Method for preparing waterborne polyurethane nano-emulsion through ultrasonic microreactor

Abstract

The invention discloses a method for preparing a waterborne polyurethane nano-emulsion through an ultrasonic microreactor. The method comprises the following steps: carrying out polymerization reaction on diisocyanate, oligomer dihydric alcohol, a hydrophilic chain extender and a primary chain extender which are used as raw materials to obtain a polyurethane prepolymer, adding a solvent to reduce the viscosity of the prepolymer, and adding a neutralizer to neutralize to obtain a polyurethane prepolymer; the method comprises the following steps: feeding a neutralized polyurethane prepolymer solution and a mixed solution of deionized water and a secondary chain extender into a static mixer through a metering pump for pre-emulsification, feeding the pre-emulsified solution into an ultrasonic micro-reactor, and carrying out ultrasonic emulsification by utilizing the micro-scale and interfacial effects of the micro-reactor and the cavitation effect of ultrasonic waves, and carrying out secondary chain extension reaction and secondary emulsification on the polyurethane prepolymer in an ultrasonic microreactor at the same time, thereby continuously preparing the waterborne polyurethane nano-emulsion. The obtained waterborne polyurethane nano-emulsion is smaller in particle size and uniform in distribution, and has the advantages that continuous and stable production can be achieved, the process is simple, the solid content of the product is high, and industrialization is easy.

Description

Technical Field

[0001] The invention relates to the cross-technical field of chemical engineering and polymer material preparation, in particular to a method for efficiently and uniformly preparing waterborne polyurethane nanoemulsion by using an ultrasonic microreactor. Background Art

[0002] Waterborne polyurethane dispersion uses deionized water as the dispersion medium, which can greatly reduce the use of volatile organic solvents (VOC). It is a non-toxic, odorless, green and environmentally friendly organic polymer material. During use, water evaporates to form a polyurethane film, which makes the film-forming material of waterborne polyurethane dispersion have the same excellent physical and chemical properties as polyurethane materials. By adjusting the formula and chemical modification, waterborne polyurethane materials can obtain high-performance materials with different hardness and chemical resistance, which are widely used in wood coatings, textile coatings, synthetic leather, plastic coatings, metal coatings, personal care, coatings, adhesives, sealants, water-based inks and other fields.

[0003] Traditional polyurethane prepolymer dispersion generally uses a high-speed disperser, which shears the prepolymer into tiny liquids through the high-speed rotation of the dispersion disk and evenly disperses it 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) the production process is overly dependent on manual labor and has a low degree of automation; (3) the temperature distribution in the dispersion barrel is uneven, the product quality is unstable, and there is a large difference between batches.

[0004] Reaction process intensification and continuous production can solve the bottleneck problem of traditional intermittent production. Patent CN108017771A greatly enhances the micro-mixing and mass transfer process by using ultra-gravity emulsification technology, and the particle size of the waterborne polyurethane obtained is relatively small, but ultra-gravity 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, but the internal components of the equipment are complex, difficult to process and install, and are not conducive to industrial scale-up production.

[0005] Microreactor is an equipment intensification technology with advantages such as fast mass and heat transfer, efficient mixing, easy process control and good safety. However, in the preparation of emulsions, micron-sized droplets with uniform particle size are easily produced in the microreactor, but it is difficult to produce emulsion droplets with nanometer particle size due to flow restrictions (low Reynolds number, low energy density). Ultrasonic emulsification breaks up droplets through the violent vibration of cavitation bubbles and the accompanying shock waves and microjets, which can easily produce nanoemulsions. However, due to the uneven distribution of the acoustic field, the particle size of the prepared emulsion is usually unevenly distributed. Summary of the invention

[0006] In view of the above-mentioned shortcomings, the object of the present invention is to provide a method for preparing an aqueous polyurethane nanoemulsion by means of an ultrasonic microreactor. Under the synergistic effect of ultrasound and a microreactor, the method has a higher energy density and a more precise ability to control the acoustic field and the flow field, and can also solve the problem of easy blockage of the channel. Therefore, the method can continuously prepare a nanoemulsion with uniform particle size, and improve the efficiency of the emulsification process and the quality of the emulsion product.

