MXPA00003585A - Method of making an absorbent member - Google Patents

Abstract

A method for making an absorbent member is disclosed. The method includes introducing fibers into an air stream to form an air-fiber mixture. This air-fiber mixture is then directed to a porous media having a first surface. The air-fiber mixture contacts the first surface and the fibers collect on the first surface and forms a fibrous mat. The air passes through the first surface and can be recovered and recycled, if desired. The air-fiber mixture is then terminated or diverted so that the fibrous mat can be removed from the first surface. The fibrous mat is wetted by water to obtain a desired moisture content. Finally, the wetted fibrous mat is compressed to a predetermined thickness to form an absorbent member, which has unique expansion properties.

Description

METHOD OF MAKING AN ABSORBENT MEMBER FIELD OF THE INVENTION This invention relates to a method for making an absorbent member that has exceptional expansion properties when wetted by an aqueous fluid. More specifically, this invention relates to a method for making an absorbent member constructed of an absorbent having unique expansion properties.

BACKGROUND OF THE INVENTION The most traditional absorbent structures consist of a static network of fibers containing a plurality of open areas located between the fibers. The open areas retain the aqueous fluid that is absorbed by the absorbent structure. The majority of the fluid is not absorbed in each individual fiber but instead the majority of fluid is stopped within the empty spaces that are formed in the network of cellulosic fibers. If the traditional absorbent member has a high absorbent capacity, it usually does not have a high transmission rate. The reason for this is that the first attribute is in conflict with the second attribute.

Efforts to find absorbing members who have both a high absorptive capacity and a high transmission rate have been only marginally successful. It has been recognized that the dynamic properties of the fibers in themselves must somehow be changed. Some success has been obtained in the calendering of a wet-laid network of bleached omechanical quimoter pulp (BCTMP). For this material a small expansion or release of the potential energy was observed with the wetting of the absorbent fibers which could increase the absorbent capacity and the transmission rate of the absorbent member. This is believed to occur because the absorbent fibers are oriented in a large extent in the horizontal plane but with some modest "z" direction to the fiber axis as they conform to an irregular surface of the forming wire.

Currently, there are a number of applications for absorbent products, both disposable and reusable, which can take advantage of the absorbent expansion properties. For example, an absorbent having a rapid expansion capability primarily in one direction can be used in an infant diaper to form a gasket with the infants' legs as the absorbent expands. This decreases the chance of runoff through the leg cuffs. A second example is the use of an absorbent pad in conjunction with a retail package that has a perishable food, for example meats and chicken. By releasing food, juices, blood, water, and other liquids, the absorbent pad can quickly expand to absorb this fluid so that a package of appealing retail foods can be presented to the consumer. Another example is the absorbent material that is placed between the joint of two pipe flanges butt to provide a waterproof seal. The use of an absorbent with tremendous expansion capabilities is advantageous in this situation since it ensures that the absorbent, the gasket or the seal will squeeze and prevent draining.

It has now been recognized that there is a real need for a method for making an absorbent member constructed of an absorbent having unique expansion properties.

SYNTHESIS OF THE INVENTION Briefly, this invention relates to a method for making an absorbent member that has exceptional expansion properties when wetted with an aqueous fluid. The method includes introducing fibers into an air stream to form a mixture of fibers and air. The air fiber mixture is then directed to a porous medium having a first surface. The mixture of fibers and air makes contact with the first surface and the fibers are collected on the first surface and form a fibrous mat. The air passes through the first surface and can be recovered and recycled if desired. The mixture of fiber and air is then terminated deflected so that the fibrous mat can be removed from the first surface. The fibrous mat is moistened with water to obtain a desired moisture content. Finally, the moistened fibrous mat is compressed to a predetermined thickness to form an absorbent sheet, which has unique expansion properties.

The general object of this invention is to provide a method for making an absorbent member having exceptional expansion properties when wetted by an aqueous fluid. More specifically, this invention relates to a method for making an absorbent member constructed of an absorbent having unique expansion properties.

Another object of the invention is to provide a method for making an absorbent member that is economical.

A further object of this invention is to provide a method for making an absorbent member that can be used to produce a cheap absorbent article that can be used for many different applications.

Still another object of this invention is the d provide a method for making an absorbent member that can expand up to about 8 times its original volume.

Still further, an object of this invention is to provide a method for making an absorbent member that can be used to construct an absorbent article which is easy to manufacture and can be formed in a variety of different configurations.

Other objects and advantages of the present invention will become more apparent to those of ordinary skill in the art in view of the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a top view of an absorbent article having exceptional expansion properties when wetted with an aqueous fluid.

Figure 2 is a cross-sectional view of the absorbent article shown in Figure 1 taken along line 2-2.

Figure 3 is a perspective view of an individual cellulosic fiber. * _ « Figure 4 is a perspective view of four randomly oriented fibers that are joined together by d-hydrogen bonds.

Figure 5 is a cross-sectional view of an absorbent article having an absorbent and a liquid-permeable cover secured to a surface thereof.

Figure 6 is a cross-sectional view of an alternate embodiment of an absorbent article having an absorbent with a liquid-permeable cover secured to a surface and a liquid-impermeable separator secured to an opposite surface.

Figure 7 is a perspective view of an absorbent article having an absorbent enclosed by a liquid permeable cover and a liquid impervious separator.

Figure 8 is a schematic representation of an infant diaper having two absorbent strips aligned to one side of the leg cuffs in the crotch section.

Figure 9 is a schematic representation of a person with an absorbent article in the form of a gasket applied around his thigh.

• * Figure 10 is a cross-sectional view of a gasket shown in Figure 7 taken along line 8-8.

Figure 11 is a cross-sectional view of an absorbent article constructed from a multitude of particle fibers enclosed in a liquid-permeable cover.

Figure 12 is an embodiment of an absorbent article in the form of a gasket used to seal two pipe flanges together.

Figure 13 is a schematic representation of a method for forming an absorbent member.

Figure 14 is a schematic representation of a continuous method for forming an absorbent member.

Figure 15 is a schematic representation of an alternate method for continuously forming an absorbent member.

