NO141590B - Absorbent disposable articles. - Google Patents

Description

The invention relates to disposable absorbent articles

such as nappies, night-wetting pads and the like.

The use of disposable articles of the above type has increased greatly in recent years due to their ease of use, low price and the obvious sanitary advantage of being able to use a new, clean disposable article without having to wash a previously used cloth or the like. The advantages of absorbent disposable articles are particularly evident through the widespread use of disposable nappies to replace the cloth nappies that have traditionally been used.

In addition to the above benefits in connection with . disposable absorbent articles are many of them provided as part of their construction with a liquid impermeable outer material which offers other utility advantages. E.g. If you use disposable diapers that are provided with such an outer foil, you will not need to wear rubber pants on the baby to prevent leakage through the diaper and the baby's clothes getting wet.

In its most basic construction, a disposable diaper simply consists of a layer of absorbent material that forms a lining against an outer layer of liquid impermeable material that can be of the disposable or reusable type. The thickness of the layer of absorbent material can vary depending on the desired application. If e.g. the nappy is to be used at night or on a larger baby, a greater absorbency will be required than a nappy which is to be used for a short time during the day or for a small baby, and consequently the absorption layer in the former case must be thicker. The length and width of the nappy can also be varied according to the baby's size. In general, the absorbent layer will be from approx. 3 to 12 mm and the nappy will have a length of approx. 30 to ^5 cm and a width of from approx. 20 to 40 cm.

Publicly available Norwegian application no. 3448/71 describes a disposable diaper consisting of an absorbent pad and a top sheet of thin flexible material in contact with said absorbent pad for placement close to the user's body, and said top sheet is a non-fibrous, hydrophobic film with a number flap valve openings, namely in an amount of from about 1.5 to 150 slots per cm film, and these slits are essentially straight and have a length of 0.13 to 1.3 cm. These slits are essentially closable to prevent contact between said absorbent material and the user's body, and to prevent backflow of liquid from the absorbent pad. The absorbent pad consists of an absorbent polymer hydrogel such as e.g. cross-linked polyethylene oxide.

Thus, although the absorbent article according to the previous Norwegian application is an improvement in relation to known articles with regard to a number of properties, it still relies on certain disadvantages. Among other things, there is the fact that even if the valve openings in the inner foil have the ability to flow through at least 20 ml of liquid within 10 seconds when wetting an area of 130 cm 2 , the initial absorption time or the initial soaking time, i.e. the time that takes before the liquid is really sucked into the absorption material, still not optimal. Put another way, the residence time for the liquid (urine in the case of diapers) before the absorption or soaking effect takes so long that discomfort can occur. Furthermore, it has been found that this nappy does not have the dimensional or relative stability which could give this nappy superior properties in relation to known articles. This is probably due to the fact that the absorbent material is placed between the inner foil and the outer foil without being attached to them, and consequently there is a tendency for the absorbent material to wander or change places in relation to the initial location and the edges of the inner and outer foil. Even though the vertically above straight valve-like openings (slits) produce the desired valve effect as previously mentioned, one does however have a problem with a certain "zipper tearing", i.e. a tendency to tear up the foil from one vertical slat to the next one. It has also been found that the aesthetic properties are not entirely satisfactory from a marketing point of view, because the inner foil seems to lack a warm appearance.

It has now been possible to remedy these shortcomings and the present invention thus relates to a moisture-absorbing disposable article comprising individual layers, e.g. diapers, continence pads and the like, comprising a hydrophobic top sheet for placement close to the user's body and with a number of openings, an essentially liquid-impermeable bottom sheet and an absorbent layer between the top sheet and the bottom sheet, and where the top sheet is arranged with valve-like closable openings that are straight or approximately straight, and where the openings prevent contact between the absorbent material and the body and prevent backflow of absorbed liquid, and the invention is characterized by a system of liquid-impermeable pits 22 pressed into the top sheet 16 between the valve-like openings, which pits extend into the absorbent layer 12 , and that the pits have a frequency of at least 0.15 per cm p of the area for ~ the absorbent pad.

