Low-swelling low-temperature adhesion polyacrylate aqueous binder as well as preparation method and application thereof

Abstract

The invention provides a low-swelling low-temperature adhesion polyacrylate water-based binder as well as a preparation method and application thereof. The polyacrylate water-based binder is a core-shell polymer obtained by polymerizing a polymeric monomer, polymeric monomers of a core polymer of the core-shell polymer comprise the following monomers in percentage by weight: 50-90% of a hard monomer, 5-30% of a soft monomer and 1-20% of a functional monomer; polymeric monomers of a shell polymer of the core-shell polymer comprise the following monomers in percentage by weight: 35-85% of a hard monomer, 15-60% of a soft monomer and 0-5% of a functional monomer. The polyacrylate aqueous binder provided by the invention is suitable for the lithium ion battery diaphragm, and solves the problems of low adhesion, high energy consumption, no environmental protection, high price and the like of the current binder for the lithium ion battery diaphragm.

Description

Technical Field

[0001] The present invention belongs to the technical field of water-based adhesives, and specifically relates to a polyacrylate water-based adhesive and a preparation method and application thereof, and in particular to a low-swelling, low-temperature adhesion polyacrylate water-based adhesive and a preparation method and application thereof. Background Art

[0002] At present, the most commonly used binder for lithium-ion batteries is polyvinylidene fluoride (PVDF). PVDF binder is a very mature binder with good bonding performance. However, the use of this binder is costly, environmentally polluting, and does not meet the current international VOC emission requirements. The preparation of traditional PVDF requires the use of 1,1-difluoro-1-chloroethane (R142b) as a raw material. R142b is a material that damages the atmosphere. The expansion of production is restricted by the international community, which in turn limits the expansion of PVDF. At the same time, PVDF's performance is gradually unable to meet the pursuit of lithium batteries in low swelling and high bonding strength. Therefore, finding a new binder with good mechanical properties and good chemical stability is a very urgent task to reduce the development cost of lithium batteries, and it should also meet people's strong demand for environmental protection, safety, and green homes. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention aims to provide a polyacrylate aqueous adhesive and a preparation method and application thereof, and in particular to provide a low-swelling, low-temperature adhesion polyacrylate aqueous adhesive and a preparation method and application thereof.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] On the one hand, the present invention provides a polyacrylate water-based binder, wherein the polyacrylate water-based binder is a core-shell polymer obtained by polymerizing monomers, wherein the polymerized monomers of the core polymer of the core-shell polymer include the following monomers by weight: 50-90% of hard monomers, 5-30% of soft monomers and 1-20% of functional monomers; and the polymerized monomers of the shell polymer of the core-shell polymer include the following monomers by weight: 35-85% of hard monomers, 15-60% of soft monomers and 0-5% of functional monomers;

[0006] The hard monomer is selected from one or a combination of at least two of methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate, and styrene;

[0007] The soft monomer is selected from one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hexyl methacrylate, tert-butyl carbonate, tetrahydrofurfuryl acrylate, lauryl acrylate, lauryl methacrylate, isobutyl acrylate or ethoxyethoxyethoxy acrylate;

[0008] The functional monomer is selected from one or a combination of at least two of acrylic acid, methacrylic acid, diacrylate phthalate, itaconic acid, isooctyl acrylate, diacetone acrylamide, ethyl acetoacetate methacrylate, divinylbenzene, aziridine, ethoxylated trimethylolpropane triacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, ethoxylated bisphenol A diacrylate, tripropylene glycol diacrylate, triethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and tris(2-hydroxyethyl)isocyanuric acid triacrylate.

[0009] In the present invention, the core-shell polymer and the core and shell polymer are respectively obtained by polymerizing hard monomers, soft monomers and functional monomers in different proportions, so that the core-shell polymer can be used as an aqueous binder and is suitable for lithium-ion battery separators, thereby solving the current problems of low adhesion, high energy consumption, environmental pollution and high prices in adhesives for lithium-ion battery separators.

