CN109400942A - A kind of composite microporous film and preparation method thereof - Google Patents
A kind of composite microporous film and preparation method thereof Download PDFInfo
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
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- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
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Abstract
This application involves a kind of composite microporous films.By the way that the nano-cellulose fiber being modified is filled into polyolefin substrate as reinforcing agent, the application has obtained a kind of ultra-thin, high-intensitive polyolefin/nano cellulose fibre composite microporous film, compared with existing composite microporous film, the composite microporous film of the application more can satisfy the thickness uniformity to microporous membrane, the ultra-thin and high-intensitive application having higher requirements, in the lithium ion battery particularly suitable for consumer fields such as power lithium-ion battery and smart phones.The application further relates to the preparation method and process units of the composite microporous film.
Description
Technical field
The present invention relates to a kind of composite microporous film, especially lithium ion battery composite microporous films, and its preparation side
Method.
Background technique
Polyolefin micro porous polyolefin membrane is for battery separator, electrolytic capacitor diaphragm, ultrafiltration membrane, microfiltration membranes and medical films etc.
Various uses.But the disadvantage is that ultra-thin polyolefin micro porous polyolefin membrane intensity is poor, using polyolefin micro porous polyolefin membrane as spacer film and electricity
Pole is easy to happen fracture when high-tension is wound together.The prior art cannot still produce ultra-thin high strength diaphragm.
Native cellulose fibre has many advantages, such as that environmentally protective, high-intensitive, low price, yield are big, therefore, is used as polyolefin
Reinforcing agent have great advantage.But natural-nanometer fiber cellulose fiber preparation process is complicated, moreover, the pole of fiber surface
Property hydroxyl makes it have hydrophily, is difficult to mix with the non-polar polyolefinic material of hydrophobicity.
In Japanese Patent No. JP200704584A1, the preparation side of a kind of cellulose and composite polyolefine material is disclosed
Method, this method is using pressurization and the measures such as crushes for the non-thermoplasticity natural polymer such as chitin, timber and thermoplasticity
Polyolefin is mixed with composite membrane.But in this composite membrane, as non-thermoplasticity natural polymer only using usual
Cellulose, and compound film strength is very low.
In Journal of Materials Science, June.1999, Volume 34, Issue 12, pp2903-
2910(R.Park,J.Jang,Performance improvement of carbon fiber/polyethylene fiber
Hybrid composites) in, a kind of preparation method of carbon fiber/polyethylene (PE) fiber hybrid composite is disclosed, and
Carbon fiber/composite polyethylene material is prepared for using this method.Compared with untreated composite material, the carbon fiber/polyethylene
The intensity of composite material shows biggish increase.But carbon fiber is not natural materials, exists and is unable to natural degradation and cost
Higher problem.
Summary of the invention
Polyolefin/cellulose composite material is disclosed in above-mentioned document, but there is following for method disclosed in it
Defect: fiber material material manufacturing technique is complicated, and there are serious pollutions to environment for some methods.In addition, since itself is tied
Structure feature, nano-cellulose fiber can neither dissolve, and cannot be dissolved in organic solvent, and these problems seriously limit nanofiber
Application of the cellulose fiber in composite microporous film.
The application be designed to provide a kind of simple process, clean and effective nano-cellulose fiber preparation method.
Further object be to provide it is a kind of it is ultra-thin, high-strength polyolefin/nano-cellulose fiber is compound micro-
The preparation method of perforated membrane.
Another purpose of the invention is that providing, one kind is ultra-thin, high-strength polyolefin/nano-cellulose fiber is compound micro-
Perforated membrane, the porosity of the composite microporous film is high, ultra-thin, the high-intensitive and the thickness uniformity that has had, can be improved battery
Performance and reduction battery cost.
Another purpose of the invention is that providing, one kind is ultra-thin, high-strength polyolefin/nano-cellulose fiber is compound micro-
The process units of perforated membrane.
To achieve the goals above, the present inventor has studied the material of nano-cellulose fiber on the basis of existing technology
Characteristic and production technology, and nano-cellulose fiber is modified, its hydrophobicity is improved, to keep nano-cellulose fine
Dimension can be evenly dispersed in organic solvent, and can be mixed well with the non-polar polyolefinic material of hydrophobicity, from
And it can be filled into using modified nano-cellulose fiber as reinforcing agent and obtain high-intensitive polyolefin/receive in polyolefin substrate
Rice cellulose fibre composite microporous film.
In addition, the present inventor it is also compound to the existing asynchronous drawing polyolefin/nano-cellulose fiber of wet process shown in FIG. 1 every
Film manufacturing process has carried out systematic Study, and used substrate composition, process units and production technology are optimized.Knot
Fruit discovery can successfully improve the spy of gained composite microporous film by being stretched again after extraction, drying steps
Property, ultra-thin, the high-strength composite microporous membrane that a kind of thickness is uniform, quality is stable are provided, the composite microporous film have 5~
100 μm of thickness, the gas permeability of 100~600 seconds/100cc and 20%~70% porosity.
The present invention is passed through using mechanical strength and the nano-cellulose fiber and polyolefin-based membrane material of excellent corrosion resistance
The composite microporous film technology of improvement, using biaxial tension high-performance production line, can continuously prepare thickness uniformly, quality
Stable new type polyolefin/nano-cellulose fiber composite microporous film further improves heat-resisting quantity, the machine of microporous membrane
The characteristics such as tool intensity.Compared with existing composite microporous film, composite microporous film of the invention more be can satisfy to micro- porous
The thickness uniformity of film, the ultra-thin and high-intensitive application having higher requirements, particularly suitable for power lithium-ion battery and intelligence
In the lithium ion battery of the consumer fields such as mobile phone.
According to the disclosure be described below and in conjunction with attached drawing, these and other purposes, aspect and the advantage of the disclosure will become
It obtains obviously.
Detailed description of the invention
Fig. 1 is the asynchronous drawing polyolefin of wet process/nano-cellulose fiber composite diaphragm manufacturing process flow diagram.
Fig. 2 is high-performance lithium battery diaphragm process units schematic diagram.
Specific embodiment
It on the one hand, should this application provides a kind of preparation method of composite microporous film (also method referred to as of the invention)
Method successively the following steps are included:
1) nano-cellulose fiber is prepared；
2) prepared nano-cellulose fiber is modified, then by modified nano-cellulose fiber and pore former
Mixing, obtains the dispersion solution of modified nano-cellulose fiber；
3) by the nano-cellulose fiber of polyolefin resin, modification disperse solution and optional additive according to be formulated into
Row melting obtains being kneaded solution；
4) the mixing solution is squeezed out from die head and is cooled into the curtain coating sheet containing pore former；
5) it stretches the curtain coating sheet to obtain the basement membrane containing pore former；
6) basement membrane containing pore former is formed to the basement membrane for being free of pore former after organic solvent extraction is dry；
7) basement membrane without pore former is stretched again in an at least axis direction；
8) thermally treated sizing obtains the composite microporous film.
