Low density paperboard articles
First Claim
1. A method for making a paperboard material comprisingproviding a papermaking furnish containing cellulosic fibers and from about 0.25 to about 10% by weight dry basis expandable microspheres;
- forming a paperboard web from the papermaking furnish;
drying the web;
calendaring the web to a caliper of from about 24 to about 35 mils and an apparent density ranging from about 6.0 to about 10 lb/3 MSF/mil; and
applying from about 0.5 to about 3.5 mil of a barrier coating on at least one of the surfaces of the calendered web, wherein the paperboard material has an average internal bond of at least about 80×
10−
3 ft-lbf and a Sheffield smoothness of at least about 300 SU.
4 Assignments
0 Petitions
Accused Products
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/3 MSF/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.
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Citations
12 Claims
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1. A method for making a paperboard material comprising
providing a papermaking furnish containing cellulosic fibers and from about 0.25 to about 10% by weight dry basis expandable microspheres; -
forming a paperboard web from the papermaking furnish; drying the web; calendaring the web to a caliper of from about 24 to about 35 mils and an apparent density ranging from about 6.0 to about 10 lb/3 MSF/mil; and applying from about 0.5 to about 3.5 mil of a barrier coating on at least one of the surfaces of the calendered web, wherein the paperboard material has an average internal bond of at least about 80×
10−
3 ft-lbf and a Sheffield smoothness of at least about 300 SU. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification