CN1292111C - Non-thermoplastic starch fibers and starch compositions and methods for their preparation - Google Patents

Abstract

Non-thermoplastic starch fiber, which does not have a melting point and an apparent peak wet tensile stress greater than about 0.2 megapascals (MPa). The fiber can be made from a composition comprising a modified starch and a cross-linking agent. The shear viscosity of the composition is from about 1 Pascal·second to about 80 Pascal·second, and the apparent tensile viscosity ranges from about 150 Pascal·second to about 13,000 Pascal·second. The composition may comprise from about 50% to about 75% modified starch, from about 0.1% to about 10% aldehyde cross-linking agent, and from about 25% to about 50% water, all by weight. The weight average molecular weight of the modified starch before cross-linking may be greater than about 100,000 g/mol.

Description

Non-thermoplastic starch fibers and starch compositions and methods for their preparation

field of invention

The present invention relates to non-thermoplastic fibers comprising modified starch and methods of making such fibers. Non-thermoplastic starch fibers can be used to make nonwoven webs and other disposable articles.

Background of the invention

Native starch is a readily available and inexpensive material. Therefore, attempts have been made to process native starch on standard equipment using techniques known to exist in the plastics industry. However, since native starches generally have a granular structure, their structure needs to be "broken" and/or modified before they can be melt-processed like thermoplastics. The spun starch material is used to produce fine diameter starch fibers, or more specifically, fibers having an average equivalent diameter of less than about 20 microns, which are suitable for the production of fabric-grade webs, such as those fibers suitable for toilet paper production, which This task is extra challenging. First, a processable starch composition must have certain rheological properties that allow one to efficiently and economically spin fine diameter starch fibers. Second, it is highly desirable that the resulting web, and thus the fine diameter starch fibers comprising the web, have sufficient wet tensile strength, flexibility, stretchability and water insolubility for a defined (use) time. .

"Thermoplastic" or "thermoplastically processable" starch compositions described in several references described below may be suitable for the production of starch fibers with good stretchability and flexibility. However, the thermoplastic starch does not possess the desired wet tensile strength, which is an important property for consumer disposable products such as toilet paper, paper towels, feminine protection products, diapers, facial tissues and the like.

In the absence of strengthening agents, for example, without high levels of relatively expensive water-insoluble synthetic polymers, crosslinking may be required to obtain adequate wet tensile strength of starch fibers. Meanwhile, chemical or enzymatic agents have typically been used to modify or destroy starch to produce thermoplastic starch compositions. For example, a mixture of starch and plasticizer can be heated to a temperature sufficient to soften the resulting thermoplastic starch-plasticizer mixture. In some cases, pressure may be used to facilitate softening of the thermoplastic mixture. The molecular structure of starch granules is melted and disordered, resulting in destroyed starch. However, the presence of plasticizers in the starch mixture hinders the cross-linking of the starch and thus prevents the resulting starch fibers from achieving sufficient wet tensile strength.

Thermoplastic or thermoplastically processable starch compositions are described in several US patents, for example: US Patent 5,280,055, issued January 18, 1994; Patent 5,314,934, issued May 24, 1994; Patent 5,362,777, issued November 1994; Patent 5,844,023, issued December 1998; Patent 6,117,925, issued September 12, 2000; Patent 6,214,907, issued April 10, 2001; and Patent 6,242,102, issued June 5, 2001 All seven of the patents just mentioned were issued to Tomka on August 1, 2000; US Patent 6,096,809, issued August 1, 2000; Patent 6,218,321, issued April 17, 2001; On the 22nd, all four patents just mentioned were issued to Lorcks et al.; US Patent 6,231,970, issued May 15, 2001 to Andersen et al. Generally, thermoplastic starch compositions can be produced by mixing starch with additives such as plasticizers, preferably without water, for example as described in the above-referenced patent US 5,362,777.

For example, US Patents 5,516,815 and 5,316,578 to Buehler et al. relate to thermoplastic starch compositions for making starch fibers using a melt spinning process. The molten thermoplastic starch composition is extruded from the spinneret to form filaments whose diameter is slightly enlarged relative to the diameter of the die orifice on the spinneret (ie, die swell effect). The filaments are then pulled down mechanically or thermomechanically by a drawing unit to reduce the fiber diameter. A major disadvantage of the starch composition of Buehler et al. is that it requires significant levels of water-soluble plasticizers, which interfere with the cross-linking reaction, resulting in an apparent peak wet tensile stress in the starch fibers.

Other thermoplastically processable starch compositions are disclosed in the following patents: U.S. Patent 4,900,361 issued August 8, 1989 to Sachetto et al; U.S. Patent 5,095,054 issued March 10, 1992 to Lay et al; US Patent 5,736,586 issued April 7, 1998 to Bastioli et al; PCT Publication WO 98/40434 issued March 14, 1997 by Hanna et al.

Some of the aforementioned attempts to produce starch fibers have primarily involved wet spinning methods. For example, a starch/solvent colloidal suspension can be extruded from a spinneret into a coagulation tank. References to wet spun starch fibers include the following patents: U.S. Patent 4,139,699 issued February 13, 1979 to Hernandez et al; U.S. Patent 4,853,168 issued August 1, 1989 to Eden et al; US Patent 4,234,480 to Hernandez et al. Patent JP 08-260,250 describes modified starch fibers made from starch and pre-coagulated amino resins and a method for their preparation. The process involves dry spinning of starch and precoagulated amino resin, followed by heat treatment. The starches used in this method are native starches such as those contained in corn, wheat, rice, potatoes and the like.

Native starch has a high weight average molecular weight - from 30,000,000 grams per mole (g/mol) to over 100,000,000 g/mol. The melt rheological properties of aqueous solutions containing such starch are not suitable for high speed spinning processes such as spunbonding or meltblowing for the production of fine diameter starch fibers.

This technology reveals a need for an inexpensive and melt-processable starch composition that allows the production of fine diameter starch fibers with good wet tensile strength properties and is suitable for the production of webs, especially fabric grade webs. Production. Accordingly, the present invention provides non-thermoplastic fine diameter starch fibers having sufficient apparent peak wet tensile stress. The invention also provides a method for preparing the non-thermoplastic starch fiber.

Summary of the invention

The present invention includes non-thermoplastic starch fibers wherein the fibers as a whole do not exhibit a melting point. The fiber has a wet tensile stress of greater than about 0.2 MPa, more specifically, greater than about 0.5 MPa, even more specifically, greater than about 1.0 MPa, more specifically, greater than about 2.0 MPa, and even more specifically, greater than about 3.0 MPa. The average equivalent diameter of the fibers is less than about 20 microns, more specifically less than about 10 microns, and even more specifically less than about 6 microns.

Fibers can be made from a composition comprising modified starch and a crosslinking agent. The composition may have a shear viscosity of from about 1 Pascal s to about 80 Pascal s, preferably from about 3 Pascal s to about 30 Pascal s, as measured at a shear rate of 3,000 sec ^-1 and a processing temperature , more preferably from about 5 Pascal·s to about 20 Pascal·s. The composition may have an apparent extensional viscosity of about 150 Pascal s to about 13,000 Pascal s, specifically, about 500 Pascal ^s to about 5,000 Pascals, more specifically, about 800 Pascals to about 3,000 Pascals.

The composition comprises from about 50% to about 75% modified starch, from about 0.1% to about 10% aldehyde crosslinker, and from about 25% to about 50% water, all by weight. The composition may also comprise a polycationic compound selected from ferric or ferric ion salts, natural polycationic polymers, synthetic polycationic polymers, and any combination thereof. The composition may also include an acid catalyst in an amount sufficient to provide a pH of the composition in the range of about 1.5 to about 5.0, more specifically about 2.0 to about 3.0, even more specifically about 2.2 to about 2.6. The weight average molecular weight of the modified starch can be greater than about 100,000 g/mol.

The aldehyde crosslinking agent may be selected from formaldehyde, glyoxal, glutaraldehyde, urea glyoxal resin, urea formaldehyde resin, melamine formaldehyde resin, methylated ethylene urea glyoxal resin, and any combination thereof. Divalent or trivalent metal ion salts may be selected from calcium chloride, calcium nitrate, magnesium chloride, magnesium nitrate, ferric chloride, ferrous chloride, zinc chloride, zinc nitrate, aluminum sulfate, and any combination thereof. The acid catalyst may be selected from hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, and any combination thereof.

In another aspect, the present invention includes fibers comprising from about 50% to about 99.5% by weight of modified starch, wherein the fiber as a whole does not exhibit a melting point. The weight average molecular weight of the modified starch prior to crosslinking is greater than about 100,000 (g/mol). In one embodiment, the modified starch comprises oxidized starch.

