WO2024028420A1

WO2024028420A1 - Nonwoven fabric and process for forming the same

Info

Publication number: WO2024028420A1
Application number: PCT/EP2023/071486
Authority: WO
Inventors: Elena Novarino; Alfredo IZZO
Original assignee: Fitesa Germany Gmbh
Priority date: 2022-08-05
Filing date: 2023-08-03
Publication date: 2024-02-08

Abstract

The present invention provides a nonwoven fabric comprising a spunbond nonwoven layer which comprises spunbond fibers, wherein the spunbond fibers are bicomponent spunbond fibers which each comprise a first component and a second component, wherein the first component comprises a polylactic acid and the second component comprises a polylactic acid and a polybutylene succinate-based polyester, and wherein the first component is present in an amount in the range of from 50-80% by weight and the second component is present in an amount in the range of from 20-50% by weight, both amounts based on the total weight of each bicomponent spunbond fiber, and wherein the amount of polybutylene succinate-based polyester is in the range of from 0.2-5% by weight, based on the total weight of each multicomponent spunbond fiber. In addition, the invention further provides a process for preparing the nonwoven fabric, and absorbent article comprising the nonwoven fabric.

Description

NONWOVEN FABRIC AND PROCESS FOR FORMING THE SAME

FIELD OF THE INVENTION

The present invention relates to a nonwoven fabric, a process for preparing the nonwoven fabric, and an absorbent article comprising the non-woven fabric.

BACKGROUND

Nonwoven fabrics are used in a variety of applications such as garments, disposable medical products, diapers, personal hygiene products, among others. New products being developed for these applications have demanding performance requirements, including comfort, conformability to the body, freedom of body movement, good softness and drape, adequate tensile strength and durability, and resistance to surface abrasion, pilling or fuzzing. Accordingly, the nonwoven fabrics which are used in these types of products must be engineered to meet these performance requirements.

Traditionally, such nonwoven fabrics are prepared from thermoplastic polymers, such as polyester, polystyrene, polyethylene, and polypropylene. These polymers are generally very stable and can remain in the environment for a long time. Recently, however, there has been a trend to develop articles and products that are considered environmentally friendly and sustainable. As part of this trend, there has been a desire to produce ecologically friendly products comprised of increased sustainable content in order to reduce the content of petroleum-based materials. Therefore, there is nowadays a need for nonwoven fabrics that are made from sustainable and degradable polymers, which polymers are preferably derivable from renewable sources.

Polylactic acid or polylactide-based polymers (PLA) provide a cost-effective path to sustainable content spunbond nonwovens that can be readily converted into consumer products. Polylactic acid (PLA) is made from vegetable renewable raw materials such as sugars from food crops such as maize, sugar beet, sugar cane and wheat or cellulose.

Polylactic acid has the advantage that it is compostable and will dissolve into carbon dioxide, biomass and water. In addition, polylactic acid is recyclable. Polylactic acid is mainly formed from the monomers lactic acid, and the cyclic di-ester, lactide. Polylactic acid is usually formed by means of ring-opening polymerization of lactide using a metal catalyst such as for instance tin octoate. Another process to form polylactic acid involves the direct condensation of lactic acid monomers. To fully capture the cost-effective benefits of PLA-based consumer products, PLA must be convertible into nonwovens and then into the final consumer product at very high speeds with minimal waste. However, due to the propensity of static generation and accumulation on fibers with PLA polymer on the surface, it is difficult to combine the steps of spinning, web formation, and bonding at the very high speeds needed for the economically attractive production of spunbond PLA with optimum fabric properties. Moreover, when 100% PLA fibers are used, low bonding temperatures are required to prevent sticking of the fibers to the calender roll. Low bonding temperatures result in poor fabric properties such as a low tensile strength and poor elongation, and thus do not allow making use of the full potential of this polymer. In addition, the electrostatic charging of 100% PLA fibers during spinning and processing also contributes to the sticking of the fibers tend to the calender roll.

To overcome these disadvantages, nonwovens have been developed with fibers having a sheath/core bicomponent structure in which the PLA is present in the core, and a synthetic polymer, such as polypropylene, is in the sheath. An example of such a nonwoven fabric is described in U.S. Pat. No. 6,506,873. The presence of such a synthetic polymer in the sheath provides the necessary properties for commercial production of nonwovens comprising PLA at high speeds. Although commercial production of nonwovens comprising PLA with synthetic polymers in the sheath is possible, this solution does not extend far enough because the industry (and its consumers) are seeking for full sustainability, and thus preferably for nonwovens being 100% PLA. Further, JP2008208483A discloses carded nonwoven webs that are made of short staple fibers with a core/sheath configuration in which the core component comprises a first copolymer of L-lactic acid and D-lactic acid and the sheath component comprises a second copolymer of polyalkylene succinate and L-lactic acid in which second copolymer the L-lactic acid is present in only a small amount. Although such carded nonwovens may be attractive from biodegradability perspective, they are fluffy and soft and display poor mechanical properties in terms of tensile strength and elongation. In addition, their basis weights are relatively high and therefore not attractive.

As an alternative to the bico approach and to also overcome these processing issues, also the use of additives such as aliphatic acid salts has been suggested. Although, such an approach shows benefits in terms of improved processing and final fabric properties, it has a number of associated disadvantages. It requires an additional process step to provide the aliphatic sulfonic acid; aliphatic sulfonic acids are environmentally unfriendly compounds of petrochemical origin which are neither sustainable nor biodegradable; and the use of the aliphatic sulfonic acids add to the overall processing costs. Just substituting PLA by other biopolymers such as polybutylene succinate (PBS) is not a feasible alternative approach because they are not available in the necessary commercial amounts, which brings along high prices making the final fabrics too expensive, but also their spinning and processing properties are more than poor.

Accordingly, there still exists a need for fabrics which comprise PI_A that exhibit improved mechanical properties in terms of tensile strength and elongation, and can be used in absorbent articles such as diapers and wipes, and which deal with disadvantages that are associated with the above mentioned alternative approaches..

SUMMARY

Surprisingly, in accordance with the present invention it has been found that the addition of a small amount of a polybutylene succinate-based polyester to one of the PLA-based components of a multicomponent spunbond fiber improves the mechanical properties of the nonwoven fabric in terms of tensile strength and elongation considerably.

Accordingly, the present invention relates to a nonwoven fabric comprising a plurality of multicomponent spunbond fibers that are bonded together to form a nonwoven web, which multicomponent spunbond fibers comprise a first component and a second component, wherein the first component comprises a single polymer composition and the second comprises a polymer blend composition, wherein the single polymer composition comprises a polylactic acid and the polymer blend composition comprises a polylactic acid and a polybutylene succinate-based polyester, wherein the first component is present in an amount in the range of from 50-80% by weight and the second component is present in an amount in the range of from 20-50% by weight, both amounts based on the total weight of each multicomponent spunbond fiber, and wherein the amount of polybutylene succinate-based polyester is in the range of from 0.2-5% by weight, based on the total weight of each multicomponent spunbond fiber.

