A method for preparing aqueous polyurethane nanoemulsions by ultrasonic microreactor

Abstract

The application discloses a method for preparing water-based polyurethane nano-emulsion by an ultrasonic micro-reactor; the method uses diisocyanate, oligomer dihydric alcohol, hydrophilic chain extender and primary chain extender as raw materials to carry out polymerization reaction to obtain polyurethane prepolymer, then solvent is added to reduce the viscosity of the prepolymer, and then a neutralizer is added for neutralization; the neutralized polyurethane prepolymer solution and a mixed solution of deionized water and secondary chain extender are together introduced into a static mixer by a metering pump to carry out pre-emulsification, and then are introduced into an ultrasonic micro-reactor to carry out secondary chain extension reaction and secondary emulsification of the polyurethane prepolymer under the ultrasonic micro-reactor, so as to continuously prepare water-based polyurethane nano-emulsion. The water-based polyurethane nano-emulsion prepared by the method has smaller particle size and uniform distribution, and has the advantages of continuous and stable production, simple process, high product solid content and easy industrialization.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of chemical engineering and polymer material preparation, specifically a method for efficiently and uniformly preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor. Background Technology

[0002] Waterborne polyurethane dispersions use deionized water as the dispersion medium, significantly reducing the use of volatile organic solvents (VOCs). They are non-toxic, odorless, and environmentally friendly organic polymer materials. During use, the water evaporates to form a polyurethane film, giving the film-forming material of the waterborne polyurethane dispersion excellent physicochemical properties comparable to those of the polyurethane material itself. By adjusting the formulation and chemical modification, waterborne polyurethane materials can be produced as high-performance materials with varying hardness and chemical resistance, finding wide applications in wood coatings, textile coatings, synthetic leather, plastic coatings, metal coatings, personal care products, coating agents, adhesives, sealants, and waterborne inks.

[0003] Traditional polyurethane prepolymer dispersion generally uses a high-speed disperser, which shears the prepolymer into tiny liquid particles through the high-speed rotation of the dispersion disc and disperses them evenly in water to form a uniform emulsion. This production process has the following main disadvantages: (1) long emulsification time, low production efficiency, and high production cost; (2) excessive reliance on manual labor and low degree of automation; (3) uneven temperature distribution in the dispersion tank, unstable product quality, and large differences between batches.

[0004] Enhanced reaction processes and continuous production can solve the bottleneck problems of traditional batch production. Patent CN108017771A greatly enhances the micro-mixing and mass transfer process by using ultragravity emulsification technology, resulting in waterborne polyurethane with relatively small particle size. However, ultragravity emulsification technology has high requirements for equipment, is difficult to operate, and is difficult to apply on a large scale. Patent CN109824913B establishes a continuous dispersion system by using a tubular disperser, which can achieve continuous and rapid dispersion of polyurethane prepolymers. However, the internal components of this equipment are complex, difficult to process and install, and not conducive to industrial scale-up production.

[0005] Microreactors are a device enhancement technology with advantages such as fast mass and heat transfer, efficient mixing, easy process control, and good safety. However, in emulsion preparation, microreactors can easily generate micron-sized droplets with uniform particle size, but due to flow limitations (low Reynolds number, low energy density), it is difficult to generate emulsion droplets with nanoparticle size. Ultrasonic emulsification can easily generate nanoemulsions by breaking droplets through the intense vibration of cavitation bubbles and the accompanying shock waves and microjets. However, due to the uneven distribution of the sound field, the particle size of the prepared emulsion is usually uneven. Summary of the Invention

[0006] To address the aforementioned shortcomings, the present invention aims to provide a method for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor. This method, through the synergistic effect of ultrasound and the microreactor, achieves higher energy density and more precise acoustic and flow field control capabilities. It also solves problems such as easy channel blockage. Therefore, it can continuously prepare nanoemulsions with uniform particle size, thereby improving the efficiency of the emulsification process and the quality of the emulsion product.

[0007] Therefore, the technical solution provided by this invention is as follows:

[0008] A method for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor, wherein the method first prepares a polyurethane prepolymer in a batch reactor, then pre-emulsifies the polyurethane prepolymer using a static mixer to prepare a preemulsion, and finally uses a secondary chain extender mixed solution to perform a secondary emulsification and secondary chain extension reaction on the preemulsion in an ultrasonic microreactor to produce an aqueous polyurethane nanoemulsion.

