HK1108010A - Polymeric structures comprising an hydroxyl polymer and processes for making same - Google Patents

Description

Polymeric structures comprising hydroxyl polymers and methods of making the same

Technical Field

The present invention relates to hydroxyl polymers. More particularly, the present invention relates to polymeric structures (particularly fibers) comprising an association agent, fibrous structures comprising such polymeric structures, and processes for making such polymeric structures and/or fibrous structures.

Background

Polymeric structures such as fibers and/or films comprising hydroxyl polymers are known in the art. However, until now, it has been difficult to obtain polymeric structures comprising an association agent, in particular in the form of fibers, in which the polymeric structure exhibits an apparent peak wet tensile stress greater than 0.2MPa and/or an average fiber diameter of less than 10 μm.

Thus, there remains a need for polymeric structures comprising an association agent, webs comprising such polymeric structures, and processes for making such polymeric structures, wherein the polymeric structures exhibit an apparent peak wet tensile stress greater than 0.2MPa and/or an average fiber diameter less than 10 μm.

Summary of The Invention

The present invention meets the above-described needs by providing polymeric structures comprising an association agent and/or webs comprising such polymeric structures, and processes for making such polymeric structures and/or webs.

In one example of the present invention, a non-naturally occurring polymeric structure is provided in the form of a fiber, wherein the fiber comprises a hydroxyl polymer and an associative agent.

In another example of the present invention, a non-naturally occurring polymeric structure comprising an association agent is provided, wherein the polymeric structure exhibits an apparent peak wet tensile stress greater than 0.2 MPa.

In another example of the present invention, a fiber comprising an association agent is provided, wherein the fiber exhibits an average fiber diameter of less than 10 μm.

In another example of the present invention, a web comprising a polymeric structure according to the present invention is provided.

In another example of the present invention, a fibrous structure comprising one or more non-naturally occurring fibers comprising a hydroxyl polymer and an association agent is provided.

In another example of the present invention, a method for manufacturing a polymeric structure comprising an association agent is provided, wherein the method comprises the step of processing a polymer of a composition comprising a hydroxyl-containing polymer of an association agent into a polymeric structure comprising an association agent.

In another example of the present invention, a method for making a polymeric structure comprising an association agent is provided, wherein the method comprises the steps of:

a. providing a hydroxyl polymer-containing composition comprising a hydroxyl polymer and an association agent; and

b. the polymer of the hydroxyl polymer-containing composition is processed into a polymeric structure comprising a hydroxyl polymer and an associative agent.

Accordingly, the present invention provides polymeric structures comprising an association agent, fibrous webs comprising such polymeric structures, and methods for making such polymeric structures and/or fibrous webs.

Brief description of the drawings

FIG. 1A is a schematic side view of a twin screw extruder barrel suitable for use in the present invention.

FIG. 1B is a schematic side view of a screw and mixing element configuration suitable for use with the barrel of FIG. 1A.

Fig. 2 is a schematic side view of a method for synthesizing a polymeric structure according to the present invention.

Fig. 3 is a schematic partial side view of the method of the present invention showing an attenuation zone.

FIG. 4 is a schematic plan view taken along line 4-4 in FIG. 3 showing one possible arrangement of a plurality of extrusion nozzles arranged to provide polymeric structures of the present invention.

Fig. 5 is a view similar to that of fig. 4 showing one possible arrangement of orifices providing boundary air around the attenuation region.

FIG. 6 is a schematic plan view of a coupon that can be used to determine the apparent peak wet tensile stress of a fiber according to the present invention.

Detailed Description

Definition of

The term "polymeric structure" as used herein refers to any physical structure formed by processing the polymer melt composition according to the present invention. Non-limiting examples of polymeric structures according to the present invention include fibers, films, and/or foams. The polymeric structures of the present invention are non-naturally occurring physical structures. In other words, they are man-made physical structures.

The term "fiber" or "filament" as used herein refers to an elongated, thin, highly flexible object having a long axis. The long axis is very long compared to two mutually orthogonal axes of the fiber perpendicular to said long axis. The fibers can exhibit an aspect ratio of a length of the major axis to an equivalent diameter of a fiber cross-section perpendicular to the major axis of greater than 100/1, more specifically greater than 500/1, and still more specifically greater than 1000/1, and even more specifically greater than 5000/1. The fibers may be continuous or substantially continuous fibers, they may also be staple fibers.

The hydroxyl polymer fibers of the present invention can have an average fiber diameter of less than about 50 μm and/or less than about 20 μm and/or less than about 10 μm and/or less than about 8 μm and/or less than about 6 μm and/or less than about 4 μm, when measured according to the average fiber diameter test method described herein. Such fibers may exhibit an average fiber diameter greater than about 1 μm and/or greater than about 2 μm and/or greater than about 3 μm.

The hydroxyl polymer fibers of the present invention can include meltblown fibers, dry spun fibers, spunbond fibers, staple fibers, hollow fibers, shaped fibers such as multilobal fibers and multicomponent fibers, especially bicomponent fibers. The multicomponent fibers, particularly bicomponent fibers, can be in a side-by-side, sheath-core, segmented pie, ribbon, islands-in-the-sea configuration, or any combination thereof. The sheath may be continuous or discontinuous around the core. The weight ratio of the sheath to the core may be from about 5: 95 to about 95: 5. The hydroxyl polymer fibers of the present invention can have different geometries including round, oval, star, rectangular, and a variety of other eccentric shapes.

In another example, the polymeric structures of the present invention can include multicomponent polymeric structures, such as multicomponent fibers, that comprise the hydroxyl polymer and the associative agent of the present invention and another polymer. As used herein, multicomponent fibers are fibers that have more than one discrete portion in a spatial relationship. Multicomponent fibers include bicomponent fibers, which are defined as fibers having two separate portions in a spatial relationship. The different components of a multicomponent fiber can be arranged in distinct zones across the cross-section of the fiber and extend continuously along the length of the fiber.

A non-limiting example of such a multicomponent fiber, in particular a bicomponent fiber, is a bicomponent fiber in which the hydroxyl polymer of the present invention is used as the core of the fiber and the other polymer is used as a sheath that surrounds or substantially surrounds the core of the fiber. Such polymeric structures derived from the polymer melt composition may include both the polymer melt composition and another polymer.

In another multicomponent, especially bicomponent fiber, embodiment, the sheath can comprise a hydroxyl polymer and a crosslinking system comprising a crosslinking agent, and the core can comprise a hydroxyl polymer and a crosslinking system comprising a crosslinking agent. The hydroxyl polymer may be the same or different and the crosslinking agent may be the same or different for the sheath and core. Further, the content of the hydroxyl polymer may be the same or different, and the content of the crosslinking agent may be the same or different.

If the polymeric structure is in the form of fibers, one or more of the polymeric structures of the present invention may be incorporated into a multi-polymeric structure product, such as a fibrous structure and/or a fibrous web. Such multi-polymeric structure products may ultimately be incorporated into commercial products such as single-or multi-ply sanitary tissue products, including, for example, facial tissues, bath tissues, paper towels and/or wipes, feminine care products, diapers, writing papers, core papers such as core paper towels, and other types of paper products.

