Water-based binder and its preparation method and use

Abstract

The present application relates to the field of lithium battery technology, and specifically provides a water-based binder, a preparation method thereof, and a use thereof. The invention aims to solve the problem that the existing water-based binders used for lithium battery negative electrodes cannot take into account both electrolyte resistance and flexibility. To this end, the water-based binder of the present application includes a core structure and a shell structure, the shell structure is coated on the outside of the core structure, the core structure includes a core main structure and a polyurea structural unit grafted onto the core main structure, and the shell structure includes a shell main structure and a polyurethane structural unit grafted onto the shell main structure. The water-based binder of the present application has good electrolyte resistance and flexibility by grafting a polyurea structural unit into the core structure and grafting a polyurethane structural unit into the shell structure, and the polyurea structural unit and the polyurethane structural unit are matched to each other.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and specifically provides a water-based binder and a preparation method and use thereof. Background Art

[0002] Current policies in areas such as energy conservation and emission reduction have driven the booming lithium battery industry. Binders, essential materials in lithium battery manufacturing, are also undergoing continuous technological upgrades. A common choice for aqueous binders in negative electrodes is a combination of styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC). This is because SBR itself is difficult to disperse, necessitating the addition of CMC as a dispersant. However, CMC exhibits high hardness, low flexibility, and moderate viscosity. When the binder dosage is limited, the bond strength is insufficient, which can lead to shedding of the conductive agent and graphite after long-term cycling, resulting in a sharp drop in battery performance. Therefore, the use of modified polyacrylic acid (PAA) as a binder, either alone or in combination with SBR or CMC, has become a mainstream choice. This is because the modified PAA structure contains functional groups such as cyano, carbonyl, ester, and carboxyl groups, which provide a certain degree of hardness and flexibility. Furthermore, carboxyl groups can form hydrogen bonds with the hydroxyl groups on the copper current collector surface, increasing bond strength.

[0003] Currently, most adhesives designed for long-term cycle performance are linear structures, and the proportion of hard monomers in the structure is relatively high to pursue high hardness and thus reduce swelling loss and improve electrolyte resistance. This leads to reduced flexibility, easy cracking of the electrodes during the production process, reduced yield, and thus increased corporate production costs.

[0004] Accordingly, this field requires a new technical solution to solve the above technical problems. Summary of the Invention

[0005] The present application aims to solve the above technical problem, that is, to solve the problem that the existing aqueous binders used for lithium battery negative electrodes cannot take into account both electrolyte resistance and flexibility.

[0006] In a first aspect, the present application provides a water-based adhesive, comprising a core structure and a shell structure, wherein the shell structure is coated on the outside of the core structure, the core structure comprising a core main structure obtained by polymerizing a first acrylate monomer, a first acrylamide monomer, and a first acrylonitrile, and a polyurea structural unit, wherein the polyurea structural unit is grafted onto the core main structure, wherein the first acrylate monomer and / or the first acrylamide monomer contains a hydroxyl group; the shell structure comprises a shell main structure obtained by polymerizing a second acrylate monomer, a second acrylamide monomer, and a second acrylonitrile, and a polyurethane structural unit, wherein the polyurethane structural unit is grafted onto the shell main structure, wherein the second acrylate monomer and / or the second acrylamide monomer contains a hydroxyl group.

[0007] In a second aspect, the present application provides a method for preparing a water-based adhesive, which comprises the following steps: S1: providing a core main structure; S2: grafting a polyurea structural unit onto the core main structure to obtain a core structure; S3: covering an outer shell main structure on the outside of the core structure; S4: grafting a polyurethane structural unit onto the outer shell main structure to obtain a water-based adhesive.

[0008] In the preferred technical solution of the above-mentioned method for preparing the water-based adhesive, step S1 specifically includes: reacting a core reaction raw material 1 with a core reaction raw material 2 to obtain a core main structure, wherein the core reaction raw material 1 includes a mixture of a first acrylate monomer, a first acrylamide monomer, a first acrylonitrile and water, and the core reaction raw material 2 includes a mixture of a first emulsifier, a first initiator and water; and / or, step S2 specifically includes: mixing and reacting a reaction system having the core main structure with a polyurea reaction raw material and a first catalyst to graft polyurea structural units onto the core main structure to obtain the core structure, wherein the first catalyst is used to catalyze the reaction of the polyurea reaction raw material to generate polyurea structural units; and / or, step S3 specifically includes: mixing and reacting a reaction system having the core structure with a shell reaction raw material 1 and a shell reaction raw material 2. , obtaining a shell main structure, and making the shell main structure cover the outer side of the core structure, wherein the shell reaction raw material 1 includes a mixture of a second acrylate monomer, a second acrylamide monomer, a second acrylonitrile and water, wherein the shell reaction raw material 2 includes a mixture of a second emulsifier, a second initiator and water, wherein the mass of the second emulsifier is greater than the mass of the first emulsifier in the raw materials used to generate the reaction system having the core structure; and / or, step S4 specifically includes: mixing the reaction system having the shell main structure with a polyurethane reaction raw material and a second catalyst for reaction, so as to graft polyurethane structural units onto the shell main structure to obtain a water-based adhesive, wherein the shell main structure in the reaction system covers the outer side of the core structure, and the second catalyst is used to catalyze the reaction of the polyurethane reaction raw materials to generate polyurethane structural units.

[0009] In the preferred technical solution of the above-mentioned method for preparing the water-based adhesive, the polyurea reaction raw materials include an aromatic polyurea resin and a first isophorone diisocyanate, and step S2 specifically includes: first uniformly mixing the reaction system having the core main structure with the aromatic polyurea resin, and then mixing and reacting the mixture with the first isophorone diisocyanate and the first catalyst to obtain a core structure grafted with polyurea structural units; and / or, the polyurethane reaction raw materials include a hydroxylated acrylic emulsion and a second isophorone diisocyanate, and step S4 specifically includes: first uniformly mixing the reaction system having the shell main structure with the hydroxylated acrylic emulsion, and then mixing and reacting the mixture with the second isophorone diisocyanate and the second catalyst to obtain a shell structure grafted with polyurethane structural units.

[0010] In a preferred technical solution of the above-mentioned method for preparing the water-based adhesive, the polyurea reaction raw materials include an aromatic polyurea resin and a first isophorone diisocyanate, the aromatic polyurea resin is added to the inner core reaction raw material one and mixed uniformly with the inner core reaction raw material one in step S1, and step S2 specifically includes: mixing and reacting the reaction system having the inner core main structure with the first isophorone diisocyanate and the first catalyst to obtain an inner core structure grafted with polyurea structural units; and / or, the polyurethane reaction raw materials include a hydroxylated acrylic emulsion and a second isophorone diisocyanate, the hydroxylated acrylic emulsion is added to the outer shell reaction raw material one and mixed uniformly with the outer shell reaction raw material one in step S3, and step S4 specifically includes: mixing and reacting the reaction system having the outer shell main structure with the second isophorone diisocyanate and the second catalyst to obtain an outer shell structure grafted with polyurethane structural units.

[0011] In the preferred technical scheme of the preparation method of the above-mentioned water-based adhesive, step S1 specifically includes: S11: providing a mixture of a first acrylate monomer, a first acrylamide monomer, a first acrylonitrile, an aromatic polyurea resin and a first solvent water to obtain a core reaction raw material one; S12: providing a mixture of a first emulsifier, a first initiator and a second solvent water to obtain a core reaction raw material two; S13: taking a portion of the core reaction raw material two and mixing it with a third solvent water, slowly stirring, and heating it to 80°C~90°C to form a reaction system; S14: uniformly adding the core reaction raw material one and the remaining core reaction raw material two to the reaction system of step S3, and after the addition is completed, keeping the temperature at a first temperature for a first preset time to obtain the core main structure; and / or, step S2 specifically includes: cooling the reaction system having the core main structure to 45°C~50°C, then adding the first isophorone diisocyanate and the first catalyst to the reaction system, and keeping the temperature at a second temperature for a second preset time, A polyurea structural unit is grafted onto the core main structure to obtain a core structure; and / or, step S3 specifically includes: S31: providing a mixture of a second acrylate monomer, a second acrylamide monomer, a second acrylonitrile, a hydroxy acrylic emulsion and a fourth solvent water to obtain a shell reaction raw material one; S32: providing a mixture of a second emulsifier, a second initiator and a fifth solvent water to obtain a shell reaction raw material two; S33: adjusting the temperature of the reaction system having the core structure to 80°C~90°C, then dripping the shell reaction raw material one and the shell reaction raw material two into the reaction system at a uniform speed, and keeping the reaction system warm at a third temperature for a third preset time after the dripping is completed; and / or, step S4 specifically includes: cooling the reaction system having the shell main structure to 45°C~50°C, then adding the second isophorone diisocyanate and the second catalyst to the reaction system, keeping the reaction system warm at a fourth temperature for a fourth preset time, and grafting a polyurethane structural unit onto the shell main structure to obtain a water-based adhesive.

[0012] In the preferred technical solution of the preparation method of the above-mentioned water-based adhesive, in step S13, 5% to 30% of the core reaction raw material 2 is mixed with the third solvent water; in step S14, before the core reaction raw material 1 and the core reaction raw material 2 are added dropwise, the rotation speed of the reaction system in step S13 is adjusted to 200 rpm to 400 rpm; and / or, in step S14, the reaction temperature is controlled not to exceed 95°C during the process of adding the core reaction raw material 1 and the core reaction raw material 2; and / or, in step S14, the core reaction raw material 1 and the core reaction raw material 2 are added dropwise within 0.5h to 1h; and / or, in step S14, the first temperature is 88°C to 92°C, and the first preset time is 1h to 1.5h; and / or, in step S2, the reaction temperature is controlled not to exceed 65°C during the process of adding the first isophorone diisocyanate and the first catalyst; and / or, in step S2, the second temperature is 58°C~62°C, and the second preset time is 1h~1.5h; and / or, in step S33, before the shell reaction raw material one and the shell reaction raw material two are added dropwise, the rotation speed of the reaction system having the core structure is first adjusted to 200rpm~400rpm; and / or, in step S33, the reaction temperature is controlled not to exceed 95°C during the process of adding the shell reaction raw material one and the shell reaction raw material two; and / or, in step S33, the shell reaction raw material one and the shell reaction raw material two are added dropwise within 1h~2h; and / or, in step S33, the third temperature is 88°C~92°C, and the third preset time is 1.5h~2.5h; and / or, in step S4, the reaction temperature is controlled not to exceed 65°C during the process of adding the second isophorone diisocyanate and the second catalyst; and / or, in step S4, the fourth temperature is 58°C~62°C, and the fourth preset time is 1h~1.5h.