[0009] The specific steps are as follows:

[0010] Step 1: Mix diisocyanate, oligomeric diol and catalyst in a batch reactor and heat to prepolymerize, and add hydrophilic chain extender and primary chain extender in sequence to obtain polyurethane prepolymer (Y1).

[0011] Step 2: Add a small amount of solvent to Y1 obtained in step 1 to reduce the viscosity of the system, and add a neutralizing agent to neutralize the carboxylic acid groups in the reaction system to obtain the neutralized polyurethane prepolymer (Y2).

[0012] Step 3: The prepolymer that has been neutralized in Step 2 and deionized water are respectively fed into a static mixer through a metering pump for mixing and pre-emulsification to obtain an aqueous polyurethane preemulsion (R1).

[0013] Step 4: Pass the mixed solution of R1 from step 3 and deionized water / post-chain extender into an ultrasonic microreactor for secondary emulsification and secondary chain extension reaction, thereby preparing an aqueous polyurethane emulsion.

[0014] Furthermore, in the above-described method for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor, the specific steps of the polyurethane prepolymer preparation process are as follows:

[0015] Step 1: Mix diisocyanate, oligomeric diol and catalyst in a batch reactor and heat to 60~90℃. React for 1~3h for prepolymerization. Add hydrophilic chain extender and primary chain extender in sequence. React at 60~90℃ for 1~3h to obtain polyurethane prepolymer Y1.

[0016] Step 2: Add solvent and neutralizing agent to the polyurethane prepolymer Y1 obtained in step 1, and react at 40~60℃ for 20~60 min to obtain the neutralized polyurethane prepolymer;

[0017] in:

[0018] The molar ratio between the diisocyanate and the oligomeric diol mentioned in step 1 is 2~5:1;

[0019] The molar ratio between the hydrophilic chain extender, the primary chain extender and the diisocyanate mentioned in step 1 is 0.1~0.5:0~0.3:1;

[0020] The molar ratio between the neutralizing agent and the hydrophilic chain extender mentioned in step 2 is 0.9~1.1:1;

[0021] More preferably, the temperature of the first chain extension reaction in step 1 is 70~90℃, and the reaction time is 1~2h.

[0022] Furthermore, in the above-mentioned method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor, the diisocyanate in step 1 is one or more selected from isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate; the diol is polyethylene glycol, polypropylene glycol, polybutylene adipate diol, polyethylene adipate diol, etc., with a number average molecular weight of 500-6000. The catalyst is one or more of stannous octoate, dibutyltin dilaurate, bismuth neodecanoate, bismuth laurate, and dibutyltin diacetate; the hydrophilic chain extender is one or more of dimethylolpropionic acid, dimethylolbutyric acid, methyl diethanolamine, diethanolamine, triethanolamine, and triisopropanolamine; the primary chain extender is one or more of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, neopentanediol, 1,6-hexanediol, and 1,8-octanediol.

[0023] Furthermore, in the above-mentioned method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor, the solvent in step 2 is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, butyl acetate, dipropylene glycol dimethyl ether, N,N-diethylformamide, and N-ethylpyrrolidone; and the neutralizing agent is one or more of triethylamine, dimethylethanolamine, formic acid, and acetic acid.

[0024] Furthermore, in the above-mentioned method for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor, the pre-emulsification method is as follows:

[0025] Step 1: The neutralized polyurethane prepolymer and deionized water are respectively fed into a static mixer through metering pumps for mixing and pre-emulsification to obtain waterborne polyurethane preemulsion R1.

[0026] The mass flow ratio between deionized water and polyurethane prepolymer is 1.5~4:1, and pre-emulsification is carried out at 10-40℃ for 0.5-10 min.

[0027] Furthermore, in the above-mentioned method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor, the secondary emulsification and secondary chain extension reaction involves passing a mixed solution of aqueous polyurethane preemulsion R1 and a secondary chain extender into an ultrasonic microreactor and performing secondary emulsification and secondary chain extension reactions at 10~40℃ for 0.5-5 min, thereby preparing the aqueous polyurethane emulsion.

[0028] in:

[0029] The molar ratio of the secondary chain extender to the diisocyanate is 0.1~0.5:1;

[0030] The mass flow ratio of the mixed solution of waterborne polyurethane preemulsion R1 and secondary chain extender is 10~40:1;

[0031] The secondary chain extender mixed solution is composed of deionized water and secondary chain extender at a mass ratio of 5~15:1;

[0032] The ultrasonic transducer has a frequency of 10kHz to 300kHz and a power of 20W to 300W.