[0010] In the present invention, the content of hard monomers in the polymerization monomers of the core polymer of the core-shell polymer can be 50%, 55%, 58%, 60%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 83%, 85%, 88% or 90%, the content of soft monomers can be 5%, 8%, 10%, 13%, 15%, 18%, 20%, 22%, 25%, 28% or 30%, and the content of functional monomers can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 15%, 18% or 20%. If the content of hard monomers in the polymerized monomers of the core polymer is less than 50% or the content of soft monomers is higher than 30%, the Tg of the core layer is low, the polymer has no supporting effect, and it is easy to block the pores of the diaphragm, resulting in a larger increase in the permeability of the diaphragm and obstruction of the lithium ion transmission channel. If the content of hard monomers is higher than 90% or the content of soft monomers is lower than 5%, the Tg of the core layer is too high, and the shell monomer is not easy to cover the core layer. If the content of functional monomers is higher than 20%, the cross-linking reaction increases, the reaction is extremely difficult to control, and the polymer particle size distribution becomes wider.

[0011] In the present invention, the content of hard monomer in the shell polymer of the core-shell polymer can be 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80% or 85%, the content of soft monomer can be 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 40%, 45%, 50%, 55% or 60%, and the content of functional monomer can be 0%, 0.5%, 1%, 2%, 3%, 4% or 5%. If the content of hard monomer in the polymerized monomer of the core-shell polymer is higher than 85% or the content of soft monomer is lower than 15%, the Tg of the shell layer is too high, and it cannot be pressed at low temperature, or the adhesion force is reduced during low temperature pressing, and the diaphragm and the pole piece are easily separated. If the content of functional monomer is higher than 5%, the cross-linking degree becomes larger and the bonding performance decreases.

[0012] Preferably, the average particle size of the polyacrylate aqueous binder is above 1 μm. The larger the particle size, the larger the gap between the pole piece and the diaphragm, the gap on the diaphragm is not easily blocked, and more electrolyte can be filled to enhance battery performance.

[0013] Preferably, the polyacrylate aqueous binder is prepared by dispersion polymerization. The present invention can ensure that the core-shell polymer is obtained by dispersion polymerization while ensuring that the particle size is above 1 μm.

[0014] On the other hand, the present invention provides a method for preparing the polyacrylate aqueous binder as described above, the preparation method comprising the following steps:

[0015] (1) preparing a bottom reaction solution and a shell polymerization monomer solution;

[0016] (2) adding a core polymerization monomer and an initiator to the reaction liquid at the bottom of the kettle to react;

[0017] (3) adding the shell polymerization monomer solution and the initiator to the reaction solution obtained in step (2), reacting to obtain the polyacrylate aqueous binder.

[0018] Preferably, the reaction liquid at the bottom of the kettle in step (1) is prepared from an organic solvent, a dispersant and deionized water.

[0019] Preferably, the organic solvent is selected from one or a combination of at least two of ethanol, ethyl acetate, methanol, isopropanol, cyclohexane, cyclohexanone, toluene cyclohexanone, pentane, hexane, and acetone.

[0020] Preferably, the dispersant is selected from one or more combinations of polyvinyl pyrrolidone, polyethylene glycol 200 or 400, such as cadmium stearate, magnesium stearate or copper stearate.

[0021] Preferably, the reaction liquid at the bottom of the kettle in step (1) comprises the following components in weight percentage: 50-95% (for example, 50%, 55%, 60%, 70%, 80%, 85%, 90% or 95%) of organic solvent, 1-5% (for example, 1%, 2%, 3%, 4% or 5%) of dispersant and 5-45% (for example, 5%, 9%, 10%, 13%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 40% or 45%) of deionized water.

[0022] Preferably, the shell polymerization monomer solution in step (1) is a solution obtained by adding shell polymerization monomers to a portion of the reaction liquid at the bottom of the kettle, and the concentration of the shell polymerization monomers in the shell polymerization monomer solution is 20-70%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or 70%.

[0023] Preferably, the weight ratio of the reaction liquid at the bottom of the kettle to the core polymerization monomer in step (2) is 1.5-7:1, for example, 1.5:1, 2:1, 2.5:1, 3:1, 4:1, 5:1, 6:1, 7:1 or 7.5:1.

[0024] Preferably, the amount of the initiator in step (2) is 1%-5% of the total mass of the core polymerization monomers, for example 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0025] Preferably, before adding the core polymerization monomer in step (2), the reaction liquid at the bottom of the kettle is heated to 50-90°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C.

