ZA200203216B - Biodegradable nonwovens with fluid management properties and disposable articles containing the same. - Google Patents

Description

BIODEGRADABLE NONWOVENS WITH IMPROVED FLUID

MANAGEMENT PROPERTIES AND DISPOSABLE ARTICLES

CONTAINING THE SAME

FIELD OF THE INVENTION

The present invention relates to a biodisintegratable nonwoven material having improved fluid management properties and to a disposable article containing the same. The nonwoven material may be produced from polymer blends. These blends may include multicomponent fibers. These multicomponent fibers comprise 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 multicomponent fiber exhibits substantial biodisintegratable properties yet is easily processed. The disposable absorbent product may be used for the absorption of fluids, such as body fluids. 16

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 : 15 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 matenals 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 i 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.

Also, while 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 wttable. 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 maternal that is biodegradable while also providing these improved fluid management properties.

SUMMARY OF THE INVENTION

It is therefore desired to provide a nonwoven material and a disposable article having improved fluid management properties.

It is also desired to provide a nonwoven material and a disposable article having faster intake times.

It is also desired to provide a nonwoven material and a disposable article having improved skin dryness.

It is also desired to provide a nonwoven material and a disposable article that are biodegradable while also providing improved fluid management properties.

It is also desired to provide a nonwoven material and a disposable article comprising a thermoplastic composition which cxhibits desired processability, liquid wettability, and thermal dimensional-stability properties.

It is also desired to provide a nonwoven material and a disposable article comprising a thermoplastic composition which may be easily and efficiently formed into a fiber.

It is also desired to provide a nonwoven material and a disposable article comprising a thermoplastic composition which is suitable for use in preparing nonwoven structures.

It 1s 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 addressed 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 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 multicomponent fiber that is substantially degradable and yet which

AMENDED SHEET - DATED 26 MARCH 2003 is easily prepared and readily processable into the desired final nonwoven structures.

One aspect of the present invention concerns a multicomponent fiber that comprises an unreacted mixture of 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.

In another aspect, the present invention concerns a nonwoven structure comprising the multicomponent fiber disclosed herein.

One embodiment of such a nonwoven structure is a frontsheet useful in a disposable absorbent product.

In another aspect, the present invention concerns a process for preparing the nonwoven material disclosed herein.

In another aspect, the present invention concerns a disposable absorbent product comprising the multicomponent fiber disclosed herein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a biodisintegratable nonwoven material and a disposable article which includes a thermoplastic composition comprising 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 0569 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 aliphatic multifunctional acid. Polybutylene succinate-co-adipate polymers are also known in the art. }

Examples of polybutylene succinate polymers and polybutylene succinate-co-adipate polymers that are suitable for use } in the present invention include a variety of polybutylene succinate polymers and polybutylene succinate-co-adipate polymers that are available from Showa Highpolymer Co., Lid., Tokyo, Japan, under the designation BIONOLLE™ 1020 polybutylene succinate polymer or BIONOLLE™ 3020 polybutylene succinate-co-adipate ~~. polymer, which are essentially linear polymers. These materials are known to be substantially biodegradable.

A polycaprolactone polymer is generally prepared by the polymerization of &-caprolactone. Examples of polycaprolactone polymers that are suitable for use in the present invention include a variety of polycaprolactone polymers that are available from Union Carbide Corporation, Somerset, New Jersey, under the designation TONE™ Polymer P767E and TONE™

Polymer P787 polycaprolactone polymers. These materials are known to be substantially biodegradable.

It is generally desired that the 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 be present in the thermoplastic composition in an amount effective to result in the thermoplastic composition exhibiting desired properties. The aliphatic polyester polymer will be present in the thermoplastic composition in a weight amount that is greater than O but less than 100 weight percent, beneficially between about 40 weight percent to less than 100 weight percent, more beneficially between about 50 weight percent to about 95 weight percent, suitably between about 60 weight percent to about 90 weight percent, more suitably between about 60 weight percent to about 80 weight percent, and most suitably between about 70 weight percent to about 75 weight percent, wherein all weight percents are based on the total weight amount of the aliphatic polyester polymer, the multicarboxylic acid, : 15 and the wetting agent present in the thermoplastic composition.

