Aqueous polyurethane dispersion, preparation method therefor, and use thereof

Abstract

The present application belongs to the technical field of polymer materials. Provided are an aqueous polyurethane dispersion, a preparation method therefor and the use thereof. Starting materials for preparing the aqueous polyurethane dispersion comprise a polyisocyanate, a polybutadiene polyol, a hydrophilic chain extender, and optionally, a small molecule chain extender and a neutralizing agent. The polybutadiene polyol having a specific structure and a specific molecular weight is used as a soft segment, and by means of the design and mutual compounding of components, the polyurethane dispersion exhibits lower polarity and surface energy, and exhibits good adaptability to materials / fillers having low surface energy, and thus can form excellent dispersion and coating effects on materials having low surface energy, thus improving the performance of slurry. In addition, the aqueous polyurethane dispersion exhibits excellent solvent resistance, low-temperature resistance, hydrolysis resistance and mechanical properties, and thus has broad application prospects in the fields such as battery slurry dispersants, photovoltaic back plate adhesives and conformal coatings.

Description

A waterborne polyurethane dispersion, its preparation method and application

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411755909.8, filed on December 3, 2024, entitled "An Aqueous Polyurethane Dispersion and Its Preparation Method and Application", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of polymer materials technology, specifically to the field of waterborne polyurethane, and specifically relates to a waterborne polyurethane dispersion, its preparation method, and its application. Background Technology

[0004] With the increasing global emphasis on green chemistry and low-carbon environmental protection, new materials and technologies that align with this international development trend have received widespread attention and application. Among them, waterborne polyurethane or polyurethane-polyurea aqueous dispersions using water as the dispersion medium have become a research hotspot due to their unique properties and advantages. These materials not only meet national policy guidance and development needs but also produce no pollution during use, making them environmentally friendly and widely used in coatings, adhesives, and other fields. However, common polyester, polyether, and polycarbonate-based polyurethane aqueous dispersions or polyurethane-polyurea aqueous dispersions often contain a large number of highly polar ester, ether, and carbonate bonds, resulting in poor adhesion to low surface energy substrates. Furthermore, the soft segments in these polyurethanes are mostly crystallizable and exhibit hydrogen bonding with the hard segments, meaning that the stability of these materials may be affected at low temperatures. The large number of polar segments and most polar organic solvents, due to the principle of "like dissolves like," pose challenges to the solvent resistance of polyurethane films. High polymer polarity combined with low surface energy substances, especially carbon fillers such as graphite and carbon black, may not achieve good dispersion and coating effects in certain specific application environments due to their poor polarity.

[0005] To address these issues, researchers have proposed various improvement methods, such as: introducing low-polarity segments by grafting silicon-containing reagents, or directly adding silicon-containing reagents to the formulation to improve the wetting and adhesion of polymers to low surface energy substrates; improving the low-temperature resistance of emulsion systems by using low-crystallinity or amorphous segments in the formulation design; and improving the solvent resistance of polyester, polyether, and polycarbonate waterborne polyurethanes by using highly crosslinked systems or increasing molecular weight. However, these methods can lead to performance balance conflicts between adhesion, cohesive energy, and film-forming properties, and all have certain limitations, requiring trade-offs and adjustments in practical applications.

[0006] CN113711383A discloses an electrode binder composition containing polyurethane. This polyurethane is obtained by reacting a polyisocyanate, a polyol, a compound having a hydrophilic group and one or more active hydrogen atoms, and a chain extender. The polyol is an olefinic polyol having 1.5 or more active hydrogen atoms and / or a carbonate diol with fewer than 6 carbon atoms in its carbonate bonds. This polyurethane, when combined with fibrous nano-carbon materials with an average fiber length of 0.5 μm or more, serves as an electrode binder. It exhibits good electrolyte stability, adhesion, and the ability to suppress the expansion and rebound of the electrode active material coating. However, this polyurethane dispersion shows significant deficiencies in its encapsulation and dispersion properties for negative electrode active materials such as graphite and conductive agents such as acetylene black.

[0007] CN114698377A discloses a method for preparing and applying a polyolefin-type waterborne polyurethane, which has excellent storage stability and adhesion to various substrates. The polyolefin polyol used in this polyurethane is obtained by copolymerizing ethylene and α-olefins with 3-8 carbon atoms to form a polyolefin, reacting it with unsaturated (poly)carboxylic acids / anhydrides to generate acid-modified polyolefins, and then reacting it with amino alcohols or epoxides to obtain polyolefin-type polyols. Inevitably, polar groups such as ester bonds still exist in the soft segment structure, which cannot perform well in some low-polarity application scenarios.

[0008] In general, current conventional waterborne polyurethane products contain a large number of highly polar ester, ether, and carbonate bonds, resulting in a high overall polarity of the polymer chain segments. This leads to insufficient dispersibility and compatibility with low-polarity, low-surface-energy substances. Furthermore, due to the "like dissolves like" principle of waterborne polyurethanes with most polar organic solvents, they exhibit significant swelling and poor solvent resistance and stability. Moreover, existing polyolefin-based waterborne polyurethane products suffer from several drawbacks: firstly, the lack of crystallinity makes it difficult to simultaneously achieve optimal polymer film strength and elongation at break; secondly, limited cohesive energy results in insufficient film hardness. Therefore, developing a waterborne polyurethane with good compatibility with low-surface-energy substances and excellent solvent resistance and mechanical properties is a pressing issue in this field. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the purpose of this application is to provide an aqueous polyurethane dispersion, its preparation method, and its application. By using polybutadiene polyol with a specific structure as the soft segment, the overall polarity of the aqueous polyurethane dispersion is reduced, resulting in excellent encapsulation and dispersion characteristics for low surface energy substances. It also exhibits excellent solvent resistance, low-temperature resistance, and mechanical properties, making it particularly suitable for applications such as battery slurry dispersants, photovoltaic backsheet adhesives, and conformal coatings.