[0026] Preferably, the reaction temperature in step (2) is 60-90°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, and the reaction time is 2-4h, such as 2h, 2.5h, 3h, 3.5h or 4h.

[0027] Preferably, the weight ratio of the shell polymerization monomer solution in step (3) to the reaction solution obtained in step (2) is 1-4:1, for example 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0028] Preferably, the amount of the initiator in step (3) is 1%-5% by weight of the shell polymerization monomer solution, for example 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0029] Preferably, the concentration of the shell polymerization monomer solution in step (3) is 30%-60%, for example 30%, 35%, 40%, 45%, 50%, 55% or 60%.

[0030] Preferably, the reaction temperature in step (3) is 70-80°C (e.g., 70°C, 73°C, 75°C, 78°C or 80°C), and the reaction time is 8-12h (e.g., 8h, 9h, 10h, 11h or 12h).

[0031] Preferably, the preparation method further comprises cooling the mixture to 55-70°C (e.g., 55°C, 60°C, 65°C, 68°C or 70°C) after the reaction in step (3) is completed, adding a residual monomer eliminator, then evaporating the organic solvent, adding deionized water and filtering, adjusting the pH to 6-9 (e.g., 6, 7, 8 or 9) at room temperature, adding an anti-precipitation agent, stirring evenly and then discharging the mixture.

[0032] Preferably, the residual monomer eliminating agent is bleaching powder and / or tert-butyl peroxide.

[0033] Preferably, the pH is adjusted using one or a combination of at least two of aqueous ammonia, sodium hydroxide, lithium hydroxide, potassium hydroxide or sodium bicarbonate.

[0034] Preferably, the anti-settling agent is selected from any one or a combination of at least two of fatty alcohol polyoxyethylene modified silicone, polyacrylate modified polyurea, polyoxyethylene fatty amine, polyoxyethylene fatty alcohol, hydroxymethyl cellulose ether, hydroxymethyl cellulose sodium, hydroxyethyl cellulose ether, polyvinyl pyrrolidone or polyvinyl alcohol.

[0035] In the present invention, the mass ratio of soft and hard components and functional monomer types and process adjustments are designed to adjust the size and distribution of particle size particles. By introducing functional groups such as ester groups into the adhesive, the prepared water-based diaphragm adhesive has low swelling, electrochemical stability and good adhesion, and has good application prospects in lithium-ion battery diaphragm coating.

[0036] In the present invention, the shell polymer monomer is added to the reaction system in the form of a solution for reaction. If the shell polymer monomer is not prepared into a solution and is directly added to the reaction system, the shell monomer is an oil phase and is unevenly dispersed after being added to the reaction system. The shell monomer is easy to self-aggregate, and the particle size distribution has multiple peaks and a very large range, resulting in a product with no adhesion.

[0037] In another aspect, the present invention provides a lithium ion battery separator, which includes the polyacrylate aqueous binder as described above.

[0038] In another aspect, the present invention provides a lithium ion battery, comprising the lithium ion battery separator as described above.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The polyacrylate aqueous adhesive of the present invention can provide higher bonding force and lower swelling rate under low temperature pressing, and is electrochemically stable, thus solving the problems of low bonding, high energy consumption, environmental pollution, and high price that currently exist in adhesives for lithium-ion battery separators. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0042] Example 1

[0043] In this embodiment, a polyacrylate aqueous binder is provided, and the preparation method thereof comprises the following steps:

[0044] (1) Selection and preparation of the reaction liquid at the bottom of the kettle, the monomer solvent, the core polymerization monomer solution, the shell polymerization monomer solution and the initiator:

[0045] The bottom reaction liquid and the monomer solvent: 90 parts of ethanol, 10 parts of deionized water and 4 parts of polyvinyl pyrrolidone are mixed evenly, and after they are evenly dissolved, 40 parts of them are taken as the bottom reaction liquid and the other 64 parts are taken as the solvent of the shell polymerization monomer;

[0046] Core polymerization monomer and shell polymerization monomer solution: 6 parts of styrene, 0.8 parts of butyl acrylate and 1 part of phthalic acid diacrylate are mixed evenly to obtain a core polymerization monomer; then 21 parts of styrene, 11 parts of butyl acrylate, 1.5 parts of isooctyl acrylate and 1.5 parts of lauryl acrylate are added to the monomer solvent to obtain a shell polymerization monomer solution;

[0047] Initiator: Prepare one 0.25 part and one 0.55 part of azobisisobutyronitrile.