[0033] Furthermore, in the above-mentioned method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor, the secondary chain extender is one or more of the following: ethylenediamine, hydrazine hydrate, 2-methyl-1,5-pentanediamine, sodium 2-[(2-aminoethyl)amino]ethanesulfonate, triethylenetetramine, diethylenetriamine, diaminodicyclohexylmethane, isophorone diamine, and toluene diamine.

[0034] Furthermore, in the above-mentioned method for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor, the ultrasonic microreactor is formed by directly bonding an ultrasonic transducer to the microreactor; the microreactor includes a fluid microchannel reaction layer, a heat exchange layer, and a top cover layer, wherein the fluid microchannel reaction layer is provided with a serpentine layout of fluid reaction channels; and the heat exchange layer is provided with serpentine layout of heat exchange layer etched channels.

[0035] The fluid reaction channel is formed by alternating connections of several fine and coarse channels; a reaction layer turbulence chip is provided in the middle of the coarse channel; and a tubular heat exchange layer turbulence chip is provided in the heat exchange layer etching channel.

[0036] The reaction layer turbulence chip has a bullet-shaped structure that is thin at both ends and thick in the middle; the end of the reaction layer turbulence chip facing the fluid input has a concave part with an arc of 100 to 140°; the concave direction of the concave part is the same as the flow direction of the fluid; a tubular heat exchange layer turbulence chip is provided in the heat exchange layer etching channel.

[0037] Furthermore, in the above-described method for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor, the ratio of the cross-sectional diameters of the fine channel to the coarse channel is 1:2 to 3; the cross-sectional diameter of the widest position of the turbulence chip in the fine and coarse channels is 1.3 to 1.7 times the cross-sectional diameter of the fine channel; the cross-sectional diameter of the narrowest position of the turbulence chip is 0.9 to 1.1 times the cross-sectional diameter of the fine channel; and the diameter of the concave portion of the turbulence chip is 0.6 to 0.9 times the cross-sectional diameter of the fine channel.

[0038] Furthermore, in the above-mentioned method for preparing aqueous polyurethane nanoemulsions via ultrasonic microreactors, the reaction devices are preferably connected in series via microtubes, and the material of the microtubes is preferably 304 stainless steel, 316L stainless steel, polytetrafluoroethylene, soluble polytetrafluoroethylene, perfluoroethylene propylene copolymer, and more preferably 316L stainless steel.

[0039] Furthermore, in the above-described method for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor, the static mixer comprises a tube body and an inner core disposed within the tube body; the inner core and the tube body constitute a mixing channel; the inner core configuration of the static mixer is preferably SV type, SK type, SX type, SH type, SL type, etc., more preferably SX type and SH type, and even more preferably SX type; the outer diameter of the inner core is preferably 6-50 mm, more preferably 10-40 mm; the inner core length of the static mixer is preferably 10-50 cm, more preferably 10-40 cm; the material of the static mixer is preferably 304 stainless steel, 316L stainless steel, silicon carbide, etc., more preferably 316L stainless steel.

[0040] This application has at least the following beneficial effects:

[0041] 1. This invention employs a static mixer and an ultrasonic microreactor to carry out the pre-emulsification process, secondary emulsification process, and secondary chain extension process. By utilizing the unique advantages of the ultrasonic microreactor, rapid and uniform preparation of waterborne polyurethane nanoemulsions is achieved, significantly improving the particle size uniformity and stability of the emulsion. This is beneficial for industrial scale-up and has good prospects for industrial application.

[0042] 2. In the preferred embodiment of the present invention, the use of a turbulence chip with a specific structure and a denser ultrasonic field can improve the emulsification effect. At the same time, the ultrasonic microreactor also has a strong heat exchange capacity and can effectively control the temperature. By precisely controlling the reaction conditions, such as ultrasonic power, frequency, time and temperature, the particle size distribution and performance of the emulsion can be flexibly adjusted to meet the application needs of different fields.

[0043] 3. The aqueous polyurethane nanoemulsion prepared by this invention has the advantages of small particle size, good dispersibility, narrow particle size distribution and high stability, and has broad application prospects in coatings, adhesives, textiles and other fields. Attached Figure Description

[0044] Figure 1 This is a system structure diagram of the ultrasonic microreactor for preparing aqueous polyurethane nanoemulsions provided by the present invention;

[0045] Figure 2 This is an exploded view of the ultrasonic microreactor provided by the present invention;

[0046] Figure 3 This is a schematic diagram of the fluid microchannel reaction layer of the ultrasonic microreactor provided by the present invention;

