Coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment and method for producing the same

Abstract

The present invention provides a coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment and a method for producing the same. [Solution] The aqueous polyurethane emulsion comprises a polyol, a diisocyanate, a carboxyl group-containing diol compound, a neutralizing agent, a chain extender, a nanofiller, and water. The aqueous polyurethane emulsion provided by the present invention obtains a prepolymer by prepolymerizing the polyol and isocyanate, uses a carboxyl group-containing diol as an internally emulsifying monomer, and achieves self-dispersion by forming an internal emulsion system through neutralization. Furthermore, by using a chain extender and a nanofiller as auxiliary components, a stable latex particle system is formed, significantly avoiding gelation and phase separation during storage. In addition, by controlling the nanofiller and chain extender, the coating has high elastic modulus, abrasion resistance, and thermal and chemical stability.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous polyurethane emulsions, and specifically provides a coagulant-free aqueous polyurethane emulsion for rubber-impregnated labor protection tools and a method for manufacturing the same.

Background Art

[0002] Conventionally, emulsion systems used in the production of labor protection tools by the rubber impregnation method often require the use of a coagulant to achieve rapid coagulation and film formation in the film formation or mold release stage, thereby improving the molding efficiency. General coagulants increase the burden of washing and wastewater treatment, and environmental and cost problems are prominent. In addition, the residue of the coagulant may affect the mechanical properties, surface touch, and adhesion of the final product. Furthermore, some coagulants may interact with the components of the substrate or emulsion, causing product defects and instability.

[0003] Therefore, in order to meet the needs of the rubber impregnation molding, the development of a coagulant-free aqueous polyurethane emulsion suitable for the rubber impregnation process is strongly desired.

Summary of the Invention

[0004] The present invention provides a coagulant-free aqueous polyurethane emulsion for rubber-impregnated labor protection tools and a method for manufacturing the same. A prepolymer is obtained by prepolymerization of a polyol and a diisocyanate. A carboxyl group-containing diol is used as an internally emulsified monomer, and an internal emulsion system is formed by neutralization to achieve self-dispersion. In addition, a chain extender and a nanofiller are used assistively to form a stable latex particle system, significantly avoiding gelation and phase separation during the storage process. Also, by controlling the nanofiller and the chain extender, the coating has high elastic modulus, abrasion resistance, and thermal and chemical stability.

[0005] The present invention provides a coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment, the aqueous polyurethane emulsion comprising a polyol, a diisocyanate, a carboxyl group-containing diol compound, a neutralizing agent, a chain extender, a nanofiller, and water.

[0006] In any of the above proposed technologies, the polyol comprises at least one of polyester polyol and polyether polyol; the diisocyanate comprises at least one of diphenylmethane diisocyanate and toluene diisocyanate; the carboxyl group-containing diol compound comprises methylolpropionic acid or its isomer; the neutralizing agent comprises at least one of triethanolamine and diethanolamine; the chain extender comprises at least one of ethylenediamine and 1,4-butanediol; and the nanofiller comprises at least one of surface-modified silica, nanocellulose, and nanoalumina.

[0007] In any of the above proposed technologies, the emulsion further contains 0 to 6.0 wt% of a nonionic hydrophilic block compound, the nonionic hydrophilic block compound being polyethylene glycol or a copolymer containing polyethylene glycol chains. In any of the above technical proposals, the polyol is one or more of PPG-2000, PPG-3000, polyethylene glycol (PEG), EO / PO copolymer ether, and poly(1,4-butylene adipate)diol. In any of the above technical proposals, the coagulant-free aqueous polyurethane emulsion is, by a total mass percentage of the emulsion, The mixture contains 35 wt% polyether polyol, diphenylmethane diisocyanate (with a molar ratio of its isocyanate groups to the hydroxyl groups in the polyether polyol of 1.8:1), 4.0 wt% dimethylolpropionic acid, 4.2 wt% triethanolamine, 1.5 wt% ethylenediamine, and 3.0 wt% surface-modified silica, with the remainder being water, for a total volume of 100 wt%.