It is preferred that in step 5), it is described to be stretched as biaxial tension, it both can be asynchronous biaxial tension, or synchronous
Biaxial tension.It is preferred that used bidirectional stretching production line has advanced thickness precision controlling and regulating system, it can be according to product
It is required that carrying out Rapid stretching and slow stretching, so as to continuous large-scale industrial production, ultra-thin, high-intensitive and thickness is equal
Even composite microporous film.
Nano-cellulose fiber
Nano-cellulose fiber have lot of advantages: 1) abundance, have it is higher activity, it is easily modified；2) at low cost
It is honest and clean；3) can it is degradable, nontoxic, biocompatibility is excellent；Etc..Cellulose origin be concentrated mainly on forest, agricultural or
In terms of food processing residue, since cost is relatively low for they, from a wealth of sources and treatment process is simple, to be answered on a large scale
With.In this application, the raw material for preparing nano-cellulose fiber are mainly derived from natural fiber, such as plant such as pineapple leaves, rice
Grass, timber, cotton, wheat stalk, peanut shell, coconut skin, mulberry tree hide fiber and animal such as crab shell and dried small shrimp source fiber
Deng.The bacteria cellulose of bacterium synthesis also can be used.From energy-saving and environment-friendly angle, preferably with agricultural wastes such as sugarcane
Slag, rice straw etc. and natural biomass such as bamboo wood, timber etc. are raw material, pass through mineral acid hydrolysis method, enzyme hydrolysis method, ultrasonic wave object
Logos, oxidizing process and ionic liquid prepare high crystallinity, high-intensitive nano-cellulose fiber.Nano-cellulose fiber is steel
Property club shaped structure, for diameter in 2-50nm, length is tens of to hundreds of nanometers.As existing most strong most hard natural material it
One, nano-cellulose fiber has a following significant characteristic: tensile strength big (up to 7500MPa), stiffness are big, and (Young's modulus is
100-140GPa), large specific surface area (150-250m2/ g) and electricity outstanding and optical characteristics.
The modified nano-cellulose fiber in surface
Due to the large specific surface area of nano-cellulose fiber, there is a large amount of hydroxyl on surface, after freeze-drying between particle very
It is easy to happen agglomeration, to make it difficult to dispersion in organic solvent, in addition its hydrophily is stronger, this hydrophilic tendency
Limit its application in composite polyolefine material.In order to improve its dispersibility in organic solvent, usually using surface
Modified method introduces stable charge on its surface or modifies the small molecule on its surface.The present invention passes through esterification modification
Or crosslinking -esterization is dual modified, reduces the surface polarity of nano-cellulose fiber, can be dispersed in paraffin oil, two
In the organic solvents such as chloromethanes.
Polyolefin resin
In the preparation of composite microporous film of the present invention, using the polyolefin that weight average molecular weight is 100,000 or more be mainly at
Point.The weight average molecular weight of polyolefin is generally 100,000~4,000,000, preferably 300,000~4,000,000, more preferably 400,000~1,000,000,
Most preferably 100,000~800,000.If less than 100,000, heat resistance is not enough, and is easily broken off when stretching, gained polyene
The intensity of hydrocarbon microporous membrane is relatively low.If the viscosity of gained polyolefin micro porous polyolefin membrane is excessively high more than 4,000,000, difficulty is squeezed out, is made
Productivity reduces.
In this application, term " polyolefin " refers to by one or more of olefinic polymerizations or is copolymerized polymer obtained, packet
Include but be not limited to polyethylene, polypropylene, polyisobutylene and polybutene.Preferred polyolefm includes: polyethylene；With polypropylene, gather it is different
One of propylene, polybutene or other similar polyolefin are a variety of.In general, polyethylene accounts for whole polyolefin resin quality
80% or more, preferably 90% or more, more preferably 95% or more.Most preferably polyolefin is only made of polyethylene, i.e. polyethylene
Account for the 100% of whole polyolefin resin quality.
Pore former
In this application, when the nano-cellulose fiber for fully disperse modified, pore former is alternatively referred to as
Dispersing agent.Pore former used in this application can must fully dissolve polyolefin and modified nano-cellulose fiber, and
It can be removed by organic solvent.It is preferred that its boiling point or following temperature can be with modified nano-cellulose fiber and polyolefin resin
Such as the organic compound that polyethylene mixes is pore former, the example includes but is not limited to n-dodecane alcohol, oleyl alcohol, octadecane
Alcohol, paraffin oil nd various combinations thereof.Due to that, as pore former, can prevent from finally preparing micro- using fixedness organic solvent
Bubble is generated in perforated membrane, obtains the relatively stable gel molding of porogen content, and therefore, more preferable pore former is not wave
Hair property organic solvent, such as paraffin oil, most preferably pore former are atoleine.
Atoleine is as pore former and the dispersing agent of the nano-cellulose fiber of modification, with for example poly- second of polyolefin resin
Olefine resin is capable of forming multilayer oriented air hole structure in the inside of porous substrate after melting mixing, extraction together, significantly
The gradually draw ratio of ground increase gel diaphragm.Draw ratio and degree of crystallization are higher, the mechanical strength of porous substrate
It is higher.Therefore, atoleine can be improved the tensile strength and puncture strength of porous film as pore former, so that porous
The filming of film is further realized.
In the preparation of the dispersion solution of modified nano-cellulose fiber, simultaneously to the dosage of pore former (or dispersing agent)
It is not particularly limited.Under normal circumstances, in terms of by all modified nano-cellulose fiber dispersion liquid for 100 mass %, modified is received
The content of rice cellulose fibre is typically about 0.1%~40%.
Optional additive
In the preparation of composite microporous film of the present invention, in addition to the nano-cellulose fiber, pore former, polyene of above-mentioned modification
Other than hydrocarbon, can also suitably add various additives as needed, such as, but not limited to antioxidant, ultraviolet absorbing agent,
Antiblocking agent, pigment, dyestuff and inorganic filling material etc..
In the following, each step of the present invention will be described in detail composite microporous film preparation method:
1) the step of preparing nano-cellulose fiber
The raw material sources for preparing nano-cellulose fiber are mainly natural cellulosic materials, such as plant such as pineapple leaves, rice
Grass, rice straw, timber, cotton, absorbent cotton, straw, wheat stalk, peanut shell, coconut skin and mulberry tree hide fiber etc.；Animal such as crab
Shell and dried small shrimp fiber etc.；The bacteria cellulose that also bacterium can be used to synthesize prepares nano-cellulose fiber as raw material.By
Smaller than the partial size of bacteria cellulose in the nano-cellulose fiber produced using plant as raw material, it is advantageous to using plant as raw material
To produce nano-cellulose fiber.From energy-saving and environment-friendly angle, preferably with agricultural wastes (such as bagasse, rice straw) or
Natural biomass (such as bamboo wood, timber) is raw material, passes through mineral acid hydrolysis method, enzyme hydrolysis method, high pressure supercritical ultrasonics technology, ultrasonic wave
Physical method, oxidizing process and ionic liquid prepare high crystallinity, high-intensitive nano-cellulose fiber.
