Patent GB-1061275-A (GB)
Title: Heat-sealable paperboard containers and method for their production
IPC: B65D5/56
Filed: 1964-03-23
Abstract: Wax coating compositions comprise 5 to 20% by weight of a copolymer of ethylene and vinyl acetate, methyl, ethyl acrylate having an acetate or acrylate content between 20 and 30% by weight of the copolymer, 10 to 20% of microcrystalline paraffin wax having a melting point between 160 DEG  and 180 DEG  F., 1 to 5% high pressure, low density polyethylene having a molecular weight between 1500 and 7000, and 55 to 85% by weight of an intermediate fraction of paraffin wax, the major portion thereof consisting of normal paraffin hydrocarbons, e.g. 60 to 75% by weight, and the remaining portion consisting of branched chain, monopolycyclic saturated (paraffin) and unsaturated (aromatic) hydrocarbons.  A preferred paraffin wax is one which contains 66% normal paraffin hydrocarbons, 20% branched chain paraffin hydrocarbons, 10% monocyclic and 3% polycyclic saturated hydrocarbons and 1% aromatic hydrocarbons.  The preferred ethylene-vinyl acetate copolymer contains between 27 and 29% vinyl acetate.ALSO:Wax coating compositions comprise 5 to 20% by weight of a copolymer of ethylene and vinyl acetate, methyl, ethyl acrylate having an acetate or acrylate content between 20 and 30% by weight of the copolymer, 10 to 20% of microcrystalline paraffin wax having a melting point between 160 DEG  and 180 DEG  F., 1 to 5% high pressure, low density polyethylene having a molecular weight between 1500 and 7000, and 55 to 85% by weight of an intermediate fraction of paraffin wax, the major portion thereof consisting of normal paraffin hydrocarbons, e.g. 60 to 75% by weight and the remaining portion consisting of branched chain, monopolycyclic saturated (paraffin) and unsaturated (aromatic) hydrocarbons.  A preferred paraffin wax is one which contains 66% normal paraffin hydrocarbons, 20% branched chain paraffin hydrocarbons and 1% aromatic hydrocarbons.  The preferred ethylene-vinyl acetate copolymer contains between 27 and 29% vinyl acetate.ALSO:A paperboard container blank adapted to be heat-sealed along at least one overlapping portion has on the outer surface a smooth coating of a wax-containing, moisture barrier and heat-sealing coating composition, and on the inner surface at least in the sealing area or areas thereof a continuous coating of the said composition with small, outwardly projecting, randomly distributed protuberances. The coating on the inner surface may be in the form of a pattern (Fig. 4 not shown).  The outer coated surface may be glossy, and the protuberances of the inner coated surface may have varied cross section, may be closely adjacent to and occasionally merged with each other and have a height between 0.00116 and 0.00508 centimeter above the base surface of the coating.  The coated inner surface may contain a plurality of score lines projecting outwardly from the inner surface in any form e.g. as arcuate, intersecting or randomly disposed lines. The scoring is accomplished before the coating is applied.  The coating composition may be applied in liquid form and whilst the coatings are still in flowable condition the coated blank may be passed through a nip formed between a doctor blade and the surface of a rotating pile fabric-covered roll, and cooled at a rate to congeal the coatings on both surfaces in the forms imparted thereto.  The wax coating compositions may comprise 5 to 20% by weight of a copolymer of ethylene and vinyl acetate, methyl, ethyl acrylate having an acetate or acrylate content between 20 and 30% by weight of the copolymer, 10 to 20% of microcrystalline paraffin wax having a melting point between 160 and 180 DEG F, 1 to 5% high pressure, low density polyethylene having a molecular weight between 1500 and 7000, and 55 to 85% by weight of an intermediate fraction of paraffin wax, the major portion thereof consisting of normal paraffin hydrocarbons e.g. 60 to 75% by weight and the remaining portion consisting of branched chain, monopolycyclic saturated (paraffin) and unsaturated (aromatic) hydrocarbons.  A preferred paraffin wax is one which contains 66% normal paraffin hydrocarbons, 20% branched chain paraffin hydrocarbons, 10% monocyclic and 3% polycyclic saturated hydrocarbons and 1% aromatic hydrocarbons.  The preferred ethylene-vinyl acetate copolymer contains between 27 and 29% vinyl acetate.  In Fig. 5 (not shown), a butter or oleo-margarine container blank has an end flap 17 scored to present raised lines 18 on the coated inner surface along with corresponding depressions 18a in the outer surface, the protuberances occuring randomly over the flap both on the raised portions 18 and in the spaces between them.