[0047] Figure 4 This is a schematic diagram of the fluid microchannel structure of the ultrasonic microreactor provided by the present invention;

[0048] Figure 5 This is a schematic diagram of the heat exchange layer of the ultrasonic microreactor provided by the present invention;

[0049] Figure 6 This is a schematic diagram of the top cover layer of the ultrasonic microreactor provided by the present invention;

[0050] Figure 7 This is a perspective view of the static mixer provided by the present invention;

[0051] Figure 8 This is a perspective view of the static mixer provided by the present invention;

[0052] Figure 9 This is the infrared detection spectrum of the product provided in the embodiments of the present invention;

[0053] Figure 10 The diagram shows the particle size and particle size distribution of the products provided in the embodiments and comparative examples of this invention.

[0054] The symbols in the diagram represent the following components and similar components:

[0055] Prepolymer reactor 1, deionized water storage tank 2, secondary chain extender mixed solution storage tank 3, static mixer 4, tube body 41, inner core 42; metering pump A, metering pump B, metering pump C, ultrasonic microreactor 5, microreactor 51. Fluid microchannel reaction layer 511; fine channel 5111, coarse channel 5112, reaction layer turbulence chip 5113; recessed portion 5114; first feed inlet 5115, second feed inlet 5116, discharge outlet 5117; heat exchange layer 512; heat exchange layer etched channel 5122, tubular heat exchange layer turbulence chip 5123; first material input pipe mounting hole 5124, second material pipe mounting hole 5125, heat exchange layer material output pipe mounting hole 5126; top cover layer 513; first material input pipe mounting hole 5131, second material pipe mounting hole 5132, material output pipe mounting hole 5133; ultrasonic transducer 52; product storage tank 6.

[0056] Specific implementation methods

[0057] The present invention will now be clearly and completely described in conjunction with embodiments thereof. It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0058] Unless otherwise specified in this invention, all equipment and components are conventional in the field.

[0059] Example 1

[0060] Before describing the specific production method of this invention, the system for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor, as described in this application, will be explained first. (Refer to...) Figure 1 The system includes a prepolymer reactor 1, a deionized water storage tank 2, and a secondary chain extender mixed solution storage tank 3. The prepolymer reactor 1 and the deionized water storage tank 2 are respectively connected to a static mixer 4 through a first microchannel and a second microchannel. The first microchannel is equipped with a metering pump A, and the second microchannel is equipped with a metering pump B. The static mixer 4 is connected to an ultrasonic microreactor 5 through a microchannel. The secondary chain extender mixed solution storage tank 3 is connected to the ultrasonic microreactor 5 through a microchannel. A metering pump C is installed on a third microchannel. The ultrasonic microreactor 5 is connected to a product storage tank 6.

[0061] The structure of the ultrasonic microreactor 5 can be referred to Figures 2 to 6It is formed by directly bonding a microreactor 51 and an ultrasonic transducer 52. The microreactor 51 includes a fluid microchannel reaction layer 511, a heat exchange layer 512, and a top cover layer 513. The microchannel reaction layer 511, the heat exchange layer 512, and the top cover layer 513 are connected by screws. A first sealing ring 515 is provided between the fluid microchannel reaction layer 511 and the heat exchange layer 512. A second sealing ring 514 is provided between the heat exchange layer 512 and the top cover layer 513 to ensure a tight connection between the layers.

[0062] The fluid microchannel reaction layer 511 is provided with a serpentine fluid reaction channel; the heat exchange layer 512 is provided with a serpentine heat exchange layer etching channel 5122, and a tubular heat exchange layer turbulence chip 5123 is provided in the heat exchange layer etching channel 5122; and a top cover layer 513.

[0063] The fluid reaction channel is formed by alternating connections of several fine channels 5111 and coarse channels 5112. The cross-sectional diameter of the coarse channel 5112 is larger than that of the fine channel 5111. A reaction layer turbulence chip 5113 is provided in the middle of the coarse channel 5112. The turbulence chip 5113 has a bullet-shaped structure that is thin at both ends and thick in the middle. The end of the turbulence chip 5113 facing the fluid input has a concave portion 5114. The concave direction of the concave portion 5114 is the same as the flow direction of the fluid. The cross-sections of the narrow channel 5111 and the coarse channel 5112 are circular; the ratio of the cross-sectional diameters of the narrow channel 5111 and the coarse channel is 1:2.5; the cross-sectional diameter of the widest part of the turbulence chip is 1.5 times the cross-sectional diameter of the narrowest part of the turbulence chip is 1 times the cross-sectional diameter of the narrow channel 5111; the diameter of the concave portion of the turbulence chip is 0.8 times the width of the narrow channel 5111; the curvature of the concave portion of the turbulence chip is 120°; the cross-sectional diameter of the narrow channel 5111 is 2 mm.

