U.S. patent application number 13/877106 was filed with the patent office on 2013-08-01 for copolymide nano-fiber non-woven fabric, process for producing the same and the use thereof.
This patent application is currently assigned to JIANGXI ADVANCE NANOFIBER S&T CO., LTD. The applicant listed for this patent is Shuiliang Chen, Chuyun Cheng, Ping He, Haoqing Hou, Xiaoming Kuang, Xiaoyi Lv, Jinsheng Ren, Xiaoping Zhou. Invention is credited to Shuiliang Chen, Chuyun Cheng, Ping He, Haoqing Hou, Xiaoming Kuang, Xiaoyi Lv, Jinsheng Ren, Xiaoping Zhou.
Application Number | 20130196562 13/877106 |
Document ID | / |
Family ID | 45891826 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130196562 |
Kind Code |
A1 |
Hou; Haoqing ; et
al. |
August 1, 2013 |
COPOLYMIDE NANO-FIBER NON-WOVEN FABRIC, PROCESS FOR PRODUCING THE
SAME AND THE USE THEREOF
Abstract
A copolyimide nano-fiber non-woven fabric, a process for
producing the same and the use thereof. The process comprises the
following steps: tetracid dianhydride monomer and diamine monomer
are polycondensated in the reaction medium of a high polar solvent
under mechanical agitation to form a solution of a copolyamic acid;
the copolyamic acid solution is electrostatically spinned under a
high voltage electric field to give a non-woven fabric of a
nano-fiber of the copolyamic acid; and then the non-woven fabric is
imidized. The copolyimide nano-fiber non-woven fabric has features
of a strong tear resistance, a high porosity, high/low-temperature
resistances and excellent mechanical properties, etc., and can be
used in battery membrane and capacitor membrane.
Inventors: |
Hou; Haoqing; (Nanchang,
CN) ; Cheng; Chuyun; (Nanchang, CN) ; Chen;
Shuiliang; (Nanchang, CN) ; Zhou; Xiaoping;
(Nanchang, CN) ; Lv; Xiaoyi; (Nanchang, CN)
; He; Ping; (Nanchang, CN) ; Kuang; Xiaoming;
(Nanchang, CN) ; Ren; Jinsheng; (Nanchang,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hou; Haoqing
Cheng; Chuyun
Chen; Shuiliang
Zhou; Xiaoping
Lv; Xiaoyi
He; Ping
Kuang; Xiaoming
Ren; Jinsheng |
Nanchang
Nanchang
Nanchang
Nanchang
Nanchang
Nanchang
Nanchang
Nanchang |
|
CN
CN
CN
CN
CN
CN
CN
CN |
|
|
Assignee: |
JIANGXI ADVANCE NANOFIBER S&T
CO., LTD
Nanchang, Jiangxi
CN
|
Family ID: |
45891826 |
Appl. No.: |
13/877106 |
Filed: |
September 30, 2010 |
PCT Filed: |
September 30, 2010 |
PCT NO: |
PCT/CN2010/077517 |
371 Date: |
March 29, 2013 |
Current U.S.
Class: |
442/327 ;
264/103 |
Current CPC
Class: |
D04H 1/00 20130101; D04H
1/4326 20130101; H01M 2/162 20130101; D04H 1/728 20130101; D04H
3/009 20130101; D01F 6/78 20130101; C08G 73/1042 20130101; D01F
6/74 20130101; D04H 3/016 20130101; C08G 73/10 20130101; Y10T
442/60 20150401; Y02E 60/10 20130101 |
Class at
Publication: |
442/327 ;
264/103 |
International
Class: |
D04H 1/00 20060101
D04H001/00 |
Claims
1.-13. (canceled)
14. A copolyimide nano-fiber non-woven fabric, characterized in
that the non-woven fabric is formed by the copolymerization of the
following four monomers of (I), (II), (III) and (IV) to form a
copolyamic acid, then electrostatical spinning and imidization:
##STR00007## said copolyimide nano-fiber is formed by the
copolymerization of the above four monomers of (I), (II), (III) and
(IV), wherein the molar ratio relationship of the four monomers is
[(I)+(II)]:[(III)+(IV)]=1:1; wherein the copolyimide has the
following chemical structure formula: ##STR00008## n is a natural
number between 50-300; m is a natural number between 50-300,
R.sub.1 and R.sub.3 are C.sub.4-C.sub.30 tetracid dianhydride
monomer residue structures; R.sub.2 and R.sub.4 are
C.sub.6-C.sub.30 diamine monomer residue structures; the ratio of
the total mole number of the tetracid dianhydride monomers to the
total mole number of the diamine monomers in the copolymerization
reaction is always kept at 1:1; and said copolyimide nano-fiber
non-woven fabric has breaking elongation of 20-30%, a porosity of
80-86%, tensile strength of 20-25 MPa, electrical breakdown
strength of 1.times.10.sup.7-1.5.times.10.sup.7 V/m, and a thermal
decomposition temperature of 510-560.degree. C.