The term "fibrous structure" as used herein refers to a unitary fibrous web structure comprising at least one fiber. For example, the fibrous structure of the present invention can comprise one or more fibers, wherein at least one fiber comprises a hydroxyl polymer fiber. In another example, the fibrous structure of the present invention can comprise a plurality of fibers, wherein at least one (and sometimes most, or even all) of the fibers comprise hydroxyl polymer fibers. The fibrous structures of the present invention may be layered such that one layer of the fibrous structure may comprise fibers and/or materials of a different composition than another layer of the same fibrous structure. The term "web" as used herein refers to a physical structure comprising at least one planar surface. In another example, a web is a physical structure that includes two flat surfaces. The web may be a film if no fibers are present in the web. The web comprising one or more fibers may be a fibrous structure.

One or more of the hydroxyl polymer fibers of the present invention can be associated together to form a web. Typically, to associate the fibers into a web, a plurality of fibers are concentrated on a forming wire and/or belt and/or a three-dimensional molding member.

In one embodiment of the present invention, the webs and/or fibrous structures of the present invention exhibit an initial total wet tensile of greater than about 3.94g/cm (10g/2.54cm (10 g/in)).

The term "hydroxyl polymer" as used herein refers to any polymer comprising greater than 10% and/or greater than 20% and/or greater than 25% by weight of hydroxyl groups.

As used herein, the term "polymer melt composition" refers to a composition comprising a polymer melt (substituted or unsubstituted).

As used herein, the terms "unsubstituted hydroxyl polymer" and/or "unsubstituted substituted hydroxyl polymer" refer to a hydroxyl polymer in which all of the original hydroxyl moieties are intact. In other words, no derivatized hydroxyl moieties are present in the hydroxyl polymer. For example, hydroxyethyl starch is not an unsubstituted hydroxyl polymer. Removal of hydrogen only from the oxygen in the hydroxyl moiety does not produce a substituted hydroxyl polymer.

The terms "substituted hydroxyl polymer" and/or "substituted version of a hydroxyl polymer" and/or "substituted version of an unsubstituted hydroxyl polymer" as used herein refer to a hydroxyl polymer that comprises a derivative of at least one original hydroxyl moiety. In other words, at least one oxygen originally present in a hydroxyl moiety is covalently bonded to a moiety other than hydrogen.

The term "associative agent" as used herein refers to a formulation that is capable of interacting with the hydroxyl polymer without being covalently bonded to the hydroxyl polymer to affect the properties of the hydroxyl polymer-containing composition, particularly the spinning (rheological) properties of the hydroxyl polymer-containing composition.

The term "non-naturally occurring" as used herein with respect to "non-naturally occurring fibers" means that the fibers in that form do not occur in nature. In other words, in order to obtain non-naturally occurring fibers, some chemical treatment of the raw material is required. For example, wood pulp fibers are naturally occurring fibers, however if the wood pulp fibers are chemically treated by, for example, a lyocell-type process, a solution of cellulose is formed. The solution of cellulose may then be spun into fibers. Thus, since such spun fiber is not directly available from nature in its current form, it would be considered a non-naturally occurring fiber.

The term "naturally occurring" as used herein means that the fiber and/or material is present in its present form in nature. An example of a naturally occurring fiber is wood pulp fiber.

"apparent peak wet tensile stress" or simply "wet tensile stress" is the condition at which the maximum (i.e., "peak") strain point exists within a polymeric structure (such as a fiber) as a result of strain generated by an external force, and more particularly an elongation force, as described in the apparent peak wet tensile stress test method described below. The stress is "apparent" in that no consideration is given to the change, if any, in the average thickness of the polymeric structure (e.g., the average fiber diameter of the fibers) resulting from the elongation of the polymeric structure in order to determine the apparent peak wet tensile stress of the polymeric structure. The apparent peak wet tensile stress of polymeric structures is proportional to their wet tensile strength, and the former is therefore used herein to quantitatively estimate the latter.

The term "weight average molecular weight" as used herein refers to the weight average molecular weight as determined by gel permeation chromatography according to the protocol presented in Colloids and Surfaces a. physico chemical & Engineering industries, volume 162, year 2000, pages 107 to 121.

The term "polymer" as used herein generally includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and syndiotactic copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" includes all possible geometric configurations of the material. Such configurations include, but are not limited to isotactic, atactic, syndiotactic and random symmetries.

The term "spinning process temperature" as used herein refers to the temperature at which the fibrous hydroxypolymer structure is drawn down on the outer surface of the spinning die as it is formed.

Fiber

The hydroxyl polymer fibers of the present invention can be polymeric structures. In other words, one or more polymers may form the fibers.

The hydroxyl polymer fibers of the present invention can be continuous or substantially continuous. In one example, a fiber is continuous if it exhibits a length greater than about 2.54cm (1 inch) and/or greater than 5.08cm (2 inches).

The hydroxyl polymer fibers of the present invention can be produced by crosslinking two or more hydroxyl polymers together. Non-limiting examples of suitable crosslinking systems for effecting crosslinking of the hydroxyl polymer, wherein the hydroxyl polymer is crosslinked by a crosslinking agent, comprise a crosslinking agent and optionally a crosslinking facilitator. Examples of suitable crosslinking systems that can be used in the present invention are described in U.S. patent application publication 2004/0249066.

In one example, the hydroxyl polymer fibers of the present invention generally exhibit no melting point. In other words, it degrades before melting.

In addition to the hydroxyl polymer fibers of the present invention, other fibers may be included in the webs of the present invention. For example, the web may include pulp fibers such as cellulose fibers and/or other polymer fibers in addition to hydroxyl polymer fibers.

In one embodiment of the invention, the hydroxyl polymer fibers of the invention exhibit an apparent peak wet tensile stress greater than 0.2MPa and/or greater than 0.5MPa and/or greater than 1 MPa.

In another example of the present invention, the hydroxyl polymer fibers of the present invention comprise at least about 50% and/or at least about 60% and/or at least about 70% to about 100% and/or to about 95% and/or to about 90% hydroxyl polymer by weight of the fiber.

In another example of the present invention, the hydroxyl polymer fibers of the present invention exhibit a pH of less than about 7 and/or less than about 6 and/or less than about 5 and/or less than about 4.5 and/or less than about 4.

In another embodiment of the present invention, the hydroxyl polymer fibers of the present invention comprise an associative agent. The associative agent can be separated and disassociated from the hydroxyl polymer. In other words, the associative agent may not be covalently bonded to the oxygen atoms of the hydroxyl moieties of the hydroxyl polymer.

Hydroxyl polymer

Hydroxyl polymers according to the present invention include any unsubstituted hydroxyl-containing polymer (e.g., native dent corn starch hydroxyl polymer and/or acid-thinned dent corn starch hydroxyl polymer) and/or any substituted hydroxyl-containing polymer (e.g., hydroxyethyl starch hydroxyl polymer).

In one example, the hydroxyl polymer of the present invention comprises greater than 10% and/or greater than 20% and/or greater than 25% by weight of hydroxyl moieties.

Non-limiting examples of hydroxyl polymers according to the present invention include polyols such as polyvinyl alcohol, polyvinyl alcohol derivatives, polyvinyl alcohol copolymers, starch derivatives, starch copolymers, chitosan derivatives, chitosan copolymers, cellulose derivatives such as cellulose ether and cellulose ester derivatives, cellulose copolymers, gums, arabinans, galactans, proteins and various other polysaccharides, and mixtures thereof.

