Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-08-31
2001-05-01
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S321000, C524S339000, C524S378000, C428S401000
Reexamination Certificate
active
06225388
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thermoplastic composition that comprises an unreacted mixture of an aliphatic polyester polymer selected from the group consisting of a polybutylene succinate polymer, a polybutylene succinate-co-adipate polymer, a polycaprolactone polymer, a mixture of such polymers, or a copolymer of such polymers; a multicarboxylic acid; and a wetting agent. The thermoplastic composition is capable of being extruded into fibers that may be formed into nonwoven structures that may be used in a disposable absorbent product intended for the absorption of fluids such as body fluids.
DESCRIPTION OF THE RELATED ART
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.
Many of the commercially-available biodegradable polymers are aliphatic polyester materials. Although fibers prepared from aliphatic polyesters are known, problems have been encountered with their use. In particular, aliphatic polyester 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. Most aliphatic polyester polymers also have much lower melting temperatures than polyolefins and are difficult to cool sufficiently following thermal processing. Aliphatic polyester polymers are, in general, not inherently wettable materials and may need modifications for use in a personal care application. In addition, the use of processing additives may retard the biodegradation rate of the original material or the processing additives themselves may not be biodegradable.
SUMMARY OF THE INVENTION
The present invention concerns a thermoplastic composition that is desirably biodegradable and yet which is easily prepared and readily processable into desired final structures, such as fibers or nonwoven structures.
One aspect of the present invention concerns a thermoplastic composition that comprises a mixture of a first component, a second component, and a third component.
One embodiment of such a thermoplastic composition comprises a mixture of an aliphatic polyester polymer selected from the group consisting of a polybutylene succinate polymer, a polybutylene succinate-co-adipate polymer, a polycaprolactone polymer, a mixture of such polymers, or a copolymer of such polymers; a multicarboxylic acid, wherein the multicarboxylic acid has a total of carbon atoms that is less than about 30; and a wetting agent which exhibits a hydrophilic-lipophilic balance ratio that is between about 10 to about 40, wherein the thermoplastic composition exhibits desired properties.
In another aspect, the present invention concerns a fiber prepared from the thermoplastic composition wherein the fiber exhibits desired properties.
In another aspect, the present invention concerns a nonwoven structure comprising a fiber prepared from the thermoplastic composition.
One embodiment of such a nonwoven structure is a backsheet useful in a disposable absorbent product.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to a thermoplastic composition which includes a first component, a second component, and a third component. As used herein, the term “thermoplastic” is meant to refer to a material that softens when exposed to heat and substantially returns to its original condition when cooled to room temperature.
It has been discovered that, by using an unreacted mixture of the components described herein, a thermoplastic composition may be prepared wherein such thermoplastic composition is substantially degradable yet which thermoplastic composition is easily processed into fibers and nonwoven structures that exhibit effective fibrous mechanical properties.
The first component in the thermoplastic composition is an aliphatic polyester polymer selected from the group consisting of a polybutylene succinate polymer, a polybutylene succinate-co-adipate polymer, a polycaprolactone polymer, a mixture of such polymers, or a copolymer of such polymers.
A polybutylene succinate polymer is generally prepared by the condensation polymerization of a glycol and a dicarboxylic acid or an acid anhydride thereof. A polybutylene succinate polymer may either be a linear polymer or a long-chain branched polymer. A long-chain branched polybutylene succinate polymer is generally prepared by using an additional polyfunctional component selected from the group consisting of trifunctional or tetrafunctional polyols, oxycarboxylic acids, and polybasic carboxylic acids. Polybutylene succinate polymers are known in the art and are described, for example, in European Patent Application 0 569 153 A2 to Showa Highpolymer Co., Ltd., Tokyo, Japan.
A polybutylene succinate-co-adipate polymer is generally prepared by the polymerization of at least one alkyl glycol and more than one aliphati
Tsai Fu-Jya
Wertheim Brigitte C.
Connelly Thomas J.
Kimberly--Clark Worldwide, Inc.
Sanders Kriellion
Schenian John R.
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