CZ20003303A3 - Absorption element exhibiting high capillary absorption for absorbing body liquids - Google Patents

Abstract

High capillary suction absorbent member absorbing bodily fluids such as urine includes at least one osmotic absorbent, preferably an absorbent polymer , forming a hydrogel, and a high surface area material a high capacity capillary suction. Capillary suction capacity is measured as the ability to absorb liquid in the high • capillary heights that generally occur when a member is placed in the absorbent article. Capillary suction capacity is in particular measured as the absorption capacity of the capillary member sorption, which is measured according to the capillary measurement method sorpce.

Description

High capillary suction absorbent member for absorbing body fluids

Technical field

The invention relates to high-capillary suction storage absorbent members for absorbing body fluids such as urine and menstrual flow. In particular, the present invention relates to absorbent articles having high capillary absorbency properties.

BACKGROUND OF THE INVENTION

The development of highly absorbent members for use as disposable diapers, incontinent pads, and panties and sanitary napkins such as sanitary napkins is of considerable commercial interest. Thinness of these products is a very desirable parameter. For example, thinner diapers are easier to wear, better fit under clothing, and less visible. They are also denser when still in their packaging, which means they are easier to carry and store. Their pack density also leads to lower distribution costs at the manufacturer and distributor, including the need for less storage space per unit per shelf.

The ability to provide thinner absorbent articles, such as diapers, has been a benefit resulting from the ability to develop relatively thin absorbent cores or structures that are capable of receiving and storing large amounts of discharged body fluids, particularly urine. In this regard, the use of certain absorbent polymers, often referred to as hydrogels, superabsorbents or hydrocolloid materials, was particularly important in this regard. See, for example, U.S. Patent 3,699,103 which discloses the use of such absorbent polymers (hereinafter referred to as hydrogel-forming absorbent polymers) in absorbent articles. Indeed, the development of thinner diapers has been a direct consequence of thinner absorbent cores which take advantage of the ability of these hydrogel-forming absorbent polymers to absorb large amounts of discharged body fluids, especially when used in combination with a fiber matrix. See, for example, U.S. Pat. Nos. 4,673,402 and 4,935,022, which disclose bilayer core structures comprising a fiber matrix and an absorbent core.

- 2 hydrogel-forming polymers, useful in forming thin, dense, not uncomfortable size diapers.

See also U.S. Pat. No. 5,562,646 and U.S. Pat. No. 5,599,335, both of which relate to absorbent cores comprising regions of high concentrations of the hydrogel-forming polymer, where the polymer forms a gel continuous liquid transporting zone upon swelling.

In addition to using hydrogel-forming absorbent polymers as primary components in absorbent article storage structures, the use of polymeric foam materials derived from high internal phase water-in-oil emulsions (HIPE materials) has also been reported. See U.S. Pat. Nos. 5,260,345, 5,387,207 and 5,560,222. Foam materials, particularly those designed to act as storage and redistribution components, have several advantages over storage structures including hydrogel-forming absorbent polymers in the foam. fiber matrix, including good wicking and liquid distribution parameters, high storage capacity under pressure, flexibility, etc.

The main focus of previous work on both hydrogel-forming absorbent polymers and HIPE foam was to maximize storage capacity in a relatively thin material. The hydrogel-forming absorbent polymer materials absorb the liquid and prevent leakage and keep the absorbent products dry. When liquid is absorbed in absorbent polymers, it is firmly retained therein by osmotic forces, helping to prevent rewetting of the upper layer of material previously absorbed by the urine, but the hydrogel-forming polymer itself has little ability to absorb liquid until the liquid is conveyed to its surface. This is especially true in the case of high capillary height when the liquid is present only in small capillaries. For example, conventional softwood pulp shows almost no suction at a capillary suction height of 100 cm. It is then not surprising that the mixture of pulp and hydrogel-forming polymer at 100 cm shows almost no uptake. Accordingly, instead of further development aimed at achieving high liquid storage capacity for thin materials, there is a continuing need to provide high storage capacity materials that also exhibit high capillary suction capability. Storage materials that exhibit high capillary suction capability allow drainage of other absorbent core materials, such as acquisition and distribution materials, one or both of which are typically included in the absorbent cores of the absorbent core.

- 3 products. By properly draining these other absorbent core components, these materials are better able to cope with further liquid intake from the user. In addition to high capillary suction capabilities in general, the ability to provide these capabilities at relatively high capillary suction heights is a particularly desirable property. Movement of liquid from the spur area, i.e. the crotch area of the article, to the front and rear of the article can provide the user with greater comfort when the article is wetted with the fluid. It is clear that the ability of the storage material to dewater other core components, particularly the distribution material, which wicks to high capillary heights by wicking, is particularly relevant to their function as absorbent materials in absorbent articles.

Therefore, it would be desirable to have the ability to provide a storage absorbent member having a high capillary suction capability, wherein the storage absorbent member would include a hydrogel-forming absorbent polymer or other material that would absorb liquids primarily by osmotic forces.

SUMMARY OF THE INVENTION

The present invention relates to absorbent members useful in storage, i.e. storage of body fluids such as urine. These storage absorbent members have a high capillary suction capability. For the purposes of this invention, capillary suction capability is measured by the ability of the members to absorb liquid at the high capillary pressures that generally occur when the member is placed in an absorbent article. In particular, capillary suction capacity is measured as the absorption capacity of a member by capillary sorption, as measured by the capillary sorption method described in the Test Methods section below.

Overview of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail by means of a drawing, in which the figures show the following:

Fig. 1 is an exploded perspective view of a diaper having an absorbent core that includes a high-capillary suction absorbent storage member of the present invention;

Figure 2a is an exploded perspective view of an example of a multilayer core to be incorporated into the diaper shown in Figure 1; Figure 2b is an exploded perspective view of another example of a multilayer core to be incorporated into the diaper Fig. 3 is a photomicrograph at a magnification of five hundred times an example of a high surface area polymeric foam usable in the absorbent articles of the present invention; Fig. 4 is a photomicrograph of a high surface area polymeric foam shown in Fig. 3; Fig. 5 is a photomicrograph of the absorbent absorbent member of the present invention comprising hydrogel-forming absorbent polymer particles and polymeric absorbent foam particles; Fig. 6 is a photomicrograph of the absorbent absorbent member of the present invention including hydrogel-absorbent absorbent polymer particles and acetate cell fibers. 7 is a photomicrograph of a storage absorbent member of the present invention including hydrogel-forming absorbent polymer particles and glass surface microfibers; FIG. 8A is a schematic view of a capillary sorption absorbency measuring apparatus of an absorbent member; Fig. 8B is an enlarged cross-sectional view of the glass pane shown generally in Fig. 8A. Fig. 8C is an enlarged cross-sectional view of the cylinder and piston assembly of the glass frit shown in Fig. 8B; Fig. 8D is an enlarged cross-sectional view of the piston of the cylinder and piston assembly shown in Fig. 8C; Fig. 9 is a schematic view of the apparatus; for forming a representative absorbent member according to the present invention, wherein the member comprises a mixture of polymeric foam particles and hydrogel-forming absorbent polymer particles; Fig. 10 is a schematic view of another apparatus for forming a representative absorbent member according to the present invention; a storage absorbent member formed using the apparatus shown in Figure 10.

DETAILED DESCRIPTION OF THE INVENTION

I. Definitions

As used herein, body fluid means in particular urine, menstrual discharge, vaginal discharge, sweat and faeces.

As used herein, the term absorbent core means a component of an absorbent article that is primarily responsible for the liquid handling properties of the article, including the uptake, transport, distribution and storage of body fluids. As such, the absorbent core generally does not include the topsheet or backsheet of the absorbent article.

As used herein, the term absorbent member means portions of the absorbent core that generally provide one or more liquid handling properties, for example, liquid acquisition, liquid distribution, liquid transport, liquid storage, etc. The absorbent member may comprise all or part of the absorbent core. the absorbent core may comprise one or more absorbent members. The storage absorbent member is a component or components of the absorbent core that function primarily to store absorbent liquids. As discussed above, the storage absorbent member may also function to distribute the liquid as a result of the vertical wick effect.

As used herein, the term layer means an absorbent member whose primary dimension is X-Y, i.e. along the length and width. It is to be understood that the term layer is not necessarily limited to only one layer or sheet of material, so that the layer may include laminates or combinations of several sheets or strips of the desired type. Accordingly, the term layer includes the terms layer and layered.

As used herein, the term osmotic absorbent refers to a material or structure that absorbs a solution in response to a chemical potential difference between absorbed and non-absorbed solutions. This difference in chemical potential generally results from a higher solute concentration for the absorbed solution. In order to prevent the concentration of the solute being equilibrated by diffusion of the solute components, the osmotic absorbent generally has a diffusing solute.

4 4 4

A 6 barrier which selectively inhibits the diffusion of at least one component from the solute. Examples of suitable diffusion barriers are (1) a semipermeable reverse-osmotic membrane, the membrane providing a diffusion barrier for soluble salts, for example NaCl, and (2) a crosslinked polyelectrolyte network, for example used in hydrogels in which the polyelectrolyte network retains dissociated counterions inside the gel on electroneutrality. Examples of osmotic packet or chamber absorbents are described in U.S. Patent Nos. 5,108,383 and 5,082,723. A particularly preferred osmotic absorbent for use in the absorbent article of the present invention is hydrogel-forming absorbent polymers, which are described in detail below.

As used herein, the term X-Y dimension means a plane perpendicular to the thickness of the member, core, or article. The X-Y dimension typically corresponds to the length and width of the member, core or article.

As used herein, the terms region (s) or zone (s) refer to portions or sections of the absorbent member.

As used herein, the dimension Z refers to a dimension perpendicular to the length and width of the member, core or article. The Z dimension typically corresponds to the thickness of the member, core or article.

For the purposes of the present invention, it is also to be understood that the term upper refers to absorbent members, such as layers that are closest to the wearer of the absorbent article and are generally relatively close to the topsheet of the absorbent article. In contrast, the term lower refers to absorbent members that are furthest from the wearer of the absorbent article and are generally closer to the backsheet.

As used herein, the term encompasses various parts, members, steps, and the like that are used together according to the present invention. Accordingly, the term comprising includes narrower concepts consisting essentially of and consisting of, wherein the narrower terms have their standard meaning as understood in the art.

All percentages, ratios, and proportions used herein are by weight unless otherwise indicated

- 7 • • «44 • 4 · 4 4 • 4 4 4 4 • 4 4 4

II. Capillary suction properties of the storage absoipation element

The storage absorbent members of the present invention exhibit a high capillary suction capability. For the purposes of the present invention, this high suction capability is measured as the ability of the member to absorb liquid at the high capillary heights generally encountered when the member is placed in an absorbent article. The Capillary Sorption Absorption Test, also referred to as the Capillary Sorption Test, measures the amount of test liquid per gram of absorbent absorbent member that is received when placed at different heights on the capillary sorption measuring apparatus. The capillary sorption absorption test is described in more detail in the Test Methods section below. Capillary sorption absorption capacity data for certain materials is shown in Table 1 below. In particular, capillary sorption absorption capacity data is given for (1) a storage absorbent member consisting of high surface area glass microfibers and hydrogel-forming absorbent polymer particles (formed according to Example 1 below), (2) a storage absorbent member consisting of particles of high surface area polymeric foams (produced according to Example 2 below), (3) a storage absorbent member consisting of large surface area polymeric foam particles and hydrogel-forming absorbent polymer particles (manufactured according to Example 5 below), and (4) a storage absorbent member consisting of fibers of acetate cellulose with a large surface area and particles of absorbent hydrogel-forming polymer (produced according to Example 6 below).

Capillary sorption absorption capacity data for the prior art materials (referred to as Comparative A and Comparative B) are also shown in Table 1. The prior art comparative sample A was a circular structure with a diameter of 5.4 cm, perforated from a member (see the discussion below), comprising a blend of cellulosic fine fibers (Flint River Pulp of Weyerhauser, Co., Washington, USA) in a weight fraction of about 42% and a hydrogel-forming absorbent polymer (available from Clariant GmbH, Frankfurt, Germany as IM 73000), in a proportion of about 58% by weight. The prior art comparative sample B is a polymeric foam material prepared according to U.S. Patent No. 5,650,222.

In one aspect, the high capillary suction storage absorbent member of the present invention has a capillary sorption absorption capability at a height of 35 cm of at least about 12 g / g, preferably at least about 14 g / g, even more preferably at least about 16 g / g, even more preferably least

about 20 g / g, more preferably at least about 27 g / g. Typically, these absorbent absorbent members will have a capillary absorption capacity of 35 cm from about 12 g / g to about 60 g / g, more typically from about 14 g / g to about 50 g / g, more typically from about 20 g / g up to about 40 g / g.

In another aspect, the high capillary suction absorbent storage material has a capillary sorption absorption capacity at a height of 70 cm of at least about 7 g / g, preferably at least about 9 g / g, even more preferably at least about 11 g / g and even more preferably at least about 14 g /G. Such storage absorbent members will generally have a capillary sorption absorption capacity at a height of 70 cm from about 7 g / g to about 35 g / g, more typically from about 9 g / g to about 30 g / g, even more typically from about 11 g / g up to about 25 g / g.

In yet another aspect, the high capillary suction storage absorbent material has a capillary sorption absorption capacity at a height of 120 cm of at least about 4 g / g, preferably at least about 5 g / g, even more preferably at least about 7 g / g, even more preferably at least about 11 g / g. g / g. Such storage absorbent members will generally have a capillary sorption absorption capacity at a height of 120 cm from about 4 g / g to about 29 g / g, more typically from about 5 g / g to about 24 g / g, even more typically from about 7 g / g. up to about 19 g / g.

In yet another aspect, the high capillary suction storage absorbent material has a capillary sorption absorption capacity at a height of 200 cm of at least about 3 g / g, preferably at least about 4 g / g, more preferably at least about 6 g / g, even more preferably at least about 8 g /G. Such storage absorbent members will generally have a capillary sorption absorption capacity at a height of 200 cm from about 3 g / g to about 25 g / g, more typically from about 4 g / g to about 20 g / g, even more typically from about 6 g / g. up to about 15 g / g.

With respect to storage absorbent members comprising osmotic absorbents and high surface area materials in addition to or as an alternative to defining the high suction capability of the subject members in terms of capillary sorption absorption capacity, particularly preferred members can be characterized, i.e., where the material is large. by the surface area of the polymer foam, the ability of the member to initially receive liquid at high altitudes at high velocity. High suction members that show both high intake at high suction and high initial effective intake rates should provide excellent dryness to the user because of the extent of partitioning from other

of absorbent cores, for example receiving or distribution materials, and its velocity will be favorably improved by the high capillary suction material. For purposes of the present invention, this second property is referred to herein as the initial member uptake rate at a capillary suction height of 200 cm, hereinafter referred to as the initial effective uptake rate at 200 cm, expressed in g / g / hour. The initial effective uptake rate of the storage absorbent member is calculated by dividing the absorption capacity by capillary suction at 200 cm by the time spent on 200 cm. The capillary suction absorption capacity and time are readily determined using the capillary sorption method, which is discussed in detail in the test method section below. Although not required, particularly preferred storage absorbent members will have an initial effective uptake rate at 200 cm of at least about 3 g / g / h, more preferably at least about 4 g / g / h, and most preferably at least about 8 g / g / h. An effective intake rate at 200 cm will generally be from about 3 to about 15 g / g / h, more typically from about 4 to about 12 g / g / h, even more typically from about 8 g / g / h to about 12 g / g / h / h.

While the aforementioned minimum capillary sorption absorption capacities are important for the absorbent members of the present invention, the members will also preferably, although not necessarily, have a capillary sorption absorption capacity of at least about 15 g / g at zero hydrostatic height, i.e., 0 cm at capillary sorption test. According to another preferred aspect, the absorbent members will simultaneously exhibit the desired intake in g / g at at least the two suction heights listed above. For example, preferred storage absorbent members will have 2 or more of the following characteristics:

(1) a capillary sorption absorption capacity at a height of 35 cm of at least about 12 g / g, preferably at least about 14 g / g, even more preferably at least about 16 g / g, even more preferably at least about 20 g / g and even more preferably at least about 27 g (2) a capillary sorption absorption capacity at a height of 70 cm of at least about 7 g / g, preferably at least about 9 g / g, even more preferably at least about 11 g / g, and even more preferably at least about 14 g / g, (3) a capillary sorption absorption capacity at a height of 120 cm of at least about 4 g / g, preferably at least about 5 g / g, even more preferably at least about 7 g / g and even more preferably at least about 11 g / g,

(4) a capillary sorption absorption capacity at a height of 200 cm of at least about 3 g / g, preferably at least about 4 g / g, even more preferably at least about 6 g / g, even more preferably at least about 8 g / g.

According to another aspect, the absorbent absorbent members of the present invention may be characterized in that they exhibit a relatively high absorption efficiency, hereinafter referred to as capillary absorption efficiency at different heights relative to the material capacity at zero hydrostatic height. Capillary absorption efficiency at a given suction height is determined by dividing the absorption capacity of the capillary suction material at a given height by the absorption capacity of the capillary suction material at zero hydrostatic height. In this regard, according to one aspect of the absorbent member, the absorbent member will have a capillary suction absorption capacity at a zero height of at least about 15 g / g, preferably at least about 20 g / g and even more preferably at least about 40 g / g and most preferably about 60 g / g. absorption efficiency at a height of 120 cm at least about 40%. In another aspect, the absorbent member will have an absorbent capacity by capillary sorption at a zero height of at least about 15 g / g, preferably at least about 20 g / g, more preferably at least about 40 g / g and most preferably at least about 60 g / g. cm at least about 30%, preferably at least about 40%, even more preferably at least about 65%. According to another aspect, the absorbent member will have a capillary sorption absorption capacity at a zero height of at least about 15 g / g, preferably about 20 g / g, even more preferably about 40 g / g and most preferably about 60 g / g. about 50%, preferably at least about 70%, even more preferably at least about 90%.

