This invention relates to a process for the production of lignin silicoformate and lignin silicate by heating a mixture of silicoformic acid, metasilicic acid and lignin with an alkali compound as the catalyst to produce lignin silicoformate and lignin silicate. The silicoformic acid and metasilicic acid apparently react chemically with the hydroxyl portion of lignin to form organic silicoformate and organic silicate compounds.
The silicoformic acid and metasilicic acid used in this process were produced by the chemical reaction of a dry alkaline earth metal metasilicate and a dry alkali metal metasilicate with a mineral acid or a hydrogen containing acid salt. The silicic acids are washed with water and filtered to remove the salt, then air dried at 25.degree. to 75.degree. C. The alkali metal carbonate catalyst may be added to the wet silicic acids to produce a pH of 9 to 11, then air dried as outlined in my U.S. Pat. No. 3,962,111. Silicoformic acid, also known as monosilanic acid, may be produced by other methods as outlined in U.S. Pats. Nos. 3,674,430; 3,929,972; 3,954,941 and 3,962,067.
The silicic acid granules produced by the chemical reaction of a dry granular sodium metasilicate with concentrated sulfuric acid or sodium hydrogen sulfate were analyzed by Infrared analysis, using the Infrared KBr disc method. The Infrared analysis showed the presences of Si-H bonds. The Infrared analysis was very similar to that obtained with Mallinckrodt's hydrated silica except for the area of 615 Frequency (cm.sup.-1), which shows evidence of Si-H bonds. The Mallinckrodt's hydrated silica (SiO.sub.2 .sup...sub.x H.sub.2 O) has a molecular weight of 60.09 .sup...sub.x H.sub.2 O. The silicic acids produced contain an active hydrogen which will reduce silver nitrate in an aqueous solution. This is evidence that Si-H bonds are present. The silicic acids produced have a melting point of 1650.degree. C.
In cryoscopic and ebullioscopic determination, the silicic acids produced were not soluble in any common organic solvent but were readily soluble in dilute alkali metal hydroxide aqueous and alcoholic solutions.
The molecular weight was determined from the boiling point elevation of the said silicic acids in a 6N sodium hydroxide aqueous solution and indicated a molecular weight of 78 .+-. 25 gm/mol. This type of reactive solution normally changes the molecular species. The silicic acids readily react with the sodium hydroxide; however, this would seen to indicate the absence of a polymeric form of silicate. On hydroflouric acid determination of the silicon content, it is found to be in the ratio of one mol of silicon to two mols of hydrogen and oxygen, giving a general formula of H.sub.2 SiO.sub.2. It has the physical activity of an acid, giving a general formula of H.SiO.OH which is silicoformic acid. By using the molecular weight and considering the active hydrogen present, the analysis indicates a possible formula of HSi(OH).sub.3 which is orthosilicoformic acid. The orthosilicoformic acid, when dried, will lose water to form silicoformic acid. The silicic acid contains about 30% to 40% of a silicic acid (metasilicic acid), which does not contain an active hydrogen (Si--H) and has a molecular weight of 78 .+-. 25 gm/mol.
Lignin may be produced from wood by several methods. It may be recovered from the waste liquors obtained from the pulping of wood by the acid sulfite process which produces a material known as sulfite lignin. In the Kraft or soda process, the waste liquors are treated by acidification, and sulfate lignin is produced. Lignin may be extracted from wood by using organic solvents. The sulfite lignin may be partially desulfonated and utilized in my process.
Various alkali metal carbonates, hydroxides and oxides may be used as the catalyst, such as sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide. Alkali metal salts of weak acids, such as sodium silicate and other alkali substances may also be used as the catalyst in the silicic acid and lignin reaction.
The silicic acid is reacted with lignin in the ratio of 1 to 2 parts by weight. The ratio may vary, depending on the available hydroxyl groups in the lignin. The alkali compound is added to adjust the pH to 9 to 11. Sodium carbonate is the preferred alkali catalyst. The mixture is heated to 50.degree. to 100.degree. C until the lignin softens and is mixed with the silicic acids; they combine chemically in about 20 to 60 minutes to form a dark gray granular compound, lignin silicoformate and silicate. Lignin silicoformate and lignin silicate are soluble in water, in water soluble organic chemicals, in acetone and other organic solvents. Lignin silicoformate and lignin silicate, in an aqueous solution, will precipitate when the solution is made acid to a pH of 4 to 5.
Lignin silicoformate and lignin silicate will form useful condensation products with aldehydes, furans and epoxy compounds. These condensation products may be used as molding powders, as protective coatings on wood and as ingredients in paints and varnishes.
Lignin silicoformate and lignin silicate may be co-polymerized with phenols, ureas, urethanes, vinyl acetate, acetonitrile, acrylonitrile, acrylic acid, vinyl compounds, rubber, isoprene, butadienes, styrenes, polysulfides and drying oils. Lignin silicoformate and lignin silicate may be treated with a perioxide to produce a black rubbery compound and may be used as a calking compound.
Lignin silicoformate and lignin silicate may be used in the production of plastics, molding powders, cast resins, coating resins, laminates, paints, enamels and varnishes. They may be used as a filler in phenoplast, silicophenoplast, aminoplast, silicoaminoplast, furan resins, natural rubber, GR-S rubber, nitrile rubber and neoprene elastomer.
The primary object of the present invention is to produce lignin silicoformate and lignin silicate, A further object is to provide a new useful organic silicoformate and organic silicate compounds. Still another object is to produce useful organic silicoformate and organic silicate compounds that can be co-polymerized into useful products. A further object is to produce an organic silicoformate and organic silicate that is soluble in aqueous and organic solvents.