[0064] Furthermore, the fluid microchannel reaction layer 511 has a first inlet 5115 and a second inlet 5116 at its fluid microchannel inlet port; and an outlet 5117 at the other port.

[0065] The top cover plate layer 513 is provided with a first material input pipe mounting hole 5131 and a second material input pipe mounting hole 5132; the heat exchange layer 512 is provided with a first material input pipe mounting hole 5124 and a second material input pipe mounting hole 5125.

[0066] The first material conveying pipe is connected to the first inlet 5115 provided on the fluid microchannel reaction layer 511 through the first material input pipe mounting hole 5131 in the cover plate layer and the first material input pipe mounting hole 5124 in the heat exchange layer. The second material conveying pipe is connected to the second inlet 5116 provided on the fluid reaction channel through the second material input pipe mounting hole 5132 in the cover plate layer and the second material pipe mounting hole 5125 in the heat exchange layer.

[0067] The top cover plate layer 513 is provided with a cover plate layer material output pipe installation hole 5133, and the heat exchange layer 512 is provided with a heat exchange layer material output pipe installation hole 5126; the material output pipe is connected to the discharge port 5117 through the cover plate layer material output pipe installation hole 5133 and the heat exchange layer material output pipe installation hole 5126.

[0068] The static mixer is described in [reference]. Figure 7 and 8 It includes a tube body 41 and an inner core 42 disposed within the tube body; the inner core and the tube body constitute a mixing channel; the inner core is of type SX, with an outer diameter of 10mm and a length of 10cm.

[0069] The method for preparing aqueous polyurethane nanoemulsions using the above-described system for preparing aqueous polyurethane nanoemulsions via ultrasonic microreactors includes the following steps in sequence:

[0070] 1) Mix 54.6g of isophorone diisocyanate, 100g of polypropylene glycol (Mn=2000) and 0.2g of stannous octoate in a prepolymer reactor 1 and react at 80℃ for 1.5h. Then add 8.33g of dimethylolpropionic acid and 3.73g of 1,4-butanediol and react at 85℃ for 2h. Then cool down to 50℃ and add 25g of N,N-dimethylformamide to reduce the viscosity of the system. Finally, add 6.29g of triethylamine to neutralize for 20min to obtain polyurethane prepolymer.

[0071] 2) The polyurethane prepolymer prepared in step 1) and deionized water are respectively fed into static mixer 3 through metering pump A and metering pump B for pre-emulsification to obtain a pre-emulsion. The mass flow rates of polyurethane prepolymer and deionized water are 5.86 g / min and 9.84 g / min, respectively. The pre-emulsification temperature is 20℃ and the residence time is 30 s.

[0072] 3) The secondary chain extender mixed solution is introduced into the ultrasonic microreactor 4 through metering pump C at a flow rate of 0.9 g / min. The mixed solution and the pre-emulsion are subjected to secondary chain extension and secondary emulsification in the ultrasonic microreactor 4 at 20℃, ultrasonic frequency of 20 kHz, ultrasonic power of 50 W, and residence time of 30 s to finally obtain an aqueous polyurethane dispersion.

[0073] in:

[0074] The mass ratio of deionized water to secondary chain extender in the mixed solution is 10:1, and hydrazine hydrate is selected as the secondary chain extender.

[0075] The mass flow ratio between deionized water and polyurethane prepolymer in the secondary chain extender mixed solution is 2:1.

[0076] The dispersion from Example 1 was dried into a film and then subjected to infrared spectroscopy testing. The detection results are as follows: Figure 9 :

[0077] The spectrum shows NH (3322 cm⁻¹) -1 C=O (1701cm) -1 ) and CO (1100cm -1 and 1236cm -1 The strong vibration peak at 2275 cm⁻¹ -1 No characteristic peak of -NCO was observed, which proves that the waterborne polyurethane was successfully synthesized.

[0078] Example 2

[0079] The preparation steps and parameters of Example 2 are the same as those of Example 1, except that dicyclohexylmethane diisocyanate is used instead of isophorone diisocyanate; the mass of dicyclohexylmethane diisocyanate is 56.34 g; the mass of 1,4-butanediol is 1.99 g; the mass flow rates of polyurethane prepolymer and deionized water are 5.88 g / min and 9.82 g / min, respectively; and the mass flow rate of the mixed solution is 0.78 g / min.

