KR101228176B1 - Elastic nonwoven sheet - Google Patents

Abstract

The present invention relates to an extensible nonwoven sheet prepared by substantially uniformly impregnating a necked nonwoven substrate or an easily extensible nonwoven substrate with an elastomeric polymer by treating the elastomeric polymer solution. Nonwoven sheets are useful in the manufacture of diapers and other hygiene products.

Nonwoven Sheets, Neck Forming, Elastomers, Hygiene Products

Description

Elastic nonwoven sheet {ELASTIC NONWOVEN SHEET}

The present invention relates to stretchable nonwoven sheets suitable for use in the manufacture of personal care products. More specifically, the extensible nonwoven sheet is formed by substantially uniformly impregnating a necked nonwoven substrate or an easily extensible raw nonwoven substrate with an elastomeric polymer.

This application supersedes US Patent Application No. 10 / 413,172, filed April 14, 2003, which is part of US Patent Application No. 10 / 353,677, now abandoned, filed January 29, 2003. Claims (these two patent applications are incorporated herein by reference) claim priority to US Provisional Application No. 60 / 565,014, filed April 23, 2004.

Elastic nonwoven materials are well known in the art. Examples of elastic nonwoven materials are "stretch-bonded" and "neck-bonded" laminates. Stretch-bonded laminates are made by bonding the pleat layer to the elastic layer, where the elastic layer is extended to gather the pleat layer as it relaxes the layers. Neck-bonded laminates are made by combining the necked inelastic layer with an elastic film on the fiber layer. The elastic layer generally comprises an elastic film or an elastic nonwoven web. These elastic nonwoven laminates require the production of two or more separate nonwoven layers or film layers.

U. S. Patent No. 4,366, 814 to Riedel is a breathable elastic comprising at least 50 wt.% Stretchable fabric that can stretch at least 30 percent without tearing, and at least 15 wt.% Elastomers impregnated in the fabric without filling holes in the fabric. Bandage materials are described.

US Pat. No. 5,910,224 to Morman discloses an elastomeric precursor by applying an elastomeric precursor to a neckable material, such as a nonwoven web, necking the neckable material, and heating the neckable material. A process for producing an extensible composite by treating is described wherein the neckable material is in a necked state to form an elastomeric layer bonded to the necked material. Preferred elastomeric precursors include latex or thermoset elastomers. The elastomeric precursor is applied to the neckable material in an amount of 5 g / m 2 to about 50 g / m 2. The elastomeric layer typically penetrates the web about 2 to about 10 fibers thick, and the extent of penetration of the elastomeric precursor is controlled so as not to penetrate the side of the web opposite the side to which the elastomeric layer is applied. Thus, the resulting stretchable composite has a film-like feel on the side comprising the elastomeric layer and retains the original soft feel of the neckable material on the opposite side of the elastomeric layer.

European Patent Application Publication No. 0472942 includes a fibrous web (eg, a nonwoven web of meltblown fibers) saturated with a polymeric material (such as elastomeric acrylic latex, polyurethane latex or nitrile rubber latex) in the Z-direction. Elastomeric saturated nonwoven materials with compressibility and recoverability of are described.

Japanese Patent Application Laid-Open No. 47-24479 relates to a belt for use in conveyors and power transmission devices, which is produced by impregnating a needlepunched nonwoven with rubber or synthetic resin.

There is a continuing need for elastic sheet materials that can be manufactured economically, have soft stretchability and good retention, and have a fabric-like feel on both sides.

Summary of the Invention

The present invention provides a method of providing a necked nonwoven substrate having a thickness, a first and a second outer surface, a machine direction and a machine direction, and an elongation in the machine direction of at least 30%; Substantially uniformly impregnating the necked nonwoven substrate with a solution comprising an elastomeric polymer dissolved in a solvent; And removing the solvent from the impregnated nonwoven substrate by wet coagulation to form a substantially uniform elastomeric polymer through the thickness of the nonwoven substrate without forming a substantially continuous elastomeric polymer layer on the first or second outer surface of the nonwoven substrate. A method of forming an extensible nonwoven sheet, comprising the step of depositing it.

The invention also has a thickness, a first and a second outer surface, a machine direction and a machine direction, an elongation in the machine direction is at least 30%, a basis weight of about 15 g / m 2 to about 100 g / m 2, and breaking strength Providing an easily extensible nonwoven substrate having a greater than 500 g / in; Substantially uniformly impregnating the readily extensible nonwoven substrate with a solution comprising an elastomeric polymer dissolved in a solvent; And removing the solvent by wet coagulation from the easily extensible nonwoven substrate to form a substantially uniform through thickness of the nonwoven substrate without forming a substantially continuous elastomeric polymer layer on the first or second outer surface of the nonwoven substrate. To a method of forming an extensible nonwoven sheet, preferably comprising depositing an elastomeric polymer.

The present invention also relates to an extensible nonwoven sheet comprising a nonwoven substrate that is necked in the necked direction and substantially uniformly impregnated with the elastomeric polymer, wherein the extensible nonwoven sheet comprises three times the extensible nonwoven sheet in the necking direction. After extending to 140%, the ratio of third cycle unloading force at 100% elongation to third cycle loading force at 100% elongation is at least 0.3: 1.

The present invention also relates to an extensible nonwoven sheet comprising an easily extensible nonwoven substrate substantially uniformly impregnated with an elastomeric polymer, wherein the extensible nonwoven sheet is 30% three times in the machine direction. After extending to, the ratio of the third cycle unloading force at 30% elongation to the third cycle loading force at 30% elongation is at least 0.15: 1.