In yet another aspect, the present invention includes non-thermoplastic starch fibers having a saline solution absorbency of less than about 2 grams of saline solution per 1 gram of fiber, more specifically, less than about 1 gram of saline solution per 1 gram of fiber, still more specifically Speaking, less than about 0.5 grams of salt solution per 1 gram of fiber.

Brief description of the drawings

Figure 1 is a schematic side view of the method of the present invention.

Figure 2 is a schematic partial side view of the process of the present invention illustrating the drawing zone.

Figure 3 is a schematic plan view taken along line 3-3 in Figure 2 illustrating one possible arrangement of multiple extrusion nozzles for providing non-thermoplastic starch fibers.

Figure 4 is a view similar to that in Figure 3, illustrating one possible arrangement of orifices for providing boundary air around the drawing zone.

Fig. 5 is a view similar to that in Fig. 3, illustrating another possible arrangement of orifices for providing boundary air around the drawing zone.

Fig. 6 is a view similar to that in Fig. 3, illustrating yet another possible arrangement of orifices for providing boundary air around the drawing zone.

Figure 7 is a schematic side view of a wiredrawing zone surrounded by physical sidewalls.

Fig. 8 is a schematic side view taken along line 8-8 in Fig. 6 .

Figure 9 is a schematic partial side view of the method of the present invention.

Figure 10 is a schematic plan view of a coupon used to determine the wet tensile stress of fibers according to the invention.

Detailed description of the invention

The following terms used herein have the following meanings.

A "non-thermoplastic starch composition" is a material which contains starch and which requires water to be softened to such an extent that the material is in a fluid state, which can be shaped as desired, and more specifically, which can be processed (e.g., using spinning method) to form a plurality of non-thermoplastic starch fibers suitable for forming flexible fibrous structures. Non-thermoplastic starch compositions cannot be influenced to become flowable only by raising the temperature. Although the non-thermoplastic starch composition may include a certain amount of other components, such as plasticizers, which can promote the flow of the non-thermoplastic composition, their content is not sufficient to make the non-thermoplastic starch composition as a whole flowable. In the flow state, the composition can be processed to form suitable non-thermoplastic fibers. Non-thermoplastic starch compositions also differ from thermoplastic compositions in that once a non-thermoplastic composition is dehydrated, eg by drying, thereby including the set state, it loses its "thermoplastic" properties. When the composition includes a crosslinking agent, the dehydrated composition effectively becomes a crosslinked thermosetting composition. A product, such as a plurality of fibers made from a non-thermoplastic starch composition, does not collectively exhibit a melting point, and does not collectively exhibit a melting temperature (characteristic of a thermoplastic composition); instead, the non-thermoplastic starch composition, as a whole , when its temperature rises to a certain level (the "decomposition" temperature), it will decompose even if it has not yet reached its fluid state. In contrast, a thermoplastic composition, whether or not water is contained therein, retains its thermoplastic properties, reaches its melting point ("melting" temperature), and becomes free-flowing when its temperature is increased.

"Non-thermoplastic starch fibers" are fibers made from non-thermoplastic starch compositions. Typically, but not necessarily, non-thermoplastic starch fibers comprise elongated and flexible structures. Non-thermoplastic starch fibers do not exhibit a melting point and decompose when the temperature is increased without attaining a flowable state, i.e., if in a flowable state, the fiber would melt as a whole and flow losing its "fibrous" character, as the fiber is intact properties, dimensions (diameter and length), etc. The word "integral" as used herein means emphatically that the fiber is considered as a complete assembly (as opposed to its discrete chemical components). It should be recognized that certain amounts of flowable substances, such as plasticizers, may be present in non-thermoplastic fibers and may exhibit "flowability". However, even if some components of the non-thermoplastic fiber can flow, the non-thermoplastic fiber does not lose its fibrous character as a whole.

"Fine diameter" starch fibers are non-thermoplastic starch fibers having an average equivalent diameter of less than about 20 microns, more specifically, less than about 10 microns.

The term "equivalent diameter" as used herein describes the cross-section of an individual non-thermoplastic fiber of the present invention, whether this cross-section is circular or non-circular, the cross-section being perpendicular to the longitudinal axis of the fiber. The cross-sectional area of any geometric shape can be determined according to the following formula: S=1/4πD ² , where S is the area of any geometric shape, π=3.14159, and D is the equivalent diameter. Using a hypothetical example, a fiber of rectangular cross-section, with a cross-sectional area S of 0.005 square microns, can be expressed as an equivalent circular area of 0.005 square microns, where the diameter "D" of the circular area. The diameter can be calculated by the following formula: S = 1/4πD ² , where S is the known area of the rectangle. In the foregoing hypothetical example, the diameter D is an equivalent diameter of a hypothetical rectangular cross section. Of course, the equivalent diameter of a fiber having a circular cross-section is the true diameter of the circular cross-section. The "average" equivalent diameter is the equivalent diameter calculated according to the arithmetic mean of the actual diameters of the fibers measured at least 3 positions along the fiber length using an optical microscope.

A "modified" starch is a starch that has been chemically or enzymatically modified. Modified starches are contrasted with native starches, which are starches that have not been chemically modified or modified by any other means.

A "multifunctional chemical crosslinking activator" is a chemical substance having two or more chemical functional groups capable of reacting with the hydroxyl or carboxyl functional groups of starch. The term "multifunctional chemical crosslinking activator" includes bifunctional chemical activators.

"Embryonic non-thermoplastic starch fibers" or simply "embryonic fibers" are non-thermoplastic starch fibers in the earliest stages of formation at the time of manufacture, primarily in the attenuation zone. When the rudimentary fibers are drawn and subsequently dewatered, they become the non-thermoplastic fibers of the present invention. Since the rudimentary fiber is an early stage of the non-thermoplastic starch fiber being produced, the rudimentary fiber and the non-thermoplastic fiber are designated by the same reference numeral 110 for the convenience of the reader.

The "drawing area" is a three-dimensional space whose planar profile is formed by the overall shape of a plurality of extrusion nozzles on a plan view (Fig. 3-6), which extends the drawing distance Z from the tip of the nozzle (Fig. 2 and 9) , the general direction of extension is the direction of motion of the fiber being prepared. "Drawing distance" is the distance extending from the extrusion nozzle tip, in the general direction of motion of the fibers being produced, within which the non-thermoplastic precursor fibers being produced can be drawn to form the resulting non-thermoplastic fibers, the individual The average equivalent diameter is less than about 20 microns.

"Processing temperature" means the temperature of the non-thermoplastic starch composition at which the non-thermoplastic starch composition of the present invention can be processed to form rudimentary non-thermoplastic starch fibers. The processing temperature may range from 50°C to 95°C as measured at the nozzle tip.

The "salt solution absorbency" of a starch sample is the ratio of the grams of saline solution absorbed by the starch sample to the grams of the starch sample, as described in the Test Methods and Examples below.

"Apparent Peak Wet Tensile Stress" or simply "Wet Tensile Stress" is the condition when the non-thermoplastic starch fiber is at its point of maximum (i.e., peak) stress as a result of the action of an external force, more specifically, is the result of the elongation force, as described in the Test Methods and Examples below. This stress is "apparent" because for testing purposes, possible changes in fiber diameter due to fiber elongation are not considered. The apparent peak wet tensile stress of a non-thermoplastic fiber is proportional to the wet tensile strength of that fiber and is used herein to quantitatively estimate the latter.

The non-thermoplastic starch fibers 110 of the present invention (Figs. 1, 7-9 and 10) can be made from a composition comprising modified starch and a crosslinking agent. In one aspect, the composition may comprise from about 50% to about 75% of a modified starch, from about 0.1% to about 10% of an aldehyde crosslinker, and from about 25% to about 50% of water, all by weight . Such compositions advantageously have a shear viscosity of from about 1 Pascal·second (Pa·s) to about 80 Pa·s, as measured at a shear rate of 3,000 sec ^-1 and a processing temperature. More specifically, the non-thermoplastic starch compositions of the present invention may comprise from about 50% to about 75% by weight of modified starch. Such compositions also advantageously have an apparent extensional viscosity of from about 150 Pa.s to about 13,000 Pa.s as measured at an extension rate of about 90 sec ^-1 and a processing temperature. Extensional viscosity and shear viscosity can be measured according to the test methods described herein.

The composition may also comprise a polycationic compound selected from ferric or ferric ion salts, natural polycationic polymers, synthetic polycationic polymers, and any combination thereof. The polycationic compound is included at about 0.1% to about 15% by weight. The composition may also comprise an acid catalyst in an amount sufficient to provide the composition with a pH in the range of about 1.5 to about 5.0, more specifically about 2.0 to about 3.0, even more specifically about 2.2 to about 2.6. Modified starches comprising the composition can have a weight average molecular weight greater than about 100,000 (g/mol).

