Absorbent article having a stable skin care composition

Details Absorbent article having a stable skin care composition Absorbent article having a stable skin care composition

2003-04-16

2004-09-21

Cameron, Erma (Department: 1762)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Cosmetic, antiperspirant, dentifrice

Reexamination Certificate

active

06793930

ABSTRACT:

BACKGROUND OF THE INVENTION
Many types of disposable absorbent products, such as diapers, training pants, adult incontinence devices, sanitary napkins, panty liners, and the like, are available that have a high capacity for absorbing urine and other body exudates. Disposal products of this type generally comprise some sort of liquid-pervious topsheet material, an absorbent core, and a liquid-impervious backsheet material. Although these types of absorbent articles may be highly efficient for the absorption of liquids, it is generally known that skin under the absorbent article is more susceptible to skin disorders, including diaper rash or diaper dermatitis, erythema (i.e., redness), heat rash, abrasion, pressure marks and skin barrier loss. Diaper rash is a common form of irritation and inflammation of those parts of an infant's body normally covered by a diaper. It is generally accepted that diaper rash or diaper dermatitis is a condition which begins as a contact irritant dermatitis. The commonly known factors linked to diaper dermatitis include ammonia, bacteria, products of bacterial action, urine pH,
candida albicans
, and moisture. This irritation and/or inflammation result from extended contact of the skin with urine, feces, or both. When absorbent articles are worn to catch and hold the body exudates, the absorbent articles not only hold the skin of the wearer in direct contact with irritants in the body exudates, but also hold the skin in an occluded condition. Often, the skin is subjected to such a condition for extended periods of time, that is, until the soiled article is changed. As the skin under the absorbent article becomes overhydrated or irritated by such prolonged and repeated exposures, the skin condition is compromised, i.e., the skin is injured and/or becomes more susceptible to skin disorders or damages. While this condition is certainly more common in infants, it is not limited to infants. Similar conditions occur in, for example, incontinent or bed-ridden adults.
Common approaches to the improvement of skin conditions in the diapered areas often focus on reducing skin hydration, such as frequent changing of diapers, using moisture absorbing powders, using superabsorbent materials, and improving air flow in diapers, and the like.
Another common approach is to apply a topical cream, ointment, lotion or paste to the affected areas. This procedure usually provide some degree of physical barrier protection to the skin against direct contact with fecal or urine irritants. However, the barrier approach may be occlusive in itself, thus not very effective once a full blown case of diaper dermatitis has developed. There is a tendency to slather on a thick layer of the diaper rash cream or ointment, which is occlusive, messy, wasteful and aesthetically displeasing. Moreover, the excess cream/ointment may transfer to the absorbent article or other clothing, such as underwear, leading to reduced absorbency or stained clothing. This procedure is also time-consuming and often forgotten. Furthermore, the cream/ointment typically comes in a reusable container and is hand-applied to the skin. The composition often has a thick, greasy and tacky consistency in order to remain on the infant's skin, the residual composition is not easily removed from the opening of the container or the hands of the care-giver, and the possibility of cross contamination between one infant to another is increased.
An alternative approach attempts to simultaneously address multiple causes or important cofactors by using a multi-ingredient skin care composition. The composition may include barrier substances, skin conditioning agents or emollients, and may even include various skin care ingredients.
The skin care ingredients may exist as insoluble particles suspended in the substantially oleagineous compositions due to their limited solubility in the oleagineous substances. Furthermore, these solid particles generally have densities much higher than the oleagineous matrix that they are dispersed in. For example, common commercial diaper rash creams or ointments comprise zinc oxide particles dispersed in an organic matrix. Zinc oxide has a density of about 5.7 g/cm
3
while the density of organics is generally about 0.9 g/cm
3
. This large difference in densities often leads to separation and processing problems.
A good suspension of the skin care ingredients in the lotion composition is highly desirable. As used herein, a “good” suspension means the particulate substances are substantially uniformly dispersed in the medium, and the dispersion is stable, i.e., no visible stratification, agglomeration or settling with the passage of time. Uniform distribution of the ingredients minimizes variation in product quality and assures that every application of the product to the skin delivers a sufficient amount of ingredients to achieve efficacy. There is no need to over-apply the product in order to achieve the desired benefits; consequently, there is less waste. Therefore, a good suspension provides the most efficient delivery of these skin care ingredients to the skin and maximizes the skin benefits. Moreover, there is no need to incorporate an extra amount of the costly ingredients to ensure efficacy; thus, an effective composition can be made at lower cost. Additionally, a good suspension also reduces the lumpiness of the lotion and provides a smooth skin feel when applied.
Generally, a suspension of particulates in a Newtonian fluid follows the Stokes law, which states that the rate of separation or settling is proportional to the density difference between the suspended particles and the suspending medium, to the square of the particle size of the suspended particles, and is inversely proportional to the viscosity of the medium. Agglomeration and gravitational settling are often observed when particulate materials are suspended in a Newtonian fluid, causing problems in storage, transportation and processing of these compositions. Where a batch process is used, the agglomeration and settling can occur in a holding tank. Moreover, as the composition flows through processing equipment, the agglomerates, formed either in the holding tank or along the process, tend to get hung up in various elements having small diameters (such as pipes, valves, slots) along the processing line. This “bridging” problem often causes clogged orifices, openings, slots and/or narrow pipes, and can severely reduce or even stop the flow of the composition through the processing equipment.
Agitation or turbulent flow can redisperse the suspended particles and avoid agglomeration and settling problems. It is known that the flow of a liquid through a pipe or like elements may be laminar or turbulent, and the transition from a laminar flow to a turbulent flow depends on the properties of the fluid, its velocity and the diameter of the pipe. However, agitation, velocity and pipe diameter are processing parameters that are constrained to a limited range for a given piece of equipment. Variations of these parameters within the equipment-limiting range often fail to solve the problem.
A variety of rheological agents, such as thickeners, thixotropic agents and dispersing agents, can be added to such a composition to alter the rheological properties of the composition. These rheological agents serve to improve the stability of the suspensions and to maintain the viscosity at a desired level for a wide range process conditions and end-use situations.
Creams or ointments containing particles of zinc oxide, anti-microbials, or protease or enzyme inhibitors are known. These compositions have traditionally been prepared as oil-in-water or water-in-oil emulsions. These emulsions are not very effective in improving the condition and/or appearance of the diapered skin, particularly when the composition is delivered via a vehicle such as an absorbent article. The absorbent core element may draw the aqueous phase away from the surface of the article thereby reducing the skin benefits provided by the composition. Additionally, the

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