Patent GB-1224474-A (GB)
Title: Elastomer-faced rollers
Inventor: CARPENTER ROBERT STANLEY
IPC: B29C70/68
Filed: 1967-07-13
Abstract: 1,224,474. Moulding printing rollers. COURTAULDS Ltd. 12 July, 1968 [13 July, 1967], No. 32228/67. Heading B5A. [Also in Divisions B6 and F2] An elastomeric faced roller, e.g. for printing, is moulded by the simultaneous centrifugal casting and polymerization of a resin within a casting cylinder lined with the elastomeric facing and rotated about its horizontal axis. In examples wherein the casting cylinder comprises a copper cylinder chromium-placted on the interior surface thereof and provided with endplates, through one whereof the resin is introduced ; (1) the casting cylinder was coated with silicone grease and lined with a release paper coated with an inwardly facing layer of polyvinyl chloride, a sheet of vulcanized natural rubber was located thereagainst and an epoxy resin composition centrifugally cast therein; (2) an epoxy resin cylinder liner was centrifugally cast into the casting cylinder and a similar sheet of rubber was then located therein against similar release means, an unfilled epoxy resin composition was then centrifugally cast within the rubber followed by a further epoxy resin composition filled with silica powder, aluminium end pieces were then sealed to the inner casting, by epoxy resin, and a steel shaft located thereto, and a flexographic printing roller was produced by adhering to the outer rubber layer, by epoxy resin, the acid-treated surfaces of a number of rubber stereos produced by vulcanizing rubber under pressure against an inverse relief image of the flexographic design; (3) the casting cylinder was coated with fluorinated hydrocarbon release agent and a transparent epoxy resin cylinder liner centrifugally cast therein, a relief image of a required design was applied to the external chromiumplated surface of a mandrel by dissolving away therefrom photographically unexposed parts of a gelatine layer applied thereto and which had been ammonium bichromate sensitized and photographically exposed through a negative transparency of the required design and a crossline screen, reinforced rubber sheet and an outer fabric sheet and an outer fabric layer were wound around the mandrel and, after autoclave vulcanizing, the rubber sleeve was peeled from the mandrel with an indented design on the outer surface, then located against design registration marks within the liner and successive layers of epoxy resin, unfilled and filled with silica powder, centrifugally cast therein to produce a gravure printing roller; (4) a gelatine relief image was similarly applied to a formaldehyde-hardened gelatine coated surface of a polyethylene terephthalate film against which was heat and pressure moulded a sheet of butadiene acrylonitrile, phthalic acid ester plasticized copolymer, the sheet bearing the indented image was located against a cellulose acetate casting cylinder liner of larger area, and coated with formaldehyde-hardened gelatine, unfilled and silica powder filled epoxy resin compositions were then sequentially centrifugally cast within the butadiene-acrylonitrile outer facing to produce a gravure printing roller with a surface partly formed of the unfilled epoxy resin. The elastomeric facing layer of the roller may also comprise a thermoplastic elastomer extruded tube, or a rubber tube cast on to a mandrel. The layer may also be vulcanized or moulded within the casting cylinder from a preformed sheet by centrifugal or by inflated bag moulding. The layer may alternatively be centrifugally cast within the casting cylinder from a solution, which may contain vulcanizing agents, or an aqueous suspension which may comprise vulcanized latex; the casting cylinder may be heated to effect vulcanization and a current of air passed into the cylinder to facilitate removal of solvent or water. The elastomeric facing may also comprise layers of different hardnesses laminated prior to or during the casting process, and the interior layer may comprise foam rubber. Adhesion between the elastomeric facing and the resin may be facilitated by adhesives, e.g. epoxy resin. The transparent cylinder liner may also be polyester resin, and the use thereof bearing design registering marks facilitates the moulding of a set of rollers for multi-colour printing. A transparent cellulose acetate or polyethylene terephthalate film bearing registration marks may alternatively be employed within a transparent liner. The facing elastomeric layer may also comprise polyurethane elastomers.