The type of hydroxyl polymer is defined by the hydroxyl polymer backbone. For example, polyvinyl alcohol and polyvinyl alcohol derivatives and polyvinyl alcohol copolymers belong to the class of polyvinyl alcohol hydroxyl polymers, while starch and starch derivatives belong to the class of starch hydroxyl polymers.

The hydroxyl polymer of the present invention may have a weight average molecular weight of greater than about 10,000g/mol and/or greater than about 40,000g/mol and/or from about 10,000 to about 80,000,000g/mol and/or from about 10,000 to about 40,000,000g/mol and/or from about 10,000 to about 10,000,000 g/mol. Higher and lower molecular weight hydroxyl polymers can be used in combination with hydroxyl polymers having weight average molecular weights within the ranges described above.

Well known modifications of hydroxyl polymers such as polysaccharides, e.g. native starch, include chemical and/or enzymatic modifications. For example, native starch may be acid thinned, hydroxyethylated, hydroxypropylated and/or oxidized. In addition, the hydroxyl polymer may comprise a native dent corn starch hydroxyl polymer.

In one example, the hydroxyl polymer of the present invention comprises a starch hydroxyl polymer. The starch hydroxypolymer may be an acid-thinned starch hydroxypolymer and/or an alkali-cooked starch hydroxypolymer. The starch hydroxypolymer may be derived from corn, potato, wheat, tapioca, and the like. The weight ratio of amylose to amylopectin in the starch hydroxypolymer may be about 10: 90 to about 99: 1, respectively. In one example, the starch hydroxyl polymer comprises at least about 10% and/or at least about 20% to about 99% and/or to about 90% by weight amylose.

The term "polysaccharide" as used herein refers to natural polysaccharides and polysaccharide derivatives or modified polysaccharides. Suitable polysaccharides include, but are not limited to, starch derivatives, chitosan derivatives, cellulose derivatives, gums, arabinans, galactans, and mixtures thereof.

Non-limiting examples of polyvinyl alcohols suitable for use as hydroxyl polymers (alone or in combination) in the present invention can be described by the general formula:

structure I

Each R is selected from C₁-C₄Alkyl radical, C₁-C₄An acyl group; and x/x + y + z is 0.5 to 1.0. In one example, the polyvinyl alcohol has no "y" and/or "z" units.

The polyvinyl alcohol herein may be grafted with other monomers to alter its properties. A number of monomers have been successfully grafted onto polyvinyl alcohol. Non-limiting examples of such monomers include vinyl acetate, styrene, acrylamide, acrylic acid, 2-hydroxyethyl methacrylate, acrylonitrile, 1, 3-butadiene, methyl methacrylate, methacrylic acid, 1-dichloroethylene, vinyl chloride, vinylamine, and various acrylates.

Associative agent

The polymer melt composition of the present invention may comprise a crosslinking agent. The associative agent is capable of associating with the hydroxyl polymers, particularly their hydroxyl moieties, typically other than by covalent bonding.

In one example, the association agent is a cationic agent. The cationic agent may be selected from the group consisting of: quaternary ammonium compounds, tetraalkylamines, tetraarylamines, imidazoline quaternary ammonium salts, polyethoxylated tetraalkylamines, and mixtures thereof.

Non-limiting examples of suitable associative agents include quaternary ammonium compounds, amine oxides, and amines.

Non-limiting examples of quaternary ammonium compounds include dodecyltrimethylammonium chloride, stearyltrimethylammonium chloride, stearyldimethylbenzylammonium chloride, didodecyldimethylammonium chloride, tetraethylammonium chloride, polyethoxylated quaternary ammonium chlorides such as Ethoquad C/12 from Akzo Nobel chemicals inc. Suitable quaternary ammonium compounds are sold under the trade name Arquad 12-50 by Akzo Nobel Chemicals Inc.

Non-limiting examples of amine oxides include cetyl dimethylamine oxide, lauryl dimethylamine oxide, cocamidopropyl amine oxide. Suitable amine oxides are sold under the trade name Ammonyl CO by Stepan company.

Non-limiting examples of amines (e.g., alkylamines) include ethoxylated dodecylamine, ethoxylated stearyl amine, and ethoxylated oleylamine. Suitable amines are sold under the trade name Ethomeen C/12 by Akzo Nobel Chemicals Inc.

The association agent may be present in the polymeric structure, such as the fibers, at a level of from greater than 0% to less than about 100%. In one example, the association agent is present in the polymeric structure at a level of greater than 0% and/or at least about 0.001% and/or at least about 0.01% and/or at least about 0.1% and/or at least about 1% to about 50% and/or to about 40% and/or to about 30% and/or to about 15% and/or to about 10% and/or to about 5% and/or to about 3%.

Hydroxyl polymer-containing composition

The hydroxyl polymer-containing composition of the present invention can comprise unsubstituted hydroxyl polymers and/or substituted hydroxyl polymers. The hydroxyl polymer-containing composition can be a blend and/or mixture of polymers, such as two or more different hydroxyl polymers, for example, an unsubstituted hydroxyl polymer (i.e., a native dent corn starch hydroxyl polymer) and a substituted hydroxyl polymer (i.e., a hydroxyethyl starch hydroxyl polymer). In another embodiment, the hydroxyl polymer-containing composition can comprise two or more different types of hydroxyl polymers, such as a starch hydroxyl polymer and a polyvinyl alcohol hydroxyl polymer.

Optional ingredients, such as fillers (inorganic and organic) and/or fibers and/or blowing agents, may also be included in the hydroxyl polymer-containing composition and/or fibrous structures made therefrom.

Compositions of hydroxyl-containing polymers may already be formed. In one example, to form a polymer melt composition, the hydroxyl polymer can be dissolved by contact with a liquid (e.g., water). For the purposes of the present invention, such liquids can be regarded as acting as external plasticizers. Alternatively, any other suitable method known to those skilled in the art for producing a polymer melt composition can be used such that the polymer melt composition exhibits suitable properties for processing the polymer melt composition into a polymeric structure according to the present invention.

When the polymeric structure is made from a polymer melt composition, the polymer melt composition may have and/or be exposed to a temperature of from about 23 ℃ to about 140 ℃ and/or from about 50 ℃ to about 130 ℃ and/or from about 65 ℃ to about 100 ℃ and/or from about 65 ℃ to about 95 ℃ and/or from about 70 ℃ to about 90 ℃. As described below, the polymer melt composition can have and/or be exposed to generally higher temperatures when making film and/or foam polymeric structures.

The pH of the polymer melt composition can be from about 2.5 to about 11 and/or from about 2.5 to about 10 and/or from about 3 to about 9.5 and/or from about 3 to about 8.5 and/or from about 3.2 to about 8 and/or from about 3.2 to about 7.5.

In another embodiment, the polymer melt composition of the present invention may comprise at least about 5% and/or at least about 15% and/or at least about 20% and/or 30% and/or 40% and/or 45% and/or 50% to about 75% and/or 80% and/or 85% and/or 90% and/or 95% and/or 99.5% of the polymer melt, by weight of the polymer melt composition.