[0010] To achieve this objective, the following technical solution is adopted in this application:

[0011] In a first aspect, this application provides an aqueous polyurethane dispersion, wherein the raw materials for preparing the aqueous polyurethane dispersion include polyisocyanate, polybutadiene polyol, hydrophilic chain extender, optionally small molecule chain extender and neutralizer; the polybutadiene polyol comprises structural units shown in Formula I, structural units shown in Formula II and optionally structural units shown in Formula III.

[0012] The molar percentage of the structural unit shown in Formula I in the polybutadiene polyol is denoted as a, the molar percentage of the structural unit shown in Formula II is denoted as b, and the molar percentage of the structural unit shown in Formula III is denoted as c, where a > c and 0 < (a + c) / b < 1; the number average molecular weight of the polybutadiene polyol is 1000-2500 g / mol.

[0013] The aqueous polyurethane dispersion provided in this application uses a polybutadiene polyol with a specific structure as the soft segment, introducing a large number of low-polarity alkyl segments into the polymer, which can effectively reduce the overall polarity of the polymer. This application controls the cis / trans ratio of 1,4-butadiene polymeric structural units and the proportion of 1,2-vinyl structural units in the polybutadiene segments. Utilizing a high proportion (0 < (a+c) / b < 1) of 1,2-vinyl structural units, the aqueous polyurethane has sufficient steric hindrance and low-polarity side chains, resulting in a low-polarity solvent-resistant "shell" during shear emulsification to form particles and micelles. Simultaneously, by designing the trans proportion of 1,4-butadiene polymeric structural units to be higher than the cis proportion (a > c), the system possesses a rigid double bond structure, improving mechanical properties while ensuring the flexibility of the chain segments. This allows the aqueous polyurethane dispersion to smoothly complete phase inversion and hydration layer construction with conventional-level mechanical energy during high-speed shear emulsification, resulting in a stable aqueous polyurethane dispersion. The process is simple and easy to prepare. Due to the presence of low-polarity aliphatic long chains and numerous alkenyl side chains in the soft segment structure, the glass transition temperature (T0) of the polyurethane in this application is [high / low]. g The surface energy (SFE) is very low, and can be controlled between -10°C and -30°C through formulation adjustments, giving the aqueous polyurethane dispersion excellent low-temperature resistance. Furthermore, it is easily activated as a dispersant. More importantly, the presence of 1,4-butadiene polymeric structural units (trans-double bonds and optionally cis-double bonds) and 1,2-vinyl structural units (side-chain suspension structures) in the polymer structure allows the polymer chains to form secondary structures with certain "cavities" during chain aggregation and entanglement. This better disperses and coats low-surface-energy materials / fillers (such as graphite, carbon black, acetylene black, carbon nanotubes, etc., commonly used in battery electrode slurries), forming a stable suspension state and avoiding agglomeration and phase separation due to temperature differences.

[0014] In summary, compared to existing polyester, polyether, and polycarbonate-based polyurethanes, this application, based on the structural design of polybutadiene polyol, enables the aqueous polyurethane dispersion to have lower polarity and surface energy, resulting in better compatibility with low surface energy materials / fillers. This allows for excellent dispersion and coating of low surface energy materials, improving slurry performance. Furthermore, the aqueous polyurethane dispersion exhibits excellent solvent resistance, low-temperature resistance, hydrolysis resistance, and mechanical properties, showing broad application prospects in areas such as battery slurry dispersants, photovoltaic backsheet adhesives, and conformal coatings.

[0015] The following are optional technical solutions for this application, but are not intended to limit the technical solutions provided in this application. The purpose and beneficial effects of this application can be better achieved through the following optional technical solutions.

[0016] In this application, the molecular structure of the polybutadiene polyol includes the structural unit shown in Formula I (trans-1,4-butadiene polymeric structural unit), the structural unit shown in Formula II (1,2-vinyl structural unit), and optionally the structural unit shown in Formula III (cis-1,4-butadiene polymeric structural unit), and the molar percentages of the three are denoted as a, b, and c, respectively, where a > c.

[0017] 0 < (a+c) / b < 1, (a+c) / b can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, and specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0018] Specifically, a + b + c = 1.

[0019] Optionally, the molar percentage 'a' of the structural unit shown in Formula I in the polybutadiene polyol is 0 < a ≤ 50%, for example, a can be 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, or 48%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list all the specific values ​​included in the range. Further, 5% ≤ a ≤ 35% can be selected.

[0020] Optionally, the molar percentage content b of the structural unit shown in Formula II of the polybutadiene polyol is 50% < b < 100%, for example, b can be 51%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, or 98%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further, 50% < b ≤ 95% can be selected.

[0021] Optionally, the molar percentage c of the structural unit shown in Formula III of the polybutadiene polyol is 0 ≤ c ≤ 25%, for example, c can be 0, 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22% or 24%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further, optionally, 0 ≤ c ≤ 18%.

[0022] In this application, the number average molecular weight of the polybutadiene polyol is 1000-2500 g / mol, for example, it can be 1200 g / mol, 1400 g / mol, 1500 g / mol, 1800 g / mol, 2000 g / mol, 2200 g / mol, 2400 g / mol, or optionally 1500-2500 g / mol.

[0023] For example, the structure of the polybutadiene polyol can be represented as follows:

[0024] In this application, the polybutadiene polyol can be purchased from the market or prepared by organic synthesis methods known in the art.

[0025] Optionally, based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender, and neutralizing agent as 100%, the mass of the polyisocyanate is 16.0%-34.0%, for example, 16.5%, 17%, 17.5%, 18.0%, 18.5%, 19%, 20%, 21%, 22%, 25%, 28%, 30%, 32%, or 33%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further optionally, it is 16.0%-29.5%.

[0026] Optionally, based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender, and neutralizing agent as 100%, the mass of the polybutadiene polyol is 58.0%-77.0%, for example, 59%, 60%, 62%, 64%, 65%, 68%, 70%, 72%, 74%, 75%, or 76%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, and further optionally, 63.0%-77.0%.

[0027] Optionally, based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender, and neutralizing agent as 100%, the mass of the hydrophilic chain extender is 3.8-5.0%, for example, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.8%, or 4.9%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, and further optionally, 4.0-4.8%.

