Nonwoven fabric and process for forming the same

Abstract

The present invention provides a A nonwoven fabric comprising a plurality of spunbond fibers that form a nonwoven web, wherein the fibers are continuous monocomponent fibers which comprise one or more polylactic acids, wherein the one or more polylactic acids are present in an amount in the range of from 67.5-99.49 wt%, based on the total weight of the monocomponent fibers, wherein the monocomponent fibers further comprise a calcium carbonate in an amount which is in the range of from 0.5-30 wt%, based on the total weight of the monocomponent fibers, wherein the calcium carbonate has an average particle size in the range of from 1 µm to 6 µm, wherein the monocomponent fibers also comprise at least one secondary alkane sulfonate which is present in an amount of 0.01-2.5 wt%, based on the total weight of the monocomponent fibers, and wherein the nonwoven web has a side with a surface having a bonded area, and wherein the bonded area is more than 9% of the total surface of the side. In addition, the invention further provides a process for preparing the nonwoven fabric, and an article comprising the nonwoven fabric.

Description

[0001] NONWOVEN FABRIC AND PROCESS FOR FORMING THE SAME

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a nonwoven fabric, a process for preparing the nonwoven fabric, and an article comprising the non-woven fabric.

[0004] BACKGROUND

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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, the dimensions of the manufactured nonwoven web are impacted due to the shrinking of the PLA fibers. In addition, because of the high melting temperature of PLA, high welding temperatures need to be applied when sheets of nonwoven webs made of PLA need to be welded together. These disadvantages 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.

[0009] 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 petrochemical-based 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 made as much as possible of PLA.

[0010] 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.

[0011] In US 2023 / 0047798 A1 , nonwoven fabrics are described that are formed from fibers which contain two polylactic polymers and a surface-treated calcium carbonate, the calcium carbonate is surface-treated to solve the processing issues that are associated with polylactic-based fibers that contain non-surface-treated calcium carbonate. The polylactic- based fibers are less sticky and biodegradable nonwoven fabrics are obtained having desirable haptic properties such as improved softness and a natural “cotton-feel” while retaining the mechanical properties. In EP 3 500 700 B1 , spunbond nonwoven fabrics are describes that are made of polylatic-based bicomponent fibers that have a sheath / core configuration. In the sheath component a secondary alkane sulfonate is incorporated to improve the bonding between fibers, as a result of which nonwovens are obtained with improved strength and toughness properties.

[0012] Accordingly, there still exists a need for fabrics which contain a high amount of PUX but which overcome disadvantages such as high area shrinkage percentages.

[0013] SUMMARY

[0014] Surprisingly, in accordance with the present invention it has been found that the addition of a particular calcium carbonate to monocomponent polylactic acid fibers reduces the area shrinkage of the nonwoven webs considerably, and allows lower welding temperatures to be applied when sheets of polylactic acid-based nonwoven webs need to be welded together.

[0015] Accordingly, the present invention relates to a nonwoven fabric comprising a plurality of spunbond fibers that form a nonwoven web, wherein the fibers are continuous monocomponent fibers which comprise one or more polylactic acids, wherein the one or more polylactic acids are present in an amount in the range of from 67.5-99.49 wt%, based on the total weight of the monocomponent fibers, wherein the monocomponent fibers further comprise a calcium carbonate which is present in an amount in the range of from 0.5-30 wt%, based on the total weight of the monocomponent fibers, wherein the calcium carbonate has an average particle size which is in the range of from at least 1 pm to 6 pm, wherein the monocomponent fibers also comprise at least one secondary sulfonate which is present in an amount of in the range of 0.01-2.5 wt%, based on the total weight of the monocomponent fibers, and wherein the nonwoven web has a side with a surface having a bonded area, and wherein the bonded area is more than 9% of the total surface of the side.

[0016] The present invention provides nonwoven fabrics, as well as sustainable composites including the present nonwoven fabrics, and sustainable articles including the present nonwoven fabrics. Examples of such sustainable articles include PLA-based hygiene articles such as diapers, containers and covers for use in respect of plants and / or agriculture applications, packaging materials, bags and pouches.

[0017] In accordance with the present invention the monocomponent fibers comprise one or more polylactic acids. Hence, the monocomponent fibers may comprise one polylactic acid, i.e. only one type of polylactic acid, or they may comprise a blend of different polylactic acids. Preferably, the monocomponent fibers in accordance with the present invention comprise one polylactic, i.e. only one type of polylactic acid. In case use is made of one type of polylactic acid, the one polylactic acid has preferably a melting temperature in the range of from 150-180 °C, more preferably a melting temperature in the range of from 155-175 °C.

[0018] The melt flow rate (MFR) of the one type of polylactic acid 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).

[0019] The one type of polylactic acid has preferably a melt flow rate 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.

[0020] When the monocomponent fibers comprise different polylactic acids, the monocomponent fibers may comprise a blend of a first polylactic acid (PLA1) and a second polylactic acid (PLA2).

[0021] In accordance with the present invention, the first polylactic acid (PLA1) suitably has a melting temperature in the range of from 160-180 °C, and the second polylactic acid (PLA2) suitably has a melting temperature in the range of from 145-165 °C. Preferably, the first polylactic acid (PLA1) has a melting temperature in the range of from 165-180 °C, and the second polylactic acid (PLA2) has a melting temperature in the range of from 150-165 °C. More preferably, the first polylactic acid (PLA1) has a melting temperature in the range of from 168-175 °C, and the second polylactic acid (PLA2) has a melting temperature in the range of from 155-163 °C.

[0022] Suitably, the difference between the melting temperatures of the first polylactic acid (PLA1) and the second polylactic acid (PLA2) is between 0-35 °C, preferably between 5-25 °C, and more preferably between 10-15 °C.

[0023] The melt flow rate (MFR) of the first polylactic acid (PLA1) and the second polylactic acid (PLA2) 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).

[0024] Preferably, the melt flow rate of the first and second polylactic acid 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 the monocompoment fibers comprise one or more polylactic acids, whereby the one or more polylactic acids are present in an amount in the range of from 67.5-99.49 wt%, preferably in an amount in the range of from 75-90 wt%, more preferably in an amount in the range of from 80-95 wt%, and most preferably in an amount in the range of from 80-92.5 wt%, based on the total weight of the monocomponent fibers.

[0025] In accordance with the present invention the monocompoment fibers comprise a calcium carbonate, whereby the calcium carbonate is present in an amount in the range of from 0.5- 30 wt%, preferably in an amount in the range of from 5-25 wt%, more preferably in an amount in the range of from 5-20 wt%, and most preferably up to 20 wt%, and most preferably in an amount in the range of from 7.5-20 wt%, based on the total weight of the monocomponent fibers.

[0026] In the present invention use is made of a calcium carbonate having an average particle size of at least 1 pm. Suitably, the average particle size of the calcium carbonate is smaller than 6 pm, preferably smaller than 5 pm, more preferably smaller than 3 pm, even more preferably between 1.0-2.5 pm, and most preferably between 1.2-2.0 pm.

[0027] The calcium carbonate to be used may contain minor amounts of one or more other components. Such components can for instance be agents to treat the surface of the calcium carbonate or other filler components. The calcium carbonate contains suitably one or more other components in an amount of less than 5 wt%. Preferably, the calcium carbonate contains one or more other components in an amount contains in an amount of less than 3 wt%, more preferably in an amount of less than 1 wt%. Most preferably, the calcium carbonate is a pure (100%) calcium carbonate.

[0028] In accordance with the present invention the nonwoven web has a side with a surface having a bonded area, and wherein the bonded area is more than 9% of the total surface of the side. The bonded area is suitably between 10-50% of the total surface of the side of the nonwoven web, and preferably between 10-20% of the total surface of the side of the nonwoven web. In another embodiment of the present invention, the bonded area is suitably between 50-100% of the total surface of the side of the nonwoven web. In the latter embodiment the bonded area is preferably between 70-100%, more preferably between 80- 100%, even more preferably between 90-100% of the total surface of the side of the nonwoven web. In a particularly preferred embodiment of the present invention the bonded area equals 100% of the total surface of the side of the nonwoven web, which means that the surface of the side is completely bonded and thus completely flat.

