CN111378057A - Graft modified polyethylene material, preparation method thereof, polyethylene porous membrane and lithium battery - Google Patents
Graft modified polyethylene material, preparation method thereof, polyethylene porous membrane and lithium battery Download PDFInfo
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- CN111378057A CN111378057A CN202010341368.XA CN202010341368A CN111378057A CN 111378057 A CN111378057 A CN 111378057A CN 202010341368 A CN202010341368 A CN 202010341368A CN 111378057 A CN111378057 A CN 111378057A
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- polyethylene
- calcium stearate
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- -1 polyethylene Polymers 0.000 title claims abstract description 138
- 239000004698 Polyethylene Substances 0.000 title claims abstract description 129
- 229920000573 polyethylene Polymers 0.000 title claims abstract description 129
- 239000000463 material Substances 0.000 title claims abstract description 41
- 239000012528 membrane Substances 0.000 title claims abstract description 30
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 12
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 12
- 235000013539 calcium stearate Nutrition 0.000 claims abstract description 50
- 239000008116 calcium stearate Substances 0.000 claims abstract description 50
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 claims abstract description 47
- 238000006243 chemical reaction Methods 0.000 claims abstract description 26
- 229910052736 halogen Inorganic materials 0.000 claims abstract description 13
- 150000002367 halogens Chemical class 0.000 claims abstract description 13
- 238000004519 manufacturing process Methods 0.000 claims abstract description 13
- 230000003213 activating effect Effects 0.000 claims abstract description 3
- 239000002245 particle Substances 0.000 claims description 18
- 230000005855 radiation Effects 0.000 claims description 12
- 239000003999 initiator Substances 0.000 claims description 10
- 239000002253 acid Substances 0.000 claims description 7
- 239000011575 calcium Substances 0.000 claims description 5
- 229910052791 calcium Inorganic materials 0.000 claims description 5
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 4
- 230000005251 gamma ray Effects 0.000 claims description 3
- 239000012798 spherical particle Substances 0.000 claims description 3
- 125000004432 carbon atom Chemical group C* 0.000 claims description 2
- 150000001451 organic peroxides Chemical class 0.000 claims description 2
- 230000006378 damage Effects 0.000 abstract description 4
- 238000001556 precipitation Methods 0.000 abstract description 4
- 230000002401 inhibitory effect Effects 0.000 abstract description 2
- 230000000717 retained effect Effects 0.000 abstract description 2
- 238000000034 method Methods 0.000 description 27
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 23
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 18
- 230000008569 process Effects 0.000 description 17
- 239000002244 precipitate Substances 0.000 description 12
- 239000002994 raw material Substances 0.000 description 12
- 239000000047 product Substances 0.000 description 11
- 239000012982 microporous membrane Substances 0.000 description 8
- 238000012545 processing Methods 0.000 description 8
- 238000005303 weighing Methods 0.000 description 8
- 239000002904 solvent Substances 0.000 description 7
- 238000001035 drying Methods 0.000 description 6
- 230000001376 precipitating effect Effects 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 150000003384 small molecules Chemical class 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- OZAIFHULBGXAKX-UHFFFAOYSA-N 2-(2-cyanopropan-2-yldiazenyl)-2-methylpropanenitrile Chemical compound N#CC(C)(C)N=NC(C)(C)C#N OZAIFHULBGXAKX-UHFFFAOYSA-N 0.000 description 2
- OMPJBNCRMGITSC-UHFFFAOYSA-N Benzoylperoxide Chemical compound C=1C=CC=CC=1C(=O)OOC(=O)C1=CC=CC=C1 OMPJBNCRMGITSC-UHFFFAOYSA-N 0.000 description 2
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 2
- 239000005662 Paraffin oil Substances 0.000 description 2
- 238000001994 activation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 235000019400 benzoyl peroxide Nutrition 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000004342 Benzoyl peroxide Substances 0.000 description 1
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 239000006057 Non-nutritive feed additive Substances 0.000 description 1
- 239000011954 Ziegler–Natta catalyst Substances 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium chloride Substances Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 150000002366 halogen compounds Chemical class 0.000 description 1
- 238000009998 heat setting Methods 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- OTCKOJUMXQWKQG-UHFFFAOYSA-L magnesium bromide Chemical compound [Mg+2].[Br-].[Br-] OTCKOJUMXQWKQG-UHFFFAOYSA-L 0.000 description 1
