FI58051B - ABSORBER STRUCTURE WITH AVSMALNANDE KAPILLARER - Google Patents

Description

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Patent and Registration Office Ansakin uttagd och utUkrHUn put> Uc «nd 29.08.80 (32) (33) (31) l *] Ryd« tty «tuolkwt —Begird pdorltst 20.12.7 * + USA (US) 535 003 (71) The Procter & Gamble Company, 301 East Sixth Street, Cincinnati, Ohio ^ 5202, USA (72) Hugh Ansley Thompson, Fairfield, Ohio, USA (7 * 0 Oy Kolster Ab (5 * +) Converging Capillaries This invention relates to coatings for absorbent articles such as diapers, sanitary napkins, drapes, bed pads, bleed pads, towels, bandages and the like, and more particularly to absorbent structures which allow the liquid to flow freely The coating is part of the absorbent device, covering the second surface of the absorbent portion and, in some applications, contacting the skin of the person using the absorbent device.

Absorbent means are articles of manufacture designed to receive and retain fluid exiting the body in the absorbent portion of the absorbent means.

Absorbent articles such as towels, sanitary napkins, sanitary napkins, bleed pads, bleed pads, towels, bandages and the like are commercial articles. Recently, disposable * disposable absorbent articles have significantly replaced durable absorbent articles intended to be washed and reused. Although the absorbent structure of the present invention can be used with reusable absorbent means, it is most useful with disposable 2 S8051 absorbent means and will be considered in this context.

Disposable absorbent devices consisting of an absorbent pad covered with a coating are well known. The absorbent means the outside of the covering to prevent the liquid-impermeable rear side of the leakage of absorbed liquids from the absorbent means and clothing, bedding etc. fouling is also well known in the art. The absorbent pad portion of the disposable absorbent device may be made of well-known materials such as crumpled cellulose wadding, airy felt, or the like. The liquid-impermeable backsheet may be formed of a variety of materials well known in the art, such as a polyethylene film.

One of the main features of a conventional absorbent device is the maceration of the skin due to prolonged contact with the absorbed fluid. One particularly common hallmark of this maceration is the common occurrence of diaperitis in the back of children. To reduce the effect of prolonged contact of the liquid with the skin, absorbent devices have been made with a body-contacting coating designed to make the surface more or less dry. For example, U.S. Patent 3,327,623, published by Johnson on March 1, 1966, discloses that a hydrophobic material in the crotch region removes moisture from a child's skin, forming a substantially dry contact surface with the child's skin. In a U.S. patent, Duncan et al. 31 · January 1967 »discloses the use of a porous, hydrophobic, nonwoven fabric as a coating. U.S. Patent 2,916,037 »published by Hansen on December 8, 1939» also discloses the use of a nonwoven coating.

U.S. Patent 3,814,101, issued to Kozak on June 4, 1974, addresses the problem of wet coating in a manner slightly different from hydrophobic nonwoven materials. Kozak proposes to use a non-fibrous hydrophobic film as a coating in which a plurality of flap-like slits are formed to prevent fluid from flowing out of the absorbent portion of the device.

Sisson Belgian Patent 811,067, August 16, 1974, which claims priority to U.S. Patent Application Serial No. 333,110, February 16, 1973, discloses a breathable, liquid-impermeable backsheet with torn assemblies. The holes of this are smaller in diameter than the capillaries shown below in order to keep the back side impermeable to liquid.

This invention relates to an absorbent structure for absorbent devices such as diapers, sanitary napkins, sanitary napkins, bed pillows, leak pillows, bandages and the like. The present invention thus relates to an absorbent structure for absorbing and retaining fluids exiting the body, in particular a disposable diaper comprising a coating made of a liquid-impermeable material and provided with openings, an absorbent portion 3,58051 and a liquid-impermeable base layer. The structure is characterized in that the coating openings are tapered capillaries, each with a base in the plane of the coating and a tip distant from the plane of the coating, with a bottom opening measuring 0.15-6.35 mm and a peak opening measuring 0.1-2.54 mm, and a taper angle of 10-60 °, with the peaks of the tapered capillaries in close contact with the absorbent portion.

The coating of this invention is an improvement over prior art coatings in that it allows fluids to move freely from the body to the absorbent portion of the device while preventing the reverse flow of these fluids, thus creating a significantly drier surface in contact with the wearer than previously achieved. Although intended primarily for single use, in disposable absorbent devices such as disposable diapers, the absorbent structure of this invention may also be used with reusable absorbent devices such as fabric diapers.

