High-solid-content and low-viscosity polyacrylate water-based binder as well as preparation method and application thereof

Abstract

The invention provides a high-solid-content and low-viscosity polyacrylate water-based binder as well as a preparation method and application thereof. The high-solid-content and low-viscosity polyacrylate water-based binder is obtained by polymerizing a polymeric monomer; the polymeric monomer comprises a hard monomer, a soft monomer, a first functional monomer and a second functional monomer; the second functional monomer is prepared from any one or a combination of at least two of sodium allysulfonate, 2-methyl-2-propylene-1-sodium sulfonate and 2-acrylamido-2-methylpropanesulfonic acid. The water-based adhesive provided by the invention is obtained by emulsion polymerization of polymeric monomers, and by introduction of soft and hard monomers and functional monomers, especially by introduction of a specific second functional monomer, the prepared water-based adhesive has high solid content and low viscosity at the same time, and the water-based adhesive provided by the invention also has good liquid resistance and relatively high adhesive force.

Description

Technical Field

[0001] The present invention belongs to the application fields of the negative electrode and the positive electrode glue of lithium ion batteries, specifically to the technical field of water-based binders for battery slurries, and relates to a water-based polyacrylate binder with high solid content and low viscosity, its preparation method and application. Background Art

[0002] The main structure of a lithium ion battery consists of a positive electrode material, a negative electrode material, a separator, an electrolyte and a casing. Among them, the positive and negative electrode materials, as carriers of lithium ions and electrons during charge and discharge, play a role in energy storage and release. The stable structure between the positive and negative electrode materials depends on the effective adhesion of the polymer binder to the conductive particles and between the conductive particles and the current collector.

[0003] Currently, the commonly used binders for lithium ion batteries mainly include polyvinyl alcohol (PVA), polyolefins (PP, PE and other copolymers), polyvinylidene fluoride (PVDF), modified SBR rubber, acrylic glue (PAA), polyurethane, etc. Binders such as PVA, PAA and polyurethane are mostly products with low solid content and high viscosity on the market. However, a too high viscosity of the binder often increases the processing difficulty of the battery slurry, which is not conducive to simplifying the process and reducing the processing cost.

[0004] Although the commonly used modified SBR rubber meets the requirements of low viscosity and high solid content, the process stability of the modified SBR rubber is poor, and it is easy to break and fail during long-term high-speed stirring.

[0005] Therefore, in this field, there is a desire to develop a binder that has a high solid content, a low viscosity, and excellent adhesion properties, etc. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a water-based polyacrylate binder with high solid content and low viscosity, its preparation method and application. Through the design of the preparation, raw materials and contents of the polyacrylate polymer, the present invention introduces branching points and rigid chains to obtain a water-based polyacrylate binder with high solid content, low viscosity and good adhesion, which has good application prospects in the positive and negative electrode materials of lithium ion batteries. The water-based binder provided by the present invention not only has a high solid content and a low viscosity, but also has excellent adhesion properties, excellent anti-mechanical action ability, excellent electrode sheet processing properties, etc.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted by the present invention:

[0008] In the first aspect, the present invention provides a water-based polyacrylate binder with high solid content and low viscosity, and the water-based polyacrylate binder with high solid content and low viscosity is obtained by polymerizing polymerization monomers;

[0009] The polymerization monomers include hard monomers, soft monomers, first functional monomers, and second functional monomers;

[0010] The second functional monomer includes any one or a combination of at least two of sodium allylsulfonate, sodium 2-methyl-2-propene-1-sulfonate, and 2-acrylamido-2-methylpropanesulfonic acid. The second functional monomer can introduce a reactive monomer group with an emulsifying effect, reduce the viscosity of the binder, and increase the solid content of the binder.

[0011] The aqueous binder provided by the present invention is obtained by simple emulsion polymerization of polymerization monomers. By introducing hard and soft monomers and functional monomers, especially by introducing a specific second functional monomer, the prepared aqueous binder has both a high solid content and a low viscosity, solving the problems of high viscosity and difficult processing, poor process stability at low viscosity, and high cost that occur in the binders for the positive and negative electrode materials of current lithium-ion batteries. Moreover, the aqueous binder provided by the present invention also has good liquid resistance and high adhesion.

[0012] Preferably, the hard monomer includes any one or a combination of at least two of methyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate, and styrene. The hard monomer can provide rigid hardness for the binder.

[0013] Preferably, the soft monomer includes any one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hexyl methacrylate, vinyl versatate, tetrahydrofurfuryl acrylate, lauryl acrylate, lauryl methacrylate, isodecyl acrylate, or ethoxyethoxyethyl acrylate. The soft monomer can provide flexibility and extensibility for the binder.