[0013] In the preferred technical solution of the above-mentioned method for preparing the water-based adhesive, in step S11, the core reaction raw material 1 includes the following components in parts by weight: 50-150 parts of a first acrylate monomer, 10-50 parts of a first acrylamide monomer, 5-20 parts of a first acrylonitrile, 20-50 parts of an aromatic polyurea resin, and 50-150 parts of a first solvent, water; and / or, in step S12, the core reaction raw material 2 includes the following components in parts by weight: 5-10 parts of a first emulsifier, 2-5 parts of a first initiator, and 50-200 parts of a second solvent, water; and / or, in step S13, the weight portion of the third solvent, water, is 100-200 parts; and / or, in step S2, the weight portion of the first isophorone diisocyanate is 5-20 parts by weight, the first catalyst is 2-5 parts by weight; and / or, in step S31, the shell reaction raw material one includes the following components in parts by weight: 100-300 parts by weight of a second acrylate monomer, 20-80 parts by weight of a second acrylamide monomer, 5-30 parts by weight of a second acrylonitrile, 50-100 parts by weight of a hydroxylated acrylic emulsion, and 50-100 parts by weight of a fourth solvent, water; and / or, in step S32, the shell reaction raw material two includes the following components in parts by weight: 10-20 parts by weight of a second emulsifier, 2-5 parts by weight of a second initiator, and 50-100 parts by weight of a fifth solvent, water; and / or, in step S4, the second isophorone diisocyanate is 5-20 parts by weight, and the second catalyst is 2-5 parts by weight.

[0014] In a preferred technical solution of the above-mentioned method for preparing the aqueous binder, the first acrylate monomer and / or the first acrylamide monomer contain a hydroxyl group, and the second acrylate monomer and / or the second acrylamide monomer contain a hydroxyl group; and / or the mass of the aromatic polyurea resin is 15% to 30% of the total mass of the first acrylate monomer, the first acrylamide monomer, and the first acrylonitrile, and the mass ratio of the first isophorone diisocyanate to the aromatic polyurea resin is 1:(2-3); and / or the mass of the hydroxylated acrylic emulsion is 12% to 80% of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile, and the mass ratio of the second isophorone diisocyanate to the hydroxylated acrylic emulsion is 1:(5-10); and / or the aromatic polyurea resin is in powder form.

[0015] In a preferred technical solution of the above-mentioned method for preparing the aqueous binder, the first acrylate monomer and / or the second acrylate monomer include one or more of hydroxyethyl acrylate, hydroxymethyl acrylate, and hydroxyethyl methacrylate; and / or the first acrylamide monomer and / or the second acrylamide monomer include one or more of N-hydroxymethyl acrylamide and N-hydroxyethyl acrylamide; and / or the mass of the hydroxy acrylic emulsion is 30% to 40% of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile.

[0016] In a preferred technical solution of the above-mentioned method for preparing the water-based binder, the first acrylate monomer and / or the second acrylate monomer further comprises one or more of ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isooctyl acrylate, lauryl methacrylate, butyl methacrylate, and n-octyl methacrylate; and / or the first acrylamide monomer and / or the second acrylamide monomer further comprises one or more of methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methyl-acyloxyethyltrimethylammonium chloride, diacetone acrylamide, and N-butoxymethyl acrylamide; and / or the first emulsifier and the second emulsifier are respectively selected from one or more of sodium p-styrene sulfonate, sodium vinyl sulfonate, and sodium dodecyl sulfonate; and / or the first initiator and the second initiator are persulfates, preferably the persulfate comprises one or more of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0017] In a preferred technical solution of the method for preparing the above-mentioned aqueous binder, the aromatic polyurea resin is selected from one or more of phenyl polyurea and dichlorophenyl polyurea; and / or the first isophorone diisocyanate and the second isophorone diisocyanate are respectively selected from one or more of Covestro's Bayhydur ultra 2759, Bayhydur 2858 XP and Bayhydur ultra 401-70 MPA / X; and / or the hydroxylated acrylic emulsion is selected from one or more of Dow Prospersetm200, Huaguoshan Houshan 0880 and DSM Neocryl XK-540; and / or the first catalyst and the second catalyst are respectively selected from one or more of bismuth isooctanoate, benzoyl chloride and triethylenediamine; and / or the cross-linking agent is one or more of adipic acid dihydrazide and aziridine.

[0018] In a third aspect, the present application provides use of an aqueous binder as a negative electrode binder in a lithium-ion battery.

[0019] Compared with the existing technology, the technical solution of this application has the following beneficial effects:

[0020] 1. The water-based adhesive of the present application is a core-shell structure, specifically including a core structure and a shell structure coated on the outside of the core structure. The core structure includes a core main structure and a polyurea structural unit grafted on the core main structure. The shell structure includes a shell main structure and a polyurethane structural unit grafted on the shell main structure. The polyurea structural unit and the polyurethane structural unit are combined to make the prepared water-based adhesive have good electrolyte resistance and flexibility.

[0021] 2. The preparation method of the water-based adhesive of the present application first forms a core main structure by reacting a core reaction raw material 1 with a core reaction raw material 2, and then reacting with a polyurea reaction raw material to form a polyurea structural unit and grafting it onto the core main structure, and then mixing with a shell reaction raw material 1 and a shell reaction raw material 2, so that the shell reaction raw material 1 and the shell reaction raw material 2 react to form a shell main structure coated on the outside of the core structure, and then reacting with a polyurethane reaction raw material to form a polyurethane structural unit and grafting it onto the shell main structure, and finally obtaining a water-based adhesive with a core-shell structure; the preparation method can complete the synthesis of the core structure and the shell structure in sequence in one device in steps, without using two devices to synthesize the core and the shell separately and then mixing them, the preparation process is simple and easy to operate, and the shell coating effect and performance of the prepared water-based adhesive are good.

[0022] 3. During the preparation process of the water-based adhesive of the present application, the proportion of polyurea structural units in the core structure is controlled by controlling the amount of polyurea reaction raw materials relative to the reaction raw materials of the core structure, and the proportion of polyurethane structural units in the shell structure is controlled by controlling the amount of polyurethane reaction raw materials relative to the reaction raw materials of the shell structure, so that the flexibility and electrolyte resistance of the prepared water-based adhesive are better. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0024] Figure 1 This is a Fourier transform infrared spectrum of the water-based adhesive of Example 1 of the present application. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present application are described below. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present application and are not intended to limit the scope of protection of the present application.

[0026] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0027] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0028] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0029] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0030] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0031] The terms "first" and "second" are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of such features.

[0032] The experimental methods in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0033] As mentioned in the background art, the existing aqueous binder for lithium battery negative electrode cannot achieve both electrolyte resistance and flexibility.

[0034] The present application provides a water-based adhesive, which has a core-shell structure, specifically including a core structure and a shell structure coated on the outside of the core structure. The core structure includes a core main structure and a polyurea structural unit grafted onto the core main structure. The shell structure includes a shell main structure and a polyurethane structural unit grafted onto the shell main structure. The polyurea structural unit and the polyurethane structural unit are combined to make the prepared water-based adhesive have good electrolyte resistance and flexibility.

[0035] Specifically, in the first aspect, the present application provides a water-based adhesive having a core-shell structure, which specifically includes a core structure and an outer shell structure, wherein the outer shell structure is coated on the outer side of the core structure. The core structure includes a core main structure obtained by polymerizing a first acrylate monomer, a first acrylamide monomer, and a first acrylonitrile, and a polyurea structural unit, wherein the polyurea structural unit is grafted onto the core main structure. , wherein the first acrylate monomer and / or the first acrylamide monomer contains a hydroxyl group, so that at least one of the first acrylate monomer and the first acrylamide monomer contains a hydroxyl group, and the polyurea structural unit can be grafted onto the core main structure; the shell structure includes a shell main structure obtained by polymerizing the second acrylate monomer, the second acrylamide monomer and the second acrylonitrile, and a polyurethane structural unit, the polyurethane structural unit is grafted onto the shell main structure, and the polyurethane structural unit is The second acrylate monomer and / or the second acrylamide monomer contains a hydroxyl group, so that at least one of the second acrylate monomer and the second acrylamide monomer contains a hydroxyl group, which enables the polyurethane structural unit to be grafted onto the main structure of the shell.

[0036] In a second aspect, the present application provides a method for preparing a water-based binder, which is used to prepare the water-based binder provided in the first aspect.

[0037] Specifically, the preparation method of the aqueous binder of the present application comprises the following steps:

[0038] S1: provides the kernel main structure;

[0039] S2: Grafting polyurea structural units onto the core main structure to obtain a core structure;

[0040] S3: The outer shell structure is covered on the outer side of the core structure;

[0041] S4: Grafting the polyurethane structural unit onto the main structure of the shell to obtain a water-based adhesive.

[0042] Preferably, step S1 specifically includes: reacting a core reaction raw material 1 with a core reaction raw material 2 to obtain a core main structure, wherein the core reaction raw material 1 includes a mixture of a first acrylate monomer, a first acrylamide monomer, a first acrylonitrile and water, and the core reaction raw material 2 includes a mixture of a first emulsifier, a first initiator and water.

[0043] Preferably, step S2 specifically includes: mixing a reaction system having a core structure with a polyurea reaction raw material and a first catalyst to react, thereby grafting polyurea structural units onto the core structure to obtain a core structure, wherein the first catalyst is used to catalyze the polyurea reaction raw material to form polyurea structural units. Specifically, the reaction system having a core structure can be the reaction system after the reaction in step S1 is completed.

[0044] Preferably, step S3 specifically includes: mixing and reacting the reaction system that produces the core structure with shell reaction raw materials 1 and 2 to produce a shell main structure, and coating the shell main structure on the outside of the core structure, wherein the shell reaction raw materials 1 include a mixture of a second acrylate monomer, a second acrylamide monomer, a second acrylonitrile, and water, and the shell reaction raw materials 2 include a mixture of a second emulsifier, a second initiator, and water, wherein the mass of the second emulsifier is greater than the mass of the first emulsifier in the raw materials used in the reaction system that produces the core structure. Specifically, the reaction system that produces the core structure can be the reaction system after the reaction in step S2 is completed.

[0045] Preferably, step S4 includes: mixing the reaction system that has produced the shell main structure with polyurethane reaction raw materials and a second catalyst to react, thereby grafting polyurethane structural units onto the shell main structure to obtain a water-based adhesive, wherein the shell main structure in the reaction system is coated on the outside of the core structure, and the second catalyst is used to catalyze the reaction of the polyurethane reaction raw materials to produce the polyurethane structural units. Specifically, the reaction system that has produced the shell main structure can be the reaction system after the reaction in step S3 is completed.

[0046] Furthermore, the pH of the reaction system in step S4 is adjusted to 7.0-7.5. Specifically, a neutralizing base is added dropwise to the reaction system in step S4 to adjust the pH to 7.0-7.5. The mixture is then mixed with a crosslinking agent, cooled to below 40° C., and sieved to remove large insoluble particles, thereby obtaining an emulsion of the aqueous binder.

