MX2011014003A - Absorbent matrix. - Google Patents

Abstract

Protected by the present invention is an absorbent matrix intended to be sued in disposable absorbent articles, which has an upper surface and a lower surface, a front portion and a rear portion, two longitudinal edges and two transversal edges, which is formed by three layers: an upper layer, a middle layer and a lower layer, so that the upper and lower layers containing lower than 25% of superabsorbent material, the middle layer having three zones with different specific weights: a reception-distribution zone; one or more transition zones and one or more anti-leakage zones.

Description

ABSORBENT MATRIX TECHNICAL FIELD OF THE INVENTION The present invention relates to an absorbent matrix. More particularly, the present invention relates to absorbent matrices such as those used, but not limited to, in disposable diapers for babies, disposable diapers for incontinents, training pants and feminine towels. Still more particularly, the present invention relates to an absorbent matrix with zones of different specific weights and densities and formed in layers.

Background of the Invention Disposable absorbent articles such as disposable baby diapers, incontinent disposable diapers, training pants and feminine towels are basically constituted by an upper layer that allows the passage of the liquid, a waterproof lower layer and an absorbent matrix placed between both. The absorbent matrix is the one in charge of absorbing and retaining liquid or semiliquid exudates that penetrate the upper layer of the article.

An absorbent matrix, in addition to fulfilling its main objectives already mentioned, must be soft and flexible, so that it fits the body of the user. In recent years the market has been inclined by thin absorbent matrices, in which, to obtain adequate absorption and retention have been using superabsorbent materials, which may be mixed with the fibers of which the absorbent matrix is formed or located in specific areas of the matrix. One of the superabsorbent materials (SAP) most commonly used in disposable absorbent articles are sodium or potassium polyacrylate particles, however many other synthetic or natural materials are known in the medium that can be used as SAP in absorbent matrices.

There are countless proposals for thin matrices that mold better to the body of the baby and that meet the needs of absorption and retention of fluids. For example, U.S. Patent No. 5,149,335 to Kellenberger, refers to a thin disposable diaper with a content of superabsorbent material within the matrix ranging from 60 to 100% and it is contained in a fibrous matrix. On the other hand, US Patent No. 5,098,423 of Heinz A. Pieniak, protects a thin diaper with a configuration such that it is very comfortable for the user, since it is very narrow in the crotch and the user is not he has to keep his legs open; The absorbent matrix of this diaper contains 200 to 1500% of a superabsorbent hydrogel.

The Patent MX 249,142 of Corona Carlos, protects an ultra-thin absorbent matrix that does not contain fibers of absorbent material, but only consists of superabsorbent material placed inside a surrounding layer of a non-woven material, whose upper part distributes the liquid before penetrate and be absorbed and retained by the superabsorbent material.

On the other hand, in order to make the functioning of absorbent matrices more efficient, several developments have been carried out incorporating areas with different specific weights and densities within an absorbent matrix, such is the case of the absorbent matrix described in patent number US4,834,735 of Alemany that protects an absorbent core with a fluid acquisition zone and a storage zone which have different densities; The liquid catchment area that is located in the front half of the core has a lower density than the rest of the core (storage area), so the liquid will be quickly captured by the collection area and distributed and stored inside it. However, the liquid will easily reach the lateral edges of the nucleus since the high density zone continues to the edges of the core; The patent US 5 849 002 of Corona Carlos, refers to an absorbent core formed by 3 zones, area of reception of fluids, a primary zone of storage and an anti-drip zone, each zone has different specific weights and densities. The Mexican patent MX 219,792, also by Corona Carlos, protects an absorbent matrix that incorporates transition zones between the reception and anti-fall zones, in these areas of transition, the density gradually decreases to avoid matrix ruptures.

Notwithstanding the above, there is still a need to develop thin absorbent matrices that are soft and comfortable for the user, as well as more efficient, that improve the characteristics of absorption speed and liquid distribution, in the present proposal, said efficiency is based on in the combination of an absorbent matrix with layers and with zones with different specific weights and densities. The matrix has a first layer of absorbent material, preferably defibrated cellulose, at the top, a second layer of absorbent material, preferably defibrated cellulose, at the bottom and a third layer comprising a mixture of fibers of absorbent material and particles of superabsorbent material (SAP), placed between the first and second layers; In addition, the intermediate layer (third layer), has within it the distribution-storage, transition and anti-drip zones. In this way a thin, soft, flexible matrix is obtained, with very good characteristics of absorption speed and distribution of liquids, also reducing the consumption of cellulose, and optimizing the use of superabsorbent powder (SAP).