[0014] Preferably, the first functional monomer includes any one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, diacetone acrylamide, ethyl acetoacetate methacrylate, divinylbenzene, tripropylene glycol diacrylate, pentaerythritol triacrylate, isoprene, polyethylene glycol diacrylate, aziridine, or a silane coupling agent. The first functional monomer can introduce functional groups or crosslinking points to provide adhesiveness.

[0015] Preferably, by weight parts, the polymerizable monomers include: 30 to 70 parts (such as 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, etc.) of hard monomers, 30 to 70 parts (such as 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, etc.) of soft monomers, 0.5 to 25 parts (such as 0.5 parts, 0.8 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 25 parts, etc.) of first functional monomers, and 0.1 to 8 parts (such as 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, etc.) of second functional monomers.

[0016] Preferably, the solid content of the high-solid-content and low-viscosity polyacrylate-based aqueous binder is 40% to 55%, such as 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 55%, etc.

[0017] Preferably, the viscosity of the high-solid-content and low-viscosity polyacrylate-based aqueous binder is less than 1000 mPa·s, such as 900 mPa·s, 800 mPa·s, 700 mPa·s, 600 mPa·s, 500 mPa·s, 400 mPa·s, 300 mPa·s, 200 mPa·s, 100 mPa·s, 50 mPa·s, etc.

[0018] In a second aspect, the present invention provides a method for preparing the high-solid-content and low-viscosity polyacrylate-based aqueous binder as described in the first aspect. The preparation method includes the following steps:

[0019] (1) Prepare a pre-emulsion, a bottom reaction solution, and an initiator solution;

[0020] (2) Add the bottom reaction solution into a reaction kettle, take out a part of the pre-emulsion as a seed emulsion and add it into the reaction kettle, raise the temperature, add a part of the initiator solution, carry out a pre-reaction, then dropwise add the remaining pre-emulsion and the remaining initiator solution. After the dropping is completed, keep the temperature, lower the temperature, then add a residual monomer eliminator, lower the temperature again, and adjust the pH value of the system to obtain the high-solid-content and low-viscosity polyacrylate-based aqueous binder.

[0021] Preferably, the raw materials for preparing the pre-emulsion include a hard monomer, a soft monomer, a first functional monomer, a second functional monomer, an emulsifier, and deionized water.

[0022] Preferably, by weight, the pre-emulsion contains 30-70 parts (such as 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, etc.) of the hard monomer, 30-70 parts (such as 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, etc.) of the soft monomer, 0.5-25 parts (such as 0.5 parts, 0.8 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 25 parts, etc.) of the first functional monomer, 0.1-8 parts (such as 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, etc.) of the second functional monomer, 0.5-5 parts (such as 0.5 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc.) of the emulsifier, and 10-70 parts (such as 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, etc.) of deionized water.

[0023] Preferably, the raw materials for preparing the bottom reaction liquid include an emulsifier, deionized water, and a buffer.

[0024] Preferably, by weight, the bottom reaction liquid contains 0.1-1 part (such as 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, etc.) of the emulsifier, 50-100 parts (such as 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, etc.) of deionized water, and 0.1-1 part (such as 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, etc.) of the buffer.

[0025] Preferably, based on parts by weight, the initiator solution is prepared from 0.1 to 1 part (such as 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, etc.) of initiator and 5 to 15 parts (such as 5 parts, 10 parts, 15 parts, etc.) of deionized water.

[0026] Preferably, the emulsifiers in the pre-emulsion and the bottom reaction liquid independently include any one or a combination of at least two of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene octylphenol ether-10, allyl hydroxypropyl sulfonate, ammonium allyloxy fatty alcohol ethoxylate sulfate, disodium succinic acid nonylphenol polyoxyethylene ether monoester sulfonate, lauryl alcohol ethoxylate, isomeric tridecyl alcohol ethoxylate, fatty acid methyl ester ethoxylate.

[0027] Preferably, the buffer includes any one or a combination of at least two of sodium bicarbonate, ammonia water, ammonium bicarbonate, sodium hydroxide, lithium hydroxide.

[0028] Preferably, the initiator is a water-soluble thermal decomposition type initiator, including any one or a combination of at least two of potassium persulfate, ammonium persulfate, sodium persulfate.

[0029] Preferably, the weight of the seed emulsion in step (2) accounts for 2% to 45% of the total weight of the pre-emulsion, such as 2%, 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc.

