Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2000-09-14
2004-02-17
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of metal
C131S358000, C131S365000, C206S268000, C206S271000, C206S273000, C428S461000, C428S464000, C428S514000, C428S522000, C428S537500, C428S905000, C428S906000
Reexamination Certificate
active
06692835
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to slip coatings for the foil layer of an innerwrap material for cigarette packages and more particularly to a polyvinyl alcohol (PVOH) slip coating.
BACKGROUND OF THE INVENTION
In cigarette packaging, it is conventional to wrap the bundle of cigarettes of a package in a sheet material known as an “innerwrap” which almost always includes a layer of paper for strength, a layer of metal foil to inhibit loss of moisture content of the cigarettes, and an adhesive to bond the foil and paper into a single sheet or laminate. The thus-wrapped cigarettes are then placed in a soft pack or a paperboard box, as the case may be, and overwrapped with a clear plastic sheet material, such as a polypropylene or polyethylene terephthalate film.
The innerwrap sheet material is typically made on laminating machines and wound up into large rolls for subsequent use. In the cigarette packaging plant, the innerwrap is unrolled, cut, and wrapped about bundles of cigarettes to be packaged in individual packs.
It is also conventional in cigarette making to make cigarettes flavored with menthol or other flavorants. In the case of a menthol flavorant, menthol can be sprayed onto or otherwise added to shredded tobacco and cigarettes can then be made from the mentholated shredded tobacco in the usual way. This is a practical method for manufacturing large quantities of menthol cigarettes in machines dedicated to producing only menthol cigarettes, but is impractical in the case of cigarette making machines, e.g., in smaller manufacturing plants, which may be used to manufacture non-flavored cigarettes as well as mentholated cigarettes. In such plants, the mentholated tobacco permeates the cigarette manufacturing equipment with the menthol flavorant which is difficult to remove from the equipment, so that an unintended menthol scent and/or taste is imparted to cigarettes subsequently made on the same equipment, even when regular, unflavored tobacco is used.
To avoid the problem of menthol-tainted machinery and to provide a way to permit cigarette manufacturing plants to make both flavored and non-flavored cigarettes on the same machinery, it is more advantageous to incorporate the menthol or other flavorant into the paper on the inner side of the innerwrap. Since menthol has a high vapor pressure, after a bundle of cigarettes is wrapped in a completed package, the menthol will diffuse into the tobacco of the cigarettes wrapped inside the innerwrap envelope, thereby imparting the desired menthol taste and aroma to the cigarettes. Typically, menthol is applied to the innerwrap at a location other than at the cigarette making machinery because the application of menthol to the innerwrap, e.g., by spraying, while simultaneously unrolling, cutting, folding, and wrapping the innerwrap about the cigarette bundles is impractical and can still result in menthol contamination of the cigarette making machinery.
Because the foil of the sheet material innerwrap is usually aluminum, and aluminum is a metal notorious for its poor bearing qualities, including a high coefficient of friction and a tendency to gall, in most cases the innerwrap must be coated on the foil side with a polymeric “slip coating,” which prevents the foil side from adhering to the rollers of the cigarette making machinery and tearing the innerwrap web. In conventional innerwraps, the slip coating is a polyacrylate or a polyester, relatively expensive polymers. Although the slip coating is thin, because of the large production volumes, the total quantity and cost of the slip coating over time can be very high.
During the time the innerwrap is being stored and shipped to the cigarette manufacturing plant in rolls of the innerwrap material, there is an inevitable loss of menthol through sublimation and vaporization of the menthol flavorant. This loss is minimal because of the large volume-to-surface ratio of the roll. Menthol loss from the roll can be further reduced by wrapping the rolls in a vapor barrier.
Most of the menthol will be lost when the innerwrap is unwound from the large roll. When the roll is unwound, menthol on the paper will immediately begin to escape as vapor. This loss can be minimized by minimizing the time between unrolling the innerwrap material and wrapping the cigarette bundles. Ordinarily, this time will be short and the menthol loss slight. One loss that cannot be minimized is the loss of menthol from the slip-coated side of the innerwrap. Only the menthol on the paper side of the innerwrap will diffuse into the cigarettes. On the other hand, menthol on the slip coating side of the innerwrap cannot pass through the foil into the paper or cigarettes and will, therefore, diffuse through the paperboard box or soft pack wrapping and the outer polypropylene overwrap clear plastic.
When the innerwrap is rolled up, the menthol can readily diffuse from the paper into the slip coating, and the menthol will quickly reach an equilibrium in which a definite proportion of the menthol is retained in the slip coating. That proportion will ultimately not be in the cigarettes and will be wasted, except to the extent it imparts a menthol aroma to the consumer externally of the package. The menthol-affinity properties of the slip coating are thus important in affecting the amount of menthol that will be available to diffuse into the cigarettes and the amount that will be lost to the surrounding environment. Although the total surface area of the fibrous paper is much larger than the surface area of the smooth foil, a substantial amount of menthol still diffuses into or adheres to the conventional polymer slip coatings.
Polyvinyl alcohol (PVOH) has previously been used in the cigarette making art as an adhesive, for example, in making cigarette filters, but not, insofar as is known, as an innerwrap slip coating. U.S. Pat. No. 4,984,589 to Riedesser refers to GB-A-21 43 150 as disclosing a cigarette paper (tubular tobacco wrapper) coated on the side confronting the tobacco with polyvinyl acetate (PVA) or polyvinyl alcohol (PVOH) to prevent the penetration of condensate or tar that could form brown spots on the cigarette paper.
Thus, it would be desirable to minimize the amount of menthol that diffuses into or adheres to the slip coating during the time a cigarette innerwrap sheet material is stored. It would also be desirable to provide a low cost, yet effective, slip coating to replace the more expensive conventional slip coatings for cigarette package innerwraps.
SUMMARY OF THE INVENTION
The present invention relates to a cigarette package innerwrap having a polyvinyl alcohol (PVOH) slip coating. It has been found that PVOH is not only less expensive than conventional slip coating materials, it also has a relatively low coefficient of friction comparable to conventional slip coatings which makes it very effective in reducing the sticking of the aluminum foil of the innerwrap to the cigarette machinery rollers. In addition, as explained in more detail hereinafter, it has been unexpectedly found that PVOH is more effective than conventional slip coating materials in preserving the mentholation of packaged cigarettes by means of a menthol coating on the innerwrap paper.
On the basis of the chemical structure of PVOH, it would be expected that menthol would readily dissolve in PVOH and therefore that the amount of menthol lost to the slip coating of the innerwrap would be even greater with a PVOH slip coating than with conventional slip coating materials. However, contrary to the expectations of those skilled in the art, PVOH has a relatively low affinity for menthol. It has been unexpectedly found that the amount of menthol lost to the slip coating is less with a PVOH slip coating than with the prior art polyacrylate and polyester slip coatings.
Although the invention is not intended to be limited thereby, it is believed that the reason for this unexpected result is that the menthol does not dissolve in or adhere to the PVOH to the same degree that it does in the prior art slip coatings. The preci
Brinks Hofer Gilson & Lione
Nakarani D. S.
R. J. Reynolds Tobacco Company
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