KR20040050899A - Composites Comprising Superabsorbent Materials Having a Bimodal Particle Size Distribution and Methods of Making the Same - Google Patents

Abstract

The present invention relates to absorbent composites containing superabsorbent materials. Superabsorbent materials exist in the form of superabsorbent particles having a dual particle size distribution. The use of a superabsorbent material having a dual particle size distribution in the absorbent structure enhances the fluid distribution induced by the capillary phenomenon of the absorbent composite and improves fluid intake. The absorbent composites of the present invention are useful in disposable personal care products.

Description

Composites Comprising Superabsorbent Materials Having a Bimodal Particle Size Distribution and Methods of Making the Same

It is known to use water-swellable, generally water-insoluble absorbent materials generally known as superabsorbents in disposable absorbent personal care products. Such absorbent materials are commonly used in absorbent products such as diapers, training pants, adult incontinence products, and feminine hygiene products to increase the absorbent volume of the product while reducing the total volume of the product. The absorbent material is generally present as a composite of superabsorbent particles (SAP) mixed in a fibrous matrix, for example a matrix of wood pulp fluff. The matrix of wood pulp fluff generally has an absorption volume of about 6 g of liquid per g of fluff. Superabsorbent materials (SAM) generally have an absorption volume of at least about 10 g of liquid per g of SAM, preferably about 20 g of liquid per g of SAM and often up to about 40 g of liquid per g of SAM. Obviously, including the absorbent material in a personal care product can reduce the total volume while increasing the absorbent volume of the product.

Capillary driven fluid distribution in the absorbent material is often hampered by the presence of superabsorbents. Fluid distribution can be improved by optimizing various superabsorbent physical and organoleptic properties, but this modification has traditionally reduced the pressure induced (forced flow) fluid intake performance of the absorbent core.

Various superabsorbent particle sizes have been used to improve various composite performance attributes such as composite intake and distribution. Large particles have been used to form larger voids when swollen to improve fluid intake rate, but the particles negatively affect fluid distribution. Smaller particles have been used to form smaller voids when swollen to improve the rate of capillary action and fluid distribution. However, none of the measures could improve either inhalation or distribution characteristics without negatively affecting other characteristics.

There is a need in the art for composite materials comprising superabsorbent materials, which should have improved distribution as well as improved inhalation.

<Overview of invention>

The present invention relates to absorbent articles containing absorbent composites. The composite includes a superabsorbent material (SAM), which contains superabsorbent particles having a dual particle size distribution. The dual particle size distribution includes large particles having a median particle size of about 850 to about 1800 microns and small particles having a mass median particle size of about 50 to about 200 microns. The dual particle size distribution of superabsorbent particles in the absorbent structure of the present invention enables fluid distribution induced by improved capillary phenomena without disturbing fluid intake of the absorbent core.

More particularly, the absorbent composite contains superabsorbent particles having a total mass median particle size of about 60 to about 1750 microns. The mass ratio of large particles to small particles is from about 90:10 to about 50:50, and the absorbent composite may comprise from about 20% to about 100% by weight of superabsorbent material.

The invention also relates to an absorbent composite comprising a superabsorbent material having a dual particle size distribution, wherein the composite has a third liquid insult suction time of less than about 100 seconds.

The invention also relates to an absorbent composite comprising a superabsorbent material uniformly distributed within the absorbent composite. The composite has a third liquid insulting suction time of less than about 100 seconds and a third intermittent vertical wicking time of less than about 600 seconds.

Absorbent composites are particularly useful in disposable personal care products, such as diapers, training pants, sanitary napkins, panty liners, incontinence products, as well as personal health products, such as wound dressings and delivery systems.

The present invention relates to an absorbent article comprising a composite containing a superabsorbent material. More specifically, the composite contains superabsorbent materials having a dual particle size distribution and exhibits improved fluid intake and distribution properties.

1 is a graph illustrating the relationship between mass fraction versus particle size for superabsorbent materials used in the present invention.

2 is an elevation view of a liquid addition apparatus.

At the level of SAM currently used in the absorbent core of the diaper (about 40%), the volume of superabsorbent material (SAM) when swelled is significantly larger than the volume of fibrous material. While fibers continue to play an important role in fluid movement induced by capillary action on subsequent fluid insulators, adjusting the packing fraction of swollen superabsorbent particles to maximize induction by capillary action is achieved by fluid wicking ( wicking can be significantly improved. As used herein, the term “packing fraction” refers to the ratio of the solid volume to the total volume of the composite.

The present invention satisfies the above needs by providing an absorbent composite with improved fluid intake of the absorbent core and improved fluid distribution induced by capillary action. A uniform distribution of superabsorbent material in the absorbent composite is preferred. In one embodiment of the present invention, the improved properties of the absorbent composite of the present invention are obtained using a SAM having a dual distribution of superabsorbent particle size in the absorbent core.

The following terms are used to describe the absorbent composites of the present invention. The general definition of each term is given below.

The term "double" as used herein refers to a superabsorbent material having two distinct peaks in the mass fraction versus particle size curve for the superabsorbent material. A graph including mass fraction versus particle size curves for several SAMs is illustrated in FIG. 1.

As used herein, the term “superabsorbent material” means a water-swellable, water-insoluble organic or inorganic material capable of absorbing at least 15 times its weight in an aqueous solution containing 0.9% by weight sodium chloride under most advantageous conditions.

The term “uniform distribution” as used herein with reference to superabsorbent materials means that the absorbent composite has the same amount of superabsorbent material in all three dimensions of the composite.

Preferably, the absorbent composite of the present invention comprises a superabsorbent material in combination with a fibrous matrix containing at least one kind of fibrous material. The absorbent composite components are discussed below.

Superabsorbent material

Materials suitable for use as the superabsorbent materials of the present invention may include natural materials such as agar, pectin, guar gum and the like, as well as synthetic materials such as synthetic hydrogel polymers. The hydrogel polymer may be an alkali metal salt of polyacrylic acid, polyacrylamide, polyvinyl alcohol, ethylene maleic anhydride copolymer, polyvinyl ether, hydroxypropyl cellulose, polyvinylmorpholinone; And polymers and copolymers of vinyl sulfonic acid, polyacrylates, polyacrylamides, polyvinylpyridine, and the like. Other suitable polymers include hydrolyzed acrylonitrile grafted starch, acrylic acid grafted starch and isobutylene maleic anhydride copolymers and mixtures thereof. The hydrogel polymer is preferably lightly crosslinked to make the material substantially water insoluble. Crosslinking can be, for example, by irradiation or by covalent, ionic, van der Waals or hydrogen bonding. Superabsorbent materials may be present in any form suitable for use in absorbent composites, including particles, flakes, spheres, and the like.