Thus, it is an object of the present invention to provide an absorbent structure for absorbent means, which structure allows fluids to move freely from the body to the absorbent portion of the absorbent device, effectively preventing liquids from escaping from the absorbent portion.

Another object of the present invention is to provide a coating for absorbent means which provides a drier surface against the wearer's skin than has hitherto been achievable.

Another object of the present invention is to provide a coating for absorbent means which feels comfortable when in contact with the skin of the wearer.

It is a further object of the present invention to provide a disposable diaper which forms a drier surface against the wearer's skin than has hitherto been possible.

Although the brochure is accompanied by claims which are particularly directed and clearly define the scope of the present invention, it is to be understood that the invention may be better understood with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an unfolded disposable diaper with parts partially exploded; of the tapered capillary used, Fig. 3 is a vertical section of the tapered capillary taken along line 3-3 in Fig. 2, Fig. 4 is a cross-sectional view of the tapered capillary shown in Fig. 3 in contact with the absorbent member.

The following discussion focuses on the use of the invention as a unique absorbent structure for disposable diapers. Although this is considered to be the preferred use of the absorbent structure, it is to be understood that 4,58051 has substantial use in a variety of absorbent articles, both disposable and reusable, such as sanitary napkins, sanitary napkins, bed pillows, bleed pillows, wipes, bandages, and the like. The detailed presentation of the absorbent structure and its use as a disposable diaper allows those skilled in the art to apply this invention to other purposes.

Figure 1 is a perspective view of a disposable diaper unfolded. Several layers have been cut open to show the structural details of this implementation in more detail. The disposable diaper is generally designated 21. The new coating of the present invention is designated 22. The other two main portions of the disposable diaper are an absorbent portion or pad 23 and a backsheet 24. The coating 22 is generally bent so as to completely cover the ends of the absorbent pad 23. The drawing of the diaper 21 shown in Figure 1 is a simplified representation of a disposable diaper. A more detailed description of the preferred implementation of the disposable diaper is contained in the aforementioned U.S. Patent No. 26,151, which is to be incorporated by reference.

The coating 22 of the present invention is made of a liquid impermeable material. A suitable example of a liquid impermeable material is low density polyethylene having a thickness of 0.0023 to 0.0031 cm. The coating 22 is provided with tapered capillaries, as shown below.

The tapered capillary 26 is shown in perspective in Figure 2 and its cross-section in Figure 3. Although the tapered capillary 26 is shown in Figures 2 and 3 as a generally truncated conical surface, it is to be understood that any generally tapered structure such as a truncated pyramid or the like polygon, is within the scope of the invention, however, circular tapered capillaries are used in this presentation for simplicity in explaining the numerous advantages of the invention. It is also to be understood that the tapered capillaries may be asymmetric (i.e., the taper angle of one side may deviate from the taper angle of the other side) and that the taper angle may continuously (i.e., curve) from 30 to 29 the opening dimension is the smallest. The term tapered capillary includes a slit formed in the coating 22 that is less than the width of the coating 22 and whose sides and end points taper at angles corresponding to the following with respect to circular tapered capillaries.

5 58051

The taper angle is indicated by the symbol a in Figure 3 · The suitable taper angle for use in the coating of this invention is about 10-60 °.

The dimension of the bottom opening, with the exception of the aforementioned gap, is determined by the maximum opening dimension of the tapered capillary 26 in the plane of the coating 22. The opening dimension of the tip, with the exception of the aforementioned gap, is determined by the maximum opening dimension at the apex of the tapered capillary 26, which tip differs from the plane of the coating 22. If the tapered capillary has a truncated conical surface, the base and peak opening dimensions are base diameter 2 poh and peak diameter 27, respectively. The base and tip diagonals are then alternatively used with the base opening dimension and peak opening dimension, respectively.

If the tapered capillary of the present invention is in the form of a gap having a length less than the width of the coating, the base opening dimension and peak opening dimension mean the smallest gap opening dimension in the plane of the coating 22 and the gap peak its length.

The diameter 27 of the apex of the tapered capillary is the diameter which allows the liquid to easily pass from the surface of the coating 22 to the absorbent pad 23 · The diameter of the apex is about 0.010 to 0.234 centimeters, preferably 0.013 to 0.031 centimeters.

The diameter 28 of the tapered capillary base is selected based on two conditions. The first of these is the subjective feeling of the surface of the coating touching the wearer's skin. It has been found that the aforementioned polyethylene can be made to feel comfortable, fabric-like, non-waxy if the base diameter is in the range of about 0.013 to 0.633 centimeters. Preferably, the diameter of the base is in the range of 0.076 to 0.132 centimeters. Another condition is that the diameter of the base of the capillary is small enough to allow the drop of liquid present to close at least one capillary. This condition is fulfilled by the above-mentioned dimensions of the disposable diaper.

