Polyacrylate microsphere material as well as preparation method and application thereof

Abstract

The invention provides a polyacrylate microsphere material as well as a preparation method and application thereof, and relates to the technical field of polymer materials. Specifically, polymeric monomers of the polyacrylate microsphere material comprise 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 olefinic bond sulfonate; the D50 particle size of the polyacrylate microsphere material is 1 [mu] m-40 [mu] m, and when the D50 particle size is 1 [mu] m-10 [mu] m, the D50 particle size is in unimodal distribution. The microsphere material provided by the invention has good adhesion, film-forming property and controllable particle size, is simple in raw material formula and preparation process and short in reaction process, can be directly used as a battery diaphragm binder, can also be used as a core material of a complex polymer material, and has a good application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a polyacrylate microsphere material and a preparation method and application thereof. Background Art

[0002] In recent years, technological innovations in the field of battery separators have continued to emerge. Among them, the application of polymer microspheres as separator coating materials is particularly eye-catching; it not only provides a new way to improve the performance of battery separators, but also opens up a new direction for optimizing the overall performance of batteries.

[0003] With respect to polymer microspheres with micron-sized core-shell structures, especially micron-sized polymer microspheres with soft core and hard shell structures, the applicant has found through a large number of experimental studies that the difficulty lies in the preparation of "micron-sized soft balls" used as seed (core layer) emulsions. For example, the prior application CN202211325940.9 discloses a large-size core-shell polymer particle and a preparation method thereof, which uses an improved aqueous suspension polymerization and / or emulsion polymerization method to prepare the polymer. When used in the field of battery separator bonding, it can improve the hardness of the battery cell and inhibit the deformation of the battery cell without affecting the air permeability; however, the preparation method still has defects such as complex formula, difficult to control particle size, and long reaction time.

[0004] Therefore, the defects that prevent polymer microsphere products from being popularized in the field of battery separators include but are not limited to: on the one hand, the current process has complex formulas and long reaction times, resulting in high production cost pressures. For example, in the mixing or reaction process of the polymerization reaction, there is a high demand for equipment (such as high-speed homogenization equipment, etc.); on the other hand, the obtained polymer microsphere products have particle size that is difficult to control and uneven particle size distribution, which may lead to a series of defects. For example, depending on the design of the battery cell, the requirements for the thickness of the polymer microsphere coating are also different. Therefore, the particle size of the polymer microsphere product is difficult to control, which will lead to problems such as the product being difficult to adapt to different battery cell designs and the thickness of the microsphere coating not meeting the requirements. For another example, the uneven particle size distribution of the polymer microsphere product will lead to poor consistency of the coating, which will in turn cause performance fluctuations of the separator and the battery cell.

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

[0006] The first purpose of the present invention is to provide a polyacrylate microsphere material, which, while meeting the adhesion and film-forming properties just required in the field of battery separators, has the advantages of simple formula, convenient particle size control, uniform particle size distribution, short reaction time, etc., and has good practicality and promotion prospects.

[0007] The second object of the present invention is to provide a method for preparing the polyacrylate microsphere material. By means of an ordinary emulsion polymerization device, micron-sized soft spheres can be prepared by this method, and high-speed homogenization equipment is not required, with low cost and a short process.

[0008] The third object of the present invention is to provide a core-shell polymer microsphere material. When the polyacrylate microsphere material is used as the core layer for further modification, a composite microsphere material with other functional or advantageous features can be obtained.

[0009] The fourth object of the present invention is to provide a secondary battery.

[0010] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted: A polyacrylate microsphere material, the polymerization monomers of which 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 ethylenically unsaturated 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 shows a single-peak distribution.

[0011] A method for preparing the polyacrylate microsphere material. When the particle size of the polyacrylate microsphere material is ≤ 10 μm, the batch method is adopted; when the particle size of the polyacrylate microsphere material is ≥ 10 μm, the semi-continuous method is adopted; The batch method includes the following steps: preparing a reaction bottom liquid containing polymerization monomers, adding an initiator, and then carrying out a heat preservation reaction to obtain the polyacrylate microsphere material; The semi-continuous method includes the following steps: preparing a reaction bottom liquid containing the second monomer, and preparing a feeding liquid containing the first monomer, the third monomer and the initiator; gradually adding the feeding liquid to the reaction bottom liquid, and then carrying out a heat preservation reaction to obtain the polyacrylate microsphere material.