15. The copolyimide nano-fiber non-woven fabric according to claim
14, characterized in that R.sub.1 and R.sub.3 are selected from one
of the following tetracid dianhydride residue structures,
respectively ##STR00009## ##STR00010##
16. The copolyimide nano-fiber non-woven fabric according to claim
14, characterized in that R.sub.2 and R.sub.4 are selected from one
of the following diamine residue structures, respectively:
##STR00011## ##STR00012##
17. A process for producing the copolyimide nano-fiber non-woven
fabric according to claim 14, characterized in that the process
comprises (1) purifying the four monomers, adding into a
polymerization reaction kettle together with an appropriate amount
of a solvent, reacting under agitation for a time period to obtain
a solution of a copolyamic acid, electrostatical spinning the
copolyamic acid solution in a high voltage electric field, and
collecting using a stainless steel roller as a collector to obtain
a non-woven fabric of a nano-fiber of the copolyamic acid, wherein
said solvent is N,N-dimethyl formamide (DMF) or N,N-dimethyl
acetamide (DMAC) in polar solvents; the polymerization reaction
temperature of said reaction kettle is 0-30.degree. C.; the
reaction time is 1-10 h; and the electric field intensity of the
high voltage electric field is 250-300 Kv; (2) placing the obtained
non-woven fabric of a nano-fiber of the copolyamic acid in a high
temperature furnace, and heating for imidization; and the
temperature rise program of said imidization process includes
heating from room temperature to 200-250.degree. C. at a
temperature rise rate of 20.degree. C./min, and maintaining at the
temperature for 30 min, heating to 330-370.degree. C. at a
temperature rise rate of 5.degree. C./min, and maintaining at the
temperature for 30 min, and shutting off the power source.
Description
SUMMARY OF THE UTILITY MODEL
[0001] The present invention relates to a copolyimide, a process
for producing the same and the use thereof, and in particular to a
copolyimide nano-fiber non-woven fabric, a process for producing
the same and the use thereof as battery membrane.
BACKGROUND ART
[0002] Chemical power source is an extremely important part of
modern life, and products, such as mobile phone batteries,
automobile power batteries in development, etc., are indispensable
for human to pursue high quality life. The safety of the batteries
is important scientific and technological issues and social
responsibility issue concerned by human, and the development of
safe battery membranes is a technology key to solve the battery
safety issues. Currently, the battery membrane of polyethylene
(PE), polypropylene (PP), etc., used in battery industry cannot
ensure the integrity thereof under a relatively high temperature
due to a low melting temperature and an over-high heat shrink
ratio, thus leading to breakage of the battery membrane due to
thermal shrinkage even melting, under the conditions of overheat,
overcharge, etc., and resulting in serious accidents, such as
thermal runaway and explosion, due to the internal short circuit of
batteries. Therefore, it is critical to develop materials with good
heat resistance and thermal shrinkage resistance and to apply the
material in battery membranes to solve the safety issues with
respect to chemical power source.
CONTENT OF THE INVENTION
[0003] An object of the present invention is to provide a
copolyimide nano-fiber non-woven fabric with the features, such as
strong tear resistance, a high porosity, high/low-temperature
resistances, excellent mechanical performances, etc.
[0004] Another object of the present invention is to provide a
method for producing the polyimide nano-fiber non-woven fabric of
the present invention.
[0005] Yet another object of the present invention is use of the
polyimide nano-fiber non-woven fabric in battery membrane.