Native starches can be chemically or enzymatically modified as is well known in the art. For example, native starch can be acid thinned, hydroxy-ethylated or hydroxy-propanolated or oxidized. Although all starches are potentially useful in the present invention, the present invention advantageously employs high amylopectin derived from agricultural sources, which has the advantage of being plentiful, easily replenished, and inexpensive. Chemical modification of starch typically involves acidic or alkaline hydrolysis, and oxidative chain scission to reduce molecular weight or molecular weight distribution. Suitable compounds for the chemical modification of starch include: organic acids such as citric acid, acetic acid, glycolic acid; and adipic acid; partial salts of inorganic and polyvalent acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, for example, KH ₂ PO ₄ , NaHSO ₄ ; Group Ia or IIa metal hydroxides such as sodium hydroxide and potassium hydroxide; ammonia; oxidizing agents such as hydrogen peroxide, benzoyl peroxide, ammonium persulfate, permanganate Potassium, hypochlorite, and the like; and mixtures thereof.

Chemical modification may also include derivatization of starch by reacting OH groups of starch with alkylene oxides and other ether, ester, urethane, carbamate or isocyanate group forming species. Hydroxyalkyl, acetyl or carbamate starches or mixtures thereof can be used as chemically modified starches. The chemically modified starch has a degree of substitution of 0.05 to 3.0, more specifically, 0.05 to 0.2. Biomodification of starch may include bacterial breakdown of carbohydrate bonds or enzymatic hydrolysis using enzymes such as amylases, pullulanases, and the like.

In general, all types of native starches can be used in the present invention. Suitable naturally occurring starches may include, but are not limited to: corn starch, potato starch, sweet potato starch, wheat starch, sago palm starch, tapioca starch, rice starch, soybean starch, arrowroot starch, pullulan, bracken starch, lotus root starch, waxy corn starch, and high amylose corn starch. Naturally occurring starches, especially corn starch and wheat starch, are especially beneficial based on their low cost and availability.

Crosslinking agents useful in the present invention comprise polyfunctional chemical reactants capable of reacting with either the hydroxyl functional groups or the carboxyl functional groups of the modified starch. Crosslinking agents used in the paper industry to crosslink wood pulp fibers are often referred to by the term "wet strength resins". These wet strength resins can also be used to crosslink starch based materials. A general discussion of wet strength resins used in the paper industry can be found in TAPPI Monograph Volume 29 "WetStrength in Paper and Paperboard, Technical Association of the Pulpand Paper Industry (New York, 1965)", based on the description applied to the paper industry For purposes of wet strength resin types, it is incorporated herein by reference. Polyamide-epichlorohydrin resins are cationic polyamide-epichlorohydrin wet strength resins which have found particular utility. Suitable types of such resins are described in the following patents: U.S. Patent 3,700,623, issued October 24, 1972, and U.S. Patent 3,772,076, issued November 13, 1973, both to Keim, which are applicable to the present invention based on the description For purposes of wet strength resin types, both are incorporated herein by reference. One commercial source of suitable polyamide-epichlorohydrin resins is Hercules Inc., Wilmington, Delaware, which sells such resins under the name Kymene ^(R) .

Glyoxylated polyacrylamide resins have also been found useful as wet strength resins. These resins are described in the following patents: U.S. Patent 3,556,932 issued January 19, 1971 to Coscia et al., and U.S. Patent 3,556,933 issued January 19, 1971 to Williams et al., based on the descriptions applicable to Both patents are incorporated herein by reference for the purposes of the wet strength resin type of the present invention. One commercial source of glyoxylated polyacrylamide resins is Cytec Co. of Stanford, CT, which sells one such resin under the name Parez ^(R) 631NC.

It has been found that non-thermoplastic starch fibers made from non-thermoplastic starch compositions have significant wet tensile strength when a suitable cross-linking agent, such as Parez ^(R) 631NC, is added to the starch composition of the present invention under acidic conditions, This can be demonstrated by testing the apparent peak wet tensile stress of the fibers, as described below. Accordingly, products produced using the non-thermoplastic starch fibers of the present invention, such as webs suitable for use in consumer disposable articles, will also have significant apparent peak wet tensile stress.

Other water soluble resins useful in the present invention may include formaldehyde, glyoxal, glutaraldehyde, urea glyoxal resins, urea formaldehyde resins, melamine formaldehyde resins, methylated ethylene urea glyoxal resins, and other glyoxal resins Base resins, and any combination thereof. Polyethylenimine type resins are also useful in the present invention. In addition, temporary wet strength resins such as Caldas ^(R) 10 (manufactured by Japan Carlit) and CoBond ^(R) 1000 (manufactured by National Starch and Chemical Company) can be used in the present invention.

Still, other crosslinking agents that may be used in the present invention include butadiene sulfone, anhydrides comprising copolymers such as styrene-maleic anhydride copolymers, dichloroacetone, dimethanol urea, for example butylene dioxide or bis(shrinkle glyceryl ether), diepoxides, epichlorohydrin, and diisocyanates.

In addition to crosslinking agents that covalently react with the hydroxyl and carboxyl functional groups of the starch, divalent and trivalent metal ions can also be used in the present invention to crosslink the starch through the formation of complexes between the metal ions and the carboxyl functional groups on the starch. In particular, oxidized starches, which have an increased content of carboxyl functional groups, can cross-link well with divalent and trivalent metal ions. In addition to polycationic metal ions, natural or synthetic polycationic polymers can also be used to crosslink starch through the formation of ion-pair complexes with carboxyl functional groups on the starch, forming a non-coacervate complex commonly referred to by the term "coacervate". dissolve the complex. Metal ion crosslinking has been found to be particularly effective when used in combination with covalent crosslinking reagents. For the present invention, suitable crosslinking agents can be added to the composition at levels varying from about 0.1% to about 10%, more typically, from about 0.1% to about 3%, all by weight.

Native, unmodified starches generally have a very high weight average molecular weight and a broad molecular weight distribution, for example, native corn starch has an average molecular weight in excess of about 40,000,000 g/mol. Therefore, native, unmodified starch does not have the intrinsic rheological properties suitable for high-speed solution spinning processes, such as spunbonding or meltblowing of nonwoven materials, to produce fine diameter fibers. These small diameters are very beneficial in achieving sufficient softness and opacity in the end product, properties that are important features for many consumer disposable products such as toilet paper, wipes, diapers, napkins and disposable towels sexual performance.

To produce the rheological properties required for high speed spinning processes, the molecular weight of native unmodified starch must be reduced. The optimum molecular weight depends on the type of starch used. For example, starches with a low content of amylose components, such as waxy maize starch, are very dispersible in aqueous solution with heating and do not undergo significant reversion or recrystallization. Because of these properties, the waxy corn starch that can be used can have a rather high weight average molecular weight, eg, in the range of 500,000 g/mol to 5,000,000 g/mol. Modified starches, such as hydroxy-ethylated dent corn starch containing about 25% amylose, or oxidized dent corn starch, are easier than waxy corn and more difficult than acid-thinned starches, tending to Inversion. Inversion or recrystallization acts as a physical crosslink, effectively increasing the weight average molecular weight of starch in aqueous solution. Thus, for hydroxy-ethylated dent corn starch, or oxidized dent corn starch, a suitable weight average molecular weight is from about 200,000 g/mol to about 1,000,000 g/mol. For acid thinned dent corn starch which is more reversible than oxidized dent corn starch, a suitable weight average molecular weight is from about 100,000 g/mol to about 500,000 g/mol.

The average molecular weight of starch can be reduced to range required by the present invention. Thermomechanical and oxidative methods offer the added advantage that they can be performed in situ during the melt spinning process. It is believed that the non-thermoplastic starch fibers of the present invention may comprise from about 50% to about 99.5% by weight of modified starch.

In the presence of an acid catalyst, native starch can be hydrolyzed, thereby reducing the molecular weight and molecular weight distribution of the composition. The acid catalyst can be selected from hydrochloric acid, sulfuric acid, phosphoric acid, citric acid and any combination thereof. Chain scission agents may also be incorporated into the spinnable starch composition so that the chain scission reaction occurs substantially simultaneously with the mixing of the starch and other components. Non-limiting examples of oxidative chain scission agents suitable for use in the present invention include ammonium persulfate, hydrogen peroxide, hypochlorite, potassium permanganate, and mixtures thereof. Typically, an effective amount of chain scission agent is added to reduce the weight average molecular weight of the starch to the desired range. It has been found that compositions containing modified starches having a suitable weight average molecular weight range have suitable shear viscosities and thus improve the processability of the compositions. Improved processability significantly reduces process interruptions (eg, shrinkage cracks, grits, defects, hang-ups) and results in better surface appearance and strength properties of the final product, such as the fibers of the present invention.

