Method for preparing WPU synthetic leather foaming layers based on pickering foam template method

A method for preparing a waterborne polyurethane synthetic leather foaming layer based on a Pickering foam template method, comprising the following steps:

• (1) selecting a soft waterborne polyurethane with a solid content of 20-40% as a raw material for the waterborne polyurethane synthetic leather foaming layer, adding a waterborne crosslinking agent thereto, and mixing uniformly to obtain a waterborne polyurethane slurry for synthetic leather;
• (2) adding the waterborne polyurethane slurry for synthetic leather to an open container, then adding hydrophobic inorganic solid particles that can be adsorbed at a water-air interface as a foam stabilizer, wherein a mass ratio of the hydrophobic inorganic solid particles to the waterborne polyurethane slurry for synthetic leather is (0.05-0.2):
• 1, a volume of a mixed solution in the container is below ½ of a volume of the container, and air is used as a dispersed phase;
• after mixing uniformly, performing emulsifying and dispersing by a high-speed emulsifier for 0.5-2 h with a speed of 8000-15000 rpm/min to obtain a Pickering waterborne foam slurry containing polyurethane latex particles;
• and
• (3) drying the Pickering waterborne foam slurry at 70-120° C. to obtain the waterborne polyurethane synthetic leather foaming layer based on the Pickering foam template method;
• wherein the waterborne polyurethane slurry for synthetic leather is prepared by the following steps:
• 1) adding a hard segment monomer diisocyanate and a soft segment monomer polymer diol to a reactor in accordance with a molar ratio of (2-5):1, adding an appropriate amount of solvent acetone, and stirring and reacting for 1 h at a temperature of 60-90° C.;
• then adding a chain extender 2,2-dimethylolpropionic acid and 1,4-butanediol and 1-2 drops of a catalyst with a molar ratio of the chain extender to the soft segment monomer polymer diol of (1-4):
• 1, and conducting a reaction at a temperature of 70-90° C. for 3-6 h with a stirring speed of 100-2000 rpm to obtain a polyurethane polymer;
• wherein a ratio of the 2,2-dimethylolpropionic acid to the 1,4-butanediol is adjusted to make an amount of the 2,2-dimethylolpropionic acid account for 4-6 wt % of all reactants added;
• 2) adding triethylamine to the reactor, performing neutralization for 0.5-2 h at a temperature of 40-50° C. and a stirring speed of 1000-2000 rpm, adjusting a pH to 3-10;
• finally adding a certain amount of deionized water to a resulting reaction product, stirring for 10-30 min at a stirring speed of 8000-10000 rpm;
• and stirring for 1-2 h at a stirring speed of 1000-3000 rpm;
• and
• 3) removing acetone by rotary evaporation, and concentrating a resulting product to a solid content of 20%-40% to obtain the waterborne polyurethane slurry for synthetic leather.