[0007] To this end, the technical solution provided by the present invention is as follows:

[0008] A method for preparing an aqueous polyurethane nanoemulsion by an ultrasonic microreactor, the method comprising the steps of first preparing a polyurethane prepolymer in a kettle reactor, then pre-emulsifying the polyurethane prepolymer by using a static mixer to prepare a pre-emulsion, and finally using a secondary chain extender mixed solution to perform secondary emulsification and secondary chain extension reaction on the pre-emulsion in an ultrasonic microreactor to prepare an aqueous polyurethane nanoemulsion.

[0009] The specific steps are as follows:

[0010] Step 1: diisocyanate, oligomeric diol and catalyst are mixed in a kettle reactor for heating and prepolymerization, and a hydrophilic chain extender and a primary chain extender are added successively to obtain a polyurethane prepolymer (Y1);

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

[0012] Step 3: The prepolymer neutralized in step 2 and deionized water are respectively introduced into a static mixer through metering pumps for mixing and pre-emulsification to obtain an aqueous polyurethane pre-emulsion (R1);

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

[0014] Furthermore, in the above method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor, the specific steps of the polyurethane prepolymer preparation process are as follows:

[0015] Step 1: Mix diisocyanate, oligomer diol and catalyst in a kettle reactor, heat to 60-90° C., react for 1-3 hours for prepolymerization, and successively add a hydrophilic chain extender and a primary chain extender, react at 60-90° C. for 1-3 hours to obtain a polyurethane prepolymer Y1;

[0016] Step 2: Add a solvent and a neutralizing agent to the polyurethane prepolymer Y1 obtained in step 1, and react at 40 to 60° C. for 20 to 60 minutes to obtain a neutralized polyurethane prepolymer;

[0017] in:

[0018] The molar ratio between the diisocyanate and the oligomer diol described in step 1 is 2 to 5:1;

[0019] The molar ratio of the hydrophilic chain extender, the primary chain extender and the diisocyanate 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 described in step 2 is 0.9 to 1.1:1;

[0021] More preferably, the temperature of the primary chain extension reaction in step 1 is 70-90° C., and the reaction time is 1-2 h.

[0022] Further, in the above method for preparing an aqueous polyurethane nanoemulsion by an ultrasonic microreactor, the diisocyanate described in step 1 is one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate; the diol is one or more of polyethylene glycol, polypropylene glycol, polybutylene adipate diol, polyethylene adipate diol, polycaprolactone diol, polycarbonate diol, and polypropylene carbonate diol having a number average molecular weight of 500-6000; the catalyst It is one or more of stannous octoate, dibutyltin dilaurate, bismuth neodecanoate, bismuth decanoate, and dibutyltin diacetate; the hydrophilic chain extender is one or more of dimethylolpropionic acid, dimethylolbutyric acid, methyldiethanolamine, 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-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and 1,8-octanediol.

[0023] Furthermore, in the above-mentioned method for preparing an aqueous polyurethane nanoemulsion by an ultrasonic microreactor, the solvent described 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 method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor, the pre-emulsification method is:

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

[0026] Wherein: the mass flow ratio between deionized water and polyurethane prepolymer is 1.5-4:1, and pre-emulsification is carried out at 10-40°C for 0.5-10 minutes.

[0027] Furthermore, in the above method for preparing an aqueous polyurethane nanoemulsion by an ultrasonic microreactor, the secondary emulsification and secondary chain extension reaction is to introduce the aqueous polyurethane pre-emulsion R1 and the secondary chain extender mixed solution into the ultrasonic microreactor, and perform the secondary emulsification and secondary chain extension reaction at 10-40° C. for 0.5-5 min, thereby preparing an aqueous polyurethane emulsion;

[0028] in:

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

[0030] The mass flow ratio of the aqueous polyurethane pre-emulsion R1 and the secondary chain extender mixed solution is 10 to 40:1;

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

[0032] The frequency of the ultrasonic transducer is 10kHz-300kHz, and the power is 20W-300W.

[0033] Furthermore, in the above-mentioned method for preparing an aqueous polyurethane nanoemulsion by an ultrasonic microreactor, the secondary chain extender is one or more of ethylenediamine, hydrazine hydrate, 2-methyl-1,5-pentanediamine, 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt, triethylenetetramine, diethylenetriamine, diaminodicyclohexylmethane, isophoronediamine, and toluenediamine.