The present nonwoven fabric has the advantage that it exhibits a considerable increase in tensile strength and elongation in both the machine direction and the cross direction in comparison to an identical nonwoven fabric that does not include the small amount of the polybutylene succinate-based polyester. For example, the present nonwoven fabric may exhibit an increase in tensile strength in both the machine direction and the cross direction of at least 50% in comparison to an identical nonwoven that does not include the small amount of the polybutylene succinate-based polyester. The increase in tensile strength allows the application of nonwoven fabrics having low basis weights, which is for instance beneficial for topsheets and backsheets. Moreover, more open bond patterns can be used without loss of mechanical performance, and improve comfort properties such as softness and drapability.

The present nonwoven fabrics particularly exhibit a high wet strength, making them most suitable for use in wipes.

In addition, the increase in elongation allows the use of the nonwoven fabrics in applications where elongation is important such as waist carriers, back ears and side panels. It also allows post mechanical treatments such as ring rolling, embossing and perforating.

The present invention provides nonwoven fabrics, as well as sustainable composites including the present nonwoven fabrics, and sustainable articles including the present nonwoven fabrics and/or present composites.

The present invention is suitably directed to a spunbond nonwoven fabric comprising a plurality of multicomponent fibers that are bonded to each other to form a coherent web, wherein the polymer blend composition is present at a surface of the plurality of fibers.

The polybutylene succinate-based polymer is present in the multicomponent spunbond fibers in a small amount, i.e. 0.2-5% by weight, based on the total weight of each multicomponent spunbond fiber. The polybutylene succinate-based polyester is preferably present in the multicomponent spunbond fibers in an amount in the range of 0.2-3.5% by weight, more preferably in the range of from 0.2-2.5% by weight, even more preferably in the range of from 0.2-2.0% by weight, and most preferably 0.2-1.5% by weight, based on the total weight of each multicomponent spunbond fiber.

The polybutylene succinate-based polyester is suitably present in an amount ranging from 1 to 10% by weight, preferably in an amount ranging from 1 to 7% by weight, and more preferably in an amount ranging from 1 to 5 % by weight, even more preferably from 1 to 4% by weight, and most preferably 1 to 3% by weight, based on the total weight of the second component.

The polylactic acid is suitably present in an amount ranging from 90 to 99% by weight, preferably in an amount ranging from 93 to 99% by weight, and more preferably in an amount ranging from 95 to 99% by weight, even more preferably from 96 to 99% by weight, and most preferably 97 to 99% by weight, based on the total weight of the second component

Preferably, the plurality of multicomponent spunbond fibers comprise bicomponent spunbond fibers. The bicomponent spunbond fibers may have a core/sheath configuration or a side-by-side configuration. Preferably, the bicomponnet spunbond fibers have a core/sheath configuration. In case the bicomponent spunbond fibers have a core/sheath configuration, the first component corresponds to the core component which comprises the single polymer composition and the second component corresponds to the sheath component which comprises the polymer blend composition. The core-sheath bicomponent spunbond fibers may have a symmetric core-sheath configuration or eccentric core-sheath configuration, preferably a symmetric core/sheath configuration.

The first component may comprise a PU\ of a first grade and the second component may comprise a PLA of a second grade, wherein the first grade and the second grade are different. Preferably, in the first component and the second component use is made of a PLA of the same grade.

The nonwoven fabrics according to the present invention and sustainable composites including said nonwoven fabrics may be used in a wide variety of applications, including diapers, feminine care products, wiper products, and incontinence products. Preferably, the present nonwoven fabrics are used in diapers and wiper products, more preferably in wiper products.

For the purposes of the present application, the following terms shall have the following meanings:

The term “fiber” can refer to a fiber of finite length or a filament of infinite length.

As used herein, the term “single polymer composition” refers to a polymer composition formed from only one type of polymer, in this case PLA. This does not exclude single polymer compositions which comprise two different types of PLA. In addition, this does not exclude additives have been added for color, anti-static properties, lubrication, hydrophilicity, liquid repellency, etc.

As used herein, the term “polymer blend composition” refers to a polymer composition formed from a blend that contains two or more different types of polymer, in this case at least PLA and polybutylene succinate-based polymer. Of course, this does not exclude polymer blend compositions to which additives have been added for color, anti-static properties, lubrication, hydrophilicity, liquid repellency, etc. Further, the polymer blend may in addition comprises other polymers such as polyhydroxyalkanoates (PHAs), poly-3-hydroxybutyrate copolymers (P3HB), poly(3-hydroxybutyrate- co-3-hydroxy hexaoate (PHBH, poly(3- hydroxybutyrate-co-3-hydroxyvalerate (PHBV), and the like.

As used herein, the term “multicomponent” refers to fibers that comprise two components (e.g., bicomponent fibers), wherein the two components are extruded from separate extruders. The single polymer composition and polymer blend composition are preferably arranged in substantially constantly positioned distinct zones across the cross-section of the fibers. The components may be arranged in any desired configuration, such as sheath-core, side-by-side, pie, island-in-the-sea, and so forth. Preferably, the multicomponent spunbond fibers have a core/sheath configuration or side-by-side configuration. More preferably, the bicomponent spunbond fibers have a core/sheath configuration. The core/sheath configuration can be a symmetric core/sheath configuration or an eccentric core/sheath configuration, preferably a symmetric core/sheath configuration. Various methods for forming multicomponent fibers are described in U.S. Pat. No. 4,789,592 to Taniguchi et al. and U.S. Pat. No. 5,336,552 to Strack et al., U.S. Pat. No. 5,108,820 to Kaneko, et al., U.S. Pat. No. 4,795,668 to Kruege, et al., U.S. Pat. No. 5,382,400 to Pike, et al., U.S. Pat. No. 5,336,552 to Strack, et al., and U.S. Pat. No. 6,200,669 to Marmon, et al..

As used herein, the terms “nonwoven,” “nonwoven web” and “nonwoven fabric” refer to a structure or a web of material which has been formed without use of weaving or knitting processes to produce a structure of individual fibers or threads which are intermeshed, but not in an identifiable, repeating manner. Nonwoven webs have been, in the past, formed by a variety of conventional processes such as, for example, meltblown processes, spunbond processes, and staple fiber carding processes.

As used herein, the term “meltblown” refers to a process in which fibers are formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries into a high velocity gas (e.g. air) stream which attenuates the molten thermoplastic material and forms fibers, which can be to microfiber diameter. Thereafter, the meltblown fibers are carried by the gas stream and are deposited on a collecting surface to form a web of random meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Buntin et al..

As used herein, the term “machine direction” or “MD” refers to the direction of travel of the nonwoven web during manufacturing.

As used herein, the term “cross direction” or “CD” refers to a direction that is perpendicular to the machine direction and extends laterally across the width of the nonwoven web.