It is generally desired that the aliphatic polyester polymer exhibit a weight average molecular weight that is effective for the thermoplastic composition to exhibit desirable melt strength, fiber mechanical strength, and fiber spinning properties. In general, oo 20 if the weight average molecular weight of an aliphatic polyester polymer is too high, this represents that the polymer chains are heavily entangled which may result in a thermoplastic composition comprising that aliphatic polyester polymer being difficult to process. Conversely, if the weight average molecular weight of an aliphatic polyester polymer is too low, this represents that the polymer chains are not entangled enough which may result in a thermoplastic composition comprising that aliphatic polyester polymer exhibiting a relatively weak melt strength, making high speed processing very difficult. Thus, aliphatic polyester polymers suitable for use in the present invention exhibit weight average molecular weights that are beneficially between about 10,000 to about 2,000,000, more beneficially between about 50,000 to about 400,000, and suitably between about 100,000 to about 300,000.

The weight average molecular weight for polymers or polymer blends can be determined by methods known to those skilled in the art.

It is also desired that the aliphatic polyester polymer exhibit a polydispersity index value that is effective for the thermoplastic composition to exhibit desirable melt strength, fiber mechanical strength, and fiber spinning properties. As used herein, “polydispersity index” is meant to represent the value obtained by dividing the weight average molecular weight of a polymer by the number average molecular weight of the polymer. The number average molecular weight for polymers or polymer blends can be determined by methods known to those skilled in the art. In general, if the polydispersity index value of an aliphatic polyester polymer is too high, a thermoplastic composition comprising that aliphatic polyester polymer may be difficult to process due to inconsistent processing properties caused by polymer segments comprising low molecular weight polymers that have lower melt strength properties during spinning. Thus, it is desired that the aliphatic polyester polymer exhibits a polydispersity index value that is beneficially between about 1to about 15, more beneficially between about 1 to about 4, and suitably between about 1 to about 3.

It is generally desired that the aliphatic poiyester : polymer be melt processable. It is therefore desired that the aliphatic polyester polymer exhibit a melt flow rate that is beneficially between about 1 gram per 10 minutes to about 200 grams per 10 minutes, suitably between about 10 grams per 10 minutes to about 100 grams per 10 minutes, and more suitably between about 20 grams per 10 minutes to about 40 grams per 10 minutes. The melt flow rate of a material may be determined, for example, according to ASTM Test Method D1238-E, incorporated in its entirety herein by reference.

In the present invention, it is desired that the aliphatic polyester polymer be substantially biodegradable. As a result, the nonwoven material comprising the thermoplastic composition will be substantially degradable when disposed of to the environment and exposed to air and/or water. As used herein, “biodegradable” is meant to represent that a material degrades from the action of naturally occurring microorganisms such as bacteria, fungi, and algae. The biodegradability of a material may be determined using

ASTM Test Method 5338.92 or ISO CD Test Method 14855, each incorporated in their entirety herein by reference. In one particular embodiment, the biodegradability of a material may be determined using a modified ASTM Test Method 5338.92, wherein the test chambers are maintained at a constant temperature of about 58°C throughout the testing rather than using an incremental temperature profile.

In the present invention, it is also desired that the aliphatic polyester polymer be substantially compostable. As a result, the nonwoven material comprising the aliphatic polyester polymer will be substantially compostable when disposed of to the environment and exposed to air and/or water. As used herein, “compostable” is meant to represent that a material is capable of undergoing biological decomposition in a compost site such that the material is not visually distinguishable and breaks down into carbon dioxide, water, inorganic compounds, and biomass, at a rate consistent with known compostable materials.

