Patent GB-787347-A (GB)
Title: Synthetic tanning agents
IPC: C14C3/20
Filed: 1955-01-26
Abstract: Solid water-soluble kneadable tanning resins are prepared by mixing sulphite waste liquor which has been treated with caustic alkali, with condensation products of aromatic sulphonic acids with aromatic hydroxy compounds and aldehydes, or condensation products of aromatic compounds containing sulphomethyl groups with aromatic hydroxy compounds and aldehydes, or incompletely sulphonated or sulphomethylated condensation products of aromatic hydroxy compounds with aldehydes, and thereafter precipitating the water-soluble resin by means of a mineral acid or an alkali metal or ammonium salt thereof.  According to examples: (1) beta-naphthol was sulphonated with sulphuric acid monohydrate at 115 DEG  C. and the product stirred with phenol, cresol and water. The mixture was subsequently condensed with formaldehyde and to the condensation mixture, there was added sulphite waste liquor which had previously been boiled with caustic soda, together with a minor amount of a moist resin obtained by boiling cresol with formaldehyde in dilute sulphuric acid and drawing off the supernatant acid.  The mixture of condensation product, alkali-pretreated sulphite waste liquor and cresol-formaldehyde resin was adjusted to pH 3.1 with sulphuric acid and the tanning resin recovered by the addition of ammonium sulphate and common salt.  (2) Dihydroxy-diphenylsulphone was homogenized with naphthalene which had been sulphonated with sulphuric acid and the mixture condensed with 30 per cent formaldehyde at 105 DEG  C.  To the condensation mixture were added sulphite was liquor which had been treated with caustic soda, and a minor amount of a moist phenol formaldehyde resin.  The pH was adjusted to 3.5 with aqueous ammonia and the tanning resin salted-out with ammonium sulphate and common salt.  (3) Naphthalene was sulphonated with sulphuric acid monohydrate and the sulphonated mixture was condensed with formaldehyde at 105 DEG  C., the condensation mixture was thereafter diluted with water and after the addition of crude pyrocatechol, was further condensed with formaldehyde.  Caustic soda treated sulphite waste liquor was then added and the tanning resin precipitated with ammonium sulphate and common salt.  (4) Naphthalene was sulphonated with sulphuric acid and mixed with ortho-chlorophenol and formaldehyde.  Sulphite waste liquor pretreated with caustic soda was added to the mixed condensation product and the mixture rendered acid by concentrated hydrochloric acid; the tanning resin was precipitated with ammonium sulphate. (5) A mixture of naphthalene and a minor portion of beta naphthol was sulphonated at below 120 DEG  C. with sulphuric acid and the mixture after diluting with water was condensed with formaldehyde at 100 DEG  C.  Separately from this mixture, a mixture of phenol and cresol was condensed with formaldehyde in the presence of sodium sulphite at 100 DEG  C.  The two condensation products were thereafter mixed at 75 DEG  C. and the mixture stirred with caustic soda pre-treated sulphite waste liquor, and the tanning resin precipitated by the addition of a saturated solution of ammonium sulphate and common salt.  (6) Into the mixture of the condensation product of naphthalene sulphonic acid and the condensation product of phenol-cresol and sodium sulphite of Example (5) above, there was introduced the reaction product of resorcinol and an aldol-acetaldehyde mixture and formic acid.  To the mixture caustic soda pre-treated sulphite waste liquor was added and the product finally salted-out with saturated ammonium sulphate solution and common salt.  The invention is stated to be applicable to other aryl sulphonic acids, for example substituted naphthalene sulphonic acids, benzene sulphonic acid, anthracene sulphonic acids, phenanthracene sulphonic acids or substitution products thereof as well as sulphomethyl compounds of the same type.  As aromatic hydroxy compounds there may be used mono-, di- or tri-hydroxy benzenes or naphthalenes which may be further substituted by alkyl, halogen or sulpho groups.  Sulphonated compounds of the Novolac type may be employed as partially sulphonated condensation products. Specifications 467,998 and 496,898 are referred to.