[0080] Example 3

[0081] The preparation steps and parameters of Example 3 are the same as those of Example 1, except that hexamethylene diisocyanate is used instead of isophorone diisocyanate; the mass of hexamethylene diisocyanate is 51.27 g; the mass of 1,4-butanediol is 7.06 g; the mass flow rates of polyurethane prepolymer and deionized water are 5.84 g / min and 9.86 g / min, respectively; and the mass flow rate of the mixed solution is 1.09 g / min.

[0082] Example 4

[0083] The preparation steps and parameters of Example 4 are the same as those of Example 1, except that the oligomer diol is polybutylene adipate diol (Mn=2000).

[0084] Example 5

[0085] The preparation steps and parameters of Example 5 are the same as those of Example 1, except that the oligomer diol is polycarbonate diol (Mn=2000).

[0086] Example 6

[0087] The preparation steps and parameters of Example 6 are the same as those of Example 1, except that the hydrophilic chain extender is dimethylolbutyric acid; the mass of isophorone diisocyanate is 54.18 g; the mass of 1,4-butanediol is 4.15 g; the amount of triethylamine is 5.69 g; the mass flow rates of polyurethane prepolymer and deionized water are 5.85 g / min and 9.85 g / min, respectively; and the mass flow rate of the mixed solution is 0.87 g / min.

[0088] Example 7

[0089] The preparation steps and parameters of Example 7 are the same as those of Example 1, except that the primary chain extender is ethylene glycol with a mass of 2.74 g; the mass of isophorone diisocyanate is 55.59 g; the mass flow rates of polyurethane prepolymer and deionized water are 5.85 g / min and 9.82 g / min, respectively; and the mass flow rate of the mixed solution is 0.89 g / min.

[0090] Example 8

[0091] The preparation steps and parameters of Example 8 are the same as those of Example 1, except that the primary chain extender is 1,6-hexanediol with a mass of 4.72 g; the mass of isophorone diisocyanate is 53.62 g; the mass flow rates of polyurethane prepolymer and deionized water are 5.83 g / min and 9.85 g / min, respectively; and the mass flow rate of the mixed solution is 0.86 g / min.

[0092] Example 9

[0093] The preparation steps and parameters of Example 9 are the same as those of Example 1, except that the solvent is N,N-dimethylacetamide.

[0094] Example 10

[0095] The preparation steps and parameters of Example 10 are the same as those of Example 1, except that the solvent is N-methylpyrrolidone.

[0096] Example 11

[0097] The preparation steps and parameters of Example 11 are the same as those of Example 1, except that the secondary chain extender is ethylenediamine with a mass of 4.72 g; the mass flow rates of polyurethane prepolymer and deionized water are 6.03 g / min and 9.67 g / min, respectively; and the mass flow rate of the mixed solution is 1.06 g / min.

[0098] Example 12

[0099] The preparation steps and parameters of Example 12 are the same as those of Example 1, except that the secondary chain extender is ethylenediamine with a mass of 9.41 g; the mass flow rates of polyurethane prepolymer and deionized water are 7.92 g / min and 7.78 g / min, respectively; and the mass flow rate of the mixed solution is 2.59 g / min.

[0100] Example 13

[0101] The preparation steps and parameters of Example 13 are the same as those of Example 1, except that the ultrasonic power is 100W.

[0102] Example 14

[0103] The preparation steps and parameters of this embodiment 14 are the same as those of embodiment 1, except that the ultrasonic power is 20W.

[0104] Example 15

[0105] The preparation steps and parameters of Example 15 are the same as those of Example 1, except that the ultrasonic frequency is 60kHz.

[0106] Example 16

[0107] The preparation steps and parameters of Example 16 are the same as those of Example 1, except that the ultrasonic frequency is 100kHz.

[0108] Example 17

[0109] The preparation steps and parameters of Example 17 are the same as those of Example 1, except that the mass flow rates of the polyurethane prepolymer and deionized water are 2.93 g / min and 4.92 g / min, respectively; and the mass flow rate of the mixed solution is 0.45 g / min.

[0110] Example 18

[0111] The preparation steps and parameters of Example 18 are the same as those of Example 1, except that the mass flow rates of the polyurethane prepolymer and deionized water are 1.47 g / min and 2.46 g / min, respectively; and the mass flow rate of the mixed solution is 0.23 g / min.

[0112] Example 19

[0113] The preparation steps and parameters of Example 19 are the same as those of Example 1, except that the secondary chain extension and secondary emulsification temperature is 10°C.

