A low-swelling, low-temperature adhesive polyacrylate waterborne binder, its preparation method and application

Abstract

This invention provides a low-swelling, low-temperature adhesive water-based polyacrylate binder, its preparation method, and its application. The water-based polyacrylate binder is a core-shell polymer obtained by polymerizing monomers. The core polymer of the core-shell polymer comprises, by weight, 50-90% hard monomers, 5-30% soft monomers, and 1-20% functional monomers; the shell polymer of the core-shell polymer comprises, by weight, 35-85% hard monomers, 15-60% soft monomers, and 0-5% functional monomers. The water-based polyacrylate binder of this invention is suitable for lithium-ion battery separators, solving the problems of low adhesion, high energy consumption, environmental unfriendliness, and high cost currently found in adhesives used in lithium-ion battery separators.

Description

Technical Field

[0001] This invention belongs to the field of waterborne adhesive technology, specifically relating to a waterborne polyacrylate adhesive, its preparation method and application, and particularly to a low-swelling, low-temperature adhesive waterborne polyacrylate adhesive, its preparation method and application. Background Technology

[0002] Currently, 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, its use is costly, causes significant environmental pollution, and does not meet current international VOC emission requirements. Traditional PVDF production requires 1,1-difluoro-1-chloroethane (R142b) as a raw material. R142b is a material that damages the atmosphere, and its production expansion is restricted by the international community, thus limiting the expansion of PVDF production. Furthermore, PVDF's performance is gradually failing to meet the demands of lithium batteries for low swelling and high bonding strength. Therefore, finding a new binder with good mechanical properties and chemical stability is a very urgent task to reduce the development cost of lithium batteries, while also meeting people's strong demand for environmental protection, safety, and a green environment. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a water-based polyacrylate adhesive, its preparation method, and its application, particularly a low-swelling, low-temperature adhesive water-based polyacrylate adhesive, its preparation method, and its application.

[0004] To achieve this objective, the present invention adopts the following technical solution:

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

[0006] The hard monomer is selected from one or a combination of at least two of the following: 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 the following: ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hexyl methacrylate, ethylene tert-carbonate, tetrahydrofurfuryl acrylate, lauryl acrylate, lauryl methacrylate, isodecyl acrylate, or ethoxyethoxyethoxyacrylate.

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

[0009] In this invention, the core-shell polymer and the polymer of the core and shell are 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 problems of low adhesion, high energy consumption, environmental unfriendliness and high price of current adhesives for lithium-ion battery separators.

[0010] In this invention, the content of hard monomers in the polymer monomers 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 polymer monomers of the core polymer is less than 50% or the content of soft monomers is higher than 30%, the core layer Tg is low, the polymer has no supporting effect, and it is easy to block the membrane pores, resulting in a larger increase in membrane permeability and obstruction of lithium-ion transport channels. If the content of hard monomers is higher than 90% or the content of soft monomers is lower than 5%, the core layer Tg is too high, and the shell monomers are not easy to coat the core layer. If the content of functional monomers is higher than 20%, the crosslinking reaction increases, the reaction is extremely difficult to control, and the polymer particle size distribution becomes wider.

[0011] In this invention, the content of hard monomers in the shell polymer of the core-shell polymer can be 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, or 85%, and the content of soft monomers can be 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 40%, 45%, 50%, 55%, or 60%. The content of functional monomers can be 0%, 0.5%, 1%, 2%, 3%, 4%, or 5%. If the content of hard monomers in the polymer monomers of the core-shell polymer is higher than 85% or the content of soft monomers is lower than 15%, the shell layer Tg is too high, making low-temperature pressing impossible, or the low-temperature pressing adhesion is reduced, and the diaphragm and electrode are prone to detachment. If the content of functional monomers is higher than 5%, the degree of crosslinking increases, and the bonding performance decreases.

[0012] Preferably, the average particle size of the aqueous polyacrylate binder is greater than 1 μm. Larger particle size increases the gap between the electrode and the separator, making it less likely for the pores on the separator to be blocked, and allowing for the filling of more electrolyte, thus enhancing battery performance.

[0013] Preferably, the aqueous polyacrylate binder is prepared by dispersion polymerization. This invention, through dispersion polymerization, ensures that the core-shell polymer is obtained while maintaining a particle size of 1 μm or larger.

