EP0893530A1 - Breathable nonwoven liquid barrier fabric and method - Google Patents
Breathable nonwoven liquid barrier fabric and method Download PDFInfo
- Publication number
- EP0893530A1 EP0893530A1 EP98108294A EP98108294A EP0893530A1 EP 0893530 A1 EP0893530 A1 EP 0893530A1 EP 98108294 A EP98108294 A EP 98108294A EP 98108294 A EP98108294 A EP 98108294A EP 0893530 A1 EP0893530 A1 EP 0893530A1
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- EP
- European Patent Office
- Prior art keywords
- film
- fabric
- liquid
- nonwoven fabric
- radiation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
- D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
- D04H3/12—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with filaments or yarns secured together by chemical or thermo-activatable bonding agents, e.g. adhesives, applied or incorporated in liquid or solid form
-
- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
- D04H1/58—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives
- D04H1/64—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives the bonding agent being applied in wet state, e.g. chemical agents in dispersions or solutions
Definitions
- This invention relates to nonwoven fabrics having a vapor breathable film layer incorporated therein, with said fabrics being substantially impermeable to liquids.
- Nonwoven fabrics are produced by a variety of processes distinguished from weaving of yarns on a loom.
- nonwoven fabrics are made from fibers or continuous filaments, and the fibers or filaments are consolidated at points of intersection by thermal or adhesive bonding, or by fiber or filament entanglement.
- nonwovens are porous and easily transmit liquids and any agents carried by or in the liquids.
- Many existing and proposed uses for nonwovens require a fabric which is essentially liquid proof, but which can breathe by allowing transmission of water vapor.
- End uses for breathable nonwovens include clothing, such as medical apparel, components of diapers or other disposable sanitary articles, building covering materials and the like.
- a nonwoven fabric may be laminated or extrusion coated with a film, and the film may be of a non-porous or microporous type, but the lamination or extrusion coating process is expensive and requires substantial space and equipment, especially if the laminate is produced on the same line with the nonwoven.
- a nonwoven with a waterproofing agent such as a fluoro compound
- a nonwoven with a waterproofing agent such as a fluoro compound
- the average pore size of nonwoven fabrics can be decreased by providing composite fabrics, such as spunbond-meltblown-spunbond (SMS) fabrics, wherein the meltblown layer comprises very fine fibers.
- SMS spunbond-meltblown-spunbond
- a nonwoven fabric is coated with a liquid, radiation curable, film forming polymer or resin to provide a continuous and unbroken film on the fabric, and the liquid polymer film is subjected to radiation to cure the polymer and to cause a durable unbroken, flexible film to form and to adhere and bond to the fabric.
- a continuous, flexible and liquid impervious film can be formed on substrates which are porous.
- the resulting coated fabric is impervious to the transfer or passage of liquids such as water, blood and alcohol but is capable of transmitting water vapor.
- the coating and curing steps require a minimal amount of space, and the operation may be carried out on line during production of the nonwoven fabric using a small production space at normal nonwoven production line speeds.
- the coating can be selectively applied to only portions of a moving nonwoven fabric web, for example, to render only certain portions impervious to liquids, as may be desired in a component of a diaper, or in medical products.
- liquid radiation curable resins are applied to a surface of a nonwoven, followed by curing of the resin, in order to increase the hydrostatic head of the fabric by a minimum of two to three times the original hydrostatic head.
- One preferred type of radiation curable resins are ultraviolet curable resins containing a monomer having one or more functional groups, a polymer or oligomer having unsaturation sites, and a photoinitiator sensitive to UV radiation.
- the photoinitiator supplies free radicals or cations to cause polymerization of the monomer with the polymer and provide a solid film.
- nonwoven fabric means a fabric comprising man-made or polymer fibers or filaments which are bonded together at points or are entangled to provide a coherent, planar fabric.
- Various types of bonding include thermal bonding and chemical and adhesive bonding.
- the types of entanglement include needling and hydroentanglement, the latter involving impingement of jets of water on an unconsolidated web supported on a porous support. Fibers may also be consolidated by wet laying techniques.
- spunbonding refers to a method by which a large number of continuous filaments are spun or extruded, drawn and deposited on a moving conveyor as a moving web. The filaments are then thermally bonded, either by virtue of the filaments having a low softening temperature, or by incorporating some fraction of binder or lower melting point filaments into the web.
- a related process is melt blowing, in which molten filaments are extruded from small apertures, and are blown and drawn by impingement of high velocity hot air toward a conveyor to form a continuous web.
- Fabrics made from fibers usually involve the formation of a fiber web by carding or air laying, and then bonding or consolidating the web.
- the web may be pattern bonded using an engraved heated calender or an ultrasonic bonder, hot air bonded, or it may be resin bonded and heated. Entanglement procedures have been described above.
