IMPROVEMENTS TO ABSORBENT MATRIX FOR A DISPOSABLE ABSORBENT ITEM
BACKGROUND OF THE INVENTION Disposable absorbent articles such as disposable baby diapers, disposable incontinent diapers, training pants or feminine towels are generally constituted by an upper layer that allows the passage of the liquid, a impermeable bottom layer and an absorbent matrix placed between them. The primary functions of the absorbent matrix are the absorption and retention of the waste that reaches it; other important characteristics of the same are the rapid capture of the fluid and its distribution within the matrix. There are a myriad of proposals to improve these characteristics, such as those described in patents US 4,610,678, US 4,765,780, US 4,673,402, patents MX 170,214, MX 171,485 as well as many that are not specifically mentioned for brevity. - Speaking specifically of disposable diapers , the total absorption capacity of the matrix is generally not used, since due to the great advances that have been achieved in terms of densities management, types of fibers and use of superabsorbent materials, liquids are trapped and retained before arriving to the areas farthest from the matrix, due to this, the tendency is to use smaller matrices and with greater efficiency, so that they are comfortable for the user and that material is not wasted. The use of straight matrices goes back to the first disposable diapers, in which the diaper was rectangular and the matrix included the total thereof; over time, both the shape of the diaper and the shape of the womb evolved, so that when the diaper was introduced with elastic, the size of the womb was reduced and it no longer covered the total of the diaper, but the upper and outer layers from it protruded from the matrix forming the outline of the diaper, both the diaper and the matrix acquired an anatomical shape, adapted to adapt to the user's body; With the evolution of both the design of the diaper and the materials from which it is made, this anatomical shape can be achieved with the diaper chassis, ie with the upper and / or outer layers, so that an absorbent matrix can be used straight, which, in addition to facilitating the process, involves the use of a smaller amount of material. A diaper of this type is exemplified in US Pat. No. 4,883,480 to McNeil-PPC, in which the exact dimensions of a "T" chassis are described, the absorbent matrix of this diaper is rectangular and covers the vertical portion of the diaphragm. "T", and breathable upper and lower layers are also described, so that at least 35% of the diaper is breathable.
With the absorbent matrix of the present invention, in addition to the fact that breathing capacity can be achieved in certain parts of the diaper, the quantity of liquids returning to the surface of the article, the result of the distribution of absorbent material within the same, is markedly diminished. , which is distributed in such a way that four zones with different specific weights are formed, a reception / distribution zone, an anti-runoff zone and two transition zones. The matrix also contains superabsorbent material distributed homogeneously within it. Objectives of the Invention An object of the present invention is to make efficient the use of absorbent material within an absorbent matrix. Another objective of the invention consists in the use of a rectangular absorbent matrix with reception / distribution, transition and anti-runoff zones that improve the efficiency thereof. A further object of the invention is to improve the return characteristics of liquids to the surface in a disposable absorbent article, such as a disposable diaper or trainer pants. A further objective of the invention consists in that the article does not become more expensive with the aforementioned improvements. Brief Description of the Drawings Figure 1 shows the matrix of the present invention. Figure 2 is a section through the line A-A 'of Figure 1. In Figure 3 a disposable diaper with the absorbent matrix of the present invention is illustrated. Detailed Description of the Invention The absorbent matrix of a disposable absorbent article is the part thereof that is responsible for absorbing and containing the liquid and semi-liquid exudates that reach it. It is desirable, in addition, that the matrix distributes the liquids properly, avoids the return of the same to the surface of the article, has good integrity and absorbs as quickly as possible, all this to take advantage of all its absorption capacity and for the user to feel comfortable and dry where possible. There is a wide variety of disposable diapers in the market with different designs of absorbent matrices, thick, thin, with zones, with distribution and transfer layers, etc., depending on the type of article for which they are used. During use, liquids tend to be deposited always in the same area and for more efforts are made to ensure that they are properly distributed and reach the entire matrix, there are areas of it to which generally, never arrive. On the other hand, the vast majority of the matrices that can be found in the market have an anatomical shape suitable to fit the body of the user and to help give body to the diaper. An anatomical matrix has, in general, a front part, a back part and a crotch part, by the rear and / or front parts thereof, it is wider and has what in the middle is known as "" ears "of the matrix, which serve mainly to give body to the article by the rear and / or frontal area of the same.Due to the great advances in technology, such as the use of superabsorbent materials within the matrix, the use of different densities To help absorb and distribute the liquid, the use of layers of transfer and many more not mentioned, it works more efficiently and the liquid is trapped inside it before reaching