[0014] On the other hand, the present invention provides a method for preparing the above-mentioned waterborne polyacrylate adhesive, the preparation method comprising the following steps:

[0015] (1) Prepare the reaction solution at the bottom of the reactor and the shell polymerization monomer solution;

[0016] (2) Add the nucleopolymer monomer and initiator to the reaction solution at the bottom of the reactor, and react;

[0017] (3) Add shell polymer monomer solution and initiator to the reaction solution obtained in step (2) and react to obtain the polyacrylate water-based binder.

[0018] Preferably, the reaction solution at the bottom of the vessel 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, toluenecyclohexanone, pentane, hexane, and acetone.

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

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

[0022] Preferably, the shell polymer monomer solution in step (1) is a solution obtained by adding shell polymer monomer to a portion of the bottom reaction liquid, and the concentration of shell polymer monomer in the shell polymer 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 bottom reaction liquid 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 initiator used in step (2) is 1%-5% of the total mass of the nuclear polymerization monomers, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0025] Preferably, before adding the nuclear polymerization monomer in step (2), the reaction liquid at the bottom of the reactor 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℃, for example 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 90℃, and the reaction time is 2-4h, for example 2h, 2.5h, 3h, 3.5h or 4h.

[0027] Preferably, the weight ratio of the shell polymer 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 initiator used in step (3) is 1%-5% of the weight of the shell polymer 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 polymer 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℃ (e.g., 70℃, 73℃, 75℃, 78℃ or 80℃), and the reaction time is 8-12h (e.g., 8h, 9h, 10h, 11h or 12h).

[0031] Preferably, the preparation method further includes cooling to 55-70℃ (e.g., 55℃, 60℃, 65℃, 68℃ or 70℃) after the reaction in step (3), 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-settling agent and stirring evenly before discharging.

[0032] Preferably, the residual monomer eliminator is sodium formaldehyde sulfoxylate and / or tert-butanol peroxide.

[0033] Preferably, the pH is adjusted using one or a combination of at least two of 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 the following: fatty alcohol polyoxyethylene modified silicone, polyacrylate modified polyurea, polyoxyethylene fatty amine, polyoxyethylene fatty alcohol, hydroxymethyl cellulose ether, sodium hydroxymethyl cellulose, hydroxyethyl cellulose ether, polyvinylpyrrolidone, or polyvinyl alcohol.

[0035] In this invention, by designing the mass ratio of soft and hard components and functional monomers and adjusting the process, the size and distribution of particles are adjusted. By introducing functional groups such as ester groups into the adhesive, the resulting waterborne separator adhesive has low swelling, electrochemical stability and good adhesion, and has good application prospects in lithium-ion battery separator coating.

[0036] In this invention, the shell polymer monomer is added to the reaction system in solution form. 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, which is unevenly dispersed after being added to the reaction system. The shell monomer is prone to self-aggregation, and the particle size distribution shows multiple peaks with a very large range, resulting in the product having no adhesive force.

[0037] On the other hand, the present invention provides a lithium-ion battery separator, the lithium-ion battery separator comprising the aqueous polyacrylate binder as described above.

[0038] On the other hand, the present invention provides a lithium-ion battery, the 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 waterborne polyacrylate adhesive of the present invention can provide high adhesion and low swelling rate under low temperature pressing, and is electrochemically stable, thus solving the problems of low adhesion, high energy consumption, environmental unfriendliness and high price of current adhesives for lithium-ion battery separators. Detailed Implementation

[0041] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely 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 water-based polyacrylate adhesive is provided, the preparation method of which includes the following steps:

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

[0045] Bottom reaction solution and monomer solvent: Mix 90 parts of ethanol, 10 parts of deionized water and 4 parts of polyvinylpyrrolidone evenly and let them dissolve evenly. Take 40 parts of it as the bottom reaction solution and the other 64 parts as the solvent for shell polymerization monomer.

[0046] Core polymerization monomer and shell polymerization monomer solution: Mix 6 parts styrene, 0.8 parts butyl acrylate and 1 part diacrylate phthalate evenly to obtain the core polymerization monomer; then take 21 parts styrene, 11 parts butyl acrylate, 1.5 parts isooctyl acrylate and 1.5 parts lauryl acrylate and add them to the monomer solvent to obtain the shell polymerization monomer solution.