[0114] Example 20

[0115] The preparation steps and parameters of Example 20 are the same as those of Example 1, except that the secondary chain extension and secondary emulsification temperature is 40°C.

[0116] Comparative Example 1

[0117] Comparative Example 1 uses a high-speed disperser to prepare an aqueous polyurethane dispersion through emulsification and secondary chain extension reactions, as follows:

[0118] Preparation method: The preparation was carried out in accordance with Example 1, except that the polyurethane prepolymer was slowly poured into a dispersion tank containing 332.3g of deionized water, and 30.47g of mixed solution was slowly added dropwise. The mixture was emulsified and subjected to secondary chain extension at a speed of 1500r / min for 3h, and finally the aqueous polyurethane dispersion was obtained.

[0119] Comparative Example 2

[0120] Comparative Example 2 uses a combination of a high-speed disperser and an ultrasonic emulsifier to emulsify and perform a secondary chain extension reaction on the polyurethane prepolymer to prepare an aqueous polyurethane dispersion, as follows:

[0121] Preparation method: The preparation was carried out in accordance with Comparative Example 1, except that while using a high-speed disperser for high-speed dispersion, an ultrasonic emulsifier was inserted into the surface of the emulsion, with the frequency set to 20kHz and the power set to 50W.

[0122] Comparative Example 3

[0123] Comparative Example 3 uses a tubular emulsifier for secondary emulsification and secondary chain extension reaction to prepare an aqueous polyurethane dispersion, as follows:

[0124] The preparation method is the same as in Example 1, except that the secondary chain extension and secondary emulsification are carried out in a tubular emulsifier without the intervention of an ultrasonic field.

[0125] The dispersions of the above-described embodiments and comparative examples were sent for testing to determine the emulsion particle size (DS) and particle size polydispersity index (PDI); the test results are as follows: Figure 10 As shown in Table 1:

[0126] Table 1

[0127] project DS / nm PDI Example 1 30 0.088 Example 2 32 0.094 Example 3 34 0.083 Example 4 35 0.09 Example 5 38 0.095 Example 6 30 0.089 Example 7 35 0.089 Example 8 38 0.091 Example 9 32 0.087 Example 10 32 0.083 Example 11 33 0.088 Example 12 37 0.089 Example 13 29 0.086 Example 14 27 0.08 Example 15 28 0.086 Example 16 30 0.095 Example 17 31 0.087 Example 18 32 0.086 Example 19 31 0.085 Example 20 38 0.093 Comparative Example 1 40 0.158 Comparative Example 2 44 0.155 Comparative Example 3 35 0.102

[0128] pass Figure 10 It is evident that, compared with emulsification methods using tubular emulsifiers, high-speed dispersers, and combinations of high-speed dispersers and ultrasonic emulsifiers, the emulsions prepared by the present invention have a smaller dispersion coefficient and relatively smaller particle size.

[0129] This invention employs a static mixer and an ultrasonic microreactor to carry out the pre-emulsification, secondary emulsification, and secondary chain extension processes. By utilizing the unique advantages of the ultrasonic microreactor, rapid and uniform preparation of waterborne polyurethane nanoemulsions is achieved, significantly improving the particle size uniformity and stability of the emulsion. This approach is beneficial for industrial scale-up and has promising prospects for industrial applications.

Claims

1. A method for preparing aqueous polyurethane nanoemulsions using an ultrasonic microreactor, characterized in that, The method involves first preparing a polyurethane prepolymer in a batch reactor, then pre-emulsifying the polyurethane prepolymer using a static mixer to prepare a preemulsion, and finally mixing the preemulsion with a secondary chain extender solution in an ultrasonic microreactor to perform a secondary emulsification and secondary chain extension reaction on the aqueous polyurethane nanoemulsion. The ultrasonic microreactor is formed by directly bonding an ultrasonic transducer to a microreactor; the microreactor includes a fluid microchannel reaction layer, a heat exchange layer and a top cover layer, the fluid microchannel reaction layer is provided with a serpentine layout of fluid reaction channels; the heat exchange layer is provided with a serpentine layout of heat exchange layer etching channels. The fluid reaction channel is formed by alternating connections of several fine and coarse channels; a flow-disrupting chip is provided in the middle of the coarse channel; The turbulence chip has a bullet-shaped structure that is thin at both ends and thick in the middle; the end of the turbulence chip facing the fluid input has a concave part with an arc of 100 to 140°; the concave direction of the concave part is the same as the flow direction of the fluid; a tubular heat exchange layer turbulence chip is provided in the heat exchange layer etching channel.

