Patent GB-414932-A (GB)
Title: Improvements in aqueous dispersions of carbon black
IPC: C09D17/00
Filed: 1933-11-07
Abstract: Aqueous dispersions of carbon black are obtained by the use as dispersing agents of one or more aromatic compounds obtained by condensing sulphonic acids of aromatic hydrocarbons or their derivatives with formaldehyde or its equivalent.  These compounds may be expressed in the formula (A--R--A<1>) So2M in which A and A<1> are two aromatic groups, which may differ, joined to an aliphatic nucleus R, which may consist of a single alkyl group or a number of such groups in straight or branched chain formation, and So3M denotes at least one sulphonic acid group or salt thereof.  They may be synthesized by direct sulphonation of a compound of the requisite configuration or by reaction between an aromatic sulphonic acid and formaldehyde, preferably in the ratio of two mols to one mol.  The preferred dispersing agent is that obtained by condensing b -napthalene sulphonic acid with formaldehyde e.g. 100 parts each of napthalene and concentrated sulphuric acid are reacted at 160 DEG  C. for 4 hours after all the napthalene has been added to the acid.  The mixture is cooled to 100 DEG  C. and diluted with 44 parts of water. It is then further cooled to 80 DEG  C. and 12 parts of a 40 per cent aqueous formaldehyde solution added; it is stirred for 3 hours at 80 DEG  C., 12 parts more of formaldehyde solution being added at the end of each hour.  The temperature is then raised over 1 hour to 95--100 DEG  C. and maintained for 18 hours with constant stirring. The mixture thickens until it reaches the consistency of thick molasses; it is then cooled, neutralized with a suitable alkali and if desired, dried.  The viscous reaction mass may also be diluted with 3 times its volume of water and neutralized with lime, e.g. a paste or suspension of slaked lime.  The slurry is filtered hot to remove calcium sulphate and then treated with sodium carbonate to obtain the sodium salt.  The sulphonation is carried out in a cast iron vessel, but the subsequent condensation is preferably carried out in enamelled or lead-lined apparatus.  Other aromatic hydrocarbons e.g. benzene, diphenyl, anthracene, phenanthrene, fluorene &c. or their homologues or derivatives may be employed in the preceding reaction.  Products derived from the benzene series are less effective than those derived from polynuclear aromatic hydrocarbons, and alkylated compounds lead to dispersing agents which are more effective than the unsubstituted compounds, although they promote the formation of foam owing to a reduction of the surface tension of water.  The dispersions may be obtained by stirring the carbon black into a solution of the dispersing agent, either with simple agitation or preferably in a ball or colloid mill or by mixing the carbon black and dispersing agent in the dry state and stirring into water or an aqueous medium.  The amount of agent used varies from 2--8 per cent of the weight of the carbon black, depending on the particle size of the carbon black.  Dilute dispersions are preferably obtaining by dilution of concentrated dispersions, which may contain up to 50 per cent of carbon black.  The dispersions are not flocculated by acids or polyvalent metal ions, asbestos, heavy metal ions or electro-positive rubber dispersions and are suitable for use in paper making, and as additions to aqueous asbestos slurries, cements, mortars or rubber latex.ALSO:Aqueous dispersions of carbon black are obtained by the use as dispersing agents of one or more compounds obtained by condensing sulphonic acids of aromatic hydrocarbons or their derivatives with formaldehyde or its equivalent.  These compounds may be expressed by the formula (A-R-A<1>) SO3M in which A and A<1> are two aromatic groups, which may differ, joined to an aliphatic residue R, which may consist of a single alkyl group or a number of such groups in straight or branched chain formation, and SO3M denotes at least one sulphonic acid group or salt thereof.  They may be synthesized by direct sulphonation of a compound of the requisite configuration or by reaction between an aromatic sulphonic acid and formaldehyde, preferably in the ratio of two mols. to one mol.  The preferred dispersing agent is that obtained by condensing b -naphthalene sulphonic acid with formaldehyde.  Benzene, diphenyl, anthracene, phenanthrene and fluorene are also mentioned as aromatic components.