[0030] Preferably, the weight of the partial initiator solution in step (2) accounts for 5% to 15% of the total weight of the initiator solution, such as 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 15%, etc.

[0031] Preferably, the residual monomer eliminator in step (2) includes sodium formaldehyde sulfoxylate and tert-butyl hydroperoxide.

[0032] Preferably, based on parts by weight, the residual monomer eliminator in step (2) includes 0.01 to 0.1 part (such as 0.01 part, 0.03 part, 0.05 part, 0.08 part, 0.1 part, etc.) of sodium formaldehyde sulfoxylate and 0.01 to 0.1 part (such as 0.01 part, 0.03 part, 0.05 part, 0.08 part, 0.1 part, etc.) of tert-butyl hydroperoxide.

[0033] Preferably, adding the bottom reaction liquid into the reaction kettle in step (2) specifically includes: adding the bottom reaction liquid into a reaction kettle at 40 to 80 °C (such as 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, etc.).

[0034] Preferably, the temperature increase in step (2) is to increase the temperature to 75 - 85°C, such as 75°C, 80°C, 85°C, etc.

[0035] Preferably, the time for the pre - reaction in step (2) is 10 - 60 min, such as 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc.

[0036] Preferably, the temperature for the dropping in step (2) is 75 - 85°C, such as 75°C, 80°C, 85°C, etc., and the dropping time is 1 - 5 h, such as 1 h, 2 h, 3 h, 4 h, 5 h, etc.

[0037] Preferably, the temperature for the heat preservation in step (2) is 84 - 90°C, such as 84°C, 85°C, 86°C, 88°C, 90°C, etc., and the heat preservation time is 0.5 - 3.5 h, such as 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, etc.

[0038] Preferably, the temperature decrease in step (2) is to decrease the temperature to 57 - 73°C, such as 57°C, 60°C, 65°C, 68°C, 70°C, 73°C, etc.

[0039] Preferably, the second temperature decrease in step (2) is to decrease the temperature below 50°C, such as 50°C, 48°C, 45°C, etc.

[0040] Preferably, adjusting the pH value of the system in step (2) is to adjust the pH value of the system to 7 - 9, such as 7, 7.5, 8, 8.5, 9, etc.

[0041] Preferably, the pH regulator used for adjusting the pH value of the system in step (2) includes any one or a combination of at least two of ammonia water, sodium hydroxide, lithium hydroxide, potassium hydroxide, and sodium bicarbonate.

[0042] Preferably, after adjusting the pH value of the system, it further includes a filtration step.

[0043] In the present invention, by controlling the mass ratio of the soft and hard components and the types of functional monomers in the pre - emulsion, a water - borne polyacrylate binder with high solid content and low viscosity is obtained. By introducing carboxylic acid, carboxylate, sulfonic acid, ester groups, and some branched chain segments into the binder, the prepared water - borne polyacrylate binder has high solid content, low viscosity, good liquid resistance, and high adhesion, and has good application prospects in the positive and negative electrode materials of lithium - ion batteries.

[0044] In the third aspect, the present invention provides an application of the high - solid - content and low - viscosity water - borne polyacrylate binder as described in the first aspect in battery slurries.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The aqueous binder provided by the present invention is obtained by simple emulsion polymerization of polymerizable monomers. By introducing soft and hard monomers and functional monomers, especially by introducing a specific second functional monomer, the prepared aqueous binder has both a high solid content and a low viscosity, solving the problems of high viscosity and difficult processing, poor process stability at low viscosity, and high cost that currently occur in binders for positive and negative electrode materials of lithium-ion batteries. Moreover, the aqueous binder provided by the present invention also has good liquid resistance and high adhesion. Description of the Drawings

[0047] Figure 1 It is a Fourier transform infrared spectrogram of the high-solid-content and low-viscosity polyacrylate aqueous binder provided in Example 1. Detailed Embodiments

[0048] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0049] Example 1

[0050] In this example, a high-solid-content and low-viscosity polyacrylate aqueous binder is provided, and the preparation method includes the following steps:

[0051] (1) Preparation of the pre-emulsion, bottom reaction solution, and initiator solution:

[0052] Pre-emulsion: Dissolve 1.06 parts of sodium nonylphenol polyoxyethylene ether monoestersulfonate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water, and then sequentially add 45.75 parts of styrene, 22 parts of n-butyl acrylate, 19.25 parts of isooctyl acrylate, 4.5 parts of acrylamide, 4 parts of methacrylic acid, and 2 parts of sodium 2-methyl-2-propene-1-sulfonate, and emulsify evenly;

[0053] Bottom reaction solution: Dissolve 0.27 parts of sodium nonylphenol polyoxyethylene ether monoestersulfonate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, and then add 0.5 parts of sodium bicarbonate to obtain the bottom reaction solution;

[0054] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain the initiator solution.

