US20200299882A1

US20200299882A1 - Thermal bonding of nonwoven textiles containing cellulose acetate fibers

Info

Publication number: US20200299882A1
Application number: US16/813,909
Authority: US
Inventors: Samuel Charles Baer; Jeremy Kenneth Steach
Original assignee: Eastman Chemical Co
Current assignee: Eastman Chemical Co
Priority date: 2019-03-21
Filing date: 2020-03-10
Publication date: 2020-09-24

Abstract

Nonwoven fabrics and textiles containing cellulose ester fibers particularly cellulose acetate fibers are thermally bonded. An aqueous plasticizing solution is applied to the surface of a nonwoven web and thereafter the web is thermally bonded to create a thermally bonded nonwoven textile. Alternatively, water can be applied to the dry surface of a nonwoven web containing organic plasticizer treated cellulose ester fibers to create the moistened nonwoven web and thereafter thermally bonding the moistened nonwoven web to make a thermally bonded nonwoven textile. The fabrics exhibit an increase in tensile strength and toughness greater than the individual contributions of water and plasticizer alone and greater than the additive contributions of water and plasticizer alone.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 62/821,514 filed on Mar. 21, 2019, the disclosure of which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

Fibers comprised of the naturally occurring polymer cellulose have properties that are very desirable and useful for many nonwoven textiles particularly those utilized in disposable applications. Cellulosic nonwoven webs can readily absorb and wick aqueous fluids which is necessary for personal hygiene products such as diapers. Cellulose fibers are preferred for cleaning most contaminants from skin or hard surfaces particularly in conjunction with a solvent. In addition to aqueous absorbency, cellulose fiber webs have a high capacity for non-polar liquids such as motor or vegetable oil which makes cellulosic wipes also desirable for industrial and restaurant wipes respectively. In recent decades the plant based (hence carbon neutral) life cycle of cellulose based fibers has become a preferred feature in comparison with the 100% fossil-fuel based fibers (polypropylene, polyester etc.) that are also commonly utilized for disposable fabrics. The biodegradable nature of cellulosic fiber is also a preferred feature over the nondegradable fossil fuel based nonwoven fibers when utilized for most disposable applications.
Cellulose acetate is a subset of cellulose esters polymers that is created by chemically reacting acetic anhydride with cellulose in an aqueous solution. Cellulose diacetate (CDA) can be dissolved at high solids levels in acetone and solution spun into continuous filaments. These filaments in turn can be crimped and cut to create staple fiber that can baled and subsequently formed by water slurry, air stream, or mechanical card into a nonwoven web.
The nonwoven web can then be bonded by suitable means into a useful fabric. However, thermal bonding is not a method for bonding webs comprised of cellulose fibers as native state cellulose (e.g., wood pulp, cotton) and reconstituted cellulose (e.g., viscose rayon, Tencel® rayon) do not exhibit thermoplastic properties. Further, many cellulose ester fibers have a glass transition temperature Tg above typical temperatures applied to commercial thermal bonding rolls, which are kept low to avoid thermally degrading other fibers.
The process for thermal bonding is desirably conducted at high productions speed. In contrast to cellulose esters, the viscose rayon or Tencel® rayon fibers noted above are comprised entirely of unmodified cellulose molecules and, therefore, have no thermoplastic properties. This limits fabric bonding methods for rayon fibers to either fiber to fiber friction (hydroentangling), adhesive applications (e.g., EVA emulsion), thermoplastic powder binder addition such as polyethylene (PE) powder, or the use of polypropylene/PE and PET/PE bicomponent fibers. The same bonding method limitations apply to natural cellulosics such as cotton, wood pulp, flax, and hemp fibers. The above bonding methods are more complex in execution than thermal bonding methods so a cellulose fiber than can be thermally bonded at production speeds is highly sought in the nonwovens industry.
The very common hydroentangling bonding process has a practical minimum in bondable web basis weight of around 35 gsm as there is a critical concentration of fibers required to achieve a usable fabric strength. The minimum basis weight of thermally bonded nonwovens is not so limited because they do not need to be hydroentagled, thereby allowing their basis weight to be decreased down to about 10-15 gsm or at a basis weight that allows for the formation of a uniform web. Not only can thermally bonded nonwoven webs containing cellulose esters be made at high speeds and lower basis weight, but the process is dramatically simplified due to the elimination of the need for adhesives or stitching threads.
However, there remains a need to develop a process that has the capability to thermally bond nonwoven webs containing cellulose ester fibers at low temperatures. There is also a need to subject nonwoven webs containing celllulosic fibers, including rayons, to a thermal bonding process. There is also a need to develop fabrics having high tensile strength in the machine direction made from thermally bonded nonwoven webs containing cellulose ester, and optionally also capable of being thermally bonded at low temperatures.

SUMMARY OF THE INVENTION

There is now provided a process for making a fabric comprising:

- a. providing a nonwoven web comprised of base fibers and binder fibers, and
- b. applying either (i) water or (ii) water and a plasticizer to the nonwoven web to produce a wetted plasticized nonwoven web, provided that water and a plasticizer are applied to the nonwoven web if the binder fibers do not contain a plasticizer; and
- c. thermally bonding the wetted plasticized nonwoven web to produce said fabric.

There is further provided a process for making a fabric comprising:

- a. providing a nonwoven web comprising cellulose ester fibers, and
- b. thermally bonding said nonwoven web at a thermal bonding temperature to make a fabric, and

wherein at least a portion of the cellulose ester fibers have a native Tg that is greater than the thermal bonding temperature, and said process is conducted in the absence of:

- (i) adding adhesives or binder onto said nonwoven web; and
- (ii) using solvents for the binder fibers.

There is also provided a process for thermal bonding, comprising feeding a wetted plasticized nonwoven web to a heat calendar roll, wherein said web is wetted with water and contains a plasticizer.
There is also provided a fabric comprising cellulose ester fibers, said fabric having a basis weight of not more than 35 gsm and destructive thermally fused bonds, wherein the fabric is obtained by thermally bonding a nonwoven web in the absence of adhesives, hydroentaglement, solvents for fusion, or thermoplastic binder powders.
There is also provided a fabric comprising cellulose ester fibers, said fabric having machine direction break force of at least 1,400 grams.
There is also provided a fabric comprising cellulose ester fibers, said fabric having machine direction toughness of at least 6,000 grams.
There is also provided a fabric comprising cellulose ester fibers, said fabric having machine direction:

- a. a break force of at least 20 grams per gsm basis weight; or
- b. a toughness of at least 100 grams per gsm basis weight; or
- c. both.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a spray technique for applying water or an aqueous solution containing plasticizer to the nonwoven web

FIG. 2 illustrates an immersion or impregnation method for saturating a nonwoven web.

FIG. 3 illustrates a lick or kiss roll method for applying the water or aqueous solution containing plasticizer to the nonwoven web.

FIG. 4 is a column chart showing the break tensile force for the cellulose acetate/rayon nonwoven variants

FIG. 5 is a column chart showing the elongation at break for the cellulose acetate/rayon nonwoven variants

FIG. 6 is a column chart showing the toughness over the stress/strain curve of cellulose acetate/rayon nonwovens.

FIG. 7 illustrates a bond pattern on a fabric.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment or in combination with any of the mentioned embodiments of the invention, there is provided a process for making a fabric comprising:

In the first step of the process, there is provided a nonwoven web. Nonwoven webs or sheets are planar, flat, or tufted porous structures containing entangled fibers (filaments or staple) that do not have a uniform identifiable entanglement pattern such as would be seen with knitted or woven fabrics. Typically, there is no intentional entanglement pattern at the fiber to fiber level. While carding operations orient the fibers in a direction, their ultimate entanglement disposition in the web is random. The entanglement of the fibers can be accomplished through wet laid, spun bond or laced, dry laid, and melt blowing processes. The nonwoven webs are not woven, knitted, or weaved. The nonwoven webs are webs that have not yet been treated with water prior to thermal bonding.
The form of the webs is not limited, and can include webs or sheets that are flat or tufted, or bats. The nonwoven web can be a dry laid web, a wet laid web, and can be monolayered or multilayered.
The nonwoven web contains binder fibers and base fibers. The base fibers are any fibers that are not thermoplastic and do not fuse to each other or other fibers with application of heat and pressure without charring or thermally degrading the fiber. The binder fibers are thermoplastic fibers or have a thermoplastic component to them, and include at least cellulose ester fibers. The cellulose ester fibers are thermoplastic, and these fibers differ from native state cellulose fibers or reconstituted cellulose fibers in the key property of thermoplastic behavior. That is, the cellulose ester fibers have a glass transition temperature and, under the proper conditions, can be thermally fused to themselves or to other fibers such as rayon or polyester.
The cellulose ester fibers can be monocomponent fibers (e.g., the entire fiber is a cellulose ester) or a bicomponent fibers. Bi-component fibers include a continuous phase containing a disperse phase such as islands in the sea, or core-sheath configurations, or side by side configuration, or other configurations known in the art. The process of preparing and bonding a low melt temperature bicomponent binder fiber is described in detail in U.S. Pat. No. 3,589,956, incorporated herein by reference.
Desirably, at least a portion of the binder fibers are mono-component fibers, meaning that there are no discrete phases, such as islands, domains, or sheaths of alternate polymers in the fiber other than the CE polymer. For example, a mono-component fiber can be entirely made of CE polymer, or a melt blend of a CE polymer and a different polymer. Desirably, at least 60% of the composition of the CE fibers in the nonwoven web and/or the wetted plasticized nonwoven web prior to thermal bonding, are CE polymers, or at least 70%, or at least 75%, or at least 80%, or at least 90%, or at least 92%, or at least 95%, or at least 98%, or at least 99%, and most preferably 100% by weight of the CE fibers are CE polymers, based on the weight of all polymers in the CE fiber having a number average molecular weight of over 500 (or alternatively based on the weight of all polymers used to spin filaments from which the CE fibers are made). For clarity, these percentages do not exclude spin or cutting finishes applied to the filaments once spun or other additives which have a number average molecular weight of less than 500.
Suitable quantities of mono-component fibers include at least 50 wt. %, or at least 60 wt. %, or at least 70 wt. %, or at least 80 wt. %, or at least 90 wt. %, or at least 95 wt. %, or at least 98 wt. %, or 100 wt. % mono-component fibers based on the weight of all fibers containing a cellulose ester polymer.
The process of the invention, the nonwoven web and/or the wetted plasticized nonwoven web prior to thermal bonding, does not rely upon binder powders, binder particles, or films to provide strength and toughness. Binding powders and particles typically consist of a polyolefin, low molecular weight polyamides, or copolymers of vinyl acetate and vinyl chloride, or other inexpensive thermoplastic powders and particles. Dispensing with binder powders, particles, or films reduces the cost of the fabric, and avoids the problem of matching powder particle size and size distribution with the particular web and avoids the problem of providing a uniform distribution of binder throughout the web.
Desirably, the nonwoven web and/or the wetted plasticized nonwoven web prior to thermal bonding, contains, or is embedded, coated, layered, or laid up with binders or thermoplastic films, sheets, powders, or particles in an amount of not more than 30 wt. %, or not more than 20 wt. %, or not more than 10 wt. %, or not more than 5 wt. %, or not more than 3 wt. %, or not more than 1 wt. %, or not more than 0.5 wt. %, or not more than 0.1 wt. %, based on the weight of the nonwoven web or fabric, or does not contain, or is not embedded, coated, layered, or laid up with binders or thermoplastic films, sheets, powders, or particles.
Desirably, at least a portion of the binder fibers are cellulose ester fibers. In one embodiment or in combination with any of the mentioned embodiments, at least 50 wt. %, or at least 60 wt. %, or at least 70 wt. %, or at least 80 wt. %, or at least 90 wt. %, or at least 95 wt. %, or at least 98 wt. %, or 100 wt. % of the binder fibers are cellulose ester fibers or mono-component cellulose ester fibers, based on the weight of all binder fibers in the non-woven web.
In one embodiment or in combination with any of the mentioned embodiments, the binder fibers include cellulose ester fibers, and the cellulose ester fibers are made from cellulose ester polymers. Suitable CE polymers include cellulose derivatized with a reactive compound to generate at least one ester linkage at the hydroxyl site on the cellulose backbone, such as cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate formate, cellulose acetate propionate, cellulose acetate butyrate, cellulose propionate butyrate, and mixtures thereof. Although described herein with reference to “cellulose acetate,” it should be understood that one or more of the above cellulose acid esters or mixed esters may also be used to form the fibers. Various types of cellulose esters are described, for example, in U.S. Pat. Nos. 1,698,049; 1,683,347; 1,880,808; 1,880,560; 1,984,147, 2,129,052; and 3,617,201, each of which is incorporated herein by reference to the extent not inconsistent with the present disclosure. As used herein, regenerated or reconstituted cellulose (e.g., viscose, rayon, or lyocell) and the fibers made therefrom are not classified as CE polymers or cellulose ester fibers or binder fibers.
Cellulose esters can be characterized as a modified cellulose polymer in that the cellulose backbone remains intact after the chemical substitution of acyl (e.g., acetyl) groups for a portion of the hydroxyl groups on the cellulose polymer chain. Cellulose esters retain many functional features of native state cellulose such as water absorbency, oil absorbency, biodegradability, and a visual appearance and tactile feel similar to that of textile grade cellulosic fibers such as Tencel® and bleached cotton.
The cellulose ester can have a degree of substitution that is not limited, although a degree of substitution in the range of from 1.8 to 2.9 is desirable. As used herein, the term “degree of substitution” or “DS” refers to the average number of acyl substituents per anhydroglucose ring of the cellulose polymer, wherein the maximum degree of substitution is 3.0. In some cases, the cellulose ester used to form fibers as described herein may have a degree of substitution of at least 1.2, or at least 1.5, or at least 1.8, or at least 1.90, or at least 1.95, or at least 2.0, or at least 2.05, or at least 2.1, or at least 2.15, or at least 2.2, or at least 2.25, or at least 2.3 and/or not more than about 2.9, or not more than 2.85, or not more than 2.8, or not more than 2.75, or not more than 2.7, or not more than 2.65, or not more than 2.6, or not more than 2.55, or not more than 2.5, or not more than 2.45, or not more than 2.4, or not more than 2.35. Desirably, at least 90, or at least 91, or at least 92, or at least 93, or at least 94, or at least 95, or at least 96, or at least 97, or at least 98, or at least 99 percent of the cellulose ester fibers have a degree of substitution of at least 2.15, or at least 2.2, or at least 2.25.
Typically, acetyl groups can make up at least about 30, or at least about 40, or at least about 50, or at least about 60, or at least about 70, or at least about 80, or at least about 90, or at least about 95, or at least about 98, or 100% of the total acyl substituents (which do not include the hydroxyl groups). Desirably, greater than 90 weight percent, or greater than 95%, or greater than 98%, or greater than 99%, and up to 100 wt. % of the total acyl substituents are acetyl substituents (C2). The cellulose ester can have no acyl substituents having a carbon number of greater than 2.
In an embodiment or in any of the mentioned embodiments, the DS of the cellulose ester polymer is not more than 2.5, or not more than 2.45. Both the industrial and home compostability of CE fibers is most effective when made with cellulose esters having a DS of not more than 2.5. Additionally, those CE fibers made with cellulose ester polymers having a DS of not more than 2.5 are also soil biodegradable under the ISO 17566 test method.
The cellulose ester may have a weight-average molecular weight (Mw) of not more than 90,000, measured using gel permeation chromatography with N-methyl-2-pyrrolidone (NMP) as the solvent. In some case, the cellulose ester may have a molecular weight of at least about 10,000, at least about 20,000, 25,000, 30,000, 35,000, 40,000, or 45,000 and/or not more than about 100,000, 95,000, 90,000, 85,000, 80,000, 75,000, 70,000, 65,000, 60,000, or 50,000.
The cellulose ester may be formed by any suitable method, and desirably the CE fibers are obtained from filaments formed by the solvent spun method, which is a method distinct from a precipitation method or emulsion flashing. In a solvent spun method, the cellulose ester flake is dissolved in a solvent, such as acetone or methyl ethyl ketone, to form a “solvent dope,” which can be filtered and sent through a spinnerette to form continuous cellulose ester filaments. In some cases, up to about 3 wt. % or up to 2 wt. %, or up to 1 weight percent, or up to 0.5 wt. %, or up to 0.25 wt. %, or up to 0.1 wt. % based on the weight of the dope, of titanium dioxide or other delusterant may be added to the dope prior to filtration, depending on the desired properties and ultimate end use of the fibers, or alternatively, no titanium dioxide is added. The continuous cellulose ester filaments are then cut to the desired length if a staple fiber is desired, leading to CE fibers having low cut length variability, and consistent L/D ratios, and the ability to supply them as dry fibers. By contrast, cellulose ester forms made by the precipitation method have low length consistency, have a random shape, a wide DPF distribution, have a wide L/D distribution, cannot be crimped, and are supplied wet.
In some cases, the solvent dope or flake used to form the CE fibers may include some or no additives in addition to the cellulose ester. Such additives can include, but are not limited to, plasticizers, antioxidants, thermal stabilizers, pro-oxidants, acid scavengers, inorganics, pigments, and colorants.
At the spinnerette, the solvent dope can be extruded through a plurality of holes to form continuous cellulose ester filaments. At the spinnerette, filaments may be drawn to form bundles of several hundred, or even thousand, individual filaments. Each of these bundles may include at least 100, or at least 150, or at least 200, or at least 250, or at least 300, or at least 350, or at least 400 and/or not more than 1000, or not more than 900, or not more than 850, or not more than 800, or not more than 750, or not more than 700 fibers. The spinnerette may be operated at any speed suitable to produce filaments, which are then assembled into bundles having desired size and shape.
One or more types of finishes may be applied to the fibers. The method of application is not limited and can include the use of spraying, wick application, dipping, or use of squeeze, lick, or kiss rollers. The location for applying a finish to a fiber can vary depending on the function of the finish. For example, the lubricant finish can be applied after spinning and before crimping, or before gathering the fibers into a bundle. Cutting lubricants and/or antistatic lubricants can be applied before or after crimping and prior to drying. Suitable amounts of all finishes (whether lubricant, cutting lubricant, antistatic electricity finish, or otherwise) on the CE fibers can be at least about 0.01, or at least 0.02, or at least 0.05, or at least 0.10, or at least 0.15, or at least 0.20, or at least 0.25, or at least 0.30, or at least 0.35, or at least 0.40, or at least 0.45, or at least 0.50, or at least 0.55, or at least 0.60 percent finish-on-yarn (FOY) relative to the weight of the dried CE staple fiber. Alternatively, or in addition, the cumulative amount of finish may be present in an amount of not more than about 2.5, or not more than 2.0, or not more than 1.5, or not more than 1.2, or not more than 1.0, or not more than 0.9, or not more than 0.8, or not more than 0.7 percent finish-on-yarn (FOY) based on the total weight of the dried fiber. The amount of finish on the fibers as expressed by weight percent may be determined by solvent extraction. As used herein “FOY” or “finish on yarn” refers to the amount of finish on the tow band less any added water, and in the context of the nonwoven webs and fabrics, the percentage on yarn or tow would be deemed to correspond to the percentage of finish on the CE fibers present in the nonwoven webs and fabrics. If a finish is applied, the desired cumulative amount of finish on the fibers is from 0.10 to 2.0, or 0.10 to 1.90, or 0.10 to 1.80, or 0.20 to 1.70, or 0.20 to 1.5, or 0.20 to 1.3, or 0.20 to 1.1, or 0.30 to 1.0, or 0.30 to 2, or 0.30 to 1.90, or 0.30 to 1.70, or 0.30 to 1.5, or 0.3 to 1.2, or 0.3 to 1, each as % FOY.
The CE fibers used to make the nonwoven web, or as added to any apparatus to make the nonwoven web, or in the nonwoven web prior to the application of water as further described below, can include some dry plasticizer or no plasticizer. By a dry plasticizer is meant that the plasticizer is already coated on or contained in the CE fibers and in dry form in the nonwoven web. Desirably, the plasticizer can be topically applied to the filament, tow, staple or fibers, and the fibers are delivered to the nonwoven line in a dry state and processed to make a nonwoven web in a dry state. The fibers can already in dry form on the fibers when making the nonwoven web, and desirably in dry form when unbaled or taken from packaging feeding equipment for making the nonwoven web. In one embodiment or in combination with any of the mentioned embodiments, the CE fibers, prior to application of water to the non-woven web, contain not more than, or have added to the filaments used to make the CE fibers, not more than 15, or not more than 12, or not more than 10, or not more than 9, or not more than 8, or not more than 7, or not more than 6, or not more than 5.5, or not more than 5, or not more than 4, or not more than 3, or not more than 2, or not more than 1.5, or not more than 1, or not more than 0.5, or not more than 0.25, or not more than 0.10, or nor more than 0.05, or not more than 0.01, or not more than 0.007, or not more than 0.005, or not more than 0.003, or not more than 0.001, or not more than 0.0007, in each case wt. % plasticizer based either as FOY, or based on the weight of the CE fibers; or the CE fibers contain no added plasticizer, whether virgin CE fibers, or waste/recycle CE fibers, or both. When present in a CE staple fiber before making the nonwoven web, the plasticizer may be incorporated into the fiber itself by spinning a dope containing a plasticizer, or contained in a flake used to make the dope, or the plasticizer may be applied to the surface of the fiber or filament by any of the methods used to apply a finish. If desired, the plasticizer can be contained in the finish formulation.
In one embodiment or in combination with any of the mentioned embodiments, no plasticizers are added to the CE fibers (whether virgin or post-consumer fibers or recycle fibers) used to make the nonwoven web. In this context, while recycle fibers can contain plasticizer when made in their virgin form, they are deemed not to have a plasticizer “added” if no plasticizer is applied to the post-consumer or recycle fibers. In another embodiment, the CE fibers used to make the nonwoven web do not contain a plasticizer.
Plasticizers are compounds that can decrease the glass transition temperature of a polymer. Examples of plasticizers suitable for addition to the CE fibers or to the nonwoven web, or present in the wetted plasticized nonwoven web, include, but are not limited to, aromatic polycarboxylic acid esters, aliphatic polycarboxylic acid esters, lower fatty acid esters of polyhydric alcohols, and phosphoric acid esters. Further examples can include, but are not limited to, the phthalate acid acetates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, dimethoxyethyl phthalate, ethyl phthalylethyl glycolate, butyl phthalylbutyl glycolate, levulinic acid esters, dibutyrates of triethylene glycol, tetraethylene glycol, pentaethylene glycol, tetraoctyl pyromellitate, trioctyl trimellitate, dibutyl adipate, dioctyl adipate, dibutyl sebacate, dioctyl sebacate, diethyl azelate, dibutyl azelate, dioctyl azelate, glycerol, trimethylolpropane, pentaerythritol, sorbitol, glycerin, glycerin (or glyceryl) triacetate (triacetin), diglycerin tetracetate, triethyl phosphate, tributyl sebacate, triethyl phosphate, tributyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, and tricresyl phosphate, triethyl citrate, polyethylene glycol, polyethylene adipate, polyethylene succinate, polypropylene glycol, polyglycolic acid, polybutylene adipate, polycaprolactone, polypropiolactone, valerolactone, polyvinylpyrrolidone, and other plasticizers having a weight average molecular weight of 200 to 800, dimethyl sebacate, glycerol, monostearate, sorbitol, erythritol, glucidol, mannitol, sucrose, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, triethylene glycol caprate caprylate, butylene glycol, pentamethylene glycol, hexamethylene glycol, diisobutyl adipate, oleic amide, erucic amide, palmitic amide, dimethyl acetamide, dimethyl sulfoxide, methyl pyrrolidone, tetramethylene sulfone, oxamonoacids, oxa diacids, polyoxa diacids, diglycolic acids, acetyl triethyl citrate, tri-n-butyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n-hexyl citrate, alkyl lactates, phthalate polyesters, adipate polyesters, glutate polyesters, diisononyl phthalate, diisodecyl phthalate, dihexyl phthalate, alkyl alylether diester adipate, dibutoxy ethoxyethyl adipate, and mixtures thereof.
Desirably, the amount of plasticizer added to the CE fibers to make a nonwoven web containing dry plasticized CE fibers is minimal (any of the amounts stated above) or no plasticizer is added to the CE fibers or recycle CE fibers before making the nonwoven web.
The CE fibers (whether virgin or recycle/post-consumer) used to make the nonwoven web, or in the nonwoven web, can include at least about 90, or at least 90.5, or at least 91, or at least 91.5, or at least 92, or at least 92.5, or at least 93, or at least 93.5, or at least 94, or at least 94.5, or at least 95, or at least 95.5, or at least 96, or at least 96.5, or at least 97, or at least 97.5, or at least 98, or at least 98.5, or at least 99, or at least 99.5, or at least 99.9, or at least 99.99, or at least 99.995, or at least 99.999 percent cellulose ester, based on the total weight of the CE fibers. The CE fibers used to make the nonwoven web, or in the nonwoven web, may include or contain not more than 10, or not more than 9.5, or not more than 9, or not more than 8.5, or not more than 8, or not more than 7.5, or not more than 7, or not more than 6.5, or not more than 6, or not more than 5.5, or not more than 5, or not more than 4.5, or not more than 4, or not more than 3.5, or not more than 3, or not more than 2.5, or not more than 2, or not more than 1.5, or not more than 1, or not more than 0.5, or not more than 0.1, or not more than 0.01, or not more than 0.005, or not more than 0.001, or not more than 0.0005, or not more than 0.0001 weight percent of plasticizers, or optionally all additives, in the cellulose ester polymer or deposited onto the cellulose ester fiber or contained on or in the CE staple fiber, including but not limited to the specific additives listed herein.
In one embodiment or in combination with any of the mentioned embodiments, the CE fibers used to make the nonwoven web, prior to their combination with base fibers or prior to carding, already contain a plasticizer. The plasticizer can be added in the solvent dope or contained in the flake used to make the dope. The plasticizer can be added onto the (i) filament fiber, (i) the bundle, or (iii) the tow band, in each case prior to baling the fibers, or prior to drying the fibers, or prior to cutting the fibers, or prior to crimping the fibers. The method of addition is not limited and can as described above. The amount of plasticizer on the fiber can be as described above.
Turning to the manufacture of the CE fibers, multiple bundles may be assembled into a filament band such as, for example, a crimped or uncrimped tow band. The filament band may be of any suitable size and, in some embodiments, may have a total denier of at least about 10,000, or at least 15,000, or at least 20,000, or at least 25,000, or at least 30,000, or at least 35,000, or at least 40,000, or at least 45,000, or at least 50,000, or at least 75,000, or at least 100,000, or at least 150,000, or at least 200,000, or at least 250,000, or at least 300,000. Alternatively, or in addition, the total denier of the tow band is not more than about 5,000,000, or not more than 4,500,000, or not more than 4,000,000, or not more than 3,500,00, or not more than 3,000,000, or not more than 2,500,000, or not more than 2,000,000, or not more than 1,500,000, or not more than 1,000,000, or not more than 900,000, or not more than 800,000, or not more than 700,000, or not more than 600,00, or not more than 500,000, or not more than 400,000, or not more than 350,000, or not more than 300,000, or not more than 250,000, or not more than 200,000, or not more than 150,000, or not more than 100,000, or not more than 95,000, or not more than 90,000, or not more than 85,000, or not more than 80,000, or not more than 75,000, or not more than 70,000.
The linear denier per filament (weight in g of 9000 m fiber length), or DPF, of the CE filaments and of the corresponding CE fibers (whether CE staple fibers or CE continuous fibers), are desirably within a range of 0.5 to less than 20. The particular method for measurement is not limited, and include ASTM 1577-07 using the FAVIMAT vibroscope procedure if filaments can be obtained from which the staple fibers are cut, or a width analysis using any convenient optical microscopy or Metso.
The DPF can also be correlated to the maximum width of a fiber. The maximum width of a fiber is measured as the longest outermost diameter dimension, and in the case of any fiber than is not round, a convenient method for measuring the longest outer diameter is to spin the fiber. Table 1 illustrates a sample of convenient correlation of DPF to maximum widths (or outer diameter) of the fibers, regardless of shape and including multi-lobal shapes.

