Patent GB-768013-A (GB)
Title: Improvements in comminuted natural or synthetic rubber-containing compositions for use in building roads
IPC: C08L95/00
Filed: 1955-02-25
Abstract: Free-flowing comminuted particles of a thermoplastic composition, for incorporation in a bituminous binder used in road building, comprise 20 to 60 parts by weight of synthetic rubber, and 30 to 60 parts by weight of a bituminous material having a softening point from 200 DEG to 350 DEG  F., as measured by the ring and ball test.  The composition may contain 0.01 to 0.5 part of blowing agent, e.g. an alkali-metal bicarbonate alone or with 0.5 part acid such as stearic or benzoic, and/or may contain up to 50 parts powdered filler, e.g. talc, clay, whiting, mica, silica or alumina.  The bituminous material may be a naturally occurring asphalt or an asphaltite such as "Gibsonite" (Registered Trade Mark), or may be coal tar or coal tar pitch, water gas tar or pitch, or oil gas tar or pitch, or a mixture of an asphaltite with asphalt or such tar or pitch.  The synthetic rubber may be in the form of reclaim containing up to 50 per cent of non-rubber material.  The synthetic rubbers mentioned include polymerized chloro-2-butadiene-1,3, copolymers of a major proportion of butadiene and a minor proportion of styrene or acrylonitrile, and copolymers of 96 to 99.5 parts by weight of isobutylene and 4 to 0.5 parts of isoprene.  A binder for aggregate used in a road-making may be prepared by blending the pellets with a bituminous material heated to 250 DEG  to 400 DEG  F., in proportions such that the resulting binder contains 1 to 15 parts of natural or synthetic rubber per 100 parts of bituminous material.ALSO:Free-flowing comminuted particles of a thermoplastic composition, for incorporation in a bituminous binder used in road building, comprise 20 to 60 parts by weight of natural or synthetic rubber, and 30 to 60 parts by weight of a bituminous material having a softening point from 200 DEG  to 350 DEG F., as measured by the ring and ball test.  The composition may contain 0,01 to 0,5 part of blowing agent, e.g. an alkali-metal bicarbonate alone or with 0,5 part acid such as stearic or benzoic and/or may contain up to 50 parts powdered filler, e.g. talc, clay, whiting, mica, silica or alumina.  The bituminous material may be a naturally "occurring" asphalt or an asphaltite such as Gilsonite (Registered Trade Mark), or may be coal tar or coal tar pitch, water gas tar or pitch, or oil-gas tar or pitch, or a mixture of an asphaltite with asphalt or such tar or pitch.  The natural or synthetic rubber may be in the form of reclaim containing up to 50 per cent of non-rubber material. The synthetic rubbers mentioned include polymerized chloro-2-butadiene 1, 3, copolymers of a major proportion of butadiene and a minor proportion of styrene or acrylonitrile, and copolymers of 96 to 99,5 parts by weight of isobutylene and 4 to 0,5 parts of isoprene.  A binder for aggregate used in a road making may be prepared by blending the pellets with a bituminous material heated to 250 DEG  to 400 DEG F., in proportions such that the resulting binder contains 1 to 15 parts of natural or synthetic rubber per 100 parts of bituminous material.  In one of the several described examples 40 lbs. of an isobutylene-isoprene copolymer are mixed in a Banbury mixer with 40 lbs. of an asphaltite having a softening point of 270 DEG  to 310 DEG F., and 20 lbs. of asphalt of softening point 300 DEG F.  The batch is sheeted and formed into pellets in a dicing machine.  In one method of road making 15 lbs. of the pellets are added to 1880 lbs. of aggregate in a pug mill and within one minute are added 105 lbs. of asphalt of softening point 116 DEG F. heated to 300 DEG  to 325 DEG F., and the mix churned for less than one minute when it is ready for transport to the road making site. Alternatively the pellets may be sprayed on to rolled dry aggregate.