FI91735B - Absorbent structure for packaging - Google Patents

Abstract

The invention relates to the packaging field and the extended duration packaging of food products, particularly by modifying their environing atmosphere by means of an absorbing structure containing hydroreactive products. The structure of the invention absorbs liquids, exsudates or condensates, and generates an active element by reaction of the agent with the liquid. It is characterized in that it is comprised of at least one matrix formed, by aeraulic process, of a substantially fibrous mixture of hydrophilic and hydrophobic materials wherein said hydroreactive agent is distributed.

Description

91735

Absorbent construction for packaging

The present invention relates to the field of packaging and aims in particular for the durable packaging of foodstuffs by modifying the air surrounding the products by means of an absorbent element containing hydroreactive substances.

Currently known methods of making encapsulated air control materials rely on either the use of absorbent bases to keep separated or condensed water separate from the packaged product or the use of active ingredients such as desiccants or bacteriostatic agents as a solid powder in a bag.

Sometimes the two methods are carried out in combination by mixing the absorbents with the active ingredients or by depositing the latter on an absorbent substrate by impregnation or brushing.

In fact, in order to preserve a food or other product in a package, the first condition 20 is to separate the liquid that has accumulated therefrom. The easiest way to make a perforated double base is as in GB Patent 1,131,848. Some boxes contain sheets of absorbent paper. U.S. Patent 4,275,811 discloses an absorbent material coated with a torn impermeable film 25 to separate food for storage from a moist absorbent material. In patent application JP 61/058 658 or U.S. Patent 4,615,923, the absorbent base comprises hydrogel-forming agents capable of retaining aqueous liquids. In order to better separate the nes-30 te from the product, it is sometimes proposed to provide a perforated double insole, as in patent application FR-2,586,653.

Various reagents are used to control the air in the kit according to the desired effect. Thus, packages often comprise silica or sodium chloride bags to remove water from the air, i.e. to convert vaporized water to liquid. It is often decided to absorb the oxygen in the package. GB patent 496,935 discloses an oxidizable metallic substance or ferrous sulphate mixed or not with other substances such as citric acid to slow down microbial activity.

Patent application EP 206 343 discloses a mixture of iron powder and electrolytic material in the form of paper. Other patents supplement the range of products capable of absorbing oxygen, such as sulfites (US 2,825,651), bisulfites (US 3,169,068) or metal oxides from the decarbonation of metal carbonates (US 3,361,531) or even ascorbic acid or its salts (FR- patent 2,394,988). As absorbent ai-15, fibers, clays, bentonites, kaolins,

active alumina and activated carbon. Patent application JP 80/29 975 discloses an impregnated material coated with an oxygen absorbing agent and a carbon dioxide generating agent. It is sometimes advantageous to produce hap-20 pea by the action of water, as in JP patent application

61/145 270, wherein the powder is included in a bag. EP patent 128,795 describes a box base which contains, in an absorbent material, not only a material capable of releasing gas from the action of an aqueous liquid, but also, by allowing the ingredients of the foodstuff, to prevent its decomposition by the action of Aero. The absorbent material is in the form of a sheet or sheet.

In order to avoid liquefaction of the active substances by the action of the liquid, the presence of an absorbent material is also necessary in bags containing these substances in the form of powder or granules. To allow reuse of the desiccant, U.S. Patent 4,615,823 discloses a composition in which water-soluble salts are retained in a bag by means of fibers, while JP Patents 35 56/143 263 and 61/103 523 disclose the retention of saline liquid in a bag by means of gelling agents. .

The active agent may be a bactericide incorporated into a cellulose pad, as disclosed in GB Patent 863,095.

Of the substances for controlling the air contained in the package, the invention relates to those which become active either by the liquid released by the product to be stored or by the liquid resulting from the condensation of the vapor.

The object of the invention is to solve a problem which comprises prolonging the action of these substances for as long as possible. An analysis of past practices has shown that this problem has not yet been addressed.

15 In fact, once the powders or granules have been isolated in the bag, they react as soon as the liquid has penetrated through the latter wall. The evolution of a gas or active material is thus uncontrolled.

