| 摘要 |
A low titre desludged uncoagulated natural rubber latex is obtained by desludging and concentrating the latex to a solids content of at least 60%, and adding an alkaline material in a quantity insufficient to preserve the latex alone, and a preservative consisting of either or both of (1) a 2-thio-thiazyl compound of the formula <FORM:0836250/IV (a)/1> wherein R is hydrogen, C1-9 alkyl radicals, benzyl, hydrocarbon-substituted aryl radicals wherein the hydrocarbon substituents are straight-chain C1-9 aliphatic hydrocarbons, carboxyl, halogen, cycloaliphatic or arylene rings formed by the pair of R-radicals on the double-bond carbons joining together; R1 is hydrogen, an alkali or alkaline earth metal, an ester-forming organic radical, a thiocarbamyl radical or a radical conforming to the radical contained within the brackets; and at least one R is not hydrogen; and (2) a thiocarbamylthio compound of the formula <FORM:0836250/IV (a)/2> wherein R is hydrogen, C1-9 alkyl, benzyl, hydrocarbon-substituted aryl radicals wherein the hydrocarbon substituents are straightchain C1-9 aliphatic hydrocarbons, or cycloaliphatic rings formed by the pair of R's on the nitrogen atom joining together; and R1 is hydrogen, an alkali or alkaline earth metal, a thiocarbamyl radical, an ester-forming organic radical, or a radical conforming to the radical contained within the brackets. Specified alkaline materials are ammonia, sodium and potassium hydroxides and phosphates, mono-, di-, and tri-(methyl or ethyl)-amine, morpholine, piperidine, tetramethyl or tetraethyl ammonium p hydroxide. Sufficient alkaline material is added to maintain the pH between 8.5 and 10.5; under these conditions, the preservative is added in quantities of from 0.1 to 1% by weight based on the water content of the latex. Anionic and non-ionic surface-active agents may also be present.
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