CA2264199A1 - Wet-laid material including water-sensitive particulate matter - Google Patents

Abstract

The present invention is directed to a novel article of manufacture which is an integrally formed sheet of wet-laid material, the sheet having a first major surface and a second major surface generally opposing the first major surface and a plurality of water-sensitive particles incorporated into the sheet. The particles are distributed between the first major surface and the second major surface along a pre-determined non-uniform distribution profile.

Description

WET-LAID MATERIAL INCLUDING WATER-SENSITIVE
PARTICULATE MATTER
FIELD OF THE INVENTION
The present invention relates to wet-laid materials, and specifically to such materials having particulate matter incorporated therein, particularly water-sensitive particulate matter.
io BACKGROUND OF THE INVENTION
Wet-laying is a common conventional method for producing integral structures of material from aqueous slurries, preferably material capable of being i 5 held together by hydrogen bonds (amongst other things). (See United States Path 5,300,192 to Hansen et al. column 11, lines 30 to 46, herein incorporated by reference for a description of hydrogen bonds and hydrogen bonding.) Structures/materials produced by a wet-laying procxss are referred to as wet-laid strucriueslmate<ials.
wet-laid struotu~/mataials hs~ne pbys~l hand propatiies that distinguish them from strut formed from other types of materials. For eRam~ple, wet-laid struduresJmateriais typically have much more hydrog~ bonding between the fibers/particles of the material than air-laid structures. Wet-laid structu~
therefore have increased cohesive strength over air-laid structures, making the wet-laid structures less likely to disintegrate. Thus structures formed from wet-laid materials are preferred in some applications.

- 2 -Materials comprising cellulose are an example of material capable of being held together by hydrogen bonds, and thus cellulosic material is typically employed in wet-laying processes. As an example, the production of paper and paper products s from wood pulp is a wet-laying process, and thus paper is an integrally formed wet-laid material. Another example is the fabrication of absorbent layers suitable for incorporation into sanitary absorbent products, such as feminine sanitary napkins.
Cellulosic materials, such as wood pulp and/or sphagnum moss, are employed in the fabrication of such layers, owing to the fact that such cellulosic materials are highly i o absorbent.
In the context of the fabrication of absorbent layers suitable for incorporation into sanitary absorbent products, it has been desired to incorporate particulate matter, and particularly water-sensitive particulate matter, into such structures. Most ~s notably, it has been desired to incorporate into these structures a class of materials comrentionally known as superabsorbents. Superabsmbeats are materials that are capable of absorbing many times their own weight in liquid, typically anywhere from 10 to 400 times their own weight. By incorporating superabsorbents into the absorbent layers of sanitary absorbent articles, highly absorbent wet-laid strucxures 2 o may be cxeated, and thus the aof cellulo~c material in the layer may be greatly reduoad. Thin lead: to absorbart layers which are n~iv~y mph unallQ
(typically in thickness), thaw layers that do not have supefabsorbeflt materials incorporated therein. Thinner absorbed articles are greatly preferred by the users of such articles, especially sanitary napkinsy and thus the incorporation of 2s superabsorbent materials in general, and into the absorbent layers thereof specifically, is now preferred.

- 3 -In order to perform their desired function, superabsorbent materials should be stable in water., i.e., they do not readily degrade when wet, nor are they water-soluble. However, superabsorbent particles do swell in water, owing to the absorption of the water, and thus form a gel.
s The difficxuy is that the fabrication of wet-laid materials incorporating water-swellable particulate matter involves the use of aqueous liquids, which is almost universally utilized in wet-laying processes. A wet-laying process typically proceeds in the following manner: First, a slurry of the desired material (in either i o fiber or particulate form) in water is produced. Next the shury is deposited on a foraminous support (such as a sceen), enabling a large majority of the free water to drain from the deposited material, herein referred to as an aggregation. The remaining water is then removed from the aggregation via mechanical means (such as pressing and/or by vacuum) and/or evaporation by subjecting the material to heat, 1 s forming the desired end product.
United States Patent 5,607,550 to Akers and European Patent Application 0,437,816 to Hoechst Celanese Corporation ("Hoechst") describe methods for fabricating a wet-laid absorbent lays of cellulosic material incorporating therein 2 o water-swellable supaseaarb~rt mata~ials (fibers iu the case of Akers and particles in the case of Iioec~t). ~ these methods, the superabsorberrt wss, ink alicS
:dmiaed into an aqueous shury with a cellulosic material, deposited on the foraminous support, and dried to form the wee-laid absorbent layer. These methods, however have sever$1 drawbadCa, owing to the water-swellable nature of superabsorbeat 2 s materials. The superabsorbent particles form a gel within the slurry, making the shury difficuh to agitate and maintain a consistent admixture. The gelled superabsorbent in the aggregation of cellulosic material deposited on the foraminous

- 4 -support hinders the drainage of water therethrough by clogging or blocking the holes in the screen. Furthermore, the aggregation requires a substantial amount of thermal energy in order to dry out the superabso~ent as well as the cellulosic material, significantly increasing the cost of the process. (By substantial it is meant that the aggregation will have to be subjected to a significantly higher amount of energy than would have been necessary if a gelled superabsorbent had not been present.) Finally, the superabsorbent will be present along a uniform distribution profile throughout the entire final superabsorbent layer thus formed. An absorbent structure having a uniform distribution profile is more likely to result in a phenomenon known in the 1 o art as gel blocking.
Gel blocking occurs when the uppermost layer of superabsorbent (i.e. the layer that is first contacted by water) swells (due to water absorbed) and such swelling prevents water from penetrating the swelled material and accessing the i5 unswelled superabsorbent material below. While some superabsorbents have recently been developed which exhibit a reduced tendency to gel block, it is nonetheless desirable to have an absorbent layer which contains superabsorbent, but where the superabsorbent is not present on or near the first water contacting surface of the absorbent layer, but instead is present at some depth therefrom, in order to 2 o reduce this problem.
European Patent Application 0,359,615 to lames River Corporation of Virginia ("James Rivel") describes a method for fabricating a composite structure comprising a wed-laid absorbed layer of cellulosic material having supe~~bsorbeat 2 5 particles dispersed over top thereof, and a cover layer. The cover layer may be made o~ amongst other materials, a wet laid cellulosic web. In accordance with the teachings of James River, the superabsorbent material is not admixed with the

- 5 -cellulosic material in the slurry, but is rather dispersed over the top of the aggregation of cellulosic material having been deposited on the foraminous support.
The dry cover layer is then placed over the top of the aggregation and the composite is pressed and dried. In this manner, a composite "sandwich-like structure"
may be s made.
The method described in James River is not, however, without its own drawbacks. Primarily, the composite structure described therein is laminar, as opposed to being integrally formed. Therefore, even if the dry cover layer is of the ~ o same composition as the layer formed by the (wet) aggregation of cellulosic materials, the bonds between the layers in the composite structure are not as strong as the bonds within each of the integrally formed layers. The layers of this composite are therefore subject to delamination, i.e. they may become separated, exposing the superabsorbent material therebetween.
As a result, there is therefore a need in the industry to provide for an i~egrally formed structure com~ising wet-laid material having water-sensitive particulate matter incorporated therein along a desired (i. e. non-random) non-uniform distribution profile, and method of production of same.
' 'lbare is also more ~e~lty a need in the Industry t0 provide far an integrally formed structure being an absorbent layer suitable for incorporating into a sanitary absorbent product, comprising cellulosic material having superabsorbent incorporated therein along a desired (i.e. non-random) noa-uniform distn 2 s profile, and a method for the production of same.
CAN-1 ~l I

