MXPA99006085A - Coformed dispersible nonwoven fabric bonded with a hybrid system and method of making same - Google Patents

Abstract

A water-dispersible coformed fibrous nonwoven fabric structure comprising a primary reinforcing polymer material, preferably capable of being meltspun;a secondary reinforcing polymer material having an average fiber length less than or equal to about 15 mm and preferably having a softening point at least about 30°C lower than the softening point of the primary reinforcing polymer;and, an absorbent material, such as pulp or a superabsorbent. The fabric structure maintains desired tensile strength and softness while being water-dispersible and flushable. The fabric produced can be incorporated into an article and can be flushed down a commode. The fabric is flushable when placed in water, with agitation, if necessary, and will disperse into unrecognizable pieces without clogging conventional plumbing or piping. A method of producing the fabric structure comprises mixing the secondary reinforcing material and absorbent material and injecting this coform blend into a stream of meltspun primary reinforcing fibers. After a web structure has been established, the structure is exposed to thermal or ultrasonic energy sufficient to soften and bond the secondary reinforcing material fibers, but not to soften the primary reinforcing material fibers. An embossed pattern can be printed on the structure.

Description

'i, NON-WOVEN FABRIC DISPERSAB E AND COFORMED UNITED WITH A HYBRID STSTEMA AND METHOD TO MAKE THE SAME CROSS REFERENCE TO THE RELATED APPLICATION The present invention is a continuation in part of the still pending application entitled "COMPOUNDS COFORM NON-WOVEN DISPERSIBLE FIBROUS IN WATER" by Jackson et al., Series number 08 / 497,629, filed June 30, 1995, and commonly assigned to the assignee of the present invention.

FIELD OF THE INVENTION The present invention relates to fibrous non-woven composite structures formed and dispersed in water comprising a primary reinforced melt-spun polymer fiber and a secondary reinforcing short-polymer fiber, and an absorbent material.

BACKGROUND OF THE INVENTION J Wet scrubbers are cloth sheets stored in a solution before use and normally used to cleanse the skin. The most common types of wet cleansers are baby cleansers typically used to clean the 'seat area during, a diaper change, and adult cleansers, used to clean hands, face and glue. Wet cleaners are often made of bonded nonwoven fabrics having sufficient tensile strength so that they do not separate during manufacture or use, but nevertheless have desirable softness characteristics for use on the skin in tender areas. . Such non-woven fabrics are commonly manufactured by melt-bonding processes, such as meltblowing and spin-bonding processes, known to those skilled in the art, because melt spinning fabrics can be produced having the characteristics of softness and resistance to tension required.

The bonding of non-woven materials generally accumulates integrity and strength in non-woven fabrics.

Many conventional joining systems are used to make non-woven fabrics, such as, but not limited to thermal bonding, resin bonding (aqueous or melted), hydroentanglement, and mechanical bonding. These broad ratings can be subdivided into a global treatment or zone treatment such as points, lines or small areas of patterns. In addition, the degree of union can be controlled. A high degree of bonding by a higher percentage added or a higher energy input usually accumulates higher resistance and vice versa. However, the joint normally negates the capacity for a waste after use by disintegration and dispersion during disposal with water discharge in the toilet.

Many of the articles or products in which the melted and bonded spinning materials are incorporated are generally viewed as being disposable products of limited use. By this it is meant that the product or products are used only a limited number of times and in some cases only once before being discarded. With growing concerns regarding solid waste disposal, there is now an increased need for materials that are either, for example, recyclable or disposable through other mechanisms in addition to their incorporation into landfills. A possible waste alternative for many products, especially in the area of personal care absorbent products and cleaners, is by discharging them with water discharge into the sewer disposal systems. As will be discussed in more detail below, the discharge with water discharge means that the material must not only be able to pass through a comfortable without clogging it, but the material must also be able to pass through the sewer laterals between a house (or other structure housing the comfortable one) and the main sewer system without being trapped in the pipeline, and it must be able to disperse into small pieces that will not create a problem for the consumer c in the sewer treatment and transport process .

In recent years, the most sophisticated approaches have been designed to impart dispersibility. Chemical binders that are either processable by melted or aqueous and processable emulsions have been developed. The material may have a high strength in its original storage environment, but it will quickly lose resistance by disuniting or dispersing when placed in a different chemical environment (for example, an ion or pH concentration), such as by discharging with discharges. of water in a comfortable with fresh water. It would be desirable to have a joining system that produces a fabric having desirable strength characteristics, but which is capable of dispersing or degrading after use in small parts. Since the machines for producing such bound non-woven fabrics are usually designed to work with a bonding system, hybrid bonding systems are generally unknown in the industry.

U.S. Patent No. 4,309,469 and 4,419,403 both issued to Varona describe a multi-part dispersible binder. Reissue patent No. 31,825 discloses a two-phase heating process (infrared preheating) for calendering with a non-woven fabric consisting of thermoplastic fibers. Even though it offers some flexibility, this is still a unique thermal bonding system. U.S. Patent No. 4,207,367 issued to Baker discloses a non-woven which is densified in individual areas by cold-etching. The chemical binders are sprayed on and the binders migrate preferentially to the densified areas by means of capillary action. The non-densified areas have a higher elevation and remain highly absorbent. However, it is not a hybrid junction system because the densification step is not an excirting process. U.S. Patent No. 4,749,423 to Vaalburg et al. Describes a two-phase thermal bonding system. In the first phase, up to 7% of polyethylene fibers in a fabric are melted to provide temporary resistance to the transfer of support to the next phase. In the second phase the primary fibers are thermally bonded to give the fabric its uniform integrity. This process in two different phases does not make the fabric have built areas of resistance and weakness. This is not suitable as a dispersible material.

Several patents describe hybrid joint systems, but they are for sanitary napkins. For example, U.S. Patent No. 3,654,924 to Duchane, U.S. Patent No. 3,616,797 to Champagne et al., And U.S. Patent No. 3,913,574. granted to Srinvasan and others. The important difference is that these products are designed to be stored dry and have a very limited wet strength for a short duration during use. In a wet cleaner there is still a need for a prolonged wet strength in a storage solution.

Fibrous non-woven materials and fibrous non-woven composite materials are widely used as products or as components of products because they can be manufactured cheaply and can be made to have specific characteristics. One approach has been to mix thermoplastic polymer fibers with one or more types of fibrous material and / or particles. The blends are collected in the form of fibrous nonwoven fabric composites which may be further bonded or treated to provide coherent nonwoven composites which take advantage of at least some of the properties of each component. For example, U.S. Patent No. 4,100,324 issued July 11, 1978 to Anderson et al. Describes a non-woven fabric which is generally a uniform blend of meltblown and pulp-molded thermoplastic polymer fibers. wood. U.S. Patent No. 3,971,373 issued July 7, 1976 to Braun discloses a nonwoven material which contains melt blown thermoplastic polymer fibers and discrete solid particles. Therefore according to this patent, the particles are uniformly dispersible and intermixed with the meltblown fibers in the nonwoven material. U.S. Patent No. 4,429,001 issued January 31, 1984 to Kolpin et al. Describes an absorbent sheet material which is a combination of melt blown thermoplastic polymer fibers and solid superabsorbent particles. The superabsorbent particles are described as being uniformly dispersed and physically maintained within a fabric of melt blown thermoplastic polymer fibers. European patent number 0080382 granted to Minto et al. Published on July 1, 1983 and European patent number 0156160 issued to Minto et al. Published on October 25, 1985, also discloses combinations of particles such as superabsorbents and blown thermoplastic polymer fibers. with fusion. U.S. Patent No. 5,350,624 issued to Georger et al. On September 27, 1994 discloses an abrasion-resistant fibrous non-woven structure composed of a meltblown fiber matrix having a first outer surface, a second outer surface and an inner part with at least one other fibrous material integrated within the meltblown fiber matrix. The concentration of meltblown fibers adjacent to each outer surface of the non-woven structure is at least about 60 percent by weight and the meltblown concentration in the inner part is less than about 40 percent by weight. weight. Many of the aforementioned combinations are mentioned co or "coform" materials because they are formed by combining two or more materials in the forming step in a single structure. The coform materials can also be produced by a spinning process, as described in U.S. Patent No. 4,902,559 issued to Eschwey et al. On February 20, 1990.