[0034] Furthermore, in the above method for preparing waterborne polyurethane nanoemulsion by ultrasonic microreactor, the ultrasonic microreactor is formed by directly bonding an ultrasonic transducer to a microreactor; the microreactor comprises 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;

[0035] The fluid reaction channel is formed by alternately connecting a number of thin channels and thick channels; a reaction layer spoiler chip is arranged in the middle of the thick channel; and a tubular heat exchange layer spoiler chip is arranged in the heat exchange layer etching channel.

[0036] The reaction layer spoiler chip is a bullet-shaped structure with thin ends and a thick middle; the end of the reaction layer spoiler chip facing the fluid input is provided with an inner concave portion with an arc of 100 to 140 degrees; the concave direction of the inner concave portion is opposite to the flow direction of the fluid; a tubular heat exchange layer spoiler chip is provided in the heat exchange layer etching channel.

[0037] Furthermore, in the above-mentioned method for preparing aqueous polyurethane nanoemulsion by means of an ultrasonic microreactor, the ratio of the cross-sectional diameters of the thin channel and the thick channel is 1:2-3; the cross-sectional diameter of the spoiler chip at the widest position of the thin channel and the thick channel is 1.3-1.7 times the cross-sectional diameter of the thin channel; the cross-sectional diameter of the spoiler chip at the narrowest position is 0.9-1.1 times the cross-sectional diameter of the thin channel; and the diameter of the inner recess of the spoiler chip is 0.6-0.9 times the cross-sectional diameter of the thin channel.

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

[0039] Further, in the above-mentioned method for preparing an aqueous polyurethane nanoemulsion by an ultrasonic microreactor, the static mixer is a tube body and an inner core arranged in 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, more preferably SX type; the outer diameter of the inner core is preferably 6-50mm, more preferably 10-40mm; the inner core length of the static mixer is preferably 10-50cm, more preferably 10-40cm; 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. The present invention adopts a static mixer and an ultrasonic microreactor to carry out the pre-emulsification process, the secondary emulsification process, and the secondary chain extension process. The unique advantages of the ultrasonic microreactor are utilized to achieve rapid and uniform preparation of the aqueous polyurethane nanoemulsion, significantly improve the particle size uniformity and stability of the emulsion, facilitate industrial scale-up, and have good industrial application prospects.

[0042] 2. In the preferred embodiment of the present invention, the use of a spoiler chip with a specific structure and a more intensive 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, temperature and other parameters, the particle size distribution and performance of the emulsion can be flexibly adjusted to meet the application requirements of different fields.

[0043] 3. The aqueous polyurethane nanoemulsion prepared by the present invention has the advantages of small particle size, good dispersibility, narrow particle size distribution, high stability, etc., and has broad application prospects in the fields of coatings, adhesives, textiles, etc. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

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

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

[0052] Fig. 9 It is the infrared detection spectrum of the product provided by the embodiment of the present invention;

[0053] Fig.10 It is a graph of the particle size and particle size distribution of the products provided by the embodiments of the present invention and the comparative examples.

[0054] The symbols in the figure represent the components and similar components as follows:

[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 spoiler chip 5113; inner concave portion 5114; first feed port 5115, second feed port 5116, discharge port 5117; heat exchange layer 5 12; heat exchange layer etching channel 5122, tubular heat exchange layer spoiler chip 5123; heat exchange layer first material input pipeline installation hole 5124, heat exchange layer second material pipeline installation hole 5125, heat exchange layer material output pipeline installation hole 5126; top cover layer 513; cover layer first material input pipeline installation hole 5131; cover layer second material pipeline installation hole 5132; cover layer material output pipeline installation hole 5133, ultrasonic transducer 52; product storage tank 6.

[0056] Specific embodiment

[0057] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. In the description of the present invention, it should be noted that, if no specific conditions are specified in the embodiments, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0058] The devices and components not particularly emphasized in the present invention are all conventional devices and components in the art.