	TABLE 1

		Approximate width
	DPF	(microns)

	1.6	22
	2.0	25
	2.4	28
	2.8	30
	3.2	32
	3.6	34
	4.0	36

Desirably, the DPF of the filaments, and of the CE fibers, are within a range of 0.5 to 17, or 1.2 to 15, or 0.5 to 10, or 1.2 to 10, 0.5 to 8, or 0.5 to less than 5, or 1 to 4, or 1 to 3, or 1.0 to 2.8, or 1.0 to 2.5, or 1.0 to 2.2, or 1.0 to 2.1, or more desirably from 1.2 to less than 3, or 1.2 to 2.8, or 1.2 to 2.5, or 1.2 to 2.3, or 1.2 to 2, or 1.2 to less than 2.0, or 1.2 to 1.9, or 1.1 to 1.9, or 1.1 to 1.8.
In another embodiment or in any one of the mentioned embodiments, the maximum width of the fibers are less than 100 microns, or not more than 80 microns, or not more than 60 microns, or not more than 50 microns, or not more than 40 microns, or not more than 36 microns, or not more than 31 microns, or not more than 30 microns, or not more than 28 microns, or not more than 27 microns, or not more than 26 microns, or not more than 25 microns, or not more than 24.5 microns, or not more than 24 microns.
In one embodiment or in combination with any of the mentioned embodiments or in any of the mentioned embodiments, at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 97% of the CE fibers have a DPF within +/−20% of any one of the above stated DPF. Alternatively, at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 97% of the CE fibers have a DPF within +/−15% of any one of the above stated DPF; or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 97% of the CE fibers have a DPF within +/−10% of any one of the above stated DPF. Desirably, at least 85%, or at least 90%, or at least 95%, or at least 97% of the CE fibers have a DPF within +/−15%, or within +/−10% of any one of the above stated DPF.
In one embodiment or in combination with any of the mentioned embodiments or in any of the mentioned embodiments, the DPF can have a small distribution span satisfying the following formula:
$\frac{d 90 - d 10}{d 50} * 100 \leq S$
where d is based on the median DPF, d₉₀is the value at which 90% of the fibers have a DPF less than target DPF, d₁₀is the value at which 10% of the fibers have a DPF less than the target DPF, d₅₀is the value at which 50% of the fibers have a DPF less than the target DPF and 50% of fibers have a DPF more than the target DPF, and S is 40%, or 35%, or 30%, or 25%, or 20%, or 15%, or 13%, or 10%, or 8%, or 7%.
The individual cellulose ester filaments discharged from the spinnerette, and the CE fibers, may have any suitable transverse cross-sectional shape. Exemplary cross-sectional shapes include, but are not limited to, round or other than round (non-round). Non-round shapes include Y-shaped or other multi-lobal shapes such as I-shaped (dog bone), closed C-shaped, X-shaped, or crenulated shapes. When a cellulose ester filament, or CE staple fiber, has a multi-lobal cross-sectional shape, it may have at least 3, or 4, or 5, or 6 or more lobes. In some cases, the filaments may be symmetric along one or more, two or more, three or more, or four or more axes, and, in other embodiments, the filaments may be asymmetrical. As used herein, the term “cross-section” generally refers to the transverse cross-section of the filament measured in a direction perpendicular to the direction of elongation of the filament. The cross-section of the filament may be determined and measured using Quantitative Image Analysis (QIA). Staple fibers will have a cross-section similar to the filaments from which they are formed without mechanically deforming the staple fibers.
In some embodiments, the cross-sectional shape of an individual cellulose ester filament and the CE fibers may be characterized according to its deviation from a round cross-sectional shape. In some cases, this deviation from perfectly round can be characterized by the shape factor of the filament, which is determined by the following formula: Shape Factor=Average Cross-Sectional Perimeter/(47×Average Cross-Sectional Area)1/2. The shape factor of filament or CE fibers having a perfect round cross-sectional shape is 1. In some embodiments, the shape factor of the individual cellulose ester filaments or CE fibers is at least 1.5 or at least 1.7, or at least 2, or at least 2.5, or at least 2.7, or at least 3, or at least 3.2, or at least 3.5, or at least 4. Fibers in this category are typically tri-lobal or Y shaped. In another embodiment, the shape factor of the individual cellulose ester filaments or CE staple fibers are not more than 1.5, or not more than 1.45, or not more than 1.40, or not more than 1.35, or not more than 1.30, or not more than 1.25, or not more than 1.20, or not more than 1.15, or not more than 1.10. Fibers in this category are typically referred to as round which can include crenulated fibers. Fibers having a good round shape are those a shape factor of not more than 1.35, or not more than 1.3, particularly those having a shape factor of not more than 1.25. The shape factor can be calculated from the cross-sectional area of a filament, which can be measured using QIA.
In one embodiment or in combination with any of the mentioned embodiments or in any of the mentioned embodiments, at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 97%, or at least 99% of the CE fibers have the stated shape.
After multiple bundles are assembled into a filament yarn (or tow band), it may be passed through a crimping zone wherein a patterned wavelike shape may be imparted to at least a portion, or substantially all, of the individual filaments. In some cases, the filaments may not be crimped, and the uncrimped filaments may be passed directly from the spinnerette to a drying zone. When used, the crimping zone includes at least one crimping device for mechanically crimping the filament yarn. Filament yarns desirably are not crimped by thermal or chemical means (e.g., hot water baths, steam, air jets, or chemical coatings), but instead are mechanically crimped using a suitable crimper. One example of a suitable type of mechanical crimper is a “stuffing box” or “stuffer box” crimper that utilizes a plurality of rollers to generate friction, which causes the fibers to buckle and form crimps. Other types of crimpers may also be suitable. Examples of equipment suitable for imparting crimp to a filament yarn are described in, for example, U.S. Pat. Nos. 9,179,709; 2,346,258; 3,353,239; 3,571,870; 3,813,740; 4,004,330; 4,095,318; 5,025,538; 7,152,288; and 7,585,442, each of which is incorporated herein by reference to the extent not inconsistent with the present disclosure. In some cases, the crimping step may be performed at a rate of at least about 50 m/min (or in each case at least 75, 100, 125, 150, 175, 200, 225, 250 m/min). Typically, the crimping rate is not more than about 750 m/min (or in each case not more than 475, 450, 425, 400, 375, 350, 325, or 300 m/min).
In one embodiment or in combination with any of the mentioned embodiments, the CE fibers are crimped CE staple fibers, and the crimped CE fibers have an average effective length that is not more than 85 percent of the actual length of the crimped CE fibers. The effective length refers to the maximum dimension between any two points of a fiber and the actual length refers the end-to-end length of a fiber if it were perfectly straightened. If a fiber is straight, its effective length is the same as its actual length. However, if a fiber is curved and/or crimped, its effective length will be less than its actual length, where the actual length is the end-to-end length of the fiber if it were perfectly straightened. In one embodiment or in combination with any of the mentioned embodiments or in any one of the embodiments described herein, the crimped fibers have an average effective length that is not more than 80, or not more than 75, or not more than 65, or not more than 50, or not more than 40, or not more than 30, or not more than 20 percent of the actual length of the bent fibers.
Low DPF CE fibers can be susceptible to breakage when cut from the filaments, or when further processed, compared to the normal frequency of crimps imparted to higher denier fibers typically used in cigarette filter tow. Crimping is a useful component of the CE fiber to enhance cohesion and entanglement with other fibers and with each other. However, if a low DPF fiber is used, a lower frequency of crimps is desirable to minimize fiber breakage when the filaments are cut to staple and when they are further processed or handled prior to their combination with the cellulosic fibers, and also to retain a high degree of retained tenacity. As used herein, the term “retained tenacity” refers to the ratio of the tenacity of a crimped filament (or staple fiber) to the tenacity of an identical but uncrimped filament (or staple fiber), expressed as a percent. For example, a crimped fiber having a tenacity of 1.3 gram-force/denier (g/denier) would have a retained tenacity of 87 percent if an identical but uncrimped fiber had a tenacity of 1.5 g/denier.
In one embodiment or in combination with any of the mentioned embodiments or in any of the mentioned embodiments, the crimped CE filaments and staple fibers are capable of having a retained tenacity of at least about 40%, or at least 50%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95%.
While the CE fibers contained in the nonwoven web and fabric may be crimped or uncrimped or obtained from filaments which were uncrimped or crimped, In one embodiment or in combination with any of the mentioned embodiments, the CE fibers (whether continuous or staple) contained in the nonwoven web or fabric have, or are obtained from continuous filaments which were crimped at, a crimp frequency of at least 5, or at least 7, or at least 10, or at least 12, or at least 13, or at least 15, or at least 17, and up to 30, or up to 27, or up to 25, or up to 23, or up to 20, or up to 19 crimps per inch (CPI), measured according to ASTM D3937-12. Higher than 30 CPI tends to result in excess breakage in the cutting of filaments to staple at the small cut lengths described below, and also reduces their retained tenacity. Fewer than 5 CPI will result in too few CE fibers manifesting a crimp when small cut lengths are employed. Desirably, the average CPI of the filaments used to make the CE fibers is a value from 6 to 30 CPI, or 7 to 30 CPI, or 7 to 27 CPI, or 7 to 25 CPI, or 7 to 23 CPI, or 8 to 20 CPI, or 8 to 30 CPI, or 9 to 27 CPI, or 8 to 25 CPI, or 8 to 23 CPI, or 9 to 20 CPI, or 7 to 18 CPI, or 7 to 16 CPI.
In one embodiment or in combination with any of the mentioned embodiments or in any of the mentioned embodiments, the ratio of the crimp frequency CPI to DPF can be greater than about 2.75:1, or greater than 2.80:1, or greater than 2.85:1, or greater than 2.90:1, or greater than 2.95:1, or greater than 3.00:1, or greater than 3.05:1, or greater than 3.10:1, or greater than 3.15:1, or greater than 3.20:1, or greater than 3.25:1, or greater than 3.30:1, or greater than 3.35:1, or greater than 3.40:1, or greater than 3.45:1, or greater than 3.50:1. In some cases, this ratio may be even higher, such as, for example, greater than about 4:1, or greater than 5:1, or greater than 6:1, or greater than or greater than 7:1 particularly when, for example, the fibers being crimped are relatively fine.
The ratio of the CPI to the DPF is a useful measure to ensure that the proper CPI is imparted for a given DPF and retain the balance of necessary crimp frequency and tenacity for a given DPF, particularly when considering the use of CE staple fibers. Examples of desirable ratios of CPI:DPF include from 4:1 to 20:1, and especially 5:1 to 14:1, or 7:1 to 12:1.
When crimped, the crimp amplitude of the fibers may vary and can, for example, be at least about 0.85, or at least 0.90, or at least 0.93, or at least 0.96, or at least 0.98, or at least 1.00, or at least 1.04 mm. Additionally, or in the alternative, the crimp amplitude of the fibers can be up to 1.75, or up to 1.70, or up to 1.65, or up to 1.55, or up to 1.35, or up to 1.28, or up to 1.24, or up to 1.15, or up to 1.10, or up to 1.03, or up to 0.98 mm.
In an embodiment, the CE staple fibers may have a crimp ratio of at least about 1:1. As used herein, “crimp ratio” refers to the ratio of the non-crimped tow length to the crimped tow length. In some embodiments, the staple fibers may have a crimp ratio of at least about 1:1, at least about 1.1:1, at least about 1.125:1, at least about 1.15:1, or at least about 1.2:1.
Crimp amplitude and crimp ratio are measured according to the following calculations, with the dimensions referenced being shown in FIG. 2: Crimped length (Lc) is equal to the reciprocal of crimp frequency (1/crimp frequency), and the crimp ratio is equal to the straight length (L0) divided by the crimped length (L0:Lc). The amplitude (A) is calculated geometrically, as shown in FIG. 2, using half of the straight length (L0/2) and half of the crimped length (Lc/2). The uncrimped length is simply measured using conventional methods.
In one embodiment or in combination with any of the mentioned embodiments, the crimped CE fibers (whether continuous or staple, and especially staple) desirably can have one or more of the following features:

- a) a crimp frequency of 7 to 30 CP, or 7 to 25 CPI, or 7 to 23 CPI, or 7 to 20 CPI, or 8 to 30 CPI, or 8 to 27 CPI, or 8 to 25 CPI, or 8 to 23 CPI, or 8 to 20 CPI crimps per inch, or
- b) a crimp amplitude of at least 1.0 mm, or
- c) an average effective length that is not more than 75% of the actual length, or
- d) a retained tenacity of at least 80%, or
- e) a CPI:DPF of 5:1 to 14:1, or 7:1 to 12:1, or
- f) any combination of two or more of the above.

After crimping (or, if not crimped, after spinning), the fibers may further be dried in a drying zone in order to reduce the moisture and/or solvent content of the filament yarn or tow band. In one embodiment or in combination with any of the mentioned embodiments or in any of the mentioned embodiments, the CE fibers are dry, as further explained below.
The CE staple fiber can have a moisture content of not more than 30 wt. % moisture, or not more than 25 wt. % moisture, or not more than 23 wt. % moisture, or not more than 20 wt. % moisture, or not more than 18 wt. % moisture, or not more than 15 wt. % moisture, or not more than 13 wt. % moisture, or not more than 10 wt. % moisture, or not more than 9 wt. % moisture, or not more than 8 wt. % moisture, as determined by oven dryness, prior to forming the nonwoven web. In one embodiment or in combination with any of the mentioned embodiments, the moisture content on the CE fibers is in substantial equilibrium with the environment in which the CE fibers are stored for at least 8 hours prior to carding or forming the nonwoven web. The final moisture content, or level of dryness, of the filament yarn (or tow band), and of the CE fibers, particularly between cutting and combining with base fibers, or on the fibers added to form the nonwoven web (or on the nonwoven web) and prior to the application of water as further described below or prior to the formation of the nonwoven web, can be at least 1 wt. %, and desirably is at least about 1 wt. %, or at least 2 wt. %, or at least 3 wt. %, or at least 3.5 wt. %, or at least 4 wt. %, or at least 4.5 wt. %, or at least 5 wt. %, or at least 5.5 wt. %, or at least 6 wt. %, based on the total weight of the CE fibers and/or not more than about 25 wt. %, or not more than 20 wt. %, or not more than 18 wt. %, or not more than 16 wt. %, or not more than 13 wt. %, or not more than 10 wt. %, or not more than 9 wt. %, or not more than 8 wt. %, or not more than 7 wt. %, based on the weight of the CE fibers, as determined by oven dryness. Suitable ranges include, but are not limited to, 3-20, or 3-18, or 3-16, or 3-13, or 3-10, or 3-9, or 3-8, or 3-7, or 3-6.5, or 4-20, or 4-18, or 4-16, or 4-13, or 4-10, or 4-9, or 4-8, or 4-7, or 4-6.5, or 5-20, or 5-18, or 5-16, or 5-13, or 5-10, or 5-9, or 5-8, or 5-7, or 5.5-20, or 5.5-18, or 5.5-16, or 5.5-13, or 5.5-10, or 5.5-9, or 6-20, or 6-18, or 6-16, or 6-13, or 6-10, in each case as wt. % based on the weight of the CE staple fiber.
The CE fibers have the advantage of not requiring their maintenance as a slurry or emulsion (e.g., greater than 30 wt. % water) during shipping as well as reducing shipping weight and its associated costs. Any suitable type of dryer can be used such as, for example, a forced air oven, a drum dryer, or a heat setting channel. The dryer may be operated at any temperature and pressure conditions that provide the requisite level of drying without damaging the yarn.
When the CE fibers are CE staple fibers, once dried, the CE fibers may be fed to a cutting zone without first baling, or may be optionally baled and the resulting bales may be introduced into a cutting zone, wherein the CE fibers in any form, whether yarn or tow band, may be cut into staple fibers. Any suitable type of cutting device may be used that is capable of cutting the filaments to a desired length without excessively damaging the fibers. Examples of cutting devices can include, but are not limited to, rotary cutters, guillotines, stretch breaking devices, reciprocating blades, and combinations thereof. Once cut, the CE fibers may be baled or otherwise bagged or packaged for subsequent transportation, storage, and/or use.
The cut length can be determined by any suitable reliable method. Commonly used optical instruments include the Metso FS-5 and the Optest FQA. The data output of these devices can provide information such as the average length and length distribution curve.
The cut length referred to herein can be the average cut length or the set point on the cutter to designate the target cut length. The CE staple fiber length is generally in the range of at least 1.5 mm and up to 150 mm. Examples of desirable cut lengths include a cut length of at least 2 mm, or at least 2.5 mm, and not more than about 150 mm, or not more than 125 mm, or not more than 100 mm, or not more than 85 mm, or not more than 70 mm, or not more than 60 mm, or not more than 50 mm, or not more than 45 mm, or not more than 40 mm, or not more than 30 mm, or not more than 20 mm, or not more than 15 mm, or not more than 10 mm, or not more than 8 mm, or not more than 7 mm, or not more than 6 mm, or not more than 5 mm, or not more than or less than 4.5 mm, or not more than or less than 4.0 mm, or not more than 3.8 mm, or not more than 3.5 mm, or not more than 3.3 mm. Examples of cut length ranges include from 1.5 to 150 mm, or 1.5 to 100 mm, or 1.5 to 80 mm, or from 1.5 to 60, or from 1.5 to 40, or from about 1.5 to 30, or from 1.5 to 20, or from 0.5 to 15, or from 1.5 to 10, or from 1.5 to 7, or from 1.5 to 6, or from 2 to 6, or from 3 to 6, or from 2.5 to 5, or from 2.5 to 4.5, or from 2.5 to 4, or from 2.5 to less than 4, or from 2.5 to 3.8 mm, in each case in mm.
In one embodiment or in combination with any of the mentioned embodiments or in any of the mentioned embodiments, at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 97% of the CE fibers have a cut length within +/−20% of any one of the above stated cut lengths. Alternatively, at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 97% of the CE fibers have a cut length within +/−15% of any one of the above stated cut lengths; or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 97% of the CE fibers have a cut length within +/−10% of any one of the above stated cut lengths. Desirably, at least 85%, or at least 90%, or at least 95%, or at least 97% of the CE fibers have a cut length within +/−15%, or within +/−10% of any one of the above stated cut lengths.
The CE fibers are fibers rather than particles. As such, the CE fibers have an aspect ratio (L/D) of at least 1.5:1, or at least 2:1, or at least 2.5:1, or at least 3:1, or at least 3.5:1, or at least 4:1, or at least 5:1, or at least 6:1, or at least 7:1, or at least 8:1, or at least 9:1, or at least 10:1, or at least 20:1, or at least 30:1, or at least 40:1, or at least 50:1.
In one embodiment or in combination with any of the mentioned embodiments, the ratio of CE staple fiber cut length to DPF of the CE staple fibers is less than 80:1, or not more than 70:1, or not more than 60:1, or not more than 50:1, or not more than 40:1, or not more than 35:1, or not more than 30:1, or not more than 20:1, or not more than 15:1, or not more than 10:1, or not more than 8:1, or not more than 5:1, or not more than 4:1, or not more than 3.1, optionally with CE fibers having a cut length of less than 80 mm, or not more than 70 mm, or not more than 60 mm, or not more than 50 mm, or not more than 40 mm, or not more than 30 mm, or not more than 20 mm, or not more than 15 mm, or not more than 10 mm, or not more than 8 mm, or not more than 7 mm, or not more than 6 mm. If short cut CE staple fibers are used, the ratio of cut length:DPF can be not more than 2.95:1, or not more than 2.9:1, or not more than 2.85:1 or not more than 2.8:1 or not more than 2.75:1 or not more than 2.6:1 or not more than 2.5:1 or not more than 2.3:1 or not more than 2.0:1. In one embodiment or in combination with any of the mentioned embodiments, the cut length:DPF is not more than 3.5:1, or not more than 3.3:1, or not more than 3:1, or not more than 2.95:1, or not more than 2.8:1, or not more than 2.5:1 at a cut length of less than 6 mm, or not more than 5 mm, or not more than 4 mm.
In one or any of the embodiments mentioned, the CE fibers can have any one or more of the following features:

- a) a cut length of less than 150 mm, or 80 mm or less, or 40 mm or less, or not more than 6.0 mm, or 2.0 to 5 mm, or
- b) an aspect ratio L/D of at least 5:1, or at least 10:1, or
- c) a cut length:DPF ratio of not more than 40, or not more than 25, or not more than 20, or not more than 15, or not more than 10, or not more than 7, or not more than 3.5, or
- d) at least 80% of the CE fibers have a cut length within +/−20% of any one of the above stated cut lengths, or
- e) any combination of two or more of any of the above.

Any suitable type of cutting device may be used that can cut the filaments to a desired length without excessively damaging the fibers. Examples of cutting devices can include, but are not limited to, rotary cutters, guillotines, stretch breaking devices, reciprocating blades, and combinations thereof. Once cut, the staple fibers may be baled or otherwise bagged or packaged for subsequent transportation, storage, and/or use.
The CE polymers used to make the CE fibers, and the CE fibers, are desirably not chemically treated to alter the chemical structure of the cellulose ester upon or after the cellulose ester is spun into the filament, such as to increase the hydroxyl number of the CE fiber. For example, the CE fibers desirably are not surface hydrolyzed. Surface hydrolysis can increase the number of —OH sites on a cellulose ester. Such a process, however, adds extra processing steps, is economically impractical, and is not needed to provide good cohesive force to the nonwoven web or tensile strength to the fabric when employing the methods described herein.
The nonwoven web and fabric can contain CE fibers in an amount of least 0.25 wt. %, or at least 0.5 wt. %, or at least 0.75 wt. %, or at least 1 wt. %, or at least 2 wt. %, or at least 3 wt. %, or at least 4 wt. %, or at least 5 wt. %, or at least 6 wt. %, or at least 7 wt. %, or at least 8 wt. %, or at least 9 wt. %, or at least 10 wt. %, or at least 12 wt. %, or at least 15 wt. %, or at least 18 wt. %, or at least 20 wt. %, based on the total weight of web or fabric. In addition or in the alternative, the amount of CE fibers in the web and fabric can be up to 100 wt. %, or up to 90 wt. %, or up to 80 wt. %, or up to 75 wt. %, or up to 65 wt. %, or up to 55 wt. %, or up to 50 wt. %, or up to 45 wt. %, or up to 40 wt. %, or up to 35 wt. %, or up to 30 wt. %, or up to 25 wt. %, or up to 20 wt. %, or up to 18 wt. %, or up to 15 wt. %, or up to 12 wt. %, or up to 10 wt. %, or up to 9 wt. %, or up to 8 wt. %, or up to 7 wt. %, or up to 6 wt. %, or up to 5 wt. %, based on the total weight of all fibers in the web and/or fabric.
Examples of suitable ranges of the CE fibers in the nonwoven web/fabric include from 0.75 to 100, or from 1 to 100, or from 3 to 100, or from 5 to 100, or from 5 to 80, or 5 to 70, or from 5 to 55, or 5 to 40, or 5 to 20, or 5 to 15, or from 10 to 100, or from 10 to 80, or 10 to 70, or from 10 to 55, or 10 to 40, or 10 to 20, or from 20 to 100, or from 20 to 80, or 20 to 70, or from 20 to 55, or 20 to 40, or from 30 to 100, or from 30 to 80, or 30 to 70, or from 30 to 55, or 30 to 40, or from 40 to 100, or from 40 to 80, or 40 to 70, or from 40 to 55, or from 50 to 100, or from 0 to 80, or 50 to 70, in each case as a wt. % based on weight of all fibers in the web and/or fabric.
The nonwoven web/fabric may contain CE fibers in an amount of least 10 wt. %, or at least 12 wt. %, or at least 15 wt. %, or at least 18 wt. %, or at least 20 wt. %, or at least 30 wt. %, or at least 40 wt. %, or at least 50 wt. %, or at least 60 wt. %, or at least 70 wt. %, or at least 80 wt. %, or at least 90 wt. %, or at least 95 wt. %, or 100%, based on the total weight of binder fibers in the web or fabric. In addition or in the alternative, the amount of CE fibers can be up to 100 wt. %, or up to 95 wt. %, or up to 90 wt. %, or up to 85 wt. %, or up to 80 wt. %, or up to 70 wt. %, or up to 60 wt. %, or up to 50 wt. %, or up to 40 wt. %, or up to 35 wt. %, based on the total weight of all binder fibers in the web and/or fabric.
Examples of suitable ranges of the CE fibers based on the weight of all binder fibers in the nonwoven web/fabric include from 10 to 100, or from 40 to 100, or from 70 to 100, or from 80 to 100, or form 90 to 100, or from 95 to 100, or from 98 to 100, or from 10 to 90, or 40 to 90, or from 60 to 90, or 80 to 90, in each case as a wt. % based on weight of all binder fibers in the web and/or fabric.
Example of other binder fibers which may be in combination with the CE fibers in the nonwoven or fabric include polyesters such as those polyethylene terephthalate (PET), polycyclohexylenedimethylene terephthalate (PCT) and other copolymers, olefinic polymers such as polypropylene and polyethylene of all varieties, sulfopolyester fibers, nylons or polyamides, copolyesters, and ethylene vinyl acetate.
The CE fibers may also be combined with base fibers, the nonwoven web and fabric may contain a combination of binder fibers and base fibers. Base fibers are any fibers other than the binder fibers. Base fibers will not exhibit thermoplastic behavior and will generally thermally degrade rather than exhibit a glass transition temperature. Base fibers can contribute to the desired physical, chemical, or mechanical properties of the nonwoven web or fabric, such as biodegradability, tensile strength, printability or dyeing capabilities, shrinkability, water or air permeability, wicking, and any other characteristics important to the requirements of the application. Examples of base fibers include natural fibers and synthetic fibers. Base synthetic fibers are those fibers that are, at least in part, synthesized or derivatized through chemical reactions, or regenerated, and include, but are not limited to, rayon, viscose, mercerized fibers or other types of regenerated cellulose (conversion of natural cellulose to a soluble cellulosic derivative and subsequent regeneration) such as lyocell (also known as Tencel), Cupro, Modal, acetates such as polyvinylacetate, glass, polyamides including nylon, poly sulfates, poly sulfones, polyethers, polyacrylates, acrylonitrile copolymers, polyvinylchloride (PVC), polylactic acid, polyglycolic acid, and combinations thereof. Base natural fibers include those that are plant derived or animal derived. Examples of plant derived natural fibers include wheat straw, rice straw, hardwood pulp, softwood pulp, and wood flour, wood cellulose, abaca, coir, cotton, flax, hemp, jute, kapok, papyrus, ramie, rattan, vine, kenaf, abaca, henequen, sisal, soy, rice, cereal straw, bamboo, reeds, esparto grass, bagasse, Sabai grass, milkweed floss fibers, pineapple leaf fibers, switch grass, lignin-containing plants, and the like. Examples of animal derived fibers include wool, silk, mohari, cashmere, goat hair, horse hair, avian fibers, camel hair, angora wool, and alpaca wool.
The base fibers, like the binder fibers, can be single-component fibers or multicomponent fibers containing islands in a sea, or sheaths, or discrete domains of two or more polymers.
The source of CE fibers, other binder fibers, or base fibers can be virgin or post-consumer or postindustrial fibers, or a combination thereof. Desirably, at least 5 wt. %, or at least 10 wt. %, or at least 15 wt. %, or at least 20 wt. %, or at least 25 wt. %, or at least 30 wt. %, or at least 40 wt. %, or at least 50 wt. %, or at least 60 wt. %, or at least 70 wt. % of the nonwoven web or fabric contains post-consumer or postindustrial fibers. Desirably, at least 5 wt. %, or at least 10 wt. %, or at least 15 wt. %, or at least 20 wt. %, or at least 25 wt. %, or at least 30 wt. %, or at least 40 wt. %, or at least 50 wt. %, or at least 60 wt. %, or at least 70 wt. % of the CE fibers, or of the binder fibers, are post-consumer or postindustrial fibers.
In one embodiment or in combination with any of the mentioned embodiments, the binder fibers are present in an amount of at least 10 wt. %, or at least 12 wt. %, or at least 15 wt. %, or at least 18 wt. %, or at least 20 wt. %, or at least 30 wt. %, or at least 40 wt. %, or at least 50 wt. %, or at least 60 wt. %, or at least 70 wt. %, or at least 80 wt. %, or at least 90 wt. %, or at least 95 wt. %, or 100%, based on the total weight of the nonwoven web or fabric. In addition or in the alternative, the amount of binder fibers can be up to 100 wt. %, or up to 95 wt. %, or up to 90 wt. %, or up to 85 wt. %, or up to 80 wt. %, or up to 70 wt. %, or up to 60 wt. %, or up to 50 wt. %, or up to 40 wt. %, or up to 35 wt. %, based on the total weight of the nonwoven web or fabric.
In one embodiment or in combination with any of the mentioned embodiments, the base fibers are present in an amount of at least 10 wt. %, or at least 12 wt. %, or at least 15 wt. %, or at least 18 wt. %, or at least 20 wt. %, or at least 30 wt. %, or at least 40 wt. %, or at least 50 wt. %, or at least 60 wt. %, or at least 70 wt. %, or at least 80 wt. %, or at least 90 wt. %, or at least 95 wt. %, or 100%, based on the total weight of the nonwoven web or fabric. In addition or in the alternative, the amount of base fibers can be up to 100 wt. %, or up to 95 wt. %, or up to 90 wt. %, or up to 85 wt. %, or up to 80 wt. %, or up to 70 wt. %, or up to 60 wt. %, or up to 50 wt. %, or up to 40 wt. %, or up to 35 wt. %, based on the total weight of the nonwoven web or fabric.
The weight ratio of CE fibers to all other synthetic fibers can be least 0.1:1, or at least 0.5:1, or at least 0.7:1, or at least 1:1, or at least 1.5:1, or at least 2:1, or at least 3:1, or at least 4:1, or at least 5:1, or at least 7:1, or at least 8:1, or at least 10:1, or at least 15:1, or at least 20:1, or at least 30:1, or at least 40:1.
In one embodiment or in combination with any of the mentioned embodiments, the nonwoven webs/fabrics contain at least 55 wt. % fibers, or at least 60 wt. % fibers, or at least 70 wt. % fibers, or at least 80 wt. % fibers, or at least 85 wt. % fibers, or at least 90 wt. % fibers, or at least 95 wt. % fibers, or at least 96 wt. % fibers, or at least 97 wt. % fibers, or at least 98 wt. % fibers, or at least 99 wt. % fibers, or at least 99.5 wt. % fibers, or at least 99.75 wt. % fibers, or at least 99.8 wt. % fibers, or at least 99.9 wt. % fibers, based on the dry weight of the nonwoven web or fabric. These fibers are any fibrous material in the nonwoven web/fabric.
In another embodiment or in any of described embodiments, the CE fibers, and depending on the nature of the other fibers if present, the nonwoven web and/or fabric can be biodegradable, meaning that such CE fibers are expected to decompose under certain environmental conditions. The degree of degradation can be characterized by the weight loss of a sample over a given period of exposure to certain environmental conditions. In some cases, the CE fibers, or the webs and/or fabrics containing or the CE fibers can exhibit a weight loss of at least about 5, 10, 15, or 20 percent after burial in soil for 60 days and/or a weight loss of at least about 15, 20, 25, 30, or 35 percent after 15 days of exposure in a composter. However, the rate of degradation may vary depending on the particular end use of the fibers, as well as the composition of the wet laid product, and the specific test. Exemplary test conditions are provided in U.S. Pat. Nos. 5,870,988 and 6,571,802, incorporated herein by reference.
The CE fibers and webs/fabrics containing the CE fibers can also exhibit enhanced levels of environmental non-persistence, characterized by better-than-expected degradation under various environmental conditions. Fibers and fibrous wet laid articles can meet or exceed passing standards set by international test methods and authorities for industrial compostability, home compostability, and/or soil biodegradability.
To be considered “compostable,” a material must meet the following four criteria: (1) the material must be biodegradable; (2) the material must be disintegrable; (3) the material must not contain more than a maximum amount of heavy metals; and (4) the material must not be ecotoxic. As used herein, the term “biodegradable” generally refers to the tendency of a material to chemically decompose under certain environmental conditions.
Biodegradability is an intrinsic property of the material itself, and the material can exhibit different degrees of biodegradability, depending on the specific conditions to which it is exposed. The term “disintegrable” refers to the tendency of a material to physically decompose into smaller fragments when exposed to certain conditions. Disintegration depends both on the material itself, as well as the physical size and configuration of the article being tested. Ecotoxicity measures the impact of the material on plant life, and the heavy metal content of the material is determined according to the procedures laid out in the standard test method.
In one embodiment or in combination with any of the mentioned embodiments or in any of the mentioned embodiments, the CE fibers, and the webs/fabrics containing the CE fibers, are industrially compostable, home compostable, or both. In this or on any of the embodiment, the CE fibers used, or the webs/fabrics containing the CE fibers, can satisfy four criteria:

- 1) biodegrade in that at least 90% carbon content is converted within 180 days;
- 2) disintigratable in that least 90% the material disintegrates within 12 weeks;
- 3) does not contain heavy metals beyond the thresholds established under the EN12423 standard; and
- 4) the disintegrated content supports future plant growth as humus; where each of these four conditions are tested per the ASTM D6400,
  or ISO 17088, or EN 13432 method.

The CE fibers, and the webs/fabrics containing the CE fibers can exhibit a biodegradation of at least 70 percent in a period of not more than 50 days, when tested under aerobic composting conditions at ambient temperature (28° C.±2° C.) according to ISO 14855-1 (2012). In some cases, the CE fibers, and the webs/fabrics containing the CE fibers, can exhibit a biodegradation of at least 70 percent in a period of not more than 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, or 37 days when tested under these conditions, also called “home composting conditions.” These conditions may not be aqueous or anaerobic. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers, can exhibit a total biodegradation of at least about 71, or at least 72, or at least 73, or at least 74, or at least 75, or at least 76, or at least 77, or at least 78, or at least 79, or at least 80, or at least 81, or at least 82, or at least 83, or at least 84, or at least 85, or at least 86, or at least 87, or at least 88 percent, when tested under according to ISO 14855-1 (2012) for a period of 50 days under home composting conditions. This may represent a relative biodegradation of at least about 95, or at least 97, or at least 99, or at least 100, or at least 101, or at least 102, or at least 103 percent, when compared to cellulose subjected to identical test conditions.
To be considered “biodegradable,” under home composting conditions according to the French norm NF T 51-800 and the Australian standard AS 5810, a material must exhibit a biodegradation of at least 90 percent in total (e.g., as compared to the initial sample), or a biodegradation of at least 90 percent of the maximum degradation of a suitable reference material after a plateau has been reached for both the reference and test item. The maximum test duration for biodegradation under home compositing conditions is 1 year. The CE fibers, and/or the webs/fabrics containing the CE fibers and the products made thereby, may exhibit a biodegradation of at least 90 percent within not more than 1 year, measured according 14855-1 (2012) under home composting conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers, may exhibit a biodegradation of at least about 91, or at least 92, or at least 93, or at least 94, or at least 95, or at least 96, or at least 97, 9 or at least 8, or at least 99, or at least 99.5 percent within not more than 1 year, or the fibers may exhibit 100 percent biodegradation within not more than 1 year, measured according 14855-1 (2012) under home composting conditions.
Additionally, or in the alternative, the CE fibers, and/or the webs/fabrics containing the CE fibers, may exhibit a biodegradation of at least 90 percent within not more than about 350, or not more than 325, or not more than 300, or not more than 275, or not more than 250, or not more than 225, or not more than 220, or not more than 210, or not more than 200, or not more than 190, or not more than 180, or not more than 170, or not more than 160, or not more than or not more than 150, or not more than 140, or not more than 130, or not more than 120, or not more than 110, or not more than 100, or not more than 90, or not more than 80, or not more than 70, or not more than 60, or not more than 50 days, measured according 14855-1 (2012) under home composting conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers, can be at least about 97, or at least 98, or at least 99, or at least 99.5 percent biodegradable within not more than about 70, or not more than 65, or not more than 60, or not more than 50 days of testing according to ISO 14855-1 (2012) under home composting conditions. As a result, the CE fibers, and/or the webs/fabrics containing the CE fibers may be considered biodegradable according to, for example, French Standard NF T 51-800 and Australian Standard AS 5810 when tested under home composting conditions.
The CE fibers, and/or the webs/fabrics containing the CE fibers can exhibit a biodegradation of at least 60 percent in a period of not more than 45 days, when tested under aerobic composting conditions at a temperature of 58° C. (±2° C.) according to ISO 14855-1 (2012). In some cases, they can exhibit a biodegradation of at least 60 percent in a period of not more than 44, or not more than 43, or not more than 42, or not more than 41, or not more than 40, or not more than 39, or not more than 38, or not more than 37, or not more than 36, or not more than 35, or not more than 34, or not more than 33, or not more than 32, or not more than 31, or not more than 30, or not more than 29, or not more than 28, or not more than 27 days when tested under these conditions, also called “industrial composting conditions.” These may not be aqueous or anaerobic conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers can exhibit a total biodegradation of at least about 65, or at least 70, or at least 75, or at least 80, or at least 85, or at least 87, or at least 88, or at least 89, or at least 90, or at least 91, or at least 92, or at least 93, or at least 94, or at least 95 percent, when tested under according to ISO 14855-1 (2012) for a period of 45 days under industrial composting conditions. This may represent a relative biodegradation of at least about 95, or at least 97, or at least 99, or at least 100, or at least 102, or at least 105, or at least 107, or at least 110, or at least 112, or at least 115, or at least 117, or at least 119 percent, when compared to cellulose fibers subjected to identical test conditions.
To be considered “biodegradable,” under industrial composting conditions according to ASTM D6400 and ISO 17088, at least 90 percent of the organic carbon in the whole item (or for each constituent present in an amount of more than 1% by dry mass) must be converted to carbon dioxide within 180 days. According to European standard ED 13432 (2000), a material must exhibit a biodegradation of at least 90 percent in total, or a biodegradation of at least 90 percent of the maximum degradation of a suitable reference material after a plateau has been reached for both the reference and test item. The maximum test duration for biodegradability under industrial compositing conditions is 180 days. The CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a biodegradation of at least 90 percent within not more than 180 days, measured according 14855-1 (2012) under industrial composting conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a biodegradation of at least about 91, or at least 92, or at least 93, or at least 94, or at least 95, or at least 96, or at least 97, or at least 98, or at least 99, or at least 99.5 percent within not more than 180 days, or the fibers may exhibit 100 percent biodegradation within not more than 180 days, measured according 14855-1 (2012) under industrial composting conditions.
Additionally, or in the alternative, the CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a biodegradation of least 90 percent within not more than about 175, or not more than 170, or not more than 165, or not more than 160, or not more than 155, or not more than 150, or not more than 145, or not more than 140, or not more than 135, or not more than 130, or not more than 125, or not more than 120, or not more than 115, or not more than 110, or not more than 105, or not more than 100, or not more than 95, or not more than 90, or not more than 85, or not more than 80, or not more than 75, or not more than 70, or not more than 65, or not more than 60, or not more than 55, or not more than 50, or not more than 45 days, measured according 14855-1 (2012) under industrial composting conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers can be at least about 97, 98, 99, or 99.5 percent biodegradable within not more than about 65, or not more than 60, or not more than 55, or not more than 50, or not more than 45 days of testing according to ISO 14855-1 (2012) under industrial composting conditions. As a result, the CE fibers, and/or the webs/fabrics containing the CE fibers may be considered biodegradable according ASTM D6400 and ISO 17088 when tested under industrial composting conditions.
The CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a soil biodegradation of at least 60 percent within not more than 130 days, measured according to ISO 17556 (2012) under aerobic conditions at ambient temperature. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers can exhibit a biodegradation of at least 60 percent in a period of not more than 130, or not more than 120, or not more than 110, or not more than 100, or not more than 90, or not more than 80, or not more than 75 days when tested under these conditions, also called “soil composting conditions.” These may not be aqueous or anaerobic conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers can exhibit a total biodegradation of at least about 65, or at least 70, or at least 72, or at least 75, or at least 77, or at least 80, or at least 82, or at least 85 percent, when tested under according to ISO 17556 (2012) for a period of 195 days under soil composting conditions. This may represent a relative biodegradation of at least about 70, or at least 75, or at least 80, or at least 85, or at least 90, or at least 95 percent, when compared to cellulose fibers subjected to identical test conditions.
In order to be considered “biodegradable,” under soil composting conditions according the OK biodegradable SOIL conformity mark of Vingotte and the DIN Geprilft Biodegradable in soil certification scheme of DIN CERTCO, a material must exhibit a biodegradation of at least 90 percent in total (e.g., as compared to the initial sample), or a biodegradation of at least 90 percent of the maximum degradation of a suitable reference material after a plateau has been reached for both the reference and test item. The maximum test duration for biodegradability under soil compositing conditions is 2 years. The CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a biodegradation of at least 90 percent within not more than 2 years, 1.75 years, 1 year, 9 months, or 6 months measured according ISO 17556 (2012) under soil composting conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a biodegradation of at least about 91, or at least 92, or at least 93, or at least 94, or at least 95, or at least 96, or at least 97, or at least 98, or at least 99, or at least 99.5 percent within not more than 2 years, or the fibers may exhibit 100 percent biodegradation within not more than 2 years, measured according ISO 17556 (2012) under soil composting conditions.
Additionally, or in the alternative, CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a biodegradation of at least 90 percent within not more than about 700, 650, 600, 550, 500, 450, 400, 350, 300, 275, 250, 240, 230, 220, 210, 200, or 195 days, measured according 17556 (2012) under soil composting conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers can be at least about 97, or at least 98, or at least 99, or at least 99.5 percent biodegradable within not more than about 225, or not more than 220, or not more than 215, or not more than 210, or not more than 205, or not more than 200, or not more than 195 days of testing according to ISO 17556 (2012) under soil composting conditions. As a result, the CE fibers, and/or the webs/fabrics containing the CE fibers may meet the requirements to receive The OK biodegradable SOIL conformity mark of Vingotte and to meet the standards of the DIN GeprOft Biodegradable in soil certification scheme of DIN CERTCO.
In some cases, CE fibers, and/or the webs/fabrics containing the CE fibers may include less than 1, or not more than 0.75, or not more than 0.50, or not more than 0.25 weight percent of components of unknown biodegradability, based on the weight of the CE staple fiber. In some cases, the fibers or fibrous wet laid articles described herein may include no components of unknown biodegradability.
In addition to the CE fibers being biodegradable under industrial and/or home composting conditions, the webs/fabrics, including wet laid non-woven articles may also be compostable under home and/or industrial conditions. As described previously, a material is considered compostable if it meets or exceeds the requirements set forth in EN 13432 for biodegradability, ability to disintegrate, heavy metal content, and ecotoxicity. The CE fibers or fibrous wet laid articles described herein may exhibit sufficient compostability under home and/or industrial composting conditions to meet the requirements to receive the OK compost and OK compost HOME conformity marks from Vingotte.
In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers and the products made thereby, may have a volatile solids concentration, heavy metals and fluorine content that fulfill all of the requirements laid out by EN 13432 (2000). Additionally, the CE fibers may not cause a negative effect on compost quality (including chemical parameters and ecotoxicity tests).
In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers can exhibit a disintegration of at least 90 percent within not more than 26 weeks, measured according to ISO 16929 (2013) under industrial composting conditions. In some cases, the fibers or fibrous wet laid articles may exhibit a disintegration of at least about 91, or at least 92, or at least 93, or at least 94, or at least 95, or at least 96, or at least 97, or at least 98, or at least 99, or at least 99.5 percent under industrial composting conditions within not more than 26 weeks, or the fibers or wet laid articles may be 100 percent disintegrated under industrial composting conditions within not more than 26 weeks. Alternatively, or in addition, the CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a disintegration of at least 90 percent under industrial compositing conditions within not more than about 26, or not more than 25, or not more than 24, or not more than 23, or not more than 22, or not more than 21, or not more than 20, or not more than 19, or not more than 18, or not more than 17, or not more than 16, or not more than 15, or not more than 14, or not more than 13, or not more than 12, or not more than 11, or not more than 10 weeks, measured according to ISO 16929 (2013). In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers may be at least 97, or at least 98, or at least 99, or at least 99.5 percent disintegrated within not more than 12, or not more than 11, or not more than 10, or not more than 9, or not more than 8 weeks under industrial composting conditions, measured according to ISO 16929 (2013).
In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers can exhibit a disintegration of at least 90 percent within not more than 26 weeks, measured according to ISO 16929 (2013) under home composting conditions. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a disintegration of at least about 91, or at least 92, or at least 93, or at least 94, or at least 95, or at least 96, or at least 97, or at least 98, or at least 99, or at least 99.5 percent under home composting conditions within not more than 26 weeks, or the fibers or wet laid articles may be 100 percent disintegrated under home composting conditions within not more than 26 weeks. Alternatively, or in addition, the CE fibers, and/or the webs/fabrics containing the CE fibers may exhibit a disintegration of at least 90 percent within not more than about 26, or not more than 25, or not more than 24, or not more than 23, or not more than 22, or not more than 21, or not more than 20, or not more than 19, or not more than 18, or not more than 17, or not more than 16, or not more than 15 weeks under home composting conditions, measured according to ISO 16929 (2013). In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers may be at least 97, or at least 98, or at least 99, or at least 99.5 percent disintegrated within not more than 20, or not more than 19, or not more than 18, or not more than 17, or not more than 16, or not more than 15, or not more than 14, or not more than 13, or not more than 12 weeks, measured under home composting conditions according to ISO 16929 (2013).
The nonwoven webs and fabrics containing the CE fibers can achieve higher levels of biodegradability and/or compostability without use of additives that have traditionally been used to facilitate environmental non-persistence of similar fibers. Such additives can include, for example, photodegradation agents, biodegradation agents, decomposition accelerating agents, and various types of other additives. Despite being substantially free of these types of additives, the CE fibers, and/or the webs/fabrics containing the CE fibers have been found to exhibit enhanced biodegradability and compostability when tested under industrial, home, and/or soil conditions, as discussed previously.
In some embodiments, the CE fibers, and/or the webs/fabrics containing the CE fibers may be substantially free of photodegradation agents added when the CE fibers are combined with the other fibers, or added to the web or fabric. Optionally, one of the CE fibers themselves, or any combination thereof, may contain not more than about 1, or not more than 0.75, or not more than 0.50, or not more than 0.25, or not more than 0.10, or not more than 0.05, or not more than 0.025, or not more than 0.01, or not more than 0.005, or not more than 0.0025, or not more than 0.001 weight percent of photodegradation agent, based on the total weight of the fiber, or the CE fibers may include no photodegradation agents. Examples of such photodegradation agents include, but are not limited to, pigments which act as photooxidation catalysts and are optionally augmented by the presence of one or more metal salts, oxidizable promoters, and combinations thereof. Pigments can include coated or uncoated anatase or rutile titanium dioxide, which may be present alone or in combination with one or more of the augmenting components such as, for example, various types of metals. Other examples of photodegradation agents include benzoins, benzoin alkyl ethers, benzophenone and its derivatives, acetophenone and its derivatives, quinones, thioxanthones, phthalocyanine and other photosensitizers, ethylene-carbon monoxide copolymer, aromatic ketone-metal salt sensitizers, and combinations thereof.
In some embodiments, the CE fibers, and/or the webs/fabrics containing the CE fibers may be substantially free of biodegradation agents and/or decomposition agents other than plasticizers. For example, the CE fibers, and/or the webs/fabrics containing the CE fibers may include not more than about 1, or not more than 0.75, or not more than 0.50, or not more than 0.25, or not more than 0.10, or not more than 0.05, or not more than 0.025, or not more than 0.01, or not more than 0.005, or not more than 0.0025, or not more than 0.0020, or not more than 0.0015, or not more than 0.001, or not more than 0.0005 weight percent of biodegradation agents and/or decomposition agents, other than plasticizers, based on the total weight of the fiber, or the fibers may include no biodegradation and/or decomposition agents. Examples of such biodegradation and decomposition agents include, but are not limited to, salts of oxygen acid of phosphorus, esters of oxygen acid of phosphorus or salts thereof, carbonic acids or salts thereof, oxygen acids of phosphorus, oxygen acids of sulfur, oxygen acids of nitrogen, partial esters or hydrogen salts of these oxygen acids, carbonic acid and its hydrogen salt, sulfonic acids, and carboxylic acids.
Other examples of such biodegradation and decomposition agents include an organic acid selected from the group consisting of oxo acids having 2 to 6 carbon atoms per molecule, saturated dicarboxylic acids having 2 to 6 carbon atoms per molecule, and lower alkyl esters of said oxo acids or said saturated dicarboxylic acids with alcohols having from 1 to 4 carbon atoms. Biodegradation agents may also comprise enzymes such as, for example, a lipase, a cellulase, an esterase, and combinations thereof. Other types of biodegradation and decomposition agents can include cellulose phosphate, starch phosphate, calcium secondary phosphate, calcium tertiary phosphate, calcium phosphate hydroxide, glycolic acid, lactic acid, citric acid, tartaric acid, malic acid, oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, acetic acid, and combinations thereof.
The CE fibers, and/or the webs/fabrics containing the CE fibers may also be substantially free of several other types of additives that have been added to other synthetic fibers to encourage environmental non-persistence. Examples of these additives can include, but are not limited to, enzymes, microorganisms, water soluble polymers, water-dispersible additives, nitrogen-containing compounds, hydroxy-functional compounds, oxygen-containing heterocyclic compounds, sulfur-containing heterocyclic compounds, anhydrides, monoepoxides, and combinations thereof. In some cases, the CE fibers, and/or the webs/fabrics containing the CE fibers may include not more than about 0.5, or not more than 0.4, or not more than 0.3, or not more than 0.25, or not more than 0.1, or not more than 0.075, or not more than 0.05, or not more than 0.025, or not more than 0.01, or not more than 0.0075, or not more than 0.005, or not more than 0.0025, or not more than 0.001 weight percent of these types of additives, based on the weight of the CE fibers, or based on the weight of all fibers. The CE fibers may be free of the addition of any of these types of additives.
In an example, the nonwoven or fabric can be compostable in industrial environment (in accordance with EN 13432 or ASTM D6400) meeting the following four criteria:

- 1. Biodegradation determined by measuring the carbon dioxide produced by the sample under controlled composting conditions following ISO 14855-1:2012, where the sample is mixed with compost and placed in a bioreactor at 58° C. under continuous flow of humidified air. At the exit, the CO2 concentration is measured and related to the theoretical amount that could be produced regarding the carbon content of the sample.
- 2. Disintegration as evaluated on a pilot-scale by simulating a real composting environment following ISO 16929:2013, where the samples in their final form are mixed with fresh artificial bioresidue. Oxygen concentration, temperature and humidity are regularly controlled. After 12 weeks, the resulting composts are sieved and the remaining amount of material in pieces >2 mm, if any, is determined.
- 3. Ecotoxicity of the resulting compost is evaluated in plants following OECD 208 (2006), where the sample material in powder form is added to a bioreactor with fresh bioresidue following the same procedure as in the disintegration test. A comparison is made with the compost resulting from blank bioreactors and bioreactors containing the material tested with regards to plant seedling emergence and growth. Both parameters higher than 90% with respect to the blank compost passes the test.
- 4. Lacking metals, where each product is identified and characterized including at least: Information and identification of the constituents, presence of regulated metals (Zn, Cu, Ni, Cd, Pb, Hg, Cr, Mo, Se, As, Co) and other hazardous substances to the environment (F), and content in total dry and volatile solids.