Objectives of the invention An object of the present invention is to provide a thin, soft, flexible absorbent matrix with suitable absorption, distribution and retention characteristics.

Another object of the invention is to provide the appropriate SAP / CELLULOSE ratio in a thin matrix with zones of different specific weights and sities and formed into layers.

A further object of the invention is that the superabsorbent material contained within the matrix does not migrate to the surface of the article.

Another objective of the invention is to reduce the amount of cellulose fibers contained in the matrix improving the efficiency thereof.

A further object of the invention is to incorporate the matrix into a disposable absorbent article.

Brief Description of the Drawings Figure 1 shows the absorbent matrix of the present invention.

Figure 2 is a side view of the absorbent matrix of the invention.

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 semiliquid exudates that reach it. The matrix must also have the capacity to distribute the liquid and to retain it, preventing its return to the upper surface of the matrix and consequently to the upper part of the article; on the other hand it must be soft and conform to the user's body.

In the following, the absorbent matrix of a disposable diaper will be described, however, said matrix can be incorporated in an absorbent insert, in a trainer brief, in a feminine towel or in any other article intended to absorb exudates and that is discarded after use.

The absorbent matrix (10) of the present invention has an upper surface (16) and a lower surface (18); as well as two longitudinal edges (20) and two transverse edges (22); The matrix (10) shown in Figure 1 is hourglass-shaped, with a front part (34), a rear part (36) and a central or crotch part (38) that is narrower than the front and rear, so that it is more comfortable for the user, however, the matrix of the invention can take any other shape known in the art, by way of example, the matrix (10) can have rectangular shape, "T" shape, shape of "I" or any straight or anatomical shape.

Figure 2 shows a longitudinal section of the absorbent matrix (10) shown in figure 1, it can be seen that the matrix is constituted by three layers: an upper layer (12) placed by the upper surface (16) of the matrix , a lower layer (13), placed by the lower surface (18) thereof and an intermediate layer (14) placed between the upper (12) and lower (13) layers.

The upper layer (12) is preferably formed 100% by fibers of absorbent material, however it can contain up to 25% particles of superabsorbent material (SAP); its primary function is to give softness and flexibility to the matrix, it captures the liquid and quickly transfers it to the intermediate layer (14), in addition to helping to contain the superabsorbent material contained in said intermediate layer (14), so that it does not arrive to the surface of the matrix and there is a risk that it is in contact with the user's skin. On the other hand, since the upper layer (12) does not contain or contains a low concentration of particles of superabsorbent material, there is no blocking effect that occurs when said superabsorbent material swells upon contact with the liquid, thus the layer upper (12) allows the fluid to pass freely to the intermediate layer faster than in matrices containing a high concentration of superabsorbent material at the top (16).

The lower layer (13), like the upper layer (12), is preferably formed of 100% fibers of absorbent material, although it may contain up to 25% of superabsorbent material mixed with the fibers of absorbent material; It has two primary functions: a) to give softness and flexibility to the matrix and b) not to allow particles of superabsorbent material to reach the lower surface of the matrix. This aspect is important since the absorbent matrix is to be incorporated into a disposable absorbent article and the lower part (18) of said matrix will be in contact with the outer layer of the article, if the particles of superabsorbent material are in contact with the layer. outside, can weaken and even cause perforations in the outer layer.

The intermediate layer (14) of the matrix, formed of a mixture of cellulose fibers (32) and particles of superabsorbent material (30), has the primary function of distributing and retaining the exudates, as well as preventing the fluids from returning to the upper part of the matrix and as a consequence, of the article to which it is incorporated. This intermediate layer has, within it, well-defined areas with different specific weights and densities: a first distribution-storage zone (24), one or more transition zones (26) and one or more anti-drip zones (28).

The distribution-storage area (24) of the intermediate layer (14) is the area with the highest concentration of fibers of absorbent material and particles of superabsorbent material, such that when it receives the liquid it distributes and stores it efficiently, avoiding its return. The distribution-storage area has a specific weight (gr / m2 of cellulose fibers + superabsorbent material) of 35% to 50% higher than the average specific weight of the transition zones (26) and 75% 100% greater than the specific weight of the anti-drip zones (28).

On the other hand, the reception-distribution zone (24) has a density A, the anti-drip zone (28) has a density B, and the transition zone (s) (26) have a density that varies throughout the same between A and B. The density A is greater than the density B. Due to this difference in densities and applying the theory of capillarity, the spaces between fibers in the distribution-storage area (24) are smaller, causing a greater fluid distribution. On the other hand, the cellulose fibers are homogeneously mixed with SAP particles, so that upon contact with the fluid, the latter absorb and retain it, while the fibers that adjoin them help the fluid not to flow. it is absorbed, it continues distributing and can be absorbed and retained.

