CZ2013219A3 - Nonwoven fabric of co-polymeric imide nanofiber, process of its preparation and use - Google Patents

Abstract

The tetracarboxylic acid dianhydride monomer and the diamine monomer are subjected to polycondensation in a highly polar solvent reaction medium in mechanical agitation to form an amide carboxylic acid copolymer solution; the amidecarboxylic acid copolymer solution is electrostatically spun in a high voltage electrical field to form a nanofiber nonwoven fabric from an amide carboxylic acid copolymer; and then the nonwoven fabric is imidized. The non-woven fabric of imide nanofiber copolymer has properties such as high tear resistance, high porosity, high and low temperature resistance, and excellent mechanical properties, etc., and can be used in the battery membrane and condenser membrane.

Description

Imolymer nanofiber copolymer nonwoven fabric, method of production and use

Field of technology

The present invention relates to an imide copolymer, to a process for its production and to its use, and in particular to a nonwoven fabric made of an imide nanofiber copolymer, to a process for its production and to its use as a battery membrane.

State of the art

Chemical energy sources are a very important part of modern life, and products such as mobile phone batteries, car batteries, etc. are essential for people's quality of life. Battery safety is an important scientific and technological task as well as a social responsibility. The technological key to solving the issue of battery safety is the development of safe battery membranes. At present, polyethylene (PE), polypropylene (PP), etc. battery membranes are used industrially, which cannot guarantee integrity at high temperatures due to low melting point and too high heat shrinkage, which leads to battery membrane failure due to heat shrinkage or even melting due to overheating, overcharging, etc., leading to serious accidents such as heat leakage and explosion caused by internal short circuit of the battery. To solve problems with the safety of chemical energy sources, the development of materials with good temperature resistance and resistance to heat shrinkage and the use of these materials in battery membranes is essential.

The essence of the invention

It is an object of the present invention to provide a copolymer imide nanofiber nonwoven fabric which is characterized by properties such as tear resistance, high porosity, high and low temperature resistance, excellent mechanical properties, etc.

Another object of the present invention is to provide a method for producing a nonwoven fabric from a polymeric imide nanofiber according to the present invention.

Another object of the present invention is the use of a polymeric imide nanofiber nonwoven fabric in a battery membrane.

To achieve the above objects, the following technical solutions are used in the present invention:

A. The imide nanofiber copolymer nonwoven fabric of the present invention is formed by copolymerizing more than three of the four monomers (1), (II), (III) and (IV) to form a polymeric amide carboxylic acid, followed by electrostatic spinning and imidization:

(and),

h ₂ n — r ₂ —nh ₂ (lil).

H ₂ N ~ R 4 - nh ₂ (IV), wherein the copolymer imide has the following chemical structural formula:

n is a natural number in the range of 50-300; m is a natural number in the range of 50-300, R 1 and R 3 are structures of a C4-C30 tetracarboxylic acid dianhydride monomeric residue; R2 and R4 are the structures of the C8-C18 diamine monomeric residue, and the ratio of the total number of moles of tetracarboxylic acid dianhydride monomers to the total number of moles of diamine monomers is always 1: 1.

Preferably, the imide nanofiber copolymer nonwoven fabric is formed by copolymerizing one tetracarboxylic acid dianhydride monomer and two diamine monomers, i.e., the above three monomers (I), (III) and (IV) or (II), (III) and (IV). The molar ratio of the three monomers (I) :( III) :( IV) or (II) :( III) :( IV) is [1]: [0.05-0.95]: [0.05-0.95 ].

Preferably, the imide nanofiber copolymer nonwoven fabric is further formed by copolymerizing two tetracarboxylic acid dianhydride monomers and one diamine monomer, i.e., the above three monomers (I), (II) and (III) or (I), (II) and (IV), wherein the molar ratio of the three monomers (1) :( 11) :( 111) or (l) :( 11) :( IV) is [0.05-0.95]: (0.05-0.95]: [ 1].