- the polymers presently used to make nonwovens include polyolefins, such as polyethylene and polypropylene, and polyester, although many others are known and can be employed, such as nylon, rayon, polyurethane, and others. It is not believed that the present invention is limited to the type of polymer or fiber employed in the nonwoven, since the film as applied mechanically interacts with the fabric and surrounds at least portions of the fibers or filaments to provide a strong mechanical bond. Continuous films are more easily applied to fabrics having a small pore size.
- the weight of the nonwoven fabric is not critical and may range in the order of 3 to 100 grams per square meter.
- the unconsolidated web of fibers or filaments is preferably bonded prior to the application of the film coating, such that the fibers or filaments are fixed in position and the web is cohesive and shape retaining.
- the degree of bonding is not critical, as long as the web is sufficiently shape retaining to allow application of the liquid film.
- nonwoven fabric means a web of fibers or filaments which has been bonded.
- the nonwoven substrate may comprise a single layer or multiple layers, and these layers may be produced by identical or different processes.
- a composite nonwoven may include spunbond and meltblown layers.
- the film may reside as an outer bonded layer or may reside as an inner layer of a composite.
- One preferred nonwoven substrate is a fabric having at least one meltblown layer and at least one spunbond layer.
- Radiation curable polymers are available from a variety of commercial sources and are furnished in liquid form, generally free of any solvents.
- the resin is normally a mixture comprising a monomer having one or more functional groups, and a polymer or oligomer having a degree of unsaturation.
- An oligomer is selected from those capable of forming a flexible film upon curing.
- the monomer is referred to as a dilutent for the polymer, with the ratio of the two being adjustable to control viscosity.
- the uncured liquid resin must be sufficiently viscous to be applied and retained as a continuous liquid film on a nonwoven fabric for a period of several seconds up to several minutes. This parameter is usually not significant, since it is normally possible to apply and cure the liquid film within a fraction of a second and up to several seconds.
- the liquid resin may be cured directly by electron beam radiation or may be cured by ultraviolet light if a photoinitiator is incorporated into the resin.
- photoinitiators There are two principal types of photoinitiators, free radical and cationic, which are selected depending on the species of resins used. Free radical initiators are employed with acrylates, while cationic photoinitiators are employed with vinyl ethers and epoxy compounds. Formulations of a large variety of radiation curable resins are available from RadTech, Northbrook, Illinois. Radiation curable resins are described in the following United States patents, incorporated herein by references: 4,125,503; 4,649,082; 4,937,173; 5,098,982; 5,281,662; and 5,352,713.
- a radiation curable resin is selected, which when polymerized into a film, will be flexible, will be impervious to the transfer or liquids, but will have a high rate of vapor transmission, allowing the film coated fabric to breathe.
- film flexibility and breathability is determined by film thickness and film chemistry, such as, for example, the percentage of monomers, the crossline density and chemical nature of the polymer backbone.
- the cured resin should be non-toxic and non-reactive.
- the composite film and fabric will have a moisture or vapor transmission rate which exceeds 500 grams per square meter per day, and preferably exceeds 3,000 g/m 2 per day, with a hydrohead in excess of 65 cm.
- the liquid resin composition comprises (A) an unsaturated polyester component containing an unsaturated polyester polymer, an unsaturated polyester oligomer or a mixture thereof; and (B) a non-polymerized, cocurable vinyl ether component which may be separate from or structurally incorporated in the unsaturated polyester component, provided that the vinyl ether component contains an average of at least two vinyl ether groups per molecule of the vinyl either component.
- a photoinitiator is added if UV curing is desired.
- additives may be added to the liquid resin prior to application. Possible additions include antistatic agents, antimicrobial agents, fillers to control weight and viscosity, pigments and the like. The limitations on additives are that they should not interfere with the radiation curing process and should be compatible with the resin system employed. Other typical additives include defoamer, adhesion promoters, flatting agents and stabilizers.
- the liquid resin coating is applied to the nonwoven, preferably a nonwoven web carried by a conveyor, by known conventional coating processes.
- coating processes include a gravure or flexigraphic printing, roll coating, blade coating, and spray coating.
- a preferred method involves transfer coating a rubber roll with a thin layer using a gravure with a doctor blade assembly and allowing the nonwoven moving on a conveyor belt to contact the web on one side.
- the coatings will be applied zonally or uniformly to the web at a coating thickness of 3 to 500 ⁇ m, with 3 to 100 ⁇ m being preferred. Coatings may be applied to one or both sides of the fabric.
- a minimum amount of liquid resin is applied to the fabric substrate to achieve the desired properties, which also allows the coating to be cured more rapidly.
- rate of application of the liquid as a uniform coating should exceed about three grams per square meter (gsm).
