MX2008007608A - Biodegradable continuous filament web - Google Patents

Abstract

A biodegradable nonwoven web comprising substantially continuous multicomponent filaments is provided. The filaments comprise a first component and a second component. The first component contains at least one high-melting point aliphatic polyester having a melting point of from about 160°C to about 250°C and the second component contains at least one low-melting point aliphatic polyester. The melting point of the low-melting point aliphatic polyester is at least about 30°C less than the melting point of the high-melting point aliphatic polyester. The low-melting point aliphatic polyester has a number average molecular weight of from about 30,000 to about 120,000 Daltons, a glass transition temperature of less than about 25°C, and an apparent viscosity of from about 50 to about 215 Pascal-seconds, as determined at a temperature of 160°C and a shear rate of 1000 sec-1.

Description

FABRIC OF CONTINUOUS FILAMENTS BIODEGRADABLE Related Requests The present application is a continuation in part of International Application number PCT / US2005 / 046178, filed at the reception office of the United States of America on December 15, 2005.

Background of the Invention Several attempts have been made to form non-woven fabrics of biodegradable polymers. Even when fibers prepared from biodegradable polymers are known, problems have been encountered with their use. For example, polylactic acid (PLA) is one of the most common biodegradable and sustained (renewable) polymers. Unfortunately, non-woven fabrics of polylactic acid generally have a low bond flexibility and high roughness due to the high glass transition temperature and low crystallization rate of polylactic acid. In turn, non-woven fabrics of thermally bonded polylactic acid often exhibit low elongation which is not acceptable in certain applications, such as in absorbent articles. Likewise, although the polylactic acid can withstand high removal rates, it requires high levels of extraction energy to achieve the necessary crystallization to withstand heat shrinkage. Other biodegradable polymers, such as polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT) and polycaprolactone (PCL), have a low glass transition temperature and similar characteristic of softness to polyethylene. However, these polymers typically have a small binding window, which leads to difficulty in forming a non-woven fabric from such polymers at high speeds.

As such, there is currently a need for a nonwoven fabric that is biodegradable and exhibits good mechanical properties.

Synthesis of the Invention In accordance with an embodiment of the present invention, a biodegradable nonwoven fabric is described comprising multi-component filaments. Multi-component filaments contain a primer component and a second component. The first component contains a first aliphatic polyester having a melting point from about 160 degrees centigrade to about 250 degrees centigrade and the second component containing a second aliphatic polyester. The melting point of the second aliphatic polyester is at least about 30 degrees centigrade lower than the melting point of the first aliphatic polyester. The second aliphatic polyester has an average molecular weight number from about 30,000 to about 120,000 daltons, a glass transition temperature of less than about 25 degrees centigrade, and an apparent viscosity from about 50 to about 215 pascal per second, as determined at a temperature of 160 degrees centigrade and at a cut-off rate of 1000 seconds "1.

In accordance with another embodiment of the present invention, a biodegradable nonwoven fabric is described comprising substantially continuous multi-component filaments. The filaments comprise a first component and a second component, the first component contains a first aliphatic polyester and the second component contains a second aliphatic polyester.

The melting point of the first component is from about 160 degrees centigrade to about 250 degrees centigrade, and the melting point of the second component is at least about 30 degrees centigrade less than the melting point of the first component. The second aliphatic polyester has an average molecular weight number from about 30,000 to about 120,000 daltons, a glass transition temperature of less than about 25 degrees centigrade, and an apparent viscosity from about 50 to about 21 5. pascals per second, as determined by a temperature of 160 degrees centigrade and a cut-off rate of 1000 seconds "1.

Other features and aspects of the present invention are described in greater detail below.

Brief Description of the Drawings A complete and authoritative description of the present invention including the best mode thereof, addressed to one skilled in the art, is pointed out more particularly in the remainder of the specification, which refers to the accompanying figures in which: Figure 1 is a schematic illustration of a process that can be used in an embodiment of the present invention to form a non-woven fabric; Figure 2 shows a photomicrograph SE (40X) of sample number 3 formed in Example 2; Figure 3 shows a SEM (40X) microphotograph of sample number 4 formed in Example 2; Figure 4 shows a SEM (40X) microphotograph of sample number 13 formed in Example 2; Figure 5 shows a SEM photomicrograph (40X) of sample number 11 formed in Example 2; Figure 6 shows an SEM microphotograph (40X) of sample number 12 formed in Example 2; Y Figure 7 is a perspective view of an absorbent article that can be formed in accordance with an embodiment of the present invention.

The repeated use of reference characters in the present specification and drawings is intended to present the same or analogous features or elements of the invention.

Detailed Description of Representative Incorporations Reference will now be made in detail to various embodiments of the invention, one or more examples of which will be noted below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the scope or spirit of the invention. For example, features illustrated or described as part of an embodiment may be made in another embodiment to produce yet another embodiment. Therefore, it is the intention that the present invention cover such modifications and variations as they come into contact with the appended claims and their equivalents.

Definitions As used herein, the term "biodegradable" or "biodegradable polymer" generally refers to a material that degrades from the action of naturally occurring microorganisms, such as bacteria, fungi, and algae, environmental heat, moisture, or other environmental factors. The biodegradation of a material can be determined using the Test Method of the American Society for Testing and Materials (ASTM) number 5338.92.

As used herein, the term "continuous filament fabric" generally refers to a nonwoven fabric containing substantially continuous filaments. The filaments may, for example, have a length much larger than their diameter, such as a length to diameter ratio ("aspect ratio") of greater than about 15,000 to 1, and in some cases greater than about 50,000 to 1.

As used herein, the term "non-woven fabric" refers to a fabric that has a structure of individual fibers (e.g., fibers or filaments) that are between placed randomly, but not in an identifiable manner, or repeated way. Non-woven fabrics include, but are not limited to, meltblowing, hydroentanglement processes, air placement, spinning processes, and bonded and bonded fabric processes. The basis weight of the non-woven fabrics can generally vary, but is typically from about 5 grams per square meter to 200 grams per square meter, in some embodiments from about 10 grams per square meter to about 150 grams per square meter, and in some additions from around 15 grams per square meter to around 100 grams per square meter.

As used herein, the term "meltblown fibers" means the fibers formed by the extrusion of a molten thermoplastic material through a plurality of thin and usually circular capillary matrix vessels with strands or filaments fused into gas jets. heated at high speed (for example, air) and converging that attenuate the filaments of molten thermoplastic material to reduce its diameter, which can be to a micro-fiber diameter. After this, the melt blown fibers are carried by the high speed gas jet and are deposited on a collecting surface to form a fabric of blown fibers with fusion dispersed at random. Such a process is described in US Pat. No. 3,849,241 issued to Butin et al. Melt-blown fibers are micro-fibers that can be continuous or discontinuous, are generally smaller than 10 microns in average diameter and are generally sticky when deposited on a collecting surface.

As used herein, the term "spunbonded fibers" refers to small diameter fibers that are formed by extruding a molten thermoplastic material as filaments through a plurality of fine spinner capillaries having a configuration circular or otherwise, with the diameter of the extruded filaments being rapidly reduced as, for example, in the patents of the United States of America numbers 4,340,563 granted to Appel et al., 3,692,618 granted to Dorschner et al., 3,802,817 granted to Matsuki and others, the patents of the United States of America numbers 3,338,992 and 3,341,394 granted to Kinney, 3,502,763 granted to Hartman; U.S. Patent Number 3,502,538 granted to Petersen; and the patent of the United States of America 3,542,615 granted to Dobo and others. Each of which is incorporated by reference in its entirety and in a manner consistent with this document. Yarn-bonded fibers are generally non-sticky when deposited on a collecting surface. Spunbonded fibers are generally continuous and have average diameters of less than about 40 microns, and are often from about 5 to about 20 microns.

As used herein, the term "multiple components" refers to filaments formed from at least two polymer components (e.g., bicomponent filaments).

Detailed description The present invention is directed to a continuous filament nonwoven fabric that is biodegradable. The filaments are multi-component and contain a first component formed from at least one high melt aliphatic polyester and a second component formed from at least one low melt aliphatic polyester. The first and second components can be arranged in any desired configuration to form the multiple filaments components according to the present invention. The configuration of such materials can be, for example, pod and core, side by side, slice of cake, islands in the sea, etc. The resulting multiple component, spunbonded filaments are substantially biodegradable, however readily processed into fibrous structures exhibiting good mechanical properties.

I. First Component As noted, the first multicomponent filament component is one or more biodegradable aliphatic polyesters and "high melting point". Typically, the melting point of such polyesters is from about 160 degrees centigrade to about 250 degrees centigrade, in some additions from about 170 degrees centigrade to about 240 degrees centigrade, and in some additions from about 180 degrees centigrade to around 220 degrees Celsius. Various "high melting point" aliphatic polyesters may be employed in the present invention, such as polyesteramides, modified polyethylene terephthalate, polylactic acid (PLA), terpolymers with polylactic acid base, polyglycolic acid, polyalkylene carbonates (such as polyethylene carbonate), polyhydroxyalkanoates (PHA), polyhydroxybutyrates (PHB), polyhydroxyvalerate (PHV), and polyhydroxybutyrate-hydroxyvalerate (PHBV) copolymers. The term "polylactic acid" generally refers to lactic acid homopolymers, such as poly (L-lactic acid), poly (D-lactic acid), poly (DL-lactic acid), mixtures thereof, and copolymers containing to lactic acid as the predominant component and a small proportion of a copolymerizable comonomer, such as 3-hydroxybutyrate, caprolactone, glycolic acid, etc.

