Nonwoven fabric comprised of crimped bast fibers

Abstract

The invention relates to a nonwoven fabric containing at least a portion of individualized bast fibers with a mean length of greater than about 6 mm which have been treated to produce a crimp, and which can be further coated with one or more thermoplastic polymers to ensure compatibility with QAC sanitizers, and which typically having a reduced level of naturally occurring pectin. The coating and crimp of the bast fibers in these nonwoven fabrics is beneficial to forming a drylaid, airlaid or wetlaid nonwoven fabric that has desirable properties related to performance in a variety of nonwoven product applications.

Claims

1. A bast fiber nonwoven fabric comprising at least about 5% bast fibers, where said bast fibers have a mean length of greater than about 6 mm and are coated to render the fiber compatible with quaternary ammonium (QAC) based sanitizers, wherein the bast fibers have been chemically or mechanically treated to impart a crimp of about 1 to about 8 crimps per centimeter, wherein the bast fibers have been coated with a polyester thermoplastic resin that is biodegradable.

2. The bast fiber nonwoven fabric of claim 1, wherein the coating improves the surface compatibility of the bast fibers with said quaternary ammonium (QAC) based sanitizers.

3. The bast fiber nonwoven fabric of claim 1, where said thermoplastic resin coating does not degrade the antimicrobial activity of said quaternary ammonium (QAC) based sanitizers.

4. The bast fiber nonwoven fabric of claim 1, where the nonwoven fabric is a drylaid, airlaid or wetlaid nonwoven bonded by one or more of thermal bonding, mechanical bonding, or adhesive bonding.

5. The bast fiber nonwoven fabric of claim 1, where said bast fibers are blended with at least one type of natural or synthetic staple fibers at a level of 5-49% bast fibers by weight.

6. The bast fiber nonwoven fabric of claim 1, where said bast fibers are blended with at least one type of natural or synthetic staple fibers at a level of at least about 51-100% of said bast fibers by weight.

7. The bast fiber nonwoven fabric of claim 1, where said bast fibers have been treated to remove naturally occurring pectin.

8. A bast fiber nonwoven fabric comprising at least about 5% bast fibers, where said bast fibers have a mean length of greater than about 6 mm and are coated with a polyester thermoplastic resin to render the fiber compatible with quaternary ammonium (QAC) based sanitizers, wherein the polyester thermoplastic resin is biodegradable.

9. A bast fiber nonwoven fabric comprising at least about 5% bast fibers, where said bast fibers have a mean length of greater than about 6 mm and are coated to render the fiber compatible with quaternary ammonium (QAC) based sanitizers, wherein the coating improves the surface compatibility of the bast fibers with said quaternary ammonium (QAC) based sanitizers.

10. A bast fiber nonwoven fabric comprising at least about 5% bast fibers, where said bast fibers have a mean length of greater than about 6 mm and are coated with a thermoplastic resin to render the fiber compatible with quaternary ammonium (QAC) based sanitizers, where said thermoplastic resin coating does not degrade the antimicrobial activity of said quaternary ammonium (QAC) based sanitizers.

11. The bast fiber nonwoven fabric of claim 1, wherein the bast fibers are extracted from flax, hemp, jute, ramie, nettle, Spanish broom, kenaf plants, or any combination thereof.

12. The bast fiber nonwoven fabric of claim 1, further comprising natural staple fibers, man-made staple fibers, or a combination thereof, the staple fibers being crimped or uncrimped.

13. The bast fiber nonwoven fabric of claim 4, where the thermal bonding includes one or more of calendering, thermal point bonding, through-air bonding, and sonic bonding.

14. The bast fiber nonwoven fabric of claim 4, where the mechanical bonding includes one or both of needlepunching and hydroentangling.

15. The bast fiber nonwoven fabric of claim 4, wherein the adhesive bonding includes one or more of coating, spraying, dip-and-squeeze, gravure roll, foam bonding, powder bonding, and hot melt adhesive application.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to provide an understanding of embodiments of the invention, reference is made to the appended drawings, in which reference numerals refer to components of exemplary embodiments of the invention. The drawings are exemplary only, and should not be construed as limiting the invention. The disclosure described herein is illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, features illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some features may be exaggerated relative to other features for clarity. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements.

(2) FIG. 1 is a schematic illustration of a method of forming a nonwoven fabric;

(3) FIG. 2 is a schematic illustration of a method of hydroentangling a nonwoven fabric;

(4) FIG. 3 is a schematic illustration of a method of needlepunching a nonwoven fabric;

(5) FIG. 4 is a schematic illustration of a method of mechanically cleaning bast fibers;

(6) FIG. 5 is an image of substantially straight, naturally-occurring bast fibers;

(7) FIG. 6 is a Scanning Electron Microscopy (SEM) image of a crimped bast fiber according to an embodiment of the invention; and

(8) FIG. 7 is an illustration of a fiber with a planar crimp.

