Polypropylene compositions for nonwoven materials

Abstract

A polypropylene composition for use in forming a nonwoven material. The polypropylene composition may include a propylene random copolymer comprising at least 95 wt.% of propylene relative to the total weight of the propylene random copolymer and not more than 2.5 wt.% of a comonomer propylene relative to the total weight of the propylene random copolymer. The propylene random copolymer may exhibit an average molecular weight (Mw) of from about 125,000 g / mol to about 250,000 g / mol as determined by gel permeation chromatography (GPC). The propylene random copolymer may exhibit a melt flow index of from about 20 dg / min to about 40 dg / min as determined in accordance with ASTM D1238, Condition L.

Description

POLYPROPYLENE COMPOSITIONS FOR NONWOVEN MATERIALSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U. S. Provisional Application Serial No.63 / 718,426 entitled “Polypropylene Compositions for Nonwoven Materials” by Ashbaugh et al. and filed November 8, 2024, which is incorporated herein by reference in its entirety for all purposes.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.TECHNICAL FIELD

[0003] The present disclosure relates generally to polypropylene compositions. More particularly, the present disclosure relates to polypropylene compositions having improved characteristics for nonwoven materials and nonwoven articles.BACKGROUND

[0004] Polypropylene is a widely used plastic that exhibits high modulus, high tensile strength, good heat resistance, and other favorable properties in the solid-state. Polypropylene with good thermal stability may be useful in such applications as composites and compounding. Composites may be formed by wetting a fiber, such as a glass fiber, with polypropylene. Polypropylene with good thermal stability may also be used to form nonwoven materials and / or nonwoven articles, such as may be used for automobiles and in filtration. Polypropylene with good thermal stability may also be used in durable good applications where high temperature resistance is desirable. Examples of such durable goods include, but are not limited to, coffee makers, hair dryers, washing machines, and dish washers.

[0005] Nonetheless, improvements in polypropylene that would allow for improved processing characteristics and / or improved materials formed from such polypropylene are needed.BRIEF SUMMARY OF DISCLOSURE

[0006] Disclosed herein, in some embodiments, is a polypropylene composition for use in forming a nonwoven material. The polypropylene composition may comprise a propylene random copolymer comprising at least 95 wt.% of propylene relative to thetotal weight of the propylene random copolymer and not more than 2.5 wt.% of a comonomer propylene relative to the total weight of the propylene random copolymer. The propylene random copolymer may exhibit an average molecular weight (Mw) of from about 125,000 g / mol to about 250,000 g / mol as determined by gel permeation chromatography (GPC). The propylene random copolymer may exhibit a melt flow index of from about 20 dg / min to about 40 dg / min as determined in accordance with ASTM D1238, Condition L.

[0007] Also disclosed herein, in some embodiments, is a nonwoven material formed from a polypropylene composition. The polypropylene composition may comprise a propylene random copolymer comprising at least 95 wt.% of propylene relative to the total weight of the propylene random copolymer and not more than 2.5 wt.% of a comonomer propylene relative to the total weight of the propylene random copolymer. The propylene random copolymer may exhibit an average molecular weight (Mw) of from about 125,000 g / mol to about 250,000 g / mol as determined by gel permeation chromatography (GPC). The propylene random copolymer may exhibit a melt flow index of from about 20 dg / min to about 40 dg / min as determined in accordance with ASTM D1238, Condition L.

[0008] Also disclosed herein, in some embodiments, is a method of forming a nonwoven material. The method may comprise providing a polypropylene composition that may comprise a propylene random copolymer comprising at least 95 wt.% of propylene relative to the total weight of the propylene random copolymer and not more than 2.5 wt.% of a comonomer propylene relative to the total weight of the propylene random copolymer. The propylene random copolymer exhibits an average molecular weight (Mw) of from about 125,000 g / mol to about 250,000 g / mol as determined by gel permeation chromatography (GPC). The propylene random copolymer exhibits a melt flow index of from about 20 dg / min to about 40 dg / min as determined in accordance with ASTM D1238, Condition L. The method may further comprise forming fibers from the polypropylene composition. The method may further comprise consolidating the fibers to form the nonwoven material.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a detailed description of exemplary embodiments of the disclosure, reference will now be made to the accompanying drawings in which:

[0010] Figure 1 is a graph illustrating the bonding temperature ranges associated with each of various nonwoven materials;

[0011] Figure 2 is a graph illustrating the tensile load at break associated with each of various nonwoven materials;

[0012] Figure 3 is a graph illustrating the fabric extension at break associated with each of various nonwoven materials; and

[0013] Figure 4 is a graph illustrating the percent change of coefficient of friction associated with each of various nonwoven materials.DETAILED DESCRIPTION

[0014] The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0015] Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness. In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to...”