Any known method of polymerization, such as polycondensation or open ring polymerization, can be used to polymerize lactic acid. In the polycondensation method, for example, the L-lactic acid, D-lactic acid, or a mixture thereof is directly subjected to dehydro-poly-condensation. In the open ring polymerization method, a lactide which is a cyclic lactic acid dimer is subjected to polymerization with the aid of a polymerization adjusting agent and a catalyst. Lactide may include L-lactide (an L-lactic acid dimer), D-lactide (a D-lactic acid dimer), DL- lactide (a condensate of L-lactic acid and D-lactic acid), or mixtures thereof. These isomers can be mixed and polymerized, if necessary, to obtain polylactic acid having any desired composition and crystallinity. A small amount of a chain extending agent (eg, diisocyanate compound, epoxy compound or anhydride acid) can also be used to increase the molecular weight of the polylactic acid. Generally speaking, the average molecular weight of polylactic acid is in the range of about 60,000 to about 1,000,000. A particularly suitable polylactic acid polymer that can be used in the present invention is commercially available from Biomer, Inc. (Germany) under the name Biomer ™ L9000. Still other suitable polylactic acid polymers are commercially available from Natureworks, LLC of Minneapolis, Minnesota.

Although not required, the high melt point aliphatic polyesters typically constitute the main ingredient of the first component. That is, aliphatic polyesters can constitute at least about 90 percent by weight, in some incorporations of at least about 92 percent by weight, and in some incorporations, of at least about 95 percent by weight of the first component. In such embodiments, the characteristics of the first component (e.g., melting point) will be substantially the same as the characteristics of the aliphatic polyesters employed. For example, the melting point of the first component can be in the range from about 160 degrees centigrade to about 250 degrees centigrade, in some additions from about 170 degrees centigrade to about 240 degrees centigrade, and in some additions, from around 180 degrees centigrade to around 220 degrees Celsius.

II. Second Component The second component is formed of one or more biodegradable "low melting point" aliphatic polyesters. Typically, such polyesters have a melting point from about 50 degrees centigrade to about 160 degrees centigrade, in some additions from about 80 degrees centigrade to about 160 degrees centigrade, and in some additions from about 100 degrees centigrade to about 140 degrees Celsius.

In addition, the melting point is also typically at least about 30 degrees centigrade, in some additions of at least about 40 degrees centigrade, and in some additions of at least about 50 degrees centigrade less than the point of melting of the "high melting point" aliphatic polyesters. "Low melting point" aliphatic polyesters are useful in that they are biodegradable at a faster rate than high melt point polyesters. In addition, they are generally softer to the touch than most "high melt point" aliphatic polyesters. The glass transition temperature ("Tg") of the low melt point polyesters may also be less than the high melt point polyesters for improved flexibility and processing of the polymers. For example, the low melt point aliphatic polyesters may have a transition temperature (Tg) of about 25 degrees centigrade or less. In some additions, around 0 degrees Celsius or less, and in some additions, around -10 degrees Celsius or less. Such glass transition temperature can be at least about 5 degrees centigrade, in some additions of at least about 10 degrees Celsius, and in some embodiments, of at least about 15 degrees Celsius less than the glass transition temperature of the high melt point polyesters.

Examples of aliphatic polyesters which may have a low melting point and glass transition temperature include aliphatic polyesters with repeated units of at least 5 carbon atoms (eg, polyhydroxyvalerate, polyhydroxybutorate-hydroxyvalerate copolymer, plicaprolactone), and aliphatic polymers with succinate base (eg, polybutylene succinate, polybutylene succinate adipate, and polyethylene succinate). More specific examples may include polyethylene oxalate, polyethylene malonate, polyethylene succinate, polypropylene oxalate, polypropylene malonate, polypropylene succinate, polybutylene oxalate, polybutylene malonate, polybutylene succinate, and mixtures and copolymers of these compounds. Among these compounds, polybutylene succinate and copolymers thereof are usually preferred.

Aliphatic polyesters are typically synthesized through the condensation polymerization of a polyol and an aliphatic dicarboxylic acid or an anhydride thereof. The polyols selected from the polyols contain from 2 to about 8 carbon atoms, the polyalkylene ether glycols contain from 2 to 8 carbon atoms, and the cycloaliphatic diols contain from about 4 to about 12 carbon atoms. Substituted polyols typically contain from 1 to about 4 substituents independently selected from halo, Ce-Cio aryl, and C?-C4 alkoxy. Examples of polyols that can be used include, but are not limited to, ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,3-butanediol, 1, - butanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene glycol, 2,2,4-trimethyl-1,6-hexanediol, thiodiethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2, 2,4,4-tetramethyl-1,3-cyclobutanediol, triethylene glycol, and tetraethylene glycol. Preferable glycols include a: 1,4-butanediol; 1,3-propanediol; ethylene glycol; 1,6-hexanediol; diethylene glycol; and 1,4-cyclohexanedimethanol. Representative aliphatic dicarboxylic acids that may be used include substituted or unsubstituted, linear or branched, non-aromatic dicarboxylic acids selected from aliphatic dicarboxylic acids containing from 2 to about 12 carbon atoms and cycloaliphatic dicarboxylic acids containing about 5 to about 10 carbon atoms. Substituted non-aromatic dicarboxylic acids typically contain from 1 to about 4 substituents selected from halo, C6-C ?aryl, and C?-C4 alkoxy. Non-limiting examples of cycloaliphatic dicarboxylic acids include malinic, succinic, glutamic, atypical, pimelic, azelaic, sebasic, fumaric, 2,2-dimethyl glutamic, suberic, 1,3-cyclopentanedicarboxylic, 1,4-cyclohexanedicarboxylic, 1, 3- cyclohexanedicarboxylic, diglycolic, itanoconic, maleic, and 2,5-norbornanedicarboxylic. The polymerization is catalyzed by a catalyst, such as a titanium-based catalyst (for example, tetraisopropylitanate, tetraisopropoxy titanium, dibutoxydiacetoacetoxy titanium, or tetrabutyltitanate).

If desired, a dissocyanate chain extender can be reactivated with the aliphatic polyester prepolymer to increase its molecular weight. Representative diisocyanates may include toluene 2, -diisocyanate, toluene 2,6-diisocyanate, 2,4 '-diphenylmethane diisocyanate, naphthylene-1, 5-diisocyanate, xylene diisocyanate, hexamethylene diisocyanate (HMDI), isophorone diisocyanate and methylenebis (2- isocyanatocyclohexane). Trifunctional isocyanate compounds can also be used which contain isocyanurate and / or biurea groups with a functionality of not less than three, or to replace the diisocyanate compounds partially with tri or polyisocyanates. The preferred diisocyanate is hexamethylene diisocyanate. The amount of chain extender used is typically from about 0.3 to about 3.5 percent by weight, in some embodiments, from about 0.5 to about 2.5 percent by weight based on the percent of the total weight of the polymer.

The aliphatic polymers may already be a linear polymer or a long chain branched polymer. The long chain branched polymers are generally prepared by the use of a low molecular weight branched agent, such as a polyol; polycarboxylic acid, hydroxy acid, etc. Representative low molecular weight polyols that can be used as branched agents include glycerol, trimethylolpropane, trimethylolethane, polyetherols, glycerol, 1,2,4-butanetriol, pentaerythritol, 1,2,6-hexanetriol, sorbitol, 1, 1, 4, 4-tetrakis (hydroxymethyl) cyclohexane, tri (2-hydroxyethyl) isocyanurate, and dipentaerythritol,. Representative high molecular weight polyols (weight molecular weight of 400 to 3000) which can be used as branched agents include triols derived from fused alkylene oxides having 2 to 3 carbons, such as ethylene oxide and propylene oxide with polyol initiators. Representative polycarboxylic acids which can be used as branched agents include hemimelitic acid, trimellitic acid (1, 2, 4-benzenetricarboxylic acid) and trimesic anhydride (1, 3, 5-benzenetricarboxylic acid), pyromellitic acid and benzenetetracarboxylic acid anhydride, tetracarboxylic acid bencenophenone, 1, 1, 2, 2-ethane-tetracarboxylic acid, 1, 1, 2-ethano-tricarboxylic acid, 1,3,5-pentanetricarboxylic acid, and 1,2,3,4-cyclopentanetetracarboxylic acid. Representative hydroxy acids that can be used as branching agents include malic acid, citric acid, tartaric acid, 3-hydroxyglutaric acid, mucic acid, trihydroxyglutaric acid, 4, carboxylic acid anhydride, hydroxyisophthalic acid, and 4- (beta-hydroxyethyl) phthalic acid. Such hydroxy acids contain a combination of 3 or more hydroxyl and carboxyl groups. Especially preferred branching agents include trimellitic acid, trimesic acid, pentaerythritol, trimethylol propane, and 1,2-butanetriol.

The polycaprolatone polymers can also be used in the present invention. The polycaprolactone polymers are generally prepared by the polymerization of e-caprolactone, which is a seven-membered ring compound that is characterized by its reactivity. The slit usually takes place in the carbonyl group. The higher molecular weight polycaprolactone can be prepared under the influence of a wide variety of catalysts, such as aluminum alkyls, organometallic compositions, such as Group IA, IIA, IIB, or IIIA metal alkyls, Grignard reagents, metal dialkyls Group II, calcium or other metal amides or alkyl amides, hexamonate alkali earth reactive products, alkali oxides and acetonitrile, aluminum trialkoxides, aluminum alkaline earth or boron hydrides, alkali metal or alkaline earth or alkali metals only . An initiator can also be used in the preparation of polycaprolactone, such as an aliphatic diol which forms a final terminal group. Examples of polycaprolactone polymers that may be suitable for use in the present invention include a variety of polycarprolactone polymers that are available from Union Carbide Corporation, of Somerset, New Jersey, under designation of TONE ™ Polymer P767E, and TONE ™ Polymer P787, polycaprolactone polymers.