In the event that liquids are formed gradually, for example over the entire storage period of a foodstuff, it is possible to prolong the action of these substances by placing them in a very large amount relative to the amount of liquid to be collected. But the products are relatively expensive and this solution is not economically advantageous.

In addition, in the bag, the powder tends to accumulate in clumps due to moisture. The part thus does not enter the liquid and becomes ineffective.

In short, the manufacture and filling of the bags 30 are costly operations. This type of tray is not economically viable in terms of its use, for example, in food packaging, of which it should represent only a small part of the price.

35 Considering the method of brushing the substrate, a problem is encountered due to the very limited amount of reagent that can be applied per unit area using this method. It is also not possible to check the effect of the product earlier. In addition, it is known that some hydroreactive agents cannot be used as aqueous solvents without being altered.

According to the invention, these drawbacks are remedied by preparing an absorbent structure comprising at least one hydroreactive substance which is intended to be placed inside a package, in particular a food-containing package, to absorb liquids which have separated or condensed and react and release on contact. at least one active material, characterized in that it comprises at least one mattress formed by a stream of air from a substantially fibrous mixture of water-soluble and water-repellent materials and inside which said hydro-reactive substance is placed.

Such a structure offers the following advantages: The placement of the active ingredient in the form of powder or granules inside the fiber mattress avoids all the dangers of lump formation. The product therefore does not lose its effectiveness. This structure offers the possibility to incorporate a relatively large amount of powder or granules.

- By appropriate selection of the amounts of hydrophilic and water-repellent materials, it is possible to adjust the wetting rate of the structure and thus control the duration of the reaction. In the case of food storage, the last 30 days of storage can be relocated much further reliably, as a lasting effect on the sealed air in the package can be guaranteed.

- The fact that the mattress is formed by means of an air stream, i.e. the fibrous materials are transported in an air stream, is then placed on a belt conveyor together with a possible powder premix, enables ♦ 5 91 735 very high manufacturing speeds and thus makes it very cheap. In addition, the materials constituting the powder carrier can be selected very cheaply.

- The airflow process makes it possible not to use water to form the mattress or, if necessary, to strengthen the mattress, thus avoiding the possible partial decomposition of the hydro-reactive substance by the water.

This structure is preferably coated on each side with a gauze or film that is permeable or impermeable as needed so as to allow liquids to penetrate into the mattress.

According to a preferred embodiment of the invention, the absorbent assembly can be reinforced according to generally known methods by using heat-meltable binders as a fiber or powder. Aqueous latices can also be used by spraying or applying them as a foam to the surface of the product. Once the assembly is thus reinforced, it can be avoided to cover it on one side with a gauze or film.

According to another preferred embodiment of the invention, the mattress containing hydroreactive materials can be combined with at least one second absorbent mattress, for example of interconnected fibers having a different wettability than the first mattress, which forms an absorbent element between the liquid source and the reagent-containing structure, that it increases the delaying effect and controls the distribution and effect of the liquid towards the other mattress.

The mattress containing the hydroreactive substance consists of at least one hydrophilic material and one clearly less hydrophilic material, that is to say, water-repellent than the first. In addition, at least one of these ingredients must be fibrous.

35 The choice can be made from the following combinations: 6 91735

Aqueous component Aqueous component .Cellulose-containing fibers .Synthetic fibers, whether or not treated .Cellulose-containing fibers .Latex-type binder 5 .Cellulose-containing fibers .Thermal meltable powder binder .Synthetic fibers .Synthetic fibers .Synthetic fibers. binder in the form of a powder. amount, or regenerated fibers such as rayon fibers, viscose-20 fibers, etc.

By treated synthetic fibers is meant synthetic fibers (PP, PE, PET, ...) whose surface has been significantly modified to make the fibers more wettable with water (e.g. PE fibers sold under the trademark Hercules Pulpex).

