LU84537A1 - SANITARY NAPKIN - Google Patents

Description

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The present invention relates to hygienic accessories and, in particular, to a sanitary napkin having better fluid transfer characteristics.

5 Two of the problems with making hygienic accessories such as diapers, incontinence pads and menstrual towels, lie in the transfer of fluids throughout the absorbent medium associated with these accessories, as well as in the comfort of these.

It is desirable that the fluid be transferred as quickly as possible from the surface of the accessory which is closest to the emission orifice, at a place situated opposite the latter. This transfer is desirable not only to keep the wearer's body dry, but also to ensure a less unpleasant visual appearance of the used accessory.

Traditionally, hygienic accessories of the type described above have included wood pulp fluff or a similar inexpensive and relatively bulky cellulosic product as the main or only absorbent component. The. fluff or the like are preferred because they are inexpensive, but always visually appealing when dry.

Although visually appealing, the plush poses problems when used as an absorbent material in hygienic accessories.

30 The fluff tends to sag when wet, so it becomes dense and loses elasticity. In addition, the plush is not particularly effective in terms of its absorption capacity by volume of material. However, due to the relatively low relative cost of the cuddly toy compared to other very absorbent materials, we have been led to use it in the same way as related related products. cellulose as the main absorbent component in

There are most hygienic accessories.

Various attempts have been made to increase the absorption capacity of lint, wood pulp and related materials without any consideration of their use in hygienic accessories. In the United States patents Nos. 1,959,845 and 2,073,410, a process is described in which several superimposed layers or layers of a material having the characteristics of blotting paper are used. These webs are prepared from high purity alpha cellulose fibers and are softened due to the stiffening associated with their formation by linting, scraping, crumpling another similar effect. This fluffing effect is used to spread and separate the fibers on both sides of the sheet.

According to these patents, a so-called "absorbent pad" is obtained from a stack of these sheets. This absorbent pad exerts an absorbent action in all directions, ensuring, across the entire surface of the sheet, a longitudinal transfer greater than that obtained in the z direction or through wet stacking. Attempts have been made to compensate for this lack of transfer in the z direction by the formation of longitudinal slits. It is believed that the transfer in the z direction is made difficult by the presence of bulky fiber fluff on each of the surfaces of the web, which gives rise to the formation of a series of alternating layers of dense central leaves and thick surfaces when these layers are stacked. Since the wicking effect occurs only from the larger 1 pore areas to the smaller pore areas, the thick fluff layers created by two adjacent fleece surfaces may tend to act in the same way as a barrier for transfer in the z-direction.

Other attempts to improve the conduction or absorbency of a pulp sheet can be found throughout the art. An example of an attempt of this type is described in US Patent No. 3,556,931, the method described in this patent consisting in depositing a sheet of pulp by the wet method, then drying the latter until '' at a moisture content of at least 301 with minimum pressure to create a soft, open-pore surface layer, either by a bending effect, or by breaking the connections between fibers, or by others means. The sheet obtained is a body of soft and flexible cellulosic fibers comprising layers having different absorption characteristics.

Another example of a sheet of cellulosic material is illustrated in US Patent No. 1,986,291 which describes a process for manufacturing a dry sheet of reduced volume. However, none of the aforementioned patents make mention of the combination of fluff or other similar conventional absorbent component with another material in order to improve the performance of a hygienic accessory. None of the materials described in the references of the prior art could alone constitute the absorbent system for these hygienic accessories. This remark is particularly true when a hygienic accessory has to absorb the blood or the menses because of the difficulty met to conduct these relatively dense biological fluids through

Ideas absorbent media.

The concepts of using a multi-component absorbent system are known, in particular, in the case of sanitary napkins.