The hydroxyl polymer, prior to crosslinking, can have a weight average molecular weight greater than about 10,000 g/mol.

The crosslinking system may be present in the polymer melt composition and/or may be added to the polymer melt composition prior to polymer processing of the polymer melt composition.

The hydroxyl polymer-containing composition can comprise: a) at least about 5% and/or at least about 15% and/or at least about 20% and/or 30% and/or 40% and/or 45% and/or 50% to about 75% and/or 80% and/or 85% of hydroxyl polymer, by weight of the hydroxyl polymer-containing composition; b) a crosslinking system comprising from about 0.1% to about 10%, by weight of the polymer melt composition, of a crosslinking agent; and c) from about 10% and/or 15% and/or 20% to about 50% and/or 55% and/or 60% and/or 70% by weight of the hydroxyl polymer-containing composition of an external plasticizer, such as water.

In addition to the crosslinking agent, the crosslinking system of the present invention may also comprise a crosslinking accelerator.

The term "crosslinking facilitator" as used herein refers to any substance capable of activating a crosslinking agent, thereby converting the crosslinking agent from its unactivated state to its activated state.

After crosslinking the hydroxyl polymer, the crosslinking agent becomes an integral part of the polymeric structure as a result of crosslinking the hydroxyl polymer, as shown in the following schematic:

hydroxyl polymer-crosslinker-hydroxyl polymer

The crosslinking facilitator may include derivatives of the material that may be present after conversion/activation of the crosslinking agent. For example, the crosslinking promoter salt is chemically converted to its acid salt and vice versa.

Non-limiting examples of suitable crosslinking promoters include acids having a pKa between 2 and 6, or their salts. The crosslinking accelerator may be a Bronsted acid and/or a salt thereof, preferably an ammonium salt thereof.

Furthermore, metal salts such as magnesium and zinc salts can be used as crosslinking promoters alone or in combination with Bronsted acids and/or their salts.

Non-limiting examples of suitable crosslinking promoters include acetic acid, benzoic acid, citric acid, formic acid, glycolic acid, lactic acid, maleic acid, phthalic acid, phosphoric acid, succinic acid, and mixtures thereof and/or salts thereof, preferably ammonium salts thereof, such as ammonium glycolate, ammonium citrate, ammonium sulfate, and ammonium chloride.

A. Synthesis of Polymer melt composition

A screw extruder, such as a vented twin screw extruder, can be used to prepare the polymer melt composition of the present invention.

The barrel 10 of an APV Baker (Peterborough, England) twin screw extruder is schematically illustrated in FIG. 1A. The cylinder 10 is divided into eight zones, labeled zones 1 through 8. A barrel 10 surrounds the extrusion screw and mixing elements, schematically shown in fig. 1B, and serves as a protective shell during extrusion. A solids feed port 12 is provided in zone 1 and a liquid feed port 14 is also provided in zone 1. Vents 16 are included in zone 7 for cooling and for reducing the level of liquid (e.g., water) in the mixture before it exits the extruder. Optional vent fillers commercially available from APV Baker can be used to prevent the hydroxyl polymer-containing composition from flowing out through vent 16. The flow of the polymer melt composition through cylinder 10 begins at zone 1 and exits cylinder 10 at zone 8.

The screw and mixing element configuration of the twin screw extruder is schematically illustrated in FIG. 1B. The twin screw extruder comprises a plurality of Twin Lead Screws (TLS) (designated a and B) and Single Lead Screws (SLS) (designated C and D) mounted in series. The screw elements (A-D) are characterized by the number of consecutive guide rods and the spacing of these guide rods.

The leadscrew is a helical flight (at a given helix angle) that wraps around the core of the screw element. The number of leaders indicates the number of flights wrapping the core at any given location along the length of the screw. Increasing the number of guide rods will reduce the volume of the screw and increase the pressure generating capacity of the screw.

The screw pitch is the distance required for the flight to completely wrap around the core. This spacing is expressed as the number of screw element diameters per full revolution of the flight. Decreasing the pitch of the screw increases the pressure generated by the screw and decreases the volume of the screw.

The length of the screw element is recorded as the ratio of the element length divided by the element diameter.

This example uses TLS and SLS. Screw element a is a TLS with 1.0 pitch and 1.5 length ratio. Screw element B is a TLS with a pitch of 1.0 and a 1.0L/D ratio. Screw element C is an SLS with 1/4 pitch and a 1.0 length ratio. Screw element D is an SLS with 1/4 pitch and 1/2 length ratio.

To enhance mixing, a Bilobal paddle E was also included as a mixing element in series with the SLS and TLS screw elements. To control the flow and the corresponding mixing time, bilobal paddles and reversing elements F of various configurations, single lead screws and double lead screws twisted in opposite directions were used.

In zone 1, the hydroxyl polymer was fed to the solids feed port at 230 grams/minute using a K-Tron (Pitman, NJ) weight loss feeder. This hydroxyl polymer was mixed in an extruder (zone 1) with water, external plasticizer, added at a rate of 2.43g/s (146 g/min) at the liquid inlet using a Milton Roy (Ivyland, Pa) diaphragm pump (0.002L/s (1.9 gallons per hour) pump head) to form a hydroxyl polymer/water slurry. The slurry is then conveyed toward the lower portion of the extruder barrel and cooked in the presence of an alkaline agent such as ammonium hydroxide and/or sodium hydroxide. Cooking causes hydrogen from at least one hydroxyl moiety on the hydroxyl polymer to become separated from the hydroxyl moiety, thereby creating a negative charge on the oxygen atom of the previous hydroxyl moiety. This oxygen atom is now open to association via an association agent such as a quaternary ammonium compound (e.g., a quaternary ammonium). Thus, an associative agent is added to the hydroxyl polymer/water slurry, thereby producing an associated hydroxyl polymer.

Table 1 describes the temperatures, pressures and corresponding functions of the various zones of the extruder.

TABLE I

Region(s)	Temperature (. degree. C. (. F.))	Pressure of	Description of the screw	Purpose(s) to
					1	21(70)	Is low in	Feeding/conveying	Feeding and mixing
2	21(70)	Is low in	Transfer of	Mixing and delivery
					3	21(70)	Is low in	Transfer of	Mixing and delivery
4	54(130)	Is low in	Pressure/deceleration transfer	Conveying and heating
					5	149(300)	In	Generating pressure	Decocting under pressure and at high temperature
6	121(250)	Height of	Reverse direction	Decocting under pressure and at high temperature
					7	99(210)	Is low in	Transfer of	Cooling and conveying (with ventilation)
8	99(210)	Is low in	Generating pressure	Transfer of

After the slurry exits the extruder, a portion of the associated hydroxyl polymer/water slurry may be dumped, while another portion (100g) may be fed into the Zenith^®PEP II (SanfordNC) pump, then pumped into a SMX type static mixer (Koch-Glitsch, Woodridge, Illinois). Static mixers are used to mix additional additives such as crosslinking agents, crosslinking promoters, external plasticizers (e.g., water) with the associated hydroxyl polymer/water slurry to form the associated hydroxyl polymer-containing composition. The additives were pumped into a static mixer via a PREP 100 HPLC pump (Chrom Tech, Apple Valley MN). These pumps provide the ability for high pressure, low volume addition. The associative hydroxyl-containing poly of the present inventionThe composition of the compound is ready to be processed by the polymer into a hydroxyl polymer polymeric structure.