[0012] A core-shell polymer microsphere material, the core layer of which includes the polyacrylate microsphere material.

[0013] A secondary battery, including the polyacrylate microsphere material.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a milk-like liquid polyacrylate microsphere material with good adhesiveness. Its D50 particle size shows an obvious single-peak distribution (especially when the D50 is in the range of 1 - 10 μm), and it has a glass transition temperature lower than room temperature. After drying, a film with adhesiveness is obtained. The microsphere material of the present invention is stored in the form of an aqueous emulsion, can be directly used as an adhesive, or can be used for subsequent modification (such as being used as the seed emulsion of "soft core and hard shell" microspheres).

[0015] (2) The present invention is prepared by using specific monomers, designing the ratio of the monomers, and based on the "aqueous dispersion polymerization" method by utilizing the difference in the solubility of the monomers and polymers in water. The formula of its preparation process is simple, the particle size of the product is easy to control, the reaction time is short, and there are no special requirements for the equipment, having good prospects for batch production. Brief Description of the Drawings

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 The particle size distribution curve of Example 1 of the present invention is provided; Figure 2 The particle size distribution curve of Example 42 of the present invention is provided; Figure 3 The SEM image of Example 1 of the present invention is provided; Figure 4 The DSC diagram of Example 1 of the present invention is provided. Specific Embodiments

[0018] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than 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 of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0019] The first aspect of the present invention is to provide a polyacrylate microsphere material, the polymerization monomers of which 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 ethylenically unsaturated sulfonate.

[0020] Meanwhile, in the present invention, the D50 particle size of the polyacrylate microsphere material is defined as 1 μm to 40 μm, and when the D50 particle size is 1 μm to 10 μm, the D50 particle size shows a single-peak distribution; specifically, when the D50 particle size is 1 μm to 10 μm, the particle size of the microsphere material of the present invention has a good single-peak distribution. Based on the particle size distribution diagram of the microsphere material, good symmetry can be seen. The peak value of the particle size distribution is about 4.9 μm, the particle size distribution width is about 0.97, and the peak shape shows good normality. In some other embodiments, when the D50 particle size is 10 μm to 40 μm, the D50 particle size is also a single-peak distribution, but the characteristics of the peak shape may not be as normal as when the D50 particle size is 1 μm to 10 μm.

[0021] In addition, the polyacrylate microsphere material in the present invention has a glass transition temperature lower than room temperature. In some alternative embodiments, the Tg of the polyacrylate microsphere material is 0 to 10 °C.

[0022] The acrylamide compound used as the first monomer in the present invention 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, serving as the basis for the growth and formation of microspheres.

[0023] As a preferred embodiment, the acrylamide compound includes one or both of diacetone acrylamide or N-isopropyl acrylamide; in some alternative embodiments, the acrylamide compound (on the basis of the previous selection) further includes N,N'-methylenebisacrylamide, and its function is to increase the crosslinking degree of the microsphere material; in some alternative embodiments, when N,N'-methylenebisacrylamide is used, its dosage in the first monomer is 0.5% to 3% by mass, including but not limited to any one or any numerical range composed of any two of 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%.

[0024] In the present invention, the acrylate compound used as the second monomer has the following characteristics: the compound itself is easily soluble in water or partially soluble in water, but its polymerization product is insoluble in water. Considering the extremely broad variety of acrylate compounds, the present invention further defines that the acrylate compound contains at least one ether bond. The role of the second monomer is to endow the microsphere material with adhesiveness and flexibility. Further, the ether bond structure can endow the microspheres with good water-oil balance, which helps to improve the stability of the microsphere emulsion.

[0025] As a preferred embodiment, the acrylate compound includes at least one of diethylene glycol monoethyl ether acrylate, tetrahydrofuran acrylate, dodecyl polyoxyethylene ether methacrylate, cyclic trimethylolpropane formal acrylate, 2-phenoxyethyl acrylate.

