DE2500962A1 - COMPOSITE ABSORBENT STRUCTURE AND DISPOSABLE DIAPER ON THE BASIS OF THIS STRUCTURE - Google Patents

Description

RECHiSA MV-'A. ITE

DR JUR. -π. - .: ^. waiter BEf ^ Jan. 10, 1975

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Our no. 19 667 Ec / br

The Procter & Gamble Company Cincinnati, Ohio _s V.St.A.

Composite absorbent structure and Disposable diaper based on this structure

The invention relates to new absorbent structures, which are characterized by compression resistance, high absorbency and softness. The new absorbent Structures are particularly suitable for use in articles that contain large amounts of moisture absorb directly, i.e. for towels, tablecloths, bed liners and disposable diapers.

It is a known problem in the manufacture of absorbent products under external conditions

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Load an effective fluid handling to achieve and maintain part. Typical absorbent products reflect a substantial compromise against,., which was closed between fluid intake and resilience to achieve a degree of universal applicability. In more general terms: when using typical absorbent Structures, the absorbent material is exposed to load forces and absorption functions; however, since the Absorption and exposure tend to be mutually exclusive, a compromise product results.

Disposable diapers are representative of typical compromise absorbent products. Generally speaking, included Disposable winch in a pliable plastic substrate or Base made of flexible plastic and an absorbent Core. The absorbent core is responsible for absorption, moisture retention and for the Resistance to compaction. Accordingly, the core of disposable diapers must have a density which is low enough -to have sufficient capacity for to provide large amounts of moisture that but it is still high enough to withstand compaction and the resulting "wringing out". the Requirements for the absorption capacity and the requirements for the carrying capacity of disposable diapers of course, a structure that represents a compromise. In addition, the structure is made of absorbent Products are also influenced by the need for a convenient product. In particular, need diapers retain their softness during use. In the diapers currently available, softness, absorbency and load-bearing capacity are primarily determined by the selection of the

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Affects the core material. The manufacturers of diapers have so far, to some extent, been dependent on such Aspects such as the size and age of the child's user and the time of use, in each case under the aforementioned Quality criteria made a compromise in order to a selection of the core material and thus to a Compromise product to arrive.

The present invention has for its object to provide an improved absorbent structure, which at the same time have high absorbency, resistance to compaction and softness is excellent and retains its absorption properties, while it absorbs a compressive force "

Another object of the invention is to provide improved disposable diapers that are absorbent, are durable and soft and retain the moisture absorbed when subjected to a user's weight are pressed together.

According to the invention, these tasks are accomplished by a composite absorbent structure released, which is characterized by " is that it (1) a flexible underlayer, (2) several spaced apart projections, protruding from the backsheet, and (3) containing an absorbent material that stays in the interstices is arranged between the projections.

In a preferred embodiment, the invention relates also a disposable diaper incorporating this absorbent structure.

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The subject of the invention is based on the drawings described in more detail below:

Figure 1 is a perspective elevation of a preferred embodiment of the absorbent structure of the present invention Invention;

Figure 2 is an enlarged section through the absorbent structure of Figure 1;

Figures 3a, ^{3 and} 5 are partial sections of various embodiments of the preferred absorbent structure which illustrate the invention;

Figure 6 is a perspective view of a preferred embodiment of the absorbent structure according to the present invention in an exploded view Arrangement; and

Figures 7 and 8 are top and perspective views, respectively, of the absorbent structure within it Use in a disposable diaper with parts cut away.

The present invention is based generally on the discovery that superior absorbent structures are produced can be established by the function of the liquid in a composite absorbent structure - uptake and the absorption function structurally separates from the support or bearing function. The resulting Structure shows increased absorbency under load and improved retention of absorbed Moisture, and this practically not at the expense of the softness that is usually found in absorbent pads and the like. These and other unexpected properties are the result, as stated earlier the unique structure, as explained in more detail below.

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As mentioned earlier, the composites contain absorbent Structures of the present invention include a pliable backsheet, several spaced apart arranged projections which protrude from the lower layer and are preferably evenly distributed on it, and an absorbent material disposed in the spaces between the protrusions. Hence it is located the seat of the puncture of the liquid absorption in the absorbent material, while the seat · the Support or bearing function is located in the projections that protrude from the lower layer.

