Polyacrylic acid or polyacrylate water-based binder, and preparation method therefor and use thereof

Abstract

Provided in the present invention are a polyacrylic acid or polyacrylate water-based binder, and a preparation method therefor and the use thereof. The polyacrylic acid or polyacrylate water-based binder is a polymer obtained by polymerizing polymeric monomers, the polymeric monomers comprising a hard monomer, a soft monomer and a functional monomer. The polyacrylic acid or polyacrylate water-based binder provided by the present invention has relatively high binding power and relatively good flexibility and electrochemical stability, and has good application prospects in the field of negative electrode sheets of lithium-ion batteries.

Description

A polyacrylic acid or polyacrylate aqueous binder and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 30, 2023, with application number 202311106539.0 and application name “A polyacrylic acid or polyacrylate aqueous binder, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the technical field of water-based adhesives, and in particular relates to a flexible, low-swelling polyacrylic acid or polyacrylate water-based adhesive, and a preparation method and application thereof. Background Art

[0003] Lithium-ion batteries, as secondary batteries, are widely used in various fields due to their advantages, including high energy conversion rate, high energy density, high charge and discharge rate, no memory effect, and environmental friendliness. Polymer binders, with their excellent bonding properties, can bind various particles together and tightly bond them to the current collector, making them an indispensable component of lithium-ion batteries. In addition to high adhesion, high-performance binders also require the following properties: good flexibility, electrolyte resistance, compactness, chemical and electrochemical stability, low cost, and environmental friendliness.

[0004] Currently, the binders used in lithium-ion batteries fall into three main categories: polyvinylidene fluoride (PVDF), styrene-butadiene rubber latex, carboxymethyl cellulose (SBR / CMC), and polyacrylic acid (PAA). PVDF offers advantages such as excellent adhesion to aluminum foil and strong electrochemical corrosion resistance, but poor adhesion to copper foil. PVDF also has a high molecular weight and lacks hydrophilic groups, making it commonly dispersed and dissolved in N-methylpyrrolidone (NMP). However, NMP solvent is sensitive to moisture, toxic, and its volatilization can pollute the environment. SBR / CMC binders have poor processing performance and demanding conditions, significantly affected by factors such as stirring, pH, and electrode material ratio. Both PVDF and SBR / CMC are relatively expensive. PAA binders, with their strong adhesion, excellent stability, low price, and environmental friendliness, are currently a hot topic in negative electrode binder research. Conventional PAA binders, however, become hard and brittle after drying, making them unsuitable for the flexibility required of negative electrode sheets.

[0005] Therefore, in this field, the PAA binder needs to be modified to simultaneously meet the requirements of adhesion, swelling rate, flexibility and electrochemical performance.

[0006] Summary of the Invention

[0007] In response to the shortcomings of the prior art, the present invention aims to provide a polyacrylic acid or polyacrylate aqueous binder, a preparation method, and applications thereof, and in particular, to provide a flexible, low-swelling polyacrylic acid or polyacrylate aqueous binder, a preparation method, and applications thereof. The polyacrylic acid or polyacrylate aqueous binder of the present invention has high bonding strength, good flexibility, and electrochemical stability, and has promising application prospects in lithium-ion battery negative electrode plates.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In one aspect, the present invention provides a polyacrylic acid or polyacrylate aqueous binder, wherein the polyacrylic acid or polyacrylate aqueous binder is a polymer obtained by polymerizing monomers, wherein the polymerized monomers include hard monomers, soft monomers, and functional monomers;

[0010] The hard monomer is selected from one or a combination of at least two of methyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate or styrene;

[0011] 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, lauric acrylate, lauryl methacrylate, isodecyl acrylate or ethoxyethoxyethoxy acrylate;

[0012] The functional monomer is selected from one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, diacetone acrylamide, ethyl acetoacetate methacrylate, divinylbenzene, aziridine, ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate or a silane coupling agent.