[0026] In the present invention, the ethylenically unsaturated sulfonate used as the third monomer can be understood as an organic sulfonate containing an alkenyl structure; its role is to improve the surface activity of the microsphere material so that it can be well dispersed in water, thereby maintaining the stability of the emulsion.

[0027] As a preferred embodiment, the third monomer includes at least one of sodium p-styrenesulfonate, sodium methallylsulfonate, and the lithium salt or sodium salt of 2-acrylamido-2-methylpropanesulfonic acid.

[0028] As a preferred embodiment, the polymerization monomer further includes a fourth monomer, the fourth monomer is a second acrylate compound, and the second acrylate compound contains at least one terminal carboxyl group. In the present invention, the role of the fourth monomer is to improve the adhesion performance of the microsphere material.

[0029] In actual production applications, the fourth monomer is usually partially substituted for the second monomer. In some alternative embodiments, the dosage ratio of the fourth monomer to the second monomer is (5% - 25%):(75% - 95%), including but not limited to any one or any ratio range formed by any two of 5%:95%, 8%:92%, 10%:90%, 15%:85%, 20%:80%, 22%:78%, 25%:75%.

[0030] As a more preferred embodiment, the fourth monomer includes at least one of carboxyethyl acrylate, carboxypropyl acrylate, or carboxybutyl acrylate.

[0031] As a preferred embodiment, for the dosage of the polymerization monomer: the mass ratio of the second monomer to the polymerization monomer is 50% to 80%, including but not limited to any one or any numerical range composed of any two of 50%, 55%, 60%, 65%, 70%, 75%, 80%.

[0032] As a preferred embodiment, for the dosage of the polymerization monomer: the mass ratio of the third monomer to the first monomer is 2% to 20%, including but not limited to any one or any numerical range composed of any two of 2%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18%, 20%.

[0033] As a preferred embodiment, the polyacrylate microsphere material is prepared by a polymerization reaction of the polymerization monomer, an initiator, and a co-dispersant; wherein, the initiator includes persulfate, and the co-dispersant includes at least one of, but not limited to, polyvinyl alcohol, polyvinylpyrrolidone, or polyoxyethylene ether. It should be noted that the microsphere material prepared in the present invention is an emulsion-like microsphere material. By adding a water-soluble polymer as a co-dispersant, the dispersion of the microsphere material in water can be promoted, and the stability of the emulsion can be further improved.

[0034] As a more preferred embodiment, the addition amount of the initiator is 0.5%wt to 1.0%wt of the total amount of all monomers. It can be understood that when the fourth monomer is also used in the present invention, the addition amount of the initiator is calculated based on the total amount of all monomers including the fourth monomer.

[0035] As a more preferred embodiment, the mass ratio of the co-dispersant to the polymerization monomer is 1% to 10%.

[0036] The second aspect of the present invention is to provide a preparation method of the polyacrylate microsphere material as described in the first aspect.

[0037] In the present invention, the preparation process is selected based on the expected particle size of the microsphere material. Specifically, when the particle size of the polyacrylate microsphere material is ≤ 10 μm, the batch method is adopted; in this method, the number of initial active sites in the reaction initial state system is relatively large, and monomers tend to polymerize at different active sites, so the growth rate of microsphere size is relatively small, and it is suitable for preparing microsphere materials with a particle size not exceeding 10 μm. Correspondingly, when the particle size of the polyacrylate microsphere material is ≥ 10 μm, the semi - continuous method is adopted; in this method, the number of initial active sites in the reaction system is relatively small, and monomers tend to polymerize at the same active site, so the growth rate of microsphere size is relatively large; moreover, 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 10 μm to 40 μm.

[0038] (I). The batch method includes the following steps: preparing a reaction bottom solution containing polymerization monomers, adding an initiator, and then carrying out a heat - preservation reaction until the polyacrylate microsphere material is obtained.

[0039] As a preferred embodiment, the reaction bottom solution includes the polymerization monomers, a co - dispersant, and deionized water; in some more preferred embodiments, the solid content of the reaction bottom solution is 15% - 30%.

