A polyacrylate microsphere material, a preparation method and application thereof

Abstract

This invention provides a polyacrylate microsphere material, its preparation method, and its applications, relating to the field of polymer materials technology. Specifically, the polymer monomers of the polyacrylate microsphere material include a first monomer, a second monomer, and a third monomer; wherein the first monomer is an acrylamide compound, the second monomer is an acrylate compound, and the third monomer is an olefinic sulfonate; the D50 particle size of the polyacrylate microsphere material is 1 μm to 40 μm, and when the D50 particle size is 1 μm to 10 μm, the D50 particle size exhibits a unimodal distribution. The microsphere material of this invention has good adhesion and film-forming properties, and its particle size is controllable. Its raw material formulation and preparation process are simple, and the reaction process is short. It can be used directly as a battery separator binder or as a core material for complex polymer materials, showing good application prospects.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a polyacrylate microsphere material, its preparation method, and its application. Background Technology

[0002] In recent years, technological innovations in the field of battery separators have emerged continuously. Among them, the application of polymer microspheres as separator coating materials is particularly noteworthy. It not only provides a new way to improve the performance of battery separators, but also opens up new directions for optimizing the overall performance of batteries.

[0003] Regarding micron-sized core-shell polymer microspheres, especially those with a soft core and hard shell structure, the applicant, through extensive experimental research, discovered that the challenge lies in the preparation of "micron-sized soft spheres" used as seed (core) emulsions. For example, the previous application CN202211325940.9 discloses a method for preparing large-diameter core-shell polymer particles using improved aqueous suspension polymerization and / or emulsion polymerization. When used in battery separator bonding, this method can improve cell hardness and suppress cell deformation without affecting permeability; however, this preparation method still suffers from drawbacks such as complex formulations, difficulty in controlling particle size, and long reaction times.

[0004] Therefore, the limitations of polymer microsphere products in the widespread adoption of battery separators include, but are not limited to: Firstly, current processes involve complex formulations and long reaction times, resulting in high production costs. Furthermore, the mixing and reaction processes in polymerization require sophisticated equipment (such as high-speed homogenizers). Secondly, the resulting polymer microspheres suffer from difficulty in controlling particle size and uneven particle size distribution, potentially leading to a series of defects. For instance, the required thickness of the polymer microsphere coating varies depending on the cell design; therefore, the difficulty in controlling the particle size results in products that are difficult to adapt to different cell designs and have coating thicknesses that do not meet requirements. Additionally, uneven particle size distribution leads to poor coating consistency, consequently causing performance fluctuations in both the separator and the cell.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The primary objective of this invention is to provide a polyacrylate microsphere material that, while meeting the essential requirements for adhesion and film-forming properties in the field of battery separators, also possesses advantages such as simple formulation, convenient particle size control, uniform particle size distribution, and short reaction time, thus demonstrating good practicality and promising prospects for widespread application.

[0007] The second objective of this invention is to provide a method for preparing the polyacrylate microsphere material described above. This method can prepare micron-sized soft spheres using a common emulsion polymerization apparatus, without the need for high-speed homogenization equipment, and is low in cost and has a simple process.

[0008] A third objective of this invention is to provide a core-shell polymer microsphere material, which, when further modified with the polyacrylate microsphere material as the core layer, yields a composite microsphere material with other functional or advantageous characteristics.

[0009] The fourth objective of this invention is to provide a secondary battery.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0011] A polyacrylate microsphere material, wherein the polymer monomers include a first monomer, a second monomer, and a third monomer;

[0012] Wherein, the first monomer is an acrylamide compound, the second monomer is an acrylate compound, and the third monomer is an olefinic sulfonate;

[0013] The D50 particle size of the polyacrylate microsphere material is 1μm~40μm, and when the D50 particle size is 1μm~10μm, the D50 particle size exhibits a unimodal distribution.

[0014] A method for preparing the polyacrylate microsphere material, wherein when the particle size of the polyacrylate microsphere material is ≤10μm, an intermittent method is used; and when the particle size of the polyacrylate microsphere material is ≥10μm, a semi-continuous method is used.

