Stock material or miscellaneous articles – Hollow or container type article – Paper containing
Reexamination Certificate
1998-02-04
2004-05-25
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Paper containing
C229S005810, C229S005840, C428S511000, C428S514000
Reexamination Certificate
active
06740373
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates generally to processes for forming paperboard products and to the products formed by such processes. More particularly, this invention relates to a method of making disposable paperboard containers with textured coatings and to the texture-coated containers formed by that method. This invention also relates to coatings having superior bulk and insulation properties.
This invention relates to paperboards on which are printed insulating and/or textured coatings having a high coefficient of friction. The static coefficient friction of the paperbound has values of about 0.2 to 2.0 and above, preferably 0.3 to 1.0 and the kinetic coefficient of friction is about 0.22 to 2 suitably 2 to 1.5 and preferably 0.22 to 0.85. These values are shown in
FIGS. 9A and 9B
and are up to five times greater than the corresponding coefficient of friction values of conventional paper plates, plastic plates and foamed plates. The printing of the coating is an efficient, precise process and allows that only at least ten percent of the container surface has to be coated to achieve the beneficial insulation and handling properties. These containers are particularly suitable for use as hot drink containers since only a small portion of the outer surface of the container has to be printed. Competing foamed polyolefin insulated coating cannot be printed on the surface of the paperboard and consequently the whole side of the paperboard has to be coated. Thus, the coated containers of this invention having superior insulation and bulk properties, have greater inherent cost advantages over the prior art foamed polyolefin extrusion coated containers. Furthermore, registered texture coated containers exhibit excellent printing clarity and accuracy which cannot be obtained when coatings are prepared from foamed polyolefins.
BACKGROUND
Disposable paper containers, such as plates, trays, bowls, airline meal containers and cafeteria containers, are commonly produced by pressing flat paperboard blanks into the desired shape between appropriately shaped and heated forming dies. Various protective coatings are typically applied to the blanks before forming to make the resulting paperboard containers moisture-resistant, grease-resistant, more readily printable, etc. Often, printing is also applied to the top surface for decoration. A large number of paper products are produced by this method every year. These products come in many different shapes and sizes, including round, rectangular and polygonal. Many such containers, including for example airline meal containers, have a number of independent compartments separated by upstanding ridges formed in the inner areas of the containers.
When a container is made by pressing a flat paperboard blank, the blank must contain enough moisture to make the cellulosic fibers in the blank sufficiently plastic to permit it to be formed into the desired three-dimensional container shape. During the pressing operation, most of this moisture escapes from the uncoated bottom surface of the blank as water vapor. Suitable methods of producing paperboard containers from moistened paperboard blanks are generally described in U.S. Pat. Nos. 4,721,499 and 4,721,500, among others.
Many people prefer disposable containers which, when handled, produce a sense of bulkiness and grippability at least suggestive of the more substantial non-disposable containers which they replace. While a sense of bulkiness may be provided to some extent in styrofoam and thick pulp-molded containers, such containers suffer a number of drawbacks. For example, unlike pressed paperboard containers, styrofoam containers are often brittle and they are environmentally unfriendly because they are not biodegradable. Also, styrofoam containers are not cut-resistant and it is difficult to apply printing to the surface of styrofoam containers. Additionally, because of their bulkiness, styrofoam containers take up large amounts of shelf space and are costly to ship. Pulp-molded containers similarly are not cut-resistant and have poor printability characteristics. Additionally, pulp-molded containers typically have weak bottoms. Pressed paperboard containers, however, are cut-resistant, readily printable, strong in all areas, and are far less bulky than styrofoam or pulp-molded containers.
The present invention thus is an improvement in pressed paperboard containers. In the present invention, environmentally friendly disposable paperboard containers are formed. By printing the insulating textured coating on at least ten percent of one surface of the paperboard, the insulating and/or textured containers were formed which give users handling them a sense of bulkiness and grippability. These new containers rely on efficient processes of press-forming paperboard blanks. The resulting product, which consists primarily of cellulosic material, is nearly entirely biodegradable. Additionally, it will withstand normal microwave conditions without any significant change in caliper, it has substantially better thermal resistance when compared to prior disposable paperboard containers made without such an insulating and/or textured coating, and it tends to stay put when resting on a smooth surface due to the coefficient of friction of the textured coating. It should be noted that prior art polyolefin foamed coatings cannot be pattern applied and therefore have to cover the whole side of the board.
The data shown in
FIGS. 9A and 9B
deomonstrates that conventioinal paper plates have a coefficient of kinetic friction of about 0.18, plastic plates have a coefficient of kinetic friction of about 0.2 and foam plates have a kinetic coefficient of friction of slightly under 0.2. The coefficient of kinetic friction of the textured plates of this invention have values of about 0.61 to 1.4 up to 2.0 and more. Thus, the coefficient of kinetic friction of our texturized plates of this invention are about three to four times greater than for our conventional paper plates. Suitable coefficient of kinetic friction for our texturized containers is about 0.22 to about 1.5 advantageously 0.4 to 0.8 preferrably 0.5 to 7.
The data shown in
FIGS. 9A and 9B
deomonstrate that conventional paper plates have a static coefficient of friction of 0.19, for plastic plates it is the same and for foam plates the static coefficient of friction is 0.2. The static coefficient of friction of the textured plates and containers of this invention have a static coefficient of friction of 0.22 to 2.0 and above, the preferred values are 0.8 to 1.6.
The texture coated cellulosic paperboard must reconcile several conflicting properties to be useful for the manufacture of plates, cups, bowls, canisters, French fry sleeves, hamburger clam shells, rectangular take-out containers, and related articles of manufacture. The coated paperboard has to have improved thermal resistance, improved formability, and, to be economical, the whole board should not be covered with the coating. All the conventional paperboards can be utilized; but for enhanced insulation properties, the fiber weight (hereinafter “w”) of the paperboard should be at least about forty pounds for each three thousand square foot ream. Fiber weight is the weight of fiber in pounds for each three thousand square foot ream. The fiber weight is measured at standard TAPPI conditions which provide that the measurements take place at a fifty percent relative humidity at seventy degrees Fahrenheit. In general, the fiber weight of a 3000 square foot ream is equal to the basis weight of such a ream minus the weight of any coating and/or size press. The fiber mat density of the paperboard utilized in the manufacture of textured containers is in the range of about 3 to 9 pounds per 3000 square foot ream at a thickness of 0.001 inch. The preferred fiber mat density is in the range of about 4.5 to 8.3 pounds per 3000 square foot ream at a fiberboard thickness of 0.001 inch. To achieve the superior properties of textured paperboard containers, it has been discov
Hartjes Timothy P.
Sandstrom Erland R.
Shanton Kenneth J.
Swiontek Anthony J.
Swoboda Dean P.
Finnegan Henderson Farabow Garrett & Dunner LLP
Fort James Corporation
Nolan Sandra M.
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