[0048] (2) Add the reaction liquid at the bottom of the kettle to the reactor, add all the core polymerization monomers at a speed of 200 rpm, heat to 77°C, add 0.25 parts of initiator, react for 2 hours, add all the shell polymerization monomer solution, add 0.55 parts of initiator, react for 8 hours, cool to 70°C, add 0.05 parts of bleaching powder and 0.05 parts of tert-butyl peroxide, then keep warm for 20 minutes, start to evaporate ethanol, add deionized water after evaporation, filter and reduce the temperature to room temperature, add 0.01 parts of sodium hydroxide and 0.05 parts of polyurea anti-settling agent, stir evenly and discharge.

[0049] Example 2

[0050] In this embodiment, a polyacrylate aqueous binder is provided, and the preparation method thereof comprises the following steps:

[0051] (1) Selection and preparation of the reaction liquid at the bottom of the kettle, the monomer solvent, the core polymerization monomer solution, the shell polymerization monomer solution and the initiator:

[0052] The bottom reaction liquid and the monomer solvent: 80 parts of ethanol, 10 parts of deionized water and 3 parts of polyvinyl pyrrolidone are mixed evenly, and after they are evenly dissolved, 40 parts are taken as the bottom reaction liquid and the other 53 parts are taken as the solvent of the shell polymerization monomer;

[0053] Core polymerization monomer and shell polymerization monomer solution: 6 parts of styrene, 0.8 parts of butyl acrylate and 1 part of phthalic acid diacrylate are mixed evenly to obtain a core polymerization monomer; then 21 parts of styrene and 11 parts of butyl acrylate are added to the monomer solvent to obtain a shell polymerization monomer solution;

[0054] Initiator: Prepare 0.3 parts and 0.6 parts of azobisisobutyronitrile.

[0055] (2) Add the reaction liquid at the bottom of the kettle to the reactor at a speed of 200 rpm. Add all the core polymerization monomers, heat to 73°C, add 0.3 parts of initiator, react for 2 hours, add the shell polymerization monomer solution, and then add another 0.6 parts of initiator. After reacting for 8 hours, cool to 70°C, add 0.05 parts of bleaching powder and 0.05 parts of tert-butyl peroxide, then keep warm for 20 minutes, start to evaporate ethanol, add deionized water after evaporation, filter and cool to room temperature, add 0.005 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent,

[0056] Stir well and then discharge.

[0057] Example 3

[0058] In this embodiment, a polyacrylate aqueous binder is provided, and the preparation method thereof comprises the following steps:

[0059] (1) Selection and preparation of the reaction liquid at the bottom of the kettle, the monomer solvent, the core polymerization monomer solution, the shell polymerization monomer solution and the initiator:

[0060] The bottom reaction liquid and the monomer solvent: 70 parts of ethanol, 20 parts of deionized water and 2.5 parts of polyvinyl pyrrolidone are mixed evenly, and after they are evenly dissolved, 46 parts of them are taken as the bottom reaction liquid, and the other 46.5 parts are taken as the solvent of the shell polymerization monomer;

[0061] The bottom reaction liquid and the monomer solvent: 6 parts of styrene, 0.8 parts of butyl acrylate and 1 part of phthalic acid diacrylate are mixed evenly to obtain a core polymerization monomer; then 22 parts of styrene and 10 parts of butyl acrylate are added to the monomer solvent to obtain a shell polymerization monomer solution;

[0062] Initiator: Prepare two 0.3 parts of benzoyl peroxide.

[0063] (2) Add the reaction liquid at the bottom of the kettle to the reactor at a speed of 300 rpm. Add all the core polymerization monomers, heat to 70°C, add 0.3 parts of initiator, react for 3 hours, add all the shell polymerization monomer solution, and then add another 0.3 parts of initiator. After reacting for 7 hours, cool to 70°C, add 0.05 parts of bleaching powder and 0.05 parts of tert-butyl peroxide, then keep warm for 20 minutes, start to evaporate ethanol, add deionized water after evaporation, filter, cool to room temperature, add 0.5 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent, stir evenly and discharge.