As used herein, the term “spunbond” refers to a process involving extruding a molten thermoplastic material as fibers from a plurality of fine, usually circular, capillaries of a spinneret, with the fibers then being attenuated and drawn mechanically or pneumatically. In contrast with staple fibers which are short, spunbond fibers are continuous fibers. Hence, spunbond fibers are much longer than staple fibers. The fibers are deposited on a collecting surface to form a web of randomly arranged substantially continuous fibers which can thereafter be bonded together to form a coherent nonwoven fabric. The production of spunbond non-woven webs is illustrated in patents such as, for example, U.S. Pat. Nos. 3,338,992; 3,692,613, 3,802,817; 4,405,297 and 5,665,300.

In general, these spunbond processes include extruding the fibers from a spinneret, quenching the fibers with a flow of air to hasten the solidification of the molten fibers, attenuating the fibers by applying a draw tension, either by pneumatically entraining the fibers in an air stream or mechanically by wrapping them around mechanical draw rolls, depositing the drawn fibers onto a collection surface to form a web, and bonding the web of loose fibers into a nonwoven fabric. The bonding can be any thermal or chemical bonding treatment, such a through-air bonding or thermal point bonding.

As used herein, the term “thermal point bonding” involves passing a material such as one or more webs of fibers to be bonded between a heated calender roll and an anvil roll. The calender roll is typically patterned so that the fabric is bonded in discrete point bond sites rather than being bonded across its entire surface.

As used herein, the term “through-air bonding” involves a process in which hot air is used to fuse the fibers at the surface of a nonwoven web and optionally internally within the nonwoven web. The hot air can either be blown through the web in an oven or sucked through the web as it passes over a porous drum as a vacuum is developed. The temperature of the hot air may be high enough to melt and/or fuse the second component (e.g. the sheath component) of a multicomponent fiber (e.g., bicomponent fiber) while not melting the first component (e.g. the core component) of the multicomponent fiber. The hot air may also initiate crimping of multicomponent fibers (e.g. bicomponent fibers). As used herein, the term “polymer” generally includes, but is not limited to, homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material, including isotactic, syndiotactic, and random symmetries.

The term “composite”, as used herein, may be a structure comprising two or more layers, such as a film layer and a fiber layer or a plurality of fiber layers molded together. The two layers of a composite structure may be joined together such that a substantial portion of their common X-Y plane interface, according to certain embodiments of the invention.

The present nonwoven fabrics comprise multicomponent spunbond fibers comprising a first component and a second component, wherein both components comprise polylactic acid and the second component comprises in addition a small amount of polybutylene succinate- based polyester. These nonwoven fabrics exhibit improvements in terms of tensile strengths and elongation.

A wide variety of different PLA resins can be used in accordance with the present invention.

The PLA resin should have proper molecular properties to be spun in spunbond processes. Examples of suitable include PLA resins are supplied from NatureWorks LLC, of Minnetonka, Minn. 55345 such as, grade 6752D, 6100D, and 6202D, which are believed to be produced as generally following the teaching of U.S. Pat. Nos. 5,525,706 and 6,807,973 both to Gruber et al. Other examples of suitable PLA resins may include L130, L175, LX530, and LX175, all from Corbion of Arkelsedijk 46, 4206 A C Gorinchem, the Netherlands.

Preferably, the nonwoven fabrics in accordance with the present invention are substantially free of synthetic polymer components, such as petroleum-based materials and polymers.

Both the first and second component of the multicomponent fibers according to the present invention may comprise one or more additional additives. In such embodiments, for instance, the additive may comprise at least a colorant, a softening agent, a slip agent, an antistatic agent, a lubricant, a hydrophilic agent, a liquid repellent, an antioxidant, and the like, or any combination thereof.

In one embodiment, the PLA polymer of the sheath component may be the same PLA polymer as that of the core component. In other embodiments, the PLA polymer of the sheath component may be a different PLA polymer than that of the core component.

The melt flow rate (MFR) of the polylactic acid material to be used in the present invention is suitably less than 100 g/10 min. The MFR of the polylactic acid is determined using ASTM test method D1238 (210°C, 2.16 kg). Preferably, the melt flow rate of the polylactic acid material is in the range of from 5-90 g/10 min, more preferably in the range of from 10-85 g/10 min, and even more preferably in the range of from 15-45 g/ 10 min.

In accordance with the present invention, both the first and second component of the multicomponent spunbond fibers may comprise a mixture of different polylactic acids.

Preferably, the first component of the multicomponent spunbond fibers comprises only one type of PLA. Preferably, the second component of the multicomponent spunbond fibers comprises only one type of PLA. Preferably, the first and second component comprise both only one type of PLA, wherein the PLA in both components is the same.

The PLA to be used has suitably a weight average molecular weight in the range of from 100,000-300,000 Dalton, preferably in the range of from 150,000-250,000 Dalton.

The PLA to be used in accordance with the present invention may have a melting point in the range of 125-180°C. For instance, the PLA in the sheath component may have a melting point in the range of from 125-135°C, and the PLA in the core component may have a melting point in the range of from 155-180°C.

Further, the different PLAs may have different weight percentages of D isomer. For instance, the PLA in the sheath component may have a weight percent of D isomer up to and including 10 % by weight, and the PLA in the core component may have a weight percent of D isomer in the range of from 90-100% by weight.

For example, the core component may comprise a PLA having a lower % D isomer of polylactic acid than that of the % D isomer PLA polymer used in the sheath component. The PLA polymer with lower % D isomer will show higher degree of stress induced crystallization during spinning while the PLA polymer with higher D % isomer will retain a more amorphous state during spinning. The more amorphous sheath component will promote bonding while the core showing a higher degree of crystallization will provide strength to the fiber and thus to the final bonded web. In one particular embodiment, the Nature Works PLA Grade PLA 6752 with 4% D Isomer can be used as the sheath while NatureWorks Grade 6202 with 2% D Isomer can be used as the core component.

The present nonwoven fabric may suitably have a basis weight in the range of from 5-150 grams per square meter (gsm). In some embodiments, the present nonwoven fabric may have a basis weight in the range of 8-100 gsm. Preferably, the present nonwoven fabric has a basis weight of less than 50 gsm. Preferably, the nonwoven fabric has a basis weight in the range of from 10-50 gsm, more preferably in the range of 10-30 gsm, and most preferably in the range of from 10-25 gsm.

The present nonwoven suitably has an area shrinkage of less than 5%, preferably less than 2%.

The polybutylene succinate-based polyester to be used in accordance with the present invention may be polybutylene succinate (PBS) or a polybutylene succinate adipate (PBSA). Suitably, use is made of polybutylene succinate homopolymer or polybutylene succinate copolymer. Preferably, use is made of polybutylene succinate homopolymer. In accordance with the present invention, the polymer blend composition of the second component of the bicomponent spunbond fibers may also comprise a mixture of different polybutylene succinate or a mixture of a polybutylene succinate and a polybutylene succinate adipate. Preferably, the polymer blend composition comprises only one type of polybutylene succinate-based polyester, preferably polybutylene succinate. Polybutylene succinate is a compostable aliphatic polyester which can be made by the polycondensation of succinic acid and 1,4-butanediol, whereas polybutylene succinate adipate can be made from 1,4- butanediol and a mixture of adipic acid and succinic acid. Polybutylene succinate polymers have for instance been described in EP 0 569 153 A2.

