Preparation method of condensed phase foaming waterborne polyurethane colored popcorn particles

Abstract

The invention discloses a preparation method of condensed-phase foamed waterborne polyurethane colored popcorn particles, which comprises the following steps: adding diisocyanate, a hydrophilic chain extender and a catalyst into dihydric alcohol subjected to vacuum dehydration, reacting to obtain a polyurethane prepolymer, adding acetone and a neutralizer into the polyurethane prepolymer, adding deionized water, dispersing and emulsifying at a high speed, adding a catalyst, and reacting to obtain the condensed-phase foamed waterborne polyurethane colored popcorn particles. A waterborne polyurethane emulsion is obtained; adding a post-chain extender to obtain a high-molecular-weight waterborne polyurethane emulsion, sequentially adding a foaming agent, a thickening agent and a pigment, and mechanically stirring to obtain a thickened high-molecular-weight waterborne polyurethane colored foaming emulsion; and finally, injecting the colored foaming emulsion into a drip nozzle mold, extruding, immersing into a flocculant aqueous solution, solidifying, forming, filtering out, washing and drying to obtain the condensed phase foaming waterborne polyurethane colored popcorn particles with excellent performance. The physical and mechanical stirring foaming operation is simple, bubbles are uniformly distributed, the energy consumption is low, the efficiency is high, the reaction condition is mild, and no pollution is caused.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical foaming and solidification molding of waterborne polyurethane materials, and specifically relates to a preparation method of condensed-phase foaming waterborne polyurethane colored popcorn particles Background Art

[0002] With the progress of technology and the continuous growth of people's needs, polymer foamed particle materials have received extensive attention due to their good elasticity, sound insulation performance and heat insulation performance. These characteristics make polymer foamed particle materials have broad application potential in the fields of shoe materials, mattresses, sound insulation materials, automotive interiors, etc. According to different foaming mechanisms, the methods for preparing foamed particles include chemical foaming method, hollow microsphere foaming method, and mechanical stirring foaming method. The chemical foaming method has strict requirements for temperature control, high energy consumption, is not suitable for materials with poor heat resistance, and may produce harmful gases during the foaming process, polluting the environment; the hollow microsphere foaming method has difficulties in uniform dispersion, may reduce the mechanical properties of the material, and also needs to avoid too high temperature and pressure to prevent damage to the microspheres and affect the foaming effect. Compared with the above methods, the mechanical stirring foaming method has the advantages of simple operation, low cost, not being restricted by specific foaming agents, uniform foam structure, and no pollution to the environment

[0003] In the early preparation process of foamed particles, there are various choices of polymer materials, such as polytetrafluoroethylene, polysulfone, polyethersulfone, and solvent-based polyurethane and other raw materials, but these materials generally face the problem of environmental pollution. In recent years, waterborne polyurethane has gradually received extensive attention due to its significant advantages of being non-toxic, non-flammable, not polluting the air and generating waste water

[0004] Prior to this, certain research progress has been made in the preparation of waterborne polyurethane foamed materials. For example, using chemical foaming agents to prepare waterborne polyurethane foamed materials, but there are problems such as high energy consumption in high-temperature heating during the preparation process, being non-environmental, rough cell structure and low expansion ratio. Patent CN201110274514.2 discloses a manufacturing method of foamed synthetic leather based on waterborne polyurethane, which uses hollow microsphere foaming agents as foaming materials and waterborne polyurethane as the main raw material for foaming to obtain foamed synthetic leather, solving the environmental pollution and other problems in the chemical foaming method, and enabling it to be applied to the manufacture of synthetic leathers such as clothing leather, luggage leather, and shoe upper leather, but there are still problems such as uneven cell structure and affecting mechanical properties. CN201510443387.2 discloses a preparation method of heat-insulating polyurethane automotive interior leather, which mechanically stirs and foams the waterborne polyurethane emulsion and cures it by heating and drying to obtain automotive interior leather, solving the defects in the hollow microsphere foaming method, but requires heating and curing, with high energy consumption

[0005] Therefore, it is necessary to explore a process for preparing waterborne polyurethane colored popcorn particles that is convenient to operate, environmentally friendly, and does not require thermal curing. This is of significant value and importance for in-depth research in the field of waterborne polyurethane foamed particles. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem of environmental pollution existing in traditional polymer foaming materials, and to provide a preparation method of condensed-phase foaming waterborne polyurethane colored popcorn particles that has low energy consumption, is easy to operate, is green and pollution-free, and does not require heating and curing, and can be used in fields such as shoe materials, so as to solve problems such as high temperature, environmental pollution, and influence on mechanical properties in existing chemical foaming methods and hollow microsphere foaming methods.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions: The first aspect of the present invention provides a preparation method of condensed-phase foaming waterborne polyurethane colored popcorn particles, including the following steps: (1) Preparation of polyurethane prepolymer: Add diol to a three-necked flask, perform vacuum dehydration, then add diisocyanate, hydrophilic chain extender, and catalyst, and carry out prepolymerization reaction at 85-95 °C. Stop the reaction when the NCO content in the system reaches 1.2-1.6 wt%, and obtain the polyurethane prepolymer; (2) Preparation of high molecular weight waterborne polyurethane emulsion: First add acetone and neutralizer to the polyurethane prepolymer obtained in step (1), carry out neutralization reaction at 30-50 °C for 0.5 h, then add deionized water, and carry out high-speed dispersion emulsification to obtain the waterborne polyurethane emulsion; Add post-chain extender to the obtained waterborne polyurethane emulsion, and carry out post-chain extension reaction at 40-50 °C for 1-1.5 h to obtain the high molecular weight waterborne polyurethane emulsion; (3) Preparation of thickened high molecular weight waterborne polyurethane colored foaming emulsion: Take a certain amount of the high molecular weight waterborne polyurethane emulsion obtained in step (2), and sequentially add foaming agent, thickener, and pigment thereto, and carry out mechanical stirring to obtain the thickened high molecular weight waterborne polyurethane colored foaming emulsion.

[0008] (4) Preparation of condensed-phase foaming waterborne polyurethane colored popcorn particles: Inject the thickened high molecular weight waterborne polyurethane colored foaming emulsion obtained in step (3) into a nozzle mold, extrude the mold, immerse the thickened high molecular weight waterborne polyurethane colored foaming emulsion in an aqueous solution of flocculant, let it stand and solidify, then filter out the formed particles, wash and dry them to obtain the condensed-phase foaming waterborne polyurethane colored popcorn particles.

[0009] Further, the diol in step (1) is one or more of polyethylene glycol, polypropylene glycol, polybutylene glycol, ethylene glycol adipate, polycarbonate diol, and tetramethylene glycol adipate polyester; the hydrophilic chain extender is one or more of dimethylolpropionic acid, dimethylolbutyric acid, and sodium 2-aminoethanesulfonate; the diisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; and the catalyst is dibutyltin dilaurate.

[0010] Further, the weight ratio of the diol to the diisocyanate in step (1) is 1.5:1 to 6:1; the weight of the hydrophilic chain extender accounts for 0.3 to 8% of the sum of the weights of the diol and the diisocyanate; and the weight of the catalyst accounts for 0.04 to 0.2% of the sum of the weights of the diol and the diisocyanate.

[0011] Further, the weight of the acetone in step (2) accounts for 15 to 35% of the sum of the weights of the diol and the diisocyanate; the neutralizing agent is triethylamine, and its weight accounts for 65 to 78% of the weight of the hydrophilic chain extender; the weight of the deionized water is 150 to 200% of the weight of the polyurethane prepolymer; the post-chain extender is one or more of ethylenediamine and isophoronediamine, and its weight accounts for 0.1 to 5% of the sum of the weights of the diol and the diisocyanate.

[0012] Further, the blowing agent in step (3) is one or more of HCFC-14LB, liquid CO2, cyclopentane, n-pentane, and isopentane; the thickener is a DSX 3800 associative thickener; and the pigment is one or more of cadmium red, iron oxide red, cadmium orange, chrome yellow, iron yellow, chrome green, and lithopone.

[0013] Further, the weight of the blowing agent in step (3) is 0.03 to 0.04% of the weight of the high molecular weight aqueous polyurethane emulsion weighed; the weight of the thickener is 0.25% of the weight of the high molecular weight aqueous polyurethane emulsion weighed; the weight of the pigment is 0.01 to 0.1% of the weight of the high molecular weight aqueous polyurethane emulsion weighed, the mechanical stirring time is 10 to 15 min, and the stirring rate is 200 to 300 r / min.

[0014] Further, the concentration of the flocculant aqueous solution in step (4) is 3 to 20 wt%, and the flocculant is one or more of oxalic acid, tartaric acid, and citric acid.