[0015] The batch method includes the following steps: preparing a reaction substrate containing polymeric monomers, adding an initiator, and then maintaining the temperature to react until the polyacrylate microsphere material is obtained;

[0016] The semi-continuous method includes the following steps: preparing a reaction base solution containing a second monomer, preparing an addition solution containing a first monomer, a third monomer and an initiator; gradually adding the addition solution to the reaction base solution, and then maintaining the temperature to react until the polyacrylate microsphere material is obtained.

[0017] A core-shell polymer microsphere material, wherein the core layer comprises the polyacrylate microsphere material described above.

[0018] A secondary battery comprising the aforementioned polyacrylate microsphere material.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) This invention provides an emulsion-state polyacrylate microsphere material with good adhesion. Its D50 particle size exhibits a distinct unimodal distribution (especially when D50 is in the range of 1~10 μm), and it has a glass transition temperature below room temperature. After drying, it yields an adhesive film. The microsphere material of this invention is stored in the form of an aqueous emulsion and can be used directly as a binder or for subsequent modification (e.g., as a seed emulsion for "soft core, hard shell" microspheres).

[0021] (2) This invention uses specific monomers and designs the monomer ratio, and utilizes the difference in solubility of monomers and polymers in water to prepare the product based on the "water-based dispersion polymerization" method. The preparation process has a simple formulation, easy-to-control product particle size, short reaction time, and no special requirements for equipment, and has good prospects for mass production. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 The particle size distribution curve of Embodiment 1 of the present invention is provided;

[0024] Figure 2 The particle size distribution curve of Embodiment 42 of the present invention is provided;

[0025] Figure 3 SEM images of Embodiment 1 of the present invention are provided;

[0026] Figure 4 A DSC diagram of Embodiment 1 of the present invention is provided. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] A first aspect of the present invention is to provide a polyacrylate microsphere material, wherein the polymer monomers include a first monomer, a second monomer, and a third monomer; wherein the first monomer is an acrylamide compound, the second monomer is an acrylate compound, and the third monomer is an olefinic sulfonate.

[0029] Furthermore, this invention specifies that the D50 particle size of the polyacrylate microsphere material is 1 μm to 40 μm, and when the D50 particle size is 1 μm to 10 μm, the D50 particle size exhibits a unimodal distribution. Specifically, when the D50 particle size is 1 μm to 10 μm, the microsphere material of this invention exhibits a good unimodal distribution, and good symmetry can be seen in the particle size distribution diagram. The peak value of the particle size distribution is approximately 4.9 μm, the particle size distribution width is approximately 0.97, and the peak shape exhibits good normality. In some other embodiments, when the D50 particle size is 10 μm to 40 μm, the D50 particle size also exhibits a unimodal distribution, but the characteristics of the peak shape may not be as good as the normality performance when the D50 particle size is 1 μm to 10 μm.

[0030] Furthermore, the polyacrylate microsphere material of the present invention has a glass transition temperature below room temperature, and in some optional embodiments, the Tg of the polyacrylate microsphere material is 0~10℃.

[0031] In this invention, the acrylamide compound used as the first monomer has the following characteristics: the compound itself is easily soluble in water, but its polymerization product is insoluble in water; its function is to precipitate insoluble active reaction sites in the form of liquid phase nucleation during the polymerization process, which serves as the basis for the growth and formation of microspheres.

[0032] In a preferred embodiment, the acrylamide compound includes one or both of diacetone acrylamide and N-isopropylacrylamide; in some optional embodiments, the acrylamide compound (based on the previous selection) further includes N,N'-methylenebisacrylamide, which serves to improve the crosslinking degree of the microsphere material; in some optional embodiments, when N,N'-methylenebisacrylamide is used, its mass ratio in the first monomer is 0.5% to 3%, including but not limited to any one or any two of 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, and 3%.

[0033] In this invention, the acrylate compound used as the second monomer has the following characteristics: the compound itself is readily soluble in water or partially soluble in water, but its polymerization product is insoluble in water. Considering the extremely wide range of acrylate compounds to choose from, this invention further limits the acrylate compound to contain at least one ether bond. The role of the second monomer is to impart adhesion and flexibility to the microsphere material. Furthermore, the ether bond structure can impart good water-oil balance to the microspheres, which helps to improve the stability of the microsphere emulsion.