DETAILED DESCRIPTION OF THE PREFERRED INCORPORATIONS Referring to Figures 1 and 2, there is shown an absorbent article 10 which includes an absorbent member 12 constructed from a multitude of randomly oriented cellulosic fibers 14. The absorbent article 10 has a high absorbent capacity and exhibits exceptional expansion properties when wetted by an aqueous fluid, such as water. The fibers 14 have an average length of from between about millimeter (mm) to about 5 millimeters and are preferably soft wood cellulosic fibers that are relatively stiff. The fibers 14 are randomly oriented and stressed or elastically stressed in one or more directions Selected Preferably, fibers 14 are quimotermomechanical softwood fibers and more preferably, these are bleached quimotermomechanical softwood fibers. Blanquead masks the yellow color that occurs due to the high percentage of lignin that is retained within each fiber.

Preferably, the fibers 14 should not be linear in configuration. At least a majority of the fibers 14 should not be of a linear configuration and should exhibit a bend, bend, curl, twist, arc, twisted, or some other non-linear shape. By "twisted" it means a tight bending and a sharp twist in a tube-like fiber. It should be noted that the complete fiber 1 does not have to be arched, bent, curled, twisted, etc., but at least a part of the fiber 14 must exhibit a non-linear geometric shape. The more twisted each fiber 14 is formed in a non-linear way, the better the absorbent properties of the absorbent 12. Linear fibers can be used but they should only represent a minority of the global fibers present. Preferably, less than about 40 percent of the fibers must be linear.

Each fiber 14 must contain at least about 20% lignin and with the remaining 80% being cellulose materials, which include cellulose plus hemicellulose other minor wood components. Lignin is the main non-carbohydrate constituent of wood and other fibrous plants. .lignin is a polymer that functions as a natural binder and provides support to cellulosic fibers. Lignin is present both within each fibr and between adjacent fibers. For the purposes of this invention it is important that the required percent of lignin be present within each fiber 14. The presence of lignin within each fiber 14 makes the fibers 14 more rigid and more difficult to bend. This is a major difference of traditional unbound cellulose absorbent fibers which are typically bleached soft wood kraft fibers which contain very little, if any, lignin within the fiber itself. Therefore, traditional fibers are soft and flaccid. Lignin functions as a thermoplastic forcing material that allows fibers to return to their natural tubular state when wetted. Cellulose and hemicellulose give the fibers properties hydrophilic and the ability to form hydrogen bonds in the presence of small amounts of water.

The fibers 14 forming the absorbent member 12 should be randomly oriented and densely compacted. The primary axis of each of the fibers 14 must be oriented in a direction x, in the direction y or in the z direction. This three-dimensional random orientation is beneficial in creating a high absorbent capacity and a high rate of transmission within the absorbent member 12. In contrast, most traditional fibers that have been wetted into a fibrous sheet have virtually all fibers placed within their long axis in the xy plane and a significant number of the fibers 14 lie in the machine direction (MD) or in the x direction. Essentially none of the fibers placed in wet are oriented in the vertical direction or z.

The fibers 14 of this invention are tensioned in an extremely compact condition to form a tangled mass which is held together by a plurality of hydrogen bonds. Some of the fibers 14 are kept in compression, some in bend and some in cut. The hydrogen bonds can be both hydrogen bonds of the interfiber and hydrogen bonds within the fiber. This is an environment where almost every fiber 14 is held in a stressed or non-relaxed condition. Tension forces can be applied in more than one direction.

Referring now to Figure 3, an individual fibr 14 is shown having a diameter "d" of minus d about 50 microns. Preferably, the diameter "d" ranges from about 10 microns to about 40 microns and more preferably, the diameter "d" varies from about 20 microns to about 30 microns. Each fiber 1 also has a length "1" of less than about millimeters (mm), preferably, the length "1" is from about 1 millimeter to about 5 millimeters, and more preferably, the length "1" is from between d 1 millimeter to about 3 millimeters. As with most natural materials, there is a distribution of properties, so that the declared dimensions do not limit this invention Each cellulosic fiber 14 has a moisture content of from between about 1% to about 20% water by fiber weight. Preferably, the moisture content of each fiber is from about 2% water to about 15% water by fiber weight. More preferably, the moisture content of each fiber 14 is from between about 5 to about 15% water by weight of fiber. This humidity level is required to obtain hydrogen bonding. However, the absorbent 12 can be heated until it dries after the joint where the moisture level within absorbent 12 has essentially fallen to zero. The cellulosic fiber 14 in a non-bound and unstressed condition has a bulk density of at least 0.01 grams per cubic centimeter (g / cc). Preferably, the volume density of all unstressed fibers 14 is from about 0.02 g / cubic centimeter to about 0. g / cubic centimeter, and more preferably, the density d volume of all non-stressed fibers 14 is from about 0.05 g / cc to about 0.08 grams per cubic centimeter. The low volume density of the cluster of unbonded and unstressed fibers allows a high level of tension to be induced in the fibers just before joining them together.

Referring again to Figures 1 and 2, it should be noted that the absorbent member 12, when the cellulosic fibers 14 are in an elastically stressed condition, will have a density sometimes referred to as "density d volume" of from between about 0.2 grams per cubic centimeter to about 1 gram per cubic centimeter. Preferably, the volume density of the absorbent 12 is between about 0.2 grams per cubic centimeter to about 0.8 grams per cubic centimeter and more preferably, the volume density of the absorbent 12 is between about 0.5 grams per cubic centimeter. 0. 5 grams per cubic centimeter to about 0.8 grams per cubic centimeter. This density is still below the density of the cellulose walls of the individual fibers 14, which is approximately 1.4 grams per cubic centimeter. Thus, there is a significant but reduced amount of open space in the tensioned and bonded absorbent member 12, of about 33 percent versus 98.6 percent for an unbonded and air-laid absorbent fiber structure.