In Figures 1 and 2, the backsheet 10 of the absorbent structure includes a layer of flexible material, which preferably has sufficient tensile strength to be torn when wetted in use resist. Suitable materials and the manner in which the backsheet 10 is made are known. For example suitable and preferred sub-layers made of flexible plastic films, such as polyethylene, Polyurethanes, ionomers, polystyrenes or polypropylenes; Paper or fabric such as cotton, rayon, dacron and the like; with rubberized materials and made of laminates, the combinations various plastic films, fabrics, paper or materials coated with rubber. The selection the material or materials used to make the backsheet 10 will depend on those desired Properties of the absorbent structure. For example, if the structure is in a disposable diaper is to be used, it is desirable to use a liquid impervious backsheet to absorb the Moisture can be contained within the absorbent structure while the outer surface

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stays dry. Therefore, they are impermeable to liquids Plastic sheeting, e.g. made of polyethylene, is a particularly preferred material for use as the backsheet 10 in a disposable diaper. Among the other physical requirements that the selection of the material from which the Underlayer 10 is produced, affect, belong e.g. the desired flexibility, strength, air permeability and strength of the absorbent to be formed Structure.

1, 2, 3, ^J 1 and 5, the absorbent structures according to the present invention are uniquely characterized by a plurality of spaced projections 11 which protrude from the backsheet, but which are not necessarily attached to the backsheet 10 .

It can be seen from Figures h and 5 that more than one surface of the underlayer can be characterized by a plurality of projections. FIG. K shows: an embodiment of the invention with staggered frontal jumps 11. However, the projections 11 can, if desired, also be arranged in a line, as is shown in FIG.

The protrusions 11 can be formed from various materials in various shapes, depending on the first Line desired properties of the end product. Of course, essentially any cross-sectional shape can be used or a mixture of different cross-sectional shapes can be used. Because the main advantage of the invention Structure lies in its improved absorption capacity under external stress, it is in everyone

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If advantageous, to maintain sufficient load-bearing capacity in the structure by means of the projections, about compressing under the load likely to be applied to the product during use will resist. Therefore, the protrusions In randomly spaced or equally spaced from each other.

A conventional way to quantitatively describe the frequency of projections and the arrangement of the position of the projections is the reference to the "gap fraction of ¹ '(" void fraction "), ie, the fraction of the horizontal Gesamfcoberflache of the structure, taken up by the absorbent material As a general rule, it has been found that effective fluid uptake with generally adequate carrying capacity is achieved by a void fraction of about 30 to about 80 % , but when the required void fraction is more precisely determined in view of the needs of a particular application several suitable arrangements of the position of the projections result for the person skilled in the art.

Although the above statements can generally be used as a guideline, in practice the form the dimensions, the frequency of occurrence and the location of the protrusions to a large extent different from that of manufacture the material used from the protrusions, as this Many different materials are available which, when properly executed, have the required load-bearing capacity result, the present invention is not directed to a particular material or to a particular shape for the Projections turned off.

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Particularly preferred arrangements of projections are explained in FIGS. 1, 2, 3, ^ and 5. In the figures 1 and 2, the projections 11 have the shape of walls or partitions with a sxnus curve-like longitudinal section, which abut at the interfaces 13. To a The projections or protuberances 11 are used to achieve additional tensile strength and easy machinability of Figure 1 are preferably connected to one another at the interfaces 13, so that a matrix of interconnected Projections is formed. Such a component in the form of a matrix can be produced by either individual projections or protuberances connects or glued together, as already described, or by appropriately perforating a sheet of the material from which the projections are to be made. In any case, the separating projections or protuberances 11 of FIG. 1 can be made of different materials getting produced. For example, flexible resilient foams result in rubber-coated materials and laminates protrusions or protuberances with sufficient load-bearing capacity for use in most Embodiments of the present invention. A particularly suitable material for separating protrusions or protuberances is a closed cell polyethylene foam. Aside from the load-bearing capacity, the protrusions are or protuberances 11 of Figure 1 particularly suitable for use in structures with small dimensions as well in structures such as diapers where consistency of touch is important.

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Figures 3 and h show columnar or spherical protrusions or protuberances 11. Even if the protrusions or protuberances 11 of Figures 3 and ^f 1 have essentially circular longitudinal sections and either a rectangular or a circular cross section, it goes without saying that that any cross-sectional shape or mixtures of different cross-sectional shapes can be used * For example, suitable projections or protuberances can be mushroom-shaped or hourglass-shaped. In addition, such projections or protuberances can be arranged at random intervals or at equal intervals from one another. As noted above, effective fluid uptake with generally sufficient carrying capacity is achieved when the void fraction is about 30 to about 80 percent . Therefore, for projections or protuberances with a circular longitudinal section, a triangular arrangement of the projections or protuberances arranged at the same distance from one another is preferred due to their applicability over the entire range of usable gap fractions. Further, the load resistance of columnar protrusions is directly related to the average ratio of height to horizontal cross-sectional area and to the average center-to-center distance between adjacent protrusions. If the ratio of height to horizontal cross-sectional area or the distance from center to center increases, the load resistance decreases. On the other hand, as the above ratio or distance becomes smaller, the structural strength becomes greater. If at the same time structural flexibility and