[0034] In a preferred embodiment, the acrylate compound includes at least one of diethylene glycol monoethyl ether acrylate, tetrahydrofuran acrylate, docosyl polyoxyethylene ether methacrylate, cyclotrimethylolpropane methyl acetal acrylate, and 2-phenoxyethyl acrylate.

[0035] The alkene-bonded sulfonate used as the third monomer in this invention can be understood as an organic sulfonate containing an alkenyl structure; its function is to improve the surface activity of the microsphere material, enabling it to be well dispersed in water, thereby maintaining the stability of the emulsion.

[0036] In a preferred embodiment, the third monomer includes at least one of sodium p-styrene sulfonate, sodium methacrylate sulfonate, and a lithium or sodium salt of 2-acrylamide-2-methylpropanesulfonic acid.

[0037] In a preferred embodiment, the polymerizing monomer further includes a fourth monomer, which is a second acrylate compound containing at least one terminal carboxyl group. In this invention, the fourth monomer serves to improve the adhesive properties of the microsphere material.

[0038] In actual production applications, the fourth monomer is usually used to partially replace the second monomer. In some optional embodiments, the ratio of the fourth monomer to the second monomer is (5%~25%):(75%~95%), including but not limited to any one or any two of the following ratio ranges: 5%:95%, 8%:92%, 10%:90%, 15%:85%, 20%:80%, 22%:78%, and 25%:75%.

[0039] In a more preferred embodiment, the fourth monomer includes at least one of carboxyethyl acrylate, carboxypropyl acrylate, or carboxybutyl acrylate.

[0040] As a preferred embodiment, the amount of the polymeric monomer is: the mass ratio of the second monomer to the polymeric monomer is 50% to 80%, including but not limited to any one or any two of 50%, 55%, 60%, 65%, 70%, 75%, and 80%.

[0041] As a preferred embodiment, the amount of the polymerizable monomer is as follows: the mass ratio of the third monomer to the first monomer is 2% to 20%, including but not limited to any one or any two of the following values: 2%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18%, and 20%.

[0042] In a preferred embodiment, the polyacrylate microsphere material is prepared by polymerization of the polymeric monomer, initiator, and dispersant; wherein the initiator includes persulfate, and the dispersant includes, but is not limited to, at least one of polyvinyl alcohol, polyvinylpyrrolidone, or polyoxyethylene ether. It should be noted that the microsphere material prepared in this invention is an emulsion-like material. By adding a water-soluble polymer as a dispersant, the dispersion of the microsphere material in water can be promoted, further improving the stability of the emulsion.

[0043] In a more preferred embodiment, the initiator is added at a rate of 0.5% wt to 1.0% wt of the total monomers. It is understood that when the fourth monomer is also used in this invention, the amount of initiator added is based on the total amount of all monomers, including the fourth monomer.

[0044] In a more preferred embodiment, the mass ratio of the dispersant to the polymeric monomer is 1% to 10%.

[0045] A second aspect of the present invention is to provide a method for preparing polyacrylate microspheres as described in the first aspect.

[0046] In this invention, the preparation process is selected based on the desired particle size of the microsphere material. Specifically, when the particle size of the polyacrylate microsphere material is ≤10μm, an intermittent method is used. In this method, the number of initial active sites in the initial reaction system is relatively large, and the monomer tends to polymerize at different active sites. Therefore, the increase in microsphere size is relatively small, and it is suitable for preparing microsphere materials with a particle size not exceeding 10μm. Correspondingly, when the particle size of the polyacrylate microsphere material is ≥10μm, a semi-continuous method is used. In this method, the number of initial active sites in the reaction system is relatively small, and the monomer tends to polymerize at the same active site. Therefore, the increase in microsphere size is relatively large. Furthermore, the size of the microspheres can be adjusted by controlling the rate of quantitative feeding; that is, the faster the feeding rate, the smaller the microsphere size, and vice versa. Thus, the semi-continuous method is suitable for preparing microsphere materials with a particle size of 10μm to 40μm.

[0047] (i) The batch method includes the following steps: preparing a reaction substrate containing polymer monomers, adding an initiator, and then keeping the reaction at a constant temperature until the polyacrylate microsphere material is obtained.

[0048] In a preferred embodiment, the reaction substrate includes the polymeric monomer, the dispersant, and deionized water; in some more preferred embodiments, the solid content of the reaction substrate is 15% to 30%.

