MXPA01006954A - Nonwoven fabrics prepared using visbroken single-site catalyzed polypropylene - Google Patents

Abstract

Nonwoven filaments having improved melt spinning process characteristics and end use properties are prepared using a visbroken single-site catalyzed propylene polymer. The propylene polymer has a first melt flow rate (MFR) before visbreaking and a second MFR after visbreaking, such that the ratio of the second MFR to the first MFR is about 1:1 to about 3:1. The nonwoven filaments exhibit less filament tension during spinning, and permit higher line speeds before breaking, than similar filaments prepared using a single-site catalyzed propylene polymer having the second MFR straight out of the reactor, and which has not been visbroken.

Description

NON-WOVEN FABRICS PREPARED USING CATALYTIC PROPYLENE OF SINGLE PARTIALLY DEGRADED SITE Field of the invention This invention relates to fabrics and prepared non-woven fibers using partially-degraded single-site catalyzed polypropylene, wherein the proportion of the melt flow rate (MFR) of the polypropylene after partially degrading its melt flow rate. before partially degrading is around 1: 1 to about 3: 1.

BACKGROUND OF THE INVENTION The conventional Ziegler-Natta-catalyzed polypropylenes have a relatively broad molecular weight distribution after leaving the reactor. It has long been known that partially degraded or "visbreak" copolymers and propylene homopolymers narrow the molecular weight distributions. Partially degrading processes are described, for example, in U.S. Patent No. 4,282,076, issued to Boynton et al. And U.S. Patent No. 5,250,631, issued to McCullough, Jr., and others. The techniques of partially degrading involve thermal degradation, radiation, and the use of peroxides and other catalysts. The partially degraded conventional polypropylenes lead to narrow molecular weight distributions (as well as to average molecular weights) because initially the larger polypropylene molecules are more susceptible to partially degraded than the initial smaller polypropylene molecules.

U.S. Patent No. 5,723,217, issued to Stahl et al., Discloses that the melt-bonding of conventional propylene (Ziegler-Natta catalyzed) polymers improves with the degradation of peroxide-using polymers. Stahl et al. Further discloses and cast-bonding of prepared propylene polymers using single-site metallocene-type catalysts. According to Stahl et al., Single-degree, reaction-grade catalyzed propylene polymers (for example, not partially degraded) provide the same advantages of fiber bonding as partially degraded Ziegler-Natta propylene polymers, because the site polymers simple have narrow molecular weight distributions leaving the reactor. These advantages include, for example, or better processing ease and the ability to make high strength, small diameter fibers. Therefore, the use of a metallocene catalyzed propylene polymer eliminates the need for a partially degraded process step.

Stahl et al. Further discloses that metallocene catalyzed propylene polymers can be partially degraded to a lower molecular weight to facilitate fiber production. Stahl et al. Claim that partially degrading does not change the molecular weight distribution, defined as the ratio of average molecular weight to the number average molecular weight. From the description of Stahl et al., For example, it may appear that a polymer grade 5 melt flow rate reaction which is partially degraded to 55 melt flow rate results in a polymer having the same distribution of narrow molecular weight as before. For purposes of cast bonding, there is no apparent incentive to partially degrade a melt flow rate metallocene polymer to a higher melt flow rate, as opposed to the spin bonding of a metallocene polymer of the reaction grade of metallocene. flow rate of upper smelting which has not been partially degraded.

Synthesis of the invention It has been discovered, unexpectedly, that a single site catalyzed propylene polymer partially degraded at a higher melt flow rate of a lower melt flow rate exhibits better melt bonding properties than a catalyzed reaction grade propylene polymer. similar simple site that initially has a higher melt flow rate, when the ratio of the melt flow rate higher than the lower melt flow rate is about 1: 1 to about 3: 1. Therefore, contrary to the teachings of the prior art, there is an advantage in partially degrading a simple site catalyzed propylene polymer of lower melt flow rate to a higher melt flow rate, rather than simply producing a upper melt flow rate in a polymerization reactor.

The present invention is directed to nonwoven fibers which are bonded from a metallocene catalyzed propylene polymer which has been partially degraded from a lower melt flow rate to a higher melt flow rate, wherein the proportion of The melt flow rate higher than the lower melt flow rate is about 1: 1 to about 3: 1. The present invention is also directed to the non-woven fabrics produced from the fibers, and to medical and personal care products that include non-woven fabrics.