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and a relatively high load resistance is required, it may be necessary to join adjacent projections together in order to achieve lateral reinforcement and thereby minimize the tendency of the projections to "wobble". The reinforcement can be achieved by a layer or layers of "suspension strands" Ik , as shown in FIG. 3, which extend between the projections 11 and are attached to them at 15. Such ropes are typically in the form of loosely interwoven, thread-like materials that are connected to the entire structure at intermediate levels of the absorbent structure or as an integral "cover" therewith. From the foregoing it can be seen that various materials can be used to produce the columnar and spherical projections or protuberances of FIGS. 3 and k . Suitable materials include, for example, foams, rubbers, and inflated thin films with cells enclosed therein. Suitable inflated cells as shown in Figure k can be made from thin plastic films such as polyethylene, ionomer and the like, and can be inflated by adding any partially compressible substance such as gases, liquids, foams, gels , Fibers or mixtures thereof, in the cells. For certain applications it may be desirable to enclose an absorbent substance in the inflated protuberances in order to provide a further absorbent in the event that a protuberance is accidentally broken.

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FIG. 5 shows projections or protuberances 11 in the form of helical spirals or feathers. Even if the spiral-shaped protuberances according to FIG. 5 are relatively small Have length to diameter ratio, there is no such limitation in the present invention intended. Therefore, the spiral protuberances can extend the length of the structure, to take on a "ribbed" appearance, or they

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can interlock so that / network of protuberances is formed, similar to how it was already described for the protuberances of Figure 1 »The The main advantage of the spiral protuberances is that their open structure allows them to be absorbent Distribute material over the entire surface of the structure and thereby prevent infiltration or distribution the absorbed moisture and thus the absorption capacity of the absorbent material to take full advantage of it. In addition, the structural integrity is ensured by the intertwining of the protuberances significantly improved with the absorbent structure.

When in the absorbent structures of the present invention If many independent projections or protuberances are used, it may be desirable to have a number of Connect protrusions to the underlayer to ensure structural integrity. When the protrusions or protuberances are connected to one another, as in FIGS. 1, 2 and 3, one is generally sufficient Gluing at individual points. Finally can

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Further structural integrity can be ensured by having a topcoat on top of the structure made of a liquid-permeable material, such as cotton or non-woven fabric, attaches.

In FIGS. 1 to 5, the absorbent material 12 of the structures according to the invention is accommodated in the spaces between the projections 11. To a suitable distribution of the absorbent material to achieve a method, is that it provides a plurality of openings 16, as shown in Figures 3 and U. The openings 16 should preferably be formed so that they nestle flush around each protrusion 11, although this is not essential. On the other hand, a suitable distribution of a fibrous absorbent can also be achieved by airlaying the absorbent directly in the interstices between the projections, ie by forming a tangled fiber fleece directly in these interstices. In order to facilitate the formation of the tangled fiber fleece, it is necessary to use an underlayer 10 which is air-permeable so that the tangled fiber fleece can be drawn into a suitable position between or - as in the case of the spiral-shaped protuberances - under the projections or protuberances by means of a vacuum.

Suitable absorbent materials include essentially any hydrophilic material whose shape is so can be adapted so that they occupy a suitable position on the substrate. For example, belong to the a variety of suitable absorbent materials

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superimposed layers of creped cellulose wadding and / or hydrophilic fiber aggregates, which are produced by one of the known processes for the production of nonwovens on a wet path or by means of air (wetlaying or airlaying procedures) as well as hydrophilic foams.

In particular, as a result of the unique structural separation of the fluid acquisition function from the support or Support function unusual absorbent materials with low density suitable for use. So are Low density tangled webs are a preferred class of absorbent materials for use in the present invention Structures. The term "absorbent non-woven fiber nonwovens with low density" is used herein nonwovens made with the use of air understood to mean forming an absorbent material having a density of about 0.02 g / cm · ^ to about 0.20 g / cm were condensed.