Currently, a common method of forming melt blown non-woven coform material involves injecting an amount of cellulose fibers or blends of cellulose fibers and short fibers from a melt blown melt stream. The coform material injected into the fiber stream is trapped or bonded to the melted fibers, which are subsequently cooled or settled. In an additional step the fabric can be joined by ultrasonically or thermally melting the meltblown fibers to join the fibers together transversely, imparting the desired tensile strength. Such bonding treatment also reduces the softness because it reduces the freedom of movement between the blown fibers in the woven structure. Therefore, the imparting of resistance has thus far resulted in a decrease in softness (apart from additional steps of softness, which affect the properties of the material and add to the production costs). In addition, because the meltblown fibers are preferably used in water dispersible fabrics due to the low denier fiber produced, the strength of the fiber is compromised. It would be desirable to produce a fabric having a desirable strength and softness characteristics, but which is dispersible in water.

The designed coform compounds can be used in a wide variety of applications including absorbent media for aqueous and organic fluids, filtration media for wet and dry applications, insulating materials, protective cushioning materials, containment and delivery systems and the cleaning means for both wet and dry applications. Many of the above applications can be satisfied, to varying degrees, through the use of more simplified structures such as absorbent structures where only wood pulp fibers are used. This has commonly been the case with, for example, the absorbent cores of absorbent personal care products such as diapers. Wood pulp fibers when formed by themselves tend to give non-woven fabric structures which have very low mechanical integrity and a higher degree of folding when wetted. The advent of the coform structures which incorporate the blown fibers with thermoplastic melting, even in small quantities, greatly improves the properties of such structures including both the tensile strength in dry and wet. The same improvements were also seen with the advent of the coform cleaning sheets.

The same reason why many coform materials provide increased benefits over conventional materials, for example meltblown thermoplastic fiber matrix, is the same reason why such materials are more difficult to recycle or dispose of with water discharge. . Many products based on wood pulp fiber can be recycled by hydrating and re-pulping the reclaimed wood pulp fibers. However, in coform structures the thermoplastic melt blowing fibers do not break easily. The meltblown fibers are difficult to separate from the wood pulp fibers, and these stay essentially continuously resulting in the possibility of sticking or otherwise damaging the recycling equipment such as pulping reducers. From the point of view of waste with discharge of water into the drainage, the current belief is that for a product to be drainable or disposable with water discharge, said product must be made of very weak or very small fibers so that the material is easily broken into smaller pieces when placed in quantities of water such as those found in toilets and, again due to the nature of the fibers, when discarded with water discharge they will not be trapped or carried inside the piping of conventional public and private sewer disposal systems. Many of these systems, especially sewer laterals may have protuberances within the pipes such as tree roots which can trap any type of material which is relatively intact. This would be the case with melt blown thermoplastic fibers non-dispersible in water in coform materials. As a result, at least for the above reasons, there is a need for a coform material which has the potential to be friendlier with respect to recycling processes and discarded through alternate means of land fill such as, for example, through waste with water discharge. Therefore, it is an object of the present invention to provide such material.

SYNTHESIS OF THE INVENTION The present invention provides a water dispersible fibrous nonwoven composite structure comprising a primary reinforcing polymer material capable of being bound with melted fibers; a second reinforcing material comprising short polymer fibers having an average fiber length of less than or equal to 15 millimeters, and an absorbent material such as pulp. Preferably, the secondary reinforcing material has a softening point of about 50 degrees centigrade down to about 50 degrees centigrade above, more preferably equal to or less than about 30 degrees centigrade lower than the softening point of the primary reinforcing material.

In a preferred embodiment, the primary reinforcing material is present in a concentration of from about 30% to about 35%, the secondary reinforcing material is present in a concentration of from about 5% to 8%, and the absorbent material is present in a concentration of from around 50% to around 55%. A method for forming a fibrous non-woven composite dispersible in water comprises providing a primary reinforcing material comprising polymer fibers; providing a secondary reinforcing material comprising polymer fibers, the polymer fibers of secondary reinforcing material have an average fiber length less than or equal to about 15 millimeters; provide an absorbent material; mix the secondary reinforcing material with the absorbent material; forming a fiber stream composed of a primary reinforced material with melted; adding an effective amount of the mixture from step (d) to the fiber stream; attenuate the fiber stream from step (f); forming a fibrous non-woven structure of the pass fiber stream (g); and, exposing the non-woven structure of step (h) to a power source selected from the group consisting of thermal energy and ultrasonic energy so that the secondary reinforcing fibers are softened while the primary reinforcing material remains essentially undisturbed.

The fiber length of limited secondary reinforcing material reduces the tendency of the final fabric to produce a twisted or "tied" when discharged with flushing in a toilet. Also, limited fiber length promotes dispersion in water in small pieces. The softening point difference between the primary and secondary reinforcing fibers allows only one or the other material to be softened during the thermal or ultrasonic bonding step of the fabric formation. This selective softening point control produces a fabric having only one of the joining components, while the other component fibers maintain the freedom of movement, thereby producing a fabric having desirable tensile strength properties but which is soft .

Therefore, it is an object of the present invention to provide a non-woven fabric structure having desirable wet tensile strength characteristics, while being dispersible in water.

It is another object of the present invention to provide a wet cleaner material capable of maintaining strength during use and being disposable with discharge of water into an ordinary toilet.

It is a further object of the present invention to provide a wet cleaner material capable of dispersing in water to form pieces that are at least about 25 millimeters in diameter and that are sufficiently small to avoid problems in the transportation system of sewerage.

Other objects, features and advantages of the present invention will be apparent from the reading of the following detailed description of the embodiments of the invention, when taken in conjunction with the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in the drawings in which the reference characters designate the same or similar parts through the Figures of which: Figure 1 is a schematic side elevation partially in section of a possible method and apparatus for producing fibrous nonwoven composite structures dispersible in water according to the present invention.

Figure 2 is a perspective view of a fragment of a fibrous non-woven composite structure produced by the method and apparatus of Figure 1.

Figure 3 is a partial schematic side elevation of another possible method and the apparatus for producing fibrous nonwoven composite structures dispersible in water according to the present invention.

DESCRIPTION OF PREFERRED INCORPORATIONS DEFINITIONS As used herein the term "non-woven fabric or fabric" means a fabric having a structure of individual fibers or threads which are interleaved, but not in an identifiable form as in a woven fabric. The non-woven fabrics or fabrics that have been formed from many processes such as, for example, meltblowing processes, spinning bond 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 (csy) or grams per square meter (gsm) and useful fiber diameters are usually expressed in microns or microns. (Note that to convert from ounces per square yard to grams per square meter, multiply ounces per square yard by 33.91).

As used herein, the term "microfibers" means small diameter fibers having an average diameter of no more than about 75 microns, for example, having an average diameter of from about 0.5 microns to about 50 microns, or more. particularly, microfibers can have an average diameter of from about 2 microns to about 40 microns. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9,000 meters of a fiber and can be calculated as fiber diameters in square microns, multiplied by the density in grams / cc multiplied by 0.00707. A lower denier indicates a finer fiber and a higher denier indicates a heavier or thicker fiber. For example, the diameter of a polypropylene fiber given as 15 microns can be converted to denier by squareing, multiplying the result by .89 g / cc and multiplying by .00707. Therefore, a 15 micron polypropylene fiber has a denier of about 1.42 (152 x 0.89 x .00707 = 1.415). Outside the United States of America, the unit of measurement is more commonly the "tex" which is defined as grams per kilometer of fiber. The tex can be calculated as denier / 9.

As used herein, the term "meltblown fibers" means fibers formed by extruding a melted thermoplastic material from a plurality of fine, usually circular, capillary vessels, such as melted threads or filaments into high velocity gas streams (eg. air example) which attenuate the filaments of the melted thermoplastic material to reduce its diameter, which can be to a microfiber diameter. Then, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collector surface to form a meltblown fiber fabric disbursed at random. Such a process is described in, for example, U.S. Patent No. 3,849,241 issued to Buntin. The melt blown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 micrometers in average diameter and are generally sticky when deposited on the collecting surface.

As used herein the term "polymer" generally includes but is not limited to homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc., and mixtures and modifications from the same. In addition, unless specifically limited otherwise, the term "polymer" will include any possible geometric configuration of the material. These configurations include, but are not limited to, isotactic, syndiotactic and random symmetries.

