HK1118255A - Breathable composite sheet - Google Patents

Description

Breathable composite sheet

Background

1. Field of the invention

The present invention relates to breathable composite sheets having a combination of enhanced moisture vapor transmission, virus barrier, and liquid barrier properties suitable for medical products such as surgical gowns and drapes.

2. Description of the related Art

The use of moisture vapor permeable (breathable) sheets to make medical products (e.g., surgical gowns and drapes) and personal care absorbent articles (e.g., diapers) that require a combination of breathability, barrier to bacteria and viruses, and liquidproofness is known in the art. U.S. patent to Lim et al, 187,696, describes a composite sheet material that combines an air-permeable film having a thickness of less than 25 microns with a fibrous substrate to form an air-permeable composite sheet structure. Extrusion coating the film onto the smoother side of the fibrous substrate. Examples of suitable fibrous substrates include thermally bonded carded webs and spunbond webs. U.S. patent 6,638,605 to Ankuda, jr. et al describes a laminate suitable for use in disposable surgical drapes and gowns comprising a breathable film layer adhesively bonded between two nonwoven layers. The nonwoven layer may be a wet laid, airlaid, spunlaced, or spunbond-meltblown-spunbond nonwoven fabric.

It would be desirable to provide a breathable composite sheet that can be economically produced, has an increased moisture vapor transmission rate, and is resistant to liquids, bacteria, and viruses.

Summary of The Invention

The present invention relates to a moisture vapor permeable composite sheet consisting of:

a nonwoven layer of absorbent fibers having two opposing surfaces, said nonwoven layer of absorbent fibers comprising 0% to 95% by weight synthetic thermoplastic fibers and 100% to 5% by weight absorbent fibers;

a repellent nonwoven layer having two opposing surfaces, said repellent nonwoven layer comprising synthetic fibers comprising a repellent composition; and

a non-porous, liquid impermeable, moisture vapor permeable film layer having a thickness of no more than 25 microns sandwiched between said repellent nonwoven layer and said absorbent nonwoven layer.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view of a multilayer composite sheet of the present invention.

Detailed Description

As used herein, the terms "nonwoven fabric", "nonwoven sheet", "nonwoven layer" and "nonwoven web" refer to a structure of individual yarns (e.g., fibers, filaments or threads) that are laid in a random manner to form a planar material (as opposed to a knitted or woven fabric) without a defined pattern. The term "fiber" is used herein to include staple fibers as well as continuous filaments. Examples of nonwoven fabrics include meltblown webs, spunbond nonwoven webs, flash spun webs, staple fiber webs (including carded and airlaid webs), spunlaced webs, and composite sheets comprising more than one layer of nonwoven web.

The term "spunlaced nonwoven web" as used herein refers to a nonwoven fabric prepared by entangling the fibers in the web to provide a strong, binder-free fabric. For example, a spunlaced fabric can be prepared as follows: the nonwoven web is supported by a porous support such as a mesh screen and the supported web is passed under a jet of water, such as a hydroentangling process. The fibers may be wound in a repeating pattern.

The term "powder bonded nonwoven web" as used herein refers to a bonded nonwoven fabric formed as follows: the powdered binder is deposited onto an unbonded web, such as a carded web, such that the powdered binder is distributed throughout the thickness of the web. The powder binder is selected to melt at a temperature below the melting point of the fibers in the web. The powder-containing web is then heated to melt the powder binder without melting the fibers of the web to form a powder-bonded nonwoven web.

As used herein, the term "spunbond fibers" refers to melt spun fibers formed by extruding molten thermoplastic polymer material as fibers from a plurality of fine, usually circular, capillaries of a spinneret with the diameter of the extruded fibers then being rapidly reduced by drawing and then quenching the fibers.

The term "meltblown fibers" as used herein, means fibers which are melt-spun by meltblowing, which comprises extruding a melt-processable polymer through a plurality of capillaries as molten streams into a high velocity gas (e.g. air) stream.

The term "spunbond-meltblown-spunbond nonwoven fabric" ("SMS") as used herein refers to a multilayer composite sheet comprising a meltblown web sandwiched between and bonded to two spunbond layers. Other spunbond and/or meltblown layers may be bonded to the composite sheet, such as spunbond-meltblown-spunbond webs ("SMMS") and the like.

The term "multicomponent fiber" as used herein refers to a fiber that is composed of at least two different polymeric components that are spun together to form a single fiber. The at least two different polymeric components are arranged in distinct, substantially constantly positioned zones across the cross-section of the multicomponent fiber, the zones extending substantially continuously along the length of the fiber.

The term "bicomponent fiber" as used herein refers to a multicomponent fiber composed of two different polymer components, such as a sheath-core fiber comprising a first polymer component forming the sheath and a second polymer component forming the core; and side-by-side fibers, wherein the first polymeric component forms at least one lobe that is adjacent to at least one lobe formed by the second polymeric component, each lobe being substantially continuous along the length of the fiber, both polymeric components being exposed at the surface of the fiber. Multicomponent fibers are distinguished from fibers that are extruded from a single homogeneous or heterogeneous mixture of polymeric materials. The term "multicomponent nonwoven web" as used herein refers to a nonwoven web comprising multicomponent fibers. In addition to multicomponent fibers, multicomponent webs may also comprise single component and/or polymer blend fibers.