[0006] To achieve the above objects, in the present invention, the
following technical solution is used:
[0007] A copolyimide nano-fiber non-woven fabric of the present
invention, is formed by the copolymerization of more than three of
the four monomers of (I), (II), (III) and (IV) to form a copolyamic
acid, then electrostatical spinning and imidization:
##STR00001##
[0008] wherein the copolyimide has the following chemical structure
formula:
##STR00002##
[0009] n is a natural number between 50-300; m is a natural number
between 50-300, R.sub.1 and R.sub.3 are C.sub.4-C.sub.30 tetracid
dianhydride monomer residue structures; R.sub.2 and R.sub.4 are
C.sub.6-C.sub.30 diamine monomer residue structures, and the ratio
of the total mole number of the tetracid dianhydride monomers to
the total mole number of the diamine monomers is always kept at
1:1.
[0010] Preferably, a copolyimide nano-fiber non-woven fabric, is
formed by the copolymerization of one tetracid dianhydride monomer
and two diamine monomers, i.e., the above three monomers of (I),
(III) and (IV) or (II), (III) and (IV). Wherein the molar ratio of
the three monomers is (I):(III):(IV) or
(II):(III):(IV)=[1]:[0.05-0.95]:[0.05-0.95].
[0011] Preferably, a copolyimide nano-fiber non-woven fabric, also
can be formed by the copolymerization of two tetracid dianhydride
monomers and one diamine monomers, i.e., the above three monomers
of (I), (II) and (III) or (I), (II) and (IV), wherein the molar
ratio of the three monomers is (I):(II):(III) or
(I):(II):(IV)=[0.05-0.95]:[0.05-0.95]:[1].
[0012] Preferably, a copolyimide nano-fiber non-woven fabric, also
can be formed by the copolymerization of two tetracid dianhydride
monomers and two diamine monomers, i.e., the above four monomers of
(I), (II), (III) and (IV), wherein the molar ratio relationship of
the four monomers is [(I)+(II)]:[(III)+(IV)]=1:1.
[0013] Preferably, R.sub.1 and R.sub.3 are selected from one of the
following tetracid dianhydride residue structures,
respectively:
##STR00003## ##STR00004##
[0014] Preferably, R.sub.2 and R.sub.4 are selected from one of the
following diamine residue structures, respectively:
##STR00005## ##STR00006##
[0015] The chemical components of the copolyimide nano-fiber of the
present invention can be 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. In particular, R.sub.1 and
R.sub.3 therein can be the same residues and also can be different
residues, and R.sub.2 and R.sub.4 can be the same residues and also
can be different residues; when R.sub.1 and R.sub.3 are the same,
R.sub.2 and R.sub.4 are different; and when R.sub.2 and R.sub.4 are
the same, R.sub.1 and R.sub.3 must be different, to ensure that the
chemical components of said copolyimide nano-fiber is formed by the
copolymerization of at least three monomers.
[0016] The copolyimide nano-fiber non-woven fabric of the present
invention has a thickness of 10-60 .mu.m and breaking elongation
not lower than 20%, is completely insoluble in a common organic
solvent, has a glass transition temperature not lower than
210.degree. C., a thermal decomposition temperature not lower than
510.degree. C. and a melting temperature higher than 350.degree.
C., even does not melt at a temperature lower than the
decomposition temperature, and has a porosity higher than 80%,
mechanical strength higher than 20 MPa and electrical breakdown
strength greater than 1.times.10.sup.7 V/m. The electrostatically
spun copolyimide nano-fiber non-woven fabric with such features has
tear resistance, thermal shrinkage resistance, high temperature
resistance and high-voltage high-current overcharge resistance, and
the imide nano-fiber non-woven fabric of the present invention has
huge potential market for use in various high-capacity and high
power battery membranes and capacitor membranes, such as
industries, like automobile power batteries and
supercapacitors.
[0017] Another object of the present invention is to provide a
process for producing the copolyimide nano-fiber non-woven fabric,
and the steps of the process comprise:
[0018] (1) purifying more than three monomers, adding into a
polymerization reaction kettle together with an appropriate amount
of a solvent, reacting under agitation for a time period to obtain
a solution of a copolyamic acid (polyimide precursor),
electrostatically spinning the copolyamic acid solution in a high
voltage electric field, and collecting using a stainless steel
roller as a collector to obtain a non-woven fabric of a nano-fiber
of the copolyamic acid.