[0040] As a preferred embodiment, in the present invention, for the preparation of any reaction bottom solution, methods such as oscillation, stirring, shaker, centrifugation, ultrasonic treatment, heating, etc. can be selected to assist, which helps to accelerate dispersion and obtain a relatively uniform dispersion system.

[0041] As a preferred embodiment, the heat - preservation reaction is carried out in an environment of a protective gas, and the protective gas includes but is not limited to nitrogen, helium, neon, argon, etc.; in some more preferred embodiments, after the reaction bottom solution is placed in the environment of the protective gas for a period of time, until there is no oxygen or air in the reaction equipment, container, and reaction bottom solution, the initiator is added and the polymerization reaction is started. The above - mentioned period of time can be implemented with reference to 0.5 h - 2 h.

[0042] As a preferred embodiment, the temperature of the heat - preservation reaction is 70 °C - 80 °C, and the time of the heat - preservation reaction is 3 h - 5 h.

[0043] (II). The semi - continuous method includes the following steps: preparing a reaction bottom solution containing a second monomer, preparing a feeding solution containing a first monomer, a third monomer, and an initiator; gradually adding the feeding solution to the reaction bottom solution, and then carrying out a heat - preservation reaction until the polyacrylate microsphere material is obtained.

[0044] As a preferred embodiment, the reaction bottom liquid includes a second monomer, a dispersing aid, and deionized water, and the feeding liquid includes a first monomer, a third monomer, an initiator, and deionized water; in some alternative embodiments, the addition amount of water is adjusted to a solid content of 15% to 30% based on the total amount of the reaction raw materials. In addition, it should also be noted that for the semi-continuous method, when a fourth monomer is further included in the polymerization monomers, the fourth monomer is added to the reaction bottom liquid instead of the feeding liquid.

[0045] As a preferred embodiment, the addition duration of the feeding liquid is 0.5 h to 2 h, and its addition speed is uniform.

[0046] As a preferred embodiment, the temperature of the heat preservation reaction is 70 °C to 80 °C, and the time of the heat preservation reaction is 3 h to 5 h; that is, there are the same reaction conditions in the semi-continuous method as in 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 feeding liquid.

[0047] The third aspect of the present invention lies in providing a core-shell polymer microsphere material, the core layer of which includes the polyacrylate microsphere material as described in the first aspect. It should be noted that the liquid polyacrylate microsphere material in the present invention can be directly used for the bonding of battery diaphragms. However, it can also be used as a polymerization substrate to realize the synthesis of more bonding functional emulsions, especially to synthesize new types of polymer materials of core-shell type or quasi-core-shell type with the polyacrylate microsphere material as the core layer. In the present invention, no restrictions are imposed on the raw materials, structure, preparation process, etc. of the core-shell polymer microsphere material. As long as a spherical polymer material is prepared with the polyacrylate microsphere material as described in the first aspect as the raw material, it can be used as an embodiment of this aspect.

[0048] The fourth aspect of the present invention lies in providing a secondary battery, including the polyacrylate microsphere material as described in the first aspect. It can be understood that the secondary battery should include positive and negative electrodes, an electrolyte, a diaphragm, and other necessary or non-necessary functional components or packaging components, etc., and those skilled in the art can make any selection and combination thereof. For the polyacrylate microsphere material, it is usually used as a component in the diaphragm, mainly as a bonding functional component in the diaphragm coating; when the diaphragm of the secondary battery contains the polyacrylate microsphere material, the secondary battery can be used as an embodiment of this aspect.

[0049] Example 1 In this example, the batch method is used for the synthesis of the microsphere material, and the specific steps are as follows: (1)Prepare the reaction materials: the first monomer (diacetone acrylamide), the second monomer (diethylene glycol monoethyl ether acrylate, accounting for 80 wt.% of the total monomers), the third monomer (sodium p-styrene sulfonate, with a dosage of 20 wt.% of the first monomer), the co-dispersant (polyvinyl alcohol 1799, with a dosage of 20 wt.% of the total monomers), and the initiator (potassium persulfate); (2)Put all the materials except the initiator into the reaction device. The reaction device uses a 500 mL four-necked flask with a stirring device, which is respectively connected with a condenser, an electric stirrer, and a nitrogen pipe; and add a measured amount of deionized water, control the water volume so that the solid content of the product is 20% ± 1%, and then start stirring; (3)Introduce nitrogen into the reaction device, and raise the temperature of the reaction device to 75 °C after 1 h; (4)Add the initiator, and the total amount of the materials is 300 g; after maintaining the temperature for reaction for 4 h, cool and collect the product to obtain a white uniform emulsion.