In the present invention, an extensible composite nonwoven sheet is provided by impregnating a necked nonwoven substrate or an easily extensible raw nonwoven substrate with a solution comprising a solvent and an elastomeric polymer. The necked nonwoven substrate or the easily extensible nonwoven substrate is impregnated under conditions that impregnate the nonwoven substrate substantially uniformly without forming a polymer layer on one surface thereof. After removal of the solvent, a breathable impregnated nonwoven sheet is obtained in which the high cycle specific load and fabric texture are unexpectedly harmonized compared to the periodic load in the machine direction (for excellent retention and smooth extensibility). In addition, the sheets of the present invention are typically simpler and thinner to manufacture than conventional multilayer extensible laminates. For example, the sheet of the present invention has a typical thickness of about 0.25 to 0.75 mm, but the extensible laminate is generally larger than 1.3 mm.

As used herein, the term “polymer” generally refers to, but is not limited to, homopolymers, copolymers (eg, blocks, grafts, random and alternating copolymers), terpolymers, and the like, and blends thereof. And modifiers. Also, unless specifically limited otherwise, the term "polymer" shall include all possible geometrical forms of the material. Non-limiting examples of this form include homogeneous, regular and irregular symmetry.

The term "polyester" as used herein will include polymers wherein at least 85% of the repeating units are condensation products of dicarboxylic acids with dihydroxy alcohols having linking groups produced by the formation of ester units. These include aromatic, aliphatic, saturated and unsaturated diacids and these alcohols. As used herein, the term “polyester” also includes copolymers (eg, block, graft, random and alternating copolymers), blends, and modifications thereof. A common example of polyester is poly (ethylene terephthalate) (PET), which is a condensation product of ethylene glycol and terephthalic acid.

As used herein, the term "polyurethane" will include block copolymers prepared by condensing difunctional polyols with diisocyanates and difunctional chain extenders, as described in detail below.

As used herein, the term "polyolefin" shall mean any hydrocarbon in a series of nearly saturated open chain polymer hydrocarbons consisting solely of carbon and hydrogen. Non-limiting examples of typical polyolefins are polyethylene, polypropylene, polymethylpentene, and various mixtures of ethylene, propylene, and methylpentene monomers.

The term "polyethylene" as used herein will include homopolymers of ethylene as well as copolymers in which at least 85% of the repeat units are ethylene units.

The term "polypropylene" as used herein will include homopolymers of propylene as well as copolymers in which at least 85% of the repeat units are propylene units.

As used herein, the term "elastomer polymer" is extensible to an elongated length that is at least about 160% of its relaxed non-bias length when it is molded into a sheet, fiber or film and also when a biasing force is applied. , Refers to any polymer that will recover at least 55% of its elongation once the stretchable bias is relaxed. For example, a 1 cm sample of material can be stretched to 1.6 cm or more and will be stretched to 1.6 cm by the application of force and will return to a length of 1.27 cm or less upon release of the force. There are many elastomeric materials that can be stretched much more (e.g. 100% or more), which is 60% of their relaxed length, many of which are readily available, e.g. 105% of their original relaxation length. Within a substantial extent of their original relaxation length.

The term "nonwoven" or "nonwoven web" as used herein, as opposed to a knitted fabric or woven fabric, is a structure of individual fibers, filaments or threads that are placed in an irregular manner without an identifiable pattern to form a flat material. It means.

The term "spunbond" filament, as used herein, is used to extrude a molten thermoplastic polymer material from a plurality of fine, generally circular spinneret capillaries as filaments, and then rapidly reduce the diameter of the extruded filaments by stretching. It means the filament to be formed. Other filament cross-sectional shapes, such as oval, multileaf, and the like can also be used. Spunbond filaments are generally continuous and have an average diameter of greater than about 5 μm. Spunbond nonwovens or nonwoven webs are formed by irregularly stacking spunbond filaments on a collecting surface, such as a porous screen or belt. Spunbond webs are generally bonded by methods known in the art, such as hot rolling calendering the web or passing the web through a saturated-steam chamber at elevated pressure. In addition, the web may be spot bonded by heat at a number of heat bond points present across the spunbond fabric.

As used herein, the term "machine direction (MD)" refers to the direction in which the nonwoven web is produced. The term "cross machine direction (XD)" generally refers to a direction perpendicular to the machine direction.

As used herein, the term "necking" refers to a nonwoven fabric, for example, by applying a force parallel to the machine direction of the nonwoven fabric to stretch the nonwoven fabric in the direction in which the force is applied, in a direction perpendicular to the stretching direction, eg For example, it refers to a method including reducing the width in the machine direction to adjust the width to the desired amount. The direction perpendicular to the stretching force is referred to herein as the "necking direction". Control of elongation and necking can occur at room temperature or above or below room temperature, and is limited to the increase in overall dimensions in the direction of stretching to the elongation required to tear or rupture the fabric.