Referring now to Figure 4, four randomly oriented fibers 14 are shown joined together by a multitude of hydrogen bonds 16. A hydrogen bond is a weak chemical bond formed between an electronegative oxygen atom and a hydrogen atom already attached to a hydrogen atom. another atom of electronegative oxygen. The hydrogen bonds 16 cause the fiber surfaces 14 to be bonded to adjacent fiber surfaces. The hydrogen bond will occur inside the fibers as well. This condition can occur when, for example, a tubular fiber is stocked or bent and the circular open lumen cross section is folded into a flattened elliptical shape. When two or more different points within the lumen are touched or forced together under pressure or tension, hydrogen bonding may occur. In the attached and elastically stressed condition, the fibers 14 exhibit stored bending, compression and cutting energy. The hydrogen bonds 16 are formed by placing the fiber surfaces 14 in intimate contact under pressure. The water that is in or on the individual fibers 14 contributes to the intimate contact and bond formation even when there is even more liquid capacity in and around the fibers 14 (unsaturated). As the ag leaves the point of contact between the fibers 14 due to drying migration to the drier areas, the surface tension causes two adjacent fibers or two areas or points within a fiber lume to become closer together allowing them to occur. e hydrogen bond. The moisture of the absorbent member 12 should be less than about 15 percent water per weight d fiber unit. Preferably, the moisture of the absorbent member 12 should be from between about 5 to about 10 percent by weight of fiber unit to allow it to form enough hydrogen bonds to close in the stressed high density condition. Insufficient moisture will inhibit the formation of hydrogen bonding according to the mechanism described, while excessive moisture disrupting hydrogen bonds with the release of stress forces.

The hydrogen bonds 16 are relatively weak bonds but these are many and strong enough to fix in the stresses created in and between the fibers 14 when the fibers 14 are tensioned in an extremely compact form of the absorbent member 12. A method for constructing the member absorbent 12 is to collect randomly oriented fibers 14 in a hopper or container and then compress the fibers 14 from a single direction in a fiber sheet. The experimental test has indicated that when the cellulosic fibers 14 compressed in only one direction, for example, in the direction z, then the major expansion will occur in opposition to that direction of compression.

The experimental test has also revealed that the fibers 14 can be compressed from 2 or more directions, and either simultaneously or in sequence. When the absorbent member 12 is compressed in two or more directions and then wetted, a rapid expansion of aqueous fluid will occur in the directions opposite the compression directions. This feature and important because it will allow the manufacturer to build an absorbent member 12 which can be tailored to the environment in which this design will work. For example, if it is desirable to construct a diaper with an absorbent member 12 which will rapidly expand in the directions y and z, then the absorbent member 12 can be compressed during formation in two directions opposite these two directions. During use in the diaper, the absorbent member 12 will experience very little expansion in the x direction but will exhibit a substantial and rapid expansion in both the directions y and z (the direction z is the radial direction). The usefulness of being able to build an absorbent member 12 with such expansion properties will be readily apparent to those with a skill in the art of disposable absorbent products.

It was mentioned earlier that the expansion occurs when wetting the aqueous fluid the absorbent member 12 Aqueous fluids are defined for the purposes of this invention as fluids containing water or are similar to water. Representative fluids include tap water, distilled water, bottled water, urine, fluid menstrual fluids of the human body, water emulsions plus hydrocarbon etc. It should also be noted that non-aqueous fluids such as oils, non-polar hydrocarbons, etc., will not release the hydrogen bonds formed in and between the fibers.

When the absorbent member 12 is moistened, the hydrogen bonds 16 are broken and the tensions enclosed by the individual fibers 14 of the absorbent member 12 are released. This causes the fibers 14 to move toward the original relaxed condition, which is a tubular shape typically in a direction opposite to the direction in which they were compressed or tensioned. As more and more hydrogen bond 16 breaks, more and more fibers 14 are free to bend back to their less stressed condition or to a relaxed condition. When this occurs, a hollow or open volume is developed between the fibers 14. These recesses are capable of receiving and containing the fluid that has been discharged into the absorbent member 12. The absorbent capacity of the absorbent member 12 is therefore increased and the absorbent member 1 becomes capable of receiving and retaining larger amounts of fluid. The increased volume of capillary vessels between the fibers promotes a higher degree of fluid flow and d transmission due to reduced friction or reduced fluid drag. Therefore, the absorbent member 12 functions in a different form from any commercially known cellulosic product sold today. Compressed regenerated cell sponges work in a somewhat similar way because they are much more expensive to produce and may not exert the pressure level of this invention.

The absorbent member 12 of this invention is unique in that the wet expansion rate is very fast. The "wet expansion rate" is defined for the purposes of this invention as the time it takes for the absorbent member 12 to expand to its maximum (unit change / volume / time) once it is surrounded by an aqueous fluid, just like water. The "wet expansion rate" for some part of the full expansion time can be determined by measuring the inclination of the curve established by drawing the change in volume of the absorbent member 12 for each moment in time over the duration of the expansion. The "wet expansion rate" is related to the density d volume of the absorbent member 12 and to the penetration depth at which the fluid must move to reach the mid point or median plane of the absorbent member 12. For example, a spherical shape, at a high density, denoted by l letter and rho "p", will have a slow maximum expansion rate since it has a low ratio of surface area to volume (r) calculated by the formula r = 6 / d, where d is the diameter of the sphere. This can be contrasted to a thin sheet like a piece of paper, where a proportion of surface area at high volume (r) is found which can be calculated by the formula r = 2 / t, where t is equal to the thick of the leaf. The expansion rate for the thin sheet will be faster for the sphere assuming that both have equal weights equal densities. For a sphere and a sheet of paper of equal weight and density, its size ratio can be expressed by the formula d = 6 gsm / p. In this formula "d" is the diameter of the sphere, "gsm" is the base weight of the thin sheet in grams per square meter, and "p" is the density of both forms.

The absorbent member 12 has the ability to absorb from about 1 gram to about 2 grams of aqueous fluid per gram of absorbent material, Preferably, the absorbent member 12 has the capacity to absorb from about 1 to about 1 g. 18 grams of aqueous fluid per gram of absorbent material. More preferably, the absorbent member 12 has the ability to absorb from about 1 to about 15 grams of aqueous fluid per gram of absorbent material. The absorbent member 12 is also capable of exhibiting rapid expansion.

Beginning with an absorbent member 12 having a predeteed initial volume, the absorbent member 12 is capable of expanding from about 1 to about 8 times the initial volume by absorbing the absorbent member 12 an aqueous fluid. Preferably, the absorbent member 12 is capable of expanding from about 5 to about 8 times its initial volume by absorbing the absorbent member 12 in an aqueous fluid.