[0049] As a preferred embodiment, in this invention, the preparation of any of the reaction base liquids can be assisted by means of oscillation, stirring, shaking, centrifugation, ultrasound, heating, etc., which helps to accelerate dispersion and obtain a relatively uniform dispersion system.

[0050] In a preferred embodiment, the heat preservation reaction is carried out in a protective gas environment, which includes, but is not limited to, nitrogen, helium, neon, argon, etc. In some more preferred embodiments, the reaction base liquid is placed in the protective gas environment for a period of time until there is no oxygen or air in the reaction equipment, container and reaction base liquid, and then the initiator is added and the polymerization reaction begins. The above-mentioned time period can be implemented as 0.5h to 2h.

[0051] In a preferred embodiment, the temperature of the heat preservation reaction is 70℃~80℃, and the heat preservation reaction time is 3h~5h.

[0052] (ii) The semi-continuous method includes the following steps: preparing a reaction base liquid containing a second monomer, preparing an addition liquid containing a first monomer, a third monomer and an initiator; gradually adding the addition liquid to the reaction base liquid, and then keeping it at a constant temperature to obtain the polyacrylate microsphere material.

[0053] In a preferred embodiment, the reaction substrate comprises a second monomer, a dispersant, and deionized water, and the addition liquid comprises a first monomer, a third monomer, an initiator, and deionized water. In some optional embodiments, the amount of water added is adjusted to a solid content of 15% to 30% based on the total amount of reactants. Furthermore, it should be noted that, for the semi-continuous method, when the polymerization monomer also includes a fourth monomer, the fourth monomer is added to the reaction substrate, not the addition liquid.

[0054] In a preferred embodiment, the addition time of the dosing solution is 0.5h to 2h, and the addition rate is uniform.

[0055] In a preferred embodiment, the temperature of the heat preservation reaction is 70℃~80℃, and the heat preservation reaction time is 3h~5h; that is, the semi-continuous method has the same reaction conditions as the batch method. However, the actual polymerization reaction time in the semi-continuous method should be the sum of the heat preservation time and the addition time of the added liquid.

[0056] A third aspect of this invention provides a core-shell polymer microsphere material, wherein the core layer comprises the polyacrylate microsphere material as described in the first aspect. It is noteworthy that the emulsion-state polyacrylate microsphere material of this invention can be directly used for bonding battery separators; however, it can also be used as a polymerization substrate to synthesize emulsions with more bonding functions, particularly by using the polyacrylate microsphere material as the core layer to synthesize novel core-shell or core-shell-like polymer materials. This invention does not impose any limitations on the raw materials, structure, or preparation process of the core-shell polymer microsphere material; any spherical polymer material prepared from the polyacrylate microsphere material as described in the first aspect can be considered an embodiment of this aspect.

[0057] A fourth aspect of the present invention provides a secondary battery comprising the polyacrylate microsphere material as described in the first aspect. It is understood that the secondary battery should include positive and negative electrodes, an electrolyte, a separator, and other necessary or non-essential functional elements or packaging components, which can be arbitrarily selected and combined by those skilled in the art. The polyacrylate microsphere material is typically used as a component in the separator, primarily as a binding functional component in the separator coating; when the separator of the secondary battery contains the polyacrylate microsphere material, the secondary battery can be considered an embodiment of this aspect.

[0058] Example 1

[0059] This embodiment uses an intermittent method to synthesize microsphere materials. The specific steps are as follows:

[0060] (1) Preparation of reaction materials: first monomer (diacetone acrylamide), second monomer (diethylene glycol monoethyl ether acrylate, accounting for 80 wt.% of the total monomers), third monomer (sodium p-styrene sulfonate, accounting for 20 wt.% of the first monomers), dispersant (polyvinyl alcohol 1799, accounting for 20 wt.% of the total monomers), initiator (potassium persulfate).

[0061] (2) Add all materials except the initiator into the reaction apparatus. The reaction apparatus is a 500mL four-necked flask with a stirring device, which is connected to a condenser, an electric stirrer and a nitrogen tube respectively. Add a metered amount of deionized water and control the amount of water so that the solid content of the product is 20%±1%. Then start stirring.

