Low density paperboard articles

• US 6,846,529 B2
• Filed: 09/19/2003
• Issued: 01/25/2005
• Est. Priority Date: 01/26/2000
• Status: Expired due to Term

• Current Assignee: Graphic Packaging International Incorporated
• Original Assignee: International Paper Company
• Inventors: Mohan, Kosaraju Krishna, Froass, Peter Matthew, Reed, David Verd, Koukoulas, Alexander A.
• Primary Examiner(s): Pyon, Harold
• Assistant Examiner(s): BRUENJES, CHRISTOPHER P
• Application Number:
  US10/666,416
• Publication Number:
  US 20040052989A1
• Time in Patent Office: 494 Days
• Field of Search: 428/34.2, 428/141, 428/153, 428/327, 428/513, 428/537.5, 220/592.17, 220/592.2, 220/592.16, 220/62.12, 220/62.7, 220/62.22, 220/677, 220/62.2, 229/103.11, 162/134, 162/164.1
• US Class Current: 428/34.2
• CPC Class Codes: D21H 19/20 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: D21H 19/22 Polyalkenes, e.g. polystyrene
• CPC Class Codes: D21H 19/28 Polyesters
• CPC Class Codes: D21H 21/54 being spherical, e.g. microcapsules, beads
• CPC Class Codes: D21H 27/10 Packing paper packaging materials of special type or form B65D65/38
• CPC Class Codes: Y10T 428/1303 Paper containing [e.g., paperboard, cardboard, fiberboard, etc.]
• CPC Class Codes: Y10T 428/1348 Cellular material derived from plant or animal source [e.g., wood, cotton, wool, leather, etc.]
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24455 Paper
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/254 Polymeric or resinous material
• CPC Class Codes: Y10T 428/273 of coating
• CPC Class Codes: Y10T 428/277 Cellulosic substrate
• CPC Class Codes: Y10T 428/2985 Solid-walled microcapsule from synthetic polymer
• CPC Class Codes: Y10T 428/31902 Monoethylenically unsaturated
• CPC Class Codes: Y10T 428/31989 Of wood
• CPC Class Codes: Y10T 428/31993 Of paper

Abstract

The invention provides a low density paperboard material for use in producing an insulated container, and is especially well-suited for making cups. The paperboard material comprises a paperboard web including wood fibers and expanded microspheres, and has a relatively low density ranging from about 6 to about 10 lb/3MSF/mil, a relatively high caliper ranging from about 24 to about 35 mil, and an internal bond strength of at least about 80×10⁻³ ft-lb_f preferably at least 100×10⁻³ ft-lb_f. For applications such as cups the material is also coated on one or both sides with a barrier coating, preferably low density polyethylene, to limit liquid penetration into the web. The low density paperboard material of the invention is convertible for manufacture of containers, particularly cups, and the surface of the low density board may have a Sheffield smoothness of 300 SU or greater.

Claims

1. An assembled paper container which comprises a sidewall and a bottom sealably joined together wherein the sidewall is provided by a paperboard material which comprises a paperboard web including wood fiber and from about 5 to about 10 wt. % dry basis expanded synthetic polymer microspheres based on the total weight of the web dispersed within the fibers, an apparent density of from about 6.0 to about 10 lb/3MSF/mil, a caliper of from about 24 to about 35 mil, an average internal bond of at least about 80×

10<sup>−

3</sup> ft-lbf, a Sheffield smoothness of about 300 SU or greater, and a barrier coating having a thickness of from about 0.5 to about 3.5 mil disposed adjacent at least one surface of the web.

2. An assembled paper cup which comprises a sidewall and a bottom sealably joined together wherein the sidewall is provided by a paperboard material which comprises a paperboard web including wood fiber and from about 5 to about 10 wt. % dry basis expanded synthetic polymer microspheres based on the total weight of the web dispersed within the fibers, an apparent density of from about 6.0 to about 10 lb/3MSF/mil, a caliper of from about 24 to about 35 mil, an average internal bond of at least about 80×

10<sup>−

3</sup> ft-lbf, a Sheffield smoothness of about 300 SU or greater, and a barrier coating having a thickness of from about 0.5 to about 3.5 mil disposed adjacent at least one surface of the web.