[0029] The embodiments of the present invention in which the bonded area is preferably between 70-100%, more preferably between 80-100%, even more preferably between 90-100%, and most preferably 100% of the total surface of the side of the nonwoven web, the nonwoven webs are particularly useful for use in containers and covers for use in respect of plants and / or agriculture applications, packaging materials, bags and pouches.

[0030] The fibers used in accordance with the present invention are continuous monocomponent fibers. Continuous fibers have infinite length and differ essentially from staple fibers which have a limited or discreet length, generally in the range of from 2-200 mm. Synthetic staple fibers typically have limited or discreet length in the range of from 20-80 mm.

[0031] 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, and incontinence products. Preferably, the present nonwoven fabrics are used in diapers. In addition, the nonwoven fabrics can be applied in the preparation of containers and covers for use in respect of plants and / or agriculture applications, packaging materials, bags and pouches.

[0032] The continuous monocomponent fibers comprise in addition at least one secondary alkane sulfonate. Suitable secondary sulfonates to be used in accordance with the present invention include those described in EP 3 500 700 B1.

[0033] The presence of the secondary alkane sulfonate to the monocomponent fibers in accordance with the present invention improves the mechanical properties of the nonwoven fabric. In particular, the nonwoven fabric may exhibit an increase in tensile strength, elongation, and toughness in at least one of the machine direction or cross direction in comparison to an identical fabric that does not include the at least one secondary alkane sulfonate. For example, the nonwoven fabric may exhibit an increase in tensile strength in at least one of the machine direction or cross direction of at least 50% in comparison to an identical nonwoven fabric in which the monocomponent fibers do not include the at least one secondary alkane sulfonate in the monocomponent fibers.

[0034] The at least one secondary alkane sulfonate is present in an amount ranging from 0.01 to

[0035] 2.5 wt%, based on the total weight of the monocomponent fibers. For example, the monocomponent fibers comprises the at least one secondary alkane sulfonate is present in the monocomponent fibers in an amount ranging from about 0.1 to 0.75 wt%, preferably in an amount in the range of from 0.2-0.6 wt%, more preferably in an amount in the range of from 0.3-0.4 wt%, based on the total weight of the monocomponent fibers.

[0036] 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 fibers carding processes.

[0037] 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 microfibers 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..

[0038] As used herein, the term “machine direction” or “MD” refers to the direction of travel of the nonwoven web during manufacturing.

[0039] 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.

[0040] 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, the spunbond monocomponent fibers to be used in accordance with the present invention are continuous fibers. Hence, spunbond continuous monocomponent fibers are much longer than staple fibers. The spunbond continuous monocomponent fibers are deposited on a collecting surface to form a web of randomly arranged 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.

[0041] In general, these spunbond processes include extruding the fibers from a spinneret, quenching the continuous 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.

[0042] 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.

[0043] 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 at least part of the surface of the continuous monocomponent fibers.

[0044] A wide variety of different polylactic acids (PLAs) can be used in accordance with the present invention.

[0045] The polylactic acids should have proper molecular properties to be spun in spunbond processes. Examples of suitable PLA resins to be used 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.

[0046] Preferably, the nonwoven fabrics in accordance with the present invention are substantially free of synthetic polymer components, such as petroleum-based materials and polymers.

[0047] The monocomponent fibers of the present invention may in addition to the one or more polylactic acids 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.

[0048] The one or more polylactic acids to be used to be used in accordance with the present invention have 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.