[0062] (3) Introduce nitrogen into the reaction apparatus, and raise the temperature of the reaction apparatus to 75°C after 1 hour;

[0063] (4) Add initiator, the total amount of material is 300g; after keeping the reaction at the temperature for 4h, cool and collect the material to obtain a white and uniform emulsion.

[0064] Example 2: Basically the same as Example 1, except that the first monomer is replaced with N-isopropylacrylamide.

[0065] Example 3: Basically the same as Example 1, except that the first monomer is replaced with diacetone acrylamide and N-isopropylacrylamide in a mass ratio of 1:1.

[0066] Example 4: Basically the same as Example 1, except that the first monomer is replaced with diacetone acrylamide and N,N'-methylenebisacrylamide in a mass ratio of 97:3.

[0067] Example 5: Basically the same as Example 4, except that the mass ratio of the two is 98:2.

[0068] Example 6: Basically the same as Example 4, except that the mass ratio of the two is 99:1.

[0069] Example 7: Basically the same as Example 4, except that the mass ratio of the two is 99.5:0.5.

[0070] Example 8: Basically the same as Example 1, except that the second monomer is replaced with tetrahydrofuran acrylate.

[0071] Example 9: Basically the same as Example 1, except that the second monomer is replaced with docosyl polyoxyethylene ether methacrylate.

[0072] Example 10: Basically the same as Example 1, except that the second monomer is replaced with cyclotrimethylolpropane methyl acetal acrylate.

[0073] Example 11: Basically the same as Example 1, except that the second monomer is replaced with 2-phenoxyethyl acrylate.

[0074] Example 12: Basically the same as Example 1, except that the amount of the second monomer is 70 wt. of the total monomer.

[0075] Example 13: Basically the same as Example 1, except that the amount of the second monomer is 60 wt. of the total monomer.

[0076] Example 14: Basically the same as Example 1, except that the amount of the second monomer is 50 wt. of the total monomer.

[0077] Example 15: Basically the same as Example 1, except that the third monomer is replaced with sodium methylpropenesulfonate.

[0078] Example 16: Basically the same as Example 1, except that the third monomer is replaced with sodium 2-acrylamide-2-methylpropanesulfonate.

[0079] Example 17: Basically the same as Example 1, except that the third monomer is replaced with lithium 2-acrylamide-2-methylpropanesulfonate.

[0080] Example 18: Basically the same as Example 1, except that the amount of the third monomer is 15 wt. of the first monomer.

[0081] Example 19: Basically the same as Example 1, except that the amount of the third monomer is 10 wt. of the first monomer.

[0082] Example 20: Basically the same as Example 1, except that the amount of the third monomer is 5 wt. of the first monomer.

[0083] Example 21: Basically the same as Example 1, except that the amount of the third monomer is 2 wt. of the first monomer.

[0084] Example 22: Basically the same as Example 1, except that the dispersant is replaced with polyvinyl alcohol 2488.

[0085] Example 23: Basically the same as Example 1, except that the dispersant is replaced with polyvinyl alcohol 4078.

[0086] Example 24: Basically the same as Example 1, except that the dispersant is replaced with polyvinylpyrrolidone-K30.

[0087] Example 25: Basically the same as Example 1, except that the dispersant is replaced with polyvinylpyrrolidone-K90.

[0088] Example 26: Basically the same as Example 1, except that the dispersant is replaced with polyoxyethylene ether 400.

[0089] Example 27: Basically the same as Example 1, except that the dispersant is replaced with polyoxyethylene ether 2000.

[0090] Example 28: Basically the same as Example 1, except that the amount of dispersant is 8 wt. of the total monomer.

[0091] Example 29: Basically the same as Example 1, except that the amount of dispersant is 5 wt. of the total monomer.

[0092] Example 30: Basically the same as Example 1, except that the amount of dispersant is 3 wt. of the total amount of monomer.

[0093] Example 31: Basically the same as Example 1, except that the amount of dispersant is 1 wt. of the total amount of monomer.

[0094] Example 32: Basically the same as Example 1, except that the second monomer is partially replaced by the fourth monomer, which accounts for 20 wt.% of the total monomer; the fourth monomer is carboxyethyl acrylate.

[0095] Example 33: Basically the same as Example 32, except that the fourth monomer is carboxypropyl acrylate.

[0096] Example 34: Basically the same as Example 32, except that the fourth monomer is carboxybutyl acrylate.