As used herein, the terms "necked nonwoven" and "necked nonwoven substrate" refer to any nonwoven shrunk in one or more directions by a process such as stretching. A "neckable nonwoven" is a nonwoven in which one or more dimensions can shrink in a necking process. The term "neck reduction" is a ratio determined by measuring the difference between the unnecked dimension and the necked dimension (measured in the necking direction), then dividing the difference by the unnecked dimension and multiplying the generated ratio by 100. Point to. The necked nonwoven is generally extendable in the necking direction in an amount corresponding to (but not in a linear relationship) the neck reduction rate during necking. The extensibility of the necked nonwovens is herein used to neck the necked nonwovens as much as possible without stretching the individual fibers in the necked nonwovens, breaking any fiber-fiber bonds in the nonwovens, or tearing the nonwovens. It is measured as elongation by stretching in the direction.

As used herein, the term "easy extendable nonwoven" refers to the "30" described in the Test Methods section, without any further processing steps (eg, necking) other than those typically used in nonwoven fabrication processes. Force of less than 200 g / in. (G / in), typically less than 100 g / in, determined by the "force required to stretch%" method, to a machine of at least 30% (typically from about 60% to about 150%) without breaking Lateral elongated nonwovens. Elongation 50% means that a 10-inch wide sample can be stretched to 15 inches. Examples of suitable easily extendable unwoven nonwovens have a basis weight of about 15 to about 100 g / m 2, typically about 30 to 80 g / m 2, and machine direction fracture toughness determined by “break strength analysis” described in the test method section. This may be greater than 500 g / in. Easily extensible nonwovens may be spunlaced (also called hydroentangled), meltblown, or heat bonded nonwovens and may be prepared by such well known processes. have.

As used herein, the term "spunlace nonwoven" refers to the injection of high pressure water into a web (which may include preformed fabrics, spin-melt webs, airlaid webs, and carded webs) or batts. Refers to a fabric formed by colliding with water. Easily extensible nonwovens include type 8075 Sontara® (Sontara is a registered trademark of EI DuPont de Nemours and Compamy), and Taipei, Taiwan Flat spunlaced nonwovens, article number 4055-T, manufactured by Sheng Hung Industrial Company.

As used herein, the term "meltblown nonwoven" refers to a nonwoven formed by extruding a molten polymer through a die into a high velocity air stream of hot air or steam that converts the resulting filaments into fine, relatively short fibers. The fibers are deposited on a moving screen or belt and then reinforced by calendering, embossing, hot air or other heat bonding processes.

As used herein, the term "heat bonded nonwoven" refers to the fibers of a web or batt when heated in the presence or absence of pressure, for example by hot air, calendering, embossing, infrared heat, or other heat bonding processes. It refers to a fabric consisting of a web or batt of fibers containing a heat sensitive material that melts and adhesively bonds into a reinforced nonwoven web, such as a specially processed low melting binder fiber or thermoplastic powder having a lower melting point than web fibers.

As used herein, the term "nonwoven substrate" refers to a substrate that may be a necked nonwoven substrate or an easily extensible nonwoven substrate.

The term "nonwoven" as used herein refers to a fabric that may be a necked nonwoven or an easily extensible nonwoven.

As used herein, the term "substantially uniformly impregnated" or "substantially uniformly impregnated" refers to dispensing a treatment or solution uniformly throughout the entire volume.

The term "wet coagulation" as used herein refers to a coagulant that is a non-woven substrate impregnated with a solution comprising an elastomeric polymer dissolved in a solvent, which is non-solvent for the elastomeric polymer but miscible with the solvent used to form the elastomeric polymer solution. Describe the process of contacting with. The coagulating solution is also chosen so as not to dissolve the nonwoven substrate. The coagulant solidifies the polymer material and the solvent is removed into the coagulation liquid. The coagulant is then removed from the polymer-impregnated nonwoven by methods such as air drying or heating.

Neckable nonwovens suitable for use in the present invention include spunbond webs, bonded carded webs, and hydraulic woven webs. The neckable nonwoven fabric is preferably necked transversely using methods known in the art to achieve neck reduction rates of typically about 25 to about 75% such that the transverse elongation is from about 30% to about A necked nonwoven substrate of 300% is obtained. Neckable nonwovens useful in the present invention can be prepared from a number of thermoplastic polymers including non-elastomeric polyolefins such as polyethylene, polypropylene, ethylene copolymers, polyamides, polyesters, polystyrenes, and poly-4-methylpentene-1. have. Preferably, the neckable nonwoven, for example, comprises polypropylene, polyester or polypropylene-polyethylene copolymer. In a preferred embodiment, the neckable nonwoven is a spunbond polypropylene fabric or carded heat bonded polypropylene or polyester fabric. The neckable starting nonwoven substrate is preferably typically having a basis weight of about 10 g / m 2 to 50 g / m 2. Particular preference is given to relatively low basis weight neckable nonwovens (eg, basis weights of from about 10 g / m 2 to about 20-30 g / m 2). Nonwoven substrates are typically water vapor permeable. The neckable nonwoven substrate is generally necked to provide a necked nonwoven substrate having a basis weight greater than about 15 g / m 2.

Necked nonwovens are known in the art and generally extend the neckable nonwovens in the machine direction to provide necked nonwovens that are necked in the machine direction. Examples of necking processes are disclosed, for example, in US Pat. Nos. 4,443,513 to Meitner, US Pat. Nos. 4,965,122, 4,981,747 and 5,114,781 to Moman. Preferred necking processes are disclosed in US Pat. No. 35,206 to Hassenboehler Jr. et al. U.S. Re-licensed Patent 35,206 is a re-licensed patent of U.S. Patent 5,244,482 and is incorporated herein by reference. Necked nonwoven webs according to Hassenboeller's method are also referred to herein as "reinforced webs".