The term "repellent nonwoven layer" as used herein refers to a nonwoven layer having an alcohol repellency of at least 2 when measured according to INDA IST 80.8.

The term "pinhole" as used herein refers to a small hole that is unintentionally formed in a film during its production or processing.

The term "polyester" as used herein is intended to include polymers in which at least 85% of the repeating units are polycondensation products of dicarboxylic acids and dihydroxy alcohols, with linkages resulting from the formation of ester units. This includes aromatic, aliphatic, saturated and unsaturated diacids and diols. The term "polyester" as used herein also includes copolymers (e.g., block, graft, random, and alternating copolymers), blends, and modifications thereof. A common example of a polyester is polyethylene terephthalate (PET), which is a polycondensation product of ethylene glycol and terephthalic acid.

The present invention relates to breathable composite sheets comprising an absorbent fibrous layer, a protective fibrous layer, and a non-porous (monolithic) breathable film layer, the fibrous layer being substantially free of pinholes therein. The breathable film layer is extrusion coated onto one side of the absorbent fibrous layer, followed by adhesive lamination of the protective fibrous layer to the side of the breathable film opposite the absorbent fibrous layer.

The absorbent fibrous layer comprises 0-95% by weight of thermoplastic synthetic fibers and 100-5% by weight of absorbent fibers. The fiber content can range from 30-70% by weight thermoplastic synthetic fibers to 70-30% by weight absorbent fibers. The percentages being calculated on the basis of the total weight of the fibres in the fibre layer. A nonwoven web is generally considered an absorbent nonwoven web if the fabric is wetted by water when a drop of water is placed on the nonwoven web. For the purposes of the present invention, a fabric is considered to be non-absorbent if the shape and condition of a drop of water placed on the fabric does not change within 5 minutes after placement on the fabric, i.e., the fabric is not wetted by the drop. Otherwise, the fabric is considered absorbent.

In one embodiment, the absorbent, synthetic fibers used to make the absorbent nonwoven layer comprise staple fibers. Examples of suitable staple fiber nonwoven fabrics include spunlaced nonwoven webs and powder bonded nonwoven webs. Hydroentanglement processes (hydraulic needling) for making spunlaced nonwoven fabrics are well known in the art. In hydroentangling, a fibrous web is placed on a screen or other foraminous carrier and subjected to a series of high pressure water jets which cause entanglement of the fibers to form a spunlaced nonwoven fabric. Conventional hydroentangling processes can be used to prepare spunlaced fabrics suitable for use in the absorbent nonwoven layer of the present invention, and these processes have been described in U.S. patents: evans 3,485,706 and Nakamae et al U.S. Pat. No. 4,891,262. Powder bonded nonwoven webs may be prepared by methods known in the art, such as those described in U.S. patent 4,845,583 to Zimmerman et al. A powder deposition apparatus is used to apply a thermoplastic binder powder to the nonwoven web. The powder falls by gravity onto the web and is distributed throughout the fibrous web. The weight of powder deposited on the nonwoven web is typically from about 8 to about 30 weight percent of the powder-bonded nonwoven web. The web containing the powder is heated to bond the web. For example, the web can be passed through an oven, such as an infrared oven, where the binder powder melts and binds the fibers. After leaving the oven, the web is typically lightly pressed in a gap.

Alternatively, the nonwoven layer of absorbent fibers can be a thermally bonded carded web or an airlaid web comprising a mixture of absorbent fibers and thermoplastic synthetic fibers. The thermoplastic fibers may consist essentially of binder fibers or may comprise a mixture of binder fibers and high melting thermoplastic fibers. The binder fibers are thermally bondable (i.e., meltable or partially meltable) at a temperature below the degradation temperature or melting point of the other fibers in the web. The binder fibers may be monocomponent fibers or may comprise multicomponent fibers. The web may be thermally bonded using methods known in the art, such as full-surface or intermittent roll bonding.

Suitable thermoplastic polymers for preparing synthetic fibers suitable for the nonwoven layer of absorbent fibers include polyesters such as polyethylene terephthalate and polytrimethylene terephthalate; polyethylene; polypropylene and polyamide. Suitable absorbent fibers for the absorbent fibrous nonwoven layer include natural cellulosic fibers, regenerated cellulosic fibers, animal fibers, absorbent synthetic fibers, and mixtures thereof. Examples of natural cellulose fibers include wood pulp and cotton. Examples of regenerated cellulose fibers include rayon, acetate, and lyocell fibers. Suitable animal fibers include wool and silk fibers.

Absorbent synthetic fibers can be prepared by topically treating synthetic fibers with a composition comprising a surfactant. Surfactants typically comprise long chain hydrocarbons having an affinity for oleophobic materials and ionic groups having an affinity for water and hydrophilic materials. Alternatively, the hydrophilic melt additive may be mixed with the polymer prior to spinning the polymer to make the absorbent synthetic fibers. In another embodiment, chemical modification of the polymer to impart absorbency can be achieved by incorporating polar linear or polar blocks into the polymer backbone. Examples of chemically modified absorbent fibers areHydrotec fibres, from DAK America (Charlotte, NC).

