CA2290321A1 - Nonwoven surfactant compositions for improved durability and wetting - Google Patents
Nonwoven surfactant compositions for improved durability and wetting Download PDFInfo
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Abstract
A nonwoven fabric treated with a combination of at least two selected surfactants provides the fabric with durable, controlled rate wetting. The durable wetting may be fast, intermediate or slow. The durable, controlled rate wetting provided by the heated fabric is useful in a wide variety of absorbent products which are typically exposed to multiple fluid insults prior to disposal.
Description
--. CA 02290321 1999-11-24 r NONWOVEN SURFACTANT COMPOSITIONS
FOR IMPROVED DURABTLITY AND WETTING
This application is a continuation-in-part of U.S. Patent Application Serial No. 09/138,157 filed 21 August 1998, which in turn is a continuation-in-part of U.S. Patent Application 08/994,828, filed 19 December 1997, which in turn is a continuation-in-part of U.S. Patent Application 08/898,188, filed 22 July 1997, the disclosures of which are incorporated herein by reference. The earliest application claims priority from U.S.
Provisional Application No. 60/025,621, filed 04 September 1996.
FIELD OF THE INVENTION
This invention relates to nonwoven webs treated with surfactant compositions which provide a combination of durability and controlled wetting. More specifically, the invention relates to nonwoven webs treated with a durable surfactant and a fast, slow, or intermediate-rate wetting surfactant, either by separate treatments or a single, combined treatment.
BACKGROUND OF THE INVENTION
Nonwoven fabrics and their manufacture have been the subject of extensive development resulting in a wide variety of materials for numerous applications. For example, nonwovens of light basis weight and open structure are used in personal care items such as disposable diapers as liner fabrics that provide dry skin contact but readily transmit fluids to more absorbent materials which may also be nonwovens of a different composition and/or structure. Nonwovens of heavier weights may be designed with pore structures making them suitable for filtration, absorbent and barner applications such as wrappers for items to be sterilized, wipers or protective garments for medical, veterinary or industrial ~..
~ CA 02290321 1999-11-24 r"
uses. Even heavier weight nonwovens have been developed for recreational, agricultural and construction uses. These are but a few of the practically limitless examples of types of nonwovens and their uses that will be known to those skilled in the art who will also recognize that new nonwovens and uses are constantly being identified. There have also been developed different ways and equipment to make nonwovens having desired structures and compositions suitable for these uses. Examples of such processes include spunbonding, meltblowing, carding, and others which will be described in greater detail below. The present invention has general applicability to nonwovens as will be apparent to one skilled in the art, and it is not to be limited by reference or examples relating to specific nonwovens which are merely illustrative.
It is not always possible to efficiently produce a nonwoven having all the desired properties as formed, and it is frequently necessary to treat the nonwoven to improve or alter properties such as wettability by one or more fluids, repellency to one or more fluids, electrostatic characteristics, conductivity, and softness, to name just a few examples.
Conventional treatments involve steps such as dipping the nonwoven in a treatment bath, coating or spraying the nonwoven with the treatment composition, and printing the nonwoven with the treatment composition. For cost and other reasons it is usually desired to use the minimum amount of treatment composition that will produce the desired effect with an acceptable degree of uniformity.
When a nonwoven web is formed of a hydrophobic material, for example, a polyolefin, it is often desirable to modify the surface of the nonwoven web using a hydrophilic surfactant to increase the wettability of the web. An external hydrophilic surfactant is typically applied to the surface of the nonwoven web. An internal hydrophilic .,, r surfactant is typically blended with the polymer used to form the nonwoven web, and later migrates to the surface after the nonwoven web is formed.
External and internal hydrophilic surfactants may be characterized in terms of their durability and wettability. The durability of a surfactant refers generally to its ability to withstand stresses, such as repeated washing cycles of the nonwoven fabric, without being removed from the fabric or otherwise losing its effectiveness. The wettability of a surfactant refers generally to its ability to transform a hydrophobic nonwoven web into a fabric which readily assimilates and distributes aqueous liquids. Surfactants which cause an otherwise hydrophobic nonwoven web to assimilate liquids at a relatively fast pace, with high fluid intake volumes, are referred to as faster wetting surfactants. Surfactants which cause the nonwoven web to assimilate aqueous liquids at a relatively slow pace, with low fluid intake volume, are referred to as slower wetting surfactants. In addition to the surfactant type, other factors affect the ability of the nonwoven web to assimilate liquids, including without limitation the nonwoven web type, nonwoven polymer type, fiber size and density, amount of surfactant, and how it is applied.
Surfactants having high durability are desirable for a variety of reasons.
However, durable surfactants often provide insufficient wetting, and do not lend themselves to optimization of wetting characteristics desired for individual end use applications. There is a need or desire for a surfactant composition having both durability and controlled wetting, whether the desired wetting is fast, slow or in between. There is also a need or desire for a nonwoven fabric having durable wetting whose rate is predetermined and controlled.
SUMMARY OF THE INVENTION
The present invention is directed to a surfactant combination, and a nonwoven web treated with a surfactant combination. The surfactant combination includes a first . CA 02290321 1999-11-24 surfactant which provides durable wetting characteristics, and a second surfactant which controls the rate of wetting (fast, slow or intermediate). Used in combination, the surfactant combination provides a nonwoven fabric having wetting characteristics that are both durable and rate-determined.
The combination of surfactants provides a nonwoven fabric with the ability to withstand at least two and, advantageously, at least three insults using the cradle test described below. The first surfactant alone need not provide this level of durability. Instead, what is important is that the combination of surfactants (accounting for all synergisms between them) provides a nonwoven fabric having this level of durability.
The combination of surfactants also provides the nonwoven fabric with a controlled rate of wetting, as characterized by the cradle test described below. Again, it is not important for the second surfactant alone to provide the desired fluid intake rate. Instead, what is important is how the two surfactants behave in the environment in which they coexist with each other. In this environment, the surfactants together (accounting for all synergisms between them) must provide a desired wetting rate as well as durable wetting to the nonwoven fabric.
With the foregoing in mind, it is a feature and advantage of the invention to provide a surfactant combination which imparts durable wettability to a nonwoven fabric at a fast, intermediate or slow rate of wetting by an aqueous medium.
It is alsa a feature and advantage of the invention to provide a nonwoven fabric which is treated with the surfactant combination to effect durable wettability at a fast, intermediate or slow rate of wetting.
FOR IMPROVED DURABTLITY AND WETTING
This application is a continuation-in-part of U.S. Patent Application Serial No. 09/138,157 filed 21 August 1998, which in turn is a continuation-in-part of U.S. Patent Application 08/994,828, filed 19 December 1997, which in turn is a continuation-in-part of U.S. Patent Application 08/898,188, filed 22 July 1997, the disclosures of which are incorporated herein by reference. The earliest application claims priority from U.S.
Provisional Application No. 60/025,621, filed 04 September 1996.
FIELD OF THE INVENTION
This invention relates to nonwoven webs treated with surfactant compositions which provide a combination of durability and controlled wetting. More specifically, the invention relates to nonwoven webs treated with a durable surfactant and a fast, slow, or intermediate-rate wetting surfactant, either by separate treatments or a single, combined treatment.
BACKGROUND OF THE INVENTION
Nonwoven fabrics and their manufacture have been the subject of extensive development resulting in a wide variety of materials for numerous applications. For example, nonwovens of light basis weight and open structure are used in personal care items such as disposable diapers as liner fabrics that provide dry skin contact but readily transmit fluids to more absorbent materials which may also be nonwovens of a different composition and/or structure. Nonwovens of heavier weights may be designed with pore structures making them suitable for filtration, absorbent and barner applications such as wrappers for items to be sterilized, wipers or protective garments for medical, veterinary or industrial ~..
~ CA 02290321 1999-11-24 r"
uses. Even heavier weight nonwovens have been developed for recreational, agricultural and construction uses. These are but a few of the practically limitless examples of types of nonwovens and their uses that will be known to those skilled in the art who will also recognize that new nonwovens and uses are constantly being identified. There have also been developed different ways and equipment to make nonwovens having desired structures and compositions suitable for these uses. Examples of such processes include spunbonding, meltblowing, carding, and others which will be described in greater detail below. The present invention has general applicability to nonwovens as will be apparent to one skilled in the art, and it is not to be limited by reference or examples relating to specific nonwovens which are merely illustrative.
It is not always possible to efficiently produce a nonwoven having all the desired properties as formed, and it is frequently necessary to treat the nonwoven to improve or alter properties such as wettability by one or more fluids, repellency to one or more fluids, electrostatic characteristics, conductivity, and softness, to name just a few examples.
Conventional treatments involve steps such as dipping the nonwoven in a treatment bath, coating or spraying the nonwoven with the treatment composition, and printing the nonwoven with the treatment composition. For cost and other reasons it is usually desired to use the minimum amount of treatment composition that will produce the desired effect with an acceptable degree of uniformity.
When a nonwoven web is formed of a hydrophobic material, for example, a polyolefin, it is often desirable to modify the surface of the nonwoven web using a hydrophilic surfactant to increase the wettability of the web. An external hydrophilic surfactant is typically applied to the surface of the nonwoven web. An internal hydrophilic .,, r surfactant is typically blended with the polymer used to form the nonwoven web, and later migrates to the surface after the nonwoven web is formed.
External and internal hydrophilic surfactants may be characterized in terms of their durability and wettability. The durability of a surfactant refers generally to its ability to withstand stresses, such as repeated washing cycles of the nonwoven fabric, without being removed from the fabric or otherwise losing its effectiveness. The wettability of a surfactant refers generally to its ability to transform a hydrophobic nonwoven web into a fabric which readily assimilates and distributes aqueous liquids. Surfactants which cause an otherwise hydrophobic nonwoven web to assimilate liquids at a relatively fast pace, with high fluid intake volumes, are referred to as faster wetting surfactants. Surfactants which cause the nonwoven web to assimilate aqueous liquids at a relatively slow pace, with low fluid intake volume, are referred to as slower wetting surfactants. In addition to the surfactant type, other factors affect the ability of the nonwoven web to assimilate liquids, including without limitation the nonwoven web type, nonwoven polymer type, fiber size and density, amount of surfactant, and how it is applied.
Surfactants having high durability are desirable for a variety of reasons.
However, durable surfactants often provide insufficient wetting, and do not lend themselves to optimization of wetting characteristics desired for individual end use applications. There is a need or desire for a surfactant composition having both durability and controlled wetting, whether the desired wetting is fast, slow or in between. There is also a need or desire for a nonwoven fabric having durable wetting whose rate is predetermined and controlled.
SUMMARY OF THE INVENTION
The present invention is directed to a surfactant combination, and a nonwoven web treated with a surfactant combination. The surfactant combination includes a first . CA 02290321 1999-11-24 surfactant which provides durable wetting characteristics, and a second surfactant which controls the rate of wetting (fast, slow or intermediate). Used in combination, the surfactant combination provides a nonwoven fabric having wetting characteristics that are both durable and rate-determined.