The second component in the thermoplastic composition is a multicarboxylic acid. A multicarboxylic acid is any acid that comprises two or more carboxylic acid groups. In one embodiment of the present invention, it is preferred that the multicarboxylic acid be linear. Suitable for use in the present invention are dicarboxylic acids, which comprise two carboxylic acid groups. It is generally desired that the multicarboxylic acid have a total number of carbons that is not too large because then the crystallization kinetics, the speed at which crystallization occurs of a fiber or nonwoven structure prepared from a thermoplastic composition of the present invention, could be slower than is desired. It is therefore desired that the multicarboxylic acid have a total of carbon atoms that is beneficially less than about 30, more beneficially between about 4 to about 30, suitably between about 5 to about 20, and more suitably between about 6 to about 10.

Suitable multicarboxylic acids include, but are not limited to, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and mixtures of such acids.

It is generally desired that the multicarboxylic acid be present in the thermoplastic composition in an amount effective to result in the thermoplastic composition exhibiting desired properties.

The multicarboxylic acid will be present in the thermoplastic composition in a weight amount that is greater than 0 weight percent, beneficially between greater than 0 weight percent to about

30 weight percent, more beneficially between about 1 weight percent to about 30 weight percent, suitably between about 5 weight percent to about 25 weight percent, more suitably between about 5 weight percent to about 20 weight percent, and most suitably between about 5 weight percent to about 15 weight percent, wherein all weight percents are based on the total weight amount of the aliphatic polyester polymer, the multicarboxylic acid, and the wetting agent present in the thermoplastic composition.

In order for a thermoplastic composition used in the present invention to be processed into a nonwoven material that exhibits the properties desired in the present invention, it has been discovered that it is generally desired that the multicarboxylic acid beneficially exists in a liquid state during thermal processing of the thermoplastic composition but that during cooling of the processed thermoplastic composition, the multicarboxylic acid turns into a i solid state, or crystallizes, before the aliphatic polyester polymer turns into a solid state, or crystallizes.

In the thermoplastic composition, the multicarboxylic acid is believed to perform two important, but distinct, functions.

First, when the thermoplastic composition is in a molten state, the multicarboxylic acid is believed to function as a process lubricant or plasticizer that facilitates the processing of the thermoplastic composition while increasing the flexibility and toughness of a nonwoven material through internal modification of the aliphatic polyester polymer. While not intending to be bound hereby, it is ~~ - ~ . . believed that .the multicarboxylic acid replaces the secondary valence bonds holding together the aliphatic polyester polymer chains with multicarboxylic acid-to-aliphatic polyester polymer valence bonds, thus facilitating the movement of the polymer chain segments. With this effect, the torque needed to turn an extruder is generally dramatically reduced as compared with the processing of the aliphatic polyester polymer alone. In addition, the process temperature required to spin the thermoplastic composition the nonwoven material is generally dramatically reduced, thereby decreasing the risk for thermal degradation of the aliphatic polyester polymer while also reducing the amount and rate of cooling needed for the nonwoven material prepared. Second, when the nonwoven material is being cooled and solidified from its liquid or molten state,

oo WO 01734215 PCT/US00/42001 the multicarboxylic acid is believed to function as a nucleating agent. Aliphatic polyester polymers are known to have a very slow crystallization rate. Traditionally, there are two major ways to resolve this issue. One is to change the cooling temperature profile in order to maximize the crystallization kinetics, while the other is to add a nucleating agent to increase the sites and degree of crystallization.

The process of cooling an extruded polymer to ambient temperature is usually achieved by blowing ambient or sub- ambient temperature air over the extruded polymer. Such a process can be referred to as quenching or super-cooling because the change in temperature is usually greater than 100° C and most often greater than 150° C over a relatively short time frame (seconds). By reducing the melt viscosity of a polymer, such polymer may generally be extruded successfully at lower temperatures. This will generally reduce the temperature change needed upon cooling, to preferably be less than 150° C and, in : some cases, less than 100° C. To customize this common process 8 further into the ideal cooling temperature profile needed to be the sole method of maximizing the crystallization kinetics of aliphatic polyesters in a real manufacturing process is very difficult because of the extreme cooling needed within a very short period of time.