During the development of the object according to the present invention, a number of methods were tried. In order to maintain the relative stability or mutual stability between the inner foil and the absorbent layer, it was first tried to adhere the inner foil to the absorbent layer with an adhesive, but it was found, however, that the improved dimensional stability was achieved at the expense of the absorbent properties and loss of softness. In order to avoid the inconvenience of the aforementioned "zipper tearing", the vertically arranged slits were abandoned and curved and V-shaped slits were used. However, it was found that these changes to curved or V-shaped slits formed flaps in the inner foil surface which opened too easily and which tended to remain open, thereby allowing the liquid to flow back through them and into contact with the skin.

Many other methods were tried, e.g. needling through the absorbent article in order to fasten the absorbent material to the inner foil, but found that this additional cost, in addition to reduced absorption and strength, gave further disadvantages that were much greater than the problems they were trying to solve.

During the development of the most favorable solution, an attempt was made

a method whereby the inner foil was connected to the absorption layer at several points along the foil's surface. The jointing was done by bringing the absorbent article into contact with a roller which had a system of protruding bodies and with the help of heat and pressure the inner foil (which is thermoplastic) could be pressed in and softened by

the contact points against these knobs, so that the fibers in the absorption layer immediately below the knobs mixed with the softened thermoplastic inner foil. On cooling the thermoplastic material, the entangled fibers were permanently embedded in the inner foil and reduced

in this way the migration or movement of the absorbent material in the nappy.

As previously mentioned, however, the liquid transport takes place through the valve gaps, which must allow the flow of liquid to the absorption layer. It will therefore be clear that if the studs are to press in and soften the thermoplastic material to a sufficient extent to "embed" the absorbent fibers in the thermoplastic film, gaps that come into contact with the studs will fuse together and thereby reduce the number of openings through which the liquid can flow, with resulting poor absorption effect. In other words, you will again find that the solution to a problem (dimensional stability) will be achieved at the expense of another quality (good absorption).

However, when the resulting absorbent material was examined and analyzed for absorbent properties, surprisingly and contrary to what was expected, it was found that the absorbency and, to an even greater extent, the wicking or suction effect were drastically improved. It was certainly surprising to find that this method produced an absorbent article with excellent absorption and suction properties, since as previously mentioned it seemed logical and obvious that if the thermoplastic material were to be treated with hot protruding studs as described above, there would be a loss ab absorption by fusion of the slots that came into contact with the hot cams.

US patent 3,221,738 describes a diaper which consists of a core of moisture-absorbing material which is completely enveloped by a liquid-insulating thin plastic film, and the main feature of the patent is that the plastic film on one of the sides of the core within the edge of the diaper , is heat-treated in such a way that the liquid-insulating property of the foil is completely or partially abolished, so that liquid that reaches the heat-treated foil surface is automatically sucked in through the foil and absorbed by the core. The method is further characterized by the fact that the foil layer is heated using a series of heated metal bodies which are placed at short distances from each other, so that the foil forms a net-like pattern of liquid insulating foil.

According to this publication, therefore, the liquid transport takes place through through pores formed by treating the foil described in the patent.....

This teaching is diametrically opposed to what is sought according to the present invention.- According to the present invention, the absorption of liquid must take place through the valve gaps as opposed to absorption through the thermoplastic inner sheet in the pressed-in areas. In this way, the valve action and as will be explained in more detail below, will regulate the desired liquid intake. The pressed-in areas according to the present invention (hereinafter called "pits") are intended to provide dimensional stability, improve the material's appearance and contribute to increased absorption, which will now be described in more detail with reference to the drawings.

The invention must be described in detail in connection with the attached drawings where: fig. 1 shows a non-drying form of a diaper according to the invention,

fig. 2 shows a section through plane 3-3 in fig. 1,

fig. 3 shows an enlarged cross-section of a part of fig. 2 and you can see part of the absorbent nappies when the pad is not fully sucked,

fig. 4 shows in a similar way as fig. 3 such a section, except that the absorbent article is saturated with liquid,

fig. 5 shows a perspective view with partially cut away parts of a disposable diaper according to another, but less favorable embodiment of the invention.