The combination of surfactants provides a nonwoven fabric with the ability to withstand at least two and, advantageously, at least three insults using the cradle test described below. The first surfactant alone need not provide this level of durability. Instead, what is important is that the combination of surfactants (accounting for all synergisms between them) provides a nonwoven fabric having this level of durability.
The combination of surfactants also provides the nonwoven fabric with a controlled rate of wetting, as characterized by the cradle test described below. Again, it is not important for the second surfactant alone to provide the desired fluid intake rate. Instead, what is important is how the two surfactants behave in the environment in which they coexist with each other. In this environment, the surfactants together (accounting for all synergisms between them) must provide a desired wetting rate as well as durable wetting to the nonwoven fabric.
With the foregoing in mind, it is a feature and advantage of the invention to provide a surfactant combination which imparts durable wettability to a nonwoven fabric at a fast, intermediate or slow rate of wetting by an aqueous medium.
It is alsa a feature and advantage of the invention to provide a nonwoven fabric which is treated with the surfactant combination to effect durable wettability at a fast, intermediate or slow rate of wetting.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic of a cradle testing apparatus used in the test procedure described below.
DEFINITIONS
The term "nonwoven fabric or web" means a web having a structure of individual fibers or threads which are interlaid, but not in a regular or identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as, for example, meltblowing processes, spunbonding processes, air laying processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91.) The term "microfibers" means small diameter fibers having an average diameter not greater than about 75 microns, for example, having an average diameter of from about 1 micron to about 50 microns, or more particularly, microfibers may have an average diameter of from about 1 micron to about 30 microns. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9000 meters of a fiber. For a fiber having circular cross-section, denier may be calculated as fiber diameter in microns squared, multiplied by the density in grams/cc, multiplied by 0.00707. A
lower denier indicates a finer fiber and a higher denier indicates a thicker or heavier fiber.
For example, the diameter of a polypropylene fiber given as 15 microns may be converted to denier by squaring, multiplying the result by .89 g/cc and multiplying by .00707.
Thus, a 15 micron polypropylene fiber has a denier of about 1.42 (15z x 0.89 x .00707 = 1.415). Outside the United States the unit of measurement is more commonly the "tex,"
which is defined as the grams per kilometer of fiber. Tex may be calculated as denier/9.
The term "spunbonded fibers" refers to small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine capillaries of a spinnerette having a circular or other configuration, with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S.
Patent 4,340,563 to Appel et al., and U.S. Patent 3,692,618 to Dorschner et al., U.S.
Patent 3,802,817 to Matsuki et al., U.S. Patents 3,338,992 and 3,341,394 to Kinney, U.S. Patent 3,502,763 to Hartman, U.S. Patent 3,502,538 to Petersen, and U.S. Patent 3,542,615 to Dobo et al., each of which is incorporated herein in its entirety by reference. Spunbond fibers are quenched and generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous and often have average diameters larger than about 7 microns, more particularly, between about 10 and 30 microns.
The term "meltblown fibers" means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity heated gas (e.g., air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed for example, in U.S.
Patent 3,849,241 to Butin. Meltblown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in diameter, and are generally self bonding when deposited onto a collecting surface. Meltblown fibers used in the present invention are preferably substantially continuous in length.
The term "substantially continuous filaments or fibers" refers to filaments or fibers prepared by extrusion from a spinnerette, including without limitation spunbonded and meltblown fibers, which are not cut from their original length prior to being formed into a nonwoven web or fabric. Substantially continuous filaments or fibers may have average lengths ranging from greater than about 15 cm to more than one meter, and up to the length of the web or fabric being formed. The definition of "substantially continuous filaments or fibers" includes those which are not cut prior to being formed into a nonwoven web or fabric, but which are later cut when the nonwoven web or fabric is cut.
The term "staple fibers" means fibers which are natural or cut from a manufactured filament prior to forming into a web, and which have an average length ranging from about 0.1-15 cm, more commonly about 0.2-7 cm.
The term "bicomponent filaments or fibers" refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the bicomponent fibers and extend continuously along the length of the bicomponent fibers. The configuration of such a bicomponent fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another or may be a side-by-side arrangement or an "islands-in-the-sea"
arrangement. Bicomponent fibers are taught in U.S. Patent 5,108,820 to Kaneko et al., U.S. Patent 5,336,552 to Strack et al., and U.S. Patent 5,382,400 to Pike et al., each of which is incorporated herein in its entirety by reference. For two component fibers, the r . r polymers may be present in ratios of 75/25, 50/50, 25/75 or any other desired ratios.
Conventional additives, such as pigments and surfactants, may be incorporated into one or both polymer streams, or applied to the filament surfaces.
The term "monocomponent" fiber refers to a fiber formed from one or more extruders using only one polymer. This is not meant to exclude fibers formed from one polymer to which small amounts of additives have been added for color, anti-static properties, lubrication, hydrophilicity, etc. These additives, e.g., titanium dioxide for color, are generally present in an amount less than 5 weight percent and more typically about 2 weight percent.
The term "polymer" includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic and atactic symmetries.
The term "pulp fibers" refers to fibers from natural sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for instance, cotton, flax, esparto grass, milkweed, straw, jute hemp, and bagasse.
The term "average fiber length" refers to a weighted average length of fibers determined using a Kajaani fiber analyzer Model No. FS-100 available from Kajaani Oy Electronics in Kajaani, Finland. Under the test procedure, a fiber sample is treated with a macerating liquid to ensure that no fiber bundles or shives are present.
Each fiber sample is dispersed in hot water and diluted to about a 0.001 %
concentration.
Individual test samples are drawn in approximately 50 to 500 ml portions from the dilute solution and tested using the standard Kajaani fiber analysis procedure. The average fiber lengths may be expressed by the following equation:
k E (X;*n;)/n X; > 0 where k - maximum fiber length, X; - individual fiber length, n; - number of fibers having length X;
and n - total number of fibers measured.
The term "superabsorbent material" refers to a water-swellable, water-insoluble organic or inorganic material capable, under the most favorable conditions, of absorbing at least about 15 times its weight and, more desirably, at least about 30 times its weight in an aqueous solution containing 0.9% by weight sodium chloride.
The term "through-air bonding" or "TAB" means a process of bonding a nonwoven, for example, a bicomponent fiber web in which air which is sufficiently hot to melt one of the polymers of which the fibers of the web are made is forced through the web.
The melting and resolidification of the polymer provides the bonding.
The term "thermal point bonding" involves passing a fabric or web of fibers to be bonded between a heated calender roll and an anvil roll. The calender roll is usually, though not always, patterned in some way so that the entire fabric is not bonded across its entire surface. As a result, various patterns for calender rolls have been developed for functional as well as aesthetic reasons. One example of a pattern has points and is the Hansen Pennings or "H&P" pattern with about a 30% bond area with about 200 bonds/square inch as taught in U.S. Patent 3,855,046 to Hansen and Pennings.
The H&P
pattern has square point or pin bonding areas wherein each pin has a side dimension of 0.038 inches (0.965 mm), a spacing of 0.070 inches (1.778 mm) between pins, and a depth of bonding of 0.023 inches (0.584 mm). The resulting pattern has a bonded area of about 29.5%. Another typical point bonding pattern is the expanded Hansen and Pennings or "EHP" bond pattern which produces a 15% bond area with a square pin having a side dimension of 0.037 inches (0.94 mm), a pin spacing of 0.097 inches (2.464 mm) and a depth of 0.039 inches (0.991 mm). Another typical point bonding pattern designated "714" has square pin bonding areas wherein each pin has a side dimension of 0.023 inches, a spacing of 0.062 inches (1.575 mm) between pins, and a depth of bonding of 0.033 inches (0.838 mm). The resulting pattern has a bonded area of about 15%. Yet another common pattern is the C-Star pattern which has a bond area of about 16.9%. The C-Star pattern has a cross-directional bar or "corduroy" design interrupted by shooting stars. Other common patterns include a diamond pattern with repeating and slightly offset diamonds and a wire weave pattern looking as the name suggests, e.g., like a window screen. Typically, the percent bonding area varies from around 10% to around 30% of the area of the fabric laminate web.
As is well known in the art, the spot bonding holds the laminate layers together as well as imparts integrity to each individual layer by bonding filaments and/or fibers within each layer.
The term "personal care product" means diapers, training pants, swim wear, absorbent underpants, baby wipes, adult incontinence products, and feminine hygiene products.
The term "durable wettability" or "durably wettable" means the ability to withstand at least two and, advantageously at least 3, insults using the runoff test described below.
The term "hydrophilic" or "wettable" means that the finished polymeric material has a surface free energy such that the polymeric material is wettable by an aqueous medium, i.e., a liquid medium of which water is a major component. The finished polymeric material may have been treated with a surfactant, a surfactant combination, or other finishing agents.
Test Procedure The "cradle test" referred to herein (also known as the Little MIST test) is performed as follows. Referring to Fig. 1, two layers 12 and 14 of a sample nonwoven fabric are weighed, and placed in the valley of an acrylic cradle 10, against the inner wall of the cradle. The cradle has a length (into the page) of 33 cm with front and back ends blocked off, a height of 19 cm, a distance between upper arms 18 and 20 of 30.5 cm, and an angle between the upper arms of 60 degrees. The cradle has a 6.5 cm wide slot 16 at its lowest point, running the length of the cradle into the page.
Each layer of the nonwoven fabric can be rectangular, with dimensions of 2.5 x 7.0 inches, or 3.0 x 7.0 inches. Then, 80 ml of blood bank saline ( 1 %
aqueous NaCI) is injected into the center of the specimen at a rate of 20 ml/sec using a nozzle normal to the center of the material and 0.25 inch above the material. Fluid not contained by the nonwoven fabric (referred to as "mnoff ~ flows over the sample edges and through the center slot 16 in the cradle. The sample material is then immediately removed from the cradle and weighed.
Fluid held by the sample nonwoven fabric is used to calculate the performance parameter, P, which reflects the amount of liquid withheld based on fabric sample volume:
r P - ~~rams of fluid contained x 100%
cc of dry sample - gams of fluid contained x dry sample density,~sJcc x 100%
grams of dry sample The nonwoven fabric sample is then desorbed by placing it on top of a fluff/superabsorbent material composite for five minutes. The composite contains 40%
by weight U.S. Alliance Coosa Pines CR-2054 pulp and 60% by weight of Stockhausen Company's FAVOR 870 superabsorbent. Other comparable materials can be used.
Then, the desorbed sample is replaced in the cradle where it receives a second insult of fluid.
This procedure is repeated for a total of three fluid insults, with about 30 minutes between insults. The nonwoven fabric sample is considered to have durable hydrophilic properties if its performance parameter does not fall by more than 10% over three insults.