The divalent or trivalent metal ion salt may include any water soluble divalent or trivalent metal ion salt, which may be selected from calcium chloride, calcium nitrate, magnesium chloride, magnesium nitrate, ferric chloride, ferrous chloride, zinc chloride, Zinc nitrate, aluminum sulfate, ammonium zirconium carbonate, and any combination thereof. The polycationic polymer can include any water-soluble polycationic polymer, such as polyethyleneimine; a quaternized polyacrylamide polymer, such as Cypro ^(R) 514 manufactured by Cytec Industries, Inc. located in West Patterson, NJ; or natural polycationic polymers. Cationic polymers, such as chitosan; and any combination thereof.

In accordance with the present invention, the non-thermoplastic starch fibers have a wet tensile stress of greater than about 0.2 MPa, more specifically, greater than about 0.5 MPa, still more specifically, greater than about 1.0 MPa, and even more specifically, greater than about 2.0 MPa, Still even more specifically, greater than about 3.0 MPa. In some embodiments, the non-thermoplastic starch fibers have a wet tensile stress greater than about 3.0 MPa. Without wishing to be bound by theory, it is believed that by reducing the weight average molecular weight of the starch, non-thermoplastic starch compositions are produced having suitable rheological properties required for high speed solution spinning of fine diameter non-thermoplastic starch fibers, which are then formed The starch is crosslinked to produce wet tensile strength in the non-thermoplastic starch fiber of the present invention. Crosslinking increases the molecular weight of the starch in the fiber being formed, thereby promoting the water insolubility of the fiber, resulting in high wet tensile strength in the resulting non-thermoplastic starch fiber.

The extensional or elongational viscosity (η _e ) relates to the extensibility of non-thermoplastic starch compositions and is especially important for drawing processes, such as fiber production processes. Extensional viscosity includes three types of deformation: uniaxial or simple extensional viscosity, biaxial extensional viscosity, and pure shear extensional viscosity. Uniaxial extensional viscosity is important for uniaxial extensional processes such as fiber spinning, melt blowing and spunbonding.

The Troughton ratio (Tr) can be used to describe the extensional flow behavior of the starch compositions of the present invention. The Troughton ratio is defined as the ratio between extensional viscosity (η _e ) and shear viscosity (η _s ),

Tr＝η _e (ε ^· ，t)/η _s

Where the extensional viscosity η _e depends on the deformation rate (ε ^· ) and time (t). For Newtonian fluids, the uniaxial tension Troughton ratio is a constant value of 3. For non-Newtonian fluids, like the starch compositions of the present invention, extensional viscosity depends on deformation rate (ε ^· ) and time (t). It has also been found that the processable compositions of the present invention typically have a Trouton ratio of at least about 3. When measured at a processing temperature and a stretching rate of 90 sec ^-1 , the Trouton's ratio can vary from about 5 to about 1,000, specifically, from about 30 to about 300, more specifically, from about 50 to 200.

The non-thermoplastic fibers of the present invention can be used in a variety of consumer disposable products such as nonwoven materials suitable for webs of fabric grade paper in the production of paper products such as toilet paper, paper towels, napkins, facial tissues, diapers, feminine Protective articles, incontinence articles, and the like. In addition, these fibers can be used in air, oil and water filters; vacuum cleaner filters; stove filters; face masks, coffee filters, tea or coffee bags; thermal and sound insulation materials; for improved moisture absorption and wearing softness, such as microfibres or breathable fabrics; structural webs with electrostatic forces for collecting and removing dust; reinforcements and webs for rigid papers, such as packaging paper, writing paper, newsprint , corrugated cardboard; medical uses, such as surgical drapes, wound dressings, bandages, skin patches, and self-dissolving sutures; and dental uses, such as dental floss or toothbrush bristles. The resulting non-thermoplastic starch fibers or webs can also be incorporated into other materials such as sawdust, wood pulp, plastics and concrete to form composite materials that can be used as building materials such as walls, support beams , pressed boards, drywall and brackets, and ceiling tiles; other medical uses such as splints, splints, and tongue depressors; and in fireplace wood for decorative and/or burning purposes.

The preparation method of the non-thermoplastic fiber according to the present invention comprises the following steps.

First, there is provided a non-thermoplastic starch composition comprising from about 50% to about 75% by weight of modified starch and from about 25% to about 50% by weight of water. In some embodiments, the step of providing a non-thermoplastic starch composition may follow the step of preparing a non-thermoplastic starch composition.

Referring to Figures 1-9, the non-thermoplastic fibers 110 of the present invention can be manufactured using a method comprising: extruding a non-thermoplastic starch composition from a plurality of nozzles 200; thereby forming a plurality of prototype fibers; using high-speed drawing air (drawing air The direction of the fiber 110 is schematically illustrated by arrow C in FIG. 2) to draw the preformed fiber so that the average single equivalent diameter of the non-thermoplastic fiber 110 is less than about 20 microns, and dehydrate the fiber 110 to a consistency of about 70% to about 99% by weight. According to the present invention, the fibers have an individual average equivalent diameter of less than about 20 microns, more specifically less than about 10 microns, and even more specifically, less than about 6 microns.

According to the present invention, the resulting individual non-thermoplastic fibers 110 comprise from about 50% to about 99.5% by weight of modified (eg, oxidized) starch which, as a whole, has no melting point, as described in detail above.

For the purpose of producing the fine diameter non-thermoplastic fibers 110 of the present invention, the beneficial timing for the desired stringing to occur is when the composition has an appropriate shear viscosity in the range of about 1 Pa·s to about 80 Pa·s, more specifically, about 3 Pa·s s to about 30 Pa·s, and even more specifically, about 5 to about 20 Pa·s, the measurement conditions are the processing temperature and the shear rate of 3,000 sec ^-1 . The step of maintaining an appropriate shear viscosity in an appropriate range may be beneficially supplemented by moistening and/or at least partially insulating the drawing area from the surrounding environment. The drawing air is provided with a relative humidity of greater than about 50%, so that the relative humidity of the air in the drawing zone may be greater than about 50%, specifically greater than about 60%, and more In particular, greater than about 70% is beneficial.

Methods of maintaining the desired humidity within the drawing area include, for example, enclosing the drawing area. In FIG. 7 , the drawing zone is at least partially enclosed by side walls 400 . Alternatively or additionally, the drawing zone may be at least partially insulated by a boundary air (arrow D in FIG. 8 ) surrounding the drawing zone. Boundary air may be supplied through a plurality of discrete orifices 300 (FIG. 4), or slits around a plurality of nozzles 200 (FIG. 5), as shown in plan view. In Figure 6, boundary air is supplied through continuous slits 320 forming the outer perimeter of the drawing zone. Other methods of maintaining the desired humidity in the drawing zone may include providing steam or water sprays (not shown) in the drawing zone. Boundary air can be supplied externally, ie independently of the mold (not shown), or alternatively or additionally, internally, ie through the mold (Figs. 4-6). Beneficially, the boundary air may be humidified to a relative humidity of greater than about 50%. The velocity of the boundary air can be equal to the velocity of the drawing air.

It is believed that, in the method of the present invention, the drawing distance may be less than about 250 millimeters (about 10 inches), more specifically, less than about 150 millimeters (about 6 inches), and even more specifically, less than about 100 millimeters (about 10 inches). 4 inches). Those skilled in the art will appreciate that, based on the nature of the process, the exact size of the draw distance is not immediately available. Likewise, the draw rate of the fibers may vary within the draw zone, for example, it is believed that the draw rate gradually decreases towards the end of the draw zone.

Depending on the purpose of producing the web, multiple extrusion nozzles may be beneficially arranged in multiple rows, as shown in Figures 3-6. Drawing air may be supplied through a plurality of discrete circular orifices surrounding the extrusion nozzle 200 as shown in FIG. 3 . This configuration is primarily described in U.S. Patent 5,476,616, December 19, 1995, and in U.S. Patent 6,013,223, issued January 2000, both to Schwarz, which are incorporated herein by reference for the purpose of illustrating single A configuration of devices that extrude nozzles, each surrounded by a circular air orifice. Both of Schwarz's patents relate to processing thermoplastic materials. It has been found that to form the non-thermoplastic fibers of the present invention, the average velocity of the drawing air can be greater than about 30 m/s, more specifically, from about 30 m/s to about 500 m/s, as measured at the nozzle tip according to the methods described herein. m/s. Those skilled in the art will appreciate that specially designed (eg convergent-divergent) nozzle geometries may be required to achieve supersonic velocity.

The step of dewatering the non-thermoplastic fibers being formed can be accomplished by providing hot drying air 109 downstream of the drawing zone, supplied by drying nozzles 112 (FIG. 9), wherein the temperature of the drying air is from about 150°C to about 480°C °C, more specifically, from about 200 °C to about 320 °C, with a relative humidity of less than about 10%.

