Abstract: A laminated protective packaging material particularly for use in making heat sealable envelopes comprises an outer paper substrate having a continuous, aqueous based heat sensitizable coating applied to one surface thereof. The outer paper substrate may consist of conventional coated or uncoated paper, bleached or unbleached kraft paper or any other similar material. The heat sensitizable coating may consist of an alkali-soluble ethylene-acrylic acid copolymer resin or other heat sensitizable ionic polymer resin with or without the addition of filler materials for increasing the viscosity of the coating and/or for improving the heat sealing characteristics of the coating. The heat sensitizable coating is particularly characterized by its ability to be heat sealed to itself and laminated to a foamed polymeric material having a cellular structure such as polyethylene foam.

Abstract: A method and apparatus is disclosed for the on-machine measurement of coat weights of coatings applied to paper webs or the like. The invention provides an accuracy of plus or minus 0.1 pound per ream of coating in the coat weight range of from about 0 to 5 pounds per ream. Higher coat weights can be measured by practicing the method of the present invention, however the accuracy of the measurements of higher coat weights is reduced with an upper limit in the range of from about 10 to 20 pounds per ream depending upon the coating formulation being applied. The invention permits separate coat weight measurements of a web coated both sides and is carried out by including a small amount of a fluorescing optical brightener in the coating applied. The level of fluorescence of the optical brightener is continuously measured under a UV light source and the readings obtained are converted to determine the coat weight applied.