BACKGROUND OF THE INVENTION

Wet consumer products are often sold in airtight packaging to prevent the products from drying out over time. For example, pre-moistened wipes, such as baby wipes, toileting wipes, or surface cleaning wipes, are frequently sold in airtight tubs, pouches, or bags, often made of plastic or foil. The package must typically remain moisture-impervious so that the wipes do not dry out during transport and storage. The package typically includes an opening mechanism to access the interior of the package to extract the wipes. Sometimes the package can be reclosed, and sometimes the packaging material is removed and disposed of. One problem unique to fully sealed flexible packages is that as wet consumer products such as moist wipes are transported, the atmospheric pressure exterior to the package can change. If the atmospheric pressure outside of the package becomes lower than the pressure inside of the package, the sealed enclosure formed by the packaging material will often swell or "balloon" outwardly. With wet consumer products such as moist wipes, neither the packaging material nor the wet consumer product is compromised by such swelling; however, such swelling is undesirable from an aesthetic standpoint. This is because some consumers associate a swelling packaging of a wet consumer product (such as a food product) as containing some element of contamination, decay, degradation, or spoilage, and consumers may thus wrongly interpret the swollen appearance as due to the production of gases associated with decay or biodegradation. Various structures have been proposed to allow pressurized air within a container to exit the container. For example, one-way valves have been employed, but such values are expensive to make and to integrate into the packaging. WO 03/008294 A1, to Sumpmann et al. and assigned to General Mills, Inc., directed to packaging material for a loosely arranged dry particular product, teaches the use of a microhole that allows air to be vented when the external pressure drops, such as during shipping. WO 2008/008804 A2, to Domingues et al. and assigned to General Mills Marketing, Inc., directed to packaging for a dough product, teaches the use of microvents to allow air to be pushed out of the interior space of the package as the dough expands and fills the excess headspace. The microvents are adapted to prevent discoloration or mold germination of the dough albeit allowing the dough to dry until, upon expansion, the dough seals off the microvents. What is missing in the art is a solution to the problem described above for a volumetrically- stable, wet consumer product packaged in packaging made from a flexible membrane. SUMMARY OF THE INVENTION

According to the present invention there is provided a package containing a substantially volumetrically stable, wet consumer product, the package comprising: at least one substantially volumetrically stable wet consumer product, a flexible substrate forming a sealed enclosure around the at least one wet consumer product, the sealed enclosure defining an interior space partially filled by the at least one wet consumer product, the flexible substrate including at least one microvent, wherein the or each microvent is adapted to vent an excess of air pressure within the interior space to reach equilibrium with air pressure outside of the interior space without loss of liquid moisture from within the interior space. Consumers naturally expect to purchase their product substantially as manufactured, as good as new. The package of the present invention retains sufficient interior moisture even while air vents, or exhales, to alleviate ballooning. Advantageously, the consumer receives wet consumer product in an unimpaired package.

Preferably, the at least one wet consumer product comprises a stack of wet wipes. Consumers of wet wipes are generally partial to fresh pre-moistened product in a well-presented package. Preferably, the stack of wet wipes has a substantially cuboids shape. This may facilitate packaging in a neat, easily-stored shape.

Preferably, each microvent vents from the interior space unfilled by the at least one wet consumer product. Free air in the vicinity of the microvent, or, if there is more than one microvent, each microvent, may assist efficient venting from the interior of the package. Preferably, the unfilled interior space constitutes at least 5 percent of the interior space. This may assist free circulation of air inside the package.

Preferably, at least one microvent is always unobstructed by the wet consumer product. The package and/or the wet consumer product may be dimensioned to inhibit intrusion upon the at least one microvent. Preferably, the volumetrically stable, wet consumer product occupies at least 75 percent of the interior space. This may facilitate efficient use of package materials.

Preferably, the package has a first end longitudinally spaced from a second opposite end, and wherein a first microvent is disposed longitudinally between the first end and the wet consumer product, and wherein a second microvent is disposed longitudinally between the second end and the wet consumer product. This may assist evenly distributed venting from the interior of the package. Preferably, each microvent is an orifice having an area of between 70 and 10,000 square micrometers. Preferably, the each microvent is substantially a circle having a diameter of between 10 and 100 micrometers. The surface tension of water vapor or droplets prevents the water particles from passing through the or each microvent. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1A shows a front top view of one embodiment incorporating principles of the present invention.

Fig. 1 B shows a perspective view of a stack of wet wipes suitable for use in conjunction with particular embodiments of the present invention. Fig. 1 C shows a cross-section view of the embodiment of Fig. 1 A taken along line 1C-1 C.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

The invention in one aspect is directed to a package 20. The package has a length direction 10 and a width direction 11. The package 20 has a first end 31 longitudinally spaced from a second end 32. The package 20 includes a wet consumer product 22, such as a stack of wet wipes as representatively illustrated in Fig. 1 B. The stack of moist wipes 22 has a length 13 that extends in a length dimension 10, a width 14 that extends in a width dimension 11 , and a height 15 that extends in a height dimension 12.

The wet consumer product 22 is substantially volumetrically stable. "Substantially volumetrically stable" means that the product 22 is not designed or configured to change volume absent the application of an external force, other than extremely small changes in volume due to factors such as temperature. An example of a volumetrically stable wet consumer product is a stack or roll of moist wipes. An example of a consumer product that is not volumetrically stable is a product that is designed to expand in the sealed package, such as popping popcorn or proofing bread dough.