[0028] Optionally, based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender, and neutralizing agent as 100%, the mass of the small molecule chain extender is ≤4.1%, for example, it can be 0, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, and further optionally, it is 0.1-3.6%.

[0029] Optionally, based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender, and neutralizing agent as 100%, the mass of the neutralizing agent is 0.5-1.5%, for example, 0.6%, 0.8%, 1%, 1.1%, 1.2%, 1.3%, or 1.4%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, and further optionally, 1.0-1.5%.

[0030] Optionally, the polyisocyanate includes any one or a combination of at least two of aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates.

[0031] Optionally, the polyisocyanate includes any one or a combination of at least two of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate, and further optionally hexamethylene diisocyanate and / or dicyclohexylmethane diisocyanate.

[0032] Optionally, the hydrophilic chain extender is a compound containing hydroxyl and carboxyl groups, and further optionally, any one or a combination of at least two of 3-hydroxypropionic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolacetic acid, trihydroxysulfonic acid, and dihydroxysuccinic acid, and further optionally, dimethylolpropionic acid.

[0033] Optionally, the small molecule chain extender is a small molecule amine chain extender.

[0034] Optionally, the molecular weight of the small molecule chain extender is 60-499 g / mol, for example, it can be 70 g / mol, 80 g / mol, 90 g / mol, 100 g / mol, 150 g / mol, 200 g / mol, 250 g / mol, 300 g / mol, 350 g / mol, 400 g / mol or 450 g / mol, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0035] Optionally, the small molecule chain extender is a linear diamine chain extender.

[0036] In this application, "linear diamine chain extender" means that the molecular structure of the diamine chain extender does not contain a branched cross-linked structure, and the diamine chain extender includes any one or a combination of at least two of aliphatic diamine chain extenders, alicyclic diamine chain extenders, and aromatic diamine chain extenders.

[0037] As an optional technical solution of this application, the small molecule chain extender is a linear diamine chain extender containing active hydrogen. On the one hand, the reactivity of diamine chain extenders is generally less than that of triamines and tetraamines, resulting in a better chain extension effect on polymers. On the other hand, the linear diamine chain extender can make the polyurethane chains in this application more flexible, avoiding the superposition of cross-linked ternary and tetraamine chain extension reactions on the secondary structure of the polymer containing "cavities," ultimately forming a highly rigid three-dimensional structure to ensure the dispersion and coating effect of the aqueous polyurethane dispersion on low surface energy fillers.

[0038] Optionally, the small molecule chain extender includes any one or a combination of at least two of ethylenediamine, hexamethylenediamine, pentamethylenediamine, isophoronediamine, 4,4'-diphenylmethanediamine, and 4,4'-diaminodicyclohexylmethane, and further optionally ethylenediamine and / or 4,4'-diaminodicyclohexylmethane.

[0039] Optionally, the neutralizing agent is an inorganic alkaline compound, and more preferably any one or a combination of at least two of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates.

[0040] As an optional technical solution of this application, the neutralizing agent is an inorganic alkaline compound, in which the hydrophilic groups of the neutralized waterborne polyurethane are more easily ionized in water, forming a more stable double electric layer and better emulsion stability; more importantly, when the waterborne polyurethane dispersion is used as a dispersant in battery slurry, it can be more compatible with the waterborne slurry system, more easily interact with the filler and form a stable suspension that is not easy to settle, thus ensuring the viscosity and fineness of the slurry.

[0041] Optionally, the alkali metal includes Li, Na, K, etc.

[0042] Optionally, the neutralizing agent includes any one or a combination of at least two of sodium hydroxide, lithium hydroxide, sodium carbonate, and sodium bicarbonate, and further optionally sodium hydroxide.

[0043] Optionally, the raw materials for preparation may also include a catalyst.

[0044] In this application, the type of catalyst is not specifically limited, and any catalyst known in the art that can catalyze the reaction of active hydrogen with NCO groups to generate carbamate groups is applicable to this application.

[0045] Optionally, the catalyst includes organobismuth catalysts and / or organotin catalysts, exemplary including but not limited to: any one or a combination of at least two of Bi@8108 (a leading US company), dimethyltin dinedecanoate, dibutyltin dilaurate, and dioctyltin dilaurate, further optionally Bi@8108 (a leading US company) and / or dimethyltin dinedecanoate, and more preferably dimethyltin dinedecanoate.

[0046] Optionally, based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender and neutralizer as 100%, the mass of the catalyst is ≤1000ppm, for example, it can be 0, 1ppm, 5ppm, 10ppm, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm or 900ppm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0047] Optionally, the raw materials used in the preparation may also include an organic solvent.

[0048] Optionally, the boiling point of the organic solvent is 40-85℃, for example, it can be 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0049] Optionally, the organic solvent includes ketone solvents, further optionally acetone and / or butanone, and more preferably butanone.

[0050] Optionally, based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender and neutralizer as 100%, the mass of the organic solvent is 100-300%, for example, it can be 120%, 150%, 180%, 200%, 220%, 250% or 280%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0051] Optionally, the solvent of the aqueous polyurethane dispersion includes water, and the solid content of the aqueous polyurethane dispersion is 10-40%, for example, it can be 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35% or 38%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, and further optionally, it is 15-30%.

[0052] The raw materials for preparing the waterborne polyurethane dispersion include water, and the amount of water used is such that the solid content of the waterborne polyurethane dispersion is 10-40%.

[0053] Optionally, the particle size of the solids in the aqueous polyurethane dispersion is 20-500 nm, for example, it can be 30 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 350 nm, 400 nm or 450 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further optionally, it is 50-250 nm.

[0054] Secondly, this application provides a method for preparing an aqueous polyurethane dispersion as described in the first aspect, the method comprising the following steps:

[0055] Polyisocyanate, polybutadiene polyol and hydrophilic chain extender are polymerized to obtain a prepolymer;

[0056] After the prepolymer undergoes a neutralization reaction with a neutralizing agent, it is dispersed in water and then subjected to a chain extension reaction with an optional small molecule chain extender to obtain the waterborne polyurethane dispersion.