The rate of fluid insult is also relevant to this test. Generally, the faster the insult, the greater the demand on the specimen to assimilate or spread out the liquid. For the testing of this invention, a fixed rate of 20 ml/sec was maintained.
DETAILED DESCRIPTION OF THE
PRESENTLY PREFERRED EMBODIMENTS
The starting material for the invention is a nonwoven web including a plurality of filaments made from one or more polymers treated with a hydrophilic surfactant combination. The nonwoven web may be a spunbond web, a meltblown web, a bonded carded web, or another type of nonwoven web, and may be present in a single layer or a multilayer composite including one or more nonwoven web layers.
The hydrophilic surfactant combination may be an internal or external surfactant combination. An internal surfactant is one which is blended with the polymer used to make the nonwoven web, and which migrates to the surface of the nonwoven web f filaments during and/or after the formation of the filaments. Often, the migration results from a stimulus, such as heat applied to the filaments. An external surfactant is one which is applied externally to the surfaces of the nonwoven web filaments after they are formed.
An external surfactant may be applied by dipping, soaking, spraying, or otherwise coating the nonwoven web with a medium containing the surfactant. Internal and external surfactant inclusion techniques are generally well known in the art.
The surfactant combination used in accordance with the invention is a combination of two or more surfactants which impart durable hydrophilicity to a nonwoven web, as well as a controlled rate of wettability. Generally, the nonwoven web is constructed from a thermoplastic polymer which is either hydrophobic or insufficiently hydrophilic. The class of nonwoven webs referred to herein as "hydrophobic or insufficiently hydrophilic"
refers to nonwoven webs which exhibit a performance parameter less than 10 using the cradle test described above, when the nonwoven web is not treated with a hydrophilic surfactant.
A wide variety of thermoplastic polymers may be used to construct the nonwoven web, including without limitation polyamides, polyesters, polyolefins, copolymers of ethylene and propylene, copolymers of ethylene or propylene with a C4-CZO
alpha-olefin, terpolymers of ethylene with propylene and a C4-CZO alpha-olefin, ethylene vinyl acetate copolymers, propylene vinyl acetate copolymers, styrene-polyethylene-alpha-olefin) elastomers, polyurethanes, A-B block copolymers where A is formed of polyvinyl arene) moieties such as polystyrene and B is an elastomeric midblock such as a conjugated diene or lower alkene, polyethers, polyether esters, polyacrylates, ethylene alkyl acrylates, polyisobutylene, polybutadiene, isobutylene-isoprene copolymers, and combinations of any of the foregoing. Polyolefins are preferred. Polyethylene and polypropylene homopolymers and copolymers are most preferred. The webs may also be constructed of bicomponent or biconstituent filaments or fibers, as defined above. The nonwoven webs may have a wide variety of basis weights, preferably ranging from about 10 grams per square meter (gsm) to about 120 gsm.
It should be understood that the invention is not limited to the use of hydrophobic and insufficiently hydrophilic polymers. The durable, controlled wetting rate surfactant combination may also be used to enhance the wetting performance of nonwoven fabric polymers which are already hydrophilic, as indicated by a performance parameter of at least 30% without a hydrophilic surfactant.
The hydrophilic combination of surfactants must provide durable wetting at a controlled wetting rate. The combination may include two or more surfactants, one of which independently provides durable wetting, and the other of which independently provides controlled rate wetting. Alternatively, the surfactant combination may include two or more surfactants which, taken alone, do not provide one or both properties, but which provide durable and controlled rate wetting when acting together in synergy.
A hydrophilic surfactant combination provides "durable wetting" if the performance parameter resulting from the third liquid insult is greater than, equal to, or up to 10% less than the performance parameter resulting from the first liquid insult using the cradle test, described above.
The hydrophilic surfactant combination must also provide wetting at a controlled rate which may be fast, intermediate or slow. A surfactant combination provides a fast wetting rate if a nonwoven fabric treated with the surfactant combination (e.g., a nonwoven fabric made from a hydrophobic or insufficiently hydrophilic thermoplastic polymer) exhibits a performance parameter of at least 50% for the first fluid insult using the ' , CA 02290321 1999-11-24 cradle test, described above. A hydrophilic surfactant combination provides an intermediate wetting rate if the performance parameter for the first fluid insult is at least 40% and less than 50%. A hydrophilic surfactant combination provides a slow wetting rate if the performance parameter for the first fluid insult is at least 30% and less than 40%.
Performance parameters below 30% are deemed insufficient.
The hydrophilic surfactant combination includes at least first and second surfactants. The first surfactant may be a durable surfactant. The first surfactant may include a compound selected from an ethoxylated hydrogenated fatty acid ester, a monosaccharide, a monosaccharide derivative, a polysaccharide, a polysaccharide derivative, and combinations thereof. For instance, the first surfactant may include a blend of ethoxylated hydrogenated castor oil and sorbitan monooleate. One such surfactant is AHCOVEL~ Base N-52, available from Hodgson Chemical Co.
Another first surfactant is a castor oil derivative of ethylene oxide. One such surfactant is sold by ICI Surfactant, Inc. under the name ATMER~ 8174.
Another suitable first surfactant may include a selected polyolefin glycol, or a derivative of a polyolefin glycol. Examples of derivatives include polyolefin glycol monooleates and dioleates, polyolefin glycol monolaurates and dilaurates, and alkyl esters of polyolefin glycols. MAPEG~ surfactants, available from PPG Industries, are made from the foregoing derivatives of polyethylene glycol.
Another suitable first surfactant is a LUROL~ surfactant, available from Goulston Technologies, Inc. LUROL~ surfactants are believed to include a polymer, a hydrophilic part with multiple hydrophobic parts. The hydrophobic parts help the surfactant interface and adhere to a hydrophobic polymer substrate. LUROL~7463 and 7514 are two samples of durable surfactants.
IS
' , CA 02290321 1999-11-24 The second surfactant may be a controlled rate wetting surfactant. The second surfactant may be a fast wetting surfactant, an intermediate wetting surfactant, or a slow wetting surfactant.
Examples of second surfactants include organosilicon compounds. MASIL~
SF-19, available from BASF Chemical Co., is an ethoxylated trisiloxane-based surfactant which typically behaves as a fast wetting surfactant. Certain polyolefin glycol derivatives serve as slow or intermediate surfactants. ANTAROX~ surfactant, available from Rhone-Poluene Chemical Co., includes alkyl ether ethoxylates derived from polyethylene glycol and polypropylene glycol, and may cause slow or intermediate wetting depending on the substrate. Another second surfactant may include an alkyl polyglycoside.
GLUCOPON~
220UP is a solution of 60% octylpolyglycoside and 40% water, and may serve as a slow or intermediate surfactant when used in combination with a first surfactant, such as a blend of ethoxylated hydrogenated castor oil and sorbitan monooleate.
Other second surfactants include ionic sulfonate-based surfactants, for example dodecylbenzene sulfonate sold under the name BIOSOFT'~ by Stephen Co.
Another ionic surfactant is AEROSOL OT, sold by the Cytec Corporation. Ionic surfactants alone are often fast-wetting but not durable.
The surfactant combination may include about 5-95 parts by weight first surfactant and about 5-95 parts by weight second surfactant, based on dry solids, per 100 parts by weight of both surfactants combined. Commonly, the surfactant combination may include about 25-90 parts by weight first surfactant and about 10-75 parts by weight second surfactant. Desirably, the surfactant combination may include about 40-80 parts by weight first surfactant and about 10-60 parts by weight second surfactant. Regardless of how the surfactants behave alone, the first surfactant generally contributes durability to the combination, and the second surfactant generally contributes controlled rate wetting. Often, the performance of both surfactants is synergized and enhanced by the combination.
The surfactant combination may be applied using internal and/or external application techniques well known in the art. The first and second surfactants may be applied in separate steps, or together. If one or both surfactants are applied externally using a solvent, the solvent may be removed using conventional evaporation techniques. On a solvent-free weight basis, the surfactant combination should constitute about 0.1-10% by weight of the nonwoven fabric to which it is applied, preferably about 0.5-5%
by weight, more preferably about 1-3% by weight. Higher levels of surfactant combination are less desirable, due to cost and other issues. Levels which are too low tend to impart less wettability to the nonwoven fabric.
The nonwoven fabrics thus formed have wettability which is both durable and rate-determined. The treated nonwoven fabric can be used in a wide variety of absorbent product applications including, in particular, personal care absorbent products. Personal care absorbent products include diapers, training pants, swim wear, absorbent underpants, baby wipes, adult incontinence products, feminine hygiene products, and the like, as well as other surge and intake material products. In most absorbent products, the treated nonwoven fabric is used as a cover sheet or containment matrix for an absorbent media. An absorbent medium may include, for instance, pulp fibers alone or in combination with a superabsorbent material. The treated nonwoven fabric can also be used in medical absorbent products, including without limitation underpads, absorbent drapes, bandages, and medical wipes.
The pulp fibers may be any high-average fiber length pulp, low-average fiber length pulp, or mixtures of the same. Preferred pulp fibers include cellulose fibers. The term "high average fiber length pulp" refers to pulp that contains a relatively small amount of ' CA 02290321 1999-11-24 short fibers and non-fiber particles. High fiber length pulps typically have an average fiber length greater than about 1.5 mm, preferably about 1.5-6 mm, as determined by an optical fiber analyzer, such as the Kajaani tester referenced above. Sources generally include non-secondary (virgin) fibers as well as secondary fiber pulp which has been screened. Examples of high average fiber length pulps include bleached and unbleached virgin softwood fiber pulps.
The term "low average fiber length pulp" refers to pulp that contains a significant amount of short fibers and non-fiber particles. Low average fiber length pulps have an average fiber length less than about 1.5 mm, preferably about 0.7-1.2 mm, as determined by an optical fiber analyzer such as the Kajaani tester referenced above.
Examples of low fiber length pulps include virgin hardwood pulp, as well as secondary fiber pulp from sources such as office waste, newsprint, and paperboard scrap.
Examples of high average fiber length wood pulps include those available from the U.S. Alliance Coosa Pines Corporation under the trade designations Longlac 19, Coosa River 56, and Coosa River 57. The low average fiber length pulps may include certain virgin hardwood pulp and secondary (i.e., recycled) fiber pulp from sources including newsprint, reclaimed paperboard, and once waste. Mixtures of high average fiber length and low average fiber length pulps may contain a predominance of low average fiber length pulps. For example, mixtures may contain more than about 50% by weight low-average fiber length pulp and less than about 50% by weight high-average fiber length pulp.
The term "superabsorbent" or "superabsorbent material" refers to a water swellable, water-insoluble organic or inorganic material capable, under the most favorable conditions, of absorbing at least about 15 times its weight and, more desirably, at least about 30 times its weight in an aqueous solution containing 0.9% by weight sodium chloride.