As a rule, the choice of fibers or fiber mixtures depends on the formation of an absorbent random fiber fleece can be used according to the desired product properties as well as according to the intended use of the product. Generally speaking, fibers are categorized based on their length. Typical for short Fibers are wood pulp, BaumwoHinters and asbestos fibers. Wood pulp fibers are most frequently used due to their easy accessibility and value for money. Both synthetic and natural fibers are typical of the staple or long fibers. Examples of synthetic Fibers are glass, cellulose acetate, vinyl chloride

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Vinyl acetate and polyamide fibers, rayon, saponified fibers Esters', cellulose ester, acrylic, polyester and polyvinyl chloride fibers. Examples of natural fibers are cotton, flax, jute, wool, silk, rag or protein fibers. When making a of suitable absorbent material, combinations of any of the above fibers can also be used will.

An example of another class of preferred absorbent materials are flexible, hydrophilic V '' polyurethane foams. As a rule, such absorbent foams are produced from a reaction mixture, which is a Polyhydroxy compound which is at least partially a polyether which, however, can also be partially a polyester, and contains mixtures of polyesters and polyethers. The following patents, which are referred to herein, describe hydrophilic (mensesphilic) Polyurethane foams that are particularly useful: US-PSS 3,586,648, 3,573,234, 3,560 416, 3,463,745, 3 457 203, 3 451 954, 3 451 953, 3 432 448, 3 388 081, 3 385 803, 3 164 565, 3 098 048, 3 042 691, 3007 883, 2 965 584, 2 9 ^ 8 69I, GB-PS 1 I80 316 and FR-PS 1 350 709.

Other hydrophilic polyurethane foams can also be used, including those described below Patent specifications referred to herein describe foams:

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US-PSS 3 535 143, 3 508 953, 3 W 338, 3 4 18 066,

3 413 245, 3 404 095, 3 382 090, 3 326 823, 3 249 465,

3,149,000, 3,094,433, 2,998,295, 2,990,378, 2,920,983 and 2 9OO 278.

When assembling the absorbent structures, the absorbent material is, as already indicated, in the Gaps housed between the projections or protuberances. As shown in Figure 6, there is one suitable method for achieving a suitable position in the formation of the absorbent material 12 as a continuous cushioning layer in which openings are made in a suitable manner. The openings 16 are arranged so as to cover the various projections or protuberances 11 protruding from the backsheet 10, surround. The absorbent material 12 is formed into a structure as shown for example in FIG is shown assembled with the carrier layer. In this way, a suitable arrangement can easily be achieved will.

The following examples illustrate the absorbent structures of the present invention.

example 1

Composite absorbent structure with a sinusoidal longitudinal section

An absorbent structure described in detail below was made by the following process:

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A sheet of closed cell polyethylene foam 0.635 cm thick was elliptically perforated, as illustrated in Figure 1, to form a plurality of spaced projections or protuberances which abut one another and have a sinusoidal longitudinal section. The matrix obtained had a void fraction of 60 % .

The matrix of protrusions or protuberances was placed on top of an air-permeable sub-layer made of polyethylene. The matrix and the sub-layer were then arranged at the bottom of a vertical air chamber on a sieve with a mesh size of 595 μm . At the top of the air chamber, ground wood pulp was introduced through a filter screen as an absorbent, and a vacuum was applied below the bottom screen. When the vacuum was applied, the wood pulp was pulled down through the air chamber and hit the matrix of the protrusions and the underlayer. The wood pulp was retained in the spaces between the protrusions. The obtained absorbent structure containing the air-drawn tangled fibers was removed from the chamber and the fibrous material was compacted.

The absorbent structure obtained was excellent in that it had high absorbency, exhibited load resistance, softness and durability to the touch.

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Example 2

Composite absorbent structures with protuberances in the form of helical spirals

Several helical spirals made of steel, as explained in FIG are, with a diameter of 0.635 cm, a length of 1.90 cm and a spiral density of 3 spiral turns per 2.54 cm were randomly selected in a horizontal position on top of an air-permeable backsheet Polyethylene arranged. The underlayer with the reinforcing protuberances was then placed on a sieve with a clear mesh size of 595 lim at the bottom of a arranged vertical air chamber. In the upper part of the air chamber, ground wood pulp was crushed through a filter sieve and a vacuum was applied beneath the bottom screen. When the vacuum has been applied the wood pulp was down through the air chamber pulled and hit the protrusions or protuberances and the underlayer. The wood pulp was in the Gaps between the protrusions held back. The obtained absorbent structure containing the air-drawn tangled fibers was made from Chamber removed and the fibrous material compacted in situ.

The absorbent structure thus obtained was excellent in that they at the same time have a high absorbency and sufficient strength and softness exhibited.

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Other absorbent structures were made according to the above Working method made with the protuberances in the form of 1.90 cm long helical spirals through 1.27 cm long steel spirals with a diameter of 0.635 cm and a spiral density of 6 spiral turns per 2.5 ^ cm, by balls of open-cell foam with a diameter of 0.635 cm or by cylindrical columns in expanded polyethylene with a diameter of 0.952 cm and a height of 0.635 cm. The received Absorbent structures were distinguished in that they had high absorbency and sufficient Exhibited load resistance and softness.