In some embodiments, it may be beneficial to provide a second drawing air (arrow C1 in FIG. 9 ), for example, provided downstream of the drawing air. The second drawing air provides additional elongation to the fibers, thereby further drawing the fibers being produced. It should be noted that while the second drawing air may contact the fibers downstream of the drawing zone, this second force primarily affects those portions of the rudiment fiber still within the drawing zone. The temperature of the second drawing air may be about 20°C to about 480°C, more specifically, about 70°C to about 320°C. Near the outlet of the second drawing air nozzle, when measured at the nearest distance (about 3mm) from the second drawing air jet outlet 700, as shown in FIG. 9, the velocity of the second drawing air can be from about 30 m/s to about 500 m/s, and more specifically, about 50 m/s to about 350 m/s. The second drawing air may be dry air, or alternatively, may be moist air.

Secondary drawing air may be applied at various locations downstream of the extrusion nozzle, if desired. For example, in FIG. 9 , the second drawing air includes air C1 supplied from the second drawing air outlet 700 and air C2 supplied from the second drawing air outlet 710 downstream of the air C1 . The second drawing air may be applied at an angle of less than 60 degrees, more specifically, from about 5 to about 45 degrees relative to the general direction of the fibers being formed.

For further processing, the resulting non-thermoplastic starch fibers can be collected on a work surface, or on a collection device 111 (FIG. 1), such as a perforated belt.

Test methods and examples

(A) Apparent peak wet tensile stress

The following test is designed to measure the apparent wet tensile stress of starch fibers during the first minute the fibers are wetted, which stress reflects realistic expectations of consumers during use of a final product such as toilet paper.

(A)(1) Equipment:

• Sunbeam ^(R) Ultrasonic Humidifier, Model 696-12, manufactured by Sunbeam Household Products Co., McMinnville, TN, USA. Humidifiers have an on/off switch and operate at room temperature. A 27" (68.6cm) long, 0.625" (1.59cm) outside diameter, 0.25" (0.64cm) inside diameter rubber hose is attached to the outlet port. When operating correctly, the humidifier will output between 0.54 grams and 0.66 grams of water per minute in the form of a mist.

The droplet velocity and droplet diameter produced by the humidifier can be measured by photogrammetry. Images can be taken using a Nikon ^(R) Japan, model D1 3 megapixel digital camera equipped with a 37mm coupling ring, a Nikon ^(R) PB-6 bellows, and a Nikon ^(R) autofocus AF Micro Nikkor ^(R) 200mm 1:4D lens. Assuming square pixels, the size of each pixel is about 3.5 microns. Shooting can be done in shaded mode, using Nano Twin Flash (High-Speed Photo-Systeme, Wedel, Germany). Images can be processed using any number of commercially available image processing packages. The system was programmed with dwell times of 5, 10 and 20 microseconds between flashes. The distance traveled by the droplet between flashes is used to calculate the droplet velocity.

The water droplets have been found to be from about 12 microns to about 25 microns in diameter. The droplet velocity at about (25 ± 5) mm from the outlet of the flexible hose was calculated to be about 27 meters per second, varying from about 15 meters per second to about 50 meters per second. Clearly, when the mist stream hits the room air, the velocity of the droplets slows down with increasing distance from the hose outlet due to drag.

The flexible hose is positioned so that the mist stream completely contains the fibers, thus thoroughly wetting the fibers. To ensure that the fibers are not damaged or interrupted by the mist flow, adjust the distance between the flexible hose outlet and the fibers until the mist flow stops at or just beyond the fibers.

- Filament Extensional Rheometer (FSR), with 1 gram load cell, Model 405A, manufactured by Aurora Scientific Inc. in Aurora, Ontario, Canada, equipped with a small metal hook. The initial settings of the instrument are:

Initial gap = 0.1cm Strain rate = 0.1s ^-1

Hencky strain limit = 4 Data points per second = 25

back move time = 0

The design of the FSR is similar to that described in the paper "A Filament Stretching Device For Measurement Of Extensional Viscosity" by Tirtaatmadja and Sridhar, published in J.Rheology 37(6), 1993, pages 1081-1102, which is incorporated herein as For reference, with the following modifications:

(a) Determine the orientation of the FSR so that the two end plates can move vertically.

(b) The FSR includes two ball screw linear actuators, model PAG001 (manufactured by Industrial Device Corp. located in Petaluma, CA, USA.), each powered by a stepper motor (such as a Zeta ^(R) 83- 135, driven by Parker Hannifin Corp., Compumotor Division, located in Rohnert Park, CA, USA). One of these motors may be equipped with an encoder (such as model number E151000C865, manufactured by Dynapar Brand, Danaher Controls, located in Gurnee, IL, USA) to track the position of the actuator. The two actuators can be arranged to move the same distance at the same speed in opposite directions.

(c) The maximum distance between end plates is approximately 813mm (about 32 inches).

A Wide Bandwidth Single Channel Signal Conditioning Module, Model 5B41-06, manufactured by Analog Devices Co. of Norwood, MA, USA, may be used to condition the signal from a load cell, model 405A, of Aurora , manufactured by Aurora Scientific Inc. of Ontario, Canada.

(B) Examples of non-thermoplastic fibers, methods for their preparation, methods for measuring apparent peak tensile stress, extensional viscosity of shear viscosity

(B) (1) The preparation method of non-thermoplastic starch fiber

Fibers are formed using small-scale equipment, a schematic of which is shown in Figure 1. Referring to Fig. 1, the composition of equipment 100 has a certain volume feeder 101, and it can provide starch composition to 18mm co-rotating twin-screw extruder 102 by at least 12 grams per minute, and this extruder is by New Jersey, the AmericanLeistritz of USA Manufactured by Extruder Co. The temperature of the barrel section of the extruder was controlled by a heating coil and water jacket (not shown) to provide the proper temperature to break down the starch mixed with the water. Add dry starch powder in the hopper 113, and add deionized water at the interface 114.

The pump 103 used was a Zenith ^(R) , PEP II type, with a load capacity of 0.6 cubic centimeters per revolution, manufactured by Parker Hannifin Corporation, Zenith Pumps division of Sanford, NC, USA. The starch flow to the mold 104 is controlled by adjusting the revolutions per minute of the pump 103 . The piping connecting the extruder 102, pump 103, mixer 116 and die 104 was electrically heated and thermostatically controlled so as to maintain a temperature of approximately 90°C.

Die 104 had several rows of spaced apart circular extrusion nozzles with a center-to-center distance P (FIG. 2) of about 1.524 millimeters (about 0.060 inches) between the nozzles. A single nozzle has an inner diameter D2 of about 0.305 millimeters (about 0.012 inches) and an outer diameter (D1) of about 0.813 millimeters (about 0.032 inches). Each nozzle is surrounded by an annular diverging funnel-shaped orifice 250 formed in a plate 260 (FIG. 2) having a thickness of about 1.9 millimeters (about 0.075 inches). The pattern of the plurality of diverging funnel-shaped orifices 250 on the plate 260 matches the pattern of the extrusion nozzles 200 . Orifice 250 has a large end diameter D4 (FIG. 2) of approximately 1.372 mm (approximately 0.054 inches) and a small end diameter D3 of 1.17 mm (approximately 0.046 inches), thereby being suitable for drawing air. The plate 260 is fixed so that the preformed fibers 110 extruded from the nozzle 200 are surrounded and drawn by the generally cylindrical flow of moist air supplied by the orifice 250 . The nozzles may extend beyond the surface 261 of the plate 260 (FIG. 2) a distance of about 1.5 mm to about 4 mm, more specifically, about 2 mm to about 3 mm. A plurality of boundary air orifices 300 (FIG. 4) are formed by plugging the outer two rows of nozzles on each side of the plurality of nozzles, as shown in plan view, so that each boundary layer orifice includes an annular hole as described above 250.

The drawing air may be provided by hot compressed air from an air source 106 heated by a resistive heater 108, such as a heater manufactured by Chromalox, Division of Emerson Electric of Pittsburgh, PA, USA. Add an appropriate amount of steam controlled by a spherical core valve with an absolute pressure of about 240 to about 420 kPa to saturate or almost soak the heated air in the electric heating constant temperature control delivery pipe 115 . Condensate is removed in an electrically heated thermostatically controlled separator 107 . The drawing air has an absolute pressure of about 130 kPa to about 310 kPa as measured within tube 115 .

A crosslinking solution comprising a crosslinking agent, such as Parez ^(R) 490, and an acid catalyst, can be prepared off-line and fed via line 116 to a static mixer, such as the Model SMX static mixer manufactured by Koch Chemical Corporation of Witchita, Kansas, USA.

The moisture content of the non-thermoplastic precursor fibers 110 being extruded is from about 25% to about 50% by weight. The dry air stream 109 is heated by a resistive heater (not shown) at a temperature of about 149°C (about 300°F) to about 315°C (about 600°F), supplied through the drying nozzle 112, and is directed relative to the non- The normal orientation of the thermoplastic precursor fibers exits at an angle of about 40 to about 50 degrees, allowing the precursor fibers 110 to dry. The moisture content of the dried preform fiber is changed from about 25% to about 5% (ie, the consistency is changed from about 75% to about 95%), and the dried preform fiber is collected on a collecting device 111, such as on a movable perforated belt.