[0050] Example 2: It is basically the same as Example 1, except that the first monomer is replaced with N-isopropylacrylamide.

[0051] Example 3: It is basically the same as Example 1, except that the first monomer is replaced with diacetone acrylamide and N-isopropylacrylamide, and the mass ratio of the two is 1:1.

[0052] Example 4: It is basically the same as Example 1, except that the first monomer is replaced with diacetone acrylamide and N,N'-methylenebisacrylamide, and the mass ratio of the two is 97:3.

[0053] Example 5: It is basically the same as Example 4, except that the mass ratio of the two is 98:2.

[0054] Example 6: It is basically the same as Example 4, except that the mass ratio of the two is 99:1.

[0055] Example 7: It is basically the same as Example 4, except that the mass ratio of the two is 99.5:0.5.

[0056] Example 8: It is basically the same as Example 1, except that the second monomer is replaced with tetrahydrofuran acrylate.

[0057] Example 9: It is basically the same as Example 1, except that the second monomer is replaced with docosyl polyoxyethylene ether methacrylate.

[0058] Example 10: It is basically the same as Example 1, except that the second monomer is replaced with trimethylolpropane methylal acrylate.

[0059] Example 11: It is basically the same as Example 1, except that the second monomer is replaced with 2-phenoxyethyl acrylate.

[0060] Example 12: It is basically the same as Example 1, except that the dosage of the second monomer accounts for 70 wt.% of the total amount of monomers.

[0061] Example 13: It is basically the same as Example 1, except that the dosage of the second monomer accounts for 60 wt.% of the total amount of monomers.

[0062] Example 14: It is basically the same as Example 1, except that the dosage of the second monomer accounts for 50 wt.% of the total amount of monomers.

[0063] Example 15: It is basically the same as Example 1, except that the third monomer is replaced with sodium methallylsulfonate.

[0064] Example 16: It is basically the same as Example 1, except that the third monomer is replaced with 2-acrylamido-2-methylpropanesulfonic acid sodium salt.

[0065] Example 17: It is basically the same as Example 1, except that the third monomer is replaced with lithium 2-acrylamido-2-methylpropanesulfonate.

[0066] Example 18: It is basically the same as Example 1, except that the dosage of the third monomer is 15 wt.% of the first monomer.

[0067] Example 19: It is basically the same as Example 1, except that the dosage of the third monomer is 10 wt.% of the first monomer.

[0068] Example 20: It is basically the same as Example 1, except that the dosage of the third monomer is 5 wt.% of the first monomer.

[0069] Example 21: It is basically the same as Example 1, except that the dosage of the third monomer is 2 wt.% of the first monomer.

[0070] Example 22: It is basically the same as Example 1, except that the co-dispersant is replaced with polyvinyl alcohol 2488.

[0071] Example 23: It is basically the same as Example 1, except that the co-dispersant is replaced with polyvinyl alcohol 4078.

[0072] Example 24: It is basically the same as Example 1, except that the co-dispersant is replaced with polyvinylpyrrolidone-K30.

[0073] Example 25: It is basically the same as Example 1, except that the co-dispersant is replaced with polyvinylpyrrolidone-K90.

[0074] Example 26: It is basically the same as Example 1, except that the dispersant aid is replaced with polyethylene glycol ether 400.

[0075] Example 27: It is basically the same as Example 1, except that the dispersant aid is replaced with polyethylene glycol ether 2000.

[0076] Example 28: It is basically the same as Example 1, except that the amount of the dispersant aid is 8 wt.% of the total amount of the monomers.

[0077] Example 29: It is basically the same as Example 1, except that the amount of the dispersant aid is 5 wt.% of the total amount of the monomers.

[0078] Example 30: It is basically the same as Example 1, except that the amount of the dispersant aid is 3 wt.% of the total amount of the monomers.