- the upper limit of coating application is based on cost considerations, and generally an application rate of twenty-five gsm will not be exceeded, providing a coating thickness of 25 microns. In general, if the liquid resin does not contain solvents, the liquid application rate will be equal to the cured film rate.
- a low basis weight of the liquid resin may be applied, such that when the resin is cured, the fabric will exhibit a substantial increase in hydrostatic head without any substantial impact on the softness, drape and flexibility of the fabric.
- low application rates for example three to seven gsm, it is normally possible to increase the hydrostatic head by a factor of two to three times, with the fabric remaining permeable to the transfer of liquid vapors.
- the liquid film resident on the surface is then rapidly cured, or is cured while the liquid resin still resides as a continuous and unbroken film on the nonwoven fabric.
- This is accomplished by exposing the resin coated nonwoven fabric to a source of suitable radiation.
- a source of suitable radiation For example, if the photoinitiator in the resin is activated by ultraviolet light, the coated substrate may be passed through an enclosure having a series of UV lamps, such as mercury lamps.
- ionizing radiation is employed by use of an electron beam, a one mil thick liquid film can be cured in air through its thickness upon exposure to a 0.5 to 5 megarads of ionizing radiation.
- ultraviolet radiation having a wavelength of 180-400 nanometers may be used to effect the cure.
- Typical medium pressure tubular mercury lamps have an output of 200 watts per inch along the length of the tube.
- the tubes can be in series and in parallel and are typically spaced a few inches from the uncured film.
- photosensitizers and photoinitiators are used in UV curing.
- photosensitizers include benzophenone, anthraquinone, and thioxamthone.
- photoinitiators include isobutyl benzoin ether, alpha, alpha-diethyozyacetophenone, and alpha, alpha-dimethoxy-alpha-phenylacetophenone.
- the apparatus for applying and curing the coating will be applied at the exit end of the line, that is, between the exit of the finished nonwoven web and a winding apparatus for winding the web into a roll.
- the web may be supported on a flat conveyor or a rotating roll, or may be passed unsupported through the coating apparatus.
- the web, coated with liquid resin is then passed through an enclosure containing the source of radiation.
- Line speeds are not critical, since continuous curing is possible at line speeds up to at least 300 meters per minute. The radiation capacity and amount of exposure is determined by liquid resin chemistry and thickness, fillers, if any, and line speed.
- the coating As the coating is being applied to the web and cured, it is desirable to prevent excessive penetration of the coating into the fabric. This can be accomplished, for example, by using a low pore size web or by initiating the radiation cure immediately after application. Also, a viscous coating may be used, which is heated to reduce viscosity during application, or a high shear coating method may be used.
- An important aspect of the present invention is the ability to significantly increase the hydrohead of light weight nonwoven fabrics while maintaining high vapor transmission.
- Treated fabrics having a basis weight of less than 50 gsm can easily obtain a hydrohead of greater than 90 cm while maintaining a moisture vapor transmission rate of greater than 3,000 g/m 2 per day.
- the hydrostatic head of a 20 gsm (grams per square meter) SMS nonwoven fabric can be increased from about 30 cm before coating to greater than 100 cm after coating.
- the moisture transmission rate of the fabric exceeds 5,000 g/m 2 per day. Since there are substantially no pores in the film layer, vapor transmission occurs through absorption at one surface and transmission to the other surface of the film.
- hydrohead refers to a standard test to measure the liquid barrier properties of a fabric.
- the hydrohead test determines the height of water (in centimeters) which the fabric will support before a predetermined amount of liquid will pass through, and is defined in Federal Test Standard No. 191A, Method 5514.
- the water vapor transmission rate (WVTR) of fabrics is specified in ASTM Standard Test Method E-96-80.
- Nonwoven fabrics are produced in bulk in the form of rolls and are later cut and converted into a wide variety of useful articles.
- breathable nonwoven fabrics which are fluid repellent, and which can be supplied at a low cost.
- Possible end uses include single or multiple use protective apparel, such as medical gowns and laboratory coats, industrial protective clothing and rain wear.
- the resin coating can be applied only to areas of the fabric requiring high repellency, such as the front panels and sleeves of an operating gown.
- the radiation curable resin can also be applied when the fabric is being converted to a final product.
- preselected areas of fabric may be coated, such as the inner surface of the outermost layer of fabric, in order to prevent leaking of liquids, while retaining a soft, cloth-like feel.
- a resin coating is applied to only one side of the fabric, and as thinly as possible, while still providing a good liquid barrier. This will assure that the composite will continue to have the soft feel of a fabric, and the uncoated side will have the appearance and tactile qualities of a porous fabric.