As used herein, the term "monocomponent fibers" refers to a fiber formed from one or more extruders using only one polymer. This does not mean that fibers formed from a polymer to which small amounts of additives have been added for coloring, antistatic properties, lubrication, hydrophilicity, etc., are excluded. These additives, for example, titanium dioxide for coloring, are generally present in an amount of less than 5 percent by weight and more specifically of about 2 percent by weight.

As used herein, the term "conjugated fibers" refers to fibers which have been formed from at least polymers extruded from separate extruders but which have been spun together to form a fiber. Conjugated fibers are also sometimes referred to as multicomponent or bicomponent fibers. The polymers are usually different from one another even though the conjugated fibers can be monocomponent fibers. The polymers are arranged in different zones placed essentially constant across the cross section of the conjugated fibers and extend continuously along the length of the conjugated fibers. The configuration of such a conjugate fiber can be, for example, a sheath / core arrangement where one polymer is surrounded by another or can be a side-by-side arrangement or an arrangement of "islands in the sea". The conjugate fibers are taught in U.S. Patent No. 5,108,820 issued to Kaneko et al., In U.S. Patent No. 5,336,552 issued to Strack et al., And in the U.S. patent. United States of America number 5,382,400 granted to Pike et al. For the two component fibers, the polymers may be present in proportions of 75/25, 50/50, 25/75 or any other desired proportions.

As used herein 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 different zones placed relatively constant across the cross-sectional area of the fiber and the various polymers are usually not continuous along the entire length of the fiber, instead of this they usually form fibrils or photofibrils which start and end at random. Biconstituent fibers are sometimes referred to as multi-constituent fibers. Fibers of this general type are discussed in, for example, U.S. Patent No. 5,108,827 issued to Gessner. Bicomponent and biconstituent fibers are also discussed in the text mixtures and polymer compounds by John A. Manson and Leslie H. Sperling, copyright 1976 by Plenum Press, a division of Plenum Publishing Corporation of New York, IBS? 0-306-30831-2, pages 273 to 277.

As used herein the term "mixture" means a combination of two or more polymers while the term "alloy" means a subclass of mixtures wherein the components are immiscible but have been compatibilized. The "misibility" and the "immissibility" are defined as mixtures having negative and positive values, respectively, for the free energy of mixing. In addition, "compatibilization" is defined as the process of modifying the interfacial properties of an immiscible polymer mixture in order to make an alloy.

As used herein the term "ultrasonic bonding" means a process carried out as, for example, by passing the fabric between a sonic horn and an anvil roll as illustrated in U.S. Patent No. 4,374,888. granted to Bornslaeger.

As used herein, "thermal point bonding" involves passing a fabric or fabric of fibers to be joined between a heated calender roll and an anvil roll. The calendering roll is usually, although not always patterned in some way so that the entire fabric is not bonded through its entire surface. As a result of this, various patterns for calendering rolls have been developed for functional as well as aesthetic reasons. An example of a pattern has dots and is the Hansen Pennings pattern or "H &P" with about a 30% bound area with about 200 joints / square inch as taught in U.S. Patent No. 3,855 .046 granted to Hansen and Pennings. The H &P pattern has square point or bolt joint areas where each bolt has a side dimension of 0.965 millimeters, a separation of 1,778 millimeters between bolts, and a joint depth of 0.584 millimeters. The resulting pattern has a bound area of about 29.5%. Another typical point bonding pattern is the expanded Hansen and Pennings junction pattern or "EHP" which produces a 15% joint area with a square bolt having a side dimension of 0.94 millimeters, a bolt spacing of 2,464 millimeters and a depth of 0.991 millimeters. Another typical point union pattern designated "714" has square bolt joint areas where each bolt has a side dimension of 0.584 mm as a gap of 1.575 mm between the bolts and a joint depth of 0.838 mm. The resulting pattern has a bound area of about 15%. Yet another common pattern is the star pattern in C which has a bound area of about 16.9%. The star pattern C has a "cord" or bar design in the transverse direction interrupted by the escape stars. Other common patterns include a diamond pattern with slightly centered and repetitive diamonds and a wire weave pattern looking like the name suggests, like a window grid. Typically, the percent bond area varies from about 10% to about 30% of the area of the fabric laminated fabric. As is well known in the art, the knit bond further retains the composite together as well as imparting integrity to the composite nonwoven by bonding the filaments and / or fibers within the composite structure.

As used herein the term "disposable with discharge of water" or drainable means that an article, when discharged with discharge of water into a conventional toilet containing water at the temperature approximately ambient, will pass through the toilet pipe, from the Sewer laterals (for example from the pipes between the house or building and the main sewer line) without clogging and will disperse into pieces no larger than about 25 millimeters in diameter.

As used herein the term "dispersible" means that the fibers of a material are capable of being de-agglutinated, resulting in the breaking of the material into smaller pieces than the original sheet. Deagglutination is generally a physical change of spreading or separation in comparison to a change of state such as dissolution, where the material goes into solution, for example the water-soluble polymer that dissolves in water.

As used herein, the term "coform" means continuous spinning reinforcing fibers interspersed with shorter absorbent fibers such as short length fibers and wood pulp fiber particles, such as sabsorbents.

As used herein the term "fibrous non-woven composite structure" refers to a structure of individual fibers or filaments with or without particles which are inter-arranged but not in an identifiable manner. Non-woven structures such as, for example, fibrous non-woven fabrics have been formed in the past, through a variety of processes known to those skilled in the art including, for example, meltblowing or melt spinning processes, union with spinning, the processes of carded and bound fabric and the like.

As used herein the term "water dispersible" or "water disintegrable" refers to a fibrous nonwoven composite structure which when placed in an aqueous environment will break with sufficient time into smaller pieces. As a result, the structure once dispersed may be more advantageously processable in recycling processes, for example, in septic and municipal sewage treatment systems. If desired, such fibrous nonwoven structures can be made more water dispersible or the dispersion can be advanced by the use of agitation and / or triggering means which are further described below. The "actual amount of time will depend at least in part on the particular end-use design criteria.For example, in the sanitary napkins incorporations described below, the fibers break in less than a minute." In other applications, longer times they may be desirable As used herein the term "fibrous nonwoven composite structure" refers to a structure of individual fibers or filaments with or without particles which are interleaved but not in a repetitive and identifiable manner.

As used herein the term "softening point" or "softening temperature" is defined according to the test method ASTM (Vicat) D-1525, which is known to those skilled in the art.

DETAILED DESCRIPTION The present invention is directed to a water-dispersible fibrous coform composite composite structure comprising a primary reinforcing polymer; a secondary reinforcing polymer fiber having a length no greater than about 15 mm, and which preferably (though not necessarily) has a softening point of at least about 30 degrees centigrade less than the primary reinforcing polymer; and an absorbent material.

The primary reinforcing polymer is preferably a melt spun fiber. By "melt spinning" is meant a fiber which is formed by a fiber-forming process which gives longer and more continuous fibers (generally in excess of 7.5 centimeters) such as are made by meltblowing processes and bonding with spinning. Examples of two such water-dispersible reinforcing fibers are meltblown fibers and spunbonded fibers. The meltblown fibers are formed by extruding the melted thermoplastic material through a plurality of thin matrix, usually circular, capillaries such as melted threads or filaments into a heated, high speed gas stream such as air, air, which attenuates the filaments of melted thermoplastic material to reduce their diameters. Then, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a fabric of confusing blown fibers randomly dispersed. The melt blowing process is well known and is described in several patents and publications, including the naval research laboratory report 4364, "Super Fine Organic Fiber Manufacturing" by B. A. endt, E. L. Boose and C.D. Fluharty; the naval research laboratory report 5265"An Improved Device for the Formation of Super Fine Thermoplastic Fibers" by K. D. Lawrence, R. T. Lukas, J. A. Young; U.S. Patent No. 3,676,242 issued July 11, 1972 to Prentice; and U.S. Patent No. 3,849,241 issued November 19, 1974 to Buntin et al. Such meltblown fibers can be made in a wide variety of diameters. Typically, such fibers will have an average diameter of no more than about 100 microns and usually no more than 15 microns.