Standard cooling methods can be used in combination with a second method of modification, though. The traditional second method is to have a nucleating agent, such as solid particulates, mixed with a thermoplastic composition to provide sites for initiating crystallization during quenching. However, such solid nucleating agents generally agglomerate very easily in the thermoplastic composition which can result in the blocking of filters and spinneret holes during spinning. In addition, the nucleating affect of such solid nucleating agents usually peaks at add-on levels of about 1 percent of such solid nucleating agents. Both of these factors generally reduce the ability or the desire to add in high weight percentages of such solid nucleating agents into the thermoplastic composition. In the processing of the thermoplastic composition, however, it has been found that the multicarboxylic acid generally exists in a liquid state during the extrusion process, wherein the multicarboxylic acid functions as a plasticizer, while the multicarboxylic acid is still able to solidify or crystallize before the aliphatic polyester during cooling, wherein the multicarboxylic acid functions as a nucleating agent. It is believed that upon cooling from the homogeneous melt, the multicarboxylic acid solidifies or crystallizes relatively more quickly and completely just as it falls below its melting point since it is a relatively small molecule. For example, adipic acid has a melting temperature of about 162° C and a crystallization temperature of about 145° C.

The aliphatic polyester polymer, being a macromolecule, has a relatively very slow crystallization rate which means that when cooled it generally solidifies or crystallizes more slowly and at a temperature lower than its melting temperature.

During such cooling, then, the multicarboxylic acid starts to crystallize before the aliphatic polyester polymer and generally acts as solid nucleating sites within the cooling thermoplastic composition.

Another major difficulty encountered in the thermal processing of aliphatic polyester polymers into nonwoven materials : is the sticky nature of these polymers. Attempts to draw the fibers, either mechanically, or through an air drawing process, will often result in the aggregation of the fibers into a solid mass. It is generally known that the addition of a solid filler will in most cases act to reduce the tackiness of a polymer melt. However, the use of a solid filler can be problematic in a nonwoven application were a polymer is extruded through a hole with a very small diameter.

This is because the filler particles tend to. clog spinneret holes and filter screens, thereby interrupting the fiber spinning process. In the present invention, in contrast, the multicarboxylic acid generally remains a liquid during the extrusion process, but then solidifies almost immediately during the quench process. Thus, the multicarboxylic acid effectively acts as a solid filler, enhancing the overall crystallinity of the system and reducing the tackiness of the fibers and eliminating problems such as fiber aggregation during drawing.

It is desired that the multicarboxylic acid have a high level of chemical compatibility with the aliphatic polyester polymer that the multicarboxylic acid is being mixed with. While the prior art generally demonstrates the feasibility of a polylactide-adipic acid mixture, a unique feature was discovered in this invention. A polylactide-adipic acid mixture can generally only be blended with a relatively minor amount of a wetting agent, such as less than about two weight percent of a wetting agent, and, even then, only with extreme difficulty. Polybutylene succinate, polybutylene succinate- co-adipate, and polycaprolactone have been found to be very compatible with large quantities of both a multicarboxylic acid and a wetting agent. The reason for this is believed to be due to the chemical structure of the aliphatic polyester polymers. Polylactide polymer has a relatively bulky chemical structure, with no linear portions that are longer than CH, In other words, each CH, segment is connected to carbons bearing either an oxygen or other side chain. Thus, a multicarboxylic acid, such as adipic acid, can not align itself close to the polylactide polymer backbone. In the case of polybutylene succinate and polybutylene succinate-co-adipate, the polymer backbone has the repeating units (CH,), and (CH,), within its structure. Polycaprolactone has the repeating unit (CH,);. These : relatively long, open, linear portions that are unhindered by oxygen - atoms and bulky side chains align well with a suitable multicarboxylic acid, such as adipic acid, which also has a (CH,), unit, thereby allowing very close contact between the multicarboxylic acid and the suitable aliphatic polyester "polymer molecules. This excellent compatibility between the multicarboxylic acid and the aliphatic polyester polymer in these special cases has been found to relatively easily allow for the incorporation of a wetting agent, the third component in the present invention. Such suitable compatibility is evidenced by the ease of compounding and fiber or nonwoven production of mixtures containing polybutylene succinate, polybutylene succinate-co-adipate, polycaprolactone, or a blend or copolymer of these polymers with suitable multicarboxylic acids and wetting agents. The processability of these mixtures is excellent, while in the case of a polylactide-multicarboxylic acid system, a wetting agent can generally not be easily incorporated into the mixture.

