JP4918480B2 - Elastic nonwoven sheet - Google Patents

Description

  The present invention relates to an extensible nonwoven sheet suitable for use in the manufacture of personal hygiene articles. More particularly, the stretchable nonwoven sheet comprises substantially homogeneous impregnation of an elastomeric polymer into a necked nonwoven substrate or an easily stretchable as-made nonwoven substrate. It is formed by.

(Cross-reference of related applications)
This application claims priority from US Provisional Patent Application No. 60 / 565,014 (Filing Date: April 23, 2004, which provisional application is a US patent application Ser. No. 10 / 413,172 ( Filed on Apr. 14, 2003) and this patent application is a part of US patent application Ser. No. 10 / 353,677 (filing date: Jan. 29, 2003, currently abandoned). Pending applications (these applications are incorporated herein by reference).

  Elastic nonwoven materials are well known to those skilled in the art. Examples of elastic nonwoven materials may include “elongated bonded” laminates and “neck bonded” laminates. Stretch bonded laminates can be gathered when the layers are loosened by keeping the elastic layers stretched and combining the elastic layers with layers that can be gathered. It is prepared by gathering in a layer. Neck bonded laminates are manufactured by matching a necked inelastic layer to an elastic film over a fiber layer. The elastic layer generally includes an elastic film or an elastic nonwoven web. For those elastic nonwoven laminates, it is necessary to prepare at least two different nonwoven or film layers.

  U.S. Patent Publication to Riedel describes at least 50 weight percent stretchable fabric capable of stretching at least 30% without tearing and at least 15 weight percent in the fabric. A breathable elastic bandage material is described which comprises an elastomer impregnated in the fabric without filling the pores.

U.S. Patent Publication to Morman discloses a neckable material such as a nonwoven web where an elastomeric precursor is applied, the neckable material is necked and stretched, and the neckable material is necked. A method is described for producing an extensible composite material by allowing the elastomeric precursor to be treated, for example, by heating, to form an elastomeric layer adhered to the necked material. . Suitable elastomer precursors include latex or thermoset elastomers. The elastomeric precursor is applied to the neckable material in an amount between 5 g / m ² and about 50 g / m ² . The elastomeric layer typically penetrates the web at a fiber thickness of about 2 to about 10 fibers, but the degree of penetration of the elastomeric precursor is adjusted to provide the side of the web to which the elastomeric layer is applied. Do not ooze to the other side. Thus, the resulting stretchable composite material has a film-like feel on the side containing the elastomeric layer and the original soft feel of the neckable material on the side opposite the elastomeric layer. Remain.

  (Patent Document 3) describes an elastomeric saturated nonwoven material having compressibility and recoverability in the Z direction, including fiber webs such as elastomeric acrylic latex, polyurethane latex, or nitrile rubber latex. Nonwoven webs, such as meltblown fibers, saturated with such polymeric materials are included.

  (Patent Document 4) aims at a belt for use in a conveyor or power transmission manufactured by impregnating a needle punched nonwoven fabric with rubber or synthetic resin.

US Pat. No. 4,366,814 US Pat. No. 5,910,224 European Patent Application No. 0472294 JP 47-24479 A U.S. Pat. No. 4,443,513 US Pat. No. 4,965,122 US Pat. No. 4,981,747 US Pat. No. 5,114,781 US Reissue Patent No. 35,206 Specification US Pat. No. 5,244,482

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

The present invention is directed to a method for forming an extensible nonwoven sheet comprising the following steps:
Providing a necked nonwoven substrate having a thickness, first and second outer surfaces, and a machine direction and a transverse direction, wherein the necked nonwoven substrate is at least 30% in the transverse direction. A process having a percent elongation;
A step of substantially uniformly impregnating the necked nonwoven fabric substrate with a solution containing an elastomeric polymer dissolved in a solvent; and removing the solvent from the impregnated nonwoven fabric substrate by wet coagulation, Depositing the elastomeric polymer substantially uniformly throughout the thickness of the material and not forming a substantially continuous layer of elastomeric polymer on either the first or second outer surface of the nonwoven substrate; Process.

The present invention is further directed to a method for forming an extensible nonwoven sheet comprising the following steps:
A thickness, a first and second outer surface, a machine direction and a transverse direction, a percent elongation of at least 30% in the transverse direction, and a basis weight between about 15 g / m ² and about 100 g / m ² ; Providing an easily stretchable unprocessed nonwoven substrate having a fracture toughness greater than 500 g / inch;
Impregnating the easily stretchable unprocessed nonwoven substrate with a solution containing an elastomeric polymer dissolved in a solvent substantially homogeneously, and the easily stretchable unprocessed nonwoven fabric Solvent is removed from the substrate by wet coagulation to deposit the elastomeric polymer substantially uniformly throughout the thickness of the nonwoven substrate and on either the first or second outer surface of the nonwoven substrate. Not forming a substantially continuous layer of elastomeric polymer.

  A further object of the present invention is an extensible nonwoven sheet comprising a nonwoven substrate that is necked in the necking direction and substantially homogeneously impregnated with an elastomeric polymer, the extensible nonwoven sheet However, when the stretchable nonwoven sheet is stretched 140% in the necking direction three times, the ratio of the stress at 100% elongation in the third dewetting cycle to the stress at 100% elongation in the third weighting cycle is It is at least 0.3: 1.

  In addition, the present invention is directed to a stretchable nonwoven sheet comprising a non-stretchable easily stretchable nonwoven substrate impregnated substantially uniformly with an elastomeric polymer. When the stretchable nonwoven sheet is stretched 30% in the transverse direction three times, the ratio of the stress at 30% elongation in the third dewetting cycle to the stress at 30% elongation in the third weighting cycle is , At least 0.15: 1.