[0097] Example 35: Basically the same as Example 32, except that the fourth monomer accounts for 16 wt.% of the total monomers.

[0098] Example 36: Basically the same as Example 32, except that the fourth monomer accounts for 12 wt.% of the total monomers.

[0099] Example 37: Basically the same as Example 32, except that the fourth monomer accounts for 8 wt.% of the total monomers.

[0100] Example 38: Basically the same as Example 32, except that the fourth monomer accounts for 4 wt.% of the total monomers.

[0101] Example 39

[0102] This embodiment uses a semi-continuous method to synthesize microsphere materials. The specific steps are as follows:

[0103] (1) Preparation of reaction materials: Same as in Example 1;

[0104] (2) Add the second monomer and the dispersant to the reaction apparatus. The reaction apparatus is a 500mL four-necked flask with a stirring device, which is connected to a feeding tube, a condenser, an electric stirrer and a nitrogen tube respectively; and add a metered amount of deionized water, and then start stirring.

[0105] (3) Dissolve the first monomer, the third monomer, and the initiator in a metered amount of deionized water, and then load them into a metering feeding device; and the “metered amount of deionized water” used in steps (2) and (3) shall make the solid content of the product 20% ± 1% in total;

[0106] (4) Introduce nitrogen into the reaction apparatus and raise the temperature of the reaction apparatus to 75°C after 1 hour;

[0107] (5) Use a quantitative feeding device to uniformly feed the material solution described in step (3) into the reaction device; control the quantitative feeding speed to be 10g / min;

[0108] (6) After the reaction apparatus is kept warm for 4 hours, the mixture is cooled and collected to obtain a white and uniform emulsion.

[0109] Example 40: It is basically the same as Example 39, except that the quantitative feeding speed is controlled to be 8g / min in step (5).

[0110] Example 41: It is basically the same as Example 39, except that the quantitative feeding speed is controlled to be 5g / min in step (5).

[0111] Example 42: It is basically the same as Example 39, except that the quantitative feeding speed is controlled at 3g / min in step (5).

[0112] Example 43: It is basically the same as Example 39, except that the quantitative feeding speed is controlled to be 1g / min in step (5).

[0113] Comparative Example 1: Basically the same as Example 1, except that the first monomer was replaced with acrylamide (both the monomer and its polymer are soluble in water). Experiments revealed that the product obtained in this comparative example was a gel and could not be used as a membrane adhesive.

[0114] Comparative Examples 2-4: These are essentially the same as Example 1, except that the second monomer is replaced with n-butyl acrylate, isooctyl acrylate, and lauryl acrylate, respectively (these three monomers do not contain ether bonds on one side of the ester group, but only saturated hydrocarbon groups of different lengths). Experiments revealed that the product obtained in these comparative examples is a white paste with a large amount of flocculent precipitates, making it unsuitable for use as a membrane binder.

[0115] Comparative Example 5: Essentially the same as Example 1, except that the second monomer was replaced with hydroxyethyl acrylate (this monomer does not contain ether bonds, but contains saturated hydrocarbon groups and hydroxyl groups, and both the monomer and its polymer are soluble in water). Experiments revealed that the product obtained in this comparative example was a gel and could not be used as a membrane adhesive.

[0116] Comparative Example 6: Basically the same as Example 1, except that the third monomer was replaced with sodium acrylate (an olefinic carboxylate). Experiments revealed that the product obtained in this comparative example was a white paste with a large amount of flocculent precipitates, making it unsuitable for use as a membrane binder.

[0117] Comparative Example 7: Basically the same as Example 32, except that the fourth monomer was replaced with ethyl acrylate (the ester group does not contain a carboxyl group at the end).

[0118] Comparative Example 8: Basically the same as Example 32, except that the fourth monomer was replaced with hydroxyethyl acrylate (the ester group does not contain a carboxyl group at the end, but does contain a hydroxyl group). Experiments revealed that the product obtained in this comparative example contained a large amount of gel, making it difficult to use as a membrane adhesive.

[0119] Comparative Example 9: It is basically the same as Example 32, except that the fourth monomer accounts for 24 wt.% of the total monomer (that is, the fourth monomer replaces 30 wt.% of the second monomer).

