GB874452A - Preservation of natural rubber latex - Google Patents

Abstract

Increased preservation of natural rubber field latex, both at normal concentration and when mechanically concentrated by centrifuging, by electrodecantation, or by heating with agitation, is obtained by maintaining the free ammonia content of the latex at not less than 1,25% of the weight of the serum in the latex and adding thereto a compound which maintains the redox potential of the latex in an oxidative condition but has no appreciable deleterious action. Preferably, the compound is added in a proportion of 0,01%-0,25% by weight of the serum in the latex, to produce redox potentials of the rubber latex immediately after the addition of at least 125 mv. but not greater than 200 mv. Examples of compounds which can be used are the borates, iodates, bromates, dichromates and ferricyanides of the alkali metals and ammonium. According to an example, the ammonia content of a field latex was adjusted to 0,35% NH3 immediately on receipt and 0,02% of ammonium laurate was added to give increased stability to the latex. The latex was then divided into two halves, one of which was used as "control" and to the other 0,15% of boric acid was added as a solution in ammonium hydroxide. The two portions of latex were concentrated by centrifuging to a 60% dry rubber content and the ammonia content was adjusted to 0,55%. After subjecting both portions of latex to the conditions of bulk transport for 6 weeks the redox potential of the latex containing ammonium borate was + 138 mv., whereas that for the control was - 117 mv. In other examples, potassium dichromate and potassium periodate were employed instead of ammonium borate.