[0055] (2) Polymerization reaction: the reaction liquid at the bottom of the kettle is added to a reactor at 40°C, the rotation speed is 120 rpm, 7 parts of the pre-emulsion are taken out as seed emulsion, added to the reactor, the temperature is raised to 75°C, 0.6 parts of initiator solution are added, and after pre-reaction for 15 minutes, the remaining pre-emulsion and initiator solution are dripped at the same time, and the dripping is continued at 78°C for 4 hours. After the dripping is completed, the temperature is kept at 87°C for 1 hour. After the insulation is completed, the temperature is lowered to 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide are added, and then the temperature is lowered to below 50°C. The pH is adjusted to 7.93 with sodium hydroxide, and the material is filtered to obtain the high solid content, low viscosity polyacrylate water-based binder.

[0056] The aqueous binder obtained in this example was dried and then subjected to Fourier transform infrared spectroscopy test. The test results are shown in Figure 1 , Figure 1 The middle curve is at 3062cm -1 Five sharp bands at 1559 cm -1 、1452cm -1 , 758cm -1 、698cm -1 The peak at 2925cm is a characteristic peak of a monosubstituted benzene ring, indicating that the system has a benzene ring. -1 The vibration peak of CH of aliphatic methylene, 1650cm -1 、1601cm -1 C=O and -NH 2 The vibration peak, 3198cm -1 For -NH 2 The stretching vibration peak of 1697cm -1 、1493cm -1 is the stretching vibration peak of carboxylate, 1728cm -1 is the stretching vibration peak of C=O of acrylic ester monomer, 1159cm -1 、1029cm -1 It is the vibration peak of CO, which means that the system contains benzene ring, acrylate group, amide group, carboxylate group and methyl structure, indicating that the polyacrylate polymer was successfully synthesized.

[0057] Example 2

[0058] In this embodiment, a high solid content, low viscosity polyacrylate aqueous binder is provided, and the preparation method comprises the following steps:

[0059] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution:

[0060] Pre-emulsion: Dissolve 1.36 parts of sodium dodecyl sulfate and 0.64 parts of isomeric tridecyl alcohol ethoxylate in 40 parts of deionized water. Subsequently, add 0.5 part of sodium allyl sulfonate, 24.25 parts of methyl methacrylate, 18 parts of tetrahydrofurfuryl methacrylate, 30 parts of n-butyl acrylate, 8.25 parts of isooctyl acrylate, 5.5 parts of acrylamide, 10 parts of acrylic acid, and 4 parts of 2-hydroxyethyl methacrylate in sequence and emulsify evenly;

[0061] Bottom reaction liquid: Dissolve 0.34 part of sodium dodecyl sulfate and 0.15 part of isomeric tridecyl alcohol ethoxylate in 70 parts of deionized water. Subsequently, add 0.5 part of sodium bicarbonate to obtain the bottom reaction liquid;

[0062] Initiator solution: Dissolve 0.6 part of sodium persulfate in 8 parts of deionized water to obtain the initiator solution.

[0063] (2) Polymerization reaction: Add the bottom reaction liquid to a reaction kettle at 50 °C with a rotation speed of 180 rpm. Take out 8.23 parts from the pre-emulsion as the seed emulsion and add it to the reaction kettle. Heat up to 80 °C, add 0.6 part of the initiator solution. After pre-reacting for 30 min, simultaneously drip the remaining pre-emulsion and initiator solution. Drip at 80 °C for 3 h. After the dripping is completed, keep warm at 85 °C for 2 h. After the heat preservation is over, cool down to 65 °C, add 0.05 part of Rongalite and 0.048 part of tert-butyl hydroperoxide. Subsequently, cool down to below 50 °C and adjust the pH to 7.45 with 25% ammonia water. Filter and discharge to obtain the high-solid-content and low-viscosity polyacrylate-based aqueous binder.