the most remote parts; specifically, the liquid almost never reaches the "ears" of the matrix. On the other hand, the advances in terms of the materials used for the inner and outer layers of the diaper make it possible to eliminate the "ears" of the matrix without affecting the diaper body. Therefore, it is proposed by the present invention the use in disposable diapers of a rectangular absorbent matrix and with reception / distribution, transition and anti-runoff zones, so that the amount of liquid returning to the surface of the diaper is remarkably reduced. . Figure 1 shows the absorbent matrix of the present invention (10), which has been divided into three parts for explanatory purposes: the front part (26), the crotch part (28) and the rear part (30); on the other hand, the matrix has two transverse edges, one front (18) and one back (20) and two longitudinal edges (22). The area identified with the reference number (12), is the area of reception / distribution of the matrix and has an area that varies between about 30 to 60% of the total area of the same. This area is located in the front (26) and crotch (28) parts of the matrix, without covering 100% of them, in the area in which liquids are generally deposited during use. This is the area of the matrix that has the highest amount of absorbent fibers per unit area, varying between about 400 and 800 g of fiber / m2 of matrix, preferably the amount of absorbent material / m2 is greater than about 600 gr / m2. The density in this reception / distribution zone is kept constant and varies between around 0.14 and 0.22 g / cm3, the preferred density being higher than around 0.17 g / cm3. The zones identified in the figure with numbers 14 and 14A are transition zones and cover between them an area no greater than about 30% of the total area of the matrix; in both the density gradually decreases, so that the first transition zone (14), in addition to giving body to the article by the front thereof, hinders the passage of fluids to the front edge (18) of the matrix. The second transition zone (14A) has the main function of preventing the matrix from splitting during use when going from a high density area to a zone with lower density, the anti-draining zone (16), which covers an area that goes from around 20 to 40% of the total area of the matrix (10), is located in the back
(30) thereof and is the one with the lowest density, so that the liquids advance within it much more slowly and an absorbent barrier is formed, such that the fluids are stopped and stored inside it. The matrix of the present invention contains particles of superabsorbent material evenly distributed therein, a ratio varying between about 70:30 and 50:50 by weight of fibers of absorbent material particles of superabsorbent material being used. Using the matrix of the present invention in a disposable diaper such as that shown in Figure 3, having a permeable top layer (32), a waterproof bottom layer
(34), the absorbent matrix (10) of the invention and a transfer layer (36), in addition to the common elements in a disposable diaper such as leg and waist elastics and fastening system, substantially improves the return of them to the surface of the article. When comparing the results obtained in a diaper using the matrix of the invention with the results obtained using a diaper with the same top layer, same bottom layer, same transfer layer and with an anatomical matrix containing approximately 30% superabsorbent material, a weight maximum base of 500 g / m and a maximum density of 0.16 g / cm3, which can exemplify an absorbent matrix such as those normally found in the market. The results obtained are shown in the following table:
As can be seen, when using the matrix of the invention in a disposable absorbent article, such as a disposable baby diaper, it is possible to decrease up to about 70% after the second and third discharge the amount of liquid returning to the surface of the article when applying pressure on it after the fluid has already penetrated; The results shown are obtained using the following method: Material Inspection table Electronic scale Stopwatch · Adjustable separating funnel Precipitation beaker Graduated cylinder 5 kg weight 3 kg weight Receptacle cylinder with internal diameter 6 cm and 6 cm height Urine synthetic Absorbent paper of 10 x 10 cm Development: Tare the scale Weigh the sample and record the data Place the product to be tested on the work table and attach it to the table Place the receiving cylinder in the liquid discharge area Place the tip of the separating funnel inside the cylinder, one inch above the sample. Dispense 50 ml of synthetic urine. Let it rest for 10 minutes. Weigh the absorbent paper and record the weight as PI. After 10 minutes place the absorbent paper on the insulting point and place the on paper a 5 kg weight, for 2 minutes Remove the weight and weigh the absorbent paper strand the data as P2 Repeat from the fourth point (place the cylinder), to calculate the second and third returns • Calculate the first return as Pl - P2, the second return as Pl - P3 and the third return as Pl - P4 The decrease to such a degree of the return of liquids to the surface of the article, ensures greater dryness on the surface of the article as well as minimal exposure of the skin to the urine, contributing significantly to the user's well-being, since exposure to moisture and contact with urine are the main causes of skin irritation during the use of disposable diapers. While the invention has been described in terms of its preferred embodiments, the scope thereof includes any type of change or modification thereto that may be apparent to a person skilled in the art. This invention relates generally to control systems, and more particularly to movable barrier control systems.