[0016] Disclosed herein are various embodiments of polypropylene compositions having improved characteristics for use in a nonwoven material. Also disclosed herein are nonwoven materials resulting from the use of the improved polypropylene compositions disclosed herein. As used herein, the terms “polypropylene,” polypropylene resin,” and “propylene polymer” may be used synonymously. Also, as used herein, the term “propylene random copolymer” may be used to denote a copolymer of propylene and at least one comonomer where the at least one comonomer is randomly distributed through the copolymer.

[0017] In some embodiments, the polypropylene composition disclosed herein may be characterized as comprising propylene random copolymers having an average molecular weight (Mw) of from about 125,000 g / mol (Daltons) to about 250,000 g / mol (Daltons) as determined by size exclusion chromatography (SEC), also referred to as gel permeation chromatography (GPC), additionally or alternatively, from about 150,000 g / mol (Daltons) to about 200,000 g / mol (Daltons), additionally or alternatively, from about 160,000 g / mol (Daltons) to about 190,000 g / mol (Daltons), additionally or alternatively, from about 165,000 g / mol (Daltons) to about 180,000 g / mol (Daltons), additionally or alternatively, from about 160,000 g / mol (Daltons) to about 175,000 g / mol (Daltons), additionally or alternatively, from about 168,000 g / mol (Daltons) to about 178,000 g / mol (Daltons), additionally or alternatively, from about 170,000 g / mol (Daltons) to about 175,000 g / mol (Daltons).

[0018] Additionally or alternatively, in some embodiments, the polypropylene composition may be characterized as comprising propylene random copolymers having a number average molar weight (Mn) of from about 40,000 g / mol (Daltons) to about 90,000 g / mol (Daltons) as determined by GPC, additionally or alternatively, from about 50,000 g / mol (Daltons) to about 80,000 g / mol (Daltons), additionally or alternatively, from about 55,000 g / mol (Daltons) to about 75,000 g / mol (Daltons), additionally or alternatively, from about 55,000 g / mol (Daltons) to about 70,000 g / mol (Daltons), additionally or alternatively, from about 60,000 g / mol (Daltons) to about 70,000 g / mol (Daltons), additionally or alternatively, from about 60,000 g / mol (Daltons) to about 65,000 g / mol (Daltons), additionally or alternatively, from about 62,000 g / mol (Daltons) to about 64,000 g / mol (Daltons).

[0019] Additionally or alternatively, in some embodiments, the polypropylene composition may be characterized as comprising propylene random copolymers having a Z average molar weight (Mz) of from about 250,000 g / mol (Daltons) to about 400,000 g / mol (Daltons) as determined by GPC, additionally or alternatively, from about 300,000 g / mol (Daltons) to about 360,000 g / mol (Daltons), additionally or alternatively, from about 315,000 g / mol (Daltons) to about 345,000 g / mol (Daltons), additionally or alternatively, from about 320,000 g / mol (Daltons) to about 340,000 g / mol (Daltons), additionally or alternatively, from about 325,000 g / mol (Daltons) to about 335,000 g / mol (Daltons).

[0020] In some embodiments, the polypropylene composition may be characterized as exhibiting a relatively narrow molecular weight distribution. For example, in someembodiments, the propylene random copolymer has a molecular weight distribution, defined as Mw / Mn, that is, the ratio of weight average molecular weight (Mw, as defined herein) relative to the number average molecular weight (Mn, as defined herein) of not more than 4.0, additionally or alternatively, a Mw / Mnof not more than 3.5, additionally or alternatively, a Mw / Mnof not more 3.0, additionally or alternatively, a Mw / Mnof not more 2.9, additionally or alternatively, a Mw / Mnof not more 2.8, a Mw / Mnof from about 1.0 to about 4.0, additionally or alternatively, a Mw / Mnof from about 2.0 to about 3.5, additionally or alternatively, a Mw / Mnof from about 2.5 to about 3.0, additionally or alternatively, a Mw / Mnof from about 2.6 to about 2.9, additionally or alternatively, a Mw / Mn of from about 2.7 to about 2.8.

[0021] In some embodiments, the polypropylene composition comprises a propylene random copolymer comprising at least 50 wt. % propylene relative to the total weight of the propylene random copolymer, additionally or alternatively, at least 60 wt. %, additionally or alternatively, at least 70 wt. %, additionally or alternatively, at least 80 wt. %, additionally or alternatively, at 90 wt. %, additionally or alternatively, at least 95 wt. %, additionally or alternatively, at least 97 wt. %, additionally or alternatively at least about 98 wt. %, additionally or alternatively, at least 98.5 wt. %, additionally or alternatively, from about 95 wt. % to about 99.9 wt. %, additionally or alternatively, from about 97 wt. % to about 99.5 wt. %, additionally or alternatively, from about 97.5 wt. % to about 99 wt. % propylene relative to the total weight of the propylene random copolymer.