Preferably, the imide nanofiber copolymer nonwoven fabric is further formed by copolymerizing two tetracarboxylic acid dianhydride monomers and two diamine monomers, i.e., the above four monomers (I), (II), (III) and (IV), wherein the molar ratio of the four monomers [(1 ) + (11)]: [(III) + (1V)] is 1: 1.

Preferably, R _x and R ₃ are selected from the following structures of tetracarboxylic acid dianhydride residues:

biphenyl dianhydride benzophenontetracarboxylic dianhydride pyromellitic acid dianhydride

diphenylsulfone dianhydride

d ife nyleth erdianhydride

naphthalene tetracarboxylic acid dianhydride

hydroquinone diphthalic anhydride cyclohexanetetracarboxylic acid dihydride cyclobutanetetracarboxylic acid dianhydride

acids with a 3,6-alkene bridge

diphenyldimethylsilantetracarboxylic acid dianhydride bis (trifluoromethyl) diphenyldianhydride difluoropyromellitic methane tetracarboxylic acid dianhydride

terphenyltetracarboxylic acid dianhydride cyclohexanetetracarboxylic acid dianhydride diphenyl disulfide dianhydride

Preferably, R ₂ and R ₄ are selected from the following diamine residue structures:

methylenedianiline

m-phenylenediamine benzidine

bisphaminophenoxyphenylsulfone

2-methyldiphenyl ether lamin

triphenyldietherdiamine diphenoxytriphenylphosphine oxide-diamine

diphenoxybisphenoldiamine

2,6-pyridinediamine

2,6-pyrimidinebiphenyldiamine

diphenoxydiphenylketondiamine 5-methyl-m-phenylenediamine

The chemical components of the copolymer imide nanofiber of the present invention are the copolymerization product of one dianhydride monomer and two diamine monomers, or the copolymerization product of two dianhydride monomers and one diamine monomer, or the copolymerization product of two dianhydride monomers and two diamine monomers. The specific residues R 1 and R 3 are the same or different, and likewise the residues R ₂ and R 4 are the same or different; when R 1 and R ₃ are the same, R ₂ and R ₄ are different; and when R ₂ and R ₄ are the same, R 1 and R ₃ must be different to ensure that the chemical components of the copolymer imide nanofiber are formed by copolymerizing at least three monomers.

The imide nanofiber copolymer nonwoven fabric of the present invention has a thickness of 10-60 μm and an elongation at break of at least 20%, is completely insoluble in common organic solvents, has a glass transition temperature of at least 210 ° C, and a thermal decomposition temperature of at least 510 °. C and a melting point higher than 350 ° C, does not melt at a temperature lower than the decomposition temperature, has a porosity higher than 80%, a mechanical strength higher than 20 MPa and a resistance to electric shock greater than 1 x 10 ⁷ V / m. The electrostatically spun imide nanofiber copolymer having these features has tear resistance, heat shrinkage resistance, high temperature resistance and high voltage and high current overcharge resistance, and the imide nanofiber nonwoven fabric of the present invention has a huge market potential for industrial use in various high-capacity and high-current battery membranes and capacitor membranes, such as automotive batteries and supercapacitors.

Another object of the present invention is to provide a method of making a nonwoven

imide nanofiber copolymer fabrics, wherein the method steps include:

(1) purification of more than three monomers, introduction into a polymerization boiler together with an appropriate amount of solvent, agitation for a period of time to form a copolymer amide carboxylic acid solution (polymeric imide precursor), electrostatic spinning of the copolymer amide carboxylic acid solution in a high voltage electric field and collection using a stainless steel cylinder as a collector to form a nanofiber amide carboxylic acid nanofiber nonwoven fabric.

The solvent used is a highly polar solvent, preferably Ν, Ν-dimethylformamide (DMF) or Ν, Ν-dimethylacetamide (DMAC); agitation time is 1-10 h, preferably 5-10 h; the reaction temperature is 0-30 ° C, preferably 5-10 ° C; the electric field strength for electrospinning is preferably 250-300 Kv / m and the diameter of the stainless steel cylindrical collector is 0.3 m.