Suitably, the polybutylene succinate-based polyester to be used in accordance with the present invention has a melt flow rate in the range of from 10-50 g/10 min. preferably in the range of from 10-40 g/10 min, more preferably in the range of from 15-35 g/10 min as determined according to ASTM D1238 (190°C, 2.16 kg).

The polybutylene succinate-based polyester to be used in accordance with the present invention suitably has a melting point between 80-120°C, preferably between 85-115°C.

The polybutylene succinate-based polyester has suitably a weight average molecular weight in the range of from 30,000-120,000 Dalton, preferably in the range of from 50,000-100,000 Dalton. io The polymer blend composition used in the second component suitably has a melt flow rate in the range of 2-100 g/10 min, preferably in the range of 4-90 g/10 min and more preferably in the range of 5-80 g/10 min, even more preferably in the range of 5-50 g/10 min, and most preferably in the range of 5-40 g/10 min, determined according to ASTM D1238 (190°C, 2.16 kg).

The multicomponent spunbond fibers to be used in accordance with the present invention suitably have a linear mass density in the range of from 1-5 dtex. In other embodiments, for instance, the multicomponent spunbond fibers suitably have a dtex in the range of from 1.5-3 dtex. In further embodiments, for example, the multicomponent spunbond fibers suitably have a linear mass density in the range of from 1.6-2.5 dtex.

According to the present invention, the first component of the multicomponent spunbond fibers, preferably bicomponent spunbond fibers, is present in an amount in the range of from 50-80% by weight and the second component of the multicomponent spunbond fibers is present in an amount in the range of from 20-50% by weight, both weights based on the total weight of each multicomponent spunbond fiber. Preferably, the first component of the multicomponent spunbond fibers is present in an amount in the range of from 55-80% by weight and the second component of the multicomponent spunbond fibers is present in an amount in the range of from 20-45% by weight, both weights based on the total weight of each multicomponent spunbond fiber. More preferably, the first component of the multicomponent spunbond fibers is present in an amount in the range of from 55-75% by weight and the second component of the multicomponent spunbond fibers is present in an amount in the range of from 25-45% by weight, both weights based on the total weight of each multicomponent spunbond fiber. Even more preferably, the first component is present in an amount in the range of from 60-75 % by weight and the second component is present in an amount in the range of from 25-40% by weight, both weights based on the total weight of each multicomponent spunbond fiber.

Advantageously, in accordance with the present invention it has been found that the addition of a small amount of a polybutylene succinate-based polyester in the second component (e.g. the sheath component) provides significant increases in mechanical properties in comparison to an identical or similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester. In this regard, nonwoven fabrics in accordance with the present invention suitably exhibit tensile strengths that are 50% greater in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester. The present nonwoven fabric may exhibit a tensile strength that is from 50% to more than 500% greater than the tensile strength of a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester.

The nonwoven fabrics in accordance with the present invention suitably exhibit increases in machine direction (MD) tensile strengths that are from about 50 to 500% or more in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester. The present nonwoven fabrics preferably exhibit an increase in MD tensile strength ranging from 50 to 500% or more, more preferably in the range of from 100 to 500 % or more, even more preferably from 200 to 500 % or more, and most preferably from 250 to 500% or more, in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester.

The nonwoven fabrics in accordance with the present invention suitably exhibit increases in cross direction (CD) tensile strengths that are from 50 to 800% or more in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester. In some embodiments, the present nonwoven fabrics preferably exhibit an increase in CD tensile strength ranging from 50 to 800% or more, more preferably from 100 to 800% or more, even more preferably from 200 to 800% or more, and most preferably from 250 to 800% or more, in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester.

The present nonwoven fabrics in accordance with the present invention also exhibit increased toughness in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester. The toughness of nonwoven fabrics may be compared by examining the product resulting from the multiplication of the observed percent elongation and the observed tensile strength of the fabric. The product of this multiplication is referred to as the Index of Toughness, which is approximately proportional to the area under the stress strain curve. As discussed below in the Test Methods section, all tensile and elongation values are obtained according to German Method 10 DIN 53857 in which a sample having a width of 5 cm and a 100 mm gauge length at a cross-head speed of 200 mm/min were recorded at peak. Since Index of Toughness results from the product of multiplying Tensile X % Elongation, the Index of Toughness has units of (N/5 cm)-%. Since all mechanical properties result from testing a 5 cm wide sample, the units for Index of Toughness in this document will be simplified to N-%.

The nonwoven fabrics in accordance with the present invention suitably exhibit an MD Index of Toughness that is in the range of from 80-2000 N-%, and in particular, in the range of from 100-1800, and more particularly, in the range of from 120-1500 N-%, and a CD Index of Toughness that is in the range of from 80-1500 N-%, and in particular, in the range of from 100-1200, and more particularly, in the range of from 120-1000 N-%.

The nonwoven fabric in accordance with the present invention suitably exhibits an increase in MD Index of Toughness in the range from 200-5700% in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester. In some embodiments, the present nonwoven fabric suitably exhibits an increase in CD Index of Toughness in the range from 160-3200% in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polymer.

To account for variations in basis weights, it may also be useful to consider Relative Index of Toughness for the inventive nonwoven fabrics in comparison to similarly prepared nonwoven fabrics that do not include the polybutylene succinate-based polymer. The present nonwoven fabrics also exhibited significant increases in toughness in comparison to the nonwoven fabrics of the comparative examples. The Relative Index of Toughness is calculated from the Index of Toughness, which is then normalized for basis weight. The Toughness Index can be divided by basis weight to provide a normalized Index of Toughness with units of N-%/g/m².

The nonwoven fabrics in accordance with the present invention may exhibit an MD Relative Index of Toughness that is in the range of from 2.5-55 N-%/g/m², and in particular, in the range of from 5-55 N-%/g/m², and more particularly, in the range of from 10-50 N-%/g/m², and a CD Relative Index of Toughness that is in the range of from 1.5-35 N-%/g/m², and in particular, in the range of from 1.8-30 N-%/g/m², and more particularly, in the range of from 2-30 N-%/g/m².

In some embodiments, the inventive nonwoven fabric may exhibit an increase in MD Relative Index of Toughness in the range from 100-3500% in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester. The present nonwoven fabric may exhibit an increase in CD Relative Index of Toughness in the range from 100-2000% in comparison to a similarly prepared nonwoven fabric that does not include the polybutylene succinate-based polyester.

By “similarly prepared nonwoven fabric” it should be understood the comparison nonwoven fabric has the identical polymer composition with the exception of the polybutylene succinate-based polyester, and that slight variations in processing conditions, such as temperature (e.g. , extruder, calendaring, and die temperatures), draw speeds, and pressures may exist.

The presence of the polybutylene succinate-based polyester helps improve bonding of the multicomponent spunbond fibers to each other, which results in improvements in the mechanical properties of the nonwoven fabrics.