The package also includes a flexible substrate 30. The flexible substrate should be a moisture impervious material to help keep the wet consumer product within the package dry. Examples of suitable flexible substrates include polymeric films, metal foil films, plastic-coated paper, or combinations thereof, all of which are known to those of skill in the art. In particular embodiments, the flexible substrate has a thickness (caliper) of between 45 micrometers and 150 micrometers, as measured by ASTM D6988-13.

The flexible substrate 30 forms a sealed enclosure 36 around the wet consumer product 22, as representatively illustrated in Fig. 1 A. The sealed enclosure 36 defines an interior space 37. The sealed enclosure 36 can be formed from a single, unitary piece of the flexible substrate 30, or it could be formed from two or more discrete pieces of the flexible substrate 30 joined together. In the illustrative example of Fig. 1A, the sealed enclosure 36 is a flow-wrap dispensing pouch, as are known in the art of wet wipes. In particular embodiments, the sealed enclosure 36 defines an interior space 37 partially filled by the at least one wet consumer product 22. In particular embodiments, the sealed enclosure 36 defines an interior space 37 only ever partially filled by the at least one wet consumer product 22. The flexible substrate 30 includes at least one microvent 40. The microvent is adapted to allow a pressure within the interior space 37 remain approximately equal to a pressure outside of the interior space. In particular embodiments, the microvents can be formed via laser, perforation rolls, high- pressure water jets, hot gas jets, hot needles, stretching, or other technique.

As noted earlier, as wet consumer products 22 such as moist wipes are transported, the atmospheric pressure exterior to the package can change. If the atmospheric pressure outside of the package becomes lower than the pressure within the interior space 37 of the package, the flexible substrate 30 forming the enclosure around the interior space 37 may "balloon" outwardly, which a consumer may wrongly interpret as due to the production of gases association with decay or biodegradation. Accordingly, the flexible substrate 30 includes at least one microvent 40. The microvent is adapted to allow a pressure within the interior space 37 to remain approximately equal to a pressure outside of the interior space 37. By substantially equalizing the pressure with the interior space 37 to the pressure outside of the interior space 37, the undesirable "ballooning" of the package will be minimized or eliminated during transport from one altitude to another, during temperature fluctuations (such as in a hot car), or during other circumstances that may cause the air pressure within the interior space 37 to exceed the atmospheric pressure outside of the interior space 37.

Preferably, each microvent 40 is large enough to allow air to escape to prevent ballooning of the sealed enclosure when the interior space 37 becomes pressurized, but small enough to resist the egress of water droplets or water vapor to prevent the wet consumer product from drying out prematurely. Therefore, in particular embodiments, each microvent has an area of between 70 and 10,000 square micrometers. The microvent may in particular embodiments be circular, elliptical, a slit, or an irregular shape, where the minimum dimension of the microvent is 10 micrometers and the maximum dimension is 100 micrometers. In particular embodiments, each microvent is a circle having a diameter of between 10 and 100 micrometers; in this way, the surface tension of the water vapor or droplets prevents the water particles from passing through the holes.

Referring to Fig. 1 C, in particular embodiments, the interior space 37 includes unfilled space 38. The unfilled space 38 is in contrast to space that is filled, or occupied, by wet consumer product 22. Preferably, every microvent 40 vents from unfilled space 38. In other words, every microvent 40 preferably is able to vent air unobstructed by the wet consumer product 22 that also resides in the interior space 37. Preferably, no microvent 40 is obstructed by the wet consumer product 22. In particular embodiments, unfilled space constitutes at least 5 percent, and more particularly at least 20 percent of the interior space when the flexible substrate 30 is expanded to its maximum volume. In particular embodiments, the volumetrically stable, wet consumer product 22 occupies at least 75 percent of the interior space 37. "Unfilled space" is the unfilled space present when the sealed enclosure is outwardly expanded, or "ballooned," to its maximum volume without any permanent deformation of the flexible membrane. The package 20 has a first end 31 longitudinally spaced from a second end 32. A first microvent

40a is disposed longitudinally between the first end 31 and the wet consumer product 22, and a second microvent 40b is disposed longitudinally between the second end 32 and the wet consumer product 22. Such a configuration can be desirable, because in certain circumstances, if the flexible substrate 30 is tightly wrapped around a wet consumer product 22 such as stack of wet wipes, the unfilled space 38 near the first end 31 may be sealed off from the unfilled space 38 near the second end 32 by the stack of wet wipes. In other instances, the product 22 may shift toward either end 31 , 32 so as to block either the first microvent 40a or second microvent 40b, but not both. By including at least one microvent 40 on each end, each unfilled space 38 can properly vent as the ratio of the air pressure within the unfilled spaced 38 relative to the atmosphere outside of the package 20 increases. By having a microvent at both ends, the need to establish airflow communication between the two ends to vent an unfilled space otherwise having no microvent is avoided.

In particular embodiments, the package 20 of wet consumer product 22 can optionally include a rigid flip lid 50, attached to the top surface 39 of the sealed enclosure 36, to provide access to the interior space 37, such as if the package 20 is intended to function as a wet wipes dispensing pack. The rigid flip lid 50 can optionally include a finger tab 74 to assist in opening the lid 50. In other embodiments of wet wipes dispenser packs, the rigid flip lid 50 is replaced by a "peel and seal" or "rigid lens" sealing membrane, both of which are known in the art of wipes dispensing packs.