[0022] In some embodiments, polypropylene composition disclosed herein comprises a propylene random copolymer comprising at least one comonomer, where the comonomer is an alpha-olefin different from propylene. For example, the comonomer may be an alpha-olefin having from one to ten carbon atoms. Suitable examples of the alpha-olefin may include, but are not limited to, ethylene, butene-1, pentene-1, hexene- 1, heptene- 1, hexene- 1 and 4-methyi-pentene-1, or combinations thereof. For example, the alpha-olefin may be ethylene, butene-1, hexene-1, or combinations thereof. In some embodiments, the alpha-olefin comprises ethylene. For example, the propylene random copolymer may comprise a random copolymer of propylene and ethylene, for example, at least 99 wt. % propylene and ethylene relative to the total weight of the propylene random copolymer, additionally or alternatively, at least 99.5 wt. %, additionally or alternatively, at least 99.6 wt. %, additionally or alternatively, at least 99.7 wt. %, additionally or alternatively, at least 99.8 wt. %, additionally oralternatively, at least 99.9 wt % propylene and ethylene relative to the total weight of the propylene random copolymer.

[0023] In some embodiments, the comonomer may comprise at least about 0.25 wt. % comonomer by weight of the propylene random copolymer, additionally or alternatively, at least 0.5 wt. %, additionally or alternatively, at least 0.75 wt. %, additionally or alternatively, at least 1.0 wt. %, additionally or alternatively, at least 1.25 wt. %, additionally or alternatively, at least 1.5 wt. %, additionally or alternatively, not more than 2.5 wt %, additionally or alternatively, not more than 2.25 wt. %, additionally or alternatively, not more than 2.0 wt. %, additionally or alternatively, not more than 1.75 wt. %, additionally or alternatively, not more than 2.5 wt. %, additionally or alternatively, from about 0.5 wt. % to about 2.5 wt. %, additionally or alternatively, from about 0.75 wt. % to about 1.5 wt. % comonomer by weight of the propylene random copolymer.

[0024] In one or more aspects, the polypropylene composition may be characterized as having a xylene solubles content ranging from about 0.1 wt. % to about 2.0 wt. %, additionally or alternatively, from about 0.2 wt. % to about 1.0 wt. %, additionally or alternatively, from about 0.25 wt.% to about 0.75 wt.% or, additionally or alternatively, about 0.5 wt. % based on the total weight of the polypropylene composition. As used herein, the term “xylene solubles” refers to the weight percent of resin that remains in solution after a sample of resin is dissolved in hot xylene and the solution is allowed to cool to 25° C, as determined in accordance with ISO 16152 or ASTM 5492.

[0025] In some embodiments, the propylene random copolymer may be characterized as exhibiting a low degree of atacticity, for example, having a relatively low atactic portion. Generally, “atacticity” may refer to a random spatial arrangement of a substituent group within a polymer, more particular, where substituent groups are generally randomly distributed and exhibit no regular pattern. For example, in some embodiments the propylene random copolymer may be characterized with respect to the content of mmmm pentads, in which the mmmm pentad indicates a pentad in which the stereochemical relationship between each of the five monomer units is a “meso” relationship. In some embodiments, the propylene random copolymer may be characterized as having a content of mmmm pentads is at least 90%, additionally or alternatively, at least. 92%, additionally or alternatively, at least 94%, additionally or alternatively, at least 96% or, additionally or alternatively, at least 98%. The content of mmmm pentads may be determined by13C-NMR analysis.

[0026] Additionally or alternatively, in some embodiments the propylene random copolymer may be characterized as having at least 90% of the at least one comonomer present as isolated comonomer units, additionally or alternatively, at least 92%, additionally or alternatively, at least 94%, additionally or alternatively, at least 96% or, additionally or alternatively, at least 98% of the at least one comonomer present as isolated comonomer units. The percentage of isolated comonomer units is given relative to the total number of comonomer units in the polypropylene random copolymer chains. The term “isolated unit” is used to denote that in the polypropylene random copolymer chain a comonomer unit is surrounded by propylene units only; that is, such that the isolated unit is adjacent only to propylene units. The content of isolated units may be determined by13C-NMR analysis.

[0027] In some embodiments, the polypropylene composition may be characterized as having a melt flow index of at least 5 decigrams (dg) / min, additionally or alternatively, at least 10 dg / min, additionally or alternatively, at least 15 dg / min, additionally or alternatively, at least 20 dg / min. Additionally or alternatively, in some embodiments, the polypropylene composition may be characterized as having a melt flow index of at most 80 dg / min, additionally or alternatively, at most 70 dg / min, additionally or alternatively, at most 60 dg / min, additionally or alternatively, at most 50 dg / min, additionally or alternatively, at most 40 dg / min. For example, in in some embodiments, the polypropylene composition may be characterized as having a melt flow index of from about 8 dg / min to about 60 dg / min, additionally or alternatively, from about 20 dg / min to about 40 dg / min, additionally or alternatively, about 25 dg / min to about 35 dg / min. As used herein, the term “melt flow index” is determined in accordance with ASTM D1238, Condition L, for instance, at 230 °C with a load of 2.16 kg.