In fig.l one sees the improved disposable diaper 10 which consists of the rectangular absorbent pad 12, the stretchable outer sheet or foil 14 of liquid impermeable material and the flexible inner foil 16 which is also of a normal liquid impermeable material. Premolding methods and material selection, as well as properties for the improved diaper shown in fig. 2 are identical to the nappy according to the generally available Norwegian application no. 3448/71j apart from differences which are particularly concerned as explained below. On the surface of the inner foil 16, a system of valve-like openings (slits) (valve slits) with the reference numeral 18a, and a system of pressed-in areas 22, pits, is cut. The slits 18a are arranged in layered rows in such a way that each row forms a line order of substantially parallel straight slits, where one group of slits is arranged at an angle in relation to each other and in relation to the lengthwise direction of the nappy. The slots are arranged in such a way that the end points for each slot lie on a line which is essentially between the end points of the corresponding slots in the intersecting neighboring set of slots. Slots to be used according to the invention must be essentially straight because if the slots are curved, V-shaped or have another shape, they will form flaps in the foil surface which open too easily and tend to stay open. Furthermore, the aforementioned angular arrangement of the slits will prevent "zipper tearing", thereby avoiding one of the biggest disadvantages of absorbent articles of the type described in the older Norwegian application. The slits should each have a length of from 0.75 to 6.3 mm and are preferably so close that there are from approx. 4.5 to 23 columns per cm p, where each slit has a length of from 1.8 to 5 mm. The best film in the applicant's opinion contains approx. 12.5 columns per cm 2 and each slot has a length of approx. 2.5 mm.

The gaps can be made in the same way as described in Norwegian application no. 3448/71. The preferred method for cutting the slits in the inner foil according to the present invention is, however, described in the generally available Norwegian application no. 3769/72 entitled "Procedure and apparatus for piercing through thin sheet-shaped material". Briefly, this publication describes a method and apparatus for piercing thin web-shaped or sheet-shaped material, such as e.g. plastic film, where the film is passed through a cutting part which is provided with many individually springing protrusions or knives and a construction member which has a mesh-formed surface. The cutting part or application part is moved in relation to the other part, so that the yielding or springy blades follow the web-embossed surface and selectively pierce the film. The cutting part can be a metal comb, a metal wire brush or a metal strip with several substantially parallel slits extending from one edge to the other edge and form the resilient projecting members.The application part can be a wire cloth, a perforated metal cloth, an engraved metal roller or an endless belt which is driven longitudinally in relation to the cutting part.

The pressed-in areas 22 (pits) are distributed along the surface of the inner foil as shown in fig. 1-4. It will thus be seen that the inner foil 16 is provided with a large number of pits which are arranged in parallel mutually offset rows along the surface of the inner foil (fig. 1) and these pits extend down lower than the plane of the inner foil (fig. 2 and 3). -The shape of these pits can be circular, elliptical, rectangular, diamond-shaped and similar, the important criterion is that they are shaped in such a way that there is no breaking up or cutting of the inner foil during or after production.

the ling.

It has been found that the full and complete advantages of the present invention are not achieved if the inner foil during pressing in of the pits is cut open, cut or melted to an extent that will prevent the regulated flow of liquid to the absorbent pad (which, as previously explained, is the function of the valve openings). It will be clear that if cuts or breaks occur in the inner foil during the making of the pits, the liquid will pass through these cuts or breaks when the absorbent pad is saturated, and when the absorbent pad is saturated or partially saturated, these inlets will also serve as outlet or return areas through which the liquid penetrates and in contact with the inner foil and the baby's skin.

For these reasons and to simplify the manufacture, it has been found that the preferred pit shape is circular as shown in fig. 1-3.

