxidant in the diaphragm, and then the residual dichloromethane in the diaphragm is taken out by constant-temperature hot air at 40 ℃ to finally obtain the primary porous film.

Then suspending nano alumina particles with the median particle size D50 of 30nm and the maximum particle size of 60nm in NMP solution at the mass concentration of 0.5%, wherein the mass of the prepared solution is 78 times of that of the pretreated diaphragm, the mass of the treated diaphragm is calculated by the hourly production of the diaphragm, and the solution needs to be demagnetized by a 12000GS magnetic rod and then used;

the above primary porous film was then pulled up the porous film at room temperature, immersed in the suspension, subjected to a treatment for 30 seconds, then pulled out under a tension of 100N per meter, and washed with pure water at 25 ℃, and dried through the microporous film at 90 ℃.

Dissolving an antioxidant (BASF Irganox 3114) into dichloromethane at the mass concentration of 0.05% at room temperature to prepare a solution, wherein the mass of the prepared solution is 100 times of that of the pretreated diaphragm, the mass of the treated diaphragm is calculated by the hourly production of the diaphragm, the solution is filtered by a 50nm filter screen, then 0.01% of ethanol is added in mass fraction, and then the solution is introduced into a semi-closed space, and meanwhile, a pure water solution is injected above the solution to prevent the solution concentration from fluctuating due to volatilization. The solution dissolved with the antioxidant is continuously self-circulated, the concentration of the solution is detected by the detection device and fed back to the control system, and the stability of the concentration is ensured.

Then drawing the dried porous membrane into a semi-closed space to be in contact with the solution for not less than 15s, wherein the drawing tension is 100N per meter, the longitudinal running speed is 50m/min, and the running distance of the membrane in the solution is 13 m;

then dried again at a drying temperature of 40 ℃.

And then the mixture is processed and shaped by constant temperature hot air at 135 ℃ for 5s to obtain a film product which contains inorganic particles and has excellent oxidation resistance.

Example 4

With respect to 100 parts by weight of the total of the high molecular weight polyethylene (VH200U, KPIC)25 parts by weight and the white oil (X430, shell) 75 parts by weight, 3 parts by weight of polyvinylidene fluoride (DS205, yoto mountain kanos) 0.2 parts by weight of an antioxidant (Irg1010(Ciba Specialty Chemicals basf)) and 0.1 parts by weight of an antioxidant (P168(Ciba Specialty Chemicals co., ltd.)) were added, and these were mixed in this order. Firstly, the ultra-high molecular weight polyethylene powder, the fluororesin and the antioxidant are uniformly mixed by using a high-speed mixer, and the mixing uniformity is determined by detecting the content of the antioxidant by infrared rays. In the kneading step, the mixed ultrahigh molecular weight polyethylene material is fed into a twin-screw extruder together with white oil and kneaded to finally prepare a gel-like composition melt.

And entering a forming process, using a T-shaped die head to extrude the composition melt, then rapidly cooling on a constant-temperature metal roller pair with the temperature of 10 ℃, and rolling into a sheet with the thickness of 1.5 mm.

The formed sheet is drawn and then subjected to a drawing process. The composition is rapidly biaxially stretched at about 1 ℃ below the melt melting point, wherein stretching at 8 magnifications is performed in both MD and TD directions. The uniformity of the temperature field needs to be controlled during stretching, and the temperature difference between different points of the temperature field in the stretching area is less than 0.5 ℃. Since the stretched separator becomes thin and is likely to wrinkle in a non-stretched state, the separator needs to be stretched under a force of 1% or less of the tensile strength of the separator and pulled into an extraction step.

In the extraction process, washing by dichloromethane is carried out to extract the white oil and the residual antioxidant in the diaphragm, and then the residual dichloromethane in the diaphragm is taken out by constant-temperature hot air at 40 ℃ to finally obtain the primary porous film.

Suspending paraffin phase change particles with a median particle size D50 of 30nm and a maximum particle size of 60nm, an inorganic shell and a phase change temperature of 80-85 ℃ in a dichloromethane solution at a mass concentration of 0.5% to prepare a suspension solution, wherein the mass of the prepared solution is 100 times that of a pretreated diaphragm, and the mass of the treated diaphragm is calculated by the hourly production of the diaphragm.

And then drawing and immersing the primary porous membrane into the suspension at room temperature, carrying out treatment for 30s, then drying again, wherein the drying temperature is 40 ℃, carrying out treatment and shaping through a hot roller at 135 ℃, and the shaping time is 3s, thus finally obtaining the film product containing the phase-change material.

Dissolving an antioxidant (BASF Irganox 3114) into dichloromethane at the mass concentration of 0.05% at room temperature to prepare a solution, wherein the mass of the prepared solution is 100 times of that of the pretreated diaphragm, the mass of the treated diaphragm is calculated by the hourly production of the diaphragm, the solution is filtered by a 50nm filter screen, then 0.01% of ethanol is added in mass fraction, and then the solution is introduced into a semi-closed space, and meanwhile, a pure water solution is injected above the solution to prevent the solution concentration from fluctuating due to volatilization. The solution dissolved with the antioxidant is continuously self-circulated, the concentration of the solution is detected by the detection device and fed back to the control system, and the stability of the concentration is ensured.

Drawing the porous membrane into a semi-closed space to be in contact with the solution for not less than 15s, wherein the drawing tension is 100N per meter, the longitudinal running speed is 50m/min, and the running distance of the membrane in the solution is 13 m;

then dried again at a drying temperature of 40 ℃.

Finally, the phase-change material film with higher oxidation resistance is obtained by constant-temperature hot air treatment and shaping at 133 ℃ for 6 s.

Example 5

The porous films obtained in examples 1 to 4 were coated. And (3) coating PVDF (polyvinylidene fluoride) coatings with the thickness of 1 micrometer on two sides of the porous membrane to obtain a porous membrane product with excellent electrical property.

The porous film obtained in the above comparative example was tested as follows

	Oxidation induction period (min)	Temperature of film breaking (. degree. C.)
			Comparative example 1	3.5	155
Comparative example 2	5.5	163
			Example 1	43	156
Example 2	46	183
			Example 3	45	165
Example 4	45	159
			Example 5	48	170