[0049] If the monocomponent fibers comprise two different polylactic acids, i.e. a first polylactic acid (PLA1) and a second polylactic acid (PLA2), the first polylactic acid (PLA1) and the second polylactic acid (PLA2) to be used in accordance with the present invention may have different weight percentages of D isomer. For instance, the second polylactic acid (PLA2) may have a weight percent of D isomer up to and including 10 % by weight, and the first polylactic acid (PLA1) may have a weight percent of D isomer in the range of from 0.2-2 % by weight.

[0050] In one particular embodiment, a blend of the NatureWorks PLA Grade PUX 6752 with 4% D Isomer and the NatureWorks Grade 6202 with 2% D Isomer can be used in the monocomponent fibers.

[0051] In a preferred embodiment of the present invention, the monocomponent fibers comprise in addition at least one polybutylene succinate-based polyester which is present in an amount in the range of from 0.02-5% by weight, based on the total weight of the monocomponent fibers.

[0052] Accordingly, the present invention relates also to a nonwoven fabric comprising a plurality of spunbond fibers that form a nonwoven web, wherein the fibers are continuous monocomponent fibers which comprises one or more polylactic acids, wherein the one or more polylactic acids are present in an amount in the range of from 62.5-99.47 wt%, based on the total weight of the monocomponent fibers, wherein the monocomponent fibers further comprise a calcium carbonate in an amount which is in the range of from 0.5-30 wt%, based on the total weight of the monocomponent fibers, wherein the calcium carbonate has an average particle size in the range of from 1 pm to 6 pm, wherein the monocomponent fibers comprise in addition at least one secondary alkane sulfonate which is present in an amount of 0.01-2.5 wt%, based on the total weight of the monocomponent fibers, wherein the monocomponent fibers comprise in addition at least one polybutylene succinate-based polyester which is present in an amount in the range of from 0.02-5 wt%, based on the total weight of the monocomponent fibers, and wherein the bonded area is more than 9% of the total surface of the side.

[0053] The additional use in the monocomponent fibers of at least one polybutylene succinate- based polyester has the advantage that the nonwoven fabric 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 in the monocomponent fibers. 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 at least one polybutylene succinate- based polyester in the monocomponent fibers.

[0054] 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.

[0055] 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.

[0056] The at least one polybutylene succinate-based polymer is present in the monocomponent fibers in a small amount, i.e. 0.02-5% by weight, based on the total weight of the monocomponent fibers. The at least one polybutylene succinate-based polyester is preferably present in the continuous monocomponent fibers in an amount in the range of 0.02-3.5% by weight, more preferably in an amount in the range of from 0.02-2.5% by weight, even more preferably in an amount in the range of from 0.02-2.0% by weight, and most preferably in an amount in the range 0.02-1 .5% by weight, based on the total weight of the monocomponent fibers.

[0057] The at least one 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, also a mixture of different polybutylene succinates or a mixture of a polybutylene succinate and a polybutylene succinate adipate can suitably e used. Preferably, the monocomponent fibers comprise 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.

[0058] Suitably, the at least one 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).

[0059] The at least one polybutylene succinate-based polyester to be used in accordance with the present invention suitably has a melting temperature between 80-120°C, preferably between 85-115°C.

[0060] The at least one 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.

[0061] Further, the monocomponent fibers may in addition comprises other polymers such as polyhydroxyalkanoates (PHAs), poly-3-hydroxybutyrate copolymers (P3HB), poly(3- hydroxybutyrate- co-3-hydroxyhexaoate (PHBH, poly(3-hydroxybutyrate-co-3- hydroxyvalerate (PHBV), and the like.

[0062] 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.

[0063] The present nonwoven suitably has an area shrinkage percentage of less than 6%, preferably less than 4%, and more preferably less than preferably less than 2%.

[0064] The polymer blend composition used in the monocomponent fibers comprising one or more polylactic acids and the at least one polybutylene succinate-based polyester, 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).

[0065] The continuous monocomponent 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 continuous monocomponent fibers suitably have a dtex in the range of from 1 .5-3 dtex. In further embodiments, for example, the continuous monocomponent fibers suitably have a linear mass density in the range of from 1.6-2.5 dtex.