The low melt point aliphatic polyesters described above are mainly aliphatic in nature, for example, the monomer constituents are mainly aliphatic, to optimize biodegradation. For example, low melt point aliphatic polyesters typically contain at least 50 mol%. In some embodiments, at least about 60 mol%, and in some embodiments, at least about 70 mol% aliphatic monomers. Although primarily aliphatic in nature, the low melt point polyesters may nevertheless contain a minor part of other monomer constituents, such as aromatic monomers (for example, terephthalic acid) which also improves the strength and tenacity of the filaments. When used, the aromatic monomers may, for example, constitute from about 1 mol% to about 50 mol%, in some embodiments from about 10 mol% to about 40 mol%, and in some embodiments , from about 155 mol to about 30 mol% of the low melting point aliphatic polyester. A particular example of an aliphatic polyester containing an aromatic terephthalic acid monomer (-22 mol%) constituent is available under the designation Ecoflex ™ F BX 7011 from BASF Corp. Another example of an aliphatic polyester containing a terphthalic acid monomer aromatic (~ 255 mol) constituent is available under the designation of ESPOL ™ 8060 from IRE Chemicals (of South Korea).

Regardless of their particular type, current inventors have discovered that aliphatic polyesters of "low melting point" having a certain combination of thermal and mechanical properties can provide improved processability and resistance to the resultant multiple component filaments. For example, aliphatic polyesters having very high molecular weight generally possess heavy chains of entangled polymer and thus result in a thermoplastic composition that is difficult to process. Conversely, aliphatic polyesters having very low molecular weight generally do not possess sufficient entanglement, which leads to a relatively weak melt strength. Thus, the "low melting point" aliphatic polyesters employed in the present invention typically have a molecular weight number average ("Mn") in the range from around 30,000 to around 120,000 daltons, in some additions from around 40,000 to around 100,000 daltons, and in some additions, from around 45,000 to around 85,000 daltons. Likewise, the "low melting point" aliphatic polyesters also typically have an average molecular weight ("Mw") in the range from about 30,000 to about 240,000 daltons. In some additions from around 50,000 to around 190,000 daltons, and in some additions from around 60,000 to around 105,000 daltons. The molecular weight distribution of the selected polymers is also relatively narrow to improve polymer processing and provide more consistency properties. That is, the ratio of the weight of the average molecular weight to the average molecular weight number ("Mw / Mn"), for example, the "poly dispersion index", is relatively low. For example, the poly-dispersion index typically ranges from about 1.0 to about 3.0, in some additions from about 1.2 to about 2.0, and in some additions, from about 1.4 to about 1.8. The weight and number of average molecular weights can determined by methods known to those skilled in the art.

To provide improved processing, the "low melting point" aliphatic polyester is also selected to have a very large apparent viscosity of an apparent viscosity which will generally be very difficult to process. On the other hand, aliphatic polyesters having very low apparent viscosity will generally result in an extruded filament lacking tensile strength and sufficient binding capacity. Therefore, in most incorporations, the "low melting point" aliphatic polyester has an apparent viscosity from about 50 to about 215 pascals per second (Pa / s), in some embodiments from about 75 to about of 200 pascals per second, and in some embodiments, from about 80 to about 150 pascals per second, as determined at a temperature of 160 degrees centigrade and a cut-off rate of 1000 seconds. "1 The present inventors have discovered that The particular combination of molecular weight and viscosity indicated above results in polymers that have improved processing capacity without adversely affecting the strength and bonding capacity of the resulting filament.

The melt flow index of the "low melting point" aliphatic polyesters can also be selected within a certain range to optimize the properties of the resulting filaments. The melt flow rate is the weight of a polymer (in grams) that can be forced through an extrusion rheometer hole (0.0825 inches in diameter) when, subjected to a force of 2160 grams in 10 minutes at 190 degrees Celsius. Generally speaking, the melt flow rate is high enough to improve the melt processing, but not high enough to interfere with the binding properties of the filaments. Thus, in most embodiments of the present invention, the "low melting point" aliphatic polyesters have a melt flow rate of from about 5 to about 200 grams per 10 minutes, in some embodiments from about 15 minutes. to about 160 grams per 10 minutes, and in some additions, from about 20 to about 120 grams per 10 minutes, measured in accordance with the test method D1238-E, from the American Society for Testing and Materials (ASTM).

The crystallinity of the aliphatic polyester also influences the properties of the resulting multi-component filaments. That is, polymers that have a higher degree of melt and crystallization enthalpy are more readily incorporated into the products of the bonded fabric. For example, such polymers are more readily able to bond at higher speeds and also have a lower degree of shrinkage, thereby improving fabric stability, tensile strength, and fabric aesthetics. Thus the aliphatic polyesters are typically selected to have a degree of crystallinity or latent heat of fusion (? Hf) of more than about 25 joules per gram ("J / g"), in some embodiments greater than about 35 joules per gram. gram, and in some additions of more than about 50 joules per gram. Likewise, aliphatic polyesters can also typically be selected to have a latent heat of crystallinity (? HC) of more than about 35 joules per gram, in some embodiments of more than 50 joules per gram, and in some additions of more than about 60 joules per gram.

A difficulty encountered in the thermal processing of the aliphatic polyester polymers in filaments is the sticky nature of these polymers. Attempts to remove the filaments, either mechanically, or through a process of air removal, often results in the addition of the filaments in a solid mass. Therefore, in accordance with the present invention, the "low melting point" aliphatic polyesters are also selected to have a relatively high crystallization temperature ("Tc"), thereby reducing stickiness. Specifically, the crystallization temperature can be in the range from about 40 degrees centigrade to about 100 degrees centigrade, in some additions from about 50 degrees centigrade to about 90 degrees centigrade, and in some additions, from about 60 degrees centigrade to around 80 degrees centigrade. As described in more detail below, the latent heat of fusion (? Hf), the latent heat of crystallization (? HC), and the temperature of crystallization can all be determined using differential scarcity calorimetry (DSC) in accordance with test D - 3417 of the American Society for Testing and Materials (ASTM).

Any of a variety of "low melting point" aliphatic polyesters may possess the desired thermal and mechanical properties referred to above. In particular embodiments of the present invention, for example, polybutylene succinate copolyesters are employed as the second component of the multicomponent filaments. A specific example of a suitable polybutylene succinate polymer is commercially available from IRE Chemicals (of South Korea) under the designation Enpol ™ G4500.

A beneficial aspect of the present invention is that the above-described thermal and mechanical properties of the "low melt point" aliphatic polyesters can be provided without the need for conventional additives. For example, many conventional biodegradable thermoplastic compositions require the use of a nucleating agent to improve processing and to facilitate crystallization during annealing. One type of such nucleating agent is a multicarboxylic acid, such as acid succinic, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebasic acid, and mixtures of such acids, as described in U.S. Patent No. 6,177,193 issued to Tsai, et al. The present inventors have discovered, however, that through the careful selection of an aliphatic polyester having certain thermal and physical properties, such nucleating agents are not necessarily required. In fact, the present inventors have discovered that excellent results can be achieved by using aliphatic polyesters as the main ingredient of the second component. That is, the aliphatic polyesters can constitute at least about 50 percent by weight, in some embodiments at least about 92 percent by weight, and in some embodiments, at least 95 percent by weight of the second component. In such embodiments, the characteristics of the second component (e.g., melting point, glass transition temperature, apparent viscosity, molecular weight, etc.) will substantially be the same as the characteristics of the aliphatic polyesters employed. For example, the melting point of the second component can be at least about 30 degrees centigrade, in some additions of at least about 40 degrees centigrade, and in some additions, at least about 50 degrees centigrade less than the melting point of the first component, and also in the range from about 50 degrees centigrade to about 160 degrees centigrade, in some incorporations from around 80 degrees centigrade to around 160 degrees centigrade, and in some additions, from around 100 degrees centigrade to around 140 degrees centigrade. However, it should be understood that nucleating agents can be used in some embodiments of the present invention. When used, however, nucleating agents are typically present in an amount of less than about 0.5 percent by weight, in some embodiments of less than about 0.25 percent by weight, and in some embodiments, less than about 0.1 percent by weight of the second component.

Even though aliphatic polyesters are the main ingredient of the second component, other ingredients can clearly be used to the second component for a variety of different reasons. For example, a wetting agent can be used in some additions of the present invention to improve the hydrophilicity of the resulting filaments. Wetting agents suitable for use in the present invention are generally compatible with the aliphatic polyesters. Examples of suitable wetting agents may include surfactants, such as the ethoxylated alcohols UNITHOX® 480 and UNITHOX® 750, or UNICID ™, ethoxylated amide acids, all available from Petrolite Corporation of Tulsa, Oklahoma. Other suitable wetting agents are described in U.S. Patent No. 6,177,193 issued to Tsai et al., Which is hereby incorporated by reference in its entirety for all relevant purposes. Still other materials that may be used include, without limitation, pigments, antioxidants, stabilizers, surfactants, waxes, flow promoters, solid solvents, plasticizers, particles, and other added materials to improve the processing of the thermoplastic composition. When used, it is normally desired that the amounts of these additional ingredients be minimized to ensure optimum compatibility and cost effectiveness. Therefore, for example, it is normally desired that such ingredients constitute less than about 10 percent by weight, in some embodiments of less than about 8 percent by weight, and in some incorporations, less than about 5 percent by weight of the second component.