The present nonwoven fabric suitably has a machine direction (MD) tensile strength at peak per gram basis weight in the range of from 0.5-2.5 (N/5 cm)/gsm. For instance, the present nonwoven fabric may comprise a MD tensile strength at peak per gram basis weight from 0.7-2.2 (N/5 cm)/gsm.

In certain embodiments, for example, the present nonwoven fabric may have a cross machine direction (CD) tensile strength at peak from 0.25-1.5 (N/5 cm)/gsm. In other embodiments, for instance, the fabric may comprise a CD tensile strength at peak from 0.3- 1.1 (N/5 cm)/gsm. In some embodiments, for example, the fabric may comprise a CD tensile strength at peak from 0.5-1.9 (N/5 cm)/gsm.

According to certain embodiments, for instance, the fabric may comprise an MD elongation percentage at peak from 20-50%. In other embodiments, for example, the fabric may comprise an MD elongation percentage at peak from 25-45%. In further embodiments, for instance, the nonwoven fabric may comprise an MD elongation percentage at peak from 28- 40%.

In certain embodiments, for example, the fabric may comprise a CD elongation percentage at peak from 20-75%. In other embodiments, for instance, the fabric may comprise a CD elongation percentage at peak from 25-60%. In some embodiments, for example, the fabric may comprise a CD elongation percentage at peak from 30-50%.

Besides additives that already be present in the polylactic acid and the polybutylene succinate-based polyester as used in the spunbond nonwoven fibers, addition of further additives is possible to provide additional properties to the fibers. Suitable further additives include thermal stabilizers, light stabilizers, slip additives, waxes, and additives to make the fabrics either hydrophilic or hydrophobic. The addition of filler materials can sometimes also be of advantage. Suitable filler materials include organic and inorganic filler materials. Suitable examples of inorganic filler materials include minerals such as calcium carbonate, metals such as aluminum and stainless steel. Suitable examples of organic filler materials include sugar-based polymers. The multicomponent spunbond fibers to be used in accordance with the present invention may in addition contain a slip agent. The slip agent is suitably added to the first and second component of the multicomponent spunbond fibers when these are made during the manufacturing process of the fabric, e.g. in form of a masterbatch during the spinning process.

The slip agent to be used in accordance with the present invention can be any slip agent which can suitably be used in the manufacturing of nonwoven fabrics. It can be an internal slip agent, which usually is compatible with the polymer matrix, or it can be an external slip agent that migrates to the fiber surface due to a certain incompatibility with the polymer matrix. Suitably, the slip agent can be a hydrocarbon compound or a fatty acid derivative having one or more functional groups selected from alcohols, carboxylic acid, aryls and substituted aryls, alkoxylates, esters, amides. Slip agents also can be fatty acid esters of multivalent alcohols, compounds comprising unsaturated C-C bonds, oxygen, nitrogen, or a compound based on a silicone-containing compound.

Typical examples of specifically attractive slip agents are for example, polyethylene and polypropylene waxes, primary and secondary amides such as for instance erucamide and oleamide, and stearyl derivatives.

The slip agent is suitably present in an amount in the range of from 0.1-5 wt%, preferably in an amount of 0.5-3 wt%, based on the total weight of the first component. The slip agent is suitably present in an amount in the range of from 0.1-5 wt%, preferably in an amount of 0.5- 3 wt%, based on the total weight of the second component.

The slip agent is suitably present in an amount in the range of from 0.1-5 wt%, preferably in an amount of 0.5-3 wt%, based on the total weight of the multicomponent spunbond fibers.

Suitably, a side of the nonwoven layer is provided with a pattern of bonded areas which defines a pattern of non-bonded areas. Preferably, the bonded areas are individualized bonded areas, meaning that the bonded areas are separately arranged, not connected to each other. Before or after the nonwoven layer is provided with a pattern of individualized bonded areas, the nonwoven layer may be subjected to a through-air bonding treatment.

Preferably, the side of the non-woven fabric is only provided with one type of pattern of bonded areas. Preferably, the bonded areas are individualized bonded areas that have a circle, diamond, rectangle, square, oval, triangle, heart, moon star, rod, hexagonal, octagonal or another polygon shape.

Preferably, at least one outer side of the spunbond nonwoven layers is provided with a pattern of individualized bonded areas, wherein the surface of the bonded areas is in the range of from 8-25%, more preferably in the range of from 8-15%, and most preferably in the range of from 10-12%, based on the total surface of the at least one outer side of the spunbond nonwoven layers.

The bonded areas may have a circle, diamond, rectangle, square, oval, triangle, rod, heart, moon star, hexagonal, octagonal or another polygon shape. For instance, the pattern of individualized bonded areas may be in various shapes such as a diamond pattern, a hexagonal dot pattern, an oval-elliptic pattern, a rod-shaped pattern or any combination thereof. Suitably, the pattern of individualized bonded areas is a continuous pattern.

Suitably, the pattern of individualized bonded areas defines a pattern of non-bonded areas, whereby the surface of the non-bonded areas is in the range of from 75-92%, preferably in the range of from 85-92%, and more preferably 88-90%, based on the total surface of the at least one outer side of the spunbond nonwoven layers.

The high surface of the non-bonded areas to be used according to the present invention provides an attractively high softness. Moreover, the large non-bonded areas allow for the fiber to bulk up and increase the bulkiness of the fabric. This is perceived as an even higher softness from both visual and the tactile perspective.

In a preferred embodiment of the present invention the bonded areas have a diamond, rod, oval or circular type of shape. More preferably, bonded areas have a diamond or rod type of shape. Most preferably, the bonded areas have a diamond type of shape.

Suitably, the bonded areas suitably have a maximum width in the range of from 0.7-1.5 mm, preferably in the range of from 0.75-1.25 mm, and more preferably in the range of from 0.8- 1.2 mm.

Suitably, the bonded areas have a surface in the range of from 0.38-1.77 mm², preferably in the range of from 0.44-1.22 mm², and more preferably in the range of from 0.50-1.13 mm². In case the individualized bonded areas are in the form of ovals may be arranged in any direction of the web. Preferably, the bonded areas in the form of ovals are arranged in such a way that adjacent ovals which are arranged in the cross direction form each in turn opposite angels with the machine direction of the web. The ovals can suitably be arranged in such a way that in the machine direction a plurality of uninterrupted regions extend continuously along the web, while in the cross direction no uninterrupted regions exist along the web. The width of these uninterrupted regions in the cross direction in this preferred arrangement of rods is suitably larger than 300 pm, and preferably the width is in the range of from 500-800 pm.

In another preferred embodiment accordance with the present invention at least one of the spunbond nonwoven layers comprises a side which is provided with an alternating pattern of individualized bonded areas which are in the form of rods which are arranged in the cross direction of the web.

Preferably, the rods are arranged in such a way that in the machine direction of the web no uninterrupted regions exist along the web while in the cross direction of the web the arrangement of the rods define a plurality of uninterrupted regions that extend continuously along the web.