Necked nonwovens can be manufactured using a relatively low cost process, and have a high degree of transverse extension and other extension properties as they require a relatively low extension (load) force to extend the nonwoven in the cross machine direction. Preferred over nonwovens. Necked nonwovens are also generally non-extensible in the machine direction. That is, it generally has an elongation of less than about 10% when applied to bias force in the machine direction. Substantially extensible in one direction is highly desirable in any end use as discussed below.

In a preferred embodiment, the necked nonwoven substrate is a reinforcing web made using the method described in Hassenboeller's patent. This method passes a bonded thermoplastic nonwoven web having a relatively low workability extension through a heating zone (such as an oven) to increase the temperature of the web to the temperature between the softening point and the melting point of the polymeric web, while the web is directed in the machine direction. Drawing to artificially deform the transversely oriented fibers and reinforce the web transversely (necking). Stretching is performed by passing the web in band at a first linear velocity and withdrawing the web at a second linear velocity exceeding the first velocity. The ratio of the second speed to the first speed is, for example, about 1.1: 1 to about 2: 1. The starting bonded nonwoven web is a neckable nonelastomeric nonwoven and has an elongation at break evaluated during hot working, at strains greater than 2500% / min and at elevated temperatures above the softening point of the polymeric web and at least 10 ° F. below the melting point. Is chosen to be less than about 4.0: 1 and greater than about 1.4: 1. Elongation at break (strain) is, for example, 2 to 40%, typically 5 to 20%, based on test method ASTM D 1117-77 using an Instron tensile tester.

The fibers in the starting web can be joined by thermal bonding, such as fiber-fiber fusion, fiber weaving, or point bonding. Typically, the fibers in the neckable nonwoven have a small average fiber diameter, for example less than about 50 μm. Bonding within the spunbond precursor is typically strong (eg, hot point bonding), which locally stretches, buckles and flexes the filament segments without affecting web integrity. In spot junctions, the junction and bond pattern are generally selected such that the area of the junction is about 5 to about 25% of the web area. The shape of the junction can be diamondoid or any of a number of shapes well known in the art.

The heat stretching step causes artificial deformation of the transverse fibers and reinforcement of the web, aligning the majority of the fibers in the stretching direction (machine direction) as a whole. As the web is stretched in the longitudinal direction, it is reinforced in the machine direction and thermosets relative to the starting nonwoven.

The necked nonwoven substrate having a transverse elongation of at least 30%, for example at least 50%, can be used to prepare the elastic nonwoven sheet of the present invention. The neck reduction rate of the nonwoven web during the reinforcing process is, for example, from about 50% to about 75%, typically from about 60% to, respectively, corresponding to an elongation of about 100% to about 300%, and 150% to 250%. 70%.

The basis weight of the necked nonwoven web may be at least three times greater than the basis weight of the neckable starting nonwoven web. The basis weight of the necked web is from about 15 g / m 2 to about 100 g / m 2, for example from about 20 g / m 2 to about 100 g / m 2, typically from about 25 g / m 2 to about 100 g / m 2. The basis weight of the necked nonwoven substrate is selected according to the desired end use. For example, when used as an elastic interliner, the basis weight of the necked nonwoven is typically from about 30 g / m 2 to 70 g / m 2, while the basis weight is typical for hygienic end uses such as diaper waistbands and the like. About 15 g / m 2 to 40 g / m 2. The basis weight of the necked nonwoven substrate should also be chosen to achieve the desired elasticity for the final impregnated nonwoven fabric. The higher the basis weight of the nonwoven substrate, the more elastomeric polymer can be impregnated into the nonwoven, thereby increasing the specific load of the impregnated nonwoven sheet.

는 예를 들어 0.45:1보다 크다.The use of relatively low basis weight nonwovens in the necking process described in Hassenboeller's patent is preferred for preparing the materials produced according to the present invention. After using these factors together and impregnating with the elastomeric polymer, an extensible nonwoven is provided having a relatively low force (load force) required to extend the material and a relatively high restoring force (non-load force) applied by the material. This feature is desirable for the end use expected for such materials. The relationship between unloading force and loading force is related to hysteresis of elastic nonwovens. For preferred products of the present invention having a transverse elongation of at least 150%, the impregnated nonwovens are extended three times to 140% and relaxed between extension, resulting in a no-load force at 100% elongation versus load at 100% elongation. The ratio of the forces is at least 0.3: 1,

Is greater than 0.45: 1, for example.

Elastomeric polymers useful in the present invention include polyurethanes, styrene-butadiene block copolymers, and polyether-ester block copolymers. In a preferred embodiment, the elastomeric polymer is a polyurethane.

Elastomeric polyurethanes useful in the present invention react polymeric glycols with diisocyanates to form capped glycols, dissolve the protected glycols (in a suitable solvent), and then have protected glycols and active hydrogen atoms. It can manufacture by making a bifunctional chain extender react. These polyurethanes are said to be "segmented" because they consist of "hard" urethane and urea segments derived from diisocyanates and chain extenders, and "soft" segments derived primarily from polymeric glycols. Suitable solvents for preparing solutions of such polymers are amide solvents such as dimethylacetamide ("DMAc"), dimethylformamide ("DMF"), and N-methyl-pyrrolidone, but dimethyl sulfoxide and tetramethylurea Other solvents such as may also be used.