2. The method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor according to claim 1, characterized in that, The specific steps in the preparation process of the polyurethane prepolymer are as follows: Step 1: Mix diisocyanate, oligomeric diol and catalyst in a batch reactor and heat to 60~90℃. React for 1~3h for prepolymerization. Add hydrophilic chain extender and primary chain extender sequentially. React at 60~90℃ for 1~3h for primary chain extension reaction to obtain polyurethane prepolymer Y1. Step 2: Add solvent and neutralizing agent to the polyurethane prepolymer Y1 obtained in step 1, and react at 40~60℃ for 20~60 min to obtain the neutralized polyurethane prepolymer; in: The molar ratio between the diisocyanate and the oligomeric diol mentioned in step 1 is 2~5:1; The molar ratio between the hydrophilic chain extender, the primary chain extender and the diisocyanate mentioned in step 1 is 0.1~0.5:0~0.3:1; The molar ratio between the neutralizing agent and the hydrophilic chain extender mentioned in step 2 is 0.9~1.1:

1.

3. The method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor according to claim 2, characterized in that, The diisocyanate mentioned in step 1 is one or more selected from isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate; the diol is polyethylene glycol, polypropylene glycol, polybutylene adipate diol, polyethylene adipate diol, polycaprolactone diol, polycarbonate diol, and polycarbonate diol, with a number average molecular weight of 500-6000. One or more of propyl diol; the catalyst is one or more of stannous octoate, dibutyltin dilaurate, bismuth neodecanoate, bismuth laurate, and dibutyltin diacetate; the hydrophilic chain extender is one or more of dimethylolpropionic acid, dimethylolbutyric acid, methyl diethanolamine, diethanolamine, triethanolamine, and triisopropanolamine; the primary chain extender is one or more of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, neopentanediol, 1,6-hexanediol, and 1,8-octanediol.

4. The method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor according to claim 2, characterized in that, The solvent mentioned in step 2 is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, butyl acetate, dipropylene glycol dimethyl ether, N,N-diethylformamide, and N-ethylpyrrolidone; the neutralizing agent is one or more of triethylamine, dimethylethanolamine, formic acid, and acetic acid.

5. The method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor according to claim 2, characterized in that, The pre-emulsification method is as follows: Step 1: The neutralized polyurethane prepolymer and deionized water are respectively fed into a static mixer through metering pumps for mixing and pre-emulsification to obtain waterborne polyurethane preemulsion R1. The mass flow ratio between deionized water and polyurethane prepolymer is 1.5~4:1, and pre-emulsification is carried out at 10-40℃ for 0.5-10 min.

6. The method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor according to claim 1, characterized in that, The secondary emulsification and secondary chain extension reaction are carried out by passing a mixed solution of waterborne polyurethane pre-emulsion R1 and secondary chain extender into an ultrasonic microreactor and performing secondary emulsification and secondary chain extension reaction at 10~40℃ for 0.5-5 min, thereby preparing waterborne polyurethane emulsion. in: The molar ratio of the secondary chain extender to the diisocyanate is 0.1~0.5:1; The mass flow ratio of the mixed solution of waterborne polyurethane preemulsion R1 and secondary chain extender is 10~40:1; The secondary chain extender mixed solution is composed of deionized water and secondary chain extender at a mass ratio of 5~15:1; The ultrasonic transducer has a frequency of 10kHz to 300kHz and a power of 20W to 300W.

7. The method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor according to claim 6, characterized in that, The secondary chain extender is one or more of the following: ethylenediamine, hydrazine hydrate, 2-methyl-1,5-pentanediamine, sodium 2-[(2-aminoethyl)amino]ethanesulfonate, triethylenetetramine, diethylenetriamine, diaminodicyclohexylmethane, isophorone diamine, and toluene diamine.

8. The method for preparing aqueous polyurethane nanoemulsions via an ultrasonic microreactor according to claim 1, characterized in that, The ratio of the cross-sectional diameters of the narrow channel and the coarse channel is 1:2 to 3; the cross-sectional diameter of the widest position of the turbulence chip in the narrow channel and the coarse channel is 1.3 to 1.7 times the cross-sectional diameter of the narrow channel; the cross-sectional diameter of the narrowest position of the turbulence chip is 0.9 to 1.1 times the cross-sectional diameter of the narrow channel; and the diameter of the concave portion of the turbulence chip is 0.6 to 0.9 times the cross-sectional diameter of the narrow channel.

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