[0008] The present invention provides a method for producing a coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment, comprising the following steps. Step S100 involves subjecting a polyol and a diisocyanate to a first stirring treatment under an inert gas atmosphere to react and form a prepolymer; Step S200 involves adding a carboxyl group-containing diol compound to the prepolymer and performing a second stirring treatment to graft the prepolymer into polymer segments; Step S300 involves cooling the polymer segments, adding a neutralizing agent, and performing a dispersion treatment to form a dispersion; and Step S400 involves adding a chain extender and nanofillers to the dispersion and reacting them to obtain a coagulant-free aqueous polyurethane emulsion.

[0009] In any of the above technical proposals, in step S100, the first stirring treatment is performed at a temperature of 70-85°C for 1-3 hours, the amount of polyol added is 20-40 wt% of the total mass percentage of the emulsion, and the molar ratio of isocyanate groups in the diisocyanate to hydroxyl groups in the polyol is (1.6-2):1.

[0010] In any of the above technical proposals, in step S200, the second stirring treatment is performed at a temperature of 70 to 85°C for a duration of 0.5 to 1.5 hours, and the amount of the carboxyl group-containing diol compound added is 2.0 to 6.0 wt% of the total mass percentage of the emulsion.

[0011] In any of the above technical proposals, in step S300, the dispersion treatment includes a high-speed shearing or dropping method at 1000 to 5000 rpm, and the temperature of the polymer segment after cooling is 40 to 60°C.

[0012] In any of the above technical proposals, in step S400, the reaction is carried out at a temperature of 30 to 50°C, the amount of chain extender added is 0.1 to 5.0 wt% of the total mass percentage of the emulsion, and the amount of nanofiller added is 0.1 to 5.0 wt% of the total mass percentage of the emulsion.

[0013] In any of the above technical proposals, step S100 further includes adding a nonionic hydrophilic blocking compound.

[0014] In any of the above technical proposals, the method further includes adjusting the pH of the coagulant-free aqueous polyurethane emulsion to 6.5-8.5 after step S400, followed by filtration and degassing to obtain the final product. [Effects of the Invention]

[0015] According to the proposed technology of this invention, the following technical effects can be achieved. 1. A prepolymer is obtained by prepolymerizing a polyol and a diisocyanate. An embedded ionic emulsion segment containing an amine or carboxyl group is used to form an internal emulsion system by neutralization, thereby achieving self-dispersion. Simultaneously, a nonionic hydrophilic segment is introduced as a cooperative stabilizer to improve wet adhesion and film formation rate. 2. By adjusting the molecular weight, the ratio of soft segments to hard segments, and the glass transition temperature, the viscosity, particle size, and film formation behavior of the emulsion can be optimized, allowing it to quickly remain on the substrate surface without the need for a coagulant, and to bond together to form a film. 3. By introducing nano-inorganic / organic composites into the emulsion as film-forming aids and interface strengtheners, the density of the film and the initial adhesion in the wet state are improved, thereby enabling nucleation during rubber impregnation. [Modes for carrying out the invention]

[0016] The present invention will be described in more detail below with reference to specific embodiments, so that the above-mentioned objectives, features, and advantages of the present invention may be more clearly understood. The embodiments and features contained herein can be combined with each other, as long as they do not contradict each other.

[0017] While the following description includes many specific details to fully understand the present invention, the scope of protection is not limited by the specific embodiments disclosed below, as the present invention can be implemented in ways other than those described herein.

[0018] The following describes in detail specific examples of this embodiment in order to make the above-mentioned objectives, features, and advantages of this embodiment clearer and easier to understand.

[0019] Traditionally, emulsion systems used in the manufacture of protective equipment by rubber impregnation often require the use of coagulants during the film formation or release stage to achieve rapid solidification and film formation, thereby improving molding efficiency. Common coagulants increase the burden of cleaning and wastewater treatment, leading to significant environmental and cost issues. Furthermore, residual coagulants can affect the mechanical properties, surface feel, and adhesion of the final product. In addition, some coagulants can interact with substrates and emulsion components, potentially causing product defects and instability.