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

[0048] (2) Add the bottom reaction liquid to the reactor, add all the core polymerization monomers at 200 rpm, heat to 77°C and add 0.25 parts of initiator. After reacting for 2 hours, add all the shell polymerization monomer solution and then add 0.55 parts of initiator. After reacting for 8 hours, cool down to 70°C, add 0.05 parts of sodium formaldehyde sulfoxylate and 0.05 parts of tert-butanol peroxide, then keep warm for 20 minutes and start to remove ethanol. After the removal is completed, add deionized water, filter and cool down to room temperature, add 0.01 parts of sodium hydroxide and 0.05 parts of polyurea anti-settling agent, stir evenly and then discharge.

[0049] Example 2

[0050] In this embodiment, a water-based polyacrylate adhesive is provided, the preparation method of which includes the following steps:

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

[0052] Bottom reaction solution and monomer solvent: Mix 80 parts of ethanol, 10 parts of deionized water and 3 parts of polyvinylpyrrolidone evenly and let them dissolve evenly. Take 40 parts of it as the bottom reaction solution and the other 53 parts as the solvent for shell polymerization monomer.

[0053] Core polymerization monomer and shell polymerization monomer solution: Mix 6 parts styrene, 0.8 parts butyl acrylate and 1 part diacrylate phthalate evenly to obtain the core polymerization monomer; then take 21 parts styrene and 11 parts butyl acrylate and add them to the monomer solvent to obtain the shell polymerization monomer solution.

[0054] Initiator: Prepare one 0.3 part and one 0.6 part azobisisobutyronitrile.

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

[0056] After mixing well, the mixture can be discharged.

[0057] Example 3

[0058] In this embodiment, a water-based polyacrylate adhesive is provided, the preparation method of which includes the following steps:

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

[0060] Bottom reaction solution and monomer solvent: Mix 70 parts of ethanol, 20 parts of deionized water and 2.5 parts of polyvinylpyrrolidone evenly and let them dissolve evenly. Take 46 parts of it as the bottom reaction solution and the other 46.5 parts as the solvent for shell polymerization monomer.

[0061] Bottom reaction solution and monomer solvent: Mix 6 parts styrene, 0.8 parts butyl acrylate and 1 part diacrylate phthalate evenly to obtain the core polymerization monomer; then take 22 parts styrene and 10 parts butyl acrylate and add them to the monomer solvent to obtain the shell polymerization monomer solution.

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

[0063] (2) Add the bottom reaction liquid to the reactor and rotate at 300 rpm. Add all the core polymerization monomers, heat to 70°C and add 0.3 parts of initiator. After reacting for 3 hours, add all the shell polymerization monomer solution and another 0.3 parts of initiator. After reacting for 7 hours, cool down to 70°C, add 0.05 parts of sodium formaldehyde sulfoxylate and 0.05 parts of tert-butanol peroxide, then keep warm for 20 minutes and start to remove ethanol. After the removal is completed, add deionized water, filter and cool down to room temperature. Add 0.5 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent, stir evenly and then discharge.

[0064] Example 4

[0065] In this embodiment, a water-based polyacrylate adhesive is provided, the preparation method of which includes the following steps:

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

[0067] Bottom reaction solution and monomer solvent: Mix 80 parts of ethanol, 20 parts of deionized water and 4 parts of polyvinylpyrrolidone evenly and let them dissolve evenly. Take 51 parts of it as the bottom reaction solution and the other 51 parts as the solvent for shell polymerization monomer.

[0068] Bottom reaction solution and monomer solvent: Mix 6 parts styrene, 0.8 parts butyl acrylate and 1.15 parts diacrylate phthalate evenly to obtain the core polymerization monomer; then take 16 parts styrene and 16 parts butyl acrylate and add them to the monomer solvent to obtain the shell polymerization monomer solution;

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

[0070] (2) Add the bottom reaction liquid to the reactor and rotate at 300 rpm. Add all the core polymerization monomers, heat to 70°C and add 0.3 parts of initiator. After reacting for 3 hours, add all the shell polymerization monomer solution and another 0.3 parts of initiator. After reacting for 7 hours, cool down to 70°C, add 0.05 parts of sodium formaldehyde sulfoxylate and 0.05 parts of tert-butanol peroxide, then keep warm for 20 minutes and start to remove ethanol. After the removal is completed, add deionized water, filter and cool down to room temperature. Add 0.5 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent, stir evenly and then discharge.

[0071] Example 5

[0072] In this embodiment, a water-based polyacrylate adhesive is provided, the preparation method of which includes the following steps:

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

[0074] Bottom reaction solution and monomer solvent: Mix 80 parts of ethanol, 20 parts of deionized water and 3 parts of polyvinylpyrrolidone evenly and let them dissolve evenly. Take 30 parts of it as the bottom reaction solution and the other 73 parts as the solvent for shell polymerization monomer.