The art abounds in references relating to sanitary napkins and / or tampons in which conventional cellulosic material is combined with another material having a substantially reduced volume and a relatively increased absorption capacity per unit volume. A class of materials known as "superabsorbents" has been particularly welcomed in the art because of the apparent ability of these materials to fix relatively large amounts of fluid with a very small volume of absorbent material. The theory has been advanced that tampons and composite pads comprising such an absorbent material in combination with conventional absorbents could constitute hygienic accessories of reduced volume accompanied by improved comfort without detrimental effect on the absorption capacity. In the case of tampons and sanitary pads, superabsorbents have apparently created more problems than they resolved. However, superabsorbents cannot reach their maximum theoretical absorption potential as a result of a phenomenon known as "gel blocking". Freezing blockage apparently occurs as a result of the extremely rapid absorption of the watery part of menstruation, as well as the simultaneous formation of an essential coating on the surface of the superabsorbent of the other components of menstrual fluid. , such as cell debris and mucoid fractions. This covering layer very quickly forms a barrier to subsequent absorption of fluids and it practically prevents the use of

Isation of these materials. The problem of gel blocking has been recognized and attempts have been made to minimize its effect by combining small amounts of superabsorbent material with other components used as release layers. However, these tests have not been fully satisfactory.

In United States Patent No. 4,057,061, a sanitary napkin is described, one component of which consists of a lint densified from 0.05 to 0.75 g / cm3. According to this patent, the densified layer ensures an adequate absorption capacity with a reduced volume. Sanitary napkins made in accordance with this patent may or may not have additional absorbent intermediate layers of reduced volume, but the essential element is the compressed absorbent pulp which is intended to be the main bulky absorbent component. However, there are problems inherent in the process described in this patent. As it is compressed, a layer of absorbent material undergoes densification. This densification results in the formation of small capillaries and, although it provides an increased entrainment effect through the envelope of the sanitary napkin, due to the smaller dimension of the capillaries, the latter tend to s obstruct and the fluid then rapidly migrates along the surface of the compressed layer since its downward transfer through the layer cannot continue. This finally results in lateral staining of the towel comprising this compressed pulp layer, due to the migration of fluids to the surface. Although the volume of the towel is reduced and it is thus made more comfortable, the risks of lateral staining are increased. In addition, the dry compression used in this patent to form the densified layer "I provides a bond in the layer itself. Repeated handling during manufacturing and storage can alter the compact appearance and the napkin will then tend to return to its original volume.

According to the present invention, there is provided a sanitary napkin comprising a first absorbent layer of a usual high volume, as well as an intermediate absorbent layer consisting of densified plush. This densified layer is truncated so that it does not extend to the edges of the upper absorbent layer. The densification gives rise to the formation of smaller capillaries and it ensures rapid absorption of the fluids through the conventional upper absorbent layer of a high volume; due to this densification, the fluid spreads along the upper surface of this second compressed absorbent layer, thus ensuring good distribution of the fluid in the interior part of the towel, away from the user.

The single appended drawing is a perspective view and partially in cross section illustrating a sanitary napkin produced according to the present invention.

As shown in this figure, there is provided a sanitary napkin having a fluid permeable cover 16 which surrounds an absorbent layer 10. This absorbent layer 10 is, in fact, a lower absorbent layer 12 when folded 30 below an intermediate absorbent layer of compressed plush 13. The absorbent layers are completely surrounded by the fluid permeable shell 16 and are sealed with an adhesive or by fusion on the surface adjacent to the fluid permeable separating layer 14 as indicated by the lines in

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8 broken lines 11. The towel is sealed at its ends by melting the fusible thermoplastic envelope 14 on itself as illustrated by the strips 15.

The particular embodiment illustrated in the appended drawing is preferred for reasons which will become apparent on reading the description below. Although, in accordance with the teachings of the present invention, it is not necessary to fold the absorbent upper layer 10 over an absorbent intermediate layer as shown in the drawing, this configuration is preferred when the upper absorbent layer is a coformed mixture plush and thermoplastic microfibers. This absorbent layer is described in US Patent 4,100,324 15 and it consists of a matrix formed in air from thermoplastic polymer fibers with an average diameter of less than 10 microns in a multitude individualized pulp fibers dispersed in the thermoplastic matrix. This layer is formed initially using a main air stream which transports the meltblown microfibers to a blending air stream containing wood pulp fibers. The fibers of the two types are then amalgamated under turbulent conditions and introduced into an integrated air stream along a forming surface.

A sanitary napkin comprising a co-formed layer which surrounds the intermediate layer of fluff of absorbent wood pulp and densified according to the invention, has better elasticity both in the wet state and in the dry state. This preferred towel also has an adequate capacity due to the better spreading of the menstrual fluid which results from the presence of the compressed absorbent intermediate layer. Although it does not have a relatively large absorption capacity for fluids, this absorbent intermediate layer allows better use of the other absorbent materials due to the horizontal wicking effect resulting from compression and densification. plush.