The pits can be pressed into the inner foil in many different ways. The easiest and therefore the best method in the applicant's opinion consists in using a roll equipped with heating means and provided with a number of lugs which protrude from the roll surface around the circumference thereof. These knobs having rounded ends can be spaced as desired on the roll to provide the desired number of pits in the absorbent article. The pits are pressed into the absorbent article preferably after cutting the valve openings, but before the finished production of the diaper article and this operation can be performed by bringing the diaper article provided with valve openings into contact with the heated roller. In this method, the absorbent pad is supported by a compliant system such as, for example. an endless conveyor belt, or a springy or resilient construction or counter roller. The depth of the pits can be regulated by changing the depth to which the knobs press the foil down. If desired, parts of the inner foil can be kept untreated (without pits). This can e.g. is carried out along a strip about 2.5 cm wide, around the circumference of the inner foil. Since the inner foil is thermoplastic, the amount of heat and pressure applied to the treated areas must be regulated to avoid re-puncturing or other damage to the inner foil. As a general rule, the added amount of heat must be large enough to soften the film and the pressure sufficient to plastically deform the film to the contour of the cam in general. It will naturally be understood that the exact and relevant conditions regarding heat and pressure will depend on, among other things, the residence time of the treating absorbent pad, i.e. the time the inner foil is in contact with the roller, the thickness of the absorbent pad, etc. However, the correct conditions can easily be established by professionals and any further description of these conditions therefore does not seem necessary. Reference is made in particular to fig. 2 and 3, and it will be seen that the pits 22 extend down a certain distance lower than the inner foil 16, and that the absorbent material 12a immediately below the pits is in a compressed state. In the area where a pit is formed over a portion of slits 18a, it will be seen that the slits are opened to a much greater extent than the corresponding slits located at a distance from the pits 22. Due to the location of the pits, the slits located between corresponding pits are opened to a greater extent than if such pits had not been pressed in. This is due to the fact that the pressure exerted on the inner foil surface by the pits causes the slits to open when the inner foil is stretched during this process. Certain parts of the compressed absorbent pad are in close contact with these open slits, and because of this connection a wicking or suction effect is achieved to a previously unknown degree. In reality, you achieve a fairly immediate suction effect. As the liquid is transported to the absorbent pad 12, this absorbs the liquid over its entire volume to full or partial saturation. As will be seen from fig. 4 (showing a saturated absorbent pad) the compressed material 12a has expanded and pushed the pits 22 upwards and closer to the plane through the inner foil 16. This serves to close the previously open gaps, so that the liquid is somehow trapped in it absorbent pad.

Thus, according to the present invention, a maximum wicking and absorption effect is achieved during the critical period when the liquid flow is strongest (when the baby urinates and the like), while the transport of liquid from the absorbent pad back through the same slot opening is essentially reduced due to of the combined valve action of slot and pit.

The pits can be arranged in different patterns on the absorbent article. The surface design can thus be diamond-shaped, rectilinear, herringbone patterned and the like. The best pattern seems to consist of a system of essentially straight, mutually offset parallel rows. Number of pits per cm. 2 on the absorbent pad can vary within a relatively large range. Improvements have been found to occur with as few as 0.15 dimples/cm 2 (where the dimples have a diameter of 1.25 mm). Furthermore, it has been found that good results occur by using up to 15 pits/cm<2 >surface (1.25 mm in diameter). One will naturally understand that the number of pits/cm of absorbent pad will depend on the size of the pits. As a general rule, the total area occupied by the pits should not exceed 20% of the absorbent material's surface area. Outstanding results are achieved when the total pit area is from 4-12% of the absorption material's area. Preferably, you use from approx. 0.45-4 pits per cm 2 (diameter 2.5 mm) and preferably from approx. 1-2,3

2

pits/cm surface.

As a general rule, the pit size can be within 0.6-6 mm in diameter. From a functional and aesthetic point of view, it is an advantage if the pit size is between approx. 2-4 mm in diameter.

According to another, but less favorable embodiment, pits are used together with the type of absorbent diaper shown in fig. 5.

As will be seen from fig. 5, the slot 18 is essentially straight and arranged in mutually offset parallel rows and in combination with the pits 22. Although according to this embodiment

of the invention achieves improved suction, dimensional stability and absorbency compared to previously known diaper articles, one will still have the problem of "zipper tearing" even though a certain improvement is achieved here as well.