It is a feature and an advantage of the invention to provide a relatively thin, strong fiber made from a partially degraded single site catalyst propylene polymer of a melt flow rate lower than a higher melt flow rate, and in which it can be thinner (thinner) than could be produced under similar conditions using a simple reaction grade site propylene polymer having a higher melt flow rate.

It is also a feature and an advantage of the invention to produce a non-woven fiber fabric made using the partially degraded single-site catalyzed propylene polymer, and various medical and personal care products that incorporate the non-woven fabric.

Definitions The term "nonwoven fabric or fabric" means a fabric in which it has a structure of individual threads or fibers which are interlaced, but not in an identifiable or regular manner as a knitted fabric. Fabrics or non-woven fabrics have been formed from many processes such as, for example, meltblowing processes, spinning processes, air laying processes, and carded and bonded tissue processes. The basis weight of the non-woven fabrics is usually expressed in ounces of material per square yard (osy) or in grams per square meter (gsm) and fiber diameters are usually expressed in microns. (Note that to convert from ounces per square yard to grams per square meter, multiply ounces per square yard by 33.91).

The term "microfibers" means small diameter fibers having an average diameter no greater than about 75 microns, for example, having an average diameter of from about 7 microns to about 30 microns. Another expression frequently used for fiber diameter is denier, which is defined as grams per 9000 meters of a fiber. For a fiber that has a denier, circular cross section can be calculated as the fiber diameter in square microns, multiplied by the density in grams per cubic centimeter, multiplied by 0.00707. A lower denier of a finer fiber and a higher denier indicates a heavier or thicker fiber. For example, the diameter of a given polypropylene fiber such as 15 microns can be converted to denier by squareing, multiply the result by .89 grams per cubic centimeter and multiply by .00707. Therefore, a 15 micron polypropylene fiber has a denier of about 1.42 calculated as (152 x 0.89 x .00707 = 1.415). Outside of the United States of America, the most common unit of measurement is "tex", which is defined as grams per kilometer of fiber. The tex can be calculated as denier by 9.

The term "spunbonded fibers" refers to fibers of small diameter which are formed by extruding molten thermoplastic material as filaments from a plurality of fine capillary vessels of a spinner having a circular or other configuration, with diameter of the extruded filaments are then rapidly reduced as, for example, in United States of America No. 4,340,563 issued to Appel et al., and United States of America No. 3 patent, 692,618 issued to Dorschner et al., US Pat. No. 3,802,817 issued to Matsuki et al., US Pat. Nos. 3,338,992 and 3,341,394 issued to Kinney, the United States patent of America No. 3,502,763 granted to Hartman, United States of America No. 3,502,538 to Petersen, and United States of America No. 3,542,615 to Dobo and others, each of which is incorporated herein by reference. its totality by reference. Spunbond fibers are submerged and are generally non-tacky when deposited on a collection surface. Spunbonded fibers are generally continuous and often have average diameters greater than about 7 microns, more generally, between about 10 and 75 microns.

The term "meltblown fibers" means that they are fibers formed by extruding a molten thermoplastic material through a plurality of capillary, usually circular, thin vessels such as filaments or filaments fused into streams (eg, air) of hot gas to High speed converging which attenuate the filaments of molten thermoplastic material to reduce its diameter, which can be a microfiber diameter. Then, the meltblown fibers are transported by the high velocity gas stream and are deposited on a collection surface to form a randomly dispersed meltblown fabric. Such a process is described, for example, in United States Patent No. 3,849,241 issued to Butin. Meltblown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in diameter, and are generally self-supporting when deposited on a collection surface. The meltblown fibers used in the present invention are preferably substantially continuous in length.

The term "monocomponent" fibers refers to fibers formed from one or more extruders that use only one polymer. This does not mean excluding fibers formed from a polymer to which small amounts of additives have been added for color, antistatic properties, lubrication, hydrophilicity, etc. These additives, for example, titanium dioxide for color, are generally present in an amount less than 5 percent by weight and more typically around 2 percent by weight.