While a wide variety of superabsorbent materials are known, the present invention relates in one aspect to the appropriate selection of superabsorbent materials to allow for the formation of improved absorbent composites and disposable absorbent garments. The present invention is directed to a method of achieving optimal performance in absorbent composites by the discovery that superabsorbent materials having specific dual particle size distributions provide unexpected improvements in the combined properties of fluid distribution and suction performance induced by capillary phenomena. More specifically, the absorbent composite of the present invention preferably contains a superabsorbent material having a dual particle size distribution, wherein the superabsorbent material has a large median particle size and a mass median particle size of about 850 to about 1800 microns. Small particles that are 50 to about 200 microns. Preferably, the superabsorbent material contains large particles having a mass median particle size of about 1000 to about 1600 microns and small particles having a mass median particle size of about 65 to about 150 microns.

Another preferred feature of the present invention is the difference between the mass median particle size of the large particles and the mass median particle size of the small particles in the absorbent composite of the present invention. Preferably, the ratio of the mass median particle size of the large particles to the mass median particle size of the small particles is about 4: 1 to about 36: 1. More preferably, the ratio of the mass median particle size of the large particles to the mass median size of the small particles is about 6: 1 to about 25: 1.

In one embodiment of the invention, the absorbent composite contains a superabsorbent material having a dual particle size distribution, wherein the superabsorbent material comprises large particles having a mass median particle size of less than about 1200 microns and a mass median particle size of less than about 150 microns. Wherein the difference between the mass median particle size of the large particles and the mass median particle size of the small particles (d _{l / s} ) is greater than about 500 microns. In further embodiments, the absorbent composite contains a superabsorbent material having a dual particle size distribution, wherein the superabsorbent material has large particles having a mass median particle size of less than about 1100 microns and a mass median particle size of less than about 100 microns. Including small particles, wherein the difference between the mass median particle size of the large particles and the mass median particle size of the small particles (d _{l / s} ) is greater than about 900 microns.

Without being bound by any particular theory, it is believed that the composites of the present invention exhibit improved fluid distribution for the following reasons. In composites containing high levels of superabsorbent material (i.e., greater than 30 wt%), the volume of the superabsorbent material when swelled is significantly greater than the volume of the fiber. If there are too many voids (void spaces) between the particles and the fibers, the capillary phenomenon of the composite system becomes too low to effectively wick the fluid to a larger area in the composite. However, if the packing of swollen superabsorbent particles can be adjusted to minimize the amount of void space between the swollen superabsorbent particles, induction by capillary phenomena in the system will be maintained and improved fluid wicking will be obtained. . Surprisingly, it has been found that composites of the present invention that exhibit improved fluid wicking also exhibit improved fluid intake.

Thus, it is desirable for the superabsorbent material to be uniformly distributed in the absorbent composite. However, the superabsorbent material can be distributed over the entire absorbent composite or can be distributed within a small local area of the absorbent composite.

The relationship between the amount of void space in the multicomponent system and the proportion of minimum and maximum particles in the system was identified. From these relationships, it is possible to determine the maximum packing of particles in the bicomponent system. CC Furnis, Industrial and Engineering Chemistry , vol. 23, no. 9, 1052-1058 (1931). The equation used is

# Page 6 Equation

Wherein ν ₁ and ν ₂ are the void spaces in the system of Particle 1 (ie, Large Particles) and Particle 2 (ie, Small Particles), respectively; ρ ₁ and ρ ₂ are the actual specific gravity of particles 1 (ie large particles) and particle 2 (ie small particles), respectively. The value of φ ₁ indicates the degree to which the large particles as the first component are saturated by the small particles as the second component. The weight of the large particles for the tightest packing will be φ ₁ and the weight of the small particles for the tightest packing will be (1-φ ₁ ).

Subsequently dividing each of these amounts by φ will give the ratio (by weight) of each component for the tightest packing. The optimal ratio of large particles to small particles can be calculated based on the maximum packing of particles at full saturation, since at this saturation level the packing in the structure will be determined primarily by the superabsorbent material rather than the fibers.

Given the above calculations, the absorbent composite of the present invention preferably contains a superabsorbent material, wherein " large " particles (i.e., samples of particles having a larger mass median particle size) versus " small " particles (i.e., The mass ratio of the sample of particles having a smaller mass median particle size is determined to be about 90:10 to about 50:50. More preferably, the absorbent composite of the present invention contains a superabsorbent material, wherein the mass ratio of "large" particles to "small" particles is about 90:10 to about 80:20. Even more preferably, the absorbent composite of the present invention contains a superabsorbent material, wherein the mass ratio of "large" particles to "small" particles is about 85:15.

In addition, the absorbent composite of the present invention preferably includes the dual particle size distribution described above and a total mass median particle size of about 60 to about 1750 microns. More preferably, the absorbent composite of the present invention preferably comprises the dual particle size distribution described above and a total mass median particle size of about 800 to about 1200 microns. Even more preferably, the absorbent composite of the present invention preferably comprises the dual particle size distribution described above and a total mass median particle size of about 900 to about 1100 microns.

In one embodiment of the invention, the superabsorbent material comprises a sodium salt of crosslinked polyacrylic acid. Suitable superabsorbent materials include Dow AFA-177-140 and Drytech 2035 (both available from Dow Chemical Company, Midland, MI), Favor SXM-880 (Stockhausen, Inc.). ), Available from Greensboro, New Kentucky, USA), Sanwet IM-632 (available from Tomen America, New York, NY) and Hysorb P-7050 (BASF Corporation, USA) Available from Pottsmouth, VA).

Fibrous material

Preferably, the absorbent composite of the present invention contains the superabsorbent material described above in combination with a fibrous matrix containing at least one kind of fibrous material. The fibrous material forming the absorbent composite of the present invention can be selected from a variety of materials including natural fibers, synthetic fibers, and blends thereof. Many suitable fiber types are disclosed in US Pat. No. 5,601,542, assigned to Kimberly-Clark Worldwide, Inc., which is hereby incorporated by reference in its entirety.

The choice of fiber depends, for example, on the intended end use of the finished absorbent composite. For example, suitable fibrous materials include natural fibers, such as non-wood fibers (cotton and cotton derivatives, manila hemp, kenaf, sabai grass, flax, African esparto grass, straw , Jute hemp, bagasse, milkweed floss fiber and pineapple leaf fiber); And wood fibers, for example fibers from deciduous and coniferous trees (softwood fibers, such as northern and southern softwood kraft fibers; hardwood fibers such as eucalyptus, maple, birch Or cottonwood, etc.), but is not limited thereto. Wood fibers can be made in high-yield or low-yield form, can be made into pulp by any known method, and can be kraft, sulfite, groundwood, thermomechanical pulp (TMP). ), Chemical thermomechanical pulp (CTMP) and bleaching chemical thermomechanical pulp (BCTMP). Regenerated fibers are also included within the scope of the present invention. Any known pulp method and bleaching method can be used.

Similarly, from regenerated cellulose fibers (eg viscose rayon and cuprammonium rayon), modified cellulose fibers (eg cellulose acetate) or synthetic fibers (eg polyester, polyamide, polyacrylic, etc.) Derived) can be likewise used alone or in combination with one another. Chemically treated natural cellulose based fibers such as mercerized pulp, chemically stiffened or crosslinked fibers, sulfonated fibers and the like can be used. Suitable papermaking fibers may also include recycled fibers, virgin fibers or mixtures thereof. If desired, blends of one or more of the aforementioned fibers can also be used.