' CA 02290321 1999-11-24 The superabsorbent materials can be natural, synthetic and modified natural polymers and materials. In addition, the superabsorbent materials can be inorganic materials, such as silica gels, or organic compounds such as cross-linked polymers. The term "cross-linked" refers to any means for effectively rendering normally water-soluble materials substantially water insoluble but swellable. Such means can include, for example, physical entanglement, crystalline domains, covalent bonds, ionic complexes and associations, hydrophilic associations, such as hydrogen bonding, and hydrophobic associations or Van der Waals forces.
Examples of synthetic superabsorbent material polymers include the alkali metal and ammonium salts of poly(acrylic acid) and poly(methacrylic acid), poly(acrylamides), polyvinyl ethers), malefic anhydride copolymers with vinyl ethers and alpha-olefins, polyvinyl pyrrolidone), poly(vinylmorpholinone), polyvinyl alcohol), and mixtures and copolymers thereof. Further superabsorbent materials include natural and modified natural polymers, such as hydrolyzed acrylonitrile-grafted starch, acrylic acid grafted starch, methyl cellulose, chitosan, carboxymethyl cellulose, hydroxypropyl cellulose, and the natural gums, such as alginates, xanthan gum, locust bean gum and the like.
Mixtures of natural and wholly or partially synthetic superabsorbent polymers can also be useful in the present invention. Other suitable absorbent gelling materials are disclosed by Assarsson et al. in U.S. Patent 3,901,236 issued August 26, 1975. Processes for preparing synthetic absorbent gelling polymers are disclosed in U.S. Patent No.
4,076,633 issued February 28, 1978 to Edwards et al. and U.S. Patent No. 4,286,082 issued August 25, 1981 to Tsubakimoto et al.
Superabsorbent materials may be xerogels which form hydrogels when wetted. The term "hydrogel," however, has commonly been used to also refer to both the wetted and unwetted forms of the superabsorbent polymer material. The superabsorbent materials can be in many forms such as flakes, powders, particulates, fibers, continuous fibers, networks, solution spun filaments and webs. The particles can be of any desired shape, for example, spiral or semi-spiral, cubic, rod-like, polyhedral, etc.
Needles, flakes, fibers, and combinations may also be used.
Superabsorbents are generally available in particle sizes ranging from about 20 to about 1000 microns. Examples of commercially available particulate superabsorbents include SANWET'~ IM 3900 and SANWET~' IM-SOOOP, available from Hoescht Celanese located in Portsmouth, Virginia, DRYTECH~ 2035LD available from Dow Chemical Co.
located in Midland, Michigan, and FAVOR~ 880, available from Stockhausen, located in Greensboro, North Carolina. An example of a fibrous superabsorbent is OASIS~
101, available from Technical Absorbents, located in Grimsby, United Kingdom.
As indicated above, the nonwoven fabric may be a cover sheet or a matrix for an absorbent medium. When employed as a matrix, the nonwoven filaments may be combined with pulp fibers and (optionally) a superabsorbent material using processes well known in the art. For example, a coform process may be employed, in which at least one meltblown diehead is axranged near a chute through which other materials are added while the web is forming. Coform processes are described in U.S. Patent 4,818,464 to Lau and 4,100,324 to Anderson et al., the disclosures of which are incorporated by reference. The substantially continuous bicomponent filaments and pulp fibers may also be combined using hydraulic entangling or mechanical entangling. A hydraulic entangling process is described in U.S. Patent 3,485,706 to Evans, the disclosure of which is incorporated by reference.
When the thermoplastic nonwoven filaments are used as a matrix for an absorbent nonwoven web composite, the composite should contain about 5-97% by weight pulp fibers, preferably about 35-95% by weight pulp fibers, more preferably about 50-95%
by weight pulp fibers. When a superabsorbent material is present, it should constitute about 5-90% by weight of the composite, preferably about 10-60% by weight, more preferably about 20-50% by weight. In either case, the thermoplastic nonwoven filament matrix should constitute about 3-95% by weight of the composite, preferably about 5-65% by weight, more preferably about 5-50% by weight.
After combining the ingredients together, the absorbent nonwoven composite may be bonded together using the thermal point bonding or through-air bonding techniques described above, to provide a coherent high integrity structure.
Examples For Examples 1-18, the nonwoven fabric employed was a polypropylene/
polyethylene side-by-side bicomponent. The surfactants were added internally by compounding into one or both polymer resins using a heated 30 mm twin screw extruder, prior to formation of the spunbond filaments. The resulting surfactant/
polymer concentrates were then added to one or both melt streams in the fiber spinning process, prior to extrusion.
The resulting treated nonwoven fabrics were then evaluated using the cradle test described above. For each of these tests, two rectangular fabric samples having dimensions of 2.5 in x 7.0 in were employed. The results of the evaluations are shown in Table 1.
Table 1: Surfactants Added Internally Level Web Performance Parameter, T i Fib W W
t % Si i b ht rea ) er e e - n ze, g ( , went Loca-Denier Ounces/Density1st 2nd 3rd per xam do tionFilamentdZ cc InsultInsultInsultChan Comments le a 2.5 Intermediate, 1 SF19 in 2.1 2.48 0.02445 40 30 -33 PP Not Durable 2 Antarox3 2.2 3.32 0.02130 29 19 _37 Slow, in PP
Not Durable 3 Antarox3 1.7 2.67 0.02338 32 20 ~7 Slow, in PP
Not Durable 4 Ahcovel3 not wettable in PP
Antarox/
5* Mapeg 3 2.3 3.14 0.02529 28 31 +7 Insufficient, ~
PP
400 Durable ML
SF
Fig. 1 is a schematic of a cradle testing apparatus used in the test procedure described below.
DEFINITIONS
The term "nonwoven fabric or web" means a web having a structure of individual fibers or threads which are interlaid, but not in a regular or identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as, for example, meltblowing processes, spunbonding processes, air laying processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91.) The term "microfibers" means small diameter fibers having an average diameter not greater than about 75 microns, for example, having an average diameter of from about 1 micron to about 50 microns, or more particularly, microfibers may have an average diameter of from about 1 micron to about 30 microns. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9000 meters of a fiber. For a fiber having circular cross-section, denier may be calculated as fiber diameter in microns squared, multiplied by the density in grams/cc, multiplied by 0.00707. A
lower denier indicates a finer fiber and a higher denier indicates a thicker or heavier fiber.
For example, the diameter of a polypropylene fiber given as 15 microns may be converted to denier by squaring, multiplying the result by .89 g/cc and multiplying by .00707.
Thus, a 15 micron polypropylene fiber has a denier of about 1.42 (15z x 0.89 x .00707 = 1.415). Outside the United States the unit of measurement is more commonly the "tex,"
which is defined as the grams per kilometer of fiber. Tex may be calculated as denier/9.
The term "spunbonded fibers" refers to small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine capillaries of a spinnerette having a circular or other configuration, with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S.
Patent 4,340,563 to Appel et al., and U.S. Patent 3,692,618 to Dorschner et al., U.S.
Patent 3,802,817 to Matsuki et al., U.S. Patents 3,338,992 and 3,341,394 to Kinney, U.S. Patent 3,502,763 to Hartman, U.S. Patent 3,502,538 to Petersen, and U.S. Patent 3,542,615 to Dobo et al., each of which is incorporated herein in its entirety by reference. Spunbond fibers are quenched and generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous and often have average diameters larger than about 7 microns, more particularly, between about 10 and 30 microns.
The term "meltblown fibers" means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity heated gas (e.g., air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed for example, in U.S.
Patent 3,849,241 to Butin. Meltblown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in diameter, and are generally self bonding when deposited onto a collecting surface. Meltblown fibers used in the present invention are preferably substantially continuous in length.
The term "substantially continuous filaments or fibers" refers to filaments or fibers prepared by extrusion from a spinnerette, including without limitation spunbonded and meltblown fibers, which are not cut from their original length prior to being formed into a nonwoven web or fabric. Substantially continuous filaments or fibers may have average lengths ranging from greater than about 15 cm to more than one meter, and up to the length of the web or fabric being formed. The definition of "substantially continuous filaments or fibers" includes those which are not cut prior to being formed into a nonwoven web or fabric, but which are later cut when the nonwoven web or fabric is cut.
The term "staple fibers" means fibers which are natural or cut from a manufactured filament prior to forming into a web, and which have an average length ranging from about 0.1-15 cm, more commonly about 0.2-7 cm.
The term "bicomponent filaments or fibers" refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the bicomponent fibers and extend continuously along the length of the bicomponent fibers. The configuration of such a bicomponent fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another or may be a side-by-side arrangement or an "islands-in-the-sea"
arrangement. Bicomponent fibers are taught in U.S. Patent 5,108,820 to Kaneko et al., U.S. Patent 5,336,552 to Strack et al., and U.S. Patent 5,382,400 to Pike et al., each of which is incorporated herein in its entirety by reference. For two component fibers, the r . r polymers may be present in ratios of 75/25, 50/50, 25/75 or any other desired ratios.
Conventional additives, such as pigments and surfactants, may be incorporated into one or both polymer streams, or applied to the filament surfaces.
The term "monocomponent" fiber refers to a fiber formed from one or more extruders using only one polymer. This is not meant to exclude fibers formed from one polymer to which small amounts of additives have been added for color, anti-static properties, lubrication, hydrophilicity, etc. These additives, e.g., titanium dioxide for color, are generally present in an amount less than 5 weight percent and more typically about 2 weight percent.
The term "polymer" includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic and atactic symmetries.
The term "pulp fibers" refers to fibers from natural sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for instance, cotton, flax, esparto grass, milkweed, straw, jute hemp, and bagasse.
The term "average fiber length" refers to a weighted average length of fibers determined using a Kajaani fiber analyzer Model No. FS-100 available from Kajaani Oy Electronics in Kajaani, Finland. Under the test procedure, a fiber sample is treated with a macerating liquid to ensure that no fiber bundles or shives are present.
Each fiber sample is dispersed in hot water and diluted to about a 0.001 %
concentration.
Individual test samples are drawn in approximately 50 to 500 ml portions from the dilute solution and tested using the standard Kajaani fiber analysis procedure. The average fiber lengths may be expressed by the following equation:
k E (X;*n;)/n X; > 0 where k - maximum fiber length, X; - individual fiber length, n; - number of fibers having length X;
and n - total number of fibers measured.
The term "superabsorbent material" refers to a water-swellable, water-insoluble organic or inorganic material capable, under the most favorable conditions, of absorbing at least about 15 times its weight and, more desirably, at least about 30 times its weight in an aqueous solution containing 0.9% by weight sodium chloride.
The term "through-air bonding" or "TAB" means a process of bonding a nonwoven, for example, a bicomponent fiber web in which air which is sufficiently hot to melt one of the polymers of which the fibers of the web are made is forced through the web.
The melting and resolidification of the polymer provides the bonding.