[0020] Therefore, there is a strong demand for the development of a coagulant-free aqueous polyurethane emulsion suitable for rubber impregnation processes. In this embodiment, a prepolymer is obtained by prepolymerizing a polyol and a diisocyanate, and a carboxyl group-containing diol is used as an internally emulsifying monomer. Self-dispersion is achieved by forming an internal emulsion system through neutralization. Furthermore, by using chain extenders and nanofillers as auxiliary agents, a stable latex particle system is formed, significantly avoiding gelation and phase separation during storage. In addition, by controlling the nanofillers and chain extenders, the coating has high elastic modulus, abrasion resistance, and thermal and chemical stability.

[0021] Specifically, the coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment of this embodiment comprises a polyol, a diisocyanate, a carboxyl group-containing diol compound, a neutralizing agent, a chain extender, a nanofiller, and water.

[0022] The components of this embodiment realize an aqueous polyurethane emulsion that can be stored stably for a long time and transported during the process without adding an anti-freezing agent from the outside through multiple designs of internal emulsification, water-phase chain extension, and nano-strengthening. After film formation, a polyurethane film with good adhesion, both elasticity and wear resistance is obtained, which is suitable for rubber-impregnated labor protection equipment, contributing to VOC reduction, improvement of the stability of the production line, and extension of the lifespan of the final product.

[0023] Preferably, the polyol contains at least one of a polyester polyol and a polyether polyol, which can provide the flexibility, elasticity, and film-forming substrate of the polyurethane, determine the comfort, ductility, and low-temperature flexibility of the film, facilitate the folding and stretching of the labor protection equipment, the polyol segment forms a soft phase after film formation, and the molecular weight and chemical type determine the segment mobility and glass transition temperature.

[0024] Preferably, the diisocyanate contains at least one of diphenylmethane diisocyanate and toluene diisocyanate. The diisocyanate reacts with the polyol to form a hard segment, imparting strength, wear resistance, and chemical stability, thereby improving the strength, solvent resistance, and heat resistance of the film, extending the service life, reacting with the isocyanate group and the hydroxy group to form an ester bond, reacting with the amine-based chain extender to form a urea bond, and forming a mechanical reinforcement structure through microphase separation of the hard / soft segments.

[0025] Preferably, the carboxyl group-containing diol compound includes dimethylolpropionic acid (DMPA) or its isomer. The carboxyl group-containing diol compound introduces a neutralizable carboxyl group into the main chain and functions as an internal emulsification site. Also, since the prepolymer can form stable latex particles in water without adding a large amount of surfactant from the outside, the addition of an external anti-coagulant is not required. The carboxyl group is converted to a carboxylate by a neutralizing agent, a hydrophilic anchor is formed in the aqueous phase, and the prepolymer forms stable latex particles by hydrophobic / hydrophilic self-assembly and is mainly stabilized by the balance between electrostatic repulsive force and cohesive force of the hydrophobic phase. After DMPA participates in the prepolymerization reaction, the carboxyl group is retained in the polymer chain. After neutralization, it becomes a carboxylate and forms a hydrophilic shell in water to stabilize the latex particles.

[0026] Preferably, the neutralizing agent includes at least one of triethanolamine and diethanolamine, and by neutralizing the carboxyl group to form a salt, it can induce the dispersion of the prepolymer in water. After neutralization, a charged / electrically neutral region is formed at the end of the polymer molecule, the surface of the latex particles becomes charged or an electric double layer is formed, and electrostatic stability is imparted. Accordingly, if a nonionic hydrophilic segment is introduced, a double stabilization mechanism by electrical / steric stabilization can also be formed.

[0027] Preferably, the chain extender comprises at least one of ethylenediamine and 1,4-butanediol, where the amine system rapidly generates urea bonds, and the ester / urethane bonds generated from the diol are relatively flexible. Ethylenediamine reacts rapidly with isocyanate groups to form urea bonds, significantly improving the density, rigidity, and wear resistance of hard segments, and rapidly increasing molecular weight and mechanical strength. However, urea bonds are relatively rigid and may reduce elasticity and ductility. The ester / urethane bonds generated from 1,4-butanediol allow the system to maintain a certain degree of flexibility, resulting in better ductility and rebound elasticity, a slower reaction rate compared to the amine system, and easier process control.