[0057] It should be noted that the chain extension reaction is optional; that is, when the raw materials contain a small molecule chain extender, the chain extension reaction will take place; when the raw materials do not contain a small molecule chain extender, the chain extension reaction will not occur.

[0058] Optionally, the polymerization reaction is carried out in the presence of an organic solvent.

[0059] Optionally, the polymerization reaction is carried out in the presence of a catalyst.

[0060] Optionally, the preparation method includes the following steps:

[0061] Polyisocyanate, polybutadiene polyol, hydrophilic chain extender, 20-80% organic solvent and optionally catalyst are mixed and polymerized to obtain prepolymer;

[0062] The prepolymer is mixed with the remaining organic solvent and then neutralized with a neutralizing agent.

[0063] The product of the neutralization reaction is dispersed in water and then subjected to a chain extension reaction with an optional small molecule chain extender to obtain an emulsion; the organic solvent in the emulsion is removed to obtain the aqueous polyurethane dispersion.

[0064] As an optional technical solution of this application, the organic solvent is added in two stages. The first stage serves as the solvent (medium) for the polymerization reaction. Assuming the total amount of organic solvent added is 100%, the amount of organic solvent added during the polymerization stage is 20-80%, for example, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 75%, and specific values ​​within the above ranges are not exhaustively listed here for space limitations and for the sake of brevity. The remaining organic solvent is mixed with the prepolymer to dilute the prepolymer.

[0065] Optionally, the neutralizing agent is added to the reaction system in the form of an aqueous solution of the neutralizing agent.

[0066] Optionally, the mass percentage of the neutralizing agent in the neutralizing agent aqueous solution is 5-50%, for example, it can be 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40% or 45%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0067] Optionally, the small molecule chain extender is added to the reaction system in the form of an aqueous solution of the small molecule chain extender.

[0068] Optionally, the mass percentage of the small molecule chain extender in the aqueous solution is 5-50%, for example, it can be 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40% or 45%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0069] Optionally, the polymerization reaction temperature is 70-90℃, for example, it can be 72℃, 75℃, 78℃, 80℃, 82℃, 85℃ or 88℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, and further optionally, it is 75-85℃.

[0070] Optionally, the polymerization reaction time is the time required for the NCO groups in the product (prepolymer) to reach the theoretical value.

[0071] Optionally, the mass percentage of NCO groups in the prepolymer is 0.8-2.5%, for example, it can be 0.82%, 0.85%, 0.88%, 0.9%, 0.92%, 0.95%, 0.98%, 1%, 1.02%, 1.05%, 1.08%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.1%, 2.2%, or 2.4%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0072] Optionally, the temperature of the neutralization reaction is 30-50°C, for example, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C or 48°C, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, and further optionally, 35-45°C.

[0073] Optionally, the neutralization reaction time is 5-40 min, for example, it can be 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 25 min, 30 min or 35 min, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further optionally, it is 10-20 min.

[0074] Optionally, the temperature of the chain extension reaction is 35-60℃, for example, it can be 38℃, 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃ or 58℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further optional, it is 40-55℃.

[0075] Optionally, the chain extension reaction time is 5-40 min, for example, it can be 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 25 min, 30 min or 35 min, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further optionally, it is 10-20 min.

[0076] Optionally, the pH value of the emulsion is >6, for example, it can be 6.2, 6.5, 6.8, 7, 7.2, 7.5, 7.8, 8, etc.

[0077] Optionally, the method for removing organic solvents includes vacuum distillation.

[0078] Thirdly, this application provides an application of the aqueous polyurethane dispersion as described in the first aspect, wherein the aqueous polyurethane dispersion is used as a battery slurry dispersant, a photovoltaic backsheet adhesive, or a conformal coating.

[0079] Fourthly, this application provides a dispersion slurry comprising inorganic particles and an aqueous polyurethane dispersion as described in the first aspect.

[0080] Optionally, the inorganic particles include any one or a combination of at least two of the following: graphite, silicon-based particles, silicon-carbon particles, carbon black, acetylene black, carbon nanotubes, Ketjen black, carbon fiber, and graphene.

[0081] Optionally, based on the solids mass of the aqueous polyurethane dispersion as 100%, the mass of the inorganic particles is 15-40%, for example, it can be 16%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35% or 38%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0082] Optionally, the solid content of the dispersion slurry is 15-25%, for example, it can be 16%, 18%, 20%, 22% or 24%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0083] Optionally, the viscosity of the dispersion slurry is 4000-6500 cp, for example, it can be 4200 cp, 4500 cp, 4800 cp, 5000 cp, 5200 cp, 5500 cp, 5800 cp, 6000 cp, 6200 cp or 6400 cp, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0084] As an optional technical solution of this application, the aqueous polyurethane dispersion can form excellent dispersion and coating effects on low surface energy substances. As a dispersant, it can give the dispersion slurry a suitable viscosity and prevent stratification, sedimentation, and other phenomena. Meanwhile, the fineness of the dispersion slurry is ≤30μm, optionally ≤25μm, and more preferably ≤20μm; the slurry residue is ≤0.1g, optionally ≤0.05g, exhibiting excellent dispersibility and stability.

[0085] Optionally, the dispersion slurry can be a negative electrode slurry or a negative electrode sheet for preparing lithium secondary batteries.

[0086] It should be noted that the negative electrode slurry also includes binders, solvents and other additives, and this application does not impose any special limitations on the aforementioned reagents.

[0087] Compared with the prior art, this application has the following advantages:

[0088] (1) In the waterborne polyurethane dispersion provided in this application, polybutadiene polyol with a specific structure and molecular weight is used as the soft segment. Through the design and mutual compounding of components, the waterborne polyurethane dispersion has lower polarity and surface energy, and good compatibility with low surface energy materials / low surface energy fillers. It can form excellent dispersion and coating effects on low surface energy materials and improve the performance of slurry. At the same time, the waterborne polyurethane dispersion has excellent solvent resistance, low temperature resistance, hydrolysis resistance and mechanical properties, taking into account the fracture strength and elongation at break. It has broad application prospects in the fields of battery slurry dispersant, photovoltaic backsheet adhesive, conformal coating and so on.