Polymeric glycols used in the production of elastomeric polyurethanes include polyether glycols, polyester glycols, polycarbonate glycols and copolymers thereof. Examples of such glycols include poly (ethylene ether) glycol, poly (tetramethylene ether) glycol, poly (tetramethylene-co-2-methyl-tetramethylene ether) glycol, poly (ethylene-co-butylene adipate) glycol, Poly (2,2-dimethyl-1,3-propylene dodecanoate) glycol, poly (pentane-1,5-carbonate) glycol, and poly (hexane-1,6-carbonate) glycol.

Useful diisocyanates include 1-isocyanato-4-[(4-isocyanatophenyl) methyl] benzene, 1-isocyanato-2-[(4-isocyanatophenyl) methyl] benzene , Isophorone diisocyanate, 1,6-hexane diisocyanate and 2,4-tolylene diisocyanate.

The chain extender may be a diol or diamine. Useful diols include ethylene glycol, 1,3-trimethylene glycol, 1,4-butanediol and mixtures thereof. The use of diol chain extenders produces polyurethane. Examples of useful diamines are ethylene diamine, 1,2-propanediamine, 2-methyl-1,5-pentanediamine, 1,3-diaminopentane, 1,4-cyclohexane-diamine, 1,3-cyclohexanediamine And mixtures thereof. In this case, the resulting polymer is polyurethaneurea (subclass of polyurethane). When polyether glycols and diamine chain extenders are used, the resulting polymer is polyetherurethaneurea, and when polyester glycols are used with diamine chain extenders, polyesterurethaneureas are produced. Monofunctional amine chain terminators (eg diethyl amine, butylamine, cyclohexylamine, etc.) may be added to control the molecular weight of the polymer. In a preferred embodiment, the elastomeric polymer is a diamine-extended polyurethane elastomer.

Suitable solvents for preparing the elastomeric polymer solution include dimethylacetamide, dimethylformamide and N-methyl-pyrrolidone. The viscosity of the elastomeric polymer solution is directly related to the concentration of polymeric material in the solution, and therefore the solution viscosity will affect the degree of penetration of the polymer into the necked nonwoven or readily extensible raw nonwoven and the amount of polymer deposited. Can be. If the solution viscosity is too low, insufficient amount of elastomer is deposited in the necked nonwoven substrate or the easily extensible nonwoven substrate, resulting in low specific load forces. If the solution viscosity is too high, the penetration of the solution into the nonwoven substrate is reduced, resulting in incomplete or non-uniform impregnation of the polymer into the nonwoven substrate, or the formation of a polymer layer on the nonwoven substrate surface. Solutions of elastomeric polymers that are impregnated into a necked nonwoven substrate or an easily extensible nonwoven substrate may, for example, have a solution viscosity measured at 25 ° C. of about 1,000 to 300,000 centipoise (“cP”), typically 10,000 to 40,000. cP. The solution may comprise about 5-20% by weight of polymer.

The necked nonwoven substrate or the easily extensible nonwoven substrate should be able to absorb the polymer solution, and the polymer solution should impregnate the nonwoven substrate substantially completely and uniformly. Thus, the necked nonwoven substrate or the easily extensible nonwoven substrate must be treated otherwise such that the polymer solution is not absorbed into the uncoated or necked nonwoven or easily extensible nonwoven. Elastomeric polymer solutions and / or nonwovens can include surfactants to promote impregnation of the web with the polymer solution. Suitable surfactants include nonionic wetting agents, such as polymeric surfactants.

Small amounts of additives such as pigments, antioxidants, ultraviolet stabilizers and lubricants can be added to the elastomeric polymer solution, provided these additives do not impair the advantages of the present invention.

In the elastomeric polymer solution there may be dispersed very short fine fibers, for example cellulose fibers from cotton pulp, cottonseed, or other synthetic or natural fibers less than about 0.10 inch (2.5 mm) in length, for example less than 0.5 mm. have. The fibers are typically small enough to allow the nonwoven to fully penetrate during the impregnation step. Short fibers may be added to the polymer solution in an amount sufficient to deposit about 3 to about 12 weight percent short fibers in the impregnated nonwoven sheet, calculated based on the total weight of the nonwoven / elastomeric polymer composite. Short fibers are typically added at about 10 to about 30 weight percent, such as about 10 to about 20 weight percent, to the elastomeric polymer solution based on the total weight of the short fibers, elastomeric polymer and solvent. The nonwoven sheet of the invention prepared by impregnating a necked nonwoven or an easily extensible nonwoven with an elastomeric polymer solution containing powdered cellulose provides a softer feel than that produced using an impregnation solution containing no short fibers. Can have Examples of very fine fibrous particulate materials suitable for use in polymer solutions are in powder form available under the trade name “Arbocel 30” available from J. Rettenmaier USA (Schocraft, Michigan, USA). Cellulose.