  In the present invention, a stretchable composite nonwoven fabric sheet is impregnated by impregnating a necked nonwoven fabric substrate or an easily stretchable non-processed nonwoven fabric substrate with a solution containing a solvent and an elastomeric polymer. Can be obtained. The necked nonwoven substrate or the easily stretchable non-processed nonwoven substrate substantially homogenizes the nonwoven substrate without forming a polymer layer on any surface of the nonwoven substrate. Impregnation is performed under conditions that allow impregnation. After removing the solvent, a breathable impregnated nonwoven sheet is obtained, which is unexpectedly high in terms of lateral weight, high degenerative cycle stress (good holding power and soft elongation) compared to the weighted cycle stress. Property) and the texture of fabric. Furthermore, the sheets of the present invention are typically easier to manufacture and thinner than conventional multilayer extensible laminates. For example, the sheets of the present invention typically have a thickness of about 0.25 mm to 0.75 mm, whereas extensible laminates are generally thicker than 1.3 mm.

  As used herein, the term “polymer” generally includes homopolymers, copolymers (eg, block, graft, random and alternating copolymers), terpolymers, and the like, and blends and modifications thereof. It is not necessarily limited to. Further, unless otherwise specified, the “polymer” is intended to include all possible configurations of the substance. Such configurations include (but are not limited to) isotactic, syndiotactic and random symmetries.

  As used herein, the term “polyester” refers to a polymer in which at least 85% of the repeating units are the condensation reaction product of a dicarboxylic acid and a dihydroxy alcohol, and the linkage is obtained by the formation of ester units. Is intended to be included. Included are aromatic, aliphatic, saturated, unsaturated diacids and diols. As used herein, the term “polyester” further includes copolymers (eg, block, graft, random and alternating copolymers), blends, and modifications thereof. A common example of a polyester is poly (ethylene terephthalate) (PET), which is a condensation product of ethylene glycol and terephthalic acid.

  As used herein, the term “polyurethane” is intended to encompass block copolymers made by condensing a bifunctional polyol with a diisocyanate and a bifunctional chain extender, This will be described in detail below.

  As used herein, the term “polyolefin” is intended to mean a series of nearly saturated open-chain polymeric hydrocarbons consisting solely of carbon and hydrogen. Exemplary polyolefins include, but are not limited to, polyethylene, polypropylene, polymethylpentene, and various combinations of ethylene, propylene, and methylpentene monomers.

  As used herein, the term “polyethylene” is intended to encompass not only ethylene homopolymers, but also copolymers in which at least 85% of the repeat units are ethylene units.

  As used herein, the term “polypropylene” is intended to encompass not only a homopolymer of propylene, but also a copolymer in which at least 85% of the repeating units are propylene units.

  As used herein, the term “elastomeric polymer” refers to at least about the length of a licking force when applied to a sheet, fiber, or film when loosened and no licking force is applied. Refers to various polymers that extend to an extension length of 160 percent and that at least 55 percent of the extension is restored when the stretched diagonal force is removed. For example, if there is a 1 centimeter material sample that can be stretched to at least 1.6 centimeters, when a force is applied to stretch to 1.6 centimeters and then the force is removed, It recovers to a length of 1.27 centimeters or less. There are many elastomeric materials that can be stretched to more than 60% of the length when no force is applied, e.g., 100 percent or more, many of which, when excluding that stretching force, It recovers to a length when substantially no force is applied to those of the original, eg, within 105 percent of the length when the original force is not applied.

  As used herein, the term “nonwoven fabric” or “nonwoven web” refers to a planar material that is randomly placed and does not have a distinct pattern, as opposed to a knitted or woven fabric. Means the structure of individual fibers, filaments, or yarns that form

  As used herein, the term “spunbond” filament refers to extruding molten thermoplastic polymer material as filaments from a plurality of fine, usually circular capillaries of a spinneret, and then stretching. It means a filament formed by rapidly reducing the diameter of the extruded filament. It is also possible to use other filament cross-sectional shapes, such as elliptical, multilobal, etc. Spunbond filaments are generally continuous and their average diameter is greater than about 5 micrometers. Spunbond nonwoven fabrics or webs are formed by randomly stacking spunbond filaments on a collection surface such as a perforated wire mesh or belt. Spunbond webs are generally bonded by methods known to those skilled in the art, for example, by heated roll calendering, or by passing the web through a saturated steam chamber under high pressure. Further, the web can be bonded by heating at a plurality of heating bonding points provided in the width direction of the spunbond fabric.

  As used herein, the term “machine direction” (MD) is used to refer to the direction in which the nonwoven web is being manufactured. The term “lateral direction” (XD) generally refers to a direction perpendicular to its longitudinal direction.

  As used herein, the term “necking” refers to applying a force to a nonwoven fabric, eg, parallel to the nonwoven machine direction, causing the nonwoven fabric to stretch in the direction of the force, It refers to a method that includes reducing the width while adjusting the perpendicular direction, eg, the lateral width, to a desired degree. In this specification, a direction perpendicular to the stretching force is referred to as a “necking direction”. It is possible to cause controlled stretching and necking at room temperature or above or below room temperature, but it increases the overall dimension in the stretched direction until stretching required for tearing or breaking the fabric. Limited.

  As used herein, the terms “necked nonwoven fabric” and “necked nonwoven substrate” refer to various nonwoven fabrics that have been deflated in at least one direction, for example by a process such as stretching. Used for. A “neckable nonwoven fabric” is a nonwoven fabric that can be deflated in at least one direction in a necking process. The term "percent neck down" measures the difference between an unnecked dimension and a necked dimension (measured in the direction of necking), then divides the difference by the unnecked dimension, The ratio is obtained by multiplying the ratio by 100. The necked non-woven fabric can generally be stretched in the necking direction to an amount (but not a linear relationship) that corresponds to a percent neck down during necking. In the present specification, the stretchability of the necked nonwoven fabric is within a range that does not stretch individual fibers in the nonwoven fabric, break the bond between the fibers in the nonwoven fabric, or tear the nonwoven fabric. Measured as percent elongation by stretching the necked nonwoven to the maximum possible in the necking direction.