DETAILED DESCRIPTION OF THE INVENTION

(9) The following definitions are presented for use in the interpretation of the claims and specification of the instant invention. Terms such as “comprising”, “comprises”, “including”, “including but not limited to”, “contains”, “containing” are not to be considered as limiting or exclusive as related to the claimed invention. “A” and “an” are not be considered as indication enumeration when preceding an element or component. The terms “invention”, “present invention” or “instant invention” are not limiting terms and are used to convey and incorporate all aspects described and discussed in the claims and the specification. The term “about” used as a modifier of a quantity refers to variations as are known and understood to occur in measuring and handling procedures as are known to those skilled in the arts of textile science and engineering. Additional definitions of technical terms and references follow.

(10) Any ranges cited herein are inclusive. The term “about” used throughout is used to describe and account for small fluctuations. For instance, “about” may mean the numeric value may be modified by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1% or ±0.05%. All numeric values are modified by the term “about” whether or not explicitly indicated. Numeric values modified by the term “about” include the specific identified value. For example “about 5.0” includes 5.0.

(11) Cellulosics, and cellulosic fibers refer to natural fibers or to synthetic fibers which are chemically ethers or esters of cellulose. Such natural fibers are obtained from the bark, wood, leaves, stems, or seeds of plants. Synthetic cellulosic fibers are manufactured from digested wood pulp and may include substituted side groups to the cellulose molecule that provide specific properties to those fibers.

(12) Bast fibers are obtained from the phloem or bast from the stem of certain plants, including but not limited to jute, kenaf, flax and hemp. The bast fibers are initially recovered as bundles of individual fibers which are adhered by pectin, which must be subsequently removed to some degree to allow the bast fibers to be processed further.

(13) Crimp is the naturally occurring convolution of waviness of a fiber, or that same property induced by chemical or mechanical means, such as crimping of synthetic fibers. The imposition of crimp to a specific frequency, as defined by a number of crimps per unit of fiber length.

(14) Natural fibers are those sourced directly from plants, animals, or minerals, noting that such fibers may require specific pre-processing in order to render them useful for textile manufacturing purposes. Synthetic fibers are those produced through polymerization processes, using naturally occurring and sustainably sourced raw materials or petroleum derived raw materials.

(15) Staple fibers are fibers with a discrete length and may be natural or synthetic fibers. Continuous fibers have an indeterminate or difficult to measure length, such as silk or those from certain synthetic fiber spinning processes. Fibers of any length may be cut into discrete lengths and that cut product is then referred to as a staple fiber.

(16) Airlaid, sometimes referred to as air laid, is a processes for producing a fibrous mat or batt using short or long staple fibers, or blends of the same. In this process, air is used to transfer the fibers from the fiber opening and aligning section of the process and to then to convey those fibers to a forming surface where the fibrous mat or batt is collected and then subjected to a further step of bonding or consolidating to produce an airlaid nonwoven fabric.

(17) Drylaid is a process for producing a fibrous mat or batt by a process using mechanical fiber opening and alignment, such as carding, where the fibrous mat or batt is transferred by mechanical rather than by means of air to a conveyor surface, where the fibrous mat or batt is then subjected to a further step of bonding or consolidating to produce a drylaid nonwoven fabric.

(18) Wetlaid, sometimes referred to as wet laid, is a process for producing a fibrous sheet through means similar to paper making where the fibers are suspended in an aqueous medium and the web is formed by filtering the suspension on a conveyor belt or perforated drum. Depending on the end use application and fibers used to produce the fabric, some means of bonding or consolidating may be required to achieve final properties in the fabric.

(19) Bonding or consolidation of fibrous mats or batts is a processing step that is common among the various technologies for producing nonwoven fabrics. The means of bonding or consolidation are commonly considered as being mechanical, thermal or adhesive, with several distinct methodologies existing under each of those headings. In general, mechanical means rely on creating entanglements between and among fibers to produce desired physical properties, where needlepunch and hydroentangling are nonexclusive examples of those means. Thermal bonding uses the thermoplastic properties of at least some fibers included in the fabric, such that the application of heat with or without pressure causes a portion of the fibers to soften and deform around each other and/or to melt and form a solid attachment between and among fibers at points of crossover when the thermoplastic material has cooled and solidified. Adhesive means use the application of adhesive in some form to create a physical bond between and among fibers at points of crossover, such means nonexclusively include liquid adhesives, dry adhesives, hot melt adhesives. These adhesives may be applied to mats or batts as sprays and foams, or via methods known in the art including but not limited to dip-and-squeeze or gravure roll.