2) the step of modified nano-cellulose fiber of preparation disperses solution
The application is by cross-linking modified, esterification modification or to be crosslinked -esterization the methods of dual modified, to reduce nano-cellulose
The surface polarity of fiber, so that nano-cellulose fiber can be uniformly dispersed in pore former (or dispersing agent) such as paraffin oil, dichloromethane
In alkane etc., it is preferred to use esterification modification, such as, but not limited to esterification, ethyl esterified, n-propyl, isopropyl esterification, N-butyl,
Isobutyl esterification, pentyl ester, oneself esterification, hexamethylene esterification, succinate etc..
In the application, by the methods of stirring, modified nano-cellulose fiber is dispersed in pore former, with
To modified nano-cellulose fiber dispersion liquid.It is in terms of 100 mass % by all modified nano-cellulose fiber dispersion solution,
The amount of modified nanometer cellulose fiber is typically about 0.1%~40%.
3) by the nano-cellulose fiber of polyolefin resin, modification disperse solution and optional additive according to be formulated into
Row melting, obtains the step of being kneaded solution
Polyolefin resin such as polyvinyl resin and optional additive are dissolved by heating fine in modified nano-cellulose
Mixing solution is prepared in dimension dispersion solution.
If average grain diameter can get better melting mixing efficiency when being 1~150 μm using powdery polyethylene.
Therefore when using powdery polyethylene, preferably its average grain diameter is 1~150 μm.
As the supply method of polyolefin resin, pore former can be dissolved in using by polyolefin resin such as polyvinyl resin
Supply them later.
It is preferably that a certain amount of polyolefin resin such as polyvinyl resin is automatic from the viewpoint of industrializing continuous production
Be sent into the hopper of double screw extruder, by modified nano-cellulose fiber disperse solution from the side solvent of double screw extruder into
Glassware is supplied to extruder.It is crowded for the nano-cellulose fiber being modified dispersion solution to be supplied to may be provided with multiple feeders
Machine out.
Alternatively, can lower than solution temperature at a temperature of, by polyolefin resin such as polyvinyl resin with modification receive
The stirring of rice cellulose fibre dispersion solution disperses and uniform mixture is made, and then, which is imported into fusible
Melt device (such as double screw extruder, single screw extrusion machine, kneader etc.) the progress melting mixing for being kneaded function, is melted
Compounding mixture.Smelting temperature is different and different according to the type of used polyolefin resin, generally, it is preferred to which smelting temperature is poly-
Fusing point+30~100 DEG C of olefin resin.For example, smelting temperature is preferably polyethylene when using polyethylene for polyolefin resin
Fusing point+30~100 DEG C melt such as the case where using molecular weight for 100,000~800,000 polyethylene as polyolefin resin
Refining temperature is preferably 160~230 DEG C, and particularly preferably 170~210 DEG C.
Total amount according to polyolefin resin such as polyvinyl resin and modified nano-cellulose fiber dispersion solution is 100 weights
% meter is measured, the amount of polyolefin resin such as polyethylene is generally 10~90% weight %, preferably 10~70% weight %, more preferably
For 10~50% weight %, most preferably 10~30 weight %.The amount of modified nano-cellulose fiber dispersion solution is generally 90
~10 weight %, preferably 90~30 weight %, more preferably 90~50 weight %, most preferably 90~70% weight %, i.e.,
The mass ratio of modified nano-cellulose fiber dispersion solution and polyolefin resin is generally 9:1 to 1:9, preferably 9:1 to 3:7,
More preferable 9:1 to 5:5, most preferably 9:1 to 7:3.
4) the step of mixing solution being squeezed out from die head and is cooled into the curtain coating sheet containing pore former
Obtained mixing solution is filtered to remove to the impurity of raw material and the polymer of non-corrosion by high capacity filter.So
Afterwards, it squeezes out obtained filtering solution to obtain gel tablet from double screw extruder die head by metering pump, by the gel film
It is cooled down in shape object input cooling device, thus obtains the curtain coating sheet containing pore former.
It is cooling to be carried out at least 50 DEG C/min or more of speed.Cooling can be realized by contacting with chill roll.So that
To gel tablet by being cooled down between chill roll and niproll.The temperature of chill roll be set as 80 DEG C hereinafter, it is preferred that
30~60 DEG C of range.If the surface temperature of above-mentioned chill roll and niproll is lower than 30 DEG C, pore former can be because of rapid cooling
And it is consolidated in the surface of roller, on the surface of gel-like sheet, generation is uneven, cannot obtain sheet material in homogeneous thickness.Phase
Instead, if temperature is 80 DEG C or more, the melting mixing mixture squeezed out from die head is cooled to the experience of the state with gel strength
Time it is long, cause pore former to be unable to solidification, it is difficult to form stomata, pore former can be attached to roller surface, lead to sheet material
It is slided between roller, sheet material cannot stretch in proportion.
5) curtain coating sheet is stretched into the step of obtaining the basement membrane containing pore former
By above-mentioned steps 4) obtained sheet material first carries out the pre-heat treatment at a temperature of 60~150 DEG C, then, by sheet material along extremely
A few axis direction is stretched, and the basement membrane containing pore former with a thickness of 5~50 μm is made.To drawing process, there is no particular restriction.It is logical
Normal tenter frame process, roller method, rolling process or a combination of these methods can be used.
Stretching, which can be, to be stretched uniaxially or biaxially.If be uniaxially stretched, device must be carried out in mechanical direction
It stretches, i.e., is only stretched in the direction TD, productivity can reduce.Uniformity, mechanical strength from finally obtained microporous membrane
From the viewpoint of, preferably progress tentering method is biaxial stretch-formed.Biaxial stretch-formed situation is being carried out, can be vertical and horizontal stretching
It carries out simultaneously, is also possible to successively carry out longitudinal stretching, cross directional stretch, or successively carry out cross directional stretch, longitudinal stretching.Simultaneously
When carrying out biaxial stretch-formed, the drawing force applied to sheet material can be reduced, there are the problem of first is that speed is slow, second is that adjustability is slightly poor,
Only cross directional stretch ratio is adjustable, longitudinal stretching than be then it is fixed, accordingly, there exist be difficult to high speed or wide cut stretch the problem of.
It is gradually biaxial stretch-formed by implementing first sequentially to carry out in mechanical direction (MD), then in width direction (TD), it obtains higher
Productivity, and can be stretched with higher multiple, each fine pores inside porous membrane are capable of forming as multilayer knot later
Structure obtains excellent stomata uniformity and mechanical strength.