[0064] Example 3

[0065] In this example, a high-solid-content and low-viscosity polyacrylate-based aqueous binder is provided, and the preparation method includes the following steps:

[0066] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution:

[0067] Pre-emulsion: Dissolve 1.06 parts of allyloxy fatty alcohol oxyethylene ether ammonium sulfate and 0.54 parts of fatty acid methyl ester ethoxylate in 40 parts of deionized water. Subsequently, add 5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 35 parts of isopropyl methacrylate, 44.2 parts of isooctyl acrylate, 3.55 parts of methacrylamide, 10 parts of acrylic acid, 4 parts of 2-hydroxyethyl methacrylate, and 3.25 parts of N-methylolacrylamide in sequence for emulsification;

[0068] Bottom reaction liquid: Dissolve 0.27 part of allyloxy fatty alcohol oxyethylene ether ammonium sulfate and 0.13 part of fatty acid methyl ester ethoxylate in 80 parts of deionized water. Subsequently, add 0.5 part of sodium bicarbonate to obtain the bottom reaction liquid;

[0069] Initiator solution: 0.6 parts of potassium persulfate was added to 10 parts of deionized water to obtain the initiator solution.

[0070] (2) Polymerization reaction: The bottom reaction liquid was added to a reaction kettle at 60 °C with a rotation speed of 140 rpm. 8.28 parts were taken out from the pre-emulsion as the seed emulsion and added to the reaction kettle. The temperature was raised to 82 °C, and 0.6 part of the initiator solution was added. After pre-reacting for 45 min, the remaining pre-emulsion and the initiator solution were simultaneously dropped in. The dropping was carried out at 82 °C for 2 h. After the dropping was completed, it was kept warm at 87 °C for 1 h. After the heat preservation was completed, the temperature was lowered to 65 °C, 0.05 part of sodium formaldehyde sulfoxylate and 0.048 part of tert-butyl hydroperoxide were added, and then it was lowered to below 50 °C. Lithium hydroxide was used to adjust the pH to 7.45, and then it was filtered and discharged to obtain the high-solid-content and low-viscosity polyacrylate-based aqueous binder.

[0071] Example 4

[0072] In this example, a high-solid-content and low-viscosity polyacrylate-based aqueous binder is provided, and the preparation method includes the following steps:

[0073] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution:

[0074] Pre-emulsion: 1.06 parts of lauryl alcohol ethoxylate and 0.54 parts of sodium dodecylbenzenesulfonate were dissolved in 40 parts of deionized water, and then 0.5 part of 2-methyl-2-propene-1-sulfonic acid sodium salt, 35 parts of isobornyl acrylate, 27.24 parts of 2-ethylhexyl acrylate, 16.25 parts of lauryl acrylate, 2.5 parts of methacrylamide, 11.76 parts of methacrylic acid, 4 parts of 2-hydroxyethyl methacrylate, and 3.25 parts of diacetone acrylamide were added in sequence for emulsification;

[0075] Bottom reaction liquid: 0.27 part of lauryl alcohol ethoxylate and 0.13 part of sodium dodecylbenzenesulfonate were dissolved in 80 parts of deionized water, and then 0.5 part of sodium bicarbonate was added to obtain the bottom reaction liquid;

[0076] Initiator solution: 0.6 parts of potassium persulfate was added to 10 parts of deionized water to obtain the initiator solution.

[0077] (2) Polymerization reaction: Add the reaction solution at the bottom of the kettle into a reaction kettle at 70 °C with a rotation speed of 200 rpm. Take out 10 parts from the pre-emulsion as the seed emulsion and add it to the reaction kettle. Heat up to 82 °C, add 0.6 parts of the initiator solution. After pre-reacting for 30 min, simultaneously drip in the remaining pre-emulsion and the initiator solution. Drip for 2 h at 82 °C. After the dripping is completed, keep the temperature at 87 °C for 1 h. After the heat preservation is over, cool down to 65 °C, add 0.05 parts of Rongalite and 0.048 parts of tert-butyl hydroperoxide, then cool down to below 50 °C, adjust the pH to 7.45 with sodium bicarbonate, filter and discharge the material, thus obtaining the high-solid-content and low-viscosity polyacrylate-based waterborne binder.