- 229910001623 magnesium bromide Inorganic materials 0.000 description 1
- 229910001629 magnesium chloride Inorganic materials 0.000 description 1
- BLQJIBCZHWBKSL-UHFFFAOYSA-L magnesium iodide Chemical compound [Mg+2].[I-].[I-] BLQJIBCZHWBKSL-UHFFFAOYSA-L 0.000 description 1
- 229910001641 magnesium iodide Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000009832 plasma treatment Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 230000003335 steric effect Effects 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- LOJPEGWUHVRGBN-UHFFFAOYSA-J tetrachlorotitanium;triethylalumane Chemical compound [Cl-].[Cl-].[Cl-].[Cl-].[Ti+4].CC[Al](CC)CC LOJPEGWUHVRGBN-UHFFFAOYSA-J 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/20—Manufacture of shaped structures of ion-exchange resins
- C08J5/22—Films, membranes or diaphragms
- C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
- C08J5/2218—Synthetic macromolecular compounds
- C08J5/2231—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds
- C08J5/2243—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds obtained by introduction of active groups capable of ion-exchange into compounds of the type C08J5/2231
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/14—Cells with non-aqueous electrolyte
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- 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
- C08J2323/26—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers modified by chemical after-treatment
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Manufacturing & Machinery (AREA)
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- Engineering & Computer Science (AREA)
- Electrochemistry (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Cell Separators (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
The invention belongs to the technical field of lithium battery diaphragms, and particularly relates to a graft modified polyethylene material, a preparation method thereof, a polyethylene porous membrane and a lithium battery. The preparation method of the graft modified polyethylene material comprises the following steps: activating treatment, namely treating the polyethylene containing halogen elements to generate active sites on the molecular chain of the polyethylene; grafting reaction, namely grafting calcium stearate on active sites of a polyethylene molecular chain; and purifying to obtain the grafted modified polyethylene material, so that the CaSt is retained in the diaphragm, thereby inhibiting the precipitation of the CaSt and reducing the damage to the production process of the product after the precipitation of the CaSt.
Description
Technical Field
The invention belongs to the technical field of lithium battery diaphragms, and particularly relates to a graft modified polyethylene material, a preparation method thereof, a polyethylene porous membrane and a lithium battery.
Background
Polyethylene feedstocks are typically prepared during the preparation process using Ziegler-Natta catalysts, such as AlCl3The weak acids can lead the raw materials to present certain acidity, the acidity of the raw materials can corrode processing equipment in the processing process, the service life of the equipment is influenced, and meanwhile, the phenomena of product performance reduction and the like can be caused after a certain amount of accumulation, so that the normal production of products is seriously influenced. In the processing process, a weak base substance is generally added to neutralize acid in raw materials to prevent the occurrence of the above conditions, however, after some small-molecule weak base is added, the small molecules are precipitated from the surface of the product in the processing process due to low surface energy of the small molecules, and are adsorbed on equipment in subsequent processes, which also influences the quality of the product.
Disclosure of Invention
The invention provides a graft modified polyethylene material, a preparation method thereof, a polyethylene porous membrane and a lithium battery.
In order to solve the technical problem, the invention provides a preparation method of a graft modified polyethylene material, which comprises the following steps: activating treatment, namely treating the polyethylene containing halogen elements to generate active sites on the molecular chain of the polyethylene; grafting reaction, namely grafting calcium stearate on active sites of a polyethylene molecular chain; and purification treatment.
In a second aspect, the present invention provides a multi-graft modified polyethylene material comprising: polyethylene containing halogen elements and calcium stearate grafted onto the molecular chain of the polyethylene.