Hydrophilic fibers are understood to mean naturally hydrophilic fibers, such as glass fibers or metaphosphates and

The hydrophilic powder may be inorganic or or-30 organic. Inorganic powders include clays, vermiculite compounds, glass, etc. Organic powders are of natural origin (guar, alginate, modified celluloses or starches, thickening, toughening or hydrogel-enhancing products) or synthetic (polyethylene oxides), polyvinyl oxides, polyvinyl oxides, polyvinyl oxides, These powders are more or less water-soluble - like fibers - »91735 7 as they may be slow to wet (water content) and / or to gel water (hydrogel-forming powder) to retain it (water solubility), which, however, seems to slow down the spread of water in the mattress - which 5 is a desired feature - when adding water-repellent materials, now defined as less water-seeking.

Briefly, the hydrophilic component of the combination may be one of the above hydrophilic components or a combination of two or more thereof. For example, a hydrophilic powder, especially a hydrogel-forming powder, can be added to the cellulosic fibers.

The ratio between water-soluble and water-dispersible materials should be chosen so that the wettability of the product is made compatible with the intended use, i.e. the nature and amount of liquids in the package. In most cases, the aim is to achieve the lowest possible wettability without the product becoming completely water-repellent; in other words, it would not be able to absorb 20 fluids.

Thus, the amount of water-repellent material can vary between 5 and 50% by weight of the absorbent structure, without the hydroreactive agent.

It is necessary to define the terms hydrophilic and 25 hydrophilic, by which some product is called.

The water attractiveness of a product depends on its surface energy. It is known that the smaller the difference in surface energies between the liquid and the solid surface, the better the wetting of a flat surface. Thus, water with a surface energy of 72 mj / m2 well wets polyester (43 mJ / m2) or cellulose (36 mJ / m2) or polypropylene (29 mJ / m2) well. The water does not wet Teflon (PTFE), which has a very low surface energy (18 mj / m2).

The former surfaces are considered to be hydrophilic, while PP, PE and, for an even greater reason, PTFE are known to be 8,91735 hydrophilic, as their surface energies are clearly lower than the surface energies of water.

In addition, the silicone-containing binder of Rhodorsil 6356 (trademark) RP (25 mJ / m2) is more water-repellent than the 5-phenolic binder with a surface energy of 42 mJ / m2 or epoxy paint Epikote 828 (trademark) (44.5 mJ / m2).

Unfortunately, the surface of the fibers is not smooth and their roughness modifies the angle of contact of the liquid with this surface.

10 To determine the wettability of a fiber, its contact angle with water can be measured, for example, according to the method of B. Miller, described in Colloids and Surfaces, 6, (1983), 49-61, which measures the amount of fiber in contact with a liquid. and the exit angle of the fiber to be withdrawn. For round fibers, Miller has obtained the following values:

Angles (degrees) Contact angle Exit angle

Teflon 118 92 20 Polypropylene 100 78

Polystyrene (PS) 95 71 PS - Polyacrylonitrile 83 51

Nylon 6 69 25 Thus, this method makes it possible to calculate the wettability degree 25. When the angles are above 90 °, the water does not wet the fiber. The fiber is completely water-repellent. Instead, some bleached sulfate cellulose fiber would prove to be completely water-retrievable at very low contact and exit angles. It follows from the foregoing that products designated as hydrophilic and water-dispersible (in the present invention) are products having substantially different angles of contact with water. The difference in angles must be more than 20 °, i.e. the fibers called so-called water-bearing have the smallest contact and exit angles and less than 90 ° in order to be called water-based.

• 9,91735

The measurement of the contact angle is crucial in assessing the water content or hydrophilicity of a material, especially fiber, as a water-soluble product can be treated to be hydrophilic on its surface and vice versa.

The described hydroactive reagents or hydroreactive materials contained in the absorbent assembly are sensitive to water, liquid and vapor.

This reactivity in the physicochemical sense manifests itself, for example, in the hydration of the material, its dissolution or its decomposition by the action of an aqueous liquid. The hydroreactive compound of the hydroreactive material is not necessarily the active ingredient of the composition.

Thus, water can decompose a hydrogenated compound into hydrogen, which under the action of a catalyst combines to achieve an oxygen-free state (U.S. Patent 3,419,400). The hydroreactive compound may be a soluble capsule containing the active ingredients.