Any suitable method of coating an elastomeric polymer solution on a necked nonwoven substrate or an easily extensible nonwoven substrate or otherwise impregnating a necked nonwoven substrate or an easily extensible raw nonwoven substrate may be that the fabric is uniformly impregnated and the coating agent Can be used as long as it is not concentrated on one or the other surface of the necked nonwoven substrate or the easily extensible nonwoven substrate. Although coating methods may be used to treat the nonwoven substrate with the elastomeric polymer solution, the solution and nonwoven characteristics and coating process conditions may be selected so that the polymer solution wets the nonwoven substrate completely or otherwise is fully absorbed or induced into the nonwoven substrate. Note that no polymer layer is formed on either surface. In general, the amount of polymer solution applied during coating can be controlled using a coating tool fixed at a predetermined distance on the necked nonwoven or easily extendable raw nonwoven substrate. The solution may also be mechanically pressed into the nonwoven substrate. Rollers, platens, scrapers, knives and the like can be used as coating tools in the method of the present invention. Spraying the solution onto the nonwoven substrate may also be effective if the elastomeric solution impregnates the nonwoven substrate substantially completely and uniformly. Spraying force can be adjusted to obtain good penetration. Nonwoven substrates are known in the art as a "soak and squeeze" method in which a fibrous web is immersed or otherwise immersed in a tank containing an elastomeric polymer solution and then, for example, pressed between nip rolls to remove excess polymer solution. It can be impregnated with an elastomeric polymer solution using a process known in the art. This method is desirable to minimize the distance between both sides of the stretchable composite nonwoven sheet.

The necked nonwoven substrate or the easily extensible nonwoven substrate is impregnated with a polymer solution sufficient to provide the desired nonload / load force ratio for the final impregnated nonwoven sheet. The nonwoven substrate is typically impregnated with a polymer solution sufficient to deposit about 10 to about 80 weight percent, such as about 30 to about 50 weight percent of the elastomeric polymer, based on the total weight of the elastomeric polymer and the nonwoven substrate. If the amount of elastomer is too small, the ratio of unloading force to loading force may be undesirably low, and if the amount of elastomer is too large, the texture of the sheet surface may be undesirably tacky. The solution concentration and / or the amount of solution impregnated into the necked nonwoven or easily extendable raw nonwoven substrate can be adjusted to achieve the desired polymer content in the impregnated sheet. For example, using a lower polymer concentration in a solution while retaining similar elastomeric content on the impregnated sheet by using a wider gap between the nip rolls during application of the solution would result in a touch and non-load / load force ratio. It was observed that a product with improved coordination of.

Once the nonwoven substrate is impregnated with a solution comprising a solvent and an elastomeric polymer, the solvent is removed. The solvent is removed by removing the coagulation liquid after wet coagulation. Wet coagulation is surprisingly softer than heat drying and provides a product with a more cloth-like feel. Wet coagulation processes are well known in the art and are commonly used in the manufacture of artificial leather. Water is preferred as a coagulating liquid for reasons of ease of handling and low cost. Other suitable coagulants include methanol, ethanol, isopropanol, acetone or methylethyl ketone. The coagulation rate can be changed by adding a solvent for the elastomeric polymer, such as dimethylformamide, dimethylacetamide or N-methyl-pyrrolidone or other additives such as surfactants, to the coagulation solution. In addition, it is possible to change the solidification rate by adjusting the temperature of the coagulation bath. The slower the coagulation rate, the more attractive the impregnated nonwoven fabric after removing the solvent.

In the impregnated nonwoven sheet of the present invention, the elastomeric polymer phase uniformly distributed throughout the necked nonwoven substrate or the easily extensible nonwoven substrate is breathable. In addition, the impregnated nonwoven sheet is typically water vapor permeable.

The texture of the impregnated nonwoven sheet can be improved by linting the fibers by sanding or napping the surface of the impregnated sheet to obtain a softer feel. Napping involves passing the fabric over a rotating roll containing small metal points that effectively brush the fabric to lint the fiber surface. In sanding, the metal brush is replaced with a rolling roll coated with sandpaper. Typically, the impregnated fabric is nested or sanded on both sides. For example, the fabric can be sanded with sand of 80 to 200 grits.

Extensible impregnated nonwoven sheets of the present invention typically have a basis weight of from about 40 g / m 2 to about 100 g / m 2. They are particularly useful for waistbands or side panels of diapers and other personal care garments (such as underwear). Diapers are commercially assembled in long, high speed lines where various diaper components are typically added in the machine direction to prevent process slowdown. This is especially the case for elastomeric materials which generally elongate before insertion. Diapers generally contain about 20 or more individual components that must be accurately positioned in the correct position of the diaper during the high speed manufacturing process. This is much easier to achieve if the components (tape, sheets, fibers, etc.) are fed in the same direction as the diaper moves. In order to add the component transversely (eg waistband), the material itself may preferably be stretched transversely and supplied as a tape in the machine direction to the diaper manufacturing process. For example, the tape may be a long piece that is 7 inches wide and only 1 inch long, which is cut from the sheet and adhered to the diaper or other disposable underwear. In this process, in order to facilitate the supply into the process, it is also preferred that the diaper component supplied into the process is substantially non-extensible in the machine direction. The extensible nonwoven sheet of the present invention is particularly suitable for use in the process because it is substantially non-extensible in the machine direction and has a highly recoverable stretch in the cross-machine direction.

The stretchable nonwoven sheet of the present invention is also useful as an elastic interliner in various garments, especially in jackets and coats. An interliner is a fabric inserted between the outer and inner layers of a garment to impart or improve shape retention, padding, insulation, reinforcement, or to increase the volume of the garment. The stretchable nonwoven sheet of the present invention is particularly useful for such applications because of its low cost and the ability to comfortably provide stretchability to permanent elasticity and body circumferential dimensions.