The term "dual-fiber fibers or filaments" refers to fibers which have been formed from at least two extruded polymers of separate extruders but bonded together to form a fiber. The polymers are arranged in substantially constantly placed in different zones across the cross section of the bicomponent fibers and continuously spread along the length of the bicomponent fibers. The configurations of such bicomponent fiber may be, for example, a pod / core arrangement where one polymer is surrounded by another or may be a side-by-side arrangement or an "islands-in-the-sea" arrangement. The bicomponent fibers are designed in U.S. Patent No. 5,108,820 issued to Kaneko et al., U.S. Patent No. 5,336,552 issued to Strack et al., And the U.S. Patent of America. No. 5,382,400 issued to Pike and others, each of which is incorporated herein in its entirety by reference. For the two component fibers, the polymers may be present in proportions of 75/25, 50/50, 25/75 any other desired proportions. Conventional additives, such as pigments and surfactants, may be incorporated in one or both polymer streams, or applied to the surfaces of the filaments.

The term "biconstituent fibers" refers to fibers which have been formed from at least two extruded polymers from the same extruder as a mixture. The term "mixture" is defined below. The biconstituent fibers do not have the various polymer components arranged in relatively constantly placed distinct zones across the cross-sectional area of the fiber and the various polymers are usually non-continuous along the entire length of the fiber, instead of that usually they form fibrils or protofibrilos which they begin and end at random. Biconstituent fibers are sometimes also referred to as multi-constituent fibers. Fibers of this general type are described in, for example, U.S. Patent No. 5,108,827 issued to Gessner. Biconstituent and bicomponent fibers are also described in the textbook Polymer Compounds and Blends by John A. Manson and Leslie H. Sperling, copyright 1976 by Plenum Press, a division of Plenum Publishing Corporation of New York, ISBN. 0-306-30831-2, on pages 273 through 277.

The term "mixture" as applied to polymers means a mixture of two or more polymers while the term "alloy" means a subclass of mixtures wherein the components are immiscible but have been compatibilized.

The term "polymer" includes, but is not limited to, homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc. and the mixtures and modifications thereof. In addition, unless otherwise specifically limited, the term "polymer" should include all possible geometric configurations of the material. These configurations include, but are not limited to, atactic, syndiotactic and isotactic symmetries.

The term "propylene polymer" includes both propylene homopolymers and the copolymers. Specifically useful are polymers containing a preponderance of propylene, such as homopolymers and copolymers containing about 90 to 100% by weight of propylene and about 0 to 10% by weight of ethylene or 0% to 50% by weight of a C4-C20 alpha olefin comonomer. Propylene homopolymers and random copolymers are especially preferred.

The term "single-site catalyzed" propylene polymers includes the propylene polymers and the copolymers produced by the single site catalysts, which include without limitation the metallocene-catalyzed copolymers and propylene homopolymers. The metallocene processes for making the polyolefin use a metallocene catalyst which is activated (eg, ionized) by a cocatalyst.

The polymers produced using metallocene catalysts have a narrow molecular weight distribution. The "narrow molecular weight distribution polymer" refers to a polymer that exhibits a molecular weight distribution of less than about 3.5. As is known in the art, the molecular weight distribution of a polymer is the ratio of the weight average molecular weight of the polymer to the average molecular weight number of the polymer. The methods to determine the molecular weight distribution are described in Encyclopedia of Engineering and Science of Polymer, volume 3, pgs. 299 to 300 (1985). Examples of the narrow molecular weight distribution polyolefins include the metallocene catalyzed polyolefins, the forced geometry catalyzed polyolefins, and other single site catalyzed polyolefins, described above. Polydispersities (Mw / Mn) of below 3.5 and even below 2 are possible for the metallocene-produced polymers. These polymers also have a narrow short chain branched distribution when compared to similar Ziegler-Natta produced polymers.

Metallocene catalysts include bis (n-butylcyclopentadienyl) titanium dichloride, bis (n-butylcyclopentadienyl) zirconium dichloride, bis (cyclopentadienyl) -scandium chloride, dichloride zirconium bis (indenyl), bis dichloride (methylcyclopentadienyl) -titanium, zirconium dichloride bis (methylcyclopentadienyl), cobaltocene, cyclopentadienyltitanium trichloride, ferrocene, hafnocene dichloride, zirconium dichloride isopropyl- (cyclopentadienyl? i-1-flourenyl), dichloride of molybdocene, niquelocene, niobocene dichloride, ruthenocene, titanocene dichloride, zirconocene chloride hydride, zirconocene dichloride, among others. A more exhaustive list of such compounds is included in U.S. Patent No. 5,374,696 issued to Rosen et al. And issued to Dow Chemical Company. Such compounds are also disclosed in U.S. Patent No. 5,064,802 issued to Stevens et al. And also assigned to Dow.