Referring to FIGS. 1 and 2, the absorbent article 10 also includes a cover 16 which is wrapped around the absorbent member 12 to at least partially enclose and preferably complete the absorbent member 12. The cover 16 may be permeable to liquid or impervious to liquid. If it is impervious to liquid, a number of openings or perforations can be formed ah to allow the fluid to reach the absorbent member 12. In the case where the absorbent article 10 is a disposable absorbent article, such as a bed pad, an infant diaper, a sanitary napkin, training underpants, a disposable swimsuit, an adult incontinent garment, a gasket, etc., the cover 16 is designed to make contact with the wearer's body. In these products, the absorbent article 10 can be constructed of woven or non-woven material which is easily penetrated by body fluids. The cover 16 can also be made d natural fibers, synthetic fibers or mixtures thereof. Suitable materials include bonded or bonded fabrics of polyester, polypropylene, polyethylene, nylon, or other fibers that can be bonded by heat. Other polyolefins, such as polypropylene and polyethylene copolymers, linear low density polyethylene, finely perforated film fabrics and network materials, also work well. A particularly preferred material is composed of a perforated thermoplastic film placed up from a non-woven fabric material. Such a composite material can be formed by extruding a polymer into a fabric of a spin-bonded material to form an integral sheet. An example of this is a perforated thermoplastic film bonded to a spin-bonded material. This material exhibits a smooth and soft outer surface, which is not irritating to the user's skin and still has a cushioned feeling due to its volume. In order to allow the cover 16 to expand to absorb the absorbent 12 the fluid, the cover 16 may be elastic or exhibit elastic properties. Alternatively, the cover 16 can be folded, creped, folded or layered to allow expansion and containment of the incoming fluid.

Another preferred material for the cover 16 is a fabric bonded with polypropylene yarn. The tissue can contain from between about 1 percent to around 6 percent titanium dioxide pigment to give it a clean and white appearance. Other bleaches can also be used such as calcium carbonate. A rough uniform of the yarn bonded is desirable because it will have sufficient strength, after being perforated in the longitudinal direction, to resist being broken apart by pulling during use. The most preferred polypropylene fabrics have a weight of between about 18 grams per square meter (gsm) to about 40 grams per square meter. An optimum weight is from between about 30 grams per square meter to about 40 grams per meter square.

Referring to Figure 5, there is shown an embodiment containing an absorbent article 10 ', in the form of an absorbent sheet, which includes an absorbent member 1 having a first major surface 18 and a second major surface 20. Secured to the first The main surface 18 is a separate and distinct layer 22. The distinct cap 22 may be a liquid-permeable cover or a liquid-impermeable separator. The materials described above for the liquid permeable cover can be used. The distinct layer 22 can be secured to the absorbent member 1 by means known to those skilled in the art of disposable absorbent products. Common fastening means include the use of a hot or cold cast adhesive, rubber, a pressure joint, a heat activated bond, a joining with heat and / or pressure, a thread, a mechanical fastener such as a thermoplastic fastener, etc.

When the layer 22 is a liquid impervious separator, it must allow air or steam to pass out of the absorbent article 10 'while blocking the passage of body fluids. The liquid impermeable separator can be made of any material that has these properties. The liquid-impermeable separator can also be constructed of a material that will block the passage of vapor as well as fluids if desired. A good material for the liquid-impermeable separator is a micro-etched polymeric film, such as polyethylene or polypropylene. Two-component films can also be used. A preferred material is a polypropylene film. More preferably the liquid impervious separator will be composed of a polyethylene film having a thickness in the range from about 0.5 millimeters (mm) to about 2.0 millimeters Referring now to Figure 6, there is shown another embodiment containing an absorbent article 10", in the form of an absorbent sheet, which includes an absorbent member 12 having a first major surface 18 and a second major surface 20. In this embodiment, a cap 22 is secured to the first main surface 18 of absorbent member 12 and a layer 24 is secured to the second main surface 20. Layer 22 may be liquid permeable and layer 24 may be impermeable to liquid. Each ca 22 and 24 can be constructed from the materials identified above.

It should be noted that for certain disposable absorbent products, such as a diaper and sanitary napkins, the liquid-permeable layer must be aligned to the side of the wearer's body. For other types of absorbent product, such as an absorbent pad used in the meat or chicken package to absorb the juices, the liquid-permeable cap may be aligned outwardly of the food product.

Referring to Figure 7, a disposable product in the form of a sanitary napkin 26 is shown having an absorbent member 14 enclosed by a liquid permeable cover 28 and a liquid impervious separator 30. The absorbent member 14 may be constructed to swell when It swells in only one direction, for example in the x direction if desired. Similarly, the absorbent member 14 must be constructed to swell, when wetted, in directions, or in three directions, if this is useful. The cover 28 and the separator 30 cooperate together to completely enclose the absorbent member 14. This is different from Figure 6 e where layers 22 and 24 only partially enclose the member. absorbent 14. In Figure 7, the cover 28 and the separator 3 are joined together to form the longitudinal seals 32 and 3 on one side of the longitudinal sides of the sanitary napkin 26. The ends of the sanitary napkin 26 are also sealed and a similar way by joining the cover 28 to the separate 30.

Referring to Figure 8, there is shown a disposable infant diaper 36 having a front section 38, a crotch section 40 and a back section 42. The crotch section 40 is located between the front section 38 and the back section 42. The diaper 36 is constructed of a cover permeable to the liquid contact with the body 44, a main absorbent body 46 and a liquid impervious separator 48. The cover 44 and the separator 48 cooperate to at least partially enclose, and preferably completely the main absorbent 46. The diaper 36 also has a front edge 50 and a trailing edge 52. Extending laterally outwardly from the trailing edge 52 are the ears 54 and 56. Each ear 54 and 56 has an adhesive appendage 58 and 60, respectively. the ears 54 and 56 are designed to wrap around the torso of an infant and the adhesive appendages 58 and 60 are designed to be fastened to the front section 38 to retain the diaper 30 securely in place. It should be noted that alternate diaper designs can be used which have a second pair of areas extending laterally outward from the front section 38.