B. Polymer processing

As used herein, the term "polymer processing" refers to any operation and/or method of forming a polymeric structure comprising a hydroxyl polymer from a hydroxyl polymer-containing composition.

Non-limiting examples of polymer processing operations include extrusion, molding, and/or fiber spinning. Extrusion and molding (casting or blowing) typically produce films, sheets, and extrudates of various shapes. Molding may include injection molding, blow molding, and/or compression molding. Fiber spinning may include spunbond, melt blown, continuous filament production, rotary spinning, and/or tow fiber production.

C. Polymeric structures

The hydroxyl polymer-containing composition can be subjected to one or more polymer processing operations such that the hydroxyl polymer-containing composition is processed into a polymeric structure comprising a hydroxyl polymer and optionally a crosslinking system as described herein.

Crosslinking systems crosslink hydroxyl polymers together by means of a crosslinking agent to produce the polymeric structures of the present invention, with or without a curing step. In other words, the crosslinking system according to the present invention can satisfactorily crosslink the hydroxyl polymers of the processed hydroxyl polymer-containing composition together by means of the crosslinking agent, thereby forming a complete polymeric structure, as determined by the initial Total Wet tensile test method described herein. The crosslinking agent is a "component part" of the polymeric structure. The polymeric structure according to the present invention cannot be formed without a cross-linking agent.

The polymeric structures of the present invention do not include a coating and/or other surface treatment applied to a preexisting form, such as a coating on a fiber, film, or foam.

In one example, the polymeric structure produced by the polymer processing operation may be cured at a curing temperature of from about 110 ℃ to about 315 ℃ and/or from about 110 ℃ to about 250 ℃ and/or from about 110 ℃ to about 200 ℃ and/or from about 120 ℃ to about 195 ℃ and/or from about 130 ℃ to about 185 ℃ for a period of time of from about 0.01 seconds and/or 1 second and/or 5 seconds and/or 15 seconds to about 60 minutes and/or from about 20 seconds to about 45 minutes and/or from about 30 seconds to about 30 minutes. Alternative curing methods may include radiation methods such as UV, electron beam, IR, and other temperature-raising methods.

In addition, the polymeric structure may also be cured at room temperature for several days after or instead of curing at room temperature as described above.

The polymeric structure exhibits an initial total wet tensile of at least about 1.18g/cm (3g/in) and/or at least about 1.97g/cm (5g/in) and/or at least about 5.91g/cm (15g/in) and/or at least about 9.84g/cm (25g/in) to about 51.18g/cm (130g/in) and/or to about 43.31g/cm (110g/in) and/or to about 35.43g/cm (90g/in) and/or to about 25.53g/cm (75g/in) and/or to about 23.62g/cm (60g/in) and/or to about 21.65g/cm (55g/in) and/or to about 19.69g/cm (50g/in) when determined according to the initial total wet tensile test method described herein.

In one example, the polymeric structure of the present invention may comprise at least about 20% and/or 30% and/or 40% and/or 45% and/or 50% to about 75% and/or 80% and/or 85% and/or 90% and/or 95% and/or 99.5% of the hydroxyl polymer, by weight of the polymeric structure.

Synthesis of polymeric structures

The following are non-limiting examples of methods for preparing polymeric structures according to the present invention.

i) Fiber formation

The hydroxyl polymer-containing composition was prepared according to the above "synthesis of hydroxyl polymer-containing composition". The polymer melt composition can be processed into a polymeric structure as shown in figure 2. By means of a pump 103, e.g. Zenith^®PEP II type pump for polymerizing hydroxyl groups present in the extruder 102The composition of the compound was pumped to a die 104 having a capacity of 0.6 cubic centimeters per revolution (cc/rev) manufactured by Parker Hannifin Corporation, Zenith Pumpsdivision, of Sanford, N.C., USA. The flow of hydroxyl polymer, such as starch, into the die 104 is controlled by adjusting the revolutions per minute (rpm) of the pump 103. The tube connecting the extruder 102, pump 103, die 104 and optional stirrer 116 was heated electrically and thermostatically controlled at 65 ℃.

The die 104 has several rows of circular extrusion nozzles 200 spaced from one another at a pitch P (fig. 3) of about 1.524 millimeters (about 0.060 in). Nozzle 200 has a single inner diameter D2 of about 0.305 millimeters (about 0.012in) and a single outer diameter (D1) of about 0.813 millimeters (about 0.032 in). Each individual nozzle 200 is surrounded by an annular and discretely flared orifice 250 formed in a plate 260 (fig. 3 and 4) having a thickness of about 1.9 millimeters (about 0.075 inches). The pattern of the plurality of discretely flared orifices 250 in the plate 260 corresponds to the pattern of the extrusion nozzle 200. The orifice 250 has a larger diameter D4 (fig. 3 and 4) of about 1.372 millimeters (about 0.054 inches) and a smaller diameter D3 of 1.17 millimeters (about 0.046 inches) for drawing long air. The plate 260 is fixed such that the embryonic fibers 110 extruded from the nozzle 200 are surrounded and elongated by a generally cylindrical stream of humidified air supplied through the orifice 250. The nozzles may extend beyond the surface 261 (fig. 3) of the plate 260 to a distance of about 1.5mm to about 4mm, more specifically about 2mm to about 3 mm. As shown in FIG. 5, a plurality of boundary air apertures 300 are formed by blocking two outer rows of nozzles on each side of the plurality of nozzles, as viewed on the plate, such that each boundary layer aperture contains the annular aperture 250 described above. Furthermore, the remaining capillary nozzles of every other row and every other column are blocked, thereby increasing the spacing between the available capillary nozzles.

As shown in FIG. 2, the extraction air may be provided by heating compressed air from source 106 with a resistive heater 108 (e.g., a heater manufactured by Chromalox, Division of Emerson Electric, of Pittsburgh, Pa., USA). An amount of water vapor 105, controlled by a globe valve (not shown), is added at an absolute pressure of about 240 to about 420 kilopascals (kPa), saturating or nearly saturating the heated air in the electrically heated thermostatically controlled delivery tube 115. The condensate is removed in an electrically heated thermostatically controlled separator 107. The elongated air has an absolute pressure of about 130kPa to about 310kPa as measured in tube 115. The extruded polymeric structural fibers 110 have a moisture content of about 20% and/or 25% to about 50% and/or 55% by weight. The polymeric structural fibers 110 are dried with a drying air stream 109 having a temperature of about 149 ℃ (about 300 ° f) to about 315 ℃ (about 600 ° f) provided by a resistance heater (not shown) through a drying nozzle 112 and discharged at a generally perpendicular angle relative to the general direction of the extruded embryonic fibers. The polymeric structural fibers are dried from about 45% moisture to about 15% moisture (i.e., from about 55% consistency to about 85% consistency) and then collected on a collection device 111, such as a movable mesh belt.

The processing parameters are as follows.