[0089] (2) The waterborne polyurethane dispersion provided in this application can form excellent dispersion and coating effects on low surface energy fillers, and the dispersion slurry containing it has excellent viscosity, fineness and slag discharge.

[0090] (3) The production process of the waterborne polyurethane dispersion provided in this application is simple, easy to operate, safe and non-toxic. Detailed Implementation

[0091] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0092] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not limited to those elements and may also include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0093] "Optionally," "optionally," or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0094] In the following specific embodiments of this application, the materials for which no preparation method is provided are all commercially available chemicals. The specific information of the materials is as follows:

[0095] (1) Polybutadiene polyol, specific information is shown in Table 1 below. In Table 1, a represents the molar percentage of trans-1,4-butadiene polymeric structural units, b represents the molar percentage of 1,2-vinyl structural units, c represents the molar percentage of cis-1,4-butadiene polymeric structural units, M n Number average molecular weight;

[0096] Table 1

[0097] (2) Polyisocyanates

[0098] Hexamethylene diisocyanate (HDI): Industrial grade, Wanhua Chemical Group Co., Ltd.

[0099] Dicyclohexylmethane diisocyanate (HMDI): Industrial grade, Wanhua Chemical Group Co., Ltd.

[0100] Isophorone diisocyanate (IPDI): Industrial grade, Wanhua Chemical Group Co., Ltd.

[0101] (3) Hydrophilic chain extender

[0102] Dimethylolpropionic acid (DMPA): Industrial grade, Persto Chemical Company.

[0103] (4) Small molecule chain extenders

[0104] Ethylenediamine: Analytical grade, Sinopharm Chemical Reagent Co., Ltd.;

[0105] 1,6-Hexanediamine: Industrial grade, Wanhua Chemical Group Co., Ltd.;

[0106] 4,4'-Diaminodicyclohexylmethane (HMDA): Industrial grade, Wanhua Chemical Group Co., Ltd.

[0107] (5) Neutralizing agent

[0108] Sodium hydroxide: analytical grade, Sinopharm Chemical Reagent Co., Ltd.

[0109] (6) Catalyst

[0110] Dimethyltin dinedecanoate, reagent grade, Bidex Pharmaceuticals.

[0111] (7) Organic solvents

[0112] Butyl ketone (MEK): Industrial grade, Zibo Qixiang Tengda Chemical Co., Ltd.

[0113] In the following specific embodiments, the testing methods for the basic physical properties of the prepolymer and polyurethane are as follows:

[0114] (1) NCO content of prepolymer: Take 0.5g of prepolymer, add 5mL of chlorobenzene to dissolve it initially, then add 20mL of di-n-butylamine standard solution quantitatively through NCO titrator, sonicate for 10min, add 50mL of ethanol to the sample, then place the test electrode in the sample solution and use NCO titrator to perform dilute hydrochloric acid titration test.

[0115] (2) Solid particle size of waterborne polyurethane dispersion: Take 0.1g of the sample to be tested, add it to 100g of deionized water, sonicate for 5min using an ultrasonic machine, and test the particle size using a Malvern particle size analyzer.

[0116] The following will use several embodiments as examples to describe in detail the specific components and preparation methods of the waterborne polyurethane dispersion described in this application, but the components and preparation methods of the waterborne polyurethane dispersion described in this application are not limited to these embodiments.

[0117] Example 1

[0118] An aqueous polyurethane dispersion is prepared from the following raw materials: high-molecular-weight isocyanate (HMDI), polybutadiene polyol P1, hydrophilic chain extender (DMPA), small molecule chain extender (ethylenediamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0119] (1) 177.8g of dehydrated polybutadiene polyol P1, 60.4g of HMDI, 11.5g of DMPA, 250g of butanone and 0.225g of dimethyltin dinecidocate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 1.00% to obtain a prepolymer.

[0120] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 250g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 985g of water for dispersion, heat to 40°C, and add 10.5g of ethylenediamine aqueous solution (2.55g of ethylenediamine dissolved in 7.95g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.4. Finally, the crude emulsion is subjected to vacuum distillation to separate the butanone and obtain the aqueous polyurethane dispersion with a solid content of 20% and a particle size of 65nm.

[0121] Example 2

[0122] An aqueous polyurethane dispersion is prepared from the following raw materials: polyisocyanate (HMDI, HDI), polybutadiene polyol P1, hydrophilic chain extender (DMPA), small molecule chain extender (ethylenediamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0123] (1) 177.8g of dehydrated polybutadiene polyol P1, 23.0g of HMDI, 23.0g of HDI, 11.5g of DMPA, 235g of butanone and 0.225g of dimethyltin dinedecanoate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 0.96%, thus obtaining a prepolymer.

[0124] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 235g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 925g of water for dispersion, heat to 40°C, and add 10.2g of ethylenediamine aqueous solution (2.25g of ethylenediamine dissolved in 7.95g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.6. Finally, the crude emulsion is separated by vacuum distillation to obtain the aqueous polyurethane dispersion with a solid content of 20% and a particle size of 73nm.

[0125] Example 3

[0126] An aqueous polyurethane dispersion is prepared from the following raw materials: polyisocyanate (HMDI, HDI), polybutadiene polyol P2, hydrophilic chain extender (DMPA), small molecule chain extender (HMDA), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0127] (1) 177.8g of dehydrated polybutadiene polyol P2, 52.0g of HMDI, 6.0g of HDI, 11.5g of DMPA, 247g of butanone and 0.225g of dimethyltin dinedecanoate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 0.93%, thus obtaining a prepolymer.

[0128] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 247g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 1000g of water for dispersion, heat to 40°C, add 35.6g of ethylenediamine aqueous solution (8.9g of ethylenediamine dissolved in 26.7g of water) and stir for chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.9. Finally, the crude emulsion is subjected to vacuum distillation to separate the butanone and obtain the waterborne polyurethane dispersion with a solid content of 20% and a particle size of 81nm.