- 6 -Moreover, absorbent layers are not the only applications for integrally formed structures of cellulosic material. An additional application is the fabrication of a plant seed germination mat. A plant seed germination mat is conventionally a layered structure typically comprising two (or more) sheets of material (typically air-s laid cotton or air-laid wood pulp) having plant seeds and adhesive therebetween.
The mats are placed upon soil and watered. The seeds germinate and grow. For various reasons, it would be desirable to fabricate an irnegrally formed structure simply having plant seeds incorporated therein (as opposed to a layered structure).
Given that conventional mats lack cohesive strength and therefore rapidly i o disintegrate, it would be desirable to produce a wet-laid product.
Prior to the present invention, conventional belief was the plant seeds could not be incorporated into a wet-laid process. Proceeding as described in Akers for example, would require placing the plain seeds in the slurry with the cellulosic ~ s material. Unfortunately, in so doing, the plant seeds would absorb the water, sof~eaing up their protecxive seed coats in preparation for germination. The seeds would then die either during the downstream processing of the mat (i.e.
drying) or simply through storage after 'its completion. In this respect, seeds are water sensitive particulate, yet, they exhibit a different type of water sensitivity than 2 o supa~ab'orbe~s. Supelabsorbertt patio ~pa~ng on the type, may be dried by them to ene~r (e.g. thermat am~r) without degadin~ or o4hawise changing the particles themselves. Their reaction with water may therefore be reversed. Unlike superabsortiems, however, the reaction of plant seeds with water is not rev~'ble by drying, or by any other step in the downstream processing of the 2 5 aggregation, or by any other step that might be incorporated into that process. The process described in Akers is therefore highly unpreferred in plant seed germination mats. Furthermore, proceeding as descn'bed in James River, would produce a composite structure, albeit wet-laid, such structure would require adhesive, be subject to delamination, and be more expensive to manufacture.
Another additional application for integral structures of cellulosic material is s the fabrication of a fertilizer mat. Fertilizer mats are similar to plain seed germination mats except that they contain fertilizer as opposed to plant seeds.
Typically they are placed in the soil of a pot (amend growing potted plant) and watered. The fertilizer therein is water-soluble and thus during watering some dissolves and is carried imo the soil, below becoming available to the plant.
io As was the case the plant seeds, prior to the present invention, conve~ional belief was the water-soluble fertilizer could not be incorporated into a wet-laid process. Water-soluble particles exhibit another type of water sensitivity than plant seeds or superabsorbern. Proceeding as described in Akers for example, would ~ s require placing the fertilizer in the shury with the cellulosic material.
Unfortunately in doing so, the fertilize: would simply dissolve in the water, and would be carried away with the water once the shury was deposited on the foraminous support.
Proceeding as described in James River, would produce a composite structure requiring adhesive and subject to delamination.
Thane is therefore a god in the industry to provide as imegrally formed wet-laid structure material generally (as opposed to simply an absorbent layer for a sanitary absorbent article) having water-sensitive particulate matter incorporated t6a~ern and particailarly water serve material having a 'ion-reversrbk"
reaction 2 s with water), and a method for the producing of same.

_ g _ OBJECTS AND STATEMENT OF THE INVENTION
It is an object of the present invention to provide an integrally formed s structure of wet-laid material (and particularly cellulosic material) having water-sensitive particulate matter incorporated therein. It is a fiuther object of the present invention to provide a method of production of same.
It is a another object of the preset inve~ion to provide an integrally formed i o structure being an absorbent layer suitable for incorporating into a sanitary absorbent article comprising cellulosic material having superabsorbent incorporated therein along a predetermined non-uniform distribution profile. It is still a further object of the present invention to provide a method of production of same.
i s As embodied and broadly described herein the present invention provides an article of manufacture comprising:
(A) an integrally formed sheet of wet-laid mataisl, said sheet having a first major surface and a second major surface generally opposing the first major surface; and 2 0 (B) a phnality of water-sensitive p~esticdes isoo~po~a~vd i~r said shoat, said particles being distn'buted between the first major toe and the second major surface along a pre-detemined non-uniform (i.e.
heterogenous) distribution profile.
2 s In accordance with the teachings of the preset invention a wide array of articles of manufacture may be manufachired. For example, within its scope are absorbent strut suitable for incorporation into sanitary absorbent articles, _ g _ absorbent structures suitable for the manufacture of animal litter, plant seed germination mats, fertilizer mats, and a variety of other articles.
By the term "sheet" it is meant an expanse of material, the dimensions of s which in two directions (i.e. length and width) are both relatively greater than in the third (i.e. thickness or depth). The sheet will thus have two major surfaces, a first major surface and a second major surface. Preferably, each major surface is planar and generally parallel to the axes along which the length and width of the article are measured. It should be understood however, that while it is preferred that the major i o s~ufaces of the article are substantially flat, such need not necessarily be the case.
Articles having first and second major surfaces having undulations and the like are also with the scope of the present inve~ion.
Sheets of the present inve~ion are structurally-integral and are integrally-i5 formed. By integrally formed, it is meant that substantially all of the material forming part of the sheet is added d~uing the sheet's fabrication in a wet state, and preferably from a slurry, so that hydrogen bonds are established through the material. Such sheets manifest a greatly reduced tendency to deiaminate, as compared with non-integrally furn~ed s~tru. Stru~res which are formed from 20 ~n or more trot hive i~,r~par~y formed and then a~dl~od togetb~r to foam s coo~oaite ~tmi~e ehuc~re (~.e. non int~lly-formed structures) sre n~
within the scope of the invention. Nor are structures wherein one or more of the componeltt layers has been dried before forming part of the laminate (such as the strucxure descn'bed in James River).
Preferably the wet-laid material is cellulosic material. The term cellulosic material should be understood as encompassing both cellulosic fibers and cellulosic particulate material. Non-limiting examples of cellulosic material thus include: all types of wood pulp, cotton linters, bagasse, flax, jute, straw, bamboo, esparto, grass, sphagnum, etc. Cellulose is the carbohydrate forming the main constituent of plant cell walls, and thus there are many types of plants that may be used to form s cellulosic materials, whether or not such plants are actually used to form such materials at the present time.
Preferably, and depending on the application to which the article will be put, the cellulosic material is wood pulp, sphagnum moss, or a combination of the two.
o Preferably, the wood pulp is Kraft wood pulp. These materials are relatively common and inexpensive. They have been widely used in the past and therefore there exists comrentional knowledge, wisdom, and experience with respect to their use. Sphagnum moss is generally much more absorbent than is wood pulp, and thus for applications where it is desired that the cellulosic material of the final article be highly absorbent, a mixture of a large part sphagnum moss and a small part wood ~rlp will be preferred.
Sheets of the present invention have incorporated therein a plurality of water-sen~tive particles along a desired non-uniform distribution profile. By '~rater-2 o x~tive" it is t6st tire particles sre not inert in water. Particle: that are not inert inchrde those that dissolve in water (eg common table sslt~ t6o'e that form a suspension in water (e.g. common clays), those that react chemically with wets, those that read biologically with water (e.g. plant seeds), and those that react physically; i.e. they change from a particle to a gel such as for example, 2s superabsorberrt particles will swell when they absorb water to form a gel .
This list of examples is not intended to be exhaustive and other non inert particles may exist that manifest a different reaction with wets, whether it be biological, chemical or physical than those described here. An example of a particle that is inert in water is a polyethylene fiber.
It should be understood that the water-sensitive particles of the present s invention may all be the same particle (in terms of chemical composition) or may be a mixhue of different particles (having different chemical compositions).
By a pre-determined non-uniform distribution profile it is meant that the presence and/or concentration of particles within the sheet varies in a desired to manner as one prod vertically (i.e. in the direction of the thickness of the sheet) from the first major surface to the second major surface. The actual profile will vary depending on the use to which the structure will be put and the particles that will be incorporated therein.
~5 It is preferred that the non-uniform distribution profile comprise:
(A) a first zone extending from the first major surface towards the second major surface, the first zone being substantially free of the particles;
(B) a second zone ceding from the first zone towards the second major surface, the second zone characte'rizxd by a pry of the particles;
(G~ a third zone eking from the sooond zone towards the ae~nd major , the third zone being substantially flee of the particles.
Distn'bution profiles of this type may be ooUoquiatly referred to as a 2 s "sandwich-type" distn'bution profile, because of the difference between the middle zone from the terminal zones. They are useful in that the zoo containing the particles (as thus the particles themselves) is protected from the environment by the two zones on either side (which do not contain particles).
In some situations it may be preferred that the non-uniform distribution s profile further comprise:
(D) a fourth zone extending from the third zone towards the second major surface, the fourth zone characterized by a substaatisl presence of said particles; and (E) a fifth zone extending from the fourth zone towards the second major i o surface, the fifth zone characterized by a substantial absence of said particles.
Distribution profiles of this type may be colloquially referred to as a "double-decker sandwich type" distribution profiles, owing to the alternation of the s pres~ce and absence of particles within the zones. They are of similar advantage as described above, except that they have the further advantage of having a single structure in which it is possible to have incorporated two different sets of particles that could not be admixed together (such as some seeds and some fertilizers).
2 o The pit i~reotion is not limited to 3 or 5 zones, but rather aouW include any number of such alternating zones.
In other pre~e~red embodiments, the non-uniform distribution profile comprises:
2 s (A) a first zone extending from the first major surface towards the second major surface, the first zone characterized by a presence of said particles; and (B) a second zone characterized by a substantial absence of said particles.
Preferably, the water-sensitive particles comprise a supe<absorbent material.
As has been previously described above, superabsorbent materials are those which s are capable of absorbing many times, preferably over 10, more preferably over 15, still more preferably over SO times, still more preferably over 100, and most preferably over 200 times their weight in water. Without the intent of being bound by the following definition, superabsorbent particles generally fall into three classes, namely starch graft copolymers, crosslinked carboxymethylcellulose derivatives and i o modified hydrophilic polyacxylates. Examples of such absorbent polymers are hydrolyzed starch-acrylonitrile copolymer graft copolymer, a n~tralized starch-acrylic acid graft copolymer, a saponified acrylic acid ester-vinyl acetate copolymer, a hydrolyzed acrylonitrile copolymer or acrylamide copolymer, a modified cross-liked polyvinyl alcohol, a neutralized self-crosslinking polyacrylic acid, a 1 s crosslinked polyacrylate salt, carboxylated cellulose, and a neutralized crosslinked isobutylene-malefic anhydride copolymer.
Most preferably, the article manufactured according to the present invention is an absorbent layer suitable for use in a sanitary absorbent article.
International 2o Patent Applicati~ WO 97/14383 to Roy et a~ pnvides examples of absorbent layers using sPhsg~m moan.
In another preferred form, the water-sensitive particles are plant seeds, and the article ma~fachued a~o~ing to the present invention is a plant seed 2s germination mat. Such a plant seed germination mat would comprise a structurally integral sheet of cellulosic material, preferably a mixture of sphagnum moss and wood pule (preferably Kraft), having incorporated therein a phuality of plant seeds.