Sample(s)	Unit of
			Long-air-flow-speed pumping long-air-temperature pumping long-steam-flow-speed pumping long-steam gauge pressure	G/min ℃ G/min kPa	250093500213

Sample(s)	Unit of
			Draw length gage pressure draw length exit temperature solution Pump velocity solution flow Rate drying air flow Rate air pipe type air pipe size drying air temperature at rate heater through Pitot static tube inside delivery pipe drying pipe angle with respect to fiber	Mm DEG at kPa of revolution/min G/min/hole G/min MmM/s DEG C	2671350.1810200 slit 356x12734260800

ii) foam formation

The hydroxyl polymer-containing composition for foam formation is prepared using a process similar to that used to prepare the hydroxyl polymer-containing composition for fiber formation, except that the water content will be less, typically about 10% to 21% by weight of the hydroxyl polymer. Higher temperatures, typically 150 ℃ to 250 ℃, may be required in extruder zones 5 to 8 (fig. 1A) due to the use of less water to plasticize the hydroxyl polymer. Also, due to the low water availability, it may be necessary to add a crosslinking system, particularly a crosslinking agent, in zone 1 together with water. To avoid premature crosslinking in the extruder, the pH of the hydroxyl polymer-containing composition should be between 7 and 8, which can be achieved by using crosslinking promoters (e.g., ammonium salts). The die is placed at the point where the extruded material emerges and is typically maintained at 160 ℃ to 210 ℃. Modified high amylose starches (e.g., greater than 50% and/or greater than 75% and/or greater than 90% amylose by weight of the starch) ground to a particle size ranging from 400 to 1500 microns are preferred for use herein. It is also advantageous to add a nucleating agent such as a microtalc, or an alkali or alkaline earth metal salt such as sodium sulfate or sodium chloride in an amount of about 1% to 8% by weight of the starch. The foam can be made into a variety of shapes.

iii) film formation

The hydroxyl polymer-containing composition for film formation is prepared using a method similar to that for preparing the hydroxyl polymer-containing composition for fiber formation, except that less water is added, typically 3% to 15% by weight of the hydroxyl polymer, and a polyol external plasticizer, such as glycerin, is included at about 10% to 30% by weight of the hydroxyl polymer. Upon foam formation, regions 5 through 7 (fig. 1A) were maintained at 160 ℃ to 210 ℃, however the slot die temperature was lower, between 60 ℃ and 120 ℃. The crosslinking system, especially the crosslinking agent, can be added to zone 1 along with water when the foam is formed, and the pH of the hydroxyl polymer-containing composition should be between 7 and 8, which can be achieved by using a crosslinking facilitator (e.g., ammonium salt).

The films of the present invention may be used in any suitable product known in the art. For example, films may be used for packaging materials.

Method for manufacturing polymeric structures

The polymeric structures of the present invention can be made by any suitable method known to those skilled in the art.

One non-limiting example of a suitable method for making a polymeric structure according to the present invention includes the step of obtaining a polymeric structure comprising a hydroxyl polymer from a hydroxyl polymer-containing composition comprising the hydroxyl polymer in a substituted form.

In another embodiment of the present invention, a method for making a polymeric structure comprising a hydroxyl polymer is provided, wherein the method comprises the step of processing a polymer of a hydroxyl polymer-containing composition comprising a hydroxyl polymer into a polymeric structure comprising a hydroxyl polymer.

In another embodiment of the present invention, a method for making a polymeric structure comprising a hydroxyl polymer is provided, wherein the method comprises the steps of:

a. providing a hydroxyl polymer-containing composition comprising a hydroxyl polymer and an association agent; and

b. the polymer of the composition containing a hydroxyl polymer comprising a hydroxyl polymer and an association agent is processed into a polymeric structure.

In one example, in the associating step, the hydroxyl polymer (and in particular, the one or more hydroxyl moieties present on the hydroxyl polymer) is associated with the associating agent for a time sufficient for a polymeric structure comprising the hydroxyl polymer and the associating agent to form. In other words, without being bound by theory, the associative agent temporarily affects the properties of the hydroxyl polymer in such a way that it can be spun and/or otherwise processed into a polymeric structure such as a fiber.

The associating step can include subjecting the hydroxyl polymer to an alkaline pH. For example, the associating step can include subjecting the hydroxyl polymer to a pH of greater than 7 and/or at least about 7.5 and/or at least about 8 and/or at least about 8.5. To obtain a basic pH, a basic agent may be used in the association step. Non-limiting examples of suitable alkaline agents may be selected from the group consisting of: sodium hydroxide, calcium hydroxide, magnesium hydroxide, potassium hydroxide, ammonium hydroxide, and mixtures thereof. Further, the associating step may occur at a temperature in the range of from about 70 ℃ to about 140 ℃ and/or from about 70 ℃ to about 120 ℃ and/or from about 75 ℃ to about 100 ℃.

The associating step can include the step of allowing the hydroxyl polymer to interact with an associating agent to form an associated hydroxyl polymer.

The step of obtaining a fiber from the associated hydroxyl polymer can include subjecting the associated hydroxyl polymer to an acidic pH. For example, the step of obtaining a fiber from the associated hydroxyl polymer can comprise subjecting the associated hydroxyl polymer to a pH of less than 7 and/or less than about 6 and/or less than about 5 and/or less than about 4.5 and/or less than about 4. To obtain an acidic pH, an acidic agent may be used in the step of obtaining the fibers. Non-limiting examples of suitable acidic agents may be selected from the group consisting of: acetic acid, benzoic acid, citric acid, formic acid, glycolic acid, lactic acid, maleic acid, phthalic acid, phosphoric acid, succinic acid, and mixtures thereof and/or salts thereof, preferably ammonium salts thereof, such as ammonium glycolate, ammonium citrate, ammonium sulfate, ammonium chloride, and mixtures thereof. Further, the step of obtaining the fibers may occur at a temperature in the range of about 60 ℃ to about 100 ℃ and/or about 70 ℃ to about 95 ℃.

The step of obtaining a polymeric structure can include spinning the associated hydroxyl polymer such that a fiber is formed that includes the hydroxyl polymer and the association agent. Spinning may be any suitable spinning operation known to those skilled in the art.

The method of the present invention may further comprise the step of collecting a plurality of fibers to form a web.

Test method

All tests described herein (including those described in the definitions section and test methods below) were performed on samples that had been conditioned for 24 hours in a conditioning chamber having a temperature of about 23 ℃ ± 2.2 ℃ (73 ° f ± 4 ° f) and a relative humidity of 50% ± 10% prior to the test. Furthermore, all tests were performed in a conditioning chamber. Prior to capturing the images, the tested sample and felt should be subjected to about 23 ℃. + -. 2.2 ℃ (73 ℃. + -. 4F) and 50%. + -. 10% relative humidity for 24 hours.

A. Apparent peak value wet tensile stress testing method

The following test is designed to determine the apparent peak wet tensile stress of starch fiber during the first minute the fiber is wetted to represent the consumer's real-life expectation of its strength properties when using a final product such as toilet paper.

(A) Device：

● 696-12 type Sunbeam^®An ultrasonic humidifier, manufactured by Sunbeam Household Products Co., Inc. of McMinnville, TN, USA. The humidifier has an on/off switch and operates at room temperature. A69 cm (27 inch) long rubber hose of 1.59cm (0.625 ") outside diameter and 0.64cm (0.25") inside diameter was connected to the outlet. When operating properly, the humidifier will discharge between 0.54 and 0.66 grams of water per minute in the form of a mist.