The metallocene process, and particularly catalysts and catalyst support systems are the subject of a number of patents. In the patent of the United States of America No. 4, 542,199 issued to Kaminsky et al. Describes a process wherein a metallocene catalyst of the general formula (cyclopentadienyl) 2MeRHal wherein Me is a transition metal, Hal is a halogen and R is a coclopentadienyl or a C1 to C6 alkyl radical or a halogen, is used to form polyethylene. U.S. Patent No. 5,189,192 issued to LaPointe et al. And assigned to Dow Chemical discloses a process for preparing additional polymerization catalysts by means of central metal oxidation. U.S. Patent No. 5,352,749 issued to Exxon Chemical Patents, Inc. describes a method for polymerizing monomers in fluidized beds. U.S. Patent No. 5,349,100 discloses the chiral metallocene compounds and the preparation thereof by creating a chiral center by the enantioselection of hydride transfer.

Cocatalysts are materials such as methylaluminoxane (MAO) which is the most common, other alkylaluminiums and boron containing compounds such as tris (pentafluorophenyl) boron, lithium tetrakis (pentafluorophenyl) boron, and dimethylanilinium tetrakis (pentafluorophenyl) boron. Research is continuing in other cocatalyst systems or the possibility of minimizing or even eliminating alkylaluminiums due to handling and contamination issues. The important point is that the metallocene catalyst is ionized to a cationic form for the reaction with the monomer (s) to be polymerized (s).

It is also possible to use a metallocene catalyst system to control the isotactity of the polymer fairly close when the selective stereo metallocene catalysts are employed. In fact, polymers have been produced that have an isotacticity in excess of 99 percent. It is also possible to produce highly syndiotactic polypropylene using this system.

To control the isotacticity of a polymer it can also result in the production of a polymer which contains blocks of isotactic material and blocks of atactic material that alternate over the length of the polymer chain. This construction results in an elastic polymer by virtue of the atactic part. Such a polymer synthesis is described in the Journal, volume 267 (January 13, 1995) on page 191 in an article by K.B. Wagner Wagner, discussing the work of Coates and Waymouth, explains that the catalyst oscillates between the stereochemical forms that result in a polymer chain that has balanced lengths of isotactic stereocenters connected to balanced lengths of atactic centers. The isotactic domain is reduced by producing elasticity. Geoffrey W. Coates and Robert M. Waymouth, in an article titled "Oscillating Stereo Control: A Strategy for Thermoplastic Elastomeric Polypropylene Synthesis" on page 217 in the same volume, describes in their work in which they used chloride metallocene of bis (2-phenylindenyl) -zirconium in the presence of methylaluminoxane (MAO), and, by varying the presence and temperature in the reactor, the polymer form oscillates between isotactic and atactic.

Commercial production of metallocene polymers is somewhat limited but growing. Such polymers are available from Exxon Chemical Company of Baytown, Texas under the brand name ACHIEVE® for polypropylene base polymers and EXACT® for polyethylene base polymers. Dow Chemical Company of Midland, Michigan has polymers commercially available under the name ENGAGE®. These materials are believed to be produced using selective non-stereo metallocene catalysts. Exxon generally refers to its metallocene catalyst technology as "single site" catalysts while Dow refers to theirs as "forced geometry" catalysts under the name INSIGHT® to distinguish those of the traditional Ziegler-Natta catalysts which It has multiple reaction sites. Manufacturers such as Fina Oil, BASF, Amoco, Hoescht and Mobil are active in this area and it is believed that the availability of polymers produced according to this technology can grow substantially in the next decade.

The term "reaction degree" refers to a propylene polymer which has not been partially degraded, for example, which has not been subjected to a molecular degradation process, after its initial production in a polymerization reactor. The term "reaction degree" is intended to exclude polymers which have been partially degraded to lower their initial molecular weight, and / or alter their initial molecular weight distribution.