[0047] The preparation method of the water-based adhesive of the present application is to first react a core reaction raw material 1 and a core reaction raw material 2 to form a core main structure, then react with a polyurea reaction raw material to form a polyurea structural unit and graft it onto the core main structure, then mix with a shell reaction raw material 1 and a shell reaction raw material 2, so that the shell reaction raw material 1 and the shell reaction raw material 2 react to form a shell main structure coated on the outside of the core structure, and then react with a polyurethane reaction raw material to form a polyurethane structural unit and graft it onto the shell main structure, finally obtaining a water-based adhesive with a core-shell structure; the preparation method can complete the synthesis of the core structure and the shell structure in sequence in one device, without using two devices to synthesize the core and the shell separately and then mix them, the preparation process is simple and easy to operate, and the shell of the water-based adhesive in the prepared water-based adhesive has a good coating effect and good performance.

[0048] Preferably, the polyurea reaction raw materials include an aromatic polyurea resin and a first isophorone diisocyanate. Specifically, the aromatic polyurea resin and the first isophorone diisocyanate react under the catalysis of a first catalyst to form polyurea structural units. Simultaneously, the first isophorone diisocyanate reacts with hydroxyl groups in the core structure, thereby grafting the generated polyurea structural units onto the core structure. Furthermore, preferably, the aromatic polyurea resin is in powder form.

[0049] It should be noted that the present application does not impose any restriction on the time point when the aromatic polyurea resin as the raw material of the polyurea reaction is added to the reaction system. In actual use, those skilled in the art can set the time point when the aromatic polyurea resin is added to the reaction system according to actual needs.

[0050] In some embodiments, an aromatic polyurea resin is added to the reaction system in step S2. Step S2 specifically comprises: first uniformly mixing the reaction system having the core main structure with the aromatic polyurea resin, and then reacting the mixture with a first isophorone diisocyanate and a first catalyst to obtain a core structure grafted with polyurea structural units. Specifically, the reaction system having the core main structure can be the reaction system obtained after the reaction in step S1.

[0051] In other embodiments, the aromatic polyurea resin is added to the core reaction raw material 1 in step S1 and uniformly mixed therewith. Step S2 specifically includes: mixing the reaction system that produces the core main structure with a first isophorone diisocyanate and a first catalyst to react to obtain a core structure grafted with polyurea structural units. Specifically, the reaction system that produces the core main structure can be the reaction system obtained after the reaction in step S1.

[0052] Since the aromatic polyurea resin does not participate in the reaction during the formation of the core main structure, adding the aromatic polyurea resin to the core reaction raw material 1 in step S1 can effectively shorten the preparation time and improve the preparation efficiency compared to adding the aromatic polyurea resin dropwise in step S2.

[0053] In a specific embodiment, step S1 specifically includes:

[0054] S11: providing a mixture of a first acrylate monomer, a first acrylamide monomer, a first acrylonitrile, an aromatic polyurea resin and a first solvent water to obtain a first core reaction raw material.

[0055] S12: providing a mixture of a first emulsifier, a first initiator, and a second solvent, water, to obtain a second core reaction raw material.

[0056] S13: Take a portion of the second core reaction raw material and mix it with the third solvent water, slowly stir it, and heat it to 80° C. to 90° C. to form a reaction system.

[0057] Preferably, 5% to 30% of the second core reaction raw material is mixed with the third solvent water to form a reaction system.

[0058] S14: adding the core reaction raw material 1 and the remaining core reaction raw material 2 to the reaction system of step S13 at a uniform speed, and maintaining the temperature at a first temperature for a first preset time after the addition is completed to obtain the core main structure.

[0059] Preferably, in step S14, before the core reaction raw materials 1 and 2 are added dropwise, the rotational speed of the reaction system in step S13 is adjusted to 200 rpm to 400 rpm. Reducing the rotational speed to 200 to 400 rpm can both disperse the added raw materials in the reaction system and avoid excessively high local concentrations, and also prevent the reaction emulsion system from breaking due to excessive rotational speed.

[0060] Preferably, in step S14, the reaction temperature is controlled to be no higher than 95° C. during the dropwise addition of the core reaction raw material 1 and the core reaction raw material 2. Heat is released during the dropwise addition, and controlling the temperature to no higher than 95° C. prevents excessively rapid reaction and increased side reactions, thereby helping to broaden the particle size distribution and increase the fineness of the final product.

[0061] Preferably, in step S14, the core reaction raw material 1 and the core reaction raw material 2 are added within 0.5 h to 1 h.

[0062] Preferably, in step S14, the first temperature is 88°C to 92°C, and the first preset time is 1 hour to 1.5 hours. After all the reaction raw materials are added dropwise, the temperature is controlled to about 90°C, and the reaction is continued for 1 to 1.5 hours to allow the first core reaction raw material and the second core reaction raw material to fully react.

[0063] Step S2 specifically includes cooling the reaction system having the core structure to 45°C to 50°C, adding a first isophorone diisocyanate and a first catalyst to the reaction system, maintaining the reaction system at a second temperature for a second predetermined time, and grafting polyurea structural units onto the core structure to obtain the core structure. Specifically, the reaction system having the core structure can be the reaction system obtained by the reaction in step S1.

[0064] Preferably, in step S2, the reaction temperature is controlled not to exceed 65° C. during the addition of the first isophorone diisocyanate and the first catalyst. Heat is released during the addition, and the temperature is controlled not to exceed 65° C. to avoid excessive reaction speed and increased side reactions.

[0065] Preferably, in step S2, the second temperature is 58°C to 62°C, and the second preset time is 1 hour to 1.5 hours. After all the reaction raw materials are added dropwise, the temperature is controlled to approximately 60°C, and the reaction is continued for 1 to 1.5 hours to allow the first isophorone diisocyanate to fully react with the aromatic polyurea resin and the hydroxyl groups in the first core reaction raw material.

[0066] Preferably, the polyurethane reaction raw materials include a hydroxylated acrylic emulsion and a second isophorone diisocyanate. Specifically, the hydroxylated acrylic emulsion and the second isophorone diisocyanate react under the catalysis of a second catalyst to generate polyurethane structural units. Simultaneously, the second isophorone diisocyanate reacts with hydroxyl groups in the main shell structure, thereby grafting the generated polyurethane structural units onto the main shell structure.

[0067] It should be noted that this application does not impose any restrictions on the time point when the hydroxyl acrylic emulsion, a raw material for the polyurethane reaction, is added to the reaction system. In actual use, those skilled in the art can set the time point when the hydroxyl acrylic emulsion is added to the reaction system according to actual needs.

[0068] In some embodiments, the hydroxylated acrylic emulsion is added to the reaction system in step S4. Step S4 specifically comprises: first uniformly mixing the reaction system having the shell main structure with the hydroxylated acrylic emulsion, and then reacting the reaction system with a second isophorone diisocyanate and a second catalyst to obtain a shell structure grafted with polyurethane structural units. Specifically, the reaction system having the shell main structure can be the reaction system after the reaction in step S3.

[0069] In other embodiments, the hydroxylated acrylic emulsion is added to the shell reaction raw material 1 in step S3 and uniformly mixed therewith. Step S4 specifically includes: mixing the reaction system that has produced the shell main structure with a second isophorone diisocyanate and a second catalyst to react to produce a shell structure grafted with polyurethane structural units. Specifically, the reaction system that has produced the shell main structure can be the reaction system after the reaction in step S3.

[0070] Since the hydroxyl acrylic emulsion does not participate in the reaction during the reaction to form the main structure of the shell, adding the hydroxyl acrylic emulsion to the shell reaction raw material 1 in step S3 can effectively shorten the preparation time and improve the preparation efficiency compared to adding the hydroxyl acrylic emulsion dropwise in step S4.

[0071] In a specific embodiment, step S3 specifically includes:

[0072] S31: providing a mixture of a second acrylate monomer, a second acrylamide monomer, a second acrylonitrile, a hydroxyl acrylic emulsion and a fourth solvent, to obtain a first shell reaction raw material.

[0073] S32: providing a mixture of a second emulsifier, a second initiator and a fifth solvent, water, to obtain a second shell reaction raw material.

[0074] S33: Adjusting the temperature of the reaction system in which the core structure is formed to 80°C to 90°C, then uniformly adding the first and second shell reaction raw materials dropwise to the reaction system. After the addition is complete, the reaction system is maintained at a third temperature for a third predetermined time. Specifically, the reaction system in which the core structure is formed can be the reaction system after the reaction in step S2.

[0075] Preferably, in step S33, before the shell reaction raw material 1 and the shell reaction raw material 2 are added dropwise, the rotation speed of the reaction system in which the core structure is generated is adjusted to 200 rpm to 400 rpm. Reducing the rotation speed to 200 to 400 rpm can both disperse the added raw materials in the reaction system and avoid excessive local concentrations, and can also prevent the reaction emulsion system from breaking due to excessive rotation speed.

[0076] Preferably, in step S33, the reaction temperature is controlled not to exceed 95° C. during the dropwise addition of the shell reaction raw material 1 and the shell reaction raw material 2. The reaction is exothermic during the dropwise addition, and the temperature is controlled not to exceed 95° C. to avoid excessive reaction speed and increased side reactions.

[0077] Preferably, in step S33, the shell reaction raw material 1 and the shell reaction raw material 2 are dripped within 1 hour to 2 hours.

[0078] Preferably, in step S33, the third temperature is 88°C to 92°C, and the third preset time is 1.5 hours to 2.5 hours. After all the reaction materials are added, the temperature is controlled to about 90°C, and the reaction is continued for 1.5 to 2.5 hours to allow the shell reaction material 1 and the shell reaction material 2 to fully react.

[0079] Step S4 specifically includes cooling the reaction system having the shell main structure to 45°C to 50°C, then adding a second isophorone diisocyanate and a second catalyst to the reaction system, and maintaining the reaction system at a fourth temperature for a fourth predetermined time, thereby grafting polyurethane structural units onto the shell main structure. Specifically, the reaction system having the shell main structure may be the reaction system after the reaction in step S3.

[0080] Preferably, in step S4, the reaction temperature is controlled to be no higher than 65° C. during the addition of the second isophorone diisocyanate and the second catalyst. Heat is released during the addition, and the temperature is controlled to be no higher than 65° C. to avoid excessive reaction speed and increased side reactions.

[0081] Preferably, in step S4, the fourth temperature is 58°C to 62°C, and the fourth preset time is 1 hour to 1.5 hours. After all the reaction raw materials are added dropwise, the temperature is controlled to approximately 60°C, and the reaction is continued for 1 to 1.5 hours to allow the second isophorone diisocyanate to fully react with the hydroxyl groups in the hydroxylated acrylic emulsion and the first shell reaction raw material.

