Lignin-containing resin adhesive

A method for producing a lignin-phenol-formaldehyde resin which comprises the steps of:

• (1) reacting a mixture of 1.5 to 3 moles of formaldehyde with 1 mole of phenol in the presence of 0.05 to 0.5 moles sodium hydroxide at a temperature of about 70.degree. to 100.degree. C. for 30 to 90 minutes to effect partial condensation of said phenol and formaldehyde;
• (2) cooling the mixture to terminate reaction;
• (3) forming a mixture of the partially condensed phenol-formaldehyde resin with 0.05 to 0.5 moles sodium hydroxide, 0.75 to 1.5 moles formaldehyde and a lignin-phenol-water concentrate solution in an amount such that the lignin contained will comprise from about 10 to about 30% of the total phenolic component in the final resin, said concentrate solution having a solids content of at least 40% and a lignin to phenol weight ratio of about 50:50;
• (4) reacting said mixture at a temperature of about 90.degree. to 100.degree. C. for a period of about 10 to 30 minutes followed by reaction at 75.degree. to 80.degree. C. for a period of about 30 to 120 minutes;
• and
• (5) recovering a lignin-phenol-formaldehyde resin.