As with other plant seed germination mats, a mat having the desired seeds therein would be selected, placed upon soil and watered, to start the seed gerrninatian process. Plant seed germination mats are described in more detail in commonly assigned co-pending International Patent Application PCT/CA98/00561.
In another aspect of the present invention, the particles to be incorporated are water-soluble, such as fertilizer.
In a preferred embodiment of the present invention, the water-sensitive 1 o particles to be incorporated form a suspension in water. By suspension it is meant that the particles, when in contact with water, break apart into much smaller particles of their constituent components and freely intermix with the water molecules.
Particles, however, which form a suspension in water to do not dissolve in water.
An example of such particles is a water-swellable clay.
As an example, ~rudut~ of the present invention wherein the cellulosic material comprises sphagnum moss and the water-sensitive particles form a suspension in water, such as a water-swellable clay, are useful as in the fabrication of animal litter. Animal litter is a particulate substance used typically to line a box 2 o where animals, and especially cats, can urinate and d~ecate indoors. 1n the manufs~u~e of animal litter, ores of the pit invention having clay incorporated therein are formed and then reduced i~o small Bake-like particles, preferably having a area of 0.5 cms or less per major .
2 5 Articles of manufacture in accordance with the teachings of the present inve~ion have several advantages over those of the prior art. Primarily they are struchwally integral. They are not laminate composite structures and do not require adhesives or other binders present to hold various layers together. They are therefore not subject to delamination or some other forms of loss of cohesion to which non-integrally formed structures are subject.
Another particular benefit provided by the present invention is that it allows for positioning of a zone (or zones) of particulate material within the structure at a certain distance (or at certain distances) from the first and/or second major surfaces, or from other internal zones. This can be relatively easily accomplished by varying the thickness of each of the zones, by having more wet-laid material in zones desired 1 o to be thicker and less wet-laid material in zones desired to be thinner.
As an example, where the structure is destined to become an absorbent layer for a sanitary absorbent article, and it is desired to have superabsorbent particles incorporated therein, it is preferred that the second zone (containing the 15 superabsorbent) be closer to the second major surface than the first major surface.
Thus, the first mne will act as a fluid capture and distribution zone in that it will absorb and preferably distribute the fluid to be absorbed by the layer throughout the layer. T6e second zone will act as a reservoir zone in that, with its superabsorbent particles; it wfll absorb and retain a large majority of the fluid to be absorbed by the 2 0 layer. F'm~lly, the third zone will act as a sub~te mne in that it will act as a ~ppos~ n~la~riat for the superabsorbent and will also absorb any stray fluid that $ to a through the reservoir (second) zone. Therefore during the fabrication of the structure (described in further detail below), the amount of material added whey forming the first (uppermost) zone is gre:~r than that added 2 s when forming the third (lowermost) zone. In this manner, if gel blocking does occur, there is a substantial portion of the structure above the second zone, which can itself absorb quantities of fluid.