(20) A percentage by weight, in reference to a fabric, is the weight of given solid component divided by the total weight of the fabric, expressed as a percentage of the fabric weight.

(21) Strength-to-weight ratio is an expression of a normalized tensile strength value for a fabric where the tensile strength of the fabric can then be considered relative to similar fabrics without the impact of basis weight differences between or among sample fabrics or grades of fabrics. Because basis weight alone can influence tensile strength values for a given fabric, the strength-to-weight ratio allows for an assessment of the impact on the strength of a fabric contributed by the inclusion of a specific fiber or a change in the process parameters, as non-exclusive examples of the usefulness of that metric.

(22) Loft relies upon the properties of bulk and resilience for a fabric. In technical terms, bulk is the inverse of density, while in common usage bulk is equated to simple fabric thickness. Resiliency is the ability of a fabric to resist permanent compression, with loss of volume, following application of an areal load.

(23) Quaternary ammonium compounds (QAC) are among the most widely used antimicrobial treatments available, having good stability and surface activity, low odor and reactivity with other cleaning, and good toxicology results. QACs are active against most bacteria, as well as some virus forms and certain fungi. Further, QACs are readily applied to surfaces, including the surfaces of fibers in a fabric construction, where it may be retained by those surfaces and also transferred from the fibers to other surfaces for the purpose of clean or disinfecting. While synthetic fiber surfaces are known to be essentially non-reactive with QACs, some cellulosic fibers, including bast fibers, react with QACs thereby reducing the efficacy of the QAC as a disinfecting and cleaning agent when those fibers are used in fabrics intended as wiping materials.

(24) Compatibility with QAC is a consideration of the ability of a treated cellulose fiber to remain stable and not react with the QAC antimicrobial sanitizers.

(25) The present invention relates to nonwoven fabrics formed and bonded by a variety of methodologies and means well known in the industry, where those nonwoven fabrics comprise at least a minority portion of bast fibers on which a planned crimp has been imparted and have a mean fiber length of at least 6 millimeters, where the bast fibers are substantially pectin free.

(26) As noted above, bast fibers utilized in this disclosure can be individualized via mechanical or chemical cleaning. Mechanical cleaning of bast fibers occurs during a process called skutching or decortication. During this process the plant stems are broken and combed to remove non-fiber components such as hemicellulose, pectin, lignin, and general debris. This process is shown in [FIG. 4]. The bale of bast fiber is unrolled in to the machine a, breaker rolls b split the stems and expose the fiber bundles, and rotating combs c clean the fiber of all trash and non-fiber material. The fibers are then discharged to a separate collection area d. Decortication is a similar process that utilizes pinned cylinders in place of rotating combs. Mechanical cleaning individualizes the bast fibers and removes less pectin than chemically cleaning

(27) Mechanically cleaned fibers have had a portion of the pectin removed from the fiber and are considered by this application to be pectin reduced. The residual level of pectin/contaminants vary from geographic region and growing season and depends on the natural retting of the fiber and the number of rotating combs/pinned rollers that the fiber is subjected to. Mechanically cleaning bast fibers is commonplace and grades of pectin-reduced fiber are known to those skilled in the art.

(28) Chemical cleaning of bast fibers occurs in several ways: water retting, chemical cleaning, or enzymatic cleaning. Natural chemical cleaning, called water retting, occurs in pools or streams whereby the bast fiber stalks are placed in the water for a period of several days to a week or more. Natural microbes remove the pectin from the fiber releasing the hemicellulose from the fiber resulting in clean, pectin reduced, individualized bast fiber. Chemical cleaning is a faster process and is performed on mechanically cleaned bast fibers and in an industrial facility possessing equipment capable of working at greater than atmospheric pressure and with temperatures ranging from 80° C. to over 130° C. The bast fiber is subjected to heat, pressure, and caustic soda or other cleaning agents to quickly remove pectin and lignin. Enzymatic cleaning is very similar to chemical cleaning with a portion of the caustic soda and other chemical agents being replaced by enzymes such as pectinase or protease.

(29) Chemically cleaned bast fibers are considered by the industry to be substantially free of pectin. US2014/0066872 to Baer et al., which is incorporated by reference herein, describes fiber with substantially reduced pectin as having less than 10%-20% by weight of the pectin content of the naturally occurring fibers from which the substantially pectin-free fibers are derived.

(30) In a preferred embodiment of the invention, the crimp level of the crimped bast fibers in the nonwoven fabric has been induced by either mechanical or chemical means of about 1 to 8 crimps per centimeter, and where some portion of fibers shorter than one centimeter in length may still exhibit at least 1 crimp.

(31) Such chemical means for inducing controlled crimp include but are not limited to exposure to strong acid or strong base baths. Such mechanical means for inducing crimp include but are not limited to edge crimping, gear crimping, stuffer boxes, and knit-deknitting.