[0066] Advantageously, in accordance with the present invention it has been found that the addition of a small amount of the at least one polybutylene succinate-based polyester to the continuous monocomponent fibers provides significant increases in mechanical properties in comparison to an identical or similarly prepared nonwoven fabric that does not include the at least one polybutylene succinate-based polyester in the continuous monocomponent fibers. 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 at least one polybutylene succinate-based polyester in the monocomponent fibers. 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 at least one polybutylene succinate-based polyester in the monocomponent fibers.

[0067] 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 at least one polybutylene succinate-based polyester in the monocomponent fibers. 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 at least one polybutylene succinate-based polyester in the monocomponent fibers.

[0068] 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 at least one polybutylene succinate-based polyester in the monocomponent fibers. 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 at least one polybutylene succinate-based polyester in the monocomponent fibers.

[0069] 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 at least one polybutylene succinate-based polyester in the monocomponent fibers. 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- %.

[0070] 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-%.

[0071] 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 at least one polybutylene succinate- based polyester in the monocomponent fibers.

[0072] 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 at least one polybutylene succinate-based polymer in the monocomponent fibers. 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 at least one polybutylene succinate-based polymer in the monocomponent fibers. The present nonwoven fabrics also exhibited significant increases in toughness in comparison to in comparison to similarly prepared nonwoven fabrics that do not include the at least one polybutylene succinate-based polymer in the monocomponent fibers. 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.

[0073] 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.

[0074] 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 at least one polybutylene succinate- based polyester in the monocomponent fibers.

[0075] 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 at least one polybutylene succinate-based polyester in the monocomponent fibers.

[0076] By “similarly prepared nonwoven fabric” it should be understood the comparison nonwoven fabric has the identical polymer composition with the exception of the at least one 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.

[0077] The presence of the at least one polybutylene succinate-based polyester helps improve bonding of the continuous monocomponent 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.

[0078] 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.

[0079] 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%.

[0080] 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%.

[0081] Besides additives that already may be present in the monocomponent 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.

[0082] The continuous monocomponent 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 continuous monocomponent fibers when these are made during the manufacturing process of the fabric, e.g. in form of a masterbatch during the spinning process.

[0083] 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 fibers 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.

[0084] 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.

[0085] The slip agent is suitably present in an amount in the range of from 0.1-5 wt%, preferably in an amount in the range of from 0.5-3 wt%, based on the total weight of the monocomponent fibers.

[0086] 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.

[0087] Preferably, the side of the non-woven fabric is only provided with one type of pattern of bonded areas.

[0088] 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.

[0089] 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.

[0090] 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 rod shape.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] Therefore, the present invention also relates to a nonwoven fabric comprising a plurality of spunbond fibers that form a nonwoven web, wherein the fibers are continuous monocomponent fibers fibers which comprise one or more polylactic acids, wherein the one or more polylactic acids are present in an amount in the range of from 67.5-99.49 wt%, based on the total weight of the monocomponent fibers, wherein the monocomponent fibers further comprise a calcium carbonate which is present in an amount in the range of from 0.5- 30 wt%, based on the total weight of the monocomponent fibers, wherein the calcium carbonate has an average particle size in the range of from 1 pm to 6 pm, wherein the monocomponent fibers also comprise at least one secondary alkane sulfonate which is present in an amount in the range of from 0.01-2.5 wt%, based on total weight of the monocomponent fibers, and wherein the nonwoven web has a side with a surface having a bonded area, wherein the bonded area is more than 9% of the total surface of the side, and wherein the bonded area comprises an alternating pattern of individualized bonded areas which are in the form of rods which are arranged in the cross direction of the web.

[0096] 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.

[0097] 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.

[0098] The surface of the bonded areas in the form of rods is more than 9% of the total surface of the side. The bonded area in the form of rods is suitably between 10-30% of the total surface of the side. In another embodiment of the present invention, the bonded area in the form of rods is suitably between 10-20% of the total surface of the side.