(2) placing the obtained nanofiber amide carboxylic acid nanofiber nonwoven fabric in a high temperature furnace and heating for imidization.

In this case, the imidization is performed in a nitrogen gas atmosphere, and the heating temperature increase program includes heating from room temperature to 200-250 ° C with a temperature rise rate of 20 ° C / min, and maintaining at a temperature for 30 minutes, heating to 330 -370 ° C with a temperature rise rate of 5 ° C / min and holding at a temperature for 30 min, and turning off the power.

(3) Characterization of properties, including measurement of absolute viscosity of copolymer amide carboxylic acid solution and spinning solution, diameter of electrostatically spun nanofiber copolymer amide carboxylic acid, thermal decomposition temperature of nonwoven fabric of copolymer imide nanofiber, mechanical properties (strength, elongation at break, etc.) of nonwoven. imide nanofiber copolymer fabrics, glass transition temperature of the imide nanofiber copolymer nonwoven fabric, specific surface area of the imide nanofiber copolymer nonwoven fabric, and resistance to electrical breakdown of the copolymer imide nanofiber fabric.

In the present invention, an NDJ-8S viscometer (Shanghai Precision & Scientific Instrument Company) is used to measure the absolute viscosity of the amide carboxylic acid copolymer solution and the spinning solution; the diameter of the electrostatically spun nanofibrous amide carboxylic acid is measured by a scanning electron microscope VEGA 3 SBU (Czech Republic); The WRT-3P thermogravimetric analyzer (TGA) (Shanghai Precision & Scientific Instrument Co., Ltd.) is used to measure the thermal decomposition temperature of a copolymer imide nanofiber nonwoven fabric; The CMT8102 universal testing apparatus (Shenzhen SANS Materials Testing Co., Ltd.) is used to measure the mechanical properties (strength, elongation at break, etc.) of a nonwoven copolymer imide nanofiber; A Diamond dynamic mechanical analyzer (DMA) (Perkin-Elmer, America) is used to measure the glass transition temperature of a copolymer imide nanofiber; the specific surface area of the porous imide nanofiber copolymer membrane or nonwoven fabric of the present invention is measured by a pore and specific surface area measuring apparatus JW-K (Beijing JWGB Sci & Tech Co., Ltd.); and the electrical puncture resistance of the copolymer imide nanofiber nonwoven fabric was measured by a DJD-20KV dielectric puncture tester (Beijing crown measurement test instrument Co., LTD).

The porosity of the imide nanofiber copolymer nonwoven fabric of the present invention is calculated according to the following formula:

porosity β = [1- (p / po)] * 100 where p is the density (g / cm ³ ) of the imide nanofiber copolymer nonwoven fabric and po is the density (g / cm ³ ) of the copolymer imide film (produced by solution casting) ).

Another object of the present invention is the use of a nonwoven copolymer imide nanofiber fabric in a battery membrane.

In the present invention, a high polarity solvent is used as the reaction medium, and dianhydride and diamine are used as the raw reaction materials, which polycondensate under mechanical agitation conditions to form a copolymeric amide carboxylic acid solution (co-PI precursor polymer). In this case, the total number of dianhydride monomers and diamine monomers is greater than three, and the total number of dianhydride functional groups is equal to or substantially equal to the total number of diamine functional groups. The obtained solution is processed into an amide carboxylic acid copolymer nanofiber nonwoven fabric by high-voltage electrospinning technology, and the nonwoven fabric is imidized at a temperature higher than 300 ² C, to form a nanofiber nonwoven fabric membrane which is resistant to high temperatures and is capable of isolate electrodes in a chemical source.

Imide nanofiber copolymer nonwoven fabric properties include high tear resistance, high porosity, high and low temperature resistance, excellent mechanical properties, and good heat and heat shrinkage resistance when used in battery membranes that do not cause the battery membrane to rupture due to thermal shrinkage or even melting during overheating, overcharging, etc., ie phenomena such as heat leakage due to internal short circuit of the batteries. In addition, imide nanofiber copolymer nonwovens have huge market potential for industrial use in a variety of high capacity and high current battery membranes and capacitor membranes, such as automotive batteries and supercapacitors.