In a third aspect, the invention provides a graft modified polyethylene porous membrane prepared from the graft modified polyethylene material.
In a fourth aspect, the present invention provides a lithium battery comprising: a diaphragm; the separator employs the graft-modified polyethylene porous membrane as described above.
The grafted modified polyethylene porous membrane material, the preparation method thereof, the porous membrane and the lithium battery have the beneficial effects that the active sites are generated on the molecular chain of the polyethylene through the active treatment, and the calcium stearate is grafted, so that the CaSt is kept in the diaphragm, the precipitation of the CaSt is inhibited, and the damage to the production process of the product after the CaSt is precipitated is reduced.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a flow chart of a process for preparing a graft-modified polyethylene material according to the present invention;
FIG. 2 is a molecular structure diagram of the activation treatment of the polyethylene of the present invention.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A first part: illustrating a specific embodiment
In the production process of the microporous membrane, the acidity of the raw material can be adjusted by adding calcium stearate (CaSt), but in the subsequent process, it is found that CaSt with lower surface energy is separated out from the interior of the membrane and adsorbed on the surface of equipment, so that the surface of the membrane product is scratched, and the performance of the product is seriously reduced. Thus, referring to fig. 1, the present invention provides a method for preparing a graft-modified polyethylene material, comprising: performing active treatment, namely treating the polyethylene containing halogen elements to generate active sites on molecular chains (including molecular chain branched chains, molecular chain heads and molecular chain ends); grafting reaction, namely grafting calcium stearate on active sites of a polyethylene molecular chain; and purification treatment.
Alternatively, high-energy ray radiation, plasma treatment technology or chemical agent treatment can be generally adopted as an active treatment method, and specific means is not required, but the treated raw material is required to have the structure shown in fig. 2 or the characteristics of grafting reaction.
Optionally, the halogen element may include chlorine, fluorine, etc. and may be added as a processing aid during the processing of the polyethylene, and all the halogen elements may be selected, because the raw material of the polyethylene may be added with a Ziegler-Natta catalyst containing a halogen compound, such as titanium tetrachloride-triethylaluminum, or other catalysts, such as magnesium chloride, magnesium iodide, magnesium bromide, etc. during the synthesis.
Optionally, the purification treatment comprises: and repeatedly washing and precipitating the product after the grafting reaction by using solvents such as dimethylbenzene, methanol and the like, collecting the precipitate, and drying the precipitate in a vacuum environment to obtain the graft modified polyethylene material.
As an alternative embodiment to grafting calcium stearate.
The grafting reaction comprises: the method comprises the following steps of enabling calcium stearate and polyethylene containing halogen elements to undergo a grafting reaction under certain reaction conditions through an initiator, namely organically combining active sites on a polyethylene molecular chain with calcium stearate small molecules (calcium stearate is an inorganic compound, wherein the calcium stearate mainly has certain requirements on physical properties such as particle size, and the selected calcium stearate particles need to be more than 300 meshes in a screening process), and fixing the calcium stearate small molecules on the polyethylene molecular chain in a grafting manner. Wherein the grafting reaction has the formula:
the reaction conditions of the grafting reaction include: microwave radiation or gamma ray radiation; the initiator can be selected from azo compounds such as azobisisobutyronitrile, or organic peroxides such as benzoyl peroxide, dibenzoyl peroxide and the like, the grafting reaction is shown as a reaction formula, and the grafting rate of the calcium stearate is calculated by a weighing method.