[0064] Example 4

[0065] In this embodiment, a polyacrylate aqueous binder is provided, and the preparation method thereof comprises the following steps:

[0066] (1) Selection and preparation of the reaction liquid at the bottom of the kettle, the monomer solvent, the core polymerization monomer solution, the shell polymerization monomer solution and the initiator:

[0067] The bottom reaction liquid and the monomer solvent: 80 parts of ethanol, 20 parts of deionized water and 4 parts of polyvinyl pyrrolidone are mixed evenly, and after they are evenly dissolved, 51 parts of them are taken as the bottom reaction liquid and the other 51 parts are taken as the solvent of the shell polymerization monomer;

[0068] The bottom reaction liquid and the monomer solvent: 6 parts of styrene, 0.8 parts of butyl acrylate and 1.15 parts of phthalic acid diacrylate are mixed evenly to obtain a core polymerization monomer; then 16 parts of styrene and 16 parts of butyl acrylate are added to the monomer solvent to obtain a shell polymerization monomer solution;

[0069] Initiator: Prepare two 0.3 parts of benzoyl peroxide.

[0070] (2) Add the reaction liquid at the bottom of the kettle to the reactor at a speed of 300 rpm. Add all the core polymerization monomers, heat to 70°C, add 0.3 parts of initiator, react for 3 hours, add all the shell polymerization monomer solution, and then add another 0.3 parts of initiator. After reacting for 7 hours, cool to 70°C, add 0.05 parts of bleaching powder and 0.05 parts of tert-butyl peroxide, then keep warm for 20 minutes, start to evaporate ethanol, add deionized water after evaporation, filter, cool to room temperature, add 0.5 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent, stir evenly and discharge.

[0071] Example 5

[0072] In this embodiment, a polyacrylate aqueous binder is provided, and the preparation method thereof comprises the following steps:

[0073] (1) Selection and preparation of the reaction liquid at the bottom of the kettle, the monomer solvent, the core polymerization monomer solution, the shell polymerization monomer solution and the initiator:

[0074] The bottom reaction liquid and the monomer solvent: 80 parts of ethanol, 20 parts of deionized water and 3 parts of polyvinyl pyrrolidone are mixed evenly, and after they are evenly dissolved, 30 parts of them are taken as the bottom reaction liquid and the other 73 parts are taken as the solvent of the shell polymerization monomer;

[0075] The bottom reaction liquid and the monomer solvent: 6 parts of styrene, 0.8 parts of butyl acrylate and 1.15 parts of phthalic acid diacrylate are mixed evenly to obtain a core polymerization monomer; then 15 parts of styrene, 15 parts of butyl acrylate, 1.5 parts of isooctyl acrylate and 1.5 parts of lauryl acrylate are added to the monomer solvent to obtain a shell polymerization monomer solution;

[0076] Initiator: Prepare 1 0.3 parts of benzoyl peroxide and 1 0.3 parts of ammonium persulfate.

[0077] (2) Add the reaction liquid at the bottom of the kettle to the reactor at a speed of 300 rpm. Add all the core polymerization monomers, heat to 72°C, add 0.3 parts of initiator ammonium persulfate, react for 3 hours, add all the shell polymerization monomer solution, and then add another 0.3 parts of initiator benzoyl peroxide. After reacting for 7 hours, cool to 70°C, add 0.05 parts of bleaching powder and 0.05 parts of tert-butyl peroxide, then keep warm for 20 minutes, start to evaporate ethanol, add deionized water after evaporation, filter, cool to room temperature, add 0.5 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent, stir evenly and discharge.

[0078] Example 6

[0079] In this embodiment, a polyacrylate aqueous binder is provided, and the preparation method thereof comprises the following steps:

[0080] (1) Selection and preparation of the reaction liquid at the bottom of the kettle, the monomer solvent, the core polymerization monomer solution, the shell polymerization monomer solution and the initiator:

[0081] The bottom reaction liquid and the monomer solvent: 70 parts of ethanol, 10 parts of deionized water and 3 parts of polyvinyl pyrrolidone are mixed evenly, and after they are evenly dissolved, 41 parts of them are taken as the bottom reaction liquid and the other 42 parts are taken as the solvent of the shell polymerization monomer;

[0082] Core polymerization monomer and shell polymerization monomer solution: 5 parts of styrene, 1 part of butyl acrylate and 1 part of phthalic acid diacrylate are mixed evenly to obtain a core polymerization monomer; then 18 parts of styrene and 14 parts of butyl acrylate are added to the monomer solvent to obtain a shell polymerization monomer solution;

[0083] Initiator: Prepare two 0.3 parts of azobisisobutyronitrile.