[0059] Example 1

[0060] Before describing the specific production method of the present invention, the system for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor is first described. Figure 1 The system comprises a prepolymer reactor 1, a deionized water storage tank 2 and a secondary chain extender mixed solution storage tank 3, wherein the prepolymer reactor 1 and the deionized water storage tank 2 are respectively connected to a static mixer 4 through a first micro-channel and a second micro-channel, wherein the first micro-channel is provided with a metering pump A, and the second micro-channel is provided with a metering pump B, wherein the static mixer 4 is connected to an ultrasonic micro-reactor 5 through a micro-channel, wherein the secondary chain extender mixed solution storage tank 3 is connected to the ultrasonic micro-reactor 5 through a micro-channel, and wherein the third micro-channel is provided with a metering pump C; wherein the ultrasonic micro-reactor 5 is connected to a product storage tank 6;

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

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

[0063] The fluid reaction channel is formed by alternating a number of thin channels 5111 and thick channels 5112, wherein the cross-sectional diameter of the thick channel 5112 is larger than that of the thin channel 5111; and a reaction layer spoiler chip 5113 is provided in the middle of the thick channel 5112; the spoiler chip 5113 is a bullet-shaped structure with thin ends and a thick middle; an inner recess 5114 is provided at the end of the spoiler chip 5113 facing the fluid input; and the recessed direction of the inner recess 5114 is opposite to the flow direction of the fluid. The cross-sections of the thin channel 5111 and the thick channel 5112 are circular; the ratio of the cross-sectional diameters of the thin channel 5111 and the thick channel is 1:2.5; the cross-sectional diameter of the widest position of the spoiler chip is 1.5 times the cross-sectional diameter of the thin channel 5111, the cross-sectional diameter of the narrowest position of the spoiler chip is 1 times the cross-sectional diameter of the thin channel 5111, the diameter of the inner recess of the spoiler chip is 0.8 times the width of the thin channel 5111, and the curvature of the inner recess of the spoiler chip is 120°; the cross-sectional diameter of the thin channel 5111 is 2 mm.

[0064] Furthermore, the fluid microchannel inlet port of the fluid microchannel reaction layer 511 is provided with a first feed port 5115 and a second feed port 5116; the other port is provided with a discharge port 5117;

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

[0066] The first material conveying pipeline is connected to the first feed port 5115 arranged on the fluid microchannel reaction layer 511 through the first material input pipeline installation hole 5131 of the cover layer and the first material input pipeline installation hole 5124 of the heat exchange layer, and the second material conveying pipe is connected to the second feed port 5116 arranged in the fluid reaction channel through the second material input pipeline installation hole 5132 of the cover layer and the second material pipeline installation hole 5125 of the heat exchange layer.

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

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

[0069] The method for preparing an aqueous polyurethane nanoemulsion by using the above-mentioned system for preparing an aqueous polyurethane nanoemulsion by using an ultrasonic microreactor comprises the following steps in sequence:

[0070] 1) 54.6 g of isophorone diisocyanate, 100 g of polypropylene glycol (Mn=2000) and 0.2 g of stannous octoate were mixed in a prepolymer reactor 1, reacted at 80° C. for 1.5 h, then 8.33 g of dimethylolpropionic acid and 3.73 g of 1,4-butanediol were added, reacted at 85° C. for 2 h, then cooled to 50° C., 25 g of N,N-dimethylformamide was added to reduce the viscosity of the system, and finally 6.29 g of triethylamine was added for neutralization for 20 min to obtain a polyurethane prepolymer;

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

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

[0073] in:

[0074] The mass ratio of deionized water to the 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 the deionized water and the polyurethane prepolymer in the secondary chain extender mixed solution is 2:1.

[0076] After the dispersion in Example 1 was dried to form a film, an infrared spectrum test was performed. The test results are as follows: Fig. 9 :

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

[0078] Example 2

[0079] The preparation steps and parameters of this 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 the 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 this 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 the 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 this embodiment 4 are the same as those of embodiment 1, except that the oligomer diol is polybutylene adipate diol (Mn=2000).