ProtectionThe nonwoven layer is comprised of fibers that comprise the hydrophobic protectant composition. The fibers may be treated with a repellent before forming the nonwoven layer or the pre-formed fibrous nonwoven layer may be treated with a repellent. Protectant compositions suitable for topical treatment generally include a fluorochemical compound, a wax, and a silicone-based long-chain hydrocarbon. When the composite sheet of the present invention is used for medical fabrics such as garments and drapes, etc., the repellent composition preferably comprises a fluorochemical compound. Suitable fluorine-containing compounds includeFluorochemical compounds from e.i. du Pont de neuro and Company, Wilmington, de (dupont). Alternatively, the repellent composition can be added to the polymer system as a melt additive prior to extruding the repellent fiber. An example of a suitable repellent melt additive is FX1801 fluorochemical, available from Minnesota mining and Manufacturing Company (st. paul, MN). The repellent nonwoven layers suitable for use in the present invention have an alcohol repellency of at least 2, and preferably at least 6, when measured according to INDA IST 80.8.

Nonwoven substrates suitable for making the repellent nonwoven layer include spunbond and spunbond-meltblown-spunbond nonwoven webs. The repellent nonwoven layer can comprise monocomponent and/or multicomponent fibers, such as bicomponent fibers. In one embodiment, the nonwoven substrate used to make the repellent nonwoven layer comprises a multiple component spunbond web, such as a bicomponent spunbond web. For example, the barrier layer may be prepared from a bicomponent spunbond web comprising bicomponent fibers of polyethylene and polyester. Polyethylene, such as linear low density polyethylene, provides soft fabrics and polyesters, such as polyethylene terephthalate, provide strength. In one embodiment, the spunbond fibers comprise a polyethylene sheath and a polyester core. In addition to providing a soft fabric, polyethylene has a lower melting point than other polymers, making it easier to bond the nonwoven web to itself or other substrates via thermal bonding.

The absorbent, repellent nonwoven fibrous substrate is selected to provide the desired strength, permeability and softness of the composite sheet. The suctionThe acquisition and containment nonwoven layers typically have a basis weight of about 0.5 to 2 oz/yd²。

FIG. 1 is a schematic cross-sectional view of a multilayer composite sheet of the present invention. A non-porous liquid impermeable moisture vapour permeable film layer 1 is sandwiched between an absorbent fibrous nonwoven layer 3 and a barrier nonwoven layer 5. Film 1 may be a single layer or a multilayer film. The multilayer moisture vapor permeable composite sheet of the present invention is prepared as follows: a nonporous liquid impermeable moisture vapor permeable film layer is formed by extrusion coating on one side of the absorbent nonwoven layer and then a repellent nonwoven layer is adhesive laminated to the side of the film opposite the absorbent nonwoven layer. The adhesive layer is located between the repellent nonwoven layer 5 and the film layer 1 but is not shown in figure 1.

Film layer 1 comprises a polymeric material that can be extruded into a thin, continuous, moisture vapor permeable, and substantially liquid impermeable film. The film layer is extruded directly onto the absorbent nonwoven layer in an extrusion coating process and is less than about 1mil (25 microns) thick, more preferably less than about 0.75mil (19 microns) thick, and most preferably less than about 0.60mil (15.2 microns) thick. The film layer 1 is preferably comprised of a block polyether copolymer, such as a block polyetherester copolymer, a polyetheramide copolymer, a polyurethane copolymer, a polyetherimide ester copolymer, polyvinyl alcohol, and combinations thereof. Preferred copolyether ester block copolymers are block elastomers having polyether soft blocks and polyester hard blocks as disclosed in Hagman, U.S. patent 4,739,012. Suitable copolyetherester block copolymers are sold under the trade name E.I.du Pont DE Nemours and Company (Wilmington, DE). A suitable copolyetheramide polymer is available from Atochem Inc. of Glen Rock, New Jersey, USA under the trade name ofThe copolyamide of (1). A suitable polyurethane is available from The B.F. Goodrch Company of C1eveland, Ohio, USA under The trade name ofThe thermoplastic polyurethane of (1). Suitable copolyetherimide esters are described in Hoeschele et al, U.S. Pat. No. 4,868,062.

In the extrusion coating process, a homogeneous (monolithic, i.e., substantially pinhole-free) melt extrudate is coated onto the absorbent nonwoven layer. When the molten polymer cools and bonds with the absorbent nonwoven web, the molten polymer and the absorbent nonwoven layer are in intimate contact. This contact and adhesion can be enhanced by passing the layers through a gap formed between two rolls. Alternatively, the molten polymer may be drawn into contact with the powder-bonded nonwoven web by: the coated web was passed through a suction inlet so that the vacuum pulled the molten polymer into contact with the web as the polymer cooled and bonded to the web. The extruded film layer is substantially free of pinholes or other defects and still has a relatively high moisture vapor transmission rate. Extrusion coating processes are known in the art, such as the process described in U.S. patent application publication 2002/0106959.