[0075] Bottom reaction solution and monomer solvent: Mix 6 parts styrene, 0.8 parts butyl acrylate and 1.15 parts diacrylate phthalate evenly to obtain the core polymerization monomer; then take 15 parts styrene, 15 parts butyl acrylate, 1.5 parts isooctyl acrylate and 1.5 parts lauryl acrylate and add them to the monomer solvent to obtain the shell polymerization monomer solution.

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

[0077] (2) Add the bottom reaction solution to the reactor and rotate at 300 rpm. Add all the core polymerization monomers, heat to 72°C and add 0.3 parts of initiator ammonium persulfate. After reacting for 3 hours, add all the shell polymerization monomer solution and another 0.3 parts of initiator benzoyl peroxide. After reacting for 7 hours, cool to 70°C and add 0.05 parts of sodium formaldehyde sulfoxylate and 0.05 parts of tert-butanol peroxide. Then keep warm for 20 minutes and start to remove ethanol. After the removal is completed, add deionized water, filter and cool to room temperature. Add 0.5 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent, stir evenly and then discharge.

[0078] Example 6

[0079] In this embodiment, a water-based polyacrylate adhesive is provided, the preparation method of which includes the following steps:

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

[0081] Bottom reaction solution and monomer solvent: Mix 70 parts of ethanol, 10 parts of deionized water and 3 parts of polyvinylpyrrolidone evenly and let them dissolve evenly. Take 41 parts of it as the bottom reaction solution and the other 42 parts as the solvent for shell polymerization monomer.

[0082] Core polymerization monomer and shell polymerization monomer solution: Mix 5 parts styrene, 1 part butyl acrylate and 1 part diacrylate phthalate evenly to obtain the core polymerization monomer; then take 18 parts styrene and 14 parts butyl acrylate and add them to the monomer solvent to obtain the shell polymerization monomer solution.

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

[0084] (2) Add the bottom reaction solution to the reactor and rotate at 300 rpm. Add all the core polymerization monomers, heat to 74°C and add 0.3 parts of the initiator. After reacting for 2 hours, add all the shell polymerization monomer solution and another 0.3 parts of the initiator. After reacting for 8 hours, cool down to 70°C, add 0.05 parts of sodium formaldehyde sulfoxylate and 0.05 parts of tert-butanol peroxide, and then keep warm for 20 minutes. Start to remove ethanol by evaporation. After evaporation, add deionized water, filter, and cool down to room temperature. Add 0.005 parts of sodium hydroxide and 0.03 parts of polyurea anti-settling agent, stir evenly, and then discharge.

[0085] Example 7

[0086] In this embodiment, a water-based polyacrylate adhesive is provided, the preparation method of which includes the following steps:

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

[0088] Bottom reaction solution and monomer solvent: Mix 90 parts of ethanol, 20 parts of deionized water and 4 parts of polyvinylpyrrolidone evenly and let them dissolve evenly. Take 70 parts of it as the bottom reaction solution and the other 44 parts as the solvent for shell polymerization monomer.

[0089] Core polymerization monomer and shell polymerization monomer solution: Mix 6 parts styrene, 2 parts butyl acrylate and 1 part diacrylate phthalate evenly to obtain the core polymerization monomer; then take 18 parts styrene and 14 parts butyl acrylate and add them to the monomer solvent to obtain the shell polymerization monomer solution.

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

[0091] (2) Add the bottom reaction solution to the reactor and rotate at 400 rpm. Add all the core polymerization monomers, heat to 75°C and add 0.3 parts of the initiator. After reacting for 3 hours, add all the shell polymerization monomer solution and another 0.3 parts of the initiator. After reacting for 8 hours, cool down to 70°C, add 0.05 parts of sodium formaldehyde sulfoxylate and 0.05 parts of tert-butanol peroxide, and then keep warm for 20 minutes. Start to remove ethanol by evaporation. After evaporation, add deionized water, filter, and cool down to room temperature. Add 0.005 parts of sodium hydroxide and 0.04 parts of polyurea anti-settling agent, stir evenly, and then discharge.