[0015] Further, the standing and solidifying time in step (4) is 0.5 to 1 h; the drying time is 1.5 to 2 h, and the drying temperature is 110 to 130 °C.

[0016] The second aspect of the present invention provides a kind of waterborne polyurethane colored popcorn particles obtained by the above preparation method, with a hardness of 8.5 - 20.5 HA and a pore size of 4 - 35 μm.

[0017] The third aspect of the present invention provides the application of the above-mentioned waterborne polyurethane colored popcorn particles in the field of shoe materials.

[0018] The significant advantages of the present invention are as follows: Compared with other polymer materials, waterborne polyurethane shows more significant environmental protection characteristics in both raw material selection and synthesis process. Applying waterborne polyurethane materials in the field of foaming materials technology reflects the application value of environmentally friendly materials. At the same time, waterborne polyurethane also has good mechanical properties, low toxicity, non-flammable and other advantages. According to the process of preparing waterborne polyurethane by the acetone method, by changing synthesis conditions, such as the ratio of hard and soft segments, the content of hydrophilic chain extender, etc., waterborne polyurethanes with different properties can be obtained. As a method commonly used in the preparation of foaming materials, the mechanical stirring method has the characteristics of low energy consumption, simple operation, no environmental pollution, etc. Applying it in the preparation of waterborne polyurethane colored popcorn particles can not only reduce resource consumption and production costs, but also help to explore the research direction of waterborne polyurethane foaming materials and broaden the application fields of waterborne polyurethane colored popcorn particles.

[0019] The key to the preparation of condensed-phase foamed waterborne polyurethane colored popcorn particles lies in using the mechanical stirring method. Adding a foaming agent to the waterborne polyurethane emulsion, and by introducing air during the high-speed rotation and stirring process of the electric stirrer, many foams are generated inside the waterborne polyurethane emulsion to achieve the foaming effect. At the same time, it can also reduce the surface tension of the waterborne polyurethane emulsion, and then immerse it in the flocculant aqueous solution and let it stand for solidification and molding to form waterborne polyurethane colored popcorn particles with a pore structure. By changing the content of the foaming agent, the pigment concentration, and the stirring rate conditions, the pore size and the coloring of the foamed particles can be adjusted, so as to prepare a foaming material with good resilience performance. Description of the Drawings

[0020] Figure 1 It is the infrared spectrum diagram of the waterborne polyurethane in Example 3 prepared.

[0021] Figure 2 It is the scanning electron microscope surface diagram of the waterborne polyurethane colored popcorn particles in Example 3 prepared.

[0022] Figure 3 It is the scanning electron microscope cross-section diagram of the waterborne polyurethane colored popcorn particles in Example 3 prepared.

[0023] Figure 4 It is the comparison diagram of the waterborne polyurethane colored popcorn particles in Example 3 prepared. Detailed Embodiments

[0024] The present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments, aiming to help those skilled in the art understand and implement the present invention more comprehensively. It should be clear that the listed embodiments are only partial embodiments of the present invention, rather than all embodiments. These specific embodiments are only used to illustrate the present invention, but should not be regarded as a limitation on the scope of the present invention.

[0025] The determination of the NCO content in the embodiments of the present invention refers to the reference: Xiong Jun, Sun Fang, Du Hongguang. Determination of Isocyanate Group in Polyurethane by Acetone-Di-n-butylamine Titration Method [J]. Chinese Journal of Analysis Laboratory, 2007, 26(8): 73-76.