[0028] Preferably, the nanofiller includes at least one of surface-modified silica, nanocellulose, and nanoalumina. The nanoparticles form strong interfacial interactions in the polymer matrix, and if the surface modification is good, they bond tightly with the polyurethane segment, suppressing crack propagation and improving fatigue life. At the same time, they can function as a local rigidifying phase and increase the modulus of elasticity. Surface-modified silica is silica modified with an organic silane, and after modification with the organic silane, it is well compatible with the polyurethane segment, improving wear resistance, hardness, and barrier properties, as well as improving thixotropy. Nanocellulose has high mechanical strength and can significantly improve modulus of elasticity and fatigue resistance. Due to its high hydrophilicity, surface treatment is required to improve compatibility with the hydrophobic polyurethane matrix. Nanoalumina can enhance wear resistance and heat resistance, making it suitable for labor protection applications where high wear resistance is required.

[0029] Furthermore, the emulsion contains an additional 0-6.0 wt% of a nonionic hydrophilic block compound (PEG or copolymer containing PEG segments), where the nonionic hydrophilic block compound is polyethylene glycol or a copolymer containing polyethylene glycol chains. The addition of a small amount of nonionic hydrophilic block compound simultaneously imparts steric hindrance stability, improves salt resistance and freeze-thaw resistance, optimizes rheology and pump transportability, and improves wettability / film formation and surface feel. PEG hydrates highly in water, forming a considerably thick hydration layer. When two particles approach each other, the segments are crushed, resulting in entropy loss and solvent repulsion, generating a repulsive force. Steric stabilization is more robust against high-electrolyte environments or high-shear impacts compared to cases where steric stabilization relies solely on electrostatic stabilization, thereby imparting / enhancing steric hindrance stability. PEG forms a non-ideal solution with water, suppressing water crystallization and reducing mechanical crushing of latex particles by ice crystals. PEG chains form a localized flexible layer in the ice phase, buffering phase transition stresses and improving freeze-thaw resistance and low-temperature stability.

[0030] For example, this embodiment also provides a method for producing a coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment, which includes the following steps. Step S100: In an inert gas atmosphere, the polyol and diisocyanate are subjected to a first stirring treatment to react and form a prepolymer. Step S200 involves adding a carboxyl group-containing diol compound to the prepolymer and performing a second stirring treatment to graft the prepolymer into polymer segments, Step S300 involves cooling the polymer segment, then adding a neutralizing agent to perform a dispersion treatment to form a dispersion, Step S400: Add the chain extender and the nanofiller to the dispersion and react them to obtain the coagulant-free aqueous polyurethane emulsion.

[0031] Preferably, in step S100, under an inert atmosphere, the stirring treatment is performed at a temperature of 70-85°C for 1-3 hours to form a prepolymer having isocyanate groups at the ends. This ensures reaction activity for subsequent grafting, dispersion, and controlled chain extension into the internal emulsification site, while carrying out the process under an inert atmosphere and specific temperature control minimizes the consumption of isocyanate groups by side reactions and free water, thus ensuring the controllability and reproducibility of the product. Synthesizing the prepolymer with a molar ratio of isocyanate group / hydroxyl group slightly greater than 1 means that many active isocyanate end groups remain on the chain after the reaction is complete. These active isocyanate end groups can then be used to increase the molecular weight through grafting or reaction with chain extenders in the aqueous phase, forming the final network.

[0032] Furthermore, performing the polymerization at 70-85°C is advantageous for polymerization with a moderate rate and controllable viscosity, while simultaneously avoiding uncontrollable crosslinking and by-products (e.g., isocyanurate cyclization) caused by excessively high temperatures. An inert gas atmosphere, including nitrogen or argon gas, can block moisture and CO2 from the air, preventing free isocyanate groups from reacting with water to produce CO2 or being saponified by carbon dioxide, thus avoiding foaming and loss of activity of the prepolymer.