Of course, a conventional plush or other similar material can also be used as the top layer, but, for the applications of the present invention, it is absolutely essential that the absorbent intermediate layer has a truncated surface, compared to a top layer. absorbent. This is true whether or not consideration is given to folding the top layer over the absorbent intermediate layer so that it surrounds the latter.

The densified intermediate layer of the present invention is compressed to a density of at least 0.1 g / cm3. The minimum degree of compression is determined by the density of the upper layer, i.e. the density of the intermediate layer must always be higher to conduct the fluid through the upper layer and onto the surface of the layer absorbent intermediate to ensure an appropriate wicking effect. Typically, the density will be in the range of 0.1 g / cm3 to 0.4 g / cm3. In addition, it is highly desirable that densification be carried out on a layer of fluff deposited in air, using water atomization and a hot calendering cylinder due to the extreme difficulty which is encountered. experiences getting something other than a temporary bond with an air deposition process. Within the limits of these parameters, it was found that a density! 0.18 g / cm3 was preferred after densification! initial tion by water deposition. (It should be noted that there is a certain recovery of the densified sheet after I / L- # a prolonged period, but this recovery is extremely weak).

This densified layer must have a uniform density throughout its mass and the formation of layers of the type described in US Patents 2,905,568 and 3,017,304 must be avoided, including that this is called a "surface film". A film of this type prevents practically any significant absorption of fluids and, for the towel to properly perform its function, it is necessary that the layer of densified fluff allows some absorption and a certain retention of fluids in the same way as a wicking effect.

15 A homogeneous densification can be carried out during the manufacture of a conventional layer of fluff deposited in the air with a supply of sufficient moisture so that the entire layer of fluff is moistened. The surface of the moistened fluff layer 20 is then compressed into the constriction defined by at least one hot cylinder. The degree of densification obtained is a function of the cylinder temperature, the flow rate and the pressure of the cylinder. Results were obtained giving a densified layer whose density is close to the preferred value, by adopting a flow rate of 3.04 meters / minute and a temperature of 82 ° C. The hot cylinder seems to entrain moisture in the fluff and no film formation is observed on the face which has received a contribution of moisture. It is believed that the homogeneous densification obtained is the result of a permanent deformation of the cellulosic fibers and / or of a bond between fibers. It may also be desirable to raise the temperature of the backing cylinder as a function of the thickness of the initial fluff layer in order to prevent the formation of a dense layer.

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111 paper-like on the underside of the tablecloth.

A sanitary napkin made with the densified layer described above has excellent absorption capacity, reduced volume and increased efficiency of use of the absorbent due to the presence of the absorbent intermediate layer. For the applications of the present invention, it is preferable that the absorbent intermediate layer has, on each side, a width at least 0.2 cm less than that of the upper absorbent layer. Preferably, this difference in width will be at least 0.5 cm. It is also desirable that the length of the absorbent intermediate layer does not extend over the entire length of the upper absorbent layer, although this parameter is not as critical.

Claims (5)

9 • V * ml 1. Sanitary napkin comprising: a) a separating layer impermeable to fluids; b) a first absorbent layer; C) a second absorbent layer of uniformly densified fluff, having a controlled absorption capacity and disposed between the first absorbent layer and the separation layer, this second absorbent layer having a density greater than that of the first layer absorbs, but does not fall below 0.1 g / cm3, while it has a width less than that of the first absorbent layer. 2. Sanitary napkin as claimed in claim 1, characterized in that the first absorbent layer consists of plush. 3. Sanitary napkin according to claim 1, characterized in that the first absorbent layer is a coformed mixture deposited in the air with cellulosic fibers and thermoplastic microfibers. 4. Sanitary napkin according to claim 3, characterized in that it comprises more than two t absorbent layers. 5. Sanitary napkin according to claim 1, 2, 3 or 4, characterized in that the first absorbent layer is folded transversely around the second absorbent layer in order to form a layer covering at least partially the face of the second layer absorbent which faces the separating layer. L · .. V K ^ '' · / "\ / \ / \ · \ 4 /". ’