[0028] In some embodiments, the polypropylene composition may be characterized as having a density of from about 0.60 grams per cubic centimeters (g / cc) to about 1.20 g / cc as determined by ASTM D-1505, additionally or alternatively, a density of from about 0.80 grams per cubic centimeters (g / cc) to about 1.00 g / cc, additionally or alternatively, a density of from about 0.85 grams per cubic centimeters (g / cc) to about.0.95 g / cc.

[0029] In some embodiments, the polypropylene composition may be characterized as having a relatively low melting temperature (Tmeit). For example, the polypropylene composition may have a melting temperature of from about 130°C (270°F) to about 160°C (320°F) determined by Differential Scanning calorimetry according to ISO 3146,additionally or alternatively, 140°C (280°F) to about 160° C (300°F), additionally or alternatively, about 145°C (293°F).

[0030] In some embodiments, the propylene random copolymer disclosed herein is obtained by polymerizing propylene and at least one comonomer with a metallocene-based polymerization catalyst. The metallocene-based polymerization catalyst may generally comprise a bridged metallocene component, a support and an activating agent.

[0031] In some embodiments, the metallocene component can be described by the following general formula, Formula I:FORMULA (I): (p-Ra)(Rb)(Rc)MX1X2where Ra, Rb, Rc, M, X1and X2are as defined below.

[0032] In some embodiments, Ramay be the bridge between Rband Rc, for example, Rais chemically connected to Rband Rc. Ramay be selected from the group consisting of — (CR1R2)P-—, — (SiR1R2)p-—, — (GeR1R2)p— -, — (NR1)P—, ~-(PR1)P“-, — (N+R1R2)P— and — (P+R1R2)p—, where p is 1 or 2, and where R1and R2are each independently selected from the group consisting of a hydrogen, a C1-C10 alkyl, a C5-C8 cycloalkyl, a C6-C18 aryl, an alkylaryl with a C1-C10 alkyl, and a C6-C18 aryl, or any two neighboring R (i.e. two neighboring R1, two neighboring R2, or R1with a neighboring R2) may form a cyclic saturated or non-saturated C4-C10 ring. Each of R1and R2may in turn be substituted. Examples of a suitable C1-C10 alkyl may include methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, and tert-butyl. Examples of a suitable C5-C8 cycloalkyl may include cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. Examples of a C6-C18 aryl may include phenyl and indenyl. Examples of a suitable alkylaryl with a C1-C10 alkyl and a C6-C18 aryl may include benzyl ( — CH2-Ph), and — (CH2)2-Ph. In some particular embodiments, Rais — (CR1R2)P— or — (SiR1R2)p— with R1, R2and p as defined above. Additionally, in some particular embodiments, R3is — (SiR1R2)p— with R1, R2and p as defined above Specific examples of Rainclude Me2C, ethanediyl ( — CH2— CH2— ), Ph2C, and Me2Si.

[0033] In some embodiments, M may be a metal selected from Ti, Zr and Hf. In some particular embodiments, M is Zr.

[0034] In some embodiments, X1and X2may be selected, independently, from the group consisting of a halogen, a hydrogen, a C1-C10 alkyl, a Ce-Cisaryl, and analkylaryl with a C1-C10 alkyl and a Ce-Cisaryl. In some particular embodiments, X1and X2may be, independently, halogen or methyl. Examples of a suitable halogen may include Cl, Br, and I. Examples of a suitable Ct-C alkyl may include methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, and tert-butyl. Examples of a C6-C18 aryl may include phenyl and indenyl. Examples of a suitable alkylaryl with a C1-C10 alkyl and a Ce-Cisaryl may include benzyl ( — CHs-Ph), and — (CH2)2-Ph.

[0035] In some embodiments, Rband Rcmay be selected, independently, from one another and comprise a cyclopentadienyl ring in some embodiments, Rband Rcmay both be substituted cyclopentadienyl, or may be independently from one another unsubstituted or substituted indenyl or tetrahydroindenyl, or Rbmay be a substituted cyclopentadienyl and Rca substituted or unsubstituted fluorenyl. In some particular embodiments, Rband Rcmay both be the same and may be selected from the group consisting of substituted cyclopentadienyl, unsubstituted indenyl, substituted indenyl, unsubstituted tetrahydroindenyl, and substituted tetrahydroindenyl. With respect to Rband Rc, the term “unsubstituted” is meant that all positions on Rband Rc, respectively, except for the one to which the bridge is attached, are occupied by hydrogen. With respect to Rband Rc, the term “substituted” is meant that, in addition to the position at which the bridge is attached, at least, one other position on Rband Rc, respectively, is occupied by a substituent other than hydrogen, where each of the substituents may independently be selected from the group consisting of C1-C10 alkyl, C5-C7 cycloalkyl, C6-C18 aryl, and alkylaryl with C1-C10 alkyl and C6-C18 aryl, or any two neighboring substituents may form a cyclic saturated or non-saturated C4-C10 ring.