[0033] Furthermore, step S100 further includes adding a nonionic hydrophilic blocking compound, which is chemically grafted / copolymerized and introduced into the segment, and PEG or PEG-diol having an active end is used as the polyol involved in the reaction. This makes the PEG a non-migratory block, resulting in a good brushing effect on the particle surface and reducing the risk of migration after film formation.

[0034] Preferably, in step S200, a neutralizable carboxyl group moiety is chemically introduced into the polyurethane main chain, i.e., an internally emulsifying monomer is grafted, thereby forming a carboxylate salt through subsequent neutralization with an amine system, establishing a molecular basis for achieving self-emulsification stability, and fundamentally avoiding the use of large amounts of externally added surfactants or anticoagulants. The carboxyl group-containing diol is grafted onto the prepolymer by reacting with an isocyanate group via its hydroxyl group, leaving a carboxyl group on the molecule. The grafted carboxyl group is converted to a carboxylate salt in a subsequent neutralization step, forming a charged hydrophilic shell layer, thereby realizing an internal emulsification mechanism, which is more controllable than the migration, foaming, or poor adhesion problems caused by externally added surfactants.

[0035] Furthermore, the stirring process, performed at a temperature of 70-85°C for 0.5-1.5 hours, is advantageous for accelerating the reaction rate and avoiding side reactions. The amount of carboxyl group-containing diol compound added, between 2.0-6.0 wt%, determines the hydrophilic / hydrophobic balance. Higher content leads to better dispersibility, higher particle charge density, smaller particle size, and better stability; however, excessively high content increases the hydrophilicity of the dried film, affecting its moisture resistance.

[0036] Preferably, in step S300, the prepolymer is converted to a hydrophilic salt by neutralization, primary latex particles are formed in water, and a target particle size distribution and a stable primary dispersion are obtained under controlled cooling and shearing conditions, thereby providing a suitable physical base for further extension of the aqueous phase chain.

[0037] Furthermore, the purpose of cooling to 40-60°C is to reduce the viscosity and reactivity of the prepolymer, avoid excessively rapid side reactions between the neutralizing agent and residual isocyanate groups, and allow for easier control of the dispersion process. The neutralizing agent converts the grafted carboxyl groups into carboxylate salts, causing the polymer segments to have a hydrophilic shell in water. The organic phase can be dispersed as micro / nanometer-sized oil droplets by high-speed shearing or dropwise methods, with the shearing rate and water addition rate jointly determining particle size and distribution. Dropwise methods are advantageous for controlling local concentrations and can reduce the risk of gelation. High-speed shearing allows for the formation of a uniform dispersion in a short time.

[0038] Preferably, in step S400, the molecular weight of the polymer is increased by chain extension in the aqueous phase, urea / ester bonds are formed to impart the target mechanical properties, and surface-modified nanofillers are introduced to improve the elastic modulus, wear resistance, and fatigue resistance, and the rheological properties are adjusted to ultimately obtain an aqueous polyurethane emulsion with controllable performance that does not require solidification. When a chain extender is added to the aqueous phase, it reacts rapidly with the remaining isocyanate groups, rapidly increasing the molecular weight and forming urea bonds or ester / urethane bonds, thereby significantly improving the mechanical strength and hard segment density of the system.

[0039] Furthermore, reacting at a low temperature of 30-50°C mitigates excessively rapid local crosslinking, avoids thermally induced side reactions, maintains a good operating window, and facilitates the addition and uniform dispersion of nanofillers during the reaction. Adding 0.1-5.0 wt% of nanofillers ensures compatibility with the polyurethane matrix while avoiding particle aggregation. The nanofillers improve fatigue life, wear resistance, and modulus through interfacial interactions within the matrix, and also contribute to controlling thixotropy.