[0084] (2) Add the reaction liquid at the bottom of the kettle to the reactor at a speed of 300 rpm. Add all the core polymerization monomers, heat to 74°C, add 0.3 parts of initiator, react for 2 hours, add all the shell polymerization monomer solution, and then add another 0.3 parts of initiator. After reacting for 8 hours, cool to 70°C, add 0.05 parts of bleaching powder and 0.05 parts of tert-butyl peroxide, then keep warm for 20 minutes, start to evaporate ethanol, add deionized water after evaporation, filter, cool to room temperature, add 0.005 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent, stir evenly and discharge.

[0085] Example 7

[0086] In this embodiment, a polyacrylate aqueous binder is provided, and the preparation method thereof comprises the following steps:

[0087] (1) Selection and preparation of the reaction liquid at the bottom of the kettle, the monomer solvent, the core polymerization monomer solution, the shell polymerization monomer solution and the initiator:

[0088] The bottom reaction liquid and the monomer solvent: 90 parts of ethanol, 20 parts of deionized water and 4 parts of polyvinyl pyrrolidone are mixed evenly, and after they are evenly dissolved, 70 parts are taken as the bottom reaction liquid and the other 44 parts are the solvent of the shell polymerization monomer;

[0089] Core polymerization monomer and shell polymerization monomer solution: 6 parts of styrene, 2 parts of butyl acrylate and 1 part of phthalic acid diacrylate are mixed evenly to obtain a core polymerization monomer; then 18 parts of styrene and 14 parts of butyl acrylate are added to the monomer solvent to obtain a shell polymerization monomer solution;

[0090] Initiator: Prepare two 0.3 parts of azobisisobutyronitrile.

[0091] (2) Add the reaction liquid at the bottom of the kettle to the reactor at a speed of 400 rpm. Add all the core polymerization monomers, heat to 75°C, add 0.3 parts of initiator, react for 3 hours, add all the shell polymerization monomer solution, and then add another 0.3 parts of initiator. After reacting for 8 hours, cool to 70°C, add 0.05 parts of bleaching powder and 0.05 parts of tert-butyl peroxide, then keep warm for 20 minutes, start to evaporate ethanol, add deionized water after evaporation, filter, cool to room temperature, add 0.005 parts of sodium hydroxide and 0.04 parts of polyurea anti-settling agent, stir evenly and discharge.

[0092] Example 8

[0093] In this embodiment, a polyacrylate aqueous binder is provided, and the preparation method thereof comprises the following steps:

[0094] (1) Selection and preparation of the reaction liquid at the bottom of the kettle, the monomer solvent, the core polymerization monomer solution, the shell polymerization monomer solution and the initiator:

[0095] The bottom reaction liquid and the monomer solvent: 70 parts of ethanol, 10 parts of deionized water and 2.5 parts of polyvinyl pyrrolidone are mixed evenly, and after they are evenly dissolved, 32 parts are taken as the bottom reaction liquid, and the other 50.5 parts are taken as the solvent of the shell polymerization monomer;

[0096] Core polymerization monomer and shell polymerization monomer solution: 7 parts of styrene, 0.8 parts of butyl acrylate and 1 part of phthalic acid diacrylate are mixed evenly to obtain a core polymerization monomer; 18 parts of styrene, 14 parts of butyl acrylate, 0.75 parts of isooctyl acrylate and 0.75 parts of lauryl acrylate are added to the monomer solvent to obtain a shell polymerization monomer solution;

[0097] Initiator: Prepare 0.3 parts of azobisisobutyronitrile and 0.4 parts of azobisisobutyronitrile.

[0098] (2) Add the reaction liquid at the bottom of the kettle to the reactor at a speed of 200 rpm. Add all the core polymerization monomers, heat to 73°C, add 0.3 parts of initiator, react for 2 hours, add all the shell polymerization monomer solution, and then add another 0.4 parts of initiator. After reacting for 8 hours, cool to 70°C, add 0.05 parts of bleaching powder and 0.05 parts of tert-butyl peroxide, then keep warm for 20 minutes, start to evaporate ethanol, add deionized water after evaporation, filter, cool to room temperature, add 0.005 parts of sodium hydroxide and 0.05 parts of polyurea anti-settling agent, stir evenly and discharge.