[0120] Comparative Example 10: It is basically the same as Example 32, except that the fourth monomer accounts for 40 wt.% of the total monomer (that is, the fourth monomer replaces 50 wt.% of the second monomer).

[0121] Comparative Example 11: It is basically the same as Example 32, except that the fourth monomer accounts for 64 wt.% of the total monomer (that is, the fourth monomer replaces 80 wt.% of the second monomer).

[0122] Comparative Example 12: It is basically the same as Example 32, except that the fourth monomer accounts for 80 wt.% of the total monomer (that is, the fourth monomer replaces 100 wt.% of the second monomer).

[0123] In the products obtained in Comparative Examples 9-12, micelle precipitates were visible, making them unsuitable as membrane binders; and the number and size of precipitates increased significantly with the increase of the amount of the fourth monomer.

[0124] Test case

[0125] The microsphere materials obtained in each embodiment and Comparative Example 7 were tested, and the results of each test were recorded in Table 1.

[0126] (1) Particle size test: A laser particle size analyzer was used to test and characterize the parameters D10, D25, D50, D75, D90, D97, D99, volumetric surface area, weight surface area, residual, and Span.

[0127] Taking Example 1 and Example 42 as examples respectively, Figure 1 and Figure 2 The representation results for both are provided separately. Figure 1 , Figure 2 All show good unimodal characteristics.

[0128] Figure 1 The characterization results are as follows: D10 is 2.833 μm, D25 is 3.736 μm, D50 is 4.912 μm, D75 is 6.263 μm, D90 is 7.612 μm, D97 is 9.092 μm, D99 is 16.588 μm, the volumetric surface area is 1.360 sq.m / cc, and the weight surface area is 1360.290 m². 2 / kg, residual of 0.035%, Span of 0.973.

[0129] Figure 2 The characterization results are as follows: D10 is 15.396 μm, D25 is 26.332 μm, D50 is 38.079 μm, D75 is 51.408 μm, D90 is 65.237 μm, D97 is 77.094 μm, D99 is 90.276 μm, the volumetric surface area is 0.924 sq.m / cc, and the weight surface area is 923.934 m². 2 / kg, residual of 0.308%, Span of 1.309.

[0130] (2) Adhesion test: The product emulsions obtained in each example and Comparative Example 7 were sprayed onto the surface of the polyolefin base film and then dried. The coating amount was 1.0 g / m. 2 The 180° peel strength of the above-mentioned sprayed film was tested using an electronic tensile testing machine. The specific test steps included:

[0131] (2.1) Cut the polyolefin-based films coated with emulsion and dried into strips 25 mm wide and 120 mm long;

[0132] (2.2) Take a smooth and flat stainless steel plate, cut a piece of 3M double-sided tape with a length of 38mm and a width of 25mm, and stick it to one end of the stainless steel plate.

[0133] (2.3) Attach each strip to the other side of the aforementioned 3M double-sided tape;

[0134] (2.4) Perform peel strength test according to the method disclosed in GB / T 2792-2014.

[0135] (3) Another microsphere emulsion prepared in Example 1 was subjected to SED detection, and the results were as follows: Figure 3 The SED image shown exhibits well-defined spherical morphology characteristics under a microscopic perspective.

[0136] (4) Another microsphere emulsion prepared in Example 1 was subjected to DSC analysis, and the results were as follows: Figure 4 The DSC curve shown indicates that it has a low glass transition temperature.

[0137] (5) The microsphere emulsion prepared in Example 1 was used as the seed (core) emulsion, and a composite of methyl methacrylate, ethylene glycol dimethacrylate, and γ-methacryloxypropyltrimethoxysilane was used as the shell material to prepare a core-shell structured microsphere emulsion with a solid content of 20% ± 1%. The resulting microspheres had a particle size of 5.2 μm. Based on the effective components, the total amount of methyl methacrylate, ethylene glycol dimethacrylate, and γ-methacryloxypropyltrimethoxysilane was equivalent to 100 wt.% of the seed; the mass ratio of methyl methacrylate, ethylene glycol dimethacrylate, and γ-methacryloxypropyltrimethoxysilane was 8:1:1.