As used herein, the term “easy-stretchable non-processed non-woven” refers to adding no additional processing steps (eg, necking) beyond the range normally used in non-woven manufacturing processes, A force of at least 30% (typically about 60% to about 150%) in lateral extension, less than 200 grams / inch (g / inch), typically less than 100 g / inch Force is used to mean a non-woven fabric that does not break upon application of the “force required to stretch 30%” method described in the Test Methods section. 50% elongation means that a 10 inch wide sample can be stretched to 15 inches. Examples of suitable easily stretchable non-processed nonwovens have a basis weight of about 15 to about 100 grams / square meter (g / m ² ), typically about 30 to about 80 g / m ^2. It is preferable that the longitudinal fracture toughness obtained by the “fracture toughness analysis” described in the test method section is larger than 500 g / inch. Easily stretchable non-processed nonwovens can be spunlaced (sometimes referred to as wet entanglement), meltblown, or thermal bonded nonwovens and can be made by their well-known processes .

  As used herein, the term “spunlaced nonwoven” refers to spraying a jet of high pressure water onto a web (which can include preformed fabrics, spunmelt webs, airlaid webs and card webs) or bats. Used to refer to the fabric formed by Non-additionally processed non-woven fabrics that can be easily stretched include Type 8075 Sontara® (Sontara® is a product of EI DuPont de Nemours and Company (E I. Dupont de Nemours and Company), and flat-type spunlaced nonwoven fabric, product number 4055-T (from Sheng Hung Industrial Company, Taipei, Taiwan) ).

  As used herein, the term “meltblown nonwoven” refers to extruding molten polymer through a die into a high velocity stream of hot air or steam, thereby converting the resulting filaments into fine, relatively short fibers. Used to refer to manufactured nonwovens. The fibers are deposited on a moving screen or belt and then consolidated by calendering, embossing, heated air or other thermal bonding methods.

  As used herein, the term “thermally bonded nonwoven” is subject to heat, such as a specially designed low melting binder fiber or thermoplastic powder having a lower melting point than the web fiber. Used to refer to fabrics made of webs or bats containing fragile materials, and their low melting binder fibers or thermoplastic powders, for example, heated air, calendering, embossing, in the presence or absence of pressure Then, it is melted by being heated by an infrared heating method, other thermal bonding methods, and the like, and a web or vat fiber is adhesively bonded to form a solidified nonwoven fabric.

  As used herein, the term “nonwoven substrate” refers to a substrate that can be either a necked nonwoven substrate or an unprocessed nonwoven substrate that is easily stretchable. Used for.

  As used herein, the term “nonwoven fabric” refers to a fabric that can be either a necked nonwoven fabric or an unprocessed nonwoven fabric that is easily stretchable. Used.

  As used herein, the terms “substantially homogeneously impregnated” or “substantially homogeneously impregnated” are used to refer to evenly dispersing the treatment agent or solution throughout the bulk volume. .

  As used herein, the term “wet coagulation” refers to a nonwoven substrate impregnated therein with a solution comprising an elastomeric polymer dissolved in a solvent, although the elastomeric polymer is non-solvent. It is used to describe the process of contacting a coagulating liquid that is miscible with the solvent used to form the elastomeric polymer solution. The coagulation liquid is further selected from such that it does not dissolve the nonwoven substrate. The coagulating liquid coagulates the polymer material and removes the solvent into the coagulating liquid. The solidified liquid is then removed from the polymer impregnated nonwoven by, for example, air drying or heating.

Neckable nonwoven fabrics suitable for use in the present invention include spunbond webs, bonded card webs, wet entangled webs, and the like. Typically, using methods known to those skilled in the art, the neckable nonwoven fabric is necked in the cross direction to achieve a percent neck down of about 25% to about 75%, thereby causing the cross direction It is preferred to obtain a necked nonwoven substrate having a percent elongation between about 30% and about 300%. The neckable nonwoven fabrics useful in the present invention can be made from a number of thermoplastic polymers such as polyethylene, polypropylene, ethylene copolymers, polyamides, polyesters, polystyrenes, and poly- Non-elastomeric polyolefins such as 4-methylpentene-1. Preferably, the neckable nonwoven fabric includes, for example, polypropylene, polyester, or polypropylene-polyethylene copolymer. In preferred embodiments, the neckable nonwoven fabric is a spunbond polypropylene fabric or a carded thermal bond polypropylene or polyester fabric. Necking possible nonwoven substrate of the starting typically preferably has a basis weight between about 10 g / m 2 ^~ about 50 g / m ^2. From about 10 g / ^{m 2,} such as to have a basis weight of between about 20 to 30 g / ^{m 2,} a relatively low necking possible nonwoven basis weight is particularly preferred. Nonwoven substrates are typically water vapor permeable. The neckable nonwoven substrate is necked to obtain a necked nonwoven substrate having a basis weight generally greater than about 15 g / m ² .

  Necked nonwoven fabrics are known to those skilled in the art, and a neckable nonwoven fabric is stretched in the machine direction to obtain a necked nonwoven fabric that is necked in the transverse direction. Examples of necking processes are disclosed, for example, in the following patents: US Patent Publication to Meitner et al. (Patent Document 5) (Meitner), US Patent Publication (Patent Document 6), US Patent Gazette (Patent Document 7), and US Patent Publication (Patent Document 8) (all above Morman). A suitable necking process is disclosed in U.S. Patent Publication (US Pat. No. 5,677,097) to Hassenboehler Jr et al. US Patent Publication (Patent Document 9) is a reissued patent of US Patent Publication (Patent Document 10), which is incorporated herein by reference. Nonwoven webs necked by the Hassenboehler process may also be referred to herein as “consolidated webs”.