In another aspect, as embodied and broadly described herein, the present invention provides a method for producing a sheet of wet-laid material having water-sensitive particles incorporated therein, the method comprising the steps:
(A) providing a first slurry comprising a liquid and particulate material in suspension in the liquid;
(B) dispensing at least a portion of the first slurry on a foraminous support to form a first aggregation of the material;
(C) dispensing the water-sensitive particles (while in a dry condition) i o onto the first aggregation;
(D) providing a second slurry comprising a liquid and material; and (E) dispensing at least a portion of the second slurry on the first aggregation to form the sheet.
1 s In the context of the present specification the water-sensitive particles should be considered to be in a dry condition when the have not been exposed to water, or have only been exposed to a small amour of water relative to the maximum amount of water with which the particles could react.
2 o In a specific examples the proOn of sn article of manufacture of the preaeat invention begins with the provision of a first s co QTY ~~8 ~' 8nd a partiwlate material in suspension in the water. The particx~latte material is any material capable of being wei-laid, and preferably comprises cellulosic material, and more preferably comprises a cellulosic material selected from the group consisting 2 s of wood pulp, sphagnum moss, and a mixture of wood pulp and sphagnum moss.
The expression "particulate" is not intended to comrey any limitation on the shape of the particles. For instance, fibers that are characterized by a geometrical extension in a certain direction are considered to be particles herein.
The preparation of the shury is according to conventional methods. In this s respell where cellulosic material is sphagnum moss for example, a mother slurry is prepared using raw sphagnum moss material in water. Preferably, the mother shury is wet classified to retain only the sphagnum moss particles having a size in the range from about 74 micros to about 2000 microns. The screened fraction is then diluted with water to rends the sherry more manageable. Optionally, wood pulp, i o polyester fibers, surfactants, etc. may be admixed with the sphagnum in the slurry, as is known in the art.
The aqueous shury is then deposited on a foraminous support such as a Fourdrinier wire. The foraminous support will act as a strainer or fiher and will ~ s retain the particulate material but will allow the water of the slunry to pass through.
In this way, an aggregation of material will be formed. The shury is generally (alt6o~ugh not always) edually distributed across the foraminous support, and thus the aggregation will typically have the appearance of a wet sheet of material.
2 o Water-serve pme tlma dispe~od on top of the agg<eg~on. The particles may be dispensod in accordance with a desired pattern (in the length-width plane of the anion (i.e. that plane parallel to the foraminous support) onto which they are being disposed) or they may be randomly dispensed in that plane.
Either pat~ned or random dispersemeat may be preferred, depending on the use to 2s which the final article will be put. As an example, where the final article is an absorbent layer contai~ng superabsorbent to be incorporated imo a sanitary absorbent article, it is sufficient that the superabsorbent be dispensed randomly on the aggregation. (It is preferred however that it be dispensed so as to have a relatively constant density per unit surface area over which it is being dispensed.) Where, however, the article is a plant seed germination mat, it may be desired to dispense the seeds in a particular pattern such that the plants that mature from the s seeds have that pattern.
A second slurry is also provided. The s0oond slurry may be the same as the first sherry or may be a different slurry. If it is the latter, the second slurry may comprise identical substituent components as the first slurry or may have the same o components in a different ratio, or partially or wholly different components. The second slurry is deposited on the foraminous support bathing the particles and the aggregation formed from the deposit of the first shury.
Once again, the foraminous support will act as a strainer and maintain the l s material but will allow the water of the slurry to pass through. In this way, a larger aggregation of material will be formed. This agg~reg~ion will also have the appearance of a wet sheet of material.
It should be noted that the amount of the second shury, and thus the amount 2 0 of material contained therein, which is deposited on the first aggregation may vary.
Depending upon the ~e and comb of the particles, eaoug6 material may be d~sited such that the particles are completely sturoimded by the material and material is present theteabove in which there are no particles. In such cases, the particles are completely encapsulated by the mstaial. Ahernatively, the amount of 2 s material deposited may be selected such that the particles are just completely covered and have no "extra" material thereabove. Further still, the amount of material may be selected such that the particles are rbt completely covered, and although being partially embedded in the material, have a portion which remains uncovered. Where the particles of are of different sizes, it may be possible to have certain particles be covered and others remaining uncovered.
Preferably, the free liquid, i.e. that liquid not absorbed or adsorbed by the material, is then removed from the aggregation to the greatest extent possible. This may be accompfished by passive means, i.e. simply allowing the aggregation to stand for a period of time necessary for the free liquid to drain by gravity from the aggregation. More likely, however, acxive means will be employed. Active means o include subjecting the aggregation to a negative pressure differential (e.g.
a partial vacuum) or in some cases pressing the aggregation or otherwise subjecting it to mechanical pressure. Case must be taken, however, so that if active means are employed, the active means do not cause the particulate matter to egress the aggregation, nor destroy the particle nor otherwise render it unsuitable for the i s purpose for which it is mended. The sheets are typically not dried to a moisture content of 0'/e, but rather Somewhere in the range of 5-25% moisture ate, depending of the partiailar use to which the final product will be put.
T6e pre~nt inventors have determined that, despite comrentional belie!; it is 2 0 possible to incorporate water Sensitive products i~o a wet-laying process.
By procee~g as described aboves despite the fad that the water Sensitive particles are bathed in water, the free water is removed quickly enough such that they retain the characteristics they manifest in a dry condition to a large extent.
2 s For exaatple, where the water sensitive particles are water soluble, the free water is withdrawn fast enough such that enough of the particle remains undissolved to remain useful in the finished article. Additionally, it is possible to undertake corrective means to compensate for the loss of material due to dissolution in water.
For example, a particle having a greater mass than is necessary in the final product could be dispersed over the first aggregation and when bathed in the shury water from the second slurry would dissolve to such an extent so as to yield a particle of the desired mass (or size, etc.) Alternatively, the total mass (or amount) of particles could be increased to compensate.
Another compensating measure is to aher the time that the particles are actually in contact with free water. The water sensitive particles employed in the i o present invention, each have a sensitization time to water. That is to say that there is a period of time which it takes for the particles to begin reacting with the water, whatever that reaction may be. For example, if the particles are water-soluble, there is a period of time which it will take for the particles to begin dissolving.
i 5 Preferably, the final step in the process is to dry the aggregation to form a sheet. This is accomplished by subjecting the aggregation to energy, preferably thermal energy (i.e. heat). Care must be taken, however, not to subject the aggregation to an amount of energy which would directly or indirectly (e.g. by raising the temperature of the aggregation) degrade the particulate matter or render it 2 o useless for the purpose for which it is mended. For instance, where the article is a plant seed germination mat, the i~ernal temperature of the aggregation should not exceed approximately 110°C, the temperature above which the seeds may be killed.
Where the particles are superabsot~e~, care must be taken not to raise the temperature to a point at which the superabsorbe~ would degrade or break down.