III. Continuous Filament Fabrics The multi-component filaments of the present invention can constitute the entire fibrous component of the continuous filament fabric or blend with other types of fibers (eg, basic fibers, filaments, etc.). For example, additional single-component and / or multi-component synthetic fibers can be used in the non-woven fabric. Some suitable polymers that can be used to form the synthetic fibers include, but are not limited to: polyolefins, for example, polyethylene, polypropylene, polybutylene, and the like; polytetrafluoroethylene; polyesters, for example, polyethylene terephthalate and the like; polyvinyl acetate; polyvinyl chloride acetate; polyvinylmethacrylate polyvinyl; polystyrene; polyvinyl alcohol; polyurethanes; polylactic acid; and similar. If desired, the biodegradable polymers, such as poly (glycolic acid) (PGA), poly (lactic acid) (PLA), and poly (3-hydroxybutyrate) (PHB). Some examples of known synthetic fibers include bicomponent sheath fibers core available from KoSa Inc., of Charlotte, North Carolina, under the designations of T-255 and T-256, both of which use a polyolefin sheath; or the T-254, which has a low cast copolyester sheath. Still other bicomponent fibers that can be used include those available from Chisso Corporation, of Moriyama, Japan, or Fibervisions LLC, of Wilmington, Delaware. Synthetic or natural cellulose polymers can also be used, including but not limited to, cellulose esters; cellulose ethers; cellulose nitrates; cellulose acetates; butyrate cellulose acetate; ethyl cellulose; regenerated celluloses, such as viscose, rayon, etc. When mixed with other types of fibers, it is usually desired that the multi-component filaments of the present invention constitute from about 20 weight percent to about 95 weight percent, in some embodiments from about 30 weight percent. weight to about 90 percent by weight, and in some embodiments, from about 40 percent by weight to about 80 percent by weight of the total amount of fibers used in the fabric.

Any of a variety of known techniques can be employed to form the continuous filament fabric of according to the present invention. Typically, the components are extruded into separate extruders, but they can also be spun together. With reference to Figure 1, for example, an embodiment of a process 10 for forming a continuous filament fabric in accordance with the present invention is shown. As illustrated, the process 10 of this embodiment is arranged to produce a continuous, bicomponent filament fabric, although it should be understood that other embodiments are contemplated by the present invention. Process 10 employs a pair of extruders 12a and 12b to separately extrude a first component A (e.g., a "high melting point" polymer component) and a second component B (e.g., a polymer component of " high melting point "). The relative quantity of components A and B can generally vary based on the desired properties. For example, the first component A can be formed from about 5 percent by weight to about 95 percent by weight, in some embodiments from about 10 percent by weight to about 90 percent by weight, and in some embodiments , from about 15 percent by weight to about 85 percent by weight of multi-component filaments. Likewise, the second component B it can be constituted from about 5 weight percent to about 95 weight percent, in some incorporations from about 10 weight percent to about 90 weight percent, and in some incorporations from about 15 weight percent. weight to about 85 percent by weight of multi-component filaments.

The first component a is supplied in the respective extruder 12a from a first hopper 14a and the second component B is supplied in the respective extruder 12b from a second hopper 14b. Components A and B are supplied from extruders 12a and 12b ("coextruded") through the respective filament conduits and are well known to those skilled in the art. For example, the spinner 18 may include a shelter containing a spinner package having a plurality of plates stacked one on top of each other and having a pattern of apertures arranged to create flow paths to direct the polymer components A and B separately through the spinner 18. The spinner 18 also has openings arranged in one or more rows. The openings form an extrusion curtain downwards of filaments when the polymers are extruded through. The spinner 18 can be arranged to form pod / core, side-by-side, cake, or other configurations.

The process 10 also employs a tempering blower 20 positioned adjacent to the curtain of filaments extending from the spinner 18. Air from the tempering air blower 20 anneals to the filaments extending from the spinner 18. The tempering air It can be directed from one side of the filament curtain as shown in Figure 1 or from both sides of the filament curtain. A fiber take-out unit or vacuum cleaner 22 is placed below the spinner 18 and receives the hardened filaments. Fiber extruder units or vacuum cleaners for use in melt spinning polymers are well known in the art. Suitable fiber take-out units for use in the process of the present invention include a linear fiber vacuum cleaner of the type shown in U.S. Patent Nos. 3,602,817 and 3,423,255, which are hereby incorporated by reference in their entirety by reference to the same for all relevant purposes. The fiber take-out unit 22 generally includes an elongated vertical conduit through which the filaments are removed by sucking in incoming air. from the sides of the duct and flows down through the duct. A heater or blower 24 supplies sucked air to the extruder unit of the fiber 22. The suction air draws the filaments and the ambient air through the extruder unit of the fiber 22. After that, the filaments are formed into a coherent fabric structure by randomly depositing the filaments on the forming surface 26 (optionally, with the aid of a vacuum) and then joining the resulting fabric using any known technique.

To initiate the formation of the filament, the hoppers 14a and 14b are initially filled with the respective components A and B. The components A and B are melted and extruded by the respective extruders 12a and 12b through polymer conduits 16a and 16b and the spinner 18. Due to the relatively low apparent viscosity of the aliphatic polyesters used in the present invention, lower extrusion temperatures can be employed. For example, extruder 12b for Component B ("low melting point" polyester) can employ one or multiple operating zones at a temperature from about 120 degrees centigrade to about 200 degrees centigrade, in some embodiments, from around from 145 degrees Celsius to around 195 degrees Celsius. Likewise, the extruder 12a for Component A ("high melting point" polyester) can employ one or multiple zones operating at a temperature from about 160 degrees centigrade to about 250 degrees centigrade, and in some embodiments, from around 10,000 seconds "1, in some incorporations from around 500 seconds" 1, to around 5000 seconds-1, and in some additions from around 800 seconds-1 to around 1200 seconds "1.

As the extruded filaments extend below the spinner 18, a jet of air from the quenching blower 20 at least partially quenches the filaments. Such a process generally reduces the temperature of the extruded polymers to at least about 100 degrees centigrade over a relatively short time (seconds). This will generally reduce the temperature change required with cooling, preferably to be less than 150 degrees centigrade and, in some cases, less than 100 degrees centigrade. The ability to use relatively low temperature of the extruder in the present invention also allows the use of lower tempering temperatures. For example, the tempering blower may employ one or more zones of operation at a temperature from about 20 degrees centigrade to about 100 degrees centigrade, and in some additions, from about 25 degrees centigrade to about 60 degrees centigrade. After tempering, the filaments are removed in the vertical conduit of the fiber take-off unit 22 by flowing a gas such as air, from the heater or blower 24, through the fiber take-out unit. The gas flow causes the filaments to pull out or attenuate which increases the molecular orientation or crystallinity of the polymers that form the filaments. The filaments are deposited through the outer opening of the fiber take-off unit 22 and on a foraminous surface 26. Due to the high strength of the filaments of the present invention high draw rates (eg, linear velocity of the foraminous surface 26 divided by the molten pumped rate of the extruders 12a and 12b) can be employed in the present invention. For example, the take-out ratio can be from about 200: 1 to about 6000: 1, in some additions from about 500: 1 to about 5000: 1, and in some additions from about 1000: 1 to about of 4000: 1.

The desired denier of the filaments may vary depending on the desired application. Typically, the filaments are formed to have one denier per filament of less than about 6, in some incorporations of less than 3, and in some incorporations, from about 0.5 to about 3. In addition, the filaments generally have an average of diameter no greater than about 100 microns, in some incorporations from about 0.5 microns to about 50 microns, and in some incorporations, from about 4 microns to about 40 microns.

An endless foraminous forming surface 26 is placed below the fiber take-out unit 22 and receives the filaments from an exit opening. The forming surface 26 moves around guide rollers 28. A vacuum 30 is placed below the forming surface 26 to draw the filaments against the forming surface 26 and consolidate the non-woven non-woven fabric. The fabric can then be compressed by a compression roller 32.

Once formed, the non-woven fabric is then bonded using any conventional technique, such as an adhesive or autogenous (e.g., fusing and / or self-adhering the filaments without an applied external adhesive). The autogenous bond, for example, can be achieved by contacting the multifilaments while being semi-fused or sticky, or simply by mixing a glutinizing resin and / or solvent with the aliphatic polyesters used to form the filaments. Suitable autogenous joining techniques can include ultrasonic bonding, thermal bonding, air binding, etc.

In Figure 1, for example, the fabric passes through a pressure point formed between a pair of rollers 34, one or both of which are heated for melt fusing of the filaments. One or both rollers 34 may also contain intermittently raised points of attachment to provide an intermittent pattern of attachment. The pattern of raised dots is generally selected in such a way that the non-woven fabric has a total binding area of less than about 50% (as determined by conventional optical microscopic methods), and in some embodiments, of less than about 30% Likewise, the binding density is also typically greater than about 100 joints per square inch, and in some additions, from about 250 to about 500 joints per bolt per square inch. Such a combination of total bonding area and bonding density can be achieved by joining the fabric with a pin joining pattern having more than about 100 bolt joints per square inch which provides a total bonding surface area of less than about 30% when it is completely in contact with a soft anvil roller. In some embodiments, the bonding pattern may have a bolt-joint density from about 250 to about 350 joints per bolt per square inch, and a total bonding surface area from about 10% to about 25%. when contacting a soft anvil roller. Exemplary binding patterns include, for example, those described in U.S. Patent No. 3,855,046 issued to Hansen et al .; U.S. Patent No. 5,620,779 issued to Levy et al .; U.S. Patent No. 5,962,112 issued to Haynes et al .; U.S. Patent No. 6,093,665 issued to Sayovitz et al .; the design patent of the United States of America number 428,267 granted to Romano and others; and the patent of design of the United States of America number 390,708 granted to Brown which are incorporated herein in their entirety by reference to the same for all purposes.

Due to particular rheological and thermal properties of the components used to form multi-component filaments, tissue binding conditions (eg, pressure point temperature and pressure) may be selected to cause the low melting point aliphatic polyester to melt and flow without substantially melting to the high melting point aliphatic polyester. For example, the binding temperature (e.g., the temperature of the rolls 34) can be from about 50 degrees centigrade to about 160 degrees centigrade, and some additions from about 80 degrees centigrade to about 160 degrees centigrade, and in some additions, from around 100 degrees centigrade to around 140 degrees centigrade. Likewise, the pressure of the pressure point may range from about 5 to about 150 pounds per square inch, in some additions from about 10 to about 100 pounds per square inch, and in some additions from around 30 to about 60 pounds per square inch.