Either separately or when mixed together, a polybutylene succinate polymer, a polybutylene succinate-co-adipate polymer, a polycaprolactone polymer, a mixture of such polymers, or a copolymer of such polymers are generally hydrophobic. Since it is desired that the nonwoven materials prepared from the thermoplastic composition generally be hydrophilic, it has been found that there is a need for the use of another component in the thermoplastic composition to achieve the desired properties. As such, the thermoplastic composition preferably includes a wetting agent.

Thus, the third component in the thermoplastic composition is a wetting agent for the polybutylene succinate polymer, polybutylene succinate-co-adipate polymer, polycaprolactone polymer, a mixture of such polymers, and/or a copolymer of such polymers. Wetting agents suitable for use in the present invention will generally comprise a hydrophilic section which will generally be compatible with the hydrophilic sections of polybutylene succinate polymer, a polybutylene succinate-co-adipate polymer, a polycaprolactone polymer, a mixture of such polymers, or a copolymer of such polymers and a hydrophobic section which will generally be compatible with the hydrophobic sections of polybutylene succinate poiymer, a polybutylene succinate-co-adipate polymer, a polycaprolactone polymer, a mixture of such polymers, or a copolymer of such polymers. These hydrophilic and hydrophobic sections of the wetting agent will generally exist in separate blocks so that the overall wetting agent structure may be di-block or random block. A wetting agent with a melting temperature below, or only slightly above, that of the aliphatic polyester polymer is preferred so that during the quenching process ~~ _ the wetting agent remains liquid after the aliphatic polyester polymer has crystallized. This will generally cause the wetting agent to migrate to the surface of the prepared fibrous structure, thereby improving wetting characteristics and improving processing of the fibrous structure. It is then generally desired that the wetting agent serves as a surfactant in a nonwoven material processed from the thermoplastic composition by modifying the contact angle of water in air of the processed material. The hydrophobic portion of the wetting agent may be, but is not limited to, a polyolefin such as polyethylene or polypropylene. The hydrophilic portion of the wetting agent may contain ethylene oxide, ethoxylates, glycols, alcohols or any combinations thereof. Examples of suitable wetting agents include UNITHOX®480 and UNITHOX®750 ethoxylated alcohols, or UNICID™ acid amide ethoxylates, all available from

Petrolite Corporation of Tulsa, Oklahoma.

Other suitable surfactants can, for example, include one or more of the following: a. surfactants composed of silicone glycol copolymers, such as D193 and D1315 silicone glycol copolymers, which are available from Dow Corning Corporation, located in

Midland, Michigan. b. ethoxylated alcohols such as GENAPOL™ 24-

L-60, GENAPOL'™ 24-1.-92, or GENAPOL™ 24-[-93N ethoxylated alcohols, which may be obtained from Hoechst

Celanese Corp., of Charlotte, North Carolina.

C. surfactants composed of ethoxylated mono- and diglycerides, such as MAZOL™ 80 MGK ethoxylated diglycendes, which is available from PPG Industries, Inc., of Gurnee, Illinois. d. surfactants composed of carboxylated alcohol ethoxylates, such as SANDOPAN™ DTC, SANDOPAN™ KST, or SANDOPAN™ DTC-100 carboxylated alcohol ethoxylates, which may be obtained from Sandoz Chemical Corp. e. ethoxylated fatty esters such as TRYLON™ 5906 and TRYLONTM 5909 ethoxylated fatty esters, which may be obtained from Henkel Corp./Emery Grp. of Cincinnati, Ohio.