BRIEF DESCRIPTION OF THE DRAWINGS
A detailed described of preferred embodiments of the present invention is provided hereinbelow with reference to the following drawings, in which:
Figure 1 is a front perspective view of a first embodiment of an article of manufacture of the present invention being an absorbent structure suitable for use in a sanitary absorbent article;
i o Figure 2 is a cross-sectional view of the article of Figure 1 taken along the line 2-2;
Figure 3 is a front perspective view of the article, similar to Figure 1, except having a portion of the article removed to reveal the particulate matter, wherein the 1 s particulate matter has been randomly dispersed;
Figure 4 is a front perspective view of the article, similar to Figures 1 & 3, except having a portion of the article removed to reveal the particulate matter, wherein the particulate master has been dispersed in a pre-determined pattern;
Figure 5 is an illustration of the process used to manufacture the several embodiments of the present invention;
Figure 6 is a cxoss-sectional view similar to Figure 2, of a second 2 s embodiment of the present invention;

Figure 7 is a cross-sectional view similar to Figure 2, of a third embodiment of the present invention;
Figure 8 is a cross-sectional view similar to Figure 2, of a fourth embodiment s of the present invention;
Figure 9 is a cross-sectional view similar to Figure 2, of a fifth embodiment of the present invention;
Figure 10 is a cross-sectional view similar to Figure 2, of a sixth embodiment of the present invemion;
Figure 11 is an illustration of the process, similar to Figure 5, used to manufacture the fourth, fifth and sixth embodiments of the present invention;
and Figure 12 is a cross-sectional view similar to Figure 2, of a sevemh embodiment of the present invention, being plant seed germination mat.
In the drawings, preferred embodiments of the invention are illustrated by 2 o way of example. It is to be expressly understood that the description and drawings are only for purpo~s of illustration and as aid to understanding, and are not intended to be a definition of the limits of the invention.
DETAILED DESCRIPZTON OF PR;EFERRm EMBOD111~iENTS
Absorbem Structures Suitable for Use in Sanitary Absorbent Articles (3-Zone Structure) Referring to Fig. 1, in its most preferred embodiment the present invention comprises an absorbent structure 20 suitable for use in a disposible sanitary absorbent article. Sanitary absorbent articles are those which are intended to be placed against the body of a human (or animal) and to absorb and retain bodily s exudate emanating therefrom. They are in almost all cases intended to be disposed of after a single use; that is, they are not intended to be laundered or otherwise regenerated, and reused.
The absorbent stmcture shown in Fig. 1 is in the shape of a square. This to shape has been chosen merely for purposes of convenience of illustration.
It is possible to fabricate such absorbent strurxures in any number of a variety of shapes including rectangular, square, oval, hour-glass, dog-bone, ~c.
The absorbent structure 20 shown in Fig. 1 has a first major surface 22 and i s an opposing second major surface 24. The structure 20 has a length 26 and a width 28, both of which are measured within a plane generally parallel to that of the first major surface 22 and the second major surface 24. In Fig. 1 the length 26 and the width 28 have been shown as being measured along the second major surface 24.
2 o The strudune 20 also has a depth (or thickness or caliper) 30 that is me$sured between the first major surface 22 and the second major surface 24, perpendicular to the plane containing the length 26 and the width 28. While the structure 20 is not necessarily shown to scale, and may be of various dimensions, the length 26 and the width 28 exceed the depth 30 by a relatively great amount.
2s As shown in Figs. 1 & 2, the structure 20 comprises a structurally integral wet-laid sheet comprising cellulosic material 32. The cellulosic material 32 preferably employed is a mixture of sphagnum moss particles and Kraft wood pulp fibers; preferably in the proportion of 20% Kraft and 80% Sphagnum moss. The sheet has a total basis weight of approximately 250 g/m2, including a moisture content of approximately 12% and 50 g/mZ of particle mass. Thus, the cellulosic material comprises about 24 g/mZ of water, about 3 S g/m2 Kraft wood pulp, and about 141 g/m2 Sphagnum moss. In some embodiments intermixed with the cellulosic material may be polyester fibres of up to 4% (by weight) of the other solid components.
1 o The sheet 20 is held together by mechanical entanglement and hydrogen bonding between its constituent elements. Incorporated into the sheet 20 are a plurality of water-sensitive particles 34, preferably superabso~fie~
particles, more preferably a ration-sodium cross-linked polyacrylate such as the product sold in granular form under the designation ASAP 2000 by Chemdal Inc. of Paltine, Illinois, USA.
The distribution profile of the particles 34 is non-uniform. As one progresses along the depth 30 of the structure 20 from the first major surface toward the second major surface 24, there is a first zone 36a which is substantially 2 o free of particles 34, a second zone 36b in which the particles 34 are concentrated, and finally a third zone 36c which is substantially free of particles 34.
Referring to Fig. 3, it can been seen that the particles are randomly dispersed in the length-width plane of the article (i. e. in the plane parallel to that in which the 2 5 length and width are measured. In the present embodiment, they simply are distributed so as have a basis weight of 50 g/m2. Alternatively, as shown in Fig. 4, in other embodiments, they may be dispersed in a desired pattern, with no particular pattern being essential to the present invention.
Referring to Fig. 5, the apparatus used for the fabrication of the structure s is similar to that used in the fabrication of paper from wood pulp. The manufacturing apparatus 100, comprises an endless, fluid-pervious Fourdrinier wire 102 which is mounted on rollers 104 to provide a horizontally extending run that is continuously advanced forward (at an approximate speed of 1.5 m/min) to support and convey a slurry of cellulosic material through various processing 1 o stations.
Headboxes 110, 114 are arranged in a spaced apart relationship along the path of travel of the wire 102. Intermediate the headboxes 110, 114, and spaced apart therefrom, is a particle dispersion unit, preferrably a vibrating conveyor. The I5 distance between the outlet 110a, from the first headbox 110 to that 112a of the particle dispersion unit 112 is approximately 0.5 m, while that between the particle dispersion unit 112 and the second headbox 114 outlet 114a is also approximately 0.5 m. The time that it takes a particular point on the Foundrinier 102 to travel between the first headbox 110 and the particle dispersion unit 112 is approximately 20 20 s, and between the particle dispersion unit I12 and the second headbox 114 is approximately 20 s.
Provided to the first headbox 110 is a shury consisting of water and solid particles, the particles being 0.2% by weight of the slurry. Specifically the solids are 2 s admixed sphagnum moss particles and Kraft wood fibers in a 4:1 ratio. A
similar slurry is provided to headbox 114.