The film layer (fig. 1) of the composite laminated sheet may be composed of multiple layers. Such films may be coextruded with a layer comprised of one or more of the breathable thermoplastic film materials described above. Examples of such multi-layer moisture vapor permeable films (typically comprising a more hydrophobic elastic layer and a more hydrophilic elastic layer) are described in Ostapchenko, U.S. patent No. 4,725,481. In a preferred embodiment, the multilayer film (implemented in two layers) is extruded onto the absorbent nonwoven layer with the more hydrophobic elastic layer facing away from the absorbent nonwoven layer and the more hydrophilic elastic layer bonded to the absorbent nonwoven layer. Generally, for a given thickness, a hydrophobic elastic layer exhibits a lower moisture vapor transmission rate than a hydrophilic elastic layer due to its lower moisture content under use conditions. However, when used in thinner layers, the effect of the hydrophobic, low moisture content film layer does not significantly reduce the moisture vapor transmission rate of the composite laminate sheet. Preferably, the relatively hydrophobic elastomer comprises 20-30% of the total thickness of the composite film layer.

The repellent nonwoven layer is bonded to the film side of the extrusion coated film/absorbent nonwoven bi-layer film using an adhesive applied to discrete areas such that the two components are intermittently bonded to each other.For example, the adhesive may be applied in a pattern or in randomly oriented filaments. Preferably, the adhesive is applied in an amount of about 1g/m²-6g/m². If the adhesive loading is too high, the resulting composite laminated sheet may be stiffer than desired. If too low, the bond strength between the film and the repellent nonwoven layer will be too low. The adhesive is preferably a heat-sensitive hot melt adhesive, such as a polystyrene-polybutadiene-polystyrene (SBS) or polystyrene-polyisoprene-polystyrene (SIS) based hot melt adhesive. Conventional adhesive lamination processes, such as melt blown, screen or gravure adhesive lamination processes, may be used. In meltblown adhesive lamination, the adhesive is deposited as random meltblown fibers onto a film layer or a repellent nonwoven layer. In screen or gravure adhesive lamination processes, hot melt adhesives are applied through patterned or engraved areas. The adhesion between the film layer and the repellent nonwoven layer can generally be improved by depositing a hot melt adhesive onto the film layer; however, pinholes may result in the film due to the high temperature of the hot melt adhesive when it comes into contact with the film. Depositing the hot melt adhesive to the repellent nonwoven layer can result in a reduction in bond strength compared to when the adhesive is deposited to the film layer, however, the correct selection of the repellent nonwoven layer can be used to provide an acceptable bond for most end uses while reducing the chance of pinhole formation. The film layer is brought into contact with the repellent nonwoven layer and passed through the nip formed between the two rolls before the hot melt adhesive cools. Alternatively, an adhesive web formed from a hot melt adhesive composition can be placed between the repellent nonwoven layer and the extrusion coated film/absorbent nonwoven bi-layer film and the layers bonded together by passing the combined layers through a heat nip formed by two rolls to form the moisture vapor permeable composite sheet of the present invention.

The moisture vapor permeable composite sheet of the present invention preferably has a moisture vapor transmission rate of at least about 3000g/m²Per 24hr, more preferably at least about 4000g/m²And/24 hr. The sheet must have sufficient virus barrier properties to meet the requirements of ASTM F1670 and F1671. The wicking rate of the sheet of the present invention is less than 100 seconds and preferably less than 50 seconds. The composite laminates of the present invention are suitable for use in medical fabrics such as garments and drapes. When used to make garments, the garments are made with absorbent nonwoven layersForming an inner layer of the garment which is adjacent to the wearer during use, while the repellent nonwoven layer forms an outer surface of the garment. The composite laminates are also suitable for use in many other applications where moisture vapor permeability is important in combination with liquid impermeability, such as protective coverings for automobiles, corn, house wraps, and headliners. The viral barrier characteristics of the present invention also facilitate its use in protective garments other than medical garments, such as protective garments that prevent the penetration of particles (e.g., asbestos); other biological agents to protect against bacteria; prevent harmful liquid such as harsh chemicals from permeating and clean room clothing. Also the composite laminates of the present invention may be used in personal care articles such as diapers, sanitary napkins and the like. The vapor permeability of the present invention facilitates its use in a vapor sterilization wrap for covering surgical instruments and supplies for sterilization. The absorbent inner layer may provide other comfort and possible applications may be medical garments and drapes, protective garments and personal care products where absorbent properties are required.

Test method

In the above description and in the following non-limiting examples, the following test methods were used to determine various reported characteristics and properties. ASTM refers to the american society for testing and materials. TAPPI refers to the technical association of the pulp and paper industry in the united states. ISO refers to the international organization for standardization. INDA refers to the nonwoven industry Association.

Thickness ofDetermined by ASTM method D177-64 and reported in mils.

Basis weightDetermined by ASTM D-3776 and given in oz/yd²(osy) is reported in units.

Grab sample tensile Strength (GTS)Determined by ASTM D5034-95 and measured in pounds.

Trapezoidal Tear Strength (TTS)Measured by ASTM D5733, where trapezoidal tear strength is the maximum tear force, reported in pounds, required to continue or propagate a tear that has begun in a sample. In this study, the average tear strength from the start to the end of the test was taken as the trapezoidal tear.