In another aspect, the preferred storage absorbent members of the present invention will have a relatively high mean absorption height, which is defined as the height at which the member has a capillary sorption absorption capacity that is 50% of the capillary sorption absorption capacity at 0 cm. In this regard, preferred storage absorbent members will have capillary sorption absorption capacity at a zero height of at least about 15 g / g, preferably at least about 20 g / g, even more preferably at least about 40 g / g and most preferably about 60 g / g and a mean absorption height of at least about 35 cm, more preferably at least about 40 cm, even more preferably at least about 50 cm, and most preferably at least about 60 cm.

-lily. Parts of high-suction storage absorbent members

Representative materials useful in preparing the absorbent articles of the present invention are described in detail below. According to one particularly preferred embodiment, the storage absorbent member will be in the form of a hydrophilic polymeric foam with a large surface area. In another particularly preferred embodiment, the storage absorbent member will be in the form of a high surface area hydrophilic polymeric foam in combination with an osmotic absorbent material (eg, a hydrogel-forming absorbent polymer). In another embodiment, the storage absorbent member will comprise a mixture of fibers with a large surface area and an osmotic absorbent (eg, a hydrogel-forming absorbent polymer).

A. Hydrophilic polymer foams with large surface area

As noted, large surface area polymer foams having a high capillary suction capability may be used as the primary component of the storage absorbent member or may be used in combination with an osmotic absorbent material. While foams usable as the primary storage material (i.e., where no filler materials that contribute significantly to the absorption capacity) are used, they will have many similar properties to foams used in combination with osmotic absorbents, there are some foam properties that will be used. vary depending on the particular embodiment. In this regard, in the discussion below of the particular properties of the foam, where no distinction is made between the foams usable as the primary storage absorbent component and cases where they are used in combination with an osmotic absorbent, it should be assumed that the description of this foam property is applicable to both embodiments. . In contrast, where different foam properties can be used depending on the particular embodiment, both embodiments are described.

To the extent that large surface area polymer foams are described herein that are useful in terms of their physical properties, it may be necessary to perform an analysis on sheet foam. Therefore, to the extent that the foam is used in a particular form and is prepared from a previously formed sheet, measurements of physical properties will be made on the foam sheet (i.e., before the particles are formed). Where foam is formed in-situ into particles (or beads)

during the polymerization process, a similar foam (in terms of chemical composition, cell size, V: O ratio, etc.) may be formed into sheets for making these measurements.

(1) General parameters of polymeric foam

Large surface area polymer foams useful in high capillary suction absorbent members comprising osmotic absorbents (e.g., a hydrogel-forming absorbent polymer) of the present invention are known in the art. Particularly preferred foams for use in combination with osmotic absorbents are those obtained by polymerizing a high internal phase water-in-oil emulsion, such as those described in U.S. Patent Nos. 5,387,207 and 5,650,222. Other, particularly preferred polymeric foams are described. more particularly in co-pending U.S. patent applications Nos. 09/042 429 and 09/042 418. Particular, particularly preferred foams described in one or both of these co-pending applications are described in the examples below.

The polymeric foams useful in the present invention are those having relatively open cells. This means that many of the individual foam cells are unobstructed in conjunction with neighboring cells. Cells in such relatively open cell foam structures have holes or windows inside the cells that are large enough to allow easy transfer of liquid from one cell to another in the foam structure.

These relatively open cell foam structures will generally be reticulated with individual cells defined by a plurality of interconnected three-dimensional branched cobwebs. These strands of polymeric material forming these branched cobwebs can be called struts. For the purposes of the present invention, the most preferred foam material will have at least about 80% of the cells in the foam structure that are at least 1 µm in size and which are in fluid communication with at least one adjacent cell.

In addition to having open cells, these polymeric foams are sufficiently hydrophilic to allow the foam to absorb aqueous liquids. The inner surfaces of the foam structures are treated to be hydrophilic by means of residual hydrophilizing surfactants

retained in the foam structure after polymerization or by selected processes for treating the foam after polymerization as described below.

The extent to which these polymeric foams are hydrophilic can be quantified by the value of the adhesive stress exhibited when in contact with an absorbable test liquid. The adhesion stresses exhibited by these foams can be determined experimentally using a procedure wherein the weight gain given by the intake of a test liquid, such as synthetic urine, is measured on a sample of known dimensions and specific capillary suction surface area. Such a procedure is described in more detail in the section entitled Test Methods in U.S. Patent No. 5,387,207, below. The foams that can be used as the high surface area materials of the present invention are generally those having an adhesion stress value of from about 15 to about 65 dynes / cm, more preferably from about 20 to about 65 dynes / cm, as is determined by capillary absorption of synthetic urine having a surface tension of 65 ± 5 dynes / cm.

The polymeric foams useful herein are preferably prepared in the form of warped (i.e., unexpanded) polymeric foams which upon contact with aqueous liquids absorb such liquids and expand when the absorbed amount reduces the combined capillary pressure and surrounding pressure below the expansion pressure of the foam described below. These warped polymer foams are usually obtained by extruding the aqueous phase from the polymerized HIPE foam by compressive forces or by heat drying or vacuum dewatering. After compression and / or heat drying / vacuum dewatering, the polymeric foams are in a collapsed unexpanded state.

The cellular structure of an exemplary warped HEPE foam from which water has been extruded by compression is shown in the photomicrograph of Figures 3 and 4 of U.S. Patent 5,650,222 cited above. As can be seen from these figures, the cellular structure of the foam is distorted, especially when compared to the expanded HIPE foam structures shown in FIGS. 1 and 2 of U.S. Pat. No. 5,650,222. FIGS. 3 and 4 also show that gaps or the pores (dark areas) in the collapsed foam structure have been flattened or elongated. It is noted that the foams shown in U.S. Patent No. 5,650,222 are sheet-shaped. (As described below, although foams in sheet form may be used in the present invention, they have a particular shape in a particularly preferred embodiment.) The cellular structure of another modified (HIPE) foam (in the expanded state) that can be used in the present invention, 3 and 4 of the present invention. Preparation of this particular foam a

similar foams are described herein in Examples 2-4, and these very high surface area foams are described in more detail in U.S. Patent Application Serial No. 09 / 092,429 and U.S. Patent Application Serial No. 09 / 092,418.

After compression and / or heat drying and vacuum dewatering, the collapsed polymeric foam may re-expand when wetted with an aqueous liquid. It is surprising that these polymeric foams remain for a considerable period of time in this warped or unexpanded shape, for example up to at least 1 year. The ability of these polymeric foams to remain in this collapsed unexpected state is probably due to the capillary forces and, in particular, the capillary pressure exerted in the foam structure. As used herein, capillary pressure means a differential pressure across the liquid-air interface due to the curvature of the meniscus within the small space that is in the foam pores. [see Chatteijee, Absorbency, Textile Science and Technology, Volume 7, 1985, p. 36],

After compression and / or heat drying and vacuum dewatering, these polymeric foams have in practice a residual water that includes both hydration water associated with the hygroscopic hydrated salt incorporated in the foams and free water absorbed in the foam. This residual water (along with the hydrated salts) probably exerts capillary pressures on the resulting collapsed foam structure. The collapsed polymeric foams of the present invention may have a residual water content of at least about 4%, typically from about 4% to about 40% by weight of the foam when stored at an ambient temperature of 22 ° C and 50% relative humidity. Particularly preferred collapsed polymeric foams have a residual water content of from about 5% to about 30% by weight of the foam.

A key parameter of these foams is their glass transition temperature Tg, which is the midpoint of the transition between the glassy and rubbery state of the polymer. Foams that have a higher _Tg than the temperature of use can be very strong but will also be very rigid and potentially will have a tendency to break. Such foams also typically take a long time before returning to an expanded state when wetted with aqueous fluids that are cooler than the T _{g of} a polymer after its deposition in the collapsed state for prolonged periods. A desirable combination of mechanical properties, in particular strength and elasticity, generally requires a relatively selective range of monomer types and levels to achieve these properties.

• ·

-15U foams used in the present invention should be as low T _g, with the foam but must at the temperatures under which it is used acceptable strength. Accordingly, the monomers are selected as much as possible so as to obtain corresponding homopolymers having a lower Tg. It was found that the chain length of the alkyl group on the acrylate and methacrylate comonomers can be longer than would be predicted from the T _{g of} the homologous homopolymer series. In particular, it has been found that homologous series of alkyl acrylate or methacrylate homopolymers have a minimum T _g over a chain length of 8 carbon atoms. By contrast, the minimum _Tg of the copolymers of the present invention occurs at a chain length of about 12 carbon atoms. (Although alkyl substituted styrene monomers may be used instead of alkyl acrylates and methacrylates, their availability is currently extremely limited.)

The shape of the glass transition region of the polymer as a function of temperature can also be important, i.e., whether it is narrow or wide. The shape of this area Tg is particularly important where the use of temperature (usually ambient or body temperature) of the polymer is at or near the T _g value. For example, a wider transition region may indicate incomplete conversion at use temperatures. If the transition at in-use temperature is still incomplete, the polymer will generally exhibit greater rigidity and less elasticity. In contrast, if the transition at use temperature is already complete, the polymer will exhibit a faster return from the compressed state when wetted with aqueous liquids. Therefore, it is desirable to control the _Tg and the width of the transition region of the polymer so as to achieve desired mechanical properties. In general, it is preferred that the temperature T _{g of the} polymer be at least about 10 ° C lower than the temperature prevailing in its use. (The temperature T _g and the width of the transition region are derived from the tangent of the temperature-loss curve from the Dynamic Mechanical Analysis (DMA) measurement as described in the Test Methods section of US Patent 5,650,222.) (2) Vertical gradient of sorption height

The large surface area polymer foams useful in the present invention can also be described by a vertical gradient of their Vertical Hang Sorption Height (VHSH). The vertical VHSH gradient at X% is the height in cm up to which it is stored in the foam of X% capacity at 0 cm (or FAC). A typical important value is VHSH at 90%, although in principle X may be any value. According to experience with the subject • ·· ·· ·· * · · * ·

By the invention, the most reproducible measure for VHSH is achieved at X = 90%. One of skill in the art will recognize that this single point value does not fully reflect the shape of the curve obtained when plotting the capacity vs. height. However, a single point serves as a practical point for comparing foams useful herein. In this regard, the foams will generally have 90% VHSH at least 20 cm, preferably at least about 70 cm, and even more preferably at least about 80 cm. Preferred polymeric foams will generally have a VHSH of 90% from about 20 cm to about 90 cm, especially from about 60 cm to about 90 cm, especially from about 70 cm to about 90 cm, more typically from about 80 cm to about 90 cm. For foams that are used alone (i.e. no osmotic absorbent is used), the foam will have 90% VHSH at least about 60 cm, preferably at least about 70 cm, even more preferably at least about 80 cm. Generally, when used alone, polymeric foams will have 90% VHSH from about 60 to about 90 cm, more preferably from about 70 to about 90 cm, even more preferably from about 80 to about 90 cm.

The difference in 90% VHSH for the foams used in the two different embodiments is mainly due to the fact that when used in combination with an osmotic absorbent, the primary advantage provided by the foam is its large surface area which contributes to the overall suction capacity of the member. That is, the foam acts primarily as a transport medium for delivering liquid to the osmotic absorbents and the absorbent capacity of the foam is of secondary importance. On the other hand, when used alone, the foam must also have a significant absorption capacity to compensate for the missing absorption capacity provided by the osmotic absorbent. In this respect, 90% of VHSH is a measure of the absorption capacity.

The method of measuring 90% VHSH is described in detail in the Test Methods section below. As noted, where the high surface area polymeric foam is in particulate form when combined with an osmotic absorbent, 90% VHSH is measured on the corresponding foam in sheet form (i.e., before particulate formation). Where the foam is formed into particles (or beads) during the polymerization process, a similar foam may be formed into sheets to determine 90% VHSH of the foam.

-17 (3) Capillary suction specific surface area

The high surface area materials have generally been described by their capillary sorption absorption capacity, but the high surface area polymer foams useful herein can also be described by their specific capillary suction surface area (abbreviated as CSSSA). CSSSA is generally a measure of the surface area that is accessible to the test liquid of a polymeric network producing a particular foam per unit weight of a block of foam material (polymeric structural material plus solid residual material). The capillary suction specific surface area is determined by both the dimensions of the cellular units in the foam and the density of the polymer and is thus a way to quantify the total amount of solid surface provided with a foam network to the extent that this surface participates in the absorbency. For the purpose of characterizing the foams that can be used in the present invention, CSSSA is measured on the sheet of the respective foam even where the foam is in particulate form when incorporated into the absorbent absorbent member.

CSSSA foam is particularly relevant as to whether the foam will provide the desired capillary suction for use in preparing the absorbent absorbent members of the present invention. This is because the capillary pressure exerted within the foam structure is proportional to the capillary suction of a specific surface area. In addition, CSSSA is relevant to whether adequate capillary pressures develop in the foam structure to keep it collapsed until wetted with aqueous liquids. Assuming that other factors such as foam density and adhesion stress are constant, this means that when CSSSA increases (or decreases), the capillary pressure in the foam structure also increases (or decreases) proportionally.

For the purposes of this invention, CSSSA is determined by measuring the amount of capillary uptake of a low surface tension liquid (e.g., ethanol) that occurs in a foam sample of known weight and size. A detailed description of this procedure for determining a specific surface area is described in the Test Methods section of U.S. Patent No. 5,387,207.

The warped polymeric foams of the present invention useful as absorbents are those having a CSSSA of at least 3 m ² / g. CSSSA is typically in the range of about 3 to about 30 m ² / g, p

9 9 9 9999 99

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Preferably from about 4 to about 17 m ² / g, most preferably from about 5 to about 15 m ² / g. Foams having such CSSSA values (with densities in the expanded state of from about 0.010 to about 0.033 g / cm ³ ) will generally have a particularly desirable balance between absorption capacity, liquid containment and liquid suction by wick effect or distribution parameters for aqueous liquids such as urine. In addition, a foam moss having such a CSSSA value exert sufficient capillary pressure to keep the foam in a collapsed unexpanded state until wetted by these aqueous liquids.

(4) Capillary pressures and forces in the foam structure

As discussed above about particularly preferred collapsible polymer foams in their collapsed state, the capillary pressures exerted in the foam structure are at least the same as those exerted by the elastic return to the original tent or the compressed polymer module. In other words, the capillary pressure required to keep the collapsed foam relatively thin is determined against the applied force exerted by the compressed polymeric foam as the foam seeks to spring back. The tendency to elastic return of polymeric foams can be estimated from the stress-strain experiment where the expanded foam is compressed to about 1/6 (17%) of the original expanded thickness and then held in that compressed state until the stress release value is measured. . Alternatively, and for the purposes of the present invention, the stress-relieved value is estimated from measurements on the polymeric foam in its collapsed state when in contact with aqueous liquids, e.g., water. This alternative value at relaxed stress is then referred to as the foam expansion filament. The expansion pressure of the collapsed polymeric foams of the present invention is about 50 kPa or less, and typically from about 7 koji to about 40 kPa. A detailed description of the foam expansion pressure estimation procedure is set forth in the section entitled Test Methods in U.S. Patent No. 5,387,207.

(5) Free absorption capacity

Another important feature of the high surface area polymeric foams useful in the present invention is their free absorbent capacity. Free Absorbent Capacity (FAC) is the total amount of test liquid (synthetic urine) absorbed by a given foam sample into its cell structure per unit weight of solid material in the sample. To be particularly suitable for the absorbent absorbent members of the present invention,

The polymeric foams should have a free absorbent capacity of from about 30 to about 100 ml, preferably from about 30 to about 75 ml of synthetic urine per gram of dry foam material. The procedure for determining the free absorbent capacity of the foam is described in the Test Methods section of U.S. Patent 5,650,222.

(6) Expansion coefficient

Upon exposure to aqueous liquids, particularly preferred collapsed polymeric foams absorb liquids and expand. Polymeric foams in their expanded state absorb more liquid than most other foams. The expansion coefficient of these foams is at least about four times (4x), i.e. the foam thickness in the expanded state is at least four times the foam thickness in the collapsed state. The warped foams preferably have an expansion coefficient ranging from about four times (4x) to about fifteen times (15x), more preferably from about five times (5x) to about ten times (10x).

For the purposes of the present invention, the relationship between the expanded thickness and the collapsed thickness of compressed dewatered foams can be empirically calculated from the following equation:

Thickness of expanded thickness of warped x ((0,0133 x V.O ratio) i 2)

Where: the expanded thickness is the expanded foam thickness, the collapsed thickness is the collapsed foam thickness, and the V: 0 ratio is the water to oil ratio of the HIPE from which the foam is made.

Thus, a typical polymeric foam is made from an emulsion with a water to oil ratio of 60: 1 and should have a predicted expansion coefficient of 8.0, ie, an expanded thickness eight times the thickness of the collapsed foam. The procedure for measuring the expansion coefficient is described below in the section entitled Test Methods in U.S. Patent 5,650,222.

(7) Resistance to compression deflection

A relevant mechanical property of the large surface area polymer foams useful in the present invention is their expanded strength as determined by Resistance to Compression Deflection (RTCD). RTCD

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The foam exhibited by the present invention is a function of the polymer modulus as well as the density and structure of the foam network. The polymer modulus is in turn determined by a) the composition of the polymer, b) the conditions under which the foam is polymerized (for example, what completeness of polymerization is achieved, particularly with respect to crosslinking, and c) the extent to which the polymer is plasticized by the remaining material, for example emulsifiers retained in the foam structure after processing.

In order to be usable as part of a large surface area absorbent member, the polymeric foams should be suitably resistant to deformation or compression by the forces occurring in use. Foams which do not have sufficient strength in terms of RTCD can provide the desired capillary suction capacity under no load conditions, but will not provide these capacities in the event of compressive stress caused by the movement and action of the user of absorbent articles containing the foam.