Draft temperature is not particularly limited, generally from room temperature to the melting temperature of high-molecular gel, preferably 80-
140 DEG C, further preferably 100~140 DEG C.
Draw ratio is different and different according to the thickness of gel shaped object, if using biaxial stretch-formed, preferred draw ratio
It is 3 times or more.In view of the restraining factors of device design, more preferably draw ratio is set in the range of 5~100 times.This
Sample operation can be eliminated since the antigradient of above-mentioned niproll is formed by thickness deviation, and whole uniform thickness distribution is obtained,
Meanwhile the so that multilayer oriented structure arranged respectively at each stomatal limiting value layer of superficial layer and interior layer.When draw ratio is less than 4
Times when, gained film strength is insufficient, when draw ratio is more than 100 times, sometimes stretch can become difficult, sometimes gained it is micro- more
The porosity of pore membrane can reduce.In addition, draw ratio also according to the type difference of used polyolefin resin such as polyethylene without
Together, it in the range that preferably film will not be broken when stretching, is stretched as far as possible with high magnification numbe, to prepare ultra-thin composite microporous film.
6) the step of basement membrane containing pore former being formed into the basement membrane for being free of pore former after organic solvent extraction is dry
The drawing sheet dipping that step 5) is obtained in organic solvent, is free of and removing pore former from drawing sheet
The perforated membrane of pore former.Organic solvent is not particularly limited, if it can extract pore former, and polyolefin used and
Modified nano-cellulose fiber keeps stablizing wherein.There are commonly solvents such as, but not limited to chlorinated hydrocarbon
Close object, preferred effumability organic solvent such as, but not limited to methylene chloride or defends alkane etc., more preferably methylene chloride.
Pore former can be extracted by various common methods, be such as, but not limited to impregnated into the side extracted in organic solvent
Method, ultrasonic extraction, the method for spraying organic solvent or the method for being combined them.It is extracted using the above method,
Until the pore former in drawing sheet be lower than 1 weight %, preferably shorter than 0.5 weight %, more preferably less than 0.1 weight %, most preferably
The amount of pore former in drawing sheet is 0.
Then, obtained microporous membrane is dried, can more fully removes organic solvent.Drying can be by adding
Heated drying the various methods such as air-dries and carries out.If be higher than extractant boiling point at a temperature of be dried, solvent is residual
Staying can be greatly decreased.But higher than 80 DEG C at a temperature of be dried when, the gas permeability of finally obtained microporous membrane is slightly
Some are poor, therefore are preferably dried in 80 DEG C of temperature below.In either case, it is caused in order to prevent because film is shunk
The quality of finally obtained polyolefin micro porous polyolefin membrane reduces, all it is preferred on one side with 0% range more than and less than 20% to film into
The fixation that row is stretched along the direction TD, removes pore former on one side.If the stretching for carrying out 20% or more along the direction TD, has
When film may be damaged.
7) by the basement membrane without pore former the step of at least an axis direction stretches again (the second stretching step)
In order to improve permeability, or diaphragm stabilisation is improved, the formation that step 6) is obtained has fine porous film to exist
Its melt temperature temperature below is heat-treated, and is stretched along at least one of MD and TD direction.When heat treatment, in device
Heat treatment temperature can be adjusted arbitrarily, and draft temperature is usually set in 90~150 DEG C of range, preferably 100~140 DEG C of model
It encloses.When more than 150 DEG C, film is not able to maintain porous structure, and the gas permeability of finally obtained microporous membrane is caused to be deteriorated.Lower than 90
DEG C when, the softening of polyolefin resin such as polyethylene is insufficient, and rupture of membranes is easy to happen in stretching, can not uniformly be drawn
It stretches.
Draw ratio is usually set to 0~0.1% times, when which is set to be lower than 0% or less (i.e. reduced width), no
The effect that permeability and pressure-resistant shrinkage improve can be obtained, quality is deteriorated.On the other hand, if draw ratio is set as 0.1%
More than, it is substantially stretched, the film near collet is easily broken.
Heat treatment time can also set the adjusting worked as according to temperature, and heat treatment time is not particularly limited, and usually 1 second
Above 10 minutes or less.It is preferred that 3 seconds~3 minutes.By the step, can mitigate with processing the time generate with heat treatment temperature phase
Corresponding polyolefin crystallization and film internal stress, and improve the stability of the microporous membrane finally prepared.
8) the step of thermally treated sizing obtains composite microporous film
The microporous membrane that step 7) is obtained carries out heat treatment shaping under the conditions of 60-140 DEG C, and setting time is generally
0.5~5.0 minute.It is fixed by heat treatment, the crystallization-stable of polyolefin micro porous polyolefin membrane.Therefore, it stretches and is formed using second
The reticular structure that is formed of fibril be kept, so as to prepare, aperture is big, microporous membrane of high mechanical strength.Heat treatment shaping
Temperature is preferably 90~120 DEG C.When lower than 90 DEG C, it is difficult to carry out reduced width, it is difficult to obtain the effect of dimensionally stable.It is greater than
At 120 DEG C, gas permeability can be remarkably decreased.
On the other hand, present invention also provides a kind of composite microporous film, which includes polyolefin resin
With modified nano-cellulose fiber.
In a preferred embodiment, the composite microporous film has 5~100 μm of thickness, 100~600 seconds/
The gas permeability of 100cc and 20%~70% porosity.
In a preferred embodiment, the composite microporous film has 5 μm~100 μm of thickness, and 300~600
The gas permeability of second/100cc and 40%~70% porosity.
In another preferred embodiment, 120 DEG C at a temperature of exposure 1 hour after, the composite microporous film
It is 2.3% or 2.3% hereinafter, and in the percent thermal shrinkage of the direction MD (mechanical direction) in the percent thermal shrinkage of the direction TD (width direction)
It is 4.2% or 4.2% or less.
In still another preferred embodiment, what the composite microporous film measured under room temperature (20 DEG C to 25 DEG C)
Puncture strength is 900gf or more, and the tensile strength in any one direction is 190Mpa or more in the direction MD and the direction TD.
In still another preferred embodiment, the film thickness of the composite microporous film is 5~12 μm, porosity 30
~50%, gas permeability is 300~600 seconds/100cc, and puncture strength is 900gf or more, any one direction in MD and TD
Tensile strength is 190Mpa or more, and under the conditions of 120 DEG C temperature exposure 1 hour, and the percent thermal shrinkage in the direction TD is 2.3%
Or 2.3% hereinafter, MD percent thermal shrinkage be 4.2% or less.
It is preferred that composite microporous film of the invention is made of polyolefin resin and modified nano-cellulose fiber, wherein
The nano-cellulose fiber of the modification accounts for the weight preferably from about 0.1%-50% of entire composite microporous film, more preferably from about
0.5%-30%, even more preferably from about 1%-10%, most preferably from about 1%-5%.
In general, the mechanical strength of film may not be sufficient if the film thickness of microporous membrane is less than 1 μm.The present invention
The film thickness of the composite microporous film of preparation is all larger than 1 μm, preferably 5~100 μm, and more preferable 5~50 μm, even more preferably from 5~24 μ
M, even more preferably from 5~14 μm, particularly preferred 5~12 μm, most preferably 5~10 μm.