In the context of the present invention the term “rod” is meant to define a linear straight shape such as a straight bar or stick.

The surface of the bonded areas in the form of rods is preferably in the range of from 8-15 %, more preferably in the range of from 9-12 % of the total surface area of the at least one outer side of the spunbond nonwoven layers.

Preferably, the individualized bonded areas in the form of rods each in their length direction form an angle of 90° with the machine direction of the web. The present patterns of bonded areas in the form of rods results in a number of improved fabric properties. The tensile strength into the cross direction is significantly improved, as the fibers are boldly bound perpendicular to their preferred lay-down direction. It is thereby of importance that no uninterrupted regions in the preferred lay-down direction (i.e. the machine direction) exist, as this would create weak areas of unbonded fibers, resulting in a reduced tensile strength. Moreover, since there are no uninterrupted regions in the machine direction along the web, the free fiber length (i.e. average length of a single fiber between its first and second bond) is comparatively short, resulting in an improved abrasion resistance. Further, this particular arrangement of rods provides uninterrupted non-bonded areas in the cross direction, significantly reducing the bending forces of the fabric and translating into an excellent drapability without sacrificing mechanical strength. This finding is surprising because these two properties usually exclude each other.

The rods may have flat ends and/or bended ends. Preferably, the bended ends have a circular shape. Preferably, the rods have a linear shape. Suitably, the individualized bonded areas in the form of rods have a length which is 2-10 times, preferably 2-8 times their width.

The discrete non-bonded areas between the rods suitably have a depth in the range of from 0.1 -0.8 mm, preferably in the range of from 0.1 -0.6 mm, more preferably in the range of from 0.15-0.5 mm, and most preferably in the range of from 0.15-0.4 mm.

Suitably, the distance between each pair of adjacent rods is in the range of from 1.8-3.0 mm, preferably 2.2-2.6 mm in the cross direction. Suitably, distance between each pair of adjacent rods is in the range of from 2.5-5.0 mm, preferably 3.3-4.2 mm in the machine direction

When the individualized bonded areas have a diamond shape, the distance between each pair of adjacent diamonds is in the range of from 0.15-3 mm, preferably 0.5-2.5 mm in the cross direction. Suitably, distance between each pair of adjacent diamonds is in the range of from 0.15-3 mm, preferably 0.5-2.5 mm in the machine direction

The multicomponent spunbond fibers to be used in accordance with the present invention do preferably have a round fiber cross-section. Other suitable fiber cross-sections include for instance ribbon-shaped or trilobal-shaped cross-sections.

The present invention also relates to a process for preparing the nonwoven fabric according to the present invention, comprising the steps of

(a) providing a stream of a molten or semi-molten polylactic acid;

(b) providing a stream of a blend of molten or semi-molten polylactic acid and molten or semi-molten polybutylene succinate-based polyester;

(c) forming from the stream of the molten or semi-molten polylactic acid and the stream of the blend of the molten or semi-molten polylactic acid and the molten or semi-molten polybutylene succinate-based polyester a plurality of multicomponent spunbond fibers which comprise a first component which comprises a single polymer composition comprising polylactic acid and a second component which comprises a polymer blend composition comprising a polylactic acid and a polybutylene succinate-based polyester, wherein the first component is present in an amount in the range of from 50-80% by weight and the second component is present in an amount in the range of from 20-50% by weight, based on the total weight of each multicomponent spunbond fiber, and wherein the amount of polybutylene succinate-based polyester is in the range of from 0.2-5% by weight, based on the total weight of each multicomponent spunbond fiber; and

(d) forming from the multicomponent spunbond fibers as obtained in step (c) the nonwoven web.

In step (d), the plurality of drawn multicomponent spunbond fibers are suitably deposited onto a collection surface. The plurality of multicomponent spunbond fibers can for instance be exposed to ions before they are bonded to form the present nonwoven fabric. According to certain embodiments, for example, forming the plurality of continuous multicomponent fibers may comprise spinning the plurality of continuous multicomponent fibers, drawing the plurality of continuous multicomponent fibers, and randomizing the plurality of continuous multicomponent fibers.

In step (c), a fiber draw speed can suitably be applied which is greater than 2500 m/min. In other embodiments, for example, the fiber drawing can occur at a fiber draw speed from 3000-4000 m/min. In further embodiments, for instance, the process may occur at a fiber draw speed from 3000-5000 m/min.

The nonwoven web as obtained in step (d) can be bonded to form the present nonwoven fabric which bonding may comprise thermal point bonding the web with heat and pressure via a calender having a pair of cooperating rolls including a patterned roll. In such embodiments, for example, thermal point bonding the web may comprise imparting a three- dimensional geometric bonding pattern onto the present nonwoven fabric. The patterned roll may comprise a three-dimensional geometric bonding pattern. In the bonding pattern the bonded areas can suitably be individualized bonded areas that have a circle, diamond, rectangle, square, oval, triangle, heart, moon star, rod, hexagonal, octagonal or another polygon shape.

The calender may include a release coating to minimize deposit of molten or semi molten polymer on the surface of one or more of the rolls. As an example, such release coating is described in European Patent Application No. 1,432,860, which is incorporated herein in its entirety by reference. The process according to the present invention may further comprise dissipating static charge from the nonwoven fabric proximate to the calender via a static control unit. In some embodiments, for example, the static control unit may comprise an ionization source. In further embodiments, for instance, the ionization source may comprise an ionization bar. However, in other embodiments, for example, dissipating static charge from the nonwoven fabric may comprise contacting the nonwoven fabric with a static bar.

The present process may further comprise cutting the nonwoven fabric to form cut nonwoven fabric, exposing the cut nonwoven fabric to ions via a third ionization source, and winding the cut nonwoven fabric into rolls. In such embodiments, for example, the third ionization source may comprise an ionization bar.

The present process may further comprise increasing humidity while forming the plurality of continuous multicomponent spunbond fibers. In such embodiments, for example, increasing humidity may comprise applying at least one of steam, fog, mist, or any combination thereof to the plurality of continuous multicomponent spunbond fibers.

The present nonwoven fabric may be produced, for example, by a conventional spunbond process on spunbond machinery such as, for example, the Reicofil-3 line or Reicofil-4 line from Reifenhauser, as described in U.S. Pat. No. 5,814,349 to Geus et al., wherein molten fiber components are extruded into continuous multicomponent spunbond fibers which are subsequently quenched, attenuated pneumatically by a high velocity fluid, and collected in random arrangement on a collecting surface. In some embodiments, the continuous fibers are collected with the aid of a vacuum source positioned below the collection surface. After filament collection, any thermal, chemical or mechanical bonding treatment may be used to form a bonded web such that a coherent web structure results. As one skilled in the art will understand, examples of thermal bonding may include thru-air bonding where hot air is forced through the web to soften the polymer on the outside of certain fibers in the web followed by at least limited compression of the web or calender bonding where the web is compressed between two rolls, at least one of which is heated, and typically one is an embossed roll.