The RTCDs exhibited by the polymeric foams useful in the present invention can be quantified by determining the amount of strain produced in the sample of saturated foam maintained at a certain surrounding pressure at a specified temperature and time. The method of performing this particular type of assay is described in the Test Methods section of U.S. Patent No. 5,650,222. The foams used herein will preferably exhibit RTCD such that a surrounding pressure of 5.1 kPa generates a strain of typically about 90% or less by compressing the foam structure when saturated to free absorbent capacity with synthetic urine having a surface tension of 65 ± 5 dynes / cm. Preferably, the deformation formed under these conditions will range from about 1 to about 90%, more preferably from about 1 to about 25%, even more preferably from about 2 to about 10%, even more preferably from about 2 to about 5%.

(8) Other properties of polymeric foam

Cells, and in particular cells that are formed by polymerizing an oil phase-containing monomer that surrounds the droplets of a water phase that is relatively monomer-free, will often be substantially spherical in shape. The size or diameter of these spherical cells is a commonly used parameter for characterizing foams in general. Since the cells in a given polymer foam sample will not necessarily be approximately the same size, the average cell size, i.e., the mean cell diameter, is often specified.

• ·

A variety of techniques are used to determine the mean foam cell size. The most useful technique for determining the mean cell diameter in a foam is a simple measurement based on scanning a photomicrograph of a foam sample taken with an electron microscope.

The cell size measurements herein are based on the number average cell size of the foam in its expanded state, e.g. as shown in Figure 1 of U.S. Patent 5,650,222. Foams useful in accordance with the present invention will preferably have a number average cell diameter. about 80 pm or less, typically from about 5 pm to about 50 pm.

The density of the foam (i.e. in grams of foam per cm ³ of foam volume in air) is given here on a dry material basis. The amount absorbed by the water-soluble residual materials, eg residual salts and liquids left in the foam, for example after ΤΠΡΕ polymerization, washing or or hydrophilization, is not taken into account when calculating and expressing the foam density. The foam density does not include, but other water insoluble residual materials such as emulsifiers present in the polymeric foam. Such residual materials may in fact make a significant contribution to the mass of the foam material.

Any suitable gravimetric procedure can be used to measure the density of the foam to determine the weight of the rigid foam material per unit volume of the foam structure. One method that can be used for density determination may be, for example, the ASTM gravimetric procedure described in more detail in the Test Methods ¹ 'section of U.S. Patent No. 5,387,207. The polymeric foams useful in the present invention have dry density values (without residual salts and / or water) ranging from about 0.1 to about 0.2 g / cm ³ , preferably from about 0.11 g / cm ³ to about 0.19 g / cm ^3, and most preferably from about 0.12 g / cm ³ to about 0.17 g / cm ³ . The polymeric foams useful herein will have dry-density values in the expanded state ranging from about 0.01 g / cm ³ to about 0.033 g / cm ³ .

Vertical wick-wicking, i.e. wicking of liquid in the direction opposite to that in which the gravitational force acts, is a desirable attribute of the activity of the polymeric foams used herein. For the purposes of the present invention, the vertical wicking rate is a reflection of the permeability of the material and hence

the ability of the material to deliver liquid to a hydrogel-forming absorbent polymer or other osmotic absorbent.

The vertical wicking rate is determined by measuring the time required for the colored test liquid (e.g., synthetic urine) in the container to swell in a foam test strip of a specified size to reach a distance of 5 cm. The vertical wicking process is described in more detail in the section entitled Test Methods in U.S. Patent No. 5,387,207, but is performed at 31 ° C instead of at 37 ° C. In order to be particularly useful in absorbent members for absorbing urine, the taps used herein will preferably be able to provide a wicking of synthetic urine (65 + 5 dynes / cm) to a height of 5 cm within 15 minutes. More preferably, the preferred foam absorbents of the present invention will provide synthetic urine wicking up to a height of 5 cm within 10 minutes.

The Vertical Wicking Absorption Capacity Test measures the amount of test liquid per gram of absorbent foam that is retained in each one inch (2.54 cm) of the vertical portion of a foam of the same standard size used in the vertical wicking test. Such determination is generally performed after the sample has been allowed to equilibrate the test liquid (e.g., for 18 hours). Like the vertical wicking test, the vertical wicking absorption capacity test is described in more detail in the section entitled Test Methods in US Patent No. 5,387,207. The high vertical wicking absorption capacities at high altitudes are theoretically equivalent to high capillary sorption absorption capacities at high altitudes. Since the sheet-like foams usable herein are applicable to the previous test and the previous test is easier and cheaper to perform, the data from the earlier test is recommended as a means to characterize this important parameter of the foams of the invention.

While high capillary suction foams may be sheet-shaped when combined with an osmotic absorbent (eg, a hydrogel-forming absorbent polymer), in a particularly preferred embodiment, the polymeric foam will be in particulate form and be mixed with the hydrogel-forming polymer particles to obtain a mixture. That is, while the foam may be initially prepared in the form of a sheet, these sheets may be converted into foam particles which are then combined with the hydrogel-forming polymer. As described above, foams useful herein and methods for their preparation are described in detail in U.S. Pat. Nos. 5,387,207, 5,650,222, and co-pending U.S. Patent Application Ser.

may be prepared by first forming a foam sheet as described in these references, followed by mechanical processing of the foam into particles of the desired dimensions, for example by powdering, slitting, chopping, etc. Alternatively, the foam particles may be prepared directly from the emulsion in the emulsion. in the form of polymeric microspheres as described in U.S. Patent Nos. 5,653,922 and 5,583,162. Particular embodiments for forming blends of polymer foam and hydrogel-forming polymer are discussed in more detail below.

It has also been found in the present invention that large surface area foams, when used as a transport medium for conveying liquid to an osmotic absorbent, may optionally include liquid so as to provide increased urine transfer to the osmotic absorbent of the storage absorbent member. The pre-wetting liquid partially fills the polymeric foam and, without being bound by any particular theory, it is believed that this will increase the rate of uptake of the foam. Ideally, the polymeric foam comprising the prewetting liquid or storage fluids should be stable with sufficiently low water activity to prevent the growth of microorganisms and prevent water loss by evaporation, and not to migrate out of the foam over time. Water may be used as a pre-wetting liquid to provide absorption performance, but may not meet all of the requirements per se.

B. Storage absorbent members comprising an osmotic absorbent and high surface area materials

As noted above, in one embodiment, the absorbent absorbent members of the present invention will include an osmotic absorbent, for example, an absorbent polymer comprising a hydrogel and a high surface area material that facilitates transport of body fluids to the osmotic absorbent. In one such embodiment, the high surface area material will be in the form of a high surface area hydrophilic polymeric foam as discussed above. Other representative materials useful in preparing the absorbent articles of the present invention are high surface area fibers, which are described in detail below. Although other osmotic absorbents may be used in the storage members, hydrogel-forming absorbent polymers are preferred. As such, these materials are described in detail.

Absorbent hydrogel-forming polymers

Chemical composition

In one preferred embodiment, the storage absorbent members of the present invention comprise at least one hydrogel-forming absorbent polymer, also referred to as a hydrogel-forming polymer. The hydrogel-forming polymers useful in the present invention include a variety of water-insoluble but water-swellable polymers capable of absorbing large quantities of liquids. Such hydrogel-forming polymers are well known in the art and any of these materials can be used in the high capillary suction absorbent articles of the present invention.

Absorbent hydrogel-forming polymers are also commonly referred to as materials called hydrocolloids or superabsorbents and may include polysaccharides such as carboxymethyl starch, carboxymethylcellulose and hydroxypropylcellulose, non-ionic types such as polyvinyl alcohol and polyvinyl ethers, cationic types such as polyvinylpyridine, polyvinylpyridine, polyvinylpyridine, polyvinylpyridine, or Ν, dim-dimethylaminopropyl acrylates and methacrylates and their respective quaternary salts. The hydrogel-forming absorbent polymers that can be used in the present invention typically have multiple anionic functional groups, such as sulfonic acid groups, and more typically carboxy groups. Examples of polymers suitable for use in this case include those polymers that are prepared from polymerizable, unsaturated, acid-containing monomers. Such monomers thus include olefinically unsaturated acids and anhydrides that contain at least one olefinic double bond between two carbons. More specifically, these monomers may be selected from olefinically unsaturated carboxylic acids and their anhydrides, olefinically unsaturated sulfonic acids and mixtures thereof. As mentioned above, the nature of the hydrogel-forming absorbent polymer is not critical to the members of the present invention. Nevertheless, the choice of the optimal polymeric material can increase the performance parameters of the members of the present invention. The following description of the invention describes particularly advantageous properties of absorbent polymers used herein. These properties should not be interpreted as limitations, but rather merely indicate the progress made over the past few years in the field of absorbent polymers.

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Certain non-acid monomers, usually in small amounts, may also be included in the preparation of the hydrogel-forming absorbent polymers herein. Such non-acidic monomers may include, for example, water-soluble or water-dispersible esters of acid-containing monomers as well as monomers which do not contain any carboxylic or sulfonic acid groups at all. Optional non-acidic monomers may thus include monomers containing the following types of functional groups: carboxylic acid or sulfonic acid esters, hydroxyl groups, amide groups, amino groups, nitrile groups, quaternary ammonium salt groups, aryl groups (e.g., phenyl groups such as which are derived from styrene monomer). These non-acidic monomers are well known materials and are described in more detail, for example, in U.S. Pat. Nos. 4,076,663 and 4,062,817.

Monomers based on olefinically unsaturated carboxylic acid and carboxylic acid anhydrides include acrylic acids, including acrylic acid, methacrylic acid, etacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, β-methacrylic acid (crotonic acid), α -phenylacrylic acid, β-acryloxypropionic acid, sorbic acid, α-chlorosorbic acid, angelic acid, cinnamic acid, p-chloroscinnamic acid, β-sterylacrylic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid , fumaric acid, tricarboxyethylene and maleic anhydride.

Olefinically unsaturated sulfonic acid monomers include aliphatic or aromatic vinyl sulfonic acids such as vinyl sulfonic acid, allylsulfonic acid, vinyltoluenesulfonic acid and styrene sulfonic acid; acrylic and methacrylic sulfonic acids such as sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-methacryloxypropylsulfonic acid and 2-acrylamide-2-methylpropanesulfonic acid.

Preferred hydrogel-forming absorbent polymers for use in the present invention contain carboxy groups. These polymers include hydrolyzed graft copolymers of starch and acrylonitrile, partially neutralized hydrolyzed graft copolymers of starch and acrylonitrile, and

-26acrylonitrile, graft copolymers of starch and acrylic acid, partially neutralized graft copolymers of starch and acrylic acid, saponified copolymers of vinyl acetate and acrylate, hydrolysed copolymers of acrylonitrile or acrylamides, slightly network-crosslinked polymers of any of the aforesaid copolymers crosslinked polymers of partially neutralized polyacrylic acid. These polymers can be used either alone or in the form of a mixture of two or more different polymers. Examples of these polymeric materials are described in U.S. Patents 3,661,875, 4,076,663, 4,093,776, 4,666,983 and 4,734,478.

The most preferred polymeric materials for use in the manufacture of absorbent hydrogel-forming polymers are slightly network-crosslinked polymers of partially neutralized polyacrylic acids and starch derivatives thereof. The hydrogel-forming absorbent polymers most preferably comprise from about 50% to about 95%, preferably about 75% neutralized, slightly crosslinked polyacrylic acid (i.e., poly (acrylic / acrylic acid) polyes). The crosslinking to the net leaves the polymer substantially water insoluble and in part determines the parameters of the absorbent capacity and extractable polymer content of the hydrogel-forming absorbent polymers. Crosslinking processes for these polymers and typical crosslinking agents are described in more detail in U.S. Pat. No. 4,076,663.

While the hydrogel-forming absorbent polymer is preferably of one type (i.e. homogeneous), blends of polymers can also be used in the present invention. For example, blends of starch-acrylic acid graft copolymers and moderately crosslinked polyacrylic acid polyacrylic acid polymers can be used in the present invention.

The hydrogel-forming polymer component may also be in the form of a mixed-bed ion exchange composition comprising a cation-exchange hydrogel-forming absorbent polymer and an anion-exchange hydrogel-forming absorbent polymer. Such mixed-bed ion-exchange compositions are described, for example, in US Patent Applications No. 09/003565, US No. 09/003905, US No. 09/003 918.

The hydrogel-forming absorbent polymers useful in the present invention may have a size, shape or morphology that varies widely. These polymers may be in particulate form,

27 which do not have the largest ratio of largest to smallest dimensions (e.g. granules, powders, particle aggregates, crosslinked particle aggregates, and the like) and may be in the form of fibers, sheets, foils, foams, flakes, and the like. low levels of one or more additives, such as silicate powder, surfactants, adhesives, binders, etc. The ingredients in this mixture may be physically or chemically combined in such a form that the component of the hydrogel-forming polymer and the non-hydrogel-forming polymer additive are not readily physically separable.

The hydrogel-forming absorbent polymers may be substantially non-porous, i.e., without intrinsic porosity, or have substantial intrinsic porosity.

For particles such as those described above, the particle size is defined as the size determined by sieve analysis, so that, for example, a particle that is retained on a US standard test screen having 710 micron apertures (e.g., US 25 screen) ) is considered to have a size greater than 710 microns; a particle that passes through a 710 micron sieve and remains on a 500 micron sieve (eg, No. 35 sieve as indicated in the US) is considered to have a particle size between 500 and 710 pm and a particle that passes through a sieve 500 microns is considered to be less than 500 µm in size. The weight median particle size of a given sample of hydrogel-forming absorbent polymer particles is defined as the particle size that divides the sample in half on a weight basis, i.e. one half of the sample will have a particle size less than the weight median particle size and one half of the sample will have particle size greater than the weight median size. A standard method of plotting a particle size in which the cumulative weight percent of a sample of particles remaining or passed through a given mesh size is plotted against the mesh aperture size in the frequency graph is typically used to determine the weight median particle size where 50% by weight does not match hole of the test sieve according to the US standard. These methods for determining the particle size of the hydrogel-forming absorbent polymer are further described in U.S. Patent 5,061,259.

For the hydrogel-forming absorbent polymer particles useful in the present invention, the particles will generally range in size from about 1 µm to about 2000 µm, more preferably from about 20 µm to about 1000 µm. The weight average particle size will generally be from about 20 µm to about

-281500 pm, more preferably from about 50 pm to about 1000 pm, even more preferably from about 50 pm to about 1000 pm, and even more preferably from about 100 pm to about 800 pm.

Where relatively high concentrations, such as 40% to 60% or more, of the hydrogel-forming absorbent polymer are used in the absorbent members of the present invention, other properties of the absorbent polymer may be important. In such embodiments, the materials may have one or more of the properties described in U.S. Patent Nos. 5,562,646 and 5,599,335.

b. Production methods

The hydrogel-forming base absorbent polymer can be formed in any conventional manner. Typical and preferred processes for producing these polymers are described in U.S. Reissue 32,649, 4,666,983 and 4,625,001.

Preferred methods of forming the hydrogel-forming base absorbent polymer are those which include solution polymerization methods wherein the solution is water or another solvent. As described in the above-mentioned US Reissue 32,649, aqueous solution polymerization involves the use of an aqueous reaction mixture to effect polymerization. The aqueous reaction mixture is then subjected to polymerization conditions that are sufficient to produce the mixture slightly into a network of crosslinked polymer that is substantially water insoluble. The mass of polymer formed can then be pulverized or chopped into individual particles.

More specifically, the aqueous solution polymerization process for producing a hydrogel-forming absorbent polymer comprises preparing an aqueous reaction mixture in which the polymerization is to be carried out. One component of such a reaction mixture is a monomer containing an acidic group that will form the backbone of the hydrogel-forming absorbent polymer to be produced. The reaction mixture will generally comprise about 100 parts by weight of monomer. Another component of the aqueous reaction mixture is a crosslinking agent. The network forming cross-linking agents that can be used to form the absorbent hydrogel-forming polymer of the present invention are described in more detail in the above-mentioned U.S. Reissue 32,649, 4,666,983 and 4,625,001. The network forming cross-linking agent will generally be present in aqueous reaction mixtures in an amount of from about 0.001 *

9 9 9 99 9 9 9 mole percent to about 5 mole percent based on 100 parts by weight of monomer). A further optional component of the aqueous reaction mixture will be a free radical initiator comprising, for example, peroxide compounds such as sodium, potassium and ammonium persulfates, caprylyl peroxide, benzoyl peroxide, hydrogen peroxide, cumene hydroperoxides, tertiary butyl piperphthalate, tertiary butyl perbenzoate, sodium percarbonate, or percarbonate. the compositions include various non-acidic comonomers, including esters of essential, unsaturated, acid functional groups containing monomers or other comonomers having no carboxylic or sulfonic acid functional groups at all.

The aqueous reaction mixture is subjected to polymerization conditions that are sufficient to form substantially insoluble but water-swellable, hydrogel-forming, absorbent, slightly crosslinked polymers in the mixture. Polymerization conditions are also discussed in more detail in the three above-mentioned patents. These polymerization conditions generally include heating (thermal activation techniques) to a polymerization temperature of from about 0 ° C to about 100 ° C, more preferably from about 5 ° C to about 40 ° C. The polymerization conditions under which the aqueous reaction mixture is maintained may include, for example, subjecting the reaction mixture or portions thereof to any conventional form of polymerization activation irradiation. Radioactive, electronic, ultraviolet or electromagnetic radiation is an alternative to conventional polymerization techniques.