The term "substantially continuous fibers or filaments" refers to filaments or fibers prepared by extrusion from a spinning organ, including without limitation meltblown and spunbonded fibers, which are not cut from their original length before being formed into a nonwoven fabric or fabric. The fibers or substantially continuous filaments may have lengths in the range greater than about 15 centimeters to more than one meter; and up to or beyond the length of the fabric or the fabric that is formed. The definition of "substantially continuous fibers or filaments" includes those which are not cut before being formed into a nonwoven fabric or fabric, but which are cut off later when the fabric or the non-woven fabric is cut.

The term "basic fibers" means the shorter fibers which are natural or cut from a manufactured filament before being formed into a fabric, and which have an average length in the range of from about 0.1 to 15 centimeters, most commonly around from 0.2 to 7 centimeters.

The term "point of adhesion" of the fibers excluded from a spinning organ refers to the maximum fiber distance, measured from the face of the spinning organ, where a metal rod placed in contact with the fibers will be able to stick thereto. A circular aluminum rod having a diameter of 0.5 inches is positioned adjacent the fibers at a long distance from the spinning organ, and is gradually moved along the adjacent fiber surfaces in the direction in which it approaches the spinner. . When the fibers begin to stick to the rod, the distance from the rod to the spinning organ is recorded as the point of adhesion.

The term "fiber tenacity" refers to a measurement made in accordance with ASTM D3822, modified to the extent of 72 filaments (instead of one) are tested using a Textechno Statiomat M measuring device. The measurement length used is 100 millimeters, the test speed is 1270 millimeters per minute, and the pretension is placed at 0.5 centimeters per text. The normal test procedure is otherwise followed.

The term "personal care product" includes diapers, underpants for training, bathing suits, absorbent underpants, baby wipes, adult incontinence products, and feminine hygiene products. , and the like, as well as other products of material that admission and emergence.

The term "medical care product" includes medical garments, interior pads, absorbent curtains, bandages, medical wipes, and the like.

Detailed description of currently preferred additions The starting material for the invention is a single-site catalyzed propylene polymer, which may be a homopolymer or any of the copolymers indicated above. Preferred propylene polymers include homopolymers and copolymers containing up to about 10% by weight of ethylene or up to about 50% by weight of a C4-C20 alpha olefin comonomer. The ethylene content should be limited because it is something of the partially degraded processes which advantageously affects the polypropylene, it can cause gelation, crosslinking and other less desirable reactions in the polyethylene type materials. Therefore, it is preferred that any ethylene comonomer be present at a low level. Propylene homopolymers and random copolymers are preferred over block copolymers, for similar reasons. Isotactic propylene homopolymers and copolymers are generally preferred over syndiotactic and atactic materials, although combinations of different stereoisomers may be advantageous in some circumstances.

The initial propylene polymer can be a simple site-catalyzed reaction grade material. For example, the starting material can be a reaction-grade metallocene-catalyzed propylene polymer, or a forced-geometry-catalyzed propylene polymer of reaction grade. The initial propylene polymer can be characterized in terms of a melt flow rate (MFR), measured at 230 ° C in accordance with ASTM D1238 (1), and recorded in grams per 10 minutes. The initial propylene polymer should stop a melt flow rate of from about 3 to about 250, preferably about 10 to about 150, more preferably about 20 to about 100.

The initial propylene polymer is subject to a partially degraded process which reduces the average molecular weight, which results in a partially degraded propylene polymer. The partially degraded can be achieved using conventional familiar techniques to people with a skill in the art. For example, the partially degraded can be achieved by using a peroxide to facilitate the molecular cleavage of the propylene molecules. The partially degraded can also be achieved by using heat (often 300 to 400 ° C), radiation, cutting (for example, using an extruder), combinations of the above techniques, or any other technique which achieves the desired level of molecular cleavage.

Preferably, the partially degraded is achieved with the assistance of a peroxide catalyst. Suitable catalysts include, for example, alkyl hydroperoxides and dialkyl peroxides, as described in U.S. Patent No. 4,282,076, issued to Boynton. A suitable peroxide is 2,5-demethyl-2,5-bis (t-butylperoxy) hexane.