Provided to the particle dispersion unit, are the granules of the ASAP 2000 superabsorbent described above.
As illustrated in Fig. S, the slurry from the first headbox 110 is laid down oa s the wire 102. The slurry flow rate is selected to deliver about 88 grams of solid per square meter (g/m2), to form an aggregation of cellulosic material (the first aggregation 116) (This flow rate has been selected such that if the first aggregation were dried to approximately 12% moisture content it would have a basis weight of about 100 g/m2). The first aggregation 116 then passes over a vacuum slot 118 to which subjects the first aggregation to a negative pressure differential to remove the majority of the free water that has not simply drained through the Fourdrinier 102.
The pressure differential of the vacuum slot is approximately -b.2 kPa (from atmospheric pressure). The residence time of the vacuum slot 118 (i. e. the time that any particular point on the Fourdrinier 102 takes to pass over the vacuum slot) is ~s approximately 18 s. After the first aggregation leaves the vacuum slot 118 and as it encounters the particle dispersion unit 112, there is litxle free water therein.
The first aggregation 116 then passes under the particle dispersion unit 112.
The particle dispersion unit is configured to deliver particles so as yield 50 g/m2 on 2 o the first aggregation. The particles are uniformly distributed over the first aggregation.
The first aggregation (overlaid with particles) 116 then passes under headbox 114, which lays a second slurry thereover. The slurry flow raze is selected to 2 s deliver about 88 g/m2 (selected as before), to foam a (now twice the size) second aggregation 120 of, inter alia, cellulosic fibers and particles. The second aggregation now has a basis weight of approximately 226 g/m2 (on a dry weight basis). The second aggregation 120 then passes over a series of vacuum slots 122, 124 which each subject the second aggregation 120 to a negative pressure differential to remove the majority of free water that has not drained through the Fourdrinier 102. The pressure differential of the first vacuum slot 122 is approximately ~.2 kPa (from atmospheric pressure); the residence time about 18 s.
The pressure of the second vacuum slot 124 is between approximately -40 kPa and - 60 kPa (from atmospheric pressure); the residence time about 3 s.
The second aggregation 120 then preferably passes under a surfactant 1 o dispersion unit 126, which supplies surfactant in the form of a foam over the top thereof. The preferred surfactant is that sold by Boehme Filalex Canada Inc.
of St-Jean-sur-Richelieu, Quebec, Canada, under the designation G-60. The purpose of the surfactant is to impart a greater rapidity to the absorption of water by the final sheet formed from the aggregation. The addition of a surfactant is not critical to the ~ s fabrication of the sheet. If the surfactant is not added, the final sheet will simply not abso~ water as rapidly as if the surfactant had been added.
The second aggregation 120 then passes through a steam hood, which causes steam to pass through the second aggregation 120. The purpose of the steam is to 2 o prat the second aggregation before drying in order to render the drying process more efficient. Steam pre-heating, however, is not critical to the present invention;
and if it is not present the drying process will be less eglcient.
The second aggregation 120 then passes through a com~entional dryer 130 2 s (used for drying cellulosic products. Once leaving the dryer, the second aggregation 120 now the sheet 132, has a water content of approximately 12% on a per weight basis. Its basis weight is approximately 250 g/mZ (including the weight of the water-sensitive particles).
The sheet 120 is then ready for final processing which may including cutting, rolling, packaging, storage, etc. The absorbent structure 20 of the present invention is cut from the sheet 120 by conventional means, die cutting being preferred.
With reference back to Fig. 1, it can be seen than that the material that comprises the third zones 36c of the structure 20 is that laid down from the first 1 o headbox 110, similarly the water sensitive particles are those dispensed from dispensing unit 112, and finally, the material that comprises the first 36a and second zones 36b is that laid down from the second headbox 114.
(2-Zone Strucxure) Referring to Figs. 6 & 7, the process and apparatus described in Figure 5 may be used to produce alternative embodiments, which may or may not be preferred depending on the use to which the article will be put. In Fig. 6, there is shown an embodiment in which only a sufficient quantity of material has been 2 o deposited from the second headbox 114 to cover the particles 634. Thus, there is no zone above the particles having a substantial absence thereof. This embodiment has only a first zone 636a having a presence of the particles 634 and a second zone 636b having an absence of particles.
2s Similarly, in the embodiment in Fig. 7, there is shown an embodiment in which the quantity of material from the second headbox is only sufficient to partially cover the particles 734. Thus, there is a portion of the particles 734 that extends from the first surface 722 of the article 720. This embodiment also, therefore only has a first zone 736a having a presence of particles 734 and a second zone 736 having an absence of particles.
(5-Zone Structure) In Fig. 8 of the present invention there is shown another alternate embodiment of the present invention, also in the form of an absorbent structure 820 suitable for use in a sanitary absorbent article, generally similar to that described 1 o above.
The absorbern structure 820 shown in Fig. 8 also has a first major surface 822 and an opposing second major surface 824. The structure 820 has a length (not shown) and a width (not shown), both of which are measured within a plane i s generally parallel to that of the first major surface 822 and the second major surface 824. The structure 820 also has a depth (~ thickness) 830 that is mbetween the first major surface 822 and the second major surface 824, perpendicular to the plane containing the length 826 and the width 28. While the structure 820 is not necessarily shown to scale, and may be of various dimensions, the length 826 and 2 o the width 828 exceed the depth 830.
As shown in Fig. 8, the structure 820 comprises an integrrally-formed wet-laid cellulosic material 832. The cellulosic material 832 preferably employed is a mixture of spbagnum moss particles and Kraft wood pulp fibers; preferably in the 2 s proportion of 20'/o Kraft and 80% Sphagnum moss. The sheet has a basis weight of approximately 400 g/m2, including a moisture content of approximately 12% and the mass of the particles. Thus, the cellulosic material (having an overall basis weight CAN-I I I

of 300 g/m2) comprises about 36 g/mz of water, about 53 g/mz Kraft wood pulp, and about 211 g/mz Sphagnum moss. In some embodiments intermixed with the cellulosic material may be polyester fibres of up to 4% (by weight) of the other solid components.
s 'The sheet 820 is held together by mechanical entanglement and hydrogen bonding between its constituent elements. Incorporated into the sheet 820 are a plurality of water-sensitive particles 834, preferably superabsorbent particles, more preferably the ASAP 2000 granules described above. The particles 834 have an overall basis weight of 100 g/m2.
The distribution profile of the particles 834 is noa-uniform. As one progresses along the depth 830 of the structure 820 from the first major surface 822 toward the second major surface 824, there is a first zone 836a having a substantial is absence of particles 834, a second zone 836b in which generally particles 834a are present, a third zone 836c having a substa~ial absence of pawcles, a fourth zone 8364 in which generally particles 834b are present, and finally a fifth zone 836e having a substantial absence.
2 o The particle con~tration in the second zone 836b and in the fourth zone 8364, need not be equal to one another. Nor do the particles 834 themselves in the second zone 836b and the fourth zone 8364 need to be the same or in the same proportions (if the particles are admixtures of more than one type of particles.) 2 s It should further be understood that the number of zones is in no way limited to five (5). It would be possible to have a structure with further alternating zones of substantial absence of particles and those having a presence of particles.

Figs. 9 & 10 show alternate 4-zone structures of this embodiment similar to the 2-zone structures shown in Figs. 6 & 7 in relation to the 3-zone embodiment.
s Referring to Fig. 11, the apparatus used for the fabrication of the structure 820 is similar to that described hereinabove in relation to Fig. 8. The manufacturing apparatus 1100, comprises an endless, fluid-pervious Fourdrinier wire I 102 which is mounted on rollers 1104 to provide a horizontally extending run 1106 that is continuously advanced forward (at an approximate speed of 1.5 m/min) to support ~ o and convey a slurry of cellulosic material through various processing stations.
Headboxes 1110, 1114, 1118 are arranged in a spaced apart relationship along the path of travel of the wire 1102. Intermediate the first and second headboxes 1110, 1114, and spaced apart therefrom, is a first particle dispersion unit.
~s Similarly, intermediate the second and third headboxes 1114, 1118, and spaced apart therefrom is a second particle dispersion unit 1116.
The distance between the outlet 1110a from the first headbox 1110 to that of the particle dispersion unit 1112 is approximately 0.5 m, while that between the 2 0 ~parricle dispersion unit 1112 and the second headbox 1114 is approximately 0. S rh.
Theali~ that it takes a particular point on the Foundrinier 1102 to travel between the flit~E~adbox 1110 and the particle dispersion unit 1112 is approximately 20 s, and between the particle dispersion unit 1112 and the outlet 1114a of the second headbox 1114 is approximately 20 s. The figures for the positioning and 2 s arrangement of second particle dispersion unit 1116 and the third headbox 1118 with respect to the second headbox 1114 are identical to these figures.