[0013] In the present invention, the hard monomers provide hardness to the binder, the soft monomers provide flexibility and promote film formation, and the functional monomers introduce functional groups or crosslinking points into the binder to improve adhesion. The combination of these hard, soft, and functional monomers results in a polyacrylic acid or polyacrylate water-based binder with high adhesion, good flexibility, and electrochemical stability.

[0014] Preferably, the amount of the hard monomer in the polymerizable monomer is 30 to 70 parts by weight (for example, 30 parts by weight, 35 parts by weight, 38 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 60 parts by weight or 70 parts by weight), the amount of the soft monomer is 30 to 70 parts by weight (for example, 30 parts by weight, 35 parts by weight, 38 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 60 parts by weight or 70 parts by weight), and the amount of the functional monomer is 0.5 to 15 parts by weight (for example, 0.5 parts by weight, 1 part by weight, 3 parts by weight, 5 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight or 15 parts by weight).

[0015] In the present invention, by selecting the amounts of the hard monomer, soft monomer, and functional monomer used in the polymerization, the resulting polyacrylic acid or polyacrylate water-based adhesive can be made to have good flexibility and high adhesion. In the present invention, if the amount of hard monomer used is too high, the adhesive film after solvent evaporation will be relatively hard, resulting in poor flexibility and loss of adhesion. If the amount of hard monomer used is too low, the adhesive film obtained after solvent evaporation will be relatively soft, with poor cohesion and reduced tear resistance, and easily broken by external forces.

[0016] In the present invention, if the amount of the functional monomer is too much, the pre-emulsion is easily demulsified and the preparation process performance is poor. If the amount of the functional monomer is too little, the overall bonding performance is reduced and the swelling is high.

[0017] The polyacrylic acid or polyacrylate aqueous binder of the present invention is obtained through emulsion polymerization.

[0018] On the other hand, the present invention provides a method for preparing the polyacrylic acid or polyacrylate aqueous binder as described above, the preparation method comprising the following steps:

[0019] (1) preparing pre-emulsion, seed emulsion, bottom reaction liquid and initiator solution;

[0020] (2) adding seed emulsion to the reaction liquid at the bottom of the kettle, heating, adding part of the initiator solution, and reacting;

[0021] (3) adding the pre-emulsion and the remaining initiator solution to the reaction solution obtained in step (2), reacting to obtain the polyacrylic acid or polyacrylate aqueous binder.

[0022] Preferably, the pre-emulsion is prepared from hard monomers, soft monomers, functional monomers, emulsifiers and deionized water.

[0023] Preferably, the pre-emulsion comprises 30 to 70 parts by weight of a hard monomer, 30 to 70 parts by weight of a soft monomer, and 0.5 to 15 parts by weight of a functional monomer.

[0024] Preferably, the total weight percentage of the hard monomer, soft monomer and functional monomer in the pre-emulsion is 30-500% of deionized water, for example 30%, 60%, 100%, 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500%.

[0025] Preferably, the amount of emulsifier in the pre-emulsion is 0.25-5% of the total weight of the hard monomer, soft monomer and functional monomer, such as 0.25%, 0.3%, 0.5%, 1%, 2%, 3%, 4% or 5%.

[0026] Preferably, the seed emulsion is a portion of the pre-emulsion taken out from the pre-emulsion.

[0027] Preferably, the bottom reaction liquid is prepared from an emulsifier, deionized water and a buffer.

[0028] Preferably, the reaction liquid at the bottom of the kettle includes the following components in parts by weight: 0.1-5 parts (for example, 0.1 parts, 0.5 parts, 1 parts, 2 parts, 3 parts, 4 parts or 5 parts) of emulsifier, 66-900 parts (for example, 66 parts, 80 parts, 100 parts, 200 parts, 300 parts, 500 parts, 800 parts or 900 parts) of deionized water, and 0.25-1 part (for example, 0.25 parts, 0.5 parts, 0.8 parts or 1 parts) of buffer.