[0082] In some preferred embodiments, in step S11, the core reaction raw material 1 includes the following components in parts by weight: 50-150 parts of a first acrylate monomer, 10-50 parts of a first acrylamide monomer, 5-20 parts of a first acrylonitrile, 20-50 parts of an aromatic polyurea resin, and 50-150 parts of a first solvent, water.

[0083] In some preferred embodiments, in step S12, the second core reaction raw material includes the following components in parts by weight: 5-10 parts of a first emulsifier, 2-5 parts of a first initiator, and 50-200 parts of a second solvent, water.

[0084] In some preferred embodiments, in step S13, the weight percentage of the third solvent water is 100-200 parts.

[0085] In some preferred embodiments, in step S2, the weight portion of the first isophorone diisocyanate is 5 to 20 parts, and the weight portion of the first catalyst is 2 to 5 parts.

[0086] In some preferred embodiments, in step S31, the shell reaction raw material 1 includes the following components in parts by weight: 100-300 parts of the second acrylate monomer, 20-80 parts of the second acrylamide monomer, 5-30 parts of the second acrylonitrile, 50-100 parts of the hydroxylated acrylic emulsion, and 50-100 parts of the fourth solvent water.

[0087] In some preferred embodiments, in step S32, the second shell reaction raw material includes the following components in parts by weight: 10-20 parts of a second emulsifier, 2-5 parts of a second initiator, and 50-100 parts of a fifth solvent, water.

[0088] In some preferred embodiments, in step S4, the weight portion of the second isophorone diisocyanate is 5 to 20 parts, and the weight portion of the second catalyst is 2 to 5 parts.

[0089] In some preferred embodiments, the weight portion of the cross-linking agent is 5 to 10 parts.

[0090] This application controls the proportion of polyurea structural units in the core structure of the water-based adhesive by controlling the amount of polyurea reaction raw materials (first isophorone diisocyanate and aromatic polyurea resin), and controls the proportion of polyurethane structural units in the shell structure of the water-based adhesive by controlling the amount of polyurethane reaction raw materials (second isophorone diisocyanate and hydroxyl acrylic emulsion), thereby making the water-based adhesive have better flexibility and electrolyte resistance. In addition, by regulating the components and amounts of the reaction raw materials of the core structure (core reaction raw material 1 and core reaction raw material 2) and regulating the components and amounts of the reaction raw materials of the shell structure (shell reaction raw material 1 and shell reaction raw material 2), the shell actively wraps the core during the synthesis of the shell to form a water-based adhesive with a core-shell structure with a better morphology.

[0091] In some preferred embodiments, the mass of the aromatic polyurea resin is 15% to 30% of the total mass of the first acrylate monomer, the first acrylamide monomer, and the first acrylonitrile, and the mass ratio of the first isophorone diisocyanate to the aromatic polyurea resin is 1:(2-3).

[0092] In some preferred embodiments, the mass of the hydroxylated acrylic emulsion is 12% to 80% of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile, and the mass ratio of the second isophorone diisocyanate to the hydroxylated acrylic emulsion is 1:(5-10).

[0093] In some further preferred embodiments, the mass of the hydroxylated acrylic emulsion is 30% to 40% of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile.

[0094] The present application controls the proportion of polyurea structural units in the core structure by further controlling and adjusting the amount of aromatic polyurea resin in the polyurea reaction raw materials relative to the total mass of the first acrylate monomer, the first acrylamide monomer, and the first acrylonitrile, and controls the proportion of polyurethane structural units in the shell structure by controlling the amount of hydroxyl acrylic emulsion in the polyurethane reaction raw materials relative to the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile, thereby improving the flexibility and electrolyte resistance of the prepared water-based adhesive.

[0095] Preferably, the first acrylate monomer and / or the first acrylamide monomer contains a hydroxyl group, and the second acrylate monomer and / or the second acrylamide monomer contains a hydroxyl group.

[0096] Specifically, the reaction raw materials of the core structure and the reaction raw materials of the shell structure both contain hydroxyl groups, which can react with isophorone diisocyanate, so that the generated polyurea structural units are grafted onto the core structure, and the generated polyurethane structural units are grafted onto the shell structure, thereby improving the electrolyte resistance and flexibility of the water-based adhesive.

[0097] More preferably, the first acrylic ester monomer and / or the second acrylic ester monomer includes one or more of hydroxyethyl acrylate, hydroxymethyl acrylate, and hydroxyethyl methacrylate.

[0098] More preferably, the first acrylamide monomer and / or the second acrylamide monomer include one or more of N-hydroxymethyl acrylamide and N-hydroxyethyl acrylamide.

[0099] Further preferably, the first acrylic ester monomer and / or the second acrylic ester monomer further comprises one or more of ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isooctyl acrylate, lauryl methacrylate, butyl methacrylate, and n-octyl methacrylate.

[0100] More preferably, the first acrylamide monomer and / or the second acrylamide monomer further comprises one or more of methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methyl-acyloxyethyltrimethylammonium chloride, diacetone acrylamide, and N-butoxymethylacrylamide.

[0101] Preferably, the first emulsifier and the second emulsifier are respectively selected from one or more of sodium p-styrene sulfonate, sodium vinyl sulfonate and sodium dodecyl sulfonate.

[0102] Preferably, the first initiator and the second initiator are persulfates, wherein the persulfates include one or more of ammonium persulfate, potassium persulfate and sodium persulfate.

[0103] Preferably, the aromatic polyurea resin is selected from one or more of phenyl polyurea and dichlorophenyl polyurea.

[0104] Preferably, the first isophorone diisocyanate and the second isophorone diisocyanate are selected from one or more of Bayhydur ultra 2759, Bayhydur 2858 XP and Bayhydur ultra 401-70 MPA / X manufactured by Covestro.

[0105] Preferably, the hydroxylated acrylic emulsion is selected from one or more of Dow Prospersetm 200, Huaguoshan Houshan 0880 and DSM Neocryl XK-540.

[0106] Preferably, the first catalyst and the second catalyst are respectively selected from one or more of bismuth isooctanoate, benzoyl chloride and triethylenediamine.

[0107] Preferably, the neutralizing base is selected from one or more of sodium hydroxide, lithium hydroxide, aqueous ammonia, sodium carbonate and sodium bicarbonate.

[0108] Preferably, the cross-linking agent is one or more of adipic acid dihydrazide and aziridine.

[0109] In a third aspect, the present application provides use of the aqueous binder provided in the first aspect as a negative electrode binder in a lithium-ion battery.

[0110] The water-based adhesive of the present application is described in detail below through several specific embodiments.

[0111] Example 1

[0112] The emulsion of the aqueous binder of the present embodiment is prepared by the following steps:

[0113] S101: 70 g of a first acrylic ester monomer (10 g of ethyl acrylate, 15 g of isooctyl acrylate, 15 g of hydroxyethyl acrylate, 10 g of lauryl methacrylate, and 20 g of butyl methacrylate), 21 g of a first acrylamide monomer (5 g of methacrylamide, 10 g of 2-acrylamido-2-methylpropanesulfonic acid, and 6 g of diacetone acrylamide), 11 g of a first acrylonitrile, 25 g of an aromatic polyurea resin (phenyl polyurea), and 70 g of deionized water are mixed, and the mixture is dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 5 minutes to obtain a core reaction raw material 1.

[0114] S102: 7 g of the first emulsifier (sodium dodecylsulfonate), 4 g of the first initiator (ammonium persulfate) and 80 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second core reaction raw material.

[0115] S103: 22% of the core reaction raw material 2 (i.e., 20 g of the core reaction raw material 2) was mixed with 200 g of deionized water, stirred at a stirring speed of 50 rpm, and heated to 82° C. to form a reaction system.

[0116] S104: The stirring speed of the reaction system in step S103 is adjusted to 300 rpm, and the core reaction raw material 1 and the remaining core reaction raw material 2 are uniformly added dropwise into the reaction system, wherein the core reaction raw material 1 is added within 45 minutes, and the remaining core reaction raw material 2 is added within 50 minutes. During the addition process, the reaction temperature is controlled not to exceed 95°C. After all the core reaction raw materials are added, the timer is started, and the temperature is kept at 90°C for 1 hour to allow the core reaction raw material 1 to be polymerized to obtain the core main structure.

[0117] S105: The reaction system after the reaction in step S104 was cooled to 45°C, and 10g of the first isophorone diisocyanate (Bayhydur ultra 2759, Covestro) and 3g of the first catalyst (triethylenediamine) were added to the reaction system while controlling the reaction temperature not to exceed 65°C. The reaction system was then kept at 60°C for 1 hour to react and generate polyurea structural units. The polyurea structural units were grafted onto the core main structure to obtain a core structure.

[0118] S106: 100 g of a second acrylic ester monomer (20 g of ethyl acrylate, 15 g of isooctyl acrylate, 25 g of hydroxyethyl acrylate, 20 g of lauryl methacrylate, and 20 g of butyl methacrylate), 39 g of a second acrylamide monomer (5 g of methacrylamide, 18 g of 2-acrylamido-2-methylpropanesulfonic acid, and 16 g of diacetone acrylamide), 14 g of a second acrylonitrile, 100 g of a hydroxy acrylic emulsion (Dow Prospersetm 200), and 60 g of deionized water were mixed, and the mixture was dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 15 minutes to obtain a shell reaction raw material 1.

[0119] S107: 15 g of the second emulsifier (sodium dodecylsulfonate), 4 g of the second initiator (ammonium persulfate) and 80 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second shell reaction raw material.

[0120] S108: Adjust the temperature of the reaction system after the reaction in step S105 to 86°C, adjust the stirring speed to 300 rpm, and uniformly drip shell reaction raw material 1 and shell reaction raw material 2 into the reaction system. The shell reaction raw material 1 is dripped within 1 hour and 30 minutes, and the shell reaction raw material 2 is dripped within 1 hour and 20 minutes. During the dripping process, the reaction temperature is controlled not to exceed 95°C. After all the dripping is completed, start timing, keep warm at 90°C for 2 hours, so that the shell reaction raw material 1 is polymerized to obtain the shell main structure, and the shell main structure is coated on the outside of the core structure.

[0121] S109: The reaction system after the reaction in step S108 was cooled to 45°C, and then 20g of a second isophorone diisocyanate (Covestro Bayhydur ultra 2759) and 3g of a second catalyst (triethylenediamine) were added. At the same time, the reaction temperature was controlled not to exceed 65°C. The mixture was then kept at 60°C for 1 hour to react and generate polyurethane structural units. The polyurethane structural units were grafted onto the main structure of the shell to obtain a water-based adhesive.

[0122] S110: Lithium hydroxide is added dropwise to the reaction system after the reaction in step S109 to adjust the pH to 7.2.