The acid functional groups of the hydrogel-forming absorbent polymer formed in the aqueous reaction mixture are also preferably neutralized. The neutralization may be carried out by any conventional method which results in that at least 25 mole percent and more preferably at least about 50 percent of the total monomer used to form the polymer from the acid group-containing monomers is neutralized by a salt-forming cation. Such salt-forming cations include, for example, alkali metals, ammonium, substituted ammonium, and amines, as discussed in more detail in the above-mentioned U.S. Reissue 32,649.

While it is preferred that particular versions of the hydrogel-forming absorbent polymer be produced using an aqueous solution polymerization process, it is also possible to carry out the polymerization process using multiphase polymerization process techniques such as inverse emulsion polymerization or inverse suspension polymerization processes. U inverse emulsion

For example, by polymerization or inverse suspension polymerization processes, the aqueous reaction mixture as described above is suspended in the form of tiny droplets in a matrix of a water immiscible inert organic solvent such as cyclohexane. The resulting hydrogel-forming absorbent polymer particles are generally spherical in shape. Inverse suspension polymerization processes are described in more detail in U.S. Patents 4,340,706, 4,506,052 and 4,735,987.

Surface crosslinking of initially formed polymers is the preferred process for obtaining hydrogel-forming absorbent polymers having a relatively highly porous Hydrogel Layer (abbreviated PHL), performance under pressure (PUP abbreviation) and saline conductivity values (Saline Flow) Conductivity (abbreviated as SFC), which may be advantageous in the context of the present invention. Suitable general methods for carrying out the surface crosslinking of the hydrogel-forming absorbent polymers of the present invention are described in U.S. Pat. No. 4,541,871, published PCT Application WO 92/16565, published PCT Application WO 90/08789, published PCT Application WO 93/05080, U.S. Patents 4,824 901, US 4 789 861, US 4 587 308, US 4 734 478, US 5 164 459, published German patent application 4 020 780 and published European patent application 509 708. See also U.S. Patents 5,562,646 and 5,599,335.

The hydrogel-forming absorbent polymer particles prepared according to the present invention are generally substantially dry. The term substantially dry is used herein to mean that the particles have a liquid content, typically water or other solution content, of less than about 50%, preferably less than about 20%, even more preferably less than about 10% by weight of the particles. The liquid content of the hydrogel-forming absorbent polymer particles ranges from about 0.01% to about 5% by weight of the particles. The individual particles may be dried in any conventional manner, such as by heating. When the particles are formed using an aqueous reaction mixture, water may alternatively be removed from the reaction mixture by azeotropic distillation. The aqueous reaction mixture containing the polymer may also be treated with a dewatering solvent such as methanol. Combinations of these drying processes may also be used. The dewatered polymer mass can then be chopped or powdered to form substantially dry hydrogel-forming absorbent polymer particles.

2. Materials with large surface area

With respect to the absorbent absorbent members of the present invention, these include an osmotic absorbent (e.g., hydrogel-forming absorbent polymers) and the member also includes a high surface area material. It is this large surface area material that provides, either alone or in combination with a hydrogel-forming absorbent polymer, members with high capillary sorption absorption capacity. As noted herein, high surface area materials are described in at least one respect on the basis of their capillary sorption absorption capacity measured without a hydrogel-forming polymer or any other optional material contained in a particular storage absorbent member such as adhesives, binding agents, etc. It is found that materials having a large surface area may be capable of receiving at very high suction heights, for example 100 cm or higher. This allows large surface area materials to perform one or both of the following functions: (1) a liquid capillary pathway for osmotic absorbents, or (2) an additional absorption capacity. Thus, while large surface area materials can be described by their surface area by weight or volume, the present application alternatively uses capillary sorption absorption capacities to describe a material having a large surface area, since the capillary sorption absorption capacity is a functionality parameter that will provide absorbent members according to the present invention, the desired absorbency to provide improved absorbent articles. It is believed that certain high surface area materials, such as glass microfibers, will not in themselves exhibit a particularly high absorption capacity by capillary sorption at all heights, especially very high heights, for example 100 cm and above. However, such materials can provide the desired liquid capillary pathway for the hydrogel-forming absorbent polymer or other osmotic absorbent to provide the desired absorbent capacities by capillary sorption even at relatively high altitudes when combined with the hydrogel-forming polymer or other osmotic absorbent.

Any material having sufficient absorbent capacity by capillary sorption when used in combination with a hydrogel-forming absorbent polymer or other osmotic absorbent will be useful in the absorbent absorbent members of the present invention. In this regard, the term high surface area material refers to any material it exhibits alone

per se, i.e., measured without an osmotic absorbent or other optional material constituting the storage absorbent member, one or more of the following capillary sorption absorption capacities: (1) a capillary sorption absorption capacity of at least about 2 g / g at a suction height of 100 cm, preferably at least about 3 g / g, more preferably at least about 4 g / g and even more preferably at least about 6 g / g at a height of 100 cm; (2) a capillary sorption absorption capacity at a height of 35 cm of at least about 5 g / g, preferably at least about 8 g / g, more preferably at least about 12 g / g; (3) a capillary sorption absorption capacity at a height of 50 cm of at least about 4 g / g, preferably at least about 7 g / g, more preferably at least about 9 g / g; (4) a capillary sorption absorption capacity at a height of 140 cm of at least about 1 g / g, preferably at least about 2 g / g, more preferably at least about 3 g / g, even more preferably at least about 5 g / g; or (5) a capillary sorption absorption capacity at a height of 200 cm of at least about 1 g / g, preferably at least about 2 g / g, more preferably at least about 3 g / g, and even more preferably at least about 5 g / g.

In one embodiment, the high surface area material will be fibrous in nature. It is hereinafter referred to as fibers having a large surface area. This provides a fiber web or fiber matrix when combined with an absorbent polymer that forms a hydrogel or other osmotic absorbent. Alternatively, in a particularly preferred embodiment, the high surface area material will be a hydrophilic open cell polymer foam, hereinafter referred to as a high surface polymer foam or, more generally, a polymer foam. These materials are described in detail above.

The high surface area fibers useful in the present invention include those that occur naturally (treated or untreated) as well as synthetically produced fibers. Fibers with a large surface area have surface areas much larger than those commonly used in absorbent articles such as wood pulp fibers. The high surface area fibers of the present invention will preferably be hydrophilic. As used herein, the term hydrophilic describes fibers or fiber surfaces that are wetted by aqueous liquids, for example, aqueous body fluids that are deposited on these fibers. Hydrophilicity and wettability are generally defined by the contact angle and surface tension of the respective liquids and solids. This is discussed in detail in the publication by the American Chemical Society entitled Contact Angle, Wettability and Adhesion, published by Robert F. Gould (Copyright 1964). Thread or

the fiber surface is considered to be wetted by the liquid, i.e., hydrophilic when either the liquid / fiber contact angle or its surface is less than 90 ° or when the liquid tends to spontaneously across the fiber surface, both conditions normally occurring simultaneously. In contrast, a fiber or surface is considered hydrophobic if the contact angle is greater than 90 ° and the liquid does not spread spontaneously across the fiber surface. The hydrophilic nature of the fibers that can be used herein can be inherited or naturally hydrophobic fibers that have been treated to become hydrophilic. Materials and methods of achieving a hydrophilic nature in naturally hydrophobic fibers are well known.

The high surface area fibers useful herein will have capillary suction specific surface areas to the same extent as the polymeric foams described below. Generally, however, fibers with a large surface area are characterized by the BET surface area.

The high surface area fibers useful herein include glass microfibers such as glass wool available from Evanite Fiber Corp. & (Corvallis, OR, USA). The glass microfibers useful herein will generally have fiber diameters of no greater than about 0.8 µm, more preferably from about 0.1 µm to about 0.7 µm. These fibers will have a surface area of at least about 2 m ² / g, more preferably at least about 3 m ² / g. Typically, the glass microfibre surface area will be from about 2 m ² / g to about 15 m ² / g. Representative glass microfibers for the present application are those available from Evanite Fiber Corp. & as type 104 glass fibers having a nominal fiber diameter of about 0.5 µm. These glass microfibers have a calculated surface area of about 3.1 m ² / g.

Other high surface area fibers useful herein are fibrillated acetate cellulose fibers. These fibers (referred to herein as fibers) have a large surface area as compared to cellulose-derived fibers commonly used in the absorbent article industry. Such fibers have very small diameter areas such that their particle size width is generally from about 0, These fibers typically have a surface area of about 20 m ² / g. Representative fibers useful herein as large surface materials are available from Hoechst Celanese Corp. (Charlotte, NC, USA) as cellulose acetate fibers. These fibers are discussed in detail, including their physical properties and methods of making them in Cellulose acetate fibers: Fibrillated

• ·

Cellulose Acetate Fibrets: A Fibrillated Pulp With High Surface Area, Smith, J. Ίζ., Ϊ́αρρΐ Journal, December 1988, p. 237, and US Patent No. 5,486,410.

In addition to these fibers, it will be apparent to those skilled in the art that other fibers, well known in the art, can be modified to have a large surface area and can be used in the present invention. Representative fibers that can be treated to achieve the large surface areas required by the present invention are described in U.S. Patent No. 5,599,335, supra (see especially columns 21 to 24).

Regardless of the nature of the high surface area fibers used, the fibers and the osmotic absorbent will be discrete materials prior to the combination. As used herein, the term discrete means that high surface area fibers and osmotic absorbents are both formed before being combined to form a storage absorbent member. In other words, the high surface area fibers are not formed subsequent to mixing with an osmotic absorbent, such as a hydrogel-forming absorbent polymer, nor is the osmotic absorbent formed in combination with the high surface area fibers. The combination of discrete components ensures that fibers with a large surface area have the desired morphology, and more importantly, they have the desired surface area.

C. Other components and materials, if any

The storage absorbent members of the present invention may include other optional components that may be present in the absorbent bands. For example, a reinforcing scrim may be placed within the absorbent absorbent member or between the respective absorbent members of the absorbent core. Such reinforcing scrims should be arranged so as not to form interfacial liquid transfer barriers, especially when placed between the respective absorbent members of the absorbent core. In addition, several binders can be used to provide the integrity of the absorbent core both dry and wet or the absorbent storage member itself. In particular, hydrophilic adhesive fibers can be used to provide bonding between high surface area materials and osmotic absorbent material. This is particularly critical for particulate materials with a large surface area. It is preferred that the amount of binder used is as low as possible in order not to impair the capillary sorption properties of the absorbent member, but it will be apparent to those skilled in the art that there are also

binders that can enhance the capillary sorption properties of the absorbent member, such as spun hydrophilic adhesive materials with a sufficiently large surface area. In this case, the hydrophilic adhesive material with a large surface area can provide both liquid handling function and integrity integrity in a single material. Also, the absorbent member or the entire absorbent core may be packaged in a liquid-permeable sheet, such as a tissue paper sheet, to prevent the free particles of the absorbent polymer from moving unless capillary continuity is compromised.

Other optional ingredients that may be included are odor control materials containing faeces, etc. Any absorbent member comprising a particulate osmotic absorbent or a high surface area material or the entire absorbent core may also be packaged in a sheet of liquid-permeable material, such as a sheet. of tissue paper to prevent free particles of absorbent polymer from moving.

IV. Other materials and properties of the absorbent member

The capillary suction storage absorbent members with high absorbent capacity of the present invention function as liquid storage members in the absorbent core. The principle function of such liquid storage members is to absorb the discharged body fluid either directly or from other absorbent members (eg, liquid acquisition and distribution members) and then retain such liquid even when subjected to pressures that normally occur as a result of the wearer's movements. However, it is to be understood that these absorbent members may serve functions other than liquid storage.

In those preferred embodiments where an osmotic absorbent is used, the amount of hydrogel-forming absorbent polymer or other osmotic absorbent contained in the storage absorbent member can vary considerably. The concentration of osmotic absorbents may further vary within the member. In other words, the member may have areas with relatively higher and relatively lower concentrations of osmotic absorbents.

Without being bound by theory, it is believed that a minimum amount of material with a large surface area mixed with a hydrogel-forming polymer or other osmotic

• ·· • 99 • 9 • • »» 99 • • • » • • • 9 • • e · · · ·· ·· t ·· • • • · ·· •

The absorbent material must be sufficient to fill the interstices between the particles of the hydrogel-forming absorbent polymer or other absorbent to such a functional stage in a dry and wet state that capillary continuity and sufficient fluid flow into the hydrogel-forming absorbent polymer are ensured.

In those preferred embodiments where the osmotic absorbent is in the form of a hydrogel-forming absorbent polymer, the weight percent of the absorbent hydrogel-forming absorbent polymer relative to the combined weight of the hydrogel-absorbent absorbent polymer and all other components (e.g., fibers, polymeric foams, etc.) ) which are present in the region containing the hydrogel-forming polymer. With this in mind, the concentration of hydrogel-forming absorbent polymers in the region of the absorbent member of the present invention may be at least about 50%, more preferably at least about 60%, even more preferably about 70%, even more preferably about 80%, and most preferably about 90% member. Similar ranges are possible where other osmotic absorbents are used.

Notwithstanding the fact that the regions of the storage absorbent member may include relatively high concentrations of hydrogel-forming absorbent polymer or other absorbent polymer where the high surface area material is fibrous in nature, the member will comprise on an aggregate basis (i.e. based on the total fiber weight of the absorbent member). the high surface area used in the member divided by the total weight of the absorbent member times 100%) of at least about 25% by weight of the high surface area fibers. It is believed that a lower limit of about 25% of the fibers is necessary to achieve the required desired capillary suction at the absorbent member. The storage absorbent members will preferably comprise at least about 30% by weight, more preferably at least about 35% by weight, of high surface area fibers. The absorbent member of the present invention will generally comprise on an aggregate basis from about 25% to about 90% by weight, more preferably from about 30% to about 85% by weight, even more preferably from about 35% to about 80% by weight of high surface area fibers.

In those embodiments where the high surface area material is a polymeric foam, the absorbent members will preferably comprise at least about 1% by weight (on an aggregate basis) of the polymeric foam. It is believed that the ability to use very low levels of polymeric foam as compared to • ·> ♦

The amount of high surface area fibers discussed above is due to various factors, including the very low density of these foams, by: foams have open cells that the foams themselves contribute to the overall absorption capacity and the like. The storage absorbent member will preferably comprise at least about 10% by weight, more preferably at least about 15% by weight, even more preferably at least about 20% by weight of the polymeric foam. Such storage absorbent members will comprise from about 1% to about 98% by weight, more typically from about 10% to about 90% by weight, even more typically from about 15% to about 85% by weight, even more preferably from about 20% to about 80% and even more preferably from about 20% to about 50% by weight of the polymeric foam material. As described above, these weight percent ranges are based on the total weight of the respective materials in the absorbent member. It is believed that the regions of the storage absorbent member may contain more and less materials.

The relative levels of osmotic absorbent, e.g., hydrogel-forming absorbent polymer and high surface area material, will be dictated, for example, by the absorbent capacity of the osmotic absorbent, the high surface area material used, the nature of the high surface area material, e.g. etc. In this regard, although high levels of osmotic absorbent provide absorbent members for the production of thin absorbent articles, to achieve the desired capillary suction level discussed above, a material with a sufficiently large surface area must be available to provide such suction capacity. Without wishing to be bound by theory, it is believed that the three primary properties of the preferred collapsible polymeric foam materials described above allow these foams to perform particularly efficiently in large absorbent storage absorbent members. These three properties are (1) relatively low density, (2) ability to readily distribute liquid therein, and (3) ability to remain collapsed, but then expand upon absorption of sufficient liquid along with preferred hydrogel-forming absorbent polymers as swell upon liquid absorption . This second property maintains contact between the foam material and the hydrogel-forming particles as the member absorbs liquid.

Figures 3,4, 5 and 6 are photomicrographed examples of storage absorbent members according to the present invention. Giant. Figures 3 and 4 show high suction polymer foams which can themselves (preferably in sheet form) act as a storage absorbent member. Giant. 5, 6 and 7

Illustrate storage absorbent members comprising an osmotic absorbent (specifically a hydrogel-forming absorbent polymer) and a high surface area material. Figure 5 illustrates a mixture of particulate hydrophilic polymeric foam materials 102 and particulate hydrogel-forming absorbent polymer 106. Adhesive fibers 110 are also shown to provide structural integrity and maintain contact of the particulate foam material 102 and hydrogel-forming absorbent polymer 106. In Figure 6. a single particle of hydrogel-forming polymer 116 surrounded by a plurality of filaments 114 is shown. FIG. 7 then shows a cross-section of a single hydrogel-forming particle 126 surrounded by a plurality of glass fibers 125.

As regards the absorbent absorbent members comprising the hydrogel-forming absorbent polymer, in addition to the high surface area material and the hydrogel-forming absorbent polymer, the absorbent absorbent members of the present invention may comprise other optional materials. For example, to ensure the integrity of the mixture of desired materials, the absorbent absorbent members may comprise an adhesive or binder material. Such materials may be particularly desirable where the high surface area material is particulate in nature.

When the integrity is achieved with a binder material, suitable binders are hot melt blown adhesives such as those described in US5560,878. The processes of combining hot melt blown adhesives with the desired hydrogel-forming polymer and high surface area material are also described in detail in US 5,560,878 .

Another example of a material that will ensure the integrity of the composition in absorbent members comprising a mixture of hydrogel-forming polymer and high surface area fibers or particulate polymeric foam may comprise a thermoplastic material. After melting at least a portion of this thermoplastic material, it migrates to the inter-portions of the respective constituents of the member, usually due to inter-particle or intercapular gradients. These intermediate portions become bonding sites for the thermoplastic material. When cooled, the thermoplastic materials solidify in these intermediate sections and form binding sites that hold the matrix of materials together.