When bonded in this manner, the low melt point polymer can therefore form a matrix within the compacted area that substantially surrounds the high melt point polymer. Because the high melt point polymer does not substantially melt, however, retains a substantially fibrous shape. The high melt point polymer is also generally oriented within the compacted area in two or more directions due to the random manner in which the filaments are deposited. A polymer, for example, can be oriented from about 60 degrees to about 120 degrees, and in some cases, about 90 degrees, relative to another polymer within a compacted area. In this way, the high melt point polymer can impart improved strength and hardness to the resulting fabric. For example, the non-woven fabric of the present invention can exhibit a relatively high "peak load", which indicates the maximum load to be broken as expressed in units of grams-force per inch. The peak load in the machine direction of the fabric may, for example, be at least about 3000 grams force per inch, in some additions, of at least about 3500 grams force, and in some additions, of at least about 4000 grams force. The peak load in the cross machine direction can also be at least about 1200 grams per inch, in some incorporations of less than about 1.5 grams per inch force, and in some additions of about 2500 grams force per inch.

In addition to contributing to the total fabric strength, the sectioned bonding conditions can also improve other mechanical properties of the fabric. For example, even when retaining its fiber form within a compacted area, the high melt point polymer normally releases or separates from the compacted area with the application of stress, rather than fracture. By releasing such tension, the polymer can continue to function as a load bearing member even after the tissue has exhibited substantial elongation. In this regard, the non-woven fabric of the present invention is capable of exhibiting improved "peak elongation" properties, for example, the percentage of tissue elongation at its peak load. For example, the nonwoven fabric of the present invention can exhibit a peak elongation in the machine direction of at least about 10%, and some additions of around 20%, and in some additions of at least about 35%. The non-woven fabric can also exhibit a peak elongation in the transverse direction to the machine of at least about 35%, in some embodiments of at least about 45%, and in some embodiments, of at least about 50%. %. Of course, in addition to having good mechanical properties the non-woven fabric is also soft, able to hang, and tactile. In addition, the non-woven fabric has good water absorption characteristics, which facilitates its ability to use in absorbent articles.

The nonwoven fabric of the present invention can be used in a wide variety of applications. For example, as indicated above, the non-woven fabric can be used in an absorbent article. An "absorbent article" generally refers to any article capable of absorbing water or other fluids. Examples of some absorbent articles include, but are not limited to, absorbent articles for personal care, such as diapers, training underpants, absorbent underwear, incontinence articles, feminine hygiene products (eg. example, sanitary napkins), swimwear, cloths for baby cleaners, etc .; medical absorbent articles, such as garments, fenestration materials, under-pads, bed pads, bandages, absorbent covers, and medical wipes; cleaning cloths for food service; articles of clothing; etc. Suitable materials and processes for forming such absorbent articles are well known to those with skill in the ate. Typically the absorbent articles include a layer substantially impermeable to liquid (e.g., outer cover), a liquid permeable layer (e.g., side-to-body lining, emergence layer, etc.) and an absorbent core. In a particular embodiment, the non-woven fabric is used to form an outer cover of an absorbent article. For example, a film capable of breathing can be laminated to a nonwoven fabric formed in accordance with the present invention.

Various embodiments of an absorbent article that can be formed in accordance with the present invention will now be described in greater detail. For purposes of illustration only, an absorbent article is shown in Figure 7 as a diaper 101. However, as noted above, the invention can be incorporated into other types of absorbent articles, such as incontinence articles, sanitary napkins, diaper briefs, feminine pads, children's underpants, etc. In the illustrated embodiment, the diaper 101 is shown to have an hourglass shape in a non-buckled configuration. However, other shapes may be used, such as a generally rectangular, T-shaped, or I-shaped shape. As shown, the diaper 101 includes a frame 102 formed by several components, including an outer cover 117, a body side liner 105, an absorbent core 103, and an emergence layer 107. It should be understood, however, that other layers may also be used in the present invention. Likewise, one or more of the layers referred to in Figure 7 may also be removed in certain embodiments of the present invention.

The outer cover 117 is typically formed of a material that is substantially impermeable to liquids. For example, the outer cover 117 may be formed of a thin film of plastic or other flexible material impervious to liquid. In one embodiment, the outer cover 117 is formed from a film of polyethylene that has a thickness from about 0.01 millimeters to about 0.05 millimeters. The film can be impermeable to liquids, but permeable to gases and water vapor (for example, able to breathe). This allows the vapors to escape from the absorbent core 103, but still prevent the liquid exudates from passing through the outer cover 117. If a further sensation of the type of fabric is desired, the outer cover 117 may be formed of a laminate. polyolefin film to a non-woven fabric. For example, a thin stretched polypropylene film having a thickness of about 0.015 millimeters can be thermally laminated to a fabric bonded with polypropylene filament yarn. If desired, the non-woven fabric of the present invention can be used to form the outer cover 117.

The diaper 101 also includes a body-side lining 105. The body-side lining 105 is generally employed to help isolate the user's skin from liquids held in the absorbent core 103. For example, the liner 105 has a surface of view to the body that is typically docile, soft to the touch, and non-irritating to the user's skin. Typically, the lining 105 is also less hydrophilic than the absorbent core 103 in such a way that its surface remains relatively dry to the user. The liner 105 may be permeable to the liquid to allow the liquid to readily penetrate through its thickness. In a particular embodiment, the liner includes a nonwoven fabric formed in accordance with the present invention. Exemplary liner constructions containing a non-woven fabric are described in U.S. Patent Nos. 5,192,606; 5,702,377; 5,931,823; 6,060,638; and 6,150,002, as well as in the patent applications of the United States of America publication numbers 2004/0102750; 2005/0054255; and 2005/0059941, all of which are incorporated herein in their entirety by reference thereto for all purposes.

As illustrated in Figure 7, the diaper 101 may also include an emergence layer 107 that helps decelerate and diffuse loads or discharges of liquid that can readily be introduced into the absorbent core 103. Desirably, the emergence layer 107 readily accepts and they temporarily hold the liquid before releasing it into the storage or retention portions of the absorbent core 103. In the illustrated embodiment, for example, the emergence 107 is interposed between an inwardly facing surface 116 of the side-to-body lining 105 and the absorbent core 103. Alternatively, the emergence layer 107 may be located on an outward facing surface 118 of the side-to-body lining 105. The emergence layer 107 is typically constructed of materials highly permeable to liquid. Suitable materials may include porous woven materials, porous nonwoven materials, and perforated films. In a particular embodiment, the emergence layer 107 includes a nonwoven fabric formed in accordance with the present invention. Other examples of suitable emergence layers are described in U.S. Patent No. 5,486,166 issued to Ellis et al. And 5,490,846 issued to Ellis et al., Which is hereby incorporated by reference in its entirety for all. purposes.

In addition to the aforementioned components, the diaper 101 may also contain various other components as is known in the art. For example, the diaper 101 may also contain a substantially hydrophilic tissue wrapping sheet (not shown) that helps maintain the integrity of the fibrous structure of the absorbent core 103. The sheet The tissue wrapper is typically placed around the absorbent core 103 on at least the two main viewing surfaces thereof, and composed of an absorbent cellulose material such as a wet high-strength or crepe debris tissue. The tissue wrapping sheet can be configured to provide a liquid transmission layer that helps to rapidly distribute the liquid over the absorbent fiber mass of the absorbent core 103. The wrapping sheet material on one side of the absorbent fibrous mass can join the wrapping sheet located on the opposite side of the fibrous mass to effectively trap the absorbent core 103.

The diaper 101 can also include a ventilation layer (not shown) that is placed between the absorbent core 103 and the outer cover 117. When used, the ventilation layer can help insulate the outer cover 117 of the absorbent core 103, by Examples of such ventilation layers may include laminates of non-woven fabrics to a film capable of breathing, such as is described in U.S. Patent No. 6,663,611 issued to Blaney et al. others, which is incorporated here by reference to it for all purposes. Such non-woven fabrics can be formed in accordance with the present invention.

The diaper 101 may also include a pair of ears (not shown) extending from the side edges 132 of the diaper 101 in one of the waist regions. The ears can be integrally formed with a selected diaper component. For example, the ears may be integrally formed with the outer cover 117 or from the material used to provide the upper surface. In alternative configurations, the ears may be provided by members connected and assembled to the outer cover 117, the upper surface, between the outer cover 117 and the top surface, or in various other configurations. As representatively illustrated in Figure 7, diaper 101 may also include a pair of containment fins 112 that are configured to provide a barrier and to contain the lateral flow of exudates from the body. The containment fins 112 may be located along laterally opposite side edges 132 of the side-to-body liner 105 adjacent the side edges of the absorbent core 103. The containment fins 112 may extend longitudinally along the entire length of the absorbent core 103, or may only extend partially along the length of the absorbent core 103. When the containment fins 112 are shorter in length than the absorbent core 103, they may be selectively placed on either side along the side edges 132 of the diaper 101 in a crotch region 110. In one embodiment, the containment flaps 112 extend along the entire length of the absorbent core 103 to better contain the exudates of the body. . Such containment fins 112 are generally well known to those skilled in the art. For example, suitable constructions and arrangements of containment fins 112 are described in U.S. Patent No. 4,704,116 issued to Enloe, which is herein incorporated in its entirety by reference thereto for all purposes.