Photogrammetry techniques can be used to determine the droplet velocity and droplet diameter of the mist produced by the humidifier. Nikon with 37mm coupling ring can be used^®PB-6 pleating bellows and Nikon^®Automatic focusing AF Micro Nikkor^®Nikon Japan of 200mm 1: 4D lens^®A D1 model 3-megapixel digital camera to capture images. Each pixel having a size of about 3.5 microns is assumed to be a square pixel. Images can be taken in shadow mode using a "Nano double flash system" (the "high speed camera system" of Wedel, germany). Many commercially available image processing packages can be used to process images. The dwell time between the two flashes of the system was set at 5, 10 and 20 microseconds. The distance the drop travels between flashes is used to calculate the velocity of the drop.

The water droplets were found to have a diameter of about 12 microns to about 25 microns. The velocity of the water drop at about (25 ± 5) mm from the flexible hose outlet was calculated to be about 27 meters per second (m/sec), a value that varied from about 15m/sec to about 50 m/sec. Clearly, when the mist stream encounters room air, the velocity of the water droplets slows down due to drag, while the distance from the hose outlet increases.

The flexible hose is placed so that the mist stream completely engulfs the fibers there, thoroughly wetting the fibers. To ensure that the fibers are not damaged or broken by the mist stream, the distance between the flexible hose outlet and the fibers is adjusted until the mist stream stops at the fibers or just past the fibers.

Model ● 405A, "Filament extensional Rheometer" (FSR) with a 1 gram "force transducer", manufactured by Aurora Scientific Inc. of Aurora, Ontario, Canada, and equipped with a small metal hook. The initial equipment set values are:

initial gap 0.1cm strain rate 0.1s^-1

Data point of Hencky strain limit 4 per second 25

Post shift time of 0

The FSR is based on a design similar to that described in a paper entitled "A FilameStretrealization Device For Measurement Of extended visual Viscosity", published in J.Rheology 37(6), 1993, pages 1081 to 1102 (tiratatmadja and Sridhar), and incorporated herein by reference, with the following changes:

(a) the FSR is oriented so that the two side plates can move in a vertical direction.

(b) The FSR includes two independent PAG001 ball screw linear actuators (manufactured by Industrial Device Corp. of Petaluma, Calif., USA), each actuator being driven by a stepper motor (e.g., Zeta)^®83-135, manufactured by parker hannifin corp., company Division, Rohnert Park, CA, USA). One of the motors may be provided with an encoder (e.g., model E151000C865, manufactured by Dynapar branch, Danaher Controls of gurnee, IL, USA) to track the position of the actuator. The two actuators can be programmed to move equal distances in opposite directions at equal speeds.

(c) The maximum distance between the side plates is about 813mm (about 32 inches).

The signal from a model 405A force transducer (manufactured by Aurora Scientific inc. of Aurora, Ontario, Canada) may be conditioned using a wide bandwidth single slot signal conditioning module, model 5B41-06, manufactured by Analog Devices co.

Fibers of hydroxyl-containing polymers and method for determining apparent peak wet tensile stress Examples of the embodiments

Twenty-five grams of an unsubstituted hydroxypolymer, such as Eclipse G starch (about 3,000,000G/mol average molecular weight acid-thinned dent corn starch, a.e. staley Manufacturing Corporation from Decatur, IL, USA), 10.00 grams of a hydroxypolymer, such as 10% Celvol 310 in water (vinyl alcohol, a homopolymer of Celanese ltd. from dallas texas, USA) (4% based on the weight of the starch), 1.00 grams of an alkaline agent, such as 25% sodium hydroxide solution (1% based on the weight of the starch), 0.67G of a substituent, such as Arquad 12-37W (trimethyldodecylammonium chloride, Akzo Nobel Chemicals Inc., from Chicago, USA (1% based on the weight of the starch), and 50 grams of water were added to a 200mL beaker. The beaker was placed in a water bath to boil for approximately one hour while the starch mixture was manually stirred to denature the starch and evaporate some of the water until about 25 grams of water remained in the beaker.

Then 1.66 grams of a crosslinking agent, such as Parez from Lanxess Corp. (formerly Bayer Corp.) Pittsburgh, Pa., USA^®490, (3% urea-glyoxal resin based on the weight of the starch) and 4.00 grams of a crosslinking promoter, e.g., a 25% ammonium chloride solution (4% based on the weight of the starch), are added to the beaker and stirred. The mixture was then allowed to cool to a temperature of about 40 ℃. A portion of the mixture was transferred to a 10 cubic centimeter (cc) syringe and extruded therefrom to form a fiber. Manually elongating the fibers such that the fibers have a diameter between about 10 μm and aboutA diameter of between 100 μm. The fibers were then suspended in ambient air for approximately one minute to allow the fibers to dry and set. The fibers were placed on an aluminum pan and cured in a convection oven at a temperature of about 130 ℃ for about 10 minutes. The cured fiber was then placed in a room having a constant temperature of about 22 ℃ and a constant relative humidity of about 25% for about 24 hours.

Since the single fibers are fragile, a coupon 90 (fig. 6) may be used to support the fibers 110. Coupon 90 may be made from ordinary office copy paper or similar lightweight material. In one illustrated example of fig. 6, coupon 90 comprises a rectangular structure having profile dimensions of about 20 millimeters long by about 8 millimeters wide, with a rectangular cutout 91 in the center of coupon 90 having a size of about 9 millimeters long by about 5 millimeters wide. Ends 110a and 110b of fibers 110 may be secured to the ends of coupon 90 with tape 95 (e.g., conventional scotch tape) or otherwise such that fibers 110 span a distance (about 9 millimeters in the present embodiment) of cutout 91 in the center of coupon 90, as shown in fig. 6. To facilitate mounting, the proof mass 90 may have a hole 98 at the top of the proof mass 90 configured to receive a suitable hook mounted on the plate of the force transducer. The average fiber diameter used for calculation can be obtained by measuring the fiber diameter at 3 positions with an optical microscope and then averaging before applying force to the fiber.

The coupons 90 may then be mounted to a fiber extensional rheometer (not shown) such that the fibers 110 are substantially parallel to the direction of the load "P" (fig. 6) to be applied. The sides of the coupon 90 that are parallel to the fiber 110 (along line 92, fig. 6) may be sheared so that the fiber 110 is the only element that bears the load.

The fibers 110 may then be fully wetted. For example, an ultrasonic humidifier (not shown) may be turned on and a rubber hose placed about 200 millimeters (about 8 inches) away from the fibers so that the exiting mist is directed at the fibers. The fiber 110 may be exposed to moisture for about one minute, after which a force load P may be applied to the fiber 110. The fibers 110 continue to be exposed to moisture during the application of the force load that imparts the elongation force to the fibers 110. It should be noted that it should be ensured that the fibers 110 are continuous within the main stream of steam exiting the humidifier when a force is applied to the fibers. When properly exposed, water droplets are typically visible on or around the fibers 110. Prior to use, the humidifier, its contents and the fibers 110 are equilibrated to ambient temperature.