Absorbent composites

As mentioned above, the absorbent structure according to the invention preferably comprises a superabsorbent material and a fibrous matrix for containing the superabsorbent material. However, it should be noted that any device capable of retaining the superabsorbent material described above and that in some cases may be disposed within a disposable absorbent garment is suitable for use in the present invention.

Many such holding devices are known to those skilled in the art. For example, the retention device may be an air-formed or wet-laid web of fibrous matrices, such as cellulosic fibers, meltblown webs of synthetic polymer fibers, of synthetic polymer fibers. Spunbonded webs, coformed matrices comprising fibers formed from cellulosic fibers and synthetic polymeric materials, airlaid heat-fused webs of synthetic polymeric materials, open-celled foams, and the like. It may include.

The retaining device is preferably a fibrous matrix generally in the form of a fibrous network, which is a random plurality of fibers that can be joined together optionally using a binder. The fibrous material may alternatively have a batt form of comminuted wood pulp fluff, tissue layer, hydroentangled pulp sheet, woven sheet, nonwoven sheet, tow or mechanically softened pulp sheet. have. Any papermaking fiber or mixtures thereof as defined above can be used to form the fibrous matrix.

The absorbent composite of the present invention may be formed from a single layer of absorbent material or a multilayer absorbent material. In the case of multiple layers, the layers can be arranged in a side-to-side or surface-to-surface relationship, and all or some layers can be joined to adjacent layers. If the absorbent composite comprises multiple layers, the overall thickness of the absorbent composite may contain one or more superabsorbent materials, or each individual layer may individually contain some superabsorbent material or contain superabsorbent materials. I never do that.

In one embodiment of the invention, the absorbent composite contains a superabsorbent material and a fibrous material, wherein the relative amounts of the superabsorbent and fibrous material used to prepare the absorbent composite are determined by the desired properties of the resulting product and the resulting product. It may vary depending on the use of. Preferably, the amount of superabsorbent material in the absorbent composite is from about 20 wt% to about 100 wt% based on the total weight of the absorbent composite and the amount of fibrous material is from about 80 wt% to about 0 wt%. More preferably, the amount of superabsorbent material in the absorbent composite is from about 30 wt% to about 90 wt% based on the total weight of the absorbent composite and the amount of fibrous material is from about 70 wt% to about 10 wt%. Even more preferably, the amount of superabsorbent material in the absorbent composite is from about 40 wt% to about 80 wt% based on the total weight of the absorbent composite and the amount of fibrous material is from about 60 wt% to about 20 wt%.

In other embodiments, the basis weight of the superabsorbent material used to make the absorbent composite of the present invention may vary depending on the desired properties in the resulting product, such as the total composite thickness and basis weight and the use of the resulting product. have. For example, absorbent composites for use in infant diapers may have a lower basis weight and thickness compared to absorbent composites for incontinence devices. Preferably, the basis weight of the superabsorbent material in the absorbent composite is greater than about 80 grams per square meter (gsm). More preferably, the basis weight of the superabsorbent material in the absorbent composite is from about 80 gsm to about 800 gsm. Even more preferably, the basis weight of the superabsorbent material in the absorbent composite is from about 120 gsm to about 700 gsm. Even more preferably, the basis weight of the superabsorbent material in the absorbent composite is from about 150 gsm to about 600 gsm.

Method of manufacturing absorbent composite

Absorbent composites of the present invention can be prepared by processes known to those skilled in the art. In one embodiment of the present invention, a method of forming an absorbent composite may include bonding a superabsorbent material containing superabsorbent particles with a substrate. Superabsorbent particles have a dual particle size distribution in which large particles have a mass median particle size of about 850 to about 1800 microns and small particles have a mass median size of about 50 to about 200 microns. Preferably, the large particles have a mass median size of about 1000 to about 1600 microns, and the small particles have a mass median size of about 65 to about 150 microns.

Alternatively, the method may include combining the superabsorbent material with the substrate, wherein the composite has a third liquid insulator suction time of less than about 100 seconds and a third intermittent vertical wicking time of less than about 600 seconds. Superabsorbent materials are evenly distributed within the composite.

In a further embodiment of the present invention, superabsorbent materials containing superabsorbent particles are included into the substrate present. Preferably, the substrate contains fibrous material. Suitable fibrous substrates include, but are not limited to, nonwovens and fabrics. In many embodiments, particularly in personal care products, the preferred substrate is a nonwoven. As used herein, the term "nonwoven" refers to a fabric having a structure of individual fibers or filaments randomly arranged in a mat-like form. Nonwovens are manufactured from a variety of processes including, but not limited to, airlaid processes, wet-laid processes, hydroentangling processes, staple fiber carding and bonding, and solution spinning. Can be. The superabsorbent material can be included as a solid particulate material into the fibrous substrate. Superabsorbent materials may be present in any form suitable for use in absorbent composites, including particles, flakes, spheres, and the like.

In a separate embodiment of the present invention, the superabsorbent material containing the fibrous material and the superabsorbent particles are simultaneously mixed to form an absorbent composite. Preferably, the composite material is mixed by air-forming processes known to those skilled in the art. Pneumatically forming a mixture of fibers and superabsorbent materials not only allows the preformed fibers to be airlaid with the superabsorbent materials, but also when the superabsorbent materials are being formed, for example, through a meltblowing process. It is intended to include all of the situations that are mixed with the fibers.

For example, the description below refers to, but is not meant to be, an example of an air forming process used to form the composite of the present invention. Several process components can be used to make the absorbent composite of the present invention. These first include a method for fiberizing a pulp sheet into a fibrous fluff. These fibrous fluff fibers are conveyed into the forming chamber by air. Subsequently, a method of adding superabsorbent particles is used to meter and transport the superabsorbent particles into the molding chamber. It has been found that one or more superabsorbent feeders are useful for controlling the individual amounts of different kinds of superabsorbent particles that are delivered to the molding chamber. The forming chamber allows the fibrous fluff fibers and the superabsorbent particles to be mixed together. A moving forming screen is placed at the base of the forming chamber. The screen is air permeable and is usually connected to a vacuum source. The vacuum removes air from the forming chamber such that fibrous fluff fibers and superabsorbent particles are deposited on the forming screen to form a composite web. The tissue can be unwound onto the forming wire so that the fibers and particles are placed on the tissue to aid in transport. The speed of the pulp sheet, superabsorbent feeder and forming screen can all be adjusted independently to control the composition and basis weight of the resulting composite. After forming the composite web on the forming wire, a roller may be used to compress the composite to the desired level. At the end of the forming screen, the composite web is wound on a continuous roll.

Properties of Absorbent Composites

Absorbent composites of the present invention have improved fluid intake as well as fluid distribution induced by improved capillary phenomena over the lifetime of the composite as compared to known absorbent composites. One method of measuring the fluid distribution induced by capillary phenomena of absorbent composites is to use an intermittent vertical wicking (IVW) test. This test measures the wicking speed of a material or composite during a series of liquid contacts.