[0029] Preferably, the emulsifiers in the pre-emulsion and the bottom reaction liquid are independently selected from one or a combination of at least two of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene octylphenol ether-10, sodium allyl hydroxypropyl sulfonate, allyloxy fatty alcohol oxyethylene ether ammonium sulfate, disodium succinate nonylphenol polyoxyethylene ether monoester sulfonate, lauryl alcohol ethoxylate, isomeric tridecyl alcohol ethoxylate or fatty acid methyl ester ethoxylate.

[0030] Preferably, the buffer is one or a combination of at least two of sodium bicarbonate, ammonia water, ammonium bicarbonate or sodium hydroxide.

[0031] Preferably, the initiator solution comprises an initiator and deionized water.

[0032] Preferably, the amount of deionized water in the initiator solution is 1 to 20 parts relative to 1 part by weight of the initiator, for example, 1 part, 3 parts, 5 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts or 20 parts.

[0033] Preferably, the initiator is selected from inorganic peroxide initiators.

[0034] Preferably, the initiator is selected from any one of potassium persulfate, ammonium persulfate or sodium persulfate, or a combination of at least two thereof.

[0035] Preferably, the amount of the initiator in the initiator solution is 0.2-0.6% of the total weight percentage of the hard monomer, the soft monomer and the functional monomer, such as 0.2%, 0.3%, 0.4%, 0.5% or 0.6%.

[0036] Preferably, the reaction in step (2) and step (3) is carried out under stirring, and the stirring speed is 100-500r / min (for example, 100r / min, 150r / min, 200r / min, 250r / min, 300r / min, 350r / min, 400r / min, 450r / min, 500r / min).

[0037] Preferably, the bottom reaction liquid is added to a reactor at 40-80°C (e.g., 40°C, 45°C, 48°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C) before the seed emulsion in step (2).

[0038] Preferably, the heating in step (2) is to 75-85°C, such as 75°C, 78°C, 80°C, 83°C or 85°C.

[0039] Preferably, the mass of the reaction liquid at the bottom of the kettle in step (2) is 12-40 times that of the seed emulsion, for example, 12 times, 15 times, 20 times, 25 times, 30 times, 35 times or 40 times.

[0040] Preferably, the portion of the initiator solution in step (2) is 5-45% of the total weight of the initiator solution, for example 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%.

[0041] Preferably, the reaction time of step (2) is 10-60 min, for example, 10 min, 13 min, 15 min, 18 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0042] Preferably, the weight ratio of the pre-emulsion in step (3) to the bottom reaction liquid in step (2) is 0.15-2.12:1, for example, 0.15:1, 0.3:1, 0.5:1, 1:1, 1.3:1, 1.5:1, 1.8:1, 2:1 or 2.12:1, etc.

[0043] Preferably, the reaction temperature in step (3) is 80-90°C, such as 80°C, 83°C, 85°C, 88°C or 90°C.

[0044] Preferably, the reaction time of step (3) is 0.5-2.5 h, for example, 0.5 h, 0.8 h, 1 h, 1.5 h, 1.8 h, 2 h or 2.5 h.

[0045] Preferably, the preparation method further comprises cooling the temperature 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 scavenger, then cooling the temperature to below 50°C (e.g., 50°C, 45°C, 40°C, 35°C, 30°C, 25°C, 20°C or 10°C, etc.), adjusting the pH to 7-8 (e.g., 7, 7.3, 7.5, 7.8 or 8), and filtering the material.

[0046] Preferably, the residual monomer eliminator is bleaching powder and tert-butyl peroxide.

[0047] Preferably, the pH is adjusted using one or a combination of at least two of ammonia water, sodium hydroxide, lithium hydroxide, potassium hydroxide or sodium bicarbonate.

[0048] Preferably, the solid content of the acrylic water-based adhesive is 10-60%, for example, 10%, 15%, 20%, 25%, 30%, 40%, 50% or 60%.