The webs/fabrics described in embodiment can also be compostable in industrial and backyard or home composting conditions.
Compostability of CE fibers with a DS of 2.5 or below can be achieved without adding any biodegradation and decomposition agents, e.g., hydrolysis assistant or any intentional degradation promoter additives.
The webs/fabrics can be biodegradable in soil medium in accordance with ISO 17556:2003 testing protocol.
If desired, biodegradation and decomposition agents, e.g., hydrolysis assistant or any intentional degradation promoter additives can be added to a web or fabric or be contained within the CE fibers. The decomposition agent can be chosen in such a way that it does not impact the article shelf-life or does not impact the plant-growth when it is a part of the soil. Those additives can promote hydrolysis by releasing acidic or basic residues, and/or accelerate photo or oxidative degradation and/or promote the growth of selective microbial colony to aid the disintegration and biodegradation in compost and soil medium. In addition to promoting the degradation, these additives can have an additional function such as improving the processability of the article or improving mechanical properties.
Examples of decomposition agents include inorganic carbonate, synthetic carbonate, nepheline syenite, talc, magnesium hydroxide, aluminum hydroxide, diatomaceous earth, natural or synthetic silica, calcined clay, and the like. If used, it is desirable that these fillers are dispersed well in the polymer matrix. The fillers can be used singly, or in a combination of two or more.
Examples of aromatic ketones used as an oxidative decomposition agent include benzophenone, anthraquinone, anthrone, acetylbenzophenone, 4-octylbenzophenone, and the like. These aromatic ketones may be used singly, or in a combination of two or more.
Examples of the transition metal compound used as an oxidative decomposition agent include salts of cobalt or magnesium, preferably aliphatic carboxylic acid (C12 to C20) salts of cobalt or magnesium, and more preferably cobalt stearate, cobalt oleate, magnesium stearate, and magnesium oleate. These transition metal compounds can be used singly, or in a combination of two or more.
Examples of rare earth compounds used as an oxidative decomposition agent include rare earths belonging to periodic table Group 3A, and oxides thereof. Specific examples thereof include cerium (Ce), yttrium (Y), neodymium (Nd), rare earth oxides, hydroxides, rare earth sulfates, rare earth nitrates, rare earth acetates, rare earth chlorides, rare earth carboxylates, and the like. More specific examples thereof include cerium oxide, ceric sulfate, ceric ammonium Sulfate, ceric ammonium nitrate, cerium acetate, lanthanum nitrate, cerium chloride, cerium nitrate, cerium hydroxide, cerium octylate, lanthanum oxide, yttrium oxide, Scandium oxide, and the like. These rare earth compounds may be used singly, or in a combination of two or more.
Examples of basic additives selected can be at least one basic additive is selected from the group consisting of alkaline earth metal oxides, alkaline earth metal hydroxides, alkaline earth metal carbonates, alkali metal carbonates, alkali metal bicarbonates, ZηO and basic Al₂O₃. Preferably, the at least one basic additive is selected from the group consisting of MgO, Mg(OH)2, MgCO3, CaO, Ca(OH)2, CaCO3, NaHCO3, Na2CO3, K2CO3, Zr10 KHCO3 and basic Al₂O₃. In another preferred aspect, the at least one basic additive is selected from the group consisting of MgO, Mg(OH)2, MgCO3, CaO, Ca(OH)2, NaHCO₃, K2CO3, Zr10, KHCO3 and basic Al₂O₃. More preferably, the at least one basic additive is selected from the group consisting of MgO, Mg(OH)2, CaO, Ca(OH)2, ZηO, and basic Al₂O₃. In one aspect, alkaline earth metal oxides, ZηO and basic Al₂O₃are particularly preferred as basic additive; thus, the at least one basic additive is more preferably selected from the group consisting of MgO, ZηO, CaO and Al₂O₃, and even more preferably from the group consisting of MgO, CaO and ZηO. MgO is the most preferred basic additive.
Examples of organic acid additives include acetic acid, propionic acid, butyric acid, valeric acid, citric acid, tartaric acid, oxalic acid, malic acid, benzoic acid, maleic acid, phthalic acid, and combinations thereof.
As noted above, the nonwoven web contains binder fibers and base fibers. The method for making the nonwoven web is any conventional or exotic method, including wet laid, spun bond or laced, dry laid, flash spun, and melt blowing processes. In a dry laid process, a compressed bale of fibers is opened, and the fibers are withdrawn and opened with opening equipment and made into a batt that is fed into equipment for making the nonwoven web, such as a carding or air laid machine.
Dry laid processes include air laying and carding. An example of a dry laid process includes fiber preparation, blending of fibers, carding, and garneting. In the dry laid process, the fibers can be collected into a web form by parallel lapping, cross lapping, or air laying lap forming. Bats can be formed by laying carded webs over each other. Cross or parallel lapped webs are not considered laminates as used herein.
An example of a wet laid process is found in paper making processes where a very dilute slurry of fibers in water is deposited onto a belt or wire, the water drained, and the wet web is passed through a series of nips and heaters to form a paper/board product.
Spun bond processes form a web from filaments immediately as they exit the extruder. Molten thermoplastic material is extruded through capillaries in spinneret as continuous filaments with the diameter substantially that of the spinneret holes. The fibers are cooled by an eductive or other drawing method. To form the nonwoven web, the spunbond filaments are randomly deposited onto a surface such as a screen or belt to form a loosely entangled web, which is then bonded by any thermal bonding technique, such as hot roll calendaring, through air bonding, or by steam bonding at elevated pressure.
Melt blown is accomplished by extruding molten polymer though very fine capillaries in a spin die or net as filaments that are partially cooled with high velocity hot air as they fall from the die head, thereby reducing their diameter. These fibers are typically finer than spun bond fibers and are often added to spun bond fibers to form SM (spun-melt) or SMS (spun-melt-spun) webs. Desirably, the nonwoven web is a dry laid nonwoven web, and in particular, an SM or SMS web or a carded or cross-lapped nonwoven web.
Once the nonwoven web is at least partially or fully formed, either (i) water or (ii) water and a plasticizer are applied to the nonwoven web, provided that if the binder fibers in the nonwoven web do not contain a plasticizer, then water and a plasticizer are applied to the nonwoven web. If desired, only water, or both water and a plasticizer can be applied to a nonwoven web that contains dry plasticized CE fibers. The result is the production of a wetted plasticized nonwoven web prior to thermal bonding, or in other words, the nonwoven web is plasticized and fed wet before being thermally bonded. The term “wetted plasticized nonwoven web” refers to the plasticizing of at least a portion of the CE fibers in the web and does not imply that all the different kinds of fibers in the web are plasticized, particularly the base fibers. Optionally, thermoplastic fibers other than CE fibers can also become plasticized along with the CE fibers. Further, a wetted plasticized nonwoven web does not imply that every CE fiber in the web is either thoroughly wetted or plasticized, but rather that the wetted plasticized nonwoven web is capable of being thermally bonded at temperatures below the native T_gof the CE fibers.
At least water is applied to the nonwoven web before it is thermally bonded. Binder fibers may already contain a plasticizer, and in this case, either (i) only water can be applied to the non-woven web or (ii) water and a plasticizer can be applied to the nonwoven web. The latter case may be desirable when the amount or type of plasticizer in the binder fibers is not sufficient or suitable to provide a thermally bonded fabric with the desired tensile strength or other property. In the event that the binder fibers are not coated with or otherwise do not contain any plasticizer, then water and a plasticizer must be applied to the nonwoven web.
The combination of water and plasticizer can be premixed. The combination can be in the form of an aqueous solution, suspension, dispersion, or emulsion to the nonwoven web. Alternatively, water and plasticizer can be separately dispensed in any order: water followed by plasticizer or plasticizer followed by water. If separately dispensed, the water can plasticizer can separately contact the nonwoven web or impinge on each other before contacting the nonwoven web. Desirably, an aqueous plasticizer is dispensed and applied to the nonwoven web. Desirably, the aqueous plasticizer is a solution. In this case, the type of plasticizer selected should be soluble in water at a temperature below 100° C., or desirably at 70° C. or lower, or at 60° C. or lower, or at 55° C. or lower, or at 30° C. or lower.
The water is desirably applied continuously to the nonwoven web, and desirably a combination of water and plasticizer is applied continuously to the nonwoven web. In one embodiment or in any of the mentioned embodiments, the nonwoven web is hydroentangled, and the water, or combination of water and plasticizer, is applied to the nonwoven web before, during, or after hydroentangling the web and before thermally bonding the web.
The method for applying water, or water and a plasticizer, to the nonwoven web to make the wetted plasticized nonwoven web is not limited and may vary depending on the type of nonwoven web and its method of manufacture. Suitable methods include spraying, wick application, dipping or immersion (also known as impregnation), centrifugal force application such as by way of a rotating drum apparatus, or coating methods such as squeeze, lick, or kiss roll coating methods. Examples of suitable coating methods and devices include an air knife coater, curtain coater, slide lip coater, die coater, blade coater, bill blade coater, short dwell blade coater, gate roll coater, film transfer coater, bar coater, rod coater, roll coater and size press. In the air knife process, an air jet impinges the web acting like a doctor blade to remove excess coating applied to the web. In a blade coating technique, a flexible doctor blade set to the desired angle removes excess coating across the web. The various blades and rollers ensure the uniform application of the coating, in this case, water or water and a plasticizer. Desirably, the water, or water/plasticizer combination or mixture, is applied by spray or coating methods, and these methods allow for control over the degree of wetting the nonwoven web.
Spray is particularly desirable if only water is applied or an aqueous solution of water and plasticizer, or when the nonwoven web is delicate, such as those with a basis weight of less than 35 g/m², especially those at or lower than 30 g/m². As shown in FIG. 1, the spray 2 can be dispended through a sprayer apparatus 1 and applied to one front side 3 or optionally front side 3 and back side 4 of the nonwoven web 5 as it passes over rolls 6 and 7, one of which may optionally be a calendar roll. The spray may be contained in a spray booth 8 and any liquid that does not remain on the web or that is not applied to the web can be collected at the bottom 9 and recirculated after filtering.
Dipping or impregnations methods are useful when the entire thickness of the nonwoven web is to be saturated and the nonwoven web has sufficient strength and basis weight to retain its integrity into the thermal bonding machine. As illustrated in FIG. 2, the nonwoven web 1 is passed through a bath 10 of water or water and plasticizer across rolls 11 and 12 and the excess liquid in saturated web 13 can be squeezed out under pressure between the nip of rollers 14, or by vacuum (no illustrated). Roll 15 guides the nonwoven web through the bath and can optionally be perforated and be the vehicle for introducing the water or aqueous solution of plasticizer. Liquid squeezed out from the saturated web can be collected in a collection zone 16 and recirculated for introduction into bath 10 after filtering.
With a lick or kiss roll method, as illustrated in FIG. 3, the nonwoven web 1 passes across guide rolls 20 and 21 and in contact with a rotating roll 23 wetted with the coating (water or water and plasticizer). The roll 23 picks up the coating by rotating into a bath 24 of the coating or across a spray or other transfer method (not illustrated) along one portion of the roll surface (e.g., bottom) 25 and the nonwoven web picks up the coating on the roll along a different surface, e.g., side or top surface 26. If needed, a knife or doctor blade 27 can be located at the exit of the roll 23 to scrape of the excess coating and collect the excess into bath 24. The lick or kiss roll method can apply the coating (water or water/plasticizer mix) to one or both sides (top and bottom) of the nonwoven web.
Coating methods are better suited for the application of a water/plasticizer combination to avoid creating an aerosol of plasticizer and providing a uniform and precise application. Kiss or lick roll techniques are the simplest methods, although knife or doctor blade coating techniques that rely on pouring the coating onto the nonwoven web ahead of the knife or doctor blade are also suitable and efficient and allow for controlling the moisture content of the nonwoven web.
In one embodiment or in combination with any of the mentioned embodiments, water and a plasticizer are applied to the nonwoven web. In this embodiment, water and plasticizer are applied to a nonwoven web containing fibers that are not or are coated or impregnated with or without dried plasticizer. With this method, the minimum desired level of plasticizer can be controlled, regardless of whether or not the fibers in the nonwoven web (e.g., base fibers or CE fibers) contain plasticizer. In some cases, the quantity of plasticizer in the fibers of the nonwoven web may not be known, such as when the nonwoven web contains recycle fibers (post-consumer or postindustrial). Even when the amount of plasticizer in the nonwoven web is known, it may be insufficient or of a type not desired by the owner of the nonwoven web. Further, the application of a water and plasticizer combination ensures that all the desired amount of plasticizer contacts water.
We have found that the development of a wetted plasticized nonwoven web has a surprisingly large effect on the tensile strength of a fabric in the machine direction that extends far beyond the effect on tensile strength by use of water alone or a plasticizer alone or even the increase in tensile strength by addition of individual effects. This unexpectedly large enhancement in tensile strength is achieved when the nonwoven web is made into a wetted plasticized nonwoven web before thermal bonding. In one embodiment or in combination with any of the mentioned embodiments, a fabric obtained from a nonwoven web wetted with water and containing a plasticizer has a tensile strength in the machine direction that is greater than the additive effect in the increase in tensile strength of a fabric made from a nonwoven web containing plasticizer without application of water and a nonwoven web containing no plasticizer but to which water is applied, relative to a nonwoven web containing no plasticizer and to which no water is applied (referred to as the “additive tensile strength effect of the individual components”).
In one embodiment or in combination with any of the mentioned embodiments, an aqueous plasticizer is applied to the nonwoven web. Desirably, an aqueous plasticizer is both dispensed and applied to the nonwoven web. The amount plasticizer applied to the nonwoven web can be at least 1 wt. %, or at least 1.5 wt. %, or at least 2 wt. %, or at least 2.5 wt. %, or at least 3 wt. %, or at least 3.5 wt. %, or at least 4 wt. %, or at least 4.5 wt. %, or at least 5 wt. %, or at least 5.5 wt. %, or at least 6 wt. %, or at least 6.5 wt. %, or at least 7 wt. %, or at least 7.5 wt. %, or at least 8 wt. %, or at least 8.5 wt. %, based on the weight of applied water and applied plasticizer. The amount of plasticizer applied to the non-woven web can be up to 30 wt. %, or up to 25 wt. %, or up to 20 wt. %, or up to 15 wt. %, or up to 13 wt. %, or up to 10 wt. %, or up to 9 wt. %, or up to 8 wt. %, or up to 7 wt. %, or up to 6 wt. %, based on the weight of applied water and applied plasticizer. In one embodiment or in combination with any of the mentioned embodiments, the amount of plasticizer applied in combination with water is sufficient to increase the tensile strength of the fabric in the machine direction beyond the additive tensile strength effect of the individual components.
In one embodiment or in combination with any of the mentioned embodiments, water is applied to a nonwoven web containing fibers coated or impregnated with a plasticizer. In this embodiment, the plasticizer coated on or contained in the CE fibers is dry when forming the nonwoven web, or in the nonwoven web before application of water. The amount and type of plasticizer coated on or contained in the CE fibers may be effective such that, upon application of water to the nonwoven web, a wetted plasticized nonwoven web can be made that thermally bonds at temperatures below the native T_gof the CE fibers or possesses any of the characteristics and/or advantages mentioned with respect to the formation of a wetted plasticized nonwoven web by application of water and plasticizer to the nonwoven web.
The amount plasticizer applied to the nonwoven web, based on the weight of the wetted plasticized nonwoven web, or the amount of plasticizer in the wetted plasticized nonwoven web based on the weight of the wetted plasticized nonwoven web, regardless of the method of wetting, can be at least 0.1 wt. %, or at least 0.25 wt. %, or at least 0.5 wt. %, or at least 0.75 wt. %, or at least 1 wt. %, or at least 1.5 wt. %, or at least 2 wt. %, or at least 2.5 wt. %, or at least 3 wt. %, or at least 3.5 wt. %, based on the weight of the nonwoven web, on a calculated or a dry weight basis. The amount of plasticizer contained in the non-woven web can be up to 30 wt. %, or up to 25 wt. %, or up to 20 wt. %, or up to 15 wt. %, or up to 13 wt. %, or up to 10 wt. %, or up to 9 wt. %, or up to 8 wt. %, or up to 7 wt. %, or up to 6 wt. %, or up to 5 wt. %, or up to 4 wt. %, or up to 3 wt. %, or up to 2.5 wt. %, or up to 2.2 wt. %, or up to 2 wt. %, or up to 1.8 wt. %, or up to 1.5 wt. %, or up to 1.3 wt. %, based on the weight of nonwoven web, on a calculated or dry weight basis.
In one embodiment or in combination with any of the mentioned embodiments, the amount and type of plasticizer applied to the nonwoven web, or contained in the wetted nonwoven web, is effective to reduce the T_gof the CE fibers by at least 5° C., or at least 8° C., or at least 10° C., or at least 12° C., or at least 15° C., or at least 18° C., or at least 20° C., or at least 22° C., or at least 24° C., or at least 26° C., or at least 28° C., or at least 30° C., or at least 31° C., or at least 32° C., or at least 35° C. In addition or in the alternative, the amount and type of plasticizer applied to the nonwoven web, or contained in the wetted nonwoven web, does not reduce the T_gof the CE fibers below a CE fiber T_gof 70° C., or 85° C., or 100° C., or 110° C., or 120° C., or 130° C., or 140° C., or 145° C., or 150° C., or 153° C., or 155° C.
The amount of water applied to the nonwoven web is sufficient to wet the web. Suitable amount of water applied to the nonwoven web include 10 wt. %, or at least 15 wt. %, or at least 20 wt. %, or at least 30 wt. %, or at least 50 wt. %, or at least 60 wt. %, or at least 70 wt. %, or at least 80 wt. %, or at least 90 wt. %, based on the weight of the nonwoven web. For example, the ratio of nonwoven web weight to applied water weight of 1:1 would be the application of water in an amount of 100%, based on the weight of the nonwoven web (before application of water). The upper amount of water applied to the nonwoven web is not limited, and can be 400 wt. %, or up to 350 wt. %, or up to 300 wt. %, or up to 250 wt. %, or up to 200 wt. %, or up to 150 wt. %, or up to 125 wt. % based on the weight of the nonwoven web. Examples of ranges include, but are not limited to, 10-400, or 30-250, or 50-200, or 50-150, in each case as wt. % based on the weight of the nonwoven web.
In one embodiment or in combination with any mentioned embodiments, there is provided a dry laid wetted plasticized nonwoven web comprising cellulose acetate fibers, water, and plasticizer, wherein the amount of water on said web is at least 5 wt. % based on the weight of the nonwoven web and the amount of plasticizer is at least 0.25 wt. % based on the weight of the nonwoven web. The moisture content of the wetted plasticized nonwoven web, or as introduced to the first element that thermally bonds the web (e.g., the nip of first heated embossing calendar rolls) is desirably at least 5 wt. %, or at least 6 wt. %, or at least 8 wt. %, or at least 10 wt. %, or at least 13 wt. %, or at least 15 wt. %, or at least 18 wt. %, or at least 20 wt. %, or at least 23 wt. %, or at least 25 wt. %, or at least 27 wt. %, or at least 30 wt. %, or at least 33 wt. %, or at least 36 wt. %, or at least 40 wt. %, based on the weight of the wetted plasticized nonwoven web, and desirably as introduced fed to the first element to thermally bond the web. The nonwoven web can have a moisture content of not more than 95 wt. %, or not more than 85 wt. %, or not more than 70 wt. %, or not more than 60 wt. %, or not more than 50 wt. %, or not more than 40 wt. %, or not more than 35 wt. %, or not more than 30 wt. %, or not more than 25 wt. %, or not more than 20 wt. %, or not more than 15 wt. %, or not more than 10 wt. % moisture, based on the weight of the wetted plasticized nonwoven web, and desirably as introduced fed to the first element to thermally bond the web. Examples of ranges include, but are not limited to, 10-95, or 10-85, or 10-70, or 10-50, or 10-40, or 10-35, or 10-30, or 10-25, or 10-20, or 10-15, or 15-95, or 15-85, or 15-70, or 15-50, or 15-40, or 15-35, or 15-30, or 15-25, or 15-20, or 20-95, or 20-85, or 20-70, or 20-50, or 20-40, or 20-35, or 20-30, or 25-95, or 25-85, or 25-70, or 25-50, or 25-40, or 25-35, in each case as wt. % based on the weight of the wetted plasticized nonwoven web, and desirably as introduced fed to the first element to thermally bond the web.
The moisture content can be measured by the weight loss of the web after placing a sample of the wetted plasticized nonwoven web in a drying oven maintaining a constant temperature of 95° C.=1-5° C. for a period of time until its weight no longer changes, measuring its dry weight, and determining the difference.
The basis weight of the nonwoven web, before addition of water and plasticizer or any other additive, whether liquid or solid, after the nonwoven web is formed, can be at least 8 g/m², or at least 10 g/m², or at least 13 g/m², or at least 15 g/m², or at least 18 g/m², or at least 20 g/m², or at least 23 g/m², or at least 25 g/m², or at least 27 g/m², or at least 30 g/m², or at least 35 g/m², or at least 40 g/m², or at least 45 g/m², or at least 50 g/m². In addition or in the alternative, the basis weight of the nonwoven web is generally not more than 750 g/m², or not more than 600 g/m², or not more than 500 g/m², or not more than 400 g/m², or not more than 250 g/m², or not more than 200 g/m², or not more than 150 g/m², or not more than 100 g/m², or not more than 80 g/m², or not more than 60 g/m², or not more than 50 g/m², or not more than 45 g/m², or not more than 40 g/m², or not more than 37 g/m², or not more than 35 g/m², or not more than 33 g/m², or not more than 30 g/m², or not more than 28 g/m², or not more than 25 g/m², or not more than 23 g/m², or not more than 20 g/m², or not more than 18 g/m².
If desired, the wetted plasticized nonwoven web may be preheated prior to thermally bonding. This step can be useful for thermally bonding nonwoven webs having a high basis weight, e.g., at or above 100 g/m², since such heavier weight webs may not reach interior temperatures at or above the T_gof the plasticized CE fibers at the line speed and roll pressures employed.
The wetted nonwoven web is thermally bonded to make a fabric. Examples of suitable thermal bonding techniques include hot calendaring, radiant heat bonding, and ultrasonic bonding. The wetted plasticized nonwoven webs have sufficient integrity to allow their passage as a web through the thermal bonding process, such as through hot calendaring rolls. In one embodiment or in combination with any of the mentioned embodiments, the nonwoven web, whether made by a dry laid, air laid, or wet laid process, has sufficiently entangled fibers to provide a cohesive web that allows it to be thermally bonded to make the fabric without the necessity for any other bonding techniques applied to the web. Typical bonding techniques which are unnecessary and desirably not applied to the nonwoven web prior to thermal bonding include a chemical bonding such as through adhesives or latex bonding or binder powders, solvent fusion, hydroentanglement, or stitching. However, the nonwoven web can be needle punched or tacked or tufted to improve handling if needed. In one embodiment or in combination with any of the mentioned embodiments, the nonwoven web, the wetted plasticized nonwoven web, and/or the fabric is not hydroentangled, or is not bonded with an adhesive or does not contain or have applied binder powders or thermoplastic sheets or films, or is not solvent fused, or is not stitched, or any combination of the foregoing.
In one embodiment or together with any of the mentioned embodiments, the thermally bonded fabric is made by thermally bonding two or more webs together, where at least one of the webs is a wetted plasticized nonwoven web, and desirably at least two webs are wetted plasticized nonwoven webs, and optionally all the webs that are bonded together are wetted plasticized nonwoven webs. In one embodiment or together with any of the mentioned embodiments, the thermally bonded fabric is obtained from a single layer of a wetted plasticized nonwoven web. Thermal bonding as used throughout this description can be thermally bonding one or more webs together wherein at least one web is a wetted plasticized nonwoven web.
The thermal bonding of the nonwoven web can be accomplished by any thermal bonding technique available. With a thermal bonding technique, heat and optionally pressure are applied to the nonwoven web causing the binder fibers to bond to each other and to the other fibers in the web. The bonds will occur at the intersection of the different fibers and are fixed in place once the bonding point cools. The thermal bonding technique does not rely upon a chemical reactions between the base fibers and binder fibers to create the bond.
The thermal bonding technique can be conducted in a variety of ways. One technique is through-air bonding in which a heated fluid such as air is forced through the nonwoven web, causing the cellulose ester fibers to bond at contact points. Another technique is ultrasonic bonding, in which friction generated by ultrasonic sound waves causes the cellulose ester fibers to bond to each other and other fibers at their contact points. The wetted plasticized nonwoven web can be passed under pressure between the anvil and sonotrode (or horn) operating at the desired frequency, such as at least 10 kHz-80 kHz, or from 15 kHz-70 kHz, or from 15 kHz-50 kHz, or from 15 kHz-45 kHz, or from 15 kHz-35 kHz, or from 15 kHz-30 kHz, or from 15 kHz-20 kHz. Desirably, the welder is a vibrational bonder. The vibrational energy caused by the ultrasonic frequencies causes localized softening or melting of the CE fibers, resulting in a bond when the vibrational energy is removed, and the localized area is cooled. The method employed can be a plunging method whereby the horn plunges toward the web and transmits the ultrasonic vibrations to the web. This method is particularly useful to make a point bonded fabric. Alternatively, the ultrasonic welding can be continuous, which is useful for sealing or creating a larger continuous area of bonding to the fabric, or a scanning method, or a rotary horn welding method, or a traverse welding method. The acoustic energy can be applied at low amplitudes, in the range of 20 microns to 150 microns, by typically would be at 25 to 100 microns. The pressure between the anvil and horn can be from 20 psi to 1000 psi, although higher pressures in excess of 1000 psi (e.g., 1000-6000 psi) can be employed depending on line speed, basis weight, material type, and welding method employed. The height, pattern, shape, and spacing of the projections on the anvil will be determined in part by the desired bonding area, the desired pattern on the fabric, and the basis weight and thickness of the web. Suitable bonding areas and basis weights are described above.
Yet another technique is infra-red bonding, in which the nonwoven web passes across an IR lamp to bond the cellulose ester fibers at their contact points. The hot calendar method is the desirably method, in which the nonwoven web is fed through the nip calendar rolls, at least one of which is heated. The belt calendaring method is also suitable. The calendaring method can be a har nip, soft nip, compact, belt, or multinip calendaring technique. Typical types of suitable hot calendar bonding methods include area bonding, point bonding, and embossing.
Desirably, the nonwoven web is thermally bonded by the hot calendaring method or the belt calendaring method, more desirably the hot calendaring method, and in particular, an embossing method such as point bonding. A point bonded fabric is a process of bonding fibers in the nonwoven web by softening, partially melting, or completely melting at least a portion of the nonwoven web at a discrete point. Thermal bonding, including point bonding, typically occurs by passing the nonwoven web through one or more heated calendar rolls. The calendar rolls may be smooth, especially for area bonding, or at least one may be embossed and/or engraved, and one is smooth. Desirably, at least one of the calendar rolls forming the embossing nip is steel roll surface. One of the calendar rolls forming an embossing nip can be a steel roll covered in a felt. In an embossed calendar roll, bonding occurs primarily at the raised edges or points on the embossed roll, created points or patterns of bonds on the web corresponding to the raised areas on the embossing roll. Examples of the types of point patterns include the square or pin point bonded patters also known as the Hansen-Pennings with about a 20-30% bond area; the expanded Hansen-Pennings with about a 10-20% bond area; the “714” pattern which also has square pin bonding areas with a bonded area of about 15%, a diamond pattern with repeating and slightly offset diamonds having about a 16% and even up to a 40% bond area; and a wire weave pattern with about an 15 to 30% bond area. In point bonding, the bonded surface area is typically not more than 60%, or not more than 50%, desirably not more than 40%, or not more than 35%, or not more than 30%, or not more than 25%, or not more than 20%, or not more than 15% of the surface area of the fabric.