  Necked nonwovens can be prepared using a relatively low cost process, have a high level of lateral stretch, and have a relatively low elongation (load) stress to stretch the nonwoven in the transverse direction. It is preferred over other stretchable nonwoven fabrics because it only requires. Further, the necked nonwoven fabric is generally substantially unstretchable in the machine direction, i.e., has a percent elongation of less than about 10% when biased in the machine direction. The ability to extend in substantially only one direction is highly desirable in certain end uses, as will be discussed later.

  In a preferred embodiment, the necked nonwoven substrate is a consolidated web prepared using the method described by Hassenboehler. The method includes passing a bonded thermoplastic nonwoven web having a relatively low work extensibility through a heating zone such as an oven to adjust the temperature of the web to the softening and melting temperatures of the polymer web. It is a process in which the web is stretched to the temperature in the meantime, and the web is stretched in the longitudinal direction, whereby the fibers oriented in the transverse direction are plastically deformed and the web is consolidated in the transverse direction (necking). . The stretching is performed by passing the web through the zone at a first linear velocity and withdrawing the first velocity at a higher second linear velocity. The ratio of the second speed to the first speed ranges, for example, from about 1.1: 1 to about 2: 1. The bonded non-woven web of starting material is a non-elastomeric neckable non-woven fabric having a draw rate higher than 2500% / min and at least 10 higher than the softening point but above the melting temperature of the polymer web. When evaluated while hot stretched at a temperature as low as 0 ° F., it is selected to have a heat stretch break ratio lower than about 4.0: 1 but higher than about 1.4: 1. The elongation at break (strain) at room temperature is, for example, between 2 and 40 percent, typically 5 to 20 percent using an Instron tensile tester according to ASTM D 1117-77 test method. Between.

  The fibers in the starting web can be bonded by fiber-to-fiber fusion, fiber entanglement, or thermal bonding methods such as point bonding. The fibers in the neckable nonwoven fabric typically have a small average fiber diameter, for example, less than about 50 micrometers. Adhesion in spunbond precursors is typically strong (such as hot spot adhesion) so that the filament segments can be locally stretched, shrunk, bent without sacrificing web integrity. Can be. In point bonding, generally the bonding points and bonding pattern are selected such that the area of the bonding points is between about 5 and about 25% of the web area. The shape of the adhesion point may be a diamond shape or other shapes well known to those skilled in the art.

  The heat drawing process causes plastic deformation of the fibers in the transverse direction and web consolidation, so that most of the fibers are generally arranged in the drawing direction (longitudinal direction). The web is consolidated and heat set in the transverse direction while being stretched in the longitudinal direction compared to the nonwoven fabric at the start.

  An elastic nonwoven sheet of the present invention can be prepared using a necked nonwoven substrate having a lateral elongation of at least 30%, such as at least 50%. The percent neck down of the nonwoven web during the consolidation process is, for example, between about 50% and about 75%, typically between about 60% and 70%, each of which is about 100% It corresponds to stretching between ˜300% and between 150% and 250%.

The basis weight of the necked nonwoven web can be greater than or equal to three times the basis weight of the starting neckable nonwoven web. The basis weight of the web was necking is between about 15 g / ^{m 2} ~ about 100g / ^{m 2,} for example between about 20 g / ^{m 2} ~ about 100g / ^{m 2,} typically about 25 g / ^{m 2} ~ about 100g / 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 has a basis weight of nonwoven fabric obtained by necking, which is typically between about ^{30g / m 2 ~70g / m 2} , such as the waistband of the diaper to it in the case of sanitary end use as is, its basis weight is typically between about ^{15g / m 2 ~40g / m 2} . The basis weight of the necked nonwoven substrate should be further selected so that the desired elasticity is obtained in the final impregnated nonwoven. In a nonwoven fabric substrate having a high basis weight, more nonwoven elastomer polymer can be impregnated into the nonwoven fabric to increase the dewetting stress of the impregnated nonwoven fabric sheet.

  In order to prepare the material produced according to the present invention, it is preferred to use a relatively low basis weight nonwoven fabric in the necking process, as described in Hassenboehler. When they are used together and impregnated with an elastomeric polymer, these factors overlap, and the stress required to stretch the material (weight stress) is relatively low, depending on the material needed to loosen it A stretchable nonwoven fabric having a relatively high shrinkage force (dewetting stress) is obtained. Such properties are preferred for end uses envisaged for this material. The relationship between the weight stress and the weight stress is related to the hysteresis of the elastic nonwoven fabric. In preferred products of the invention having a percent elongation in the transverse direction of at least 150%, the impregnated nonwoven is 100% stretched after being stretched to 140% three times (while loosening during stretching). The ratio of the dewetting stress at 100% elongation to the weighted stress is at least 0.3: 1 and y is greater than, for example, 0.45: 1.

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

  Elastomeric polyurethanes useful in the present invention react with a high molecular weight glycol with a diisocyanate to form a capped glycol, dissolve the capped glycol (in a suitable solvent), and then convert the capped glycol to an active hydrogen atom. It can be prepared by reacting with a bifunctional chain extender having Such polyurethanes are referred to as being “segmented” because they are derived from “hard” urethane and urea segments derived from diisocyanates and chain extenders and primarily from high molecular weight glycols. This is because it consists of “soft” segments. Suitable solvents for the solution to prepare such polymers are amide solvents such as dimethylacetamide ("DMAc"), dimethylformamide ("DMF"), and N-methyl-pyrrolidone, but other solvents such as dimethyl Sulphoxide, tetramethylurea and the like can also be used.