The term "thermal point bonding" involves passing a fabric or web of fibers to be bonded between a heated calender roll and an anvil roll. The calender roll is usually, though not always, patterned in some way so that the entire fabric is not bonded across its entire surface. As a result, various patterns for calender rolls have been developed for functional as well as aesthetic reasons. One example of a pattern has points and is the Hansen Pennings or "H&P" pattern with about a 30% bond area with about 200 bonds/square inch as taught in U.S. Patent 3,855,046 to Hansen and Pennings.
The H&P
pattern has square point or pin bonding areas wherein each pin has a side dimension of 0.038 inches (0.965 mm), a spacing of 0.070 inches (1.778 mm) between pins, and a depth of bonding of 0.023 inches (0.584 mm). The resulting pattern has a bonded area of about 29.5%. Another typical point bonding pattern is the expanded Hansen and Pennings or "EHP" bond pattern which produces a 15% bond area with a square pin having a side dimension of 0.037 inches (0.94 mm), a pin spacing of 0.097 inches (2.464 mm) and a depth of 0.039 inches (0.991 mm). Another typical point bonding pattern designated "714" has square pin bonding areas wherein each pin has a side dimension of 0.023 inches, a spacing of 0.062 inches (1.575 mm) between pins, and a depth of bonding of 0.033 inches (0.838 mm). The resulting pattern has a bonded area of about 15%. Yet another common pattern is the C-Star pattern which has a bond area of about 16.9%. The C-Star pattern has a cross-directional bar or "corduroy" design interrupted by shooting stars. Other common patterns include a diamond pattern with repeating and slightly offset diamonds and a wire weave pattern looking as the name suggests, e.g., like a window screen. Typically, the percent bonding area varies from around 10% to around 30% of the area of the fabric laminate web.
As is well known in the art, the spot bonding holds the laminate layers together as well as imparts integrity to each individual layer by bonding filaments and/or fibers within each layer.
The term "personal care product" means diapers, training pants, swim wear, absorbent underpants, baby wipes, adult incontinence products, and feminine hygiene products.
The term "durable wettability" or "durably wettable" means the ability to withstand at least two and, advantageously at least 3, insults using the runoff test described below.
The term "hydrophilic" or "wettable" means that the finished polymeric material has a surface free energy such that the polymeric material is wettable by an aqueous medium, i.e., a liquid medium of which water is a major component. The finished polymeric material may have been treated with a surfactant, a surfactant combination, or other finishing agents.
Test Procedure The "cradle test" referred to herein (also known as the Little MIST test) is performed as follows. Referring to Fig. 1, two layers 12 and 14 of a sample nonwoven fabric are weighed, and placed in the valley of an acrylic cradle 10, against the inner wall of the cradle. The cradle has a length (into the page) of 33 cm with front and back ends blocked off, a height of 19 cm, a distance between upper arms 18 and 20 of 30.5 cm, and an angle between the upper arms of 60 degrees. The cradle has a 6.5 cm wide slot 16 at its lowest point, running the length of the cradle into the page.
Each layer of the nonwoven fabric can be rectangular, with dimensions of 2.5 x 7.0 inches, or 3.0 x 7.0 inches. Then, 80 ml of blood bank saline ( 1 %
aqueous NaCI) is injected into the center of the specimen at a rate of 20 ml/sec using a nozzle normal to the center of the material and 0.25 inch above the material. Fluid not contained by the nonwoven fabric (referred to as "mnoff ~ flows over the sample edges and through the center slot 16 in the cradle. The sample material is then immediately removed from the cradle and weighed.
Fluid held by the sample nonwoven fabric is used to calculate the performance parameter, P, which reflects the amount of liquid withheld based on fabric sample volume:
r P - ~~rams of fluid contained x 100%
cc of dry sample - gams of fluid contained x dry sample density,~sJcc x 100%
grams of dry sample The nonwoven fabric sample is then desorbed by placing it on top of a fluff/superabsorbent material composite for five minutes. The composite contains 40%
by weight U.S. Alliance Coosa Pines CR-2054 pulp and 60% by weight of Stockhausen Company's FAVOR 870 superabsorbent. Other comparable materials can be used.
Then, the desorbed sample is replaced in the cradle where it receives a second insult of fluid.
This procedure is repeated for a total of three fluid insults, with about 30 minutes between insults. The nonwoven fabric sample is considered to have durable hydrophilic properties if its performance parameter does not fall by more than 10% over three insults.
The rate of fluid insult is also relevant to this test. Generally, the faster the insult, the greater the demand on the specimen to assimilate or spread out the liquid. For the testing of this invention, a fixed rate of 20 ml/sec was maintained.
DETAILED DESCRIPTION OF THE
PRESENTLY PREFERRED EMBODIMENTS
The starting material for the invention is a nonwoven web including a plurality of filaments made from one or more polymers treated with a hydrophilic surfactant combination. The nonwoven web may be a spunbond web, a meltblown web, a bonded carded web, or another type of nonwoven web, and may be present in a single layer or a multilayer composite including one or more nonwoven web layers.
The hydrophilic surfactant combination may be an internal or external surfactant combination. An internal surfactant is one which is blended with the polymer used to make the nonwoven web, and which migrates to the surface of the nonwoven web f filaments during and/or after the formation of the filaments. Often, the migration results from a stimulus, such as heat applied to the filaments. An external surfactant is one which is applied externally to the surfaces of the nonwoven web filaments after they are formed.
An external surfactant may be applied by dipping, soaking, spraying, or otherwise coating the nonwoven web with a medium containing the surfactant. Internal and external surfactant inclusion techniques are generally well known in the art.
The surfactant combination used in accordance with the invention is a combination of two or more surfactants which impart durable hydrophilicity to a nonwoven web, as well as a controlled rate of wettability. Generally, the nonwoven web is constructed from a thermoplastic polymer which is either hydrophobic or insufficiently hydrophilic. The class of nonwoven webs referred to herein as "hydrophobic or insufficiently hydrophilic"
refers to nonwoven webs which exhibit a performance parameter less than 10 using the cradle test described above, when the nonwoven web is not treated with a hydrophilic surfactant.
A wide variety of thermoplastic polymers may be used to construct the nonwoven web, including without limitation polyamides, polyesters, polyolefins, copolymers of ethylene and propylene, copolymers of ethylene or propylene with a C4-CZO
alpha-olefin, terpolymers of ethylene with propylene and a C4-CZO alpha-olefin, ethylene vinyl acetate copolymers, propylene vinyl acetate copolymers, styrene-polyethylene-alpha-olefin) elastomers, polyurethanes, A-B block copolymers where A is formed of polyvinyl arene) moieties such as polystyrene and B is an elastomeric midblock such as a conjugated diene or lower alkene, polyethers, polyether esters, polyacrylates, ethylene alkyl acrylates, polyisobutylene, polybutadiene, isobutylene-isoprene copolymers, and combinations of any of the foregoing. Polyolefins are preferred. Polyethylene and polypropylene homopolymers and copolymers are most preferred. The webs may also be constructed of bicomponent or biconstituent filaments or fibers, as defined above. The nonwoven webs may have a wide variety of basis weights, preferably ranging from about 10 grams per square meter (gsm) to about 120 gsm.
It should be understood that the invention is not limited to the use of hydrophobic and insufficiently hydrophilic polymers. The durable, controlled wetting rate surfactant combination may also be used to enhance the wetting performance of nonwoven fabric polymers which are already hydrophilic, as indicated by a performance parameter of at least 30% without a hydrophilic surfactant.
The hydrophilic combination of surfactants must provide durable wetting at a controlled wetting rate. The combination may include two or more surfactants, one of which independently provides durable wetting, and the other of which independently provides controlled rate wetting. Alternatively, the surfactant combination may include two or more surfactants which, taken alone, do not provide one or both properties, but which provide durable and controlled rate wetting when acting together in synergy.
A hydrophilic surfactant combination provides "durable wetting" if the performance parameter resulting from the third liquid insult is greater than, equal to, or up to 10% less than the performance parameter resulting from the first liquid insult using the cradle test, described above.
The hydrophilic surfactant combination must also provide wetting at a controlled rate which may be fast, intermediate or slow. A surfactant combination provides a fast wetting rate if a nonwoven fabric treated with the surfactant combination (e.g., a nonwoven fabric made from a hydrophobic or insufficiently hydrophilic thermoplastic polymer) exhibits a performance parameter of at least 50% for the first fluid insult using the ' , CA 02290321 1999-11-24 cradle test, described above. A hydrophilic surfactant combination provides an intermediate wetting rate if the performance parameter for the first fluid insult is at least 40% and less than 50%. A hydrophilic surfactant combination provides a slow wetting rate if the performance parameter for the first fluid insult is at least 30% and less than 40%.
Performance parameters below 30% are deemed insufficient.
The hydrophilic surfactant combination includes at least first and second surfactants. The first surfactant may be a durable surfactant. The first surfactant may include a compound selected from an ethoxylated hydrogenated fatty acid ester, a monosaccharide, a monosaccharide derivative, a polysaccharide, a polysaccharide derivative, and combinations thereof. For instance, the first surfactant may include a blend of ethoxylated hydrogenated castor oil and sorbitan monooleate. One such surfactant is AHCOVEL~ Base N-52, available from Hodgson Chemical Co.
Another first surfactant is a castor oil derivative of ethylene oxide. One such surfactant is sold by ICI Surfactant, Inc. under the name ATMER~ 8174.
Another suitable first surfactant may include a selected polyolefin glycol, or a derivative of a polyolefin glycol. Examples of derivatives include polyolefin glycol monooleates and dioleates, polyolefin glycol monolaurates and dilaurates, and alkyl esters of polyolefin glycols. MAPEG~ surfactants, available from PPG Industries, are made from the foregoing derivatives of polyethylene glycol.
Another suitable first surfactant is a LUROL~ surfactant, available from Goulston Technologies, Inc. LUROL~ surfactants are believed to include a polymer, a hydrophilic part with multiple hydrophobic parts. The hydrophobic parts help the surfactant interface and adhere to a hydrophobic polymer substrate. LUROL~7463 and 7514 are two samples of durable surfactants.
IS
' , CA 02290321 1999-11-24 The second surfactant may be a controlled rate wetting surfactant. The second surfactant may be a fast wetting surfactant, an intermediate wetting surfactant, or a slow wetting surfactant.
Examples of second surfactants include organosilicon compounds. MASIL~
SF-19, available from BASF Chemical Co., is an ethoxylated trisiloxane-based surfactant which typically behaves as a fast wetting surfactant. Certain polyolefin glycol derivatives serve as slow or intermediate surfactants. ANTAROX~ surfactant, available from Rhone-Poluene Chemical Co., includes alkyl ether ethoxylates derived from polyethylene glycol and polypropylene glycol, and may cause slow or intermediate wetting depending on the substrate. Another second surfactant may include an alkyl polyglycoside.