The present invention is further described in detail together with exemplary embodiments.

Detailed description of the design

The method of making a copolymer imide nanofiber nonwoven fabric of the present invention, the method steps comprising:

1) While maintaining an equivalent total molar amount of dianhydride functional groups to the total molar amount of diamine functional groups:

mixing an appropriate amount of one dianhydride monomer and two diamine monomers or mixing an appropriate amount of two dianhydride monomers and one diamine monomer or mixing an appropriate amount of two dianhydride monomers and two diamine monomers, placing in a polymerization boiler together with an appropriate amount of solvent, agitating for some time amide carboxylic acid solution (polymer imide precursors), electrostatic spinning of the copolymer amide carboxylic acid solution in a high voltage electric field, and collecting using a stainless steel cylinder as a collector to form a porous membrane or nonwoven nanofiber fabric of the copolymer amide carboxylic acid. The solvent in this case is preferably Ν, Ν-dimethylformamide (DMF) or Ν, Ν-dimethylacetamide (DMAC); the temperature in the reaction vessel is 0-30 ° C; the agitation time is preferably 1-10 h; electric field strength at high voltage is 250-300 Kv / m; and the diameter of the stainless steel cylindrical collector is 0.3 m.

2) Placing the obtained nanofiber amide carboxylic acid nanofiber nonwoven fabric in a high temperature furnace and heating for imidization. In this case, the heating temperature rise program includes heating from room temperature to 200-250 ° C with a temperature rise rate of 20 ° C / min, and maintaining at a temperature for 30 minutes, heating to 330-370 ° C with a temperature rise rate 5 ° C / min, and holding at temperature for 30 min, and turning off the power.

3) Characterization of properties including measurement of absolute viscosity of copolymer amide carboxylic acid and spinning solution, diameter of electrostatically spun nanofiber of copolymer amide carboxylic acid, thermal decomposition temperature of nonwoven fabric of copolymer imide nanofiber, mechanical properties (strength, elongation at break, etc.) of copolymer imide n porous membranes or nonwovens, glass transition temperatures of the copolymer imide nanofiber nonwoven fabric, specific surface area of the copolymer imide nanofiber nonwoven fabric, and electrical breakdown resistance of the copolymer imide nanofiber nonwoven fabric.

Examples of embodiments of the invention

Example 1

One tetracarboxylic acid dianhydride monomer and two diamine monomers were selected for copolymerization. Purified biphenyl dianhydride (BPDA), p-phenylenediamine (PPD) and oxydianiline (ODA) were mixed in a molar ratio of 1: 0.5: 0.5 and reacted in N, N-dimethylformamide (DMF) as a solvent according to the above steps. In reaction step 1), in this example, the temperature of the reaction boiler is 10 ° C, the agitation time is 6 h, and the electric field intensity at high voltage for electrospinning is 300 Kv / m; and in reaction step 2) the temperature rise program comprises heating from room temperature to 200 ° C with a temperature rise rate of 20 ° C / min, and maintaining at a temperature for 30 minutes, heating to 350 ° C with a temperature rise rate of 5 ° C / min. min, and maintaining at 350 ° C for 30 min, turning off the power and cooling naturally to room temperature.

Characterization of properties: mass concentration of copolymer amide carboxylic acid solution (polymeric imide precursor) is 7% and its absolute viscosity is 5.2 Pa-s, copolymer amide carboxylic acid nanofiber is 100-400 nm with main distribution at 250 nm, and nonwoven fabric made of copolymer imide nanofiber has a tensile strength of 25 MPa, elongation at break 24%, glass transition temperature 285 ° C, thermal decomposition temperature 530 C, and porosity 84.2%, specific surface area 37.4 m ² / g and resistance to electrical breakdown 1.2 χ 10 ⁵ V / cm or 12 V / pm.