[0036] A substituted cyclopentadienyl may, for example, be represented by the general formula C5R3R4R5R6. A substituted indenyl may, for example, be represented by the general formula C9R7R8R9R10R11R12R13R14. A substituted tetrahydroindenyl may, for example, be represented by the general formula C9H4R15R16R17R18. A substituted fluorenyl may, for example, be represented by the general formula C13R19R20R21R22R23R24R25R26. Each of the substituents R3to R26may independently be selected from the group consisting of hydrogen, C1-C10 alkyl, C5-C7 cycloalkyl, C6-C15 aryl, and alkylaryl with C1-C10 alkyl and C6-C18 aryl, or any two neighboring R may form a cyclic saturated or non-saturated C4-Ci3ring; provided, however, that not all substituents simultaneously are hydrogen.

[0037] in some particular embodiments, metallocene components may have C2-symmetry or those having Ci-symmetry. For example, the metallocene componentsmay be those having C2-symmetry. Particularly suitable metallocene components are those wherein Rband Rcare the same and are substituted cyclopentadienyl, preferably wherein the cyclopentadienyl is substituted in the 2-position, the 3-position, or simultaneously the 2-position and the 3-position. Additionally or alternatively, particularly suitable metallocene components are also those wherein Rband Rcare the same and are selected from the group consisting of unsubstituted indenyl, unsubstituted tetrahydroindenyl, substituted indenyl and substituted tetrahydroindenyl. Substituted indenyl may be substituted in the 2-position, the 3-position, the 4-position, the 5-position or any combination of these, more preferably in the 2-position, the 4-position or simultaneously in the 2-position and the 4-position. Substituted tetrahydroindenyl may be substituted in the 2-position, the 3-position, or simultaneously the 2-position and the 3-position.

[0038] In various embodiments, the metallocene-based polymerization catalyst may be supported via any suitable support. For example, the support may be any suitable organic or inorganic solid, more particularly, a porous support such as talc, an inorganic oxide, or a resinous support material such as a polyolefin. In some particular embodiments, the support material is an inorganic oxide in a finely divided form.

[0039] In some embodiments, the polypropylene composition comprising the propylene random copolymer, as disclosed herein, is obtained by contacting a propylene polymerization product with an active prodegradant in order to modify the rheology thereof and thereby yield the propylene random copolymer. Not intending to be bound by theory, the prodegradant may be effective to reduce the molecular weight and / or to narrow the molecular weight distribution of a polypropylene polymerization product. Generally, the prodegradant may be allowed to react with the polypropylene polymerization product at elevated temperatures, such as during extrusion and / or pelletization thereof.

[0040] In various embodiments, the active prodegradants may comprise an organic peroxide ora salt of transition metals such as iron, nickel, cobalt, or manganese, which react with oxygen to promote the breaking of chemical bonds in the molecular structure of a polymer. Nonlimiting examples of suitable prodegradants may include 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane (commercially available from NOURYON as Trigonox 301), 1,2,4,5,7,8-hexoxonane (commercially available from NOURYON as Trigonox 501, 3,6,9-trimethyl-3,6,9-tris(alkyl) derivatives, 2,5-dimethyl-2,5-di(tert-butylperoxy) hexane (commercially available from NOURYON as Trigonox 101-10PP), and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (commercially available from ARKEMA as Luperox 101).

[0041] In some embodiments, the polypropylene composition may further comprise one or more additives as desirable to modify one or more parameters thereof. Examples of such an additive include stabilizers such as antioxidants, chlorine absorbers and ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, colorants, and the like. Not intending to be bound by theory, the relatively low melting temperature exhibited by the polypropylene composition comprising the propylene random copolymers as disclosed herein may advantageously allow for improved migration and / or incorporation of any such additives.

[0042] In various embodiments, the polypropylene composition comprising the propylene random copolymers as disclosed herein may be advantageously employed in the production of various nonwoven materials, for example, a nonwoven fabric, comprising a plurality of fibers, filaments, and / or threads (collectively, “fibers") comprising the polypropylene composition as disclosed herein. Generally, in various embodiments, the nonwoven material (for example, nonwoven fabric) may comprise a web of fibers formed from the propylene random copolymers as disclosed herein disposed such that the plurality of the fibers is mechanically entangled or interconnected and consolidated, bonded, or fused together. For example, the plurality of fibers may be interlaid such that the plurality of fibers does not form any identifiable repeating patterns, such as in a knitted or woven fabric and, then, subjected to a bonding or consolidation process so as to bond at least a portion of the fibers together to form the nonwoven material. In various embodiments, the nonwoven material may be formed by any suitable process, examples of which may include, but are not limited to, spunbonding, meltblowing, and carding and bonding.