In general, cannot get good gas permeability when the porosity of microporous membrane is lower than 20%, if porosity is super
70% is crossed, sufficient mechanical strength cannot be obtained sometimes.When microporous membrane is used as battery diaphragm, if mechanical strength is not
Foot, the risk that battery short circuit occurs will be bigger.The porosity of composite microporous film prepared by the present invention is 20%~
70%, preferably 30~70%, more preferable 30~50%.
In general, when microporous membrane is used as battery diaphragm, if the gas permeability of microporous membrane less than 100 seconds/100cc,
Permeability may not be sufficient, if gas permeability is greater than 600 seconds/100cc, aperture can become excessive sometimes, on the contrary, if ventilative
Property in the range of 100~600 seconds/100cc, battery capacity can be relatively large, circulating battery characteristic also relatively preferably.The present invention
The gas permeability of the composite microporous film of preparation is 100~600 seconds/100cc, preferably 100~500 seconds/100cc, and more preferable 150
~500 seconds/100cc.
In general, by microporous membrane be used as battery diaphragm when, the percent thermal shrinkage of microporous membrane if it is greater than 10%, then due to
Battery winding body when high temperature is bigger in the thermal shrinkage force of width direction, it is possible to generate inter-electrode short-circuit in inside battery.
Under the conditions of temperature exposure 1 hour of 120 DEG C, percent thermal shrinkage of the composite microporous film prepared by the present invention in the direction TD and MD is equal
10% hereinafter, it is preferred that below 5%.
In general, the case where microporous membrane is used as battery diaphragm, if puncture strength is lower than 300gf, it is possible to can send out
Raw battery short circuit.The puncture strength of composite microporous film prepared by the present invention is in 300gf or more, preferably in 500gf or more, more
It is preferred that 700gf or more, most preferably 900gf or more.
If microporous membrane is easy to happen rupture in general, the tensile strength of microporous membrane is lower than 170Mpa.The present invention
The composite microporous film of preparation tensile strength in any one direction in MD and TD is 170Mpa or more.Therefore, load is not had to
The heart can rupture of membranes.
Composite microporous film of the invention can be used as battery diaphragm in lithium battery.Therefore, the application further relates to one
Kind includes the battery diaphragm and a kind of lithium battery comprising composite microporous film of the present invention of composite microporous film of the present invention.In this hair
When bright composite microporous film is as battery diaphragm, single layer can be, be also possible to multilayer.When battery diaphragm is single layer,
Then this layer uses composite microporous film of the invention.When battery diaphragm is multilayer, wherein at least one layer is answered to be of the invention
Close microporous membrane.
Composite microporous film of the invention is produced using diaphragm process units shown in Fig. 2, which includes:
A) biaxial extruder, the biaxial extruder are used for the dispersion in polyolefin resin, the nano-cellulose fiber of modification
Liquid and optional additive realize high-temperature mixing and cryogenic forming when feeding, and improve production efficiency and safety, it is ensured that product matter
Amount, has superelevation torque, low speed may be implemented and squeeze out and cryogenic forming, to obtain being orientated, high-tension, high added value
High-quality ultrathin film product.Compared with single screw extrusion machine, which has less energy consumption ratio, can reduce operation
Cost.Can according to operating condition it is quick variation switch over, reduce raw material caused by lose, thus reduce raw material at
This.
The biaxial extruder contains direct extrusion system, for realizing raw material high speed be kneaded and it is evenly dispersed, and effectively
Ground controls resin temperature.
The biaxial extruder can also contain large capacity screening washer, the polymer filter for being suitble to high speed, continuous production,
Can effectively filter stock impurity and non-eroding polymer, to improve the yield rate of film.
B) casting machine, the casting machine are connect with the biaxial extruder, including chill roll and niproll, for that will come from institute
The mixture for stating biaxial extruder is cooling, to obtain gel molding.
C) the first stretching device, the stretching device are connect with the casting machine, for stretching the gel shaped object
To drawing sheet.The tensile strength of film is associated with filming technology.The stretching device can be used and is stretched uniaxially or biaxially.But it is single
When axis stretches, ultrathin membrane is different from the intensity of vertical direction in the stretching direction.High glaze, high-tension, height are additional in order to obtain
The film of value preferably has biaxial stretch-formed device (for example, biaxial stretcher used in Example 1).Using it is biaxial stretch-formed when,
The film of preparation can be close in the tensile strength consistency of both direction.The TD tensile strength of stretching device will reach 100MP or more,
And MD tensile strength cannot be too big, excessive to will lead to the increase of MD shrinking percentage, this contraction can increase lithium battery positive and negative anodes short circuit
Probability.
It is preferred that first stretching device has the feature that
Break with big volume, undercut, the biaxial stretch-formed device of super deep channel type, there is TD/MD draw ratio automatic regulating function
And the visual numerical control system of operating is stretched, it can be confirmed on the basis of each section situation during monitoring stretches operating；
All TD/MD draw ratio adjust automatically units are all made of individual motor driven, and TD/MD can be greatly shortened
The setting time of stretch mode；
It supports special TD/MD stretch mode, passes through driving side in TD/MD draw ratio adjust automatically unit and operation
Side uses completely self-contained drive system, copes with the special stretch mode of ultra-thin stretch mode.
D) drying device is extracted, which connect with the stretching device, including extraction tank and drying machine, uses
In removing pore former and drying from the drawing sheet from first stretching device, the basement membrane for being free of pore former is formed.
E) the second stretching device, second stretching device are connect with extraction drying device, for that will come from the dry dress of extraction
The basement membrane without pore former set stretches again in an at least axis direction, is implemented in the embodiment of the present application 1 using stenter
The stretched operation again.
F) heat-treating machine, the heat-treating machine are connect with the second stretching device, for will from the second stretching device film heat
Processing sizing, to obtain composite microporous film.
G) coiling machine, the coiling machine are connect with heat-treating machine, include work beam, for will answering from the heat-treating machine
Microporous membrane is closed to batch in rolls.From the viewpoint of being broken when preventing ultra-thin microporous membrane from batching, preferred low-tension devices for taking-up.
In a preferred embodiment, the process units further include:
H) thickness control system (Fig. 2 is not shown), the system include biaxial stretch-formed test device and quick feedback control system
System, for detecting and controlling the thickness of film automatically,
Wherein the biaxial extruder of the process units also contains injection pump, connect, is used for quick feedback control system
The stabilization of mixture pulse free is injected into quick feedback control system.
The thickness control system preferably has highly accurate online non-contact testing device.The thickness uniformity of film
Including TD the thickness uniformity and MD the thickness uniformity, MD the thickness uniformity is particularly important.Preferred film thicknesses are controlled at ± 0.5 micron
Within.It is preferred that the cascade Mach-Zehnder interferometer mode of high-performance computer control.Cascade Mach-Zehnder interferometer mode is being control pair with sheet cross sectional shape
In the major loop of elephant, it is arranged using head bolt temperature as the subloop of control object.Cascade Mach-Zehnder interferometer mode detects film sections shape
Shape deviation is used to correct the object section shape of diaphragm, and detection sheet cross sectional shape deviation is used to control the adjusting of head bolt
Amount.The influence for just eliminating T-type head step and slab step as quick as thought in subloop, reduces the shadow to film stretching step
It rings, therefore the stabilization of ultra-thin microporous membrane is easily implemented, the micropore distribution of accurate control consistent and uniform.