  High molecular weight glycols used in preparing elastomeric polyurethanes can include polyether glycols, polyester glycols, polycarbonate glycols, and copolymers thereof. Such glycols may include the following: 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-isocyanato-phenyl) methyl] benzene, isophorone diisocyanate, 1,6-hexane. Examples include diisocyanate and 2,4-tolylene diisocyanate.

  The chain extender may be a diol or a diamine. Useful diols include ethylene glycol, 1,3-trimethylene glycol, 1,4-butanediol, and mixtures thereof. If a diol chain extender is used, polyurethane can be obtained. Useful diamines include ethylenediamine, 1,2-propanediamine, 2-methyl-1,5-pentanediamine, 1,3-diaminopentane, 1,4-cyclohexane-diamine, 1,3-cyclohexanediamine, and the like And the like. In this case, the resulting polymer is a polyurethaneurea (a subclass of polyurethane). When polyether glycol and a diamine chain extender are used, the resulting polymer is a polyether urethane urea, and when polyester glycol is used in combination with a diamine chain extender, a polyester urethane urea is obtained. . It is possible to adjust the molecular weight of the polymer by adding monofunctional amine chain terminators such as diethylamine, butylamine, cyclohexylamine and the like. In a preferred embodiment, the elastomeric polymer is a diamine-stretched polyurethane elastomer.

  Suitable solvents for preparing the elastomeric polymer solution can include dimethylacetamide, dimethylformamide, and N-methyl-pyrrolidone. Since the viscosity of an elastomeric polymer solution is directly related to the concentration of the polymer material in the solution, the solution viscosity is polymer into a necked nonwoven fabric or an easily stretchable non-processed nonwoven fabric. Can affect both the degree of penetration and the amount of polymer deposited therein. If the solution viscosity is too low, the amount of elastomer that can be deposited in a necked nonwoven substrate or in an unprocessed nonwoven substrate that can be easily stretched is insufficient, and the dewetting stress is reduced. It will be lower. If the solution viscosity is too high, the penetration of the solution into the nonwoven substrate will be reduced, so that the polymer impregnation into the nonwoven substrate or the polymer layer on the surface of the nonwoven substrate Formation may be incomplete or inhomogeneous. Solutions of elastomeric polymers that are impregnated into a necked nonwoven substrate or an easily stretchable non-processed nonwoven substrate are, for example, about 1000-300,000 centipoise (“cPs”) measured at 25 ° C. ), Typically having a solution viscosity of 10,000 to 40,000 cPs. The solution may contain about 5% to 20% polymer by weight.

  Necked nonwoven substrate or easily stretchable non-processed nonwoven substrate can absorb the polymer solution and the polymer solution is impregnated into the nonwoven substrate substantially completely and homogeneously It is necessary to be done. Thus, a necked nonwoven substrate or an easily stretchable non-processed nonwoven substrate is in a polymer solution necked nonwoven fabric or an easily stretchable non-processed nonwoven fabric. There must be no coatings or other treatments that would prevent it from being absorbed. The elastomeric polymer solution and / or the non-woven fabric may include a surfactant to facilitate the web to be impregnated with the polymer solution. Suitable surfactants include nonionic wetting agents such as high molecular weight surfactants.

  Additives such as pigments, antioxidants, ultraviolet light stabilizers and lubricants can be added in small amounts to the elastomeric polymer solution, but such additives negate the benefits of the present invention. Should not be.

  Elastomeric polymer solutions include very short fine fibers, such as wood pulp, cotton dust, etc., having a length of less than about 0.10 inch (2.5 mm), such as less than 0.5 mm, dispersed therein. Cellulose fibers from synthetic or natural fibers may be included. These fibers are typically small enough to penetrate completely into the nonwoven fabric during the impregnation process. The short fibers are sufficient to deposit the short fibers in the impregnated nonwoven sheet in an amount between about 3 and about 12 weight percent, calculated based on the total weight of the nonwoven / elastomeric polymer composite. Can be added to the polymer solution in an amount. Short fibers are typically between about 10 to about 30 weight percent, for example about 10 to about 20 weight percent, based on the total amount of short fibers, elastomeric polymer, and solvent in the elastomeric polymer solution. Add in between. The nonwoven sheet of the present invention, prepared by impregnating a necked nonwoven fabric or an easily stretchable non-processed nonwoven fabric with an elastomeric polymer solution containing powdered cellulose, comprises short fibers. Compared to those prepared by impregnating in a solution not containing, it can have a softer hand. An example of a very fine fibrous particulate material suitable for use in a polymer solution is described in J.A. It is a powdered cellulose available under the trade name "Arbocel 30" from J. Rettenmeier USA (Schoolcraft, Michigan).