[0099] Preferably, the individualized bonded areas in the form of rods each in their length direction form an angle of substantially 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 fibers length (i.e. average length of a single fibers 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] The monocomponent spunbond fibers to be used in accordance with the present invention do preferably have a round fibers cross-section. Other suitable fibers cross-sections include for instance ribbon-shaped or trilobal-shaped cross-sections.

[0105] The present invention also provides a process for preparing a nonwoven fabric according to the present invention, the process comprising the following steps:

[0106] (a) providing a stream of one or more molten or semi-molten polylactic acids;

[0107] (b) blending the calcium carbonate having an average particle size in the range of from

[0108] 1 pm to 6 pm and the at least one secondary alkane sulfonate with at least one of the molten or semi-molten polylactic acids;

[0109] (c) forming from the blend obtained in step (b) spunbond continuous monocomponent fibers, whereby the calcium carbonate is present in an amount in the range of from 0.5-30 wt%, the one or more polylactic acids are present in an amount in the range of from 67.5- 99.49 wt%, and the at least one secondary alkane sulfonate is present in an amount of 0.01- 2.5 wt%, all weights based on the total weight of the monocomponent fibers;

[0110] (d) depositing the plurality of the continuous monocomponent fibers as obtained in step (c) onto a collection surface; and

[0111] (e) bonding the plurality of continuous monocomponent fibers as obtained in step (d) to obtain the nonwoven fabric comprising a nonwoven web having a side with a surface having a bonded area which is more than 9% of the total surface of the side.

[0112] In step (e) the bonding is carried out so as to obtain a nonwoven having a side with a surface with a bonded area which is between 50-100% of the total surface of the side. When the monocomponent fibers in addition contain a small amount of butylene succinate- based polyester, the polybutylene succinate-based polyester is suitably also blended into at least one or more molten or semi-molten polylactic acids in step (b).

[0113] When the monocomponent fibers in addition contains at least one secondary alkane sulfonate, the at least one secondary alkane sulfonate is suitably also blended into at least one the one or more molten or semi-molten polylactic acids in step (b).

[0114] Preferably, in step (a) is provided one molten or semi-molten polylactic acid, i.e. only one type of polylactic acid.

[0115] In step (c), a fibers draw speed can suitably be applied which is greater than 2500 m / min. In other embodiments, for example, the fibers drawing can occur at a fibers draw speed from 3000-4000 m / min. In further embodiments, for instance, the process may occur at a fibers draw speed from 3000-5000 m / min.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] The present process may further comprise increasing humidity while forming the plurality of continuous monocomponent 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 monocomponent fibers.

[0120] The present nonwoven fabric may be produced, for example, by a conventional spunbond process on spunbond machinery wherein a molten fiber components are extruded into continuous monocomponent 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 monocomponent 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 through-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.

[0121] 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.

[0122] 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.

[0123] 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 continuous monocomponent fibers which comprise one or more polylactic acids, wherein the one or more polylatic acids are present in an amount in the range of from 67.5-99.49 wt%, based on the total weight of the monocomponent fibers, wherein the monocomponent fibers further comprise a calcium carbonate which is present in an amount in the range of from 0.5-30 wt%, based on the total weight of the monocomponent fibers, wherein the calcium carbonate has an average particle size in the range of from 1 pm to 6 pm, wherein the monocomponent fibers comprise in addition at least one secondary sulfonate which is present in an amount of in the range of 0.01-2.5 wt%, based on the total weight of the monocomponent fibers, and wherein the nonwoven web has a side with a surface having a bonded area, and wherein the bonded area is more than 9% of the total surface of the side.

[0124] The continuous monocomponent fibers to be used in such embodiment may be any of the continuous monocomponent fibers described previously above, including continuous monocomponent fibers which in addition comprise at least one secondary alkane sulfonate in an amount in the range of from 0.01-2.5 wt%, based on the total weight of the monocomponent fivers, and / or at least one polybutylene succinate-based polyester which is present in an amount in the range of from 0.02-5% by weight, based on the total weight of the monocomponent fibers.