[0099] Comparative Example 1

[0100] The polyacrylate aqueous adhesive prepared in Example 1 of CN 117106393 A was used as a comparative example.

[0101] Comparative Example 2

[0102] The difference from Example 1 is that the amounts of the components in the core polymerization monomer are 6 parts of styrene, 3 parts of butyl acrylate, and 2 parts of phthalic acid diacrylate. The rest are the same as Example 1.

[0103] Comparative Example 3

[0104] The difference from Example 1 is that the amounts of the components in the shell polymerization monomer are: 18 parts of styrene, 1 part of butyl acrylate, 1 part of isooctyl acrylate, and 1 part of lauryl acrylate, and the rest are the same as in Example 1.

[0105] Comparative Example 4

[0106] The difference from Example 1 is that the amounts of the components in the polymerization monomers of the core polymer are: 6 parts of styrene, 0.6 parts of butyl acrylate, and 3.7 parts of phthalic acid diacrylate. The rest are the same as in Example 1.

[0107] Comparative Example 5

[0108] The difference from Example 1 is that the amounts of the components in the polymerization monomers of the shell polymer are: 21 parts of styrene, 11 parts of butyl acrylate, 2.5 parts of isooctyl acrylate, and 2.5 parts of lauryl acrylate. The rest are the same as in Example 1.

[0109] The polyacrylate aqueous binder of the embodiment and the comparative example, as well as PVDF and PMMA as binders are used for lithium-ion battery separators. The polyacrylate aqueous binder is coated on a polyethylene separator, and after drying in an oven at 55°C, the coated surface is fitted with the positive electrode sheet and pressed. The pressing conditions are 35°C, 3Mpa, and 10s. After completion, its performance is tested. The positive electrode sheet mentioned in this step was purchased from Guangdong Candlelight New Energy Co., Ltd.

[0110] (1) Peel strength: After the pressing is completed according to the above steps, the peel strength is tested on a tensile testing machine at a speed of 50 mm / min;

[0111] (2) Swelling rate: The wet film is placed in an oven at 65°C to form a dry film. The film is taken out and its mass is tested. The film is then placed in a glass bottle containing electrolyte. The glass bottle is placed in an oven at 65°C for 3 days and then taken out and its film weight is tested. The increased mass of the dry film divided by the mass of the dry film itself is the swelling rate.

[0112] The test results are shown in Table 1.

[0113] Table 1

[0114] Peel strength (N / m) Swelling rate (%) Example 1 22.34 35.56％ Example 2 15.79 30.45％ Example 3 23.13 48.88％ Example 4 12.35 50.01％ Example 5 19.73 50.38％ Example 6 10.91 31.93％ Example 7 20.88 38.41％ Example 8 21.04 37.69％ Comparative Example 1 5.23 77.89％ Comparative Example 2 0 99.01％ Comparative Example 3 1.01 75.38％ Comparative Example 4 3.32 83.33％ Comparative Example 5 25.51 150％ PVDF 0 354％ PMMA 0 115％

[0115] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the polyacrylate water-based adhesive and its preparation method and application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polyacrylate water-based adhesive, characterized in that: The polyacrylate aqueous binder is a core-shell polymer obtained by polymerizing monomers, wherein the polymerized monomers of the core polymer of the core-shell polymer include the following monomers by weight: 50-90% of hard monomers, 5-30% of soft monomers and 1-20% of functional monomers; the polymerized monomers of the shell polymer of the core-shell polymer include the following monomers by weight: 35-85% of hard monomers, 15-60% of soft monomers and 0-5% of functional monomers; The hard monomer is selected from one or a combination of at least two of methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate, and styrene; The soft monomer is selected from one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hexyl methacrylate, tert-butyl carbonate, tetrahydrofurfuryl acrylate, lauryl acrylate, lauryl methacrylate, isobutyl acrylate or ethoxyethoxyethoxy acrylate; The functional monomer is selected from one or a combination of at least two of acrylic acid, methacrylic acid, diacrylate phthalate, itaconic acid, isooctyl acrylate, diacetone acrylamide, ethyl acetoacetate methacrylate, divinylbenzene, aziridine, ethoxylated trimethylolpropane triacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, ethoxylated bisphenol A diacrylate, tripropylene glycol diacrylate, triethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and tris(2-hydroxyethyl)isocyanuric acid triacrylate.