(B) (2) Example 1 of non-thermoplastic fiber and its wet tensile stress measuring method

25 grams of StaCote ^(R) H44 starch (oxidized waxy corn starch with a weight average molecular weight of about 500,000 g/mol) from AE Staley Manufacturing Corporation of Decatur, IL, USA, 1.25 grams of anhydrous calcium chloride (5% by weight of starch) , 1.66 grams of Parez ^(R) 490 from Bayer Corp. of Pittsburgh, PA, USA (urea-glyoxal resin at 3% by weight of starch), and 45 grams of 0.1M potassium phosphate aqueous buffer (pH=2.1) were Add to 200ml beaker. The beaker was set in a water bath to boil for about one hour while the starch mixture was manually stirred to break up the starch and allow the water to evaporate until about 25 grams of water remained in the beaker. The temperature of the mixture was then cooled to about 40°C. A portion of the mixture was delivered to a 10 cubic centimeter syringe and extruded from there to form fibers. The fibers were elongated by hand so that the diameter of the fibers was between about 10 microns and about 100 microns. The fibers were then exposed to ambient air for about 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 120°C for about 10 minutes. The cured fibers were then placed in a room at a constant temperature of about 22°C and a relative humidity of about 25% for about 24 hours.

Due to the fragility of individual fibers, a coupon 90 (FIG. 10) may be used to support the fibers 110. Coupon 90 may be made of regular office copy paper or similar thin material. In the illustrative embodiment of FIG. 10 , coupon 90 includes a rectangular structure with outline dimensions of about 20 millimeters by about 8 millimeters, with a rectangular cutout in the center of coupon 90 measuring about 9 millimeters by about 5 millimeters. Go to section 91. The ends 110a and 110b of the fibers 110 can be secured to the ends 110a and 110b of the coupon 90 using adhesive tape 95 (e.g., conventional scotch tape) or other means such that the fibers 110 span the cutout 91 at the center of the coupon 90 length (about 9 mm in this embodiment), as shown in Figure 10. For ease of installation, there is a hole 98 in the top of the sample block 90 configured to receive a suitable hook mounted on the upper plate of the load cell. Before applying force to the fiber, the diameter of the fiber can be measured at 3 locations using an optical microscope and averaged to obtain the average fiber diameter for calculation.

The coupon 90 was then mounted on a fiber extensional rheometer (not shown) such that the fibers 110 were substantially parallel to the direction of the applied load "P" (Fig. 10). Portions of the sides of the coupon 90 parallel to the fibers 110 can be trimmed (along line 92 in FIG. 10) so that the fibers 110 are the only load bearing elements.

The fibers 110 can then be fully wetted. For example, an ultrasonic humidifier (not shown) can be turned on, using a rubber hose about 200 mm (about 8 inches) from the fibers, thereby directing the mist output directly at the fibers. The fibers 110 may be exposed to the steam for about one minute before the load P is applied to the fibers 110 . The load creates an elongation force on the fiber 110, and during the application of the load, the fiber 110 is continuously exposed to the vapor. Care is taken to ensure that the fiber 110 is always in the main output stream of the humidifier when force is applied to the fiber. Water droplets are typically visible on or around fibers 110 when properly exposed. The temperature of the humidifier, its contents, and fibers 110 may be allowed to equilibrate to ambient temperature prior to use.

Using the load value and the measured diameter value, the wet tensile stress in MPa can be calculated. This test can be repeated a number of times, for example eight times. Take the average of the eight wet tensile stress values obtained. The force readings from the load cell were corrected by subtracting the average load cell signal collected after fiber breakage from the overall force reading based on the mass of the remaining coupon. The fracture stress of the fiber is calculated by dividing the maximum stress induced on the fiber by the cross-sectional area of the fiber, which is based on the average equivalent diameter of the fiber measured with an optical microscope prior to performing the test. The actual initial plate separation (bps) may depend on the particular sample being tested, but it is recorded to calculate the actual engineering strain of the sample. In this example, the obtained average wet tensile stress was 0.33 MPa with a standard deviation of 0.29.

(B) (3) Example 2 of non-thermoplastic fiber

25 grams of Clinton(R ⁾ 480 starch (oxidized dent corn starch, weight-average molecular weight of about 740,000 g/mol), available from Decatur, Illinois, USA's Archer, Daniels, Midland Co., 1.25 grams of anhydrous calcium chloride (based on starch weight 5%), 1.66 grams of Parez(R) 490 (3% urea-glyoxal resin by weight of starch), and 45 grams of 0.5% by weight aqueous citric acid were added to a 200 ml beaker. Fibers were produced and prepared according to the procedure described in Example 1 above, and then the method described in Example 1 was used to determine the wet tensile stress of the fibers. The average wet tensile stress obtained was 2.1 MPa with a standard deviation of 1.25 and a maximum wet tensile stress of 3.4 MPa.

(B) (4) Example 3 of non-thermoplastic fiber

25 grams of Ethylex ^(R) 2005 starch (hydroxyethylated dent corn starch, 2% by weight ethylene oxide substitution, weight average molecular weight of about 250,000 g/mol) from AEStaley Manufacturing Corporation, 5.55 grams of Parez ^(R) 490 (a starch 10% by weight of urea-glyoxal resin), 2.0 grams of N-300 polyacrylamide 1.0% by weight solution, from WestPatterson, NJ, Cytec Industries, Inc. of USA, and 45 grams of 0.5% by weight of citric acid aqueous solution were Add to 200ml beaker. Fibers were produced and prepared according to the procedure described in Example 1 above, and then the method described in Example 1 was used to determine the wet tensile stress of the fibers. The resulting average wet tensile stress was 0.45 MPa with a standard deviation of 0.28.

Although the above-described method of determining the wet tensile stress of individual fibers provides a direct measure of important fiber performance characteristics, such measurements are time consuming. Another method that can be used to measure the degree of crosslinking of a fiber, and thus its tensile strength, is to measure the saline solution absorbency of the fiber. This method is based on the fact that, when placed in water or a salt solution, cross-linked starch absorbs the water in the solution. A measurable change in solution concentration is a result of absorption of the starch fiber solution. A high degree of fiber crosslinking reduces the absorbent capacity of the fibers.

The following method uses Blue Dextran ^(R) solution. Blue Dextran ^(R) molecules are large enough not to penetrate the starch fibers or granules, while water molecules can penetrate and be absorbed by the starch fibers. Thus, as a result of the water absorption of the starch fibers, the Blue Dextran ^(R) in solution is concentrated and it can be accurately measured using optical absorption measurements.

A Blue Dextran(R) ^solution was prepared by dissolving 0.3 grams of Blue ^Dextran (R) (available from Sigma, St. Louis, MO) in 100 mL of distilled water. A 20 ml dose of Blue Dextran ^(R) solution was mixed with 80 ml of saline solution. The salt solution was prepared by mixing 10 grams of sodium chloride, 0.3 grams of calcium chloride dihydrate and 0.6 grams of magnesium chloride hexahydrate in a 1.0 liter flask and adding distilled water until the flask was filled.

The optical absorption of Blue Dextran ^(R) /saline solution (blank or baseline measurement) can be measured at a wavelength of 617 nm using a standard one centimeter dichroic cuvette using a DR/4000UUV/VIS Spectrophotometer manufactured by HACH Company of Loveland, Colorado, USA.

Films of starch were prepared by "breaking" the starch by heating 25 grams of starch and 25 grams of distilled water in a glass beaker in a water bath that had been heated to 95°C for about one hour. After the starch is broken, Parez ^(R) 490 crosslinker and phosphoric acid catalyst are added to form a starch mixture and stirred. The mixture was poured onto a one foot square sheet of Teflon ^(R) material and spread to form a film. The films were allowed to dry at room temperature for one day and then cured in an oven at about 120°C for 10 minutes.

The dried film was broken up and placed on an IKA All Basic grinder manufactured by IKA Works, Inc. of Wilmington, NC, USA, at 25,000 rpm for about one minute. The ground starch is then sieved through a 600 micron sieve (e.g., mesh 30, according to U.S. Standard Sieve Series, A.S.T.M E-11 Specifications, manufactured by Dual Mfg. Co. of Chicago, IL, USA) Separation onto a 300 micron sieve (mesh 50).