[0026] Example 1: (1) Preparation of polyurethane prepolymer: Add 8 g of polypropylene glycol with an average molecular weight of 1000 and 29 g of polypropylene glycol with an average molecular weight of 2000 into a three-necked flask. Adjust the oil bath temperature to 120 °C, carry out mechanical stirring at a rotation speed of 200 r / min, and remove water under vacuum for 1 h to obtain polypropylene glycol after vacuum dehydration; then lower the oil bath temperature to 60 °C, and sequentially add 12.7 g of isophorone diisocyanate, 1.2 g of dimethylolpropionic acid, and 0.02 g of dibutyltin dilaurate to the obtained polypropylene glycol after vacuum dehydration, and carry out mechanical stirring reaction at a rotation speed of 200 r / min for 10 min. Subsequently, raise the oil bath temperature to 90 °C and continue the reaction until the NCO content in the reaction system is 1.6 wt% to obtain a polyurethane prepolymer; (2) Preparation of high molecular weight aqueous polyurethane emulsion: Lower the oil bath temperature to 30 °C, take 50 g of the polyurethane prepolymer obtained in step (1), sequentially add 12 g of acetone and 0.9 g of triethylamine thereto, carry out mechanical stirring reaction at a rotation speed of 200 r / min for 30 min, then add 80 g of deionized water, and continue mechanical stirring at a rotation speed of 1000 r / min and carry out high-speed dispersion emulsification for 30 min to obtain an aqueous polyurethane emulsion; raise the oil bath temperature to 40 °C, add 1.4 g of ethylenediamine to the obtained aqueous polyurethane emulsion, and carry out mechanical stirring reaction at a rotation speed of 150 r / min for 1 h to obtain a high molecular weight aqueous polyurethane emulsion; (3) Preparation of thickened high molecular weight aqueous polyurethane colored foaming emulsion: Take 100 g of the high molecular weight aqueous polyurethane emulsion obtained in step (2), sequentially add 3.2 g of foaming agent (HCFC-14LB), 0.25 g of associative thickener (DSX3800), and 0.05 g of cadmium red pigment thereto, and carry out mechanical stirring at room temperature and a rotation speed of 200 r / min for 10 min to obtain a thickened high molecular weight aqueous polyurethane colored foaming emulsion; (4) Preparation of condensed-phase foamed aqueous polyurethane colored popcorn particles: Inject the thickened high-molecular-weight aqueous polyurethane colored foaming emulsion obtained in step (3) into a nozzle mold with a diameter of 3 mm, extrude the mold to completely immerse the thickened high-molecular-weight aqueous polyurethane colored foaming emulsion in a 10 wt% citric acid aqueous solution, let it stand at room temperature for 1 h to solidify and form, then filter out the formed particles, wash them 2-3 times with deionized water, and then dry them in an oven at 120 °C for 2 h to obtain condensed-phase foamed aqueous polyurethane colored popcorn particles.

[0027] The condensed-phase foamed aqueous polyurethane colored popcorn particles prepared in this example are light red-white in color, showing a uniformly distributed cell structure, with the cell size ranging from 6 to 35 μm and a hardness of 18 HA.

[0028] Example 2: (1) Preparation of polyurethane prepolymer: Add 8 g of polypropylene glycol with an average molecular weight of 1000 and 29 g of polypropylene glycol with an average molecular weight of 2000 to a three-necked flask, adjust the oil bath temperature to 120 °C, carry out mechanical stirring at a rotation speed of 200 r / min, and remove water under vacuum for 1 h to obtain polypropylene glycol after vacuum dehydration; then lower the oil bath temperature to 60 °C, and sequentially add 12.7 g of isophorone diisocyanate, 1.2 g of dimethylolpropionic acid, and 0.02 g of dibutyltin dilaurate to the obtained polypropylene glycol after vacuum dehydration, and carry out mechanical stirring reaction at a rotation speed of 200 r / min for 10 min, and then raise the oil bath temperature to 90 °C and continue the reaction until the NCO content in the reaction system is 1.6 wt% to obtain a polyurethane prepolymer; (2) Preparation of high-molecular-weight aqueous polyurethane emulsion: Lower the oil bath temperature to 30 °C, take 50 g of the polyurethane prepolymer obtained in step (1), sequentially add 12 g of acetone and 0.9 g of triethylamine thereto, carry out mechanical stirring reaction at a rotation speed of 200 r / min for 30 min, then add 80 g of deionized water, and continue mechanical stirring at a rotation speed of 1000 r / min and carry out high-speed dispersion emulsification for 30 min to obtain an aqueous polyurethane emulsion; raise the oil bath temperature to 40 °C, add 1.4 g of ethylenediamine to the obtained aqueous polyurethane emulsion, and carry out mechanical stirring reaction at a rotation speed of 150 r / min for 1 h to obtain a high-molecular-weight aqueous polyurethane emulsion; (3) Preparation of thickened high-molecular-weight aqueous polyurethane colored foaming emulsion: Take 100 g of the high-molecular-weight aqueous polyurethane emulsion obtained in step (2), sequentially add 3.4 g of foaming agent (HCFC-14LB), 0.25 g of associative thickener (DSX3800), and 0.10 g of cadmium red pigment thereto, and carry out mechanical stirring at room temperature and a rotation speed of 220 r / min for 10 min to obtain a thickened high-molecular-weight aqueous polyurethane colored foaming emulsion; (4)Preparation of coagulated-phase foamed aqueous polyurethane colored popcorn particles: Inject the thickened high-molecular-weight aqueous polyurethane colored foaming emulsion obtained in step (3) into a nozzle mold with a diameter of 3 mm, extrude the mold to completely immerse the thickened high-molecular-weight aqueous polyurethane colored foaming emulsion in a 10 wt% aqueous citric acid solution, let it stand at room temperature for 1 h to solidify and form, then filter out the formed particles, wash them with deionized water 2 - 3 times, and then dry them in an oven at 120 °C for 2 h to obtain coagulated-phase foamed aqueous polyurethane colored popcorn particles.