The individual thermoplastic materials useful herein may be in any of a variety of forms, including particles, fibers, or combinations of particles and fibers. Thermoplastic fibers are a particularly preferred form because they are capable of forming multiple bonding sites. Suitable thermoplastic materials

they can be made of any thermoplastic polymer that can be melted at temperatures that do not significantly damage the materials that make up the absorbent member. The melting point of the thermoplastic material will preferably be less than about 190 ° C and preferably in the range of about 75 ° C to about 175 ° C. In any case, the melting point of the thermoplastic material should not be less than the temperature at which the thermally bonded absorbent structures are likely to be stored when used in absorbent articles. The melting point of the thermoplastic material is generally not less than about 50 ° C.

Thermoplastic materials, and in particular thermoplastic fibers, can be made from a variety of thermoplastic polymers, including polyolefins such as polyethylene (e.g., PULPEX® and polypropylene, polyesters, copolyesters, polyvinyl acetate, polyethylene vinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylates, polyamides, copolyamides, copolymers of the above polymers such as vinyl chloride / vinyl acetate, etc. One particularly preferred thermoplastic bonding fiber is PLEXAFIL®, which is polyethylene microfibers (manufactured by DuPont), which are also available as an approximately 20 percent blend with 80% cellulose fibers sold under the trade name KITTYHAWK® (manufactured by Weyerhauser Co.) Depending on the desired parameters for the resulting thermally bonded absorbent member, thermoplastic materials include hydrophobic fibers that have been treated to be hydrophilic, such as fibers or silicate treated fibers derived from, for example, polyolefins such as polyethylene or polypropylene, polyacrylates, polyamides, polystyrenes, polyurethanes and the like. The surface of the hydrophobic thermoplastic fibers may be treated to be hydrophilic by treatment with a surfactant such as a nonionic or anionic surfactant, e.g., by spraying the fibers with a surfactant, dipping the fibers in the surfactant, or including surfactants such as parts of the polymer melt in the manufacture of thermoplastic fibers. After melting and re-solidifying, the surfactant tends to remain on the surface of the thermoplastic fibers. Suitable surfactants include nonionic surfactants such as Brij® 76, manufactured by ICU Americas, Inc. from Wilmington, Delaware, USA, and various surfactants sold under the trademark Pegosperse® by Glyco Chemical, Inc. from Greenwich, Connecticut, USA. In addition to nonionic surfactants, anionic surfactants can also be used

surfactants. These surfactants can be applied to thermoplastic fibers at levels, for example, from about 0.2 g / cm ² to about 1 g / cm ^{2 of} thermoplastic fibers.

Suitable thermoplastic fibers may be made from a single polymer (monocomponent fibers) or may be from more than one polymer, for example bicomponent fibers. The term bicomponent fibers as used herein refers to thermoplastic fibers which consist of a core-forming fiber that is made of one polymer and a core-surrounding thermoplastic sheath made of a different polymer. The sheath-forming polymer often melts at a different, generally lower temperature than the core-forming polymer. As a result, these bicomponent fibers provide thermal bonding by melting the sheathing polymer while maintaining the desired strength characteristics of the core forming polymer.

Suitable two-component cores for use in the present invention may include sheath and core fibers having the following polymer combinations: polyethylene / polypropylene, polyethylene vinyl acetate / polypropylene, polyethylene / polyester, polypropylene / polyester, copolyester / polyester and the like. Particularly suitable thermoplastic fibers for use in the present invention are those having a polypropylene or polyester core and a lower melting copolyester, polyethylene vinyl acetate or polyethylene as a sheath (e.g., bicomponent fibers of DANAKON®, CELBOND® or CHISSO®). The bicomponent fibers may be concentric or eccentric. The terms concentric and eccentric, as used herein, mean whether the sheath has a thickness that is uniform or uneven across the cross-sectional area of the bicomponent fibers. Eccentric bicomponent fibers may be desirable in that they provide greater compressive strength at a lower fiber thickness. Suitable bicomponent fibers may be crimped by typical textile means, such as a crimping method or a crimping method to obtain predominantly two-dimensional or flat curl.

In the case of thermoplastic fibers, their length may vary depending on the particular melting point and other properties required for the fibers. These thermoplastic fibers generally have a length of from about 0.3 to about 7.5 cm, preferably from about 0.4 to about 3.0 cm, and most preferably from about 0.6 to about 1.2 cm. The properties, including the melting point of these thermoplastic fibers, can also be adjusted by varying the outer diameter (caliper) of the fibers. The diameter of these thermoplastic fibers is generally defined by parameters such as either denier

-41 (weight in g per 9000 m length) or decitex (weight in g per 10 000 m length). Suitable bicomponent thermoplastic fibers may have a decitex in the range of about 1.0 to about 20, preferably about 1.4 to about 10, and most preferably about 1.7 to about 3.3.

The modulus of compressibility of these thermoplastic materials and especially thermoplastic fibers may also be important. The modulus of compressibility of the thermoplastic fibers is influenced not only by the length and diameter, but also by the composition and properties of the polymer or polymers from which they are made, the shape and arrangement of the fibers (e.g., being concentric or eccentric, curled or unclean) and similar factors. Differences in the compressibility modulus of these thermoplastic fibers can be used to vary the properties and, in particular, the density parameters of the respective absorbent members during the preparation of the absorbent core.

Other materials known in the art can be included in absorbent storage members provided they are included at levels low enough to achieve the desired capillary suction properties. Optionally, other fibrous materials that are commonly combined with hydrogel-forming absorbent polymers may be included in the storage members of the present invention. For example, wood fibers and synthetic fibers can be included, but since such materials will tend to reduce the capillary suction capability of storage members comprising a high surface area material and a hydrogel-forming polymer, they will be included at relatively low levels so that the members continue to provide the desired absorbency. capillary suction capacity. It may be preferred to avoid the use of such fibers as they increase bulkiness and reduce the capillary sorption capacity on a mass basis.

Numerous methods known in the art can be used to combine a hydrogel-forming polymer (or other osmotic absorbent) and a high surface area material. Of course, the physical form (eg, fibrous, particulate, etc.) of the high surface area material and the hydrogel-forming absorbent polymer (or other osmotic absorbent) will dictate at least to some extent what methods can be used to form particular embodiments of the absorbent absorbent members.

In one embodiment, the hydrogel-forming absorbent polymer particles may be attached to the fibrous material to prevent undesirable migration of particles during manufacturing, storage, or wear. The attachment of absorbent particles to the molten polymeric material is described in U.S. Pat

-42EP 156 160 describing a molten polymeric material extruded to form a stream of molten blown polymeric microfibres and while still sticky, absorbent particles are fed therein to adhere to the fibers.

A method for trapping particulate absorbent materials in a meltblown web is disclosed in U.S. Patent No. 4,923,454, which discloses absorbent structures comprising microfibers and absorbent articles in which wettable, hydrophilic, nylon, meltblown microfibers and hydrogel-forming polymer particles as well as absorbent articles are described. U.S. Pat. No. 4,773,903, which discloses meltblown microfibers and hydrogel-forming polymer particles and crimped staple fibers and a hydrophilizing agent.

Anchoring of the high surface area materials and the hydrogel-forming absorbent polymer by the method generally described in US 4 764 325 is also possible. The high surface area material and the hydrogel-forming polymer may also be encapsulated by the methods generally described in U.S. Patent Application Serial No. 08 / 585,278.

While the basis weight of the storage absorbent members of the present invention is not critical and will vary depending on the end use of the member (ie, incorporated in, for example, a feminine hygiene product, infant diaper, incontinent adult product, bandage) basis weight from about 5 g / m ² to about 3000 g / m ² , or more preferably from about 40 g / m ² to about 2500 g / m ² , or even more preferably from about 100 g / m ² to about 2000 g / m 2 ² , or even more preferably from about 150 g / m ² to about 1500 g / m ² , or even more preferably from about 250 g / m 2 to about g / m 2.

As mentioned, particularly preferred absorbent absorbent members are those wherein a large capillary suction polymer foam is used as the high surface area material. In one embodiment, the polymeric foam is particulate and is mixed with the particulate hydrogel-forming absorbent polymer to form a homogeneous mixture. Giant. 9 is a diagram of an apparatus 320 for forming such a homogeneous mixture. It can be seen from Figure 9 that the absorbent member is prepared by introducing the polymeric foam particles from the first inlet 301 into the first measuring device 302, wherein the device 302 is preferably a weight loss fluidized bed system that will control the amount of particulate polymeric material measured to line based

Weight loss from the device over a specified period of time, and introducing particulate hydrogel-forming polymer from the second inlet 303 into the second measuring device 304. wherein the device 304 is preferably a weight loss measuring system commonly used in the commercial manufacture of diapers and sanitary articles for women. , for example, a weight loss weighing system from Acrison, Inc., Moonachi, NY, USA. This step adjusts the basis weight of the hydrogel-forming absorbent polymer in the product. The polymeric foam particles and the hydrogel-forming polymer particles are introduced into a single mixing chamber 305. A homogeneous mixture of the two components is formed in the mixing chamber 305. This mixture is then conveyed by an air stream 306 using, for example, a venturi ejector to increase the kinetic energy of the particles, through a fibrous adhesive stream exiting site 307. Alternatively, the foam and hydrogel-forming polymer pieces may be agglomerated by any process capable of forming a relatively homogeneous mixture. a bonding or binding material together, obtaining a free-flowing mixture which is admitted into the air stream 306. The fibrous adhesive stream may be injected using a meltblown adhesive system which is available, for example, from J&M Laboratories, Inc., Dawsonville, GA, USA. This sticky fiber stream entangles the polymeric foam particles and hydrogel-forming polymer to form composite 308. Homogeneous mixing can be accomplished in an inlet chamber of, for example, a Venturi ejector from Fox, Dover, NJ, USA. If homogeneous mixing in chamber 305 is not feasible, two separate conveying streams may be needed to combine foam in the particles and hydrogel-forming absorbent polymer particles with the fibrous adhesive supplied from site 307. The composite 308 is then optionally positioned between the first web introduced through the first device 309 and a second belt introduced over the second device 310 to form the absorbent bearing member 311. The entire absorbent bearing member 311 may then be compressed, for example, using the spacing between the rotating rollers to achieve the target density and overall thickness of the member. According to one particular embodiment, one particular web is preferably a liquid distribution material as described above and the other web is a core covering material such as a nonwoven or a highly aerated material that is located adjacent the backsheet of the absorbent article.

A process similar to that described in the preceding paragraph can be used to combine large surface area fibers with an osmotic absorbent, e.g., a particulate hydrogel-forming absorbent polymer. That is, the filaments may be introduced by a device similar to the first material supply device 301 shown in FIG.

-44pict. 10. Other well known methods of combining fibers and hydrogel-forming polymers can also be used. An example of a composition for preparing such a composite is described in Example 1 below.

An alternative method of mixing and accelerating the particulate polymeric foam and hydrogel-forming polymer utilizes electrostatic forces. In this embodiment, both types of materials are charged to create an attractive force between them. This force is used to form a homogeneous mixture of the two materials and potentially creates a driving force to accelerate the mixture through the adhesive stream, thereby eliminating one of the process air streams.

In another preferred embodiment, the particulate, hydrogel-forming absorbent polymer is positioned between two sheets of polymeric foam material. The laminated combination is then handled (e.g., cut along its width) in the machine or in a transverse direction to cause the sheets to separate into strips or pieces to ensure that the storage absorbent member includes small portions of the laminated combination. It is noted that the laminate formed prior to cutting can also be used as a storage absorbent member and can provide the advantages of commercial scale production, but it has been found within the present invention that further processing provides a storage absorbent member having a particularly high capillary sorption absorbency. at high suction heights. Giant. 10 illustrates an apparatus 420 for manufacturing such a laminate combination, and FIG. 11 illustrates a laminated sectioned combination that can be used as an absorbent storage member of the present invention. In the apparatus 420 shown in FIG. 10, the first stretched sheet of polymeric foam material 402 is measured by any well known means in the art. Particularly, a stream of particulate hydrogel-forming absorbent polymer is measured from measuring device 403, wherein the device 403 is an optional weighing and loss measuring system commonly used in the commercial manufacture of diapers and feminine hygiene products, such as the measuring system available from Acrison. lne. The hydrogel-forming polymer is measured into an accelerator 404 (eg, a Venturi ejector or fluidized bed such as the Flexispray ™ system available from Nordson, Inc., Atlanta, GA, USA) where it is transported in an air stream towards the fibrous (preferably hydrophilic) adhesive 406 (e.g., Cycloflex ™ 34-5652 from National Starch, Bridgewater, NJ, USA) from site 405. The fibrous adhesive is entangled with the hydrogel-forming polymer particles and immobilized to form a mixture 407. O a little further downstream, after the point where the fibrous adhesive and the hydrogel-forming polymer are combined, a second stretched sheet of polymeric foam 408 is measured.

the adhesive carries the mixture to the gap point 409 where the sheets 402 and 408 are combined. This results in a laminated composite 410 comprising a hydrogel-forming polymer layer and an adhesive that is between the two sheets of polymeric foam material. The composite 410 is then combined with the nonwoven material 411 and the combination is led to a folding plate 412 that folds (preferably into e) the nonwoven material 411 around the composite 410. (The nonwoven material ensures the integrity of the composite during subsequent forming operations and also ensures further integrity in the final The wrapped composite is then introduced into the first forming apparatus 413 and the second forming apparatus 414. In the forming apparatus 413 and 414, the wrapped composite is selectively cut in multiple directions using shear planes. The shear planes divide the packaged composite into columns of polymer foam and hydrogel-forming layers of polymer and adhesive fibers. The reshaping operation also reduces the basis weight of the composite, including the nonwoven material around the shear planes.

To fully understand the physical nature of a particularly preferred embodiment of the composite formed by the above operation, FIG. 11 shows in detail the composite 410 (without showing the nonwoven wrapping) after being deformed in the devices 413 and 414. Embodiment One of the deforming devices cut the composite over its entire thickness into several strips in cross-section, while another deforming device cut the composite over its entire thickness in the machine direction. The result is a composite consisting of a plurality of discrete layered stacks 451. One of these stacks 451 is shown in an exploded view of FIG. 13, which more clearly shows that each stack 451 includes hydrogel-forming polymer particles 452, fiber adhesive 453, sandwiched. between the bars 454 and 455 of the polymeric foam material. To increase the interface between the hydrogel-forming absorbent polymer and the polymeric foam material, gentle mixing (e.g., use of shear forces) of composite 410 during or after deformation in devices 413 and 414 may be used.

V. Absorbent products

The high suction storage absorbent members of the present invention are particularly useful as a storage portion of absorbent structures (e.g., absorbent cores or core elements) for various absorbent articles. Absorbent articles herein are consumer products which are capable of absorbing significant amounts of urine, menstrual discharge, or other liquids (eg, liquids).

-46 such as aqueous faeces (liquid diarrhea), which are excreted by the incontinent wearer or user of the product. Examples of such absorbent articles include disposable diapers, incontinence garments, menstrual articles such as tampons and sanitary napkins, disposable training pants, bed pillows, bandages and the like. The absorbent articles herein are particularly suitable for use in articles such as diapers, cushions or garments worn in incontinence, garment protection, dressings, and the like.

In its simplest form, the absorbent article of the present invention only needs to include a storage absorbent member of the present invention, but will generally include a backsheet, typically relatively liquid impermeable, and a high suction storage member. In another simple form, the absorbent article only needs to include a backsheet, a receiving material, and a high suction storage material. The components will be joined so that the receiving material is positioned to receive the liquid secreted by the wearer of the absorbent article. The highly absorbent member described herein is positioned to be in fluid communication with the receiving member or with an optional liquid distribution member that is in fluid or capillary communication with the receiving member. Liquid impermeable backsheets may include any such material, such as polyethylene or polypropylene, having a thickness of about 0.038 mm to help retain liquid in the absorbent article.

More commonly, these absorbent articles will also include a liquid pervious topsheet element that covers the side of the absorbent articles that touches the wearer's skin. In this arrangement, the article comprises an absorbent core comprising one or more storage absorbent members of the present invention disposed between the backsheet and the topsheet. The liquid-permeable topsheets may include any material such as polyester, polyolefin, rayon, and the like, which is substantially porous and allows body fluid to readily pass through and into the underlying absorbent core. The topsheet material will preferably have no tendency to maintain aqueous liquids in the area of contact between the topsheet and the wearer's skin.

In addition to the absorbent absorbent member of the present invention, the absorbent core of the absorbent articles of the present invention may also include other, e.g., conventional, elements or materials. In one embodiment comprising a combination of said absorbent member and other absorbent materials, the absorbent articles may employ a multilayered configuration.

An absorbent core wherein the core layer comprising one or more absorbent storage members of the present invention may be used in combination with one or more additional discrete core layers including other absorbent structures or materials. Such other absorbent structures or materials may, for example, comprise air-laid or wet-laid strips of wood pulp or other cellulosic fibers. These other absorbent structures may also include foams, for example absorbent foams, or even sponges, used as parts useful for receiving and distributing liquid as described in U.S. Patent 5,563,179.

Another preferred embodiment comprises further subdividing the various elements of the absorbent core. This preferred absorbent core comprises a receiving layer only around the crotch region of the wearer to handle the initial rapid fluid ejection. The distribution layer is positioned vertically to the front and back of the receiving layer so as to suck the liquid away from the solution region. The storage layer is located at a location adjacent to the front and rear waist regions and only in contact with the distribution material. The storage absorbent member or members must then be able to absorb liquid from the distribution layer and overcome both the force given by gravity and the force given by the desorption pressures of the distribution material. This described product removes liquid from the crotch area at the time available between individual vents. the area is relatively dry and ready for further liquid intake, further maintaining the shape of the garment and keeping the crotch area relatively dry resulting in healthier skin. See, for example, co-pending U.S. patent applications Ser. No. 08 / 825,072, U.S. Ser. No. 08/825071 and U.S. Patent No. 5,827,253.

Giant. 1 illustrates a preferred embodiment of a diaper 60 in which the topsheet 61 and the backsheet 62 are equally sized and have length and width dimensions that are generally larger than the absorbent core 28. The topsheet 61 is bonded to the backsheet 62, thereby the edge defines the outer periphery or edges of the diaper 60.

