GB691608A - Improvements in compounding rubber - Google Patents

Abstract

Synthetic rubber, exemplified by butyl rubber and copolymers of butadiene with compounds such as styrene or acrylonitrile having a H2C=C< group copolymerizable with butadiene, including copolymers of butadiene and styrene which contain a high proportion of styrene, is mechanically worked at elevated temperature to form a hot plastic mass, wet lignin floc obtained by precipitation of lignin from a solution thereof is added, and the lignin is distributed in the rubber by continuing the working until the water has evaporated. Other compounding materials may be incorporated with the rubber simultaneously with the lignin floc; a wet coagulum of lignin floc containing occluded pulverulent compounding material, e.g. carbon black, for incorporation into the rubber may be made by forming a dispersion of the compounding material in aqueous alkali metal or ammonium lignate solution and precipitating the lignin from the solution.ALSO:Rubber is mechanically worked at elevated temperature to form a hot plastic mass, wet lignin floc obtained by precipitation of lignin from a solution thereof is added, and the lignin is distributed in the rubber by continuing the working until the water has evaporated. Other compounding materials may be incorporated with the rubber simultaneously with the lignin floc; a wet cougulum of lignin floc containing occluded pulverulent compounding material for incorporation into the rubber may be made by forming a dispersion of the compounding material in aqueous alkali metal or ammonium lignate solution and precipitating the lignin from the solution. The rubber may be natural rubber or a synthetic rubber, e.g. a copolymer of butadiene with styrene or with acrylonitrile, or butyl rubber. According to an example, lignin powder was dissolved in aqueous caustic soda, a lignin floc precipitated from this solution by adding acetic acid, and the floc concentrated by centrifuging, washed, and again concentrated to a 20 per cent. paste; 175 parts of this paste were incorporated into 100 parts of rubber which had been rendered hot and plastic by working on a roller mill, and working on the roller mill was continued, for about 1 hour, until the water had evaporated; sulphur, mercaptobenzothianzole, zinc oxide and stearic acid were then milled into the rubber-lignin mixture and the resulting compound was moulded and vulcanized