[0092] Example 8

[0093] In this embodiment, a water-based polyacrylate adhesive is provided, the preparation method of which includes the following steps:

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

[0095] Bottom reaction solution and monomer solvent: Mix 70 parts of ethanol, 10 parts of deionized water and 2.5 parts of polyvinylpyrrolidone evenly and let them dissolve evenly. Take 32 parts of it as the bottom reaction solution and the other 50.5 parts as the solvent for shell polymerization monomer.

[0096] Core polymerization monomer and shell polymerization monomer solution: Mix 7 parts styrene, 0.8 parts butyl acrylate and 1 part diacrylate phthalate evenly to obtain the core polymerization monomer; then take 18 parts styrene, 14 parts butyl acrylate, 0.75 parts isooctyl acrylate and 0.75 parts lauryl acrylate and add them to the monomer solvent to obtain the shell polymerization monomer solution.

[0097] Initiator: Prepare one 0.3 part azobisisobutyronitrile and one 0.4 part azobisisobutyronitrile.

[0098] (2) Add the bottom reaction liquid to the reactor and rotate at 200 rpm. Add all the core polymerization monomers, heat to 73°C and add 0.3 parts of initiator. After reacting for 2 hours, add all the shell polymerization monomer solution and another 0.4 parts of initiator. After reacting for 8 hours, cool down to 70°C, add 0.05 parts of sodium formaldehyde sulfoxylate and 0.05 parts of tert-butanol peroxide, then keep warm for 20 minutes and start to remove ethanol. After the removal is completed, add deionized water, filter and cool down to room temperature. Add 0.005 parts of sodium hydroxide and 0.05 parts of polyurea anti-settling agent, stir evenly and then discharge.

[0099] Comparative Example 1

[0100] The polyacrylate water-based 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 each component in the nuclear polymerization monomer are 6 parts styrene, 3 parts butyl acrylate, and 2 parts diacrylate phthalate. All other aspects are the same as in Example 1.

[0103] Comparative Example 3

[0104] The difference from Example 1 is that the amount of each component in the shell polymer monomer is: 18 parts styrene, 1 part butyl acrylate, 1 part isooctyl acrylate, 1 part 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 each component in the monomer of the core polymer are: 6 parts styrene, 0.6 parts butyl acrylate, and 3.7 parts diacrylate phthalate; the rest are the same as in Example 1.

[0107] Comparative Example 5

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

[0109] The aqueous polyacrylate binder used in the examples and comparative examples, as well as the use of PVDF and PMMA as binders, were applied to lithium-ion battery separators. The aqueous polyacrylate binder was applied to a polyethylene separator, dried in an oven at 55°C, and then the coated surface was bonded to the positive electrode sheet and pressed under the following conditions: 35°C, 3 MPa, and 10 s. After completion, its performance was tested. The positive electrode sheet mentioned in this step was purchased from Guangdong Zhuguang New Energy Co., Ltd.

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

[0111] (2) Swelling rate: After the wet film is baked into a dry film in an oven at 65℃, it is taken out and its mass is tested. Then it is placed in a glass bottle containing electrolyte. The glass bottle is placed in an oven at 65℃ for 3 days and then taken out and its film weight is tested. The increase in mass of the dry film divided by the mass of the dry film itself is its 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 this invention illustrates the polyacrylate water-based adhesive, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials in the product, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A water-based polyacrylate adhesive, characterized in that, The aqueous polyacrylate binder is a core-shell polymer obtained by polymerizing monomers. The polymer monomers of the core polymer of the core-shell polymer include, by weight, the following monomers: 70-90% hard monomers, 5-28% soft monomers, and 10-18% functional monomers; the polymer monomers of the shell polymer of the core-shell polymer include, by weight, the following monomers: 35-85% hard monomers, 30-50% soft monomers, and 0-5% functional monomers. The hard monomer in the core polymerization monomer is selected from one or a combination of at least two of methyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, acrylonitrile or styrene. The soft monomer in the core polymerization monomer is selected from one or a combination of at least two of the following: ethyl acrylate, n-butyl acrylate, n-octyl acrylate, isooctyl acrylate, tetrahydrofurfuryl acrylate, lauryl acrylate, or lauryl methacrylate. The functional monomer in the nuclear polymerization monomer is selected from one or a combination of at least two of acrylic acid, methacrylic acid, dipropyl phthalate, itaconic acid, diacetone acrylamide, or ethyl acetoacetate of methacrylic acid. The hard monomer in the shell polymer monomer is selected from styrene; The soft monomer in the shell polymer monomer is selected from n-butyl acrylate and / or lauryl acrylate; The functional monomer in the shell polymer monomer is selected from isooctyl acrylate; The aqueous polyacrylate binder is prepared by dispersion polymerization; the particle size of the prepared aqueous polyacrylate binder is greater than 1 μm. The polyacrylate aqueous adhesive is prepared according to the following preparation method, which includes the following steps: (1) Prepare the bottom reaction solution and the shell polymerization monomer solution; (2) Add the nucleopolymer monomer and initiator to the reaction solution at the bottom of the reactor, and react; (3) Add shell polymer monomer solution and initiator to the reaction solution obtained in step (2) and react to obtain the polyacrylate water-based binder.

