Patent GB-723318-A (GB)
Title: Improvements in rubber compositions
Inventor: BARNETT GEORGE
IPC: C08L61/06
Filed: 1951-06-14
Abstract: A vulcanizable rubber composition comprises natural rubber, e.g. smoked sheet or crepe rubber, or latex, a rubber vulcanizing agent and as a reinforcing agent 10 to 100 parts by weight based on 100 parts by weight of rubber of either (a) an inherently heat-hardenable monohydric phenol-amine-aldehyde resin for example formed from a monohydric phenol an aromatic or aliphatic amine and an aldehyde reacted together in the presence of an alkaline catalyst, or (b) a mixture of a monohydric phenol-amine-aldehyde resin (e.g. formed from a monohydric phenol, an amine and an aldehyde reacted together in the presence of an acid catalyst) which is not inherently heat-hardenable and a hardening agent such as hexamethylenetetramine.  When rubber latex is used the resin is incorporated therein as an aqueous dispersion and precipitated with the rubber as a coagulum.  In an example a monohydric phenol-amine-formaldehyde resin was prepared by adding 48 parts of aniline to a mixture of a 122 parts of xylenol and 90 parts of 37 per cent aqueous solution of formaldehyde cooling the mixture and keeping the temperature at 60 DEG  C., adjusting the pH to 1.6 by adding oxalic acid and refluxing the mixture for 45 minutes, evaporating off the water and steam distilling the product to give a brittle resin.  The resin was ground and blended with 10 per cent of its weight of hexamethylenetetramine and added to rubber by masticating 100 parts of smoked sheet rubber on a mill at 100 DEG C. and then feeding into the nip 50 parts of the ground mixture of resin and hexamethylenetetramine and continuing milling for 10 minutes with cutting after which the compound was sheeted off and milled on cooled rolls with vulcanizing agents, viz. 2 parts stearic acid, 5 parts zinc oxide, 1 part benzothiazyl disulphide and 3 parts sulphur, and with 1 part material sold under the Registered Trade Mark Irgalit Red as colouring agent.  The resulting composition was cured for 30 minutes at 140 DEG  C. under 1/2 ton-sq. in. pressure to give a hard reinforced resilient rubber of bright red colour. Specifications 572,232 and 633,438 are referred to.ALSO:A vulcanizable rubber composition comprises natural rubber e.g smoked sheet or crepe rubber, or latex, a rubber vulcanizing agent and as a reinforcing agent 10 to 100 parts by weight based on 100 parts by weight of rubber of either (a) an inherently heat hardenable monohydric phenolamine-aldehyde resin for example formed from a monohydric phenol, an aromatic or aliphatic amine and an aldehyde reacted together in the presence of an alkaline catalyst, or (b) a mixture of a monohydric phenol-amine-aldehyde resin (e.g. formed from a monohydric phenol, an amine and an aldehyde reacted together in the presence of an acid catalyst) which is not inherently heat-hardenable and a hardening agent such as hexamethylenetetramine.  When the rubber latex is used, the resin is incorporated therein as an aqueous dispersion and precipitated with the rubber as a coagulum.  In an Example, 100 parts of smoked sheet rubber were masticated on a mill at 100 DEG C. until it became banded and then 50 parts of a ground mixture of a monohydric phenol-amine-formaldehyde resin prepared from aniline, xylenol and formaldehyde, and 10 per cent. of hexamethylenetetramine was fed into the nip and milling was continued for 10 minutes with cutting after which the compound was sheeted off and milled on cooled rolls with vulcanizing agents, viz., 2 parts stearic acid, 5 parts zinc oxide, 1 part benzothiazyl disuphide and 3 parts sulphur, and with 1 part material sold under the R.T.M. "Irgalit" Red as colouring agent. The resulting composition was cured for 30 minutes at 140 DEG C. under half ton/sq. in pressure to give a hard reinforced resilient rubber of bright red colour. Specifications 572,232, [Group IV], and 633,438, [Group IV(a)], are referred to.