Example 1

An absorbent pad consisting of eight layers of absorbent cotton with approximate dimensions 30 x 40 cm x 4.77 mm placed in the middle of a polyethylene foil with dimensions 30.6 x 40.6 cm x 0.030 mm, and with an interwoven taffeta pattern.

0.030 mm ethylene-ethyl acrylate foil was pierced by feeding between a roller provided with a large number of small knives

along the circumference in mutually staggered rows and one-yielding against the roller. The knife roller had a blade density of approx. 20 knives/cm 2 and the resulting perforated film therefore also a slot density of 20 slots/cm 2 , where each slot measured approx. 2.5 mm.

The punctured film was cut to approx. 30.6 x 40.6 cm and placed on the absorbent cotton pad, so that this was between the perforated film and the polyethylene film. The edges around the whole thing were heat sealed.

This combination was placed under the previously described cylinder and subjected to tests to find the absorption properties. 30 ml of liquid, i.e. saline solution containing 0.3 N sodium chloride at body temperature (simulated urine) was poured into the cylinder. The liquid was completely absorbed through the inner foil and into the absorbent material within 74 seconds.

The inner foil was then carefully removed and placed on top of an identical absorbent material, whereupon the edges were heat sealed.

The absorbent article was brought into contact with a roller equipped with heating devices and provided with approx. 1.5 knots/cm, which protruded along the circumference of the roller. The diameter of the lugs was 2.78 mm and the lug ends were spherically rounded with a radius of approx. 1.39 mm. The absorbent diaper was supported by a yielding counter-roll. The knobs were heated to approx. 150°C using circulating hot oil which maintained 178°C. The absorbent product had approx. 1.5 pits per cm 2 surface. The absorption article was examined with regard to initial absorption and absorbency as previously explained. The following results were obtained: The liquid was completely absorbed through the inner foil and into the absorbent material within 14 seconds.

Example 2

This example shows that without valve openings, little or no liquid will pass through the pits in the inner foil.

An absorbent article identical to the one described

in Example 1, was prepared except that the cutting was omitted. An absorbent nappy was therefore used as described in Example 1 except that the inner foil was not provided with valve openings (slits). The absorbent diaper was tested for water absorption in the same manner as described in Example 1. After a period of 3 minutes, no significant absorption of liquid into the absorbent material could be determined. The liquid remained as a pond on the surface of the inner foil. Thus, no or very little liquid passed through the pits of the inner foil.

Example 3

An absorbent pad consisting of eight layers of absorbent wadding and measuring approximately 30 x 40 cm x 4.77 mm was placed in the center of a sheet of polyethylene film measuring 30.6 x 40.6 cm x 0.030 mm in thickness and embossed taffeta pattern.

A 0.030 mm thick foil of ethylene-ethyl acrylate was perforated by bringing it into contact with a reciprocating rod fitted with a number of small knife blades of approx. 2.5 cm distance from each other on the surface of the rod. The formed pierced film had about 11 parallel slits/cm p, with a length of 0.25 mm.

The perforated film was cut up to approx. 30.6 x 40.6 cm outer dimensions and placed at the top of the absorbent pad which was thereby enclosed between the perforated film and the polyethylene film. The edges around the whole thing were heat sealed.

This composition was placed under the cylinder with a diameter of 10 cm and examined with regard to absorption properties by pouring on 30 ml of liquid (simulated urine). The liquid was completely absorbed through the foil and into the absorbent pad within 57 seconds.

The inner foil was carefully removed and placed on an identical absorbent pad and the edges were again heat sealed.

The absorbent article was brought into contact with a roller provided with heating means and approx. 1.5 studs/cm 2 protruding along the roller circumference. The cam diameter was approx. 2.78 mm and the rounded end had a radius of approx. 1.39 mm. The absorbent article was supported by a yielding counter-roll. The knobs were heated to a temperature of approx. 150°C using circulating hot oil that held 177 o C. The absorbent product had approx. 1.5 pits/cm<2 >along the surface of the absorbent article. Mån examined the nappy with regard to absorption properties as previously explained and the liquid was then completely absorbed through the inner foil and into the absorbent material within 4 seconds.

