Method for preparing lignin phenolic resin adhesive by using microwave-CuO to treat papermaking waste liquid

Abstract

The invention discloses a preparation method for preparing a lignin phenolic resin adhesive by using activated lignin to replace part of phenol to react with formaldehyde. The preparation method comprises the following steps: treating papermaking waste liquid with microwave and CuO, then filtering, adjusting the pH value to be about 2-3 by using hydrochloric acid, putting into a drying oven, standing for a period of time at a set temperature, filtering while the liquid is hot, washing to be neutral, and drying to obtain acidified lignin for later use; and taking the dried lignin to replace part of phenol, and performing phenolization, hydroxymethylation and phenolic reaction to prepare the lignin phenolic resin adhesive. By using the method disclosed by the invention, the replacement rate of phenol by lignin is improved, the cost is reduced, the pollution to the environment is reduced, the adhesive is high in bonding strength and low in free formaldehyde content, and various properties of the adhesive accord with national standards.

Description

technical field [0001] The present invention relates to a preparation field of lignin in microwave-CuO modified papermaking black liquor for partially replacing phenol to prepare lignin-phenolic resin adhesive, and a method for remodifying modified lignin (that is, phenolization and methylolation) to prepare lignin-phenolic resin adhesives. The present invention belongs to the intersecting field of organic chemistry and physical chemistry. Background technique [0002] In nature, lignin reserves are second only to cellulose, and are regenerated at a rate of 50 billion tons per year. The pulp and paper industry separates approximately 140 million tons of cellulose from plants each year, while obtaining approximately 50 million tons of lignin by-products. But so far, more than 95% of lignin is still directly discharged into rivers as "black liquor" or burned after being concentrated, which not only has not been effectively utilized, but also caused serious pollution to the e...

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Problems solved by technology

Alonso M V et al. (Bioresource Technology, 2005, 96(9): 1013 -1018) catalyzed ammonium lignosulfonate with oxalic acid, and phenolized it with phenol at 120 °C for 160 minutes, and prepared phenolic resin with this product instead of phenol. The preferred alternative The rate is 30%. The shortcoming of this method is that the replacement rate of lignin to phenol is low, and the bonding strength of the prepared phenolic resin adhesive is not high; Sudan et al. (Process for preparing a black liquor formaldehyde thermoset resin[P] .US: 6632912, 2003-10-16) After the black liquor was phenolized and modified under alkaline conditions, it was made into LPF resin with good performance, in which the proportion of lignin instead of phenol reached 60%; Liu Gangyong (Fine Chemicals, 2009 , 26(4): 399-402) LPF adhesives for national standard Class I boards were prepared by phenolization modification of wheatgrass lignin under alkaline conditions, in which lignin can replace up to 70% of phenol, which is currently reported The example with the highest substitution rate of phenol by lignin, but its bonding strength is still not high enough; An Xinnan (Chemistry and Industry of Forest Products, 1995, 15( 3): 36-42) extracted lignin with dimethyl sulfide in After high temperature demethylation at 225~235℃, it can be completely used as phenol to make wood adhesive with good performance, but the preparation process is complicated and the cost is high. However, with the increase of the lignin substitution rate, the bonding strength of the LPF adhesive decreases; the American Klonn-Tererba Company uses sodium sulfide to process the thick black liquor at 250°C to decompose the methoxyl group of the lignin, and prepare di Methyl sulfide, dimethyl sulfide is evaporated, and the rest is black liquor containing demethylated lignin, which can be used to produce phenolic resin adhesives

Although this method can greatly increase the number of active sites of lignin, the preparation process is complicated and the cost is high.

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