In another embodiment, the thermal bonding method employed is an area bonding technique. In area bonding, the bonded surface is generally at least 70%, or at least 80%, or at least 90%, or at least 95%, or 100% of the surface area of the fabric. Area bonding is also a hot calendaring technique that typically employs a hot metal roll opposed by a wool, cotton, or other fibrous composition roll. On smooth calendar rolls, bonding occurs wherever the fibers cross each other and contact the calendar roll.
Two roll calendars (one nip or gap), three roll calendars (two nips or gaps), and four-roll calendars (three nips or gaps) can be employed depending on the basis weight of the web and the degree of bonding. For lighter weight materials at or below 35 g/m2, the two-roll calendar is sufficient to accomplish area thermal bonding. For higher basis weights, three roll calendars can be used, or the roll surface temperature is increased, the line speed is reduced, or a combination of these activities can be taken to obtain a satisfactory thermal bond. The three-roll bonding can also impart specialized finishing effects on one of the surfaces of the web. The four-roll calendar can produce specialized finishing effects on both surfaces (top and bottom) of the web, can process high basis weight materials, and can have temperature gradients in the machine direction of the web travel as desired.
The calendar nips can include serial nips in order to superimpose one pattern over the other on the web. Alternatively, the embossing patterns can be made through parallel nips, which is useful for fabrics of two or more plies. The thermal bonding of two or more plies of wetted plasticized nonwoven webs can be accomplished without the use of adhesives by spot or pattern bonding the plies.
In one embodiment or in combination with any of the mentioned embodiments, there is provided a process for thermal bonding, comprising feeding a wetted plasticized nonwoven web to a heated calendar roll, wherein said web is wetted with water and contains a plasticizer. The wetted plasticized nonwoven web is passed through at least one calendar nip having at least one heated calendar roll, or at least one heated embossing roll (also known as a patterned roll) having protruding members corresponding the pattern of the bonded portions, and at least one smooth roll. One or both of the calendar rolls creating the nip can be heated. The wetted plasticized nonwoven web is introduced into the nip, passed through the nip, and exits the nip, and the portion of the wetted nonwoven web that contacts the protrusions is the portion that is thermally bonded. The size of the gap between the tip of the protruding patterns on the embossing/pattern roll and the smooth roll is also a factor defining the depth of the recess or thickness of the bonded portion. If desired, instead of a smooth roll, two opposing patterned rolls can be employed in which the protrusions of a first roll fit into the recessed portions of the second roll, and the protrusions of the second roll fit into the recesses of the first roll.
Instead of roll calendaring, the embossing to make a pattern or points can be by way of passing the wetted plasticized nonwoven web through flat plates, which are particularly useful when the web is cut into discrete lengths.
The embossing roll or pattern roll, or plate can have a machined surface, or be etched, engraved, molded, or otherwise formed to have the desired pattern of protrusions and recesses. The protrusion height is not particularly limited and will depend on the basis weight and thickness of the web to be patterned and the desired nip gap. In general, protrusion heights of from 0.2 to 1.5 mm, or from 0.3 to 1 mm, or 0.4 to 1 mm, or 0.4 to 0.9 mm are suitable.
The calendar rolls can be pressed against each other at varying pressures depending on the thickness and basis weight of the nonwoven web, line speed, degree of bonding desired, and desired thickness of bond points and fabric. The wetted plasticized nonwoven web can pass through more than one calendar nip. At least one of the calendar rolls, and optionally both calendar rolls are internally heated to radiate heat to the surface of the rolls at a temperature sufficient or higher to bond the wetted plasticized nonwoven web at the roll pressure. The surface temperature of a least one of the calendar rolls desirably exceeds the Tg of the wetted and plasticized CE fibers in the wetted plasticized nonwoven web. It is desirable that the surface temperature of at least one calendar roll is also sufficiently high to transfer heat at a temperature at or above the Tg of the wetted plasticized fibers at the line speeds employed. The combination of transferred heat at the line speeds employed and the pressure exerted on the nonwoven web induces a flow or diffusion of cellulose ester sufficient and create a bond at crossover points between CE fibers and either other CE fibers, other binder fibers, or base fibers when cooled and relieved of pressure. The surface temperature of the calendar rolls at the line speeds and dwell time employed should not exceed the temperature at which any of the fibers in the wetted plasticized nonwoven web thermally degrade (or char). In one embodiment or in combination with any of the mentioned embodiments, the surface temperature of the calendar rolls at the line speeds and dwell time employed does not exceed or is below the melting point of the CE fibers, and desirably does not exceed or is below the melting point of any binder fibers. In one embodiment or in combination with any of the mentioned embodiments, the surface temperature of the calendar rolls is below any of the temperatures at which the fibers thermally degrade, or below the melting point of the CE fibers or binder fibers, irrespective of line speed or dwell time.
To avoid thermally degrading the CE fibers, or other binder or base fibers in the web, and to save on energy costs, it is desirably the at least one, or a majority (greater than 50% of the rolls), or all calendar roll temperatures have a surface temperature that is low. While many grades of cellulose acetate have a Tg (e.g., 192° C.) that is above the typical operating range commonly employed in the nonwovens industry, the thermal bonding of the wetted plasticized nonwoven web enables the use of cellulose acetate binder fibers in nonwoven webs that are thermally bonded.
In one embodiment or in combination with any of the mentioned embodiments, the upper temperature limit of at least one calendar roll, or desirably on all calendar rolls, is below the temperature at which any of the fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web, will thermally degrade at the line speed and nip forces applied. In one embodiment or in combination with any of the mentioned embodiments, the upper temperature limit of at least one calendar roll, or desirably on all calendar rolls, is below the thermal degradation temperature of any and all fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web (independent of line speed or nip forces applied).
In one embodiment or in combination with any of the mentioned embodiments, the upper temperature limit of at least one calendar roll, or desirably on all calendar rolls, is below the temperature at which any of the fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web, melt at the line speed and nip forces applied. In one embodiment or in combination with any of the mentioned embodiments, the upper temperature limit of at least one calendar roll, or desirably on all calendar rolls, is below the melting point temperature of any fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web (independent of line speed or nip forces applied).
In one embodiment or in combination with any of the mentioned embodiments, the upper temperature limit of at least one calendar roll, or desirably on all calendar rolls, or the first heated calendar roll contacting the wetted plasticized nonwoven web, is below the temperature at which binder fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web, in their native state will melt at the line speed and nip forces applied. As used throughout, when referring to an effect such as melting or softening (Tg), the native state temperature is the temperature at which the stated effect takes place without the presence of a plasticizer. In one embodiment or in combination with any of the mentioned embodiments, the upper temperature limit of at least one calendar roll, or desirably on all calendar rolls, is below the native melting point temperature of the binder fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web (independent of line speed or nip forces applied).
In one embodiment or in combination with any of the mentioned embodiments, the upper temperature limit of at least one calendar roll, or desirably on all calendar rolls, is below the temperature at which the CE fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web, would reach their native Tg at the line speed and nip forces applied. In one embodiment or in combination with any of the mentioned embodiments, at least one calendar roll temperature does not exceed, or alternatively the majority of calendar roll temperatures do not exceed, or alternatively no calendar roll temperature exceeds the native Tg of the CE fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web (independent of line speed or nip forces applied).
Since the plasticizer will lower the Tg of the CE fibers, one of the advantages of the wetted plasticized nonwoven web is that cooler roll temperatures can be used to effect the thermal bonding, resulting in energy savings on heat and opening a wider window of fiber selections in the web. If desired, rather than realizing all of the potential energy savings, line speeds and output can be increased at the same and even slightly lower calendar roll temperatures, thereby creating production efficiencies without adding equipment. By maintaining the calendar roll temperatures below the melting point of the binder fibers or the CE fibers, or even at or below the Tg of the CE fibers in their native state, one can better ensure the integrity of the web, and take advantage of energy savings or higher line speeds.
In one embodiment or in combination with any of the mentioned embodiments, one calendar roll temperature does not exceed, or alternatively the majority of calendar roll temperatures do not exceed, or alternatively no calendar roll temperature, or alternatively the first calendar roll(s) contacting the wetted plasticized nonwoven web, either (i) do not exceed or are below the native Tg of the CE fiber, or (ii) are at a temperature below the temperature at which the native Tg of the CE fibers would be reached at the line speeds and nip pressures applied, in each case by at least 5° C., or at least 8° C., or at least 10° C., or at least 12° C., or at least 15° C., or at least 18° C., or at least 20° C., or at least 22° C., or at least 24° C., or at least 26° C., or at least 28° C., or at least 30° C., or at least 31° C., or at least 32° C., or at least 35° C. and in each case at or above the Tg of the plasticized CE fibers.
In one embodiment or in combination with any of the mentioned embodiments, at least one calendar roll exceeds the Tg of the CE fibers in their plasticized state.
In one embodiment or in combination with any of the mentioned embodiments, at least one calendar roll temperature, or two calendar roll temperatures, are at or above a temperature sufficient to apply or raise the temperature of the plasticized CE fibers in the nonwoven web to their Tg temperature at the line speeds and nip pressure applied. In one embodiment or in combination with any of the mentioned embodiments, at least one calendar roll temperature, or two calendar roll temperatures, are at or above the Tg of the plasticized CE fibers in the nonwoven web.
Non-limiting examples of suitable temperatures of at least one calendar roll (or a majority of calendar rolls or all calendar rolls to which heat energy is applied), are at least 150, or at least 200, or at least 230, or at least 260, or at least 280, or at least 300, in each case as ° F. and generally need not exceed 450, or not exceed 430, or not exceed 420, or not exceed 410, or not exceed 400, or not exceed 390, or not exceed 380, or not exceed 376, or not exceed 370, or not exceed 365, or not exceed 360, or not exceed 355, or not exceed 350, or not exceed 345, or not exceed 340, or not exceed 335, or not exceed 330, or not exceed 325, or not exceed 320, in each case ° F. Non-limiting examples of suitable ranges include 230-376, 280-370, 280-365, 280-360, 260-355, 260-350, 300-345, or 300-340, or 300-335, or 280-335, in each case ° F.
If a hot calendaring thermal bonding process is employed, desirably a pair of cooling rolls are also included in the process in order to relieve stresses introduced in the web when placing the web under tension while hot.
In addition to the surface temperature of the calendar roll(s) transferring sufficient heat energy to cause the wetted plasticized CE fibers arrive at or exceed their Tg, pressure is also applied to the web to force the softening, partially melted, or melted CE fibers to diffuse or flow in and around other fibers and create bonds at their intersecting points when cooled. Suitable nip forces can include those ranging from 75 to 1500 PLI, or 100-1200, or 200-1200 PLI, or 250-800 PLI, or 250 to 800 PLI, or 250 to 700 PLI, or 250 to 600 PLI for many applications, although the nip force can be less or more depending on the application, the type of thermal bonding, the basis weight of the nonwoven web, the type of base fiber, the line speed, and the temperature at the roll surface, and whether the nonwoven is dry laid or wet laid. For example, in wet laid application for corrugated paperboard and linerboard, the PLI at the nip can be from 800-6000.
The calendaring technique can be single pass, double pass, S wrap, or Z configuration. The calendaring can also be a cold calendaring process, in which no heat energy is applied to the surface of the calendar rolls and they typically operate at room temperature.
The number of points per square inch is not particularly limited, and can include at least 10, or at least 20, or at least 40, or at least 50, or at least 70, or at least 90, or at least 100, or at least 130, or at least 150, or at least 175, or at least 200, or at least 225, and up to 700, or up to 600, or up to 500, or up to 400, or up to 350, or up to 300, or up to 275, or up to 250, or up to 225, or up to 200, or up to 175, or up to 150, in each case points per square inch. Examples of ranges are from 10-600, or from 20-500, or from 10-400, or from 10-300, or from 50-250, or from 100-250, in each case points per square inch.
In one embodiment or in combination with any of the mentioned embodiments, at least 10%, or at least 25%, or at least 50%, or at least 75%, or at least 80%, or at least 90%, or at least 95%, or at least 100% of the seam, point, or pattern bonds created are destructive bonds, meaning that the non-bonded web surrounding the bond tears or separates before the bond delaminates or tears.
In one embodiment or in combination with any of the mentioned embodiments, the bonds created between two or more plies do not delaminate throughout the packaging manufacturing process and as delivered to the end user. In one embodiment or in combination with any of the mentioned embodiments, the fabric comprises of two or more plies has a bond strength of an average load (over a 4 inch delamination length) of at least 1.0, or at least 1.5, or at least 2.0, or at least 2.5, or at least 3.0, or at least 3.5, or at least 4.0 N/50 cm, as measured by peel strength in accordance with ASTM D2724. In one embodiment or in combination with any of the mentioned embodiments, the fabric can achieve a bond strength of peak load of at least 2.0, or at least 2.5, or at least 3.0, or at least 3.5, or at least 4.0, or at least 4.5, or at least 5.0, or at least 5.5, or at least 6.0, or at least 6.5, or at least 7.0 N, as measured by peel strength in accordance with ASTM D2724. The samples can be tested as received (no laundering, dry cleaning, etc), using procedure 11.
The line speed can be any line speed adapted to provide maximum output at the applied calendar roll temperatures, nip pressure, and basis weight to effect thermal bonding. Line speeds of at least 10 m/min, or at least 30, or at least 40, or at least 50, or at least 80, or at least 100, or desirably at least 150, or at least 200, or at least 250, or at least 300, or at least 400, or at least 500, or at least 600, or at least 700, in each case as meters/minute are suitable, with the particular line speed selected being dependent on the types of fibers, equipment design, basis weight and thickness of the web, roll temperatures, and other process variables.
The basis weight of the nonwoven webs that can be processed can be at least 10, or at least 15, or at least 20, or at least 30, or at least 35, or at least 40, or at least 45, or at least 50, or at least 55, or at least 60, or at least 65, or at least 70, or at least 75, or at least 80, or at least 85, or at least 90, and in addition or in the alternative, up to 500, or up to 450, or up to 400, or up to 350, or up to 300, or up to 250, or up to 200, or up to 175, or up to 150, or up to 125, or up to 100, or up to 175, or up to 150, or up to 100, or up to 90, or up to 80, or up to 70, or up to 60, or up to 50, or up to 40, or up to or less than 35, or up to 33, or up to 30, or up to 28, or up to 25, or up to 23, or up to 20, or up to 18, or up to 16, in each case grams per m2 (gsm). Examples of ranges include 10-500, or 10-300, or 10-200, or 10-150, or 10-100, or 10-90, or 10-70, or 10-60, or 10-50, or 10-45, or 10-40, or 10-35, or 10-33, or 10-30, or 10-28, or 10-25, or 28-500, or 30-500, or 33-500, or 35-500, or 35-250, or 35-200, or 35-150, or 35-100, in each case in gsm.
In one embodiment or in combination with any of the mentioned embodiments, fabrics can now be obtained from low basis weight nonwoven webs that are thermally bonded to a strength that provides destructive bonds, and this is accomplished in the absence of adhesives, binder powders, or hydroentanglement. This is particularly advantageous for delicate nonwoven webs, such as those having a basis weight of 35 gsm or less, or even 32 gsm or less, or 30 gsm or less, or 28 gsm or less, or 25 gsm or less, or 23 gsm or less, or 20 gsm of less. The destructive bond is one in which the nonbonded web surrounding the bond will tear before or rather than the thermally bonded portion of the web delaminating. Dispensing with binder powders, adhesives, or hydroentanglement processes results in a large cost, allergen, and touch and feel advantage.
In one embodiment or in combination with any of the mentioned embodiments, the nonwoven web, including the wetted plasticized nonwoven web and fabrics do not contain a film or are not process with a film or sheet of non-fibrous material. In one embodiment or in combination with any of the mentioned embodiments, the nonwoven web, the wetted plasticized nonwoven web, or the fabrics, or any combination or the foregoing, are not a laminate or laminated.
In one embodiment or in combination with any of the mentioned embodiments, the fabric is a nonwoven web containing thermally bonded fibers at discrete bonding portions or discrete bonded points. Desirably, the thermally bonded portions or points are fibers fused at their intersections. The fabric contains a plurality of bonded and unbonded portions in which the bonded portions are discontinuous from each other and the unbonded portions are contiguous to each other. For example, at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 98%, or at least 99% of the number of bonded portions are discontinuous from each other, and alternatively or in addition, at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 98%, or at least 99% of the surface area of the unbonded portions are contiguous to each other, in each case by surface area.
In one embodiment or in combination with any of the mentioned embodiments, the ratio of the cumulative surface area of unbonded portions to the cumulative surface area of bonded portions can be at least 1:1, or at least 2:1, or at least 3:1, or at least 4:1, or at least 5:1, or at least 5.5:1, or at least 6:1, or at least 6.5:1, or at least 7:1, and can go up to 100:1, or 90:1, or 80:1, or 70:1, or 60:1, or 50:1, or 40:1, or 30:1, or 20:1, or 15:1, or 13:1, or 10:1, or 9:1, or 8:1, or 7:1, or 6:1, or 5:1, or 4:1, or 3:1, or 2:1.
In one embodiment or in combination with any of the mentioned embodiments, the thickness of the unbonded portion is greater than the thickness of the bonded portions. Desirably, the top surface of the bonded portions is recessed relative to the top surface of the unbonded portions. In one embodiment or in combination with any of the mentioned embodiments, the top and bottom surfaces of the bonded portions are recessed relative to the corresponding top and bottom surfaces of the unbonded portions. The ratio of the thickness of at least any 80% of the unbonded portions to at least any 80% of the bonded portions can be at least 2:1, or at least 3:1, or at least 4:1, or at least 5:1, or at least 6:1.
Instead of a hot calendaring method, the wetted plasticized nonwoven webs can be thermally bonded by the belt calendaring process, which is similar in many respects to the hot calendaring method, but differs in two major respects: the dwell time in the calendar nip and the nip pressure. In the hot calendaring method, the dwell time of the web in the nip is on the order of milliseconds, or less than 0.1 seconds, or not more than 0.05 seconds, or not more than 0.001 seconds. In the belt method, the dwell time can be 1 second or more, even up to 5 or 10 seconds. In the belt method, the nip force or pressure is between a roll and a belt or blanket, and is substantially less than the hot calendar method. The belt method is useful for thermally bonding fibers with sharp melting points.
One of the advantages of the formation of a wetted plasticized nonwoven web introduced into a thermal bonding process is the formation of a fabric that does not require adhesive bonding agents, hydroentanglement of the web, or stitching or solvent fusion, while obtaining a fabric with good tensile strength. In one embodiment or in combination with any of the mentioned embodiments, the fabric is devoid of adhesives added to the web. In one embodiment or in combination with any of the mentioned embodiments, the fabric is formed without (i) binder powders, or (ii) without hydroentangling or stitching the web, or (iii) without adhesives, or (iv) without needling the web, or (v) without a thermoplastic film or sheet, or without (vi) solvent fusion, or (vii) without any combination of (i)-(vi).
Other alternative processes for thermally bonding the wetted plasticized nonwoven web include through-air bonding techniques which are particularly useful when some of the binder fibers are multicomponent fibers having different melting points. In general, a through-air bonding process directs a stream of heated air against through the nonwoven web and negative pressure on the other side of the web pulls the stream of hot air through the web, thereby forming bonds at the binder fiber intersections. The temperature of the heated air is at or above the Tg of the CE fibers and at or above the polymer melting temperature of the lowest melting polymer component in a multicomponent fibers, if one is employed, and below the melting temperature of higher melting polymer component in the multicomponent fiber if one is employed.
Another alternative process for thermally bonding the wetted plasticized nonwoven web is an ultrasonic process. This process generates heat energy through localized frictional forces created by ultrasonic sound waves. The ultrasonic vibrations cause alternating compressive forces, and the resulting stresses on the fibers are converted to heat energy which can soften the localized area of fibers presses against each other. Once the ultrasonic vibration is discontinued, the local area cools and solidifies the bond points. The ultrasonic welding process is particularly well suited for spot or pattern bonding the wetted plasticized nonwoven web to make a bonded fabric, or to spot or pattern bond fabrics made from the wetted plasticized nonwoven web. The ultrasonic welding technique can also be used to bond fabrics to itself or to other fabrics and webs to make patterned composites and laminates.
Yet another alternative process for making a fabric from the wetted plasticized nonwoven webs is a radiant heat bonding process, in which the wetted plasticized nonwoven web is exposed to radiant energy in the infrared range, thereby softening and/or melting the binder fibers, including the CE fibers, with bonding occurring when the radiant heat source is removed and the area is cooled.
The articles that can be produced through thermally bonding the wetted plasticized nonwoven webs can include wipes, filters, non-medical garments such as shirts or pants or jackets or socks or undergarments, geotextiles, roofing felts, insoles, paper maker felts, fiberfill webs, needle felts including floor coverings, furniture fill and fabric, sanitary products, medical products such as wound dressings or bandages or sterilization wraps or medical bedding, medical garments such as surgical caps and hoods or face masks or drapes or surgical gowns or caps, automobile interior fabric and cushion fill, bedding (comforters, mattresses), protective clothes, moisture permeable heat retention films and sheets for agriculture/crop protection, carpet backing webs, packing material, wall paper fabrics, art paper-fabric, clothing including interlinings, construction insulation webs, coverstock, upholstery, food coverings, tea bags, personal care products such as diapers or adult incontinence products or feminine hygiene products or training pants, protective covers for vehicles or outdoor equipment, outdoor table covers, and other outdoor fabric covers such as tarpaulins or canopies or tents or agricultural fabrics.
The fabric or wipes may be cut into suitable shapes such as rectangles. The wiped may be treated (e.g., coated, impregnated, moistened) with additives such as surfactants, biocides, cleaners, disinfectants, cosmetics, medicaments, or any other additive to provide end use functionality.
In one embodiment or in combination with any of the mentioned embodiments, a nonwoven web can now be thermally bonded at temperatures that are below the native Tg of CE fibers contained in the nonwoven web. The thermal bonding can also be accomplished without the adding adhesives or binder onto the nonwoven web, or without applying solvents to the binder fibers. By accomplishing thermal bonding at a temperature below the native Tg of the CE fibers in the nonwoven web, the window for processing a wider range of web basis weights and energy savings can be realized. The thermal bonding can be at a temperature which is at least 2° C., or at least 3° C., or at least 5° C., or at least 8° C., or at least 10° C., or at least 12° C., or at least 15° C., or at least 18° C., or at least 20° C., or at least 22° C., or at least 24° C., or at least 26° C., or at least 28° C., or at least 30° C., or at least 31° C., or at least 32° C., or at least 35° C. below the native Tg of the CE fibers. The native Tg of the CE fibers is as defined above.
The benefit of improved energy savings, or higher line speeds, or dispensing with cost adding solvents or adhesives, or having to engage hydroentagling methods or other methods described above, is not at the cost of sacrificing the tensile strength of the resulting fabrics. To the contrary, the tensile strength of the fabric is greater than the increase in tensile strength obtainable by use of water alone, or by plasticize alone, or by the combined increase of water and plasticizer. The increase in tensile strength over the increase in tensile strength obtained by water alone or by plasticizer alone (whichever is higher) is at least 25%, or at least 50%, or at least 75%, or at least 100%, or at least 125%, or at least 150%, or at least 175%, or at least 200%, or at least 225%, or at least 250%, or at least 275%, or at least 300%. The increase in tensile strength over the increase in additive tensile strength of the individual components is at least 25%, or at least 50%, or at least 75%, or at least 100%, or at least 125%. In each of these cases, the increase is based on break force in the machine direction under test method Nonwovens Standard Procedure NWSP 110.4.R0 (15) Breaking Force and Elongation of Nonwoven Materials, Option A, using 25+/−1 mm tensile strip, constant-rate-of-extension (CRE) tensile testing instrument, extension rate of 300 mm/min, gage length set to 75 mm.
The benefit of improved energy savings, or higher line speeds, or dispensing with cost adding solvents or adhesives, or having to engage hydroentagling methods or other methods described above, is not at the cost of sacrificing the toughness of the resulting fabrics. To the contrary, the toughness of the fabric is greater than the increase in toughness obtainable by use of water alone, or by plasticizer alone, or by the combined increase of water and plasticizer. The increase in toughness over the increase in toughness obtained by water alone or by plasticizer alone (whichever is higher) is at least 25%, or at least 50%, or at least 75%, or at least 100%, or at least 125%, or at least 150%, or at least 175%, or at least 200%, or at least 225%, or at least 250%, or at least 275%, or at least 300%. The increase in toughness over the increase in toughness of the individual components is at least 25%, or at least 50%, or at least 75%, or at least 100%, or at least 125%. In each of these cases, the increase is based on toughness in the machine direction determined by calculating the area under the curve created by plotting the tensile force as a function of elongation from the elongation to the elongation point at which the fabric ruptures, where such measurements are taken under test method Nonwovens Standard Procedure NWSP 110.4.R0 (15) Breaking Force and Elongation of Nonwoven Materials, Option A, using 25+/−1 mm tensile strip, constant-rate-of-extension (CRE) tensile testing instrument, extension rate of 300 mm/min, gage length set to 75 mm.
In one embodiment or in combination with any mentioned embodiments, there is provided a thermally bonded fabric comprising cellulose ester fibers, said fabric possessing the property of either:

- a. a machine direction tensile strength break force and a basis weight, wherein the ratio of the machine direction tensile strength break force in grams to the basis weight of the fabric, or the nonwoven web(s) used to make the fabric, in grams per square meter is at least 20 g/gsm, or
- b. a machine direction toughness and a basis weight, wherein the ratio of the machine direction toughness in grams and the basis weight of the fabric, or the nonwoven web used to make the fabric, in grams per square meter, is at least 100 g/gsm.

In one embodiment or in combination with any of the mentioned embodiments, there is now provided a fabric containing cellulose ester fibers, and the fabric has a tensile break force of at least 1400 grams, or least 1500 grams, or least 1600 grams, or least 1700 grams, or least 1800 grams, or least 1900 grams, or least 2000 grams, or least 2100 grams, or least 2200 grams, or least 2300 grams, or least 2400 grams, or least 2500 grams, or least 2600 grams, or least 2700 grams, or at least 2800 grams, or at least 2900 grams, or at least 3000 grams.
In one embodiment or in combination with any of the mentioned embodiments, there is now provided a fabric containing cellulose ester fibers, and the fabric has a toughness of at least 6000 grams, or least 7000 grams, or least 8000 grams, or least 9000 grams, or least 10000 grams, or least 11000 grams, or least 12000 grams, or least 13000 grams, or least 14000 grams, or least 15000 grams, or least 16000 grams, or least 17000 grams.
There is also now provided a fabric that has a high tensile strength relative to the basis weight of the nonwoven web. In one embodiment or in combination with any of the mentioned embodiments, the fabric containing cellulose ester fibers can have a machine direction tensile break force in grams per basis weight in gsm of the (i) fabric, or the (ii) nonwoven web (prior to application of water and plasticizer or any other compositions between making the web and feeding to the first element effective to thermally bond the web), in each case of at least 20 g/gsm, or at least 25 g/gsm, or at least 30 g/gsm, or at least 35 g/gsm, or at least 40 g/gsm, or at least 45 g/gsm, or at least 50 g/gsm, or at least 55 g/gsm, or at least 60 g/gsm.
There is also now provided a fabric that has a high toughness relative to the basis weight of the nonwoven web. In one embodiment or in combination with any of the mentioned embodiments, the fabric containing cellulose ester fibers can have a machine direction toughness in grams per basis weight in gsm of the (i) fabric or (ii) the nonwoven web (prior to application of water and plasticizer or any other compositions between making the web and feeding to the first element effective to thermally bond the web), in each case of at least 100 g/gsm, or at least 125 g/gsm, or at least 150 g/gsm, or at least 175 g/gsm, or at least 200 g/gsm, or at least 225 g/gsm, or at least 250 g/gsm, or at least 275 g/gsm, or at least 300 g/gsm.

EXAMPLES

Experimental Procedure for Examples

A nonwoven fabric is made by carding a 50% cellulose acetate/50% viscose rayon fiber mix into a nonwoven web and lightly needle-tacking the web to allow handling. The untreated or treated nonwoven web, as described in the examples below, is then fed through the nip of a pair of heated steel rolls where one roll is smooth, and the second roll is engraved to create an array of point bond projections on its surface. This set of rolls selectively fuse the fibers to produce the thermal emboss pattern in the web shown in FIG. 7. The cellulose acetate fibers are Vestera™ 1.8R1738-A cellulose acetate fibers available from Eastman Chemical of Kingsport Tenn., having a cut length of 38 mm, and a dpf of 1.8. The rayon fibers were Tairiyon 1.5 dpf×40 mm available form Formosa Chemicals and Fibre. The surface temperature for the emboss rolls is measured at 190° C. by an IR method, which is at the native T_gof the cellulose acetate fibers. This procedure is applied to all examples.

Example 1

Variant #1 “Dry”: The fibers and nonwoven web made from the fibers are not modified prior to being fed into the thermal embossing rolls

Example 2

Variant #2 “Triacetin Pre-Treated”: Prior to formation into a nonwoven web, the cellulose acetate fibers are topically treated with an 5% aqueous solution of Triacetin and then dried. The amount of triacetin added to the cellulose acetate fibers is 9 wt. %, based on the weight of the cellulose acetate fibers. (Separate laboratory analysis has shown that the addition of 10 wt. % triacetin to this grade of cellulose acetate fiber reduces the T_gfrom 190° C. to about 162° C.) When the treated cellulose acetate fibers are later blended with an equal amount of the rayon fibers, the aggregate concentration of triacetin is 4.5 wt. %, based on the weight of the nonwoven web. The carded nonwoven web is needle tacked and fed dry into the set of thermal emboss rolls without further modification.

Example 3

Variant #3 “Water Only Spray”: A web identical to the Variant #1 material is sprayed with water at an amount of 1-gram water/1-gram web. The web is then passed through the thermal emboss rolls exactly five minutes after completion of spraying. The five-minute wait time was designed to approximately simulate the application of water to the fiber blend at the fiber opening step of the fabric production process; the web was still damp when fed to the bonding rolls.

Example 4

Variant #4 “Triacetin Solution Spray”: The nonwoven web identical to the Variant #1 material is sprayed with an 5% aqueous solution of Triacetin at an amount of 1-gram solution/1-gram web. The triacetin concentration and solution topical add-on yields a triacetin concentration 0.05 gr (triacetin)/1-gram web or a 5% concentration of triacetin based on the weight of the nonwoven web. The still wet web was then passed through the thermal emboss rolls exactly 5 minutes after completion of spraying.

Experimental Results

Below in Table 2 is a summary of the strip tensile test results for the four material variants described above. The materials are cut into machine direction (MD) oriented strips of 1-inch×8 inches and tested according to method # NWSP 110.4 with 7 or 8 strips tested per variant. The gage length is 75 mm and the tensile test rate is 300 mm/minute.

TABLE 2

	MD			Bonded
	Break	MD Break	MD	Basis
Fiber/Web Pre-	Force	Elongation	Toughness	Weight
Bonding Treatment	(gr)	(%)	(gr)	(gsm)

V#1 Dry	108	33.91*	1771.18*	67.3
V#2 Dry + 4.5%	1,091	5.5	3,476	62.6
Triacetin
V#
3 1 gr/gr H2O	719	16.7	5,096	59.3
V#4 1 gr/gr of 5%	3,868	8.6	18,386	57.6
Triacetin Solution

*These values for the bonded dry web (V#1) are likely elevated relative to the other bonded webs due to V#1 having no clear web rupture point during the test.

The Table 2 data is presented in column format in FIGS. 4, 5, and 6.
As shown in FIG. 4 and Table 2, Variant #1 or the untreated, dry sample had by far the lowest tensile strength indicating little or no thermal bonding as measured by the recorded level of break force and toughness. The indicated tensile strength of Variant 1 is largely a product of the post carding needletacking that allowed transfer and hand feeding of the nonwoven web into the lab scale thermal embossing rolls. The toughness values for Variant #1 as shown in FIG. 6 is possibly overstated given the way the test responded to the break elongation of the bonded fabric as shown in FIG. 5.
The addition of triacetin (Variant #2) and of water (Variant #3) by themselves result in a significant increase in both break force and toughness as shown in FIGS. 4 and 6 and Table 2. The triacetin has the greater increase for break elongation force while water has the greater increase in toughness. These differing tensile test performances suggests that water and triacetin impact the thermoplastic behavior of cellulose acetate by different mechanisms.
The increase in tensile strength break force and toughness in Variant 4 are much higher than the increase in tensile strength and toughness obtained by Variant 3 water alone, or by Variant 2 plasticizer alone. The increase in tensile strength in Variant 4 is 254% greater than Variant 3 (the higher of Variant 2 and 3), and the increase in toughness in Variant 4 is 260% greater than Variant 3 (the higher of Variant 2 and 3).
Another significant unexpected result is that the simultaneous combination of water and triacetin in Variant 4 to make a wetted plasticized nonwoven web fed to the thermal rolls results in a dramatic increase in both break strength and toughness above the additive impacts on fabric strength of triacetin (Variant #2) and water (Variant #3) applied independently. For example, when one adds the increase in tensile break strength obtained by water individually and plasticizer individually, the increase obtained by Variant 4 over the additive effects is about 100% in tensile break strength in the machine direction and 114% over the additive effects of the individual elements in toughness.

Claims

What we claim is:

1. A process for making a fabric comprising:

a. providing a nonwoven web comprising cellulose ester fibers, and

b. thermally bonding said nonwoven web at a thermal bonding temperature to make a fabric,

(i) adding adhesives or binder onto said nonwoven web; and

(ii) using solvents for the binder fibers.

2. The process of claim 1, comprising a nonwoven web obtained from dry laid or spun bond fibers.

3. The process of claim 1, comprising a nonwoven web comprising base fibers and binder fibers, said binder fibers comprising monocomponent fibers comprising cellulose ester fibers, wherein at least 90 wt. % of the cellulose ester fibers are solvent spun monocomponent fibers, based on the weight of the fibers containing cellulose ester polymer.

4. The process of claim 1, comprising a nonwoven web that does not contain any binder powder, binder particles, or binder films or sheets.

5. The process of claim 1, comprising a nonwoven web comprising cellulose ester fibers that are not coated or otherwise do not contain a dry plasticizer or are coated or otherwise contain a dry plasticizer in an amount of not more than 2 wt. % FOY.

6. The process of claim 1, comprising a nonwoven web comprising binder fibers, said binder fibers comprising CE fibers having one or more of the following features:

a) a crimp frequency of 7 to 30 CP, or 7 to 25 CPI, or 7 to 23 CPI, or 7 to 20 CPI, or 8 to 30 CPI, or 8 to 27 CPI, or 8 to 25 CPI, or 8 to 23 CPI, or 8 to 20 CPI crimps per inch, or

b) a crimp amplitude of at least 1.0 mm, or

c) an average effective length that is not more than 75% of the actual length, or

d) a retained tenacity of at least 80%, or

e) a CPI:DPF of 5:1 to 14:1, or 7:1 to 12:1, or

f) any combination of two or more of the above.

7. A process for making a fabric comprising:

a. providing a nonwoven web comprised of base fibers and binder fibers, and

b. applying either (i) water or (ii) water and a plasticizer to the nonwoven web to produce a wetted plasticized nonwoven web, provided that water and a plasticizer are applied to the nonwoven web if the binder fibers do not contain a plasticizer; and

c. thermally bonding the wetted plasticized nonwoven web to produce said fabric.

8. The process of claim 7, comprising applying water and a plasticizer to the nonwoven web before thermal bonding, optionally as a solution.

9. The process of claim 7, comprising applying water and a plasticizer to the nonwoven web in a spray or by a coating method comprising a squeeze, lick, or kiss roll coating method.

10. The process of claim 7, comprising thermally bonding a water wetted plasticized nonwoven web obtained from a nonwoven web comprising CE fibers coated with or containing a dry plasticizer, wherein water is applied to said web to create a wetted plasticized nonwoven web.

11. The process of claim 7, comprising thermally bonding a water wetted plasticized nonwoven web obtained from a nonwoven web, wherein an aqueous solution of plasticizer is continuously applied before, during, or after hydroentangling the nonwoven web.

12. The process of claim 7, comprising applying water to the nonwoven web before thermal bonding to produce a wetted plasticized nonwoven web having a moisture content, or a moisture content as introduced to an element for thermal bonding, of at least 10 wt. %, based on the weight of the wetted plasticized nonwoven web.

13. The process of claim 7, comprising thermally bonding a wetted plasticized nonwoven web, said nonwoven web not being solvent fused, hydroentangled, or stitched.

14. The process of claim 7, comprising thermally bonding a wetted plasticized nonwoven web, said thermal bonding process comprising point bonding.

15. The process of claim 7, comprising thermally bonding, at a line speed and nip force, a wetted plasticized nonwoven web obtained from a nonwoven web, said thermal bonding process comprising one or more calendar rolls, and the upper temperature limit of at least one calendar roll, or on all calendar rolls, is below the native melting point temperature of CE fibers in the nonwoven web, or in the wetted plasticized nonwoven web at the line speed and nip forces applied.

16. The process of claim 7, comprising thermally bonding a wetted plasticized nonwoven web obtained from a nonwoven web comprising CE fibers, said thermal bonding process comprising one or more calendar rolls, and the temperature of at least one calendar roll, or the first calendar roll effective to thermally bond the wetted plasticized nonwoven web, or on the majority of calendar rolls, or on all calendar rolls, (i) is below the temperature at which the CE fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web, would reach their native Tg at the line speed and nip forces applied, or (ii) are below the native Tg of the CE fibers in the nonwoven web, or alternatively in the wetted plasticized nonwoven web, by at least 5° C., or at least 8° C., or at least 10° C., or at least 12° C., or at least 15° C., or at least 18° C., or at least 20° C., or at least 22° C., or at least 24° C., or at least 26° C., or at least 28° C., or at least 30° C., and in each case, the calendar roll at said temperature also exceeds the Tg of the CE fibers in their plasticized state.

17. A fabric comprising cellulose ester fibers, said fabric having a basis weight of not more than 35 gsm and destructive thermally fused bonds, wherein the fabric is obtained by thermally bonding a nonwoven web in the absence of adhesives, hydroentaglement, solvents for fusion, or thermoplastic binder powders.

18. The fabric of claim 17, comprising thermally bonding a wetted plasticized nonwoven web obtained from a nonwoven web, said thermal bonding process comprising point bonding to produce a fabric having at least 10 points per square inch.

19. The fabric of claim 17, wherein at least 80% of the bonds are destructive bonds, and said wetted plasticized nonwoven web is not hydroentangled and does not contain binder powders, and the fabric does not contain adhesives and is not laminated with a thermoplastic film.

20. The fabric of claim 17, wherein the ratio of the cumulative surface area of unbonded portions to the cumulative surface area of bonded portions is at least 2:1, and the thickness of unbonded portions are greater than the thickness of the bonded portions.

21. The fabric of claim 17, wherein said fabric is ultrasonic welded.

22. The fabric of claim 17, wherein said fabric comprises wipes, filters, non-medical garments such as shirts or pants or jackets or socks or undergarments, geotextiles, roofing felts, insoles, paper maker felts, fiberfill webs, needle felt including floor coverings, furniture fill and fabric, sanitary products, medical products such as wound dressings or bandages or sterilization wraps or medical bedding, medical garments such as surgical caps and hoods or face masks or drapes or surgical gowns or caps, automobile interior fabric and cushion fill, bedding (comforters, mattresses), protective clothes, moisture permeable heat retention films and sheets for agriculture/crop protection, carpet backing webs, packing material, wall paper fabrics, art paper-fabric, clothing including interlinings, construction insulation webs, coverstock, upholstery, food coverings, tea bags, personal care products such as diapers or adult incontinence products or feminine hygiene products or training pants, protective covers for vehicles or outdoor equipment, outdoor table covers, or other outdoor fabric covers such as tarpaulins or canopies or tents or agricultural fabrics.

23. The fabric of claim 17, said fabric having:

a. a break force tensile strength greater than the combined increase in tensile strength obtainable by the individual use of water and plasticizer, as measured by NWSP 110.4.R0 (15) using 25+/−1 mm tensile strip, constant-rate-of-extension (CRE) tensile testing instrument, extension rate of 300 mm/min, and gage length set to 75 mm, or

b. a toughness greater than the combined increase in toughness obtainable by the individual use of water and plasticizer, calculated from break force and elongation measurements taken under NWSP 110.4.R0 (15) using 25+/−1 mm tensile strip, constant-rate-of-extension (CRE) tensile testing instrument, extension rate of 300 mm/min, and gage length set to 75 mm.

24. The fabric of claim 17, said fabric having:

a. a ratio of machine direction tensile break force in grams to basis weight of the fabric or nonwoven web used to make the fabric in gsm, of at least 40 g/gsm, or

b. a ratio of toughness to basis weight of the fabric or nonwoven web used to make the fabric in gsm, of at least 100 g/gsm, or at least 175 g/gsm.