[0040] Furthermore, after process S400, the pH of the coagulant-free aqueous polyurethane emulsion is adjusted to 6.5-8.5, filtered, and degassed to obtain the final product. This finishing process ensures the chemical and physical stability of the emulsion, removes fine gels and bubbles to improve appearance and printability / coatingability, and controls the pH to an optimal range for the substrate and stability. Adjusting the pH to 6.5-8.5 is advantageous for maintaining the stability of the carboxylate salt to the maximum extent without making the emulsion excessively alkaline or acidic. An appropriate pH (6.5-8.5) also suppresses the risk of biological degradation and coagulation promotion by metal ions. Filtration removes large particles, aggregates, or undispersed material, improving appearance and preventing clogging in subsequent processes. Degassing is performed to remove any remaining bubbles or CO2 in the system, preventing pores during the film formation process and defects on the final product surface.

[0041] In general, step S100 determines the active end and prepolymer properties, step S200 determines the internal emulsification capacity and the shell layer of the final particles, step S300 determines the primary particle size / distribution and process operability, and step S400 determines the molecular weight increase and the mechanical properties and functionalization of the final film.

[0042] Example 1 This example provides a coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment and a method for producing the same, wherein the aqueous polyurethane emulsion is, by total mass percentage of the emulsion, The mixture contains 35 wt% polyether polyol, diphenylmethane diisocyanate (with a molar ratio of its isocyanate groups to the hydroxyl groups in the polyether polyol of 1.8:1), 4.0 wt% dimethylolpropionic acid, 4.2 wt% triethanolamine, 1.5 wt% ethylenediamine, and 3.0 wt% surface-modified silica, with the remainder being water, for a total volume of 100 wt%. Here, the polyether polyol is PPG-2000. The manufacturing method includes the following steps: Step S100 involves subjecting a polyether polyol and diphenylmethane diisocyanate to a first stirring treatment at 80°C for 2 hours under a nitrogen gas atmosphere to react and form a prepolymer. Step S200 involves adding dimethylolpropionic acid to the prepolymer, performing a second stirring treatment at 80°C for 1 hour, and grafting the prepolymer to form polymer segments. Step S300 involves cooling the polymer segment to 50°C, adding triethanolamine, and performing a high-speed shear dispersion treatment at 3000 rpm to form a dispersion. Step S400 involves adding ethylenediamine and surface-modified silica to a dispersion, reacting it at 40°C for 1 hour, adjusting the pH to 7.5, filtering, and degassing to obtain a coagulant-free aqueous polyurethane emulsion.

[0043] Example 2 This example provides a coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment and a method for producing the same, wherein the aqueous polyurethane emulsion is, by total mass percentage of the emulsion, The mixture contains 35 wt% polyester polyol, toluene diisocyanate (with a molar ratio of its isocyanate groups to the hydroxyl groups in the polyester polyol of 1.6:1), 5.5 wt% dimethylolbutanoic acid, 4.5 wt% diethanolamine, 0.8 wt% 1,4-butanediol, 1.2 wt% nanoalumina, and 4.0 wt% polyethylene glycol, with the remainder being water, for a total volume of 100 wt%. Here, the polyester polyol is poly(1,4-butylene adipate)diol, with a molecular weight of 2000. The manufacturing method includes the following steps: Step S100: In a nitrogen gas atmosphere, polyester polyol, toluene diisocyanate, and polyethylene glycol are subjected to a first stirring treatment at 75°C for 1.5 hours to react and form a prepolymer. Step S200 involves adding dimethylolbutanoic acid to the prepolymer, performing a second stirring treatment at 75°C for 0.5 hours, and grafting the prepolymer to form polymer segments. Step S300 involves cooling the polymer segment to 45°C, adding diethanolamine, and performing a high-speed shear dispersion treatment at 2000 rpm to form a dispersion. Step S400 involves adding 1,4-butanediol and nanoalumina to the dispersion, reacting at 35°C for 1.5 hours, adjusting the pH to 8.0, filtering, and degassing to obtain a coagulant-free aqueous polyurethane emulsion.