GLUCOPON~
220UP is a solution of 60% octylpolyglycoside and 40% water, and may serve as a slow or intermediate surfactant when used in combination with a first surfactant, such as a blend of ethoxylated hydrogenated castor oil and sorbitan monooleate.
Other second surfactants include ionic sulfonate-based surfactants, for example dodecylbenzene sulfonate sold under the name BIOSOFT'~ by Stephen Co.
Another ionic surfactant is AEROSOL OT, sold by the Cytec Corporation. Ionic surfactants alone are often fast-wetting but not durable.
The surfactant combination may include about 5-95 parts by weight first surfactant and about 5-95 parts by weight second surfactant, based on dry solids, per 100 parts by weight of both surfactants combined. Commonly, the surfactant combination may include about 25-90 parts by weight first surfactant and about 10-75 parts by weight second surfactant. Desirably, the surfactant combination may include about 40-80 parts by weight first surfactant and about 10-60 parts by weight second surfactant. Regardless of how the surfactants behave alone, the first surfactant generally contributes durability to the combination, and the second surfactant generally contributes controlled rate wetting. Often, the performance of both surfactants is synergized and enhanced by the combination.
The surfactant combination may be applied using internal and/or external application techniques well known in the art. The first and second surfactants may be applied in separate steps, or together. If one or both surfactants are applied externally using a solvent, the solvent may be removed using conventional evaporation techniques. On a solvent-free weight basis, the surfactant combination should constitute about 0.1-10% by weight of the nonwoven fabric to which it is applied, preferably about 0.5-5%
by weight, more preferably about 1-3% by weight. Higher levels of surfactant combination are less desirable, due to cost and other issues. Levels which are too low tend to impart less wettability to the nonwoven fabric.
The nonwoven fabrics thus formed have wettability which is both durable and rate-determined. The treated nonwoven fabric can be used in a wide variety of absorbent product applications including, in particular, personal care absorbent products. Personal care absorbent products include diapers, training pants, swim wear, absorbent underpants, baby wipes, adult incontinence products, feminine hygiene products, and the like, as well as other surge and intake material products. In most absorbent products, the treated nonwoven fabric is used as a cover sheet or containment matrix for an absorbent media. An absorbent medium may include, for instance, pulp fibers alone or in combination with a superabsorbent material. The treated nonwoven fabric can also be used in medical absorbent products, including without limitation underpads, absorbent drapes, bandages, and medical wipes.
The pulp fibers may be any high-average fiber length pulp, low-average fiber length pulp, or mixtures of the same. Preferred pulp fibers include cellulose fibers. The term "high average fiber length pulp" refers to pulp that contains a relatively small amount of ' CA 02290321 1999-11-24 short fibers and non-fiber particles. High fiber length pulps typically have an average fiber length greater than about 1.5 mm, preferably about 1.5-6 mm, as determined by an optical fiber analyzer, such as the Kajaani tester referenced above. Sources generally include non-secondary (virgin) fibers as well as secondary fiber pulp which has been screened. Examples of high average fiber length pulps include bleached and unbleached virgin softwood fiber pulps.
The term "low average fiber length pulp" refers to pulp that contains a significant amount of short fibers and non-fiber particles. Low average fiber length pulps have an average fiber length less than about 1.5 mm, preferably about 0.7-1.2 mm, as determined by an optical fiber analyzer such as the Kajaani tester referenced above.
Examples of low fiber length pulps include virgin hardwood pulp, as well as secondary fiber pulp from sources such as office waste, newsprint, and paperboard scrap.
Examples of high average fiber length wood pulps include those available from the U.S. Alliance Coosa Pines Corporation under the trade designations Longlac 19, Coosa River 56, and Coosa River 57. The low average fiber length pulps may include certain virgin hardwood pulp and secondary (i.e., recycled) fiber pulp from sources including newsprint, reclaimed paperboard, and once waste. Mixtures of high average fiber length and low average fiber length pulps may contain a predominance of low average fiber length pulps. For example, mixtures may contain more than about 50% by weight low-average fiber length pulp and less than about 50% by weight high-average fiber length pulp.
The term "superabsorbent" or "superabsorbent material" refers to a water swellable, water-insoluble organic or inorganic material capable, under the most favorable conditions, of absorbing at least about 15 times its weight and, more desirably, at least about 30 times its weight in an aqueous solution containing 0.9% by weight sodium chloride.
' CA 02290321 1999-11-24 The superabsorbent materials can be natural, synthetic and modified natural polymers and materials. In addition, the superabsorbent materials can be inorganic materials, such as silica gels, or organic compounds such as cross-linked polymers. The term "cross-linked" refers to any means for effectively rendering normally water-soluble materials substantially water insoluble but swellable. Such means can include, for example, physical entanglement, crystalline domains, covalent bonds, ionic complexes and associations, hydrophilic associations, such as hydrogen bonding, and hydrophobic associations or Van der Waals forces.
Examples of synthetic superabsorbent material polymers include the alkali metal and ammonium salts of poly(acrylic acid) and poly(methacrylic acid), poly(acrylamides), polyvinyl ethers), malefic anhydride copolymers with vinyl ethers and alpha-olefins, polyvinyl pyrrolidone), poly(vinylmorpholinone), polyvinyl alcohol), and mixtures and copolymers thereof. Further superabsorbent materials include natural and modified natural polymers, such as hydrolyzed acrylonitrile-grafted starch, acrylic acid grafted starch, methyl cellulose, chitosan, carboxymethyl cellulose, hydroxypropyl cellulose, and the natural gums, such as alginates, xanthan gum, locust bean gum and the like.
Mixtures of natural and wholly or partially synthetic superabsorbent polymers can also be useful in the present invention. Other suitable absorbent gelling materials are disclosed by Assarsson et al. in U.S. Patent 3,901,236 issued August 26, 1975. Processes for preparing synthetic absorbent gelling polymers are disclosed in U.S. Patent No.
4,076,633 issued February 28, 1978 to Edwards et al. and U.S. Patent No. 4,286,082 issued August 25, 1981 to Tsubakimoto et al.
Superabsorbent materials may be xerogels which form hydrogels when wetted. The term "hydrogel," however, has commonly been used to also refer to both the wetted and unwetted forms of the superabsorbent polymer material. The superabsorbent materials can be in many forms such as flakes, powders, particulates, fibers, continuous fibers, networks, solution spun filaments and webs. The particles can be of any desired shape, for example, spiral or semi-spiral, cubic, rod-like, polyhedral, etc.
Needles, flakes, fibers, and combinations may also be used.
Superabsorbents are generally available in particle sizes ranging from about 20 to about 1000 microns. Examples of commercially available particulate superabsorbents include SANWET'~ IM 3900 and SANWET~' IM-SOOOP, available from Hoescht Celanese located in Portsmouth, Virginia, DRYTECH~ 2035LD available from Dow Chemical Co.
located in Midland, Michigan, and FAVOR~ 880, available from Stockhausen, located in Greensboro, North Carolina. An example of a fibrous superabsorbent is OASIS~
101, available from Technical Absorbents, located in Grimsby, United Kingdom.
As indicated above, the nonwoven fabric may be a cover sheet or a matrix for an absorbent medium. When employed as a matrix, the nonwoven filaments may be combined with pulp fibers and (optionally) a superabsorbent material using processes well known in the art. For example, a coform process may be employed, in which at least one meltblown diehead is axranged near a chute through which other materials are added while the web is forming. Coform processes are described in U.S. Patent 4,818,464 to Lau and 4,100,324 to Anderson et al., the disclosures of which are incorporated by reference. The substantially continuous bicomponent filaments and pulp fibers may also be combined using hydraulic entangling or mechanical entangling. A hydraulic entangling process is described in U.S. Patent 3,485,706 to Evans, the disclosure of which is incorporated by reference.
When the thermoplastic nonwoven filaments are used as a matrix for an absorbent nonwoven web composite, the composite should contain about 5-97% by weight pulp fibers, preferably about 35-95% by weight pulp fibers, more preferably about 50-95%
by weight pulp fibers. When a superabsorbent material is present, it should constitute about 5-90% by weight of the composite, preferably about 10-60% by weight, more preferably about 20-50% by weight. In either case, the thermoplastic nonwoven filament matrix should constitute about 3-95% by weight of the composite, preferably about 5-65% by weight, more preferably about 5-50% by weight.
After combining the ingredients together, the absorbent nonwoven composite may be bonded together using the thermal point bonding or through-air bonding techniques described above, to provide a coherent high integrity structure.
Examples For Examples 1-18, the nonwoven fabric employed was a polypropylene/
polyethylene side-by-side bicomponent. The surfactants were added internally by compounding into one or both polymer resins using a heated 30 mm twin screw extruder, prior to formation of the spunbond filaments. The resulting surfactant/
polymer concentrates were then added to one or both melt streams in the fiber spinning process, prior to extrusion.
The resulting treated nonwoven fabrics were then evaluated using the cradle test described above. For each of these tests, two rectangular fabric samples having dimensions of 2.5 in x 7.0 in were employed. The results of the evaluations are shown in Table 1.
Table 1: Surfactants Added Internally Level Web Performance Parameter, T i Fib W W
t % Si i b ht rea ) er e e - n ze, g ( , went Loca-Denier Ounces/Density1st 2nd 3rd per xam do tionFilamentdZ cc InsultInsultInsultChan Comments le a 2.5 Intermediate, 1 SF19 in 2.1 2.48 0.02445 40 30 -33 PP Not Durable 2 Antarox3 2.2 3.32 0.02130 29 19 _37 Slow, in PP
Not Durable 3 Antarox3 1.7 2.67 0.02338 32 20 ~7 Slow, in PP
Not Durable 4 Ahcovel3 not wettable in PP
Antarox/
5* Mapeg 3 2.3 3.14 0.02529 28 31 +7 Insufficient, ~
PP
400 Durable ML
SF
6* 3 1.9 3.96 0.03438 36 36 -5 m PE
00 Dm.able ML
Antarox/
00 Dm.able ML
Antarox/
7* 3 1.9 3.35 0.03034 33 32 -6 m PE
00 D,,~ble ML
Antarox/
00 D,,~ble ML
Antarox/
8 Atmer 3 1.9 3.60 0.03112 21 23 +92 Insufficient in PE
SF
Mapeg 2 1.2 2.68 0.02550 35 30 -40 Fit, ~
PP
400 Not Durable ML
SF
3 1.2 2.70 0.02551 45 37 -27 Fast m PP
00 , ML
1/1 Not Durable SF
11 Mapeg 3 1.2 2.77 0.02650 45 41 _ Fast, in 1 PP g 600 Not Durable DO
SF
F~~
~covel2 1.2 2.63 0.02651 47 43 -16 in PP
12 Not Durable Level Web Performance Parameter, Treat-(%) Fiber Wei W
in Size ht b , g e , ment Loca-Denier Ounces/Density1st 2nd 3rd per Exam atio tion Filamentd~ cc InsultInsultInsultChan Comments to a SF
13 Mapeg 3 1.2 2.66 0.03154 50 46 -15 Fast' in PP
600 Not Durable DS
14 SF19/ 2 1.2 3.01 0.02748 47 45 _6 Intermediate, ~
Atmer both Durable SF
Ahcovel, 15 PP, 2 1.2 2.60 0.03051 50 50 _2 Fast, m SF19/ both Durable Atmer, PE
SF
F~~
16 Ahcovel3 1.2 2.25 0.02952 50 50 -'1 in PP
Doable SF
Slow, 17 Ahcovel3 3.0 2.54 0.02339 43 41 +5 in PP
Durable SF
Slow, ~, Ahcovel3 3.0 2.25 0.02531 36 37 +19 18 in PP
Dm.able * (Tests conducted on 3x7" samples in a different cradle setup) For Examples 19-33, the same nonwoven fabric was used, but the surfactants were added externally instead of internally. An aqueous surfactant mixture/emulsion was applied to the nonwoven fabric using dipping followed by vacuum drying, or foam application. The surfactant levels employed (on a solvent free basis) were somewhat lower than for Examples 1-18. However, when surfactants are added externally instead of internally, the entire amount added is present at the surface where it achieves the greatest wetting. The treated nonwoven fabrics were evaluated using the cradle test.