The IVW test consists of contacting the lower edge of the vertically suspended absorbent composite with the solution, which is described in detail below. The fluid distribution profile obtained from the IVW test can be analyzed by liquid saturation of the composite at varying distances from the lower edge of the absorbent composite. Preferably, the absorbent composite of the present invention exhibits liquid saturation at 3 to 3.5 inches from the bottom edge of the absorbent composite, which is equal to at least 65% of the liquid saturation at 0 to 0.5 inches from the bottom edge of the absorbent composite. More preferably, the liquid saturation at 4 to 4.5 inches from the bottom edge of the absorbent composite is equal to at least 50% of the liquid saturation at 0 to 0.5 inches from the bottom edge of the absorbent composite, even more preferably The liquid saturation at 4.5 to 5.0 inches from the bottom edge is equal to at least 35% of the liquid saturation at 0 to 0.5 inches from the bottom edge of the absorbent composite.

In addition, the absorbent composite of the present invention preferably exhibits a third intermittent vertical wicking pickup time of less than about 600 seconds. More preferably, the absorbent composite exhibits a third intermittent vertical wicking pick-up time of less than about 300 seconds.

One method of measuring fluid intake of an absorbent composite is to use a fluid intake assessment (FIE) test, which is described in detail below. The test measures the inhalation capacity of a substance or composite when exposed to liquid insults multiple times.

Preferably, the absorbent composite of the present invention has a third liquid insult inhalation time of less than about 100 seconds, more preferably less than about 85 seconds, even more preferably less than about 60 seconds.

Another unique feature of the absorbent composite of the present invention is that the superabsorbent particles contained in the composite have different swelling times because of the distinct size of the particles. Swelling time is defined as the amount of time it takes for superabsorbent particles to reach 60% liquid volume and can be measured using the Blotted FAUZL test detailed below. Preferably, the swelling time of the small particles used in the absorbent composite of the present invention is about 15 seconds to about 35 seconds, and the swelling time of the large particles is about 300 seconds to about 700 seconds. More preferably, the swelling time of the small particles is about 20 seconds to about 30 seconds, and the swelling time of the large particles is about 400 seconds to about 600 seconds. In addition, the swelling time of the small particles is preferably about 20 times shorter than the swelling time of the large particles.

How to use the absorbent structure

In one embodiment of the invention, there is provided a disposable absorbent article comprising a liquid-permeable topsheet, a backsheet attached to the topsheet and an absorbent composite of the invention disposed between the topsheet and the backsheet. Those skilled in the art will know suitable materials for use as the topsheet and backsheet. Exemplary materials suitable for use as topsheets are liquid-permeable materials such as spunbonded polypropylene or polyethylene having a basis weight of about 15 to about 25 g / square meter. Exemplary materials suitable for use as backsheets are liquid-impermeable materials such as polyolefin films and vapor-permeable materials such as microporous polyolefin films.

Disposable absorbent articles according to all aspects of the present invention are generally exposed to multiple insults of body fluids during use. Thus, the disposable absorbent article can preferably absorb multiple insults of body fluids in an amount to which the absorbent article and the structure will be exposed during use. Insulations are usually separated from one another at regular time intervals. The absorbent article of the present invention should be present in an amount effective to form a superabsorbent composition effective to absorb the desired amount of liquid.

Absorbent composites according to the invention are suitable for absorbing many fluids, including body fluids such as urine, menstrual blood and blood, and are suitable for absorbing disposable absorbent products, for example disposable personal care products, for example absorbent garments, for example diapers. , Incontinence products, bed pads, and the like; Sanitary products such as sanitary napkins, panty liners, tampons, and the like; It is particularly suitable for use in personal health products such as wound dressings and delivery systems as well as wipes, bibs, food packaging materials and the like. Thus, in another aspect, the present invention relates to a disposable absorbent garment comprising an absorbent composite as described above. A wide variety of absorbent garments are known to those skilled in the art. Absorbent composites of the present invention can be incorporated into such known absorbent garments. Exemplary absorbent garments are described in US Pat. No. 4,710,187 to Boland et al., Dec. 1, 1987; 4,762,521, issued to Roessler et al. On August 9, 1988; 4,770,656, issued to Proxmire et al. On Sep. 13, 1988; 4,798,603, issued to Meyer et al. On January 17, 1989.

In general, an absorbent disposable garment according to the present invention is a bodyside liner suitable for contact with the wearer's skin, an outer cover overlapping with the liner and overlapping the outer cover and lying between the bodyside liner and the outer cover. Absorbent composites such as those described above.

<Test method>

Assays for testing superabsorbent materials :

Methods for determining the particle size distribution and mass median particle size of a given sample of superabsorbent material are described below. In addition, the method of determining the swelling time and gel bed void space of the superabsorbent particles is described below.

Particle Size Distribution (PSD) Assay

The PSD test method used in the present invention determines the particle size distribution of the superabsorbent material by sieve size analysis. Stacks of sieves with holes of different sizes are used to determine the particle size distribution of a given sample. Thus, for example, particles retained on a sieve having 710 micron holes are considered to have a particle size greater than 710 microns in principle. Particles passing through a sieve having 710 micron holes and retained on a sieve having 500 micron holes are considered to have a particle size of 500 to 710 microns. Moreover, particles passing through a sieve having 500 micron holes are considered to have a particle size of less than 500 microns.

The sieve is placed in the order of the size of the holes to have the largest hole on the top of the stack and the smallest hole on the bottom of the stack. A 25 g sample of superabsorbent particles is placed in a sieve with the largest hole. The sieve stack is shaken for 10 minutes using a Ro-Tap Mechanical Sieve Shaker Model B (available from WS Tyler, Mentor, Ohio) or other similar shaking device. . After shaking, the superabsorbent particles retained on each sieve are removed and weighed and recorded. The percentage of particles retained on each sieve is calculated by dividing the weight of particles retained on each sieve by the original sample weight.

Mass Median Particle Size Test

As used herein, the term “mass median particle size” of a given sample of superabsorbent particles is defined as the particle size that divides the sample by half on a mass basis, ie, half of the sample (by weight) is greater than the mass median particle size. It has a large particle size and half of the samples (by mass) have a particle size below the mass median particle size. Thus, for example, if half of the sample (by weight) is retained on a sieve having a hole of 500 microns, the mass median particle size of the sample of superabsorbent particles is 500 microns.

Blotted FAUZL (Flooded Absorbency Under Zero Load) Test

Weigh the Absorbency Under Load (AUL) cup and plunger and record as "Me". AUL cups are made from 1 inch inner diameter thermoplastic tubes that are slightly processed to achieve concentricity. The AUL cup has a 400 mesh stainless steel screen attached to the base of the cup with an adhesive. Alternatively, the screen can be fused to the base of the cylinder by heating the wire screen in flame until heated red, then holding the AUL cup on the screen until cooled. A soldering iron can be used to correct the seal in case of failure or failure. Care should be taken to keep the base smooth and smooth and not to twist the inside of the AUL cup. The plunger is made from 1 inch diameter solid material (eg Plexiglass) and processed to fit snugly without being bound in an AUL cup. Before placing the superabsorbent on the screen of the AUL cup, the superabsorbent material is sieved to the appropriate size for the test.