Adhesive Strength (BS)Generally determined according to ASTM D2724-87. The test is carried out using a constant draw rate tensile tester such as an lnstron bench tester. A5 cm (2.0in) by 20.32cm (8.0in) sample was delaminated by about 3.18cm (1.25in) by initiating separation between the web and the moisture vapor permeable film. The separated sample faces were held in the jaws of a tester set at 5.08cm (2.0in) separation. The tester was run with a cross beam of 30.5cm/min (12.0 in/min). Samples were stratified by approximately 10cm (4in), during which time sufficient readings were collected to provide a representative data average. The bond strengths between the 2 "and 4" separations were averaged as the average bond strength in grams. By dividing by two inches, the average bond strength is obtained in grams/inch.

Static head (HH)Measured according to IST 80.4, at 100cm²Water permeability resistance was measured on a test sample of circular area. Water pressure was applied to the fabric side of the test sample until the sample was penetrated by water at three locations. Hydrostatic head is measured in centimeters. For the film-based laminate products in this study, a carrier screen material was used to prevent the laminate from tearing and stretching the material.

Blocking virusesPerformance was measured according to ASTM F1671. Astm f1671 is a standard test method for measuring the penetration of materials used in protective clothing against bloodborne pathogens. According to the method, 10 with a size similar to that of hepatitis C virus (0.028 microns) is used⁸Phi-X174 phage three samples of sheet material tested were tested with the surface tension adjusted to 0.042N/m and the pressure differential over a 24 hour period to 2psi (13.8 kPa). The penetration of the sample by the active virus was determined using an analytical procedure. The test results are reported in plaque forming units per ml PFU/ml. If 0PFU/ml is detected after a 24 hour test period, the sample passes the test.

ASTMF1670The same test equipment as used in ASTM F1671 but using an artificial blood solution as the test solution was used to determine the liquid permeability against artificial blood. Applying the same pressure 2psi. The sample failed the test if visible penetration was observed.

Moisture Vapor Transmission Rate (MVTR)Measured according to IST70.4 using a Mocon Permatran-W model 100K Instrument. MVTR value, rate of vertical flow to surface per unit area of water vapor at 37.8 ℃ and 60% RH in g/m²The unit is reported as/24 hr.

Wicking effectMeasured according to IST 10.1. Samples 25mm wide and 100mm long were cut and immersed vertically in water. The time in seconds for the water to rise by 25mm (line) was determined.

The Absorption Capacity (AC) was determined by GATS (Gravimetricabsorb absorption Testing), Model M/K201 from M/K Svstems, Inc. The double diameter samples were cut, weighed and placed on a test machine. After introducing water to the sample, the percent absorbency was calculated based on all water absorbed divided by the weight of the sample.

Alcohol Repellency (AR)Measured according to INDA IST 80.8. IST80.8 is a standard test for determining the permeability of nonwoven fabrics against aqueous isopropanol solutions. The grade of alcohol repellency is reported in terms of alcohol concentration. The highest value of the test solution that did not penetrate the test sample within five minutes was recorded.

Electrostatic attenuationMeasured according to INDA IST 40.2. IST40.2 is a standard test method for determining the time required to dissipate charge from the surface of a test sample. The test sample is charged by a positive or negative high voltage (5000V) and the time of charge depletion is determined. Static decay is reported in seconds.

Examples

Example 1.5

In these examples, three different powder-bonded nonwoven layers were used as the absorbent inner layer, the layers being adjacent to the breathable film layer and having a basis weight of 1. Ooz/yd²(34g/m²) (available from HDKGcompany, Greenville, South Carolina). The powder-bonded non-woven layerPrepared from polyester (polyethylene terephthalate) and rayon staple fibers in three different weight blend ratios (70/30, 50/50, and 30/70 rayon/polyester). A copolyester powder binder was used at a loading of 20% by weight, based on the total weight of powder binder and staple fibers in the nonwoven web.

For preparing the double-layer composite structure, use is made ofA polymeric film layer of copolyether ester, a breathable film layer extrusion coating the powder-bonded nonwoven web. Three Hytrel G4778 layers (melting point 208 ℃, Vicat softening point 175 ℃, Shore D hardness 47 and absorption rate 2.3% by weight) and(melting point 200 ℃, Vicat softening point 151 ℃, Shore D hardness 45 and absorbency 30% by weight) (all from DuPont) were co-extrudedA thin film layer. Preparation of three layersWherein the two outer layers consist of more than 50% G4778, 8206 and colored pigment and the inner layer consists of 8206, colored pigment and Ti0₂And (4) forming. The thickness of the inner layer is about three times the thickness of each outer layer.

Andthe total percentages of (a) and (b) are 23% and 70%, respectively. Selecting two kinds ofOf gradeThe mixture is to create an excellent balance between the breathability and softness of the bilayer and the strength and low absorbency of the bilayer. Due to the fact thatMore ether than ester moieties than byThe sheet material produced is a softer sheet material and a higher MVTR. It has been found thatProviding ratioHigher strength and lower absorption capacity. In addition to the Hytrel polymer, 5% by weight of colorant and 2% by weight of Ti0 were added for color and opacity₂And (3) concentrating.