2. The method for preparing the aqueous polyacrylate adhesive according to claim 1, characterized in that, The preparation method includes the following steps: (1) Prepare the bottom reaction solution and the shell polymerization monomer solution; (2) Add the nucleopolymer monomer and initiator to the reaction solution at the bottom of the reactor, and react; (3) Add shell polymer monomer solution and initiator to the reaction solution obtained in step (2) and react to obtain the polyacrylate water-based binder.

3. The preparation method according to claim 2, characterized in that, The reaction solution at the bottom of the reactor in step (1) is prepared from organic solvent, dispersant and deionized water.

4. The preparation method according to claim 3, characterized in that, The organic solvent is selected from one or a combination of at least two of the following: ethanol, ethyl acetate, methanol, isopropanol, cyclohexane, cyclohexanone, toluenecyclohexanone, pentane, hexane, and acetone.

5. The preparation method according to claim 3, characterized in that, The dispersant is selected from one or more combinations of polyvinylpyrrolidone, polyethylene glycol 200 or 400.

6. The preparation method according to claim 3, characterized in that, The reaction solution at the bottom of the reactor in step (1) comprises the following components by weight percentage: 50-95% organic solvent, 1-5% dispersant and 5-45% deionized water.

7. The preparation method according to claim 2, characterized in that, The shell polymer monomer solution in step (1) is a solution obtained by adding shell polymer monomer to part of the bottom reaction liquid in the reactor, and the concentration of shell polymer monomer in the shell polymer monomer solution is 20-70%.

8. The preparation method according to claim 2, characterized in that, The weight ratio of the bottom reaction liquid to the core polymerization monomer in step (2) is 1.5-7:

1.

9. The preparation method according to claim 2, characterized in that, The amount of initiator used in step (2) is 1%-5% of the total mass of the nuclear polymerization monomers.

10. The preparation method according to claim 2, characterized in that, Before adding the nuclear polymerization monomer in step (2), the reaction solution at the bottom of the reactor should be heated to 50-90℃.

11. The preparation method according to claim 2, characterized in that, The reaction temperature in step (2) is 60-90℃ and the reaction time is 2-4h.

12. The preparation method according to claim 2, characterized in that, The weight ratio of the shell polymer monomer solution in step (3) to the reaction solution obtained in step (2) is 1-4:

1.

13. The preparation method according to claim 2, characterized in that, The amount of initiator used in step (3) is 1%-5% of the weight of the shell polymer monomer solution.

14. The preparation method according to claim 2, characterized in that, The concentration of the shell polymer monomer solution in step (3) is 30%-60%.

15. The preparation method according to claim 2, characterized in that, The reaction temperature in step (3) is 70-80℃ and the reaction time is 8-12h.

16. The preparation method according to claim 2, characterized in that, The preparation method further includes cooling to 55-70°C after the reaction in step (3), 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-settling agent and stirring evenly before discharging.

17. The preparation method according to claim 16, characterized in that, The residual monomer eliminator is sodium formaldehyde sulfoxylate and / or tert-butanol peroxide.

18. The preparation method according to claim 16, characterized in that, pH is adjusted using one or a combination of at least two of ammonia, sodium hydroxide, lithium hydroxide, potassium hydroxide, or sodium bicarbonate.

19. The preparation method according to claim 16, characterized in that, The anti-settling agent is selected from any one or a combination of at least two of the following: fatty alcohol polyoxyethylene modified silicone, polyacrylate modified polyurea, hydroxymethyl cellulose ether, sodium hydroxymethyl cellulose, or hydroxyethyl cellulose ether.

20. A lithium-ion battery separator, characterized in that, The lithium-ion battery separator includes the polyacrylate aqueous binder as described in claim 1.

21. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium-ion battery separator as described in claim 20.