The results are shown in Table 2.
Table 2: Surfactants Added Externally Web Treat- Fiber Weight,Web __Performance Size, Parameter, ~
went Add-onDenier Ounces/Densitylst 2nd 3rd per xam atio % FilamentdZ cc InsultInsultInsultChan Comments le a Intermediate, 19 SF 0.15 1.1 2.5 0.03046 37 31 -33 Not Durable Intermediate 20 SF19 0.38 1.1 2.5 0.03048 42 32 -33 Not Durable Intermediate, 21 SF19 0.75 1.1 2.5 0.03046 43 39 -15 Not Durable Intermediate, 22 SF19 1.5 1.1 2.5 0.03047 44 41 -13 Not Durable Ahcovel/
23 Glucopon0.38 1.1 2.5 0.03014 18 21 +50 Insufficient (3/1) Ahcovel/
24 Glucopon0.75 1.1 2.5 0.03028 36 38 +36 Insufficient (3/1) Ahcovel/
Slow, 25 Glucopon1.5 1.1 2.5 0.03038 41 42 +11 Durable (3/1) Ahcovel/
Intermediate 26 Glucopon3.0 1.1 2.5 0.03043 41 42 -2 Doable (3/1) 27 Ahcovel/0,75 1.1 2.5 0.03051 48 49 -4 Fast, SF19 Durable (3/1) 28 Ahcovel/1.5 1.2 2.5 0.03048 45 46 ~ ntermediate, I
SF19 Durable (3/1) 29 ~coveU1.0 1.1 2.6 0.03855 54 56 +2 Fit, SF19 Durable (3/1) 30 ~coveU1.0 3.0 2.7 0.02443 43 43 0 ntermediate, I
SF19 Durable (3/1) Ahcovel/ I ntermediate, 31 1.0 2.0 3.9 0 49 44 48 -2 SF19 . Durable (3/1) 32 ~coveU1,0 3.0 2.4 0.02438 38 39 +2 Slow, SF19 Durable (2/1) 33 ~covel/0.6 3.0 2.8 0 40 39 40 0 ntermediate, SF19 . Durable As shown above, for both internally and externally added surfactants, only certain combined surfactants gave both durability and controlled wetting.
Surfactants used ,, individually, which exhibited sufficient wetting, did not possess durability when applied to the nonwoven webs. Notably, only some of the surfactant combinations delivered both durability and controlled wetting, while others did not. Also, the performance of a particular surfactant combination varied with the total amount applied, and the ratio of ingredients used.
Examples 34-57 illustrate the performance of additional surfactants, alone and in combination with each other. Again, a polypropylene/polyethylene side-by-side bicomponent nonwoven web was used (with average fiber size of 1.1 dpf, basis weight of 2.7 osy, and density of 0.03 g/cc). The surfactants were added externally. For some of the samples (Examples 34-36 and 43-45), a minor quantity of hexanol (0.5%) was added with the surfactants to ease the treatment. Table 3 gives the results of the cradle test. Again, a surfactant (LLIROL), which alone is slow or insufficient, operates much faster (with durability) when used with a co-surfactant, and also operates more effectively at lower levels of the combination.
Table 3: Surfactants Added Externally Performance Parameter, Treatment Add-on 1st 2nd 3rd Exam do % InsultInsultInsultChan Comments le a 34 Luro17463 0.5 16 20 21 +31 Insufficient 35 Luro17463 1.0 28 34 42 +50 Insufficient Intermediate, 36 Luro17463 1.9 40 46 47 +18 Doable 37 Luro17463 0.5 27 21 28 +4 Insufficient Intermediate, 38 Luro17463 1.0 43 49 50 +17 Durable Intermediate, 39 Luro17463 1.9 40 49 50 +25 Durable 40 Aerosol 0.5 55 52 46 -16 Fast, Not OT Durable 41 Aerosol 1.0 56 52 47 -16 Fast, Not OT Durable Performance Parameter, Treatment Add-on1st 2nd 3rd Exam do % InsultInsultInsultChan Comments le a 42 Aerosol 1.9 54 51 44 -19 Fast, Not OT Durable Lurol/Glucopon0.5 39 47 35 -10 Slow Durable 43 (3/1) , Luro (3 1.0 38 49 52 +37 Slow i~ opon Durable , 45 Lm'ol/ Glucopon2.0 45 50 52 +16 Intermediate, (3/1) Durable 46 Lm' ~3 ~ 0.5 61 60 52 -15 Fast osol Not Durable , 47 Lur ( A 1.0 58 55 56 -3 Fast ~ osol Durable , 48 Lar ~ i~osol2.0 57 54 53 -7 Fast Durable , Lurol/Aerosol Intermediate, 49 0.5 44 49 50 +14 (9/1) Dm.able Lurol/Aerosol Intermediate, 50 I.0 47 50 56 +19 (9/1) Dm.able Lurol/Aerosol Intermediate, 51 2.1 43 52 53 +23 (9/I) Durable Lurol/Masil Intermediate, 52 SF19 0.5 49 50 27 -45 (3/I) Not Durable Lurol/Masil I~ SF19 1.0 51 53 54 +6 Fast 53 Durable , (3/1) , 54 L~ol/Masjl 2,0 53 50 52 -2 Fast SF19 Durable , 55 LurolBiosoft0.6 23 28 33 +43 Insufficient (3/1) 56 LurolBiosoft1.1 35 45 49 +40 Slow, Durable (3/1) 57 LurolBiosoft(3/I)2.0 45 49 53 +Ig Intermediate, Durable While the embodiments disclosed herein are presently preferred, various modifications and improvements can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated by the appended claims, and all changes that fall within the meaning and range of equivalents are intended to be embraced therein.
SF
Mapeg 2 1.2 2.68 0.02550 35 30 -40 Fit, ~
PP
400 Not Durable ML
SF
3 1.2 2.70 0.02551 45 37 -27 Fast m PP
00 , ML
1/1 Not Durable SF
11 Mapeg 3 1.2 2.77 0.02650 45 41 _ Fast, in 1 PP g 600 Not Durable DO
SF
F~~
~covel2 1.2 2.63 0.02651 47 43 -16 in PP
12 Not Durable Level Web Performance Parameter, Treat-(%) Fiber Wei W
in Size ht b , g e , ment Loca-Denier Ounces/Density1st 2nd 3rd per Exam atio tion Filamentd~ cc InsultInsultInsultChan Comments to a SF
13 Mapeg 3 1.2 2.66 0.03154 50 46 -15 Fast' in PP
600 Not Durable DS
14 SF19/ 2 1.2 3.01 0.02748 47 45 _6 Intermediate, ~
Atmer both Durable SF
Ahcovel, 15 PP, 2 1.2 2.60 0.03051 50 50 _2 Fast, m SF19/ both Durable Atmer, PE
SF
F~~
16 Ahcovel3 1.2 2.25 0.02952 50 50 -'1 in PP
Doable SF
Slow, 17 Ahcovel3 3.0 2.54 0.02339 43 41 +5 in PP
Durable SF
Slow, ~, Ahcovel3 3.0 2.25 0.02531 36 37 +19 18 in PP
Dm.able * (Tests conducted on 3x7" samples in a different cradle setup) For Examples 19-33, the same nonwoven fabric was used, but the surfactants were added externally instead of internally. An aqueous surfactant mixture/emulsion was applied to the nonwoven fabric using dipping followed by vacuum drying, or foam application. The surfactant levels employed (on a solvent free basis) were somewhat lower than for Examples 1-18. However, when surfactants are added externally instead of internally, the entire amount added is present at the surface where it achieves the greatest wetting. The treated nonwoven fabrics were evaluated using the cradle test.
The results are shown in Table 2.
Table 2: Surfactants Added Externally Web Treat- Fiber Weight,Web __Performance Size, Parameter, ~
went Add-onDenier Ounces/Densitylst 2nd 3rd per xam atio % FilamentdZ cc InsultInsultInsultChan Comments le a Intermediate, 19 SF 0.15 1.1 2.5 0.03046 37 31 -33 Not Durable Intermediate 20 SF19 0.38 1.1 2.5 0.03048 42 32 -33 Not Durable Intermediate, 21 SF19 0.75 1.1 2.5 0.03046 43 39 -15 Not Durable Intermediate, 22 SF19 1.5 1.1 2.5 0.03047 44 41 -13 Not Durable Ahcovel/
23 Glucopon0.38 1.1 2.5 0.03014 18 21 +50 Insufficient (3/1) Ahcovel/
24 Glucopon0.75 1.1 2.5 0.03028 36 38 +36 Insufficient (3/1) Ahcovel/
Slow, 25 Glucopon1.5 1.1 2.5 0.03038 41 42 +11 Durable (3/1) Ahcovel/
Intermediate 26 Glucopon3.0 1.1 2.5 0.03043 41 42 -2 Doable (3/1) 27 Ahcovel/0,75 1.1 2.5 0.03051 48 49 -4 Fast, SF19 Durable (3/1) 28 Ahcovel/1.5 1.2 2.5 0.03048 45 46 ~ ntermediate, I
SF19 Durable (3/1) 29 ~coveU1.0 1.1 2.6 0.03855 54 56 +2 Fit, SF19 Durable (3/1) 30 ~coveU1.0 3.0 2.7 0.02443 43 43 0 ntermediate, I
SF19 Durable (3/1) Ahcovel/ I ntermediate, 31 1.0 2.0 3.9 0 49 44 48 -2 SF19 . Durable (3/1) 32 ~coveU1,0 3.0 2.4 0.02438 38 39 +2 Slow, SF19 Durable (2/1) 33 ~covel/0.6 3.0 2.8 0 40 39 40 0 ntermediate, SF19 . Durable As shown above, for both internally and externally added surfactants, only certain combined surfactants gave both durability and controlled wetting.