Optionally, the molecular weight of the polyethylene is 50000-1000000, optionally 120000, 200000; the polyethylene is spherical particles with an average particle size of 5-50 μm, preferably 10-40 μm, and more preferably 20-30 μm, and the uniform polyethylene particles are favorable for the uniformity and dispersibility of the grafting reaction. The molecular weight of the polyethylene is used for ensuring the basic characteristics of film making, and the selection of the polyethylene with the molecular weight of 5-100 ten thousand can ensure that the polyethylene with various molecular weight combinations can be selected, thereby not only ensuring the mechanical performance of the polyethylene, but also reducing the difficulty of the processing process as much as possible; the spherical particles and particle size are selected because of their maximum particle surface area and maximum modification during the activation process. At least 2 calcium stearate small molecules are grafted in each 10000 carbon atoms of the polyethylene molecular chain, and at least two calcium stearate small molecules are grafted on at least one polyethylene carbon chain with the molecular weight of less than 80000. The grafting mode can improve the lubricity among molecular chains, and can efficiently neutralize free acid in the raw materials, so that the free acid is not easy to separate from the raw materials and separate out, thereby causing harm to processing equipment and product quality. Meanwhile, the molecular structure design can ensure a certain mass fraction of calcium stearate in the raw materials, if the mass fraction exceeds the limit, the processing process of the film is influenced, the mechanical strength of the film is reduced, and if the mass fraction is less than a certain numerical value, the halogen in the raw materials cannot be neutralized.
Optionally, the calcium stearate comprises: calcium stearate powder with fineness of more than 300 meshes; and the calcium stearate powder has a sieve residue of less than 0.1%, a calcium content of more than 6.5%, and a free acid content of less than 0.4%. The smaller the particle size of the calcium stearate is, the smaller the volume occupied on the surface of the polyethylene particles is, the steric effect among the calcium stearate particles can be reduced, and the grafting success rate of the calcium stearate particles is improved. The content is the most direct index that the calcium stearate can play the role of acid removal, and the calcium element and the halogen can be combined into a calcium halide form to better perform grafting reaction.
In the grafting reaction of the embodiment, calcium aliphatate micromolecules are organically combined with active sites on a polyethylene molecular chain through an initiator under the reaction condition of microwave radiation or gamma ray radiation, the grafting rate of the calcium aliphatate micromolecules is high, and the stability is strong, so that the CaSt is kept in the diaphragm, and the CaSt cannot be kept in the production process of the diaphragm
Further, the invention provides a graft modified polyethylene material, comprising: polyethylene containing halogen elements and calcium stearate grafted onto the molecular chain of the polyethylene.
Further, the invention provides a graft modified polyethylene porous membrane prepared from the graft modified polyethylene material.
Optionally, the graft modified polyethylene material may be prepared by a wet method or a dry method, wherein the wet method is specifically performed by the following steps: 1) firstly, mixing the graft modified polyethylene material with paraffin oil, carrying out melt extrusion through an extruder, and forming a polyethylene melt sheet through a T-shaped die; 2) in the cooling crystallization process of the sheet, a cooling roller is adopted to rapidly cool the sheet, which is beneficial to the sheet to form a crystalline state so as to ensure the mechanical property of the film; 3) in the longitudinal stretching process of the sheet, the film is stretched along the trend of the film, so that a longitudinal hole structure is formed inside the film; 4) transversely stretching, namely transversely stretching the membrane perpendicular to the longitudinal direction to gradually increase the pores in the membrane, wherein the pore diameter is uniform; 5) extracting, namely extracting and removing paraffin oil in the film completely by adopting volatile solvents such as dichloromethane and the like; 6) and in the heat setting process, the membrane is treated at a certain temperature, so that the membrane is retracted to ensure the mechanical property of the membrane, and finally the graft modified polyethylene porous membrane is obtained.
Further, the present invention provides a lithium battery including: a diaphragm; the separator employs the graft-modified polyethylene porous membrane as described above.
A second part: some examples are given below
Example 1
(1) Dissolving 200g of polyethylene with the average molecular weight of 120000 and the average particle size of 22 mu m in a certain amount of dimethylbenzene, adding an initiator and calcium stearate, continuously stirring by using a magnetic stirrer in the process to dissolve the polyethylene, controlling the rotating speed to be 100-150 r/min, heating to about 50 ℃, and placing in a radiation environment for 30min for treatment; repeatedly washing the irradiated solution by using solvents such as dimethylbenzene, methanol and the like, precipitating, collecting precipitates, placing the precipitates in a vacuum environment for drying to obtain the graft modified polyethylene material, weighing and calculating the grafting rate.