It is generally desired that the wetting agent exhibit a weight average molecular weight that is effective for the thermoplastic composition to exhibit desirable melt strength, fiber mechanical strength, and fiber spinning properties. In general, if the weight average molecular weight of a wetting agent is too high, the wetting agent will not blend well with the other components in the thermoplastic composition because the wetting agent's viscosity will be so high that it lacks the mobility needed to blend. Conversely, ff the weight average molecular weight of the wetting agent is too low, this represents that the wetting agent will generally not blend well with the other components and have such a low viscosity that it causes processing problems. Thus, wetting agents suitable for use in the present invention exhibit weight average molecular weights that are beneficially between about 1,000 to about 100,000, suitably between about 1,000 to about 50,000, and more suitably between about 1,000 to about 10,000. The weight average molecular weight

Claims (46)

CLAIMS What is claimed is:

1. A biodisintegratable nonwoven material comprising a plurality of fibers of a thermoplastic composition, wherein the thermoplastic composition comprises: a 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, wherein the aliphatic polyester polymer exhibits a weight average molecular weight that is between about 10,000 to about 2,000,000, wherein the aliphatic polyester polymer is present in the thermoplastic composition in a weight amount that is between about 40 to less than 100 weight percent;

b. a multicarboxylic acid having a total of carbon atoms that is less than about 30, wherein the multicarboxylic acid is present in the thermoplastic composition in a weight amount that is between greater than 0 weight percent to about 30 weight percent; and

C. a wetting agent, which exhibits a hydrophilic- lipophilic balance ratio that is between about 10 to about 40, in a weight amount that is greater than 0 to about 25 weight percent, wherein all weight percents are based on the total weight amount of the aliphatic polyester polymer, the multicarboxylic acid, and the wetting agent present in the thermoplastic composition; wherein the thermoplastic composition exhibits an Apparent Viscosity value at a temperature of about 170°C and a shear rate of about 1000 seconds” that is between about 5 Pascal seconds and about 200 Pascal seconds.

2. The biodisintegratable nonwoven material of Claim I, wherein the aliphatic polyester polymer is a polybutylene succinate polymer.

3. The biodisintegratable nonwoven material of Claim 1, wherein the aliphatic polyester polymer is a polybutylene succinate- co-adipate polymer.

4. The biodisintegratable nonwoven material of Claim 1, wherein the aliphatic polyester polymer is a polycaprolactone polymer.

5. The biodisintegratable nonwoven material of Claim I, wherein the aliphatic polyester polymer is present in the thermoplastic composition in a weight amount that is between about 50 weight percent to about 95 weight percent.

6. The biodisintegratable nonwoven material of Claim 5, wherein the aliphatic polyester polymer 1s present in the thermoplastic composition in a weight amount that 1s between about 60 weight percent to about 90 weight percent.

7. The biodisintegratable nonwoven material of Claim I, wherein the multicarboxylic acid is selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and a mixture of such acids.

8. The biodisintegratable nonwoven material of Claim 7, wherein the multicarboxylic acid is selected from the group consisting of glutaric acid, adipic acid, and suberic acid.

9. The biodisintegratable nonwoven material of Claim 1, wherein the multicarboxylic acid is present in the thermoplastic composition in a weight amount that is between about 1 weight percent to about 30 weight percent.

10. The biodisintegratable nonwoven material of Claim 9, wherein the multicarboxylic acid is present in the thermoplastic composition in a weight amount that is between about 5 weight percent to about 25 weight percent.

11. The biodisintegratable nonwoven material of Claim I, wherein the multicarboxylic acid has a total of carbon atoms that is between about 4 to about 30.

12. The biodisintegratable nonwoven material of Claim 1, wherein the wetting agent exhibits a hydrophilic-lipophilic balance ratio that is between about 10 to about 20.

13. The biodisintegratable nonwoven material of Claim 1, wherein the wetting agent is present in the thermoplastic composition in a weight amount that is between about 0.5 weight percent to about 20 weight percent.

14. The biodisintegratable nonwoven material of Claim 1, wherein the wetting agent is present in the thermoplastic composition in a weight amount that is between about ! weight percent to about 15 weight percent.