The hydroreactive material consists of one or more pure or mixed products, inorganic or organic products that are at least partially soluble or remain combined with water or react or mix. These include, for example, mineral salts (NaCl, CaCl2), organic salts (gluconates ...), bases (Ca (OH) 2, NaOH ..) or acids (citric acids, ascorbic acids), solubilizers (sugar), oxides ( CaO, MnO), peroxides (percarbonate 2Na 2 CO 3, 3H 2 O 2), hydrides, metals, whether or not encapsulated (Na, Fe ...) and carboxymethylcelluloses.

When the hydroreactive material consists of two or more components, it is possible to divide each component into a separate fibrous mattress or a separate layer of the mattress, which mattress is thus multilayered.

The hydroreactive material may already be "stabilized", i.e., treated to be less reactive with atmospheric water, which further has the secondary effect of smoothing and delaying the reactivity of the material with water.

The hydroreactive material may be in the form of powder, granules, flakes, chips, filaments or even fibers. As an example, the behavior of three products according to the invention compared to the behavior of two products according to the prior art is described by means of three tests.

10 The first test makes it possible to calculate the total and instantaneous absorption of the product. Naturally, poor wettability is desired to retard the reaction. But this is sufficient to allow the liquid to be absorbed in practice as it discharges.

15 For this test, place a test piece 6 x 10 cm above the horizontal. Irrigate it with a certain amount of water. The support plate is then tilted 30 ° and excess, flowing water is collected. The difference is the total absorption of the test piece.

A second test piece, identical to the first, is then placed on a surface inclined at 30 °. The burette is used to immediately pour in an amount of water that is 50% greater than what the product is able to absorb to become saturated, and collect the excess water. The difference 25 is calculated as the instantaneous absorption, which can be expressed as a percentage of the total absorption and can be called wettability.

To calculate the total reactivity of the product, the procedure is as follows for the following second test. A test piece of the product is placed in an Erlen-Meyer flask, which is closed with a stopper pierced by two holes. On top of the first is a flask through which an amount of water 50% greater than the total absorption of the test piece is introduced. The other is connected to a water manometer which can monitor the pressure due to the release of gas. If the maximum pressure is measured as a column of water and the total time of the reaction, then the time required for the column of water to settle to half of the highest value reached is calculated; this determines the reaction time.

5 The purpose of the third test is to simulate the wetting of the product placed on the bottom of the container. The container is never quite horizontal, so that the liquid usually drains to the edges of the product. Absorption takes place by capillary according to Lucas' law, it is practically independent of the tilt angle of the pum-10. The terminal test can be used to monitor the rise of a liquid over time with a horizontally suspended specimen by measuring the wetting height and the amount of water absorbed.

At the end of the test, the total absorption is immersed by immersing the test piece and then dropping it vertically.

Thus, the absorption at any given time as a percentage of the total absorption can be expressed by the immersion-drying method.

20 Example 1

A hydroreactive powder mixture is prepared starting from a three-part mixture of percarbonate and an organic dibasic acid and one part of a neutral salt acting as a binder, such as sodium chloride. The percarbonate used is stabilized. In an aqueous environment, it releases oxygen (13%) and carbon dioxide under the influence of acid.

The bags are made of 6 x 10 cm non-woven fabric sold under the Sericel trademark, which consists of a plastic grid to which two cellulose clay sheets are glued.

For the first test, 0.72 g is placed in the first bag and 2 g in the second. It is noted that in both cases the total absorption is 5.7 g and the instantaneous absorption of ab-35 is 88%.

12 91735

For the second test, place 2 g again in one bag. The pressure is observed to rise rapidly and reach a maximum of 33 cm of water column in a reaction time of 2 minutes. It can be concluded that the presence of water triggers the release of the gas immediately, without a delaying effect. The pressure then decreases due to the dissolution of the gases. The reaction time is 60 minutes.

By comparison, 2 g of a hydroreactive powder hydrolyzed with 120 ml of water causes a pressure increase of 10 cm from the water column in a reaction time of 5 minutes. The reaction time of the powder alone is about 35 minutes. This example, as well as Example 2, show that the reaction time remains unchanged and that the reaction time is less than twice when the powder is combined with absorbent materials according to the art level.

