Lignin polyurethane and preparation method thereof

Abstract

The invention discloses a method for preparing lignin polyurethane, which comprises the following steps of: using an organic solvent to dissolve the lignin which is extracted and separated from residues after producing ethanol from straws by sodium hydroxide; removing the residues, and depositing the mixture with water; separating the lignin; modifying the lignin with an epoxide; dissolving the lignin into a polylol; and finally compounding the lignin with raw materials of isocyanate and the like to obtain a polyurethane material. The lignin used in the method has high reactivity which can be further enhanced through modification so as to obtain a lignin polyurethane material; the polylol used in the method not only can be used as a solvent but also can take part in a synthetic reaction, has good dissolvability to the lignin, and ensures that undissolved lignin particles cannot appear in a polyurethane foam material; and the link for polyurethane synthesis uses no volatile organic solvents, so the production process causes no pollution to the environment, and simultaneously the cost of a polyurethane product is reduced.

Description

technical field [0001] The invention belongs to the field of polymer chemistry, in particular to a preparation method of lignin polyurethane. Specifically, the present invention relates to a method for preparing high-strength rigid polyurethane foam materials from lignin. Background technique [0002] Lignin is one of the three main components in plant fiber raw materials. It is a natural aromatic polymer with a three-dimensional network structure that is second only to cellulose in reserves. In plant fiber raw materials, there are chemical linkages between lignin and cellulose and hemicellulose. There are active groups such as aromatic groups, phenolic hydroxyl groups, alcoholic hydroxyl groups, carbonyl groups, methoxyl groups, carboxyl groups, conjugated double bonds, etc. in lignin molecules, which can carry out a variety of chemical reactions, and are a potential chemical raw material. However, so far, human beings have not fully utilized lignin. The industrial ligni...

AI Technical Summary

Problems solved by technology

For example, lignosulfonate usually contains a large amount of sodium ions, which will promote the reaction prepolymer to form a gel, affect the foam shape, and be unfavorable to the reaction; ordinary alkali lignin obtained by alkaline cooking is more condensed, and the hydroxyl content Low, so the solubility in polyols is not good, and more alkali lignin does not participate in the reaction with isocyanate and leaves particles in polyurethane products; lignin obtained by oxygen-alkali cooking is oxidized during cooking reaction, so its molecules contain more carboxylate ions, and the solubility in organic solvents is not ideal; this method does not use appropriate methods to remove alkali metal ions (usually sodium ions) in lignin, so it is easy to cause polyurethane foaming Too fast and unsatisfactory cell shape; although high-boiling alcohol lignin has good performance, due to the difficulty in recovering high-boiling alcohol, the current high-boiling alcohol pulping method has not been applied on a large scale, so it is difficult to obtain sufficient industrial-scale production. High boiling alcohol lignin products

In addition, tetrahydrofuran is used as a solvent when preparing polyurethane from high-boiling alcohol lignin, but tetrahydrofuran does not participate in the reaction of preparing polyurethane and needs to be removed after the reaction, which makes subsequent treatment difficult and pollutes the environment

Therefore, there is room for improvement in each of the above methods