In commercial manufacture, the absorbent structures of the invention are preferably made by continuous Process manufactured. For example, a tangled fiber fleece made of absorbent material with air directly formed in the spaces between the projections or protuberances 11 by a continuous process -will. Various other known continuous processes are, however, also for the preparation of the present invention absorbent structures.

In addition to the aforementioned properties of the absorbent Structures according to the invention have been found to have these structures natural absorbency of the above absorbent materials. In its normal use, a pad can be made of absorbent Material can only effectively absorb a relatively limited amount of moisture. The absorbed The amount of moisture is generally due to the tendency of moist fibers to agglomerate, with the absorption

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medium densified and the distances between the fibers are reduced, and the tendency of the overall structure ₉ to "ball up", below the theoretical maximum value. The structure of the present absorbents counteracts these tendencies. The supporting protrusions protruding from the backsheet 10 act as partitions that separate the material into less discrete absorbent areas with proportionally less tendency to densify or agglomerate. Accordingly, the absorbent structures according to the invention serve to increase absorption by not only reducing the compression pressures of external loads, but also optimizing the natural absorption properties of the absorbent material. It follows from this that an effectiveness can be achieved with the absorbent structures according to the invention which is equivalent to that of continuously accessible absorbents, but less absorbent needs to be used.

To ensure adequate moisture retention it is preferred that the outer surface 17 of the absorbent material 12 is slightly below the End surfaces 18 of the projections 11 lies (see FIGS. 2 to 5) · In this way, for the sake of convenience some compression of the projections acceptable, without a loss of absorption properties.

It is obvious that the absorbent structures according to the invention for a variety of absorbent Products are useful. Examples of particularly useful embodiments are absorbent products that

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must retain their absorption properties when they are subjected to external stress. Accordingly are typical products such as towels, tablecloths, bed liners, surgical dressings, and disposable diapers Like. Embodiments of the absorbent structures according to the invention.

FIGS. 7 and 8 show the adaptability of the absorbent structures according to the invention for use in various types of winds. The disposable diaper 20 comprises the usual components of such an article, which usually includes a thin, water-impermeable backsheet (preferably made of thin plastic, such as polyethylene) and a topsheet of nonwoven fabric or similar material, with an absorbent core between the backsheet and the topsheet or an absorbent pad is arranged. The diaper may have embossed fold flaps, such as those labeled 21, 22, 23, and 2k , so that it tends to fold in a similar pattern to the diaper shown in U.S. Patent 3,710; to which reference is made. As shown in Figure 7, the improved absorbent structure of the invention can be incorporated into a diaper 20 to serve as an absorbent pad and backsheet. In Figure 8, the arrangement of the diaper 20 is shown in use.

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Claims (9)

Patent claims: Composite absorbent structure characterized in that it (1) comprises a flexible backsheet, (2) a plurality of spaced apart protrusions protruding from the backsheet, and (3) an absorbent one Contains material disposed in the spaces between the protrusions. 2. Absorbent structure according to claim 1, characterized in that that the projections have the shape of abutting partition walls with a sine curve similar Have longitudinal section. 3. Absorbent structure according to claim 1, characterized in that the protrusions ₄ in the form of columns and are arranged on the undercoat layer at equal intervals such that they form repeating triangles. 4. Absorbent structure according to claim 1, characterized in that that the projections are spherical. 5. Absorbent structure according to claim 1, characterized in that the projections are in the form of helical spirals exhibit. 6. Absorbent structure according to claim 1, characterized in that that the projections are made of a closed cell polyethylene foam. 509840/069 7. Absorbent structure according to claim 1, characterized in that it has a gap fraction of about to about 80 % . 8. Absorbent structure according to claim 1, characterized in that the absorbent material consists of a random fiber fleece with a density of about 0.02 to about 0.20 g / cm ³ . 9. Disposable diaper based on a composite Absorbent structure according to claim 1, characterized in that that they (1) have an underlayer of flexible, liquid-impermeable polyethylene, (2) a plurality of spaced apart projections made of a polyethylene foam with closed cells with a sinusoidal longitudinal section, (3) one of several superimposed layers absorbent material consisting of creped cellulose, which is arranged in the spaces between the projections and (4) includes a liquid pervious cover layer. For: The Procter & Gamble Company Cincinnati, / Ohio, V.St-A. Dr.H.J.WoIff Lawyer 509840/069 2 IS Blank page