[0044] Example 3 This example provides a coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment and a method for producing the same, wherein the aqueous polyurethane emulsion is, by total mass percentage of the emulsion, The mixture contains 40 wt% polyether / polyester mixed polyol, toluene diisocyanate (with a molar ratio of its isocyanate groups to the hydroxyl groups in the polyether / polyester mixed polyol of 2.0:1), 2.0 wt% dimethylolpropionic acid, 4.5 wt% triethanolamine, 0.8 wt% ethylenediamine, and 1.2 wt% composite filler, with the remainder being water, for a total volume of 100 wt%, and the composite filler is nanocellulose:surface-modified silica = 1:1 (mass ratio). Here, the aforementioned polyether / polyester mixed polyol is a mixture of PPG-2000 and poly(1,4-butylene adipate)diol, with a mass ratio of PPG-2000 to poly(1,4-butylene adipate)diol in the mixture of 1:1, and the molecular weight of poly(1,4-butylene adipate)diol is 2000. The manufacturing method includes the following steps: Step S100 involves subjecting a polyether / polyester mixed polyol and toluene diisocyanate to a first stirring treatment at 85°C for 3 hours under a nitrogen gas atmosphere to react and form a prepolymer. Step S200 involves adding dimethylolpropionic acid to the prepolymer and performing a second stirring treatment at 85°C for 1.5 hours to graft the prepolymer into polymer segments. Step S300 involves cooling the polymer segment to 45°C, adding triethanolamine, and performing a high-speed shear dispersion treatment at 2000 rpm to form a dispersion. Step S400 involves adding ethylenediamine and a composite filler to the dispersion, reacting at 30°C for 2 hours, adjusting the pH to 6.5, filtering, and degassing to obtain a coagulant-free aqueous polyurethane emulsion.

[0045] Comparative Example 1 In this comparative example, a coagulant-free aqueous polyurethane emulsion for rubber-impregnated work protective equipment is provided, and this aqueous polyurethane emulsion was obtained as a commercially available product.

[0046] Test data Emulsion performance tests were conducted for Examples 1-3 and Comparative Example 1, and the results are shown in Table 1. Coating film performance tests were also conducted, and the results are shown in Table 2. [Table 1] While the particle size of the emulsions in Examples 1-3 was 110 nm or less, the particle size of the emulsion in Comparative Example 1 was 150 nm, ensuring good penetration during rubber impregnation. Furthermore, Examples 1-3 of this application exhibited significantly superior freeze-thaw / high-temperature stability compared to Comparative Example 1, demonstrating that phase separation is suppressed by internal emulsification + nanofiller. The mechanical stability and 6-month storage stability confirmed the possibility of long-term storage, overcoming the bottleneck of conventional emulsions being prone to gelation.

[0047] [Table 2] While the film formation time for the emulsions in Examples 1-3 was 28 seconds or less, the film formation time for the emulsion in Comparative Example 1 exceeded 60 seconds. The nanofiller promotes interfacial nucleation, freeing the user from reliance on coagulants, resulting in superior overall mechanical properties. Tensile strength, elastic modulus, and abrasion resistance are improved, meeting the requirements for protection during heavy-duty work. Chemical resistance and low-temperature toughness demonstrate environmental adaptability through the synergistic effect of chain extension and fillers, and overall performance significantly surpasses that of commercially available products.

[0048] In this specification, descriptions such as “one example,” “several examples,” and “specific examples” mean that the specific features, structures, materials, or properties described in such example or example are included in at least one example or example of the present invention. In this specification, the suggestive expressions of the above terms do not necessarily refer to the same example or example. Furthermore, the specific features, structures, materials, or properties described may be implemented in appropriate combinations in any one or more examples or examples.

[0049] Although the present invention is disclosed as described above, it is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Accordingly, the scope of protection of the present invention shall be limited to the scope defined by the claims.