[0084] Example 5

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

[0086] Example 6

[0087] The preparation steps and parameters of this Example 6 are the same as those of Example 1, except that the hydrophilic chain extender is dihydroxymethylbutyric 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 the 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 this Example 7 are the same as those of Example 1, except that the primary chain extender is ethylene glycol, and its mass is 2.74 g; the mass of isophorone diisocyanate is 55.59 g; the mass flow rates of the 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 this 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 the 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] Embodiment 11

[0097] The preparation steps and parameters of this Example 11 are the same as those of Example 1, except that the secondary chain extender is ethylenediamine, and its mass is 4.72 g; the mass flow rates of the 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 this Example 12 are the same as those of Example 1, except that the secondary chain extender is ethylenediamine, and its mass is 9.41 g; the mass flow rates of the 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 this Example 13 are the same as those of Example 1, except that the ultrasonic power is 100W.

[0102] Embodiment 14

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

[0104] Embodiment 15

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

[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 100 kHz.

[0108] Embodiment 17

[0109] The preparation steps and parameters of this 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] Embodiment 18

[0111] The preparation steps and parameters of this 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] Embodiment 19

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

[0114] Embodiment 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 temperatures are 40°C.

[0116] Comparative Example 1

[0117] In this comparative example 1, a high-speed disperser is used to perform emulsification and secondary chain extension reaction to prepare an aqueous polyurethane dispersion, and the implementation is as follows:

[0118] Preparation method: Prepared by referring to Example 1, except that the prepared polyurethane prepolymer is slowly poured into a dispersion barrel filled with 332.3g of deionized water, 30.47g of the mixed solution is slowly dripped in during the process, emulsification and secondary chain extension are carried out at a rotation speed of 1500r / min for 3h, and finally an aqueous polyurethane dispersion is obtained.

[0119] Comparative Example 2

[0120] In this comparative example 2, a high-speed disperser and an ultrasonic emulsifier are combined to emulsify the polyurethane prepolymer and perform a secondary chain extension reaction to prepare an aqueous polyurethane dispersion, and the implementation is as follows:

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

[0122] Comparative Example 3

[0123] In this comparative example 3, a tubular emulsifier was used to perform secondary emulsification and secondary chain extension reaction to prepare an aqueous polyurethane dispersion, and the implementation was as follows:

[0124] The preparation method is prepared by referring to 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-mentioned embodiments and comparative examples were sent for testing to detect the particle size (DS) and particle size polydispersity index (PDI). The test results are as follows: Fig.10 As shown in Table 1:

[0126] Table 1

[0127]

[0128]

[0129] pass Fig.10 It can be seen that compared with the emulsification method using a tubular emulsifier, a high-speed disperser, or a high-speed disperser combined with an ultrasonic emulsifier, the emulsion prepared by the method of the present invention has a smaller dispersion coefficient and a relatively smaller particle size.

[0130] The present invention uses a static mixer and an ultrasonic microreactor to carry out the pre-emulsification process, the secondary emulsification process and the secondary chain extension process, and utilizes the unique advantages of the ultrasonic microreactor to achieve rapid and uniform preparation of the aqueous polyurethane nanoemulsion, significantly improve the particle size uniformity and stability of the emulsion, facilitate industrial scale-up, and have good industrial application prospects.

Claims

1. A method for preparing an aqueous polyurethane nanoemulsion by an ultrasonic microreactor, characterized in that: The method comprises the following steps: firstly preparing a polyurethane prepolymer in a kettle reactor, then pre-emulsifying the polyurethane prepolymer by using a static mixer to prepare a pre-emulsion, and finally using a secondary chain extender mixed solution to perform secondary emulsification and secondary chain extension reaction on the pre-emulsion and an aqueous polyurethane nanoemulsion in an ultrasonic microreactor.

2. The method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor according to claim 1, characterized in that: The specific steps of the polyurethane prepolymer preparation process are as follows: Step 1: Mix diisocyanate, oligomer diol and catalyst in a kettle reactor, heat to 60-90° C., react for 1-3 hours for prepolymerization, and successively add a hydrophilic chain extender and a primary chain extender, react at 60-90° C. for 1-3 hours for a primary chain extension reaction to obtain a polyurethane prepolymer Y1; Step 2: Add a solvent and a neutralizing agent to the polyurethane prepolymer Y1 obtained in step 1, and react at 40 to 60° C. for 20 to 60 minutes to obtain a neutralized polyurethane prepolymer; in: The molar ratio between the diisocyanate and the oligomer diol described in step 1 is 2 to 5:1; The molar ratio of the hydrophilic chain extender, the primary chain extender and the diisocyanate in step 1 is 0.1-0.5:0-0.3:1; The molar ratio between the neutralizing agent and the hydrophilic chain extender described in step 2 is 0.9 to 1.1:

1.