[0043] For example, in some embodiments, at least a portion of the plurality of fibers may comprise spunbond fibers. Generally, spunbond fibers are formed by extruding molten thermoplastic material via a plurality of small holes of a spinneret and then stretching the resultant threads so as to reduce the with the diameter of the extruded threads. In various embodiments, at least a portion of the plurality of fibers (for example, spunbond fibers) may be characterized as continuous fibers, for example, fibers which have not been cut from their original length prior to being formed into a nonwoven fabric. In some embodiments, the spunbond fibers may be collecteddeposited to form a nonwoven web, which may be consolidated to form the nonwoven material.

[0044] Additionally or alternatively, in some embodiments, at least a portion of the plurality of fibers may comprise meltblown fibers. Generally, meltblown fibers are formed by extruding a molten thermoplastic material through a plurality of fine die capillaries to form molten threads or filaments that are introduced into a high velocity, high temperature gaseous stream so as to reduce the diameter of the threads or filaments. Then, the meltblown fibers may be carried via the high velocity, gaseous stream and deposited onto a collecting surface to form a web of randomly disbursed meltblown fibers, which may be consolidated to form the nonwoven material. In various embodiments, the meltblown fibers may be continuous or discontinuous.

[0045] Additionally or alternatively, in some embodiments, at least a portion of the plurality of fibers may comprise staple fibers. Generally, staple fibers are formed by cutting a filament to form small, discrete fibers. The staple fibers may then be carded, for example, by collecting the staple fibers to form a non-consolidated web on a support, and bonded to form the nonwoven material.

[0046] In various embodiments, the fibers may be consolidated by bringing and bonding together at least a portion of the fibers of a nonwoven web For exa ple, in various embodiments the fibers may be thermally fused together, chemically bonded together, and / or mechanically entangled together at a bonding site(s). In some embodiments, the fibers may be softened or melted and, optionally, subsequently or simultaneously compressed to form deformations in the fibers and bond the fibers together.

[0047] In some embodiments, the relatively low melting temperature exhibited by the polypropylene composition comprising the propylene random copolymers as disclosed herein may be particularly advantageous with respect to production of various nonwoven materials, for example, a nonwoven fabric. Particularly, the relatively low melting temperature exhibited by the polypropylene composition allows for the consolidation of fibers to occur at a relatively lower temperature. For example, fibers formed from the propylene random copolymers as disclosed herein may exhibit a consolidation temperature of from about 130°C (270°F) to about 160°C (320°F), additionally or alternatively, 140°C (280°F) to about 160°C (300°F), additionally or alternatively, about 145°C (293°F). As such, the use of fibers formed from the polypropylene composition disclosed herein lowers the onset of melting and / orsoftening when forming the nonwoven material. Consequently, a nonwoven material formed from fibers formed of the polypropylene composition disclosed herein may be thermally bonded at reduced temperatures.

[0048] Additionally, the relatively low melting temperature exhibited by the polypropylene composition enables the production of a nonwoven material having desirable physical parameters, particularly, in comparison to conventional nonwoven materials formed from a polypropylene having a relatively higher melting temperature. For example, a nonwoven material formed from the disclosed polypropylene composition may be characterized as exhibiting improved tensile strength. For example, a nonwoven material formed from the disclosed polypropylene may be characterized as exhibiting a tensile load at break of at least 6.5 pounds (lbs.) as determined via a Model 5565A Instron® Universal Testing Machine, or equivalent, in accordance with the procedures described herein, additionally or alternatively, at least 6.75 lbs. at break, additionally or alternatively, at least 7.0 lbs. at break, additionally or alternatively, at least 7.1 lbs. at break, additionally or alternatively, at least 7.2 lbs. at break.

[0049] Also, a nonwoven material formed from the disclosed polypropylene may be characterized as exhibiting an extension at break of at least 1.0 inches (in.) as determined via a Model 5565A Instron® Universal Testing Machine, or equivalent, in accordance with the procedures described herein, additionally or alternatively, at least 1.1 in. at break, additionally or alternatively, at least 1.2 in. at break, additionally or alternatively, at least 1.3 in. at break

[0050] Tensile load and / or extension at break may assessed on a sample of the nonwoven material having a size of 1 inch by 6 inches. The assessment is conducted under standard laboratory conditions, generally, at a temperature of about 23°C.+ / −3°C. (73°F.+ / −5°F.) and a relative humidity of 35%±5%. The apparatus is configured with a 50 N load cell and pneumatic grips. The sample is secured in the grips of the apparatus, balanced, and tested at 12 in / min. Not intending to be bound by theory, conventional polypropylenes having a relatively higher melting temperature required to soften, melt, and / or consolidate the polypropylene fibers, as a result of the higher temperatures required for processing, may exhibit a decrease in the crystallinity of the conventional polypropylenes, which is believed to result in a decrease in tensile strength. Surprisingly, the disclosed polypropylene has been found to exhibit improved tensile strength.