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Dispersion Chemistry (AREA)
- Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
- Laminated Bodies (AREA)
- Synthetic Leather, Interior Materials Or Flexible Sheet Materials (AREA)
- Manufacturing Of Multi-Layer Textile Fabrics (AREA)
- Nonwoven Fabrics (AREA)
Abstract
A porous, nonwoven fabric made from bonded fibers and/or filaments
is provided, and a continuous film or layer of a liquid radiation curable resin
is applied to the fabric surface. The liquid film is subjected to radiation to
cure the liquid into a solid film bonded to the surface of the fabric. The film
renders the fabric impervious to liquids but allows passage of liquid vapor, and
the technique provides an alternative to more expensive ways to achieve the
same barrier properties.
Description
This invention relates to nonwoven fabrics having a vapor breathable
film layer incorporated therein, with said fabrics being substantially
impermeable to liquids.
Nonwoven fabrics are produced by a variety of processes distinguished
from weaving of yarns on a loom. In general, nonwoven fabrics are made
from fibers or continuous filaments, and the fibers or filaments are
consolidated at points of intersection by thermal or adhesive bonding, or by
fiber or filament entanglement.
Most nonwovens, as commercially produced, are porous and easily
transmit liquids and any agents carried by or in the liquids. Many existing and
proposed uses for nonwovens require a fabric which is essentially liquid proof,
but which can breathe by allowing transmission of water vapor. End uses for
breathable nonwovens include clothing, such as medical apparel, components
of diapers or other disposable sanitary articles, building covering materials and
the like.
Many attempts have been made to provide a nonwoven with the above
properties. As one example, a nonwoven fabric may be laminated or extrusion
coated with a film, and the film may be of a non-porous or microporous type,
but the lamination or extrusion coating process is expensive and requires
substantial space and equipment, especially if the laminate is produced on the
same line with the nonwoven. It is also known to treat a nonwoven with a
waterproofing agent, such as a fluoro compound, but such compounds are
relatively expensive, do not fill the pores of the fabric, and require separate
treatment and drying steps. The average pore size of nonwoven fabrics can be
decreased by providing composite fabrics, such as spunbond-meltblown-spunbond
(SMS) fabrics, wherein the meltblown layer comprises very fine
fibers. Even composite fabrics, however, do not provide a high barrier to
liquids and normally require topical treatments or an extruded film layer to
achieve high liquid barrier properties.
Many of the present solutions to the barrier problem are inadequate in
that the treated or film laminated nonwoven is not very durable, and the initial
properties are degraded upon handling, fabrication, washing and the like.
Also, treated and film laminated fabrics tend to be stiff and unsuitable for
many applications.
In accordance with the present invention, a nonwoven fabric is coated
with a liquid, radiation curable, film forming polymer or resin to provide a
continuous and unbroken film on the fabric, and the liquid polymer film is
subjected to radiation to cure the polymer and to cause a durable unbroken,
flexible film to form and to adhere and bond to the fabric. Surprisingly, a
continuous, flexible and liquid impervious film can be formed on substrates
which are porous. Within ordinary levels of resin application, the resulting
coated fabric is impervious to the transfer or passage of liquids such as water,
blood and alcohol but is capable of transmitting water vapor.
The coating and curing steps require a minimal amount of space, and
the operation may be carried out on line during production of the nonwoven
fabric using a small production space at normal nonwoven production line
speeds. Advantageously, the coating can be selectively applied to only
portions of a moving nonwoven fabric web, for example, to render only
certain portions impervious to liquids, as may be desired in a component of a
diaper, or in medical products.
In another aspect of the present invention, liquid radiation curable
resins are applied to a surface of a nonwoven, followed by curing of the resin,
in order to increase the hydrostatic head of the fabric by a minimum of two to
three times the original hydrostatic head.
One preferred type of radiation curable resins are ultraviolet curable
resins containing a monomer having one or more functional groups, a polymer
or oligomer having unsaturation sites, and a photoinitiator sensitive to UV
radiation. The photoinitiator supplies free radicals or cations to cause
polymerization of the monomer with the polymer and provide a solid film.
The use of a radiation curable, film forming polymer, greatly reduces
the costs compared to current alternative practices, since only a liquid
applicator and radiation source are required. The cost of relatively expensive
treating agents, and the use of extra heating, film extrusion, and lamination
steps, are eliminated.
As used herein, the term "nonwoven fabric" means a fabric comprising
man-made or polymer fibers or filaments which are bonded together at points
or are entangled to provide a coherent, planar fabric. Various types of
bonding include thermal bonding and chemical and adhesive bonding. The
types of entanglement include needling and hydroentanglement, the latter
involving impingement of jets of water on an unconsolidated web supported on
a porous support. Fibers may also be consolidated by wet laying techniques.
