GB461372A - Improvements in moulding pulp articles - Google Patents

Abstract

461,372. Moulding pulp. MOULDED PULP CORPORATION. Nov. 16, 1935, Nos. 31824, 31825, and 31826. Convention dates, Jan. 25, Feb. 11, and March 9. [Class 87 (ii)] Hollow articles are moulded from pulp by introducing a suspension of fibres into a foraminous mould under a pressure not substantially above atmospheric, introducing a second liquid while the pulp is in a loosely matted condition so as to flush the partially laid pulp to continue its deposition and smooth the inner surface, and subsequently introducing a gaseous medium to complete the deposition and compact the fibres into a rigid wall. Pulp in a container 10 is introduced into the mould 17 by gravity through a nozzle 25 at a super-pressure up to about 10 lbs. per sq. inch. A flushing liquid is then introduced from a tank 23 through the pipe 24 under a pressure of 10 to 30 lbs. per sq. inch supplied from an air compressor 45 through pipe 46. After the pulp fibres have been thus evenly deposited, a short blast of air is admitted under a pressure of 20 to 45 lbs. per sq. inch from the container 26 through the valve 30 to drive out the residual water. Air under higher pressure up to 65 lbs. per sq. inch is finally admitted from a container 40 through a pipe 42, the air being preferably heated to about 675‹ F. by a burner 39. The moulded article can then be removed by separating the mould after the pressure has been relieved by opening valve 43. The moulded articles can be dried by passing through a drier on an endless belt. In a modification, the first pulp suspension may contain relatively coarse fibres while the flushing liquid in the tank 23 may comprise a thinner suspension of finer fibres which form a smooth inner surface on the article. If an impervious inner wall is desired, the second suspension may comprise nitrocellulose fibres which are subsequently caused to coalesce by spraying or otherwise treating the interior of the moulded article with a suitable solvent such as acetone, methyl alcohol &c., with a plasticizer such as dibutyl phthalate. Another suitable suspension comprises a paraffin emulsion containing cornstarch, wax emulsion and aluminium sulphate. In this case the moulded articles are pressed between heated dies, Fig. 4, to melt the paraffin. Suspensions of lacquers, gums or resins may also be used.