15. The biodisintegratable nonwoven material of Claim 1, wherein the wetting agent is selected from the group consisting of ethoxylated alcohols, acid amide ethoxylates, and ethoxylated alkyl phenols.

16. The biodisintegratable nonwoven material of Claim 1, wherein the aliphatic polyester polymer is present in the thermoplastic composition in a weight amount that is between about 50 weight percent to about 95 weight percent, the multicarboxylic acid is selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and a mixture of such acids and is present in the thermoplastic composition in a weight amount that is between about 1 weight percent to about 30 weight percent, and the wetting agent is selected from the group consisting of ethoxylated alcohols, acid amide ethoxylates, and ethoxylated alkyl phenols and is present in the thermoplastic composition in a weight amount that is between about 0.5 weight percent to about 20 weight percent.

17. A biodisintegratable nonwoven material comprising a plurality of multicomponent fibers, wherein the multicomponent fibers are prepared from a thermoplastic composition, wherein the thermoplastic composition comprises:

a. 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, wherein the aliphatic polyester polymer exhibits a weight average molecular weight that is between about 10,000 to about 2,000,000, wherein the aliphatic polyester polymer is present in the thermoplastic composition in a weight amount that is between about 40 to less than 100 weight percent;

b. a multicarboxylic acid having a total of carbon atoms that is less than about 30, wherein the multicarboxylic acid is present in the thermoplastic composition in a weight amount that is between greater than 0 weight percent to about 30 weight percent; and

C. a wetting agent, which exhibits a hydrophilic- lipophilic balance ratio that is between about 10 to about 40, in a weight amount that is greater than 0 to about 25 weight percent, wherein all weight percents are based on the total weight amount of the aliphatic polyester polymer, the multicarboxylic acid, and the wetting agent present in the thermoplastic composition. wherein the fiber exhibits an Advancing Contact Angle value that is less than about 70 degrees and a Receding Contact Angle value that is less than about 60 degrees.

18. The biodisintegratable nonwoven material of Claim 17, wherein the aliphatic polyester polymer is present in the thermoplastic composition in a weight amount that is between about 50 weight percent to about 95 weight percent.

19. The biodisintegratable nonwoven material of Claim 18, wherein the aliphatic polyester polymer is present in the thermoplastic composition in a weight amount that is between about 60 weight percent to about 90 weight percent.

20. The biodisintegratable nonwoven material of Claim 17, wherein the multicarboxylic acid is selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and a mixture of such acids.

21. The biodisintegratable nonwoven material of Claim 20, wherein the multicarboxylic acid is selected from the group consisting of glutaric acid, adipic acid, and suberic acid.

22. The biodisintegratable nonwoven material of Claim 17, wherein the multicarboxylic acid is present in the thermoplastic composition in a weight amount that is between about 1 weight percent to about 30 weight percent.

23. The biodisintegratable nonwoven material of Claim 22, wherein the multicarboxylic acid is present in the thermoplastic composition in a weight amount that is between about 5 weight percent to about 25 weight percent.

24. The biodisintegratable nonwoven material of Claim 17, wherein the multicarboxylic acid has a total of carbon atoms that is 3 between about 4 to about 30.

25. The biodisintegratable nonwoven material of Claim 17, wherein the wetting agent exhibits a hydrophilic-lipophilic balance ratio that is between about 10 to about 20.

26. The biodisintegratable nonwoven material of Claim 17, wherein the wetting agent is present in the thermoplastic composition in a weight amount that 1s between about 0.5 weight percent to about 20 weight percent. RE

27. The biodisintegratable nonwoven material of Claim 26, wherein the wetting agent is present in the thermoplastic composition in a weight amount that is between about 1 weight percent to about 15 weight percent.

28. The biodisintegratable nonwoven material of Claim 17, wherein the wetting agent is selected from the group consisting of ethoxylated alcohols, acid amide ethoxylates, and ethoxylated alkyl phenols.

29. The biodisintegratable nonwoven material of Claim 17, wherein the fiber exhibits an Advancing Contact Angle value that is less than about 65 degrees.

v WO 01/34215 PCT/US00/42001

30. The biodisintegratable nonwoven material of Claim 17, wherein the fiber exhibits a Receding Contact Angle value that is less than about 55 degrees.