[0049] In the present invention, by designing the mass ratio of soft and hard components and functional monomer types in the pre-emulsion, a flexible and low-swelling polyacrylic acid or polyacrylate aqueous binder is obtained. By introducing carboxylic acid, carboxylate, and ester groups into the binder, the prepared polyacrylic acid or polyacrylate aqueous binder has good flexibility, electrochemical stability, and good bonding strength, and has good application prospects in lithium-ion battery negative electrode plates.

[0050] On the other hand, the present invention provides a negative electrode plate for a lithium ion battery, wherein the negative electrode plate for the lithium ion battery comprises the polyacrylic acid or polyacrylate aqueous binder as described above.

[0051] In another aspect, the present invention provides a lithium-ion battery, comprising the lithium-ion battery negative electrode sheet as described above.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The polyacrylic acid or polyacrylate aqueous binder of the present invention has the characteristics of good flexibility, low swelling, strong bonding force and good electrochemical stability, and solves the problems of low adhesion, environmental pollution and high price of the current binders used for lithium ion battery negative electrodes. DETAILED DESCRIPTION

[0054] 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.

[0055] Example 1

[0056] In this embodiment, a polyacrylic acid or polyacrylate aqueous binder and a preparation method thereof are provided, wherein the preparation method comprises the following steps:

[0057] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0058] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then add 43.75 parts of methyl methacrylate, 37 parts of n-butyl acrylate, 9.25 parts of isooctyl acrylate, 2 parts of acrylonitrile, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0059] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0060] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0061] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.93 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a flexible low-swelling polyacrylic acid or polyacrylate water-based binder.

[0062] Example 2

[0063] In this embodiment, a polyacrylic acid or polyacrylate aqueous binder and a preparation method thereof are provided, wherein the preparation method comprises the following steps:

[0064] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0065] Pre-emulsion: Dissolve 1.06 parts of disodium nonylphenol polyoxyethylene ether sulfonate monohydrate and 0.54 parts of isotridecyl alcohol ethoxylate in 40 parts of deionized water. Then, add 42.25 parts of methyl methacrylate, 37 parts of butyl acrylate, 9.25 parts of isooctyl acrylate, 0.5 parts of acrylamide, 8 parts of acrylic acid, and 3 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0066] A bottom reaction solution was prepared by dissolving 0.27 parts of disodium nonylphenol polyoxyethylene ether sulfonate monosodium succinate and 0.13 parts of isomeric tridecyl alcohol ethoxylate in 70 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0067] Initiator solution: Add 0.6 parts of sodium persulfate to 8 parts of deionized water to obtain an initiator aqueous solution.

[0068] (2) Add the reaction liquid at the bottom of the kettle to a reactor at 50°C at a speed of 120 rpm. Take out 8.23 ​​parts of seed emulsion from the pre-emulsion and add it to the reactor. Heat it to 80°C, add 0.6 parts of initiator solution, react for 30 minutes, and then drop the remaining pre-emulsion and initiator solution at the same time. After the addition is complete, keep it at 87°C for 1 hour. After the end of the heat preservation, cool it to 65°C, add 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide, then cool it to below 50°C, adjust the pH to 7.45 with 1.5 parts of sodium hydroxide, and filter the material to obtain a flexible low-swelling polyacrylic acid or polyacrylate water-based binder.

[0069] Example 3

[0070] In this embodiment, a polyacrylic acid or polyacrylate aqueous binder and a preparation method thereof are provided, wherein the preparation method comprises the following steps:

[0071] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0072] Pre-emulsion: Dissolve 1.06 parts of allyloxy fatty alcohol oxyethylene ether ammonium sulfate and 0.54 parts of fatty acid methyl ester ethoxylate in 40 parts of deionized water, then add 35 parts of isopropyl methacrylate, 51.25 parts of isooctyl acrylate, 0.5 parts of methacrylamide, 6 parts of methacrylic acid, 4 parts of hydroxyethyl methacrylate, and 3.25 parts of N-hydroxymethyl acrylamide in this order for emulsification;

[0073] A bottom reaction solution was prepared by dissolving 0.27 parts of allyloxy fatty alcohol oxyethylene ether ammonium sulfate and 0.13 parts of fatty acid methyl ester ethoxylate in 80 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0074] Initiator solution: Add 0.6 parts of potassium persulfate to 10 parts of deionized water to obtain an initiator aqueous solution.

