Aqueous polyurethane and preparation method thereof

Abstract

The present invention provides a preparation method for aqueous polyurethane. The method comprises the following steps: mixing aliphatic diisocyanate, an aliphatic polyol, dimethylol propionic acid and a catalyst, and carrying out a reaction to obtain a prepolymer; adding a neutralizing agent to the prepolymer, and carrying out a stirring reaction to obtain an intermediate product; adding water and a chain extender to the intermediate product, stirring and dispersing to obtain the aqueous polyurethane, wherein the chain extender is polyoxyethylene polyamine or polyoxypropylene polyamine. The invention further provides the aqueous polyurethane prepared by the method. According to the present invention, the bulk polymerization method is adopted, the use of the organic solvent is not required, and no environmental pollution is generated; the polyoxyethylene polyamine or the polyoxypropylene polyamine is adopted as the chain extender, and is used for emulsion chain extending, such that the obtained polyurethane emulsion has good film-forming flexibility, the mechanical property of the obtained polyurethane can not be reduced, the large R value is not required, and the final produced polyurethane film is soft.

Description

technical field [0001] The invention belongs to the technical field of leather auxiliary agents, and in particular relates to a water-based polyurethane and a preparation method thereof. Background technique [0002] Water-based polyurethane is a polyurethane system with water as the dispersion medium, also known as water-dispersed polyurethane, water-based polyurethane or water-based polyurethane. Compared with solvent-based polyurethane, it has the advantages of non-combustibility, low odor, energy saving, and convenient operation. It is widely used as a leather finishing agent, coating, and adhesive. [0003] At present, water-based polyurethane is generally prepared by conventional acetone method or prepolymer method. In the production process, organic solvents are generally used to reduce the viscosity of the reaction system or as co-solvents to ensure the smooth progress of the reaction; some of these organic solvents, such as N-methylpyrrolidone, N, N-dimethylformami...

AI Technical Summary

Problems solved by technology

[0004] The prior art discloses a variety of methods for preparing polyurethanes that do not contain organic solvents. For example, the Chinese patent document with the publication number CN1995086A discloses a method for preparing water-based non-toxic and degradable polyurethane elastomers. In this method, the polymer binary Mix alcohol, diisocyanate and catalyst, prepolymerize for 45-120 minutes; add the first low-molecular-weight chain extender for chain extension reaction for 100-240 minutes; add water and the second low-molecular-weight chain extender under strong stirring conditions for emulsification and chain extension. At the same time, KOH or NaOH is used as a neutralizing agent to obtain a water-based polyurethane dispersion after emulsification, and to obtain a polyurethane elastomer after molding. This method does not use organic solvents and will not cause environmental pollution, but it directly adds water to the prepolymer. , Realize emulsification and dispersion by means of strong stirring, the prepared emulsion has a large particle size, is unstable, and is prone to precipitation and layering, which is not conducive to use

The Chinese patent document whose publication number is CN101759843A discloses a preparation method of water-based nontoxic anionic polyurethane, which firstly mixes dicyclohexylmethane diisocyanate, aliphatic polymeric diol, DMBA containing hydrophilic groups and a catalyst for prepolymerization , to obtain a prepolymer, then add deionized water containing a neutralizing agent to neutralize and emulsify, finally add a diamine chain extender, continue to emulsify, and obtain a water-based polyurethane after chain extension. This method does not use organic solvents and will not cause environmental pollution. pollution, but this method uses small molecule diamines as chain extenders for emulsion chain extension, which will increase the hardness of the resin film and reduce the flexibility. After finishing on the leather, it will have an obvious plastic feeling, which cannot reach the level of automobile leather finishing. Performance

At the same time, this method is neutralized after emulsification and dispersion, and the neutralization effect is poor. The particle size of the obtained emulsion micelles is large, and precipitation and layering are prone to occur, which is not conducive to use