The diaper 101 may include various elastic or stretch-able materials, such as a pair of elastic leg members 106 attached to the side edges 132 to further prevent filtration of body exudates and to support the absorbent core 103. In addition, a pair of elastic waist members 108 can attached to the longitudinally opposite waist edges 115 of the diaper 101. The elastic leg members 106 and the waist elastic members 108 are generally adapted to closely fit around the user's legs and waist in use to maintain a positive contact relationship with the user and to effectively reduce or eliminate filtration of body exudates from diaper 101. As used herein, the terms "elastic" and "able to stretch" include any material that can stretch and return to its original shape when relaxed. Suitable polymers for forming such materials include, but are not limited to, block copolymers of polystyrene, polyisoprene, and polybutadiene; to ethylene copolymers, natural rubbers and urethanes, etc. Particularly suitable are the styrene-butadiene block copolymers sold by Kraton Polymers, of Houston, Texas, under the brand name of Kraton®. Other suitable polymers include ethylene copolymers, including without limitation ethylene vinyl acetate, ethylene methyl acrylate, ethylene ethyl acrylate, ethylene acrylic acid, ethylene-propylene copolymers capable of stretching, and combinations thereof. Also suitable co-extruded compounds of the above and stable integrated elastomeric compounds where the basic fibers of Polypropylene, polyester, cotton and other materials are integrated into a blown fabric with elastomeric melting. Certain metallocene-catalyzed or elastomeric single-site olefin polymers and copolymers are also suitable for side panels.

The diaper 101 may also include one or more fasteners 130. For example, two flexible fasteners 130 are illustrated in Figure 7 on opposite side edges of waist regions to create a waist opening and a pair of leg openings around the wearer . The shape of the fasteners 130 may generally vary, but also includes, for example, generally rectangular shapes, square shapes, circular shapes, triangular shapes, oval shapes, linear shapes, etc. The fasteners may include, for example, a hook material. In a particular embodiment, each fastener 130 includes a separate piece of hook material attached to the inner surface of a flexible backing.

The various regions and / or components of the diaper 101 can be assembled together using any known attachment mechanism, such as adhesive, ultrasonic and thermal bonds, etc. Suitable adhesives may include, for example, hot melt adhesives, pressure sensitive adhesives, etc. When used, the adhesive can be applied as a uniform layer, a patterned layer, a spray pattern, or any separate lines, swirls or dots. In the illustrated embodiment, for example, the outer cover 117 and the side-to-body lining 105 are assembled together and the absorbent core 103 using an adhesive. Alternatively, the absorbent core 103 may be connected to the outer cover 117 using conventional fasteners, such as buttons, hook-and-loop type fasteners, adhesive tape fasteners, etc. Similarly, other diaper components, such as elastic leg members 106, waist elastic members 108, and fasteners 130, may also be assembled into the diaper using any attachment mechanism.

While various configurations of a diaper have been described above, it should be understood that other diaper and absorbent article configurations are also included within the scope of the present invention. In addition, the present invention is nevertheless limited to diapers. In fact, several examples of absorbent articles are described in the patents of the United States of America numbers 5,649,916 granted to DiPalma and others; 6,110,158 granted to Kielpikowski; 6,663,611 issued to Blaney and others; which are hereby incorporated in their entirety by reference to the same for all purposes. Still other suitable articles are described in the patent application of the United States of America publication number 2004/0060112 In the name of Fell et al., As well as United States of America patents 4,886,512 issued to Damico et al .; 5,558,659 issued to Sherrod and others; 6,888,044 granted to Fell and others; and 6,511,465 granted to Freiburger and others, all of which are incorporated herein in their entirety for all purposes.

The present invention can be better understood with reference to the following examples.

Test Methods Molecular PTSO: The molecular weight distribution of a polymer was determined by gel permeation chromatography (GPC). The samples were initially prepared by the 0.5 percent by weight addition of sample polymer solutions in chloroform in 40-millimeter glass vials. For example, 0.05 ± 0.0005 grams of polymer were added to 10 milliliters of chloroform. The prepared samples were placed on an orbital shaker and agitated overnight. The dissolved sample was filtered through a 0.45 micron PTFE membrane and analyzed using the following conditions: Columns: Styragel HR 1,2,3,4,5 & 5E (5 in series) at 41 degrees Celsius Solvent / Solvent: Chloroform at 1-0 milliliter per minute HPLC: Waters 600E gradient pump and controller, Waters 717 self-sampling Detector: Waters 2414 Refractor Differential at sensitivity = 30, at 40 degrees Celsius and scale factor of 20 Sample concentration: 0.5% polymer "as is" Injection Volume: 50 microliters Standard Calibrations: MW polystyrene, 30 micro liters of injected volume.

Average Number of Molecular Weight (MWn), Average Weight Molecular Weight (MWW) and first moment of average viscosity of molecular weight (MWZ) were obtained.

Apparent viscosity: The rheological properties of the polymer were determined using a 2003 Gottfert Geography capillary rheometer with the WinRHEO analysis software, version 2.31. The fixation included a pressure transducer at 2000 bar pressure and a round hole capillary matrix of 30/1: 0/180. The sample load was made by alternating between the addition of sample and the packing with a rod. A melting time of 2 minutes preceded each test to allow the polymer to completely melt at the test temperature (usually 160 to 220 degrees centigrade). The capillary rheometer determined the apparent viscosity (Pa-s) at 7 different cutting rates: 50, 100, 200, 500, 1000, 2000, and 50003"1. The resulting rheological curve of apparent cut-off rate against viscosity apparent gave an indication of how the polymer could run at temperature in an extrusion process.

Melt Flow Index: The melt flow index is the weight of a polymer (in grams) forced through an orifice of the extrusion rheometer (0.0825 inches in diameter) when subjected to a force of 2160 grams in 10 minutes at 190 degrees centigrade. The melt flow rate was measured in accordance with the Test Method of the American Society for Testing and Materials (ASTM) D 1238E.

Thermal Properties (melting point, Tg and% crystallinity): The melting temperature, the glass transition temperature and the degree of crystallinity of a material were determined by differential scanning calorimetry (DSC). The differential scanning calorimeter was the Thermal Analyzer 2910 Differential Scanning Calorimeter, which was established with a nitrogen-cooled accessory liquid and with a THERMAL ANALYST 2200 (version 8.10), analysis software program, both available from the T.A. Instruments, Inc., of New Castle, Delaware. To avoid handling the samples, tweezers and other utensils were used. The samples were placed in an aluminum tray and weighed to an accuracy of 0.01 milligrams on an analytical balance. A lid was curled on top of the sample of material on the tray. Typically resin granules were placed directly on the weighing tray, and the fibers were cut to accommodate placement on the weighing tray and covering it by the cover.

The differential scanning calorimeter was calibrated using a standard Indian metal and a baseline correction was performed, as described in the operation manual for the differential scanning calorimeter. A sample of material was placed in the test chamber of the differential scanning calorimeter for the test, and an empty tray was used as a reference. All tests were run at 55 cubic centimeters per minute of nitrogen purge (industrial grade) on the test chamber. For the samples of resin granules, the program of heating and cooling was of 2 test cycles that began with a camera balance at -25 degrees Celsius, followed by a first warm-up period at a heating rate of 10 degrees Celsius per minute at a temperature of 200 degrees Celsius, followed by the balance of the sample at 200 degrees Celsius. 3 minutes, followed by a first cooling period at a cooling rate of 20 degrees Celsius per minute at a temperature of -25 degrees Celsius, followed by the balance of the sample at -25 degrees Celsius for 3 minutes, and then a second heating period at a heating rate of 10 degrees centigrade per minute at a temperature of 200 degrees Celsius. For the fiber samples, the heating and cooling program was from a first test cycle that started with a camera balance at -25 degrees Celsius., followed by a warm-up period at a rate of 20 degrees centigrade per minute at a temperature of 200 degrees Celsius, followed by a balance of the sample at 200 degrees Celsius for 3 minutes, and then a cooling period at a rate cooling of 10 degrees Celsius per minute at a temperature of -25 degrees Celsius. All tests were performed with a nitrogen purge liquid of 55 cubic centimeters (industrial grade) on the test chamber.

The results were evaluated using the THERMAL ANALYST 2200 analysis software program, which identified and quantified the glass transition temperature of the intellection, the endothermic and exothermic peaks, and the areas under the peaks on the DSC markers. The transition temperature to the glass was identified as the region on the line where a different change in inclination occurred, and the melting temperature was determined using an automatic inflection calculation. The areas under the peaks of the DSC areas were determined in terms of joules per gram of sample (J / g). For example, the endothermic heat of a resin's melt was determined by the integration of the endothermic peak area. The values of the area were determined by converting the areas under the DSC markers (for example, the endothermic area) into the units of joules per gram using the computer software. The percentage of crystallinity was calculated as follows: % crystallinity = 100 * (A-B) / C where: A is the sum of the endothermic peak areas (J / g: is the sum of the exothermic peak areas (J / g); Y C is the endothermic heat of the melt value of the selected polymer where such polymer has 100% crystallinity (J / g). For polylactic acid, C is 93.7 joules per gram (Cooper-White, J.J. and MacKay, M.E., Polymer Science Journal, Polymer Physics Edi., P.1806, vol.37 (1999)). The areas under any exothermic peaks found in the DSC scan due to insufficient crystallinity that were subtracted from the area under the endothermic peak to approximately represent the degree of crystallinity.

Stress Properties: The tensile strength values of the strip were determined in accordance with the standard test D-5034 of the American Society for Testing and Materials (ASTM). Specifically, a sample of the non-woven fabric was cut or otherwise provided with size dimensions that measured 25 millimeters wide by 127 millimeters long. A type of constant rate of extension of the tension tester was employed. The voltage test system was the MTS SYNTECH 200 Voltage Tester, available from the MTS Systems Corporation of Eden Prairie, Minnesota. The voltage tester was equipped with the TESTWORKS 4.08B test software from the MTS Corporation, to support the test. An appropriate load cell was selected in such a way that the tested value fell in the range of 10-90% of the full scale load. The sample was maintained between handles that have a front and rear face measurement of 25.4 millimeters by 76 millimeters. The grip faces were coated with rubber, and the largest grip dimension was perpendicular to the pulling direction. The grip pressure was rheumatically maintained at a pressure of 40 pounds per square inch. The tension test was performed at a rate of 300 millimeters per minute with a caliber length of 76 millimeters and a breaking sensitivity of 40%.