In the transition zones (26), as the density decreases gradually from A to B, by the same theory of capillarity, the velocity of fluid distribution, which is stored between the fibers and within the SAP particles, also decreases. Finally, in the anti-drip zones, the density B is even lower, so that the fluid is lodged between the fibers and does not reach the transverse edges (22) of the matrix.

Absorbed cellulose is preferably used as the absorbent material, although other absorbent materials known in the medium such as cotton, rayon, etc. may be used. Sodium or potassium polyacrylate particles are preferably used as superabsorbent material, however other synthetic or natural superabsorbent materials can be used.

The layered absorbent matrix of the present invention exhibits optimum performance, rapidly captures the fluid, distributes it and retains it in such a way that most of the matrix is used, preventing it from reaching the transverse edges. On the other hand, the matrix is very soft and flexible, since the upper (12) and lower (13) layers thereof are constituted mostly by fibers of absorbent material (30). The low concentration of SAP in the upper and lower surfaces of the matrix prevents: a) that this material could come into contact with the skin of the user; b) that there could be breakage or weakening of the lower layer of the disposable absorbent article to which the matrix (10) is incorporated and c) blockage by the upper part of the matrix due to the swelling of the superabsorbent particles.

The matrix 10 of the invention can be incorporated in any type of disposable absorbent article, such as disposable diapers, training pants, feminine towels or absorbent inserts, understood as an absorbent insert, an article formed by an upper layer, a lower layer and the absorbent matrix 10 placed between these layers.

An additional advantage of the matrix (10) of the invention is that it is possible to decrease the amount of absorbent material used without affecting the functionality of the matrix, resulting in considerable savings, as can be seen in the following examples: Example 1 Traditional matrix: Bio Baby diaper size 4 manufactured in December 2010.

Matrix (10): Bio Baby diaper size 4 with new matrix Example 2 Traditional matrix: Moltex diaper size 4 manufactured in December 2010.

Matrix (10): Moltex diaper size 4 with new matrix Test methods Return of liquids to the surface of a diaper (rewet), penetration time and fluid distribution.

Material and equipment to be used 1. 1.1 Inspection table. 1. 1.2 Electronic scale 1. 1.3 Stopwatch 1. 1.4 Separation funnel set to 7 +/- lml / s or similar 1. 1.5 Beaker 1. 1.6 Graduated 150 ml test tube 1. 1.7 Weighs with acrylic receiving cylinder of 3.5 kg, 10 cm. of external diameter and 2.54 cm. of internal diameter and 22 cm of height (for baby and adult diapers) (0.7 PSI) 1. 1.8 Weighs 2.5 Kg with base 8 cm. diameter. (0.7psi) 1. 1.9 Adhesive tapes 1. 1.10 Synthetic urine (purified or distilled water solution and 0.9% NaCl) 1. 1.11 Frames of unwound tissue and cellulose 10x10 cm development 1. 2.1 Weigh the sample and record the data. 1. 2.2 Place the extended product on the work table with the inner cover (Non Woven) facing upwards, with the diaper tapes facing the opposite side of the person carrying out the test and holding it from the corners with adhesive tape. 1. 2.3 Make a mark on the center of the product from the front edge of the core, at a distance according to Table No.l TABLE No. 1 4 Place the weight with the applicator cylinder mentioned in step 5.1.7 above the mark. 5 Place the tip of the separation funnel inside the cylinder. 6 Pour or dose the appropriate amount of synthetic urine according to the product 7 Take the time from the opening of the separating funnel key until the synthetic urine is fully absorbed, recording the data as the first time of absorption. 8 Let stand for 10 minutes and remove the weight with the dosing mentioned in step 5.1.7, 9 Immediately after weighing a cellulose box of 10x10 cm, register as Pl, place it on the discharge in such a way that it is in contact with the sample and centered with respect to the point of urination, place on the frame the weight mentioned in step 5.1.8, for 2 minutes. 1. 2.10 during these 2 minutes measure the length reached by the synthetic urine and record it as the first distribution. 1. 2.11 At the end of the 2 minutes, remove the weight. 1. 2.12 Immediately weigh the cellulose, record the data as P2. 1. 2.13 For the second and third REWET, repeat steps 5.2.6 to 5.2.14, the second and third penetration time and the second and third distribution are also recorded. 1. 3 Calculations 1. 3.1 REWET = Pl - P2 In one of the embodiments, both the lower layer (13) and the upper layer (12), comprise from 75% to 100% fibers of absorbent material, also contain from 0 to 25% superabsorbent material; it is also possible to make a combination of an upper layer containing from 75% to 100% of fibers of absorbent material and from 0% to 25% of superabsorbent material while the lower layer only comprises 100% of fibers of absorbent material and vice versa .