About 0.160 g of superabsorbent material is placed in an AUL cup, where the superabsorbent material is evenly distributed over the bottom of the cup. 4.0 g of plunger is placed on top of the dry superabsorbent material to produce a pressure of about 0.01 psi. Weigh the AUL cup, plunger and dry superabsorbent material and record as "Mo". 0.9 wt% saline solution is added to the Petri dish (2 inches or more in diameter) about 0.5 cm deep. A plastic screen with about 16 holes per square inch is placed on the base of the petri dish.

The AUL cup is placed in saline for 15 seconds so that the saline is absorbed into the superabsorbent material. The bottom of the AUL cup is quickly placed on a paper towel to remove any liquid in the screen or in the gap space between the superabsorbent particles. The time to remove the AUL cup from the brine and place it on a paper towel should be 3 seconds or less. Move the cup to the dry portion of the paper towel until the liquid from the cup to the towel is no longer visible. The AUL cup, plunger and superabsorbent material are then weighed and the mass is recorded as "Mt". The total time for removing liquid from the gap space, weighing the AUL cup and putting the AUL cup back into the brine should be less than 30 seconds. The AUL cup is quickly put back into the saline for an additional 15 seconds so that the saline is absorbed into the superabsorbent material. Again, the bottom of the cup is dried and Mt is determined. Mt is obtained for the following cumulative exposure time, where "exposure time" is defined as the time the superabsorbent is immersed in the liquid: 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 10, 20 , 40 and 60 minutes.

The entire test is performed three times for each superabsorbent material tested and the average pickup for the three tests is determined for each exposure time.

Data analysis :

The amount of brine picked up during each exposure time is determined by the equation

g brine / g superabsorbent = (Mt-Mo) / (Mo-Me)

The g / g pickup value at the 60 minute cumulative exposure time is determined and recorded as g / g (e). The characteristic time to reach 60% of the 60 min g / g pickup value is determined by the following equation.

Characteristic pickup value = 0.6 * g / g (e)

A table listing the exposure time and pickup value is used to interpolate the characteristic time to pick up 60% of the 60 minute pickup value.

Gel bed void space experimental procedure

Centrifuge Retention Capacity (CRC) of superabsorbent particles is measured to obtain the full saturation volume of the gel particles. Then 2.0 g of dry superabsorbent particles are measured. The amount of (2.0 x CRC) g of 0.9 wt% saline solution is measured into a 200 ml beaker. 2.0 g of dry superabsorbent particles are added to 0.9 wt% salt solution and stirred for 10 seconds to prevent the particles from agglomerating. The beaker is then covered with paraffin or a suitable cover and the superabsorbent is swelled and allowed to stand for at least 2 hours to swell to reach equilibrium. After the swollen superabsorbent reaches equilibrium, the average is achieved by placing a light-weight acrylic platen (<0.02 psi) on top of the swollen gel bed and labeling the height of the base of the platen on the side of the beaker. The swelling height is labeled in the beaker. The contents of the beaker are then emptied. The beaker is weighed and then filled with water up to the label indicating the height of the swollen gel bed. The beaker is weighed to obtain the total volume of swollen gel bed using the following formula.

Volume = Weight (g) /1.0 gm / cc

The void space is then determined by subtracting the volume due to brine and gel using the following formula.

Pore = water volume — [((2.0 × CRC) / (specific gravity of 0.9 wt% saline)) + (2.0 g superabsorbent / 1.5 gm / cc)].

Test Methods for Testing Absorbent Composites :

Test methods for determining the saturation capacity (SC), intermittent vertical wicking (IVW) and fluid intake assessment (FIE) of a given absorbent composite are described below.

Saturation Capacity (SC) Test

Only a composite or fluff of superabsorbent and fluff is air-forming on the tissue at the desired basis weight and density. The composite sample is cut to the desired size, in which case the composite sample is cut into a 3.5 inch (8.89 cm) x 10 inch (25.40 cm) rectangle. The weight of each composite sample is then measured and recorded. This is the dry weight of the composite. The composite sample is then immersed in a 0.9 wt% NaCl solution bath for 20 minutes. After soaking for 20 minutes, the composite sample is placed for 5 minutes under 0.5 psi (14 "H ₂ O) vacuum pressure. The composite sample is then reweighed. This is the wet composite weight. The volume of each composite sample is wet for each sample. Calculated by subtracting dry composite weight from composite weight.

Intermittent Vertical Wicking (IVW) Test

The intermittent vertical wicking (IVW) test measures the wicking speed and fluid distribution profile of a material or composite during a series of liquid contacts. The test consists of three separate contacts between the bottom edge of the vertically suspended absorbent composite sample and the salt solution. Liquid insulator for each separate contact or composite represents 15% of the saturation volume of the absorbent composite as measured in the SC test described above. Since each separate liquid insulator is (0.15) x (m _total ) in the IVW test, the composite will have the desired volume of absorption during each insult. The absorbent composite sample wicks the liquid as follows.

The superabsorbent and fluff composites are air-formed onto the tissue at the desired basis weight and density. The composite sample is cut to the desired size, in which case the composite sample is cut into 3.5 inch (8.89 cm) x 10 inch (25.40 cm) rectangles. The saturation volume (m _total ) of the sample is determined as described above. Calculate the same amount as (0.15) × (m _total ).

The separate sample is vertically suspended so that the long dimension of the sample is in the vertical direction. The suspended sample is attached to the strain gauge. The sample is then lowered into a reservoir containing 0.9 wt% NaCl solution. The amount of sample in contact with the solution should be less than 1/4 inch. The amount of liquid pickup is measured as a function of time and continues until 15% [(0.15) x (m _total )] of the saturation volume of the absorbent composite is recorded on the strain gauge. The sample is then removed from the NaCl solution but kept in vertical form.

After 30 minutes, the sample is lowered back into 0.9 wt% NaCl solution. The amount of liquid pickup is measured as a function of time and continues until 15% [(0.15) x (m _total )] of the saturation volume of the absorbent composite is recorded on the strain gauge. The sample is then removed from the NaCl solution but kept in vertical form.

After 30 minutes, the sample is third lowered into a 0.9 wt% NaCl solution. The amount of liquid pickup is measured as a function of time and continues until 15% [(0.15) x (m _total )] of the saturation volume of the absorbent composite is recorded on the strain gauge. The sample is then removed from the NaCl solution but kept in vertical form.