These samples were tested by using the test load along the machine direction and three samples were tested by using the test load along the transverse direction. In addition to voltage resistance, peak load, peak elongation (eg,% elongation at peak load), and peak energy were measured. The tensile loads of the peak strip were from each sample tested and were arithmetically averaged to determine the tensile strength in the machine direction and in the transverse direction.

Cup Break: The cup break test evaluates the softness of the fabric by measuring the peak load (also called cup breaking load or cup break only) required per foot formed of 4.5 centimeters hemispherical diameter to break a piece of 23 centimeter fabric by 23 centimeters formed in an inverted cup of approximately 6.5 centimeters by 6.5 centimeters, while that the cloth is in the shape of a cup surrounded by approximately a cylinder of 6.5 centimeters to maintain a uniform deformation of the cloth in the shape of a cup. An average of 10 readings is used. The foot and cup are aligned to avoid contact between the cup and foot walls that can affect the peak load. The peak load is measured while the foot descends at a rate of about 0.25 inches per second (38 centimeters per minute) and is measured in grams. The cup break test also produces a value for the total energy required to break a sample (cup breaking energy), which is the energy from the start of the test to the peak load point, for example, the area under the curve formed by the load in grams of an axis and the distance that the foot moves in millimeters over the other. Lower cup break values indicate a softer fabric. A suitable device for measuring cup breaking is a load cell model FTD-G-500 (range of 500 grams) available from the Schaevitz Company, of Pennsauken New Jersey). Cup breaking values are reported in grams of force.

Trapezoid Tearing: The trapezoid or trapped tear test is a stress test applicable to a non-woven fabric. The entire width of the sample is clamped between clamps, so the test mainly measures the joint or the interlock and the strength of the individual fibers directly in the stress load, rather than the strength of the composite structure of the fabric as a whole. The test measures the resistance of the fabric to the propagation of tears under a constant rate of extension. A fabric cut over an edge is hugged along the non-parallel sides of a trapezoid shaped sample and pulled, causing a tear propagation in the sample perpendicular to the load. The test can be conducted either in the machine direction and in the transverse direction. When driving the trapped tear test, a trapezoid delineation is drawn on a 3 by 6 inch (75 by 152 millimeter) sample, with a larger dimension in the direction being tested, and the sample is cut in trapezoid shape. The trapezoid has a side of 4 inches (102 millimeters) and a side of 1 inch (25 millimeters) that are parallel and that are separated by 3 inches / 6 millimeters). A preliminary small cut of 5/8 inches (15 millimeters) is made in the middle of the shorter parallel sides. The sample is held in, for example, the Model TM constant rate extension tester, available from the Instron corporation, 2500 Washington St. , from Canton, Massachusetts, or a Thwing-Albert model INTELLECT II, available from the Thwing-Albert Instruments Co. , from 10960 Dutton Rd., Philadelphia, Pennsylvania 19154, which has parallel clamps 3 inches long (76 millimeters). The sample is hugged along the non-parallel sides of the trapezoid such that the fabric on a longer side is loose and the fabric along the shorter side hangs, and with the cut in half between the clamps. A continuous load is applied to the sample in such a way that the tear propagates through the width of the sample. It should be noted that the largest direction is the direction being tested even when the tear is perpendicular to the length of the sample. The force required to completely tear the sample is recorded in pounds with higher numbers indicating greater tear resistance. The test method used conforms to standard test D1117-14, from the American Society for Testing and Materials (ASTM), except that the tear load is calculated as the average of the first peak and highest peak recorded instead of the highest peaks. low and more high Five samples for each sample are typically tested. The presented data include first and highest peak values.

Lips take Lis ter: The Lister test is used to determine the liquid collection time of a test sample from a non-woven fabric. The time taken through is the time taken for a specific amount of liquid to be absorbed in the non-woven fabric. An adequate test procedure is the test number 150.9-1 EDANA (test of liquid intake time). In accordance with one method, a sample of 4 inches by 4 inches (10.2 centimeters by 10.2 centimeters) of the selected nonwoven fabric material is weighed and placed on top of 4 inches by 4 inches (10.2 centimeters by 10.2 centimeters) of a 5 strat paper filter, type ERT FF3 (available from Hollingsworth & Vose Co., of East Walpole Massachusetts). The sample set is then placed under a Lister tester. A suitable Lister tester is available from W. Fritz Mezger Inc., of Spartanburg, South Carolina. A capture plate is used for the test and is placed on the test sample and under the Lister test equipment. An amount of 5 milliliters of a 0.9% saline solution is supplied on the sample set. The liquid absorption time (intake time) is automatically measured by the Lister test equipment and displayed. Subsequently, a new set of 5-layer dryer is quickly placed under the non-woven sample within 20 seconds, and the 5-milliliter salt is again supplied. In total, the 5 milliliter sample supplied with liquid is made 5 times on the selected non-woven sample, and each take-up time is recorded. The sample is weighed again after the sequence of five times. For a given sample of the non-woven fabric, the five-fold sequence test is repeated three times, and the 15 results are averaged to provide the material take-up time.

Abrasion resistance : The reciprocal abrasion test (RAT) involves striking the sample, usually a 5.5-inch by 7-inch cloth (140 millimeters by 180 millimeters) with a silicone rubber abrasive and then evaluating the fabric by peeling, stringing, and curling. An abrasion tester Dual reciprocating horizontal head was obtained from United States Testing Company, Inc., of Hoboken, New Jersey, model 8675. Reinforced silicone solid rubber fiberglass reinforced material has a Shore A hardness surface of 81 ± 9, and a size of 36 inches (914 millimeters) by 4 inches (102 millimeters) by 0.005 inches (0.127 millimeters) (available with catalog number 4050 from Flight Insulations Inc.). Before the test, the sample and the equipment are conditioned at standard temperature and humidity by recycling about 200 times a piece of the material to be tested. The test sample was generally freed from bends, and wrinkles, and mounted on the instrument on a cork backing, cleaned of the residual surface fibers with a brush. The abrasive arm was lowered and the cycle began at a total weight of 2.6 pounds (1180 grams) with the weight of each of the two abrasive arms. After the set number of cycles, each sample was removed from the machine and compared to a set of standard photographs. Each sample was assigned a number based on a comparison of the abrasive material to the standard material. Five is the best rate with the one being the worst.

EXAMPLE 1 Several physical properties of the following aliphatic polyesters were tested.

Pl: Polybutylene Succinate obtained from IRE Chemicals, of South Korea under the name EnPolmarca G4500 (Class CE272); P2: Polybutylene Succinate obtained from IRE Chemicals, from South Korea under the name EnPolmarca G4500 (Class CE241); P3: Polybutylene succinate obtained from IRE Chemicals, of South Korea under the name EnPolmarca G4500 (Class CE242); P: Polybutylene succinate obtained from IRE Chemicals, of South Korea under the name EnPolmarca G4560J; P5: Polybutylene succinate obtained from IRE Chemicals, of South Korea under the name EnPolmarca G4500 (Class CE272 - High MFI); P6: Polybutylene succinate obtained from IRE Chemicals, of South Korea under the name EnPolmarca G4500 (Class CE272 - Mid MFI); P7: Polybutylene succinate obtained from Showa, Japan under the name Bionollemarca 1020; P8: Polybutylene succinate obtained from Showa, Japan under the name Bionollemarca 1903; P9: Polybutylene succinate obtained from Showa, Japan under the name Bionollemarca 1003; PÍO: Polylactic acid obtained from Biomer Inc., from Germany under the name Biomermarca L9000; Pll: Polylactic acid obtained from Natureworks, LLC under the name EcoPlamarca 6201D; Y P12: Polylactic acid obtained from Natureworks, LLC under the name EcoPlamarca 6300.

The results are set down in Tables 1 and 2 Table 1: Molecular Weight and Melt Properties Table 2: Rheological Properties (30/1/180 Roundhole) As indicated, the Bionolle polymers (P7-P9) were very viscous in comparison to the EnPolmarca G4500 (P2-P4) polymers.

EXAMPLE 2 The ability to form a non-woven fabric according to the present invention was demonstrated. As indicated in Table 3 below, various combinations of polymers were tested. The polylactic acid and the polybutylene succinate polymers were placed in separate drying drier and dried at the temperature and time conditions within the supplier's recommendations. Each polymer was then rheumatized with dry air to separate extruder hoppers which were also sealed to prevent moisture pickup. The polylactic acid polymer was fed to an extruder A, and the polybutylene succinate polymer was fed into the extruder B. The heating profile of extruder A was set to achieve a melting of the final polylactic acid polymer at a temperature of 215. ° C at 230 ° C at a production of 210 to 270 kilograms per hour. The heating profile of extruder B was set to achieve a polymer melt of final polybutylene succinate at a temperature of 200 ° C to 215 ° C at a production of 30 to 90 kilograms per hour. Each extruder pumped the respective melt streams through a melt filter of standard mesh size and to a metering pump. Each of the positive displacement pumps controlled the production of the polymers to the aforementioned productions. The range of revolutions per minute of extruder was put under control at a standard of constant pump inlet pressure to persons skilled in the art. The melted polymers were then fed separately into a single heated yarn paging set. The yarn package assembly arranged to two polymer streams for an array of filaments emerging from the spinning member in a bicomponent sheath / core configuration. The sheath was composed of polybutylene succinate polymer and the core was composed of polylactic acid polymer. The total pump rate was 300 kilograms per hour. The individual pump rates were adjusted at different times to produce the filaments in the range of 10 to 90% sheath and 30% to 70% core. The bicomponent filaments leaving the spinning organ were cooled to standard air flows and at air temperatures according to the experts in the art using a line attached with yarn available from Reifenhauser GmbH & Company KG Maschinefabrik under the designation REICOFIL® 4. The filaments were pulled pneumatically down to a final diameter of between 14 to 16 micrometers.