[0078] Example 5

[0079] In this example, a high-solid-content and low-viscosity polyacrylate-based waterborne binder is provided, and the preparation method includes the following steps:

[0080] (1) Preparation of pre-emulsion, reaction solution at the bottom of the kettle and initiator solution:

[0081] Pre-emulsion: Dissolve 1.06 parts of lauryl alcohol ethoxylate and 0.54 parts of sodium dodecylbenzenesulfonate in 40 parts of deionized water, and then add 35 parts of isobornyl methacrylate, 0.5 parts of 2-methyl-2-propen-1-sulfonic acid sodium salt, 1 part of allyl sulfonic acid sodium salt, 20 parts of isooctyl acrylate, 10 parts of n-butyl acrylate, 8 parts of lauryl acrylate, 5 parts of isodecyl acrylate, 2 parts of acrylamide, 10 parts of methacrylic acid, 6 parts of 2-hydroxyethyl methacrylate, and 4 parts of diacetone acrylamide in sequence for emulsification;

[0082] Reaction solution at the bottom of the kettle: Dissolve 0.27 parts of lauryl alcohol ethoxylate and 0.13 parts of sodium dodecylbenzenesulfonate in 70 parts of deionized water, and then add 0.5 parts of sodium bicarbonate to obtain the reaction solution at the bottom of the kettle;

[0083] Initiator solution: Add 0.6 parts of potassium persulfate to 10 parts of deionized water to obtain the initiator solution.

[0084] (2) Polymerization reaction: Add the reaction solution at the bottom of the kettle into a reaction kettle at 60 °C with a rotation speed of 120 rpm. Take out 10 parts from the pre-emulsion as the seed emulsion and add it to the reaction kettle. Heat up to 78 °C, add 0.6 parts of the initiator solution. After pre-reacting for 30 min, drip at 85 °C for 1 h, and simultaneously drip in the remaining pre-emulsion and the initiator solution. After the dripping is completed, keep the temperature at 87 °C for 1 h. After the heat preservation is over, cool down to 60 °C, add 0.05 parts of Rongalite and 0.048 parts of tert-butyl hydroperoxide, then cool down to below 50 °C, adjust the pH to 7.45 with sodium hydroxide, filter and discharge the material, thus obtaining the high-solid-content and low-viscosity polyacrylate-based waterborne binder.

[0085] Example 6

[0086] In this example, a high-solid-content and low-viscosity polyacrylate aqueous binder is provided, and the preparation method includes the following steps:

[0087] (1) Preparation of pre-emulsion, bottom reaction solution and initiator solution:

[0088] Pre-emulsion: Dissolve 1.06 parts of sodium sulfonate of nonylphenol polyoxyethylene ether monosuccinate and 0.54 parts of sodium dodecylbenzenesulfonate in 40 parts of deionized water, and then add 3 parts of 2-acrylamido-2-methylpropanesulfonic acid, 17 parts of vinyl acetate, 20 parts of styrene, 20 parts of isooctyl acrylate, 15 parts of n-butyl acrylate, 13.75 parts of lauryl acrylate, 5 parts of vinyl versatate, 3.75 parts of acrylamide, 12 parts of methacrylic acid, 4 parts of hydroxyethyl methacrylate, and 3.25 parts of diacetone acrylamide in sequence for emulsification;

[0089] Bottom reaction solution: Dissolve 0.27 parts of sodium sulfonate of nonylphenol polyoxyethylene ether monosuccinate and 0.13 parts of sodium dodecylbenzenesulfonate in 60 parts of deionized water, and then add 0.5 parts of sodium bicarbonate to obtain the bottom reaction solution;

[0090] Initiator solution: Add 0.6 parts of potassium persulfate to 10 parts of deionized water to obtain the initiator solution.

[0091] (2) Polymerization reaction: Add the bottom reaction solution to a reaction kettle at 60 °C with a rotation speed of 120 rpm. Take out 10 parts from the pre-emulsion as the seed emulsion and add it to the reaction kettle. Heat up to 78 °C, add 0.6 parts of the initiator solution. After pre-reacting for 30 min, simultaneously drop the remaining pre-emulsion and initiator solution, dropwise add at 75 °C for 5 h. After the dropping is completed, keep warm at 87 °C for 1 h. After the heat preservation is over, cool down to 60 °C, add 0.05 parts of sodium formaldehyde sulfoxylate and 0.048 parts of tert-butyl hydroperoxide, then cool down to below 50 °C, and use 25% ammonia water to adjust the pH to 7.20, filter and discharge to obtain the high-solid-content and low-viscosity polyacrylate aqueous binder.

[0092] Example 7

[0093] The difference between this example and Example 1 is only that the dosage of the second functional monomer (sodium 2-methyl-2-propene-1-sulfonate) is 0.1 part.

[0094] Example 8

[0095] The difference between this example and Example 1 is only that the dosage of the second functional monomer (sodium 2-methyl-2-propene-1-sulfonate) is 8 parts.

[0096] Example 9

[0097] The difference between this example and Example 1 is only that the dosage of the second functional monomer (sodium 2-methyl-2-propene-1-sulfonate) is 0.05 parts.