2. The polyacrylate aqueous adhesive according to claim 1, characterized in that: The particle size of the polyacrylate aqueous binder is above 1 μm.

3. The polyacrylate aqueous adhesive according to claim 1, characterized in that: The polyacrylate aqueous binder is prepared by dispersion polymerization.

4. The method for preparing the polyacrylate aqueous binder according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) preparing a bottom reaction solution and a shell polymerization monomer solution; (2) adding a core polymerization monomer and an initiator to the reaction liquid at the bottom of the kettle to react; (3) adding the shell polymerization monomer solution and the initiator to the reaction solution obtained in step (2), reacting to obtain the polyacrylate aqueous binder.

5. The preparation method according to claim 4, characterized in that: The reaction liquid at the bottom of the kettle in step (1) is prepared from an organic solvent, a dispersant and deionized water; Preferably, the organic solvent is selected from one or a combination of at least two of ethanol, ethyl acetate, methanol, isopropanol, cyclohexane, cyclohexanone, toluene cyclohexanone, pentane, hexane, and acetone; Preferably, the dispersant is selected from one or more combinations of polyvinyl pyrrolidone, polyethylene glycol 200 or 400, such as cadmium stearate, magnesium stearate or copper stearate; Preferably, the reaction liquid at the bottom of the kettle in step (1) comprises the following components in weight percentage: 50-95% organic solvent, 1-5% dispersant and 5-45% deionized water.

6. The preparation method according to claim 4 or 5, characterized in that: The shell polymerization monomer solution in step (1) is a solution obtained by adding shell polymerization monomers to a portion of the reaction liquid at the bottom of a kettle, wherein the concentration of the shell polymerization monomers in the shell polymerization monomer solution is 20-70%; Preferably, the weight ratio of the reaction liquid at the bottom of the kettle to the core polymerization monomer in step (2) is 1.5-7:1 Preferably, the amount of the initiator in step (2) is 1%-5% of the total mass of the core polymerization monomers; Preferably, the reaction liquid at the bottom of the kettle is heated to 50-90° C. before adding the core polymerization monomer in step (2); Preferably, the reaction temperature in step (2) is 60-90° C. and the reaction time is 2-4 h.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The weight ratio of the shell polymerization monomer solution in step (3) to the reaction solution obtained in step (2) is 1-4:1; Preferably, the amount of the initiator in step (3) is 1%-5% by weight of the shell polymerization monomer solution; Preferably, the concentration of the shell polymerization monomer solution in step (3) is 30%-60%; Preferably, the reaction temperature in step (3) is 70-80° C. and the reaction time is 8-12 h.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The preparation method further comprises cooling the mixture to 55-70° C. after the reaction in step (3) is completed, adding a residual monomer eliminator, then evaporating the organic solvent, adding deionized water and filtering, adjusting the pH to 6-9 at room temperature, adding an anti-precipitation agent, stirring evenly, and then discharging the mixture; Preferably, the residual monomer eliminator is bleaching powder and / or tert-butyl peroxide; Preferably, the pH is adjusted using one or a combination of at least two of aqueous ammonia, sodium hydroxide, lithium hydroxide, potassium hydroxide or sodium bicarbonate; Preferably, the anti-settling agent is selected from any one or a combination of at least two of fatty alcohol polyoxyethylene modified silicone, polyacrylate modified polyurea, polyoxyethylene fatty amine, polyoxyethylene fatty alcohol, hydroxymethyl cellulose ether, hydroxymethyl cellulose sodium, hydroxyethyl cellulose ether, polyvinyl pyrrolidone or polyvinyl alcohol.

9. A lithium ion battery separator, characterized in that: The lithium-ion battery separator comprises the polyacrylate aqueous binder according to any one of claims 1 to 3.

10. A lithium ion battery, characterized in that: The lithium ion battery comprises the lithium ion battery separator according to any one of claims 1 to 3.