Spunbonded fibers are formed by extruding a melted thermoplastic material as filaments of a plurality of fine capillary vessels, usually circular, in a spinner organ with the diameter of the extruded filaments then being rapidly reduced, for example, by mechanisms of pulling eductive or non-eductive fluid or other well-known spinning bonding mechanisms. The production of non-woven fabrics bonded with yarn is illustrated in U.S. Patent No. 4,640,563 issued to Appel et al.; 3,802,817 issued to Matsuki and others; 3,692,618 issued by Dorschner and others; 3,338,992 and 3,341,394 granted to Kinney; 3,276,944 granted to Levy; 3,502,538 issued to Peterson; 3,502,763 granted to Hartman; 3,542,615 issued to Dobo and others; and Canadian patent number 803,714 granted to Harmon.

The primary reinforcing material can be made of a polymer such as, but not limited to polyesters, copolyesters, polyamides, copolyamides, polyethylene terephthalates, vinyl alcohols, co-poly (vinyl alcohol), acrylates, methacrylates, cellulose esters, a mixture of at least two or more of these materials and copolymers of acrylic acid and methacrylic acid and the like. The main requirement of the material is that it is meltable and dispersible in water.

A preferred polymer is a proprietary blend of a polyamide provided with the code number NP 2068 by H. B. Fuller Company of San Paul, Minnesota. The code number NP 2074 is also a preferred material which is similar to NP 2068. The viscosity of polymer NP 2068 was 95 pascals / seconds at a temperature of 204 degrees centigrade. The smoothing temperature range of polymer NP 2068 was 128 degrees Celsius / 145 degrees Celsius but was best processed at 210 degrees Celsius to make meltblown microfibers. The NP 2068 polymer is described in greater detail in the Examples given below.

The polymer fibers are preferably less than about 5 denier. Another usable material is a proprietary copolyester blend provided with the code number NS-70-4395, available from National Starch and Chemical Company, of Bridgewater, New Jersey. Alternatively, a mixture of polymers can be used which can provide different composite composition control characteristics depending on the polymers used.

The secondary reinforcing material of the present invention is made of a thermoplastic polymer and is formed by any of a number of known processes such as, but not limited to, melt spinning techniques. After the continuous fibers are pulled, they are cut to form shorter lengths of fibers, commonly called short fibers.

There are many currently available thermoplastic short fibers which can be made from a variety of polymers including, but not limited to, polyolefins, polyesters, polyether block amides, nylon, poly (ethylene-co-vinyl acetate) ), polyurethanes, co-poly (ether ester), and bicomponent and multicomponent materials made thereof, and the like. In addition, several different types and / or sizes of such fibers can be used in the coform structure. A preferred polymer is a polyester available from Minifibers Limited, of Johnson City, Tennessee, which is a 5 denier by 6 millimeter fiber having a smoothing point of 88 degrees centigrade. Alternatively, the secondary reinforcing material can be a bicomponent or multicomponent material, a conjugate material or a mixture thereof. A possible bicomponent material is the polyester of minifibres such as the sheath and a polypropylene, polyethylene or polyethylene terephthalate as a core.

It is critical that the secondary reinforcing polyethylene fibers have less than about 15 millimeters in length, and more preferably less than about 6.35 millimeters. This short fiber length minimizes the possibility of entanglement and twisting (also known as stringing) of the final fabric product in the pipe. The length of secondary reinforcing fiber material in excess of about 15 millimeters produces fabric-dispersible pieces larger than desirable and can become entangled and twisted in the pipe.

Additionally, it is preferable (although not mandatory) that at least one component of the secondary reinforcing polymer material has a softening point of at least about 30 degrees centigrade less than the primary reinforcing polymer. In a preferred embodiment, the secondary reinforcing material has a softening point of about 50 degrees centigrade above about 50 degrees centigrade below the softening point of the primary reinforcing material. The secondary reinforcing material preferably has a softening point of from about 50 degrees centigrade to about 200 degrees centigrade, as measured by the ASTM test method (Vicat) D-1525. Alternatively, the primary reinforcing material may have a softening point of about 50 degrees centigrade above about 50 degrees centigrade below the softening point of the secondary reinforcing material. In a preferred narrower embodiment the primary reinforcing material has a softening point of about 57 degrees centigrade and the secondary material has a softening point of about 88 degrees centigrade. The important feature is that the primary and secondary materials have smoothing points that are markedly different so that during a smoothing process (for example by the application of thermal or ultrasonic energy) only one of the polymers softens and binds , while the other material is not materially softened. This is important during the over-union step in the fabric forming process as will be discussed in more detail below.

The absorbent material of the present invention is commonly referred to as pulp or pulp fibers. Pulp fibers are generally obtained from natural sources such as woody or non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, benzene dusts, straw, jute and bagasse. In addition, synthetic wood pulp fibers are also available and many are used with the present invention. Woody pulp fibers typically have lengths of about 0.5 to 10 millimeters and a maximum width to length ratio of about 10: 1 to 400: 1. A typical cross section has an irregular width of about 30 micrometers and a thickness of about 5 micrometers. A wood pulp suitable for use with the present invention is the Kimberly-Clark CR-54 wood pulp from Kimberly-Clark Corporation of Neenah, Wisconsin.

In addition to the wood pulp fibers, the fibrous nonwoven structure according to the present invention can employ superabsorbent materials. The superabsorbent materials are absorbent materials capable of absorbing at least 10 grams of aqueous liquid (eg distilled water) per gram of absorbent material while they are immersed in a liquid for 4 hours and which will contain essentially all of the liquid absorbed while they are under a compression force of up to about 10 kiloPascals (kPa). Super-absorbent materials are produced in a wide variety of ways including, but not limited to, particles, fibers and flakes. Such superabsorbent materials can be used in the present invention in combination with water-dispersible reinforcing fibers and shorter absorbent fibers or instead of artificial fibers. The particles may be, for example, carbon, clay, starches and / or hydrocolloid particles (hydrogel).

Due to the more continuous and larger nature of the fibers formed by the above meltblown and meltblown processes, such fibers and the resulting non-woven fabrics including the coform fabrics do not break easily due to the inherent toughness of the fibers blown with fusion and / or joined with spinning. As a result of this, coform materials which are predominantly wood pulp fibers but which still contain larger fibers such as polyolefin meltblown fibers are difficult to claim in such apparatuses as the reducers back to pulp. In addition, these more continuous and larger fibers also tend to hang on or over the protuberances on the sides of the sewer thereby making such composite materials difficult to transfer through the drainage treatment system. The fibrous non-woven composite structures according to the present invention use a water dispersible reinforcing fiber which can be made, for example, through the aforementioned and described meltblown and spunbond processes.

The coform materials may have subsequent end uses which involve exposing structures to aqueous liquids including, but not limited to, tap water, waste water, and body fluids such as blood and urine. Conventional coform fibrous non-woven structures are used as absorbent products either alone, as in the form of cleansers, or as components of other absorbent devices such as absorbent articles for personal care including, but not limited to, diapers, the underpants for learning, the incontinence garments, the sanitary napkins, the plugs, the wound dressings, the bandages and the like. It is therefore desirable that the fibrous nonwoven composite structures of the present invention be able to withstand the rigors of their intended uses., and then, upon completion of the particular uses, the composite structures of fibrous nonwoven fabric should be made dispersible in water. to achieve this, water dispersible polymers employing a number of firing mechanisms can be used as the polymers to form the water dispersible reinforcing fibers of the fibrous nonwoven composite structure of the present invention.

Certain polymers are only dispersible in water when exposed to sufficient quantities of an aqueous liquid within a certain pH range. Outside of this range, these will not degrade. Therefore, it is possible to choose a pH-sensitive water dispersible polymer which will not be degraded in a liquid or aqueous liquids in a pH range, for example a pH of 3 to 5, but which will be dispersible in an excess of Tap water. See, for example, U.S. Patent No. 5,102,668 issued to Eichel et al. Therefore, when fibrous nonwoven compounds are exposed to body fluids such as urine, water-dispersible reinforcing fibers will not degrade. After use, such fibrous nonwoven composite structure can be placed in excess amounts of higher pH liquids such as tap water which will cause degradation of the water dispersible polymer constituting the reinforcing fibers. As a result of this, the more continuous and larger reinforcing fibers will begin to break and separate either by themselves or with sufficient agitation so that discrete fibrous components, such as wood pulp fibers, can be reclaimed, recycled or dispersed by waste with liquid discharge. Examples of the polymers which may be used to form this type of fiber may include copolymers of methylacrylic or acrylic-ester acid and mixtures such as those designated N-10, H-10 or X-10 as supplied by AtoFindley. Adhesives, Inc., of Milwaukee, Wisconsin. These materials are stable to the pH conditions of the body (or when cushioned against body fluids), but will break in the toilet water during the waste process with water discharge (excess water).