Example 2

One tetracarboxylic acid dianhydride monomer and two diamine monomers were selected for copolymerization. Purified pyromellitic dianhydride (PMDA), oxydianiline (ODA) and benzidine (Bz) were mixed in a molar ratio of 1: 0.6: 0.4 and reacted in N, N-dimethylformamide (DMF) as a solvent according to the above steps; in this example, in reaction step 1), the temperature of the reaction boiler is 5 ° C, the agitation time is 6 h, and the electric field strength at high voltage for electrospinning is 250 Kv / m; and in reaction step 2) the temperature rise program comprises heating from room temperature to 250 ° C with a temperature rise rate of 20 ° C / min, and maintaining at a temperature for 30 minutes, heating to 370 ° C with a temperature rise rate of 5 ° C / min. min, and maintaining at 370 ° C for 30 min, turning off the source and cooling naturally to room temperature.

Characterization of properties: mass concentration of copolymer amide carboxylic acid (polymer imide precursor) solution is 5% and its absolute viscosity is 4.8 Pa-s, copolymer amide carboxylic acid nanofiber is 100-300 nm with main distribution at 200 nm, and nonwoven fabric of imide nanofiber copolymer has a tensile strength of 24 MPa, an elongation at break of 23%, a glass transition temperature of 298 ° C, and a thermal decomposition temperature of 560 ° C, and a porosity of 82.0%, a specific surface area of 38.8 m ² / g and a resistance to electrical breakdown 1.3 χ 10 ⁵ V / cm or 13 V / pm.

Example 3

One tetracarboxylic acid dianhydride monomer and two diamine monomers were selected for copolymerization. Purified pyromellitic dianhydride (PMDA), methylenedianiline (MDA) and oxydianiline (ODA) were mixed in a molar ratio of 1: 0.5: 0.5, and reacted in N, N-dimethylformamide (DMF) as a solvent according to the above steps; in this example, in reaction step 1), the temperature of the reaction boiler is 5 s, the agitation time is 10 h, and the electric field strength at high voltage for electrospinning is 250 Kv / m; and in reaction step 2) the temperature rise program comprises heating from room temperature to 250 ° C with a temperature rise rate of 20 ° C / min and maintaining at a temperature for 30 minutes, heating to 370 ° C with a temperature rise rate of 5 ° C / min , and maintaining at 370 ° C for 30 minutes, turning off the power and cooling naturally to room temperature.

Characterization of properties: the mass concentration of the polymer imide copolymer (copolymer amide carboxylic acid, co-PAA) solution is 6% and its

Even the absolute viscosity is 4.8 Pa-s, the diameter of the copolymer annide carboxylic acid is 100-400 nm with a main distribution at 250 nm, and the nonwoven fabric of copolymer imide nanofiber has a tensile strength of 20 MPa, elongation at break 21%, temperature glass transition temperature 296 ° C, and thermal decomposition temperature 510 ° C, and porosity 85.1%, specific surface area 36.9 m ² / g and electric shock resistance 1.1 x 10 ⁵ V / cm or 11 V / pm.

Example 4

One tetracarboxylic acid dianhydride monomer and two diamine monomers were selected for copolymerization. Purified diphenylsulfone dianhydride (DSDA), bis (aminophenoxyphenyl) sulfone (BAPS) and oxydianiline (ODA) were mixed in a molar ratio of 1: 0.3: 0.7 and reacted in Ν, Ν-dimethylformamide (DMF) as a solvent according to the above steps. ; in this example, in reaction step 1), the temperature of the reaction boiler is 5 ^e C, the agitation time is 10 ha, and the electric field intensity at high voltage for electrospinning is 250 Kv / m; and in reaction step 2) the temperature rise program comprises heating from room temperature to 200 ° C with a temperature rise rate of 20 ° C / min, and maintaining at a temperature for 30 minutes, heating to 330 ° C with a temperature rise rate of 5 ° C / min. min, and maintaining at 330 ° C for 30 min, turning off the power and cooling naturally to room temperature.

