Patent GB-1337345-A (GB)
Title: Producing capsule-coated sheets
IPC: B41M5/124
Filed: 1971-11-26
Abstract: 1337345 Pressure sensitive record sheets; coating apparatus FUJI PHOTO FILM CO Ltd 26 Nov 1971 [30 Nov 1970] 55104/71 Headings D1L and D2B [Also in Division B2] Capsule-coated sheets are produced by applying to a moving sheet support an excess of a coating composition containing microcapsules and having a solids content of 20-80 weight percent and a viscosity of 50-50,000 cp, and thereafter applying shearing force to the coated composition by contacting a solid member therewith to remove excess coating composition and to spread the composition uniformly over the support. The capsule-coated compositions may contain a water-soluble binder or a synthetic resin emulsion. In one embodiment as shown in Fig. 1, a pond-type blade coater comprises a rubber-coated backing roll 5 passing a support 6 to be coated, a coater consisting of a flexible blade 1 and a supporting frame 2 which holds a capsulecoating composition by forming a reservoir between blade 1 and backing roll 5, and a tap 4 for supplying the coating composition to a liquid reservoir 3 formed by the coater and the running support sheet 6. As shown in Fig. 2 the coating composition containing microcapsules is supplied under pressure to a coating tool 12 by a pump 18, whereby an excess of coating composition is extruded through a slit 13 with a coating tool 12 on to a running support sheet 6 passed by a rubber-coated backing roll 11. The coating composition applied to an excess coated zone 15 of the sheet 6 is metered by pressing a flexible blade 17 held by supporter 16 against the sheet 6. In another embodiment as shown in Fig. 3 a micro-capsule coating composition is introduced into liquid reservoir 21, a metering bar 24 is supported by supporter 25 is applied to the coated surface of support sheet 23, the metering bar 24 rotating in a direction reverse to that of the running direction of the support sheet 23. A roll 28 positioned at the back of the metering bar 24 serves to determine the convex angle between the support sheet and the metering bar 24. As shown in Fig. 4 in another type of metering bar coater, a microcapsule coating composition is introduced into liquid reservoir 32 through feed inlet 31 and removed via outlet 33. The composition is picked up by applicator roll 34 and by lowering a backing roll 35 a running support sheet 36 is made to contact the applicator roll 34 transferring an excess amount of coating composition on to the sheet. The excess coating composition is metered by metering bar 38 preferably rotating in the direction opposite to the running direction of the support sheet 36. The metering bar 38 is supported by a flexible blade holder 39 fixed transversely to the support sheet 36, the blade 39 being fixed to a holding frame 40. The pressure of the metering bar 38 on the composition coated on the sheet is changed by moving the frame 40. The Examples relate to the production of a pressure-sensitive, colour-forming copy sheet and perfume-incorporated capsule sheets. In a typical Example a composition comprising capsules consisting of gellatin and gum arabic formed around oil droplets having colourformer dissolved therein and formed by coacervation and an aqueous solution of sodium salt of carboxymethyl cellulose is applied to a base sheet using a fountain blade coater as shown in Fig. 2 to produce a pressure-sensitive colour-forming copy sheet. In another Example capsules having walls of polymerised tolylene diisocyanate and bis phenol A and containing a perfume are redispersed in an aqueous starch solution and coated on to a polyethylene film using a pond-type blade coater as shown in Fig. 1.