Another suitable peroxide is 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane-3. These peroxides are available under the brand name LUPERSOL® from Pennwalt Corporation.

The peroxide can be added to the propylene polymer in a molten state at about 180 to 300 ° C in an extruder, for example. The amount of heat by affecting the rate and extent of the partially degraded. The peroxide may be added at about 0.001 to 2.0% by weight of the propylene polymer, preferably about 0.1 to 1.0% by weight of the polymer, more preferably about 0.2 to 0.7% by weight of the propylene polymer.

The partially degraded conditions should be selected and controlled so that the partially degraded propylene polymer exhibits only a relatively small amount of degradation, compared to the initial propylene polymer. The partially degraded propylene polymer should have a melt flow rate that is about 1.0 to 3.0 times the melt flow rate of the initial propylene polymer. The partially degraded propylene polymer has a melt flow rate that is about 1.3 to 2.7 times the melt flow rate of the initial propylene polymer, more preferably about 1.5 to 2.5 times the melt flow rate of the polymer of initial propylene. Also, the partially degraded propylene polymer should have a melt flow rate of at least about 10, preferably about 20 to 150, more preferably about 30 to 100, to render it particularly useful for bonding applications with foundry.

Partially degraded propylene polymer can be used only in a melt bonded process, or it can be combined with one or more other polymers. For example, the partially degraded propylene polymer may be combined with one or more polymer selected from polyamides, polyesters, polyolefins, copolymers of ethylene and propylene, copolymers of ethylene or propylene with a C4-C20 alpha olefin, of ethylene terpolymers with propylene and a C4-C20 alpha olefin, the ethylene vinyl acetate copolymers, the propylene vinyl acetate copolymers, the styrene-poly (ethylene-alpha olefin) elastomers, the polyurethanes, the copolymers of block AB where A is formed of poly (vinyl sand) moieties such as polystyrene and B is an elastomeric middle block such as a conjugated diene or a lower alkene, polyethers, polyether esters, polyacrylates, acrylates of ethylene alkyl, polyisobutylene, poly-1-butene, poly-1-butene copolymers including copolymers of ethylene-1-butene, polybutadiene, copolymers of ethylene-1-butene Sobutylene-isoprene, and the combinations of the above. Copolymers and polyolefin homopolymers are preferred as additional polymers. Copolymers and polypropylene and polyethylene homopolymers are most preferred.

If the partially degraded propylene polymer is blended or in alloy with a polymer, it is generally preferred that the mixture or alloy then partially take place to degrade the single site catalyzed propylene polymer. In this way, the process of partially degrading will not and can influence the properties of the additional polymer. When biconstituent or blended fibers or filaments are made, the amount of partially degraded propylene polymer relative to the additional polymer may vary considerably depending on the application. The actual polymer blend includes at least 10% by weight of the partially degraded single site catalyzed propylene polymer, preferably at least 25% by weight, more preferably at least 50% by weight.

The partially degraded propylene polymer and one or more additional polymers can also be extruded adjacent to one another in the form of fibers or filaments of components. Again, the proportions of each polymer can vary considerably depending on the application. The component filaments should include at least 10% by weight of the partially degraded single site catalyzed propylene polymer, preferably at least 25% by weight, more preferably at least 50% by weight.

The non-woven fabric produced by the processes of bonding with cast iron may be a bound bonded fabric, a confused blown fabric, a bonded carded fabric, a fabric laid by air, or any other type of non-woven fabric, and may be present in a single layer or in a multilayer composite including one or more layers of non-woven fabric. Whether the partially degraded propylene polymer is used alone or in combination with another polymer, the main functions of the partially degraded polymer are to facilitate the production of fine fibers (for example very fine fibers) having acceptable strength for various applications of use. final .

Non-woven fabrics containing partially degraded single-site catalyzed propylene polymer can be manufactured using a wide variety of cast-bonding processes, including conventional cast-bonding processes. A bonding process with appropriate casting is described in U.S. Patent No. 3,802,817, issued to Matsuki et al., Which is incorporated herein by reference. That process can also be referred to as a line of partially oriented yarn (POY). In that process, a curtain of filaments bonded with cast iron are extruded from a spinning organ and pulled to a desired filament diameter with the aid of air jet streams applied on both sides of the curtain. The air jets are oriented such that they interact to create a suction force which pulls the filaments followed by their extrusion. The average diameter of the manufactured filaments is influenced, to an extent, by the diameter of the apertures of the spinning organ as well as the tensile force exhibited by the polymer material, which is opposed to the suction force exerted by the streams of air.

