Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-11-09
2001-07-31
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S166000, C525S186000, C525S190000, C528S354000, C528S363000, C524S378000, C524S518000, C442S327000, C428S221000, C428S297400, C428S297700, C428S480000
Reexamination Certificate
active
06268434
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a biodegradable nonwoven material having improved fluid management properties. The nonwoven material may be produced from polymer blends. These blends may include multicomponent fibers. These multicomponent fibers comprise an unreacted mixture of a poly(lactic acid) polymer, a polybutylene succinate polymer or a polybutylene succinate adipate polymer or a mixture of such polymers, and a wetting agent. The multicomponent fiber exhibits substantial biodegradable properties yet is easily processed. The biodegradable nonwoven materials may be used in a disposable absorbent product intended for the absorption of fluids, such as body fluids.
BACKGROUND OF THE INVENTION
Disposable absorbent products currently find widespread use in many applications. For example, in the infant and child care areas, diapers and training pants have generally replaced reusable cloth absorbent articles. Other typical disposable absorbent products include feminine care products such as sanitary napkins or tampons, adult incontinence products, and health care products such as surgical drapes or wound dressings. A typical disposable absorbent product generally comprises a composite structure including a topsheet, a backsheet, and an absorbent structure between the topsheet and backsheet. These products usually include some type of fastening system for fitting the product onto the wearer.
Disposable absorbent products are typically subjected to one or more liquid insults, such as of water, urine, menses, or blood, during use. As such, the outer cover backsheet materials of the disposable absorbent products are typically made of liquid-insoluble and liquid impermeable materials, such as polypropylene films, that exhibit a sufficient strength and handling capability so that the disposable absorbent product retains its integrity during use by a wearer and does not allow leakage of the liquid insulting the product.
Although current disposable baby diapers and other disposable absorbent products have been generally accepted by the public, these products still have need of improvement in specific areas. For example, many disposable absorbent products can be difficult to dispose of. For example, attempts to flush many disposable absorbent products down a toilet into a sewage system typically lead to blockage of the toilet or pipes connecting the toilet to the sewage system. In particular, the outer cover materials typically used in the disposable absorbent products generally do not disintegrate or disperse when flushed down a toilet so that the disposable absorbent product cannot be disposed of in this way. If the outer cover materials are made very thin in order to reduce the overall bulk of the disposable absorbent product so as to reduce the likelihood of blockage of a toilet or a sewage pipe, then the outer cover material typically will not exhibit sufficient strength to prevent tearing or ripping as the outer cover material is subjected to the stresses of normal use by a wearer.
Furthermore, solid waste disposal is becoming an ever increasing concern throughout the world. As landfills continue to fill up, there has been an increased demand for material source reduction in disposable products, the incorporation of more recyclable and/or degradable components in disposable products, and the design of products that can be disposed of by means other than by incorporation into solid waste disposal facilities such as landfills.
As such, there is a need for new materials that may be used in disposable absorbent products that generally retain their integrity and strength during use, but after such use, the materials may be more efficiently disposed of. For example, the disposable absorbent product may be easily and efficiently disposed of by composting. Alternatively, the disposable absorbent product may be easily and efficiently disposed of to a liquid sewage system wherein the disposable absorbent product is capable of being degraded.
Although degradable monocomponent fibers are known, problems have been encountered with their use. In particular, known degradable fibers typically do not have good thermal dimensional stability such that the fibers usually undergo severe heat-shrinkage due to the polymer chain relaxation during downstream heat treatment processes such as thermal bonding or lamination.
For example, although fibers prepared from poly(lactic acid) polymer are known, problems have been encountered with their use. In particular, poly(lactic acid) polymers are known to have a relatively slow crystallization rate as compared to, for example, polyolefin polymers, thereby often resulting in poor processability of the aliphatic polyester polymers. In addition, the poly(lactic acid) polymers generally do not have good thermal dimensional-stability. The poly(lactic acid) polymers usually undergo severe heat-shrinkage due to the relaxation of the polymer chain during downstream heat treatment processes, such as thermal bonding and lamination, unless an extra step such as heat setting is taken. However, such a heat setting step generally limits the use of the fiber in in-situ nonwoven forming processes, such as spunbond and meltblown, where heat setting is very difficult to be accomplished.
Additionally, one of the more important components of many personal care articles is the body-side liner. The liner is usually comprised of a surfactant-treated polyolefin spunbond. For a spunbond to be implemented as a liner, it is desired that the material be wettable to promote intake of fluid insults. In addition to rapid intake, it is desired that the composite absorbent product keep the user's skin dry. In addition, it is desirable for the spunbond material to feel soft against the skin. The current spunbond diaper liner has a number of problems associated with it. First, it is comprised of polyolefinic materials and does not degrade. Due to the hydrophobic nature of these materials, the liner must be treated with a surfactant to make it wettable. Because there is no permanent anchoring of the surfactant to the polyolefin, it has a tendency to wash off during multiple insults, increasing intake times of the nonwovens.
Accordingly, there is a need for a nonwoven material useful as a wettable structure with improved fluid management properties such as faster intake times and improved skin dryness. Additionally there is a need for a nonwoven material that is biodegradable while also providing these improved fluid management properties.
SUMMARY OF THE INVENTION
It is therefore desired to provide a nonwoven material having improved fluid management properties.
It is also desired to provide a nonwoven material having faster intake times.
It is also desired to provide a nonwoven material having improved skin dryness.
It is also desired to provide a nonwoven material that is biodegradable while also providing improved fluid management properties.
It is also desired to provide a nonwoven material comprising a thermoplastic composition which exhibits desired processability, liquid wettability, and thermal dimensional-stability properties.
It is also desired to provide a nonwoven material comprising a thermoplastic composition which may be easily and efficiently formed into a fiber.
It is also desired to provide a nonwoven material comprising a thermoplastic composition which is suitable for use in preparing nonwoven structures.
It is also desired to provide a disposable absorbent product that may be used for the absorption of fluids such as bodily fluids, yet which such disposable absorbent product comprises components that are readily degradable in the environment.
These desires are fulfilled by the present invention which provides a nonwoven material comprising a thermoplastic composition that is substantially biodegradable and yet which is easily prepared and readily processable into desired final nonwoven structures.
One aspect of the present invention concerns a nonwoven material having a thermoplastic composition that comprises a mixture of a first component, a seco
Tsai Fu-Jya Daniel
Wertheim Brigitte C.
Hampton-Hightower P.
Kilpatrick & Stockton LLP
Kimberly - Clark Worldwide, Inc.
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