Low density paperboard articles

• US 7,682,486 B2
• Filed: 09/27/2007
• Issued: 03/23/2010
• Est. Priority Date: 01/26/2000
• Status: Expired due to Fees

• Current Assignee: Graphic Packaging International Incorporated
• Original Assignee: International Paper Company
• Inventors: Mohan, Kosaraju Krishna, Froass, Peter Matthew, Koukoulas, Alexander A, Reed, David Verd
• Primary Examiner(s): FORTUNA, JOSE A
• Application Number:
  US11/904,609
• Publication Number:
  US 20080171186A1
• Time in Patent Office: 908 Days
• Field of Search: 162/100, 162134-137, 162/123, 162/125, 162/127, 162129-130, 162/158, 162/164.1, 162/168.1, 162/141, 162/169, 162204-206, 428340-342, 428/34.2, 428/323, 428/195.1, 428/172, 428/332, 428/402, 428/402.21
• US Class Current: 162/158
• 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 and associated method 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-lbf., preferably at least 100×10⁻³ lft-lbf. 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 exhibits insulative properties comparable to higher cost materials conventionally used to make cups. Also, the surface of the low density board may have a Sheffield smoothness of 300 SU or greater compared with the surface smoothness of 160 to 200 SU for conventional cupstock, the latter having been thought necessary for adequate print quality. However, it has been found that the low density board exhibits good printability on flexo printing machines despite its relatively rough surface, which is surprising and bonus effect realized along with the insulative and other properties of the board.

Claims

1. A paperboard material, comprising a paperboard web comprising wood fibers and expanded microspheres dispersed within the fibers;

the web having an apparent density of from about 6.0 to about 10 lb/3MSF/mil, a caliper of from 24 to about 35 mil, an average internal bond of at least about 80×

10<sup>−

3</sup> ft-lbf, and a Sheffield smoothness of at least about 300 SU.

2. The paperboard material according to claim 1, wherein the density of the web is at least about 6.5 lb/3MSF/mil and the caliper of the web is at least about 28 mil.

3. The paperboard material according to claim 1, wherein the average internal bond of the web is at least about 100×

10<sup>−

3</sup> ft-lbf.

4. The paperboard material according to claim 1, wherein the average internal bond of the web is at least about 100×

10<sup>−

3</sup> ft-lbf.

5. The paperboard material according to claim 1, comprising a barrier coating on at least one surface of the web.

6. The paperboard material according to claim 5, wherein the barrier coating is present all surfaces of the web.

7. The paperboard material according to claim 6, wherein the barrier coating has an average thickness of from about 0.5 to about 3.5 mil.

8. The paperboard material according to claim 5, wherein the barrier coating has an average thickness of from about 0.5 to about 3.5 mil.

9. The paperboard material according to claim 5, wherein the barrier coating comprises at least one member selected from the group consisting of polyethylene, EVOH, and polyethylene terephthalate.

10. The paperboard material according to claim 9, wherein the barrier coating has an average thickness of from about 0.5 to about 3.5 mil.

11. The paperboard material according to claim 5, wherein the barrier coating comprises a low density polyethylene.

12. The paperboard material according to claim 11, wherein the barrier coating has an average thickness of from about 1 to about 3 mil.

13. The paperboard material according to claim 5, wherein the barrier coating has an average thickness of from about 1 to about 3 mil.

14. The paperboard material according to claim 1, wherein the material contains printing directly on at least one surface thereof.

15. The paperboard material according to claim 1, wherein the web has a PPS10 smoothness of about 6.5 microns or less.

16. The paperboard material according to claim 1, wherein the cellulosic fibers in the web comprise from about 20 to about 40% by weight dry basis softwood fibers and from about 60 to about 80% by weight dry basis hardwood fibers.

17. The paperboard material according to claim 1, wherein the expanded microspheres in the web comprise synthetic polymeric microspheres.

18. The paperboard material according to claim 1, wherein the expanded microspheres comprises from about 0.25 to about 10 wt. % of the total weight of the web on a dry basis.

19. The paperboard material according to claim 1, wherein the expanded microspheres comprises from about 5 to about 7 wt. % of the total weight of the web.

20. The paperboard material according to claim 1, wherein the expanded microspheres comprises from about 0.25 to about 5 wt. % of the total weight of the web.