Patent GB-804834-A (GB)
Title: Filled natural or synthetic rubber and other elastomers, plastics, paper, fabric and leather
IPC: C01B33/113
Filed: 1955-04-15
Abstract: Natural substances containing free or combined silica are treated in aqueous suspension at 150-280 DEG  C. under elevated pressure with an alkaline earth metal hydroxide whereby improved silicate products are obtained.  Preferred solid : liquid ratios in the suspension are from 1 : 6 to 1 : 10.  In a modification, the products may be after-treated with acids or acidic agents to form neutral or acid silicates, or silica.  Suitable natural substances which may be treated and used are sand, clay (bentonite), kaolin and loam.  The hydrothermal reaction may be carried out in the presence of neutral salts, e.g. sodium chloride, or with the assistance of turbulent motion produced e.g. by ultrasonic vibrations to effect a change in structure or reduction in grain size.  In examples, bentonite, sand or substantially pure silica are reacted in aqueous suspension at 200 DEG  C. and 18-19 atmospheres with calcium oxide, and in the case of the sand product in one example, extracted with dilute hydrochloric acid to remove 1/4 of the bonded lime. Specification 726,250 is referred to.ALSO:Natural rubber, synthetic rubber and other elastomers, and plastics may be filled with a silicate obtained by hydrothermal treatment of a silica-containing natural substance with an alkaline earth metal hydroxide, or filled with a silicate or silica thus obtained and subsequently reacted with an acid or acidic substance (see Group III).  The filler may be used in admixture with active or neutral fillers, e.g. bentonite or sand treated hydrothermally with lime may be used in admixture with pyrogenically prepared or precipitated silicon or with carbon black or alumina. Specified elastomers and plastics are butadiene polymers, butadiene copolymers with styrene or acrylonitrile, polyisobutylene, polyethylene, polyvinyl chloride or acetate, polystyrene, polyacrylic acid esters, silicone rubbers, fibre-forming polyamides and phenol, urea and ester resins.  When preparing the final polymer by reacting an initial polymer such as polymethacrylic acid ester with a suitable monomer and working up with a polymerization catalyst such as benzoyl peroxide or a Redox system, one of the components may have the filler added thereto before final polymerization.  For natural rubber vulcanisates, amines, dispersing agents and accelerators may be added.  In examples (1) and (4) stated proportions of smoked sheets, the filler of the invention (or in comparative examples a coated silicate or an active silica filler), stearic acid, pine wood tar or paraffin oil, phenyl-b -naphthylamine, zinc and possibly magnesium oxides, dibenzthiazyl disulphide and sulphur were vulcanized at 150 DEG  C.  In examples (2) and (3) copolymers of 60 per cent butadiene and 30 per cent styrene or of butadiene-acrylonitrile are mixed with the filler of the invention and with stearic acid, zinc oxide, pine wood tar or dibenzyl ether, dibenzthiazyl disulphide and sulphur and vulcanized at 151 DEG  C. and 4 at.  The latter products are compared with products filled with kaolin.  Specification 726,250, [Group III], is referred to.