[0019] Wherein the solvent used is a high polar solvent, preferably
one of N,N-dimethyl formamide (DMF) and N,N-dimethyl acetamide
(DMAC); the time of the reaction under agitation is 1-10 h,
preferably 5-10 h; the reaction temperature is 0-30.degree. C.,
preferably 5-10.degree. C.; the electric field intensity for the
electrostatic spinning is preferably 250-300 Kv/m; and the diameter
of the stainless steel roller collector is 0.3 m.
[0020] (2) placing the obtained non-woven fabric of a nano-fiber of
the copolyamic acid in a high temperature furnace, and heating for
imidization.
[0021] In this situation, the imidization is performed in a
nitrogen gas atmosphere, and the temperature rise program of the
heating process includes heating from room temperature to
200-250.degree. C. at a temperature rise rate of 20.degree. C./min,
and maintaining at the temperature for 30 min, heating to
330-370.degree. C. at a temperature rise rate of 5.degree. C./min,
and maintaining at the temperature for 30 min, and shutting off the
power source.
[0022] (3) Property characterization, comprising measuring the
absolute viscosity of the copolyamic acid solution and the spinning
solution, the diameter of the electrostatically spun copolyamic
acid nano-fiber, the thermal decomposition temperature of the
copolyimide nano-fiber non-woven fabric, the mechanical properties
(strength, breaking elongation, etc.) of the copolyimide nano-fiber
non-woven fabric, the glass transition temperature of the
copolyimide nano-fiber non-woven fabric, the specific surface area
of the copolyimide nano-fiber non-woven fabric, and the electrical
breakdown strength of the copolyimide nano-fiber non-woven
fabric.
[0023] In the present invention, a NDJ-8S viscometer (Shanghai
Precision & Scientific Instrument Company) is used to measure
the absolute viscosity of the polyamic acid solution and the
spinning solution; the diameter of the electrostatically spun
polyamic acid nano-fiber is measured by a scanning electron
microscope VEGA 3 SBU (Czech Republic); a WRT-3P thermogravimetric
analyzer (TGA) (Shanghai Precision & Scientific Instrument Co.,
Ltd.) is used to measure the thermal decomposition temperature of
the copolyimide nano-fiber non-woven fabric; a CMT8102 electronic
universal testing machine (Shenzhen SANS Materials Testing Co.,
Ltd.) is used to measure the mechanical properties (strength,
breaking elongation, etc.) of the copolyimide nano-fiber non-woven
fabric; a Diamond dynamic mechanical analyzer (DMA) (Perkin-Elmer,
America) is used to measure the glass transition temperature of the
copolyimide nano-fiber; the specific surface area of the
copolyimide nano-fiber porous membrane or non-woven fabric of the
present invention is measured by a JW-K pore distribution and
specific surface area measuring instrument (Beijing JWGB Sci &
Tech Co., Ltd.); and the electrical breakdown strength of the
copolyimide nano-fiber non-woven fabric is measured by a dielectric
breakdown tester DJD-20 KV (Beijing crown measurement test
instrument Co., LTD).
[0024] The porosity of the copolyimide nano-fiber non-woven fabric
of the present invention is calculated by the following
formula:
porosity .beta.=[1-(.rho./.rho..sub.0)].times.100
wherein .rho. is the density (g/cm.sup.3) of the copolyimide
nano-fiber non-woven fabric, and .rho..sub.0 is the density
(g/cm.sup.3) of a copolyimide body film (produced by a solution
casting method).
[0025] Yet another object of the present invention is use of the
copolyimide nano-fiber non-woven fabric in battery membrane.