Another mechanism which can be used to trigger degradability in water is ion sensitivity. Certain polymers contain acid-based (R-COO "or R-S03") components which are held together by hydrogen bonding. In a dry state, these polymers remain solid. In an aqueous solution which has a relatively high concentration of cation, such as urine, the polymers will still remain relatively intact. However, when the same polymers are then exposed to large amounts of water with a diluted ion content, such as can be found in a toilet rate, the cation concentration will be diluted and the hydrogen bond will begin to break. When this happens, the polymers themselves will begin to break in the water. See, for example, U.S. Patent No. 4,419,403 issued to Varona. Polymers that are stable in solutions with high cation concentrations (e.g., baby or adult urine and menstrual fluids) can be sulfonated polyesters as supplied by Eastman Chemical Company of Kingsport, Tennessee under AQ29 codes, AQ38 or AQ55. The Eastman AQ38 polymer is composed of 89 percent per mole of isophthalic acid, 11 percent per mole of sodium sulfoisophalic acid, 78 percent per mole of diethylene glycol and 22 percent per mole of 1,4-cyclohexanedimethanol. It has a nominal molecular weight of 14,000 daltons, a hydrophilic number of less than 10, and a glass transition temperature of 38 degrees centigrade. Other examples may be mixtures of poly (vinyl alcohol) copolymers combined with polyacrylic or methylacrylic acid or polyvinylmethyl ether mixed with polyacrylic or methylacrylic acid. Eastman polymers are stable in solutions with high cation concentrations, but will break quickly if placed in water in sufficient excess such as tap water to dilute the cation concentration. Other polymers that are usable as this ion trigger equipment include proprietary copolyet blends, such as, but not limited to NS-70-4395 and NS-70-4442 having different molecular weights and melt viscosities available from National Strach Chemical Company, which are materials defined by the mixture of narrow molecular weight.

Still other means for making a polymer dispersible in water is through the use of a temperature change. Certain polymers exhibit a turbid point temperature. As a result, these polymers will precipitate out of a solution at a particular temperature which is the turbid point. These polymers can be used to form fibers which are insoluble in water above a certain temperature but which will be soluble and therefore dispersible in water at a lower temperature. As a result of this, it is possible to select or mix a polymer which will not degrade in body fluids such as urine, at or near "body temperature (37 degrees centigrade) but which will degrade when it is Place in water at temperatures below the body temperature, for example, at room temperature (23 degrees Celsius). An example of such a polymer is polyvinyl methyl ether which has a turbidity point of 34 degrees centigrade. When this polymer is exposed to body fluids such as urine at 37 degrees Celsius, it will not degrade since this temperature is above its turbidity point (34 degrees Celsius). However, if the polymer is placed in water at room temperature (23 degrees Celsius) the polymer will, over time, return to the solution as it is not exposed to water at a temperature below its turbid point. Consequently, the polymer will begin to degrade.

Other cold water soluble polymers include the poly (vinyl alcohol) graft copolymers supplied by the Nippon Synthetic Chemical Company Limited of Osaka, Japan which are encoded Ecomaty AX2000, AX10000 and AX300G.

Other polymers are dispersible in water only when exposed to sufficient amounts of water. Thus, these types of polymers may be suitable for use in low water volume solution environments such as, but are not limited to, panty liners, light incontinence products, baby or adult cleaners, and the like. Examples of such materials may include aliphatic polyamides NP 2068, NP 2074 or NP 2120 as supplied by H. B. Fuller Company of Vadnais Heights, Missesota, as discussed above.

Having described the various components which can be used to form a fibrous nonwoven composite structure dispersible in water according to the present invention, examples of various processes which can be used to form such materials will be described. A process for forming the water dispersible fibrous nonwoven fabric structures according to the present invention is shown in Figure 1 of the drawings. In this drawing, a primary reinforcing polymer is extruded through a die head 10 into a stream of primary gas 11 of high velocity, heated gas (usually air) supplied from nozzles 12 and 13 to attenuate the melted polymer in long and somewhat continuous fibers. As these dispersible primary reinforcing fibers are being formed, the primary gas stream 11 is fused with a secondary gas stream 14 containing the short fibers and the individualized wood pulp fibers or other materials including particles to integrate the different fibrous materials in a unique fibrous nonwoven composite structure. The apparatus for forming and delivering the secondary gas stream 14 including the wood pulp fibers may be an apparatus of the type described and claimed in United States Patent No. 3,793,678 issued to Appel. This apparatus comprises a conventional defibrator roll 20 having the shredding teeth to separate the pulp sheets 21 into individual fibers. The pulp sheets 21 are fed radially, for example, along a defibrator roll radius, to the defibrator roll 20 by means of the rollers 22. By breaking the teeth on the defibrator roll 20 the pulp sheets 21 in the individual fibers, the resulting separated fibers are carried downward toward the primary air stream through a duct or forming nozzle 23. A box 24 encloses the defibrator roll 20 and provides a duct 25 between the box 24 and the surface of the defibrator roll. The process air is supplied to the defibrator roll in the duct 25 through the duct 26 in an amount sufficient to serve as a means to carry the fibers through the duct 23 at a rate approaching that of the shredder teeth. . The air can be supplied by conventional means such as, for example, a fan. The secondary reinforcing polymer fibers and the pulp fibers of the present invention can be mixed before being fused with the primary gas stream 11 to form a coform mixture. Alternatively, the secondary reinforcing fibers and the pulp fibers can be added as two streams intersecting with the primary gas stream 11.

The mixing of secondary reinforcing fibers (short) and pulp fibers can be achieved through any of several processes known to those skilled in the art. Such processes are used where two types of pulp material or a pulp and a superabsorbent material are mixed before the addition to the melt spinning material. For example, in a mixing process a bale of short fibers is defibrated and the short fibers are blown into the pulp fiber air stream, mixing before the addition of the melt spinning air stream. In a different process the short fibers are combined in the formation of the pulp in a conventional paper-forming process. In any of the mixing processes, the ratio of short fiber to pulp may vary according to the material properties of the desired final fabric. Preferably, about 30% or less of the short fiber was used in the pulp / short fiber blend.

As illustrated in Figure 1, the primary and secondary gas streams 11 and 14 are preferably moving perpendicular to one another at the melting point, even though other melting angles may be employed if desired to vary the degree of mixed and / or to form the concentration gradients through the structure. The velocity of the secondary stream 14 is essentially lower than that of the primary stream 11 so that the integrated stream 15 resulting from the melt continues to flow in the same direction as the primary stream 11. The melting of the two streams is somewhat as an aspirating effect whereby the mixture of coform fiber (for example the mixture of pulp and short fiber) in the secondary stream 14 is pulled into the primary stream 11 as it passes the outlet of the duct 23. If a uniform structure, it is important that the speed difference between the two gas streams be such that the secondary current is integrated with the primary current in a turbulent form so that the coform mix fibers in the secondary stream are completely mixed with the blown fibers with fusion in the primary current. In general, increasing the speed differences between the primary and secondary currents results in more homogenous integration of the two materials while the lower velocities and the smaller velocity differences will produce concentration gradients of the components in the fibrous non-woven composite structure. For maximum production rates, it is generally desirable that the primary air stream have an initial sonic velocity within the nozzles 12 and 13 and that the secondary air stream has a subsonic velocity. As the primary air stream leaves the nozzles 12 and 13, it immediately expands with a resultant decrease in velocity.

The deceleration of the high velocity gas stream carrying the melt blown fibers dispersible in water and blown with fiber-free melting of the pulling forces which initially form these from the mass of water dispersible polymer. By relaxing the water-dispersible reinforcing fibers, they are better able to follow the minute swirls and tangle and capture the relatively short coform blend fibers while both fibers are dispersed and suspended in the gaseous medium. The resulting combination is an intimate mixture of the coform blend fibers and the primary water-dispersible reinforcing fibers integrated by physical entrapment and mechanical entanglement.