[0029] The coagulated-phase foamed aqueous polyurethane colored popcorn particles prepared in this example are light pink in color, presenting a uniformly distributed cell structure. The cell size is distributed between 5 - 25 μm, and the hardness is 12 HA.

[0030] Example 3: (1)Preparation of polyurethane prepolymer: Add 8 g of polypropylene glycol with an average molecular weight of 1000 and 29 g of polypropylene glycol with an average molecular weight of 2000 to a three-necked flask, adjust the oil bath temperature to 120 °C, carry out mechanical stirring at a rotation speed of 200 r / min, and remove water under vacuum for 1 h to obtain polypropylene glycol after water removal under vacuum; then lower the oil bath temperature to 60 °C, and successively add 12.7 g of isophorone diisocyanate, 1.2 g of dimethylolpropionic acid, and 0.02 g of dibutyltin dilaurate to the obtained polypropylene glycol after water removal under vacuum, carry out mechanical stirring reaction at a rotation speed of 200 r / min for 10 min, and then raise the oil bath temperature to 90 °C and continue the reaction until the NCO content in the reaction system is 1.6 wt% to obtain a polyurethane prepolymer; (2)Preparation of high-molecular-weight aqueous polyurethane emulsion: Lower the oil bath temperature to 30 °C, take 50 g of the polyurethane prepolymer obtained in step (1), successively add 12 g of acetone and 0.9 g of triethylamine thereto, carry out mechanical stirring reaction at a rotation speed of 200 r / min for 30 min, then add 80 g of deionized water, and continue mechanical stirring at a rotation speed of 1000 r / min for high-speed dispersion and emulsification for 30 min to obtain an aqueous polyurethane emulsion; raise the oil bath temperature to 40 °C, add 1.4 g of ethylenediamine to the obtained aqueous polyurethane emulsion, and carry out mechanical stirring reaction at a rotation speed of 150 r / min for 1 h to obtain a high-molecular-weight aqueous polyurethane emulsion; (3)Preparation of thickened high-molecular-weight aqueous polyurethane colored foaming emulsion: Take 100 g of the high-molecular-weight aqueous polyurethane emulsion obtained in step (2), successively add 3.6 g of foaming agent (HCFC-14LB), 0.25 g of associative thickener (DSX3800), and 0.15 g of cadmium red pigment thereto, and carry out mechanical stirring at room temperature and a rotation speed of 250 r / min for 10 min to obtain a thickened high-molecular-weight aqueous polyurethane colored foaming emulsion; (4)Preparation of condensed-phase foamed aqueous polyurethane colored popcorn particles: Inject the thickened high-molecular-weight aqueous polyurethane colored foaming emulsion obtained in step (3) into a nozzle mold with a diameter of 3 mm, extrude the mold to completely immerse the thickened high-molecular-weight aqueous polyurethane colored foaming emulsion in a 10 wt% aqueous citric acid solution, let it stand at room temperature for 1 h to solidify and form, then filter out the formed particles, wash them 2-3 times with deionized water, and then dry them in an oven at 120 °C for 2 h to obtain condensed-phase foamed aqueous polyurethane colored popcorn particles.

[0031] The condensed-phase foamed aqueous polyurethane colored popcorn particles prepared in this example are peach red in color, showing a uniformly distributed cell structure, with cell sizes ranging from 5 to 20 μm and a hardness of 8.5 HA.