Characterization of properties: mass concentration of polymeric imide copolymer (copolymer amide carboxylic acid, co-PAA) solution is 8% and its absolute viscosity is 4.2 Pa s, nanofiber diameter of copolymer annide carboxylic acid is 100-300 nm with main distribution at 180 nm, and the imide nanofiber copolymer nonwoven fabric has a tensile strength of 20 MPa, an elongation at break of 25%, a glass transition temperature of 238 ° C, and a thermal decomposition temperature of 520 ° C, and a porosity of 81.3%, a specific surface area of 36.9 m ² / ga breakdown resistance 1.4 x 10 ⁵ V / cm or 14 V / pm.

I. · ·. · · · · 4 * * • ζ · · a · · · 4 a ····

Example 5

AND

Two tetracarboxylic acid dianhydride monomers and one diamine monomer were selected for copolymerization. Purified biphenyl dianhydride (BPDA), pyromellitic dianhydride (PMDA) and oxydianiline (ODA) were mixed in a molar ratio of 0.5: 0.5: 1 and reacted in N, N-dimethylformamide (DMF) as a solvent according to the above steps. In this case, in reaction step 1), the temperature of the reaction boiler is 5 ° C, the agitation time is 10 h, and the electric field intensity at high voltage for electrospinning is 250 Kv / m; and in reaction step 2) the temperature rise program comprises heating from room temperature to 250 ° C with a temperature rise rate of 20 ° C / min, and maintaining at a temperature for 30 minutes, heating to 370 ° C with a temperature rise rate of 5 ° C / min. min, and maintaining at 370 ° C for 30 min, turning off the source and cooling naturally to room temperature.

Characterization of properties: the weight concentration of the copolymeric amide carboxylic acid solution is 6% and its absolute viscosity is 5.5 Pa-s, the diameter of the copolymer amidecarboxylic acid is 150-400 nm with a main distribution at 280 nm, and the nonwoven fabric of copolymeric imide nanofiber has and tensile strength 23 MPa, and elongation at break 22%, glass transition temperature 295 ° C, and thermal decomposition temperature 550 ° C, and porosity 85.0%, specific surface area 36.9 m ² / g and resistance to electric shock 1 , 1 χ 10 ⁵ V / cm or 11 V / pm.

Example 6

Two tetracarboxylic acid dianhydride monomers and one diamine monomer were selected for copolymerization. Purified hydroquinone diphalanic anhydride (HQ.DPA), pyromellitic dianhydride (PMDA) and oxydianiline (ODA) were reacted in a molar ratio of 0.5: 0.5: 1 in appropriate amounts of N, N-dimethylformamide (DMF) solvent according to the above steps. In this example, in reaction step 1), the temperature of the reaction boiler is 10 ° C, the agitation time is 5 h, and the electric field intensity at high voltage for electrospinning is 300 Kv / m; and in reaction step 2) the temperature rise program comprises heating from room temperature to 200 ° C s

I temperature rise rate of 20 ° C / min, and holding at a temperature for 30 min, heating to 350 ° C with a temperature rise rate of 5 ° C / min, and holding at 350 ° C for 30 min, switching off the source and natural cooling to room temperature.

Characterization of properties: the weight concentration of the copolymeric amide carboxylic acid solution is 8% and its absolute viscosity is 4.2 Pa-s, the diameter of the copolymer amidecarboxylic acid is 80-300 nm with a main distribution at 150 nm, and the nonwoven fabric of copolymeric imide nanofiber has tensile strength 23 MPa, elongation at break 24%, glass transition temperature 278 ° C, and thermal decomposition temperature 540 ° C, and porosity 81.4%, specific surface area 41.8 m ² / g and resistance to electrical breakdown 1.4 χ 10 ⁵ V / cm or 14 V / pm.

Example 7

Two tetracarboxylic acid dianhydrides and two diamines were selected for copolymerization. Purified benzophenontetracarboxylic acid dianhydride (BTDA), pyromellitic dianhydride (PMDA), benzidine (Bz) and oxydianiline (ODA) were mixed in a molar ratio of 1: 1: 1: 1 and reacted in appropriate amounts of Ν, Ν-dimethylacetamide (DMAc) as solvent according to the above steps. In this example, in reaction step 1), the temperature of the reaction boiler is 5 ° C, the agitation time is 6 h, and the electric field strength at high voltage for electrospinning is 250 Kv / m; and in reaction step 2) the temperature rise program comprises heating from room temperature to 250 ° C with a temperature rise rate of 20 ° C / min, and maintaining at a temperature for 30 minutes, heating to 370 ° C with a temperature rise rate of 5 ° C / min. min, and maintaining at 370 ° C for 30 min, turning off the source and cooling naturally to room temperature.