The diaper 36 further has a pair of leg cuffs 62 and 64 located on the outer edges of the crotch section 40. Into the leg cuffs 62 and 6 are the absorbent packs 66 and 68. The absorbent gaskets 66 and 68 they can be formed from the absorbent member 1 discussed above and can be constructed so that they will expand or swell in one or more directions when they are moistened with an aqueous fluid, such as urine. In addition, the diaper 36 is shown with a front absorbent gasket 70 and a back absorbent gasket 72. The front and rear gaskets 70 and 72 respectively will prevent fluid from leaking out of the diaper 36 on either side of the infant's waist. Runoff in these places can occur when the infant is sleeping or lying on his stomach, on his side or on his back.

It should be noted that the diaper 36 has a main absorbent member 46 and four separate gaskets 66, 68, 70, and 72. However, a smaller number or a greater number of gaskets may be employed if desired. In similar form, additional absorbent layers may be used if desirable. The absorbent that is used to form the main absorbent member 46 and each of the gaskets 66, 68, 70 and 72 can be constructed so that each one carries out optimally the function for which they were designed. For example, the main absorbent member 46 can be constructed to expand in the directions x and y by taking the body fluid while the packings 66, 68, 70 and 72 can be designed to swell in the vertical direction or z to absorb fluid from the body. The vertical swelling of the packings 66, 68, 70 and 72 will cause a loose seal that is formed with the body as it expands and this will decrease the possibility of fluid runoff from the diaper 36 in these places. Therefore one can see that by building each absorber within a particular article in a certain way, that the function of the article can be greatly increased. In the case of the diaper 36, the gaskets 66, 68, 70 and 72 will confine the body fluid in the crotch section 40 for a longer period of time and thus give the main absorbent member 46 an added time to absorb the fluid. . Additionally, gaskets 66, 68, 70 and 72 will expand and swell when wetted to form prey, against the legs and the infant torso to decrease the possibility of runoff at these locations. The end result is a diaper that works much better with the use of less absorbent material. Therefore, the cost of the diaper can be reduced and the infant may be able to use the diaper for a longer period of time. In addition, by decreasing or by avoiding the incidences of fluid runoff, there will be less times than the outer clothing worn by the infant will get dirty.

Referring to Figures 9 and 10, there is shown a circular gasket 74 placed around the thigh of a person to prevent the passage of fluid. The gasket 7 may be sized and configured to be placed around another member or appendage of a human or animal body. The gasket 74 may be used for medical purposes, for example to prevent blood from leaking from a wound or to absorb other blood. body fluids such as urine. The gasket 74 includes an absorbent member 14 at least partially, and preferably completely enclosed by an outer layer 76 and an inner layer 78. The layers 76 and 7 may be either liquid permeable or liquid impervious. The absorbent member 14 must be constructed so that it can be expanded or inflated when it is wetted in a direction perpendicular to the body part it surrounds. When the gasket 74 is to prevent passage of the urine down the thigh, the absorbent member 14 will increase in size by initially contacting the urine. As the absorbent swells, a tighter seal will form which will provide greater assurance that the flow of additional urine down the thigh will not pass beyond the packing 74.

One or more gaskets 74 may be incorporated in a diaper, in the training pants, and in a swimsuit etc., and shall be used to prevent the passage of the urine down the thighs of an infant or child. In a similar form, two packings 74 may be incorporated in a pair of underpants for adults and prevent the passage of urine down the thigh of the adult user.

Referring to Figure 11, there is shown an alternate incorporation of an absorbent article 80 having a multitude of fibers 82 and particles 84 enclosed in a liquid-permeable cover 86. The absorbent article 8 can be used for a variety of purposes and especially Useful in situations where spilled fluid requires quick attention. For example, in the case where a liquid is spilled on a carpet, the absorbent article 80 can be rubbed onto the spilled liquid and pull a significant amount of liquid out of the threads and of the absorbent fibers of the carpet. / or pressing the absorbent article 80 against the wet carpet will pull the liquid out and retain it in the fibers 82 and the particles 84. The liquid-permeable cover 86 will allow a quick take of liquid while the fibers are retained 82 and the particles 84 with a unit for easy disposal. The absorbent article 8 can also be used to collect a spill on a hard surface. The absorbent article 80 can be constructed to readily absorb up to about 15 grams of liquid per gram of absorbent.

Referring to Figure 12, the first and second pipes, 88 and 90 respectively, are shown. The pipes 88 and 90 may be concrete pipes that have a large diameter of about 12 inches or more. The first pipe 88 has an elongate flange 92 formed at one end 94 The elongated flange 92 is dimensioned and designed to receive end 96 of the second pipe 90. When the two pipes 8 and 90 are joined together, a small space 98 will be present. In order to close the space 98 and form a tight seal between the two pipes 88 and 90, an absorbent packing 100 can be placed in the space 98. It has been found that the absorbent packing 100 can be used where swelling with accumulated pressure want to contact with humidity. A particular use is in the concret pipes used to carry drainage and runoff water. When the two pipes 88 and 90 are placed in a trench formed in the ground, a larger gap is usually present on either the upper or lower surface of the pipes 88 and 90. In the past, Oakite® has been used. as the packing material. The Oakite® has a rope with appearance and can be placed in the space between the two pipes to provide a tight seal that will absorb some of the moisture to prevent runoff. Placement of Oakite® material in position will require that Oakite® material. have very few expansion properties.

The absorbent member 12 of this invention can be formed in the gasket 100 and placed between the pipes 88 and 90. The absorbent member 12 exhibits a high pressure for very small expansion conditions and is capable of expanding to a greater extent for larger separations. . Thus, a loose fitting assembly of two pipes 88 and 9 can be easily sealed by an absorbent packing 100 when the absorbent member 12 is contacted by a small amount of moisture or water.

It should also be noted that the germicides can be added to the absorbent gasket 100 to preclude bacterial degradation when the gasket 100 is in contact with the ground, for example, when used in an underground manner.

The absorbent member 14 can also be formed into other products. One such product is a cleaning cloth which can be used to clean up spills. Currently, most commercially available cleaning cloths made of tissue can quickly reach a liquid content that results in leaving a water clue or mud behind. achieve its absorbing capacity. A cleaning cloth formed of absorbent 14 of the invention will be able to cope with the possibility that a trace is left behind due to its ability to absorb additional liquid upon being wetted.