In the process units, extraction drying device, the second stretching device and heat-treating machine can be individually present can also
To integrate respectively.In a preferred embodiment, the second stretching device and heat-treating machine integrate, thus
Heat treatment shaping can be carried out while implementing and stretching (second stretches) operation again.
In another preferred embodiment, it extracts drying device and the second stretching device integrates, so as to energy
Enough while extracting removing pore former with organic solvent, film is carried out along the direction TD with 0% range more than and less than 20%
It stretches and fixes.
In still another preferred embodiment, extraction drying device, the second stretching device and heat-treating machine are integrated in
Together.
To prepare the composite microporous film with excellent properties, the adjustment of relevant parameter can be carried out according to table 1.
The setting table of 1 film relevant parameter of table
It further illustrates by the following examples, it should be understood that specific embodiment described herein is used only for solving
The present invention is released, rather than for limiting the present invention.
Embodiment
In embodiment, composite microporous film of the invention is prepared using process units shown in Fig. 2, polyethylene is with quotient
Name of an article 030S derives from Mitsui Chemicals, Inc., is 5 × 10 with the average molecular weight that Mitsui Chemicals method measures5, with 3418 method of ASTMD
The fusing point measured is 136 DEG C.
Embodiment 1
It is that diameter is less than 1mm that dry wheat-straw is crushed with high-performance pulverizer (UF-11, Uenotex Co., Ltd.)
Fiber fines, impregnate in deionized water 24 hours, then utilize Ultrasonic cell smash (UX-600 type, three hole motors
Jing Xie Co., Ltd.) it is ultrasonically treated 30 minutes under conditions of output power 800W.Obtain nano-cellulose fiber suspension.So
Afterwards, which is centrifuged 10 minutes under the conditions of 1000r/min with high speed freezing centrifuge (CR22N, Hitachi, Japan),
The substance being suspended in solution after centrifuge separation is nano-cellulose fiber.Finally, by aaerosol solution freeze drier
(FDS-1000, Co., Ltd. Bei Bang make institute) freeze-drying, obtains nano-cellulose fiber crystal, is placed in 4 DEG C of refrigerators
It refrigerates spare.
It is under the conditions of ice-water bath, dry nano-cellulose fiber is 10 minutes ultrasonic in toluene.Then, second is added
(1 gram of nano-cellulose fiber corresponds to the toluene of 25ml, the acetic acid of 20ml, the perchloric acid of 0.1ml, 7ml for acid, perchloric acid, acetic anhydride
Acetic anhydride), reacted at 50 DEG C, reaction stirred 3 hours.Then, with ethanol washing 3 times.By receiving for obtained modification
Rice cellulose fibre solution is put into freeze drying box, and freeze-drying to constant weight obtains the solid powder of white, as esterification modification
Nano-cellulose fiber.
0.8 parts by weight of nano-cellulose fiber of esterification modification are added to atoleine (MORESCO company, trade mark P-
350) in 99.2 parts by weight, stir process 18 hours, the atoleine dispersion liquid of modified nano-cellulose fiber is obtained.
30 mass parts of polyethylene are put into biaxial extruder via charger, by the side feeder of the biaxial extruder
The modified nano-cellulose fiber atoleine dispersion liquid of 70 mass parts is supplied, melting mixing is carried out under the conditions of 180 DEG C, double
Melt solution is modulated in screw extruder.Resulting melt solution is rolled into from the T mould for being set to biaxial extruder front end molten
Melt object, squeeze out in the form of sheets, above-mentioned gel-like sheet is made to be respectively maintained at 30 DEG C of chill roll and clamping by surface temperature immediately
It is pulled out between roller, is configured to 1000 μm of thickness of gel-like sheet.By the gel-like sheet using biaxial stretcher 110
6 times of stretchings are carried out along mechanical direction (MD) at DEG C, then stretch 7 times at width direction (TD), it, will after implementing above-mentioned gradually stretching
The drawing sheet is immersed in the liquid tank full of methylene chloride, is dissolved out and is obtained the base without pore former after extraction liquids paraffin
The basement membrane without pore former is dried film by drying machine.Microporous membrane after gained is dry is using built-in temperature
130 DEG C of stenter stretches 0.05% along the direction TD, while be heat-treated within 2 minutes.It then, is 110 DEG C by built-in temperature
Heat-treating machine, by free shrink on the direction TD reduced width 3.5%, fixation is dried, is rolled up with work beam
It takes.Obtain desired composite microporous film.
To the thickness of gained composite microporous film, tensile strength, puncture strength, porosity, gas permeability and percent thermal shrinkage
It is determined respectively, specific measurement method is as follows:
The test method of thickness: using direct-reading Thickness measuring instrument prepared by the rugged preparation of Japanese tail, according to ASTM
D5947 measurement.It is measured along longitudinal direction with being spaced in the width range of 10.0cm for 1.0cm with direct-reading Thickness measuring instrument,
Then film thickness average value is obtained.
The test method of tensile strength: tensile strength is measured according to ASTM D882 method.By the sheet material of preparation cut out for
10mm rectangle test film, then, using cupping machine (Japanese Shimadzu prepares institute, AG 100N), at room temperature, with test
Speed 50mm/min is stretched, until sheet material is broken.Tensile strength is the peak load until fracture.MD indicates to press machinery side
To tensile strength, TD be width direction tensile strength.
The test method of puncture strength: puncture strength is measured according to ASTM D-3736.By the film of preparation cut out for
The square film of 50mm × 50mm, then, using puncture strength tester (Japanese Kato~Tech company, KES~G5), in room
It is the needle of diameter 1mm (0.5mmR) using front end under temperature, peak load when measurement was with speed 2mm/ seconds puncture microporous membranes
Value.Each sample measures 10 positions, finds out average value.
The measuring method of gas permeability: it is measured according to ASTMD726.The film of preparation is cut out as 50mm × 50mm just
Quadrangular membrane, then, using Amada Co., Ltd.'s Toyo Seiki manufacture institute densometer, at room temperature, measurement up to
Time needed for 100cc air passes through microporous membrane.
The test method of porosity: using the mercury injection apparatus of CARLO ERBA INSTRUMENTS company, according to ASTM
D2873 is measured.Porosity is the value using mass method measurement.That is, porosity %=100 × (w2-w1)/w2, wherein
“w1" be microporous membrane actual weight, " w2" it is the weight with the same imporosity film of same size and thickness.
The test method of percent thermal shrinkage: using Shimadzu preparation institute percent thermal shrinkage analyzer, according to ASTM D1204 progress
Measurement.The sheet material of preparation is cut out into the square sheets for 50mm × 50mm, then, stands 1 hour in 120 DEG C of baking oven.So
Afterwards, sheet material is taken out, the change in size that front and back is stood in baking oven is measured.Percent thermal shrinkage be by microporous membrane at 120 DEG C
The shrinking percentage in the direction MD and the direction TD after processing 1 hour, measures 3 times respectively, calculates average value and the value that obtains.