[0075] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 60°C at a rotation speed of 120 rpm. 8.26 parts of seed emulsion were taken out from the pre-emulsion and added to the reactor. The temperature was raised to 82°C, 0.6 parts of initiator solution were added, and the reaction was continued for 45 minutes. The remaining pre-emulsion and initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.45 using 1.5 parts of lithium hydroxide. The material was filtered to obtain the flexible low-swelling polyacrylic acid or polyacrylate aqueous binder.

[0076] Example 4

[0077] In this embodiment, a polyacrylic acid or polyacrylate aqueous binder and a preparation method thereof are provided, wherein the preparation method comprises the following steps:

[0078] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0079] Pre-emulsion: Dissolve 1.06 parts of lauryl ethoxylate and 0.54 parts of sodium dodecylbenzenesulfonate in 40 parts of deionized water, then add 35 parts of isobornyl acrylate, 35 parts of isooctyl acrylate,

[0080] 16.25 parts of lauryl acrylate, 0.5 parts of methacrylamide, 6 parts of methacrylic acid, 4 parts of hydroxyethyl methacrylate, and 3.25 parts of diacetone acrylamide were emulsified;

[0081] A bottom reaction solution was prepared by dissolving 0.27 parts of lauryl alcohol ethoxylate and 0.13 parts of sodium dodecylbenzenesulfonate in 80 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0082] Initiator solution: Add 0.6 parts of potassium persulfate to 10 parts of deionized water to obtain an initiator aqueous solution.

[0083] (3) The reaction liquid at the bottom of the kettle was added to a reactor at 70°C at a speed of 120 rpm. 8.26 parts of seed emulsion were taken out from the pre-emulsion and added to the reactor. The temperature was raised to 82°C. 0.6 parts of initiator solution were added. After the reaction for 30 minutes, the remaining pre-emulsion and initiator solution were added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added. The temperature was then lowered to below 50°C. The pH was adjusted to 7.45 with 1.5 parts of sodium bicarbonate. The material was filtered to obtain a flexible low-swelling polyacrylic acid or polyacrylate water-based binder.

[0084] Example 5

[0085] In this embodiment, a polyacrylic acid or polyacrylate aqueous binder and a preparation method thereof are provided, wherein the preparation method comprises the following steps:

[0086] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0087] Pre-emulsion: Dissolve 1.06 parts of lauryl alcohol ethoxylate and 0.54 parts of sodium dodecylbenzenesulfonate in 40 parts of deionized water, then add 32 parts of isobornyl methacrylate, 20 parts of isooctyl acrylate, 15 parts of butyl acrylate, 13.75 parts of lauryl acrylate, 5 parts of isodecyl acrylate, 1 part of acrylamide, 6 parts of methacrylic acid, 4 parts of hydroxyethyl methacrylate, and 3.25 parts of diacetone acrylamide in this order for emulsification;

[0088] A bottom reaction solution was prepared by dissolving 0.27 parts of lauryl alcohol ethoxylate and 0.13 parts of sodium dodecylbenzenesulfonate in 70 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0089] Initiator solution: Add 0.6 parts of potassium persulfate to 10 parts of deionized water to obtain an initiator aqueous solution.

[0090] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 60°C at a speed of 120 rpm. 8.26 parts of seed emulsion were taken out from the pre-emulsion and added to the reactor. The temperature was raised to 78°C, 0.6 parts of initiator solution were added, and the reaction was continued for 30 minutes. The remaining pre-emulsion and initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 60°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.45 with 1.5 parts of sodium hydroxide, and the material was filtered to obtain a flexible low-swelling polyacrylic acid or polyacrylate water-based binder.