[0129] Example 4

[0130] An aqueous polyurethane dispersion is prepared from the following raw materials: polyisocyanate (HMDI, IPDI), polybutadiene polyol P1, hydrophilic chain extender (DMPA), small molecule chain extender (ethylenediamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0131] (1) 177.8g of dehydrated polybutadiene polyol P1, 37.0g of HMDI, 37.0g of IPDI, 11.5g of DMPA, 263g of butanone and 0.237g of dimethyltin dinecidocate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 2.1% to obtain a prepolymer.

[0132] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 263g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 1058g of water for dispersion, heat to 40°C, add 27.5g of ethylenediamine aqueous solution (7.5g of ethylenediamine dissolved in 20g of water), stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.6. Finally, the crude emulsion is separated by vacuum distillation to obtain the aqueous polyurethane dispersion with a solid content of 20% and a particle size of 57nm.

[0133] Example 5

[0134] An aqueous polyurethane dispersion is prepared from the following raw materials: high-molecular-weight isocyanate (HMDI), polybutadiene polyols P1 and P2, hydrophilic chain extender (DMPA), small molecule chain extender (hexamethylenediamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0135] (1) 88.5g of dehydrated polybutadiene polyol P1, 88.5g of dehydrated polybutadiene polyol P2, 60.3g of HMDI, 11.5g of DMPA, 249g of butanone and 0.224g of dimethyltin dinedecanoate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 0.94%, thus obtaining a prepolymer.

[0136] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 249g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 994g of water for dispersion, heat to 40°C, and add 23.2g of hexamethylenediamine aqueous solution (5.8g of ethylenediamine dissolved in 17.4g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.5. Finally, the crude emulsion is subjected to vacuum distillation to separate the butanone and obtain the aqueous polyurethane dispersion with a solid content of 20% and a particle size of 48nm.

[0137] Example 6

[0138] An aqueous polyurethane dispersion is prepared from the following raw materials: high-molecular-weight isocyanate (HMDI), polybutadiene polyol P1, hydrophilic chain extender (DMPA), small molecule chain extender (diethylenetriamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0139] (1) 177.8g of dehydrated polybutadiene polyol P1, 60.4g of HMDI, 11.5g of DMPA, 250g of butanone and 0.225g of dimethyltin dinecidocate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 1.00% to obtain a prepolymer.

[0140] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 250g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 987g of water for dispersion, heat to 40°C, and add 10.92g of diethylenetriamine aqueous solution (2.92g of diethylenetriamine dissolved in 8g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.7. Finally, the crude emulsion is separated by vacuum distillation to obtain the aqueous polyurethane dispersion with a solid content of 20% and a particle size of 56nm.

[0141] Example 7

[0142] An aqueous polyurethane dispersion is prepared from the following raw materials: high-molecular-weight isocyanate (HMDI), polybutadiene polyol P1, hydrophilic chain extender (DMPA), small molecule chain extender (ethylenediamine), neutralizing agent (triethylamine), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0143] (1) 177.8g of dehydrated polybutadiene polyol P1, 60.4g of HMDI, 11.5g of DMPA, 250g of butanone and 0.225g of dimethyltin dinecidocate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 1.00% to obtain a prepolymer.

[0144] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 250g of butanone and cool it down to 35°C again. Add 25.0g of triethylamine aqueous solution (5.0g of triethylamine dissolved in 20.0g of water) and stir for 10min. Then add 1010g of water for dispersion, heat to 40°C, and add 10.5g of ethylenediamine aqueous solution (2.55g of ethylenediamine dissolved in 7.95g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.6. Finally, the crude emulsion is separated by vacuum distillation to obtain the aqueous polyurethane dispersion with a solid content of 20% and a particle size of 75nm.

[0145] Comparative Example 1

[0146] An aqueous polyurethane dispersion is prepared from the following raw materials: high-molecular-weight isocyanate (HMDI), polybutadiene polyol P3, hydrophilic chain extender (DMPA), small molecule chain extender (ethylenediamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0147] (1) 177.8g of dehydrated polybutadiene polyol P3, 60.4g of HMDI, 11.5g of DMPA, 250g of butanone and 0.225g of dimethyltin dinecidocate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 1.46%, and a prepolymer was obtained.

[0148] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 250g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 985g of water for dispersion, heat to 40°C, and add 10.5g of ethylenediamine aqueous solution (2.55g of ethylenediamine dissolved in 7.95g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.4. Finally, the crude emulsion is subjected to vacuum distillation to separate the butanone and obtain the aqueous polyurethane dispersion with a solid content of 20% and a particle size of 103nm.

[0149] Comparative Example 2

[0150] An aqueous polyurethane dispersion is prepared from the following raw materials: high-molecular-weight isocyanate (HMDI), polybutadiene polyol P4, hydrophilic chain extender (DMPA), small molecule chain extender (ethylenediamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0151] (1) 177.8g of dehydrated polybutadiene polyol P4, 60.4g of HMDI, 11.5g of DMPA, 250g of butanone and 0.225g of dimethyltin dinecidocate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 0.85%, and a prepolymer was obtained.

[0152] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 250g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 985g of water for dispersion, heat to 40°C, and add 10.5g of ethylenediamine aqueous solution (2.55g of ethylenediamine dissolved in 7.95g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.4. Finally, the crude emulsion is separated by vacuum distillation to obtain the aqueous polyurethane dispersion with a solid content of 20% and a particle size of 42nm.

[0153] Comparative Example 3

[0154] An aqueous polyurethane dispersion is prepared from the following raw materials: high-molecular-weight isocyanate (HMDI), polybutadiene polyol P5, hydrophilic chain extender (DMPA), small molecule chain extender (ethylenediamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0155] (1) 177.8g of dehydrated polybutadiene polyol P5, 60.4g of HMDI, 11.5g of DMPA, 250g of butanone and 0.225g of dimethyltin dinecidocate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 0.93%, and a prepolymer was obtained.

[0156] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 250g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 985g of water for dispersion, heat to 40°C, and add 10.5g of ethylenediamine aqueous solution (2.55g of ethylenediamine dissolved in 7.95g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.5. Finally, the crude emulsion is subjected to vacuum distillation to separate the butanone and obtain the waterborne polyurethane dispersion with a solid content of 20% and a particle size of 52nm.