Will be sphericalThe polymer and additive concentrate were fed to two screw extruders, melted at 440F (227℃.) to 385F (196℃.) and fed to a die in a heated die jacket maintained at 430F (221℃.). The powder bonded nonwoven substrate was about 19.5 inches (49.5cm) below the die. The film was extruded at a rate of 325ft/min (99m/min) to a film thickness of 0.7mil (18 microns). For a film thickness of O.8mil (20 μm), the line speed was reduced to 280 min scratches (85 m/min). The film was bonded to the fiber powder bonded nonwoven substrate by passing the coated web through a pair of horizontally placed nip rolls (nip pressure 10psi) to form a composite laminated sheet. The press roll facing the polymer melt had a silicone rubber roll with a matte finish and the other roll was metal. The quench bath was adjacent to the side of the rubber roll opposite the metal roll and was maintained at 80F (27 c).

Five two-layer film examples were prepared (table 1) according to two film thicknesses (o.7mil and o.8mil) and three fiber blend ratios (70/30, 50/50 and 30/70 rayon/polyester) for the powder-bonded nonwoven fabric.

To form a three-layer composite structure, the basis weight was 1. Ooz/yd²With protective spunbonded polyester/polyethylene bicomponent nonwoven adhesive bonded to the two-layer compositeA thin film layer. The spunbond bicomponent fabric was a sheath/core structure of 50% Linear Low Density Polyethylene (LLDPE)/50% polyethylene terephthalate and pre-bonded by heat and pressure. For alcohol repellency and antistatic properties, use(fluorochemicals sold by DuPont) and Zelec TY antistatic agents (a mixture of isobutyl phosphate and diisobutyl phosphate sold by Stepan Company (Northfield IL)) topically treat the spunbond nonwoven material.

Laminating spunbond polyester/polyethylene nonwoven fabrics to a substrate using meltblown adhesive laminationFilm side of the double layer laminate. The hot melt adhesive used in these examples was H2900 (available from Bostik Findley, Wauwatosa, Wis.) based on a polystyrene-polybutadiene-polystyrene (SBS) linear block copolymer. The amount of the binder added was 5g/m²。

The hot melt adhesive was fed to a hopper, melted, and transferred through a heat insulated pipe to a J equipped with 18 holes/inch of the tip&M hot melt meltblown threads of nozzles. Melt blowing adhesive to two layer composites at line speed of 200ft/min and air pressure of 40psiAnd (5) a thin film surface. The distance from the showerhead to the bilayer substrate was 1.5 inches and the distance between the nozzles and the gap was 60 inches. Selecting a feed hopper, a heat-insulating pipe and a spray head according to the melt viscosity performance of the hot melt adhesiveAnd air temperature. For H2900, the feed hopper, insulation, spray head and air temperatures were 310, 320 and 350 ° F, respectively.

All of these examples had a hydrostatic head of over 300 seconds and passed through ASTM F-1670 and F-1671. Other physical properties of these examples are provided in table 1 below.

Examples 6 to 11

In these examples, a spunlaced nonwoven fabric made from a mixture of polyester and lyocell fibers was used as the absorbent inner layer. The spunlaced nonwoven had a basis weight of 1.18osy and three different blend ratios were used: 65/35, 50/50 and 35/65 lyocell/PET.

Using the same processing conditions as described in example 1.5Andthe spunlaced lyocell/pET nonwoven web was extrusion coated with 3 polymer films. 6 examples of absorbent nonwoven/film bilayers were prepared from spunlaced nonwoven fabrics with two film thicknesses (O.7mil and O.8mil) and three blend ratios (65/35, 50/50 and 35/65 lyocell/polyester).

To prepare the three-layer laminated composite structure of the present invention, the extrusion coated bilaminate was laminated with a 1.0osy spunbond core/sheath polyester/polyethylene bicomponent nonwoven web by the meltblown adhesive lamination process described in examples 1-5. All of these examples had a hydrostatic head of over 300 seconds and passed ASTM F-1670 and F-1671. Other physical properties of these examples are provided in table 1 below.

Example 12

In this example, a spunlaced nonwoven fabric made from a mixture of polyester and rayon was used as the absorbent inner layer. The spunlaced nonwoven layer had a basis weight of 1.18osy and a blend ratio of 30/70 weight rayon/PET.

Using the same processing conditions as described in examples 1-5Andthe spunlaced rayon/PET nonwoven web was extrusion coated with 3 polymer films to a film thickness of o.8mil. The resulting extrusion coated rayon/PET film bi-laminate was bonded to the 1.Oosy spunbond core/sheath polyester/polyethylene bicomponent nonwoven web described in examples 1-5 using the meltblown adhesive lamination process described in examples 1-5 to prepare a tri-laminate. The hydrostatic head of this example exceeds 300 seconds and passes ASTM F-1670 and F-1671. Other physical properties of this example are provided in table 1 below.