  The elastomeric polymer solution is coated on a necked nonwoven substrate or an easily stretchable non-processed nonwoven substrate, or otherwise necked nonwoven substrate or easily stretchable addition Various methods suitable for impregnating an unprocessed nonwoven substrate can be used, provided that the fabric is homogeneously impregnated and necked nonwoven substrate or easily stretched It is necessary that the coating not be concentrated on one or the other possible non-processed nonwoven substrate. Although it is possible to use a coating method to treat a nonwoven substrate with an elastomeric polymer solution, the polymer solution completely wets the nonwoven substrate, selecting the nature of the solution and the nonwoven and the coating process conditions Note that alternatively, or alternatively, it is completely absorbed or driven into the nonwoven substrate so that the polymer layer does not form on any surface of the nonwoven substrate. Generally, the amount of polymer solution added during coating is used with the coating device held at a predetermined distance from the top of the necked nonwoven fabric or easily stretchable non-processed nonwoven substrate. Can be adjusted. The solution may further be mechanically pressed into the nonwoven substrate. The process of the present invention can also use rollers, hotplates, scrapers, knives and the like as coating devices. Spraying the solution onto the nonwoven substrate also allows the elastomeric solution to effectively impregnate the nonwoven substrate substantially completely and homogeneously. By adjusting the spray force, good penetration can be obtained. Nonwoven substrates can be impregnated into an elastomeric polymer solution using a process known in the industry as a “dip and squeeze” method, in which a fibrous web is impregnated with an elastomeric polymer solution. Excess polymer solution is removed by dipping into the containing tank or otherwise impregnating and then squeezing, for example, between nip rolls. This method is preferred for minimizing the difference between the surfaces on both sides of the stretchable composite nonwoven sheet.

  By impregnating a necked nonwoven substrate or an easily stretchable non-additionally processed nonwoven substrate with sufficient polymer solution, the desired weight loss / weighted stress ratio in the final impregnated nonwoven sheet can be obtained. it can. Nonwoven substrates are typically impregnated with sufficient polymer solution to provide between about 10 and about 80 weight percent elastomeric polymer, based on the total weight of the elastomeric polymer and the nonwoven substrate. For example, between about 30 and about 50 weight percent of the elastomeric polymer is deposited therein. If the amount of elastomer is too small, the ratio of dewetting stress to weighted stress can be undesirably low, and if the amount of elastomer is too large, the surface of the sheet can be undesirably tacky. End up. Adjusting the concentration of the solution and / or the amount of solution impregnated into the necked nonwoven fabric or easily stretchable unprocessed nonwoven substrate to achieve the desired polymer concentration in the impregnated sheet Can be obtained. For example, by using a low polymer concentration in the solution and maintaining the same elastomeric content on the impregnated sheet, while widening the nip gap when applying the solution, touch and dewetting It was observed that a product with an improved balance of the / weighted stress ratio was obtained.

  The nonwoven substrate is impregnated with a solution containing a solvent and an elastomeric polymer, and then the solvent is removed. The solvent is removed by wet coagulation and then the coagulated liquid is removed. By wet coagulation, a product is obtained that is surprisingly softer and has a more cloth-like feel than in the case of heat drying. Wet solidification processes are well known to those skilled in the art and are commonly used in the manufacture of artificial leather. As the coagulating liquid, water is preferable because it is easy to handle and low in cost. Other usable coagulating liquids include methanol, ethanol, isopropanol, acetone, or methyl ethyl ketone. It is also possible to add other solvents such as dimethylformamide, dimethylacetamide, or N-methyl-pyrrolidone or surfactants for the elastomeric polymer to the coagulation liquid to change the coagulation rate. Further, the coagulation rate can be changed by adjusting the temperature of the coagulation bath. The slower the solidification rate, the more attractive the touch of the impregnated nonwoven fabric after removing the solvent.

  In the impregnated nonwoven sheet of the present invention, the elastomeric polymer phase that is homogeneously dispersed throughout the necked nonwoven substrate or the easily stretchable non-processed nonwoven substrate is breathable. Furthermore, the impregnated nonwoven sheet is typically also water vapor permeable.

  The feel of the impregnated nonwoven sheet can be improved by sanding or napping, and a softer feel can be obtained by raising the fibers on the impregnated sheet. Napping involves passing the fabric over a rotating roll having small metal points, which effectively brush the fabric and raise the fibers on its surface. In sanding, the metal brush is replaced with a rotating roll covered with sandpaper. Typically, the impregnated fabric nappings or sands both sides. For example, the fabric can be sanded with 80-200 grit sandpaper.

The stretchable impregnated nonwoven sheet of the present invention typically has a basis weight between about 40 g / m < ² > and about 100 g / m < ² >. They are particularly useful in diapers and other personal sanitary garments such as waistbands or side panels of underwear. Commercially, diapers are long and assembled on high speed lines, where various diaper parts are typically added longitudinally to avoid slowing down the process speed. This is especially true for elastomeric materials that are usually stretched and then inserted. A diaper typically includes about 20 or more individual parts, all of which must be placed in a precise position on the diaper in a high speed manufacturing process. This is more easily achieved if those parts (tapes, sheets, fibers, etc.) are fed in the same direction that the diaper is moving. In order to add parts (e.g. waistband) in the transverse direction, it is preferable if the material itself can be stretched in the transverse direction and thereby fed as a longitudinal tape into the diaper manufacturing process. For example, the tape is 7 inches wide and only 1 inch long, cut from a sheet and bonded to a diaper or other disposable undergarment. In such a process, it is also preferable that the diaper part supplied to the process is substantially unstretchable in the machine direction so that it can be easily supplied to the process. The stretchable nonwoven sheet of the present invention is substantially non-stretchable in the machine direction but has a high degree of recoverable extensibility in the cross direction, thereby being used in such processes. It is especially suitable for doing.

  The stretchable nonwoven sheet of the present invention is further useful as an elastic interliner for various garments, particularly jackets and coats. An “interliner” is a fabric that is inserted between an outer layer and an inner layer of a garment, the purpose of which is to impart shape retention, lining, thermal insulation, stiffening, or bulkiness to the garment. There is to improve. The extensible nonwoven sheet of the present invention is particularly useful for this application because of its low cost, permanent elasticity and ability to stretch comfortably to the size around the body. Because.

