| abstract |
Lignin of improved reinforcing properties in polymers, is prepared by steps comprising: A. LAUNDERING CRUDE LIGNIN IN AN AQUEOUS MEDIUM UNTIL SUBSTANTIAL AMOUNTS OF NON-LIGNIN MATERIAL ARE SOLUBILIZED AND SEPARATED, B. REFORMING THE LIGNIN BY ONE OF (I) PRECIPITATING WITH ACID AT A PH of about 2 to about 3 at a temperature of about 88* to 95*C; and (ii) conditioning wet lignin precipitate at said pH and said temperature, and C. WASHING THE PRECIPITATE TO REMOVE SOLUBLE MATERIAL AND DRYING THE RESULTING SOLIDS. Laundering additives have been used in step (a), and impurity dispersants in step (b). Polymer latices can be added before precipitation (b) and the lignin-latex coprecipitated. The lignin can be milled directly into rubber to give ultimate tensile strengths at least of the order of 2,800 p.s.i. This lignin can also be used as a reactive reinforcing filler in plastics. |