METHOD Referring to Figure 13, there is shown a method for making an absorbent article 12 of a multitude of absorbent fibers 14. The method includes introducing the multiple fibers 14 of quimotermomechanical softwood or quimotermomechanical softwood wood bleached into an air stream 102. The fibers 14 are carried in the air stream 102 to form a mixture of air fibers 104. Preferably, the air stream 102 is turbulent to increase the mixture of the fibers 14.

It should be noted that the method described above refers to introducing fibers 14 into air stream 102. However, particles 84, as described in reference to Figure 11, can be introduced in conjunction with fibers 14 if desired .

The fiber and air mixture 104 is then directed to a porous medium 106, such as a wire mesh grid. The porous media 106 have a first surface 108 that receives the initial contact by the air fiber stream. The size and configuration of the porous media 10 may vary. For very good results, a wire mesh value of "standard 32 mesh" works well. Alternatively, the porous medium 106 may be a perforated plate having a plurality of circular openings formed therethrough. A perforated plate having a plurality of openings d about 0.038 inches in diameter with a spacing of 0.050 between them works well. The aforementioned reference plate will have an open area of about 45 percent. It should be noted that the dimensions of the openings and the flat areas may vary to suit the particular needs of one.

It should also be noted that the porous medium 106 may be a tissue sheet, a non-woven sheet, a porous wire, a grid or some other structure. The porous medium 106 may be planar in configuration or have an arcuate surface in one or more directions. When the porous media 106 has one or more arcuate surfaces, this allows the formation of the absorbent member 12 on the drums as well as the formation of three-dimensional shapes.

The mixture of air fibers 104 should be evenly distributed over the first complete surface 108 of the porous media 106 with a differential pressure to through the porous media 106 ranging from about 3 inches to about 30 inches of water pressure. The air part of the mixture 104 will pass through the porous media 106 while the fibers 14 will be collected on the first surface 108. As the air passes through the porous media 106, it will leave the fibers 14 behind. The air can then be recycled and reused if desired. The multitude of fibers 14 are separated from the air and accumulate on a mat on the first surface 108 of the porous medium 106. E The middle porous 106 acts as a filter separating the fibers 14 d from the air stream 102. When the desired amount of the fibers 14 has accumulated in a fibrous mat 110 having a predetermined thickness "t", the air stream 102 is stopped. The air stream 102 may lie either diverted or switched off as in an intermittent operation. The amount of fiber accumulated to form the fibrous mat 110 may vary from about 20 to about 1000 grams of fiber per square meter.

The fibrous mat 110 is then removed from the first surface 108 of the porous medium 106. The mat fibros 110 can be weighed to determine its basis weight and moisture content. The water 112 is then added to the fibrous mat 110 to obtain a predetermined percent moisture. East The predetermined wet value can be any desired value, for example, 5 percent, 10 percent, 15 * • .- percent etc., depending on the last steps of the process Water 112 may be added to the fibrous mat 110 in a number of different ways. Some of these ways include spraying the water 112 on the fibrous mat 110, placing the fibrous ester 110 in a humidity chamber, or passing the vapor through the fibrous mat 110. The amount of water 112 added will determine the weight gain of the fibrous mat 110 Knowing the initial basis weight of the fibrous mat 110 and the basis weight of the fibrous mat 110 after the addition of a certain amount of water 112, one can control the percent d moisture in the fibrous mat 110. The initial amount The amount of water present in the fibers 14 constituting the mat fibros 110 will partially determine how much water 112 should be added. The amount of water 112 added is established by knowing the water level of the fibers 14 before adding the additional water 112. This can be determined by weighing a sample of the fibers 14 and then placing the fibers 14 on a balance. which is in a heated ambient (greater than about 100 degrees centigrade) to evaporate any moisture until there is no additional loss of weight. The difference in weight divided by the original weight is the part of the water present. Therefore, the amount of water 112 necessary for it to be added to the fibrous mat 110 may be established from the desired percentage of moisture (for example 10 percent) and from the initial moisture level measured.

Immediately after the addition of water 112 the fibrous mat 110 is subjected to a tensioning condition and / or a compression step. The compression of the fibrous mat 110 can be achieved by using a pair of flat plates to create a dimensional change or by using plates configured to create an absorbed structure arcuately or curvedly. The amount by which the fibrous mat 110 is compressed may be limited by the desired final thickness "t" of the absorbent member 12 or may be limited by the maximum desired pressure that may be applied during the compression pass.

Referring again to Figure 13, the fibrous ester 110 is placed between two plates 114 and 116, at least one of which is movable. The plates 114 and 116 can be heated, if desired, to expel excess moisture when present. As the first plate 11 moves to the second plate 116, the absorbent sheet 12 is compressed to a desired thickness. In addition to using a pair of plates 114 and 116 the absorbent sheet 12 can be compressed by using a standard press or by bringing the absorbent sheet 12 through the pressure point of a pair of contact or closure pressure rollers.

It has been found that a final clamp point compression of about 0.03 inch is desired for a fibrous mat 110 having an initial thickness of about inches, so that the compression should be done in a series of progressive steps. The steps will depend on the diameter of the pressure rollers. One sequence will be to compress the fibrous ester 110 from an initial thickness of about 2 inch (about 51 millimeters) down to about 0.2 inches (about 6.4 millimeters) to about 0.0 inches (about 0.76 millimeters). This can be accomplished by using a steel roll of 12 inches in diameter (30 millimeters) interacting with a 4 inch diameter (102 millimeters) steel roller. This is the final step in the manufacture of the absorbent member 12. Depending on the level of humidity, it is sometimes desirable to compress the fibrous mat 110 to less than the desired thickness and allow the absorbent member 12 to spring back to the desired thickness. For example, compressing the fibrous mat 110 to a thickness of about 0.027 inches (about 0.69 millimeters) will allow it to jump back to a thickness of about 0.03 inches (about 0.76 millimeters).