Test Methods

Force required to stretch 30%

This analysis was performed on an Instron Model 5565 with a Merlin data acquisition software system. Merlin systems and instrument hardware are both available from Instron Corporaiton (Braintree, Massachusetts, USA). A nonwoven sheet sample 1 inch ± 0.05 inch wide (2.54 cm ± 0.13 cm) and about 8 inch (20.32 cm) in length is secured to a jaw of an Instron machine with a sample length of 3.00 inch (7.62 cm). The sample is made so that the length of the sample is aligned in the machine direction of the nonwoven. Samples are stretched at a rate of 6 inches / minute (15.24 cm / minute) to 30% elongation. Record the force (g) at 50% elongation.

Breaking strength analysis

This analysis was performed on an Instron Model 5565 equipped with a Merlin data acquisition software system. Merlin systems and instrument hardware are both available from Instron Corporation (Braintree, Massachusetts, USA). A nonwoven sheet sample of 1 inch ± 0.05 inch (2.54 cm ± 0.13 cm) and approximately 8 inch (20.32 cm) in length is secured to the jaw of an Instron machine with a sample length of 3.00 inch (7.62 cm). The sample is made so that the length of the sample is aligned in the machine direction of the nonwoven. The sample is stretched at a rate of 6 inches / minute (15.24 cm / minute) until the sample tears in two parts, and the maximum force in grams (g) is recorded.

Basis weight

The rectangular sample of the nonwoven sheet about 1.0 inches by 8.0 inches (2.54 cm by 20.32 cm) is carefully relaxed to avoid wrinkles. The length and width of the sample are measured to millimeters and the sample is weighed to one tenth of a milligram. The weight is divided by the calculated area and the result is expressed in g / m 2 up to 0.1 g.

Load force and non-load force analysis

This analysis was performed on an Instron Model 5565 equipped with a Merlin data acquisition software system. Merlin systems and instrument hardware are both available from Instron Corporation (Braintree, Massachusetts, USA). A nonwoven sheet sample of 1 inch ± 0.05 inch (2.54 cm ± 0.13 cm) and approximately 8 inch (20.32 cm) in length is secured to the jaw of an Instron machine with a sample length of 3.00 inch (7.62 cm). The sample is made so that the length of the sample is aligned in the machine direction of the nonwoven. The sample is stretched at a rate of 6 inches / minute (15.24 cm / minute) to 140% elongation and then relaxed to its original length. Repeat this two more times and record the forces (load forces) applied by the material in the extension cycle in the third cycle at 50%, 100% and 135% elongation based on the original sample length and similarly in the third relaxation cycle. The force (non-load force) applied by the material is also recorded at the same elongation. The results are expressed as re-cycle load and non-load forces at appropriate elongation.

Shinto analysis

A loose piece of non-wrinkle 1 inch (2.54 cm) wide and about 8 inches (20.32 cm) long nonwoven fabric is marked with a pen with two points 4.0 inches (10.2 cm) about the same distance from both ends of the fabric. Then, hold both ends of the fabric firmly with the thumb and index finger of both hands and extend the sample sufficiently but not so far that the sample will tear or cause any mechanical damage. Maximum elongation is seen by the person performing the test as a marked increase in resistance to elongation by the fabric. Then, the length between two mark points of the nonwoven is measured and the elongation (%) is calculated by the following formula (initial length is 10.2 cm):

% Elongation = {(extended length-initial length) / initial length} X 100%

When elongation is measured in the necking direction, the fabric sample is cut with the length aligned in the machine transverse direction (necking direction).

Example 1

Nip rolls of 30-inch (76.2 cm) wide, 15 g / m 2 wetted spunbond polypropylene nonwovens made by Avgol Nonwovens, Israel, at a speed of 89 feet / minute (27 m / min) Through a second nip roll operated at 115 ft / min (35 m / min) through a 72 inch (1.83 cm), 290 ° F. (143 ° C.) forced convection oven. In this process, a 30 inch wide (76.2 cm) nonwoven fabric is uniformly and smoothly reinforced ("necked") to 10 inches wide (25.4 cm) in the transverse direction. With minimal force, it was able to extend back to its original 30 inches (76.2 cm) transverse width. The necked nonwovens were essentially zero in machine direction elongation and had a basis weight of 32.0 g / m 2.

The necked nonwoven fabric has a 1800 molecular weight poly (tetramethylene ether) glycol, 1-isocyanato-4-[(4-isocyanato) on one surface by a 15 mil (0.38 mm) doctor knife. 20 weights of polyurethaneurea derived from phenyl) methyl] benzene (1.69 molar ratio of diisocyanate to glycol), chain extender (9: 1 molar ratio of ethylene diamine and 2-ethyl-1,5-pentanediamine) and diethylamine It was coated with% dimethylacetamide (DMAC) solution. The following additives were also used: bis (4-isocyanatocyclohexyl) methane) and polymers of (3-t-butyl-3-aza-1,5-pentanediol) (Methacrol®) 2462B, a registered trademark of Ei DuPont de Nemua & Co.) 0.5 wt%, titanium dioxide 0.3 wt%, silicone oil 0.6 wt%, 2,4,6-tris (2,6-dimethyl-4-t-butyl -3-hydroxybenzyl) isocyanurate (Cyanox® 1790, registered trademark of Cytec Industries) 1.4 wt%, and 4 wt% mixture of huntite and hydromagnesite % (All percentages are based on polyurethaneurea weight). The polyurethaneurea-DMAC solution fully wetted the nonwovens.

