Patent GB-945398-A (GB)
Title: Heat sealable label, label roll and method of manufacture
Inventor: SMITH JAMES EDWARD
IPC: B65D65/38
Filed: 1961-05-15
Abstract: 945,398. Laminates. CROWN ZELLERBACH CORPORATION. May 15, 1961, No. 17556/61. Heading B5N. [Also in Divisions B2, B8 and D1] A label roll of a continuous flexible sheet having adjacent sections adapted to be cut into individual labels, has a heat sealable, flexible, solid thermoplastic coating on one surface thereof, the coating being in the form of discrete projections providing small irregularities in the order of several thousandths of an inch in height presenting reduced area of sealing contact whereby to obviate blocking in the roll as the sheet is unwound. The sheet sections may be separated by transversely extending areas on the coated surface which are also free of the coating to enable the sheet to be cut through such areas by cutting means. The coating may consist essentially of a homogeneous blend of at least 50% by weight polyethylene and the remainder additive material imparting to the coating a decrease in melting- point and viscosity, and increase in tackiness at about its melting-point compared to such properties of the polyethylene alone. The polyethylene may have a melting-point of 200‹ to 220‹ F., a molecular weight of 1500 to 14,000, a density of 0.905 to 0.930 and a viscosity at 300‹ F. of 600 to 7000 c.p.s. The additive may be polyterpenes, rosin and rosin derivatives such as the glycerol esters of hydrogenated rosin, polyamides, hydrocarbon and methylated hydrocarbon resins, poly-α-methyl styrene, polybutenes, rubber, paraffin, microcrystalline and synthetic waxes, hydrogenated fats and oils, fatty acid amides and the triglyceryl esters of fatty acids. The flexible base sheet may be porous or pervious and may be cellulosic, e.g. paper. The coating may be maintained in a hot molten state and applied from such state in the form of discrete projections providing said irregularities. A knurled rotogravure applictor roll may be employed to apply the coating to the sheet. A relatively wide roll of coated sheet is first formed and a plurality of relatively narrow individual label rolls cut therefrom. As shown, base sheet 2 is coated by passage between knurled applicator coating roll 7 and back-up roll 6 having transversely spaced sections 8 of resilient material, e.g. rubber, to produce bands of tooth like discrete solid projections 21 and valleys 23 therebetween. Shaped apertures 12 may be punched out of the coated sheet which is sliced along lines 13 to produce a plurality of narrower width tapes from which the individual labels having notched corners may be produced by cutting along lines 14a. Uncoated strips 24 provide pull tabs for facilitating removal of the label. The base sheet 2 with projections 38 may be laminated by heat and pressure to paper 36 having wax coatings 37, 38, the projections penetrating through coating 38 to adhere to the paper. The labels may be sealed to materials such as wax coated and uncoated paper, lacquer coated and uncoated regenerated cellulose, polyolefins, e.g. polyethylene, and metal foil, e.g. aluminm foil, which may take the form of a packagng, e.g. a bread wrapper.