[0091] Example 6

[0092] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0093] Pre-emulsion: Dissolve 1.06 parts of disodium nonylphenol polyoxyethylene ether succinate sulfonate and 0.54 parts of sodium dodecylbenzenesulfonate in 40 parts of deionized water, then add 12 parts of vinyl acetate, 20 parts of styrene, 20 parts of isooctyl acrylate, 15 parts of butyl acrylate, 13.75 parts of lauryl acrylate, 5 parts of versatate, 1 part of acrylamide, 6 parts of methacrylic acid, 4 parts of hydroxyethyl methacrylate, and 3.25 parts of diacetone acrylamide in this order for emulsification;

[0094] A bottom reaction solution was prepared by dissolving 0.27 parts of disodium nonylphenol polyoxyethylene ether succinate sulfonate and 0.13 parts of sodium dodecylbenzenesulfonate in 70 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0095] Initiator solution: Add 0.6 parts of potassium persulfate to 10 parts of deionized water to obtain an initiator aqueous solution.

[0096] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 60°C at a speed of 120 rpm. 8.26 parts of seed emulsion were taken out from the pre-emulsion and added to the reactor. The temperature was raised to 78°C, 0.6 parts of initiator solution were added, and the reaction was continued for 30 minutes. The remaining pre-emulsion and initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 60°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.20 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a flexible low-swelling polyacrylic acid or polyacrylate water-based binder.

[0097] Comparative Example 1

[0098] In this comparative example, unlike Example 1, no hard monomer is included in this comparative example.

[0099] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0100] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then add 43.75 parts of lauryl acrylate, 37 parts of n-butyl acrylate, 9.25 parts of isooctyl acrylate, 2 parts of acrylonitrile, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0101] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0102] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0103] (2) Add the reaction liquid at the bottom of the kettle to a reactor at 40°C at a speed of 120 rpm. Take out 7 parts of the pre-emulsion as the seed emulsion and add it to the reactor. Heat it to 75°C, add 0.6 parts of the initiator solution, react for 15 minutes, and then drop the remaining pre-emulsion and initiator solution simultaneously. After the addition is complete, keep it at 87°C for 1 hour. After the end of the heat preservation, cool it to 65°C, add 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide, then cool it to below 50°C, adjust the pH to 7.23 with 1.5 parts of 25% aqueous ammonia, and filter the material to obtain a polyacrylic acid or polyacrylate water-based binder.

[0104] Comparative Example 2

[0105] In this comparative example, unlike Example 1, no soft monomer is included in this comparative example.

[0106] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0107] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then, add 43.75 parts of methyl methacrylate, 37 parts of styrene, 9.25 parts of isobornyl methacrylate, 2 parts of versatate, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0108] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0109] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0110] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.07 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a polyacrylic acid or polyacrylate water-based binder.

[0111] Comparative Example 3

[0112] In this comparative example, unlike Example 1, no functional monomer is included in this comparative example.

[0113] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0114] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water, then add 43.75 parts of methyl methacrylate, 37 parts of n-butyl acrylate, 9.75 parts of isooctyl acrylate, 2 parts of acrylonitrile, 3 parts of lauryl acrylate, and 3.5 parts of lauryl methacrylate in this order until emulsified uniformly;

[0115] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0116] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0117] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.22 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a polyacrylic acid or polyacrylate water-based binder.

[0118] Comparative Example 4

[0119] In this comparative example, the difference from Example 1 is that the amount of hard monomer used in this comparative example is lower, namely 15 parts by weight.

[0120] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0121] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then add 13 parts of methyl methacrylate, 37 parts of n-butyl acrylate, 41 parts of isooctyl acrylate, 2 parts of acrylonitrile, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0122] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0123] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0124] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a rotation speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor, the temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.38 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a polyacrylic acid or polyacrylate water-based binder.

[0125] Comparative Example 5

[0126] In this comparative example, the difference from Example 1 is that the amount of hard monomer used in this comparative example is higher, 80 parts by weight.

