Abstract: A repulpable sheet of moisture resistant corrugated board having a first and second linerboard sheets with a fluted or corrugated sheet of corrugating medium therebetween. The corrugating medium is coated with a moisture resistant coating, which does not detract from the repulpability of the corrugated board, and first and/or second linerboard sheets may be coated with moisture resistant coatings, which do not detract from the repulpability of the corrugated board.

Abstract: A paper web impulse drying apparatus and method. A paper or paperboard web, typically of indefinite length, is treated after issuing from a Fourdrinier or other paper making apparatus by passing it through the nip of a pair of rolls, at least one of which is heated. The rolls both compress the web and raise it to a relatively high temperature. Such treatment enhances certain properties of the web. Web delamination due to flashing of superheated water, after the web leaves the nip, is prevented by both (a) a steam chamber on the exit side of the nip through which the web passes, and (b) heating the web prior to its entrance into the nip. This permits lower roll temperatures to be employed, thereby decreasing the magnitude of the sudden decrease in pressure experienced by the web as it exits from the roll nip. By preheating the sheet and passing it through the steam chamber, the temperature of the heated drying roll or rolls can be decreased to 120.degree.-150.degree. C.

Abstract: A method and apparatus for making an embossed or dimpled combined board is disclosed. The combined board has two outer or facing layers or webs of paperboard which sandwich an embossed or dimpled middle paperboard layer or web. The middle web is embossed by passing it over two apertured vacuum drums. Embossments extending in one direction are vacuum formed on one surface of the middle web by the first vacuum drum, while embossments extending in the opposite direction are formed on the other surface of the middle web by the second vacuum drum. The embossments, i.e., concave and convex impressions, are located in a generally chess board pattern. The vacuum openings or apertures of the second drum are larger (larger average diameter) than those of the first drum, to thereby compensate for diminishing flexibility of the middle web due to drying as it passes sequentially over the first and second vacuum drums.

Abstract: A method and apparatus for making an embossed or dimpled combined board is disclosed. The combined board has two outer or facing layers or webs of paperboard which sandwich an embossed or dimpled middle paperboard layer or web. The middle web is embossed by passing it over two apertured vacuum drums. Embossments extending in one direction are vacuum formed on one surface of the middle web by the first vacuum drum, while embossments extending in the opposite direction are formed on the other surface of the middle web by the second vacuum drum. The embossments, i.e., concave and convex impressions, are located in a generally chess board pattern. The vacuum openings or apertures of the second drum are larger (larger average diameter) than those of the first drum, to thereby compensate for diminishing flexibility of the middle web due to drying as it passes sequentially over the first and second vacuum drums.

Abstract: An apparatus for drying a web of roll material has two rows of comparatively low and high temperature cylinders, and a metal belt and a felt belt entrained in parallel for transporting the web on a serpentine path around the cylinders. The metal belt is pre-heated at an input side to each low temperature cylinder to a temperature from 140.degree. C. to 170.degree. C. An input press roll applies a nip pressure to the metal belt against the web, felt belt, and low temperature cylinder from 60 to 200 pli (pounds per linear inch). The surface of the low temperature cylinder is heated to an intermediate temperature from 100.degree. C. to 140.degree. C. The temperature of the heated belt at an input side is maintained only about 20.degree. C. higher than that of the low temperature cylinder. The low temperature cylinder has air pressure grooves for maintaining a negative air pressure in the range of 0.1 to 0.7 bar at its surface for lowering the vapor pressure for water evaporated from the web.