(Test method)
(Power required to stretch 30%)
This analysis was performed using an Instron model 5565 equipped with a Merlin data collection software system. Both the Merlin system and equipment hardware are available from Instron Corporation of Braintree, Massachusetts. A sample of a non-woven sheet having a width of 1 inch ± 0.05 inch (2.54 cm ± 0.13 cm) and a length of about 8 inches (20.32 cm) is set to a sample length of 3.00 inch (7.62 cm). Clamp the jaws of the Instron measuring instrument. The sample was prepared so that the length direction of the sample was the transverse direction of the nonwoven fabric. The sample is stretched to 30% elongation at a speed of 6 inches / minute (15.24 cm / minute). Record the stress (grams) at 50% elongation.

(Fracture toughness analysis)
This analysis was performed using an Instron model 5565 equipped with a Merlin data collection software system. Both the Merlin system and equipment hardware are available from Instron Corporation of Braintree, Massachusetts. A sample of a non-woven sheet having a width of 1 inch ± 0.05 inch (2.54 cm ± 0.13 cm) and a length of about 8 inches (20.32 cm) is set to a sample length of 3.00 inch (7.62 cm). Clamp the jaws of the Instron measuring instrument. The sample was prepared so that the length direction of the sample was the transverse direction of the nonwoven fabric. The sample is stretched at a rate of 6 inches / minute (15.24 cm / minute) until the sample is broken in two and the maximum stress in grams at the break is recorded.

(Basis weight)
Carefully spread a sample of rectangular nonwoven sheet of about 1.0 inch × 8.0 inch (2.54 cm × 20.32 cm) so that the sample is free of folds and wrinkles. The sample length and width are measured to the nearest millimeter and the sample weight is weighed to the nearest 1/10 milligram. Divide the weight by the calculated area and express the result in grams / square meter (up to 0.1 gram units).

(Weighting and weight stress analysis)
This analysis was performed using an Instron model 5565 equipped with a Merlin data collection software system. Both the Merlin system and equipment hardware are available from Instron Corporation of Braintree, Massachusetts. A sample of a non-woven sheet having a width of 1 inch ± 0.05 inch (2.54 cm ± 0.13 cm) and a length of about 8 inches (20.32 cm) is set to a sample length of 3.00 inch (7.62 cm). Clamp the jaws of the Instron measuring instrument. The sample was prepared so that the length direction of the sample was the transverse direction of the nonwoven fabric. The sample is stretched at a rate of 6 inches / minute (15.24 cm / minute) to an elongation of 140% and then relaxed to its original length. This was repeated two more times, and in the third cycle, the stress applied to the material in the case of an elongation cycle (weighted stress) was recorded at 50%, 100% and 135% based on the length of the original sample. Similarly, the stress (dewetting stress) applied to the material in the case of the third relaxation cycle is also recorded at the same elongation point. The results are expressed in grams as weighted stress and degenerative stress at a given percent elongation for the third cycle.

(Percent elongation analysis)
2 points 4.0 inches (10.2 cm) apart of a loose strip of non-woven fabric that is 1.0 inches (2.54 cm) wide and about 8 inches (20.32 cm) long without folds or wrinkles Mark them with a pen so that they are approximately the same distance from the edge of the fabric. The fabric is then held firmly with both thumbs and index fingers, and the sample is stretched to the extent that the sample does not tear or suffer any mechanical damage. The point of maximum elongation is known to the test performer as the resistance to elongation due to the fabric is significantly increased. The length between the two marked points on the nonwoven is then measured and the percent elongation is calculated by the following formula, where the initial length is 10.2 cm:
Percent elongation = {(length after stretching−initial length) / initial length} × 100%

  If percent elongation is measured in the necking direction, the fabric sample is cut at a length aligned with the transverse direction (necking direction).

Example 1
A 30-inch (76.2 cm) wide, 15 g / m ² wet spunbond polypropylene nonwoven fabric (Avol Nonwovens, Israel) was placed in a nip roll at 89 ft / min (27 m / m). Second) running at 115 ft / min (35 m / min) through a forced air circulating oven at 290 ° F. (143 ° C.) 72 inches (1.83 m) long It was sent to the nip roll and then to the take-up roll. In this process, a 30 inch (76.2 cm) wide nonwoven was consolidated ("necked") in a 10 inch (25.4 cm) width in a lateral and homogeneous manner. It was re-stretched to its original 30 inch (76.2 cm) lateral width with minimal force. The necked nonwoven had substantially zero longitudinal elongation and a basis weight of 32.0 g / m ² .

  Using a 15 mil doctor knife on one side of the necked nonwoven, poly (tetramethylene ether) glycol 1-isocyanato-4-[(4-isocyanato) with a molecular weight of 1800 Phenyl) methyl] benzene (molar ratio of diisocyanate to glycol 1.69), chain extender (ethylenediamine and 2-methyl-1,5-pentanediamine (molar ratio 9: 1)), and polyurethaneurea derived from diethylamine Coated with 20 wt% dimethylacetamide (DMAC) solution. The following additives were also used: 0.5 wt% bis (4-isocyanatocyclohexyl) methane) and (3-tert-butyl-3-aza-1,5-pentanediol) polymer (metachlor) (Methacryl, registered trademark) 2462B, registered trademark of EI Du Pont de Nemours and Company, 0.3 wt% titanium dioxide, 0.6 Wt% silicone oil, 1.4 wt% 2,4,6-tris (2,6-dimethyl-4-tert-butyl-3-hydroxybenzyl) isocyanurate (Cyanox® 1790, Cytec・ Industries (registered trademark of Cytec Industries), and quadruple % Of a mixture of huntite and hydro magnesite. (All percentages are based on the weight of the polyurethaneurea.) The polyurethaneurea-DMAC solution completely wetted the nonwoven.

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

  The resulting impregnated nonwoven sheet had an equivalent (dry, woven-like) feel and texture on both sides. From the micrograph of the cross-section of the impregnated nonwoven sheet, it was found that there was a homogeneous composite structure over the entire thickness of the material and that there was substantially no continuous polyurethane region on any surface.