The various methods for making nonwovens are well known and will
not be described herein in detail. The term spunbonding refers to a method by
which a large number of continuous filaments are spun or extruded, drawn and
deposited on a moving conveyor as a moving web. The filaments are then
thermally bonded, either by virtue of the filaments having a low softening
temperature, or by incorporating some fraction of binder or lower melting
point filaments into the web. A related process is melt blowing, in which
molten filaments are extruded from small apertures, and are blown and drawn
by impingement of high velocity hot air toward a conveyor to form a
continuous web.
Fabrics made from fibers usually involve the formation of a fiber web
by carding or air laying, and then bonding or consolidating the web. For
example, the web may be pattern bonded using an engraved heated calender or
an ultrasonic bonder, hot air bonded, or it may be resin bonded and heated.
Entanglement procedures have been described above.
The polymers presently used to make nonwovens include polyolefins,
such as polyethylene and polypropylene, and polyester, although many others
are known and can be employed, such as nylon, rayon, polyurethane, and
others. It is not believed that the present invention is limited to the type of
polymer or fiber employed in the nonwoven, since the film as applied
mechanically interacts with the fabric and surrounds at least portions of the
fibers or filaments to provide a strong mechanical bond. Continuous films are
more easily applied to fabrics having a small pore size. The weight of the
nonwoven fabric is not critical and may range in the order of 3 to 100 grams
per square meter.
The unconsolidated web of fibers or filaments is preferably bonded
prior to the application of the film coating, such that the fibers or filaments are
fixed in position and the web is cohesive and shape retaining. The degree of
bonding is not critical, as long as the web is sufficiently shape retaining to
allow application of the liquid film. As used herein, the term "nonwoven
fabric" means a web of fibers or filaments which has been bonded.
The nonwoven substrate may comprise a single layer or multiple layers,
and these layers may be produced by identical or different processes. For
example, a composite nonwoven may include spunbond and meltblown layers.
The film may reside as an outer bonded layer or may reside as an inner layer
of a composite. One preferred nonwoven substrate is a fabric having at least
one meltblown layer and at least one spunbond layer.
Radiation curable polymers are available from a variety of commercial
sources and are furnished in liquid form, generally free of any solvents. The
resin is normally a mixture comprising a monomer having one or more
functional groups, and a polymer or oligomer having a degree of unsaturation.
An oligomer is selected from those capable of forming a flexible film upon
curing. The monomer is referred to as a dilutent for the polymer, with the
ratio of the two being adjustable to control viscosity. For the purposes of the
present invention, the uncured liquid resin must be sufficiently viscous to be
applied and retained as a continuous liquid film on a nonwoven fabric for a
period of several seconds up to several minutes. This parameter is usually not
significant, since it is normally possible to apply and cure the liquid film
within a fraction of a second and up to several seconds.
The liquid resin may be cured directly by electron beam radiation or
may be cured by ultraviolet light if a photoinitiator is incorporated into the
resin. There are two principal types of photoinitiators, free radical and
cationic, which are selected depending on the species of resins used. Free
radical initiators are employed with acrylates, while cationic photoinitiators are
employed with vinyl ethers and epoxy compounds. Formulations of a large
variety of radiation curable resins are available from RadTech, Northbrook,
Illinois. Radiation curable resins are described in the following United States
patents, incorporated herein by references: 4,125,503; 4,649,082; 4,937,173;
5,098,982; 5,281,662; and 5,352,713.
For the purpose of the present invention, a radiation curable resin is
selected, which when polymerized into a film, will be flexible, will be
impervious to the transfer or liquids, but will have a high rate of vapor
transmission, allowing the film coated fabric to breathe. In general, film
flexibility and breathability is determined by film thickness and film chemistry,
such as, for example, the percentage of monomers, the crossline density and
chemical nature of the polymer backbone. If the fabric is to be used in
articles such as clothing or disposable sanitary articles, the cured resin should
be non-toxic and non-reactive. For many of these articles, it is important to
prevent penetration and transfer of liquids such as blood or liquid waste, while
allowing transmission of water vapor for increased comfort. Preferably, the
composite film and fabric will have a moisture or vapor transmission rate
which exceeds 500 grams per square meter per day, and preferably exceeds
3,000 g/m2 per day, with a hydrohead in excess of 65 cm.
An especially suitable resin system is described in U.S. patent no.
5,536,760, incorporated herein by reference. The liquid resin composition
comprises (A) an unsaturated polyester component containing an unsaturated
polyester polymer, an unsaturated polyester oligomer or a mixture thereof; and
(B) a non-polymerized, cocurable vinyl ether component which may be
separate from or structurally incorporated in the unsaturated polyester
component, provided that the vinyl ether component contains an average of at
least two vinyl ether groups per molecule of the vinyl either component. A
photoinitiator is added if UV curing is desired.
Various additives may be added to the liquid resin prior to application.