[0123] S111: Add 5 g of a cross-linking agent (3 g of adipic acid dihydrazide and 2 g of aziridine) to the reaction system obtained in step S110, cool to below 40° C., and pass through a 300-mesh sieve to obtain an emulsion of a water-based adhesive.

[0124] The aqueous binder obtained in Example 1 was subjected to FT-IR test and the following results were obtained: Figure 1 The Fourier transform infrared spectrum shown in Figure 1 The FT-IR spectrum of Example 1 shows a peak at 3300-3500, indicating an NH structure; and a peak at 1600-1700, indicating a C=O structure. Both the polyurea structural unit and the polyurethane structural unit contain these two structures. Therefore, it can be seen that the water-based adhesive of this application contains polyurea structural units and polyurethane structural units. Furthermore, scanning electron microscopy analysis of the water-based adhesive of Example 1 shows a core-shell structure, in which the outer shell structure envelops the outer core structure.

[0125] Example 2

[0126] The preparation method of the aqueous binder emulsion of this embodiment is the same as that of Example 1. The only difference between this embodiment and Example 1 is that the types of the first isophorone diisocyanate in step S105 and the second isophorone diisocyanate in step S109 are different.

[0127] Specifically, in this embodiment, the first isophorone diisocyanate and the second isophorone diisocyanate are both Bayhydur 2858 XP from Covestro.

[0128] Example 3

[0129] The preparation method of the aqueous binder emulsion of this embodiment is the same as that of Example 1. The only difference between this embodiment and Example 1 is that the types of the first isophorone diisocyanate in step S105 and the second isophorone diisocyanate in step S109 are different.

[0130] Specifically, in this embodiment, the first isophorone diisocyanate and the second isophorone diisocyanate are both Bayhydur ultra 401-70 MPA / X from Covestro.

[0131] Example 4

[0132] The preparation method of the aqueous binder emulsion of this embodiment is the same as that of Example 1. The only difference between this embodiment and Example 1 is that the types of the aromatic polyurea resin in step S101 and the hydroxy acrylic emulsion in step S106 are different.

[0133] Specifically, in this embodiment, the aromatic polyurea resin is dichlorophenyl polyurea, and the hydroxylated acrylic emulsion is DSM Neocryl XK-540.

[0134] The preparation methods of the aqueous binder emulsions of Examples 5 to 7 are the same as those of Example 1. The difference from Example 1 lies in the different components and amounts of the raw materials. The components and amounts of the raw materials of Examples 5 to 7 are shown in Table 1.

[0135] Table 1 Raw material ratios for Examples 5 to 7

[0136]

[0137]

[0138] Example 8

[0139] The emulsion of the aqueous binder of the present embodiment is prepared by the following steps:

[0140] S101: 100 g of a first acrylic ester monomer (10 g of ethyl acrylate, 10 g of isooctyl acrylate, 10 g of n-propyl acrylate, 20 g of hydroxyethyl acrylate, 10 g of lauryl methacrylate, 20 g of butyl methacrylate, 20 g of n-octyl methacrylate), 30 g of a first acrylamide monomer (10 g of N-hydroxymethyl acrylamide, 5 g of methacrylamide, 10 g of methyl-acyloxyethyl trimethyl ammonium chloride, 5 g of N-butoxymethyl acrylamide), 15 g of a first acrylonitrile, 25 g of an aromatic polyurea resin (dichlorophenyl polyurea) and 100 g of deionized water are mixed, and the mixture is dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 5 minutes to obtain a core reaction raw material one.

[0141] S102: 7 g of the first emulsifier (sodium p-styrenesulfonate), 3 g of the first initiator (potassium persulfate) and 120 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second core reaction raw material.

[0142] S103: 22% of the core reaction raw material 2 (i.e., 28.6 g of the core reaction raw material 2) was mixed with 150 g of deionized water, stirred at a stirring speed of 50 rpm, and heated to 82° C. to form a reaction system.

[0143] S104: The stirring speed of the reaction system in step S103 is adjusted to 300 rpm, and the core reaction raw material 1 and the remaining core reaction raw material 2 are uniformly added dropwise into the reaction system, wherein the core reaction raw material 1 is added dropwise within 45 minutes, and the remaining core reaction raw material 2 is added dropwise within 50 minutes. During the addition process, the reaction temperature is controlled not to exceed 95°C. After all the additions are completed, the timing is started, and the temperature is kept at 90°C for 1 hour. The core reaction raw material 1 is polymerized to obtain the core main structure.

[0144] S105: The reaction system after the reaction in step S104 was cooled to 45°C, and 12g of the first isophorone diisocyanate (Bayhydur ultra 2759, Covestro) and 3g of the first catalyst (bismuth isooctoate) were added to the reaction system while controlling the reaction temperature not to exceed 65°C. The reaction system was then kept at 60°C for 1 hour to react and generate polyurea structural units. The polyurea structural units were grafted onto the core main structure to obtain a core structure.

[0145] S106: 200 g of a second acrylic ester monomer (35 g of ethyl acrylate, 15 g of isooctyl acrylate, 50 g of hydroxyethyl acrylate, 20 g of lauryl methacrylate, 20 g of butyl methacrylate, 20 g of n-propyl acrylate, 20 g of n-butyl acrylate, 20 g of n-octyl methacrylate), 50 g of a second acrylamide monomer (5 g of methacrylamide, 13 g of 2-acrylamido-2-methylpropanesulfonic acid, 16 g of diacetone acrylamide, 16 g of N-hydroxymethyl acrylamide), 17 g of a second acrylonitrile, 75 g of a hydroxylated acrylic emulsion (Dow Prospersetm 200), and 75 g of deionized water were mixed, and the mixture was dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 15 minutes to obtain a shell reaction raw material 1.

[0146] S107: 15 g of the second emulsifier (sodium p-styrene sulfonate), 3 g of the second initiator (potassium persulfate) and 75 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second shell reaction raw material.

[0147] S108: Adjust the temperature of the reaction system after the reaction in step S105 to 86°C, adjust the stirring speed to 300 rpm, and uniformly drip shell reaction raw material 1 and shell reaction raw material 2 into the reaction system. The shell reaction raw material 1 is dripped within 1 hour and 30 minutes, and the shell reaction raw material 2 is dripped within 1 hour and 20 minutes. During the dripping process, the reaction temperature is controlled not to exceed 95°C. After all the dripping is completed, start timing, keep warm at 90°C for 2 hours, so that the shell reaction raw material 1 is polymerized to obtain the shell main structure, and the shell main structure is coated on the outside of the core structure.

[0148] S109: The reaction system after the reaction in step S108 was cooled to 45°C, and then 15g of a second isophorone diisocyanate (Covestro Bayhydur ultra 2759) and 3g of a second catalyst (bismuth isooctoate) were added. At the same time, the reaction temperature was controlled not to exceed 65°C. The mixture was then kept at 60°C for 1 hour to react and generate polyurethane structural units. The polyurethane structural units were grafted onto the main structure of the shell to obtain a water-based adhesive.

[0149] S110: Sodium hydroxide is added dropwise to the reaction system after the reaction in step S109 to adjust the pH to 7.2.

[0150] S111: Add 7 g of a cross-linking agent (7 g of adipic acid dihydrazide) to the reaction system obtained in step S110, cool to below 40° C., and pass through a 300-mesh sieve to obtain an emulsion of a water-based adhesive.

[0151] The preparation methods for the aqueous binder emulsions of Examples 9 to 14 were the same as those of Example 8, differing only in the amounts of the aromatic polyurea resin and the first isophorone diisocyanate used. All other raw material components and amounts were the same as those of Example 8. Specifically, the amounts of the aromatic polyurea resin and the first isophorone diisocyanate used in Examples 9 to 14 are shown in Table 2.

[0152] Table 2 Ratios of different dosages of Examples 9 to 14 and Example 8

[0153]

[0154] The preparation methods for the aqueous binder emulsions of Examples 15 to 18 were the same as those of Example 8, differing only in the amount of the first isophorone diisocyanate used. The other raw material components and amounts used were the same as those of Example 8. Specifically, the amounts of the first isophorone diisocyanate used in Examples 15 to 18 are shown in Table 3.

[0155] Table 3 Proportions of Examples 15 to 18 and Example 8 with different dosages

[0156]

[0157] The preparation methods for the aqueous binder emulsions of Examples 19 to 24 were the same as those of Example 8, differing only in the amounts of the hydroxylated acrylic emulsion and the second isophorone diisocyanate used. All other raw material components and amounts were the same as those of Example 8. Specifically, the amounts of the hydroxylated acrylic emulsion and the second isophorone diisocyanate used in Examples 19 to 24 are shown in Table 4.

[0158] Table 4 Proportions of Examples 19 to 24 and Example 8 with different dosages

[0159]

[0160] The preparation methods for the aqueous binder emulsions of Examples 25 to 28 were the same as those of Example 8, differing only in the amount of the second isophorone diisocyanate used. The other raw material components and amounts used were the same as those of Example 8. Specifically, the amounts of the second isophorone diisocyanate used in Examples 25 to 28 are shown in Table 5.

[0161] Table 5 Proportions of Examples 25 to 28 and Example 8 with different dosages

[0162]

[0163] Comparative Example 1

[0164] The emulsion of the aqueous binder of this comparative example was prepared by the following steps:

[0165] S101: 70 g of a first acrylic ester monomer (10 g of ethyl acrylate, 15 g of isooctyl acrylate, 15 g of hydroxyethyl acrylate, 10 g of lauryl methacrylate, and 20 g of butyl methacrylate), 21 g of a first acrylamide monomer (5 g of methacrylamide, 10 g of 2-acrylamido-2-methylpropanesulfonic acid, and 6 g of diacetone acrylamide), 11 g of a first acrylonitrile, and 70 g of deionized water were mixed, and the mixture was dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 5 minutes to obtain a core reaction raw material 1.

[0166] S102: 7 g of the first emulsifier (sodium dodecylsulfonate), 4 g of the first initiator (ammonium persulfate) and 80 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second core reaction raw material.

[0167] S103: 22% of the core reaction raw material 2 (i.e., 20 g of the core reaction raw material 2) was mixed with 200 g of deionized water, stirred at a stirring speed of 50 rpm, and heated to 82° C. to form a reaction system.

[0168] S104: The stirring speed of the reaction system in step S103 is adjusted to 300 rpm, and the core reaction raw material 1 and the remaining core reaction raw material 2 are uniformly added dropwise into the reaction system, wherein the core reaction raw material 1 is added within 45 minutes, and the remaining core reaction raw material 2 is added within 50 minutes. During the addition process, the reaction temperature is controlled not to exceed 95°C. After all the core reaction raw materials are added, the timing is started, and the temperature is kept at 90°C for 1 hour to allow the core reaction raw material 1 to be polymerized to obtain the core structure.