The attenuation of the water-dispersible primary reinforcing fibers occurs both before and after the entanglement of these fibers with the coform blend fibers. In order to convert the coform mixture into the integrated stream 15 into a fibrous nonwoven structure, the stream 15 can be passed into the pressure point of a pair of vacuum rollers 30 and 31 having the perforated surfaces rotating continuously over a pair of fixed vacuum nozzles 32 and 33. When the integrated stream 15 enters the pressure point of the rollers 31 and 33, the carrier gas is sucked into the two vacuum nozzles 32 and 33 while the fiber mixture is held and is slightly compressed by the opposite surfaces of the two rollers 30 and 31. This forms a self-supporting fibrous non-woven composite structure. integrated 34 having sufficient integrity to allow it to be removed from the roller pressure point with vacuum and be carried to a winding roller 35. More preferably, rather than a pair of vacuum rollers 30 and 31, a perforated collector wire (not shown), known to those skilled in the art.

The containment of the coform mix fibers in the integrated primary reinforcing fiber matrix is obtained without any additional treatment or processing of the composite structure placed by air. However, if it is desired to improve the strength of the fibrous nonwoven composite structure 34, the composite structure or fabric 34 can be etched or bonded using heat and / or pressure. Etching can be accomplished using, for example, ultrasonic bonding and / or mechanical bonding as well as through the use of smooth and / or patterned tie rolls which may or may not be heated. Such joining techniques are well known to those skilled in the art. In Figure 1 the composite structure 34 is passed through an ultrasonic bonding station comprising an ultrasonic calendering head 40 which vibrates against an anvil roller with pattern 41. The bonding conditions (e.g., pressure, velocity, strength and the like) and how the bonding pattern can be appropriately selected to provide the desired characteristics in the final product. See Figure 2.

The relative weight percentages of the water-dispersible reinforcing fibers and coform blend fibers can be varied according to the particular end use. Generally speaking, increasing the percent by weight of water-dispersible primary reinforcing fibers will increase the overall tensile strength and integrity of the resultant fibrous composite non-woven structure.

A preferred formation process which can be used to form the water dispersible fibrous nonwoven compounds according to the present invention is shown in Figure 3 of the drawings. An exemplary apparatus for forming an abrasion-resistant fibrous non-woven composite structure is shown in Figure 3 which is generally represented by the reference numeral 110. In the formation of the fiber-resistant non-woven composite abrasion-resistant structure of the present invention, pellets or chips or the like (not shown) of a thermoplastic polymer are introduced into the pellet hoppers 112 of one or more extruders 114.

Extruders 114 have extrusion screws (not shown) which are driven by a conventional drive motor (not shown). As the polymer advances through the extruders 114 due to the rotation of the extrusion screw by the drive motor, the polymer is progressively heated to a molten state. The heating of the thermoplastic polymer to the melted state can be achieved in a plurality of discrete steps with its temperature being gradually raised as it passes through the discrete heating zones of the extruder 114 to two meltblowing dies 116 and 118, respectively. The meltblowing dies 116 and 118 can still be another heating zone wherein the temperature of the thermoplastic resin is maintained at a high level for extrusion.

Each meltblown matrix is configured so that two streams of attenuation gas usually heated by matrix converge to form a single stream of gas which carries and attenuates the melted yarns of the primary reinforcing polymer, as the yarns exit from the small holes 124 in the meltblown matrix. The melted yarns are attenuated in the fibers 120, or depending on the degree of attenuation, the microfibers, of a small diameter which is usually smaller than the diameter of the holes 124. Thus, each meltblown matrix 116 and 118 has a corresponding single gas stream 126 and 128 containing the carried and attenuated polymer fibers. The gas streams 126 and 128 containing the polymer fibers are aligned to converge in a striking zone 130.

One or more types of coform mix fibers (pulp and short polymer) 132 and / or particles are added to the two streams 126 and 128 of fibers or microfibers of primary reinforcing polymer 120 in the striking zone 130. The introduction of the coform blend fibers 132 into the two streams 126 and 128 of the reinforcing polymer fibers 120 is designed to produce a graduated distribution of the coform mix fibers 132 within the combined streams 126 and 128 of the primary reinforcing fibers. This can be achieved by fusing a secondary gas stream 134 containing the coform blend fibers 132 between the two streams 126 and 128 of the primary reinforcing polymer fibers 120 so that all three gas streams converge in a controlled manner.

The apparatus for achieving this fusion can include a conventional set-off defibrillator roll 136 which has a plurality of teeth 138 which are adapted to separate a block or mat 140 from coform mix fibers in the individual coform blend fibers 132. The mat or block of coform 140 fibers which is supplied to the defibrator roll 136 may be a sheet of pulp fibers (if a mixture of two components of secondary reinforcing fibers and pulp fibers is desired). In embodiments where, for example, an absorbent material is desired, the coform blend fibers 132 are absorbent fibers and the polymer material as described above. The short fibers of the coform blend fibers 132 can be as described above.

The sheets or mats 140 of the coform mix fibers 132 can be fed to the defibrator roll 136 by means of a roller array 142. After the teeth 136 of the defibrator roll 136 have separated the coform 140 mixing mats into the separate coform mix fibers 132 the individual coform mix fibers 132 are brought to the stream of thermoplastic polymer fibers or microfibers 120 through a nozzle 144. A box 146 encloses the defibrator roll 136 and provides a gap or duct 148 between the box 146 and the surface of the teeth 138 of the defibrator roll 136. A gas such as air is supplied to the duct or separation 148 between the surface of the defibrator roll 136 and the box 146 via a gas duct 150. The gas duct 150 can enter the duct or partition 148 generally at the joint 152 of the nozzle 144 and the partition 148. The gas is supplied in an amount sufficient to serve as means for bringing the coform mix fibers 132 through the nozzle 144. The gas supplied from the duct 150 also serves as an auxiliary to remove the coform mix fibers 132 from the teeth 138 of the defibrator roll 136. The gas can be supplied through any conventional arrangement such as, for example, an air blower (not shown). It is contemplated that the additives and / or other materials may be added to or carried in the gas stream to treat the coform blend fibers 132 or to provide the desired properties in the resulting fabric.

Generally speaking, the individual coform blend fibers 132 are carried through the nozzle 144 at about the rate at which the fibers of the coform mix 132 leave the teeth 138 of the pickup roller 136. In other words, the fibers of the coform mix 132, by leaving the teeth 138 of the defibrator roll 136 and entering the nozzle 144 generally maintain their velocity in both the magnitude and the direction from the point where they leave the teeth 138 of the defibrator roll 136. Such arrangement, which it is discussed in more detail in U.S. Patent No. 4,100,324 issued to Anderson et al. it helps to essentially reduce fiber flocculation.

The width of the nozzle 144 should be aligned in a direction generally parallel to the width of the meltblown dies 116 and 118. Desirably, the width of the nozzle 144 should be about the same as the width of the meltblown dies 116 and 118. Usually, the width of the nozzle 144 should not exceed the width of the sheets or mats 140 that are being supplied to the defibrator roll 136. Generally speaking, it is desirable that the length of the nozzle 144 that separates the defibrator from the hitting area 130 is as short as the equipment design allows.

The defibrator roll 136 can be replaced by a conventional particle injection system to form a fibrous nonwoven composite structure 154 which contains several secondary particles (e.g., superabsorbents as described above). A combination of both secondary particles and coform blend fibers can be added to the primary reinforcing polymer fibers 120 prior to the formation of the fibrous nonwoven composite structure 154 if a conventional particulate injection system was added to the system illustrated in FIG. Figure 3 Due to the fact that the water-dispersible thermoplastic polymer fibers in the fiber streams 126 and 128 are usually still semi-squeezed and sticky at the time of the incorporation of the coform mix fibers 132 into the fiber streams 126 and 128, the fibers Co-molding mix 132 are usually not only mechanically entangled within the matrix formed by the water dispersible fibers 120 but also thermally bonded or bound to the primary reinforcing fibers.