Surfactants used ,, individually, which exhibited sufficient wetting, did not possess durability when applied to the nonwoven webs. Notably, only some of the surfactant combinations delivered both durability and controlled wetting, while others did not. Also, the performance of a particular surfactant combination varied with the total amount applied, and the ratio of ingredients used.
Examples 34-57 illustrate the performance of additional surfactants, alone and in combination with each other. Again, a polypropylene/polyethylene side-by-side bicomponent nonwoven web was used (with average fiber size of 1.1 dpf, basis weight of 2.7 osy, and density of 0.03 g/cc). The surfactants were added externally. For some of the samples (Examples 34-36 and 43-45), a minor quantity of hexanol (0.5%) was added with the surfactants to ease the treatment. Table 3 gives the results of the cradle test. Again, a surfactant (LLIROL), which alone is slow or insufficient, operates much faster (with durability) when used with a co-surfactant, and also operates more effectively at lower levels of the combination.
Table 3: Surfactants Added Externally Performance Parameter, Treatment Add-on 1st 2nd 3rd Exam do % InsultInsultInsultChan Comments le a 34 Luro17463 0.5 16 20 21 +31 Insufficient 35 Luro17463 1.0 28 34 42 +50 Insufficient Intermediate, 36 Luro17463 1.9 40 46 47 +18 Doable 37 Luro17463 0.5 27 21 28 +4 Insufficient Intermediate, 38 Luro17463 1.0 43 49 50 +17 Durable Intermediate, 39 Luro17463 1.9 40 49 50 +25 Durable 40 Aerosol 0.5 55 52 46 -16 Fast, Not OT Durable 41 Aerosol 1.0 56 52 47 -16 Fast, Not OT Durable Performance Parameter, Treatment Add-on1st 2nd 3rd Exam do % InsultInsultInsultChan Comments le a 42 Aerosol 1.9 54 51 44 -19 Fast, Not OT Durable Lurol/Glucopon0.5 39 47 35 -10 Slow Durable 43 (3/1) , Luro (3 1.0 38 49 52 +37 Slow i~ opon Durable , 45 Lm'ol/ Glucopon2.0 45 50 52 +16 Intermediate, (3/1) Durable 46 Lm' ~3 ~ 0.5 61 60 52 -15 Fast osol Not Durable , 47 Lur ( A 1.0 58 55 56 -3 Fast ~ osol Durable , 48 Lar ~ i~osol2.0 57 54 53 -7 Fast Durable , Lurol/Aerosol Intermediate, 49 0.5 44 49 50 +14 (9/1) Dm.able Lurol/Aerosol Intermediate, 50 I.0 47 50 56 +19 (9/1) Dm.able Lurol/Aerosol Intermediate, 51 2.1 43 52 53 +23 (9/I) Durable Lurol/Masil Intermediate, 52 SF19 0.5 49 50 27 -45 (3/I) Not Durable Lurol/Masil I~ SF19 1.0 51 53 54 +6 Fast 53 Durable , (3/1) , 54 L~ol/Masjl 2,0 53 50 52 -2 Fast SF19 Durable , 55 LurolBiosoft0.6 23 28 33 +43 Insufficient (3/1) 56 LurolBiosoft1.1 35 45 49 +40 Slow, Durable (3/1) 57 LurolBiosoft(3/I)2.0 45 49 53 +Ig Intermediate, Durable While the embodiments disclosed herein are presently preferred, various modifications and improvements can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated by the appended claims, and all changes that fall within the meaning and range of equivalents are intended to be embraced therein.
Claims (41)
1. A treated nonwoven fabric comprising polymer filaments treated with a surfactant combination including at least first and second surfactants, the treated nonwoven fabric having durable hydrophilic properties defined as a performance parameter of initially at least 30% which does not fall by more than 10% between the first and third fluid insults using the cradle test.
2. The treated nonwoven fabric of Claim 1, wherein the surfactant combination comprises a durable, fast wetting combination which exhibits an initial performance parameter of at least 50%.
3. The treated nonwoven fabric of Claim 1, wherein the surfactant combination comprises a durable, intermediate wetting surfactant combination which exhibits an initial performance parameter of at least 40% and less than 50%.
4. The treated nonwoven fabric of Claim 1, wherein the surfactant combination comprises a durable, slow wetting surfactant combination which exhibits an initial performance parameter of at least 30% and less than 40%.
5. The treated nonwoven fabric of Claim 1, wherein at least one of the surfactants is applied internally.
6. The treated nonwoven fabric of Claim 1, wherein at least one of the surfactants is applied externally.
7. The treated nonwoven fabric of Claim 1, wherein the polymer filaments comprise bicomponent filaments including at least two distinct polymer components, wherein at least one of the polymer components is treated with the surfactant combination.
8. The treated nonwoven fabric of Claim 1, wherein the first surfactant comprises a polyolefin glycol derivative selected from polyolefin glycol monooleates and dioleates, polyolefin glycol monolaurates and dilaurates, alkyl esters of polyolefin glycols, and combinations thereof.
9. The treated nonwoven fabric of Claim 1, wherein the second surfactant comprises an organosilicon compound.
10. The treated nonwoven fabric of Claim 8, wherein the second surfactant comprises an ethoxylated trisiloxane.
11. The treated nonwoven fabric of Claim 1, wherein the second surfactant comprises an alkyl ether ethoxylate derivative of a polyolefin glycol.
12. The treated nonwoven fabric of Claim 8, wherein the second surfactant comprises an alkyl ether ethoxylate derivative of a polyolefin glycol.
13. The treated nonwoven fabric of Claim 1, wherein the first surfactant comprises a castor oil derivative of ethylene oxide.
14. The treated nonwoven fabric of Claim 9, wherein the first surfactant comprises a castor oil derivative of ethylene oxide.
15. The treated nonwoven fabric of Claim 1, wherein the first surfactant comprises a blend of ethoxylated hydrogenated castor oil and sorbitan monooleate.
16. The treated nonwoven fabric of Claim 9, wherein the first surfactant comprises a blend of ethoxylated hydrogenated castor oil and sorbitan monooleate.
17. The treated nonwoven fabric of Claim l, wherein the second surfactant comprises an alkyl polyglycoside.
18. The treated nonwoven fabric of Claim 15, wherein the second surfactant comprises an alkyl polyglycoside.
19. The treated nonwoven fabric of Claim 1, wherein the first surfactant comprises a hydrophilic parts and a plurality of hydrophobic parts.
20. The treated nonwoven fabric of Claim 19, wherein the second surfactant comprises an alkyl polyglycoside.
21. The treated nonwoven fabric of Claim 1, wherein the second surfactant comprises an ionic surfactant.
22. The treated nonwoven fabric of Claim 19, wherein the second surfactant comprises an ionic surfactant.
23. The treated nonwoven fabric of Claim 21, wherein the second surfactant comprises dodecylbenzene sulfonate.
24. The treated nonwoven fabric of Claim 19, wherein the second surfactant comprises an organosilicon compound.
25. An absorbent nonwoven composite comprising an absorbent medium in combination with a nonwoven fabric treated with a surfactant combination, the treated nonwoven fabric exhibiting fast, durable wetting.
26. The absorbent nonwoven composite of Claim 25, wherein the treated nonwoven fabric serves as a cover sheet for the absorbent medium.
27. The absorbent nonwoven composite of Claim 25, wherein the treated nonwoven fabric provides a matrix and the absorbent medium is contained within the matrix.
28. An absorbent nonwoven composite comprising an absorbent medium in combination with a nonwoven fabric treated with a surfactant combination, the treated nonwoven fabric exhibiting intermediate, durable wetting.
29. The absorbent nonwoven composite of Claim 28, wherein the treated nonwoven fabric serves as a cover sheet for the absorbent medium.
30. The absorbent nonwoven composite of Claim 28, wherein the treated nonwoven fabric provides a matrix and the absorbent medium is contained within the matrix.
31. An absorbent nonwoven composite comprising an absorbent medium in combination with a nonwoven fabric treated with a surfactant combination, the treated nonwoven fabric exhibiting slow, durable wetting.
32. The absorbent nonwoven composite of Claim 31, wherein the treated nonwoven fabric serves as a cover sheet for the absorbent medium.
33. The absorbent nonwoven composite of Claim 31, wherein the treated nonwoven fabric provides a matrix and the absorbent medium is contained within the matrix.
34. A treated nonwoven fabric comprising polymer filaments treated with a surfactant combination including at least first and second surfactants;
the first surfactant comprising a polyolefin glycol or derivative thereof;
the second surfactant comprising an organosilicon compound.
the first surfactant comprising a polyolefin glycol or derivative thereof;
the second surfactant comprising an organosilicon compound.
35. The treated nonwoven fabric of Claim 34, wherein the first surfactant comprises a polyolefin glycol derivative comprises a material selected from polyolefin glycol monooleates and dioleates, polyolefin glycol monolaurates and dilaurates, alkyl esters of polyolefin glycols, and combinations thereof.
36. The treated nonwoven fabric of Claim 34, wherein the second surfactant comprises an ethoxylated trisiloxane.
37. A treated nonwoven fabric comprising polymer filaments treated with a surfactant combination including at least first and second surfactants;
the first surfactant comprising a castor oil derivative of ethylene oxide;
the second surfactant comprising an organosilicon compound.
the first surfactant comprising a castor oil derivative of ethylene oxide;
the second surfactant comprising an organosilicon compound.
38. The treated nonwoven fabric of Claim 36, wherein the second surfactant comprises an ethoxylated trisiloxane.
39. A treated nonwoven fabric comprising polymer filaments treated with a surfactant combination including at least first and second surfactants;
the first surfactant comprising a polymer having both hydrophobic and hydrophilic parts;
the second surfactant comprising a material selected from ionic surfactants and organosilicon compounds.
the first surfactant comprising a polymer having both hydrophobic and hydrophilic parts;
the second surfactant comprising a material selected from ionic surfactants and organosilicon compounds.
40. The treated nonwoven fabric of Claim 39, wherein the second surfactant comprises an ethoxylated trisiloxane.
41. The treated nonwoven fabric of Claim 39, wherein the second surfactant comprises an ionic surfactant.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US20752198A | 1998-12-08 | 1998-12-08 | |
| US09/207,521 | 1998-12-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2290321A1 true CA2290321A1 (en) | 2000-06-08 |
Family
ID=31714210
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2290321 Abandoned CA2290321A1 (en) | 1998-12-08 | 1999-11-24 | Nonwoven surfactant compositions for improved durability and wetting |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2290321A1 (en) |
-
1999
- 1999-11-24 CA CA 2290321 patent/CA2290321A1/en not_active Abandoned
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