Example 4

An absorbent pad consisting of eight layers of absorbent cotton and measuring approximately 30 x 40 cm x 4.77 mm was placed in the center of a sheet of polyethylene film measuring 30.6 x 40.6 cm x 0.030 mm and having an embossed taffeta pattern .

A sheet of ethylene-ethyl acrylate of thickness 0.030 mm was perforated by bringing it into contact with a reciprocating rod having a large number of small blades "striated" at a distance of 4 mm from each other on the surface of the rod. The film received approx. 1.5 parallel rollers/cm 2 with approx. 2.5 mm length on each slit.

The perforated film was cut to approx. 30-.6 x 40.6 cm and placed on top of the absorbent pad which was thereby enclosed between the perforated film and the polyethylene film. The edges were heat sealed.

The whole thing was placed under the cylinder with a diameter of 10 cm and examined for suction properties. The liquid was completely absorbed through the inner foil and into the absorbent material within 36 seconds.

The inner foil was then carefully removed and placed on one

identical absorbent pad and the edges were heat sealed again.

The absorbent article was brought into contact with a roller equipped with heating means and approx. 1.5 knots/cm 2 around the circumference of the roller. The cam diameter was 2.78 mm and the cam end had a ball-shaped end with a radius of approx. 1.39 mm. The absorbent article was supported by a resilient counter-roll. The knobs were heated to a temperature of approx. 150°C by a circulating hot oil system, where the temperature of the oil was kept at 177°C. The resulting absorption product had approx. 1.5 pits/cm 2 arranged along the absorbent article's inner foil.

The diaper was then examined for absorption properties as previously explained and the liquid (simulated urine) was completely absorbed through the inner foil and into the absorbent material within 3 seconds.

Example 5

An absorbent pad consisting of eight layers of absorbent cotton and measuring approximately 30 x HO cm x 4.77 mm was placed in the center of an acre of polyethylene film with approximate dimensions 30.6 x 40.6 cm x 0.030

mm and with an embossed taffeta pattern.

A sheet of ethylene-ethyl acrylate film 0.030 mm thick was perforated by contacting a reciprocating rod with a number of small blades spaced 3-5 mm apart on the surface of the rod. The treated perforated film had approx. 12 parallel slits/cm <2> with a length of approx. 1.8 mm for each slot.

The pierced filem was cut into approx. 30.6 x 40.6 cm outer dimensions and placed on top of the absorbent pad which was thereby enclosed between the perforated film and the polyethylene film. The edges were heat sealed.

The absorbent diaper was placed under the 10 cm cylinder and examined for suction properties. The liquid (simulated urine) was completely absorbed through the inner foil and into the absorbent material within 87 seconds.

The inner foil was carefully removed and placed on an identical nappy and the edges heat sealed again.

The absorbent article was brought into contact with a roller provided with heating means and approx. 1.5 knots/cm 2 which extended around the circumference of the roller. The lug diameter was 2.78 mm and the ends of the lugs had a spherical end with a radius of approx. 1.39 cm. The absorbent article was examined by a yielding counter roll. The knobs were heated to a temperature of approx. 150°C by circulating hot oil which held 177°C. The absorption product had approx. X, 5 pits/cm 2 . The absorbent article was examined for absorbency in the same way as previously explained and the liquid (simulated urine) was completely absorbed through the inner foil and into the absorbent material within 5 seconds.

Example 6

An absorbent pad that consisted of eight layers of absorbent

wadding and with approximate dimensions of 30 x 40 cm x 4.77 mm was placed in the center of a sheet of polyethylene film with dimensions of 30.6 x 40.6 cm x 0.030 mm and with an embossed taffeta pattern.

An ethylene-ethyl acrylate film with a thickness of 0.030 mm was perforated by passing the film through the apparatus described in publicly available Norwegian application no. 3769/72. The device consisted of a 9-mesh wire cloth and the perforating means was a metal comb. The resulting perforated film had an appearance as shown in Fig. 2 and contained 12.6 slits/cm 2 , each slit had a length of approx. 2.5 mm.

