Personal care products having reduced leakage

Details Personal care products having reduced leakage Personal care products having reduced leakage

2000-09-01

2004-04-20

Lo, Weilun (Department: 3761)

Surgery

Means and methods for collecting body fluids or waste material

Absorbent pad for external or internal application and...

Reexamination Certificate

active

06723892

ABSTRACT:

FIELD OF THE INVENTION
The invention is related to absorbent personal care products. More particularly, it concerns absorbent disposable articles such as feminine care napkins, diapers and training pants, wound care dressings and bandages, and adult incontinence products.
BACKGROUND OF THE INVENTION
Personal care products typically are made with a top sheet material (also referred to as a cover sheet or liner) an absorbent core and a liquid impervious back sheet. Some may also have a surge layer or other specialized layers between the top sheet and absorbent core.
An ideal feminine care product would have no leakage and deliver comfort and discretion to the user. Current feminine care products have relatively high leakage and thus offer only modest protection to the consumer. However, a leak is rather arbitrarily defined in the art and thus consumer perceived leakage is much less. Severe leakage occurs much less frequently.
In the art, a leak is defined as menstrual discharge which stains, contacts or discolors the underwear. All leakage is categorized by three key causes: fluid does not absorb into the product, fluid is absorbed into the product but subsequently leaves it, or fluid never contacts the product. The specific reasons for this leakage may be expressed further in terms of definitive mechanisms. For instance, it may not have suitable space for absorption due to localized saturation or low contact area of the product. It may not have a suitable driving force for absorption because the pores do not have the right balance of permeability and capillarity. The interfiber spaces may be partially full of fluid. Fluid may contact the pad and run-off. The fluid may be too viscous or the pores or interfiber spaces are not large enough to allow fluid to pass.
Various product attempts have been defined to reduce leakage. For instance, wings were developed to cover the underwear and thus reduce leakage by reducing the area of the underwear that could be soiled or contacted. Others have defined emboss lines or shaping lines which cause the pad to fold in a predefined manner to concentrate fluid loading in a specific area or to increase the contact area of the pad with the body. Still others have attempted to reduce leakage by focusing on side or edge leakage presumably caused by compression of the pad by the legs thereby reducing the contact area of the target zone. These product designs have focused on keeping absorbed fluid away from the edges of the product and directing it toward the center. In many cases this is a function not only of the assembly of materials of different size and shape but also their ability to conform to and contact the body in predefined ways.
In all cases, the material systems and their concentration in a specific product design dramatically impact leakage. In the field of material systems design, leakage is a function of materials shaping and conformability as well as intake, distribution, retention and transfer.
For the purpose of this invention, intake is the absorption of body exudates over the lifetime of the product. As such it includes the initial absorption of fluid into a dry product as well as the continued uptake of that fluid into the absorbent structure. Development of superior intake systems requires an understanding of environmental conditions including the nature of the fluid and its discharge. Developing functional intake structures requires an understanding of material characteristics and their interaction with the fluid as components and systems of components including interfaces and product design. Product design includes the arrangement and geometric design of material components and their interaction with the body and fluid.
The environmental conditions surrounding the characteristics of menstrual fluid and its expulsion from the body are well understood in the art. It is this understanding which has permitted the development of suitable intake structures. Menses is a complex, heterogeneous fluid composed of plasma, red blood cells, mucin and tissue/debris. The menses simulant described in this text replicates a specific range of real menstrual fluid properties. The viscosity and elasticity of menstrual fluid span a range of 0 to 1.5 Poise and an elastic stress of 0 to 1.5 dynes/cm{circumflex over ( )}2.
It has been found that continuous flow insults in feminine hygiene products average 1 ml/hr and are not literally continuous or constant, but rather variable in rate and may even pause during a cycle. “Gush flow” is defined as a sudden heavy flow condition and occurs at flow rates of from 0.2 to 1 ml/sec or higher. During a gush, 1-5 ml of fluid is released from the body onto the product. The term “continuous flow” is used to define any flow which falls outside of the definition of gush flow. Combining continuous and gush flow conditions results in variable flow. Essentially, “variable flow” is defined as continuous flow with intermittent gush flow occurrences. The response to this problem is termed “variable flow management” and is defined as the ability to absorb and contain continuous and light flow (1-2 ml/hr) as well as multiple gushes or sudden heavy flow insults (0.5 ml/sec with a total volume of 1-5 ml) over the life of the product. In considering environmental conditions, one must also make note of the temperature, humidity, anatomy, activity, characteristics of skin and pubic hair as well as characteristics of undergarments.
Initial intake of menstrual fluid into an absorbent article is a function of the characteristics of the liner or topsheet material and the upper absorbent composite. Intake of menstrual fluid into these materials is a function of the material characteristics including the ratio of to void volume of fiber surface area, fiber orientation and fiber surface wettability. These intrinsic material characteristics specifically define the more familiar material properties of permeability, capillarity and fiber wettability which can be easily calculated and measured by techniques well known in the art. Suitable liner material characteristics are well defined in the art. These have primarily taken the form of apertured film and nonwoven covers and multi-layer composites thereof. Apertured film covers which range from structures having high permeability and low capillarity to those with high permeability and high capillarity. Nonwoven covers typically have much lower permeability with higher levels of capillarity. Regardless of the characteristics of the liner, a suitable absorbent core must be matched to it to permit fluid communication and transfer and thus good fluid intake. Both the interface between the cover and absorbent core as well as the material characteristics are important. Several researchers have defined suitable intake structures for absorption of fluids for personal care articles. For instance, Latimer et. al. (5,364,382) teaches an absorbent article having a retention and surge portion. The surge portion of the invention was defined to uptake and hold at least three successive surges of fluid and direct each to target zone and release it to the retention portion. Dodge, II et al. 20 (WO 98/22066) describes a wettable web of fibers of at most 30 microns in diameter and a permeability of 250 to 1500 Darcy's, a capillary tension of 1.5 to 5 cm and which maintains that permeability and capillarity over the life of the web. Burnes et al. (U.S. patent application Ser. No. 09/072,172) defines an absorbent which wicks artificial menses according to a horizontal wicking test a distance of at least about 1 inch in less than about five minutes. It also denotes as a dependent claim that such fabrics have a density less than 0.15 g/cc.
Intake alone is insufficient in defining absorbency. Absorbent products must also be able to contain the body exudate in such a way as to keep the wearer comfortable and protected from fluid being expressed back onto the wearer or the undergarments. Such materials, particularly for feminine hygiene product usage, can be somewhat stiff and uncomfortable. The layers of the

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