The topsheet 61 is compliant, soft to the touch and does not irritate the wearer's skin. The topsheet 61 is liquid pervious permitting liquids to readily penetrate through its thickness. A suitable topsheet 61 can be made from a wide variety of materials such as porous foams, reticulated foams, apertured plastic foils, natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polyester or polypropylene fibers), or a combination of natural and synthetic fibers. The topsheet 61 is generally made of

The hydrophobic treatment causes an initial wettability of the topsheet so that liquid effluents can penetrate through the topsheet. The hydrophobic treatment is initially hydrophilic to initially hydrophilic to isolate the wearer ' s skin from liquids in the storage absorbent member. A particularly suitable topsheet 61 comprises polypropylene sold by Hercules Inc. from Wilmington, Delaware, USA. As used herein, the term staple length fibers means those fibers having a length of at least about 15.9 mm.

There are a number of manufacturing techniques that can be used to produce the topsheet 61. For example, the topsheet 61 may be woven, nonwoven, spunbonded nonwoven, carded, and the like. The preferred topsheet is carded and thermally bonded by means well known to those skilled in the textile industry. The topsheet 61 preferably has a weight of from about 18 to about 25 g / m ² , a minimum dry tensile strength of at least 400 g / cm in the machine direction and a wet tensile strength of at least about 55 g / cm in the cross machine direction.

It is preferred that the topsheet is the material closest to the user's skin, but is not necessary. It is also contemplated that a suitable absorbent core configuration could be used without the topsheet and yet produce desirable results such as comfort and absorbency, as well as ease of manufacture and cost savings. For example, the body-side surface of the absorbent core could be made of liquid, permeable, soft, pliable, non-irritating materials that replace a particular topsheet. Such an absorbent core would only need to be used in combination with the backsheet to provide comfort and absorbency in the absorbent article.

The backsheet 62 is impervious to liquids and is preferably made of a thin plastic film, although other liquid impervious materials may also be used. The backsheet 62 is preferably a polyethylene film having a thickness of from about 0.012 mm to about 0.051 cm, although other flexible, liquid impermeable materials may be used. As used herein, the term refers to flexible materials that are compliant and that will readily conform to the general shape and contours of the wearer's body.

A suitable polyethylene film is manufactured by Monsanto Chemical Corporation and is sold on the market as film # 8020. The backsheet 62 is preferably embossed or matt in order to form

-49 has achieved more fabric appearance. Further, the backsheet 62 may be breathable and allow vapors to escape from the absorbent core 28 while still preventing exudates from passing through the backsheet 62. It is contemplated that the backsheet is highly breathable but substantially impermeable to the backsheet. liquid may be desirable for some products.

The size of the backsheet 62 is dictated by the size of the absorbent core 28 and the precisely selected diaper design. In a particularly preferred embodiment, the backsheet 62 has a modified hourglass shape extending below the absorbent core 28 and a minimum distance of at least about 1.3 cm to about 2.5 cm around the entire edge of the diaper.

The topsheet 61 and the backsheet 62 are joined together in some suitable manner. The term bonded as used herein includes arrangements wherein the topsheet is directly bonded to the backsheet 62 by fastening the topsheet 61 directly to the backsheet 62 and an arrangement wherein the topsheet 61 is indirectly bonded to the backsheet 62 by fastening the topsheet 61 to In a particularly preferred embodiment, the topsheet 61 and the backsheet 62 are attached directly to each other at the edge of the diaper by a fastener (not shown), such as an adhesive or some other fastener known in the art. in the field. For example, a uniform continuous layer of adhesive, a patterned layer of adhesive, or a pattern of spaced lines or spots of adhesive may be used to secure the topsheet 61 to the backsheet 62.

The fastening tabs 65 are typically applied to the waistband 63 in the waist region of the diaper 60 to provide fastening means for holding the diaper on the wearer. The fastening tabs 65 are generally applied to the waistband 63 in the waist region of the diaper 60 to provide a fastening means for holding the diaper on the wearer. The illustrated fastening tabs 65 are just one possible example. The fastening tabs 65 may be as is well known in the art, such as the fastening tab described in U.S. Patent 3,848,594. These tabs or other diaper fastening means are generally used near the corners of the diaper 60.

The elastic members 69 are positioned adjacent the edge of the diaper 60, preferably along each longitudinal edge 64 such that the elastic members tend to pull and hold the diaper 60 against the wearer's legs. In addition, the elastic members 67 may be positioned adjacent to one or both regions of the belt 63 in the region of the region 63. ·· ·· · ♦ ···

A waistband of diaper 60 to form a waistband and leg cuffs. A suitable belt is described, for example, in U.S. Pat. No. 4,515,595, which is incorporated by reference. In addition, a method and apparatus suitable for making a disposable diaper having elastically contractible elastic members is disclosed in U.S. Patent 4,081,301.

The elastic members are affixed to the diaper 60 in an elastically contractible condition so that in a normal, unrestricted configuration, the elastic members effectively shrink or fold the diaper 60. The elastic members can be secured in the elastically contractible condition in at least two ways. For example, the elastic members may be stretched and secured while the diaper 60 is in an uncontrolled state. The diaper 60 may alternatively be shrunk, for example, by pleating, and the elastic members may be fastened and attached to the diaper 60 while the elastic members are in their non-relaxed or unstretched condition. The elastic members may extend along a portion of the length of the diaper 60. Alternatively, the elastic members may extend over the entire length of the diaper 60 or any other length suitable to provide an elastically shrinkable line. The length of the elastic members is dictated by the diaper design.

In use, the diaper 60 is fastened to the wearer by placing one region of the belt below the back of the wearer and guiding the remainder of the diaper 60 between the legs of the wearer such that another region of the belt is positioned across the front of the wearer. The tape tabs 65 or other fasteners are then preferably mounted to the outer front region of the diaper 60. During use of the disposable diaper or other absorbent articles including the absorbent absorbent members of the present invention, they tend to store liquids more efficiently and remain dry due to high absorbent capacity. and high suction capacity of the absorbent members.

When used as an absorbent core in a disposable diaper 60, a particularly preferred embodiment of the absorbent core 28 of the present invention is positioned such that the acquisition strip 52 is in fluid communication with the topsheet 61 and serves to rapidly receive and distribute body exudates from the wearer ' The adhesive bonding of the receiving strip 52 to the topsheet 61 can enhance fluid bonding by providing an interface bond to prevent the separate topsheet from blocking fluid flow. The distribution material 51 moves the liquid in the x and y directions in the core 28 and the liquid is then desorbed by the absorbent absorbent member 10, which is the absorbent absorbent member of the present invention.

While components 52 and 51 are generally shown to be straight and of the same size, other shapes and size relationships may also be utilized. As can be seen, generally the straight components have a width 53 corresponding to a suitable width for the crotch region 66 of a disposable diaper. Also, the length of the respective core components may be varied to provide a suitable size for wearers of different sizes.

As can be seen in FIG. 1, the storage absorbent member 10 may include two storage absorbent members 20 and 30 such that there is no element of the storage absorbent member 10 positioned in the diaper in the region of the liquid ejection. Because such a storage absorbent member 10 has little or no liquid storage material (the distribution material 51 may have considerable storage capacity and will contain liquid at least until it is desorbed by the material with a higher suction storage capacity) in the center of the core (corresponding to the crotch region of the core or region). products containing such cores can ensure that they fit better and provide more wearer comfort both when the product is dry and after it has been filled with several doses of body fluid. See, for example, co-pending U.S. Patent Application Serial Nos. 08/825,072, 08/825,071, and US Patent 5,827,253. 2a shows an exploded perspective view and an absorbent core 28 having two separate elements, each consisting of a storage absorbent element according to the present invention. The front panel 20 generally corresponds to the portion of the disposable diaper that the wearer wears at the front. Similarly, the back panel 30 corresponds to the disposable portion of the diaper that the wearer wears at the back.

Alternatively, the storage absorbent member 10 may be a monolayer or layers (i.e., where the dashed lines 70 in Figure 1 indicate that the storage absorbent member 10 is in the liquid discharge area) of the storage absorbent material of the present invention. Such an embodiment of the absorbent core 28 is shown in FIG. 2b.

In one embodiment, the acquisition strip 52 will be a liquid handling layer located in an area where the user of the article discharges liquid that is in the form of a high airy, nonwoven material, but preferably is in the form of a liquid acquisition layer comprising a layer of modified cellulosic fibers, e.g. crimped cellulose fibers and preferably up to about 10% by weight of the liquid acquisition and distribution layer of the polymeric gelling material. In a particularly preferred embodiment, the acquisition layer 52 will be

Include a very air chemically bonded polyethylene terephthalate (PET) nonwoven layer (eg having a basis weight of about 42 g / m ² ) covering a layer of stiffened, curled cellulose fibers (eg available from Weyerhauser Co.). , WA, USA as CMC®, also available from The Procter & Gamble Co., Paper Technology Division, Cincinnati, OH), such that the nonwoven PET layer is disposed between the stiffened, curled, cellulose fibers and the 6T topsheet Modified The cellulosic fibers used in the liquid acquisition layer 52 of such a preferred absorbent article are preferably wood pulp fibers that have been solidified and curled by chemical and / or heat treatment. Such modified cellulose fibers are of the same type as that used in the absorbent articles described in U.S. Patent No. 4,935,022. The preferred embodiment is one wherein the liquid distribution layer 51 is as described in copending U.S. patent application Ser. (042,418) or U.S. Pat. No. 5,800,416. (In the preferred embodiment utilizing the fibrous distribution materials described in U.S. Pat. No. 5,800,416), the distribution material passes through at least two rollers, each having notches and grooves having such a low tolerance therebetween, Similar processes have been developed for the production of stretched laminate materials and are described in U.S. Pat. No. 5,167,897, which relates to stretched materials. This process essentially constitutes a mechanical treatment of the strip. usually located between the (top) layer which handles a liquid (e.g., liquid acquisition material) and a high absorbent (lower) absorbent storage layer and is in fluid communication therewith. Absorbent articles that may utilize the absorbent absorbent members of the present invention in a lower liquid storage layer lying below the liquid receiving and distribution topsheet comprising stiffened, curled, cellulose fibers are described in more detail in U.S. Patent 5,147,345.

As used herein, disposable absorbent articles are those articles that are intended to be disposed of after a single use (e.g., the original absorbent article as a whole is not intended to be cleaned or otherwise restored to its original use). condition or reused as absorbent article, although certain materials or the entire absorbent article may be recycled, reused or composted). The term diaper, as used herein, refers to a garment which is generally worn by young children and incontinent persons and which the wearer wears around the lower torso. However, it is to be understood that the present invention also applies to other absorbent articles, such as incontinence briefs,

-53 · «» 3 • ·

4 4 4 • • 4 4 • • 4 4 • 44 · «··>

4 4 4

4 4 4

4 4

44 444 incontinent pads, sports pants, diaper pads, faeces cushions, sanitary pads, tampons, bandages, facial tissues, paper napkins and the like.

VI. Test methods

A. Capillary sorption

Purpose

The purpose of this test is to measure the absorption capacity or capacity by capillary sorption as a function of the height of the storage absorbent members of the present invention. (The test is also used to measure the capillary sorption absorption capacity as a function of the height of high surface area materials, i.e., without an osmotic absorbent such as a hydrogel-forming absorbent polymer or other optional materials utilized in the absorbent member. the method as used to measure the entire storage absorbent member.) Capillary sorption is an essential property of each absorbent that controls how liquid is absorbed into the absorbent structure. In capillary sorption experiments, the capacity of the absorbent by capillary sorption is measured as a function of the liquid pressure given by the sample height in relation to the test liquid reservoir.

The method of determining capillary sorption is well known, see Burgeni, A. A. and Kapur, C., Capillary Sorption Balances in Fibrous Materials, Textile Research Journal, 37 (1967), 356366; Chatterjee, P.K., Absorbency, Textile Science and Technology 7, Chapter II, pp. 29-84, Elsevier Science Publishers B.V., 1985; and U.S. Pat. No. 4,610,678, which discusses a method for measuring capillary sorption of absorbent structures.

Principle

The porous glass frit is connected via an uninterrupted column of liquid to the liquid reservoir on the scale. The sample is maintained at a constant restraining mass during the experiment. As the porous structure absorbs liquid as desired, the weight loss in the liquid container of the scale is recorded as liquid intake, which is treated, for glass-frit-like intake 4 44 • · • 4 4 7

-54 * ·· 44 44 444 • · ·

4 ·

height and evaporation functions. Intake or capacity is measured at different capillary suction (hyrostatic stresses or heights). An increase in absorption occurs due to an incremental reduction of the frit (i.e., a reduction in capillary suction).

The time is also monitored during the experiment to allow the calculation of the initial effective uptake rate (g / g / h) at 200 cm height.

Reagents

Test liquid: synthetic urine is prepared by completely dissolving the following materials in distilled water:

Compound F.W. Concentration (g / liter) KC1 74.6 2,0 Na ₂ SO ₄ 142 2,0 (NH4) ₄ H2PO 115 0.85 (NH 4) 2 HPO ₄ 132 0.15 CaCl ₂ 2H ₂ O 147 0.25 MgClŽ.óKtO 203 0.5

General description of the apparatus settings

The capillary sorption device 220 shown in Figure 8A used in this assay is operated under TAPPI conditions (50% RH, 25 ° C). The test sample is placed on a glass frit 202, see FIG. 8A, which is connected by a continuous column of test liquid (synthetic urine) to a liquid reservoir 206 on the scale containing the test liquid. This cartridge 206 is located on a scale 207 which is connected to a computer (not shown) by an interface. The scale should be able to weigh to the nearest 0,001 g. Such a scale is available from Mettler Toledo as type PR 1203 (Hightstown, NJ, USA). The glass frit 202 is positioned vertically sliding on a drive rack 201, shown schematically in Figure 8A, which allows the test sample to be moved vertically so that it is exposed to varying suction height. The vertically displaceable stand with drive 201 may be a contactless motion mechanism

-55 which is connected to the computer to record suction heights and corresponding times for measuring fluid intake into the test sample. The preferred contactless motion mechanism is available from Industrial Devices (Novato, CA, USA) as the 202X4X34N-1D4B-84-PC-SE type, which can be powered by the ZETA 6104-83-135 motor drive available from CompuMotor. (Rohnert, CA). Where data is measured and sent from a vertically movable drive rack 201 and weighing scale 207, capillary sorption absorption capacity data can be easily generated for each test sample. Also, the computer interface to the vertically displaceable rack with drive 201 may allow controlled vertical movement of the glass frit 202. For example, the drive 201 may be directed to move the glass frit 202 vertically only after equilibrium (as defined below) has been reached in each suction. height.

The bottom of the glass frit 202 is connected to a Tygon® tube 203 that connects the frit 202 to a three-way drain shut-off valve 209. The drain shut-off valve 209 is connected to the liquid reservoir 205 by a glass tube 204 and a shut-off valve 210. The glass tube 211 connects the liquid reservoir 205 to the liquid reservoir 206 through the stopcock 210. The liquid reservoir 206 consists of a light glass bowl 206A with a diameter of 12 mm and a lid 206B. The lid 206B has an opening through which the glass tube 211 is in contact with the liquid in the reservoir 206. The glass tube 211 must not be in contact with the lid 206B, or an unstable weight reading will occur and the test sample measurement cannot then be used.

The diameter of the glass frit must be sufficient to accommodate the piston and cylinder apparatus described below to hold the specimen. The glass frit 202 has a jacket that allows constant temperature control from the heating bath. The frit is a 350 ml funnel with a frit disc having pores of 4 to 5.5 µm and available from Corning Glass Co. (Corning, NY, USA) as No. 36060-350F. The pores are fine enough to keep the frit surface moistened at capillary suction heights (the glass frit does not allow air to enter the continuous column of test liquid under the glass frit).

As noted, the frit 202 is connected by tubing to the liquid container 205 or liquid container 206 on the scale. depending on the. position of the three-way shut-off valve 210.

• 4

4 4

The glass frit 202 is provided with a sheath to which water from a constant temperature bath enters. This ensures that the temperature of the glass frit is maintained at a constant temperature of 31 ° C during the test procedure. As shown in Fig. 8A, the glass frit 202 is provided with an inlet port 202A and an outlet port 202B, which form a closed circuit with a circulating thermal bath 208. (In Fig. 8A, the glass jacket is not shown but water introduced into the glass frit 202 s). the bath jacket 208 is not in contact with the test liquid and the test liquid does not circulate through the constant temperature bath. The water in the constant temperature bath circulates through the jacket of the glass frit wall 202.)

The reservoir 206 and the weight 207 are closed in the box 212. to minimize evaporation of the test liquid from the weighing container and to increase the stability of the weight during the experiment. This box 212 has a top and walls wherein the top has an opening through which a tube 211 is inserted.

The glass frit 202 is shown in more detail in FIG. 8B. Giant. 8B is a cross-sectional view of a glass frit shown without inlet port 202A and outlet port 202B. As noted, the glass frit is a 350 ml funnel with a frit disc having pores of 4 to 5.5 µm. Referring to FIG. 8B, the glass frit 202 comprises a cylindrical funnel 250 with a sheath, and a glass frit disc 260. The glass frit 202 further comprises an assembly 265 comprised of a cylinder and a piston (which includes a cylinder 266 and a piston 268). which retains the specimen 270 and provides little restraining pressure on the specimen. To prevent excessive evaporation of the test liquid from the glass frit disc 260, a Teflon® ring 262 is disposed on the glass frit disc 260. The Teflon® ring 262 is 0.0127 cm thick (available as a sheet material from McMasterCarr as No. 8569K16 from which it is cut in the appropriate size) and is used to cover the surface of the frit disc outside the cylinder 266 to minimize evaporation from the glass frit . The outside diameter of the ring and the inside diameter of the ring 262 are 7.6 and 6.3 cm, respectively. The inner diameter of the Teflon® ring 262 is about 2 mm smaller than the outer diameter of the cylinder 266. A Viton® o-ring (available from McMasterCarr as AS568A-150 and AS568A151) is placed on the Teflon® ring 262. which serves to seal the space between the inner wall of the sheathed tubular funnel 250 and the Teflon ring 262 to further help prevent evaporation. If the outer diameter of the o-ring exceeds the inner diameter of the jacketed funnel 250, the diameter of the o-ring is reduced to match the funnel as follows: o-ring is. cuts, the necessary part of the material, o • · Λ

The ring is cut and the o-ring is again glued so that the o-ring is in contact with the inner wall of the cylindrical funnel 250 along the entire circumference.