[0098] Example 10

[0099] The difference between this example and Example 1 is only that the dosage of the second functional monomer (sodium 2-methyl-2-propene-1-sulfonate) is 9 parts.

[0100] Comparative Example 1

[0101] The difference between this comparative example and Example 1 is only that the second functional monomer (sodium 2-methyl-2-propene-1-sulfonate) is not added when preparing the pre-emulsion in step (1).

[0102] Performance tests were carried out on the polyacrylate-based waterborne binder provided in the examples and comparative examples of the present invention, and the test methods are as follows:

[0103] (1) Solid content: Tested by the drying specific gravity method. Take 1 - 3 g of the polyacrylate-based waterborne binder and dry it at 150 °C for 35 min until constant weight. Solid content = mass after drying / mass before drying × 100%;

[0104] (2) Viscosity: At 25 °C, use 62#60R to test the viscosity of 500 mL of liquid;

[0105] (3) Peel strength: Take the graphite slurry without adding the binder, and then mix the graphite slurry and the polyacrylate-based waterborne binder. Among them, the solid component of the graphite slurry: the solid component of the polyacrylate-based waterborne binder = 100:2.2 (mass ratio), stir evenly to obtain the mixed slurry; Take 20 - 30 g of the mixed slurry, evenly coat it on the copper foil with a coater, bake it at 65 °C for 200 s to obtain a pole piece with a thickness of 80 - 90 μm; Cut the pole piece into a 30 mm wide spline, use the 180 °C peeling method, and stretch the spline at a stretching speed of 50 mm / min to obtain the peel strength;

[0106] (4) Swelling ratio: Dry the polyacrylate-based waterborne binder at 65 °C to make a film. Take 1.5 g of the film and soak it in DMC (dimethyl carbonate) at 65 °C for three days, weigh the mass after soaking, and calculate the swelling ratio according to the following formula: Swelling ratio = (mass after soaking - mass before soaking) / mass before soaking × 100%.

[0107] The performance test results are shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] As can be seen from Table 1, the aqueous binders provided in Examples 1-8 of the present invention all have a high solid content (44.1% - 52.1%), a low viscosity (56.7 - 943.2 mPa·s), and a relatively high adhesive force (peel strength: 5.39 - 7.84 N / m).

[0112] Compared with Example 1, the aqueous binder provided in Example 9 has a relatively high viscosity, which is not conducive to production and processing. Although the aqueous binder provided in Example 10 has a relatively low viscosity, its peel strength is slightly lower, its adhesiveness is poor, and its swelling is large, which easily affects the service life of the battery.

[0113] Compared with Example 1, the aqueous binder provided in Comparative Example 1 has a relatively high viscosity, which is not conducive to production and processing.

[0114] The applicant declares that the present invention uses the above examples to illustrate the high-solid-content, low-viscosity polyacrylate-based aqueous binder of the present invention and its preparation method and application. However, the present invention is not limited to the above examples, that is, it does not mean that the present invention must rely on the above examples to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A high solid content, low viscosity polyacrylate water-based binder, characterized in that: The high solid content, low viscosity polyacrylate aqueous binder is obtained by polymerizing monomers; The polymerizable monomers include hard monomers, soft monomers, first functional monomers, and second functional monomers; The second functional monomer includes any one of sodium allyl sulfonate, sodium 2-methyl-2-propylene-1-sulfonate, and 2-acrylamido-2-methylpropane sulfonic acid, or a combination of at least two thereof.

2. The high solid content, low viscosity polyacrylate aqueous binder according to claim 1, characterized in that: The hard monomer includes any one or a combination of at least two of methyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate, and styrene; Preferably, the soft monomer includes any one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hexyl methacrylate, tert-butyl carbonate, tetrahydrofurfuryl acrylate, lauryl acrylate, lauryl methacrylate, isobutyl acrylate or ethoxyethoxyethyl acrylate; Preferably, the first functional monomer includes any one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, diacetone acrylamide, ethyl acetoacetate methacrylate, divinylbenzene, tripropylene glycol diacrylate, pentaerythritol triacrylate, isoprene, polyethylene glycol diacrylate, aziridine or a silane coupling agent.

3. The high solid content, low viscosity polyacrylate aqueous binder according to claim 1 or 2, characterized in that: The polymerizable monomers include, by weight, 30 to 70 parts of hard monomers, 30 to 70 parts of soft monomers, 0.5 to 25 parts of first functional monomers, and 0.1 to 8 parts of second functional monomers.