  The nonwoven sheet was then lightly sanded using 220 grit sandpaper. The resulting material clearly has a softer feel when compared to a completely smooth surface that does not project the fibers before sanding, and a myriad of individual short fibers are visible to the surface. It was found that it protruded from. Unexpectedly, this process succeeded in obtaining a softer touch without significantly impairing the visual aesthetics and the elastic properties of the sheet.

The resulting impregnated nonwoven sheet had a basis weight of 71.4 g / m ² and exhibited a polyurethane urea content of 39.4 grams / square meter, or an elastomeric polymer of about 55% by weight.

  When the resulting material was stretched laterally by hand, it exhibited an elongation of between about 160% and 180%.

  The following results were obtained from the weighted and degenerate stress analysis:

  Comparing the data in the table, it can be seen that the ratio of degenerative stress to weighted stress at 100% elongation was 0.54.

(Example 2)
In this example, a 55 g / m ² flat type spunlaced nonwoven fabric (Shenheung Industrial Company of 116 Hou Kang Street, Shih-Lin District, Taipei, Taiwan, ROC) A 30 inch long piece of a 10 inch (25.4 cm) wide roll made by Sheng Hung Industrial Co., product number 4055-T) was run continuously. The nonwoven substrate is first available from the present applicant of T-162 Lycra® dimethylacetamide (DMAC) solution with a solids content of 12.5% (Wilmington, DE). ) To be impregnated. The fabric speed was 3 feet / minute and the total fabric length in the bath was about 6 inches. Excess polymer solution was removed by passing the impregnated fabric between nip rolls with a gap of 0.007 inches.

The resulting impregnated fabric was then passed through a bath of 40% DMAC in water followed by two independent 100% water baths. The fabric speed when passing through these baths was 3 ft / min. The total length of the fabric in each bath was 8 feet. Both baths were kept at room temperature, approximately 72 ° F. (40 ° C.). When the fabric thus obtained was air-dried, a breathable stretchable nonwoven fabric with attractive elasticity and a basis weight of 80 g / m ² (45 wt% T-162 Lycra®) was obtained. .

  From the percent elongation analysis by hand in the transverse direction of the obtained elastic nonwoven fabric, it was found that the elongation was 50% to 60%. Analysis of weighted stress and dewetting stress in the third cycle was performed as described in the Test Methods section, except that the sample was stretched to a maximum elongation of 50% and the weighted stress and the degenerative shrinkage stress were 20 Recorded at%, 30%, and 40% elongation. The following results were obtained from this modified weighted and deweighted stress analysis:

  Comparing the data in the table, it can be seen that the ratio of degenerative stress to weighted stress at 30% elongation was 0.33.

Claims (12)

A method for forming an extensible nonwoven sheet comprising:
The thickness, and the first and second outer surface, the longitudinal and transverse directions, and a percent elongation of at least 30% in the lateral direction, and a basis weight between ^{15g / m 2 ~100g / m 2} , 500g / With a fracture toughness higher than inches, the “force required to stretch 30%” method provides at least 30% lateral strength without breaking even when forces less than 200 grams / inch (g / inch) are applied. Providing a stretchable unprocessed nonwoven substrate having an elongation in the direction ;
Homogeneously impregnating the stretchable unprocessed nonwoven substrate with a solution comprising an elastomeric polymer dissolved in a solvent; and
The solvent is removed from the stretchable unprocessed nonwoven substrate by wet coagulation to deposit the elastomeric polymer uniformly over the entire thickness of the nonwoven substrate, and the first or second of the nonwoven substrate A method comprising not forming a continuous layer of elastomeric polymer on any of the two outer surfaces. The method of claim 1, wherein the stretchable unprocessed nonwoven substrate has a percent elongation between 60% and 150% in its transverse direction. Claims wherein the nonwoven fabric base material which is not stretched can be added processing, characterized in that it is a non-woven fabric that has not been possible additional processing stretching has a basis weight of between 30g ^/ m ² ~80g / m 2 The method according to 1.   The method of claim 1, wherein the elastomeric polymer is polyurethane. The elastomeric polymer is deposited on the substrate in an amount of 10 to 80 weight percent , based on the combined weight of the substrate and the elastomeric polymer. The method described in 1.   The method according to claim 1, further comprising sanding or napping at least one of the outer surfaces of the nonwoven sheet after removing the solvent to raise fibers on the surface of the sheet. . A stretchable nonwoven sheet, homogeneously impregnated with an elastomeric polymer, with a force less than 200 grams / inch (g / inch) by the “force required to stretch 30%” method A stretchable unprocessed nonwoven substrate having a lateral elongation of at least 30% without breaking when added,
The sheet comprises 10 to 80 weight percent elastomeric polymer, based on the total weight of the elastomeric polymer and the nonwoven substrate;
The nonwoven sheet has a basis weight between ^{40g / m 2 ~100g / m 2} ,
After the stretchable nonwoven sheet has been stretched 50% in the transverse direction 3 times, at least 0.15: 1, 30% of the stress at 30% elongation of the 3rd weight cycle, 30% of the 3rd weight cycle A stretchable nonwoven sheet characterized by having a ratio to the stress at elongation.   8. The stretchable nonwoven sheet of claim 7, wherein the ratio of dewetting stress to weighted stress is at least 0.3: 1.   A personal sanitary garment comprising the stretchable nonwoven sheet according to claim 7.   The personal sanitary garment according to claim 9, wherein the garment includes a diaper.   The personal sanitary garment according to claim 9, wherein the garment includes underwear.   A clothing article comprising the stretchable nonwoven sheet according to claim 7, wherein the stretchable nonwoven sheet is an interliner.