Referring now to Figure 14, a method for forming an absorbent member 12 in a continuous form is shown. This method includes introducing the fibers 14 into the air stream 102 and forming a mixture of air fiber 104. This mixture of fiber and air 104 is then directed to an endless belt 118. The endless belt 118 can be formed as a fine mesh wire and has an outer surface 120. The fibers 14 will be collected on the outer surface 120 of the band 118 while the air part of the mixture 104 will be allowed to pass through the endless band and recover if desired The level of differential pressure maintained through the endless belt 118 will affect the density of the fibrous ester 110. At about 3 inches (about 7 millimeters) of water pressure, the bulk density of the fibrous mat 110 can be 0.01 grams / cubic centimeter (g / cubic centimeter) while at about 30 inches (around 762 millimeters) of water pressure, the densified can reach 0.1 grams per cubic centimeter. The linear speed of the endless belt 118 will affect the length of the forming cavity needed to deposit the proper fiber 14 to form the fibrous mat 110.

The fibrous mat 110 formed in the wiry strip 118 is then stripped from the outer surface 120 and s brought into contact with the water 112. The water 112 can be sprayed on one or both sides of the fibrous mat 110. Preferably, an amount is sprayed. preselected water 112 over the full width of the fibrous mat 110. This provides a uniform distribution of the hydrogen bond to occur across the complete fibrous mat 110. The fibrous mat 11 is then directed through a pressure point 122 formed by two pressure rollers ^ interacting 124 and 126. What Pressure rollers 126 and 124 can be heated to remove any excess moisture from the fibrous mat 110 if required. The compression clamping point 122 will densify the fiber network and allow hydrogen bonding to occur to form a compressed fibrous mat 128. The compressed fibrous mat 128 can then be directed to a cutter or cutter in slots 130 where the fibrous mat compresses. 128 is cut and / or cut into slits in the desired sizes of the absorbent member 12. Alternatively, the compressed fibrous mat 128 may be directed outwardly from the cutter 13 and may be wound on the hollow cores to form the finished rolls, if desired.

Referring now to Figure 15, still an alternate method is shown to continuously form an absorbent member 12. This method includes introducing the fibers 14 into the air stream 102 and forming a mixture of air fiber 104. The fiber mixture of air 104 is then directed to the first continuous layer 132. The first layer 132 is unwound from the supply roll 134 and is carried by a driving mechanism 136 in a desired direction. The first layer 132 can be a porous fabric, a non-woven fabric or any other type of natural or synthetic material. The drive 136 may be a drive motor, a worm belt, or some other means of pulling the first layer 132. As the first layer 132 of the roll is unwound from supply 134 this is passed to a place 138 where the mixture d fiber and air 104 is deposited thereon.

The fiber-air mixture 104 can be deposited on the first layer 132 at a single location 138 or can be deposited on the first layer 132 at multiple locations (n shown), to progressively accumulate the fibers 14. E thickness of the fibrous mat 110 it can be varied by controlling the rate at which the mixture of fiber and air 104 e deposited on the first layer 132 and by controlling the speed of the first layer 132.

As shown above for Figure 14, the water 112 can be directed on one or both sides of the fibrous ester 110. After the addition of water 112, a second layer 140 can be added to the fibrous mat 110. The second layer 140 can be unwound from a supply roll 142 / it may be similar or different from the first layer sheet 132.

It should be noted that either one or both of the first and second layers 132 and 140 respectively, can become part of the finished absorbent 12. For example, the first layer 132 can be a liquid permeable cover and the second layer 140 can be a waterproof separator. to the liquid. The finished product will be a laminate of all three layers, cover 132, d fibrous mat 110 and separator 140.

When the first and / or second layers 132 and / or 14 respectively, are constructed of porous materials such as tissue, nonwovens or textiles, the fibrous mat 110 will have a tendency to be mechanically fastened to the adjacent layer or layers when the composite is directed. through the compression pressure point 122. Impervious layers, such as polymer films can be attached to the fibrous mat 110 with either adhesive or by a corona treatment before passing the layers through the compression pressure point 122. .

If it is desirable to increase the integrity of the fiber of the fibrous mat 110, this can be achieved by adding the binder fibers. The binder fibers can be mixed with the fibers 14 within the air stream 102 to form the mixture 104 which is then deposited in the first layer 132. To increase the integrity, the long fibers have a length greater than about 4. millimeter can be added to air stream 102. Long fibers will provide mechanical entanglement and friction. Materials such as rayon, cotton, wool, etc., are good for introducing long fibers into the fibrous mat 110.

In addition, the thermosetting fibers may be mixed in the air stream 102 to increase integrity. One type of thermal settling fibers is known as "Pulpex" and is available from Hercules, Inc. Hercules, Inc. has a sales office in Wilmington, Delaware. The thermosetting fibers can be blown directly into the airstream, for example blown fibers with melting. These thermal settling fibers must be heated and cooled while the fibrous mat 110 has its lowest density and before compression and hydrogen bonding. The use of the heated compression clamping point 122 can be adverse if thermal bonding between the fibers in the state of high compressed density is allowed. Therefore, a heated compression clamping point should be avoided when thermosetting fibers are used.

Once the first and second layers 132 and 140 respectively and the fibrous mat 110 pass through the pressure point rollers 124 and 126, a compressed fibrous mat 144 is formed. This compressed fibrous mat 144 can be directed to a cutter. 130, as explained above, to form the individual articles 146. Alternatively, the compressed fibrous mat 144 can be rolled into a larger roll if desired.

Other chemicals or particles may also be included within the fiber mat 110 by introducing them into an air stream 102 with the fibers 14. Such chemicals and particles may include particles or superabsorbent materials, deodorant particles, dyes encapsulated, encapsulated fragrances, catalytic particles germicidal particles, etc.