Comparative examples A and B

Comparative examples a and B were prepared using the same extrusion coating process and melt blown adhesive lamination process described in examples 1-5. In these embodiments, a non-absorbent inner layer is used in place of the absorbent inner layer. The non-absorbent inner layer used was a 0.5osy powder bonded 100% polyester nonwoven web and a 1.0osy spunbond polyester/polyethylene web, with film thicknesses of 0.6mil and 0.7mil, respectively, for comparative examples a and B. The hydrostatic head of the two comparative examples exceeded 300 seconds and passed ASTM F-1670 and F-1671. Other physical properties are provided in table 1 below.

Both trilaminates gave similar performance but the MVTR values were lower than those of examples 1-12. Comparative example A had a lower basis weight and film thickness while comparative example B had the same or lower basis weight (1.0osy) and the same film thickness (0.8 mil). It is possible to consider the MVTR values of comparative example A to be significantly higher while those of comparative example B are at least the same as those of examples 1-12.

The higher MVTR values obtained for examples 1-12 may be due to the positioning of the absorbent inner layer adjacent to the breathable layer, which enables moisture vapor to be absorbed or transmitted to the film layer at a faster rate, although the invention is not limited by any theory. The diffusion mechanism of moisture vapor transmission through the breathable layer can be controlled by a number of factors, including thickness. One factor observed with the present invention is: a higher humidity environment may be created by absorbing the moisture vapor absorbed by the inner layer. The higher humidity environment adjacent to the breathable film may increase breathability (MVTR), which may be explained by the diffusion mechanism of the greater moisture vapor density gradient. The comfort can be improved by the increased breathability of the absorbent inner layer of the invention.

The test results of examples 1 to 12 and comparative examples are listed in table 2 below.

TABLE 1

	Ex1	Ex2	Ex3	Ex4	Ex5	Ex6	Ex7	Ex8	Ex9	Ex10	Ex11	Ex12	ExA	ExB
															Inner layer	70/30r/PET	50/50r/PET	50/50r/PET	30/70r/PET	30/70r/PET	65/35VPET	65/35I/PET	50/50l/PET	50/50l/PET	35/65l/PET	35/65l/PET	30/70r/PET	0.5oSyPET	1.0osyPET/PE
Thickness of film	0.7	0.8	0.7	O.8	0.7	0.7	0.8	0.7	0.8	0.7	0.8	0.8	O.6	O.B
															BW	2.8	2.96	2.85	2.73	2.91	3.04	3.07	2.8B	3.19	3	2.98	3.09	2.5	3.15
Thickness of examples	19	18	18	18	18	21	19	20	22	19	20	20	14	17
															GTS MD/CD	33/25	31/23	34/25	29/25	28/24	34/23	39/29	34/25	36/25	3g/25	40/26	41/29	33/23	3a/23
TTS MD/CD	7.1/13.5	8.3/13.4	7.9/13.0	8.4/14.2	6.8/12.8	7.9/14.4	7.6/13.4	8.6/13.7	82/15.5	8.2/5.7	7.4/15.7	9.4/17.4	6.6/12.9	8.5/11.5
															2' Peel off MD/CD	29/11	23/11	27/10	26/13	23/10	26/14	22/15	Z3/16	24/15	29/12	28/15	35/14	21/13	21/11
Inner layer BS MD/CD	16/55	58/91	92/81	103/127	255/72	113/67	130/78	172/g7	190/118	275/124	54/82	112/58	166/128	23/14
															Outer layer BS MD/CD	275/377	400/320	40B/332	343/369	392/341	179/177	620/430	455/387	344/453	534/333	271/414	350/280	414/337	298/327
MVTR	6486	5161	6224	5933	6195	7553	6199	5878	5978	7076	5620	5289	4934	3716
															Wicking effect	8.4	7	23.7	26.7	63.6	6.8	6.5	19.5	12.2	46.4	38.4	27.2	N/A	N/A
AC	207	190	191	177	174	242	231	227	226	209	207	223	N/A	N/A

Comparative examples C to F

Comparative examples C-F shown in table 2 below have been commercially sold in composite laminate application fields similar to examples 1-5. All of these examples are used in areas requiring barrier properties by ASTM F1670/F1671 and breathability as measured by MVTR values. All examples except example a are tri-layer laminates and are further described below:

comparative example C is a double layer laminate of a spunbond nonwoven sheet and a film layer prepared by thermal bonding from Medline.

Comparative example D is a tricool, a trilaminate of two outer spunbond nonwoven sheets and an inner film layer made by thermal bonding, available from Kimberly-Clark.

Comparative example E is SmartGown^TMA trilaminate of a repellent spunmelt nonwoven outer layer, a film inner layer, and a spunbond nonwoven outer layer made by adhesive lamination was produced from Allegiance.

Comparative example F is a trilaminate of an absorbent nonwoven outer layer, a film inner layer and a nonwoven outer layer made by thermal bonding.