Possible additions include antistatic agents, antimicrobial agents, fillers to
control weight and viscosity, pigments and the like. The limitations on
additives are that they should not interfere with the radiation curing process
and should be compatible with the resin system employed. Other typical
additives include defoamer, adhesion promoters, flatting agents and stabilizers.
The liquid resin coating is applied to the nonwoven, preferably a
nonwoven web carried by a conveyor, by known conventional coating
processes. Examples of coating processes include a gravure or flexigraphic
printing, roll coating, blade coating, and spray coating. A preferred method
involves transfer coating a rubber roll with a thin layer using a gravure with a
doctor blade assembly and allowing the nonwoven moving on a conveyor belt
to contact the web on one side. Depending on end use requirements, the
coatings will be applied zonally or uniformly to the web at a coating thickness
of 3 to 500 µm, with 3 to 100 µm being preferred. Coatings may be applied
to one or both sides of the fabric.
A minimum amount of liquid resin is applied to the fabric substrate to
achieve the desired properties, which also allows the coating to be cured more
rapidly. To provide a cured film free of pinholes, it has been found that the
rate of application of the liquid as a uniform coating should exceed about three
grams per square meter (gsm). The upper limit of coating application is based
on cost considerations, and generally an application rate of twenty-five gsm
will not be exceeded, providing a coating thickness of 25 microns. In general,
if the liquid resin does not contain solvents, the liquid application rate will be
equal to the cured film rate.
Although less preferred, a low basis weight of the liquid resin may be
applied, such that when the resin is cured, the fabric will exhibit a substantial
increase in hydrostatic head without any substantial impact on the softness,
drape and flexibility of the fabric. At low application rates, for example three
to seven gsm, it is normally possible to increase the hydrostatic head by a
factor of two to three times, with the fabric remaining permeable to the
transfer of liquid vapors.
The liquid film resident on the surface is then rapidly cured, or is cured
while the liquid resin still resides as a continuous and unbroken film on the
nonwoven fabric. This is accomplished by exposing the resin coated
nonwoven fabric to a source of suitable radiation. For example, if the
photoinitiator in the resin is activated by ultraviolet light, the coated substrate
may be passed through an enclosure having a series of UV lamps, such as
mercury lamps.
Suitable curing procedures are described in the aforesaid U.S. patent
no. 5,536,760. If ionizing radiation is employed by use of an electron beam,
a one mil thick liquid film can be cured in air through its thickness upon
exposure to a 0.5 to 5 megarads of ionizing radiation.
If a photoinitiator is incorporated into the resin, ultraviolet radiation
having a wavelength of 180-400 nanometers may be used to effect the cure.
Typical medium pressure tubular mercury lamps have an output of 200 watts
per inch along the length of the tube. The tubes can be in series and in
parallel and are typically spaced a few inches from the uncured film.
Both photosensitizers and photoinitiators are used in UV curing.
Examples of photosensitizers include benzophenone, anthraquinone, and
thioxamthone. Examples of photoinitiators include isobutyl benzoin ether,
alpha, alpha-diethyozyacetophenone, and alpha, alpha-dimethoxy-alpha-phenylacetophenone.
If cured coatings are to be applied on a continuous nonwoven
production line, the apparatus for applying and curing the coating will be
applied at the exit end of the line, that is, between the exit of the finished
nonwoven web and a winding apparatus for winding the web into a roll.
During application of the liquid resin, the web may be supported on a flat
conveyor or a rotating roll, or may be passed unsupported through the coating
apparatus. The web, coated with liquid resin, is then passed through an
enclosure containing the source of radiation. Line speeds are not critical,
since continuous curing is possible at line speeds up to at least 300 meters per
minute. The radiation capacity and amount of exposure is determined by
liquid resin chemistry and thickness, fillers, if any, and line speed.
As the coating is being applied to the web and cured, it is desirable to
prevent excessive penetration of the coating into the fabric. This can be
accomplished, for example, by using a low pore size web or by initiating the
radiation cure immediately after application. Also, a viscous coating may be
used, which is heated to reduce viscosity during application, or a high shear
coating method may be used.
An important aspect of the present invention is the ability to
significantly increase the hydrohead of light weight nonwoven fabrics while
maintaining high vapor transmission. Treated fabrics having a basis weight of
less than 50 gsm can easily obtain a hydrohead of greater than 90 cm while
maintaining a moisture vapor transmission rate of greater than 3,000 g/m2 per
day. For example, the hydrostatic head of a 20 gsm (grams per square meter)
SMS nonwoven fabric can be increased from about 30 cm before coating to
greater than 100 cm after coating. In spite of the significant increase in
repellant characteristics, the moisture transmission rate of the fabric exceeds
5,000 g/m2 per day. Since there are substantially no pores in the film layer,
vapor transmission occurs through absorption at one surface and transmission
to the other surface of the film.