31. The biodisintegratable nonwoven material of Claim 17, wherein the fiber exhibits a Receding Contact Angle value that is less than about 50 degrees.

32. The biodisintegratable nonwoven material of Claim 17, wherein the aliphatic polyester polymer is present in the thermoplastic composition in a weight amount that is between about 50 weight percent to about 95 weight percent, the multicarboxylic acid is selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and a mixture of such acids and is present in the thermoplastic composition in a weight amount that is between about 1 weight percent to about 30 weight percent, and the wetting agent is selected from the group consisting of ethoxylated alcohols, acid amide ethoxylates, and ethoxylated alkyl phenols and is present in the thermoplastic composition in a weight amount that is between about 0.5 weight percent to about 20 weight percent.

33. The biodisintegratable nonwoven material of Claim 17, wherein the aliphatic polyester polymer is polybutylene succinate polymer, the multicarboxylic acid is adipic acid, and the wetting agent is an ethoxylated alcohol.

34, The biodisintegratable nonwoven material of Claim 17, wherein the aliphatic polyester polymer is polybutylene succinate- co-adipate polymer, the multicarboxylic acid is adipic acid, and the wetting agent is an ethoxylated alcohol.

35. The biodisintegratable nonwoven material of Claim 17, wherein the aliphatic polyester polymer is a mixture of polybutylene succinate polymer and polybutylene succinate-co-adipate polymer, the multicarboxylic acid is adipic acid, and the wetting agent is an ethoxylated alcohol.

36. The biodisintegratable nonwoven material of Claim 17, wherein the aliphatic polyester polymer is a mixture of polybutylene succinate polymer and polybutylene succinate-co-adipate polymer, the multicarboxylic acid is glutaric acid, and the wetting agent is an ethoxylated alcohol.

37. The biodisintegratable nonwoven material of Claim 17, wherein the aliphatic polyester polymer is a mixture of polybutylene succinate polymer and polybutylene succinate-co-adipate polymer, the multicarboxylic acid is suberic acid, and the wetting agent is an ethoxylated alcohol.

38. The biodisintegratable nonwoven material of Claim 17, wherein the aliphatic polyester polymer is polycaprolactone polymer, the multicarboxylic acid is adipic acid, and the wetting agent is an ethoxylated alcohol.

39. A biodisintegratable nonwoven material comprising a ] plurality of multicomponent fibers, wherein the multicomponent fibers exhibit an Advancing Contact Angie value that is less than about 70 degrees and a Receding Contact Angle value that is less than about 60 degrees.

40. A disposable absorbent product comprising a liquid- permeable topsheet, an absorbent structure, and a liquid- impermeable backsheet, wherein at least one of the liquid-permeable . topsheet or the liquid-impermeable backsheet comprises the biodisintegratable nonwoven material of Claim 1.

wwe... - 4L- - - The disposable absorbent product of Claim 40, wherein the liquid-permeable topsheet and the liquid-impermeable backsheet comprise the biodisintegratable nonwoven material.

42. The disposable absorbent product of Claim 40, further comprising a fluid acquisition layer.

43. The disposable absorbent product of Claim 42, wherein the liquid-permeable topsheet, the fluid acquisition layer, and the liquid-impermeable backsheet comprise the biodisintegratable nonwoven material.

v WO 01/34215 PCT/US00/42001

44. A disposable absorbent product comprising a liquid- permeable topsheet, an absorbent structure, and a liquid- impermeable backsheet, wherein at least one of the liquid-permeable topsheet or the liquid-impermeable backsheet comprises the biodisintegratable nonwoven material of Claim 17.

45. The disposable absorbent product of Claim 44, further comprising a fluid acquisition layer.

46. The disposable absorbent product of Claim 45, wherein the liquid-permeable topsheet, the fluid acquisition layer, and the liquid-impermeable backsheet comprise the biodisintegratable nonwoven material.