The measurement result of gained composite microporous film characteristic is as shown in table 2.
Embodiment 2
Rice straw is cut into the fiber of 1-2cm long, it is straight for being crushed with high-performance pulverizer (UF-11, Uenotex Co., Ltd.)
Diameter is less than the fiber fines of 1mm, is soaked in the sodium hydroxide solution of 2.5mol/L at room temperature 24 hours, obtains sediment.
The sediment is washed with deionized to neutrality, the sediment after washing is soaked in 3% dilute nitric acid solution 24 hours,
Obtain sediment.The sediment is washed with deionized to neutrality, is dried in 60 DEG C of baking ovens.Then, it is soaked at room temperature
It steeps in the hydrochloric acid of 1.0mol/L 24 hours, then obtained precipitate washed with water to neutrality, is dried in 60 DEG C of baking ovens
4 hours, white solid powder is obtained, as the raw material for preparing nano-cellulose fiber.The white of gained cellulose is consolidated
Body powder is put into 64% sulfuric acid solution by solid-to-liquid ratio 1:20, and is stirred in 60 DEG C of interior machinery of water-bath (DF-101S, UCHEN)
It mixes 40 minutes, then, is centrifuged with high speed freezing centrifuge (CR22N, Hitachi, Japan) 12000r/min, by supernatant in room
Temperature lower temperature dialysis 5 days, obtains nano-cellulose fiber suspension.Finally, by the suspension with freeze drier (FDS-1000,
Co., Ltd. Bei Bang makes institute) freeze-drying, obtain nano-cellulose fiber crystal.It is spare to be placed in refrigeration in 4 DEG C of refrigerators.
In addition to this, remaining operating process is identical with the corresponding part of above-described embodiment 1.
The measurement result of gained composite microporous film characteristic is as shown in table 2.
Embodiment 3
Medical absorbent cotton is added in 50% hydrochloric acid and is hydrolyzed, hydrolysis temperature is maintained at 60 DEG C, handles 60 minutes.It is cold
But, the deionized water then measured with 2 times dilutes, and stands 24 hours, obtains powder precipitate, as preparing nano-cellulose
The raw material of fiber.Gained powder precipitate is handled in 90 DEG C of water-baths (DF-101S, UCHEN) with 5% sodium hydroxide solution
40 minutes, then, with ion water washing to neutrality, then use high speed freezing centrifuge (CR22N, Hitachi, Japan)
12000r/min is centrifuged expelling water, then with ethyl alcohol to be washed till smoke filtrate colourless, finally, being washed once with acetone again.The precipitating that will be obtained
Object is dried in 80 DEG C of baking ovens, is then crushed with high-performance pulverizer (UF-11, Uenotex Co., Ltd.), logical to sieve with 100 mesh sieve
Obtain nano-cellulose fiber.
In addition to this, remaining operating process is identical with the corresponding part of above-described embodiment 1.
The measurement result of gained composite microporous film characteristic is as shown in table 2.
Comparative example 1
Other than not preparing nano-cellulose fiber and the modified nano-cellulose fiber of addition, operating process with it is upper
The identical of embodiment 1 is stated, polyolefin micro porous polyolefin membrane is obtained.
The measurement result of gained microporous membrane characteristic is as shown in table 2.
Comparative example 2
The comparative example does not carry out the preparation of nano-cellulose fiber and the modification procedure of nano-cellulose fiber, but will
0.8 part by weight of cellulose is added directly into 99.2 part by weight of liquid paraffin, remaining operating process is complete with above-described embodiment 1
It is identical, obtain composite microporous film.
The measurement result of gained composite microporous film characteristic is as shown in table 2.
The measurement result of 2. microporous membrane characteristic of table
If membrane ruptures, short circuit will occur, reduce yield rate.Therefore it is required that in battery assembly and charge and discharge structure
In use process, mechanical strength that diaphragm itself needs to have certain.The mechanical strength of diaphragm can be strong with puncture strength and stretching
Degree is to measure.By Examples 1 to 3 compared with the comparative example 1 for being not added with modified nano-cellulose fiber reinforcing agent, it is seen that addition
After modified nano-cellulose fiber reinforcing agent, the tensile strength of gained microporous membrane, puncture strength and gas permeability are obvious
It improves.The nano-cellulose fiber of about 1.8% modification is only added, the longitudinal tensile strength of gained composite microporous film just reaches
To 218MPa (embodiment 1), with the polyolefin micro porous polyolefin membrane (comparative example 1) for being not added with modified nano-cellulose fiber reinforcing agent
It compares, longitudinal tensile strength improves about 22.5%.
Through performance can be used under certain time and pressure, by the amount of diaphragm gas number characterize, it is main anti-
Reflect the patency that lithium ion penetrates diaphragm.Through performance is measured with gas permeability, porosity index substantially now.Gas permeability is general
Between 200s/100cc -500s/100cc.By Examples 1 to 3 and it is not added with modified nano-cellulose fiber reinforcing agent
Comparative example 1 is compared, and gas permeability and hole rate score significantly improve, this shows modified nano-cellulose fiber compound micro- more
It is well dispersed in pore membrane, and fiber reunion does not occur, micropore is formd well.
In power battery field, the safety of lithium ion battery becomes the link of lithium battery producer paid attention to the most.Poly-
The percent thermal shrinkage of alkene microporous membrane is low, when especially longitudinal direction percent thermal shrinkage is low, can prevent from causing to gather because of battery abnormal heating
Alkene diaphragm retracts, so as to cause battery short circuit.By Examples 1 to 3 and it is not added with modified nano-cellulose fiber reinforcing agent
Comparative example 1 compare, the percent thermal shrinkage of the composite microporous film of embodiment 1 is 1.7%, and the polyolefin of comparative example 1 is micro- porous
The percent thermal shrinkage of film is up to 3.7%, it is seen that polyolefin micro porous polyolefin membrane can be greatly reduced by adding modified nano-cellulose fiber
Percent thermal shrinkage improves the safety of lithium ion battery.
In addition, using Examples 1 to 3 with only use cellulose as the comparative example 2 of reinforcing agent compared with, it is seen that it is of the invention
The properties of composite microporous film are superior to the composite microporous film of comparative example 2, and also found that comparative example 2 is prepared compound
The mechanical property of microporous membrane is very low.Using comparative example 2 with being not added with modified nano-cellulose fiber compared with reinforcing agent
Example 1 is compared, and permeability value shows that cellulose fibre may disperse unevenly in composite microporous film, and cellulose fiber occurs
The reunion of dimension.