Two grams of sieved starch were added to 15 grams of the Blue Dextran ^(R) /salt solution, using a closed beaker to prevent evaporation, with continuous stirring at room temperature for about 15 minutes. The solution is then filtered through a 5 micron syringe filter such as a Spartan ^(R) -25 nylon membrane filter available from Schleicher & Schuell Co. of Keene, NH, USA. The absorbance of the filtered solution can be measured similarly to the Blue Dextran ^(R) /salt blank measurement. The "salt solution absorbency" of a starch sample can be expressed as a ratio of grams of salt solution (GA) absorbed per gram of starch sample (GS) and calculated as follows:

GA/GS=(15-((blank absorbance/sample absorbance)×15))/2

Non-thermoplastic starch fibers can be tested using the Saline Solution Absorbency Test Method by substituting fibers for starch granules. According to the present invention, the non-thermoplastic starch fibers have a saline solution absorbency of less than about 2 grams of saline solution per 1 gram of fiber, more specifically, less than about 1 gram of saline solution per 1 gram of fiber, still more specifically, less than about 0.5 gram of salt solution per 1 gram of fiber.

Example

Sieved granules of the following starches were prepared and measured according to the method just described above. Each starch sample comprising Parez ^(R) 490 crosslinker, phosphoric acid catalyst, and optionally calcium chloride crosslinker, all as active solids, is listed in the table below by its solution absorbency value. starch type %Parez 490 % phosphoric acid % Calcium Chloride grams of solution absorbed per gram of starch ^Ethylex® 2005 1.0 0.75 0 0.47 StaCote ^(R) H44 1.0 0.75 5.0 1.23 ^Purity® Gum 1.0 0.75 0 2.27 ClearCote ^(R) 615 1.0 0.75 0 1.45 Clinton ^(R) 480 5.0 0.75 5.0 1.02 ^Ethylex® 2005 5.0 0.75 0 0.38 StaCote ^(R) H44 5.0 0.75 5.0 0.84

(C) Shear viscosity

The shear viscosity of the non-thermoplastic starch composition of the present invention can be measured using a capillary rheometer, which is a model Rheograph 2003 manufactured by Goettfert, USA, Rock Hill SC, USA. The measurement method can be realized by using a capillary mold with a diameter D of 1.0 mm and a length L of 30 mm (ie L/D=30). The die was attached to the lower end of the rheometer barrel and its temperature was maintained at the test temperature (t), which varied from about 25°C to about 90°C. A sample of the composition can be preheated to the test temperature and loaded into the cartridge section of the rheometer to substantially fill the cartridge (approximately 60 grams of sample is used). The barrel is maintained at the specified test temperature (t).

If air bubbles rise to the surface after filling, compaction can be used to remove entrapped air from the sample before running the test. A plunger is used to push the sample in the cartridge through the capillary die at a selected rate. As the sample travels from the barrel through the capillary die, the sample experiences a pressure drop. The apparent shear viscosity can be calculated from the pressure drop and flow rate of the sample as it passes through the capillary die. The logarithmic curve of shear viscosity versus shear rate is then drawn, and the curve is fitted according to the following power law, η=Kγn-1, where K is a material constant and γ is the shear rate. The resulting apparent shear viscosity of the compositions of the present invention is an extrapolated value at a shear rate of 3,000 sec ^-1 using a power law relationship.

(D) extensional viscosity

The extensional viscosity of the non-thermoplastic compositions of the present invention can be measured using a capillary rheometer, model Rheograph 2003 manufactured by Goettfert USA. This measurement can be performed using a semi-hyperbolic mold with an initial equivalent diameter _Dinitial of 15 mm, a final equivalent diameter ( _Dfinal ) of 0.75 mm and a length L of 7.5 mm.

The semi-hyperbolic shape of the mold is determined by two formulas. Where Z is the axial distance from the initial equivalent diameter position, and D(z) is the equivalent diameter of the mold at _{the initial} distance z position from D.

A mold can be attached to the lower end of the barrel, which is maintained at a fixed test temperature t, which is about 75°C, roughly corresponding to the temperature at which the non-thermoplastic starch composition is being processed. A sample of the starch composition can be preheated to mold temperature and loaded into the cylinder of the rheometer to substantially fill the cylinder. If air bubbles rise to the surface after filling, compaction can be used to remove air trapped in the molten sample before running the test. A plunger is used to push the sample in the cartridge through the hyperbolic die at a selected rate. The sample experiences a pressure drop as it travels from the barrel through the orifice die. The apparent extensional viscosity can be calculated from the pressure drop and flow rate of the sample through the die using the following formula:

Apparent extensional viscosity = (ΔP/extension rate/E _h )×10 ⁵ ,

where apparent extensional viscosity, that is, extensional viscosity not calibrated for shear viscosity effects, is in Pascal seconds (Pa s), ΔP ^is pressure drop in bar, and extension rate is in seconds- ¹ is the flow rate of the sample through the die, and E _h is the dimensionless logarithmic strain. Logarithmic strain is strain based on strain time or strain history. The strain induced by a flowing component of a non-Newtonian fluid depends on its kinematic history, i.e.

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; t</span>}}{<span\; class="notranslate">\; \&Integral;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}^{<span\; class="notranslate">\; \&Center\; Dot;</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}$

The logarithmic strain _E for this die design was 5.99, which was determined by:

E _h =1n[( _Dinitial / _Dfinal ) ² ]

The apparent extensional viscosity can be calculated as a function of the extension rate 90 sec ^-1 using a power law relationship. A detailed disclosure of extensional viscometry using a semi-hyperbolic die can be found in U.S. Patent 5,357,784, issued to Collier on October 25, 1994, for the limited purpose of describing extensional viscometry, the disclosure of which The contents are incorporated herein by reference.

(E) Molecular weight

The weight average molecular weight (Mw) of non-thermoplastic starch can be determined by gel permeation chromatography (GPC) using an ion exchange mixed column. The composition of high performance liquid chromatography (HPLC) is as follows:

Pump: Millenium ^(R) , Model 600E, from Milford, MA, USA

Manufactured by Waters Corporation

System Controller: Waters Model 600E

Autosampler: Waters Model 717 Plus

Injection volume: 200μL

Column: PL gel 20μm Mixed A column (gel molecular weight is 1,000

g/mol to 40,000,000g/mol), length

It is 600mm and the inner diameter is 7.5mm

Guard column: PL gel 20μm, length 50mm, inner diameter 7.5mm

Column heater: CHM-009246, manufactured by Waters Corporation

Column temperature: 55℃

Detector: DAWN ^(R) Enhanced Optical System (EOS) from Santa Barbara, CA,

Manufactured by Wyatt Technology of USA, Laser Scattering Detector,

K5 battery, 690nm laser. The odd detector gain is set to

101. The even detector gain was set to 20.9. Wyatt

The Optilab ^(R) Differential Refractometer from Technology was set at 50°C.

The gain is set to 10.

Mobile phase: HPLC grade dimethyl sulfoxide with 0.1% w/v LiBr

Mobile phase flow rate: 1mL/min, isocratic

GPC control software: ^Millennium (R) software, version 3.2, by Waters

Produced by Corporation.

Detector software: Wyatt Technology's Astra ^(R) software, version 4.73.04

Running time: 30 minutes

Starch samples are prepared by dissolving starch in the mobile phase, typically 3 mg starch per 1 mL mobile phase. The samples were covered and then stirred using a magnetic stirrer for approximately 5 minutes. The samples were then placed in a convection oven at 85°C for about 60 minutes. The samples were then allowed to cool to room temperature on their own. The sample is then filtered through a 5 μm syringe filter (eg, 5 μm nylon membrane, type Spartan-25, manufactured by Schleicher & Schuell of Keene, NH, US), which is injected into a 5 mL autosampler vial using a 5 milliliter (mL) syringe.

For each series of measured samples, inject a blank solvent sample into the column. Control samples were then prepared in a manner similar to that involving the samples described above. The control sample contained 2 mg/mL pullulan (manufactured by Polymer Laboratories), and its weight average molecular weight was 47,300 g/mol. Control samples were analyzed prior to analysis of each set of samples. Tests on the blank, control, and non-thermoplastic starch test samples can be run in duplicate. The final run can be the third run of the blank sample. Operation of the light scattering detector and differential refractometer may be performed in accordance with the "EOS Light Scattering Instrument Hardware Manual" and the "Optilab ^(R) DSP Interferometric Refractometer Hardware Manual", both made by Wyatt Technology Corp. of Santa Barbara, CA, USA, both This article is incorporated by reference.

The weight average molecular weight of the samples was calculated using Astra ^(R) software produced by Wyatt Technology Corp. The dn/dc (differential change in refractive index versus concentration) value used was 0.066. Baselines for laser detectors and refractive index detectors were corrected to remove effects from detector dark current and solvent scatter. If the signal of the laser detector is saturated or exhibits excessive noise, it is not used for molecular mass calculations. The molecular weight signature was chosen so that both the 90° detector signal for laser light scattering and refractive index were each greater than 3 times the baseline noise level. Typically, the high molecular weight side of the chromatogram is limited by the refractive index signal and the low molecular weight side is limited by the laser signal.