[0032] Example 4: (1)Preparation of polyurethane prepolymer: Add 8 g of polypropylene glycol with an average molecular weight of 1000 and 29 g of polypropylene glycol with an average molecular weight of 2000 to a three-necked flask, adjust the oil bath temperature to 120 °C, carry out mechanical stirring at a rotation speed of 200 r / min, and remove water under vacuum for 1 h to obtain polypropylene glycol after water removal under vacuum; then lower the oil bath temperature to 60 °C, and sequentially add 12.7 g of isophorone diisocyanate, 1.2 g of dimethylolpropionic acid, and 0.02 g of dibutyltin dilaurate to the obtained polypropylene glycol after water removal under vacuum, and carry out mechanical stirring reaction at a rotation speed of 200 r / min for 10 min. Subsequently, raise the oil bath temperature to 90 °C and continue the reaction until the NCO content in the reaction system is 1.6 wt% to obtain a polyurethane prepolymer; (2)Preparation of high-molecular-weight aqueous polyurethane emulsion: Lower the oil bath temperature to 30 °C, take 50 g of the polyurethane prepolymer obtained in step (1), sequentially add 12 g of acetone and 0.9 g of triethylamine thereto, carry out mechanical stirring reaction at a rotation speed of 200 r / min for 30 min, then add 80 g of deionized water, and continue mechanical stirring at a rotation speed of 1000 r / min for high-speed dispersion and emulsification for 30 min to obtain an aqueous polyurethane emulsion; raise the oil bath temperature to 40 °C, add 1.4 g of ethylenediamine to the obtained aqueous polyurethane emulsion, and carry out mechanical stirring reaction at a rotation speed of 150 r / min for 1 h to obtain a high-molecular-weight aqueous polyurethane emulsion; (3)Preparation of thickened high-molecular-weight aqueous polyurethane colored foaming emulsion: Take 100 g of the high-molecular-weight aqueous polyurethane emulsion obtained in step (2), sequentially add 3.8 g of foaming agent (HCFC-14LB), 0.25 g of associative thickener (DSX3800), and 0.20 g of cadmium red pigment thereto, and carry out mechanical stirring at room temperature and a rotation speed of 270 r / min for 10 min to obtain a thickened high-molecular-weight aqueous polyurethane colored foaming emulsion; (4)Preparation of condensed-phase foamed waterborne polyurethane colored popcorn particles: Inject the thickened high-molecular-weight waterborne polyurethane colored foaming emulsion obtained in step (3) into a nozzle mold with a diameter of 3 mm, extrude the mold to immerse the thickened high-molecular-weight waterborne polyurethane colored foaming emulsion completely in a 10 wt% aqueous citric acid solution, let it stand at room temperature for 1 h to solidify and form, then filter out the formed particles, wash them 2 - 3 times with deionized water, and then dry them in an oven at 120 °C for 2 h to obtain condensed-phase foamed waterborne polyurethane colored popcorn particles.

[0033] The condensed-phase foamed waterborne polyurethane colored popcorn particles prepared in this example are pink in color, presenting a uniformly distributed cell structure, with the cell size ranging from 4 - 30 μm and a hardness of 10.5 HA.

[0034] Example 5: (1)Preparation of polyurethane prepolymer: Add 8 g of polypropylene glycol with an average molecular weight of 1000 and 29 g of polypropylene glycol with an average molecular weight of 2000 into a three-necked flask, adjust the oil bath temperature to 120 °C, carry out mechanical stirring at a rotation speed of 200 r / min, and remove water under vacuum for 1 h to obtain polypropylene glycol after water removal under vacuum; then lower the oil bath temperature to 60 °C, and successively add 12.7 g of isophorone diisocyanate, 1.2 g of dimethylolpropionic acid, and 0.02 g of dibutyltin dilaurate to the obtained polypropylene glycol after water removal under vacuum, carry out mechanical stirring reaction at a rotation speed of 200 r / min for 10 min, then raise the oil bath temperature to 90 °C and continue the reaction until the NCO content in the reaction system is 1.6 wt% to obtain a polyurethane prepolymer; (2)Preparation of high-molecular-weight waterborne polyurethane emulsion: Lower the oil bath temperature to 30 °C, take 50 g of the polyurethane prepolymer obtained in step (1), successively add 12 g of acetone and 0.9 g of triethylamine thereto, carry out mechanical stirring reaction at a rotation speed of 200 r / min for 30 min, then add 80 g of deionized water, and continue mechanical stirring at a rotation speed of 1000 r / min, and carry out high-speed dispersion emulsification for 30 min to obtain a waterborne polyurethane emulsion; raise the oil bath temperature to 40 °C, add 1.4 g of ethylenediamine to the obtained waterborne polyurethane emulsion, and carry out mechanical stirring reaction at a rotation speed of 150 r / min for 1 h to obtain a high-molecular-weight waterborne polyurethane emulsion; (3)Preparation of thickened high-molecular-weight waterborne polyurethane colored foaming emulsion: Take 100 g of the high-molecular-weight waterborne polyurethane emulsion obtained in step (2), successively add 4 g of foaming agent (HCFC-14LB), 0.25 g of associative thickener (DSX3800), and 0.25 g of cadmium red pigment thereto, and carry out mechanical stirring at room temperature and a rotation speed of 300 r / min for 10 min to obtain a thickened high-molecular-weight waterborne polyurethane colored foaming emulsion; (4)Preparation of condensed-phase foamed waterborne polyurethane colored popcorn particles: Inject the thickened high-molecular-weight waterborne polyurethane colored foaming emulsion obtained in step (3) into a nozzle mold with a diameter of 3 mm, squeeze the mold to completely immerse the thickened high-molecular-weight waterborne polyurethane colored foaming emulsion in a 10 wt% aqueous citric acid solution, let it stand at room temperature for 1 h to solidify and form, then filter out the formed particles, wash them 2-3 times with deionized water, and then dry them in an oven at 120 °C for 2 h to obtain condensed-phase foamed waterborne polyurethane colored popcorn particles.