The sample is then tested to determine the fluid distribution profile of the sample. Any assay can be used to determine the fluid distribution profile of the sample. One known method is to cut the absorbent composite into 1/2 inch (1.27 cm) pieces of width and weigh the pieces to determine the amount of fluid in a given piece. In the sample, 20 pieces of 1/2 inch (1.27 cm) wide and 3.5 inches (8.89 cm) long are formed from each composite sample. The fluid distribution profile is determined by weighing each piece to determine the amount of fluid in each piece. The amount of fluid is determined for each piece by the following formula: amount of fluid per piece = wet weight of the piece-(dry weight of the whole sample / 20).

The IVW procedure is further repeated for two composite samples cut from the same composite material. The average pickup time is determined for three first liquid pickups, three second liquid pickups and three third liquid pickups. In addition, the average amount of liquid in each 1/2 inch section of the three composite samples is determined as described above.

Fluid Intake Assessment (FIE) Test

The Fluid Intake Assessment (FIE) test measures the ability to inhale a substance or composite. The test consisted of contacting the absorbent composite with three liquid insults, where each liquid insult represents 30% of the saturation volume of the composite as determined by the SC test described above. Three liquid inlets are applied at 15 minute intervals.

The composite of superabsorbent and fluff is air-formed onto the tissue at the desired basis weight and density. The composite sample is cut to the desired size, in which case the composite sample is cut into a 3.5 inch (8.89 cm) x 5 inch (12.70 cm) rectangle. The saturation volume (m _total ) of the sample is determined as described above. Calculate the same amount as (0.30) × (m _total ).

The liquid addition device 10 as shown in FIG. 2 is cut about 0.13 psi (8966 dynes /) onto a separate composite sample 12 (also cut into a 3.5 inch (8.89 cm) x 5 inch (12.70 cm) rectangle). Place to create a pressure of cm ² ). The liquid addition apparatus includes an additional brass weight 16 to bring the total mass of the base 14 and the apparatus 10 to 1223 g. The liquid is introduced through the tube 18 disposed on the liquid adding device 10 to bring the liquid into contact with the sample 12. A first liquid insult of 0.9 wt% NaCl solution equal to 30% [(0.30) × (m _total )] of the saturation volume of the absorbent composite is introduced through the tube 18 to make contact with the composite sample 12. The amount of time required for all of the first liquid insult to soak into the composite sample 12 is measured. 15 minutes after starting the first insult, contacting the composite sample 12 with a second liquid insert of 0.9 wt% NaCl solution equal to 30% [(0.30) × (m _total )] of the saturation volume of the absorbent composite Let's do it. The amount of time required for all of the second liquid insult to soak into the composite sample 12 is measured. An additional 15 minutes after the start of the second insulation, a third liquid insert of 0.9 wt% NaCl solution equal to 30% [(0.30) × (m _total )] of the saturation volume of the absorbent composite was prepared. Contact with. The amount of time required for all of the third liquid insult to soak into the composite sample 12 is measured.

The procedure is repeated with two composite samples cut from the same composite material. The average suction time is calculated for three first, three second and three third liquid inlets. In addition, the total insulated average inhalation time is calculated as the sum of the first, second and third insulated average inhalation times.

Those skilled in the art will readily appreciate that the superabsorbent materials and absorbent composites of the present invention may be advantageously used in the manufacture of a wide variety of products including, but not limited to, absorbent personal care products designed to contact body fluids. The article may comprise only a single layer of absorbent composite, or may comprise a combination of members as described above. While the superabsorbent materials and absorbent composites of the present invention are particularly suitable for personal care products, the superabsorbent materials and absorbent composites can be advantageously used in a wide variety of consumer products.

The invention is further illustrated by the following examples which should not be construed as limiting the scope of the invention in any way. On the contrary, after reading the specification herein, may be resorted to by various other embodiments, modifications, and equivalents thereof that would come to mind to one skilled in the art without departing from the spirit of the invention and / or the scope of the appended claims. Should be clearly understood.

<Example>

In the examples below, the absorbent composites were prepared using the following superabsorbent and fibrous materials.

Superabsorbent material :

AFA-177-9A, AFA-177-9B, AFA-177-140 and Drytech 2035 from Dow Chemical Company.

Fibrous material :

Fluff pulp fiber, CR-1654 (AllianceForest Products, Kusa Pines, Alabama).

<Example 1>

Determination of Particle Size Distribution of Superabsorbent Material Samples

Two 100 g samples of AFA-177-9A and AFA-177-9B were supplied from Dow Chemical Company. The particle size distribution of each sample was measured using the PSD test method described above. Sieves with the following mesh sizes were used for sample AFA-177-9A: 1680 microns, 1190 microns, 1000 microns and 850 microns. Sieves with the following mesh sizes were used for sample AFA-177-9B: 150 microns, 105 microns and 63 microns.

Particle size distributions of samples AFA-177-9A and AFA-177-9B are shown in Tables 1 and 2 below.

Particle Size Distribution of Sample AFA-177-9A Granularity (micron) Mass% in total Over 1680 0.02 1190-1680 31.2 1000-1190 27.25 850-1000 36.51 Less than 850 5.03

Particle Size Distribution of Sample AFA-177-9B Granularity (micron) Mass% in total More than 150 1.74 105-150 45.05 63-105 48.97 Less than 63 4.23

As can be seen from Tables 1 and 2 above, the mass median particle sizes of the particles in samples AFA-177-9A and AFA-177-9B are about 1100 microns and 100 microns, respectively.

<Example 2>

Preparation of Absorbent Composites of the Invention

Absorbent composites were formed using superabsorbent material AFA-177-140 (manufactured by Dow Chemical Company) and pulp fiber CR-1654 (manufactured by Alliance Forest Products). Superabsorbent material AFA-177-140 had essentially the same chemical composition as the samples AFA-177-9A and AFA-177-9B of Example 1. AFA-177-140 superabsorbent material was ground using methods known in the art to provide two samples with similar particle size distributions to samples AFA-177-9A and AFA-177-9B described in Example 1, namely Sample 1A. And Sample 1B was obtained. Composites were formed through conventional air-forming units. The mass ratio of Sample 1A (large particles) to Sample 1B (small particles) in the composite changed as follows: 50:50, 70:30, 80:20 and 90:10. The composite had a target total basis weight of 500 gsm, a target density of 0.2 g / cc and an SAP concentration of 50 mass%.

The median median particle size of the particles in Samples 1A and 1B was determined at the saturation level of 30 g of 0.9 wt% NaCl solution per gram of SAP. In addition, the pore space and specific gravity of the particles in the saturated superabsorbent particle bed were determined experimentally using the Gel Bed Void Space Experimental Procedure. The results are shown in Table 3 below.

Parameters for Calculating Theoretical Particle Ratios Mass Median Dry Diameter (micron) Mass Median Saturation Diameter (microns) Void at 30g / g (ν) Specific gravity (ρ) Ingredient 1 1100 3930 0.18 1.02 Component 2 105 375 0.07 1.02

Experimentally determined values for νl (pore space in the system of sample 1A particles), ν2 (pore space in the system of sample 1B particles), ρi (real specific gravity of sample 1A particles), and ρ2 (real specific gravity of sample 1B particles) Using this equation together, the theoretical optimal ratio of large particles (sample 1A particles) to small particles (sample 1B particles) was determined as shown below.