The punctured film was cut to approx. 30.6x

40.6 cm outer measurement and placed on top of the absorbent pad which was thereby enclosed between the perforated film and the polyethylene film. The edges were heat sealed around the absorbent material.

The whole thing was placed under the measuring cylinder and examined with regard to absorption. The liquid was completely absorbed through the inner foil and into the absorbent material within 4 seconds.

The inner foil was then carefully removed and placed on an identical absorbent pad plus outer foil, and the edges were heat sealed again. ;

The absorbent article was brought into contact with a roller of the same construction and dimensions as previously described and in absorption tests as previously explained, it was found that the liquid was completely absorbed through the inner foil and into the absorbent material within 3.2 seconds.

Example 7

The procedure from Example 6 was repeated, except

that the gap size was approx. 1.8 mm in length. All other conditions were maintained. The following results were obtained:

Absorption time

The following examples 8-12 show that the amount of absorption in baby diapers according to the present invention is affected by the number of dimples/cm 2 impressed in the inner foil. In the previous test methods, the liquid was poured onto manufactured diapers, while the part of the diaper that was in contact with the liquid lay in a horizontal position. In order to imitate in a more relevant way the real suction effect that occurs when the nappy is worn on a baby, the following test method was devised: The test nappies were placed on and held on a plate with an angle of inclination of 45°. A separating funnel with a delivery rate of 40 ml/30 seconds was placed over the plate so that the opening was 2.5 cm above the nappy's inner foil. The funnel was set so that the liquid that dripped from the funnel fell on the diaper's inner foil and would move approx. 28 cm linear length across the nappy. The liquid was a water solution (0.3N NaCl) which was kept at room temperature. Said 40 ml was dripped from the funnel within 30 seconds and the amount that ran off the diaper, i.e. the amount that was not absorbed, was measured.

The test nappy was made from the same cotton roll and the same roll of inner foil (ethylene-ethyl acrylate) as before. They were produced as described in Example 3, except that the number of pits/cm 2 was varied as appears below:

Three trials are carried out under each example (with different nappies), and the average numerical result appears in Table I.

The procedure in Examples 16-20 is the same as in Examples 8-12 except that the angle of the inclined plate was increased to 60°. The results appear in Table II:

The following Example 18 shows the increase of the wet strength or the wet consistency of a diaper which is provided with pits according to the present invention. Paper fluff was used as an absorbent ion pad since these pulp fluff lose wet strength to a greater extent than water.

The following experiments were carried out:

In a test apparatus where a sample of 10 x 10 cm of the composite cushion prepared for the test by wetting with twice its dry weight with water and a humidity equalization for one minute, was clamped between two annular, flat metal rings of aluminum with an opening with an internal diameter of 8.9 cm. The middle bottom part of this 8.9 cm sample clamped in the aforementioned manner, which on a first plate with a diameter of 3 to 8 cm coated with polyurethane foam of thickness 1.5 mm. Another plate with a diameter of 2.5 cm coated with polyurethane foam, thickness 1.5 mm, was placed in the center and pressed down towards the upper side of the sample with a pressure of 0.89 kg/cm and the sample was further moistened with twice dry weight of water and equilibrated for one minute. The first plate that pressed against the underside of the preliminary search mat could rotate in the plane of the sample, while the second plate that pressed against the upper side was stored so that it could turn in an arc of 45° with a frequency of 55 times/minute. The rotary motion of the first and second plates tended to tear open the clamped test diaper in a circle around the central press pleat 2.5 cm in diameter.

A test period for this simulator test with the described rotary movement was 4 minutes and the test results were listed as tear grading from 0 to 3 by visual assessment, where tear numbers greater than 1 mean unsatisfactory results for real use. The degree of tearing with the individual samples had the following meaning: Degree of tearing 1 - tearing in an area of less than a total of 10° around the compressed area.

Tearing degree 2 - tearing in a total amount of 10°-90°

around the compressed area.

