1. Field of the Invention
The present invention relates to a polypropylene wrap having particular application for tampons and, more specifically, to end seals and a process for sealing the ends of a voided polypropylene film wrap.
A tampon is enclosed in a wrap or a package prior to use to prevent the tampon from becoming soiled and also from coming into contact with moisture, either of which harmfully effects the tampon. Besides preventing the tampon from soiling and from contacting water, the wrap and its end seals need to be strong enough so as not to tear or separate during handling, yet the end seals need to tear readily to permit a user to obtain easily the tampon from within.
2. Description of the Prior Art
Paper has been used as a medium for a tampon wrap since it is pliable and readily permits sealing of its ends by mechanical crimping. However, a paper tampon wrap has drawbacks such as the paper can be torn relatively easily, water can easily damage the paper wrap and thus the enclosed tampon and paper does not seal out ambient moisture. Also, moisture effects paper, namely, moisture causes paper to seal. Therefore, a paper wrap is difficult to manufacture since the moisture in the wrap during manufacturing must be controlled or else the paper wrap may seal prematurely.
Thermoplastics have been used as the medium for a tampon wrap. However, thermoplastic materials, due to their nature, heretofore, could not readily be mechanically sealed and could not provide a mechanical crimped seal with the strength provided by the present invention. In particular, prior art thermoplastic tampon wraps have end seals which are formed by heat and pressure.
Specifically, U.S. Pat. No. 2,200,971 to Sonneborn, et al. provides a system for making, filling, and sealing packages from a thermoplastic web material in which heat and pressure are applied to form a seal. Corrugations are formed at the seal area due to the corrugations on the faces of the sealing members. This patent also provides that the end seal has beyond it a narrow unsealed margin containing a notch to facilitate opening of the package.
U.S. Pat. No. 2,257,823 to Stokes is directed to a web which may be made of "Pliofilm", Cellophane, paper or other sheet material coated with, impregnated with, or consisting of thermoplastic material. The outer seal is formed by tools under conditions of temperature, pressure, and time suitable to the thermoplastic applied to or comprised in the web to thermoplastically join marginal edges of the web.
U.S. Pat. No. 2,430,995 to Roos provides a process for sealing thermoplastic containers in which the end seals are formed by simultaneously crimping and heat sealing.
U.S. Pat. Nos. 4,102,111 to Nack, et al. and 4,106,262 to Aterianus are directed to wrapping machines which simultaneously crimp or pressurize and heat seal a thermoplastic tube.
Lastly, U.S. Pat. No. 4,254,601 to Prager et al. is directed to an assembly for forming a plurality of individual packages each made from polypropylene. The assembly includes cooperating roller members for simultaneously heat sealing, crimping, notching, and severing a tubular plastic strip which is generally polypropylene. This patent provides that the polypropylene is heated to a temperature sufficient to melt the polypropylene so as to form a heat seal. A notch S.sup.1 is provided at each end to facilitate opening.
While the prior art patents include those which use heated knurled wheels for sealing by mechanically crimping and heat sealing thermoplastics, including polypropylene, wraps and also suggest that parameters such as temperature and pressure may be adjusted as desired, see U.S. Pat. No. 2,200,971 to Sonneborn, et al., page 4, col. 1, lines 41 through 50; U.S. Pat. No. 2,257,823 to Stokes, page 2, col. 1, lines 67 to col. 2, line 2, not one of the prior art patents suggests using heated knurled wheels to form only a mechanically crimped end seal as provided by the present invention.