Patent GB-1053129-A (GB)
IPC: C07C9/14
Filed: 1964-08-17
Abstract: 1,053,129. Coated paper. LAMSON PARAGON Ltd. Aug. 17, 1964 [Sept. 17, 1963], No. 33554/64. Heading B2E. [Also in Divisions D1 and D2] Tissue paper having pin holes therein is prepared for the reception of a carbon ink coating by applying a composition including at least one resin and a volatile solvent to one surface of a continuously moving web of the tissue paper, filling the pin holes and simultaneously substantially removing any excess of the composition from the web surface by passing this surface across the sharp edge of a blade, and drying the web, whereby the pin holes are filled with the resin. The pin hole filling composition may include a thermoplastic resin, a plasticizer and a volatile solvent. Polyvinyl acetate dissolved in methyl alcohol is specified. A preferred composition comprises a mixture of resins extracted from pine wood resin, 0.1 to 1.5 per cent by weight of oleic acid as plasticizer and 30 to 50 per cent by weight of methyl alcohol as volatile solvent. The composition may have a viscosity of between 40 and 50 centipoises at 24C. The tissue web 2, Fig. 1, passes from a supply roll 1 over a guide roll 3, between nip rolls 4 and to an extruder 5 which coats the web with the filler composition. The web 2 then passes over a blade 6 to force the composition into the pin holes and the interstices between the fibres and scrapes off excess solution which drops into a trough 7 and flows into a storage tank 8 in which it is filtered. Additional solvent may be added in the tank 8 to replace that which has been evaporated during, the treating operation, a viscosity regulator may be provided in the tank 8. A pump P pumps the composition to the extruder 5. The blade 6 is inclined at an angle of approximately 75-110 degrees with respect to the advancing web 2, this angle being adjustable and dependent on the size and number of pin holes of the tissue paper so that the composition does not spray through the pores thereof. Preferably, the web 2 approaches the blade 6 at an upward angle of between 10 and 20 degrees, preferably 16 degrees, to the horizontal. The tension of the web 2 during filling and scraping is preferably between 1¢ and 2¢ lbs. per linear inch. The web 2 passes into a dryer 9 in which it floats between air jets heated to 200-300F. impinging on the top and bottom surfaces thereof. The web 2 is then smoothed by a rotating bowed roll 10 to remove wrinkles, passes around a tension indicator roll 11, then around a chill cylinder 12 against which it is held by a nip roll 13, over guide rolls 14, under a dance roll 15 and over a guide roll 16 to be rewound on to a roll 17, the roll 15 controlling the web tension in the rewound roll. The extruder 5 comprises a container 20, Fig. 2 closed by plates 22 the thickness of each of which increases towards the centre. An extrusion slot 23 is left between the plates 22 and rectangular bars 24 are slidable in each end thereof to regulate the effective length of the slot. A pipe 25 communicates with the pump P. After drying, the treated web is coated with carbon ink applied in a molten state, usually about 170F., and spread evenly thereon by a blade or roller and allowed to cool. The ink comprises one or more natural or synthetic waxes and ink oil coloured with a pigment or dye, e.g. carbon black or methyl violet.