[0157] Comparative Example 4

[0158] An aqueous polyurethane dispersion is prepared from the following raw materials: polyisocyanate (HMDI), hydrogenated polybutadiene polyol P6, hydrophilic chain extender (DMPA), small molecule chain extender (ethylenediamine), neutralizing agent (sodium hydroxide), and catalyst (dimethyltin dinedecanoate); the specific preparation method is as follows:

[0159] (1) 177.8g of dehydrated hydrogenated polybutadiene polyol P6, 60.4g of HMDI, 11.5g of DMPA, 250g of butanone and 0.225g of dimethyltin dinedecanoate were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The mixture was stirred at 75°C until the mass percentage of NCO groups in the mixture reached 1.00%, and a prepolymer was obtained.

[0160] (2) After cooling the prepolymer obtained in step (1) to 50°C, dissolve it in 250g of butanone and cool it down to 35°C again. Add 28g of sodium hydroxide aqueous solution (3.1g of sodium hydroxide dissolved in 24.9g of water) and stir for 10min. Then add 985g of water for dispersion, heat to 40°C, and add 10.5g of ethylenediamine aqueous solution (2.55g of ethylenediamine dissolved in 7.95g of water). Stir and chain extension reaction for 20min to obtain a crude emulsion with a pH of 7.7. Finally, the crude emulsion is subjected to vacuum distillation to separate the butanone and obtain the waterborne polyurethane dispersion with a solid content of 20% and a particle size of 69nm.

[0161] Application examples

[0162] A dispersion slurry comprising inorganic particles (conductive carbon black Super P) and an aqueous polyurethane dispersion, wherein the aqueous polyurethane dispersion is provided by Examples 1-7 and Comparative Examples 1-4, respectively; the preparation method of the dispersion slurry is as follows:

[0163] Take 142g of waterborne polyurethane dispersion (solid content of 20%) and place it in a dispersion tank. Add 18g of deionized water, stir evenly, and then add 5g of conductive carbon black Super P. Use a disperser to stir at 3000rpm for 30min to prepare a dispersion slurry with 20% solid content, and then conduct subsequent tests.

[0164] (1) Slurry viscosity: A No. 63 rotor was selected, the speed was 12 rpm, and a viscometer was used for testing at a temperature of 25℃.

[0165] (2) Slurry fineness: The fineness is tested using a 0-100μm fineness plate. The lower the fineness, the better the performance of the slurry.

[0166] (3) Slurry discharge: 100g of dispersed slurry was filtered using a 100-mesh steel wire filter. After drying, the quality of the filtered residue was recorded by differential method. The lower the quality of the discharged residue, the better the performance of the slurry.

[0167] (4) Solvent resistance of waterborne polyurethane dispersion: The waterborne polyurethane dispersion to be tested was spread into a polytetrafluoroethylene film-forming mold to obtain a polyurethane film with a thickness of 0.5 mm, a length of 2 cm and a width of 2 cm. The original mass of the polyurethane film was recorded. Then, in a glove box, the polyurethane film was immersed in an electrolyte (1M LiPF6 electrolyte, with diethyl carbonate, ethylene carbonate and propylene carbonate in a volume ratio of 1:1:1) and sealed. It was then placed in a 50℃ oven for 2 days. The polyurethane film was then removed and the surface was wiped dry with absorbent paper. The mass was recorded and the percentage increase in mass was calculated. The lower the percentage increase in mass, the better the solvent resistance.

[0168] (5) 100% modulus and elongation at break of waterborne polyurethane dispersion: The waterborne polyurethane dispersion to be tested was spread into a polytetrafluoroethylene film forming mold to obtain a polyurethane film with a thickness of 0.5 mm. The polyurethane film was then cut into dumbbell shape as the test sample. Finally, the polyurethane test sample was tested using a MTS Model E43 tensile tester at a stretching speed of 10 mm / min.

[0169] The test results are shown in Table 2:

[0170] Table 2

[0171] According to the test data in Table 2, this application uses polybutadiene polyols with specific structures and molecular weights as soft segments. Through the design and compounding of components, the waterborne polyurethane dispersion can possess excellent slurry dispersibility, solvent resistance, and mechanical properties. Specifically, the waterborne polyurethane dispersions provided in Examples 1-5 are compounded with inorganic fillers to prepare dispersion slurries with a viscosity of 4000-6500 cp., a fineness of ≤20 μm, and a residue of ≤0.05 g. Solvent resistance tests after the waterborne polyurethane dispersion is made into a film show that the percentage increase in mass before and after immersion in electrolyte is 36-49%, the 100% modulus is 1.9-2.3 MPa, and the elongation at break is 150-300%.

[0172] Furthermore, this application optionally employs diamine chain extenders and inorganic neutralizers, which, when combined with the soft and hard segment structures, impart superior overall performance to the waterborne polyurethane dispersion. Compared to Examples 1-3, Example 6, due to the use of trifunctional diethylenetriamine as a small molecule chain extender, resulted in a decrease in slurry viscosity and a residue output greater than 0.05g, as well as a significant decrease in the elongation at break of the film. Compared to Examples 1-3, Example 7, due to the use of the organic neutralizer triethylamine, resulted in a slurry viscosity less than 4000cp., a residue output greater than 0.05g, and a decrease in solvent resistance and 100% modulus after film formation.

[0173] In the waterborne polyurethane dispersion of Comparative Example 1, the soft segment is a hydroxyl-terminated polybutadiene polyol with a molecular weight of 3100, which results in an excessively long polyolefin portion in the polymer. The polymer molecular chain undergoes excessive self-folding and phase separation, and the viscosity of the slurry decreases significantly after dispersion. This also means that the slurry is unstable and prone to stratification. At the same time, the fineness decreases significantly, with agglomerated particles larger than 30 μm appearing. Slag discharge is also very obvious, and the slurry performance is obviously insufficient.