Example 2

The same hydroreactive mixture in the same amount as in Example 1 is introduced into a bag made by joining together one cellulosic fibrous web, the fibers of which are combined by spraying latex with a basis weight of 60 g / m 2. / m2.

A bag measuring 6 x 10 cm and weighing 3.5 g, which contains 2 g of a hydroreactive mixture - the structure is according to the prior art - provides an absorption of 9.7 g and a wettability of 88%. (Wettability without powder is 95%).

The bag wets rapidly, resulting in increased hydrolysis of the reagent, which is contrary to the goal. In fact, according to the second test, it is found that the reaction time is shorter (3 min) for a maximum pressure of 28 cm from the water column. The reaction time of 45 minutes is likewise less than in Example 1.

The third test confirms that this bag is wetter than the previous one and the effectiveness of the hydroreactive mixture is lower. The total absorption here is 7.5 g for a 2.5 g test piece. The absorbances are as follows: 65% after one minute 84% after 10 minutes 5 84% after one hour The absorption of this product after one hour is more than 75% of the intake power.

Example 3

According to the invention, an absorbent whole comprising the same hydroreactive material is formed. For this purpose, cellulose fiber pulp (product sold by ITT under the trademark Rayfloc J) and synthetic polyethylene pulp (fibers sold by Mitsui under the trademark SWP) are defibered in a ratio of 95/5. 120% of the hydroreactive powder of the mixture described in Example 1 is added to the air stream 15 loaded with these fibers. The assembly is impregnated onto tissue paper having a basis weight of 18 g / m 2, calendered and heat-bonded in an oven at a temperature of 30 to 150 ° to allow the thermosetting fibers of the water-based polyethylene to melt. 20 The assembly is glued with hotmelt glue on one side to the polyethylene film and on the other side to the nonwoven fabric.

Gluing of the nonwoven can be avoided by replacing the tissue paper with two-component polypropylene-polyethylene fibers (Jacob Holm trademark 25 Danaklon ES), which allows the nonwoven to be joined to the absorbent mattress by melting the nonwoven polyethylene materials and the absorbent mattress. The quality of the nonwoven fabric, the lubrication treatment of its constituent fibers, and the heat resistance of the lubrication determine the wettability of the final product.

The composition of the product with a basis weight of 530 g / m2 is: - tissue paper 18 g / m2 - cellulose fibers 200 g / m2 35 - synthetic fibers 10 g / m2 »• · 91735 14 - hydroreactive powder 250 g / m2 (47%) - binders 6 g / m2 - polyethylene film 28 g / m2 - non-woven fabric 18 g / m2 5 A test piece measuring 6 x 10 cm and weighing 3.2 g absorbs 16.5 g and has a wettability of 82%. The momentary absorption of a large amount of fluid is slightly slowed, allowing for strong capillary absorption.

The reaction time of the product according to the invention has considerably increased, i.e. 330 minutes, at a constant maximum pressure of 30 cm from the water column. The reaction time is thus 485 minutes for this 3.85 g test piece containing 1.85 g of hydroreactive material.

Capillary absorption measurements show that the wetting of the product is low, which allows 12.6 g of absorption (3.3 g of product) to be absorbed by weak hydrolysis of the reagents.

Absorbances according to the third test are: 51% after 1 minute 20 64% after 10 minutes 64% after 60 minutes

Absorption after one hour is much less than 75% of capacity.

Example 4 The procedure is as in Example 3, but more polyethylene fibers are introduced into the fiber mixture, instead of 5%, 15% to further modify the reactivity of the product.

The composition of the product with a basis weight of 400 g / m2 is: 30 - tissue paper 18 g / m2 - cellulose fibers 160 g / m2 - synthetic fibers 24 g / m2 - hydroreactive powder 144 g / m2 (36%) - adhesives 6 g / m2 35 - polyethylene film 28 g / m2 - non-woven fabric 18 g / m2 15 91735

A test piece measuring 6 x 10 cm and weighing 2.2 g, containing 0.8 g of a hydroreactive mixture, has an absorption of 10.6 g and a wettability of only 6%.