Characterization of properties: mass concentration of copolymeric amide carboxylic acid solution is 6% and its absolute viscosity is 4.3 Pa-s, the diameter of the copolymer amidecarboxylic acid is 100-300 nm with a main distribution at 150 nm, and the nonwoven fabric of copolymeric imide nanofiber has tensile strength 22 MPa, elongation at break 24%, glass transition temperature

288 ° C, and a thermal decomposition temperature of 540 ° C, and a porosity of 80.5%, a specific surface area of 41.8 m ² / g and an electric shock resistance of 1.5 x 10 ⁵ V / cm or 15 V / pm.

Example 8

Two tetracarboxylic acid dianhydrides and two diamines were selected for copolymerization. Purified biphenyl dianhydride (BPDA), hydroquinone diphalanic anhydride (HQDPA), p-phenylenediamine (PPD) and oxydianiline (ODA) were mixed in a molar ratio of 1: 1: 1: 1 and reacted in appropriate amounts of β, β-dimethylformamide (DMAc) as a solvent according to above steps. In this example, in reaction step 1), the temperature of the reaction boiler is 10 ° C, the agitation time is 10 h, and the electric field strength at high voltage for electrospinning is 300 Kv / m; and in reaction step 2) the temperature rise program comprises heating from room temperature to 250 ° C with a temperature rise rate of 20 ° C / min, and maintaining at a temperature for 30 minutes, heating to 350 ° C with a temperature rise rate of 5 ° C / min. min, and maintaining at 320 ° C for 30 min, turning off the source and cooling naturally to room temperature.

Characterization of properties: the weight concentration of the copolymeric amide carboxylic acid solution is 8% and its absolute viscosity is 4.0 Pa-s, the diameter of the copolymer amidecarboxylic acid is 50-250 nm with a main distribution at 150 nm, and the nonwoven fabric of copolymeric imide nanofiber has tensile strength 21 MPa, elongation at break 23%, glass transition temperature 284 ° C, thermal decomposition temperature 530 ° C, porosity 80.2%, specific surface area 42.0 m ² / g resistance to electric shock 1.5 χ 10 ⁵ V / cm or 15 V / pm.

The above examples are not intended to limit the scope of the present invention in any way. Those skilled in the art may make some minor modifications and adaptations of the present invention in accordance with the foregoing, which still fall within the scope of the present invention.

Claims (2)