[0035] The condensed-phase foamed waterborne polyurethane colored popcorn particles prepared in this example are red in color, showing a uniformly distributed cell structure, with the cell size ranging from 6 to 32 μm and a hardness of 16 HA.

[0036] Figure 1 It is the infrared spectrum of the waterborne polyurethane in Example 3 prepared. As can be seen from the figure, there is no characteristic peak of free NCO groups at 2270 cm -1 , which means that IPDI is completely incorporated into the waterborne polyurethane; the absorption peak at 3334 cm -1 corresponds to the N-H bond in the urethane group and the urea bond group, the absorption peak at 1707 cm -1 corresponds to the C=O bond in the urethane group and the urea bond group, and the absorption peak at 1242 cm -1 corresponds to the C-O bond in the urethane group, proving the formation of the waterborne polyurethane. Figure 2 It is the scanning electron microscope surface image of the waterborne polyurethane colored popcorn particles in Example 3 prepared, and the cell size distribution range is 5.61-25.0 μm. Figure 3 It is the scanning electron microscope cross-sectional image of the waterborne polyurethane colored popcorn particles in Example 3 prepared, and it can be seen that the cells are evenly distributed. Figure 4 It is the comparison diagram of the waterborne polyurethane colored popcorn particles in Example 3 prepared. As can be seen from the figure, the added cadmium red pigment has good compatibility with the waterborne polyurethane emulsion, the color is uniform, there is no agglomeration, and the color is bright after mixing.

[0037] Table 1 shows the parameters and performance characterization results of the preparation of condensed-phase foamed waterborne polyurethane colored popcorn particles in Examples 1-5. From the results shown in Table 1, it can be seen that with the increase in the content of the blowing agent (HCFC-14LB) and the mechanical stirring rate, the pore size distribution range and the particle hardness both show non-monotonic changes (the pore size distribution range first shrinks and then expands, and the particle hardness first decreases and then increases), indicating that the pore structure and the particle hardness are synergistically regulated by the blowing agent content and the mechanical stirring rate; when the concentration of the blowing agent (HCFC-14LB) is 3.6 g and the mechanical stirring rate is 250 r / min, the hardness is the smallest, the resilience is the best, the pore size is more uniform, and the foaming effect is the best. With the increase in the content of the (cadmium red) pigment, the color of the waterborne polyurethane colored popcorn particles is closer to red.

[0038] Table 1 Parameters and performance characterization results of the preparation of condensed-phase foamed waterborne polyurethane colored popcorn particles in Examples 1-5 It should be noted that although the above examples have been described in this article, the patent protection scope of the present invention is not limited thereby. Therefore, based on the innovative concept of the present invention, the changes and modifications made to the examples described in this article, or the equivalent structural or equivalent process transformations made using the content of the specification of the present invention, directly or indirectly applying the above technical solutions to other related technical fields are all included in the patent protection scope of the present invention.