5 A test piece measuring 7 x 12 cm and weighing 3.8 g, containing 1.4 g of a hydroreactive mixture, releases the gas in 150 minutes, reaching a maximum of 36 cm of water. The effect sought by the invention is undeniably achieved, namely to allow the gradual release of a gas which is staggered over time. For a reaction time of 150 minutes, the reaction time is 300 minutes. These values are clearly higher than those obtained with prior art products.

The absorption by immersion is 8.1 g for a test piece-15 weighing 2.7 g. Absorbances with capillary rise are as follows: 40% after 1 minute 57% after 10 minutes 57% after 60 minutes 20 Absorption after one hour does not exceed 75% of capacity. It is less than the absorption of a product containing only 5% aqueous fibers.

Example 5

The procedure is as in Example 4, but the nonwoven fabric covering one surface of the product 25 is replaced by the above-mentioned dry process paper Homecel with a basis weight of 60 g / m 2. It is an absorbent nonwoven fabric with a higher wettability than the lower layer comprising polyethylene fibers SWP.

30 The purpose of this example is to show that one or more operations can produce multilayer entities. There are other ways to place the fibers or powders locally, for example in pieces, inside the pulp.

35 It is conceivable that an active substance is released by the reaction of two products A and B, at least one of which # 91735 16 is hydroreactive, these substances A and B being sensibly arranged in different layers or different areas of the whole to increase the retention effect.

The test piece, measuring 6 x 10 cm and weighing 2.4 g, containing 1 g of the hydroreactive mixture, has an absorption of 13.7 g and a wettability on the Homecel surface of 80%. This side is very water-repellent compared to the more water-resistant surface containing the hydro-reactive material.

A test piece measuring 7 x 12 cm, containing about 1.3 g of hydroreactive substances, reaches a maximum pressure of 10 cm of water column under the action of water during a reaction time of 1 minute. The reaction time is more than 300 minutes. The pressure remains constant between 8 and 9 cm from the water column.

This entity, in which water is partitioned between the reagent-free zone and the reactive zone, makes it possible to limit the release of gas and to achieve a high reaction time.

The third test ensures that this whole is 20 wetter. The total absorption is 11.8 g (test piece weight 2.8 g).

The absorptions are as follows: 54% after 1 minute 63% after 10 minutes 25 66.5% after 60 minutes

Absorption after one hour does not exceed 75% of capacity.

These examples demonstrate the advantages of the products of the invention over generally known products. In fact, the hydrolysis times of the hydroreactive material are more than double here, which was the desired effect, thanks to the use of selected, reasonably combined absorbent materials.

This effect is obtained according to the described method using 5 to 15% of thermoplastic fibers, such as Mit-suin SWP fibers or Hercules Pulpex fibers.

91735 17

It is also possible to use fibers spun, cut, curled or not, JACOB HOLM DANAKLON polyethylene fibers or bicomponent DANAKLON ES fibers or even UNITIKA MELTY fibers (trademarks). These 5 fibers melt well to join the fiber mattress. The use of heat-meltable powders, such as EASTMAN's low-melting polyester powder, makes it possible to obtain more flexible products.

The hydrophilic material consists of natural or regenerated fibers or pulps, or fibers or pulp or absorbent nonwovens, which are synthetic, hydrophilic treated materials. The same material, when partially processed, may provide the desired properties, combining water solubility and water dissipation. Example 6 According to this embodiment, a fibrous web is formed in the first step by a dry method, i.e. by means of an air flow. A powder is then placed on the surface, which is caused to penetrate into the web by the possession of airwood, by sucking through the thickness of the web or by combining both means.

This web, which contains all or part of the powder, can likewise be covered with an additional web formed using an air stream which does not contain or contains another part of the hydro-reactive powder.

Thus, a web with a basis weight of 300 g / m 2 containing 20% of polyethylene fibers and comprising a hydroreactive powder having the same composition as in Example 1 has been prepared from cellulosic fibers.

