Method for preparing waterborne polyurethane dispersion

Abstract

The invention discloses a method for preparing a waterborne polyurethane dispersion. The method comprises the following steps of: a, mixing polyhydric alcohol and an organic solvent of ketone and an anionic hydrophilic chain extender by stirring, adding isomerized diphenylmethane diisocyanate with stirring so as to perform complete reactions in the system to form a pre-polymer of blocked isocyanate; and b, after cooling, adding a anionic hydrophilic polyurethane salt forming agent into the pre-polymer, stirring the mixture to make the pre-polymer form the salt, adding the deionized water to emulsify the pre-polymer, adding the amine or alcohol chain extender with secondary chain extension to the pre-polymer and stirring, and after the reaction is finished, performing heating, decompression and removal of the organic solvent of ketone to obtain the waterborne polyurethane dispersion finally. The method for preparing the waterborne polyurethane dispersion is simple, and the prepared waterborne polyurethane dispersion has the advantages of high bonding strength and high hardness and has low cost and a good development prospect.

Description

technical field [0001] The invention relates to the field of manufacturing chemical raw materials, in particular to a method for preparing a low-cost, high-performance water-based polyurethane dispersion. Background technique [0002] In recent years, due to the enhancement of people's awareness of environmental protection, the voice of reducing volatile organic compounds (VOC) is getting higher and higher, as well as the increasing shortage of resources and energy, consumer culture, the improvement of living standards, environmental protection has become a world trend, etc.; especially the price of solvents The rise of polyurethane products is transitioning from solvent-based to water-based. Water-based polyurethane adhesives are constantly being used in packaging, shoemaking, furniture, textiles, and composites due to their solvent-free, odor-free, pollution-free, non-combustible, soft and hard properties, good adjustability, and good modification. Films, automotive inter...

AI Technical Summary

Problems solved by technology

[0004] At present, the isocyanates commonly used in the preparation of water-based polyurethanes include aliphatic isocyanates such as isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), naphthalene-1,5-diisocyanate (NDI), etc. Acid, although the water glue produced with aliphatic isocyanic acid has stable performance, yellowing resistance, and production process is also easy to control, but its price is expensive, resulting in high production costs; and the lower price of toluene diisocyanate (TDI) raw materials At present, it mainly focuses on low-end water glue products; while polyurethane prepared from pure diphenylmethane-4,4'-diisocyanate (MDI) has high mechanical properties, but the reactivity of MDI is high. When dispersed in water, it is easy to react with water to form flocs, making it difficult to implement production; and use diphenylmethane diisocyanate (MDI) as raw material to prepare water-based polyurethane dispersion, and use hydroxyl end-capping to avoid the NCO group of MDI The method of reacting with water, the prepared aqueous polyurethane dispersion has the disadvantages of low bonding strength and low hardness when used as adhesives and coatings