[0026] In the present invention, dianhydride and diamine are used
as the reaction raw materials and a high polar solvent as the
reaction medium, and polycondensed under mechanical agitation, to
form a solution of copolyamic acid (co-PI precursor polymer). In
this situation, the total number of the dianhydride monomers and
the diamine monomers is more than three, and the total number of
the dianhydride functional groups is equal to or substantially
equal to the total number of the diamine functional groups. The
obtained solution is processed into a non-woven fabric of a
nano-fiber of the copolyamic acid by high voltage electrostatic
spinning technology, and the non-woven fabric is imidized at a high
temperature higher than 300.degree. C., to form a high temperature
resistant nano-fiber non-woven fabric battery membrane capable of
isolating the electrodes in chemical power source. The copolyimide
nano-fiber non-woven fabric has features, such as strong tear
resistance, a high porosity, high/low-temperature resistances,
excellent mechanical performances, etc., and has good heat
resistance and thermal shrinkage resistance when used in battery
membranes, not leading to the breakage of the battery membrane due
to thermal shrinkage even melting, under the conditions of
overheat, overcharge, etc., and thus the phenomena, such as thermal
runaway, etc., due to the internal short circuit of the batteries.
In addition, the copolyimide nano-fiber non-woven fabric has huge
potential market for use in various high-capacity and high power
battery membranes and capacitor membranes, such as industries, like
automobile power batteries and supercapacitors.
[0027] The present invention is further described in detail in
conjunction with examples.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0028] A process for producing the copolyimide nano-fiber non-woven
fabric of the present invention, the steps of the process
comprise:
[0029] (1) On the basis of an equal total molar amount of the
dianhydride functional groups to the total molar amount of the
diamine functional groups, mixing appropriate amounts of one
dianhydride monomer and two diamine monomers or mixing appropriate
amounts of two dianhydride monomers and one diamine monomer or
mixing appropriate amounts of two dianhydride monomers and two
diamine monomers, adding into a polymerization reaction kettle
together with an appropriate amount of a solvent, reacting under
agitation for a time period to obtain a solution of a copolyamic
acid (polyimide precursor), electrostatically spinning the
copolyamic acid solution in a high voltage electric field, and
collecting using a stainless steel roller as a collector to obtain
a porous membrane or non-woven fabric of a nano-fiber of the
copolyamic acid. In this situation, the solvent is preferably one
of N,N-dimethyl formamide (DMF) and N,N-dimethyl acetamide (DMAC);
the temperature of the reaction kettle is 0-30.degree. C.; the time
of the reaction under agitation is preferably 1-10 h; the electric
field intensity of the high voltage electric field is 250-300 Kv/m;
and the diameter of the stainless steel roller collector is 0.3
m.
[0030] (2) Placing the obtained non-woven fabric of a nano-fiber of
the copolyamic acid in a high temperature furnace, and heating for
imidization. In this situation, the temperature rise program of the
heating process includes heating from room temperature to
200-250.degree. C. at a temperature rise rate of 20.degree. C./min,
and maintaining at the temperature for 30 min, heating to
330-370.degree. C. at a temperature rise rate of 5.degree. C./min,
and maintaining at the temperature for 30 min, and shutting off the
power source.
[0031] (3) Property characterization: comprising measuring the
absolute viscosity of the copolyamic acid solution and the spinning
solution, the diameter of the electrostatically spun copolyamic
acid nano-fiber, the thermal decomposition temperature of the
copolyimide nano-fiber non-woven fabric, the mechanical properties
(strength, breaking elongation, etc.) of the copolyimide nano-fiber
porous membrane or non-woven fabric, the glass transition
temperature of the copolyimide nano-fiber non-woven fabric, the
specific surface area of the copolyimide nano-fiber non-woven
fabric, and the electrical breakdown strength of the copolyimide
nano-fiber non-woven fabric.
Embodiment 1
[0032] One tetracid dianhydride monomer and two diamine monomers
were selected as the comonomers. Purified biphenyl dianhydride
(BPDA), p-phenylenediamine (PPD) and oxydianiline (ODA) were mixed
at a molar ratio of 1:0.5:0.5, and reacted in N,N-dimethyl
formamide (DMF) as a solvent following the above steps. In reaction
step (1), the temperature of the reaction kettle of the example is
10.degree. C., the time of the reaction under agitation is 6 h, and
the electric field intensity of the high voltage electric field for
the electrostatic spinning is 300 Kv/m; and in reaction step (2),
the temperature rise program includes heating from room temperature
to 200.degree. C. at a temperature rise rate of 20.degree. C./min,
and maintaining at the temperature for 30 min, heating to
350.degree. C. at a temperature rise rate of 5.degree. C./min, and
maintaining at 350.degree. C. for 30 min, shutting off the power
source, and naturally cooling to room temperature.