In another type of partially oriented yarn fiber line, the filaments can be mechanically pulled using pull rolls, for example, instead of being pulled by air. In each type of partially oriented yarn line, the filaments are pulled while in a partially melted or molten state, after being extruded from a spinning organ.

The fibers containing the partially degraded single-site catalyzed propylene polymer exhibit reduced intention at a rate (eg, mechanically driven rolls) of given fiber pull. For example, it has been found that fibers made entirely of a single site partially degraded catalyst propylene polymer at a given melt flow rate exhibit less stress at a given fiber pulling speed than a site catalyzed propylene polymer. simple degree of reaction that has the same simple flow rate. Conversely, at a given tension, a higher fiber pulling speed is achieved which results in fibers having smaller average diameters. The increase in pull speed achieved also facilitates the manufacture of finer nonwoven fibers in other processes of bonding with cast iron, in which the fiber diameter is controlled by air suction or other different mechanisms. The improved pull facility, coupled with the integrity and strength of the high fiber, also reduces the incidence of breakage, damage, swelling of the fiber, and other detrimental processing factors. Therefore, higher production rates can be achieved without the interference of these factors.

The produced nonwoven fibers may be in the form of substantially continuous fibers, shorter (staple) basic fibers. A wide variety of non-woven fiber diameters can be achieved depending on the processes of bonding with cast iron used, the conditions of the processes, the specific characteristics of the catalyzed propylene polymer of single site partially degraded, and if the partially degraded polymer is used alone or in combination with other polymers. While large diameter fibers can be produced, a key feature of the invention is the possibility of fine fiber production. The fibers produced using partially degraded single site catalyzed propylene polymer can have diameters of less than 1 micron to about 75 microns, preferably about 7 microns to about 30 microns, more preferably, about 15 microns to about 25 microns. microns.

The non-woven fabrics prepared according to the invention can be used in a wide variety of applications including, in particular, personal care products. Personal care products include, but are not limited to, diapers, training underpants, swimsuits, absorbent underpants, baby wipes, adult incontinence products, feminine care products , and similar. In the absorbent products, the non-woven fabric can be used as a cover sheet or a binding binder of an absorbent medium. The treated non-woven fabric can also be used in medical products, including without limitation medical garments, interior pads, absorbent curtains, sales, and medical cleansing wipes.

And emplos A metallocene catalyzed polypropylene having a reaction melt flow rate of 24 grams per 10 minutes was partially degraded using a peroxide, at a melt flow rate of 50 grams per 10 minutes. The partially degraded polypropylene that was cast bonded using a partially oriented yarn fiber line (POY) which uses the mechanical drive rolls to pull the fibers. A similar metallocene-catalyzed polypropylene resin, which was not partially degraded but had a reaction melt flow rate of 50 grams per 10 minutes, was bonded with cast iron in the same line by comparison.

Fibers made with partially degraded polypropylene exhibited reduced bond line tension (especially at a higher acceleration rate), as well as the distance of the top adhesion point, the higher breakthrough velocity, and the superior toughness, compared to the fibers made with the reaction grade polypropylene. Table 1 summarizes the results.

TABLE Although the embodiments of the present invention described 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 in the appended claims and all changes that fall within the meaning and range of equivalent are intended to be encompassed here.

Claims (38)

R E I V I N D I C A C I O N S

1. A nonwoven fabric that includes a plurality of melt spun filaments; the spunbond filaments comprise a biscrit single site catalyzed propylene polymer having a first melt flow cap prior to biosromption and a second melt flow rate after bromromination; The second melt flow rate has a value which is about 1-3 times the value of the first melt flow rate.

2. The non-woven fabric as claimed in clause 1, characterized in that the second melt flow rate is about 1.3-2.7 times the first melt flow rate.

3. The non-woven fabric as claimed in clause 1, characterized in that the second melt flow rate is about 1.5-2.5 times the first melt flow rate.