[0138] The obtained microsphere emulsion was coated onto the surface of a polyolefin membrane at a coating amount of 0.3 g / m². 2 Subsequently, the coated surface of the diaphragm was pressed together with the graphite negative electrode sheet at 25℃ and 5MPa. The 180° peel strength of the pressed surface was tested using an electronic tensile testing machine, and the result reached 7.2N / m.

[0139] Table 1

[0140]

[0141] Based on Table 1, it can be seen that: First, by introducing N,N'-methylenebisacrylamide into the monomer, the crosslinking degree of the microsphere material is increased, thus making it denser, reducing the material size, and increasing the peel strength; Second, reasonably controlling the partial replacement of the second monomer with the fourth monomer can significantly improve the peel strength; Third, the semi-continuous method can effectively obtain microsphere materials with larger particle sizes; Fourth, in Comparative Example 7, replacing the second monomer with a fourth monomer without terminal carboxyl groups did not significantly improve the peel strength.

[0142] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A polyacrylate microsphere material, characterized in that, The polymer monomers of the polyacrylate microsphere material are a first monomer, a second monomer, and a third monomer, or the polymer monomers of the polyacrylate microsphere material are a first monomer, a second monomer, a third monomer, and a fourth monomer. Wherein, the first monomer is an acrylamide compound, the second monomer is an acrylate compound, and the third monomer is an olefinic sulfonate; The acrylamide compounds include one or both of diacetone acrylamide and N-isopropylacrylamide; the acrylamide compounds also include N,N'-methylenebisacrylamide; The acrylate compound contains at least one ether bond; the acrylate compound includes at least one of diethylene glycol monoethyl ether acrylate, tetrahydrofuran acrylate, docosyl polyoxyethylene ether methacrylate, cyclotrimethylolpropane methyl acetal acrylate, and 2-phenoxyethyl acrylate. The third monomer includes at least one of sodium p-styrene sulfonate, sodium methacrylate sulfonate, and a lithium or sodium salt of 2-acrylamide-2-methylpropanesulfonic acid. The fourth monomer is a second acrylate compound, and the second acrylate compound contains at least one terminal carboxyl group; the fourth monomer includes at least one of carboxyethyl acrylate, carboxypropyl acrylate, or carboxybutyl acrylate; The D50 particle size of the polyacrylate microsphere material is 1μm~40μm, and when the D50 particle size is 1μm~10μm, the D50 particle size exhibits a unimodal distribution. The preparation method of the polyacrylate microsphere material includes: When the particle size of the polyacrylate microsphere material is ≤10μm, an intermittent method is used; when the particle size of the polyacrylate microsphere material is ≥10μm, a semi-continuous method is used. The batch method includes the following steps: preparing a reaction substrate containing polymeric monomers, adding an initiator, and then maintaining the temperature to react until the polyacrylate microsphere material is obtained; The semi-continuous method includes the following steps: preparing a reaction base solution containing a second monomer, preparing an addition solution containing a first monomer, a third monomer and an initiator; gradually adding the addition solution to the reaction base solution, and then maintaining the temperature to react until the polyacrylate microsphere material is obtained.

2. The polyacrylate microsphere material according to claim 1, characterized in that, The mass ratio of the second monomer to the polymeric monomer is 50% to 80%.

3. The polyacrylate microsphere material according to claim 1, characterized in that, The mass ratio of the third monomer to the first monomer is 2% to 20%.

4. The polyacrylate microsphere material according to claim 1, characterized in that, The ratio of the fourth monomer to the second monomer is (5%~25%) : (75%~95%).

5. The polyacrylate microsphere material according to claim 1, characterized in that, In the intermittent method and / or the semi-continuous method, the temperature of the heat preservation reaction is 70℃~80℃, and the time of the heat preservation reaction is 3h~5h; In the semi-continuous method, the addition time of the added solution is 0.5h to 2h, and the addition rate is uniform.

6. The polyacrylate microsphere material according to claim 1, characterized in that, The heat preservation reaction is carried out in a protective gas environment; And / or, before the start of the heat preservation reaction, the reaction raw materials are placed in a protective gas environment for 0.5h to 2h.

7. A core-shell polymer microsphere material, characterized in that, The core layer of the core-shell polymer microsphere material includes the polyacrylate microsphere material as described in any one of claims 1 to 6.

8. A secondary battery, characterized in that, The secondary battery comprises the polyacrylate microsphere material as described in any one of claims 1 to 6.

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