Provided to each of the headboxes 1110, 1114, 1118 is a slurry as described hereinabove in relation to the 3-zone embodiment. Similarly, provided to each of the particle dispersion units 1112, 1116 are superabsorbent particles also as described hereinabove in relation to the 3-zone embodiment.
As illustrated in Fig. 11, the slurry from the first headbox 1110 is laid down on the wire I 102. The shury flow rate is selected to deliver about 88 grams of solid per square meter (g/m2), to form an aggregation of cellulosic material (the first aggregation 1120), which would have a basis weight of about 100 g/mZ if dried to a l 0 12% moisture content. The first aggregation 1120 then passes over a vacuum slot 1122 which subjects the first aggregation to a negative pressure differential to remove the majority of the free water that has not simply drained through the Fourdrinier 1102. The pressure dift'erential of the vacuum slot 1122 is approximately -6.2 kPa (from atmospheric pressure). The residence time of the 1 s vacuum slot 1 I 22 (i. e. the time that any particular point on the Fourdrinier 1102 takes to pass over the vacuum slot 1122) is approximately 18 s. After the first aggregation l I20 leaves the vacuum slot 1122 and as it encounters the particle dispersion unit 1112.
2 o The first aggreg~ion 1120 then passes under the first particle dispersion unit 1112. The particle dispersion unit is configured to deliver particles at a rate to form a layer having a basis weight of 50 g/mZ.
The fn-st aggregation (overlaid with particles) 1120 then passes under the 2 s second headbox 1114, which lays a second slurry thereover. The slurry flow rate is selected to deliver about 88 g/m2, to form a (now twice the size) second aggregation 1124 of cellulosic material and particles. The second aggregation now has a basis weight of approximately 176 g/m2 (on a dry weight basis). The second aggegation 1124 then passes over a vacuum slot 1126 which subjects the second aggregation 1124 to a negative pressure differential to remove the majority of the free water that has not simply drained through the Fourdrinier 1102. The pressure differential of s the vacuum slot 1126 is approximately -6.2 kPa (from atmospheric pressure).
The residence time of the vacuum slot 1126 is approximately 18 s. After the second aggregation 1124 leaves the vacuum slot 1126 and as it encounters the second particle dispersion unit 1116.
1 o The second aggregation 1124 then passes under the second particle dispersion unit 1116. The second particle dispersion unit 1116 is configured to deliver particles at a rate to form a layer having a basis weight of 50 g/mz.
The second aggregation (overlaid with particles) 1124 then passes under 1 s headbox 1118, which lays a third slurry thereover. The shury flow rate is selected to deliver about 88 g/mZ, to form a (now even larger) third aggregation 1128 of cellulosic fibers and particles. The third aggregation 1128 now has a basis weight of approximately 264 g/m2 (on a dry weight basis). The third aggregation 1128 then passes over a series of vacuum slots 1130, 1132, which subject the third aggregation 2 0 1128 to a negative pressure differential to remove the majority of free water that has not drained through the Fourdrinier 1102. The pressure of the first vacuum slot 1130 is approximately is approximately -6.2 kPa (from atmospheric); the residence time about 18 s. The ire of the second vacuum slot 1132 is between approximately -40 kPA and -b0 kPa (from atmospheric); the residence time about 2 5 S.

The downstream processing of the third aggregation 1128 to form a sheet is as described above.
With reference back to Fig. 8, it can be seen than that the material that s comprises the fifth zone 836e of the structure 820 is that laid down from the first headbox 1110, similarly the water sensitive particles 834b are those dispensed from first dispensing unit 1112, the material that comprises the third 636c and fourth 636b zones is that laid down from the second headbox 1114, the water sensitive particles 834a are those dispensed from the second dispensing unit 1116, and finally, the io material that comprises the first 636a and second 636b zones is that laid down from the third headbox 1118.
Plant Seed Germination Mats 1 s Referring to Fig. 12, in an alternate embodiment the preset invention comprises a plant seed germination mat. The mat IZ20 comprises a structurally integral, integrally formed wet-laid sheet comprising cellulosic material, preferably a mixture of sphagnum moss particles and Kraft wood pulp fibers in a 4.1 ratio (by weight including 12~/o water.). The sheet is held together by mechanical 2 o entanglement and hydrogen bonding between its consatuert elements.
Incorporated into the sheet are a phuality of water-~nsitive particles, namely plant seeds 1234.
The fabrication of the mat 1220 proceeds as descn'bed heranabove in reference to Fig. 5 with regard to an absorbent structure suitable for use in a sanitary 2 s absorbent article, with the following exceptions:

The headboxes 110, 114 each contain a slurry consisting of about 0.8% by weight solids being about 70-90% by weight sphagnum moss / about 30-10% by weight Kraft wood pulp, prepared as previously described. Intermediate the headboxes 110, 114, after vacuum slot 118, is a seed dispersion unit 112, which s supplies seeds.
A first shiny from the first headbox 110 is laid down upon the Fourdrinier 102. The flow rate of the slurry is selected to deliver about 9 to 90 grams of solids per square meter upon the wire, 45 grams of solid per square meter being most i o preferred. (So as to be capable of forming a layer having a basis weight of 50 grams per square meter (including approximately 12% water content.)) It is these solids is which will form the third zone 1236c of the structurally integral sphagnum layer 1232. The aggregation 116 of cellulosic material is passed over the vacuum slot 118 (pressure differential from atmospheric being about -6.2 kPa). Subsequently, seeds are randomly sprinkled upon the aggegation to yield a seed density of approximately 645 seedsJm2 (for flowering plant seeds), 30,000 seeds/mZ (for grass seeds), and 100-200 seeds/m2 (for vegetable plant seeds). Next, a second slurry (having a composition similar to the first) is laid down upon the first slurry/seed combination from the second headbox 114. The flow rate of the shury is selected to z o deliver between about 45 to 450 grams of solids per square meter. It is these solids which will form the first zone 1236a of the struc~ually integral sphagnum layer 1232. The preferred values for this flow rate are dependent upon the actual seeds to be incorporated into the mat, as the first zone 1236a must be capable of being penetrated by a shoot, yet preferably has a high enough basis weight to cover the zs entire seed. For small seeds (i.e. seeds with a diameter of less than 3 mm), the preferred flow rate is 135 grams of solids per square meter (yielding an first zone 1236a having a basis weight of 150 grams of solids per square meter (including approximately 12% water content)); for medium seeds (i.e. seeds with a diameter of between 3 and 12 mm), the preferred flow rate is 175 grams of solids per square meter (yielding a first zone 1236a having a basis weight of 200 grams of solids per square meter (including approximately 12% water content)); and for large seeds (i.e.
seeds with a diameter of greater than 12 mm), the preferred flow Late is 265 grams of solids per square meter (yielding an first zone 1236a having a basis weight of grams of solids per square meter (including approximately 12% water content)).
Examples of small seeds include varieties of the plants commonly known as chive, basil, marjoram, and dill. Those of medium seeds include varieties of the plants to commonly known as radishes and tomatoes. Those of large seeds include varieties of the plants commonly known as corn, peas, and squash.
A non-toxic surfactant and steam may optionally be applied as described above.
The resultant product is then manipulated as was described above (including passage over vacuum slot 118b) however, it is necessary to cont~nl the temperature of the dryer 120 so as preferably not to earceed about 110°C. The product may then be cut imo mats of a desired size and shape.
As descxi'bed hereinabove in relation to the absorbent stnx~ures for sanitary absorbent articles, it is within the scope of the present invention to fabricate plait seed germination mats having multiple particle containing zones (e.g a 5-zee mat).