[0079] Example 31: It is basically the same as Example 1, except that the amount of the dispersant aid is 1 wt.% of the total amount of the monomers.

[0080] Example 32: It is basically the same as Example 1, except that part of the second monomer is replaced with a fourth monomer, and the fourth monomer accounts for 20 wt.% of the total amount of the monomers; the fourth monomer is 2-carboxyethyl acrylate.

[0081] Example 33: It is basically the same as Example 32, except that the fourth monomer is 3-carboxypropyl acrylate.

[0082] Example 34: It is basically the same as Example 32, except that the fourth monomer is 4-carboxybutyl acrylate.

[0083] Example 35: It is basically the same as Example 32, except that the fourth monomer accounts for 16 wt.% of the total amount of the monomers.

[0084] Example 36: It is basically the same as Example 32, except that the fourth monomer accounts for 12 wt.% of the total amount of the monomers.

[0085] Example 37: It is basically the same as Example 32, except that the fourth monomer accounts for 8 wt.% of the total amount of the monomers.

[0086] Example 38: It is basically the same as Example 32, except that the fourth monomer accounts for 4 wt.% of the total amount of the monomers.

[0087] Example 39 In this example, the semi-continuous method is adopted for the synthesis of the microsphere material, and the specific steps are as follows: (1) Prepare the reaction materials: The same as in Example 1; (2) Put the second monomer and the dispersing aid into the reaction device. The reaction device uses a 500 mL four-necked flask with a stirring device, which is respectively connected with a feeding pipe, a condenser, an electric stirrer and a nitrogen pipe; and add a measured amount of deionized water, and then start stirring; (3) Dissolve the first monomer, the third monomer and the initiator in a measured amount of deionized water, and then load them into a quantitative feeding device; and the "measured amount of deionized water" used in steps (2) and (3) makes the solid content of the product 20% ± 1%; (4) Pass nitrogen into the reaction device, and after 1 h, raise the temperature of the reaction device to 75 °C; (5) Use the quantitative feeding device to uniformly feed the material solution described in step (3) into the reaction device; control the quantitative feeding speed to be 10 g / min; (6) Keep the reaction device under heat preservation for 4 h, then cool and collect the material to obtain a white uniform emulsion.

[0088] Example 40: It is basically the same as Example 39, except that in step (5), the quantitative feeding speed is controlled to be 8 g / min.

[0089] Example 41: It is basically the same as Example 39, except that in step (5), the quantitative feeding speed is controlled to be 5 g / min.

[0090] Example 42: It is basically the same as Example 39, except that in step (5), the quantitative feeding speed is controlled to be 3 g / min.

[0091] Example 43: It is basically the same as Example 39, except that in step (5), the quantitative feeding speed is controlled to be 1 g / min.

[0092] Comparative Example 1: It is basically the same as Example 1, except that the first monomer is replaced with acrylamide (both this monomer and its polymer can dissolve in water). It is found through experiments that the product obtained in this comparative example is a gel and cannot be used as a separator binder.

[0093] Comparative Examples 2 to 4: It is basically the same as Example 1, except that the second monomer is replaced with n-butyl acrylate, isooctyl acrylate and lauryl acrylate respectively (the ester group side of these three monomers does not contain an ether bond and only contains saturated hydrocarbon groups with different lengths). It is found through experiments that the products obtained in this comparative example are white pastes and a large amount of flocculent precipitates can be seen, and it is difficult to be used as a separator binder.

[0094] Comparative Example 5: It is basically the same as Example 1, except that the second monomer is replaced with 2-hydroxyethyl acrylate (this monomer does not contain an ether bond, but contains a saturated hydrocarbon group and a hydroxyl group, and both the monomer and its polymer can dissolve in water). It is found through experiments that the product obtained in this comparative example is a gel and cannot be used as a separator binder.

[0095] Comparative Example 6: It is basically the same as Example 1, except that the third monomer is replaced with sodium acrylate (an ethylenically unsaturated carboxylate). It was found through experiments that the product obtained in this comparative example was a white paste, and a large amount of flocculent precipitates could be seen, making it difficult to be used as a separator binder.