4. The non-woven fabric as claimed in clause 1, characterized in that the second melt flow rate is at least about 10.

5. The non-woven fabric as claimed in clause 1, characterized in that the second melt flow rate is around 20-150.

6. The non-woven fabric as claimed in clause 1, characterized in that the second melt flow rate is around 30-100.

7. The non-woven fabric as claimed in clause 1, characterized in that the single-site catalyzed propylene polymer comprises a propylene homopolymer.

8. The non-woven fabric as claimed in clause 1, characterized in that the single-site catalyzed propylene polymer biscrot comprises a propylene copolymer containing up to about 10% by weight of ethylene.

9. The non-woven fabric as claimed in clause 1, characterized in that the bisrot single-site catalyzed propylene polymer comprises a propylene copolymer containing up to about 50% by weight of a C4-C20 alpha-olefin comonomer.

10. The non-woven fabric as claimed in clause 1, characterized in that the catalyzed single-site bis-propylene polymer comprises a metallocene-catalyzed propylene polymer.

11. The non-woven fabric as claimed in clause 1, characterized in that the spunbond filaments consist essentially of a biscrot single-site catalyzed propylene polymer.

12. The nonwoven fabric as claimed in clause 1, characterized in that the meltblown filaments further comprise one or more additional polymers blended with the single site catalyzed propylene polymer.

13. The non-woven fabric as claimed in clause 1, characterized in that the spunbond filaments comprise bicomponent filaments.

14. The non-woven fabric as claimed in clause 1, characterized in that it comprises a fabric bonded with yarn.

15. The non-woven fabric as claimed in clause 1, characterized in that it comprises a meltblown fabric.

16. The non-woven fabric as claimed in clause 1, characterized in that it comprises a carded and bonded fabric.

17. The non-woven fabric as claimed in clause 1, characterized in that it comprises a fabric placed by air.

18. A nonwoven fabric that includes a priority of melt spun filaments having an average diameter of up to about 75 microns; The meltblown filaments comprise a baryoprotone single site catalyzed propylene polymer having a first melt flow rate before bromromination and a second melt flow rate after brazing; The second melt flow rate has a value which is about 1-3 times the value of the first melt flow rate.

19. The non-woven fabric as claimed in clause 18, characterized in that the average filament diameter is about 7-30 microns.

20. The non-woven fabric as claimed in clause 18, characterized in that the average filament diameter is about 15-25 microns.

21. The non-woven fabric as claimed in clause 18, characterized in that the bromromination is achieved using a peroxide.

22. The non-woven fabric as claimed in clause 18, characterized in that the bromromination is achieved using heat.

23. The non-woven fabric as claimed in clause 18, characterized in that the bromromination is achieved using radiation.

24. The non-woven fabric as claimed in clause 18, characterized in that the bromromination is achieved using cut.

25. A personal care product comprising a non-woven fabric; The non-woven fabric includes a biscrit single-site catalyzed propylene polymer having a first melt flow rate before bromromination and a second melt flow rate after bromromination; The second melt flow rate has a value which is about 1-3 times the value of the first melt flow rate.

26. The personal care product as claimed in clause 25, characterized in that it comprises a diaper.

27. The personal care product as claimed in clause 25, characterized in that it comprises training underpants.

28. The personal care product as claimed in clause 25, characterized in that it comprises swimming clothing.

29. The personal care product as claimed in clause 25, characterized in that it comprises absorbent underpants.

30. The personal care product as claimed in clause 25, characterized in that it comprises a cleaning cloth for a baby.

31. The personal care product as claimed in clause 25, characterized in that it comprises a product for adult incontinence.

32. The personal care product as claimed in clause 25 comprising a product for the hygiene of women.

33. A medical product comprising a non-woven fabric; The non-woven fabric includes a biscrit single-site catalyzed propylene polymer having a first melt flow rate before bromromination and a second melt flow rate after bromromination; The second melt flow rate has a value which is about 1-3 times the value of the first melt flow rate.

34. The medical product as claimed in clause 33, characterized in that it comprises a medical garment.

35. The medical product as claimed in clause 33, characterized in that it comprises an underpants.

36. The medical product as claimed in clause 33, characterized in that it comprises an absorbent diaper.

37. The medical product as claimed in clause 33, characterized in that it comprises a bandage.

38. The medical product as claimed in clause 33, characterized in that it comprises a medical cleaning cloth.