It is also possible to tension the fibers 1 within the fibrous mat 110. By using the method described above, one can introduce the fibers 14 into the stream 102 to form the fibers carried in the mixture d fiber and turbulent air 104. fibers 14 are then separated from the fiber and air mixture in the porous medium 106, the endless web 118 or the carrier sheet 132. When the fibers 14 are deposited using gravity on a surface by using the electrostatic attraction of the fibers 1 on the surface, a low density fibrous mat 110 (less than about 0.1 grams / cubic centimeter) is created. This low density fibrous mat 110 has the fibers 14 arranged in a random orientation, for example, the long axis of the fibers 14 is likely to be oriented in the directions x, y and z. When the fibers 14 contain a significant percentage of their original lignin content, eg, about 80 percent, there will be stresses developed within the fibers 14 when they are bent, twisted, crushed or otherwise changed from their relaxed form. By using an external force or restriction, a large number of the fibers 14 can be twisted and therefore stressed in a dense condition. This allows one to change the fibers 14 from a low density condition to a high density condition. Due to the random orientation of the fibers 14, a large percentage of the fibers 14 will have a significant movement while compressing. For example the thickness of the fibrous mat 110 can be reduced from about 2 inches (about 51 millimeters) to a thick about 0.03 inches (about 0.76 millimeters) This movement during compression, together with the power for many of the different fibers 14 to prevent or limit any fiber from moving in relation to its entire length, leads to a stressed condition.

The tensioning of the fibers 14 in two or three directions can be induced by successive partial compression of the fibers 14 in two or more different directions. The compression in three different directions can be achieved by forcing the low density fibers 14 through a funnel-shaped extruder wherein the progressively smaller diameters will compress the fibers 14 in a radial direction while the pushing mechanism will compress the fibers. fibers 14 in an axial direction. The addition of moisture to the fibers 14 will facilitate the binding of hydrogen in the compressed condition. The tensions created in the fibers 14 and in the fibrous mat 110 show directionally when the fibers are relieved. This means that when the hydrogen bonds break, the fibers 14 will wish to expand outwardly in a direction opposite to the direction in which they were compressed. A example of this was carried out in a test laboratory. The bleached quimotermomechanical softwood fibers 14 were placed in contact and formed on a fibrous mat 110 using the method shown in Figure 13. The fibrous mat 110 has an initial density of 0.02 grams per cubic centimeter and a thickness of about 2. inches (about 51 millimeters). The moisture level in the fibrous mat 110 was adjusted to about 10 percent and the fibrous mat 110 was compressed in one direction (the z direction) to reduce its thickness down to about 0.03 inches (about 0.76 millimeters). The water was then applied to the fibrous mat 110 to cause expansion and swelling. The expansion was almost complete in the z direction, opposite the force vector that was used to compress the fibrous mat 110. The fibrous mat saturates 110 expanded from a thickness of about 0.03 inches (about 0.76 millimeters) to a thickness of around 0.25 inches (about 0.64 millimeters) or an increase of about 700 percent. There was minimal expansion only in the x and y directions from around 10 percent to around 20 percent.

Although the invention has been described in conjunction with a specific embodiment it will be understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Therefore, this invention is intended to encompass all those alternatives, modifications and variations that fall within the spirit and scope of the appended claims.

Claims (20)

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

1. A method for making an absorbing member comprising the steps of: a) introducing fibers into an air stream to form a fiber mixture; b) directing said mixture of air and fiber to a porous medium having a first surface; c) collecting said fibers on said surface to form a fibrous mat while allowing said air to pass through said surface; d) finishing said air and fiber mixture removing said fibrous mat from the first surface; e) moistening said fibrous mat with water to obtain a desired moisture content; Y f) tensioning said wetted fibrous mat a predetermined thickness to form said absorbent member.

2. The method as claimed in clause 1 characterized in that said porous means is a rejill of wire mesh.

3. The method as claimed in clause 2 characterized in that said wire mesh grid is a standard mesh number 32.

4. The method as claimed in clause 1 characterized in that said porous means is a perforated plac.

5. The method as claimed in clause 4 characterized in that said perforated plate has a plurality of circular openings formed therein.

6. The method as claimed in clause 1 characterized in that said moistens are stressed by compression.

7. The method as claimed in clause 1 characterized in that said fibrous mat has a thickness of about 2 inches.

8. The method as claimed in clause 1 characterized in that said fibrous mat is moistened by spraying water on it.

9. The method as claimed in clause 1 characterized in that said fibrous mat is moistened by spraying water on it.

10. A method for making an absorbing member comprising the steps of: a) introducing fibers into an air stream to form a fiber mixture; b) directing said mixture of air and fiber to a porous medium having a first movable surface; c) collecting said fibers on said first movable surface to form a fibrous mat while allowing said air to pass through said first movable surface; d) removing said fibrous mat from said first movable surface; e) moistening said fibrous mat with water to obtain a desired moisture content; Y f) tensioning said moistened fibrous mat to a predetermined thickness to form said absorbent member.

11. The method as claimed in clause 10 characterized in that said first surface said porous medium is continuously in motion.

12. The method as claimed in clause 11 characterized in that said porous means is an endless band.

13. The method as claimed in clause 12 characterized in that said endless band is a wire mesh grid.

14. "The method as claimed in clause 10 characterized in that said fibrous mat has a thickness of about 1 inch.

15. A method for making an absorbing member comprising the steps of: a) introducing fibers into an air stream to form a mixture of air and fiber; b) directing said mixture of air and fiber to a mobile carrier sheet; c) depositing said fibers on said leaf mobile carrier to form a fibrous mat; d) removing said fibrous mat from said mobile carrier sheet; e) moistening said fibrous mat with water to obtain a desired moisture content; Y f) tensioning said wetted fibrous mat a predetermined thickness to form said absorbent member.

16. The method as claimed in clause 15 characterized in that said carrier sheet is a porous tis.

17. The method as claimed in clause 15 characterized in that said carrier sheet is a non-woven tel.

18. The method as claimed in clause 15 characterized in that said mixture of air and fiber is deposited on the carrier sheet in multiple places.

19. The method as claimed in clause 15 characterized in that said fibrous mat is moistened with water.

20. The method as claimed in clause 15 characterized in that said fibrous mat has a thickness of at least about 1 inch. i i E U M E N A method for making an absorbent member is described. The method includes introducing fibers into an air stream to form a mixture of air and fiber. This mixture of air and fiber is then directed to a porous medium which has a first surface. The mixture of air and fiber in contact with the first surface and the fibers is collected on the first surface and forms a fibrous mat. The air passes through the first surface and can be recovered recycled if desired. The mixture of air and fiber is then terminated or deflected so that the fibrous mat can be removed from the first surface. The fibrous mat is moistened with water to obtain a desired moisture content. Finally, the wetted fibrous mat is compressed to a predetermined thickness to form an absorbent member which has unique expansion properties.