Fertilizer Mats Not shown in the drawings (as it would be identical to Fig. 12), in yet another embodiment, the present invention provides a fertilizer mat_ A
fertilizer mat s is similar to a plant seed germination mat with the exception that the mat contains fertilizer as opposed to plant seeds. They are typically designed to be used with potted houseplants, and are thus likely to be circular and capable of fitting within a pot and around a growing plant. In use they are simply placed around the growing plarn and watered (as the plant is watered). Their purposes to provide a relatively i o simple means of providing the plant with required nutrients.
Such mats are fabricated in a manner ide~ical to that described above, with the obvious exception that the particle dispersion unit contains fertilizer as opposed to plant seeds. The preferred fertilizer is a slow-release polymer coated multi-1 s component f~ilizer such as that sold under the designation NUTRYON
(POLYON) by Pursell Industries of Sylaguala, Alabama, USA.
Although not shown in the drawings, it would be possible (before fiuthef treatment of the laminate) to add additional layers of seeds and sphagnum (in a similar manner to that described above) to produce plant seed germination mats 2 o having ahernating layers of sphagnum and seeds.
Animal Litter Not shown in the drawings (as it would like identical to Fig. 12), in yet 2 s another embodiment, the present invention provides an animal litter mat.
An animal litter mat is a mat that can be placed in a litter box to absorb the waste product of (typically domestic) animals.
Such mats are fabricated in a manner identical to that described above, with s the obvious exception that the particle dispersion unit contains typically cbmains clay as opposed to superabsorbent.
After manufacture, the mats may be severed into cubes of relatively small dimension (e.g. 1 cm3 or smaller) to form animal litter particle. (Which also may be 1 o placed in animal litter boxes for the same purpose.) The above description of preferred embodiments should not be interpreted in a limiting manner since other variations, modifications and refinements are possible within the spirit and scope of the present invention. The scope of the inve~ion is 1 s defined in the appended claims and their equivalents.
Su~absorbent Papg Figure 12 might also illustrate another embodiment of the present invention, 2 o superabsorbent paper. In such case the cellulosic 1232 comprises wood pulp, preFa~tbly Kraft wood pulp, and the particles 1234 are supe:abaorbeat particles, such as the ASAP 2000 descn'bed above. The paper 1220 is fabricated as described above.
2 s In one specific example, the paper 1220 has a total basis weight of about g/m2 on a dry weight basis. The wood pulp material of the first zone 1236a has basis weight about 30 g/mZ, while that of the second 1236b and third 1236c zones has a basis weight of 1 S g/mz. The particles 1234 have a basis weight of about 23 g/m2. (All on a dry weight basis.) In another example, the paper 220 has a total basis weight of about 80 g/mZ, the basis weight of the particles 1234 being about 35 g/m2. (The basis weights of the wood pulp are as described above.)

Claims (27)

-40-

1. An article of manufacture comprising:
(A) an integrally formed sheet of wet-laid material, said sheet having a first major surface and a second major surface generally opposing the first major surface; and (B) a plurality of water-sensitive particles incorporated into said sheet, said particles being distributed between the first major surface and the second major surface along a pre-determined non-uniform distribution profile.

2. An article of manufacture as recited in claim 1, comprising:
(A) a first zone extending from the first major surface towards the second major surface, the first zone being substantially free of said particles;
(B) a second zone extending from the first zone towards the second major the second zone characterized by a presence of said particles;
and (C) a third zone extending from the second zone towards the second major surface, the third zone being substantially free of said particles.

3. An article of manufacture as recited in claim 2, comprising:
(D) a fourth zone extending from the third zone towards the second major surface, the fourth zone characterized by a presence of said particles;
and (E) a fifth zone extending from the fourth zone towards the second major surface, the fifth zone being substantially free of said particles.

4. An article of manufacture as recited in claim 1, comprising:
(A) a first zone extending from the first major surface towards the second major surface, the first zone characterized by a presence of said particles; and (B) a second zone extending from the first zone towards the second major surface, the second zone being substantially free of said particles.

5. An article of manufacture as recited in claim 1, wherein said wet-laid material comprises cellulosic material.

6. An article of manufacture as recited in claim 5, wherein the cellulosic material is selected from the group consisting of wood pulp, sphagnum moss, and a mixture of wood pulp and sphagnum moss.

7. An article of manufacture as recited in claim 6, wherein said particles comprise a superabsorbent material.

8. An article of manufacture as recited in claim 7, wherein the article is an absorbent structure suitable for use in a sanitary absorbent article.

9. An article of manufacture as recited in claim 6, wherein said particles are plant seeds.

10. An article of manufacture as recited in claim 9, wherein the article is a plant seed germination mat.

11. An article of manufacture as recited in claim 6, wherein said particles are water-soluble.

12. An article of manufacture as recited in claim 11, wherein said particles are fertilizer.

13. An article of manufacture as recited in claim 6, wherein said particles form a suspension in water.

14. An article of manufacture as recited in claim 13, wherein said particles comprise clay.

15. An article of manufacture suitable for use as an absorbent structure in a sanitary absorbent article, the article comprising:
(A) an integrally formed sheet of wed-laid cellulosic material, said sheet having a first major surface and a second major surface generally opposing the first major surface; said sheet including:
(i) a fluid distribution zone extending from the first surface towards the second surface, (ii) a reservoir zone extending from the fluid distribution zone towards the second surface, and (iii) a substrate zone extending from the reservoir zone to the second surface;
(B) a plurality of superabsorbent particles incorporated into the reservoir zone of said sheet, the fluid distribution zone being substantially free of superabsorbent particles.

16. An article of manufacture as recited in claim 15, wherein the cellulosic material is selected from the group consisting of wood pulp, sphagnum moss, and a mixture of wood pulp and sphagnum moss.

17. A method for producing a sheet of wet-laid material having water-sensitive particles incorporated therein, the method comprising the steps:
(A) providing a first slurry comprising a liquid and particulate material in suspension in the liquid;
(B) dispensing at least a portion of the first slurry on a foraminous support to form a first aggregation of the particulate material;
(C) dispensing the water-sensitive particles onto the first aggregation;
(D) providing a second slurry comprising a liquid and particulate material in suspension in the liquid; and (E) dispensing at least a portion of the second slurry on the first aggregation to form the sheet.

18. A method for producing a sheet of wet-laid material as recited in claim 17, further comprising the steps of:
(F) mechanically removing substantially all of the free liquid from the sheet; and (G) imparting heat to the sheet to dry the sheet to a desired water content.

19. A method for producing a sheet of wet-laid material as recited in claim 18, wherein the second slurry is dispensed in an amount sufficient to completely cover the particles.

20. A method for producing a sheet of wet-laid material as recited in claim 18, wherein the second slurry is dispensed in an amount to leave the particles partially exposed.

21. A method as recited in claim 19 or claim 20, wherein the liquid of the first slurry and the liquid of the second slurry are water.

22. A method as recited in claim 21, wherein the particulate material of the first slurry and the particulate material of the second slurry are each cellulosic material.

23. A method as recited in claim 22, where the cellulosic material comprises a material selected from the group consisting of wood pulp and sphagnum moss.

24. A method as recited in claim 22, wherein the particles are dispersed randomly on the first aggregation of the cellulosic material.

25. A method as recited in claim 22, wherein the step of removing substantially all of the water from the sheet includes the step of subjecting the sheet to a pressure differential.

26. A method as recited in claim 22, wherein the particles are water-soluble.

27. A method as recited in claim 22, wherein the first water-sensitive particles form a suspension in water.