In order to convert the composite stream 156 of the primary reinforcing fibers 120 and the coform blend fibers 132 into a fibrous nonwoven composite structure 154 composed of a coherent matrix of primary reinforcing fibers 120 having the coform mix fibers 132 distributed there, a collector device is located the path of the composite stream 156. The collector device can be an endless perforated band 158 conventionally driven by the rollers 160 and which is rotating as indicated by the arrow 162 in Figure 3. Other collecting devices are well known to those skilled in the art and can be used in place of the endless belt 158. For example, a porous rotary drum arrangement can be used. The fused streams of primary reinforcing fibers and coform blend fibers are collected as a coherent fiber matrix on the surface of the endless belt 158 to form the fibrous nonwoven composite fabric or structure 154. The vacuum boxes 164 aid in the retention of the matrix on the surface of the band 158. The vacuum can be set to about 2.5 to about 10 centimeters of water column.

The fibrous non-woven composite structure 154 is coherent and can be removed from the web 158 as a non-woven self-supporting material. Generally speaking, the fibrous nonwoven composite structure 154 has adequate strength and integrity to be used without any subsequent treatments such as pattern bonding and the like. If desired, a pair of pinch rollers or pattern bonding rollers (not shown) can be used to join parts of the material. Although such treatment can improve the integrity of the fibrous nonwoven composite structure 154 it also tends to compress and densify the structure.

In addition to the above processes, there are a number of other processes which are suitable for manufacturing various types of coform materials. For example, U.S. Patent No. 4,604,313 issued to McFarland et al. On Aug. 5, 1986, is directed to a process for forming a multi-layer coform material that includes meltblown fibers and pulp fibers. wood in a layer and in a second layer which contains meltblown fibers, wood pulp fibers and superabsorbent particles. Another process is described in U.S. Patent No. 4,902,559 issued to Eschwey et al. On February 20, 1990. This patent discloses a process wherein the endless filaments are spun through a long spinning organ in a conduit to form what is most commonly referred to as yarn-bound fibers. At the same time, the smaller hydrophilic or oleophilic fibers are fed into the stream of fibers bound with yarn. Optionally, the superabsorbent particles can also be introduced into the above fiber mixture.

An important aspect of the present invention is the novel use of the hybrid link system for balancing the tensile strength, the softness and the water dispersibility. Hitherto only single or double raw bonding systems were used to impart tensile strength, the present invention presents a process whereby a first bond occurs during the addition of secondary reinforcing fibers into the air stream of reinforcing fibers. primary, whereby the secondary reinforcing fibers are entangled, trapped and otherwise stuck to the primary reinforcing fibers. The second bond occurs when the composite fiber fabric is softened using a thermal or ultrasonic energy above the softening point of only one of the primary or secondary reinforcing polymers and below that of the smoothing point of the other reinforcing polymer, so that fibers which are softened with union to the other fiber. In a preferred embodiment the polymer of secondary reinforcing material has a softening point of not less than about 30 degrees centigrade lower than the softening point of the primary reinforcing polymer material. In such a case, the primary reinforcing fibers remain without softening and without melting, resulting in a bond that produces an increased tensile strength, but with freedom of movement of the primary reinforcing fibers. Where the softening point of the polymer of the secondary reinforcing material is at least about 30 degrees centigrade above that on the primary reinforcement, the primary reinforcing material softens and bonds, creating tensile strength, while the secondary reinforcing material maintains the freedom of movement. It is the rest of the tensile strength, of the softness of dispersibility in water that is obtained by the composition of the materials and the joining system of the present invention. The conventional meltblown materials used in wet cleaners are weaker because they are composed of a fine denier and a material that allows dispersion in water. Unfortunately, such weak materials do not produce wet cleansers that have sufficient strength to withstand normal use. The fabric of the present invention is stronger due to the addition of the secondary reinforcing material. The use of secondary reinforcing fibers having a length of about 15 millimeters or less reduces the possibility of entanglement and twisting of the fabric formed thereof in a sewer / plumbing system. Additionally, such dimensioned fibers produce water dispersible fabric pieces of a desirable size.

The material of the present invention can be used in a number of articles, including but not limited to baby cleaners, adult cleaners, feminine protection articles, industrial cleansers, bandages, absorbent gauzes, and the like.

Having described various components and processes which can be used to form the water-dispersible fibrous non-woven composite structures according to the present invention, a series of examples were prepared to demonstrate the present invention. The parts and percentages that appear in such examples are by weight unless otherwise stipulated.

E J E M P L O S Test Methods: Strip Tension Test: The strip tension test is a measure of the breaking strength and elongation or tension of a fabric when subjected to unidirectional stress. This test is known in the art. The results are expressed in grams at the break and percentage of alrargamiento before the break. The upper numbers indicate a stronger fabric. The term "load" means the maximum load or force, expressed in units of weight, required to break or fracture the specimen in a stress test. The term "tension" or "total energy" means the total energy under a load curve versus elongation as expressed in units of weight-length. The term "elongation" means the increase in length of a specimen during a stress test. The values for strip tensile strength and strip elongation are obtained using a specified cloth width, usually 2 inches (50 millimeters), the same clamp width and a constant extension rate, the sample is the same width that the handle to give representative results of the effective resistance of the fibers in the grasped width. The specimen is grasped in, for example, a constant rate extension tension tester designated as Sintech 2, model 3397-139, available from Sintech Corporation of Cary, North Carolina, which has 2 parallel lugs 51 millimeters long . These fabric stress conditions simulate actual use very closely.

EXAMPLE 1 Sample 1 was made of 50% primary reinforcing polymer code number NS 70-4395 from National Starch and Chemical Company and 50% pulp / secondary reinforcing polymer blend. The pulp / secondary reinforcing polymer mixture was composed of 80% pulp CR 54, available from Kimberly-Clark Corporation of Neenah, Wisconsin and 20% polyester of 6 millimeters and 5 denier supplied by Minifibers Limited. Also included were 1.5 kilograms / ton of Berocel ™ debonder (available from Akzo Nobel Chemical), which improves fiberization by the defibrator.

Sample 2 was made of 40% primary reinforcing polymer? 70-4395 and 60% secondary polymer / pulp reformer mixture. The secondary polymer / pulper reinforcement mix was composed of 80% CR 54 pulp and 20% of a 6-mm 5 denier polyester provided by Minifibers Limited. Also included were 1.5 kilograms / ton of Berocel ™ debonder.

The absorbent structure was produced using a twin extruder and a pulp fiberizing system as shown in Figure 3. The coformmed composites were formed on either a porous tissue carrier sheet or a polypropylene nonwoven carrier sheet bonded with yarn . Optionally, the coform compounds can be formed directly on a forming wire. The base weights of the coformed absorbent structures were 70 grams per square meter (gsm). The absorbent structures were then patterned in a separate process using a heated calender pressure point with a total bound area of approximately 20 percent. The pattern roller was set to 91.6 degrees Celsius as the anvil roller set to 79.4 degrees Celsius - 90.5 degrees Celsius, the pressure was 10 pounds per square inch over the atmospheric pressure (703 g / square centimeter). It seems that a range of 15-30 pounds / linear inch is usable. See, for example, U.S. Patent No. D315,990 issued April 9, 1991 to Blenke et al.

Table 1 shows the summary of the aging data. The tension was measured in grams / 25 millimeters / width.

T A B A The storage solution was the Natural Care ™ solution available from Kimberly-Clark Corporation of Neenah Wisconsin with an added 1% sodium sulfate (as a condom trigger). Tension tests carried out on a Sintech tension tester used 22,680 grams (load cell with a jaw separation speed of 30.48 centimeters / minute and a jaw extension of 4,508 centimeters.

Sample 1 had an average dry stress after engraving of 1386 g / 2.54 centimeters in the machine direction and 574 g / 2.54 centimeters in the transverse direction. Sample 2 had an average dry stress after engraving of 955 g / 2.54 centimeters in the machine direction and 255 g / inch in the transverse direction.

Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications to the example embodiments are possible without departing materially from the novel teachings and advantages of this invention. Therefore, all such modifications are intended to be included within the scope of the invention as defined in the following claims. In the claims, the media clauses plus function are intended to cover the structures described herein as carrying out the recited function and not only the structural equivalents but also the equivalent structures. Therefore, even though a screw and a nail may be equivalent structures in the sense that a nail employs a cylindrical surface to secure the wooden parts together, while a screw employs a helical surface, in the environment of the fastening of parts of wood, a screw and a nail can be equivalent structures.