(2) And (3) putting the grafted modified polyethylene material into an extruder, and preparing the grafted modified polyethylene porous membrane by adopting a preparation method of a polyethylene wet microporous membrane.
Example 2
(1) Dissolving 200g of polyethylene with the average molecular weight of 130000 and the average particle size of 31 mu m in a certain amount of dimethylbenzene, adding an initiator and calcium stearate, continuously stirring by using a magnetic stirrer in the process to dissolve the polyethylene, controlling the rotating speed at 100-150 r/min, heating to about 50 ℃, and placing in a radiation environment for 30min for treatment; repeatedly washing the irradiated solution by using solvents such as dimethylbenzene, methanol and the like, precipitating, collecting precipitates, placing the precipitates in a vacuum environment for drying to obtain the graft modified polyethylene material, weighing and calculating the grafting rate.
(2) And (3) putting the grafted modified polyethylene material into an extruder, and preparing the grafted modified polyethylene porous membrane by adopting a preparation method of a polyethylene wet microporous membrane.
Example 3
(1) Dissolving 200g of polyethylene with the average molecular weight of 200000 and the average particle size of 38 mu m in a certain amount of xylene, adding an initiator and calcium stearate, continuously stirring by using a magnetic stirrer in the process to dissolve the polyethylene, controlling the rotating speed at 100-150 r/min, heating to about 50 ℃, and placing in a radiation environment for 30min for treatment; repeatedly washing the irradiated solution by using solvents such as dimethylbenzene, methanol and the like, precipitating, collecting precipitates, placing the precipitates in a vacuum environment for drying to obtain the graft modified polyethylene material, weighing and calculating the grafting rate.
(2) And (3) putting the grafted modified polyethylene material into an extruder, and preparing the grafted modified polyethylene porous membrane by adopting a preparation method of a polyethylene wet microporous membrane.
Example 4
(1) Dissolving 200g of polyethylene with the average molecular weight of 50000 and the average particle size of 5 mu m in a certain amount of dimethylbenzene, adding an initiator and calcium stearate, continuously stirring by using a magnetic stirrer in the process to dissolve the polyethylene, controlling the rotating speed to be 100-150 r/min, heating to about 50 ℃, and placing in a radiation environment for 30min for treatment; repeatedly washing the irradiated solution by using solvents such as dimethylbenzene, methanol and the like, precipitating, collecting precipitates, placing the precipitates in a vacuum environment for drying to obtain the graft modified polyethylene material, weighing and calculating the grafting rate.
(2) And (3) putting the grafted modified polyethylene material into an extruder, and preparing the grafted modified polyethylene porous membrane by adopting a preparation method of a polyethylene wet microporous membrane.
Example 5
(1) Dissolving 200g of polyethylene with the average molecular weight of 1000000 and the average particle size of 50 mu m in a certain amount of dimethylbenzene, adding an initiator and calcium stearate, continuously stirring by using a magnetic stirrer in the process to dissolve the polyethylene, controlling the rotating speed to be 100-150 r/min, heating to about 50 ℃, and placing in a radiation environment for 30min for treatment; repeatedly washing the irradiated solution by using solvents such as dimethylbenzene, methanol and the like, precipitating, collecting precipitates, placing the precipitates in a vacuum environment for drying to obtain the graft modified polyethylene material, weighing and calculating the grafting rate.
(2) And (3) putting the grafted modified polyethylene material into an extruder, and preparing the grafted modified polyethylene porous membrane by adopting a preparation method of a polyethylene wet microporous membrane.
Comparative example 1
200g of polyethylene with the average molecular weight of 180000 and the average particle size of 24 mu m is directly put into an extruder without graft modification, and the conventional polyethylene porous membrane is prepared by adopting a preparation method of a polyethylene wet microporous membrane.
Comparative example 2
200g of polyethylene with the average molecular weight of 220000 and the average particle size of 35 mu m is directly put into an extruder without grafting modification, and the conventional polyethylene porous membrane is prepared by adopting a preparation method of a polyethylene wet microporous membrane.