Industrial applicibility
Composite microporous film prepared by the present invention is since ultra-thin, the thickness uniformity is good, tensile strength and puncture strength are high, power
It is good to learn performance, therefore the high level that battery may be implemented dissolves and high output, can satisfy to film thickness, mechanical strength and safety
The application that property has higher requirements.It is particularly suitable for the electrical storage devices such as capacitor purposes, capacitor purposes, battery use, can help to mention
High security and high output property.It is particularly suitable for battery diaphragm field, more specifically high density dynamic lithium battery and intelligent hand
The contour output septum for lithium ion battery of machine lithium battery.
Composite microporous film prepared by the present invention can be applicable to the filtering such as humidification membrane, Water warfare film, artificial dialysis film
In the various fields such as film and cell proliferation substrate.
It should be understood that the present invention is not limited to above-mentioned example embodiment and embodiment, to the common skill in this field
For art personnel, it can be modified or changed according to the above description, and all these modifications and variations all should belong to institute of the present invention
Attached scope of protection of the claims.
Claims (9)
1. a kind of composite microporous film, the composite microporous film includes polyolefin resin and modified nano-cellulose fiber,
It is preferred that the polyolefin resin is polyethylene, the more preferably polyethylene of molecular weight 100,000~800,000,
It is preferred that the nano-cellulose fiber of the modification is cross-linking modified, esterification modification or is crosslinked the dual modified nanometer of -esterization
Cellulose fibre, the most preferably nano-cellulose fiber of esterification modification.
2. composite microporous film according to claim 1, the composite microporous film is included
5~100 μm of thickness, preferably 5~50 μm of thickness, more preferable 5~24 μm of thickness, even more preferably from 5~14 μm of thickness
Degree, particularly preferred 5~12 μm of thickness, most preferably 5~10 μm of thickness；
The gas permeability of 100~600 seconds/100cc, the preferably gas permeability of 100~500 seconds/100cc, more preferable 150~500 seconds/
The gas permeability of 100cc；With
20%~70% porosity, preferably 30~70% porosity, more preferable 30~50% porosity,
It is preferred that the puncture strength that the composite microporous film measures at room temperature is 300gf or more, preferably puncture strength is
500gf or more, more preferable puncture strength are 700gf or more, and most preferably puncture strength is 900gf or more；
It is also preferred that composite microporous film tensile strength in any one direction in the direction MD and the direction TD is 170Mpa
More than；
The direction TD and MD percent thermal shrinkage 10% hereinafter, more preferably below 5%.
3. composite microporous film according to claim 1 or 2, the composite microporous film is by polyethylene and modified nanometer
Cellulose fibre composition, wherein the nano-cellulose fiber of the modification accounts for the weight of entire composite microporous film preferably from about
0.1%-50%, more preferably from about 0.5%-30%, even more preferably from about 1%-10%, most preferably from about 1%-5%.
4. a kind of method for preparing composite microporous film described in any one of claim 1-3, the method successively includes following
Step:
1) nano-cellulose fiber is prepared；
2) prepared nano-cellulose fiber is modified, then mixes modified nano-cellulose fiber with pore former
It closes, obtains the dispersion solution of modified nano-cellulose fiber；
3) nano-cellulose fiber of polyolefin resin, modification is dispersed into solution and optional additive mixes, described poly-
Melting obtains being kneaded solution at a temperature of fusing point+30~100 DEG C of olefin resin；
4) the mixing solution is squeezed out from die head, and 30~80 DEG C of ranges at a temperature of be cooled into the stream containing pore former
Prolong sheet；
5) it stretches the curtain coating sheet to obtain the basement membrane containing pore former；
6) by the basement membrane containing pore former, formation is free of the basement membrane of pore former after organic solvent extraction, dry；
7) basement membrane without pore former is stretched again at least one of MD and TD direction；
8) microporous membrane for obtaining step 7) carries out thermal finalization processing under the conditions of 60-140 DEG C, obtains described compound micro- porous
Film,
It is preferred that stretching step 5) in described be stretched as asynchronous biaxial tension or synchronous bidirectional stretches；
It is also preferred that extraction drying steps 6) in organic solvent extract remove pore former while, with 0% more than and less than
20% range stretch along the direction TD to film and be fixed；
It is also preferred that the draw ratio stretched again described in step 7) is set as 0~0.1% times.
5. according to the method described in claim 4, wherein the pore former is selected from n-dodecane alcohol, oleyl alcohol, octadecanol, paraffin
Oil and combinations thereof, preferably pore former are paraffin oil, more preferably atoleine；And the organic solvent is volatile chloro hydrocarbon
Class compound, the optional additive are antioxidant, ultraviolet absorbing agent, antiblocking agent, pigment, dyestuff and inorganic fill
One of material is a variety of.
6. a kind of device for producing composite microporous film described in any one of claim 1-3, the process units include:
A) biaxial extruder, the biaxial extruder contain direct extrusion system, for realizing polyolefin resin, the Nanowire of modification
The high speed that cellulose fiber disperses solution and optional additive is kneaded and evenly dispersed, and efficiently controls resin temperature；
B) casting machine, the casting machine are connect with the biaxial extruder, including chill roll and niproll, described double for that will come from
The mixture of axis extruder is cooling, to obtain gel molding；
C) the first stretching device, the stretching device are connect with the casting machine, are drawn for stretching the gel shaped object
Stretch piece；
D) drying device is extracted, which connect with first stretching device, including extraction tank and drying machine, uses
In removing pore former and drying from the drawing sheet from first stretching device, the basement membrane for being free of pore former is formed；
E) the second stretching device, second stretching device connects with extraction drying device, for will be from extracting drying device
The basement membrane without pore former stretches again in an at least axis direction；
F) heat-treating machine, the heat-treating machine are connect with the second stretching device, for that will be heat-treated from the film of the second stretching device
Sizing, to obtain the composite microporous film；
G) coiling machine, the coiling machine are connect with heat-treating machine, include work beam, for will be from the compound micro- of the heat-treating machine
Perforated membrane batches in rolls,
It is preferred that e) second stretching device and f) heat-treating machine integrates；
It is also preferred that described d) extract drying device and e) the second stretching device integrates.
7. device according to claim 6, wherein c) the first stretching device is biaxial stretch-formed device, and the process units
Further include:
H) thickness control system, the thickness control system include biaxial stretch-formed test device and quick feedback control system, are used for
Automatically the thickness of film is detected and controlled,
The biaxial extruder of the process units contains injection pump, connect with quick feedback control system, for by mixture without
The stabilization of pulsation is injected into quick feedback control system.
8. a kind of battery diaphragm, the battery diaphragm includes composite microporous film according to any one of claim 1-3.
9. a kind of lithium battery, the lithium battery pack contains composite microporous film conduct according to any one of claim 1-3
Battery diaphragm.
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| CN111016489A (en) * | 2019-12-31 | 2020-04-17 | 广东高璐美数码科技有限公司 | Degradable and scratch-resistant microporous ink-jet printing photographic paper and preparation method thereof |
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| WO2022127224A1 (en) * | 2020-12-15 | 2022-06-23 | 上海恩捷新材料科技有限公司 | Polyolefin microporous membrane, manufacturing system therefor, battery separator, and electrochemical device |
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