Claims

1. A preparation method of a condensed-phase foaming aqueous polyurethane colored popcorn particle, characterized in that, It includes the following steps: (1) Add diisocyanate, hydrophilic chain extender and catalyst to the vacuum-dehydrated diol, and carry out a prepolymerization reaction at 85-95 °C. Stop the reaction after the NCO content in the system reaches 1.2-1.6 wt%, and obtain a polyurethane prepolymer; (2) First add acetone and neutralizer to the polyurethane prepolymer obtained in step (1), carry out a neutralization reaction at 30-50 °C for 0.5 h, then add deionized water for high-speed dispersion emulsification to obtain an aqueous polyurethane emulsion; add a post-chain extender to the obtained aqueous polyurethane emulsion, and carry out a post-chain extension reaction at 40-50 °C for 1-1.5 h to obtain a high-molecular-weight aqueous polyurethane emulsion; (3) Take a certain amount of the high-molecular-weight aqueous polyurethane emulsion obtained in step (2), and sequentially add a foaming agent, a thickener and a pigment thereto, and carry out mechanical stirring to obtain a thickened high-molecular-weight aqueous polyurethane colored foaming emulsion; (4) Inject the thickened high-molecular-weight aqueous polyurethane colored foaming emulsion obtained in step (3) into a nozzle mold, extrude the mold, immerse the thickened high-molecular-weight aqueous polyurethane colored foaming emulsion in an aqueous solution of a flocculant and let it stand for solidification and molding, then filter out the molded particles, wash and dry them to obtain aggregated-phase foaming aqueous polyurethane colored popcorn particles.

2. The preparation method according to claim 1, wherein: In step (1), the diol is one or more of polyethylene glycol, polypropylene glycol, polybutylene glycol, polyethylene adipate, polycarbonate diol, and tetramethylene glycol adipate polyester; the hydrophilic chain extender is one or more of dimethylolpropionic acid, dimethylolbutyric acid, and sodium 2-aminoethanesulfonate; the diisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; the catalyst is dibutyltin dilaurate.

3. The preparation method according to claim 1, wherein: In step (1), the weight ratio of the diol to the diisocyanate is 1.5:1-6:1; the weight of the hydrophilic chain extender accounts for 0.3-8% of the sum of the weights of the diol and the diisocyanate; the weight of the catalyst accounts for 0.04-0.2% of the sum of the weights of the diol and the diisocyanate.

4. The preparation method according to claim 1, wherein: In step (2), the weight of the acetone accounts for 15-35% of the sum of the weights of the diol and the diisocyanate; the neutralizer is triethylamine, and its weight accounts for 65-78% of the weight of the hydrophilic chain extender; the weight of the deionized water is 150-200% of the weight of the polyurethane prepolymer; the post-chain extender is one or more of ethylenediamine and isophoronediamine, and its weight accounts for 0.1-5% of the sum of the weights of the diol and the diisocyanate.

5. The preparation method according to claim 1, characterized in that: In step (3), the foaming agent is one or more of HCFC-14LB, liquid CO2, cyclopentane, n-pentane, and isopentane; the thickener is a DSX 3800 associative thickener; the pigment is one or more of cadmium red, iron oxide red, cadmium orange, chrome yellow, iron yellow, chrome green, and lithopone.

6. The preparation method according to claim 1, wherein: In step (3), the weight of the foaming agent is 0.03 - 0.04% of the weight of the high molecular weight aqueous polyurethane emulsion weighed; the weight of the thickener is 0.25% of the weight of the high molecular weight aqueous polyurethane emulsion weighed; the weight of the pigment is 0.01 - 0.1% of the weight of the high molecular weight aqueous polyurethane emulsion weighed, the mechanical stirring time is 10 - 15 min, and the stirring rate is 200 - 300 r / min.

7. The preparation method according to claim 1, wherein: In step (4), the concentration of the flocculant aqueous solution is 3 - 20 wt%, and the flocculant is one or more of oxalic acid, tartaric acid, and citric acid.

8. The preparation method according to claim 1, characterized in that: In step (4), the standing and solidifying time is 0.5 - 1 h; the drying time is 1.5 - 2 h, and the drying temperature is 110 - 130 °C.

9. A condensed-phase foamed waterborne polyurethane colored popcorn particle obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The hardness of the condensed phase foamed aqueous polyurethane colored popcorn particles is 8.5 - 20.5 HA, and the pore size is 4 - 35 μm.

10. Application of the condensed phase foamed aqueous polyurethane colored popcorn particles according to claim 9 in the field of shoe materials.

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