[0096] Comparative Example 7: It is basically the same as Example 32, except that the fourth monomer is replaced with ethyl acrylate (the ester group terminus does not contain a carboxyl group).

[0097] Comparative Example 8: It is basically the same as Example 32, except that the fourth monomer is replaced with 2-hydroxyethyl acrylate (the ester group terminus does not contain a carboxyl group, but contains a hydroxyl group). It was found through experiments that the product obtained in this comparative example contained a large amount of gel, making it difficult to be used as a separator binder.

[0098] Comparative Example 9: It is basically the same as Example 32, except that the fourth monomer accounts for 24 wt.% of the total monomers (that is, the fourth monomer replaces 30 wt.% of the second monomer).

[0099] Comparative Example 10: It is basically the same as Example 32, except that the fourth monomer accounts for 40 wt.% of the total monomers (that is, the fourth monomer replaces 50 wt.% of the second monomer).

[0100] Comparative Example 11: It is basically the same as Example 32, except that the fourth monomer accounts for 64 wt.% of the total monomers (that is, the fourth monomer replaces 80 wt.% of the second monomer).

[0101] Comparative Example 12: It is basically the same as Example 32, except that the fourth monomer accounts for 80 wt.% of the total monomers (that is, the fourth monomer replaces 100 wt.% of the second monomer).

[0102] In the products obtained in Comparative Examples 9 to 12, micelle-like precipitates could be seen and they could not be used as separator binders; and as the amount of the fourth monomer increased, the number and size of the precipitates increased significantly.

[0103] Test Example The microsphere materials obtained in each example and Comparative Example 7 were tested, and the items were as follows; and the results of each test item were recorded in Table 1.

[0104] (1) Particle size test: It was tested using a laser particle size analyzer, and the parameter results of D10, D25, D50, D75, D90, D97, D99, volume specific surface area, weight specific surface area, residual, and Span were characterized.

[0105] Taking Example 1 and Example 42 as examples respectively, Figure 1 AndFigure 2 The characterization results of the two are provided respectively. From Figure 1 , Figure 2 a good single-peak feature can be seen in both.

[0106] Figure 1 The characterization results of are as follows: D10 is 2.833μm, D25 is 3.736μm, D50 is 4.912μm, D75 is 6.263μm, D90 is 7.612μm, D97 is 9.092μm, D99 is 16.588μm, the volume specific surface area is 1.360 sq.m / c.c., the weight specific surface area is 1360.290 m 2 / kg, the residual is 0.035%, and Span is 0.973.

[0107] Figure 2 The characterization results of are as follows: D10 is 15.396μm, D25 is 26.332μm, D50 is 38.079μm, D75 is 51.408μm, D90 is 65.237μm, D97 is 77.094μm, D99 is 90.276μm, the volume specific surface area is 0.924 sq.m / c.c., the weight specific surface area is 923.934 m 2 / kg, the residual is 0.308%, and Span is 1.309.

[0108] (2) Adhesion test: The product emulsions obtained in each example and Comparative Example 7 were sprayed onto the surface of the polyolefin-based film and then dried, and the coating amount was 1.0 g / m 2 . An electronic tensile testing machine was used to test the 180° peel strength of the above-mentioned sprayed film. The specific test steps include: (2.1) Cut the polyolefin-based film sprayed with each emulsion and dried into strips with a width of 25 mm and a length of 120 mm; (2.2) Take a smooth and flat stainless steel plate, cut a piece of 3M double-sided tape with a length of 38 mm and a width of 25 mm, and stick it to one end of the stainless steel plate; (2.3) Stick each strip to the other side of the aforementioned 3M double-sided tape; (2.4) Conduct the peel strength test according to the method disclosed in GB / T 2792-2014.

[0109] (3) Another SED detection was carried out on the microsphere emulsion prepared in Example 1, and the SED diagram as shown in Figure 3 was obtained. A good spherical morphology feature can be seen under the microscope.

[0110] (4) Another DSC detection was carried out on the microsphere emulsion prepared in Example 1, and the DSC curve as shown in Figure 4 was obtained; it can be seen that it has a relatively low glass transition temperature.