φ ₁ = [(1-ν ₁ ) · ρ ₁ ] ÷ [(1-ν ₁ ) · ρ ₁ + ν ₁ · (1-ν ₂ ) · ρ ₂ ]

= [(1-0.18) · 1.02] ÷ [(1-0.18) · 1.02 + 0.18 · (1-0.07) · 1.02]

= 0.83

Φ = φ ₁ + (1-φ ₁ )

= 0.83 + (1-0.83)

= 1

The theoretical weight percentage of each component will be as follows:

φ ₁ / Φ = weight percent of component:

Wt% of sample 1A (large particles) = (φ ₁ / Φ) × 100 = 83%

Wt% of sample 1B (small particles) = [(1-φ ₁ ) / Φ] × 100 = 17%

Since both components are assumed to be at the same saturation level in equilibrium, the dry weight percentage will be equal to the calculated saturated weight percentage.

<Example 3>

Preparation of Control Absorbing Composite Using Conventional Particle Size Distribution

The control absorbent composite was prepared using the same material as in Example 2 except that the superabsorbent material had a particle size distribution in the range of 0 to 850 microns. This control is referred to herein as control 1. Specifically, Control 1 was determined to have a particle size distribution as shown below.

Mass Median Particle Size Distribution of Control Group 1 Granularity (micron) Mass% in total 600-850 25 300-600 50 65-300 25

The second control composite was made using 50% Drytech 2035 (Dow Chemical Company) and 50% Alliance CR-1654 fluff (Alliance Forest Products). The composites were formed to compare the composites of the present invention to composites comprising representative superabsorbent materials used in commercial products. The control composite containing Drytech 2035 is hereinafter referred to as Control 2. Table 5 describes the particle size distribution of control group 2.

Mass Median Particle Size Distribution of Control Group 2 Granularity (micron) Mass% in total 600-850 20 300-600 55 65-300 25

<Example 4>

Wicking performance of absorbent composites and control composites of the present invention

The wicking performance of the composites of Examples 2 and 3 was evaluated using the intermittent vertical wicking (IVW) test described above. The fluid distribution in each composite was analyzed by determining the amount of liquid in each 0.5 inch section of the composite after the third liquid insult. The amount of liquid in each section was divided by the amount of liquid for the sample in the 0-0.5 inch section for the sample. This value was multiplied by 100 to obtain the percentages shown in Table 6 below.

Average Fluid Distribution After Third Insulation Distance from lower edge (inches) Average fluid distribution after absorption of tertiary absorbent composite (% of lowest segment saturation level) 50:50 70:30 80:20 90:10 Control group 1 Control 2 0-0.5 100% 100% 100% 100% 100% 100% 0.5-1.0 110% 102% 103% 95% 101% 98% 1.0-1.5 98% 97% 94% 92% 94% 93% 1.5-2.0 89% 91% 92% 78% 95% 83% 2.0-2.5 83% 83% 83% 81% 84% 77% 2.5-3.0 78% 79% 74% 68% 63% 71% 3.0-3.5 68% 69% 70% 69% 49% 62% 3.5-4.0 65% 61% 54% 59% 44% 57% 4.0-4.5 58% 50% 42% 47% 26% 45% 4.5-5.0 47% 39% 28% 32% 14% 33% 5.0-5.5 32% 28% 10% 25% 4% 12% 5.5-6.0 15% 13% 5% 10% 4% One% 6.0-6.5 4% 5% 5% 5% 4% 0% 6.5-7.0 3% 4% 4% 5% 3% 0%

As can be seen from the data in Table 6, better fluid distribution and wicking were observed in composites containing a double superabsorbent particle size distribution. This is clearly evidenced by the greater amount of fluid located in the higher part of the composite (> 5 ").

The fluid distribution of the absorbent composite of the present invention was enhanced by the presence of a dual particle size distribution, as can be seen by the increased amount of fluid in the higher portion of the composite. It was also found that the fluid pickup rate during the IVW test was improved in some dual systems as shown in Tables 7 and 8 below.

Average 3rd Inlet Pickup vs Time Time interval in seconds Absorption Composite Average Third Inlet Pickup Amount at a Given Time (g) 50:50 70:30 80:20 90:10 Control group 1 Control 2 50 8.5 10.5 15.5 10.5 11.0 12.3 100 12.0 15.5 18.5 12.5 14.1 15.0 150 14.0 17.5 22.0 15.0 17.0 18.0 200 16.0 20.5 24.5 16.5 17.7 19.6 250 16.5 22.5 25.0 17.5 18.9 20.5 300 17.0 23.0 18.5 20.5 19.5 350 19.5 23.5 20.0 21.7 20.9 400 21.0 24.0 21.5 22.7 22.1 450 21.5 24.5 22.0 24.2 23.1 500 21.8 25.0 23.0 24.8 23.9 Target Pickup Amount (gm) 25.0 25.0 25.0 25.0 25.0 31.0

Average 3rd Inlet Pickup Time interval in seconds Average third insert pickup amount expressed as a percentage of absorbent composite target pickup amount 50:50 70:30 80:20 90:10 Control group 1 Control 2 50 34% 42% 62% 42% 44% 40% 100 48% 62% 74% 50% 56% 48% 150 56% 70% 88% 60% 68% 58% 200 64% 82% 98% 66% 71% 63% 250 66% 90% 100% 70% 76% 66% 300 68% 92% 74% 82% 63% 350 78% 94% 80% 87% 67% 400 84% 96% 86% 91% 71% 450 86% 98% 88% 97% 75% 500 87% 100% 92% 99% 77%

As can be seen from the data in Tables 7 and 8, the wicking rate is affected by the amount of large and small particles present in the absorbent composite. The average third insulator fluid pickup suggests that the presence of too many small or large particles negatively affects the wicking speed of the composite. It is believed that the tendency of small particles to cause gel blocking and reduced capillary phenomena caused by large particles negatively affect the wicking speed of the composite.

In addition, it should be noted that the wicking rate of the absorbent composites having a dual particle distribution and 80:20 wt / wt ratio improved compared to the control composite with regular particle distribution.

The data in Table 6-8 above suggest that fluid distribution and wicking rate can be improved in composites containing moderately large to small particle ratios in the superabsorbent double particle size distribution.

Example 5

Fluid Suction Performance of Absorbent and Control Composites of the Invention

Inhalation performance of the composite of Example 2 and the control composite of Example 3 was evaluated using a fluid inhalation assessment (FIE) as described in the “assay” section above. The FIE results are shown in Table 9 below.