[0127] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0128] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then add 78 parts of methyl methacrylate, 3.75 parts of n-butyl acrylate, 9.25 parts of isooctyl acrylate, 2 parts of acrylonitrile, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0129] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0130] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0131] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a rotation speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor, the temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.10 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a polyacrylic acid or polyacrylate water-based binder.

[0132] Comparative Example 6

[0133] In this comparative example, the difference from Example 1 is that the functional dosage in this comparative example is smaller, namely 0.1 parts by weight.

[0134] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0135] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water, then add 43.75 parts of methyl methacrylate, 37 parts of n-butyl acrylate, 17.15 parts of isooctyl acrylate, 2 parts of acrylonitrile, and 0.1 part of acrylic acid in this order until emulsified uniformly;

[0136] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0137] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0138] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.93 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a flexible low-swelling polyacrylic acid or polyacrylate water-based binder.

[0139] The adhesives obtained in the examples and comparative examples were subjected to performance tests, and the test methods were as follows:

[0140] (1) Take graphite slurry without adding adhesive, then add adhesive in an amount of 2% of the solid component of the graphite slurry to the solid component of the adhesive, stir evenly, and obtain a mixed slurry. Take 30g of the mixed slurry, apply it evenly on the copper foil with a coater, bake it at 65℃ for 200s, and obtain a pole piece with a thickness of 85μm. Cut the pole piece into 30mm wide strips, stick the strips to the plywood with 3M tape, use a 2kg standard rolling wheel to roll the strips back and forth 3 times to compact them, and then stretch the strips at a stretching speed of 50mm / min to obtain the peel strength;

[0141] (2) After the adhesive solution is dried at 65°C to form a film, 1.5 g of the film sample is cut and immersed in an electrolyte at 65°C for 3 days. The film sample is weighed and the swelling ratio is calculated: swelling ratio = (weight after swelling - weight before swelling) / weight before swelling × 100%;

[0142] (3) The dried film is bent on a mandrel with a diameter of 1-20 mm. The smallest mandrel diameter that does not damage the film after bending is used as the index. The mandrel diameters are 1, 2, 5, 10, 15, and 20 mm. The smaller the bending diameter, the greater the elongation of the outer surface of the film. Therefore, the flexibility is best when the diameter is 1 mm, and the worst when it is 20 mm.

[0143] The test results are shown in Table 1.

[0144] Table 1

[0145] As can be seen from the data in Table 1, by designing the mass ratio of soft and hard components and functional monomer types, better bonding and more stable bonding can be achieved. The peel strength can reach 15-20.07N / m, the swelling rate is below 36.6%, and a 1mm shaft can be bent without breaking, showing good flexibility.

[0146] The applicant declares that while the above-described embodiments illustrate the polyacrylic acid or polyacrylate water-based adhesive, its preparation method, and its application, the present invention is not limited to these embodiments, nor does it necessarily rely on these embodiments for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for raw materials in the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A polyacrylic acid or polyacrylate aqueous binder, characterized in that: The polyacrylic acid or polyacrylate aqueous binder is a polymer obtained by polymerizing a polymerized monomer, wherein the polymerized monomer includes a hard monomer, a soft monomer and a functional monomer; The hard monomer is selected from one or a combination of at least two of methyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate or 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, lauric acrylate, lauryl methacrylate, isodecyl acrylate or ethoxyethoxyethoxy acrylate; The functional monomer is selected from one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, diacetone acrylamide, ethyl acetoacetate methacrylate, divinylbenzene, aziridine, ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate or a silane coupling agent.

2. The polyacrylic acid or polyacrylate aqueous binder according to claim 1, characterized in that: The amount of the hard monomer in the polymerizable monomer is 30 to 70 parts by weight, the amount of the soft monomer is 30 to 70 parts by weight, and the amount of the functional monomer is 0.5 to 15 parts by weight.

