Patent GB-1116992-A (GB)
Title: Process and apparatus for coating and impregnating
Inventor: HNOT WALTER RUDOLPH
IPC: D21H17/60
Filed: 1965-12-13
Abstract: 1,116,992. Coating apparatus; coated fibreboard. ESSO RESEARCH & ENGINEERING CO. 13 Dec., 1965, No. 52842/65. Headings B2K and B2L. Apparatus for coating and impregnating articles comprises an elongated housing 12 including a bath 28, an endless conveyor 16 having a series of individual article holding means 24, guide means for causing the conveyor to pass from a lower run 17b to a downwardly inclined run 16a for submerging the articles in the bath of coating and impregnating material and thereafter passing the conveyor into an upper run 17a and finally again into the lower run 17b such that each article passing from the bath to the upper run is rotated through substantially 180‹ for drainage along the upper run and finally is again rotated through substantially 180‹ for drainage along the lower run, and means (fans 32 and heater 33) for applying heat to the articles during their passage through the upper and lower runs. In the arrangement shown fibreboards 1 are fed from platform 2 on to inlet conveyor 7 which feeds them through an opening 15 of an enclosure 12a. In the vicinity of opening 15 the conveyor is deflected by rollers 15a to separate adjacent holding means for the reception of the fibreboard therebetween. The conveyor consists of a pair of endless chains spaced apart and supporting the article holding means therebetween. Each article holding means is of open construction (Fig. 5, not shown) or is made of expanded metal material formed into tapered folds (Fig. 6, not shown). The conveyor transports the fibreboards through the bath 28 of, for example, molten wax and then through the heated chamber 12 firstly on the upper run of the conveyor and then on the lower run, suitable retaining devices being provided where necessary to prevent the fibreboards slipping out from between the holding means. The chamber 12 is heated by hot air circulated by fans 32 and heated by steam coils 33. The fibreboards are removed from chamber 12 by being allowed to drop through an outlet opening 40 in the enclosure 12a and guided by guide 41 on to a conveyor 42, where they are transported through a cooling zone 44. Cooling may be effected by a exhaust duct 45 continuously drawing in surrounding air and by water sprays 46. The boards are finally deposited at the unloading station 48. In one application corrugated fiberboards 60 in. x 48 in. x 0.5 in. are passed at the rate of 60 boards per minute through a bath of molten wax composition maintained at a temperature of 180‹ to 215‹F. The boards are subsequently drained and heat cured at an oven temperature of 250‹ to 270‹F and subsequently cooled. The retention time in the wax bath is about 15 sees and in the heat curing oven about 5 minutes. The wax composition may comprise (1) at least 60 wt.% e.g. 75 wt.% of crystalline refined, substantially oil-free paraffin wax having a melting point of about 120 to 160‹F., e.g. 130 to 155‹F. (2) up to 30 wt.% e.g. about 5 to 15 wt.% of a microcrystalline wax having a melting point above 160‹F., (3) up to 8 wt.% e.g. 1 to 4 wt.% of a polyolefin, e.g. polyethylene having a molecular weight in the range of 1500 to 25,000, and (4) about I to 25 wt.% e.g. 5 to 10 wt.% of a solid polymer resin having a softening point of at least 158‹F. e.g. 207 to 218‹F. and a molecular weight of about 1000 to 1200, said resin being selected from the group consisting of petroleum polymer resins and styrene polymer resins. Alternatively the wax composition may be as above but without the polyolefin e.g. at least 40 wt.% of the paraffin wax, up to 30 wt.% of the microcrystalline wax and about 10 to 30 wt.% of the solid petroleum polymer or styrene polymer resin.