[0169] S105: 100 g of a second acrylic ester monomer (20 g of ethyl acrylate, 15 g of isooctyl acrylate, 25 g of hydroxyethyl acrylate, 20 g of lauryl methacrylate, and 20 g of butyl methacrylate), 39 g of a second acrylamide monomer (5 g of methacrylamide, 18 g of 2-acrylamido-2-methylpropanesulfonic acid, and 16 g of diacetone acrylamide), 14 g of a second acrylonitrile, 100 g of a hydroxylated acrylic emulsion (Dow Prospersetm 200), and 60 g of deionized water were mixed, and the mixture was dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 15 minutes to obtain a shell reaction raw material 1.

[0170] S106: 15 g of the second emulsifier (sodium dodecylsulfonate), 4 g of the second initiator (ammonium persulfate) and 80 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second shell reaction raw material.

[0171] S107: Adjust the temperature of the reaction system after the reaction in step S104 to 86°C, adjust the stirring speed to 300 rpm, and uniformly drip shell reaction raw material 1 and shell reaction raw material 2 into the reaction system. The shell reaction raw material 1 is dripped within 1 hour and 30 minutes, and the shell reaction raw material 2 is dripped within 1 hour and 20 minutes. During the dripping process, the reaction temperature is controlled not to exceed 95°C. After all the dripping is completed, start timing, keep warm at 90°C for 2 hours, so that the shell reaction raw material 1 is polymerized to obtain the shell main structure, and the shell main structure is coated on the outside of the core structure.

[0172] S108: The reaction system after the reaction in step S107 was cooled to 45°C, and then 20g of a second isophorone diisocyanate (Covestro Bayhydur ultra 2759) and 3g of a second catalyst (triethylenediamine) were added. At the same time, the reaction temperature was controlled not to exceed 65°C. The mixture was then kept at 60°C for 1 hour to react and generate polyurethane structural units. The polyurethane structural units were grafted onto the main structure of the shell to obtain a water-based adhesive.

[0173] S109: Lithium hydroxide is added dropwise to the reaction system after the reaction in step S108 to adjust the pH to 7.2.

[0174] S110: Add 5 g of a cross-linking agent (3 g of adipic acid dihydrazide and 2 g of aziridine) to the reaction system obtained in step S109, cool to below 40° C., and pass through a 300-mesh sieve to obtain an emulsion of a water-based adhesive.

[0175] Comparative Example 2

[0176] The emulsion of the aqueous binder of this comparative example was prepared by the following steps:

[0177] S101: 70 g of a first acrylic ester monomer (10 g of ethyl acrylate, 15 g of isooctyl acrylate, 15 g of hydroxyethyl acrylate, 10 g of lauryl methacrylate, and 20 g of butyl methacrylate), 21 g of a first acrylamide monomer (5 g of methacrylamide, 10 g of 2-acrylamido-2-methylpropanesulfonic acid, and 6 g of diacetone acrylamide), 11 g of a first acrylonitrile, 25 g of an aromatic polyurea resin (phenyl polyurea), and 70 g of deionized water are mixed, and the mixture is dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 5 minutes to obtain a core reaction raw material 1.

[0178] S102: 7 g of the first emulsifier (sodium dodecylsulfonate), 4 g of the first initiator (ammonium persulfate) and 80 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second core reaction raw material.

[0179] S103: 22% of the core reaction raw material 2 (i.e., 20 g of the core reaction raw material 2) was mixed with 200 g of deionized water, stirred at a stirring speed of 50 rpm, and heated to 82° C. to form a reaction system.

[0180] S104: The stirring speed of the reaction system in step S103 is adjusted to 300 rpm, and the core reaction raw material 1 and the remaining core reaction raw material 2 are uniformly added dropwise into the reaction system, wherein the core reaction raw material 1 is added within 45 minutes, and the remaining core reaction raw material 2 is added within 50 minutes. During the addition process, the reaction temperature is controlled not to exceed 95°C. After all the core reaction raw materials are added, the timer is started, and the temperature is kept at 90°C for 1 hour to allow the core reaction raw material 1 to be polymerized to obtain the core main structure.

[0181] S105: The reaction system after the reaction in step S104 was cooled to 45°C, and 10g of the first isophorone diisocyanate (Bayhydur ultra 2759, Covestro) and 3g of the first catalyst (triethylenediamine) were added to the reaction system while controlling the reaction temperature not to exceed 65°C. The reaction system was then kept at 60°C for 1 hour to react and generate polyurea structural units. The polyurea structural units were grafted onto the core main structure to obtain a core structure.

[0182] S106: 100 g of a second acrylic ester monomer (20 g of ethyl acrylate, 15 g of isooctyl acrylate, 25 g of hydroxyethyl acrylate, 20 g of lauryl methacrylate, and 20 g of butyl methacrylate), 39 g of a second acrylamide monomer (5 g of methacrylamide, 18 g of 2-acrylamido-2-methylpropanesulfonic acid, and 16 g of diacetone acrylamide), 14 g of a second acrylonitrile, and 60 g of deionized water were mixed, and the mixture was dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 15 minutes to obtain a shell reaction raw material 1.

[0183] S107: 15 g of the second emulsifier (sodium dodecylsulfonate), 4 g of the second initiator (ammonium persulfate) and 80 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second shell reaction raw material.

[0184] S108: Adjust the temperature of the reaction system after the reaction in step S105 to 86°C, adjust the stirring speed to 300 rpm, and uniformly drip shell reaction raw material 1 and shell reaction raw material 2 into the reaction system. The shell reaction raw material 1 is dripped within 1 hour and 30 minutes, and the shell reaction raw material 2 is dripped within 1 hour and 20 minutes. During the dripping process, the reaction temperature is controlled not to exceed 95°C. After all the dripping is completed, start timing, keep warm at 90°C for 2 hours, so that the shell reaction raw material 1 is polymerized to obtain a shell structure, and the shell structure is coated on the outside of the core structure, that is, a water-based adhesive is obtained.

[0185] S109: Lithium hydroxide is added dropwise to the reaction system after the reaction in step S108 to adjust the pH to 7.2.

[0186] S110: Add 5 g of a cross-linking agent (3 g of adipic acid dihydrazide and 2 g of aziridine) to the reaction system obtained in step S109, cool to below 40° C., and pass through a 300-mesh sieve to obtain an emulsion of a water-based adhesive.

[0187] Comparative Example 3

[0188] The emulsion of the aqueous binder of this comparative example was prepared by the following steps:

[0189] S101: 70 g of a first acrylic ester monomer (10 g of ethyl acrylate, 15 g of isooctyl acrylate, 15 g of hydroxyethyl acrylate, 10 g of lauryl methacrylate, and 20 g of butyl methacrylate), 21 g of a first acrylamide monomer (5 g of methacrylamide, 10 g of 2-acrylamido-2-methylpropanesulfonic acid, and 6 g of diacetone acrylamide), 11 g of a first acrylonitrile, and 70 g of deionized water were mixed, and the mixture was dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 5 minutes to obtain a core reaction raw material 1.

[0190] S102: 7 g of the first emulsifier (sodium dodecylsulfonate), 4 g of the first initiator (ammonium persulfate) and 80 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second core reaction raw material.

[0191] S103: 22% of the core reaction raw material 2 (i.e., 20 g of the core reaction raw material 2) was mixed with 200 g of deionized water, stirred at a stirring speed of 50 rpm, and heated to 82° C. to form a reaction system.

[0192] S104: The stirring speed of the reaction system in step S103 is adjusted to 300 rpm, and the core reaction raw material 1 and the remaining core reaction raw material 2 are uniformly added dropwise into the reaction system, wherein the core reaction raw material 1 is added within 45 minutes, and the remaining core reaction raw material 2 is added within 50 minutes. During the addition process, the reaction temperature is controlled not to exceed 95°C. After all the core reaction raw materials are added, the timing is started, and the temperature is kept at 90°C for 1 hour to allow the core reaction raw material 1 to be polymerized to obtain the core structure.

[0193] S105: 100 g of a second acrylic ester monomer (20 g of ethyl acrylate, 15 g of isooctyl acrylate, 25 g of hydroxyethyl acrylate, 20 g of lauryl methacrylate, and 20 g of butyl methacrylate), 39 g of a second acrylamide monomer (5 g of methacrylamide, 18 g of 2-acrylamido-2-methylpropanesulfonic acid, and 16 g of diacetone acrylamide), 14 g of a second acrylonitrile, and 60 g of deionized water were mixed, and the mixture was dispersed and stirred at 500 rpm in a disperser at room temperature and pressure for 15 minutes to obtain a shell reaction raw material 1.

[0194] S106: 15 g of the second emulsifier (sodium dodecylsulfonate), 4 g of the second initiator (ammonium persulfate) and 80 g of deionized water were mixed, and dispersed and emulsified at 6000 rpm using a high-speed disperser at room temperature and pressure for 1 minute to obtain the second shell reaction raw material.

[0195] S107: Adjust the temperature of the reaction system after the reaction in step S104 to 86°C, adjust the stirring speed to 300 rpm, and uniformly drip shell reaction raw material 1 and shell reaction raw material 2 into the reaction system. Shell reaction raw material 1 is dripped in 1 hour and 30 minutes, and shell reaction raw material 2 is dripped in 1 hour and 20 minutes. During the dripping process, the reaction temperature is controlled not to exceed 95°C. Start timing after all the dripping is completed, and keep warm at 90°C for 2 hours to polymerize the shell reaction raw material 1 to obtain a shell structure, and the shell structure is coated on the outside of the core structure to obtain a water-based adhesive.

[0196] S108: Lithium hydroxide is added dropwise to the reaction system after the reaction in step S107 to adjust the pH to 7.2.

[0197] S109: Add 5 g of a cross-linking agent (3 g of adipic acid dihydrazide and 2 g of aziridine) to the reaction system obtained in step S108, cool to below 40° C., and pass through a 300-mesh sieve to obtain an emulsion of a water-based adhesive.

[0198] Comparative Example 4

[0199] The preparation method of the water-based binder in this comparative example is the same as that in Example 1. The only difference between this comparative example and Example 1 is that the components and contents of the inner core reaction raw material 1 and the outer shell reaction raw material 1 are different.

[0200] Specifically, in this comparative example, the core reaction raw material one is composed of the following components: 70g of a first acrylate monomer (15g of ethyl acrylate, 20g of isooctyl acrylate, 15g of lauryl methacrylate, 20g of butyl methacrylate), 21g of a first acrylamide monomer (5g of methacrylamide, 10g of 2-acrylamido-2-methylpropanesulfonic acid, 6g of diacetone acrylamide), 11g of a first acrylonitrile, 25g of an aromatic polyurea resin (phenyl polyurea) and 70g of deionized water.