[0125] In such multilayer nonwoven fabric embodiment, at least one of the meltblown layers also comprises a polylactic acid.

[0126] 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.

[0127] Spunbond fibers are continuous monocomponent fibers that have a fibers diameter in the range of from 10-100 pm, 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.

[0128] Meltblown fibers are continuous fibers that have a fibers 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.

[0129] 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 polylactic acid 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.

[0130] 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.

[0131] The present invention also provides an article comprising the nonwoven fabric according to 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.

[0132] 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 baby care (diapers, wipes), for femcare (pads, sanitary towels, tampons), for adult care (incontinence products), or for cosmetic applications (pads). Other possible uses include agricultural applications such as crop covers, industrial applications, for example work wear coveralls, airline pillows, automobile trunk liners, sound proofing, packaging materials, bags, pouches, and household products, for example mattress coil covers and furniture scratch pads.

[0133] Accordingly, the present invention also provides to an article comprising a diaper, a sanitary pad, a container or a cover for use in respect of plants and / or agricultural applications.

[0134] 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.

[0135] 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.

[0136] Examples

[0137] Example 1 (according to the present invention')

[0138] In this Example 1 , a nonwoven fabric is made of monocomponent fibers comprising 79.7 wt% of LX530 PLA (available from Corbion, and having a weight percent of D isomer of less than 2 % by weight); 0.3 wt% of a masterbatch of Sukano Antistatic Product S 546 (a secondary alkane sulfonate) and 20 wt% of Omyafiber MB165-CBN (CaCO3-masterbatch available from Omya and having an average particle size of less than 5 micron) which are both added to the LX530 PLA at the polymer extruder to provide the monocomponent fibers. The nonwoven fabric is produced at spin beam temperatures of 230 °C at the extruder and 235 °C at the die. Draw speed was adjusted such that the fiber had an average diameter of 15-17 pm. The calender had calender temperatures of 160 °C for the pattern roll and 150 °C for the anvil roll and a calender pressure of 40 N / mm. The bonded pattern obtained had a bonded area of 25% and the individual areas had a diamond shape. The nonwoven fabric so obtained had a basis weight of 25 gsm.

[0139] The area shrinkage of a part of the nonwoven fabric so obtained is measured before and after the nonwoven fabric is dried for 24 hours at a temperature of 55°C, and the area shrinkage percentage observed is shown in Table 1.

[0140] Comparative Example 1

[0141] In this comparative Example, the same nonwoven fabric was made and used as in Example 1 according to the present invention, except that the monocomponent fibers contained 100 wt% of LX530 PLA.

[0142] The area shrinkage of a part of the nonwoven fabric so obtained is measured, using the same method as used in Example 1 , before and after the nonwoven fabric is dried for 24 hours at a temperature of 55°C, and the area shrinkage percentage observed is shown in Table 1.

[0143] Comparative Example 2

[0144] In this comparative Example, the same nonwoven fabric was made and used as in Example 1 according to the present invention, except that the monocomponent fibers contained 99.7 wt% LX530 PLA and 0.3 wt% of the masterbatch of Sukano Antistatic Product S 546.

[0145] The area shrinkage of a part of the nonwoven fabric so obtained is measured, using the same method as used in Example 1 , before and after the nonwoven fabric is dried for 24 hours at a temperature of 55°C, and the area shrinkage percentage observed is shown in Table 1.

[0146] Comparative Example 3

[0147] In this comparative Example, the same nonwoven fabric was made and used as in Example 1 according to the present invention, except that the monocomponent fibers contained 80 wt% LX530 PLA and 20 wt% of Omyafiber MB165-CBN.

[0148] The area shrinkage of a part of the nonwoven fabric so obtained is measured, using the same method as used in Example 1 , before and after the nonwoven fabric is dried for 24 hours at a temperature of 55°C, and the area shrinkage percentage observed is shown in Table 1.

