Patent GB-694665-A (GB)
Title: Method of producing water-soluble products from black liquor lignin
IPC: C08H5/02
Filed: 1950-12-22
Abstract: A process for converting black liquor lignin into water-soluble products is characterized in that the black liquor lignin is sulphonated at an elevated temperature (e.g. 50 DEG  to 200 DEG  C.) with sulphurous acid or a salt thereof, or with a substance yielding sulphurous acid.  Before, during or after sulphonation the lignin may be reacted with an aldehyde.  A product containing -CH2SO3H groups is produced when the aldehyde is formaldehyde.  The product may then be further sulphonated in the absence of an aldehyde.  The black liquor lignin may be obtained by digesting hardwood or coniferous wood or other lignocellulose containing materials according to the soda or sulphate cellulose processes.  Sulphonation may be effected under acid, neutral or alkaline conditions, e.g. with alkali metal or ammonium sulphites or bisulphites.  Before or during sulphonation the lignin may be oxidized, e.g. by passing air or oxygen through its solution, if desired in the presence of iron, copper or cobalt.  In the oxidation, sulphate black liquor lignin which contains combined sulphur is converted to a product containing sulphonic groups.  In examples: (1) black liquor lignin is reacted in alkaline solution with sodium sulphite and sulphate and sulphite ions are removed from the product by dialysis; (2) black liquor lignin, sodium sulphite and formalin are heated together, the product is treated with a hydrogen-ion-saturated cation exchanger, and evaporated to dryness. The product which contains one sulphonic acid group to about 5 methoxyl groups is converted to its barium and calcium salts; (3) a procedure similar to (2) but with isolation of the product by salting out is followed; (4) black liquor lignin, sodium hydroxide, sodium sulphite and formalin are heated together.  The product is purified by dialysis; (5) the lignin is heated with sodium sulphite and sodium hydroxide.  After passing sulphur dioxide through the solution, the product is reacted with formalin; (6) the product of (2) is reacted with sodium pyrosulphite; (7) sulphite process black liquor lignin in boiling alkaline solution is oxidized by passing oxygen through.  The product, containing sulphonic acid groups, is reacted with sodium sulphite and dialysed; (8) sulphate black liquor lignin, sodium hydroxide and sodium sulphite are heated in solution in two batches, through only one of which air is passed; (9) the product of (1) is reacted with sodium sulphite and formalin; (10) the product of (2) is reacted with a formalin-bisulphite addition product; (11) sulphate black liquor lignin is oxidized with air in alkaline solution and the product heated with a formaldehyde-bisulphite addition compound.  The products are useful in tanning leather and as emulsifying and dispersing agents, e.g. in printing inks, and cutting and drilling oils, as levelling agents in dyeing, as fillers for caoutchouc, and as dispersing, hardening promoting, and strength-increasing additives for cement.ALSO:A process for converting black liquor lignin into water-soluble products is characterized in that the black liquor lignin is sulphonated at an elevated temperature, e.g. 50 DEG  to 200 DEG  C. with sulphurous acid or a salt thereof or with a substance yielding sulphurous acid.  The black liquor lignin may be obtained by digesting hardwood or coniferous wood or other lignocellulose-containing materials according to the soda or sulphate cellulose processes.  Sulphonation may be effected under acid, neutral or alkaline conditions, e.g. with alkali metal or ammonium sulphites or bisulphites.  Before or during sulphonation the lignin may be oxidized e.g. by passing air or oxygen through its solution, if desired in the presence of catalysts such as salts of iron, copper or cobalt.  Before or during sulphonation the lignin may be reacted with an aldehyde, a product containing -CH2SO3H groups then being produced when the aldehyde is formaldehyde.  The product may then be further sulphonated in the absence of aldehyde.  Previously sulphonated lignin may also be reacted with aldehydes.  The molecular weight of the products is about 1000 to 3000, being lower when sulphate liquor lignin is employed in the reaction.  Sulphate black liquor lignin contains combined sulphur mainly in the form of sulphide, thiol and disulphide groups, which in the oxidation step are converted to sulphonic acid groups.  In examples: (1) black liquor lignin is reacted in alkaline solution with sodium sulphite, and sulphate and sulphite ions are removed by dialysis; (2) black liquor lignin, sodium sulphite and formalin are heated together, the product is treated with a hydrogen-ion-saturated cation exchanger, and evaporated to dryness.  The product, which contains one sulphonic acid group to about 5 methoxyl groups is converted to its barium and calcium salts; (3) a procedure similar to (2) but with isolation of the product by salting out is followed; (4) black liquor lignin, sodium hydroxide, sodium sulphite and formalin are heated together. The product is purified by dialysis; (5) the lignin is heated in alkaline solution with sodium sulphite and sodium hydroxide.  After cooling, SO2 is passed through and the product reacted with formalin and isolated as in (1); (6) the product of (2) is reacted with sodium pyrosulphite; (7) sulphate process black liquor lignin in boiling alkaline solution is oxidized by passing oxygen through.  The product, containing sulphonic groups, is reacted with sodium sulphite and dialysed to remove sulphite ions; (8) sulphate black liquor lignin, sodium hydroxide, and sodium sulphite are heated in solution while passing air through the mixture.  The product is not precipitated by acetic acid.  The process is repeated in the absence of air to give a product which is precipitated by acetic acid; (9) the product of (1) is reacted with sodium sulphite and formalin; (10) the product of (2) is reacted with a formaldehyde-bisulphite addition product; (11) sulphate black liquor lignin is heated in alkaline solution while passing air through.  The product is heated with formaldehyde-bisulphite addition compound.  The products are useful in tanning leather and as emulsifying and dispersing agents, e.g. in printing inks and cutting and drilling oils, as levelling agents in dyeing, as fillers for caoutchouc, and as dispersing, hardening-promoting and strength-increasing additives for cement.