It should also be noted that any patents, applications or publications mentioned herein are incorporated by reference in their entirety.

Claims (32)

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

1. A fibrous non-woven composite structure dispersible in water comprising: a) a primary reinforcing material comprising polymer fibers; b) a secondary reinforcing material comprising polymer fibers, said polymer fibers of secondary reinforcing material having an average fiber length of less than or equal to about 15 mm; Y c) an absorbent material.

2. The structure as claimed in clause 1 characterized in that the primary reinforcing material is a material capable of being spun with melted.

3. The structure as claimed in clause 1 characterized in that said primary reinforcing material is meltable and dispersible in water.

4. The structure as claimed in clause 1 characterized in that the primary reinforcing material is a material selected from the group consisting of polyesters, copolyesters, polyamides, copolyamides, polyethylene terephthalates, vinyl alcohols, co-poly (vinyl alcohol), acrylates, methacrylates, cellulose esters, a mixture of at least two of these materials, and copolymers of acrylic acid and methacrylic acid.

5. The structure as claimed in clause 1 characterized in that the fibers formed from said primary reinforcing material have an average diameter of less than about 100 microns.

6. The structure as claimed in clause 1 characterized in that said fibers formed from said primary reinforcing material have an average diameter of less than about 15 micrometers.

7. The structure as claimed in clause 1 characterized in that said secondary reinforcing material is a polymer selected from the group consisting of polyolefins, polyesters, polyether block amides, nylons, poly (ethylene-co-vinyl acetate), polyurethanes, -poly (ether-ester), and bicomponent and multicomponent materials made from them.

8. The structure as claimed in clause 1 characterized in that said secondary reinforcing material has a softening point of about 50 degrees centigrade up to about 50 degrees centigrade below the softening point of said primary reinforcing material.

9. The structure as claimed in clause 1 characterized in that the secondary reinforcing material has a melting point equal to at least about 30 degrees centigrade lower than the softening point of said primary reinforcing material.

10. The structure as claimed in clause 1 characterized in that said primary reinforcing material has a smoothing point equal to or at least about 30 degrees centigrade lower than the smoothing point of said secondary reinforcing material.

11. The structure as claimed in clause 1 characterized in that said secondary reinforcing material has a softening point of from about 50 degrees centigrade to about 200 degrees centigrade, as measured by the ASTM test method (Vicat) D- 1525

12. The structure as claimed in clause 1 characterized in that said secondary reinforcing material has a softening point of about 88 degrees centigrade, as measured by the ASTM test method (Vicat) D-1525.

13. The structure as claimed in clause 1 characterized in that the secondary reinforcing material comprises a plurality of different polymers.

14. The structure as claimed in clause 1 characterized in that said secondary reinforcing material has an average fiber length of about 6 millimeters.

15. The structure as claimed in clause 1 characterized in that said absorbent material is selected from the group consisting of a superabsorbent material, wood fiber, pulp, particulate material, and an odor reducing agent.

16. The structure as claimed in clause 1 characterized in that said absorbent material has an average length of about 0.5 to about 10 millimeters.

17. The structure as claimed in clause 1 characterized in that the absorbent material has an average maximum length to width ratio of about 10: 1 to about 400: 1.

18. The structure as claimed in clause 1 characterized in that said primary reinforcing material is present in a concentration of from about 30% to about 35%, said secondary reinforcing material is present in a concentration of from about 5% to about 8%, and said absorbent material is present in a concentration of from about 20% to about 80%.

19. The structure as claimed in clause 1 characterized in that said primary reinforcing material is present in a concentration of from about 30% to about 35%, said secondary reinforcing material is present in a concentration of from about 5% to about 8%, and said absorbent material is present in a concentration of from about 40% to about 60%.

20. An absorbent article for personal care which includes a non-woven fibrous structure dispersible in water as claimed in clause 1.

21. The absorbent article for personal care as claimed in clause 20, characterized in that said article is selected from the group consisting of a cleanser, a diaper, a training underpants, a pant liner, a sanitary napkin , an incontinence device, a wound dressing and a bandage.

22. A method for forming a fibrous nonwoven composite structure comprising: a) provide a primary reinforcing material; b) providing a secondary reinforcing material comprising polymer fibers, said polymer fibers of secondary reinforcing material having an average fiber length less than or equal to 15 mm; c) providing an absorbent material, d) forming a mixture of the secondary reinforcing material and said absorbent material, e) forming a fiber stream composed of primary fiber reinforcing material bonded with yarn; f) adding an effective amount of the mixture from step d) to the fiber stream; g) forming a fibrous non-woven structure of the fiber stream of step f); and h) exposing said non-woven structure of step h) to a power source selected from the group consisting of thermal energy and ultrasonic energy so that one of the primary and secondary reinforcing materials is softened while the other reinforcing material remains essentially free of charge. soften.

23. The method as claimed in clause 20 further characterized in that it comprises engraving a pattern on said non-woven structure.

24. The structure as claimed in clause 22 characterized in that said primary reinforcing material is a material selected from the group consisting of polyesters, copolyesters, polyamides, copolyamides, polyethylene terephthalates, vinyl alcohols, co-poly (vinyl alcohol), acrylates , methacrylates, cellulose esters, a mixture of at least two of these materials, and copolymers of acrylic acid and methacrylic acid.

25. The structure as claimed in clause 22 characterized in that said secondary reinforcing material is a polymer selected from the group consisting of polyolefins, polyesters, polyether block amides, nylons, poly (ethylene-co-vinyl acetate), polyurethanes, -poly (ether-ester), and two-component and multi-component materials made from them.

26. The structure as claimed in clause 22 characterized in that said secondary reinforcing material has a softening point of about 50 degrees centigrade up to about 50 degrees centigrade below the softening point of said primary reinforcing material.

27. The structure as claimed in clause 22 characterized in that said secondary reinforcing material has a softening point equal to or at least about 30 degrees centigrade lower than the smoothing point of said primary reinforcing material.

28. The structure as claimed in clause 22 characterized in that said primary reinforcing material has a softening point equal to or at least about 30 degrees centigrade lower than the smoothing point of said secondary reinforcing material.

29. The structure as claimed in clause 22 characterized in that said secondary reinforcing material has an average fiber length of about 6 millimeters.

30. The structure as claimed in clause 22 characterized in that said absorbent material is selected from the group consisting of a superabsorbent material, wood fiber, pulp, particulate material, and an odor reducing agent.

31. A disposable article with water discharge produced by the method as claimed in clause 22.

32. A disposable article with water discharge containing a fibrous nonwoven material, said fibrous nonwoven material comprising: a) a primary reinforcing material comprising polymer fibers; b) a secondary reinforcing material comprising polymer fibers, said polymer fibers of secondary reinforcing material having an average fiber length of less than or equal to about 15 mm; Y c) an absorbent material, whereby said disposable article with discharge of water is capable of being discharged with discharge of water into a toilet and into the associated pipe and plumbing, entering the sewer system without clogging said plumbing and said pipe, and dispersing into no more pieces. large ones of around 25 millimeters in diameter. E S U M E N A water-dispersible fibrous nonwoven web structure comprising a primary reinforcing polymer material, preferably capable of being spun with melted; a secondary reinforcing polymer material having an average fiber length of less than or equal to about 15 mm and preferably having a softening point of at least about 30 degrees centigrade lower than the softening point of the primary reinforcing polymer and an absorbent material such as pulp or a superabsorbent. The fabric structure maintains the tensile strength and softness desired while it is water dispersible and disposable with water discharge. The fabric produced can be incorporated into an article and can be disposed of with flushing water in a toilet. The fabric is disposable with water discharge when placed in water, with agitation, if necessary and will disperse into unrecognizable pieces without clogging the pipe or conventional drainage. A method for producing the fabric structure comprises mixing the secondary reinforcing material and the absorbent material and injecting this coform mixture into a stream of primary melt spinning reinforcing fibers. After a fabric structure has been established, the structure is exposed to sufficient thermal or ultrasonic energy to soften and bond the fibers of secondary reinforcing material, but not to soften the fibers of primary reinforcing material. An engraving pattern can be printed on the structure.