3. The method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor according to claim 2, characterized in that: The diisocyanate described in step 1 is one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate; the diol is one or more of polyethylene glycol, polypropylene glycol, polybutylene adipate diol, polyethylene adipate diol, polycaprolactone diol, polycarbonate diol, and polypropylene carbonate diol with a number average molecular weight of 500-6000; the catalyst is stannous octoate, dibutyltin dilaurate, One or more of bismuth neodecanoate, bismuth decanoate, and dibutyltin diacetate; the hydrophilic chain extender is one or more of dimethylolpropionic acid, dimethylolbutyric acid, methyldiethanolamine, 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-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and 1,8-octanediol.

4. The method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor according to claim 2, characterized in that: The solvent described 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.

5. The method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor according to claim 2, characterized in that: The method of pre-emulsification is: Step 1: The neutralized polyurethane prepolymer and deionized water are respectively introduced into a static mixer through metering pumps for mixing and pre-emulsification to obtain an aqueous polyurethane pre-emulsion R1. Wherein: the mass flow ratio between deionized water and polyurethane prepolymer is 1.5-4:1, and pre-emulsification is carried out at 10-40°C for 0.5-10 minutes.

6. The method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor according to claim 1, characterized in that: The secondary emulsification and secondary chain extension reaction is to introduce the mixed solution of the aqueous polyurethane pre-emulsion R1 and the secondary chain extender into an ultrasonic microreactor, and perform the secondary emulsification and secondary chain extension reaction at 10-40° C. for 0.5-5 minutes, thereby preparing the aqueous polyurethane emulsion; in: The molar ratio of the secondary chain extender to the diisocyanate is 0.1 to 0.5:1; The mass flow ratio of the aqueous polyurethane pre-emulsion R1 and the secondary chain extender mixed solution is 10 to 40:1; The secondary chain extender mixed solution is composed of deionized water and the secondary chain extender in a mass ratio of 5 to 15:1; The frequency of the ultrasonic transducer is 10kHz-300kHz, and the power is 20W-300W.

7. The method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor according to claim 6, characterized in that: The secondary chain extender is one or more of ethylenediamine, hydrazine hydrate, 2-methyl-1,5-pentanediamine, 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt, triethylenetetramine, diethylenetriamine, diaminodicyclohexylmethane, isophoronediamine, and toluenediamine.

8. The method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor according to claim 1, characterized in that: The ultrasonic microreactor is formed by directly bonding an ultrasonic transducer to a microreactor; the microreactor comprises 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 alternately connecting a number of thin channels and thick channels; a spoiler chip is arranged in the middle of the thick channel.

9. The method for preparing aqueous polyurethane nanoemulsion by ultrasonic microreactor according to claim 8, characterized in that: The reaction layer spoiler chip is a bullet-shaped structure with thin ends and a thick middle; the end of the reaction layer spoiler chip facing the fluid input is provided with an inner concave portion with an arc of 100 to 140 degrees; the concave direction of the inner concave portion is opposite to the flow direction of the fluid; a tubular heat exchange layer spoiler chip is provided in the heat exchange layer etching channel.

10. The method for preparing aqueous polyurethane nanoemulsion by using an ultrasonic microreactor according to claim 8, characterized in that: The cross-sectional diameter ratio of the fine channel and the thick channel is 1:2-3; the cross-sectional diameter of the spoiler chip at the widest position of the fine channel and the thick channel is 1.3-1.7 times the cross-sectional diameter of the fine channel; the cross-sectional diameter of the spoiler chip at the narrowest position is 0.9-1.1 times the cross-sectional diameter of the fine channel; the diameter of the inner recess of the spoiler chip is 0.6-0.9 times the cross-sectional diameter of the fine channel.

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