[0149] Table 1

[0150] From Table 1 it is clear that the use of calcium carbonate in combination with the secondary alkane sulfonate in the monocomponent fibers brings about an unexpectedly high reduction in area shrinkage, which reduction is much higher than the sum of each of the effects obtained in Comparative Examples 2 and 3 separately.

Claims

CLAIMS1 . A nonwoven fabric comprising a plurality of spunbond fibers that form a nonwoven web, wherein the fibers are continuous monocomponent fibers which comprise one or more polylactic acids, wherein the one or more polylactic acids are present in an amount in the range of from 67.5-99.49 wt%, based on the total weight of the monocomponent fibers, wherein the monocomponent fibers further comprise a calcium carbonate in an amount which is in the range of from 0.5-30 wt%, based on the total weight of the monocomponent fibers, wherein the calcium carbonate has an average particle size in the range of from 1 pm to 6 pm, wherein the monocomponent fibers also comprise at least one secondary alkane sulfonate which is present in an amount of 0.01-2.5 wt%, based on the total weight of the monocomponent fibers, and wherein the nonwoven web has a side with a surface having a bonded area, and wherein the bonded area is more than 9% of the total surface of the side.

2. A nonwoven fabric according to claim 1 , wherein the at least one polylactic acid has a melting temperature in the range of from 150-180 °C.

3. A nonwoven fabric according to claim 1 or 2, wherein the calcium carbonate- containing component is present in an amount in the range of from 0.5-20 wt%, based on the total weight of the monocomponent fibers.

4. A nonwoven fabric according to claim 3, wherein the calcium carbonate is present in an amount in the range of 5-20 wt%, based on total weight of the monocomponent fibers.

5. A nonwoven fabric according to any one of claims 1-4, wherein the average particle size of the calcium carbonate is smaller than 5 pm.

6. A nonwoven fabric according to any one of claims 1-5, wherein the average particle size of the calcium carbonate is in the range of from 1.2-2.0 pm.

7. A nonwoven fabric according to any one of claims 1-6, wherein the bonded area is between 50-100% of the total surface area of the side.

8. A nonwoven fabric according to any one of claims 1-7, wherein the bonded area is between 90-100% of the total surface area of the side.

9. A nonwoven fabric according to any one of claims 1-8, wherein the monocomponent fibers comprise in addition at least one polybutylene succinate-based polyester which is present in an amount in the range of from 0.02-5% by weight, based on the total weight of the monocomponent fibers.

10. A nonwoven fabric according to any one of claims 1-9, wherein the monocomponent fibers comprise one type of polylactic acid.

11. A process for preparing a nonwoven fabric according to claim 1 , the process comprising the following steps:(a) providing a stream of one or more molten or semi-molten polylactic acids;(b) blending the calcium carbonate having an average particle size in the range of from 1 pm to 6 pm and the at least one secondary alkane sulfonate with at least one of the molten or semi-molten polylactic acids;(c) forming from the blend obtained in step (b) spunbond continuous monocomponent fibers, whereby the calcium carbonate is present in an amount in the range of from 0.5-30 wt%, the one or more polylactic acids are present in an amount in the range of from 67.5- 99.49 wt%, and the at least one secondary alkane sulfonate is present in an amount of 0.01- 2.5 wt%, all weights based on the total weight of the monocomponent fibers;(d) depositing the plurality of the continuous monocomponent fibers as obtained in step (c) onto a collection surface; and(e) bonding the plurality of continuous monocomponent fibers as obtained in step (d) to obtain the nonwoven fabric comprising a nonwoven web having a side with a surface having a bonded area which is more than 9% of the total surface of the side.

12. A process according to claim 11 , wherein in step (f) the bonding is carried out so as to obtain a nonwoven having a side with a surface with a bonded area which is between 50-100% of the total surface of the side.

13. An article comprising the nonwoven fabric according to any one of claims 1- 10.

14. An article according to claim13, wherein the article comprises a diaper, asanitary pad, a container or cover for use in respect of plants and / or agriculture applications, a packaging material, a bag or pouch.

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