[0051] Additionally, the relatively low melting temperature exhibited by the polypropylene composition may yield a nonwoven material having relatively fewer pinholes and / or burn-through. For example, and again not intending to be bound by theory, conventional polypropylenes having a relatively higher melting temperature required to soften, melt, and / or consolidate the polypropylene fibers, when processed, may result in “pinholes" or “burn-through,” for example, where the relatively high temperatures required to consolidate such conventional fibers cause deformations in the resultant material. That is, the relatively low-temperature bonding window of the disclosed polypropylene can prevent burn through or pinholes in nonwoven materials (e.g., fabrics) formed therefrom. Also, the relatively low-temperature bonding window of the disclosed polypropylene can be effective to save energy associated with bonding, for example, as a result of the lower required temperatures.

[0052] Additionally, the relatively low melting temperature exhibited by the polypropylene composition also exhibits improved softness.

[0053] In one or more embodiments, the polypropylene composition disclosed herein may be used in the production of an end-use article such as a non-woven, fiber-based article, examples of which include, but are not limited to bags, totes, diapers, face masks, medical gowns, medical masks, filter media, and oil absorbent wipes. The disclosed polypropylene composition, as a result of the relatively low melting point, provides superior nonwoven fabric performance such as strength and barrier, desirable characteristics, such as softness for final applications.EXAMPLES

[0054] The aspects having been generally described, the following examples are given as particular aspects of the disclosure and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification of the claims in any manner.

[0055] In order to demonstrate the advantageous use of the disclosed polypropylene composition, a nonwoven polypropylene material made according to the disclosure herein (“Roll #10 New Development PP”) was compared to two commercially available polypropylene nonwoven materials (“Roll #1 35 MFR PP Spunbond” and “Roll #8A24 MFR PP Spunbond”). Roll#135 MFR PP Spunbond is a visbroken polypropylene homopolymer produced via a Zeigler-Natta catalyst and Roll#8A 24 MFR PP Spunbond is a polypropylene homopolymer produced via a metallocene catalyst.

[0056] Figure 1 illustrates the bonding temperature ranges associated with each of the nonwoven materials, Roll #10 New Development PP, Roll#1 35 MFR PP Spunbond, and Roll #8A 24 MFR PP Spunbond. Figure 1 illustrates that Roll #10 New Development PP exhibits a lower bonding temperature than the commercially available materials.

[0057] Figure 2 illustrates the tensile load at break associated with each of the nonwoven materials, Roll #10 New Development PP, Roll#1 35 MFR PP Spunbond, and Roll #8A 24 MFR PP Spunbond. Figure 2 illustrates that Roll #10 New Development PP exhibits an improved tensile load in comparison to the commercially available materials.

[0058] Figure 3 illustrates the fabric extension at break associated with each of the nonwoven materials, Roll #10 New Development PP, Roll#1 35 MFR PP Spunbond, and Roll #8A 24 MFR PP Spunbond. Figure 3 illustrates that Roll #10 New Development PP exhibits a lower bonding temperature than the commercially available materials.

[0059] Figure 4 illustrates the percent change of coefficient of friction (“COF”) associated with each of Roll #10 New Development PP and Roll #8A 24 MFR PP Spunbond. Figure 4 illustrates that Roll #10 New Development PP exhibits a lower and more consistent COF in comparison to the commercially available material.

[0060] While various aspects have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the disclosure. The aspects described herein are exemplary only and are not intended to be limiting. Many variations and modifications of the aspects disclosed herein are possible and are within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greaterthan 0.10 includes0.11, 0.12, 0.13, etc.). Use of the term "optionally" with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim. Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc.

[0061] Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an aspect of the present disclosure. Thus, the claims are a further description and are an addition to the aspects disclosed herein. The discussion of a reference herein is not an admission that it is prior art to the present disclosure, especially any reference that may have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent that they provide exemplary, procedural or other details supplementary to those set forth herein.

Claims

CLAIMSWhat is claimed is:

1. A polypropylene composition for use in forming a nonwoven material, the polypropylene composition comprising:a propylene random copolymer comprising at least 95 wt.% of propylene relative to total weight of the propylene random copolymer and not more than 2.5 wt.% of a comonomer propylene relative to the total weight of the propylene random copolymer,wherein the propylene random copolymer exhibits an average molecular weight (Mw) of from about 125,000 g / mol to about 250,000 g / mol as determined by gel permeation chromatography (GPC), andwherein the propylene random copolymer exhibits a melt flow index of from about 20 dg / min to about 40 dg / min as determined in accordance with ASTM D1238, Condition L.