PATENT CLAIMS An imide nanofiber copolymer nonwoven fabric, characterized in that it is formed by copolymerizing more than three of the following four monomers (I), (II), (III) and (IV) to form a copolymeric amide carboxylic acid, followed by electrostatic spinning, and by imidization: (II). H ₂ N — R ₂ —NH ₂ H ₂ N — R 4 — nh ₂ (III), (IV), wherein the copolymer imide has the following chemical structural formula: n is a natural number in the range of 50-300; m is a natural number in the range of 50-300, R 1 and R 8 are structures of a C4-C30 tetracarboxylic acid dianhydride monomeric residue; R2 and R4 are the structures of the C6-C30 diamine monomeric residue, and the ratio of the total number of moles of tetracarboxylic acid dianhydride monomers to the total number of moles of diamine monomers is always 1: 1. Imolymer nanofiber copolymer nonwoven fabric according to claim 1, characterized in that the imide nanofiber copolymer is formed by copolymerizing the three above-mentioned monomers (I), (III) and (IV), or (II), (III) and (IV). ), where the molar ratio of the three monomers (I) :( III) :( IV) or (II) :( III) :( IV) is [1]: [0.05-0.95]: [0.05 -0.95]. Imolymer nanofiber copolymer nonwoven fabric according to claim 1, characterized in that the imide nanofiber copolymer is formed by copolymerizing the three above-mentioned monomers (I), (II) and (III) or (I), (II) and (IV) , where the molar ratio of the three monomers is (1) :( 11) :( 111) or (l) :( 11) :( IV) is [0.05-0.95] :( 0.05-0.95] [1]. Imolymer nanofiber copolymer nonwoven fabric according to claim 1, characterized in that the imide nanofiber copolymer is formed by copolymerizing said four monomers (I), (II), (III) and (IV), wherein the molar ratio of the four monomers [(1) ) + (11)]: [(1H) + (1V)] is 1: 1. Imolymer nanofiber copolymer nonwoven fabric according to any one of claims 1 to 4, characterized in that R 1 and R ₃ are selected from the following structures of tetracarboxylic acid dianhydride residues: benzophenontetracarboxylic dianhydride pyromellitic acid dianhydride biphenyl dianhydride diphenylsulfonic anhydride d ifeny leth erdia n hydrid naphthalene tetracarboxylic acid dianhydride hydroquinone digthal anhydride cyclohexanetetracarboxylic acid diahydride with 3,6-alkene bridge cyclobutantetracarboxylic acid dianhydride diphenyldimethylsilane dianhydride bis (trifluoromethyl) diphenyldifluoropromellitic tetracarboxylic acid dianhydride terphenyltetracarboxylic acid dianhydride methane tetracarboxylic acid cyclohexanetetracarboxylic acid dianhydride diphenyl disulfide dianhydride Imolymer nanofiber copolymer nonwoven fabric according to any one of claims 1 to 4, characterized in that R ₂ and R ₄ are selected from the following diamine residue structures: benzidine bis (aminophenoxyphenyl) sulfone triphenyldietherdiamine 2,6-pyridinediamine h ₃ c (3,3'-dimethyl) diphenylmethanediamine 5-methyl-m-phenylenediamine Imolymer nanofiber copolymer nonwoven fabric according to any one of claims 1 to 4, characterized in that it has an elongation at break of 20-30%, a porosity of 80-86%, a tensile strength of 20-25 MPa, an electric shock resistance 1 χ 10 ⁷ -1, 5 χ 10 ⁷ V / m and thermal decomposition temperature 510-560 ° C. 8. A process for producing a nonwoven fabric from a copolymer imide nanofiber according to claim 1, characterized in that 1) more than three of the dianhydride and diamine monomers are purified, then placed in a polymerization vessel together with an appropriate amount of solvent, agitated for a period of time to form a copolymeric amide carboxylic acid solution as a polymeric imide precursor, the copolymeric amidecarboxylic acid solution is electrospun electrostatically high voltage field, collection is performed using a stainless steel roller as a collector to form a nonwoven nanofiber copolymer amide carboxylic acid fabric; 2) The obtained nanofiber nanofiber copolymer amide carboxylic acid fabric is placed in a high temperature furnace and heated for imidization. 9. A method of making a copolymer imide nanofiber nonwoven fabric according to claim 8, wherein the solvent is polar. A process for producing a nonwoven fabric from a copolymer imide nanofiber according to claim 8, characterized in that the polar solvent is Ν, Ν-dimethylformamide (DMF) or Ν, Ν-dimethylacetamide (DMAC). A process for producing a nonwoven fabric from a copolymer imide nanofiber according to claim 8, characterized in that the polymerization temperature in the reaction boiler is 0-30 ° C, the reaction time is 1-10 h, and the electric field intensity at high voltage is 250-300. Kv. A method of making a copolymer imide nanofiber nonwoven fabric according to claim 8 or 11, wherein the imidization temperature rise program comprises heating from room temperature to 200-250 ° C with a temperature rise rate of 20 ° C / min and maintaining at a temperature for 30 minutes, heating to 330-370 ° C with a temperature rise rate of 5 ° C / min and maintaining at a temperature for 30 minutes, and turning off the power. Use of a copolymer imide nanofiber nonwoven fabric according to claim 1 in the battery membrane.