As noted, the cylinder and piston assembly 265, shown schematically in FIG. 8B, encloses the test sample therein and provides little restraining pressure on the test sample 270. FIG. 8C shows that the assembly 265 consists of a cup piston cylinder 266 268 from Teflon® and, if necessary, from one or more weights (not shown) that can be inserted inside the piston 268. (Any weights will be used if necessary to adjust the combined weight of the piston and weights This is discussed below.) Cylinder 266 is a piece of Lexan® rod and has the following dimensions: 7.0 cm outside diameter, 6.0 cm inside diameter and height 6.0 cm. The Teflon® piston 268 has the following dimensions: an outer diameter that is 0.02 cm smaller than the inner diameter of the cylinder 266. As shown in Fig. 8D, the end of the piston 268 that is not in contact with the specimen is drilled to create a diameter of 5.0 cm to a depth of 1.8 cm to form a chamber 290 where any weights will come (determined by the specific dry test diameter) needed to obtain a limiting pressure of 1.4 kPa per test sample. In other words, the total weight of the piston 268 and any weights (not shown) divided by the actual diameter of the test sample (when dry) should be such that a limiting pressure of 1.4 kPa is achieved. The cylinder 266 and the piston 268 (and any weights) are allowed to equilibrate at 31 ° C for at least 30 minutes prior to capillary sorption absorption capacity measurements.

To cover the glass frit 202 during capillary sorption experiments, a perforated film (14 cm x 14 cm) that is not treated with a surfactant (not shown) is used to minimize air destabilization around the sample. The openings are large enough to prevent condensation on the underside of the film during the experiment.

Preparation of the test sample

The test sample can be obtained by punching a 5.4 cm diameter sample of the structure from the receiving absorbent member using a round punch. When the member is part of an absorbent article, other parts of the article must be removed prior to testing. In those situations where the member cannot be isolated from other components of the product without. substantial-changes yours. structures (e.g., density,

• 9

-58 the relative arrangement of the component materials, the physical properties of the materials used, etc.) or where the member is not part of the absorbent article, the test sample is prepared by combining all materials of which the member consists such that the combination represents the member.

The sample weight per supha (used below to calculate the capillary sorption absorption capacity) is the weight of the test sample prepared as described above under ambient conditions.

Experiment design

1. Clean, clean glass frit 202 is placed in a funnel holder attached to the vertically displaceable rack 201. The funnel holder of the vertically displaceable rack is moved so that the glass frit is 0 cm high.

2. The apparatus components are arranged as shown in Fig. 8A and described above.

3. A 12 cm diameter fluid reservoir 206 is placed on a scale 207. A plastic lid 206B is placed above the liquid reservoir 206 and a plastic lid is also placed on the weighing box 212, each lid m (j small holes for glass tubes 211 which The glass tubes must not touch the lid 206B of the liquid reservoir 206 on the scale 207 as this would cause an unstable reading on the scale and the measurement would not be possible to use.

4. The stopcock 210 closes towards the tube 204 and opens into the glass tube 211. The liquid reservoir 205 previously filled with the test liquid is opened so that the test liquid can enter the tube 211 and fill the liquid reservoir 206 on the scale 207.

5. The glass frit 202 is brought to the correct level and fixed in place. It is also ensured that the glass frit is dry.

6. The Tygon® tube 203 is connected to the stopcock 209. (The tube should be long enough to reach the glass frit 202 at the highest point 200 cm without handles.) This Tygon® tube 203 is filled with test liquid from reservoir 205 to liquid.

7. The tube 203 is connected to the glass frit 202 and then the stopcock 209 and the stopcock 210 that open from the liquid container 205 to the glass frit 202 are opened. (Stopcock 210 should be closed to the glass tube 210.) The test liquid fills the glass frit 202 and removes all air in the glass frit 202. During filling, the filling is continued until the liquid level exceeds the top of the glass frit disc 260. The funnel is •

-59purges and removes any air bubbles in the tube and inside the funnel. The air bubbles can be removed by inverting the glass frit 202, thereby allowing the air bubbles to rise up and escape the drain at shut-off valve 209. (Air bubbles generally collect at the bottom of the glass frit disc 260.) The frit is repositioned at such a low level, The frit level is re-adjusted using a sufficiently small level to sit within the jacket funnel 250 and on the surface of the glass frit disc 260.

8. The glass frit is zeroed with a liquid reservoir 206 on a scale 207. To do this, a piece of a Tygon® tube of sufficient length is taken and filled with test liquid. One end is placed in a liquid weighing container 206 and the other end is used to position the glass frit 202. The level of test liquid indicated by the tube (which is equivalent to the level of the liquid weighing container) is 10 mm below the top of the glass frit disc 260. to do so, either adjust the amount of liquid in the container or reset the zero position on the vertically displaceable rack 201.

9. Connect the outlet and inlet ports from the thermal bath 208 through tubes to the inlet and outlet ports 202A and 202B of the glass frit. The temperature of the glass frit disc 260 is allowed to reach 31 ° C. This can be measured by partially filling the glass frit with test liquid and measuring its temperature after it has reached equilibrium temperature. The bath will need a setting slightly higher than 31 ° C to account for heat loss during the passage of water from the bath to the glass frit.

10. Allow the glass frit to equilibrate for 30 minutes.

Capillary sorption parameters

The following describes a computer program that will determine how long a glass frit will remain at each level.

In the capillary sorption software program, the test sample is at a specific height from the liquid reservoir. As mentioned above, the fluid reservoir is on the scale so that the computer can read the scale value at the end of the known time interval and calculate the flow (delta value / time interval) between the test sample and the reservoir. For the purposes of this method, a test sample is considered to achieve equilibrium when the flow is less than the specified flow rate.

-60flow for a specified number of consecutive time intervals. It is believed that for certain materials the true equilibrium may not be reached when the determined equilibrium constant is reached. The time interval between readings is 5 seconds.

The number of readings in the delta table is determined in the capillary sorption menu as equilibrium samples. The maximum number of deltas is 500. The flow constant is specified in the capillary sorption menu as the equilibrium constant.

The equilibrium constant is inserted in g / s and is in the range of 0.0001 to 100,000.

Below is a simplified example of logic. The table shows weight and delta flow readings calculated for each time interval.

Equilibrium samples = 3 Equilibrium constant ~ 0.0015

in

Time interval

• φ

Time interval Weight value (g) Delta flow rate (g / s) 0 0 1 0,090 0.0180 2 0.165 0.0150 3 0.225 0.0120 4 0.270 0.0090 5 0.295 0.0050 6 0.305 0.0020 7 0.312 0,0014 8 0.316 0.0008 9 0.318 0.0004

Delta Table

Time 0 1 2 3 4 .5 6 7 8 9 Delta 1 9999 0.0180 0.0180 0.0180 0.0090 0.0090 0.0090 0,0014 0,0014 0,0014 Delta 2 9999 9999 0.0150 0.0150 0.0150 0.0050 0.0050 0.0050 0.0008 0.0008 Delta 3 9999 9999 9999 0.0120 0.0120 0.0120 0.0020 0.0020 0.0020 0.0004

The equilibrium intake for the above example is 0.318 g.

Below is the C code used to determine equilibrium income.

/ * takedata.C * / int take_data {int equilsamples. double equilibriumconstant} {

double delta;

static double deltas [500]; / * table to store up to 500 delta values * / double value;

double prevvalue;

clockt nexttime;

int i;

-62for (i = 0; i <equil_samples; i ++) deltasfi] = 9999;

deltatableindex = 0;

equilibriumreached ~ 0;

nexttime = clock ();

prevreading = 0;

while (lequilibriumreached) {nexttime + = 5000L while (clock <) <nexttipie);

value = getbanancereading (); delta = fabs (prev_value-value) /5.0;

prevvalue = value;

deltas [delta table index] = delta;

delta_table_index ++;

if (deltatableindex = ^ quilsamples)

/ * initialize all values in the delt table to 9999. gms / sec * / / * initialize where to store another delta in the table * / / * initialize a flag indicating that an equilibrium has not been reached * / / * initialize when to read again * / / * initialize the value from the previous reading of the weight value * / / * start the balance check loop * / / * calculate when to perform the next reading * / / * wait until 5 seconds have passed since the previous reading * / / * read the weight value in grams * / / * calculate absolute flow value in the last 5 seconds * / / * store instantaneous value for next loop * / / * store instantaneous delta value in delta value table * / / * incremental pointer to next position in table * / / * when is the number delta = number * / / * equilibrium samples specified, / * f * reset pointer to the beginning of the table. Thus the * / / * table always contains the last xx continuous samples. * /

-63equilibriumreached = 1;

for (i = 0; i <equilsamples; i ++) if (deltas [i]> = equilibriqmconstant) equilibriumreached = 0;

}}

/ * has been set to indicate equilibrium * / / * check all values in delta table * / / * if any value is> or = equilibrium constant * / / * set equilibrium label to 0 (not to equilibrium) * / / * go to the beginning of the loop * /

Capillary sorption parameters

Load description (limiting pressure: 1.4 kPa) Equilibrium samples (n): 50 Equilibrium constant: 0 _p 0005 g / s Height setting: 100 cm Final height: 0 cm

Hydrostatic height parameters: 200, 180, 160, 140, 120, 100, 90, 80, 70, 60, 50, 45, 40 35, 30, 25, 20, 15, 10, 5 and 0 cm.

The capillary sorption procedure is performed using all of the above heights to measure the capillary sorption absorption capacity in the order indicated. While it is desirable to determine the absorption capacity by capillary sorption at a certain height (e.g., 35 cm), it is necessary to complete a series of hydrostatic height parameters in that order. Although all of these heights are used in the performance of the capillary sorption test to create capillary sorption isotherms for the test sample, the present invention describes storage absorbent members under absorbent properties at specific heights of 200, 140, 100, 50, 35, and 0 cm.

Capillary sorption procedure

1) Follow the experiment setup procedure.

2) Check that the tempering bath 208 is turned on and that the water is circulating through the glass frit 202 and that the temperature of the glass frit disc 260 is 31 ° C.

• · · · · · · · ·

A glass frit 202 is placed at a suction height of 200 cm. The stopcocks 209 and 210 are opened to connect the glass frit 202 to the liquid reservoir 206 on the scale. (The stopcock 210 is closed toward the liquid reservoir 205.) The glass frit 202 is allowed to stabilize for 30 minutes.

4) The above capillary sorption parameters are entered into the computer.

5) The stopcocks 209 and 210 are closed.

6) The glass frit 202 is moved to a set height of 100 cm.

7) The Teflon® ring 262 is placed on the surface of the glass frit disc 260. The O-ring 264 is placed on the Teflon® glass frit ring 262. The preheated roller 266 is placed concentrically on the ring 262 of Teflon®. The test sample 270 is placed concentrically in the cylinder 266 on the glass frit disc 260. A piston 268 is inserted into the cylinder 266. If necessary, additional restraining weights are placed in the chamber 290 of the piston 268.

8) The glass frit 202 is covered with an apertured film.

9) The value read on the scale at this time determines zero or tare.

10) The glass frit 202 is moved to 200 cm.

11) The shut-off taps 209 and 210 are opened (shut-off tap 210 is closed to the liquid reservoir 2051 and the reading of the value indicated by the weight and time is started.

Glass frit correction (empty reception correction)

Since the glass frit disc 260 is a porous structure, it is necessary to determine the absorption uptake by capillary sorption of the glass frit (202) (correction of the void uptake) and read it to obtain the actual uptake absorption by capillary sorption of the test sample. Glass frit correction is performed for each newly used glass frit. The capillary sorption procedure proceeds as described above, but without the test sample to obtain no-load intake (g). Elapsed time at each specified altitude equals the no-load time (s).

Evaporative loss correction

1) The glass frit 202 is moved up to 2 cm above zero and allowed to align at this height for 30 minutes with the shut-off valves 20 and 210 open (closed to the cartridge 205).

2) Taps 209 and 210 are closed.

653) The Teflon® ring 262 is placed on the surface of the glass frit disc 260. The ring 264 is placed on the Teflon® ring 262. The preheated roller 266 is placed concentrically on the ring 262 of Teflon®. The piston 268 is inserted into the cylinder 266. Perforated film is placed on the glass frit 202.

4) The stopcocks 209 and 210 are opened (closed to container 205) and the value indicated by the weight and the time for 3.5 h are recorded. The cold sore (g / h) of the sample is calculated as follows:

[value indicated by weight at 1 h - value indicated by weight at 3.5 h] / 2.5 h

Even after all the above precautions have been taken, there will still be some evaporation loss, typically around 0.10 g / h for both the test sample and the frit correction. The evaporation of the sample is best measured for each newly installed glass frit 202.

Cleaning equipment

When installing a new glass frit 202. a new Tygon® pipe is used. The glass tubes 204 and 211, the liquid container 205 and the liquid container 206 on the scale are cleaned with a 50% Clorox Bleach® solution in distilled water, followed by rinsing with distilled water if microbial contamination is visible.

a. Purification after each experiment

At the end of each experiment (after the test sample has been removed), the glass frit is flushed forward (ie, the test liquid is fed under the glass frit) with 250 ml of test liquid from the liquid reservoir 205 to remove the remaining test sample from the glass pores. of a frit disc. The taps 209 and 210 are opened into the liquid container 205 and sealed into the liquid container 206 on the scale, the glass frit is removed from the holder, turned upside down and rinsed first with the test liquid, then rinsed with acetone and test liquid. During flushing, the glass frit must be tilted upside down and the flushing liquid is sprayed onto the contact surface of the glass frit disc test piece. After rinsing, the glass frit is rinsed forward for the second time with 250 ml of synthetic urine. Finally, the glass frit is inserted back into the holder and the frit surface is leveled.

b. Monitoring the operation of the glass frit

The operation of the glass frit must be monitored after each cleaning process and for each newly installed glass frit, with the glass frit set to 0 cm. Pour 50 ml of test liquid onto the surface of a flattened glass frit disc (without Teflon® ring, o-ring and cylinder and piston parts). The time it takes for the liquid level to drop to 5 mm above the surface of the glass frit disc is recorded. If this time exceeds 4.5 min, periodic cleaning is required.

c. Periodic cleaning

The glass frits are periodically cleaned (see the above-mentioned frit monitoring) to avoid clogging. The wash liquids are distilled water, acetone, 50% Clorox Bleach® in distilled water (to eliminate bacterial growth) and test liquid. Cleaning involves removing the glass frit from the holder and detaching all tubes. The glass frit is flushed forward (i.e. the flushing liquid is introduced at the bottom of the glass frit), the frit being upside down and the respective liquids used in the following amounts and order:

250 ml distilled water

100 ml acetone

250 ml distilled water

100 ml of 50:50 Clorox® / distilled water

250 ml distilled water

250 ml of test liquid

The cleaning process is satisfactory when the operation of the glass frit is within the specified liquid flow criteria (see above) and when no residue is observed on the surface of the glass frit disc. If cleaning cannot be performed successfully, the frit must be replaced.

Calculations

The computer is set up to provide a message containing capillary suction height in cm, time, and grams reception at each height indicated. From this data, the absorption capacity can be calculated by capillary suction, which is corrected for both frit uptake and evaporation losses. Based • ·· • ·

The absorption capacity at 0 cm by capillary suction can also be used to calculate the absorption efficiency at specified heights. In addition, an initial effective reception rate of 200 cm is calculated.

Correction for blank reception

Vacancy adjustment (g)

No-load time (s) * sample evaporation (g / h) = no-load reception (g) -3600 (s / h)

Capillary Suction Absorption Capacity (CSAC)

Sample time (s) * Sample evaporation (g / h)

Sample Receipt (g) --- No-Receive Correction (g)

3600 s / h

CS AC (g / g) = Dry sample weight (g)

Initial effective intake speed at 200 cm (IEUR)

CSAC at 200 cm (g / g)

IEUR (g / g / h) = 200 cm (s) sampling time

Reporting

For each test sample, at least two measurements should be taken and the uptake should be averaged at each height to calculate the absorption capacity by capillary sorption for a given absorbent member or high surface material.

B. Vertical sorption height gradient (VHSH)

The vertical slope sorption test is carried out by taking a foam strip of suitable length (generally at least 60 cm) with a width generally of about 1 cm. The strip is suspended in a chamber controlled at 31 ° C using the strip suspension clips. The bottom of the strip is immersed in a test liquid which also has a temperature of 31 ° C. Preferably, the test fluid is synthetic urine as described in U.S. Patent No. 5,599,335. Over a period of time, the test fluid is soaked into the strip and reached an equilibrium point where no further wicking occurs. The test liquid may be stained to facilitate determination of the equilibrium point. Care should be taken to prevent evaporation from the samples, for example _by enclosing them with a glass tube

-68 ·· ♦ · • · with the glass not touching the sample and by appropriately closing the sample tube. The time to equilibrium may vary for the materials of the present invention and may range from about 24 to 96 hours or more. When the observable change in the height of the rising liquid for 1 h is no longer achieved, this condition is considered to be equilibrium.