The above figures can be compared to SMS fabrics treated with
fluorocarbon repellents. For example, U.S. patent 5,482,765 reports a 54 gsm
SMS fabric having a hydrohead of 92-96 cm and a moisture vapor
transmission rate of 4720-4830 g/m2 per day.
The term "hydrohead" as used herein refers to a standard test to
measure the liquid barrier properties of a fabric. The hydrohead test
determines the height of water (in centimeters) which the fabric will support
before a predetermined amount of liquid will pass through, and is defined in
Federal Test Standard No. 191A, Method 5514. The water vapor transmission
rate (WVTR) of fabrics is specified in ASTM Standard Test Method E-96-80.
Nonwoven fabrics are produced in bulk in the form of rolls and are
later cut and converted into a wide variety of useful articles. Presently, there
is a need for breathable nonwoven fabrics which are fluid repellent, and which
can be supplied at a low cost. Possible end uses include single or multiple use
protective apparel, such as medical gowns and laboratory coats, industrial
protective clothing and rain wear. In some cases, the resin coating can be
applied only to areas of the fabric requiring high repellency, such as the front
panels and sleeves of an operating gown.
The radiation curable resin can also be applied when the fabric is being
converted to a final product. For example, during the production of
disposable sanitary articles, such as diapers, preselected areas of fabric may be
coated, such as the inner surface of the outermost layer of fabric, in order to
prevent leaking of liquids, while retaining a soft, cloth-like feel.
For most end use applications, a resin coating is applied to only one
side of the fabric, and as thinly as possible, while still providing a good liquid
barrier. This will assure that the composite will continue to have the soft feel
of a fabric, and the uncoated side will have the appearance and tactile qualities
of a porous fabric.
Claims (14)
- A method for making a breathable nonwoven liquid barrier fabric, said method comprising the steps of preparing a bonded porous nonwoven fabric, applying a coating of a liquid, radiation curable resin onto at least one surface of the fabric to form a continuous film thereon, and then radiating said film to provide a cured, continuous solid film on said fabric, said cured film being substantially impervious to liquids and pervious to vapors.
- The method of claim 1 wherein said nonwoven fabric is produced continuously on a production line, and wherein said radiation curable resin is applied and cured in said production line.
- The method of claim 1 wherein said bonded nonwoven fabric comprises continuous filaments.
- The method of claim 1 wherein said bonded nonwoven fabric comprises fibers.
- The method of claim 1 wherein said coating is applied at a thickness of from about five to five hundred microns.
- The method of claim 5 wherein said coating is applied at a thickness of from about three to about one hundred microns.
- The method of claim 1 wherein said liquid, radiation curable resin comprises a monomer, a polymer and a photoinitiator.
- The method of claim 1 wherein said radiation curable resin comprises a vinyl ether ester.
- The method of claim 1 wherein said liquid radiation curable resin is coated only on portions of said nonwoven fabric.
- A breathable nonwoven liquid barrier fabric comprising a nonwoven fabric having opposed outer surfaces, and a continuous film of radiation cured resin adhered to one of said surfaces, said film being substantially impervious to liquids and pervious to vapor.
- A vapor permeable, liquid impermeable composite, said composite comprising a porous nonwoven fabric having first and second surfaces, and a radiation cured film having a thickness of 3 to 100 microns bonded to said first surface, said second surface being free of radiation cured film.
- The composite of claim 11 wherein said radiation cured film comprises polyester polymers and a cocured vinyl ether.
- The composite of claim 11 wherein said composite has a vapor transmission rate in excess of 500 grams per square meter per day, and a hydrohead in excess of 65 cm.