The height of the tapered capillary is determined by the distance between the top surface of the coating 22 (i.e., the surface that normally contacts the wearer's skin) and the tip 29 of the tapered capillary 26. This height naturally depends on the aperture diagonal 27 »of the aperture diagonal 28 and the taper angle α selected as described above. The height of the tapered capillary should form the structure that tends to collapse the least during use. The properties of the material used to make the coating 22 largely determine the appropriate range of height. If the coating 22 is low density polyethylene having a thickness of 0.025 to 0.050 centimeters and a peak diameter 27 6 58051 and a base diameter 28 are in the recommended range and the taper angle α is in its critical range, the height of the tapered capillary may be 0.008 to 0.404 centimeters.

It is necessary that the apex 29 of the tapered capillary effectively contact the absorbent pad 25 * Useful absorbent means * such as disposable diapers must be made so that there is no counterflow of fluid when the absorbent portion is pressurized, such as when a child is sitting or moving wet. Protection against this pressure-induced discharge flow is achieved if the absorbent part is manufactured in such a way that it is not completely saturated by the expected maximum liquid content. This means that the absorbent member must be designed and manufactured to be able to contain a significantly greater amount of liquid than is expected of the absorbent device under normal conditions of use. For the recommended absorbent pad presented below, the expected liquid load of 3-6 times the dry weight of the pad is satisfactory. It should be noted that this allowable load is slightly higher than acceptable on the basis of the wetting properties of the surface if a conventional nonwoven coating is used in connection with a disposable diaper. One advantage of this increased load is the possible reduction in the amount of material used in the absorbent pad of the present invention compared to conventional disposable diapers.

Another obvious condition is obvious to those skilled in the art: the coating must allow the liquid to pass rapidly through it. This rate of transition depends on several factors such as the rate of fluid removal from the body, the viscosity of the fluid, the proportion of open surface area of the coating, the minimum diameter of the tapered capillaries, etc. The proper combination of parameters for each application can be easily determined by simple experiments. The recommended dimensions shown here for the disposable diaper ensure a rapid transition of urine to the absorbent pad.

From the relative dryness of the surface of the coating, it is apparent that most of the liquid in contact with the coating passes through it to the absorbent portion. This in turn indicates that each individual drop of liquid in contact with the coating must be in contact with the bottom opening of the tapered capillary. This situation can best be achieved when the intermediate area (the surface area between the bottoms of the tapered capillaries) is kept as small as possible. The limiting minimum value is reached in the case where the conical tapered capillaries or pyramidal tapered capillaries are formed as a tightly packed arrangement (wherein the outer circumference of each capillary base JO contacts the outer circumferences of adjacent capillary bases JO on each side). The recommended arrangement of the minimum intermediate range seeks to ensure that the individual droplets contact at least one tapered capillary. The preferred arrangement of the disposable diaper is achieved when there are approximately 3-23 I capillaries per square centimeter of tapered capillaries arranged as described above. The coating 22 containing tapered capillaries 26 can be prepared in any of a number of ways known in the art. One particularly suitable method is to make a hot mold containing male embryos of the desired shape and arrangement of tapered capillaries (hereinafter referred to as a pin mold).

Each male embryo is mounted so that its apex extends upward from the base of the mold. A liquid impermeable material is brought into contact with the heated mold between the mold and the flexible base plate. The pressure is applied to a combination of a mold, a liquid-impermeable material and a flexible base plate, forming tapered capillaries in the liquid-impermeable material to form the coating of the present invention. An alternative way of making the coating of this invention is to perform vacuum forming on a liquid impermeable material using a suitable mold according to methods well known in the art. A third way to make the coating 22 used in the present invention is to mold the coating into a suitable mold resembling the above mold. After shaping the tapered capillaries, in one of the three ways mentioned above, it may be necessary to physically remove material from the peaks of the tapered capillaries to bring the diameter of the peaks to the desired value. This removal of material can be performed, for example, by carefully grinding the peaks or by heating the formed coating to melt the peaks open.

The absorbent portion 23 of the disposable diaper shown in Figure 1 may be a material conventionally used in absorbent means and is well known in the art. As a suitable absorbent material for the part 23, it is preferable to use ground wood pulp, which is generally referred to as aerated felt. If aerated felt is used, the tissue paper normally used in disposable diapers can be omitted. Other materials may also be used as the absorbent member 23 such as multiple layers of cellulose wadding crepe and the like.