The coated nonwoven was suspended in air substantially vertically for about 1 minute to allow the polymer solution to fully penetrate into the nonwoven and then immersed in a 70 ° F. (21 ° C.) bath of 40 volume% DMAC in water. After 1 minute, the impregnated fabric was continuously transferred to 30% by volume, 20% by volume and 10% by volume DMAC / water solution for 1 minute, and finally soaked in 100% water bath for 2 minutes. The impregnated fabric was dried in air at room temperature.

The resulting impregnated nonwoven sheet exhibited the same texture and texture (dry, fabric-like) on both sides. From the photograph of the cross section of the impregnated nonwoven sheet, the thickness of the material showed that the composite structure was uniform and substantially free of zones of continuous polyurethane on both surfaces.

The nonwoven sheet was then lightly sanded with 220 g of sandpaper. The resulting material showed a noticeably softer texture, and visual observation showed that there were a large number of individual short fibers protruding from the surface as compared to a perfectly smooth surface without fibers protruding before sanding. Unexpectedly, this treatment succeeded in providing a softer feel with little compromise to the visual aesthetic or elastic properties of the sheet.

The basis weight of the resulting impregnated nonwoven sheet was 71.4 g / m 2, indicating a polyurethaneurea content of 39.4 g / m 2, or about 55% by weight of elastomeric polymer.

The resulting material was stretched by hand in the machine direction, resulting in about 160-180% elongation.

Load and non-load analysis provided the following results:

3rd cycle load

Elongation% Load force (g) 50 67.3 100 211.2 135 409.7

Third cycle non-load force

Elongation% Specific load capacity (g) 50 22.7 100 114.7 135 340.7

As a result of comparing the data in the table, the ratio of unloading force to loading force at 100% elongation was 0.54.

Example 2

헝 Part No. 4055-T, 55 g / m 2, of a flat spunlaced nonwoven fabric manufactured by Hung Industrial Company (Taiwan Sheen-Lingu Hou River 116, Taiwan), approx. 30 in length Pits were used in this example, which was run continuously. The nonwoven substrate was first obtained from INVISTA Inc. (Wilmington, Delaware, USA), T-162 Lycra (registered trademark) in dimethylacetamide (DMAC) with a solid content of 12.5%. Impregnation). The fabric speed was 3 ft / min and the total fabric length in the bath was about 6 inches. Removal of excess polymer solution was accomplished by passing the impregnated fabric through a nip roll at 0.007 inch intervals.

The resulting impregnated fabric was then passed through a bath of 40% DMAC dissolved in water, followed by two separate baths of 100% water. The fabric speed through these baths was 3 ft / min. The total fabric length in each bath was 8 feet. All baths were operated at room temperature, about 72 ° F. (40 ° C.). The resulting fabric was air dried to obtain a breathable stretchable nonwoven having attractive elastic properties and a basis weight of 80 g / m 2 (45 weight percent of T-162 lycra).

Passive elongation analysis of the resulting elastic nonwoven in the transverse direction showed that the elongation was 50 to 60%. Load and unload forces in the third cycle were performed as described in the Test Methods section, except that the sample was stretched to a maximum elongation of 50% and recorded unload resilience at 20%, 30% and 40% elongation. . This modified load and unload force analysis gave the following results:

3rd cycle load

Elongation% Load force (g) 20 92.6 30 227.2 40 425.9

Third cycle non-load force

Elongation% Load force (g) 20 20.0 30 75.9 40 192.0

As a result of comparing the data in the table, the ratio of specific load to loading force at elongation 30% was 0.33.

Claims (19)

Thickness, first outer surface and second outer surface, machine direction and machine direction, elongation at least 30% in machine direction, basis weight of 15 g / m 2 to 100 g / m 2, and breaking strength in excess of 500 g / in; Applying a force of less than 200 g / inch determined by the " force required to stretch 30% " method to provide a stretchable nonwoven substrate that is transversely stretched to at least 30% without breaking; Uniformly impregnating the extensible nonwoven substrate with a solution comprising an elastomeric polymer dissolved in a solvent; The solvent is removed from the extensible nonwoven substrate by wet coagulation to uniformly distribute the elastomeric polymer over the thickness of the nonwoven substrate without forming a continuous elastomeric polymer layer on the first or second outer surface of the nonwoven substrate. A method of forming an extensible nonwoven sheet, comprising depositing. The method of claim 1 wherein the elastomeric polymer is polyurethane. The method of claim 1, wherein the elastomeric polymer is deposited on the substrate at 10 to 80% by weight based on the total weight of the substrate and the elastomeric polymer. The method of claim 1, further comprising sanding or napping one or more of the outer surfaces of the nonwoven sheet after removing the solvent to lint the fibers on the sheet surface. After extending the stretchable nonwoven sheet to 50% three times in the machine direction, the ratio of the third cycle unloading force at 30% elongation to the third cycle loading force at 30% elongation is at least 0.15: 1, and the elastomeric polymer Comprises an impregnated nonwoven substrate which is uniformly impregnated and which is transversely stretched to at least 30% without breaking by applying a force of less than 200 g / inch determined by the "force required to stretch 30%" method, 10 to 80 weight percent of the elastomeric polymer, based on the total weight of the elastomeric polymer and the nonwoven substrate, The basis weight is 40g / m 2 to 100g / m 2, Extensible nonwoven sheet. delete delete A personal care garment comprising the stretchable nonwoven sheet of claim 5. The personal care garment of claim 8 comprising any one selected from the group consisting of diapers and underwear. A garment comprising the stretchable nonwoven sheet of claim 5 which is an interliner. delete delete delete delete delete delete delete delete delete