[0111] (5) Another microsphere emulsion prepared in Example 1 was taken as the seed (core layer) emulsion, and a composite of methyl methacrylate, ethylene glycol dimethacrylate, and γ-methacryloxypropyltrimethoxysilane was used as the shell layer raw material to prepare a core-shell structured microsphere emulsion with a solid content of 20% ± 1%. The prepared microspheres had a particle size of 5.2 μm. By weight of the active ingredient, 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.

[0112] The obtained microsphere emulsion was coated on the surface of the polyolefin separator, and the coating amount was 0.3 g / m 2 , and then the coated surface of the separator was pressed together with the graphite negative electrode sheet at 25°C and 5 MPa. The 180° peel strength of the pressed surface was tested using an electronic tensile testing machine, and the result could reach 7.2 N / m.

[0113] Table 1

[0114] It can be seen from Table 1 that: First, by introducing N,N'-methylenebisacrylamide into the monomer, the crosslinking degree of the microsphere material becomes higher, so it becomes denser, the material size becomes smaller, and at the same time the peel strength increases; Second, reasonably controlling part of the fourth monomer to replace the second monomer can significantly improve the peel strength; Third, a microsphere material with a higher particle size can be effectively obtained by the semi-continuous method; Fourth, when the fourth monomer without a terminal carboxyl group replaces the second monomer in Comparative Example 7, there is no significant improvement in the peel strength.

[0115] Although the present invention has been illustrated and described with specific embodiments, it should be realized that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A polyacrylate microsphere material, characterized in that, The polymerization monomers of the polyacrylate microsphere material include a first monomer, a second monomer, and a third monomer; Among them, the first monomer is an acrylamide compound, the second monomer is an acrylate compound, and the third monomer is an ethylenically unsaturated 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 shows a single-peak distribution.

2. The polyacrylate microsphere material according to claim 1, wherein The acrylamide compound includes one or both of diacetone acrylamide or N-isopropylacrylamide; The acrylamide compound further includes N,N'-methylenebisacrylamide.

3. The polyacrylate microsphere material according to claim 1, wherein, 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 formal acrylate, 2-phenoxyethyl acrylate; And / or, the mass ratio of the second monomer to the polymerization monomers is 50% to 80%.

4. The polyacrylate microsphere material according to claim 1, wherein The third monomer includes at least one of sodium p-styrenesulfonate, sodium methallylsulfonate, and the lithium salt or sodium salt of 2-acrylamido-2-methylpropanesulfonic acid; And / or, the mass ratio of the third monomer to the first monomer is 2% to 20%.

5. The polyacrylate microsphere material according to claim 1, characterized in that, The polymerization monomers further include a fourth monomer, 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; And / or, the dosage ratio of the fourth monomer to the second monomer is (5% to 25%):(75% to 95%).

6. The preparation method of the polyacrylate microsphere material according to any one of claims 1 to 5, characterized in that, When the particle size of the polyacrylate microsphere material is ≤10 μm, the batch method is adopted; when the particle size of the polyacrylate microsphere material is ≥10 μm, the semi-continuous method is adopted; The batch method includes the following steps: preparing a reaction bottom liquid containing polymerization monomers, adding an initiator, and then carrying out a heat preservation reaction to obtain the polyacrylate microsphere material; The semi-continuous method includes the following steps: preparing a reaction bottom liquid containing a second monomer, and preparing a feeding liquid containing a first monomer, a third monomer, and an initiator; gradually adding the feeding liquid to the reaction bottom liquid, and then carrying out a heat preservation reaction to obtain the polyacrylate microsphere material.

7. The preparation method of the polyacrylate microsphere material according to claim 6, characterized in that, In the batch method and / or the semi-continuous method, the temperature of the heat preservation reaction is 70 °C to 80 °C, and the time of the heat preservation reaction is 3 h to 5 h; In the semi-continuous method, the addition time of the feeding liquid is 0.5 h to 2 h, and the addition speed is uniform.

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

9. A core-shell polymer microsphere material, characterized in that, The core layer of the core-shell polymer microsphere material includes the polyacrylate microsphere material according to any one of claims 1 to 5.

10. A secondary battery, characterized in that, The secondary battery includes the polyacrylate microsphere material according to any one of claims 1 to 5.

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