[0174] In the aqueous polyurethane dispersion of Comparative Example 2, the soft segment is a hydroxyl-terminated polybutadiene polyol with a molecular weight of 1900, a > c but (a+c) / b > 1. This results in insufficient construction of the polymer's alkyl side chains (1,2-vinyl structure), which cannot form a sufficient solvent-resistant "protective shell." The solvent resistance of the film deteriorates significantly, and the overall polymer chain segments are too extended, resulting in too close interaction with the conductive carbon black. After slurry dispersion, the slurry viscosity increases significantly, the fineness decreases significantly, and agglomerated particles larger than 35 μm appear. Slag discharge is also very obvious. The resulting film has excessive strength and insufficient elongation at break.

[0175] In the aqueous polyurethane dispersion of Comparative Example 3, the soft segment is a hydroxyl-terminated polybutadiene polyol with a molecular weight of 2000 and (a+c) / b < 1 but a < c < 1. The excessive cis-1,4-butadiene units cause the polymer chain segments to fold excessively and lack flexibility. When mechanically dispersed with conductive carbon black, it cannot effectively encapsulate the filler through conformational adjustment, resulting in a significant decrease in slurry viscosity to only 1832 cp. The fineness and slag discharge are not ideal.

[0176] In the aqueous polyurethane dispersion of Comparative Example 4, the soft segment is a hydrogenated hydroxyl-terminated polybutadiene polyol with a molecular weight of 2100. Although the ultra-low polarity of the soft segment provides excellent solvent resistance to the polymer, it also leads to the most severe microphase separation of the polymer chain segments. The low polarity and conformationally free-rotating carbon-carbon bonds cause the soft segments to approach and entangle with each other, which is actually detrimental to the dispersion and encapsulation of conductive carbon black. The slurry has low viscosity and significant fineness and slag discharge. At the same time, due to the excessive flexibility of the soft segment, the 100% modulus of the overall film also decreases significantly.

[0177] The applicant declares that this application illustrates the aqueous polyurethane dispersion, its preparation method, and its application through the above embodiments, but this application is not limited to the above embodiments, that is, it does not mean that this application must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this application, equivalent substitutions of the raw materials of the product, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this application.

Claims

1. An aqueous polyurethane dispersion, characterized in that, The raw materials for preparing the aqueous polyurethane dispersion include polyisocyanate, polybutadiene polyol, hydrophilic chain extender, optional small molecule chain extender and neutralizer; The polybutadiene polyol comprises structural units of Formula I, structural units of Formula II, and optionally structural units of Formula III; The molar percentage of the structural unit shown in Formula I in the polybutadiene polyol is denoted as a, the molar percentage of the structural unit shown in Formula II is denoted as b, and the molar percentage of the structural unit shown in Formula III is denoted as c, where a > c and 0 < (a + c) / b < 1. The number-average molecular weight of the polybutadiene polyol is 1000-2500 g / mol.

2. The aqueous polyurethane dispersion according to claim 1, characterized in that, Based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender, and neutralizing agent as 100%, the mass of the polyisocyanate is 16.0-34.0%, the mass of the polybutadiene polyol is 58.0-77.0%, the mass of the hydrophilic chain extender is 3.8-5.0%, the mass of the small molecule chain extender is ≤4.1%, and the mass of the neutralizing agent is 0.5-1.5%.

3. The aqueous polyurethane dispersion according to claim 1 or 2, characterized in that, The polyisocyanate includes any one or a combination of at least two of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate; And / or, the hydrophilic chain extender includes any one or a combination of at least two of 3-hydroxypropionic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolacetic acid, trihydroxysulfonic acid, and dihydroxysuccinic acid; And / or, the small molecule chain extender includes any one or a combination of at least two of ethylenediamine, hexamethylenediamine, pentamethylenediamine, isophoronediamine, 4,4'-diphenylmethanediamine, and 4,4'-diaminodicyclohexylmethane; And / or, the neutralizing agent is an inorganic alkaline compound.

4. The aqueous polyurethane dispersion according to claim 1, characterized in that, The raw materials used in the preparation also include a catalyst; The mass of the catalyst is ≤1000ppm, based on the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender and neutralizer as 100%. And / or, the raw materials for preparation may further include organic solvents; The organic solvent comprises 100-300% of the total mass of the polyisocyanate, polybutadiene polyol, hydrophilic chain extender, small molecule chain extender and neutralizer, which is 100% of the total mass.

5. The aqueous polyurethane dispersion according to claim 1, characterized in that, The solvent of the aqueous polyurethane dispersion includes water, and the solid content of the aqueous polyurethane dispersion is 10-40%. And / or, the particle size of the solids in the aqueous polyurethane dispersion is 20-500 nm.

6. A process for the preparation of an aqueous polyurethane dispersion as claimed in any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: Polyisocyanate, polybutadiene polyol and hydrophilic chain extender are polymerized to obtain a prepolymer; After the prepolymer undergoes a neutralization reaction with a neutralizing agent, it is dispersed in water and then subjected to a chain extension reaction with an optional small molecule chain extender to obtain the waterborne polyurethane dispersion.

7. The production method according to claim 6, wherein The preparation method includes the following steps: Polyisocyanate, polybutadiene polyol, hydrophilic chain extender, 20-80% organic solvent and optionally catalyst are mixed and polymerized to obtain prepolymer; The prepolymer is mixed with the remaining organic solvent and then neutralized with a neutralizing agent. The product of the neutralization reaction is dispersed in water and then subjected to a chain extension reaction with an optional small molecule chain extender to obtain an emulsion; the organic solvent in the emulsion is removed to obtain the aqueous polyurethane dispersion.

8. The production method according to claim 6 or 7, characterized by, The polymerization reaction is carried out at a temperature of 70-90℃; The prepolymer contains 0.8-2.5% NCO groups by mass. The neutralization reaction is carried out at a temperature of 30-50℃ for 5-40 minutes. The chain extension reaction is carried out at a temperature of 35-60℃ for 5-40 minutes.

9. Use of an aqueous polyurethane dispersion according to any one of claims 1 to 5, characterized in that, The aqueous polyurethane dispersion is used as a battery slurry dispersant, photovoltaic backsheet adhesive, or conformal coating.

10. A dispersion slurry, characterized in that, The dispersion slurry comprises inorganic particles and the aqueous polyurethane dispersion as described in any one of claims 1-5.

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