Carefully remove the test strip from the test chamber to prevent liquid from being expelled. The strip is cut lengthwise into 2.5 sections and each section is weighed. Initial portions below about 50% of the entire expanded height can be cut into sections that are 5.1 cm long. These weights are then divided by the weight of the foam after drying to calculate the capacity (g / g) at different foam heights. From these results, the graph shown in Fig. 5 can be constructed by plotting the dependence of capacities on the heights at which the slices were made. The VHSH height with X% is the height in cm where it remains in the X% foam capacity at 0 cm (or FAC). A typical important value is VHSH at 90%. In principle, X can be any value. In the present invention, the most reproducible measure for VHSH is achieved at X - 90%. It will be apparent to those skilled in the art that this single point value does not fully reflect the shape of the curve obtained by plotting the capacity versus height. However, one point serves as a practical point for comparing the foams of the present invention.

-69VII. Examples

Example 1

A storage absorbent member comprising glass microfibers

This example describes a large capillary suction absorbent member comprising a hydrogel-forming absorbent polymer and a large surface glass microfibre as formed using a wet end forming process for increased density and structural organization following conventional air laying processes. The following procedure is used to form such a hydrogel-forming absorbent polymer comprising a member that approaches a homogeneous distribution of the absorbent polymer in the glass microfibre matrix.

A blend of 4.0 g ASAP 2300 (available from Chemdal LTD, American Colloid Co., Arlington Heights, Ill., USA; also available from The Procter & Gamble Co., Paper Technology Division, Cincinnati, OH); 0 g of glass microfibers (available as Q-FBBERS, Code 108, 110 Bulk from Manville Sales Corp., Denver, Co.) is combined in an explosion-proof, trigonal (11.36 liter) commercial Warner blender with approximately 500 ml 3A alcohol (95% ethanol, 5% methanol) or isopropanol or similar liquids that do not degrade or absorb into the structure or mixture of the polymers. Liquids which will not absorb into the structure or the mixture of the hydrogels concerned are understood to mean that these liquids will only absorb to the structure or the mixture to an insignificant extent or within less than about 5 g of liquid per gram of the respective hydrogel-forming absorbent polymer (about 5 g). / g by weight). The mixture is poured into a paper mill box of 152 mm x 152 mm with an 80 mesh nylon forming mesh (available from Appleton Mfg. Div., Productive Solutions, Inc., Neenah, WI, USA) at the bottom of the top of the forming box. The liquid level is adjusted to 203 mm above the sieve by adding 3 A alcohol or a suitable solution. A paddle is used to thoroughly mix the solution above the sieve in the box. A valve is opened underneath the forming sieve and the liquid is drained off quickly to ensure uniform placement on the forming sieve. The sieve is removed from the forming box, placed on a vacuum source to remove loosely held liquid and allowed to dry overnight in a desiccator containing a desiccant (such as DRIERLTE,

Sigma Chem. Co., St. Louis, MO 63178) to ensure a uniform moisture content. Once dried, the absorbent member is removed from the forming screen.

A 5.4 cm diameter cylindrical structure is pierced into the arc by a capillary sorption absorption capacity measuring member. The capillary sorption absorption capacity data for the storage absorbent member is summarized in Table 1 below.

Example 2

Preparation of high surface area foam from HIPR

A) Preparation of HIPE

Anhydrous calcium chloride (36.32 kg) and peroxydual potassium sulfate (189 g) were dissolved in 378 liters of water. This is ensured by the water phase stream, which is used in a continuous process to form the JIPE.

To a combination of monomers including distilled divinylbenzene (42.4% hollybenzene and 57.6% ethylstyrene) (2640 g), 2-ethylhexyl acrylate (4400 g) and hexanedioideacrylate (960 g) were added diglycerol mono-oleate emulsifier (480 g), di-sodium dimethylammonium methylsulfate g) and Tinuvin 765 (20g). The diglycerol monooleate emulsifier (Grindsted Products; Brabrand, Denmark) comprises approximately 81% diglycerol monooleate, 1% other diglycerol monoesters, 3% polyols and 15% other polyglycerol esters provides a minimum oil / water interface voltage of approximately 2.7 dynes / cm and has a critical aggregate concentration oil / water approx. 2.8 wt. %. After mixing, this combination of materials is allowed to settle overnight. No visible residue is formed and the entire mixture is withdrawn and used as an oil phase in a continuous process to form an HIPE emulsion.

The individual streams of the oil phase (25 ° C) and the water phase (53-55 ° C) are supplied to the dynamic mixing apparatus. Thorough mixing of the combined streams in the dynamic mixing apparatus is achieved by means of a pin rotor. The pin rotor comprises a 36.5 cm long shaft with a diameter of about 2.9 cm. The shaft holds six rows of pegs, three rows having 33 pegs and three rows having 34 pegs, and each of the three pegs at each level is angled

-71120 ° C, each level below which is offset by 60 ° relative to the adjacent level, each level being separated by 0.03 mm, each having a diameter of 0.5 cm extending outward from the central axis of the shaft to a length of 2.3 cm. The pin rotor is mounted in a cylindrical housing that creates a dynamic mixing apparatus and the pins have a gap of 1.5 mm from the walls of the cylindrical housing.

A small portion of the material emerging from the dynamic mixing apparatus is withdrawn and enters the recirculation zone as shown in the figure in US 5,827,909.

The static mixer (TAH Industries Model 100-812) has 12 elements with an outside diameter of 2.5 cm. The hose is mounted downstream of the static mixer to facilitate delivery of the emulsion to the equipment used for crosslinking. Alternatively, another static mixer is used to provide additional back pressure to keep the hose filled. An optional static mixer may be a 2.5 cm diameter tube, the twelve element mixer (McMaster-Carr, Aurora, OH, USA, type 3529K53).

The combined mixing and recirculating apparatus is filled with an oil phase and a water phase in a ratio of 4 parts water to 1 part oil. The dynamic mixing apparatus is vented to allow air to escape and completely fill the apparatus. The flow rates during filling are 7.57 g / s oil phase and 30.3 cm ³ / s water phase.

Once the assembled apparatus is filled, stirring is started in a dynamic stirrer, with its rotor at 1750 rpm and recirculation is started at a rate of about 30 cm ³ / s. The water phase flow rate is then steadily increased over a period of about 1 minute to a rate of 151.3 cm ³ / s and the oil phase flow rate is reduced to 3.03 g / s in about 3 minutes. The recirculation rate then increases steadily up to about 150 cm ³ / s. The back pressure created at this point by the dynamic zone and the static agitators is about 137 kPa, which represents the overall pressure drop of the system. The Waúkesha pump type (30) then decreases steadily until a recirculation rate of about 75 cm ³ / s is reached.

9 ·

9 9 9

9 9

9 9 9

9 9

989 99 9

-72 • ·· · *

9

9

9 Λ 9 9

999 99 99

IP) HIPE polymerization

The HIPE flowing from the static mixer at this point is collected in a round polyethylene container of 102 cm diameter and 31.8 cm height with removable sides resembling a spring mold for baking cakes. The tubular polyethylene liner with a diameter of 31.8 cm at its bottom is firmly fixed to the center of the foundation and is 31.8 cm high. HIPE-containing tubes are maintained in a 65 ° C room for 18 hours to effect polymerization and foam formation.

C) Foam washing and dewatering

The crosslinked HIPE foam is removed from the crosslinking vessels. The foam at this point has a residual aqueous phase (containing dissolved emulsifiers, electrolyte initiator residues, and initiator) of about 48 to 52 times the weight of the polymerized monomers. The foam is cut with a sharp rectilinear moving saw blade into 4.7 mm thick blades. These sheets are then subjected to compression in the gap between two vacuum-equipped rollers, thereby gradually reducing the residual water phase content of the foam to about six times the weight of the polymeric material. At this point, the leaves are re-saturated with a 1.5% CaCL solution at 60 ° C, then the gaps of a row of three porous cylinders equipped with a vacuum to a water phase content of about four times are squeezed. The CaCl2 content of the foam is between 8 and 10 percent.

The foam remains compressed behind the last gap at a thickness of about 0.053 cm. The foam was then air dried for 16 hours. Such drying reduces the moisture content to about 9 to 17% by weight of the polymeric material. At this point, the foam sheets are very flexible and thin.

The capillary sorption absorption capacity data for the storage absorbent member is summarized in Table 1 below.

Example 3

HIPE large surface foam preparation

A) Preparation of HIPE

An aqueous and oil phase suitable for use in a continuous process for forming an HIPE emulsion is prepared according to Example 1. A separate stream of oil phase (25 ° C) and aqueous phase (53 ° C to 55 ° C) are fed to a dynamic mixer as this is described in detail in Example 1.

Once the apparatus is filled, stirring is started with a dynamic stirrer, with its rotor at 1700 rpm and recirculation is started at a rate of about 30 cm ³ / s. The water phase flow rate is then steadily increased up to 151.3 cm ³ / sec for about 1 minute and the oil phase flow is reduced to 3.36 g / sec over a period of about 3 minutes. The back pressure created by the dynamic zone and static mixers at this location is about 136 kPa, which represents an overall pressure drop of the system. The Waukesha pump speed is then continuously reduced to achieve a recirculation rate of about 75 crrts.

B) HIPE polymerization

HIPE flowing from the static mixer is collected at this point and crosslinked to the polymeric foam as described in detail in Example 1.

C) Foam washing and drainage

The crosslinked HIPE foam is removed from the crosslinking vessels. At this point, the foam has a residual water phase (containing dissolved emulsifiers, electrolyte, initiator residues, and initiator) in an amount of 43 to 47 times the weight of the polymerized monomers. The foam is cut with a sharp sheet of 4.7 mm straight-moving saws. These sheets are then subjected to compression in the gap between a pair of vacuum cylinders which gradually reduce the residual water phase content of the foam to about six times the weight of the polymeric material. At this point, the leaves are then re-saturated with a 1.5% CaCl 3 solution, are compressed in the gap of a row of 3 porous cylinders equipped with a vacuum to a water phase content of about 4 times. _CaCl2 content of the foam is between 8 and 10%.

After the last gap, the foam remains compressed at a thickness of about 0.071 cm). Then the foam is air dried for about 16 hours. Drying reduces the moisture content to about 9 to 17% by weight of the polymeric material. At this point, the foam sheets are very flexible and thin.

• · 4

4

-74Example 4

Preparation of foam with large surface area from HIPE

A) Preparation of HIPE

An aqueous and oil phase suitable for use in a continuous process for forming an HIPE emulsion is prepared according to Example 1. A separate oil phase stream (25 ° C) and an aqueous phase (53 ° C to 55 ° C) are fed to a dynamic mixing apparatus as is described in detail in Example 1.

Once the apparatus is filled, stirring is started with a dynamic stirrer, with its rotor at 1700 rpm and recirculation is started at a rate of about 30 cm ³ / s. The water phase flow rate is then steadily increased up to 151.3 cm ³ / sec for about 1 minute and the oil phase flow is reduced to 3.78 g / sec over a period of about 3 minutes. The recirculation rate then increases steadily to about 150 cm ³ / s. The back pressure created by the dynamic zone and the static mixers at this point is about 129 kPa, which represents the overall pressure drop of the system. The Waukesha pump speed is then continuously reduced to achieve a recirculation rate of about 75 cm s.

B) HIPE polymerization

HEPE flowing from the static mixer is collected at this point and crosslinked to the polymeric foam as described in detail in Example 1.

C) Foam washing and drainage

The crosslinked HIPE foam is removed from the crosslinking vessels. At this point, the foam has a residual water phase (containing dissolved emulsifiers, electrolyte, initiator residues, and initiator) in an amount of 38 to 42 times the weight of the polymerized monomers. The foam is cut with a sharp sheet of 4.7 mm straight-moving saws. These sheets are then subjected to compression in the gap between a pair of vacuum cylinders which gradually reduce the residual water phase content of the foam to about six times the weight of the polymeric material. At this point, the leaves are then re-saturated with a 1.5% CaCl2 solution, compressed in

the gap of a row of 3 porous cylinders equipped with a vacuum for water phase content about 4 times. The CaCE content in the foam is between 8 and 10%.

After the last gap, the foam remains compressed at a thickness of about 0.071 cm). Then the foam is air dried for about 16 hours. Drying reduces the moisture content to about 9 to 17% by weight of the polymeric material. At this point, the foam sheets are very flexible and thin.

Example 5

A storage absorbent member comprising a large surface area polymeric foam material

This example describes a large surface area absorbent member comprising a hydrogel-forming absorbent polymer and a large suction polymeric foam material prepared according to Example 3. In order to construct a hydrogel-forming absorbent polymer approaching a relatively homogeneous distribution of the absorbent polymer and polymer foam, following procedure.

g of dry-dried foam (prepared according to Example 3 above) is placed in a mixer (Osterizer, type 848-36L) equipped with a 1.25 liter vessel into which 1 liter of a 2% potassium chloride solution is placed. After ensuring that all the foam material is submerged, the mixer is stirred in Liquify mode (a high setting) for 10 seconds and then stirred in Grate mode for 5 seconds. The resulting slurry was then transferred to a Buchner funnel (Coors USA, type 60283) lined with a paper napkin. Approximately 500 ml of liquid is freely drained from the sample. The sample is then covered with a rubber membrane and vacuum is applied (approximately 500 mm Hg) to dewater the sample to a weight of 50 to 60 grams.

The sample is returned to the dry mixing vessel and dispersed by mixing in Liquify mode, while the vessel and base are inverted and returned several times to disperse the sample into approximately individual particles. The dispersed sample is then air dried under ambient conditions and then the foam particles are combined with a hydrogel-forming absorbent polymer (ASAP 2300, available from Chemdal Corporation of Palantine, EL, USA; also available from The Procter & Gamble Co) ., Paper Technology Division, Cincinnati, OH, USA) to ensure the formation of a storage absorbent member consisting of. from homogeneous mixture 50%

% by weight of a hydrogel-forming polymer; and 50% by weight of a high surface area polymer foam.

Capillary sorption absorption capacity data for this storage absorbent member is summarized in Table 1 below.

Example 6

A storage absorbent member comprising large surface area fibers

This example describes a large capillary suction absorbent member comprising a hydrogel-forming absorbent polymer and a large surface area fiber. Large surface area fibers available from Hoechst Celanese Corp. (Charlotte, NC) as Fibrets® acetate cellulose fibers are combined with a hydrogel-forming absorbent polymer (ASAP 2300, available from Chemdal Corporation of Palantine, IL, also available from The Procter & Gamble Co., Paper Technology Division). (Cincinnati, OH, USA) to provide a storage absorbent member consisting of a homogeneous mixture of 50 wt% hydrogel-forming polymer and 50 wt% fibers.

Capillary sorption absorption capacity data for this storage absorbent member is shown in Table 1 below.

Table 1

CSAC’0 cm (g / g) CSAC 35 cm (g / g) CSAC ’70cm (g / g) CSAC ’120cm (g / g) CSAC’200cm (g / g) Example 1 21.8 14.1 7.0 2.8 0.4 Example 3 36.3 31.1 8.5 5.3 4.2 Example 5 23.0 13.6 9.7 7.7 5.9 Example 6 17.2 10.6 7.3 5.2 3.1 Comparative 21.9 5.0 1.1 0.8 0.5 Comparative 43.9 9.9 6.3 1.9 0.5

*) CSAC = absorption capacity by capillary sorption

Claims (10)

PATENT REQUIREMENTS 1. A high capillary suction storage absorbent member having at least one of the following: - an absorption capacity by capillary sorption at a height of 35 cm of at least 12 g / g, - an absorption capacity by capillary sorption at a height of 70 cm of at least 7 g / g, an absorption capacity by capillary sorption at a height of 120 cm of at least 4 g / g, or - an absorption capacity by capillary sorption at a height of 200 cm of at least 3 g / g. Storage absorbent member according to Claim 1, characterized in that it has an absorption capacity by capillary sorption at a height of 35 cm of at least 14 g / g, preferably of at least 20 g / g. Storage absorbent member according to claim 1 or 2, characterized in that it has an absorption capacity by capillary sorption at a height of 70 cm of at least 9 g / g, preferably at least 11 g / g · Storage absorbent member according to claims 1 to 3, characterized in that it has an absorption capacity by capillary sorption at a height of 120 cm of at least 5 g / g, preferably at least 7 g / g. 5. The absorbent article of claim 1, wherein the absorbent member has a capillary sorption absorption capacity of 200 cm at least 4 g / g, preferably at least 6 g / g. A storage absorbent member according to claims 1-5 wherein the member comprises a collapsible polymeric foam structure having interconnected open cells that, upon contact with aqueous liquids, can expand and absorb liquids, wherein the polymeric foam structure has an equilibrium 90 percent vertical sorption height gradient of at least 60 cm. A storage absorbent member according to claims 1-5 comprising osmotic absorbents and a high surface area discrete material, wherein the high surface area material is selected from the group consisting of high surface area fibers, high surface area hydrophilic polymeric foam. surface and with open cells and mixtures thereof. • «and« ·· ·· · -788. The storage absorbent member of claim 7, wherein the osmotic absorbent is a hydrogel-forming absorbent polymer. 9. A large capillary suction storage absorbent article comprising an osmotic absorbent and a large surface area discrete material, wherein the member having a capillary sorption absorption capacity of 0 cm at least 15 g / g and having a mean absorption height of at least 15 g / g an average absorption height of at least 35 cm, preferably at least 40 cm, more preferably at least 50 cm. 10. A large capillary suction storage absorbent article comprising an osmotic absorbent and a discrete material having a large surface area, having a capillary sorption absorption capacity of 0 cm at least 15 g / g and at least one of the following: - at least 25% capillary absorption efficiency at a height of 120 cm, - a capillary absorption efficiency at a height of 70 cm of at least 30%, a capillary absorption efficiency at a height of 35 cm of at least 50%. 11. An absorbent article comprising a storage absorbent member according to claims 1 to 10.