2. The polypropylene composition of claim 1, wherein the propylene random copolymer exhibits a melting temperature of from about 130°C (270°F) to about 160°C (320°F) determined by Differential Scanning calorimetry according to ISO 3146.

3. The polypropylene composition of claim 2, wherein the melting temperature is from about 140°C (280°F) to about 160°C (300°F) determined by Differential Scanning calorimetry according to ISO 3146.

4. The polypropylene composition of one of claims 1 -3, wherein the melt flow index is from about 25 dg / min to about 35 dg / min.

5. The polypropylene composition of one of claims 1-4, wherein the propylene random copolymer exhibits a density of from about 0.60 grams per cubic centimeters (g / cc) to about 1.20 g / cc as determined by ASTM D-1505.

6. The polypropylene composition of one of claims 1-5, wherein the propylene random copolymer exhibits a number average molar weight (Mn) of from about 40,000 g / mol (Daltons) to about 90,000 g / mol (Daltons) as determined by GPC.

7. The polypropylene composition of claim 6, wherein the propylene random copolymer exhibits a molecular weight distribution (Mw / Mn) of from about 2.5 to about 3.0.

8. A nonwoven material formed from a polypropylene composition, the polypropylene composition comprising:a propylene random copolymer comprising at least 95 wt.% of propylene relative to total weight of the propylene random copolymer and not more than 2.5 wt.% of a comonomer propylene relative to the total weight of the propylene random copolymer,wherein the propylene random copolymer exhibits an average molecular weight (Mw) of from about 125,000 g / mol to about 250,000 g / mol as determined by gel permeation chromatography (GPC), andwherein the propylene random copolymer exhibits a melt flow index of from about 20 dg / min to about 40 dg / min as determined in accordance with ASTM D1238, Condition L.

9. The nonwoven material of claim 8, wherein the propylene random copolymer exhibits a melting temperature of from about 130°C (270°F) to about 160’C (320°F) determined by Differential Scanning calorimetry according to ISO 3146.

10. The nonwoven material of claim 9, wherein the melting temperature is from about 140°C (280°F) to about 160°C (300°F) determined by Differential Scanning calorimetry according to ISO 3146.

11. The nonwoven material of one of claims 8-10, wherein the melt flow index is from about 25 dg / min to about 35 dg / min.

12. The nonwoven material of one of claims 8-11, wherein the propylene random copolymer exhibits a density of from about 0.60 grams per cubic centimeters (g / cc) to about 1.20 g / cc as determined by ASTM D-1505.

13. The nonwoven material of one of claims 8-12, wherein the propylene random copolymer exhibits a number average molar weight (Mn) of from about 40,000 g / mol (Daltons) to about 90,000 g / mol (Daltons) as determined by GPC.

14. The nonwoven material of claim 13, wherein the propylene random copolymer exhibits a molecular weight distribution (Mw / Mn) of from about 2.5 to about 3.0.

15. A method of forming a nonwoven material, the method comprising: providing a polypropylene composition comprising:a propylene random copolymer comprising at least 95 wt.% of propylene relative to total weight of the propylene random copolymer and not more than 2.5 wt.% of a comonomer propylene relative to the total weight of the propylene random copolymer,wherein the propylene random copolymer exhibits an average molecular weight (Mw) of from about 125,000 g / mol to about 250,000 g / mol as determined by gel permeation chromatography (GPC), andwherein the propylene random copolymer exhibits a melt flow index of from about 20 dg / min to about 40 dg / min as determined in accordance with ASTM D1238, Condition L;forming fibers from the polypropylene composition; andconsolidating the fibers to form the nonwoven material.

16. The method of claim 15, wherein the propylene random copolymer exhibits a melting temperature of from about 130°C (270°F) to about 160°C (320°F) determined by Differential Scanning calorimetry according to ISO 3146.

17. The method of claim 16, wherein the melting temperature is from about 140°C (280°F) to about 160°C (300°F) determined by Differential Scanning calorimetry according to ISO 3146.

18. The method of one of claims 15-17, wherein the melt flow index is from about 25 dg / min to about 35 dg / min19. The method of one of claims 15-18, wherein the propylene random copolymer exhibits a density of from about 0.60 grams per cubic centimeters (g / cc) to about 1.20 g / cc as determined by ASTM D-1505.

20. The method of one of claims 15-19, wherein the propylene random copolymer exhibits a number average molar weight (Mn) of from about 40,000 g / mol (Daltons) to about 90,000 g / mol (Daltons) as determined by GPC.

21. The method of claim 20, wherein the propylene random copolymer exhibits a molecular weight distribution (Mw / Mn) of from about 2.5 to about 3.0.

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