The present invention is further related to a method for forming the matrix (10) which comprises forming a lower layer (13) an upper layer (12) which comprises from 75% to 100% of fibers of absorbent material, likewise the layer lower and upper contain from 0% up to 25% superabsorbent material; the method comprises the additional step of forming a distribution-storage zone (24) of an intermediate layer (14) wherein the distribution-storage zone has a specific gravity (g / m2 of cellulose fibers + superabsorbent material) of a 35% to 50% greater than the average specific weight of the transition zones (26) and from 75% to 100% higher than the specific weight of the anti-fall zones (28); the method further comprises making the appropriate cuts according to the shape of the absorbent matrix and then placing the absorbent matrix made with the knowledge of the present description in, but not limited to, disposable diapers for babies, disposable incontinent diapers, training pants and feminine towels.

A system for forming an absorbent matrix comprising the means necessary to form an absorbent matrix with the knowledge of the present and incorporating it into an absorbent article.

While the invention has been described in terms of a presently preferred embodiment, it is evident that various changes and modifications may be made thereto, such changes and modifications being within the spirit and scope of the invention, as defined in the appended claims.

Claims (15)

1. - An absorbent matrix to be used in a disposable absorbent article having a top surface and a bottom surface, a front part, a back part and a crotch part, two longitudinal edges and two transverse edges, characterized in that it is formed by three layers : a top layer, an intermediate layer and a bottom layer, such that: the upper and lower layers are formed by a homogeneous mixture of fibers of absorbent material and particles of superabsorbent material in a concentration less than 25% by weight. the intermediate layer is formed by fibers of absorbent material homogeneously mixed with particles of superabsorbent material and has three zones with different specific weights: a reception-distribution zone; one or more transition zones and one or more fallout zones

2. - An absorbent matrix for use in a disposable absorbent article such as that described in claim 1, characterized in that the specific weight expressed in gr / m2 of absorbent material plus material superabsorbent, of the reception-distribution zone of the intermediate layer of the matrix, is from 75% to 100% greater than the specific weight of absorbent material plus superabsorbent material of the zone of leakage

3. An absorbent matrix for use in a disposable absorbent article such as that described in claims 1, 2 and 3, characterized in that the specific weight expressed in g / m2 of absorbent material plus superabsorbent material, of the transition zone (s) of the intermediate layer, decreases gradually towards the transverse edges of the matrix.

4. - An absorbent matrix for use in a disposable absorbent article such as that described in previous claims, characterized in that the specific weight expressed in g / m2, of absorbent material plus superabsorbent material of the reception-distribution zone of the intermediate layer, is 30 to 50% greater than the average specific weight of absorbent material more superabsorbent material of the transition zone.

5. - An absorbent matrix for use in a disposable absorbent article such as that described in the preceding claims, characterized in that the upper and lower layers are formed 100% by fibers of absorbent material.

6. - An absorbent matrix for use in a disposable absorbent article such as that described in previous claims, characterized in that the density of the distribution receiving zone of the intermediate layer of the matrix is greater than the average density of the transition zone (s).

7. - An absorbent matrix for use in a disposable absorbent article such as that described in previous claims, characterized in that the density of the distribution receiving zone of the intermediate layer of the matrix is greater than the average density of the anti-drip zone (s).

8. - An absorbent matrix for use in a disposable absorbent article such as that described in previous claims, characterized in that the average density of the transition zone (s) of the intermediate layer of the matrix is greater than the density of the anti-drip zone (s).

9. - An absorbent matrix for use in a disposable absorbent article such as that described in previous claims, characterized in that the fibers of absorbent material are cellulose fibers.

10. - An absorbent matrix for use in a disposable absorbent article such as that described in previous claims, characterized in that the superabsorbent material is sodium or potassium polyacrylate particles.

11. - An absorbent matrix for use in a disposable absorbent article such as that described in previous claims, characterized in that it is incorporated into a disposable diaper.

12. - An absorbent matrix for use in a disposable absorbent article such as that described in claims 1 to 10, characterized in that it is incorporated into a disposable pant.

13. - An absorbent matrix for use in a disposable absorbent article such as that described in claims 1 to 10, characterized in that it is incorporated into a female towel.

14. - An absorbent matrix for use in a disposable absorbent article such as that described in previous claims, characterized in that it is incorporated in an absorbent insert.

15. - A method of manufacturing an absorbent matrix for use in a disposable absorbent article as described in the preceding claims.