The filaments were then deposited directly on the perforated surface under vacuum to make a randomly formed nonwoven fabric. The perforated surface was rotated to form a non-woven fabric at 3900 kilograms per hour. Directly after the filaments formed a tissue, the fabric was tempered and stabilized under a rotating roller with a surface temperature of 40 ° C to 60 ° C and a standard clamping point pressure in a manner familiar to those skilled in the art. The stabilized fabric was then transferred through a calendering roller pressure point and subjected to heat and pressure. The bonding pattern was a diamond bonding pattern of less than 30% bonded area and more than 100 bolts per square inch. The bonded fabric was then wound onto a standard design surface driven wheel for persons skilled in the art. The conditions of tissue formation for the samples are set forth below in Table 3 in greater detail.

Tissue Formation Conditions Table Several properties of the resulting non-woven fabrics were tested. The results are set down in Tables 4-6.

Table 4: Mechanical Properties 0 5 Table 5: Resistance to Abrasion and Water Absorption Table 6: Resistance to Tearing Rigidity As indicated above, the samples were formed according to the present invention (for example samples 11-14) exhibited excellent mechanical properties, softness, abrasion resistance and excellent water function characteristics.

In addition to the tests mentioned above, optical micrographs (seen in reflected / transmitted light) of the junction points of several samples were also taken.

For example, Figures 2-3 showed binding points for samples numbers 3-4, respectively, both of which were formed of 100% polylactic acid. As illustrated, the points of attachment are poorly defined. The fibers in the joints are melted and flattened and the limit of the point of union is abrupt, lacking in smoothness and continuity. On the other hand, figures 4-6 show the junction points for sample 13 (pod 10% PBS), sample 11 (pod of 20% PBS), and sample 12 (30% pod PBS), respectively. The samples generally had an increased level of fiber frameworks within the junction point, and also had a smoother phase between the junction point limit. In Figure 5, for example, the fiber frames were clearly visible inside the melted polymer pond. In addition, fiber orientation at the junction point it was at least almost two perpendicular directions, which was also confirmed by Azimuthal X-ray diffraction scans.

Although the invention has been described in detail with respect to the specific embodiments thereof, it will be appreciated by those skilled in the art to achieve an understanding of the foregoing, that alterations, variations and equivalents of these additions can be easily conceived. Therefore, the scope of the present invention should be evaluated as that of the appended claims and any equivalents thereof.

Claims (42)

R E I V I N D I C A C I O N S

1. A biodegradable nonwoven fabric comprising essentially continuous multiple component filaments, wherein the multi component filaments comprise a first component and a second component, the first component contains a first aliphatic polyester having a melting point of from about 160 ° C at about 250 ° C and the second component contains a second aliphatic polyester, wherein the melting point of the second aliphatic polyester is at least 30 ° C less than the melting point of the first aliphatic polyester, and wherein the second aliphatic polyester has a number average molecular weight of from about 30,000 to about 120,000 daltons, a glass transition temperature of less than about 25 ° C and an apparent viscosity of from about 50 to about 215 pascal-seconds as determined at a temperature of 160 ° C and a cut-off rate of 1,000 seconds "1.

2. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the first aliphatic polyester is polylactic acid.

3. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester has an apparent viscosity of from about 80 to about 150 pascal-seconds as determined at a temperature of 160 ° C and at a cutoff of 1,000 seconds-1.

4. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester has a melting point of at least about 40 ° C less than the melting point of the first aliphatic polyester.

5. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester has a melting point of from about 100 ° C to about 140 ° C.

6. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester has a number average molecular weight of from about 40,000 to about 100,000 daltons.

7. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester has a Polydispersity Index of from about 1.0 to about 3.0.

8. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester has a melt flow rate of from about 20 to about 120 grams per 10 minutes, measured at a force of 2,160 grams and a temperature of 190 ° C according to the test method ASTM D1238-E.

9. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester has a glass transition temperature of about 0 ° C or less.

10. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester has a glass transition temperature of about -10 ° C or less.

11. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the second aliphatic polyester is polybutylene succrate.

12. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the filaments have a sheath / core or side-by-side configuration.

13. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the fabric exhibits a peak elongation in the machine direction of at least about 10%.

14. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the fabric exhibits a peak elongation in the machine direction of at least about 35%.

15. The biodegradable non-woven fabric as claimed in clause 1, characterized in that the fabric exhibits a peak elongation in the transverse direction to the machine of at least about 35%.

16. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the fabric exhibits a peak elongation in the transverse direction to the machine of at least about 50%.

17. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the fabric exhibits a peak load in the machine direction of at least about 3,500 grams-force per inch.

18. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the fabric exhibits a peak elongation in the transverse direction to the machine of at least about 1,500 grams-force per inch.

19. The biodegradable nonwoven fabric as claimed in clause 1, characterized in that the filaments are autogenously bonded in intermittent compacted areas.

20. The biodegradable nonwoven fabric as claimed in clause 19, characterized in that at least a portion of the high melting point aliphatic polyester within the compacted areas retains an essentially fibrous shape.

21. The biodegradable nonwoven fabric as claimed in clause 20, characterized in that the high melting point essentially fibrous polymer is oriented in two or more directions.

22. A method for forming the biodegradable nonwoven fabric as claimed in clause 1, the method comprises: co-extruding a first thermoplastic composition and a second thermoplastic composition to form the multicomponent filaments, the first thermoplastic composition comprises the first aliphatic polyester and the second thermoplastic composition comprises the second aliphatic polyester; randomly deposit the filaments on a forming surface; Y melt-fuse the filaments into intermittent binding regions.

23. The method as claimed in clause 22, characterized in that the second thermoplastic composition is extruded at a temperature ranging from about 145 ° C to about 195 ° C.

24. The method as claimed in clause 22, characterized in that the filaments are melted-fused by passing the fabric through a pressure point formed between two rollers.

25. The method as claimed in clause 24, characterized in that one or both of the rollers are heated to a temperature of from about 50 ° C to about 160 ° C.

26. The method as claimed in clause 24, characterized in that one or both of the rollers They are heated to a temperature of from around 100 ° C to around 140 ° C.

27. The method as claimed in clause 24, characterized in that a pressure of from about 5 to about 150 pounds per square inch is applied to the clamping point.

28. The method as claimed in clause 24, characterized in that a pressure of from about 30 to about 60 pounds per square inch is applied to the clamping point.

29. The method as claimed in clause 22, characterized in that the joining regions cover less than 50% of a tissue surface.

30. An absorbent article comprising an absorbent core positioned between a layer essentially impermeable to liquid and a liquid permeable layer, wherein the layer substantially permeable to liquid contains the biodegradable nonwoven fabric as claimed in clause 1.

31. The absorbent article as claimed in clause 30, characterized in that the layer essentially impermeable to liquid forms an outer cover of the absorbent article.

32. The absorbent article as claimed in clause 30, characterized in that the biodegradable nonwoven fabric is laminated to a film capable of breathing.

33. A biodegradable nonwoven fabric comprising essentially continuous multiple component filaments, wherein the multi-component filaments comprise a first component and a second component, the first component has a first aliphatic polyester and the second component contains a second aliphatic polyester, wherein the melting point of the first component is from about 160 ° C to about 250 ° C and the melting point of the second component is at least about 30 ° C less than the melting point of the first component wherein the second aliphatic polyester has an average molecular weight of from around 30,000 to around 120,000 daltons, a glass transition temperature of less than about 25 ° C and an apparent viscosity of from about 50 to about 215 pascal-seconds as determined at a temperature of 160 ° C and at a cut-off rate of 1,000 seconds-1.

34. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the first aliphatic polyester is polylactic acid.

35. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the second aliphatic polyester has an apparent viscosity of from about 80 to about 150 pascal-seconds as determined at a temperature of 160 ° C and at a cutoff of 1,000 seconds-1.

36. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the second aliphatic polyester has a melting point of at least about 40 ° C less than the melting point of the first aliphatic polyester.

37. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the second aliphatic polyester has a melting point of from about 100 ° C to about 140 ° C.

38. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the second aliphatic polyester has a number average molecular weight of from about 40,000 to about 100,000 daltons.

39. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the second aliphatic polyester has a polydispersity index of from about 1.0 to about 3.0.

40. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the second aliphatic polyester has a glass transition temperature of about 0 ° C or less.

41. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the second aliphatic polyester is polybutylene succinate.

42. The biodegradable nonwoven fabric as claimed in clause 33, characterized in that the filaments are autogenously bonded in intermittent compacted areas. SUMMARY A biodegradable nonwoven fabric comprising essentially continuous multiple component filaments is provided. The filaments comprise a first component and a second component. The first component contains at least one high melting point aliphatic polyester having a melting point of from about 160 ° C to about 250 ° C and the second component contains at least one low melting point aliphatic polyester. The melting point of the low melting point aliphatic polyester is at least about 30 ° C less than the high melting point aliphatic polyester. The low melting point aliphatic polyester has a number average molecular weight of from about 30,000 to about 120,000 daltons, a glass transition temperature of less than about 25 ° C and an apparent viscosity of from about 50 to about 215 pascal-seconds as determined at a temperature of 160 ° C and at a cut-off rate of 1,000 seconds-1.