[0033] Property characterization: the mass concentration of the
copolyamic acid (polyimide precursor) solution is 7% and the
absolute viscosity thereof is 5.2 Pas, the diameter of the
copolyamic acid nano-fiber is 100-400 nm and is mainly distributed
at about 250 nm, and the copolyimide nano-fiber non-woven fabric
has tensile strength of 25 MPa, breaking elongation of 24%, glass
transition temperature of 285.degree. C., thermal decomposition
temperature of 530.degree. C., a porosity of 84.2%, a specific
surface area of 37.4 m.sup.2/g and electrical breakdown strength of
1.2.times.10.sup.5 V/cm or 12 V/.mu.m.
Embodiment 2
[0034] One tetracid dianhydride monomer and two diamine monomers
were selected as the comonomers. Purified pyromellitic dianhydride
(PMDA), oxydianiline (ODA) and Benzidine (Bz) were mixed at a molar
ratio of 1:0.6:0.4, and reacted in N,N-dimethyl formamide (DMF) as
a solvent following the above steps; in reaction step (1), the
temperature of the reaction kettle of the example is 5.degree. C.,
the time of the reaction under agitation is 6 h, and the electric
field intensity of the high voltage electric field for the
electrostatic spinning is 250 Kv/m; and in reaction step (2), the
temperature rise program includes heating from room temperature to
250.degree. C. at a temperature rise rate of 20.degree. C./min, and
maintaining at the temperature for 30 min, heating to 370.degree.
C. at a temperature rise rate of 5.degree. C./min, and maintaining
at 370.degree. C. for 30 min, shutting off the power source, and
naturally cooling to room temperature.
[0035] Property characterization: the mass concentration of the
copolyamic acid (polyimide precursor) solution is 5% and the
absolute viscosity thereof is 4.8 Pas, the diameter of the
copolyamic acid nano-fiber is 100-300 nm and is mainly distributed
at about 200 nm, and the copolyimide nano-fiber non-woven fabric
has tensile strength of 24 MPa, breaking elongation of 23%, a glass
transition temperature of 298.degree. C., a thermal decomposition
temperature of 560.degree. C., a porosity of 82.0%, a specific
surface area of 38.8 m.sup.2/g and an electrical breakdown strength
of 1.3.times.10.sup.5 V/cm or 13 V/.mu.m.
Embodiment 3
[0036] One tetracid dianhydride monomer and two diamine monomers
were selected as the comonomers. Purified pyromellitic dianhydride
(PMDA), methylene dianiline (MDA) and oxydianiline (ODA) were mixed
at a molar ratio of 1:0.5:0.5, and reacted in N,N-dimethyl
formamide (DMF) as a solvent following the above steps; in reaction
step (1), the temperature of the reaction kettle of the example is
5.degree. C., the time of the reaction under agitation is 10 h, and
the electric field intensity of the high voltage electric field for
the electrostatic spinning is 250 Kv/m; and in reaction step (2),
the temperature rise program includes heating from room temperature
to 250.degree. C. at a temperature rise rate of 20.degree. C./min,
and maintaining at the temperature for 30 min, heating to
370.degree. C. at a temperature rise rate of 5.degree. C./min, and
maintaining at 370.degree. C. for 30 min, shutting off the power
source, and naturally cooling to room temperature.
[0037] Property characterization: the mass concentration of the
copolyimide precursor (copolyamic acid, co-PAA) solution is 6% and
the absolute viscosity thereof is 4.8 Pas, the diameter of the
copolyamic acid nano-fiber is 100-400 nm and is mainly distributed
at about 250 nm, and the copolyimide nano-fiber non-woven fabric
has tensile strength of 20 MPa, breaking elongation of 21%, a glass
transition temperature of 296.degree. C., a thermal decomposition
temperature of 510.degree. C., a porosity of 85.1%, a specific
surface area of 36.9 m.sup.2/g and electrical breakdown strength of
1.1.times.10.sup.5 V/cm or 11 V/.mu.m.