FIE Results for Absorbent Composites Sample Weight ratio of sample 1A to sample 1B First Insulation Average Suction Time (sec) Second Insulation Average Suction Time (sec) Third Insulation Average Suction Time (sec) Total Insulation Average Suction Time (sec) Example 2 50:50 71.2 73.2 96.2 240.6 Example 2 70:30 38.7 38.6 63.6 140.9 Example 2 80:20 45.2 29.5 46.8 121.5 Example 2 90:10 61.6 38.9 80.8 181.3 Control group 1 n / a 46.6 101.2 170.2 318.0 Control 2 n / a 41.6 55.7 108 205.3

As can be seen from the data in Table 9, as well as the lowest total insult average inhalation time in composite samples where the superabsorbent material weight ratio is 80 wt% of Sample 1A (large particles) to 20 wt% of Sample 1B (small particles) The lowest average second and third insult inhalation times were obtained.

<Example 6>

Determination of Swell Time of Superabsorbent Particles in Absorbent Composites of the Invention

The swelling time of the large particles of sample AFA-177-9A and the small particles of sample AFA-177-9B was determined using the Blotted FAUZL test as described above. The test results are shown in Table 10 below.

Swelling Time of Super Absorbent Particles Granularity Time to reach 60% saturation (seconds) Sample AFA-177-9A (Large Particles) 578 Sample AFA-177-9B (Small Particles) 28.3

The disclosed embodiments are preferred embodiments and are not intended to limit the scope of the invention in any way. Various modifications apparent to those skilled in the art and other embodiments and uses of the disclosed superabsorbent polymers are also contemplated as being within the scope of this invention.

Claims (44)

An absorbent composite comprising a superabsorbent material, the superabsorbent material having a dual particle size distribution in which the large particles have a mass median particle size of about 850 to about 1800 microns and the small particles have a mass median particle size of about 50 to about 200 microns. An absorbent composite comprising superabsorbent particles. The absorbent composite of claim 1, wherein the large particles have a mass median particle size of about 1000 to about 1600 microns. The absorbent composite of claim 1, wherein the small particles have a mass median particle size of about 65 to about 150 microns. The absorbent composite of claim 1, wherein the superabsorbent particles have a total mass median particle size of about 60 to about 1750 microns. The absorbent composite of claim 1, wherein the superabsorbent particles have a total mass median particle size of about 800 to about 1200 microns. The absorbent composite of claim 1, wherein the mass median particle size of the large particles and the mass median particle size of the small particles differ by at least about 500 microns. The absorbent composite of claim 6, wherein the ratio of the mass median particle size of the large particles to the mass median particle size of the small particles is from about 4: 1 to about 36: 1. 7. The absorbent composite of Claim 6 wherein the ratio of the mass median particle size of the large particles to the mass median particle size of the small particles is from about 6: 1 to about 25: 1. The absorbent composite of claim 6, wherein the mass median particle size of the large particles is about 1000 to about 1200 microns and the mass median particle size of the small particles is about 50 to about 150 microns. The absorbent composite of claim 6, wherein the mass median particle size of the large particles is about 1000 to about 1100 microns and the mass median particle size of the small particles is about 50 to about 100 microns. The absorbent composite of claim 1, wherein the mass ratio of large particles to small particles is about 90:10 to about 50:50. The absorbent composite of claim 1, wherein the mass ratio of large particles to small particles is about 90:10 to about 80:20. The absorbent composite of claim 1 wherein the mass ratio of large particles to small particles is about 85:15. The absorbent composite of claim 1, wherein the superabsorbent material is uniformly distributed within the absorbent composite. The absorbent composite of claim 1, wherein the absorbent composite comprises from about 20 wt% to about 100 wt% superabsorbent material. The absorbent composite of claim 1, wherein the absorbent composite comprises from about 30 wt% to about 90 wt% superabsorbent material. The absorbent composite of claim 1, further comprising a retention device. The absorbent composite of claim 16, wherein the retaining device is a fibrous matrix. The absorbent composite of claim 1, wherein the third liquid insulator suction time of the absorbent composite is less than about 100 seconds. The absorbent composite of claim 1, wherein the third liquid insulator suction time of the absorbent composite is less than about 85 seconds. The absorbent composite of claim 1, wherein the third liquid insulator suction time of the absorbent composite is less than about 60 seconds. The absorbent composite of claim 1, wherein the third intermittent vertical wicking pick-up time of the absorbent composite is less than about 600 seconds. The absorbent composite of claim 1, wherein the third intermittent vertical wicking pick-up time of the absorbent composite is less than about 300 seconds. The absorbent composite of claim 1, wherein the swelling time of the small particles is about 15 to about 35 seconds and the swelling time of the large particles is about 300 to about 700 seconds. The absorbent composite of claim 24, wherein the swelling time of the small particles is about 20 times shorter than the swelling time of the large particles. An absorbent composite comprising a superabsorbent material, the superabsorbent material comprising superabsorbent particles having a dual particle size distribution, wherein the third liquid insulator suction time of the absorbent composite is less than about 100 seconds. 27. The absorbent composite of Claim 26 wherein the third liquid insulator suction time of the absorbent composite is less than about 85 seconds. 27. The absorbent composite of Claim 26 wherein the third liquid insulator suction time of the absorbent composite is less than about 60 seconds. 27. The absorbent composite of Claim 26, wherein the third intermittent vertical wicking pick-up time of the absorbent composite is less than about 600 seconds. 27. The absorbent composite of Claim 26, wherein the third intermittent vertical wicking pick-up time of the absorbent composite is less than about 300 seconds. 27. The absorbent composite of Claim 26, wherein the superabsorbent material is uniformly distributed within the composite. 27. The absorbent composite of Claim 26, wherein the superabsorbent particles comprise small particles having a swelling time of about 15 to about 35 seconds and large particles having a swelling time of about 300 to about 700 seconds. 33. The absorbent composite of Claim 32, wherein the swelling time of the small particles is about 20 times shorter than the swelling time of the large particles. 27. The absorbent composite of Claim 26, wherein the superabsorbent particles comprise large particles having a mass median particle size of about 850 to about 1800 microns. 27. The absorbent composite of Claim 26, wherein the superabsorbent particles comprise small particles having a mass median particle size of about 50 to about 200 microns. 27. The absorbent composite of Claim 26, wherein the absorbent composite comprises from about 30% to about 90% by weight superabsorbent material. 27. The absorbent composite of Claim 26, wherein the mass ratio of large particles to small particles is from about 90:10 to about 50:50. An absorbent composite comprising a superabsorbent material, wherein the superabsorbent material is uniformly distributed within the composite, wherein the third liquid insulator suction time of the composite is less than about 100 seconds and the third intermittent vertical wicking pickup time is less than about 600 seconds. Absorbent composites. The absorbent composite of claim 38, wherein the third liquid insulator suction time of the absorbent composite is less than about 85 seconds. The absorbent composite of claim 38, wherein the third liquid insulator suction time of the absorbent composite is less than about 60 seconds. The absorbent composite of claim 38 wherein the third intermittent vertical wicking pick-up time of the absorbent composite is less than about 300 seconds. The absorbent composite of claim 38, wherein the absorbent composite comprises from about 20 wt% to about 100 wt% superabsorbent material. The absorbent composite of claim 38, wherein the absorbent composite comprises from about 30 wt% to about 90 wt% superabsorbent material. The absorbent composite of claim 38, further comprising a retaining device.