TABLE 2

	Film layer	Film thickness (mil)	ASTM F1670	ASTM F1671	MVTR(g/m2Day)	Static decay (seconds, +/-)	Top alcohol repellency	Overall alcohol repellency
									Examples 1 to 12	Breathable film	0.7 or 0.8	By passing	By passing	5161-7553	Less than 1	9	2-5
Example A	Breathable film	0.6	By passing	By passing	4934	Less than 1	9	3
									Example B	Microporous membrane	0.8	By passing	By passing	3716	Less than 1	9	4
Example C	Microporous membrane	About 1.2	By passing	By passing	20762	Infinite number of elements	1	1
									Example D	Microporous membrane	About 1	By passing	By passing	8008	Less than 1	1	1
Example E	Breathable film	About 0.6	By passing	By passing	5017	Less than 1	10	10
									Example F	Breathable film	About 1	Has not passed through	Without data	4182	Less than 1	1	1

The data in table 2 show that: the composite laminated material adopting the protective and absorbing layer has protective, absorbing and antistatic performances and resistance and air permeability performances relative to the commodity of the composite laminated material. Also, inventive examples 1-12 had better MVTR values than laminates of similar film layers, comparative examples E and F, while maintaining the resistance performance. Comparative examples C, D and E did not have the absorbency of the nonwoven inner layer. Comparative examples C, D and F did not have the protective properties of the top layer.

Claims (16)

1. A moisture vapor permeable composite sheet comprising:

a nonwoven layer of absorbent fibers having two opposing surfaces, said nonwoven layer of absorbent fibers comprising 0% to 95% by weight synthetic thermoplastic fibers and 100% to 5% by weight absorbent fibers;

a repellent nonwoven layer having two opposing surfaces, said repellent nonwoven layer comprising synthetic fibers, said synthetic fibers comprising a repellent composition; and

a non-porous, liquid impermeable, moisture vapor permeable film layer having a thickness of no more than 25 microns sandwiched between said repellent nonwoven layer and said absorbent nonwoven layer.

2. The moisture vapor permeable composite sheet of claim 1, wherein the absorbent fibrous nonwoven layer comprises from 30 weight percent to 70 weight percent synthetic thermoplastic fibers and from 70 weight percent to 30 weight percent absorbent fibers.

3. The moisture vapor permeable composite sheet of claim 1, wherein the absorbent fibrous nonwoven layer comprises thermoplastic synthetic fibers selected from the group consisting of: polyethylene terephthalate, polypropylene terephthalate, polyethylene, polypropylene and polyamide.

4. The moisture vapor permeable composite sheet of claim 1, wherein the absorbent fiber nonwoven layer comprises absorbent fibers selected from the group consisting of: natural cellulose fibers, regenerated cellulose fibers, absorbent synthetic fibers, animal fibers, and mixtures thereof.

5. The moisture vapor permeable composite sheet of claim 1, wherein the moisture vapor permeable film layer is formed by extrusion onto one surface of the absorbent nonwoven layer and one surface of the repellent nonwoven layer is bonded to the moisture vapor permeable film layer by an intermediate adhesive layer.

6. The moisture vapor permeable composite sheet of claim 1, wherein said moisture vapor permeable film layer is selected from the group consisting of: block polyetherester copolymers, polyetheramide copolymers, polyurethane copolymers, polyetherimide ester copolymers, polyvinyl alcohols, and combinations thereof.

7. A moisture vapor permeable composite sheet comprising:

a nonwoven layer of staple fiber absorbent fibers having two opposing surfaces;

a repellent nonwoven layer having two opposing surfaces, said repellent nonwoven layer comprising synthetic fibers comprising a repellent composition; and

a non-porous, liquid impermeable, moisture vapor permeable film layer having a thickness of no more than 25 microns sandwiched between said repellent nonwoven layer and said absorbent nonwoven layer.

8. The moisture vapor permeable composite sheet of claim 7, wherein the absorbent fibrous nonwoven layer is powder bonded.

9. The moisture vapor permeable composite sheet of claim 1, wherein the absorbent fibrous nonwoven layer is hydroentangled.

10. A moisture vapor permeable composite sheet comprising:

a nonwoven layer of absorbent fibers having two opposing surfaces, and

a non-porous, liquid impermeable, moisture vapor permeable film layer having a thickness of no more than 25 microns.

11. The composite sheet of claim 10 wherein said absorbent fibrous nonwoven layer comprises from 0% to 95% by weight synthetic thermoplastic fibers and from 100% to 5% by weight absorbent fibers.

12. The composite sheet of claim 11 wherein said thermoplastic synthetic fibers are selected from the group consisting of: polyethylene terephthalate, polypropylene terephthalate, polyethylene, polypropylene and polyamide and mixtures thereof.

13. The composite sheet of claim 1, wherein the absorbent fibers are selected from the group consisting of: natural cellulose fibers, regenerated cellulose fibers, absorbent synthetic fibers, animal fibers, and mixtures thereof.

14. The moisture vapor permeable composite sheet of claim 10, wherein the absorbent fibrous nonwoven layer is powder bonded.

15. The moisture vapor permeable composite sheet of claim 7, wherein the absorbent fibrous nonwoven layer is hydroentangled.

16. The composite sheet of claim 10 wherein said film layer is made from a composition selected from the group consisting of: block polyetherester copolymers, polyetheramide copolymers, polyurethane copolymers, polyetherimide ester copolymers, polyvinyl alcohols, and combinations thereof.