4. The high solid content, low viscosity polyacrylate aqueous binder according to any one of claims 1 to 3, characterized in that: The solid content of the high-solid content, low-viscosity polyacrylate water-based binder is 40% to 55%; Preferably, the viscosity of the high solid content, low viscosity polyacrylate aqueous binder is less than 1000 mPa·s.

5. A method for preparing a high solid content, low viscosity polyacrylate aqueous binder as claimed in any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) preparing a pre-emulsion solution, a bottom reaction solution and an initiator solution; (2) adding the reaction liquid at the bottom of the kettle to the reactor, taking out a portion of the pre-emulsion as a seed emulsion and adding it to the reactor, heating, adding a portion of the initiator solution, pre-reacting, and then dripping the remaining pre-emulsion and the remaining initiator solution. After the dripping is completed, the temperature is kept high, the temperature is lowered, and then a residual monomer scavenger is added. The temperature is lowered again, and the pH value of the system is adjusted to obtain the high solid content, low viscosity polyacrylate water-based binder.

6. The preparation method according to claim 5, characterized in that: The raw materials for preparing the pre-emulsion include hard monomer, soft monomer, first functional monomer, second functional monomer, emulsifier and deionized water; Preferably, the pre-emulsion comprises, by weight, 30 to 70 parts of hard monomer, 30 to 70 parts of soft monomer, 0.5 to 25 parts of first functional monomer, 0.1 to 8 parts of second functional monomer, 0.5 to 5 parts of emulsifier and 10 to 70 parts of deionized water; Preferably, the raw materials for preparing the bottom reaction liquid include an emulsifier, deionized water and a buffer; Preferably, the reaction liquid at the bottom of the kettle comprises, by weight, 0.1 to 1 part of an emulsifier, 50 to 100 parts of deionized water and 0.1 to 1 part of a buffer; Preferably, the initiator solution is prepared from 0.1 to 1 parts of initiator and 5 to 15 parts of deionized water in parts by weight.

7. The preparation method according to claim 6, characterized in that: The emulsifiers in the pre-emulsion and the bottom reaction liquid independently include any one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene octylphenol ether-10, sodium allyl hydroxypropyl sulfonate, ammonium allyloxy fatty alcohol oxyethylene ether sulfate, disodium succinate nonylphenol polyoxyethylene ether monoester sulfonate, lauryl alcohol ethoxylate, isomeric tridecyl alcohol ethoxylate, and fatty acid methyl ester ethoxylate, or a combination of at least two thereof; Preferably, the buffer comprises any one of sodium bicarbonate, ammonia water, ammonium bicarbonate, sodium hydroxide, lithium hydroxide or a combination of at least two thereof; Preferably, the initiator is a water-soluble thermal decomposition initiator, including any one of potassium persulfate, ammonium persulfate, sodium persulfate, or a combination of at least two thereof.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The weight of the seed emulsion in step (2) accounts for 2% to 45% of the total weight of the pre-emulsion; Preferably, the weight of the partial initiator solution in step (2) accounts for 5% to 15% of the total weight of the initiator solution; Preferably, the residual monomer eliminating agent in step (2) comprises bleaching powder and tert-butyl peroxide; Preferably, in parts by weight, the residual monomer eliminating agent in step (2) comprises 0.01 to 0.1 parts of bleaching powder and 0.01 to 0.1 parts of tert-butyl peroxide.

9. The preparation method according to any one of claims 5 to 8, characterized in that: The step (2) of adding the reaction liquid at the bottom of the kettle into the reactor specifically comprises: adding the reaction liquid at the bottom of the kettle into the reactor at a temperature of 40 to 80° C.; Preferably, the temperature in step (2) is raised to 75-85°C; Preferably, the pre-reaction time in step (2) is 10 to 60 minutes; Preferably, the temperature of the dripping in step (2) is 75 to 85° C., and the dripping time is 1 to 5 hours; Preferably, the insulation temperature in step (2) is 84 to 90° C., and the insulation time is 0.5 to 3.5 h; Preferably, the cooling in step (2) is to cool to 57-73°C; Preferably, the cooling again in step (2) is cooling to below 50°C; Preferably, the pH value of the system is adjusted to 7 to 9 in step (2); Preferably, the pH adjusting agent used to adjust the pH value of the system in step (2) includes any one of ammonia water, sodium hydroxide, lithium hydroxide, potassium hydroxide, and sodium bicarbonate, or a combination of at least two thereof; Preferably, the step of filtering is further included after adjusting the pH value of the system.

10. Use of the high-solid content, low-viscosity polyacrylate aqueous binder according to any one of claims 1 to 4 in battery slurry.

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