(32) FIG. 5 shows naturally straight bast fibers. Bast fibers are substantially straight and, as a result, exhibit poor fiber-to-fiber cohesion.

(33) FIG. 6 shows examples of bast fibers that have been subjected to crimp. The circles indicate various crimps appearing in the image.

(34) FIG. 7 shows a diagram of a mechanical planar crimp. Crimp angle and number of crimps per centimeter are determined by the method of mechanical crimping.

(35) The inclusion of crimp bast fibers in at least a minority portion of the total weight of fibers in the bast fiber nonwoven fabric, provides improved processing efficiency and improved physical properties of those fabrics as compared to similarly formed fabrics with the same portion of straight bast fibers. The improved physical properties include but are not limited to the fabric loft and the fabric strength-to-weight ratio.

(36) In one embodiment of the invention, the nonwoven fabric contains at least about 5% by weight of crimped bast fibers, with a majority of other staple fibers selected from natural or synthetic fiber types. This bast fiber nonwoven fabric of this embodiment exhibits the described improvement in physical properties as compared to a bast fiber nonwoven fabric that does not include crimped bast fibers.

(37) In a further preferred embodiment of the application, the crimped bast fibers may be blended with one or more other types of natural or synthetic staple fibers at a weight percent of at least about 5% to 49% crimped bast fibers with a mean length of greater than 6 mm to form the nonwoven fabric.

(38) In another preferred embodiment, the crimped bast fibers may be blended with one or more other types of natural or synthetic staple fibers at a weight percent of at least about 51% to 100% crimped bast fibers with a mean length of greater than 6 mm to form the nonwoven fabric, with the other natural or synthetic fibers comprising about 49% to 0% of the fabric weight.

(39) In a most preferred embodiment of the invention, the inclusion of at least about 5% by weight of the crimped bast fibers with a mean length of greater than 6 mm in the fabric provides an improvement in the strength-to-weight ratio and improved loft as compared to other similarly manufactured bast fiber containing nonwoven fabrics where those bast fibers are essentially straight and do not exhibit crimp.

(40) It is a further embodiment of the invention that the one or more types of natural fibers included in a blend with the crimped bast fibers may include bast fibers that do not exhibit a minimum of 1 crimp per centimeter of fiber length.

(41) It is an aspect of the present invention that the crimped bast fiber nonwoven fabric may be produced by any of the drylaid, airlaid or wetlaid nonwoven technologies and may be bonded or consolidated by any of the adhesive, mechanical or thermal bonding means. It is understood that such means may be used in combination to produce the final fabric form, where for example a carded mat or batt might be combined with an airlaid mat or batt where either layer or the laminate may be subjected to one or more of the bonding or consolidating means in order to produce the desired physical and aesthetic properties of the final fabric.

(42) In certain embodiments, the bast fiber nonwoven fabric may be a laminate of at least two nonwoven fabrics in a laminate where at least one fabric of the laminated comprises at least 5% of crimped bast fibers and where each of the fabrics may be formed by drylaid, airlaid or wetlaid forming processes and where each of the fabrics may be bonded by thermal, mechanical or adhesive means prior to forming the laminate configuration.

(43) It is a further embodiment of the present disclosure that bast fibers may be coated with one or more thermoplastic polymer resin to provide a bast fiber nonwoven fabric that is compatible with QAC sanitizers. The purpose of the thermoplastic polymer resin coating is to protect the QAC from deactivation by interaction with the surface chemistry of the bast fibers. Such pretreatment followed contact with QAC produces a bast fiber nonwoven fabric with improved efficacy of antimicrobial activity as compared to other bast fiber nonwoven webs that have not been so pretreated before contact with QAC. In addition, coating the bast fibers in one or more thermoplastic polymers and then subjecting those fibers to crimp improves the permanency of the crimp. Crimp permanency ensures that the desirable performance properties of the crimped bast fibers remain stable and present throughout the nonwoven fabric formation process.

(44) It is an aspect of the present invention that the controlled crimp bast fiber nonwoven fabrics as described herein will be find use end product applications including but not limited to baby wipes, cosmetic wipes, perinea wipes, disposable washcloths, kitchen wipes, bath wipes, hard surface wipes, glass wipes, mirror wipes, leather wipes, electronics wipes, disinfecting wipes, surgical drapes, surgical gowns, wound care products, protective coveralls, sleeve protectors, diapers and incontinent care and feminine care articles, nursing pads, air filters, water filters, oil filters, furniture or upholstery backing.

(45) The foregoing is considered to provide examples of the principles of the invention. The scope of modifications as may be made to the invention are not limited beyond that imposed by the prior art and as set forth in the claims herein.