- The composite of claim 11 wherein said radiation cured film extends only over a portion of said nonwoven fabric.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US899589 | 1986-08-25 | ||
US89958997A | 1997-07-24 | 1997-07-24 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0893530A1 true EP0893530A1 (en) | 1999-01-27 |
Family
ID=25411253
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98108294A Withdrawn EP0893530A1 (en) | 1997-07-24 | 1998-05-07 | Breathable nonwoven liquid barrier fabric and method |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0893530A1 (en) |
JP (1) | JPH11158777A (en) |
CA (1) | CA2236402A1 (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001046505A2 (en) * | 1999-12-23 | 2001-06-28 | Kimberly-Clark Worldwide, Inc. | Nonwoven webs having liquid impermeability |
WO2001049913A1 (en) * | 2000-01-04 | 2001-07-12 | Yamil Alfredo Abdo Mina | Method for plasticizing a nonwoven with polyethylene or molten polypropylene for the manufacture of disposable garments used as bibs and for surgical applications |
EP2415428A1 (en) * | 2010-08-04 | 2012-02-08 | Polymer Group, Inc. | Breathable laminate and method of making the same |
US9765459B2 (en) | 2011-06-24 | 2017-09-19 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US9827755B2 (en) | 2011-06-23 | 2017-11-28 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US9827696B2 (en) | 2011-06-17 | 2017-11-28 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US10369769B2 (en) | 2011-06-23 | 2019-08-06 | Fiberweb, Inc. | Vapor-permeable, substantially water-impermeable multilayer article |
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EP0017364A1 (en) * | 1979-03-15 | 1980-10-15 | Rohm And Haas Company | Radiation-curable allyl benzoylbenzoate copolymers, their use, products thereof, and methods of making these products |
WO1989008554A1 (en) * | 1988-03-14 | 1989-09-21 | Sili-Tex, Inc. | Silicone polymer-internally coated webs |
US4871611A (en) * | 1985-11-15 | 1989-10-03 | Mead Release Products, Inc. | Breathable backing or release liner and process for forming the same |
WO1996036757A2 (en) * | 1995-05-17 | 1996-11-21 | Nextec Applications, Inc. | Barrier webs |
-
1998
- 1998-04-30 CA CA002236402A patent/CA2236402A1/en not_active Abandoned
- 1998-05-07 EP EP98108294A patent/EP0893530A1/en not_active Withdrawn
- 1998-07-23 JP JP10222477A patent/JPH11158777A/en active Pending
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EP0017364A1 (en) * | 1979-03-15 | 1980-10-15 | Rohm And Haas Company | Radiation-curable allyl benzoylbenzoate copolymers, their use, products thereof, and methods of making these products |
US4871611A (en) * | 1985-11-15 | 1989-10-03 | Mead Release Products, Inc. | Breathable backing or release liner and process for forming the same |
WO1989008554A1 (en) * | 1988-03-14 | 1989-09-21 | Sili-Tex, Inc. | Silicone polymer-internally coated webs |
WO1989008553A1 (en) * | 1988-03-14 | 1989-09-21 | Sili-Tex, Inc. | Silicone polymer fiber encapsulated webs |
WO1996036757A2 (en) * | 1995-05-17 | 1996-11-21 | Nextec Applications, Inc. | Barrier webs |
Cited By (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001046505A2 (en) * | 1999-12-23 | 2001-06-28 | Kimberly-Clark Worldwide, Inc. | Nonwoven webs having liquid impermeability |
WO2001046505A3 (en) * | 1999-12-23 | 2002-01-03 | Kimberly Clark Co | Nonwoven webs having liquid impermeability |
GB2375723A (en) * | 1999-12-23 | 2002-11-27 | Kimberly Clark Co | Nonwoven webs having liquid impermeability |
WO2001049913A1 (en) * | 2000-01-04 | 2001-07-12 | Yamil Alfredo Abdo Mina | Method for plasticizing a nonwoven with polyethylene or molten polypropylene for the manufacture of disposable garments used as bibs and for surgical applications |
EP2415428A1 (en) * | 2010-08-04 | 2012-02-08 | Polymer Group, Inc. | Breathable laminate and method of making the same |
US20120034837A1 (en) * | 2010-08-04 | 2012-02-09 | Polymer Group, Inc. | Breathable laminate and method of making same |
US9029277B2 (en) | 2010-08-04 | 2015-05-12 | Polymer Group, Inc. | Breathable laminate and method of making same |
US10800073B2 (en) | 2011-06-17 | 2020-10-13 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US9827696B2 (en) | 2011-06-17 | 2017-11-28 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US9827755B2 (en) | 2011-06-23 | 2017-11-28 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US10369769B2 (en) | 2011-06-23 | 2019-08-06 | Fiberweb, Inc. | Vapor-permeable, substantially water-impermeable multilayer article |
US10850491B2 (en) | 2011-06-23 | 2020-12-01 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US11123965B2 (en) | 2011-06-23 | 2021-09-21 | Fiberweb Inc. | Vapor-permeable, substantially water-impermeable multilayer article |
US11383504B2 (en) | 2011-06-23 | 2022-07-12 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US10253439B2 (en) | 2011-06-24 | 2019-04-09 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US9765459B2 (en) | 2011-06-24 | 2017-09-19 | Fiberweb, Llc | Vapor-permeable, substantially water-impermeable multilayer article |
US10900157B2 (en) | 2011-06-24 | 2021-01-26 | Berry Global, Inc. | Vapor-permeable, substantially water-impermeable multilayer article |
US11866863B2 (en) | 2011-06-24 | 2024-01-09 | Berry Global, Inc. | Vapor-permeable, substantially water-impermeable multilayer article |
Also Published As
Publication number | Publication date |
---|---|
CA2236402A1 (en) | 1999-01-24 |
JPH11158777A (en) | 1999-06-15 |
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