Using the force load and diameter measurements, the wet tensile stress in megapascals (MPa) can be calculated. The test may be repeated a plurality of times, for example eight times. The results of the wet tensile stress measurements for the eight fibers were averaged. The force readings from the force transducer are corrected for the mass of the remaining coupon by subtracting the average force transducer signal collected after fiber breakage from the entire set of force readings. The breaking stress of the fiber can be calculated by dividing the maximum force generated on the fiber by the cross-sectional area of the fiber (based on optical microscope measurements of the average fiber diameter of the fiber determined prior to performing the test). The actual starting plate separation (bps) may depend on the particular sample being tested, but the actual bps are recorded in order to calculate the actual engineering strain of the sample. In the present example, an average wet tensile stress with a standard deviation of 0.29 was obtained with results of 0.33 MPa.

B. Average fiber diameter test method

A web containing fibers of the appropriate basis weight (about 5 to 20 grams per square meter) was cut into a rectangle approximately 20mm wide and 35mm long. The sample was then gold plated with SEM sputter coater (EMS Inc, PA, USA) to make the fibers relatively opaque. Typical coating thicknesses are between 50nm and 250 nm. The specimen was then held between two standard microscope slides and pressed together with a small binding clip. The sample was imaged with a 10X objective on an Olympus BHS microscope with the light collimating lens of the microscope as far away from the objective as possible. Images were taken with a Nikon D1 digital camera. The spatial distance of the image was calibrated using a glass microscope micrometer. The approximate resolution of the image is 1 μm/pixel. Typically, the image will show a significant bimodal distribution on the intensity histogram corresponding to the fibers and background. Camera adjustments or different basis weights are used to obtain an acceptable bimodal distribution. Typically, 10 images are taken for each sample, and the image analysis results are then averaged.

Images were analyzed using a method similar to that described in B.Pourdeyhimi, R.and R.Dent, Measuring fiber distribution in nowcovers (Textile Res.J.69(4), 233-. The digital images were analyzed with a computer using MATLAB (version 6.3) and MATLAB image processing toolkit (version 3.). The image is first converted to grayscale. The image is then binarized into black and white pixels using a threshold value that minimizes the combined variance of the black and white pixels after the threshold value. Once the image is binarized, the image is skeletonized to determine the location of each fiber center in the image. A distance transform of the binarized image is also determined by the computer. The scalar product of the skeletonized image and the distance map provides an image with zero pixel intensity or fiber radius at that location. A pixel within a radius of an intersection between two overlapping fibers is not counted if the pixel represents a distance less than the radius of the intersection. The remaining pixels are then used to calculate a length-weighted histogram of the fiber diameters contained in the image.

C. Initial total wet tension test method

Polymeric structural strips approximately 2.54cm (lin) wide and greater than 7.62cm (3in) long were used, with an electronic tensile Tester (Thwing-Albert EJA Materials Tester, Thwing-Albert Instrument Co., 10960 Dutton Rd., Philadelphia, Pa., 19154), and operated at a chuck speed of approximately 10.16cm (4.0in) per minute and a gauge length of approximately 2.54cm (1.0 in). The ends of the strip were placed in the upper jaw of the machine and then the centre of the strip was placed around a stainless steel nail (diameter 0.5 cm). After verifying that the strip was bent evenly around the nail, the strip was soaked in distilled water at about 20 ℃ for 5 seconds before starting the collet movement. The initial results of the test are a list of data expressed as load (grams force) versus chuck displacement (centimeters from the starting point).

The samples were tested in two directions, referred to herein as MD (machine direction, i.e., the same direction as the continuous winding axis and the direction of the forming fabric) and CD (cross direction, i.e., 90 ° from MD). MD and CD wet tensile were measured using the above equipment and calculated as follows:

initial total wet tension ITWT (g)_fIn ═ peak load_MD(g_f) /2 (inches)_{Width of}) + Peak load_CD(g_f) /2 (inches)_{Width of})

The basis weight of the test strip was then normalized to the "initial total wet tension" value. The normalized basis weight used was 36g/m²And is calculated as follows:

normalized { ITWT } - [ 36 (g/m) }²) Basis weight of the strip (g/m)²)

A crosslinking system of the present invention is acceptable if the initial total wet tensile of the polymeric structure comprising the crosslinking system is at least 1.18g/cm (3g/in) and/or at least 1.57g/cm (4g/in) and/or at least 1.97g/cm (5g/in), and is within the scope of the present invention. The initial total wet tension is preferably less than or equal to about 23.62g/cm (60g/in) and/or less than or equal to about 21.65g/cm (55g/in) and/or less than or equal to about 19.69g/cm (50 g/in).

D.Associative agentPresence test method

Standard test methods, i.e. HPLC-mass spectrometry or GC-mass spectrometry or capillary electrophoresis-mass spectrometry, can be used to determine whether the associative agent is present in a polymeric structure, such as a fiber, and/or in a fiber structure, and/or in a sanitary tissue product, examples of which are described in Vogt, cara; train analysis of surfactants using chromatographic and electrophoretic techniques. Fresenius' Journal of Analytical Chemistry (1999), 363(7), 612-. CODEN: FJACES ISSN: 0937-0633. CAN 130: 283696 AN 1999: 255335 CAPLUS

All documents cited in the detailed description of the invention are, in relevant part, incorporated herein by reference. The citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. The terms or phrases defined herein are reference standards even though they have different definitions in documents incorporated by reference.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims (12)

1. A polymeric structure in the form of a fiber, wherein the fiber comprises an unsubstituted hydroxyl polymer, and wherein the fiber exhibits an apparent peak wet tensile stress greater than 0.2 MPa.

2. The fiber of claim 1, wherein the unsubstituted hydroxyl polymer has a weight average molecular weight of at least 10,000 g/mol.

3. The fiber of claim 1, wherein the unsubstituted hydroxyl polymer comprises starch.

4. The fiber of claim 1, wherein the fiber has an average fiber diameter of less than 50 μ ι η.

5. The fiber of claim 1, wherein the fiber further comprises a substitution agent.

6. The fiber of claim 1, wherein the fiber exhibits a pH of less than 7.

7. Use of a fiber according to any of the preceding claims in a web, wherein the web exhibits an initial total wet tensile of greater than 10g/in (10g/2.54 cm).

8. A process for making a fibre according to any preceding claim, wherein the process comprises the steps of:

a. providing an unsubstituted hydroxyl polymer;

b. (ii) substituting the unsubstituted hydroxyl polymer to produce a substituted hydroxyl polymer; and

c. polymer processing the fiber from the substituted hydroxyl polymer.

9. The method of claim 8, wherein the step of substituting the unsubstituted hydroxyl polymer comprises subjecting the unsubstituted hydroxyl polymer to an alkaline pH.

10. The method of claim 8 or 9, wherein the step of substituting the unsubstituted hydroxyl polymer further comprises reacting the unsubstituted hydroxyl polymer with a cationic agent.

11. The method of any one of claims 8 to 10, wherein the step of obtaining the fiber from the substituted hydroxyl polymer comprises subjecting the substituted hydroxyl polymer to an acidic pH.

12. The method of any one of claims 8 to 11, wherein the method further comprises the step of collecting a plurality of the fibers to form a web.