Claims

1. A coagulant-free aqueous polyurethane emulsion for rubber immersion work protective equipment, wherein the aqueous polyurethane emulsion comprises a polyol, a diisocyanate, a carboxyl group-containing diol compound, a neutralizing agent, a chain extender, a nanofiller, and water, and further comprises 0 to 6.0 wt% of a nonionic hydrophilic block compound which is polyethylene glycol or a copolymer containing polyethylene glycol chains. The polyol comprises at least one of a polyester polyol and a polyether polyol. The diisocyanate comprises at least one of diphenylmethane diisocyanate and toluene diisocyanate. The carboxyl group-containing diol compound includes dimethylolpropionic acid or its isomers. The neutralizing agent comprises at least one of triethanolamine and diethanolamine. The chain extender comprises at least one of ethylenediamine and 1,4-butanediol. The nanofiller comprises at least one of surface-modified silica, nanocellulose, and nanoalumina. However, the polyol, the nonionic hydrophilic blocking compound, the neutralizing agent, and the chain extender are all different compounds. The aforementioned coagulant-free aqueous polyurethane emulsion is characterized by containing, by total mass percentage of the emulsion, 20 to 40 wt% of polyol, 2.0 to 6.0 wt% of carboxyl group-containing diol compound, 0.1 to 5.0 wt% of chain extender, and 0.1 to 5.0 wt% of nanofiller, and containing diisocyanate in an amount such that the molar ratio of isocyanate groups in the diisocyanate to hydroxyl groups in the polyol is (1.6 to 2):1, with the remainder being water, and is a coagulant-free aqueous polyurethane emulsion for rubber immersion work protective equipment.

2. The aforementioned coagulant-free aqueous polyurethane emulsion is, by total mass percentage of the emulsion, A coagulant-free aqueous polyurethane emulsion for rubber-immersed work protective equipment according to claim 1, characterized in that it comprises 35 wt% polyether polyol, diphenylmethane diisocyanate (with a molar ratio of its isocyanate groups to the hydroxyl groups in the polyether polyol of 1.8:1), 4.0 wt% dimethylolpropionic acid, 4.2 wt% triethanolamine, 1.5 wt% ethylenediamine, and 3.0 wt% surface-modified silica, with the remainder being water, for a total volume of 100 wt%.

3. A method for producing a coagulant-free aqueous polyurethane emulsion for rubber-immersed work protective equipment according to claim 1, Step S100 involves subjecting the above polyol and the above diisocyanate to a first stirring treatment under an inert gas atmosphere to react and form a prepolymer, Step S200 involves adding the carboxyl group-containing diol compound to the prepolymer and performing a second stirring treatment to graft the prepolymer into polymer segments, Step S300: After cooling the polymer segment, add the neutralizing agent and perform a dispersion treatment to form a dispersion. The process includes step S400, in which the chain extender and the nanofiller are added to the dispersion and reacted to obtain the coagulant-free aqueous polyurethane emulsion. The amount of polyol added is 20 to 40 wt% by total mass percentage of the emulsion. The molar ratio of isocyanate groups in the diisocyanate to hydroxyl groups in the polyol is (1.6 to 2):

1. The amount of the carboxyl group-containing diol compound added is 2.0 to 6.0 wt% of the total mass percentage of the emulsion. The amount of the chain extender added is 0.1 to 5.0 wt% of the total mass percentage of the emulsion. The amount of nanofiller added is 0.1 to 5.0 wt% by total mass percentage of the emulsion. A method for producing an emulsion, further comprising adding a nonionic hydrophilic block compound in step S100 in an amount of 0 to 6.0 wt% of the total mass percentage of the emulsion.

4. The manufacturing method according to claim 3, characterized in that in step S100, the first stirring treatment is performed at a temperature of 70 to 85°C for a duration of 1 to 3 hours.

5. In step S200, the second stirring treatment is performed at a temperature of 70 to 85°C for a duration of 0.5 to 1.5 hours. In step S300, the dispersion process includes a high-speed shearing or dropping method at 1000 to 5000 rpm. The manufacturing method according to claim 3, characterized in that the temperature of the polymer segment after cooling is 40 to 60°C.

6. The manufacturing method according to claim 3, characterized in that in step S400, the reaction takes place at a temperature of 30 to 50°C.

7. The manufacturing method according to claim 3, further comprising adjusting the pH value of the coagulant-free aqueous polyurethane emulsion to 6.5 to 8.5 after step S400, filtering, and degassing to obtain the final product.

8. Use of a coagulant-free aqueous polyurethane emulsion for rubber-immersed work protective equipment according to claim 1 or 2 in the manufacture of work protective gloves.

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