The weight average molecular weight can be calculated using a "First Order Simm Diagram" defined in the Astra ^(R) software. If the weight average molecular weight of the sample is greater than 1,000,000 g/mol, both first order and second order Simm diagrams are calculated, and the result with the smallest error from the regression fit is used to calculate the molecular mass. The reported weight average molecular weight is the average of two sample tests.

(F) relative humidity

Relative humidity can be measured using wet bulb and dry bulb temperature measurements and associated measurement charts. When measuring wet bulb temperature, wrap a cotton sleeve over the bulb of the thermometer. Then, place the cotton-covered thermometer into the hot water until the water temperature is above the expected wet-bulb temperature, more specifically, above about 82°C (about 180°F). Place the thermometer in the drawing air stream about 3 mm (about 1/8 inch) from the tip of the extrusion nozzle. Initially the temperature will drop as the water evaporates from the cotton sleeve. The temperature will stabilize at the wet bulb temperature, then, once the cotton sleeve loses its retained moisture, the wet bulb temperature will rise. The stable temperature is the wet bulb temperature. If the temperature does not decrease, the water must be heated to a higher temperature. The dry bulb temperature was measured using a 1.6mm J-type thermocouple placed approximately 3mm downstream from the extrusion nozzle tip.

Relative humidity can be determined based on a standard atmospheric humidity calculation chart or an Excel add-in, such as "MoistAirTab" produced by ChemicaLogic Corporation. Instead of a chart, relative humidity is read based on wet bulb and dry bulb temperatures.

(G) Air velocity

Air velocity can be measured using a standard pitot tube. Insert the pitot tube into the air stream and take a dynamic pressure reading from the associated pressure gauge. The dynamic pressure reading, together with the dry bulb temperature reading, is used with the standard formula to obtain the air velocity. A 1.24 mm (0.049 inch) pitot tube manufactured by the United Sensor Company of Amherst, NH, USA can be connected to a handheld digital differential pressure gauge (manometer) for rate measurement.

(H) Fiber diameter

Fiber diameter can be measured according to the following procedure. A rectangular sample is cut from a web made of non-thermoplastic starch fibers. The samples were cut to fit the size of a microscope slide, each measuring about 6.35 millimeters (about 0.25 inches) by about 25.4 millimeters (about 1 inch), and sandwiched between two glass slides. Clamp the two slides together with adhesive clamps to flatten the specimen. Place the sample and slide on a microscope slide stage, using a 10x objective. An Olympus ^(R) BHS microscope available from the Fryer Company of Cincinnati, OH, USA may be used. Remove the light-collimating lens of the microscope and keep it as far away from the objective as possible. A digital camera, such as Nikon ^(R) D1 digital camera, can be used to take pictures of slides, and the resulting file in TIFF format can be imported into a computer, using software such as Nikon ^(R) , Capture Software, version 1.1. The TIFF format files can be loaded into the image analysis software package Optimus ^(R) , version 6.5, produced by Media Cybernetics Inc. of Silver Spring, MD, USA. Select the appropriate calibration file for your specific microscope and objective. Optimus ^(R) software was used to manually select and measure fiber diameters. In the Optimus ^(R) software, using the length measurement tool, take measurements of at least 30 fibers, preferably without tangles, displayed on the computer screen. These fiber diameters are averaged to obtain the average fiber diameter for a given sample. Prior to this analysis, a spatial calibration can be performed to obtain fiber diameters using appropriate scaling and units, as known to those skilled in the art.

The examples listed in the table below were produced using the equipment described above, see Figures 1 and 2 . An aqueous solution of Purity Gum ^(R) 59 (available from National Starch & Chemical Company of Bridgewater, NJ USA) was prepared in the extruder and fed to the die. The solution contains about 65% starch and 35% water.

A pair of drying tubes was used in each case. The drying tubes are arranged symmetrically with respect to the spinning fiber channel. Tilt the drying tube so that the drying air stream is in close contact with the fiber stream.

surface sample unit A B C Drawing air flow rate g/min 375 375 364 Drawing air temperature ℃ 40 40 95 Drawing steam flow rate g/min 140 140 106 Drawing Steam Gauge Pressure kPa 220 220 290 Drawing gauge pressure in delivery pipe kPa 126 126 180 Drawing outlet temperature ℃ 80 80 77.8 Solution pump speed revs/min 20 10 20 Solution flow rate g/min/hole 0.66 0.33 0.66 dry air flow rate g/min 972 972 910 air tube type Seam Seam ^Windjet® Air pipe size mm 51×5 51×5 concrete model Velocity through the pitot-static tube m/s 34 34 304 Drying air temperature at heater ℃ 260 260 260 The distance between the drying tube and the mold mm 125 125 150 Angle of drying tube relative to fiber Spend 45 45 45 average fiber diameter Micron 13.6 8.2 10.1

Example A produced fibers with an average equivalent diameter of about 14 microns. Example B included a modification of the flow rate of the non-thermoplastic solution to a lower value. This condition produced a smaller average equivalent diameter of about 8 microns. Example C included a second high velocity drawing air. In Example C, a Windjet ^(R) Model Y727-AL air nozzle from Spraying System Co. of Wheaton, Illinois USA was used to generate higher air velocities for drying air.

Claims (20)

1. non-thermoplastic starch fibers, the wet tensile stress of the apparent peak value of described non-thermoplastic starch fibers is greater than 0.2 megapascal (MPa) (MPa), and wherein said non-thermoplastic starch fibers does not have fusing point as a whole.

2. fiber as claimed in claim 1, the wet tensile stress of the apparent peak value of wherein said fiber is greater than 0.5MPa.

3. fiber as claimed in claim 1, the wet tensile stress of the apparent peak value of wherein said fiber is greater than 1.0MPa.

4. fiber as claimed in claim 1, the wet tensile stress of the apparent peak value of wherein said fiber is greater than 2.0MPa.

5. fiber as claimed in claim 1, the wet tensile stress of the apparent peak value of wherein said fiber is greater than 3.0MPa.

6. fiber as claimed in claim 1, wherein said fiber is made by the composition that comprises modified starch and crosslinking agent.

7. fiber as claimed in claim 1, the average equivalent diameter of wherein said fiber is less than 20 microns.

8. fiber as claimed in claim 1, the average equivalent diameter of wherein said fiber is less than 10 microns.

9. fiber as claimed in claim 1, the average equivalent diameter of wherein said fiber is less than 6 microns.

10. be used to prepare the non-thermoplastic starch composition of the non-thermoplastic starch fibers of claim 1, it comprises:

50% to 75% modified starch by weight;

0.1% to 10% aldehyde cross-linking agent by weight; With

25% to 50% water;

Wherein said composition is 3000 seconds in processing temperature and shear rate ^-1Condition under the shear viscosity that records be 1 pascal second to 80 pascal second.

11. non-thermoplastic starch composition as claimed in claim 10, described composition also comprises 0.1% to 15% polycation compound by weight, described polycation compound is selected from divalence or trivalent metal ion salts, natural polycationic polymer, synthesizes polycationic polymer and their any combination.

12. non-thermoplastic starch composition as claimed in claim 10, described composition also comprises acid catalyst, and it is 1.5 to 5.0 pH value that the amount of described acid catalyst is enough to for described composition provides scope.

13. non-thermoplastic starch composition as claimed in claim 10, the weight average molecular weight of wherein said modified starch be greater than 100,000g/mol.

14. non-thermoplastic starch composition as claimed in claim 10, wherein said aldehyde cross-linking agent be selected from formaldehyde, glyoxal, glutaraldehyde, urea glyoxal resin, urea-formaldehyde resin, melamine resin, the ethene that methylates urea glyoxal resin, and their any combination.

15. non-thermoplastic starch composition as claimed in claim 11, wherein said divalence or trivalent metal ion salts are selected from calcium chloride, calcium nitrate, magnesium chloride, magnesium nitrate, iron chloride, frerrous chloride, zinc chloride, zinc nitrate, aluminum sulfate, ammonium zirconium carbonate, and their any combination.

16. non-thermoplastic starch composition as claimed in claim 12, wherein said acid catalyst is selected from hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, and their any combination.

17. non-thermoplastic starch composition as claimed in claim 10, wherein said composition is 90 seconds in processing temperature and rate of extension ^-1Condition under the apparent tensile viscosity that records be 150 pascal seconds to 13,000 pascal second.

18. non-thermoplastic starch fibers as claimed in claim 1, the salting liquid absorbability of described non-thermoplastic starch fibers is less than the per 1 gram fiber of 2 gram salting liquids.

19. non-thermoplastic starch fibers as claimed in claim 18, the salting liquid absorbability of wherein said non-thermoplastic starch fibers is less than the per 1 gram fiber of 1 gram salting liquid.

20. non-thermoplastic starch fibers as claimed in claim 19, the salting liquid absorbability of wherein said non-thermoplastic starch fibers is less than the per 1 gram fiber of 0.5 gram salting liquid.

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