Embodiment 4
[0038] One tetracid dianhydride monomer and two diamine monomer
were selected as the comonomers. Purified diphenyl sulfone
dianhydride (DSDA), bis(aminophenoxyphenyl) sulfone (BAPS) and
oxydianiline (ODA) were mixed at a molar ratio of 1:0.3:0.7, and
reacted in N,N-dimethyl formamide (DMF) as a solvent following the
above steps; in reaction step (1), the temperature of the reaction
kettle of the example is 5.degree. C., the time of the reaction
under agitation is 10 h, and the electric field intensity of the
high voltage electric field for the electrostatic spinning is 250
Kv/m; and in reaction step (2), the temperature rise program
includes heating from room temperature to 200.degree. C. at a
temperature rise rate of 20.degree. C./min, and maintaining at the
temperature for 30 min, heating to 330.degree. C. at a temperature
rise rate of 5.degree. C./min, and maintaining at 330.degree. C.
for 30 min, shutting off the power source, and naturally cooling to
room temperature.
[0039] Property Characterization: the mass concentration of the
copolyimide precursor (copolyamic acid, co-PAA) solution is 8% and
the absolute viscosity thereof is 4.2 Pas, the diameter of the
copolyamic acid nano-fiber is 100-300 nm and is mainly distributed
at about 180 nm, and the copolyimide nano-fiber non-woven fabric
has tensile strength of 20 MPa, breaking elongation of 25%, a glass
transition temperature of 238.degree. C., a thermal decomposition
temperature of 520.degree. C., a porosity of 81.3%, a specific
surface area of 36.9 m.sup.2/g and electrical breakdown strength of
1.4.times.10.sup.5 V/cm or 14 V/.mu.m.
Embodiment 5
[0040] Two tetracid dianhydride monomers and one diamine monomer
were selected as the polymerization monomers. Purified biphenyl
dianhydride (BPDA), pyromellitic dianhydride (PMDA) and
oxydianiline (ODA) were mixed at a molar ratio of 0.5:0.5:1, and
reacted in N,N-dimethyl formamide (DMF) as a solvent according to
the above steps. In this situation, in reaction step (1), the
temperature of the reaction kettle of the example is 5.degree. C.,
the time of the reaction under agitation is 10 h, and the electric
field intensity of the high voltage electric field for the
electrostatic spinning is 250 Kv/m; and in reaction step (2), the
temperature rise program includes heating from room temperature to
250.degree. C. at a temperature rise rate of 20.degree. C./min, and
maintaining at the temperature for 30 min, heating to 370.degree.
C. at a temperature rise rate of 5.degree. C./min, and maintaining
at 370.degree. C. for 30 min, shutting off the power source, and
naturally cooling to room temperature.
[0041] Property characterization: the mass concentration of the
copolyamic acid solution is 6% and the absolute viscosity thereof
is 5.5 Pas, the diameter of the copolyamic acid nano-fiber is
150-400 nm and is mainly distributed at about 280 nm, and the
copolyimide nano-fiber non-woven fabric has a tensile strength of
23 MPa, a breaking elongation of 22%, a glass transition
temperature of 295.degree. C., a thermal decomposition temperature
of 550.degree. C., a porosity of 85.0%, a specific surface area of
36.9 m.sup.2/g and electrical breakdown strength of
1.1.times.10.sup.5 V/cm or 11 V/.mu.m.
Embodiment 6
[0042] Two tetracid dianhydride monomers and one diamine monomer
were selected as the polymerization monomers. Purified hydroquinone
diphthalic anhydride (HQDPA), pyromellitic dianhydride (PMDA) and
oxydianiline (ODA) were reacted at a molar ratio of 0.5:0.5:1 in an
appropriate amount of solvent of N,N-dimethyl formamide (DMF)
following the above steps. In this situation, in reaction step (1),
the temperature of the reaction kettle of the example is 10.degree.
C., the time of the reaction under agitation is 5 h, and the
electric field intensity of the high voltage electric field for the
electrostatic spinning is 300 Kv/m; and in reaction step (2), the
temperature rise program includes heating from room temperature to
200.degree. C. at a temperature rise rate of 20.degree. C./min, and
maintaining at the temperature for 30 min, heating to 350.degree.
C. at a temperature rise rate of 5.degree. C./min, and maintaining
at 350.degree. C. for 30 min, shutting off the power source, and
naturally cooling to room temperature.