In some embodiments of the present process, the collection surface may comprise conductive fibers. The conductive fibers may comprise monofilament wires made from polyethersulfone conditioned with polyamide (e.g., Huycon — LX 135). In the machine direction, the fibers comprise polyamide conditioned polyethersulfone. In the cross-machine direction, the fibers comprise polyamide conditioned polyethersulfone in combination with additional polyethersulfone.

The present nonwoven fabrics may be used to prepare a variety of different structures. For example, in some embodiments, the present nonwoven fabric may be combined with one or more additional layers to prepare a composite or laminate material. Examples of such composites/laminates may include a spunbond composite, a spunbond-meltblown (SM) composite, a spunbond-meltblown-spunbond (SMS) composite, or a spunbond-meltblown- meltblown-spunbond (SMMS) composite. In some embodiments, composites may be prepared comprising a layer of the inventive nonwoven fabric and one or more film layers.

The present invention further provides a nonwoven fabric comprising at least two nonwoven spunbond layers which each comprise spunbond fibers, and one or more meltblown nonwoven layers which each comprise meltblown fibers, wherein the one or more meltblown nonwoven layers are arranged between spunbond nonwoven layers, wherein the spunbond fibers of the spunbond nonwoven layers are multicomponent fibers which comprises a first component and a second component, wherein the first component comprises a single polymer composition and the second comprises a polymer blend composition, wherein the single polymer composition comprises a polylactic acid and the polymer blend composition comprises a polylactic acid and a polybutylene succinate-based polyester, wherein the first component is present in an amount in the range of from 50-80% by weight and the second component is present in an amount in the range of from 20-50% by weight, both amounts based on the total weight of each multicomponent spunbond fiber, and wherein the amount of polybutylene succinate-based polyester is in the range of from 0.2-5% by weight, based on the total weight of each multicomponent spunbond fiber.

In such multilayer nonwoven fabric embodiment, at least one of the meltblown layers also comprises a polylactic acid.

The spunbond fibers and meltblown fibers are suitably joined by bonding to form a coherent web structure. Suitable bonding techniques include, but are not limited to, chemical bonding and thermal bonding, for example thermal calendering or air-through bonding using a hot air stream.

Spunbond fibers are generally continuous and have a fiber diameter in the range of from 10- 100 m, preferably in the range of from 10-50 pm, more preferably in the range of 10-35 pm, and most preferably in the range of from 10-30 pm.

Meltblown fibers are generally continuous and have a fiber diameter in the range of from 0.1- 10 pm, preferably in the range of from 0.5-8 pm, more preferably in the range of from 1-5 pm.

In these multilayer structures, the basis weight of the nonwoven fabric layer may range from as low as 5-150 g/m². In such multilayered laminates, both the meltblown and spunbond fibers could have PLA on the surface to insure optimum bonding. In some embodiments in which the spunbond layer is a part of a multilayer structure (e.g., SM, SMS, and SMMS), the amount of the meltblown in the structure may range from about 5 to 30%, and in particular, from about 5 to 15% of the structure as a percentage of the structure as a whole.

Multilayer structures in accordance with embodiments can be prepared in a variety of manners including continuous in-line processes where each layer is prepared in successive order on the same line, or depositing a meltblown layer on a previously formed spunbond layer. The layers of the multilayer structure can be bonded together to form a multilayer composite sheet material using thermal bonding, mechanical bonding, adhesive bonding, hydroentangling, or combinations of these. In certain embodiments, the layers are thermally point bonded to each other by passing the multilayer structure through a pair of calender rolls.

The present invention also provides an absorbent article. The absorbent article comprises a nonwoven fabric in accordance with the present invention. In one embodiment, a sustainable composite may be provided that includes at least two nonwoven fabric layers such that at least one nonwoven fabric layer comprises a layer of the present nonwoven fabric. The present nonwoven fabric layer comprise a plurality of multicomponent spunbond fibers in which the polybutylene succinate-based polyesters and the PLA are present at the surface of the plurality of multicomponent spunbond fibers.

The present nonwoven fabric can be used in wide variety of articles and applications. For instance, embodiments of the invention may be used for personal care applications, for example products for babycare (diapers, wipes), for femcare (pads, sanitary towels, tampons), for adult care (incontinence products), or for cosmetic applications (pads). Other possible uses include agricultural applications, for example root wraps, seed bags, crop covers, industrial applications, for example work wear coveralls, airline pillows, automobile trunk liners, sound proofing, and household products, for example mattress coil covers and furniture scratch pads.

When the absorbent is a diaper which comprises an absorbent core which is sandwiched between a topsheet and a backsheet, one or both of the topsheet and the backsheet may comprise the present nonwoven fabric and/or a sustainable composite including the present nonwoven fabric layer. The topsheet will be positioned adjacent an outer surface of the absorbent core and is preferably joined thereto and to the backsheet by attachment means such as those well known in the art. For example, the topsheet may be secured to the absorbent core by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines, spirals, or spots of adhesive.

Hence, the present nonwoven fabrics can suitably be used in topsheets and backsheets of diapers. Moreover, in view of their high wet strength the present nonwoven fabrics can advantageously be used in wipes. In addition, the nonwoven fabrics exhibit a high elongation which allows them to be used in diaper parts such as waist carriers, back ears and side panels

EXAMPLES

The following examples are provided for illustrating one or more embodiments of the present invention and should not be construed as limiting the invention.

Test Methods

Titer was calculated from microscopic measurement of fiber diameter and known polymer density per German textile method C-1570.

Basis Weight was determined generally following the German textile method CM-130 from the weight of 10 layers of fabric cut into 10x10 cm squares.

Tensile was determined in accordance with Method 10 DIN 53857 using a sample with 5 cm width, 100 mm gauge length, and cross-head speed of 200 mm/min. Tensile strengths were measured at peak.

Elongation was determined in accordance with Method 10 DIN 53857 using a sample with 5 cm width, 100 mm gauge length, and cross-head speed of 200 mm/min. Elongations were measured at peak.

Both the tensile strengths and elongation were determined under dry and wet conditions. Under wet conditions the nonwoven fabric was wetted with water.

Comparative Example 1

In Comparative Example 1 , a 100% PLA bicomponent fabric was prepared on a Reicofil-4 beam. A press roll (R-4 press roll) was positioned on the collection surface downstream of where the fibers are deposited on the collection surface. The fibers were bicomponent 30/70 PLA NatureWorks Grade 6202/ PLA NatureWorks Grade 6202/sheath/core. PLA NatureWorks Grade 6202 has a melt flow rate of 15-30 g/10 min (as determined according to ASTM D1238 (190°C, 2.16 kg} and a melting point of 155-170°C.

The nonwoven fabrics of Comparative Example 1 were produced at a spin beam temperature of 235°C at the extruder and 235°C at the die. The fabric of Comparative Example 1 was produced with a throughput of 270 kg/h and a cabin pressure of 4800 Pa. The calender for Comparative Example 1 had calender temperatures of 125°C for the pattern roll and 125°C for the anvil roll and a calender pressure of 40 N/mm. The bonded areas had a diamond shape, the fibers had a titer of 2.65 dtex, and the nonwoven fabric had a basis weight of 28.5 gsm.