And a third part: contrast parameter Performance
In this section, the physical properties of the separators (the thickness of the separator is 10 μm) prepared in examples 1 to 3 and comparative examples 1 to 2 were measured, and the thickness was measured using a horse thickness gauge; testing the grafting rate of the raw materials and the porosity of the membrane by adopting a weighing method; respectively detecting the pH values of the polyethylene material, the grafted modified polyethylene material and the prepared diaphragm by adopting pH test paper, wherein the detection process is to dissolve a detected substance in dimethylbenzene with a certain proportion for testing; the polyethylene material before and after grafting and the ironwork are contacted for a long time to observe the corrosivity of the raw materials to iron, and the mass of rust is calculated by adopting a weighing method, so that the corrosivity change of the graft modified polyethylene material is determined. Wherein, the polyethylene materials in each example and the corresponding detection results are shown in table 1.
Table 1 shows the parameters of the polyethylene material and the results of the measurement
It can be seen from table 1 that the film prepared from the grafted polyethylene of the graft modified polyethylene material of the present invention has a performance difference of less than 10% from the film prepared without the grafted polyethylene; the calcium stearate micromolecules are fixed on the polyethylene molecular chains in an organic combination mode, the grafting rate of polyethylene is more than 1%, and the corrosion gain of grafted polyethylene to iron products is less than 0.1%, namely the preparation method of the graft modified polyethylene material grafts the calcium stearate on the polyethylene molecular chains through graft reaction, so that the problem of precipitation of the calcium stearate micromolecules can be solved, and the mechanical properties of the polyethylene material and the diaphragm cannot be influenced.
In summary, different from the traditional method of directly adding additives, the graft modified polyethylene material, the preparation method thereof, the polyethylene porous membrane and the lithium battery of the invention generate active sites on the molecular chain of polyethylene through active treatment, and the calcium stearate is grafted, so that the CaSt is retained in the diaphragm, thereby inhibiting the CaSt from being precipitated, and reducing the damage to the production process of the product after the CaSt is precipitated.
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (10)
1. A preparation method of a graft modified polyethylene material is characterized by comprising the following steps:
activating treatment, namely treating the polyethylene containing halogen elements to generate active sites on the molecular chain of the polyethylene;
grafting reaction, namely grafting calcium stearate on active sites of a polyethylene molecular chain; and
and (5) purifying.
2. The production method according to claim 1,
the grafting reaction comprises: the calcium stearate and the polyethylene containing halogen elements are subjected to grafting reaction through an initiator under certain reaction conditions, namely
Active sites on the polyethylene molecular chain are organically combined with calcium stearate small molecules, and the calcium stearate small molecules are fixed on the polyethylene molecular chain in a grafting mode.
3. The production method according to claim 2,
the reaction formula of the grafting reaction is as follows:
4. the production method according to claim 2,
the molecular weight of the polyethylene is 50000-1000000;
the polyethylene is spherical particles with the average particle size of 5-50 μm;
at least 2 small calcium stearate molecules are grafted per 10000 carbon atoms on the polyethylene molecular chain, and
at least one polyethylene carbon chain with the molecular weight less than 80000 is grafted with at least two calcium stearate small molecules.
5. The production method according to claim 2,
the initiator includes azo type and organic peroxide type.
6. The production method according to claim 2,
the reaction conditions of the grafting reaction include: microwave radiation or gamma ray radiation.
7. The production method according to claim 1,
the calcium stearate comprises: calcium stearate powder with fineness of more than 300 meshes; and
the calcium stearate powder has a screen residue of less than 0.1%, a calcium content of more than 6.5%, and a free acid content of less than 0.4%.
8. A graft-modified polyethylene material, comprising:
polyethylene containing halogen elements and calcium stearate grafted onto the molecular chain of the polyethylene.
9. A graft-modified polyethylene porous membrane prepared from the graft-modified polyethylene material of claim 8.
10. A lithium battery, comprising:
a diaphragm;
the graft-modified polyethylene porous membrane according to claim 9 is used for the separator.
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Application publication date: 20200707 |