Tearing degree 3 - tearing at a distance of more than 90°

around the compressed area.

Example 18

An absorbent pad containing 30 g of cellulose, of which 22 g was pulp fluff, and measuring 30 x 40 cm x 4.77 mm was placed in the center of a sheet of polyethylene film measuring approximately 30.6

x 40.6 cm x 0.030 mm with embossed taffeta pattern.

A foil with a thickness of 0.030 mm of ethylene-ethyl acrylate film was perforated by passing it through the apparatus described in publicly available Norwegian application no. 3769/72. The device consisted of a 9-mesh wire cloth and the perforation part consisted of a metal comb. The resulting perforated film had the appearance shown in fig. 2 and contained 12.5 slits/cm p, with a length of 2.5 mm.

The punctured film was cut to approx. 30.6 x 40.6 cm and placed on top of the absorbent pad which was thereby enclosed between the perforated film and the polyethylene film. The edges around the whole thing were heat sealed. The nappy was then tested for wet resistance as described above and the result was a tearing rating equal to 2.

Another diaper of the same type was produced. The diaper was brought into contact with a roller equipped with heating means and approx.

1.5 knots/cm around the roller. The knob diameter was 2.78 mm and the knob ends had a ball-shaped end with a radius of approx. 1.39 mm.

The absorbent article was supported by a resilient counter-roll. The knobs were heated to a temperature of approx. 150°C using circulating hot oil. The absorbent product had around 1.5 pits/cm along the inner foil of the absorbent article. The article was tested with regard to wet strength and one could note a degree of tearing equal to 1 according to the rating scale.

Example 19

A diaper was constructed using the same materials and method as in Example 6, except that this time the slits measured 1.8 mm in length and the pit radius was 2.14 mm. The nappy was examined with regard to absorption in the same way as in Example 6 with the following results:

As will be seen from the above examples and the rest of the description, the absorbent product according to the present invention has excellent properties in all the areas listed a) to d). Variations are conceivable within the framework of the invention, particularly by omitting certain features which, even if one would then not get an optimal product that was better than the previously known products. For example, the fibers in the absorbent pad do not need to stick to the lower parts of the pressed-in pits. One would lose some in dimensional stability, but the other advantages would not be significantly affected. Instead of passing the absorbent product through such a dimpling process, the inner foil can be pre-treated by pressing in such dimples and then the inner foil can be combined with the other parts of the product.

In the following patent claims, the term "pits" is used to denote the aforementioned pressed-in areas. This term shall thus include the impressed or pressed-in areas on the surface of the inner foil, which areas have been pressed down to a plane lower than the plane of the inner foil and which have been carried out in such a way that no significant tearing, melting or cutting of the inner foil takes place during or after the manufacture in such a way that it would prevent the regulated flow of liquid to the absorbent pad.

The pressed-in pits are thus essentially impermeable to liquids.

Claims (4)

1. The moisture absorbent.de disposable article comprising individual layers, e.g. nappies, incontinence pads etc., comprising a hydrophobic top sheet for placement close to the user's body and with a number of openings, an essentially liquid impermeable bottom sheet and an absorbent layer between the top sheet and the bottom sheet, and where valve-like closable openings are arranged in the top sheet which are straight or approximate straight, and where the openings prevent contact between the absorbent material and the body and prevent back-flow of absorbed liquid, characterized by a system of liquid-impermeable pits (22) pressed into the topsheet (16) between the valve-like openings, which pits extend into the absorbent layer (12), and that the pits have a frequency of at least 0.15/cm 2 of the area for the absorbent pad. 2. Article according to claim 1, characterized in that the pits (22) are placed on the top sheet (16) in an amount of 0.15-15j, preferably 0.45-4 and preferably 1-2.3 pits/cm of surface. 3. Article according to claims 1 and 2, characterized in that the total area occupied by the pits (22) is less than 20%, preferably 4-12%, of the area of the absorbent pad (12). 4. Article according to claim 1, characterized in that the pits (22) have a circular shape with a diameter of about 0.635-6.35 mm, preferably 1.905-3.81 mm.