As mentioned above, the absorbent pad 23 must be in contact with the peaks 29 of the tapered capillaries 26 of the coating of this invention. In addition, the absorbent pad 23 must absorb substantially liquid from the peaks 29 of the tapered capillaries 26.

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The liquid-impermeable backsheet 24 may be of any material known in the art. The preferred material is low density polyethylene with a thickness c of 0.0023 to 0.0031 centimeters.

The components of the final disposable diaper - a coating 22 with tapered capillaries, an absorbent pad 23 and accessories such as a liquid impermeable backsheet 24 can be assembled into a practical, economical disposable diaper by methods known in the art. An example of such assembly into a disposable diaper is admirably disclosed in the aforementioned U.S. Patent No. He 26,131.

As mentioned, the coating containing tapered capillaries of the present invention is shown in connection with a disposable diaper. Other absorbent devices well known in the art, such as sanitary napkins, sanitary napkins, bed pads, bleed pads, towels, bandages, and the like, can be advantageously prepared using the tapered capillary coating of this invention. Examples of sanitary napkins and sanitary napkins in which the coating of this invention may be used can be found in U.S. Patent 3,600,797, issued Tunc August 2, 1374, and U.S. Patent 3,815,601, issued Schaefer June 11, 1974, incorporated herein by reference.

In order that this invention may be better understood, but not limited,, the following examples are included.

Example 1

Conical tapered capillaries with a base diameter of 1 mm and a peak diameter of 0.3 mm and a taper angle of 49 ° · were formed by a pin mold into a 0.0375 mmsn "Surlyn" film, a liquid-impermeable ionomer film manufactured by EIdu Pont de Nemoura and Company * A total of 113 capillaries per square centimeter were pressed into the membrane in regular order. The coating was positioned so that the tips of the tapered capillaries were in contact with an absorbent pad made of aerated felt of soft wood fibers. The resulting absorbent structure allowed the saline solution to pass through the coating onto the absorbent pad. The surface of the coating felt dry and was pleasant to the touch.

Example 2

Example 1 was repeated except that 49 conical capillaries with a base diameter of 1.3 mm and a peak diameter of 0.3 mm and a taper angle of 45 ° were formed as a regular pattern per square centimeter for a "Surlyn" film and a low density polyethylene film having a thickness of 0.0375 mm. Substantially the same results were obtained * 9 58051

Example 3

Pyramidal tapered capillaries with a square bottom of 1.3 mm each side and a square peak of 0.3 mm each side and a taper angle of 45 ° · were pressed into a 0.0375 mm thick low density polyethylene sheet. A total of 60 capillaries were formed per square centimeter of membrane. Substantially the same results as in Example 1 were observed when the coating was properly placed in contact with the aerated felt of Example 1. This absorbent structure was further used to make a disposable diaper according to the aforementioned Re 26 121 of Duncan et al. When used properly for infants, the surface of the disposable diaper was drier and more comfortable against the child's skin than can be achieved with a conventional hydrophobic nonwoven coating.

Example 4

Example 2 was repeated, including contacting the formed cones with an absorbent aerated felt, wherein the base diameter, peak diameter, taper angle, and number of capillaries per square centimeter of the formed cones were as follows: 0.76 mm, 0.23 mm 45 ° # 200; 1.52 mm, 0.30 mm, 60 °, 49; And 2.54 mm, 0.375 mm, 30 °, 11.5 · In each case, satisfactory results were obtained in terms of fluid flow and surface feel.

Claims (3)

10 58051 An absorbent structure for absorbing and retaining body fluids, in particular a disposable diaper, comprising a coating (22) made of a liquid-impermeable material and provided with openings (26), an absorbent portion (23) and a liquid-impermeable base layer (24), characterized in that that the openings in the coating (22) are tapered capillaries (26), each having a base (30) in the plane of the coating And a peak (29) distant from the plane of the coating And having a dimension of the bottom opening (28) of 0.15-6.35 mm And the dimension of the aperture (27) is 0.1-2.54 mm and the taper angle is 10-60 °, whereby the peaks of the tapered capillaries are in close contact with the absorbent part (23) · Absorbent structure according to Claim 1, characterized in that the dimension of the bottom opening (28) is 0.76 to 1.52 mm and the dimension of the apex opening (27) is 0.12 to 0.51 mm. Absorbent structure according to Claim 2, characterized in that the capillaries (26) have the shape of a frustoconical surface.