[0201] The shell reaction raw material 1 is composed of the following components: 100 g of a second acrylic ester monomer (30 g of ethyl acrylate, 20 g of isooctyl acrylate, 30 g of lauryl methacrylate, 20 g of butyl methacrylate), 39 g of a second acrylamide monomer (5 g of methacrylamide, 18 g of 2-acrylamido-2-methylpropanesulfonic acid, 16 g of diacetone acrylamide), 14 g of a second acrylonitrile, 100 g of a hydroxylated acrylic emulsion (Dow Prospersetm 200), and 60 g of deionized water.

[0202] Test example

[0203] The aqueous adhesives prepared in Examples 1 to 28 and Comparative Examples 1 to 4 were subjected to electrolyte resistance and flexibility tests, and the test results are shown in Table 6.

[0204] The electrolyte resistance test method is as follows: the prepared aqueous adhesive emulsion is poured into a Teflon mold and baked at 85°C for 24 hours to form a dry adhesive. Next, 3±0.2g (initial mass) of the dry adhesive is immersed in commercially available McLean L769384 electrolyte at 60°C. The dry adhesive mass is recorded before immersion. The adhesive is then removed every 24 hours and the surface electrolyte is wiped clean with dust-free paper. The adhesive mass is measured and recorded. The test continues for 30 days. The final measured dry adhesive mass is recorded as the final mass. The dissolved mass percentage of the dry adhesive after the final measurement is calculated as: (initial mass - final mass) ÷ initial mass × 100%.

[0205] The flexibility test method is as follows: Use a wet film applicator to apply a 200μm thick, 10cm wide, and 30cm long adhesive emulsion to the surface of the copper foil. Immediately place the foil in an oven and bake it at 60°C for 24 hours. The foil is then removed and cut into 16cm wide and 36cm long sections, completely enclosing the adhesive dry film. Flexibility testing is then performed using winding needles of varying diameters: 5mm, 4mm, 3mm, 2mm, 1.5mm, and 1mm, with the smallest needle diameter being 1mm. The procedure involves bending the copper foil with the dry film 180° around the winding needle and inspecting the outer edge of the bend for cracks. If no cracks are present, reduce the winding needle diameter, reposition the foil, and bend again until cracks appear on the outer edge of the dry film, or until a 1mm winding needle is used for testing. The diameter of the winding needle used when cracks appear is recorded as the flexibility test result. That is, the minimum winding needle diameter without cracks is the flexibility test result (for example, if cracks appear when using a 1.5mm winding needle, the flexibility test result is 2mm).

[0206] Table 6 Test results of examples and comparative examples

[0207]

[0208]

[0209] From the experimental data in Table 6, we can see that:

[0210] 1. Comparing Example 1 with Comparative Examples 1-3, it can be seen from the comparison of Comparative Example 2 and Comparative Example 3 that when the polyurea structural unit is introduced only into the core structure of the aqueous binder, the electrolyte resistance can be significantly improved, but the flexibility cannot be improved; comparing Comparative Example 1 and Comparative Example 3, it can be seen that when the polyurethane structural unit is introduced only into the shell structure of the aqueous binder, the flexibility can be significantly improved, but there is almost no improvement in the electrolyte resistance; comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that the electrolyte resistance of Example 1 is better than that of Comparative Example 2 and the flexibility of Example 1 is better than that of Comparative Example 1. Therefore, it can be seen that only by introducing the polyurea structural unit into the core structure of the aqueous binder and the polyurethane structural unit into the shell structure at the same time, can an aqueous binder with good flexibility and good electrolyte resistance be prepared, and the technical effect achieved when the polyurethane structural unit and the polyurea structural unit act synergistically is far better than the technical effects of the single polyurea structural unit and the single polyurethane structural unit.

[0211] 2. Comparing Examples 1 to 3, it can be seen that Example 1 has the best electrolyte resistance and flexibility. Therefore, when the isophorone diisocyanate is Covestro Bayhydur ultra 2759, the best technical effect is achieved. Therefore, it is most preferred that the first isophorone diisocyanate and the second isophorone diisocyanate are Covestro Bayhydur ultra 2759.

[0212] 3. Comparing Examples 8 to 14, the electrolyte resistance of Examples 10, 9, 8, 11, 12, and 13 gradually improved, while the electrolyte resistance of Example 14 decreased significantly compared to Example 13. This shows that as the percentage of the mass of the aromatic polyurea resin to the total mass of the first acrylate monomer, the first acrylamide monomer, and the first acrylonitrile increases, that is, as the proportion of the polyurea structural unit in the aqueous binder increases, the electrolyte resistance of the aqueous binder first increases and then decreases rapidly. Therefore, it is necessary to control the proportion of the polyurea structural unit in the aqueous binder within a certain range. Preferably, the mass of the aromatic polyurea resin is 15% to 30% of the total mass of the first acrylate monomer, the first acrylamide monomer, and the first acrylonitrile, and more preferably, the mass of the aromatic polyurea resin is 20% to 30% of the total mass of the first acrylate monomer, the first acrylamide monomer, and the first acrylonitrile.

[0213] 4. Comparing Examples 8 and 15 to 18, the electrolyte resistance of Examples 15, 8, 16, and 17 gradually increased, while the electrolyte resistance of Example 18 decreased significantly compared to Example 17. It can be seen that when the amount of the first isophorone diisocyanate is the same, as the amount of the aromatic polyurea resin increases, the electrolyte resistance of the aqueous binder first increases and then decreases rapidly. Therefore, it is necessary to control the mass ratio of the first isophorone diisocyanate to the aromatic polyurea resin within a certain range. Preferably, the first isophorone diisocyanate: aromatic polyurea resin is 1: (2~3), and more preferably, the first isophorone diisocyanate: aromatic polyurea resin is 1: (2.5~3).

[0214] 5. Comparing Example 8 and Examples 19-24, the flexibility of Example 19, Example 20, Example 8, and Example 21 gradually increases, and the flexibility of Example 23 and Example 24 decreases relative to Example 21 and Example 22. It can be seen that as the mass of the hydroxyl acrylic emulsion as a percentage of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile increases, that is, the proportion of the polyurethane structural unit in the aqueous binder increases, the flexibility of the aqueous binder first increases and then decreases. Therefore, it is necessary to control the proportion of the polyurethane structural unit in the aqueous binder within a certain range. Preferably, the mass of the hydroxyl acrylic emulsion is 12% to 80% of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile, and more preferably, the mass of the hydroxyl acrylic emulsion is 30% to 40% of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile.

[0215] 6. Comparing Example 8 with Examples 25 to 28, the electrolyte resistance of Example 25, Example 8, Example 26, and Example 27 gradually increased, while the electrolyte resistance of Example 28 decreased significantly compared with Example 27. It can be seen that when the amount of the second isophorone diisocyanate is the same, as the amount of the hydroxylated acrylic emulsion increases, the flexibility of the aqueous binder first increases and then decreases. Therefore, it is necessary to control the mass ratio of the second isophorone diisocyanate to the hydroxylated acrylic emulsion within a certain range, and preferably the second isophorone diisocyanate: hydroxylated acrylic emulsion is 1: (5~10).

[0216] 7. Comparing Example 1 with Comparative Example 4, the electrolyte resistance and flexibility of Comparative Example 4 are worse than those of Example 1. This shows that when neither the first acrylate monomer nor the first acrylamide monomer contains a hydroxyl group, and neither the second acrylate monomer nor the second acrylamide monomer contains a hydroxyl group, the generated polyurea structural unit cannot be grafted onto the main structure of the core and exists independently in the system. The generated polyurethane structural unit cannot be grafted onto the main structure of the shell and exists independently in the system. The polyurea structural unit and the polyurethane structural unit free in the emulsion cannot improve the electrolyte resistance and flexibility of the water-based adhesive. Only when the polyurea structural unit is grafted onto the main structure of the core and the polyurethane structural unit is grafted onto the main structure of the shell can the electrolyte resistance and flexibility of the water-based adhesive be effectively improved.

[0217] Thus far, the technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A water-based adhesive, characterized in that The water-based adhesive comprises a core structure and a shell structure, wherein the shell structure is coated on the outside of the core structure. The core structure includes a core main structure and a polyurea structural unit obtained by polymerizing a first acrylate monomer, a first acrylamide monomer, and a first acrylonitrile, wherein the polyurea structural unit is grafted onto the core main structure, wherein the first acrylate monomer and / or the first acrylamide monomer contains a hydroxyl group; The polyurea structural unit is generated by reacting a polyurea reaction raw material with the core main structure, the polyurea reaction raw material includes an aromatic polyurea resin and a first isophorone diisocyanate, the mass of the aromatic polyurea resin is 15% to 30% of the total mass of the first acrylate monomer, the first acrylamide monomer, and the first acrylonitrile, and the mass ratio of the first isophorone diisocyanate to the aromatic polyurea resin is 1:(2-3); The shell structure includes a shell main body structure and a polyurethane structural unit obtained by polymerizing a second acrylate monomer, a second acrylamide monomer, and a second acrylonitrile, wherein the polyurethane structural unit is grafted onto the shell main body structure, wherein the second acrylate monomer and / or the second acrylamide monomer contains a hydroxyl group; The polyurethane structural unit is generated by reacting a polyurethane reaction raw material with the main structure of the shell. The polyurethane reaction raw material includes a hydroxyl acrylic emulsion and a second isophorone diisocyanate. The mass of the hydroxyl acrylic emulsion is 12% to 50% of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile, and the mass ratio of the second isophorone diisocyanate to the hydroxyl acrylic emulsion is 1: (5 to 10).

2. A method for preparing a water-based adhesive, for preparing the water-based adhesive according to claim 1, characterized in that: The preparation method comprises the following steps: S1: provides the kernel main structure; S2: Grafting polyurea structural units onto the core main structure to obtain a core structure; S3: covering the outer shell main structure on the outer side of the core structure; S4: Grafting the polyurethane structural unit onto the main structure of the shell to obtain a water-based adhesive.

3. The method for preparing the aqueous binder according to claim 2, wherein: Step S1 specifically includes: reacting a first core reaction raw material with a second core reaction raw material to obtain a core main structure, wherein the first core reaction raw material includes a mixture of a first acrylate monomer, a first acrylamide monomer, a first acrylonitrile, and water, and the second core reaction raw material includes a mixture of a first emulsifier, a first initiator, and water; And / or, step S2 specifically includes: mixing a reaction system having the core main structure with a polyurea reaction raw material and a first catalyst to react, so as to graft polyurea structural units onto the core main structure to obtain the core structure, wherein the first catalyst is used to catalyze the reaction of the polyurea reaction raw material to form the polyurea structural units; And / or, step S3 specifically includes: mixing and reacting the reaction system that produces the core structure with a first shell reaction raw material and a second shell reaction raw material to obtain a shell main structure, and coating the outer surface of the core structure with the shell main structure, wherein the first shell reaction raw material comprises a mixture of a second acrylate monomer, a second acrylamide monomer, a second acrylonitrile, and water, and the second shell reaction raw material comprises a mixture of a second emulsifier, a second initiator, and water, wherein the mass of the second emulsifier is greater than the mass of the first emulsifier in the raw materials used in the reaction system that produces the core structure; And / or, step S4 specifically includes: mixing a reaction system having a shell main structure with a polyurethane reaction raw material and a second catalyst to react, so as to graft polyurethane structural units onto the shell main structure to obtain a water-based adhesive, wherein the shell main structure in the reaction system is coated on the outside of the core structure, and the second catalyst is used to catalyze the reaction of the polyurethane reaction raw material to generate polyurethane structural units.