3. The method for preparing the polyacrylic acid or polyacrylate aqueous binder according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) preparing a pre-emulsion, a seed emulsion, a kettle bottom reaction liquid and an initiator solution; (2) adding seed emulsion to the reaction liquid at the bottom of the kettle, raising the temperature, adding part of the initiator solution, and reacting; (3) adding the pre-emulsion and the remaining initiator solution to the reaction solution obtained in step (2) to react, The polyacrylic acid or polyacrylate aqueous binder is obtained.

4. The preparation method according to claim 3, characterized in that: The pre-emulsion is prepared from hard monomers, soft monomers, functional monomers, emulsifiers and deionized water; Preferably, the pre-emulsion includes 30 to 70 parts by weight of hard monomer, 30 to 70 parts by weight of soft monomer and 0.5 to 15 parts by weight of functional monomer; Preferably, the total weight percentage of the hard monomer, soft monomer and functional monomer in the pre-emulsion is 30-500% of deionized water; Preferably, the amount of the emulsifier in the pre-emulsion is 0.25-5% of the total weight of the hard monomer, the soft monomer and the functional monomer.

5. The preparation method according to claim 3 or 4, characterized in that: The seed emulsion is a portion of the pre-emulsion taken out from the pre-emulsion; Preferably, the reaction liquid at the bottom of the kettle is prepared by emulsifier, deionized water and buffer; Preferably, the reaction liquid at the bottom of the kettle comprises the following components in parts by weight: 0.1-5 parts of emulsifier, 66-900 parts of deionized water, and 0.25-1 part of buffer.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The emulsifiers in the pre-emulsion and the bottom reaction liquid are independently selected from one or a combination of at least two of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene octylphenol ether-10, sodium allyl hydroxypropyl sulfonate, ammonium allyloxy fatty alcohol oxyethylene ether sulfate, disodium nonylphenol succinate polyoxyethylene ether monoester sulfonate, lauryl alcohol ethoxylate, isomeric tridecanol ethoxylate or fatty acid methyl ester ethoxylate; Preferably, the buffer is one or a combination of at least two of sodium bicarbonate, ammonia water, ammonium bicarbonate or sodium hydroxide.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The initiator solution comprises an initiator and deionized water; Preferably, the amount of deionized water in the initiator solution is 1 to 20 parts relative to 1 part by weight of the initiator; Preferably, the initiator is selected from inorganic peroxide initiators; Preferably, the initiator is selected from any one or a combination of at least two of potassium persulfate, ammonium persulfate or sodium persulfate; Preferably, the amount of the initiator in the initiator solution is 0.2-0.6% of the total weight percentage of the hard monomer, the soft monomer and the functional monomer.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The reaction in step (2) and step (3) is carried out under stirring, and the stirring speed is 100-500r / min; Preferably, before the seed emulsion in step (2), the bottom reaction liquid is first added into a reaction kettle at 40-80°C; Preferably, the temperature in step (2) is increased to 75-85°C; Preferably, the mass of the reaction liquid at the bottom of the kettle in step (2) is 12-40 times that of the seed emulsion; Preferably, the portion of the initiator solution in step (2) is 5-45% of the total weight of the initiator solution; Preferably, the reaction time in step (2) is 10-60 min; Preferably, the weight ratio of the pre-emulsion in step (3) to the bottom reaction liquid in step (2) is 0.15-2.12:1; Preferably, the reaction temperature in step (3) is 80-90°C; Preferably, the reaction time in step (3) is 0.5-2.5h; Preferably, the preparation method further comprises cooling the temperature to 55-70° C. after the reaction in step (3) is completed, adding a residual monomer eliminator, then cooling the temperature to below 50° C., adjusting the pH to 7-8, and filtering the material; Preferably, the residual monomer eliminator is bleaching powder and 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 solid content of the acrylic water-based adhesive is 10-60%.

9. A negative electrode plate for a lithium ion battery, characterized in that: The negative electrode plate of the lithium-ion battery comprises the polyacrylic acid or polyacrylate aqueous binder as claimed in claim 1 or 2.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium-ion battery negative electrode sheet as claimed in claim 9.

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