30 This web is heat bonded by placing it in an oven. The dissolution rate of the hydro-reactive substance is checked by measuring the dissolution rate of the hydro-reactive substance after pouring 120 cm3 of water onto the test piece.

Thus, while the hydroreactive agent alone causes an equilibrium gas release corresponding to the pressure of a 16 cm water column over a reaction time of 2 minutes, the reactor web regularly and for a longer period of time. The pressure of the liberated gas at equilibrium is 15 cm from the water column for a reaction time of 12 minutes.

Example 7 Three webs of cellulosic fibers containing 0%, 5% and 15% synthetic SWP fibers and percarbonate as a powder are prepared by the dry process. The formed webs are placed in an oven at 150 ° for six minutes.

10 To calculate the dissolution rate of this peroxidized salt, the dissolution time is measured according to the fourth test, i.e. the time required for the test piece immersed in distilled water to reach equilibrium when mixed with the water-dissolved salt solution. It is found that the peroxide dissolution times increase under the influence of the hydrophilic fibers of the products P5 and P15 as well as, as above, the hydration times of the percarbonate.

PO P5 P15 20 P Cellulose + Cellulose Cellulose

Reference 0.5 g 0.5 g + 5% SWP + 15% SWP

percarbo-percarbo- + 0.5 g 0.5 g of sodium naate percarbo- percarbo- _nate of sodium 25 basis weight 220 280 310 (g / m2)

Test 4 initial pH 5.2 5.2 5.2 5.2 30 Equilibrium pH 11.0 11.0 11.0 11.0

Duration of dissolution (s) pH = 10.4 14 38 50 80 «91735 19

Example 8

As in Example 7, mixtures are prepared containing citric acid as a powder instead of percarbonate.

Similarly, the dissolution rate of the hydroreactive acid is checked using the method of the fourth test by immersing the test piece in distilled water previously adjusted to pH 8 with soda.

C CO C5 C15

Reference 0.5 g Cellulose + Cellulose Cellulose

10 lemons - 0.5 + 5% SWP + 15% SWP

acid citric- + 0,5 g 0,5 g acid citric- citric_acid_acid

Bulk density 265 280 310 15 (g / m2)

Test 4 Initial pH 8.2 8.2 8.2 8.2

Equilibrium pH 2.6 2.6 2.6 2.6 20 Duration of dissolution (s) pH = 3.2 10 23 28 * 600

Claims (11)

An absorbent structure comprising at least one hydro-reactive material and intended to be deposited in a package, especially for food, for at least partial absorption of separated or condensed liquids, wherein the material in contact with them reacts and releases at least one active component , characterized in that it consists of at least one pad formed by a stream of air of a substantially fibrous mixture of a hydrophilic and hydrophobic material, and in which the hydroreactive material is placed. 2. Absorbent structure according to claim 1, characterized in that the hydrophilic material The fibers are fibers which are optionally blended with hydrophilic powders. 3. Absorbent structure according to claim 2, characterized in that the fibers are cellulose fibers, such as wood, cotton or viscose fibers. 4. Absorbent structure according to any of the preceding claims, characterized in that the hydrophobic materials consist of hydrophobic fibers, a binder or a powder. Absorbent structure according to any of the preceding claims, characterized in that the pad, without the hydro-reactive material, consists of 5 - 60% by weight of hydrophobic material. Absorbent structure according to any one of the preceding claims, characterized in that the hydro-reactive material is in the form of powders, granules, flakes, buckles, trees or fibers. Absorbent structure according to claim 6, characterized in that the weight of the pad is located in the pad, 0.1 to 20 times the weight of the pad, without the pad. 91735 Absorbent structure according to any of the preceding claims, characterized in that the cushion is coated at least on one side with a permeable web or with an impervious membrane. 9. Absorbent structure according to any of the preceding claims, characterized in that the pad is stabilized with a binder. Absorbent structure according to any of the preceding claims, characterized in that it comprises a second fibrous pad having a greater wettability than the first pad. Absorbent structure according to any of the preceding claims, wherein the hydro-reactive material is formed of at least two components, characterized in that it comprises at least two layers or two fibrous pads, each containing one of the hydro-reactive materials. the components of the material. «I