Preparation method of aqueous polyurethane based on anionic azo hydrophilic chain extender

Abstract

The invention discloses a preparation method of aqueous polyurethane based on an anionic azo hydrophilic chain extender. According to the preparation method, the anionic azo hydrophilic chain extender containing azo color radicals is utilized for partially or completely replacing a normal hydrophilic chain extender, so as to prepare azo anionic aqueous polyurethane; the problem that the content of hydrophilic groups in a polyurethane system is greatly limited or reduced by a traditional copolymerization method cannot be caused by the addition of the color radicals. According to the azo anionic aqueous polyurethane prepared by virtue of the preparation method, the azo color radicals are located at side chains of polyurethane molecular chains, the azo hydrophilic chain extender with strong hydrophily is distributed on the surfaces of emulsified sphere particles to form a stable double electric layer structure in a self-emulsifying process, the reversible cis-trans isomerism change can be caused by virtue of relatively low energy excitation, the quantity of the azo groups linked into aqueous polyurethane is large, and the change of polyurethane emulsion particle size caused by ultraviolet irradiation shows that functional materials can be used as ultraviolet light responsive nano carriers.

Description

1. Technical field [0001] The invention relates to a method for preparing water-based polyurethane, in particular to a method for preparing water-based polyurethane based on an anionic azo hydrophilic chain extender, and belongs to the technical field of water-based polyurethane materials. 2. Background technology [0002] At present, non-functional hydrophilic chain extenders such as dihydroxymethylpropionic acid and diaminoalkyl sulfonate are often used in the production of water-based polyurethane. The production of functional water-based polyurethane also requires blending or copolymerization to add other functional substances or monomers. body. For example, the existing methods for making polyurethane have azo characteristics can be divided into two types: host-guest doping type and reactive type. Although the host-guest doping method has a simple process, it only needs to mix some azo small molecule compounds into the polyurethane matrix, but in fact, a mixture is obt...

AI Technical Summary

Problems solved by technology

Although the host-guest doping method has a simple process, it only needs to mix some azo small molecule compounds into the polyurethane matrix, but in fact, a mixture is obtained by this method, and the small molecule azo compounds are mixed with the matrix. Not only the doping concentration is limited, but also problems such as migration in the mixture material and oozing out of the material often occur during use, resulting in a decrease in material performance; the reactive method is to use azo small molecule compounds as polymers The reacted monomer, through the active functional group of the azo compound, participates in the polymerization to obtain the polyurethane containing the azo chromophore structure

[0003] Chinese patent 201310573640.7 discloses a method for preparing azo-type water-based polyurethane through azodiols. This method uses azodiols instead of small-molecule diol chain extenders to prepare target materials, and solves the problem of blending azo compounds It causes problems such as poor material migration resistance, but the amount of azodiol added is affected by the ratio of raw materials (the molar ratio of isocyanate to hydroxyl in polyurethane synthesis is generally between 0.8-1.2, and the addition of azodiol will rapidly increase the polyurethane The content of hydroxyl groups in the proportion) is very limited. In this patent, azodiol only partially or completely replaces the small molecule diol used in polyurethane synthesis. Azodiol is used in non-aqueous and non-solvent substances in water-based polyurethane Content up to 15wt%

After the water-resistant azodiol is added, the water-resistant azo component enters the interior of the electric double layer structure of the water-based polyurethane emulsion ball after the self-emulsification process, and it is difficult for the weakly penetrating ultraviolet light to irradiate the inner surface of the emulsion ball. Azo groups, which affect the cis-trans isomerization efficiency of azo groups (under the irradiation of ultraviolet light of a specific wavelength, the percentage of trans-configuration of azobenzene converted to cis-configuration), it is difficult to reach 100%

In short, this method has certain limitations for the synthesis of azo-type anionic waterborne polyurethanes.

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