Inventive Example 1

In Inventive Example 1, a nonwoven fabric is made of bicomponent fibers having a 30/70 sheath/core structure. The masterbatch from which sheath was made comprised a PLA resin (Naturworks Grade 6202) to which 3% by weight of polybutylene succinate (BioPBS FZ78TM / PTT MCC BioChem) was added. BioPBS FZ78TM / PTT MCC BioChem has a melt flow rate of 22 g/10 min (as determined according to ASTM D1238 (190°C, 2.16 kg) and a melting point of 115°C. The setup of the system is the same as described above for Comparative Example 1. The nonwoven fabric of Inventive Example 1 was produced at spin beam temperatures of 235°C at the extruder and 235°C at the die. The fabric of Inventive Example 1 was produced with a throughput of 270 kg/h and a cabin pressure of 4500 PA. The calender for Inventive Example 1 had calender temperatures of 161 °C for the pattern roll and 161 ° C for the anvil roll and a calender pressure of 40 N/mm. The bonded areas had the same diamond shape as in Comparative Example 1, the fibers had a titer of 2.96 dtex, and the nonwoven fabric had a basis weight of 29.2 gsm. Properties of Inventive Example 1 and Comparative Example 1 are summarized in Tables 1 and 2 below.

Table 1

Table 2

From Tables 1 and 2, it can be seen that the nonwoven fabric according to the present invention exhibits significant improvements in mechanical properties in comparison with Comparative Example 1 in which use is made of an identically prepared PLA nonwoven fabric that does not include the polybutylene succinate. Based on this data, it can be seen that the inventive nonwoven fabrics exhibited an increase in tensile strengths of greater than 50% in comparison to the Comparative Example 1. Table 1 shows that the nonwoven fabric in accordance with the present invention exhibited a significant increase in both MD tensile strength and CD tensile strength.

In addition, Table 2 shows that the nonwoven fabric in accordance with the present invention exhibited a significant increase in both MD elongation CD elongation.

Further, the wet tensile strength obtained with the nonwoven fabric of Inventive Example 1 shows that the nonwoven fabric according to the present invention can advantageously be used in wipe applications.

From Tables 1 and 2 it is clear that significant increases in tensile strength and elongation are obtained when use is made of a small amount of PBS (3 wt%) in the sheath component, in comparison to a sheath component only made of PLA. To further evaluate the basis for the increases in tensile strengths, elongation, and toughness of the inventive nonwoven fabrics, SEM images of the fabric surfaces of Comparative Example 1 and Inventive Example 1 were obtained. Figures 1 and 2 SEM images of Comparative Example 1 and Inventive Example respectively, taken at a magnification of 200x. The images were obtained with the Keyence VHX digital microscope.

A significant difference in bonding between the fibers was observed. In particular, the bond points of the fabric of Comparative Example 1 showed that the individual fibers were loosely bonded together, and that there was minimal polymer flow bonding adjacent fibers to each other. In comparison, the bond points of the fabric of Inventive Example 1, showed significant melting and flowing of the polymer of the individual fibers. Thus, the nonwoven fabric exhibited significant improvement in bonding in comparison to the comparative nonwoven fabric that did not include the small amount of polybutylene succinate.

From the above it is clear that the nonwoven fabric according to the present invention, containing only a small amount of PBS exhibited significant improvements in MD and CD tensile strength, MD and CD elongation, as well as bonding capacities, in comparison to Comparative Example 1 that included PLA resin in the sheath component, but no PBS.

Claims

1. A nonwoven fabric comprising a plurality of multicomponent spunbond fibers that are bonded together to form a nonwoven web, which multicomponent spunbond fibers comprise a first component and a second component, wherein the first component comprises a single polymer composition and the second comprises a polymer blend composition, wherein the single polymer composition comprises a polylactic acid and the polymer blend composition comprises a polylactic acid and a polybutylene succinate-based polyester, wherein the first component is present in an amount in the range of from 50-80% by weight and the second component is present in an amount in the range of from 20-50% by weight, both amounts based on the total weight of each multicomponent spunbond fiber, and wherein the amount of polybutylene succinate-based polyester is in the range of from 0.2-5% by weight, based on the total weight of each multicomponent spunbond fiber.

2. The nonwoven fabric according to claim 1 , wherein the multicomponent spunbond fibers are bicomponent spunbond fibers having a core-sheath structure in which the core part comprises the first component and the sheath part comprises the second component.

3. The nonwoven fabric according to claim 1 or 2, wherein the first component is present in an amount in the range of from 55-80% by weight and the second component is present in an amount in the range of from 20-45% by weight, based on the total weight of each multicomponent spunbond fiber.

4. The nonwoven fabric according to any one of claims 1-3, wherein the amount of polybutylene succinate-based polyester is in the range of from 0.2-2.5% by weight, based on the total weight of each multicomponent spunbond fiber.

5. The nonwoven fabric according to any one of claims 1-4, wherein the amount of polybutylene succinate-based polyester is in the range of from 0.2-2.0% by weight, based on the total weight of each multicomponent spunbond fiber.

6. The nonwoven fabric according to any one of claims 1-5, wherein the amount of polybutylene succinate-based polyester is in the range of from 0.2-1.5% by weight, based on the total weight of each multicomponent spunbond fiber.

7. The nonwoven fabric according to any one of claims 1-6, wherein the polybutylene succinate-based polyester is polybutylene succinate.

8. The nonwoven fabric according to any one of claims 1-7, wherein the single polymer composition comprises a polylactic acid having a melt flow rate in the range of from 15-45 g/10 min as determined according to ASTM D1238 (210°C, 2.16 kg), and the polymer blend composition comprises a polylactic acid having a melt flow rate in the range of from 15- 45 g/10 min as determined according to ASTM D1238 (210°C, 2.16 kg) and a polybutylene succinate-based polyester having a melt flow rate in the range of from 15-35 g/10 min as determined according to ASTM D1238 (190°C, 2.16 kg).

9. The nonwoven fabric according to any one of claims 1-8 having a basis weight of less than 50 g/m².

10. The nonwoven fabric according to any one of claims 1 -9, wherein a side of the spunbond nonwoven layer is provided with a pattern of bonded areas.

11. The nonwoven fabric according to claim 10, wherein the bonded areas are individualized bonded areas that have a circle, diamond, rectangle, square, oval, triangle, heart, moon star, rod, hexagonal, octagonal or another polygon shape.

12. A process for preparing the nonwoven fabric according to claim 1 , comprising the steps of

(a) providing a stream of a molten or semi-molten polylactic acid;

(d) forming from the multicomponent spunbond fibers as obtained in step (c) the spunbond nonwoven web.

13. An absorbent article comprising the nonwoven fabric according to any one of claims 1-11.

14. An absorbent article according to claim 13 which is selected from the group consisting of hygiene articles, incontinence articles, diapers, sanitary pads, wipes, and femcare articles.

15. An absorbent article according to claim 14 which is a wipe.