[0043] Property characterization: the mass concentration of the
copolyamic acid solution is 8% and the absolute viscosity thereof
is 4.2 Pas, the diameter of the copolyamic acid nano-fiber is
80-300 nm and is mainly distributed at about 150 nm, and the
copolyimide nano-fiber non-woven fabric has tensile strength of 23
MPa, breaking elongation of 24%, a glass transition temperature of
278.degree. C., a thermal decomposition temperature of 540.degree.
C., a porosity of 81.4%, a specific surface area of 41.8 m.sup.2/g
and electrical breakdown strength of 1.4.times.10.sup.5 V/cm or 14
V/.mu.m.
Embodiment 7
[0044] Two tetracid dianhydrides and two diamines were selected as
the comonomers. Purified benzophenonetetracarboxylic dianhydride
(BTDA), pyromellitic dianhydride (PMDA), benzidine (Bz) and
oxydianiline (ODA) were mixed at a molar ratio of 1:1:1:1 and
reacted in an appropriate amount of N,N-dimethylacetamide (DMAc) as
a solvent following the above steps. In this situation, in reaction
step (1), the temperature of the reaction kettle of the example is
5.degree. C., the time of the reaction under agitation is 6 h, and
the electric field intensity of the high voltage electric field for
the electrostatic spinning is 250 Kv/m; and in reaction step (2),
the temperature rise program includes heating from room temperature
to 250.degree. C. at a temperature rise rate of 20.degree. C./min,
and maintaining at the temperature for 30 min, heating to
370.degree. C. at a temperature rise rate of 5.degree. C./min, and
maintaining at 370.degree. C. for 30 min, shutting off the power
source, and naturally cooling to room temperature.
[0045] Property characterization: the mass concentration of the
copolyamic acid solution is 6% and the absolute viscosity thereof
is 4.3 Pas, the diameter of the copolyamic acid nano-fiber is
100-300 nm and is mainly distributed at about 150 nm, and the
copolyimide nano-fiber non-woven fabric has tensile strength of 22
MPa, breaking elongation of 24%, a glass transition temperature of
288.degree. C., a thermal decomposition temperature of 540.degree.
C., a porosity of 80.5%, a specific surface area of 41.8 m.sup.2/g
and electrical breakdown strength of 1.5.times.10.sup.5 V/cm or 15
V/.mu.m.
Embodiment 8
[0046] Two tetracid dianhydrides and two diamines were selected as
the comonomers. Purified biphenyl dianhydride (BPDA), hydroquinone
diphthalic anhydride (HQDPA), p-phenylenediamine (PPD) and
oxydianiline (ODA) were mixed at a molar ratio of 1:1:1:1, and
reacted in an appropriate amount of N,N-dimethyl formamide (DMAc)
as a solvent following the above steps. In this situation, in
reaction step (1), the temperature of the reaction kettle of the
example is 10.degree. C., the time of the reaction under agitation
is 10 h, and the electric field intensity of the high voltage
electric field for the electrostatic spinning is 300 Kv/m; and in
reaction step (2), the temperature rise program includes heating
from room temperature to 250.degree. C. at a temperature rise rate
of 20.degree. C./min, and maintaining at the temperature for 30
min, heating to 350.degree. C. at a temperature rise rate of
5.degree. C./min, and maintaining at 320.degree. C. for 30 min,
shutting off the power source, and naturally cooling to room
temperature.
[0047] Property characterization: the mass concentration of the
copolyamic acid solution is 8% and the absolute viscosity thereof
is 4.0 Pas, the diameter of the copolyamic acid nano-fiber is
50-250 nm and is mainly distributed at about 150 nm, and the
copolyimide nano-fiber non-woven fabric has tensile strength of 21
MPa, breaking elongation of 23%, a glass transition temperature of
284.degree. C., a thermal decomposition temperature of 530.degree.
C., a porosity of 80.2%, a specific surface area of 42.0 m.sup.2/g
and electrical breakdown strength of 1.5.times.10.sup.5 V/cm or 15
V/.mu.m.
[0048] The above examples should not be understood to limit the
scope of the present invention. Those skilled in the art can make
some non-intrinsic modification and adjustment to the present
invention according to the above contents of the present invention,
which still belong to the scope of the present invention.
* * * * *