4. The method for preparing the aqueous binder according to claim 3, wherein: The polyurea reaction raw materials include an aromatic polyurea resin and a first isophorone diisocyanate. Step S2 specifically includes: first uniformly mixing the reaction system having the core main structure with the aromatic polyurea resin, and then mixing and reacting the mixture with the first isophorone diisocyanate and the first catalyst to obtain a core structure grafted with polyurea structural units; And / or, the polyurethane reaction raw materials include hydroxy acrylic emulsion and second isophorone diisocyanate, and step S4 specifically includes: first uniformly mixing the reaction system having the shell main structure with the hydroxy acrylic emulsion, and then mixing and reacting with the second isophorone diisocyanate and the second catalyst to obtain a shell structure grafted with polyurethane structural units.

5. The method for preparing the aqueous binder according to claim 3, wherein: The polyurea reaction raw materials include an aromatic polyurea resin and a first isophorone diisocyanate. The aromatic polyurea resin is added to the first core reaction raw material and uniformly mixed with the first core reaction raw material in step S1. Step S2 specifically includes: mixing the reaction system having the core main structure with the first isophorone diisocyanate and the first catalyst to react to obtain a core structure grafted with polyurea structural units; And / or, the polyurethane reaction raw materials include a hydroxylated acrylic emulsion and a second isophorone diisocyanate, the hydroxylated acrylic emulsion is added to the shell reaction raw material one and uniformly mixed with the shell reaction raw material one in step S3, and step S4 specifically includes: mixing the reaction system having the shell main structure with the second isophorone diisocyanate and the second catalyst for reaction to obtain a shell structure grafted with a polyurethane structural unit.

6. The method for preparing the aqueous binder according to claim 5, wherein: Step S1 specifically includes: S11: providing a mixture of a first acrylate monomer, a first acrylamide monomer, a first acrylonitrile, an aromatic polyurea resin, and a first solvent, to obtain a first core reaction raw material; S12: providing a mixture of a first emulsifier, a first initiator, and a second solvent, water, to obtain a second core reaction raw material; S13: taking a portion of the second core reaction raw material and mixing it with the third solvent water, slowly stirring, and heating it to 80° C. to 90° C. to form a reaction system; S14: uniformly adding the core reaction raw material 1 and the remaining core reaction raw material 2 to the reaction system of step S13, and maintaining the temperature at a first temperature for a first preset time after the addition is completed, to obtain the core main structure; And / or, step S2 specifically includes: cooling the reaction system having the core main structure to 45° C. to 50° C., then adding the first isophorone diisocyanate and the first catalyst to the reaction system, maintaining the temperature at a second temperature for a second preset time, and grafting polyurea structural units onto the core main structure to obtain a core structure; And / or, step S3 specifically includes: S31: providing a mixture of a second acrylate monomer, a second acrylamide monomer, a second acrylonitrile, a hydroxyl acrylic emulsion, and a fourth solvent, water, to obtain a first shell reaction raw material; S32: providing a mixture of a second emulsifier, a second initiator, and a fifth solvent, water, to obtain a second shell reaction raw material; S33: adjusting the temperature of the reaction system in which the core structure is generated to 80° C. to 90° C., then dripping the shell reaction raw material 1 and the shell reaction raw material 2 into the reaction system at a uniform rate, and maintaining the reaction system at a third temperature for a third preset time after the dripping is complete; And / or, step S4 specifically includes: cooling the reaction system having the shell main structure to 45°C~50°C, then adding the second isophorone diisocyanate and the second catalyst to the reaction system, keeping the temperature at a fourth temperature for a fourth preset time, and grafting a polyurethane structural unit on the shell main structure to obtain a water-based adhesive.

7. The method for preparing the aqueous binder according to claim 6, wherein: In step S13, 5% to 30% of the second core reaction raw material is mixed with the third solvent water; And / or, in step S14, before the core reaction raw material 1 and the core reaction raw material 2 are added dropwise, the rotation speed of the reaction system in step S13 is adjusted to 200 rpm to 400 rpm; and / or, in step S14, controlling the reaction temperature to not exceed 95° C. during the process of dropwise adding the core reaction raw material 1 and the core reaction raw material 2; and / or, in step S14, the core reaction raw material 1 and the core reaction raw material 2 are dripped within 0.5 h to 1 h; And / or, in step S14, the first temperature is 88° C. to 92° C., and the first preset time is 1 hour to 1.5 hours; and / or, in step S2, controlling the reaction temperature to not exceed 65° C. during the process of adding the first isophorone diisocyanate and the first catalyst; and / or, in step S2, the second temperature is 58°C to 62°C, and the second preset time is 1 hour to 1.5 hours; And / or, in step S33, before the shell reaction raw material 1 and the shell reaction raw material 2 are added dropwise, the rotation speed of the reaction system in which the core structure is generated is adjusted to 200 rpm to 400 rpm; and / or, in step S33, controlling the reaction temperature to not exceed 95° C. during the process of dropwise adding the shell reaction raw material 1 and the shell reaction raw material 2; and / or, in step S33, the shell reaction raw material 1 and the shell reaction raw material 2 are dripped within 1 hour to 2 hours; And / or, in step S33, the third temperature is 88°C to 92°C, and the third preset time is 1.5h to 2.5h; and / or, in step S4, controlling the reaction temperature to not exceed 65° C. during the process of adding the second isophorone diisocyanate and the second catalyst; And / or, in step S4, the fourth temperature is 58° C. to 62° C., and the fourth preset time is 1 hour to 1.5 hours.

8. The method for preparing the water-based binder according to claim 6, wherein: In step S11, the core reaction raw material 1 includes the following components in parts by weight: 50-150 parts of a first acrylate monomer, 10-50 parts of a first acrylamide monomer, 5-20 parts of a first acrylonitrile, 20-50 parts of an aromatic polyurea resin, and 50-150 parts of a first solvent, water; And / or, in step S12, the second core reaction raw material comprises the following components in parts by weight: 5-10 parts of a first emulsifier, 2-5 parts of a first initiator, and 50-200 parts of a second solvent, water; And / or, in step S13, the weight portion of the third solvent water is 100-200 parts; And / or, in step S2, the weight portion of the first isophorone diisocyanate is 5 to 20 parts, and the weight portion of the first catalyst is 2 to 5 parts; And / or, in step S31, the shell reaction raw material 1 includes the following components in parts by weight: 100-300 parts of a second acrylate monomer, 20-80 parts of a second acrylamide monomer, 5-30 parts of a second acrylonitrile, 50-100 parts of a hydroxylated acrylic emulsion, and 50-100 parts of a fourth solvent, water; And / or, in step S32, the shell reaction raw material 2 includes the following components in parts by weight: 10-20 parts of a second emulsifier, 2-5 parts of a second initiator, and 50-100 parts of a fifth solvent, water; And / or, in step S4, the weight portion of the second isophorone diisocyanate is 5 to 20 parts, and the weight portion of the second catalyst is 2 to 5 parts.

9. The method for preparing the aqueous binder according to any one of claims 4 to 8, characterized in that: The first acrylate monomer and / or the first acrylamide monomer contains a hydroxyl group, and the second acrylate monomer and / or the second acrylamide monomer contains a hydroxyl group; and / or, the mass of the aromatic polyurea resin is 15% to 30% of the total mass of the first acrylate monomer, the first acrylamide monomer, and the first acrylonitrile, and the mass ratio of the first isophorone diisocyanate to the aromatic polyurea resin is 1:(2-3); and / or, the mass of the hydroxylated acrylic emulsion is 12% to 80% of the total mass of the second acrylic ester monomer, the second acrylamide monomer, and the second acrylonitrile, and the mass ratio of the second isophorone diisocyanate to the hydroxylated acrylic emulsion is 1:(5-10); And / or, the aromatic polyurea resin is in powder form.

10. The method for preparing the water-based adhesive according to claim 9, characterized in that: The first acrylic acid ester monomer and / or the second acrylic acid ester monomer include one or more of hydroxyethyl acrylate, hydroxymethyl acrylate, and hydroxyethyl methacrylate; And / or, the first acrylamide monomer and / or the second acrylamide monomer include one or more of N-hydroxymethyl acrylamide and N-hydroxyethyl acrylamide; And / or, the mass of the hydroxy acrylic emulsion is 30% to 40% of the total mass of the second acrylate monomer, the second acrylamide monomer, and the second acrylonitrile.

11. The method for preparing the water-based adhesive according to claim 10, characterized in that: The first acrylic acid ester monomer and / or the second acrylic acid ester monomer further comprises one or more of ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isooctyl acrylate, lauryl methacrylate, butyl methacrylate, and n-octyl methacrylate; And / or, the first acrylamide monomer and / or the second acrylamide monomer further comprises one or more of methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, methyl-acyloxyethyltrimethylammonium chloride, diacetone acrylamide, and N-butoxymethyl acrylamide; and / or, the first emulsifier and the second emulsifier are respectively selected from one or more of sodium p-styrene sulfonate, sodium vinyl sulfonate and sodium dodecyl sulfonate; And / or, the first initiator and the second initiator are persulfate.

12. The method for preparing the water-based adhesive according to claim 11, characterized in that: The persulfate includes one or more of ammonium persulfate, potassium persulfate and sodium persulfate.

13. The method for preparing the aqueous binder according to any one of claims 4 to 8, characterized in that: The aromatic polyurea resin is selected from one or more of phenyl polyurea and dichlorophenyl polyurea; and / or, the first isophorone diisocyanate and the second isophorone diisocyanate are each selected from one or more of Covestro Bayhydur ultra 2759, Covestro Bayhydur 2858 XP, and Covestro Bayhydur ultra 401-70 MPA / X; And / or, the hydroxylated acrylic emulsion is selected from one or more of Dow Prospersetm 200, Huaguoshan Houshan 0880 and DSM Neocryl XK-540; And / or, the first catalyst and the second catalyst are respectively selected from one or more of bismuth isooctanoate, benzoyl chloride and triethylenediamine.

14. Use of the aqueous binder according to claim 1 as a negative electrode binder in a lithium ion battery.

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